bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolism and ventilation in acute hypoxia: a comparative analysis in small mammalian species
Authors: Frappell P. , Lanthier C. , Baudinette R. V. , Mortola J. P.
Published: December 2017

O2 consumption (VO2), CO2 production (VCO2), and minute ventilation (VE) have been measured during normoxia and hypoxia (10-20 min in 10% O2) in specimens of 27 species from 6 mammalian orders, ranging in body mass (M) from a few grams to several kilograms. In normoxia, both metabolism and VE scaled close to M3/4, VE/VO2 and VE/VCO2 therefore being independent of M. In hypoxia, VE/metabolism increased in all species (on average greater than 100%), mostly because of a drop in VO2. On average, VE was 23% above the normoxic value but in some species decreased below normoxia. VO2 dropped in all but one species, on average 35%. Body temperature decreased by variable amounts, usually more in the smallest species. The decrease in metabolism during hypoxia was positively correlated with the resting metabolic rate of the species in a manner very similar to what can be calculated from data of previously studied newborn mammals. Hence hypoxia may decrease metabolic rate by decreasing thermogenesis, with larger effects in smaller animals, whether newborns or adults, because of their higher thermogenic requirements. We conclude that 1) hypoxic hypometabolism is a general characteristic of the mammalian response to hypoxia and cannot be neglected in the interpretation of ventilatory and cardiovascular responses and 2) its magnitude is inversely related to the resting VO2 of the species and therefore could be less prominent or possibly absent in adults of larger species.
Differential inhibition of fat intake in two strains of rat by the peptide enterostatin
Authors: Okada S. , York D. A. , Bray G. A. , Mei J. , Erlanson-Albertsson C.
Published: December 2017

The effect of enterostatin, the amino-terminal pentapeptide of pancreatic procolipase, on food intake was investigated in two strains of rat, the dietary fat-sensitive Osborne-Mendel (OM) rat and the dietary fat-resistant S5B/Pl rat. After an overnight fast, enterostatin inhibited intake of high-fat (HF) but not low-fat (LF) diets in OM rats, but had no effect in S5B/Pl rats. When fed a macronutrient three-choice diet, OM rats selected fat preferentially, whereas S5B/Pl rats selected carbohydrate. Enterostatin specifically inhibited the intake of fat in OM rats but not S5B/Pl rats fed a three-choice macronutrient diet. The activity of pancreatic colipase was increased in S5B/Pl rats on both HF and LF diets compared with OM rats. Pancreatic colipase activities were negatively related to the voluntary intake of fat on three-choice macronutrient diets. The data support the hypothesis that enterostatin may control the intake of dietary fat.
Effects of water immersion on sympathoadrenal and dopa-dopamine systems in humans
Authors: Grossman E. , Goldstein D. S. , Hoffman A. , Wacks I. R. , Epstein M.
Published: December 2017

Water immersion to the neck increases central blood volume and evokes a marked diuresis and natriuresis. The present study examined simultaneously effects of water immersion on activities of three endogenous systems thought to participate in sodium homeostasis: the sympathetic nervous system, the atrial natriuretic peptide system, and the renal dopa-dopamine system. Hourly urine collections and antecubital venous blood samples were obtained from 10 normal subjects before, during, and after sitting in a water-immersion tank for 3 h; four control subjects were studied while seated without immersion. Urine volume was increased by more than threefold after 1 h of immersion (from 1.2 +/- 0.2 ml/min at baseline to 5.9 +/- 0.7 ml/min, P less than 0.001) and peaked during the second hour. Urinary sodium excretion increased by more than twofold (from 103 +/- 17 mu eq/min at baseline to 196 +/- 36 mu eq/min at 1 h, P less than 0.001) and peaked during the third hour. Plasma levels and urinary excretion of norepinephrine (NE) and epinephrine were suppressed consistently during immersion (P less than 0.05). There was a marked, prompt, and sustained increase in plasma levels of immunoreactive atrial natriuretic factor (irANF) from 6.9 +/- 1.9 pg/ml baseline to 17.3 +/- 4.3 pg/ml at 1 h (P less than 0.001). Urinary excretion of dopa, dopamine, and 3,4-dihydroxyphenylglycol, a neuronal metabolite of NE, changed in a triphasic pattern, with decreased excretion during the first hour of immersion (P less than 0.01), small but consistent increases during the next 2 h, and decreased excretion, to below baseline, during recovery (P less than 0.01 for dopa and dopamine).(ABSTRACT TRUNCATED AT 250 WORDS)
Rat brain natriuretic peptide is localized in atrial granules and released into the circulation
Authors: Thibault G. , Charbonneau C. , Bilodeau J. , Schiffrin E. L. , Garcia R.
Published: December 2017

Rat brain natriuretic peptide (BNP) was detected by radioimmunoassay in heart atria and ventricles and in plasma. We have investigated its localization in atria and the possibility of cosecretion of atrial natriuretic factor (ANF) and BNP into the circulation. BNP was detected by chromatographic analysis and immunoblotting in the isolated atrial granules together with ANF: It consisted of two immunoreactive proteins of 14,000 and 2,500 apparent molecular weight. By immunohistochemical methods, BNP was particularly found in the perinuclear region of atrial cardiocytes. Double-labeling immunocytochemical methods colocalized BNP and ANF in the same atrial secretory granules. Basal plasma BNP levels ranged from 2.6 to 4.4 fmol/ml. After stimuli by morphine injection or an aortocaval shunt, BNP levels increased by 4- and 7-fold, respectively, whereas ANF levels rose by 50- and 6-fold, respectively. Depending on the stimulus, BNP release into the circulation is not necessarily proportional to ANF, indicating that BNP may originate not only from the atrial granules but also from other tissues such as the ventricles. These results suggest that BNP may participate with ANF in blood pressure control and salt and water homeostasis.
Daily torpor in the absence of the suprachiasmatic nucleus in Siberian hamsters
Authors: Ruby N. F. , Zucker I.
Published: December 2017

