bluuebunny/crossref_metadata_2025 huggingface dataset:
Alterations in body fat stores and plasma insulin levels with daily intervals of heat exposure in Holtzman rats
Authors: De Souza C. J. , Meier A. H.
Published: December 2017

The ability of timed daily increases in ambient temperature (from 22 +/- 1 degree C to 40 +/- 1 degree C for 2 h) to alter body fat stores, blood lipid levels, and insulin resistance were tested in male Holtzman rats. Of the six times of day tested only temperature pulses administered 16 h after light onset consistently decreased body weights, retroperitoneal fat stores, and plasma insulin levels. Subsequently, temperature pulses were administered either 0 (TP0) or 16 (TP16) h after light onset (light-dark 12:12 h). While no differences were observed between the TP0 group and the constant temperature (22 degrees C) controls, decreases in body weight gain, food consumption, retroperitoneal fat stores, and plasma concentrations of insulin, cholesterol, and triglycerides were consistently observed in the TP16 group. Although changes in plasma glucose during an oral glucose tolerance test were similar when the two treatment groups were compared with their respective controls, glucose tolerance was achieved with less insulin in the TP16 animals than in their respective controls. Insulin effectiveness was greater in the TP16 group as indicated by a decrease in plasma glucose, after insulin injection, that was of greater magnitude and longer duration than in controls. Hence, timed daily increases in ambient temperature may decrease obesity in part by decreasing plasma insulin levels apparently as a consequence of increased tissue sensitivity to insulin (greater glucose tolerance and less insulin intolerance). Because the treatment is effective only at a particular time of day the findings support a role for circadian neuroendocrine interactions in the regulation of these metabolic states.
Psychoneuroendocrine profile associated with hypertension or hyperactivity in spontaneously hypertensive rats
Authors: Castanon N. , Hendley E. D. , Fan X. M. , Mormede P.
Published: December 2017

The behavioral and neuroendocrine reactivity to a novel environment (open field) and the adrenocorticotropic hormone (ACTH)/corticosterone response to a corticotropin-releasing factor (CRF) challenge were measured in 2-mo-old rats from four inbred strains derived from the Wistar-Kyoto rat: spontaneously hypertensive rats (SHRs), hypertensive and behaviorally hyperactive to novelty; WKY, neither hypertensive nor hyperactive; WKHA, hyperactive but normotensive; and WKHT, only hypertensive. The ACTH response to CRF was much lower in SHRs than WKYs, this reduced reactivity being clearly associated with the hyperactivity trait, since it was present in the WKHA and absent in the WKHT strain. On the other hand, the ACTH/corticosterone response to a psychological stimulus (open field) could not clearly discriminate the four strains. The largest difference was found in the prolactin response. Post-open-field levels were much lower in the WKHA (27.11 +/- 4.69 ng/ml) than in the parent WKY strain (83.65 +/- 6.84 ng/ml), the hypertensive strains having intermediate levels (WKHT: 58.05 +/- 7.65 ng/ml; SHR: 64.13 +/- 7.19 ng/ml). Other differences were also found in the levels of aldosterone and renin activity. These results indicate that these strains are an excellent model to study neuroendocrine correlates of hypertension and hyperactivity, which are associated in the SHR strain and may be of interest for the study of the association between neuroendocrine and behavioral characteristics.
Interaction between temperature and hypoxia in the alligator
Authors: Branco L. G. , Portner H. O. , Wood S. C.
Published: December 2017

Hypoxia elicits behavioral hypothermia in alligators. Under normoxic conditions, the selected body temperature is 27.8 +/- 1.2 degrees C. However, when inspired O2 is lowered to 4%, selected body temperature decreases to 15.4 +/- 1.0 degrees C. The threshold for the behavioral hypothermia is between 4 and 5% inspired O2, the lowest threshold measured so far in terrestrial vertebrates. This study assessed the physiological significance of the behavioral hypothermia. The body temperature was clamped at 15, 25, and 35 degrees C for measurements of ventilation, blood gases, metabolic rate, plasma lactate, and acid-base status. Hypoxia-induced changes in ventilation, acid-base status, oxygen consumption, and lactate were proportional to body temperature, being pronounced at 35 degrees C, less at 25 degrees C, and absent at 15 degrees C. The correlation between selected body temperature under severe hypoxia and the measured parameters show that behavioral hypothermia is a beneficial response to hypoxia in alligators.
Acute exercise and skeletal muscle antioxidant and metabolic enzymes: effects of fiber type and age
Authors: Lawler J. M. , Powers S. K. , Visser T. , Van Dijk H. , Kordus M. J. , Ji L. L.
Published: December 2017

Inhibition of metabolic enzyme activity has been associated with free radical stress in locomotor muscle with prolonged or intense exercise. However, it is not known whether such alterations with acute exercise in skeletal muscle are influenced by muscle fiber type or age. Twenty 4-mo-old and twenty 24-mo-old female Fischer-344 rats were divided at random into young exercised (YE; n = 10), old exercised (OE; n = 10), young control (YC; n = 10), and old control (OC; n = 10) groups. Animals in both YE and OE groups ran on a treadmill (10% uphill grade) for 40 min at approximately 75% of each age-group's maximal O2 consumption. Immediately after the treadmill run, white gastrocnemius (WG), red gastrocnemius (RG), and soleus (SOL) muscles were removed and quick-frozen in liquid nitrogen. Malondialdehyde was significantly increased (P < 0.05) in RG of YE vs. YC rats. Glutathione peroxidase activity was significantly elevated (P < 0.05) in the WG of YE rats. Analysis of variance revealed a significant over-all increase in superoxide dismutase activity with exercise. Activities of phosphofructokinase (PFK), citrate synthase, succinate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase were unchanged (P > 0.05) with acute exercise in the SOL. However, PFK activity was decreased in the WG by 60% in OE but only 33% in YE, and in the RG by 41% in OE but only 21% in YE. We conclude that maximal glycolytic flux in the gastrocnemius may be adversely affected by acute exercise, and this effect was more pronounced in the 24-mo-old group.
Identification and characterization of CCK-B/gastrin receptors in human pancreatic cancer cell lines
Authors: Smith J. P. , Liu G. , Soundararajan V. , McLaughlin P. J. , Zagon I. S.
Published: December 2017

