bluuebunny/crossref_metadata_2025 huggingface dataset:
Organization of energy provision in rainbow trout during exercise
Authors: Parkhouse W. S. , Dobson G. P. , Hochachka P. W.
Published: December 2017

The purpose of this investigation was to examine the fuels supporting high-intensity progressive exercise and their regulation within rainbow trout. During the sustained swim, red muscle (RM) used 97% (17.5 mumol/g) of its glycogen, whereas white muscle (WM) glycogen only declined 31% (7.3 mumol/g). During the burst swim, WM glycogen content decreased 10.4 mumol/g at a rate that exceeded the sustained swim rate by 6.2-fold. Lactate content increased 11-fold at a rate 25 times its sustained swim rate. The exhaustive swim resulted in a decrease of 36.6 mumol/g in liver glycogen, whereas WM glycogen content declined to very low values and lactate reached 43 mumol/g. RM glycogen levels remained low during these exercise bouts. Phosphocreatine (PCr)-buffered ATP declines (WM 7.3-2.7 mumol/g, RM 3.4-1.6 mumol/g) with the time course of the large ATP decreases being related to near depletion of PCr. Decreases in the total adenylate pool were compensated for by the accumulation of inosine 5'-monophosphate in both tissue types. Free ADP (ADPf) contents increased in both tissues by three- to fivefold. ATP/ADPf and cytosolic phosphorylation potentials decreased from 7- to 20-fold. Cytosolic redox potential remained relatively constant at approximately 145 within both fiber types. The changes in adenine nucleotide parameters are associated with the respective activation of the different fiber types and glycolytic flux.
Characterization of branchial transepithelial calcium fluxes in freshwater trout, Salmo gairdneri
Authors: Perry S. F. , Flik G.
Published: December 2017

Experiments were performed to determine whether gill transepithelial calcium fluxes in the freshwater trout (Salmo gairdneri) are passive or require active transport and to characterize the mechanisms involved. A comparison of the in vivo unidirectional flux ratios with the flux ratios calculated according to the transepithelial electrochemical gradients revealed that calcium uptake from the water requires active transport of Ca2+. The inhibition of calcium uptake by external lanthanum, the specific deposition of lanthanum on the apical surface of chloride cells, and the favorable electrochemical gradient for calcium across the apical membrane suggest that the initial step in branchial calcium uptake is the passive entry of calcium into the cytosol of chloride cells through apical channels that are permeable to calcium. The study of gill basolateral plasma membrane vesicles demonstrated the existence of a high-affinity calmodulin-dependent calcium-transporting system [half-maximal Ca2+ concentration (K0.5) = 160 nM, Vmax = 1.86 nmol.min-1.mg protein-1]. This system actively transports calcium from the cytosol of chloride cells into the plasma against a sizeable electrochemical gradient, thereby completing the transepithelial uptake of calcium. Calcium efflux occurs passively through paracellular pathways between chloride cells and adjacent pavement cells or between neighboring pavement cells.
Chronic atrial appendectomy alters sodium excretion in conscious monkeys
Authors: Benjamin B. A. , Metzler C. H. , Peterson T. V.
Published: December 2017

The purpose of this study is to determine whether chronic removal of atrial appendages alters renal response to volume expansion in the conscious monkey. Chronic bilateral atrial appendectomy (ATX) was performed in six animals. Six additional animals served as sham-operated controls. Monkeys were studied 1-2 wk after chronic surgery. The protocol consisted of three consecutive 10-min urine collections followed by 20% ischemic blood volume expansion (VE) and 120 min of post-VE measurements. In sham animals, VE caused an increase in plasma atrial natriuretic peptide (ANP) levels (48 +/- 7 pg/ml to a peak of 108 +/- 34 pg/ml). Urine flow increased from 0.43 +/- 0.07 to 1.07 +/- 0.24 ml/min, sodium excretion increased from 17.9 +/- 2.6 to 74.9 +/- 12.0 mu eq/min, and fractional sodium excretion increased from 0.67 +/- 0.10 to 2.43 +/- 0.28%. ATX attenuated the increase in ANP (34 +/- 8 pg/ml to a peak of 38 +/- 9 pg/ml) in four of six animals. In these animals, renal response to VE was significantly attenuated. Urine flow increased from 0.21 +/- 0.05 to 0.30 +/- 0.01 ml/min, sodium excretion increased from 19.3 +/- 6.02 to 37.8 +/- 5.05 mu eq/min, and fractional sodium excretion increased from 0.79 +/- 0.08 to 1.43 +/- 0.17%. Renal response of two ATX animals with normal increases in atrial natriuretic factor was similar to the sham group. Effect of volume expansion on mean arterial pressure, central venous pressure, and renal hemodynamics was not altered by ATX. These findings demonstrate that bilateral atrial appendectomy in the monkey attenuates the increase in ANP and reduces renal response to VE.
Role of atrial natriuretic peptide in natriuresis in volume-expanded rats
Authors: Kaneko Kenzo , Okada Koji , Ishikawa San-e , Kuzuya Takeshi , Saito Toshikazu
Published: December 2017

Pages R877–R882: Kenzo Kaneko, Koji Okada, San-e Ishikawa, Takeshi Kuzuya, and Toshikazu Saito. “Role of atrial natriuretic peptide in natriuresis in volume-expanded rats.” Pages R878–R881: “antinatriuretic peptide” in legends to Figs. 1–6 and Table 1 should read “atrial natriuretic peptide.”
Hemodynamic significance of the carotid rete during changes in arterial blood pressure
Authors: Dieguez G. , Garcia-Villalon A. L. , Gomez B. , Lluch S.
Published: December 2017

