bluuebunny/crossref_metadata_2025 huggingface dataset:
Pulsatile release of antipyretic neuropeptide alpha-MSH from septum of rabbit during fever
Authors: Bell R. C. , Lipton J. M.
Published: December 2017

The effects on fever of central administration of alpha-melanocyte-stimulating hormone (alpha-MSH) and its antiserum, the specific increase in central concentration of alpha-MSH during fever, and related results indicate that this neuropeptide is important to central nervous system (CNS) regulation of the febrile response. The present experiments were designed to establish whether alpha-MSH is released from septal tissue during fever and, if so, in what temporal course relative to the febrile response. alpha-MSH release at localized push-pull perfusion sites within the septum during fever induced by intravenous interlukin-1 occurred in two basic patterns: prolonged or repeated release over sequential 10-min sample periods or a more discrete pulse largely confined to a single 10-min period. The greatest increases in concentration and the greatest number of increases occurred during the chill phase of fever, when temperature was rising rapidly, rather than during the plateau phase. Such episodic release is similar to that known to occur in neuroendocrine and other physiological systems, and it provides further support for a physiological role of alpha-MSH in CNS control of fever.
Recombinant tumor necrosis factor and interleukin 1 enhance slow-wave sleep
Authors: Shoham S. , Davenne D. , Cady A. B. , Dinarello C. A. , Krueger J. M.
Published: December 2017

The cytokines interleukin 1 (IL 1) and interferon (IFN) are immune response modifiers that are also pyrogenic and somnogenic. Tumor necrosis factor (TNF) (cachectin) is another pyrogenic monocyte product whose production can be elicited by somnogenic agents such as endotoxin. Human recombinant TNF (rTNF), therefore, was assayed for somnogenic activity. Intravenous (iv) or intracerebroventricular (ICV) injections of rTNF enhanced slow-wave sleep (SWS) and electroencephalographic slow-wave (0.5-4.0 Hz) activity. Recombinant TNF also suppressed rapid-eye-movement sleep (REM) and induced biphasic fevers whether given by intravenous or ICV injection. Responses to rTNF were compared with those elicited by human recombinant beta-IL 1 (rIL 1). Sleep responses elicited by rIL 1 were similar to those previously reported for native IL 1 and to those elicited by rTNF. However, unlike rTNF, rIL 1 induced monophasic fevers. Animal behavior and brain temperature changes that occur during the transition from one arousal state to another remained undisturbed after either rTNF or rIL 1 treatment. The fact that TNF and IL 1 as well as other immunoactive substances, e.g., IFN, muramyl peptides, and endotoxin, enhance SWS suggests that SWS is linked to the immune response. We conclude that TNF, in addition to IL 1 and IFN, is an endogenous somnogen.
Circadian rhythms of rabbits during restrictive feeding
Authors: Jilge B. , Hornicke H. , Stahle H.
Published: December 2017

Without a zeitgeber the circadian rhythms of five physiological functions free-ran with a period length greater than 24 h. Restricted feeding time (RF) masked the free-running rhythms. In addition to masking, entrainment with RF occurred. This process was most evident in locomotor activity and visits to the food box. RF thus had zeitgeber properties in these rabbits. However, in most rabbits the RF zeitgeber was not strong enough to entrain the circadian rhythm completely. A small component free-ran during RF. Following return to continuous food access the whole circadian rhythm resumed to free-run again. In some animals its phase was determined by the RF zeitgeber and in others by the small free-running fraction present during RF. The results suggest that in addition to the light-dark-entrainable circadian oscillator system a feeding-entrainable oscillator exists that takes over phase control of the majority of the rhythm during RF.
Acid-base status and electrolytes in red blood cells and plasma of turtles submerged at 3 degrees C
Authors: Maginniss L. A. , Hitzig B. M.
Published: December 2017

Two groups of adult Chrysemys picta bellii were studied; control turtles were maintained at 24 degrees C with free access to air, and diving animals were continuously submerged for 8.5-9.5 wk in aerated water at 3 degrees C. Cold submergence elicited a substantial lactic acidosis (blood pH 7.70; plasma [lactate-] 42.5 meq/l H2O). This acid load was largely balanced by changes in plasma strong ions; [Cl-] decreased, and [Ca2+] and [Mg2+] increased. Phosphorus nuclear magnetic resonance showed a significant reduction in the transerythrocyte pH gradient of diving animals (control, delta pH 0.66-0.90; diving, 0.00-0.11). This relative alkalosis of submerged turtle red cells was related to changes in blood cell (RBC) volume and composition; mean corpuscular concentration of hemoglobin [( Hb]) and RBC H2O content measurements revealed a 39% increase in RBC volume. Cell volume change was effected by a proportionally greater influx of K+ than Cl-, providing ionic compensation for the lactic acidosis. The obligatory H2O influx, which decreased the effective concentration of protein anion, and a 77% reduction of RBC [ATP] further contributed to the relative alkalosis. The combined effects of RBC alkalization and reduced [ATP] account for the observed Hb-O2 binding properties previously reported for submerged turtles at 3 degrees C (15).
Metabolism in lizards: low lactate turnover and advantages of heterothermy
Authors: Guppy M. , Bradshaw S. D. , Fergusson B. , Hansen I. A. , Atwood C.
Published: December 2017

