bluuebunny/crossref_metadata_2025 huggingface dataset:
Dietary regulation of liver and muscle transport of amino acid
Authors: Adibi SA , Morse EL , Mirsky IA
Published: December 2017

Distribution ratios (intracellular concn/extracellular concn) of alpha-amino isobutyric acid (AIB) after intravenous injection were determined in fed, 12-h, 1-day, and 5-day starved rats. Progressive increases (over fourfold) in the distribution ratios of AIB in the liver and progressive decreases (over threefold) in the gastrocnemius muscle occurred within these periods. On full day of protein deprivation was without effect on AIB distribution ratios, but after 5 days it produced an increased distribution ratio of AIB in the liver (twofold), without affecting that of the muscle. A sudden increase in hepatic glucose output, induced by phlorizin, was followed by an increase in the liver distribution ratio of AIB. In starvation the increase in plasma concentration of glucagon and decrease in insulin level preceded the changes in AIB distribution ratios; in protein deprivation there was no change in plasma concentrations of these hormones. It is concluded that caloric restriction profoundly affects amino acid transport by the liver and by the skeletal muscle. These transport changes would enhance the availability of substrates for increased gluconeogenesis during starvation.
Reflex effects of thermal stimulation on sympathetic nerve activity to skin and kidney
Authors: Ninomiya I , Fujita S
Published: December 2017

Effects of peripheral and central thermoreceptor reflexes on sympathetic nerve activity to the skin (SkNA) and kidney (RNA) were compared in anesthetized cats. Sudden warming of the skin produced a rapid increase of RNA, wheras sudden cooling produced a rapid increase of SkNA. When the bath temperature (TB) was 17.6, 29.7, and 41.9 degrees C, the normalized SkNA was 100, 82, and 48%, while the normalized RNA was 81, 90, and 100%, respectively. Similarly, under open baroceptor loop conditions, SkNA changed inversely with TB, while RNA changed proportionally to TB. Changes in the temperature of the whole brain including hypothalamus (Thy) modified the amplitude of grouped RNA and SkNA synchronously with the cardiac cycle. At TB of 32.4 degrees C, when Thy was altered in a range of 30-42 degrees C, SkNA reached a maximum level at a Thy of 38.4 degrees C, whereas RNA reached a maximum above 42 degrees C. In a Thy range of 38-42 degrees C, the slopes of the Thy-SkNA curve and Thy-RNA curve were 30 and +4%/degrees C, respectively. At Thy below 38 degrees C, SkNA and RNA changed in parallel with Thy. Continuous cooling of the skin modified the slope of the TB-SkNA curve, but a small change of Thy caused a shift of the TB-SkNA curve.
Effects of chlorobutanol and bradykinin on myocardial excitation
Authors: Hermsmeyer K , Aprigliano O
Published: December 2017

The negative inotropic effect of a commonly used formulation of bradykinin (Sandoz BRS-640) was found to be due to chlorobutanol, a constituent of the preparation. Solutions containing up to 100 mug of crystalline bradykinin/ml had no effect on tension or action-potential shape. Chlorobutanol (500 mug/ml) caused a 30% decrease in contraction amplitude and a 20% increase in action-potential duration. Chlorobutanol lowered conduction velocity and induced conduction failure and automaticity within isolated ventricular muscle strips. Chlorobutanol affected neither positive nor negative treppe. We conclude that bradykinin has no direct action on toad, frog, or rat myocardium. However, chlorobutanol does have direct effects on myocardial cells, acting on the cell membrane and decreasing isometric tension produced by the heart.
Renin-angiotensin-aldosterone system in experimental renal hypertension in the rabbit
Authors: Lohmeier TE , Davis JO
Published: December 2017

Hypertension was produced in 25 rabbits by constricting the right renal artery and leaving the opposite kidney intact (two-kidney hypertension). After 30 days mean arterial pressure and plasma renin activity (PRA) were significantly elevated (P less than 0.01), and arterial pressure was correlated with PRA (r = 0.551, P less than 0.01); however, not all hypertensive rabbits had elevated PRA, and in animals in which sodium balance was monitored, only rabbits in negative sodium balance had increased levels of PRA. To investigate the role of angiotensin II (A-II) in the hypertension, [1-sarcosine,8-alanine]angiotensin II was infused at 6 mug/kg per min for 30 min in anesthetized hypertensive animals (n = 25). For the group, arterial pressure fell significantly (P less than 0.01), but several animals with minimal hypertension failed to give a depressor response. The declines in arterial pressure were highly correlated with PRA (r = 0.853, P less than 0.01). Aldosterone secretion in hypertensive animals was correlated with PRA (r = 0.851, P less than 0.01). Thus, two-kidney hypertension in the rabbit persists with normal PRA, but during periods of spontaneous sodium depletion, A-II plays a role in the maintenance of the hypertension.
Characteristics of intestinal phase of gastric secretion
Authors: Konturek SJ , Kaess H , Kwiecien N , Radecki T , Dorner M , Teckentrupp U
Published: December 2017

