bluuebunny/crossref_metadata_2025 huggingface dataset:
Muscle fiber involvement during training of different intensities and durations
Authors: Terjung RL
Published: December 2017

The extent of skeletal muscle fiber type involvement during exercise training was evaluated by assessing the increase in oxidative markers in the muscles of rats trained by various exercise programs. Rats were trained by running 6 days/wk at 1 mph for 12 wk by one of four protocols: group I-10% grade, 2 h/day; group II-10% grade, 4 h/day; group III-30% grade, 40 min/day; and group IV-30% grade, 2 h/day. No distinction was found between the different programs for the increase in cytochrome c content or citrate synthase (CS) activity of mixed muscle. The more intense programs utilizing a 30% grade induced an increase in CS activity in the fast-twitch white (FTW) fiber that was twice that found in the 10% grade groups. The fast-twitch red (FTR) fibers of the 2 h/day or more groups showed a similar increase (90-95%) in CS activity except for the group that ran for only 40 min/day. These data suggest that: 1) running durations of moderately intense exercise longer than 2 h/day do not further increase the oxidative capacity of the working muscles; and 2) more intense exercise builds on the performance of previously used FTR fibers and additionally involves the low oxidative FTW fibers.
Biliary secretion in elasmobranchs. I. Bile collection and composition
Authors: Boyer JL , Schwarz J , Smith N
Published: December 2017

Bile composition and secretion were studied in tow elasmobranch species, Squalus acanthias (spiny dogfish shark) and Raja erinacea (small skate), after ligation of the common duct and insertion of cannulas into the gallbladder lumen. Fish were then allowed to swim freely in large pools and bile was collected in balloons attached to the externalized cannulas. Both species secreted bile for periods of 4-7 days at a maximum rate of 1.77 +/- .89 ml/kg per 24 h in Squalus acanthias and 2.66 +/- .89 ml/kg per 24 h in Raja erinacea. Comparison of the composition of cannula and gallbladder bile indicated that hepatic bile could be collected by this technique in both species without effective contact with gallbladder epithelium. The low concentrations of HCO3- and CL- and the gigh bile salt levels in dogfish gallbladder bile indicate that mechanisms for concentration and acidification of bile in the gallbladder developed early in vertebrate evolution. These results indicate that gallbladder cannulation in free-swimming elasmobranchs is a useful technique for the study of bile secretory and excretory function in marine species.
Sodium balance and the natriuresis of hypertonic saline infusion in dogs
Authors: Diaz-Buxo JA , Haas JA , Ott CE , Cuche JL , Marchand GR , Knox FG
Published: December 2017

Recently, a paradoxical effect of dietary salt intake on the natriuresis following hypertonic saline infusion was observed in rats. In these experiments the effects of alterations in dietary sodium on the natriuretic response to a hypertonic saline load was studied in dogs. Dogs maintained on a high-sodium diet did not have a significantly different natriuresis than those on a low-sodium diet. When differences in sodium balance were amplified by the use of deoxycorticosterone, furosemide, and manipulation of dietary sodium, dogs in positive sodium balance showed a significantly enhanced initial excretion of sodium followed by a reversal of the pattern. Consequently, the cumulative sodium excretion was not different between low- and high-sodium groups. Since the cumulative natriuretic response to isotonic saline infusion was larger in dogs in positive sodium balance compared to those in negative sodium balance, the failure to detect a difference following hypertonic saline infusion was probably because of the increased plasma sodium concentration.
Cutaneous heat flow during heating and cooling in Alligator mississipiensis
Authors: Smith EN
Published: December 2017

Direct in vivo measurement of heat flow across the skin of the American alligator (Alligator mississipiensis) showed increased heat flow during warming. Mean values at 25 degrees C during warming (15-35 degrees C) in air (airspeed 300 cm/s) were 17.9 +/- 92 SE cal/cm2 per h (mean alligator wt 3.27 kg). Cooling heat flow at the same temperature was 13.6 +/- 0.57 cal/cm2 per h. Subdermal heat flow was reduced during warming and was not significantly different from cutaneous heat flow during cooling. This indicated that the alligator was able to control its rate of heat exchange with the environment by altering cutaneous perfusion. Atropine, phenoxybenzamine, nitroglycerin, and Xylocaine did not affect cutaneous heat flow or heating and cooling rates. Atropine blocked bradycardia during cooling.
Effect of nitrogen and calorie restriction on protein synthesis in the rat
Authors: Stein TP , Oram-Smith JC , Leskiw MJ , Wallace HW , Long LC , Leonard JM
Published: December 2017

The effect of a deficiency of calories and/or nitrogen on protein metabolism in the rat was investigated. During the 5 days of the study, the rats received all nutrients except water via intravenous hyperalimentation. Four diets were used: I) 1.25 g amino acids, 12.5 g glucose/day; II) 1.25 g amino acids/day; III) 1.25 g glucose/day; and IV) 12.5 glucose/day. The rate of protein synthesis in heart, lung, muscle, kidney, and liver was estimated by a modification of the technique of Garlick et al. (The diurnal response of muscles and liver protein synthesis in vivo in meal-fed rats. Biochem. J. 136: 935-945, 1973) except that [15N]glycine was used as the tracer. Heart and lung protein synthesis was depressed by both caloric and nitrogen restriction. Muscle protein synthesis was only significantly affected by omission of calories from the diet. Kidney nitrogen content increased with the amino acid diets and decreased with the nitrogen-deficient diets. The major response of the liver to a dietary deficiency was to lose nitrogen via an increase in the rate of liver protein catabolism.
Equilibration of 15N-labeled amino compounds in man
Authors: Stein TP , Leskiw MJ , Wallace HW
Published: December 2017

