bluuebunny/crossref_metadata_2025 huggingface dataset:
Norepinephrine turnover in brown adipose tissue of young rats: effects of rearing temperature
Authors: Bertin R. , Mouroux I. , De Marco F. , Portet R.
Published: December 2017

Brown adipose tissue (BAT) has an important role in the thermogenesis of newborn mammals and cold-acclimated rodents. Heat production within the tissue is regulated by the sympathetic nervous system (SNS) via norepinephrine (NE) release. As only little is known of the progressive role of SNS during the developmental period, NE content and turnover were determined in BAT of infant rats 1-33 days of age. The dams and the pups were kept at either 28 or 16 degrees C. It was observed that the NE level in the tissue and the mediator turnover had an almost parallel evolution during the experimental period. In the first week of life, level and turnover of NE were higher in the 28 degrees C group than in the 16 degrees C group. During the second week, the level remained constant in rats kept at 28 degrees C, but the NE turnover slightly decreased. In contrast, a large increase of both parameters was observed in rats kept at 16 degrees C. Then a decrease occurred in both groups until weaning. Subsequently the values remained almost constant. It must be noted that, from the end of the first week, NE content and turnover were always significantly higher in the 16 degrees C group than in the 28 degrees C group. At the end of the first month, the level was 50% higher in cold-acclimated rats and turnover was four times as high as in controls.(ABSTRACT TRUNCATED AT 250 WORDS)
Metabolic characteristics of cat kidney: failure to adapt to metabolic acidosis
Authors: Lemieux G. , Lemieux C. , Duplessis S. , Berkofsky J.
Published: December 2017

During studies performed on domestic cats made acidotic with ammonium chloride, it was found that the cat kidney is unable to adapt to metabolic acidosis. Renal proximal tubules do not increase their production of ammonia or glucose from glutamine during acidosis. During in vivo studies, the renal excretion of ammonia did not change much during acidosis. Other metabolic parameters in the cat were not very different from those found in other animals such as rat or dog. However, it was found that cats may show a relatively high plasma glucose concentration compared with other animals. Plasma insulin concentration was normal, and the animals showed no evidence of diabetes mellitus. It is not known whether limitation of ammoniagenesis and elevated plasma glucose concentration also characterize larger felidae such as panthers and cougars.
Continuous servo-controlled replacement of urinary sodium loss in conscious dogs
Authors: Andersen S. E. , Bie P.
Published: December 2017

A method for continuous servo-controlled infusion of sodium chloride to dogs is reported. The servo system consists of a sodium-sensitive electrode, a modified commercial flowmeter, a thermistor, a control unit, and a pump. Based on analog inputs from electrode, flowmeter, and thermistor, the control unit generates appropriate numbers of voltage steps, which drive the pump infusing a concentrated solution of sodium chloride. Inputs from the thermistor are necessary to correct for the influence of fluctuations in urine temperature. The sodium servo system has been tested together with a weight servo mechanism in conscious water-diuretic dogs. Furosemide (1 microgram.kg-1.min-1) was infused to change the rate of sodium excretion by a factor of 17 from 3 +/- 1 to 50 +/- 15 mumols/min. Within this range, the apparatus replaced the sodium losses with great accuracy. From seven experiments the average system response in micromoles per minute (NaIn) measured in 10-min periods against mean renal excretion of sodium (NaEx) was NaIn = 0.98.NaEx - 1.37. The servo system provides a tool for accurate maintenance of body sodium irrespective of large changes in the rate of sodium excretion.
Effect of fourth ventricular neuropeptide Y and peptide YY on ingestive and other behaviors
Authors: Corp E. S. , Melville L. D. , Greenberg D. , Gibbs J. , Smith G. P.
Published: December 2017

We studied the effect of fourth intracerebroventricular administration of neuropeptide Y (NPY) and peptide YY (PYY) on ingestive and other behaviors in awake nondeprived rats. Injection of NPY or PYY into the fourth ventricle produced a significant dose-related increase in food intake and reduction in the latency to eat. PYY was more potent than NPY in increasing food intake and decreasing latency to eat, suggesting that PYY-preferring receptors sensitive to the orexigenic effects of NPY and PYY exist in the hindbrain. In addition, both peptides increased water intake when food was present but not when food was absent, suggesting that a neural substrate supporting a direct action of NPY and PYY on water intake is not present in the hindbrain. In time sampling of behaviors occurring during a 90-min feeding test, we found that both peptides increased the time spent eating and reduced grooming. In addition PYY, but not NPY, reduced apparent sleep and increased exploratory activity. This suggests that PYY, but not NPY, influences a hindbrain neural substrate involved in sleep and activity.
Accelerated gastric emptying in VMH-lesioned rats is secondary to excess weight gain
Authors: Black R. M. , Conover K. L. , Weingarten H. P.
Published: December 2017

This experiment evaluates the hypothesis that an accelerated rate of gastric emptying accounts for the hyperphagia and obesity after lesions of the ventromedial hypothalamus (VMH). Gastric emptying was measured for 16 days after the production of VMH lesions in rats maintained either ad libitum or on restricted eating. Only ad libitum VMH-lesioned rats demonstrated faster than normal rates of emptying. However, VMH rats maintained at control weights showed normal rates of gastric emptying and, even in ad libitum rats, accelerated emptying was not apparent immediately after lesions. These findings indicate that changes of emptying are not a primary effect of VMH lesions but that this dysfunction develops secondarily as a consequence of excess eating and weight gain. Measurement of stomach secretions demonstrated, however, that VMH lesions did result in an immediate and direct effect on gastric secretion. These findings mitigate the importance of gastric emptying in the etiology of the VMH syndrome. Other data consistent with this conclusion are reviewed.
Effect of outflow pressure on liver lymph flow in unanesthetized sheep
Authors: Drake R. E. , Gabel J. C.
Published: December 2017

