bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypertension and alterations in central catecholamines after preoptic recess lesions
Authors: Van Huysse J. W. , Bealer S. L.
Published: December 2017

Catecholamine concentrations were measured in brain regions of rats with lesions of the anteroventral third ventricle (AV3V-X rats) or parietal cortex (CORT-X) and of control-operated (CONT) rats. Three hours after surgery, total norepinephrine (NE) concentrations in all brain regions measured of AV3V-X rats were less than those of CONT or CORT-X rats. Epinephrine (EPI) concentrations were decreased in the medulla and hypothalamus, but dopamine levels were unchanged. Also, extracellular NE concentration, estimated by in vivo microdialysis techniques, was increased in the anterior hypothalamic nucleus (AHNE) and dorsomedial medulla (DMMNE) of AV3V-X rats compared with CONT rats. Increased DMMNE paralleled blood pressure increases. DMMNE did not change after blood pressure was increased by intravenous angiotensin II infusion (60 ng/min) in CONT rats. Thus 1) AV3V lesions result in decreased NE and EPI concentrations in multiple brain regions; 2) acute reductions in central NE in AV3V-X rats are associated with increased extracellular NE in the AH and DMM, suggesting increased NE release; and 3) although increased DMMNE is temporally related to increased blood pressure following AV3V lesions, increased DMMNE is not a response to the hypertension per se.
Adrenalectomy and response to corticosterone and MSH in the genetically obese yellow mouse
Authors: Shimizu H. , Shargill N. S. , Bray G. A.
Published: December 2017

Animals with the viable yellow (Avy/a) gene and their corresponding lean control black mice (a/a) were adrenalectomized or sham adrenalectomized, and changes in body weight, body composition, corticosterone, and GDP-binding to mitochondria isolated from interscapular brown adipose tissue (IBAT) were measured. Adrenalectomy slowed the weight gain of both the yellow obese mice and the black lean mice, but the reduction was greater in the yellow mice. Food intake was significantly reduced in the yellow mice. Adrenalectomy in the yellow mouse was associated with an increase in lean mass and a significant decrease in weights of fat depots. Blood glucose concentrations of the adrenalectomized yellow mice were reduced to levels similar to those of lean mice, but insulin levels, although lower than sham-adrenalectomized yellow mice, remained significantly higher than in lean animals. GDP binding to IBAT mitochondria increased after adrenalectomy in both phenotypes to values that were similar. Corticosterone replacement in adrenalectomized yellow mice produced a dose-dependent increase in body weight that was associated with a decrease in muscle weight and an increase in adipose tissue weight. Both desacetyl-melanocyte-stimulating hormone (MSH) and alpha-MSH interacted with corticosterone to increase body weight gain of adrenalectomized yellow mice. Desacetyl-MSH was more effective than alpha-MSH on increasing adipose tissue and liver weights. The effects of desacetyl-MSH on food intake, weight gain, and tissue weights were independent of the adrenal gland or of corticosterone.
Neuronal and cardiovascular responses to ANF microinjected into the solitary nucleus
Authors: Ermirio R. , Ruggeri P. , Cogo C. E. , Molinari C. , Calaresu F. R.
Published: December 2017

The effect on single-unit activity, arterial pressure, and heart rate of a microinjection of atrial natriuretic factor (ANF) into 78 histologically verified sites in the nucleus tractus solitarii (NTS) was investigated in rats. Injections of 50 nl of 10(-7) M ANF excited 34 neurons (44%), mainly localized at the level of the obex, inhibited 15 (19%), and had no effect on the remaining 29 (37%). The increase in firing frequency of the 34 excited neurons was always followed by a decline in mean arterial pressure [MAP, -10.6 +/- 1.8 (SE) mmHg; P less than 0.01] and heart rate [HR, -9.6 +/- 3.1 (SE) beats/min; P less than 0.05]. When injections of ANF caused either no effect or inhibition of single-unit activity, no changes in either MAP or HR were observed. Single units excited by injections of ANF were also excited by activation of arterial baroreceptors and inhibited by baroreceptor unloading. Control injections of an inactive peptide analogue of ANF or of vehicle never produced any effects on neuronal firing frequency or on MAP and HR. Similar results were obtained from animals paralyzed and artificially ventilated. These results support the hypothesis that ANF plays a role in the chemical transmission of baroreceptor information within the NTS.
Effect of fasting on glucose turnover in a carnivorous fish (Hoplias sp)
Authors: Machado C. R. , Garofalo M. A. , Roselino J. E. , Kettelhut I. C. , Migliorini R. H.
Published: December 2017

Intravenous glucose tolerance tests and measurements with [6-3H]glucose of rate of glucose replacement, transit time, and body glucose mass were performed in fed and fasted Hoplias malabaricus. Both glycemia levels and the rate of decline of blood glucose following intravenous administration of 500 mg/kg glucose were significantly lower in 60-day-fasted than in fed fish. Changes in plasma free fatty acids were opposite to those in blood glucose. The rate of glucose replacement, calculated graphically from mean +/- 3 SE plots of glucose specific radioactivity, was 0.71 (0.66-0.77) mg.kg-1.min-1 in fed H. malabaricus and decreased to 0.51 (0.46-0.56) mg.kg-1.min-1 after 60 days without food, with a concomitant reduction of body glucose mass (mmin, 138 vs. 83 mg/kg). In fish starved for 10 mo the rate of glucose replacement and body glucose mass were further reduced to 0.35 (0.29-0.42) mg.kg-1.min-1 and 57 mg/kg (mmin), respectively. It is concluded that a progressive decline in the rate of glucose utilization contributes to the adaptation of fish to prolonged fasting.
Development of potassium transport capability by choroid plexus of infant rats
Authors: Parmelee J. T. , Johanson C. E.
Published: December 2017

