bluuebunny/crossref_metadata_2025 huggingface dataset:
Spinoreticular cell responses to intrarenal injections of bradykinin
Authors: Ammons W. S.
Published: December 2017

Thirty cats were anesthetized with alpha-chloralose, paralyzed, and artificially ventilated. Extracellular unit activity was recorded from 63 spinoreticular tract (SRT) neurons in the T12-L2 segments. All cells were excited by renal nerve stimulation and had somatic receptive fields. Intrarenal injection of bradykinin (4 micrograms/kg) increased activity of 36 cells from 7 +/- 1 to 23 +/- 5 spikes/s. Latency to onset of responses averaged 11 +/- 2 s and latencies to peak were 26 +/- 5 s. Intrarenal injection of isotonic saline vehicle or intravenous injection of the same dose of bradykinin failed to alter activity. Responses increased as dosage increased from 2 to 12 micrograms/kg. Seventeen cells exhibited tachyphylaxis to repeated injections. Cells most likely to respond to bradykinin received both A delta- and C-fiber renal inputs and/or were located in lamina V of the spinal gray matter. Mechanical pressure applied to the renal capsule excited eight of the cells that responded to bradykinin. These results show that activation of renal afferent fibers with bradykinin leads to activation of T12-L2 SRT neurons. These cells may participate in the ascending limb of supraspinal reflexes initiated by renal receptors.
Cardiovascular responses to intrathecal vasopressin in conscious and anesthesized rats
Authors: Martinez-Arizala A. , Holaday J. W. , Long J. B.
Published: December 2017

Increases in mean arterial pressure and heart rate have been documented after the intrathecal administration of [Arg8]vasopressin (AVP) in rats. Prior studies in our laboratories with conscious rats indicated that these cardiovascular changes were associated with a marked hindlimb sensorimotor dysfunction. In this study, which represents the first systematic comparison of the effects of intrathecal AVP in conscious and anesthesized rats, we demonstrate that in conscious male Sprague-Dawley rats 1) the motor dysfunction induced by intrathecal AVP is accompanied by a rise in mean arterial pressure that is significantly greater than that produced by an equal intravenous dose of AVP, and 2) both paralytic and pressor effects of intrathecal but not intravenous AVP are blocked by the intrathecal administration of the V1-receptor antagonist d(CH2)5[Tyr(Me)2]AVP (V1-ANT) but are not blocked by intravenous phenoxybenzamine, hexamethonium, or [Sar1, Thr8]angiotensin II, an angiotensin II antagonist. In contrast, in anesthesized rats the arterial pressor response to intrathecal AVP was blocked by intrathecal V1-ANT, intravenous hexamethonium, and intravenous phenoxybenzamine. Furthermore, conscious but not anesthesized rats exhibited a tachyphylaxis to intrathecal AVP. These results indicate that intrathecal AVP produces both the cardiovascular changes and the sensorimotor deficits through interactions with centrally located V1-receptors. In addition, sympathetic catecholaminergic mechanisms mediate the rise in mean arterial pressure produced by intrathecal AVP in anesthesized rats, but they do not in conscious rats.
Behavioral and hormonal influence on blood volume restitution after hemorrhage in swine
Authors: Carlson D. E. , DeMaria E. J. , Campbell R. W. , Gann D. S.
Published: December 2017

Hemorrhage of 14 ml.kg-1.5 min-1 was done in two groups of chronically prepared, splenectomized Yorkshire pigs that were conditioned behaviorally to lie in a Panepinto sling. In group 1 the conditioning included early use of active restraint. It was done before the preparative surgery and on postoperative day 3 before the experiment on day 4. In group 2 the use of active restraint was minimized during conditioning that was extended to postoperative days 4 and 5 before the experiment on day 6. Before hemorrhage, core temperature and plasma catecholamines, cortisol, adrenocorticotropin, vasopressin, and renin were greater in group 1 than in group 2; but blood volume, hematocrit, and body weight were identical. Peak hormonal concentrations were greater or more sustained during the 1st h after hemorrhage in group 1 than in group 2. Restitution of blood volume was greater in group 1 than in group 2 at 4 and 7 h. Greater total peripheral resistance at 2 h after hemorrhage and greater restitution of plasma protein by 7 h in group 1 contributed to its accelerated volume restoration. Comparison of arterial pressure and of right atrial volume (conductance catheter) between groups suggested that a greater response of arterial or right atrial stretch receptors in group 1 could not account for the results. We suggest that the method and duration of behavioral conditioning and the time for recovery from surgery are important determinants of the hemodynamic and hormonal responses to hemorrhage and their subsequent influence on the restitution of blood volume.
Brain stem mechanisms and the inhibition of angiotensin-induced drinking
Authors: Ohman L. E. , Johnson A. K.
Published: December 2017

The present studies examine the effect of lesions of the ventrolateral region of the lateral parabrachial nucleus (VLLPBN) and of the area postrema and medial region of the nucleus of the solitary tract (AP/mNTS) on water intake induced by intracerebroventricular administration of angiotensin II (ANG II) and of the cholinergic receptor agonist, carbachol. Water intake was measured in rats with bilateral electrolytic lesions of the VLLPBN or thermocautery ablation of the AP/mNTS after intracerebroventricular delivery of ANG II (50 and 100 ng/2 microliter), carbachol (100 and 250 ng/2 microliter), and isotonic saline (2 microliter). Rats with lesions of the VLLPBN drank significantly more water during a 30-min test period to both doses of ANG II, but not to carbachol, than did sham lesion rats. Similarly, AP/mNTS lesion rats drank significantly more than sham lesion animals in response to the high dose of ANG II but not to carbachol. These results suggest that the previously reported exaggerated drinking responses to systemically administered ANG II demonstrated by rats with either VLLPBN or AP/mNTS lesions is not the result of a direct peripheral action of the octapeptide. Furthermore, the similarity of the induced drinking responses produced by these two lesions suggests that the AP/mNTS and the VLLPBN may be linked in a common thirst-mediating pathway.
Sleep patterns in the genetically obese Zucker rat: effect of acarbose treatment
Authors: Danguir J.
Published: December 2017

