bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny of heart rate regulation in the bullfrog, Rana catesbeiana
Authors: Burggren W. , Doyle M.
Published: December 2017

Heart rate (fH) at 20-23 degrees C was recorded in six different developmental stages of the bullfrog, Rana catesbeiana (n = 104, body mass 40 mg to 90 g), at rest after normoxic acclimation, during acute changes in O2 availability, and after brief but intense activity. The effects of cholinergic blockade and combined cholinergic and beta-adrenergic blockade on the response to this experimental protocol were also assessed. Mild tonic vagal inhibition of fH was evident during larval development but disappeared after metamorphosis. There was no tonic sympathetic stimulation of fH at rest in any developmental stage. Intense activity produced a tachycardia in all developmental stages but newly hatched larvae. In adults, tachycardia during activity resulted from beta-adrenergic stimulation but in larvae may have resulted from the direct effects of increased venous return stretching the cardiac pacemaker. Neither acute hypoxia or hyperoxia affected fH in any developmental stage, with the single exception of a severe depression of fH occurring at a PO2 of 30 Torr in newly hatched larvae. These results indicate that, although the heart of the newly hatched larvae is essentially devoid of regulation, cholinergic and beta-adrenergic mechanisms for reflex regulation of fH appear early in larval development. These mechanisms, although most fully expressed in the adult bullfrog, are essentially intact before metamorphosis of the larva.
Growth and hepatic composition in the guinea pig after long-term parenteral hyperalimentation
Authors: Lu C. J. , Redmond D. , Baggs R. B. , Schecter A. , Gasiewicz T. A.
Published: December 2017

This study examined the feasibility of maintaining male Hartley guinea pigs on long-term hyperalimentation. Data from animals fed ad libitum, but infused with 0.9% saline, indicated that there was minimal effect from catheter implantation, sepsis, or the infusion of large volumes of fluid. This group compared with animals fed and watered ad libitum demonstrated a nearly identical growth rate (6.33 +/- 1.18 and 6.12 +/- 1.32 g/day, respectively), serum chemistry, tissue weights, and hepatic composition and morphology. Animals infused with a total parenteral diet demonstrated growth rates of 4.06 +/- 1.46 g/day for up to 25 days. Loss of infused animals was due in varying degrees to sepsis, mechanical failure, improper placement of the cannula, loss of patency, and death from unknown causes. Morphological analysis of animals fed by total parenteral nutrition revealed an altered distribution and increased size of lipid droplets in hepatic parenchymal and Kupffer cells and glycogen accumulation by the parenchymal cells. Decreased hepatic content of total protein and lipid, as well as cytochrome P450, was also observed. Similarly, serum values of triglyceride were decreased in animals fed by the total parenteral diet. This study indicated that the guinea pig fed by hyperalimentation may be a useful animal model for a number of clinical and basic research applications.
Metabolic features of diet-induced obesity without hyperphagia in young rats
Authors: Levin B. E. , Triscari J. , Sullivan A. C.
Published: December 2017

Diet-induced obesity (DIO) developed in 1-mo-old male Sprague-Dawley rats over an 8-wk period on a relatively high-fat (16%) high-calorie (4.6 kcal/g) diet (DIO diet). Percent carcass lipid (56%) and body weight gain (15%) were greater, whereas food intake was decreased over the first 3-5 wk in DIO diet-compared with chow-fed controls. Overall, 8-wk body weight gain (15%), percent carcass lipid (26%), and feed efficiency (15%) were greater, but food intake was not increased. Norepinephrine (NE) turnover rate, indicative of organ sympathetic activity, increased in interscapular brown adipose tissue (IBAT; 57-218%), heart (21-44%), and pancreas (25%) during the first 3 wk and remained elevated for the entire 8 wk. IBAT weight (51%) and in vitro lipolytic capacity (68%) increased by 1 wk and brown adipocyte size (43%) by 3 wk; IBAT thermogenic capacity (maximal NE-stimulated in vitro O2 consumption) increased by 5 wk (39%). Plasma insulin levels were similar in both diet groups over the entire 8-wk period. Why DIO diet-fed rats had increased metabolic efficiency is unknown, but activation of IBAT metabolism and thermogenesis failed to prevent the development of DIO.
Thermal and metabolic adaptation to first cold-water immersion in juvenile penguins
Authors: Barre H. , Roussel B.
Published: December 2017

Juvenile king and macaroni penguins are terrestrial seabirds and must face an intensive and prolonged energetic demand during their passage from shore to marine life in cold subantarctic seawater. Evidence for progressive thermal adaptation was sought by measurement of metabolic rate (MR) and body (Tb) and skin (Tsk) temperatures in unrestrained, fully immersed penguins. Steady-state responses obtained after the 3rd h of immersion in never-immersed (NI) penguins were compared with those of penguins acclimatized to seawater temperature (A). NI macaroni penguins, unlike NI king penguins, showed a fall in Tb on their first immersion but, once acclimatized, were able to maintain their homeothermy due to an increase (greater than 3.2 W/kg) in regulatory thermogenesis. In NI king penguins, during a simulation of seawater adaptation by 10 successive immersions, MR at 7 degrees C water temperature (Tw) rose from 6.0 to 9.4 W/kg (becoming 3-5 times higher than in air), whereas Tb rose from 37.6 to 38.4 degrees C. In both species occurrence of peak MR at much lower Tw, progressive increase in thermogenesis capacity, and lower conductance in water after adaptation to marine life (28 and 36% less in A king and macaroni penguins, respectively) showed that the passage from shore to marine life consisted of a true cold acclimatization.
Na-dependent D-glucose and L-alanine transport in eel intestinal brush border membrane vesicles
Authors: Storelli C. , Vilella S. , Cassano G.
Published: December 2017

