bluuebunny/crossref_metadata_2025 huggingface dataset:
Atrial natriuretic factor during head-out immersion at night
Authors: Miki K. , Shiraki K. , Sagawa S. , de Bold A. J. , Hong S. K.
Published: December 2017

The present investigation was undertaken to test the hypothesis that a circadian variation in the atrial natriuretic factor (ANF) response is responsible for the nocturnal inhibition of renal responses to head-out immersion (HOI). Plasma ANF responses to a 3-h HOI (water temperature 34.5 +/- 0.5 degrees C) were studied during day (1000-1300) and night (2400-0300) in six hydropenic male human subjects. In agreement with the previous observations, the renal responses, especially the diuresis, to HOI were attenuated at night compared with the day; furthermore, plasma renin activity decreased to the same low level during HOI at both day and night. Plasma ANF during time control periods was 30-40 pg/ml without showing any circadian variation. Moreover, plasma ANF showed a similar twofold increase within 1 h of HOI and was maintained at this elevated level throughout the 3-h HOI period in both the daytime and the nighttime series. On termination of HOI, plasma ANF decreased linearly to the pre-HOI level within 1 h. Hematocrit during time control periods was higher during the day compared with the night (P less than 0.05). Although HOI appears to induce a transient increase in plasma volume (as indicated by decreases in hematocrit) during the 1 h of HOI, the magnitude of the decrease in the latter parameters was not different between day and night. It is concluded that nocturnal inhibition of renal responses to HOI cannot be fully accounted for by circadian differences in the ANF and fluid shift response to HOI.
Spectral analysis of heart rate variability of lizard, Gallotia galloti
Authors: Gonzalez Gonzalez J. , De Vera Porcell L.
Published: December 2017

The beat-to-beat heart rate of the lizard, Gallotia galloti, at rest shows short-term oscillations, the frequency of which varies with body temperature. Spectral analysis of the heart rate variability signal shows that, above 20 degrees C, two major frequency components are present: the first component has a mean frequency ranging from 0.032 at 20 degrees C to 0.070 Hz at 35 degrees C and the second from 0.039 at 20 degrees C to 0.10 Hz at 35 degrees C of body temperature. The beat-to-beat heart rate variability does not seem to be correlated with ventilatory activity. The two spectral components could be associated as in mammals with the activity of the control systems that regulate the circulation, especially with the cutaneous vasomotor thermoregulatory and endogenous pressure vasomotor activities. Transient interactions between both components are described.
Reflex effects of prolonged cardiopulmonary baroreceptor unloading in humans
Authors: Mohanty P. K. , Sowers J. R. , McNamara C. , Thames M. D.
Published: December 2017

Most studies of the reflex responses to cardiopulmonary baroreceptor unloading with lower body negative pressure (LBNP) have assessed responses during the first few minutes of LBNP. It is unknown if these early changes are representative of the steady state. Thus we determined the response of heart rate, arterial pressure, forearm vascular resistance (FVR), and plasma norepinephrine (NE), renin (PRA), and aldosterone to prolonged (20 min) LBNP in nine normal subjects. All measurements were obtained at base line and after 3, 10, and 20 min of LBNP (-10, -20, and -40 mmHg). A 20-min recovery period was interposed between each period of LBNP. The heart rate and mean arterial pressure responses to LBNP during all levels of suction were not significantly different at 3, 10, and 20 min of continuous suction. Changes in FVR at 3, 10, and 20 min, respectively, were 18.4 +/- 3.2, 26.3 +/- 4.2, and 19.6 +/- 4.2 U during LBNP -10 mmHg; 33 +/- 7, 30.5 +/- 7.6, and 30 +/- 5.2 U during LBNP -20 mmHg; and 53.6 +/- 11.7, 57 +/- 8.8, and 49.4 +/- 12 during LBNP -40 mmHg, thus indicating a near maximal vasoconstrictor response at 3 min that was sustained throughout the 20 min during all levels of LBNP. Plasma NE rose to near peak level by 3 min. However, PRA and aldosterone changed significantly only after 20 min during LBNP at -10 and -20 mmHg. These data indicate that LBNP activates the sympathetic nervous system early, whereas activation of the renin-angiotensin-aldosterone axis is delayed. Our data should be taken into consideration in the design of future investigations of reflex neurohumoral responses to LBNP.
Osmoregulation in pseudopregnant and prolactin-treated rats: comparison with normal gestation
Authors: Barron W. M. , Lindheimer M. D.
Published: December 2017

Osmoregulation was studied throughout rodent pregnancy focusing on the importance of the fetoplacental unit and prolactin in the observed alterations. Plasma osmolality (Posmol) and plasma sodium (PNa), similar in 8-day gravid and virgin Sprague-Dawley rats, decreased significantly by gestational day 10, reaching a nadir 8-10 mosmol/kg and 3-5 meq/l, respectively, below virgin levels by day 14 (both P less than 0.001). Despite this, plasma arginine vasopressin (PAVP) was measurable and similar in all pregnant and virgin groups. Osmotic thresholds for arginine vasopressin (AVP) secretion, similar in 8-day gravid and virgin rats, decreased 7.7 and 10.7 mosmol/kg in 12- and 14-day pregnant rats, respectively (both P less than 0.001). In contrast, Posmol decreased less than 2 mosmol/kg in 12- to 14-day pseudopregnant animals. When pseudopregnancy was prolonged to 18 days by prior hysterectomy, Posmol was only 2.6 mosmol/kg below that of cycling, hysterectomized controls. In other studies 14 days of hyperprolactinemia evoked by estradiol or treatment with ovine or rat prolactin had minimal effect on Posmol. We conclude that parallel decrements in Posmol and osmotic thresholds for AVP release occur during early rodent pregnancy, alterations that cannot be explained by gestational increases in circulating prolactin. In addition, the failure of pseudopregnancy. to mimic the hypotonicity of gestation suggests an important role for the fetoplacental unit in the osmoregulatory changes of rat pregnancy.
Contribution of paraventricular nucleus to afferent renal nerve pressor response
Authors: Caverson M. M. , Ciriello J.
Published: December 2017

