bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the Effects of Growth Hormone and Thyroxine on Proinsulin Synthesis and Insulin Formation in the Isolated Islets of Langerhans of the Rat
Authors: Sun A. M. , Lin B. J. , Haist R. E.
Published: April 2011

By using pulse-chase and islet-fractionating techniques, proinsulin synthesis and insulin formation in isolated islets from normal and hypophysectomized (Hx) rats have been studied. In both groups of rat islets, proinsulin synthesis took place in the microsomal fraction and its conversion to insulin in the granular fraction (which includes the Golgi complex). The total incorporation of 3H-leucine into proinsulin and insulin in the islets from Hx rats during the 30 min period of pulsing was 48% of the value obtained in the normal islets from control rats. When growth hormone (GH) was added to the incubation medium for islets from Hx rats, a substantial increase (79% of that found in normal islets) in total incorporation of 3H-leucine into proinsulin and insulin was observed. When the incubation mixture was supplemented with thyroxine (THY) along with growth hormone, the conversion of proinsulin to insulin was increased during the pulsing and chasing periods. The enhancement of insulin biosynthesis as a result of both GH and THY was confirmed by straight pulsing experiments. The possible mechanisms for the enhanced effect are discussed.
Adsorption and Conduction-Block of Opiate Narcotics on Nerve Membranes: Identical Effects of Levo- and Dextro-Forms
Authors: Seeman P. , Chau-Wong M. , Moyyen S.
Published: April 2011

(1) In order to detect the possible existence of stereospecific binding sites for the opiate narcotics, the adsorption and conduction-blocking action of the enantiomers of methadone and levorphanol were tested on nerve membranes.(2) The adsorption of radioactive dextro- and levo-methadone to homogenates of guinea pig brains were identical. The addition of nonradioactive levo-methadone displaced equal amounts of the radioactive dextro- and levo-methadones.(3) Simultaneous adsorption of 3H-levo-methadone and 14C-dextro-methadone to homogenates of various brain regions also did not reveal any stereoselective adsorption of the levo-isomer.(4) In vivo perfusion of guinea pig brain with 3H-levo-methadone simultaneously with 14C-dextro-methadone did not reveal any methadone uptake which was stereoselective for the levo-isomer and which was significantly different from skeletal muscle. In vivo perfusion with 3H-dextro-methadone simultaneously with 14C-levo-methadone also did not reveal stereoselectivity for the levo-form.(5) The synaptosome membrane/buffer partition coefficients for dextro- and levo-methadone were identical, having a value of 300 at 22°, and about 430 at 37° (in 10 mM sodium phosphate, pH 7). In 0.9% NaCl, the methadone partition coefficient fell to 32 (at 22 °C). The adsorption isotherm indicated only one set of binding sites.(6) The minimum concentrations required to block impulse conduction in rat phrenic nerve were 9.5 × 10−6 M for both dextro- and levo-methadone, 2 × 10−4 M for levorphanol, and 3 × to 4 × 10−4 M for dextrorphan.(7) It is possible that the binding is not stereospecific but that it is only the efficacy on the receptor which is stereospecific.
Acute and Chronic Myocardial Hypoxia: Effect on the Ventricular Action Potential
Authors: Saldeña T. A. , Zumino A. Ponce , Draque J. , Estrade J. R. E. Suárez
Published: April 2011

The intracellular electrical activity of ventricular fibers was studied in perfused hearts under normal oxygenation and acute hypoxia. The experiments were made on normal control rats (group I) and on rats subjected to simulated high altitude for 30 days (group II). The latter group under normal oxygenation showed a lengthening of the action potential due to a decrease in repolarization rate. In both groups acute hypoxia produced a shortening of the action potential and a fall in resting and action potential amplitude. Under this condition the action potential duration of group II consistently remained always longer than in the control group.
Extracellular K+ Activity and Slow Potential Changes in Spinal Cord and Medulla
Authors: Krnjević K. , Morris Mary E.
Published: April 2011

In cats under Dial, repetitive stimulation of primary afferent fibers evokes a negative potential change in the cuneate nucleus or the dorsal horn of the lumbar spinal cord, which is associated with a clear increase in extracellular K+ activity, recorded by K+ selective microelectrodes.
Effect of Phenobarbital Pretreatment on the Sensitivity of the Isolated Guinea Pig Vas Deferens to Various Agonists
Authors: Gascon André L. , Cloutier G.
Published: April 2011

The influence of phenobarbital pretreatment was studied on the sensitivity of the isolated guinea pig vas deferens to various agonists. The results reported in this communication show that such pretreatment produces an unspecific supersensitivity to catecholamines, histamine, and acetylcholine. Furthermore, the anticholinergic actions of atropine, the antihistaminic action of diphenhydramine, and the α-blocking property of phentolamine are reduced by the phenobarbital pretreatment. In conclusion, it is proposed that the supersensitivity observed is of the postsynaptic type and probably related to the facilitation of the energetic process involved in the smooth muscle contraction.
Effects of d,l-Propranolol, d-Propranolol, l-Propranolol, and Sotalol on Myocardial Contractility and Coronary Resistance
Authors: Tremblay G. M. , de Champlain J. , Nadeau R. A.
Published: April 2011