We used lymph flow rate (QL) to lymphatic vessel outflow pressure (Po) relationships to analyze lymphatic flow in five unanesthetized sheep with liver lymphatic cannulas. The olecranon was the zero reference level for pressures. Increases in Po did not change QL until Po exceeded 19 +/- 4 (SD) cmH2O. However, for Po greater than 19 +/- 4 cmH2O, QL decreased linearly with increases in Po. We fit regression lines to the QL vs. Po data for Po greater than 19 cmH2O and estimated the effective lymphatic resistance (RL) as -delta Po/delta QL. The effective pressure driving lymph (PL) was the Po at which QL = 0. At baseline, RL = 0.18 +/- 0.10 cmH2O.min.microliter-1 and PL = 29.6 +/- 3.4 cmH2O. When we increased hepatic vein pressure by 5.7 +/- 1.7 cmH2O, QL increased to 6.2 +/- 3.2 times baseline, RL decreased to 0.050 +/- 0.015 cmH2O.min.microliter-1, and PL increased to 37.1 +/- 3.5 cmH2O (P less than 0.05). Thus 1) liver lymph flow is very sensitive to increases in hepatic vein pressure, 2) there is a substantial QL vs. Po plateau for liver lymphatics, and 3) after hepatic venous pressure elevations, liver lymph flow increases as if it were driven by a higher pressure through a lower resistance.
Preoptic area injection of corticotropin-releasing hormone stimulates sympathetic activity
Authors: Egawa M. , Yoshimatsu H. , Bray G. A.
Published: December 2017

To investigate the sites of action of corticotropin-releasing hormone (CRH) on sympathetic nerve activity to interscapular brown adipose tissue (IBAT), we injected CRH into the third cerebroventricle, medial preoptic area (MPOA), and other hypothalamic areas in anesthetized rats. The multiunit discharges of sympathetic nerves to IBAT were recorded electrophysiologically. The intracerebroventricular injection of CRH increased sympathetic nerve activity in a dose-dependent manner over the range 250-1,000 pmol. The microinjection of CRH (200 pmol) into the unilateral MPOA increased the sympathetic nerve activity to IBAT by +150.6 +/- 25.9% at 30 min after injection. However, the injection of saline (0.15 M NaCl) and glucagon (200 pmol) into the MPOA did not increase sympathetic nerve activity. The microinjection of CRH (200 pmol) into the anterior hypothalamic area, paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, and lateral hypothalamic area had no significant effect on nerve activity. We conclude that central administration of CRH increases the sympathetic nerve activity to IBAT and that the MPOA is one of the sites for this action. The result is consistent with the hypothesis that CRH is a neurochemical stimulator of the sympathetic nervous system, which may be involved in control of energy expenditure in rodents.
Control of ventilation in adult rats hypoxic in the neonatal period
Authors: Okubo S. , Mortola J. P.
Published: December 2017

Three groups of 50-day-old (i.e., postpuberty) rats have been studied: controls, rats exposed to 6 days of hypoxia [inspired fraction of O2 (FIo2) = 10% O2] when newborn (Nb-Hypox), and rats exposed to the same level and duration of hypoxia after weaning (Ad-Hypox). Ventilation during normoxic breathing was higher in Nb-Hypox than in controls or Ad-Hypox. The ventilatory response to acute hypoxia (10 min of 10% O2) was about one-half in Nb-Hypox than in the other two groups. Additional measurements performed on Nb-Hypox and controls showed minimal or no differences between the two groups in the ventilatory responses to hyperoxia and hypercapnia, heart rate and blood pressure at various FIO2, and blood biochemistry. Analysis of the Hering-Breuer reflexes, during barbiturate anesthesia, suggested a decreased central inhibition on inspiratory activity in Nb-Hypox, which with a lower sensitivity to inputs from the peripheral chemoreceptors may contribute to the normoxic hyperventilation and the blunted response to acute hypoxia. The ventilatory patterns of Nb-Hypox rats bear numerous similarities with those of high-altitude natives and could suggest that the highlander's ventilatory responses are not genetic characteristics but relate to chronic hypoxia early in life.
Receptor interactions in modulating ventilatory activity
Authors: Mitchell G. S. , Douse M. A. , Foley K. T.
Published: December 2017

The ventilatory control system utilizes a variety of sensory receptor groups, including chemoreceptors and mechanoreceptors, to provide feedback concerning the status of controlled variables. Most ventilatory responses to altered receptor inputs generally involve a complex interaction between several receptor groups, central integrative mechanisms, and other modulatory inputs (e.g., “state,” hormonal, or neurotransmitter status). Because the control system is complex, nonlinear, and dynamic, the ultimate ventilatory response elicited by a given stimulus is not easy to predict based on the reflex effects of individual receptor groups studied in isolation. A full understanding of the role that sensory receptors play in ventilatory control requires information concerning interactions among receptor groups and with other elements of the control system. The complexity of the problem and the lack of a uniform definition of the term “interaction” has hindered research in this area. An interaction is defined as a nonadditive relationship between independent inputs to the system. Within this definition, five domains of interaction are described. 1) Algebraic interactions occur in ventilation and/or its components because of their multiplicative and nonlinear relationship. 2) Closed-loop interactions occur because of the prevalence of feedback loops within the respiratory control system. 3) Neural interactions reflect central nervous system integration of simultaneous receptor inputs and are demonstrated when feedback loops are opened. Three subdomains of neural interactions are defined: modulatory, dynamic, and range-specific neural interactions. 4) Mechanical interactions result from nonlinear transformations of motoneuron output into mechanical actions. 5) Adaptive interactions occur when paired receptor or modulatory inputs alter future responses. To understand the role of any sensory receptor group in ventilatory control, it is necessary to define its interactions with other control system elements in each of these domains. Understanding the mechanisms of these interactions requires detailed information about the physical system subserving ventilatory control (mechanics and gas exchange) and the relevant properties of the neural network coordinating their actions.
Catecholamines depress endolymphatic sac direct current potential in guinea pigs
Authors: Mori N. , Uozumi N. , Sakai S.
Published: December 2017

