bluuebunny/crossref_metadata_2025 huggingface dataset:
Cardiovascular responses to microinjection of ANF into dorsal medulla of rats
Authors: McKitrick D. J. , Calaresu F. R.
Published: December 2017

Atrial natriuretic factor (ANF) has been suggested as a putative neurotransmitter in central pathways involved in the control of the cardiovascular system. To investigate this possibility, 50 nl of 10(-7) M ANF were microinjected into discrete sites in the nucleus of the tractus solitarius (NTS) where baro- and chemoreceptor afferents terminate. Injections into 36 of a total of 66 sites in the NTS of paralyzed artificially ventilated Wistar rats under urethan anesthesia were found to produce a significant decline in heart rate [HR; -9.2 +/- 2.9 (SE) beats/min, P less than 0.05] and mean arterial pressure [MAP; -11.1 +/- 1.2 (SE) mmHg, P less than 0.01]. Similar responses were also present in anesthetized animals breathing spontaneously. Microinjection of an inactive peptide analogue or of saline did not produce cardiovascular changes. It was also found that ANF injection into the cuneate nucleus (20 of 38 sites) and the spinal trigeminal complex (28 of 42 sites) produced a decrease in MAP and HR that were of the same magnitude as those seen in the NTS. Injections of ANF into the medial longitudinal fasciculus (n = 22), hypoglossal nucleus (n = 9), area postrema (n = 16), and dorsal motor nucleus of the vagus (n = 11) did not change HR or MAP. These results suggest that ANF may serve as a neurotransmitter involved in cardiovascular reflexes mediated by specific nuclei in the dorsal medulla.
Real importance of alanine in renal metabolism: in vitro studies in rat and dog
Authors: Lemieux G. , Berkofsky J. , Lemieux C. , Quenneville A. , Marsolais M.
Published: December 2017

In vitro studies were performed on cortical renal tubules to clarify possible differences between dog and rat with regard to alanine production and to define more precisely the role of alanine on ammonia and glucose production by the kidney. It was established that glutamate-pyruvate transaminase has an activity that is seven times lower in the rat than in the dog kidney. At the same time, alanine production from lactate, pyruvate, and glutamate is three times lower in the rat than in the dog kidney. The enzymatic reaction could be completely inhibited in a competitive fashion with aminooxyacetate. O2 consumption and CO2 production by the renal tubules were lower than that observed with glutamine. CO2 production in the rat was lowest. Production of ammonia and glucose by the kidney from alanine during acidosis averaged less than 20% of that produced with L-glutamine. Furthermore, during metabolic acidosis the production of ammonia and glucose from alanine was not augmented and failed to be influenced by increasing the concentration of alanine in the incubation medium.
Angiotensin-related sodium appetite and thirst in cattle
Authors: Blair-West J. R. , Denton D. A. , McKinley M. J. , Weisinger R. S.
Published: December 2017

Cows depleted of Na by loss of saliva from a parotid fistula for 46 h had an avid appetite for Na solution. They drank 21.0 +/- 1.6 liter of 0.3 M NaHCO3-NaCl solution during 2 h of access but little or no water during that time. Solutions of angiotensin II or captopril were infused for 3 h intravenously or into a lateral ventricle (intracerebroventricular) beginning 1 h before access to Na solution. Intravenous angiotensin II increased Na intake (to 26.8 +/- 2.9 liter, P less than 0.01) but did not alter water intake. Intracerebroventricular angiotensin II increased water intake but did not alter Na intake. Intravenous captopril reduced Na intake (to 11.0 +/- 2.1 liter, P less than 0.001) and concurrent intravenous angiotensin II prevented the reduction but concurrent intracerebroventricular angiotensin II did not. Intracerebroventricular captopril did not alter Na or water intake. Intravenous captopril reduced to zero the water intake during the hour before Na access, and concurrent intravenous angiotensin II prevented that reduction also. The dipsogenic action of intracerebroventricular angiotensin II was potentiated by intravenous captopril. The results of these experiments suggest that if angiotensin II receptors involved in the mechanism regulating Na appetite are in the brain, they are accessible only from the blood, e.g., in circumventricular organs. Thirst was inhibited by reduction of angiotensin II in blood but was stimulated only by angiotensin II acting inside the blood-brain barrier.
Pituitary involvement in renal adaptation to phosphate deprivation
Authors: Tenenhouse H. S. , Klugerman A. H. , Gurd W. , Lapointe M. , Tannenbaum G. S.
Published: December 2017

The present study was undertaken to examine 1) the effect of phosphate restriction on growth hormone (GH) secretory dynamics in freely moving, chronically cannulated rats and 2) the effect of hypophysectomy on the renal adaptive responses to phosphate deprivation. Phosphate restriction led to an increase in renal brush-border membrane Na+-dependent phosphate transport (2,511 +/- 283 vs. 1,006 +/- 122 pmol.mg protein-1.15 s-1, P less than 0.001) and in the plasma concentration of 1 alpha,25-dihydroxyvitamin D [1,25(OH)2D] (127 +/- 10 vs. 63 +/- 4 pg/ml, P less than 0.001). In contrast, phosphate deprivation had no effect on either amplitude or frequency of spontaneous GH secretory bursts and did not alter pituitary GH concentration. Hypophysectomy led to a decrease in brush-border membrane Na+-dependent phosphate transport (669 +/- 78 vs. 1,006 +/- 122 pmol.mg protein-1. 15 s-1, P less than 0.003) and to a fall in plasma 1,25(OH)2D (42 +/- 9 vs. 63 +/- 4 pg/ml, P less than 0.02). Phosphate restriction of hypophysectomized rats elicited a twofold increase in Na+-dependent phosphate transport (1,312 +/- 106 vs. 669 +/- 78 pmol.mg protein-1.15 s-1, P less than 0.001) but no rise in plasma 1,25(OH)2D. We conclude that the renal adaptive responses to phosphate deprivation are not mediated by specific alterations in pulsatile GH secretion. Moreover, we demonstrate that the adaptive increase in brush-border membrane phosphate transport occurs after hypophysectomy, is not dependent on increased vitamin D hormone production, and is most likely subject to a different regulatory mechanism.
Entrainment of hamster pup circadian rhythms by prenatal melatonin injections to the mother
Authors: Davis F. C. , Mannion J.
Published: December 2017

