bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of hemodynamic factors on urinary calcium and magnesium excretion
Authors: Gonda A. , Wong N. , Seely J. F. , Dirks J. H.
Published: April 2011

The effects of unilateral vasodilatation and alterations in the mean arterial pressure upon the renal handling of calcium and magnesium were studied by clearance methods in dogs. Unilateral vasodilatation was produced by infusion of acetylcholine or bradykinin into the left renal artery, while arterial pressure was altered by aortic constriction, carotid occlusion and vagotomy, or by systemic infusion of angiotensin. Urinary electrolyte excretion was increased markedly by the infusion of each vasodilator and also varied directly with the mean arterial pressure, despite the absence of any significant changes in the filtered load. The fractional excretion of both calcium and magnesium correlated significantly with that of sodium. These results indicate that acute changes in renal hemodynamics modify the tubular reabsorption of divalent cations as well as alter sodium reabsorption.
Microcirculatory effects of prostaglandins
Authors: Viguera M. G. , Sunahara F. A.
Published: April 2011

In vivo microscopy was utilized to evaluate the vasomotor action of prostaglandin E1 (PGE1) and prostaglandin F2α (PGF2α) in the mesocecal and cremasteric muscle circulation of the rat. Vessel dimensions were monitored by using a novel system consisting of microscope, image-splitting eyepiece, television camera, videoscreen, and a write-out apparatus giving exact minute to minute measurements of the microvessel lumen diameter. Intravenous administration of PGE1 decreased systemic blood pressure with a concomitant increase in diameter of the metarterioles of the cremaster muscle and a decrease in diameter of the metarterioles of the mesocecum; it effectively inhibited the constrictor effect of topically applied norepinephrine and epinephrine on the mesocecum metarterioles. Constrictor effects of topically applied angiotensin II were not altered. Intravenous PGF2α increased systemic blood pressure with a concomitant decrease in metarteriolar diameter in both the mesocecum and cremaster muscles. The vascular effects of PGE1 could be explained by its apparent ability to block at the postganglionic sympathetic neuroeffector site where PGE1 acts on the vascular tissue, modulating its response to adrenergic stimulants, whereas PGF2α acts as a direct stimulant of the vascular smooth muscle.
Glass electrode measurement of ion transfers during rewarming of the single rat tail artery
Authors: Friedman Sydney M. , Nakashima Miyoshi , Palatý Vladimír
Published: April 2011

Capillary glass electrodes were used in two separate procedures to examine the kinetics of exchange of Na+ for K+ during rewarming of the precooled rat tail artery. In the first system, the intravascular medium remains stationary in the artery for intervals of 3, 6, or 9 min, and the change in ion concentrations in this small volume (approximately 25 × 10−3 ml) is then measured by difference against a parallel "dummy" system. In the second procedure, the intravascular medium moves continuously at 0.01 ml/min and is collected in fine bore polyethylene tubing for later passage through the electrodes at 0.15 ml/min. Both systems yielded similar quantitative data but the first system was less precise and it is possible that the artery was less well maintained. The second system clearly revealed an extra complement of Na+ liberated from the tissue well in advance of an observable, metabolically driven uptake of K+ and provided a detailed substantiation of previously reported deductions of this fact. The final equilibrium transcellular Na+ and K+ gradients attained after rewarming were lower in stretched than in unstretched arteries.
Rate of release of amino acids from the cerebral cortex in the cat as affected by brainstem and thalamic stimulation
Authors: Jasper Herbert H. , Koyama Ikuko
Published: April 2011

The rate of release of amino acids from the cerebral cortex has been measured by a surface superfusion technique in spinal (encephale isolé) cat preparations in relation to the state of cortical activation by stimulation or destruction of the midbrain reticular formation (MRF). Reticular stimulation, with desynchronized cortical activation simulating "arousal", was found to cause a selective increase three-to seven-fold (0.3 to 2.0 mμmoles/min per cm2) in the liberation of glutamic acid without significant change in glutamine, valine, and leucine, suggesting that glutamic acid may be involved either directly or indirectly in the chemical mediation of reticulo–cortical activation. Uniformly lower values were obtained during slow-wave sleep. A smaller and less consistent increase was found in aspartic acid, glycine, and taurine. Free GABA was released in the cortical superfusate in amounts ranging from 0.2 to 2.0 mμmoles/min per cm2 only during periods of slow-wave sleep or following lesions of the MRF. GABA was reduced to undetectable amounts by reticulo–cortical activation with desynchronization of the EEG, confirming previous studies showing an increase in free GABA during sleep. An increase in the rate of liberation of acetylcholine (ACh) by mesial thalamic stimulation in preparations in which the same stimulation produced no increase in glutamic acid shows that it is possible to dissociate certain of the anatomical pathways responsible for cholinergic cortical activation from those responsible for the release of glutamic acid. Quantitative comparison between the increases in ACh and glutamic acid by MRF stimulation would suggest that glutamic acid may be as important as ACh in neurochemical mechanisms underlying the reticulo–cortical arousal response, even though different release mechanisms may be involved.
The effect of triiodothyronine on cyclic AMP, phosphorylase, and adenyl cyclase in rat heart
Authors: McNeill John H. , Muschek Lawrence D. , Brody Theodore M.
Published: April 2011