Developmental maturation of K transport and Na+-K+-adenosinetriphosphatase (ATPase) function in the choroid plexus (CP) was investigated in infant rats. K fluxes (86Rb), Na+-K+-ATPase enzyme activities, and [3H]ouabain binding were measured in isolated, lateral CPs removed from anesthetized Sprague-Dawley rats of several ages ranging from 1 day to 6 wk. Morphological integrity of incubated tissue was confirmed by electron microscopy. CP epithelia accumulated K at a lower level during the 1st wk after birth (40 nmol/mg wet wt) compared with CP from rats aged 11-28 days (56 nmol/mg wet wt). However, efflux curves and efflux rate coefficients among the age groups were similar. Both Na+-K+-ATPase activity in CP tissue homogenates and [3H]ouabain binding to isolated CP began to increase between age 10 and 14 days. It is concluded that CP Na+-K+-ATPase has limited capacity in the lateral CP of neonatal rats but that this important transport function matures rapidly in the 1st 2-3 wk after birth.
Regulation of VO2 in red muscle: do current biochemical hypotheses fit in vivo data?
Authors: Connett R. J. , Honig C. R.
Published: December 2017

Observations used to test biochemical models of the regulation of O2 consumption (VO2) by cytosolic phosphate energy state must include a change in intracellular pH and/or a change in the adenine nucleotide or phosphate pools [Connett, R. J. Analysis of metabolic control: new insights using a scaled creatine kinase model. Am. J. Physiol. 254 (Regulatory Integrative Comp. Physiol. 23): R949-R959, 1988]. Data were collected over a wide range of energy turnover from canine muscles in situ. Intracellular PO2, glycolytic intermediates, adenine nucleotides, creatine, phosphocreatine (PCr), phosphate, and intracellular pH were determined for each muscle. PO2 was used to eliminate muscles in which VO2 could have been O2 limited (PO2 less than 0.5 Torr). This removed an important source of heterogeneity. Because adenine nucleotide and phosphate pools were constant relative to the creatine pool, discrimination among models depended solely on pH. The observed pH range from 7.2 to 5.9 did not permit separation of [PCr] from log[( ATP4-]/[ADP3-][H2PO4-]) (phosphorylation potential) as a regulatory parameter for VO2. However, [ADP] could be eliminated as an independent regulator. Because 90% of variability in VO2 was accounted for by phosphate energetics, an independent redox component must be small when intracellular PO2 greater than 0.5 Torr.
Regional hemodynamic changes following hypovolemia in conscious rats
Authors: Gardiner S. M. , Compton A. M. , Bennett T.
Published: December 2017

Regional hemodynamic responses to subcutaneous injection of hyperoncotic polyethylene glycol (PEG) were assessed in Long-Evans (i.e., normal) and Brattleboro [i.e., arginine vasopressin (AVP)-deficient] rats with chronically implanted, pulsed Doppler probes. The results were compared with saline-injected time controls. PEG injection elicited an early (30 min) selective mesenteric vasoconstriction in Long-Evans rats; 4-5 h after PEG the mesenteric vasoconstriction was greater in Long-Evans than in Brattleboro rats, but the renal and hindquarters vasoconstrictions were similar in both strains. There was a transient mesenteric vasodilatation [with no change in blood pressure (BP)] in Long-Evans rats given an antagonist of the V1-receptor actions of AVP 5 h after PEG. In the presence of the AVP antagonist, Long-Evans rats showed a marked dependence on the vasoconstrictor actions of the renin-angiotensin system for the maintenance of BP, similar to Brattleboro rats. Both strains also showed marked hypotensive responses to inhibition of sympathoadrenal activity (with pentolinium). Hence, AVP has clear-cut hemodynamic effects after PEG administration, but its role is not indispensable.
Influence of hematocrit on whole blood glucose levels: new evidence from marine mammals
Authors: Castellini M. A. , Castellini J. M.
Published: December 2017

The water content and glucose concentration in the whole blood of marine mammals were found to be correlated to red blood cell concentration. Because hematocrit (Hct) undergoes significant periodic shifts in these mammals during periods of apnea and/or diving, the measured values of whole blood glucose change due to alterations in Hct, independent of shifts in metabolite regulatory pathways. In contrast to humans, where red blood cell and plasma glucose concentrations are equivalent, in most other mammalian species red blood cell glucose concentration is much lower than that in plasma. Therefore, as Hct increases, the whole blood concentration of glucose must decrease in a linear manner, depending on the magnitude of the Hct change and the concentration of glucose in the blood cells. This study demonstrates that water and metabolite distribution must be considered when interpreting whole blood metabolite data. The results suggest that plasma or serum analysis of metabolites would avoid distribution problems. This is especially critical in species where Hct varies during the course of the experiment, as in exercising or diving mammals.
Glomerular and vascular atrial natriuretic factor receptors in adrenalectomized rats
Authors: Cachofeiro V. , Schiffrin E. L. , Cantin M. , Garcia R.
Published: December 2017