Experiments were done in alpha-chloralose-anesthetized, paralyzed, and artificially ventilated cats to determine the effect of afferent renal nerve (ARN) stimulation on the firing frequency of neurons in the paraventricular nucleus of the hypothalamus (PVH), whose axons project directly to the neurohypophysis (NH), and the contribution of these neurons to the pressor response elicited by ARN stimulation. In the first series of experiments, 474 single units were extracellularly recorded in the PVH region. Of these units 86 were antidromically excited by stimulation of the NH. Seventeen of the antidromic units (20%) responded orthodromically to ARN stimulation; 10 responded to ARN stimulation only, and 7 units responded to both ARN and buffer nerve stimulation. All PVH-NH-projecting neurons that responded to ARN stimulation were excited. In the second series the contribution of PVH neurons to the pressor response elicited by ARN stimulation was investigated in animals with the aortic depressor, carotid sinus, vagus, and cervical sympathetic nerves cut bilaterally. The ARN pressor response has previously been shown to be due to the activation of the sympathetic nervous system and to the release of arginine vasopressin (AVP). The primary and secondary (AVP component) components of the pressor response were attenuated by 51 and 69%, respectively, by bilateral injections of procaine hydrochloride into PVH or bilateral electrolytic lesions of PVH. Control injections of saline into PVH or electrolytic lesions of hypothalamic regions anterior, dorsal, or ventral to PVH did not alter the ARN pressor response. These experiments demonstrate that sensory information originating in renal receptors excites magnocellular neurosecretory neurons in PVH and suggest that this renal-paraventricular reflex loop may contribute to the elevated arterial pressure and AVP release during conditions when ARN are activated.
Vascular control of brain cooling in reindeer
Authors: Johnson H. K. , Folkow L. P.
Published: December 2017

The cold venous effluent returning from the nose of the heat-stressed reindeer may be distributed through angular oculi veins for selective cooling of the brain and through facial veins for general body cooling. In vitro experiments indicate that adrenergic receptors of the angular oculi vein are exclusively of the alpha-adrenergic type, whereas facial veins contain mainly beta-adrenergic receptors. We suggest that the antagonistic adrenergic neuroeffector organization of these veins plays a major role in control of brain cooling. Thus simultaneous sympathetic stimulation results in constriction of angular oculi veins and release of a preexisting stretch-induced tone in facial veins. In this situation cold venous blood is directed via facial veins and used for general body cooling. Reduction of sympathetic activity, on the other hand, results in dilatation of angular oculi veins and constriction of facial veins, due to development of myogenic tone in the latter vessels. In this situation cold venous blood is distributed via angular oculi veins and used for selective cooling of the brain.
Metabolic and structural adaptations to exercise in chronic intermittent fasted rats
Authors: Favier R. J. , Koubi H. E.
Published: December 2017

The effect of repetitive alternance of 3 days fasting and 3 days refeeding on morphological and biochemical ability to perform exercise was investigated in adult male rats. At the end of 10 wk of chronic intermittent fasting, the rats had consumed 20% less food but were able to maintain their initial body weight. Intermittent fasted rats (IF) had significantly lower carcass fat but had maintained the percent contribution of proteins to total carcass weight. The relative mass of liver, heart, kidney, and muscles was not affected by such dietary manipulation. Both glycolytic and oxidative enzyme capacities were reduced in IF rat muscles. In response to exercise (2 h of swimming), control rats displayed hypoglycemia, whereas IF rats were able to maintain plasma glucose level in spite of a reduced energy supply from liver (low glycogen stores) and adipose tissue (low plasma free fatty acid levels). This had been obtained by accumulating glycogen and triglycerides in muscles and by deriving energy for muscular contraction from the in situ breakdown of these energetic substrates. In addition, although IF rats displayed a markedly reduced liver protein content, the liver exercise-induced protein breakdown was abolished in these animals.
Analysis of metabolic control: new insights using scaled creatine kinase model
Authors: Connett R. J.
Published: December 2017

The creatine kinase-adenylate kinase equilibria equations are given a dimensionless form by normalizing to total creatine concentration. Analysis with appropriate equilibrium and cation-binding constants identified two sharply separated phases of energy depletion. In the "buffering" phase, energy is derived from phosphocreatine. In the "depleting" phase, adenine nucleotides are the source of energy. Defining the state of the adenine nucleotide pool requires only pH, phosphocreatine, and creatine concentrations. Analysis of data from skeletal muscle, heart, brain, and smooth muscle demonstrated that the [free adenine nucleotide]/[total creatine] and [total phosphate]/[total creatine] are essentially constant over the greater than 20-fold concentration range among tissues and species. This result permits quantitative evaluation of cell energetics with data scaled to the total phosphate, as obtained with nuclear magnetic resonance studies, or to total creatine, as obtained in chemical analysis of freeze-trapped tissue. By applying the stability of the tissue parameters to the equations, it is demonstrated that unique identification of a hypothesis describing the recruitment of O2 uptake requires testing at several pH values.
Hepatic control of feeding: effect of glucose, fructose, and mannitol infusion
Authors: Tordoff M. G. , Friedman M. I.
Published: December 2017

