bluuebunny/crossref_metadata_2025 huggingface dataset:
Alpha 2-noradrenergic feeding rhythm in paraventricular nucleus: relation to corticosterone
Authors: Bhakthavatsalam P. , Leibowitz S. F.
Published: December 2017

The feeding response induced by the paraventricular nucleus (PVN) injection of norepinephrine (NE) in rats has been shown to correlate positively in magnitude with the level of circulating corticosterone. The present study examined the feeding responses induced by NE and clonidine (CLON) injected into the PVN and CLON injected intraperitoneally, as a function of diurnal cycle and also in adrenalectomized animals with and without peripheral corticosterone replacement. A periodicity in the effectiveness of PVN-injected NE and CLON, as well as intraperitoneal CLON, was observed, with a significantly stronger eating response occurring near the onset of dark period compared with the response produced in the early light period. Adrenalectomy abolished the feeding induced by each of these alpha-noradrenergic agonists, and acute corticosterone replacement restored the response. The feeding induced by intraperitoneally injected 2-deoxy-D-glucose was unaffected. These findings indicate the importance of corticosterone to the action of peripherally and centrally administered alpha-noradrenergic agonists and also suggest that the diurnal rhythm of corticosterone plays an important role in determining the rhythm for the feeding response induced by PVN alpha 2-noradrenergic activation.
Independent Na+ and Cl- active transport by urinary bladder epithelium of brook trout
Authors: Marshall W. S.
Published: December 2017

Brook trout (Salvelinus fontinalis) urinary bladder in vitro had a low serosa-positive transepithelial potential (6.7 +/- 1.2 mV), low transmural conductance (0.23 +/- 0.03 mS. cm-2), and net absorptive transport of Na+ and Cl-. The net flux of Na+ was equivalent to that of Cl- and much larger than the membrane current, indicating neutral NaCl uptake. Na+ uptake was not coupled to that of Cl-, since absorptive Na+ transport continued in (Cl-)-free media. In the absence of Cl-, the net absorption of Na+ was accompanied by net secretion of titratable acidity, suggestive of Na+-H+ exchange on the luminal surface. Active Cl- transport persisted in dilute (2.0 mM) tetraethylammonium chloride with zero K+ and zero Na+, indicating full independence of the Cl- transport from cation coupling and suggesting the presence of Cl(-)-HCO-3 exchange. The kinetics of Cl- uptake (K1/2 = 35-37 mM, maximal transport rate = 3.0-3.4 mu eq . cm-2 . h-1) were not significantly affected by removal of mucosal Na+ . Cl- uptake was inhibited partially by 10(-4) M amiloride but not by 10(-4) M bumetanide. The results strongly support a model for active NaCl transport involving paired ion exchangers, likely located at the luminal membrane.
Metabolic response to a specific lipid-depleting factor in parabiotic rats
Authors: Harris R. B. , Martin R. J.
Published: December 2017

Parabiosis has been used as a technique for demonstrating the existence of a humoral factor in the control of body fat. The timing and metabolic basis for specific loss of fat from parabiotic partners of obese rats were examined. One member of a pair received 200% control intake, by stomach tube, for 8, 23, 39, or 57 days. Their partners ate 9.8 +/- 0.1 g/day. Members of ad libitum-fed pairs ate 9.6 +/- 0.1 g/day. All rats received the same diet. After 39 days, body fat in partners of obese rats was 6 +/- 1 g/rat compared with 17 +/- 1 g/rat in members of ad libitum pairs. Body protein was not different. In vitro hepatic fatty acid synthesis (FAS) and esterification (FAE) and inguinal FAS, FAE, and glycerol release suggested that fat loss was due to inhibition of adipose FAE. Partners of overfed rats and members of ad libitum pairs were then compared after 27 days of tube feeding when loss of fat was expected to be most rapid. Hepatic FAS, FAE, and fatty acid oxidation were the same for both groups. Inguinal FAS and FAE were decreased in partners of obese rats. An unidentified "lipid-depleting" agent, originating in obese rats, appears to inhibit adipose FAS and FAE in their partners independently of changes in feeding.
Reoxygenation injury in isolated hepatocytes: effect of extracellular ATP on cation homeostasis
Authors: Hayashi H. , Chaudry I. H. , Clemens M. G. , Hull M. J. , Baue A. E.
Published: December 2017

The aims of this study were to determine 1) the effects of anoxia and reoxygenation on electrolytes and ATP content of isolated hepatocytes and 2) whether exogenous ATP-MgCl2 has any beneficial effects on the cellular alterations that are produced during the reoxygenation period. After 90 min anoxia, intracellular Na and inorganic phosphate (Pi) increased, K and ATP decreased, whereas Ca and Mg did not change. After 60 min of reoxygenation, intracellular Mg and Na levels decreased, Ca increased, and Pi levels returned to normal, but ATP levels remained low. These results suggest that the plasma membrane is relatively impermeable to divalent ions such as Ca2+, Mg2+, and HPO2-4 during anoxia but becomes permeable to them after reoxygenation. When anoxic cells were treated with ATP-MgCl2 during reoxygenation, intracellular ATP and Mg levels increased, but accumulation of Ca and Pi was also observed. Thus enhancement of Mg transport and specific stimulation of Ca-Pi sequestration occurs with ATP-MgCl2 treatment. Na and K levels exhibited biphasic reciprocal dose-response changes to ATP-MgCl2 treatment; i.e., 0.1 mM ATP-MgCl2 (low-dose) treatment increased K and decreased Na, whereas 1 mM ATP-MgCl2 (high-dose) treatment decreased K and increased Na. These results indicate that although addition of a single high-dose ATP-MgCl2 was deleterious over a period of 60 min, low-dose ATP-MgCl2 accelerates the recovery of postanoxic cellular electrolyte homeostasis.
Excitatory and inhibitory interactions among renal and cardiovascular afferent nerves in dorsomedial medulla
Authors: Felder R. B.
Published: December 2017