The renal and vascular responses to atrial natriuretic factor (ANF) and glomerular and vascular ANF receptors were studied in adrenalectomized (ADR) rats with or without deoxycorticosterone (DOC) or dexamethasone (Dexa) replacement therapy. As expected, adrenalectomy elicited hypotension, hemoconcentration, and increased plasma renin activity, but no changes in plasma levels of either ANF-(1-98) or ANF-(99-126) were detected. Dexa treatment decreased both ANF-(1-98) and ANF-(99-126), whereas DOC treatment increased only ANF-(1-98). The acute renal response to ANF and furosemide was reduced in ADR rats and partially restored either by steroid replacement or by raising blood pressure. The blunted natriuretic response to ANF in ADR rats was associated with an increased density of glomerular receptors. Norepinephrine-precontracted vascular strips from ADR rats were more sensitive to ANF (ED50: 1.7 x 10(-8) M) than those from sham-operated animals (ED50: 1.5 x 10(-7) M). However, vascular ANF receptor density in mesenteric vessels from ADR animals was decreased. Dexa treatment restored vascular response to that observed in sham-operated animals without a concomitant change in vascular receptor density. Because the presence of guanylate cyclase-coupled and noncoupled ANF receptor subtypes have been described in different tissues, we conclude that the apparent lack of correlation between the biological response to ANF and total binding of ANF to glomeruli or mesenteric artery membranes in ADR rats may be in part caused by a differential regulation of both receptor subtype populations.
Ontogeny of isoproterenol-stimulated renin secretion from sheep renal cortical slices
Authors: Nakamura K. T. , Page W. V. , Sato T. , Klinkefus J. M. , Robillard J. E.
Published: December 2017

The ontogeny of renin secretion from renal cortical slices was studied in two groups of fetal (107-109 days of gestation and 131-136 days of gestation; term is 145 days), newborn (3-9 days old), and adult nonpregnant sheep. Isoproterenol (ISO; 10(-8)-10(-5) M) significantly increased active renin secretion in all age groups (P less than 0.05), with newborns having the highest values at all concentrations. However, the percent changes in active renin secretion were similar among all ages. Inactive renin secretion also increased with ISO stimulation, with newborns having the highest rate of inactive renin secretion. The percent of total renin in the active form differed among ages, ranging at base line from 60 +/- 10% in fetuses at greater than 130 days of gestation to 88 +/- 6% in fetuses at less than 110 days of gestation (P less than 0.05). Propranolol (1 microM) inhibited ISO (10(-6) M)-stimulated active renin secretion at all ages. On the other hand, the prostaglandin (PG) synthase inhibitor aspirin (1.6 x 10(-5) M) did not inhibit ISO (10(-6) M)-mediated increases in active renin secretion in fetal (greater than 130 days of gestation) kidney slices and produced values intermediate between base line and ISO alone in newborns and adults.(ABSTRACT TRUNCATED AT 250 WORDS)
Vasopressin reduces oxygen uptake in intact dogs but not in sinoaortic-denervated dogs
Authors: Liard J. F.
Published: December 2017

We have investigated the effect of infusions of arginine vasopressin on cardiac output and O2 uptake in the presence and in the absence of sinoaortic reflexes to better understand the mechanism of the exaggerated decrease in cardiac output elicited by vasopressin. Chronically instrumented dogs received, on separate days, 30-min infusions of vasopressin (0.2, 1, 5, 20, and 60 ng.kg-1.min-1), phenylephrine (1, 3, and 10 micrograms.kg-1.min-1), and angiotensin II (ANG II) (10, 20, and 50 ng.kg-1.min-1). These infusions all increased mean arterial pressure to a maximum of 63 +/- 8.2 mmHg during the highest phenylephrine infusion rate. Vasopressin reduced cardiac output (electromagnetic flowmeter) more than the other vasoconstrictors for equivalent increases in arterial pressure. Vasopressin also produced dose-dependent decreases in O2 uptake, measured by collection of expired air. Such decreases were not observed with the other two agents. On the contrary, ANG II and phenylephrine increased O2 uptake significantly when they decreased cardiac output the most. The decrease in O2 uptake induced by vasopressin was significantly correlated with the decrease in cardiac output. Pretreatment of the dogs with atropine prevented the decrease in O2 uptake and blunted the fall in cardiac output induced by vasopressin at a rate of 5 ng.kg-1.min-1. In dogs surgically deprived of sinoaortic receptors, vasopressin given at 1 and 5 ng.kg-1.min-1 failed to reduce O2 uptake and cardiac output significantly.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of ANP on circulating blood volume
Authors: Sugimoto E. , Shigemi K. , Okuno T. , Yawata T. , Morimoto T.
Published: December 2017

The effects of rat atrial natriuretic peptide (rANP) on blood volume (BV) were determined by the continuous measurement of BV, mean arterial pressure (MAP), and central venous pressure (CVP). Immediately after a single-bolus injection of rANP-(1-28), 1 nmol/100 g body wt, in conscious rats, BV began to decrease. Peak reduction of -0.22 +/- 0.03 ml/100 g body wt was reached 14.5 min after the injection. Thereafter, BV levels returned gradually to -0.08 +/- 0.03 ml/100 g body wt compared with the control value. In volume expansion experiment, the nephrectomized, anesthetized rats were divided into two groups: the control group, with only a saline infusion, and the ANP group, with an infusion of saline with rANP (1 nmol/100 g body wt). In the ANP group, increases in BV were not as great, and recovery was threefold faster than that of the control group. In the ANP group, the recovery time of BV to the starting control levels was 8.5 min, and the time constant of recovery was 3.6 +/- 0.3 min-1. The control group times were 25 min and 11.5 +/- 0.8 min-1, respectively. The effective vascular compliances were approximately 2.8 ml.mmHg-1.kg body wt-1 in both groups, and the capillary filtration coefficient was 0.47 ml.mmHg-1.min-1.kg body wt-1 in the ANP group and 0.33 ml.mmHg-1.min-1.kg body wt-1 in the control group. Thus the whole body capillary filtration coefficient was 1.5-fold higher in the ANP group than in the control group. This suggests that ANP may increase the permeability of capillaries.
Effect of upper airway CO2 pattern on ventilatory frequency in tegu lizards
Authors: Ballam G. O. , Coates E. L.
Published: December 2017

