bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of hypothermia on myocardial metabolism
Authors: Russ Clem , Lee John C.
Published: December 2017

Effect of hypothermia of 25 C for 24 hr was determined on myocardial metabolism and efficiency in dogs fasted for approximately 15 hr and anesthetized with sodium pentobarbital. Coronary blood flow, cardiac output, myocardial oxygen and substrate utilization, and mechanical efficiency of the heart were determined at normal and reduced body temperatures. Prolonged reduction of myocardial temperature with concomitant reduction in coronary blood flow led to diminished oxygen and substrate utilization. Myocardial glycolysis began after 12 hr of cooling when pyruvate utilization stopped in negative balance. After 24 hr the heart stopped utilizing carbohydrates with negative arteriovenous differences for these substrates (in the presence of normal arterial carbohydrate levels), but continued to utilize nonesterified fatty acid. The coefficient of oxygen utilization for the heart increased following 24 hr of cooling, suggesting a relative state of myocardial hypoxia. The appearance of hypoxia and glycolysis during the late hours of cooling suggests that the limit of tolerance of the heart to cooling was near.
Stability of pulmonary artery pressure during emboli-induced pulmonary edema in dogs
Authors: Weisberg H. , Jortner R. T. , Kline I. K. , Ellis A. , Katz L. N.
Published: December 2017

Changes in some facets of cardiovascular hemodynamics occurring after acute unilateral pulmonary starch embolization were studied in the anesthetized closed-chest dog. While bilateral pulmonary edema and reduced cardiac output occurred in starch-embolized dogs, these phenomena were not seen in control animals. Pulmonary arterial pressure changes were not significant during the present experiments, but the consistent rise in pulmonary vascular resistance after embolization indicates that the latter may be a better index of pulmonary vascular effects of emboli than are pressure changes. The fall in cardiac output was of sufficient magnitude to more completely neutralize the pulmonary artery pressure rise usually expected with increased pulmonary vascular resistance following pulmonary embolization.
Effect of renal insufficiency on gastrointestinal transport of calcium
Authors: Kessner David M. , Epstein Franklin H.
Published: December 2017

Chronic experimental renal insufficiency induced by subtotal nephrectomy decreased the ability of the isolated rat duodenal gut sac to transport calcium against a chemical gradient. The defect in intestinal transport was not reproduced by metabolic acidosis, uremia of short duration, or addition of urea to the ambient solution bathing the gut sac. The transport of calcium by the intestine of uremic rats was increased by pretreatment with high doses of vitamin D and, at the dose level employed, there was no evidence of "resistance" to vitamin D. Dietary restriction depressed the gastrointestinal transport of calcium and may play a role in producing the defect in calcium transport of chronic uremia.
Content and synthesis of hepatic pyridine nucleotides in fetal and neonatal rabbits
Authors: Roux Jacques F. , Gordon Edwin E. , Baker Herman
Published: December 2017

The concentration and the synthesis of pyridine nucleotides in the liver and placenta of the rabbit have been studied as a function of developmental age. The concentration of total hepatic pyridine nucleotides increased progressively during fetal and neonatal development, reaching a maximal level in the adult period. This increase was due primarily to elevation in diphosphopyridine nucleotide (DPN) and reduced triphosphopyridine nucleotide (TPNH). In the postmature state, hepatic reduced diphosphopyridine nucleotide (DPNH) and triphosphopyridine nucleotide (TPN) levels were less than in term or 5-day-old rabbits. The concentration of total pyridine nucleotides in the placenta diminished during gestation. Following parenteral administration of nicotinamide to the pregnant rabbit, the concentration of nicotinamide increased to the same extent in maternal and fetal blood plasma and the total pyridine nucleotide concentration increased in both maternal and fetal liver. The latter increment was greater in maternal than in fetal liver, and in fetal liver was greatest at term. The increase was due largely to increase in DPN in the developing fetus and neonate, and in the adult rabbit to increase in all pyridine nucleotides.
Pattern of function of left ventricle of mammals
Authors: Holt J. P. , Kines Helga , Rhode E. A.
Published: December 2017

Since, over a limited range, rubber has elastic properties similar to contracted cardiac muscle, a method for determining the elasticity constant of rubber left ventricle models has been developed and used to determine the elasticity constant of the contracted mammalian left ventricle. Serial determinations of left ventricular end-systolic pressure, enddiastolic volume, end-systolic volume, and stroke volume were carried out following increased blood volume and stepwise hemorrhages in rabbits, dogs, swine, horses, and cattle. The end-systolic pressure-volume relationship of the ventricle of these animals was found to be similar to that of rubber ventricle models, hemiprolate spheroids, and thick-walled spheres; evidence is presented that the contracted left ventricle, and rubber models of it, function as an equivalent thick-walled sphere having the same wall mass and internal volume. From the linear relationship between "average" wall stress and "average" circumference, equations are derived relating chamber internal volume and: systolic pressure, total potential energy, and energy dissipated in ejection of the stroke volume.
Limited hypertensive effect of infusion of angiotensin
Authors: Day Michael D. , McCubbin James W. , Page Irvine H.
Published: December 2017