Central interactions between renal afferent nerves (RN) and carotid sinus (CSN) and aortic (AN) nerves were investigated by recording extracellular action potentials from single units in and around the nucleus tractus solitarius (NTS) in alpha-chloralose-anesthetized cats. Forty-nine units were activated by electrical stimulation of the renal nerve; twenty-seven of these also were excited by CSN, AN, or both. Summation of inputs was demonstrated during simultaneous subthreshold or suprathreshold stimulation of RN and CSN or AN. In 10 units excited by simultaneous stimulation of RN and AN or CSN, a conditioning stimulus (333 Hz for 10 ms) applied to RN caused prolonged (up to 150 ms) inhibition of responses to stimulation of AN or CSN; reciprocal inhibitory interactions were also shown. These studies show that renal afferent input interacts with cardiovascular afferent input at neurons in the NTS region of dorsal medulla and suggest that the outcome of these interactions at the single cell level may be critically dependent on the temporal relationships among afferent impulses converging on common central synapses.
Dose-related suppression of feeding by intraportal glucagon infusion in the rat
Authors: Weick B. G. , Ritter S.
Published: December 2017

Continuous intraportal infusion of pancreatic glucagon during a feeding test conducted in the dark phase of the circadian photoperiod produced a dose-related suppression of feeding in rats. At the end of the 30 min of infusion, food intake was suppressed 10% at the infusion rate of 0.33 micrograms X kg-1 X min-1 and 45% at the highest infusion rate studied (100 micrograms X kg-1 X min-1). At infusion rates of 33 and 100 micrograms X kg-1 X min-1, the suppression of cumulative intake persisted for 30 min after the termination of the infusion, but no effect on 24-h intake was observed. Glucagon's glycemic effects were measured for two glucagon doses (1 and 10 micrograms X kg-1 X min-1) in the absence of food using a paradigm similar to that used for the feeding tests. In contrast to the suppression of food intake, the hyperglycemic effects of glucagon were not dose related for the two doses tested. The hyperglycemia was similar in magnitude 5 min after the start of the infusion at both infusion rates. Subsequently, plasma glucose concentrations declined more rapidly at the higher than at the lower glucagon dose. This difference in the effect of glucagon on glucose disposal may be important for glucagon's satiating effect.
Intravascular pulmonary macrophages: a novel cell removes particles from blood
Authors: Warner A. E. , Brain J. D.
Published: December 2017

Clearance of radiolabeled gold colloid from the blood and relative organ distribution of retained colloid and magnetic iron oxide particles were compared between rats and calves. When unanesthetized calves 1 wk of age were injected intravenously with these two particle types, uptake was predominantly pulmonary. In contrast, in the rat there was overwhelming hepatic uptake. Similar pulmonary localization of injected particulate material was found in adult goats. When lung tissue was examined by electron microscopy, injected iron oxide was found within intravascular pulmonary macrophages. The mononuclear phagocyte system removes particulate material of both exogenous and endogenous origin from the circulation; hepatic and splenic uptake of such material usually predominates. We found that, unlike the species previously studied, ruminants have actively phagocytic cells within the pulmonary vasculature. Thus pulmonary intravascular macrophages constitute an important part of the mononuclear phagocyte system in some species.
Inhibition of gastric emptying and feeding by fenfluramine
Authors: Robinson P. H. , Moran T. H. , McHugh P. R.
Published: December 2017

To assess the mechanism by which the anorectic agent fenfluramine influences feeding, we examined in Macaca mulatta the effect of intragastric fenfluramine (2 mg/kg) on both feeding and the gastric emptying of saline and glucose test meals. Gastric emptying was measured by the dye-dilution technique, using chronic indwelling intragastric cannulas. The emptying of normal saline was inhibited by fenfluramine as was the initial bolus phase of the emptying of glucose. In contrast, the subsequent controlled phase of glucose emptying was unaffected in two out of four animals, slightly inhibited in one, and strongly inhibited in only one monkey. Rhesus monkeys trained to drink a glucose solution to satiety drank, on average, 21% less after fenfluramine. The emptying of the consumed glucose solution from the stomach was reduced by 39%, whereas gastric volume at satiety was reduced by only 10%. The reduction of intake was strongly related to the degree of inhibition of gastric emptying. These results support an important role for the inhibition of gastric emptying in fenfluramine-induced suppression of feeding.
Rat endogenous pyrogen and fever
Authors: Morimoto A. , Watanabe T. , Ono T. , Sakata Y. , Murakami N.
Published: December 2017

Rat endogenous pyrogen (EP), prepared from the white blood cells of lipopolysaccharide-pretreated rats, produced a fever in both rabbits and rats. The effects of human, rabbit, and rat EP on the body temperatures of rabbits and rats were investigated to clarify differences in the febrile response to each kind of EP. The latency to fever onset and the time to peak fever induced by rat EP in rabbits and rats were significantly greater than those induced by human and rabbit EP. The maximum elevation of the body temperature induced by rat EP in both animals was almost identical to that induced by human and rabbit EP. In a comparison of the febrile responses to various EPs between rabbits and rats, the latency to fever onset, the time to peak, and the maximum elevation of fever in rats were approximately half those observed for rabbits. Furthermore, the threshold dosage to induce a fever response in rats was greater than that necessary for rabbits. It is concluded that rat EP could be obtained by in vitro techniques and that rats have the physiological mechanisms to develop a fever through production of EP.
Energy expenditure by doubly labeled water: validation in humans and proposed calculation
Authors: Schoeller D. A. , Ravussin E. , Schutz Y. , Acheson K. J. , Baertschi P. , Jequier E.
Published: December 2017

