bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of inulin for determining volume flow in rat renal cortical tubules
Authors: Marsh Donald , Frasier Charles
Published: December 2017

The recovery of inulin was complete when perfused by micropuncture into single proximal tubules and collected from the corresponding distal tubule. Systemic infusion of inulin during similar experiments revealed no inulin secretion. Inulin-C14 was completely recovered in the urine when injected into single proximal tubules. These experiments provide direct affirmation of the assumption that inulin is conserved in the tubule lumen.
Mechanisms of cardioaccelerator action of angiotensin
Authors: Krasney J. A. , Paudler F. T. , Smith D. C. , Davis L. D. , Youmans W. B.
Published: December 2017

The cardioaccelerator influence of synthetic angiotensin observed in dogs having baroreceptors denervated or blood pressure buffered was studied. In dogs which had received morphine (3 mg/kg) and chloralose (90 mg/kg) and which had the sinoaortic zones denervated, angiotensin, in doses of 1 µg/kg intravenously, still caused cardiac acceleration after transection of the spinal cord at C6 or C7 or after removal of sym-pathetic chains bilaterally from the stellate through T4 or T5. In intact dogs under morphine-chloralose which had received full ganglionic blocking doses of either tetraethylammonium chloride or pentolinium tartrate, angiotensin produced marked cardiac acceleration. Administration of bretylium tosylate, in doses of 10 mg/kg intravenously, largely or completely prevented the cardioaccelerator action of angiotensin. The beta receptor blocking agents nethalide and Inderal had effects similar to those of bretylium tosylate. The studies indicate that there is a peripheral adrenergic basis for much or all of the cardiac acceleration produced by these doses of angiotensin. In the intact animal this influence would be expected to counteract much of the cardiac inhibition elicited reflexly from baroreceptors.
Activation of thrombolysis by streptokinase in the cat
Authors: Fleming L. Brian , Cliffton Eugene E.
Published: December 2017

The activation of thrombolysis by streptokinase in the cat has been studied by the measurement of multiple parameters. It is postulated that streptokinase in optimal dosage will directly activate plasminogen to plasmin, and that an excess of streptokinase will combine stoichiometrically with this plasmin to form activator. It is also suggested that fibrinogen may act as a transfer vehicle for activator, releasing it in response to a falling concentration of the plasmin or when fibrinogen is converted to fibrin. It appears that the level of fibrinogen in cats measured by the method of Quick is dependent on the concentration of activator in the plasma sample.
Relationship between blood histamine and centrally evoked hypotensive response
Authors: Tuttle Richard S.
Published: December 2017

In the pyramidal cat, an intense and potentially lethal hypotensive response may be evoked by stimulation of a narrow zone dorsal to the median raphe of the posterior medulla. The present investigation concerns some of the pharmacology and hemodynamics of this response. The evidence suggested that an active vasodilator was released into the systemic circulation. The delay observed between the period of medullary stimulation and the cardiovascular response was attributed to either the time involved in the release process or the time required for the substance to reach the general circulation. Pharmacological and chemical isotopic analysis based on the incorporation of histidine-C14 into histamine-C14 indicated that histamine release was associated with the fall in systemic pressure and increase in blood flow. Since atropine blocks the response, as do the antihistaminics, a cholinergic mechanism may be involved in the release process.
Myocardial catecholamines and stimulation of the stellate ganglion in hemorrhagic shock
Authors: Glaviano Vincent V. , Klouda Mary Ann
Published: December 2017

Cardiac responses to electrical stimulation of the right or left stellate ganglion were recorded from 16 open-chest anesthetized dogs in hemorrhagic shock. Shock was induced by bleeding the animals to a mean blood pressure of 40 mm Hg. This level of pressure was maintained for 4 hr, during which time blood pressure, heart rate, force of myocardial contraction, and intraventricular pressures were recorded. Stimulation of the stellate ganglion for 15–40 sec every 30 min after hemorrhage showed a gradual decrease in these parameters to levels below control. The reinfusion of blood and the infusion of exogenous l-norepinephrine did not restore an increase in force of cardiac contraction to stellate stimulation. Myocardial epinephrine and norepinephrine levels in shock were found not to differ from those in 14 normal dog hearts. In contrast to almost complete myocardial refractoriness to stellate stimulation in hemorrhagic shock, stimulation of the vagus nerve elicited bradycardia and eventual cardiac arrest. The decrease observed in force of cardiac contraction to stimulation of the stellate ganglion in hemorrhagic shock may be due to depletion of norepinephrine stores in the heart.
Mechanism of blocked lipogenesis induced in rats by feeding extremely hydrogenated fat
Authors: Horst Antoni , Paluszak Janusz , Rozynkowa Danuta , Bialecki Mieczyslaw
Published: December 2017

In order to explain the disappearance of depot fat in rats fed on a diet containing 50% by weight of extremely hydrogenated vegetable fat, experiments were performed in which the diet inhibiting lipogenesis was enriched with biotin. Biotin was effective in maintaining normal adipose tissue stores. The dermal essential fatty acid deficiency syndrome which occurred in this dietary group was prevented by the administration of linoleic acid. Cecal contents of rats kept on diets with hydrogenated fat were analyzed for biotin concentration and showed depressed intestinal synthesis of this vitamin by the bacterial flora. These data suggest that the inhibited lipogenesis in animals fed extremely saturated fat is the result of essential fatty acid deficiency and thereby of a reduced synthesis (and increased utilization) of biotin required as coenzyme of fatty acid synthesis in the nonmitochondrial system of lipogenesis.
Bone sodium as a function of serum sodium in rats
Authors: Forbes Gilbert B. , McCoord Augusta
Published: December 2017