Sleep patterns were continuously recorded in the genetically obese Zucker rat. Under normal feeding conditions, Zucker rats showed large amounts of slow-wave sleep (SWS) and normal amounts of pardoxical sleep (PS). In addition, both SWS and PS were equally distributed throughout the nychthemeron. When acarbose (an alpha-glucosidase inhibitor that slows absorption of glucose, reduces plasma insulin, and increases plasma somatostatin) was added to food pellets, the daily duration of SWS was markedly decreased, whereas PS was significantly increased. These results clearly show that sleep in the Zucker rat differs substantially from that classically observed in normal lean rats. In addition, they suggest that anomalies of insulin and somatostatin production and/or levels may cause the sleep disturbances observed in Zucker rats.
Regional hemodynamic effects of calcitonin gene-related peptide
Authors: Gardiner S. M. , Compton A. M. , Bennett T.
Published: December 2017

Cardiovascular responses to infusions of rat alpha-calcitonin gene-related peptide (CGRP; 0.06, 0.6, 6.0 nmol/h) or rat alpha-atrial natriuretic peptide (ANP; 3.7 nmol/h) were measured in conscious rats. During infusion of the low dose of CGRP, when mean arterial pressure (MAP) was little affected, there were reductions in common carotid, renal, mesenteric, and hindquarter vascular resistances (the magnitude of the responses in the same descending order). However, only flow in the common carotid vessels was increased above base line. After infusion, there was a hindquarter vasoconstriction. During infusion of the higher doses of CGRP, there were dose-related decreases in MAP and increases in heart rate associated with (hyperemic) hindquarter vasodilatations and mesenteric vasoconstrictions. The common carotid vasodilatation peaked with the intermediate dose of CGRP; the changes in renal vascular resistance were not dose related. After infusion of the high dose of CGRP there were persistent (at least 60 min) common carotid and hindquarter vasodilatations and mesenteric vasoconstriction, with a transient overshoot in renal vascular resistance. Infusions of CGRP and ANP matched for their effects on MAP had similar influences on mesenteric hemodynamics, but all other variables were affected differently.
Stereospecific feeding modulation by endogenous organic acid gamma-lactone in rats
Authors: Sakata T. , Terada K. , Arase K. , Fujimoto K. , Oomura Y. , Okukado N. , Uchikawa O.
Published: December 2017

Stereospecificity of 3,4-dihydroxybutanoic acid gamma-lactone (3,4-DB) and 2,4,5-trihydroxypentanoic acid gamma-lactone (2,4,5-TP) in their effects on feeding behavior and humoral factors was assessed by infusion into the rat third cerebroventricle. Initial transient food intake was most potently affected by infusion of 2.50 mumol of the 2S,4S-stereoisomer of 2,4,5-TP (80%) at 1100 h. Among the others, 2.50 mumol of the 2R,4S-isomer was somewhat potent in feeding elicitation (20%). Feeding induced by these isomers was not accompanied by periprandial drinking. Ambulation increased with elicitation of feeding. During the first dark period after infusion at 1940 h, 2.50 mumol of the 3S-isomer of 3,4-DB decreased food intake, including reduced meal size, and prolonged postprandial intermeal interval, but the 3R-isomer did not. Potent hypoglycemia with hyperinsulinemia was caused by the 2S,4S-isomer of 2,4,5-TP, and the S-isomer of 3,4-DB caused responses that were reciprocal to those to 2,4,5-TP. The remaining isomers did not affect feeding or humoral factors. The results suggest that the S- or S,S-stereo-isomer of the endogenous organic acid gamma-lactones may be important in modulating food intake through the hypothalamus.
Posttranslational processing of opioid pro-opiomelanocortin products in piglets
Authors: Moss I. R. , Inman J. G. , Slaughter C. A.
Published: December 2017

We have measured levels of beta-lipotropin, beta-endorphin, and N-acetyl-beta-endorphin in the plasma, cerebrospinal fluid (CSF), and caudal medullary brain containing the respiratory-related portion of the nucleus tractus solitarius (NTS) of 2.5 +/- 1.0- (SD) and 38.2 +/- 3.7-day-old naive uninstrumented piglets. Time of day, ambient atmosphere, temperature, handling, sound, light, and nutritional status were kept constant. Experimental procedure included decapitation and rapid collection, processing, and freezing of tissues until analysis by radioimmunoassay. Young, compared with older piglets, have higher measured levels of beta-lipotropin in the plasma and CSF and of N-acetyl-beta-endorphin in all three body compartments. Although measured levels of beta-endorphin-like immunoreactivity are also higher in the plasma and CSF of the young group, the calculated level of beta-endorphin is higher only in the CSF. In the NTS, both the measured and calculated active endorphin appear higher in the older group, but this difference is not significant. Excess beta-endorphin in the CSF of neonates may explain the relative immaturity of their respiratory functions at birth.
Structure and concentrating ability in the avian kidney
Authors: Goldstein D. L. , Braun E. J.
Published: December 2017