The effects of d,l-propranolol, d-propranolol, l-propranolol, and sotalol on myocardial contractility and vascular coronary resistance (V.C.R.) were studied on isolated perfused rat and guinea pig hearts, using a modified Langendorff technique. Left ventricular intracavitary pressure (L.V.P.) and maximum dp/dt were depressed by d,l-propranolol and d-propranolol but not by sotalol and l-propranolol. At constant coronary flow, perfusion pressure was decreased to 40% of control values by d,l-propranolol and d-propranolol but perfusion pressure remained unchanged with l-propranolol and increased with sotalol. The drop in V.C.R. following d,l-propranolol and d-propranolol preceded the fall of L.V.P. and occurred in fibrillating hearts as well. The same effect was obtained in noradrenaline-depleted hearts following pretreatment with 6-OH-dopamine. These observations suggest that d,l-propranolol has a coronary vasodilator action unrelated to its adrenergic-receptor blocking properties, and which appears specifically to be an effect of its dextro-isomer.
Intestinal Fluid Transport: Studies with the Gut of Ascaris lumbricoides
Authors: Harpur R. P. , Popkin J. S.
Published: April 2011

Sacs from the one-cell-thick intestinal wall of the pig round worm, Ascaris lumbricoides, were used to study fluid movement. Techniques were developed for making everted and noneverted sacs of this delicate tissue, and fluid movement was followed by the change in weight of the sacs. Fluid moved freely in response to an osmotic gradient but under isosmotic conditions it moved from the mucosal to the pseudocelomic side. With noneverted sacs the fluid movement, small under N2:CO2, 95:5, was inhibited by oxygen. There was a net inward movement of Na+ (pseudocelomic to mucosal side) which was unaffected by the gas phase. With everted sacs large fluid intakes were observed and these increased under aerobic conditions. Glucose increased fluid movement and was itself transported across the gut against a concentration gradient although at no time was a difference in osmosity detected. With the everted sacs there was a net movement of Na+ from the mucosal side to the inside of the sacs. Despite the large influx in fluid caused by glucose, the net movement of Na+ was unaffected by the presence of the sugar. Ouabain (10−2 mM) increased fluid movement provided the medium was not low in Na+. Photomicrographs showed that the intercellular spaces dilate during fluid transport.
II. Pharmacology of Angiotensin Antagonists
Authors: Regoli D. , Park W. K. , Rioux F.
Published: April 2011

The pharmacological properties of three antagonists of angiotensin II (ATII) have been characterized on the rat isolated stomach strip.(8-Gly)-ATII, a newly synthesized antagonist of ATII, as well as (8-Leu)-ATII and (1-Sar-8-Leu)-ATII displace to the right the dose–response curve of ATII and the displacement is proportional to the dose of antagonist.Dose–response curves of ATII remain parallel to that of the control in the presence of (8-Gly)-ATII and (8-Leu)-ATII, while parallelism is lost with (1-Sar-8-Leu)-ATII. This antagonist also depresses the maximal response to ATII.All data presented in this paper indicate that (8-Gly)-ATII and (8-Leu)-ATII are competitive antagonists of ATII with different affinities for the receptors, (8-Gly)-ATII being about 12 times less potent than (8-Leu)-ATII. This compound competes with ATII on a one to one basis: pA2 of (8-Leu)-ATII has the same value as pD2 of ATII.(1-Sar-8-Leu)-ATII does not fulfil the criteria of a competitive antagonist. This compound is very potent and the onset of action is as rapid (5 min) as for the other two compounds. All data obtained with (1-Sar-8-Leu)-ATII are consistent with the assumption that this compound is competitive in the sense that it acts on the same receptor site as ATII, but owing probably to slow rate of inactivation by tissue aminopeptidases, it dissociates slowly from the receptors and it acts as a specific long-acting antagonist.
Cyclic AMP and Intestinal Glycoprotein Synthesis: The Effect of β-Adrenergic Agents, Theophylline, and Dibutyryl Cyclic AMP
Authors: Forstner Gordon , Shih Michael , Lukie Bryan
Published: April 2011

Incorporation of [1-14C]glucosamine by acid-precipitable protein was enhanced in intestinal slices by isoproterenol, epinephrine, theophylline, and dibutyryl cyclic AMP. Moreover, the effect of either isoproterenol or epinephrine on [1-14C]glucosamine incorporation was markedly potentiated by the addition of theophylline. Uptake of [1-14C]glucosamine into the acid-soluble compartment of intestinal slices was not significantly affected by isoproterenol, epinephrine, or theophylline.The stimulatory effect of isoproterenol and theophylline was completely inhibited by cycloheximide. Subfractionation of intestinal slice homogenates indicated that increased synthesis was not confined to one glycoprotein class but appeared to effect mucins and glycocalyx glycoproteins equally. These results indicate that β-adrenergic hormones and cyclic AMP stimulate intestinal glycoprotein synthesis and may control the production of glycoproteins located at the intestinal surface.
Varying the Temperature Around the Scrotum of a Conscious Dog Between 15 °C and 31 °C does not Affect Respiration or Metabolism
Authors: Plewes J. L. , Jennings D. B.
Published: April 2011

A jockstrap which contained a temperature-controlled water perfusion system was placed around the scrotum of a resting conscious dog. Two series of experiments (five studies each) were carried out. In one series scrotal perfusion temperature was lowered in steps at 30-min intervals at temperatures of 31, 27, 23, 19, and 15 °C. Another comparable series of experiments was carried out except that the scrotal perfusion temperature was increased in the same steps from 15 to 31 °C. In both experiments there was a fall in hypothalamic and rectal temperatures with time but this was not different from control studies over a similar time in which scrotal perfusion temperature was maintained constant. Warming the scrotal area resulted in an increase in scrotal temperature and cooling the scrotal area resulted in a decrease in scrotal temperature. Despite these changes in local perfusion and scrotal temperatures, there were no significant changes in respiration or oxygen consumption. There was only a small increase in heart rate in the order of 12 beats/min with scrotal warming. It is unlikely that changes in thermal stimulation of the scrotum due to postural variations in resting conscious dogs are primarily responsible for variations in cardio–respiratory function for the conditions of this study.
Peripheral Neural Control of Thermoregulatory Salivary Secretion in the Rat
Authors: Rodland Karin D. , Hainsworth F. Reed
Published: April 2011

