Hemolytic-uremic syndrome: a diagnostic and therapeutic dilemma for the surgeon. The hemolytic-uremic syndrome consists of microangiopathic hemolytic anemia, acute renal failure, and thrombocytopenia following a prodromal illness of gastroenteritis or upper respiratory infection. The syndrome can present in dramatic fashion with severe abdominal pain and signs of peritonitis suggesting an acute surgical crisis. In a series of 25 patients, 40% had abdominal pain, 25% had abdominal tenderness, and 20% had peritoneal signs. Clues to diagnosis in the early stages of the acute illness were mild to moderate hypertension, abnormal peripheral blood smear, anemia despite dehydration, and proteinuria. Significant abdominal pain and x-ray evidence of colitis may occur before development of typical laboratory findings, and these were evident in at least one case. Three patients underwent laparotomy for suspected bowel perforation. Colitis without perforation was found in all cases. In the absence of documented perforation, toxic megacolon, or intussusception, the decision to perform laparotomy in patients with hemolytic-uremic syndrome who have signs of peritonitis must be individualized. Failure to recognize the underlying renal problem can lead to serious errors in fluid and electrolyte management and delay of appropriate therapy.


Surgery in patients with hemoglobin-S disease. Sixty-eight patients with sickle cell disease who underwent surgery are reviewed. Fifty-two were homozygous for hemoglobin-S, whereas 16 had heterozygous variants. Associated diseases were common. Both the types of operative procedures and the complications of surgery, in large measure, were determined by these associated diseases. Splenectomy (12 patients) and cholecystectomy (11 patients) were the common major operations; infections (21 patients) were the most common complications. Precise management ensured acceptably low morbidity and mortality (1 death) in this series.


Hirschsprung's disease: absence of serotonergic neurons in the aganglionic colon. The distribution of enteric serotonergic neurons was studied in patients with Hirschsprung's disease. Specimens of bowel obtained at surgery were incubated in vitro with tritiated serotonin (3H-5-HT) in the presence of a high concentration of nonradioactive norepinephrine. Sites of high-affinity 3H-5-HT uptake were visualized by light-microscopic autoradiography. Specimens taken from ganglionic regions of the intestine (distal ileum or colon) showed intense labeling of the neuropil within the myenteric plexus. Silver grains were localized in a pericellular distribution around ganglion cells, but the ganglion cells themselves were relatively free of overlying silver grains. Corresponding regions of aganglionic colon or rectum demonstrated silver grain densities equivalent to background levels. Specific labeling was absent over the large nerve trunks in this region. These results suggest that 5-HT-containing neurons are present in the normal human intestine and that these neurons are absent in the aganglionic segment in Hirshsprung's disease.


The value of radionuclide scanning in early diagnosis of intestinal infarction. Small focal areas of intestinal infarction were produced experimentally in mice by two techniques: (1) intussusception and (2) suture strangulation of a loop of jejunum. The radionuclide technetium 99m diphosphonate (99mTc-diphosphonate) was subsequently administered intravenously, and abdominal scans were obtained. The scans demonstrated focal infarcted lesions accurately, and every positive scan was associated with an area of infarction, as demonstrated by pathologic examination. However, negative scans did not definitely exclude an area of infarction: in the intussusception study there were five false negative scans in 25 animals, and in the loop ligation study there were two false negative scans in 28 animals. The technique may have clinical application in such intestinal diseases as necrotizing enterocolitis in infancy in which early diagnosis of small areas of necrosis is currently difficult by clinical and radiologic methods.


Anterior ectopic anus: a common cause of constipation in children. Anterior ectopic anus is increasingly being recognized as a cause of constipation in infancy. Experience is reported with surgical treatment of 20 patients with anterior ectopic anus. This form of anal ectopia is associated with a syndrome of constipation that begins at birth, straining on defecation, and anterior displacement of an otherwise normal anus and sphincter. It is seen almost exclusively in females. Posterior anoplasty with sphincterotomy is curative.


N-type anorectal malformations.

N-type anorectal malformations. Three cases of N-type anorectal malformations have been encountered. Two girls with anorectal-vestibular fistulas (one with a normal anus and the other with mild stenosis) were typical of 15 other such cases in the literature. A boy with an anorectal-urethral fistula and covered anus had a lesser variant than most of the other 8 males in the literature. The frequently accompanying esophageal, renal, and skeletal anomalies were not present, nor did he have anterior urethral hypoplasia. The constellation of other major associated anomalies in the boys, but not in the girls, follows the pattern of other types of anorectal malformations and suggests an earlier and/or more severe teratogenic insult in the boys. Anterior perineal resection of the fistula is appropriate for girls with N-type fistulas and for those boys with normal anterior urethras. An additional urethroplasty is necessary for boys with anterior urethral hypoplasia. Our experience and that from the literature suggest that N-type anorectal malformations constitute a rare but real entity,  akin to N-type tracheoesophageal fistulas. A plea is made that they be included in classifications of anorectal anomalies.


Fourteen years of gastric tubes.

Fourteen years of gastric tubes. Since 1964 gastric tube replacement of the esophagus has been done in 30 infants and children. This report reviews and brings up to date our entire series, which includes follow-up of 15 children over 5 yr, 7 of whom have been followed for more than 10 yr. The two-stage proximally based reversed antiperistaltic gastric tube placed retrosternally is still our procedure of choice, although since our last report in 1973 several other methods (one-stage, transthoracic, subcutaneous) have been used, and the spleen has not been removed in our more recent operations. Whether the esophagogastric tube anastomosis is primary or secondary or is in the chest or neck, leakage is still the most common complication (63%), with all but three closing spontenously. A continuing problem may be an anastomotic stricture (43%) that will require some dilatations. Mild sacculation or tortuosity of the gastric tube has been encountered only once. Despite the above problems, the eventual outcome in the growing child with a gastric tube replacement continues to be a satsifying one. We continue to use the gastric tube operation when replacement of the esophagus is required.


Thal fundoplication: a simple and safe operative treatment for gastroesophageal reflux. One hundred patients with complications of severe gastroesophageal reflux were treated surgically by the Thal fundoplication. In all patients the symptoms of reflux were eliminated by the operation, although 4 recurred within 8 months. Two of these were due to disruption of the fundoplication and two were due to hiatus hernia not recognized and repaired at initial operation. There were 8 deaths, none related to gastroesophageal reflux or the operation. Four patients required re-operation for intestinal obstruction. The Thal fundoplication is a simple procedure which fixes the distal esophagus within the abdomen and produces an acute angle of His. It is effective in prevention of reflux and the patient is able to burp and vomit if necessary. It has not been associated with dysphagia or "gas bloat" which may follow the Nissen fundoplication.


Cholinergic nerve development of fetal lung in vitro. The development of the cholinergic or parasympathetic nervous system was studied in embryonic lung dissociated from the central nervous system and placed in organ culture. In vitro development was similar to that seen in vivo. This study demonstrated that migration of neuroblasts from the central nervous system to the trachea takes place before day 12. Neuroblasts differentiate to small immature ganglia and then to larger more mature ganglia that give off nerve fibers to the submucosa and the epithelium. This isolated lung preparation was used to study neurostimulators. Thyroxine (T4) was found to accelerate nerve fiber growth and differentiation of ganglia in vitro. The neuroepithelial body, an epithelial cell with acetylcholine-esterase-positive granules, also differentiated in vitro. This cell may fill the morphologic criteria of an intrapulmonary chemoreceptor.


Clinical application of endotracheal cryotherapy. A nitrous oxide cryoprobe has been developed that may be used through the infant bronchoscope. A total of 19 discrete airway lesions have been treated in 17 patients ranging in age from 2 mo to 30 yr. Three patients with periglottic lesions have had complete eradication of these lesions without the need for tracheostomy. Six patients with subglottic stenoses have been treated, with one successful extubation and one patient approaching extubation. Five patients have been treated for distal tracheal strictures, with two successful extubations and a third pending extubation. Five patients have been treated for endotracheal granulation tissue, and 3 patients have been successfully extubated. Cryotherapy allows bloodless resection of these lesions with rapid tissue healing not accompanied by residual scarring.


Esophageal atresia with tracheoesophageal fistula: end-to-end versus end-to-side repair. Despite early enthusiasm by some authors for the end-to-side repair of esophageal atresia with tracheoesophageal fistula, many have returned to the end-to-end technique. The present study compares the results of these two operative procedures. A retrospective analysis was made of 52 consecutive cases in which primary repair was performed. The patients were divided according to the three preoperative risk groups descibed by Waterston. The mortality for the end-to-end and end-to-side repairs was similar in each of the three risk groups. Similarly, there was no significant differnences in the incidence of anastomotic leak or recanalization of the fistula. However, the rate of anastomotic stricture in the end-to-end group was significantly higher (p less than 0.001) than in the end-to-side group. A description of the end-to-side technique is given, and its advantages are outlined.


Bronchial atresia: a recognizable entity in the pediatric age group. Bronchial atresia, a congenital lesion that develops after the 16th wk of fetal life, may be more common than previously believed, and this probably explains some cases of so-called congenital lobar emphysema. It may produce symptoms of pulmonary infection, wheezing, and respiratory distress severe enough to justify elective resection of that part of the lung distal to the atresia. The roentgenographic features that make this a recognizable entity are the following: (1) There is localized hyperinflation of lung in a segmental or lobar distribution, with a circular or oval parahilar radiodensity. Bronchography will demonstrate that there is no filling of the bronchus supplying this part of the lung. (2) The occasional neonate with this condition may present with an intrathoracic mass suggesting retained fetal lung fluid in lobar distribution. Bronchography will demonstrate that there is no filling of the bronchus to that part of the lung. (3) A plug of desquamated tissue and mucus in the cyst-like bronchus just distal to the point of atresia appears to be an unvarying component of the syndrome. It most commonly presents as a round or oval density, but in some cases it may be shaped like a rod or tree and rarely contains an air-fluid level.


Vesicointestinal fissure revisited.