Siberian hamsters express torpor spontaneously after several weeks of exposure to short days. In long days, torpor is expressed only when food intake is restricted. Hamsters maintained in a long photoperiod (16 h light/day) at 15 degrees C expressed daily torpor during food restriction both before and after bilateral ablation of the suprachiasmatic nucleus (SCN). Hamsters housed in short days (8 h light/day, ambient temperature 15 degrees C) and fed ad libitum displayed torpor before, but not after, ablation of the SCN (SCNX). Torpor was reinstated in all short-day SCNX hamsters during postoperative food restriction and persisted in several animals even after ad libitum feeding was reinstated. Torpor was entrained to the light-dark cycle in both long- and short-day hamsters preoperatively but appeared to occur in a temporally random fashion in SCNX animals. SCNX hamsters, unlike control animals, displayed multiple torpor bouts per 24 h. The SCN is not essential for the expression of torpor but plays a crucial role in its temporal organization.
Dexamethasone stimulates release of an ANP-like substance from rainbow trout cardiocytes
Authors: Powell W. H. , Miller H. A.
Published: December 2017

A substance that cross-reacts with antiserum to human atrial natriuretic peptide (ANP) is found in fish hearts. This ANP-like material increases sodium output from the gill and kidney while inhibiting sodium uptake in the gut. Mammalian ANP secretion is stimulated by glucocorticoids, and cortisol injection increases sodium output in salt-loaded fish. Therefore, we wanted to determine if the release of ANP in fish is sensitive to dexamethasone. Ventricle cardiocytes from the rainbow trout Oncorhynchus mykiss were treated with various doses of dexamethasone for 18 or 72 h. Single ventricle cells were then assayed for ANP release using a reverse hemolytic plaque assay and antiserum to human alpha-ANP. Incubation with 100 microM dexamethasone almost doubled the population of ventricle cells committed to ANP release (basal, 15.0 +/- 0.3% vs. Dexamethasone, 28.3 +/- 1.4%; values are percent plaque formation +/- SE). Stimulation of ANP secretion was dependent on dose and time of exposure to dexamethasone. These results suggest that ANP secretion in fish is regulated by glucocorticoids.
Comparative aspects of lipid digestion and absorption: physiological correlates of wax ester digestion
Authors: Place A. R.
Published: December 2017

Our understanding of lipid digestion and absorption is largely derived from studies with glyceride-based dietary lipids. Yet for a great majority of marine species, wax esters (long-chain fatty alcohols esterified to long-chain fatty acids) are the dominant dietary neutral lipid. Many birds, especially seabirds (9 species) and some passerines (2 species), have a unique capacity for assimilating wax esters with higher efficiencies (greater than 90%) than that attainable by mammals (less than 50%). This unique capacity is correlated with several factors. One factor is an elevated intestinal bile salt concentration approaching 50 mM and a gallbladder concentration exceeding 600 mM. A second factor involves regular retrograde movement of duodenal contents to the gizzard. Thus not only is gastric emptying closely tied to the receptiveness of the duodenum for further handling of digesta as in mammals, but in birds the reflux returns the digesta (both gastric and duodenal) for further processing to the gizzard. A third key factor in wax ester utilization is a nearly equivalent hydrolysis of wax esters and triglycerides. Although similarities in fat digestion exist between birds and mammals, there do exist differences that make nonpolar lipid assimilation (i.e., wax esters) more efficient in birds, especially for seabirds.
Ca(2+)-related hepatocellular alterations during intra-abdominal sepsis
Authors: Rose S. , Thompson K. D. , Sayeed M. M.
Published: December 2017

Intra-abdominal sepsis was induced in rats by implanting into their abdominal cavities fecal-agar pellets impregnated with Escherichia coli and Bacteroides fragilis. Sham-operated rats received sterile pellets. A group of sterile- and septic-implanted rats was treated intraperitoneally with diltiazem (1.2 mg/kg) 8 h after implantations. Septic- and sterile-implanted rat hepatocytes were loaded with 1) the fluorescent dye indo-1 to quantify hepatocyte basal and vasopressin (100 nM)-elevated cytosolic Ca2+ concentration and 2) 45Ca to quantify Ca2+ flux and cellular content of exchangeable Ca2+. Lipid peroxidation was determined by measuring conjugated dienes (CD) and thiobarbiturate-reactive substances (TBA-RS) in liver homogenates. In septic-implanted rats, the basal cytosolic [Ca2+], cellular exchangeable Ca2+, Ca2+ flux, CD, and TBA-RS were significantly higher than in sterile-implanted rats. Although vasopressin caused a significant elevation in cytosolic [Ca2+] in septic rat hepatocytes, the magnitude of this elevation was significantly smaller than that found in the sterile group. Diltiazem treatment of septic rats significantly decreased basal cytosolic [Ca2+], cellular exchangeable Ca2+ content, Ca2+ flux, CD, and TBA-RS. Also, vasopressin-induced increase in hepatocyte cytosolic [Ca2+] in diltiazem-treated septic rats was significantly greater than that observed in untreated septic rats. Both Ca2+ and membrane lipid alterations were attenuated with diltiazem treatment of septic rats. These results suggest that prevention or attenuation of Ca2+ channel-mediated Ca2+ influx restores both Ca2+ homeostasis and membrane lipid alteration.
Dynamics of gastric emptying during and after stomach fill
Authors: Kaplan J. M. , Spector A. C. , Grill H. J.
Published: December 2017

