bluuebunny/crossref_metadata_2025 huggingface dataset:
Méthode de mesure des vitesses d'épuration métabolique et de sécrétion du cortisol chez l'anguille (Anguilla anguilla L.)
Authors: Leloup-Hatey Jeanine
Published: April 2011

Classical methods for the analysis of steroid dynamics were adapted to measure the metabolic clearance rate and the secretion rate of cortisol in the European eel using [1,2-3H]cortisol as a tracer.1. Measurements were made whilst the eels were in the steady state; stresses which usually result from anaesthesia and handling were avoided by chronic catheterization of the blood vessels of the swim bladder. In this way, the plasma cortisol level were constant; thus, it was possible to obtain valid measurements of the cortisol secretion rate knowing the metabolic clearance rate and the plasma cortisol level.2. In the eel, cortisol and cortisone together form a 'chemical compartment', derived originally from cortisol secreted by the interrenal gland and subsequently transformed partially into cortisone in the plasma and maintained thenceforth in dynamic reversible equilibrium. Consequently, the metabolic clearance rate of cortisol has been calculated from the known changes in concentration of both [1,2-3H]cortisol and [1,2-3H]cortisone in the plasma deduced from dichloromethane-extractable plasma radioactivity, 72% of which is always attributable to these two steroids from the moment that the radioactivity begins to decline regularly as a function of time (15–30 min after the injection).3. After a single injection of [1,2-3H]cortisol, the interpretation of the disappearance curve by compartmental analysis is complicated by the delay of tracer distribution and by the evident variability in the initial portion of the curve. Disappearance curves have accordingly been analysed in a more rigorous fashion either by integrating the area under each curve which allows one to calculate individually the metabolic clearance rates, or by integrating according to Normand, M., and Fortier, C. (1970. Can. J. Physiol. Pharmacol. 48, 274–281) which allows one statistical treatment of data.4. Estimates of the metabolic clearance rate of cortisol were made in a satisfactory manner by either one of the two integration methods. They were also very similar to estimates obtained by prolonged infusion of [1,2-3H]cortisol to constant specific activity into eels maintained under identical experimental conditions.
Potassium and the recovery of splenic capsular smooth muscle after cold storage
Authors: Bose D. , Innes I. R.
Published: April 2011

Cat spleen capsular smooth muscle, depleted of potassium and enriched with sodium by cold storage in a potassium free medium, relaxed and underwent transient reduction in responsiveness to noradrenaline when potassium was introduced into the bathing medium. Both these effects could be blocked by ouabain, lithium substitution for sodium or low ambient temperature, suggesting possible involvement of the sodium pump. In the continued presence of potassium, relaxation was maintained but sensitivity to noradrenaline increased, possibly due to restoration of normal intracellular sodium and potassium concentrations.
Effects of isoproterenol on cylic-AMP metabolism in rat ventral prostate
Authors: Tsang B. K. , Singhal R. L.
Published: April 2011

β-Adrenergic stimulation of the ventral prostate cyclic-AMP system was investigated by examining the influence of isoproterenol on endogenous cyclic-AMP levels as well as on the activities of adenylate cyclase (EC 4.6.1.1) and cyclic-AMP-dependent and independent protein kinases (EC 2.7.1.37). Administration of isoproterenol (1 mg/kg, ip) resulted in rapid elevation of adenylate cyclase activity (119%) and cyclic-AMP levels (593%). The observed isoproterenol-stimulated changes in cyclic-AMP metabolism of the ventral prostate were time-dependent and maximal stimulation was seen 5 min after treatment with this β-adrenergic agonist. The increases in prostatic adenylate cyclase and cyclic-AMP also were related to the dose of isoproterenol administered and maximal enhancement of these parameters was seen with 1 mg/kg dose of the agonist. Whereas pretreatment of rats with propranolol (3 mg/kg, ip) partially reversed these alterations, administration of an α-adrenergic antagonist, phentolamine, even at a dose of 5 mg/kg, failed to elicit any appreciable effect. Stimulation of prostatic soluble protein kinase by isoproterenol was associated with a decrease (33%) in the activity of the cyclic-AMP-dependent protein kinase with a concomitant increase (25%) in that of the independent enzyme. Whereas the ability of the enzyme to bind cyclic-[3H] AMP in vitro was decreased (54%) following isoproterenol treatment, the protein kinase activity ratio (−cyclic-AMP/+cyclic-AMP) was significantly elevated from 0.51 ± 0.05 to 0.95 ± 0.08. Although propranolol alone had little or no effect on these parameters, it inhibited partially the isoproterenol-induced alterations in cyclic-AMP-dependent protein kinase and the cyclic-AMP binding capacity. Treatment with propranolol also blocked the increases in the kinase activity ratio and in the activity of cyclic-AMP-independent enzyme seen with isoproterenol. Data suggest that the concentration of ventral prostate cyclic-AMP as well as the activities of adenylate cyclase and cyclic-AMP-dependent and independent form of protein kinases are subject to modulation by β-adrenergic stimulation.
Action potential fatigue in nonmyelinated nerve fibers: garfish olfactory and rabbit vagus nerve
Authors: Hill Douglas A. , Sherebrin M. H.
Published: April 2011

