bluuebunny/crossref_metadata_2025 huggingface dataset:
Graded activation in rabbit mesotubarium smooth muscle
Authors: Meiss RA
Published: December 2017

The outer margin of the mesotubarium superius, an accessory ligament from the femal rabbit reproductive system, contains a long and slender bundle of smooth muscle fibers well aligned with the long axis of the tissue. Very little connective tissue is present. Massive alternating-current electrical field stimuli (variable in frequency, amplitude, and duration) applied to isolated mesotubaria from mature, nonpregnant animals produced contractions in which isometric force (P) and its first derivative (dP/dt) could be continuously graded; an optimum existed for stimulus frequency and amplitude, but not for its duration. Twitchlike contractions could not be produced. Isometric contractions in which P was plotted against dP/dt to generate a phase-plane trajectory were used to predict the ultimate (time = infinity) force (Po) in graded contractions; this value agreed with the Po derived from isotonic force-velocity curves fitted to the Hill equation. Quick stretches applied during the rise of contractile force revealed a slow onset of the ability to bear the Po force.
Effect of bile salts on amino acid transport by rabbit intestine
Authors: Hajjar JJ , Khuri RN , Bikhazi AB
Published: December 2017

The effect of bile salts on alanine absorption across four regional sites of rabbit intestine was examined using an in vivo single-pass perfusion technique. Na-deoxycholate at a concentration of 3 mM reduced alanine absorption across all levels of the intestine, and a higher concentration (10 mM) of Na-taurodeoxycholate (TDC) caused only a minimal reduction of alanine absorption in the jejunum. TDC, however, was more effective in in vitro experiments, causing an incrase in transmural serosal-to-mucosal flux of alanine and phenylalanine, particularly when present in both the mucosal and serosal media. It also reduced the mucosal-to-serosal alanine flux rate when present only in the mucosal medium. The influx of these amino acids across the mucosal brush border membrane was also decreased by TDC. These amino acid transport changes correlated fairly well with some observed histological changes of the intestinal epithelium. This suggests that bile salt inhibition of amino acid absorption is nonspecific in type and can be mainly explained as being the result of an injurious action of these surface-active agents on the rabbit intestine.
Role of medullary Na-K-ATPase in renal potassium adaption
Authors: Finkelstein FO , Hayslett JP
Published: December 2017

Since recent studies have shown that chronic potassium loading stimulates the specific activity of Na-K-ATPase in renal tissue, experiments were performed to determine whether increased enzyme acitivity correlated with renal adaptation for accelerated potassium excretion. The Na-K-ATPase activity in different renal zones was correlated with the maximum rate of potassium excretion during the intravenous infusion of KCl in animals with normal and reduced renal function, animals on a varied potassium diet and animals treated with methylprednisolone or deoxycorticosterone acetate. The enhanced ability to excrete a potassium load was associated with increased enzyme activity in the outer or red medulla, whether the change in Na-K-ATPase was caused by chronic potassium loading, methylprednisolone treatment, or partial nephrectomy. There was no evidence that a rise in enzyme activity in the cortex influenced the rate of potassium secretion. Moreover, stimulation of Na-K-ATPase in the inner medulla-papilla did not augment the rate of potassium excretion above that found in animals with an increase in enzyme in the outer medulla alone. These experiments provide evidence that links Na-K-ATPase to the mechanism of renal potassium adaptation and suggest that the major increment in potassium secretion by the adapted kidney occurs in the outer medulla.
Dispersed rat parotid acinar cells. I. Morphological and functional characterization
Authors: Mangos JA , McSherry NR , Butcher F , Irwin K , Barber T
Published: December 2017

Morphologically and functionally intact acinar cells have been obtained from the rat parotid gland through enzymatic dispersion with pure collagenase, hyaluronidase, and trypsin as well as mild mechanical forces. Cell yields of 30-50% of the original tissue weight with over 95% acinar cells were accomplished. The cells in suspension assumed a more or less spherical shape but the intracellular polarity of organelle distribution was maintained. The cells in suspension at 37 degrees C maintained stable monovalent cationic composition but lost potassium and gained sodium rapidly upon exposure to ouabain, 10(-5) M. The intracellular amylase concentration and the patterns of secretion of amylase and of synthesis of cyclic AMP by the cells in response to adrenergic stimulation with epinephrine or isoproterenol were comparable to those of the intact gland in situ. In addition, the cells showed good O2 consumption and maintained it constant for periods up to 8 h. These cells could be used as experimental tools for in vitro studies of receptor physiology and biochemistry, cell membrane function, cellular secretory mechanisms, and other parameters of exocrine gland cell physiology.
Ba++ as a gastric stimulant: release of histamine
Authors: Rangachari PK
Published: December 2017

Ba++ added to the serosal solution bathing a resting frog stomach increased transmucosal resistance and induced acid secretion. The increase in acid secretion was associated with an increased leak of histamine from the mucosa into the serosal solution. Pretreatment with burimamide inhibited the secretory response to Ba++. After a pulse treatment with Ba++ (2 mM for 5 min), the effects on resistance were transient but the effects on acid secretion were sustained. A pulse treatment with histamine also led to a sustained increase in acid secretion, and this increase was blocked by burimamide. It is concluded that Ba++ releases histamine which then stimulates acid secretion.
Metabolic effects of calcitonin in the newborn
Authors: Garel JM , Barlet JP , Kervran A
Published: December 2017

