Human amelogenesis. I: High resolution electron microscopy study of ribbon-like crystals. Ribbon-like crystals, from developing enamel of human fetuses, were studied by high resolution electron microscopy. These crystals were classically described as the first organized mineral formed during amelogenesis. They were characterized by a mean width-to-thickness ratio (W.T-1) of 9.5, and 40% were bent. On lattice images we noted the presence of the central dark line (CDL) associated with white spots. Both structures were found in crystals with a minimum thickness of 8-10 nm. CDLs were localized in the center of the crystals and seemed to be linked to the initial growth process, but their exact structure and function were not fully determined. We were able to study the structure of the ribbon-like crystals with a Scherzer resolution close to 0.2 nm. The good correspondence between experimental and computed images showed that their structure was related to hydroxyapatite (HA). In addition, the presence of ionic substitutions and deficiencies were also compatible with HA. In this study, about 50% of the crystals showed structural defects. Screw dislocations were the most often noted defects and were observed within crystals aligned along five different zone axes. Low- and high-angle boundaries were also detected. Low-angle boundaries, found in the center of the crystals, could thus be related to CDLs and be implicated in the nucleation step of crystal formation, whereas high-angle boundaries could result from the fusion of ribbon-like crystals. Such mechanisms could induce an acceleration of the growth in thickness of the crystal observed during the maturation stage of amelogenesis.


Alterations of the mineralization profile and osteocalcin concentrations in osteoarthritic cortical iliac crest bone. The relation between bone mineralization and osteocalcin content was investigated in iliac crest cortical bone obtained at necropsy in young females and in two groups of elderly women with and without osteoarthritis of the hands evaluated by X-ray. Using density fractionation technique, the bone was separated into fractions of increasing density from 1.72 to 2.30 g/ml. The mineralization profile revealed a significant shift to higher densities in the osteoarthritis cases compared with young adults (P less than 0.005) and age-sex-matched controls (P less than 0.001). The ash, calcium, and phosphorus content of the bone increased with increasing density of the fractions whereas collagen content, measured as hydroxyproline, decreased. The osteocalcin concentration of each fraction was determined in the supernatants obtained after EDTA-extraction in the presence of protease inhibitors. In the young control and osteoarthritis group, the osteocalcin content in the lowest density fractions was higher compared with the older non-osteoarthritic group. Osteocalcin content of the high density fractions, representing highly mineralized osteons, was the same in the three groups studied. These findings support the hypothesis that quality differences in bone may explain the inverse relationship between osteoarthritis and osteoporosis.


Effects of a short course of oral phosphate treatment on serum parathyroid hormone(1-84) and biochemical markers of bone turnover: a dose-response study. To investigate the possible use of oral phosphate as an activator of bone remodeling in coherence treatment of osteoporosis, 82 postmenopausal females, aged 50-75 years, were randomized to treatment with oral phosphate (750, 1500, or 2550 mg/day) or placebo for 7 days and followed for 4 months thereafter. All patients had sustained at least one previous fracture of the distal forearm and had a bone mineral content of the contralateral forearm or bone mineral density of the lumbar spine lower than normal mean for age. Urinary phosphate/creatinine ratio increased in a dose-dependent fashion during treatment (P less than 0.001), whereas no significant changes were seen in serum phosphate or serum calcium. Serum parathyroid hormone (PTH) rose significantly (P less than 0.05) during treatment to a maximum of 36 and 33% in the groups receiving 1500 and 2250 mg/day, respectively, whereas serum 1,25-dihydroxycholecalciferol remained unchanged. In the group receiving 1500 mg/day, mean serum osteocalcin was increased in the period from day 1 to day 28 (P less than 0.05), but no significant changes were observed in urinary hydroxyproline/creatinine ratio, or serum bone alkaline phosphatase. We conclude that a short course of oral phosphate treatment increases serum PTH considerably. Furthermore, 1500 mg/day but not 2250 mg/day increases serum osteocalcin. No clear biochemical evidence, however, of increased activation of bone remodeling could be demonstrated in either group.


Successful treatment of low turnover osteoporosis resulting from prolonged reserpine therapy with intermittent calcitonin and phosphate therapy. Coherence therapy, popularly known by the acronym ADFR (Activate, Depress, Free, Repeat), was designed to increase bone mass in osteopenic patients. Accordingly, we report a case of a hypogonadal male with histologically proven low bone turnover osteoporosis and a progressive vertebral fracture syndrome, who responded favorably to ADFR treatment with the use of salmon calcitonin and inorganic phosphate. Dramatic increments in bone mass were observed during a 68-month period of therapy. Serial quantitative computerized tomography demonstrated a 146% increase from baseline in bone mineral density for the first 30 months of treatment, and dual energy radiography yielded a 36.5% increase for the subsequent 31-68 months. Furthermore, no episode of fracture occurred since coherence therapy was initiated.


Interactions between growth hormone and dexamethasone in skeletal growth and bone structure of the young mouse. The present study investigated the interactions of growth hormone (GH) and glucocorticoid on skeletal growth and bone structure in young mice. The purpose of this study was to examine the possible prevention by GH of the damage inflicted by dexamethasone (Dex) at sites of skeletal growth and ossification. Dex (1 mg/kg) with or without rat GH (rGH) or bovine GH (bGH), 1 mg/kg, was given for 4 weeks, from age 3-7 weeks, to female ICR mice. Tibiae, humerus, and vertebrae were analyzed morphometrically and biochemically. Growth, as determined by the mouse weight, tibial length, and humerus protein content was found to be compromised by dexamethasone. This was prevented by rGH or bGH. The epiphyseal growth plate width, trabecular bone volume, cortical bone width, mineral bone content, and alkaline and acid phosphatase activity were decreased by dexamethasone. These were prevented by rGH or by bGH. The findings of the present study suggest that in the mouse, GH can decrease or even avoid some of the pathological features in growing bones inflicted by high-dose glucocorticoid treatment.


Mechanism of action of beta-glycerophosphate on bone cell mineralization. Experiments were performed to determine whether beta-glycerophosphate (beta-GP) promoted mineralization in vitro by modulating bone cell metabolic activity and/or serving as a local source of inorganic phosphate ions (Pi). Using MC3T3-E1, ROS 17/2.8, and chick osteoblast-like cells in the presence of beta-GP or Pi, we examined mineral formation, lactate generation, alkaline phosphatase (AP) activity, and protein and phospholipid synthesis. Neither beta-GP nor Pi modulated any of the major biosynthetic activities of the bone cells. Thus, we found no change in the levels of phospholipids, and the total protein concentration remained constant. Measurement of lactate synthesis showed that beta-GP did not effect the rate of anaerobic glycolysis. Evaluation of medium Pi levels clearly indicated that beta-GP was hydrolyzed by bone cells; within 24 hours, almost 80% of 10 mM beta-GP was hydrolyzed. It is likely that this local increase in medium Pi concentration promoted rapid mineral deposition. Chemical, energy dispersive X-ray, and Fourier transform infrared analysis of the mineral formed in the presence of beta-GP showed that it was nonapatitic; moreover, mineral particles were also seen in the culture medium itself. Experiments performed with a cell-free system indicated that mineral particles formed spontaneously in the presence of AP and beta-GP and were deposited into a collagen matrix. We conclude that medium supplementation with beta-GP or Pi should not exceed 2 mM. If this value is exceeded, then there will be nonphysiological mineral deposition in the bone cell culture.


Avian osteoblast conditioned media stimulate bone resorption by targeting multinucleating osteoclast precursors. Osteoblasts are thought to secrete factors that regulate the rate of osteoclastic bone resorption. We studied the effect of osteoblast conditioned medium on bone degradation by multinucleated osteoclast-like cells generated in vitro from mononuclear precursors and found that the medium stimulates bone degradation primarily through interactions with osteoclast precursors. The conditioned medium also stimulates expression of the osteoclast-specific antigen 121F. The increased bone degradation, but not increased 121F expression, is due to the conditioned medium maintaining activity of the osteoclast precursors. Although the osteoclast precursors exhibit the DNA fragmentation characteristic of apoptosis, the osteoblast conditioned medium does not prevent such fragmentation. Chicken macrophage growth factor neither mimics nor augments the ability of the conditioned medium to stimulate bone degradation. Studies of osteoclast generation or function should carefully consider whether the effects are dependent on the viability of the resorbing cells.


Light and electron microscopic abnormalities in diastrophic dysplasia growth cartilage. Light and electron microscopic studies of diastrophic dysplasia iliac crest growth cartilage performed on five occasions in two patients from 1 to 10 years of age reveal extensive cell and matrix abnormalities at each time period. Light microscopy shows atypical chondrocytes with extreme variation in size and shape, and premature cytoplasmic degeneration, and formation of target ghost cells. Prominent, densely staining fibrotic foci are present throughout the cartilage. Ultrastructure reveals some structurally intact chondrocytes with a single large fat inclusion, slightly dilated rough endoplasmic reticulum, and abundant glycogen. As early as 1 year of age cystic degeneration of chondrocyte cytoplasm is evident with indistinct organelles seen. The cartilage matrix demonstrates a general increase in fibrous tissue as well as the fibrotic foci. The collagen in these foci is remarkably abnormal. It is composed of short, extremely broad fibrils ranging from 150 to 950 nm in width which are separated at their terminal ends but fused to each other centrally in random fashion. On cross-section there are very few round fibrils but rather a marked irregularity in shape giving the appearance of having fibrils randomly added to others to form enlarged nonuniform fibril aggregates. On longitudinal sectioning, regular cross-banding across the entire fibril width is seen but fibril splitting and aggregation are highly irregular.(ABSTRACT TRUNCATED AT 250 WORDS)


Effect of ipriflavone and estrogen on the differentiation and proliferation of osteogenic cells. The effect of ipriflavone (IP) on the proliferation and differentiation of rat osteoblast-like (ROB) cells and human periodontal ligament fibroblasts (HPLF) was studied in the presence and absence of estrogen. ROB cells were isolated from newborn rat calvaria by sequential collagenase digestion and HPLF from the outgrowth of human periodontal ligament in culture. The alkaline phosphatase (ALP) activity, employed as a marker of bone cell differentiation, was significantly enhanced by IP in both cell types; however, the concentration at which IP had a maximal effect was lower in ROB cells than in HPLF (10(-10) versus 10(-7) M, respectively). Cell proliferation judged by DNA content was either constant (ROB cells) or slightly increased (HPLF) by IP up to 10(-10) M, and decreased significantly above that concentration. In addition, the dose-dependent effect of estrogen on the growth and differentiation of each cell type in the presence and absence of IP was also tested. At the concentrations of IP which showed maximum effects in the induction of ALP, 10(-10) M for ROB cells and 10(-7) M for HPLF, IP inhibited DNA increase in an estrogen-independent manner. Estradiol (10(-11)-10(-9) M) itself increased the growth rate of both cell types significantly in a dose-dependent manner. Regardless of the concentrations of estradiol tested, ALP activities of both ROB cells and HPLF were elevated by the addition of IP. The ratio of ALP in the presence and absence of IP was similar over the range of estradiol concentrations tested.(ABSTRACT TRUNCATED AT 250 WORDS)


Stimulatory effect of ipriflavone on formation of bone-like tissue in rat bone marrow stromal cell culture. The effects of ipriflavone (IP) (10(-5) M) on bone formation were studied in stromal cells from the femoral bone marrow of young adult rats cultured for 21 days in the presence of beta-glycerophosphate and dexamethasone. Stereoscopic microscopy showed nodule formation after 14 days of culturing, and both the number and the size of the nodules increased with time. The alizarin-red-stained calcified area in the nodules in the IP group was nearly 4 times as large as that in the control after 21 days. Light and electron microscopy revealed the presence of many osteoblast-like cells with developed rough endoplasmic reticulum and Golgi apparatus in the nodules in the control group after 14 days, and a collagenous fibril network was seen among the cells. After 21 days, calcification of the dense collagenous fibril network and bone matrix-like tissue were observed in many nodules, resulting in the formation of bone-like tissue containing osteocyte-like cells. In the IP group, the collagenous fibril network area in the nodules was greater than that in the control after 14 days, and a further increase in both the dense collagenous fibril network area and calcified bone-like tissue area was observed after 21 days. These findings indicate that IP stimulates bone-like tissue formation in the rat bone marrow stromal cell culture, suggesting that the promotion of collagen production by osteoblasts is involved in the stimulation of bone-like tissue formation by IP.


