Growth, development, and site location of the trematode Himasthla quissetensis in the chick following cloacal drop infections with cercariae. Infections with Himasthla quissentensis were obtained per cloaca in the domestic chick using cercariae. Worms showed a preference for the ileum where they grew and developed to maturity at a rate comparable to those raised in the gull (Stunkard, 1938). Those from the bursa of Fabricius showed relatively little growth and exhibited gonadal atrophy in some instances.


Robenidine resistance in Eimeria tenella. Robenidine protected chickens against cecal coccidiosis infections initiated by a strain of the parasite that had no previous exposure to drugs. No cross resistance was found with 13 strains resistant to other anticoccidials. A strain of Eimeria tenella that was serially propagated in chickens fed mash containing robenidine became resistant to the chemical. No cross resistance was detected when this experimental strain was tested against 12 other anticoccidials.


The life cycle of Eimeria dispersa Tyzzer 1929 from the turkey in gallinaceous birds. The life cycle of a turkey strain of Eimeria dispersa was studied in chickens, Chukar partridge, Ring-necked pheasant, and Bobwhite quail. Endogenous development in partridge and quail differed from development in chickens and pheasant. In partridge and quail, mature 1st-, 2nd-, and 3rd-generation schizonts, macrogamets, and oocysts were found in tissue sections at an earlier time interval, mature 1st-generation schizonts were larger, and mature 1st-, 2nd-, and 3rd-generation schizonts contained a greater number of merozoites that were longer. The only apparent similarity among the 4 hosts was the size of mature 2nd- and 3rd-generation schizonts. The life cycle was completed in all 4 species of birds. The prepatent period was approximately 6 hr shorter in partridge and quail than in chickens and pheasant. Two partridge and 2 quail given 50,000 sporulated oocysts each shed a total of 23 million and 135 million oocysts, respectively, during 4-day interval. Two chickens and 2 pheasant given the same dosage shed a total of only 70,000 and 1 million oocysts, respectively, during the same interval. Oocysts from partridge and quail sporulated more quickly and were slightly larger than those from chickens and pheasant.


Climbing behavior and host-finding larval rabbit ticks (Haemaphysalis leporispalustris). The rabbit tick (Haemaphysalis leporispalustris) is highly host-specific. Adults feed almost exclusively on rabbits. Immatures feed primarily on rabbits but will attack birds. When larvae leave the daytime resting form of the rabbit, they climb up to a position on vegetation where they can encounter a host. Experiments using glass rod models to represent vegetation showed that ticks selected a position which had greatest substrate curvature and was at rabbit body height. This strato-orientation restricts the tick's host spectrum to rabbits and ground-dwelling or feeding birds.


Repeated feeding of Amblyomma herbraeum (Acarina: Ixodidae) immatures on laboratory hosts. Host effects on tick yield, engorged weight and engorgement period. Rabbits and sheep are unable to acquire a resistance to larvae and nymphs of Amblyomma hebraeum. After repeated infestation of hosts there is no progressive decline in either the tick yield or the engorged weight of fed ticks. Seasonal fluctuations in engorged weights do occur however, with the weight declining in early to midwinter and increasing in early to midsummer. Changes in hose physiology as a result of low temperature acclimatization appear to be responsible for the fluctuations. Tick yield is determined by the amount of grooming undertaken by hosts. The feedings periods of larvae and nymphs are dependent on the skin temperature of the host.


Arousal as a necessary condition for attitude change following induced compliance. This study examined whether arousal is or is not a necessary condition for attitude change in the induced compliance paradigm. In a 2 times 3 design, experimental subjects were induced to write counterattitudinal essays under either high- or low-choice conditions. All subjects were led to believe that a pill, which they had just taken in the context of a separate experiment, was a placebo. In reality, subjects were given a pill that contained either phenobarbital (tranquilizer condition), amphetamine (amphetamine condition), or milk powder (placebo condition). In this last condition, the results yielded the usual dissonance effect: High choice produced more attitude change in the direction of the essay than low choice. When subjects were given a tranquilizer, this effect was virtually eliminated; when subjects were given amphetamine, attitude change increased under high choice and was exhibited for the first time under low choice. These results are consistent with the notion that attitude change is in the service of reducing arousal and with the idea that arousal from other sources can be misattributed to attitude-discrepant behavior.


Phase solubility analysis and PMR study of complexing behavior of dinoprostone with beta-cyclodextrin in water. The mechanism of inclusion compound formation by dinoprostone (prostaglandin E2) with beta-cyclodextrin was studied by phase solubility analysis and PMR spectroscopy. As indicated by the linear increase of aqueous solubility of dinoprostone with beta-cyclodextrin concentration, some types of molecular interactions definitely exist between dinoprostone and the complexing ligands. The temperature dependence of a 1:1 complex formation constant yielded the following thermodynamic data at 20 degrees : deltaG degrees = -4.11 kcal/mole, deltaH degrees = 7.20 kcal/mole, and deltaS degrees = 10.5 e.u. Since water was the solvent system, these parameters appear to be largely determined by solvent reorganization through hydrogen bonding rather than solely by the binding of desolvated free dinoprostone and beta-cyclodextrin entities. PMR data indicate that dinoprostone is included within the cavity and also interacts with protons on the exterior of the beta-cyclodextrin molecule. A model consisting of a 1:1 complex, in which a dinoprostone molecule is partially included within the cavity and the remainder of the molecule extends around the edge of the opening of the cavity to the exterior of the beta-cyclodextrin molecule, is proposed as the most probable structure of this inclusion compound.


Simultaneous determination of pseudoephedrine and chlorpheniramine in pharmaceutical dosage forms. A simple and sensitive high-pressure liquid chromatographic (HPLC) determination of pseudoephedrine and chlorpheniramine in a pharmaceutical dosage form is described. Quantities of 1.5 microgram of pseudoephedrine and 0.1 microgram of chlorpheniramine are sufficient to determine concentrations in an aqueous solution. Small volume samples, without any extraction procedures, can be treated for direct drug concentration measurement with a high-pressure liquid chromatograph. The stability-indicating property and the accuracy of this method are comparable to those of an established GLC method. The HPLC method can be applied directly and successfully for dissolution studies. The latter application eliminates the need for volume replacement or subsequent mathematical corrections.


Dissolution of nonspherical powders.

Dissolution of nonspherical powders. To elucidate the effect of particle shape on the dissolution profile of a powder, an equation was derived for the dissolution of powders whose particles are rectangular parallelepipeds and log-normally distributed by introducing three-dimensional parameters instead of diameter in the Brooke equation for the spherical powder dissolution. By using some hypothetical values for constants in the equation, it is shown that the smallest side length, alphao does greatly affect the dissolution profile but that the other two side lengths, and betaalphao, do not, even with rather large values of alpha and beta. Nonisotropic dissolution also is discussed.


Anticonvulsant activity and inhibition of respiration in rat brain homogenates by substituted trimethoxybenzamides. Ten N-[4-[4-(arylthiosemicarbazido)carbonyl]phenyl]-3,4,5-trimethoxybenzamides were synthesized and characterized by their sharp melting points, elemental analyses, and IR and NMR spectra. All substituted benzamides were evaluated for their anticonvulsant activity. The degree of protection afforded by these compounds (100 mg/kg ip) against pentylenetetrazol (90 mg/kg sc)-induced convulsions in mice ranged from 10 to 80%. The ability of substituted benzamides to inhibit respiratory activity was observed by inhibition of oxidation of pyruvate, alpha-ketoglutarate, NADH, and succinate by rat brain homogenates. Inhibition of pyruvic acid oxidation was concentration dependent. The anticonvulsant activity of substituted benzamides was not related to their ability to inhibit cellular respiratory activity.


Effect of repeated skin application on percutaneous absorption of salicylic acid. Various concentrations of salicylic acid in hydrophilic ointment were applied repeatedly at daily or weekly intervals to rats in vivo. Salicylic acid absorption through treated skin was monitored by determining the penetration fluxes of salicylic acid through skin excised at various times. A gradual decrease in the salicylic acid penetration flux was observed following weekly applications of either 5 or 10% salicylic acid in hydrophilic ointment. The penetration flux of 1% salicylic acid remained constant. In the daily applications of 5 and 10% salicylic acid, the penetration flux increased after approximately 2 days of treatment and declined thereafter. The penetration flux of salicylic acid from the 1% salicylic acid increased slightly after 3--4 days of treatment.


ESTRIP, a BASIC computer program for obtaining initial polyexponential parameter estimates. A new BASIC exponential stripping program, ESTRIP, allows the relatively rapid calculation of initial polyexponential parameter estimates, as does the previously published FORTRAN IV program, CSTRIP. The potential advantages of the new program are that it can be run on microcomputers and minicomputers with BASIC capability and a relatively small core and that it can be easily modified by the user.


Assay of tocainide in blood by high-pressure liquid chromatography. A sensitive, specific, high-pressure liquid chromatographic assay for the determination of tocainide in whole blood is described. The residue from a methylene chloride extract of alkalinized blood was resolvated in a mobile phase of methanol--water (47:53) containing 1% acetic acid and 6.16 mM 1-octanesulfonic acid, adjusted to pH 4.0. Chromatography was performed on a reversed-phase column with detection at 254 or 225 nm. The limits of accurate measurement were 2 microgram/ml for a 1-ml blood sample monitored at 254 nm and 0.2 microgram/ml for a 2-ml sample monitored at 225 nm. The assay was tested on samples from emergency protocol patients and was also found suitable for single-dose pharmacokinetic studies.


New microporous cholestyramine analog for treatment of hypercholesterolemia. A new, microporous, uniformly reticulated preparation of cholestyramine is described. The preparation, cholpor, has a higher exchange capacity for chloride than does cholestyramine and swells very little in water. It is 15--20% more potent than chloestyramine in the in vitro binding of sodium cholate; moreover, the binding velocity is considerably higher than that of cholestyramine. Colestipol hydrochloride, also used as a reference anion-exchange resin, is about half as potent as the other two resins; its binding velocity is similar to that of cholpor. Cholpor may be prepared in a suspension form of good palatability. Preliminary clinical findings in short-term trials showed a cholesterol-lowering effect similar to that of cholestyramine with lower doses and fewer side effects.


