bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of hypoxia on iron absorption and mobilization in the rat
Authors: Strohmeyer Georg W. , Miller Stephen A. , Scarlata Robert W. , Moore Edward W. , Greenberg Mortimer S. , Chalmers Thomas C.
Published: December 2017

Rats exposed to an atmosphere of 10% oxygen increase their absorption of a test dose of iron after 6 8 hr. Release of tissue storage iron begins within 2 hr of the start of hypoxia and continues for at least 8 hr. An oral iron load does not prevent the release of tissue iron in response to hypoxia. Iron-loaded rats also release iron from storage depots and increase their minimal absorption in response to hypoxia. Iron-deficient rats apparently have a diminished tissue release and also increase absorption above their elevated base-line levels. Xanthine loading had no effect on the release of tissue iron or changes in absorption with hypoxia, and there was no evidence that changes in xanthine oxidase activity in the liver or bowel were directly associated with tissue release or absorption of iron.
Cadmium hypertension in rats
Authors: Schroeder Henry A.
Published: December 2017

Rats receiving small amounts of cadmium in drinking water exhibited systolic hypertension, the incidence being greater in females than in males. In males the disorder appeared later in life. Cadmium-free rats seldom became hypertensive. Rats also exposed to a choice of 1% NaCl solution when young and when old appeared to show more hypertension than those not exposed; females took 65% more cadmium. The hypertension was usually associated with increased mortality and renal vascular changes.
Effect on kidney S35O4 uptake of compounds related to SO4 transport and metabolism
Authors: Deyrup Ingrith J.
Published: December 2017

Experiments have been carried out to test the effects on S35O4 accumulation by rat kidney cortex slices in vitro of 1) compounds known to affect renal SO4 reabsorption (thiosulfate, amino acids); 2) compounds secreted by the kidney, or known to affect specific cellular transport systems (including tetraethylammonium ions, guanidine, creatinine, carinamide, probenecid, phloretin, diethylstilbestrol, ethylenediaminetetraacetate sodium); and 3) compounds related to SO4 metabolism (aryl sulfatase substrates). Under the conditions of the experiment, net S35O4 uptake was depressed by thiosulfate, certain amino acids, carinamide, phloretin, diethylstilbestrol, and aryl sulfatase substrates. It was enhanced by ethylenediaminetetraacetate sodium. Other compounds were without effect. These results are discussed from the point of view of the possible relationship between SO4 accumulation in vitro and transport in vivo.
Arterial blood flow to the ruminant stomach
Authors: Sellers A. F. , Stevens C. E. , Dobson A. , McLeod F. D.
Published: December 2017

In seven of eight adult bovine females, increase in right ruminal or omasal artery flow was seen upon feeding. This increase continued beyond the act of feeding and was independent of weight-volume and motility change. Blood flow recorded from posterior mesenteric or hypogastric arteries did not show increase on feeding. Feeding under conditions where rumen fermentation was minimal limited the increase in ruminal blood flow to the period when the animal was eating. The passive transfer of feed into the rumen under these circumstances gave no blood flow stimulation. In five adult animals, an increase in CO2 tension within the reticulorumen increased blood flow. Acetate, propionate, and butyrate also stimulated blood flow. Concentration increments of the three organic acids showed increase in amount absorbed per unit time, but no regular relation to blood flow. A method of studying confined volumes is described.
Effects of temperature on isometric contraction of rat muscle
Authors: Truong Xuan T. , Wall Betty Jo , Walker Sheppard M.
Published: December 2017

The effects of temperature on the basic characteristics of isometric contraction were studied in the triceps surae of white albino rats. The influences of tetanic fusion and Wedensky inhibition on tension development were analyzed. The results showed linear increase of maximal isometric tetanic tension and increase in the rate of rise and fall of twitch and tetanic isometric contractions with increase in temperature. Indirect stimulation produced somewhat lower tetanic tensions than direct stimulation. The optimal frequency of stimulation for maximal tetanic tension development was usually lower than the critical frequency of tetanic fusion. Reduction of tension by excessively high frequencies of stimulation, due to the Wedensky effect, was observed with indirect stimulation, and occurred at a lower frequency than the critical frequency of fusion.
Decreased longevity of strain 129 dystrophic mice parabiosed at weaning
Authors: Pope R. S. , Murphy E. D. , West W. T.
Published: December 2017

Sixty dystrophic mice, maintained on a diet containing high-quality protein, were parabiosed to normal mice at weaning. Life span and weight gain were compared with the findings in a control group of 60 sham-operated dystrophics housed with sham-operated normal partners. Parabiosed dystrophics attained only 52% of the lifespan of the control dystrophics. Weight gains of normal and dystrophic parabionts were retarded. There was no evidence of remission or cure of the disease clinically or histologically.
Renal handling of α-ketoglutarate by the dog
Authors: Balagura Sulamita , Pitts Robert F.
Published: December 2017