We attempted to characterize in the goat the hemodynamic response of the carotid rete during large, passive changes in blood pressure in the afferent limb of the rete produced by mechanical constriction of the thoracic aorta or the inferior vena cava. Experiments in 12 anesthetized goats demonstrated that calculated resistance through the rete decreases in hypertension and increases in hypotension, whereas changes in resistance through brain vessels follow opposite directions. The consequence of this is that the carotid rete, by passively decreasing its resistance to blood flow in hypertension, acts as a flow-facilitating system in a situation in which smooth muscle of brain vessels contracts in response to stretch. Contrariwise, by increasing its resistance to blood flow during systemic hypotension, the carotid rete "limits" the passage of blood when active relaxation of brain vessels takes place.
Characteristics of L-alanine uptake in freshly isolated hepatocytes of elasmobranch Raja erinacea
Authors: Ballatori N. , Boyer J. L.
Published: December 2017

The specific transport mechanisms that mediate the hepatic uptake of L-[3H]alanine and of an unnatural homologue, alpha-[14C]methylaminoisobutyric acid (MeAIB), were analyzed in hepatocyte suspensions from Raja erinacea. Aminooxyacetate, an inhibitor of aminotransferase activity was used to prevent alanine metabolism. After 3 h of incubation with either 0.5 mM alanine or MeAIB, hepatic concentrations of these amino acids were significantly higher in the presence than absence of Na+ (8 vs. 1 and 1 vs. 0.1 mM, respectively). Kinetic studies indicated that both alanine and MeAIB transport occurred via sodium-dependent saturable mechanisms. [14C]MeAIB uptake was completely inhibited by excess L-alanine. Uptake of [3H]alanine was inhibited by a 40-fold excess of serine and cysteine (53-54%), by MeAIB and methylalanine (26-31%), and by leucine (14%), whereas D-alanine, beta-alanine, taurine, and glutamate had no effect. Insulin and glucagon were unable to stimulate [3H]alanine uptake. Glucose release from hepatocytes was unaffected by 10 mM alanine or 2 mM aminooxyacetate, indicating that alanine is not a major gluconeogenic precursor in this marine elasmobranch. These results suggest that uptake of L-alanine by skate hepatocytes occurs predominantly via a sodium-dependent system, with properties similar to those exhibited by the ASC neutral amino acid transport system previously characterized in Ehrlich ascites tumor cells and rat hepatocytes.
Neural control of renal function in edema-forming states
Authors: DiBona G. F. , Herman P. J. , Sawin L. L.
Published: December 2017

To define the role of the renal nerves in renal sodium-retaining edema-forming states, experiments were conducted in conscious chronically instrumented rats with congestive heart failure (myocardial infarction), nephrotic syndrome (adriamycin injection), and hepatic cirrhosis (common bile duct ligation). In each experimental model, renal excretion, as water or sodium, of an acutely administered oral or intravenous isotonic saline load was significantly less than that in control rats. Bilateral renal denervation of the experimental rats restored their renal excretory response to that of the control rats. In addition, in response to the acute administration of a standard intravenous isotonic saline load, the decrease in efferent renal sympathetic nerve activity was significantly less in all three experimental models compared with that of control rats. These results suggest that the impaired ability to excrete an acute isotonic saline load in these experimental models is partially dependent on an increase in basal efferent renal sympathetic nerve activity that fails to suppress normally in response to the isotonic saline load.
Comparison of fibrinolytic activities of human and bovine endothelial cells
Authors: Bartha K. , Wojta J. , Wagner O. F. , Binder B. R.
Published: December 2017

Human aortic (HAE), human umbilical vein (HUVE), and bovine aortic (BAE) endothelial cells were compared in their synthesis and release of fibrinolytic components during culturing. After isolation, the cultures were grown to confluency and then studied under identical conditions for release of tissue plasminogen activator (t-PA) antigen and plasminogen activator inhibitor (PAI) into serum-free medium. HAE cells released 10 times more t-PA antigen than HUVE cells, and the respective cell lysates also contained comparably higher values. Free PAI capacity was found in the conditioned media of both HAE and HUVE cells. BAE cell t-PA release was much lower than that of the HAE cells, and free inhibitor capacity was not found in the conditioned medium. BAE cells contained significant amounts of PA activity in cell membrane-bound form. This PA activity on the cell surface was not stimulated by addition of CNBr fibrinogen fragments but could be partially inhibited by activated bovine PAI and antibodies against human t-PA and urokinase PA, respectively.
Osmolality, NaCl dietary intake, and regulation of ventilation by CO2
Authors: Anderson J. W. , Jennings D. B.
Published: December 2017

The ventilatory response to CO2 (VR) was examined in six awake dogs during the 2nd week of sequential dietary periods of low NaCl (less than 5 meq NaCl/day), high NaCl (approximately 120 meq NaCl/day), and then repeated low NaCl. Water intake was maintained constant at 77 ml.kg-1.day-1. PCO2 of arterial blood (PaCO2) and the PaCO2 threshold of the VR increased between the high-NaCl and the second low-NaCl period; the PaCO2 threshold did not change between the first low-NaCl and the high-NaCl period. In contrast, arterial [H+] ([H+]a) threshold of the VR increased between the first low-NaCl period and the high-NaCl period, but did not change further in the second low-NaCl period. Variations in [H+]a threshold of the VR between dogs on high- and low-NaCl diets were correlated with plasma osmolality, and this accounted for a positive linear relation between [H+]a and plasma osmolality. During the high-NaCl period, the arterial strong ion difference [[SID]a = ([Na+] + [K+]) - ([lactate-] + [Cl-])] decreased, forcing [H+]a to increase. However, during high-NaCl diet, PaCO2 decreased relative to plasma osmolality, counterbalancing the decrease in [SID]a and maintaining the relation between [H+]a and plasma osmolality. The compensatory mechanism for the decrease in PaCO2 during high NaCl was a shift in the relation between PaCO2 threshold of the VR and plasma osmolality to a lower PaCO2 threshold. Chemoreceptor, osmoreceptor, and/or humoral mechanisms are potentially involved in these respiratory adaptations to alterations in electrolyte and water balance.
Group housing accelerates growth and induces obesity in adult hamsters
Authors: Borer K. T. , Pryor A. , Conn C. A. , Bonna R. , Kielb M.
Published: December 2017