Though single injections of angiotensin cause extreme rise in arterial pressure, infusion fails to elevate pressure to the degree usually found in experimental renal hypertension. The maximal pressure level obtainable by infusing angiotensin into anesthetized dogs was approximately the same in different dogs and was independent of the initial pressure. The vagus nerves did not importantly influence the "ceiling" response but if arterial pressure was then elevated by carotid occlusion the ceiling was raised. The combination of renal artery constriction and infusion of angiotensin failed to give a higher ceiling than angiotensin alone. In dogs with chronic renal hypertension the ceiling was higher than in normal dogs, presumably because of an upward shift in the range of response of cardiovascular reflexes. The results support the view that compensatory cardiovascular reflexes and tachyphylaxis to large amounts of infused angiotensin suppress the response and that these factors are much less effective in limiting response to quick injection.
Pentobarbital sodium anesthesia in the dog
Authors: Gilmore J. P.
Published: December 2017

Studies have been done in the dog to determine some of the circulatory effects of anesthetic amounts of pentobarbital sodium. The results indicate that a) except for the initial transient hypotension that occurs on injection of the anesthetic, pentobarbital sodium has little influence on the mean arterial blood pressure of the normotensive dog; b) cardiac output is unchanged 1 hr following anesthesia, then decreases approximately 25% and remains at this level from the 2nd to at least the 4th hr of anesthesia; c) estimated hepatic blood flow is not modified by pentobarbital sodium but the splanchnic A-V oxygen difference decreases; d) pentobarbital sodium does not modify arterial oxygen saturation, plasma volume, or red cell mass; e) the apparent hemodilution of the pentobarbitalized dog appears to result from the splenic sequestration of erythrocytes; f) the leukopenia which occurs in the dog under pentobarbital sodium also occurs in the splenectomized dog and appears to result, at least in part, from the pooling of leukocytes in the pulmonary bed; and g) the splenic blood of the normal unanesthetized dog does not appear to have a cell-to-plasma ratio different from that of the peripheral blood.
Influence of chromium, cadmium, and lead on rat aortic lipids and circulating cholesterol
Authors: Schroeder Henry A. , Balassa Joseph J.
Published: December 2017

Male and female rats were given 5 ppm lead, cadmium, and chromium (III) in drinking water from the time of weaning until death, on a diet deficient or low in these metals. Mean serum cholesterol of males on each metal was lower than that of controls at two ages; levels of females on lead and chromium were higher. A 31% increase occurred with age in both sexes on cadmium. There was more sudanophilia (staining with Sudan IV) in aortas of rats on cadmium and lead than in the controls and the chromium fed. Extractable aortic lipids were highest in cadmium-fed animals. Plaques, visible under fluorescent light, were present in 31 of 165 aortas from the lead, cadmium, and control groups and 1 of 48 from the chromium. Lowered circulating cholesterol was associated with increased aortic lipid in rats given cadmium.
Respiratory metabolism in rat tissues after autolysis in situ
Authors: Sanders A. P. , Hale D. M. , Miller A. T.
Published: December 2017

Rat tissues were subjected to autolysis in situ by incubation of the decapitated carcass at 37 C. After variable periods, samples of liver, kidney, and brain were either frozen in liquid propane (–190 C) for measurement of ATP or homogenized in sucrose-EDTA medium for polarographic measurements. The rate of disappearance of ATP was in the order brain > liver > kidney, and the "stable" ATP concentration after 60-min autolysis was greatest in kidney and least in brain. After 90-min autolysis, the "basal" (nonstimulated) oxygen consumption of homogenates was either increased (liver) or unchanged (kidney, brain), and the ADP-stimulated oxygen consumption was depressed in all three tissues. Respiratory control (stimulation of oxygen uptake by ADP) was abolished in brain after 60-min autolysis and in liver and kidney after 90 min when the substrates were alpha-ketoglutarate or glutamate; some control was observed when succinate was the substrate. Oxidative phosphorylation (ADP:O ratio) was not affected by 60-min autolysis. It is concluded that autolysis of 60-min duration results in depression of the rate at which ATP can be synthesized without affecting the energetic efficiency of ATP formation.
Some effects of hypoxia on respiratory metabolism and protein synthesis in rat tissues
Authors: Sanders A. P. , Hale D. M. , Miller A. T.
Published: December 2017

Nembutalized rats were pump ventilated with 5% oxygen-95% nitrogen for periods of 60 or 105 min. Samples of liver, kidney, and brain obtained at the end of the period of hypoxia were used for ATP determinations and for polarographic measurements of respiration, respiratory control, and oxidative phosphorylation. In some experiments, leucine-C14 was injected intravenously after 60 min of hypoxia, and tissue uptake and incorporation of leucine into protein determined after an additional 45-min period of hypoxia. After 105 min of hypoxia, brain ATP was reduced 20%, liver ATP 40%, and kidney ATP was unchanged. The incorporation of leucine-C14 into protein was moderately depressed in brain and kidney and almost completely abolished in liver. The polarographic studies indicated that the capacity of tissue homogenates for basal and ADP-stimulated respiration and for oxidative phosphorylation was not impaired by 60 or 105 min of severe hypoxia. It is concluded that the damaging effects of hypoxia, of the severity and duration studied, are due mainly to the reduction in tissue ATP levels rather than to damage of the ATP-producing system.
Relation between inhibition of gastric secretion and absorption of fatty acids
Authors: Long James F. , Brooks Frank P.
Published: December 2017