Crystal and molecular structure of quinidine. The structure of the free base quinidine was determined by single crystal X-ray diffraction. Quinidine crystallizes from absolute ethanol as the ethanolate, with the molecular formula C20H24N2O2.C2H6O and molar mass 370.491 units. It crystallizes in the orthorhombic space group P212121 with unit cell dimensions a = 1321.1(3), b = 989.3(2), and c = 1651.5(3) pm. The measured density was 1.15 g/cm3; the density calculated for Z = 4 was 1.164 g/cm3. The diffraction data were collected by using MoKalpha radiation. A final R value of 0.055 was obtained. Evidence for intermolecular hydrogen bonding was found. The crystal analysis is in agreement with the structure proposed by other methods. The absolute configuration is based on the published structure of 10-bromo-10,11-dihydroepiquinidine.


Dissolution kinetics of cholesterol in simulated bile II: influence of simulated bile composition. Normal human gallbladder bile and gallbladder bile of patients undergoing chenodeoxycholic acid therapy were simulated by using appropriate combinations of taurine and glycine conjugates of cholic, chenodeoxycholic, and deoxycholic acids. Also, the total bile acid concentration and the total bile acid to lecithin ratio were varied over physiological ranges. Dissolution rates of cholesterol monohydrate pellets (model gallstone) in these solutions were 90--99% interfacially controlled. Even under conditions favorable for dissolution, i.e., high bile acid concentration and high bile acid to lecithin ratio, the interfacial resistances were extremely large. These results are of the same order of magnitude as those found in the limited studies with actual gallbladder bile and suggest that the bile acids, lecithin, and the electrolytes are the primary determinants of the interfacial resistance for cholesterol dissolution. Furthermore, the kinetics of dissolution were always much faster with the chenodeoxycholic acid-rich compositions than with the corresponding normal compositions. This finding suggests, therefore, that in addition to desaturating bile with respect to cholesterol, the feeding of chenodeoxycholic acid further facilitates cholesterol gallstone dissolution by reducing the interfacial resistance of the process.


Kinetic and thermodynamic aspects of in vitro interphase transfer of tetracyclines I: influence of hydroxyl group substitution. The influence of hydroxyl group substitution on the kinetic and thermodynamic aspects of the interphase transfer of three tetracycline derivatives was studied in a two-phase in vitro system composed of an aqueous pH 5.5 buffer and 1-octanol. Data are reported on the kinetic and thermodynamic parameters of activation, the net thermodynamic parameters for interphase transfer, and the contribution of hydroxyl group substituents to the energy changes associated with partitioning. For each derivative, deltaH, deltaS, T deltaS, and deltaF were positive with enthalpy dominating the entropic energy contribution. Introduction of a hydroxyl group at C-5 on the tetracycline nucleus promoted partitioning through an entropy-dominated decrease in the "apparent" free energy of partitioning, whereas shifting the hydroxyl group to C-6beta retarded partitioning due to an enthalpy-dominated gain in the apparent free energy.


Kinetic and thermodynamic aspects of in vitro interphase transfer of tetracyclines II: influence of divalent metal salts. With a two-phase in vitro model composed of an aqueous pH 5.5 buffer and 1-octanol, the kinetics of the interphase transfer of tetracycline derivatives were examined in the presence and absence of calcium and magnesium salts, and the contribution of some functional group substituents to the "apparent" free energy changes for partitioning of tetracyclines was evaluated. Only small changes were observed in kf, kb, K0w, and apparent functional group free energy changes, deltaFG deltaF, in the presence of divalent metals as compared to values observed in the absence of these metals. Introduction of the C-6beta hydroxyl group on the tetracycline nucleus decreased the apparent K0w because of a positive apparent deltaFG deltaF contribution, whereas introduction of C-5 hydroxyl, C-6alpha methyl, or C-7 chloro groups increased the apparent K0w through negative apparent deltaFG deltaF contributions.


GLC determination of nanogram quantities of a new analgesic, nefopam, in human plasma. A sensitive and specific method was developed for the quantitative GLC determination of plasma nefopam levels. The method includes a multiple-step solvent extraction of the analgesic drug and the internal mass standard, orphenadrine. The accuracy, expressed as the relative error, was--4,6,6, and 4% at 20, 40, 70, and 130 ng/ml, respectively. The precision, expressed as relative standard deviation, was 17, 7, 3, and 5% at these same concentrations, respectively. Quantitation of nefopam in human plasma is possible down to 20 ng/ml with a 2-ml plasma sample; the sensitivity can be increased by using larger plasma samples. The methods was applied successfully to the determination of plasma nefopam levels in humans in pharmacokinetic studies at therapeutic doses.


Antineoplastic agents III: effects of dibromoethyl and vinyl esters of N-benzyloxycarbonyl-l-phenylalanine on Ehrlich ascites tumor cell metabolism. Evidence is presented that N-benzyloxycarbonyl-L-phenylalanine vinyl ester and 1,2-dibromoethyl ester are inhibitors of Walker 256 carcinosarcoma and Ehrlich ascites carcinoma tumor growth. The major effects of these two agents on Ehrlich ascites cell metabolism were the inhibition of deoxyribonucleic acid and protein synthesis and the alteration of cellular regulatory processes controlling cytokinetics. Deoxynucleotide (purine) kinase enzymes appeared to  be the focal site for inhibition of deoxyribonucleic acid synthesis with marginal inhibition of thymidylate synthetase activity. Cyclic adenosine monophosphate levels were elevated by drug treatment whereas chromatin protein phosphorylation, cell respiration, and lysosomal activities were inhibited. N-Benzyloxycarbonyl-L-phenylalanine 1,2-dibromoethyl ester was a latent in vitro chymotrypsin inhibitor. Some preliminary evidence suggests that these activated esters may inhibit cellular enzymatic activity by alkylating imidazole and lysine residues of proteins.


Comparison of operational characteristics of different dissolution testing systems. Three dissolution apparatus, the rotating basket, the rotating paddle, and the rotating filter--stationary basket, were evaluated for their suitability as production control tools and their relation to blood level studies in dogs. The rotating basket and rotating paddle assemblies were easier to use and less variable than the rotating filter--stationary basket. When relative levels of agitation and the pH of the dissolution medium were held constant, all three apparatus correlated with each other and equally well with the serum drug levels from experimental formulations of an oral hypoglycemic drug after administration to dogs. Such an observed relationship cannot, of course, be used to predict blood levels in other species; however, it does suggest that the choice of one apparatus over another cannot be made a priori.


High-pressure liquid chromatographic analysis of estrogens in pharmaceuticals by measurement of their dansyl derivatives. A high-pressure liquid chromatographic method is described for the analysis of estrogens in pharmaceutical tablet and injectable dosage forms. In general, the estrogens are isolated, an internal standard is added, the dansyl derivatives are formed, and the dansyl estrogen solution is injected into a liquid chromatograph. Linear response is experienced between the mass of estrogen and the ratio of the estrogen peak height to the internal standard peak height, using a microparticle silica column and chloroform--n-heptane mobile phases. With fluorometric measurement, limits of detectability for ethinyl estradiol and estradiol were 0.04 and 0.05 ng, respectively. Methyltestosterone, an androgen in combination with ethinyl estradiol, was analyzed simultaneously. Commercial pharmaceutical preparations containing estrone, ethinyl estradiol, and estradiol were analyzed by the proposed method. The results indicate the method to be sensitive, reasonably precise (less than 2%), and accurate in the analysis of estrogen in dosage forms.


Synthesis and evaluation of sulfur-containing steroids against methylmercuric chloride toxicity. Sulfur-containing steroids, analogs, and derivatives were synthesized for evaluation in mice suffering acute toxicity from methylmercuric chloride. Steroids were administered by intraperitoneal injection, by stomach tube feeding, or by absorption through the tail skin. Thiocholesterol and the thiocholanoic acids were effective if given prior to poisoning. The thiosteroids were significantly more effective than penicillamine or dimercaprol under these conditions.


Molecular connectivity and substructure analysis. Antimicrobial and antiviral data sets were analyzed by molecular connectivity. Standard structure--activity relationship equations of high quality were produced in both cases. For phenyl propyl ether activity against Staphylococcus aureus, the three variables 1chi, 3chiP, and 4chiUPC yielded an r of 0.957, significantly better than a pi,sigma analysis. Analysis of benzimidazole antiviral data (Lee strain, B flu virus) revealed that the one variable, 6chiP, yielded an r of 0.950, also better than a reported Hansch analysis. Both data sets were further analyzed by partitioning the important regression variables into terms representing various structural features of the molecules. For the phenyl propyl ethers, the para-region of the phenyl ring is important for improved activity and the negative coefficient on 3chiP corresponds to decreased activity for vic-dihydroxy compounds. For the alkylbenzimidazoles, substitution on the five-membered ring is highly important. No discrimination of six-membered ring positions was revealed. These structure--activity relationship observations can form the basis for synthetic decisions to improve activity.


GLC--mass spectrometry of several important anticancer drugs II: doxorubicin and daunorubicin aglycone analogs. By using previously developed pertrimethylsilylation and methoxime formation procedures, the GLC--mass spectra of pertrimethylsilyl and pertrimethylsilyl methoxime derivatives of 12 doxorubicin and daunorubicin glycone analogs, mostly synthesized in this laboratory, were studied. The fragmentation pathways were readily interpretable, and the patterns were highly specific for corresponding structural changes, thus supporting the previous contention that this method has potential for the identification of doxorubicin and daunorubicin metabolites. Four aglycone metabolites were identified, on the basis of their GLC--mass spectra, in the hydrolysate of the 1-butanol extract of bile obtained from a doxorubicin-treated rabbit.


Limit test for determination of free ferricyanide and ferrocyanide in sodium nitroferricyanide. A simple and rapid procedure for the isolation and determination of free ferricyanide and ferrocyanide in sodium nitroferricyanide (nitroprusside) was developed. The method, employing aluminum oxide column chromatography, was sensitive enough to detect ferricyanide and ferrocyanide at the 0.05% level.


Determination of carbocysteine from human plasma. A fast and accurate GLC procedure for determining carbocysteine, using a sulfur photometric detector, is described. Interferences from nonsulfur constituents are eliminated. The method is linear from 2 to 15 micrograms. Results from the application of this method to a bioavailability study in humans are given.


High-pressure liquid chromatographic determination of plasma dobutamine concentrations. A sensitive and specific high-pressure liquid chromatographic method was developed for measuring dobutamine in human plasma samples. Nylidrin is employed as an internal standard. Following extraction and separation on a C18 reversed-phase column, the drug is detected by a fluorescence detector with an excitation wavelength of 195 nm and a 330-nm emission cutoff filter. The retention times of dobutamine and nylidrin are 5.2 and 19.2 min, respectively. The minimum level of sensitivity is 10 ng/ml. Reproducibility was +/- 5% over a 25--300-ng/ml range. Several drugs were screened for possible interference, but none interfered with the dobutamine analysis.