To determine whether variable body heat loss may influence control of growth and regulation of body fat content in hamsters, mature female hamsters were housed for 7-14 wk in one of three conditions: individually in metal cages (n = 6), individually in plastic boxes with bedding (n = 6), or communally (6 per box) in plastic boxes with bedding. Their resting metabolic rate (RMR) was measured individually or in pairs of two between days 65 and 75. When thermal properties of shelter varied alone, singly housed hamsters regulated energy balance fairly accurately by compensatory changes in food intake, and their rate of growth was unaffected. In contrast, group housing induced acceleration of growth and obesity without hyperphagia, was associated with an acute inhibition of RMR in hamsters tested in pairs, and was associated with a chronic inhibition of RMR in hamsters tested individually. We conclude that conspecific body contact in mature group-housed hamsters accelerates somatic growth and increases fat deposition. Energy for this anabolism is derived, in part, from reduced RMR and, in part, from a slight increase in food consumption.
Muramyl dipeptide-induced sleep and fever: effects of ambient temperature and time of injections
Authors: Shoham S. , Krueger J. M.
Published: December 2017

Sleep-promoting factors isolated from rabbit brain and human urine enhance slow-wave sleep (SWS) when administered to rabbits and other mammalian species. These substances were identified as muramyl peptides (MPs). A simple synthetic chemical analogue to these substances, N-acetylmuramyl-L-alanyl-D-isoglutamine (or MDP for muramyl dipeptide), was also found to enhance SWS. MDP is also pyrogenic and can alter rapid eye movement (REM) sleep. However, the effects of MDP on rabbit REM sleep and the relationship between thermoregulation and MDP-altered sleep have not been investigated. We tested, therefore, MDP in rabbits. We found that 1) intracerebroventricular administration of 125 pmol of MDP reduced REM sleep time from 10 +/- 3% of total recording time after vehicle to 4 +/- 3%; 2) a stereoisomer of MDP, N-acetylmuramyl-D-alanyl-D-isoglutamine, failed to have any effects on the sleep and temperature parameters measured; 3) acute elevation of ambient temperature from 21 to 27 degrees C enhanced SWS (37 +/- 3-55 +/- 3%) but not REM sleep; 4) at 27 degrees C MDP further enhanced SWS to 67 +/- 3% and its REM sleep suppression effect persisted; and 5) intravenously injected MDP had greater effects on body temperature during light hours than if administered during dark hours. We conclude that MDP reduces REM sleep in rabbits, that its effects on thermoregulatory processes depend on the time of injection, and that the effects of the thermoregulatory process on sleep are independent of, in part, the effects of MDP on sleep.
Electroencephalogram analysis of non-rapid eye movement sleep in rats
Authors: Trachsel L. , Tobler I. , Borbely A. A.
Published: December 2017

Sleep states and power spectra of the electroencephalogram were determined for consecutive 4-s epochs during 24 h in rats that had been implanted with electrodes under deep pentobarbital anesthesia. The power spectra in non-rapid eye movement sleep (NREMS) showed marked trends: low-frequency activity (0.75-7.0 Hz) declined progressively throughout the 12-h light period (L) and remained low during most of the 12-h dark period (D); high-frequency activity (10.25-25.0 Hz) rose toward the end of L and reached a maximum at the beginning of D. Within a single NREMS episode (duration 0.5-5.0 min), slow-wave activity (0.75-4.0 Hz) increased progressively to a plateau level. The rise was approximated by a saturating exponential function: although the asymptote level of the function showed a prominent 24-h rhythm, the time constant remained relatively stable (approximately 40 s). After short interruptions of NREMS episodes, slow-wave activity rose more steeply than after long interruptions. The marked 24-h variation of maximum slow-wave activity within NREMS episodes may reflect the level of a homeostatic sleep process.
Physiological changes during thermoregulation and fever in urethan-anesthetized rats
Authors: Malkinson T. J. , Cooper K. E. , Veale W. L.
Published: December 2017

Adult male Wistar rats were anesthetized with urethan (1.5 g/kg). They were unable to maintain body temperature (Tb) in a warm (32 degrees C) or cool (9 degrees C) environment or at a laboratory room temperature of 22 degrees C. Tb was allowed to fall to 35.8, 34.5, or 33.3 degrees C, and prostaglandin E1 (PGE1, 400 ng) was delivered into a lateral cerebral ventricle. An immediate feverlike rise in Tb resulted, accompanied by vigorous shivering. Animals were vasoconstricted throughout. When Tb was raised to and maintained at 38.3 or 39.5 degrees C, animals also responded with a fever; however, the magnitude of the fever diminished as the starting Tb increased. In a series of experiments in which Tb was maintained (36.8-37.4 degrees C) by means of a heating pad, PGE1 delivered into a lateral cerebral ventricle or into the anterior hypothalamus caused a dose-dependent change in Tb, which was similar in time of onset, magnitude, and duration to that observed in conscious animals. This fever was accompanied by shivering and increased O2 uptake, heart rate, arterial blood pressure, respiratory rate, and intracranial pressure during the rising phase of the fever, and vasodilation of the paws occurred during defeveresence. Animals were also able to develop a dose-dependent rise in Tb in response to purified human interleukin 1.
Effect of burn and first-pass splanchnic leucine extraction on protein kinetics in rats
Authors: Karlstad M. D. , DeMichele S. J. , Istfan N. , Blackburn G. L. , Bistrian B. R.
Published: December 2017