Gastric contents were sampled at various points during and after intragastric infusions of glucose solution (6.25, 12.5, 25%) delivered at rates typical of normal ingestion in the rat. The postinfusion results were consistent with those reported in the literature in that glucose solute emptied at a relatively stable rate over time and across stimulus concentrations. During fill (1.0 ml/min; experiment 1), by contrast, solute (caloric) emptying rate increased about threefold as stimulus concentration was raised. For each concentration, emptying rate was uniformly higher during than after fill (approximately 4 times higher at the lowest concentration). In experiment 2, gastric emptying rate during 12-min intragastric infusions of 12.5% glucose varied directly with the volumetric rate (0.5, 1.0, 2.0 ml/min) at which they were delivered. These results show that different rules govern gastric emptying during and after stomach fill. The results also suggest that a large proportion of a liquid meal may empty before feeding is terminated and that variations in the rate of ingestion could affect the gastric/postgastric distribution of ingesta and, in turn, the satiation process.
Effects of fasting and hibernation on ion secretion in ground squirrel intestine
Authors: Carey H. V.
Published: December 2017

Ground squirrels were used to study the effects of fasting and hibernation on small intestinal secretory function. Muscle-stripped sheets of jejunum set up in flux chambers were challenged with a variety of secretory agonists, and changes in short-circuit current (Isc) were recorded. Mucosal wet weights per centimeter and crypt dimensions were not affected by a 3-day fast in active squirrels, but villus height and area were significantly reduced in hibernators that had not eaten for over 6 wk. Tissue conductance was significantly greater in fasted and hibernating squirrels compared with fed animals. Maximal changes in Isc evoked by electrical stimulation of submucosal neurons, normalized to serosal surface area, were greater in fasted compared with fed or hibernating squirrels. When responses were normalized to crypt area, neurally evoked changes in Isc were greatest in the hibernators. Carbachol and serotonin evoked dose-dependent changes in Isc that were greater in fasted compared with fed squirrels at all concentrations. Histamine (100 microM) and theophylline (1 mM) also produced greater increases in Isc in fasted than in fed squirrels. The results suggest that a 3-day fast, or the extended fast of hibernation, results in enhanced secretory capacity in the ground squirrel jejunum.
ANP-mediated volume depletion attenuates renal responses in humans
Authors: Ebert T. J. , Groban L. , Muzi M. , Hanson M. , Cowley A. W.
Published: December 2017

Brief low-dose infusions of atrial natriuretic peptide (ANP) that emulate physiological plasma concentrations in humans have little if any effect on renal excretory function. This study explored the possibility that ANP-mediated reductions in cardiac filling pressures (through ANP's rapid effect on capillary dynamics) could attenuate its purported renal effects. Protocol A consisted of 16 healthy subjects (ages 19-27 yr old) who underwent three consecutive 45-min experimental sequences: 1) placebo, 2) ANP (10 ng.kg-1 x min-1), and 3) ANP alone (n = 8) or ANP with simultaneous lower body positive pressure (LBPP, n = 8). Electrocardiogram and direct measures of arterial and central venous pressures were continuously monitored. Blood was sampled at the end of each 45-min sequence before subjects stood to void. Compared with control (placebo), ANP produced a hemoconcentration and increased plasma norepinephrine, but did not change heart rate, blood pressure, plasma levels of renin, aldosterone, or vasopressin, or renal excretion of volume or sodium. In subjects receiving LBPP to maintain central venous pressure during the last 45 min of ANP infusion, norepinephrine did not increase and urine volume and sodium excretion increased (P < 0.05). In a second study (protocol B), five healthy subjects received a placebo infusion for 45 min followed by two consecutive 45-min infusions of ANP (10 ng.kg-1 x min-1). Central venous pressure was maintained (LBPP) at placebo baseline throughout the two ANP infusion periods. Urine volume and sodium excretion rates increased progressively and significantly during both ANP infusion periods (P < 0.05) without significant changes in creatinine clearance, blood pressure, or heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Sepsis- and endotoxin-induced increase in organ glucose uptake in leukocyte-depleted rats
Authors: Lang C. H. , Bagby G. J. , Dobrescu C. , Ottlakan A. , Spitzer J. J.
Published: December 2017

Both gram-negative infection and bacterial endotoxin (lipopolysaccharide, LPS) produce a marked neutropenia and increase glucose disposal by peripheral tissues. The purpose of the present study was to determine whether leukocyte depletion before these insults would diminish the commonly observed increases in tissue glucose uptake. Rats were depleted of circulating and marginated leukocytes with cyclophosphamide (CPA). Under basal postabsorptive conditions the subcutaneous injection of live Escherichia coli into control animals enhanced whole body glucose disposal that resulted in part from a stimulation of glucose uptake by the liver, spleen, intestine, and lung. These increases in tissue glucose uptake were not associated with an increase in neutrophil number, as assessed by myeloperoxidase (MPO) activity. CPA-induced leukopenia did not alter the sepsis-induced increase in glucose uptake by these tissues and whole body glucose use remained elevated. In contrast, skin and muscle proximal to the site of infection showed an increase in both glucose uptake and MPO activity. Furthermore, leukocyte depletion attenuated the elevated glucose uptake by skin and muscle near the inflammatory focus. The intravenous injection of LPS also increased whole body glucose disposal and enhanced glucose uptake by the lung, liver, spleen, intestine, and skin in saline-treated rats. Of these tissues the lung, liver, and spleen had a corresponding increase in neutrophil number. The LPS-induced increases in tissue glucose uptake in leukopenic rats were comparable, with the exception of liver and lung. In these tissues the incremental increase in glucose uptake after LPS was reduced 40-50% in leukopenic animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Differential effects of centrally injected AVP on heart rate, core temperature, and behavior in rats
Authors: Diamant M. , De Wied D.
Published: December 2017