Plasma fuels, pancreatic hormones, liver glycogen, and food and water intake were measured immediately before or during the nocturnal feeding period of rats given hepatic portal or jugular infusions of glucose, fructose, and mannitol (0.3 M x 10 ml/2 h). Compared with mock and saline control infusions, hepatic portal glucose, fructose, and mannitol reliably and equally decreased food intake. Jugular fructose and mannitol also decreased food intake when infused before rats ate but not while they ate. Jugular glucose infusion did not affect food intake. Hepatic portal glucose did not reliably elevate systemic plasma glucose or insulin but increased hepatic glycogen content, indicating that most infused glucose was taken up by the liver. In contrast, jugular glucose increased systemic plasma glucose and insulin but did not affect hepatic glycogen. Hepatic portal fructose decreased plasma ketones and increased triglycerides and liver glycogen. Jugular fructose also decreased ketone levels and tended to increase liver glycogen. Mannitol by either route decreased plasma glucose and increased plasma free fatty acids. These results indicate that hepatic portal infusions that produce changes in plasma fuel concentrations within the physiological range decrease food intake. They strongly suggest this is accomplished by a direct action of the infusates on the metabolism of the liver.
Energy balance in adrenalectomized ob/ob mice: effects of dietary starch and glucose
Authors: Warwick B. P. , Romsos D. R.
Published: December 2017

Effects of different carbohydrate types on energy balance, fatty acid synthesis, and plasma insulin concentrations in adrenalectomized ob/ob mice were investigated. Obese (ob/ob) and lean mice adrenalectomized at 4 wk of age received one of four high-carbohydrate powdered diets for 3 wk: stock, glucose, starch, or starch plus wheat bran. Adrenalectomy reduced energy intake of ob/ob mice equally independent of diet type, whereas energetic efficiency, in vivo rates of fatty acid synthesis in liver and white adipose tissue, and plasma insulin concentrations were substantially reduced to approach values in lean mice in all adrenalectomized ob/ob mice except those fed glucose. The ability of adrenalectomy to normalize energy balance in ob/ob mice depends on factors other than the reduced circulating concentration of glucocorticoids alone. Diet composition is a crucial factor, and striking differences exist between semipurified diets containing a simple sugar (glucose) and those containing a complex carbohydrate (starch), with no additional effect of dietary fiber (wheat bran).
Increase in vagal activity during hypotensive lower-body negative pressure in humans
Authors: Sander-Jensen K. , Mehlsen J. , Stadeager C. , Christensen N. J. , Fahrenkrug J. , Schwartz T. W. , Warberg J. , Bie P.
Published: December 2017

Progressive central hypovolemia is characterized by a normotensive, tachycardic stage followed by a reversible, hypotensive stage with slowing of the heart rate (HR). We investigated circulatory changes and arterial hormone concentrations in response to lower-body negative pressure (LBNP) in six volunteers before and after atropine administration. LBNP of 55 mmHg initially resulted in an increase in HR from 55 +/- 4 to 90 +/- 5 beats/min and decreases in mean arterial pressure (MAP) from 94 +/- 4 to 81 +/- 5 mmHg, in central venous pressure from 7 +/- 1 to -3 +/- 1 mmHg, and in cardiac output from 6.1 +/- 0.5 to 3.7 +/- 0.11/min. Concomitantly, epinephrine and norepinephrine levels increased. After 8.2 +/- 2.3 min of LBNP, the MAP had decreased to 41 +/- 7 mmHg and HR had decreased to 57 +/- 3 beats/min. Vasopressin increased from 1.2 +/- 0.3 to 137 +/- 45 pg/ml and renin activity increased from 1.45 +/- 4.0 to 3.80 +/- 1.0 ng.ml-1.h-1 with no further changes in epinephrine, norepinephrine, and vasoactive intestinal polypeptide. A tardy rise in pancreatic polypeptide indicated increased vagal activity. After atropine. LBNP also caused an initial increase in HR, which, however, remained elevated during the subsequent decrease in MAP to 45 +/- 6 mmHg occurring after 8.1 +/- 2.4 min.(ABSTRACT TRUNCATED AT 250 WORDS)
Central interactions between aldosterone and vasopressin on cardiovascular system
Authors: Janiak P. , Brody M. J.
Published: December 2017

Although the presence of mineralocorticoid binding sites have been demonstrated in brain, little is known about their physiological role. The purpose of this study was to evaluate possible interactions between a relatively short 2-day central infusion of aldosterone (5 ng/h) and a diverse group of centrally acting pressor agents. The intracerebroventricular infusion of aldosterone selectively attenuated the pressor response produced by the injection of arginine vasopressin (AVP, 10-400 ng) into the lateral ventricle without altering the responses to ventricular administration of 50-200 ng angiotensin II (ANG II), 150 ng carbachol, and 0.5 and 1 M hypertonic sodium chloride. No aldosterone-vasopressin interaction occurred in rats receiving a simultaneous central infusion of aldosterone and RU 28318 [7 beta-hydroxy-3-oxo-7 alpha-propyl(17 alpha)-pregn-4-ene-21-potassium carboxylate], a specific mineralocorticoid receptor antagonist. Baroreflex reactivity and the pressor response to intravenous AVP were not modified by the aldosterone treatment, indicating that overall cardiovascular reactivity was not depressed. Because the vascular reactivity of the mesenteric artery to AVP and norepinephrine remained unchanged after 2 days of central aldosterone infusion, and because plasma levels of aldosterone were not altered, the selective inhibition by this mineralocorticoid of the central AVP response appears to be purely central in origin. This specific central effect of aldosterone is mediated through interaction with mineralocorticoid receptors.
Enzymatic and transport characteristics of isolated snake renal brush-border membranes
Authors: Benyajati S. , Dantzler W. H.
Published: December 2017

