bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of food manipulation on the GnRH-LH-estradiol axis of young female rats
Authors: Bronson F. H.
Published: December 2017

Female rats were prevented from growing and developing reproductively by restricting their food intake from the time they reached 80-85 g (27-29 days of age) until they were 2 mo old. A return to ad libitum feeding then typically yielded the pubertal ovulation during the third or fourth dark period. Ad libitum feeding for 48 h increased the frequency of luteinizing hormone (LH) pulsing in ovariectomized females. This treatment also depressed the level of circulating estradiol in ovariectomized females implanted with Silastic capsules. It had no effect on the rate at which estradiol was cleared from the blood in a 1-h test, however, nor did it affect the pool of assayable gonadotropin-releasing hormone (GnRH) in the hypothalamus, the pool of assayable LH in the pituitary, the response of the pituitary to GnRH, or the rate at which LH was cleared from the blood. In toto, the present results suggest that food restriction inhibits pubertal development by acting rather specifically on GnRH secretion via an ovarian steroid-independent pathway. The presumed supplemental role for enhanced negative-feedback sensitivity could not be evaluated because of the aberrant results with encapsulated estradiol.
Epinephrine release from the heart during left stellate ganglion stimulation in dogs
Authors: Peronnet F. , Nadeau R. , Boudreau G. , Cardinal R. , Lamontagne D. , Yamaguchi N. , De Champlain J.
Published: December 2017

Plasma epinephrine (E) and norepinephrine (NE) concentrations were measured (radioenzymatic assay) in blood samples simultaneously withdrawn from the aorta (Ao) and coronary sinus (CS) on 10 anesthetized dogs immediately before and during a 1-min period of electrical stimulation of the left stellate ganglion (4 V, 4 ms, 10 Hz). Heart rate and systolic blood pressure significantly increased in response to electrical stimulation (152 +/- 8 to 180 +/- 15 beats/min and 128 +/- 12 to 149 +/- 12 mmHg, mean +/- SE; P less than 0.05). Plasma NE concentrations were not significantly different in the Ao and the CS (432 +/- 110 and 319 +/- 67 pg/ml) before the stimulation, whereas a net removal of E was present across the myocardium (Ao, 172 +/- 61; CS, 71 +/- 22 pg/ml). A large NE spillover in the CS was observed during the stimulation (Ao, 1,555 +/- 513; CS, 10,583 +/- 3,753 pg/ml). A significant output of E from the myocardium was also present (Ao, 165 +/- 42; CS, 291 +/- 74 pg/ml) during the stimulation. Determination of NE and E concentrations by high-performance liquid chromatography in five of the dogs confirmed the observation made with the radioenzymatic assay, i.e., a significant uptake (66%) of blood-borne E was present across the myocardium in the control situation (Ao, 320 +/- 97; CS, 110 +/- 23 pg/ml), whereas plasma E concentrations in the CS (280 +/- 61 pg/ml) were 1.5 times the values found in Ao (184 +/- 56 pg/ml) under electrical stimulation. These observations give further support to the hypothesis that endogenous tissue E can act as a cotransmitter of sympathetic fibers.
Hypothalamic GABA suppresses sympathetic outflow to the cardiovascular system
Authors: Wible J. H. , Luft F. C. , DiMicco J. A.
Published: December 2017

We studied the cardiovascular effects of altering GABA-ergic tone in the posterior hypothalamus in rats. Animals were equipped with chronic guide cannulas placed in the posterior hypothalamus, arterial and venous catheters, and a bipolar electrode on the splanchnic nerve. Microinjected bilaterally into the posterior hypothalamus in conscious rats, the postsynaptic gamma-aminobutyric acid (GABA) antagonists bicuculline methiodide and picrotoxin rapidly increased heart rate, blood pressure, and sympathetic nerve activity. Microinjection of the GABA agonist muscimol into this same region decreased heart rate, blood pressure, and sympathetic nerve activity in conscious rats. In contrast, muscimol infused into the posterior hypothalamus of anesthetized rats failed to alter heart rate or blood pressure. We conclude that 1) the posterior hypothalamus contains a sympathoexcitatory system that is modulated by changes in GABA-ergic tone and 2) tonic GABA-ergic inhibition is sufficient to completely suppress the activity of this hypothalamic sympathoexcitatory system in anesthetized animals but not in conscious rats.
Involvement of prostaglandin E2, cAMP, and vasopressin in lithium-induced polyuria
Authors: Sugawara M. , Hashimoto K. , Ota Z.
Published: December 2017

The involvement of prostaglandin E2 (PGE2), adenosine 3',5'-cyclic monophosphate (cAMP), and vasopressin in lithium-induced polyuria was investigated in rats. Administration of LiCl (4 mmol/kg body wt) for 7 days induced a marked polyuria with a significant excretion of urinary PGE2. Administration of indomethacin (IND, 5 mg/kg body wt) for 4 days to lithium-induced diabetes insipidus (LiDI) rats diminished urine volume by 80% and urinary PGE2 by 85%. The in vitro data of the intact rat kidney showed that lithium stimulated arginine vasopressin (AVP)-induced PGE2 production and suggested that PGE2 suppressed cAMP synthesis in rat renal medulla. The AVP-induced PGE2 synthesis was greater and the AVP-stimulated cAMP production lower in the LiDI rat kidney in vitro. Interference of the vasopressin-associated cAMP system and the increased PGE2 synthesis in the kidney may be involved in the development of LiDI. The reduced cAMP production in the LiDI rat kidney might be partly due to the increased PGE2 synthesis. In LiDI rats plasma vasopressin increased, whereas AVP concentration in the hypothalamus and the neurohypophysis significantly decreased. It is postulated that lithium stimulates vasopressin release from the central nervous system and that elevated plasma vasopressin potentiates PGE2 production in the kidney synergistically with lithium.
Electrophysiological study of neural activity in penile nerve of the rat
Authors: Steers W. D. , Mallory B. , de Groat W. C.
Published: December 2017