We quantified various aspects of the morphology of the kidney in seven bird species and related these measures to urinary concentrating ability (the concentration of ureteral urine in dehydrated animals) for six of the species. Kidney mass, number of glomeruli, and number of medullary cones all tended to increase with body mass. Smaller birds, with smaller kidneys, had smaller nephrons with smaller glomeruli. Lengths of medullary cones tended to increase with body mass and were exceptionally long in the macaroni penguin. The proportion of nephrons that were mammalian-type (MT, with loops of Henle) ranged from 7% (ring-necked pheasant) to 30% (zebra finch, glaucous-winged gull) and was unrelated to kidney mass. The percent of kidney mass comprised of medullary cones varied from 5 to 13%, unrelated to kidney mass. The number of reptilian-type (without loops of Henle) nephrons associated with each medullary cone tended to increase with kidney mass. Of the variables examined, length of the medullary cones, and hence of the longest loops of Henle, was most strongly correlated with urinary concentrating ability; however, this correlation was negative. Concentrating ability was also strongly negatively correlated with body mass (small birds concentrate better). No significant relation existed between concentrating ability and proportion of MT nephrons. Our data suggest that, in a broad interspecific comparison, the quantitative extent of the renal medulla is not the primary determinant of urinary concentrating ability in birds.
Chronic CEI alters effect of low Na+ diet in normal and coarcted pups. II. Na+ and H2O balance
Authors: Bagby S. P. , Fuchs E.
Published: December 2017

To assess angiotensin (ANG II) dependence of evolving neonatally induced coarctation hypertension (NICH) in inbred pups, we randomized sex-matched littermates to high-dose converting enzyme inhibitor (CEI: MK-421, 3 mg/kg) or placebo from the time of neonatal aortic banding (coarcted) vs. no banding (control). During phase 1 studies over 4 mo postbanding during ad libitum Na+ intake (Bagby and Fuchs, Hypertension Dallas in press). CEI failed to prevent evolution of proximal blood pressure (BP) excess or to impair renal function. Phase 2 studies examine, in the same pups, responses to low Na+ (LS) diet superimposed on chronic CEI at 4 mo, timed to allow development of BP increase in untreated NICH. The present report details metabolic handling and balances of Na+, K+, and fluid for 3 days before (normal Na+ intake) and daily for 11 days after initiation of LS diet, a companion paper describes BP, renin-angiotensin (RA), and renal functional responses. In no case did metabolic responses of coarcted pups to LS diet differ from those of controls, whether on CEI or placebo, whereas responses to LS diet and to CEI reveal positive findings of independent interest. LS diet induced expected renal and fecal Na+ conservation, no net effect on K+ balance, and, despite unexpected free-water diuresis, mild hyponatremia. Chronic CEI impaired maximal renal (but not fecal) Na+ conservation during LS diet, caused exaggerated free-water diuresis but no change in fluid balance, and thus, with the larger Na+ deficit, accounted for greater hyponatremia. CEI caused no net effect on K+ balance. Results indicate normal renal handling of fluid, Na+, and K+ in evolving NICH and provide no evidence for selective intrarenal RA activation or exaggerated ANG II dependence. Findings also suggest that, during LS diet, ANG II is 1) essential for maximum renal Na+ conservation and normal free-water handling, and 2) not essential for fecal Na+ and water conservation or for maintenance of normal water and K+ balances. Results are also compatible with a CEI-induced thirst stimulation and/or osmotic insensitivity and with functional vasopressin deficiency during LS diet.
Effects of brain natriuretic peptide on renal nerve activity in conscious rabbits
Authors: Morita H. , Nishida Y. , Motochigawa H. , Kangawa K. , Minamino N. , Matsuo H. , Hosomi H.
Published: December 2017

Responses of renal nerve activity (RNA) to intravenous infusion of brain natriuretic peptide (BNP) were examined in chronically instrumented conscious rabbits with all baroreflexes intact, sinoaortic baroreceptor denervation (SAD), and SAD plus vagotomy. In intact rabbits, an infusion of BNP at a rate of 0.3 microgram.kg-1.min-1 for 30 min decreased mean arterial pressure (MAP) by 8 +/- 1 mmHg and increased RNA by 48 +/- 4% but did not alter heart rate (HR). The decrease in MAP in SAD rabbits (20 +/- 3 mmHg) was greater than in intact rabbits, whereas RNA increased less (21 +/- 7%). After SAD plus vagotomy, BNP lowered MAP by 25 +/- 4 mmHg, whereas RNA was not altered significantly. To further examine the effects of BNP on baroreflex control of HR and RNA, the baroreceptors were stimulated or unloaded by raising or lowering MAP by injections of phenylephrine or glyceryl trinitrate, respectively. The maximum change in each HR or RNA response to phenylephrine or glyceryl trinitrate was plotted against the maximum change in each MAP response and a logistic function curve was fitted to the MAP-HR and MAP-RNA relationship. BNP did not alter the slope of either curve but shifted both curves to the left. These results indicate that 1) in intact rabbits, BNP increases RNA due to sinoaortic and cardiopulmonary baroreflexes and 2) BNP resets the baroreflex control of HR and RNA to a lower arterial pressure.
Semiparametric approach to pharmacokinetic-pharmacodynamic data
Authors: Verotta D. , Beal S. L. , Sheiner L. B.
Published: December 2017

A semiparametric model for analysis of pharmacokinetic (PK) and pharmacodynamic (PD) data arising from non-steady-state experiments is presented. The model describes time lag between drug concentration in a sampling compartment, e.g., venous blood (Cv), and drug effect (E). If drug concentration at the effect site (Ce) equilibrates with arterial blood concentration (Ca) slower than with Cv, a non-steady-state experiment yields E vs. Cv data describing a counterclockwise hysteresis loop. If Ce equilibrates with Ca faster than with Cv, clockwise hysteresis is observed. To model hysteresis, a parametric model is proposed linking (unobserved) Ca to Cv with elimination rate constant kappa ov and also linking Ca to Ce with elimination rate constant kappa oe. When kappa oe is greater than (or less than) kappa ov clockwise (or counterclockwise) hysteresis occurs. Given kappa oe and kappa ov, numerical (constrained) deconvolution is used to obtain the disposition function of the arterial compartment (Ha), and convolution is used to calculate Ce given Ha. The values of kappa oe and kappa ov are chosen to collapse the hysteresis loops to single curves representing the Ce-E (steady-state) concentration-response curve. Simulations, and an application to real data, are reported.
Blood pressure responses to cyclic blood volume changes in awake and anesthetized dogs
Authors: Brown D. R. , Cowley A. W. , Young D. B.
Published: December 2017