The bobtail lizard (Tiliqua rugosa) encounters environmental temperatures that range from 7 to 40 degrees C. We have studied the effects of temperature on the whole-body turnover of glucose, lactate, and fatty acid. At 35 degrees C turnover rates of glucose and fatty acid account for the majority of O2 uptake and reflect the low metabolic rate of the bobtail compared with that of a mammal of equivalent mass. Lactate turnover at rest is very low. The low rates of lactate production correlate with a lack, or relative lack, of those tissues that normally produce most of the lactate in a resting mammal, such as nonnucleated red blood cells, renal medulla, and smooth muscle associated with blood vessels. Q10 (change in rate with a 10 degrees C change in temperature) values for turnover rates of glucose and fatty acid increase as temperature decreases. It is concluded that there is an inverse temperature effect that minimizes fuel usage during torpor.
Tyrosine transport in winter flounder intestine: interaction with Na+-K+-2Cl- cotransport
Authors: Musch M. W. , McConnell F. M. , Goldstein L. , Field M.
Published: December 2017

Tyrosine absorption across the brush border of the intestinal epithelium of the winter flounder Pseudopleuronectes americanus was studied in Ussing chambers modified to determine early rates of uptake. At 0.1 mM tyrosine, the 4-min rate of uptake (influx) of tyrosine across the brush border averaged 37.5 nmol X cm-2 X h-1. Omission of Na decreased influx by 60%, indicating that tyrosine influx occurs, at least in part, by a Na-coupled process. Ouabain inhibited influx by 80%. Inhibition of brush border Na+-K+-2Cl- cotransport by bumetanide, 8-bromo-cyclic GMP, or Cl replacement stimulated tyrosine influx 2.5- to 4-fold. However, atriopeptin III, which also inhibits Na+-K+-2Cl- cotransport, did not stimulate tyrosine influx. Cyclic AMP, which does not appear to inhibit ion cotransport, did not stimulate tyrosine influx. Both cyclic GMP and bumetanide also stimulated the net mucosa-to-serosa tyrosine flux (43 and 29%, respectively) and increased the cellular concentration of tyrosine by 50%. Thus tyrosine's influx is increased to a greater extent than is its transmural flux or its cellular concentration, suggesting that the main change occurs at the brush border and represents large increases in both influx and efflux of tyrosine across this membrane.
Dehydration and arginine vasotocin and angiotensin II in CSF and plasma of pekin ducks
Authors: Gray D. A. , Simon E.
Published: December 2017

Osmolalities and, by radioimmunoassay, the contents of arginine vasotocin (AVT) and angiotensin II (ANG II) in simultaneously collected cisternal cerebrospinal fluid (CSF) and plasma samples were determined in chronically prepared conscious Pekin ducks (Anas platyrhynchos) adapted to either freshwater (FW ducks) or salt water (2% saline, SW ducks) for drinking. In FW ducks the AVT in CSF was approximately 10-fold higher than in plasma; ANG II concentration in CSF was about two-thirds of that in plasma. In SW ducks concentrations of AVT were increased approximately threefold and of ANG II fourfold in both CSF and plasma. Dehydration in FW ducks (24-48 h) increased AVT and ANG II in both CSF and plasma, the relative rise being greater in plasma. Within 150 min after rehydration plasma AVT fell at unchanged CSF AVT, whereas CSF ANG II fell at unchanged plasma ANG II. Hydration of SW ducks with freshwater had similar effects. The results indicate separate avenues of release of central and systemic AVT and ANG II and support the idea of an independent control of central ANG II as a mediator in osmoregulation, with CSF AVT reflecting the state of osmoregulatory activity of the hypothalamopituitary vasotocinergic system.
Diuretic and natriuretic properties of prestegane B, a mammalian lignan
Authors: Plante G. E. , Prevost C. , Chainey A. , Braquet P. , Sirois P.
Published: December 2017

The effect of increasing doses of prestegane B, a synthetic lignan, was examined in the anesthetized normal rat, using clearance methodology. Increasing doses of prestegane B 0.5, 1.0, 2.0, and 5.0 mg) were administered intravenously in our separate groups of hydropenic rats. Urine flow increased by 2.8 +/- 0.3, 4.5 +/- 0.5, 7.7 +/- 0.5, and 18.2 +/- 0.8 microliters/min, respectively, above control values. The rise of urinary sodium secretion was of similar magnitude and averaged 0.4 +/- 0.1, 0.8 +/- 0.2, 1.1 +/- 0.3, and 2.4 +/- 0.3 mu eq/min, respectively. No significant change in urinary phosphate excretion was obtained in all groups of rats, and glomerular filtration rate remained constant from control to experimental clearance periods. The natriuretic effect of prestegane B observed in this in vivo model could be related to the inhibition of the Na+-K+-adenosine triphosphate activity demonstrated in vitro in previous studies from our laboratory. The action of this substance is likely to be situated beyond the proximal tubule, since urinary phosphate was not altered. Prestegane B mimics the effects of other endogenous diuretic and natriuretic hormones, but its site of action and its effect on renal hemodynamics are obviously different.
Ouabain binding in tadpole ventral skin. I. Kinetics and effect on intracellular ions
Authors: Robinson D. H. , Mills J. W.
Published: December 2017

The short-circuit current across tadpole skin is inhibited by only 50% after 2 h of exposure to 10(-2) M ouabain [Am. J. Physiol. 237 (Regulatory Integrative Comp. Physiol. 6): R74-R79, 1979]. To determine the Na pump sensitivity to ouabain, the kinetics of ouabain binding in tadpole epidermis and the effect of ouabain on intracellular Na and K were tested. In tadpole epidermis a high-affinity dissociation constant (KD) for ouabain of 1.21 +/- 0.20 X 10(-7) M was found, which is similar to the KD in frog skin (1.27 +/- 0.16 X 10(-7) M). Incubation of tadpole epidermis in ouabain for 1 h increased intracellular Na concentration from 48.8 +/- 3.3 to 66.2 +/- 4.9 mM (P less than 0.005) and decreased K concentration from 115 +/- 7 to 104 +/- 9 mM (P less than 0.01). Two hours of ouabain exposure increased intracellular Na concentration from 41.4 +/- 2.4 to 73.3 +/- 4.3 mM (P less than 0.0005) and decreased K concentration from 113 +/- 10 to 85.9 +/- 5.3 mM (P less than 0.05). Regression analysis of the change in Na and K concentrations reveals a slope of 14.7 +/- 2.5 mM/h for the Na gain, which is similar in magnitude to the rate of K decrease (-13.8 +/- 4.7 mM/h). It is hypothesized that the residual short-circuit current seen in tadpole skin after ouabain exposure is a result of current being carried through the tissue by a slow gain of Na across the apical membrane and an equivalent loss of K across the basolateral membrane.
Role of angiotensin in sodium appetite of sodium-deplete sheep
Authors: Weisinger R. S. , Denton D. A. , Di Nicolantonio R. , McKinley M. J. , Muller A. F. , Tarjan E.
Published: December 2017