Electrophysiological techniques were used to examine the axonal composition and reflex activity of the penile nerve of the rat. Stimulation of either the pelvic nerve, hypogastric nerve, or sympathetic chain elicited synaptic and axonal volleys in the penile nerve. Synaptic responses were suppressed by nicotinic ganglionic blockade, indicating that they were mediated by cholinergic transmission in peripheral ganglia. Axonal volleys represented in part afferent pathways from receptors in the pelvic muscles, perineum, and anus. Stimulation of the penile or pelvic nerves increased intracavernous pressure. Stimulation of the dorsal nerve of the penis elicited central reflexes (50- to 150-ms latencies) in the penile nerve. Those reflexes were not eliminated by acute or chronic spinalization (T8) but were abolished by transection of preganglionic nerves, indicating an origin in the lumbosacral spinal cord. Thus the penile nerves are composed of a heterogenous population of afferent and efferent axons. Reflex activity elicited in these nerves by stimulation of pathways from the penis is probably involved in the initiation of penile erection.
Cholecystokinin inhibits independent ingestion in neonatal rats
Authors: Robinson P. H. , Moran T. H. , McHugh P. R.
Published: December 2017

The ability of the octapeptide of cholecystokinin (CCK-8) to inhibit independent ingestion was examined in 8-h deprived 1- to 10-day-old rat pups consuming milk from the surface of a test chamber. CCK significantly reduced the volume of milk ingested in 1-day-old rat pups at a dose of 100 ng/kg. The threshold effective dosage for inhibition of intake increased with age up to 10 days of age. The specificity of this suppression was evaluated in three ways. First, behavioral observation indicated that ingestive but not noningestive behaviors were suppressed by CCK. Second, desulfated CCK-8 was ineffective in suppressing milk ingestion. Finally, CCK inhibited milk intake stimulated by deprivation but did not affect dehydration-induced milk ingestion in 3-day-old rat pups. In addition to inhibiting intake, CCK inhibited the rate of gastric emptying of saline test meals in 1- and 3-day-old rat pups, and the threshold dosages for this suppression were identical to the thresholds for the inhibition of ingestion. These results indicate that the gastrointestinal peptide CCK is both behaviorally and physiologically active in newborn rat pups and support a role for gastric inhibition in the satiety action of CCK.
Cardiovascular and renal responses to stress in borderline hypertensive rat
Authors: Sanders B. J. , Cox R. H. , Lawler J. E.
Published: December 2017

Wistar-Kyoto (WKY) and borderline hypertensive rats (BHR) were exposed to either a normal or high-sodium chloride (NaCl) diet for 8 wk. Cardiovascular and renal data were collected from arterial and bladder catheters, respectively, in conscious animals during control and stress (aversive classical conditioning) sessions. Results indicated that BHR on a high-NaCl diet exhibited no increase in blood pressure in response to stress compared with BHR on a normal diet. A high-NaCl diet diminished the recovery of blood pressure to base line during stress in WKY compared with normal NaCl controls. Also, a high-NaCl diet and stress interacted in the BHR to decrease sodium excretion and renal plasma flow during stress compared with the control session (3.8 vs. 4.8 mueq.min-1.100 g body wt-1; 3.6 vs. 4.0 ml.min-1. 100 g body wt-1, respectively). Finally, increased dietary NaCl blunted the norepinephrine response to stress in WKY but not in BHR (263 vs. 767 pg/ml). These data suggest that the interaction of genetic and environmental factors are important variables for the development of hypertension.
Suppression of evoked potentials with continued ion transport during anoxia in turtle brain
Authors: Feng Z. C. , Rosenthal M. , Sick T. J.
Published: December 2017

A key to turtle brain survival during anoxia is continued ion transport and avoidance of anoxic depolarization. Previous findings that ATP concentration remained constant during prolonged anoxia and calculations that ATP production decreased indicate that compensatory processes, other than consumption of energy stores or increased anaerobic glycolysis, must also contribute to ion homeostasis and brain survival. To determine whether preservation of ion transport is associated with changes in electrophysiology during loss of oxidative metabolism, the brains of pentobarbital sodium-anesthetized turtles were electrically stimulated 1) to provoke measurable increments in extracellular K+ activity (a degrees k) for determination of rates of K+ reaccumulation at the stimulus site and 2) to elicit polysynaptic extracellular field potentials (evoked potentials) recordable in the olfactory bulb. During anoxia, base-line a degrees k rose only a few millimolar, and rates of reaccumulation of K+, incremented by stimulation were slightly but not significantly slowed. In contrast, postsynaptic orthodromic responses of olfactory bulb granule cells were markedly depressed by anoxia. Monosynaptic responses of granule cells to antidromic stimulation of the lateral olfactory tract were less affected, and compound action potentials in the olfactory nerve were unchanged by anoxia. These data suggest that synaptic transmission in turtle brain, as in that of mammal, is highly dependent on oxidative metabolism and that the turtle brain may effectively conserve energy for ion transport during anoxia by depression of electrical activity.
Pressor responses from electrical or glutamate stimulations of the dorsal or ventrolateral medulla
Authors: Chai C. Y. , Lin R. H. , Lin A. M. , Pan C. M. , Lee E. H. , Kuo J. S.
Published: December 2017