Gastric secretion stimulated by a 100-g meat meal was inhibited by oleic acid and triolein and the inhibition correlated with absorption of the respective lipids in dogs with vagally innervated gastric pouches. Twenty-six milliliters of lipid were infused into the duodenum at 0.76 ml/min through a duodenal fistula starting 5 min before feeding. Gastric secretion was collected every 30 min and analyzed for acid and pepsin concentrations. Paraffin oil infused at the same rate gave results similar to feeding alone. Lipid absorption was determined by measuring venous plasma radioactivity at 1, 2, 3, 4, and 6 hr after feeding and infusing of C14-labeled oleic acid or triolein. Lipid in intestinal content for 3 hr after feeding was determined in acute experiments. The duration of gastric inhibition was longer and the absorption was slower with oleic acid than with triolein.
Effect of increased pressure within a right heart cul-de-sac on heart rate in dogs
Authors: Goetz Kenneth L.
Published: December 2017

Increases in heart rate consistently were elicited by moderate increases in pressure within a right heart cul-de-sac of a modified canine right heart bypass preparation. Higher elevations in cul-de-sac pressure caused slowing of the heart rate. Similar results were obtained after cervical vagotomy and sympathetic blockade. This study is interpreted as giving evidence against the existence of any cardiac accelerator or decelerator reflexes elicited by changes in right heart pressure. The alterations in heart rate appear to be produced by local mechanisms within the heart.
Antihistamines and vascular reactivity
Authors: Altura Burton M. , Zweifach Benjamin W.
Published: December 2017

The purpose of the present set of experiments was to determine the contribution of the dilator principle, histamine, to peripheral vascular homeostasis. This was done by means of direct microscopic observation of the mesocecal microcirculation through the use of antihistamines. These drugs were found not only to produce a contraction of the microvessels but also to increase the responsiveness to topically applied cate-cholamines and antihistamines as well. The evidence does not preclude the possibility that histamine is a naturally occurring regulator of local tissue blood flow; but on the other hand, one cannot with any confidence accept this possibility.
Evidence for a direct effect of parathyroid hormone on urinary acidification
Authors: Hellman Dorothea E. , Au William Y. W. , Bartter Frederic C.
Published: December 2017

The effects of intravenously administered parathyroid extract and of a purified parathyroid hormone on urinary acidification and on solute excretion were measured in six thyroparathyroidectomized dogs, in three normal women, and in a patient with diabetes insipidus. Parathyroid extract and the purified parathyroid hormone produced an immediate rise in urinary pH and bicarbonate with a fall in titratable-acid-minus-bicarbonate and in ammonia in all subjects. This was usually associated with a rise in urinary sodium and potassium. The changes in urinary acidification usually preceded any rise in glomerular filtration rate, and were associated with no increase in serum bicarbonate concentration. They also preceded a rise in the excretion of phosphate in most experiments, and thus did not depend on a rise in urinary buffer content. It is postulated that parathyroid hormone inhibits sodium-for-hydrogen ion exchange in the renal tubules, perhaps by interfering directly with the ability of the kidney to maintain a hydrogen ion gradient between the body fluids and the tubular urine.
Distribution in the rat of physiological amounts of injected Cr51(III) with time
Authors: Hopkins L. L.
Published: December 2017

Cr51 trichloride was injected intravenously into rats at the levels of 0.01 and 0.1 µg Cr/100 g body wt and its distribution was studied at timed intervals from 1/4 hr to 4 days. There was little difference in blood clearance, tissue distribution, or excretion due to either dose level, previous diet, or sex. After 4 days, the heart, pancreas, lung, and brain retained only 10–31% of their initial radioactivity while the spleen, kidney, testis, and epididymis retained from 104 to 200%. The other tissue values were intermediate. The spleen and kidney continued to concentrate Cr51 over the 4-day period while the peak retention in the testis and epididymis was at 4 and 8 hr, respectively. Young growing rats retained greater amounts of Cr51 in the bones whereas mature animals showed higher retention in the spleen, kidney, testis, and epididymis. Chromium was excreted mainly in the urine although minor amounts were found in the feces.
Pancreatic secretion in vitro in "Cl–-free," "CO2-free," and low-Na+ environment
Authors: Rothman S. S. , Brooks F. P.
Published: December 2017

Pancreatic secretion from the rabbit pancreas in vitro was not maintained in "Cl–-free," "CO2-free," or low-Na+ environments. When the missing ion was added to the bath, secretion recovered. Results show that "primary" HCO3– secretion need not be "isotonic" and that a HCO3–-Cl– exchange mechanism may not be of major importance in producing a secretion of variable electrolyte composition. There was an interdependence of Cl– and HCO3– output, suggesting that these ions are not secreted by independent mechanisms. HCO3– output in the absence of an exogenous CO2 source was about 10% of control values. Na+ and Cl–, as well as HCO3–, may be secreted primarily transcellularly. A "unicellular" model of pancreatic secretion based on the active secretion of Na+ and accumulation of K+ by the secreting pancreatic cell is presented.
Effect of renin, ischemia, and plasma protein loading on the isolated perfused kidney
Authors: Rosenfeld Sheldon , Kraus Roy , McCullen Avile
Published: December 2017