Renal excretion, reabsorption, utilization, and peritubular transport of α-ketoglutarate were measured in the anesthetized dog under conditions of normal acid-base balance and in metabolic and respiratory acidosis and alkalosis. In the normal dog, the reabsorption of α-ketoglutarate is Tm limited. Chronic metabolic acidosis, induced by the feeding of ammonium chloride, and acute respiratory acidosis, induced by breathing CO2-O2 mixtures, increase Tm values significantly. Acute respiratory alkalosis, induced by hyperventilation and acute metabolic alkalosis, induced by the infusion of THAM (tris (hydroxymethyl) aminomethane), reduce Tm values significantly. Comparable states of acute metabolic alkalosis, induced by the infusion of sodium bicarbonate, do not reduce Tm to an extent comparable to that induced by hyperventilation or the infusion of TIIAM. For a variety of reasons, Tm of α-ketoglutarate seems to be more responsive to changes in intracellular than in extracellular hydrogen ion concentration. Transport of α-ketoglutarate into tubular cells both from tubular lumen and from peritubular fluid is probably active, i.e., against electrochemical gradients. It is suggested that both processes are affected by alterations of pH of intracellular fluid.
Control of renin secretion in the anesthetized dog
Authors: Vander Arthur J. , Miller Richard
Published: December 2017

Renin concentrations of renal venous plasma were indirectly measured by bio-assaying the pressor activity produced by plasma incubation under standardized conditions. Pressor activity was detectable in 85% of control dogs, was reciprocally related to sodium excretion, but did not correlate with arterial blood pressure. Reduction of mean renal arterial pressure to 90 mm Hg by an aortic clamp decreased sodium excretion and produced sustained increases in renin secretion and arterial blood pressure proximal to the clamp. Release of the aortic clamp resulted in gradual return of these variables toward control values. Induction of diuresis (osmotic diuretics, chlorothiazide, or acetazolamide) prior to aortic clamping minimized or completely prevented the usual clamp-induced rises in renin secretion and proximal blood pressure. Induction of diuresis during aortic clamping returned the elevated renin secretion and proximal blood pressure toward control values. These effects of diuretics could not be explained by changes in renal hemodynamics or plasma composition. Elevation of ureteral pressure in nondiuretic dogs also increased renin secretion and arterial blood pressure. We conclude that renin secretion is not controlled by blood pressure, per se, or intrarenal pressure, but by the flow or composition of intratubular fluid, probably at the level of the macula densa.
Intestinal loss of creatine by normal and vitamin E-deficient rabbits
Authors: Fitch Coy D. , Maben Sam
Published: December 2017

The distribution of radioactivity after an intravenous injection of creatine-1-C14 was used to estimate loss of creatine. Both the control and vitamin E-deficient rabbits lost creatine into the intestine with as much as 25% of the initial dose of creatine-1-C14 being recovered from the gastrointestinal tract and its contents. Destruction of creatine in the colon was confirmed by finding large quantities of radioactivity in expired CO2 soon after an injection of creatine-1-C14 directly into the ascending colon. In 4-hr balance studies very little of the intravenously injected creatine-1-C14 appeared in the urine of control rabbits, whereas 28–48% of the initial dose was present in the urine of vitamin E-deficient rabbits. Despite the large proportion of creatine-C14 lost in the urine, the vitamin E-deficient rabbits had specific activities of muscle creatine as high as the control values. The latter observation was presumed to be the result of a low concentration and short turnover time of muscle creatine in vitamin E-deficient rabbits.
Effect of hemorrhagic hypotension on oxygen consumption of dogs
Authors: Smith Elvin E. , Crowell Jack W.
Published: December 2017

The effects of hematocrit, Dibenzyline, and epinephrine on oxygen consumption were studied in 220 dogs whose arterial pressure was lowered to and maintained at 30 mm Hg. Oxygen consumption was recorded previous to and during the period of hypotension. The average oxygen consumption was 7.20 ml/kg min prior to hemorrhage. Ten minutes after hemorrhage the oxygen consumption was 3.58 ml/kg min (50% of control). After 30 min of hypotension the oxygen consumption was 4.70 ml/kg min (65% of control), and the oxygen consumption increased to 5.33 ml/kg min (74% of control) after 1 hr. Pretreatment with Dibenzyline increased the oxygen consumption during the early stages of hypotension but had little effect in the latter stages. Epinephrine administration decreased the oxygen consumption during the entire hypotensive period. Previous studies have shown that the oxygen utilization coefficient approaches its maximal value during the hypotensive period; therefore, oxygen uptake becomes limited by the blood flow and the changes in oxygen consumption indicate changes in flow rate to active tissue. Simultaneous studies showed that the hematocrit influenced oxygen transport by effects on both the blood oxygen content and the blood flow. The results illustrate that animals with hematocrits of 35–39 are able to transport more oxygen than animals with other hematocrits. Evidence is presented to show that the initial fall and the subsequent rise in oxygen consumption during hypotension may be a local autoregulation of blood flow.
Hemodynamic alterations after 30 minutes of pentobarbital sodium anesthesia in dogs
Authors: Barlow George , Knott David H.
Published: December 2017

In order to study the effects of pentobarbital sodium (Nembutal) anesthesia on the cardiovascular system, mean arterial pressure, cardiac output, stroke volume, total peripheral resistance, plasma and blood volumes, and the circulation time were measured in 20 board-trained unanesthetized dogs and in 20 animals 30 min subsequent to anesthetization with 30 mg/kg Nembutal. The mean arterial pressure, heart rate, cardiac output, and peripheral resistance were all markedly increased ( P < .001) in the anesthetized dogs, while the average blood volume in this group was significantly decreased, presumably due to a decrement in the circulating red cell mass. As might be expected from these results, the circulation time was decreased ( P < .001) in the anesthetized group. These data indicate that pentobarbital sodium exerts a profound influence on the cardiovascular system and serve as a reminder that the ubiquity of Nembutal anesthesia in experimental medicine mandates that the investigator appreciate the altered cardiovascular system with which he is working.
Antepartum and postpartum transfer of gamma globulin-I131 in the rat
Authors: Quinlivan Leslie G.
Published: December 2017

