bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of hypothyroidism on tolerance of rats to heat
Authors: Fregly Melvin J. , Cook Kenneth M. , Otis Arthur B.
Published: December 2017

Hypothyroid (propylthiouracil-treated) rats show slower rates of rise of both colonic and skin temperatures than do control rats when both groups are restrained and exposed to air at 40 C. The increased tolerance to heat does not appear to be associated with increased heat conductance through skin but rather with lower heat production (oxygen consumption). Metabolic rate of hypothyroid rats decreases slightly during heat exposure while that of controls increases. When both groups are compared at the same colonic temperatures during heating, the metabolic rate of hypothyroid rats is significantly less than that of controls. The lower metabolic rate may be a reflection of the lower level of spontaneous muscular activity observed in these animals during heating. The greater tolerance of hypothyroid rats to heat thus appears to be associated with an ability to resist an increase in heat production as colonic temperature rises.
Bio-assay of circulating renin-like pressor material by isovolemic cross circulation
Authors: Schaechtelin G. , Regoli D. , Gross F.
Published: December 2017

The renin-like pressor material present in blood under various experimental conditions was determined by isovolemic cross circulation using nephrectomized rats as assay animals and rats having different concentrations of renin in the kidney as "donor" animals. Cross circulation was established by connecting the femoral arteries of both animals with the corresponding femoral veins and maintaining a constant flow. In intact anesthetized rats, a "basic" concentration of renin-like pressor material is demonstrable in the blood which is not influenced by unilateral nephrectomy. In the rat made hypertensive by clamping one renal artery, leaving the other kidney untouched, an increase in circulating renin-like pressor material is demonstrable. In unilaterally nephrectomized rats in which the artery of the remaining kidney is clamped, the concentration of circulating pressor material is not elevated. In adrenalectomized rats, an increase of circulating pressor material coincides with an elevated concentration of renin in the kidneys. There is a good correlation between the concentration of renin in the kidney and of pressor material in the blood, while the level of circulating renin-like substance is not correlated with the height of blood pressure.
Fate of H3-noradrenaline in skeletal muscle before and following sympathetic stimulation
Authors: Rosell Sune , Kopin Irwin J. , Axelrod Julius
Published: December 2017

The vascular bed of dog musculus gracilis in situ was perfused with blood at a constant flow rate. Infused H3-noradrenaline was retained and then released spontaneously at a slow rate. The major fraction of released radioactivity has been identified as normetanephrine, 3-methoxy-4-hydroxymandelic acid, and 3-methoxy-4-hydroxyphenylglycol. Upon vasomotor nerve stimulation, there was a concomitant reduction in outflow of total radioactivity and in noradrenaline metabolites and delayed elevation of noradrenaline outflow. After cessation of the stimulus, return of peripheral resistance and decline in noradrenaline outflow were parallel. Vasomotor nerve stimulation after pretreatment with phenoxybenzamine resulted in an immediate and larger increase in noradrenaline outflow. Vasomotor nerve stimulation did not induce any net change in the outflow of metabolic products. Rebinding of liberated noradrenaline and diffusion and removal by the circulation appear to be the major mechanisms for ending the action of noradrenaline. Transcapillary transport is reduced by the liberated noradrenaline and this serves to prolong the action of the neurohumor.
Passive transfer of dextran anaphylactoid reaction in rats
Authors: Adamkiewicz V. W. , Sacra P. J.
Published: December 2017

The anaphylactoid reaction produced in donor rats by an intravenous injection of 12 mg of dextran/100 g body wt., can be transferred passively, 60 min later, into acceptor rats, by an intravenous injection of 0.5 ml of the serum from donors. The anaphylactoid reaction resulting in the acceptors is due to a factor, produced in the serum of donors, which is other than the original dextran, histamine, serotonin, or heparin. The production of this factor is potentiated when the rats are presensitized to dextran. It is suggested that the dextran anaphylactoid reaction belongs together with anaphylaxis to the class of immediate hypersensitivities.
Chronic effect of exercise on liver cholesterol of normal and hypercholesteremic rats
Authors: Gollnick Philip D.
Published: December 2017

Two groups of male albino rats of the Sprague-Dawley strain, with average initial body weights of about 265 g, were trained for 22 weeks on an exercise program of swimming one-half hour daily in water at 35 C. One trained group was fed a normal diet containing 18% casein. The other trained group received an isocaloric diet containing 1% cholesterol which was designed to produce hypercholesteremia. Two nonexercised groups, one fed the normal and the other the 1% cholesterol diet, served as controls. The adrenals and heart ventricles of both trained groups were larger than their respective controls. Exercise had no hypocholesteremic effect on the sera of either trained group. Fat and cholesterol accumulation in the livers of rats fed the 1% cholesterol diet were not affected by training, but training significantly lowered the fat and cholesterol of the livers of the normal rats.
Effect of the spleen in norepinephrine action on blood volumes of the dog
Authors: Chacalos Elias H. , Moore James C.
Published: December 2017