A circadian pacemaker, thought to be within the suprachiasmatic nucleus (SCN) of the hypothalamus, begins to function before birth in rodents. Prenatal entrainment of the pacemaker appears to be mediated by signals regulated by the maternal SCN; ablation of the mother's SCN during gestation disrupts the normal phase of the pups' rhythms. The present paper presents an experimental approach for identifying candidate entraining signals and for testing when they are effective during development. The candidate signal examined in these experiments was the pineal gland hormone, melatonin. Female golden hamsters (Mesocricetus auratus) received SCN lesions on day 7 of gestation. During the last week of gestation, they were given two daily subcutaneous injections of oil 12 h apart. One of the injections each day contained melatonin (10, 50, or 100 micrograms). The phases of the pups' activity rhythms were measured at weaning and were found to be related to the timing of the daily injection that contained melatonin, demonstrating that the melatonin directly or indirectly set the phase of the pups' rhythms. Injections given over 4 days of gestation were found to be as effective as injections given over 7 days. Although a physiological role for melatonin as an entraining signal has not been demonstrated, the results show that exogenous, prenatal treatment can predictably set the phase of the offsprings' circadian rhythms.
Angiotensin II-induced relaxation of fowl aorta
Authors: Yamaguchi K. , Nishimura H.
Published: December 2017

Angiotensin II (ANG II) decreases blood pressure of fowl. To characterize the vasodilating action of ANG II and its underlying mechanisms, we examined the effect of [Asp1, Val5]ANG II (fowl ANG II) on isometric tension of fowl aortic rings. [Val5]ANG II (10(-8) to 10(-5) M) produced rapid, reversible, dose-dependent relaxation of aortas precontracted with phenylephrine. [Sar1,Ile8]ANG II blocked ANG II-induced relaxation; propranolol, atropine, methysergid, pyrilamine, and cimetidine did not. Endothelium removal abolished relaxation responses to ANG II and acetylcholine but not to isoproterenol or sodium nitroprusside. Inhibitors of phospholipase or arachidonic acid metabolism (quinacrine, indomethacin, 5,8,11,14-eicosatetraenoic acid, hydroquinone, metyrapone, SKF 525A) and a calcium channel blocker (verapamil) did not inhibit ANG II-induced relaxation, whereas indomethacin nearly completely blocked arachidonic acid-induced dilation of aortas with or without endothelia. Guanosine 3',5'-cyclic monophosphate (cGMP) levels in the aorta increased 15 s after ANG II application. Aortic relaxation was caused by 8-bromo-cGMP with or without intact endothelium. These results suggest that ANG II-induced relaxation of fowl aortas involves 1) an endothelium-dependent mechanism and 2) cGMP but not arachidonic acid metabolites.
Exercise inhibits reproductive quiescence induced by exogenous melatonin in hamsters
Authors: Pieper D. R. , Borer K. T. , Lobocki C. A. , Samuel D.
Published: December 2017

Voluntary exercise inhibits the reproductive regression associated with a short photoperiod in male or female hamsters. The question addressed by the present study was whether exercise would also attenuate the reproductive regression associated with injection of exogenous melatonin. In male hamsters exercise inhibited the testicular regression, decline in gonadotropin secretion, and reduction in testosterone release associated with two daily injections (15 micrograms) of melatonin in pinealectomized hamsters on long days. After the reproductive system of the sedentary melatonin group had regressed, one-half of these hamsters were placed in cages with exercise wheels. Access to the exercise wheels stimulated testicular recrudescence and restored gonadotropin secretion to levels found in vehicle-injected hamsters. Sedentary female hamsters injected with melatonin tended to go into a state of constant diestrus associated with daily afternoon increases in serum luteinizing hormone, whereas most exercising hamsters injected with melatonin generally continued having regular estrous cycles with proestrus luteinizing-hormone surges. The ability of exercise to inhibit the effect of exogenous melatonin in pinealectomized hamsters suggests that exercise acts, at least in part, by mechanisms other than altering melatonin secretion.
Acetyl-CoA hydrolase: relation between activity and cholesterol metabolism in rat
Authors: Ebisuno S. , Isohashi F. , Nakanishi Y. , Sakamoto Y.
Published: December 2017

