bluuebunny/crossref_metadata_2025 huggingface dataset:
Hemodynamic, hormonal, and drinking responses to reduced venous return in the dog
Authors: Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

The effect of an acute reduction in venous return, caused by reversible constriction of the thoracic vena cava, on drinking and secretion or arginine vasopressin (AVP) was examined in the dog. Plasma AVP levels rose immediately from a control level of 1.4 +/- 0.1 pg/ml (mean +/- SE) to a plateau ranging between 36 and 42 pg/ml during the first 30 min after constriction but declined to 12.6 +/- 4.2 pg/ml 2 h after constriction even though systemic arterial hypotension was maintained. Drinking occurred with a latency of 22 +/- 6 min and 13.2 +/- 1.8 ml H2O/kg was consumed during 2 h of vena caval constriction. Water intake was significantly correlated with the average reduction in blood pressure (r = 0.86; n = 8; P less than 0.01) but not with plasma renin activity. The role of angiotensin II (ANG II) in the drinking and secretion of AVP in response to decreased venous return was evaluated using the ANG II receptor blocker, saralasin, infused intravenously (iv) or intracerebroventricularly (icv). Intravenous, but not icv, infusion of saralasin during vena caval constriction reduced the ability of the dogs to maintain arterial blood pressure (P less than 0.05). However, neither iv nor icv saralasin significantly affected water intake or the rise in plasma AVP in response to vena caval constriction when compared to their respective controls. Taken together, these data show that angiotensin is important in the maintenance of systemic arterial blood pressure but is not essential for the rise in plasma AVP or drinking in response to an acute reduction in venous return. It is suggested that either arterial baroreceptors or "low-pressure" volume receptors or both mediate the drinking and AVP responses in the presence of central blockade of the effects of circulating angiotensin.
Reflex relaxation of tracheal smooth muscle by thin-fiber muscle afferents in dogs
Authors: Kaufman M. P. , Ordway G. A. , Longhurst J. C. , Mitchell J. H.
Published: December 2017

Although the reflex cardiovascular and ventilatory responses evoked by stimulation of groups III and IV muscle afferents have been extensively investigated, less is known about the effects of stimulation of these afferents on airway caliber. Therefore, in 11 chloralose-anesthetized dogs, we recorded transverse smooth muscle tension from an innervated segment of the trachea, while we stimulated groups III and IV muscle afferents with capsaicin and bradykinin. Injection of both substances into the arterial supply of the skinned hindlimb evoked dose-dependent decreases in tracheal tension, whereas injection into the femoral vein either increased tension or had no effect on it. Injection of capsaicin and bradykinin into the arterial supply of the gracilis muscle also decreased tracheal tension. In addition, cutting the sciatic, gracilis, and femoral nerves abolished the decreases in tracheal tension caused by injection of capsaicin and bradykinin into the arterial supply of the hindlimb. We conclude that chemical stimulation of groups III and IV muscle afferents causes reflux relaxation of tracheal smooth muscle in dogs.
Postpyloric regulation of gastric emptying in rhesus monkeys
Authors: McHugh P. R. , Moran T. H. , Wirth J. B.
Published: December 2017

Saline (0.9% NaCl) empties rapidly and exponentially from the stomach of the rhesus monkey, but glucose solutions empty at a calorie-constant rate of 0.4 kcal/min. By means of indwelling intragastric and intraduodenal cannulae we can demonstrate an inhibition on the delivery of saline from the stomach provoked by glucose placed beyond the pylorus. The inhibition varies directly with the glucose calories in the intestine and averages 2.5 min/kcal. That these two results (0.4 kcal/min and 2.5 min/kcal) are reciprocals suggests a feedback inhibition on the gastric emptying of nutrients arising from beyond the pylorus and adequate to explain the rate of glucose delivery to the intestine. A control theory description of gastric emptying that includes such feedback regulation can be derived from these data to explain the different gastric emptying patterns of nutrients and nonnutrient solutions. These patterns give this visceral system a precision in its management of nutrients that can provide information crucial to preabsorptive satiety.
Early responses to hemorrhage in the conscious rat: effects of corticosterone
Authors: Barton R. N. , Passingham B. J.
Published: December 2017

There is evidence for a physiological role of the adrenal cortex in the early responses to limb ischemia in the rat. Trilostane, which inhibits steroid production and prevents the usual rise in corticosterone concentration, impairs compensatory fluid movement during the 3 h after removal of bilateral hindlimb tourniquets and truncates the accompanying hyperglycemia. We have now studied whether altering the corticosterone concentration has similar effects over a 3-h period after a 35% hemorrhage in the conscious rat. After hemorrhage there was only a small rise in plasma glucose concentration, which was unaffected by inhibition of the adrenocortical response with trilostane or its prolongation with adrenocorticotrophic hormone. However, if hindlimb tourniquets were applied 4 h beforehand, the hyperglycemia after hemorrhage was as large as after tourniquet removal and was similarly curtailed by trilostane. Compensatory fluid movement, in contrast, was unaffected by any of the alterations in corticosterone concentration, with or without tourniquets. Thus the method of producing fluid loss is critical in determining whether glucocorticoids play a role in compensation but not in maintaining hyperglycemia after injury.
Comparative study of platelet dense granule constituents
Authors: Meyers K. M. , Holmsen H. , Seachord C. L.
Published: December 2017