Nasal CO2-sensitive receptors are reported to depress ventilatory frequency in several reptilian species in response to constant low levels of inspired CO2. The purpose of this study was to determine the influence of phasic patterns of CO2 in the upper airways on ventilation. Awake lizards (Tupinambis nigropunctatus) breathed through an endotracheal tube from an isolated gas source. A second gas mixture was forced at constant flow into the external nares. A concentration of 4% CO2 was intermittently pulsed through the nares in a square-wave pattern with a frequency of 60, 12, 6, 4.2, 1.8, and 0.6 cycles/min. Concentrations of 2, 3, 4, and 6% CO2 were also pulsed through the nares at 12 cycles/min and compared with sustained levels of 1, 1.5, 2, and 3%. Additionally, 0 or 3% CO2 was forced through the upper airways with a servo system designed to mimic normal ventilatory flow and gas concentrations. No changes in breathing pattern were noted during any of the pulsing protocols, although a significant breathing frequency depression was present with sustained levels of CO2 of comparable mean concentrations. We conclude that ventilatory control is selectively responsive to sustained levels of environmental CO2 but not to phasic changes in upper airway CO2 concentration.
Site of action of putative lipostatic factor: hypothalamic metabolism of parabiotic rats
Authors: Kasser T. R. , Harris R. B. , Martin R. J.
Published: December 2017

Studies were conducted to determine whether metabolic adaptation occurred in the hypothalamus of overfed parabiotic rats and their partners to distinguish between the adaptations caused by increased caloric intake and those caused by the production of a "lipostatic factor." The induction of overfed obesity in one parabiotic partner was employed to test the hypothesis that a putative lipostatic factor produced in the obese parabiotic elicited the hypophagic-lipid-mobilizing effect observed in the lean parabiotic via alterations in hypothalamic fatty acid and glucose metabolism. Fatty acid oxidation in the ventrolateral hypothalamus (VLH) of overfed parabiotic rats and their partners was lower than in ad libitum parabiotic rats. Net flux of glucose through the VLH gamma-aminobutyric acid (GABA) shunt was elevated in overfed parabiotic rats compared with the net flux observed in their partners and ad libitum parabiotic rats, the levels being similar in these last two groups. Net flux of glucose through the ventromedial hypothalamic (VMH) pentose shunt in overfed parabiotic rats and their partners was elevated relative to ad libitum parabiotic rats. The putative lipostatic factor may act to regulate energy balance through modification of VLH fatty acid oxidation and/or glucose flux via the VMH pentose shunt.
Hemodynamic effects of activation of renal and mesenteric sensory nerves in rats
Authors: Janssen B. J. , van Essen H. , Struyker Boudier H. A. , Smits J. F.
Published: December 2017

Afferent nerves from the kidney and mesentery reflexly influence the cardiovascular system when activated. To examine the specificity of these reflexes, comparisons were made of the regional hemodynamic responses elicited by intra-arterial infusion of various agents into the renal (ir) and mesenteric (im) circulation. Experiments were performed in conscious rats, chronically instrumented with Doppler flow probes. Local ir as well as im infusions of bradykinin caused a hemodynamic reflex pattern characterized by a dose-dependent increase in arterial pressure, heart rate, and resistance in the renal and mesenteric vascular beds, whereas hindquarter resistance did not change. Similar hemodynamic reflex patterns were evoked by ir and im infusions of adenosine and 5-hydroxytryptamine. Thus neither application of different chemicals nor their route of infusion resulted in qualitatively different hemodynamic reflex patterns. This suggests that afferent nerve fibers from the kidney and mesentery share a common physiological function.
In vitro evidence for an inhibitor of lipogenesis in serum from overfed obese rats
Authors: Harris R. B. , Bruch R. C. , Martin R. J.
Published: December 2017

Involvement of a humoral agent in regulation of energy balance has been demonstrated by parabiosis experiments. Overfed obese rats produce a blood-borne factor that inhibits adipose fatty acid synthesis in their partners, resulting in loss of body fat without significant inhibition of food intake. An in vitro bioassay was developed to test small serum samples for antilipogenic activity. Epididymal adipocytes from ad libitum-fed rats were preincubated for 12 h with 2% serum. Basal adipocyte fatty acid synthesis, measured in a subsequent serum-free incubation, was inhibited by obese serum. Insulin response was not changed. Characterization studies indicated that the factor was probably a protein, larger than 30 kDa, but not a protease or a low-density lipoprotein and was not associated with serum albumin. Physiological experiments demonstrated that the agent was produced when body weight was raised substantially above "set-point." Inhibitory activity was neither species specific nor pituitary dependent. Structure, origin, and physiological significance of the factor are unknown, but it may be involved in the control of body fat content.
Glucose metabolism in pregnant sheep when placental growth is restricted
Authors: Owens J. A. , Falconer J. , Robinson J. S.
Published: December 2017

The effect of restricting placental growth on glucose metabolism in pregnant sheep in late gestation was determined by primed constant infusions of D-[U-14C]- and D-[2-3H]glucose and antipyrine into fetuses of six control sheep and six sheep from which endometrial caruncles had been removed before pregnancy (caruncle sheep). In the latter, placental and fetal weights were reduced, as was the concentration of glucose in fetal arterial blood. Fetal glucose turnover in caruncle sheep was only 52-59% of that in controls, largely because of lower umbilical loss of glucose back to the placenta (38-39% of control) and lower fetal glucose utilization (61-74% of control). However, fetal glucose utilization on a weight-specific basis was similar in control and caruncle sheep. Significant endogenous glucose production occurred in control and caruncle fetal sheep. Maternal glucose production and partition of glucose between the gravid uterus and other maternal tissues were similar in control and caruncle sheep. In conclusion, when placental and fetal growth are restricted, fetal glucose utilization is maintained by reduced loss of glucose back to the placenta and mother and by maintaining endogenous glucose production.
Effects of converting-enzyme inhibitor on hemodynamic actions of ANP in renal hypertensive rats
Authors: Salom M. G. , Fenoy F. J. , Ingles A. C. , Martinez L. , Quesada T.
Published: December 2017