Normal renal function has been maintained in an isolated artificial heart-lung, whole-blood perfused rabbit kidney for periods of 2–4 hr. The isolated kidney responds to changes in perfusion pressure, changes in plasma protein concentration, and exposure to a 10-min period of ischemia, in a manner similar to that described for the kidney of the normal intact animal. Elevation of the plasma protein concentration produces a fall in the rate of urine flow, sodium excretion, and creatinine clearance, and a marked proteinuria. The administration of renin produces a marked diuresis, natriuresis, and proteinuria. This effect is also produced by the exposure of the isolated kidney to a 10-min period of ischemia, suggesting that this response may be mediated by a renin mechanism. The responses of the kidney to these two procedures differ only in that ischemia produces an increase in renal blood flow and renin produces a slight reduction in renal blood flow and a more pronounced proteinuria.
Bradykinin and renal function in normal man: effects of adrenergic blockade
Authors: Gill John R. , Melmon Kenneth L. , Gillespie Louis , Bartter Frederic C.
Published: December 2017

Renal function was studied in five normal subjects during the infusion of bradykinin at 0.1 and 0.4 µg/kg per min, and in four additional normal subjects during the infusion of norepinephrine at dosages beginning with 1–3 µg/ min. Bradykinin at both dosages decreased glomerular filtration rate (GFR) and tended to increase renal blood flow (ERPF). It increased sodium excretion (UNaV) at the lower dosage, but did not increase it further at the higher dosage. At all dosages, norepinephrine decreased ERPF and UNaV. The effects of bradykinin cannot be explained solely as effects of norepinephrine released by the bradykinin. During adrenergic blockade produced by guanethidine, bradykinin, 0.1 µg/kg per min, slightly decreased GFR and UNaV; at 0.4 µg/kg per min, it further decreased GFR and UNaV and tended to decrease ERPF as well. It did not lower blood pressure. The data suggest that in normal man, bradykinin increases UNaV only at low dosages. During adrenergic blockade, endogenous release of angiotensin could have prevented bradykinin from lowering blood pressure and could have caused the decreases in GFR, ERPF, and UNaV. A possible role is suggested for bradykinin in the physiologic control of renal function, and as a causative agent in producing the changes in renal function found in certain disease states characterized by excessive production of kinins.
Comparison of creatinine and inulin clearances in male and female rats
Authors: Harvey Alice M. , Malvin Richard L.
Published: December 2017

Creatinine and inulin clearances were compared in anesthetized male and female rats. Continuous intravenous infusion, midpoint arterial blood sampling, and ureteral catheterization aided accurate measurements. Average inulin clearances were 1.0 ml/min per 100 g. In the control male rat the creatinine clearance persistently exceeded that of inulin. The elevated CCr: CIn ratio could be reduced to 1 by probenecid, PAH, mercury, or high plasma levels of creatinine. In females a single intramuscular dose of testosterone elevated the ratio to that seen in male rats. This effect declined within 6 hr. Manipulations with steroids other than testosterone did not affect results in either sex. It is suggested that male rats secrete creatinine under the influence of androgens and that inulin is therefore a better measurement of the glomerular filtration rate in the male rat.
Quantitative measurement by telemetry of ovulation and oviposition in the fowl
Authors: Winget C. M. , Averkin E. G. , Fryer T. B.
Published: December 2017

A radio telemetry system was used to establish a deep body temperature cycle in a domestic male and a female fowl under continuous light of constant intensity. Certain sex differences were noted. In the female, the maximum body temperature was reached at time of oviposition. There were two peaks in temperature during the daily temperature maxima in the animal, which laid an egg the next day. Oviposition may account for one peak and ovulation the other. The female had a 28-hr cycle and the male a 24-hr cycle. The data were evaluated by autocovariance, power spectral analysis, harmonic regression, and other methods.
Growth hormone effect on the role of fat in nitrogen metabolism
Authors: Katorski Barbara , Delaney Patrick F. , Fenton Paul F.
Published: December 2017

Nitrogen balance of mice was affected adversely when they received protein and a carbohydrate-fat mixture at different times of day. Administration of growth hormone overcame this adverse effect, although in the dosage employed the hormone had no measurable effect when protein and carbohydrate-fat were administered simultaneously. In other experiments we showed that fat feeding reduced the loss of nitrogen. Administration of fat and growth hormone (in a dose which by itself was ineffective) reduced the nitrogen loss to minimal levels. In animals which had previously become adapted to high-fat rations, fat showed a large nitrogen-sparing action which could not be further enhanced by growth-hormone treatment. The data suggest that one function of growth hormone is to speed adaptation to efficient fat utilization which is reflected in nitrogen retention.
Relation between bicarbonate concentration and rate of canine pancreatic secretion
Authors: Birnbaum David , Hollander Franklin
Published: December 2017

Most investigators have reported that the mathematical relation between [HCO3] and volume-rate ( V) in canine pancreatic secretion under various conditions is represented by plateau curves with [HCO3] asymptotes, but with shapes and parameters which differ widely. Analysis of the present data, regardless of stimulus and dog, reveals similar curves with plateau values of 145 mEq/ liter, extending from about 0.7 to 2.1 ml/min. This graph was unaffected by adjustment of V for body weight. A breakdown according to stimulus yielded three regression lines with different parameters. Several operational factors are described to aid in attaining curves of uniform pattern hereafter. The fact has been ignored that each sample collected comprises some fluid retained in the collecting system from the preceding period, as well as some secreted during the collection period. Consequently, we must recognize the difference between rate of secretion and composition of the juice at its cellular source, and rate of collection and composition at the distal end of the duct. Errors from this source may contribute materially to the irregularity among the curves reported.
Comparison of intestinal discrimination between calcium 47, strontium 85, and barium 133
Authors: Marcus C. Silber , Wasserman R. H.
Published: December 2017