A decrease in amplitude and conduction speed in the compound action potential is observed with time in gar olfactory and rabbit vagus nerve when it is stimulated between 4 and 15 Hz at 26 °C in vitro. The amplitude decays exponentially for 1–3 min before reaching a steady state. Recovery also occurs exponentially. The fatigue exponential time constant is 15 s for gar olfactory nerve and 50 s for rabbit vagus nerve. The steady state values are 14% and 36% of the original amplitude, respectively, and conduction speeds are reduced by 25% in both nerves. The effect results from competition between ion flow during the action potential and active transport. The accumulation of K+ ions and depletion of Na+ ions in the restricted extracellular space contributes to the amplitude fatigue while the depletion of Na+ ions alone causes the decrease in conduction speed. Ouabain increases the fatigue rate in both preparations, but more so for gar. The fatigue and recovery measurements may provide a useful method to investigate active pumping, including both the total pumping rate and the electrogenic component.
Cocaine self-injection behaviour under schedules of delayed reinforcement in monkeys
Authors: Stretch R. , Gerber G. J. , Lane Elizabeth
Published: April 2011

Rates of lever pressing, maintained either by response-dependent intravenous injections of cocaine (250 μg/kg per injection) or by food-pellet presentation, were compared and found to vary systematically as a function of the delay (5–100 s) imposed between the response(s) and the occurrence of reinforcement. The control of responding by two schedules of delayed reinforcement was studied. The first scedule permitted responses to occur during the delay period without any programmed consequence; the second schedule required a response, and then the elapse of x seconds without any additional response(s). At imposed delays of 50 and 100 s, response rates were reduced significantly when the second schedule was in effect by comparison with the first. The effect was observed when responding was maintained either by intravenous cocaine injections or by food-pellet presentation. Across all comparable conditions, response rates were higher when maintained by scheduled cocaine injections than by food pellets. Rate enhancement, generally induced by drugs of the psychomotor stimulant type, could account for the observed difference.
Mean velocity of optically detected intraaxonal particles measured by a cross-correlation method
Authors: Smith R. S. , Koles Z. J.
Published: April 2011

A method which uses the cross correlation of optical signals is described for the determination of the mean velocity of somatopetally moving particles within nerve fibers. The method was validated by simulation experiments and by comparing the results with those obtained by averaging collections of velocities of individual particles. The significant contribution of the method is that it allows objective and rapid serial evaluations of mean particle velocity within individual nerve fibers with good accuracy and precision. A series of results from normal myelinated nerve fibers from Xenopus laevis is presented. Considerable variation (up to 50%) in mean velocity was found between individual nerve fibers. The mean of all determinations indicates that the mean velocity of somatopetally moving particles in axons with diameters > 10 μm is in the region of 1.14 μm/s at a temperature of 22–24 °C. The findings are compared with the small collection of such determinations which have been reported in the literature.
Release of [3H]noradrenaline from perfused rat hearts by potassium and its modifications by 6-hydroxydopamine and reserpine
Authors: Carpenter J. R. , Nash C. W.
Published: April 2011

The sources of noradrenaline (NA) released by excess potassium from isolated perfused rat hearts were investigated by labelling the hearts from normal, reserpine-treated, and 6-hydroxydopamine-treated (6-OHDA-treated) rats with [3H]NA, and measuring the increased rate of efflux induced by perfusion with a Krebs solution containing varying amounts of excess potassium. The [3H]NA and its metabolites in the effluent were separated by adsorption on alumina and a cation-exchange resin (Dowex-50). The release induced by potassium was a linear function of the log of the increased potassium concentration. Following a 1-h efflux period after labelling with [3H]NA, the hearts from reserpine-treated rats retained [Formula: see text] as much [3H]NA and released, in response to a 56 mM elevation in the potassium concentration, less than [Formula: see text] as much tritium label as the hearts from untreated (control) animals. In contrast, the hearts from 6-OHDA-treated animals retained [Formula: see text] of the amount of [3H]N A and released [Formula: see text] of the 3H label as did the control hearts. The potassium-induced increase of 3H-labelled substances in the effluent from the control hearts showed a large (threefold) percentage increase in the [3H]NA fraction, whereas the effluents from the hearts of reserpine- and 6-OHDA-treated animals contained only small increases in the [3H]NA fraction. Based on the assumptions that reserpine prevented retention of NA in the storage granules whereas 6-OHDA prevented almost all neuronal storage, it was concluded that more than 80% of the NA released by potassium excess from perfused normal hearts originated from the storage vesicles of the nerves, the remainder being largely from the cytoplasm of the nerves, with only a small portion from extraneuronal sources.
Effects of saline infusion and acute metabolic acidosis and alkalosis on water and electrolyte transport in the human colon
Authors: Crepeau R. , Romeder J. M. , Devroede G. , Plante G. E.
Published: April 2011

Both the kidney and colon secrete bicarbonate and transport water and electrolytes. The respective contributions of these two organs to acid–base and electrolyte balance in normal man has thus been studied in eight healthy male volunteers who underwent simultaneous renal clearance studies, and colonic perfusion with a 0.9% saline or 7.2% mannitol solution, during metabolic alkalosis and acidosis, extracellular volume expansion, and control conditions. There was no influence of these acid–base conditions on electrolyte transport in the colon. In the urine, preferential loss of chloride over sodium averaged 81, 143 (P < 0.001), and 141 (P < 0.05) μequiv./min, during control, metabolic acidosis, and extracellular volume expansion conditions, respectively. During alkalosis more sodium than chloride was lost (146 μequiv./min) (P < 0.001). Colonic pH averaged 7.41 during saline and 6.75 (P < 0.005) during mannitol perfusion. Titratable acid was not produced in the colon during saline perfusion, and averaged 18 μequiv./min during mannitol perfusion. Urinary titratable acid increased from 19 to 25 μequiv./min (P < 0.01) during volume expansion. With saline perfusion, bicarbonate secretion rate in the colon rose from 249 μequiv./min during control conditions to 289 μequiv./min during metabolic alkalosis (P < 0.05). More bicarbonate was excreted in the urine during alkalosis when mannitol was introduced in the colon (243 μequiv./min) than when saline was perfused (152 μequiv./min) (P < 0.05). This study indicates that the response of the human colon is trivial compared with that of the kidney during acute changes in acid–base balance.
Effect of subacute dosing and phenobarbital and 3-methylcholanthrene pretreatment on the metabolism of acetaminophen in rats
Authors: Thomas Barry H. , Zeitz Walter , Beaubien Arthur R.
Published: April 2011

