bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal excretion of bile acids: taurocholic, glycocholic, and cholic acids
Authors: Weiner I. M. , Glasser James E. , Lack Leon
Published: December 2017

The renal clearance (in dogs) of taurocholate, after correction for plasma-protein binding, is less than the glomerular filtration rate. Clearance increases toward, but does not attain, the filtration rate as filtered load is increased. Clearance is not influenced by changes in urinary pH or flow, nor by administration of probenecid or benzmalecene (20–25 mg/kg). The site of reabsorption demonstrated in stop-flow studies is the proximal tubule. Tubular fluid-to-plasma ultrafiltrate ratios less than unity were observed. The results are interpreted as indicating active reabsorptive transport. Glycocholate and cholate are handled in a similar manner. Possible mechanisms of interaction of this reabsorptive system with the organic acid secretory system are considered.
Active cation transport by kidney tubules at 0 C
Authors: Burg Maurice B. , Orloff Jack
Published: December 2017

In order to determine the capacity of renal cells to transport actively electrolytes at 0 C, separated rabbit renal tubules were incubated at this temperature and the effects of various inhibitors on Na, K, Cl, and water content and the fluxes of Na and K were measured. In contrast to previous studies with kidney slices, these observations indicate that cell K is completely exchangeable at 0 C and significant active transport persists. Thus, at 0 C as at higher temperatures, anoxia, strophanthidin, 2,4-DNP, and cyanide reduce the transcellular concentration gradients for Na, K, and Cl and cause the tubules to swell. In the presence of strophanthidin, both influx and efflux of K are slowed. It is concluded that at 0 C, as at higher temperatures, active cation transport by renal tubule cells accounts for the maintenance of transcellular electrolyte concentration gradients and limits colloid osmotic swelling.
Effects of renal venous occlusion on renal hemodynamics and concentrating ability
Authors: Selkurt Ewald E. , Elpers Mary Jo , Womack Isaac
Published: December 2017

Following periods of occlusion of 2–30 min, blood flow showed a phase of increase which was greatest after the short periods of blockade, and became progressively less with longer periods of occlusion. Minimal impairment of clearances resulted from 2 to 5 min of obstruction, but significant and prolonged decrements followed 15- and 30-min periods. Urine volume, CNa, Cosm, and TcHH2O were also markedly decreased after the longer occlusion periods. Decrease in U/Posm and U/Pcr gave further evidence of impairment of the concentrating mechanism. Changes in these indices were detectable during the period of occlusion, at a time when the medullary sodium gradient of the experimental kidney was not significantly altered from control, suggesting that the ability of the collecting-duct epithelium to respond to ADH had been impaired in the presence of an adequate osmolar gradient. Following occlusion, marked decrement of GFR in the face of adequate blood flow allowed for washout of the gradient, providing an additional factor responsible for the ensuing prolonged period of loss of concentrating ability.
Hemodynamic effects of normovolemic polycythemia in dogs at rest and during exercise
Authors: Weisse Allen B. , Calton Farrell M. , Kuida Hiroshi , Hecht Hans H.
Published: December 2017

The hemodynamic effects of acutely induced normovolemic polycythemia were studied in four anesthetized and seven unanesthetized dogs at rest and, in three of the latter, during treadmill exercise. Control observations were made in four other animals. Volume of packed red cells values of 60–79% were produced by exchange transfusion with washed centrifuged red cells. Normovolemic polycythemia in both anesthetized and unanesthetized resting animals was associated with a decrease in cardiac output and oxygen transport; little change in pulmonary artery, carotid artery, right atrium, and pulmonary artery wedge pressures; and increases in calculated total systemic and pulmonary vascular resistances. Mixed venous oxygen saturation was not necessarily reduced. The relative increase in cardiac output and oxygen transport in response to exercise was similar before and after normovolemic polycythemia, but the absolute increments were significantly less after normovolemic polycythemia. Results obtained are consistent with the concept that cardiac output reduction with normovolemic polycythemia is mediated by increased peripheral resistance.
Acute and long-term effects of X-irradiation on skeletal growth in the rat
Authors: Phillips Richard D. , Kimeldorf Donald J.
Published: December 2017

The early and long-term effects of X-irradiation on skeletal growth were investigated with respect to the age at exposure. Rats exposed at a juvenile age (37 days) to a sublethal dose (430 rad) exhibited a retardation in femur, tibia, and tail growth within 14 days after exposure. The maximal deficit was attained within 30 days after exposure and remained approximately constant for the next 300 days. In animals which were exposed to X-rays as young adults (101 days of age), femur and tibia length did not differ from those of controls for the first 2 months after exposure. However, there was a deficit in femur and tibia length in these animals at the end of life span. The magnitude of the bone length reduction at the end of life span was dose dependent. The two major differences in response between the two age groups were the time course of the radiation effect on growth and the magnitude of the deficit. The reduction in bone length occurred faster and was greater in the younger irradiated group.
Metabolism of chylomicrons and triglyceride emulsions by perfused rat adipose tissue
Authors: Rodbell Martin , Scow Robert O.
Published: December 2017