Brush-border membranes (BBM) of proximal tubules were isolated from the kidney of the garter snake (Thamnophis sirtalis) by a procedure involving hypotonic lysis, Ca precipitation, and differential centrifugation. The isolated membranes were enriched 15-fold in brush-border enzyme activities (alkaline phosphatase, gamma-glutamyl transpeptidase) compared with whole kidney homogenates and were substantially free of other contaminating membranes. The yield of the BBM preparation was 40%. The BBM vesicular transport of several organic solutes was characterized by a rapid filtration technique at 25 degrees C. D-glucose, p-aminohippurate (PAH), and urate entered the same osmotically active space (2-3 microliter/mg protein) and binding was minimal (less than 20% for PAH). An uptake overshoot for 3-O-methyl-D-glucose (20 microM) by reptilian BBM was observed only in the presence of an inwardly directed NaCl gradient and was abolished by 0.1 mM phlorizin. Reptilian BBM exhibited Na-gradient-stimulated uptake of PAH (90 microM) with an overshoot that was inhibited by other organic acids and by 4-acetamido-4'-isothiocyanostilbene-2, 2'-disulfonic acid (SITS). In contrast, urate uptake (30 microM) appeared to be Na independent and not appreciably affected by other organic anions or SITS. The presence of specific transport systems for organic solutes in the isolated membrane preparation distinctly characterizes the BBM of reptilian kidney.
Natriuresis during atrial distension and a concurrent decline in plasma atriopeptin
Authors: Goetz K. L. , Wang B. C. , Bie P. , Leadley R. J. , Geer P. G.
Published: December 2017

In the conscious dog, left atrial distension elicits a composite response that modulates both cardiovascular and renal function. The response to atrial distension may be mediated by the combined effects of neural reflexes and the release of atriopeptin. To assess the relative contributions of atrial reflex mechanisms and circulating atriopeptin to the renal response elicited by atrial distension, alpha-human atrial natriuretic peptide (alpha-hANP) was infused into conscious dogs at 50 ng.kg-1.min-1 for 60 min. Then the infusion was stopped abruptly, and left atrial pressure was increased 8 mmHg by inflating a balloon positioned above the mitral valve. Plasma atriopeptin decreased during the 40-min period of atrial distension, but urine flow and sodium excretion increased during this time. In another series of experiments, volume expansion was substituted for atrial distension. Saline (24 ml/kg) was infused intravenously for 5 min immediately after the 60-min period of alpha-hANP infusion. Urine flow and sodium excretion increased after administration of saline even though plasma atriopeptin decreased substantially during the same time period. These results provide evidence that circulating levels of atriopeptin do not play a dominant role in influencing sodium excretion either during atrial distension or in response to saline infusion.
Growth hormone-releasing factor enhances sleep in rats and rabbits
Authors: Obal F. , Alfoldi P. , Cady A. B. , Johannsen L. , Sary G. , Krueger J. M.
Published: December 2017

Previously, it was suggested that a hypothalamic mechanism links somatotropin [growth hormone (GH)] secretion to sleep regulation, and this may explain the temporal correlation between GH release and nonrapid eye movement sleep (NREMS) on sleep onset. The purpose of these experiments was to study whether growth hormone-releasing factor (GRF), a hypothalamic peptide responsible for stimulation of GH secretion, also has the capacity to promote sleep in rats and rabbits. Artificial cerebrospinal fluid or GRF (human GRF-[1-40], 0.01, 0.1, and 1 nmol/kg) was intracerebroventricularly injected to rats at dark onset, and the electroencephalogram (EEG), brain temperature (Tbr), and motor activity were recorded for 24 h. Rabbits received the same doses of GRF during the light period, and sleep-wake activity was monitored for 6 h. GRF promoted NREMS and rapid eye movement sleep (REMS) and increased EEG slow-wave activity in both rats and rabbits. NREMS increased in postinjection hour 1 after low doses of GRF, whereas the effect was more prolonged after higher doses. REMS increased in response to the low and middle doses of GRF in postinjection hour 1 in rats and in hour 2 after each dose in rabbits. The diurnal rhythms of sleep-wake activity, motor activity, and Tbr were not affected in rats. Because GRF promotes sleep and also stimulates GH secretion, it is a likely candidate for linking GH secretion and sleep regulation.
Polycythemia and hydration: effects on thermoregulation and blood volume during exercise-heat stress
Authors: Sawka M. N. , Gonzalez R. R. , Young A. J. , Muza S. R. , Pandolf K. B. , Latzka W. A. , Dennis R. C. , Valeri C. R.
Published: December 2017