The metabolism of 14C-ring-labelled acetaminophen was studied in male Wistar rats. Pretreatment with phenobarbital increased the initial rate of elimination of 14C from the blood and increased the amount of acetaminophen glucuronide excreted in the urine. Pretreatment with 3-methylcholanthrene did not significantly affect the rate of elimination from the blood and decreased the amount of acetaminophen glucuronide in the urine. Daily dosing with acetaminophen for up to 3 weeks increased the rate of elimination of 14C from the blood after 4 h, and increased the urinary excretion of both total 14C and the glucuronide and sulfate conjugates. Subacute dosing with acetaminophen had a diuretic effect but this did not correlate with the increased excretion of the drug. It is concluded that acetaminophen elimination is increased by phenobarbital pretreatment and by subacute dosing with acetaminophen, but by different mechanisms.
Regional cerebral energy metabolism in acute carbon monoxide intoxication
Authors: MacMillan V.
Published: April 2011

The regional cerebral metabolic effects of 30 min of exposure to 0.5, 1.0, 1.5, and 2.0% carbon monoxide (CO) were studied in lightly anesthetized rats by measurement of energy phosphates and glycolytic – citric acid cycle substrates in the basal ganglia, hippocampus–thalamus, and cerebellum. In all three regions 0.5 and 1.0% CO gave rise to increases in tissue lactate, but since ATP and the energy charge of the adenylate pool (ECP) remained unchanged from control, it is concluded that energy state was unaltered at these levels of CO. At 1.5% CO the basal ganglia region showed decreases in ATP and ECP, whereas these values for cerebellum and hippocampus–thalamus were unchanged from control. At 2.0% CO all areas showed decreases in ATP and ECP and increases in ADP and AMP. The patterns of change in glycolytic and citric acid cycle substrates were similar in all three areas. The results indicated that the energy homeostasis of the basal ganglia is less well maintained in this form of experimental hypoxia.
Antagonism of biogenic amine-induced depression of cerebral cortical neurones by Na+,K+-ATPase inhibitors
Authors: Sastry B. S. R. , Phillis J. W.
Published: April 2011

The effects of iontophoretically applied Na+-,K+-dependent adenosinetriphosphatase (Na+,K+-ATPase) (EC 3.6.1.3) inhibitors (ouabain, digitoxin, digitoxigenin, strophanthin K, strophanthidin, thevetin A and B, ethacrynate, and harmaline) on the depression of rat cerebral cortical neurones by noradrenaline, 5-hydroxytryptamine, and histamine have been studied. The inhibitors antagonized depressions of spontaneously active neurones evoked by these amines, but not those evoked by γ-aminobutyric acid, adenosine, adenosine 5′-monophosphate, or calcium. The antagonistic potencies of the various inhibitors appeared to be proportional to their known potencies as inhibitors of Na+,K+-ATPase. The data therefore support the hypothesis that amines depress central neurones by activating an electrogenic sodium pump.
Effect of clofibrate treatment on chronic hyperlipidemia induced by an ACTH-producing tumor
Authors: Gianoulakis C. , Passerini L. , Lis M. , Davignon J. , Chrétien M.
Published: April 2011

Plasma triglyceride and cholesterol levels were significantly increased in rats bearing an MtT-F4 tumor for 31–41 days. Addition of clofibrate at a dose of 30 mg kg−1 day−1 to the diet of rats bearing the tumor resulted in the complete elimination of the tumor effect on the plasma triglycerides, and to a great extent prevented the rise in the plasma cholesterol.
Superior colliculus cell responses to electrical stimulation of the retina
Authors: Molotchnikoff S. , L'archevêque P.
Published: April 2011

Superior colliculus cell discharges in response to electrical stimulation of the retina were investigated in rabbit. In contrast with the responses at the optic tract level both polarities evoked discharges of equal latencies suggesting a convergence of ON- and OFF-centre retinal ganglion cells upon one collicular unit. Three typical patterns of responses could be distinguished. Thus, 40% of cells reacted with a burst, 47% with a prolonged discharge, and 5% responded by a transient inhibition. The responses of the remaining cells could not be classified.
Noradrenergic synapses and effects of noradrenaline on interneurons in the ventral horn of the cat spinal cord
Authors: Jordan Larry M. , McCrea David A. , Steeves John D. , Menzies John E.
Published: April 2011