In rats, rabbits, and cats anesthetized with alpha-chloralose and urethan, responses of the pressor areas of the dorsal portion (DM) and ventrolateral portion (VLM) of medulla and pons were compared. Electrical stimulation (monopolar square-wave pulses) on monosodium glutamate solution (Glu, 100-200 nl, 1 M) was delivered through an electrode-needle tubing connected to a Hamilton syringe for semimicroinjection. In all three of these species, pressor responses were elicited from both DM and VLM by either Glu or electrical stimulation. The most active parts of DM were found in the dorsomedial reticular formation of the rostral medulla to mid-medulla. In the pons and caudal medulla, the Glu-induced response was mild, although the electrically induced response was marked. Application of kainic acid (KA) to either DM or VLM produced an initial pressor response but was followed by a reduction of the pressure rise on subsequent electrical stimulation. Glu, unlike electrical stimulation, excites neural perikarya, not fibers of passage. KA initially excites the neural perikarya before causing damage that spares axons. These results thus suggest that both DM and VLM contain neural perikarya that mediate pressor effects.
Fetal and adult urine flow and ANF responses to vascular volume expansion
Authors: Brace R. A. , Miner L. K. , Siderowf A. D. , Cheung C. Y.
Published: December 2017

Isotonic saline (2% of body wt) warmed to body temperature was infused intravascularly over 10 min into chronically catheterized, near-term fetal sheep and into nonpregnant adult sheep. Although both groups of animals underwent the same initial increase in urine flow rate relative to body weight, the diuresis was significantly more prolonged in the adult compared with the fetus. The adult demonstrated a sustained increase in plasma atrial natriuretic factor (ANF) concentration with a suppression of plasma renin activity (PRA) and plasma arginine vasopressin (AVP). In the fetus, only a transient rise in plasma ANF with no change in PRA or AVP occurred. The increases in blood volume and arterial pressure were significantly greater in the adult compared with the fetus, but the venous pressure changes were the same. Thus it appears that fetal and adult kidneys have the same initial urine flow response to rapid vascular volume loading presumably due to a pressure diuresis and elevations in ANF. The more prolonged diuresis in the adult appears attributable to more extensive and prolonged changes in plasma hormone concentrations. The latter, in turn, may be due to the greater intravascular retention of the infused fluid in the adult than in the fetus.
Rare fatty acids in brown fat are substrates for thermogenesis during arousal from hibernation
Authors: Carneheim C. , Cannon B. , Nedergaard J.
Published: December 2017

Because brown adipose tissue lipids are the preferred substrate for thermogenesis during arousal from hibernation, the fatty acid composition of brown fat lipids was followed during cold acclimation and during a hibernation bout. In control golden hamsters (living at 22 degrees C), the fatty acid composition of the white adipose tissue closely resembled that of the food, but brown adipose tissue contained more animal-derived fatty acids. As an effect of acclimation to cold, the fatty acid composition of brown adipose tissue changed to resemble that of the food, and no marked differences between white and brown adipose tissue were then evident. During a hibernation bout, a major part of the fatty acids accumulated in brown fat during entry into hibernation consisted of "rare" acids, such as homo-gamma-linoleic acid. Homo-gamma-linoleic, together with eicosadienoic acid and lignoceric acid, was preferentially utilized during the early phase of arousal. During this phase, "bulk" fatty acids, such as linoleic acid, were spared, whereas in late arousal, linoleic acid was the preferred substrate. It was concluded that rare fatty acids are of quantitative significance in brown adipose tissue during hibernation and arousal.
Differences in perinatal NaCl exposure alters blood pressure levels of adult rats
Authors: Contreras R. J.
Published: December 2017

To determine the effect of differences in NaCl intake early in development on adult blood pressure levels, adult Sprague-Dawley female rats were maintained on diets containing either 0.12, 1.0, or 3.0% dietary NaCl throughout pregnancy and lactation. The offspring were continued on these same diets to 30 days postpartum. Thereafter, all offspring were maintained on the same stock diet containing 1% NaCl. Beginning at 60 days, systolic blood pressure and heart rate were measured weekly for the next 6 wk by tail-cuff plethysmography in lightly etherized rats. Mean arterial pressure (MAP) and heart responses to the subcutaneous sequential administration of 100 micrograms/kg angiotensin II and 15 micrograms/kg isoproterenol were then obtained from the catheterized femoral or carotid artery in awake unrestrained rats. Rats raised on 3% NaCl diet had significantly higher base-line MAPS (127.1 mmHg) than rats raised on the 1% (117.4 mmHg) or 0.12% (115.8 mmHg) salt diets. The highest salt group was also significantly more responsive to the pressor effects of angiotensin II (+46.4 mmHg) and the depressor effects of isoproterenol (-41.4 mmHg) than the mid- (+35.6 and -32.2 mmHg) and low- (+26.9 and -32.5 mmHg) salt groups. Thus there is a sensitive period early in ontogenesis of the normotensive Sprague-Dawley rat during which blood pressure and blood pressure responsiveness to angiotensin II and isoproterenol may be influenced permanently by dietary NaCl.
Prostaglandin formation in the hypothalamus in vivo: effect of pyrogens
Authors: Sirko S. , Bishai I. , Coceani F.
Published: December 2017