We studied the effects of autologous erythrocyte infusion on thermoregulation and blood volume during exercise in the heat. Specifically, we wanted to determine whether heat-acclimated subjects, as well as hypohydrated subjects, would have a thermoregulatory advantage from acute polycythemia during exercise in the heat. Five heat-acclimated males attempted four heat stress tests (HSTs): two pre- and two postinfusion. Autologous erythrocyte infusion was accomplished with 500 ml of a NaCl-glucose-phosphate solution containing approximately 60% hematocrit. One HST, both pre- and postinfusion, was done while subjects were euhydrated, and one HST was done while subjects were hypohydrated (-5% of body wt). After 30 min of rest in a 20 degrees C antechamber, the HST consisted of a 120-min exposure (2 repeats of 15 min rest and 45 min walking) in a hot (35 degrees C, 45% relative humidity) environment. The findings concerning acute polycythemia in heat-acclimated subjects are summarized: 1) polycythemia increased (P less than 0.05) sweating rate and reduced (P less than 0.01) core temperature during exercise-heat stress for both euhydrated and hypohydrated subjects; 2) the erythrocyte infusion caused an increased (P less than 0.05) plasma volume and increased (P less than 0.01) blood volume; 3) the increased plasma volume was associated with an increased (P less than 0.05) total circulating protein mass; 4) the increased total circulating protein mass tended to better maintain plasma volume when hypohydrated; and 5) heat acclimation may increase extravascular protein mass. Therefore, it is concluded that erythrocyte infusion provides a thermoregulatory advantage during exercise in the heat for heat acclimated subjects when both euhydrated and hypohydrated.
Capsaicin attenuates suppression of sham feeding induced by intestinal nutrients
Authors: Yox D. P. , Ritter R. C.
Published: December 2017

Satiety appears to be mediated in part by neurally transmitted signals from the gastrointestinal tract. Capsaicin is a neurotoxin that selectively destroys small unmyelinated primary sensory neurons including some of those innervating the abdominal viscera. Therefore, we examined suppression of sham feeding induced by cholecystokinin octapeptide (CCK-8) or intraintestinal nutrient infusions in capsaicin-treated rats. Suppression of sham feeding induced by CCK-8 was significantly attenuated in rats treated with capsaicin. Suppression of sham feeding induced by intraintestinal infusions of maltose, oleic acid, or L-phenylalanine was also attenuated in capsaicin-treated rats. In contrast, capsaicin treatment did not attenuate the suppression of sham feeding induced by intraintestinal casein hydrolysate (mixed amino acids). Intraintestinal infusions of octanoic acid or D-phenylalanine solutions did not significantly suppress sham feeding in either vehicle- or capsaicin-treated rats. These results indicate that the suppression of feeding by some intestinal stimuli may be mediated by nutrient or peptide-sensitive visceral afferent neurons that are sensitive to damage or destruction by capsaicin.
Neurogenic and humoral factors maintaining arterial pressure in conscious dogs
Authors: Hasser E. M. , Bishop V. S.
Published: December 2017

This study examined the contribution of each primary pressor system to resting arterial pressure and the ability of each to maintain pressure in the absence of the other systems in conscious dogs. In dogs with intact carotid sinus baroreflexes, ganglionic blockade (GB) reduced blood pressure by 13 +/- 3 mmHg, whereas blockade of the renin-angiotensin (RAS) and arginine vasopressin (AVP) systems did not significantly alter arterial pressure. After removal of the other two systems, the depressor response to blockade of the sympathetic nervous system (SNS) with hexamethonium and atropine was significantly augmented (-33 +/- 3 mmHg), whereas captopril (CAP) blockade of the RAS reduced pressure 14 +/- 4 mmHg, and AVP blockade decreased pressure 12 +/- 2 mmHg. In sinoaortic-denervated (SAD) dogs, the SNS exhibited a greater contribution (28 +/- 4 mmHg) to resting pressure compared with intact, and the role of the RAS (10 +/- 2 mmHg) was also augmented, whereas the effects of AVP blockade were unaltered. Effects of GB and CAP were unaltered after blockade of the other systems in SAD animals, whereas the depressor response to AVP antagonist (-13 +/- 2 mmHg) was significantly augmented. Results indicate the SNS is the primary pressor system in resting intact or SAD conscious dogs, whereas the RAS also contributes to resting blood pressure in SAD animals. The ability of the SNS alone to maintain arterial pressure after acute removal of the other systems is also significantly greater than that of AVP or the RAS.
Allometry of the kidney: implications for the ontogeny of osmoregulation
Authors: Beuchat C. A. , Braun E. J.
Published: December 2017

In reptiles, there are two pairs of kidneys at birth: the mesonephros and the metanephros. The metanephric kidney in reptiles, as in all amniote vertebrates, is retained as the functional kidney in adults. However, the reptilian mesonephros does not degenerate until after birth, and its function during this time is unknown. In neonates of the iguanid lizard Sceloporus jarrovi, the metanephric kidney is only 63% as large as predicted from the allometric relationship between kidney mass and body mass in adults. However, the kidney mass of neonatal lizards conforms to this prediction if the mesonephric and metanephric masses are combined. Some other amniote vertebrates appear to follow this pattern as well: in marsupials, which retain the mesonephros for a short period after birth, the sum of mesonephric and metanephric mass in neonates conforms to the allometry of kidney mass on body mass for adults. In contrast, the mesonephros of eutherian mammals is degenerate at birth and the metanephric kidney alone is of the predicted size. That the scaling of kidney mass in neonatal lizards and marsupials is the same as that of adults only if the mass of both the mesonephros and metanephros are combined suggests that the mesonephric kidney in these vertebrates plays a significant role in the regulation of water and ion balance during development and for at least a short time after birth.
Neuronal activity during sleep and complete bouts of hibernation
Authors: Krilowicz B. L. , Glotzbach S. F. , Heller H. C.
Published: December 2017