Cat, cattle, dog, horse, human, mink, pig, and rabbit platelets were separated from plasma by gel filtration. The gel-filtered platelets (GFP) were treated with thrombin to induce maximal granule secretion and the potential dense granule constituents ATP, ADP, serotonin (5-HT), Ca2+, and Mg2+ were measured in GFP and in the control and thrombin-treated platelets and in the respective supernatants. The amount of Ca2+, Mg2+, 5-HT, ATP, and ADP within the nonreleasable pool for all species varied between 3.1 and 10.0 mumol/10(11) platelets for Ca2+ and Mg2+ was less than 1.5 mumol/10(11) platelets for ADP and 5-HT and was between 2.0 and 5.0 mumol/10(11) platelets for ATP. Marked differences were observed in the releasable fraction. Human platelets were characterized by the largest releasable Ca2+ pool (greater than 10 mumol/10(11) platelets), the smallest secretable 5-HT and Mg2+ pool (less than 0.5 mumol/10(11) platelets), and the lowest ATP-to-ADP ratio (greater than 1.0). Pig platelets had the highest amount of releasable Mg2+ (approximately 8.0 mumol/10(11) platelets). Rabbits platelets released the most 5-HT (greater than 3.0 mumol/10(11)) and had the highest ATP/ADP (greater than 5.0). The releasable pool of Ca2+, Mg2+, ATP, and ADP in the remaining species varied in mumol/10(11) platelets from approximately 1.5-4.0, approximately 1.0-3.0, 0.5-3.5, and approximately 0.5-1.5, respectively.
Baroreceptor reflex gain is not diminished in spontaneous hypertension
Authors: Morrison S. F. , Whitehorn D.
Published: December 2017

The magnitudes of both spontaneous and hypothalamically evoked sympathetic nerve activity are greater in spontaneously hypertensive rats (SHR) than in normotensive Wistar-Kyoto rats (WKY). Because the baroreceptor reflex influences the magnitude and time course of the sympathetic response to hypothalamic stimulation, we evaluated the role of the baroreceptor reflex in this sympathetic hyperresponsiveness. Changes in spontaneous nerve activity following comparable shifts in mean blood pressure (static reflex gain) were not different between the two strains. The effect of alterations in prestimulation blood pressure on the size of the evoked sympathetic response (response gain) was greater in SHR. Baroreceptor reflex inhibition resulting from the evoked blood pressure rise during hypothalamic stimulation (dynamic gain) was also greater in SHR. Expressing response magnitudes and gains as a percent of the spontaneous activity eliminated these strain differences. Interruption of the baroreceptor reflex resulted in equivalent percent increases in spontaneous and evoked activity in the two strains. Postdenervation levels of spontaneous and evoked nerve activity were greater in SHR. The results show that sympathetic hyperreactivity in SHR is not due to deficient baroreceptor reflex function.
Choriodecidual adhesion promotes decidual prolactin transport by human fetal membrane
Authors: McCoshen J. A. , Tagger O. Y. , Wodzicki A. , Tyson J. E.
Published: December 2017

The theory of human decidualized endometrium to produce prolactin (PRL) throughout gestation has led to the implication that such production is related to the source of amniotic fluid PRL (afPRL). This study confirms that fetal membranes, amnion and amniochorion with or without adherent decidua, are unable to transfer significant quantities of exogenously administered PRL from the maternal to fetal compartments in vitro. Incubation of amniochorion with decidua adherent to chorion results in a significant increase in the amount of endogenous PRL appearing on the fetal side of the membrane concomitant with a rise in decidual PRL on the maternal side. The results suggest that transport of decidual PRL to amniotic fluid is predicated on retention of the cellular adhesion between maternal decidua and fetal chorion as exists in vivo. Disruption of decidual contact with fetal membrane results in failure of PRL transport to the fetal side despite a steady accumulation of PRL on the maternal side. We conclude that human fetal membranes are highly permeable to decidual PRL in vivo, and that decidua probably represents the major source of afPRL.
Cessation of thermoregulation during REM sleep in the pocket mouse
Authors: Walker J. M. , Walker L. E. , Harris D. V. , Berger R. J.
Published: December 2017

Electrophysiological sleep patterns, respiration frequency, brain temperature (Tbr), and ear temperature (Tear) were recorded from five pocket mice (Perognathus longimembris) exposed to ambient temperatures (Ta) of 22.5, 27.5, 32.5, and 35.0 degrees C. Thermoregulation was curtailed during rapid-eye-movement (REM) sleep, since Tbr declined following REM onsets at Ta's below thermoneutrality and increased at Ta's above thermoneutrality. Tbr subsequently returned to pre-REM levels following the termination of each REM episode. Respiratory frequency was inversely related to Ta but not as strongly during REM sleep as during slow-wave sleep (SWS). These results confirm previous reports of loss of thermoregulatory ability during REM sleep. Mean duration and proportions of wakefulness, SWS, and REM sleep were unaffected by Ta, consistent with earlier findings on ground squirrels, but differing from reports of decreased REM sleep in nonhibernators. Hibernators may have lower peripheral thermosensitivities than nonhibernators, facilitating sleep at low ambient temperatures and during entrance into hibernation.
Effect of forebrain lesions on response to chronic intraventricular angiotensin II
Authors: Fink G. D. , Bryan W. J. , Mann M. E.
Published: December 2017