In intact and splenectomized dogs the plasma and cell volumes were measured simultaneously by means of Risa and P32-tagged erythrocytes. Two measurements were made in each dog; first during a control period and second during a constant norepinephrine infusion or, in some dogs in the splenectomized group, after neurogenic vasoconstriction. Average values were as follows: In the intact group norepinephrine produced a decrease in the F factorcells (0.884 to 0.820), an increase in the excess plasma volume (9.7 to 14.8 ml/kg), and a small decrease in total plasma volume (50.1 to 48.5 ml/kg). In the splenectomized group norepinephrine or neurogenic vasoconstriction caused a rise in the Fcells factor (0.806 to 0.858), a decrease in the excess plasma (13.8 to 9.3 ml/kg), and a more marked fall in the total plasma volume (44.9 to 39.6 ml/kg). A norepinephrine-induced redistribution of splenic blood in the intact animals could not quantitatively explain the observed changes. It was concluded that the ejection of splenic blood modifies antagonistically the effects of norepinephrine on the plasma and excess plasma volumes by counteracting the vasoconstrictor effect of norepinephrine on vessels small enough to contain plasma-rich blood.
Adipose tissue in experimental nephrotic syndrome
Authors: Gutman Alisa , Shafrir Eleazar
Published: December 2017

Epididymal adipose tissue of aminonucleoside-treated rats, investigated 3 to 6 days after induction of the nephrotic syndrome, had low glycogen levels and showed impaired esterification of free fatty acids and assimilation of lipoprotein triglyceride and markedly reduced liberation of lipoprotein lipase. These results were found to be influenced by the inadequate food intake of the acutely nephrotic animals and comparable to the values of control rats fasted for 2 days. On return to adequate nutrition, which occurred 12–20 days after aminonucleoside treatment, adipose tissue glycogen and free fatty acid assimilation returned toward normal levels but lipoprotein-lipase liberation remained below normal. In rats rendered nephrotic by antikidney serum, the assimilation of free fatty acids and lipoprotein-triglyceride by adipose tissue was impaired in spite of only minor reduction in food consumption. The results indicate that the defective metabolism of adipose tissue in nephrotic animals may be contributory to the nephrotic hypertriglyceridemia.
Role of aortic and vagus nerves in arterial baroreflex bradycardia in rabbits
Authors: Alexander Natalie , Cuir Marjorie De
Published: December 2017

The mechanism that eventually restores heart rate to normal during continuous arterial baroreceptor stimulation is not known. One step toward an understanding of this mechanism was to assess the relative contribution of afferent and efferent nerve pathways to the initial reflex bradycardia elicited by a rise of arterial pressure. The amount of reflex slowing at the end of a 10-min infusion of angiotensin into conscious rabbits was studied before and after sectioning vagus or aortic nerves. A 20–30 mm Hg rise in arterial pressure caused an average decrease in heart rate of 23% in control rabbits, 10% in aortic denervated, 3% in vagus denervated, and 9% after atropine block. These results indicate that the major contribution from afferent pathways to cardiac reflex slowing is through aortic nerves rather than carotid sinus or other afferent nerves. On the efferent side, vagus nerves have more effect on cardiac slowing than does sympathetic nerve inhibition.
Influence of route of administration on hemodynamic effects of endotoxin
Authors: Jacobson Eugene D. , Farrar W. Edmund
Published: December 2017

The effect of route of administration of endotoxin upon subsequent hemodynamic events was evaluated in a perfused canine small intestinal preparation. One ld50 of Shigella flexneri endotoxin was injected into either the superior mesenteric artery (6 animals), a mesenteric vein (6 animals), or the right femoral vein (6 animals). Pressures were monitored in the superior mesenteric artery, a mesenteric vein, and the left femoral artery for 30 min after injection of endotoxin. In the three groups of dogs the same qualitative effects were observed: portal venous hypertension, systemic arterial hypotension, and an increase in small intestinal vascular resistance. However, portal hypertension was greatest when endotoxin was injected into the portal circulation, systemic arterial hypotension was most profound when endotoxin was injected into a femoral vein, and mesenteric vascular resistance was most prolonged when endotoxin was injected into the mesenteric artery. These findings suggest that the hemodynamic response of a regional vascular bed to endotoxin is influenced by the initial plasma concentration of lipopolysaccharide.
Effect of nephrectomy on citrate metabolism in the rat
Authors: Simpson David P.
Published: December 2017

The transient rise in plasma citrate which occurs after nephrectomy was studied in rats by measuring plasma citrate concentrations and the rate of conversion of intravenously administered C14-labeled citrate to respiratory CO2. Two hours after nephrectomy plasma citrate was greatly elevated and the rate of oxidation of radioactive citrate was slow. Twenty-four hours after nephrectomy both plasma citrate and rate of oxidation of labeled citrate were normal. In a parathyroidectomized rat in which little rise in plasma citrate followed nephrectomy the rate of conversion of radioactive citrate to CO2 was almost normal. Injection of a large intraperitoneal dose of citrate before administering C14-labeled citrate resulted in a delayed recovery of respiratory C14O2. These results indicate that no decrease in the rate of oxidation of plasma citrate occurs after nephrectomy and that nonrenal tissues are able to metabolize circulating citrate at a substantial rate. Consequently the rise in plasma citrate after nephrectomy probably is due to a temporary increase in the rate of production of plasma citrate rather than to a decrease in the rate of citrate oxidation.
Influence of pilocarpine on transport by salivary gland slices
Authors: Schneyer L. H. , Schneyer C. A.
Published: December 2017