After intracerebroventricular (icv) injection of arginine-vasopressin (AVP; 0.1, 1, 3, 10, 30 and 100 ng) or artificial cerebrospinal fluid (aCSF), heart rate (HR), core temperature (CT), and gross activity were monitored by a wireless telemetry system in rats in the home cage for a 60-min period. In addition, the simultaneous occurrence of various behaviors was recorded by an observer. Also, two structurally related peptides, oxytocin (OXT) and desglycinamide-arginine vasopressin (DGAVP), were tested (10 and 100 ng). Both the time-effect and dose-response relationships of AVP-induced changes in HR and CT were biphasic. Lower doses of AVP produced a tachycardia, whereas injection of higher doses of AVP caused a tachycardia preceded by a significant bradycardia. The concomitant mild rise in CT seen in rats treated with 1 and 3 ng AVP or with aCSF was attenuated in rats given 10 ng AVP; 30 ng AVP resulted in an immediate significant fall in CT, which was restored to control values at 30 min after administration. An inverted U-shaped dose-response relationship was observed for gross activity, locomotion, and rearing behavior, whereas grooming behavior was most marked after the highest dose of AVP. OXT induced a grooming response and cardiac acceleration at the 100-ng dose only, whereas DGAVP produced no effect. To investigate the role of endogenous AVP in the maintenance of tonic ANS activity under resting conditions, rats were treated intracerebroventricularly (icv) with the V1 antagonist d(CH2)5-[Tyr(Me)2]AVP or polyclonal antiserum (W1E) against AVP. During the first 10 min after icv injection of 3 and 10 ng of the antagonist, an increase in HR, CT, and behavioral activation was observed, effects opposite to those produced by the higher dose of AVP. The same variables remained unchanged after administration of 100 ng of the antagonist. W1E injected icv was without effect. In summary, central effects of AVP on autonomic and behavioral activity seem to be mediated by differential neural pathways. In addition, a structure-activity relation seems to exist for the AVP-induced effects. Finally, these results suggest that AVP plays but a minor role in the maintenance of tonic activity of the ANS.
Evidence for a novel angiotensin II receptor involved in angiogenesis in chick embryo chorioallantoic membrane
Authors: Le Noble F. A. , Schreurs N. H. , van Straaten H. W. , Slaaf D. W. , Smits J. F. , Rogg H. , Struijker-Boudier H. A.
Published: December 2017

Angiotensin II acts as a growth factor in the cardiovascular system and has been implicated in angiogenesis. The existence of at least two types of angiotensin II receptors, the AT1 and the AT2 receptors, has been suggested by ligand binding studies. We used three different AT receptor antagonists to study the receptor mediating angiotensin II-induced angiogenesis in the chorioallantoic membrane (CAM) of the chick embryo. Angiotensin II caused pronounced angiogenesis of pre- and postcapillary vessels of 30-40%. This response could only be blocked by adding the peptidergic AT2 antagonist CGP-42112A. The nonpeptidergic AT2 antagonist PD123319 and AT1 antagonist losartan (DuP 753) were not effective. In addition, we used radioligand binding studies with a range of ligands to define the nature of the receptor. Our results show a high density of specific single class AT receptor with a total number of binding sites of 1,190 fmol/mg protein and an affinity constant for angiotensin II of 2.7 nM. The inhibitory concentrations (IC50) for CGP-42112A, PD 123319 and losartan were 724, > 100,000, and 59,000 nM, respectively. Our studies suggest that these binding sites act as receptors for angiotensin II-induced angiogenesis. Both functional and radioligand binding studies suggest that the receptor is different from the classical mammalian AT1 and AT2 receptors.
Changes in the brain levels of GABA and related amino acids in anoxic shore crab (Carcinus maenas)
Authors: Nilsson G. E. , Winberg S.
Published: December 2017

The effects of anoxia on the brain concentrations of gamma-aminobutyric acid (GABA), glutamate, aspartate, glutamine, alanine, and taurine were measured in the shore crab (Carcinus maenas) and compared with data previously obtained from anoxia-tolerant vertebrates. C. maenas was found to survive 12 h in nitrogen-bubbled water. The changes found in brain amino acid levels were strikingly similar to those seen in anoxia-tolerant vertebrates. Thus, during anoxia, the brain of C. maenas displayed considerable increases in the concentrations of GABA (2.4-fold increase after 12 h) and alanine (8-fold increase after 12 h). By contrast, the brain levels of glutamate, aspartate, and glutamine fell significantly during anoxia, whereas the taurine level remained unchanged. Because GABA is a major inhibitory neurotransmitter in arthropods (as well as in most animal phyla), it is suggested that the increased level of GABA could promote the anoxic metabolic depression displayed by C. maenas and thus prolong anoxic survival. It is also possible that the decreases in glutamate and aspartate levels could play similar roles.
Role of nitric oxide synthase-containing vascular nerves in cerebrovasodilation elicited from cerebellum
Authors: Iadecola C. , Zhang F. , Xu X.
Published: December 2017