To further validate the doubly labeled water method for measurement of CO2 production and energy expenditure in humans, we compared it with near-continuous respiratory gas exchange in nine healthy young adult males. Subjects were housed in a respiratory chamber for 4 days. Each received 2H2(18)O at either a low (n = 6) or a moderate (n = 3) isotope dose. Low and moderate doses produced initial 2H enrichments of 5 and 10 X 10(-3) atom percent excess, respectively, and initial 18O enrichments of 2 and 2.5 X 10(-2) atom percent excess, respectively. Total body water was calculated from isotope dilution in saliva collected at 4 and 5 h after the dose. CO2 production was calculated by the two-point method using the isotopic enrichments of urines collected just before each subject entered and left the chamber. Isotope enrichments relative to predose samples were measured by isotope ratio mass spectrometry. At low isotope dose, doubly labeled water overestimated average daily energy expenditure by 8 +/- 9% (SD) (range -7 to 22%). At moderate dose the difference was reduced to +4 +/- 5% (range 0-9%). The isotope elimination curves for 2H and 18O from serial urines collected from one of the subjects showed expected diurnal variations but were otherwise quite smooth. The overestimate may be due to approximations in the corrections for isotope fractionation and isotope dilution. An alternative approach to the corrections is presented that reduces the overestimate to 1%.
Methionine-enkephalin and vasopressin in SHR: effects of dehydration
Authors: Ota K. , Share L. , Crofton J. T. , Brooks D. P.
Published: December 2017

Enkephalins are found in the posterior pituitary, can alter vasopressin secretion, and have greater pressor effects in spontaneously hypertensive rats (SHR) than in Wistar-Kyoto (WKY) rats. Measurement of the plasma methionine-enkephalin concentration (PMet-Enk) has provided equivocal results in humans and has not been reported in rats. We have developed a highly specific and sensitive Met-Enk radioimmunoassay and determined that Met-Enk circulates in rats but that PMet-Enk is no different between SHR and WKY rats (7.6 +/- 0.8 and 9.2 +/- 0.8 pg/ml, respectively). Water deprivation for 48 h increased the plasma vasopressin concentration (PADH) and 24-h urinary vasopressin excretion (UADHV) in SHR and WKY rats, but PMet-Enk was not altered. There were no differences in PADH and UADHV between SHR and WKY rats in either the euhydrated or dehydrated state. These results suggest that it is unlikely that circulating Met-Enk contributes importantly to the maintenance of hypertension in SHR. There was also no evidence for a greater secretion of vasopressin in SHR than in WKY rats, in contrast to previous reports.
Increased hexokinase activity in forebrain of water-deprived and diabetes insipidus rats
Authors: Krukoff T. L. , Turton W. E. , Calaresu F. R.
Published: December 2017

Metabolic studies using the 2-[14C]deoxy-D-glucose and cytochrome oxidase techniques have demonstrated changes in the activity of central sites associated with the hypothalamoneurohypophysial system in water-deprived (WD) and diabetes insipidus (DI) rats. Another method that may be used as an index of metabolic activity in discrete regions of the central nervous system is the measurement of hexokinase (HK) activity. This study describes changes in metabolic activity, as measured by HK histochemistry, in regions of the forebrain of WD and DI rats. Significant increases in HK activity measured by densitometric analysis were observed in the magnocellular component of the paraventricular nucleus of the hypothalamus, supraoptic nucleus, nucleus circularis, and neurohypophysis of WD and DI rats. In addition, increased HK activity was observed in the preoptic area and subfornical organ of DI rats. These data demonstrate that metabolic changes occur in the forebrain of WD and DI rats within structures involved in body fluid regulation. The present study also demonstrates that HK histochemistry may be used as a marker of metabolic activity in discrete regions of the central nervous system.
Effects of bombesin on thermoregulatory responses and hypothalamic neuronal activities in the rat
Authors: Lin K. S. , Lin M. T.
Published: December 2017

Direct administration of bombesin (1, 10, and 100 ng/microliter) into the preoptic anterior hypothalamic area caused a dose-related fall in rectal temperature at ambient temperatures (Ta) of 8 and 22 degrees C. The hypothermia in response to bombesin was brought about by a decrease in metabolism at Ta 8 degrees C, whereas at Ta 22 degrees C the hypothermia was brought about by both a decrease in metabolism and an increase in cutaneous temperature. However, at Ta 30 degrees C, intrahypothalamic administration of bombesin caused an insignificant change in thermoregulatory responses. On the other hand, 51 single neurons in the preoptic anterior hypothalamic area were examined in 20 rats under urethan anesthesia. Each animal was subjected to scrotal warming or cooling and to the administration of bombesin. Microiontophoretic application of bombesin resulted in inhibition of the majority (62.5%) of cold-responsive neurons as well as excitation of the majority (50%) of warm-responsive neurons recorded in the preoptic anterior hypothalamic area. However, the majority (74%) of thermally unresponsive neurons were not affected by bombesin application. The data indicate that bombesin, when administered intrahypothalamically, excites warm-responsive neurons and inhibits cold-responsive neurons within the preoptic anterior hypothalamic area to induce hypothermia by promoting an increase in heat loss and a decrease in heat production.
Fetal cardiovascular and endocrine responses to prolonged fetal hemorrhage
Authors: Brace R. A. , Cheung C. Y.
Published: December 2017

