bluuebunny/crossref_metadata_2025 huggingface dataset:
Proton-stimulated Cl-HCO3 antiport by basolateral membrane vesicles of lobster hepatopancreas
Authors: Ahearn G. A. , Grover M. L. , Tsuji R. T. , Clay L. P.
Published: December 2017

Purified epithelial basolateral membrane vesicles were prepared from lobster hepatopancreas by sorbitol gradient centrifugation. Na+-K+-adenosinetriphosphatase, alkaline phosphatase, and cytochrome-c oxidase enzyme activities in the final membrane preparation were enriched 9.6-, 1.4-, and 0.4-fold, respectively, compared with their activities in the original tissue homogenate. Vesicle osmotic reactivity was demonstrated using 60-min equilibrium 36Cl uptake experiments at a variety of transmembrane osmotic gradients. 36Cl uptake into vesicles preloaded with HCO3 was significantly greater than into vesicles lacking HCO3. This exchange process was stimulated by a transmembrane proton gradient (internal pH greater than external pH). Proton-gradient-dependent Cl-HCO3 exchange was potential sensitive and stimulated by an electrically negative vesicle interior. 36Cl influx (4-s exposures) into HCO3-loaded vesicles occurred by the combination of 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid sensitive, carrier-mediated transfer and "apparent diffusion." 36Cl influx was a hyperbolic function of both internal [HCO3] and internal [Cl]. The two internal anions displayed a 100-fold difference in apparent affinity constants with HCO3 being strongly preferred. 36Cl influx was stimulated more by preloaded monovalent than by divalent anions. Na was an inhibitor of proton-dependent anion antiport, whereas K had no effect. A model for HCl-HCO3 antiport is suggested that employs combined transmembrane concentration gradients of Cl and HCO3 to power anion exchange and transfer protons against a concentration gradient.
Renal nerves and renal responses to head-up tilt in dogs
Authors: Peterson T. V. , Hurst N. L. , Richardson J. A.
Published: December 2017

Experiments were performed in anesthetized dogs to compare the effects of acute and chronic unilateral renal denervation on the renal responses to head-up tilt and to assess denervation hypersensitivity to infused norepinephrine (NE). Responses of the denervated kidney were compared with those of the contralateral innervated kidney in each animal. With acute denervation, 40 min of 45 degrees head-up tilt decreased urine flow (V) 37%, absolute sodium excretion (UNaV) 53%, and fractional sodium excretion (FENa+) 44% in the innervated kidneys, but no decreases occurred in the denervated kidneys. NE infusion (125 ng X kg-1 X min-1) increased arterial pressure by 11 mmHg and increased V, UNaV, and FENa+ in both kidneys. In the chronically denervated animals (2-4 wk prior to experiment) tilt decreased V by 32%, UNaV by 44%, and FENa+ by 21% in the innervated kidneys, but again no changes occurred in the denervated kidneys. NE infusion in this group also increased arterial pressure approximately 11 mmHg and caused V, UNaV, and FENa+ to increase in the innervated kidneys but decrease in the denervated kidneys. These results demonstrate that the renal responses to tilt are abolished by both acute and chronic renal denervation even though the chronically denervated kidney is hypersensitive to NE-stimulated fluid reabsorption. Therefore endogenous plasma NE levels must not increase enough during tilt such that this hypersensitivity phenomenon can compensate for chronic ablation of the renal nerves.
Satiety effects of intragastric meals containing triglycerides with different chain lengths
Authors: Maggio C. A. , Koopmans H. S.
Published: December 2017

Intragastric meals containing triglycerides with chain length of 2-18 significantly reduced intake in deprived Sprague-Dawley rats feeding 20 min after infusion. Satiety after long-chain triglyceride (LCT) infusions must have been mediated via a gastroenteric signal, since feeding was reduced prior to delivery of these fats into the bloodstream. Equicaloric infusions of triglycerides with chain length of 6 to 18 had similar inhibitory effects, indicating that the satiety effects of these triglycerides depended more on the number of calories infused than on chain length. Shorter-chain triglycerides were initially more effective in reducing feeding. Except for a poorly absorbed LCT the infusions did not result in conditioned taste aversion and thus did not appear to induce discomfort. Gastric recovery of a nonabsorbable marker at the time of the feeding test indicated that gastric emptying, like satiety, was related to the caloric properties of the infusions. These effects could be mediated through neural and/or hormonal mechanisms that are stimulated through energy-related properties of triglycerides.
Acute suppression of plasma vasopressin and thirst after drinking in hypernatremic humans
Authors: Thompson C. J. , Burd J. M. , Baylis P. H.
Published: December 2017

Drinking rapidly abolishes thirst and vasopressin secretion in dehydrated humans before major changes in plasma osmolality are observed. We studied the effects of drinking on plasma vasopressin and thirst in seven healthy volunteers rendered hypernatremic by the infusion of hypertonic (855 mmol/l) sodium chloride solution. Thirst was measured on a visual analogue scale (0-10 cm). Infusion of hypertonic saline caused linear increases in plasma osmolality (289 +/- 1 to 306 +/- 1 mosmol/kg, mean +/- SE, P less than 0.001), plasma vasopressin (0.6 +/- 0.2 to 6.4 +/- 1.9 pmol/l, P less than 0.001), and thirst (1.4 +/- 0.4 to 7.4 +/- 0.5 cm, P less than 0.001). Water was allowed 15 min after cessation of the infusion, and within 5 min of drinking both plasma vasopressin and thirst were significantly lower than postinfusion. After 20 min of drinking, plasma vasopressin had fallen from 6.5 +/- 0.9 to 1.3 +/- 0.3 pmol/l (P less than 0.001) and thirst from 7.7 +/- 0.5 to 1.0 +/- 0.2 cm (P less than 0.001) despite no significant change in plasma osmolality (306 +/- 0.9 to 304 +/- 0.8 mosmol/kg, P = 0.17), and the drinking of 1,200 +/- 60 ml of water, over 85% of the mean cumulative water intake in the 30-min drinking period. Control studies in the same subjects showed comparable rises in plasma vasopressin, plasma osmolality, and thirst during hypertonic saline infusion but no fall in any of these parameters during an equivalent 30-min period after the infusions, during which water was withheld.(ABSTRACT TRUNCATED AT 250 WORDS)
Development of postglucoprivic insulin-induced suckling and feeding in rats
Authors: Williams C. L. , Blass E. M.
Published: December 2017