We previously reported that chronic (10 days) intracerebroventricular (ivt) infusion of angiotensin II (ANG II) into conscious rabbits produced a significant rise in mean arterial pressure (MAP), water intake (WI), and urinary sodium excretion (UNaV), and a significant fall in plasma sodium (PNa) and potassium (PK) concentrations. Urinary potassium excretion (UKV) and body fluid volume were not changed significantly. In the present experiments, similar chronic infusions were carried out in intact rabbits and in rabbits with an electrolytic lesion placed in the anteroventral third cerebral ventricle (AV3V) region. Integrity of the AV3V area is essential for normal expression of a variety of acute physiological responses to ANG II injected into the brain. In rabbits with AV3V lesions, chronic ivt infusion of ANG II did not significantly alter MAP, but WI and fractional UNaV increased, and PNa decreased in a manner identical to that of sham-lesioned control rabbits. Plasma and extracellular fluid volumes increased, and body weight and food intake decreased in all rabbits during ANG II infusion, but to a slightly greater extent in the AV3V-lesioned rabbits. We conclude that an intact AV3V region is crucial for the hypertensive effect of chronic ivt fusions of ANG II in the rabbit but is not necessary for most of the fluid and electrolyte alterations associated with such infusions.
Water deprivation-induced drinking in rats: role of angiotensin II
Authors: Barney C. C. , Threatte R. M. , Fregly M. J.
Published: December 2017

The role of angiotensin II in the control of water intake following deprivation of water for varying lengths of time was studied. Male rats were deprived of water for 0, 12, 24, 36, or 48 h. Water intakes were measured with and without pretreatment with the angiotensin I-converting enzyme inhibitor, captopril (50 mg/kg, ip). Captopril had no significant effect on water intake following either 0 or 12 h of water deprivation. However, captopril significantly attenuated water intake following 24-48 h of water deprivation with the magnitude of the attenuation increasing as the length of the period of water deprivation increased. Plasma renin activity was significantly increased over control levels after 24-48 h of water deprivation but not after 12 h of water deprivation. Plasma renin activity tended to increase as the length of the water-deprivation period increased. Serum osmolality and sodium concentration were significantly increased over control levels following 12-48 h of water deprivation. Serum osmolality and sodium concentration failed to show any further increases with increasing length of water deprivation beyond the increases following 12 h of water deprivation. The data indicate that the water intake of water-deprived rats can be divided into an angiotensin II-dependent component and angiotensin II-independent component. The angiotensin II-independent component appears to be more important in the early stages of water deprivation whereas the angiotensin II-dependent component becomes more important as the length of the water-deprivation period increases.
Role of venoconstriction in the cardiovascular responses of ducks to head immersion
Authors: Langille B. L.
Published: December 2017

Central venous pressure of ducks rose from resting values of 0.31 +/- 0.16 (SE) to 1.75 +/- 0.20 kPa during forced head immersion. Because a similar increase in mean circulatory pressure (Pmc) was also observed (0.71 +/- 0.16 to 2.15 +/- 0.20 kPa) the rise in central venous pressure was attributed to a venoconstrictor mechanism. When this venoconstrictor-induced rise in central venous pressure was prevented by graded withdrawal of venous blood, then immersion bradycardia was inhibited, and the reduced cardiac output associated with head immersion was largely the result of reduced stroke volume. When compared with normal dives, this intervention resulted in greater myocardial energy requirements, as assessed by the pressure-rate product. It is concluded that venoconstriction increases central venous pressure during head immersion. The increase in central venous pressure alters cardiac function through the Frank-Starling mechanism such that myocardial energy requirements are minimized during this period of low oxygen availability.
Effect of spaceflight on periosteal bone formation in rats
Authors: Wronski T. J. , Morey E. R.
Published: December 2017

Male Wistar rats were placed in orbit for 18.5 days aboard the Soviet COSMOS 1129 biological satellite. Tetracycline was administered before and after spaceflight to label areas of bone formation. An inhibition of periosteal bone formation occurred during spaceflight in the tibial and humeral diaphyses, but this defect was corrected during the postflight period. The increased extent of arrest lines at these skeletal sites suggested that periosteal bone formation may have even ceased during spaceflight. The rib exhibited a small but nonsignificant decrease in periosteal bone formation. Endosteal bone resorption was not affected markedly by spaceflight conditions. The observed inhibition of periosteal bone formation may be a result of mechanical unloading, but endocrine factors cannot be ruled out.
Kinetics of trace element chromium(III) in the human body
Authors: Lim T. H. , Sargent T. , Kusubov N.
Published: December 2017

Chromium(III) has been reported to be an essential trace element involved in the control of glucose metabolism by insulin. We have studied the distribution and kinetics of intravenous [51Cr]chromium(III) in six human subjects using a whole-body scintillation scanner, a whole-body counter, and plasma counting. Principal concentrations were found in the liver, spleen, soft tissue, and bone. The data were fit to a model consisting of a plasma pool in equilibrium with fast (T1/2 = 0.5–12 h), medium (1–14 days), and slow (3–12 mo) compartments, and transfer rates were calculated for exchanges between compartments. Each of the imaged organs appeared to contain varying proportions of each compartment. Two patients with hemochromatosis, in which iron overload is postulated to exclude chromium transport, were found to have altered rate constants. The results should be useful in assessing the metabolism and nutritional requirement of chromium(III) in humans and its importance in disease processes such as diabetes.
Some effects of aldosterone on sodium kinetics and distribution in porcine arterial wall
Authors: Llaurado J. G. , Madden J. A. , Smith G. A.
Published: December 2017