To examine whether cytosolic acetyl-CoA hydrolase in rat liver is involved in regulation of cholesterol biosynthesis, we investigated the alteration of the enzyme activity under conditions of stimulation (cholestyramine treatment) and suppression [cholesterol feeding, a potent competitive inhibitor of microsomal 3-hydroxy-3-methylglutaryl-CoA reductase (CS 514) treatment, and a hypolipidemic drug [alpha-(p-chlorophenoxy)isobutyric acid, CPIB] injection) of cholesterol biosynthesis. The enzyme activity in rat liver increased significantly in the early diabetic, cholesterol-fed, CS 514-, and CPIB-treated groups, but no change in its activity was observed in chronic diabetic groups. Cholestyramine treatment to cholesterol-fed rats made the enzyme activity return to the initial level. When chronic diabetic rats were given a cholesterol diet or treated with CS 514 or CPIB, the activity increased significantly. Inhibition of cholesterol biosynthesis caused by these treatments induced increase in the enzyme activity with increase in the enzyme protein, judging from results obtained by enzyme-linked immunosorbent assay. These results suggest that this enzyme has a physiological role in maintenance of the equilibrium between the cytosolic acetyl-CoA concentration and CoA-SH pool for cholesterol metabolism.
Brain tissue elastic behavior and experimental brain compression
Authors: Schettini A. , Walsh E. K.
Published: December 2017

This study was designed to test the hypothesis that the progressive expansion of an extradural mass causes detectable changes in brain mechanical response properties, in particular the nonlinear elastic behavior, before any significant changes in intracranial cerebrospinal fluid pressure can be detected. In 10 chronically prepared and anesthetized dogs, incremental inflation (0.07 ml/s) of an extradural balloon caused 1) a progressive fall in the brain nonlinear elastic parameter (G0, mmHg/mm2), 2) nonsignificant changes in brain tissue elasticity (G0, mmHg/mm), 3) a disproportionate progressive rise in subpial tension, and 4) a progressive fall in local cerebral blood flow (H2 clearance), despite a modest decrease in cerebral perfusion pressure (extracranial). In previous brain compression experiments (Brain Res. 305: 141-143, 1984) we have shown that the compression site becomes compacted and stiffer (increased G0) and its nonlinear elastic parameter (G0) increases markedly. These earlier findings, coupled with the present observation of a loss in tissue nonlinearity distally to the compression site, are most likely the major mechanisms by which, with a rapidly expanding intracranial mass, tissue pressure gradients and brain displacement, including transtentorial herniation, develop.
Blockade of spinal pathways decreases pre- and postganglionic discharge differentially
Authors: Qu L. , Sherebrin R. , Weaver L. C.
Published: December 2017

Although discharge of many sympathetic nerves decreases substantially on transection of the spinal cord in cats, firing of splenic and mesenteric postganglionic nerves continues unabated (R. L. Meckler and L. C. Weaver, Brain Res. 338: 123-135, 1985; R. D. Stein and L. C. Weaver. J. Physiol. Lond. 396: 155-172, 1988). Therefore, ongoing sympathetic outflow directed to the splanchnic circulation was proposed to be less dependent on supraspinal excitatory drive than that directed to other vascular beds. Blockade or transection of cervical spinal pathways in chloralose-anesthetized cats significantly decreased firing of gastric, hepatic, adrenal, and lumbar chain sympathetic nerves. Discharge of gastric and hepatic nerves decreased as much as that of adrenal and lumbar chain nerves; therefore, sustained discharge in the absence of bulbospinal excitation is not a characteristic of all sympathetic nerves innervating the splanchnic circulation. In contrast, discharge of the preganglionic greater splanchnic nerves was not decreased after spinal transection, although it changed from a rhythmic to an asynchronous pattern. This provocative finding suggests that rhythmicity of preganglionic discharge may be important for effective synaptic transmission to some postganglionic neurons, since postganglionic gastric, hepatic, and adrenal nerve firing decreased in the presence of sustained but asynchronous preganglionic input.
Ca2+-stimulated ATPase activities in the gill of the eel: interactions of Mg2+ ions
Authors: Naon R. , Mayer-Gostan N.
Published: December 2017

Enriched plasma membrane preparations of the branchial epithelium of freshwater-adapted eels were used to study adenosine triphosphatase (ATPase) activities insensitive to ouabain and responding to Ca2+ and Mg2+. Ca2+ induced ATP hydrolysis; two kinetics were observed in the presence or absence of chelators, one with a high-affinity site (0.3 microM) and one with a lower affinity site (10-20 microM). The high-affinity Ca2+ site or enzyme had a prerequisite for Mg2+ (endogenous Mg2+ being sufficient to satisfy the Mg2+ need) but was inhibited by exogenous Mg2+ (Ki0.5 less than 10 microM Mg2+). The low-affinity site or enzyme appears to have kinetic parameters comparable to those found for Mg2+-induced ATP hydrolysis. In the absence of Ca2+ ligands and with no exogenous Mg2+, the two Ca2+ sites or enzymes can be considered stimulated. The results are discussed in relation to the branchial ion environment and transport ion capacities.
Lack of caloric regulation in rats during short-term feeding
Authors: Swiergiel A. H. , Cabanac M.
Published: December 2017

Rats were trained to feed 2 h daily. Each rat was presented during three 10-day-long alimentary periods with each of the following diets: control (C), low calorie (L), and high calorie (H). The food was placed at an ambient temperature of -15 degrees C at 16 m from a warm refuge. It was found that the rats ingested similar amounts of food, regardless of energy density of the diet, and therefore did not compensate for variations in the caloric density of a diet. This was despite the recognition of a novel diet on the first day of its presentation as manifested by a change in rats' meal pattern. L diet was eaten slowly, suggesting that it was less palatable than the C or H diets. The results suggest that the rat placed in a closed economy with only short-term access to food imposed by a hostile environment does not adjust its food intake in accordance with energy value of the food. Its momentary food intake appears to be controlled by the gustatory properties of the food.
Evidence for a physiological role for CCK in the regulation of food intake in mice
Authors: Silver A. J. , Flood J. F. , Song A. M. , Morley J. E.
Published: December 2017