A dynamic analysis of blood pressure regulation was performed in conscious and anesthetized dogs. The mean arterial pressure (MAP) responses to 5 and 10% sinusoidal changes in total blood volume with cycle lengths of 1, 4, and 8 min were measured in anesthetized 1) control dogs, 2) carotid and vagal baroreflex (CVB)-denervated animals, and 3) spinal-ablated dogs; in addition, the MAP responses to 10% sinusoidal blood volume changes with cycle lengths ranging from 0.25 to 8 min were measured in conscious control and CVB-denervated dogs. The presence of the baroreflexes in both the conscious and anesthetized control dogs essentially eliminated MAP excursions during the cyclic volume changes. The MAP changes in both the conscious and anesthetized denervated dogs were large. However, the responses in the anesthetized denervated dogs were linear, stationary, and cycle-length insensitive with respect to the sinusoidal forcing function, whereas the responses in the conscious CVB-denervated dogs were nonlinear, nonstationary, and cycle-length dependent. These results indicate that the cardiovascular system in the anesthetized CVB-denervated and spinal-ablated dogs is passive or "hydraulic" in nature; conversely, factors other than the carotid and vagal baroreflexes appear to exist that alter the arterial pressure responses to cyclic blood volume perturbations in the conscious CVB-denervated dogs.
Effects of exercise-rest cycles on energy balance in rats
Authors: Richard D. , Lachance P. , Deshaies Y.
Published: December 2017

The present study investigated the nutritional energetics of rats exercised either intermittently or continually. Male rats were divided into three groups: a sedentary group, an intermittently trained group, and a continually trained group. Continually trained rats were exercised every day for a period of 8 wk. Over the same period, intermittently trained rats were exercised for 4 wk, each week being followed by a week of rest. Rats were trained on a rodent treadmill at a moderate intensity. Carcasses were analyzed for energy, fat, and protein contents. Brown adipose tissue (BAT) thermogenesis was assessed by measuring mitochondrial guanosine 5'-diphosphate binding. Energy intake was lower in both intermittently and continually trained rats than in sedentary animals. The weight, fat, and protein gains were, in continually trained rats, significantly lower than in sedentary animals. Similarly, intermittently trained rats had lower gains than sedentary animals, although the difference between the two groups was not as marked as the difference between sedentary and continually trained animals. Energy expenditure, which represents the difference between energy intake and energy gain, was less than sedentary controls in both intermittently and continually trained rats. The low expenditure in trained groups did not, however, relate to changes in facultative BAT thermogenesis.A low energy expenditure on components such as basal metabolic rate and obligatory diet-induced thermogenesis would most likely account for the difference in expenditure between sedentary and trained rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Body weight of rats following area postrema ablation: effect of early force-feeding
Authors: Kenney N. J. , Kott J. N. , Tomoyasu N. , Bhatia A. J. , Ruiz A. S. , McDowell M. M.
Published: December 2017

This study examined the effect of intragastric force-feeding of a milk diet on body weights of rats with lesions of the area postrema/caudal medial nucleus of the solitary tract (AP/cmNTS). Force-feeding was conducted over the first 10 days after the ablation. Body weight was monitored both during and after force-feeding. Food intake was measured during all ad libitum feeding periods. During force-feeding, rats with AP/cmNTS lesions gained weight at the same rate as force-fed sham-lesioned rats or sham-lesioned rats that voluntarily ingested an equal amount of the milk. When returned to ad libitum feeding, lesioned rats that had been force-fed were not hypophagic and did not lose weight. Body weights of such rats remained above those of lesioned rats that were not force-fed and similar to those of nonlesioned rats throughout this study. Despite their normal weights, preliminary analysis indicated that body fat of the force-fed lesioned rats may have been reduced. These findings suggest that the effects of AP/cmNTS ablation are multiple and that reduction of body weight need not be the primary effect of such lesions.
Effects of anorexigenic treatments on gastric motility in rats
Authors: Flanagan L. M. , Verbalis J. G. , Stricker E. M.
Published: December 2017

In these experiments we examined the effects on gastric motility of cholecystokinin, LiCl, hypertonic NaCl solution, gastric distension, and intraduodenal glucose loads, five dissimilar treatments known to reduce food intake in rats. In addition, we investigated whether any observed effects were dependent on the afferent vagus nerve by pretreating subjects with the neurotoxin capsaicin. Each of the five treatments virtually eliminated the gastric contractions seen after rats had consumed a large meal of chow; these effects were rapid in onset and continued for up to 30 min. The inhibitory effects of cholecystokinin and gastric distension were eliminated by pretreatment with capsaicin, whereas the effects of the other treatments were attenuated only slightly or not at all. Because most of these treatments have been shown to stimulate pituitary oxytocin secretion in rats as well as to inhibit food intake and gastric motility, these results are consistent with the hypothesis that the hypothalamic paraventricular nucleus is a site at which information is integrated in the coordinated control of food intake, gastric function, and neuroendocrine secretion.
Sinoaortic denervation attenuates the reflex responses to hypotension in fetal sheep
Authors: Wood C. E.
Published: December 2017