In four dogs provided with special gastroduodenal fistulas allowing for the complete separation of stomach and duodenum without interrupting the vagal connections between them, the magnitude of the gastric and intestinal phases was compared and their contribution to the total gastric response to a meal was established. A liver extract (LE) meal, confined to the stomach and maintained at pH 5.0 by an intragastric titration technique, produced acid output reaching 66% of the maximal response to histamine (MRH). Perfusion of the LE meal into the duodenum resulted in acid secretion amounting to 57% of MRH. The combination of the gastric and intestinal phases caused the highest acid output, amounting to about 90% of MRH. Gastric and intestinal phases induced separately were accompanied by a significant elevation in serum gastrin concentrations which reached the highest values when both phases were evoked simultaneously. Acidification of the intestinal meal resulted in pH-dependent inhibition of gastric secretion falling to the basal values at pH 1.0. These secretory changes were mimicked by exogenous secretin. Serum gastrin levels remained essentially unaffected by the acidification of the intestinal meal while exogenous secretin significantly lowered them. In conclusion, in the intact stomach with undisturbed nervous connections between the stomach and duodenum, a peptone meal in the intestine is capable of evoking a potent gastric acid and pepsin stimulation by a mechanism involving the release of antral hormone.
Inhibition of gastric secretion in the dog by 16,16-dimethyl prostaglandin E2
Authors: Mihas AA , Gibson RG , Hirschowitz BI
Published: December 2017

The synthetic prostaglandin 16,16-dimethyl E2 (PGE2) given by intravenous infusion at 0.4 mug/kg-h inhibited gastric secretion of H+, K+, Cl-, and pepsin in four fistula dogs stimulated by histamine (H), pentagastrin (P), urecholine (U), and 2-deoxy-D-glucose (2-DG). When given for 90 min during steady infusions of near-maximal doses of H, P, and U, PG-E2 caused 75% inhibition of H+ maximally at 90 min and over 85% inhibition of pepsin secretion maximally at 45 min. Recovery of secretion took 1-2 h after infusion of PGE2 was stopped. Injection of KCl, 1 meq/kg, during inhibition of histamine by PGE2 gave only a 15-min transient reversal in inhibition. When PGE2 was given as background to 45-min step-dose responses, 0.1 mug/kg competitively inhibited histamine stimulation and 0.4 mug/kg-h gave 100% inhibition. Against pentagastrin, 0.1 mug PGE2/kg-h had no effect and 0.4 mug caused uncompetitive inhibition; against urecholine, 0.4 mug PGE2/kg-h caused competitive inhibition of H+ secretion. Pepsin was more markedly inhibited in each case. There were no side effects at either dose of PGE2, which is a potent inhibitor of gastric secretion with all forms of stimuli.
Effects of age and fasting on gluconeogenesis from glycerol in dogs
Authors: Hall SE , Hall AJ , Layberry RA , Berman M , Hetenyi G
Published: December 2017

The extent of gluconeogenesis from glycerol was examined in pups and adult dogs. With use of the SAAM-26 program, a four compartment model was formulated from tracer data to calculate the kinetics of the glycerol:glucose system. In the postabsorptive state gluconeogenesis from glycerol declines with age: 13.8% of glucose carbon originated from glycerol in 0- to 4-day-old pups, 6% in adults. Approximately 50% of glycerol carbon is converted to glucose carbon independent of age. During fasting, a) the percentage of glucose carbon arising from glycerol carbon increased to 13.3% and 10.3% in adult dogs and pups 5-19 days old, respectively, in younger pups it declined to 3.4%; b) glycerol production increased in adults, but decreased in the youngest pups; c) glucose production and utilization decreased at all ages, and a smaller percentage of glycerol carbon was converted to glucose carbon, especially in the youngest pups. Thus in neonates fasting decreases gluconeogenesis from glycerol.
Gastroduodenal motor gradients in the dog after pyloroplasty
Authors: Ormsbee HS  , Bass P
Published: December 2017

Circular muscle contractile activity of the antrum and duodenum and gastric emptying of a liquid test meal were investigated in unanesthetized dogs in which the gastroduodenal junction (GDJ) was altered (Heineke-Mikulicz pyloroplasty). After pyloroplasty, antralization (antral-like contractions occurring in the first portion of the duodenum) was observed during the digestive state. Antralization replaced the normal periods of inhibition that separate periods of duodenal contractions during the interdigestive burst. Bethanechol (0.1 mg/kg sc) and metoclopramide (2.0 mg/kg iv) were capable of stimulating interdigestive contractile activity in the altered GDJ. Pentagastrin (1.0 mug/min iv) produced a differential stimulation on the antrum without appreciably affecting duodenal contractile activity. Pyloroplasty also enhanced the emptying of a 300-ml citrate-fat liquid test meal. An intact hypomuscular segment between the antrum and duodenum is important for normal coordinated contractile activity between the antrum and the duodenum and for the normal gastric emptying of liquids.
Natriuresis induced by intracarotid infusion of hypertonic NaCl
Authors: Zucker IH , Kaley G
Published: December 2017

The intracarotid infusion of hypertonic sodium chloride in anesthetized dogs pretreated with vasopressin and mineralocorticoid resulted in an increase in sodium excretion as well as an increase in the percent of the filtered load of sodium excreted. This increase was not due to changes in renal hemodynamics or arterial blood pressure. The change in fractional sodium excretion was approximately 1%. Intracarotid infusion of isotonic sodium chloride did not result in a natriuretic response. The intracarotid infusion of hyperosmotic glucose did not evoke an increase in sodium excretion. Femoral vein infusions of hypertonic sodium chloride failed to evoke any natriuretic response. These data indicate that a sodium-sensing mechanism may exist in the brain that can alter the renal handling of sodium. The efferent mechanism of the response is discussed.
Concentration-dependent dissociation of factor VIII in 1 M NaCl
Authors: Sussman  , Rosner W , Weiss HJ
Published: December 2017