The effects of L-364,718, a cholecystokinin receptor antagonist, on cholecystokinin octapeptide-induced inhibition of food, and its effect on food intake when given alone, were studied in mice using several different feeding paradigms. In all studies, L-364,718 (100 micrograms/kg, 1.0 mg/kg) reversed the ability of cholecystokinin octapeptide to decrease food intake. L-364,718 enhanced food consumption compared with controls in nonfasted mice (100 microgram/kg) and in prefed mice (50, 100, 250 micrograms/kg). The number of reinforcements, using a lever press, was also enhanced by L-364,718 (100 micrograms/kg) compared with control. In other paradigms, L-364,718 failed to enhance food intake. These results are compatible with the suggestion that cholecystokinin may play a physiological role in the regulation of food intake.
Initiation and perpetuation of obesity and obesity resistance in rats
Authors: Levin B. E. , Hogan S. , Sullivan A. C.
Published: December 2017

A search was made for predisposing factors and sequelae of diet-induced obesity (DIO) or resistance to DIO (DR). During 3 mo on a high-energy (CM) diet, two-thirds of the male Sprague-Dawley rats ate 16% more calories over the first 30 days and developed DIO. The remaining one-third were DR, gaining the same amount of weight as chow-fed controls. Basal and norepinephrine (NE)-stimulated in vivo O2 consumption, performed before rats were placed on the CM diet, was the same in those rats that later became DR or DIO after 3 mo on the CM diet. DR rats were 4% lighter, whereas DIO rats were equal to chow-fed rats before their exposure to the CM diet. When CM-fed rats were switched to chow, DIO rats took 14 wk to reduce their body and retroperitoneal fat pad weights to those of chow-fed controls, whereas DR rats gained only 40% of the body weight, and fat pads were 34% lighter than controls. After 14 wk, DIO rats were neither hyperinsulinemic nor insulin resistant, whereas DR rats had 64% reduced areas under their insulin curves after intravenous glucose (1 g/kg) compared with controls. Unlike younger rats, animals here had inconsistent plasma NE responses to intravenous glucose. Therefore the CM diet produces DR and DIO states that tend to become self-perpetuating once established.
Autoradiographic distribution in rat tissues of binding sites for endothelin: a neuropeptide?
Authors: Koseki C. , Imai M. , Hirata Y. , Yanagisawa M. , Masaki T.
Published: December 2017

Endothelin (ET) is a potent and long-acting vasoconstrictor peptide consisting of 21 amino acids and recently isolated from a medium of cultured porcine endothelial cells. To determine the possible sites of ET action, we have conducted autoradiography and receptor binding assays with 125I-labeled ET in rat tissues. The displaceable binding sites of the ligand were widely distributed, not only in the arteries and heart but also in various other organs, e.g., brain, kidney, lung, adrenal gland, and intestine. The systemically injected ET did not cross the blood-brain barrier, whereas the ligand, applied in vitro, was mainly located in the hypothalamic and thalamic areas, lateral ventricular region, subfornical organ, globus pallidus, and caudate putamen. Both membrane preparations from the brain stem including diencephalon and from the heart ventricle had similar, specific, and high-affinity binding sites for 125I-ET. We suggest that ET is involved in the regulation of a large variety of organ functions and may also act as a neuropeptide.
Dietary carbohydrates modify cardiac myosin isoenzyme profiles of semistarved rats
Authors: Morris G. S. , Herrick R. E. , Baldwin K. M.
Published: December 2017

Although food restriction reduces the relative expression of the rodent cardiac myosin isoenzyme V1, the contribution of accompanying metabolic changes to the induction and maintenance of this isoenzyme shift remains unknown. Hence, this study was undertaken to determine the role of carbohydrate (CHO) utilization in the regulation of cardiac myosin isoenzyme distribution in food-restricted rats. Female Sprague-Dawley rats received either a mixed diet (55% of calories as CHO, M) or a high-carbohydrate diet (75% of calories as CHO, HC). Additional animals in each dietary group received daily injections of triiodothyronine (T3; 0.075 microgram/100 microM + T3, HC + T3). Three weeks of food restriction reduced left ventricular Ca2+-activated myofibrillar adenosinetriphosphatase activity by 24% and the relative amount of the myosin V1 isoenzyme by 57% in the M group relative to free-eating controls (P less than 0.05). In contrast, these measures were reduced by only 9 and 21%, respectively, in the HC group. Administration of T3 exerted no apparent effect on V1 expression, regardless of diet. Furthermore, the increased expression of V1 in both HC and HC + T3 groups occurred independently of changes in several measures of thyroid status including serum T3 levels, O2 consumption, heart rate, and systemic blood pressure. These results further suggest that metabolic factors, specifically those associated with CHO utilization, can influence cardiac myosin isoenzyme expression.
Ventromedial hypothalamic regulation of hormonal and metabolic responses to exercise
Authors: Vissing J. , Wallace J. L. , Scheurink A. J. , Galbo H. , Steffens A. B.
Published: December 2017