Gamma globulin-I131 was injected into rats during the last 3 days of gestation and during the first 9 days postpartum. Transfer in utero was shown to take place at a rapid rate. The amount of gamma globulin-I131 present in the infants bore a direct relation to the duration of suckling. Older infants absorbed more than younger ones during the same period of time.
Regulation of Ca45 transfer in rat salivary and lacrimal glands in vitro
Authors: Dreisbach Robert H.
Published: December 2017

The transfer in vitro of Ca45 either into or out of rat salivary and lacrimal glands is stimulated by sympathetic and parasympathetic agents. The transfer of Sr85 in both directions is also similarly stimulated by acetylcholine. The stimulation of Ca45 transfer in both directions by acetylcholine is inhibited by Na lack and by metabolic inhibitors such as azide, dinitrophenol, cyanide, mercuric ion, fluoride in absence of Ca and Mg, lack of oxygen, iodoacetate, and low temperatures. The acetylcholine effect on inward transfer is also reduced or inhibited by increased Ca or Sr, or by EDTA, but is apparently not affected by altered concentrations of K or Mg. In contrast, the acetylcholine effect on outward transfer is not affected by altered Ca concentration or addition of EDTA. Exogenous substrate is not necessary for stimulation of movement in either direction.
Mechanism of decrease in cardiac output caused by opening the chest
Authors: Fermoso Jose D. , Richardson Travis Q. , Guyton Arthur C.
Published: December 2017

The cardiac output in ten dogs fell an average of 18.8% (±1.1 sem) when the chest was opened. Opening the chest, which increased the extracardiac pressure, shifted the cardiopulmonary-function curve (relating right atrial pressure to cardiac output) toward higher atrial pressure levels. This caused the cardiopulmonary curve to equate with the animal's systemic-function curve at a lower cardiac output; the greater the extracardiac pressure the lower the output. Thus, changes in extracardiac pressure can alter cardiac output even though the pumping ability of the heart is not altered.
Intrarenal distribution of urea and related compounds: effects of nitrogen intake
Authors: Truniger Bruno , Schmidt-Nielsen Bodil
Published: December 2017

Nitrogen and NaCl intake influence the excretion of urea. In rats maintained on a low-protein, high-salt intake the urea-to-inulin clearance ratio decreases to 0.01. In antidiuretic "low-protein" rats the urea concentrations in the inner medulla are higher than in the urine, whereas in rats on high-protein diet the urea concentration in the inner medulla is lower than in the urine. The specific activity of urea-C14 1 hr after subcutaneous injection is approximately the same in plasma, renal cortex, and outer and inner medulla. The intrarenal distributions of acetamide and methylurea show the same pattern and are influenced by nitrogen intake in the same way as urea, whereas thiourea concentrations in urine are always higher than in the papilla. It is concluded a) that urea formation cannot account for papilla urea concentrations higher than urine concentrations; b) that the handling of urea and related compounds in the collecting duct changes in a similar way with changes in the nitrogen and salt intake; and c) that in the rat urea, methylurea, and acetamide are either reabsorbed in the collecting duct against their concentration gradients or bound by the papilla tissue.
Effects of abruptly elevating ureter pressure during mannitol diuresis
Authors: Ullmann Elisabeth , Wilde Walter S.
Published: December 2017

In anesthetized dogs undergoing mannitol diuresis one ureter was connected abruptly to a reservoir containing freshly excreted urine with inulin-C14 added and maintained at a constant pressure 25 mm Hg below arterial to arrest urine outflow. Six minutes later free urine flow was restored. Stop-flow analysis was used to compare this procedure and simple clamping of the ureter. Filtration markers injected intravenously at the moment of simple clamping demonstrated migration of filtrate into the blocked nephrons. Instantaneous elevation of ureter pressure prevented filtrate from reaching far distal regions, but still allowed invasion of proximal tubules. Retrograde movement of fluid and of tagged inulin from the reservoir into the kidney also occurred. In some, but not all experiments, this backflow reached nephron segments capable of absorbing sodium. Backflow caused by raising ureter pressure abruptly dilated the pelvis more than a similar pressure rise due to arrest of forward-flowing urine in simple ureter obstruction.
Certain aspects of cholesterol metabolism and hepatic protein synthesis in the rat
Authors: Saito Shiro , Fillios Louis Charles
Published: December 2017

Hepatic protein synthesis was studied in rats fed a hypercholesteremic diet, containing cholesterol and cholic acid, and high in fat. If such a diet was fed for periods of at least 4 weeks a lowered capacity of amino acid incorporation into liver protein in vivo and in vitro was observed. The animals selected were rats which had been previously characterized by such a dietary assay as being neither refractory nor susceptible to induction of high serum cholesterol levels. When "hypo-responders" (i.e., rats which are relatively refractory to hypercholesteremia) were compared to "hyper-responders" significant differences in protein synthesis in vivo were observed after only 2 weeks of dietary treatment; the capacity for incorporation of amino acids in the livers of hyper-responders was significantly lower than that in the hypo-responders. Several studies were also carried out in vitro including an attempt to determine which intracellular components of the liver may be affected; it appears that the defect(s) is primarily related to the endoplasmic reticulum. Thus, diet may act as the modus operandi for revealing any purported inherent defect(s).
Tissue glycogen levels in animals treated with the aminonucleoside of puromycin
Authors: Kmetec Emil , Heymann Walter
Published: December 2017