Vesicointestinal fissure revisited. This complicated anomaly of bladder exstrophy, intestinal fistula, and various degrees of colonic atresia with imperforate anus is readily recognizable. The long-term result of conventional management has been disappointing. Fecal and urinary incontinence have been unavoidable and a source of disappointment to patients and parents. An alternative method of total management is detailed. This variation of management may result in earlier and more complete social acceptability of the child so afflicted. At as young an age as possible, the vesicointestinal connection is detached and the bladder defect as well as the intestinal opening closed. The short colon is freed and transected at its midpoint. The right half of the colon is brought out through a separate wound as a colostomy. The distal half of the divided colon is brought out as mucous fistula on the left. This distal colonic segment is the proposed future colonic loop for urinary diversion to be fashioned in the first year of life. The exstrophied bladder is removed at a later date. Epispadias in the male may be repaired later. A Pediatric Ostomy Club has been organized to include a pediatric stomal therapist and involved nurses and physicians. The group gives the parents advice and moral support. We believe that this approach will permit the child to go to school and carry on relatively normal activity and to be socially acceptable. An overview of our total experience in the management of 25 patients with vesicointestinal fistula details the result in 9 surviving patients.


Acute iron intoxication with intestinal infarction. A fatal case of acute iron intoxication with intestinal infarction is reported, with emphasis on the acute gastrointestinal effects of iron ingestion. The patient demonstrated the progressive necrotizing effects of retained iron on the gastrointestinal tract. Although moderate amounts of iron may be irritating and may produce diarrhea, larger amounts may cause paralytic ileus. Localized concentrations of iron may then exert corrosive effects and cause segmental infarctions and perforations. Emphasis must be given to the purging of iron products from the bowel. Should surgery become necessary because of localized infarction or perforation, we believe that it is advisable to not only thoroughly irrigate the peritoneal cavity but also irrigate the lumen of the bowel so as to remove as much of the remaining iron as possible, lest further areas of necrosis and perforation develop because of continued corrosive effects.


Adenocarcinoma at the site of ureterosigmoidostomies for exstrophy of the bladder. Adenocarcinoma of the colon is a rare complications of ureterosigmoidostomy done for exstrophy of the bladder. Only 13 cases have been previously reported, occurring from 10 to 46 yr after the procedure. In a series of 150 patients who have had ureterosigmoidostomies carried out at the Children's Hospital Medical Center, Boston, over the past 40 yr, 4 patients have been treated at our institution for this complication. The tumor was noted 20 to 32 yr after the initial procedure. Two patients are alive and well 1 and 4 yr after resection. The increasing incidence of this complication with advancing age will require careful observation and will undoubtedly influence the indications for the procedure. An additional question of great importance is how to evaluate and follow the thousands of patients who have had this procedure done at one time in their lives. It is suggested that an annual intravenous pyelogram is indicated in those patients with functioning ureterostomies and that a colonoscopy to the level of the anastomoses be carried out at 6-mo intervals in all patients. In those patients in whom the ureterosigmoidostomies have been taken down, a sleeve resection of that area of the colon should be strongly considered.


A retrospective epidemiologic study of pediatric fibrosarcomas. One hundred eighty-two patients with histologically diagnosed fibrosarcoma below the age of 19 yr reported to the End Results Section of the National Cancer Institute before 1971 were analyzed. Race, sex, and age did not significantly affect prognosis. Site of the primary lesion and extent of disease at diagnosis did significantly affect prognosis. Overall 3-yr survival was 80%, and this remained constant over the next 5 yr. Survival of patients with upper extremity lesions exceeded 90%, whereas those with retroperitoneal primary sites had 17% survival. Patients with localized disease at diagnosis had 5-yr survival of 90%, but those with disseminated disease had a median survival of 6 mo, and 22% 1-yr and 5-yr survival.


Imperforate anus: avoiding a colostomy.

Imperforate anus: avoiding a colostomy. Early assessement of imperforate anus, combining clinical and radiographic data, determines the course of treatment. "High" lesions most often require combined abdominal and sacroperineal repair, usually preceded by a decompression colostomy.  "Low" lesions are repaired through a perineal or sacroperineal approach not requiring a previous colostomy. Patients who do not have an apparent fistulous tract through which accurate radiographic assessment can be made frequently undergo preliminary colostomy to avoid colonic perforation. This occurs in patients who have "low" lesions and in whom colostomy may be avoided. Combining a new procedure and an old procedure may avoid unnecessary colostomy. A 14 Medicut intravenous cannula is inserted in the perineum and under fluoroscopic control is advanced into the radiolucent area identified in the pelvis as the probable lower rectal pouch. The position is confirmed by aspiration of gas or meconium and injection of contrast material. A limited contrast enema will clearly identify the level of the lesion and identify a fistula if one is present. If a low lesion is identified and no fistula is present to allow temporary colonic decompression, a fistulous tract may be created mechanically. A No. 4 Fogarty catheter is inserted through the previously placed cannula, the catheter balloon is inflated, and the entire apparatus is extracted under tension. This creates a small fistulous tract to the perineal surface. Subsequent dilation of this tract allows colonic decompression, and definitive operative repair may be planned at the most appropriate time. By employing this technique, we have avoided colostomy in 4 of 6 patients.


Effects of concomitant aspirin administration on the pharmacokinetics of indomethacin in man. Ten healthy volunteers each received single and multiple 50-mg doses of indomethacin orally and a single 25-mg dose of [14C]indomethacin intravenously in the absence of and concomitantly with 1200 mg of aspirin as a single dose and in a chronic t.i.d. regimen. Systematic analysis of the data resulted in the isolation and quantification of aspirin's effects on the absorption, distribution, biotransformation, excretion, enterohepatic circulation, and accumulation of indomethacin. The effects of chronic aspirin were to suppress the renal clearance, to increase the biliary clearance, to decrease the efficiency of gastrointestinal absorption, and to enhance the enterohepatic circulation of indomethacin. On concomitant administration of 1200 mg of aspirin t.i.d., mean plasma levels of indomethacin were depressed by 20% after a single oral dose, by a smaller margin after multiple oral doses, and not at all after a single intravenous dose of indomethacin. The mean plasma concentration of orally administered indomethacin was decreased by 8% when given concurrently with a single 1200 mg dose of aspirin. Concomitant chronic therapeutic dosages of indomethacin had no effect on salicylate accumulation from repetitive doses of aspirin.


Pharmacokinetic interpretation of the enterohepatic recirculation and first-pass elimination of morphine in the rat. Morphine was administered to rats by oral, intraportal, and intravenous routes in a dose of 7.6 mg . kg-1. From the serum concentration data after intraportal administration it was calculated that the first-pass elimination of morphine in the liver amounts to 72 +/- 2% (SD). The first-pass fraction eliminated after oral administration was 85 +/- 7% (SD), thus yielding a contribution by the gut mucosa of 46% to the overall first-pass elimination after an oral dose. The results were obtained with a general compartmental model which included the kinetics of enterohepatic recirculation. The oral availability was also estimated with the aid of pharmacological effect data. This availability was in good agreement with the corresponding value determined from the serum concentration data. The results suggest that morphine is subjected to enterohepatic recirculation and that the slowest phase of decline of morphine concentrations in serum might be due to this physiological process.


Mathematical prediction of drug distribution in vivo: studies with doxantrazole in rats. A pharmacokinetic model incorporating 14 compartments and 29 transfer coefficients has been developed from experimental data obtained after intravenous administration of a single dose to describe the distribution of doxantrazole in the rate. The distribution calculated from the model agreed closely with that determined experimentally. In addition, the model was able to predict with considerable accuracy the distribution of doxantrazole after repeated dosing.


Critical evaluation of the potential error in pharmacokinetic studies of using the linear trapezoidal rule method for the calculation of the area under the plasma level--time curve. The linear trapezoidal rule method is commonly used for the estimation of the area under the plasma level-time curve. Error analyses are performed when the method is used in first-order absorption and first-order elimination kinetics in the one-compartment system. It is found that significant underestimations and overestimations in area during the absorption phase and postabsorption phase, respectively, can occur when the method is improperly used. During the exponential postabsorption phase the relative error is only a function of the ratio (n) of the time interval over the half-life of the two plasma data points in the interval. The error from the linear trapezoidal rule method at n = 0.5 is about 1%. The error increases to 15.5% and 57.1% when n is increased to 2 and 4, respectively. It is recommended that for most absorption studies the linear trapezoidal method be used for prepeak and plateau plasma data and the logarithmic trapezoidal method for postpeak plasma data.


Statistical moments in pharmacokinetics. Statistical moments are parameters that describe the characteristics of the time courses of plasma concentration (area, mean residence time, and variance of residence time) and of the urinary excretion rate that follow administration of a single dose of a drug. The relationship between the moments of a time-course curve and pharmacokinetic profiles of drug disposition, i.e., absorption, distribution, metabolism, and excretion, is described. The moments are related to the extent and rate of bioavailability, and it is shown that they can be effectively applied to the deconvolution operation.


Effect of route of administration and distribution on drug action. The extent and time course of drug action can be markedly affected by the route of drug administration into the patient as well as the pattern of drug distribution within the patient. Drugs which are rapidly cleared by hepatic processes will show a decreased extent of availability following oral administration due to metabolism of drug on its first pass through the liver. The magnitude of this first pass will depend on the blood flow to the liver and the intrinsic clearing ability of the liver (i.e., the ability of the organ to eliminate the drug independent of the rate at which drug is brought to the organ). Drug distribution in the patient will depend on the blood flow to various sites in the body as well as the partition coefficient of the drug between the blood and the distributive organs. Protein binding both in the plasma and in the tissues will markedly affect this distribution. However, free drug concentrations are generally relieved to be the effective determinant in drug therapy. Often a redistribution due to changes in protein binding will have little effect on the therapeutic efficacy since, although total drug distribution changes, free concentrations in the plasma remain essentially similar.


In vivo studies on the relationship between target organ alkylation and the pulmonary toxicity of a chemically reactive metabolite of 4-ipomeanol. The pulmonary toxin, 4-ipomeanol, selectively alkylates the lungs of rats. Time-course and dose-response studies demonstrate a close correlation between the pulmonary alkylation and the lung toxicity of the compound. Without prior metabolism, 4-ipomeanol is not sufficiently reactive to alkylate tissue macromolecules. Inhibitors of the metabolism of 4-ipomeanol decrease both the pulmonary alkylation and toxicity of the compound, which suggests that the toxicity is due to an alkylating metabolite. Studies with inducers of the hepatic metabolism of 4-ipomeanol are consistent with the view that the toxic metabolite of the compound is actually formed in situ in the target tissue. Pretreatment of animals with diethylmaleate strikingly increases both the pulmonary alkylation and the lung toxicity of 4-ipomeanol. Studies of the tissue alkylating properties and toxicities of 4-ipomeanl analogs demonstrate the requirement for the furan moiety. The toxic metabolites of 4-ipomeanol appears to be a highly electrophilic reactant capable of binding irreversibly with nucleophilic macromolecular constituents of target tissue.