Plasma, cryoprecipitate, Hemofil, and human factor VIII concentrate were dissolved in 1.0 M NaCl and chromatographed on Bio-Gel A-5m. With high concentrations of factor VIII the activity eluted as a symmetrical peak in the void volume; with a low factor VIII concentration the procoagulant activity was retarded. Dilution curves were performed for several human factor VIII concentrates. When the concentration of factor VIII was decreased, elution patterns showed a gradual transition from a peak in the void volume to a peak with a Ve/Vo of 1.7. Cryoprecipitate exhibited a similar behavior in 1.0 M NaCl, but the percent dissociation was greater than expected at high concentrations of factor VIII. When gel filtration was performed with 0.25 M CaCl2, significant dissociation occurred at all concentrations of factor VIII tested. The behavior of factor VIII in 1.0 M NaCl closely fit a theoretically derived curve for the dissociation of a protein from its binder. We conclude that the dissociation of factor VIII in 1 M NaCl is dependent on the concentration and purification of the procoagulant protein.
Calcium homeostasis during hypertonic volume expansion in the hypothyroid rat
Authors: Lebwohl DJ , Lee HN , DiScala VA
Published: December 2017

The clearance characteristics of calcium and the relationship of coupled Na+ and Ca++ renal transport were evaluated in the hypothyroid rat (TX) during volume expansion with 1.5% saline. Despite similar hydropenic plasma calcium, after 11 ml/100 g body wt of infusion volume, the plasma calcium was significantly lower in the TX group (TX, 6.1 +/- 0.2; TI, 7.0 +/- 0.1; P less than .001). With continued infusion, plasma calcium in the TX group continued to drop to 5.3 +/- 0.3 while in the control rats (TI group) it rose to 8.0 +/- 0.1. This marked hypocalcemia in the TX group could not be explained by urinary losses of calcium, hemodilution, deficient parathyroid response, or changes in ultrafilterable plasma calcium. The higher fractional calcium excretion found in the TX group paralleled the higher fractional sodium excretion, and the coupling between calcium and sodium excretion was preserved in hypothyroidism under these conditions. Our results indicate an abnormal calcium homeostasis in the hypothyroid rat. The data do not support a renal cause for this disturbance but are consistent with the view that mobilization of calcium from the bone is sluggish in hypothyroidism during volume expansion.
Intracellular concentrations of the salt gland of the herring gull Larus argentatus
Authors: Schmidt-Nielsen B
Published: December 2017

Attempts were made to measure intra- and extracellular concentrations in secreting and inactive salt gland tissue of the herring gull. 14C-labeled polyethylene glycol (mol wt 4,000) was used as a marker for extracellular fluid. Fluid separated by centrifugation at 36,000 g appeared by three independent criteria to represent primarily extracellular fluid. It could not, however, be fully ascertained if this fluid was mixed with a small amount of intracellular fluid. Therefore, intracellular concentrations were calculated from the concentrations in centrifuged fluid as well as from plasma concentrations. By either method it was found that secreting and inactive glands showed no difference in extracellular and intracellular fluid concentrations of Na, K, Cl and Ca. Secreting glands had lower intracellular water content and a higher intracellular Mg concentration than inactive glands. The absence of evidence for intracellular accumulation of Na and Cl ions in secreting glands suggests that active ion transport takes place across the apical rather than the basal and lateral membranes in spite of the fact that Na-K-activated ATPase is associated with the extensive infoldings of these plasma membranes.
Nonshivering thermogenesis induced by repetitive hypothalamic cooling in the rat
Authors: Banet M , Hensel H
Published: December 2017

The effect of prolonged and repetitive cooling of the preoptic/anterior hypothalamic area on the sensitivity to the metabolic effect of noradrenaline and on the resistance to cold exposure was studied in the white rat. The preoptic area of 18 unanesthetized animals was cooled 9 h/day 5 days/wk, for a total of 80-150 h. One hour after a noradrenaline test injection (0.4 mg/kg), the experimental animals in which the preoptic area had been cooled to about 24 degrees C increased oxygen uptake by 81%, whereas those in which the preoptic area had been cooled to about 28 degrees C increased oxygen uptake by 48% (the control animals by only 37%). Despite their increased capacity for nonshivering thermogenesis, the experimental animals did not tolerate cold exposure (-10 degrees C) better than the controls. This development of nonshivering thermogenesis is thought to have been mediated by the hypothalamic temperature-sensitive neurons, and the possibility that it could explain the shift from shivering to nonshivering thermogenesis seen during adaptation to cold is discussed.
Distribution of renal blood flow in dogs with congestive heart failure
Authors: Westenfelder C , Arruda JA , Lockwood R , Boonjarern S , Nascimento L , Kurtzman NA
Published: December 2017

Studies were performed to determine whether the intrarenal distribution of cortical blood flow is altered in congestive heart failure. Utilizing the radioactive microsphere method, we studied eight dogs that developed congestive heart failure secondary to the construction of an aortocaval fistula. They had marked reduction in total renal blood flow not accompanied by intracortical redistribution of blood flow. All dogs had developed edema and/or ascites, and gained a mean of 3.4 kg; glomerular filtration rate, hematocrit, and urinary sodium excretion fell significantly. Renal vascular resistance increased; mean blood pressure and filtration fraction were unchanged. Furosemide was administered to a second group of nine fistula dogs. The drug produced a marked natriuresis associated with a decrease in outer cortical blood flow (zone 1) and an increase in midcortical zones 2 and 3; no change was observed in zone 4. We conclude: 1) chronic salt retention occurs in high-output heart failure in the absence of redistribution of renal cortical blood flow, and 2) the effect of furosemide on intrarenal hemodynamics of dogs with heart failure is similar to that seen in normal animals.
Mechanisms of blood vessel constriction during hemorrhage
Authors: Hall JE , Schwinghamer JM , Lalone B
Published: December 2017