A mathematical treatment of data is described for comparing the fractional rates of Sr and Ca movement in gastrointestinal absorption. This is done by assuming that the ratio of various rate constants of absorption for the two elements is a constant which we have called the instantaneous intestinal strontium-calcium discrimination factor and designated as K. It was observed that this K value averaged 0.72 in studies on strontium and calcium absorption by the entire gastrointestinal tract of rats under in vivo conditions. This was in good agreement with a similar value for the reabsorption of these alkaline earths by mammalian kidney, reported by others as 0.7. The comparative absorption of barium could not be characterized by this mathematical model. Any treatment that alters the over-all comparative absorption of strontium and calcium can do so in two ways: by changing the absorption of both alkaline earths proportionally, and by changing the comparative rate constants of strontium and calcium transport. These two effects can be experimentally delineated. In the present study both lactose and lysine, which are known to alter Sr-Ca discrimination, were found to do so by increasing absorption and not by changing the rate constants.
Normal and myotonic goats receiving diazacholesterol
Authors: Burns Thomas W. , Dale Homer E. , Langley Paul L.
Published: December 2017

The administration of diazacholesterol, a cholesterol-lowering agent, to unaffected and myotonic goats was associated with the appearance of myotonia in the former, worsening of myotonia in the latter, and accumulation of desmosterol in the plasma, erythrocyte membrane, and muscle in both groups. Discontinuation of diazacholesterol was accompanied by a marked reduction in plasma and erythrocyte desmosterol, by a concomitant rise in cholesterol, and by a return of muscle function to pretreatment status.
Central neural regulation of carotid baroreceptor reflexes in the cat
Authors: Reis Donald J. , Cuenod Michel
Published: December 2017

Reflex changes of the mean aortic blood pressure (BP) to carotid sinus stretch or carotid occlusion in anesthetized vagotomized cats were observed following ablation or electrical stimulation of brain. Decerebration produced augmentation of the depressor response to sinus stretch, reduction of the pressor response to carotid occlusion, and fall of BP. Subsequent cerebellectomy produced an increase of depressor and pressor responses. Midpontine section produced disappearance of the pressor response to carotid occlusion and appearance of a "paradoxical" pressor response to sinus stretch. Stimulation within hypothalamus and reticular formation produced augmentation and a barbiturate-sensitive poststimulus depression of pressor response without changes in BP. It is concluded that baroreceptor reflex responsiveness is under tonic and phasic control of brain structures above medulla and that pressor and depressor limbs of the reflex are not reciprocal and modified independently of each other and of the BP. This suggests functional separation of brainstem neurons involved in reflex and tonic BP control and that some cerebral regulation of BP is indirectly mediated through vascular reflexes.
Adrenergic mechanisms in the bullfrog and turtle
Authors: Azuma Takehiko , Binia Alberto , Visscher Maurice B.
Published: December 2017

Epinephrine and norepinephrine contents of tissues and perfusates have been measured by fluorimetric methods to ascertain which catecholamine is the sympathetic transmitter in bullfrogs and turtles. Except for adrenal and sympathetic chain, the predominant catecholamine in bullfrogs is epinephrine. In snapping turtles, norepinephrine predominates. During perfusion of bullfrog heart or liver without stimulation, only traces of catecholamine appear in perfusates, whereas during sympathetic nerve stimulation a large output of epinephrine occurs. In the bullfrog epinephrine rather than norepinephrine seems to be the sympathetic mediator. The situation may be the reverse in the turtle. Environmental temperature did not alter bullfrog tissue catecholamine. Cardiac sympathetic denervation did not decrease myocardial catecholamine within 6 weeks at low temperatures, but in animals maintained at 20 C survival was not achieved. Epinephrine levels in bullfrog ventricle were not lowered by 5 hr of contractions induced by electrical stimulation at 30/min compared with controls in arrest. The fact that myocardial catecholamine stores are not depleted by contractile activity may result either from absence of utilization or from equivalence between breakdown and synthesis.
Analysis of countercurrent diffusion exchange in blood vessels of the renal medulla
Authors: Marsh D. J. , Segel L. A.
Published: December 2017

Page 817: D. J. Marsh and L. A. Segel. "Analysis of countercurrent diffusion exchange in blood vessels of the renal medulla." Page 822, column 2, lines 13 and 14 should read, in lower case roman, paragraphed and run in, "The method used to measure linear flow speed tracks erythrocytes." Page 826, column 1, the equation in footnote 1 should read:

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Page 826, the figure labeled Fig. 5 is Fig. 6; the figure labeled Fig. 6 is Fig. 5. The legends are correct.
Plasma K plus and insulin: changes during KCl infusion in normal and nephrectomized dogs
Authors: Pettit GW , Vick RL , Swander AM
Published: December 2017