Effects of pilocarpine on net movements of water and electrolytes in gland cells were investigated in vitro, using slices from submaxillary gland of rat. Slices were depleted of K, and loaded with Na, Cl, and water, by incubation in Krebs-Ringer phosphate with nitrogen atmosphere. After this, the slices were transferred to Krebs-Ringer phosphate with oxygen atmosphere. During this period with O2, pilocarpine caused apparent loss of water from cells, since tissue total water decreased and inulin space remained almost unchanged. Without pilocarpine during this time, water in cells increased. Electrolyte movements were also affected by pilocarpine. Specifically, there occurred reduction in net accumulation of K in total tissue and cells. Reduction in net extrusion of Na was suggested. Since, in vivo, an early effect of stimulation involves depletion of gland K, it appears that the current observations have relevance to normal secretion to the extent, at least, that in both circumstances stimulating agents reduce the ability of the cells to maintain stores of K.
Labeled glycine of collagens of different-aged normal and cortisone-treated rats
Authors: Smith Q. T.
Published: December 2017

Injections of glycine-2-C14 into control and cortisone-treated weanling, young adult, and adult male rats were followed by determination of the specific activity of glycine from citrate-soluble and mature skin collagen and total femur collagen. The time for the specific activity of glycine from citrate-soluble collagen to decrease to that of glycine from mature collagen increased with increasing age. Faster metabolic turnover of femur collagen than skin collagen was indicated in each group of control rats. Synthesis of collagen under conditions of constant collagen content was indicated in adult rats by incorporation of radioactivity into skin and femur collagen. Cortisone treatment resulted in significant changes in the specific activity of collagen glycine only in weanling and young adult rats. In cortisone-treated rats, significant changes in the specific activity of glycine from mature skin collagen were less prominent than, and were associated with, changes in total skin collagen, but significant changes in the specific activity of glycine from femur collagen were more evident than, but not always associated with, changes in quantity of femur collagen.
Effect of potassium on secretion and potential of frog's gastric mucosa in Cl–-free solutions
Authors: Davis T. L. , Rutledge J. R. , Rehm W. S.
Published: December 2017

In previous work it was shown that the potential difference of the secreting mucosa bathed in Cl–-free solutions (SO4– replacing Cl–) is negative (nutrient side negative). In the present work it was found that an increase of the K+ concentration (K+ substituted for Na+) of the bathing fluid on the secretory side produced an increase in H+ secretory rate. The effect of voltage-clamping at zero and at +100 mv on the H+ rate, with various K+ concentrations in the bathing fluids, yielded results predicted by the electrogenic H+ theory, but not by a forced exchange concept.
Enzyme studies of skeletal muscle in mice with hereditary muscular dystrophy
Authors: McCaman Marilyn W.
Published: December 2017

The activities of 20 enzymes in normal, heterozygous, and dystrophic mouse muscle were studied by means of quantitative microchemical methods. Enzyme activities in normal and heterozygous muscle were essentially the same. In dystrophic muscle glucose-6-P dehydrogenase, 6-P-gluconic dehydrogenase, glutathione reductase, peptidase, ß-glucuronidase, and glucokinase activities were significantly higher than in normal muscle, while α-glycero-P dehydrogenase and lactic dehydrogenase activities were significantly lower. The pattern of enzyme activities found in normal gastrocnemius denervated by nerve section was strikingly similar to that in dystrophic muscle.
Urea utilization by rabbits fed a low-protein ration
Authors: Houpt T. Richard
Published: December 2017

Utilization of urea by adult rabbits fed straw, carrots, and sucrose was investigated. 1) In a 24-hr period following intravenous injection of 290 mg urea-N/kg body wt., part of the exogenous urea was excreted in urine and part was stored in body fluids; the remainder could not be accounted for and was presumed utilized in amino acid synthesis. An average of 212 ± 54 (sd) mg urea-N were utilized in eight such experiments (control urea-N excretion was 151 mg/day). Urea given per os over several days was also utilized. 2) When drinking water was removed, utilization of urea given per os, as reflected in nitrogen balance, increased; or, if no urea was given, nitrogen excretion decreased. 3) Antibacterial agents per os reduced exogenous urea utilization; or, if no urea was given, urea excretion increased, representing endogenous urea normally utilized (up to 40% of that formed in the body). 4) In acute experiments, blood urea moved into the saline-filled cecum at rates commensurate with the rates of utilization found in the other experiments. It was concluded that adult rabbits under these conditions can utilize urea at rates significant in nitrogen metabolism.
Consumption of oxygen by thoracic and abdominal aorta of the rat
Authors: Priest Robert E.
Published: December 2017

Consumption of oxygen in vitro by thoracic and abdominal aorta and of liver and kidney of rats was measured by direct Warburg manometry and related to the weight of tissue and to the content of nitrogen and of deoxyribonucleic acid (DNA). On the basis of numbers of cells present, as determined by the content of DNA, thoracic aorta respires at a rate one-fifth that of liver. Thoracic aorta respires more actively than abdominal aorta but also contains more nitrogen and more DNA per unit weight than abdominal aorta. The difference in consumption of oxygen between these two segments of aorta can be explained largely, although not entirely, on the basis of numbers of cells present. Because of the lesser content of nitrogen and DNA in abdominal aorta, it must contain larger amounts of some substance which contributes to weight and has a low nitrogen content.
Regulation of extracellular potassium in hypothermia
Authors: Kanter G. S.
Published: December 2017