Histochemical and fine structural study of bone of ipriflavone-treated rats. Bone labeling, histochemical, and fine structural studies were performed in order to clarify the effects of ipriflavone (IP) on rat bone tissue in vivo and in vitro. Labeling experiments showed a slight increase in bone formation during 3 days' administration. It was also noted that many osteoclasts detached from the bone surface at 1, 2, and 6 hours after administration in vivo. In addition, irregular localization of tartrate-resistant acid phosphatase (TRACPase) activity was observed in osteoclasts. Fine structurally, IP-treated osteoclasts exhibited irregularity in their ruffled borders, as reported in calcitonin administration, and many enlarged rough endoplasmic reticuli and vacuoles were observed. However, osteoclasts at 12 hours after administration, as well as the control, indicated recovery features from the effect of IP. Osteoblast proliferation and differentiation led to increasing alkaline phosphatase activity (ALPase) with time as well as the development of rough endoplasmic reticuli and Golgi apparatus with well-developed fine structure. These findings imply active synthesis of bone matrix. In our in vitro experiment, osteoclasts and osteoblasts displayed histochemical and fine structural characteristics similar to those observed in our in vivo experiment. Moreover, fewer TRACP-positive mononuclear cells were observed after 24-hour culture with IP than with the control. These results suggest that IP inhibits directly and/or indirectly differentiation and activity of osteoclasts and also promotes differentiation of osteoblast-lineage cells and their bone-forming activity.


Effects of ipriflavone on calcitonin synthesis in C cells of the rat thyroid. Ipriflavone is known to stimulate calcitonin (CT) secretion from the thyroid glands of female animals, but the exact mechanism of this action remains unknown. In the present study, an increase of CT production in thyroid C cells of female rats, but not of male rats, was proven immunohistochemically. Furthermore, the parallel increase of CT mRNA in those thyroid glands was confirmed by Northern blot analysis. These results proved that ipriflavone stimulates not only CT secretion but also CT synthesis in thyroid C cells and that the changes were gender dependent (greater in females). In order to investigate the effect of estrogen on the ipriflavone-induced increase of CT in female rat thyroid gland, CT and CT mRNA in the thyroid glands of untreated, ovariectomized, and estrone-treated (postovariectomy) rats were examined by both immunohistochemistry and Northern blot technique. Serum levels of CT and calcium were also examined. Against expectation, estrone failed to produce any significant effect on the ability of ipriflavone to induce CT synthesis and secretion.


Inhibitory effect of ipriflavone on pit formation in mouse unfractionated bone cells. Effects of ipriflavone (7-isopropoxyisoflavone) on osteoclast-induced bone resorption were evaluated using an unfractionated bone cell culture system containing mature osteoclasts from the femur and tibia of newborn mice. When cells were cultured for 4 days on dentin slices in the presence of 5% fetal bovine serum and 10(-8) M 1 alpha, 25(OH)2D3, ipriflavone (3 x 10(-7) -3 x 10(-5) M) inhibited pit formation and caused a decrease in the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs). The lowest significant effect was observed at a concentration of 10(-6) M. Unlike ipriflavone, calcitonin inhibited pit formation 4 days after the culture was started without affecting the number of TRAP-positive MNCs. Ipriflavone still inhibited pit formation when the culture period was 13 days, when new osteoclasts were expected to be formed. These findings suggest that ipriflavone inhibits new osteoclast formation and bone resorption at the cellular level.


Effect of ipriflavone on bone mineral density and calcium-related factors in elderly females. The effects of ipriflavone (7-isopropoxy-3-phenyl-4H-1-benzopyran-4-one) on bone mineral density (BMD) of the 3rd lumbar vertebra and on calcium (Ca)-related factors, including serum calcitonin (CT) levels before and after rapid calcium infusion (4 mg/kg for 5 minutes), were studied in 11 elderly female subjects (80 +/- 2 years of age, mean +/- SE). Ipriflavone (IP) administration (600 mg/day, 7 months) resulted in inhibition of BMD loss in 7 patients (responders, mean change of BMD value 2.2 +/- 2.3%), whereas 4 patients showed a loss of BMD (nonresponders, mean change of BMD value -13.1 +/- 2.6%) compared with pretreatment values. The responder group showed a significant increase in mean pretreatment serum CT levels (from 20 +/- 2 pg/ml to 42 +/- 7 pg/ml, P < 0.05) after treatment with IP, and a significant decrease in the mean basal serum level of corrected Ca (from 9.6 +/- 0.2 mg/dl to 8.7 +/- 0.1 mg/dl, P < 0.01) after treatment with IP; nonresponders did not show these changes. For responders, both the percentage of change and the maximal value of serum CT in response to Ca infusion were maintained at rather high levels, both before and after IP treatment; nonresponders showed almost no response to a stimulation test for CT. These findings suggest that IP inhibits bone loss in elderly female subjects possibly through the mechanism of increasing CT secretion.


Ipriflavone inhibits murine osteoclast formation in vitro. Ipriflavone, one of the isoflavone derivatives, is a therapeutic drug for osteoporosis. The mechanism is thought to be the inhibition of bone resorption. In the present paper, we report that ipriflavone inhibited formation of osteoclasts from murine spleen cells co-cultured with stromal cells cloned from murine bone marrow. In this system, ipriflavone inhibited osteoclast generation in a dose-dependent manner (10(-7)-10(-5) M). Ipriflavone also inhibited prostaglandin E2 production in MC3T3-E1 cells, which are widely employed as osteoblasts. Moreover, ipriflavone inhibited the proliferation of stromal cells (10(-6)-10(-5) M), but not osteoblastic cells. These results suggest that one mechanism for the inhibitory effects of ipriflavone on bone resorption is the inhibition of osteoclast formation through inhibiting prostaglandin E2 production in osteoblasts and thereby suppressing proliferation of stromal cells.


Sex differences in the evolution of the electrocardiographic QT interval with age. To investigate sex differences in the evolution of the QT interval with age. A community-based representative North American population sample of 14,379 children and adults aged from birth to 75 years. The measured QT intervals (QTm) were determined by a computer algorithm and QTm, corrected for heart rate (HR), was expressed as QT index: QTI = (QTm/Tp) x 100, where QTp is the predicted QT from the formula QTp (ms) = 656/(1 + HR/100). The QTI values of females were significantly longer than of males in all age groups from 15 to 50 years tested at yearly intervals. This difference was due to a 20 ms drop in rate-corrected QT values in adolescent males after puberty, whereas QT values of females remained unchanged throughout the growth, maturation and reproductive years. The new QT prediction formula explained 83% of total QT variance in females and 82% in males after adjustment for heart rate and for the observed significant influence of ventricular excitation time (QRS duration) on QT interval in both sexes and a correction for QT age trend in males. The sex difference in the QT interval is due to QT shortening in males after puberty rather than QT prolongation in women during reproductive years. The fact that QRS duration is a significant determinant of the QT interval has important theoretical implications for attempts to model the ventricular repolarization process and it indicates that the traditional concept of reverse sequence of ventricular repolarization is not universally valid in all myocardial regions.


The reuse of cardiac pacemakers.

The reuse of cardiac pacemakers. To provide decision makers with a synthesis of the relevant information concerning the safety of pacemaker reuse, the ethical and legal issues which it raises and the extent of financial savings which may result. Medline data bank and the bibliographies of review articles in English concerning refurbishment and reuse of cardiac pacemakers published up to June 1991. Since 1978, reports of safe reuse of pacemakers have appeared in 11 countries. By 1984, review of nearly 2000 installations had produced no evidence of increased mortality or morbidity. The norms which must be respected to ensure safety are now well-known. The savings that might result from reuse can only be approximated. In Canada in 1989, 8684 pacemakers were installed. Assuming that 20% might be available for reuse, this practice might save approximately $4,000,000 per year to the Canadian health care system. Properly carried out, pacemakers can be reused at an acceptably low risk. Any institution contemplating pacemaker reuse should define and approve appropriate guidelines and protocols governing the process. A registry to document the reuse of pacemakers for the next few years is desirable.


Directional coronary atherectomy at the Toronto and Mount Sinai Hospitals: report of the initial 120 procedures. To assess the procedural success and complication rates of the first 120 directional coronary atherectomy cases performed at two Toronto hospitals. Case series in tertiary referral centres. One hundred and thirteen patients in whom 120 atherectomy procedures were attempted between July 1990 and April 1992. Directional coronary atherectomy. Angiographic success was obtained in 115 of 120 procedures (96%) involving 117 of 123 lesions (95%). Procedural success (angiographic success without death, myocardial infarction or coronary bypass surgery) was obtained in 110 of 120 procedures (92%). Adjunctive balloon angioplasty was required in 20 procedures (17%). There was one death at 36 h in an elderly patient who underwent an emergency procedure while in cardiogenic shock. Periprocedural non-Q wave myocardial infarction occurred in five patients. There were no Q wave myocardial infarctions. Three patients required coronary bypass surgery prior to discharge and vascular complications occurred in five patients. Directional coronary atherectomy can be performed with procedural success and complication rates comparable to conventional balloon angioplasty. Randomized trials are underway to determine if atherectomy results in a lower restenosis rate.