Calcitonin was injected in newborn rats and newborn lambs to study the metabolic effects of the hormone. Subcutaneous injection of salmon calcitonin (140 MRC U/kg) induced a clearing effect on plasma from suckling newborn rats that was naturally lactescent. A lower dose given by the same route (14 MRC U/kg) strongly decreased plasma triglyceride and amino acid levels in suckling newborn rats. This was mainly the result of gastric emptying inhibition. The gastrointestinal action of calcitonin in suckling newborn rats was substantiated by the absorption of [14C]triolein and 14C-labeled amino acids. Hormonal changes that were associated were a decrease in plasma insulin level and an increase in plasma growth hormone concentration. Intravenous calcitonin at a physiological dose (0.03 MRC U/kg) injected into newborn lambs inhibited increases in total plasma lipids, amino acids, and blood-glucose levels at the time of the first suckling period without changing serum calcium levels. One of the physiological roles of calcitonin in the newborn may be the regulation of nutrient absorption from milk rich in lipids.
Effects of theophylline on Na and alanine transport across isolated rabbit ileum
Authors: Fromm D , Field M
Published: December 2017

Addition of theophylline to isolated rabbit ileal mucosa resulted in a persistent increase in short-circuit current (SCC) and a persistent decrease in DC conductance. Under short-circuit condition, net Na flux (JNanet) was reversed by theophylline from absorption to secretion (-0.6 mueq/h cm2) and was due to a decrease in unidirectional mucosal- (M) toserosal (S) flux (JNams). Addition of L-alanine to theophylline-treated m-ucosa increased SCC, JNanet, and JNams. Theophylline reduced JAlanet by 25%. Na flux ratios, determined in the presence of theophylline at +26 and -11 mV (mucosal reference), differed from flux ratios expected for a diffusional process by less than 8%. In contrast, Na flux ratios, determined in the absence of theophylline and presence of glucose at +26 and O mV, differed from diffusional ratios by 35%. The results are consistent with the hypothesis that theophylline inhibits active Na absorption, but the data do not conclusively demonstrate the diffusional nature of unidirectional Na fluxes in the presence of theophylline.
Effect of primary bile acids on bile lipid secretion from perfused dog liver
Authors: Hoffman NE , Donald DE , Hosmann AF
Published: December 2017

An isolated canine liver perfusion technique featuring a second dog as the pump oxygenator was used to compare biliary lipid secretion during randomized, steady-state perfusions at two different rates of cholyl taurine or chenodeoxycholyl taurine infusions. The hepatic extraction of the trihydroxy-conjugated bile acid was considerably greater than that of the dihydroxy conjugate, possibly explained by ultrafiltration experiments which indicated that cholyl taurine was less protein bound than chenodeoxycholyl taurine. Both bile acids induced phospholipid and cholesterol secretion that was linearly proportional to bile acid secretion. However, each mole of secreted chenodeoxycholyl taurine induced a greater relative secretion of phospholipid and cholesterol than did that of cholyl taurine. Thus in the canine liver, the two primary bile acids are extracted at different rates and induce biliary secretion of different relative lipid composition.
Effect of sodium nitrate loading on electrolyte transport by the renal tubule
Authors: Kahn T , Bosch J , Levitt MF , Goldstein MH
Published: December 2017

Effects of sodium nitrate were compared with sodium chloride loading on transport of electrolytes by the nephron. Maximal levels of free water clearance/clomerular filtration rate (CH2O/GFR) averaged 8.4% with nitrate loading and 14.4% with saline loading. Since ethacrynic acid and chlorothiazide exert their major natriuretic effect in the distal nephron, the increment in Na ad Cl reabsorbed beyond the proximal tubule. The administration of these agents resulted in an increase in fractional sodium excretion (CNa/GFR) of 21.1%, urinary sodium excretion (UNaV) of 1,126 mueq/min, and urinary chloride excretion (UClV) of 848 mueq/min during nitrate loading compared with an increase in CNa/GFR of 37.6%, UNaV of 2,362 mueq/min, and UClV of 2,397 mueq/min during saline loading. The smaller diuretic-induced increment in Na and Cl excretion in the nitrate studies suggests, as do the hydrated studies, that less Cl and Na are reabsorbed in the distal nephron during nitrate than saline loading. At every level of UNaV, fractional bicarbonate reabsorption was higher, urine pH was lower, and urinary potassium excretion (UKV) was higher in the nitrate studies. Thus, compared with saline loading, sodium nitrate decreases chloride and sodium reabsorption in the distal nephron. The higher hydrogen and potassium secretion in the nitrate studies may be consequent to the decreased ability of the distal nephron to reabsorb chloride.
Neural mechanisms of sneeze
Authors: Batsel HL , Lines AJ
Published: December 2017

Sneezes were induced in anestized cats by repetitive stimulation of the ethmoidal nerve. Activity of bulbar respiratory neurons during sneezing was recorded extracellularly through tungsten microelectrodes. Most expiratory neurons could be locked onto the stimulus pulses so that they responded either throughout inspiration as well as expiration or so that they began responding at some time during inspiration. As inspiration approached termination, multiple spiking occurred, finally to result in high-frequency bursts which just preceded active expiration. A fraction of expiratory neurons were activated only in bursts. Latent expiratory neurons were recruited in sneezing. Inspiratory neurons near nucleus ambiguus and most of those near fasciculus solitarius displayed similar response patterns consisting of silent periods followed by delayed smooth activations. Temporal characteristics of the silent periods, "inhibitory gaps," suggested that they resulted from inhibition whose source was the expiratory neurons which were driven throughout inspriation. Some inspiratory neurons in the area of fasciculus solitarius failed to exhibit inhibitory gaps.
Drinking and feeding induced by jugular and portal infusions of 2-deoxy-D-glucose
Authors: Russell PJ , Mogenson GJ
Published: December 2017