Following an overnight fast, either 15N-labeled glycine, or ammonium chloride, or L-aspartate was orally administered to human volunteers in equal hourly aliquots for 8-12 h. In a parallel series of experiments, [15N]glycine and [15N]ammonium chloride were given intravenously at a constant rate for 10-12 h. The amount of 15N given ranged between 2.7 and 27.3 mg/h. Five hundred milligrams of sodium benzoate were given hourly. Venous blood and urine samples were collected serially. The 15N enrichment of the plasma amino nitrogen, urinary ammonia, hippuric acid, and urea were determined. Irrespective of the 15N carrier used or the route of administration, the plasma amino nitrogen, urinary ammonia, and hippuric acid 15N enrichments approached a plateau within 6-10 h. We concluded that human [15N]glycine metabolism was not atypical of amino acids and that mixing, rather than nitrogen interchange reactions, determines the rate in attaining an approximate plateau.
Histidine decarboxylase-mediated histamine synthesis in glomeruli from rat kidneys
Authors: Heald JI , Hollis TM
Published: December 2017

Enzymatic histamine synthesis by renal glomeruli of the rat has been examined. Assays of the partially purified enzyme demonstrated a pH optimum of 6.2, a Michaelis-Menten constant of 2.4 X 10(-4) histidine, and lack of potentiation by benzene. These data thus indicate that renal glomeruli contain the histidine-specific histidine decarboxylase.
Eelctrophysiologic and ultrastructural characteristics of the canine tricuspid valve
Authors: Bassett AL , Fenoglio JJ  , Wit AL , Myerburg RJ , Gelband H
Published: December 2017

Collagen extending from chordae tendineae sweeps into each tricuspid leaflet in a loose fanlike arrangement merging with the annulus. Each leaflet contains variable amounts of cardiac muscle in continuity with right atrial muscle; valve fibers are sparse, and scattered myofibers and/or bundles of myofibers usually extend only 2-3 mm into the leaflet body. Valve myofibers are structurally identical to working right atrial muscle but are 2-3 mum in diameter compared to 5-7 mum in working muscle. Electrical stimulation of the low right atrial wall often induces propagated activity in the leaflet. Transmembrane recordings obtained from isolated Tyrode superfused leaflets showed low maximum diastolic potential, action potential amplitude, and rate of depolarization; action potentials usually had prominent plateaus. Excitation of discrete regions in tricuspid leaflets did not excite atrial wall, but valve muscle fibers often developed spontaneous diastolic depolarization and automaticity after stretch or exposure to catecholamines Automaticity was suppressed by acetylcholine. Physiological and pathophysiological significance of tricuspid muscle may reside in its participation in valve closure during ventricular contraction and the fact that it is a site of abnormal impulse formation.
Effects of temperature transients on gas exchange and acid-base status of turtles
Authors: Jackson DC , Kagen RD
Published: December 2017

Pulmonary ventilation (VE), O2 consumption (VO2), and CO2 production (VCO2) were measured continuously on each of 10 turtles, Pseudemys scripta elegans, at 20 degrees C, during and for 1 h after heating to 30 degrees C and during and for 1 h after cooling to 20 degrees C. In seven of the animals, arterial blood was sampled at the three temperature plateaus. Ventilatory ratios (VE/VO2 and VE/VCO2) and metabolic rate adjusted promptly to temperature change, stabilizing at values similar to those observed previously in turtles following 1 day or more at each temperature. Likewise, mean blood pH and PCO2 values conformed both in absolute values and in temperature-dependence to data previously obtained from animals exposed to the various temperatures for longer time periods or from turtle blood thermally equilibrated in vitro. Total plasma [CO2] did not change significantly, suggesting that steady-state CO2 exchange prevailed throughout the experiment. In accordance with this, R(VCO2/VO2) did not change significantly during the 20-30 degrees C transition; however, R rose during the 30-20 degrees C transition, suggesting possible hyperventilation at this stage. We conclude that the respiratory control of blood acid-base status adjusts rapidly to temperature change in the turtle and its adjustment minimizes disturbance to CO2 balance.
Cerebrospinal fluid [Ca2+] and rectal temperature response during exercise in dogs
Authors: Sobocinska J , Greenleaf JE
Published: December 2017

Rectal temperature (Tre) was measured in five dogs during 1 h of rest and 1 h of moderate treadmill exercise (1.2 m/s up a 12 degree slope), with no infusion and with continuous infusion (40 mul/min) of normocalcic (1.3 mM Ca2+, 151.5 mM Na+) and hypercalcic (2.6 mM Ca2+, 149.6 mM Na+) concentrations of artificial cerebrospinal fluids into the left lateral cerebral ventricle. There was no effect of the normo- or hypercalcic infusions on resting Tre. In comparison with the postexercise Tre level of 39.9 degrees C (deltaTre= +1.4 degrees C) with no infusion, Tre rose to 40.0 degrees C (delta Tre = +1.4 degrees C) with normocalcic infusion (NS); there was a significantly smaller (P less than 0.01) rise in Tre to 39.2 degrees C (delta Tre = +0.8 degrees C) with hypercalcic infusion. The smaller rise in Tre in response to excess Ca2+ in cerebrospinal fluid was not due to plasma fluid or electrolyte shifts. During exercise the mean body weight loss was greater with hypercalcic infusion (-2.7%) compared with normocalcic (-1.0%) and no infusion (-1.4%) values. The results suggest that Ca2+ ions affect the sensitivity of the central thermoreceptor to thermal stimuli and cause an increased heat loss during physical exercise in dogs.
Relation between Na-K-ATPase activity and respiratory rate in the rat kidney
Authors: Silva P , Torretti J , Hayslett JP , Epstein FH
Published: December 2017