To test the possibility that catecholamines have an influence on the function of the endolymphatic sac (ES), which is known to absorb the endolymph, the effect of catecholamines on the ES direct current potential (ESP) was examined in the guinea pig. The ESP was recorded extradurally by the posterior occipital approach. Isoproterenol (Iso), epinephrine (Epi), and norepinephrine (NE) were administered intravenously for 4 min using an infusion pump. Catecholamines reversibly depressed the ESP with the rank order of potency Iso greater than Epi greater than NE. The threshold doses were 0.021, 0.27, and 1.94 micrograms/kg for Iso, Epi, and NE, respectively. beta-Antagonist (propranolol) blocked the action of catecholamines on the ESP but alpha-antagonist (phentolamine) did not. This indicates that beta-adrenergic action induces the ESP change. This study implies that catecholamines may regulate the function of the ES.
Atrial natriuretic factor and blood pressure control: role of sodium and aldosterone
Authors: Gaillard C. A. , Mizelle H. L. , Montani J. P. , Brands M. W. , Hildebrandt D. A. , Hall J. E.
Published: December 2017

This study examined the long-term actions of atrial natriuretic factor (ANF), at physiological levels, on renal function and mean arterial pressure (MAP) and the importance of Na intake and the renin-angiotensin-aldosterone system in modulating those effects. After a control period, ANF was infused intravenously at a rate of 10 ng.kg-1.min-1 for 7 days, followed by 7 days of 20 ng.kg-1.min-1 and 7 days of recovery. After 7 days of ANF at 10 ng.kg-1.min-1, MAP decreased from 87 +/- 3 to 80 +/- 2 mmHg in normal dogs on low sodium intake (LS, 7 meq Na/day) and from 89 +/- 2 to 79 +/- 2 mmHg in adrenalectomized dogs (ADX, 7 meq Na/day) given constant mineralocorticoid replacement. In both groups, no significant change in glomerular filtration rate (GFR) was observed, although sodium excretion increased transiently. ANF failed to cause significant changes in MAP, GFR, or sodium excretion in normal dogs on high sodium intake (HS, 269 meq Na/day). In LS and HS no long-term effects of ANF on plasma renin activity (PRA) and aldosterone were observed. In ADX, as expected, no change in aldosterone was observed. Thus, in normal and adrenalectomized dogs on LS, chronic ANF infusion caused sustained reductions in MAP. HS markedly attenuated the hypotensive effect of ANF. Our data suggest that the long-term effect of ANF is salt sensitive but that decreases in PRA and aldosterone are not essential for the long-term hypotensive effect of ANF.
Identification of candidate genes for a factor regulating body weight in primates
Authors: Wilson B. E. , Meyer G. E. , Cleveland J. C. , Weigle D. S.
Published: December 2017

A weight gain of 20-30% above baseline, induced by gastrostomy overfeeding of subhuman primates or gavage overfeeding of rats, was found to completely suppress voluntary food consumption. When overfeeding was discontinued, body weight and oral intake returned in a coordinated fashion to baseline or “set point” values. This regulatory response could have been due to a circulating peptide that was secreted by adipocytes in proportion to the total body energy store and that mediated satiety at the level of the central nervous system. To search for this factor, a subtractive cDNA cloning strategy was developed, permitting the isolation of primate adipocyte genes with augmented expression in the overfed state. A 1.8-kb cDNA clone prepared by subtraction was found to hybridize to a 5-kb message expressed preferentially in the adipose tissue of overfed macaques and rats. This message, which was restricted in distribution among nonadipose tissues, was also detected in human subcutaneous fat. Candidate genes for satiety factors identified by this approach could be used in further studies of body weight regulation and obesity.
Effects of pregnancy and ovarian steroids on fatty acid synthesis and uptake in Syrian hamsters
Authors: Bhatia A. J. , Wade G. N.
Published: December 2017

The effects of pregnancy and ovarian steroids on the in vivo distribution of newly synthesized fatty acids (incorporation of tritium from 3H2O into fatty acid) in Syrian hamsters (Mesocricetus auratus) were examined. During late, but not early, gestation hamsters had reduced levels of newly synthesized fatty acids in heart, liver, uterus, and white adipose tissues (parametrial and inguinal fat pads). Treatment of ovariectomized hamsters with estradiol + progesterone significantly decreased fatty acid synthesis-uptake in heart, liver, and inguinal white adipose tissue. Treatment with either estradiol or progesterone alone was without significant effect in any tissue. Pretreatment of hamsters with Triton WR-1339 (tyloxapol), an inhibitor of lipoprotein lipase activity and tissue triglyceride uptake, abolished the effects of estradiol + progesterone in white adipose tissue and heart but not in liver. Thus hamsters lose body fat during pregnancy in part because of decreased de novo lipogenesis. The effect of pregnancy on lipogenesis is mimicked by treatment with estradiol + progesterone but not by either hormone alone. Furthermore, it appears that the liver is the principal site of estradiol + progesterone action on lipogenesis in Syrian hamsters.
Cardiovascular influences on rat parabrachial nucleus: an electrophysiological study
Authors: Jhamandas J. H. , Aippersbach S. E. , Harris K. H.
Published: December 2017