Increased food or milk intake in response to insulin-induced hypoglycemia cannot be demonstrated in the rat until pups reach weaning age. However, when food and suckling are withheld from insulin-treated 5- to 25-day-old rats until their altered blood glucose levels return to normal, their rate of milk intake via suckling from their anesthetized dam is increased over saline-treated control pups. This postglucoprivic action of insulin could not be demonstrated in rats consuming wet mash until pups reached 25-30 days of age. Nonnutritive oral stimulation from dry suckling during the glucoprivic episode is sufficient to disrupt postglucoprivic suckling in 20-day-old rats. In contrast consuming a small quantity of wet mash became an effective inhibitor of postglucoprivic suckling only when pups reached 25 days of age. These data demonstrate the existence of an insulin-sensitive neural system for suckling and feeding in infant rats and point to the involvement of multiple and changing oral factors during development in insulin-induced postglucoprivic feeding.
Role of brain serotonergic pathways and hypothalamus in regulation of renin secretion
Authors: Gotoh E. , Murakami K. , Bahnson T. D. , Ganong W. F.
Published: December 2017

To investigate the role of brain serotonergic neurons in the regulation of renin secretion, we measured changes in plasma renin activity (PRA), and, in some instances, plasma renin concentration (PRC), plasma angiotensinogen, and plasma adrenocorticotropic hormone (ACTH) in rats with lesions of the dorsal raphe nucleus and lesions of the paraventricular nuclei, dorsomedial nuclei, and ventromedial nuclei of the hypothalamus. We also investigated the effects of p-chloroamphetamine (PCA), immobilization, head-up tilt, and a low-sodium diet in the rats with dorsal raphe, paraventricular, and dorsomedial lesions. Lesions of the dorsal raphe nucleus abolished the increase in PRA produced by PCA but had no effect on the increase produced by immobilization, head-up tilt, and a low-sodium diet. Paraventricular lesions, which abolish the increase in plasma ACTH produced by PCA, immobilization, and head-up tilt, decreased plasma angiotensinogen. The paraventricular lesions abolished the PRA and the PRC responses to PCA and the PRA but not PRC response to immobilization, head-up tilt, and a low-sodium diet. The ventromedial lesions abolished the PRA and PRC responses to PCA and did not reduce plasma angiotensinogen. The data suggest that paraventricular lesions depress angiotensinogen production by the liver and that the paraventricular and ventromedial nuclei are part of the pathway by which serotonergic discharges increase renin secretion. They also suggest that the serotonergic pathway does mediate the increases in renin secretion produced by immobilization, head-up tilt, and a low-sodium diet.
Inhibition of VP and OT release by water in hypovolemia is independent of opioid peptides
Authors: Rosella-Dampman L. M. , Hartman R. D. , Summy-Long J. Y.
Published: December 2017

Overhydration inhibits release of vasopressin (VP) and oxytocin (OT) from the hypothalamo-neurohypophysial system during hypovolemia. We investigated whether opioid peptides mediate the inhibitory effect of water on secretion of these hormones. Conscious male rats were made hypovolemic by hemorrhage (HEM, 0.51 ml/min) of 20 and 35% of the blood volume or by injection of either subcutaneous polyethylene glycol (PEG, 20,000 mol wt, 35 ml/kg) or intraperitoneal histamine (HIS, 15 mg/kg, 1 ml/kg). Animals were intubated orally 1-4 min (HEM, HIS) or 6.75 h (PEG) later with or without administration of water (40 ml/kg). Four to seven min after intubation rats were injected with saline (1 ml/kg) or naloxone (2 or 5 mg/kg) and then decapitated 6-10 min later. Control animals were treated similarly but were not stimulated by hypovolemia. VP and OT were extracted from plasma and quantified by radioimmunoassay. Data were analyzed by analysis of variance. In HEM animals blood pressure fell and plasma osmolality increased, both of which correlated positively with the rise in plasma [VP] and [OT]. Overhydration lowered the plasma osmolality, attenuated the fall in blood pressure, and reduced [VP] and [OT] in plasma of HEM animals. The opiate receptor antagonist, naloxone, did not alter these changes in blood pressure or plasma osmolality, or the plasma [VP] after HEM in rats treated with or without water. Plasma [OT] was, however, increased by naloxone in both normally hydrated and overhydrated rats. Thus, regardless of the hydrational state of the animal, opioid peptides inhibited release of OT but not VP during hemorrhage. Data consistent with this interpretation were also obtained from rats made hypovolemic with PEG or HIS.(ABSTRACT TRUNCATED AT 250 WORDS)
Leukocytic pyrogen effects on prostaglandins in hypothalamic tissue slices
Authors: Scott I. M. , Fertel R. H. , Boulant J. A.
Published: December 2017