The relation between Na-k-ATPase activity in homogenates of rat kidney and oxygen consumption in kidney slices was studied by employing different physiological maneuvers known to change the activity of renal Na-K-ATPase. Treatment of euthyroid rats with 3,5,3'-triiodo-1-thyronine increased Na-K-ATPase activity, sodium-dependent oxygen consumption (QO2[t]), and para-aminohippurate (PAH) accumulation by kidney slices without changing glomerular filtration rate or net sodium reabsorption by the intact kidney. Treatment with methylprednisolone also increased Na-K-ATPase, QO2[t], and PAH transport. Chronic potassium loading, on the other hand, increased renal Na-K-ATPase to the same degree as the first two procedures, but QO2[t] and PAH accumulation were unchanged. Partial nephrectomy induced an increase in the activity of Na-K-ATPase in homogenates of the remaining kidney fragment, but QO2[t] did not change significantly and PAH uptake was unaltered. An increase in the activity of Na-K-ATPase in kidney homogenates is therefore not necessarily associated with a parallel change in oxygen consumption by the intact cell.
Lipolytic activity of swine adipocytes
Authors: Mersmann HJ , Brown LJ , Beuving RD , Arakelian MC
Published: December 2017

Lipolysis in isolated swine adipocytes was stimulated by epinephrine, dibutyryl cyclic AMP, and weakly by adrenocorticotropin but not by glucagon or cyclic AMP. Theophylline, a phosphodiesterase inhibitor, stimulated lipolysis and greatly enhanced the activity of adrenocorticotropin. The epinephrine-stimulated lipolytic activity, expressed on a tissue or cell volume basis, was greatest at 25 days postpartum, whereas, expressed on a cell basis, the activity was maximal at day 80. Regardless of the mode of expression, the activity at day 150 was low. Cells from younger animals were more sensitive to epinephrine than cells from older animals.
Effect of protein intake on weight gain and plasma amino acid levels in uremic rats
Authors: Wang M , Vyhmeister I , Kopple JD , Swendseid ME
Published: December 2017

Chronically uremic rats weighing approximately 180-200 g and sham-operated controls of similar weight were pair fed diets containing 5, 15 or 23% protein for 10-12 wk. At each level of protein intake, uremic animals gained less weight and had lower protein efficiency ratios than controls. In addition, certain plasma amino acid levels were altered in the uremic animals. These included tyrosine and the tyrosine/phenylalanine ratio, which were decreased, and citrulline, glycine, and the methylhistidines, which were increased. In both uremic and control rats, plasma concentrations of certain amino acids, primarily nonessential ones, varied inversely with protein intake; with the 5% protein diet, the ratio of essential to nonessential amino acids was significantly reduced. These observations indicate that both uremia and reduced protein intake may affect growth and amino acid metabolism in rats with chronic renal failure. The finding that uremic rats utilize protein less efficiently may indicate that marked reductions in protein intake may be particularly hazardous to the nutritional status of the uremic patient.
Changes in intestinal vascular diameter during norepinephrine vasoconstrictor escape
Authors: Guth PH , Ross G , Smith E
Published: December 2017

The hypothesis that escape from norepinephrine-induced vasoconstriction in the intestine is due to relaxation of initially constricted vessels was tested in 18 anesthetized cats. Intestinal blood flow was measured by an electro magnetic probe on the superior mesenteric artery. Intestinal submucosal and muscle arterioles and small mesenteric arteries were studied by in vivo microscopy with an image-splitting technic. Continuous recordings of mesenteric flow and vessel diameter were made during the infusion into the superior mesenteric artery of norepinephrine (NE) at a rate of 1-2 mug/min for 3 min. Mesenteric flow decreased soon after the NE infusion began but then escaped. Microscopically, arterial constriction and escape were noted in submucosal, muscle, and mesenteric vessels with a time course similar to that for flow. Arteriovenous anastomoses were not seen. These findings support the hypothesis that escape from Ne-induced vasoconstriction is due to relaxation of initially constricted vessels.
Inhibition of NaCl absorption from perfused rat ileum by furosemide
Authors: Humphreys MH
Published: December 2017

The effect of furosemide on intestinal absorption of water and electrolytes was studied using segments of rat ileum perfused in vivo. Furosemide (1 mM) in the perfusion fluid reduced absorption of Na, Cl, and water by 50% from a balanced electrolyte solution without changing the transepithelial potential difference (PD). This effect was also observed in the absence of luminal glucose and was largely reversible. Substitution of all Na in perfusion fluid with choline produced secretion of Na and water and abolished Cl absorption; substitution of all Cl with SO4 reduced Na absorption to 20% of control values. Under both these conditions, furosemide had only trivial effects on electrolyte absorption and exerted no effect on PD. Measurements of unidirectional fluxes of Na and Cl showed that furosemide decreased net flux by reducing lumen-to-blood flux of these ions rather than increasing blood-to lumen flux. These results resemble those obtained in this tissue following exposure to acetazolamide, and suggest that furosemide inhibits a coupled, neutral process of NaCl transport from lumen to blood. Although this effect could be a result of carbonic anhydrase inhibition it more likely occurs from a separate action of furosemide on ileal transport.
Effect of prolactin on diluting and concentrating ability in the rat
Authors: Wallin JD , Lee PA
Published: December 2017