Rats exposed to heat stress increase heat loss by evaporating saliva groomed onto body surfaces. Both the submaxillary glands and the parotid glands secrete saliva in response to heat, and both are innervated by parasympathetic and sympathetic nerves. The results of previous investigations have indicated that the parasympathetic nervous supply is of major importance in controlling salivary secretion from the submaxillary glands of heat-stressed rats. In this study saliva was collected directly from the mouth of rats exposed to heat stress, and the saliva was analyzed for sodium concentration to determine the relative contribution of the submaxillary–sublingual and parotid glands. The results indicate that parasympathetic denervation of either the submaxillary glands or the parotid glands greatly reduces secretion from that gland, without affecting the body temperature at which secretion begins. Following sympathetic denervation, salivary secretion seems to start at a higher body temperature.
The Response of the Ductus Arteriosus to Prostaglandins
Authors: Coceani F. , Olley P. M.
Published: April 2011

Effects of various prostaglandin types on strips of lamb ductus arteriosus were investigated under anaerobic and aerobic conditions. Prostaglandins E1 and E2 relaxed markedly the anoxic ductus over a dose range from 10−9 to 10−5 M whereas they had little or no effect on the tissue after exposure to oxygen. This is in contrast to papaverine which relaxed the ductus to a similar degree before and after exposure to oxygen. An additional finding was that prostaglandins E1 and E2 are less active on the anoxic tissue depolarized by excess potassium. The greater effectiveness of prostaglandins on the anoxic ductus suggests a role for these compounds in the regulation of the vessel tone during fetal life.
A Cellular Calcium Pool for Contraction of Rabbit Ileal Muscle
Authors: Joiner Paul D.
Published: April 2011

Calcium ions (Ca2+) are accumulated by a cellular depot in isolated rabbit ileal longitudinal smooth muscle during incubation of this tissue in high Ca2+ medium. Transfer of the muscle to Ca2+-free solution results in a transient contractile response. The magnitude of the contraction appears to be a rectangular hyperbolic function of the Ca2+ concentration in the cellular compartment. When 10−6M acetylcholine (ACh) is present in the Ca2+-free solution, the muscle is stimulated, and the magnitude and duration of the mechanical activity occurring in the Ca2+-free environment is enhanced. When 10−6 or 10−7M epinephrine (Epi) is present in the Ca2+-free medium, the magnitude and duration of the contraction occurring in the Ca2+-free solution is reduced. Neither agent alters significantly the rate of loss of radioactive 45Ca from the muscle strips. Rather, these agents may be acting by influencing the operation of a saturable Ca2+ transport system located between the cellular Ca2+ pool and the contractile machinery. Evidence indicates that ACh increases and Epi decreases the turnover rate and/or number of active Ca2+ sites associated with this transport mechanism.
Noradrenaline Liberation from the Dog Heart In Vivo
Authors: Yamaguchi Nobuharu , Champlain Jacques de , Nadeau Reginald
Published: April 2011

The liberation of radioactive noradrenaline from the heart was studied in anesthetized open-chest dogs after a single injection of tritiated noradrenaline (15 μCi/kg in 1 ml Ringer) into the left anterior descending coronary artery. Radioactivity was counted in blood samples collected simultaneously from the coronary sinus and from one femoral artery. The output of radioactivity from the heart, i.e. the difference between the radioactivity of coronary sinus and femoral artery blood, decreased rapidly in the first 60 min until equilibrium between arterial and coronary sinus blood was reached. Bolus intracoronary injections of tyramine (10–100 μg) caused long-lasting dose-dependent increases in the output of radioactivity from the heart. After electrical stimulation of the left stellate ganglion (7 V, 2 ms, 2.5 min), the output of radioactivity from the heart increased markedly but rapidly returned to initial levels at the end of the stimulation period. The maximum liberation of radioactivity was observed at a frequency of 10 Hz corresponding to the optimal physiological responses in coronary sinus blood flow, left ventricular pressure, femoral arterial pressure, and heart rate. It appears that this preparation is sensitive enough to detect the liberation of noradrenaline after both drug-induced and electrical sympathetic nerve stimulation, and that it could be usefully applied to correlate various parameters of cardiac function with noradrenaline release from cardiac sympathetic fibers.
The Effects of Melatonin and Serotonin on Blood Flow Fraction and Testosterone Metabolism in Selected Organs of the Male Rat
Authors: Kinson G. A. , MacDonald Nora E. , Liu C-C.
Published: April 2011

The fractional distribution of cardiac output to the testes, adrenals, liver, and kidneys and the conversion of testosterone to 4-androstenedione by hepatic and renal homogenates in vitro were measured 4 weeks after implantation of male rats with melatonin and serotonin. The fractional blood flow to these organs was not significantly influenced by the indoles. There was, however, a tendency for the adrenal fraction to be lower in indole-treated rats. Blood levels of corticosterone in these animals were reduced, but significantly so only in the rats implanted with serotonin. The ability of liver preparations to metabolize testosterone in the presence of excess nicotinamide–adenine dinucleotide was enhanced after treatment with both indoles suggesting that at least one of the 17β-hydroxysteroid dehydrogenases had been stimulated. In the case of the kidney, melatonin administration gave rise to depression of the NAD-linked conversion whereas serotonin treatment caused reductions in testosterone conversions in the presence of either NAD or NADP.
Repolarization-Induced Reactivation of Contracture Tension in Frog Skeletal Muscle
Authors: Foulks J. G. , Miller J. A. D. , Perry Florence A.
Published: April 2011