The gastrointestinal peptide cholecystokinin (CCK) is known to stimulate growth of human pancreatic cancer in a receptor-mediated fashion. The purpose of this study was to characterize the receptor responsible for the trophic effects of CCK in cancer cells. With the use of homogenates of PANC-1 human pancreatic cancer cells grown in vitro, the binding characteristics and optimal conditions of radiolabeled selective CCK-receptor antagonists ([3H]L-365,260 and [3H]L-364,718) were examined. Specific and saturable binding was detected with [3H]L-365,260, and Scatchard analysis revealed that the data were consistent for a single site of binding with a binding affinity of 4.3 +/- 0.6 nM and a binding capacity (Bmax) of 283 +/- 68 fmol/mg protein in log phase cells. Binding was dependent on protein concentration, time, temperature, and pH and was sensitive to Na+, K+, Mg2+, and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid. In contrast to log phase cells, Bmax decreased by 80 and 92% in confluent and postconfluent cultures, respectively. Subcellular fractionation studies revealed that binding was in the membrane fraction. Competition experiments indicated that L-365,260 and gastrin were more effective at displacing the radiolabeled L-365,260 than CCK. No binding was detected with the CCK-A antagonist [3H]L-364,718. Assays performed with [3H]L-365,260 on five additional human pancreatic cancer cell lines in vitro and tumor tissue from xenografts in nude mice also revealed specific and saturable binding. These results provide the first identification of a CCK-B/gastrin receptor in human pancreatic cancer cells and tumors and explain the effects of CCK on the growth of this malignancy.
Strain differences in hypothalamic-pituitary-adrenal activity and stress ulcer
Authors: Redei E. , Pare W. P. , Aird F. , Kluczynski J.
Published: December 2017

Strain differences in stress responsiveness have been previously described, but specific components of the hypothalamic-pituitary-adrenal (HPA) axis responsible for stress hypo- or hyperactivity have not yet been characterized. This study proposed to analyze the effect of restraint stress on different measures of HPA function and stress ulcer in stress-ulcer prone Wistar-Kyoto (WKY) and Fisher 344 (F-344) rats and in the ulcer-resistant Wistar strain. Adult male rats of these strains were sham adrenalectomized, adrenalectomized, and adrenalectomized-replaced with corticosterone pellet. Ten days after surgery, animals were subjected to the 2-h ulcerogenic water-restraint stress and killed 2 h later. Intact WKY rats had dramatically more ulcers and higher anterior pituitary adrenocorticotropic hormone (ACTH) and proopiomelanocortin mRNA levels than the other two strains. In WKY rats, adrenalectomy increased ulcer incidence but did not affect thymus weight, ACTH content, or hypothalamic corticotropin-releasing factor mRNA levels, in contrast to the profound effects of adrenalectomy on these parameters in the other strains. Furthermore, corticosterone replacement was either without effect or enhanced the effect of adrenalectomy on these parameters in WKY rats, while it reversed the effects of adrenalectomy in the other strains. These data imply that WKY rats respond to stress with enhanced and prolonged changes in peripheral functions that are regulated by glucocorticoids, suggesting the presence of impaired efficacy of the glucocorticoid negative feedback on HPA function.
Nitric oxide-dependent and -independent components of cerebrovasodilation elicited by hypercapnia
Authors: Iadecola C. , Zhang F.
Published: December 2017

We studied the effect of nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on the increases in cerebral blood flow (CBF) elicited by stepwise elevations in arterial partial pressure of CO2 (PaCO2) from normocapnia up to 204 mmHg. Rats were anesthetized with halothane and ventilated. CBF was monitored over the parietal cortex using a laser-Doppler flowmeter. Increasing levels of hypercapnia elicited graded elevations in CBF that reached a plateau at PaCO2 = 82 +/- 1 mmHg (CBF +215 +/- 25%; n = 8; P < 0.05, analysis of variance). L-NAME (40 mg/kg i.v.; n = 8), but not nitro-D-arginine methyl ester (n = 8), reduced resting CBF (-42 +/- 4%) and attenuated the increase in CBF elicited by hypercapnia. The attenuation occurred only at PaCO2 40-80 mmHg and was maximal (-75 +/- 8%; P < 0.05) at 54 +/- 2 mmHg. At PaCO2 > or = 100 mmHg, L-NAME (40-80 mg/kg) did not attenuate the response (P > 0.05). Reduction of resting CBF (-50 +/- 4%; n = 6) by administration of chloralose (20-40 mg/kg i.v.) did not attenuate the CBF response to hypercapnia (P > 0.05). We also found that the attenuation by L-NAME of resting CBF (n = 5) and of the cerebrovasodilation elicited by hypercapnia (n = 6) has a relatively slow time course, the effects reaching a maximum 45-60 min after intravenous administration of the drug. We conclude that L-NAME does not attenuate the CBF response to CO2 uniformly at all levels of hypercapnia.(ABSTRACT TRUNCATED AT 250 WORDS)
Transport of PAH, urate, TEA, and fluid by isolated perfused and nonperfused avian renal proximal tubules
Authors: Brokl O. H. , Braun E. J. , Dantzler W. H.
Published: December 2017