In experiments of a few hours' duration, alterations in bone sodium induced by hypo- or hypernatremia were limited to that fraction contained in the fluid phase of bone, while acidosis per se produced no change (11, 14). The present report describes the results of chronic (5-day) hypo- and hypernatremia in the rat. Under these circumstances a change occurred in both the crystal and fluid Na of bone, and this change was proportional, and in the same direction, to that of serum Na. Young animals showed a greater change in bone Na than did adults. When hypertonic NH4Cl was given for 5 days there was no evidence of mobilization of Na from bone, nor was Na stored when alkaline Na salts were administered. Bone Na reflects the concentration of this element in body fluids, and is not influenced by acid-base balance.
Effect of ureteral stop flow on renal tissue creatinine, PAH, K, and P in dogs
Authors: Carrasquer Gaspar , Baldwin A. Louise
Published: December 2017

Experiments have been designed to study tubular function by analysis of renal tissue under conditions of oliguria and mannitol diuresis. A 50-min ureteral obstruction of one kidney was induced by forcing previously excreted urine into the renal pelvis. Without releasing the obstruction, the experimental and control kidneys were removed simultaneously. Relationships between tissue concentration and tubular function have been demonstrated. Substances that are reabsorbed in medulla accumulate in its interstitium during free flow, and this accumulation is reduced by ureteral obstruction. Persistent filtration during stop flow is manifested by accumulation of creatinine throughout the kidney, and is attributed to a distal leak induced by sodium reabsorption. Accumulation of PAH in cortex is enhanced by ureteral obstruction in mannitol diuresis, but the localized effect on PAH is obscured by high levels of persistent filtration in oliguria. The maintenance of phosphorus and potassium levels during stop flow is attributed to their high intracellular concentrations.
Effects of a pyrogen reaction on urine concentration in the dog
Authors: Cohen Jay A. , Goodman Berney , Yunis Stuart L. , Levitt Marvin F. , Kahn Melvin
Published: December 2017

The administration of Piromen, a pyrogenic extract, to anesthetized, dehydrated, vasopressin-supplemented dogs uniformly produced a fall in urine concentration without a significant change in solute excretion. In seven hydropenic animals, urine osmolality decreased from 1,664 to 855 milliosmols/kg and urine flow increased from 0.41 to 1.00 ml/min. In 17 animals a pyrogenic reaction was produced during a solute diuresis, in 11 during a rising or stable Tchh2o-Cosm relationship, and in 6 during a spontaneously falling Tchh2o. In the former group Tchh2o fell 1.9 ml/min and in the latter 3.1 ml/min. In five studies hypotonic urine was excreted. In three studies, appreciably increasing Cosm by hypertonic infusion produced a gradual decline of Thh2o in two and no change in one. These data are interpreted as indicating that pyrogen impairs renal concentration by decreasing medullary solute content as a consequence of renal hyperemia. Alterations in distal tubular membrane permeability to water cannot be excluded.
Amino acid and α-keto acid concentrations in plasma and blood of the liverless dog
Authors: McMenamy R. H. , Vang Johannes , Drapanas Theodore
Published: December 2017

The plasma unbound amino acid concentrations and the blood concentrations of pyruvate, α-ketoglutarate, lactate, and the α-keto analogues of leucine plus isoleucine plus valine were determined in hepatectomized dogs. The concentrations of leucine, isoleucine, valine, α-amino- n-butyric acid, methionine and the α-keto analogues of leucine plus isoleucine plus valine decreased after hepatectomy. When leucine, isoleucine, valine, α-ketoisocaproic acid, α-ketoisovaleric acid, and/or methionine were infused intravenously in the liverless dog, the major portion of these compounds was found to be taken up by the tissues. The concentrations of all amino acids except leucine, isoleucine, valine, α-amino- n-butyric acid, and methionine increased after hepatectomy. Pyruvate, α-ketoglutarate, and lactate concentrations rose immediately after hepatectomy and remained generally elevated throughout the survival of the liverless animal. The lactate-to-pyruvate ratio was the same in the preoperative and postoperative animals.
Different properties of two mucigogues, pilocarpine and mercuric acetate
Authors: Robert André , Nezamis James E. , Phillips J. Paul
Published: December 2017

Hexosamine content of gastric juice and gastric tissue (corpus and antrum separately) was determined in rats an estimation of mucus. Pilocarpine increased mucus secretion thout reducing mucus content of the mucosa. Tissue mucus was even slightly elevated after constant infusion. Rise in juice mucus was not due to contamination from saliva since it persisted after cauterization of salivary gland ducts. Oral administration of mercuric acetate also increased gastric juice mucus but produced a marked depletion of mucus in the mucosa. Whereas pilocarpine did not produce histological alterations in the stomach, after mercuric acetate the mucosa was eroded and clusters of cells were found in the gastric cavity, embedded into a thick layer of mucus. Volume of secretion increased with both compounds. Pilocarpine stimulated acid and pepsin formation at low doses; in contrast, acid secretion was blocked by mercuric acetate and pepsin secretion was markedly reduced. It is concluded that a) mucus secretion can be stimulated by at least two different pathways, neural (pilocarpine being considered as simulating the action of parasympathetic stimulation) and topical (as exemplified by mercuric acetate); b) pilocarpine exerts its mucigogue effect both by eliciting extrusion of mucus granules from the cells and by stimulating mucus synthesis within the same cells, the two processes taking place simultaneously; c) pilocarpine appears to be mucigogue chiefly by acting directly on mucus cells, and not simply through a squeezing-out effect due to the gastric contractions elicited by the drug.
Glycogen and CO2 production from glucose and lactate by red and white skeletal muscle
Authors: Bar Uwe , Blanchaer M. C.
Published: December 2017