Reverse redistribution on exercise thallium scintigraphy: relationship to coronary patency and ventricular function after myocardial infarction. To define prevalence, pathophysiology and relation to thrombolytic therapy of reverse redistribution (appearance of a new, or worsening of an existing, scintigraphic defect on 4 h delayed images compared with the stress thallium image). Randomized, double-blind, placebo-controlled trial. Referral centre. Sixty-three patients with acute myocardial infarction. Tomographic exercise thallium scintigraphy, radionuclide angiography, and quantitative coronary angiography. Tomographic exercise thallium scintigraphy performed at day 10 revealed fixed defects in 15 patients, reversible defects in 22 patients and reverse redistribution in 26 patients; no difference in treatment assignment (tissue plasminogen activator versus placebo) was found among the three groups. Left ventricular function was similar in patients with fixed or reversible defects and reverse redistribution; global ejection fraction was 48 +/- 14, 51 +/- 10 and 48 +/- 5%, respectively, and regional infarct ejection fraction was 36 +/- 15, 40 +/- 13 and 37 +/- 18%, respectively. However, nitroglycerin administration resulted in a significantly greater improvement in regional ejection fraction in reverse redistribution patients (5 +/- 4%) than that in patients with fixed defect (2 +/- 5%, P < 0.05) or reversible defects (3 +/- 5%, P < 0.05). The infarct-related artery had a greater cross-sectional area in reverse redistribution patients (1.5 +/- 1.42 mm2) compared with those with reversible defects (0.50 +/- 0.26 mm2, P < 0.05), but was similar to fixed defect patients (1.04 +/- 0.88). Reverse redistribution on tomographic thallium scintigraphy is a frequent phenomenon (occurring in 40% of patients following acute myocardial infarction) and is independent of thrombolytic therapy. Patients with reverse redistribution have a more widely patent infarct-related artery and similar ventricular function, but significantly greater functional improvement following nitroglycerin administration compared with those with reversible or fixed defects. These data suggest myocardial salvage within the infarct zone in some patients with reverse redistribution.


Effect of atropine and isoproterenol on tachycardia induction in asymptomatic patients with Wolff-Parkinson-White electrocardiographic pattern. To determine if pharmacological interventions aimed at altering autonomic tone would allow induction of orthodromic atrioventricular reentrant tachycardia in asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. Prospective interventional protocol in consecutive eligible patients. University hospital. Eighteen asymptomatic patients (13 male and five female) with the Wolff-Parkinson-White electrocardiographic pattern without inducible tachycardia in the drug-free state. Electrophysiological assessment was performed at baseline, after intravenous administration of atropine (0.03 mg/kg) and during isoproterenol infusion (0.5 to 2 micrograms/min). Orthodromic reciprocating tachycardia was not inducible at baseline because of absent retrograde accessory pathway conduction in seven patients. In five patients, orthodromic atrial echo beats could be induced (which blocked retrogradely in the accessory pathway in three patients and anterogradely in the atrioventricular node in two). In the remaining six patients, neither orthodromic echo beats nor reciprocating tachycardia could be induced despite intact retrograde accessory pathway conduction. Following atropine administration (mean dose 1.9 +/- 0.3 mg), anterograde and retrograde accessory pathway effective refractory periods decreased from 360 +/- 172 to 284 +/- 62 ms and from 340 +/- 38 to 296 +/- 32 ms, respectively (both P < 0.05 versus control). Orthodromic reciprocating tachycardia was induced in two patients (nonsustained in one). During isoproterenol infusion (mean dose 1.0 +/- 0.3 micrograms/min), anterograde and retrograde accessory pathway effective refractory periods decreased further to 243 +/- 23 and 248 +/- 22 ms, respectively (both P < 0.05 versus after atropine); two further patients had inducible orthodromic reciprocating tachycardia (nonsustained in one). No patient with absent retrograde accessory pathway conduction developed retrograde accessory pathway conduction or reciprocating tachycardia with isoproterenol and/or atropine. Isoproterenol and/or atropine allowed tachycardia induction in four of 18 asymptomatic patients with the Wolff-Parkinson-White electrocardiographic pattern. In the majority of these patients, tachycardia is not inducible because of deficient retrograde accessory pathway conduction which does not improve with autonomic facilitation.


Left main coronary artery dissection during cardiac catheterization. A 70-year-old man with a downward sloping origin of the left main coronary artery developed left main dissection at coronary angiography and died despite emergency coronary by-pass surgery. Autopsy showed that the left main coronary artery had an acute angle take off and dissection had originated at the junction of the superior wall of the left main and the aorta. The combination of left main stenosis secondary to dissection and severe right coronary atherosclerosis had caused circumferential subendocardial left ventricular infarction. The left main coronary artery had mild atherosclerosis and lacked cystic medial necrosis. An angulated left main coronary artery may be a risk factor for dissection at angiography.


Mycobacterium avium-intracellulare endocarditis causing rupture: replacement and repair with aortic homograft. Aortic valve endocarditis with extension to the tricuspid annulus and ventricular septum in an intravenous drug abuser - with Mycobacterium avium-intracellulare identified as the offending organism - forms the basis of this report. The aortic root and ventricular septal defect were successfully repaired using an aortic cryopreserved homograft. This case is of particular interest because M avium-intracellulare has not been recognized as a cause of endocarditis. The incidence of atypical organisms as a cause of endocarditis may increase in the future because of the rise of drug abuse and the acquired immune deficiency syndrome in North America.


Anterior wall myocardial infarction in a 15-year-old diabetic female associated with spontaneously resolving coronary thrombosis. Myocardial infarction is an uncommon event in childhood and adolescence, and only rarely is found to be due to atherosclerotic disease. This report describes a 15-year-old diabetic female with an acute anterior wall myocardial infarction in whom initial coronary angiography showed a thrombus of the proximal anterior descending coronary artery which had resolved spontaneously by the time a follow-up study was carried out six weeks later. None of the usual precipitating causes of myocardial infarction in childhood were found, and repeat angiography did not demonstrate any fixed coronary artery disease. The relevant literature is reviewed and it is speculated that endothelial dysfunction, coronary spasm and altered coagulability may have contributed to the formation of intraluminal thrombus and subsequent infarction in this patient.


Use of transtelephonic electrocardiographic monitoring in children with suspected arrhythmias. Arrhythmias in children can produce various symptoms and their assessment often is difficult with usual methods. Transtelephonic electrocardiographic monitoring was used in 136 symptomatic patients (palpitations [112], syncope [six], chest pain [18]) for a mean duration of 86 +/- 65 days; mean age was 11.1 +/- 4.8 years and 62% were female. Of 398 recordings sent (mean 2.9 per patient) 32 revealed significant arrhythmias (8%). Of the 67 patients reporting symptoms during the recording period, only 24 had documented arrhythmias - 23 supraventricular tachycardia and one junctional tachycardia. The negative predictive value is 100%, compared with a low positive predictive value of 36%; sensitivity and specificity are, respectively, 100 and 62%. Of the 24 patients with documented arrhythmias, 54% were treated versus 13% of those with normal recordings (P < 0.01). At the end of the follow-up (mean duration 1.6 +/- 1.2 years), 63% of the patients with negative recordings had not complained of further symptoms versus 22% of those with documented arrhythmias (P = 0.001). Transtelephonic electrocardiographic monitoring is an important tool for documenting infrequent arrhythmias in children and even more for reassuring the patient and his or her family in the absence of significant arrhythmias.


Time course of myocardial bloodflow changes during healing of myocardial infarct in pigs. To define the time course of changes in bloodflow and microsphere content at intervals between one and 28 days after surgical ligation of the circumflex coronary artery. After the ligation, pigs were assigned to six groups; all pigs in a group were reanesthetized at either one, three, seven, 14, 21 or 28 days post ligation to determine myocardial bloodflow distribution using radionuclide-labelled (15 +/- 2 microns) microspheres. Bloodflow to the infarct zone, 10 mins post ligation, was 7.3 +/- 1.4% of the normal flow. At one and three days post occlusion, infarct bloodflow was about 50% of the 'normal', declining after day 7 to between 20 and 25%. Bloodflow in the noninfarct zone was significantly elevated during the initial 14 days, declining thereafter to within the normal range. Microspheres in the infarct zone injected prior to the occlusion became concentrated and were diluted in the noninfarct zone; the ratio of infarct:noninfarct microsphere content rose progressively, reaching a 2.5-fold rise by day 28. The initial stages of infarct healing are associated with a marked rise in bloodflow with a subsequent fall. A more prolonged augmentation of flow is evident in the noninfarct zone. Microspheres are useful in estimating the relative magnitude of changes in the myocardium accompanying the healing (shrinkage) of the infarct and hypertrophy occurring in the noninfarct zone after a coronary occlusion.


Intraoperative transesophageal echocardiographic demonstration of mitral leaflet tear following resection of a subaortic membrane. A patient developed a tear of the anterior mitral leaflet following surgical resection of a stenotic subaortic membrane. This complication was diagnosed by intraoperative transesophageal echocardiography leading to successful repair of the mitral leaflet tear.


Successful treatment of severe heart failure caused by idiopathic giant cell myocarditis. A 53-year-old woman presented with increasing dyspnea over one month and signs of severe heart failure. A right ventricular biopsy revealed giant cell myocarditis. She was treated with a combination of cyclosporine, imuran and prednisone and improved dramatically--left ventricular ejection fraction increased from 13 to 66%. That such a response is possible has important implications with respect to both the etiology and treatment of this rare disorder.


Thrombolytic therapy for right heart lesions. Thrombolytic agents are accepted therapy for occlusion of coronary and peripheral arteries as well as for venous thromboses. Although the treatment of left heart prosthetic valve thrombosis has been evaluated, there are limited data showing the benefit of thrombolysis of right heart clots. Two patients with past histories of multiple cardiac operations were given fibrinolytic therapy for thrombosis involving right heart structures. The first patient had thrombosis of a prosthetic pulmonary valve. The second patient was a type IB tricuspid atresia who developed a Fontan duct stenosis and right atrial clot. Thrombolytic therapy may provide a safe alternative to surgical intervention for thrombosis of right heart structures and, even when incompletely effective, may provide additional time to prepare patients for surgical correction and possible protection against distal embolization during surgical intervention.


Kallmann's syndrome and dilated cardiomyopathy. A 52-year-old male previously known to have Kallmann's syndrome was admitted with congestive cardiac failure. He was found to have a dilated cardiomyopathy and died despite medical therapy. This report is the first known case of Kallmann's syndrome and dilated cardiomyopathy.