The uptake and metabolism of chylomicrons and artificial emulsions of triglycerides by adipose tissue has been studied in the perfused parametrial fat body of the rat. The triglyceride preparations were labeled with either glyceryl-C14 or with glyceryl-C14 and palmitate-H3. The uptake of both chylomicrons and emulsions was proportional to the blood triglyceride concentration and to the duration of infusion; the uptake of chylomicron triglycerides was about 40% greater than that of the artificial emulsion. About two-thirds of the triglycerides removed were hydrolyzed to glycerol and fatty acids and the rest was retained, without being hydrolyzed, in the fat cells. The uptake and metabolism of triglycerides was greatly reduced when the fat donors were deprived of food for 2 days. About 70% of the fatty acids cleaved from blood triglycerides were incorporated into tissue lipids, whereas less than 15% of those infused as free fatty acids were esterified by the perfused adipose tissue. Labeled glycerol was released to the venous blood for several minutes after the blood stream had been flushed of labeled triglycerides. The findings suggest that a major part of the hydrolysis of blood triglycerides occurred after the triglycerides had been removed from the blood stream.
Cardiovascular hemodynamics in the fetal lamb before and after lung expansion
Authors: Assali N. S. , Morris John A. , Beck Russell
Published: December 2017

Cardiovascular hemodynamic studies were carried out on fetal lambs before and after lung ventilation as well as before and after cord clamping. The findings are as follows: 1) Before lung expansion, pressures, output, and work in the right side of the heart are greater than those in the left side. This relation is reversed promptly after lung expansion. 2) When compared to adults, effective fetal cardiac output is high before lung expansion and falls significantly after lung expansion. 3) In the fetus, total pulmonary vascular resistance is considerably higher than systemic resistance. This relation is reversed immediately after lung expansion. 4) In the fetus, the flow of blood in the aorta and pulmonary artery is largely governed by inertial factors. 5) Cord clamping increases systemic resistance through elimination of low vascular resistance of the placental bed.
Vascular effects of the Krebs intermediate metabolites
Authors: Frohlich Edward D.
Published: December 2017

The vascular effects of seven intermediary products of oxidative metabolism (acetate, citrate, fumarate, malate, α-ketoglutarate, oxalacetate, and succinate) were studied on the constantly perfused kidney or forelimb in 32 dogs. Significant vasodilation was obtained at submaximal dosages, usually 2.47 µmole/min, in both vascular beds for all agents without changing systemic pressure. At maximal infusion rates renal resistance decreased approximately 20%. Saline had no effect. When segmental resistances were calculated for the forelimb by measuring pressures in large and small arteries and veins, active dilation was localized to small vessel segment (25% fall). Arterial and venous segment resistances were unchanged. It is concluded that the Krebs intermediates should be included among those agents termed "vasodilating metabolites," and that these compounds could be exceedingly important in the local regulation of blood flow.
Mineralocorticoid bioassay on adrenal venous plasma from regenerating adrenals
Authors: Rapp John P.
Published: December 2017

The mineralocorticoid activity of the mixture of steroids obtained by pooling chloroform and ethyl acetate extracts of adrenal venous plasma from regenerating or intact rat adrenal glands was bioassayed by use of the urinary Na/K ratio as a response. In rats drinking either tap water or 1% saline, the mineralocorticoid production per rat was less in animals with adrenal regeneration than in controls. These results are taken as evidence against the idea that adrenal regeneration hypertension results from production of excess mineralocorticoid activity arising either from unknown steroids, unusual ratios of steroids, or high mineralocorticoid production relative to the sodium intake.
Metabolic responses during myocardial reactive hyperemia in the unanesthetized dog
Authors: Olsson Ray A. , Gregg Donald E.
Published: December 2017

Studies of myocardial metabolism during reactive hyperemia in unanesthetized dogs reveals that A-V oxygen difference is consistently decreased during reactive hyperemia. Myocardial oxygen consumption rate is increased, however, as the increase in coronary blood flow rate is greater than the decrease in A-V oxygen difference. Oxygen debt is always, though variably, overpaid. Studies of A-V lactate and pyruvate differences show that occlusions of more than 6 sec regularly lead to lactate production, while occlusions shorter than this do not. It is suggested that myocardial reactive hyperemia is a metabolic response to a metabolite produced by even mild degrees of anoxia. The effects of this metabolite on coronary blood flow appear to be out of proportion to the anoxic stimulus.
Comparison of molecular weight of myosin from normal and failing dog hearts
Authors: Conway Gene F. , Roberts Joe L.
Published: December 2017

The molecular weight of myosin from dog hearts was determined with the analytic ultracentrifuge and by light scattering. Both normal dog hearts and hearts with surgically induced left ventricular failure were used The molecular length was calculated from the light-scattering data. The molecular weight of normal myosin was 554,000 from ultracentrifugation and 512,000 by light scattering. For myosin from failing left ventricles the molecular weight was 502,000 by ultracentrifugation and 510,000 by light scattering. The molecular lengths calculated for a rod model were 1,750 A for myosin from normal hearts and 2,000 A for that from failing left ventricles. The molecular weight and length determined by this work for myosin from failing hearts do not differ significantly from the molecular weight and length of myosin from normal hearts ( P > .1).
Supersensitivity to l-norepinephrine of the denervated sinoatrial node
Authors: Donald David E. , Shepherd John T.
Published: December 2017