Transport rate constants for Na+ exchanges and relative Na+ compartment distribution in isolated pig carotid wall were determined with the aid of 22Na+ as tracer that was continuously washed out. A three-compartment model consisting of 1) extracellular, 2) intracellular, and 3) subcellular spaces was found to represent adequately the kinetics of 22Na+. It was found that d-aldosterone (0.85 X 10(-6) M) added to the incubating medium for 3 h causes significant changes in two transport rate constants and in the distribution of sodium within different compartments. Total tissue water, nonradioactive sodium (tracee), and potassium are not altered by aldosterone; however, when amounts of Na+ tracee are calculated for each compartment, aldosterone significantly reduces the amount of Na+ in compartment 2. Overall, the results indicate that aldosterone induces a translocation of Na+ into the extracellular space at the expense of the intracellular space. The findings are interpreted in the light of recent reports on the role of altered function of the Na+-K+ pump under aldosterone influence or arterial hypertension.
Food intake response to modulation of secretion of cholecystokinin in Zucker rats
Authors: McLaughlin C. L. , Peikin S. R. , Baile C. A.
Published: December 2017

Exogenous administration of cholecystokinin (CCK) decreases food intake and elicits satiety behaviors. In the present experiments, feeding behaviors of Zucker obese and lean rats were measured in response to treatments that influence endogenous secretion of CCK from the duodenum. Secretion of CCK was increased by administration of phenylalanine, a stimulant of CCK release, and of trypsin inhibitor, which binds to trypsin, a negative-feedback signal for CCK release. Both of these treatments decreased the size of the first meal after a 6-h fast and average daily meal size and increased meal frequency. Administration of trypsin, proported to decrease secretion of CCK, increased average daily meal size and decreased meal frequency. Pancrease, a pancreatic enzyme concentrate, also hypothesized to act as a negative-feedback signal for CCK release, elicited feeding behaviors similar to those of trypsin. Thus the effects of these compounds on the feeding behavior of Zucker obese and lean rats may be related to their effects on CCK secretion. The feeding behaviors of obese rats were affected less than those of lean rats by exogenous administration of CCK, but in these experiments were affected more than in lean rats by modulation of endogenous release of CCK.
Effects of hypoxia on oxygen affinity, hemoglobin pattern, and blood volume of early chicken embryos
Authors: Baumann R. , Padeken S. , Haller E. A. , Brilmayer T.
Published: December 2017

We have investigated the influence of hypoxia (13.5% O2) on the oxygen affinity, hemoglobin pattern, and blood volume of chicken embryos. Data were collected between 4 and 9 days of incubation. It was found that the transition from embryonic to adult hemoglobin starts earlier in hypoxic embryos, due to a premature appearance of definitive red cells in the circulation. Blood oxygen capacity and total blood volume (related to embryonic weight) were not different from the controls. However, hypoxic embryos weighing more than 0.1-0.2 g have a significantly increased oxygen affinity (and decreased red cell adenosine 5'-triphosphate concentration). The higher O2 affinity partly compensates for the adverse effects of the lowered environmental PO2. In hypoxic embryos younger than 6 days, the Bohr effect is drastically increased, which allows a better oxygen extraction. Thus, the chicken embryo seems to be able to develop adaptive changes of blood O2 transport during hypoxia. The results support the view that the particular ontogenetic pattern of O2 affinity changes seen in avian or mammalian embryos arose from the need to adapt to the steadily changing conditions for O2 uptake.
Hypothalamic lesions abolish cardiovascular responses to chronic saline ingestion
Authors: Sasaki S. , Bunag R. D.
Published: December 2017

In rats made to drink isotonic saline solution instead of water for 5 wk, systolic pressure and heart rate, whether recorded indirectly from the tail or directly from femoral catheters, rose slightly. When the ventromedial hypothalamus was stimulated electrically, increases in arterial pressure and sympathetic neural firing were larger in saline-drinking than in water-drinking rats. By contrast, pressor responses to injections of norepinephrine or tyramine were unaltered. Following bilateral destruction of the ventromedial hypothalamus in other rats, none of the effects of chronic saline ingestion was elicited. Although neither the site nor the mechanism causing sympathetic overactivity has been determined, our results are in accord with the interpretation that salt loading elevates blood pressure, at least in part, by stimulating the ventromedial hypothalamus to increase sympathetic activity.
Factors that alter the plasma renin activity of the marmot
Authors: Ray W. J. , Zatzman M. L.
Published: December 2017

The effects of low doses of norepinephrine (NE) and furosemide and a volume load (nonhibernators only) on plasma renin activity (PRA), mean arterial pressure (MAP), heart rate (HR), left renal (RBF) and right iliac (IBF) blood flow, cardiac index (CI), and total peripheral resistance (TPR) were determined in euthermic and hibernating marmots. In nonhibernating marmots NE produced an increase in CI and TPR and a decrease in RBF. In hibernators this dose of NE caused an increase in MAP, HR, and renal resistance, whereas it decreased PRA and did not alter iliac resistance. Furosemide infusions led to an increase in PRA in both groups and an increase in TPR in nonhibernators. The volume load in nonhibernators produced only a decrease in PRA. A comparison of control data from the two groups indicated that the renal and iliac beds contribute only a small portion to the increase in TPR that occurs during hibernation.
Inappropriate drinking and secretion of vasopressin after caval constriction in dogs
Authors: Thrasher T. N. , Moore-Gillon M. , Wade C. E. , Keil L. C. , Ramsay D. J.
Published: December 2017