Potassium chloride was administered by constant, intravenous infusion in splenectomized, but otherwise normal, dogs. The concentration of potassium, [K+], and of insulin, [insulin], in the arterial plasma was measured at frequent intervals. To assess the relative contributions of extrarenal and renal mechanisms toward the maintenance of normal plasma [K+], the results were compared with data obtained previously in splenectomized, nephrectomized dogs. During the infusion, plasma [K+] increased in the dogs with kidneys intact at a mean rate slightly less than that in the nephrectomized dogs. After the infusion was stopped, plasma [K+] declined to about 0.75 meq/liter above control values in both groups of animals. The results indicate the operation of both renal and extrarenal homoeostatic mechanisms. The renal mechanisms contributed measurably during the infusion of KCl, but not immediately after the infusion was stopped. Simultaneous measurements of plasma [K+] and plasma [insulin] indicate that insulin may be involved in the extrarenal homeostatic response.
Transport of H plus and other electrolytes across isolated gastric mucosa of the rabbit
Authors: Fromm D , Schwartz JH , Quijano R
Published: December 2017

The relationship of transmural and cellular phenomena to the rate of spontaneous luminal HH+ secretion by short-circuited gastric mucosa bathed in HCO3- and CO2-free Ringer solution was studied by the pH-stat technique. The bulk of luminal acidification can be accounted for by the appearance of H+ and not by organic acids. Acid secretion requires the presence of O2 and exogenous substrate but is not limited by endogenous CO2 production. The rate of H+ secretion is matched by the serosal appearance of alkali. The greater appearance of CO2 on the serosal side of the mucosa is consistent with hydroxylation of CO2 and greater permeability of the serosal border to HCO3-. Luminal changes in H+ concentrations affect H+ secretion but serosal changes do not, suggesting that the gradient produced by H+ secretion is at the luminal border. Steady-state isotopic Na+ and Cl- fluxes indicate net secretion of both ions, but net K+ transport is negligible.
Contractures in partially depolarized muscle treated with caffeine or nitrate
Authors: Geffner ES , Taylor SR , Sandow A
Published: December 2017

Frog toe muscles partially depolarized with a subcontracture concentration (15 or 20mM) of K+ rapidly developed tension when exposed to 1 mM caffeine, which alone did not cause contracture. This action resulted from a lowering of the mechanical threshold by the caffeine and thus was similar to that caused by replacement of Cl- with NO3-. Maximal tension was the same in the caffeine and NO3- media but took much longer to develop in the former. Equilibrating the muscles with caffeine for 60 s (the time calculated for complete diffusion) did not reduce contraction time significantly. However, prolonging the exposure of muscles to caffeine beyond this time enhanced the drug's capacity to potentiate both the twitch and 30 mM K+ contractures and shortened the contraction time of the contractures. Toe muscles that had undergone a contracture in 100 mM K+ and were recovering in 15 mM K+-Ringer generated tension in the presence of 1 mM caffeine or NO3- but only after enough repolarization had been achieved so that a response to a second challenge with 100 mM K+ could be demonstrated. Although prolonged immersion in the K+-enriched recovery solution caused a disappearance of sensitivity to a test depolarization, addition of 1 mM caffeine or replacement of Cl- with NO3- promptly evoked a contracture. These results imply a reversible step in the recovery process that is both potential and time dependent. Since application of 5 mM caffeine to either normally polarized or depolarized muscles always immediately causes contracture, more than one site of action for caffeine is indicated. After disruption of the transverse tubules, partially depolarized muscles showed no response to NO3- or 1 mM caffeine but contracted vigorously when exposed to 5 mM caffeine.
Afferent sympathetic nerve fibers with mechanoreceptors in the right heart
Authors: Uchida Y
Published: December 2017

Mechanosensitivity of afferent sympathetic nerve fibers from the right heart and the pulmonary artery has been examined. Action potentials of the afferent fibers that responded to tapping the right heart and the pulmonary artery were derived from upper thoracic communicating rami of both sides of anesthetized dogs. The fibers were composed of myelinated Adelta fibers and unmyelinated fibers. The receptive fields of both groups of fibers were located widely in the right heart and the pulmonary artery. Myelinated fibers ceased to fire quickly whereas unmyelinated fibers continued to fire after withdrawl of a brief mechanical stimulus. In the myelinated group, the pressure threshold was 3-50, 6-58, and 3-10 mmHg for right ventricular, pulmonary and right atrial threshold was 15-58, 22-34, and 4-8 mmHg for right ventricular, pulmonary, and right atrial fibers, respectively. Spontaneous discharge of myelinated fibers was synchronous with each rise and/or fall in intracardiac or pulmonary pressure whereas that of unmyelinated fibers was irregular and independent. A rise in pressure produced by pulmonary embolization or occlusion caused an augumented discharge whereas a fall caused by caval vein occulsion eliminated the discharge. The results indicate the existence of both myelinated and unmyelinated fibers with mechanoreceptors in the right heart and the pulmonary artery.
Hormone-substrate responses to total fasting in lean and obese mice
Authors: Cuendet GS , Loten EG , Cameron DP , Renold AE , Marliss EB
Published: December 2017