Conscious cats were used to study the local release of prostaglandin (PG) E2 and thromboxane (Tx) B2 (the stable TxA2 by-product) from the preoptic-anterior hypothalamus (AH-POA) and the tuberal-posterior hypothalamus (PH-Tu) using a modified "push-pull" perfusion procedure. In the absence of fever, PGE2 release was steady from the 2nd h of perfusion onward, its rate at either site ranging between 0.08 and 0.12 pg/min. Local treatment with probenecid (1 mM) increased PGE2 release about threefold. Compared with PGE2, basal release of TxB2 was greater (0.15-0.43 pg/min) and, occasionally, tended to fall with time. Both compounds were found in higher amounts (2- to 10-fold increase) after locally injecting endotoxin, and the effect was greater in AH-POA than PH-Tu. Conversely, intravenous endotoxin (bolus) or interleukin 1 (IL-1) (bolus plus infusion) at doses causing a sustained fever selectively stimulated the formation of PGE2, but the response itself did not differ between AH-POA and PH-Tu. In either region, the degree of enhancement in PGE2 release correlated with the magnitude of the fever. Intravenous indomethacin (2 mg/kg) reversed both the fever and PGE2 elevation. These findings support an intermediary role for PGE2 in the central action of pyrogens and the ensuing fever. Blood-borne pyrogens may act at multiple sites in brain, which are tentatively identified with the circumventricular organs.
Central effect of angiotensin II on baroreflex regulation in conscious rabbits
Authors: Matsumura Y. , Hasser E. M. , Bishop V. S.
Published: December 2017

Central effects of angiotensin II (ANG II) on arterial baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) were examined in conscious rabbits. Intravenous infusions of ANG II (5-320 ng.kg-1.min-1) significantly reduced the baroreflex inhibition of HR compared with phenylephrine (PE) (0.5-16 micrograms.kg-1.min-1), whereas reflex inhibition of RSNA was unaltered. Background intravenous infusions of ANG II did not alter the baroreflex responses of RSNA nor HR to increases (with PE) or decreases in mean arterial pressure (with nitroglycerin or inferior vena cava occluder). When ANG II was infused into the vertebral artery (VA) the integrated pressor response was greater than intravenous infusions. Progressive VA infusions of ANG II resulted in a significantly blunted baroreflex inhibition of HR compared with intravenous infusions, whereas the reflex inhibition of RSNA was identical between VA and intravenous infusions. These results suggest that ANG II produces central pressor effects via a hindbrain site and reduces baroreflex inhibition of HR without altering baroreflex inhibition of RSNA.
Role of rumen and saliva in the homeostatic response to rehydration in cattle
Authors: Silanikove N.
Published: December 2017

It has been shown recently that the circulation created by the continuous secretion of voluminous amounts of saliva rich in Na+ to the large store of fluid sequestered in the rumen and its reabsorption from the gut is an integral part of water and Na+ homeostasis in cattle. The role of this system in water and Na+ restitution following acute dehydration and rapid rehydration was studied. Cattle were able to withstand dehydration of 18% of their initial mass and to replenish their water losses in one drinking. The water imbibed was first retained in the rumen and slowly released. Rapid expansion (or dilution) of their blood as a result of large influxes of hypotonic water from the rumen was prevented by a parallel increase in the secretion of hypotonic saliva. The accelerated saliva secretion refluxed back to the rumen almost half of the water absorbed. Saliva electrolyte concentration varied simultaneously with an increase or decrease in saliva flow. Na+, HCO3-, HPO3-, and pH were inversely related to saliva flow rate while Cl and K+ were positively related. It seems that visceral afferent response was involved in activation of salivary flow rate.
Arousal state vs. temperature effects on neuronal activity in subcoeruleus area
Authors: Grahn D. A. , Radeke C. M. , Heller H. C.
Published: December 2017

It is believed that thermoafferent neurons synapse in the subcoeruleus area (SC). To assess the effect of arousal state on thermoafferent information processing, we recorded SC unit activity in unanesthetized rats. No responses to changes in ambient temperature were observed within an arousal state, but 85% of the units dramatically altered their firing rates as the arousal state changed. We replicated previous experiments on anesthetized animals which were the basis for ascribing thermoafferent function to the SC. Additionally, we monitored electroencephalographic (EEG) activity. In lightly anesthetized rats, five distinct EEG states could be defined, and the temperature profile of the animal was a primary determinant of the EEG state. No thermoresponses were observed within an EEG state, but 78% of the units dramatically altered their firing rates in synchrony with EEG pattern changes. Transient responses to noxious stimuli were also reflected in both the EEG patterns and single-unit activity. We conclude that SC single-unit activity is not specific for processing of thermal information but is correlated with EEG activity, which in turn is determined by a variety of factors including thermal stimuli.
Sex differences result in increased morbidity from hyponatremia in female rats
Authors: Fraser C. L. , Kucharczyk J. , Arieff A. I. , Rollin C. , Sarnacki P. , Norman D.
Published: December 2017