Diaphragm and external oblique muscle of the abdomen were identified histochemically as red and white muscles, respectively, in the rat. Administration of glucose orally to fasted rats 3 hr before sacrifice increased the glycogen in the red but not in the white muscle. Paired red and white muscles were incubated 2 hr in oxygen at 29 C in Krebs-Ringer phosphate medium at pH 74 containing 11 mm glucose and 40 mm dl-lactate. Glycogen increased in all the samples except in the red muscle specimens with high initial glycogen levels. The glycogen change and glucose-U-C14 incorporation into glycogen were both inversely related to the initial glycogen and were both greater in red than in white muscle. These differences between the muscles were suppressed by increasing the oral glucose dose. C14O2 production from glucose-U-C14 and lactate-1-C14 was greater in red than in white muscle.
Velocity of contraction as a determinant of myocardial oxygen consumption
Authors: Sonnenblick Edmund H. , Ross John , Covell James W. , Kaiser Gerard A. , Braunwald Eugene
Published: December 2017

In 12 dogs on right-heart bypass with heart rate, stroke volume, and aortic pressure constant, the velocity of contraction was augmented comparably by three fundamentally distinct interventions in the same heart: 1) sustained postextrasystolic potentiation produced by paired, electrical stimulation; 2) norepinephrine infusion; and 3) calcium infusion. In each instance the correlation between velocity of contraction and MVo2 was striking. During paired stimulation, maximum rate of left ventricular ejection increased by an average of 50.3% ± 3.8% (se of mean) above control, MVo2 increased by 1.96 ± 0.10 ml/100 g per min (39.8% ± 1.6% above control), while the tension-time index (TTI) fell 12.4% ± 1.1%. With norepinephrine, and with calcium, left ventricular ejection rates were increased 52.9 ± 3.2% and 55.1 ± 3.2%, respectively, and MVo2 was augmented 2.03 ± 0.08 ml/100 g per min and 1.87 ± 0.04 ml/100 g per min, while the TTI decreased 15.9 ± 0.6% and 12.4 ± 2.4%. Since MVo2 always increased substantially while TTI fell, tension cannot be considered to be the sole determinant of MVo2. Since comparable increases in velocity of contraction produced by different interventions were associated with similar large augmentations of MVo2, it appears that the velocity of contraction is an important determinant of MVo2. Furthermore, it is likely that the so-called O2 wasting effect exerted by norepinephrine on myocardial metabolism may be explained largely by an increased velocity of contraction.
Effect of insulin on potassium and glucose movement in perfused rat liver
Authors: Burton Stanley D. , Ishida Tadashi
Published: December 2017

When the liver from a normal rat is transferred to an extracorporeal perfusion apparatus, there is a marked release of potassium and glucose to the perfusing medium attributed primarily to the anoxia incident to removal of the liver from the intact animal. This glycogenolytic response subsided within 30 min as reflected by a rapid uptake of glucose in the absence of a recovery of potassium when livers were perfused with whole blood and a decreased outflow of glucose when livers were perfused with diluted blood. The administration of insulin during this recovery phase resulted in a prompt uptake of potassium from whole-blood perfusate which preceded any demonstrable increase in the uptake of glucose by the liver. These findings indicate that the extracorporeal perfused rat liver is responsive to added insulin despite the initial anoxia and suggest 1) that insulin is required by the liver for the recovery of potassium lost during glycogenolysis and 2) the transfer of glucose into the liver is dissociated from the transfer of K+. In perfusions with diluted blood, insulin inhibited the net accumulation of perfusate glucose, an effect possibly accounted for by a net decrease in the breakdown of liver glycogen.
Effects of Mg deficiency and parathyroidectomy on gastrointestinal Ca transport in the rat
Authors: Morehead Richard M. , Kessner David M.
Published: December 2017

An open-ended, everted gut-sac technique was used to measure in vitro duodenal transfer of calcium in magnesium-deficient and pair-fed control animals with and without parathyroid glands. In contrast to previous studies employing the closed gut-sac technique in calcium-deprived animals, we were unable to demonstrate an effect of parathyroidectomy on the in vitro transport of calcium across the duodenum. Magnesium deficiency resulted in enhanced intestinal transport of calcium. These data confirm our previous studies and demonstrate that this effect of magnesium deficiency is linear over 2 hr of incubation. This enhancing effect of magnesium deficiency on gastrointestinal calcium transport was blocked by parathyroidectomy. The results of this study are consistent with the hypothesis that magnesium deficiency increases calcium transfer of the isolated everted gut-sac of rats by stimulating the secretion of parathyroid hormone.
Role of angiotensin II in experimental renal hypertension in the rabbit
Authors: Johnson JA , Davis JO , Braverman B
Published: December 2017