Reduction of rectal temperature by ice packing in anesthetized dogs resulted in a fall in plasma potassium concentration in spite of the fall in arterial pH. Such a decrease in extracellular pH in normothermia would cause an increase in plasma K concentration. It was suggested that due to previously shown depression of renal acidification mechanisms in hypothermia, there occurred a K+ for Na+ exchange in the renal tubule with K+ being excreted instead of H+. It was expected that removal of renal function during hypothermia would allow the alteration in pH to cause an increase in extracellular K. Renal function was therefore removed by bilateral nephrectomy in five dogs and by ligation of both ureters in four dogs. Contrary to expectations, it was found that in the absence of renal function during hypothermia plasma K still fell markedly. No difference was found in the nephrectomized or ureter-tied dogs. It was proposed that in hypothermia, in the absence of renal function, some function of intracellular metabolism controlled extracellular K. Possibly intracellular pH decreased relatively more than did extracellular pH with a resultant movement of H+ out of the cell and K+ in. With renal function present in hypothermia, the influx of K into the cell seen in nephrectomized and ureter-tied dogs is reversed by the renal gradient which causes both a decrease in cellular and extracellular K.
Glucose kinetics in normal, fasting, and insulin-treated cows
Authors: Kronfeld D. S. , Raggi Fiora
Published: December 2017

Plasma glucose concentration in four cows averaged 58 mg/100 ml. It fell to 48 mg/100 ml during fasting, and to 29 mg/100 ml when long-acting insulin was given daily. From 45 until 150 min after a single injection of glucose-C14 the curves for plasma glucose specific activity plotted logarithmically against time approximated straight lines. The line during fasting lay above the normal line, while the line during insulin treatment fell below it. This suggests that there are two types of hypoglycemia, distinguished by different changes in the glucose pool. Characteristics of the pool sampled as plasma glucose were calculated from the slope and intercept of the lines from 45 to 150 min after injection. During fasting, the amount of exchangeable glucose fell to two-thirds and the glucose entry rate to half normal. This suggests that hypoglycemia develops during fasting because glucose utilization (outflow) exceeds glucose formation (inflow) with a decrease in the amount of glucose. In contrast, during insulin administration, the amount of exchangeable glucose was greater than normal, the entry rate was increased by one-third, and the apparent volume of glucose distribution was increased to 64% of the body weight. This suggests that insulin-induced hypoglycemia is due to an increase in the glucose "space" associated with the accumulation of exchangeable glucose inside some cells.
Regulation of glucose oxidation in the white rat
Authors: Depocas Florent
Published: December 2017

The rate of oxidation of glucose has been measured in 43 rats acclimated to 30 C, at rates of turnover of 8–105 mg glucose carbon/100 g body wt. per hour (mg C/100 g·hr) by the technique of priming and continuous infusion of trace amounts of C14-glucose. This range of glucose turnover values had been obtained by using rats in various nutritive states or by continuous infusion of nonlabeled glucose. Oxidation was directly proportional to turnover between rates of turnover of 8 and 40 mg C/100 g·hr with a slope of about 0.5. At higher rates of turnover the ratio of oxidation to turnover decreased to 0.35, thus indicating that oxidation was approaching a maximum. At the highest rates of glucose turnover, a maximum of 63% of the respiratory CO2 was derived from body glucose, although the amount of non-labeled glucose carbon injected per minute exceeded the respiratory CO2 carbon by a factor of 1.8. Therefore, oxidation of glucose in the intact rat is closely regulated by its availability, but body glucose does not appear to serve as sole substrate for respiration even when its rate of turnover exceeds the respiratory output of carbon.
Synthesis of serum glycoproteins in response to injury
Authors: Chandler Albert M. , Neuhaus Otto W.
Published: December 2017

The transient elevations in rat serum globulins in response to injury were studied by precipitating the seromucoid fraction following the intraperitoneal injection of C14-labeled algal hydrolysate and C14-labeled glycine. Rats, injured by sponge implantation, showed a parallel increase in seromucoid protein and radioactivity. Partial hepatectomy, which reduced the response to stress, yielded a seromucoid fraction of high specific activity when the labeled amino acid was injected 2 hr prior to sacrifice. Chemical hepatic necrosis, produced by administration of carbon tetrachloride, reduced the level of the seromucoid fraction. Subsequent injury yielded a striking response both in the seromucoid protein and in the amount of seromucoid radioactivity. It is concluded that these data are consistent with an active synthesis of protein in response to injury.
Excretion of Krebs cycle acids in relation to the cycle's function in avian kidney
Authors: Lotspeich William D. , Woronkow Seraphim
Published: December 2017

In the chicken, unilateral renal portal perfusion with certain intermediates of the Krebs cycle (notably sodium α-ketoglutarate, succinate, and fumarate) increased excretion of other cycle acids, particularly citrate and α-ketoglutarate. These were excreted at a much higher rate from the ipsilateral kidney. This phenomenon was even more striking during infusion of sodium pyruvate with one-seventh the amount of sodium fumarate, α-ketoglutarate, or oxaloacetate. This resembles the catalytic, or "sparking" effect of these same dicarboxylic acids on pyruvate oxidation by the Krebs cycle in certain tissues, a resemblance strengthened by the fact that this sparked excretion of cycle acids is blocked by sodium malonate or ammonium salts which also block the effect in tissues. These observations are discussed in terms of 1) the possible renal tubular synthesis and secretion of these cycle acids from their infused precursors, and 2) the increased excretion of citrate and α-ketoglutarate in alkalosis.
Urinary adrenaline and noradrenaline response to simulated weightless state
Authors: Goodall McC. , McCally Michael , Graveline Duane E.
Published: December 2017