The effect of prolactin on free water clearance (C(H2O)) and reabsorption (T(cH2O)) was assessed in hereditary hypothalamic diabetes insipidus (HHDI) and hydropenic Sprague-Dawley rats. Infusion of ovine prolactin (200 nmol/kg per h) ablated C(H2O) in HHDI rats but had no effect on T(cH2O) in hydropenic rats. Additional experiments in HHDI rats employing submaximal infusions of both ovine and rat prolactin indicated that with increasing infusion rates of these hormones, urine osmolality progressively increased with a maximum effect being reached at 30-40 nmol/kg per h with ovine and 15-20 nmol/kg per h with rat prolactin. In similar experiments, using synthetic lysine-arginine vasopressin, maximum effect on urine osmolality was achieved with an infusion rate of 25-75 pmol/kg per h. During infusion of all three hormones, urinary cyclic AMP excretion increased significantly in a similar fashion. These data suggested that prolactin had a direct effect on collecting tubule permeability and acted through stimulation of cyclic AMP production.
Insulin and jejunal electrical activity in dogs and sheep
Authors: Bueno L , Ruckebusch M
Published: December 2017

The effect of insulin on jejunal myoelectric activity was studied in conscious dogs and sheep by injection of insulin and stimulation of insulin release. In dogs, the migrating myoelectric complex (MMC), characteristic of fasting, was replaced by a continuous pattern of activity after feeding, injection of insulin, or infusion of D-glucose, L-leucine, or L-arginine. The response to feeding was reduced in alloxan-diabetic dogs and completely abolished following additional vagotomy when only exogenous insulin induced the "fed" pattern. Vagotomy alone had only minor effects on the response to feeding. Sheep exhibit a continuous sequence of MMC, regardless of feeding, but infusion of insulin or volatile fatty acids produced activity similar to that seen after feeding in dogs. In alloxan-diabetic sheep the recurrence and intensity of the MMC were decreased, and the effect of volatile fatty acids was eliminated. Insulin injection restored the pattern to normal. Thus, insulin levels are of importance in the control of the jejunal motor profile and may mediate the postprandial disappearance of MMC in dogs.
Uptake of and response to norepinephrine by certain tissues of hypertensive rats
Authors: LeLorier J , Hedtke JL , Shideman FE
Published: December 2017

A decrease in the capacity of the sympathetic nervous system of hypertensive rats to take up norepinephrine (NE) has been previously described. In the present study, rats were made hypertensive by one of the following technics: "adrenal regeneration," figure-of-eight knot around one kidney, ingestion of a 10% NaCl solution. After 2 mo, the adrenal regeneration rats were hypertensive, and there was a significant decrease in the capacity of their hearts to take up NE as well as a significant increase in the inotropic response to the amine. Similar results were obtained with hearts and aortic strips of renal hypertensive rats, as well as of rats made hypertensive by drinking a 10% NaCl solution. In renal hypertensive rats, there was no appreciable difference in the time of appearance of hypertension, the decrease in NE uptake by the heart or aorta, or the increase of the inotropic response. Previous work showing a decrease of NE uptake in rats made hypertensive by administration of deoxycorticosterone has been confirmed utilizing three other models of the disease.
Effect of epinephrine on vascular space of gills and head of rainbow trout
Authors: Girard JP , Payan P
Published: December 2017

The filling of the gills and head vascular space of a teleost fish was measured in vitro by perfusing an isolated head of a trout with a Ringer solution containing 131I-labeled human serum albumin. The presence of epinephrine in the Ringer solution significantly increased afferent (ventral aortic) flow rate and efferent (dorsal aorta) flow rate, whereas branchial venous system circulation was reduced. When perfused with an epinephrine-free Ringer, the branchial vascular space appears 5-6 times greater than the head vascular space (per 100 g of tissue). Epinephrine, 10(-5) M, in the Ringer solution significantly decreased the branchial vascular space without modifying that of the head. The increase in perfusion rate and decrease in branchial vascular space due to the epinephrine can only be interpreted by taking into account a branchial nonlamellar compartment of a considerable volume.
Vitamin D metabolism: physiological regulation in egg-laying Japanese quail
Authors: Kenny AD
Published: December 2017

Homogenates of kidney removed from reproductivity active female Japanese quail were incubated with tritiated 25-hydroxyvitamin D3, and the metabolites were extracted and identified by chromatographic methods. Kidneys removed from birds with and without an egg in the oviduct revealed that ovulation results in enhanced production of 1, 25-dihydroxyvitamin D3, the active hormonal form of vitamin D3. Further examination of this phenomenon in relation to the ovulatory cycle revealed that 1, 25-dihydroxy-vitamin D3 production is enhanced throughout the 24 h following ovulation. Particularly important is the finding that its synthesis is already enhanced during the first 6 h after ovulation, at a time before any calcification of the egg shell begins. If, following oviposition, no ovulation occurs, 1, 25-dihydroxy-vitamin D3 production decreases rapidly and significantly within the first 6 h following oviposition. This study has revealed for the first time a physiological state, namely the reproductive period in the female bird, in which endogenous control over 1, 25-dihydroxyvitamin D3 production is exhibited without any previous manipulation, dietary or otherwise, of the animals.
Cardiac actomyosin ATPase activity after prolonged physical conditioning and deconditioning
Authors: Malhotra A , Bhan A , Scheuer J
Published: December 2017

