bluuebunny/crossref_metadata_2025 huggingface dataset:
Sweating responses and body temperatures during nocturnal sleep in humans
Authors: Sagot J. C. , Amoros C. , Candas V. , Libert J. P.
Published: December 2017

The changes in the central control of sweating were investigated in five sleeping subjects under neutral and warm conditions [operative temperature (To) = 30, 33, and 34 degrees C; dew-point temperature = 10 degrees C]. Esophageal (Tes) and mean skin (Tsk) temperatures, chest sweat rate (msw,1), and concomitant electroencephalographic data were recorded. Throughout the night, msw,1 was measured under a local thermal clamp of 38 degrees C. Results showed that the thermal environment exerted a strong influence on both the levels and the time patterns of body temperatures. Moreover, local sweating rate correlated positively with Tes, and this relationship varied according to sleep stages. For a given Tes level, there was a sleep stage-related gradation in msw,1 that was higher in slow-wave sleep (SWS) than in stage 1-2 and the lowest in rapid-eye-movement (REM) sleep. This is explained by a change in the excitability or the sensitivity of the thermoregulatory system. The msw,1 differences between stage 1-2 and SWS are accounted for by a decrease in the Tes threshold (Tset) for sweating while the slope of the msw,1-Tes relation remains unchanged. The lower msw,1 in REM sleep is explained by a lesser slope for the msw,1-Tes relation without any Tset change from stage 1-2.
Angiotensin II does not alter ACTH responses to hypoglycemia in conscious dogs
Authors: Keller-Wood M. , Kimura B. , Phillips M. I.
Published: December 2017

These experiments were designed to test for an interaction between angiotensin II (ANG II) and stress in the control of plasma adrenocorticotropin hormone (ACTH), corticosteroids, and aldosterone. The stimulus to ACTH used in this study was insulin-induced hypoglycemia, a stimulus that does not increase plasma ANG II concentrations. Five trained dogs with exteriorized carotid arteries were studied. Each dog was infused with ANG II intravenously (10 ng X kg-1 X min-1) or into the carotid artery (1 ng X kg-1 X min-1) or with saline (iv) for 80 min. Twenty minutes after the start of the infusion, insulin (0.10 U/kg iv) was injected. Intravenous infusion of ANG II increased mean arterial pressure (MAP) and plasma aldosterone concentrations but did not increase ACTH or corticosteroid responses to hypoglycemia. Intracarotid infusion of ANG II did not increase MAP and also failed to increase ACTH and corticosteroid responses to hypoglycemia. Since ANG II infusions did not increase basal corticosteroids, the failure of ANG II to stimulate ACTH is not a result of steroid negative feedback. Thus it appears that increased plasma ANG II concentrations do not increase ACTH responses to hypoglycemic stress.
Intestinal glucose transport and salinity adaptation in a euryhaline teleost
Authors: Reshkin S. J. , Ahearn G. A.
Published: December 2017

Glucose transport by upper and lower intestinal brush-border membrane vesicles of the African tilapia (Oreochromis mossambicus) was characterized in fish acclimated to either freshwater or full-strength seawater. D-[3H]-glucose uptake by vesicles was stimulated by a transmembrane Na gradient, was electrogenic, and was enhanced by counter-transport of either D-glucose or D-galactose. Glucose transport was greater in the upper intestine than in the lower intestine and in seawater animals rather than in fish acclimated to freshwater. Glucose influx (10-s uptake) involved both saturable and nonsaturable transport components. Seawater adaptation increased apparent glucose influx Kt, Jmax, apparent diffusional permeability (P), and the apparent Na affinity of the cotransport system in both intestinal segments, but the stoichiometry of Na-glucose transfer (1:1) was unaffected by differential saline conditions or gut region. It is suggested that increased sugar transport in seawater animals is due to the combination of enhanced Na-binding properties and an increase in number or transfer rate of the transport proteins. Freshwater animals compensate for reduced Na affinity of the coupled process by markedly increasing the protein affinity for glucose.
Glucose turnover in 48-hour-fasted running rats
Authors: Sonne B. , Mikines K. J. , Galbo H.
Published: December 2017

In fed rats, hyperglycemia develops during exercise. This contrasts with the view based on studies of fasted human and dog that euglycemia is maintained in exercise and glucose production (Ra) controlled by feedback mechanisms. Forty-eight-hour-fasted rats (F) were compared to fed rats (C) and overnight food-restricted (FR) rats. [3-3H]- and [U-14C] glucose were infused and blood and tissue sampled. During running (21 m/min, 0% grade) Ra increased most in C and least in F and only in F did Ra not significantly exceed glucose disappearance. Plasma glucose increased more in C (3.3 mmol/l) than in FR (1.6 mmol/l) and only modestly (0.6 mmol/l) and transiently in F. Resting liver glycogen and exercise glycogenolysis were highest in C and similar in FR and F. Resting muscle glycogen and exercise glycogenolysis were highest in C and lowest in F. During running, lactate production and gluconeogenesis were higher in FR than in F. At least in rats, responses of production and plasma concentration of glucose to exercise depend on size of liver and muscle glycogen stores; glucose production matches increase in clearance better in fasted than in fed states. Probably glucose production is stimulated by “feedforward” mechanisms and “feedback” mechanisms are added if plasma glucose decreases.
Influence of spinal and hypothalamic warming on metabolism and sleep in pigeons
Authors: Graf R. , Heller H. C. , Sakaguchi S. , Krishna S.
Published: December 2017