The effects of burn and first-pass splanchnic leucine extraction (FPE) on protein kinetics and energy expenditure were assessed by measuring O2 consumption, CO2 production, nitrogen balance, leucine kinetics, and tissue fractional protein synthetic rates (FSR-%/day) in enterally fed rats. Anesthetized male rats (200 g) were scalded on their dorsum with boiling water (25-30% body surface area) and enterally fed isovolemic diets that provided 60 kcal/day and 2.4 g of amino acids/day for 3 days. Controls were not burned. An intravenous or intragastric infusion of L-[1-14C]leucine was used to assess protein kinetics on day 3. FPE was taken as the ratio of intragastric to intravenous plasma leucine specific activity. There was a 69% reduction in cumulative nitrogen balance (P less than 0.001) and a 17-19% increase in leucine oxidation (P less than 0.05) and total energy expenditure (P less than 0.01) in burned rats. A 15% decrease in plasma leucine clearance (P less than 0.05) was accompanied by a 20% increase in plasma [leucine] (P less than 0.01) in burned rats. Burn decreased rectus muscle FSR from 5.0 +/- 0.4 to 3.5 +/- 0.5 (P less than 0.05) and increased liver FSR from 19.0 +/- 0.5 to 39.2 +/- 3.4 (P less than 0.01). First pass extraction of dietary leucine by the splanchnic bed was 8% in controls and 26% in burned rats. Leucine kinetics corrected for FPE showed increased protein degradation with burn that was not evident without FPE correction. This hypermetabolic burn model can be useful in the design of enteral diets that optimize rates of protein synthesis and degradation.
Characterization of glucagon and catecholamine effects on isolated sheep hepatocytes
Authors: Morand C. , Yacoub C. , Remesy C. , Demigne C.
Published: December 2017

The purpose of this study was to characterize the glycogenolytic response to catecholamines and glucagon in isolated sheep hepatocytes. In this species, epinephrine appeared to exert its action on hepatic glycogenolysis by altering the cytosolic concentrations of both adenosine 3',5'-cyclic monophosphate (cAMP) and Ca2+. In contrast to results obtained in rat hepatocytes, glucagon failed to induce a rise in free cytosolic Ca2+ in sheep liver. Experiments on isolated hepatocytes or on liver plasma membranes showed that in sheep, glucagon was more efficient than epinephrine in promoting the production of cAMP. In the presence of glucagon or epinephrine, the activation of the glycogen phosphorylase a always appeared greater in sheep than in rat liver cells, whereas the variations in cellular cAMP were quite limited in sheep. The alpha 1- and beta-agonists (phenylephrine and isoproterenol) were alone as efficient as epinephrine in promoting phosphorylase a activation in sheep hepatocytes. All these results indicate the existence in sheep liver of a glycogen phosphorylase highly responsive to hormones.
Renal hemodynamics and vascular reactivity in canine DOCA-salt hypertension
Authors: Goering J. L. , Raich P. C. , Zimmerman B. G.
Published: December 2017

Because of the potential role that the kidney may play in deoxycorticosterone acetate (DOCA)-salt hypertension, changes in renal blood flow, renal vascular reactivity, and renal adrenergic vascular tone were followed in the conscious instrumented dog. DOCA-salt was administered daily after obtaining control measurements. Systemic mean arterial blood pressure (MAP) was monitored with an indwelling catheter, renal blood flow (RBF) was measured electromagnetically using an implanted blood flow probe, and drugs were administered intrarenal arterially through an indwelling renal artery catheter. During the first week of DOCA-salt administration MAP increased from 106 +/- 3 to 118 +/- 2 mmHg and at week 2 to 123 +/- 2 mmHg (P less than 0.01). RBF increased from 275 +/- 32 to 336 +/- 34 during week 1 (P less than 0.05) and to 324 +/- 29 ml/min during week 2. The log ED50 of norepinephrine administered intra-arterially decreased from 1.66 +/- 0.114 to 1.48 +/- 0.091 and 1.41 +/- 0.067 ng/ml (P less than 0.05), and of angiotensin II from 2.58 +/- 0.072 to 2.31 +/- 0.09 (P less than 0.05) and 2.38 +/- 0.05 pg/ml, during weeks 1 and 2, respectively. There was, however, no increase in adrenergic vascular tone as determined by the change in RBF obtained with the intra-arterial infusion of alpha-adrenoceptor antagonists. These experiments indicate that RBF is not compromised in canine DOCA-salt hypertension, and renal adrenergic tone is no greater in the hypertensive than in the normotensive control period.
Tracheal and phrenic responses to neurotensin applied to ventral medulla
Authors: Haxhiu M. A. , Deal E. C. , Trivedi R. D. , van Lunteren E. , Cherniack N. S.
Published: December 2017