Following attempted denervation of the heart by the technic of regional neural ablation, dogs with incomplete cardiac denervation were shown to have the same supersensitivity to l-norepinephrine as dogs in which the denervation of the heart was complete. Dogs with chronic bilateral stellate ganglionectomy or those pretreated with reserpine had cardiac acceleration in response to the administration of tyramine or to stimulation of the stellate cardiac nerves, but did not demonstrate supersensitivity to l-norepinephrine. No supersensitivity was seen in dogs with chronic bilateral cervical vagotomy. Excision of the right stellate and caudal cervical ganglia and the immediately adjacent right vagus nerve resulted in supersensitivity to l-norepinephrine. In these animals cardiac acceleration resulted from stimulation of the left stellate cardiac nerves or from the administration of tyramine. The supersensitivity was lost after excision of the sinoatrial node. It is concluded that one can uniquely denervate the sinus node and that dogs so treated will develop supersensitivity to l-norepinephrine despite the presence of functional sympathetic nerves to the rest of the heart.
Splanchnic blood flow in the monkey during hemorrhagic shock
Authors: Abel Francis L. , Waldhausen John A. , Selkurt Ewald E.
Published: December 2017

Blood flow in the celiac and superior mesenteric arteries was measured in nine Macaca monkeys during a standardized hemorrhagic shock procedure. Simultaneous pressures were obtained from the hepatic vein, portal vein, and aorta. Each animal was bled rapidly to an arterial pressure of 40 mm Hg and maintained at this level until 30% of the bled volume had spontaneously reinfused. The remaining blood was then rapidly reinfused and the animal observed until death. The results show a lack of overshoot of venous pressure on reinfusion, grossly pale intestines with some microscopic congestive changes, and a decrease in splanchnic conductance throughout the postinfusion period. Hepatic venous pressure exceeded portal pressure in six of the nine animals during the period of hemorrhage. The results are interpreted as indicative of insignificant splanchnic pooling during hemorrhagic shock in this animal.
Cardiovascular reflexes following lesions in medullary reticular formation
Authors: Manning John W.
Published: December 2017

In 19 anesthetized cats acute destruction of large portions of the medullary reticular formation was achieved with the aid of a radio-frequency lesion maker. Midline structures were spared by confining the lesions to the dorsolateral medulla. Tissue injury extended from a level rostral to the inferior olivary complex to the obex. These lesions in the medullary vasomotor area did not alter significantly the cardiovascular reflex adjustments to bilateral occlusion of the carotid arteries or to the stimulation of the central end of the cut sciatic nerve. In addition, an increase in contractile force, heart rate, and blood pressure evoked by stimulation of pressor areas in the posterior hypothalamus could be obtained following the lesions. The preparations were critically dependent upon supramedullary connections to maintain vascular tone and circulatory reflex adjustments, for decerebration in the lesioned animal brought about a reduction in blood pressure and a loss of vascular reflex responses. These findings suggest that supramedullary centers exert tonic as well as phasic influences on vascular and cardiac activity that is independent of the medullary vasomotor area.
Metabolic pathways for urea production by the amphibian kidney
Authors: Brodsky William A. , Carlisky Nestor J. , Gonzalez Carlos F. , Shamoo Yousif E.
Published: December 2017

Homogenized kidneys, pooled from bullfrogs ( Rana catesbiana), produce urea in amounts of 1.4–6.4 µmole/g of wet tissue after 1 hr of incubation in substrate-free media. The maximal rate of endogenous urea production under present conditions, 16 µmoles/g kidney per hr, was found during the first 10 min of incubation. In standard tests with added substrates, activity of frog kidney arginase was greater than that of frog liver arginase. However, argininosuccinase, easily detected in frog liver, dog liver, and dog kidney cortex, could not be detected in frog kidney. Additional tests showed that frog kidney homogenates contain uricase, allantoicase, and allantoicase in concentrations similar to those of frog liver tissue. This means that urea forming in frog kidney tissue comes from at least two pathways: one terminating in hydrolysis of arginine, and one terminating in hydrolysis of allantoic acid. In the absence of argininosuccinase, arginine could be derived from degradation of protein or peptides. In view of the oxygen dependency of uric acid-loaded homogenates, allantoic acid is derived from hydrolysis of allantoin which, in turn, derives from the oxidation of uric acid.
Motility, lymphatic contractility, and distention pressure in intestinal absorption
Authors: Lee J. S.
Published: December 2017

With an in vitro rat intestine preparation, it was found that intraluminal distention pressure, intestinal motility, and mesenteric lymphatic contractility are essential factors in the elevation of lymphatic pressure and lymph flow, which are correlated with fluid absorption rate. Epinephrine and Na pentobarbital inhibit motility and decrease lymphatic pressure and lymph flow. Serotonin and physostigmine stimulate motility and increase lymphatic pressure and lymph flow. In segments without motility, lymphatic pressure depends on distention pressure. At zero distention pressure with little motility, epinephrine stimulates lymphatic contractility and increases lymphatic pressure. These observations seem to suggest that distention pressure, lymphatic contractility, and intestinal motility increase net fluid absorption by promoting lymph flow.
Pressoceptive and chemoceptive aortic reflexes in decorticate and in decerebrate cats
Authors: Baccelli G. , Guazzi M. , Libretti A. , Zanchetti A.
Published: December 2017