Twelve chronically catheterized fetal sheep averaging 131 +/- 1 (SE) days gestation (term = 145-150 days) were hemorrhaged an average of 30.8 +/- 1.8% of their initial blood volume over 2 h by removing blood at 10-min intervals. During the hemorrhage, fetal blood volume decreased by 14.3 +/- 1.4%, and arterial pressure (AP), venous pressure (VP), and heart rate (HR) did not change significantly, although fetal plasma renin activity (PRA), arginine vasopressin (AVP), and norepinephrine (NE) were elevated to 1.5-2.5 times their initial values (P less than 0.05). Circulating levels of PRA, AVP, and NE began to rise when 5-10, 10-15, and 20-30%, respectively, of the initial blood volume was removed. Three to five hours after the hemorrhage, blood volume had returned to normal, AP was reduced by an average of 6 mmHg, VP was unchanged, and HR was elevated by an average of 20 beat/min; PRA, AVP, and NE averaged two to three times control (P less than 0.05). Twenty-two hours after the hemorrhage, blood volume was 5.4 +/- 2.4% above control; AP and HR returned toward normal; VP was elevated by an average of 2 mmHg; PRA and NE levels remained elevated (P less than 0.05), but AVP was not different from control. Plasma concentrations of epinephrine, dopamine, and prolactin showed little change during or after the hemorrhage. Thus these studies indicate that the fetus rapidly returns its blood volume to normal after a substantial loss of blood. In addition, the fetal cardiovascular and endocrine responses to a prolonged fetal hemorrhage of moderate volume are substantially less than those that occur after rapid hemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)
Control of renin secretion by Ca2+ and cyclic AMP through two parallel mechanisms
Authors: Park C. S. , Sigmon D. H. , Han D. S. , Honeyman T. W. , Fray J. C.
Published: December 2017

The cellular mechanism of action of cyclic AMP (cAMP) mediating the beta-adrenergic stimulation of renin secretion was studied, with special reference to its interactions with the inhibitory pathway of renin secretion by Ca2+ calmodulin. Forskolin, a potent stimulator of adenyl cyclase that bypasses the hormone-receptor interactions, stimulated renin secretion in vitro from rabbit renal cortical slices in a concentration-dependent manner. Renin secretion stimulated by submaximal concentration of forskolin was partly or completely antagonized or blocked by raising intracellular Ca2+ concentration by incubating slices in a high-K+ depolarizing medium, but renin secretion stimulated by the maximal effective concentration of forskolin was not inhibited by Ca2+. In addition, the maximal effective concentration of forskolin (10(-5) M) increased renin secretion by a fixed amount independent of medium (by inference, intracellular) Ca2+ concentration in the range of 10(-8) to 10(-6) M in a high-K+ medium. Furthermore, the degree of stimulation of renin secretion by forskolin was greater with greater removal of the inhibitory effect of Ca2+ calmodulin pathway on renin secretion with use of potent calmodulin antagonists, suggesting that the stimulatory effect of cAMP on renin secretion may be maximal in the absence of the inhibitory influence of Ca2+. These results are consistent with the hypothesis that cAMP (by inference, the beta-adrenergic stimulus) stimulates renin secretion through a cellular mechanism independent of that through the Ca2+ -calmodulin pathway.
Gastric emptying of glucose loads in rats: effects of insulin-induced hypoglycemia
Authors: McCann M. J. , Stricker E. M.
Published: December 2017

Previous work has established that the increased food intake of rats in response to insulin-induced hypoglycemia can be inhibited by the intravenous infusion of fructose, a sugar that cannot cross the blood-brain barrier and nourish cerebral chemoreceptors, and that this effect of fructose is abolished by hepatic vagotomy. The present series of experiments examined the effects of these treatments on gastric emptying of various glucose solutions in rats. Gastric emptying of the administered loads decreased in proportion to increasing concentration of glucose solution but not by enough for caloric delivery to be regulated precisely. Insulin-induced hypoglycemia increased the rate at which the glucose solutions emptied from the stomach. This enhanced emptying was suppressed by infusion of fructose, and that suppression was eliminated by hepatic vagotomy. These and other findings support previous proposals that food intake is controlled in part by satiety signals reflecting the nutrient content of the stomach and in part by satiety signals related to the delivery of utilizable calories to the liver.
Volume influences on thirst and vasopressin secretion in dehydrated sheep
Authors: Park R. G. , Congiu M. , Denton D. A. , McKinley M. J.
Published: December 2017

The contribution of extracellular fluid volume (ECFV) to water consumption and plasma vasopressin concentration (PAVP) after water deprivation for 52 h was examined in sheep. Intravenous infusion of isotonic NaCl, equivalent to either estimated ECFV loss or total body water loss, significantly reduced water intake by 37% when water was offered 3 h after infusion but not when water was offered 1 h after infusion. Plasma osmolality (POsm) was reduced after 3 h. Infusion of 200 mM NaCl, which maintained POsm, decreased water consumption by the same degree as isotonic NaCl infusion. Thus large decreases in POsm had no effect on water intake in this experimental protocol. Lack of inhibition of drinking 1 h after infusion suggests that the decrease observed after 3 h may have been mediated by receptors in the interstitial fluid (ISF) compartment and not the intravascular compartment. PAVP was reduced 3 h after infusion of NaCl but not at 1 or 2 h after infusion. POsm was also decreased at 3 h. Thus reduction of PAVP by NaCl infusion may have been caused by either ISF or intracellular fluid volume expansion.
Cardiovascular and endocrine responses to head-up tilt and vasopressin infusion in humans
Authors: Bie P. , Secher N. H. , Astrup A. , Warberg J.
Published: December 2017