In the present study, we have evaluated whether the hemodynamic effects of atrial natriuretic peptide (ANP) infusion in two-kidney, one-clip (2K, 1C) hypertensive rats are mediated by inhibition of the renin-angiotensin system (RAS). Hemodynamic determinations were performed by thermodilution in conscious, chronically instrumented animals. ANP (1.5 micrograms.kg-1.min-1) and converting-enzyme (CE) inhibitor captopril (1 mg/kg plus 1 mg.kg-1.h-1), produced a similar fall of blood pressure through different hemodynamic mechanisms. ANP induced hypotension by decreasing cardiac index (CI; from 337.3 +/- 24.9 to 255.1 +/- 21.3 ml.min-1.kg-1, P less than 0.001), whereas a fall in total peripheral resistance (TPR) was observed during CE inhibition (from 0.568 +/- 0.02 to 0.488 +/- 0.02 mmHg.min.ml-1.kg, P less than 0.05). In addition, the ANP-induced decrease in CI was not significantly modified by previous CE inhibition. Furthermore, the decrease in TPR induced by CE inhibition did not change when CE inhibitor was administered during ANP treatment. The results of the present study indicate that the acute hemodynamic responses to ANP in 2K, 1C hypertensive rats are not mediated through antagonism of the vasoconstrictor actions of the RAS.
Natriuretic response to hypervolemia is absent in rats with papillary necrosis
Authors: Keeler R. , Wilson N.
Published: December 2017

The renal responses to acute expansion of the blood volume (20%), acute saline loading (5% body wt), or administration of atrial natriuretic peptide (ANP) were investigated in rats 7-10 days after inducing experimental renal papillary necrosis by the injection of bromoethylamine hydrobromide. In normal rats, urinary Na output (UNaV) increased from 1 +/- 0.4 to 16.6 +/- 1.7 mumol/min. In rats with papillary necrosis, UNaV only increased from 1.1 +/- 0.2 to 2.5 +/- 0.5 mumol/min. In contrast, the natriuretic responses to saline loading in normal rats (from 1.7 +/- 0.2 to 21.6 +/- 2.4 mumol/min) and to the infusion of ANP (from 0.8 +/- 0.1 to 7.6 +/- 0.8 mumol/min) were not significantly attenuated in rats with papillary necrosis. The absence of a natriuretic response to hypervolemia in rats with papillary necrosis was not a result of failure to secrete ANP, because plasma levels of immunoreactive ANP increased three- to four-fold in rats with papillary necrosis and in untreated rats. It is concluded that the mechanisms mediating the natriuretic and diuretic responses to acute expansion of the blood volume mainly involve alterations in inner medullary function. In contrast, natriuretic responses to saline loading and pharmacological doses of ANP are apparently mediated by more superficial cortical nephrons.
Adaptability of marine teleost renal inorganic sulfate excretion: evidence for glucocorticoid involvement
Authors: Renfro J. L.
Published: December 2017

The marine winter flounder, Pseudopleuronectes americanus, ingests seawater (SW) and excretes most of the resultant divalent ion load by renal tubule secretion. The site of secretion is generally thought to be the proximal tubule. Although sulfate clearance ratios (C ratio-sulfate clearance/polyethylene glycol clearance) have been reported as high as 12 in SW-acclimated animals, the present study shows that net secretion ceases after acclimation to 10% SW (SO4 free). Intravenous infusion of sulfate into the latter induced net secretion within 5 h (C ratio increased from 0.83 +/- 0.23 to 2.12 +/- 0.33). Increased sulfate secretion coincided with an increase in the magnitude of HCO3-SO4 exchange in brush-border membrane vesicles (BBMV) isolated from flounder renal tubules. Treatment of 10% SW-acclimated flounder with 60 micrograms dexamethasone/100 g body wt also caused an increase in the HCO3-SO4 exchange in BBMV to a level comparable to that of BBMV from SW fish. The glucocorticoid effect was further tested in flounder renal tubule primary monolayer cultures. Measurement of unidirectional sulfate fluxes (J) showed that in the presence of cortisol net secretion (serosal-to-mucosal flux) dominated (Js----m = 111 +/- 6.5, Jm----s = 9 +/- 4.3, Jnet = 102 +/- 2.2 nmol.h-1.cm-2). Removal of cortisol from the culture medium significantly reduced net sulfate secretion to one-third of control (Js----m = 39 +/- 13.9, Jm----s = 6 +/- 1.0, Jnet = 33 +/- 14.1 nmol.h-1.cm-2).
Brown fat GDP binding and circulating metabolites during hibernation and arousal
Authors: Nizielski S. E. , Billington C. J. , Levine A. S.
Published: December 2017