Sixteen normal subjects were placed in a simulated weightless state, i.e., water immersion. After 6 hr of water immersion, urine samples were collected and bio-assayed for adrenaline and noradrenaline. The excretion of adrenaline was moderately increased ( P < 0.15 > 0.10), possibly related to the anxiety associated with the immersion. The excretion of noradrenaline was significantly ( P < 0.01) reduced during immersion. Six subjects were also studied during passive vertical tilt following the immersion. The increase in pulse rate and decrease in pulse pressure were significantly greater than those observed during a control tilt. The results of these experiments indicate that the decrease in orthostatic tolerance following a simulated weightless state is probably related to a decrease in sympathetic nerve activity, which in turn is reflected by a decline in the urinary output of the sympathetic neurohormone noradrenaline.
Effects of carnitine on acetyl-CoA oxidation by heart muscle mitochondria
Authors: Fritz Irving B. , Yue Kenneth T. N.
Published: December 2017

Acetyl-1-C14-CoA was oxidized by heart muscle mitochondria incubated in the absence of ATP and carnitine at a rate approximately 1/100 that at which acetic acid-1-C14 was converted to CO2 in the presence of ATP. Carnitine addition increased the degradation of acetyl-1-C14-CoA by over 50-fold whereas it had no effect on acetate-1-C14 oxidation under conditions described. Carnitine simultaneously augmented oxygen uptake by heart mitochondria in the absence of ATP when acetyl-CoA was the substrate, but had little or no effect on respiration when acetate was the substrate in the presence or absence of ATP. Acetylcarnitine decreased the carnitine enhancement of acetyl-1-C14-CoA conversion to CO2, most likely by isotope dilution via operation of the carnitine acetyltransferase reaction: acetyl-CoA + carnitine ⇆ acetylcarnitine + CoA. It was tentatively concluded that the acetyl group of acetyl-CoA cannot readily penetrate mitochondrial barriers in the absence of a suitable transfer system, but that carnitine acetyltransferase and carnitine may function as a shuttle system to facilitate acetyl-group movement across mitochondrial membranes. Additional data presented demonstrate that carnitine influences the metabolism of the acyl groups of other chain-length acyl-CoA derivatives.
Serum requirement for release of heparin-induced lipase from perfused rat heart
Authors: Crass M. F. , Meng H. C.
Published: December 2017

The release of a lipolytic enzyme from the isolated perfused rat heart was studied. The perfusion medium was a Krebs-Henseleit bicarbonate buffer, pH 7.4, with or without heparin and/or serum. The lipolytic activity of perfusates was determined by incubating the perfusate in a phosphate buffer, pH 7.4, at 37 C for 1 or 2 hr using coconut oil emulsion, rat chylomicrons, or cottonseed oil emulsion as a substrate in the presence of serum albumin. Both heparin and serum were required for optimal enzyme release; the optimal concentrations of heparin and serum were 50 µg/ml and 10% by volume, respectively. Addition of serum to the assay system could not replace its effect in the perfusion medium. The appearance of the enzyme in the perfusion medium was rapid; 55% of the total lipolytic activity was released within 2 min. The lipolytic activity of this enzyme was inhibited by protamine, NaCl, NaF, and taurocholate.
Phosphorylase activity and glycogenolysis in the working turtle heart
Authors: Reeves Robert B.
Published: December 2017

Measurements of phosphorylase a and t activities were made on perfused aerobic and anaerobic hearts from Pseudemys scripta and Emydoidea blandingi. Aerobically a/t ratio averaged 25% and was independent of arterial pressure (Pa) and work rate; anaerobically, the ratio ranged from 50 to 75% and was dependent on Pa but not on work rate. Phosphorylase t activity in O2 or N2 ranged from 15 to 45 µmoles Pi/g min (assayed at 37.5 C). Phosphorylase isolated from turtle hearts by starch column chromatography yielded the following Km values: Kglym = 1.0 mg/ml; Kampm = 0.25 mm; Kpim = 7.2 mm. Direct tissue analyses for (Pi), (AMP), and (ATP) permitted estimate of phosphorylase activity in working hearts. Tissue (AMP) was approximately equal to KAMPM aerobically and 8 x KAMPM anaerobically, permitting high phosphorylase b activity in vivo. It is estimated that the greatest limitation on rate of glycogenolysis is attributable to (Pi). Anaerobic rate of glycogen breakdown could be accounted for by phosphorylase t activity, (Pi), (AMP), and (ATP). Aerobic glycogenolysis rate is smaller by at least an order of magnitude than estimated rate computed on same basis.
Transmembrane action potentials and contractions of human atrial muscle
Authors: Sleator William , Gubareff Taisija De
Published: December 2017

Transmembrane action potentials and contractions were recorded from pieces of human atrial muscle stimulated electrically in Krebs solution. These preparations exhibit a new type of behavior characterized by periodic "cycling" between two phases: high-phase contractions are two to eight times those in low phase, and action potentials have two or more spikes. The phenomenon can occur in a piece of any size, and is most likely at temperatures between 20 C and 33 C. Acetylcholine weakens contractions, reduces duration of action potential (AP) plateau, and usually abolishes double spikes and cycling; this suggests relatively low K+ permeability during the long low plateau. Epinephrine shortens the cycling period and makes low- and high-phase contractions more nearly equal; additional epinephrine leads to bizarre APs and spontaneous activity. This behavior of human atrial tissue reflects intrinsic capabilities of the cell membrane not previously observed in heart. General hypotheses are proposed to account for the double-spiked APs, for cycling, and for relations between the unique contraction patterns and AP configurations.
Cardiovascular response to acute hypocapnia due to overbreathing
Authors: Little Robert C. , Smith Charles W.
Published: December 2017