Some studies suggest that leukocytic pyrogen (LP) increase hypothalamic prostaglandins which, in turn, affect hypothalamic thermoregulatory neurons to produce fever. The present study used radioimmunoassays to quantitate the ability of guinea pig hypothalamic tissue slices to produce prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), and thromboxane B2 (TxB2). Dose- and time-dependent prostaglandin increases occurred when these slices were perfused with LP media. Steady-state levels of tissue release were reached at 0-3 min for 6-keto-PGF1 alpha, at 6-9 min for PGE2 and PGF2 alpha, and at 12-15 min for TxB2. With the exception of 6-keto-PGF1 alpha, all substances showed continuous dose-response relationships for concentrations ranging from 0.001 to 0.25 LP dilutions. Tissue PGE2, for example, was 0.7 pg X min-1 X mg-1 with the 0.001 LP dilution and 8.7 pg X min-1 X mg-1 with the 0.25 LP dilution. Indomethacin blocked much of the LP-induced prostaglandin increase. Although there is a relationship between hypothalamic LP and prostaglandins in response to physiological LP levels, tissue prostaglandins are several orders of magnitude lower than concentrations necessary to produce fever by hypothalamic microinjection. This suggests that prostanoids, such as PGE2, may not be the sole mediators of fever induced by leukocytic pyrogen.
Effects of renal receptor activation on neurosecretory vasopressin cells
Authors: Day T. A. , Ciriello J.
Published: December 2017

Electrical stimulation of afferent renal nerves (ARN) has been shown to excite neurosecretory vasopressin (AVP) cells of the supraoptic nucleus (SON). To investigate the sensory modality of the ARN involved, the present study examined in pentobarbital-anesthetized rats the responses of putative AVP cells to procedures intended to differentially activate renal receptor populations. Neurosecretory SON cells were identified by antidromic invasion from the neurohypophysis and classified as AVP secreting on the basis of spontaneous activity patterns and responses to arterial baroreceptor activation. Neither elevation of systemic arterial pressure (50-100 mmHg, 9 cells) following sinoaortic and cardiopulmonary afferent nerve transection nor renal venous occlusion (15 cells) altered AVP cell discharge. Renal ischemia, produced by renal arterial occlusion (50-120 s, 14 cells), and renal arterial infusion of adenosine (1-50 micrograms, 8 cells) were also without effect. However, infusions into the renal artery of bradykinin (1-3 micrograms) excited 9/15, of capsaicin (1-3 micrograms) excited 13/15, and of sodium cyanide (5-40 micrograms) excited 1/11 AVP cells examined. These data demonstrate that, in the anesthetized rat, putative neurosecretory AVP cells in the SON are responsive to activation of bradykinin- and capsaicin-sensitive renal receptors and suggest that activation of these receptors contributes to the hormonal regulation of the circulation.
Behavioral and metabolic effects of sucrose-supplemented feeding in hyperactive rats
Authors: Hendley E. D. , Conti L. H. , Wessel D. J. , Horton E. S. , Musty R. E.
Published: December 2017

Two hyperactive rat strains [spontaneously hypertensive rats (SHR) and SHR-Wistar-Kyoto cross (WK-HA)] and their nonhyperactive genetic control strain (Wistar-Kyoto) were fed ad libitum sucrose-supplemented rat chow, or chow alone in controls, to determine the effects of dietary sugar on behavior. The diets were given either overnight (acute sugar) or for 14-18 days (chronic sugar), and testing was carried out on the morning after each of the dietary schedules. The metabolic studies revealed significant strain, sex, and age differences in appetite for sucrose, caloric intake, postprandial plasma levels of glucose and insulin, and weight gain after sucrose feeding. The findings indicate that sugar feeding led to increased plasma glucose and insulin levels; however, total caloric intake was decreased, and less weight gain was observed than in chow-fed controls, particularly among the hyperactive strains. In behavioral tests, sugar feeding did not alter spontaneous activity levels in any of the strains after either acute or chronic diets. There were also no significant effects of sucrose consumption on spatial learning and memory in a plus-shaped maze as determined by use of a shock-avoidance paradigm. The only significant behavioral effects of sucrose observed were an impairment in habituation and distractibility among the WK-HA females, the most hyperactive group among these strains.
Adrenergic mediation of vasopressin secretion in newborn pigs
Authors: Leffler C. W. , Busija D. W. , Share L. , Crofton J. T. , Brooks D. P. , Beasley D. G. , Green R. S. , Mirro R.
Published: December 2017

Effects of inhibition of alpha 1-(prazosin) and alpha 2-(yohimbine) adrenoreceptors on plasma lysine vasopressin concentration during normotension and hemorrhagic hypotension were studied in unanesthetized newborn pigs. During the normotensive period, treatment with prazosin and yohimbine both increased plasma lysine vasopressin concentration (vehicle = 3.4 +/- 1.21 microU/ml; prazosin = 35.8 +/- 10.8 microU/ml; and yohimbine = 20.1 +/- 9.5 microU/ml). Prazosin caused a decline in arterial pressure (vehicle = 60 +/- 6 mmHg; prazosin = 49 +/- 5 mmHg), which may account for the increase in plasma lysine vasopressin concentration, whereas yohimbine increased arterial pressure (73 +/- 3 mmHg). On hemorrhage to equivalent arterial pressure, plasma lysine vasopressin concentration increased to similar levels in vehicle- (110.3 +/- 28.7 microU/ml) and prazosin-treated (92.6 +/- 14.2 microU/ml) piglets. In contrast, on hemorrhage of yohimbine-treated piglets, the increase in plasma lysine vasopressin concentration was augmented remarkably (527.0 +/- 103.2 microU/ml) in comparison to the other groups. We conclude that, in unanesthetized newborn pigs, treatment with the alpha 2-adrenoreceptor antagonist yohimbine increased plasma lysine vasopressin concentration and markedly accentuated the vasopressin response to hemorrhage. An alpha 2-adrenergic receptor-mediated mechanism appears to be an important inhibitory component in the vasopressin secretory system of the newborn pig.
Analysis of BP response and Ca2+ metabolism using the saturation kinetics model
Authors: Karanja N. , Metz J. A. , Mercer L. P. , McCarron D. A.
Published: December 2017