The intravenous injection into rats of 200 mg/kg of aminonucleoside (6-dimethylamino-9-(3'-amino-3'-deoxy-ß-d-ribofuranosyl) purine) resulted in an immediate decrease within 1 hr of liver glycogen followed by the storage of this carbohydrate after a 24-hr fast that was two to four times the amount found in pair-fed control animals. The latter effect persisted for about 2 days after aminonucleoside was given; thereafter, liver glycogen content decreased to near depletion on fasting at the time when the renal disease resembling the nephrotic syndrome developed. Muscle and kidney glycogen values were essentially unchanged as a result of the aminonucleoside. Similarly, when rabbit tissues were examined 2 days after 133 mg/kg of aminonucleoside was administered, the liver contained higher levels of glycogen in the fasted state than did the control tissue, while no change was found in muscle and kidney. Glucose 6-phosphatase activity was found to be unchanged from the control in livers of rats 2 days after aminonucleoside injection, although the activity of this enzyme in kidney was reduced by 39%. The rate of glucose formation from glycogen catalyzed by rat liver homogenates was found to be decreased by almost 40% in the presence of 6.43 mm aminonucleoside. No in vitro effect of the nucleoside on glucose 6-phosphatase could be demonstrated with concentrations up to 10 mm. The aminonucleoside effects did not appear to be related to the development and appearance of the induced kidney disease in rats.
Tissue blood flow during varied perfusion conditions
Authors: Reller Carl R. , Sheridan Judson D. , Aust J. Bradley
Published: December 2017

Under the conditions of isolated perfusion, total body perfusion, and a normal anesthetized state, antipyrine-I131 and K42 were used to determine limb tissue blood flow in dogs. As the isolated perfusion rate increased, skin values ranged from .010 to .035 ml/min g while muscle flows ranged from .01 to .60 ml/min g. During total body perfusion no muscle flow was found at a perfusion rate of 50 ml/min kg while at 100 ml/min kg, tissue flow values were equal to those of the normal anesthetized state and an isolated perfusion rate of 15–30 ml/min. The total body perfusion and bolus studies under general anesthesia showed that total limb flow was primarily tissue flow as opposed to arterial-venous shunting.
Liberation of antidiuretic hormone: pharmacologic blockade of ascending pathways
Authors: Mills Elliott , Wang S. C.
Published: December 2017

Water diuresis was established and maintained in dogs anesthetized with chloralose. Both ureters were cannulated and a continuous recording of urine flow obtained. ADH release was obtained from stimulation of the central end of a vagus nerve (the vagus-pituitary reflex), and ulnar nerve (nociceptive response) as well as from stimulation of reactive areas in the brain stem. Meperidine (10–15 mg/kg) and morphine (1–4 mg/kg) blocked the response to ulnar nerve stimulation and some brain-stem responses, but not the vagus-pituitary reflex. Similarly, the adrenergic blocking agents, Hydergine (0.3–0.6 mg/kg), phenoxybenzamine (2.0 mg/kg) and phentolamine (0.25 mg/ kg) markedly reduced the ulnar response and some brain-stem responses but not the vagus-pituitary reflex. However, larger doses of phenoxybenzamine (5 mg/kg) and Hydergine (1 mg/ kg) did inhibit the vagus-pituitary reflex. The anticholinergic agents, atropine (1–10 mg/kg) and ethybenztropine (0.5–2.0 mg/kg), were not effective blocking agents themselves but did render the inhibitory action of the adrenergic blocking agents more effective. These results suggest the existence of at least two different ascending pathways for ADH liberation. In addition, the evidence is compatible with the participation of adrenergic as well as cholinergic mechanisms in ADH liberation.
Lipid synthesis by rabbit lung tissue in vitro
Authors: Nasr K. , Heinemann H. O.
Published: December 2017

Mammalian lung tissue can synthesize various lipids in vitro. This can be demonstrated by incubating minced tissue or perfusing the intact organ with C14-labeled acetate as a precursor. The newly formed lipids include fatty acids, neutral and phospholipids. Of the phospholipids, lecithin has the highest rate of acetate incorporation. This is of interest because lecithin is known to be a component of the surface tension-lowering lipid-protein complex which lines the alveoli.
Effects of hypermagnesemia on general and coronary hemodynamics of the dog
Authors: Maxwell George M. , Elliott Robert B. , Burnell Richard H.
Published: December 2017

Vascular pressures, cardiac output (Fick), and coronary flow (N2O Fick) were measured before and after the induction of hypermagnesemia with MgCl2. A significant tachycardia and hypotension resulted. There was no effect upon coronary flow, coronary vascular resistance, or myocardial O2 and CO2 metabolism.
Mechanism of volume replacement and vascular constriction following hemorrhage
Authors: Haddy F. J. , Scott J. B. , Molnar J. I.
Published: December 2017