The effect of hibernation and arousal on brown adipose tissue (BAT) cytochrome-c oxidase activity and GDP binding, as well-circulating metabolites, have been studied in the 13-lined ground squirrel. Control animals (warm adapted) were housed continuously at 23 degrees C, while the remaining animals were transferred into a cold room (4 degrees C) for 8 days to induce hibernation. Hibernating animals were killed while deeply hibernating. Aroused animals were manually stimulated to induce arousal or had spontaneously aroused on the day of the experiment. BAT weight as well as mitochondrial mass were increased in both groups of cold-adapted animals, relative to controls. A substantial increase in GDP binding, however, was seen only in aroused animals, an observation confirmed by Scatchard analysis. Arousal was also accompanied by marked alterations in the levels of several circulating metabolites. Plasma free fatty acids declined by approximately 20% despite a three- to fourfold increase in plasma glycerol concentrations. Plasma lactate levels increased eightfold, while concentrations of beta-hydroxybutyrate were five times lower during arousal than hibernation. These data are consistent with the idea that the oxidation of free fatty acids, glucose, and ketone bodies are all increased during arousal. In conclusion, we have found that cold adaptation and subsequent hibernation increases BAT thermogenic capacity in the 13-lined ground squirrel. However, this increase in thermogenic potential is not manifested as a substantial increase in BAT thermogenic activity until arousal is initiated.
Central effects of somatostatin: pressor response, AVP release, and sympathoinhibition
Authors: Rettig R. , Geist R. , Sauer U. , Rohmeiss P. , Unger T.
Published: December 2017

The effects of intracerebroventricular (icv) administration of somatostatin(1-14) (SS1-14) on mean arterial blood pressure (MAP), heart rate (HR), plasma arginine vasopressin (AVP) concentration, and splanchnic nerve activity (SpNA) were studied in conscious rats. In addition, the effects of peripheral alpha-adrenergic receptor blockade with prazosin, vasopressinergic V1-receptor blockade with [d(CH2)5Tyr(Me)]AVP, and chronic bilateral sinoaortic denervation (SAD) on central SS1-14-induced MAP, HR, and SpNA responses were investigated. SS1-14 icv elicited dose-dependent increases in MAP and plasma AVP concentration as well as decreases in HR and SpNA. Prazosin iv did not significantly affect SS1-14-induced pressor and bradycardic responses but augmented the decrease in SpNA. The V1-AVP receptor antagonist iv significantly attenuated the effects of SS1-14 icv on MAP, HR, and SpNA. Following SAD the pressor responses to SS1-14 icv were significantly enhanced and were associated with significantly smaller decreases in HR and SpNA. We conclude that central administration of SS1-14 causes a pressor response via release of AVP while at the same time inhibiting peripheral sympathetic outflow. Our results support the hypothesis that SS1-14 in the brain by its effects on AVP release and sympathetic outflow may participate in central cardiovascular regulation.
Volume expansion attenuates baroreflex sensitivity in the conscious nonhuman primate
Authors: Cornish K. G. , Barazanji M. W. , Yong T. , Gilmore J. P.
Published: December 2017

We examined the effect of intravascular volume expansion (VE) on the arterial baroreflex control of pulse rate (PR) in conscious, chronically instrumented monkeys tethered in their cages. A total of five monkeys was studied after surgical implantation of catheters in the descending aorta, the left atrium, and the internal jugular vein. Mean arterial blood pressure (MABP)-PR stimulus response curves were constructed by decreasing and increasing blood pressure with nitroprusside and phenylephrine, respectively. The data were analyzed with a regression analysis that generated a sigmoid curve and the maximum sensitivity (slope) of the curve. The data were obtained before and after VE with an isotonic isoncotic dextran solution equal to 20% of the estimated blood volume. After VE, the MABP-PR curve shifted to the right at the high blood pressures, and there was a significant decrease in the maximum sensitivity from 5.65 +/- 1.44 for control to 2.14 +/- 0.63 after VE (P less than 0.05). We concluded that VE attenuates the baroreflex control of heart rate in the conscious nonhuman primate.
Suprachiasmatic nucleus: phase-dependent activation during the hibernation cycle
Authors: Kilduff T. S. , Radeke C. M. , Randall T. L. , Sharp F. R. , Heller H. C.
Published: December 2017

The suprachiasmatic nucleus (SCN) of the golden-mantled ground squirrel undergoes a phase-dependent change in its accumulation of 2-[14C]deoxy-D-glucose (2-DG) relative to other brain structures during the hibernation cycle. The greatest relative 2-DG uptake (R2DGU) is observed in the SCN during entrance into and during deep hibernation. A circadian fluctuation in R2DGU of the SCN is not evident in the euthermic ground squirrel but can be increased during the subjective day by photic stimulation. An increase in R2DGU by the paraventricular nucleus (PVN) correlates with the increase in R2DGU by the SCN during entrance to hibernation but not with the increase in SCN R2DGU evoked by photic stimulation during euthermia. The periventricular nuclei of the hypothalamus (PEV) also have high levels of R2DGU during the latter phase of the entrance. These observations support the hypothesis that the SCN, PEV, and PVN may play important roles in hibernation and suggest progressive activation of synaptic input to and within the SCN during entrance into this state.
Effect of beta-adrenergic blockade on lung liquid secretion during fetal asphyxia
Authors: Hooper S. B. , Harding R.
Published: December 2017

The hypothesis tested in this study was that beta-adrenergic stimulation is responsible for the inhibition of fetal lung liquid production during moderate fetal asphyxia. In chronically catheterized fetal sheep, net lung liquid production rates were measured over three consecutive periods: a control period, a period of reduced uterine blood flow (RUBF) or epinephrine infusion, and periods of RUBF or epinephrine infusion in the presence of the beta-adrenergic receptor antagonist propranolol. The net production rate of fetal lung liquid was decreased from a mean control value of 7.7 +/- 1.0 to 1.5 +/- 0.4 ml/h (P less than 0.001) by RUBF; the administration of propranolol had no further effect on these liquid production rates (1.1 +/- 0.5 ml/h). In other experiments epinephrine infusion reduced the net production rate of fetal lung liquid from a mean control value of 7.2 +/- 1.4 to 1.7 +/- 1.8 ml/h (P less than 0.025); the addition of propranolol reversed this inhibition (secretion rate 6.1 +/- 1.4 ml/h, P less than 0.005). We conclude that the inhibition of fetal lung liquid production induced by moderate fetal asphyxia does not solely result from catecholamine stimulation of pulmonary beta-receptors.
Energy expenditure and diet-induced thermogenesis in presence and absence of hyperphagia induced by insulin
Authors: Dulloo A. G. , Girardier L.
Published: December 2017