Recent studies have indicated a neural regulation of hormonal and metabolic responses to exercise. Studies on the ventromedial hypothalamus (VMH) suggest that the VMH might be involved in neural control of exercise metabolism. We therefore studied 25 rats with or without Marcain-anesthetized VMH (Marcain and control rats, respectively) at rest or during treadmill running (26 m/min). The rats had cannulas aimed bilaterally at the VMH and chronic catheters in the left jugular vein and right carotid artery. At rest, glucose turnover and plasma concentrations of glucose, lactate, glycerol, epinephrine, norepinephrine, insulin, and corticosterone remained stable in control rats, whereas in Marcain rats these parameters, except for unchanged insulin and glucose utilization, increased after Marcain administration along with increases in hepatic and muscular glycogenolysis. During exercise, glucose turnover, hepatic and muscular glycogenolysis, and plasma concentrations of glucose, lactate, glycerol, catecholamines, and corticosterone increased, and insulin decreased in both Marcain and control rats. However, during exercise, initial hepatic glucose production, plasma catecholamines, and subsequent plasma glucose concentrations and overall hepatic glycogenolysis were lower in Marcain compared with control rats. In conclusion, glucose mobilization is enhanced by the VMH during exercise. The results suggest that decreased and increased activity in sympathetic inhibitory and facilitating VMH areas, respectively, are involved in the VMH's response to exercise.
Stimulating somatic afferent fibers alters coronary arterial resistance
Authors: Pitetti K. H. , Iwamoto G. A. , Mitchell J. H. , Ordway G. A.
Published: December 2017

We used a constant flow preparation to study the changes in left circumflex coronary arterial (LCCA) pressure and resistance evoked by electrical stimulation of branches of muscle, cutaneous, and mixed nerves in the hindlimb of anesthetized dogs. Stimulation (20 Hz) of all three nerve types at 20, 70, 100, and 200 times the voltage threshold that evoked compound action potentials significantly (P less than 0.05) increased LCCA resistance. Stimulation at three and five times threshold had no effect on this same variable. Cooling the nerve to 2-4 degrees C, temperatures that block myelinated nerve fibers, attenuated but did not abolish the increase in LCCA resistance. Combinations of beta- and alpha-adrenergic and cholinergic blockade established that the biphasic change evoked by nerve stimulation was due to an initial alpha-adrenergic vasoconstriction followed by a metabolite-induced vasodilation. These data demonstrate that stimulation of muscle, cutaneous, or mixed nerve afferent C-fibers increases coronary arterial resistance by alpha-adrenergic vasoconstriction.
Calcitropic actions of prolactin in freshwater North American eel (Anguilla rostrata LeSueur)
Authors: Flik G. , Fenwick J. C. , Wendelaar Bonga S. E.
Published: December 2017

In freshwater-acclimated American eels (Anguilla rostrata LeSueur), ovine prolactin and grafts of the part of the pituitary gland containing the prolactin cells induced hypercalcemia. The hypercalcemia was associated with increased uptake of calcium from the water (resulting from increased influx and decreased efflux) and with enhanced high-affinity Ca2+-adenosinetriphosphatase (ATPase) activity in the gills, the putative biochemical correlate of the branchial Ca2+ pump. Kinetic analyses of ATPase-mediated Ca2+ transport in plasma membrane vesicles of branchial epithelium provided evidence that prolactin enhanced the maximum velocity of the Ca2+ pump. Prolactin treatments raised plasma cortisol levels slightly but significantly in eels. However, cortisol per se was not hypercalcemic in eels and did not stimulate the branchial Ca2+ pump. We conclude that the hypercalcemic potency of prolactin in fish relates to its stimulatory action on active Ca2+ transport in the gills.
Renal sympathetic nerve activity and renal responses during head-up tilt in conscious dogs
Authors: Miki K. , Hayashida Y. , Tajima F. , Iwamoto J. , Shiraki K.
Published: December 2017

Renal sympathetic nerve activity (RSNA) was measured in conjunction with functional responses of the kidney during head-up tilt in eight conscious female dogs. A 40 degree head-up tilt resulted in a sustained increase in RSNA by 53 +/- 10% (P less than 0.05) relative to control level. Urine flow and osmolal and sodium excretions decreased significantly to a nadir of -55 +/- 4, -42 +/- 7, and -59 +/- 10%, respectively, whereas free water clearance and creatinine clearance did not change significantly during head-up tilt. The systemic arterial pressure (at kidney level) increased significantly from 110 +/- 4 to 129 +/- 6 mmHg, and central venous pressure decreased significantly from -0.7 +/- 0.5 to -7.6 +/- 0.6 mmHg. The chronic bilateral renal denervation, which was performed 2-4 wk before the experiment, abolished both the antidiuretic and antinatriuretic responses to heald-up tilt. These results indicate that an increase in RSNA plays a significant role in the decrease in urine flow and sodium excretion induced by 40 degree head-up tilt in conscious dogs.
Amino acid transport systems in intestinal brush-border membranes from lepidopteran larvae
Authors: Giordana B. , Sacchi V. F. , Parenti P. , Hanozet G. M.
Published: December 2017

Experiments with intestinal brush-border membrane vesicles from lepidopteran larvae disclosed the occurrence of unique cotransporter proteins that use K+ as the driver cation for the transmembrane transfer of amino acids across the luminal border of midgut enterocytes. Six apical membrane amino acid transport systems have been identified. These systems are 1) a neutral amino acid transporter with a broad spectrum of interactions with most neutral amino acids, which is highly concentrative, strongly K+- and electrical potential-dependent, poorly stereospecific, and recognizes histidine, but not proline, glycine, or alpha-(methylamino)isobutyric acid (MeAIB); 2) a specific system for L-proline; 3) a specific system for glycine with a higher affinity for Na+ than for K+; 4) a specific system for L-lysine, which is dependent on membrane potential, is highly sensitive to external K+, and does not interact with L-arginine or neutral amino acids; 5) a specific K+-dependent process for glutamic acid, which does not recognize aspartic acid; and last, 6) an apparently unique K+- driven mechanism for D-alanine, which is potential-dependent and strongly stereospecific.
Effect of stimulation of facial nerve on regional cerebral blood flow and glucose utilization in cats
Authors: Goadsby P. J.
Published: December 2017