Patients with symptomatic ischemia have larger thallium perfusion abnormalities and more adverse prognosis than patients with silent ischemia. To evaluate the mechanism for silent ischemia and the effect on prognosis. To test the hypothesis that patients with silent (compared with symptomatic) ischemia have less severe ischemia and a more favorable prognosis, the authors prospectively evaluated 152 consecutive patients with a positive exercise electrocardiogram with exercise thallium scintigraphy and followed them for two years. Tertiary care university-based hospital. Asymptomatic patients during the exercise test had a greater exercise duration (9.4 +/- 3.1 versus 6.3 +/- 2.5 mins, P < 0.01), maximal heart rate (155 +/- 20 versus 136 +/- 20 beats/min, P < 0.01), systolic blood pressure (184 +/- 21 versus 176 +/- 23 mmHg, P < 0.05) and double product than patients who were symptomatic with chest pain. Although there was no difference in the magnitude of ST depression, time to ST depression was greater in the asymptomatic (5.6 +/- 2.7 mins), compared with symptomatic (4.6 +/- 2.6 mins), group (P < 0.01). Thallium ischemic score was smaller during asymptomatic ischemia (2.1 +/- 2.7) compared with symptomatic ischemia (3.9 +/- 3.1, P < 0.01). These findings were also demonstrated in a subgroup of 107 patients with both a positive exercise electrocardiogram and positive thallium scan. The patients with asymptomatic ischemia had a two-year cardiac event rate of 5.1% compared with 13.8% in the symptomatic patients (P = 0.065). Patients with asymptomatic ischemia have less severe myocardial ischemia and a better prognosis than patients with symptomatic myocardial ischemia during exercise testing.


In vivo skeletal muscle metabolism during dynamic exercise and recovery: assessment by nuclear magnetic resonance spectroscopy. The purpose of this study was to define temporally phosphorus metabolism and pH in the gastrocnemius muscles of 21 normal adult subjects during rest, dynamic exercise to exhaustion, and early and late recovery. In vivo nuclear magnetic resonance spectroscopy. At rest, the ratio of phosphocreatine to the alpha peak of ATP averaged 2.26 +/- 0.25, the inorganic phosphate to ATP ratio averaged 0.31 +/- 0.08 and pH averaged 7.10 +/- 0.04. The phosphorus metabolites exhibited immediate and progressive changes with exercise, reaching their minimum (phosphocreatine, 0.95 +/- 0.41) or maximum (inorganic phosphate, 1.95 +/- 0.75) values at exhaustion, after an average exercise of 11 +/- 4 mins. In contrast, pH changed slowly during early exercise, but fell abruptly thereafter and averaged 6.76 +/- 0.17 at exhaustion. Phosphocreatine and inorganic phosphate began to return rapidly towards preexercise values immediately on cessation of exercise. However, pH declined further in the period immediately following cessation of exercise, reaching a nadir of 6.56 +/- 0.24 an average of 2 mins into recovery. Exercise duration did not correlate highly with any metabolic variable. The data support the concept that the metabolic physiology underlying physical exhaustion of dynamic exercising muscle is multifactorial. The post exercise drop in pH also suggests that normal subjects have a greater contribution to high energy phosphate production from glycolysis, as opposed to oxidative metabolism, in early recovery.


Comparison of Doppler echocardiography and cardiac catheterization in patients requiring valve surgery: search for a 'gold standard'. To compare the sensitivities of Doppler echocardiography and cardiac catheterization in the diagnosis of severe valvular heart disease in patients requiring valve surgery. Retrospective analysis of Doppler echocardiograms and cardiac catheterizations. Tertiary referral cardiovascular centre in a university setting. Sixty-nine patients undergoing valve surgery between July 1988 and July 1990. The sensitivities of echocardiography and cardiac catheterization were 84 and 87%, respectively (P = 1.0) in 32 patients who underwent aortic valve surgery primarily for severe aortic stenosis; 83 and 67%, respectively (P = 1.0) in six patients with severe aortic regurgitation, and 100 and 85%, respectively (P = 1.0) in seven patients with combined severe aortic stenosis and regurgitation. The sensitivities of echocardiography and cardiac catheterization in 11 patients who underwent mitral valve surgery for severe mitral stenosis were 73 and 91%, respectively (P = 0.6) and 69 and 92%, respectively (P = 0.3) in 13 patients with severe mitral regurgitation. Sensitivities of echocardiography and cardiac catheterization in the diagnosis of severe tricuspid regurgitation in five patients who had tricuspid valve repair were 100 and 80%, respectively (P = 1.0). Two patients with severe aortic stenosis by echocardiography, but not by catheterization, did not undergo aortic valve replacement during valvular surgery; both required aortic valve replacement within two years of initial surgery because of heart failure. Four patients with severe tricuspid regurgitation identified by echocardiography did not have tricuspid repair; three had pulmonary hypertension and these patients had resolution of tricuspid regurgitation on follow-up. One patient with severe tricuspid regurgitation and absence of pulmonary hypertension required reoperation for tricuspid valve repair 10 months after initial operation. The sensitivity of echocardiography and cardiac catheterization in the detection of severe valvular lesions requiring surgery is similar. Discordant results should be reviewed carefully with knowledge of the inherent pitfalls of both techniques in order to ensure optimal patient outcome.


HMG-CoA reductase inhibitors: a look back and a look ahead. This review is a follow-up to the Vancouver Symposium on hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors held in May 1990 (Can J Cardiol 1992;8 [Supplement A]: March 1992). The aim is to provide an update on the issues discussed at the time, focusing primarily on aspects of practical importance for the clinician and new developments. The available literature on HMG-CoA reductase inhibitors from May 1990 to May 1991 was systematically reviewed. The review focuses especially on human studies which provide a better understanding of mechanisms of action, pharmacokinetics, efficacy, safety and tolerance, as well as structure-function relationships. A look back indicates that HMG-CoA reductase inhibitors, as a class, appear to be safe and effective for long term use and constitute a major drug addition for the control of hypercholesterolemia. Combination therapy may enhance effectiveness but close monitoring is needed when used in conjunction with fibrates and nicotinic acid because of potential muscle toxicity. A look ahead uncovers new properties that may be of potential benefit in the treatment of atherosclerosis, hypertension, cholelithiasis, mild renal disease and possibly thrombogenesis and cancer. In view of the fact that the magnitude of low density lipoprotein cholesterol lowering is commensurate with the degree of atherosclerosis regression, HMG-CoA reductase inhibitors provide a unique tool for the control of aggressive atherosclerotic vascular disease and for secondary prevention of coronary artery disease.


Reset of the osmotic threshold for vasopressin in rats fed a low NaCl, K-free diet. Activation of the renin-angiotensin system induced by feeding a low NaCl, K-free (LS) diet is associated with polydipsia and a chronic reduction in effective plasma osmolality (efPosm). We have recently shown that converting enzyme inhibition with enalapril (EP) abolishes polydipsia. The present study was designed to test the hypothesis that the osmotic threshold for vasopressin is reset in rats fed the LS diet and to examine the effect of EP on ambient and osmotically stimulated plasma vasopressin levels (PAVP). Animals were fed the LS diet or a control salt diet and treated with vehicle or the lowest dose of EP sufficient to prevent polydipsia (7.5 mg.kg-1.day-1) in rats fed the LS diet. PAVP and efPosm were measured under ambient conditions and after osmotic loading. Urine osmolality (Uosm) was measured under ambient conditions and after water loading. The chronic reduction in efPosm in LS rats was associated with the excretion of a Uosm 1-2 times greater than the corresponding Posm, PAVP similar to controls (LS, 2.27 +/- 1.08 vs. control, 1.19 +/- 0.22 pg/mL) and the ability to excrete a water load. Following osmotic loading, efPosm and PAVP increased significantly and similarly in both LS and control rats. EP administration had no effect on water intake, ambient efPosm and PAVP, and the AVP response to osmotic loading in rats fed the control diet. EP prevented polydipsia in LS rats, however it had no significant effect on ambient or osmotically stimulated PAVP or efPosm.(ABSTRACT TRUNCATED AT 250 WORDS)


Normal blood flow but lower oxygen tension in diabetes of young rats: microenvironment and the influence of sympathectomy. Studies of rats with experimental streptozotocin (STZ)-induced diabetes at 4 months have identified sciatic nerve trunk oligemia and hypoxia, but it is uncertain how early these abnormalities develop or which develops first. We studied young (4-week-old) rats after 6 or 16 weeks of STZ-induced diabetes (or after citrate buffer injection in controls) by recording multi-fiber conduction in three different nerve territories and by measuring sciatic endoneurial blood flow (NBF) and oxygen tension (PnO2) at end point. To evaluate the impact of sympathectomy on this diabetic model, separate animal groups were treated for 5 weeks with guanethidine monosulfate given at the onset of diabetes (group 1, end point 6 weeks) or after 6 weeks of diabetes (group 2, end point 16 weeks). Diabetes was associated with deficits in sensory and motor caudal conduction and increased resistance to ischemic conduction failure (RICF). NBF was comparable to control animals at both time points and was within the published normal range of NBF. In contrast, oxygen tensions were shifted to lower values in diabetic animals. Sympathectomy was associated with blunting of the RICF increase in group 2 but worsened caudal sensory conduction despite evidence of modest improvement in sciatic nerve oxygenation. Our findings support the concept that neuropathy occurs early in diabetes and that hypoxia develops before oligemia. Sympathectomy did not benefit this diabetic model.


Influence of pregnancy on mean systemic filling pressure and the cardiac function curve in guinea pigs. To assess the degree of circulatory fullness and to evaluate the influence of peripheral and cardiac factors in the regulation of cardiac output during pregnancy, the following studies were conducted using pentobarbital-anesthetized, open-chest nonpregnant and late term pregnant guinea pigs. Mean circulatory filling pressure was taken as the equilibrium pressure when the pulmonary artery was constricted. Total vascular compliance was assessed by +/- 5-mL changes in blood volume performed while this constriction was maintained. A separate group of guinea pigs was prepared with a pulmonary artery electromagnetic flow probe and right atrial catheter. Rapid infusion of saline was used to increase right atrial pressure while the cardiac output was determined. Pregnancy was characterized by the following changes relative to nonpregnant controls: 51Cr-labelled RBC blood volume increased from 55 +/- 3 to 67 +/- 3 mL/kg; mean circulatory filling pressure increased from 7.1 +/- 0.2 to 8.0 +/- 0.5 mmHg (1 mmHg = 133.322 Pa); right atrial pressure decreased from 3.4 +/- 0.2 to 2.1 +/- 0.3 mmHg; and cardiac output increased from 71.8 +/- 3.9 to 96.8 +/- 3.3 mL.min-1.kg-1. Total vascular compliance was not changed (2.1 +/- 0.1 mL.kg-1.mmHg-1) and most of the expanded blood volume was accommodated as unstressed volume. The cardiac function curve was shifted upwards in pregnant animals. The resistance to venous return, as determined from the slope of the venous return curves, was not changed. These data suggest that the circulation of the pregnant guinea pig is slightly overfilled.(ABSTRACT TRUNCATED AT 250 WORDS)


Effect of omega-3 fatty acids, docosahexaenoic and eicosapentaenoic, on norepinephrine-induced contractions. The relaxant responses of the rat thoracic aorta to omega-3 fatty acids, docosahexaenoic and eicosapentaenoic, on norepinephrine- and potassium-induced contractions were investigated. Relaxation was enhanced in vessels contracted with norepinephrine. Docosahexaenoic acid at concentrations as low as 1, 3, and 10 microM evoked significant relaxant responses (15, 23, 30%) in norepinephrine-contracted vessels as compared with responses (5, 9, 12%) in potassium-contracted vessels. Results for eicosapentaenoic acid under similar conditions were 3, 8, and 19% in norepinephrine-contracted vessels and 3, 3, and 8% in potassium-contracted vessels. Pretreatment with eicosapentaenoic (10 microM) or docosahexaenoic acids (1-10 microM) decreased the contractile response to physiologic concentrations of norepinephrine. In the presence of calcium-free medium, the omega-3 fatty acids (1-30 microM) significantly abolished sustained norepinephrine contractions but did not reduce the phasic contractions when incubated prior to norepinephrine contraction. Comparatively, the effects of docosahexaenoic acid were greater than eicosapentaenoic acid. These findings suggest that the relaxant effects of the omega-3 fatty acids are specific to the mode of contraction, i.e., alpha-adrenoceptor stimuli. This effect may be related to intracellular calcium mechanisms, since both fatty acids reversed norepinephrine-induced sustained contractions in the absence of extracellular calcium.