Transport of organic anions [p-aminohippurate (PAH) and urate] and organic cations [tetraethylammonium (TEA)] and reabsorption of fluid were studied for the first time in individual renal proximal tubules isolated from avian kidneys. In isolated nonperfused tubules, PAH and urate uptake occurred against electrochemical gradients, whereas TEA uptake appeared to result from the electrical gradient. Radiolabeled PAH uptake and radiolabeled urate uptake were inhibited to an equal extent by high concentrations of unlabeled PAH and probenecid, suggesting that they might share the same transport system. However, the rate of uptake of radiolabeled PAH was significantly stimulated by preloading with alpha-ketoglutarate (alpha-KG), suggesting PAH/alpha-KG countertransport as in mammals and reptiles, whereas uptake of radiolabeled urate was not clearly stimulated. In isolated perfused tubules, net fluid reabsorption averaged approximately 2 nl.min-1.mm-1 and was inhibited by ouabain with or without bicarbonate in the perfusate and bathing medium. In these perfused tubules, the unidirectional bath-to-lumen fluxes of PAH and urate exceeded the unidirectional lumen-to-bath fluxes, indicating net secretion of both compounds. During the bath-to-lumen fluxes the uptake across the basolateral membrane was against an electrochemical gradient for both compounds. However, for PAH the steady-state intracellular concentration was about half that observed in nonperfused tubules, as generally expected during net secretion, whereas for urate the steady-state intracellular concentration was about twice that observed in nonperfused tubules, suggesting stimulation of uptake during net secretion. During the PAH lumen-to-bath flux, the steady-state intracellular concentration was significantly above that in the perfusate, suggesting that this flux involved transport into the cells from the lumen against an electrochemical gradient. However, during the urate lumen-to-bath flux, there was no urate in the cells, suggesting that this flux, as in reptiles, occurred by a paracellular route.
Energy and protein requirements for molt in the king penguin Aptenodytes patagonicus
Authors: Cherel Y. , Charrassin J. B. , Challet E.
Published: December 2017

Adult king penguins annually fast ashore for 1 mo for molting. By the end of molt, they have lost 44% of their prefasting body mass. About 18% of new feather synthesis occurs at sea, thus reducing both nutrient requirement and fasting duration. Plumage synthesis continues during the first 3 wk of fasting. Loss of old feathers occurs between day 12 and day 21 of the molt, and it is associated with a peak in daily body mass loss. The dry mass of epidermal structure synthesized during molt is 395 g. Body composition analysis indicates that fat oxidation accounts for 85% of total energy expenditure. The proportion for protein is 15%, a value twofold higher than during the breeding (nonmolting) fast. The mean energy expenditure is also 21% higher during the molting fast (3.04 W/kg). Compared with other birds, the energetic cost of feather synthesis is the lowest in king penguins (85 kJ/g) and consequently the energetic efficiency is the highest (25%). Changes in tissue composition during molt show that integument is the main lipid source (72% of the lipid loss) and thus the main source of energy (61% of the total energy expenditure). The integument and the pectoral muscles play a major role in molting protein metabolism, providing 20 and 57%, respectively, of the total protein needs for feather synthesis and/or energy expenditure. This result emphasizes the role of integument as a protein source, because the large premolting muscle hypertrophy is not sufficient to account for the totality of the protein cost of molt.
Surfactant composition and function in lungs of air-breathing fishes
Authors: Smits A. W. , Orgeig S. , Daniels C. B.
Published: December 2017

Examination of lung washings from primitive air-breathing fishes (ropefish, bichirs, and gar) revealed a lipid-based surfactant with an average disaturated phospholipid-to-total phospholipid ratio five times lower than in mammals. The lung lavage of fishes was exceptionally rich in cholesterol, resulting in average cholesterol-to-phospholipid ratios three times higher, and cholesterol-to-disaturated phospholipid ratios nearly 15 times higher, than those of mammals. Removal of lung surfactant doubled the pressures necessary to initially open the anterior regions of collapsed lungs in all three fish species but had little or no effect on pressures required to fill the lung (i.e., compliance) after the initial opening. The elevated cholesterol content found in pulmonary surfactant of these fishes is consistent with such findings in other ectotherms, suggesting that the proportional elevation of cholesterol may serve to stabilize the fluidity of the lung surfactant over broader temperature ranges. The influence of surfactant on lung opening pressures rather than on compliance contrasts with that seen in mammals and supports an "antiglue" role of pulmonary surfactant in the simpler open-design lungs of lower vertebrates.
Effects of renal denervation on postprandial sodium excretion in experimental heart failure
Authors: Villarreal D. , Freeman R. H. , Johnson R. A. , Simmons J. C.
Published: December 2017