Experiments in the anesthetized dog suggest that fluid moves into the vascular system following hemorrhage because of fall in capillary hydrostatic pressure subsequent to decrease in aortic and right atrial pressures and increase in precapillary resistance. Postcapillary resistance also rises but not sufficiently to prevent the fall in capillary pressure. The increase in precapillary resistance results from active constriction, passive constriction, and, very transiently, increase in blood viscosity. The active constriction of precapillary vessels is due to a baroreceptor-induced sympathico-adrenal discharge and to some nonadrenal, nonrenal circulating vasoconstrictor substance. The active vasoconstriction is not well maintained in forelimb, intestine, or kidney because of local regulation ("autoregulation") and baroreceptor-induced lessening of the sympathico-adrenal discharge subsequent to movement of tissue fluid into the vascular system. This waning constriction together with a rise in perfusion pressure permits partial recovery of flow. The increase in forelimb postcapillary resistance results mainly from passive constriction. Active constriction subsequent to the sympathico-adrenal discharge is seen only with large hemorrhage.
Effects of cortisone on lipid and cholesterol metabolism in the rabbit and rat
Authors: Friedman Meyer , Bosch Jozef Van Den , Byers Sanford O. , St. George Shirley
Published: December 2017

Cortisone, 5 mg/day, first increased the plasma triglyceride levels of 2.5-kg male rabbits fed stock, high-fat, fat-free, or semistarvation diets. Later, hypercholesteremia was observed only in those plasmas in which triglyceride levels exceeded 400 mg/ml. Cortisone diminished accumulation of stainable fat in livers of animals fed fat, and of carbon particles in Kupffer cells; it caused parenchymal cells to enlarge and show vacuolization, abnormal nuclei, and fragmented cell walls. Rate of loss from plasma of parenterally administered triglyceride was similar in cortisone-treated and hepatectomized rabbits. Cortisone did not alter: lipid absorption, liver cholesterol, incorporation of acetate into cholesterol, bile cholesterol, rate of exit of cholesterol from plasma, Triton-induced hyperlipemia, or lipoprotein-lipase. Concentration of liver glycogen did not correlate with cortisone-induced lipemia. The authors suggest that cortisone induces hypercholesteremia only indirectly as a result of a sufficient degree of preceding hypertriglyceridemia, which stems in part from a relative inability of the liver to remove triglyceride from plasma.
Effects of carotid occlusion and left atrial distention on plasma vasopressin titer
Authors: Share Leonard
Published: December 2017

This investigation was directed toward the clarification of the role of left atrial stretch receptors in the regulation of the blood level of vasopressin. Occlusion of both common carotid arteries in the anesthetized dog resulted in a marked elevation of the plasma titer of ADH. This response was blocked by the simultaneous inflation of a balloon in the left atrium. Balloon inflation was ineffective in the vagotomized dog. It is concluded that activation of stretch receptors in the wall of the left atrium results in an inhibition of the release of ADH from the neurohypophysis and that the afferent nerve fibers for these receptors are carried by the vagi.
A melanocyte-stimulating hormone-releasing factor in hypothalamic extracts
Authors: Taleisnik S. , Orías R.
Published: December 2017

Intravenous injection of rat stalk median eminence (SME) extracts to rats produced a decrease in the pituitary melanocyte-stimulating hormone (MSH) activity. This effect was not obtained with injection of cerebral cortex extract, nor with histamine, norepinephrine, vasopressin, or oxytocin. A slight decrease occurred with epinephrine. The response to 2, 1, 1/2, 1/4, and 1/8 of SME was linearly related to the logarithm of the doses. It is inferred that hypothalamic extracts evoked a decrease in MSH pituitary content, since doses of 1/4 SME, which lowered the pituitary MSH activity more than 50%, did not modify the concentration in ACTH. No changes in MSH pituitary activity were obtained in animals submitted to stress. It is concluded that SME extracts contain a MSH-releasing factor which acts directly on the hypophysis and not through the nervous system, since it is effective in rats with hypothalamic lesions in the median eminence area.
Inhibition by insulin of hepatic glucose production in the normal dog
Authors: Steele R. , Bishop J. S. , Dunn A. , Altszuler N. , Rathgeb I. , de Bodo R. C.
Published: December 2017

Glucose-C14 was given intravenously in trace amount as an initial dose followed by continuous infusion to tag the circulating glucose of normal unanesthetized dogs in the post-absorptive state. The rate of dilution of this circulating tagged glucose by new (C12) glucose produced endogenously was measured. The release to the blood of such new glucose, presumably almost entirely from liver, was reduced by half during the 1st hr of intravenous insulin infusion at 0.1 U/kg per hr or more, provided that enough glucose was also infused to limit hypoglycemia. During the 2nd hr new glucose release was reduced by three-quarters or more. Insulin infusion at lower rates (02–.04 U/kg per hr), along with glucose, produced smaller effects. Glucose alone, infused intravenously in amounts sufficient to raise plasma glucose concentration, and hence presumed to enhance endogenous insulin secretion, reduced new glucose release by half during the 1st hr of infusion at one-half to one and one-half times the resting endogenous glucose production rate In the 2nd or 3rd hr, with glucose infusion increased to two to five times the resting endogenous glucose production rate, new glucose release was reduced by three-fourths or more.
Kinetic studies on transport of PAH and other organic acids in isolated renal tubules
Authors: Huang K. C. , Lin Dorothy S. T.
Published: December 2017

Studies were made on the uptake and washout of PAH and other organic acids in isolated renal tubules and cells at 25 C. The renal tubules accumulated PAH rapidly in the first 30-min period. Probenecid, its diethyl- and dimethyl analogues, hippuric acid, and 2,4-dinitrophenol inhibited the tubular transport of PAH competitively. A relationship between the inhibitory effect and the partition coefficient of the compound was observed; the higher the partition coefficient, the greater the inhibition. DNP was also accumulated in the isolated renal tubules. This accumulation was depressed by probenecid, indicating that DNP is probably transported by the same tubular transport mechanism for PAH and other organic acids. In washout experiments probenecid and DNP showed a biphasic action, namely, they stimulated the PAH washout in low concentration and inhibited it in high concentration However, hippuric acid, which has a low partition coefficient, demonstrated an augmentation of PAH washout even at a concentration of 2 x 10–2 m
Contraction enhancement in skeletal muscles of normal and dystrophic mice
Authors: Brust Manfred
Published: December 2017