Respiratory activity and airway tone can be significantly affected by perturbations confined to superficial areas of the ventrolateral surface of the medulla (VMS). It is not clear which neuromediators are responsible for these changes. Neurotensin (NT), a tridecapeptide, fulfills many of the criteria required for a neurotransmitter or a neuromodulator. In this study, we determined whether NT applied topically to the intermediocaudal area of VMS could alter tracheal tone (Ptseg) and phrenic nerve activity (Ph) in alpha-chloralose-anesthetized cats hyperventilated with O2 to neural apnea. Also, the effects of NT on the responses of tracheal tone and phrenic nerve activity to steady-state hyperoxic hypercapnia (3% CO2 in O2) and isocapnic hypoxia (12% O2) were tested. Application of pledgets containing NT (10(-5)-10(-3) M) caused significant increases in Ptseg and Ph activity without significant changes in blood pressure. Both tracheal and phrenic responses to hypercapnia and hypoxia were also increased by an earlier application of NT. Application of lidocaine (2%) to the VMS rapidly reversed NT-induced responses and prevented them on reapplication of NT. Phosphoramidon, a neutral endopeptidase inhibitor, potentiated responses to NT, suggesting that a mechanism exists at the VMS that could reverse NT effects. Earlier topical administration of hexamethonium bromide to the VMS did not influence the effects of NT, indicating that NT was not acting by causing the release of acetylcholine. Intravenous administration of atropine (1 mg/kg) blocked tracheal but not phrenic responses to NT. These findings suggest that neurotensin may be a neuromodulator involved in central chemosensitivity and that it may participate in the regulation of phrenic activity and parasympathetic tone of airway smooth muscle.
Area postrema stimulation induced cardiovascular changes in the rat
Authors: Ferguson A. V. , Marcus P.
Published: December 2017

The studies described here have utilized electrical stimulation techniques to examine the effects of activation of neural elements within the area postrema (AP) on cardiovascular control mechanisms. A total of 45 urethananesthetized male Sprague-Dawley rats were used in these experiments. Low-frequency electrical stimulation (10 Hz, 200 microA) in the AP resulted in rapid onset (less than 2 s), short-lasting (less than 5 s after end of stimulation) decreases in mean arterial blood pressure (-34.8 +/- 2.7 mmHg, n = 17 rats). In contrast, similar stimulation in the adjacent nucleus tractus solitarius (NTS) caused similarly timed increases in blood pressure (+43.1 +/- 6.7 mmHg, n = 5 rats). Activation of neural elements within the AP was found to significantly (Student's t test, P less than 0.01) reduce heart rate, an effect that was also specific to the AP site as similar stimulation in the NTS was without effect. These data support an important role for AP in cardiovascular control mechanisms. They demonstrate that stimulation in AP results in rapid reversible decreases in mean arterial blood pressure and heart rate. Such findings further emphasise the potential roles of this circumventricular structure in autonomic control mechanisms.
Paraventricular nucleus stimulation causes gastroduodenal mucosal necrosis in the rat
Authors: Ferguson A. V. , Marcus P. , Spencer J. , Wallace J. L.
Published: December 2017

The effects of stimulation in the paraventricular nucleus (PVN) of the hypothalamus on the development of gastrointestinal ulceration have been examined in urethan-anesthetized male Sprague-Dawley rats. Electrical stimulation (200 microA, 60 Hz, 100-microseconds pulse width) in the PVN was performed for 1 h, after which samples of the stomach and duodenum were fixed for subsequent histological assessment of damage. Such damage was scored, blindly, on a 0 (normal) to 3 (severe) scale. Stimulation in the PVN resulted in necrosis and hemorrhage in both the stomach (mean damage score of 1.8 +/- 0.3) and duodenum (1.7 +/- 0.4). In contrast, similar stimulation in regions immediately adjacent to the PVN was found to be without significant effect on the stomach (0.3 +/- 0.1) or duodenum (0.6 +/- 0.2). In a second series of studies PVN stimulation following bilateral vagotomy resulted in damage scores (stomach: 0.2 +/- 0.1; duodenum: 0.1 +/- 0.1) that were significantly reduced compared with the PVN-stimulated vagal-intact group (P less than 0.05) but were not significantly different from the group stimulated in regions outside the PVN (P greater than 0.1). These data suggest an important role for PVN efferents influencing medullary vagal preganglionic neurons in the development of acute gastroduodenal ulceration.
Na deficiency and other physiological influences on voluntary Na intake of BALB/c mice
Authors: Denton D. , McBurnie M. , Ong F. , Osborne P. , Tarjan E.
Published: December 2017

BALB/c mice exhibited a small hedonic intake of 0.3 M NaCl, which was not influenced by change from high to low salt diet or by withholding access to NaCl solution for 1 day. Sodium deficiency produced by furosemide injection consistently caused a highly significant increase in sodium intake. Sodium deficiency was corrected rapidly over 10 min. The appetite was specific for sodium in a cafeteria experiment and was exhibited by naive animals on the first experience of sodium deficiency and subsequent access to salt. The appetite was significantly related to the extent of body deficit, but overdrinking proportionate to initial deficit was characteristic. No increase in sodium intake occurred with repeated experience of sodium deficit. Water deprivation caused a subsequent increase of sodium intake. Total deprivation of food for 48 h caused a large sustained increase of sodium intake, but reduction of food intake by 40% did not influence sodium appetite.
Regulation of [3H]GABA release from strips of guinea pig urinary bladder
Authors: Shirakawa J. , Taniyama K. , Iwai S. , Tanaka C.
Published: December 2017

The presence of receptors that regulate the release of gamma-aminobutyric acid (GABA) was studied in strips of the guinea pig urinary bladder. GABA (10(-8)-10(-5) M) and muscimol (10(-8)-10(-5) M), but not baclofen (10(-5) M), reduced the Ca2+-dependent, tetrodotoxin-resistant release of [3H]GABA evoked by high K+ from the urinary bladder strips preloaded with [3H]GABA. The inhibitory effect of muscimol was antagonized by bicuculline and potentiated by diazepam, clonazepam, and pentobarbital sodium. The potentiating effect of clonazepam was antagonized by Ro 15-1788. Acetylcholine (ACh) inhibited the high K+-evoked release of [3H]GABA. The inhibitory effect of ACh was antagonized by atropine sulfate and pirenzepine but not by hexamethonium. Norepinephrine (NE) inhibited the evoked release of [3H]GABA. The inhibitory effect of NE was mimicked by clonidine, but not by phenylephrine, and was antagonized by yohimbine but not by prazosin. These results provide evidence that the release of GABA from strips of guinea pig urinary bladder is regulated via the bicuculline-sensitive GABAA receptor, M1-muscarinic, and alpha 2-adrenergic receptors.
Control of sodium excretion in NE-ACTH hypertension: role of pressure natriuresis
Authors: Woods L. L. , Mizelle H. L. , Hall J. E.
Published: December 2017