Pretreatment with triiodothyronine (T3) greatly enhanced the epinephrine-induced increase in rat cardiac phosphorylase a. T3 treatment, however, did not increase the level of adenosine-3′,5′-monophosphate (cyclic AMP) in rat heart. T3 treatment also did not increase the activity of rat heart adenyl cyclase or change the sensitivity of the enzyme to epinephrine when activity was determined in vitro. It is suggested that if thyroid hormone affects the activity of adenyl cyclase in vivo the effect is lost in the preparation of the enzyme for assay in vitro.
Influence of microsomal enzyme inducers on the reactivity of the isolated guinea pig seminal vesicle to angiotensin and tyramine
Authors: Gascon A. L. , Brodeur J.
Published: April 2011

The reactivity of the isolated guinea pig seminal vesicles to angiotensin and tyramine was investigated after chronic pretreatment of the animals with some potential microsomal enzyme inducers. After pretreatment with phenobarbital, 3-methylcholanthrene, SKF 525-A, glutethimide, and DDT, there was a marked increase in the reactivity of the isolated seminal vesicles to angiotensin and (or) tyramine. However, other inducers, such as meprobamate and chlorcyclizine, failed to alter the reactivity of the preparation. This effect of the inducers is possibly related to an increased protein synthesis, since the action of phenobarbital was completely abolished by actinomyein D. It is suggested that the microsomal enzyme inducers might stimulate the synthesis of the enzymes responsible for the formation of catecholamines in the seminal vesicles.
Vitamin C activity of D-isoascorbic acid for the guinea pig
Authors: Pelletier Omer , Godin Claude
Published: April 2011

Guinea pigs fed with a synthetic diet or a rabbit ration were depleted of vitamin C for 17 days. The scorbutic animals were treated daily during 2 months with 40 mg D-isoascorbic acid (IAA) or 2 mg L-ascorbic acid (AA). Both isomers restored the growth of the animals and caused the disappearance of scorbutic symptoms. For 3 weeks, the two diets gave similar response, after which the animals fed with the rabbit ration grew much less. Animals given IAA ate less and had smaller weight gains than those given AA; this effect was overcome by pair-feeding. Only a small proportion of administered IAA was recovered in the organs and in the urine. The total ascorbic acid content (AA and IAA) of the IAA-treated animals was less than that of the AA-treated animals. The low AA content of the organs of the IAA-treated animals indicated that IAA had no significant sparing action on AA.
Comparative effect of procainamide and lidocaine on myocardial contractility
Authors: Nahas M. , Lachapelle J. , Tremblay G. M.
Published: April 2011

The effect of procainamide and lidocaine on myocardial contractility was studied in an isovolumic isolated rat heart perfusion preparation following the Langendorff technique. As a measure of myocardial contractility, the left ventricular intracavitary pressure and maximum dp/dt were determined and were found to be depressed proportionately to the dose of these agents. At the same concentration, lidocaine showed a more negative inotropic effect than procainamide (although the former seems clinically innocuous at therapeutic doses). In addition, procainamide produced in about one-half of the experiments a biphasic effect characterized by a slight transitory positive inotropic effect followed by a negative inotropic effect.
Uptake of choline by the isolated perfused rat liver
Authors: Tuma D. J. , Beckenhauer H. C. , Keefer R. C. , Barak A. J.
Published: April 2011

This work has demonstrated that when choline is added to the perfusate of isolated livers, these take up the base throughout the duration of the experiment. A sensitive method is described, in which 1,2-14C-choline is used, for estimating the uptake of choline by the liver.
The efficacy of antiarrhythmic drugs in the prevention of recurrence of aconitine-induced atrial fibrillation after electrical conversion
Authors: Byrne Jeffrey E. , Dresel Peter E.
Published: April 2011

We have developed an experimental model to assess the ability of drugs to maintain slow supraventricular rhythm after electrical conversion of atrial fibrillation. Fibrillation was produced by application of a saturated solution of aconitine to the surface of the right atrium of open-chest dogs. Right and left atrial electrograms, the lead II electrocardiogram, and blood pressure were recorded. A capacitor discharge (30 watt-seconds) was applied through electrodes placed on the right atrium and the left ventricle. Atrial rhythm was improved for 1 to 20 s following defibrillation; then atrial fibrillation returned owing to the continued presence of aconitine. Quinidine in doses up to 4 mg/kg did not convert the arrhythmia but increased the duration of recovery after defibrillation up to 49 s. Pronethalol in doses up to 8 mg/kg and propranolol in doses up to 0.8 mg/kg occasionally converted atrial fibrillation to normal rhythm, but had no effect upon the duration of recovery after defibrillation. Diphenylhydantoin was tested in doses up to 20 mg/kg. Rapid injection of doses above 10 mg/kg slowed or converted the arrhythmia. Slow injections of diphenylhydantoin had no direct effect on the atrial fibrillation, but the period of recovery after defibrillation was prolonged up to 700 s. These experiments show that drugs can enhance the ability of the heart to maintain a slow rhythm following electrical conversion of atrial fibrillation. Those agents which most effectively convert atrial fibrillation are not the most effective agents for preventing the return of fibrillation after conversion.
Functional maturation of renal PAH transport in the dog
Authors: Hook J. B. , Williamson H. E. , Hirsch G. H.
Published: April 2011