In solutions containing perchlorate in place of chloride frog toe muscles or small bundles of semitendinosus fibers undergo maximum potassium (K) contractures of long duration at low [K]0 (5–10 mM). After relaxation at high [K]0, large protracted "reactivation" contractures (70–90% of maximum tension) again develop when repolarization is accomplished by a reduction of [K]0 to 2.5–10 mM. Somewhat smaller contractures also appear during repolarization at lower perchlorate concentrations (8–12 mM). The effects of perchlorate include disproportionate shifts in the relation between log [K]0 and K-contracture tension, and between log [K]0 and relaxation rate. Similar but smaller effects are observed in the presence of 1 mM caffeine or 1.5 mM chloroform. These observations implicate at least two potential-dependent processes in the regulation of contraction in frog twitch muscle.
Brain Chromatin Template Activity of Rats Treated with Δ9-Tetrahydrocannabinol
Authors: Hodgson John R. , Woodhouse Edward J. , Castles Thomas R.
Published: April 2011

Brain chromatin isolated from rats given a 10 mg/kg intraperitoneal injection of Δ9-tetrahydrocannabinol exhibited a significantly lower capacity to promote RNA synthesis than chromatin from vehicle-treated rats. The effect was not caused by either ribonuclease or an RNA polymerase inhibitor extracted with the chromatin.
Effect of a Meal on Cardiopulmonary and Metabolic Changes During Exercise
Authors: Jones N. L. , Haddon R. W. T.
Published: April 2011

Four subjects exercised at two levels of power output, approximating to 30% and 60% of their maximum O2 uptake, on three occasions: after a 24-h fast, after a 12-h fast, and 1 h after a 3000 Cal mixed meal. Measurements during exercise did not show any consistent effect on O2 uptake or heart rate. CO2 output, the respiratory exchange ratio, and ventilation were increased following the meal. Changes in blood lactate and the lactate/pyruvate ratio were variable and small. The increase in blood glycerol with exercise was least following the meal, indicating a lower level of fat mobilization; blood free fatty acids were lower. Blood glucose fell (from high resting levels) in three subjects following the meal, suggesting an increased usage of blood-borne glucose. The physiological effects of a meal on exercise performance in healthy subjects appear to be due mainly to inhibition of free fatty acid mobilization. This leads to an increased usage of carbohydrate energy sources, higher respiratory exchange ratio, and CO2 output, in turn leading to higher ventilation. No cardiovascular effects were detected.
Uric Acid Nephropathy in Shocked Rats after Blocking of Uricase Activity with Triazine Compounds
Authors: Boda D. , Pénzes P. , Gecse A. , Streitman K. , Zsilinszky E. , Karády I.
Published: April 2011

Uricase was inhibited by oxonic acid in rats subjected to sublethal tourniquet shock. Uric acid levels in serum and renal tissue increased considerably in animals thus treated. Following uricase inhibition and shock the animals developed uric acid nephropathy, which was well discernible macroscopically and also proved by polarization microscopy. The results support the assumption that uric acid nephropathy might be an additional factor in the development of renal failure due to shock in man. The absence of uricase in man may account for the high susceptibility of the human to acute renal failure.
Kinetics of Inulin Penetration in Cortex and Medullary Kidney Slices
Authors: Jairala Sara Weinschelbaum de , Vieyra Adalberto , Garcia Antonio Placer , Rasia Marta Luisa
Published: April 2011

The inulin space of dog kidney slices obtained from cortex and outer and inner medulla was evaluated by incubating the tissue at different time intervals in inulin Ringer. When the kidney was cut normal to the major axis of Henle's loops and collecting ducts, inulin uptake appeared to follow a single exponential time function in each renal region.When the organ was cut parallel to the major axis of Henle's loops the inulin space was greater and inulin uptake appeared to follow two exponential functions of time in each of the three renal regions. This would indicate that the plane of section can influence the apparent size of the extracellular space of kidney slices, as measured by the distribution of inulin.
Transfer of Anions Across Phospholipid Membranes
Authors: Singer M. A.
Published: April 2011

The permeability of phospholipid spherules to 11 anions was examined by measuring volume alterations under conditions in which these alterations reflect changes in anion movement. Chloride and bromide cross the membrane by some type of electrically neutral process not involving the species HCl or HBr. By comparison, iodide, thiocyanate, and salicylate are permeable in the charged form. Furthermore, the transport of these three anions is reduced by incorporation of cholesterol into the bilayer structure; iodide being affected more than thiocyanate or salicylate. Formate, acetate, propionate, benzoate, p-hydroxybenzoate, and p-aminobenzoate all permeate as undissociated acids. The relative permeabilities of these anions correlate well with organic solvent – water partition coefficients. Salicylate (o-hydroxybenzoate) can penetrate both in the undissociated and dissociated states. As opposed to the other aromatic anions, salicylate is capable of adsorbing to the lipid membrane in the ionic form. This property may partially explain the ability of this benzoate derivative to traverse the membrane as an ion. Salicylate can also facilitate the movement of anions such as acetate by virtue of its ability to make the lipid bilayer more permeable to hydrogen ions.
Cytochrome Oxidase of Skeletal Muscle: Adaptive Response to Chronic Disuse
Authors: Booth Frank W. , Kelso James R.
Published: April 2011