Regional cerebral blood flow was determined using the tracer [14C]iodoantipyrine and regional brain dissection, and regional cerebral glucose utilization was determined using the 2-deoxyglucose method in the alpha-chloralose-anesthetized cat to evaluate the effect of electrical stimulation of the facial nerve. The nerve was sectioned intracranially to isolate it from the brain stem and the distal portion stimulated before entry into the internal auditory meatus. Stimulation led to a global increase in cortical (frontal, parietal, temporal, occipital, and cingulate cortex) and white matter blood flow. This effect was predominantly ipsilateral to the side stimulated, although significant effects were also noted on the contralateral side. The latter were confined to the more anterior cortical structures. In contrast, there were no significant changes in regional metabolic activity as assessed by the rate of glucose utilization. This study provides direct evidence for a neurogenic vasodilator effect of activation of the facial-greater superficial petrosal pathway that is independent of regional brain metabolic activity.
Frequency of spontaneous contractions in longitudinal and transverse bladder strips
Authors: Potjer R. M. , Constantinou C. E.
Published: December 2017

The frequency components of spontaneous contractility of rabbit bladder strips were examined with respect to their orientation and position. Spectra of longitudinal and transverse strips of bladder were studied in vitro in consecutively dissected segments from the same bladder. The frequency characteristics of these strips were characterized at rest and also with incremental extension to 125% of original length. Results show that transverse and longitudinal strips of bladder muscle undergo continuous spontaneous contractions in the frequency range of 0.01-0.25 Hz. The amplitude of the spontaneous contractions is not dependent on the amount of resting tension in either longitudinal or transverse strips. Longitudinal strips have a higher frequency of spontaneous variations of tension compared with the transverse strips. The amplitude of transverse strips is lowest at the base of the bladder, and the frequency components of activity increases in magnitude toward the bladder dome. Extension of transverse strips shows the generation of frequency peaks of tissues located at the middle of the bladder having a significantly lower rate of relaxation than the proximal or distal strips. Spontaneous contractility of the bladder indicates the presence of a potentially significant parameter that must be considered when tissue response to mechanical, electrical, or pharmacological stimulation is interpreted.
Influence of lung inflation reflex on vascular capacitance in the systemic circulation
Authors: Cheng E. Y. , Kay J. , Hoka S. , Bosnjak Z. J. , Coon R. L. , Seagard J. L. , Kampine J. P.
Published: December 2017

The effects of sustained lung inflation on systemic vascular capacitance (SVC), systemic vascular resistance (SVR), and cardiac sympathetic efferent nerve activity (SENA) were investigated in anesthetized dogs. By use of a total cardiopulmonary bypass, the lungs were inflated to tracheal pressures of 10, 15, and 20 mmHg. Tracheal pressures of 10, 15, and 20 mmHg increased system vascular capacitance by 1.4, 3.1, and 4.3 ml/kg and decreased systemic vascular resistance by 0.11, 0.15, and 0.16 mmHg.kg.min-ml-1, respectively, at low carotid sinus pressure (CSP) of 41 mmHg. SENA showed a concomitant decrease. Bilateral vagotomy attenuated the change in SVR by 69%, SVC by 62%, and SENA by 97% when lungs were inflated to a tracheal pressure of 20 mmHg at a low CSP. These results indicate that lung inflation causes a reflex induced increase in SVC as well as a decrease in both SVR and SENA. The lung inflation reflex is mediated primarily through vagal afferent nerve fibers with a small contribution from other afferent nerve pathways.
Capsaicin attenuates hindbrain neuron responses to circulating cholecystokinin
Authors: Ritter R. C. , Ritter S. , Ewart W. R. , Wingate D. L.
Published: December 2017

Capsaicin is a neurotoxin that destroys small sensory neurons with unmyelinated axons, including a subpopulation of vagal sensory neurons. Capsaicin treatment attenuates suppression of food intake induced by systemic administration of cholecystokinin (CCK) but not by gastric distension. However, both gastric distension and intravascular CCK alter the discharge of dorsal hindbrain neurons by a vagal mechanism. Therefore, it is plausible that some hindbrain neurons receive convergent input from capsaicin-sensitive vagal neurons that are responsive to CCK and also from capsaicin-insensitive neurons that are responsive to gastric distension. To investigate this possibility we made extracellular recordings from gastric distension-responsive hindbrain neurons during intra-arterial cholecystokinin octapeptide (CCK-8) administration in anesthetized intact and capsaicin-pretreated rats. We found that capsaicin-pretreated rats exhibit attenuated neuronal discharge responses to CCK-8 but not to gastric distension. These results are consistent with the existence of convergent CCK-sensitive and gastric distension-sensitive afferent inputs to hindbrain neurons and suggest that various gastrointestinal sensory modalities may be communicated to the brain by populations of neurons that can be distinguished by their sensitivity to neurotoxins.
Single-unit responses of serotonergic neurons to glucose and insulin administration in behaving cats
Authors: Fornal C. A. , Litto W. J. , Morilak D. A. , Jacobs B. L.
Published: December 2017