Most investigations dealing with the development of renal transport mechanisms have utilized in vitro systems for measuring transport. The purpose of this investigation was to observe the pattern of development of renal PAH transport in vivo by measuring TmPAH in anesthetized dogs ranging in age from 1 week to adult. Puppies from each litter were studied at 1, 2, 4, 6, and 8 weeks of age in acute experiments. The maximal ability to transport PAH was determined by increasing the plasma concentration in a stepwise manner until Tm was exceeded. The Tm data obtained were compared with transport data obtained from other animals at similar ages using the in vitro slice method of Cross and Taggart. TmPAH was found to increase from 1 week to 8 weeks of age. At 8 weeks TmPAH was still less than in the adult whether based on kidney weight or body weight. In contrast, when measured in vitro, PAH transport (S/M) was found to increase to a maximum at 4 weeks and decline to adult levels. These data demonstrate that the cellular function (S/M) and apparent functional mass (Tm) of renal cortical tissue are low at birth and increase with age, but do so at different rates.
Some properties of an adenosine triphosphatase obtained from beef corneal epithelium
Authors: Allin W. D. , Miller J. R. , Matuk Y.
Published: April 2011

A partially purified ATPase preparation obtained from beef corneal epithelium was studied. The dialyzed enzyme had an absolute requirement for Mg++, and a Mg: ATP ratio of 1:1 appears to be necessary for optimum reaction. The enzyme was stimulated by the addition of low concentrations of KCl, NaCl, and choline chloride. Higher concentrations of the salts, however, decreased the activity observed in the presence of MgCl2 alone. NaCl increased the inhibition caused by KCl and vice versa. Ouabain had no effect, but N-ethylmaleimide, EDTA, and CaSO4 decreased the activity of the enzyme.
Effect of cardiac sympathectomy, reserpine, and environmental temperatures on the catecholamine levels in the chicken heart
Authors: Lin Y. C. , Sturkie P. D. , Tummons J.
Published: April 2011

Cardiac catecholamine levels were spectrofluorometrically determined in adult male chickens following two treatments: (1) denervation of the cardioaccelerator nerves or (2) reserpine administration after acclimatization of the birds to low, intermediate, or high ambient temperatures. Marked depletion of cardiac catecholamines (80 to 90%) was found 2 weeks after denervation and 24 h after injection of reserpine. Acclimatization did not alter the response to reserpine.
Influence of cyclohexylamine on the adrenergic cardiopathy
Authors: Classen H. G. , Solymoss B. , Varga S.
Published: April 2011

In rats pretreated with 9α-fluorocortisol, the effects of epinephrine on blood glucose, potassium, and free fatty acids were markedly enhanced by the conjoint administration of cyclohexylamine. The myocardial potassium depletion caused by 9α-fluorocortisol was less pronounced on the fifth day, when sympathomimetic amine was given additionally; however, cardiac necroses developed after epinephrine injections and were most severe and general when epinephrine was given in combination with cyclohexylamine.
Regional distribution of blood flow in the bat (Myotis lucifugus) during arousal from hibernation
Authors: Rauch Josefine C. , Hayward J. S.
Published: April 2011

The distribution of injected 86Rb was used to assess the relative blood flow rates of various organs and tissues of bats during arousal from hibernation. Blood flow rates during arousal were 11.7 times greater than the control, non-arousal rates in brown fat, and 3.3 times greater in anterior muscle. Such large blood flow changes in these tissues testify to their specialized role in arousal thermogenesis. Relative blood flow to the liver, kidneys, and gastrointestinal tissues was greatly reduced during arousal.
Isoproterenol-induced cardiac lesions in frog observed in vivo
Authors: Poupa O. , Carlsten A.
Published: April 2011

In some winter (October–February) frogs (R. pipiens) that died at a high environmental temperature (+29 °C) the cardiac ventricle showed aneurysm-like formations. An attempt was made to produce a similar type of cardiac lesion in living animals. Frogs kept at +25 °C for 3 days and injected simultaneously with isoproterenol (150–200 mg/kg body weight twice in 48 h) showed various types of cardiac lesions in vivo: (i) initial stage, (ii) blisters, (iii) aneurysm-like formations. Preliminary microscopic findings showed large intramural hematomas in the cardiac wall where in vivo aneurysm-like formations were observed. No stromatic reaction occurred in freshly killed specimens. These lesions observed in the living beating heart in situ showed the following: (a) paradoxical movement of aneurysms, (b) size and shape dependent on intraventricular pressure, (c) shifts from one to another type of lesion, (d) a certain degree of reversibility, (e) simultaneous occurrence in the same heart of many types of injury. Typical localization of the aneurysm-like formations was observed: most were situated in the left and right upper corner and at the apex of the ventricle. This type of experimentally produced cardiac lesion can be studied in detail, the general circulation being intact for hours in the beating heart, provided suitable conditions (temperature and humidity) are preserved. This living and dynamic model of cardiac lesions is open to further experimental research: hemodynamic, pharmacodynamic, and ultrastructural.
The effect of temperature on the oxygen consumption of isolated human umbilical arteries
Authors: Colthart Carol , Roach Margot R.
Published: April 2011

The oxygen consumption [Formula: see text] of isolated segments of 40 human umbilical arteries was measured at different temperatures from 5 °C to 37 °C with a modified Fenn microrespirometer. The values varied from 8 μl/g per h at 8 °C to 70 μl/g per h at 37 °C. The Arrhenius plot was nonlinear, and the Q10 varied from 0.11 (30–40 °C) to 1.8 (20–30 °C) and 7.1 (10–20 °C). This suggests that the metabolic processes may be different at high and low temperatures. The results were consistent for at least 5 h post partum, and did not seem to vary from one segment of the cord to another.
Ventilation in anemia and polycythemia
Authors: Cropp Gerd J. A.
Published: April 2011