After 4 weeks of skeletal muscle disuse produced with hind-limb casts, the cytochrome oxidase activities were significantly lower in the "red" portions of the rectus femoris and gastrocnemius muscles. However, the cytochrome oxidase activities in the "white" portion of the disused gastrocnemius and in the disused soleus were not significantly different from respective control muscles. These results suggest a decreased aerobic capacity in muscle fibers with high oxidative enzyme activity as a result of immobilization.
The Effects of Thyroxine and Isopropylnoradrenaline on Cytochrome Oxidase Activity in Brown Adipose Tissue
Authors: Heick H. M. C. , Vachon C. , Kallai Mary Ann , Bégin-Heick Nicole , LeBlanc J.
Published: April 2011

Groups of animals were treated with injections of isopropylnoradrenaline, thyroxine, or both hormones together. The effects of these hormonal treatments on the size, protein content, and level of some mitochondrial enzymes, in particular the cytochrome oxidase, were determined and compared to the effect on these parameters produced by cold adaptation. The changes observed were correlated with the resistance of the animals to cold stress and with their metabolic response to injections of isopropylnoradrenaline. All treatments increased the size of the brown adipose tissue. Whereas thyroxine had little effect on the protein content and cytochrome oxidase, both isopropylnoradrenaline and cold adaptation produced increases in these parameters. It appears that the isopropylnoradrenaline-treated animals mimic more closely the cold-adapted animals than do those with thyroxine treatment. However, the isopropylnoradrenaline-treated animals are not as resistant to cold as the cold-adapted animals.
Calcium Movement in Vascular Smooth Muscle and its Detection Using Lanthanum as a Tool
Authors: Freeman D. J. , Daniel E. E.
Published: April 2011

Lanthanum (La3+) (2 mM).initially increased efflux of 45Ca from rings of rabbit aorta, but also caused an increased retention of 45Ca after prolonged washing of the tissue in La3+-containing solution for 60 min. La3+ was also found to inhibit the uptake of 45Ca into this preparation. Exposure to high potassium for 60 min during uptake of 45Ca increased the amount of tracer retained after the La3+ wash, but the extra amount retained was in excess of that required to activate contraction, and much more than the extra retention after exposure to high potassium for 5 min sufficient to produce maximal tension. Exposure to noradrenaline during 45Ca uptake produced a smaller extra retention of isotope following La3+ washing. In the presence of high potassium, exposure to noradrenaline had a greater effect on the extra retention of 45Ca.The potassium-induced contracture of rabbit aortic rings was prevented and/or relaxed by La3+ (2 mM); and while the sustained response to noradrenaline was similarly affected, the initial phasic response to this agent could still be elicited in the presence of La3+.These results suggest that La3+ can displace Ca2+ from extracellular sites and inhibit influx of extracellular Ca2+ and part of the efflux of intracellular Ca2+. The potassium-induced contractures and the sustained response to noradrenaline involve transmembrane Ca2+ movements, while the phasic response to noradrenaline does not. However, results of 45Ca uptake studies cannot be interpreted as showing that La3+ seals the membrane to Ca2+, or that extra Ca2+ retained by La3+ is related to contraction.
The Effect of Heat, Cold, and Exercise on Plasma Dopamine-β-Hydroxylase Activity in Man
Authors: Frewin D. B. , Downey J. A. , Levitt M.
Published: April 2011

The effect of a standardized exercise procedure on plasma dopamine-β-hydroxylase (DBH) activity has been assessed in five normal human subjects. The activity of the enzyme was measured using a sensitive, nonradioactive assay based on the conversion of tyramine to octopamine. Each subject was tested at an ambient temperature of 40 °C and on a subsequent day at a temperature of 10 °C. The resting levels of DBH activity were significantly higher in the cold. A small increase in enzyme activity occurred with exercise at 40 °C, but there was no change in this parameter with exercise in the cold. It is suggested that the rise in plasma DBH activity seen in the cold and with exercise results from increased sympathetic activity. However, the failure of DBH activity to increase with exercise in the cold is poorly understood.
An Improved Microprocedure for the Determination of Heparin
Authors: Sue T. K. , Jaques L. B.
Published: April 2011

The microelectrophoresis method described by Jaques et al. (Can. J. Physiol. Pharmacol. 46, 351–360 (1968)) for identification and quantitation of microquantities of heparin was improved by using the differential effects of inorganic electrolytes on the solubility of quaternary ammonium – mucopolysaccharide complex. Samples were applied to agarose gel coated microscope slides for electrophoresis. The slides were then immersed in 0.1% cetylpyridinium chloride (CPC) in M NaCl at 35 °C with constant agitation for 5 h, washed thoroughly with 0.1% CPC, then stained with toluidine blue. As a result of this treatment, only heparin in concentrations of 0.25–2.0 μg produced optically dense spots on the slides for measurement. Heparin was identified by the combined information from electrophoretic migration, salt fractionation, and metachromatic activity.
Adrenergic Innervation of Brown Adipose Tissue from the Ground Squirrel (Citellus richardsonii)
Authors: Cottle M. K. W. , Cottle W. H. , Nash C. W.
Published: April 2011