Comparison of the release of vasoactive factors from venous and arterial bovine cultured endothelial cells. The release of endothelium-derived relaxing factor (EDRF), prostacyclin (PGI2), and endothelin-1 (ET-1) was measured from endothelial cells (EC) cultured from either bovine vena cava (BVCEC) or bovine aorta (BAEC). EDRF release was determined by using the superfusion bioassay technique, whereas ET-1 and PGI2 were measured by specific radioimmunoassays. Bradykinin (BK) (0.05-30 pmol) given through columns of venous or arterial EC induced a dose-dependent release of EDRF. BK (0.05 pmol) evoked a release of EDRF from venous EC that was similar to the effect of a dose of 1 pmol from arterial EC. As with BAEC, infusions of NG-monomethyl-L-arginine (30 microM) caused an inhibition of EDRF release from BVCEC that was partially reversed by coinfusions of L-arginine (L-Arg; 100 microM). BK also induced a dose-dependent release of PGI2 from BVCEC. BVCEC and BAEC produced PGI2 in equivalent amounts when arachidonic acid (9.2 and 32 pmol) was added to the Krebs' solution perfusing the cells. BVCEC and BAEC released detectable amounts of ET-1 (0.4 +/- 0.1 and 0.9 +/- 0.3 ng/mL, respectively), over a 4-h period, and the release of ET-1 was increased approximately twofold by coincubations with thrombin (0.05-1 U/mL). These findings demonstrate that venous EC have a similar capacity to arterial EC to release vasoactive factors, thus supporting the hypothesis that veins have a functional endothelium that may modulate venous tone and platelet function.


Role of corticosteroids in distal acidification of amiloride-treated rats. The role of amiloride-dependent sodium channels in the action of adrenal cortical steroids on urine-blood PCO2 (U-B PCO2) differences was studied in bicarbonate-infused and amiloride-treated adrenalectomized rats. U-B PCO2 was significantly reduced by amiloride in bicarbonate-infused control rats. Adrenalectomy further reduced U-B PCO2 in amiloride-treated, bicarbonate-infused rats (from 27.9 +/- 1.82 mmHg in sham-operated rats to 21.3 +/- 1.58 mmHg in adrenalectomized (ADX) rats) (1 mmHg = 133.322 Pa). Acute administration of corticosterone and 18-hydroxycorticosterone (18-OH-B), but not of aldosterone, caused recovery of U-B PCO2 to the level of sham-operated animals treated with amiloride. Aldosterone did not affect U-B PCO2 in the presence of amiloride (21.9 mmHg ADX group vs. 20.98 mmHg aldosterone group). Results are compatible with aldosterone affecting distal H ion secretion mostly by a sodium and potential difference dependent mechanism, while corticosterone and 18-OH-B should act by other mechanisms (e.g., increased luminal buffer level).


Hypertension during chronic exposure to cold: comparison between Sprague-Dawley and Long-Evans strains. It is now well established that chronic exposure of rats to cold (5-6 degrees C) induces an elevation of systolic, diastolic, and mean blood pressures and cardiac hypertrophy within 3 weeks. Since rats of the Long-Evans (LE) strain are known to be resistant to the induction of deoxycorticosterone salt induced hypertension, their cardiovascular responses to chronic exposure to cold were compared with those of rats of the Sprague-Dawley (SD) strain. The results of these studies revealed clear differences between the LE and SD strains of rats. Thus, rats of the SD strain had a significant elevation in their blood pressure; a significantly increased urinary output of norepinephrine and epinephrine; a significantly greater dipsogenic responsiveness to acute administration of angiotensin II, and significant increases in weights of the heart, kidneys, adrenals, and brown adipose tissue compared with their warm-adapted controls. All of these changes are characteristic of rats acclimated to cold. In contrast, rats of the LE strain appear to be less responsive to cold in that blood pressure failed to rise as sharply and to attain as high a level. Furthermore, urinary outputs of norepinephrine and epinephrine were significantly lower in cold-treated rats of the LE strain compared with cold-treated rats of the SD strain, but dipsogenic responsiveness to angiotensin II was unchanged. Although increases in the weight of the previously mentioned organs were also observed in cold-treated rats of the LE strain compared with their warm-adapted controls, weights of the heart and interscapular brown adipose tissue of both groups were significantly less than those of counterparts of the SD strain.(ABSTRACT TRUNCATED AT 250 WORDS)


Intratracheal injection of nickel chloride and copper-zinc superoxide dismutase activity in lung of rats. Superoxide radical (O2-) is a free radical that may be involved in various toxic processes. Cu--Zn superoxide dismutase catalyses the dismutation of the superoxide free radical and protects cells from oxidative damage, and it has been used clinically. The concentration of Ni2+ and Cu--Zn superoxide dismutase activity were measured in lungs of rats at time intervals of 5, 12, 19, 26, 33, and 40 days following an intratracheal injection of 127 nmol of NiCl2. Nickel chloride increased nickel content and resulted in a significant increase of Cu--Zn superoxide dismutase activity in lungs. This elevation of Cu--Zn superoxide dismutase activity was highest on the 12th day (approximately threefold) and is at levels comparable to controls rats on day 40 onwards. Since Cu--Zn superoxide dismutase activity was increased in lung throughout our experimental period without corresponding increases of Cu2+ and Zn2+, we speculate that the elevation of Cu--Zn superoxide dismutase activity might be due to an increased half-life of the enzyme, induced by nickel.


Competitive antagonism of pressor responses to angiotensin II and angiotensin III by the angiotensin II-1 receptor ligand losartan. Losartan (DuP 753) and PD123177 are nonpeptide angiotensin (ANG) receptor ligands for subtypes of ANG II receptors ANG II-1 and ANG II-2, respectively. We examined the effects of losartan and PD123177 on dose - mean arterial pressure (MAP) response curves for ANG II and ANG III in eight groups (n = 6 each) of conscious rats. Saline (0.9% NaCl), losartan (1 x 10(-6) and 9 x 10(-6) mol/kg), and PD123177 (2 x 10(-5) mol/kg) were i.v. bolus injected 15 min before the construction of ANG II dose - response curves in groups I, II, III, and IV, respectively. Groups V-VIII were treated similarly to I-IV except that ANG III was given in place of ANG II. Losartan dose dependently shifted the dose-response curves of ANG II and ANG III to the right with similar dissociation constants (-log KI of 6.6 +/- 0.7 and 6.6 +/- 0.1 mol/kg, respectively) and no change in the maxima. PD123177 affected neither maximum MAP nor ED50 values for ANG II or ANG III. Our results show that losartan but not PD123177 is a competitive antagonist of the MAP effects of ANG II and ANG III.


Production of tumour necrosis factor by cells exposed to sulphonamide reactive metabolites. Hypersensitivity reactions are the most common adverse events associated with therapy with the sulphonamide antibiotics. These reactions have been shown to occur among individuals with pharmacogenetically determined differences in the capacity of their cells to detoxify reactive products of oxidative metabolism of the sulphonamides. These reactions appear to be propagated by an inflammatory response by the immune system. To investigate the role of the cytokine tumour necrosis factor (TNF-alpha) in these reactions, we studied the production of TNF-alpha by peripheral blood mononuclear cells (PBMCs) that had been incubated with sulfamethoxazole and murine microsomes in the presence and absence of a microsomal-activating system and TNF-alpha production by PBMCs in the presence and absence of the hydroxylamine derivative of sulfamethoxazole. The PBMCs showed a time-related increase in the production of TNF-alpha. There was no increase in TNF-alpha production seen during incubation with sulphonamide reactive metabolites; rather, there was a decrease in TNF-alpha elaboration that was most marked when PBMCs were incubated with the hydroxylamine of sulfamethoxazole. There is no evidence from these in vitro studies that TNF-alpha is involved as a mediator of the inflammatory response in sulphonamide hypersensitivity adverse drug reactions.


Digitaloid pregnanes promote potassium-sparing diuresis in the guinea pig. The synthesis of 17 alpha-acetoxy-3 beta-[(beta-D-glucopyranosyl)oxy]- 6 alpha-methylpregn-4-en-20-one, the glucoside of medroxyprogesterone acetate (MPA-glu), is described. MPA-glu and 14-amino-20 beta-hydroxy-3 beta-[(alpha-L-rhamnopyranosyl)oxy]-5 beta, 14 beta-pregnane (LND 623), pregnane glycosides that bind to the digitalis receptor, and digoxin, a cardiac glycoside, were infused intravenously into the anesthetized guinea pig. Each of the three steroids significantly enhanced urinary volume and sodium excretion without affecting blood pressure and creatinine clearance. Potassium excretion was markedly enhanced by digoxin but unaffected by MPA-glu or LND 623. These observations conform to previous work that demonstrated, in the rat, potassium-sparing diuresis by the glucoside of 14 beta-hydroxyprogesterone, a cardiotonic pregnane. There is a dissociation between potency to inhibit [3H]ouabain binding and the extra ATPase actions of the digitaloid pregnanes.


Differential effects of blood insulin levels on microsomal enzyme activities from hepatic and extrahepatic tissues of male rats. Microsomal glutathione S-transferase, UDP-glucuronyl transferase, and aniline hydroxylase activities were determined in liver, renal cortex, and small intestine of control, streptozotocin-diabetic, alloxan-diabetic, and untreated insulin-injected male Wistar rats. Renal microsomal glutathione S-transferase activity showed a direct linear relationship with insulin blood levels, in agreement with our previous report on cytosolic glutathione S-transferase. This result suggests a possible regulatory mechanism of insulin that needs to be further examined. The hepatic microsomal UDP-glucuronyl transferase was only decreased in streptozotocin-diabetic rats and was not restored by insulin treatment. Intestinal UDP-glucuronyl transferase exhibited an opposite response in streptozotocin-treated animals that was not normalized by the administration of insulin. Hepatic aniline hydroxylase showed the same behaviour as intestinal UDP-glucuronyl transferase. These results suggest that streptozotocin and (or) its metabolites have a direct effect on hepatic and intestinal UDP-glucuronyl transferase activity and on hepatic aniline hydroxylase activity. On the other hand, insulin regulation of enzyme activity varies from one organ to another.