Hypertension was produced in rabbits by constricting the left renal artery; in nine rabbits the opposite kidney was removed and in eight rabbits the opposite kidney was left intact. To investigate the role of angiotensin II (A-II), 1-sarcosine-8-alanine angiotensin II, a competitive antagonist of A-II, was infused at 6 mug/min per kg body wt for 30 min. In a control group of seven unilaterally nephrectomized rabbits mean arterial pressure averaged 81 mmHg and infusion of the A-II antagonist did not alter the arterial pressure. In a group of Na-depleted rabbits, arterial pressure decreased from 81 to 63 mmHg (P less than 0.01) in response to the A-II analogue. Thirty days after renal artery constriction, seven of the nine one-kidney hypertensive rabbits had normal values for plasma renin activity (PRA) and during infusion of the A-II antagonist arterial pressure was unchanged. However, two rabbits had elevated PRA and the arterial pressure decreased during infusion of the angiotension analogue. In the two-kidney hypertensive rabbits, PRA was normal and arterial pressure was unchanged by infusion of the A-II antagonist. These studies provide evidence that hypertension developed with either a high or normal A-II plasma level in the one-kidney animals; the two-kidney rabbits developed chronic hypertension in which no role for A-II could be demonstrated.
Autoregulation of blood flow in the rat kidney
Authors: Arendshorst WJ , Finn WF , Gottschalk CW
Published: December 2017

We present evidence showing that renal blood flow (RBF) in the anesthetized nondiuretic rat can be measured reliably and accurately using a noncannulating flow transducer and an electromagnetic flowmeter. In vitro calibration yielded a linear relationship (r=0.998) between flowmeter output voltage and blood flow rates from 0.2 to 10.3 ml/min. Excellent agreement was observed between simultaneous determinations of RBF by the flowmeter and the PAH clearance technique. Glomerular filtration rate and RBF for a kidney with a flow transducer around its renal artery did not differ significantly from corresponding values for the undisturbed contralateral kidney. The relationship of mean RBF with steady-state variations in perfusion pressure was evaluated in 13 nondiuretic rats. RBF averaged 6 ml/min.g kidney wt at arterial pressures (AP) above 100 mmHg. A high degree of autoregulatory efficiency was observed when mean AP varied between 105 and 145 mmHg. Over this pressure range RBF changed only 3% as changes in intrarenal vascular resistance and AP were directly related (r=0.994). Below 95-105 mmHg RBF decreased in a curvilinear fashion with the concavity toward the pressure axis.
Acid-induced excitation of afferent cardiac sympathetic nerve fibers
Authors: Uchida Y , Murao S
Published: December 2017

The effect of acids on activity of afferent sympathetic nerve fibers from the left ventricle has been examined. Action potentials were derived from the upper thoracic communicating rami of the left side of anesthetized dogs. Application of a solution of lactic acid to the left ventricular surface caused excitation in both myelinated and unmyelinated fibers. The minimum concentration required for excitation was 7.5-75 mug/ml for the unmyelinated fibers and 375-750 mug/ml for the myelinated fibers. Excitation of the unmyelinated fibers induced by coronary occlusion was suppressed by pretreatment with sodium bicarbonate, 500 mg/kg. However, excitation of the myelinated fibers was influenced little by the agent. Pretreatment with a large dose of Trasylol failed to suppress excitation induced by coronary occlusion. The result suggests that acidosis plays a role in excitation of the unmyelinated fibers induced by myocardial ischemia, but not in excitation of the myelinated fibers.
Gluconeogenesis in arctic ground squirrels between periods of hibernation
Authors: Galster W , Morrison PR
Published: December 2017

The hibernation season in the arctic ground squirrel (Citellus undulatus) is broken into 8- to 18- day cycles by short homeothermal periods during which the carboydrate reserves depleted during hibernation are replenished. This study follows a number of metabolities in tissues and body fluids to assess the sources for reconstitution of the glucose reserves: lactate, urea, ammonia, free fatty acid, glycerol, triglyceride, and glucose in plasma; glycogen in liver and muscle; and urea and ammonia nitrogen in urine. Fat is the major energy source during both homeothermal and heterothermal periods, the contribution from glucose being limited to glycolysis. Reconstitution of glycogen is accomplished prior to reentry through maximal use of substrates from all sources including glycolysis, fat, and protein metabolism. Of the new gluconeogenic substrate, one-fourth is supplied from protein and three-fourths from fat.
Mechanism of NaCl reabsorption by hamster thin ascending limbs of Henle's loop
Authors: Marsh DJ , Azen SP
Published: December 2017

Two models of ypertonic urine formation in the inner medulla were tested. The active model asserts that thin ascending limbs of Henle's loop (ALH) reasorb NaCl hypertonically by active transport; the passive model suggests the reabsorption is by diffusion down a concentration gradient. Using (Na+) in ascending vasa recta (AVR) as a measure of interstitial (Na+), we found no concentration difference between loop tubular fluid and AVR, when the comparison was made at the bend of the loop, or at an ALH sampling site 1 mm from the bend; the results were the same in antidiuresis and saline diuresis. In saline diuresis with flow of tubular fluid to the ALH slowed by simultaneous collection at the bend of the loop,ALH (Na+) fell below AVR levels, a result consistent with active transport, but not with a purely passive mechanism. Although contragradient transport was shown only with flow slowed and the corticomedullary gradient reduced, a model suggests the active component contributes almost half the observed Na+ flux in antidiuresis.
Central nervous system control of cardiorespiratory nasopharyngeal reflexes in the rabbit
Authors: White S , McRitchie RJ , Korner PI
Published: December 2017