Brush border membrane vesicles (BBMV) were prepared from eel (Anguilla anguilla) intestine by a Mg-ethylene-glycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid precipitation technique; the BBMV were enriched 16, 12, and 13 times in leucine aminopeptidase, maltase, and alkaline phosphatase activities with respect to the starting mucosal scraping. D-[3H]glucose and L-[3H]alanine transport by these vesicles was studied by a rapid filtration technique. D-Glucose uptake was stimulated by a transmembrane Na gradient but not by an identical Na gradient in the presence of phloridzin or by a choline gradient. The Na-dependent D-glucose uptake was increased by rendering the vesicle interior electrically negative, suggesting electrogenic cotransport of the sugar with Na+. Kinetic analysis gave an apparent affinity constant (Kapp) of 0.20 mM and maximal rate (Jmax) of 6.87 nmol X mg protein-1 X min-1 for glucose influx in the presence of a Na gradient. In addition, a significant apparent diffusional permeability of these membranes to glucose (1.41 microliters X mg protein-1 X min-1) was observed. L-Alanine uptake in eel BBMV was shown to occur via 1) saturable Na-dependent pathway (Kapp = 1.29 mM, Jmax = 3.61 nmol X mg protein-1 X min-1), 2) a saturable Na-independent pathway (Kapp = 0.59, Jmax = 1.49), and 3) a nonsaturable component representing apparent diffusion (permeability coefficient P = 0.57 microliter X mg protein-1 X min-1). These findings suggest that similar transport systems for glucose and alanine are found in the fish and mammalian intestinal brush border membrane.
Enhancement of slow-wave sleep by endotoxin and lipid A
Authors: Krueger J. M. , Kubillus S. , Shoham S. , Davenne D.
Published: December 2017

Some muramyl peptides derived from bacterial peptidoglycan enhance slow-wave sleep (SWS). The purpose of this study was to test whether another cell wall component, lipopolysaccharide (LPS), and its lipid A moiety also have an effect on sleep. When injected intravenously, both LPS and lipid A enhanced the duration of SWS, increased electroencephalogram delta-wave amplitudes, suppressed rapid eye movement (REM) sleep, and induced biphasic fevers. The effects of intravenously administered lipid A and LPS on SWS were present primarily during the first 3 h postinjection. Intraventricular lipid A administration enhanced SWS, did not suppress REM, and induced a monophasic fever; the SWS effect had a 3-h latency, whereas temperature started to rise during the second hour. Regardless of the route of administration, within the dose range used here, sleep was normal by the following criteria: sleep was episodic, animals could be easily aroused, and brain temperature, although elevated to "febrile" levels, continued to fluctuate during sleep-state transitions indistinguishably from control conditions. We conclude that LPS and lipid A are capable of modulating sleep.
Does serotonin play a role in entrance into hibernation?
Authors: Canguilhem B. , Miro J. L. , Kempf E. , Schmitt P.
Published: December 2017

To study the role of brain serotonin in entrance into hibernation, intraventricular injections of 5,7-dihydroxytryptamine, electrolytic lesions of small parts of the median raphe nucleus, and chemical lesions of the same nucleus were undertaken on the European hamster in winter. All the lesions led to a variable decrease of serotonin levels in all parts of the brain areas examined. However, hibernation was suppressed only in those animals whose serotonergic neurons were destroyed in a small anterior part of the median raphe nucleus. Electrolytic lesions as well as chemical lesions in the other parts of the median raphe nucleus or the 5,7-dihydroxytryptamine injections into lateral ventricles do not prevent hibernation. These data suggest that in the European hamster only a specific group of serotonergic neurons of the median raphe nucleus are involved in the process of entrance into hibernation.
Cystic fibrosis and beta-adrenergic response of airway epithelial cell cultures
Authors: Widdicombe J. H.
Published: December 2017

Confluent cell sheets were cultured from the tracheal epithelium of normal humans or from tracheal and nasal epithelia of patients with cystic fibrosis (CF). Changes in short-circuit current (Isc) or cyclic AMP (cAMP) levels in response to 10(-5) M isoproterenol were measured. In CF tracheal cells the response to isoproterenol was transient, and the maximal increase in Isc was one-tenth normal. In CF nasal cells, isoproterenol or epinephrine caused only small transient increases in Isc. However, in both CF nasal and tracheal cells, the Ca ionophore, A23187, caused relatively large increases in Isc that were inhibited by the Cl transport blocker, bumetanide, suggesting that Cl secretion can be induced by raising intracellular levels of Ca. In normal tracheal cell sheets, cAMP levels increased within 15 s of isoproterenol addition and continued to increase for up to 20 min. Resting levels of cAMP in CF tracheal cells were not statistically different from those of normal cells and showed linear increases for up to 4 min after addition of isoproterenol. Changes in cAMP in CF nasal cells were similar to the changes in CF tracheal cells. After 2 min, all three cell types showed cAMP levels elevated approximately equal to 10-fold. These results suggest that receptor-activated stimulation of adenylate cyclase is normal in CF. However, though raised cAMP levels stimulate Cl secretion in normal, they are unable to do so in CF airway epithelial cells.
Dorsomedial hindbrain participation in cholecystokinin-induced satiety
Authors: Edwards G. L. , Ladenheim E. E. , Ritter R. C.
Published: December 2017