Drug contamination of mortars and pestles. Evidence is presented suggesting that potent water-insoluble antipentylenetetrazol agents triturated in porcelain mortars and pestles are not removed from this mixing device by the usual laboratory washing procedure. Moreover, amounts sufficient to contaminate the next substance triturated in this vessel can be demonstrated by the subcutaneous pentylenetetrazol seizure threshold test. The data show that a rigorous washing routine must be followed to achieve a "clean" mortar and pestle. Attention is also directed to the importance of using disposable hypodermic syringes, test tubes, etc., whenever possible and of designing an internal control test to determine when implements that must be reused are "clean."


Quaternary acetate and propionate esters of 3-hydroxyquinolizidine. The preparation of the quaternary acetate and propionate esters of 3-hydroxyquinolizidine is described. Tentative structures are assigned on the basis of NMR data. Results of preliminary pharmacological screening of the methiodide and hydrochloride salts are given.


GLC determination of tilidine, nortilidine, and bisnortilidine in biological fluids with a nitrogen-sensitive detector. A sensitive and specific GLC method is described to determine therapeutic levels of tilidine and its two main metabolites, nortilidine and bisnortilidine, in plasma and urine. The method involves the extraction of the compounds and an internal standard with cyclohexane from alkalinized samples, followed by back-extraction into 1 N HCl. The hydrochloric acid solution is evaporated to dryness. After liberation of the free bases with ammonia, the residue is subjected to GLC analysis with a nitrogen-phosphorus detector and a 1.8-m (6-ft) glass column packed with 1% CRS 101 and 1.5% LAC-4-R-886 on Gas Chrom Q. Sensitivity in plasma and urine is approximately 1 ng/ml for a 5-ml sample.


Toxic substances produced by Fusarium V: occurrence of zearalenone, diacetoxyscirpenol, and T-2 toxin in moldy corn infected with Fusarium moniliforme Sheld. Sweet corn infected with Fusarium moniliforme Sheld. (CMI-IMI 204057) while growing in the fields was shown to contain zearalenone, diacetoxyscirpenol, and T-2 toxin. Assays by spectral, chemical, and biological methods established the presence of these substances, with zearalenone being the most abundant. In vitro cultures of the fungus also produced the three toxins.


Synthesis and evaluation of 3-substituted 1-[4-(2-indol-3-ylethyl)piperazinyl]ureas as potential antihypertensive agents. A series of 3-substituted 1-[4-(2-indol-3-ylethyl)piperazinyl]ureas was synthesized and screened for antihypertensive activity in spontaneously hypertensive rats. Two compounds with aryl urea substituents were very potent and lowered blood pressure 55 mm or more at oral doses of 100 mg/kg. However, both compounds failed to produce a cardiovascular response in the normotensive dog.


Direct determination of acetaminophen in plasma by differential pulse voltammetry. A rapid, simple method for the direct determination of acetaminophen in plasma at toxic levels was developed. The method is based on the oxidation of the phenolic moiety of acetaminophen at a carbon paste electrode in a differential pulse voltammetric mode. Linear calibration curves are obtained from 20 to 400 microgram/ml. No sample cleanup is required.


Respiratory oscillations in discharge frequency of chemoreceptor afferents in sinus nerve and anaesthetized cats at normal and low arterial oxygen tensions. 1. The discharge of chemoreceptor afferents in preparations of the sinus nerve in spontaneously breathing anaesthetized cats has been subjected to an averaging procedure in records obtained when the animals breathed (a) air and (b) a hypoxic gas mixture. 2. The mean discharge frequency was higher in hypoxia than at normal oxygen tension. 3. Oscillations in chemoreceptor discharge frequency with the same period as respiration were obtained by the averaging procedure both at normal arterial oxygen tensions and in hypoxia, but there was no significant increase in oscillation amplitude with hypoxia. 4. The carotid body response to arterial PCO2 oscillations does not therefore appear to be amplified by hypoxia. This finding is discussed in relation to the reported dependence upon hypoxia of the ventilatory effects of tube breathing in man.


Studies on neurotrophic regulation of murine skeletal muscle. 1. A quantitative comparison was made of the effects of the paralysis caused by botulinum toxin (BoTx) type A with those of surgical denervation on the development of tetrodotoxin (TTX) resistant action potentials and of extrajunctional acetylcholine (ACh) receptors in rat and mouse skeletal muscle.2. After surgical denervation, TTX resistant action potentials were present in all fibres on the third day and their rate of rise and amount of overshoot reached peak values at the fifth day. BoTx poisoning failed, despite causing complete paralysis, to induce TTX resistant action potentials in all fibres and their average rate of rise was at all times (4-12 days) only about half that in denervated fibres. Similarly BoTx poisoning induced a smaller increase than surgical denervation in the number of extrajunctional ACh receptors, measured as (3)H-labelled Naja naja siamensis alpha-neurotoxin binding sites.3. Surgical denervation of BoTx poisoned muscles induced TTX resistant action potentials in all fibres and their rate of rise and amount of overshoot were 2-3 times those in BoTx poisoned muscles only. Denervation also significantly increased the binding of labelled alpha-neurotoxin. These effects of denervation were prevented by the administration of actinomycin D, a blocker of protein synthesis.4. Administration of the alpha-neurotoxin to BoTx poisoned animals resulted in the appearance of TTX resistant action potentials in all fibres and in a significant increase in their rate of rise and overshoot.5. The results show that, despite causing complete paralysis, BoTx is less effective than surgical denervation in inducing denervatory changes in skeletal muscle. This suggests that the BoTx poisoned nerve has an influence which suppresses the appearance of denervation signs. Since the alpha-neurotoxin blocked this influence remaining release of ACh, quantal or non-quantal, may be responsible for this neurotrophic action.


Possible mediators of functional hyperaemia in skeletal muscle. 1. (a) In experiments on gastrocnemius muscles of the cat performing external work, the work was graded, either by altering the intensity of motor nerve stimulation or by changing the load. Only under the former conditions was the steady-state increase in blood flow conductance at all consistently related to the work performed. (b) In such experiments, efflux of inorganic phosphate and of potassium were closely correlated with the increase in vascular conductance, in the form of a typical dose-response curve. There was no significant relationship between changes in plasma osmolarity and conductance. 2. (a) Whereas most soleus muscles in the cat exhibit virtually no functional vasodilation, those with a relatively low resting flow tend to do so. (b) There was a relationship between the vasodilation, if any, and release of phosphate in fifteen out of seventeen experiments on soleus muscles. No relationship was found between any release of potassium or change of plasma osmolarity, and absence or extent of functional vasodilation. 3. (a) Terminal arterioles and collecting venules in the rat's spinotrapezius muscle were observed in vivo under low power magnification while the muscle was bathed in various test solutions, so that the vasodilator properties of hyperosmolar solutions, potassium and phosphate could be studied. (b) The dilator effect of hyperosmolar solutions was much the weakest: solutions of 340 m-osmole/kg elicited the largest responses, but these seldom exceeded 50% mM-K+ and 3.2--6.4 mM-Pi (as NaH2PO4) elicited 25--50% of maximum dilation, while 9--10 mM-K+ and 16--20 mM-Pi dilated arterial vessels fully. The latency to onset of dilation was shortest (5 sec) with Pi and longest (15 sec) with K+. 4. These findings, together with those already in the literature, lead to the conclusions that (a) hypersomolarity is unlikely to be in an important factor initiating or maintaining functional hyperaemia in skeletal muscle, (b) while K+ release may contribute in fast muscle it can hardly be the factor initiating the response, and (c) inorganic phosphate is the only substance tested so far whose efflux is consistently related to the vascular response in all muscles under a variety of experimental conditions, and whose efficacy as a vasodilator seems adequate.


Destruction of a single cell in the central nervous system of the leech as a means of analysing its connexions and functional role. A method has been devised for killing an individual neurone in the C.N.S. of the leech by injecting it with Pronase. The technique has been used to examine the role of individual sensory and motor cells involved in producing reflex movements.1. After a neurone was injected with Pronase, either in an intact animal or an isolated ganglion, its cell body lost its resting and action potentials. Some hours later the injected cell's axons in the periphery failed to conduct impulses. In the intact animal the cell body could no longer be discerned after a few weeks.2. To test for destruction of processes within the neuropile, cells were injected first with the enzyme horseradish peroxidase (HRP) and then several hours later with Pronase. Absence of the characteristic HRP reaction product indicated that Pronase had spread throughout the arborization of the cell.3. Injection of Pronase into one cell did not produce overt electrophysiological or anatomical changes in other cells in the ganglion including neurones that were originally electrically coupled to the killed cell.4. Evidence that an individual cell was the only motoneurone supplying particular muscles was provided by destruction of that cell in otherwise intact animals, which resulted in a characteristic motor deficit in the area supplied by the killed cell. Over a period of months, functional recovery of the affected muscles occurred by way of homologous cells in adjacent ganglia.5. A further application of the technique was to trace the connexion that a particular sensory neurone makes onto two motoneurones that are electrically coupled. Normally, the sensory neurone gives rise to excitatory potentials in both post-synaptic cells. Synaptic potentials could still be recorded in one motor cell after the other had been destroyed by Pronase, indicating that synapses were made directly onto both of the motoneurones.


A role for extraocular afferents in post-critical period reversal of monocular deprivation. 1. In order to investigate the phenomenon of acute reversibility of cortical ocular dominance, pressure block of the retinal ganglion cells and local anaesthetic block of the extraocular afferents were applied to the normal eye of six monocularly deprived cats. 2. Neither pressure blinding nor retrobulbar anaesthesia alone produced a significant increase in the proportion of single neurones recorded from area 17 which could be driven by the deprived eye. 3. Following combined pressure blinding and retrobulbar blockade, sixty-four cells (54% of all encountered) could be stimulated through the deprived eye. 4. Of the sixty-four cells driven by the deprived eye following both treatments a number showed direction (thirty) and orientation (thirteen) selectivity, but the majority showed non-specific receptive field properties. 5. In four separate cases, out of the nine where the experiment could be carried out, it was possible to observe an individual neurone shift its ocular dominance. In the presence of a retrobulbar block, the four neurones could be driven first by the experienced eye alone, then by the deprived eye alone, and finally by the experienced eye again, all within a few minutes of the introduction and removal of pressure blinding. 6. These findings support previous studies which have revealed the presence of significant numbers of potentially functional cortical inputs from the deprived eye. Our new finding is that removal of tonic activity from the experienced eye, while it seems to be necessary to reveal these inputs, is not sufficient. An additional role in this phenomenon is played by extraocular afferents, possibly those involved in proprioception from the eye muscles.