The purpose of this study was to test the hypothesis that, in the presence of high circulating catecholamines, ACTH decreases renal excretory capability and that its natriuretic effects are caused by increased renal arterial pressure (RAP). In six conscious dogs, norepinephrine (NE, 0.4 micrograms.kg-1.min-1) alone for 5 days caused a small but significant rise in arterial pressure (AP) from 102 +/- 6 to 115 +/- 8 mmHg. An infusion of ACTH (600 micrograms/day) for 7 days, superimposed upon the NE, caused a further rise in AP to a plateau of 143 +/- 9 mmHg after 5 days while cumulative sodium balance fell to -149 +/- 41 meq by the 7th day. Cumulative water balance fell to -660 +/- 232 ml by the 3rd day and then increased slightly. In contrast, when ACTH infusion was repeated during NE infusion while RAP was prevented from increasing using a servo-controlled aortic occluder, cumulative sodium balance increased to 197 +/- 35 meq and AP rose from 108 +/- 5 to 168 +/- 5 mmHg after 7 days and did not plateau. Cumulative water balance rose to 2,325 +/- 445 ml. Thus, in dogs receiving a background infusion of NE, ACTH causes moderate hypertension and natriuresis. However, when RAP is not allowed to rise, ACTH is associated with sodium retention and severe systemic hypertension, suggesting that the natriuretic effects of ACTH are caused by increased RAP and that the natriuresis blunts the chronic hypertensive effects of ACTH.
Glomerular filtration changes during vasotocin-induced antidiuresis in kelp gulls
Authors: Gray D. A. , Erasmus T.
Published: December 2017

In conscious kelp gulls, intravenous infusion of arginine vasotocin (AVT) at rates of 0.03, 0.1, 0.3, and 1.0 ng.kg-1.min-1 resulted in a linear relationship between the log values of the AVT plasma concentrations (measured by radioimmunoassay) and the infusion rates, which indicated a plasma clearance rate for AVT of 15.4 ml.min-1.kg-1 when endogenous AVT formation is considered. Evaluation of the renal actions of AVT at each dose level showed that antidiuresis was consistently associated with reductions in glomerular filtration rate as well as changes in tubule water permeability. Thus the water-conserving action of plasma AVT on the kelp gull kidney involves contributions from both glomerular and tubular mechanisms over the entire physiological range found in these birds.
Intracerebroventricular infusions of 3-OHB and insulin in a rat model of dietary obesity
Authors: Arase K. , Fisler J. S. , Shargill N. S. , York D. A. , Bray G. A.
Published: December 2017

We examined the effect of dietary fat on the response to 3-hydroxybutyrate (3-OHB) and insulin infused chronically into the third ventricle in three strains of rats with differing susceptibility to obesity induced by a high-fat diet: Osborne-Mendel rats are most susceptible; Sprague-Dawley-rats are intermediate; and S 5B/Pl rats are most resistant. Ten days after implantation of cannulas into the third ventricle, rats were fed either a low-fat diet or a high-fat diet for 14 days. On day 7, osmotic minipumps were attached to the ventricular cannulas. 3-OHB infusions (3.6 mumol/24 h) reduced food intake and body weight in Sprague-Dawley and Osborne-Mendel rats eating either diet. The dietary fat-resistant S 5B/Pl rats did not respond to the intracerebroventricular infusion of 3-OHB. The infusion of insulin (10 mU/24 h) lowered food intake and body weight in animals eating the low-fat (high-carbohydrate) diet but not in animals eating the high-fat diet. Diet profoundly affects the response to intracerebroventricular infusions of insulin but is without effect on the response to 3-OHB.
Intracranial ethanol and ambient anoxia elicit selection of cooler water by goldfish
Authors: Crawshaw L. I. , Wollmuth L. P. , O'Connor C. S.
Published: December 2017

Goldfish were either subjected to anoxia for 5 h at 10 degrees C, normoxia for 5 h at 10 degrees C, or were implanted with an intracranial microinjection cannula. All groups were subsequently tested in a temperature gradient. The previously anoxic goldfish selected cooler temperatures (12.8 +/- 1.0 degrees C; mean +/- SE) than the corresponding normoxic control group (17.5 +/- 0.7 degrees C) for the first 20 min in the gradient. Intracranial microinjections of 0.0475 ng ethanol in 0.2 microliter 0.7% NaCl led to the immediate selection of water 8.7 +/- 1.5 degrees C below that of base-line levels, whereas control animals injected with 0.7% NaCl selected water 0.9 +/- 1.0 degree C cooler. Increased effects were obtained with higher concentrations of ethanol. The effective site was limited to the anterior aspect of the nucleus preopticus periventricularis; injections into 54 other loci were without effect. Goldfish tolerate anoxia by the conversion of lactate to ethanol, which diffuses across the gills. As the lost ethanol cannot be oxidatively metabolized, this process is energetically inefficient. Because the concentration of the ethanol injections was considerably lower than reported ethanol concentrations in the tissues of anoxic goldfish, endogenously produced ethanol may have induced the selection of cooler water by the anoxic goldfish. This alteration in thermoregulatory behavior would lead to a lower metabolic rate, significantly increasing survival time during anoxia.
Experience affects exercise-induced changes in catecholamines, glucose, and FFA
Authors: Scheurink A. J. , Steffens A. B. , Dreteler G. H. , Benthem L. , Bruntink R.
Published: December 2017