Pulmonary ventilation was measured during breathing of 100%, 20%, and 10% oxygen in lightly anesthetized dogs. The animals were divided into three groups; dogs in each group were studied at their normal hematocrit and after complete recovery from exchange transfusions with either plasma, packed red cells, or normal blood. Exchange transfusions with normal blood or elevating the hematocrit to a mean of 54% did not alter minute ventilation at any of the inspired oxygen concentrations tested. When dogs were made anemic (mean hematocrit 11%), they consistently ventilated more at all inspired oxygen concentrations, and they had a faster and approximately 40% greater ventilatory response to hypoxia than before they were made anemic. At a given inspired oxygen concentration [Formula: see text] was the same, but [Formula: see text] was consistently lower in anemic than in non-anemic animals. Ventilation increased as [Formula: see text] fell, and this relation was independent of existing hematocrits. A hypothesis has been proposed that pulmonary ventilation may, in part, be regulated by average tissue [Formula: see text] and systemic vascular resistance, with baroreceptors acting as the mediators of the response. We also observed that hemoglobin levels and hematocrits rose significantly during acute hypoxia in non-splenectomized dogs, causing an increase in the oxygen-carrying capacity of approximately 25% in anemic, of 6% in normal, and of 3% in polycythemic dogs.
Clinical and pathological parameters in albino rats fed from weaning on a diet containing no protein
Authors: Boyd Eldon M.
Published: April 2011

Male albino rats fed from weaning on a diet containing no protein lose body weight in spite of an adequate caloric intake per kilogram body weight. While loss of body weight is primarily associated with loss of weight in muscle and skin, it is particularly marked in certain organs such as liver, salivary glands, spleen, testes, and thymus gland. Loss of weight appeared to be due to inhibition of development and growth of body organs; for example, the red pulp of the spleen, the thymocytic lobules in the thymus gland, and spermatogenic tissue in the testes were undeveloped. Loss of weight may have been due also to impaired digestion of food since there were few zymogenic granules in the serous salivary glands and in the acinar glands of the pancreas. The terminal effect was the gradual development of an acidotic hypothermic cachexia, with death after 6–8 weeks from weaning, in the rats fed a diet containing no protein.
The effect of diethylstilbestrol on nitrogen excretion in sheep
Authors: Huber T. L.
Published: April 2011

Administration of 2 mg of diethylstilbestrol (DES) daily to lambs reduced total urinary nitrogen excretion, urea excretion, plasma urea concentrations, and liver arginase activity. The percent of filtered urea reabsorbed was greater in untreated lambs, thus suggesting that the increased nitrogen conservation observed following DES administration to ruminants is not the result of a direct effect of DES on tubular reabsorption of urea but on nitrogen metabolism.
Lipids of the intestinal mucosa of normal and essential fatty acid deficient rats
Authors: Yurkowski M. , Walker B. L.
Published: April 2011

Mucosal lipids were isolated from the proximal, middle, and distal intestinal sections of rats fed diets containing either 10% corn oil or 10% hydrogenated coconut oil, the latter diet being deficient in essential fatty acids. By a combination of column and thin-layer chromatography, the lipids were fractionated and the major components found to consist of triglycerides, free fatty acids, cholesterol, phosphatidylcholine, and phosphatidylethanolamine. Several minor constituents were present. Triglycerides and free fatty acids were generally present in higher concentrations in animals fed corn oil, and the concentration of mucosal triglycerides decreased towards the distal end of the intestine whereas free fatty acids increased in this group. Essential fatty acid deficiency resulted in lower levels of linoleic and arachidonic acids and higher levels of palmitoleic, oleic, and eicosatrienoic acids in the mucosal lipids. Mono- and di-enoic fatty acids tended to decrease in concentration from the proximal to the distal end of the intestine; the polyunsaturated acids and, to some extent, the saturated acids, were lowest in the proximal section of the intestine.
The Action of Carnitines on Cortical Neurons
Authors: Falchetto S. , Kato G. , Provini L.
Published: April 2011

Compounds related to carnitine have been applied iontophoretically from five-barrelled micropipettes to neurons of the cerebral cortex of anesthetized cats. Both optically active and racemic mixtures of carnitine, acetyl carnitine, carnitine nitrile, and acetylcarnitylcholine had an excitatory action on cells excited by acetylcholine. The levorotatory forms were generally, but not invariably, stronger excitants than their enantiomers. Atropine administered intravenously blocked the action of all carnitines and acetylcholine. These derivatives (like ACh itself) had a depressant effect on some cells which were not excited by ACh.
Effect of Isoproterenol on Brown and White Fat of the Adult Rat
Authors: Derry D. M. , Ransom J. , Morrow E.
Published: April 2011

The effects of isoproterenol on brown and white fat were studied by analyzing the total percentage lipid of the tissue and by the fluorescent histochemical method for catecholamines in sympathetic fibers. At dosages which were well below the LD50, isoproterenol selectively emptied brown fat without affecting the white fat at all. It was suggested that the rise in free fatty acids in the blood seen afer injection of isoproterenol is partly due to an emptying of brown fat.
Sea Water Drinking and Water Flux in Starved and in Fed Harbor Seals, Phoca vitulina
Authors: Depocas Florent , Hart J. Sanford , Fisher H. Dean
Published: April 2011