Hypotension in fetal sheep stimulates reflex decreases in heart rate and increases in the secretion of several hormones, including adrenocorticotropin (ACTH), cortisol, vasopressin, and renin. However, little is known about the afferent limb(s) of the reflex(es) controlling these responses. Fetal sheep between 122 and 134 days gestation were prepared with chronic vascular catheters, intravascular balloon-tipped catheters, and amniotic fluid catheters. Seven fetal sheep were also subjected to sinoaortic denervation, and nine remained intact. After recovery from surgery for 2-5 days, fetuses were subjected to a 10-min period of hypotension produced by vena caval obstruction, produced by inflation of balloons in the superior and inferior venae cavae. Vena caval obstruction produced decreases in fetal heart rate and increases in fetal plasma ACTH, vasopressin, and renin activity, which were related to the degree of hypotension. Prior sinoaortic denervation attenuated all of these responses. It is concluded that afferent fibers in the carotid sinus and/or aortic depressor nerves mediate part of the heart rate, ACTH, vasopressin, and renin responses to vena caval obstruction in late-gestation fetal sheep.
Anterior and posterior pituitary hormone release induced in sheep by cholecystokinin
Authors: Ebenezer I. S. , Thornton S. N. , Parrott R. F.
Published: December 2017

The effect of an intravenous bolus injection of cholecystokinin octapeptide (CCK-8; 0.85 micrograms/kg) on the release of cortisol, prolactin, vasopressin, and oxytocin was studied in sheep (n = 10). Concentrations of these hormones were measured in blood samples taken before (-10, 0 min) and after (5, 10, 20 min) administration of a saline vehicle or vehicle + CCK. Following CCK treatment, levels of cortisol were raised after 10 and 20 min, prolactin and vasopressin concentrations were increased after 5 min, and oxytocin secretion was unaffected.
Maternofetal potential difference in pigs
Authors: Boyd R. D. , Glazier J. D. , Sibley C. P. , Ward B. S.
Published: December 2017

The maternofetal potential difference (PD) between catheters in maternal and fetal blood vessels has been measured in conscious sows between 97 and 107 days of gestation. The maternofetal PD was -18 +/- 4 mV (mean +/- SE, n = 13, fetus negative) on the day of surgery and -29 +/- 5 mV (n = 6) on the day after surgery. Injection of 2, 20, or 200 micrograms of epinephrine into the fetuses caused a marked rapid change in maternofetal PD such that the fetus became less negative and, in some cases, became positive with respect to the mother. The maximum change, obtained with 20 micrograms, was 19.9 +/- 5.6 mV (n = 7); measurements of fetal plasma epinephrine concentrations (using high-performance liquid chromatography) after injection of this dose gave a time 0-extrapolated concentration of 436.5 +/- 169.0 nmol/l (n = 4). Injection of 20 micrograms of the beta-agonist isoprenaline caused a maximum change in PD of 20 +/- 4 mV (n = 6); 2 mg of the alpha-agonist phenylephrine was required to produce a similar change (15 +/- 2 mV, n = 6). Injection of the beta-antagonist propranolol (1 mg) reduced the effect of 20 micrograms epinephrine by 40%. The effect of catecholamine on maternofetal PD is similar in polarity and specificity to that found for transplacental PD in vitro in the same species. There is, however, a difference between resting maternofetal and transplacental PD that remains unexplained.
Thermoregulatory control of expired air temperature in diving harp seals
Authors: Folkow L. P. , Blix A. S.
Published: December 2017

Expired air temperature (Tex), metabolic rate (MR), and skin (Ts) and body (Tb; rectal) temperatures were recorded in four or five young (1-2 yr) harp seals (Phoca groenlandica) in air [mean air temperature (Ta) = -30, -10, or 10 degrees C] and in water [mean water temperature (Tw) = 2.3 or 24.8 degrees C, with Ta = -30, -10, 0, or 10 degrees C]. Apparent lower critical temperature was below -10 degrees C in air. Above this Ta, mean MR was 5.85 W.kg-0.75 (2.23 W.kg-1), while mean MR was 12.56 W.kg-0.75 (4.69 W.kg-1) at Ta -30 degrees C. When seals were immersed in water of 2.3 degrees C, mean MR was 6.13 W.kg-0.75 (2.31 W.kg-1), regardless of Ta.At Ta -30, -10, and 10 degrees C, mean Tex in air were 9.5, 13.0, and 25.0 degrees C, respectively. The corresponding values for seals in water (Tw = 2.3 degrees C) were 8.0, 9.5, and 15.5 degrees C, respectively. The low Tex recorded at Ta -30 and -10 degrees C in air and at all Ta in water (Tw = 2.3 degrees C) suggests that heat was conserved by nasal heat exchange. At Ta 10 degrees C, mean Tex of seals in air was approximately 10 degrees C higher than mean Tex of seals in water (Tw = 2.3 degrees C). Furthermore, seals subjected to a Tw of 24.8 degrees C at Ta 0 degrees C had a mean Tex 10 degrees C higher than when subjected to Tw 2.3 degrees C at the same Ta. These observations suggest that Tex in seals is under thermoregulatory control. In a series of forced dives of up to 5-min duration Tex was found to be the same before and after the dive regardless of dive duration and Ta.
Control of thermoregulatory sweating during exercise in the heat
Authors: Sawka M. N. , Gonzalez R. R. , Young A. J. , Dennis R. C. , Valeri C. R. , Pandolf K. B.
Published: December 2017