Determinations of noradrenaline (NA) content and observations of histochemical fluorescence were carried out on the axillary brown fat pad of ground squirrels Citellus richardsonii kept at two temperatures, 20 °C and 5 °C. For comparison, NA content of hearts and intrathoracic brown adipose tissue were also determined. Like interscapular brown adipose tissue from cold-acclimated rats, the axillary brown fat of cold-acclimated ground squirrels contained a high level of NA. The NA content of the fat pad from ground squirrels living at 20 °C, however, though somewhat lower was not statistically different from that of the fat pad from the cold-acclimated animals. Fine adrenergic nerve fibers were observed between the adipocytes and more intense and extensive networks were present around arterioles. The density of adrenergic innervation appeared similar in the axillary brown fat of the two groups. The NA content of the hearts of ground squirrels living at 5 °C was lower than that for hearts from animals at 20 °C. Intrathoracic brown fat tissue from both groups of animals showed large variation.
Inhibitory Effect of Sodium Pumping on Spontaneous Contractility of Rabbit Myometrium
Authors: Johns Anthony , Paton David M.
Published: April 2011

The effects of K+ and related cations on the spontaneous contractility of estrogen-dominated rabbit myometrial strips were examined in vitro with isometric force-displacement transducers. Addition of 5–40 mM KCl, RbCl, or CsCl caused increased contractility of strips in medium containing 5.4 mM K+. Removal of K+ from the medium generally increased contractility. Addition of KCl, RbCl, CsCl, or LiCl to strips in K+-free medium caused an immediate rapid inhibition of contractility, the relative potencies being K+ = Rb+ > Cs+ > Li+. This effect was produced by 0.25–40 mM KCl or RbCl and was inhibited by 10−5 M ouabain. It was concluded that addition of K+, Rb+, Cs+, or Li+ to tissues in K+-free medium probably activated electrogenic Na+ pumping with resultant membrane hyperpolarization and inhibition of mechanical activity.
Dantrolene Sodium: Effects on Crustacean Muscle
Authors: Odette L. L. , Atwood H. L.
Published: April 2011

The effect of dantrolene sodium, a muscle relaxant effective on vertebrate skeletal muscle, has been studied on the stretcher muscle of a crab (Callinectes sapidus). The drug rapidly and reversibly attenuates the muscle contractile response to direct and indirect stimulation. Neuromuscular transmission is unaffected, as are the electrical properties of the muscle membrane. It is concluded that dantrolene sodium uncouples excitation–contraction mechanisms in crustacean tonic muscle.
Analysis of the Movements of Myogenic Cells during Muscle Organogenesis in Vitro
Authors: Noble P. B. , Peterson S. C.
Published: April 2011

The paths taken by myoblasts during the proliferation and fusion phases have been analyzed. It was found that, although the criteria for the two-dimensional random-walk theory were not satisfied, analyses of related parameters showed important differences between cell movement in these two phases. It appears that cell movement just prior to fusion is characterized by longer steps and a smaller angle of departure from the previous direction of motion when compared with cells in the proliferative cells.
Regional Sweating in Eskimos Compared to Caucasians
Authors: Schaefer Otto , Hildes J. A. , Greidanus Peter , Leung Dominic
Published: April 2011

After pharmacological stimulation, prints of functioning sweat glands were obtained from 17 skin sites on the face, body, and limbs of 37 adult male Eskimos and 21 Caucasian controls.Eskimos showed greater numbers and greater activity of functioning sweat glands on exposed parts of the face such as nose and cheeks, while responding with significantly less sweat gland activity on all body surfaces that are normally heavily clothed in winter. Trunks, arms, hands, legs, and feet showed a progressive reduction of sweat gland response in the order of one-half on the trunk to one-fifth on feet when comparing mean sweat gland counts per square centimeter in Eskimos and controls. The comparative reduction of sweat gland response in the Eskimos progressed in the same order as the distance of the part from the body core, and as the risk of the part to freezing. Therefore, this reduction of sweat gland activity may represent a morphological and/or functional adaption to environmental conditions including climate and clothing.
Hereditary Vasopressin-Resistant Diabetes Insipidus in SWV Mice
Authors: Virgo N. Sheila , Miller James R.
Published: April 2011

Old female mice of the SWV strain have an hereditary polydipsia–polyuria defect with a severe increase in water turnover and with hypotonic urine which contains no glucose, blood, or protein; that is, they have diabetes insipidus. Their responses to exogenous vasopressin (negative) and water deprivation (positive) and the normal amount of neurosecretory material in their posterior pituitaries indicate that they have nephrogenic diabetes insipidus. The females also have a progressive kidney defect which, although it resembles nephronophthisis in some aspects and hypokalemia in others, is unique. There is a progressive anemia. Amyloid kidneys, polycystic kidneys, diabetes mellitus, and nephronophthisis have been ruled out as the cause of the defect but hypokalemia and hypercalcemia are still possibilities. The SWV males have a milder form of the defect which develops at an older age and shows no signs of histopathology.
The Inotropic and Chronotropic Responses of the Guinea Pig and Dog Myocardium to Isoprenaline and Salbutamol
Authors: Hughson R. L. , Ledsome J. R.
Published: April 2011

The relative effects of isoprenaline and salbutamol on the inotropic and chronotropic responses of the denervated myocardium of the chloralose anesthetized dog and of the isolated guinea pig atrium, and the inotropic response of the isolated dog papillary muscle were studied. Both the in vivo dog heart and the in vitro guinea pig atrium displayed a similar relative response pattern to isoprenaline and salbutamol with regard to their inotropic and chronotropic responses. However, a comparison of the relative inotropic responses of the dog heart in vivo and in vitro showed that in vitro, salbutamol has a much lower affinity and efficacy for the adrenergic receptors than isoprenaline.
Effects of Local Anesthetics and Hemicholinium-3 on 45Ca Efflux in Barnacle Muscle Fibers
Authors: Chen Stephen S.
Published: April 2011