Harbor seals maintained in sea water were either starved or fed graded amounts of herring of known water and total chloride contents. Total body water and exchangeable chloride in the seals were measured by initial dilution of injected tritiated water and Na36Cl. The decline in specific activities of plasma water and chloride was then followed for 12 to 14 days. Average daily fluxes of water and Cl− were calculated. Sea water ingestion was calculated from the daily chloride flux and the chloride contents of the food and sea water. In five animals fed from 0 to 1500 g herring/day, total water flux was linearly related to food intake and ranged from 500 to 1590 ml water per day. In the same animals ingested sea water and metabolic plus inspired water were also linearly related to food intake, and ranged respectively from 35 to 140 ml and 470 to 625 ml water per day. The data provide definitive evidence that starving Harbor seals derive sufficient oxidative water to satisfy the major part of their needs and that they drink very little sea water. In feeding seals the sum of preformed water and metabolic plus inspired water accounts for about 90% of the total water flux, which is comparable in magnitude to that of most terrestrial mammals. The small volume of sea water ingested by Harbor seals, and its linear relationship to food intake, show compellingly that sea water ingestion is coincident to swallowing food under water rather than due to deliberate drinking.
Effects of Cardiac Glycosides Injected into the Atrioventricular Node Artery of the Dog
Authors: Nadeau R. A. , Amir-Jahed A. K. , Gauthier P. , Porlier G. A.
Published: April 2011

The direct injection of cardiac glycosides into the atrioventricular (A-V) node artery of the dog resulted in the appearance of various arrhythmias and conduction disturbances originating in the junctional tissues of the heart. Three short-acting preparations were studied: acetyl-strophanthidin, digoxin, and desacetyllanatoside C, in doses of 1, 5, 10, and 25 μg. Latency of onset, within 4 min, and duration of effect, usually less than 3 h, appeared to depend upon the concentration of glycoside injected. Impaired conduction, ranging from simple PR lengthening to complete A-V block, was obtained with all three substances. A-V nodal tachycardia was seen in a limited number of dogs after acetylstrophanthidin only. The effects of acetylstrophanthidin on A-V propagation were unmodified by atropine pretreatment. However, an enhanced response to vagus nerve stimulation, as well as to intranodally injected acetylcholine, was demonstrated. In addition, acetylstrophanthidin decreased the amount of A-V nodal acceleration obtained from left stellate ganglion stimulation.
Dose–Effect Relationship in Desoxycorticosterone Hypertension : Reduced Sensitivity in Adrenalectomized Rats and Its Possible Significance to the Etiology of Adrenal-Regeneration Hypertension
Authors: Hall C. E. , Ayachi S.
Published: April 2011

Experiments were conducted to determine the smallest dose of DOCA which would cause saline polydipsia and induce hypertensive disease in unilaterally nephrectomized rats. This was found to be about 25 μg/day with the dosages used. This dose, and one five times as great, were then used to compare the sensitivity of adrenalectomized rats with that of animals having intact adrenals. Completely adrenalectomized animals were less responsive to the blood pressure effect at either dosage, whereas animals with regenerating or accessory adrenal glands were even more so. Adrenalectomized animals given either dosage of hormone had a lower serum protein concentration, red cell count, hematocrit, hemoglobin concentration, and red cell volume than did controls, but these parameters were within normal limits in animals found at necropsy to have residual or regenerating adrenal tissue. The hematologic characteristics appear to be useful criteria for distinguishing, during the course of experimentation, completely adrenalectomized rats from those having residual adrenal function. Clearly adrenal insufficiency diminishes the ability of DOCA to induce high blood pressure, and therefore it appears unlikely that adrenal-regeneration hypertension in the rat can be ascribed to heightened sensitivity to mineralocorticoid activity during the state of adrenal insufficiency.
Effects of Inhibitors of Active Transport on 22Na and 42K Movements and on Nucleotide Levels in Rat Uteri at 25 °C
Authors: Daniel E. E. , Robinson Kathleen
Published: April 2011

The effects of inhibitors of the sodium pump (K-free solution or ouabain) on Na and K fluxes, water content, and adenine nucleotides were studied in rat uterine horns. The same four-compartment model [Formula: see text] was applied to K efflux as to Na efflux. However, for K efflux the larger cellular fraction, C, contained 70% of tissue K, and D could usually be ignored. K-free solutions did not alter ATP, ADP, or AMP levels, and had only small effects on efflux of Na from fresh or Na-rich tissues. In these tissues ouabain decreased Na efflux from the faster, larger cellular fraction (BK2 ↓) without affecting adenine nucleotide levels. K-free solutions or ouabain increased sodium influx, but neither inhibitor caused swelling. The inhibitors decreased water content of fresh tissues and failed to interfere with extrusion of water accompanying Na from Na-rich tissues. In addition to the ouabain-sensitive pump, another Na pump insensitive to K levels or ouabain was postulated to be responsible for control of cell volume and part of Na efflux in uteri. The K efflux was increased by ouabain, but not by K-free solutions. The K influx was decreased by K-free solutions, but was not affected by ouabain. Increasing external K (concentrations of 18.4 mM and higher) did not diminish the effects of ouabain on Na or K efflux. Neither cocaine nor adrenaline prevented the effect of ouabain on the Na or K efflux or on the increased Na influx. No evidence was obtained that a Na exchange–diffusion system operated in K-free solutions. It was concluded that the accepted views about the operation of a Na pump involving (Na+ + K+)-activated, ouabain-sensitive ATPase have to be modified for rat uteri.
Thyroid Status in Relation to Catecholamines in Cold and Warm Environment
Authors: Sellers E. A. , Flattery K. V. , Shum A. , Johnson G. E.
Published: April 2011