The provision of supplemental dietary calcium (dCa) lowers blood pressure (BP) in the spontaneously hypertensive rat (SHR). Whether calcium's antihypertensive effects can be expressed in the presence of potentially hypertensinogenic nutrients is not known. Furthermore, the amount of dCa required to attenuate hypertension in the SHR remains undetermined. Along with establishing the effects of dCa on BP under conditions of a high Na+ intake, we sought to define the lowest dose of dCa associated with the greatest attenuation in arterial pressure in the young SHR. Thirty-five 6-wk-old SHR were fed one of five diets containing either 0.1, 0.25, 0.5, 1.0, or 2.0% dCa. All diets contained 1.0% Na+. The rates of change (delta) in body weight, BP, and serum ionized calcium were determined between 6 and 20 wk of age. Bone density (BD) was measured only at 20 wk of age. The data were analyzed using the saturation kinetics model. Results indicate that the half-maximal dose (K50) of dCa needed to lower pressure is 0.67 +/- 0.18%, which is higher than the K50 for weight (0.23 +/- 0.18) and BD (0.36 +/- 0.22). It is concluded that supplemental dCa lowers BP despite a high Na+ intake. Furthermore, a dose of approximately 1.5 dCa is sufficient to attenuate the rate of hypertension in the young growing SHR.
Effect of diltiazem on intracellular Ca2+ mobilization in hepatocytes during endotoxic shock
Authors: Maitra S. R. , Sayeed M. M.
Published: December 2017

Effects of Salmonella enteritidis endotoxin on intracellular Ca2+ mobilization were studied in hepatocytes. Rats were given intravenous injections of saline (control), endotoxin (20 mg/kg), or endotoxin (20 mg/kg) plus diltiazem (1.2 mg/kg). They were killed 5 h later, at which time endotoxin-injected rats showed signs of shock. The involvement of myoinositol 1,4,5-trisphosphate (IP3) and arachidonic acid (AA) in intracellular Ca2+ mobilization was tested using saponin-permeabilized hepatocytes. Added Ca2+ was sequestered by intracellular organelles in the presence of ATP until the medium free Ca2+ concentration was lowered to a near steady-state level. In control cells subsequent addition of 10(-6) M IP3 and AA, respectively, caused a rapid increase in free Ca2+ concentration from 130 +/- 31 to 257 +/- 54 nM (P less than 0.01) and from 111 +/- 21 to 196 +/- 37 (P less than 0.01). By use of experimental conditions designed to permit selective Ca2+ accumulation, it was determined that all of the Ca2+ released by IP3 and AA originated from the endoplasmic reticulum. The intracellular release of Ca2+ by IP3 and AA was significantly attenuated in endotoxic shock. Treatment of endotoxic rats with a calcium channel blocker, diltiazem, effected an increase in free Ca2+ concentration by IP3 from 124 +/- 18 to 240 +/- 41 nM (P less than 0.01) and by AA from 109 +/- 15 to 192 +/- 32 (P less than 0.01). These data suggest that during endotoxic shock there is an attenuation of IP3- and AA-induced intracellular Ca2+ release, which could be prevented by treatment of animals with diltiazem.
Partition of carotid baroreceptor response in two-kidney renal hypertensive dogs
Authors: Koushanpour E. , Behnia R.
Published: December 2017

This study evaluated the mechanism of carotid sinus baroreceptor resetting in two-kidney one-clip Goldblatt hypertension in dogs by partitioning the resetting between carotid sinus wall compliance and receptor neural elements. With dogs under halothane anesthesia, the left renal artery was constricted 70-80% with a Goldblatt clamp without disturbing the contralateral kidney. Ten weeks later, when mean blood pressure had risen to 151 +/- 6 mmHg (means +/- SE) compared with 105 +/- 5 mmHg in controls, we measured simultaneously whole nerve action potentials (N) and carotid sinus volume (V) during step changes in intrasinus pressure (P). Hypertensive N vs. P relationship was sigmoid shaped and shifted toward the P-axis compared with controls. Hypertensive V vs. P relationship was not significantly different from controls. The hypertensive N vs. V relationship derived from the composite plots of N vs. P and V vs. P was sigmoid shaped and shifted toward the V-axis compared with controls. These results suggest that the resetting of baroreceptors is due to changes in receptor properties rather than carotid sinus wall compliance.
Resistance to adipocyte hyperplasia in ground squirrels given high-fat diets
Authors: Faust I. M. , Mrosovsky N.
Published: December 2017

Mammalian hibernators prepare for the winter by depositing fat in existing fat cells. There is little, if any, production of new fat cells. This is curious because equivalent fat deposition in rats is associated with substantial fat cell production. To determine whether degree of weight gain, diet composition, or some special mechanism militating against adipocyte hyperplasia may underlie the absence of adipocyte hyperplasia in hibernators, male Richardson's ground squirrels, Spermophilus richardsonii, were fed a fattening high-fat diet for either 5 mo or 1 yr. The 5-mo high-fat feeding period caused peak body weights to increase 36% relative to the peak body weights seen in control animals fed ordinary chow. Despite this increase, there was no apparent increment in fat cell number in any of the major fat depots. Animals fed the diet for 1 yr reached body weights similar to those of the 5-mo group but showed significant adipocyte hyperplasia in all fat depots studied. Thus adult ground squirrels are clearly capable of enlarging their pool of mature fat cells, but they fail to do so, at least at certain times, in response to conditions of weight gain that cause considerable adipocyte hyperplasia in rats.
Protection against fat cell hyperplasia in a hibernator, Glis glis
Authors: Mrosovsky N. , Nash P. , Faust I. M.
Published: December 2017

