bluuebunny/crossref_metadata_2025 huggingface dataset:
Bright morning light advances the human circadian system without affecting NREM sleep homeostasis
Authors: Dijk D. J. , Beersma D. G. , Daan S. , Lewy A. J.
Published: December 2017

Eight male subjects were exposed to either bright light or dim light between 0600 and 0900 h for 3 consecutive days each. Relative to the dim light condition, the bright light treatment advanced the evening rise in plasma melatonin and the time of sleep termination (sleep onset was held constant) for an average approximately 1 h. The magnitude of the advance of the plasma melatonin rise was dependent on its phase in dim light. The reduction in sleep duration was at the expense of rapid-eye-movement (REM) sleep. Spectral analysis of the sleep electroencephalogram (EEG) revealed that the advance of the circadian pacemaker did not affect EEG power densities between 0.25 and 15.0 Hz during either non-REM or REM sleep. The data show that shifting the human circadian pacemaker by 1 h does not affect non-REM sleep homeostasis. These findings are in accordance with the predictions of the two-process model of sleep regulation.
Skeletal muscle calcium uptake in bacteremic rats
Authors: Westfall M. V. , Sayeed M. M.
Published: December 2017

To determine whether cellular Ca2+ regulation is altered in bacteremic rat skeletal muscle, 45Ca2+ uptake was measured in soleus muscles 12 h after an intraperitoneal bacterial (Escherichia coli) injection. Some rats received diltiazem (2.4 mg/kg iv) 10 h after bacterial injection to determine whether calcium blockers could inhibit changes in Ca2+ regulation. Cellular exchangeable Ca2+ was measured in soleus muscles incubated for 5 min to 4 h in Krebs-Ringer bicarbonate (KRB) media (pH 7.4) containing 45Ca2+ (1.5 muCi/ml) and subsequently "washed" in La3+-containing, Ca2+-free KRB media. Bacteremia had no effect on steady-state exchangeable Ca2+, but it significantly reduced the time required to reach half-maximal uptake compared with controls. Diltiazem treatment returned the half-maximal Ca2+ uptake toward control values in bacteremic rat muscles. Depolarization of soleus muscles with high K+ (60 mM) transiently increased Ca2+ uptake in control and bacteremic rat muscles, although the increase was significantly greater (P less than 0.05) in bacteremic rat muscles. The altered skeletal muscle Ca2+ regulation may be due to excessive stimulation of Ca2+ messenger systems, sarcolemmal Ca2+ channels, and/or Ca2+ release from the sarcoplasmic reticulum in response to bacteremia.
Adrenergic receptors on cerebral microvessels: pericyte contribution
Authors: Elfont R. M. , Sundaresan P. R. , Sladek C. D.
Published: December 2017

R224-R230, 1989.--[125I]iodocyanopindolol ([125I]ICYP) and [3H]rauwolscine were used to quantitate, respectively, the beta- and alpha 2-adrenergic receptors in freshly isolated bovine cerebral microvessels and in pericyte cultures derived from these microvessels. Morphological and immunocytochemical criteria distinguished the pericytes from endothelial cells. Competitive binding studies established the specificity of the radioligand binding. The maximal number of binding sites (Bmax) for [125I]ICYP in the pericytes constituted only 8% of that in the microvessels (3.5 +/- 1.3 vs. 44.4 +/- 6.6 fmol/mg protein). In contrast, the Bmax for [3H]rauwolscine in the pericytes was 50% of that in the microvessels (55.4 +/- 11.8 vs. 111.1 +/- 9.5 fmol/mg protein). The dissociation constants for both [125I]ICYP and [3H]rauwolscine were similar in the two preparations. No alpha 1-adrenergic receptors, as defined by the specific binding of [3H]prazosin, were identified either in the pericytes or microvessels. Overall, our results suggest that pericytes contribute minimally to the total beta-adrenoceptor number of cerebral microvessels, and thus the beta-adrenoceptors must be located predominantly on endothelial cells. However, the contribution of pericytes to the total alpha 2-adrenoceptor number of the microvessels may be substantial.
Effect of ambient temperature on respiratory quotient of lean and obese Zucker rats
Authors: Refinetti R.
Published: December 2017