Animals were prepared with electrooculogram (EOG), cortical electroencephalogram (EEG), and electromyogram (EMG) electrodes and with spinal and/or hypothalamic thermodes. Experiments were run at a cold and a neutral ambient temperature (Ta) during the dark portion of a 24-h light-dark cycle. Metabolic rate, temperatures, EEG, EMG, and EOG were measured continuously for 4-h periods with hypothalamic or spinal temperature unmanipulated or warmed to the level measured during the light. The cold Ta increased metabolic rate over the neutral Ta, but did not influence total sleep time (TST) or rapid-eye-movement sleep (REM) as percent TST. At the cold Ta, spinal warming resulted in reduction in REM as a percent TST. Spinal warming frequently caused a fall in body temperature (Ta). A plot of REM as a percent TST vs. the fall in Tb, including data for all animals and all conditions, revealed a clear correlation between fall in Tb and reduction in REM. Hypothalamic warming had no influence on metabolic rate, Tb, or distributions of arousal states. Cold thermal stimuli caused by a fall in Tb can inhibit REM in birds as it can in mammals independently of thermoregulatory drive.
Effect of endotoxic shock on skeletal muscle intracellular electrolytes and amino acid transport
Authors: Karlstad M. D. , Sayeed M. M.
Published: December 2017

Soleus muscle intracellular electrolytes and alpha-aminoisobutyric acid (AIB) uptake and its regulation by insulin were investigated during endotoxic shock in vivo. Fasted rats (90 g) were injected with [14C]AIB (1-10 mg/kg, iv) and Salmonella enteritidis endotoxin (20 mg/kg, iv) or saline and killed 1-5 h later. AIB uptake into muscle was corrected for uptake into extracellular space (measured as insulin distribution in muscle in vivo) and expressed as [AIB]/[AIB] ratios to assess active transport. The maximum level of active AIB cell transport by extracellular endotoxic muscles [3.3 +/- 0.2 (SE)] was lower than control muscles (4.9 +/- 0.3) at the time when plasma insulin concentration in endotoxic rats (16.8 +/- 2.0 uU/ml) was greater than controls (7.9 +/- 1.7 uU/ml). Insulin-stimulated AIB transport was significantly lower in endotoxic muscles (from a basal value of 3.3 +/- 0.2 to 4.4 +/- 0.5, 5.0 +/- 0.3, and 4.9 +/- 0.3 at 125, 250, and 500 mU/kg intravenous insulin, respectively) than in control muscles (from 4.9 +/- 0.3 to 5.7 +/- 0.2, 8.0 +/- 0.4, and 10.8 +/- 0.8). The intracellular electrolyte concentrations in endotoxic soleus muscles ([Na] = 15.87 +/- 0.9, [K] = 145 +/- 1.7, [Cl] = 14.61 +/- 0.9) were substantially altered when compared with control muscles ([Na] = 9.33 +/- 1.1, [K] = 164 +/- 1.5, [Cl] = 4.1 +/- 0.6) 5 h postinjection. The membrane potential, estimated from chloride equilibrium potential was lower in endotoxic muscles (-52.7 +/- 1.6 mV) when compared with control muscles (-89 +/- 3.5 mV).(ABSTRACT TRUNCATED AT 250 WORDS)
Infusion of CCK-8 into hepatic-portal vein fails to reduce food intake in rats
Authors: Greenberg D. , Smith G. P. , Gibbs J.
Published: December 2017

If the putative satiating effect of endogenous cholecystokinin (CCK) is produced through a circulating hormonal mechanism, then administration of exogenous CCK into the hepatic-portal vein should decrease meal size. To test this, one form of endogenous CCK, the C-terminal octapeptide CCK-8, was infused intraportally in doses of 4 and 8 micrograms/kg just prior to a test meal. Neither dose decreased food intake after intraportal infusion even though intraperitoneal administration of 4 micrograms/kg CCK-8 decreased meal size approximately 50% in the same rats. The results suggest that if endogenous CCK-8 has a satiating effect, it acts primarily through a paracrine mechanism.
Atrial natriuretic factor decreases whole-body capillary absorption in rats
Authors: Trippodo N. C. , Barbee R. W.
Published: December 2017

Previous studies suggested that exogenous atrial natriuretic factor (ANF) altered extracellular fluid partition between plasma and interstitium. The effect of ANF and a similarly effective diuretic dose of furosemide on whole-body transcapillary fluid movement was studied in anesthetized rats by measuring changes in urine and plasma volumes, while accounting for the volume of fluid administered. After 75 min of infusion, urine volume was 9.9 +/- 1.0 ml/kg in rats receiving ANF (0.5 micrograms X min-1 X kg-1), and plasma volume decreased by 3.7 ml/kg (P less than 0.01) compared with rats receiving vehicle only. In the furosemide rats, urine volume was 12.3 +/- 1.9 ml/kg, yet plasma volume was not significantly different from that in the vehicle rats. These results suggested that unlike furosemide, which allowed sufficient capillary absorption to maintain plasma volume constant despite the large diuresis, ANF attenuated whole-body net capillary absorption. The effect of ANF on capillary absorption was quantitated in anephric rats by measuring the increase in plasma volume after intravenous administration of hyperoncotic albumin. After accounting for the volume administered, whole-body net capillary absorption was less (P less than 0.05) in the rats receiving ANF (4.8 +/- 0.4 ml/kg) than in those receiving vehicle (5.9 +/- 0.2 ml/kg). Plasma protein concentration was greater in other anephric rats receiving a similar ANF infusion than in those receiving vehicle. These findings suggest that ANF decreased capillary absorption because of increased average capillary hydrostatic pressure and not because of altered capillary permeability.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiac control of salt appetite
Authors: Toth E. , Stelfox J. , Kaufman S.
Published: December 2017