Cardiac actomyosin ATPase was increased by making rats swim 150 min/day, 5 days/wk for 8 wk. Changes in Ca2+ -stimulated ATPase activity were then studied in these conditioned rats and in similarly conditioned animals in which swimming was subsequently discontinued (group A), reduced to 45 min/day (group B), or continued at the original level for an additional 8 wk (group C). After the 8-wk initial program actomyosin ATPase activity averaged 22% higher in hearts of conditioned rats than in hearts of sedentary controls (P is less than 0.001). In group A, actomyosin ATPase activity declined rapidly and reached the level found in sedentary controls by the 13th day. In group B, actomyosin ATPase activity declined to the control level by the 30th day. At the end of 16 wk the percent increase in actomyosin ATPase activity in group C over that in hearts of sedentary animals was approximately the same as after 8 wk. These results demonstrate that elevation in cardiac actomyosin ATPase caused by moderate physical training in rats is not maintained if the training program is decreased or discontinued. The training program must be continued at or near the initial level if the increases in cardiac actomyosin ATPase are to be sustained.
Recovery heat production of mammalian fast- and slow-twitch muscles
Authors: Wendt IR , Gibbs CL
Published: December 2017

Relationships between initial heat and recovery heat in fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat have been investigated by estimating the ratio of total heat (initial + recovery) to estimated initial heat. Results obtained from SOL agreed well with earlier data from amphibian skeletal muscle and indicated that in tetanic contractions of SOL the ratio,total heat/initial heat, was slightly greater than 2. Experiments on EDL revealed complexities not previously reported for amphibian muscle. Anaerobic total heat production by EDL was as much as 75% of aerobic heat production. When the initial heat was estimated under anaerobic conditions and with iodacetate present, the apparent ratio of total heat/initial heat in tetanic contractions of EDL approached a value of 2. The results are discussed in relation to the enzymatic characteristics of these muscles, and it is suggested that the recovery heat of SOL arises mainly from mitochondrial oxidative metabolism while that of EDL arises, to a large extent, from glycolytic activity.
Lung lymph and free interstitial fluid protein composition in sheep with edema
Authors: Vreim CR , Snashall PD , Demling RH , Staub NC
Published: December 2017

In 10 anesthetized sheep with mild or moderate pulmonary edema we determined whether the protein composition of lung lymph is representative of free interstitial fluid. We measured protein concentration and albumin fraction in 1-mul samples of plasma, lung lymph, and free interstitial fluid. We also measured lung lymph flow. In five sheep with edema caused by increased pulmonary microvascular pressure, the average (+/- 1 SE) plasma protein concentration was 6.0 +/- 0.4 g/100 ml, lung lymph 3.4 +/- 0.2, and interstitial fluid 3.1 +/- 0.3. Lymph flow increased from an average base-line value of 9.4 ml/h to 43.4 ml/h during edema. Average albumin fractions in lymph and interstitial fluid were 0.56 +/- 0.02 and 0.50 +/- 0.01, respectively, compared with 0.44 +/- 0.01 for plasma. In five sheep with increased-permeability edema, average plasma protein concentration was 5.7 +/- 0.3 g/100 ml, lung lymph 4.1 +/- 0.4, and interstitial fluid 4.6 +/- 0.4. Base-line lymph flow was 11.0 ml/h and increased to 27.8 ml/h during edema. Average albumin fractions in lymph and interstitial fluid were 0.53 +/- 0.01 and 0.50 +/- 0.02, respectively, compared with 0.43 +/- 0.01 for plasma. We conclude in both high-pressure and altered-permeability edema, the protein composition of lung lymph collected from the major lung efferent lymphatic is representative of the free interstitial edema fluid.
Restitution of blood volume after hemorrhage: role of the adrenal cortex
Authors: Pirkle JC  , Gann DS
Published: December 2017

Splenectomized and adrenalectomized-splenectomized dogs, anesthetized with pentobarbital, were bled so that the role of cortisol in restitution of blood volume could be examined. Intact dogs and adrenalectomized dogs infused with cortisol at a high rate (17 mug/min) showed restoration of blood volume and plasma protein at 24 h, preceded by an early increase in plasma osmolality. Adrenalectomized dogs infused with cortisol at basal rates (2 mug/min) showed no increase in plasma osmolality and no restoration of blood volume or plasma protein at 24 h unless extracellular fluid volume was expanded by exogenous fluid. It is concluded that hemorrhage leads to an increase in extracellular osmolality mediated in part by increased cortisol concentrations. As a consequence, there is a shift of intracellular fluid to the interstitium. The resulting increase in interstitial pressure accelerates lymphatic movement of interstitial protein to the vascular system. This results in a reequilibration of extracellular fluid toward the plasma, thus completing the restitution of blood volume. The osmotically active agents mobilized by cortisol do not appear to be glucose, sodium, or potassium.
Heart rate and rhythm and intracranial pressure
Authors: Krasney JA , Koehler RC
Published: December 2017