The effects of passive tilt on arterial and central venous pressures (MAP and CVP), heart rate (HR), arterial concentrations of vasopressin (AVP) and aldosterone (ALDO), osmolality, and hematocrit were studied in eight healthy young men. Tilting was performed at 30 degrees/min to 20 or 40 degrees and maintained for 45 min. The 20 degrees tilt did not change MAP while CVP fell by 5.9 mmHg (P less than 0.01) and HR increased by 5 beats/min (51-56 beats/min, P less than 0.05). AVP and ALDO concentrations were unchanged. At 40 degrees, MAP increased by 5.7 mmHg (86.0-91.7 mmHg, P less than 0.01), CVP decreased by 7.4 mmHg (P less than 0.01), HR rose by 8 beats/min (55-63 beats/min, P less than 0.01), and pulse pressure fell by 6 mmHg (P less than 0.05). ALDO increased fivefold (P less than 0.05), but AVP did not change. Infusions of AVP at 0.25 or 1.0 ng X min-1 X kg body wt-1 elevated plasma AVP to 11 +/- 1 and 52 +/- 8 pg/ml. Only the larger dose caused a small increase in MAP while CVP and HR remained unchanged; however, washout of a subcutaneous depot of Xe was reduced greater than 60% even by the lower dose. It is concluded that small-angle nonhypotensive passive tilt does not affect AVP measurably despite substantial reductions of CVP and a marked increase in ALDO. Elevations of AVP elicit marked subcutaneous vasoconstriction also in the absence of changes in CVP, HR, and MAP.
Locomotion without lungs: energetics and performance of a lungless salamander
Authors: Full R. J.
Published: December 2017

Lungless salamanders (4.1 g) were exercised on a treadmill enclosed in a Plexiglas respirometer at a range of speeds (0.05-0.24 km/h). O2 consumption (VO2) was determined continuously by open-flow respirometry. At the onset of exercise VO2 increased to a "steady state" in approximately 2-5 min. VO2 (ml O2 X g-1 X h-1) increased linearly with speed (S), VO2 = 2.3 (S) + 0.1 (r2 = 0.74). The minimum cost of transport (2.3 ml O2 X g-1 X km-1) was three-fourths of that predicted for a vertebrate of the same mass. Maximum O2 consumption (VO2max) was attained at 0.16 km/h (maximum aerobic speed), where this VO2 was six to nine times above standard rates. The net rate of whole-body lactate production (WBL) was insignificant at slow speeds (less than 46% VO2max) but did increase at submaximal work loads (85% VO2max). The highest WBL (0.07 mg X g-1 X min-1) was measured at a speed (0.20 km/h) that exceeded the maximum aerobic speed. Salamanders sustained exercise at slow speeds for over 2 h. The greatest decline in endurance (i.e., from 120 to 10 min) occurred at speeds below the maximum aerobic speed, where being lungless may have little consequence. At fast rates of locomotion a limited VO2max was associated with a low maximum aerobic speed and a modest capacity for sustained activity.
Sympathetic denervation impairs responses of brown adipose tissue to VMH stimulation
Authors: Minokoshi Y. , Saito M. , Shimazu T.
Published: December 2017

Effects of unilateral surgical denervation of the interscapular brown adipose tissue (IBAT) on its thermogenic and lipogenic responses to electrical stimulation of the ventromedial hypothalamic (VMH) nucleus were studied in anesthetized rats. The rapid rise in IBAT temperature in response to VMH stimulation was greatly suppressed in the denervated IBAT, whereas the temperature response was not impaired in the contralateral innervated IBAT in the same animals. Similarly, the increased rates of conversion of [14C] glucose and [3H]H2O to fatty acids and glyceride glycerol in vivo in IBAT after VMH stimulation were almost completely inhibited by sympathetic denervation. These results indicate clearly that the increases in lipogenic and thermogenic activities in IBAT in response to VMH stimulation are mediated by the sympathetic nerve supply of this tissue.
Renal regulation of interorgan glutamine flow in metabolic acidosis
Authors: Welbourne T. C. , Childress D. , Givens G.
Published: December 2017

The regulation of interorgan glutamine flow was studied in control and chronically metabolically acidotic rats. Net glutamine extraction or production across the kidneys, gut, liver, and hindquarters was determined in fasted anesthetized animals from organ blood flows and the arteriovenous glutamine concentration difference. In control animals glutamine flows from the hindquarters to the splanchnic bed. In chronic acidosis glutamine production by the hindquarters rose threefold and was redirected to the kidneys; splanchnic bed glutamine uptake was eliminated. Associated with this was a 39% fall and a 62% rise in arterial glutamine and ammonia concentrations, respectively. Removing the kidneys from the circulation returned arterial glutamine and ammonia concentrations to control nonacidotic levels within 30 min. Net glutamine production by the hindquarters decreased, whereas splanchnic bed glutamine extraction increased. Hindquarter glutamine production appears to be modulated by renal venous ammonia; splanchnic bed glutamine extraction is load dependent, reflecting the influence of renal glutamine consumption on the steady-state arterial levels. Thus the removal of the kidneys returns interorgan glutamine flow to that observed in nonacidotic animals consistent with a major role of the kidneys in regulating glutamine flow and nitrogen metabolism in chronic metabolic acidosis.
Osmoregulation during high salt intake: relative importance of drinking and vasopressin secretion
Authors: Cowley A. W. , Skelton M. M. , Merrill D. C.
Published: December 2017