The hormone-substrate milieu has been investigated in male fasted lean (C57BL/6-+/+) mice and mutant obese mice of the same strain (C57BL/6-obob). The lean mouse, in winter, mobilized insufficient fat (due to inadequate stores) to permit survival beyong 3 days and was unable to achieve any degree of conservation of vital protein stores. By contrast, in summer, the same animals survived 7 days and showed evidence of greater and more sustained fat mobilization and ketosis and the ability to conserve protein. The insulin, glucagon, and insulin/glucagon molar ratios changed in both groups in a direction consistent with conversion to a catabolic state, and hence were probably largely responsible for the mobilization of substrates and stimulation of gluconeogenesis and ketogenesis. The seasonal difference in response is unexplained. The obob mice, generally employed as a model for obesity, hyperglycemia, and hyperinsulinemia showed these features but also adapted to fasting in a fashion permitting prolonged survival during this state. In a fashion analogous to that known to occur in man, these animals developed fall in glycemia, rise in circulating fat-derived substrates, and marked protein conservation. Profound fall in insulinemia was associated with a fall in glucagonemia, the latter from normal levels. Thus the initial markedly "anabolic" insulin/glucagon molar ratio diminished, but nevertheless remained higher than at any time in the lean mice. Pancreatic contents of insulin showed markedly different changes with fasting in obob compared with lean mice. The ability of the obese mouse to adapt to prolonged fasting in a fashion largely analogous to that of man renders it a useful model for the study of metabolism in this state, with the potential of applicability of findings to man.
Rat brain regional uptake and decarboxylation of L-DOPA following carotid injection
Authors: Wade LA , Katzman R
Published: December 2017

Using the carotid injection technique, the regional uptake and decarboxylation of L-DOPA at the blood-brain barrier in the rat was studied. After a single intracarotid injection in the rat followed by decapitation 15 S later, the uptake of L-DOPA was measured relative to tritiated water injected simultaneously as a diffusible internal standard. Decarboxylation was investigated with an injection mixture of L-[carboxy-14C]DOPA and L-[2,3-3H]DOPA. Uptake of L-DOPA studied over the range of 15-5,076 nmol/ml appeared to be a composite of two separate mechanisms. The saturable component had a half-maximal velocity transport value, K-t, of 336 muG. A diffusional, nonsaturable component had a diffusion constant of 0.018. A regional study showed that uptake operated at approximately the same rate in the various brain areas despite marked regional variation in catecholamine concentration. The decarboxylation of L-DOPA also occurred at a similar rate in all regions. Even when L-DOPA was injected at a concentration of 3 mM, 33-51% was decarboxylated within the 15-S period. These results support the hypothesis that L-DOPA movement into the brain occures via a neutral amino acid transport mechanism common to cerebral capillaries of different regions of the brain.
Methods for serial study of renin-angiotensin system in the unanesthetized rat
Authors: Carvalho JS , Shapiro R , Hopper P , Page LB
Published: December 2017

Micromethods for measurement of plasma renin concentration (PRC) and plasma renin-substrate concentration (PSC) have been developed for rat plasma with radioimmunoassay of angiotensin I. An improved technique for aortic implantation of plastic cannulas was developed for use in experiments 1-2 wk in duration. The effects on components of renin system of anesthesia and tail cutting were studied. Arterial blood was sampled through cannulas without animal manipulation. PRC varied little in unanesthetized rats, was moderately and variably increased during pentobarbital anesthesia, and was markedly and consistently elevated during ether anesthesia. PSC was unchanged during anesthesia. PRC was increased in blood obtained by tail cutting within 1-2 min after cutting. With the use of the methods and techniques described here serial studies of the renin system in plasma of unanesthetized rats are shown to be feasible. A role for the sympathetic nervous system in the mediation of renin secretion by ether is proposed.
Plasma hormone and renal function changes in unrestrained dogs exposed to cold
Authors: Sadowski J , Kurkus J , Chwalbinska-Moneta J
Published: December 2017

Renal clearances and plasma antidiuretic hormone (ADH), 17-hydroxycorticoids, and norepinephrine were measured in unrestrained dogs before and during exposure to ambient cold (minus 4 to + 4 degrees C). Some dogs were treated with an inhibitor of cortisol biosynthesis, Metopirone, either alone or combined with dexamethasone, a potent glucocorticoid suppressing ACTH release. Plasma ADH increased in the Metopirone-treated group (P smaller than 0.02) but changed little in other dogs. Plasma 17-hydroxycorticoids in untreated dogs rose from a control value of 14.4 plus or minus 1.9 (SE) to 1.82 plus or minus 1.2 mug/100 ml after 20 min of exposure (P smaller than 0.01), an increase comparable with that previously observed in restrained dogs. Plasma norepinephrine increased from 0.98 plus or minus 0.07 to 1.15 plus or minus 0.08 mug/liter (P smaller than 0.01) after 20 min of exposure. Urine flow, C-Cr, and C-PAH tended to increase spontaneously in nonexposed control dogs. Exposure to cold abolished or reversed this tendency, most distinctly in the Metopirone-dexamethasone group. The urine concentration, measured as T-c-H2O/C-Cr, did not change in cold, in contrast to a decrease previously observed in restrained dogs. The data do not support the key role of plasma cortisol elevation in the mechanism of urine-concentration defect in cold and demonstrate important differences between responses of restrained and unrestrained animals.
Resistance of gluconeogenic and glycogenic pathways in obese-hyperglycemic mice
Authors: Kreutner W , Springer SC , Sherwood JE
Published: December 2017