To study the role of the dorsomedial hindbrain in cholecystokinin (CCK)-induced satiety, lesions were produced in the region of the obex. We observed that lesions that were limited to the area postrema (AP) and immediately adjacent nucleus of the solitary tract (NST) did not attenuate the satietogenic effects of CCK. Similarly, lesions of the medial NST rostral to the AP had no effect on CCK-induced satiety. However, when the majority of the medial and commissural subnuclei of the NST as well as the AP were lesioned, there was a significant attenuation of the satietogenic effect of CCK. Since this lesion includes the bulk of the terminal field from the gastric branch of the vagus nerve, these results support the role of gastric afferent projections in the mediation of CCK-induced satiety. Although we do not rule out the possibility that the AP itself monitors circulating CCK, our data clearly show that the AP is not essential for induction of satiety by exogenous CCK.
Neuroendocrine factors mediating polydipsia induced by dietary Na, Cl, and K depletion
Authors: Saikaley A. , Bichet D. , Kucharczyk J. , Peterson L. N.
Published: December 2017

We investigated whether the increased intake of water during dietary electrolyte depletion is related to activation of the renin-angiotensin system. Young adult male rats were fed a low Na-, Cl-, K-free (low-salt) diet for 2 wk during which measurements were made of daily water intake and urine volume, plasma osmolality (Posm) and electrolytes, and plasma renin activity (PRA) and angiotensin I (ANG I) concentration. Water intake and urine output increased on day 3 of the low-salt diet, reached a maximum on day 4, and remained elevated, paralleling the time course of increases in PRA and ANG I plasma concentrations. Posm was normal after 2 days on the low-salt, although it was significantly lower by day 11. Renal concentrating ability was not different from controls after 6 days, but was significantly reduced after 11 days of treatment. Electrolytic lesions of the subfornical organ (SFO) abolished the low-salt diet-induced polydipsia, but had no effect on the diet-induced increases in PRA and plasma ANG I concentration. These data demonstrate that polydipsia induced by feeding a low-salt diet can develop in the presence of a normal or reduced Posm and precedes the development of a renal concentrating defect. The primary polydipsia is associated with elevated PRA and ANG I and appears to be mediated by angiotensin receptors in the SFO.
Photoperiod modifies circadian resetting responses in sparrows
Authors: Binkley S. , Mosher K.
Published: December 2017

Circadian responses to photoperiod were studied in house sparrows (Passer domesticus) by subjecting them to 4-h light pulses and measuring the subsequent phases of their circadian rhythms. The direction and magnitude of phase shifts in response to 4-h light pulses following pretreatment with light-dark cycles (LD) 16:8 or LD 8:16 varied with time of day; advances (3.4 h) occurred when pulses were imposed in the late subjective night on both groups of birds; delays (-2.1 h) occurred when the pulses were imposed in the early subjective night on the LD 8:16 birds. The time profiles for responses to light pulses that scanned 24 h (phase-response curves) were modified by long and short photoperiod. Short photoperiod 1) increased amplitude (1.7 h), 2) increased time from the prior lights-out to the peak of advances (6 h), and 3) decreased the mean phase shift (0.9 h).
Kinetics of protein binding determine rates of uptake of drugs by brain
Authors: Robinson P. J. , Rapoport S. I.
Published: December 2017

A mathematical model describing the kinetics of binding and release of substances by plasma proteins is presented. The effects of protein binding on the uptake of substances such as drugs from the capillary network of the brain are discussed. The model assumes equilibration between bound and free forms of drug in arterial blood and incorporates the on-off rate constants for the drug-protein complex and rate constants for passage of free drug across the blood-brain barrier and for drug metabolism in the brain. Regional cerebral blood flow and the related capillary transit time are important parameters in the model. Analytical expressions for bound and free drug concentrations and for the net extraction of drug are derived where practicable, and numerical solutions also are presented. Effects of changes in the total drug and protein concentrations in the plasma are discussed with special reference to the uptake of bilirubin by the brain.
Glucagon stimulation of brown adipose tissue growth and thermogenesis
Authors: Billington C. J. , Bartness T. J. , Briggs J. , Levine A. S. , Morley J. E.
Published: December 2017