Latency-relaxation in single muscle fibres. 1. Latency relaxation and twitch tension were recorded simultaneously in single isolated muscle fibres of Xenopus laevis. 2. During low frequency (0.6 or 1 pulse/sec) repetitive stimulation, three successive phases of twitch tension were observed: negative staricase (a slight drop in tension), positive staircase (about 15% increase in tension) and fatigue. At the same time the amplitude of latency relaxation decreased monotonically, and near the peak of positive staircase, the amplitude decreased almost to an undetectable level. 3. The application of caffeine (0.1--1.5 mM) increased peak twitch tension by 15--200%, but decreased the latency relaxation amplitude by 30--93%. 4. The application of Ca-release inhibitors, deuterium oxide and dantrolene sodium, caused a 43--89% decline in peak twitch tension but no change in latency relaxation amplitude. 5. The lack of correlation between changes in peak twitch tension and latency relaxation amplitude suggests that latency relaxation is associated with the mechanism which triggers Ca2+ relase rather than with Ca2+ release itself.


Stretch receptor control of renin release in perfused rat kidney: effect of high perfusate potassium. 1. These studies were conducted in the isolated perfused rat kidney to determine the effect of high perfusate K on the renin release induced by low perfusion pressure, renal vasoconstriction and isoprenaline, and to determine whether the magnitude of the K-induced inhibition equalled that observed with renal vasodilation and high perfusion pressure. 2. Raising perfusate K concentration from 4.2 to 56 mM suppressed basal renin release, and the 56 mM-K inhibited the renin release induced by low perfusion pressure (50 mmHg) or phenylephrine (0.83 micrometers). 3. Isoprenaline (0.79 micrometers) induced a marked increase in renin release; but high perfusate K, propranolol (0.28 mM), papaverine (0.39 mM), or high perfusion pressure (150 mmHg) inhibited this effect. 4. It is concluded that high perfusate K has a powerful inhibitory effect on the renin release induced by renal hypotension, vasoconstriction, and isoprenaline infusion, and that this effect may be mimicked by high perfusion pressure or renal vasodilation. A mechanism is proposed whereby these signals may inhibit renin release by depolarizing the juxtaglomerular granular cells.


The regulation of dopamine and noradrenaline in the rat carotid body and its modification by denervation and by hypoxia. 1. The mechanism whereby hypoxia lasting 20 min elicits a decrease in the dopamine content of rat carotid bodies was studied. 2. The concentrations of dopamine, noradrenaline, dihydroxyphenylacetic acid and homovanillic acid in carotid body were measured by a mass-fragmentographic procedure. The turnover rate of dopamine was determined by measuring the elimination rate of dihydroxyphenylacetic acid immediately after inhibition of monoamine oxidase by injection of pargyline. The turnover rate of noradrenaline was derived from measurements of the rate of decline of noradrenaline content after injection of L-methyl-p-tyrosine. 3. The results indicate that hypoxia increases the rate of dopamine release without changing its turnover rate thereby accounting for the decrease in dopamine content. The content and turnover rate of noradrenaline remained unchanged during exposure to hypoxia. 4. Neither the carotid sinus nerve nor the sympathetic innervation appeared to participate in the regulation of dopamine content or turnover rate in carotid bodies of rats either before or during hypoxia. 5. Since transection of the carotid sinus nerve or/and ganglionectomy failed to prevent the decrease of dopamine content caused by hypoxia, it is inferred that low arterial PO2 depletes dopamine stores independently of the above mentioned innervation.


Measurements of muscle stiffness and the mechanism of elastic storage of energy in hopping kangaroos. 1. A kangaroo hopping above a certain speed appears to consume less oxygen than a quadrupedal mammal, of similar weight, running at the same speed (Dawson & Taylor, 1973). This is thought to be achieved by storage of elastic energy in tendons and ligaments. 2. Energy can be stored in a tendon by stretching it, but only if the muscle fibres in series with it are stiff enough to resist most of the length change. We have measured length and tension changes in the contracting gastrocnemius muscle of the wallaby Thylogale during rapid, controlled stretches, and from this determined the amount of movement in muscle fibres and tendon (method of Morgan, 1977). 3. When the muscle was developing close to its maximum isometric tension, up to eight times as much movement occurred in the tendon as in the muscle fibres. This is made possible by the wallaby having a long and compliant tendon. 4. Measurement of work absorption by the muscle with a full length of free tendon and when the tendon had been shortened, showed that with the shortened tendon a larger proportion of movement occurred in the muscle fibres, producing a steep rise in work absorption by the muscle and a consequent increase in energy loss.


The effect of sodium, calcium and metabolic inhibitors on calcium efflux from goldfish heart ventricles. 1. 45Ca efflux and tissue Ca content were examined in goldfish ventricles under conditions known to affect cellular Ca movements. 2. EGTA or Ca-EGTA was added to the washout solutions in sufficient concentration (10 mM) to avoid retardation of the apparent tissue 45Ca efflux by extracellular 45Ca binding or backflux. 3. After a variable initial increase, the cellular Ca content usually stabilizes within 60 min when ventricles are immersed in Li- or K-substituted saline containing 1.8 mM Ca0 (under these conditions the internal Ca2+ concentration is below 10(-5) M). 4. 45Ca efflux is maximally activated by external concentrations of Ca2+ as low as 10(-6) M, in both Na-containing and Na-free saline. 5. 45Ca efflux decreases in Na-free solutions. It is reactivated by Na-saline. The effect of different external Na concentration on 45Ca efflux is comparable at external Ca2+ concentrations between 10(-6) M and 2 x 10(-3) M. 6. Reactivation of Ca efflux after Na0 readmission is inhibited by metabolic poisoning, or in the presence of 10 mM-caffeine. Loading with 45Ca at very low external Ca2+ concentration prevents the inhibition of Ca efflux in Na-free medium. 7. Caffeine (10 mM) produces contractions of about equla size when K-depolarized preparations are immersed in either Na- or Li-saline. At the same time there is a similar increase in 45Ca efflux in absence of Na0 and in its presence. 8. In the virtual absence of Ca2+0 (10(-5) M-Ca, 10(-2) M-EGTA) and Na+0, the residual 45Ca efflux is reversibly inhibited by cyanide (2 mM). 9. The results are roughly compatible with the general concept of ATP-dependent Na-Ca exchange in internal Ca2+ homeostasis. However, this hypothesis should probably be modified to account for the fact that under physiological concentrations Na+0 and Ca2+0 do not compete for activating 45Ca efflux. Metabolic products may be involved in Na0- and Ca0-dependent Ca efflux. It is therefore not excluded that a Na-independent active mechanism co-operates with Na-Ca exchange in Ca extrusion.


Control of water content of respiring kidney slices by sodium chloride and polyethylene glycol. 1. Cortical slices from kidneys of adult rats were incubated for 1 and 2 hr at 25 degrees C in oxygenated solutions containing 5 mM-K, 2.5 mM-Ca and Mg, 0.007 M-phosphate buffer (pH 7.4) and 5 mM-glucose, together with 1, 2, 4 and 6% polyethylene glycol (PEG 6000) and 46, 92, 123, 154 and 231 mM-NaCl.2. There were no significant differences in water content between slices incubated for 1 and for 2 hr.3. The slices contained more water when the concentration either of NaCl or of PEG 6000 was lower.4. Larger increases in the contribution of NaCl to total osmolarity were required to prevent increases in water content accompanying relatively small reductions in the contribution of PEG 6000. At a physiological salt concentration around 300 m-osmole/l., it took 10 m-osmole/l. of additional NaCl to compensate for the loss of 1 m-osmole/l. PEG 6000 and keep the volume of cell water normal.5. The much greater contribution, osmole for osmole, which PEG 6000 made to tonicity suggests that metabolic activity failed to make the cell membranes effectively semipermeable; they were still substantially permeable to NaCl.6. Comparison with earlier results suggested that ionic strength affected colloid osmolarity similarly in respiring and in non-metabolizing cells; and that respiration at 25 degrees C somehow kept the concentration of diffusible solutes in the cells sufficiently lower than outside to compensate for a swelling effect of intracellular colloid osmolarity which, in the absence of metabolism, could be balanced by 20 m-osmole/l. PEG 6000 added to the medium.


Inhibition of noradrenaline release by adenosine. 1. Release of [3H]noradrenaline evoked by stimulation (5 Hz) of the pre-labelled rat vas deferens was reduced to 50% by adenosine (10(-6) g/ml.). Inhibition of release was dependent on the concentration of adenosine and was inversely related to the frequency of stimulation. Phenoxybenzamine did not interfere with the action of adenosine on release. 2. Exposure of the pre-labelled rat vas deferens to 135 mM-K+ released almost 10 times more [3H]noradrenaline than exposure to 45 mM-K+. Release induced by 45 mM-K+ was almost abolished by adenosine (10(-6) g/ml.) but that induced by 135 mM-K+ was reduced to only 45%. 3. Inhibition of [3H]noradrenaline release was observed in salivary gland, heart and portal vein of the rat, and in the guinea-pig heart and vas deferens. A very high concentration of adenosine (10(-4) g/ml.) reduced the release (about 50%) in the rabbit heart, but the cat heart was totally insensitive to the inhibitory action of adenosine. 4. Aminophylline (2 x 10(-4) g/ml.) antagonized the inhibitory action of adenosine (10(-6) g/ml.) on the release of [3H]noradrenaline in the phenoxybenzamine-treated vas deferens. 5. Tetraethylammonium (8 x 10(-4) g/ml.) enhanced stimulation-evoked release in the rat salivary gland by almost tenfold. In the presence of tetraethylammonium, even higher concentrations (2 x 10(-5) g/ml.) of adenosine failed to interfere with release. 6. Elevation of external K+ (19 mM) blocked stimulation-evoked release in the rat vas deferens by about 55%. Combination of high K+ and adenosine (10(-6) g/ml.), which blocked release by about 40%, caused still greater inhibition (80%) of the release. 7. The possible mechanism of action of the inhibitory effect of adenosine on the stimulation-evoked release of noradrenaline is discussed in relation to the calcium hypothesis.