The role of different central nervous regions in the reflex apnea, bradycardia, and mesenteric vasoconstriction evoked by nasopharyngeal stimulation with cigarette smoke was examined in unanesthetized shamoperated, thalamic, and pontine rabbits with intact and sectioned carotid sinus and aortic nerves (CS and AN). Apnea occurred in all preparations. In pontine animals with intact CS and AN, the heart rate response was reduced but not the mesenteric vasoconstriction. The role of suprabulbar and bulbospinal regions became more apparent when individual components of the input profile were examined in animals with controlled ventilation. The bradycardia and mesenteric vasoconstriction evoked by apnea without smoke, but not by smoke without apnea, were reduced in pontine animals. Prior section of the CS and AN attenuated the response in all neural preparations but to the least extent when cerebral hemispheres were intact. The data indicate that the respiratory reflex is predominantly integrated at bulbospinal sites, but the cardiovascular reflex is integrated at both bulbospinal and suprabulbar sites, or is integrated at bulbospinal and modulated from suprabulbar sites.
Renal glutaminase adaptation and ammonia excretion in infant rats
Authors: Benyajati S , Goldstein L
Published: December 2017

The purpose of this investigation was to determine the role of enzyme adaptation in the response of ammonia excretion to acidosis in developing rats. The response of renal ammonia excretion was low in infant rats (7-12 days old) following administration of a single dose of acidifying salt (5 mmol NH4CL/kg). However, repeated administration (2 times daily) of the salt increased ammonia excretion two- to threefold within 2 days. This adaptive response was associated with a concomitant rise in renal phosphate-dependent glutaminase (PDG) activity; PDG activity increased from approximately 36% adult level in untreated infants to 79% adult level in infants given NH4Cl for 2 days. Ammonia excretion and PDG activity decreased in parallel following cessation of NH4Cl treatment. Administration of the antibiotic, actinomycin D (100 mug/kg, ip, 2 times daily for 2 days) completely inhibited the response of PDG to repeated NH4Cl administration. In contrast to the situation previously observed in adult rats, actinomycin D treatment prevented the acid-induced rise in renal ammonia excretion. These results suggest that the level of renal PDG plays a more direct role in the adaptation of ammonia excretion to acidosis in infant rats than in adults.
Response of active transport of ions and spontaneous water flux to osmotic gradients in gastric mucosa
Authors: Villegas L
Published: December 2017

The effects of symmetric changes of the mucosal and serosal bathing solution on cell water content, net ion flux, and net water movement were studied in the isolated frog gastric mucosa. Similar to transmucosal concentration gradients that induce water movement and changes in cell water content, symmetric osmolality changes of the bathing solutions also produce changes in these functional parameters. Thus, increments from 165 to 286 mosmol/kg water in the osmolality of both solutions reduce cell water content from 2.37 plus or minus 0.12 to 1.30 plus or minus 0.20 ml/g wt, the net ion flux (acid secretion plus short-circuit current) from 4.83 plus or minus 0.36 to 3.44 plus or minus 0.26 mueq/cm2 per h, and the net water flux from 10.6 plus or minus 1.1 to 2.4 plus or minus 1.2 mul/cm2 per h. These osmotically induced flux changes of water and ions must be considered when osmotic gradients are being used to generate and to evaluate water movement across the gastric mucosa.
Kinetics of unidirectional leucine transport into brain: effects of isoleucine, valine, and anoxia
Authors: Betz AL , Gilboe DD , Drewes LR
Published: December 2017

The rate of unidirectional uptake, v, of L-[4,5-3H]leucine was studied in 17 isolated dog brains by means of an indicator-dilution technique using 22Na as the intravascular reference. The arterial leucine concentration was varied in increments by adding unlabeled leucine to the blood and v was determined after each change. The valine and isoleucine concentrations were varied independently to permit evaluation of their effect on leucine transport. A preliminary analysis indicated that both valine and isoleucine are competitive inhibitors. Therefore, all data were fitted to an equation that describes Michaelis-Menten kinetics in the presence of two competitive inhibitors. These calculations yielded an apparent Km for leucine transport of 1.58 mM plus or minus .28 SE, a V max of 0.323 mumol/g per min plus or minus .035 SE, and an apparent K i for inhibition of leucine transport of 1.76 mM plus or minus .34 SE for valine and 0.73 mM plus or minus .14 SE for isoleucine. In four isolated brains perfused with blood having a constant leucine level, indicator-dilution injections were made before, and at 1, 5, and 10 min after the start of perfusion with anoxic blood. These findings showed that, unlike glucose transport (Brain Res. 67: 307-316, 1974), the rate of lucine transport is unaffected by 10 min of anoxia.
Excretion of Na and H2 O and hypertension after adrenal enucleation or compression
Authors: Hall CE , Ayachi S , Hall O
Published: December 2017

An attempt was made to analyze the participation of the several independent variables that must contribute to the reproted inability of large male adrenal-enucleate rats withintact kidneys to normally excrete sodium following a light oral sodium load. This was prompted by a desire to understand whether the phenomenon was improtant to development of adrenal-regeneration hypertension (ARH). The results indicated that sdoium retention required the presence of both kidneys as it was not evident in unilaterally nephrectomized rats. The failure of ARH to develop in rats having both kidneys argues against a cause-and-effect relationship between the two phenomena. Sex does not appear to be important to sodium retention. Various fasting periods were employed, but with none of them did rats with a single kidney exhibit sodium retention. Since the conditions necessary to elicit imparied sodium excretion are incompatible with the induction of ARH and those essential to development of ARH prevent significant sodium retention, the two must be considered as independent manifestations of distrubed glandular function.
Skeletal muscle respiratory capacity, endurance, and glycogen utilization
Authors: Fitts RH , Booth FW , Winder WW , Holloszy JO
Published: December 2017