Anesthetized dogs were maintained by artificial respiration at a fixed rate and depth. The composition of inspired CO2 was varied while O2 content was maintained at control levels. Cardiac output was measured by the indicator-dilution technique. Acute reduction of end-expiratory CO2 levels below the normal value caused a decrease in blood pressure, pulse pressure, stroke volume, and cardiac output, no essential change in heart rate and an increase in total peripheral resistance. Mean systemic blood pressure and net vascular resistance were less with hypocapnia than they were at the same cardiac output at normal CO2 levels. However, the over-all vascular resistance was greater with hypocapnia than it was in the same animal at normal CO2 levels and control output values. Analysis of these data leads to the conclusion that the hypocapnia produced by overbreathing causes some degree of net vasodilation. The hypotension associated with hyperventilation appears to result in these experiments from the drop in cardiac output and to a lesser degree the relatively less than normal compensatory increase in total peripheral resistance.
Intestinal absorption of hexoses in the dog
Authors: Annegers John H.
Published: December 2017

Solutions (310 mosmoles/liter) containing NaCl and 14–280 mm/liter hexose were perfused through jejunal or ileal fistulas in unanesthetized dogs. Each hexose was given alone and in combination with several concentrations of another hexose. Glucose, galactose, and fructose absorption rates increased in nearly hyperbolic fashion with increasing lumen concentrations whereas the absorption rate for sorbose was nearly directly proportional to its concentration in both jejunal and ileal loops. The perfusate hexose concentration for one-half maximal absorption rate differed between glucose, galactose, and fructose although all three sugars approached a similar maximum absorption rate. When pairs of hexoses were perfused, glucose and galactose seemed to compete for absorption whereas glucose and fructose, galactose and fructose, glucose and sorbose, and galactose and sorbose were absorbed nearly independently.
Transport of sodium and chloride by the isolated rumen epithelium
Authors: Stevens Charles E.
Published: December 2017

Transepithelial electrical potential, short-circuit current, and resistance measurements were made under different conditions of tissue collection and maintenance. The collection procedure greatly affected tissue resistance and, since the magnitude of the current was relatively independent of the procedure, potential was affected to about the same degree. The highest and least variable resistances were recorded when the tissue was removed from the anesthetized cow and the epithelium carefully dissected free. Short-circuit current and net ion flux decreased with time but the decrease was relatively linear and sufficiently slow to allow their comparison. Rumen epithelium of both species demonstrated active transport of Na and Cl in the direction of lumen to blood. Calculation of partial Na conductances indicated that part of the sodium was transported by exchange diffusion or a sodium chloride transport system.
Measurement of cortical pH in spreading cortical depression
Authors: Rapoport Stanley I. , Marshall Wade H.
Published: December 2017

The pH of the rabbit cortex was measured during the course of spreading cortical depression. Spreading cortical depression was elicited by chemical (group I) and by electrical (group II) means. Cortical d-c potential changes were recorded separately by a glass membrane pH electrode and by a pore electrode. Records were made of each against an indifferent ground and also of the algebraic addition of the pH electrode and the pore electrode. The maximum cortical d-c potential changes in the initial negative and later positive phase of spreading cortical depression, as recorded by each electrode, were compared statistically. A significant ( P < 0.05) pH change of –0.027 ± .005 (se of mean) pH units was demonstrated for the positive phase. No pH change was found for the negative phase. Sources of error are discussed. The results do not support the hypothesis that large pH changes are involved in the genesis and mechanism of spreading cortical depression.
Small bowel motility and colonic transit are altered in dogs with moderate renal failure
Authors: Lefebvre Hervé P. , Ferré Jean-Pierre , Watson A. David J. , Brown Cathy A. , Serthelon Jean-Paul , Laroute Valérie , Concordet Didier , Toutain Pierre-Louis
Published: December 2017

Although gastrointestinal complications are common in patients with renal disease, the effects of renal dysfunction on bowel motility and gut transit times are not well known. We assessed gastrointestinal electromyographic activity, gastric emptying rate, orocolonic transit time, oroanal transit time, and xylose absorption before and after surgically inducing a 66% decrease in glomerular filtration rate in dogs. Moderate renal failure induced no gross or microscopic gastrointestinal lesions but caused a 16–42% increase in gastrointestinal motility indexes. We found a 24% decrease in the propagation velocity of the myoelectrical migrating complex in the duodenojejunal segment, a 30% decrease in phase I duration in duodenal and jejunal regions, a 20% increase in the total irregular electrical activity of the small intestine, and a 22% increase in duration of the meal response in the duodenum and jejunum. Renal failure did not change xylose absorption, gastric emptying rate, and orocolonic transit time but decreased colonic transit time by 38%. The mean weight of feces was increased. These results indicate that moderate renal failure alters duodenojejunal motility and decreases colonic transit time.
Activation of α2-receptors in the rostral ventrolateral medulla evokes natriuresis by a renal nerve mechanism
Authors: Menegaz Rubia Grecco , Kapusta Daniel R. , Mauad Helder , de Melo Cabral Antonio
Published: December 2017