Despite long-standing observations of a whole-body thermogenic effect of glucagon, the role of glucagon in activating thermogenesis in brown adipose tissue has not often been studied. We investigated the ability of administered glucagon to produce alterations in brown adipose tissue similar to changes produced by accepted stimuli of brown fat activity: cold, norepinephrine, and overfeeding. Eighteen days of glucagon injections (1 mg/kg) to male Sprague-Dawley rats produced, relative to saline-injected controls, decreases in feed efficiency and increases in brown adipose tissue weight, protein content, DNA content, and mitochondrial mass as reflected in cytochrome oxidase activity. The observed changes were similar, though of lesser magnitude, to changes produced in these same parameters induced by administration of norepinephrine (250 micrograms/kg) for a positive control group. Four days of glucagon administration (1 mg/kg) produced increases in specific activity of cytochrome oxidase and lipoprotein lipase. After 8 days of glucagon administration, changes in whole-pad activity similar to those seen with 18 days of administration were present. Glucagon also increased whole-pad lipoprotein lipase activity after 4 and 8 days. Surgically denervated interscapular brown adipose tissue retained its ability to respond to exogenous glucagon, though the magnitude of the response was diminished. Guanosine 5'-diphosphate (GDP) binding to brown adipose tissue mitochondria was measured as an assessment of functional state after 5 days of glucagon (1 mg/kg). There was an increase in GDP binding relative to controls whether expressed as picomoles per milligram mitochondrial protein or nanomoles per pad.(ABSTRACT TRUNCATED AT 250 WORDS)
Sex-related differences in fever development of rats
Authors: Murakami N. , Ono T.
Published: December 2017

Lipopolysaccharide (LPS) or partially purified endogenous pyrogen (EP) was injected intravenously into rats of both sexes to induce fever. In LPS fever, which was easily produced in 24-h dehydrated rats with an intravenous injection of LPS, the female rats showed an attenuated febrile reaction as measured by both the maximum increase of rectal temperature (Tre) and the thermal response index (TI). Although castrated female rats showed the same magnitude of febrile reaction to that in normal female rats, castrated male rats had less of a febrile response than normal male rats. During EP fever, the maximum increase of Tre and TI between the male and female rats was also observed to be different. However, castration of rats of both sexes did not affect the febrile reaction to intravenous injection of EP. Ten-week-old female rats, treated by a subcutaneous injection of testosterone propionate on the 1st day after birth, produced a similar magnitude of febrile reaction to that in the normal male rats that were comparable in age. It is concluded that there are sex-related differences in fever development, due both to EP production and structural sexual differences in the central nervous system pathways regulating fever.
Effects of endurance training and captivity on activity metabolism of lizards
Authors: Garland T. , Else P. L. , Hulbert A. J. , Tap P.
Published: December 2017

Two groups of Amphibolurus nuchalis, an Australian agamid lizard, were maintained in captivity for 8 wk. The “trained” group was given submaximal exercise at 1 km/h on a motorized treadmill, 30 min/day, 5 days/wk; the treadmill was inclined 10% for the last 5 wk. The “sedentary” group was not exercised. Endurance capacity did not change significantly in either group, but sprint speed decreased in trained lizards. The sedentary group exhibited significant decreases in maximal O2 consumption, standard metabolic rate, and heart mass, but an increase in liver mass. Trained lizards exhibited significant decreases in heart and thigh muscle masses, but significant increases in liver mass, hematocrit, liver pyruvate kinase, and heart citrate synthase activities. It is concluded that the adaptive response to endurance training, typical of mammals, does not generally occur in lizards. Moreover, levels of chronic activity that would elicit adaptive responses in mammals may be excessive for lizards and may induce pathological effects in joints and skeletal muscle. The ecological and evolutionary significance of these conclusions is discussed.
Yolk platelet degradation in preemergence Artemia embryos: response to protons in vivo and in vitro
Authors: Utterback P. J. , Hand S. C.
Published: December 2017

Alteration of intracellular pH (pHi) influences yolk platelet degradation during preemergence development in Artemia embryos. Cysts incubated for 10 h under conditions of aerobic development (aqueous medium equilibrated with 60% N2-40% O2, pHi greater than or equal to 7.9) exhibit a significant decrease in numbers of yolk platelets and platelet protein. In contrast, cysts incubated for 10 h under aerobic acidosis (60% CO2-40% O2, pHi = 6.8) show no significant decrease in numbers of yolk platelets or platelet protein. When subjected to alkaline conditions in vitro, yolk platelets release protein exponentially as a function of time. The process is essentially complete in 40 min. The extent of protein and lipid release from platelets increases markedly as pH of the medium is raised in increments from 6.3 to 8.0. Concomitant with these changes are reduction (50%) in platelet dry weight and reduction (21%) in platelet diameter. Transmission electron microscopy does not reveal major structural differences between isolated yolk platelets and those contained in hydrated embryos. The proton effects on platelet composition and size detected in vitro may explain in part the mechanism of platelet degradation observed during aerobic development and its suppression under conditions of acidic pHi.
Neurohypophyseal secretion in hypovolemic rats: inverse relation to sodium appetite
Authors: Stricker E. M. , Hosutt J. A. , Verbalis J. G.
Published: December 2017

Subcutaneous injection of polyethylene glycol (PEG) solution in rats produces exponential increases in secretion of arginine vasopressin (AVP) and oxytocin (OT) in proportion to the induced plasma volume deficits. Previously, we reported that acute water loads eliminated the neurohypophyseal hormone responses to hypovolemia, whereas hypertonic NaCl potentiated them. The present experiments indicated that AVP and OT secretion after PEG treatment were blunted by prior maintenance of rats on a sodium-deficient diet for 2 days. In contrast, plasma AVP and OT levels after PEG treatment were enhanced by prior adrenalectomy or ligation of the inferior vena cava or by concurrent administration of phentolamine in association with arterial hypotension. AVP and OT responses to hypovolemia were similarly potentiated in rats made uremic by bilateral nephrectomy or by puncturing their bladders. These results parallel previous findings that osmotic dilution and sodium deprivation each enhance the sodium appetite induced by PEG treatment in rats, whereas hyperosmolality, hypotension, and uremia each abolish it. Consequently, they support our previous hypothesis that sodium appetite is inversely related to the activity of hypothalamic oxytocinergic neurons.
Adaptation to extreme ambient temperatures in cold-acclimated gerbils and mice
Authors: Oufara S. , Barre H. , Rouanet J. L. , Chatonnet J.
Published: December 2017