The object of this study was to determine if chronic thoracic vena caval constriction affected mechanisms regulating water balance, independent of known changes in sodium metabolism in the dog. Fluid and electrolyte balances were determined for 5 days before and 14 days after constriction of the vena cava (n = 5) and in a separate population of time controls (n = 4). Cardiac output was reduced and heart rate was increased in response to chronic caval constriction although blood pressure was maintained at control levels. Water intake and plasma arginine vasopressin (AVP) increased from 31 +/- 4 ml/kg and 1.3 +/- 0.2 pg/ml during the control period to 81 +/- 6 ml/kg and 3.4 +/- 0.6 pg/ml during the period of caval constriction. The caval dogs developed a positive water balance, which preceded the development of a positive sodium balance. This led to a significant fall in plasma osmolality from a control mean of 296 +/- 1 to 284 +/- 4 mosmol/kg during caval constriction and dilutional hyponatremia. Plasma and blood volume increased significantly in response to constriction and were accompanied by formation of 123 +/- 10 ml/kg of ascitic fluid. These results show that water intake and plasma levels of AVP were increased in spite of a fall in plasma osmolality and an increase in vascular volume. These responses cannot be secondary to sodium retention because water was retained in excess of sodium hence hyponatremia. Therefore, chronic caval constriction causes a profound primary disturbance in mechanisms regulating water balance, which may contribute to the formation of edema fluid.
Circadian pacemakers in lizards: phase-response curves and effects of pinealectomy
Authors: Underwood H.
Published: December 2017

Phase-response curves (PRCs) for 6-h fluorescent light pulses are described for both intact (sham-pinealectomized) and pinealectomized iguanid lizards (Sceloporus occidentalis). Although strongly diurnal in habit the PRC for intact lizards is more typical of those seen in nocturnal rodents. Other "nocturnal" characteristics of this lizard include the fact that the average free-running period (tau) is less than 24 h and the average tau in continuous light is longer than that observed in continuous darkness. The PRC for pinealectomized lizards is greatly distorted relative to that obtained from intact lizards. This "distortion" is discussed in terms of the role of the pineal as a coupling device or as a pacemaker within a multioscillator circadian system. In some individuals pinealectomy was also associated with 1) increased instability in free-running activity rhythms or arrhythmicity and 2) nocturnal entrainment to LD 12:12.
Phase-resetting action of light on the circadian activity rhythm of Rattus exulans
Authors: Gander P. H. , Lewis R. D.
Published: December 2017

The phase resetting action of light on the circadian rhythm of locomotor activity has been examined in wild-caught Polynesian rats (Rattus exulans). Phase-response curves to 4-, 8-, and 16-h light pulses have been derived. All three curves conform to the generalization that pulses occurring during late subjective day and early subjective night produce delays, whereas advances occur in response to pulses coinciding with the late subjective night and early subjective day. Weak (type 1) phase resetting is observed in response to 4-h pulses and perhaps 8-h pulses, whereas strong (type 0) resetting apparently occurs in response to 16-h pulses. These data evidently constitute the first report of strong phase resetting in mammalian circadian rhythms. The phase relationship between an entrained activity rhythm and the light-dark cycle is dependent on the photoperiod and, in 24-h cycles, on the period difference between the rhythm and the zeitgeber. In longer zeitgeber cycles, activity onset is delayed by a direct masking effect of light. A primarily nonparametric action of light in natural entrainment is consistent with these data and with field observations.
Regulation of canine platelet function II. Catecholamines
Authors: Meyers K. M. , Huston L. Y. , Clemmons R. M.
Published: December 2017

The action of epinephrine (E) on canine platelet aggregation is described. Although E did not induce a change in platelet shape or aggregation, potentiation of aggregation induced by the following agents was observed at physiological E concentrations (that is, less than 10 nM/1): arachidonic acid; the dense granule agonists, ADP and serotonin (5-HT); and collagen. Epinephrine-induced potentiation was in part independent of formation of arachidonic acid metabolites, and E potentiated the aggregating action of the bivalent cationophore A23187. Potentiation was inhibited by alpha-adrenergic receptor antagonists phenoxybenzamine, phentolamine, and ergotamine, and mimicked by alpha-adrenergic receptor agonists norepinephrine, clonidine, and in some cases, phenylephrine. The beta-adrenergic receptor agonists isoproterenol and dobutamine inhibited ADP-induced aggregation, and this action was presented by pretreating the platelets with propranolol and dichloroisoproterenol. An augmentation of the aggregation response of platelets to arachidonic acid was observed in blood samples withdrawn when circulating catecholamines were elevated. The physiological implication of epinephrine acting as a gain controller that alters the relationship between actuating signal and the platelet response to an agonist is discussed.
Thermoregulatory responses to central injections of excess calcium in monkeys
Authors: Gisolfi C. V. , Wall P. T. , Mitchell W. R.
Published: December 2017