Effects of NO3–, 1 mm caffeine, and 0.1 mm Zn++ on tension output of excised, curarized normal and dystrophic mouse gastrocnemius muscles have been studied. NO3– increased twitch tension in normal muscles to 133% of control values and in dystrophic muscles to 177%. It also increased tetanus tension in dystrophic muscles to 126% of control values without affecting tetanus tension of normal muscles. Twitch duration shortened and twitch speed increased in both muscle groups. Caffeine increased twitch and tetanus tensions to 120 and 114% of control values, respectively, in normal muscles, and to 129 and 113% in dystrophic muscles. Twitch durations increased slightly. Both agents reduced tetanus fusion frequency. Zn++ did not affect either muscle group. Thus, NO3– and caffeine extend the duration of the active state plateau in normal and dystrophic muscles. NO3– also intensifies the active state but only in dystrophic muscles, while caffeine does so in both groups. The pronounced effect of NO3– on dystrophic muscles suggests a derangement of Ca++ sites in the diseased membrane.
Dynamics of blood flow in the ductus arteriosus
Authors: Morris John A. , Bekey George A. , Assali N. S. , Beck Russell
Published: December 2017

The instantaneous pulsatile flow-pressure relationships across the ductus arteriosus were studied in fetal lambs before and after progressive lung expansion. Analysis of the same flow-pressure relationship was simulated on an analog computer using a mathematical model of the fetal circulation. The results demonstrate that 1) the blood flow through the ductus has a distinctive inertial characteristic and 2) there exists an asynchrony between the ejection of the two ventricles; the ejection of the right ventricle precedes that of the left. Both these factors explain the paradox of flow across the ductus from pulmonary artery to aorta (right-to-left shunt) which is seen when the lungs are incompletely expanded and the aortic pressure is higher than the pulmonary artery pressure.
Mechanisms regulating aldosterone secretion during sodium depletion
Authors: Binnion Peter F. , Davis James O. , Brown Torrey C. , Olichney Michael J.
Published: December 2017

Steroid secretion was studied in conscious dogs before and during 4 days of Na depletion. A threefold increase in aldosterone secretion occurred but corticosterone output was unchanged. Plasma renin was markedly elevated. Plasma Na and K concentrations were unchanged until the 4th day of Na depletion at which time plasma Na was decreased and plasma K was elevated. The Na content of the adrenal cortex expressed as fat-free tissue solids was decreased. It seems likely that the adrenocortical Na loss was extracellular; adrenocortical K content was unaltered. It is suggested that the normal rate of corticosterone secretion during Na depletion is maintained by a negative corticosteroid feedback mechanism, since corticosterone output was consistently increased in Na-depleted hypophysectomized dogs. Aldosterone secretion was three times as great in the presence as in the absence of the anterior pituitary during Na depletion. It is concluded that increased activity of the renin-angiotensin system is the primary mechanism leading to hyperaldosteronism during Na depletion and that the adenohypophysis plays an important supportive role.
Pharmacological studies of recurrent cortical inhibition and facilitation
Authors: Brooks V. B. , Asanuma H.
Published: December 2017

Injection of tetanus toxin into the pericruciate cortex reduced or abolished cortical recurrent inhibition produced by medullary conditioning stimulation. These changes occurred when the electrocorticogram began to show small spikes and bursts, but before onset of large seizure discharges. Intravenous injections of subconvulsive doses of strychnine or of picrotoxin reduced recurrent inhibition slightly and reversibly; convulsive doses precluded such measurements. Intravenous injections of dihydro-beta-erythroidin or of atropine had no specific effects on recurrent inhibition, although in some cases there were slight increases or decreases.
Iodoacetate depression in Xenopus sciatic single nerve fibers
Authors: Schoepfle Gordon M. , Atkins Eliska , Schafer Larry A.
Published: December 2017

Under conditions of continuous fluid exchange at a pH 7.55, a 10-min exposure of Xenopus sciatic single nerve fibers to iodoacetate results in eventual decline in the maximum rate of change of membrane potential, even after a delay of an hour or more during which no changes are apparent. This delayed effect is obtained over an iodoacetate concentration range of 0.1–20.0 mm sodium iodoacetate. Neither the resting membrane potential nor the maximal limiting response obtained during hyperpolarization are affected at a time when iodoacetate has appreciably depressed the spike in the nonpolarized fiber. These findings are taken to indicate that iodoacetate blocks a chain of reactions at a link remote from the process directly concerned with maintenance of the resting level of the sodium conductance. Neither lactate nor pyruvate can be relied on to bring about recovery from the iodoacetate depression.
Secretion of aldosterone by rats
Authors: Cade Robert , Perenich Theresa
Published: December 2017