Intravenous infusions of three levels of 2-deoxy-D-glucose (2DG) were made through chronically implanted jugular and portal cannulas in rats. Food and water intakes were unaffected by 100 mg/kg 2DG, enhanced by 200 and 400 mg/kg 2DG, and unrelated to the route of administration. Drug-induced drinking occurred as readily when food was present as in its absence. Infusions of 2DG also produced stupor and ataxia whose severity was proportional, as was feeding and drinking, to the dose administered. Drinking induced by 2DG is inconsistent with the glucoprivic theory of feeding, and it was proposed that the consummatory and aberrant behaviors elicited by 2DG may result from hypoglycemia-induced seizures in limbic structures of the brain.
Rapid insulin release after ingestion of a meal in the unanesthetized rat
Authors: Strubbe JH , Steffens AB
Published: December 2017

Blood glucose and insulin levels were measured in undisturbed and free-moving rats. The insulin level rises already in the 1st min after the start of food ingestion, whereas the glucose level begins to increase only in the 3rd min if carbohydrate-rich food is eaten. This early rise in insulin level is observed also under conditions in which either carbohydrate-free food or even "food" without any caloric value is offered. The smell of food cannot produce this early insulin response. It is concluded that in the rat other factors besides a rise in nutrient content in the blood produce insulin release in the first minutes after food ingestion.
Hemodynamic consequences of delayed ventriculoconal conduction in the frog Rana catesbeiana
Authors: Liberthson RR , Szidon JP , Bharati S , Lev M , Fishman AP
Published: December 2017

We investigated the function of the conus arteriosus in the bullfrog Rana catesbeiana using a combination of anatomical and physiological techniques. Although there is a normal delay in ventriculoconal conduction and we could induce a spectrum of ventriculoconal conduction disturbances by manipulating the region of the ventriculoconal junction, we found no histological evidence of specialized conducting myocardial tissue in this region. The performance of the conus arteriosus was explored during various disturbances of ventriculoconal conduction and also during hemodynamic disturbances produced by hemorrhage and afterloading. The conus was found to contribute little to forward flow under ordinary circumstances, but its contribution increased greatly during bleeding or partial occlusion of the truncus. In contrast to the conclusion of others, no evidence could be adduced to support the idea that the conus serves as a depulsating chamber. Disparities in previous reports concerning the operation of the conus as a booster pump are attributed to special experimental circumstances.
Extrarenal erythropoietin and erythrogenin production in the anephric rat
Authors: Zucali  , Mirand EA
Published: December 2017

Serum erythropoietin and liver erythrogenin activity were studied in nephrectomized, male rats under variations in intensity and length of hypoxic exposure. In the anephric rat, serum erythropoietin levels parallel liver erythrogenin activity under both mild hypoxia (0.42 atm of air) and severe hypoxia (0.35 atm of air) over a 30-h time period. Further studies demonstrate that anephric rats subjected to 24 h of mild hypoxia, at a time when no elevated serum erythropoietin was detected, could once again be stimulated to produce extrarenal serum erythropoietin which was associated with elevated liver erythrogenin activity. These observations suggest that extrarenal erythropoietin production involves an erythrogenin-serum mechanism similar to the one postulated for renal erythropoietin production.
Hypothalamic map of stimulation current thresholds for inhibition of feeding in rats
Authors: Beltt BM , Keesey RE
Published: December 2017

The rat hypothalamus was mapped for the purpose of identifying regions at which electrical stimulation caused the feeding behavior of a hungry animal to be inhibited. At each inhibitory site a determination was also made of the minimal stimulation current necessary for the inhibition of feeding. The results indicated that the inhibitory sites with the lowest current thresholds tended to form a discrete cluster in the lateral part of the ventromedial nucleus and the adjacent neuropil bordering it ventrolaterally. A few low thresholds were also found in the anterior hypothalamic area. The higher thresholds formed an orderly ascending gradient radiating away from the ventromedial nucleus and its ventrolaterally situated anatomical projections. In areas related to ascending monoamine pathways, including the lateral hypothalamus, preoptic region, and arcuate nucleus, as well as in the mammillary bodies, stimulation usually failed to suppress feeding behavior. Implications bearing on neuroregulatory models of feeding behavior are discussed.
An analysis of the time course of gustatory neural adaptation in the rat
Authors: Smith DV , Steadman JW , Rhodine CN
Published: December 2017

Neural responses were recorded from the rat chorda tympani nerve following stimulation of the tongue with several concentrations of NaCl. These responses were integrated using a fast time constant (47 ms), and the time course of the decline in neural discharge from the peak of the transient response was computer analyzed. The time course of the adaptation process was described by a constant term and two exponentially decaying components, which most likely reflect the existence of two separate mechanisms contributing to the adaptation process in taste. The constant term and the amplitude of the second gradual exponential decay were correlated with NaCl concentration, whereas the amplitude of the initial rapidly declining exponential component was independent of stimulus intensity. The initial transient response of the chorda tympani nerve may be a function of the rate of stimulus adsorption, whereas the gradual second decline in the neural response may reflect an adaptive mechanism of the taste receptor cell.
Metabolic background for glucose tolerance: mechanism for epinephrine-induced impairment
Authors: Skikama H , Ui M
Published: December 2017