The development of symptomatic hyponatremia in otherwise healthy young women can result in death or permanent brain damage. The reasons for the increased female susceptibility to complications from hyponatremia are, however, unclear. To determine whether mechanisms that normally defend the brain against damage from hyponatremia are less effective in females than males, we studied both sodium transport in the brains of hyponatremic male and female rats and the effects of parenteral arginine vasopressin on brain high-energy phosphate metabolism and intracellular pH. Basal sodium uptake in synaptosomes prepared from whole brain of females (2.20 nmol/mg protein) and males (2.98 nmol/mg protein) was not statistically different. In contrast, veratridine-stimulated sodium uptake in female brain was 8.20 nmol/mg protein, which was 86% greater (P less than 0.001) than the 6.12 nmol/mg protein observed for male brain. Additionally, sodium uptake between 5 and 60 s was significantly (P less than 0.001) greater in females than males. These data suggest that the Na+-K+-adenosinetriphosphatase (ATPase) pump function in female rat brain synaptosomes is less effective than in males. To determine whether arginine vasopressin, a peptide hormone that promotes water retention by the kidney, had any effects on cerebral energy metabolism, we performed phosphorus-31 (31P) magnetic resonance spectroscopy (MRS) studies on the brain of normonatremic young adult male and female rats subjected to high (20 IU) peripheral doses of arginine vasopressin.We found decreased high-energy phosphate generation, elevated inorganic phosphate, and intracellular acidosis after arginine vasopressin administration in females but not males.(ABSTRACT TRUNCATED AT 250 WORDS)
Afferent renal nerve effects on plasma vasopressin and oxytocin in conscious rats
Authors: Simon J. K. , Kasting N. W. , Ciriello J.
Published: December 2017

Experiments were done in conscious, unrestrained, baroreceptor-intact rats to investigate the effects of afferent renal nerve (ARN) stimulation on circulating levels of arginine vasopressin (AVP) and oxytocin (OXY). Electrical stimulation of ARN elicited a rise in arterial pressure (AP) of 12 +/- 2 mmHg and no significant change in heart rate (HR). Plasma concentrations of AVP and OXY measured by radioimmunoassay were significantly increased immediately after the stimulation period. AVP increased from control levels of 1.89 +/- 0.72 to 4.59 +/- 1.19 pg/ml after stimulation of ARN and OXY increased from 4.3 +/- 0.35 to 10.0 +/- 1.00 pg/ml. AVP remained significantly elevated at 1 h after stimulation and gradually returned to control levels by 3 h after stimulation. On the other hand, OXY values were at control levels at 1 h after stimulation. Stimulation of ARN, after cutting ARN proximal to the stimulating electrode, and sham ARN stimulation did not alter AP, HR, or plasma levels of AVP and OXY. Plasma osmolality was not altered during the experiments. These data demonstrate that, in the conscious rat, afferent information from the kidney alters the release of AVP and OXY from the neurohypophysis and suggests that ARNs are important components of a neuronal circuit that modulates differentially the release of these hormones, which function in the homeostatic regulation of AP and fluid balance.
Adipose tissue dynamics during cyclic weight loss and weight gain of ground squirrels
Authors: Dark J. , Stern J. S. , Zucker I.
Published: December 2017

Ad libitum fed golden-mantled ground squirrels undergo marked annual fluctuations in body mass; during the first cycle, peak and trough masses were approximately 291 and approximately 192 g, respectively. Peak masses were significantly higher (9%) during the second than the first cycle, reflecting a 15% increase in fat-free dry mass and a 12% increase in lipid reserves. The reduction in body mass during the weight loss phase was almost entirely due to an 84% decrease in total lipid reserves and reflected a decrease in adipocyte size but not number. All measured fat depots decreased at similar rates, and there was no evidence of preferential utilization or sparing of individual depots. Fat cell size decreased progressively in each depot during the transition from peak to trough masses and did not vary among the several depots at any stage of annual cycle. Adipocyte number increased in parametrial and retroperitoneal depots but not in the subcutaneous fat between the first and second body mass peaks; fat cell size in these two depots decreased by 28 and 20%, respectively, from the first to the second peak in body mass. Reduced lipid filling of adipocytes at the second peak mass, concomitant with adipocyte hyperplasia, suggests that total lipid mass, not simply fat cell size, is regulated during the annual body mass cycle. Maturation of the subcutaneous fat depot before the initial entry into hibernation may be adaptive in providing insulation during dormancy.
Fetal responses to long-term hypoxemia in sheep
Authors: Kitanaka T. , Alonso J. G. , Gilbert R. D. , Siu B. L. , Clemons G. K. , Longo L. D.
Published: December 2017

The effect of acute or short-term hypoxia on fetal cardiovascular hemodynamics has been well known; however, little is known about the effect of long-term hypoxemia. To determine the fetal hemodynamic responses to this stress we studied two groups of animals: 1) pregnant ewes (n = 20) at 110-115 days of gestation subjected to hypoxia for up to 28 days and 2) pregnant ewes (n = 4) that served as normoxic controls. We chronically catheterized the fetal brachiocephalic artery and vein. Five to 6 days after surgery, control measurements were made of mean arterial blood pressure, heart rate, arterial PO2, O2 saturation, hemoglobin, hematocrit, blood volume, and the concentrations of erythropoietin, cortisol, epinephrine, and norepinephrine. The next day the ewes were placed in a chamber with an inspired O2 fraction of 12-13%. Within a few minutes fetal arterial PO2 decreased from control value of 29.7 +/- 2.1 to 19.1 +/- 2.1 Torr, where it remained. Hemoglobin increased from 10.0 +/- 1.0 to 12.9 +/- 1.9 g/dl by day 7, where it remained. This was associated with an increase of erythropoietin from 22.8 +/- 2.2 to 144 +/- 37 mU/ml within 24 h, but by day 7 it had returned to levels slightly above normal. Epinephrine also increased moderately and remained elevated throughout the study. However, values of mean arterial pressure and heart rate did not differ from controls. Perhaps surprisingly, these fetuses were able to compensate so that at term their body weights were normal, 3.77 +/- 0.2 kg.
Injection of muscimol into posterior hypothalamus blocks stress-induced tachycardia
Authors: Lisa M. , Marmo E. , Wible J. H. , DiMicco J. A.
Published: December 2017