The contribution of α2-receptor mechanisms in the rostral ventrolateral medulla (RVLM) in mediating the enhanced renal excretory responses evoked by the intravenous infusion of the α2-receptor agonist xylazine was examined in ketamine-anesthetized rats. In ketamine-anesthetized rats, the bilateral microinjection of the α2-receptor antagonist yohimbine into the RVLM significantly reduced the enhanced levels of urine flow rate (V) and urinary sodium excretion (UNaV) produced by xylazine. In contrast, microinjection of yohimbine into the RVLM of chronically bilaterally renal-denervated rats significantly reduced the xylazine-evoked diuretic, but not natriuretic, response. In separate ketamine-anesthetized rats, intravenous xylazine infusion produced a near complete inhibition of renal sympathetic nerve activity (RSNA). The subsequent microinjection of yohimbine into the RVLM reversed this neural response and concurrently decreased V and UNaV. Together, these results indicate that during intravenous infusion, xylazine activates α2-receptor mechanisms in the RVLM to selectively promote urinary sodium excretion by a renal nerve-dependent pathway. In contrast, activation of α2-receptor in the RVLM affects the renal handling of water by a pathway independent of the renal nerves. This latter pathway may involve an interaction with other brain regions involved in antidiuretic hormone release (e.g., paraventricular nucleus of the hypothalamus).
Unsteady-state gas exchange and storage in diving marine mammals: the harbor porpoise and gray seal
Authors: Boutilier R. G. , Reed J. Z. , Fedak M. A.
Published: December 2017

Breath-by-breath measurements of end-tidal O2and CO2concentrations in harbor porpoise reveal that the respiratory gas exchange ratio (RR; CO2output/O2uptake) of the first lung ventilation in a breathing bout after a prolonged breath-hold is always well below the animal's metabolic respiratory quotient (RQ) of 0.85. Thus the longest apneic pauses are always followed by an initial breath having a very low RR(0.6–0.7), which thereafter increases with each subsequent breath to values in excess of 1.2. Although the O2stores of the body are fully readjusted after the first three to four breaths following a prolonged apneic pause, a further three to four ventilations are always needed, not to load more O2but to eliminate built-up levels of CO2. The slower readjustment of CO2stores relates to their greater magnitude and to the fact that they must be mobilized from comparatively large and chemically complex HCO[Formula: see text]/CO2stores that are built up in the blood and tissues during the breath-hold. These data, and similar measurements on gray seals (12), indicate that it is the readjustment of metabolic RQ and not O2stores per se that governs the amount of time an animal must spend ventilating at the surface after a dive.
Cardiovascular and renal responses to a high-fat diet in Osborne-Mendel rats
Authors: Fitzgerald Sharyn M. , Henegar Jeffrey R. , Brands Michael W. , Henegar Lisa K. , Hall John E.
Published: December 2017

This study examined the cardiovascular, renal, and hormonal responses of dietary-induced obesity in Osborne-Mendel (OM) rats. Male OM rats were fed either a low (LF; n = 10)- or high-fat (HF; n = 11) diet for 17 wk. During week 15 of the study, arterial pressure was measured directly, 24 h/day, from chronically indwelling catheters. Body and kidney weights were 46 ± 5 and 33 ± 5% greater, respectively, in rats fed HF vs. LF diet. Left and right ventricular weights were also greater in rats fed HF diet (21 ± 7 and 36 ± 6%, respectively). Direct measurement of arterial pressure revealed only a slight increase in mean arterial pressure (88 ± 1 in rats fed HF diet vs. 85 ± 1 mmHg in rats fed LF diet), whereas there was no difference in resting heart rate between the two groups. Consumption of HF diet was also associated with a 3.5-fold increase in plasma insulin, a 16 ± 4% higher blood glucose, and a 40 ± 6% reduction in plasma renin activity compared with LF-fed rats. Thus feeding OM rats HF diet led to obesity, cardiac and renal hypertrophy, and hyperinsulinemia but only a slight increase in mean arterial pressure.
Insulin-independent, MAPK-dependent stimulation of NKCC activity in skeletal muscle
Authors: Wong Jennifer A. , Gosmanov Aidar R. , Schneider Edward G. , Thomason Donald B.
Published: December 2017

Na+-K+-Cl−cotransporter (NKCC) activity in quiescent skeletal muscle is modest. However, ex vivo stimulation of muscle for as little as 18 contractions (1 min, 0.3 Hz) dramatically increased the activity of the cotransporter, measured as the bumetanide-sensitive86Rb influx, in both soleus and plantaris muscles. This activation of cotransporter activity remained relatively constant for up to 10-Hz stimulation for 1 min, falling off at higher frequencies (30-Hz stimulation for 1 min). Similarly, stimulation of skeletal muscle with adrenergic receptor agonists phenylephrine, isoproterenol, or epinephrine produced a dramatic stimulation of NKCC activity. It did not appear that stimulation of NKCC activity was a reflection of increased Na+-K+-ATPase activity because insulin treatment did not stimulate NKCC activity, despite insulin's well-known stimulation of Na+-K+-ATPase activity. Stimulation of NKCC activity could be blocked by pretreatment with inhibitors of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2) activity, indicating that activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) MAPKs may be required. These data indicate a regulated NKCC activity in skeletal muscle that may provide a significant pathway for potassium transport into skeletal muscle fibers.
Overexpression of sarcolemmal calcium pump attenuates induction of cardiac gene expression in response to ET-1
Authors: Piuhola Jarkko , Hammes Annette , Schuh Kai , Neyses Ludwig , Vuolteenaho Olli , Ruskoaho Heikki
Published: December 2017