Cardiac slowing during elevated intracranial pressure (ICP) could be due to direct activation of central nervous system (CNS) centers or it may be secondary to baroreceptor reflexes activated by the associated pressor response. In five pentobarbital-anesthetized dogs when ICP was raised to 50 mmHg the heart rate decreased 34.4 beats/min (+/-4.8 SE). This cardiac slowing occurred when ICP was elevated after sinoaortic denervation (-24 +/- 4.43 beats/min) and also during elevated ICP when changes in arterial pressure were prevented (-32.3 +/- 4.25 beats/min). These results indicate that the cardiac slowing is largely of CNS origin. In dogs given morphine with pentobarbital to achieve slower heart rates, raising ICP to 50 mmHg by left-sided intracranial balloon inflation led to cardiac dysrhythmias in 9 of 12 dogs. By contrast, raising ICP to 50 mmHg by right-sided intracranial balloon inflation only produced progressive sinus bradycardia. These responses were related to a combined enhancement of vagal and sympathetic activity. Differences observed between right- and left-sides balloon inflation may be partly related to asymmetrical engagement of the cardiac autonomic nerves. The results suggest that left-sided intracranial lesions are more likely to produce cardiac dysrhythmias.
Baroreceptor effects on renal and adrenal nerve activity
Authors: Nijima A
Published: December 2017

Spontaneous efferent discharges were recorded from nerve filaments dissected from adrenal and renal nerve bundles in the rabbit. Raising of the systemic blood pressure or stimulation of the depressor nerve caused a decrease in discharge rate in these nerve filaments. Portal vein occlusion or elevation of mesenteric venous pressure caused a depression of activity in these nerves. It is suggested that adrenal and renal sympathetic nerve cells receive inputs from baroreceptors in the systemic arterial system and from mechanoreceptors in the portal and mesenteric veins that cause reflex inhibition of activity in these nerve cells.
Reduced high-energy phosphate levels in rat hearts. I. Effects of alloxan diabetes
Authors: Allison TB , Bruttig SP , Crass MF  , Eliot RS , Shipp JC
Published: December 2017

Significant alterations in heart carbohydrate and lipid metabolism are present 48 h after intravenous injection of alloxan (60 mg/kg) in rats. It has been suggested that uncoupling of oxidative phosphorylation occurs in the alloxanized rat heart in vivo, whereas normal oxidative metabolism has been demonstrated in alloxan-diabetic rat hearts perfused in vitro under conditions of adequate oxygen delivery. We examined the hypothesis that high-energy phosphate metabolism might be adversely affected in the alloxan-diabetic rat heart in vivo. Phosphocreatine and ATP were reduced by 58 and 45%, respectively (P is less than 0.001). Also, oxygen-dissociation curves were shifted to the left by 4 mmHg, and the rate of oxygen release from blood was reduced by 21% (P is less than 0.01). Insulin administration normalized heart high-energy phosphate compounds. ATP production was accelerated in diabetic hearts perfused in vitro with a well-oxygenated buffer. These studies support the hypothesis that oxidative ATP production in the alloxan-diabetic rat heart is reduced and suggest that decreased oxygen delivery may have a regulatory role in the oxidative metabolism of the diabetic rat heart.
Hyperosmolarity: effects on nerves and smooth muscle of cutaneous veins
Authors: McGrath MA , Shepherd JT
Published: December 2017

Helical strips from dogs' saphenous veins were mounted in an organ bath (Krebs-Ringer solution, 37 degrees C) for isometric tension recording. Additional strips were incubated with [7-3H]norepinephrine and mounted for superfusion and isometric tension recording. The perfusate was collected every 2 min for estimation of total radioactivity and for column chromatographic separation of [3H]norepinephrine and its metabolites. Increasing osmolarity by sucrose caused a slow contraction that was maximal at 500-550 mosM and was accompanied by a reduction in total 3H efflux. The contraction was unaffected by a Ca2+-free medium, alpha-adrenegic blockade, and beta-adrenergic stimulaton. It was depressed by cooling (29 degrees C) and by anoxia combined with a glucose-free medium. Contractions elicited by K+ and Ba2+ were augmented by hyperosmolarity, but those caused by sympathetic nerve stimulation, tyramine, and norepinephrine were depressed. The output of [3H]norepinephrine during nerve stimulation was reduced. Thus, the hyperosmolarity causes 1) contraction of vascular smooth muscle, 2) augmentation of the contractile response to K+ and Ba2+, 3) depression of the excitation caused by norepinephrine, and 4) inhibition of the neuronal release of norepinephrine.
Fever and antipyresis in the lizard Dipsosaurus dorsalis
Authors: Bernheim HA , Kluger MJ
Published: December 2017

Lizards (Dipsosaurus dorsalis) were placed in a desertlike environment in which the ambient temperature (Ta) at night (1800-0600 h) was 12 degrees C and the day (0600-1800 h) Ta was between 30 and 55 degrees C depending on the location within the chamber. When dead Aeromonas hydrophila (4 X 10(9) organisms) was injected into nine lizards, an elevation in body temperature (Tb) of 2.7 degrees C was observed during the same day. On the day after bacterial injection the lizards' body temperatures averaged 41.6 degrees C, an increase of 4.2 degrees C over their control day Tb. Further investigations on the febrile response of D. dorsalis were conducted at the University of Wisconsin's Biotron, where there exists a simulated desert environment with the light intensity, temperature, and humidity closely parelleling a typical spring day in the southwestern desert of the United States (the natural habitat of Dipsosaurus). In this environment injection of dead bacteria into seven lizards led to an average febrile response of similar magnitude (Tb = 40.5 degrees C) but with a longer latency than that found at the University of Michigan. Injection of 13 lizards with live A. hydrophila (5 X 10(9) organism subcut.) in the simulated desert at Michigan led to a daytime fever averaging 2.3 degrees C (mean Tb = 40.6 degrees C) over a 5-day period. During the 6th and 7th day the lizards' body temperature returned to the normal or afebrile level. Injections of sodium salicylate along with dead A. hydrophila resulted in a dose-dependent attenuation of the febrile response. These results demonstrate that the reptilian febrile response is strikingly similar to avian and mammalian fever and suggest a common origin and perhaps function for the febrile mechanism.
Responses of rat brainstem neurons to carotid occlusion
Authors: Nosaka S
Published: December 2017