We have previously shown that the physiological and behavioral manifestations of emotional stress are produced when drugs impairing gamma-aminobutyric acid (GABA)-mediated synaptic inhibition are injected into the posterior hypothalamic nucleus in rats [Wible, J.H., Jr., F.C. Luft, and J.A. DiMicco. Am. J. Physiol. 254 (Regulatory Integrative Comp. Physiol. 23): R680-R687, 1988]. The purpose of this study was to assess further the potential role of GABA receptors in this region in the response to stress using muscimol, a GABAA receptor agonist. In six chronically instrumented conscious rats, air stress after vehicle treatment evoked marked and sustained tachycardia (+130 +/- 14 beats/min at +10 min) accompanied by a less dramatic increase in arterial pressure (+14 +/- 3 mmHg). Microinjection of muscimol (10 ng; 88 pmol) at the same posterior hypothalamic site in which GABA blockade causes cardiovascular changes similar to those seen in stress produced a modest depression of cardiovascular function in unstressed animals (-28 +/- 5 beats/min and -6 +/- 3 mmHg). However, similar treatment with muscimol virtually abolished the stress-induced tachycardia in the same rats (+9 +/- 8 beats/min), while having no significant effect on baroreflex-evoked increases in heart rate caused by intravenous infusion of sodium nitroprusside (4 micrograms). These findings support a role for activation of neurons in the posterior nucleus of the hypothalamus in the generation of stress-induced cardiovascular changes and for control of this mechanism by local GABA receptors.
Surgical removal of brown fat results in rapid and complete compensation by other depots
Authors: Rothwell N. J. , Stock M. J.
Published: December 2017

Interscapular, scapular, and cervical brown adipose tissue (BAT) depots were removed from young male rats (BATX). These depots represented 40% of both the total dissectible mass and cytochrome oxidase content of BAT in these animals. Sham-operated and BATX rats were fed a low (8%) protein diet for periods of 9 or 16 days. Over both periods, body weight gain and energy intake, gain, expenditure, and efficiency were almost identical in sham and BATX groups. Four days after lipectomy the maximal thermogenic response (increase in O2 consumption) to norepinephrine (400 micrograms/kg sc) was 30% lower for BATX rats than for controls, but by day 13 this difference had disappeared. Nine days after lipectomy the total mass and cytochrome oxidase activity of the remaining dissectible BAT was comparable to that of the sham-operated controls, although the protein content was slightly reduced. The specific mitochondrial GDP binding (an index of thermogenic activity) was increased significantly in BATX rats, and total BAT mitochondrial GDP binding was no different from control values. At the end of the experiment (day 16), no regeneration of excised tissue had occurred, but the remaining BAT depots had shown almost complete compensation; the mass and the oxidative and thermogenic capacity of the total dissectible brown fat were virtually identical in both groups.
Neurons in rostral VLM are inhibited by chemical stimulation of caudal VLM in rats
Authors: Agarwal S. K. , Gelsema A. J. , Calaresu F. R.
Published: December 2017

Recent evidence suggests that neurons in the caudal ventrolateral medulla (CVLM) exert a tonic inhibition on the neurons in the rostral ventrolateral medulla (RVLM) that are essential for the maintenance of arterial pressure (AP). To test the hypothesis that selective activation of cell bodies in the CVLM can inhibit the discharge of neurons in the RVLM, activity from 88 neurons in the RVLM was recorded extracellularly while 2-30 nl sodium glutamate (Glu; 0.15 M) were microinjected into depressor sites of the CVLM of urethan-anesthetized male Wistar rats. Results obtained from spontaneously breathing and artificially ventilated rats were essentially similar and are presented together. Twenty-five neurons were characterized as cardiovascular because they were inhibited by baroreceptor activation and showed rhythmicity of their spontaneous activity in synchrony with the cardiac cycle. Activation of cell bodies in the CVLM inhibited the firing rate of 23 of these cardiovascular neurons and excited 2. The remaining 63 neurons could not be considered cardiovascular because they either were not barosensitive or lacked cardiac cycle-related rhythmicity. Injection of Glu into the CVLM inhibited 26 of these neurons, excited 22, and had no effect on 15. These results provide direct evidence for the existence of an inhibitory pathway from neurons located in the CVLM to cardiovascular neurons in the RVLM.
Acidemia stimulates ACTH, vasopressin, and heart rate responses in fetal sheep
Authors: Wood C. E. , Chen H. G.
Published: December 2017

Adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), and renin responses to hemorrhage are highly correlated to the hemorrhage-induced decreases in arterial pH. The present study was designed to test the responses of these three systems to acute fetal acidemia, produced by intravenous infusion of H+. HCl was infused into chronically catheterized fetal sheep at rates of 0.02 (n = 5), 0.10 (n = 6), and 0.50 (n = 5) meq/min. Infusions at rates of 0.10 and 0.50 meq/min significantly decreased fetal arterial pH and increased arterial PCO2. Fetal heart rate and plasma concentrations of ACTH, cortisol, and AVP were significantly increased during infusion of HCl at 0.5 meq/min. Neither fetal plasma renin activity nor fetal arterial blood pressure was significantly altered by any of the infusions. The results of these experiments suggest that fetal ACTH, AVP, and heart rate are stimulated by decreases in arterial pH and/or increases in arterial PCO2. We speculate that these responses are chemoreceptor mediated, although we cannot distinguish the apparent relative roles of peripheral and central chemoreceptors on the basis of the present study.
Osmoregulation and body fluid compartmentalization in dehydrated heat-exposed pigeons
Authors: Arad Z. , Horowitz M. , Eylath U. , Marder J.
Published: December 2017