Inflation of a balloon for 2 h at the superior vena caval-right atrial junction of the rat reduced the salt intake of animals that had been sodium and water depleted by peritoneal dialysis with hyperoncotic colloid. After the balloons were deflated, the experimental group drank more than the control group so that the total sodium intake of the two groups was the same. Thus stimulated increased venous return to the heart attenuates salt appetite. Since this phenomenon might be secondary to a reflex reduction in plasma renin activity, the experiment was repeated using a model of salt appetite in which the renin-angiotensin system is known to be suppressed, namely the deoxycorticosterone acetate-treated rat. Salt intake was again significantly reduced by inflation of the right atrial balloon. It is concluded that pathways exist, independent of the renin-angiotensin system, whereby information obtained from the cardiac volume receptors regarding the state of filling of the vasculature may be used to regulate salt intake.
Extracellular fluid and plasma volumes during water immersion in nephrectomized dogs
Authors: Miki K. , Hajduczok G. , Hong S. K. , Krasney J. A.
Published: December 2017

Extracellular fluid volume (ECF, [125I]iothalamate space), blood volume (BV, 51Cr-labeled erythrocyte space), and hematocrit were measured continuously to study the kinetics of fluid movements between intracellular, interstitial, and plasma compartments during water immersion (WI) at 38 degrees C in seven splenectomized and acutely nephrectomized dogs. ECF and plasma volume (PV) increased linearly during WI by 10 +/- 2 ml/kg (4% of initial ECF volume, P less than 0.05) and 12 +/- 2 ml/kg (33% of initial PV, P less than 0.05), respectively, above the control level by 120 min of WI. We estimate that 83% of the fluid entering the intravascular compartment is derived from the intracellular space at 120 min of WI. The results of this study indicate that WI leads to a sustained fluid movement of intracellular fluid toward the intravascular compartment. The increase in interstitial hydrostatic pressure (wick method) by 28.5 mmHg from the control level at 5 min of WI in response to the external water pressure exceeds the increase in mean capillary pressure by 10-11 mmHg relative to the control level. We postulate that this negative hydrostatic pressure gradient across the capillary wall leads to an increase in PV during WI.
Regulation of anaerobic ATP-generating pathways in trout fast-twitch skeletal muscle
Authors: Dobson G. P. , Parkhouse W. S. , Hochachka P. W.
Published: December 2017

In the process of defining the recruitment of fuel and pathway selection in rainbow trout fast-twitch white skeletal muscle, it was clear that the near-maximal myosin adenosinetriphosphatase activity during a 10-s sprint was supported solely by phosphocreatine hydrolysis. A conservative estimate of the ATP turnover was 188 mumol X g wet wt-1 X min-1. It was not until the rate and force of contraction decreased that the relative contribution of anaerobic glycogenolysis became increasingly important. Over a 10-min period of burst swimming at approximately 120% of maximum aerobic steady-state swimming velocity of trout determined in a Brett-type swim tunnel, fatigue was associated with the near-depletion of glycogen in white muscle. The ATP turnover supported by anaerobic glycogenolysis was 78 mumol X g wet wt-1 X min-1. The glycolytic pathway appeared functional at this time with control sites being identified at hexokinase and phosphofructokinase (PFK-1). PFK-1 did not appear to be inhibited by low muscle pH (pH 6.66). In another exercise protocol lasting 30 min, complete exhaustion was related to glycogen depletion. The sum of all glycolytic intermediates from glucose 6-phosphate to pyruvate at exhaustion decreased by a dramatic 80% compared with the 25% decrease for the 10-min fatigue swimming protocol. This large depletion of glycolytic intermediates was accompanied by an 80% fall in ATP, a 70-80% reduction in the ATP/ADP and phosphorylation potential, and a 2.5-fold increase in the NAD/NADH. Associated with these changes was a marked displacement of the phosphoglycerate kinase (PGK), and the combined glyceraldehyde-3-phosphate dehydrogenase-PGK reactions from thermodynamic equilibrium. As a general conclusion, fatigue and exhaustion should be viewed as a multicomponent biochemical process in response to low glycogen and not leveled at one particular step of the glycolytic pathway.
Concentration of adrenocortical hormones in relation to cation homeostasis in birds
Authors: Rosenberg J. , Hurwitz S.
Published: December 2017

The effects of dietary Na+, K+, and Cl- and of acute stress on plasma levels of Na+, K+, aldosterone, and corticosterone were evaluated in vivo in birds. The dietary effects were studied in growing White Rock chicks, whereas the larger turkey was preferred for the acute stress study. Although plasma corticosterone remained unaffected, plasma aldosterone concentration decreased with increasing levels of dietary Na+ reaching a minimum at a dietary level of 72 meq/kg. Plasma Na+ remained unchanged when dietary Na+ levels increased up to 72 meq/kg but then rose with increasing Na+ intake. Plasma K+ was slightly depressed by high levels of dietary Na+ and increased by dietary K+. Neither plasma Na+ nor circulating adrenal hormones were affected by dietary K+ or dietary Cl-. Acute stress stimulated both aldosterone and corticosterone without any effect on the levels of the plasma minerals. The results suggest that of the two main corticoids, only aldosterone responds to dietary Na+ in chicks. This is in contrast to the indiscriminate stimulation of both hormones by stress, indicating different pathways of stimulation. The results also suggest that aldosterone is involved in the regulation of plasma Na+ only at low intakes of Na+ and that dietary K+ and Cl- are not involved in the aldosterone-Na+ feedback relationship.
Pancreatic vagal nerve is receptive to somatostatin in rats
Authors: Nakabayashi H. , Niijima A. , Kurata Y. , Jiang Z. Y. , Usukura N. , Takeda R.
Published: December 2017