We studied whether the increases in cortical cerebral blood flow (CBF) elicited by stimulation of the cerebellar fastigial nucleus (FN) are attenuated by systemic administration of inhibitors of nitric oxide synthase (NOS) and, if so, whether NOS-containing perivascular nerves arising from the sphenopalatine ganglia (SPG) are the source of NO during FN stimulation. Rats were anesthetized (1-3% halothane) and artificially ventilated. The FN or the pontine reticular formation (PRF) was stimulated electrically through a stereotaxically implanted microelectrode. To eliminate the elevation in arterial pressure (AP) elicited by FN or PRF stimulation the cervical spinal cord was transected and AP was maintained by intravenous phenylephrine. CBF was measured by a laser-Doppler probe placed over the parietal cortex. Systemic administration of the NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME; 5-40 mg/kg) reduced resting CBF, an effect that was maximal at 10 mg/kg (-30 +/- 4%; n = 6; P < 0.003, analysis of variance). L-NAME, but not its inactive isomer D-NAME, attenuated the increases in CBF elicited by FN stimulation or hypercapnia in a dose-dependent fashion (10-40 mg/kg). At 40 mg/kg, the response to FN stimulation was reduced by 80 +/- 6% (n = 6; P < 0.05) and that to hypercapnia was reduced by 70 +/- 9% (P < 0.05). In contrast, the increases in CBF elicited by PRF stimulation were not affected (10-40 mg/kg; P > 0.05; n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)
Induction and prevention of low-T3 syndrome in exercising women
Authors: Loucks A. B. , Callister R.
Published: December 2017

To investigate the influence of exercise on thyroid metabolism, 46 healthy young regularly menstruating sedentary women were randomly assigned to a 3 x 2 experimental design of aerobic exercise and energy availability treatments. Energy availability was defined as dietary energy intake minus energy expenditure during exercise. After 4 days of treatments, low energy availability (8 vs. 30 kcal.kg body wt-1.day-1) had reduced 3,5,3'-triiodothyronine (T3) by 15% and free T3 (fT3) by 18% and had increased thyroxine (T4) by 7% and reverse T3 (rT3) by 24% (all P < 0.01), whereas free T4 (fT4) was unchanged (P = 0.08). Exercise quantity (0 vs. 1,300 kcal/day) and intensity (40 vs. 70% of aerobic capacity) did not affect any thyroid hormone (all P > 0.10). That is, low-T3 syndrome was induced by the energy cost of exercise and was prevented in exercising women by increasing dietary energy intake. Selective observation of low-T3 syndrome in amenorrheic and not in regularly menstruating athletes suggests that exercise may compromise the availability of energy for reproductive function in humans. If so, athletic amenorrhea might be prevented or reversed through dietary reform without reducing exercise quantity or intensity.
Beta-adrenergic blockade attenuates insulin resistance induced by tumor necrosis factor
Authors: Lang C. H.
Published: December 2017

The macrophage secretory product tumor necrosis factor (TNF) impairs insulin action on peripheral glucose uptake and hepatic glucose output. Because circulating catecholamines are also elevated by TNF, the present study was performed to determine the role of the adrenergic system in eliciting the insulin resistance. Human recombinant TNF (1 microgram.h-1.kg-1) was infused intravenously into chronically catheterized fasted rats for approximately 18 h. Before TNF, an infusion of either saline, propranolol (nonselective beta-antagonist), atenolol (selective beta 1-antagonist), or phentolamine (alpha-antagonist) was started and continued throughout the experimental protocol. Infusion of either the alpha- or beta-receptor antagonist failed to prevent the TNF-induced increase in basal glucose uptake or hepatic glucose output. Under euglycemic hyperinsulinemic conditions, whole body glucose disposal was lower in TNF-infused rats than in control animals. This resulted from a decreased rate of insulin-stimulated glucose uptake by skeletal muscle, skin, and intestine. In propranolol-infused rats, but not in those receiving atenolol or phentolamine, the TNF-induced decrease in whole body glucose uptake was partially prevented. Propranolol attenuated the development of peripheral insulin resistance by selectively preventing the decrease in glucose uptake by skeletal muscle but not by skin and ileum. Propranolol was also able to ameliorate the hepatic insulin resistance produced by TNF. These results suggest that beta-adrenergic stimulation, probably mediated by a beta 2-adrenergic mechanism, is partially responsible for the development of both peripheral and hepatic insulin resistance in animals infused with TNF.
Central respiratory control of A5 and A6 pontine noradrenergic neurons
Authors: Guyenet P. G. , Koshiya N. , Huangfu D. , Verberne A. J. , Riley T. A.
Published: December 2017

Sympathetic nerve discharge (SND), phrenic nerve discharge (PND), and unit activity of locus ceruleus (LC) and of putative A5 noradrenergic cells were recorded in vagotomized rats anesthetized with urethan. SND was activated by stimulation of carotid chemoreceptors with hypoxia (N2 inhalation, 5-15 s or 12% O2 inhalation, 2-5 min) and displayed a prominent central respiratory modulation during the hypoxic challenge (postinspiratory pattern). LC cells were also activated by peripheral chemoreceptor stimulation. The discharge of most LC units (28 of 31) exhibited central respiratory modulation. 15 LC units had a postinspiratory pattern and 11 had an inspiratory one. Putative A5 cells were also excited by hypoxia and also displayed a clear central respiratory modulation (mostly postinspiratory pattern). These experiments indicate that 1) the firing rate of most pontine noradrenergic cells is increased by peripheral chemoreceptor stimulation, and 2) pontine noradrenergic neurons receive afferent information of a respiratory nature, possibly from their ventrolateral medullary inputs.
Characterization of organic osmolytes in avian renal medulla: a nonurea osmotic gradient system
Authors: Lien Y. H. , Pacelli M. M. , Braun E. J.
Published: December 2017