Benzocaine, which occurs in the uncharged form in the physiological range of pH, caused inhibition of 45Ca efflux in barnacle muscle fibers. By contrast, in the presence of a low external Ca2+ concentration, it produced stimulation of the efflux. Both the inhibitory and stimulatory actions of benzocaine appeared to be less potent than those of procaine. Hemicholinium-3 (HC-3), on the other hand, which exists only in the charged form, caused a large stimulation of the 45Ca efflux following microinjection, and the potency of this action was found to be at least 10 times greater than that of procaine. External application of HC-3 produced inhibition occasionally. Effects of tetracaine were similar to those produced by procaine; however, its inhibitory action was greater in more alkaline solution, which is the opposite of that observed with procaine. Lidocaine produced a less consistent effect than procaine; the inhibitory action of the former was less potent but the stimulatory action of the two anesthetics were comparable. p-Aminobenzoic acid was without effect on 45Ca efflux. These results indicate that both the charged and uncharged forms of local anesthetics are capable of causing stimulatory and inhibitory effects on 45Ca efflux in barnacle muscle fibers, and that the inhibition produced is the result of action on the Ca–Ca exchange system whereas the stimulation is the result of release of Ca from internal storage sites.
Intracellular Mg2+ increases neuronal excitability
Authors: Krnjević K. , Puil E. , Werman R.
Published: April 2011

Injection of Mg2+into spinal motoneurons of cats leads to a depolarization, associated with a fall in membrane conductance, diminution in post-spike hyperpolarization, and increased excitability. This action has an apparent reversal level substantially more negative than the resting potential, and can be ascribed to a fall in K+ membrane conductance. Since these effects are opposite to those produced by intracellular Ca2+, it is suggested that Mg2+ probably competes with Ca2+ the Ca2+ -activated K+ ionophores. Neuronal excitability can be regulated by the ratio of internal free Ca2+/Mg2+.
Characteristics of accumulation of ephedrine in rabbit atria
Authors: Golko D. S. , Paton D. M.
Published: April 2011

The characteristics of uptake of (±)-[β-14C]ephedrine were studied in isolated rabbit atria. Ephedrine was rapidly accumulated against the concentration gradient. From 5 × 10−7 to 10−2 M, uptake occurred at a uniform initial rate. Uptake was slightly inhibited by high concentrations of ouabain, cocaine, desipramine, lidocaine and phenethylamines, and by a reduction in the external Na+ concentration. Uptake was not, however, reduced by omission of K+ from the medium, by metabolic inhibitors or by a variety of drugs known to inhibit the extraneuronal uptake and binding of noradrenaline. Pretreatment of animals with 6-hydroxydopamine very significantly reduced the uptake of (±)-[3H]metaraminol, but did not alter the uptake of ephedrine. It was concluded that the uptake of ephedrine in rabbit atria occurred predominantly in extraneuronal tissues possibly as a result of passive diffusion followed by binding.
Observations on the effect of salicylate in fever and the regulation of body temperature against cold
Authors: Pittman Q. J. , Veale W. L. , Cooper K. E.
Published: April 2011

Prostaglandins appear to be mediators, within the hypothalamus, of heat production and conservation during fever. We have investigated a possible role of prostaglandins in the nonfebrile rabbit during thermoregulation in the cold. Shorn rabbits were placed in an environment of 20 °C, and rectal and ear skin temperatures, shivering and respiratory rates were measured. A continuous intravenous infusion of leucocyte pyrogen was given to establish a constant fever of approximately 1 °C, and after observation of a stable febrile temperature for 90 min, a single injection of 300 mg of sodium salicylate, followed by a 1.5 mg/min infusion was then given. After the salicylate infusion was begun, rectal temperature began to fall, and reached nonfebrile levels within 90 min. Shivering activity ceased, respiratory rates increased, and in two animals, ear skin temperature increased. When these same rabbits were placed in an environment of 10 °C, at a time they were not febrile, and an identical amount of salicylate was given, rectal and ear skin temperatures, shivering and respiratory rates did not change. These results indicate that prostaglandins do not appear to be involved in heat production and conservation in the nonfebrile rabbit.
Effective vascular compliance and venous diameter in dogs
Authors: Larochelle Pierre , Ogilvie Richard I.
Published: April 2011

Total effective vascular compliance was measured repeatedly in open-chest dogs without circulatory arrest, utilizing a closed-circuit venous bypass system with a constant cardiac output. Mutual inductance coils were used to measure the diameter of the inferior vena cava above the diaphragm at the position where the pressure change was recorded during a volume load (ΔV). In all experiments, there was a relationship which tended to be curvilinear between the diameter of the inferior vena cava and the venous pressure before ΔV. No relationship was demonstrated between the initial diameter or pressure and the calculated effective vascular compliance. During aortic constriction or infusion of noradrenaline, the effective compliance was reduced in value at any given initial venous diameter and pressure. An unaltered venous diameter and plasma volume excluded the possibility of a large change in initial venous volume as a cause of the observed changes in compliance during aortic constriction or during infusion of noradrenaline. A relationship was observed between compliance and calculated venous wall tension so that as the wall tension, developed during a fixed volume load, increased, there was an associated reduction in compliance. These results demonstrate that the measurement of effective compliance provides an assessment of combined active and passive venous wall tension and venous tone.
Action of prostaglandin synthetase inhibitors on rostral hypothalamic neurones: thermoregulation and biogenic amines
Authors: Jell Ralph M. , Sweatman Paul
Published: April 2011