Two types of vagal preganglionic motoneurones projecting to the heart and lungs. 1. A study has been made of eighty-four cells in the cat's nucleus ambiguus whose axons projected to the cardiac (seventy-four) and pulmonary (ten) branches of the right vagus. Their axonal conduction velocities were all in the range of B fibres (2.8-15.5 m/sec).2. Pulmonary branch projecting neurones were usually spontaneously active (nine out of ten) and fired in phase with inspiration. Their activity showed no pulse modulation.3. Ten cardiac branch projecting neurones had properties indistinguishable from those of pulmonary branch projecting neurones. Inspiratory-firing cells projecting to either branch are believed to be bronchoconstrictor in function.4. The remaining sixty-four cells that projected to the cardiac branch had properties expected of cardioinhibitory neurones. Most (fifty-four) were silent until activated by ionophoresis of excitant amino acids. All showed an expiratory discharge when active, and of twenty-seven tested twenty-three showed a cardiac modulation of their discharge. When the aortic baroreceptors were denervated, the cardiac rhythm was always abolished reversibly by carotid occlusion.5. Ionophoretic activation of expiratory firing (presumed cardioinhibitory) cells slowed the heart (fifteen out of eighteen neurones tested). Excited inspiratory-firing cells never had this effect (eleven tested).6. Both types of neurones were found in the nucleus ambiguus, but presumed cardioinhibitory cells tended to be found more caudally and ventrally than presumed bronchoconstrictor neurones.


The baroreceptor input to cardiac vagal motoneurones. 1. A study has been made of twenty-three cardiac vagal motoneurones (c.v.m.s) in the nucleus ambiguus of chloralose-anaesthetized cats.2. C.v.m.s were identified as described previously (McAllen & Spyer, 1978). They were either spontaneously active (five units) or induced to fire by the ionophoresis of DL-homocysteic acid (DLH). Evidence is presented that above threshold, the DLH dose is not critical for the ability to show a baroreceptor influence.3. The influence of the baroreceptors was determined by plotting pulse-triggered histograms of c.v.m. activity. If the aortic baroreceptors were denervated, the pulse synchronous activity disappeared reversibly on carotid occlusion (eight out of eight cases). In five out of fifteen cells studied, when aortic baroreceptor pathways were intact, a small degree of cardiac modulation survived carotid occlusion.4. Estimates of the central delay of the baroreceptor-vagal reflex were made by timing the c.v.m. response to both electrical stimulation of the sinus nerve and natural baroreceptor stimulation. When both methods were used on individual units, electrical stimulation invariably gave shorter values. Natural stimulation gave values that fell into two ranges (20-60 msec and 70-110 msec), suggesting the involvement of two pathways.5. Using higher currents, four c.v.m.s were induced to fire tonically during inspiration. Their activity in this phase showed a cardiac rhythm just as during expiration. Similarly, they responded to sinus nerve stimulation throughout the respiratory cycle.6. This result is discussed in relation to the observation of others that the baroreceptor-cardiac reflex is ineffective during inspiration. It is proposed that there is no need to invoke a ;gate' early in the pathway but that this phenomenon and the present observations are best explained by summation of influences at the c.v.m. cell membrane.


Effects of temperature on the transport of galactose in human erythrocytes. The transport of galactose in human erythrocytes has been resolved recently into a mechanism which involves two asymmetric carriers operating in antiparallel fashion. The effects of temperature on this mediated transport system in the range of 0--25 degrees C show the following features. The Michaelis constants for zero-trans influx and efflux and for equilibrium-exchange efflux, do not vary with temperature. Arrhenius plots of the maximal velocities show breaks between 3 and 15 degrees C with activation energies two- to threefold larger below the break than above it. The relative contribution of the two types of carriers to the total transport rate is not affected by temperature. The kinetic properties of the prevalent type of carriers are analysed in terms of the simple carrier model as formulated by Lieb & Stein (1974). This analysis shows that the relative concentration of the unloaded carrier at the inner interface of the membrane increases upon cooling. The free energy of translocation of the unloaded carrier and the change in entropy involved in this step are significantly larger in the low temperature range (0--5 degrees C) than in the higher range (15--25 degrees C). The results are discussed briefly in terms of possible lipid-protein interaction and the physicochemical nature of the erythrocyte membrane.


Metabolic rate: its circadian rhythmicity in the female domestic fowl. 1. In quasi-natural cyclic lighting, a circadian rhythm was observed in seven fowls; the range of oscillation of the rhythm was 50% of the mean metabolic level. Little variation was present between the individuals. 2. In fowls maintained for 15 days in isolation under 700 lx (ten fowls) or 0.07 lx (four fowls) constant lighting and at constant temperature free-running rhythms were evident; the range of oscillation was about 12% of the mean level. Large variation prevailed between the individuals in the range of oscillation and in the portion of variance accounted for by periodic regression. In dim light, rhythmicity declined to become non-significant by 8 days of exposure. 3. In four fowls maintained in a 6L/6D regimen for 12 days, metabolic rate was entrained to an ahemeral rhythm; there was no evidence of circadian influence on the metabolic response to light. Little variation was present between the individuals. Rhythmicity was maintained over the experimental period. 4. Metabolic levels were similar on 0.07 lx, 700 lx constant light, during the dark phase of the 6L/6D regimen and during night time in the quasi-natural cyclic lighting. They were also similar on the light phase of the 6L/6D regimen and the quasi-natural lighting.


The inhibitory effects of vasoactive intestinal polypeptide on the mechanical and electrical activity of canine antral smooth muscle. 1. The inhibitory effects of vasoactive intestinal polypeptide (VIP) on the electrical and mechanical activity of canine antral smooth muscle were investigated. 2. In concentrations ranging from 5 X 10(-9) to 1 X 10(-7) M, VIP decreased the force of spontaneous contractions but had no measurable effect on spontaneous action potential complexes. 3. VIP had no effect on the increase in the amplitude and duration of the plateau potential and on the amplitude of contraction caused by a maximally effective concentration of acetylcholine. 4. VIP caused a significant decrease in the force of contraction caused by ED50 and threshold concentrations of acetylcholine. However, VIP had no measurable effect on the increase in the size of the action potential plateau caused by either concentration of acetylcholine. 5. VIP antagonized the increase in the amplitude of the plateau potential and the force of contraction induced by pentagastrin. It had no consistent effect on the pentagastrin-induced increase in frequency. 6. The data indicate that VIP acts as an inhibitor in this tissue in two distinct ways. It uncouples electromechanical coupling during spontaneous and acetylcholine-induced electrical and mechanical activity, and antagonizes pentagastrin-induced increases in electrical and mechanical activities.


Pressure-flow relationships and effects of noradrenaline and isoprenaline on the hepatic arterial and portal venous vascular beds of the dog. 1. The innervated hepatic arterial and portal venous vascular beds of the dog were perfused simultaneously, in situ. Under control conditions, the pressures, blood flows and calculated vascular resistances in these beds were similar to those previously reported in preparations where one bed was perfused alone. 2. The pressure-flow curves in both the hepatic arterial and portal venous vascular beds were almost linear over the pressure ranges 30--200 and 2.5--12.0 mmHg respectively. There was no evidence of pressure-induced autoregulation of flow in either circuit. 3. Increases in hepatic arterial blood flow  and perfusion pressure were associated with a linearly related increase in hepatic portal vascular resistance. Occlusion of the hepatic artery caused a mean fall of 21.3% in portal vascular resistance. 4. Increases in hepatic portal blood flow and perfusion pressure were associated with a linearly related incease in hepatic arterial vascular resistance. Occlusion of the hepatic portal vein caused a mean fall of 16.0% in hepatic arterial vascular resistance. 5. Intra-arterial injections of noradrenaline (0.1--50 microgram) caused biphasic changes in hepatic arterial vascular resistance, and a rise in hepatic portal vascular resistance. Both hepatic vascular effects had a significantly shorter latency than any succeeding systemic cardiovascular effects. 6. Intraportal injections of noradrenaline (0.1--50 microgram) caused hepatic portal vasoconstriction, and a biphasic change in the hepatic arterial resistance. Both of these effects had a significantly shorter latency than any succeeding systemic effects. 7. Intra-arterial injections of isoprenaline (0.1--10 microgram) caused dose-dependent hepatic arterial vasodilatation but little change in portal vascular resistance. Intraportal isoprenaline caused little change in portal resistance but elicited dose-dependent hepatic arterial vasodilatation. 8. The time courses of the responses to intra-arterial and intraportal noradrenaline and isoprenaline indicate that the responses of the liver vascular bed which does not receive the direct injection were not due to recirculation of the vasoactive material. 9. It is postulated that vasoactive material injected into one inflow circuit of the liver elicits changes in the vascular resistance of the other inflow circuit by an intrahepatic effect.


Vagal glucoreceptors in the small intestine of the cat. 1. In anaesthetized cats, the unitary activity of seventy-eight sensory vagal neurones was recorded in nodose ganglia by means of extracellular glass microelectrodes. 2. These neurones were stimulated by perfusion of the small intestine (duodenum and first part of jejunum) with glucose or other different carbohydrates at concentrations of 1--20 g/l. (i.e. 55--1100 m-osmole/l.). 3. The neurones were slowly adapting to stimulation and their discharge frequency was always low (1--30 Hz). 4. The activity of these neurones depended on the particular carbohydrate used and on its concentration: the discharge frequency generally increased when the concentration rose. 5. The neurones were of the C type (conduction velocities: 0.8--1.4 m/sec; mean, 1.1 m/sec). 6. In contrast with the known neurones connected to the gastro-intestinal tension receptors, they were not obviously activated by intestinal contractions or distensions. 7. In the same way, the stimuli which produced the response of other known endings, i.e. the mucosal receptors, were not effective; these stimuli included in particular stroking of the mucosa, over-distension of the bowel, intestinal perfusion with alkaline or acid solutions. On the other hand, the use of substances other than glucose (KCl and NaCl of the same osmolarity) showed that the osmotic pressure was not directly related to the receptor activation. 8. Therefore it is proposed to call the endings corresponding to these neurones 'glucoreceptors'. 9. The effect of glycaemia and intestinal motility were also studied. These variables acted presumably by changing the intestinal absorption rate. 10. The functional characteristics of the glucoreceptors (in particular the short latency of their response) strongly suggested that they were located close to the intestinal epithelium. 11. An ultrastructural study was performed in an attempt to identify the histological site of the receptors. Many non-medullated fibres were observed in the villi, especially beneath the epithelial layer. They gave complex branchings with abundant swellings. Some of them, at least, belonged to the vagal sensory component, because they were less numerous after unilateral selective sensory vagotomy. Therefore these complex endings could serve as the vagal glucoreceptors. 12. The roles of vagal intestinal glucoreceptors are discussed. Their functional characteristics as well as the clinical and experimental data suggest that they may be involved in the regulation of different types of alimentary behaviour (hunger, thirst, alliesthesia) and energy balance.