Rats were exposed to 4 °C and were then made hyperthyroid or hypothyroid by injecting 100 μg l-thyroxine (T4) subcutaneously daily or by giving 0.05% methimazole in lieu of drinking water. Rats, similarly treated, were maintained at 27 °C. Untreated euthyroid animals were also placed at both temperatures. The urinary excretion rates of norepinephrine (NE), epinephrine (E), and their major metabolites were measured for a 10- to 17-day period, after which the animals were killed and tissue catecholamines measured. At 4 °C, the methimazole-treated group failed to adapt as hypothermia developed and several deaths ensued, despite a dramatic increase (18 times) in excretion of norepinephrine. Cardiac catecholamine levels were very low in this hypothyroid group suggesting (1) that synthesis of NE was insufficient to maintain normal tissue levels or ensure adequate heat production, and (2) that catabolism of intraneuronal and secreted catecholamine may have been altered. At 4 °C, the T4-treated group excreted less NE, E, and metabolites than the hypothyroid and euthyroid groups. At 27 °C, T4 treatment resulted in hyperthermia, hypermetabolism, and several deaths. NE excretion in this group was double that of the control and hypothyroid animals, but cardiac levels of NE were low suggesting a discrepancy between synthesis, secretion, and re-uptake.The experiments demonstrate that the reciprocal relationship between thyroid hormones and catecholamines in heat production during cold adaptation is partial only, and that both are essential.
Effect of Dietary Calcium, Phosphorus, and Vitamin D3 on Alkaline Phosphatase Activity of Intestinal Mucosa of Chicks
Authors: Motzok I. , Ritcey Gwendolyn M. , Davies Muriel I.
Published: April 2011

Diets with varying levels of Ca, inorganic phosphorus (P1), and vitamin D3 were fed to chicks from 1 day of age. Alkaline phosphatase of intestinal mucosa was twofold higher at 3 weeks in female chicks fed 0.16% of P1 than in chicks fed 0.48% of P1 when the diets contained 7500 I.C.U. of vitamin D3 per kilogram and 1% of Ca. The effect of low dietary P1 was less pronounced when the diets contained 450 I.C.U. of vitamin D3 per kilogram and 1% of Ca but no definite pattern in enzyme activities due to level of P1 was observed with 0.53% of Ca. In male chicks there was a small but consistent increase (35–45%) in the activity of intestinal phosphatase when the diets were low in Ca, P1, or both. The level of vitamin D3 had no effect on the intestinal enzyme in male birds.
Degeneration and Regrowth of Adrenergic Nerve Fibers in the Rat Peripheral Tissues after 6-Hydroxydopamine
Authors: Champlain J. de
Published: April 2011

Histofluorescent and biochemical changes in the adrenergic nervous system were followed up in rat tissues after one single intravenous injection of a high dose of 100 mg/kg of 6-hydroxydopamine (6-OH-DA). This treatment results in the rapid disappearance of terminal and preterminal fibers in the iris, atria, and small arteries of rats, whereas endogenous noradrenaline pools of the heart are 95% depleted. The capacity of the adrenergic nerve to take up and accumulate tritiated noradrenaline is reduced proportionally to the reduction in endogenous noradrenaline levels. These changes are compatible with the concept of a complete sympathectomy induced by the specific toxic action of 6-OH-DA on the adrenergic fibers. This sympathectomy is not permanent, however, and numerous bundles of preterminal fibers start to grow in the iris and atria within 4 to 5 days following injection. Progressively, in the following weeks, these fibers distribute over the whole organ and give birth to terminal fibers which form a new adrenergic plexus in these tissues. A completely normal innervation is restored 2 to 3 months after administration of 6-OH-DA. The endogenous noradrenaline levels rise progressively in parallel to the development of the new plexus of fibers. Since a complete regeneration of the adrenergic innervation can be demonstrated in the weeks following injection of 6-OH-DA, it appears that this compound can selectively destroy the adrenergic terminal and preterminal fibers without causing a degeneration of the adrenergic ganglion cells.
Erythrocyte Flow in Tubes of Capillary Size
Authors: Rowlands S. , Skibo Leona
Published: April 2011

Pressure–velocity measurements on red cells and rouleaux in glass tubes of capillary size confirm Prothero and Burton's findings (Biophys. J. 1962. 2, 199–212) of very low resistance to flow and are contrary to conclusions drawn from a recently proposed mathematical model.
Evaporative Cooling in the Rat: Differences Between Salivary Glands as Thermoregulatory Effectors
Authors: Hainsworth F. Reed , Stricker Edward M.
Published: April 2011

Rats cool themselves in the heat by evaporating saliva groomed onto their body surfaces. Previous reports indicated that surgical removal of the submaxillary glands severely impaired evaporative water loss and body temperature regulation, whereas parotid desalivation had little effect. In the present experiments saliva was collected directly from the oral cavities of rats exposed to heat stress and was identified by its sodium concentration to determine the roles of individual salivary glands as thermoregulatory effectors. The fundamental difference between the glands was that submaxillary secretion was initiated at a lower level of hyperthermia (38.5 °C) than parotid secretion (40.0 °C), and thus made a greater contribution to thermoregulation. For example, normal rats secreted only submaxillary saliva at an ambient temperature of 36 °C and secreted three times more submaxillary saliva than parotid saliva at 40 °C. These results indicate that the submaxillary glands are primary thermoregulatory effectors of rats during heat stress, and that the parotid glands provide supplementary secretion only during pronounced hyperthermia.
Factors Affecting Behavior Maintained by Response-Contingent Intravenous Infusions of Amphetamine in Squirrel Monkeys
Authors: Stretch Roger , Gerber Gary J. , Wood Susan M.
Published: April 2011