Studies determined the relative contribution of drinking vs. vasopressin secretion in the regulation of extracellular osmolality in response to changes of Na intake. Daily Na intake was increased from 30 to 200 meq in dogs maintained under three conditions: normal dogs with ad libitum drinking, normal dogs with "fixed drinking," and neurohypophysectomized dogs with "fixed drinking" and vasopressin replaced by continuous infusion. (Drinking was fixed to that amount consumed during the normal Na control period.) The mechanisms of osmoregulation were highly nonlinear. As daily Na intake increased from 30 to 100 meq, renal natriuretic mechanisms predominated with only small contributions from either the thirst or vasopressin systems. At high levels of Na intake (200 meq/day), both drinking and vasopressin release contributed significantly to osmoregulation. The studies also determined that, in the absence of excess vasopressin secretion and increased drinking, plasma osmolality rose to nearly twice the levels as those observed in normal dogs that increased vasopressin secretion. We conclude that vasopressin-related renal conservation of water contributes to buffering the rise of osmolality when Na intake is increased without increased drinking. The studies also confirm that with available water to drink, the thirst mechanism together with renal Na excretory mechanisms are the predominant controllers of osmolality in situations of high sodium intake.
Some metabolic and behavioral effects of adrenalectomy on obese Zucker rats
Authors: Castonguay T. W. , Dallman M. F. , Stern J. S.
Published: December 2017

Ten-week-old female obese and lean Zucker rats were given access to three separate macronutrient sources (casein, starch, and lard) for 7 days. They were then either adrenalectomized (ADX) or given a sham operation. Rats were assigned to one of three groups and given a daily injection of either 0, 2, or 10 mg of corticosterone. They continued to select a diet for another 17 days, after which they were killed, and their blood was assayed for corticosterone, adrenocorticotropin hormone (ACTH), insulin, glucose, and triglyceride. Retroperitoneal and parametrial fat depots were excised and sampled for lipoprotein lipase activity, fat cell size, and number. Body composition was also determined. Selection patterns of lean and obese rats were markedly affected by both ADX and corticosterone replacement. All three groups of sham-operated obese rats ate significantly more fat than did sham-operated lean rats. Adrenalectomy significantly reduced fat intakes in both obese and lean rats. Corticosterone therapy restored fat appetites of lean and obese rats in a dose-dependent fashion. In comparison to ADX lean rats, ADX obese rats reduced their normally elevated levels of blood glucose, plasma triglycerides, and insulin to within normal limits. Similarly, adipose cellularity of the ADX obese rats was reduced to that of sham-operated lean rats. Carcass fat was significantly reduced after adrenalectomy. Corticosterone therapy prevented the reduction in a dose-dependent way.
A limit cycle mathematical model of the REM sleep oscillator system
Authors: McCarley R. W. , Massaquoi S. G.
Published: December 2017

A limit cycle mathematical model of the rapid-eye-movement (REM) sleep oscillator system has been developed from a structural model of interaction of populations of REM-on and REM-off neurons. The marked differences in latency, amplitude, and duration of the first REM sleep period seen with circadian variation and depressive pathology are modeled by beginning the REM oscillation at different initial points relative to the final position in the limit cycle. Beginning from a point that is graphically interior to the limit cycle produces a long-latency, short-duration, and less intense first REM period. Beginning from a point graphically exterior to the limit cycle produces a short-latency, long-duration, and more intense first REM period. In the model the determinant of whether the oscillation begins exterior or interior to the limit cycle is the time course of decay of the REM-off population discharge activity at sleep onset. When this time course is made to depend on circadian phase, the model produces a very close match to the empirically observed large shifts between the first and second REM periods in duration (often a 50% change) and intensity and also closely mimics the empirically observed shifts in REM latency as human sleep begins at different circadian phases. Although this variation in limit cycle entry accounts for the major changes in REM sleep over the night, the model also postulates a continuous but small circadian variation (of the order of +/- 5% change in REM parameters) acting throughout the course of a night's sleep. Because the model is derived from actual physiological data, rather than being a purely ad hoc or phenomenological construct, it offers the possibility of direct tests of its postulates through neurobiological studies in animals, by circadian phase-related manipulations of the sleep cycle, and through perturbations of the system in humans by the use of drugs. Indeed, an explicit phase-response curve of the system to cholinergic agonists has been developed; this will permit experimental tests of the model in both animals and humans.
Development of bronchiolar epithelium in rats
Authors: Massaro Gloria D. , Massaro Donald
Published: December 2017

Page R783: Gloria D. Massaro and Donald Massaro. “Development of bronchiolar epithelium in rats.” Pages R785–R786: the values for the nuclear numerical density in Fig. 1 and Tables 1 and 2 of the original article should be multiplied by 4. The error does not effect in any way the statistical calculations or the conclusions. Corrected Fig. 1 and Tables 1 and 2 should be substituted.