The contributions of sympathetic nerves, circulating hormones, and passive vascular recoil to vasoconstriction and transcapillary fluid reabsorption in skin and skeletal muscle were examined in the forelegs of 55 pentobarbitalized dogs by using a combined gravimetric and segmental resistance technique. Hemorrhage elicited large increases in forelimb segmental vascular resistances and in the rate of extravascular fluid reabsorption. Only a small part of these responses could be attributed to the passive effects of reducing forelimb perfusion pressure.
Localization of mesenteric hyperemia during digestion in dogs
Authors: Chou CC , Hsieh CP , Yu YM , Kvietys P , Yu LC , Pittman R , Dabney JM
Published: December 2017

For localization of the site of post-prandial mesenteric hyperemia, low-fat, low-protein food was placed in either the stomach, duodenum, or jejunum while blood flow was measured in the celiac artery, superior mesenteric artery (SMA), or jejunal vein of anesthetized dogs. Distribution of flow in the jejunal wall was also measured. After intragastric placement of food, celiac arterial flow increased within 5 min and remained elevated for 30-60 min; SMA flow increased within 30 min and stayed up for at least 3 h. Intra-duodenal infusion of digested food increased SMA flow but did not alter celiac flow or flow to an isolated jejunal segment. Placement of digested food into one jejunal segment increased flow to that segment did not affect flow was localized to the mucosal layer. These studies indicate that during digestion, blood flow increases in the mucosa of the intestine when exposed to chyme and is not changed in other areas of the gastrointestinal tract. Postprandial mesenteric hyperemia induced by low-fat, low-protein food is a local phenomenon.
Propranolol and pyrogen effects of shivering and nonshivering thermogenesis in rats
Authors: Horwitz BA , Hanes GE
Published: December 2017

Injection of bacterial endotoxin (Piromen) into unanesthetized rats elicited increases in shivering and nonshivering thermogenesis as well as in colonic temperature. In animals exposed to 24-25 degrees C, treatment with propranolol (a beta-adrenergic antagonist) markedly diminished the pyrogen-induced increases in oxygen consumption (heat production) and colonic temperature with little change occurring in shivering activity. In contrast, in rats exposed to mild cold (17-18 degrees C), propranolol did not significantly alter the magnitude of the pyrogen-evoked thermogenesis. Rather in these animals, shivering tended to increase when nonshivering thermogenesis was blocked. These data are interpreted as reflecting differential effects of pyrogen on the pathways controlling the two modes of heat production in the rat.
Role of distal delivery of filtrate in impaired renal dilution of the hypothyroid rat
Authors: Michael UF , Kelley J , Alpert H , Vaamonde CA
Published: December 2017

Free water clearance (CH2O) was measured during hypotonic saline infusion in Sprague-Dawley and in Brattleboro (DI) rats with 131I-induced hypothyroidism and their age-matched controls. At peak urine flow, which was similar in hypothyroid DI (HDI) and control DI (CDI) rats, inulin clearance (CIn/kg) and CH2O/kg were 23 and 20% (P less than 0.02) lower in HDI. Fractional urine flow and fractional sodium excretion were 30 and 40% (P less than 0.001) higher in HDI. Utilization of distal delivery of filtrate for CH2O, formation was 16% less in HDI (P less than 0.01). Papillary osmolality was not higher in HDI rats. Data in Sprague-Dawley rats were similar to those of the DI rats, indicating that endogenous ADH was effectively suppressed. It is concluded: 1) delivery of filtrate out of the proximal tubule was not diminished in hypothyroid rats in spite of a decrease in CIn; 2) despite a similar delivery of filtrate to the distal diluting site, CH2O formation was less in hypothyroid rats than in controls; 3) these data suggest that a defect in the diluting segment could be unmasked at high rates of filtrate delivered to the distal nephron; 4) this defect could be either due to impaired sodium chloride reabsorption or due to increased backdiffusion of water in the distal nephron.
Plasma secretin and gastrin responses to a meat meal and duodenal acidification in dogs
Authors: Lee KY , Tai HH , Chey WY
Published: December 2017

In five conscious dogs with gastric fistula and two duodenal cannulas, plasma RIA secretin and gastrin levels were determined in response to 1) infusion of 0.1 N HCl in the proximal duodenal cannula, 2) ingestion of a meal, and 3) intraduodenal infusion of 0.1 N HCl following ingestion of a meal. Significant increases in plasma RIA secretin levels occurred during duodenal acidification. However, no significant change occurred in the secretin levels after ingestion of a meal, whereas significant increase in plasma gastrin level was observed. Postprandial duodenal pH remained above 4.5 for 3 h.
Hypothalamic and brachial nerve effects on circulation of isolated canine forelimb,
Authors: Menninger RP , Baker CH
Published: December 2017

Canine forelimbs were vascularly isolated and perfused at either constant inflow or constant inflow pressure. A comparison of the effects of electrical stimulation of hypothalamic pressor areas and brachial nerves was made on several vascular parameters. During constant pressure perfusion, forelimb resistance increased and total forelimb volume decreased. Additionally active vascular volumes measured with 131I-labeled albumin and 51Cr-labeled red cells decreased significantly. Capillary diffusion capacity product calculated from extraction of 86RbCl also decreased significantly as did the capillary filtration coefficient (CFC). The only significant differences between hypothalamic and brachial nerve stimulation were noted in the larger decreases in active volumes and CFC during the latter stimulations.
Effect of hemorrhagic shock on renal release of prostaglandin E
Authors: Johnston PA , Selkurt EE
Published: December 2017