To explain tolerance of heat and cold in gerbils (Gerbillus campestris) in their natural environment, a comparative study was made of thermoregulatory reactions in these animals and white mice (Mus musculus) of the same body mass exposed for 2-3 h to ambient temperatures (Ta) ranging from -23 to 40 degrees C. Metabolic rate (MR), evaporative heat loss (EHL), colonic temperature (Tb), and electromyographic activity (EMG) were measured. Nonshivering thermogenesis (NST) was also evaluated from the increase in MR after norepinephrine injection. In gerbils, tolerance of cold was higher than in mice; there was no fall in Tb in cold-acclimated (CA) and control (TN) gerbils after 3 h of exposure at -20 and -10 degrees C Ta, respectively; peak MR (PMR) reached five to six times resting MR (RMR) in gerbils and four to five times in mice. In gerbils, RMR was 35% below that of mice. In TN gerbils, EHL did not increase before 38 degrees C Ta; EHL increased at 26 degrees C in mice. In both animals, cold acclimation increased cold tolerance, PMR, RMR, and NST. Low RMR, high Tb, and mainly burrowing habits preserve gerbils from overheating and save water in hot and arid environments, and a conspicuous tolerance of cold allows them to live and forage in the wild during the cold night.
Regional circulatory responses to head-out water immersion in conscious dogs
Authors: Hajduczok G. , Miki K. , Claybaugh J. R. , Hong S. K. , Krasney J. A.
Published: December 2017

We determined the regional blood flow responses to head-out water immersion (WI) in intact (INT) and cardiac-denervated (CD) conscious dogs. Immersing dogs in thermoneutral water (37 degrees C) in the quadruped position for 100 min resulted in significant increases in cardiac output (Qco) above control values by 38.7% in the INT dogs and 39.2% in the CD dogs (P less than 0.01). Arterial pressure increased by 32 and 34.7% in the INT and CD groups, respectively, during WI, with no significant changes occurring in the calculated total peripheral resistance. Regional blood flow responses were measured with 15-microns radiolabeled microspheres. Flows in the INT and CD groups increased significantly to the heart (40, 38%), skin (93, 96%), fat (79, 83%), diaphragm (44, 48%), and intercostal muscles (58, 55%), whereas there were no changes in renal cortical blood flows during WI. Total brain blood flows did not change significantly on immersion; however, blood flows in both INT and CD animals were increased to the cerebellum (19, 22%), but a significant decrease in pituitary flow (52%) was observed only in the CD group during WI. Gastrointestinal tissue flows increased only during early WI in both INT (45%) and CD (47%) animals. However, blood flows to the skeletal muscles increased only during late WI in the INT (53%) and CD (47%) groups. There were no significant differences between the INT and CD groups. Rectal temperatures and systemic O2 consumption (VO2) were unchanged during WI in both groups of animals. These observations indicate that WI leads to a sustained elevation of Qco accompanied by selective increases in regional tissue perfusion that may be accounted for in some tissues by an increase in metabolic demand or by local heating responses and produces a time-dependent redistribution of blood flow away from the gastrointestinal tissues toward skeletal muscle tissues, which may be due to a partial uncoupling of the normal Q/VO2 relationship. This may be caused by thermal or central neurohumoral mechanisms. These regional circulatory responses are not dependent on the presence of the cardiac nerves.
Effect of antipyretic drugs on circadian rhythm in body temperature of rats
Authors: Scales W. E. , Kluger M. J.
Published: December 2017

In many species, including the laboratory rat, body temperature varies on a circadian (24 h) basis. There is considerable evidence that the circadian rise in body temperature is attributable to an elevation in thermoregulatory set point. We hypothesized that this rise in set point may be mediated by prostaglandins. If this hypothesis is correct, then it should be possible to block or reduce the nighttime rise in body temperature by the administration of prostaglandin synthesis inhibitors. Rats were injected with the prostaglandin synthesis inhibitors sodium salicylate, acetylsalicylic acid, and indomethacin at 5:00 P.M. and at 9:00 A.M. Administration of these drugs had little effect on body temperature during the day but caused a significant fall in body temperature at night when temperature is normally in the rising or plateau phase of the cycle. We conclude that prostaglandin synthesis is an important component of the circadian rise in body temperature in the rat. In addition, evidence is presented that there exists a cryogenic factor that opposes the nighttime prostaglandin-mediated rise in body temperature.
Amiloride-sensitive sodium channels and expression of sodium appetite in rats
Authors: Bernstein I. L. , Hennessy C. J.
Published: December 2017