Osmoregulatory and volume-regulatory responses of heat-acclimated pigeons (Columba livia) were studied during normal hydration and dehydration combined with heat exposure. Dehydrated heat-exposed pigeons (exposure to 50 degrees C following 48 h of water deprivation; 16-18% mass loss) could recover 97% of their initial body mass within 30 min of free drinking at the end of heat exposure. At the end of heat exposure, body temperature increased by 3 degrees C and hematocrit increased by 12.5%. Serum electrolyte and protein concentrations increased by 33-53% (P less than 0.001). Serum osmolality reached an outstanding mean value of 436.7 +/- 28.5 mosmol/kg (n = 11), 30.5% higher than the normal mean value. Serum glutamic-pyruvic transaminase and glutamic-oxaloacetic transaminase concentrations did not change during dehydration, suggesting no impairment in circulatory function. Blood urea nitrogen increased sixfold, indicating a total shutdown of the kidney. Relative plasma volume was maintained during dehydration at the expense of extravascular spaces and with a decreased vascular permeability as indicated by the increase in Evans blue-labeled albumin half-life (control, 104 +/- 53 min; dehydration, approaching infinity). Altogether, extracellular fluid volume and intracellular fluid volume contributed 53 and 47% of the evaporative water loss, respectively. It is concluded that plasma volume regulation may play an important role in the effective thermoregulatory responses of heat-exposed dehydrated pigeons. This regulation is achieved by preferential shifts of body water reserves among the various body water compartments coinciding with a remarkable tolerance to high osmotic pressures.
Effects of norepinephrine and denervation on brown adipose tissue in Syrian hamsters
Authors: Hamilton J. M. , Bartness T. J. , Wade G. N.
Published: December 2017

Daily injections of either 0.8 or 3.2 mg norepinephrine (NE)/kg for 2 wk failed to stimulate brown adipose tissue (BAT) growth, GDP binding, or cytochrome-c oxidase activity (COA) in Syrian hamsters (Mesocricetus auratus). However, a single injection of 1.6 mg NE/kg produced a small (23%) but significant acute increase in BAT GDP binding without affecting COA. Thus there is some loss of sensitivity to NE with chronic treatment in Syrian hamsters. Unilateral sympathectomy by surgical denervation of the interscapular BAT (IBAT) resulted in decreased GDP binding and COA in the denervated pad. Chronic NE treatment in hamsters with denervated IBAT only partially reversed the denervation-induced decreases in GDP binding and COA. It therefore appears that NE is not solely responsible for the maintenance and stimulation of thermogenic activity and COA in Syrian hamster BAT. Denervation of IBAT also resulted in elevated levels of lipoprotein lipase (LPL) in this tissue, a surprising finding since brown and white adipose tissue LPL activity were both stimulated by chronic NE treatment. Therefore, although NE has a stimulatory effect on LPL activity, the primary influence of the neural input to IBAT on this enzyme is inhibitory. These data exemplify dramatic differences between rats and hamsters in the mechanisms controlling BAT thermogenesis and white and brown adipose tissue LPL activity.
Increased interleukin 1 beta in human skeletal muscle after exercise
Authors: Cannon J. G. , Fielding R. A. , Fiatarone M. A. , Orencole S. F. , Dinarello C. A. , Evans W. J.
Published: December 2017

Interleukin 1 beta (IL-1 beta) is a protein released from blood monocytes and related cells in response to infectious or inflammatory stimuli. Although IL-1 beta is elevated in the circulation for only a few hours after an acute inflammatory challenge or exercise, it has been proposed to mediate anabolic and catabolic processes that can last for several days. In this report, eccentric exercise was used as a noninfectious inflammatory stimulus. IL-1 beta was found in muscle tissue up to 5 days after exercise using specific immunohistochemical tissue staining. Increased IL-1 beta immunoreactivity was observed in muscle tissue from four human subjects who performed the exercise, but not in tissue obtained at the same time intervals from two subjects who did not exercise. Little immunohistochemical evidence of interleukin-1 alpha or tumor necrosis factor alpha was observed before or after exercise. These results implicate IL-1 beta in the metabolic adaptations of muscle tissue, which occur in response to noninfectious stresses.
Fetal cardiovascular, endocrine, and fluid responses to atrial natriuretic factor infusion
Authors: Brace R. A. , Bayer L. A. , Cheung C. Y.
Published: December 2017

The purpose of this study was to determine the effects of atrial natriuretic factor (ANF) in the fetus and to explore the interactions among the fetal cardiovascular, endocrine, and fluid responses to ANF. In 12 chronically catheterized fetal sheep at 130 +/- 1 (SE) days gestation, ANF was infused intravenously for 30 min at 14-300 ng.min-1.kg-1. Fetal arterial plasma ANF concentration increased by 174 to 5,410 pg/ml from a preinfusion value of 163 +/- 13 pg/ml. The clearance of ANF from the circulation was 122 +/- 28 ml.min-1.kg-1 and the half-life was 0.46 +/- 0.07 min. When plasma ANF was greater than 2,000 pg/ml, fetal arterial pressure decreased, venous pressure increased transiently, and heart rate was unchanged. Plasma arginine vasopressin (AVP) concentration and plasma renin activity (PRA) increased with high ANF concentrations, while norepinephrine concentrations were unaffected. Fetal blood volume decreased in all fetuses, and urine flow increased significantly but not in every fetus. Blood and urine osmolalities did not change. On terminating the infusion, venous pressure and urine flow decreased below control, while blood volume and arterial pressure remained reduced. Plasma AVP concentration increased further, and this was accompanied by an increase in urine osmolality. Thus the most consistent effect of ANF in the fetus was a reduction in blood volume, which was independent of urine flow changes. Other cardiovascular, endocrine, and fluid responses to ANF as well as interactions among them appeared to occur largely at supraphysiological concentrations and may be secondary to the changes in blood volume.(ABSTRACT TRUNCATED AT 250 WORDS)
Simple and inexpensive delivery of halogenated inhalation anesthetics to rodents
Authors: Henry R. T. , Casto R.
Published: December 2017