The effect of hemorrhage and reinfusion on renal release of prostaglandin E (PGE), arterial [PGE], mixed-venous [PGE], and renal function was observed in anesthetized dogs. Following hemorrhage to 60 mmHg arterial pressure, arterial [PGE] rose significantly from 405 to 740 pg/ml. Renal release of PGE remained near control (8 ng/min), as renal blood flow (RBF) decreased from 4.7 to 2.2 ng/min per gram kidney weight (KW). Mixed-venous [PGE] remained near the control value (960 pg/ml). Reinfusion of shed blood restored RBF to 4.0 ml/min per KW. Renal release of PGE rose significantly to 190 ng/min. Arterial [PGE] remained elevated, but mixed-venous [PGE] was not significantly different from control. Indomethacin, a prostaglandin synthesis inhibitor, caused a significant decrease in renal release of PGE. Arterial [PGE] remained elevated following treatment. The inhibition of PGE release from the kidney by indomethacin indicates that increased renal release of PGE following reinfusion is the result of accelerated PGE synthesis. The data suggest that the elevated arterial [PGE] may be the result of alteration of the handling of PGE by the lung.
Effects of saline drinking on malignant course of renal hypertension in rats
Authors: Mohring J , Petri M , Szokol M , Haack D , Mohring B
Published: December 2017

In rats with unilateral renal artery stenosis and an intact contralateral kidney, a malignant course of hypertension (MH) may develop, which is characterized by 1) high BP levels, 2) sodium and water loss and a polyuric-polydipsic syndrome, 3) marked activation of the renin-angiotensin system, 4) malignant nephrosclerosis in the contralateral kidney and high plasma urea concentrations, and 5) deterioration of the animals' general condition. (Some rats exhibit signs of a cerebral vascular crisis; some rats die). When such rats are offered in addition to water 0.9% NaCl, they compulsively drink the saline, BP falls for some days to levels found in the other hypertensive animals, and signs of MH nearly or completely disappear. It is concluded that high saline intake has, for a limited period, a beneficial effect on the malignant course of renal hypertension in rats. The observations made are consistent with the hypothesis that salt and water loss, which ensue subsequent to an increase of BP into a critical high range might trigger the onset of malignant hypertension.
Ba2+ and K+ alteration of K+ conductance in spontaneously active vascular muscle
Authors: Hermsmeyer K
Published: December 2017

The spontaneous spiking of vascular muscle in hepatic portal vein was converted from a burst pattern to single spiking by K+ concentrations greater than 20 mM. A pronounced decrease in contraction amplitude was always associated with the conversion of bursts of spikes to single spikes. The single spikes were accompanied by contractions that were only 1-5% of the magnitude of the contractions associated with spike bursts. Ba2+ (1 mM) increased the number of spikes per burst in myovascular cells at low(less than 10 mM) K+ concentrations. Even though Ba2+ caused depolarization, which itself tended to cause conversion to single spiking, the number of spikes per burst and contraction amplitude were greater in Ba2+ solutions. The slope of the Em-log [K+]o relationship depended on the time allowed for changes in [K+], and a maximum slope of 36 mV/decade and an extrapolated [K+]i of 160 mM were the highest slope and lowest [K+]i values recorded. Ba2+ slightly decreased (to 28 mV/decade) the slope of the curve but did not alter the intercept at [K+] = 160 mM. Ba2+ caused an increase in input resistance (rin) and depolarization independent of CL- concentration, and thus appeared to decrease K+ conductance. K+ concentration increases tended to increase K+ conductance (decrease rin) with depolarization. Spontaneously active vascular muscle thus appears to have a K+ conductance that can be altered and to show different spike patterns and altered conduction, resulting in a marked change in contractions. The spike pattern appears to depend at least partially on the combination of K+ conductance and Em.
Independence of onset of compensatory kidney growth from changes in renal function
Authors: Katz AI , Toback FG , Lindheimer MD
Published: December 2017

Renal function was measure before and shortly after uninephrectomy in mice to evaluate if work expended in the reabsorption of glomerular filtrate plays a role in the initiation of compensatory growth. To exclude the possibility of small but undetectable increments in glomerular filtration rate and absolute sodium reabsorption these functions were experimentally reduced immediately after uninephrectomy and sham nephrectomy. The onset of growth was indicated by an increased rate of [14C]choline incorporation into phospholipid in renal cortical slices. [14C]choline incorporation increased significantly only after uninephrectomy and remained unchanged after sham operation regardless of the magnitude or direction of the concurrent change in sodium reabsorption. The rate of incorporation increased by 40 +/- 8% (P less than 0.005) in uninephrectomized animals whose sodium reabsorption was reduced by 34 +/- 6% (P less than 0.001) and rose 45 +/- 11% (P less than 0.005) when sodium reabsorption remained unchanged. These results indicate that compensatory kidney growth is not triggered by an increase in renal work expended in the reabsorption of glomerular filtrate; in fact, it can occur when reabsorptive work is substantially decreased.
Effect of tachycardia on left ventricular blood flow distribution during coronary occlusion
Authors: Becker L
Published: December 2017