The distribution and features of cardiovascular neurons (CVN) were studied in the brainstem of chloralose-anesthetized rats. Only neurons yielding an immediate response to carotid occulsion (CO) were considered as CVN. The criterion was deduced from the response patterns of cardiovascular afferent (carotid sinus nerve) and efferents (sympathetic and vagal nerves) during CO. Seventy-two CVN were identified and were observed to be mostly in the medullarly reticular formation and to some extent in the nucleus tractus solitarius and nucleus ambiguus. Fifty-five CVN (type A) decreased their firing rates in response to CO where 17 CVN (type B) increased their rates. Analyses of the time courses of their responses to CO revealed the convergence of the chemoreceptor and baroreceptor inputs onto some type A neurons. Electrical stimulation of the spinal cord evoked orthodromic responses in some neurons in both types. The evoked responses were blocked by CO in type A neurons whereas they were facilitated in those of type B. These results suggest that input from arterial baroreceptors, arterial chemoreceptors, and spinal ascending afferents is integrated within CVN.
Role of oxalacetate in lipoate effect on frog gastric mucosa
Authors: Chacin J , Park OH , Harris JB , Alonso D
Published: December 2017

The mechanism of action of lipoate on frog gastric mucosa was investigated. Oxalacetate (OAA) reversed lipoate-inhibited QO2 and QH+ of chambered mucosas by 70 and 40%, respectively. Pyruvate or glucose produced similar effects. Neither activity was affected by OAA when added after glucose, pyruvate, decanoate, butyrate, or lipoate-propionate-inhibited mucosa. Lipoate-treated or lipoate-propionate-treated mucosa did not respond to histamine; OAA addition prior to histamine restored responsiveness. Tracer and chromatographic techniques showed that lipoate reduced and pyruvate increased OAA formation. Preincubation of mitochondrial extracts of gastric mucosa with 2 mM lipoate increased pyruvic dehydrogenase activity 110%. Pyruvic carboxylase (PC) activity was primarily in the mitochondrial fraction of the gastric mucosa. The PC preparation was shown to have an absolute requirement for CoASAc, contained biotin, was not inhibited by lipoate, and had an apparent Km approximately equal to 3.6 X 10(-4) M for pyruvate. The results suggest that OAA concentration is regulated by PC activity and is one of the factors controlling QO2 and QH+ in the frog gastric mucosa.
Propagation of stimulated slow waves in cat intestinal muscle
Authors: Specht PC
Published: December 2017

This study was designed to examine the propagation and propagation failure of the slow wave. Spontaneous slow waves and action potentials were recorded from the longitudinal muscle layer of small strips of cat jejunum. Slow waves could be stimulated electrically at intervals shorter than the spontaneous interval, and the velocity of propagation of these slow waves was slower than the spontaneous slow waves. The velocity of propagation was approximately proportional to the time between slow waves. At intervals about one-half the normal spontaneous interval the propagation became slow and unstable, which would result in the periodic failure of a single slow wave. This type of failure may underlie the formation of the slow-wave frequency gradient observed in the intact intestine. The wave shape of the external recording of the slow wave, together with the measurement of electrotonic current spread in strips of isolated muscle, suggest that the slow wave propagates by local circuit currents in an electrically excitable cablelike tissue.
Determinants of glomerular filtration rate in the dog
Authors: Ott CE , Marchand GR , Diaz-Buxo JA , Knox FG
Published: December 2017

Micropuncture techniques were used to evaluate the determinants of glomerular filtration in hydropenic dogs. Stop-flow and servo-null techniques were used to estimate the glomerular capillary and proximal tubule hydrostatic pressures. The validity of stop-flow estimates was verified by comparisons with direct puncture of glomerular capillaries in Munich-Wistar rats. Efferent arteriolar oncotic pressure was calculated from the filtration fraction and systemic protein concentrations. This calculation was verified in separate experiments by measurement of the protein concentration in blood collected directly from efferent arterioles. In 14 dogs, estimated glomerular capillary pressure (GCP) averaged 65.8 +/- 2.9 mmHg and proximal tubule pressure (PT) averaged 20.5 +/- 1.3 mmHg. The net hydrostatic filtration pressure (GCP - PT) of 45.3 +/- 2.7 mmHg was significantly higher than the efferent arteriolar oncotic pressure (piEA) of 33.2 +/- 2.8 mmHg (P less than .001). These findings indicate that filtration dynamics in the dog are characterized by filtration pressure disequilibrium.
Maturation of contractile response of ductus arteriosus to oxygen and drugs
Authors: Noel S , Cassin S
Published: December 2017

Contractile responses of rings of ductus arteriosus from fetal and neonatal guinea pigs were studied in buffered Krebs-Henseleit solutions of various oxygen tensions. Oxygen-induced contraction of ductus arteriosus increased with gestational age, peaking at term and attenuating within 24 h after birth. Contractions of ductus in response to potassium were not different in term and preterm fetuses. Maximal contractile response of pre- and postductal aortic rings to oxygen was 8.3% of the maximal oxygen-induced contraction of ductal rings from the same fetuses. Pulmonary artery was quite insensitive to oxygen. Of 12 ductus exposed to bradykinin in the absence of oxygen seven contracted (maximal response was obtained with 15.0 ng/ml). Exposure of ductus to bradykinin in the absence of oxygen enhanced subsequent contractions of ductal smooth muscle rings to air. Atropine failed to inhibit the oxygen-induced contraction of ductus. These data suggest that acetylcholine is not essential for oxygen-induced contraction of the guinea pig ductus arteriosus.
Effect of potassium on ammoniagenesis by renal mitochondria
Authors: Tannen RL , Kunin AS
Published: December 2017