Lingual application of amiloride hydrochloride blocks a sodium transport system in the mammalian gustatory system. Effects of exposure to amiloride on subsequent licking for 3% NaCl by rats were found to differ as a function of the animal's sodium balance. Licking for 3% NaCl was significantly increased in sodium-replete rats and significantly decreased in sodium-deplete rats by amiloride pretreatment. In fact, expression of sodium appetite was virtually eliminated by pretreatment with amiloride. This suggests that the recognition of sodium solutions in animals with a sodium deficit is dependent on amiloride-sensitive sodium transport at the taste bud.
Effects of hypothalamic stimulation and lesion on adrenal nerve activity
Authors: Yoshimatsu H. , Oomura Y. , Katafuchi T. , Niijima A.
Published: December 2017

Activity changes of efferent adrenal sympathetic nerves in response to bilateral manipulations of the hypothalamus, partly after intra-third cerebroventricular injection of 2-deoxy-D-glucose (2-DG) were investigated in anesthetized rats. Stimulation of the middle part of the lateral hypothalamic area (LHAm) increased adrenal nerve activity, whereas lesion caused rapid and remarkable decrease. Stimulation of the anterior part of the LHA (LHAa) tended to decrease the activity, and lesion produced either rapid decrease or late moderate increase. Stimulation of the ventromedial hypothalamic nucleus (VMH) did not affect the nerve activity, but lesion increased it gradually and then remarkably. Cerebroventricular infusion of 2-DG caused remarkable increase in activity that was suppressed by LHAm lesion. Subsequent infusion of 2-DG during the period of suppressed activity was no longer effective. The increased firing rate after 2-DG was suppressed by stimulation of the VMH, whereas lesion caused no change. These findings indicate that the central regulation of adrenal nerve activity is connected with individual hypothalamic regions and consequently depends on the degree and mode of activation of the sympathoadrenal system.
Dynamic and static phases of obesity following lesions in PVN and VMH
Authors: Fukushima M. , Tokunaga K. , Lupien J. , Kemnitz J. W. , Bray G. A.
Published: December 2017

The effect of electrolytic lesions in the ventromedial hypothalamus (VMH) and the paraventricular nucleus (PVN) has been compared during both the dynamic and static phase of weight gain. Hyperphagia and weight gain were greater in the VMH-lesioned rats than in the PVN-lesioned rats. Food intake increased at night after both lesions but increased in the daytime only in VMH-lesioned rats. During the dynamic phase of rapid weight gain, the diurnal pattern of corticosterone was blunted to a similar degree in both lesioned groups. The morning insulin concentrations were higher in both lesioned groups than in the sham-operated controls, but in the static phase only the VMH-lesioned rats had higher insulin levels. In the afternoon the insulin was higher in the VMH-lesioned rats than in either the sham-operated or PVN-lesioned rats. In the dynamic phase the weight of interscapular brown adipose tissue was significantly increased in the VMH-lesioned rats, but the specific GDP binding was depressed both in the morning and afternoon when compared with either the sham-operated or PVN-lesioned groups. In both the dynamic and static phases GDP binding was similar in sham-operated and PVN-lesioned animals. The differences in concentration of corticosterone in morning and afternoon were smaller in the lesioned groups than in the controls. These data are consistent with the hypothesis that animals with PVN lesions do not show the disturbances in food intake or in the autonomic nervous system that characterize the VMH-lesioned rats.
Elevated renal nerve activity after spinal transection: effects on renal function
Authors: Osborn J. W. , Livingstone R. H. , Schramm L. P.
Published: December 2017

Spinal transection approximately doubles renal sympathetic activity (RSA) in rats. These experiments localized spinal pathways inhibiting RSA and determined the effects of transection-elicited renal sympathetic hyperactivity on renal circulation and renal function. Experiments were conducted in chloralose-anesthetized, paralyzed, artificially respired, male Sprague-Dawley rats. RSA was measured from an electrode on the left renal nerve. Renal arterial blood flow (RABF), glomerular filtration rate, urine flow rate, and renal sodium and potassium excretions were also measured. Localized lesions of the cervical spinal cord indicated that spinal generators of RSA were inhibited by pathways descending in the dorsal cervical cord. Autoregulation of RABF prevented transection-elicited increases in RSA from affecting renal vascular resistance. Renal sodium and potassium excretions were dramatically reduced after spinal transection, although these reductions were ameliorated somewhat by fixing posttransection renal arterial pressure at pretransection levels. We conclude that the vascular effects of transection-elicited elevations in RSA are minimized by autoregulation of RABF and that posttransection changes in renal function result from changes in both arterial pressure and RSA.
Intracellular pH of astrocytes increases rapidly with cortical stimulation
Authors: Chesler M. , Kraig R. P.
Published: December 2017

Modulation of intracellular pH is widely implicated in the control of cell growth and metabolism, yet little is known about intracellular pH and brain function. To determine how stimulation of brain may affect the intracellular pH of mammalian glial cells, rat cortical astrocytes were studied for the first time in vivo using pH-sensitive electrodes of submicron caliber. Stimulation of the cortical surface caused a cytoplasmic alkaline shift of tenths of a pH within seconds. Cessation of induced electrical activity was followed by pH recovery and a small acid rebound. Recordings obtained during cortical-spreading depression revealed similar but generally larger intracellular pH shifts. Production of metabolic acids is known to occur when the brain is stimulated and has led to the long-held presumption that brain cells accordingly become more acidic. The observation that glia initially become more alkaline during electrical activity is thus paradoxical. The correlation of glial alkalinization with evoked electrical activity suggests that modulation of intracellular pH of glia may have important functional implications.
Osmoregulation and control of vasopressin secretion in healthy humans
Authors: Baylis P. H.
Published: December 2017