In unanesthetized monkeys (4-8 kg), artificial cerebrospinal fluid (ACSF) containing excess (greater than 1.3 mM) amounts of Ca2+ was infused at 20 microliters/min for 5 min into the cerebral ventricles. Core and skin temperatures, respiratory gas exchange, heart rate, and sweat rate were monitored. At 22 degrees C, intracerebroventricular infusions of 13-39 mM Ca2+ produced a dose-related hypothermia associated with a dose-related fall in metabolic rate and heart rate and a rise in average skin temperature. General body sweating was not initiated, and respiratory water loss was unaffected; however, exercise activated sweating and elevated it from 0.05 to 0.22 mg X (cm2 X min)-1. At 35 or 40 degrees C, infusion of 26 mM Ca2+ failed to influence ongoing general body sweating; however, subsequent exercise increased sweat rate by 63%. Heart rate was unaffected. At 15 degrees C metabolic rate increased 50%. After infusing 26 mM Ca2+, metabolism decreased 6% and core temperature declined 0.8 +/- 0.24 degrees C. Skin temperatures continued to fall, heart rate fell, and sweating was not initiated. In contrast, infusing ACSF increased metabolism 11% and core temperature fell only 0.18 +/- 0.14 degrees C. The inability of exogenous Ca2+ to 1) initiate sweating at 22 degrees C, 2) elicit vasodilation at 15 degrees C, 3) initiate or stimulate sweating at 35 or 40 degrees C, or 4) lower core temperature at 35 or 40 degrees C argues against a set-point function for this cation.
A further characterization of the effects of AV3V lesions on ingestive behavior
Authors: Lind R. W. , Johnson A. K.
Published: December 2017

Rats prescreened for responses to dipsogens received anteroventral third cerebral ventricular (AV3V) or sham lesions (ether anesthesia). Many known effects of AV3V lesions were observed, and new findings include a failure to drink adequately in response to polyethylene glycol (PEG) and water deprivation (regardless of responses to other dipsogens) and abnormally high levels of water intake during food deprivation. The groups did not differ in the osmotic suppression of deprivation-induced feeding. Drinking responses to angiotensin, isoproterenol, and PEG were highly intercorrelated in the experimental animals, perhaps due to destruction of an angiotensin-related substrate. Five months after surgery, rats with lesions were hyperphagic and hyperdipsic per gram of body weight, but actually ate a smaller amount of food than control rats, and absolute levels of water intake did not differ. The range of amount of daily water intake, but not food intake, was significantly greater in the experimental rats. These findings suggest that lower levels of neural organization mediate fluid balance in rats with AV3V lesions.
Widespread neural excitation initiated from cardiac spinal afferent nerves
Authors: Weaver L. C. , Meckler R. L. , Fry H. K. , Donoghue S.
Published: December 2017

Reflex effects of cardiac sympathetic afferent nerve excitation on cardiac and renal components of sympathetic outflow have been well investigated, but the extent of these cardiac afferent influences on other sympathetic nerves or on respiratory or cortical neural systems is unknown. Therefore such influences were investigated electrophysiologically in anesthetized, vagotomized, baroreceptor-denervated cats. Stimulation of cardiac sympathetic spinal afferent neurons by the noxious substance bradykinin caused excitation of cardiac, renal, splenic, gastrohepatic, adrenal, and deep peroneal (muscle) vasoconstrictor sympathetic nerves, as well as excitation of phrenic nerves and concomitant desynchronization of the electroencephalogram. Possible supraspinal pathways mediating these responses were investigated. Sympathetic reflexes caused by cardiac afferent stimulation were unchanged after decerebration, thereby demonstrating that supramedullary mediation was not essential to the sympathetic responses. Potential contributions of the medulla to the observed sympathetic or other responses were demonstrated by recording from medullary neurons responsive to electrical and chemical stimulation of the afferent nerves. In summary, noxious stimulation of cardiac sympathetic afferent neurons leads to widespread neural excitation which may contribute to sensory, visceral, and somatic responses caused by cardiac pain or which occur during activated states such as exercise or emotional stress.
Hemodynamic responses to amygdaloid stimulation in spontaneously hypertensive rats
Authors: Galeno T. M. , Brody M. J.
Published: December 2017

Our studies were done to determine 1) the regional hemodynamic effects of stimulating the central amygdaloid nucleus in conscious and anesthetized rats and 2) whether these effects differ between normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Flow was recorded with miniaturized pulsed Doppler probes placed on the renal and superior mesenteric arteries and the lower abdominal aorta. In rats anesthetized with Dialurethane, electrical stimulation elicited a depressor response accompanied by a decrease in hindquarter vascular resistance, with little or no change in heart rate or renal or mesenteric resistance in both SHR and WKY. By contrast, in conscious rats, stimulation was accompanied by a pressor response, tachycardia, and renal and mesenteric vasoconstriction in both groups. Hindquarter vascular resistance was unchanged in WKY and decreased at higher frequencies in SHR. There were no significant differences between SHR and WKY, whether anesthetized or awake, in hemodynamic responses to amygdaloid stimulation. Despite previous evidence indicating that the central amygdaloid nucleus contributes to the development of spontaneous hypertension, our results show that stimulation of this region does not elicit exaggerated cardiovascular responses in SHR.
Effect of water deprivation on urinary excretion of PGE2 in the dog
Authors: Zucker A. , Nasjletti A. , Schneider E. G.
Published: December 2017