The hormonal, hemodynamic and renal excretory changes after an oral load of sodium were examined in renal-denervated dogs with an arteriovenous (AV) fistula and the syndrome of compensated high-output heart failure. After ingestion of a meal containing 125 meq of sodium, the total postprandial urinary sodium excretion and fractional sodium excretion were approximately twofold higher in the renal-denervated AV fistula dogs, compared with a control group with intact renal nerves (P < 0.05). The postprandial elevations in right atrial pressure, plasma atrial natriuretic factor, and filtered load of sodium were similar in the two groups (P > 0.05). Mean arterial pressure and plasma renin activity remained unchanged from baseline in the two subsets of animals (P > 0.05). In the renal-denervated AV fistula dogs, ingestion of a low-salt meal containing 2-3 meq of sodium produced elevations in creatinine clearance and filtered load of sodium of similar magnitude to the high-salt meal. However, the increases in sodium excretion and plasma atrial natriuretic factor were modest and inconsistent. These results demonstrate that the renal nerves play an important modulatory role for postprandial sodium metabolism after a high-salt meal in experimental compensated high-output heart failure. It is suggested that the renal nerves attenuate the expression of postprandial natriuretic mechanisms via a direct tubular mechanism of action.
Quantitative modeling and biology: the multivariate approach
Authors: Benigni R. , Giuliani A.
Published: December 2017

Even though elegant examples of mathematical modeling of biological problems exist, such approaches still remain outside the domain of most biologists. It is proposed that, for a wider and more systematic use of mathematical models in biology, the soft modeling approaches, which are applicable to phenomena with a limited level of definition, should be investigated and preferred. In particular, multivariate data analysis (MDA) is indicated as an important tool toward fulfilling this goal. This paper reviews the general principles of MDA and examines in detail principal component analysis and cluster analysis, which are two of the most important MDA techniques. A number of applications to real biological problems are presented. These examples show how the construction of classifications corresponds to the generation of new knowledge and new concepts, which are hierarchically on a higher level than the initial information. This new form of knowledge is obtained without superimposing a priori theories on the data. It is demonstrated how the MDA can lead to the identification of biological systems; also shown is their ability to describe multiple scale phenomena, a typical feature of biological systems. Moreover, the multivariate analyses provide new descriptors for a given biological system; these descriptors are quantitative, thus allowing the system to be described in a "metric space," where it then becomes possible to use any other mathematical tool.
Modulation of autonomic nervous system adjustments to heat stress by central ANG II receptor antagonism
Authors: Kregel K. C. , Stauss H. , Unger T.
Published: December 2017

The purpose of this study was to determine whether central angiotensin II (ANG II) participates in mediating selected sympathetic nervous system and neuroendocrine adjustments to heat stress in conscious freely moving rats. Mean arterial pressure (MAP), heart rate (HR), splanchnic sympathetic nerve activity (SpNA), plasma arginine vasopressin (AVP) concentration, and colonic temperature were measured before and during whole body heating (42 degrees C ambient temperature). Heating was stopped when a colonic temperature of 41 degrees C was attained. On consecutive days, rats received an intracerebroventricular (icv) injection of saline (0.9%) or 25 micrograms of the ANG II AT1-selective receptor antagonist losartan 20 min before the start of heating. Neither treatment influenced control levels of any parameter. The increase above baseline for MAP at the end of heating was attenuated by > 50% in the losartan, compared with the saline trial (P < 0.05), while HR remained unchanged from control values for both trials. Pretreatment with losartan icv eliminated the increase in SpNA observed during the heating period in the saline trial. Furthermore, the magnitude of change in plasma AVP during heating was significantly elevated in rats after icv administration of saline compared with losartan. These findings indicate that central ANG II receptor antagonism significantly attenuates the heating-induced elevations in MAP, sympathetic neural activity to visceral regions, and plasma AVP and suggest that the central nervous system actions of endogenous ANG II are required for full expression of the sympathoexcitatory, pressor, and neuroendocrine responses associated with nonexertional heat stress in the conscious rat.
Temporal cascade of plasma level surges in ACTH, corticosterone, and cytokines in endotoxin-challenged rats
Authors: Givalois L. , Dornand J. , Mekaouche M. , Solier M. D. , Bristow A. F. , Ixart G. , Siaud P. , Assenmacher I. , Barbanel G.
Published: December 2017

The present study was designed to investigate the coupling mechanisms linking the immune and the neuroendocrine corticotropic systems in an integrated defense response triggered by an infectious aggression. The experimental paradigm used consisted of the exploration in individual conscious rats of the temporal pattern of increased plasma concentrations of the two stress hormones, adrenocorticotropic hormone (ACTH) and corticosterone (Cort), and of three cytokines known as ACTH stimulators, tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, and IL-6, after intra-arterial infusions of lipopolysaccharide (LPS) given at three doses, 5 micrograms/kg (LPS-5), 25 micrograms/kg (LPS-25), and 1 mg/kg (LPS-1,000). Blood samples were taken 30 min and immediately before LPS injection (t0) and at 15, 30, 60, 120, 300, and 480 min post-LPS. The three doses of LPS induced ACTH and Cort surges, starting after 30 min for LPS-5 and LPS-25 or 15 min for LPS-1,000 and peaking with a similar amplitude at 60 min before receding slowly to baseline at 480 min for the two lower LPS doses. On the other hand, whatever the LPS dose, none of the three cytokines rose above undetectable basal levels before 60 min. They increased thereafter to culminate 10- to 30-fold above baseline at 60 min (TNF-alpha) or 120 min (IL-1 beta and IL-6) after LPS and declined back to basal levels at 300 min (TNF-alpha, all doses, and IL-6 for LPS-5 and LPS-25). After LPS-25, only IL-1 beta had not regressed to baseline levels at 480 min.(ABSTRACT TRUNCATED AT 400 WORDS)
Characterization of the urea transporter in outer medullary descending vasa recta
Authors: Pallone T. L.
Published: December 2017