To investigate whether somatostatin, one of the pancreatic islet hormones, influences the afferent firing activity of the vagus innervating the pancreas and whether there is any relevant morphological basis for the electrophysiological event, cyclic somatostatin-14 was injected into the rat pancreatic artery. The somatostatin injection at a physiological (0.61 pmol) or a pharmacological (3.05 pmol) dose significantly increased the afferent firing discharge rate of the pancreatic vagus in rats anesthetized with urethan and chloralose. The present histological examination disclosed a glomuslike neurovascular body in the rat peripancreatic sinusoidal vein. The body included many small corpuscles, and the corpuscle contained a structure like the afferent nerve ending. The immunohistochemical study revealed that the structure preferentially bound exogenous somatostatin. These electrophysiological and histological findings suggest that the vagal pancreatic nerve is receptive to somatostatin and that there exists a local neural monitoring system for somatostatin secreted from the islets.
Heart rate and body temperature during free diving of Weddell seals
Authors: Hill R. D. , Schneider R. C. , Liggins G. C. , Schuette A. H. , Elliott R. L. , Guppy M. , Hochachka P. W. , Qvist J. , Falke K. J. , Zapol W. M.
Published: December 2017

We have developed and successfully used the first microprocessor-controlled monitors for collection of data on depth, heart rate, and body temperature of one fetal and five adult male freely swimming Weddell seals. Adult seals almost invariably experienced a prompt bradycardia at the start of each dive, and the mean heart rate during diving was significantly lower for dives greater than 20 min (P greater than 0.999). The heart rate was also significantly greater during the ascent portion of dives when compared with the descent portion (P greater than 0.95). The fetal seal experienced a slow onset of bradycardia when its mother dived; during diving the fetal heart rate decreased by an average of 1.1 beats/min for each minute of the dive. The fetal heart rate generally took approximately 10 min to recover to predive levels after its mother resurfaced to breathe. The body temperature of one adult male Weddell seal showed a decrease of greater than 1.5 degrees C from resting levels before dives of greater than 15 min were initiated and a drop of over 2 degrees C before dives of greater than 30 min duration.
Allopurinol kinetics in humans as a means to assess liver function: comparison of different models
Authors: van Waeg G. , Groth T. , Niklasson F. , de Verdier C. H.
Published: December 2017

To describe the mechanisms involved in allopurinol kinetics after intravenous injection in humans, a number of alternative computer-based biodynamic models were designed. Distribution processes were described with two-compartment as well as with three-compartment kinetics for both allopurinol and its metabolite oxipurinol. These two major physiological alternatives were combined with biochemical models assuming either competitive or tight-binding-complex inhibition kinetics. The four resulting basic models were evaluated (and successively improved) using sets of plasma allopurinol and oxipurinol concentration curves, measured after intravenous injection in healthy subjects and in patients with different degrees of liver function. A three-compartment model with tight-binding-complex inhibition was selected and used to analyze the 35 loading tests performed. One of the parameters estimated in this way, the fractional rate constant for transport of allopurinol from the central compartment to the metabolically active (liver) compartment (kA31), turned out to be a powerful discriminative parameter between a group of healthy subjects, a group of patients with slightly to moderately reduced overall liver function, and a group with severely reduced overall liver function [kA31(min-1) = 0.136 +/- 0.042 (mean +/- SD, n = 13), 0.072 +/- 0.024 (n = 13), and 0.025 +/- 0.015 (n = 8), respectively].
Placental and renal control of plasma osmolality in chronically cannulated ovine fetus
Authors: Towstoless M. K. , Congiu M. , Coghlan J. P. , Wintour E. M.
Published: December 2017

This study investigated placental and renal control of plasma osmolality in mature (greater than 120 days, term 142-152 days) and immature (less than 120 days) chronically cannulated ovine fetuses. A transplacental osmotic gradient was generated by the rapid infusion of 20% mannitol (500 ml) into each of 20 pregnant cross-bred Merino ewes on at least two occasions. Maternal plasma osmolality increased by 29.2 +/- 1.0 (n = 29) mosmol/kg water (means +/- SE). Fetal plasma osmolalities increased to the same extent [14.8 +/- 0.9 (n = 29)] in immature and mature fetuses despite significantly higher plasma arginine vasopressin (AVP) concentrations [24.3 +/- 3.6 (n = 13) vs. 13.6 +/- 1.6 (n = 12) pg/ml] and significantly greater renal water retention in mature than immature fetuses (8.7 +/- 1.7 vs. 4.4 +/- 0.8 ml/h, P less than 0.05). Infusion of AVP intravenously to the fetus, at rates of 35-140 ng/h, for 1 h before the maternal mannitol did not alter fetal plasma osmolality. AVP, infused at 35-140 ng/h during the maternal mannitol infusions, did not alter fetal plasma osmolality increases. The conclusions are that 1) placental water transfer is the major determinant of fetal plasma osmolality and 2) the experiments suggest that placental water flux in the sheep is not regulated by endogenous or exogenous AVP.
Neuropeptide Y increases food intake in mice
Authors: Morley J. E. , Hernandez E. N. , Flood J. F.
Published: December 2017

Neuropeptide Y (NPY) stimulates eating in a number of species. In the studies reported here, intracerebroventricular administration of porcine NPY increased eating in mice. In the presence of food, NPY caused enhancement of water intake, whereas in the absence of food, NPY suppressed water intake. Behavioral analysis showed that NPY decreased the latency to eat, increased the time spent eating, and decreased grooming. Human NPY also increased food intake, whereas the free acid of NPY was inactive. Although some minor discrepancies in response were noted overall, NPY was as effective at stimulating food intake in genetically obese (ob/ob) mice compared with their lean littermates (ob/-), in genetically diabetic mice (db/db) and their nondiabetic heterozygote control (db/m), in streptozocin-induced diabetic mice and their controls, and in adult (8 mo old) compared with old (25 mo old) mice.
Effect of diltiazem on altered cellular calcium regulation during endotoxic shock
Authors: Sayeed M. M. , Maitra S. R.
Published: December 2017