Anatomy of the renal innervation: intrarenal aspects and ganglia of origin. The intrinsic innervation of the kidney is described based on studies using ultrastructural, fluorescent, immunocytochemical, and autoradiographic techniques. The efferent sympathetic innervation reaches all the segments of the renal vasculature and to a much lesser extent the tubular nephron. The afferent renal nerves are localized predominantly in the pelvic region, the major vessels, and the corticomedullary connective tissue. The pathways of the renal innervation to the corresponding ganglia, as reported from observations resulting from the combination of axonal transport labeling and immunocytochemical methods, are presented. In the rat the ganglia of origin of the sympathetic efferent innervation include T13-L1 ipsilateral and contralateral paravertebral ganglia and the prevertebral superior mesenteric and celiac ganglia. The sensory afferent innervation presents a different segmental distribution of the dorsal root ganglia for the right and left kidney. For the left kidney, the corresponding ganglia extend from T8 to L2 with the greatest numbers in T12 and T13. For the right kidney, ganglia as high as T6 and as low as L2 harbor neurons innervating the kidney. Current knowledge of the anatomical bases of the function of the renal nerves is discussed.


Neuronal control of the kidney: contribution to hypertension. The renal nerves contribute to hypertension in experimental models of the disease, and appear to play a role in human hypertension. Several lines of evidence indicate that both in spontaneously hypertensive rats and in deoxycorticosterone acetate--NaCl rats, the full development of hypertension is dependent on renal efferent nerves and their induction of excess sodium retention. Renal sensory (afferent nerve) feedback to the central nervous system does not contribute to either of these forms of hypertension. In contrast, renovascular hypertension in rats and aortic coarctation hypertension in dogs are mediated, at least in part, by overactivity of renal afferent nerves and a resultant increase in systemic sympathetic nervous system activity. These forms of hypertension are not associated with sodium retention, and selective sensory denervation of renal afferent nerves by dorsal rhizotomy and total renal denervation result in similar reductions in hypertension. Surprisingly, the renal nerves do not contribute to dietary NaCl exacerbated hypertension in the spontaneously hypertensive rat, dietary NaCl-induced hypertension in the Dahl NaCl-sensitive rat, or the chronic hypertensive and nephrotoxic effects of cyclosporine A therapy in the rat, despite the finding that in all three forms of hypertension, overactivity of the sympathetic nervous system is prominent. Clinical studies indicate that the renal afferent and efferent nerves contribute to hypertension of different etiologies. Together these data point to the complex role that the renal nerves likely play in human essential hypertension.


Central peptidergic mechanisms controlling reproductive hormone secretion: novel methodology reveals a role for the natriuretic peptides. A variety of neural factors can influence reproductive hormone secretion by neuromodulatory actions within the hypothalamus or neuroendocrine actions within the anterior pituitary gland. Passive immunoneutralization and antagonist administration protocols have suggested physiological roles for a number of these factors; however, both experimental approaches have severe technical limitations. We have developed novel methodology utilizing cytotoxin cell targeting with neuropeptides linked to the toxic A chain of the plant cytotoxin ricin. With this methodology we can target and destroy in vivo or in vitro cells bearing receptors for that peptide. Ricin A chain conjugated to atrial natriuretic peptide (ANP), a neuropeptide known to pharmacologically inhibit luteinizing hormone-releasing hormone (LHRH) release, was injected into the cerebroventricular system of intact, cycling rats and ovariectomized rats. Cytotoxin conjugate treatment significantly lengthened the estrous cycle. In ovariectomized rats the luteinizing hormone surge induced by steroid priming was completely inhibited. LHRH content of the median eminences of these rats was not significantly altered. These data suggest that ANP binding to clearance receptors in the hypothalamus displaces the C-type natriuretic peptide (CNP) from the shared clearance receptor, making more CNP available to inhibit LHRH release. In the absence of cells bearing the clearance receptor all available CNP binds to the ANPR-B receptor and exerts its effect via an inhibitory interneuron, since LHRH fibers are spared by this treatment.


Central actions of angiotensin in cardiovascular control: multiple roles for a single peptide. Angiotensin II (ANG II) acts peripherally as a hormone, with actions on the vasculature, adrenals, and kidney. In addition, certain actions of ANG II in the central nervous system are directed toward cardiovascular control and fluid volume homeostasis. Dense binding sites for ANG II are found at circumventricular organs, which apparently have the ability to relay information to cardiovascular centers via neural circuitry. Microinjection of ANG II into the subfornical organ (SFO) or area postrema (AP) produces site-specific increases in blood pressure. In addition, electrophysiological studies demonstrate profound effects of ANG II, acting at the SFO, on activity of neurohypophysial neurons and release of oxytocin and vasopressin, which can be antagonized by ANG II blockers or attenuated by SFO lesions. Evidence from microinjection, electrophysiological, and lesion studies indicate a complex interaction between central sites involved in mechanisms of cardiovascular control: the SFO, AP, organum vasculosum of the lamina terminalis, and paraventricular and supraoptic nuclei of the hypothalamus. Not only is ANG II a humoral messenger in this central scenario, but evidence suggests it acts as a neurotransmitter or neuroendocrine substance within specific CNS pathways, suggesting multiple roles for this peptide in central cardiovascular control.


Central arginine vasopressin and endogenous antipyresis. Arginine vasopressin (AVP) is a centrally synthesized nonapeptide that exerts classical endocrine effects as well as a host of centrally mediated actions. A strong case can be argued in support of a neurotransmitter-neuromodulator role for AVP. Acting within the central nervous system (CNS), AVP has been demonstrated to be involved in the modulation of febrile body temperature. Because AVP acts to reduce pyrogen-induced fevers, but not normal body temperature, its actions are deemed to be antipyretic. However, to demonstrate an endogenous antipyretic function, AVP must be shown to be active during conditions where fever is naturally suppressed. This review will focus on five such conditions where the absence of pyrogen-induced fever can be linked to the endogenous activity of AVP within the brain. In the neonatal rat pup, the use of specific antagonists to the AVP receptor has revealed a role for CNS AVP in the absence of fever following peripheral injections of bacterial endotoxin. These results may help to explain a similar lack of fever in other newborn species. In parturient animals a reduced or absent febrile response has been linked to the increased presence of AVP within the septal area of the brain. The combined use of AVP receptor antagonism as well as immunohistochemistry has shown enhanced AVP activity within the ventral septal area of the rat and guinea pig brain during tolerance to intravenous pyrogens. These results suggest that the mechanism of fever suppression following repeated systemic injections of bacterial pyrogen includes centrally acting AVP.(ABSTRACT TRUNCATED AT 250 WORDS)


Investigating the role of angiotensin II in thirst: interactions between arterial pressure and the control of drinking. Several lines of evidence suggest that angiotensin II plays a physiological role in the control of thirst. Establishing that, however, has been surprisingly difficult, given our current knowledge about the renin-angiotensin systems in the circulation and the brain and the variety of techniques available to measure and manipulate them. A major problem is that stimulating or blocking the renin-angiotensin system affects several physiological variables simultaneously. Since several of these variables also influence the controls of water intake directly or indirectly, the interpretation of the effect on drinking becomes more difficult. To illustrate the problem and recent developments, this paper describes some of the interactions between the effects of angiotensin II on arterial pressure and thirst, and it shows how they have contributed to the controversy over the physiological role of the peptide.


Studies of the inhibitory activity of MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-indol- 2-yl]-2,2-dimethyl propanoic acid) on arachidonic acid metabolism in human phagocytes. We have investigated the inhibitory activity of compound MK-0591 (3-[1-(4-chlorobenzyl)-3-(t-butylthio)-5-(quinolin-2-yl-methoxy)-i ndol-2- yl]-2,2-dimethyl propanoic acid) on 5-lipoxygenase (5-LO) product synthesis in various human phagocytes stimulated with either the ionophore A23187, opsonized zymosan (OPZ), platelet-activating factor (PAF), or formyl-methionyl-leucyl-phenylalanine (fMLP). The lipoxygenase products were analyzed by reversed-phase HPLC. MK-0591 inhibited the formation of 5-hydroxyeicosatetraenoic acid, leukotriene (LT) B4, its omega-oxidation products, and 6-trans-isomers with IC50 values of 2.8-4.8 nM in A23187-stimulated neutrophils. In these conditions, arachidonic acid at a concentration of 10 microM had no effect on MK-0591 inhibitory activity. In neutrophils stimulated with OPZ, the synthesis of LTB4, its omega-oxidation products, and 6-trans-isomers was inhibited with IC50 values of 9.5-11.0 nM. MK-0591 inhibited 5-LO product synthesis in A23187-stimulated blood monocytes, eosinophils, and alveolar macrophages with IC50 values of 0.3-0.9, 3.7-5.3, and 8.5-17.3 nM, respectively. In neutrophils primed with granulocyte--macrophage colony-stimulating factor and stimulated with PAF, lipoxygenase product synthesis was inhibited with IC50 values of 7.7-8.7 nM. At the concentration of 1 microM, MK-0591 had no inhibitory effect on 15-lipoxygenase activity in human polymorphonuclear leukocytes, nor on human platelet 12-lipoxygenase and cyclooxygenase. In conclusion, MK-0591 is a very potent and specific inhibitor of 5-LO product synthesis in various types of human phagocytes.


Effects of torbafylline on muscle atrophy: prevention and recovery. The effects of torbafylline on the prevention of and the recovery from 5 weeks of hindlimb suspension induced atrophy were analyzed in rat soleus and extensor digitorum longus muscles. Muscle alterations were investigated by determining a suite of electrophysiological, histochemical, and muscle ultrastructural characteristics. Administration of torbafylline during the suspension period was ineffective in preventing any of the observed muscle atrophic changes. Application of torbafylline during the recovery period resulted in a faster recovery of some soleus muscle structural and functional properties. Mitochondrial volume densities and capillary to fiber ratios returned towards baseline values earlier in the recovery process with torbafylline. Furthermore, the drug significantly improved soleus muscle fatigue resistance 4 weeks after cessation of hindlimb suspension.