This study was undertaken to evaluate the relationship between physical performance capacity and the mitochondrial content of skeletal muscle. Four groups of rats were trained by means of treadmill running 5 days/wk for 13 wk. One group ran 10 min/day, a second group ran 30 min/day, a third group ran 60 min/day, and a fourth group ran 120 min/day. The magnitude of the exercise-induced adaptive increase in gastrocnemius muscle respiratory capacity varied over a twofold range in the four groups. There were significant correlations between the levels of three mitochondrial markers (cytochrome c, citrate synthase, respiratory capacity) in the animals' gastrocnemius muscles and the duration of a run to exhaustion. There was also a significant correlation between the amounts of glycogen remaining in liver and skeletal muscle after a 30-min-long exercise test and the respiratory capacity of the animal's leg muscles. These findings are compatible with the interpretation that a close relationshiop exists between skeletal muscle mitochondrial content and the capacity to perform endurance exercise.
Inotropic and intracellular acid-base changes during metabolic acidosis
Authors: Gonzalez NC , Clancy RL
Published: December 2017

Experiments in isolated, Ringer-perfused isovolumic rabbit hearts showed that metabolic acidosis resulted in a decrease in peak left ventricular pressure and dP/dt. Concomitantly, the decrease in extracellular pH from 7.28 plus or minus 0.02 to 6.82 plus or minus 0.02 at constant PaCO2 was associated with a negative av HCO3- difference that lasted throughout the duration of acidosis. This negative av HCO3- difference indicated that either HCO3- moved into the intravascular space or H+ moved in the opposite direction during acidosis. During perfusion with normal pH solution av HCO3- was not significantly different from zero. Washout of the extracellular space with the acid solution can account for only 32 percent of the total amount of HCO3-recovered in the venous perfusate during the 30 min of acidosis. The remaining 68 percent (10.7 plus or minus 3.1 mmol times kg-1 of cardiac tissue) must then have originated in the cellular fluid. When intracellular fluid volume is taken into account, it can be calculated that 21.3 plus or minus 6.1 mmol of HCO3- moved into the vascular space per liter of intracellular water. The magnitude of this HCO3- flux suggests that significant myocardial cellular acid-base changes are associated with metabolic acidosis.
Local specialization at ileocecal junction of the cat and opossum
Authors: Conklin JL , Christensen J
Published: December 2017

In 10 cats and 10 opossums, serial transverse strips of muscularis propria 2 mm wide, from about 1.5 cm above to about 1.5 cm below the ileocecal mucosal junction, were separately stretched to discover the relationship between length and tension and were separately subjected to electrical field stimulation. In both species, ileal strips showed stimulus relaxations, sometimes accompanied by contractions after the stimulus trains (off responses), whereas colonic strips generally did not. These responses were abolished by tetrodotoxin, 3 times 10-7 M in the opossum, 3 times 10-6 M in the cat. Length-tension slopes were greatest just above the ileocecal junction where stimulus relaxation occurred. Tetrodotoxin at 3 times 10-7 M raised basal tension in ileal strips in both species and in colonic strips only in the cat. Muscle of the ileocecal junction resembles that of the esophagogastric and gastroduodenal junctions in showing a relatively high degree of resistance to stretch and prominent neurogenic stimulus relaxation. However, the ileocecal junction, in contrast, also possesses a tonic inhibitory innervation.
Changes in vascular ionic content and distribution across aortic coarctation in the dog
Authors: Villamil MF , Matloff J
Published: December 2017

Eight dogs were subjected to 80-90 percent coarctation of thoracic aorta, which produced a mean blood pressure gradient of 40 mmHg; six normal dogs were used as controls. Proximal aorta was compared with distal aorta, and carotid and femoral arteries removed after coarctation were compared against the contralateral vessels removed before coarctation. After 4 wk of coarctation, proximal aorta contained more total and intracellular Na (derived from 24Na fluxes and space measurements), more Mg, Cl, hydrolyzable SO4 equals to, and H2O than distal aorta. Hydrolyzable SO4 equals to was also higher in proximal than in distal noncoarcted aorta. Carotid arteries removed after coarctation had higher total and "noninulin" Na, higher Ca, and similar hydrolyzable SO4equals to and total hexosamine than the contralateral normal vessels. Aortic coarctation had no effect on ionic composition of femoral arteries. The data suggest that an increase in intravascular pressure has direct effects on vascular ionic composition. Although ionic changes may vary in different vessels, increased intracellular Na seems to be the most consistent finding.
Passage of glucose through the cell membrane of capillary endothelium
Authors: Rasio EA
Published: December 2017