The purposes of this study were the following: 1) to determine whether erythrocyte infusion alters the control of thermoregulatory sweating and 2) to demonstrate how increases and decreases of both plasma tonicity and blood volume influence the thermoregulatory control parameters of threshold temperature and sweating sensitivity. Six non-heat-acclimated and five heat-acclimated males attempted heat stress tests (HSTs) both before and shortly after (48-96 h) autologous erythrocyte infusion. The non-heat-acclimated subjects were euhydrated for both HSTs, whereas the heat-acclimated subjects were studied in a euhydrated and a hypohydrated (-5% body wt) condition both pre- and postinfusion (500 ml of solution containing approximately 60% hematocrit of autologous erythrocytes). The HSTs consisted of treadmill exercise (335 W.m-2) in a hot (35 degrees C, 45% relative humidity) environment, and esophageal temperature and local sweating rate were continuously measured during 25 min of exercise. These experiments resulted in a matrix of conditions where both plasma tonicity and blood volume were increased or decreased relative to control conditions (euhydration, preinfusion). The findings concerning thermoregulatory sweating during exercise in the heat were summarized as follows: 1) acute polycythemia decreases the threshold temperature and increases the sweating sensitivity, 2) both threshold temperature and sweating sensitivity are increased or decreased from control levels dependent on the combined influence of plasma tonicity and blood volume, and 3) equations are presented that describe how plasma tonicity and blood volume alter threshold temperature and sweating sensitivity values.
Prostaglandins in carotid sinus enhance baroreflex in rabbits
Authors: McDowell T. S. , Axtelle T. S. , Chapleau M. W. , Abboud F. M.
Published: December 2017

The purpose of this study was to examine the possible influence of endogenous prostaglandins in the carotid sinus on the arterial baroreflex. Lumbar sympathetic nerve activity (LSNA) and arterial pressure were recorded during step increases in isolated carotid sinus pressure in rabbits anesthetized with chloralose. Baroreflex responses were facilitated after intrasinus administration of prostacyclin (PGI2; 5 and 10 microM, n = 6) or arachidonic acid (10 microM, n = 12). PGI2 (10 microM) increased the slope of the carotid sinus pressure-LSNA relation (gain) from -0.32 +/- 0.09 to -1.19 +/- 0.38 spikes.s-1.mmHg-1 and decreased the pressure at which 50% of the maximum inhibition of LSNA occurred (EP50) from 127 +/- 5 to 98 +/- 4 mmHg (P less than 0.05). Similar responses were observed with arachidonic acid. Baroreflex responses were attenuated after intrasinus administration of indomethacin (40 and 80 microM, n = 5) or aspirin (1 and 2 mM, n = 7). Indomethacin (80 microM) decreased the gain of the baroreflex from -1.02 +/- 0.24 to -0.47 +/- 0.16 spikes.s-1.mmHg-1 and increased the EP50 from 121 +/- 6 to 133 +/- 7 mmHg (P less than 0.05). Both indomethacin (80 microM) and aspirin (2 mM) reduced the maximum percent inhibition of LSNA significantly. The results indicate that prostaglandins within the carotid sinus facilitate the baroreflex control of LSNA. The attenuation of the baroreflex after inhibition of cyclooxygenase suggests that endogenous prostaglandins contribute to the activation of baroreceptors during increases in carotid sinus pressure.
Kinetic analysis of electrogenic 2 Na+-1 H+ antiport in crustacean hepatopancreas
Authors: Ahearn G. A. , Clay L. P.
Published: December 2017

Na+ uptake by short-circuited brush-border membrane vesicles of the hepatopancreatic epithelium from the freshwater prawn Macrobrachium rosenbergii was Cl- independent, amiloride sensitive, and stimulated by a transmembrane proton gradient ([H+]i greater than [H+]o). Na+ influx (3-s uptake) was a sigmoidal function of [Na]o (2.5-150 mM), when pHi = 6.0, pHo = 8.0, and followed the Hill equation for binding cooperativity [maximal Na+ influx (Jm) = 140.6 nmol mg-1s-1; affinity constant (K') = 82.2 mM Na+; Hill coefficient (n) = 2.07]. Influx kinetic analyses at physiological conditions suggested two external cation-binding sites shared by Na+ and H+ (proton dissociation constant Pk1 = 5.7; Pk2 = 4.0) and a single internal cation site used only by H+ (Pk = 6.5). Amiloride was a competitive inhibitor of Na+ transport at both external binding sites (Ki1 = 50 microM; Ki2 = 1,520 microM). Electrogenic Na+-H+ exchange by these vesicles was demonstrated using an equilibrium-shift method of analysis and a transmembrane electrical potential difference as the only driving force for transport. In addition, electrogenic net Na+ influx (3-s uptake) was observed in vesicles loaded with 5 mM 22Na at pH 7.0 and exposed to media containing several 22Na or proton concentrations. Results suggest the following exchange model: low [Na]o, (1 Na+ and 1 H+)-1 H+; high [Na+]o, 2 Na+-1 H+. This antiport mechanism may account for two major functional operations of the gastrointestinal tract in these animals: 1) proton secretion against considerable concentration gradients leading to stomach luminal acidification, and 2) Na+ absorption from lumen to cytoplasm potentially making a significant contribution to organismic ion balance.
Effect of exercise training on energy balance of orchidectomized rats
Authors: Rivest S. , Landry J. , Richard D.
Published: December 2017