Turnover rates of blood glucose in rats were calculated from the decay of [14C]glucose. A glucose load suppressed glucose appearance and this was reversed by epinephrine or glucagon. Incorporation of [14C]bicarbonate into liver glycogen and blood glucose demonstrated that these hormones did not alter gluconeogetic rate but, rather the proportion of glucose recovered in the two products. The glucose enhanced by glucagon, probably through increased insulin secretion. In contrast, epinephrine decreased peripheral glucose uptake.
Adrenergic mechanisms in canine gastric circulation
Authors: Zinner MJ , Kerr JC , Reynolds DG
Published: December 2017

The effects of adrenergic stimulation and blockade on the gastric circulation were studied in anesthetized dogs. Blood flow through the right and left gastric artery was measured electromagnetically. Norepinephrine and isoproterenol were injected intra-arterially and intravenously before and after alpha- and beta-adrenergic blockade. Isoproterenol caused vasodilation of both right and left gastric circulations and this effect was attenuated by beta blockade. Epinephrine and norepinephrine induced constriction followed by dilation in both circulations. The constrictor components were attenuated or abolished by alpha-adrenergic blockade and the dilator components were attenuated by beta-adrenergic blockade. The right and left gastric vascular beds demonstrated quantitatively different responses to the same dose of each adrenergic amine. The left gastric circulation had a greater vasodilator response than did the right gastric circulation. These data support the classical concepts that epinephrine and norepinephrine are "mixed" adrenergic agonists and isoproterenol is a "pure" beta-adrenerigic agonist. The data further suggest that there is a differential in beta-adrenergic receptor distribution with the left gastric vasculature demonstrating greater dilator responses than the right.
45Ca efflux from anterior byssus retractor muscle in phasic and catch contraction
Authors: Bloomquist E , Curtis BA
Published: December 2017

Phasic or catch contractions in Mytilus anterior byssus retractor muscle (ABRM) were activated by acetylcholine (ACh) and catch relaxation was initiated by 5-hydroxytryptamine (5HT). During phasic contraction and early in catch there is a brief increase in 45Ca efflux. When catch occurs, there is a subsequent drop in 45Ca efflux which then slowly recovers as catch tension declines. With catch relaxation by 5HT there is a biphasic increase in 45Ca efflux, identical to that seen when 5HT is applied to resting muscle. Compartment analyses based on the magnitude of pairs of these responses at varying times of the washout indicated that the increase in 45Ca efflux with activation originates from a compartment with the same time constant as the intermediate (80--100 min) compartment already described by previous resting efflux experiments. The decrease in 45Ca efflux during catch also involves this compartment. The increase in 45Ca efflux with 5HT originates from a more slowly exchanging Ca store with a time constant of approximately200 min.
Vasomotor inhibition in rabbits by vagal nonmedullated fibers from cardiopulmonary area
Authors: Thoren PN , Mancia G , Shepherd JT
Published: December 2017

In anesthetized rabbits with sinus and aortic nerve cut, when the cervical vagal nerves were cooled to 12, 8, 6, and 0degreeC, there were progressive increases in aortic blood pressure of 7 +/- 1, 15 +/- 2, 25 +/- 1, and 41 +/- 2 mmHg (SE), respectively. For comparison, during cooling of the aortic and vagal nerves, at 12degreesC there was a decrease in firing in the afferent fibers from aortic baroreceptors (48 +/- 4%) and pulmonary stretch receptors (57 +/- 5%), and at 6degreesC all activity was abolished. Thus, at 6degreesC the activity in medullated fibers from the aortic baroreceptors and pulmonary stretch receptors is blocked, but the increase in aortic blood pressure with vagal cooling is only 60% of that with cooling to 0degreeC. This demonstrates that cardiopulmonary receptors with nonmedullated vagal afferents (C fibers) contribute to the tonic inhibition of the vasomotor center. Because of overlap in sensitivity of different vagal fibers to cooling, the total contribution of these C fibers cannot be evaluated.
Phosphaturic effect of furosemide: role of PTH and carbonic anhydrase
Authors: Haas J. A. , Larson M. V. , Marchand G. R. , Lang F. C. , Greger R. F. , Knox F. G.
Published: December 2017

The first objective of this study was to examine the effects of furosemide on renal phosphate excretion in the presence and absence of a constant level of parathyroid hormone (PTH) while extracellular fluid volume was held constant. In the absence of PTH, furosemide did not significantly increase fractional phosphate excretion (FEP%, 4.2 +/- 2.7 to 6.2 +/- 1.9%; five dogs). In the presence of PTH, furosemide increased FEP% from 23.4 +/- 3.7 to 33.8 +/- 6.0% (P less .025; five dogs). Thus, the phosphaturia induced by furosemide was dependent on the presence of PTH. The second objective was to evaluate the hypothesis that furosemide exerts its phosphaturic effect through carbonic anhydrase inhibition, and therefore we tested for additivity of the phosphaturic effect of furosemide, and acetazolamide. In the presence of a constant level of PTH, acetazolamide increased FEP % from 24.5 +/- 1.8% to 40.7 +/- 5.1% P less than .025, five dogs. The subsequent administration of furosemide did not further increase FEP%, delta 3.3 +/- 8.9%; NS. Thus, the phosphaturic effect of furosemide was not additive to that of acetazolamide, indicating that acetazolamide and furosemide may share similar mechanisms for inhibiting phosphate reabsorption.
Freeze-fracture electron microscopy: relationship of membrane structural features to transport physiology
Authors: Wade J. B. , Kachadorian W. A. , DiScala V. A.
Published: December 2017