The genetically obese-hyperglycemic mouse, C57 BL/6J-ob, exhibits hyperglycemia and hyperinsulinemia. We have investigated the in vivo hepatic response to a glucose load in female obese mice and their lean littermates. Within 15 min after the administration of glucose (1.5 g/kg) to fasted lean mice, gluconeogenesis from [14C]alanine markedly decreased, endogenous hepatic levels of alanine and other gluconeogenic precursors increased, and glycogen synthetase was activated by virtue of an increase in the precent of synthetase I. These changes persisted up to 60 min and then returned to fasting values. In contrast, obese mice did not produce any of the above changes when given a similar glucose load. Failure to activate glycogen synthetase occurred despite the presence of synthetase D phosphatase activity. In lean mice [14C]glucose synthesis from [14C]glycerol exceeded that from [14C]alanine and was not suppressed by glucose administration, indicating the site of control of gluconeogenesis to be below the triose phosphate step. Insulin resistance in obese mice may involve the liver, as well as peripheral tissues studied by others.
Potassium-sparing effect of enhanced renal ammonia production
Authors: Tannen RL , Terrien T
Published: December 2017

The effect of a primary alteration in renal ammonia production on potassium excretion was explored in normal men utilizing ingestion of glutamine to increase ammonia production independent of concomitant acid-base manipulations. After ingesting a constant-formula diet of normal electrolyte content for 3 days, normal men underwent on separate occasions in a rigidly paired fashion an acute study with ingestion of glutamine (4.3 mmol/kg) or only water. Glutamine ingestion under conditions of normal acidification or concomitant with an acute acidifying stimulus resulted in an increase in ammonium and concomitant decrease in potassium excretion. The potassium conservation could not be accounted for by changes in urinary sodium excretion or in plasma potassium or acid-base parameters. Furthermore, when NaHCO3 was ingested for 3 days preceding both the water and glutamine studies, the influence of glutamine on both ammonium and potassium excretion was reduced significantly. These studies suggest that altered ammonia production can affect potassium excretion, providing further evidence in support of a renal potassium-ammonia homeostatic mechanism.
Fate of labeled angiotensin II microinfused into individual nephrons in the rat
Authors: Pullman TN , Oparil S , Carone FA
Published: December 2017

14C-labeled angiotensin II ([14C]AII) and tritiated inulin ([3H]In) were infused into individual nephrons in Inactin-anesthetized rats and urinary excretion was measured. Site of infusion was identified by neoprene injection and microdissection. In other experiments with higher doses of [14C]AII, microperfused at 10-4-10-5 M (concentrations 10-5-10-6 higher than contained in plasma), [14C]AII and its urinary metabolites were identified and quantified by two-dimensional peptide mapping. Recovery of 14C was 10.9% when proximal tubules were infused and 94.8% when distal tubules were infused. There was no correlation with tubular length in either case. For proximal tubules, two-thirds of the 11% recovered from urine appeared as peptide fragments of AII. With distal tubules almost all 14C activity appeared as intact AII. The principal metabolic product recovered from urine after proximal injection was the chymotryptic peptide, and its recovery was inversely related to tubular length. It is suggested that rapid removal of [14C]AII by proximal tubular cells occurs by enzymatic cleavage at the luminal surface with reabsorption of most of the products and excretion of the remainder
Lung vascular smooth muscle as a determinant of pulmonary hypertension at high altitude
Authors: Tucker A , McMurtry IF , Reeves JT , Alexander AF , Will DH , Grover RF
Published: December 2017

The pulmonary hypertensive response to chronic hypoxia varies markedly among mammalian species. An explanation for this variability was sought by exposing seven species to hypobaric hypoxia (PB equal to 435 mmHg) for 19-48 days. Control animals were studied at 1,600 m (PB equal to 630 mmHg). The pulmonary hypertension that developed varied in the following order of decreasing severity: calf and pig (severe); rat and rabbit (moderate); sheep, guinea pig, and dog (mild). Right ventricular hypertrophy developed in proportion to the elevation in right ventricular systolic pressure. These interspecies variations in response were not correlated with the degree of arterial hypoxemia, degree of polycythemia, elevation in heart rate, or postnatal age. However, the medial thickness of the small pulmonary arteries in control animals was highly correlated with the development of pulmonary hypertension and right ventricular hypertrophy in hypoxic animals. Thus, the amount of lung vascular smooth muscle inherent within each species is a major determinant of the pulmonary hypertensive response to high altitude and contributes to the interspecies variability in this response.
Analysis of a periodic breathing pattern associated with Mayer waves
Authors: Preiss G , Iscoe S , Polosa C
Published: December 2017

Cats subjected to common carotid artery occlusion and hemorrhage developed a waxing and waning of respiratory amplitude recurring with a period of 24 s (range 10-60). Occasionally the waning phase terminated with apnea. This respiratory pattern, reminiscent of "periodic" breathing, was usually associated with an oscillation of sympathetic neural activity, and of systemic arterial pressure, of the same period. A similar pattern of modulation of phrenic nerve activity was observed during neuromuscular block and artificial ventilation and when, at the same time, the associated systemic arterial pressure oscillation was eliminated. These findings suggest that this breathing pattern is not the result of an analogous pattern in the discharge of gas tension-sensitive and/or blood flow- and pressure-sensitive receptors that is fed back to the central nervous system (CNS). Hence the pattern must be generated within the CNS with no need of rhythmic sensory information. The pattern can be accounted for by the assumption that the central respiratory drive potentials are riding on top of a slow oscillation of phrenic motoneuron membrane potential with a 24-s period.