Monophasic and biphasic effects of angiotensin II and III on norepinephrine uptake and release in rat adrenal medulla. Angiotensin II and III have hypertensive effects. They induce vascular smooth muscle constriction, increase sodium reabsorption by renal tubules, stimulate the anteroventral third ventricle area, increase vasopressin and aldosterone secretions, and modify catecholamine metabolism. In this work, angiotensin II and III effects on norepinephrine uptake and release in rat adrenal medulla were investigated. Both angiotensins decreased total and neuronal norepinephrine uptake. Angiotensin II showed a biphasic effect only on evoked neuronal norepinephrine release (an earlier decrease followed by a later increase), while increasing the spontaneous norepinephrine release only after 12 min. On the other hand, angiotensin III showed a biphasic effect on evoked and spontaneous neuronal norepinephrine release. Both angiotensins altered norepinephrine distribution into intracellular stores, concentrating the amine into the granular pool and decreasing the cytosolic store. The results suggest a physiological biphasic effect of angiotensin II as well as angiotensin III that may be involved in the modulation of sympathetic activity in the rat adrenal medulla.


Trophic regulation of action potential in bullfrog sympathetic neurones. These experiments tested the hypothesis that the normal electrophysiological properties of mature bullfrog sympathetic ganglion (BFSG) neurones are maintained by the retrograde supply of nerve growth factor-like molecules from peripheral target tissues. Maintenance of these cells in explant culture in the absence of nerve growth factor (NGF) for up to 30 days produced electrophysiological changes that resemble those previously shown to accompany axotomy in vivo. These included (i) an increase in action potential (ap) duration (spike width), (ii) a decrease in the amplitude of the afterhyperpolarization (ahp), which follows the ap, and (iii) a rapidly developing decrease in ahp duration. When murine NGF (2.5 s; 50 ng/mL) was included in the culture medium there was less attenuation of ahp amplitude. Inclusion of affinity-isolated sheep IgG antibodies (0.5 micrograms/mL; raised against murine 2.5 s NGF) in the culture medium promoted a greater reduction in ahp amplitude than was seen in the "control" explants that were maintained in the absence of NGF. By contrast, the decrease in ahp duration that occurred in control explants was neither attenuated by exposure to NGF nor was it enhanced by NGF antibodies. Also, the increase in spike width that was seen in control explants was enhanced both by murine NGF and by NGF antibodies. Although some of the data support the hypothesis that factor(s) with some similarity to NGF may be synthesized by BFSG in vitro, loss of the retrograde transport of such factors does not explain all aspects of the electrophysiological response to target deprivation and (or) axotomy.


Ca2+ transport through the brush border membrane of human placenta syncytiotrophoblasts. The calcium (Ca2+) uptake by brush border membrane vesicles isolated from fresh human placentas has been characterized. This process was saturable and time- and concentration-dependent. It exhibited a double Michaelis-Menten kinetics, with apparent Km values of 0.17 +/- 0.03 and 2.98 +/- 0.17 mM Ca2+, and Vmax values of 0.9 +/- 0.13 and 2.51 +/- 0.45 pmol.micrograms-1.5 s-1. It was not influenced by the presence of Na+ or Mg2+ in the incubation medium. It was not increased by K+ or anion diffusion potentials, inside negative. At a steady state of 1 mM Ca2+ uptake, a large proportion (approximately 94%) of the Ca2+ was bound to the internal surface of the membranes. Preincubation of these membrane vesicles with voltage-dependent Ca2+ channel blockers (nifedipine and verapamil) had no influence on Ca2+ uptake. However, this uptake was very sensitive to pH. In the absence of a pH gradient, the Ca2+ uptake increased with alkalinity. When the intravesicular pH was kept constant while the pH of the incubation medium was increased, Ca2+ uptake was also stimulated by alkaline pH. In contrast, when the pH of the incubation medium was kept constant and the intravesicular pH was progressively increased, Ca2+ uptake was diminished with alkaline pH. Therefore, H+ gradient (H+ in trans-position greater than H+ in cis-position) favored Ca2+ transport, suggesting a H+/Ca2+ exchange mechanism. Finally, in contrast to the basal plasma membrane, the brush border membrane did not show any ATP-dependent Ca2+ transport activity.


Conserved charge of glomerular and mesangial cell proteoglycans: possible role of amino acid-derived sulphate. Sulphation of proteoglycans was studied in isolated glomeruli and cultured rat mesangial cells. Both preparations produced heparan, dermatan, and chondroitin sulphates, recoverable both from the tissue layers and the conditioned media. The proportion of heparan sulphate made by mesangial cells was independent of the age of the culture, but declined in later passage. These preparations differed from several other nontransformed cell types studied to date in that the degree of proteoglycan sulphation was independent of the concentration of inorganic sulphate provided. Even when no exogenous sulphate was added, sulphation-dependent charge density of newly synthesized proteoglycans was conserved. Both isolated glomeruli and cultured mesangial cells produced proteoglycans with 35S-labelled sulphate esters when [35S]methionine was provided as the sole source of labelled sulphate. Conversion of methionine to cysteine and subsequent oxidation of organic sulphate via the sulphinyl pyruvate pathway is the only mechanism known in eukaryotic cells that can account for this observation. We conclude that facile oxidation of sulphur-containing amino acids can contribute to sulphation of glomerular proteoglycans and may serve to sustain the charge density of these multifunctional molecules when the supply of inorganic sulphate is otherwise compromised.


Improved sensitivity of the mouse interstitial cell testosterone assay with the addition of forskolin. Modification of the mouse interstitial cell testosterone assay by the addition of 1.5 microM forskolin to the incubation medium has improved the sensitivity of this luteinizing hormone bioassay from approximately 100 to 3 pg/tube of NIH rLH RP-2. Luteinizing hormone can be clearly detected in 1 microL of serum from rats castrated 1 week previously and 5 microL of serum from intact rats. Parallelism was noted between dilution curves of serum from intact and castrated rats, and the luteinizing hormone standard curve. Luteinizing hormone detected in serum samples from 30 intact rats by the improved bioassay and by radioimmunoassay was significantly correlated (r = 0.85). Secretion patterns of circulating luteinizing hormone in individual rats were similar when detected by either bioassay or radioimmunoassay. Thus, with the addition of forskolin, the mouse interstitial cell testosterone assay has been improved so that luteinizing hormone can be detected in small volumes of serum or plasma from male rats.


Vasodepressor reaction induced by inferior vena caval occlusion and isoproterenol. Testing for the susceptibility for vasodepressor reaction in humans involves the combination of restriction of venous return by passive upright tilting and the administration of isoproterenol. To explore the basis of the vasodepressor test in humans, the present experiment examined whether a reduced cardiac volume coupled with adrenergic stimulation causes a vasodepressor reaction in rats. Vasodepressor reaction was defined as paradoxical heart rate slowing in conjunction with hypotension during inferior vena caval occlusion. Inferior vena caval occlusion was performed for 60 s and the maximum changes in R-R were measured during seven states as follows. (A) Under control conditions inferior vena caval occlusion alone accelerated the rate in 32 of 32 rats (delta R-R, -13.9 +/- 1.7 ms, p less than 0.001). (B) When inferior vena caval occlusion was performed during an infusion of isoproterenol (0.5-1.0 micrograms.min-1), a vasodepressor reaction was observed in all rats as the heart rate slowed (delta R-R, +138.1 +/- 14.8 ms, p less than 0.001). The vasodepressor reaction was further examined during isoproterenol and inferior vena caval occlusion under five additional states. (C) After atropine the vasodepressor reaction was unchanged (delta R-R, +132.7 +/- 24.8 ms, p less than 0.001). (D) After bilateral vagotomy the paradoxical slowing was eliminated. (E) After intrapericardial lidocaine the paradoxic slowing was eliminated. (F) After bilateral stellectomy nonsignificant slowing was still present, but this was markedly reduced when compared with B (p less than 0.001). (G) Following chronic chemical sympathetic denervation with 6-hydroxydopamine the paradoxic bradycardia was eliminated. (1) Reduced cardiac volume combined with adrenergic stimulation can stimulate a vasodepressor reaction; (2) the vasodepressor reaction requires signalling by the afferent but not efferent vagal fibers; (3) the bradycardia is mainly due to withdrawal of sympathetic efferent tone.


Localization of the reflex pathway responsible for the vasodepressor reaction induced by inferior vena caval occlusion and isoproterenol. Vasodepressor reactions were induced in 27 rats by a combination of inferior vena caval occlusion and an infusion of isoproterenol. A vasodepressor reaction was defined as paradoxical heart rate slowing during inferior vena caval occlusion. The R-R intervals were measured at 5-s intervals before, during, and after 60 s of inferior vena caval occlusion. The purpose of this study was to examine the role of the right and left vagus nerve and the right and left stellate ganglia in this reflex. Under control conditions inferior vena caval occlusion accelerated the rate (R-R, -15.9 +/- 0.9 ms). During an infusion of isoproterenol (0.5-1.0 micrograms.min-1), inferior vena caval occlusion produced paradoxical rate slowing, i.e., a vasodepressor reaction (R-R, +75.0 +/- 2.2 ms). The vasodepressor reaction was examined during inferior vena caval occlusion and isoproterenol under the following additional states: atropine methyl bromide or right vagotomy did not alter the reaction; left vagotomy eliminated the reaction; and right or left stellectomy greatly reduced the vasodepressor reaction. We conclude the following: (1) left vagal afferents mediate the vasodepressor reaction; (2) cardiac sympathetic fibers participate in the vasodepressor reaction by withdrawing efferent tone through the right stellate ganglion, and by generating the afferent signal, which triggers the vasodepressor reaction through the left stellate ganglion.


The effects of sympathetic denervation on spontaneous ventricular defibrillation in the rat. Ventricular tachycardia or ventricular fibrillation was electrically induced in 38 normal rats (group 1) and 24 sympathetically denervated rats (6-hydroxydopamine) (group 2). The time for spontaneous reversion to sinus rhythm was measured during (1) control, (2) isoproterenol, and (3) the combination of isoproterenol and phenylephrine. The time for spontaneous reversion was the same in both groups in the three states. The reversion time was prolonged threefold by isoproterenol, and restored to control values when phenylephrine was added to the infusion of isoproterenol. The tachycardia duration and the refractory period were inversely related: log10 (tachycardia duration) = 3.466-0.091 (refractory period). Ventricular tachycardia/fibrillation induction was examined as follows: (i) Ventricular tachycardia/fibrillation was induced in 100% of normal rats (group 1), but only 42% of the denervated rats (group 2, p less than 0.001); (ii) during isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of rats of both groups; and (iii) when phenylephrine was added to isoproterenol, ventricular tachycardia/fibrillation was induced in 100% of group 1 rats versus 82% of group 2 rats, (p = NS). These observations suggest (1) the induction of ventricular tachycardia/fibrillation is highly dependent on intact sympathetic innervation, and (2) exogenous adrenergic agonists modulate the duration of ventricular fibrillation through their effects on ventricular refractory period, independent of sympathetic innervation.