The mechanisms of glucose passage through the cell membrane of vascular endothelium were studied in vitro with a preparation of pure blood capillaries isolated from the rete mirabile of the eel swimbladder. In countertransport experiments, no competition for a common carrier could be detected between D-glucose and 3-O-methylglucose or between D-glucose and L-glucose. In the endothelial cells, inward and outward fluxes of labeled sugars were not changed when studied against concentration gradients of corresponding unlabeled sugars. The distribution of 3-O-methylglucose-14C and L-glucose-14C at equilibrium between intracellular and extracellular water was not modified by reducing their specific activity in the medium over a wide range. The addition to the medium of phlorizin 10-5 or 10-7 M, 3-O-methylglucose 60 mM, or L-glucose 60 mM did not reduce the rate of glucose utilization by the capillary tissue. The temperature coefficient for glucose uptake between 27 and 37 degrees C averaged 1.4. Insulin had no effect on the initial rate of 3-O-methylglucose-14C entry into cellular water. It is concluded that in the eel capillaries the mechanism of glucose passage into the vascular endothelial cell is compatible with the kinetics of free diffusion.
Inhibition of renal vasoconstriction by elevated ureteral pressure
Authors: Schramm LP , Carlson DE
Published: December 2017

These experiments were prompted by the observation that elevated ureteral pressure inhibited renal vasoconstrictions elicited by electrical stimulation of "defense regions" of the central nervous system (DNS) in cats. Experiments were designed to detect the relative contributions to this inhibition of CNS reflexes and interactions between autoregulatory and neural controls of the renal circulation. Cats were anesthetized with either chloralose or pentobarbital. Renal blood flow was measured electromagnetically. Elevated ureteral pressure lowered prestimulus renal vascular resistance. Renal vasoconstrictions elicited by electrical stimulation of the CNS or the peripheral renal nerves and by infusion of catecholamines into the renal artery were equally inhibited by elevated ureteral pressure. Equal inhibition of CNS and renal nerve-evoked vasoconstrictions suggested that a reflex was not involved. Equal inhibition of vasoconstrictions elicited by renal nerve stimulation and by catecholamine infusions suggested that elevated ureteral pressure acted primarily at a postsynaptic site. Inhibition of prostaglandin synthesis by indomethacin diminished, but did not abolish, the ureteral pressure-induced inhibition of neurogenic vasoconstrictions.
Effects of physical training on cardiac myosin ATPase activity
Authors: Bhan AK , Scheuer J
Published: December 2017

Cardiac myosin from rats exercised 90 or 150 min daily for 8 wk was compared with the myosin from the hearts of matched sedentary controls. The Ca++-ATPase activity was increased 17 percent in rats exercised 90 min and 30 percent in rats exercised 150 min daily. In the exercised group 0.18 M KCl increased the myosin ATPase activity by 50 percent but had no effect in the control group. Ethylene glycol activated the Ca++-ATPase in control myosin preparations, but had no significant effect on myosin from conditioned hearts. Heavy meromyosin (HMM) from conditioned hearts had a higher Ca++-ATPase activity than from controls. Fluorescence with 8-anilinonaphthalene sulfonate (ANS) was increased 30 percent in HMM from conditioned hearts. The results suggest that the increased myosin ATPase activity in the hearts of exercised animals may be due to a local conformational change at or near the active site.
Defective gastrointestinal recovery after irradiation in W/Wv mice
Authors: Torok BJ , Boggs SS
Published: December 2017

W/Wv mice are white, sterile, and have macrocytic anemia, all due to defective function of pertinent stem cell compartments. Sterility and coat color reflect stem cell failure during embryogenesis, while anemia results from a defective hematopoietic stem cell system which is active throughout life. Studies of radiation damage and recovery were undertaken to determine if the stem cell compartment of the intestinal mucosa, also active throughout life, is likewise affected. W/Wv mice "cured" of their hematopoietic defect, and normal littermates were exposed to 1,250 rads of whole-body irradiation. Mean survival time of controls was 8.4 plus or minus 0.31 days compared to only 5.85 plus or minus 0.18 days (P = LESS THAN0.001) FOR W/Wv. Incorporation of 3HTdR into mucosal cells of controls was minimum 2 days after exposure and exceeded nonirradiated levels by day 3, W/Wv values were lower than controls on days 2-4 and never significantly exceeded nonirradiated values. Changes in gut weight followed the same pattern. These studies suggest that the W/Wv defect involves stem cells of the gut and that the defect is a failure to proliferate and/or differentiate.
Depression of pulmonary 5-hydroxytryptamine uptake by metabolic inhibitors
Authors: Steinberg H , Bassett DJ , Fisher AB
Published: December 2017

Energy requirements for uptake of 14-C labeled 5-hydroxytryptamine ([14-C]5-HT) were studied in isolated guinea pig lungs, ventilated with 95% O2-5% CO2 and perfused in a recirculating system with Krebs-Ringer-bicarbonate solution containing 4% bovine serum albumin and 5 mM glucose. After 14 min preincubation with various inhibitors, lungs were perfused for 30 min with 0.25 times 10- minus 6 M [14-C]5-HT. Aliquots of perfusate were analyzed for [14-C]5-HT and metabolic products. Control lungs had a fractional serotonin clearance of 0.57 plus or minus 0.04. The rate of removal of [14-C]5-HT was inhibited 96% by imipramine, 88% by chlorpromazine, and 65% by ouabain, but was unaffected by iproniazid. Anoxia and cyanide each inhibited uptake by 68%. Omitting glucose from the perfusate reduced uptake by 30%. 2-Deoxyglucose and iodoacetate decreased the rate of [14-C]5-HT removal by 44 and 70%, respectively. Uptake was not affected by lung weight gain nor by changes in lung mechanical properties produced by [14-C]5-HT. [14-C]5-HT uptake by guinea pig lung requires a metabolic source of energy providing additional evidence for transport by an active process.
Electrolyte excretion and free-water production during onset of acute diuresis
Authors: Mudge GH , Cooke WJ , Berndt WO
Published: December 2017