Dormice, Glis glis, were fed a high-fat diet for 11 mo in one experiment: in another experiment they were fed a high-fat diet for 5 mo, either at room temperature (21.5 degrees C) or in a warm room (27 degrees C). Only in the latter group did adipocyte hyperplasia occur; this was significant in all the fat depots studied (inguinal, retroperitoneal, and gonadal). In the other groups there was no evidence of fat cell hyperplasia, despite weight gains from approximately 160 g (peaks on chow diet) to approximately 250 g (maximums on high-fat diet). Instead, fat cell size, assessed from biopsies of the inguinal area, became considerably enlarged. Taken together with earlier data from other species, the results suggest that hibernators are protected against fat cell hyperplasia. In dormice this protection appears to be present at all phases of their seasonal weight cycles. For species that experience several cycles of weight gain and loss in their lives, it may be adaptive to avoid increases in adipocyte number.
Effects of parathyroid hormone on blood flow in different regional circulations
Authors: Crass M. F. , Jayaseelan C. L. , Darter T. C.
Published: December 2017

Parathyroid hormone and, in particular, its 1-34 aminoterminal fragment, PTH-(1-34), are potent vasodilators of the coronary circulation. In addition the hormone exerts a powerful hypotensive effect in a variety of animals, suggesting that the polypeptide hormone is vasoactive in peripheral regional circulations as well. The purpose of this study was to determine the regional circulations that were responsive and the relative sensitivity of each to the vasoactive properties of the hormone fragment. An anesthetized instrumented open-chest and/or open-abdomen dog model was used. Blood flow was continuously monitored in left circumflex, left pulmonary, right renal, celiac, and superior mesenteric arteries. Doses of synthetic human PTH-(1-34) ranging from 0.00024 to 0.24 nmol/kg were administered by bolus intra-arterial injections. Although PTH-(1-34) produced a dose-related vasodilation in each of the above regional vascular beds, marked differences in sensitivity were observed. The peptide elicited large increases in coronary (178%) and celiac (162%) blood flow. Maximal renal and pulmonary responses were relatively small (increases of 30 and 23%, respectively). Compared with control values, blood flow in the superior mesenteric circulation increased only at the highest dose tested. Thus sensitivity to the vascular effects of the hormone fragment differs markedly between the regional vascular beds of the dog.
Effects of exercise training on energy balance of ovariectomized rats
Authors: Richard D. , Rochon L. , Deshaies Y. , Denis R.
Published: December 2017

The purpose of the present study was to investigate both the respective and interactive roles of exercise training and ovarian hormones on the regulation of energy balance. Female rats were divided into sedentary and exercise-trained groups. Each group thus formed was further divided into a sham-operated group, an ovariectomized group, or ovariectomized estradiol-treated group. Rats were exercise trained on a rodent motor-driven treadmill. After 33 days of treatment, rats were killed and the energy contents of carcasses, feces, and food were determined. Brown adipose tissue (BAT) thermogenesis was assessed through mitochondrial GDP binding. The results show that ovariectomy led to increases in food intake, body weight, and protein gains, whereas estradiol treatment abolished these effects. The results also show that exercise training reduced fat gain. Exercise training interacted with ovariectomy on energy gain; in sedentary rats ovariectomy enhanced the energy gain, an effect that disappeared in exercise-trained rats. However, exercise training was found to alter neither body weight and protein gains nor energy intake. Ovariectomy did not affect energy expenditure when the results are expressed in relative terms (kJ.kg body wt-0.67.day-1). Similarly, exercise training did not modify energy expenditure (kJ.kg body wt-0.67.day-1) once the cost of the training program was subtracted. BAT mitochondrial GDP binding was not affected by any of the experimental treatments. The present results therefore suggest that neither ovariectomy nor exercise training affect energy expenditure through regulatory forms of BAT-mediated thermogenesis.
Interleukin 1 affects glucose homeostasis
Authors: del Rey A. , Besedovsky H.
Published: December 2017

Alterations in glucose metabolism are known to occur during certain types of inflammation and infectious diseases. Interleukin 1 (IL 1), an immune-derived cytokine released during these processes, is proposed to function as a mediator of such alterations, since administration of low subpyrogenic doses of human rIL 1 to mice and rats produced hypoglycemia. In mice this effect was paralleled by increased insulin, glucagon, and corticosterone blood levels. When IL 1 was repeatedly injected, mice remained hypoglycemic for at least 14 h after the last injection. Furthermore, these animals responded normally to a challenge with glucose, thus suggesting that the proper function of the pancreas was preserved. A moderate hypoglycemia, paralleled by increased glucagon and corticosterone blood levels, was also observed in IL 1-injected rats, but no increase in insulin levels was detected. IL 1 administration to adrenalectomized rats resulted in a more marked hypoglycemia and in a profound hypoinsulinemia. The results suggest that IL 1 causes hypoglycemia by increasing insulin blood levels and probably also by mechanisms independent of the insulin secretagogue action of this cytokine.
Vasoconstrictor and vasodilator sites within anteroventral third ventricle region
Authors: Mangiapane M. L. , Brody M. J.
Published: December 2017