Exercise training has a heparin-like effect on lipoprotein lipase activity in muscle. Lipoprotein lipase (LPL) is anchored with high affinity to heparan sulphate proteoglycans on the luminal surface of the capillary endothelium. The levels of pre-heparin perfusate LPL activity increased from 16 +/- 1 to 145 +/- 6 U/hindlimb (nine-fold increase) in hindlimb muscle of exercise-trained rats measured immediately after the last bout of work. At the same time, post-heparin perfusate LPL activity decreased from 63 +/- 2 to 13 +/- 1 U/hindlimb (p less than 0.001). These results provide evidence that exercise-training has a heparin-like effect on capillary-bound LPL. The total amount of LPL (i.e., pre-heparin perfusate plus post-heparin perfusate) was twofold greater in the hindlimb of the trained animals versus the controls. The effect of exercise on muscle LPL activity appears to last for as long as 5 days after cessation of exercise. Serum triglycerides were reduced 38% and plasma free fatty acids increased fourfold. These results provide evidence that training increases the capacity to remove triglycerides from circulation.


gamma-Aminobutyric acid activity in the olfactory bulb of the rat during the sexual cycle and response to olfactory stimuli. Glutamic acid decarboxylase activity in the main and accessory olfactory bulbs throughout the sexual cycle of the rat was studied. The effect of male pheromonal secretion on enzyme activity during proestrus and estrus day was also tested. The enzyme activity showed circadian rhythm during the estrous cycle. This rhythm was disrupted during diestrus-2 afternoon in the main bulb and came back during proestrus afternoon. A different pattern of enzyme activity was present in the accessory bulb, since the circadian rhythm was altered during proestrus morning, returning during estrus afternoon. Male odor exposition did not change enzyme profile activity during proestrus day and during estrus morning in the main bulb. In contrast, in the accessory bulb the olfactory stimuli induced opposite changes to that found in rats from the vivarium during proestrus. Comparison of enzyme activity in olfactory stimuli-deprived rats with that of pheromone-stimulated rats during proestrus showed that male odor exposure specifically affects accessory bulb enzyme activity. It is concluded that the changes of the olfactory bulb GABAergic system during proestrus and estrus day, or that evoked by odor stimuli, demonstrate the discriminative response of this system between the accessory olfactory bulb and the main olfactory bulb.


Reduced Ca(2+)-induced Ca2+ release from skeletal muscle sarcoplasmic reticulum at low pH. The purpose of this investigation was to determine the effects of reduced pH on Ca(2+)-induced Ca2+ release (CICR) from skeletal muscle sarcoplasmic reticulum (SR). Frog semitendinosus fiber bundles (1-3/bundle) were chemically skinned via saponin treatment (50 micrograms/mL, 20 min), which removes the sarcolemma and leaves the SR functional. The SR was first depleted of Ca2+ then loaded for 2 min at pCa (log free Ca2+ concentration) 6.6. CICR was then evoked by exposing the fibers to pCa 5-7 for 5-60 s. CICR was evoked both in the absence of ATP and Mg2+ and in the presence of beta, gamma-methyleneadenosine-5'-triphosphate (AMPPCP, a nonhydrolyzable form of ATP) and Mg2+. Ca2+ remaining in the SR was then assayed via caffeine (25 mM) contracture. In all cases, CICR evoked at pH 6.5 resulted in larger caffeine contractures than that evoked at 7.0, suggesting that more Ca2+ was released during CICR at the higher pH. Accordingly, rate constants for CICR were significantly greater at pH 7.0 than at pH 6.5. These results indicate that reduced pH depresses CICR from skeletal muscle SR.


Electrolytes, protein, and lactate dehydrogenase isozymes of parotid saliva in mineralocorticoid-treated rats. Small quantities of parotid saliva were obtained from 7 of 11 rats in which hypokalemia was induced by treatment with deoxycorticosterone acetate (DOCA). Thirst in the treated rats was indicated by an increase in water consumption. A decrease of 28% in plasma potassium levels indicated that the DOCA-treated rats had become hypokalemic; chloride decreased 6-7% while sodium was unchanged. Saliva showed significant increases in potassium and protein and a decrease in sodium; lactate dehydrogenase-2 and -4 bands appeared darker on the electrophoretic profile. These changes are relevant to the clinical manifestations and diagnosis of hypokalemia.


Biotransformation of glyceryl trinitrate by rat brain homogenate. Incubation of glyceryl trinitrate (GTN) with 5% (w/v) rat brain homogenate (RBH) resulted in biotransformation of the organic nitrate vasodilator drug to a mixture of glyceryl-1,2-dinitrate (1,2-GDN) and glyceryl-1,3-dinitrate (1,3-GDN). Heating of the RBH at 100 degrees C for 5 min and (or) pretreatment with 5 mM N-ethylmaleimide at 37 degrees C for 10 min demonstrated that about two-thirds of the GTN biotransformation activity was due to a sulfhydryl-dependent enzymatic process resulting in the predominant formation of 1,2-GDN, and that the remaining biotransformation activity was due to a sulfhydryl-dependent nonenzymatic process resulting in the selective formation of 1,3-GDN. In a preliminary experiment, nitric oxide formation was observed during the incubation of GTN with RBH under anaerobic conditions. These data support the idea that some of the therapeutic and adverse effects of GTN are mediated through its action in the central nervous system.


Mechanism of cerebral vasospasm following subarachnoid hemorrhage in monkeys. This paper reviews our recent studies on the mechanism of cerebral vasospasm following subarachnoid hemorrhage (SAH) in monkeys. Middle cerebral artery (MCA) vasospasm was maximal at 7 days, resolving by 14 days, and absent at 28 days after SAH. Arterial fibrosis was not detected during vasospasm, although there was intimal hyperplasia with fibrosis 28 days after SAH. On scanning electron microscopy, smooth muscle cells from vasospastic arteries had corrugated cell membranes and appeared similar to cells contracted pharmacologically, suggesting that vasospastic smooth muscle is contracted. Morphometric analysis of arteries obtained 7 days after SAH showed no significant increases in arterial wall area of vasospastic arteries compared with normal MCAs. The results suggest vasospasm in monkeys is not due to hypertrophy, hyperplasia, or fibrosis in the arterial wall. Vasospasm may be mainly vascular smooth muscle contraction, which damages the arterial wall, leading to secondary structural changes in the arterial wall which occur after angiographic vasospasm.


During repetitive forebrain ischemia, post-ischemic hypothermia protects neurons from damage. In rodents damage from repetitive transient cerebral ischemia is more severe than that seen with a single ischemic insult of similar duration. Mild hypothermia has been shown to be very effective in protecting the brain during single ischemic insults. We tested the protective effects of hypothermia in repetitive ischemic insults. We used the gerbil model of repetitive ischemia (three minutes ischemia repeated at one hourly intervals three times) and histological evaluation was done using the silver staining technique. Our study reveals that a decrease in body and scalp temperature by 1-2 degrees Celsius can significantly reduce neuronal damage in the cerebral cortex, CA1 region of the hippocampus and substantia nigra reticulata during repetitive ischemia. As the hypothermia was induced after the initial insult, we believe this offers an opportunity for intervention in the clinical settings.


The influence of indomethacin and guanethidine on experimental streptozotocin diabetic neuropathy. In diabetic animals, reduced endoneurial perfusion and oxygen content have been linked to neuropathic abnormalities and might be amenable to pharmacological manipulation. In streptozotocin-induced diabetic rats, we studied the influence of guanethidine adrenergic sympathectomy, indomethacin treatment and a combined strategy on: serial in vivo motor and sensory conduction, resistance to ischemic conduction failure, in vitro myelinated and unmyelinated conduction, endoneurial perfusion and endoneurial oxygen tension. Unlike previous work diabetic animals had normal endoneurial perfusion but lower endoneurial oxygen tensions after six months of hyperglycemia. Guanethidine worsened sensory conduction despite lower microvascular resistance and an improvement in endoneurial oxygen tension. In contrast, indomethacin improved motor and sensory conduction but not oxygen tension. These studies do not support a linkage between conduction deficits and early endoneurial microangiopathy in experimental diabetes. Indomethacin, or related agents may offer a new therapeutic approach toward diabetic neuropathy through a mechanism independent of the endoneurial microvasculature.


Absence of HTLV-I and HTLV-II proviral genome in the brains of patients with multiple sclerosis and amyotrophic lateral sclerosis. Previous studies have failed to provide serological evidence to incriminate a retroviral infection in the cause of multiple sclerosis. Gene amplification techniques have also failed to identify retroviral footprints in DNA from peripheral blood leukocytes. Here we provide evidence that proviral DNA of HTLV-I and HTLV-II is not found in the central nervous system tissues of patients with multiple sclerosis, patients with amyotrophic lateral sclerosis and controls.


Excitatory amino acid receptor antagonist in murine motoneuron disease (the wobbler mouse). Recent evidence has suggested a potential role for involvement of excitatory amino acids (EAA) in the pathogenesis of the neuron loss in motoneuron diseases. We have examined the ability of an antagonist of N-methyl-D-aspartate (NMDA) receptors to halt or retard the progression of neurological symptoms in a murine form of motoneuron disease. The wobbler mouse is an autosomal recessive mutant which develops progressive neurological symptoms secondary to motoneuron loss. Treatment of wobbler mice with the NMDA receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo(a,d)cyclohepten-5, 10-imine maleate (MK-801) did not retard neurological deterioration as assessed by a semiquantitative clinical scale. We conclude that NMDA receptor activation is probably not involved in the pathogenesis of motoneuron loss in the wobbler mouse.


The increased susceptibility of women to multiple sclerosis. Many diseases with an auto-immune etiology have a skewed sex distribution. In the majority of instances, women are affected more frequently than men. A review of population studies demonstrates that the preponderance of women in multiple sclerosis (MS) is almost constant. We show that this preponderance is further increased in early as well as in late-onset cases, in familial cases as well as in MS twin pairs and that the HLA-DR2 allele, which has been associated with MS in Caucasian populations, is significantly more frequent in women than in men with MS. "Rules" have been established for multifactorial diseases; MS contravenes most of those rules. The skewed sex distribution in MS could be attributed to the known hormonal and gender influences on the immune response, as well as to genetic influences.


The neurology of cobalamin.

The neurology of cobalamin. The following review indicates that the impact of cobalamin on neurologic disease extends far beyond the traditional myelopathy of classical pernicious anemia. The delineation of a broad spectrum of inherited disorders of cobalamin processing has served to illustrate and precisely define each step in the normal absorption, transport and intracellular metabolism of this essential vitamin. Recent clinical work has extended the boundaries of acquired cobalamin deficiency to encompass a variety of neuropsychiatric disturbances without identifiable concomitant hematologic derangements and emphasized the utility and sensitivity of new laboratory tests. These findings will demand increased vigilance from clinicians so that atypical and subtle cobalamin deficiency states will be readily diagnosed. The wide range of neurologic dysfunction observed in both inherited and acquired disorders of cobalamin metabolism challenges basic scientists to delineate cobalamin's presumed important role in the normal development and homeostasis of the nervous system.