Graded electrical stimulation of three different components of the aortic nerve has been performed in decorticate cats, and later repeated after intercollicular decerebration. Threshold stimuli, involving only the largest fibers probably originating from pressoceptors, slightly decrease blood pressure and respiration both in quiet decorticate and in decerebrate cats. However, in decorticate animals during "spontaneous" fits of sham rage, inhibition of all somatic and visceral components of rage behavior is observed. When aortic nerve stimuli also involve intermediate-threshold fibers presumably of chemoceptive origin, excitation of rage behavior accompanied by strong hypertension and hyperventilation is seen in decorticate preparations, while after decerebration reflex hyperpnea is accompanied by hypotension or by no consistent pressor change. Stronger stimuli activating smaller fibers of probable pressoceptive origin still have conspicuous excitatory effects in decorticate animals, as shown by appearance of rage activity and pressor reactions, whereas after decerebration prominent hypotension with hyperpnea is observed. The predominance of excitatory cardiovascular responses to aortic nerve stimuli in decorticate animals, and of inhibitory reactions after decerebration, is discussed.
Responses of nerve-free vessels to vasoactive amines and polypeptides
Authors: Somlyo Avril V. , Woo Chi-Yuan , Somlyo Andrew P.
Published: December 2017

Contractile responses of helically cut strips of noninnervated human umbilical artery and vein were determined. Spontaneous, rhythmic contractions were exhibited by both preparations, but were greater in magnitude and duration in umbilical veins. Vasoconstriction elicited by sympathomimetic amines was variable, and generally of a low order. The response to norepinephrine was not potentiated by cocaine (10 µg/ml) but was blocked by Dibenamine (1.0–1.5 µg/ml). Umbilical vasoconstrictor response to tyramine (1.0–10.0 µg/ml) indicated the direct vasoconstrictor effect of this agent. The similar norepinephrine-to-tyramine sensitivity ratios of umbilical vessels and canine main pulmonary artery were interpreted as evidence against the indirect action of tyramine in vitro. Isoproterenol produced no vasodilation in umbilical vessels, suggesting the absence of ß-adrenergic pathways. Oxytocin (>>0.1 mU/ml) was a highly effective umbilical vasoconstrictor. Native and synthetic oxytocin preparations were equiactive and produced tachyphylaxis to each other. Native and synthetic lysine-8-vasopressin (>>0.005 U/ml) and angiotensin amide (>>0.002 µg/ml) produced only minimal and inconsistent vasoconstriction, while serotonin (>>0.004 µg/ml) was as effective as oxytocin.
Effect of vasoconstrictor tone on pressure responses to epinephrine and norepinephrine
Authors: Kendrick J. E.
Published: December 2017

Increasing sympathetic activity by either carotid occlusion or raising intracranial pressure increases the incidence and magnitude of the depressor response to both epinephrine and norepinephrine in dogs whose total circulation is maintained at a constant rate by a perfusion pump. Decreasing sympathetic activity by raising carotid sinus pressure reduces the incidence of this response to these drugs. Similarly, in the hindlimb perfused at a constant rate, the depressor response to these agents increased in frequency and magnitude during carotid occlusion or electrical stimulation of the sympathetic chain. This enhancement of the depressor effects seems to be a peripheral effect rather than a direct inhibitory effect of the catecholamines upon transmission through sympathetic ganglia.
Effects of hypothermia on disappearance of ethanol from arterial blood
Authors: MacGregor D. C. , Schönbaum E. , Bigelow W. G.
Published: December 2017

Normothermic and hypothermic (24 C) dogs were given ethanol intravenously and the rates of accumulation and disappearance of ethanol from arterial blood were studied, with the following results: 1) The rate of decrease of ethanol concentration in the arterial blood in normo- and hypothermic dogs was similar. 2) Extrapolation of concentration vs. time curves after equilibration showed reduction in apparent total available body-water space in hypothermic dogs. 3) Equilibration took twice as long in hypothermic as in normothermic dogs. 4) A fourfold increase of tidal volume did not affect the disappearance of ethanol in a normothermic dog. 5) The disappearance rate of ethanol in hypothermic dogs was decreased by hexamethonium or a small dose of epinephrine, but normalized by a pressor dose of epinephrine. It is suggested that the effects of hypothermia on hepatic blood flow and on alcohol dehydrogenase activity tend to cancel each other out. Modification of the rate of alcohol disappearance by hexamethonium and by epinephrine probably results from changes in hepatic circulation.
Analysis for dependence between sequential responses evoked in visual cortex
Authors: Vastola E. F.
Published: December 2017

The chi-square method has revealed dependence at a high level of significance between the amplitudes of successive responses elicited in secondary visual cortex by repetitive electrical stimulation of the visual radiation fibers. Dependence has been demonstrated to exist between responses as far apart as 6 sec. In many sequences dependence at a high level of significance was found between responses at the longer intervals of separation when absent 1 sec earlier. In three cases the sequences behaved like stationary, first-order Markov chains, insofar as all observed transition matrices for intervals of 2–5 sec could be generated by probability matrices estimated from the observed transition matrices for immediately consecutive responses. In four cases there was agreement between observed and predicted transition matrices only for intervals up to 2 or 3 sec, and it is suggested that these represented chains of some order higher than one.
Effects of ligation and morphine on electric and motor activity of dog duodenum
Authors: Bass Paul , Wiley James N.
Published: December 2017