Cellular free and exchangeable Ca2+ were quantitated in livers of rats injected with saline (control), Salmonella enteritidis endotoxin (20 mg/kg), or diltiazem (0.8-1.2 mg/kg) plus the endotoxin (20 mg/kg). Injection of endotoxin alone resulted in signs of endotoxic shock in animals 5 h later. All rats were killed 5 h postinjection, and their livers were excised. Hepatocytes were prepared for the measurement of cytosolic [Ca2+] under basal and hormone-stimulated (1 and 10 microM epinephrine) conditions by means of quin 2 fluorescence technique. Liver slices were labeled with 45Ca, and the radioactivity was washed out to determine cellular exchangeable Ca2+. The apparent basal level of cytosolic Ca2+ in endotoxic rat hepatocytes [525 +/- 92 (SE) nM] was significantly (P less than 0.05) higher than in controls (146 +/- 23). A significant increase in the basal [Ca2+] occurred after stimulation with epinephrine in controls but not in endotoxic rat hepatocytes. In the endotoxic rats receiving diltiazem, basal [Ca2+] was significantly lower than in rats given endotoxin alone, and a significant elevation of cytosolic [Ca2+] with epinephrine also occurred. The cellular exchangeable Ca2+ in endotoxic rats (564 +/- 27 nmol/g) was significantly higher than in controls (427 +/- 23). Diltiazem treatment of endotoxic rats restored the exchangeable Ca2+ level to that found in controls. The endotoxic accumulation of cellular Ca2+ and its restoration toward control levels by diltiazem could be due to catecholamine-mediated Ca2+ influx and its blockade by diltiazem.
Serotonin and feeding responses of rats to amino acid imbalance: initial phase
Authors: Gietzen D. W. , Rogers Q. R. , Leung P. M. , Semon B. , Piechota T.
Published: December 2017

The role of serotonin in the anorexic response of rats to an amino acid-imbalanced diet was investigated. After chronic depletion of serotonin with parachlorophenylalanine (PCPA, 300 mg/kg) or 5,7-dihydroxytryptamine (DHT, 200 micrograms/rat, intracisternally), initial intake of a mild isoleucine-imbalanced diet was reduced by 60% vs. a 17% reduction after saline injection. After acute treatment with the agonist, quipazine (quip, 5 mg/kg ip) or the precursor, tryptophan (TRP, 1% added to the diet), imbalanced diet intake was also exacerbated. PCPA and DHT may have caused receptor supersensitivity, such that the food intake depression after serotonin depletion was similar to that seen with the quip and TRP treatments. Injection of the autoreceptor agonist, 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT, 500 micrograms/kg sc), to reduce transmission in the serotonergic systems resulted in an attenuation of the usual food intake depression of the amino acid-imbalanced diet (only a 7%, nonsignificant reduction). Also measurements made in the absence of pharmacological treatment showed that the ratio 5-hydroxyindole acetic acid-to-serotonin, a putative index of serotonin turnover, was increased 155% in the raphe nuclei and 140% in the hippocampus 3.5 h after ingestion of the mild isoleucine-imbalanced diet. Therefore increased serotonergic activity in some brain areas may be associated with the initial depression of food intake in rats fed an imbalanced amino acid diet.
Renal response to volume expansion in atrial-appendectomized dogs
Authors: Benjamin B. A. , Metzler C. H. , Peterson T. V.
Published: December 2017

The purpose of this study was to determine whether chronic removal of the atrial appendages alters the renal response to volume expansion (VE) in anesthetized dogs. Chronic bilateral atrial appendectomy (ATX) was performed in 10 animals. Six animals served as sham-operated controls (S). The animals were studied 10-14 days after chronic surgery. The protocol consisted of a 20-min control period followed by isochemic VE (20%) and 120 min of post-VE measurements. The dogs were studied a second time, 2 wk later, after acute bilateral cervical vagotomy. Results from the vagi-intact study showed that VE caused a diuresis, natriuresis, and increase in fractional sodium excretion in ATX that did not differ from the response observed in S. VE also caused equivalent increases in central venous and mean arterial pressures in S and ATX. Atrial appendectomy, however, failed to significantly attenuate the increase in atrial natriuretic factor (ANF) after VE. Plasma ANF increased from 27.2 +/- 4.8 to 47.0 +/- 7.3 pg/ml in ATX and from 27.2 +/- 7.8 to 59.0 +/- 17.9 pg/ml in S. After vagotomy, VE caused transient increases in urine flow and sodium excretion. The changes in central venous and mean arterial pressures were not different from the vagi-intact study and vagotomy did not affect the increase in ANF after VE. Circulating ANF levels increased from 26.4 +/- 5.5 to 75.0 +/- 14.0 pg/ml in ATX and from 28.1 +/- 5.7 to 73.0 +/- 22.6 pg/ml in S. These results demonstrate that, in the dog, bilateral ATX does not alter the renal response to volume expansion or attenuate the increase in ANF. In addition, these results show that vagal pathways are not required for the release of ANF and that vagotomy fails to uncover any effect of atrial appendectomy on renal function.
Thermoregulatory effects of intracranial norepinephrine injections in goldfish
Authors: Wollmuth L. P. , Crawshaw L. I. , Panayiotides-Djaferis H.
Published: December 2017