The rat pontine parabrachial nucleus is a prominent recipient of autonomic-related information from the more caudal levels of the neuraxis. The present experiments examined the responsiveness of neurons within the parabrachial nucleus to the following three specific cardiovascular stimuli: the activation of peripheral arterial baroreceptors, right atrial stretch receptors, and the administration of systemic angiotensin (ANG) II. Extracellular recordings in urethan-anesthetized animals indicate the presence of cells, mostly within the lateral parabrachial nucleus, that increase (17.5%, 28 of 160 cells) and decrease (48.1%, 77 of 160 cells) their excitability consequent to baroreceptor activation. A similar profile of alteration in cellular firing rates was observed with intravenous ANG II (increase in 15.8%, 16 of 101 cells; decrease in 28.7%, 29 of 101 cells). In contrast, fewer neurons located within the medial parabrachial and the Kolliker-Fuse nuclei were activated by these stimuli. A majority of cells (80%, n = 15) displayed a lack of response to right atrial stretch receptor activation. Of ANG II-sensitive lateral parabrachial cells, 23% (n = 43) revealed an alteration in excitability that could not be explained on the basis of a response to elevation in blood pressure. It is possible that this group of cells may be activated by the actions of systemic ANG II on neurons of the area postrema, a circumventricular structure, whose central projections are directed toward the parabrachial nucleus. These findings also support the notion of a diversity of cardiovascular inputs to topographically segregated regions within the parabrachial nucleus.
Central arterial hemodynamics in larval bullfrogs (Rana catesbeiana): developmental and seasonal influences
Authors: Pelster B. , Burggren W. W.
Published: December 2017

Central arterial hemodynamics (blood pressure and velocity) as a function of ontogeny and season were determined in larval Rana catesbeiana (body mass 0.3-8.7 g, 20-22 degrees C). Ventricular systolic pressure increased from 1.8 mmHg at stage (St) II to 11.9 mmHg at St XIII, while ventricular diastolic pressures usually were less than 1.0 mmHg. In early stages (up to St V-VII) of fall/winter larvae, the pressure waveform in the conus arteriosus was often biphasic. The first peak was due to weak ventricular contraction (sometimes inadequate to eject blood into the arterial tree), and a stronger second peak resulted from conal contraction. In these young fall/winter larvae, the conus--not the ventricle--was the major circulatory pump. Older larvae (greater than St X) showed "adultlike" central hemodynamics, with the ventricle ejecting blood through the conus into the central arterial circulation. Systolic blood pressure was considerably higher in young spring/summer (April-June) larvae, and the ventricle rather than the conus was the main circulatory pump at all stages, in contrast to fall/winter larvae. Thus both season and development have profound influences on the central hemodynamics of bullfrog larvae.
Characteristics of facial nerve-elicited cerebral vasodilatation determined using laser Doppler flowmetry
Authors: Goadsby P. J.
Published: December 2017

Cerebral cortical perfusion was monitored continuously with laser Doppler flowmetry and quantitative measurements of cerebral blood flow performed with the freely diffusible tracer 4-iodo[N-methyl-14C]antipyrine in the alpha-chloralose-anesthetized cat. The facial nerve was isolated from the brain stem via a posterior fossa craniotomy and electrically stimulated at frequencies of 1, 2, 5, 10, and 20 s-1. A stimulus-locked frequency-dependent increase in cerebral perfusion was seen in the parietal cortex; the mean maximum increase was 91 +/- 22% at 20 s-1. This compared with an absolute flow of 116 +/- 3 ml.100 g-1.min-1 at the same site. In addition, the response was associated with a marked increase in cerebral venous O2 content indicating that it is a primary neurogenic dilator response. This response could be blocked by hexamethonium but not by atropine and was thus mediated by an autonomic ganglion but not by the classical muscarinic postsynaptic receptor. Sectioning of the facial nerve did not alter cerebrovascular reactivity to hypercapnia. These data confirm the vasodilator effect of activation of the facial nerve and document its mediation through an intermediate parasympathetic ganglion. Consistent with previous data, the facial nerve does not appear to play a role in hypercapnic cerebral vasodilatation. Furthermore, this study highlights the usefulness of laser Doppler flowmetry in the cerebral circulation and in particular in the setting where repeated measures are required, such as in pharmacological studies.
Ovine fetal renal and hormonal responses to changes in plasma epinephrine
Authors: Ervin M. G. , Castro R. , Sherman D. J. , Ross M. G. , Padbury J. F. , Leake R. D. , Fisher D. A.
Published: December 2017