The effect of heart rate on the amount and distribution of collateral blood flow was determine in open-chested dogs 1 h after coronary artery ligation. Flows to ischemic and nonischemic regions of left ventricle were measured with 7- to 10- mum diam radioactive microspheres during base-line conditions (118 +/- 6 beats/min) and again during atrial pacing at rates 20 and 40% above control (141 +/- 7 and 165 +/- 9 beats/min). During pacing aortic and left atrial pressures and cardiac output did not change significantly, whereas ST segment elevation in epicardial electrograms increased markedly. In nonischemic myocardium, mean flow increased approximately in proportion to the increase in rate, but subepicardial (EPI) flow increased somewhat more than subendocardial (ENDO) flow. In ischemic myocardium, overall flow did not change significantly, but a redistribution from ENDO to EPO was seen. At the faster rate ENDO flow fell 25% (P less than 0.02), EPI flow increased slightly, and ENDO/EPI fell in 8/9 animals (mean 0.54-0.43, P less than 0.01). The ENDO/EPI maldistribution present in ischemic muscle is thus accentuated by tachycardia; this may account for part of the harmful effect of tachycardia in acute myocardial infarction and may help explain the disproportionate ENDO ischemia seen in angina pectoris.
Protein synthesis and RNA in tissues of the pig
Authors: Garlick PJ , Burk TL , Swick RW
Published: December 2017

The rate of protein synthesis in 75-kg pigs was measured by continuous intravenous infusion of [14C]tyrosine. In the whole body, over 600 g of protein were synthesized each day. In pigs, rats, and man the rate of protein synthesis in the whole body was related to metabolic rate. The fractional rate of synthesis of protein in the tissues was also measured. The proteins of visceral organs (liver kidney, lung, and spleen) were renewed at rates close to 20% per day, those of brain at 8% per day, heart 7% per day, and skeletal muscle 4% per day. A significant correlation was observed between the fractional rate of protein synthesis in the tissue and RNA concentration. Calculation of the total amount of protein synthesized in skeletal muscle of the pig (fractional rate of synthesis X protein content) shows that muscle contributes 42% of whole-body synthesis. By contrast, in the rat only 19% of whole-body synthesis occurs in muscle.
Ligandin and Z protein in binding of thyroid hormones by the liver
Authors: Lichter M , Fleischner G , Kirsch R , Levi AJ , Kamisaka K , Arias IM
Published: December 2017

Sephadex G-100 chromatography of rat liver supernatant after addition of [125I]T3 revealed four peaks of protein-bound radioactivity in the void volume, albumin, ligandin, and Z-containing regions, respectively. The peaks were identified by cochromatography of BSP and [125I]T3 and immonodiffusion with antiratligandin IgG and antirat Z IgG. Binding of [125I]T4 to rat liver supernatant occurred in void volume, albumin, and Z regions only. Studies in vivo reveal a pattern of [125I]T3 binding to rat liver supernatant fractions quantitatively different from that observed in vitro. [125I]T4 binding to liver supernatant fractions in vivo occurred in all four peaks. BSP or bilirubin added to liver supernatant decreased T3 and T4 binding by each fraction. Flavaspidic acid inhibited binding of T3 and T4 to albumin, ligandin, and Z protein. Phenobarbital pretreatment of rats increased binding of T3 by ligandin and of T4 by albumin-containing fractions. Circular dichroism studies with purified rat liver ligandin suggest that T3 and T4 bind competitively to the same site as does bilirubin; the association constants of T3 and T4 for ligandin are 10(6) and 10(5) M-1, respectively. T4 was bound only by purified ligandin and not by ligandin in liver supernatant. To determine whether unconjugated bilirubin interferes with hepatic uptake of T3, [125I]T3 was administered to icteric homozygous and phenotypically normal heterozygous Gunn rats. Hepatic uptake and supernatant binding [125I]T3 were significantly reduced in homozygous Gunn rats. Hepatic uptake of [125I]T3 was also reduced in vivo by infusion of BSP with or without flavaspidic acid. BSP infusion abolished [125I]T3 binding to ligandin; BSP and flavaspidic acid abolished binding to ligandin and Z. These observations suggest that ligandin and Z protein are thyroid hormone binding proteins in rat liver cytosol and may influence the net flux of iodothyronies from plasma into the liver.
Ground substance mucopolysaccharides and plasma proteins: their role in capillary water balance
Authors: Wiederhielm CA , Fox  , Lee DR
Published: December 2017

The osmotic interaction of mucopolysaccharides and plasma proteins, normally present in the interstitium, has been investigated. It has been found that hyaluronate-plasma protein mixtures may be treated as a two-phase system and that the two phases are in osmotic equilibrium. The osmotic pressures exerted by these mixtures are higher than the algebraic sum of the two components. At concentrations normally present in the interstitium of skin and muscle (0.6% mucopolysaccharides and 2% protein), the osmotic pressure exerted by the mixture is on the order of 10 mmHg, which is in agreement with predictions from earlier computer-simulation studies. The partition of fluid between the gel-like mucopolysaccharide compartment and the free-fluid containing the protein is approximately 50% in the "gel" phase at concentrations found in the interstitium. The volume exclusion effects of the interstitial mucopolysaccharides are significant, both in terms of selection of tracer molecules for interstitial volume measurements and also as an osmotic buffering mechanism which aids in maintaining the partition of fluid between the circulation and the interstitial space.
Active state of normal and dystrophic mouse muscle
Authors: Sabbadini RA , Baskin RJ
Published: December 2017