Ammonia production by rat renal cortical mitochondria was studied with both in vivo and in vitro manipulation of potassium to further elucidate the mechanisms relating potassium homeostasis and renal ammonia production. Mitochondria from potassium-depleted animals demonstrated an increase in ammonia production at all glutamine concentrations studied, which ranged from 0.5 to 10 mM. This increase in ammoniagenesis compared favorably in degree of change with and was of sufficient absolute magnitude to entirely account for the findings observed both in renal cortical slices studied in vitro and in the intact animal. When rotenone is added to the medium, increased ammoniagenesis is still detected, indicating that either glutamine entry into the mitochondria and/or the activity of phosphate-dependent glutaminase are critical rate-controlling steps. In contrast to studies with renal slices, a decrease in ammonia production was not apparent with cortical mitochondria from chronically potassium-loaded animals. In vitro alterations of the potassium homeostasis. Therefore, these experimental manipulations either do not activate an effector mechanism which takes place in vivo, or the alteration in ammoniagenesis requires an adaptation over time that is not achieved with this in vitro approach.
Suppressive effect of endotoxin on erythropietin-responsive cells in mice
Authors: Schade SG , Fried W
Published: December 2017

Infection may be associated with failure of erythropoiesis, and endotoxin has been shown to cause a decrease in the number of erythroid cells in the marrow of mice. We have investigated the effect of endotoxin on erythropoiesis in BDF1 mice by studying its effect on the incorporation of intravenously administered 59Fe into peripheral red cells. In normal mice the injection of endotoxin 2 and 3 days prior to the administration of 59Fe results in suppression of its incorporation into red cells. In exhypoxic polycythemic mice, endotoxin suppresses the response to erythropoietin injection when the endotoxin is given prior to or at the same time as the erythropoietin. This effect is much less marked when endotoxin is given after erythropoietin. We conclude that endotoxin either 1) impairs the function of erythropoietin-responsive cells, 2) competively decreases erythroid progenitors by stimulating granulocytes, or 3) inactivates erythropoietin.
Digestion of tripeptides and disaccharides: relationship with brush border hydrolases
Authors: Arvanitakis C , Ruhlen J , Folscroft J , Rhodes JB
Published: December 2017

Intestinal digestion of two tripeptides (leucyl-glycyl-glycine, prolyl-glycyl-glycine) and two disacchrarides (sucrose, maltose) was examined in the hamster by intestinal perfusion in vivo and hydrolysis of the substrates by microvillus membranes. Perfusion studies showed that luminal disappearance rates of leucyl-glycl-glycine were significantly higher than prolyl-glycyl-glycine (P less than o.001), sucrose (P less than 0.001), and maltose (P less than 0.005). Hydrolytic products of leucyl-glycyl-glycine, sucrose, and maltose were detected in the gut lumen in appreciable concentrations, whereas negligible concentrations of prolyl-glycyl-glycine products were present. Leucyl-glycyl-glycine hydrolysis in microvillus membranes was markedly higher than prolyl-glycyl-glycine (P less than 0.001), which was predominant in the cytoplasmic fraction. These results indicate that leucyl-glycyl-glycine, like sucrose and maltose, is hydrolyzed at the membrane. With some tripeptides, i.e., leucyl-glycyl-glycine, digestion occurs at the microvillus membrane with subsequent transport of hydrolytic products into the intestinal epithelial cell. Other tripeptides, i.e., prolyl-glycyl-glycine, may cross the membrane and undergo intracellular hydrolysis by cytoplasmic peptidases.
Sympathetic nervous control of cat ileocecal sphincter
Authors: Pahlin PE , Kewenter J
Published: December 2017

A perfusion method was designed in order to investigate that effects of stimulation of the splanchnic and lumbar colonic nerves on the ileocecal sphincter (ICS) of the cat. Splanchnic and lumbar colonic nerve stimulation at physiological frequencies, i.e., below 10-12 impulses/s, elicited a contraction of the sphincter concomitant with an inhibition of the motility of the adjacent parts of the small and large intestines. It is concluded that the splanchinc and lumbar colonic nerves contract the ICS by a direct effect on the sphincter and not via a contraction of the intestine surrounding the sphincter. Guanethidine and phenoxybenzamine but not propranolol blocked the contraction of the ICS. It is suggested that the splanchnic and lumbar colonic nerves control the sphincter via an alpha-adrenergic mechanism. Inhibitory fibers within the splanchnic or lumbar colonic nerves to the ICS were not found. The excitatory in the ICS elicited by adrenaline, nor-adrenaline, or phyenylephrine infusion was completely blocked by phenoxybenzamine. Propranolol did not block the effect on ICS of these drugs. On the contrary, an augmented response could be shown, indicating unmasking of an excitatory alpha-receptor response by blockade of inhibitory beta-receptors. Further support for these inhibitory beta-receptors was provided by the finding that isoprenaline had a relaxing effect on the sphincteric muscle, an effect that was blocked by propranolol. In order to block the inhibitory effect on the small and large intestine elicited by splanchnic and lumbar colonic nerve stimulation, both phenoxybenzamine and propranolol had to be administered.