The influence of experimental hyperinsulinemia on energy intake, energy expenditure, and body composition was investigated in rats treated chronically with high doses of insulin. Energy balance studies, each of 2-wk duration, were conducted with two different long-acting insulins (Protamine and Monotard), administered in the morning (IM), the late afternoon (IA), or both (IMA) and in animals of three different ages, namely in 4-, 8-, and 12-wk-old rats. The results indicate that the level of hyperphagia induced by insulin was markedly influenced by the type of long-acting insulin (P less than 0.001; Protamine greater than Monotard), by age (P less than 0.001; 12 greater than 8 greater than 4 wk), as well as by the timing of insulin administration (P less than 0.002, IMA greater than IM or IA). Body protein deposition was unaltered, but body fat and energy expenditure increased in parallel to the level of hyperphagia. Regression analysis shows a strong linear correlation (r = 0.963) between the change in energy expenditure and the change in energy intake in response to insulin and indicates that approximately 50% of the excess calories consumed was dissipated as heat. In the absence of hyperphagia, however, insulin administration had no effect on energy expenditure nor on energy partitioning. Similarly, the influence of altered meal pattern, induced by administering insulin at different times of the day, was also found to have no impact on energy expenditure. The current investigations therefore refute the notion that high doses of insulin via hyperinsulinemia and/or altered meal pattern have an inhibitory influence on whole body thermogenesis. In contrast, our data demonstrate that the adaptive phenomenon that tends to minimize the accumulation of excess caloric intake, i.e., diet-induced thermogenesis, persists in the hyperinsulinemic state.
Active chloride transport in isolated posterior midgut of tobacco hornworm (Manduca sexta)
Authors: Chao A. C. , Koch A. R. , Moffett D. F.
Published: December 2017

The short-circuited posterior midgut of larval tobacco hornworm (Manduca sexta) actively transports Cl- from lumen to hemolymph as measured by unidirectional fluxes of 36Cl-. Potentials and Cl- activities in cytosol and goblet cavity were measured using double-barreled Cl--selective microelectrodes. In the short-circuited tissue, the goblet cavity was electrically positive to the bathing solution, and Cl- activity was below electrochemical equilibrium with luminal fluid. The cytosol was electrically negative to the bathing solution, and Cl- activity was above electrochemical equilibrium. Thus Cl- is pumped from goblet cavity into cell. Although the Cl- that is pumped into the cell can cross the basal membrane, its Cl- conductance is quite low. The Cl- conductance is also quite low in apical membranes of columnar cells. Depression of intracellular Cl- after exposure of the luminal side to high HCO-3 suggested that these membranes have a Cl- for HCO-3 exchange mechanism. The paracellular pathway for Cl- comprises approximately 10% of the total transepithelial conductance.
Energy metabolism, ion homeostasis, and evoked potentials in anoxic turtle brain
Authors: Chih C. P. , Feng Z. C. , Rosenthal M. , Lutz P. L. , Sick T. J.
Published: December 2017

Unlike the mammalian brain, the turtle brain maintains ion homeostasis and avoids anoxic depolarization during prolonged anoxia. The mechanisms by which turtle brains avoid and recover from anoxic depolarization were investigated by relating changes in cellular ATP levels to extracellular K+ (K+o) and evoked potential activities after 6 h of anoxia and during anoxic depolarization induced by superfusion of the brain surface with iodoacetate during anoxia. ATP levels were maintained during 6 h of anoxia despite marked decreases in energy production, but ATP was lowered during inhibition of both oxidative phosphorylation and glycolysis. K+o activity was unchanged during 6 h of anoxia but increased when ATP levels decreased. Ion homeostasis in the turtle brain appears to be linked to ATP levels but is unaffected by rate of energy production. In contrast, amplitudes of evoked potentials decreased when ATP levels were maintained, but rate of energy production declined. ATP and K+o levels recovered after anoxic depolarization, but evoked potential activity was not restored. These data suggest that the basic strategy for turtle brain to survive anoxia is to avoid anoxic depolarization by maintaining ATP levels.
Effect of cholecystokinin octapeptide analogues on food intake in the dog
Authors: Inui A. , Okita M. , Inoue T. , Sakatani N. , Oya M. , Morioka H. , Oimomi M. , Baba S.
Published: December 2017