Halogenated inhalation anesthetics offer several advantages over injectable anesthetics for small-animal surgery. Benefits include rapid induction, easy adjustment of anesthetic depth, and a short period of recovery. Although the cost of most inhalation anesthetics is low, present delivery systems are often prohibitively expensive for rodent uses. This report describes a low-cost, portable system that can be used with halothane or isoflurane for general surgery or stereotaxic applications with or without intubation. Also included is a description of rodent nose cones for both general surgery and stereotaxic surgery that allow for simple evacuation of waste gases.
Changes in uterine fluid composition and acid-base status during shell formation in the chicken
Authors: Arad Z. , Eylath U. , Ginsburg M. , Eyal-Giladi H.
Published: December 2017

The aim of this study was to characterize the dynamic changes in uterine fluid composition and acid-base status during shell calcification in the chicken. Uterine eggs at timed intervals were manually aborted and the accompanying fluid collected and analyzed for composition of osmolytes, enzymes, and acid-base parameters. Blood samples were analyzed for comparison. No considerable change in blood gases took place in relation to residence time of the calcifying egg in the uterus. A significant acidosis occurred at latter stages. Only minor changes were revealed in plasma osmotic and biochemical composition throughout egg calcification. In contrast, major changes were revealed in uterine fluid composition and acid-base status during calcification. The most prominent phenomenon was the sharp increase in CO2 partial pressure, from 82.2 Torr at 0 h to 132.8 Torr at 10 h. As bicarbonate concentration remained almost stable, fluid pH dropped from 7.412 to 7.250 within this stage. Uterine fluid sodium and chloride concentrations and osmolality dropped significantly in the course of calcification, whereas potassium concentration significantly increased. A sharp increase in glucose, calcium, and magnesium concentrations was measured in the early stages of calcification. These findings are discussed in relation to existing models for transport mechanisms of the uterine epithelial tissue. The comprehensive picture that emerges from the present study should enable future application in establishing a self-contained culturing system in vitro for studies of embryonic development.
Electrogenic sodium-proton exchange in membrane vesicles from crab (Carcinus maenas) gill
Authors: Shetlar R. E. , Towle D. W.
Published: December 2017

Plasma membrane vesicles from Na+-absorbing posterior gills of the green crab Carcinus maenas were shown to contain a Na+-H+ antiporter sensitive to amiloride (Ki = 280 mumol/l), using a fluorometric assay based on acridine orange. Lithium was found to support Li+-H+ exchange, giving Michaelis-Menten kinetics (K0.5 = 20 mmol/l) and a Hill coefficient of 1.32 +/- 0.06, indicating a stoichiometry of 1 Li+:1 H+. The stoichiometry of Na+-H+ exchange, however, appeared to be 2 Na+:1 H+. The dependence of exchange rate on Na+ concentration followed a sigmoid relationship (K0.5 = 34 mmol/l), producing a Hill coefficient of 1.99 +/- 0.18. Measurements made with the potential-sensitive dye 3,3'-dipropylthiadicarboxocyanine iodide directly demonstrated electrogenicity of Na+-H+ exchange. Na+-loaded vesicles showed greater potential change upon addition to Na+-free medium than upon addition to Na+-containing medium, and the developed potential was reversed by the addition of external Na+. Amiloride reduced the rate of membrane polarization and abolished the reversal by external Na+. The crustacean Na+-H+ antiporter therefore bears similarities to the vertebrate antiporter but is uniquely electrogenic.
Atropine-induced cutaneous vasodilation decreases esophageal temperature during exercise
Authors: Kolka M. A. , Stephenson L. A. , Allan A. E. , Rock P. B.
Published: December 2017

Four healthy adult males volunteered for this study, which followed informed-consent procedures administered by our local Human Use Committee. Esophageal (Tes) and mean skin (Tsk, eight site) temperatures, forearm sweating rate (ms), metabolism (M), heart rate (HR), and forearm blood flow (FBF) were measured at rest and during forearm blood flow (FBF) were measured at rest and during exercise [55% oxygen consumption (Vo2) peak] during control experiments and after 2 mg im atropine (ATR). Experiments were randomized and separated by at least 72 h. ATR increased heart rate at rest by 15 beats/min and during exercise by 24 beats/min. ATR decreased whole body sweating by 57%. All eight local skin temperatures were higher in ATR than in control. Tsk was 32.6 degrees C in ATR and 31.0 degrees C in control (P less than 0.01). During exercise, ATR increased vasodilation of the forearm compared with control. The slope of FBF to Tes increased over 300% in ATR experiments compared with control (P less than 0.05). The higher sensible heat flux from this vasodilation decreased Tes during exercise, which further decreased sweating. Skin blood flow remained elevated as Tes decreased, suggesting that local vasodilatory factors promoted atropine-induced cutaneous vasodilation.