The effect of isoniazid and other drugs on the acetylation of procainamide in the intact rat. The effects of isoniazid (INH), hydralazine, salicylazosulfapyridine, and sulfapyridine on the quantitative disposition of procainamide (PA) in the intact rat were examined. A dose-dependent inhibition of PA acetylation was observed after coadministration of PA with INH via nasogastric intubation. The 24-hr urinary excretion of N-acetylprocainamide was noted to decline in the presence of INH whereas that of the unchanged drug exhibited a coincident rise. A reduction in the systemic clearance of PA and a prolongation in its half-life of elimination was also observed. INH increased PA hepatic levels and decreased N-acetylprocainamide hepatic content. In contrast hydralazine affects not only PA acetylation but also its absorption rate and transformation by other metabolic pathways. Salicylazosulfapyridine did not affect PA acetylation whereas high doses of sulfaphridine did.


Developments of computer-based estimation of pA2 values and associated analysis. The standard statistical-computing package GLIM is used to analyze data from agonist-antagonist studies for the estimation of the dissociation constant of the antagonist. The method follows the general approach of D.R. Waud (Analysis of dose-response curves. In Methods in Pharmacology, vol. 3, Smooth Muscle, ed. by E.E. Daniel and M. Paton, Plenum Press, New York, 1975) in employing an iterative nonlinear least-squares curve-fitting procedure. However, it differs in two important respects: 1) it is interactive; and 2) it allows linear adjustments for covariates and experimental design variables. This paper develops develops an alternative useful formulation of departure from simple competitivity and also a graphical display called a "Clark plot" showing how the spacings of the dose-response lines fit the theory of simple competitive antagonism. This plot provides an alternative to the popular Schild plot for which, of necessity, the zero antagonist (control) dose-response line is heavily used both in the experimental design and in the analysis associated with it.


Alteration of renal cortical palmitate utilization and p-aminohippurate (PAH) accumulation after penicillin treatment of neonatal rabbits. The renal organic anion transport system has been linked to the selective extraction of nonesterified fatty acids (NEFA) from arterial blood. Consequently, p-aminohippurate (PAH) and palmitate may compete for a common intracellular binding site or may be handled by a common enzymatic pathway. The purpose of this study was to identify sites of interaction by correlating alterations in PAH accumulation and palmitate metabolism after selective stimulation of the PAH transport system. Penicillin treatment of immature rabbits increased PAH accumulation by suspensions of proximal tubules prepared nonenzymatically) and altered distribation of incorporated palmitate[14C] within tubule lipid classes. Penicillin increased palmitate[14C] esterified to triglycerides and decreased 14C recovered as NEFA. Administration of iodipamide had no effect on PAH accumulation and did not alter palmitate utilization. Penicillin treatment of mature rabbits did not alter either tubule PAH accumulation or palmitate esterification. These results suggested that palmitate and PAH share a common intracellular binding site and that penicillin enhanced PAH accumulation by removing endogenous inhibitors (NEFA).


Salicylate excretion in the rat; free flow micropuncture experiments. As in other animals, the renal clearance of salicylate in the rat is greater when the urine is alkaline than when it is acid. In none of the present experiments was the rate of salicylate excretion greater than the rate of its glomerular filtration. Nevertheless, net secretion of salicylate was observed in the proximal tubules of alkalotic, nonalkalotic diuretic, and normal hydropenic animals when the plasma concentration of salicylate was below 150 microgram/ml. Alkalosis enhanced the salicylate content of proximal tubular fluid (approximately 30%). The enhancement is less than would be expected from published reports of proximal tubular fluid pH, if non-ionized salicylate were the only permeant form of the drug. In the absence of alkalosis and at high plasma concentrations, net reabsorption in the proximal tubule was observed. In some circumstances there is net reabsorption of salicylate between the end of the accessible portion of the proximal tubule and the beginning of the distal. Salicylate is reabsorbed from the distal tubule. There was only a small difference in distal reabsorptive rate between normal and alkalotic animals.


The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on the renal tubular secretion of phenolsulfonphthalein. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known to have profound ultrastructural and biochemical effects on hepatic and renal tissues. However, there is little information concerning the effect of TCDD on renal function. Therefore, the steady-state secretion rate of phenolsulfonphthalein (PSP) was measured in vivo in control rats and in rats pretreated with TCDD. Five to 7 days after a single intraperitoneal injection of TCDD (10 microgram/kg) there was: 1) an increase in the apparent affinity of the secretory system for PSP since a significant increase in the tubular secretion rate of PSP occurred at low plasma levels of PSP; 2) no increase in the maximum secretory capacity for PSP (Tm-PSP); 3) a significant decrease in the glomerular filtration rate; from 1.17 +/- 0.10 to 0.90 +/- 0.06 (mean +/- S.E.) ml-min-1 . g-1 wet kidney wt. The decrease  in glomerular filtration in the rats treated with TCDD occurred without a change in the mean arterial pressure; this suggests that the glomerular structures may have a high sensitivity to this agent. The effect of TCDD on the tubular secretion of PSP is discussed in relation to the available information concerning the inducing effect of TCDD on renal tissue ligandin content.


Similar effects of phenytoin and tetrodotoxin on cyclic nucleotid regulation in depolarized brain tissue. Veratridine, ouabain, glutamate and high concentrations of K+, agents which cause depolarization of excitable cells, markedly elevate levels of adenosine 3':5'-monophosphate (cyclic AMP) and guanosine 3':5'-monophosphate (cyclic GMP) in brain tissue, in vitro. Phenytoin inhibits veratridine (5 micron)- and ouabain (100 micron)-induced accumulations of both cyclic nucleotides in slices of mouse cerebral cortex. As little as 10 to 30 micron phenytoin produces a statistically significant depression, and 100 to 400 micron inhibits more than 90%. In contrast, at concentrations up to 400 micron, the drug has little or no effect on elevations of cyclic AMP or cyclic GMP caused by glutamate (10 mM) or K+ (64 mM). The inhibitory action of phenytoin on ouabain-induced elevations of cyclic nucleotides appears to be noncompetitive; inhibition of the veratridine effects probably is also noncompetitive. Tetrodotoxin also inhibits ouabain- and veratridine-induced elevations of cyclic nucleotides in brain slices, but it is 3 orders of magnitude more potent than phenytoin. Like phenytoin, tetrodotoxin does not inhibit the effects of glutamate or K+ on cyclic nucleotide regulation. These data suggest that, similar to tetrodotoxin phenytoin blocks sodium channels in excitable membranes. Possibly this mechanism is responsible for the antiepileptic action of phenytoin.


Carbamazepine suppression of post-tetanic potentiation at the neuromuscular junction. The effects of carbamazepine (CBZ) on post-tetanic potentiation (PTP) were evaluated using an in vivo cat coleus neuromuscular preparation. CBZ was administered i.p. and plasma CBZ concentrations were determined by gas liquid chromatography during PTP tests over a 90-min period. CBZ produced a concentration-dependent depression of PTP. Significant depression was first noted at about 12 microgram/ml and 50% depression occurred at 20 microgram/ml; this depression was time-dependent. No effect was observed on unpotentiated, supramaximal twitches. CBZ also modified the pattern of tetanic contraction; the most predominant change was an enhancement of the initial falling phase of the tetanus. Antidromically propagated post-tetanic repetitive afterdischarges (PTR) were monitored in single isolated vertral root filaments innerving the soleus muscle. CBZ inhibited PTR without affecting conduction velocity or the capacity of the fiber to follow the high frequency (tetanic) stimulation. These results are similar to those previously reported for phenytoin. CBZ inhibits PTP in this preparation by inhibition of PTR through a presynaptic effect; possible mechanisms are discussed. These observations may contribute to the understanding of the actions of this drug in epilepsy and neuromyotonia.


The effects of lysergic acid diethylamide and mescaline-derived hallucinogens on sensory-integrative function: tactile startle. Tactile startle responding by male Sprague-Dawley rats given 60 presentations of air-puff stimuli (37.5 psi) was measured after the intraperitoneal administration of graded doses of hallucinogens and other psychoactive drugs. Among the drugs tested were the indoleamine-derived compounds, lysergic acid diethylamide (LSD), N,N-dimethyltryptamine and psilocin, and the phenylethylamine-derived compounds, mescaline, 2,5-dimethoxy-4-methylamphetamine and a series of active and inactive congeners of 2,5-dimethoxy-4-methylamphetamine. All of the active phenylethylamines increased startle response magnitudes throughout the test session. This pattern of augmented startle suggests that these drugs increase reactivity. However, none of the indoleamine hallucinogens increased startle responding. Of the nonhallucinogenic drugs tested, only apomorphine increased startle responding, while clonidine significantly decreased it, and amphetamine, chlorimipramine, scopolamine and methysergide had no effect. In additional studies with LSD, it was found that LSD increased the response to  only the first stimulus when more intense air-puffs were used (50 psi). Furthermore, when the number of stimuli was increased from 60 to 240 (1 hr) so that appreciable habituation was evident in controls, LSD impaired this habituation. Whereas the response magnitudes of the control group decreased by 70% across the session, the responses of LSD-treated rats decreased by only 32%. These results suggest that LSD and phenylethylamine-derived hallucinogens may differ in their effects on tactile startle responding.