The role of the renin-angiotensin system (RAS) in the Na appetite of Na-deplete sheep was investigated. Intravenous infusion of the angiotensin-converting enzyme inhibitor, captopril, at 0.01 or 0.1 mg X kg-1 X h-1 did not cause any change in Na intake, although the higher dose caused a marked decrease in mean arterial blood pressure. Intravenous infusion of captopril at 1.0 mg X kg-1 X h-1 over 24 h decreased Na intake by 45-55% in the absence of any change in Na loss. The decrease in Na intake was restored to base-line level or above by concurrent intravenous infusion of angiotensin II (ANG II) at 3.8 or 24 micrograms/h over 24 h but not by intracerebroventricular (ICV) ANG II at 3.8 micrograms/h. In addition, ICV infusion of 0.7 M mannitol (1 ml/h over 3 h), which reduced cerebrospinal fluid (CSF) and brain extracellular fluid [Na], still increased Na intake when combined with intravenous captopril. Water intake was not altered during intravenous captopril or ANG II alone but was increased during ICV ANG II or 0.7 M mannitol (with or without iv captopril). In conclusion, these results suggest that the RAS is involved in the Na appetite of the Na-deplete sheep. Furthermore, it would appear that the brain area involved is one without a blood-brain barrier but with a CSF-brain barrier, such as one of the circumventricular organs. Also, it would appear that the effect of lowered cerebral Na and the effect of activation of the renin-angiotensin system on Na appetite are independent.
Glomerular filtration, renal blood flow, and solute excretion in conscious aging rats
Authors: Corman B. , Michel J. B.
Published: December 2017

Measurement of daily food and water intakes and of renal water and solute excretion in 10-, 20-, and 30-mo-old female rats revealed that they ate the same amounts of food and excreted the same amounts of glucose, sodium, and potassium irrespective of age but that in the 30-mo-old rats phosphate, calcium, and magnesium excretion rose. The glomerular filtration rate and p-aminohippuric acid clearance measured in conscious animals following moderate volume expansion did not differ with age, when expressed per 100 g body wt, but decreased markedly in the 30-mo-old rats when compared with kidney weight. This was related to the senile hypertrophy of the kidneys in the 30-mo-old group, which was reflected by increases in glomerular volume and length of the proximal tubules and by enlargement of the medulla, with the number of nephrons remaining constant with age. There was no evidence of glomerulosclerosis or kidney disease, and proteinuria remained at a low level in all three age groups. These results suggest that the diminished renal filtration rate observed in both conscious and anesthetized senescent rats is due to a reduced supply of blood per gram of kidney tissue and not to loss of nephrons.
Brown fat thermogenesis in a rat model of dietary obesity
Authors: Fisler J. S. , Lupien J. R. , Wood R. D. , Bray G. A. , Schemmel R. A.
Published: December 2017

The effects of chronic feeding of a high-fat diet or a cafeteria-type diet on weight gain and thermogenesis in brown adipose tissue as measured by the binding of a purine nucleotide (guanosine 5'-diphosphate, GDP) to mitochondria of brown adipose tissue have been studied in two strains of rats that differ in their susceptibility to dietary obesity. S 5B/Pl rats, which are resistant to developing obesity when eating a high-fat diet or drinking sucrose solutions, have greater specific GDP binding in interscapular brown adipose tissue (IBAT) than do Osborne-Mendel rats, which are sensitive to fat-induced obesity. A high-fat diet, fed isoenergetically to the low-fat diet, did not increase the growth of IBAT and decreased specific GDP binding in both strains. Feeding a cafeteria diet resulted in obesity and increased mass and protein content of the IBAT in both strains of rats. However, specific GDP binding increased in response to cafeteria feeding only in the Osborne-Mendel rats. These studies show that thermogenesis, as measured by GDP binding to mitochondria in brown adipose tissue, is suppressed by both isoenergetic and ad libitum feeding of a high-fat diet. The higher basal GDP binding in the brown fat of the S 5B/Pl rats suggests that higher thermogenesis of this tissue contributes to the resistance of this strain to fat-induced obesity. The inability of S 5B/Pl rats to further increase thermogenesis when eating a cafeteria diet may contribute to their becoming obese.
Lactate kinetics in exercising Thoroughbred horses: regulation of turnover rate in plasma
Authors: Weber J. M. , Parkhouse W. S. , Dobson G. P. , Harman J. C. , Snow D. H. , Hochachka P. W.
Published: December 2017