Efflux of inorganic phosphate from mammalian non-myelinated nerve fibres. 1. Uptake and release of radiophosphate were measured in desheathed rabbit vagus nerve. 2. During incubation in Locke containing 0.2 mM-[32P]phosphate a slow labelling of water soluble compounds of the nerve was found; the labelling of the non water soluble compounds was much smaller. During washing with inactive Locke, the label was almost entirely released from the water soluble compounds; the radioactivity of these compounds was therefore used as the basis for the calculation of the efflux rate constants. 3. The efflux of radiophosphate increased with increasing phosphate concentration of the washing fluid. 4. A similar effect of external phosphate on the efflux of radiophosphate was seen when the phosphate concentration was suddenly changed. The rate constants were in 0.2 mM-phosphate 1.29 X 10(-3) min-1, in 0.2 mM 1.95 X 10(-3) min-1, and in 2 mM 3.21 X 10(-3) min-1 at 37 degrees C. After changing the external solution the efflux reached a new level with a time constant of about 9 min. 5. Addition of arsenate also increased the efflux of radiophosphate; on a molar basis the effect of arsenate was slightly smaller than the effect of phosphate. 6. Addition of malate or malonate did not affect the efflux of radiophosphate. 7. When the Na of the Locke was replaced by Tris, the efflux of radiophosphate was lowered by 76%, the new level was reached with a time constant of 7.7 min. In Tris-Locke changes in external phosphate did not affect the phosphate efflux. 8. A lowering of the phosphate efflux by 52% was found in Li-Locke; the efflux was then no longer affected by the external phosphate concentration. 9. The effect of external phosphate on the efflux and in the radiophosphate was also measured at intermediate Na concentrations. At different Na concentrations the ratio between the Na dependent effluxes in 2 and 0.2 mM-phosphate was approximately equal to the ratio between the Na dependent influxes in 2 and 0.2 mM-phosphate. 10. The efflux of 22Na had a rate constant of 0.050 min-1 in Locke and 0.046 min-1 in Tris-Locke. 11. It is concluded that part of the efflux of phosphate is mediated by a Na-dependent transport system; the system appears to be able to exchange phosphate between the inside and the outside and to mediate net movements of phosphate in both directions.


The effect of duodenal infusion of milk, casein, lactose and fat on gastric emptying and acid secretion in the milk-fed calf. 1. The effect of infusion of the duodenum with milk, casein, lactose and fat on gastric acid secretion and abnormal emptying of a saline meal was studied in milk-fed calves. 2. Compared with sodium bicarbonate, infusion with casein or lactose, alone or together, caused a small but statistically significant slowing of gastric emptying but did not effect gastric acid secretion. 3. Infection of the duodenum with cows' milk replacer or bovine milk fat slowed gastric emptying markedly and reduced gastric acid secretion significantly below levels obtained with sodium bicarbonate infusion. 4. The experiments provide evidence for the existence of mechanisms which prevent the passage of substantial amounts of whole milk into the duodenum before it has been subjected to gastric digestion.


Responses of olfactory receptor cells to step pulses of odour at different concentrations in the salamander. 1. The response properties of single olfactory receptor cells in the salamander have been analysed in unitary recordings obtained with platinum-black metal-filled micro-electrodes. 2. Stimulation has been carried out using an apparatus which delivers odour pulses of abrupt onset, steady plateau and abrupt termination. The pulses have been monitored near the site of stimulation on the olfactory epithelium during the experiments. 3. The main type of response was a discharge of impulses that was time locked to the stimulus pulse. The pattern of the responses consisted of a relatively brief latency of onset, a rapid rise in impulse frequency, a continuation of impulse firing during the plateau of the pulse, and an abrupt termination of the discharge correlated with the termination of the pulse. 4. There was a clear relationship between the receptor responses and odour concentration. In general, impulse firing frequency increased with increasing odour concentration. The firing frequency ranged from approximately 1--3 impulses/sec at threshold, up to 20 impulses/sec at the highest concentration. 5. Two types of reduced impulse activity were observed. One occurred after the termination of the pulse and lasted 1--3 sec; this was a common occurrence. The other type was seen during a pulse as a reduction of impulse activity compared to the background level; this type was rarely observed. 6. The receptor responses resembled those of mitral cells in the olfactory bulb to odour pulses in their sensitivity to odour concentration. They differed in that mitral cells show primary response categories consisting of brief excitation followed by suppression, and pure suppression, that are rarely seen at the receptor level. These differences may be ascribed to synaptic interactions in the olfactory bulb. 7. It is concluded that the majority of receptor cells have a stereotyped discharge response pattern and a systematic relation to odour concentration. These properties appear to reflect the simple time course of the odour pulses used in these experiments. This represents an initial step toward analysing olfactory coding at the receptor level using stimuli controlled in a manner similar to that used in other sensory systems.


Adaptive properties of olfactory receptors analysed with odour pulses of varying durations. 1. The adaptive properties of salamander of olfactory receptors have been analysed in extracellular unit recordings. Stimulation has been by step pulses of odour of varying durations for 1--10 sec. 2. The most common response was a prolonged impulse discharge that continued throughout the duration of the pulse and terminated abruptly within 1 sec of the end of the pulse. The interval for termination was relatively independent of the pulse duration. Pulses were frequently followed by a period of impulse inactivity lasting 1--3 sec, usually independent of previous pulse duration. 3. The impulse discharges were typically slowly adapting. Initially, during the first 1--2 sec, the frequency rose to 5--10 impulses/sec, at threshold concentration. In some cases, the initial level was maintained throughout the pulse, with little or no adaptation. More commonly, there was a distinct initial phasic peak, followed by decay to a lower level of 4--8 impulses/sec, which was maintained during the pulse. It was concluded that most olfactory receptors are slowly adapting, with variable phasic responsiveness dependent on odour concentration and other factors. 4. Reductions in impulse activity, compared with background, during a pulse were rarely seen. Methods for increasing the level of background activity and the use of very long duration pulses were necessary in order to bring out this type of response. Uniformly reduced activity throughout a pulse was seen clearly in only one case. A pattern consisting of a waning and then recovery of impulse frequency during a pulse was also observed in rare cases. 5. The results have shown that olfactory receptor discharges characteristically have a relatively precise relation to step pulses of odour of varying duration. The properties of the response have implications for the steps involved in the overall processes of activation and inactivation of receptor mechanisms at the olfactory mucosa.


The transplacental potential difference as distinguished from the maternal-fetal potential difference of the guinea-pig. 1. We measured the differences in electrical potential between mother and fetus in the guinea-pig. The fetus was 33 +/- 2 (S.E. of mean) mV negative with respect to the mother. 2. Salts of bromine, sulphate, rubidium, and lithium were injected into pregnant sows and blood samples were obtained from the sows and their fetuses at various times after injection. The transplacental electrical potentials at which each of these ions would be in electrochemical equilibrium across the placental exchange barrier were calculated from the Nernst equation and the concentrations in maternal and fetal plasmas. 3. The differences in transplacental electrical potential calculated from the steady-state concentrations of these ions in maternal and fetal plasmas were within 1 mV of zero. 4. These observations are consistent with a very small difference in electrical potential across the placental exchange barrier itself, and the generation of a potential difference between mother and fetus at a site other than the exchange barrier.


Observations on the elimination of polyneuronal innervation in developing mammalian skeletal muscle. 1. The mechanism responsible for the elimination of polyneuronal innervation in developing rat soleus muscles was studied electrophysiologically and histologically. 2. Initially all the axons contacting a single end-plate have simple bulbous terminals. As elimination proceeds one axon develops terminal branches while the other terminals remain bulbous and may be seen in contact with, or a short distance away from, the end-plate. It is suggested that the branched terminal remains in contact with the muscle fibre while the other terminals withdraw. 3. At a time when polyneuronal innervation can no longer be detected electrophysiologically, the histological technique still shows the presence of end-plates contacted by more than one nerve terminal. 4. The effect of activity on the disappearance of polyneuronal innervation was examined. Activity was increased by electrical stimulation of the right sciatic nerve. This procedure also produced reflex activity in the contralateral limb. In both cases polyneuronal innervation was eliminated more rapidly in the active muscles. 5. The finding that proteolytic enzymes are released from muscles treated with acetylcholine (ACh), and the observation of the more rapid elimination of supernumerary terminals at the end-plates of active muscles, lead to the suggestion that superfluous nerve-muscle contacts are removed by the proteolytic enzymes in response to neuromuscular activity. The selective stabilization of only one of the terminals is discussed in the light of these results.


Some properties of spinal gamma-motoneurones in the cat, determined by micro-electrode recording. 1. Micro-electorde recordings were made from motoneurones in the lumbo-sacral region of the cat spinal cord whose axonal conduction velocities were 10--55 m/sec. Most of these may be presumed to be fusimotor in function. 2. Intracellular records from twelve gamma-motoneurones revealed six with short (2--4 msec) and six with long (30--100 msec) duration after-hyperpolarizations following an antidromically conducted action potential. 3. Using extracellular recording, the excitability of eighty-nine other gamma-motoneurones following an antidromic impulse was tested with a second antidromic action potential. In eighty-four of these neurones, the minimum antidromic response interval was short, 1.5--3.5 msec, implying that in most gamma-motoneurones, after-hyperpolarization was of limited effectiveness and of short duration. In the remaining five neurones, the minimum response interval was longer, 20--80 msec. 4. There was a lack of monosynaptic excitation from group 1 afferent axons in the dorsal roots in eleven of the twelve motoneurones from which intracellular records were obtained. Polysynaptic excitation was commonly observed. 5. In these anaesthetized preparations, there was a lack of recurrent i.p.s.p.s even though such evidence of Renshaw inhibition could be found in the neighbouring alpha-motoneurones. 6. The mean input resistance of gamma-motoneurones was shown to be 1.55 Momega and the principal time constant 8.5 msec by passing hyperpolarizing current through the recording micro-electrode in a bridge circuit. These values are open to error because of the small numbers of neurones investigated, and of the use of the single micro-electrode method. 7. Depolarizing current passed through the recording micro-electrode caused a maintained discharge of action potentials at a high rate. After-hyperpolarization had little effect on discharge rate. The threshold for injected current to cause discharge was very low, and the discharge rate increased rapidly with the magnitude of the current. 8. These properties of gamma-motoneurones arediscussed in relation to their function.