The concentration of major urinary solutes was studied in ureteral urine collected at 15- to 30-s intervals at the onset of acute diuresis induced in anesthetized dogs either by high-ceiling diuretics (mainly ethacrynic acid) or by osmotic diuretics. Phosphate/inulin clearance ratios remained unchanged; potassium/inulin clearance ratios rose rapidly. Principal attention is given to the mechanisms underlying a transient rise in urinary sodium and chloride concentrations during the onset of diuresis. When the data are corrected for washout artifacts from the pelvis and ureter, it can be shown that the initial collection periods are associated with a transient increase in free-water production and by the simultaneous secretion of urea from the interstitium into the tubular fluid. The former coincides in time with the rise in urinary chloride concentration and represents an augmentation of water reabsorbed in the collecting duct, which is relatively impermeable to chloride. Both responses are quantitatively consistent with the transition from a hyperosmotic to isosmotic medullary interstitium.
Arterial water, cations, and norepinephrine in early and late renovascular hypertension
Authors: Constantopoulos G , Kusumoto M , Rojo-Ortega JM , Granger P , Boucher R , Genest J
Published: December 2017

In dogs made hypertensive renal artery stenosis and contralateral nephrectomy, the arterial and myocardial tissue content of water, cations (sodium, potassium, magnesium, calcium), and norepinephrine was measured 20 and 60 days after the operation. Hypertensive animals autopsied at the earlier stage of hypertension had significantly lower (-25 to-50%, P smaller than 0.01) arterial norepinephrine than either the sham or nonhypertensive animals. The water and cation content of arteries was unchanged, but aortic tissue contained significantly more water, sodium, potassium, and magnesium than the nonhypertensives. Hypertensives autopsied at 60 days also had lower arterial norepinephrine content than sham and nonhypertensive animals, but this refuction was not significant. Their arterial and aortic tissue contained more water and cations than the nonhypertensive, sham, unoperated, and unilaterally nephrectomized dogs. It is suggested that in the initial stage of renovascular hypertension the arterial norepinephrine content is reduced significantly, whereas at a later stage the arterial water and cations may be involved in the maintenance of an elevated blood pressure.
Calcium and angiotensin tachyphylaxis in rat uterine smooth muscle
Authors: Freer RJ
Published: December 2017

Studies were carried out to investigate the relationship between extracellular Ca++ and the ability of a particular smooth muscle to develop tachyphylaxis to angiotensin II (AII). Stimulation of rat uterus by AII was found to be dependent on extracellular Ca++. Placing the tissue in 0 Ca++ completely blocked AII-induced contractions as did the presence of the "Ca++ antagonists" verapamil (10- minus 5M), SKF 525-A (10- MINUS 5M), tetracaine (10- minus 4M), Mn++ (8 times 10- minus 3M), or La-3+ (10- minus 3M). In addition, it is no longer possible to produce tachyphylaxis to AII in deplorazed rat uterus under conditions of pH and Ca++ concentration in which a normally polarized preparation would be unresponsive. Verapamil, on the other hand, was an even more effective antagonist of AII in depolarized preparations (ID50 of 10- minus 8M) than in normal tissues (ID50 of 2.0 times 10- minus 7M). Like the rat uterus, the smooth muscle of the guinea pig ileum also develops tachyphylaxis to AII, and the effect of this peptide was also blocked by 10- minus 5 M verapamil. Rabbit aorta, however, was found to be relatively resistant to both development of tachyphylaxis under conditions of low Ca++ and low pH and also to inhibition by even very high concentrations of verapamil (10- minus 4M). The results of these studies suggest that the Ca++ site involved in the tachyphylactic response to AII may be a physiologically important one in those smooth muscles in which movement of extracellular Ca++ contributes to the inward ion currents during excitation. Verapamil, however, appears to act at a common step in the excitation-contraction sequence in rat uterus. A working model of the interaction of AII with rat uterine smooth muscle is presented.
Prostaglandin F and E levels during endotoxin-induced pulmonary hypertension in calves
Authors: Anderson FL , Tsagaris TJ , Jubiz W , Kuida H
Published: December 2017

Prostaglandin F and E (PGF and PGE) concentrations in sequential blood samples obtained simultaneously from the pulmonary artery (PA) and pulmonary vein (PV) during endotoxin-induced pulmonary hypertension in calves were determined by radioimmunoassay. Three groups of calves were studied. In nine control calves in which no endotoxin was given PA pressure and PGF and PGE concentrations in four pairs of samples taken at 0, 5, 15, and 45 min did not change. In 17 calves given 1 mg E. coli endotoxin, PGF concentrations were increased significantly in the PV and to a lesser degree in the PA in the 15-and 45-min samples. The increased PGF concentration in the 15-min sample corresponded to an increased PA pressure of 74 plus or minus 4 mmHg (mean plus or minus SE). In three of the endotoxin-treated calves studied a second time and three separate calves indomethacin pretreatment completely blocked the hemodynamic effect of endotoxin as well as PGF release. PGE concentrations did not change in either group. These data suggest that endotoxin-induced pulmonary hypertension may be mediated by PGF, a known pulmonary pressor agent in the bovine, and that blockade of this effect by indomethacin may be due to inhibition of prostaglandin synthesis and/or release.