Tolerance development to the biphasic effects of morphine on locomotor activity and brain acetylcholine in the rat. The development of tolerance to the depressant and stimulant actions of morphine on locomotor activity and brain acetylcholine (ACh) utilization (indirect turnover) was investigated in the rat. When administered to nontolerant rats, 1.0 mg/ kg s.c. of morphine produced an increase in locomotor activity and a concomitant increase in ACh utilization. Larger doses produced biphasic effects on locomotor activity, but only 10 mg/kg s.c. resulted in both an initial decrease and subsequent increase in ACh utilization in whole rat brain. The depressant and stimulant actions of morphine on both endpoints were antagonized by 1.0 mg/kg i.p. of naloxone administered 30 min before the maximum effect. Tolerance to morphine was produced by t.i.d. injections of increasing doses. Rapid tolerance developed to the locomotor depressant actions of morphine and to the decrease in brain ACh utilization. Tolerance to the depressant effects resulted in an enhanced stimulant action. Tolerance also developed to the stimulant actions of morphine but only when large doses of drug were administered daily. Biphasic effects of 10 mg/kg of morphine on brain ACh utilization were also observed in the hippocampus, thalamus and hypothalamus. Only a decrease in ACh utilization was observed in the caudate nucleus. Tolerance developed to the decreases and increases in ACh utilization in these discrete brain regions. This study demonstrates that tolerance development to the depressant and stimulant actions of morphine is complex and involves different dose and time schedules. It is not possible therefore to study tolerance to the actions or morphine without specifying the precise endpoint studied and the tolerance schedule utilized.


Tolerance to the effects of baclofen and gamma-butyrolactone on locomotor activity and dopaminergic neurons in the mouse. Acute injections of baclofen or gamma-butyrolactone (GBL) into mice caused dose-dependent depression of locomotor activity and an elevation of the dopamine content and a reduction of dopamine turnover in the brain. An acute injection of baclofen, but not of GBL, was less effective in producing these effects in mice maintained on a diet containing baclofen for 10 to 12 days. This suggests that baclofen and GBL may influence dopamine neurons by different mechanisms. Acute injections of both baclofen and GBL were less effective in producing behavioral and neurochemical effects in mice pre-treated for 13 days with injections of GBL. Tolerance to the behavioral and neurochemical actions of baclofen and GBL do not appear to be the result of metabolic tolerance but possibly result from changes in the properties of the dopamine neurons.


In vivo antagonism by naloxone of morphine, beta-endorphin and a synthetic enkephalin analog. The in vivo equivalent of pA2 values were determined in rat tail-flick and mouse hot-plate tests for naloxone against morphine, beta-endorphin and a synthetic enkephalin analog, (D-Met2,Pro5)-enkephalinamide, as analgesics. In mice the apparent pA2 value of naloxone against morphine (6.86) was similar to that found by previously and essentially the same values were obtained against the opioid peptides, indicating homogenous receptor population for the analgesics studied. In rats the pA2 of naloxone against morphine (7.17) was lower than against either beta-endorphin (7.55) or (D-Met2,Pro5)-enkephalinamide (7.51), warning that in rats such a homogeneity of the "analgesic" receptor population as was observed for mice may not exist.


Alterations in the antagonism by naloxone of morphine-induced respiratory depression and analgesia after morphine pretreatment. Mice were pretreated either acutely or chronically with morphine to test the effect of such pretreatments on the antagonism by naloxone of morphine-induced respiratory depression and analgesia and to compare the development of tolerance to the two effects. A s.c. injection of 20 mg/kg of morphine 6 hr before testing produced a shift of the apparent pA2 of morphine-naloxone for analgesia from 7.05 to 7.33, while the same pretreatment did not change the apparent pA2 for respiratory depression. However, s.c. implantation of a morphine pellet for 72 hr produced a shift in the apparent pA2 of morphine-naloxone for respiratory depression from 7.35 to 7.63, which represents less than a 2-fold increase in naloxone potency. The same pretreatment produced a further shift of the apparent pA2 for analgesia to 7.58, representing a greater than 3-fold increase in naloxone potency. After morphine pellet implantation mice showed a much greater degree of tolerance to morphine-induced analgesia than to respiratory depression. These results provide further evidence that narcotic-induced respiratory depression and analgesia are mediated by different receptor interactions.


Effects of prenatal alcohol exposure on growth and development in rats. Pregnant rats were intubated daily throughout gestation with 4.0 or 6.0 g/kg of ethanol. Pair-fed vehicle-treated, and nontreated rats fed ad libitum served as controls. All pups were removed from their biological mothers at birth and were raised by non-drug-treated surrogate mothers. Ethanol treatment reduced food and water consumption and body weight of pregnant animals relative to nontreated controls. Litter weight but not litter size was reduced in alcohol-treated groups. Pups exposed to the lower dosage regimen exhibited postnatal "catch up" growth, relative to ad libitum controls, but pups from the higher dosage group remained significantly lighter in weight than either their pair-fed controls or ad libitum animals. However, motor activity at 16 and 20 days of age was impaired in both alcohol-treated groups relative to their pair-fed controls. Both alcohol-treated groups also experienced greater postnatal mortality than did pair-fed or ad libitum controls. Since pair-fed animals did not differ from ad libitum controls, and all animals were raised by surrogate mothers, these results cannot be attributed to alcohol-related inhibition of maternal food and water consumption or postnatal maternal factors.


Scanning microfluorimetric studies of anticholinergic drugs in Schistosoma mansoni. A microfluorimetric technique has been used to analyze fluorescence in specimens of Schistosoma mansoni labeled with a dansylated analog of acetylcholine. Anticholinergic drugs inhibit the fluorescent labeling of living specimens. The effectiveness of anticholinergic agents can be expressed as a fractional decrease in observed fluorescence of specimens, and several drugs have been compared in this context. Atropine, eserine, carbachol and mecamylamine block fluorescence only at high concentrations (10(-4)--10(-3) M) while trifluoperazine and hycanthone block strongly at lower concentrations (10(-5) M). The findings reported here suggest that the relative activity of anticholinergic drugs is different in schistosomes and vertebrates.


Reversal of the physiological effects of brief periods of monocular deprivation in the kitten. 1. Five normally reared kittens were monocularly deprived from day 32 to day 42 and then subjected to varying periods (from 6 to 14 days) of deprivation reversal using the technique of reverse suturing. Data obtained from single unit recordings in striate cortex of these kittens were compared to control data from seven normal kittens (aged 32 days to 22.5 weeks) and three normally reared kittens given monocular deprivation from day 32 to day 42. 2. Analysis of cortical ocular dominance patterns in these reverse-sutured kittens revealed a progressively greater shift of influence away from the originally experienced eye and toward the originally deprived eye as the duration of the period of deprivation reversal increased. Most cortical cells were monocularly driven in these animals, but at each stage of the reversal process some binocular neurones were found. 3. The distribution of interocular differences in preferred orientation for binocular cells from these kittens was not significantly different from that for normal kittens, indicating that the pattern of connexions established by the originally deprived eye during reinnervation of striate cortex was very similar to that present before deprivation. 4. Previous studies on reversal of the effects of longer periods of monocular deprivation have indicated that during reinnervation of cortex by fibres representing the originally deprived eye an entirely new and different pattern of connexions is formed. On the basis of these results, it is hypothesized that short-term monocular deprivation causes a reversible silencing of otherwise intact synapses, while terminals are physically disrupted when deprivation is prolonged. 5. This hypothesis is supported by the results of an additional set of experiments in which receptive fields, many of which were highly specific, could be demonstrated for about one-half of the cells studied after removal of the non-deprived eye in two normally reared kittens given 10 days of monocular deprivation beginning on day 32. Similar experiments in two kittens deprived from eye opening to day 42 revealed functional input to less than 20% of the cells studied and no evidence of response specificity.


Cell membrane potential and resistance in liver. 1. Isolated segments of mouse liver were placed in a Perspex bath through which physiological saline solutions of varying composition were circulated. Two microelectrodes were inserted in different liver cells under microscopic control allowing measurement of distance between the two micro-electrode tips. Current pulses were injected through one of these electrodes, causing electrotonic potential changes in nearby cells by current spread through intercellular junctions. These electrotonic potential changes were recorded with the second micro-electrode. The spatial decrement of the amplitude of the electrotonzpotential changes and their dependence on extracellular ion concentrations were analysed by three-dimensional cable analysis, modified to account for the geometry of the tissue. 2. During exposure to control solution the mean resting cell membrane potential was -37 mV, the space constant for intracellular current spread (lambda3 = square root of Rm/chrRi) was 390 micron and Ri, a measure which includes the intracellular resistivity and the junctional resistances, was 1.4 komegacm. From these values, and an estimate of tissue cell membrane density (chi) obtained by others, the specific membrane resistance (Rm) was calculated to be 5.1 komegacm2. 3. Replacement of extracellular Na+ by K+ resulted in a large depolarization and a large decrease in the membrane resistance. Replacement of extracellular Na+ by choline resulted in a small transient hyperpolarization and a small increase in the membrane resistance. Replacement of extracellular Cl- by methylsulphate or sulphate or of NaCl by sucrose resulted in a small transient depolarization and a large increase in the membrane resistance. 4. Glucagon (10(-7) M) and adrenaline (10(-5) M) evoked membrane hyperpolarization and reduction of membrane resistance (Rm). 5. The resting membrane ion conductance can be considered to consist of three components, Cl conductance (GCl), GK and GNa. The results suggest that GCl greater than GK greater than GNa. Changes in extracellular ion concentrations specifically alter the permeability properties of the cell membrane. The glucagon action can be explained in part by an increase in GK.


Properties of two unmyelinated fibre tracts of the central nervous system: lateral Lissauer tract, and parallel fibres of the cerebellum. 1. Monoplar tungsten micro-electrodes were used to stimulate and platinun plated tungsten micro-electrodes to record from single, unmyelinated cerebellar parallel fibres and lateral Lissauer tract axons in cats. 2. Stimulation of the lateral Lissauer tract resulted in the activation of a narrow, longitudinal 'beam', much as on the cerebellar surface. 3. Following impulse conduction, parallel and Lissauer tract fibres showed a supernormal conduction velocity (up to 25% increase) and increased excitability (up to 40% increase). No subnormality was encountered following supernormality. Some Lissauer tract fibres had prolonged relative refractory periods and no supernormal periods. 4. Chronaxies ranged from 155 to 380 microseconds. 5. Single fibres exhibited a remarkable increase in conduction velocity (up to 18% and excitability (up to 40%) following a single subthreshold stimulus. The duration of this effect (up to 20 msec) was much longer than expected from membrane time constant estimates.