Histochemical and electrophysiological procedures were carried out to determine the cell types in the ventral horn which are in close contact with noradrenergic terminals and to identify the types of neurons in the ventral horn which are influenced by noradrenaline (NA). Fluorescence histochemical studies revealed that noradrenaline-containing fibers rarely form intimate contacts with alpha motoneurons, whereas many small interneurons which are closely invested with fluorescent fibers can be found near the motoneurons. The effects of microiontophoretically applied NA on interneurons were examined in the lateral motor areas of the lumbar spinal cord ventral horn. NA had a substantial depressant action on 43% of cells in chloralose-anesthetized and decerebrate cats; it excited 6% of the cells, and was without effect on the rest. The cells which were depressed by NA could be excited by electrical stimulation of high threshold muscle afferents or skin afferents, and they could be influenced from a variety of exteroceptive and proprioceptive inputs. Owing to considerable convergence on the affected interneurons, no distinct population of NA-sensitive interneurons could be identified. Many of the interneurons strongly depressed by NA were found near the motor nuclei. The hypothesis is presented that inhibitory actions of NA on interneurons in the motor nuclei might explain its hyperpolarizing action on motoneurons.
Red blood cell catechol O-methyltransferase activity in thyroid dysfunction
Authors: Coulombe P. , Dussault J. H. , Lescault A. , Walker P.
Published: April 2011

Using a modification of the method of Mannl et al. (Mannl, H. F. K., Hempel, K., and Kubler, W. 1972. Catechol O-methyltransferase in human erythrocytes. Arch. Pharmacol. 272, 265–276), we have measured the activity of catechol O-methyltransferase (COMT) (EC 2.1.1.6) in red blood cells (RBC) of patients with hyperthyroidism and hypothyroidism to establish whether thyroid dysfunction is associated with alterations in catecholamine catabolism. The activity of COMT averaged 4.4 ± 0.54 nmol/ml RBC per hour of incubation (mean ± SEM) in euthyroid subjects compared to 4.76 ± 0.64 nmol/ml RBC per hour of incubation in hyperthyroidism and 4.42 ± 0.81 nmol/ml RBC per hour of incubation in hypothyroidism; these values are not significantly different. There were no significant differences observed in urinary excretion of vanillylmandelic acid, epinephrine, and norepinephrine among the three groups. These data are compatible with the possibility that thyroid status has little influence on the degradation of circulating catecholamines and suggest that hypothyroidism, with its attendant elevations in serum norepinephrine concentration, may be related to a compensatory noradrenergic response.
Sequential changes in hepatic polyamine, deoxyribonucleic acid, and cyclic adenosine 3′,5′-monophosphate metabolism after subacute exposure to cadmium in rats
Authors: Kacew S. , Merali Z. , Thakur A. N. , Singhal R. L.
Published: April 2011

Heavy metal treatment (2 × 1 mg/kg per day) for 3, 5, and 7 days resulted in progressive augmentation in the incorporation of [14C]thymidine into hepatic DNA. In contrast with the observed enhancement in DNA synthesis, cadmium exposure tended to produce a decrease in the activity of hepatic ornithine decarboxylase (EC 4.1.1.17) at 1, 3, or 5 days with the lowest (34% of control values) enzymic activity seen after 7 days. A similar reduction in the activity of S-adenosylmethionine decarboxylase (EC 4.1.1.50) was observed in livers of rats treated with cadmium for 1–7 days. Subacute exposure to cadmium significantly lowered the hepatic levels of spermidine and spermine whereas the endogenous concentration of putrescine remained unaltered. In addition to the observed effects on the biosynthesis of polyamines and DNA, heavy metal treatment produced stimulation of the hepatic adenylate cyclase (EC 4.6.1.1) – cyclic AMP system. Significant increases in the activity of hepatic adenylate cyclase and endogenous cyclic AMP levels were detected as early as 1 day and the observed alterations persisted during the entire 1-week period of cadmium exposure. The depression in polyamine formation was accompanied by enhanced DNA biosynthesis as well as stimulation in the adenylate cyclase – cyclic AMP system of rat liver.
Effect of neuronal uptake inhibitors on the adrenergic-neuron blockade produced by guanethidine in rabbit vas deferens
Authors: Huston L. J. , Golko D. S. , Paton D. M.
Published: April 2011

The effect of neuronal-uptake inhibitors on the guanethidine-induced inhibition of responses of rabbit vas deferens to transmural stimulation was investigated. The twitch and sustained reponses were inhibited by about 70% by 1.2 × 10−5 M guanethidine. Prior or subsequent exposure to the noradrenaline-uptake inhibitors, 3.3 × 10−5 M cocaine, 10−5 M nisoxetine, and 10−7 M desipramine prevented or reversed these effects of guanethidine. The depressant effects of guanethidine were not modified by the serotonin-uptake inhibitor, 10−6 M fluoxetine. The uptake of 5 × 10−8 M (−)-[3H]noradrenaline by rabbit vas deferens was significantly reduced by guanethidine, cocaine, nisoxetine, and desipramine, but not by fluoxetine. It was concluded that guanethidine inhibited both the twitch and sustained responses of the vas by producing adrenergic-neuron blockade and that these effects were dependent on continued transport into adrenergic neurons.
Effect of parathyroid hormone on renal excretion of sodium and hydrogen ions
Authors: Hermkens Hubert , Nawar Tewfik , Caron Claude , Plante Gerard E.
Published: April 2011