Cholecystokinin octapeptide, administered into the third cerebral ventricle (icv), suppresses feeding in sheep, pigs, chicken, rats, and dogs. Because of the species differences in the feeding response to cholecystokinin (CCK), we studied the pharmacological characterization of this peptide on feeding in 16-h-fasted dogs. We examined the effects of CCK-(26-33)-NH2 (CCK-8) and a variety of its analogues, nonsulfated CCK-(26-33)-NH2 (desulfated CCK-8), CCK-(26-33)-OH (deamidated CCK-8), (Nle28,31)-CCK-(26-33)-NH2 [(Nle28,31)-CCK-8], succinyl-CCK-(27-33)-NH2 (Suc-CCK-7) succinyl-Thr28, Leu29, MePhe33-CCK-(27-33)-NH2 [Suc-Thr28, Leu29, MePhe33)-CCK-7], CCK-(29-33)-NH2 (CCK-5), and CCK-(30-33)-NH2 (CCK-4) on food intake after iv injection. Systemic dose-response studies appeared to reveal the following rank order of potencies: Suc-CCK-7 = Suc-(Thr28, Leu29, MePhe33)-CCK-7 greater than CCK-8 = (Nle28,31)-CCK-8 greater than desulfated CCK-8 greater than deaminated CCK-8 greater than CCK-5 = CCK-4 = 0. Smaller COOH-terminal fragments acted as antagonists to the satiety effects of CCK-8. These data demonstrate in the dog that the structural requirements for the behavioral activity of CCK-8 are the COOH-terminal amide group, the sulfate ester of the tyrosine moiety, and the conformational constraints observed in CCK-7.
A1 cell group mediates solitary nucleus excitation of supraoptic vasopressin cells
Authors: Day T. A. , Sibbald J. R.
Published: December 2017

Stimulation of the nucleus tractus solitarius (NTS) excites putative vasopressin-secreting cells of the supraoptic nucleus (SON) via a catecholaminergic projection to hypothalamus. Despite recent evidence of a direct catecholaminergic projection from NTS to SON, we have performed single-unit recording experiments in pentobarbital sodium-anesthetized rats to investigate the possibility that NTS stimulation effects on SON vasopressin cells are indirect, being relayed via the A1 noradrenergic cell group of the caudal ventrolateral medulla. The effects of single-pulse NTS and A1 region stimulation on the activity of antidromically identified SON neurosecretory cells that had been functionally characterized as vasopressin secreting were compared. NTS stimulation excited 81% of all putative vasopressin-secreting cells tested (n = 83), with a mean onset latency of 51 +/- 1 ms. A1 region stimulation excited 76% of all cells tested and 90% of units responsive to NTS stimulation, with a mean latency of 39 +/- 1 ms. Consistent with previous work NTS stimulation excited only a minority of oxytocin cells tested (3/13), and of these two-thirds also responded to A1 stimulation. Bilateral electrolytic lesions of the A1 region abolished the effects of NTS stimulation on putative vasopressin cells. Ipsilateral A1 region injections of the inhibitory neurotransmitter gamma-amino-butyric acid reversibly blocked NTS stimulation effects on putative vasopressin cells in animals where the contralateral A1 region had already been lesioned. These results support the proposal that excitation of SON vasopressin-secreting cells after NTS stimulation is due to activation of a relay projection through the A1 noradrenergic cell group of the caudal ventrolateral medulla.
Chemoreceptor stimulation on sympathetic activity: dependence on respiratory phase
Authors: Katona P. G. , Dembowsky K. , Czachurski J. , Seller H.
Published: December 2017

Experiments were performed on chloralose-anesthetized, vagotomized, paralyzed, and artificially ventilated cats breathing 100% O2. Peripheral chemoreceptors were stimulated by rapid injections of CO2-saturated NaHCO3 in different phases of the respiratory cycle. Responses of cardiac and renal sympathetic nerves were computed by digital integration. Spontaneous sympathetic activity was consistently modulated by respiration, the modulation being greater for cardiac than for renal nerves. Cardiac nerve responses to peripheral chemoreceptor stimulation depended on the respiratory phase for at least one experimental condition in four of seven animals: the responses were largest during late inspiration and smallest (or absent) during postinspiration and early expiration. Renal nerve responses depended on respiratory phase in only two of eight animals. An average end-tidal CO2 concentration increase from 4.6 +/- 0.8% (SD) to 6.7 +/- 0.9% enhanced the respiratory modulation of spontaneous activity but reduced the responses to peripheral chemoreceptor stimulation. The results indicate that the respiratory modulation of chemoreceptor-induced sympathetic responses was less prominent than the modulation of spontaneous activity. It is hypothesized that the phase dependence of the responses is caused by the spontaneously occurring expiratory diminution of sympathetic activity rather than by an inherent gating of the chemoreceptor reflex.
Heterogeneous renal responses to atrial natriuretic factor. II. Cirrhotic dogs
Authors: Maher E. , Cernacek P. , Levy M.
Published: December 2017

The renal response to atrial natriuretic factor (ANF) (175 ng.kg-1.min-1) was tested in nine dogs during a control period and again after the appearance of experimental cirrhosis, ascites, and avid sodium retention. During the cirrhotic phase, plasma volume had increased by 28.4% (P less than 0.05), renal perfusion and glomerular filtration rate (GFR) were unchanged from control values, and plasma immunoreactive ANF (iANF) had declined from 71.6 +/- 9.5 to 34.7 +/- 5.4 pg/ml (P less than 0.05). During the control phase, change of urinary sodium excretion rate (delta UNaV) increased by 132 +/- 22 mu eq/min but was attenuated in the cirrhotic phase (delta UNaV = 29 +/- 12.5 mu eq/min). Of these nine cirrhotic dogs, five responded with a delta UNaV ranging from 20 to 114 mueq/min (mean delta UNaV = 59.6 +/- 10.6 mu eq/min), whereas 4 were nonresponders (delta UNaV = 1.3 +/- 0.6 mu eq/min). In neither group could delta UNaV be correlated to changes in GFR, clearance of p-aminohippurate, or filtration fraction. In an additional 10 dogs studied only during cirrhosis, 5 were natriuretic responders and 5 were nonresponders. Atrial content of ANF, half time of infused ANF, and plasma levels of iANF did not differentiate the two groups. We conclude that, like chronic caval dogs with ascites, salt-retaining cirrhotic dogs show heterogeneity of natriuretic response to infused ANF, which is unexplained by differences in renal perfusion.