Showing papers in "American Journal of Physiology in 1957"
TL;DR: The hemodynamic determinants of myocardial oxygen utilization were ascertained in the isolated, metabolically supported, nonfailing canine heart and the primary determinant was found to be the total oxygen requirement.
Abstract: The hemodynamic determinants of myocardial oxygen utilization were ascertained in the isolated, metabolically supported, nonfailing canine heart. The primary determinant was found to be the total t...
1,289 citations
TL;DR: The normal venous return curve has been determined in 12 open- chest dogs with intact circulatory reflexes and in 14 open-chest areflex dogs.
Abstract: The normal venous return curve has been determined in 12 open-chest dogs with intact circulatory reflexes and in 14 open-chest areflex dogs. These curves show that venous return reaches a maximum v...
454 citations
TL;DR: Cold- Adapted spinal rats showed a greater increase in oxygen consumption following adrenaline than did warm-adapted ones and Thyroidectomy reduced the responses of warm- and cold- adapted spinal rats.
Abstract: Cold-adapted spinal rats showed a greater increase in oxygen consumption following adrenaline than did warm-adapted ones. Thyroidectomy reduced the responses of warm- and cold-adapted spinal rats t...
263 citations
TL;DR: Although the general dependence of coronary flow on myocardial qo2 was confirmed in an in situ heart preparation, changes in aortic pressure and cardiac output were observed to be capable of influencing this relationship.
Abstract: Although the general dependence of coronary flow on myocardial qo2 was confirmed in an in situ heart preparation, changes in aortic pressure and cardiac output were observed to be capable of influe...
228 citations
TL;DR: It was shown that increased glucose uptake by the tissues is much more important than decreased delivery of glucose by the liver in bringing about insulin-induced hypoglycemia and recovery from hypoglycesmia is brought about by increased glucose delivery by the Liver and not by a decrease in tissue uptake of glucose below the preinsulin level.
Abstract: C 14 glucose was adminisered continuously to unanesthetized normal dogs by intravenous infusion following a priming dose at a rate which maintained the specific activity of the circulating glucose at a nearly constant level. Glucagon-free insulin was then administered intravenously in varying doses. Samples of blood were collected at intervals throughout the experiment and more frequently just subsequent to insulin injection. The glucose concentration of the circulating blood and the specific activity of this glucose, when considered together, allow calculations to be made of a ) the outflow of glucose toward the tissue cells, and b ) the inflow of glucose from the liver during the period after insulin injection. By this means it was shown that increased glucose uptake by the tissues is much more important than decreased delivery of glucose by the liver in bringing about insulin-induced hypoglycemia. It was also shown that recovery from hypoglycemia is brought about by increased glucose delivery by the liver and not by a decrease in tissue uptake of glucose below the preinsulin level. Alternative methods of calculation of absolute values for glucose inflow and outflow during periods of changing blood glucose concentrations are discussed and evaluated.
209 citations
TL;DR: It is concluded that insulin decreases the release of fatty acids from tissue stores but does not accelerated their removal from blood.
Abstract: The mechanism by which carbohydrate utilization reduces the concentration of nonesterified fatty acids (NEFA) in plasma was studied by comparing the clearance of C14-labeled palmitic acid before and after the administration of insulin. The rate of disappearance from blood of a single injection of C14-labeled palmitic acid was identical before and after an intravenous injection of insulin (0.1 µ/kg) although the expected significant fall in total NEFA concentration occurred. When steady concentration of labeled NEFA was maintained by a constant infusion, the administration of insulin produced a significant increase in specific activity. It is, therefore, concluded that insulin decreases the release of fatty acids from tissue stores but does not accelerated their removal from blood.
176 citations
TL;DR: The ganglionic blocking agent hexamethonium chloride and the adrenolytic agent piperoxane hydrochloride prevented the increase in oxygen consumption otherwise observed in curarized, cold-adapted animals.
Abstract: The ganglionic blocking agent hexamethonium chloride and the adrenolytic agent piperoxane hydrochloride prevented the increase in oxygen consumption otherwise observed in curarized, cold-adapted ra...
175 citations
TL;DR: Observations support the view that membrane transport in muscle is a site of insulin action and explains the inefficacy of fructose in relieving the symptoms of hypoglycemia.