Recent observations utilizing freeze-fracturing electron microscopy are discussed which indicate that the membrane structural features visualized by this technique may in some instances be related to specialized membrane transport properties. The occurrence of organized aggregates of intramembrane particles observed in vasopressin or cAMP-treated toad urinary bladder has been found to be closely correlated with induced changes in the permeability of the luminal membrane. Although a cautious interpretation is considered appropriate, these observations raise the possibility that some aspects of hormone action may be restricted to limited regions of membrane. Difficulties in interpretation and some serious limitations of the freeze-fracture technique are discussed.
A smooth muscle active factor isolated from renal cortex of the rabbit
Authors: Brown C. B. , Drum D. E. , Hollenberg N. K.
Published: December 2017

Homogenates of rabbit renal cortex contained a water-soluble material with striking activity on smooth muscle derived from the rabbit aorta, rat stomach, and guinea pig ileum--but not rat colon or chick rectum. Evidence derived from the spectrum of its pharmacologic activity, the influence of specific competitive antagonists on the smooth muscle responses to the factor, the influence of proteolytic enzymes and its elution position during molecular sieve filtration on Sephadex G-10 made it unlikely that the factor was a prostaglandin, renin, angiotensin, a catecholamine, serotonin, bradykinin, a nucleotide, a small organic product of local metabolism, or a small ion. The agent was not found in extracts of renal medulla, spleen, myocardium, or lung. The smooth muscle response to the factor was blocked by phenoxybenzamine. The renal cortical factor in subthreshold concentration also potentiated responses of the rabbit aorta to angiotensin and norepinephrine. The factor's intrinsic activity and ability to potentiate the smooth muscle actions of endogenous vasoconstrictors make it a candidate as a mediator of smooth muscle responses in a number of states.
A reinvestigation of the function of the mammalian urinary bladder
Authors: Lewis S. A.
Published: December 2017

The function of adult mammalian urinary bladder is evaluated in light of recent in vitro experiments. The discrepancy between in vivo and in vitro experimental results is examined and a possible solution proposed. Techniques for eliminating edge damage and measuring apical membrane surface area are described. A new chamber design for microelectrode studies is illustrated. The possibility of apical cell membrane damage caused by microelectrodes is critically examined and tested using the polyene antibiotic Nystatin. Using data from transepithelial and microelectrode experiments, a model for net Na+ transport across the bladder is proposed and then critically analyzed. The possible clinical implications of the in vitro experiments are briefly discussed.
Function of the thin ascending limb of Henle of rats and hamsters perfused in vitro
Authors: Imai M.
Published: December 2017

In order too examine whether there is species difference in the function of the thin ascending limb of Henle (tALH), segments isolated from rat and hamster kidneys were perfused in vitro and compared to results obtained by identical techniques from rabbits. The net water flux and the transtubular potential difference were not different from zero. The osmotic water permeability of the rat and hamster tALH was unmeasurably small. Isotopic and electrically determined permeabilities for Cl- and Na+ were quite high in both species, with Cl- being approximately twice as permeable as Na+. Urea permeability across the tALH of both species was moderate. Solute permeability to NaCl, urea, and raffinose (10(-5) cm sec-1) of the tALH of both species was determined by measuring changes in osmolality of the collected fluid when each solute was added to the bath at the same osmolality. They were 82.2, 38.3, and 6.9, respectively. The relative permeabilities to various ions were estimated from the deflection of the transtubular potential difference when NaCl in the bathing medium was replaced by various salts. The following sequence of permeabilities was obtained across the tALH from both the rat and hamster: Cl- greater than or equal to Br- greater than or equal to SCN- greater than or equal to I- greater than or equal to Na+ = K+ greater than Li+ greater than choline+ greater than or equal to HCO3- greater than acetate- greater than or equal to cyclamate-. These data indicate that membrane characteristics of the tALH of rats and hamsters are similar to the previously published values of rabbits. The conclusion is drawn that the principle of the passive equilibrating model of the countercurrent multiplication system is operative in other mammalian species besides the rabbit.
Effect of potassium on utilization of (1-14C)palmitic acid in renal cortex of the rat
Authors: Wagner M. E. , Heinemann H. O.
Published: December 2017

The renal cortex has an unusually high rate of palmitic acid utilization. The uptake, oxidation, and distribution of this fatty acid in the cortex, unlike other tissues, responds to variations in medium and tissue potassium content. This potassium dependency is mimicked and amplified by rubidium. These observations indicate that in the renal cortex, both potassium and rubidium promote the accumulation, oxidation, and esterification of palmitic acid.
Stimulation of renal sodium reabsorption by angiotensin II
Authors: Johnson M. D. , Malvin R. L.
Published: December 2017