We measured the organic osmolytes present in the renal cortex and medullary cones of adult female domestic fowl before and after 48 h of water deprivation. Urine osmolality increased from 198 +/- 82 to 569 +/- 42 mosmol/kgH2O after water deprivation. In water-deprived birds, the major organic osmolytes, myoinositol, betaine, and taurine, in the medullary cones increased by 40, 100, and 24%, respectively, compared with control birds. No sorbitol was detected, and glycerophosphorylcholine (GPC) content was not affected by water deprivation. In the renal cortex, only betaine content increased significantly (4.8 +/- 0.6 vs. 3.1 +/- 0.3 mmol/kg wet wt) after water deprivation. In this study, we demonstrated that birds, like mammals, accumulate organic osmolytes in response to the increased interstitial osmolality that occurs during antidiuresis. Because urea is nearly absent in the avian medullary interstitium, our observation that GPC is not osmoregulated in the avian kidney supports the idea that GPC is the “counteracting osmolyte” for urea in the mammalian kidney. Furthermore, the organic osmolytes present in avian medullary cones are remarkably similar to those of the mammalian outer medulla. This similarity may be relevant to the morphological analogy of the two regions.
Changes in bladder and external urethral sphincter function after spinal cord injury in the rat
Authors: Kruse M. N. , Belton A. L. , de Groat W. C.
Published: December 2017

Spinal cord injury (SCI) in humans results in inappropriate contractions of the external urethral sphincter muscle (EUS) during micturition (bladder-sphincter dyssynergia), leading to urinary retention. The major goal of this study was to determine whether SCI in rats has similar detrimental effects on micturition. After chronic SCI, urethan-anesthetized rats had a significantly (15-fold) increased bladder capacity and impaired voiding (31-fold increase in residual volume) compared with control rats. Bladder contractions in SCI rats were accompanied by abnormal tonic EUS electromyographic activity, whereas the EUS electromyograms of control rats exhibited a burst pattern (4-8 Hz) during voiding. Suppression of EUS activity with neuromuscular blockade did not improve the fraction of urine voided in SCI rats and reduced the fraction voided in control rats. Therefore, both tonic activity and complete quiescence of the rat's EUS appear to be detrimental to voiding, suggesting that the normal bursting EUS activity facilitates bladder emptying. In summary, rats and humans exhibit similar micturition dysfunctions after SCI (e.g., bladder-sphincter dyssynergia and impaired voiding).
Metabolism and energetics in squid (Illex illecebrosus, Loligo pealei) during muscular fatigue and recovery
Authors: Portner H. O. , Webber D. M. , O'Dor R. K. , Boutilier R. G.
Published: December 2017

The concentrations of intermediate and end products of anaerobic energy metabolism and of free amino acids were determined in mantle musculature and blood sampled from cannulated, unrestrained squid (Loligo pealei, Illex illecebrosus) under control conditions, after fatigue from increasing levels of exercise, and during postexercise recovery. Phosphagen depletion, accumulation of octopine (more so in Illex than in Loligo), and accumulation of succinate indicate that anaerobic metabolism contributes to energy production before fatigue. Proline was a substrate of metabolism in Loligo, as indicated by its depletion in the mantle. In both species, there was no evidence of catabolism of ATP beyond AMP. A comparison of the changes in the free and total levels of adenylates and the phosphagen indicates an earlier detrimental effect of fatigue on the energy status in Loligo. The acidosis provoked by octopine formation in Illex was demonstrated to promote the use of the phosphagen and to protect the free energy change of ATP such that the anaerobic scope of metabolism during swimming is extended and expressed more in Illex than in Loligo. In both species, there was no decrease in the sum of phospho-L-arginine, octopine, and L-arginine, and thus no release of octopine from the mantle, thereby supporting our earlier claim that octopine and associated protons are recycled in the mantle tissue. Overall, the metabolic strategy of Loligo is much less disturbing for the acid-base status. This strategy and the alternative strategy of Illex to keep acidifying protons in the tissue may be important for the protection of hemocyanin function in the two species.
Intragastric glucose but not fructose conditions robust flavor preferences in rats
Authors: Sclafani A. , Cardieri C. , Tucker K. , Blusk D. , Ackroff K.
Published: December 2017

Prior work indicates that glucose and fructose differ in their postingestive reinforcing effects. The present study investigated this phenomenon by training rats to associate the intake of flavored water with intragastric (IG) infusions of 16% sugar solutions. In experiment 1, rats had one flavor [conditional stimulus (CS)] paired with IG sugar infusions (CS+; e.g., cherry) and another flavor paired with IG water (CS-; e.g., grape) 23 h/day; Chow was available ad libitum. In subsequent choice tests, rats infused with glucose displayed a strong preference (89%) for the CS+ flavor, whereas rats infused with fructose showed only a small and nonreliable CS+ flavor preference (62%). When next trained to associate one flavor (e.g., orange) with IG glucose and another flavor (e.g., strawberry) with IG fructose, rats in both groups developed a significant preference (81%) for the glucose-paired flavor. In experiment 2, food-deprived rats were trained 2 h/day to associate a CS+ flavor with IG sugar and a CS- flavor with IG water infusions. The glucose-reinforced rats displayed a near-total preference (95%) for the CS+ flavor, whereas fructose-reinforced rats showed a much smaller CS+ preference (67%). The preference findings indicate that the postingestive consequences of glucose are much more reinforcing than those of fructose. It appears that food conditioning is mediated by chemospecific actions of nutrients rather than their general satiating or energy repleting effects.
Splenectomy alters blood pressure response to incremental treadmill exercise in horses
Authors: McKeever K. H. , Hinchcliff K. W. , Reed S. M. , Hamlin R. L.
Published: December 2017