Plasma lactate turnover rate of Thoroughbred racehorses was measured by bolus injection of [U-14C]lactate at rest and two levels of submaximal treadmill exercise (3-4 m/s trot, 6% incline, and 6.5 m/s horizontal canter). Our goals were 1) to determine the relative effects of changes in cardiac output and in plasma lactate concentration on turnover rate [using cardiac output data from Weber et al. (28)] and 2) to assess the importance of lactate as a metabolic fuel in a trained animal athlete. Lactate turnover rates were 9.3 mumol.min-1.kg-1 (rest), 75.9 mumol.min-1.kg-1 at the beginning of the trot protocol [45% maximum O2 uptake (VO2max)], 50.3 mumol.min-1.kg-1 later in the same protocol (50% VO2max), and 66.1 mumol.min-1.kg-1 during the canter protocol (55% VO2max). Both changes in cardiac output and in plasma lactate concentration had a significant effect on turnover rate. Variation in plasma lactate fluxes of Thoroughbreds during exercise follows the standard mammalian pattern, but this substrate only plays a minor role as an oxidizable fuel in horses. The oxidation of plasma lactate accounts for less than 5% of metabolic rate (VO2) during submaximal work. Adjustments in cardiac output and in metabolite concentration represent, respectively, the coarse and fine controls for the regulation of plasma metabolite turnover rate.
Control of canine ACTH by corticosteroids: interaction between dose and time
Authors: Keller-Wood M.
Published: December 2017

These experiments were designed to test for interactions between dose and time of administration of steroids in control of adrenocorticotropin hormone (ACTH). Five dogs were infused for 30 min with cortisol and corticosterone in a 2:1 ratio at a total rate of 1.5 or 3.0 micrograms.kg-1.min-1 beginning 120, 90, 60, 30, or 0 min before injection of insulin (0.5 U/kg). The infusions increased total plasma corticosteroids to approximately 50 or 80 ng/ml. Inhibition of basal ACTH occurred when infusion of steroid at either rate began greater than or equal to 60 min earlier. The degree of inhibition of stimulated ACTH was dependent on both steroid dose and timing of steroid infusion relative to the stimulus. Increasing corticosteroids to 50 ng/ml reduced the ACTH response to hypoglycemia if the infusion began 30 min, but not 60, 90, or 120 min earlier. Increasing corticosteroids to 80 ng/ml inhibited the response if the infusion began 120 or 60 min before injection of insulin. The data suggest that 1) inhibition of stimulated ACTH required less than or equal to 30 min to appear; 2) the duration of corticosteroid feedback is steroid-dose related; 3) basal ACTH secretion is more sensitive than stimulated ACTH to steroid inhibition; 4) small increments in plasma corticosteroids over short periods of time can inhibit canine ACTH.
Effect of arterial pressure on drinking and urinary responses to angiotensin II
Authors: Evered M. D. , Robinson M. M. , Rose P. A.
Published: December 2017

To investigate the relationship between angiotensin II (ANG II) and mean arterial pressure (MAP) in the control of drinking in rats, we infused ANG II intravenously at constant rates (either 50 or 100 ng.kg-1.min-1 for 90 min) and varied MAP by intravenous injections of diazoxide (5-20 mg/kg). Rats were pretreated with captopril to block the endogenous synthesis of ANG II. When given alone, low and high doses of ANG II increased MAP approximately 30 and 50 mmHg, respectively. The low but not the high dose significantly increased water intake above control levels. Both doses caused such a large diuresis and natriuresis that the net effect was fluid loss. Reducing MAP toward normal greatly increased the drinking response to the high but not the low dose of ANG II and reduced the urinary solute and water loss to both doses. These results support the hypothesis that water intake and net fluid gain are inhibited when MAP is above normal. When MAP was reduced below normal in rats given constant infusions of ANG II the amount of water drunk and net fluid gain was proportional to the dose of ANG II but not the dose of diazoxide, the degree of hypotension, or urinary losses. This is consistent with previous reports that ANG II is essential for the drinking response to hypotension. Furthermore, it demonstrates that ANG II is not merely permissive but probably the signal controlling water intake when arterial pressure is reduced below normal.
Ventricular receptors stimulate vasopressin release during hemorrhage
Authors: Wang B. C. , Flora-Ginter G. , Leadley R. J. , Goetz K. L.
Published: December 2017

These experiments were designed to investigate whether a reflex arising from ventricular receptors is capable of stimulating vasopressin secretion during hemorrhage. Three groups of conscious dogs (sham operated, cardiac denervated, and ventricular denervated) were hemorrhaged slowly until 30 ml blood/kg body wt had been removed. Hemorrhage produced comparable decreases in stroke volume, central venous pressure, and left atrial pressure in each group of dogs but produced a different pattern of heart rate response in each group. Plasma vasopressin concentrations before hemorrhage did not differ in the three groups of dogs. In sham-operated dogs plasma vasopressin increased from a control level of 2.4 +/- 0.3 to 6.2 +/- 1.7, 200.0 +/- 65.4, and 991.3 +/- 220.9 pg/ml after 10, 20, and 30 ml/kg of blood had been removed, respectively. In contrast, plasma vasopressin did not increase in either cardiac-denervated or ventricular-denervated dogs after 10 ml/kg of blood had been removed, and the increases in circulating vasopressin after 20 and 30 ml/kg hemorrhage were markedly attenuated by cardiac denervation and by ventricular denervation. The magnitude of the increase in plasma vasopressin in the cardiac-denervated and ventricular-denervated dogs did not differ significantly at comparable levels of hemorrhage. The results are consistent with the possibility that a reflex initiated by ventricular receptors is primarily responsible for stimulating the secretion of vasopressin during hemorrhage in conscious dogs.
Spinoreticular cell responses to renal venous and ureteral occlusion
Authors: Ammons W. S.
Published: December 2017