Sensitivity of neurones in the rostral hypothalamus of methoxyflurane anesthetized cats to the prostaglandin synthetase inhibitors (PGSIs), salicylate and fenoprofen, has been examined using the technique of microiontophoresis. Results were compared with sensitivity to prostaglandin (PG) E1 and no noradrenaline (NA) and 5-hydroxytryptamine (5HT). Simultaneous applications of PGSIs and NA or 5HT were made to investigate the role of PG in monoamine induced changes in neuronal excitability. PGSIs did not excite these cells, but depressions were common, particularly with fenoprofen. PGE1 did not reverse the depressions. NA and 5HT responses were generally unaffected by simultaneous PGSI application and responsiveness to PGSIs was found to be unrelated to amine sensitivity.The results support the conclusion that PGSIs have a depressant action on neurones in this region, which may not be related to inhibition of prostaglandin synthesis, and that the actions of microiontophoretically applied NA and 5HT are not dependent upon PG.
Unmasking of sympathetic vasoconstriction of the coronary vessels after acute administration of reserpine to dogs
Authors: Szentiványi M. , Kunos G. , Juhász-Nagy A.
Published: April 2011

Acute intravenous administration of reserpine or pretreatment of dogs with Segontin selectively abolished coronary vasodilation and unmasked a constrictor response to stimulation of the cardiac sympathetics. In view of earlier findings of separate coronary vasomotor and cardiostimulatory sympathetic innervation, the results are interpreted to indicate the existence of reserpine-resistant short (vasomotor) and reserpine-sensitive long (cardiostimulatory) sympathetic postganglionic neurons.
The role of insulin in the glucostatic control of food intake
Authors: Rezek Milan
Published: April 2011

Insulin, a primary metabolic hormone, plays a dominant role in the regulation of food intake. An increase in the level of circulating insulin produced by its prandial release from endogenous stores is associated with the state of satiety. On the other hand, an increase in the insulin level produced by its exogenous administration, as well as by its excessive and prolonged release in certain pathological states or during the period of nocturnal overeating, paradoxically gives rise to the sensation of hunger. This differential effect of endogenous and exogenous insulin is analyzed in view of experimental and clinical evidence concerning the principal mechanisms in the regulation of food intake. These include the interrelation of central and peripheral glucosensitive systems, the involvement of the enteroinsular axis, and the effects on these regulatory mechanisms of the physiological state produced by changes in circulating insulin levels. The essential role of the vagus nerve in mediating the hunger and satiety induced by the lack or excess of glucose for cellular oxidation places the short-term glucostatic control in the periphery where the insulin is primarily acting. A unifying hypothesis concerning the role of insulin in the regulation of food intake is proposed and its clinical implications suggested.
Effects of an ATP analogue (α,β-methylene-adenosine-5′-triphosphate) on cyclic AMP and cyclic GMP levels, 45Ca efflux, and protein secretion from rat pancreas
Authors: Heisler Seymour
Published: April 2011

The effects of the α,β-methylene analogue of ATP (Ap(CH2)pp), described as a competitive inhibitor of adenylate cyclase (EC 4.6.1.1), were studied in the rat pancreas in vitro. The analogue did not alter basal cyclic AMP production and basal or carbachol-stimulated efflux of 45Ca from isotope-preloaded glands. On the other hand, Ap(CH2)pp reduced the secretory responses to carbachol, carbachol in the presence of dibutyryl cyclic AMP, pancreozymin (PZ), and the calcium ionophore, A-23187. Release of pancreatic protein in response to dibutyryl cyclic AMP itself was unaffected by the ATP analogue, suggesting that the other secretagogues tested share a common, Ap(CH2)pp-inhibitable pathway in their respective stimulatory actions. Though carbachol, PZ, and A-23187 all stimulated a rapid production (30 s) of pancreatic cyclic GMP, these responses were not affected by Ap(CH2)pp. Additional studies with the analogue indicated that it has a slow onset of action (30–45 min), i.e., its effect on secretion is preceded by secretagogue-induced changes in nucleotide levels and calcium efflux. Nonetheless, the analogue may affect cellular calcium homeostasis, if not during the initial events triggering secretion, then during those events which maintain continued secretory output in the presence of a stimulus.
Differences in the altered energy metabolism of hemorrhagic shock and hypoxemia
Authors: Chaudry Irshad H. , Sayeed Mohammed M. , Baue Arthur E.
Published: April 2011

The effect of hemorrhagic shock, hypoxemia, and anoxia on the levels of adenine and pyridine nucleotides of liver and kidney was assessed. ATP levels in liver and kidney of animals in shock or animals subjected to 7 min of anoxia decreased by 85 and 73%, respectively. Under hypoxic conditions (arterial [Formula: see text] at 18 mmHg), the decrease was only 62 and 48% in liver and kidney, respectively. Tissue NAD levels decreased and NADH levels increased during shock but were found to be essentially unaltered during experimental hypoxemia. Thus, shock produced greater alterations in adenine and pyridine nucleotides than did hypoxemia alone, indicating that stagnant hypoxemia due to shock is more deleterious to energy metabolism than is severe hypoxemia with an otherwise normal circulation. The results also suggest that if an arterial [Formula: see text] of 18 mmHg represents the initial stages of tissue hypoxia, then tissue ATP levels are a more sensitive indicator of this than NAD levels.