Computer-controlled quick releases were used to determine the kinetics of active state tension decay in normal and dystrophic EDL muscles of the mouse (129/Re-J). Also included are measurements of the duration of the active state plateau, isometric twitch and tetanus parameters, and the stress-strain properties of the elastic elements. Alterations in the isometric tension characteristics of dystrophic muscles confirm previous investigations and indicate that dystrophic sarcomeres have a diminished ability to shorten and produce tension. The compliance of the series-elastic elements is not changed, whereas a 50% reduction in the interanl extension of the series elements is noted for dystrophic muscle. The rate of decay and maximum intensity (Po) of active state decay is reduced 60-70% in dystrophic muscles. The first-order rate constant and the total duration of the active state are not altered. These results are discussed in terms of the possible involvement of the contractile proteins and the sarcoplasmic reticulum in determining active state deficits.
Effects of some vasodilator drugs on transcapillary fluid exchange in renal cortex
Authors: Baylis C , Deen WM , Myers BD , Brenner BM
Published: December 2017

In 23 Munich-Wistar rats with surface glomeruli, the determinants of glomerular ultrafiltration and peritubular capillary uptake of proximal reabsorbate were studied before and during intra-arterial infusions of mildly vasodepressor doses of prostaglandin E1,acetylcholine, and bradykinin. For each drug single-nephron glomerular filtration rate remained unchanged from normal hydropenic values while glomerular plasma flow rate increased, resulting in declines in single-nephron filtration fraction (SNFF). Mean glomerular transcapillary hydraulic pressure difference (delta P) increased or remained unchanged on average. Declines in SNFF were accompanied by reductions in efferent arteriolar oncotic pressure (piE). Filtration pressure equilibrium, equality between pi E and delta P, obtained before but not during drug infusions. In the latter situation values for the glomerular capillary ultrafiltration coefficient were calculated and found to be significantly reduced from published control values. Despite marked falls in pi E during drug infusion, absolute proximal reabsorption was not reduced significantly, due, it is suggested, to the opposing effects of increases in efferent arteriolar plasma flow and interstitial hydraulic pressure.
Kidney pressures after temporary renal artery occlusion in the rat
Authors: Tanner GA , Sophasan S
Published: December 2017

Acute kidney failure was produced in the anesthetized rat by 1 h of complete renal artery occlusion. Kidney function was studied either immediately after release of the occlusion or 1 day later using clearance, micropuncture, histological, and nephron dissection techniques. Polyfructosan clearance was decreased to 5% of normal after temporary occlusion. Proximal tubular pressure (PTP) averaged 13-14 mmHg in normal kidneys, 39 mmHg immediately after release of unilateral occlusion, 19 mmHg 1 day after unilateral occlusion, and 25 mmHg 1 day after bilateral occlusion. The increased PTP reduces the glomerular filtration rate (GFR). Glomerular capillary pressure, estimated from the sum of the stop-flow and arterial plasma colloid osmotic pressures, was not decreased after temporary ischemia. Single-nephron GFR, measured without intratubular pressure control, was only slightly below normal 1 day after bilateral occlusion. Most distal tubules from ischemia-damaged kidneys contained hyaline casts. Tubular obstruction is a major factor in this model of acute kidney failure.
A comparative study of pulsatile arterial hemodynamics in rabbits and guinea pigs
Authors: Avolio AP , O'rourke MF , Mang K , Bason PT , Gow BS
Published: December 2017

Pulsatile pressure and flow were measured in the ascending aorta and other arteries of 22 anesthetized rabbits and 16 anesthetized guinea pigs. Pressure/flow relationships were expressed as vascular impedance. Aortic flow waves were almost identical in the two species, but pressure waves were quite different. Reflected pressure waves returned earlier from the periphery in guinea pigs, augmenting pressure during late systole and resulting in relatively high external left ventricular work, an inappropriately larger difference between mean systolic and mean diastolic pressure and absence of any aortic diastolic pressure wave. Values of impedance modulus and phase were similar but differed in the frequency at which maxima and minima occurred. In both species, impedance curves were interpreted to indicate a functionally discrete reflecting site in the lower body whose position corresponded to the region of the aortic bifurcation. In addition, rabbits showed evidence of an upper body reflecting site approximately one-third as far distant from the heart. As in dogs, the arterial system in both species can be represented by an asymmetrical T-shaped model of realistic dimensions.
Short-loop feedback control of luteinizing hormone in the rabbit
Authors: Molitch M , Edmonds M , Jones EE , Odell WD
Published: December 2017

A radioimmunoassay for rabbit luteinizing hormone (rLH) in which rLH shows no significant cross-reaction with human LH (hLH) or human chorionic gonadotropin (HCG) was employed to test for the existence of a short-loop feedback for LH in the rabbit. Two weeks after castration, hCG and hLH were administered intravenously to rabbits, and the effects on circulating rLH were measured. Purified hLH (10 ng or 100 IU) produced significant depression of blood rLH within 30-60 min of intravenous injection. Saline administered to the same animals produced no changes in rLH. Injection of hCG (2,000 IU) under the same conditions also produced a significant fall in rLH. However, hCG administered to rabbits castrated 6 wk prior to study failed to suppress endogenous rLH. These data demonstrate, by direct radioimmunoassay quantification of blood hormones, the existence of a short-loop negative feedback for LH in the rabbit. They also suggest that the sensitivity of the short-loop changes with time after castration.
Intracellular osmoregulatory role of amino acids and urea in marine elasmobranchs
Authors: Forster RP , Goldstein L
Published: December 2017