Abstract: The effect of insulin on transport of d-glucose, d-mannose, d-fructose, d-xylose, l-arabinose and d-ribose through the cell membrane has been studied. Each sugar was infused into eviscerated rats with or without insulin for 1 or 2 hours. The accumulation of free sugar within the cell was determined in the diaphragm, heart, gastrocnemius and brain. Intracellular sugar was estimated by subtracting the amount of sugar in the extracellular fluid space, as determined with mannitol-1-C14, from the total tissue sugar. In muscle virtually no intracellular free sugar was detected in the absence of insulin whereas, in the presence of insulin, large amounts were found except in the case of d-ribose. Since these sugars do not arise by intracellular metabolism, it was concluded that insulin accelerated their transport through the cell membrane. These and other observations support the view that membrane transport in muscle is a site of insulin action. The transport process is distinct from phosphorylation and presumably involves combination of the sugar with a constituent of the cell membrane. In brain, no effect of insulin was observed. d-Mannitol, d-ribose and d-fructose did not pass the blood-brain barrier to a measurable extent. This explains the inefficacy of fructose in relieving the symptoms of hypoglycemia.
152 citations
TL;DR: A single injection of endotoxin derived from Gram negative bacteria caused an increased survival in lethally irradiated animals when given immediately after or 24 hours before irradiation.
Abstract: A single injection of endotoxin derived from Gram negative bacteria caused an increased survival in lethally irradiated animals when given immediately after or 24 hours before irradiation. Mice responded better to the injection before irradiation and hamsters to the injection after irradiation. The effect was associated with a reduction in infection, very pronounced in the case of α-streptococcus or Proteus and still significant in the case of Pseudomonas infection. No beneficial effect was obtained when mice were given three endotoxin injections during 1 week or six injections during 2 weeks prior to irradiation. The beneficial effect is not necessarily associated with the granulocytosis which begins within a few hours after the endotoxin injection, or with the conditions under which nonirradiated animals show an increased resistance to bacterial challenge.
135 citations
TL;DR: Radioactive iodinated serum albumin and dextran fractions of average molecular weights of 51,000– 255,000 are injected into nembutalized dogs, and concentration changes of these substances are observed.
Abstract: Radioactive iodinated serum albumin and dextran fractions of average molecular weights of 51,000– 255,000 are injected into nembutalized dogs, and concentration changes of these substances are foll...
131 citations
TL;DR: The nitrogen excretion was studied in the one-humped camel, Camelus dromedarius, and found that when a growing camel was maintained on a low N intake (dates and hay), the amount of N excreted in the form of urea, ...
Abstract: The nitrogen excretion was studied in the one-humped camel, Camelus dromedarius. When a growing camel was maintained on a low N intake (dates and hay) the amount of N excreted in the form of urea, ...
TL;DR: The results are interpreted to mean that the collecting system is a limiting factor in the outflow of urine from the kidney, and is an important determinant of the intratubular pressure, particularly at high rates of urine flow.
Abstract: A method is described for the identification of proximal and distal tubules on the surface of the living rat kidney. In 32 anesthetized rats, under control conditions, the hydrostatic pressure in the proximal tubules averaged 12.5 ± 2.2 mm Hg and 6.7 ± 1.6 mm Hg in the distal tubules. During infusion of hypertonic solutions of mannitol, glucose, urea and sodium chloride, the lumina of the proximal and distal tubules dilated and the intratubular pressures and rate of urine flow increased. Also during diuresis, the clear-cut difference between proximal and distal intratubular pressures disappeared and, in general, there was a linear relation between distal intratubular pressure and rate of urine flow. These results are interpreted to mean that the collecting system is a limiting factor in the outflow of urine from the kidney, and is an important determinant of the intratubular pressure, particularly at high rates of urine flow.
TL;DR: An investigation was undertaken to determine the effects of water deprivation during meals in rats, finding that food intake, gastrointestinal solids water content, rate of digestion and tissue water content were affected.
Abstract: An investigation was undertaken to determine the effects of water deprivation during meals in rats. Food intake, gastrointestinal solids water content, rate of digestion and tissue water content we...
TL;DR: It is concluded that inhibition of lipoprotein lipase activity by Triton is due to modification of the substrate such that the enzyme can no longer act and it is suggested that the chief cause of Trit on hyperlipemia is coating of the plasma lipoproteins by Trito resulting in their faulty catabolism.
Abstract: When postheparin plasma was incubated with a coconut oil substrate, a decrease in optical density and an increase in unesterified fatty acids occurred. The increase in unesterified acids was prevented by previous intravenous injection of Triton to rats. Addition of post-Triton plasma to a system containing postheparin plasma and coconut oil emulsion inhibited the lipoprotein lipase activity. Incubation of Triton with coconut oil substrate before addition of postheparin plasma caused inhibition of lipoprotein lipase activity. It is concluded that inhibition of lipoprotein lipase activity by Triton is due to modification of the substrate such that the enzyme can no longer act. Further, it is suggested that the chief cause of Triton hyperlipemia is coating of the plasma lipoproteins by Triton resulting in their faulty catabolism.