Electric activities and intraluminal pressures were simultaneously recorded from the duodenum of unanesthetized dogs. The effects of ligation and morphine were examined. The temporal relation of spike potentials to the basic electric rhythm (BER) was not altered by ligation or morphine. The BER below the ligature was decreased by extending the distal portion of the electrical complex. The propagation of the BER was also disturbed to generate a pattern suggestive of multiple foci activity. The morphine-enhanced motor activity bore a 1:1 ratio with the altered BER. The maintenance of this ratio is taken as evidence that the BER governs the conditions for discharge of spike potentials which determine duodenal contractions. Spike potentials indicate smooth muscle activity, the number and duration determining the magnitude of contractions. The data advance the concept that duodenal rhythmic changes in pressure (type 1 contractions) do not migrate and are concerned with rhythmic segmentation rather than caudal propulsion.
Intestinal transport of amino acids studied with l-valine
Authors: Reiser Sheldon , Christiansen Philip A.
Published: December 2017

l-Valine (0.003 m) was transported against a concentration gradient by everted rat intestinal sacs. After 5 min a mucosa-rich fraction had near-maximum valine concentration. There was a 45-min lag before the valine concentration in the serosal medium became equal to that in the tissue water. Placing valine either in the mucosal or serosal medium resulted in the same final ratio of valine between them (8/1, serosal/mucosal after 2 hr). Net transport was inhibited by substrate concentrations greater than 0.01 m, whereas tissue uptake was proportional to the initial substrate concentration through the range 0–0.05 m. The apparent Michaelis constant for valine net transport was 2.89 x 10–3 m and the maximal velocity of the system was 16.3 µmoles valine/500 mg tissue per hr. Potent inhibitors of tissue uptake and net transport were anaerobiosis, cyanide (0.002 m), p-chloromercuribenzoate (0.0004 m), 2,4-dinitrophenol (0.0002 m) (noncompetitively), and l-leucine (0.005 m) (competitively). Neutral l-amino acids having lipophilic side chains inhibited valine translocation in a predictable manner on the basis of competitive inhibition for an acceptor site on the tissue.
Contribution of left ventricle and small bowel in irreversible hemorrhagic shock
Authors: Regan T. J. , LaForce F. M. , Teres D. , Block J. , Hellems H. K.
Published: December 2017

To determine if alterations taking place in the heart itself contribute to the development of an irreversible stage in hemorrhagic shock, 16 intact anesthetized dogs were bled until mean arterial blood pressure reached 30 mm Hg; the blood was reinfused 4–5 hr later, and the animals were observed for an additional 7 hr or until demise. The ratio of maximal systolic rate of left ventricular pressure rise (MRPR) (in mm Hg/sec) to end-diastolic pressure (LVEDP) was used as an index of contractility. All animals exhibited a rise in contractility within 90 min, but in nine dogs who developed irreversible shock there occurred a progressive rise in LVEDP beginning at 2 hr of hypotension. Simultaneously there was a rise in transaminases (SGOT) level in coronary sinus blood, presumably due to muscle necrosis. Contractility was not restored after reinfusion and declined until death. No decrease in contractility was found in seven dogs whose circulatory failure proved to be reversible except for a brief period following retransfusion. Enterectomy, reported to protect against irreversibility, was performed in five additional dogs. An early decline in contractility, which progressed until demise, indicated that bowel pathology was not essential for irreversible shock. Thus, it would appear that an early decline in ventricular function, initiated within the first 2 hr of hypotension, reflects a potential contribution of the heart to the development of an irreversible stage in hemorrhagic shock.
Left ventricle heat production in intact anesthetized dogs
Authors: Afonso Skoda , Rowe George G. , Lugo Jorge E. , Crumpton Charles W.
Published: December 2017

Only a part of heat produced by the left ventricle is removed by the coronary blood. During a cold saline infusion into the right ventricle, LV myocardial temperature decreases and the myocardium loses a measurable amount of heat. A part of this heat is also removed by the coronary blood. If simultaneous thermal curves are recorded from the aorta and coronary sinus during the infusion it is possible to calculate left ventricle heat production by the following formula: H = LV weight x ΔT x Δt x K x 60:A, where ΔT = myocardial temperature drop during the infusion; Δt = coronary sinus-aorta blood temperature difference prior to infusion; K = specific heat of myocardium; A = difference of areas of superimposed coronary sinus and aorta's thermal curves. Heat production estimated by the formula in 19 determinations has been compared with the heat production calculated from myocardial oxygen consumption. Measurements obtained by this method seem to be representative of left ventricle heat production.
T wave of normo- and hyperkalemic canine heart: Effect of vagal stimulation
Authors: Greenspan Kalman , Wunsch Charles , Fisch Charles
Published: December 2017

The effect of vagal stimulation on ventricular repolarization of normokalemic and hyperkalemic canine hearts was investigated. During the normokalemic state stimulation of the vagus decreased the amplitude of the T wave when the polarity of the wave prior to vagal activity was upright. When the control T waves were biphasic or inverted the effect of vagal stimulation was an increase in negativity. In all cases the T waves became upright and increased in amplitude during potassium (K+) infusion regardless of the initial T configuration prior to the infusion of the cation. As the plasma K+ levels were increasing the amplitude of these heightened T waves was further enhanced by vagal stimulation. It is concluded that vagal activity does effect ventricular repolarization and this effect is exaggerated as the plasma K+ level is progressively elevated.
Exchange of calcium between blood, brain, and cerebrospinal fluid
Authors: Graziani Leonard , Escriva Anthony , Katzman Robert
Published: December 2017