Partially because of facilitated transport of urea, urea permeability (Pu) of the outer medullary descending vasa recta (OMDVR) frequently exceeds sodium permeability by more than an order of magnitude. This study characterizes the OMDVR urea transporter. Application of the urea analogue thiourea (200 mM) to the abluminal surface of microperfused OMDVR inhibited Pu by 33%. When osmolarity due to thiourea was balanced by addition of mannitol or thiourea, similar results were obtained. Thiourea produced graded inhibition of Pu from 343 +/- 54 (SE) to 191 +/- 43 x 10(-5) cm/s as concentration was increased from 0 to 100 mM. The thiourea concentration needed for half-maximal inhibition was 19 mM. The abilities of urea analogues to reduce Pu were compared by addition of 50 mM concentrations to the bath and perfusate. Thiourea and methylurea produced 32 and 34% inhibition of Pu, respectively, whereas urea and acetamide produced only 3 and 11% inhibition, respectively. The transporter showed negligible saturation as the transmural urea gradient was increased from 0 to 200 mM. Phloretin and p-chloromercuribenzenesulfonate inhibited Pu in a concentration-dependent fashion. It is concluded that a transporter confers high Pu to OMDVR. Pu is equally high when measured by urea influx or efflux. Properties of the transporter are similar to those expressed by the inner medullary collecting duct.
Thermal signals in control of selective brain cooling
Authors: Kuhnen G. , Jessen C.
Published: December 2017

In species with a carotid rete, the arterial blood destined for the brain can be cooled on its passage through the rete. The temperature difference between the blood before the rete and the brain is termed selective brain cooling (SBC). The onset and degree of cooling depend on internal body temperature. The aim of this study was to determine the brain sites where the temperature signals driving SBC are generated. Thirty-six experiments were performed in three conscious goats, which were prepared with an arteriovenous shunt, carotid loops, and hypothalamic thermodes to manipulate the temperatures of the trunk (Ttr), the hypothalamus (Thyp), the extrahypothalamic brain (Texh), or the whole brain (Tbr). In all experiments, Ttr was clamped at 39.5 degrees C. The increase of SBC was 2.1 degrees C per 1 degree C increase of Tbr (gain = 2.1). The rise of Thyp at constant Texh yielded a gain of 1.6, whereas the gain of Texh at constant Thyp was 0.7. It is concluded that onset and degree of SBC are predominantly determined by temperature signals generated in the hypothalamus itself.
Modeling red muscle power output during steady and unsteady swimming in largemouth bass
Authors: Johnson T. P. , Syme D. A. , Jayne B. C. , Lauder G. V. , Bennett A. F.
Published: December 2017

We recorded electromyograms of slow-twitch (red) muscle fibers and videotaped swimming in the largemouth bass (Micropterus salmoides) during cruise, burst-and-glide, and C-start maneuvers. By use of in vivo patterns of stimulation and estimates of strain, in vitro power output was measured at 20 degrees C with the oscillatory work loop technique on slow-twitch fiber bundles from the midbody area near the soft dorsal fin. Power output increased slightly with cycle frequency to a plateau of approximately 10 W/kg at 3-5 Hz, encompassing the normal range of tail-beat frequencies for steady swimming (approximately 2-4 Hz). Power output declined at cycle frequencies simulating unsteady swimming (burst-and-glide, 10 Hz; C-start, 15 Hz). However, activating the muscle at 10 Hz did significantly increase the net work done compared with the work produced by the inactive muscle (work done by the viscous and elastic components). Thus this study provides further insight into the apparently paradoxical observation that red muscle can contribute little or no power and yet continues to show some recruitment during unsteady swimming. Comparison with published values of power requirements from oxygen consumption measurements indicates a limit to steady swimming speed imposed by the maximum power available from red muscle.
Substance P, calcitonin gene-related peptide, and capsaicin release serotonin from cerebrovascular mast cells
Authors: Reynier-Rebuffel A. M. , Mathiau P. , Callebert J. , Dimitriadou V. , Farjaudon N. , Kacem K. , Launay J. M. , Seylaz J. , Abineau P.
Published: December 2017

Rabbit leptomeningeal arteries contain granular cells resembling mast cells that frequently contact autonomic and sensory nerve profiles. In the present in vitro study, we determined whether these cells could be stimulated by substance P (SP) and calcitonin gene-related peptide (CGRP), which are stored and released by sensory C fibers. Immunohistochemistry of the middle cerebral artery showed that 5-HT was stored only in mast cell-like granules. This pool of 5-HT decreased in a dose-dependent manner when exogenous SP and CGRP were added to the incubation solution or when endogenous neuropeptides were released from nerve terminals by capsaicin. The simultaneous administration of CGRP and SP induced a dramatic exocytosis and a 5-HT release significantly greater than the sum of the individual effects of the two neuropeptides. We conclude that, as in classical connective tissue mast cells, the amine content of these granular cells can be released by a degranulation process induced by neuropeptides. The effects of capsaicin suggest that this phenomenon can be triggered by axon reflex of C fibers. The data also provide the first evidence of a synergistic action of SP and CGRP on mast cell degranulation.
GLUT3 glucose transporter isoform in rat testis: localization, effect of diabetes mellitus, and comparison to human testis
Authors: Burant C. F. , Davidson N. O.
Published: December 2017