Six intact (IN) and five splenectomized (SP) mares were subjected to an incremental exercise test to examine the effects of splenectomy on blood pressure responses during exercise. During the test the horses ran up a 6 degree grade on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s every 1 min until heart rate (HR) reached a plateau. Hemodynamic data were collected continuously and analyzed for the last 18 s of the 4, 5, 6, and 7 m/s steps of the exercise test. There were no differences (P > 0.05) between the groups for resting means for any parameter measured in the study. HR increased (P < 0.05) in both groups of horses during exercise with significantly greater HR in the SP horses during the first two steps of the test. There were no differences (P > 0.05) in maximal HR between the groups. Right atrial pressure (RAP) did not change during exercise in the SP horses; however, it did increase 20 mmHg (493%, P < 0.05) in the IN horses. Right ventricular pressure (RVP) increased (P < 0.05) during exercise with no differences (P > 0.05) between the groups. Right ventricular maximum change in pressure over time increased (P < 0.05) in a similar fashion in both groups of animals. Mean arterial pressure (MAP) increased 29 mmHg (30%, P < 0.05) in SP horses, reaching a plateau by the 5 m/s step of the test.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiovascular actions of dogfish urotensin II in the dogfish Scyliorhinus canicula
Authors: Hazon N. , Bjenning C. , Conlon J. M.
Published: December 2017

Bolus injections of synthetic dogfish urotensin II (0.1-1.0 nmol) into the celiac artery of the conscious dogfish Scyliorhinus canicula (n = 8) resulted in sustained and dose-dependent increases in arterial blood pressure and pulse pressure. A maximum rise in mean arterial pressure of 10.5 +/- 1.2 mmHg (equivalent to 38.6 +/- 4.2% over mean basal values) and a maximum increase in pulse pressure of 3.9 +/- 0.8 mmHg was elicited by injection of 0.5 nmol of peptide. In comparison, a bolus injection of epinephrine (5 nmol) elicited a rise of 24.8 +/- 3.3% in mean arterial pressure. Bolus injection of 0.5 nmol synthetic goby (Gillichthys mirabilis) urotensin II under the same conditions did not elicit a significant hypertensive response. When dogfish urotensin II (0.5 nmol) was administered 3 min after an intra-arterial injection of phentolamine, the rise in arterial blood pressure was completely abolished. Dogfish urotensin II produced a dose-dependent contraction (pD2 = 6.58 +/- 0.07; n = 8) of isolated rings of vascular muscle prepared from the first afferent branchial artery of the dogfish. A maximum contractile force of 1.3 mN was produced by 10(-5) M peptide. The urotensin II-induced contraction of the vascular rings was unaffected by pretreatment with tetrodotoxin (1 microM) or indomethacin (14 microM). It is concluded that urotensin II has potent hypertensive activity in the dogfish that is mediated, at least in part, through release of catecholamines, but the sustained nature of the pressor response suggests that the peptide may have a direct action on the heart.
Plasma catecholamine and corticosterone and their in vitro effects on lizard skeletal muscle lactate metabolism
Authors: Gleeson T. T. , Dalessio P. M. , Carr J. A. , Wickler S. J. , Mazzeo R. S.
Published: December 2017

Lizard skeletal muscles utilize primarily lactate as a gluconeogenic substrate for glycogen replenishment following exercise. To understand the influence of selected hormones on this process, we measured changes in plasma catecholamines and corticosterone resulting from exercise in the lizard Dipsosaurus dorsalis and then investigated the physiological effects of those hormones on skeletal muscle lactate and glucose metabolism in vitro. Plasma epinephrine (Epi), norepinephrine, and corticosterone (Cort) increased 5.8, 10.2, and 2.2 times, respectively, after 5 min of exhaustive exercise. Epi and Cort levels remained elevated after 2 h of recovery. Skeletal muscle fiber bundles isolated from the red and white regions of the iliofibularis muscle were incubated 2 h at 40 degrees C in the presence of postexercise concentrations of [14C]lactate (15 mM) and glucose (8.5 mM) in the presence and absence of Epi or Cort. Red muscle oxidized both substrates at 2-3 times the rate of white muscle, and both red and white fibers oxidized lactate at 5-10 times the rate of glucose oxidation. Epi had a stimulatory effect on lactate oxidation by white muscle. Lactate incorporation into glycogen proceeded at 2-3 times the rate of glucose incorporation in both muscle types, with rates in red muscle again 2-3 times that for white muscle. Epi stimulated lactate carbon incorporation into glycogen by 50-140% in both red and white muscle but had no effect on glucose incorporation into glycogen in either tissue. We interpret these data as evidence that epinephrine stimulates lactate removal by skeletal muscle. Cort had no effect on lactate metabolism in either muscle type.(ABSTRACT TRUNCATED AT 250 WORDS)
Reduced ionic conductance in turtle brain
Authors: Doll C. J. , Hochachka P. W. , Reiner P. B.
Published: December 2017

Whole cell recording techniques were employed to measure whole cell (Gw) and specific membrane (Gm) conductance in turtle and rat pyramidal neurons in slices. Results indicate that rat neurons are 4.2 times more conductive compared with turtle neurons at 25 degrees C, which is accentuated by temperature, so that rat neurons at 37 degrees C are 22 times more conductive than turtle neurons at 15 degrees C. A conductance Q10 of 1.9 was measured for both turtle (15-25 degrees C) and rat (25-35 degrees C) pyramidal neurons. Conductance measurements of turtle pyramidal neurons over 6-9 h of anoxia indicate no statistical difference between Gm or Gw from normoxic control measures. These results indirectly support the concept of low ATP-dependent ion pump activity in the turtle brain as one mechanism for reduced energy expenditure in the normoxic state.
Impairment of renal function precedes establishment of hypertension in spontaneously hypertensive rats
Authors: Uyehara C. F. , Gellai M.
Published: December 2017