Changes in arousal state in a euthermic mammal exert powerful influences on major neural regulatory systems. Changes in behavioral state occur at body temperature (Tb) greater than 25 degrees C during hibernation. However, no information exists regarding alterations in arousal states during deep torpor. In this study we used a combination of electroencephalographic, electromyographic, and posterior thalamic neuronal activity in ground squirrels (Spermophilus lateralis) to evaluate arousal states during deep hibernation. No state homologous to rapid-eye-movement sleep was observed below Tb = 21 degrees C during hibernation. However, the animals did continue to cycle through states homologous to electrophysiologically defined wakefulness (AW) and non-rapid-eye-movement (NREM) sleep at all temperatures examined (Tb = 14-36 degrees C). These results extend previous observations that hibernation is not a homogeneous state. Instead, deep torpor consists primarily of a state similar to NREM sleep, interrupted periodically by short intervals of a form of AW. These periodic alterations in state should be accompanied by changes in the properties of many regulatory systems and must be accounted for in any theory of the neural control of hibernation.
Thermal acclimation induces adaptive changes in subcellular structure of fish skeletal muscle
Authors: Egginton S. , Sidell B. D.
Published: December 2017

Stereological analyses of electron micrographs were used to quantify physiologically important ultrastructures of slow-twitch oxidative (red) and fast-twitch glycolytic (white) muscle fibers from striped bass (Morone saxatilis) acclimated to 25 and 5 degrees C. The fraction of cell volume occupied by the mitochondria [volume density, Vv (mit,f)] of red fibers increases from 0.286 +/- 0.018 to 0.448 +/- 0.024 between 25 and 5 degrees C; Vv (mit,f) of white fibers increased from 0.027 +/- 0.003 and 0.040 +/- 0.004 at 25 and 5 degrees C, respectively. Because of a concomitant increase in the mass of oxidative muscle, acclimation from 25 to 5 degrees C results in an increase in total mitochondrial volume per 100 g body wt from 2.58 to 6.73 cm3 in oxidative muscle and from 2.46 to 3.40 cm3 in fast glycolytic muscle. Mitochondria of red fibers are in more clustered arrays after cold acclimation. Size and cristae surface densities of individual mitochondria are not affected markedly by acclimation, suggesting true cold-induced proliferation rather than enlargement of organelles. Harmonic means of intermitochondrial spacing in red fibers decreases from 2.64 to 1.43 micron between 25 and 5 degrees C. This reduces diffusion path lengths between sarcoplasmic and mitochondrial compartments proportionately, compensating for decreases in diffusivity of aqueous solutes. Intracellular lipid droplets of red fibers markedly increase in volume density from 0.006 +/- 0.003 at 25 degrees C to 0.079 +/- 0.014 at 5 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)
Two-phase change of sympathetic rhythms in brain ischemia, Cushing reaction, and asphyxia
Authors: Kocsis B. , Fedina L. , Pasztor E.
Published: December 2017

The present study was designed to determine the extent to which the brain stem neural networks, normally capable of synchronizing the sympathetic nerve discharge (SND) into 2- to 6- and 10-Hz rhythmic fluctuations, contribute to the control of autonomic reactions during brain hypoxia and/or hypercapnia. Vertebral, cardiac, and renal nerve discharges were recorded electrophysiologically in 34 anesthetized, curarized, and artificially ventilated cats. The sympathetic nerve responses to cerebral ischemia (elicited by reducing the blood supply to the brain), intracranial pressure elevation (Cushing reaction), and systemic asphyxia were tested with special focus on the rhythmic structure of the SND. It has been found that there are two phases of SND changes during cerebral ischemia differing mainly in the frequency content of the signals and less in the compound action potential amplitude. During the first phase the rhythmic generators controlling the tonic sympathetic outflow are more strongly activated, which is reflected in a stronger, more regular, and more widespread manifestation of these rhythms on the efferent neurograms. After some time the normal SND structure abruptly changes to a desynchronized activity with loss of the three main sympathetic rhythms and responsiveness to baroreceptor reflex activation. The same stereotyped changes can be observed regardless of the way in which the brain hypoxia and/or hypercapnia has been produced. Nor does the denervation of peripheral baro- and chemoreceptors substantially alter the general pattern of the responses.
Adrenal and sympathetic catecholamines in exercising rats
Authors: Scheurink A. J. , Steffens A. B. , Bouritius H. , Dreteler G. H. , Bruntink R. , Remie R. , Zaagsma J.
Published: December 2017

The effects of adrenodemedullation and/or adrenoceptor agonists and antagonists on plasma epinephrine (E) and norepinephrine (NE) concentrations during exercise were investigated in rats. Exercise consisted of strenuous swimming against a countercurrent for 15 min in a pool with water of 33 degrees C. Before, during, and after swimming, blood samples were taken through a permanent heart catheter. E was not detectable in plasma of adrenodemedullated (Adm) rats. A marked reduction in the normal exercise-induced increase in plasma NE concentrations occurred in both Adm rats as well as in intact rats injected with the beta 2-selective adrenoceptor antagonist ICI 118551. Intravenous infusion of either E or the beta 2-selective agonist fenoterol restored the increase in plasma NE in Adm rats. Injection of the alpha 2-selective antagonist yohimbine in combination with infusion of the beta 2-selective agonist fenoterol into Adm rats caused an enormous increase in plasma NE. It is concluded that all NE in plasma as released during exercise originates from the peripheral nerve endings of the sympathetic nervous system. Adrenal E influences the release of NE via activation of presynaptic beta 2-adrenoceptors.
Release of hypothalamic cholecystokinin in cats: effects of nutrient and volume loading
Authors: Schick R. R. , Yaksh T. L. , Roddy D. R. , Go V. L.
Published: December 2017