Various parameters of renal function were studied before, during, and after the infusion of physiological increments of angiotensin II directly into one renal artery of anesthetized dogs. During water diuresis and during antidiuresis induced with exogenous antidiuretic hormone (ADH), angiotensin II consistently reduced UNaV, UKV, and CPAH, and increased the filtration fraction in the infused kidney. Urinary osmolality was increased only in the presence of ADH, while during water diuresis angiotensin II had no apparent effect on urinary osmolality or flow rate. During saline diuresis, a mean increment of angiotensin II concentration of 14 pg/ml was sufficient to significantly reduce UNaV and urinary flow rate. Changes in CCr, CPAH, and filtration fraction did not correlate with changes in sodium excretion, and intracortical distribution of blood flow remained unaltered. These data support the hypothesis that normal circulating levels of angiogensin II play a direct renal role in the control of sodium, potassium, and water homeostasis, and that angiotensin II exerts a direct, stimulatory effect on tubular sodium reabsorption independent of changes in GFR, RPF, filtration fraction, or intracortical distribution of blood flow.
pH gradients in the developing teeth of young mice from autoradiography of [14C]DMO
Authors: Lyman G. E. , Waddell W. J.
Published: December 2017

The distribution of the weak acid [14C]DMO was studied in mice, 10-19 days old, by an autoradiographic technique that does not translocate or remove the compound. Calculations of pH values in areas of the developing teeth of these animals were made by comparing the photometric density of the distribution of [14C]DMO, as an indicator of pH, with that of 14C]NAAP, as an indicator of water content, which was reported in the companion paper. The cellular layers, i.e., odontoblasts, ameloblasts, etc., had pH values of 7.1 +/- 0.1; the pH values in enamel, predentine, and dentine ranged from 7.3 to 8.5. It is suggested that an alkaline matrix promotes nucleation and growth of hydroxyapatite.
Electron probe microanalysis: its present, its future
Authors: Lechene C. P.
Published: December 2017

Electron probe microanalysis (EPM) is a method of elemental ultramicroanalysis based on the spectrometry of the characteristic X rays which are emitted when a target sample is excited by an electron beam. In the same sample many more elements (from carbon and up in the periodic table) in much smaller volumes (less than 1 micronm3 or 10(-15) liter) can be analyzed with EPM than with any other ultramicroanalytical method. Quantitation down to 10(-15) g is relatively easy. Any application of EPM in biology depends on the development of suitable methods for biological sample preparation. Liquid droplets of 10(-11)-liter volumes are routinely analyzed. Elemental content in isolated cells can be quantitated. The analysis of cellular, extracellular, and intercellular content in the same preparation is in sight: a general method for the analysis of diffusible elements in different compartments in tissue relies on the manipulation of frozen hydrated tissue near liquid nitrogen temperature. Localization in the same preparation of several organic compounds at high resolution will be possible by use of appropriate tags. All fields of microphysiology are likely to benefit from this new discipline.
Effects of alpha-adrenergic blockade on renal function in hemorrhagic shock
Authors: Feigen L. P. , Coleman B. , Glaviano V. V.
Published: December 2017

This study was undertaken to determine whether alpha-adrenergic blockade would reverse the altered kidney function in hemorrhagic shock. Urinary excretion of Na+, K+, and total solute were studied in 10 anesthetized dogs before and after administration of phenoxybenzamine (PBZ) in shock. Five of the 10 dogs were used to evaluate the effect of shock on renal hemodynamics. Another group of five dogs was used as controls. Normovolemic shock caused a reduction in renal blood flow (RBF) from 9.0 +/- 1 to 6.0 +/- 0.6 ml/min per kg, and an increase in renal vascular resistance (RVR) (P less than .05). When compared to the untreated shock animals, phenoxybenzamine caused an 83% increase in RBF and a 53% decrease in RVR. Treatment of control animals with phenoxybenzamine resulted in a 10-fold increase in urinary [Na+], while urinary [K+] remained unchanged. Neither urinary [K+] nor urinary [Na+] was affected significantly by PBZ in the shock group. Although the excretion rate for Na+ was increased severalfold in the untreated shocked animals when compared to controls (14.0 +/- 3 vs. 1.7 microneq/min) the excretion rates for K+ (P less than .05) and total osmotically active substances (P less than .01) diminished. Phenoxybenzamine caused significant increases in the excretion rates for Na+ and K+ in both the control and shocked dogs. The observed changes in excretion rates when PBZ was given most likely reflect drug-induced changes in renal hemodynamics.
Tracer Na fluxes in Necturus proximal tubule
Authors: Spring K. R. , Giebisch G.
Published: December 2017

Steady-state bidirectional sodium fluxes were measured across Necturus proximal tubules. New methods for capillary perfusion and collection of venous effluent enabled flux determination to be made from the appearance of luminal tracer in the capillaries. Fluxes and permeability were measured in the absence of net fluid reabsorption. The sodium permeability measured in the plasma-to-lumen direction was 3 X 10(-6) cm/s. The flux ratio (lumen-to-plasma/plasma-to-lumen) was about twice the passive value calculated from the measured concentrations and potentials. Estimates for the permeability and flux across the shunt pathway were obtained from nonsteady-state flux determinations. The shunt pathway appeared to be the most significant route for passive sodium movement from plasma-to-lumen. Nonsteady-state tracer measurements also enabled an estimate to be made of the lumenal cell membrane permeability and unidirectional sodium flux. Two-thirds of the lumen-to-plasma flux was calculated to traverse the cellular path and the remainder through the shunt. Approximately one-third of the intracellular sodium was found to exchange rapidly with tracer.
Active hydrogen excretion and sodium absorption through isolated frog skin
Authors: Ehrenfeld J. , Garcia-Romeu F.
Published: December 2017