The contribution of parathyroid hormone (PTH) to the renal adjustment of phosphate transport has been extensively investigated, whereas the action of this hormone on bicarbonate and hydrogen excretion has not received as much attention.Nineteen dogs were studied before and during a 2-h infusion of PTH in the left renal artery (8 mU/min per kilogram) under slight expansion of extracellular volume (fractional sodium excretion = U/FNa = 3.8 ± 0.3%). Group I (n = 7) was studied under normal acid–base condition while group II (n = 6) was studied during metabolic acidosis. Bicarbonate titration curves were obtained from group III (n = 6) in which the right kidney was used as control. In all studies, plasma pCO2 was kept constant.[Formula: see text] rose from 4.2 ± 1.1 to 15.6 ± 3.0% and from 3.8 ± 0.4 to 25.0 ± 3.5% in groups I and II, respectively. U/FNa was unchanged in both groups. [Formula: see text] rose from 5.8 ± 0.6 to 10.1 ± 0.7% in group I but remained at 1.0 ± 0.2% in group II during PTH. Urinary titratable acid and ammonium were not influenced by PTH in group II. In group III, plasma HCO3 was progressively increased from 15 to 40 mM/litre. For all plasma values exceeding 22 mM/litre, HCO3 reabsorption was 1 mM/litre of filtrate lower in the left than in the right kidney. Glomerular filtration and renal plasma flow remained constant during PTH.The results indicate that PTH affects sodium and hydrogen excretion in a very modest fashion. Bicarbonaturia obtains whenever plasma HCO3 exceeds 22 mM/litre during PTH. This phenomenon is associated with a demonstrable reduction in tubular HCO3 reabsorption per unit of filtrate.
Effects of pH on excitation and contraction in frog twitch muscle
Authors: Foulks J. G. , Perry Florence A.
Published: April 2011

The electrical and mechanical behaviour of frog twitch muscle in response to changes in membrane potential has been examined over a wide range of hydrogen ion concentration (pH 3.0–11.0). The changes in resting and action potentials, twitches, and maximum potassium-induced contractures (K contractures) were remarkably small when the pH was varied between 5.0 and 10.0. The time course of action potentials generally displayed small graded changes with variation in pH, possibly as the result of changes in surface potential.The amplitude of twitches and maximum K contractures was substantially decreased when pH was reduced to 4.0 or raised to 11.0 without significant alteration in membrane resting potential or consistent suppression of excitation, but maximum caffeine-induced contractures were unchanged. Replacement of chloride with perchlorate promptly antagonized the depressant effects of pH extremes (4.0, 11.0) on both twitch amplitude and maximum K-contracture tension. Acid-induced reductions in maximum K-contracture tension also were partially antagonized by increased calcium concentration. The onset and recovery from the contraction-depressant effects of pH extremes were too slow to be explained by the titration of groups immediately accessible at the membrane surface but too rapid to be accounted for by changes in intracellular pH. Thus, excitation and contraction apparently were uncoupled by sufficient alteration in extracellular pH. Changes in external pH had little effect on the impairment of maximum K contractures by media lacking divalent cations, or on the restoration of such responses by perchlorate except at very alkaline pH (10.0–11.0).The threshold for K contractures was reduced at pH 11.0, but otherwise was little affected by variation in pH at normal concentrations of divalent cations. Altered pH did not modify the usual effects of increased calcium concentration on the relation between potassium concentration and K-contracture tension. When K contractures were maintained by perchlorate in the absence of divalent cations, hydrogen ions displayed calcium-like actions on the relation between external K concentration ([K]0) and K-contracture tension, and also on the time course of submaximum K contractures. These observations are compatible with similar effects of hydrogen and calcium ions on surface potential.The problem of identifying putative charged groups which might influence the linkage between contractile responses and changes in membrane potential is discussed.
Effects of acetylcholine mustard aziridinium ion and its choline analogue on choline transport into synaptosomes
Authors: Rylett B. Jane , Colhoun E. Howard
Published: April 2011

A compound thought to be choline mustard aziridinium ion was found previously in our laboratory to inhibit choline transport into human erythrocytes. Experiments with synaptosomes prepared from brain of rat now show that the aziridinium ion of choline mustard hydrochloride inhibited high- and low-affinity choline transport, with the inhibitory effect being about 10 times less than that of hemicholinium-3. Acetylcholine mustard aziridinium ion also inhibited the transport of choline, but it was less potent than its choline analogue. Studies with choline mustard aziridinium ion may yield important information about the transport of substances into the presynaptic nerve terminal.
Purification of rabbit transcobalamin II by labile ligand affinity chromatography
Authors: Nexø Ebba
Published: April 2011

Rabbit transcobalamin II has been purified to homogeneity from serum containing 5–30 nmol unsaturated transcobalamin II. The method described consists of labile ligand affinity chromatography and G-200 Sephadex gel filtration. The recovery of pure protein was about 80%.
Cardiac reflex activity in chemically sympathectomized dogs in response to hypotension or hypertension
Authors: Gauthier Pierre , Nadeau Réginald A. , Champlain Jacques de
Published: April 2011

The cardiac responses to hypotension and hypertension induced by intravenous injections of nitroglycerin and phenylephrine were studied in unanesthetized dogs before and after chemical sympathectomy with 6-hydroxydopamine (6-OHDA) (50 mg/kg) and β-receptor blockade with sotalol (8 mg/kg). Three days after sympathectomy, the fall in blood pressure induced by nitroglycerin administration was increased significantly whereas the reflex tachycardia was markedly decreased, although it was not completely abolished. A significant increase in heart rate (27 ± 5 beats/min) persisted after 6-OHDA pretreatment. A similar cardiac response to nitroglycerin was observed after β-receptor blockade in normal and sympathectomized dogs. The chronotropic response observed after sympathetic blockade was accompanied by a disappearance of the normally observed sinus arrhythmia, and its magnitude seemed to be related to the initial heart rate. In contrast, the reflex slowing of the heart after phenylephrine-induced hypertension remained unchanged after pretreatment with 6-OHDA or sotalol. However, the blood pressure threshold necessary to trigger a reflex bradycardia was lower after chemical sympathectomy. The present study suggests that reflex tachycardia in response to hypotension results from reciprocal changes in sympathetic and parasympathetic activity of the heart while the bradycardia in response to hypertension is predominantly of vagal origin.
The development of the hypothalamo–pituitary axis in the neonatal rat: sexual maturation in male and female rats as assessed by hypothalamic LHRH and pituitary and serum LH and FSH concentrations
Authors: Dussault J. H. , Walker P. , Dubois J. D. , Labrie F.
Published: April 2011