Crayfish stretch receptor: an investigation with voltage-clamp and ion-sensitive electrodes. 1. The membrane characteristics of the slowly adapting stretch receptor from the crayfish, Astacus fluviatilis, were examined with electrophysiological techniques consisting of membrane potential recording, voltage clamp and ion-sensitive microelectrodes. 2. The passive membrane current (Ip) following step changes of the membrane potential to levels above 0 mV required more than a minute to decay to a steady-state level. 3. The stretch-induced current (SIC, where SIC = Itotal--Ipassive) was not fully developed until the Ip had decayed to a steady state. 4. With Ip at the steady state and the stretch-induced current at the O-current potential, a slow stretch-induced inward current was isolated. The latter reaches a maximum after 1 sec of stretch and declines even more slowly after stretch. The I-V relation of the slow current had a negative slope and reversed sign near the resting potential. It is suggested that this current is due to a Cl- conductance change. 5. The stretch-induced current, consisting of a rapid transient phase and a steady component can be isolated from the slow stretch-induced current at a holding potential corresponding to the resting potential. 6. The SIC-Em relation is non-linear and reverses sign at about +15 mV. 7. In a given cell, the reversal potential of the stretch-induced potential change obtained with current clamp coincided with the 0-current potential of the stretch-induced current obtained by voltage clamp. The average value from twenty-six cells was +13 +/- 6.5 mV; cell to cell variability seemed to be correlated with dendrite length. 8. Tris (mol. wt. 121) or arginine (mol. wt. 174) susbstituted for Na+ reduces but does not abolish the stretch-induced current. 9. The permeability ratios of Tris:Na and arginine:Na were estimated from changes in the 0-current potential as these cations replaced Na+ in the external medium. The PTris:PNa was somewhat higher (0.31) than the Parginine:PNa ratio (0.25). 10. Changes in the external Ca2+ concentration had no effect on the 0-current potential in Na or Tris saline. However, reducing Ca2+ did augment the stretch-induced current in either saline. A tenfold reduction of Ca2+ increased the conductance (at the 0-current level) about twofold. 11. Intracellular K+ and Cl- activities were obtained with ion sensitive electrodes. The average values from six cells were aiK = 133 +/- 34 mM and aiCl = 15.2 +/- 1.8 mM S.D.). EK was about 20 mV more negative than Em and ECl was about 10 mV more positive than Em. 12. aik and resting Em undergo large changes in K+-free solutions. After 60 min, ak was reduced eightfold and Em was reduced from -67 to -40 mV. Reduced Ca2+ in K+-free augments the rate of these changes. Receptor potential amplitude was also reduced in K+-free solution but could be restored upon polarizing the membrane to the pre-existing resting level.


Some anatomical and electrophysiological properties of tooth-pulp afferents in the cat. 1. The responses of nerves which could be excited by electrical stimulation of the canine tooth-pulp were recorded from the trigeminal ganglion. 2. Preliminary experiments showed that the responses of mandibular canine pulpal afferents were recorded from the postero-lateral part of the trigeminal ganglion whereas the responses of maxillary canine pulpal afferents were recorded from the central part of the ganglion. 3. The conduction velocity differed in various parts of these nerves; the conduction velocity inside the tooth tended to be slower than that from the tooth to the trigeminal ganglion; the mean conduction velocity in the part of the nerve peripheral to the trigeminal ganglion was faster than that in the part central to the ganglion, and in the central part the conduction velocity decreased caudally. 4. Collision experiments combining tooth stimulation and stimulation of sites in the trigeminal sensory nuclear complex were carried out to investigate the projections of individual pulpal afferents. 5. The results of these experiments showed that some tooth-pulp afferents bifurcate and project to both the main sensory nucleus and the nucleus caudalis. For other pulpal afferents only a projection to the main sensory nucleus or the nucleus caudalis could be demonstrated. 6. Pulpal afferents that bifurcated had faster conduction velocities than those for which no bifurcation could be shown.


A comparison of threshold and suprathreshold appearance of gratings with components in the low and high spatial frequency range. 1. The appearance of square gratings with some of their Fourier components missing has been investigated for both threshold and suprathreshold contrasts.2. If high frequency components are removed from a square grating there is only a very small effect on the detection threshold, or suprathreshold appearance, unless the components are visible by themselves.3. If the fundamental frequency is removed from a square-wave grating which has a spatial frequency lower than 1 cycle per degree (c/d) the contrast sensitivity is not altered. This is a generalisation of the Craik-Cornsweet illusion. If the contrast is raised above the detection threshold the grating is indistinguishable from a square grating, unless the contrast is high enough to see the fundamental when it is presented alone.4. If the fundamental is removed from a square grating which has a spatial frequency higher than 1 c/d the contrast threshold and the appearance at all contrasts are changed. At threshold it appears as a sinusoidal grating of three times the fundamental frequency. The threshold is dictated solely by the amplitude of the third harmonic. If the contrast is further raised, so that the fifth harmonic also reaches threshold, the periodictiy of the fundamental is seen.5. Therefore, gratings of many different luminance profiles (including the Craik-Cornsweet profile) all produce the perception of a square grating simply because those missing components which would be required in each case to produce a perfect square are by themselves undetectable. The visual system responds as though hardwired to detect square gratings and edges by means of quasi-Fourier analysis.6. These results are analagous to the missing fundamental, or residue, effect in hearing.


Influence of rate of induction of hypoxia on the ventilatory response. 1. We have studied the influence of rate of induction of hypoxia on the duration of the phases of the respiratory cycle in seven conscious healthy subjects.2. Nine hypoxic procedures were performed on each subject, comprising three different rates of induction of hypoxia each at three different levels of P(CO2). Ventilation vs. arterial O(2) saturation plots were constructed and patterns of response were analysed in terms of ventilation vs. tidal volume and tidal volume vs. inspiratory duration (T(I)) and vs. expiratory duration (T(E)).3. The highest ventilatory responses were observed during steady-state hypoxia when P(CO2) was held at a level similar to the control mixed venous level; progressive hypoxia at this P(CO2) failed to stimulate ventilation to comparable levels. The ventilatory response was not influenced by rate of induction of hypoxia when P(CO2) was maintained at an end-tidal P(CO2) close to the control level.4. As tidal volume increased in response to hypoxia, T(I) and T(E) shortened. The progressive decrease in cycle duration occurred at all levels of P(CO2) and at all rates of induction of hypoxia, but was most marked under eucapnic conditions during steady state.5. It is concluded that steady-state hypoxia may produce a higher ventilatory response than progressive, non-steady-state hypoxia. Inspiratory time shortens as tidal volume increases irrespective of the rate of induction of hypoxia.


Nucleoside and glucose transport in erythrocytes from new-born lambs. 1. Glucose and inosine transport by erythrocytes from new-born lambs and adult sheep were compared. Uptake of both permeants was considerably faster in the new-born. Inosine uptake by erythrocytes from nucleoside-permeable and impermeable lambs were not significantly different at birth. The difference between the two phenotypes was first apparent 30 days after birth.2. The post-natal changes in glucose and inosine transport activity closely paralleled the progressive decrease in the percentage of fetal erythrocytes (i.e. cells containing fetal haemoglobin) in the circulation. Cell fractionation studies confirmed that the permeability changes were directly related to changes in the relative proportions of fetal and adult haemoglobin containing erythrocytes.3. The results demonstrate that fetal cells are highly permeable to both glucose and inosine. These cells are replaced by erythrocytes which contain adult haemoglobin and which have a much lower, but still significant, glucose permeability and either low or negligible inosine transport activity depending on the genotype of the animal.4. Inosine transport by fetal erythrocytes from both nucleoside-permeable and impermeable animals was mediated by a nucleoside transport system which had similar properties to that responsible for nucleoside transport in adult nucleoside-permeable cells. Glucose transport in both fetal and adult cells was highly stereo-specific, indicating the presence of a selective transport system.5. It is suggested that the regulatory mechanism responsible for initiating the switch from fetal to adult haemoglobin synthesis may also be responsible for the changes in glucose and nucleoside transport activity.


The intracellular sodium activity of cardiac Purkinje fibres during inhibition and re-activation of the Na-K pump. 1. The intracellular Na activity, aiNa, of sheep heart Purkinje fibres was continuously monitored using Na+-sensitive glass micro-electrodes. The effects of removal and restoration of external K, and of application and removal of various cardioactive steroids, were investigated. 2. The aiNa increased in K-free solutions and rapidly recovered on addition of external K. The rate of this recovery depended on both the external K concentration, [K]o, and the aiNa. The rate of aiNa recovery was found to be half maximally activated at a [K]o of about 10 mM. If corrections are applied to allow for changes in the net passive Na influx at various [K]o, then this value is increased to approximately 12.5 mM. 3. At a given [K]o, there appeared to be a linear relationship between the rate of aiNa recovery and the level to which aiNa had increased in K-free solution (over the range of aiNa from 7.5 to 31 mM). 4. Addition of the cardioactive steroids strophanthidin, acetylstrophanthidin, actodigin (AY 22,241) or dihydro-ouabain produced rapid changes of aiNa. At low concentrations, these compounds sometimes produced a small decrease in aiNa, while at concentrations above 10(-7) M they produced a dose-dependent increase. 5. The effects on aiNa of both low and high concentrations of all these cardioactive steroids were readily reversible within 120 min. The time course of the aiNa recovery mainly depended on the concentration of the cardioactive steroid applied, and on the level to which aiNa had increased. 6. Upon addition of a cardioactive steroid (above 10(-7) M, aiNa at first increased almost linearly with time. The rates of such an increase were measured during this period at various cardioactive steroid concentrations and used to produce dose-response curves. The concentrations that produced a half-maximum rate of aiNa increase were near to 10(-6) M for strophanthidin and acetylstrophanthidin, but near to 10(-5) M for actodigin and dihydro-ouabain. 7. The mean maximum rate of aiNa increase produced by the addition of a high cardioactive steroid concentration was 0.49 +/- 0.17 mM/min (+/-S.D., n = 21). This would indicate a net passive Na influx into the cells of approximately 2.8 p-mole/cm2sec. 8. This maximum rate of aiNa increase could be achieved by the addition of 10(-5) M-strophanthidin or acetylstrophanthidin, but 10(-4) to 10(-3) M-actodigin or dihydro-ouabain was required to produce a similar rate of increase. 9. The addition of these high cardioactive steroid concentrations produced an initially rapid increase of aiNa. After 15-30 min this aiNa increase slowed considerably. The aiNa appeared to reach a 'plateau' within 2-4 hr at levels much below those predicted for a Na electrochemical equilibrium across the cell membrane.