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Effect of permanent access to operant heating on energy balance of growing pigs
Authors: Swiergiel A. H.
Published: December 2017

Early-weaned littermate piglets were acclimated to cold for 3 wk and then housed for 6 wk at a room temperature of 10 degrees C in individual cages. Half the littermates (OP) could switch on a heater and thus adjust temperature within a cage; the other half (CP) had access to a source of light only. Food was available ad libitum. It was found that when the room temperature was 10 degrees C OP maintained cage temperature at 17.3 degrees C, whereas that of CP was at 10.4 degrees C (P less than 0.001); rectal temperature of OP was 0.4 degree C (P less than 0.01), and locomotor activity 19.9% (P less than 0.001) higher than in CP. Oxygen consumption measured at 25 degrees C was 12.5% lower (P less than 0.05) in OP than CP, but did not differ when measured at 10 degrees C. There were no differences in food intake and growth rate, but the food conversion ratio was improved by 10.9% (P less than 0.01) in OP in comparison with CP. By the end of the experiment CP had shorter bodies, tails and snouts and smaller heads and ears than CP. No difference in distribution of tissues, size of internal organs, or dry matter and energy content in tissues was observed between the groups. The role of autonomic vs. behavioral thermoregulation in maintaining a mammal's energy balance and thermal homeostasis is discussed.
Level of alimentation and line of breeding on oxygen uptake by ovine jejunal mucosa
Authors: Rompala R. E. , Johnson D. E. , Rumpler W. V. , Phetteplace H. W. , Parker C. F.
Published: December 2017

Targhee rams from a selected and control line of breeding were provided with the same diet at either 100 or 40% of ad libitum feed intake levels for 28 days. The rams were killed in a serial fashion over a 35-day period. A sample of the jejunum mucosa was taken, and O2 consumption rates with and without ouabain were measured. Total O2 consumption and ouabain-sensitive respiration rates of the jejunal mucosa taken from rams of the select line were greater than for samples taken from the control rams. Line of breeding did not influence the percent of the total O2 consumption that was ouabain sensitive and the proportion of the jejunum that was mucosa. Differences in rates of total and ouabain-sensitive O2 consumption attributed to level of feed intake were not detected as significant. Both the percentage of the total respiration rates that was ouabain sensitive and the proportion of the jejunum that was mucosa were greater for rams fed at high intake levels compared with rams fed at low intake levels. Thus both breeding sheep on the basis of improved growth potential and level of alimentation influenced aspects of jejunal mucosa respiration that was Na+-K+-adenosinetriphosphatase dependent.
Control of atrial natriuretic factor release from a rat heart-lung preparation
Authors: Dietz J. R.
Published: December 2017

These experiments examined the effects of altering venous return, aortic pressure, or perfusate sodium concentration on the release of atrial natriuretic factor (ANF) from a rat heart-lung preparation. Changes in perfusate ANF concentration during each time period (delta ANF) were used as an index of ANF secretion. Raising the height of the venous return reservoir from 2-3 to 5-7 cm above the heart increased delta ANF from 88 +/- 19 to 748 +/- 154 pg X ml-1 X 10 min-1 (P less than 0.01, n = 7). In control experiments where the height of the reservoir was not increased, delta ANF was unchanged (65 +/- 35 vs. 43 +/- 26 pg X ml-1 X 10 min-1, n = 6). Increasing aortic pressure from 60 to 100 mmHg increased ANF from 43 +/- 10 to 107 +/- 20 pg X ml-1 X 15 min-1 (P less than 0.05, n = 6). Separate groups of heart-lung preparations were perfused with solutions with sodium concentrations of 132 +/- 1, 144 +/- 2, or 166 +/- 1 meq/l (n = 8/group). delta ANF was 45 +/- 14, 50 +/- 17, and 52 +/- 22 pg X ml-1 X 10 min-1, respectively. These values were not significantly different. These results suggest that ANF plays a role in the control of blood volume and blood pressure but do not support a role for ANF in the control of plasma sodium concentration.
Dynamics of insulin resistance in denervated slow and fast muscles in vivo
Authors: Turinsky J.
Published: December 2017

Sciatic nerve in one hindlimb of rats was sectioned, and animals were investigated 3, 6, 9, and 24 h and 3, 8, and 17 days after surgery. Cellular uptakes of 2-deoxy-D-glucose (DG) and alpha-aminoisobutyric acid (AIB) by soleus, plantaris, and gastrocnemius muscles of the denervated and contralateral sham hindlimb were compared in vivo. Effects of insulin on DG and AIB uptakes by soleus and plantaris muscles, but not gastrocnemius muscles, were reduced 20-58% as early as 3-6 h after denervation. Three to 17 days after denervation, soleus muscle did not respond to insulin stimulation of DG uptake, whereas plantaris and gastrocnemius muscles responded, but the insulin-induced increment in DG uptake was reduced 24-68% compared with the sham muscles. In contrast, none of the denervated muscles increased AIB uptake in response to insulin stimulation 3-17 days after surgery. The levels of creatine phosphate and ATP in calf muscles frozen in situ 3 days after denervation were increased 7 and 9%, respectively, and those of ADP, AMP, glucose-6-phosphate, and lactate were unchanged compared with sham muscles. It is concluded that muscle denervation results in a rapid development of insulin resistance, the effect of denervation depends on muscle fiber population, and insulin resistance of denervated muscles is not due to a cellular energy deficit.
Hypoxic moderation of systemic hypertension in the spontaneously hypertensive rat
Authors: Henley W. N. , Tucker A.
Published: December 2017