O2 consumption and CO2 production were measured in lean and obese Zucker rats under these conditions: thermal neutrality (acclimation and test at 25 degrees C), acute cold (acclimation to 25 degrees C and test at 15 degrees C), and chronic cold (acclimation and test at 15 degrees C). The respiratory quotient (RQ) of ad libitum-fed animals was 0.92 at neutrality, 0.87 at acute cold, and 0.77 at chronic cold. Lean and obese animals had comparable RQs under the three conditions. These results confirm previous investigations on the effect of ambient temperature on gaseous exchange in rats but fail to demonstrate a difference in substrate utilization in the metabolism of lean and obese Zucker rats.
Tonic influences from the rostral medulla affect sympathetic nerves differentially
Authors: Yardley C. P. , Stein R. D. , Weaver L. C.
Published: December 2017

Tonically active neurons in the rostral ventrolateral medulla (RVLM) that project to the autonomic regions of the spinal cord are essential for maintenance of arterial blood pressure at normal levels. Microinjection of glycine into the RVLM in anesthetized cats to inhibit the tonic discharge of these neurons caused variable initial responses in renal and mesenteric nerve discharge and arterial blood pressure. These initial responses were consistently followed by more prolonged decreases in renal and mesenteric nerve discharge and decreases in arterial blood pressure. The tonic influences of neurons in the RVLM were found to be distributed unequally to sympathetic nerves because activity of renal nerves was decreased significantly more than that of mesenteric nerves. The variable nerve and cardiovascular responses during the first 1-3 min after glycine injection were not solely due to loading or unloading of baroreceptors because similar initial responses were seen in vagotomized and sinoaortic denervated cats. Additionally, when muscimol was microinjected into the same sites, only consistent and prolonged decreases in nerve discharge and blood pressure occurred. The inhibitory actions of muscimol on RVLM neurons caused significantly greater decreases in renal than mesenteric nerve activity. Together, these findings demonstrate that the tonic discharge of neurons in the RVLM has unequal influences on renal and mesenteric nerves.
Vasopressin and ANG II in the control of ACTH secretion and arterial and atrial pressures
Authors: Brooks V. L.
Published: December 2017

Hypotension stimulates the secretion of adrenocorticotropin (ACTH) and vasopressin (AVP) and increases plasma levels of angiotensin II (ANG II). Because AVP and ANG II increase ACTH secretion, the present experiments were performed to evaluate the role of these peptides in the increases in plasma ACTH and glucocorticoid concentrations produced by hypotension in conscious dogs. This was accomplished by determining whether administration of receptor antagonists to vasopressin, [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 2-(O-methyl)tyrosine]Arg8-vasopressin, and ANG II (saralasin), reduced the ACTH and glucocorticoid responses to infusion of four doses of the vasodilator nitroprusside. Nitroprusside (NP) infusion produced dose-dependent decreases in mean arterial pressure. Larger decreases in arterial pressure were produced in dogs pretreated with the AVP antagonist or with both saralasin and the vasopressin antagonist. Left and right atrial pressures also fell with NP infusion, and larger decreases in atrial pressures were found in dogs pretreated with the AVP antagonist. Finally, NP infusion increased plasma glucocorticoid concentration and plasma ACTH concentration. Both the glucocorticoid and the ACTH responses to hypotension were reduced in dogs given the AVP antagonist and in dogs given both saralasin and the AVP antagonist, but there was no difference in the effect of AVP blockade alone vs. the effect of combined AVP and ANG II blockade. These data suggest that AVP, but not ANG II, is required for normal glucocorticoid and ACTH responses to hypotension. They also suggest that AVP is necessary for normal maintenance of arterial blood pressure and atrial pressures during NP infusion.
LiCl and CCK inhibit gastric emptying and feeding and stimulate OT secretion in rats
Authors: McCann M. J. , Verbalis J. G. , Stricker E. M.
Published: December 2017

Systemic injection of the nauseogenic agent LiCl is known to increase neurohypophyseal secretion of oxytocin (OT) in rats. The present results indicated that the induced OT secretion was related exponentially to the inhibition of food intake. A similar relation between OT secretion and food intake also was observed after systemic injection of the peptide hormone cholecystokinin (CCK). However, the effects of each agent on food intake lasted much longer than the observed increases in OT secretion. In contrast, both LiCl and CCK produced a dose-dependent inhibition of gastric emptying in rats that was closely related temporally to the inhibition of food intake. The similarity of these three responses to LiCl and CCK suggests that both agents stimulate common central mechanisms, apparently involving both magnocellular and parvocellular neurons in the paraventricular nucleus of the hypothalamus, whereby these neuroendocrine, behavioral, and autonomic functions are integrated.
Clearance function of type C receptors of atrial natriuretic factor in rats
Authors: Almeida F. A. , Suzuki M. , Scarborough R. M. , Lewicki J. A. , Maack T.
Published: December 2017