The functional characteristics of osmoregulated vasopressin secretion can be defined in terms of an osmotic threshold for its release and a sensitivity of the osmoreceptor and vasopressin-secreting unit. Osmotically stimulated thirst has features similar to osmoregulated vasopressin. There are wide individual variations in the functional characteristics of both thirst and vasopressin release in healthy humans, probably genetic in origin. The influence of aging appears to enhance the sensitivity of vasopressin secretion but blunt thirst appreciation. Yet in many physiological situations changes in osmoregulated vasopressin release and thirst occur in parallel. The fall in plasma osmolality associated with human pregnancy is accounted for entirely by a lowering of the osmotic thresholds for thirst and vasopressin release. Similar but less marked alterations accompany the ovulatory luteal phase of the menstrual cycle. A major nonosmotic stimulus to vasopressin secretion is hypotension and/or hypovolemia, mediated by high- (carotid sinus) and low- (left atrial) pressure receptors. Circulating catecholamines influence the release of vasopressin by alpha- and beta-adrenergic pathways. Drinking by hypertonic humans provides immediate reduction in thirst and vasopressin secretion probably mediated by pathways from the oropharynx. The modest but variable rise in plasma vasopressin in response to hypoglycemia appears to be due to cellular neuroglycopenia and is independent of parasympathetic pathways. Although osmotic and hemodynamic stimuli to vasopressin release do not act independently of each other, the precise subtle interactions between them and other nonosmotic stimuli remain to be clarified.
Role of motor center activity for hormonal changes and substrate mobilization in humans
Authors: Kjaer M. , Secher N. H. , Bach F. W. , Galbo H.
Published: December 2017

The study evaluated the hypothesis that during exercise autonomic neuroendocrine activity and, in turn, substrate mobilization, is subjected to feed-forward stimulation from motor centers. Eight young healthy men bicycled for two 20-min periods without (control, C) as well as during partial neuromuscular blockade with tubocurarine (Cu). 3-[3H]glucose was infused, and arterialized hand vein blood was sampled. In period 1 O2 consumption (VO2) (56% VO2 max), heart rate, and blood lactate were identical in Cu compared with C experiments, whereas hand grip strength was lower and perceived exertion [14.0 +/- 1.5 vs. 9.1 +/- 1.2 (SE) points, P less than 0.01] higher in Cu experiments, indicating higher motor center activity. Concentrations of norepinephrine [7.39 +/- 1.18 (Cu) vs. 5.14 +/- 1.06 (C) nmol/l], epinephrine (1.69 +/- 0.33 vs 0.87 +/- 0.16 nmol/l), growth hormone (25.9 +/- 7.3 vs. 11.5 +/- 4.7 mU/l), and adrenocorticotropin hormone (11.3 +/- 1.3 vs. 5.5 +/- 0.7 pmol/l) attained higher values in Cu than in C experiments (P less than 0.05). The initial increase in glucose production was enhanced in Cu (8.1 +/- 1.6 mumol.min-1.kg-1) compared with C experiments (3.9 +/- 1.9, P less than 0.05), and plasma glucose only increased in Cu experiments. Free fatty acid (P less than 0.05) and glycerol (P less than 0.1) concentrations were higher in Cu than in C experiments. In period 2 identical perceived exertion was achieved in the two experiments by reducing work load in Cu experiments. In this period hormonal responses were similar in the two experiments.(ABSTRACT TRUNCATED AT 250 WORDS)
Pressor sensitivities to vasopressin, angiotensin II, or methoxamine in diabetic rats
Authors: Hebden R. A. , Bennett T. , Gardiner S. M.
Published: December 2017

We investigated the pressor sensitivities to vasopressin, angiotensin II, and methoxamine of intact and ganglion-blocked rats that had been treated 21 days earlier with streptozotocin or saline. No differences in blood pressure or heart rate responses to vasopressin or angiotensin II were found between the intact groups when these peptides were administered intravenously in equimolar doses. After ganglion blockade a significant enhancement in pressor responsiveness to both vasopressin and angiotensin II was observed in the control groups, but in the streptozotocin-treated animals no enhancement in pressor sensitivity to vasopressin was found. Furthermore, although a significant augmentation of the responses to angiotensin II was observed, it was smaller than that seen in the ganglion-blocked control group. Neither group showed enhanced pressor responsiveness to methoxamine. These results indicate that the previously observed diminished contributions from endogenous vasopressin and the renin-angiotensin system to blood pressure recovery following ganglion blockade in streptozotocin-treated rats may have been due, at least in part, to diminished pressor responsiveness.
Carotid baroreceptor-muscle sympathetic relation in humans
Authors: Rea R. F. , Eckberg D. L.
Published: December 2017

The purpose of this study was to define the relation between carotid distending pressure and muscle sympathetic activity in humans. Carotid baroreceptors of nine healthy subjects were compressed or stretched for 5 s with graded neck pressure or suction (+40 to -65 mmHg), and muscle sympathetic nerve activity was recorded. The results delineate several features of human baroreflex function. First, the carotid-muscle sympathetic relation is well described by an inverse sigmoid function. Second, a linear relation exists between carotid distending pressure and sympathetic outflow over a range of approximately 25 mmHg. Third, sympathetic responses to changes of carotid pressures are asymmetric; increases of sympathetic activity during carotid compression are much greater than reductions of sympathetic activity during carotid stretch. Fourth, at rest, normal subjects operate near the threshold level for sympathetic excitation. Thus the carotid-muscle sympathetic baroreflex is poised to oppose reductions more effectively than elevations of arterial pressure, and the range of pressures over which the reflex is active is wider than thought hitherto.
Cardiac output distribution in thermally dehydrated rodents
Authors: Horowitz M. , Samueloff S.
Published: December 2017