Facilitative hexose transporter expression was compared in rat and human testes. In rat testis, only GLUT1 and GLUT3 proteins were expressed. By contrast, human testis expressed GLUT1 and GLUT3 in addition to GLUT5. Immunocytochemical studies showed that GLUT3 was expressed in all cells of the seminiferous epithelium of rat testis, including sperm. In human testis, GLUT3 was expressed exclusively in cells juxtaposed to the lumen of the seminiferous tubule and ejaculate sperm, a pattern of expression that was identical to that of GLUT5. Induction of insulinopenic diabetes mellitus in the rat did not alter the levels or the distribution of GLUT3 protein or mRNA in the testis. Moreover insulin treatment of the diabetic rats did not produce changes in GLUT3 mRNA or protein levels. The results show that rat and human testis express the high-affinity glucose transporter GLUT3, which allows for the efficient uptake of glucose. In addition, the testis may be protected from changes in glucose transporter expression in experimental diabetes.
Regulation of NPY/NPY Y1 receptor/G protein system in rat brain cortex
Authors: Michel M. C. , Lewejohann K. , Farke W. , Bischoff A. , Feth F. , Rascher W.
Published: December 2017

Neuropeptide Y (NPY) content, NPY receptors, and alpha-subunits of the G proteins Go and Gi were determined in cerebral cortex of male normotensive Wistar-Kyoto and spontaneously hypertensive rats at 3-28 wk of age and of adult female rats. NPY lacked major effects on adenylate cyclase or inositol phosphate formation. NPY content was similar in all normotensive groups but lower in spontaneously hypertensive rats at all ages. 125I-NPY labeled a homogeneous population of Y1-like receptors. The Y1 NPY receptor number gradually increased with age with similar values in both strains but was significantly smaller in female than in male rats. The Y1 NPY receptor affinity was similar in all male groups but greater in female rats. The abundance of immunodetectable Go alpha and Gi alpha and of pertussis toxin substrates was less at 3 wk than in older rats but similar in both sexes and strains. We conclude that rat cerebral cortex contains Y1-like receptors; sex, age, and blood pressure differentially regulate NPY content, Y1 NPY receptors, and Go alpha and Gi alpha.
Dopamine-1 receptors in the proximal convoluted tubule of Dahl rats: defective coupling to adenylate cyclase
Authors: Ohbu K. , Kaskel F. J. , Kinoshita S. , Felder R. A.
Published: December 2017

We have previously reported a defect in the coupling of the renal dopamine-1 receptor (D1) to adenylate cyclase (AC) in the proximal convoluted tubule (PCT) of the spontaneously hypertensive rat (Okamoto-Aoki strain). To determine if this defect is present in another model of hypertension, we microdissected PCTs from Dahl salt-sensitive (DSS) and Dahl salt-resistant (DSR) rats on low- or high-NaCl diet. The ability of two selective D1 agonists, fenoldopam and SND-919-C12, and forskolin to stimulate AC activity in PCT was determined in each of the four groups of rats. Fenoldopam (10(-7) M) and SND-919-C12 (10(-6) M) failed to stimulate AC activity in the PCT of DSS rats whether on a low- or high-NaCl diet. In DSR rats, however, both fenoldopam and SND-919-C12 stimulated AC activity by 289-320% and 220-270%, respectively, whether on a low- or high-NaCl intake. Forskolin (10(-5) M), which directly stimulates AC activity, increased AC activity in all four groups. These studies show that in DSS rats the D1 receptor in the PCT fails to respond to D1 agonists. This defect is not a consequence of the hypertension because it was present in the DSS rats on a low-salt diet and before blood pressure elevation.
Mesenteric vascular responses to vasopressin during development of DOCA-salt hypertension in male and female rats
Authors: Stallone J. N.
Published: December 2017

Deoxycorticosterone acetate (DOCA)-salt hypertension develops to a greater extent in male (M) than in female (F) rats. To determine the role of the vasculature, reactivity to arginine vasopressin (AVP) and prostanoid output were examined in the isolated perfused mesenteric vasculature of hypertensive (HT) and normotensive-control (NTC) M and F rats after acute (1-wk) and chronic (4-wk) DOCA-salt treatment. Systolic blood pressure was significantly higher in M than in F HT rats (187 +/- 3 vs. 151 +/- 3 mmHg after 4 wk; P < 0.02). After acute treatment, vascular reactivity to AVP (maximal perfusion pressure) in HT was elevated in M (181 +/- 18 mmHg; P < 0.02) but not in F (135 +/- 6 mmHg) compared with NTC (90 +/- 6 mmHg, M vs. 119 +/- 5 mmHg, F). After chronic treatment, vascular reactivity to AVP in HT was elevated in both sexes (P < 0.02), although more in F (175 +/- 13 mmHg) than in M (141 +/- 11 mmHg). In contrast, vascular responsiveness to phenylephrine did not differ significantly between M and F NTC or HT preparations after either acute or chronic treatment. Sex differences in basal and AVP-induced 6-ketoprostaglandin (6-keto-PG) F1 alpha and PGE2 output by HT and NTC vasculature were reciprocal to sex differences in the vasoconstriction responses to AVP. After acute treatment, AVP-stimulated 6-keto-PGF1 alpha output by HT was elevated slightly in F (33.6 +/- 1.7 ng/3 min; P < or = 0.02) but not in M (49.9 +/- 4.3 ng/3 min) compared with NTC (23.5 +/- 2.6 ng/3 min, F vs. 34.7 +/- 4.9 ng/3 min, M). After chronic treatment, output by HT was enhanced in both sexes (P < or = to 0.02), although more in M (109 +/- 15.4 ng/3 min) than in F (68 +/- 6.6 ng/3 min)> These findings suggest that sex differences in the relative balance between AVP-induced vasoconstriction and vasodilatory prostanoid release may contribute to male-female differences in mesenteric vascular reactivity to AVP in NT and that disturbances in this balance may be responsible, at least in part, for the sex- and time-dependent changes in reactivity to AVP observed during the development of DOCA-salt hypertension.
Glutamine and glucose metabolism in enterocytes of the neonatal pig
Authors: Wu G. , Knabe D. A. , Yan W. , Flynn N. E.
Published: December 2017