Little skates, Raja erinacea, and stingrays, Dasyatis americana, were gradually transferred over a period of 4-5 days from full strength to approximatley 50% seawater. Plasma and muscle osmolarity fell. Hematocrits were essentially unchanged. Extracellular fluid volume (ECF) of muscle, estimated as the chloride space, increased 70% during this period. Regulation of muscle cell volume was associated with sharp declines in cellular concentrations of total amino acids (ninhydrin-positive materials) and urea. The osmoregulatory importance of the free amino acid pool in erythrocytes and muscle was a particularly prominent feature in both species. Intracellular amino acid concentration in R. erinacea muscle fell from 214 to 144 mmol/liter during transfer to 50% seawater, urea from 398 to 264, and trimethylamine oxide (TMAO) dropped from 63.9 to 35.8 mmol/liter. TMAO plasma levels were similar in stingray and skate, but muscle TMAO concentrations were much higher in the former. Urea content in stingray plasma greatly exceeded that in R. erinacea-630 and 574 mmol/liter in two specimens-perhaps the highest recorded.
Thermal homeostasis in rats after intrahypothalamic injections of 6-hyroxydopamine
Authors: Van Zoeren JG , Stricker EM
Published: December 2017

Specific destruction of at least 90% of the noradrenergic neurons in the preoptic/anterior hypothalamic region (PO/AH) by local injection of 9-hyroxydopamine (6-HDA) did not disrupt thermoregulation by rats either in the heat or the cold. Examination of the multiple effector mechanisms suggested that thermal balance was maintained in a normal fashion, and that compensatory adjustments did not conceal individual dysfunctions. In contrast with the ineffectual 6-HDA lesions of the PO/AH were the outstanding impairments seen in rats following electrolytic lesions of this area. All the latter animals became severely hyperthermic during the 1st h of exposure to an ambient temperature of 40 degrees C, and half of them were additionally unable to maintain body temperatures when exposed to an ambient temperature of 6 degrees C. The electrolytic lesions reduced norepinephrine levels in the PO/AH, but the 50-70% depletions were substantially smaller than those found in 6-HDA-treated rats. These results raise new doubts about whether central noradrenergic fibers have an important role in the regulation of body temperature by rats.
Interactions of diphenylhydantoin and cardiac glycosides on atrial potassium
Authors: Loh CK , Katz AM , Peirce EC
Published: December 2017

Effects of diphenylhydantoin (DPH) on amphibian atrial myocardium K were investigated using a method which permits both total tissue K and tension response to be monitored continuously. In normal (nondigitalized) preparations, DPH caused a decrease in average K efflux, a net gain of tissue K, and negativeinotropy at low perfusate K concentrations. However, the DPH-induced gain of tissue K was abolished at high perfusate K concentrations while marked negative inotropy was still observed. It is concluded that a gain of tissue K is not the cause of DPH-induced negative inotropy. When digitalis-induced inotropy was associated with tissue K loss, DPH reversed tissue K loss and positive inotropy and caused a decrease in average K efflux. In the presence of toxic effects of digitalis, DPH reversed the K loss and the contracture, but the loss of developed tension was not reversed by DPH. Transmembrane resting potentials and action potential duration were reduced by digitalis and were returned to or above control levels in the presence of DPH. The present findings are consistent with the hypothesis that the therapeutic effect of DPH in digitalis toxicity is brought about by an inhibition of K efflux. This would tend to minimize the loss of tissue K which results from sodium pump inhibition.
Response of primate heart to emotional stress before and after cardiac denervation
Authors: Randall DC , Kaye MP , Randall WC , Brady JV , Martin KH
Published: December 2017

Eleven chair-restrained rhesus monkeys were classically conditioned to a 1-min, 900-Hz tone (CSf) followed by food and a 1-min, 3.4-5Hz tone (CSs) followed by shock. Each conditional stimulus produced large, sudden, and highly significant (P less than .01) increases in left ventricular systolic pressure (LVP), its first time derivative (d(LVP)/dt), and heart rate (HR). The animal's hearts were sugically denervated following control studies of the conditional responses. Two to four weeks later, these responses were reexamined by again presenting CSf and CSs to five surviving monkeys following a format identical to that used in the control experiments. Complete cardiac denervation virtually eliminated the sudden increases in each of the measured variables. Denervation also "unmasked" small-magnitude, delayed chronotropic and inotropic responses during CSs (but not CSf). These effects were ascribed to the action of circulating catecholamines known to be secreted during "emotional" stress. Four monkeys studied for 6 mo or more postoperatively showed evidence for varying degrees of cardiac reinnervation. Loss of nervous control of the nonhuman primate heart greatly compromises the cardiovascular response to these environmental and behavioral stress situations.
Free fatty acids and albumin as mediators of thrombin-stimulated fibrinogen synthesis
Authors: Pickart LR , Thaler MM
Published: December 2017

Mobilization of FFA in mice, triggered with an injection of thrombin, was followed within 24 h by a 2.5-fold increase in fibrinogen synthesis and a 30% increase in plasma fibrinogen concentration. In mouse liver slices, incubated in plasma, additions of palmitate or stearate in amounts similar to those expected in vivo in FFA mobilization stimulated fibrinogen synthesis 5.6- to 6.1-fold while unsaturated and short-chain FFA were less effective. Palmitate and linoleate also augmented albumin synthesis although not as stongly as fibrinogen synthesis. These observations raised the possibility that the greater effectiveness of saturated FFA in stimulating fibrinogen synthesis may reflect higher FFA/albumin ratios within hepatocytes in the presence of saturated FFA. Injection of exogenous defatted albumin into mice before thrombin injection prevented the FFA-associated rise in fibrinogen synthesis and plasma concentration. In incubated liver slices, defatted albumin abolished the FFA stimulation of fibrinogen synthesis when FFA/albumin ratios were maintained to the physiological range. These studies indicate that the FFA/ALBUMIN RATIO MAY PLAY A MAJOR ROLE IN THE REPLENISHMENT OF FIBRINOGEN AFTER PERIODS OF RAPID DEFIBRINOGENATION.