Circulating epinephrine alters atrial natriuretic factor (ANF) and arginine vasopressin (AVP) secretion, and all three hormones influence renal function. To quantify the relationships among fetal plasma epinephrine levels, fetal ANF and AVP secretion, and fetal renal function, six chronically catheterized fetal lambs (132 +/- 1 days gestation) received successive 40-min epinephrine infusions (0.1, 0.4, and 1.8 micrograms.min-1.kg-1). The second epinephrine infusion dose evoked significant increases in urine flow (V; 0.7 +/- 0.2 to 1.2 +/- 0.2 ml/min), free water clearance (CH2O; 0.3 +/- 0.1 to 0.7 +/- 0.1 ml/min), glomerular filtration rate (GFR; 3.9 +/- 0.7 to 5.4 +/- 0.8 ml/min), fractional water excretion (V/CH2O; 19 +/- 3 to 25 +/- 2%), mean arterial pressure (MAP; 45 +/- 3 to 51 +/- 4 mmHg), and a 94% increase in plasma ANF levels. A fourfold increase in the infusion dose significantly increased osmolar clearance (0.3 +/- 0.1 to 0.6 +/- 0.1 ml/min), sodium excretion (28 +/- 8 to 53 +/- 13 mueq/min), and plasma AVP levels (2.4 +/- 0.5 to 6.4 +/- 2.4 pg/ml) with no additional effect on V, CH2O, GFR, V/GFR, MAP, or plasma ANF levels. Urine osmolality and fractional sodium excretion did not change in response to epinephrine infusion. Our results demonstrate that epinephrine infusion stimulates fetal ANF secretion and to a lesser extent AVP secretion and significantly influences fetal renal function.
Suprachiasmatic and paraventricular control of photoperiodism in Siberian hamsters
Authors: Bittman E. L. , Bartness T. J. , Goldman B. D. , DeVries G. J.
Published: December 2017

The effects of lesions of the suprachiasmatic (SCN) and paraventricular nuclei (PVN) of the hypothalamus on photoperiodic responses were examined in adult Siberian hamsters. SCN lesions reduced nocturnal water intake in long days, whereas PVN lesions increased body weight and food intake in both short and long days. SCN or PVN lesions blocked short-day-induced decreases in body, fat pad, and testes weights and in food intake. Serum prolactin (PRL), but not follicle-stimulating hormone, levels were increased. The distribution of immunostained neurons and fibers for gonadotropin-releasing hormone (GnRH), beta-endorphin, arginine vasopressin (AVP), and vasoactive intestinal polypeptide (VIP) resembled that of other rodent species. Short-day exposure reduced AVP staining in lateral septum, medial amygdala, and bed nucleus of the stria terminalis but not in the PVN of the thalamus or the SCN. Short-day-exposed hamsters had fewer beta-endorphin-positive arcuate nucleus cells and tended to have fewer GnRH-positive preoptic cells than long-day controls. VIP staining was unaffected by photoperiod. Most day length effects on immunostaining were eliminated by either lesion. These results establish the importance of the SCN and PVN in the photoperiodic control of several seasonal responses in Siberian hamsters.
Role of renal nerves in sodium retention of cirrhosis and congestive heart failure
Authors: DiBona G. F. , Sawin L. L.
Published: December 2017

To define the role of renal nerves in renal Na retention of cirrhosis and congestive heart failure (CHF), experiments were done in rats with cirrhosis due to common bile duct ligation (CBDL) and CHF due to myocardial infarction from left coronary artery ligation. Two weeks after induction of CBDL or CHF, diseased and sham diseased (Sham) rats were subjected to bilateral renal denervation (DNX) or sham renal denervation (innervated, INN). Five days after DNX or INN, 26-day metabolic balance studies were carried out in all rats. Daily dietary Na intake averaged 2.0-3.0 meq/day on days 1-6 and 22-26 and averaged 0.120 meq/day on days 7-21. Cumulative Na balance was greater in CBDL and CHF rats, INN or DNX, than in Sham/CBDL or CHF rats throughout the study. On day 6 at the end of the normal dietary Na intake period (days 0-6), cumulative Na balance was not affected by renal denervation in Sham/CBDL or CHF rats (INN, 2.02 +/- 0.19 meq, n = 10; DNX, 2.04 +/- 0.17 meq, n = 11), CBDL rats (INN, 4.21 +/- 0.39 meq, n = 10; DNX, 3.78 +/- 0.37 meq, n = 10), or CHF rats (INN, 3.74 +/- 0.72 meq, n = 9; DNX, 3.22 +/- 0.55 meq, n = 10).(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiac mechanical restitution in active and hibernating Richardson's ground squirrel
Authors: Zhou Z. Q. , Liu B. , Dryden W. F. , Wang L. C.
Published: December 2017

The cardiac mechanical restitution was compared in papillary muscles between the active and the hibernating Richardson's ground squirrels at 0.1, 2.8, and 5 mM external Ca2+ concentration [( Ca2+]o). The amplitude of the restitution was significantly higher in hibernating animals between 37 and 7 degrees C at all [Ca2+]o. The first postrest contraction (F1) was highest at 20 degrees C and lower at 37 and 7 degrees C in both groups. The pause duration for maximum F1 was 30 s in active but 10 s in hibernating animals at 37 degrees C and increased to 100 s in both groups at 7 degrees C. The postrest potentiation was eliminated by 10(-6) M ryanodine at 20 degrees C in both groups, and this inhibitory effect was more pronounced in the hibernating group. Together, our results suggest that the activator Ca2+ for excitation-contraction coupling is mainly derived from the sarcoplasmic reticulum (SR) pool in both active and hibernating ground squirrel, and the dependence on SR Ca2+ release via ryanodine-sensitive Ca2+ channels is more marked in the hibernating state. Furthermore, there is no significant difference in sensitivity of the cardiac mechanical restitution to [Ca2+]o between the active and the hibernating condition.
Cortisol inhibits ACTH secretion in late-gestation fetal sheep
Authors: Wood C. E.
Published: December 2017