Responses of 65 thoracolumbar spinoreticular neurons to renal vein or ureteral occlusion were studied in 40 alpha-chloralose-anesthetized cats. Cells were antidromically activated from the medial medullary reticular formation and all responded to somatic stimuli as well as renal nerve stimulation. Renal vein occlusion excited 17 of 40 cells. Activity increased from 6 +/- 1 to 13 +/- 2 spikes/s, with little adaptation. Depressor responses occurred in 9 cats and pressor responses in 12 cats. Pressor responses, but not depressor responses, were abolished by renal denervation. Ureteral occlusion increased activity of 28 of 50 cells. Responses were always rapid in onset but were either nonadapting, slowly adapting, or completely adapting. Activity increased from 7 +/- 1 to a peak of 17 +/- 3 spikes/s. Pressor responses occurred in 22 of 25 cats and tachycardia in 15 cats. Transection of renal nerves abolished cardiovascular responses. Twenty-five cells were tested for responses for both stimuli. Ten were excited by both, six by only ureteral occlusion, and nine failed to respond to either. The responding group of cells had a significantly greater incidence of A delta- and C-fiber renal input compared with nonresponding cells. Nonresponding cells tended to have only A delta-input. The results show that renal and ureteral mechanical stimuli which evoke cardiovascular reflexes excite spinoreticular cells. These cells may be part of supraspinal reflex arcs initiated by renal receptors.
Ontogeny of alpha-adrenoceptor responses in renal vascular bed of sheep
Authors: Matherne G. P. , Nakamura K. T. , Robillard J. E.
Published: December 2017

The renal hemodynamic response to renal arterial infusions of guanabenz (alpha 2-adrenoceptor agonist) and phenylephrine (alpha 1-adrenoceptor agonist) were compared in conscious and chronically instrumented fetal (132-140 days gestation; term 145 days), newborn (6-15 days postnatal), and nonpregnant adult sheep. Phenylephrine produced similar dose-related decreases in renal blood flow velocity in all three groups at low concentrations (less than 1.8 X 10(-7) M) of drug in renal blood, whereas at the highest concentration adults demonstrated the most vasoconstriction and newborns the least (P less than 0.05 ANOVA). Responses to phenylephrine infusion during renal alpha 1-adrenoceptor blockade with prazosin were completely inhibited. Guanabenz produced greater renal vasoconstriction in adult sheep (P less than 0.05 ANOVA) at all concentrations (0.6 X 10(-6) to 8 X 10(-6) M) when compared with fetal and newborn sheep. Guanabenz-mediated vasoconstriction was not affected by alpha 1-adrenoceptor blockade with prazosin but was completely inhibited by the addition of an alpha 2-adrenoceptor antagonist idazoxan. Results of the present study demonstrate that renal vasoconstriction is mediated by both alpha 1- and alpha 2-adrenoceptors in fetal, newborn, and adult sheep. Moreover, these results suggest that renal alpha 1- and alpha 2-adrenoceptor-mediated vasoconstrictor responses mature at different rates.
Electrical stimulation of paraventricular nucleus increases plasma renin activity
Authors: Porter J. P.
Published: December 2017

Studies employing direct electrical stimulation of the renal nerves have shown that, depending on the frequency used, selective effects on renal function can be evoked. With low frequencies, an increase in renin secretion can be elicited without affecting glomerular filtration rate, sodium excretion, or renal blood flow. In the present investigation the possibility was addressed that the central nervous system (CNS) is also organized to evoke selective changes in renal function. The paraventricular nucleus (PVN) of the hypothalamus was electrically stimulated in conscious rats with 150 microA and frequencies of 2.5, 5, 10, and 15 Hz. Blood samples for determination of plasma renin activity (PRA) were collected before and at the end of each 5-min stimulation period. The lower frequencies had no effect on PRA, but stimulation with 10 and 15 Hz produced a significant increase. This effect on PRA was not accompanied by changes in arterial pressure or renal blood flow. In a separate group of animals, stimulation of the PVN with 15 Hz produced a marked decrease in urine volume, but sodium excretion did not change. These data raise the possibility that the CNS is organized to evoke selective increases in sympathetic outflow to the kidney and to produce separate changes in renal functions.
A slow potassium conductance after action potential bursts in rabbit vagal C fibers
Authors: Siegel R. M. , Birks R. I.
Published: December 2017

Sucrose gap recordings were made from vagus nerve in rabbit to examine the mechanisms underlying the generation of the hyperpolarization that follows a burst of evoked action potentials in unmyelinated C fibers. Analysis of the posttetanic hyperpolarization was made by fitting the membrane potential changes with the sum of two exponential components. The posttetanic hyperpolarization consisted of two separable components with time constants of approximately 0.5 and 30 s. The slower exponentially decaying component was dependent on an increase in electrogenic sodium pumping as shown by the effect of ouabain and changes in extracellular chloride. The faster-decaying exponential component was caused by a potassium conductance as shown by the effect of varied extracellular potassium. This potassium conductance appears to be novel as its dynamics vary with the frequency and duration of the burst yet increases in reduced calcium. It is suggested that this slow decaying and modifiable potassium conductance can play a role in modulation of preganglionic and presynaptic action potential conduction.
Characterization of a broad-scope amino acid transport system in sand dollars
Authors: Davis J. P. , Bellis S. , Stephens G. C.
Published: December 2017

Both echinoderm embryos and adults take up alpha-amino acids by an apparent broad-scope transport system. This transporter can be characterized as follows: alanine transport is not blocked by alpha-(methylamino)isobutyric acid. Leucine and other lipophilic neutral amino acids are preferentially transported. Transport is sodium dependent and blocked by 2-aminobicyclo-[2,2,1]heptane-2-carboxycylic acid. Lysine and aspartate transport is inhibited by lipophilic neutral amino acids. Taurine, a beta-neutral amino acid, is translocated via a second and independent carrier.
Pyrogenicity of interferon and its inducer in rabbits
Authors: Won S. J. , Lin M. T.
Published: December 2017