Glutamine and glucose metabolism was studied in 0- to 21-day-old pig enterocytes. Cells were incubated at 37 degrees C for 30 min in Krebs-Henseleit bicarbonate buffer (pH 7.4) in the presence of 2 mM [U-14C]glutamine with or without 5 mM glucose, or 5 mM [U-14C]glucose with or without 2 mM glutamine. Glutamine was metabolized to ammonia, glutamate, alanine, aspartate, CO2, citrulline, ornithine, and proline, whereas glucose was converted to lactate, pyruvate, and CO2 in pig enterocytes. CO2 production from glutamine accounted for 32-36% and 3-4% of utilized glutamine carbons in 0- to 7-day-old and 14- to 21-day-old pigs, respectively. The rates of O2 consumption and metabolism of glutamine and glucose decreased in enterocytes from 2- to 14-day-old pigs compared with 0-day-old pigs. By day 14 after birth, the oxidation of glutamine and glucose as well as citrulline production had decreased by 90-95%. Arginine synthesis from glutamine occurred in cells from 0- to 7-day-old pigs but not 14- to 21-day-old ones. Glucose (5 mM) had no effect on glutamine utilization and oxidation or the production of glutamate and arginine but stimulated the formation of alanine, citrulline, and proline at the expense of aspartate. In contrast, glutamine (2 mM) inhibited glycolysis and glucose oxidation in cells from 0- to 7-day-old pigs and had no effects in 14- to 21-day-old pigs. As a result, glutamine contributed approximately 2-fold greater amounts of ATP to 0- to 7-day-old pig enterocytes than glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
Gurmarin inhibition of sweet taste responses in mice
Authors: Ninomiya Y. , Imoto T.
Published: December 2017

The inhibitory effects of gurmarin (a peptide isolated from the leaves of Gymnema sylvestre) on sweet taste responses were studied by examining the chorda tympani nerve responses to various taste substances before and after lingual treatment with gurmarin in C57BL and BALB mice. Treatment with gurmarin at 3 micrograms/ml or more selectively suppressed responses to sucrose without affecting responses to NaCl, HCl, and quinine in C57BL mice, whereas gurmarin at 100 micrograms/ml did not significantly suppress sucrose responses in BALB mice. Responses to various sweet substances in C57BL mice decreased to approximately 45-75% of control after gurmarin, and the suppressive effect of gurmarin was reversible. The profile of the residual responses of C57BL mice to various sweeteners after gurmarin was almost identical to that of BALB mice, which was hardly affected by gurmarin. These results strongly suggest that there are at least two types of sweet taste receptors in mice, gurmarin-sensitive and -insensitive. Probably, C57BL and BALB mice share an identical gurmarin-insensitive receptor, and C57BL mice also have a gurmarin-sensitive receptor.
The physiology of heat regulation
Authors: Webb P.
Published: December 2017

Heat regulation is presented as the physiological method of handling metabolic heat, instead of temperature regulation. Experimental evidence of heat regulation from the literature is reviewed, including more than 20 years of calorimetric studies by the author. Changes in heat production are followed by slow exponential changes in heat loss, which produce changes in body heat storage. Heat balance occurs at many levels of heat production throughout the day and night, and at each level there is a related level of rectal temperature. Heat flow can be sensed by the transcutaneous temperature gradient. The controller for heat loss appears to operate like a servomechanism, with feedback from heat loss and possibly feedforward from heat production. Physiological responses defend the body heat content, but heat content varies over a range that is related to heat load. Changes in body heat content drive deep body temperatures.
Chemoreceptor-sensitive neurons in commissural subnucleus of nucleus tractus solitarius of the rat
Authors: Chitravanshi V. C. , Sapru H. N.
Published: December 2017

Experiments were carried out in pentobarbital-anesthetized, vagotomized, paralyzed, and artificially ventilated male Wistar rats with a pneumothorax. Blood pressure, heart rate, and phrenic nerve activity were recorded. Extracellular neuronal recordings were made by glass micropipettes in a midline area in the commissural subnucleus of the nucleus tractus solitarius. At the end of the experiment, the recording sites were marked. Chemoreceptors were stimulated by tracheal administration of N2 or injection of CO2-saturated saline (50 microliters) near the carotid body. The baroreceptors were stimulated by an intravenous injection of phenylephrine (1-3 micrograms). Neurons that were excited by chemoreceptor stimulation but not baroreceptor stimulation were found in the commissural subnucleus of nucleus tractus solitarius and were designated as chemoreceptor-sensitive neurons. They exhibited a continuous discharge (9.9 +/- 1.3 spikes/s) that showed no apparent relation to either phrenic nerve bursts or arterial pulses. Such neurons were not found in the rostral portions of the nucleus tractus solitarius. These results confirm and extend our previous reports in which a discrete chemoreceptor projection site was identified in the commissural subnucleus of the rat.
Estradiol attenuates the antidiuretic action of vasopressin in ovariectomized rats
Authors: Wang Y. X. , Crofton J. T. , Liu H. , Sato K. , Brooks D. P. , Share L.
Published: December 2017