The effect of sodium deprivation on adrenal blood flow and secretion of aldosterone and corticosterone was measured in intact rats. The changes induced by sodium deprivation were then compared with those resulting from infusion of angiotensin and vasopressin into hypophysectomized-nephrectomized animals and with the effect of angiotensin in oil given chronically to hypophysectomized rats. Sodium deprivation caused increased secretion of aldosterone but decreased secretion of corticosterone. Small doses of angiotensin infused acutely increased secretion of corticosterone but had no effect on aldosterone secretion. Large doses of either polypeptide increased both corticosterone and aldosterone. Chronic administration of small doses of angiotensin in oil increased corticosterone secretion but had no effect on secretion of aldosterone. Because angiotensin and vasopressin increase while sodium deprivation decreases secretion of corticosterone, it is concluded that neither of these polypeptides is responsible for the stimulation of aldosterone secretion which occurs with sodium deprivation.
C14-labeled glucose metabolism by bone from normal and parathyroid-treated rats
Authors: Chattopadhyay Haripada , Freeman Smith
Published: December 2017

Calvaria and the metaphyseal and epiphyseal sections of tibia and femora freed of bone marrow from young growing rats were incubated in vitro for 2 hr at 37 C in Krebs-Ringer bicarbonate buffer containing 2 mm glucose. The glucose was labeled either in the 1 position or in the 6 position or uniformly in all positions with C14. The incorporation of C14 into citrate, lactate, and various tricarboxylic acid cycle intermediates was studied. The release of C14O2 and the incorporation of C14 into bone matrix were also measured. Results obtained from bones of untreated control, parathyroid extract-treated, and parathyroidectomized animals were compared. It was found that treatment of animals with parathyroid extract increased the total accumulation of labeled citrate and malate as well as the incorporation of these acids into bone mineral. Bones from extract-treated animals also exhibited a significant decrease in the total accumulation of radioactive fumarate, succinate, and pyruvate. Lactate was the major end product of glucose metabolism, but its accumulation was only slightly influenced by parathyroid extract.
Role of chemical factors in regulation of flow through kidney, hindlimb, and heart
Authors: Scott J. B. , Daugherty R. M. , Dabney J. M. , Haddy F. J.
Published: December 2017

In the anesthetized dog, blood flow or metabolic rate was varied in kidney, hindlimb, or heart (experimental organ) while simultaneously diverting a portion of the venous outflow through forelimb or kidney (bioassay organ). The resistance to blood flow through the experimental organ gradually rose in the first few minutes following a large increase in flow and gradually fell following a large decrease in flow. Resistance to blood flow through an experimental organ (hindlimb) fell following increase in metabolic rate. In each case, bioassay organ resistance changed in the same direction when the assay organ was the forelimb and in the opposite direction when the assay organ was the kidney. These findings suggest that active hyperemia, reactive hyperemia, and autoregulation of blood flow result, at least in part, from alteration in the chemical environment of the blood vessels. Other findings in this study support the possibility that adenosine triphosphate contributes to the change in environment.
Effect of free fatty acids on metabolism of pyruvic and lactic acids
Authors: Weil Rudolf , Ho Peh-Ping , Altszuler Norman
Published: December 2017

The influence of infused free fatty acid (FFA) and of FFA-mobilizing hormones: growth hormone, epinephrine, and norepinephrine, on blood concentrations of glucose, pyruvate, and lactate subsequent to intravenous glucose loads were determined in normal dogs. Infusion of glucose (500 mg/kg in 30 min) to dogs injected with bovine growth hormone for 4 days (1 mg/kg per day) resulted in higher levels of pyruvate, but not lactate, than in control experiments. Intravenous infusion of palmitate alone had no discernible effect on blood pyruvate and lactate; however, administration of glucose immediately following palmitate infusion resulted in higher concentrations of blood pyruvate and lactate than in animals given glucose alone. Infusion of norepinephrine alone elevated only plasma FFA but not glucose; nevertheless a superimposed glucose load resulted in higher values for blood pyruvate and lactate than in control animals given glucose alone. These studies suggest that increased utilization of FFA influences the metabolic fate of glucose, resulting in higher concentrations of tissue and subsequently blood pyruvate and lactate.
Cardiac metabolism in the hypothermic ground squirrel and rat
Authors: Zimny Marilyn L. , Taylor Steve
Published: December 2017

A biochemical and electrocardiographic study of cardiac function during hypothermia in the ground squirrel (7–17 C) and the rat (11–19 C) revealed that, in the ground squirrel heart, adenosine triphosphate (ATP) and phosphocreatine (PC) each decreased significantly 60% thus maintaining their ratio (2.6/1), whereas in the rat heart ATP decreased 61%, PC decreased 48%, and lactate increased 194%. Histochemical studies demonstrated an increase in succinic dehydrogenase and a decrease in triphosphopyridine nucleotide diaphorase in the rat heart. As rectal temperature decreased in the ground squirrel the components of the electrocardiogram lengthened and voltage was maintained. In the rat, voltage decreased with decreasing rectal temperature and the electrocardiographic pattern reflected myocardial anoxia. The metabolic integrity of cardiac muscle cells and the membrane potential are apparently maintained in the ground squirrel during hypothermia. In the rat, however, this is not so and conduction difficulties become evident at 20–15 C. Disruption of mitochondrial morphology, presently being investigated, is thought to be responsible for the metabolic and conduction problems which occur in the rat heart during hypothermia.
Effects of ubiquinone and related substances on secretion of aldosterone and cortisol
Authors: Fabre Louis F. , Banks Robert C. , McIsaac William M. , Farrell Gordon
Published: December 2017