Extracellular single-unit activity of serotonergic neurons in the dorsal raphe nucleus (DRN) was recorded in response to glucose loading and insulin administration in conscious, freely moving cats. Serotonergic neurons were identified based on their discharge characteristics, activity across states of behavioral arousal, response to systemic administration of serotonin autoreceptor agonists, and histological localization to the DRN. The spontaneous activity of serotonergic neurons varied in association with behavioral state, reaching their highest level during arousal and their lowest level during rapid-eye-movement sleep, when cells typically stopped firing. The activity of serotonergic DRN neurons was not significantly altered by a glucose load (500 mg/kg iv) that produced an approximately 3.5-fold increase in blood glucose levels. Furthermore, serotonergic DRN neuronal activity was not significantly altered after insulin administration (2-4 IU/kg iv), which lowered blood glucose approximately 50% below control levels, or after the rapid reversal of hypoglycemia by subsequent glucose administration. These results indicate that the activity of serotonergic DRN neurons is unrelated to alterations in blood glucose and is not sensitive to elevations of endogenous circulating insulin levels or to exogenous insulin administration. Furthermore, changes in the activity of serotonergic DRN neurons does not appear to be a component of glucoregulatory mechanisms invoked by either hyper- or hypoglycemia. Overall, these results do not support a role for serotonergic DRN neurons in glucoregulation in the cat.
Relationship between energy expenditure and ion channel density in the turtle and rat brain
Authors: Edwards R. A. , Lutz P. L. , Baden D. G.
Published: December 2017

Synaptosomes were isolated from turtle and rat brains to determine whether differences in brain ion channel densities accounted for the turtle's ability to survive anoxia compared with the mammal. The Na(+)-channel binding neurotoxin brevetoxin showed high-affinity specific binding in both turtle and rat synaptosomes, suggesting specific ligand-receptor interaction. The maximum binding capacity (Bmax) value for the turtle was only about one-third of that found for the rat synaptosomes, suggesting that the turtle synaptosome has a correspondingly lower Na+ channel density than the rat. This apparent difference in Na+ channel density is not reflected in metabolic rates, since at the same temperature (31 degrees C) the O2 consumption of both the rat and turtle synaptosome was almost identical. The large reductions in energy expenditure seen in synaptosomes incubated in Na(+)-free media and in media containing ouabain (approximately 50% turtle, 80% rat) are probably related to the halting of transmembrane Na(+)-K+ exchange. The greater reduction in the rat may be related to the apparent greater density of Na+ channels in the rat brain. However, compared with the 90% reduction in brain metabolism that occurs when the turtle brain becomes anoxic, the differences in ion channel density and in the costs of ion pumping between the rat and turtle brain are trivial. Closing Na+ channels with tetrodotoxin and increasing Na+ channel activation with veratridine caused substantial decreases and increases in synaptosome energy consumption, respectively. This suggests that the modulation of ion channel conductance has a significant effect on metabolic cost and may be an important mechanism to reduce energy consumption and electrical activity in the anoxic turtle brain, while still maintaining ionic gradients.
Synthetic capsaicin reversibly impairs vasopressin-mediated blood pressure recovery
Authors: Gardiner S. M. , Bennett T. , O'Neill T. P.
Published: December 2017

The vasopressin-mediated recovery of arterial pressure observed in adult rats following pharmacological blockade of the sympathetic nervous and renin-angiotensin systems is reduced by neonatal capsaicin treatment. We now demonstrate a similar but reversible effect following treatment of adult Wistar or Sprague-Dawley rats with N-vanillylnonanamide (50 mg/kg sc). One day after treatment, Wistar, but typically not Sprague-Dawley, rats had lost weight and exhibited increased sensitivity to the anesthetic effects of methohexital sodium. In both strains, captopril treatment caused hypotension. After captopril and ganglionic blockade, vasopressin-mediated recovery of arterial pressure was significantly inhibited. Furthermore, treated Wistar rats had reduced sensitivity to the ocular irritancy of N-vanillylnonanamide when examined 2 days postdose. All deficits reversed within 2 wk of dosing. These data suggest that capsaicin-sensitive systems participate in homeostatic mechanisms engaged during acute hypotension. Because the dose of N-vanillylnonanamide employed in the present study has previously been shown to destroy unmyelinated afferent fibers when administered to adult rats, recovery of the functional deficits may reflect regeneration of damaged processes or assumption of their function by undamaged neurons innervating adjacent sites. By extrapolation from other studies of capsaicin, damage to some central neurons may also be involved.
Role for central angiotensin II in control of blood pressure during pregnancy
Authors: Hines T. , Porter J. P.
Published: December 2017

It is known that the pressor response to intravenous angiotensin II (ANG II) is blunted in pregnancy. In the present study we examined the pressor response to intracerebroventricular ANG II to determine whether central ANG II effects are also attenuated in conscious pregnant rats. Two to three days before experimentation, animals were instrumented with arterial and venous catheters and a ventricular guide cannula. Pressor responses to 10, 50, and 100 ng iv of ANG II, and 30, 100, and 300 ng iv of norepinephrine were significantly reduced in pregnant animals. The pressor response to 5, 20, and 50 ng iv of vasopressin was not attenuated in pregnant rats. The pressor response to intracerebroventricular 100 ng ANG II was significantly increased in pregnancy. Blockade of the vasopressin V1 receptor and the sympathetic ganglia indicated that the greater pressor response to intracerebroventricular ANG II in pregnancy may be the result of a larger contribution by the sympathetic nervous system. We conclude that the central effects of ANG II are augmented in pregnancy, suggesting a significant role for central ANG II in blood pressure regulation.
Effect of fall mating on ovarian development in the red-sided garter snake
Authors: Mendonca M. T. , Crews D.
Published: December 2017