Behavior developed and maintained in previously untrained monkeys by a modified progressive-ratio schedule of response-contingent intravenous infusions of d-amphetamine is described. Availability of amphetamine infusions can be restricted to relatively brief (2 h) daily sessions, once responding has been established, without disruption of self-administration behavior. When amphetamine infusions are replaced by saline, responding is reduced immediately to a low rate; when amphetamine infusions are replaced by saline and the session is preceded by an intramuscular injection of the drug (1.5 mg/kg), the pattern of responding is indistinguishable from that observed when drug infusions are available. If an external discriminative stimulus, normally associated with those periods in which infusions are available, is withdrawn, responding is reduced to a low rate. The discriminative stimulus entered into control of the behavior only when amphetamine had been administered by intravenous infusion or by intramuscular injection beforehand, reflecting, therefore, some form of 'state dependence'. Possible sources of interoceptive stimulation, arising from an infusion per se, did not control behavior to any significant extent. Results emphasize the need for specific control procedures when drug self-administration is to be conceptualized as an operant reinforcement effect.
The Oral Absorption of Water
Authors: Miles T. S. , Dellow P. G.
Published: April 2011

A perfusion system was designed whereby the oral cavity of the rabbit under urethane anesthesia could be exposed to water in isolation from the remaining gastrointestinal system and the nasal cavity. Tritiated water was recovered from one external jugular vein within 40 s of the commencement of oral perfusion. The recovery rate increased linearly up to 200 s, arriving at a level of water averaging 1.7 × 10−3 ml/ml of venous blood. Rabbits dehydrated for 24 h were observed to have a relatively continuous water intake period ranging 85–200 s from the time of reexposure to water. It may be concluded that water can be absorbed from the mouth during the drinking period of a thirsty rabbit. Under normal circumstances the level of absorption can be assumed to be greater than the experimental because of the influences of muscular activity, blood flows, and increased areas of mucosal exposure. The data may be associated with the oropharyngeal metering of water intake.
Comparison of Dihydrotachysterol and Calciferol
Authors: Kaye Michael , Just G. , Wilson M.
Published: April 2011

Dihydrotachysterol (DHT) was found to be more potent in normal rats than equivalent doses of calciferol as judged by the degree of hypercalcemia produced. On an essentially calcium-free diet only a very small change in plasma calcium was seen following calciferol whereas DHT remained equally effective suggesting that it was acting predominantly on bone resorption whereas calciferol was mainly augmenting calcium absorption from the gut. The commercial preparation Hytakerol appeared similar to DHT both chemically and biologically.
Studies on Hemorrhagic Hypotension in Domestic Fowl
Authors: Wyse D. George , Nickerson Mark
Published: April 2011

White Leghorn hens were Wed at a constant rate to a mean arterial pressure of 50 mm Hg and maintained at this pressure by further hemorrhage. Average duration of hypotension tolerated by mature hens anesthetized with paraldehyde was about 5 h, and the bleeding volume during this interval was almost three-quarters of the initial measured blood volume. Younger chickens and those anesthetized with barbiturate responded similarly, but died somewhat earlier, apparently because of respiratory difficulties. The response to hemorrhage was characterized by a large, rapid fall in mean arterial pressure after a relatively small loss of blood, and by a large influx of protein-poor fluid into the vascular space. The latter was at least twice as rapid as and four times the volume of maximal extravascular fluid mobilization by dogs. In contrast to dogs, no phase of decompensation and hemoconcentration was demonstrable in these experiments, and may not occur in chickens. This was associated with absence of "irreversibility to transfusion"; reinfusion of the shed blood even at the time of terminal circulatory collapse produced a stable cardiovascular state. Comparison of the present observations on chickens with the published results of similar experiments on dogs indicates that homeostatic mechanisms operate predominantly to maintain the blood volume in the former and the blood pressure in the latter.
The Effects of Changes in the Rate of Infusion of Vasopressin in Anesthetized Dogs
Authors: Mason J. M. , Ledsome J. R.
Published: April 2011

The dose rate of infusion of vasopressin which can be expected to provide maximal effects upon urine formation is difficult to predict in anesthetized dogs. The anesthetic agents, the state of hydration, and the osmolal excretion may all influence the effectiveness of vasopressin. The experiments demonstrate that in moderately hydrated anesthetized dogs when the rate of vasopressin infusion is changed from 0.4 to 0.04 mU/kg min−1 there is a transient dilution of the urine. The lower dose of vasopressin is four times that which completely inhibits water diuresis in conscious dogs and is larger than the dose of 0.025 mU/kg min−1 used in many experiments on anesthetized dogs to eliminate the effects of antidiuretic hormone on the kidney. It appears necessary in experiments in which an attempt is made to eliminate or to assess the effects of vasopressin upon a mechanism producing diuresis either to establish a maximum effective dose for the particular experimental cirmustances, or to examine the dose–response relationship between vasopressin and the diuresis in the particular experimental procedure.
Effect of Posterior Hypothalamic Lesions on Renal Function in the Rat
Authors: Novakova Alena , Stevenson J. A. F.
Published: April 2011