Cannulas were implanted into forebrain loci of goldfish (Carassius auratus; 45-90 g) to determine the effects and site of action of intracranial norepinephrine (NE) injections on behavioral thermoregulation. Following 30 min in a thermal gradient, implanted fish were injected with norepinephrine-bitartrate salt (2.5-500 ng NE) in 0.2 microliter 0.7% NaCl. Injections of 5, 10, 25, and 50 ng NE into the anterior aspect of the nucleus preopticus periventricularis (NPP, Ref. 25) led to consistent dose-dependent decreases in selected temperature (Tsel). No effect on Tsel was observed following injections of 2.5 ng NE or control injections of 100 ng tartaric acid. The effects of injections into other loci, including intraventricular injections, were dependent on the dose and proximity to the anterior NPP; at sites adjacent to the anterior NPP, larger doses were required, and the effects became inconsistent. At sites further removed, no effect on Tsel was observed. Included in this category were more caudal sites within the NPP and the nucleus preopticus. We postulate that in fish the anterior NPP is an important locus for thermoregulatory integration and that increased release of NE in this area leads to the selection of cooler water.
Cardiac output and oxygen consumption in exercising Thoroughbred horses
Authors: Weber J. M. , Dobson G. P. , Parkhouse W. S. , Wheeldon D. , Harman J. C. , Snow D. H. , Hochachka P. W.
Published: December 2017

This study characterizes the effects of exercise on the cardiac output (Q) and the metabolic rate (VO2) of trained Thoroughbred racehorses. Heart rate, Q, and arteriovenous (a-v)O2 difference were measured at rest and at three levels of submaximal treadmill exercise (1.6 m/s walk and 3-4 m/s trot at 6% incline, and 6.5 m/s horizontal canter). Heart rate and (a-v)O2 difference were also measured during maximal exercise (12.5 m/s gallop, 5% incline) to obtain an estimate of maximum O2 uptake (VO2max). The walk, trot, and canter represented 25, 45, and 55% VO2max. Mean heart rate went from 48.9 (rest) to 197 beats/min (gallop). Q ranged from 106 (rest) to 571 ml.min-1.kg-1 (canter), and stroke volume went from 1.34 (rest) to a maximum of 1.58 liters (walk). Thoroughbreds were able to bring hematocrit from 38 (rest) to 63% (gallop), and this adjustment allowed them to reach an impressive (a-v)O2 difference of 23 vol%, which represents a fivefold increase over resting values. These outstanding athletes probably support an aerobic scope of 40-fold.
Electrogenic ATP-dependent Cl- transport by plasma membrane vesicles from Aplysia intestine
Authors: Gerencser G. A.
Published: December 2017

A Cl--stimulated adenosinetriphosphatase (ATPase) activity and an ATP-dependent Cl- transport process were found in Aplysia enterocyte plasma membranes. In an attempt to further elucidate this transport process plasma membrane vesicles from Aplysia enterocytes were prepared utilizing differential centrifugation and sucrose density gradient techniques. Electrogenicity of the ATP-dependent Cl- transport was confirmed in three ways. First, an inwardly directed valinomycin-induced K+ diffusion potential, making the vesicle interior electrically positive, enhanced ATP-driven Cl- uptake compared with vesicles lacking the ionophore. Second, ATP plus Cl- increased intravesicular negativity measured by lipophilic triphenylmethylphosphonium distribution across the vesicular membrane. Third, both vanadate and thiocyanate inhibited the ATP plus Cl--dependent intravesicular negativity. These results are consistent with the hypothesis that the active electrogenic Cl- transport mechanism in Aplysia intestine could be a Cl--stimulated ATPase found in the enterocyte plasma membrane.
Calcium metabolism in the rat: a temporal self-organized model
Authors: Staub J. F. , Tracqui P. , Brezillon P. , Milhaud G. , Perault-Staub A. M.
Published: December 2017

Based on consideration of rat plasma Ca and 45Ca concentrations, we analyze the circadian behavior of Ca metabolism of the rat as the temporal expression of a self-organized system. We present a self-oscillatory model M for rat Ca metabolism based on a compartmental formalism, which includes a second-order autocatalytic process. M describes the entire mass of Ca as made up of eight compartments and predicts a distinction between 1) the amount of Ca deposited in zones of rapid bone growth and reutilized during bone maturation and 2) the amount of Ca in mature bone subdivided into four compartments. Two of these compartments, largely self-oscillating, may represent Ca-P associations at bone liquid/solid interface and are subject to osteoblast-osteocyte control. The other two compartments can be thought of as made up of a large expanding pool of hydroxyapatite (HA) crystals, which are largely unavailable as such, and a small pool or more available HA crystals. Bone Ca influx and rhythmic efflux play a major role in the regulation of Ca in extracellular fluid but must be dissociated from bone accretion and resorption. Application to Ca deficiency was analyzed. Conceptual consequences of the connection of Ca metabolism to a self-regulated system are discussed.
Thyroxine, renal beta-adrenergic receptors, and dipsogenesis in food-deprived rats
Authors: Yeh L. F. , Baker S. P. , Katovich M. J.
Published: December 2017

The effect of thyroxine (T4) replacement on the increased renal beta-adrenergic receptor number and the increased beta-adrenergic dipsogenic responsiveness of fasted rats was studied in male Sprague-Dawley rats. Food deprivation significantly decreased serum thyroxine (T4) and triiodothyronine (T3) levels, increased the dipsogenic response to isoproterenol, and elevated renal beta-adrenergic receptor concentration. Daily administration of T4 (40 micrograms/kg) to food-deprived rats restored serum thyroid levels to normal. Thyroxine replacement also reduced the increased beta-adrenergic dipsogenic responsiveness in the food-deprived rats to control levels. In addition, daily administration of thyroxine reduced the beta-adrenergic receptor concentration in renal cortices to that observed in controls. Thyroid treatment tended to decrease the isoproterenol-induced renin release in food-deprived rats and increase the response in the control rats. These results suggest that the relative hypothyroid state observed in the food-deprived rat may be responsible for the increased concentration of renal beta-receptors and the associated activation of the renin-angiotensin system, which may be partially responsible for the observed increased dipsogenic response induced by isoproterenol. Collectively, the data reaffirm the interaction of thyroid hormone and beta-adrenergic responsiveness, although it is of interest that, in regard to renal beta-receptors, the concentrations are decreased to normal by thyroid treatment, whereas previous studies in hypothyroid rats demonstrate an increase to normal of cardiac beta-receptors. This would suggest thyroid hormone may normalize a response in an opposite direction depending on the direction of the disturbance.
Protein and lipid utilization during long-term fasting in emperor penguins
Authors: Robin J. P. , Frain M. , Sardet C. , Groscolas R. , Le Maho Y.
Published: December 2017