The mechanism by which chronic, moderate, hypobaric hypoxia attenuates systemic systolic blood pressure (SBP) in the spontaneously hypertensive rat (SHR) was investigated in a three-part study. In experiment 1, 10 wk of hypoxia (3,658 m altitude) commencing in 7-wk-old rats was partially effective in preventing the rise in SBP [hypoxic SHR (SHR-H) 154 mmHg vs. normoxic SHR (SHR-N) 180 mmHg; P less than 0.01]. When hypoxia was initiated in 5-wk-old SHR (experiments 2 and 3), protection against hypertension was nearly complete (experiment 2: SHR-H 122 mmHg vs. SHR-N 175 mmHg; P less than 0.001; experiment 3: 135 vs. 152 mmHg, respectively; P less than 0.05). Elevations in O2 consumption (VO2) and rectal temperature (Tre) in SHR vs. normotensive [Wistar-Kyoto (WKY)] rats provided evidence that the SHR is a hypermetabolic animal. Thyroid hormonal indices suggested that SHR changed from a low to high thyroid status at a time that rapid blood pressure elevation occurred; however, hypoxia did not influence thyroid status. Acute, significant decrements in VO2 and Tre in SHR-H (experiments 2 and 3) accompanied the attenuation of SBP by hypoxia, whereas large decrements in VO2 and SBP did not occur in hypoxic WKY. Timely administration of moderate hypoxia protects against the development of hypertension in the SHR. This protection may relate to a metabolic adaptation made by the hypoxic SHR.
Basolateral glucose transport by intestine of teleost, Oreochromis mossambicus
Authors: Reshkin S. J. , Ahearn G. A.
Published: December 2017

Transport characteristics of D-glucose by isolated basolateral membrane vesicles of the teleost fish, Oreochromis mossambicus, were measured. Specific activity of the vesicle Na-K-adenosinetriphosphatase was increased 11-fold, whereas specific activities of brush-border and organelle membrane enzymes were enriched only 0.3- to 0.8-fold. Vesicles had diameters of 0.1-0.4 micron, 70% of vesicles were leaky (unsealed), and 60% of sealed vesicles were inside out. D-Glucose transport occurred by stereospecific facilitated diffusion, independent of 120 mM gradients of either NaCl or KCl, and was inhibited by sulfhydryl reagents, phloretin, and cytochalasin B, but not by phloridzin. Competition studies with a range of sugars demonstrated that aldohexoses in the C-1 chair conformation were preferred substrates and probably share the same carrier. Kinetic analysis of glucose influx yielded a Kt of 10 mM and a Jmax of 3,910 pmol X mg protein-1 X min-1. Fish intestinal basolateral D-glucose transport closely resembles that of mammalian or avian intestinal epithelia and of red blood cell plasma membrane. The magnitude of transport is much lower in fish than in other vertebrates, which may be related to lower metabolic rates in these poikilotherms.
Hormonal regulation of hepatic glycogenolysis in the carp, Cyprinus carpio
Authors: Janssens P. A. , Lowrey P.
Published: December 2017

Carp (Cyprinus carpio) liver maintained normal glycogen content and enzyme complement for several days in organ culture. Epinephrine-stimulated glycogenolysis, phosphorylase activation, and cyclic AMP (cAMP) accumulation in a concentration-dependent manner with EC50s of 100, 100, and 500 nM, respectively. These actions were blocked by the beta-adrenergic antagonist, propranolol, but not by the alpha-adrenergic antagonist phentolamine. Glycogenolysis and tissue cAMP were uninfluenced by 10(-6) M arginine vasotocin, arginine vasopressin, lysine vasotocin, lysine vasopressin, mesotocin, or oxytocin, but were slightly increased by 10(-5) M isotocin and slightly decreased by 10(-6) M angiotensin II. [125I]-iodocyanopindolol (ICP), a beta-adrenergic ligand, bound to isolated carp liver membranes with a KD of 83 pM. Maximum binding of 45 fmol/mg protein was at 600 pM. Propranolol, isoprenaline, epinephrine, phenylephrine, norepinephrine, and phenoxybenzamine displaced ICP with KDs of 100 nM, 2, 20, 20, 60, and 200 microM, respectively. The alpha-adrenergic antagonists, yohimbine and prazosin, showed no specific binding. These data provide evidence that catecholamines act via beta-adrenergic receptors in carp liver and that alpha-adrenergic receptors are not present. Vasoactive peptides play no significant role in regulation of carp liver glycogenolysis.
Does vasopressin-induced vasoconstriction persist during prolonged infusion in dogs?
Authors: Liard J. F.
Published: December 2017

I have examined the systemic and regional hemodynamic effects of an intravenous arginine vasopressin (AVP) infusion at a rate of 220 pg X kg-1 X min-1 maintained for 48 h in 12 conscious dogs. Plasma AVP concentration increased from 2.8 +/- 1.1 to 8.2 +/- 1.4 pg/ml, and plasma osmolality fell from 294.8 +/- 1.4 to 287.1 +/- 1.5 mosmol/kg. Mean arterial pressure increased slightly but significantly despite a reduction in blood volume. Contrary to what we previously observed with 1-h AVP infusion at the same rate, cardiac output and heart rate did not decrease, and total peripheral resistance did not increase. Most vascular beds sensitive to the acute vasoconstrictor effects of AVP, such as those of the skeletal muscle, fat, colon, and skin, did not show any significant reduction in blood flow after 48 h. Only in the pancreas and in the thyroid gland was there a significant flow decrease, which was similar in magnitude to that measured after 1 h of infusion. It therefore appears that vasoconstriction induced by modest increases in plasma concentrations of AVP is not maintained during prolonged administration in most vascular beds. However, injection of a specific antagonist of the pressor action of AVP [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine]arginine vasopressin, 10 micrograms/kg, induced a significant increase in cardiac output and heart rate, as well as a fall in total peripheral resistance and significant increases in myocardial, fat, and skin blood flows after 48 h of AVP infusion.(ABSTRACT TRUNCATED AT 250 WORDS)