Previous studies have shown that electrical stimulation of the rat anteroventral third ventricle (AV3V) region produces a characteristic pattern of hemodynamic effects, i.e., renal and mesenteric vasoconstriction, and hindquarters vasodilation. In the present study, we localized the vasoconstrictor and vasodilator effects to specific subregions of the AV3V. In urethan-anesthetized rats prepared with arterial catheters and pulsed Doppler flow probes, we assessed the effects of electrical stimulation of four nuclei within AV3V on mean arterial pressure and renal, mesenteric, and hindquarters resistance. These nuclei were the organum vasculosum lamina terminalis (OVLT), ventral nucleus medianus (median preoptic nucleus), anterior (precommissural) nucleus medianus (median preoptic nucleus), and periventricular preoptic nuclei. Stimulation was carried out by use of a tungsten microelectrode. Stimulation of the OVLT consistently provoked stimulus-locked increases in arterial pressure coupled with increases in mesenteric and renal vascular resistance. Ganglionic blockade with chlorisondamine prevented these responses, demonstrating that they were mediated neurogenically. Stimulation of the three remaining nuclei produced decreases in arterial pressure, hindquarters vasodilation, and little change in mesenteric and renal vascular resistance. No changes in heart rate were observed with stimulation of any of the four nuclei. These results suggest that the vasoconstrictor and pressor functions of the AV3V region are localized in or near the OVLT region, whereas the remaining nuclei of the AV3V region mediate vasodilator and depressor responses.
Extracellular Ca2+, force, and energy state in cardiac tissue of rainbow trout
Authors: Hansen S. P. , Gesser H.
Published: December 2017

The importance of ATP and phosphocreatine (PCr) concentrations for myocardial force development was examined in electrically paced ventricular strips from rainbow trout. Three metabolic situations were studied involving either an aerobic block (N2, 5 mM NaCN), both an aerobic and a glycolytic block (1 mM iodoacetate), or no metabolic inhibitors. Increasing extracellular Ca2+ from 1.25 to 5 mM enhanced twitch-force development in all of these situations but caused no change in resting force or ATP and PCr content, except for the noninhibited preparations for which PCr increased. Anaerobiosis caused a decrease in the PCr concentration together with a fall in twitch force and an increase in resting force. Notably the changes in the contractile system associated with a given reduction in PCr were smaller in the absence than in the presence of iodoacetate. The results show that an increased Ca2+ availability stimulates the twitch-force development also at markedly lowered levels of high-energy phosphates. A maintained Ca2+ regulation appears to be one important reason for this. Furthermore, glycolysis seems to protect contractility in a way not reflected in the level of high-energy phosphates.
Organic cation secretion in flounder renal tissue
Authors: Miller D. S. , Holohan P. D.
Published: December 2017

In the winter flounder, Pseudopleuronectes americanus, renal clearance experiments showed that the model organic cations, tetraethylammonium (TEA) and N'-methylnicotinamide (NMN), were strongly secreted; organic cation-to-polyethylene glycol (glomerular filtration rate marker) clearance ratios averaged 130 and 30, respectively. TEA uptake by isolated renal tubular masses was concentrative and saturable. Transport was inhibited by competitor organic cations and reduced by exposure to NaCN,2,4-dinitrophenol, ouabain, and HgCl2. Organic anions did not reduce TEA uptake. NMN was the poorest inhibitor of TEA uptake of all the organic cations tested. In addition, the rate of NMN uptake was slower than that of TEA, and the steady-state tissue-to-medium ratio was lower (5 for NMN vs. 10 for TEA; both at 25 microM). The data show the presence of an organic cation secretory system in flounder tissue that resembles the mammalian systems in several respects.
Thermoregulatory responses of febrile sheep to spinal and hypothalamic heating
Authors: Blatteis C. M. , Necker R. , Hales J. R. , Fawcett A. A. , Hirata K.
Published: December 2017

Fever was induced by the intravenous injection of 0.25 microgram/kg of lipopolysaccharide (LPS) from Escherichia coli in eight conscious sheep exposed to ambient temperatures adjusted to the lower range of thermoneutrality. Chronic spinal or hypothalamic thermodes were perfused with water of 44 degrees C for 20 min or for most of the rising phase of fever (100 min of the mean 166 min total rise time). The effects of spinal and hypothalamic heating were identical. Thus, before LPS, spinal or hypothalamic heating did not affect the rate of O2 consumption (VO2) but increased skin blood flow (as indicated by skin temperatures) and elicited panting; therefore rectal temperature (Tre) fell. During fever rise, the already reduced skin blood flow and respiratory rate were not affected by spinal or hypothalamic heating, but the increased VO2 was reduced; consequently, the rise in Tre was attenuated. During the plateau phase of fever, all responses were similar to those seen before LPS. In febrilysis, heating strongly enhanced the operating heat loss mechanisms and, hence, augmented the fall in Tre. Thus, although the thermoeffectors activated by spinal or hypothalamic heating were modified during the different stages of fever, the effect on body temperature was nearly the same. Therefore there seems to be no change in spinal or hypothalamic thermosensitivity during fever in sheep.
Pain sensitivity, thermal capability, and brain monoamine turnover in hypertensive rats
Authors: Tsai C. F. , Lin M. T.
Published: December 2017