The purpose of the present study was to investigate both the respective and interactive roles of exercise training and testosterone on energy balance. Male rats were divided into sedentary and exercise-trained groups. Each group formed was further divided into a sham-operated group, an orchidectomized group, or an orchidectomized group treated with testosterone. Rats were exercised on a motor-driven treadmill for 1 h/day over 28 consecutive days, after which rats were killed. Energy balance measurements, body composition analyses, and serum testosterone assay were then performed. The weight, protein content, and cytochrome-c oxidase activity of interscapular brown adipose tissue (IBAT) were also measured. Results indicate that total food intake, final body weight, and body weight gain were generally lower in exercise-trained rats than in sedentary animals. In orchidectomized rats treated with testosterone, gains of both fat and protein were lower in exercise-trained than in sedentary animals. There was no difference in metabolizable energy intake and body energy gain between trained and sedentary rats that underwent orchidectomy without replacement therapy. In orchidectomized groups of rats, energy gain was lower in trained rats that were treated with testosterone than in those that did not receive any treatment. Furthermore, in trained orchidectomized rats treated with testosterone, both energetic efficiency and energy density of body weight gain were lower than those of trained orchidectomized rats that were not treated. Finally, a significant reduction in IBAT weight was observed in exercise-trained animals, whereas neither exercise nor the various hormonal manipulations affected IBAT protein content and cytochrome-c oxidase activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Anorexia induced by interleukin 1: involvement of corticotropin-releasing factor
Authors: Uehara A. , Sekiya C. , Takasugi Y. , Namiki M. , Arimura A.
Published: December 2017

It has recently been demonstrated by three independent research groups including ours that interleukin 1 (IL-1), a polypeptide hormone produced by activated monocytes or macrophages, or both, stimulates the release of hypothalamic corticotropin-releasing factor (CRF). Since CRF acts centrally in the brain to reduce food intake, we hypothesized that IL-1 might induce anorexia through this central action of CRF. The present study was carried out to examine the hypothesis, using male Wistar rats. Based on three lines of evidence, we report here that IL-1, both endogenously released and exogenously administered, induces the suppression of food intake in rats and that endogenous CRF in the brain is involved in the IL-1-induced anorexia. First, lipopolysaccharide (LPS), a potent stimulant of the release and production of endogenous IL-1, caused anorexia in a dose-related manner, and this effect was significantly blocked by pretreatment with glucocorticoid hormones, which have been shown to inhibit the production of endogenous IL-1 by LPS. Second, intraperitoneal injection of IL-1 resulted in a dose-related suppression of food intake. Third, anorexia induced by IL-1 was diminished by the immunoneutralization of endogenous CRF in the brain. These results provide further evidence of the existence of bidirectional communication between the immune and neuroendocrine systems. Furthermore, this connection between IL-1 and CRF may represent a mechanism by which anorexia results from the activation of the immune system by such immunological challenges as acute infectious diseases.
Prior immobilization stress alters adrenal hormone responses to hemorrhage in rats
Authors: Graessler J. , Kvetnansky R. , Jezova D. , Dobrakovova M. , Van Loon G. R.
Published: December 2017

The effect of prior immobilization stress (IMO) on the plasma epinephrine (EPI), norepinephrine (NE), adrenocorticotropic hormone (ACTH), and corticosterone (CS) responses to acute hemorrhage was studied in conscious male rats with chronic catheters in tail artery, using two combinations of IMO and hemorrhage. IMO per se led to significant increases of EPI, NE, ACTH, and CS in all animals. Hemorrhage of 25% of estimated blood volume (EBV) performed immediately after 150 min IMO caused exaggerated release of EPI and NE, whereas CS remained unchanged at the level previously elevated by IMO. ACTH response to initial blood loss of 12.5% was diminished in previously immobilized rats. Hemorrhage of 35% EBV after 60 min IMO and a 10-min recovery period also resulted in potentiated increases in EPI and NE, suppressed ACTH secretion, and no further change in stress-elevated CS concentration. No differences between groups were observed in relative mean arterial blood pressure, plasma protein, and lactate responses to 35% hemorrhage. Posthemorrhagic increase of plasma concentration of several tissue enzyme activities was significantly higher in prestressed rats. Furthermore, 24-h mortality rate increased by 49%. In summary, our results indicate that prior IMO potentiated activation of the sympathoadrenomedullary system and suppressed ACTH response to subsequent hemorrhage. Altered neuroendocrine responsiveness and stress-induced prehemorrhagic tissue damage may play roles in the increased susceptibility of the organism to blood loss.
Effect of age and gender on thermoregulation
Authors: McDonald R. B. , Day C. , Carlson K. , Stern J. S. , Horwitz B. A.
Published: December 2017

Previous investigations have shown that during cold exposure 24-mo-old male Fischer 344 (F344) rats do not thermoregulate as well as do 12-mo-old animals. To determine if this deficiency also occurs in female rats, we measured oxygen consumption (thermogenesis) and colonic temperature of male and female rats 5, 23, and 27 mo of age at rest and during 6 h of exposure to 6 degrees C. In addition, nonshivering thermogenesis (NST) was evaluated from the capacity of brown adipose tissue (BAT) mitochondria isolated from cold-exposed rats to bind guanosine 5'-diphosphate (GDP). Neither age nor gender had a significant effect on resting or cold-exposed oxygen consumption expressed on a mass-independent basis (l/kg body mass0.67) or on a lean body mass independent basis (l/kg lean body mass0.67). The drop in colonic temperature in response to cold was greater in the male rats. However, females exhibited increased BAT mass and relatively constant GDP binding with advancing age, whereas males showed decreased mass and GDP binding. Although the data suggest greater NST capacity in the female rats, rates of cold-induced oxygen consumption were similar in older female vs. male rats. Taken together, our data indicate that gender has a significant impact on thermoregulation and that, under the cold exposure conditions of the study, this effect involves differential heat conservation rather than heat production.
Osmotic control of vasopressin in male and female rats
Authors: Crofton J. T. , Share L.
Published: December 2017