The in vitro skin of Rana esculenta was studied in open-circuit conditions. It was shown that when the external face is bathed in a 2-meq solution of NaCl, sodium is absorbed at a significantly higher rate than chloride. The ionic balance is maintained by excretion of hydrogen. With a mucosal solution of 2 meq Na2SO4 the equation relating sodium absorption to proton excretion is JnH+ = (-25 +/- 7) - (0.73 +/- 0.04) JnNa+. The correlation between the two variables is highly significant. Hydrogen excretion obeys saturation kinetics in relation to the sodium concentration of the mucosal solution. Maximum excretion occurs at a sodium concentration of 4 meq. When the mucosal solution is a 115-meq solution of Na2SO4 the net flux of sodium is 2.3 times higher than that of hydrogen. The balance is maintained by absorption of SO42-. The effects of various substances on the Na+ext/H+int exchange were studied. With a mucosal solution of 2 meq Na2SO4 and short-circuit conditions it was shown that the hydrogen excretion is active and nearly the same as in open circuit, the short-circuit current is equal (to within 8%) to the sum of the sodium and hydrogen net fluxes, and the correlation between the movements of the two ions is low. A model relating the active proton excretion with the sodium transport mechanism is proposed.
Effect of glycine and glucagon on glomerular filtration and renal metabolic rates
Authors: Johannesen J. , Lie M. , Kiil F.
Published: December 2017

A rise in glomerular filtration rate (GFR) during saline infusion increases outer medullary more than cortical metabolic rate. To determine whether other GFR-increasing agents have a similar effect, renal metabolic rates were estimated by the heat-production technique during infusion of glycine or glucagon. Glycine and glucagon increased GFR by 17 +/- 2 and 32 +/- 2%, renal blood flow (RBF) by 34 and 21%, and outer medullary metabolic rate by 42 +/- 3 and 59 +/- 4%, respectively. Cortical metabolic rate rose by 7 +/- 1% during glucagon, and it increased by 29 +/- 2% during glycine infusion, suggesting a stimulation unrelated to sodium reabsorption. To determine whether glucagon influenced renal metabolism independent of its GFR-increasing effects, vasodilation was achieved by ureteral or suprarenal aortic constriction. Glucagon was without effect on RBF, GFR, and metabolic rate, but infusion of acetylcholine still raised RBF. We conclude that glucagon increases GFR by dilating vascular segments participating in autoregulation, and that energy-requiring NaCl reabsorption in the outer medulla is increased secondary to increased delivery of NaCl.
Neurogenic regulation of renal tubular sodium reabsorption
Authors: DiBona G. F.
Published: December 2017

The evidence supporting a role for direct neurogenic control of renal tubular sodium reabsorption is reviewed. Electron microscopic and fluorescence histochemical studies have demonstrated adrenergic nerve terminals in direct contact with basement membranes of mammalian (rat, dog, and monkey) renal tubular epithelial cells. Low-level direct or baroreceptor reflex stimulation of renal sympathetic nerves produces an increase in renal tubular sodium reabsorption without alterations in glomerular filtration rate, renal blood flow, or intrarenal distribution of blood flow. Antinatriuresis was prevented by prior treatment of the kidney with guanethidine or phenoxybenzamine. Rat kidney micropuncture studies have localized a site of enhanced tubular sodium reabsorption to the proximal tubule. Possible indirect mediation of the antinatriuresis by other humoral agents known to be released from the kidney on renal nerve stimulation (angiotensin II, prostaglandin) was excluded by experiments with appropriate blocking agents. The possible effects of anesthesia and uncertainties about the completeness of surgical renal denervation and other tubular segmental sites of action are critically analyzed. The clinical implications of this mechanism in pathologic conditions of sodium and water retention are discussed and and a prospectus for future work is presented.
Renal energy metabolism and sodium reabsorption after 2,4-dinitrophenol administration
Authors: Johannesen J. , Lie M. , Kiil F.
Published: December 2017

2,4-Dinitrophenol (DNP) (10 mg/kg body wt i.v.) increased renal cortical and outer medullary heat production rates and oxygen consumption by 70–90% in anesthetized dogs over a 90-min observation period without exerting any natriuretic effect. To examine whether DNP inhibited proximal reabsorption and increased distal delivery, ethacrynic acid (3 mg/kg body wt) was infused during maximal DNP effect. Sodium reabsorption fell by 14 +/- 6% in the cortex and 55 +/- 8% in the outer medulla, not significantly different from control experiments without DNP. Conversely, after ethacrynic acid administration, DNP had no additional natriuretic effect. Since DNP did not stimulate renal anaerobic metabolism (no lactate release), the effect of DNP was examined during hypoxia induced by intravenous infusion of NaCN (0.2 mumol/kg body wt-min) until renal metabolic rates fell. Subsequent infusion of DNP reduced tubular sodium reabsorption from 90 +/- 2 to 78 +/- 6%. Thus, DNP may raise renal metabolic rates by 70–90% without inhibiting sodium reabsorption, but, under conditions of hypoxia, DNP reduces sodium reabsorption and increases sodium excretion.
Indirect measurement of total exchangeable potassium
Authors: Shizgal H. M. , Spanier A. H. , Humes J. , Wood C. D.
Published: December 2017