Intracellular studies of hair cells in the mammalian cochlea. 1. Intracellular recordings were made from inner hair cells in the first turn of the guinea-pig cochlea, the recording sites being confirmed by the injection of Procion yellow dye and subsequent histology. 2. The receptor potential, in response to a pure tone burst, consisted of an AC response which followed the wave form of the stimulus and was analogous to the extracellularly recorded cochlear microphonic and a depolarizating DC response which followed the envelope of the tone burst and was analogous to the extracellularly recorded summating potential. 3. The DC response was broadly tuned at high sound pressure having a maximal amplitude of 27 mV at a sound pressure level of ca. 100 db; however the bandwidth of the response was reduced at lower sound pressure level. Isoamplitude curves for the DC response were indistinguishable from the threshold curves for auditory nerve fibres. 4. The AC response was tuned in a similar fashion to the DC response except that it was attenuated at 6-9 db/octave with respect to the DC response. It is suggested that this difference was due to the effect of membrane capacitance and resistance on the AC response. In contrast the extracellularly recorded AC component was not subject to this attenuation. 5. The total resistance and capacitance in three cells were found to be 46-61 Momega and 7.8-15.8 muF respectively. 6. Intracellular resistance changes were measured during sound stimulation, the resistance change being proportional to the DC receptor potential, indicating constant current flow through the hair cell. The current varied between 0.37 and 0.81 nA between cells. The time constant for seven cells was found to lie between 0.31 and 0.76 msec. 7. A map of the basilar membrane showing position of hair cells against characteristic frequency corresponded to the cut-off frequencies of the basilar membrane mechanical measurements and the innervation sites of spiral ganglion cells.


Reciprocal inhibition during the tonic stretch reflex in the decerebrate cat. 1. The aim of this study was to investigate post-synaptic reciprocal Ia inhibition during the stretch reflex; particularly the extent to which an increased Ia excitation of the Ia inhibitory interneurones will be counteracted by recurrent inhibition from motor axon collaterals. For this purpose we investigated depression of monosynaptic test reflexes antagonist flexors (reciprocal inhibition) during static stretch of quadriceps or triceps surae in unanaesthetized decerebrate cats. 3. With increasing stretch of the extensor muscle there was first a linear augmentation of reciprocal inhibition, but along with the stretch reflex in the extensor a plateau appeared in the inhibition of the flexors, although the extensor stretch reflex (judged by the e.m.g.) increased with further stretching. Within the range of stretching of triceps surae which gave increased stretch reflexes the plateau in the reciprocal inhibition was usually maintained, while during stretching of quadriceps a second phase of augmenting reciprocal inhibition often appeared. Stretch beyond the level which increased the stretch reflex activity gave augmenting reciprocal inhibition both in case of quadriceps and triceps surae. 3. Excitability measurements from central terminals of Ia afferents revealed that the increasing reciprocal inhibition during increasing stretch reflex activity in quadriceps was associated with a primary afferent depolarization in knee flexor Ia afferents; there was no corresponding effect in ankle flexor Ia afferents during stretch reflexes in triceps surae. 4. The primary afferent depolarization evoked in knee flexor Ia afferents by electrical nerve stimulation was then compared with the presynaptic inhibition of knee flexor monosynaptic test reflexes produced by the same stimuli. The results suggest that the second phase of increasing reciprocal inhibition in knee flexors is due to presynaptic inhibition and accordingly that the depth of post-synaptic reciprocal inhibition remains constant at different degrees of stretch reflex activity in both knee and ankle extensors. 5. It is postulated that during increasing stretch reflex activity the increment in Ia excitation and recurrent inhibitio; on to the Ia inhibitory interneurones almost exactly balance each other. It is suggested that recurrent inhibition of Ia inhibitory interneurones may serve as a segmental autoregulatory mechanism to keep 'alpha-gamma-linked reciprocal inhibition' at a constant depth during different levels of agonist activity.


The distribution of motoneurones supplying chick hind limb muscles. 1. The motor nuclei supplying many of the hind limb muscles were localized in late chick embryos (stage 36-37; 10-11 days) by utilizing the technique of retrograde transport of horseradish peroxidase. 2. Each nucleus was found to be localized in a characteristic position in both the rostro-caudal and transverse plane of the spinal cord with only slight individual variation. 3. Each motor nucleus consisted of an elongate, coherent cluster of labelled cells, with few cells occurring outside the cluster. Thus, there did not appear to be extensive overlap of nuclei nor extensive intermingling of motoneurones projecting to different muscles. 4. The position of a motor nucleus in the transverse plane was not correlated with whether its muscle was used as an extensor or flexor; nor were adjacent nuclei necessarily co-activated during normal unrestrained walking movements as deduced from e.m.g. recordings. The position of a motor nucleus also was not correlated in a topographical manner with the adult position in the limb of the muscle to which it projected. 5. Further, while no correlation was found between the rostrocaudal position of a motor nucleus and the embryonic muscle mass from which its muscle was derived, such a relationship existed for the medio-lateral position; all muscles arising from the dorsal muscle mass, regardless of their function or adult position, were innervated by laterally situated motoneurones, all muscles arising from the ventral muscle mass by medially situated motoneurones. 6. It is concluded that motoneurone position is most closely correlated with ontogenetic events presumaeriphery. It can also be inferred that the central connexions onto motoneurones, responsible for their proper activation, cannot be achieved by a simple mechanism based largely on the position of the motoneurone soma.


The development of motor projection patterns in the chick hind limb. 1. Retrograde transport of horseradish peroxidase was used to map the initial projection patterns of lumbosacral motoneurones to the embryonic chick hind limb. 2. The stage 28 segmental projection pattern to each of the four primary muscle masses was characteristic and indistinguishable from the stage 36 projection pattern to the sum of the muscles derived from that mass. In addition, the adductor motoneurone pool was found to be similar in position (both rostro-caudal and mediolateral) at stages 29, 30, 32, 33 1/2 and 36. 3. Therefore axons from lumbosacral motoneurones project for the most part only to appropriate regions from early times shortly after they grow into the limb bud. Furthermore, the attainment of the segmental projection pattern occurs prior to the normal time of, and therefore without the aid of, cell death. This conclusion was supported by electrophysiological recordings made from muscle nerves. 4. A regionalization of the projection patterns within a single muscle mass could be shown both anatomically and physiologically prior to the cleavage of the mass into individual muscles and the projections were in a general way appropriate for the muscles derived from those regions. 5. Therefore the process of muscle cleavage does not in itself create the specific projection patterns observed, and motoneurone axons appear to grow to and to ramify and make synapses only within regions which correspond to their adult muscles. 6. Finally, the termination site of each motoneurone axon in the early limb was found to be tightly correlated in a somatotopic fashion with the position occupied by its soma in the cord. This suggests that some feature of the motoneurone related to its position may be of importance in achieving the specific projection patterns observed.


Mucosal receptors in the gastric antrum and small intestine of the rat with afferent fibres in the cervical vagus. 1. Electrical stimulation of the abdominal vagi revealed that abdominal vagal fibres are distributed throughout the cervical vagal trunk. Conduction velocities of the main group of abdominal fibres ranged from 0.4 to 1.5 m.sec-1. 2. Thirty-seven single afferent fibres, with endings in the gastric and intestinal mucosa, were isolated from the cervical vagus of adult rats. Conduction velocities of eighteen of these endings ranged from 0.5 to 2.5 m.sec-1. 3. Light mechanical stimulation, such as stroking the mucosa, evoked a rapidly adapting response from these endings. Sustained pressure or distension with fluid or air did not excite these endings although excessive stretching of the mucosa excited three units. Balloon distension usually evoked an 'on-off' response due to phasic stimulation of the mucosa by the balloon during inflation and deflation. 4. These same endings also functioned as non-specific, slowly adapting chemoreceptors responding to various organic and inorganic acids, tap water and distilled water, alcohol, hypertonic saline, NaOH, NH4Cl, CuSO4, casein hydrolysate, mustard powder and cayenne pepper. Hypertonic glucose and guinea-pig bile were ineffective as stimuli. 5. In the presence of an excess of chloride ions the effectiveness of acids in stimulating these endings was in part determined by the pK of the acid. However pH per se was not the basic determining factor but rather the molecular size of the acid.


Modulation of single vagal efferent fibre discharge by gastrointestinal afferents in the rat. 1. A single fibre dissection technique was used to record activity from efferent fibres in the left cervical vagus nerve of urethane anaesthetized rats. 2. The efferent discharge, in all units, was modulated by gastric inflation, gastric contractions or compression of the stomach wall. The receptors mediating these effects are the slowly adapting 'in-series' tension receptors in the gastric musculature with afferent fibres in the vagus nerves. 3. Efferent units were classified according to their response to passive gastric distension and active gastric contractions. 4. Four distinct types of efferent unit were isolated. Type I units were excited and Type II units were inhibited by gastric distension and contraction. Type III units were excited at low or moderate levels of inflation and inhibited at high levels of inflation or during gastric contractions. Type IV units were inhibited by low levels of inflation but excited at higher levels. 5. Since there is clearly a reciprocal organization at least of some neurones in the vagal nucleus the possibility of reciprocal control of antagonist, cholinergic and 'purinergic' vagal pathways is discussed.


Amino acid and peptide absorption from partial digests of proteins in isolated rat small intestine. 1. Absorption of each of sixteen amino acids, free and peptide-bound, has been measured in isolated rat small intestine perfused with five partial digests of proteins. 2. At low concentrations net absorption of each amino acid was proportional to its luminal concentration and independent of the nature of the amino acid. 3. A series of first-order multiple regressions was found to describe well the characteristics of absorption. 4. Rate constants for disappearance of free and peptide-bound amino acids from the lumen were closely similar. However, substantial back-flux occurred of amino acids derived from peptide hydrolysis. Hence 60-70% of the amino-N entering the serosal tissue fluid probably had left the lumen as free amino acids. 5. Intact peptides crossed the mucosa during absorption from a soy bean hydrolysate and in substantial quantities during absorption from one casein digest but not from another. With other hydrolysates there was no evidence for passage of peptides to the serosa. 6. In several cases there was a serious discrepancy between the amount of amino-N absorbed from the lumen and the amount accounted for as peptide or free amino acid in the serosal secretion. 7. The characteristics of absorption were similar (apart from the exceptions in 5 above) for all the digests studied except for soy bean hydrolysate.