Using specific radioimmunoassay techniques, we have measured hypothalamic LHRH concentration and pituitary and serum LH and FSH concentrations in neonatal rats from 0 to 60 days after birth. There were no sex differences demonstrable for hypothalamic LHRH concentration, which rose from minimal values at 2 days to peak concentrations at 22–28 days and declined significantly with the approach of puberty. Pituitary LH concentration in the two sexes rose to peak values at 19–25 days, with significantly higher values observed in females (p < 0.01). Serum LH concentration was high in both sexes at birth, the values in females being significantly higher than those observed in males (p < 0.01). While the serum LH concentration remained relatively stable throughout the study period in males, it declined rapidly to a nadir at 28 days in females. Pituitary FSH concentration was low at birth in both sexes. Females demonstrated a marked rise to peak concentrations at 16 days while males achieved significantly lower peak prepuberal values (p < 0.01) at 28 days. Serum FSH concentration was significantly higher in females (p < 0.01) at birth and rose further to peak values at 16 days. Males attained peak serum FSH concentrations at 35 days. These data demonstrate that the maturation of the hypothalamo–pituitary–gonadal axis develops in the neonatal period in the rat and confirm the presence of significant differences in hypothalamic sexual differentiation and control. The possibility of this developmental process in the neonatal rat as a model for the study of the midgestational hypothalamic maturation of the human foetus is discussed.
Effects of verapamil on (Na+ + K+)-ATPase, Ca2+-ATPase, and adenylate cyclase activity in a membrane fraction from rat and guinea pig ventricular muscle
Authors: Hoeschen Robert J.
Published: April 2011

The electrophysiologic properties and the negative inotropic effect of verapamil are most likely due to the inhibition of calcium movement across the sarcolemmal membrane. A possible biochemical basis for this inhibition of calcium movement was studied in a membrane fraction rich in (Na+ + K+)-ATPase (EC 3.6.1.3) and adenylate cyclase (EC 4.6.1.1) activity and which demonstrated Ca2+-ATPase (EC 3.6.1.3) activity. Since each of these enzymes has the potential for influencing transsarcolemmal calcium movements, the effect of verapamil on their activities was studied in this membrane fraction isolated from rat and guinea pig hearts. Ca2+-ATPase activity in the rat was 37.7 μmol Pi/mg per hour compared with 13.8 ± 2.9 in the guinea pig (p < 0.01). Corresponding values for (Na+ + K+)-ATPase activities were 7.9 ± 0.9 μmol Pi/mg per hour versus 10.2 ± 1.4. Adenylate cyclase activity in the rat was 240 ± 8 pmol/mg per minute compared with 299 ± 27. It was found that verapamil in concentrations of 0.01–100 mg/litre (2.1 × 10−8 to 2.1 × 10−4 M) had no effect on the activity of the above enzymes in either species and it was concluded that a biochemical basis for the effect of verapamil on calcium flux has yet to be defined.
The influence of pH on the effects of organic anions in frog skeletal muscle
Authors: Foulks J. G. , Perry Florence A. , Tsang P.
Published: April 2011

The depressant effect of acidity on twitches and K contractures in frog skeletal muscle was greatly accentuated in the presence of organic anions, particularly anions such as butyrate, which also reduced these responses at neutral pH. Conversely, alkaline pH antagonized the depression of contractile responses by butyrate. Most of the effects of acid pH were rapid in onset and were accomplished without any change in membrane resting or action potentials, although depolarization developed in the presence of carboxylate anions when pH was reduced below 6.0. Simultaneous variation in pH and butyrate concentration showed that the undissociated acid exerted a prominent depressant effect only when its concentration reached 1–10 mM, and that the marked depressant action of butyrate at neutral pH was produced primarily by the dissociated anion. Similar experiments showed that the dissociated anion also was largely responsible for the enhanced depolarizing effect of acidity in media containing carboxylates. Acid-induced depolarization was not facilitated in media containing methane sulfonate, but in spite of its low pKa, this anion also increased the sensitivity of contractile responses to the depressant effects of acidity. Hence, the accentuation of the effects of organic anions by acid pH must be exerted on the sequence of membrane events which link excitation and contraction. The effect of acidity was greater when longer apolar hydrocarbon chains were attached to the anionic group for both the carboxylate and the sulfonate series of ions. These depressant effects may be produced by interference with the membrane-stabilizing actions of divalent cations, and may involve increased membrane fluidity.
Effect of monoamine receptor agonists and antagonists on cyclic AMP accumulation in human cerebral cortex slices
Authors: Tsang David , Lal Samarthji
Published: April 2011