To determine which ovarian hormone is involved in the sexually dimorphic antidiuretic action of vasopressin, the antidiuretic response to vasopressin was examined in sham-operated nonestrous female rats chronically treated with vehicle and in ovariectomized rats treated with vehicle, progesterone, estradiol, or the combination of estradiol and progesterone, respectively. Three-week-old female rats were sham operated or ovariectomized, and a slow-release hormone pellet was implanted at the 6th wk. The experiment was performed at the 10th to 12th wk in conscious, chronically instrumented rats hydrated with tap water (2% body wt). Infusion of vasopressin at rates of 10-1,000 pg.min-1.kg body wt-1 resulted in a dose-dependent antidiuretic response that was significantly enhanced in ovariectomized rats compared with the intact nonestrous females. Progesterone had no effect, whereas estradiol attenuated and restored the antidiuretic response to vasopressin to a level similar to that in intact nonestrous female rats. These results suggest that it is estrogen, but not progesterone, that reduces the antidiuretic response to vasopressin in the female rat.
Naloxone attenuates poststimulatory respiratory depression of laryngeal origin in the adult cat
Authors: Mutolo D. , Bongianni F. , Corda M. , Fontana G. A. , Pantaleo T.
Published: December 2017

Poststimulatory depression in respiratory activity induced by superior laryngeal nerve (SLN) stimulation was quantitatively investigated in 20 adult cats. The role played in this phenomenon by endogenous opioids was studied using the opiate antagonist naloxone. The effects of hypercapnia on the same phenomenon were also investigated for comparison. Experiments were performed on cats anesthetized with pentobarbitone or alpha-chloralose, vagotomized, paralyzed, and artificially ventilated with 100% O2. Some animals were also carotid sinus denervated. Respiratory output was monitored as integrated phrenic nerve activity. SLN stimulation produced apnea, which outlasted the stimulation period; when respiration resumed, it was markedly depressed as revealed mainly by a decrease in phrenic minute output, respiratory frequency, and rate of rise of inspiratory activity. Phrenic output recovered gradually to control levels following an exponential time course. These effects varied as a function of the duration of SLN stimulation. Naloxone administration (0.8 mg/kg iv) significantly reduced the duration of poststimulatory apnea and attenuated the depression of phrenic minute output of the first recovery breath as a result of changes in peak phrenic activity; it also accelerated the time course of recovery. Hypercapnia did not affect the duration of poststimulatory apnea, but attenuated the initial poststimulatory depression because of changes in respiratory frequency; the rate of recovery was reduced. The results provide characterization of poststimulatory respiratory depression of laryngeal origin in the adult cat and suggest a role of endogenous opioids in its genesis or modulation.
Intracisternal rat pancreatic polypeptide stimulates gastric emptying in the rat
Authors: McTigue D. M. , Chen C. H. , Rogers R. C. , Stephens R. L.
Published: December 2017

Pancreatic polypeptide (PP) has been shown to alter gastrointestinal functions, including increased gastric acid secretion and motility following brain stem injections of PP. The present study investigated the effect of an intracisternal injection of PP on the rate of gastric emptying. Additionally, the efficacy of the rat and bovine forms of the peptide was compared. Rats anesthetized with ether received an intracisternal injection of rat PP, bovine PP, or vehicle and, upon regaining consciousness, were fed a liquid test "meal." Intracisternal rat PP produced a marked enhancement in gastric emptying compared with control animals. Bovine PP, at doses equimolar to or three times greater than the effective rat PP dose, produced no change in gastric emptying. Pretreatment with systemic atropine prior to central injection of rat PP eliminated the stimulation of emptying, suggesting that PP acts through a cholinergic mechanism. When equimolar doses of rat or bovine PP were microinjected directly into the dorsal vagal complex, the region containing PP receptors, both were capable of stimulating antral motility. The response to bovine PP, however, was delayed and reduced compared with that seen following rat PP. The results suggest that rat PP strongly stimulates gastric emptying in rats and that bovine PP, depending on the route of administration, is either ineffectual or a weaker agonist for central PP receptors.
Renal response of roosters with diabetes insipidus to infusions of arginine vasotocin
Authors: Brummermann M. , Braun E. J.
Published: December 2017

In a strain of white Leghorn chicken with symptoms of hereditary diabetes insipidus (DI) and with elevated circulating levels of the antidiuretic hormone arginine vasotocin (AVT), we investigated whether the defect is based on nonfunctional endogenous AVT or on a diminished renal response to AVT. DI chickens responded to hyposmotic infusions with a higher urine flow and lower glomerular filtration rate (GFR) than healthy control birds. Urine osmolality, fractional excretion, and clearance of sodium were lower in DI birds while potassium values were similar in both groups. Hence, the high urine flow rates of the DI birds were predominantly based on a water diuresis. When infused with AVT, the GFR and the urine flow of the control birds decreased and urine osmolality increased, showing both glomerular and tubular effects of AVT. During AVT infusion, the GFR of DI birds increased, urine flow decreased only moderately, and urine osmolality was half that of the control birds. In control birds, the clearance of sodium was unchanged, whereas that of potassium decreased. In DI birds, which experienced a strong natriuresis, the clearance of both sodium and potassium increased. These data suggest that the sensitivity of the DI birds to AVT is reduced at the tubular level. The AVT-induced increase in GFR may be related to vascular effects of high AVT doses, added to the already high basal AVT level of the DI birds, in combination with an imbalance in the function of V1 and V2 receptor subtypes in these chickens.