To examine the osmotic control of vasopressin release, hypertonic saline was infused in conscious unrestrained male rats and female rats in each phase of the estrous cycle. The progressive increase in plasma osmolality was accompanied by a progressive increase in the plasma vasopressin concentration, but the magnitude of the former was smaller in metestrus than in other phases of the cycle and in males (P less than 0.01). The osmotic threshold for vasopressin release was higher in males than in females in each phase of the estrous cycle (P less than 0.05 to P less than 0.01), but the sensitivity of the osmotic control of vasopressin release was similar in male and female rats. Although the pressor response to hypertonic saline was greater in estrous females than in the other females (P less than 0.05 to P less than 0.01), the reduction in blood pressure, after a V1 antagonist 30 min after starting the hypertonic saline infusion, was similar in males and females. Thus there are gender-related differences in the osmotic control of vasopressin release and, in females, cycle-dependent differences in the cardiovascular responses to hypertonic saline.
Effect of cortisol on vasopressin response to hypertonic saline in fetal sheep
Authors: Bennett T. L. , Rose J. C.
Published: December 2017

To determine the effect of cortisol on vasopressin responses to hyperosmolality, we infused hypertonic saline (HS) (12 meq/kg NaCl) into nine chronically cannulated fetal sheep ranging from 110 to 132 days of gestation. The experiment was performed twice on each fetus, once during a continuous cortisol infusion and once during a vehicle infusion. Administration of HS resulted in a prompt increase in serum osmolality from 292.1 +/- 1.8 to 310.4 +/- 2.5 mosmol/kg. Decreases were seen in pH, partial pressure of O2, and hematocrit from 7.37 +/- 0.01 to 7.31 +/- 0.01, from 22.5 +/- 1.6 to 20.0 +/- 2.0 mmHg, and from 35.6 +/- 1.7 to 32.6 +/- 1.6, respectively. Mean arterial pressure increased from 41.3 +/- 1.4 to 48.9 +/- 2.0 mmHg (P less than 0.01). Arginine vasopressin (AVP) rose from base line after HS (P = 0.11 vehicle experiments, P = 0.04 cortisol experiments), and AVP responses were greater in the cortisol experiments than in the vehicle experiments (delta AVP = 21.9 +/- 10.9 vs. 3.1 +/- 0.9 pg/ml, P = 0.05). Also there was a correlation noted between differences in AVP response and cortisol levels (P less than 0.04). We conclude that cortisol exerts a positive influence on the AVP response to HS in fetal sheep.
Immunoreactive atriopeptin in plasma of fishes: its potential role in gill hemodynamics
Authors: Evans D. H. , Chipouras E. , Payne J. A.
Published: December 2017

With the use of antibodies raised against human atriopeptin (AP), immunoreactive AP (APir) was quantified in the plasma of five species of marine fishes, including members of the Agnatha, Chondrichthyes, and Osteichthyes. Concentrations of APir in fish plasma are in the same range as those described for mammalian species, indicating that AP was present in the earliest vertebrates and has retained at least partial structural similarity during the course of vertebrate evolution. Acclimation of two species to very dilute seawater was associated with a significant reduction in plasma APir, suggesting that salt loading, rather than volume expansion, may be the primary stimulus for AP release in fishes. Heterologous rat atriopeptin (AP101-126) vasodilated preconstricted, perfused gills and unstimulated isolated vascular rings from the ventral aorta of the marine teleost Opsanus beta with an apparent half maximum effective concentration (EC50) of 3-4 x 10(-9) M, similar to sensitivities to AP described for mammalian vascular smooth muscle. Acclimation of toadfish to approximately 5% seawater (hyposmotic to plasma) did not alter the sensitivity of the perfused gills but reduced the apparent EC50 of rat AP on aortic rings to 3 x 10(-10) M. Extracts from O. beta atrium, ventricle, and brain also produced dilation of aortic rings, with ventricular extracts producing the greatest effect per milligram extracted tissue, suggesting that the ventricle may be a major site source of atriopeptin in fishes. An atriopeptin-induced increase in blood flow to the fish gill would theoretically have detrimental osmotic consequences, but may stimulate salt transport, again suggesting that a putative atriopeptin may be involved in salt, rather than osmotic, balance in fishes.
Calcium-channel blockade in canine hemorrhagic shock
Authors: Horton J. W.
Published: December 2017

The effect of verapamil (VER) resuscitation from shock on cardiac function, regional blood flow, as well as skeletal muscle transmembrane potential (TMP) and electrolyte redistribution were studied. Two hours of hypotensive shock in the dog significantly impaired cardiac function and coronary perfusion; TMP fell from 89.9 +/- 0.9 to 75.1 +/- 1.2 mV. Skeletal muscle (SMS) extracellular water decreased 40 +/- 2%, whereas intracellular sodium and chloride increased and intracellular potassium fell. Serum hypocalcemia was accompanied by a significant rise in total myocardial tissue calcium (from 312 +/- 20 to 415 +/- 21 micrograms/g dry wt; P = 0.01); total SMS tissue calcium tended to increase during this time (from 259 +/- 24 to 305 +/- 46 micrograms/g dry wt). After 2 h of shock, all dogs received shed blood and lactated Ringer solution (60 ml/kg); 21 dogs received VER, 20 micrograms/kg with fluid resuscitation; 21 dogs received fluid resuscitation only. Volume replacement improved hemodynamic function to a similar extent in all dogs. However, TMP, intracellular water, sodium, and potassium returned closer to base-line values after VER compared with dogs given only fluid resuscitation. SMS calcium was lower in VER dogs (148 +/- 4 micrograms/g) compared with dogs treated with fluid alone (322 +/- 24 micrograms/g, P = 0.01). Myocardial calcium fell in all dogs after volume replacement regardless of calcium-channel blockade (VER: 148 +/- 8, Ringer: 165 +/- 17 micrograms/g; P greater than 0.05). Our data indicate a potential role for calcium-entry blockade in the treatment of hemorrhagic shock.