This study compared the pain sensitivity, thermal capability, and brain monoamine turnover in normotensive and hypertensive rats. Either the spontaneously hypertensive rats, the experimentally (renal or deoxycorticosterone acetate) hypertensive rats, or their normotensive controls were tested for pain sensitivity by the hot-plate procedure, with the plate maintained at 55 degrees C. The spontaneously hypertensive rats, but not the experimentally hypertensive rats, showed an elevated level of spontaneous pain threshold compared with their appropriate controls. However, both the spontaneously and the experimentally hypertensive rats displayed a reduced sensitivity of analgesic responses to morphine administration. In addition the thermal responses to external stresses in these groups of animals were assessed. It was found that, over an ambient temperature range of 8-30 degrees C, either spontaneously or experimentally hypertensive rats maintained their rectal temperature within a normal limit displayed by their appropriate controls. However, the metabolic rate levels of both spontaneously and experimentally hypertensive rats were elevated at ambient temperatures less than 22 degrees C. Furthermore, compared with their appropriate controls, these hypertensive rats also showed a greater degree of hypothermic responses to chlorpromazine injection. Biochemical examination revealed that either the spontaneously or the experimentally hypertensive rats had a lower serotonin, but a higher catecholamine, turnover in both the hypothalamus and the brain stem compared with their appropriate normotensive controls. The data indicate that, in a hypertensive state, changes in the monoamine turnover of different brain regions may be correlated with the above-mentioned alterations in pain sensitivity and in thermal capability.
Effect of VIP on sweat secretion and cAMP accumulation in isolated simian eccrine glands
Authors: Sato K. , Sato F.
Published: December 2017

Although vasoactive intestinal peptide (VIP)-immunoreactive nerves have been identified around the eccrine sweat glands, their functional significance is unknown. We found that VIP evokes eccrine sweat secretion in isolated monkey palm eccrine sweat glands in vitro as profusely as does isoproterenol (Iso), however, at concentrations two orders of magnitude lower than that of Iso. Like Iso sweating, the VIP sweating was relatively insensitive to removal of Ca2+ from the medium. The time course of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in the secretory coil paralleled that of sweat secretion. However, unlike Iso stimulations, both VIP-induced cAMP level and VIP sweat rate markedly declined with time. The attenuation of VIP sweat rate was reversed by forskolin and by theophylline, suggesting that the attenuation is caused partially by desensitization of the receptor-cyclase complex and/or by cAMP breakdown by phosphodiesterase. Forskolin stimulated the VIP-induced cAMP level more than can be expected from a simple additive effect. The sudorific effects of a submaximal concentration of VIP (6 X 10(-9) M) and that of methacholine (MCh) (10(-8) M) were only additive. The VIP-induced cAMP level was markedly augmented by MCh and further enhanced by Iso with or without theophylline. Thus the most salient biochemical consequence of the VIP-ergic component of sweat gland innervation is to induce synergistic amplification of tissue cAMP accumulation. The functional significance of synergistically accumulated cAMP in physiological eccrine sweating remains to be studied.
2,5-anhydro-D-mannitol: a fructose analogue that increases food intake in rats
Authors: Tordoff M. G. , Rafka R. , DiNovi M. J. , Friedman M. I.
Published: December 2017

We examined the effects on food intake and plasma fuels of 2,5-anhydro-D-mannitol (2,5-AM; 2-deoxy-D-fructose), a fructose analogue that inhibits hepatocyte gluconeogenesis and glycogenolysis in vitro. 2,5-AM (50-800 mg/kg po) given to rats during the diurnal fast produced a dose-related increase in food intake during the 2 h after administration. A 200-mg/kg dose of 2,5-AM decreased plasma glucose, increased plasma ketone bodies, free fatty acids, and glycerol, and had no effect on triglycerides. Normal and diabetic rats given 2,5-AM (200 mg/kg ip) increased food intake to the same extent. These results suggest that, unlike other substrate analogues that increase food intake, 2,5-AM increases feeding by creating a metabolic state that resembles fasting.
Fluid secretion in glomerular renal proximal tubules of freshwater-adapted fish
Authors: Cliff W. H. , Beyenbach K. W.
Published: December 2017

Tubular secretion by renal proximal tubules, as a mechanism for delivering fluid and electrolytes to the urine, has received little attention in modern conceptions of renal function in vertebrates even though it is the mechanism for urine production in aglomerular fish. This report demonstrates that some proximal tubules of glomerular kidneys of freshwater-adapted euryhaline fish spontaneously secrete fluid. The fluid consists primarily of Na (138 mM) and Cl (160 mM). NaCl and fluid secretion can be stimulated by adenosine 3',5-cyclic monophosphate, suggesting that tubular fluid secretion is under hormonal control. Fluid secretion driven by NaCl secretion in glomerular proximal tubules of fish that already filter NaCl and water suggests that secretion of fluid and NaCl may play a fundamental role in vertebrate renal function beyond a preadaptation for aglomerular urine formation.
Refeeding hypertension in dietary obesity
Authors: Ernsberger P. , Nelson D. O.
Published: December 2017

A novel model of nutritionally induced hypertension in the rat is described. Dietary obesity was produced by providing sweet milk in addition to regular chow, which elicited a 52% increase in caloric intake. Despite 54% greater body weight gain and 139% heavier retroperitoneal fat pads, 120 days of overfeeding failed to increase systolic pressure in the conscious state (125 +/- 8 vs. 121 +/- 4 mmHg in chow-fed controls) or mean arterial pressure under urethan anesthesia (71 +/- 4 vs. 63 +/- 3 mmHg). In contrast, mild hypertension developed in intermittantly fasted obese animals (a 21-mmHg increase in systolic blood pressure measured in the conscious state and a 16-mmHg increase in mean arterial pressure under anesthesia relative to chow-fed controls). The first 4-day supplemented fast was initiated 4 wk after the introduction of sweet milk, when the animals were 47 g overweight relative to chow-fed controls. Thereafter, 4 days of starvation were alternated with 2 wk of refeeding for a total of 4 cycles. A rapid fall in systolic blood pressure (12 +/- 2 mmHg at 2 days) accompanied the onset of supplemented fasting and was maintained thereafter (2.7 +/- 2.6 mmHg further decrease during the latter half of the fast). With refeeding, blood pressure rose precipitously (13 +/- 3 mmHg in the 1st 2 days), despite poststarvation anorexia. Blood pressure tended to rise slightly over the remainder of the realimentation period (5.2 +/- 2.8 mmHg). After the 4th supplemented fast, hypertension was sustained during 30 days of refeeding. Cumulative caloric intake in starved-refed rats fell within 2% of that in chow-fed controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Mechanisms of altered sodium excretion after preoptic hypothalamic lesions
Authors: Bealer S. L. , Caldwell R. W. , Songu-Mize E.
Published: December 2017