The effect of thermal dehydration (37 degrees C) on the integrated response of the circulation was studied in conscious laboratory rats and in the desert species Psammomys obesus, the latter being studied prior to and following acclimation to heat. Cardiac output (CO) and its distribution were measured using labeled microspheres with the reference organ technique. At low dehydration (7-9% body wt loss) rats showed peripheral vasodilation coincidentally with splanchnic vasoconstriction, whereas the desert species exhibited an increased CO and peripheral vasodilation with no change in splanchnic blood perfusion. At severe dehydration (10-18% body wt loss), closure of skin arteriovenous anastomoses together with splanchnic vasodilation was observed in both species. These changes were discussed in relation to plasma volume conservation mechanism and its deterioration. Acclimation to heat resulted in no change in CO, whereas blood flow to splanchnic and skin capillaries increased remarkably. Dehydration in heat-acclimated P. obesus (5-10% body wt loss) brought about a significant fall in CO. However, most organs maintained relatively stable blood flow. This might contribute to better survival during heat stress.
Effects of a 1-wk spaceflight on morphological and mechanical properties of growing bone
Authors: Shaw S. R. , Vailas A. C. , Grindeland R. E. , Zernicke R. F.
Published: December 2017

The morphological and mechanical responses of tibia and humerus were assessed in growing male rats after a 1-wk spaceflight aboard NASA Spacelab 3. In contrast to flights of longer duration, changes in middiaphysial cross-sectional morphology were minimal. Inhibition of longitudinal growth was not found in the tibia but was apparent in the humerus. The normal age-related increase in tibial middiaphysial density was not observed in the flight animals. Three-point bending tests indicated that a 1-wk spaceflight impeded the maturation of bone strength and stiffness, with the effects more pronounced in the tibia than in the humerus. Material property alterations in bone thus overshadowed morphological factors in determining the bone's mechanical response. It is likely that deprivation of normal weight-bearing loads was a major factor contributing to the observed changes, but endocrine and other local factors must also be considered.
Fasting in king penguin. I. Hormonal and metabolic changes during breeding
Authors: Cherel Y. , Robin J. P. , Walch O. , Karmann H. , Netchitailo P. , Le Maho Y.
Published: December 2017

During long-term fasting in birds and mammals, protein utilization initially decreases (phase I), is thereafter maintained at a low value (phase II), and then further increases (phase III). To delineate hormonal and biochemical changes responsible for these modifications, the effect of food deprivation for 50 days was studied in 6 male king penguins captured at the beginning of their natural breeding fast. During phase II, both rate of mass loss and plasma uric acid concentration remained at low levels, whereas plasma beta-hydroxybutyrate concentration increased. In phase III there was by contrast a 2.5-fold increase in the rate of mass loss, an eightfold increase in plasma uric acid, and an 80% drop in plasma beta-hydroxybutyrate. Plasma corticosterone was low and steady in phase II and increased three times in phase III. During the overall fast, there were no significant variations in plasma insulin, but there was a fourfold increase in plasma glucagon and a decrease in plasma thyroxine and triiodothyronine. These findings suggest that protein sparing (phase II) requires low levels of corticosterone, insulin, and thyroid hormones, whereas the further increase in protein utilization (phase III) is due to an increase in plasma corticosterone. The high plasma glucagon concentration in phase III is presumably responsible for a transient increase in plasma glucose observed at this stage; such increase in glucagon could enhance gluconeogenesis from amino acids.
Simultaneous measurement of preferred ambient temperature and metabolism in rats
Authors: Gordon C. J.
Published: December 2017

A recent study from this laboratory found that rats placed in a temperature gradient preferred ambient temperatures (Ta) that were significantly below the lower critical Ta of the thermoneutral zone for elevating metabolic rate (MR). To further evaluate the interaction between preferred Ta and MR in the rat, a system was developed where preferred Ta, MR (i.e., O2 consumption), and activity could be automatically monitored in the unrestrained rat. Two groups of male Sprague-Dawley rats, a light-weight group and a heavy-weight group, were placed in a longitudinal temperature gradient for 90 min. These animals were further divided into two groups. One group was permitted free run in the gradient with a temperature range of 7-40 degrees C, whereas another group was restricted to the warm end of the gradient where the coolest available temperature was approximately equal to the lower critical Ta (29 degrees C). The preferred Ta and MR data were statistically analyzed over the last 20 min of the experimental run. Rats allowed to run freely in the gradient selected Ta of 17-20 degrees C and had MR significantly higher than animals restricted to a range of Ta no cooler than the lower critical Ta. Animals that selected the cooler Ta were much more active than those forced to remain at the warmer Ta. In conclusion, the interaction between behavioral and autonomic thermoregulation in the rat is unique compared with other rodent species such as the mouse, hamster, and guinea pig, which prefer Ta associated with thermoneutrality.