In human cerebral cortex slices noradrenaline, isoproterenol (a β-adrenergic agonist), dopamine, apomorphine (a dopaminergic agonist), and serotonin stimulated cyclic AMP formation: noradrenaline ≥ isoproterenol > dopamine = apomorphine = serotonin. Clonidine (an α-adrenergic agonist) was ineffective in stimulating cyclic AMP formation in temporal cortex slices. The stimulatory effect of noradrenaline and isoproterenol was blocked by propranolol (a β-adrenergic blocker) but not by phentolamine (an α-adrenergic blocker). Pimozide (a selective dopaminergic antagonist) inhibited the increase of cyclic AMP formation induced by dopamine or apomorphine but not that induced by noradrenaline, isoproterenol, or serotonin. Neither propranolol or phentolamine had any effect on dopamine- or serotonin-stimulated cyclic AMP formation. Chlorpromazine blocked the increase of cyclic AMP formation induced by noradrenaline, dopamine, or serotonin, while cyproheptadine, a putative central serotonergic antagonist, was ineffective. These observations suggest that there may be at least two monoamine-sensitive adenylate cyclases in human cerebral cortex which have the characteristics of a β-adrenergic and a dopaminergic receptor, respectively, and also possibly a serotonergic receptor.
Effect of bile salts on the biliary excretion of glycodihydrofusidate in the rat
Authors: Montet J. C. , Gerolami A.
Published: April 2011

The biliary elimination of glycodihydrofusidate (GDHF), a structural analogue of bile salts, was studied in bile fistula rats. GDHF was excreted in bile with a maximal excretory rate (Tm = 0.80 μmol min−1 kg−1) which is much lower than bile salts Tm. The effects of dehydrocholate and taurocholate on GDHF biliary secretion suggest a stimulatory effect of bile salts on canalicular excretion of the drug.(a) When a bolus intravenous injection of 3 μmol of GDHF was followed after 2 min by a continuous dehydrocholate perfusion (10 μmol min−1 kg−1), biliary excretion of GDHF was increased in comparison with control rats.(b) Upon attaining the biliary Tm by continuous perfusion of GDHF at a rate of 1.35 μmol min−1 kg−1, infusion with either taurocholate or dehydrocholate increased its Tm to a similar degree.These results are similar to those previously obtained with the effects of bile salt infusions on the Tm of bromosulfophthalein. They suggest therefore that hepatic transport of GDHF and bile salts occurs by routes which are distinct for canalicular transport in spite of the striking structural similarities between GDHF and bile salts.
Effects of prolactin, progesterone, and 17β-hydroxy-5α-androstan-3-one on squalene production by the preputial gland of the immature female rat
Authors: Wielgosz George J. , Armstrong David T.
Published: April 2011

To examine further the previously demonstrated synergism between prolactin and progesterone on preputial glands of hypophysectomized, ovariectomized, immature rats their effects on squalene production were determined and compared with the ability of 17β-hydroxy-5α-androstan-3-one (DHT) and prolactin to increase the amount of squalene in the preputial glands.Glands from progesterone-treated rats incubated in vitro with [14C]mevalonic acid incorporated radioactivity into squalene (identified by chromatographic mobility) more rapidly than glands from controls or prolactin-treated rats. Using the same in vitro system, glands from prolactin-treated rats incorporated more [14C]acetate into squalene than those from progesterone-treated animals. In addition, results showed that prolactin and DHT increased nonradioactive squalene (identified by mass spectral analysis) content in the gland while progesterone had no effect. It is proposed that prolactin increases preputial gland squalene content by enhancing synthesis of mevalonic acid, while progesterone increases incorporation of mevalonic acid into squalene.
Contractile responses of intrapulmonary vessels from three species to arachidonic acid and an epoxymethano analog of PGH2
Authors: Gruetter Carl A. , McNamara Dennis B. , Hyman Albert L. , Kadowitz Philip J.
Published: April 2011

The contractile effects of arachidonic acid (AA) and an epoxymethano analog, chemically similar to PGH2, were investigated in helical strips of intrapulmonary artery (IPA) and vein (IPV) isolated from bovine, rabbit, and canine lung. The analog increased isometric force in a concentration-related manner in IPV from the three species and in IPA from bovine and rabbit lung over the concentration range from 10−12 to 10−6 M. Concentration of the analog up to 10−7 M had no significant contractile effects in canine IPA, although the same vascular strips responded well to a depolarizing potassium solution both before and after exposure to the analog. Of IPA and IPV from the three species, only rabbit IPA contracted in response to 10−5 M AA. Contractions of rabbit IPA induced by 10−8–10−5 M AA were blocked by 10−6 M indomethacin, a cyclooxygenase inhibitor. In contrast, AA elicited concentration-related relaxation in canine IPA partially contracted by phenylephrine. AA had no consistent effect in partially contracted canine and rabbit IPV. These results demonstrate that the epoxymethano analog exerted potent contractile effects in IPA and IPV, except in canine IPA. Since the analog is chemically similar to PGH2 and has been shown to mimic the endoperoxides or possibly TXA2, the results suggest that these intermediates may be highly potent stimulants of IPA and IPV contraction. However, the precursor of endoperoxides and thromboxanes, AA, induced significant contractile activity only in rabbit IPA. These results suggest that local production of active intermediates in IPA and IPV is low, or that the intermediates formed are broken down so rapidly that contractile effects do not occur except possibly in rabbit IPA.
Enkephalin and substance P effects related to trigeminal pain
Authors: Andersen R. K. , Lund J. P. , Puil E.
Published: April 2011