A technique is described for the indirect measurement of total exchangeable potassium (Ke) that involves neither the rapidly decaying radioisotopes of potassium nor a total body counter. Total exchangeable sodium (Nae) and total body water (TBW) are measured by isotope dilution. Ke is calculated from Ke = R (TBW) - Nae, where R is the ratio of the sodium plus potassium content divided by the water content, in a sample of whole blood. In 19 normal rats and four rats with uremia there was an insignificant difference between the indirect determination of Ke and its direct measurement by carcass analysis. A similar insignificant difference was recorded between the indirect determination of Ke and its direct measurement by potassium-42 dilution in 15 normal dogs, five dogs with uremia, 14 dogs in an hyposmolar state, and in 20 patients. In 25 normal volunteers, Ke was determined indirectly. The regression of Ke on TBW and the 95% confidence intervals of this population was similar to published data in which Ke was determined by potassium-42 dilution. The indirect measurement of Ke was, therefore, validated experimentally.
Bicarbonate transport by isolated perfused rabbit proximal convoluted tubules
Authors: Burg M. , Green N.
Published: December 2017

Proximal convoluted tubules were dissected from rabbit kidneys and perfused in vitro in order to investigate the relationship between the reabsorption of fluid and of bicarbonate. Bicarbonate was absorbed when it was initially present in the perfusate. At slow rates of perfusion the mean concentration of total CO2 was 9 mM in collected fluid with 25 mM bicarbonate in the bath. At faster rates of perfusion the mean rate of reabsorption was 13.6 pmol cm-1 tubule length s-1. Absorption of bicarbonate was inhibited to a large but not complete extent by elimination of sodium from the perfusate and bath or potassium from the bath, and by addition of ouabain. It was not inhibited by elimination of the organic solutes from the perfusate nor by elimination of chloride from the perfusate and bath. Considered with previous measurements of fluid absorption these results are consistent with the existence of a linked sodium-for-hydrogen ion exchange mechanism at the luminal border of the tubule cells, but there are other possibilities which are discussed. Additionally, the effect of acetazolamide was investigated. The drug virtually completely inhibited bicarbonate absorption and inhibited fluid absorption by 30-40%.
Effect of basement membrane and colloid osmotic pressure on renal tubule cell volume
Authors: Linshaw M. A. , Stapleton F. B. , Cuppage F. E. , Grantham J. J.
Published: December 2017

Renal tubule cell volume is thought to be kept constant by a cation pump. When active transport is blocked, intracellular impermeant solutes cause cells to swell. Cell size is then determined by transmembrane hydrostatic and colloid osmotic forces. We studied the importance of passive transmembrane forces in determining cell size in isolated rabbit proximal straight tubules (PST). We blocked active solute transport with ouabain and evaluated subsequent changes in cell size by measuring outer diameter of nonperfused tubules. Tubules in a ouabain and 6 g/100 ml protein bath swelled only 40% above control. However, removal of the tubule basement membrane with collagenase dissipated a transmembrane hydrostatic pressure and caused more swelling. Final cell volume was determined largely by bath protein concentration. Tubules in ouabain and collagenase swelled enormously in hyponcotic protein, moderately in isoncotic protein, and could be shrunk below control in hyperoncotic protein. Intracellular colloid osmotic pressure was estimated to exceed 38 cmH20. We conclude that hydrostatic and colloid osmotic forces are major determinants of cell size in isolated PST treated with ouabain.
pH-temperature dependence of organic acid transport in rat kidney slices
Authors: Park Y. S. , Solomon S.
Published: December 2017

Uptake of p-aminohippurate (PAH) by rat kidney slices was optimal at a pH of around 7.3 when incubation temperature was 37 degrees C. At 25 degrees C, however, optimal pH was increased to about 7.5. When the uptake was evaluated as a function of the OH/H ratio of the medium, it was found that optimal uptake is at a constant OH/H. Data showing the same characteristics of OH/H dependence were also observed for phenol red. Passive uptake of PAH was pH independent. Efflux rates for PAH also showed the pH optimal which was identical to that of uptake. At both 25 and 37 degrees C the Km appeared to be independent of pH while the maximum rate of active influx. An optimal OH/H ratio determines maximal velocity and this ratio is fixed and independent of temperature.
Renal sodium reabsorption following induction of recovery from volume expansion
Authors: Knight T. F. , Weinman E. J.
Published: December 2017

In the rat, infusion of a volume of isotonic saline equal to 2% of body weight resulted in an 82% increase in delivery of filtrate out of the proximal tubule but little or, in some animals, no change in the urinary excretion of sodium. By contrast, further degrees of volume expansion resulted in lesser increases in the distal delivery of filtrate, but were associated with a marked increase in the urinary excretion of sodium. Sixty minutes following completion of volume expansion, while the animals were still in positive sosium balance, the urinary excretion of sodium decreased 52% compared to a decrease of only 24% in the distal delivery of filtrate. During the course of progressive volume expansion and during the recovery phase, there was a dissociation between alterations in sodium reabosrption in the proximal convoluted tubule and in the whole kidney. These studies indicate that although the proximal tubule is more sensitive to changes in the extracellular fluid volume, distal nephron sites are ultimately responsible both for the natriuresis of volume expansion and the relative antinatriuresis of the recovery periods.