Systemic cholecystokinin (CCK) suppresses food intake in various species and has therefore been proposed to act as a satiety factor. Because CCK is also present in the hypothalamus and furthermore meets neurotransmitter criteria, the hypothesis was tested whether CCK participates in the transmission of satiety messages at the lateral hypothalamic (LH) level. The results of this study demonstrate that in halothane-anesthetized cats, neurons located in the LH will indeed release CCK-like material after a carbohydrate-protein meal in a time-dependent fashion. This release, as water loads demonstrate, is most likely due to volumetric distension rather than to the nutrient content. The releasable CCK does not originate from peripheral sources, since intravenously infused CCK octapeptide (CCK-8) does not appear in the perfusate. The release occurs only in discrete neurons and is not universal to CCK-releasing systems within the LH, and also, CCK-releasing systems are not present at all locations. The molecular form of CCK in feline hypothalamus is the COOH-terminal octapeptide (CCK-8) as shown by high-performance liquid chromatography. No gastrin-17 is present. CCK-8 is also the predominant form found in meal-induced as well as in KCl-induced CCK released from hypothalamic neurons. These results suggest a correlated role for hypothalamic CCK in the termination of food intake.
Characteristics of fever and acute-phase response induced in rabbits by IL-1 and TNF
Authors: Morimoto A. , Sakata Y. , Watanabe T. , Murakami N.
Published: December 2017

We investigated the effect of human recombinant interleukin 1 alpha (hrIL-1 alpha) and human recombinant tumor necrosis factor (hrTNF) on body temperature and acute-phase response, including changes in the plasma concentration of iron, zinc, and copper and in circulating leukocyte count. The intravenous injection of a smaller dose of either hrIL-1 alpha (0.5 micrograms/kg) or hrTNF (2 micrograms/kg) produced a monophasic fever, whereas a larger dose (hrIL-1 alpha, 2 micrograms/kg; hrTNF, 10 micrograms/kg) produced a biphasic fever. The intracerebroventricular injection of hrIL-1 alpha or hrTNF produced a dose-dependent fever. The intravenous injection of either hrIL-1 alpha or hrTNF decreased the plasma concentration of iron and zinc and increased the plasma copper concentration and the circulating leukocyte count. The intracerebroventricular injection of hrIL-1 alpha induced those responses, although the intracerebroventricular injection of hrTNF did not. The present results show that two kinds of monokines, hrIL-1 alpha and hrTNF, are intrinsically pyrogenic and induce the acute-phase response. Furthermore, it is suggested that hrIL-1 alpha induces febrile and acute-phase responses through its action on both the peripheral target organs and the central nervous system. However, hrTNF induces those responses only by its action on the peripheral target organs outside the blood-brain barrier.
Renal sympathetic nerve activity and natriuresis during water immersion in conscious dogs
Authors: Miki K. , Hayashida Y. , Sagawa S. , Shiraki K.
Published: December 2017

The role of renal sympathetic nerve activity (RSNA) in the natriuresis and diuresis induced by head-out water immersion (WI) was studied in eight conscious female dogs. The dog was instrumented chronically with a stainless steel electrode for the measurement of RSNA and two catheters for the measurements of systemic arterial (Pa) and central venous (Pv) pressures. The WI caused an immediate reduction of RSNA by 43 +/- 7% (P less than 0.05), and this low level was sustained throughout a 120-min WI under thermoneutral conditions (37 degrees C). Urine flow and sodium excretion increased by 211 +/- 54 (P less than 0.05) and 240 +/- 122% (P less than 0.05), respectively, but creatinine clearance did not change significantly during WI. A step increase in Pa (by 10 +/- 4 mmHg, P less than 0.05) and Pv (by 10.0 +/- 0.8 mmHg, P less than 0.05) was observed also during WI. In another series of studies, renal denervations were performed 2-4 wk before the experiment in six of the same dogs. Dogs with renal denervation showed no significant changes in urine flow and sodium excretion in response to WI, whereas Pa and Pv increased by 10 +/- 7 and 10.0 +/- 2.0 mmHg relative to the control level, respectively. It is concluded that the reduction of RSNA observed during WI plays a major role in the natriuresis in the dog.
Activation by saccharides of a cation-selective pathway on canine lingual epithelium
Authors: Simon S. A. , Labarca P. , Robb R.
Published: December 2017

Responses of isolated canine lingual epithelium in an Ussing chamber to D-glucose and fructose reveal events associated with taste transduction. With the use of isotopic flux studies, together with ion substitution and pharmacological and voltage clamp measurements, it was found that the stimulation of ion transport by D-glucose arises from an increase in the influx of cations through a cation-selective pathway. This influx of cations is completely inhibited by 0.1 mM amiloride. The stimulation of transport by fructose in 0.05 M KCl and by D-glucose in 0.05 M RbCl was also inhibited by amiloride, demonstrating that the saccharide-stimulated entry pathway was specific for neither hexose sugars nor for Na. Saccharide stimulation of canine lingual epithelia does not appear to be modulated by increases in intracellular levels of adenosine 3',5'-cyclic monophosphate, guanosine 3',5'-cyclic monophosphate, or Ca. The Na that enters taste cells on saccharide stimulation exits them via the ouabain inhibitable Na+-K+-adenosinetriphosphatase located in the serosal membranes.
Effect of blood glucose concentration on osmoregulation in diabetes mellitus
Authors: Thompson C. J. , Davis S. N. , Baylis P. H.
Published: December 2017