TL;DR: The strength-interval curve of dog ventricular myocardium has been measured with anodal and cathodal stimulation and it is shown that during diastole the anodals threshold is higher than the cathodals.
Abstract: The strength-interval curve of dog ventricular myocardium has been measured with anodal and cathodal stimulation. During diastole the anodal threshold is higher than the cathodal. As anodal stimuli...
TL;DR: Ouabain induces a moderate increase in the contractility of the nonfailing heart of the dog with a complete circulatory system in doses which do not produce electrocardiographic signs of digitalis intoxication and has two primary hemodynamic effects in the normal animal, namely, a direct cardiac stimulant action and a peripheral action resulting in a decreased venous return.
Abstract: Ouabain induces a moderate increase in the contractility of the nonfailing heart of the dog with a complete circulatory system in doses which do not produce electrocardiographic signs of digitalis ...
TL;DR: In dogs prepared with both a vagus denervated Heidenhain pouch and a total pancreatic fistula, the intravenous injection of pancreatic secretin (Lilly) produced a profuse secretion of pancreatIC juice and a simultaneous marked inhibition of gastric secretion.
Abstract: In dogs prepared with both a vagus denervated Heidenhain pouch and a total pancreatic fistula, the intravenous injection of pancreatic secretin (Lilly) produced a profuse secretion of pancreatic ju...
TL;DR: Effects of various concentrations of CO2 on brain excitability and electrolyte distribution in rats were studied and also some properties of seizures induced by abrupt withdrawal from high concentrates were studied.
Abstract: Effects of various concentrations of CO2 on brain excitability and electrolyte distribution in rats were studied, and also some properties of seizures induced by abrupt withdrawal from high concent...
TL;DR: In the fasting rat the injection of protamine, an antiheparin agent, produces an increase in all serum lipids, but the increase occurs in the low-density lipoproteins, and in the rat fed carbohydrate this lipemia-inducing effect of protamines is practically abolished.
Abstract: Fasting in the rat is accompanied by an increase in serum cholesterol concentration reflecting an increase in high-density lipoproteins. The feeding of carbohydrate results in decreases in both low- and high-density lipoproteins, the former occurring acutely, and the latter occurring more slowly. In the fasting rat the injection of protamine, an antiheparin agent, produces an increase in all serum lipids, but the increase occurs in the low-density lipoproteins. In the rat fed carbohydrate this lipemia-inducing effect of protamine is practically abolished. The feeding of carbohydrate has no effect, however, on the rate of clearance of intravenously administered chylomicrons. These phenomena are discussed in relation to current theories of lipid transport.
TL;DR: A preparation consisting of a papillary muscle and attached bundle of Purkinje fibers has been employed to study refractoriness of single cardiac fibers of the dog heart.
Abstract: A preparation consisting of a papillary muscle and attached bundle of Purkinje fibers has been employed to study refractoriness of single cardiac fibers of the dog heart. Transmembrane stimulation ...
TL;DR: The preparation of chronic gastric fistula rats, their care and how they may be used for physiological and pharmacological studies on gastric secretion is described and Statistically significant differences between the control output of acid and the response to 1 mg of histamine diphosphate were obtained.
Abstract: The preparation of chronic gastric fistula rats, their care and how they may be used for physiological and pharmacological studies on gastric secretion is described. The rat has a large interdigestive secretion and secretes free acid (pH 4.5) after 48–72 hours of fasting. For controlled studies this requires the replacement of fluid and chlorides. Statistically significant differences between the control output of acid and the response to 1 mg of histamine diphosphate were obtained. The threshold dose of the diphosphate is approximately 0.1 for a 350-gm rat. The least amount of histamine diphosphate to yield an average maximum output of acid (10 mg/hr.) is 0.5 mg subcutaneously every 15 minutes. The body dose of histamine required to stimulate gastric secretion is about the same in man, dog, cat and the rat. On the basis of body weight, the amount of histamine base required to yield a maximum output of acid in the rat is 34.6 µg/kg/min. as compared with 1.6 µg/kg/min. in the dog.
TL;DR: Using two or three microelectrodes inserted into single muscle fibers of the toad sartorius, the electric impedance of the muscle fiber membrane was measured with a.c. between 25 and 1500 cps.
Abstract: Using two or three microelectrodes inserted into single muscle fibers of the toad sartorius, the electric impedance of the muscle fiber membrane was measured with a.c. between 25 and 1500 cps. It was found that the capacity of the muscle fiber membrane is practically independent of the frequency of the measuring a.c. The membrane capacity determined from the time constant of potential rise in the foot of a propagated muscle action potential agrees with the value determined by a.c. impedance measurement. It was emphasized that the a.c. method of determining the cable constants of the muscle fiber (based on eq. 1 under methods) is simple and gives satisfactory results.