We examined the influence of the state of hydration on the urinary excretion of prostaglandin E2 (PGE2) and kallikrein in the dog. Immunoreactive PGE2 and kallikrein were measured in the urine of conscious dogs during periods of water deprivation and periods of free access to drinking water and in the urine of time-control dogs that had free access to water throughout the study. During water deprivation the excretion of kallikrein did not change significantly, but PGE2 excretion increased by 50 and 75% (P less than 0.05) after 2 and 4 days, respectively, associated with reductions of body weight and urine flow and with elevation of plasma renin activity, plasma sodium, and both plasma and urine osmolality. Dehydrated dogs drank copiously when allowed free access to water, and over the following 4 days both PGE2 excretion and plasma renin activity fell significantly, associated with elevation of body weight and urine volume and with lowering of plasma sodium and plasma and urine osmolality. In contrast, if after 4 days of water deprivation the dogs were kept at a constant level of dehydration by restricting their water allotment on subsequent days to 300 ml/day, PGE2 excretion and most other variables remained at the dehydration level. In conclusion, these results suggest that renal PGE2 production is dependent on the state of hydration in the dog.
Effects of guanethidine sympathectomy on ventromedial hypothalamic obesity
Authors: Powley T. L. , Walgren M. C. , Laughton W. B.
Published: December 2017

Since ventromedial hypothalamic (VMH) lesions apparently produce chronic increases in parasympathetic activity and decreases in sympathetic responses, two experiments were performed to determine whether decreases in sympathetic tone alone are sufficient either to produce elements of the VMH syndrome or to potentiate the expression of the syndrome in animals with lesions. In experiment 1, rats that had been injected with guanethidine sulfate for 5 wk (40 mg X kg-1 X day-1) to produce a permanent sympathectomy (SympX) were maintained on a high-fat diet and subsequently subjected to VMH lesions. In experiment 2, adrenal-demedullated animals were treated with guanethidine for 6 wk and then subsequently underwent VMH lesions. SympX in the studies (81 and 85% depletion of superior cervical ganglia neurons, respectively) did duplicate the effects of VMH lesions on salivary gland weights. In neither experiment, however, did SympX alone or in combination with demedullation mimic the effects of VMH lesions on food intake, body weight, or body fat. Determinations of free fatty acids (FFAs) in the experiments confirmed that VMH lesions elevate basal FFA levels, but they also indicated that effective VMH lesions need not impair the FFA mobilization to 2-deoxyglucose challenges as some basomedial hypothalamic lesions do. In addition, experiment 2, which employed a prolonged period of high-fat feeding, revealed that SympX plus adrenal demedullation could potentiate (a 13% increase) the effects of VMH lesions on body weight. The results taken together do not support the conclusion that a preponderance of the VMH syndrome can be accounted for by the type of reduction in sympathetic tone produced by guanethidine.
Brain and deep abdominal temperatures during induced fever in pregnant rabbits
Authors: Naccarato E. F. , Hunter W. S.
Published: December 2017

Rectal (Tre), hypothalamic (Thy), and uterine (Tut) temperatures were monitored before and during the course of prostaglandin E1 (PGE1)-induced fever in pregnant rabbits on days 10, 12, 16, 18, 24, 26, 29, and 31 after mating. Tre and Tut were consistently higher than Thy in both nonpregnant and pregnant normothermic does, but changes in the three parameters were closely correlated. In near-term rabbits, both Tre and Thy were significantly lower than in the same does before pregnancy, and the Tre-Thy difference was significantly less than for the same animals before pregnancy, with near-term Thy maintained at a relatively higher level than Tre or Tut. Fever height in the various stages of pregnancy was not different from that observed before mating.
Renal ammoniagenesis and acid excretion in the dogfish, Squalus acanthias
Authors: King P. A. , Goldstein L.
Published: December 2017

Renal ammoniagenesis and acid excretion were investigated in normal dogfish (Squalus acanthias) and dogfish made acidotic by HCl injection (0.65 meq X kg-1). After acid loading, renal ammonia excretion doubled, rising from 0.11 to 0.25 mueq X h-1, and titratable acid output increased from 28.6 to 44.9 mueq X h-1. Trimethylamine excretion averaged 23.2 mueq X h-1 and did not change in response to the acidosis. During the first 24 h postinjection, the increase in renal acid excretion accounted for the elimination of 15% of the acid load. In vitro studies with kidney slices demonstrated that the dogfish kidney has the capacity to synthesize ammonia from a number of amino acids including glutamine, glutamate, alanine, aspartate, and glycine, with the greatest ammonia production resulting from glutamine. The relatively high glutamine concentration in the kidney, compared with the blood, suggested a high renal capacity for glutamine synthesis. In renal homogenates, enzymatic activities for both the deamidation (glutaminase) and synthesis (glutamine synthetase) of glutamine were investigated. The Michaelis constant (Km) values for the two enzymes were found to be almost equal (4.48 mM glutamine and 4.33 mM glutamate) and at the same levels as the substrate concentrations in the kidney (3.69 mM glutamine and 3.36 mM glutamate). Subcellular localization revealed that both enzymes occur predominantly in the mitochondria. The activities of glutaminase and glutamine synthetase in the renal mitochondria suggest the presence of a substrate cycle that could be modulated to increase ammonia production during acidosis.
Metabolic adjustments to diving and recovery in the African lungfish
Authors: Dunn J. F. , Hochachka P. W. , Davison W. , Guppy M.
Published: December 2017