Female Wistar rats were infused with an isotonic solution (110 mM NaCl + 25 mM NaHCO3) containing 5 mU of Pitressin per milliliter, at a nonexpanding rate of 0.016 ml/min. Per-corten (1.25 mg i.m.) was given 1 h before the experiment. Urine flow rate, sodium and potassium excretion, and creatinine clearance were measured over 20-min periods. After the control values were obtained, bilateral electrolytic lesions were made in the posterior hypothalamus or the lateral hypothalamic area. Another group of rats was sham operated, and in controls an equivalent current was passed through the body. Posterior hypothalamic lesions were immediately followed by significant increases in the urine flow rate, UNa, and UNaV. Creatinine clearance increased insignificantly. However, the significant decrease of the fractional sodium reabsorption indicated that the natriuresis was mainly of tubular origin. This diuresis and natriuresis were not associated with significant changes in the arterial blood pressure. Changes were still detectable 60 min after lesioning, but were returning to control levels. No changes in renal function followed lesions in the lateral hypothalamus, sham operation, or application of electric current. The role of the posterior hypothalamus in the renal excretion of sodium is discussed.
Accumulation of Adenosine 3′,5′-Monophosphate and Relaxation in the Rat Uterus In Vitro
Authors: Polacek Ivo , Bolan Jean , Daniel Edwin E.
Published: April 2011

Theophylline, diazoxide, and papaverine in low concentrations relaxed the uterus with minimal or no elevation of cyclic AMP (cAMP) levels. In higher concentrations, theophylline relaxed the uterus and increased its cAMP levels, but imidazole reversed the increase in cAMP without causing recontraction. Imidazole and NaF caused uterine contractures but did not detectably decrease cAMP levels until several minutes after the onset of contractures. The uterine relaxations produced by theophylline and/or dibutyryl cAMP in amounts which increased uterine cAMP were not reversed by propranolol. These results eliminate the possibility that propranolol interfered with a relaxant action of cAMP. Along with previous data, these results also show that uterine contractile activity was not determined primarily by the general levels of cAMP and that phosphodiesterase activity in the uterus was insufficient to rapidly affect these cAMP levels. Also, substances like theophylline, diazoxide, and papaverine, postulated to inhibit phosphodiesterase activity, did not bring about their relaxant effects by this mechanism.
Effect of Dietary Rapeseed Meal on the Serum Proteins of Rats
Authors: Lo M. T. , Hill D. C.
Published: April 2011

Two experiments were conducted in which growing male rats were fed three diets containing as protein sources, casein (C), rapeseed meal variety Bronowski (BM), and B. napus meal (NM). In the first experiment the diets were fed to both thyroidectomized rats and to sham-operated rats with thyroid intact. Poorest gains were recorded for rats fed the NM diet irrespective of whether the thyroids were removed or intact, indicating that the toxicity of B. napus meal was not confined to the effect on the thyroid gland. In the second experiment four groups of rats were fed BM diet, NM diet, and C diet. The latter diet was given to both thyroidectomized rats and rats with intact thyroid to provide controls for the study of the effect on the thyroid of the glucosinolate in rapeseed. As in experiment 1, weight gain of rats receiving NM diet was less than that of either of the two groups of rats receiving C diet. After 25 days the serum protein and the thyroxine-binding properties of serum proteins were examined by disc gel electrophoresis. Rats fed NM or C diet (with thyroid removed) showed an altered serum protein pattern as compared to rats fed C or BM diets. The 131I-thyroxine-binding ability of the albumin band was much greater for the serum of rats receiving diets NM and C (with thyroid removed), 37% and 46% versus 22% of the total 131I-thyroxine recovered on the gel.
Blockade of the Antiadrenergic Action of Bretylium by an Aqueous Extract of the Leaves of Rhoeo spathacea
Authors: Garcia M. , Miyares C. , Menendez E. , Sainz F.
Published: April 2011

In isolated rabbit ileum, bretylium-induced blockade of the inhibitory response to stimulation of the adrenergic nerve supply is prevented by an aqueous extract of the leaves of Rhoeo spathacea, apparently as a result of its dopamine content.
Partial Splenectomy in Dogs: An Experimental Tool for Studies of the Spleen
Authors: Boer Jan de , Downie Harry G.
Published: April 2011

A simple, rapid, and reliable technique has been developed and is described for partial splenectomy in the dog.
Effect of Changes in the Osmolality of the Luminal Fluid on Water and Glucose Transport across the Hamster Jejunum
Authors: Dinda P. K. , Beck Marjorie , Beck Ivan T.
Published: April 2011

Paired experiments were performed in vitro using two adjacent segments of hamster jejunum. Fluid and glucose transport and the intracellular concentration of glucose were compared in the intestinal segments incubated in isotonic mucosal solution (control) and in hypotonic or hypertonic mucosal solution (experimental). Hypotonic mucosal solution (212 mOsmol/kg) caused a significant increase in the serosal transfer of glucose and water, and a significant decrease in the ratio of the intracellular concentration of glucose to the concentration of glucose in the serosal fluid (T/S at the end of the experiments). Increasing the osmolality of the mucosal solution to 342, 392, and 442 mOsmol/kg caused a progressive reduction in fluid and glucose transfer to the serosal side and a progressive increase in the T/S ratio. Statistical analysis of data shows that the serosal transfer of glucose was negatively correlated with the T/S ratio and positively correlated with the serosal transfer of water. It is concluded that in the presence of a reduced solvent drag, an increased T/S ratio may not result in an increased serosal transfer of glucose.