The effects of intracerebral administration of interferon (IFN) or its inducer polyriboinosinic acid-polyribocytidylic acid (poly I:C) on thermoregulatory responses were assessed in conscious rabbits. Administration of IFN (10(2)-10(6) IU) or poly I:C (0.012-12 micrograms) into the preoptic anterior hypothalamus or the third cerebral ventricle caused a dose-dependent fever in rabbits at three ambient temperatures (Ta) tested. In the cold (Ta = 8 degrees C), the fever was due to increased metabolism, whereas in the heat (Ta = 32 degrees C) the fever was due to a reduction in respiratory evaporative heat loss and ear skin blood flow. At the moderate environmental temperature (Ta = 22 degrees C), the fever was due to increased metabolism and cutaneous vasoconstriction. Compared with the febrile responses induced by cerebroventricular route injection of IFN or poly I:C, the hypothalamic route of injection required a much lower dose of IFN or poly I:C to produce a similar fever. Furthermore, the fever induced by intrahypothalamic injection of IFN or poly I:C was reduced by pretreatment of animals with a systemic dose of indomethacin (an inhibitor of all prostaglandins formation) or cycloheximide (an inhibitor of protein synthesis). The data indicate that IFN or its inducer may act through the endogenous release of a prostaglandin or a protein factor of an unknown chemical nature in the preoptic anterior hypothalamic region to induce fever in rabbits. The fever induced by IFN or its inducer is brought about by a decrease in heat loss and/or an increase in heat production in rabbits.
Adrenodemedullation affects endurance but not hepatic fructose 2,6-bisphosphate
Authors: Yang H. T. , Hammer R. L. , Sellers T. L. , Arogyasami J. , Carrell D. T. , Winder W. W.
Published: December 2017

Sham-operated (SHAM) and saline (ADM-S)- or epinephrine (ADM-E)-infused adrenodemedullated rats were run on a treadmill (21 m/min, 15% grade) for 80 min or until exhaustion. ADM-S rats had significantly lower endurance run times (116 +/- 6 min) than ADM-E rats (136 +/- 8 min) and SHAM rats (150 +/- 6 min). Liver glycogen content dropped from 56 +/- 4 to 10 +/- 2 mg/g in SHAM and from 54 +/- 4 to 18 +/- 5 mg/g in ADM-S and to 20 +/- 8 mg/g in ADM-E rats at 80 min. Liver glycogen was depleted in all rats at exhaustion. Liver fructose 2,6-bisphosphate was decreased markedly in exercising rats, and the extent of decrease was not influenced by adrenodemedullation or by epinephrine infusion. ADM-S rats showed impaired glycogen depletion in the white vastus lateralis and soleus muscles, hypoglycemia, and low blood lactate at 80 min and at exhaustion. Infusion of epinephrine into ADM rats reversed these deficiencies. These data indicate that the adrenal medulla is unessential for normal endurance exercise as long as liver glycogen is available. After liver glycogen is depleted, epinephrine from the adrenal medulla prevents hypoglycemia and is essential for allowing continuation of exercise.
Altered heart rate-arterial pressure relation during head-out water immersion in conscious dog
Authors: Yoshino H. , Curran-Everett D. C. , Hong S. K. , Krasney J. A.
Published: December 2017

The influence of head-out water immersion (WI) (37 degrees C) on baroreflex control of heart rate was studied in five trained, instrumented, conscious dogs. Arterial pressure was raised and lowered using occluder cuffs implanted around the aorta and inferior vena cava. Function curves relating transmural systolic arterial pressure (TSAP = systolic arterial pressure-pleural pressure) to heart rate (HR) were constructed to compare responses in air and during WI. The resting TSAP in air [142 +/- 8 mmHg (mean +/- SE) at 78 +/- 6 beats/min] increased significantly during WI (161 +/- 9 mmHg at 109 +/- 9 beats/min). During WI, the saturation TSAP at the bradycardia plateau of the relation increased significantly, by 19 mmHg, whereas the average gain (slope) of the relation decreased significantly, from -1.426 to -0.752 beats.min-1.mmHg-1. Therefore, WI elicits both a resetting and a decrease of the average gain of the TSAP-HR relation. The heart rate range increased during WI as well. After cholinergic blockade with atropine, WI did not elicit a resetting of the relation and the change in average gain was abolished. However, after beta 1-blockade with metoprolol, the resting TSAP increased significantly during WI and resetting persisted, but the decrease of average gain was abolished. Therefore, the alteration of the TSAP-HR relation in WI is achieved via a modulation of both adrenergic and cholinergic regulation of HR.
Temperature effects on pH of mitochondria isolated from carp red muscle
Authors: Moyes C. D. , Buck L. T. , Hochachka P. W.
Published: December 2017

Mitochondria isolated from red muscle of carp (Cyprinus carpio) were used to investigate the effects of temperature and extramitochondrial pH (pHe) on the mitochondrial pH gradient and respiratory properties. Mitochondria from animals acclimated to 10 degrees C were isolated and incubated in KCl-based media with 0.2 mM lauroylcarnitine (C-12) as substrate. Maximal respiratory control ratios (RCR = state 3/state 4) were 16-18 between pH 6.7 and 7.4 at 10 degrees C; RCR values were 9-12 between pH 6.5 and 7.1 at 30 degrees C. Changes in RCR values were due primarily to changes in the state 3 rate (in the presence of ADP). Mitochondrial pH was determined by measuring 5,5-[2-14C]dimethyloxazolidine-2,4-dione distribution, using [14C]sucrose as an extramatrical marker. The pH gradient was inversely related to pHe. At any particular pHe, the mitochondrial pH gradient decreased with increasing temperature. However, if pHe was varied in the same manner that intracellular pH changes with temperature in vivo, the pH gradient was maintained constant at approximately 0.4 U at 10, 20, and 30 degrees C. These data suggest that carp red muscle mitochondria defend an appropriate mitochondrial pH gradient with temperature-induced changes in intracellular pH.
Spinally mediated inhibition of abdominal and lumbar sympathetic activities
Authors: Taylor R. F. , Schramm L. P.
Published: December 2017