Ca exchange was measured in anesthetized cats during steady-state ventriculocisternal perfusions. When Ca45 was added to the perfusate the efflux coefficient from CSF averaged 0.025 ml/min of CSF cleared of Ca45. This coefficient was independent of CSF Ca concentration, indicating passive diffusion. About onethird of this isotope was recovered in brain tissue, two-thirds presumably diffused into blood. The brain radioactivity was localized to areas immediately adjacent to the CSF pathway. When the isotope was given systemically, the efflux coefficient into the ventricular system averaged 0.015 ml/min of serum effectively cleared of Ca45. In these experiments the specific activity of the CSF approached that of the serum. At the same time the specific activity of the brain Ca was low. Hence, the chief source of the Ca entering CSF must be blood. The rate of movement of Ca45 from blood to CSF was not altered when CSF formation was suppressed by adding acetazolamide or lowering the pH of the perfusate. This suggests that Ca transport is independent of the bulk fluid formation.
Size of cell nuclei in hypothalamus of the rat as a function of salt loading
Authors: Lichardus Branislav , Mitro Alexander , Cort Joseph H.
Published: December 2017

Rats were given only 2% saline to drink ad libitum for 10 days. A control group drank tap water ad libitum. The hypothalami were then sectioned, and the volumes of 200 cell nuclei were determined in each animal for each of the following nuclei: posterior, ventromedial, dorsomedial, and arcuate (over 8,000 nuclei measured in a total of 14 rats). The distribution of cell nuclear volume size showed a statistically significant decrease only in the posterior hypothalamic nucleus. In the other nuclei, cell nuclear size increased to an insignificant degree. It is suggested, in concert with other evidence, that the posterior nucleus of the hypothalamus may have a neuroendocrine function.
Kinetic studies on renin-angiotensinogen reaction after nephrectomy
Authors: Blaquier Pedro
Published: December 2017

The injection of renin into a rat nephrectomized 24 hr previously potentiates the pressor response of this enzyme due to an increased production of angiotensin. In vitro renin produces a greater amount of angiotensin from plasma of nephrectomized than from that of normal rats. To evaluate the basis for this difference, kinetic studies on the renin-angio-tensinogen reaction were made which included measurements of the Michaelis constant. The difference in rate of angiotensin formation was found to be due to a 15-fold difference between the substrate concentration in the plasma of normal and nephrectomized animals. No difference was detected between the "turnover numbers" or the K m's for the action of hog renin on angiotensinogen from these two sources. The turnover number for hog renin in the presence of hog or rat plasma is similar even though the Km of the enzyme is significantly different for the two substrates.
Angiotensin and electrolyte excretion in renovascular hypertension
Authors: Borkowski Abraham J. , Howards Stuart S. , Laragh John H.
Published: December 2017

Under conditions of saline, urea, ADH infusion diuresis during anesthesia we observed that in normal rats angiotensin infusion regularly produced natriuresis and diuresis, the degree of which was more closely related to dosage than to increment in blood pressure. Potassium excretion often did not rise appreciably or actually fell during natriuresis, suggesting inhibition of tubular secretion. In animals with a clamp on the left renal artery in which hypertension did not ensue, the renal response to angiotensin was strikingly changed when studied by bilateral ureteral catheterization. Instead of diuresis the peptide produced either no effect or sodium and water retention in both kidneys. In the hypertensive rats, angiotensin consistently produced marked diuresis on the clipped side. Sodium excretion increased much more than urine flow. Simultaneously, in the opposite, unprotected kidney, angiotensin produced quite different effects—sodium and water excretion either did not change or were reduced. Renovascular reflexes and renal renin activity may be involved in determining whether angiotensin induces sodium retention or natriuresis.
Renal and pressor action of angiotensin in the normal dog
Authors: Healy John K. , Barcena Carlos , O'Connell J. M. Brian , Schreiner George E.
Published: December 2017

The renal and pressor actions of angiotensin in relation to dose were studied in unanesthetized dogs. Low doses caused depression of urine flow, electrolyte excretion, glomerular filtration rate (GFR), and Cpah. With higher doses, the initial depression of urine flow, GFR, and Cpah was greater, but subsequently these functions rose toward control values. In fact, diuresis occurred, accompanied by natriuresis, chloruresis, and kaliuresis. The natriuresis occurred at a time when GFR was significantly depressed. In longer experiments at high doses it was found that the natriuresis declined after 50 min despite continued angiotensin infusion; however, potassium excretion gradually increased throughout. These results help clarify the confusing literature regarding the effects of angiotensin on renal function in dogs and also support the hypothesis that angiotensin can block tubular sodium reabsorption. The pressor response was found to be proportional to the logarithm of the dose of angiotensin. It was also inversely related to the control blood pressure of the dog.
Renal hypertrophy in metabolic acidosis and its relation to ammonia excretion
Authors: Lotspeich William D.
Published: December 2017