Tension and heat production during isometric contractions and shortening in the anterior byssus retractor muscle of Mytilus edulis. 1. Tension and heat production were measured during phasic isometric contractions and isovelocity shortening in the anterior byssus retractor muscle (ABRM) of Mytilus edulis at 20 degrees C. 2. Isometric tension at lo was 550 +/- 40 mN/mm2 (S.D. for 173 observations in nine muscles), while the isometric maintenance heat rate was 1.0 +/- 0.2 mW/g wet wt. (S.D. for seventy-eight observations in eight muscles). 3. Isometric tension and heat production were measured as functions of muscle length over a range of 0.79--1.14 lo and were found to bear a linear relation to each other. 4. The force-velocity relation was determined in isovelocity releases imposed during tetanic stimulation and was found to fit the Hill equation with parameters alpha/Po = 0.07 +/- 0.01 and b/lo = 0.016 +/- 0.0007 sec-1 (S.E. from non-linear least-squares regression of the pooled data from seven experiments). 5. Heat production measured in the same experiments showed that shortening heat is produced with a shortening heat coefficient alpha/Po of 0.15. Shortening heat does not appear to be force-dependent, and separate experiments confirmed that it is a linear function of the amount of shortening.


Discrimination between different entry mechanisms for neutral amino acids in rabbit ileal mucosa. 1. Influx of neutral and basic amino acids into the mucosal epithelium of the rabbit ileum was measured in the presence of high and low concentrations of Na. Uptake measured at an amino acid concentration of 1 mM varied from 10 to 16 nmole . cm-2 . min-1. Removal of Na inhibited the uptake of short-chain amino acids more than long-chain amino acids. 2. Inhibition of uptake of glycine, alanine, leucine and phenylalanine by a selection of non-radioactive amino acids was found to follow a particular pattern. Long-chain amino acids inhibited the uptake of all test amino acids; short-chain amino acids inhibited preferentially the uptake of glycine. 3. The maximum inhibition serine could cause to the uptake  of other amino acids was found to vary. Serine inhibited completely the uptake of glycine but a portion of uptake of long-chain amino acids was found to persist, even in the presence of high concentrations of serine. This is taken as evidence for the presence of an amino acid uptake mechanism having no affinity for serine. 4. The apparent affinities of neutral amino acids for the serino-inhibitable system (system 1) varied from about 0.5 mM (for long-chain amino acids) to about 3 mM (for short-chain amino acids). The total uptake of individual amino acids by system 1 was essentially similar when compared at an amino acid concentration of 1 mM. 5. The serine-resistant uptake of neutral amino acids (system 2) constituted up to two fifths of total uptake for long-chain amino acids, measured at amino acid concentrations of 1mM. The affinities of long-chain amino acids for system 2 is thought to be less than for system 1. Serine appears not to interact with system 2. 6. A second component to serine uptake was found to be related linearly to the concentration of serine in the medium. A similar component may contribute to the total uptake of phenylalanine. The possibility that such a component could arise as a space marker artifact is discussed. 7. An independent kinetic analysis of phenylalanine uptake by rabbit ileal mucosa showed that it could not be accounted for on the basis of a single entry system. However uptake could be described kinetically, assuming two systems of mediated entry to be present. The possible presence of a third non-saturable component to uptake does not affect these conclusions. 8. It is concluded that least two systems exist for the mediated entry of neutral amino acids into rabbit ileal mucosa. This fact should be taken into account in any future mechanistic interpretation of carrier-mediated amino acid transport in the small intestine.


Slow inactivation of the sodium conductance in squid giant axons. Pronase resistance. 1. Squid giant axons internally perfused with CsF have their Na conductance inactivated due to the low value of the resting potential. When hyperpolarized with voltage clamp to normal values of resting potential, the Na conductance recovers with an exponential time course. The time constant of recovery is of the order of 30 sec at a membrane potential of -70 mV and at 5 degrees C. The recovery from slow inactivation has a Q10 of about 3. 2. The development of inactivation during depolarization is also slow. The time constant varies between 10 and 20 sec at 5 degrees C, depending upon the value of the membrane potential. 3. Slow inactivation is also observed in NaF perfused axons and in intact axons with a low resting potential. 4. Although internal perfusion with pronase (or a purified fraction of this enzymic complex) blocks the fast (h) inactivation of the Na conductance, the slow inactivation remains. The recovery is similar before and after the proteolytic treatment. However, slow inactivation appears to develop faster after enzymic perfusion. 5. Slow inactivation develops without any apparent change in distributed or local membrane surface charge. 6. The experiments suggest that slow inactivation is a general property of the Na conductance as in many other conductance channels in excitable membranes. The experiments can be interpreted by proposing that slow inactivation is a phenomenon independent of fast inactivation, and that pronase somehow accelerates the onset of slow inactivation. 7. An alternative model, in which slow inactivation is coupled to fast inactivation, is proposed. This model is consistent with the results presented here and is very similar to one proposed to explain the frequency response of the sodium currents in Myxicola giant axons (Rudy, 1975, 1978).


Spatial and temporal contrast sensitivity of neurones in areas 17 and 18 of the cat's visual cortex. 1. We have examined the spatial and temporal tuning properties of 238 cortical neurones, recorded using conventional techniques from acutely prepared anaesthetized cats. We determined spatial and temporal frequency tuning curves using sinusoidal grating stimuli presented to each neurone's receptive field by a digital computer on a cathode ray tube. 2. We measured tuning curves either by determining response amplitude as a function of spatial or temporal frequency, or by measuring contrast sensitivity (the inverse of the contrast of the grating that just elicited a detectable response). The two measures give very similar tuning curves in all cases. 3. We recorded from 184 neurones in area 17; of these 156 had receptive fields within 5 degrees of the area centralis. The range of preferred spatial frequency for these neurones was 0.3--3 c/deg, and their spatial frequency tuning band widths varied from 0.7 to 3.2 octaves at half-amplitude. The most common band width was roughly 1.3 octaves. Simple and complex cells in area 17 did not differ in their distributions of preferred spatial frequency, although complex cells were, on average, slightly less selective for spatial frequency than simple cells. 4. We recorded from fifty-four neurones from area 18, and performed several experiments in which we recorded from corresponding portions of both area 17 and area 18 in the same electrode penetration. Neurones in area 18 preferred spatial frequencies that were, on average, one third as high as those preferred by area 17 neurones at the same retinal eccentricity. Thus the range of preferred spatial frequency in area eighteen cells having receptive fields within 5 deg of the area centralis was between less than 0.1 and 0.5 c/deg. The distributions of optimum spatial frequency in the two areas were practically non-overlapping at eccentricities as high as 15 deg, the greatest eccentricity we examined. Neurones in area 18 were about as selective for spatial frequency as were neurones in area 17. 5. We determined temporal frequency tuning characteristics for some neurones from each area, using gratings that moved steadily across the screen. Neurones from area 17 all responded well to low temporal frequencies, and less well to higher frequencies (in excess of, usually, 2 or 4 Hz). In contrast, neurones recorded from area 18 sometimes had similar tuning properties, but more commonly showed a pronounced reduction in response as the temporal frequency was moved either above or below some optimum value (usually 2--8 Hz). 6. We conclude from these results that areas 17 and 18 act in parallel to process different aspects of the visual information relayed from the retina via the lateral geniculate complex. Some or all of the differences between the areas may be attributable to the predominance of Y cell input to area 18 and the predominance of X cell input to area 17...


The blockade of GABA mediated responses in the frog spinal cord by ammonium ions and furosemide. 1. A variety of compounds which are known to block chloride transport in a variety of systems have been examined for their effects on amino acid and synaptic responses in the frog spinal cord in vitro. 2. A number of monocarboxylic aromatic acids, copper sulphate, and acetazolamide had no effect on any of the responses. 3. Ammonium ions blocked the motoneurone hyperpolarizing responses to all the neutral amino acids. In addition it selectively blocked dorsal root potentials and the action of GABA and beta-alanine on primary afferents. 5. Intracellular recording from dorsal root ganglion cells demonstrated that furosemide had little effect on the reversal potential for the GABA response. These results suggest that furosemide acts primarily by blocking the conductance increase elicited by GABA. 6. The results with furosemide provide indirect evidence that chloride ions are involved in generating the GABA depolarizations of primary afferent terminals and dorsal root potentials.


Electrophysiological characteristics of renorenal reflexes in the cat. 1. Experiments were done in anaesthetized, paralysed and artificially ventilated cats to determine the fibre composition of renal nerves and to study the functional characteristics of reflex responses recorded in efferent renal nerves during electrical stimulation of contralateral and ipsilateral afferent renal nerves. 2. Renal nerves were found to contain three afferent fibre groups (Abeta, Adelta and C); the majority of these fibres reach the sympathetic chain through the least splanchnic nerve. Efferent sympathetic nerves to the kidney were found to originate from the greater, lesser and least splanchnic nerves through a synapse in the coeliac ganglion. 3. Two contralateral renorenal reflex responses were demonstrated during selective stimulation of renal afferent A and C fibres. The first (A renorenal reflex) was elicited by stimulation with trains of pulses at low voltage and high frequency (200 Hz), had an onset latency of approximately 100 msec and was followed by post-excitatory depression. The second (C renorenal reflex) was demonstrated by trains of pulses at high voltage and low frequency (20--30 Hz), had an onset latency of approximately 350 msec and was also followed by post-excitatory depression. 4. Ipsilateral renorenal reflexes with characteristics similar to the contralateral reflexes were also demonstrated. 5. Renorenal reflexes were abolished by destruction of the spinal cord and administration of nicotine sulphate (5--20 mg/kg, i.v.), but were not affected by bicuculline (0.4 mg/kg, i.f.). 6. The significance and the physiological role of these renorenal reflexes as well as their pathways within the central nervous system remain to be determined.


The correlation between ouabain binding and potassium pump inhibition in human and sheep erythrocytes. 1. [3H]Ouabain binding to human and sheep red blood cells was shown to be specific for receptors associated with Na/K transport. Virtually all tritium binding was abolished by dilution with unlabelled drug. Saturation levels of binding were independent of glycoside concentration and were identical to those associated with 100% inhibition of K pumping. 2. [3H]Ouabain binding and 42K influx were measured simultaneously in order to correlate the degree of K pump inhibition with the amount of glycoside bound. Results by this method agreed exactly with those obtained by pre-exposing cells to drug, followed by washing and then measuring K influx. 3. Plots of [3H]oubain binding vs. K pump inhibition were rectilinear for human and low K (LK) sheep red cells, indicating one glycoside receptor per K pump site and functional homogeneity of pump sites. High K (HK) sheep red cells exhibited curved plots of binding versus inhibition, which were best explained in terms of one receptor per pump, but a heterogeneous population of pump sites. 4. External K reduced the rate of glycoside binding, but did not alter the relationship between binding and inhibition. 5. The number of K pump sites was estimated as 450--500 per human cell and 30--50 per LK sheep cell. HK sheep cells had 90--130 sites per cell, of which eighty to ninety were functionally dominant. The number of K pump sites on LK sheep cells was not changed by anti-L, although the maximum velocity of pump turnover was increased.