Relationship of fetal and placental weight in human beings: fetal/placental weight ratios at various gestational ages and birth weight distributions. Two thousand consecutive deliveries occurring over an 11-month period were studied for fetal and placental (F/P) weight characteristics. Infant and placental weight pairs were analyzed according to their gestational ages and growth categories (AGA, SGA, LGA). Graphs were constructed to depict normal placental weight gain and F/P ratio changes over a wide range of gestational ages (23 to 43 weeks). Mean placental weights and F/P ratios continued to increase through 42 weeks' gestation in the AGA and LGA groups, though placental weight showed no change in the SGA group after 36 weeks. F/P ratio continued to increase in the SGA group and was indistinguishable from that of the other two groups. Fetal and placental weight were linearly related in the total sample as well as in the individual growth categories. However, when F/P ratio was plotted against placental weight, the infants were segregated into three completely distinct curves, depending upon their growth characteristics. A wide range of placental weight and f/p ratios existed within all three infant birth weight groups. When one-minute Apgar scores were considered, infants with F/P ratios of greater than 10.00 had significantly higher risks of an Apgar score of less than 6.


Muscle irritation caused by different products containing oxytetracycline. Muscle irritation studies were done in rabbits using 9 different commercial products. Eight products had propylene glycol and 1 had polyvinylpyrrolidone as a vehicle. Macroscopical examination 3,6 and 10 days after intramuscular injection indicated that the irritation caused by the 8 products with propylene glycol as a vehicle were very similar. The product with polyvinylpyrrolidone caused much less damage and healing took place more quickly. Saline used as a control caused no tissue damage.


An introduction to diseases of pigeons in South Africa. The paper mainly deals with racing pigeons. Beginning with organization, importance and cost of the pigeon sport it then details investigational procedures and techniques for drug administration before discussing some of the infectious diseases common in South Africa as well as the problem of poor racing performance.


Ultrastructure of luteolysis induction by prostaglandin F2-alpha in the non-pregnant ewe. Ultrastructural morphology was monitored at intervals of time in corpora lutea of superovulated ewes following treatment with Prostaglandin F2-alpha. Lutein cells displayed an initial increased metabolic rate as marked by lipid accumulation, spherical mitochondria and a high respiratory rate. Three hours following injection, complete disorganisation of the cell was apparent; mitochondria are ruptured and a clear state of autolysis exists. The possible mode of luteolytic action of Prostaglandin F2-alpha in the ewe is discussed.


Heat stress mortality in nicarbazine fed chickens. Significantly higher mortalities were found in nicarbazine fed chickens than in amprolium fed chickens when exposed to the same heat stress conditions.


Meningioma in a dog.

Meningioma in a dog. The history, clinical signs and pathological findings in a 9-year-old Labrador dog with an intracranial tumour, are described. The tumour conformed to the rare meningiothelial meningioma with focal ossification.


[Pathological changes in the tendons of the pectineal muscles in a case of canine hip dysplasia (author's transl)]. This report gives radiological and pathological evidence of bilateral ossification of the aponeurotic tendons of insertion of the pectineal muscles in a dog. This was associated with a severe grade 3 hip dysplasia of which the pathological changes are described. The ossification of the tendons is considered to have resulted from excessive and continous tension of the pectineus muscles. Various aetiological factors are discussed and some substantiation provided for the theory that pathology of the pectineal muscles and their tendons of insertion may be a contributing factor in the pathogenesis of hip dysplasia.


[Gastroscopic photo report of achalasia in the dog]. Five dogs with achalasia were examined pre- and post-operatively. Photos were taken of the diseased oesophagus, cardia, cardia with retroversion and the cardia following surgery. The normal structures are also shown.


The effect of some organophosphorus acaricides and the time of application on larvae of common ticks in the Eastern Cape of South Africa. Mortality curves of larvae of five common tick species dipped in dioxathion, chlorphenvinphos and oxionthiophos are presented. The mortality of three species of ticks were examined at various times of the day. The results showed that at 14h00 the larvae were more sensitive to acaricide treatments than at other times of the day.


Preliminary report on some ultrasonic methods for detecting carotid artery disease. The use of both Doppler and pulse-echoultrasonic equipment for detecting carotid artery disease is discussed. The need for new non-invasive techniques, capable of detecting small stenoses, is demonstrated and the development of two techniques (analysis of blood velocity waveforms and the measurement of arterial wall movement) is described. The arterial wall movement showed no change with disease, but analysis of the blood velocity waveforms proved capable of detecting even minor stenosis in some cases. Methods for confirming these preliminary results are discussed.


Power reclined wheelchair back.

Power reclined wheelchair back. The mechanism herein described is a simple, safe and resonably inexpensive way to add a power reclining feature to an electric wheelchair. Because of its novel linkage arrangement the device is compact and fits within the perimeter of the existing wheelchair without the need to relocate the battery or otherwise alter the chair. It is a device which can increase the independence of those severely handicapped individuals who use electrically powered reclining wheelchairs.


Evaluation of kinetic and energetic parameters of active sodium transport. Active sodium transport is classically analyzed in terms of an equivalent circuit, comprising an active conductance Ka and an electromotive force of sodium transport ENa. Although ENa is commonly considered the driving force of transport, model experiments have suggested that ENa is a composite parameter, incorporating both kinetic and energetic factors. An alternative approach considers both transport and the associated oxidative metabolism in terms of a nonequilibrium thermodynamic (NET) formulation, involving phenomenological coefficients and the affinity A, presumed to represent kinetic and energetic factors, respectively. Model experiments testing the NET formulation suggest that the affinity is indeed an energetic parameter. Calculated values of A in untreated frog skins and toad bladders range from about 20 to 80 kcal per mole of O2 consumption. Assuming a P/O ratio of 3, this range corresponds to about 3--13 kcal per mole of ATP utilization, values compatible with reported direct measurements. Although brief perturbations of transepithelial electrical potential deltapsi resulted in linear current-voltage relationship, indicating constancy of ENa and Ka, 15-min perturbations of deltapsi resulted in nonlinearity, indicating changes in ENa and Ka; perturbations of deltapsi enhancing active transport were associated with decrease of ENa and increase of Ka; slowing of active transport produced the converse effects.


Comparison of toad bladder aldosterone-induced proteins and proteins synthesized in vitro using aldosterone-induced messenger RNA as template. Using double-labeled isotope techniques, it can be shown that aldosterone induces the synthesis of several proteins in the mitochondria-rich (MR) cells of the toad's urinary bladder. Induced proteins have been identified both in the plasma membrane (mol wt = 170,000, 85,000 and 12,000) and the cytosol (mol wt = 36,000, 12,000 and 6,000) fractions of these mucosal cells. We have also shown that aldosterone (Aldo) induces the synthesis of a class of RNA having the properties of messenger RNA (mRNA). mRNA isolated from Aldo-treated mucosal cells was used as template in a cell-free protein-synthesis system prepared from rabbit reticulocytes. Preparations charged with mRNA from Aldo-treated cells synthesized two proteins that were not labeled when mRNA from control tissues was used as template. The electrophoretic mobility of one of these proteins was similar to an Aldo-induced membrane protein (mol wt = 70,000) found in the intact tissue.


Epithelial cell electrolytes in relation to transepithelial sodium transport across toad urinary bladder. Aspects of the relationships between cellular composition and transepithelial sodium transport across toad urinary bladder are reviewed. Changes in cellular sodium produced by amiloride, vasopressin, aldosterone, hypoxia, ouabain, and sodium-free media are consistent with a cellular sodium transport pool. Metabolic studies suggest that this pool gains its sodium from the mucosal medium and that there is little recycling of sodium between cell and serosal medium. One-third of the cellular potassium equilibrates readily with serosal potassium. The rate of exchange of potassium is much less than the rate of sodium transport supporting the contention that sodium transport in this tissue is electrogenic. Studies with 36Cl suggest that chloride does not cross the apical cellular membranes, but exchanges with serosal chloride. Possible relationships between transepithelial sodium transport and cellular volume regulation are discussed.


Physiology of transport regulation.

Physiology of transport regulation. The regulation of biological transport is discussed on the basis of studies on sodium transport through amphibian skin. The following types of regulation are briefly considered: 1) Hormonal regulation 2) Regulation of Na entry by apparent or real saturation of entry path by outside Na 3) Regulation of Na transport by changes in resistance to the counter ion (mostly chloride) 4) Role of cellular Na concentration which may act both by controlling the passive entry of Na and by influencing the pumping rate. 5) Dependence of Na entry upon cell volume. It is shown that a moderate osmotic swelling of ouabain-poisoned skins leads to excessive swelling of the whole epithelium when NaCl is present on the outside. This indicates that cell swelling leads to opening of the Na channels, but it also indicates coupling between the different layers of the epithelium.


Volume changes and potential artifacts of epithelial cells of frog skin following impalement with microelectrodes filled with 3 m KCl. Cells of isolated frog skin epithelium were observed microscopically during impalement with standard microelectrodes of 5 to 20 Momega resistance, filled with 3 m KCl. Impaled cells, as well as some neighboring cells, were seen to swell 10 to 100 sec after impalement, while the negative potential recorded by the microelectrode depolarized (open circuit conditions). Apparently, osmotic swelling of small epithelial cells may be caused by diffusion of KCl from such electrodes. This conclusion is supported by calculations quoted from the literature of KCl loss from microelectrodes. Intracellular recordings from epithelia with destructed cellular membranes gave negative "pre-tip potentials" of up to mV. The potentials could be altered by electrode movement, by decreasing the ambient pH or the tip-pH and by modifying the fixed charges of the tissue chemically. It is shown that even a moderate loss of KCl, which will not result in appreciable swelling, can produce negative potentials in front of the electrode tip if the protoplasm has a high density of negative fixed charges. We suggest the use of 3 m KCl electrodes with resistances above 30 Momega if after impalement compression of intracellular material by the tip can be avoided. Where such compression cannot be avoided, it is best to fill the microelectrode with an isotonic solution which mimics the electrolyte composition of the cytosol.