Poorly controlled insulin-dependent diabetes mellitus is associated with considerable elevations of plasma vasopressin concentrations, although well-controlled diabetics have normal osmoregulated thirst and vasopressin release. We studied the effect of blood glucose concentration on osmoregulated thirst and vasopressin secretion in insulin-dependent diabetes mellitus. Blood glucose was maintained overnight, and for the duration of the study, in either the euglycemic (4-5 mmol/l) or hyperglycemic (10-12 mmol/l) range, and patients underwent infusion of hypertonic (855 mmol/l) sodium chloride solution. Plasma sodium was lower during the hyperglycemic study, but elevation in plasma sodium concentration by infusion of saline caused progressive linear increases in both thirst and plasma vasopressin concentrations in both studies. Linear regression analysis defined lowered plasma sodium thresholds for both thirst appreciation and vasopressin release during the hyperglycemic study, although the sensitivity of the osmoreceptors remained unchanged. Analysis of the data in terms of plasma osmolality, corrected for the increase in blood glucose in the hyperglycemic study, revealed no differences in the osmotic thresholds for thirst or vasopressin release; sensitivity of the osmoreceptors also remained the same. Drinking abolished thirst and lowered plasma vasopressin concentrations before major changes in plasma sodium were observed. These results show that insulin-dependent diabetic patients osmoregulate appropriately when moderately hyperglycemic but that the threshold plasma sodium for vasopressin secretion and thirst appreciation is lowered by an unknown mechanism.
In vitro stimulation of Na+-K+-ATPase activity and ouabain binding by cortisol in coho salmon gill
Authors: McCormick S. D. , Bern H. A.
Published: December 2017

To investigate the hormonal control of gill Na+-K+-adenosinetriphosphatase (ATPase) (the sodium pump) in coho salmon, a technique for the culture of primary gill filaments for up to 4 days was developed. Trypan blue exclusion was greater than 99.9%, histological appearance of the cells was normal, and total [Na+], [K+], and protein content of gill filaments cultured for 2-4 days was unchanged from initial levels (measured immediately after isolation). In fish with initially low gill Na+-K+-ATPase activity (presmolts), cortisol (0.1, 1.0, and 10.0 micrograms/ml) caused a significant dose-dependent increase in gill Na+-K+-ATPase activity over initial (41%) and control levels (45%) after 4 days in culture. In fish with initially high gill Na+-K+-ATPase activity (postsmolts), cortisol partially prevented the decline in activity that occurred during 4 days of culture. The relative ability of steroids to increase gill Na+-K+-ATPase activity was dexamethasone greater than cortisol = 11-deoxycortisol greater than cortisone. Insulin (0.1, 1.0, and 10.0 micrograms/ml), alone or in combination with cortisol, had no significant effect on gill Na+-K+-ATPase activity. Cortisol treatment significantly increased maximum binding capacity of [3H]ouabain in gill tissue (from 2.92 to 5.22 pmol/mg dry wt) but had no significant effect on the dissociation constant. These results demonstrate that cortisol has direct effects on the osmoregulatory physiology of the teleost gill.
Age sensitivity of osmoregulation and of its neural correlates in Aplysia
Authors: Skinner T. L. , Peretz B.
Published: December 2017

Osmoregulation was studied in the marine mollusc Aplysia californica in young, mature, and old adults. To monitor volume and osmoregulation, we measured body weight, hemolymph osmolality, and chloride concentration. These parameters were measured at regular intervals with animals in 90% artificial seawater (90% ASW) for up to 36 h. They showed that the rates at which Aplysia osmo- and volume regulate were significantly slowed with increased age. However, no age effect was found in osmoregulation when the hemolymph was diluted to 90% of control in animals without an external stress, i.e., by injection of distilled H2O and keeping animals in 100% ASW. Because the dilution bypassed the sensory receptors that detect external changes of osmolality, this finding suggested that the slowed osmoregulation involved age-impaired functioning of the neural pathway mediating osmoregulation. Other evidence was from mature adults whose osmoreceptive organ, the osphradium, was lesioned; they mimicked osmoregulation measured in old adults. In preparations containing a portion of the osmoregulatory pathway, the osphradium was stimulated by 90% ASW, and the responsiveness of neuron R15, which putatively regulates antidiuresis, was tested. The stimulus inhibited spiking in R15 from mature adults but not in R15 from old adults or from osphradiallesioned mature ones. In old Aplysia the refractoriness of R15 to osphradial stimulation demonstrated that the effecacy of the pathway was impaired with increased age; it helped explain the slower rate of osmoregulation. Possible changes of osmoregulatory mechanisms and behavior compensating for the age sensitivity of osmoregulation are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of endogenous opioids in the cardiovascular responses to asphyxia in fetal sheep
Authors: Espinoza M. , Riquelme R. , Germain A. M. , Tevah J. , Parer J. T. , Llanos A. J.
Published: December 2017

Intravenous administration of the opioid receptor antagonist naloxone to asphyxiated fetal sheep increases the arterial blood pressure. We examined the hypothesis that endogenous opioids modify the cardiac output distribution during asphyxia due to changes in the vascular resistance of some fetal organs. Thirteen fetal sheep (0.8-0.9 of gestation) were chronically catheterized. Fetal asphyxia was induced by reducing the uterine blood flow with an inflatable occluder around the common internal iliac artery to approximately 50% of control for 40 min. Naloxone solution or the solvent alone was added for the last 20 min. Asphyxia caused hypertension, and the fetal arterial blood pressure further increased when asphyxiated fetuses received naloxone. Heart, brain, and adrenal blood flows increased due to the increase in blood pressure, with no changes in their vascular resistances. In contrast, kidney and carcass blood flows decreased, and their vascular resistances increased. We conclude that endogenous opioids inhibit the vasoconstriction of these vascular beds during fetal asphyxia.