The function of the plasma membrane calmodulin-dependent calcium ATPase (PMCA) in myocardium is unknown. PMCA is localized in caveolae, 50- to 100-nm membrane invaginations, which also contain receptors for endothelin-1 (ET-1) and various other ligands. PMCA has been suggested to play a role in regulation of caveolar signal transduction. We studied the effects of the hypertrophic agonist ET-1 and increased coronary perfusion pressure on cardiac synthesis of B-type natriuretic peptide (BNP) in transgenic rats overexpressing the human PMCA 4CI in isolated perfused heart preparation. ET-1 infusion for 2 h increased BNP mRNA levels twofold in left ventricles (LV) of nontransgenic rats, whereas no increase was noted in PMCA rat hearts. Similar responses were seen in adrenomedullin and c- fos mRNA levels, and in immunoreactive BNP secretion. Increased mechanical load produced by elevated perfusion pressure induced similar 1.5- to 1.6-fold increases in LV BNP mRNA in both nontransgenic and PMCA rat hearts. These results show that cardiac overexpression of PMCA attenuates ET-1-stimulated early induction of cardiac gene expression, suggesting that PMCA may modulate myocardial growth responses.
Hyperglycemia modulates angiotensinogen gene expression
Authors: Gabriely Ilan , Yang Xiao Man , Cases Jane A. , Ma Xiao Hui , Rossetti Luciano , Barzilai Nir
Published: December 2017

Elevated plasma angiotensinogen (AGT) levels have been demonstrated in insulin-resistant states such as obesity and type 2 diabetes mellitus (DM2), conditions that are directly correlated to hypertension. We examined whether hyperinsulinemia or hyperglycemia may modulate fat and liver AGT gene expression and whether obesity and insulin resistance are associated with abnormal AGT regulation. In addition, because the hexosamine biosynthetic pathway is considered to function as a biochemical sensor of intracellular nutrient availability, we hypothesized that activation of this pathway would acutely mediate in vivo the induction of AGT gene expression in fat and liver. We studied chronically catheterized lean (∼300 g) and obese (∼450 g) Sprague-Dawley rats in four clamp studies ( n= 3/group), creating physiological hyperinsulinemia (∼60 μU/ml, by an insulin clamp), hyperglycemia (∼18 mM, by a pancreatic clamp using somatostatin to prevent endogenous insulin secretion), or euglycemia with glucosamine infusion (GlcN; 30 μmol · kg−1· min−1) and equivalent saline infusions (as a control). Although insulin infusion suppressed AGT gene expression in fat and liver of lean rats, the obese rats demonstrated resistance to this effect of insulin. In contrast, hyperglycemia at basal insulin levels activated AGT gene expression in fat and liver by approximately threefold in both lean and obese rats ( P < 0.001). Finally, GlcN infusion simulated the effects of hyperglycemia on fat and liver AGT gene expression (2-fold increase, P < 0.001). Our results support the hypothesis that physiological nutrient “pulses” may acutely induce AGT gene expression in both adipose tissue and liver through the activation of the hexosamine biosynthetic pathway. Resistance to the suppressive effect of insulin on AGT expression in obese rats may potentiate the effect of nutrients on AGT gene expression. We propose that increased AGT gene expression and possibly its production may provide another link between obesity/insulin resistance and hypertension.
Gastrin-releasing peptides fromXenopus laevis: purification, characterization, and myotropic activity
Authors: Kim Joseph B. , Johansson Ågot , Holmgren Susanne , Conlon J. Michael
Published: December 2017

Two molecular forms of gastrin-releasing peptide (GRP) were isolated from an extract of the intestine of the tetraploid frog Xenopus laevis. The primary structure of GRP-1 (APTSQQHTEQ10LSRSNINTRG20SHWAVGHLM.NH2) differs from that of GRP-2 by a single amino acid substitution (Asn15→ Thr15). GRP-(20–29) peptide (neuromedin C) was also isolated from the extract. Synthetic GRP-1 produced concentration-dependent contractions of longitudinal smooth muscle strips from Xenopus cardiac stomach (pD2= 8.93 ± 0.32; n = 6). The responses were unaffected by tetrodotoxin, atropine, and methysergide, indicating a direct action of the peptide on smooth muscle cells. GRP-1 elicited concentration-dependent relaxations of precontracted (5 μM carbachol) circular smooth muscle strips from the same region (pD2= 8.96 ± 0.21; n = 8). The responses were significantly ( P < 0.05) attenuated (71 ± 24% decrease in maximum response; n = 6) by indomethacin, indicating mediation, at least in part, by prostanoids. Despite the fact that Xenopus GRP-1 differs from pig GRP at 15 amino acid sites, both peptides are equipotent and equally effective for both contractile and relaxant responses, demonstrating that selective evolutionary pressure has acted to conserve the functional COOH-terminal domain in the peptide. The data suggest a physiologically important role for GRP in the regulation of gastric motility in X. laevis.