The chronic ingestion of NH4Cl causes a true growth of the rat kidney. This involves a symmetrical increase in wet weight, dry weight, and nitrogen of the kidney tissue. Total DNA and RNA are also elevated, indicating that both cell numbers and cell size have increased. The renal hypertrophy in chronic metabolic acidosis is the same order of magnitude as that seen in the remaining kidney after unilateral nephrectomy. The renal growth-stimulating effects of acidosis and unilateral nephrectomy are additive. In the acidotic rat the renal hypertrophy that occurs after unilateral nephrectomy can maintain a high rate of ammonia excretion without any further change in renal glutaminase activity of the remaining kidney. Thus in certain species the stimulation of renal growth may play a part in the increasing capacity to excrete ammonia during sustained metabolic acidosis.
Transmucosal movement of selenium
Authors: McConnell Kenneth P. , Cho Gloria J.
Published: December 2017

The transmucosal movement of selenium in the everted intestinal sacs of the golden hamsters was studied. The movement of selenium in the form of Na2Se75O3, dl-seleno-75 cystine, l-seleno-75 methionine and dl-C14 methyl-labeled selenomethionine was examined. It was found that selenomethionine was transported against a concentration gradient, and selenite and selenocystine were not. The transport of l-selenomethionine is inhibited by the corresponding sulfur analogue, l-methionine. The transport of selenite and selenocystine were not inhibited by sulfite and cystine, respectively. Selenite, selenocystine, and selenomethionine in the concentration used did not inhibit the active transport of glucose.
Influence of refined villikinin on motility of intestinal villi
Authors: Kokas Eszter , Johnston Charles L.
Published: December 2017

Villikinin is extracted from both canine and human intestinal mucosa. Data are presented to show the influence of crude canine extracts on intestinal villi motility in dogs. By utilizing continuous-flow electrophoresis of the crude materials, highly refined villikinin preparations are made. It is shown that there are no detectable differences in the preparations from the two sources. They do not influence intestinal peristalsis, bile flow, or blood pressure. Villikinin is soluble in water and dilute acid and resists heating up to 100 C. Pepsin and trypsin treatment does not alter its activity. By the use of both crude and refined materials strong support is provided for the concept that villikinin is a specific intestinal hormone.
Effects of O2, CO2, and drugs on estimating coronary blood flow from Rb86 clearance
Authors: Love William D. , Tyler Myra D. , Abraham Ralph E. , Munford Robert S.
Published: December 2017

The accuracy of predictions of myocardial blood flow based on Rb86 clearance rates was determined in dogs receiving vasoactive drugs or subjected to hypoxemia or hypercapnia. In controls, the highest rate of coronary blood flow was 16.5 ml/g myocardium per 10 min. Flow could be predicted from clearance (tissue Rb86 uptake/arterial blood Rb86 concentration) with a mean error of 7.8% in this group. With hypoxemia estimates of flow averaged 13.8% too low when arterial blood was from 50 to 75% saturated with oxygen, and were more unreliable at lower values. Carbon dioxide tension had no effect in the range from 20 to 60 mm Hg, but at higher levels estimates of flow were frequently much too low. Reserpine slowed the pulse and resulted in predicted rates of flow which averaged 13.7% below actual rates. Angiotensin, l-norepinephrine, dipyridamole, and digitoxin had no significant effect on the prediction of flow from clearance in the range of flow observed in controls. Thus Rb86 clearance is a valid index of coronary flow in the range of CO2 tension, arterial oxygen saturation, and drug effects commonly observed.
Mechanism for cardiac stimulation during hypoxia
Authors: Penna Mario , Linares Francisco , Cáceres Laura
Published: December 2017

In isolated guinea pig atria, hypoxia was induced by bubbling nitrogen through Tyrode solution. A significant increase in both the amplitude and frequency of the contractions occurred, followed by a decrease. Average rate in 11 control atria was 138 ± 9.2 contractions/min and increased during hypoxia by an average value of 12.7 ± 2.3 contractions/min ( P < 0.001). Amplitude of shortening increased by an average of 10.5 ± 2.12% ( P <0.001). In 19 preparations pretreatment with reserpine blocked the transient stimulant effect of hypoxia on both amplitude and frequency of contractions. Isometric contractions were recorded from 30 isolated cat papillary muscles. The developed isometric tension increased during hypoxia by an average of 17.3 ± 2.8% ( P < 0.001). Later, a decrease in contractile force was observed. Pretreatment of the animals with guanethidine and chronic cardiac sympathectomy blocked and pretreatment with reserpine decreased the stimulant effect of hypoxia on the cat papillary muscle. The transient stimulant effect of hypoxia was compared to the staircase phenomenon. Both chronic cardiac sympathectomy and pretreatment with reserpine blocked the increase in force induced by a change in rate from 60 to 120.
Binding of cardioglobulin-C-Ca45 to cardiac muscle and release by cardioglobulin-A
Authors: Hajdu Stephen , Leonard Edward
Published: December 2017