The interference of the experimental conditions on the exercise-induced alterations in plasma catecholamines, plasma free fatty acids, and glucose and insulin concentrations was investigated in rats. Exercise consisted of strenuous swimming against a countercurrent (0.22 m/s) for 15 min in a pool with water of 33 degrees C. Before, during, and after swimming, blood samples were taken through a permanent heart catheter. The blood component levels in rats that were confronted with exercise for the very first time were compared with the levels in rats that were well accustomed to the exercise conditions. The very first time rats swam caused an enhanced release of epinephrine from the adrenal medulla and a reduced output of norepinephrine from the sympathetic nerve endings. Furthermore, in the first time swim group, blood glucose levels were higher and plasma free fatty acid concentrations were lower compared with the well-accustomed animals. There were no differences in plasma insulin concentrations. It is concluded that the experimental conditions may interfere considerably with the hormonal and metabolic response to exercise. Furthermore the results reinforce the idea that the two parts of the sympathoadrenal system are functionally and metabolically dissociated.
Osmoregulation of vasopressin secretion and thirst during the estrous cycle of pigs
Authors: Rollin C. , Kucharczyk J. , Lemoine J. , Bichet D. , Tsang B. K.
Published: December 2017

The influence of the reproductive cycle on ingestive behaviors, osmotically induced fluid intake, and peripheral blood levels of several hormones involved in fluid electrolyte balance was investigated in young adult female pigs. Food, water, and salt intakes and plasma aldosterone levels were significantly lower during estrus compared with the luteal and follicular phases, whereas plasma sodium (PNa) was higher. Plasma renin activity and lysine vasopressin (LVP) levels did not vary with the cycle. Regression analyses of the relationship between plasma LVP and PNa in unanesthetized, unstressed animals infused for 2 h with intravenous 5% NaCl revealed no significant differences in terms of the osmotic threshold and sensitivity of LVP release at different stages of the reproductive cycle. In contrast, when osmotic loading was carried out with continuous access to water, the osmotic threshold for drinking was found to be significantly higher and the rate of drinking lower during estrus. The results indicate that in the adult female pig the stage of the reproductive cycle has an influence on ingestive behaviors and the osmoregulation of thirst. Osmoregulation of vasopressin secretion, on the other hand, appears to be independent of the estrous cycle in this species.
Differential effects of cooling in hibernator and nonhibernator cells: Na permeation
Authors: Zhou Z. Q. , Willis J. S.
Published: December 2017

Unidirectional Na influx is less inhibited by cooling in guinea pig red blood cells than in ground squirrel cells. To isolate the source of this difference, component pathways of 24Na entry were estimated by use of selective inhibitors (ouabain, bumetanide, amiloride). Amiloride slightly inhibited influx in ground squirrel cells at every temperature between 37 and 5 degrees C. Amiloride did not consistently inhibit Na influx at 37 degrees C in guinea pig cells but caused a 44% inhibition at 25 degrees C and a 35% inhibition at 5 degrees C. Cytoplasmic acidification caused an increase in amiloride-sensitive influx in guinea pig cells, which was greater at 20 degrees C than at 37 degrees C; cytoplasmic acidification decreased amiloride-sensitive Na influx in ground squirrel cells at 37 degrees C and had no effect at 20 degrees C.
Systemic vascular autoregulation amplifies pressor responses to vasoconstrictor agents
Authors: Metting P. J. , Stein P. M. , Stoos B. A. , Kostrzewski K. A. , Britton S. L.
Published: December 2017

Experiments were performed in seven conscious dogs to evaluate the contribution of total systemic autoregulation to the increase in mean arterial pressure (MAP) produced by the intravenous administration of pressor agents. Each dog was instrumented for the measurement of aortic pressure, central venous pressure, and cardiac output, and all dogs received hexamethonium to block autonomic ganglionic transmission. Angiotensin II (ANG II), arginine vasopressin (AVP), or norepinephrine (NE) were titrated over a 15- to 20-min period until MAP was increased to a new steady-state value approximately 50-55% above the normotensive control. Then while a constant infusion of the pressor agents was maintained, MAP was controlled via a gravity reservoir for 15-min periods at either the hypertensive value or at the animal's normotensive value. With all three pressor agents, total peripheral resistance (TPR) was greater when MAP was controlled at the hypertensive value than when the vasculature was protected from the elevated pressure by controlling MAP at the normotensive value. Thus a portion of the increase in TPR during the infusion of ANG II, AVP, or NE was due to autoregulatory-mediated vasoconstriction elicited by the increase in MAP. The fractions of the increases in TPR and MAP contributed by primary vasoconstriction vs. autoregulation were determined from the pressure-flow relationships. The pressure-induced increases in TPR accounted for 74% of the total increase in MAP produced by AVP, 62% of the pressor response to NE, and 34% of the response to ANG II. These results demonstrate that the direct vasoconstrictor effects of pressor agents can be significantly amplified by secondary autoregulatory responses.
Clearance and urinary excretion of vasopressin in conscious dogs
Authors: Sondeen J. L. , Claybaugh J. R.
Published: December 2017