These experiments investigated cardiovascular and hormonal responses during the natriuresis and subsequent sodium retention following electrolytic lesions of the periventricular tissue surrounding the anteroventral third ventricle (AV3V-X) in the rat. Four hours following treatment, AV3V-X resulted in a significant increase in blood pressure (18 +/- 3 mmHg), bradycardia (-68 +/- 20 beats/min), and natriuresis (212 +/- 36 mu eq/h), compared with control-operated (control: 2 +/- 4 mmHg, -14 +/- 18 beats/min, 89 +/- 34 mu eq/h) and unanesthetized control (UC) animals (-1 +/- 3 mmHg, -5 +/- 12 beats/min, 74 +/- 25 mu eq/h). Preventing the hypertensive response in AV3V-X rats abolished the natriuresis. Twenty-four hours after treatment, blood pressure, heart rate, urine flow, and sodium excretion were similar between experimental groups. However, sodium excretion by AV3V-X rats was significantly smaller than control 24-48 h following treatment. AV3V-X rats had significantly elevated plasma concentrations of aldosterone and corticosterone 4, 24, and 48 h and increased plasma renin 24 and 48 h after treatment. These data suggest that the acute natriuresis following AV3V-X is mediated by increased arterial blood pressure, whereas the subsequent sodium retention could be due to activation of the renin-aldosterone system.
Dynamic changes in venous outflow by baroreflex and left ventricular distension
Authors: Hoka S. , Bosnjak Z. J. , Siker D. , Luo R. J. , Kampine J. P.
Published: December 2017

We examined the dynamic changes in venous outflow from the splanchnic and extrasplanchnic vascular beds in response to carotid sinus (CS) baroreflex and left ventricular (LV) distension in 12 dogs anesthetized with pentobarbital sodium. Splenic sympathetic nerve activity was measured in an additional group of six dogs. A heart-lung bypass was used with constant cardiac output and constant venous pressure. LV distension was produced by inflating a balloon in the LV. LV distension and an increase in CS pressure from 50 to 200 mmHg decreased blood pressure by 26 +/- 5 and 30 +/- 6 mmHg and increased vascular capacitance by 5.5 +/- 0.9 and 4.5 +/- 1.2 ml/kg, respectively. Splanchnic venous outflow exhibited a transient decrease, whereas extrasplanchnic venous outflow showed a transient increase, in response to LV distension and increasing CS pressure, accompanied by a sustained decrease in splenic nerve activity. The results indicate important differences between splanchnic and extrasplanchnic components of the total venous system in terms of the regulation of venous capacitance. It is suggested that changes in venous capacitance produced by LV distension and CS baroreflex are primarily due to active changes in splanchnic venous tone.
Diencephalic regions contributing to sympathetic nerve discharge in anesthetized cats
Authors: Huang Z. S. , Varner K. J. , Barman S. M. , Gebber G. L.
Published: December 2017

We reported that the forebrain is responsible for a significant component (38%) of inferior cardiac postganglionic sympathetic nerve discharge (SND) in baroreceptor-denervated cats anesthetized with alpha-chloralose [Huang et al., Am. J. Physiol. 252 (Regulatory Integrative Comp. Physiol. 21): R645-R652, 1987]. The current study was initiated to assess the contribution of various diencephalic regions to the forebrain-dependent component of SND in this preparation. For this purpose, the reductions in inferior cardiac SND and blood pressure produced acutely by midbrain transection at stereotaxic plane A3 in nonlesioned control cats were compared with those in cats in which diencephalic lesions were made with radio-frequency current. Lesions of the anterior medial hypothalamus including the paraventricular nucleus failed to attenuate the decreases in SND and blood pressure produced by midbrain transection. In contrast, the effects of midbrain transection were significantly attenuated by lesions of the lateral hypothalamus (including medial forebrain bundle), posterior medial hypothalamus, or the medial thalamus. We conclude that both the hypothalamus and medial thalamus contribute to SND in anesthetized cats.
Stretch-induced reduction in atrial content of natriuretic factor is locally mediated
Authors: Meikle A. D. , Kaufman S.
Published: December 2017

Two groups of male Wistar rats were chronically implanted with small inflatable balloons at the right superior vena caval (SVC)-atrial junction. The balloons were inflated for 60 min in one-third of the rats in each group; the remainder served as noninflated controls. Extract was prepared from the right atria of the first and from the left atria of the second group and bioassayed in male Wistars to determine the content of atrial natriuretic factor (ANF). The bioassay rats received either two injections of sham extract (control) or an initial injection (I1) of sham extract followed by an injection (I2) of balloon-inflated extract (experimental). For right atrial extract, the incremental response to the experimental injection (I2/I1) was significantly less than the response to the control injection (experimental, 1.15 +/- 0.09 mueq/min, n = 14; control, 1.59 +/- 0.15 mueq/min, n = 13; P less than 0.01). However, in the case of left atrial extract, there was no such difference between the control group (1.35 +/- 0.13 mueq/min, n = 19) and the experimental group (1.25 +/- 0.11 mueq/min, n = 11; Student's t test). We conclude that right atrial distension causes release of ANF from the right atrium, but not the left, and that this release is probably locally mediated.