Although spring mating is an important factor in initiating vitellogenesis in female red-sided garter snakes (Thamnophis sirtalis parietalis), some females can become vitellogenic without having mated in the spring. Two hypotheses have been proposed to explain this phenomenon: 1) long-term storage of copulatory stimuli from mating the previous fall, or 2) additional cue(s) overcoming the lack of mating to stimulate vitellogenesis. Through oviductal biopsy, the presence of sperm in females returning to the hibernaculum in the fall was assessed. Laparotomies performed just before and 6 wk after hibernation indicated that although fall mating may stimulate slight ovarian development in the fall, there appears to be no effect of fall mating on spring ovarian recrudescence. Spring mating seems to be the most important factor in determining ovarian maturation. Therefore, it appears that there is no long-term storage of copulatory cues and that other as yet unknown cues are responsible for initiating vitellogenesis in spring unmated females.
Effects of hyperosmolality and diuretics on heat-induced limb vasodilation in baboons
Authors: Proppe D. W.
Published: December 2017

Dehydration attenuates the increase in limb skin blood flow elicited by environmental heating (EH). This study sought to determine which of the two primary effects of dehydration, increased body fluid osmolality or decreased body fluid volume, was primarily responsible for this cutaneous vasoconstrictor bias in baboons. Unanesthetized chronically instrumented baboons were exposed to EH while in euhydrated state, after 65-69 h of water deprivation (dehydration), after infusion of a small volume of hypertonic (20%) saline to raise plasma osmolality and sodium concentration to dehydration levels, and after injections of the diuretic furosemide over a 64-h period to produce an isosmotic fall in extracellular fluid volume. EH consisted of an acute elevation of ambient temperature to 39.5-42.0 degrees C until internal temperature reached 39.5-39.8 degrees C. The normal increases in external iliac artery blood flow and iliac vascular conductance during EH were unchanged by hyperosmolality but were attenuated by 39 and 31%, respectively, after furosemide treatment and by 42 and 46%, respectively, during dehydration. Thus the fall in extracellular fluid volume is the component of dehydration that attenuates the increase in hindlimb blood flow during EH in the same way as dehydration itself.
Apparent influence of metabolism on cardiac isomyosin profile of food-restricted rats
Authors: Morris G. S. , Surdyka D. G. , Haddad F. , Baldwin K. M.
Published: December 2017

In addition to thyroid hormone, carbohydrate oxidation appears to influence the relative distribution of rodent cardiac isomyosin (V1, V2, V3), especially in diabetic, thyroid-deficient, and food-restricted animals. To determine whether metabolic variations within the myocardium itself contribute to cardiac isomyosin distribution, food-restricted rats (predominantly V3) were treated with oxfenicine, a cardiospecific inhibitor of fatty acid metabolism. Animals received a mixed diet (50% carbohydrates) ad libitum (FE-M) or in restricted quantities (45% of FE-M; FR-M). Additional food-restricted animals received oxfenicine (75 mg/kg, twice daily) and either a mixed diet (FR-M-OXF) or a high-carbohydrate diet (75% carbohydrates, FR-HC-OXF). After 3 wk, hemodynamic and metabolic measurements were taken, serum 3,5,3'-triiodothyronine (T3) levels were measured, and cardiac citrate synthase (CS) activity and isomyosin distribution (percent V1, V2, V3) was determined. Relative to the FE-M group, thyroid status (CS, T3) was reduced only in the FR-M-OXF and the FR-HC-OXF groups (P less than 0.05). Oxfenicine treatment of food-restricted animals partially preserved the isomyosin profile of the FE-M group (P less than 0.05), suggesting that, within the context of food restriction, cardiac metabolism can influence cardiac isomyosin distribution independently of thyroid status.
GABAergic responses in ventrolateral medulla in spontaneously hypertensive rats
Authors: Smith J. K. , Barron K. W.
Published: December 2017

Gamma-Aminobutyric acid (GABA) and the GABA antagonist bicuculline methiodide were used to investigate the role of GABAergic transmission in the rostral and caudal ventrolateral medulla in 12- to 13-wk-old spontaneously hypertensive (SH) (n = 7) and normotensive, control Wistar-Kyoto (WKY) (n = 7) rats. Animals were anesthetized with urethan (1.25 g/kg sc), paralyzed with gallamine triethiodide (10 mg/kg iv), and artificially ventilated. Femoral arterial and venous catheters were inserted for the measurement of mean arterial pressure (MAP) and heart rate responses and for intravenous infusions. The ventral surface of the brain stem then was exposed. The responsiveness of the rostral ventrolateral medulla to GABA was compared in SH and WKY rats using unilateral microinjections (30 nl) of GABA at 1, 10, and 100 mM concentrations, which produced significantly (P less than 0.05) larger decreases of MAP in SH rats compared with WKY at the 10 and 100 mM concentrations (-37.3 +/- 2.8 mmHg for SH vs. -27.3 +/- 2.7 mmHg for WKY at 100 mM). Tonic GABAergic inhibition was gauged using bilateral microinjections (30 nl) of bicuculline (2 and 4 mM) into the rostral ventrolateral medulla, which caused significantly larger increases in MAP in the WKY group (+84.8 +/- 8.5 mmHg at 4 mM) compared with the SH group (+14.9 +/- 5.8 mmHg at 4 mM). In contrast, the ability to drive sympathetic outflow by microinjection of L-glutamate in the rostral ventrolateral medulla was not significantly different between WKY and SH rats.(ABSTRACT TRUNCATED AT 250 WORDS)