The purpose of this study was to determine the relationship between plasma arginine vasopressin (PAVP) levels and the urinary clearance rate, the nonurinary plasma clearance rate, and the urinary excretion rate of AVP. Female conscious dogs were given an intravenous infusion of p-aminohippuric acid and inulin, and, after a 90-min control period, the infusion was either continued or AVP was added to the infusate to produce doses of 0, 40, 100, and 200 microU.kg-1.min-1 for the last 90 min of the experiment. The resulting PAVP levels were 1.2, 8.2, 11.4, and 21.6 microU/ml, respectively. The urinary clearance rate of AVP nearly doubled between the infusion rates of 0 and 100 microU.kg-1.min-1. Likewise, the nonurinary plasma clearance rate of AVP also nearly doubled between the infusion rates of 40 and 100 microU.kg-1.min-1. However, at the rate of infusion of 200 microU.kg-1.min-1, both the urinary and nonurinary clearance rates were unchanged compared with the 100-microU.kg-1.min-1 rate. The largest incremental rise in PAVP was observed between the doses of 100 and 200 microU.kg-1.min-1, when the clearance rates were apparently plateaued. The urinary excretion rate of AVP was linearly correlated with PAVP (R = 0.91) under the conditions of this study. The results suggest that the measurement of the urinary excretion rate of AVP is a reliable method of assessing PAVP and that the clearance of AVP increases when PAVP is elevated.
Energy expenditure during stress ulcer formation in vulnerable rats
Authors: Greenberg D. , Ackerman S. H.
Published: December 2017

Rat pups separated early from their mothers at day 15 become vulnerable to hypothermia and gastric erosion formation when food deprived and physically restrained on postnatal day 30 (S.H. Ackerman, M. A. Hofer, and H. Weiner, Science Wash. DC. 201: 373-376, 1978, and Gastroenterology 75: 649-654, 1978). We tested the hypothesis that this hypothermia is associated with a decrease in oxidative metabolism. We measured O2 consumption of 30-day-old rat pups that had been previously separated at either day 15 (15w) or day 21 (21w). When food was available, 15w rats used as much O2 as 21w rats. When rats were food deprived or food deprived and restrained, 15w rats used significantly less O2 than 21w rats, implying less heat production. We hypothesized that this decrease in heat production during food deprivation and/or restraint was due to impaired thermogenesis resulting from inadequate release of endogenous norepinephrine (NE), which is a stimulant of brown adipose tissue- (BAT) mediated thermogenesis. To test this hypothesis we administered exogenous NE to 15w to 21w rats. Exogenous NE failed to increase O2 consumption in 21w or 15w rats when injected during either food deprivation or restraint. We concluded that 30-day-old 15w rats have decreased oxidative metabolism during food deprivation and restraint and therefore become hypothermic. This decreased oxidative metabolism does not appear to be attributable to insufficient endogenous NE, since it is not reversed by the addition of exogenous NE. We suggest that a decrease in oxidative metabolism may explain susceptibility to stress ulcers in a number of previously reported experimental models.
Calcitonin gene-related peptide increases cAMP, tension, and rate in rat atria
Authors: Wang X. , Fiscus R. R.
Published: December 2017

Calcitonin gene-related peptide (CGRP) was studied in rat isolated atria to ascertain the role of cyclic nucleotides in the positive chronotropic and inotropic actions of this novel cardiac neuropeptide. In electrically driven left and right atria, CGRP (3-100 nM) caused concentration-dependent increases in contractile tension that developed slowly and persisted for greater than 30 min while CGRP remained in the bath. In spontaneously beating right atria, CGRP (3-100 nM) caused concentration-dependent prolonged increases in heart rate and small transient increases in contractile force. CGRP (100 nM, 2 min) elevated adenosine 3',5'-cyclic monophosphate (cAMP) content in left atria 2-fold and right atria 1.6-fold. Time courses and concentration-response relationships for cAMP elevation correlated well with chronotropic and inotropic responses. Guanosine 3',5'-cyclic monophosphate (cGMP) levels in both atria were not altered by CGRP. Compared with norepinephrine (NE), CGRP was 14-fold more potent at increasing rate [50% effective concentration (EC50) = 4.55 +/- 0.48 nM for CGRP and 64.8 +/- 10.5 nM for NE] and 60-fold more potent at increasing contractile force (EC50 = 3.31 +/- 0.57 nM for CGRP and 201 +/- 18 nM for NE). Preincubation with atenolol (3 microM) or indomethacin (3 microM) did not alter chronotropic, inotropic, and cAMP responses to CGRP in atria, indicating that these responses were not mediated by released catecholamines or prostaglandins. The data are consistent with the hypothesis that CGRP causes positive chronotropic and isotropic effects via activation of cAMP responses in rat atrial myocardium.
Peripheral and central consequences of immobilization stress in genetically obese Zucker rats
Authors: Chaouloff F. , Laude D. , Merino D. , Serrurier B. , Elghozi J. L.
Published: December 2017

Peripheral and central effects of acute and chronic immobilization stress were measured in lean and obese Zucker female rats. Thus hypothalamic serotonergic metabolism was analyzed by measuring the concentrations of serotonin (5-hydroxytryptamine, 5-HT), tryptophan (TRP; the precursor of 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA; 5-HT metabolite). In addition, plasma total TRP, free fatty acid (FFA), insulin, and corticosterone concentrations were measured. Analysis of stress-induced changes in food consumption were also included. A single 2-h restraint stress was found to increase TRP availability in the hypothalamus of both rats; this promoted an increase in 5-HIAA in the lean rats and increases in 5-HT and 5-HIAA in the obese (fa/fa) rats. These modifications were associated with marked decreases in plasma total TRP and insulinemia in the lean and obese rats. Whereas stress triggered similar hypercorticosteronemia and hyperglycemia, FFA was increased in the lean rats only. Consecutive hypophagia was noted in all the rats. Twenty-four hours after the last of the four 2-h stress sessions, hypothalamic 5-HIAA was increased in the obese rats and plasma TRP and FFA levels decreased in both rats. Although both groups of rats were normoglycemic, stress-induced hyperinsulinemia was evidenced in the lean rats, thus suggesting that chronic stress promotes insulin resistance. These metabolic variations were associated with normal food consumption and increased body weight gains in the lean and obese Zucker rats.