The cardiotonic action of cardioglobulin on the frog heart is a result of the interaction of three globulins, cardioglobulin-A, -B, and -C. Cardioglobulin-B binds to the heart. It has been shown that cardioglobulin-C binds to a cardioglobulin-B heart, but not to a heart without cardioglobulin-B. Cardioglobulin-C binding has been demonstrated both by biological activity and by persistence of cardioglobulin-C-Ca45 counts on the heart. The addition of cardioglobulin-A to a cardioglobulin-B-C heart causes the characteristic cardiotonic action of the system. Addition of cardioglobulin-A is associated with release of tracer from bound cardioglobulin-C-Ca45, measured as a decrease in heart radioactivity. The correlations between biological activity and localization of Ca45 of labeled cardioglobulin-C are consistent with the hypothesis that cardioglobulin action is associated with the release of cardioglobulin-C calcium into the cell. The amount of calcium involved has been estimated to be of the order of 10–4 µm for an 80-mg frog heart.
Tracer microinjection studies of renal tubular permeability
Authors: Gottschalk Carl W. , Morel Francois , Mylle Margaret
Published: December 2017

Renal tubular permeability was studied in rats with a tracer microinjection technique in which radioactive inulin and another isotope were simultaneously microinjected into proximal or distal convoluted tubules during osmotic diuresis and their excretion by that kidney measured. Noninulin radioactivity excreted with a time course similar to that of inulin is termed direct recovery and that excreted more slowly, delayed recovery. The absence of inulin excretion by the contralateral kidney demonstrated that there was no transtubular efflux of this substance under these conditions. Inulin transit time averaged 0.84 min and 0.33 min following proximal and distal microinjection, respectively. Excreted sodium 22 molecules apparently followed closely the path of inulin molecules, since they appeared in the urine simultaneously. There was no delayed recovery of sodium 22. There was considerable direct and delayed recovery of urea-C14, indicating its diffusion into the tubular epithelial cells and subsequent return to the lumen. There was very little delayed and almost no direct recovery of tritiated water under these conditions in which physiologically maximally effective amounts of ADH were probably present. The injected quantity of isotope minus its direct recovery is believed to approximate its total tubular efflux.
Hepatic and renal clearance of vasopressin from plasma of dogs
Authors: Lauson Henry D. , Bocanegra Manuel , Beuzeville Carlos F.
Published: December 2017

The fraction of vasopressin removed from portal venous plasma by the liver (hepatic portal extraction ratio) was estimated in conscious, hydrated female dogs. Antidiuretic responses to physiological doses of beef Pitressin (Parke, Davis) given as 5-min infusions via a splenic vein catheter were compared with responses to the same dose infused via a foreleg vein. The fraction of vasopressin removed during passage through the left kidney was estimated in experiments of analogous design. Antidiuretic responses of the right kidney to physiological does given as 5-min infusions via a catheter implanted transaortically in the left renal artery were compared with responses of the right kidney to the same dose given via a foreleg vein. Infusions were given by the alternate routes at hourly intervals. The hepatic portal extraction ratio for vasopressin averaged 12%. The renal extraction ratio averaged 25%. The renal extraction ratio, estimated by bioassay of arterial and renal venous plasma, was somewhat smaller (20%) in anesthetized dogs in which the concentration of vasopressin in the plasma was raised to unphysiologically high values by a constant infusion of beef Pitressin. From measurements of plasma flow through these organs and the extraction ratios, the clearances of vasopressin in the liver and both kidneys were calculated. The respective estimates, expressed as percent of plasma volume cleared per minute, were: hepatic, 4.6; renal (physiological plasma concentrations), 9.4; and renal (high plasma concentrations), 5.8.
Left ventricular heat production during induced tachycardia in the intact dog
Authors: Afonso Skoda , McKenna David H. , O'Brien George S. , Rowe George G. , Crumpton Charles W.
Published: December 2017

It is well established that heart rate is a determinant of myocardial oxygen consumption. However, it has not been demonstrated that the increase of oxygen consumption at faster rates actually represents loss of energy, degraded as heat. Control measurements of systemic and coronary hemodynamic and metabolic parameters and left ventricular heat production (measured by a recently reported method) were obtained in 10 dogs. Tachycardia was then induced electrically and the same parameters redetermined. Significant increases occurred in coronary blood flow, cardiac metabolic rate of oxygen, and left ventricular heat production. The elevated myocardial oxygen consumption at higher rates is associated with increased heat production.
Response of human umbilical artery to changes in transmural pressure
Authors: Davignon Jean , Lorenz Robert R. , Shepherd John T.
Published: December 2017

Human umbilical artery was perfused with Krebs-Ringer bicarbonate-glucose medium at 37 C and pH 7.4. An increase in transmural pressure elicited a vasoconstriction. The artery wall contained no significant amount of norepinephrine, which supports the anatomic evidence of absence of nerve supply. Thus, the response to stretch is due to a smooth muscle cell-borne positive feedback mechanism. The myogenic reflex could still be elicited at 44 C but was reversibly abolished by cooling to 4 C. It was reversibly abolished in the absence of calcium. K2SO4-Ringer solution (50 mm in K) markedly increased the tone of the artery after an initial vasodilatation and induced rhythmicity when the perfusion pressure was increased. Bradykinin, 5-hydroxytryptamine, and angiotensin caused vasoconstriction when the artery no longer responded to stretch. Stretch could induce vasoconstriction when angiotensin no longer elicited a response because of tachyphylaxis. The stretch reflex was not blocked by phenoxybenzamine which suppressed the response to 5-hydroxytryptamine. Tachyphylaxis was not observed with bradykinin; the effect of bradykinin was not blocked by phenoxybenzamine.