To determine renal function throughout development of hypertension in the spontaneously hypertensive rat (SHR) and its normotensive counterpart, the Wistar-Kyoto rat (WKY), renal clearance studies were performed at 2-wk intervals from 4 to 12 wk and again at 16 wk of age in conscious chronically instrumented rats after recovery (4-6 days) from surgery. The data indicate that the critical period for the development of hypertension in SHR was between 4 and 6 wk of age. Mean arterial pressure sharply increased from 107 +/- 5 (n = 6) to 145 +/- 6 mmHg (n = 6) between 4 and 6 wk of age, did not change between 6 and 10 wk of age, and gradually rose between 10 and 16 wk of age to 183 +/- 3 mmHg. In WKYs, blood pressure increased only slightly from 97 +/- 3 mmHg at 4 wk of age (n = 8) to 110 +/- 3 mmHg at 8 wk of age (n = 8), where it remained through adulthood. Glomerular filtration rate (GFR) in the 4-wk-old SHR was significantly decreased compared with WKY (0.94 +/- 0.03 vs. 1.11 +/- 0.04 ml.min-1 x g wet kidney wt-1), and it recovered to normal level and stabilized by 6 wk of age (1.14 +/- 0.04 ml.min-1 x g wet kidney wt-1). Renal blood flow was lower in the SHR only at 4 and 16 wk; it increased with age in both groups. Renal vascular resistance was higher in the SHR at 4 wk and remained elevated throughout the observation period.(ABSTRACT TRUNCATED AT 250 WORDS)
Endotoxin stimulates drinking in rats without changing dehydrational signals controlling thirst
Authors: Wang K. , Evered M. D.
Published: December 2017

Intravenous injections of endotoxins from Escherichia coli or Salmonella minnesota stimulate drinking and reduce urinary excretion of water and solutes in rats. E. coli endotoxin (0.15 or 0.45 mg/kg i.v.) stimulated drinking without increasing plasma osmolality or sodium concentration, hematocrit, blood hemoglobin, or plasma protein concentration and without decreasing arterial pressure. Similarly, a dipsogenic dose of S. minnesota endotoxin (0.25 mg/kg i.v.) did not reduce arterial or venous pressures or change heart rate. Blocking the renin-angiotensin system with captopril or blocking histamine receptors with pyrilamine and cimetidine did not reduce drinking or urinary fluid retention caused by E. coli endotoxin. Injections of 10 or 450 ng E. coli endotoxin into a lateral cerebral ventricle increased body temperature but not water intake. In contrast to its stimulatory effect in water-replete rats, E. coli endotoxin (0.45 mg/kg i.v.) inhibited drinking in 24-h water-deprived rats. Thus we find no evidence to support the hypothesis that endotoxin causes thirst by changing known physiological signals of cellular or extracellular dehydration. The mechanism remains unknown.
Role of NO in goat basal cerebral circulation and after vasodilatation to hypercapnia or brief ischemias
Authors: Dieguez G. , Garcia J. L. , Fernandez N. , Garcia-Villalon A. L. , Monge L. , Gomez B.
Published: December 2017

The role of nitric oxide (NO) in the cerebral circulation under basal conditions and after vasodilatation to hypercapnia or reactive hyperemias was studied in 17 anesthetized goats. The intravenous administration of NG-nitro-L-arginine methyl ester (L-NAME, 3-4 or 8-10 mg/kg), an inhibitor of nitric oxide production, reduced middle cerebral artery (MCA) flow (electromagnetically measured) by 19 and 30% and increased systemic arterial pressure by 21 and 26%, respectively, whereas heart rate did not significantly change; MCA resistance increased by 48 and 86%, respectively. These hemodynamic effects were reversed by L-arginine (200-300 mg/kg iv; 5 goats). Different levels of hypercapnia (PCO2 of 30-35, 40-45, and 55-65 mmHg) (12 goats) produced arterial PCO2-dependent increases in MCA flow that were similar under control and L-NAME treatment. Graded cerebral hyperemia occurred after 5, 10, and 20 s of MCA occlusion in 5 goats, but its magnitude was decreased during L-NAME treatment. It suggests that, in the cerebral circulation, nitric oxide 1) produces a basal vasodilator tone and 2) is probably not involved in the vasodilatation to hypercapnia but may mediate hyperemic responses after short brain ischemias.
Biological actions of brain natriuretic peptide in thoracic inferior vena caval constriction
Authors: Clavell A. L. , Stingo A. J. , Aarhus L. L. , Burnett J. C.
Published: December 2017

Brain natriuretic peptide (BNP) shares structural and functional similarities to atrial natriuretic peptide (ANP). Although BNP and ANP interact with the same biologically active guanylate cyclase-coupled receptor, recent reports conflict with regard to the biological actions of exogenous BNP in sodium-retaining and edematous states. We studied the biological actions of BNP in normal dogs (n = 5) and sodium-avid dogs with chronic thoracic inferior vena caval constriction (TIVCC) (n = 6). In normal dogs BNP increased glomerular filtration rate, renal blood flow, and urinary sodium excretion and decreased proximal and distal fractional reabsorption of sodium with activation of urinary guanosine 3',5'-cyclic monophosphate (cGMP). These renal actions occurred in association with marked hypotensive actions and activation of systemic cGMP. In TIVCC, a state characterized by chronic reductions of cardiac output, avid sodium retention, edema, and activation of the renin-angiotensin-aldosterone system (RAAS), the renal actions of BNP were absent in association with marked attenuation of the urinary cGMP response. In contrast, an enhanced hypotensive response with preserved activation of systemic cGMP was observed. In neither normal dogs nor TIVCC dogs did BNP inhibit the RAAS. These studies report that BNP is a potent vasoactive and natriuretic peptide with potent proximal and distal tubular actions in normal dogs. These studies also demonstrate that in TIVCC, a model of low cardiac output and congestive failure that results in marked sodium retention with edema in which there is activation of the RAAS, the renal actions of BNP are attenuated while the vasoactive actions are enhanced.