The body mass of male emperor penguins is approximately 38 kg at the beginning of the 4-mo winter fast connected with breeding, and it is an estimated approximately 18 kg in leanest birds at time of spontaneous refeeding. For a 38- to 18-kg range, we investigated the changes in the rate of body mass loss, body composition, and plasma concentrations of uric acid and urea. After the first few days (phase I) a steady state (phase II) was reached in the proportions of the energy derived from proteins and lipids with proteins accounting for a constant 4%, and the remaining 96% being from lipids. The same proportions were maintained until body mass had decreased to 24 kg. Below this value the proportion of energy derived from proteins increased progressively (phase III), being 14 times higher at 18 kg than during phase II. Rate of body mass loss and plasma uric acid and urea concentrations closely reflected the changes in protein utilization: being at a low and steady value throughout phase II and increasing during phase III. Emperor penguins also fast during the spring, but for periods of only 2-3 wk. We found a 2.5 times higher value for rate of body mass loss, uric acid, and urea during spring phase II, suggesting lower effectiveness in protein sparing at that time. It may be attributed to the lower initial lipid reserves of spring birds. Would these findings be generalized to the wide variety of birds and mammals that spontaneously fast under natural conditions?(ABSTRACT TRUNCATED AT 250 WORDS)
Increased ANF secretion after volume expansion is preserved in rats with heart failure
Authors: Chien Y. W. , Barbee R. W. , MacPhee A. A. , Frohlich E. D. , Trippodo N. C.
Published: December 2017

To examine whether the failing heart has reached a maximal capacity to increase plasma atrial natriuretic factor (ANF) concentration, the change in plasma immunoreactive ANF level due to acute blood volume expansion was determined in conscious rats with chronic heart failure. Varying degrees of myocardial infarction and thus heart failure were induced by coronary artery ligation 3 wk before study. Compared with controls, infarcted rats had decreases in mean arterial pressure (-10 mmHg, P less than 0.01), cardiac index (-27%, P less than 0.001), renal blood flow (-35%, P less than 0.01), and peak left ventricle-developed pressure after aortic occlusion (an index of pressure generating ability; -15%, P less than 0.01), and increases in central venous pressure (+1.7 mmHg, P less than 0.01), left ventricular end-diastolic pressure (+10 mmHg, P less than 0.001), total peripheral resistance (+28%, P less than 0.01), and plasma ANF level (752 +/- 109 vs. 244 +/- 33 pg/ml, P less than 0.001). Plasma ANF was correlated with infarct size, cardiac filling pressures, and left ventricle pressure-generating ability. At 5 min after 25% blood volume expansion, plasma ANF in rats with heart failure increased by 2,281 +/- 345 pg/ml; the magnitude of the changes in circulating ANF and hemodynamic measurements was similar in controls. The results suggest that plasma ANF level can be used as a reliable index of the severity of heart failure, and that the capacity to increase plasma ANF concentration after acute volume expansion is preserved in rats with heart failure. There was no evidence of a relative deficiency of circulating ANF in this model of heart failure.
Neurohumoral interactions in conscious dehydrated rabbit
Authors: Trapani A. J. , Undesser K. P. , Keeton T. K. , Bishop V. S.
Published: December 2017

The purpose of this study was to examine the role of angiotensin II (ANG II), arginine vasopressin (AVP), and neurogenic mechanisms in maintaining arterial pressure (MAP) in conscious water-deprived rabbits. Water deprivation produced marked increases in plasma renin activity and the concentration of AVP; however, plasma catecholamine concentrations were unchanged. Arterial baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) was similar in water-replete and dehydrated animals. Administration of an ANG II receptor antagonist (ANG IIX) to water-deprived animals produced a small decrease in MAP but no significant changes in HR or mesenteric and hindquarters vascular resistances. Similarly, there was no significant effect on MAP, HR, or regional hemodynamics when dehydrated animals received an AVP-V1 antagonist (AVPX). RSNA increased by maximums of 61 and 43% in response to ANG IIX and AVPX, respectively. Combined administration of ANG IIX and AVPX produced significant decreases in MAP (-9 mmHg) and hindquarters resistance (-24%) and 117% and 23 beat/min increases in RSNA and HR, respectively. The effect on mesenteric resistance was variable; however, the response was generally a decrease. We conclude that ANG II and AVP pressor mechanisms are activated to sustain MAP in the dehydrated state. In contrast, the basal level and baroreflex control of sympathetic nervous system activity are unchanged from the water-replete state. However, activation of sympathetic nerve activity may become important in maintaining peripheral resistance when ANG II and AVP receptors are blocked in water-deprived animals.
Effects of plasma angiotensin II and hypernatremia on subfornical organ neurons
Authors: Gutman M. B. , Ciriello J. , Mogenson G. J.
Published: December 2017