In sheep, parturition is initiated by an increase in fetal adrenal secretion of cortisol. In term fetuses, adrenocorticotropic hormone (ACTH) secretion is increased despite increasing plasma concentrations of cortisol. The present study was performed to investigate whether fetal ACTH secretion is under negative-feedback control by cortisol. Ten chronically catheterized fetal sheep (140 days gestation) were used in this study. Five were infused with hydrocortisone sodium succinate (10 micrograms/min) and five with 0.9% physiological saline for 5 h. Fetal and maternal blood samples were drawn at 1-h intervals. Infusion of hydrocortisone sodium succinate significantly increased fetal plasma cortisol concentration from 38.2 +/- 8.4 ng/ml to mean levels between 74.6 +/- 11.6 and 88.5 +/- 4.7 ng/ml. Fetal plasma ACTH concentration was significantly decreased from 129 +/- 36 to 31 +/- 5 pg/ml after 5 h of infusion. Infusion of saline did not alter fetal plasma cortisol or ACTH concentration. Neither of the infusions significantly altered maternal plasma concentrations of ACTH or cortisol, or fetal or maternal blood gases, or plasma concentrations of sodium or potassium. With one exception, all fetuses were born alive at 145 +/- 1 and 144 +/- 1 days gestation in the saline- and hydrocortisone sodium succinate-infused groups, respectively. The results of this study demonstrate that at 140 days gestation fetal ACTH secretion is under negative-feedback control by cortisol.
Conduction blockade in myelinated fibers by gaseous and volatile substances
Authors: Carpenter F. G.
Published: December 2017

The minimum ambient partial pressure required to reversibly disrupt conducted responses in myelinated nerve fibers (Pblock) was determined for 11 gases and chloroform. For all but one substance, Pblock was inversely proportional to their nonaqueous solubility; large-diameter fibers were less vulnerable than fibers of small diameter. No "anesthetic" effect was displayed by SF6. At the Pblock for three of the agents, the time for completion of their anesthetic action (tb) was proportional to their lipid-to-aqueous solubility ratio. When the ratio was large, tb was longer than when the ratio was small; blockade became complete after the partial pressure of the agent in the lipid or nonaqueous phase of the axon membrane became equal to Pblock. The access of these substances to an nonaqueous site was neither pH nor frequency dependent, but in the case of SF6 access did appear to be limited by its molal volume.
Effects of anoxia and metabolic arrest on turtle and rat cortical neurons
Authors: Doll C. J. , Hochachka P. W. , Reiner P. B.
Published: December 2017

The responses of turtle and rat cortical pyramidal neurons to various pharmacological treatments were measured using intracellular recordings. Turtle neurons survived both anoxia and pharmacological anoxia for 180 min with no noticeable effect. Rat pyramidal neurons responded with a loss in membrane resistance, followed by a transient hyperpolarization, and a subsequent depolarization to a zero membrane potential (41.3 +/- 6.5 min, anoxia; 25.8 +/- 12.6 min, pharmacological anoxia). Metabolic arrest caused a rapid loss in membrane resistance, transient hyperpolarization, and a rapid depolarization in both turtle (4.6 +/- 1.1 min) and rat (3.1 +/- 0.5 min) neurons. Iodoacetate alone had a similar effect on the rat as metabolic arrest (6.5 +/- 0.8 min), but the turtle exhibited more prolonged survival (53.5 +/- 4.6 min). Ouabain caused a rapid depolarization in the rat cortical neuron (8.6 +/- 1.1 min), but no initial loss in membrane resistance or a hyperpolarization. These results demonstrate that the turtle neuron, which survives anoxia, is no better at surviving total metabolic inhibition than the rat neuron. In addition, anoxia takes 13 times longer to depolarize a rat cortical neuron than metabolic arrest, and neither of these treatments is totally mimicked by ouabain alone.
Role of erythrocyte organic phosphates in blood oxygen transport in anemic quail
Authors: Riera M. , Fuster J. F. , Palacios L.
Published: December 2017

The effects of two different degrees of experimentally induced anemia and the consequent high percentage of circulating immature erythrocytes on oxygen affinity (pH 7.5 and 41 degrees C), erythrocyte organic phosphates, and Hb fractions have been studied in quail. Blood reticulocytes reached percentages of 24 and 69-87% in the first and second experiments, respectively. Variations in the phosphate levels found during the anemic process were related to the amount of circulating reticulocytes. The erythrocyte [ATP] (brackets indicate concentration) and [ATP]/[Hb] molar ratio increased with the release of reticulocytes and returned to control levels as they matured. The erythrocyte [inositol pentakisphosphate (InsP5)] decreased significantly when circulating reticulocytes showed their highest values, whereas there was hardly any effect on the [InsP5]/[Hb] molar ratio, which changed only slightly. Hb-O2 affinity also exhibited no statistical changes associated with acute anemia. These latter findings indicate that InsP5, at physiological concentrations, is the primary modulator of quail Hb function; the observed rise in [ATP] has no additional influence on Hb-O2 affinity. It is suggested that InsP5 tends to maintain the blood oxygen affinity in both mature erythrocytes and reticulocytes. The main compensatory response at blood level is a rapid bulk reticulocyte release from medulla.
Metabolism and cardiovascular effects of leukotrienes in warm- and cold-acclimated American bullfrogs (Rana catesbeiana)
Authors: Herman C. A. , Charlton G. A. , Cranfill R. L.
Published: December 2017