Iontophoretic applications of enkephalin (20–150 nA) reduced the spontaneous firing frequency of nociceptive neurons in the trigeminal nucleus caudalis of decerebrated cats. The response evoked by noxious stimulation (tooth pulp) was gradually inhibited during the 1st minute of application of the opioid and generally remained depressed for 5 min after the current was turned off. These effects of enkephalin were blocked by intravenously or iontophoretically administered naloxone. Nonnociceptive neurons or nociceptive neurons responding to nonnoxious inputs were less frequently inhibited by enkephalin. When tested on nonnociceptive cells, similar applications of substance P usually had little effect. Nociceptive neurons, however, were strongly excited by substance P. This action was not constant and was interrupted by periods of inactivation. Both types of peptide action were similar in temporal aspects. The results suggest a functional interrelationship between enkephalin and substance P in a trigeminal system mediating nociception.
Effects of pH and flow rate on the release of 'bound' red cells from the splenic pulp
Authors: Levesque M. J. , Groom A. C.
Published: April 2011

On perfusion of isolated, denervated spleens with Ringer solution, immature and abnormal red cells are released into the venous outflow much more slowly than normal mature cells, being delayed through adherence to fine structures of the red pulp (Am. J. Physiol. 231, 1665–1671 (1976)). Evidence suggested that the rate at which such cells are released from the 'bound' state might depend on local pH and fluid shear rate within the pulp. Therefore, the rate of washout for this slow component of red cells, from cat spleens, was measured as a function of pH and flow rate of the perfusate. The volume of solution (V½) for 50% washout of 'bound' cells decreased as pH was lowered from 7.8 to 6.6, especially (from 97 to 18 ml/g) between 7.4 and 6.6. The percentage total red cell outflow thus represented rose from 0.06 to 0.5 as pH fell from 7.8 to 6.6. At a high perfusion rate (14–16 ml/min) the V½ value was only one-half that prevailing at a lower rate (4–6 ml/min), and the percentage flow of 'bound' red cells was more than three times greater. Both acidic pH and augmented blood flow thus assist release of adherent red cells from the splenic pulp.
Hypothalamic catecholaminergic effects on prolactin release in vitro
Authors: Friend W. C. , Brown G. M. , Kirpalani S. , Wilson D.
Published: April 2011

Hypothalamic catecholaminergic influences on prolactin release were investigated in vitro. Both dopamine and norepinephrine caused long lasting inhibition of prolactin release from either an isolated hemipituitary or a hemipituitary coincubated with a hypothalamus. Epinephrine also inhibited prolactin release. L-Dihydroxyphenylalanine (L-dopa) inhibited prolactin release from pituitaries in the presence of a hypothalamus but not in isolated pituitaries. DL-Threodihydroxyphenylserine (threodops), serotonin, 5-hydroxy-L-tryptophan (5-HTP), tyramine, octopamine, synephrine, thyrotropin-releasing hormone (TRH), luteinizing hormone releasing hormone (LH-RH), and somatostatin all failed to alter prolactin release. Results confirm that dopamine and norepinephrine directly inhibit prolactin release from pituitary and suggest that the hypothalamic mechanism inhibiting prolactin involves dopamine but not norepinephrine.
Stimulating actions of various prostaglandins and noradrenaline in strips of rabbit renal artery
Authors: Rioux F. , Gagnon G. , Regoli D.
Published: April 2011

The myotropic effects of prostaglandins E1, E2, F2α, A1, and noradrenaline were evaluated in spirally cut strips of rabbit renal arteries suspended in a physiological salt solution maintained at 37 °C. The four prostaglandins as well as noradrenaline elicited contractions of the isolated rabbit renal artery. At concentrations higher than 1.0 × 10−7 g ml−1 the contracting effect of prostaglandin E1 diminished. The vasoconstrictor actions of prostaglandins E2 and F2α were potentiated by cocaine and inhibited by phentolamine. On the other hand, phentolamine did not inhibit the vasoconstrictor effect of prostaglandins E2 and F2α on strips of rabbit renal arteries removed from rabbits pretreated with reserpine. These results were taken as an indication that part of the contractile effects of prostaglandins E2 and F2α on the isolated rabbit renal artery may be due to the release of noradrenaline from adrenergic nerve terminals.
Effect of 6-hydroxydopamine on brain and blood catecholamine, ammonia, and amino acid metabolism in rats subjected to high pressure oxygen induced convulsions
Authors: Singh A. K. , Banister E. W.
Published: April 2011

Effects of 6-hydroxydopamine (6-OHDA) on rat brain and blood adrenaline (A), noradrenaline (NA), ammonia (NH3), γ-aminobutyric acid (GABA), and amino acid metabolism prior to and after high pressure oxygen (OHP) induced convulsions have been studied. 6-OHDA reduces GABA and glutamate (Glu) prior to OHP exposure in rat brain so that the concentration is even equal to that seen in nondrugged animals after convulsion. Concomitantly, 6-OHDA reduces the latency of OHP-induced convulsion significantly, and increases brain NH3, glutamine, and asparagine significantly. Although 6-OHDA, in increasing dosage, elevates blood A concentration, convulsion produces a significant further increase in A. Blood NA was not significantly changed in drugged, convulsed animals and was much less than blood NA concentrations in nondrugged convulsed animals. Increasing doses of 6-OHDA also increase NH3 in the blood significantly and convulsion increases its concentration further. Latency of convulsion seems to be related to certain monoamine levels since in some drugged animals where A and total catecholamines are still reduced 96 h after the first of two doses of 6-OHDA, NA concentrations are recovered to relatively normal and the convulsion latency time is also increased although it remains significantly abbreviated from undrugged animals' convulsion time. Low brain GABA levels seem to be a prime effector of convulsive activity.