Previous studies had demonstrated the presence of a lipid-soluble factor in pineal extracts which inhibits aldosterone secretion when infused intravenously into intact dogs. Evidence is presented that ubiquinone, a constituent of the lipid fractions, is in large part responsible for this phenomenon. Both isolated and authentic ubiquinone cause significant reductions in aldosterone secretion, while reductions in cortisol secretion are only marginally significant. The reduced (quinol) and the cyclized (ubichromenol) forms were found to be much less active.
Effects of glycine and other instillates on concentration of gastric acid
Authors: Moody Frank G. , Durbin Richard P.
Published: December 2017

Instillation of isosmotic glycine solution on the mucosal surface of the histamine-stimulated canine stomach increases the concentration of HCl beyond its value in gastric juice. This was found to be primarily due to a reduction in the rate of water flow toward the lumen. Other instillates, including isosmotic sucrose, mannitol, and NaCl also produced an increase in the measured acidity. The effect is therefore not exclusively a result of the buffering of H ions by glycine. Instillation of urea did not significantly change the secreted acidity, and HCl instillation was accompanied by a decrease in acidity. The results can be most easily explained by assuming that the water component of gastric acid flows in response to an osmotic gradient due to secreted HCl. Instillation of the more impermeable solutes (sucrose, mannitol, NaCl) presumably reduces this gradient by dilution, while glycine acts in addition to reduce the gradient by buffering H ions.
Effects of removal of calcium from bathing media on frog stomach
Authors: Jacobson Ahren , Schwartz Manuel , Rehm Warren S.
Published: December 2017

Removal of Ca++ from the solutions bathing the frog gastric mucosa results in an initial increase in resistance (first phase) and a subsequent marked decrease in resistance (second phase). During the first phase the H+ secretory rate is decreased by 39% and the potential difference (PD) by 10%. During the second phase the measured H+ rate decreased to zero and the PD to near zero. Anoxia or DNP, which ordinarily produce a marked increase in resistance, failed to do so in the absence of Ca++. Comparable effects of Ca++ removal are found with Cl–-free bathing solutions. Replacement of Ca++ to the secretory solution on the nutrient side reversed these effects. Addition of Ca++ to the secretory solution readily reversed the second phase but only partly reversed the first phase. The inability of Ca++ on the secretory side in contrast to Ca++ on the nutrient side to reverse completely the first phase indicates that the secretory membrane may be much less permeable to Ca++ than the nutrient membrane.
Influence of periodicity of eating in the chicken
Authors: Leveille Gilbert A. , Hanson Richard W.
Published: December 2017

Male chickens were fed either ad libitum (nibblers) or allowed access to food for only 2 hr daily (meal eaters). The influence of these feeding regimens on body weight, body composition, plasma cholesterol, relative size of the digestive tract, and liver lipids was studied over a 14-week period. Body weight and percent body fat of meal-eating chicks were significantly lower throughout the study period. Plasma cholesterol levels were higher for meal-eating chicks at the 3- and 6-week sampling periods, but not after 10 and 14 weeks on the experimental regimens, suggesting that meal eating induces a transient hypercholesterolemia. Relative size of the digestive tract was increased in the meal-eating chicks. The rate of lipogenesis from acetate was higher in meal-eating chicks both in vivo and in vitro. In vivo fatty acid synthesis from glucose was also enhanced by meal feeding. The data presented suggest that the meal-eating chick and rat are metabolically similar.
Responses of cold- and warm-adapted dogs to infused norepinephrine and acute body cooling
Authors: Nagasaka Tetsuo , Carlson Loren D.
Published: December 2017

Oxygen consumption, heart rate, and colonic, pinna, and paw temperatures were recorded continuously in warm-adapted (W-A) and cold-adapted (C-A) dogs anesthetized with pentobarbital sodium (30 mg/kg), paralyzed with Flaxedil (5 mg/kg per hr), and mechanically ventilated. The dogs were infused with norepinephrine (1.25 µg/kg per min) for 20 min at 30 C and after 45 min of acute cold exposure to 5 C. Oxygen consumption of C-A dogs increased with a slight increase in the heart rate during the initial 18–20 min of body cooling. O2 consumption decreased continuously during cold exposure in W-A dogs. Calorigenic effects of infused noradrenaline were similar in C-A and W-A dogs at 30 C and 5 C. Heart rate increased in W-A dogs at 30 and 5 C. These results show that nonshivering thermogenesis is well developed by cold acclimation in dogs, and suggest that the increase may be due to an increase in noradrenaline in blood rather than to increased sensitivity of the animals to the calorigenic effects of noradrenaline.
Systemic and pulmonary vasomotor waves
Authors: Ferretti Ricardo , Cherniack Neil S. , Longobardo Guy , Levine O. Robert , Morkin Eugene , Singer Donald H. , Fishman Alfred P.
Published: December 2017

Rhythmic oscillations in systemic arterial blood pressure (Mayer waves) were produced in the dog by metabolic acidosis; hypoxia generally augmented the amplitude of the Mayer waves. When the Mayer waves exceeded 20 mm Hg in amplitude, they were associated with rhythmic fluctuations in pulmonary arterial pressure. The pulmonary arterial waves resembled the Mayer waves with respect to frequency and independence of the breathing pattern but were generally smaller in amplitude Measurements of instantaneous pulmonary arterial blood flow indicate that the rhythmic fluctuations in pulmonary arterial pressure represent the passive effects of fluctuations in pulmonary blood flow rather than fluctuations in pulmonary vasomotor activity. In turn, the swings in pulmonary arterial blood flow appear to originate in rhythmic variations in systemic vasomotor activity.