Sulfidopeptide leukotrienes are important mediators in mammals, but much less is known of their metabolism and action in nonmammalian vertebrates. This study examines the cardiovascular effects of leukotrienes on blood pressure and heart rate and compares the metabolism of leukotrienes in vivo and in vitro in warm- and cold-acclimated bullfrogs. Leukotriene C4 (LTC4) is more potent than leukotriene D4 (LTD4) and leukotriene E4 (LTE4) in eliciting hypotension. The leukotrienes are more potent in warm-acclimated animals. Conversion of [3H]LTC4 to [3H]LTD4 occurs rapidly in warm-acclimated bullfrogs, with 15.2 +/- 1.7% of the [3H]LTC4 remaining at 1.5 min. Conversion is slower in vivo in cold-acclimated frogs, with 20.2 +/- 1.7% of the [3H]LTC4 remaining by 6 min. In blood taken from warm-acclimated frogs, conversion of [3H]LTC4 to [3H]LTD4 occurs more rapidly at 22 than at 5 degrees C. This pattern is similar in blood taken from cold-acclimated frogs, suggesting that no modification of gamma-glutamyl transpeptidase occurs at low temperature. [3H]LTE4 production is not observed in vivo or in vitro during the time course of the experiments. The rapid metabolism of LTC4 to LTD4 may represent an inactivation mechanism in amphibians. The cardiovascular effects of LTC4 in vivo may be much greater than current measurements indicate because of rapid conversion of LTC4 to the less potent LTD4.
Prostaglandins, oviducal function, and parturient behavior in nonmammalian vertebrates
Authors: Guillette L. J. , Dubois D. H. , Cree A.
Published: December 2017

Extensive data show that in mammals and birds, prostaglandins (PGs) are associated with ovulation, luteal function, oviposition, and parturition, and that also in mammals they are associated with birth-related behavior and sexual receptivity. In mammals and birds, the ability of PGs to stimulate oviducal contractions varies regionally along the oviduct (i.e., there is a functional cervix or uterovaginal region that acts to retain eggs or embryos in utero during shelling or embryonic development). Furthermore, at least in mammals, there is neural control over oviducal contractions. In reptiles, PGs stimulate oviducal contractions, and these contractions may be overridden by neural control. No data are available on whether PGs stimulate oviducal contractions in amphibians or whether there is a functional cervix in amphibians or reptiles. We suggest that in ancestral amphibians with oviparity and external fertilization, eggs moved rapidly through the oviduct after ovulation and that ovarian and oviducal PGF served as an endocrine hormone coordinating oviducal contractions and central nervous system-controlled oviposition behavior. Furthermore, we hypothesize that there was little or no neural control over oviducal contractions and no functional cervix. These conditions may still exist in present-day oviparous amphibians. In contrast, we suggest that modern-day oviparous reptiles have evolved a functional cervix and neural control over PG-induced uterine contractions, allowing egg passage to be blocked and thus the development of egg retention. These characteristics may be viewed as exaptations for the evolution of viviparity.
TNF-induced anorexia and learned food aversions are attenuated by area postrema lesions
Authors: Bernstein I. L. , Taylor E. M. , Bentson K. L.
Published: December 2017

Tumor necrosis factor (TNF) or cachectin has been proposed as an important mediator of cancer anorexia and cachexia. The present studies examined the extent to which TNF administration generates symptoms similar to those produced by tumor growth. Like the growth of certain tumors, TNF administration was found to be associated with the development of strong aversions to a novel diet. Area postrema lesions were found to significantly attenuate the effects of TNF on intake of a novel diet, a finding previously reported for tumor anorexia. In addition, the anorexic effects of TNF differed considerably as a function of the novelty of the diet. When the available diet was novel, effects of TNF in lowering food intake were substantial, whereas more modest effects were seen when the diet was familiar. These findings provide evidence for parallels between TNF- and tumor-induced anorexias. Nonetheless, these studies also confirm previous observations of the rapid development of tolerance to the anorexic effects of TNF, a finding that is not consistent with a role for TNF as a critical mediator of tumor anorexia.
Neuronal and cardiovascular responses to ANF microinjected into nucleus ambiguous
Authors: Ermirio R. , Ruggeri P. , Cogo C. E. , Molinari C. , Calaresu F. R.
Published: December 2017

Effects of microinjection of atrial natriuretic factor (ANF) into cardioinhibitory sites in the nucleus ambiguous (NA) or on single vagal cardioinhibitory neurons (VCN) were investigated in urethan-anesthetized rats. Sites containing cardioinhibitory neurons were identified by observing a marked and reproducible bradycardia in response to microiontophoretically applied (20-40 nA) or microinjected (20 nl) 0.1 M L-glutamate. In 35 of the 40 (87.5%) cardioinhibitory sites identified by microinjection of glutamate, ANF (20 nl of 10(-7) M) decreased heart rate (HR; -47.1 +/- 2.5 beats/min). No responses were elicited in the other five sites. In animals paralyzed and artificially ventilated, the HR effects of ANF were not significantly different before and after muscle paralysis. Microinjections of 10 nl of 10(-7) M ANF caused excitation of 19 of 21 VCN (90%), which was followed by a decrease in HR (-20.8 +/- 2.3 beats/min); no neuronal or cardiovascular responses were elicited by ANF in the remaining two VCN. Bilateral vagotomy or atropine sulfate (1 mg/kg iv) abolished cardiac slowing without affecting neuronal activation, whereas propranolol (2 mg/kg iv) did not affect either response to ANF. These results suggest that ANF is a neuromediator involved in the excitation of cardioinhibitory neurons in the NA.
Intake and use of milk nutrients by rat pups suckled in small, medium, or large litters
Authors: Fiorotto M. L. , Burrin D. G. , Perez M. , Reeds P. J.
Published: December 2017