Renal, splenic, and lumbar sympathetic nerve activities were recorded in the paralyzed, anesthetized, artificially ventilated, and spinally transected rat. Electrical stimulation of the dorsolateral funiculus caudal to the spinal transection was used to generate stimulus-response curves for changes in sympathetic activity in each of the three sympathetic nerves using five stimulus frequencies. In all rats, spinal stimulation inhibited sympathetic activity in renal and splenogastric nerves by approximately 50%. In grouped data, threshold frequency for inhibition of renal and splenogastric sympathetic nerve activity was 5 Hz, and inhibitions were maximal (50-60%) at 10 Hz. In contrast, activity in the lumbar sympathetic chain was inhibited in only two of five rats, and grouped data did not exhibit any statistically significant inhibitions. We conclude that lumbar sympathetic activity which remains after spinal transection can be inhibited only marginally by spinal stimulation, which substantially reduces renal and splenogastric sympathetic activity.
Systemic exchangeability of enteral leucine: relationship to plasma flux
Authors: Istfan N. W. , Ling P. R. , Bistrian B. R. , Blackburn G. L.
Published: December 2017

The exchangeability of enterally infused leucine within the systemic compartment was estimated in fasted and fed rats using L-[1-14C]leucine as a tracer. The experimental design consisted of enteral and parenteral feedings with intravenous or intragastric tracer infusions. During continuous intragastric feeding, only 73 +/- 6% (SE) of the intragastric leucine tracer infusion was accounted for in the systemic circulation. When comparing intravenous vs. intragastric tracer, the estimate of the contribution of protein breakdown to plasma leucine flux was 6 +/- 1 (SE) mumol.h-1.100 g-1 and 18 +/- 3 (SE) mumol.h-1.100 g-1 (P less than 0.01), respectively, for the two routes of administration. Correction of enteral input (either isotope or total leucine), by a factor of 27% for first-pass extraction, eliminated all significant differences in plasma leucine kinetics. Of the 27% of enterally infused tracer not appearing systemically, only 3% could be accounted for in newly synthesized protein in the liver. The remainder is hypothesized to represent first-pass utilization of leucine in intestinal protein synthesis and other metabolic pathways in the splanchnic bed. In contrast, systemic appearance of enteral leucine was essentially complete in the fasted rats, indicating less splanchnic metabolism of leucine in this state. These data indicate that significant error can result in estimating the contribution of endogenous protein breakdown to plasma leucine flux during feeding if the systemic exchangeability of dietary leucine is not considered.(ABSTRACT TRUNCATED AT 250 WORDS)
Solitary nucleus excitation of supraoptic vasopressin cells via adrenergic afferents
Authors: Day T. A. , Sibbald J. R.
Published: December 2017

Recent studies confirm that the supraoptic nucleus (SON) receives a direct projection from the nucleus of the solitary tract (NTS). We have examined the effect of NTS stimulation on antidromically identified SON neurosecretory cells that were classified as arginine vasopressin (AVP) or oxytocin (OXY) secreting in accord with basal activity patterns and responsiveness to arterial baroreceptor activation. Medial NTS stimulation at the level of the obex or area postrema excited 78% (59 of 76) of putative AVP cells (onset latency 52 +/- 1 ms) but only 20% (3 of 15) of putative OXY cells. Commissural NTS stimulation did not excite AVP cells (n = 13). After complete SON catecholamine afferent disruption, achieved by local injection of 6-hydroxydopamine, AVP cells tested were unresponsive to medial NTS stimulation (12 of 13), although arterial baroreceptor activation inhibited four of four cells. These data indicate that medial NTS stimulation preferentially excites SON AVP cells and that this effect involves an adrenergic input to SON. A direct projection from the A2 catecholamine cell group of the NTS may be involved, although the long latency to excitation and the poor correspondence between effective NTS stimulation sites and the location of the A2 group within NTS raise the possibility that a relay projection, possibly through the A1 catecholamine cell group of the ventrolateral medulla, may be involved.
Pentobarbital potentiates natriuretic response to acute volume expansion in monkeys
Authors: Gilmore J. P. , Cornish K. G. , Barazanji M. W.
Published: December 2017

We determined the influence of pentobarbital sodium on the renal responses of the monkey to acute intravascular volume expansion. Before volume expansion, the anesthetized animals had a significantly lower blood pressure and creatinine clearance and a significantly higher urine flow and sodium excretion than the conscious animals. After volume expansion with an isotonic, isoncotic, dextran solution, sodium excretion and urine flow increased significantly in both groups of animals. However, both responses were significantly greater in the anesthetized animals. The greater natriuresis in the anesthetized animals was associated with a greater fractional sodium excretion than in the conscious animals. The potentiated response of the anesthetized animal may be the result of a direct renal tubular effect of pentobarbital and/or the result of the anesthetic removing an inhibitory influence on sodium excretion.
Development of bronchiolar epithelium: time course of response to oxygen and recovery
Authors: Massaro G. D. , McCoy L. , Massaro D.
Published: December 2017