Distribution and characteristics of the occluding junctions in a monolayer of a cell line (MDCK) derived from canine kidney. On solid substrates MDCK, a cell line derived from normal dog kidney, forms a confluent monolayer that is studded with "blisters". Previous studies with this cell line suggest that these hemicysts develop as a result of active fluid accumulation between cell sheet and substratum. One factor that may determine when and how hemicysts appear only in localized sites is the interruption of occluding junctions in nonhemicyst areas. To study this possibility, we compared the permeability characteristics of the occluding junctions in hemicysts and in an uninterrupted monolayer of MDCK grown on a permeable support of collagen-coated nucleopore filter. The spontaneous electrical potential differences were small, without statistical differences between them. Relative ionic permeability coefficients were evaluated from the voltage deflections to imposed salt gradients or to a single ion substitution across both structures. The results showed that the relative permeability ratios for Na+, K+, choline+, and Cl- were the same in hemicysts and the uninterrupted monolayer. These and other results indicate that the junctional complex encircling the apical surface of a sheet of MDCK cells can provide an effective permeability barrier constituting a true occluding junction with the same properties in hemicyst and nonhemicyst areas.


Hybridization by cosonication of pigeon erythrocyte membrane with exogenous lipid vesicles. Concentrated mixtures of lipid vesicles and pigeon erythrocyte membrane were cosonicated in order to produce functional hybrid vesicles. From the properties of the resulting material, we conclude that hybrids were very probably formed. These properties were as follows: (i) The presence of membrane increased the sonic fragmentability of lipid vesicles. Sonic fragmentability was assessed by measuring sonication-induced release of previously trapped [14C]-choline and trapping of external [3H]-choline. (ii) Space enclosed by lipid was served by the membrane-like properties of 36Cl- permeability and ATP-dependent 45Ca++ uptake activity. (iii) 36Cl-permeability was more readily and fully induced into the more easily fragmented lipid vesicles. Further sonication caused loss of the induced 36Cl--permeability. This loss was less rapid with the less easily fragmented lipid vesicles; i.e., less easily fragmented lipids protected 36Cl--permeability better. (iv) Glycine uptake activity was partially protected from sonic damage by the presence of lipid vesicles. (v) On centrifugation in bovine serum albumin density gradients, cosonicated material showed lipid properties (enclosed choline and 32Pi space and [3H]-cholesterol) and membrane properties (36Cl--permeability and ATP-dependent 45Ca2+ uptake) coinciding at a density intermediate between those reached by separately sonicated membrane and lipid vesicles. (vi) Electron micrographs showed the disappearance of pure membrane-like structures and the appearance of large amounts of new vesicles whose appearance is consistent with a hybrid structure.


The paracellular pathway in toad urinary bladder: permselectivity and kinetics of opening. Determination of serosa-to-mucosa fluxes of Na, K, and Cl yields information about the properties of the shunt pathway in toad urinary bladder. We show that measurement of these fluxes at 30-sec intervals following an abrupt increase in mucosal osmolality yields evidence on the rate of opening of the path and of its permselectivity. The relationship between the fluxes of any pair of these ions indicates that the shunt is paracellular both before and after the increase in conductance effected by hyperosmolality and that the transepithelial PD affects the permselectivity properties (at 0 mV, PK/PNa/PCl=1:0.71:0.57; at + 25 mV, Pk/PNaPCl=1:0.71:0.99). The relationship between any of the fluxes and the total transepithelial conductance is linear and yields an estimate of cellular conductance (the intercept of this regression on the conductance axis) which is in accord with that measured electrically. These studies provide information on tight junction permeability to nonelectrolytes, as well. Finally, they provide new information about the role of the shunt path as a controlling influence on transepithelial sodium transport and raise the possibility that, in both leaky and tight epithelia, differences in transepithelial conductance from tissue to tissue, organ to organ, and species to species may be due, in the absence of edge damage, to changes in conductance of the paracellular pathway.


A model for anomalous rectification: electrochemical-potential-dependent gating of membrane channels. A model is presented for "anomalous rectification" based upon electrical measurements on the egg cell membrane of the starfish. The objective is to postulate a plausible molecular mechanism which yields an expression for the conductance similar to that deduced empirically by Hagiwara and Takahashi (1974), i.e.,: formula: (see text), where B, deltaVh and v are constant, cK is the external K+ concentration, and deltaV (= V - V0) is the displacement of the membrane potential from its resting value. It is shown that a similar dependence of the conductance on deltaV is expected for a particular class of models in which the K+ ions are also implicated in "gating". To give a specific example, we consider the case in which the formation of ion-permeable pores requires a voltage-induced orientation of membrane-bound, electrically-charged groups and subsequent complexation of these groups with the external cations. Furthermore, the proportionality between GK and CK1/2, when the internal K+ concentration is constant, is accounted for by conventional descriptions of the ionic fluxes using Eyring's rate reaction theory. In terms of the present model, B and deltaVh are explicit functions of the internal K+ concentrations and are thus constant only as long as this is unvaried. The particular value of v required to fit the data (v congruent to 8.4 mV) is rationalized by the assumption that each of the orientable groups carries three negative elementary charges. In addition, the predictions of the present model are compared with those deduced from an alternative viewpoint, which is related to Armstrong's "blocking particle hypothesis", in that the probability for opening and closing of the pore is assumed to depend on whether the pore is occupied or empty. Differences and similarities between the two models, as well as ways to discriminate between them, are discussed.


Reversible inhibition of anion exchange in human erythrocytes by an inorganic disulfonate, tetrathionate. Tetrathionate (S4O6--) markedly inhibits anion exchange across the human erythrocyte membrane. This phenomenon has been studied in order to obtain further insight into the mechanism of action of reversible inhibitors, in particular disulfonate inhibitors, of anion exchange. Anion fluxes were measured by tracer techniques at equilibrium. The following results were obtained: Tetrathionate, although an inorganic compound, inhibits the self-exchange of sulfate and of divalent organic anions (oxalate, malonate) noncompetitively at Ki values (less than or equal to 0.5 mM) as yet only observed for amphiphilic inhibitors. The inhibitor is effective only from the outside of the cell. The inhibition is temperature-dependent, Ki increasing by a factor of 5 between 5 and 35 degrees C, and instantaneously and fully reversible. The presence of small monovalent anions (fluoride, bromide, chloride, nitrate, acetate) counteracts inhibition by tetrathionate to a varying and concentration-dependent extent, divalent anions have only a minor effect at high concentrations. Chloride exchange is also inhibited, while glycolate and lactate fluxes are much less sensitive or almost insensitive, in agreement with their alleged transfer by a different transport system. Tetrathionate is unique in its inhibitory action, its structural congeners, peroxodisulfate (S2O8--) and ethanedisulfonate (C2H4S2O6--) are much less effective. The results can be interpreted by assuming that tetrathionate inhibits the movement of anions via the inorganic anion exchange system by binding--in a 1 : 1 stoichiometry--to inhibitory "modifier sites", for which it competes with other anions. These sites are located only on the exofacial surface of the membrane. The high affinity of tetrathionate is probably due to a local excess of pi electrons in the region of its central disulfide bond. These may stabilize the binding by their ability to form electron donor-acceptor complexes with membrane sites, thus compensating for the absence of a hydrophobic binding domain in tetrathionate.


Evidence for a K+, Na+ permeable channel in sarcoplasmic reticulum. Potassium and sodium cation permeabilities of skeletal sarcoplasmic reticulum vesicles were characterized by means of 3H-choline, 22Na+ and 86Rb+ isotope efflux and membrane potential measurements. Membrane potentials were generated by diluting K gluconate filled sarcoplasmic reticulum vesicles and liposomes into Tris or Na gluconate media, in the presence or absence of valinomycin, and were measured using the voltage-sensitive membrane probe 3,3'-dipentyl-2,2'-oxacarbocyanine. About 2/3 of the sarcoplasmic reticulum vesicles, designated Type I, were found to be permeable to Rb+,  K+ and Na+. The remaining 1/3, Type II vesicles, were essentially impermeable to these ions. The two types of vesicles were impermeable to larger cations such as choline or Tris. Both were present in about the same ratio in fractions derived from different parts of the reticulum structure. Studies with cations of different size and shape suggested that in Type I vesicles permeation was restricted to molecules fitting through a pore with a cross-section of 4--5 A by 6 A or more. When vesicles were sonicated, vesicles permeable to K+ decreased more than those impermeable to K+. These data suggest the existence of K+, Na+ permeable channels which are probably randomly dispersed in the intact reticulum structure at an estimated density of 50 pores/micrometer2. The function of the channel may be to allow rapid K+ movement to counter Ca2+ fluxes during muscle contraction and relaxation.


Electrophoretic transport of T1+ in mitochondria. The distribution of T1+ between rat liver mitochondria and the medium was studied; millimolar or smaller concentrations of T1+ were labeled with 204T1. The T1+ distribution responded to transient diffusion potentials in a way that indicated electrophoretic movements of T1+. The diffusion potentials were induced by efflux of K+ in response to addition of valinomycin to nonrespiring mitochondria suspended in a medium with low concentrations of K+ or by efflux of H+ induced by making the medium more alkaline in the presence of a protonophorous (proton-conducting) uncoupling agent. Changes in membrane potential induced by valinomycin were followed with the aid of safranine. T1+ brought about collapse of the diffusion potential. It is concluded that T1+ is able to penetrate the mitochondrial membrane electrophoretically.


Fine structure of the nasal barbel of the channel catfish, Ictalurus punctatus. Ultrathin sections of the nasal barbel of the channel catfish, Ictalurus punctatus, were studied in the electron microscope and the fine structure was compared to that of barbels of other teleosts and to the mandibular (dentary) barbels of I. punctatus. While the overall histology of the nasal barbel is similar to that of barbels described previously, this study revealed far greater cellular complexity and variability than was previously reported. A layer of stratified epidermal cells rests upon a connective tissue dermis containing a cartilage rod, a large number of nerve fibers and numerous blood vessels, fibroblasts and pigment cells. Taste buds are present in the epidermal layer. This layer was found to contain probably 16 kinds of cell types, several of which may represent transitional stages, in addition to taste bud cells. Observations were made pertaining to innervation and cell types in the taste buds. A new terminology for designating the barbels of I. punctatus is suggested.