We investigated the extent to which the altered weight gain of rat pups suckled in litters of varying sizes (4, 10, and 16 pups/litter) is attributable to differences in milk nutrient intake. Milk intake was estimated from the rate of dilution over 2 days of a dose of 3H2O administered at 4, 8, and 14 days of age after correction for the water and milk carbon deposited in body tissues over the measurement period. Protein and energy intakes were estimated from the volume of milk consumed by individual pups and the composition of milk from each dam. Significant effects of litter size on milk fat and protein concentration were observed. Weight gain was highly correlated with energy intake in pups suckled in litters of 4 and 10 but not 16. These findings were attributed to a higher energy expenditure of pups less than 10 days old suckled in litters of 16; specifically these pups had higher maintenance energy needs than pups suckled in litters of 4 and 10 and a higher energy cost of tissue synthesis. The latter was ascribed to an ability of immature pups to maximize the efficiency of protein utilization, thereby blunting the deleterious effects of a reduced nutrient intake on protein deposition.
Involvement of angiotensin II in water intake of genetically polydipsic mice
Authors: Katafuchi T. , Hattori Y. , Nagatomo I. , Koizumi K. , Silverstein E.
Published: December 2017

The involvement of angiotensin II (ANG II) in the genetic polydipsia of the STR/N strain of mice was investigated. Daily water intake of the polydipsic inbred STR/N of both sexes ranged between five and eight times that of nonpolydipsic controls: STR/1N, a mutant of the STR/N, and Swiss-Webster (S/W) mice. Nevertheless the diurnal pattern of drinking was maintained in the STR/N. There was no difference in daily food intake, arterial blood pressure, and plasma renin activity among the three groups. Drinking responses to 48 h of water deprivation were not significantly different between the polydipsic mice and their control groups. Captopril, an angiotensin I converting-enzyme inhibitor, injected subcutaneously just before the dark period, reduced drinking for 6 h in the polydipsic strain only. Food intake of all three groups of mice was not affected. Similarly the ANG II antagonist saralasin, [Sar1,-Ile8]ANG II, injected into the lateral cerebroventricle just before the dark period, significantly reduced water intake for 6 h after injection in the polydipsic mice only. Intracerebroventricular injection of ANG II increased drinking in the nondeprived controls but not in the polydipsic mice. These findings suggest that the polydipsia in the STR/N mice may involve, at least in part, the ANG II system in the brain.
Inactivation of 6-phosphofructo-2-kinase during anaerobiosis in the marine whelk Busycon canaliculatum
Authors: Bosca L. , Storey K. B.
Published: December 2017

6-Phosphofructo-2-kinase (PFK-2) was analyzed in four organs of the anoxia-tolerant marine gastropod mollusk Busycon canaliculatum. Whelk PFK-2 resembled the nonhepatic enzyme from mammals with highest activity occurring in gill (22 pmol.min-1.g-1). Hepatopancreas PFK-2 was purified over 8,000-fold to a final specific activity of 11 mU/mg protein (at 20 degrees C) and gave a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was a dimer with a native molecular mass of 142 kDa and a subunit molecular mass of 67 kDa. The purified enzyme showed negligible fructose-2,6-bisphosphatase (FBPase-2) activity, although the activity ratio of PFK-2 to FBPase-2 was 0.625 in crude extracts. In response to environmental anoxia, the activity of PFK-2 dropped in all organs to 34-56% of the corresponding aerobic value (half-time was 2 h in gill), and the Michaelis constant for fructose 6-phosphate increased by 50% (to 92 microM in gill). These changes paralleled decreases in organ fructose 2,6-bisphosphate concentration and pyruvate kinase activity and contribute to the overall glycolytic rate depression induced by anoxia in this facultative anaerobe. In vitro treatment of the anoxic form of hepatopancreas PFK-2 with alkaline phosphatase increased enzyme activity, suggesting that the aerobic and anoxic enzyme forms are interconverted by reversible protein phosphorylation. However, the protein kinase involved in this process is not yet known; incubation of aerobic PFK-2 with Mg-ATP plus adenosine 3',5'-cyclic monophosphate-dependent protein kinase or protein kinase C did not alter enzyme activity.
Effects of endothelin-1 and sarafotoxin S6b on regional hemodynamics in the conscious dog
Authors: Leadley R. J. , Zhu J. L. , Goetz K. L.
Published: December 2017

Endothelin, a potent vasoconstrictor, also is capable of producing transient vasodilation in some situations. We examined the changes in regional hemodynamics in response to constant infusions of endothelin-1 (ET-1) at 5, 10, or 20 ng.kg-1.min-1 for 1 h into conscious dogs. The dogs were instrumented with ultrasonic flow probes for measurement of blood flow in the ascending aorta (cardiac output) and in the coronary, mesenteric, renal, and iliac arteries. A compound structurally similar to ET-1, sarafotoxin S6b (S6b), was also infused in identical experiments to determine whether the responses to these two peptides might differ. Basal plasma levels of immunoreactive ET-1 averaged approximately 6 pg/ml. After 55 min of infusion of ET-1 at 5, 10, and 20 ng.kg-1.min-1, plasma immunoreactive ET-1 increased to approximately 55, 130, and 520 pg/ml, respectively. When given at 20 ng.kg-1.min-1, ET-1 increased total peripheral resistance and arterial pressure and decreased cardiac output and heart rate. ET-1 decreased coronary, mesenteric, and renal blood flow but did not change iliac flow. In comparison with ET-1, S6b produced relatively smaller changes in total peripheral resistance, cardiac output, heart rate, and coronary, mesenteric, and renal blood flow. Iliac resistance did not change in response to ET-1, but it increased during infusions of S6b. Similar but less pronounced responses were observed when these peptides were infused at 5 and 10 ng.kg-1.min-1. The regional variability in the hemodynamic response to ET-1 and the difference in regional responses to ET-1 and S6b are consistent with the existence of heterogenous receptor subtypes for these peptides.