TL;DR: Obesity in mice is accompanied by changes in organ weight that appear to be nonspecific effects of prolonged hyperphagia, and a wider recognition of the differences between obesities of various etiologies and pathogeneses is emphasized.
Abstract: Obesity in mice is accompanied by changes in organ weight. Certain changes, like the enlargement of the liver, heart and kidneys appear to be nonspecific effects of prolonged hyperphagia. Such changes are seen in ‘regulatory’ as well as in ‘metabolic’ obesities. Other changes may be part of a syndrome of which obesity is also a component; for example, in the hereditary obese-hyperglycemic syndrome, a metabolic form of obesity, the pancreas and the thymus are enlarged and the size of the brain decreased. These findings emphasize the need for a wider recognition of the differences between obesities of various etiologies and pathogeneses.
TL;DR: Medulla oblongata of 80 vagotomized cats was explored with microelectrodes and spontaneous respiratory neuronal activities and chest movements were recorded simultaneously with a twin beam cathodes.
Abstract: Medulla oblongata of 80 vagotomized cats was explored with microelectrodes. Spontaneous respiratory neuronal activities and chest movements were recorded simultaneously with a twin beam cathode ray...
TL;DR: This investigation was designed primarily to study three closely related questions about rhythmic breathing: a) how is apneusis (apneustic respiration) initiated and modified? b) Is the isolated me...
Abstract: This investigation was designed primarily to study three closely related questions about rhythmic breathing: a) how is apneusis (apneustic respiration) initiated and modified? b) Is the isolated me...
TL;DR: It is postulated that both the conductivity drop during spreading depression and a similar drop observed after asphyxiation of the brain are caused by a transport of ions from the intercellular compartment into cortical cellular elements.
Abstract: Spreading depression is accompanied by a slow potential change, a drop in cortical conductivity and by vascular changes. The latter were investigated in histological preparations of cortex frozen while a spreading depression was in progress. In the cat and rabbit a broad wave of vasodilatation was observed. In the rabbit this appeared to be preceded by a narrow region of vasoconstriction. Spreading depression can be changed into spreading convulsive activity by administering CO 2 in the respiratory air (7–12%). CO 2 markedly decreased the drop in cortical conductivity but affected the magnitude of the slow potential change only moderately. It is postulated that both the conductivity drop during spreading depression and a similar drop observed after asphyxiation of the brain are caused by a transport of ions from the intercellular compartment into cortical cellular elements. The relationship between the slow potential change, conductivity drop, vascular changes and the changes in the electrocorticogram during spreading depression is discussed.
TL;DR: Electrical stimulation of helically cut strips of rabbit carotid artery, mounted so as to allow development of tension isometrically, causes a contraction-relaxation cycle which remains reproducibl...
Abstract: Electrical stimulation of helically cut strips of rabbit carotid artery, mounted so as to allow development of tension isometrically, causes a contraction-relaxation cycle which remains reproducibl...
TL;DR: Results indicate that parathyroid extract has a direct action on the renal tubule in theChicken, in which a renal portal system facilitates separation of renal tubular from systemic and glomerular effects.
Abstract: The renal action of parathyroid extract has been studied in the chicken, in which a renal portal system facilitates separation of renal tubular from systemic and glomerular effects. It was found that net secretion of phosphate occurs in the chicken kidney both at endogenous plasma phosphate levels and during the infusion of phosphate. The rate of secretion seems to be independent of the plasma phosphate concentration. Infusion of parathyroid extract into one renal portal system results in a unilateral increase in phosphate excretion. In some experiments unilateral net secretion of phosphate occurred. No consistent changes in glomerular filtration rate or plasma phosphate concentration occur when parathyroid extract is administered. These results indicate that parathyroid extract has a direct action on the renal tubule in the chicken.
TL;DR: Fasting reduced or completely prevented the accumulation of liver lipid brought about by the administration of ethanol to intact rats; the longer the fast, the greater the degree of inhibition.
Abstract: Fasting reduced or completely prevented the accumulation of liver lipid brought about by the administration of ethanol to intact rats; the longer the fast, the greater the degree of inhibition. Thi...
TL;DR: The injection of long-lasting epinephrine into dogs was followed in 1 hour by a rise in the concentration of serum triglycerides that was sustained for 24 hours, and the concentrations of serum lipid p...
Abstract: The injection of long-lasting epinephrine into dogs was followed in 1 hour by a rise in the concentration of serum triglycerides that was sustained for 24 hours. The concentrations of serum lipid p...