Experiments were done in urethan-anesthetized rats to investigate the effect of plasma angiotensin II (ANG II) and hypernatremia on the excitability of subfornical organ (SFO) neurons projecting directly to paraventricular nucleus of the hypothalamus (PVH), supraoptic nucleus (SON), and nucleus medianus (NM). Extracellular recordings were made from 106 antidromically identified neurons in the SFO. The firing frequency of 53 (50%) was increased by the intracarotid infusion of ANG II and/or 0.5 M hypertonic NaCl. The intracarotid infusion of isotonic saline or the intravenous infusion of phenylephrine did not alter the discharge rate of these SFO neurons. Of 38 PVH projecting neurons, 21 (55%) responded to ANG II and/or hypertonic NaCl: 9 to ANG II only, 8 to hypertonic NaCl only, and 4 to both. Similarly, of 42 SON projecting neurons, 30 (71%) responded to ANG II and/or hypertonic NaCl: 10 to ANG II only, 15 to hypertonic NaCl only, and 5 to both. Finally, of 26 NM projecting neurons, one increased its firing frequency to ANG II and one other to 0.5 M NaCl. An additional eight SFO neurons were found to send collateral axons to both the PVH and SON (n = 6) and PVH and NM (n = 2): four responded in various combinations to intracarotid infusion of ANG II and 0.5 M NaCl. These data suggest that blood-borne ANG II and plasma hypernatremia can influence arterial pressure and the release of vasopressin from the neurohypophysis by altering the discharge rate of SFO neurons projecting to forebrain structures that contain magnocellular neurosecretory vasopressin neurons and neurons that are components of sympathoexcitatory pathways.
A novel endogenous sugar acid depolarizes ventromedial hypothalamic neurons in vitro
Authors: Fukuda A. , Oomura Y. , Plata-Salaman C. R. , Minami T. , Ito C.
Published: December 2017

2-Buten-4-olide (2-B-4-O) has been identified in the serum of fasted rats and proved to act as a feeding suppressant. The effect of 2-B-4-O on neurons in the ventromedial hypothalamic (VMH) nucleus was investigated with intracellular recordings in brain slice preparations of rats. 2-B-4-O, applied by perfusion (0.1-10 mM) or drops (50-100 mM), dose dependently depolarized 30% of the VMH neurons tested. The depolarization by 2-B-4-O application persisted after complete elimination of synaptic inputs during perfusion with Ca2+-free/high-Mg2+ solution. The depolarization, accompanied by a decrease in membrane conductance, reversed polarity around -95 mV and was dependent on extracellular K+ concentration. The VMH neurons depolarized by 2-B-4-O had some specific electrophysiological properties corresponding with those of glucoreceptor neurons. The results suggest that 2-B-4-O directly excites VMH neurons, presumed to be glucoreceptor neurons, by decreasing K+ conductance, and this effect may participate in the feeding suppressive action of 2-B-4-O.
Ovine fetal and adult atrial natriuretic factor metabolism
Authors: Ervin M. Gore , Ross Michael G. , Castro Robert , Sherman Dany , Lam Robert W. , Castro Loni , Leake Rosemary D. , Fisher Delbert A.
Published: December 2017

Pages R40–R46: M. Gore Ervin, Michael G. Ross, Robert Castro, Dany Sherman, Robert W. Lam, Loni Castro, Rosemary D. Leake, and Delbert A. Fisher. “Ovine fetal and adult atrial natriuretic factor metabolism.” Pages R42–R43: The mean residence time (MRT) values published were incorrect. Corrected values are listed below:

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Norepinephrine turnover in iron deficiency at three environmental temperatures
Authors: Beard J. , Tobin B. , Smith S. M.
Published: December 2017

Iron-deficient anemic rats had a significant elevation in urinary norepinephrine (NE) after 7 days at 30 and 24 degrees C, but not at 10 degrees C, compared with control animals. NE turnover studies were performed to examine sympathetic nervous system activity in a tissue-specific fashion. NE content in myocardium decreased by nearly 50% in hypertrophied iron-deficient hearts at all three temperatures, whereas fractional turnover rates were compensatorily increased. In contrast, interscapular brown adipose tissue NE turnover was significantly reduced to 30% of normal in iron-deficient animals at both 30 and 10 degrees C. Serum triiodothyronine concentrations were similar to controls at 30 degrees C but were decreased at lower temperatures. Serum tetraiodothyronine concentrations were lower in iron-deficient animals at all three environmental temperatures. We conclude that increased sympathetic nervous system activity compensatory to temperatures below thermoneutrality is less well controlled in iron-deficient animals than in controls, and at a low environmental temperature this may possibly explain the poor thermoregulatory capacity of iron-deficient animals. A generalized hypernoradrenergic state is not supported by our NE turnover study and does not explain the elevated urine NE concentrations.
Atrial distension of isolated rabbit hearts and release of atrial natriuretic factor
Authors: Synhorst D. P. , Gutkowska J.
Published: December 2017

Interventions that increase atrial pressures in humans or laboratory animals release atrial natriuretic factor (ANF) into the circulation. We studied the relation between distension of the right or left atrium and release of ANF in retrograde-perfused isolated rabbit hearts. A fluid-filled balloon within the right or left atrium was inflated to a mean pressure of 5, 10, 15, or 20 mmHg, and ANF in the cardiac effluent was measured by radioimmunoassay. The slope of the regression line relating ANF release to atrial distending pressure was steeper for the left than right atrium (P less than 0.001), indicating that, at comparable increases in mean pressures, the left atrium releases more ANF than does the right atrium. Left atrial tissue concentration of ANF was greater than right atrial (1.58 +/- 0.15 vs. 1.05 +/- 0.09 micrograms ANF/mg protein, P less than 0.01). In contrast to previous studies showing right atrial dominance in rats, the left atria of isolated, perfused rabbit hearts contain more ANF and release more in response to atrial distension.