Modulation of ouabain binding and potassium pump fluxes by cellular sodium and potassium in human and sheep erythrocytes. 1. Erythrocytes were treated with nystatin to alter internal Na (Nai) and K (Ki) composition. Although the rates of K pumping and [3H]ouabain binding were altered dramatically, the relationship between glycoside binding and K pump inhibition was unaffected. 2. Human cells with high Nai and low Ki exhibited an increased rate of ouabain binding as compared to high Ki, low Nai cells; this paralleled the stimulated K pump activity of high Nai cells. 3. At constant Ki, increasing internal Na stimulated K pump and ouabain binding rates concomitantly. 4. At low Nai, increasing Ki inhibited both K pumping and ouabain binding. However, at high Nai, increasing Ki from 4 to 44 mM stimulated the rate of glycoside binding, parallel to its effect of increasing the rate of active K influx. 5. Anti-L, an isoantibody to low K (LK) sheep red cells, increased the rate of ouabain binding via its stimulation of K pump turnover. Since the latter effect is the result of affinity changes at the internal cation activation site(s) of the pump (Lauf, Rasmusen, Hoffman, Dunham, Cook, Parmelee & Tosteson, 1970), the antibody's effect on ouabain binding reflected the positive correlation between the rates of K pump turnover and glycoside binding. 6. These data provide the first evidence in intact cells for the occurrence of a Nai-induced conformational change in the Na/K pump during its normal operational cycle.


Interpretation of perceived motor commands by reference to afferent signals. 1. Weights were lifted by flexing the distal joints of the anaesthetized thumbs. A weight-matching task was used to determine the perceived heaviness of a reference weight during control estimates when it was freely lifted, and during experimental estimates when the weight was not lifted, but simply 'gave way' when a reference isometric tension of the same magnitude was attained. 2. Limitation of the afferent input, by anaesthesia of the digit and by replacing lifting with a sudden unloading, did not grossly impair the judgement of heaviness. The sense of heaviness increased when the muscles became fatigued. 3. These results suggest that the central nervous system can interpret the voluntary motor command as an index of heaviness even when provided with only a crude peripheral signal that the weight has been moved.


Measurement of flow and sampling of digesta in the preruminant calf. 1. Methods of measuring and sampling the flow of digesta passing through intestinal cannulas in preruminant calves were studied and compared. 2. The effect of collecting digesta from a duodenal cannula on abomasal emptying in a calf given whole milk was determined. When digesta were collected and returned to the duodenum manually in large amounts (about 200 g) the outflow of abomasal contents was intermittent. When digesta were returned to the animal either manually or automatically in amounts of less than about 50 g abomasal emptying was smooth. 3. An automatic apparatus for measuring and sampling the flow of digesta continuously was developed. The device allowed effluent to be returned smoothly to an ingoing cannula at the same rate that digesta left the outgoing cannula. After a feed of whole milk abomasal contents were observed to enter the duodenum in an orderly series of gushes. Each gush consisted of about 5--30 g of digesta. 4. The apparatus was rearranged to measure the effects of composition of duodenal digesta on abomasal emptying. Replacement of duodenal digesta with a suspension containing heated soyabean flour slowed the abomasal outflow of a feed containing casein. 5. Automatic apparatus was used to collect digesta arriving at the distal ileum. Withholding effluent from the large intestine did not affect the movement of digesta from the ileum.


Electrical activity of human colonic smooth muscle in vitro. 1. Extracellular and intracellular recordings were made of the electrical activity of isolated strips of human colonic smooth muscle, cut from sixty surgical specimens. 2. Strips of taenia were spontaneously active. The myogenic activity consisted in half the strips of intermittent periods of regular spike activity (frequency 22 +/- 5 (S.D.) c/min) accompanied by tetanic contractions; in the other half of the strips activity was continuous. In half the specimens, slow potentials were recorded between periods of spike activity. Slow potentials were not accompanied by contractions. 3. Spikes in taenia were abolished by verapamil. Spikes disappeared in low Ca and low Na solutions, but in low Na solution spikes could be stimulated by 15 mM-KCl. 4. ACh and physotigmine produced tetanic contractions in taenia. 5. Circular muscle was not spontaneously active within 1 h of incubation in the water bath, possibly due to inhibition by prostaglandins. 6. Circular muscle responded to ACh with irregular bursts of spikes associated with discrete contractions. Similar activity was seen after inhibition of prostaglandin synthesis with indomethacin. After treatment with tetrodotoxin, ACh produced regular spikes and tetanic contractions in circular muscle. 7. The possible relationships of these results to the myoelectrical activity of the human colon in vivo are discussed.


Glucose, glycine and diglycine in test meals at stimuli to a duodenal osmoreceptor slowing gastric emptying. 1. Five subjects took 210 test meals of 750 ml. water containing 30--300 m-molal glucose or glycine, or 15--150 m-molal diglycine, or plain water. 2. The greater the concentration of solute, the greater was the volume of original meal recovered from the stomach after a fixed time. 3. On a molal basis glucose was half as effective as diglycine in slowing gastric emptying. This was consistent with the osmoreceptor being exposed to the diglycine after it had been split by the hydrolase of the cytosol of enterocytes (the absorbing cells of the small intestine). 4. The slowing of gastric emptying (ml./mole.1.) was about 10% greater for glycine than it was for glucose. There was apparently a threshold concentration below which glycine did not slow gastric emptying. 5. It was proposed that the response of the doudenal osmoreceptor might depend upon shrinking and swelling of the lateral intercellular space around the enterocytes.


Electrophysiology of the afferent innervation of the penis of the domestic ram. 1. The discharge of impulses in afferent fibres dissected from the dorsal nerve of the penis of chloralose-anaesthetized rams was recorded electrophysiologically during controlled natural stimulation of the surgically exposed penis maintained at body temperature and mechanically stabilized in a plaster of Paris mould. 2. Fifty-eight slowly adapting mechanorecptor units were examined and their pressure, velocity and displacement thresholds were determined. Units often responded best to integumental stretch. Few had resting discharges. During a sustained perpendicularly applied displacement most units adapted to silence within 1.5 min. The units were classified into types from an analysis of their adapted impulse trains in response to a sustained mechanical stimulus. 3. Twenty-five mechanoreceptive units had rapidly adapting responses. Most units had typical rapid adapting characteristics and discharged impulses only during the dynamic phase of the application of the displacement. A subgroup had intermediate adapting characteristics, and discharged intermittently during steady displacement of the integument. 4. The mechanical sensitivity of most receptors altered when the temperature of the receptive field was changed with a positive correlation in eleven units, a negative correlation in six. Six slowly adapting units were thermally insensitive. Twelve rapidly adapting units were tested. Six had a positive thermal correlation and four a negative correlation. 5. The conduction velocities of axons of mechanoreceptor units in the dorsal nerve of the penis were in the Aalpha range (12--77 msec-1). 6. Two specific warm and five specific cold units were found. The conduction velocities of the axons supplying warm receptors were 45.4 msec-1 (one unit) and those for cold receptors were 7.5, 7.8, 30, 45.5, 48.7 msec-1. 7. No correlation could be found between the receptor submodality and the profuse receptor end bulb population demonstrated histologically.


Projections of primary afferent fibres from muscle to neurones of the spinocervical tract of the cat. 1. Micro-electrode recordings were made from axons in the spinocervical tract of decerebrate-spinal cats. 2. The effect of electrical stimulation of afferent fibres in muscle nerves was examined. 3. Stimulation of group III fibres in muscle nerves excited hair only and hair and pressure units in the spinocervical tract. Hair and pressure units also responded to electrical stimulation of group IV fibres. 4. Units of the spinocervical tract excited by stimulation of muscle nerves had receptive fields in the skin overlying the relevant muscles. 5. Stimulation of group III fibres in muscle nerves produced long lasting inhibition of spinocervical tract units. In two such units the inhibitory action of afferent myelinated fibres was enhanced by increasing the stimulus strength so that group IV fibres were recruited.


Gastrins in cat and dog: evidence for a biosynthetic relationship between the large molecular forms of gastrin and heptadecapeptide gastrin. 1. Extracts of antral, duodenal and jejunal mucosa contained the same concentrations and molecular forms of gastrin in cat and dog. In both species component III constituted 93%, component II 4% and components I and IV each 1% of the total immunoreactivity. 2. During electrical vagal stimulation or feeding in (a) anaesthetized cats with ligated kidney vessels and resected jejunum and ileum, (b) anaesthetized normal cats or (c) conscious normal cats, release of the large molecular forms of gastrin, components I and II, was not detectable. 3. Luminal perfusates of cat antrum contained only component III and occasionally less than 2% of component IV. 4. Intravenous injections into conscious cats of components I, II and III isolated from cat antrum revealed a significantly slower elimination of the large components (t1/2 approximately 4.2 and 4.0 min respectively) than of component III (t1/2 approximately 1.1 min). Thus the absence of components I and II in cat blood cannot be due to rapid degradation. 5. During feeding, components I and II constituted 20% of the total gastrin immunoreactivity in antral venous blood of dogs. This amount is sufficient to account for the predominance of large components in peripheral venous blood in dogs considering their slow metabolic clearance rates. 6. Luminal perfusates of dog antrum contained components I, II and III in proportions corresponding to those found in antrum. 7. The results indicate that components I and II are synthesized in the same proportions in gastrin cells of cat and dog. In the cat, components I and II are, however, never released from the cells. Since these components contain heptadecapeptide gastrin within their sequeaces, they probably represent biosynthetic precursors of the principal gastrin, the heptadecapeptide (component III). The predominance of component III in gastric juice suggests that the feline gastrin cell secretes only component III, which degrades to component IV in blood.


A quantitative analysis of the effects of 2,3-diphosphoglycerate, adenosine triphosphate and inositol hexaphosphate on the oxygen dissociation curve of human haemoglobin. 1. Oxygen dissociation curves have been measured for human haemoglobin solutions with different concentrations of the allosteric effectors 2,3-diphosphoglycerate, adenosine triphosphate and inositol hexaphosphate. 2. Each effector produces a concentration dependent right shift of the oxygen dissociation curve, but a point is reached where the shift is maximal and increasing the effector concentration has no further effect. 3. Mathematical models based on the Monod, Wyman & Changeux (1965) treatment of allosteric proteins have been fitted to the data. For each compound the simple two-state model and its extension to take account of subunit inequivalence were shown to be inadequate, and a better fit was obtained by allowing the effector to lower the oxygen affinity of the deoxy conformational state as well as binding preferentially to this conformation.