Hyperoxia (greater than 95% O2) reversibly suppresses the early postnatal development of rat bronchiolar epithelium. We now show that blunting of the normal increase in nuclear numerical density per centimeter cubed of Clara and ciliated cells becomes apparent within 24 h of exposure to O2 (age 2 days) and reaches a maximum on the last day of hyperoxia (age 7 days). The intergroup differences began to disappear within 48 h after removal from O2. During air breathing, Clara cell mitosis increased sixfold between the ages of 1 and 2 days and returned to day 1 values by age 7 days. During O2 breathing, Clara cell mitosis increased threefold between age 1 and 2 days, returned to day 1 values by day 4, but exhibited a second peak 24 h post-O2 (day 8) not present in unexposed pups. The onset of differences in the volume of Clara cell organelles and glycogen was variable, but the differences were partly or completely eliminated 48 h post-O2 exposure. We conclude hyperoxia reversibly impairs mitosis by Clara cells.
Influence of temperature and adrenergic stimulation on rat sinoatrial frequency
Authors: Bolter C. P. , Atkinson K. J.
Published: December 2017

We examined the effect of temperature and adrenergic stimulation on atrial rate in the rat. Right atrial preparations were maintained for 65 min at 38.0 degrees C and then exposed to high or moderate concentrations of isoproterenol (ISO) or left as controls. Temperature was cycled through four different values between 35.6 and 42.8 degrees C and allowed to stabilize at each value before atrial rate was measured. The rate-temperature loops exhibited a modest hysteresis; higher values for rate were obtained on the ascending limb. Hysteresis was found to result from a transient overshoot of the rate response to a temperature step. The linear response of atrial rate to temperature ranged from 20.3 +/- 1.3 to 22.6 +/- 0.7 beats.min-1.degrees C-1 (mean +/- SE) for control and high ISO (P greater than 0.05). Data were analyzed by applying the Arrhenius equation and by calculating the Q10 effect. ISO, while increasing atrial rate, reduced the measures of temperature sensitivity. Q10 and mu (temperature characteristic) were 2.1 and 59.8 +/- 2.1 for control and 1.7 and 40.0 +/- 1.5 for high ISO groups, respectively. The direct effect of an increase in temperature on sinoatrial rhythm would contribute significantly to the increase in heart rate seen in exercise.
Thirst in Brattleboro rats
Authors: Fuller L. M. , Fitzsimons J. T.
Published: December 2017

Thirst mechanisms in Brattleboro rats are activated because of a deficiency in circulating vasopressin. Plasma osmolality, renin, and angiotensin II (ANG II) are increased. We measured the responsiveness of Brattleboro rats and appropriate control strains to cellular and extracellular thirst stimuli taking the spontaneous base-line water intake into account. Brattleboro rats drank more in response to intraperitoneal hypertonic NaCl than controls, but when their fluid losses were prevented by nephrectomy they did not overdrink. Despite low urinary concentration, Brattleboro rats excreted the sodium load at least as rapidly as the controls. Brattleboro rats drank after intracranial injection of renin, renin substrate, and ANG I and II. The dose-response curves were similar to controls, although the Nottingham Long-Evans control strain drank significantly less in response to some doses of the peptides. Intracranial captopril inhibited renin- and ANG I-induced but not ANG II-induced drinking. Isoproterenol reduced spontaneous drinking of Brattleboro rats but increased drinking in controls. However, when urinary losses were prevented by ureteric ligation, isoproterenol caused markedly greater water intake in Brattleboro rats than in controls. Subcutaneous captopril in moderate, thirst-enhancing doses also caused a larger increase in water intake in Brattleboro rats than in controls. Therefore the renin-angiotensin system of Brattleboro rats is more responsive to renin-dependent thirst challenges than that of normal controls.
Changes in vasopressin and cortisol secretion during operant drinking in dehydrated pigs
Authors: Parrott R. F. , Thornton S. N. , Baldwin B. A. , Forsling M. L.
Published: December 2017

Two studies were carried out to examine endocrine changes during a 60-min period of operant drinking in 24-h dehydrated pigs. Measurements were made of water intake, osmolality, hematocrit, and plasma concentrations of lysine vasopressin (LVP) and cortisol during rehydration (experiment 1) and of fluid intake, osmolality, and LVP levels during consumption of isotonic saline (experiment 2). Increases in osmolality and LVP produced by dehydration in experiment 1 were rapidly reversed during rehydration with the result that osmolality returned to predeprivation levels after 20 min and LVP after 30 min, but there was no evidence of a decrease in LVP before absorption. Plasma cortisol concentrations were unaffected by dehydration although they declined during the final 40 min of experiment 1. In experiment 2, osmolality remained elevated during saline drinking, but plasma concentrations of LVP declined abruptly. The results suggest that oropharyngeal factors inhibiting vasopressin release, revealed during saline ingestion, are obscured during normal rehydration as a result of the rapid rate at which water is absorbed by the gut in this species.
Brain and cerebrospinal fluid ion composition after long-term anoxia in diving turtles
Authors: Cserr H. F. , DePasquale M. , Jackson D. C.
Published: December 2017

Prolonged anoxia in turtles is associated with marked disturbances in plasma composition. This study examines brain and cerebrospinal fluid (CSF) ion homeostasis in the freshwater turtle, Chrysemys picta bellii, in response to 8-10 days of submergence anoxia at 10 degrees C. For comparison, it also examines the response to experimental elevation of plasma [K], [Ca], and [Mg] in normoxic turtles. Long-term anoxia resulted in marked changes in brain and CSF composition. These included elevated [K], [Ca], [Mg], and [lactate] and reduced [Cl], and the composition of CSF approached that of plasma. Brain water content increased by 17%, which we suggest was an intracellular edema linked largely to an 11% increase in total brain K. In contrast to the lack of effective homeostasis during anoxia, CSF composition was controlled in normoxic animals. We conclude that there is homeostasis of K, Ca, and Mg in the extracellular fluids of normoxic turtle brain, as in other vertebrates, but that this homeostasis fails during long-term anoxia.