The metabolic potentials of the heart, brain, white muscle, and liver in the African lungfish were estimated by enzymatic data. Metabolic effects of a 12-h submergence were monitored using metabolite measurements. Heart was the most oxidative tissue but also showed the greatest anaerobic potential. The brain displayed relatively low oxidative capabilities. White muscle remained almost inert. Although high-energy phosphate concentrations in brain and heart did not fall during submergence, glycolysis was activated as indicated by crossover plots, depletion of endogenous glycogen stores, and lactate accumulation. Blood-tissue lactate and glucose gradients indicated 1) that the heart and brain released lactate throughout submergence, 2) that after 12 h of submersion the brain and heart were probably obtaining all their required glucose from the blood, 3) that the liver released glucose throughout submergence, and 4) that white muscle was metabolically isolated from the rest of the body during submergence. It appeared that perfusion adjustments occurring during submergence were directed more toward regulating intertissue exchange of metabolites than toward oxygen conservation. Comparisons are made to diving responses in mammals.
A bladder contractility constant
Authors: Byrne J. C. , Tozeren A.
Published: December 2017

Muscle contractility can be characterized by two related properties: force and velocity. The initial velocity of a tetanic contraction is inversely related to preload. This was demonstrated experimentally by Hill and quantified in his well-known empiric equation. Subsequent investigators argued that a theoretical maximum contractile element velocity (V max) could be predicted from the rate of change of isometric force. V max has been applied clinically in heart studies, prompting others to use similar methods to evaluate bladder contractility. These attempts have so far been unsuccessful. The present study shows for whole canine bladders that the time to reach maximum isometric force from the moment of onset of active contraction is a constant independent of muscle length, preload, and maximum force. This can be expressed as a frequency constant (omega) whose calculation appears similar to that for V max. In contrast to V max, omega is obtained only from the active component of pressure.
Cerebral metabolism in hypoglycemic and hyperglycemic fetal lambs
Authors: Richardson B. S. , Hohimer A. R. , Bissonnette J. M. , Machida C. M.
Published: December 2017

To investigate the mechanism whereby glucose affects fetal breathing movements (FBM), cerebral metabolism was studied in 12 unanesthetized fetal lambs, during fasting-induced hypoglycemia and after a subsequent fetal infusion of glucose. Preductal arterial and sagittal sinus blood samples were analyzed for glucose and oxygen concentrations and for blood gases and pH. Measurements of regional brain blood flow were made with radioactive microspheres. Maternal fasting of 24- to 36-h duration resulted in a decrease in fetal blood glucose from 1.061 +/- 0.085 mmol X l-1 to 0.664 +/- 0.053 (P less than 0.001). Although cerebral glucose and O2 uptake remained unchanged, sagittal sinus CO2 partial pressure (Pco2) and [H+] were significantly decreased and may have contributed to the observed decrease in FBM. A 2-h infusion of glucose to the fetuses of fasted animals resulted in an increase in blood glucose to 2.452 +/- 0.173 mmol X l-1. Cerebral O2 consumption was again unchanged; however, cerebral glucose consumption was significantly increased as were sagittal sinus Pco2 and [H+], which may have contributed to the observed increase in FBM. These findings are consistent with the hypothesis that glucose affects the incidence of FBM in part by altering the environment of central chemoreceptors.
Metabolic adjustments of small passerine birds for migration and cold
Authors: Dawson W. R. , Marsh R. L. , Yacoe M. E.
Published: December 2017

Passerines (members of the order Passeriformes such as finches, chickadees, jays, and warblers) are predominantly small birds characterized by relatively intense metabolic rates. Members of this group breeding at middle or high latitudes may either evade winter cold by migration or enhance their resistance to it by acclimatization. We review the energetic consequences associated with these two modes of response. Despite their apparent dissimilarity, migration and winter acclimatization both depend on substantial aerobic endurance, and both involve extensive power outputs by the flight muscles in locomotion or shivering. Such power outputs entail extensive deposition and catabolism of fat. Information available on these processes and their control in passerine birds is discussed. Knowledge of them is still in a formative stage, but it is already clear that aerobic capacity of passerines is stable at a high level throughout the year. However, changes are observed in the activity of certain enzymes involved in the catabolism of fats and carbohydrates. Full interpretation of these findings must await additional research. Nevertheless it is evident that the complex processes of migration and winter acclimatization are intimately linked with the metabolic properties of the highly aerobic skeletal muscle contained within the flight apparatus of passerines.
Analysis of platelet aggregation using particle collision theory
Authors: Davis T. M. , Bown E.
Published: December 2017

The aggregometer monitors changes in light transmission through stirred suspensions of aggregation platelets. Arbitrary measurements from aggregometer recorder tracings have been used to investigate platelet aggregation without regard to mechanisms involved. To determine the applicability of particle collision theory to assessment of in vitro platelet sensitivity to proaggregating agents, platelet-rich plasma (PRP) from five volunteers was used to obtain recorder tracings after addition of ADP in five doses (0.4-4.0 mumol/l PRP) to aliquots of PRP stirred and incubated in an aggregometer. Using the equation describing light transmission through particulate suspensions, particle collision theory, and s (the probability of particle union after collision), a subject- and dose-independent relationship between aggregation rate (dn/dt) and particle number (n) at the recorder tracing inflection point was found (dn/dt = -k X s X n1.56, where k is a constant dependent on particle size and speed and on the proportion of unreactive particles). Determinations of mean particle size at the tracing inflection point indicated that k was also dose independent. Dose-response curves of ADP added vs. s could therefore be constructed. This methodology provides conveniently obtainable quantitative information concerning in vitro platelet “stickiness.”