The overwhelming majority of atrial natriuretic factor (ANF) receptors in kidney and vascular tissues do not mediate any of the known functional effects of the hormone. To test whether these receptors (C-ANF receptors) function as clearance receptors for circulating ANF-(1-28), we determined the effects of C-ANF-(4-23) [des[Gln18Ser19Gly20Leu21Gly22]rANF-(3-23)-NH2], a specific ligand of C-ANF receptors, on the pharmacokinetics and hydrolysis of 125I-labeled ANF-(1-28) in anesthetized rats. Radioactivity in plasma was characterized by trichloroacetic acid solubility and high-pressure liquid chromatography. C-ANF-(4-23) (1 and 10 micrograms.min-1.kg body wt-1) led to marked dose-dependent increases in initial plasma concentration of administered 125I-ANF-(1-28) and decreases in its volume of distribution at steady state (Vss), metabolic clearance rate (MCR), and appearance of hydrolytic products ([125I]monoiodotyrosine and free 125I) in plasma (Pm). At the highest dose, C-ANF-(4-23) decreased Vss from 97 +/- 12 to 36 +/- 2 ml/100 g body wt, MCR from 50 +/- 4 to 12 +/- 1 ml.min-1.100 g body wt-1, and Pm from 54 +/- 8 to 11 +/- 2% of initial plasma 125I-ANF-(1-28). The data demonstrate that C-ANF receptors are mainly responsible for the very large volume of distribution and fast MCR of ANF in the rat. In this manner, C-ANF receptors are likely to play an important role in the homeostasis of circulating ANF.
Neuromodulation of intestinal transport in the suckling mouse
Authors: Carey H. V. , Cooke H. J.
Published: December 2017

The influence of enteric nerves on intestinal ion and sugar transport was investigated in 3- to 4-wk-old suckling mice. Whole thickness segments of jejunum were mounted as flat sheets in flux chambers equipped to electrically stimulate nerves in the intestinal wall. Tetrodotoxin significantly reduced basal short-circuit current in a subset of tissues containing 3-O-methylglucose in the mucosal bath. Electrical field stimulation of intrinsic nerves evoked an increase in short-circuit current of 86 +/- 15 microA/cm2 that was due to an increase in active chloride secretion with no significant change in the net movement of other ions. The secretory response to neural stimulation was abolished by tetrodotoxin and reduced by the muscarinic antagonist, atropine. Mucosal-to-serosal fluxes of 3-O-methylglucose were not altered by the cholinergic agonist carbachol. These results show that ion transport in the suckling mouse jejunum is regulated by the enteric nervous system. Neural stimulation evokes a chloride secretory response that is mediated by acetylcholine and other noncholinergic transmitters. Sugar transport in the murine small intestine does not appear to be influenced by muscarinic cholinergic agonists.
Amiloride effect on diurnal cyclic Na and K excretion in rats
Authors: Dalton P. L. , Rabinowitz L.
Published: December 2017

Amiloride was administered to rats during the peak and minimum of Na and K diurnal rhythmic excretion (i.e., during early dark phase and early light phase). In rats receiving a normal-K diet (2.34 meq/day) amiloride decreased K excretion from 186 to 37 mueq/h (dark phase) and from 31 to 4 mueq/h (light phase). Amiloride increased Na excretion from 91 to 344 mueq/h (dark phase) and from 35 to 164 mueq/h (light phase). Rats receiving a high-K diet (10.4 meq/day) showed a higher diurnal peak and minimum for K excretion. During high-K intake, amiloride decreased K excretion from 787 to 191 mueq/h (dark phase) and from 197 to 40 mueq/h (light phase) and increased Na excretion from 237 to 891 mueq/h (dark phase) and from 31 to 222 mueq/h (light phase). Whenever given, amiloride reduced K excretion to approximately 20% of control excretion. It is concluded that rhythmic changes in amiloride-sensitive distal transport are largely, but not entirely, responsible for the diurnal K cycle, but do not cause the concurrent Na cycle. Thus the diurnal cycles in Na and K are expressed through changes in different transport mechanisms. In rats maintained on a high-K diet there is an increase in rhythmic K secretion and Na reabsorption by amiloride-sensitive transport. To maintain Na excretion unchanged, Na reabsorption must be correspondingly depressed at an amiloride-insensitive site.
Regulated nocturnal hypothermia induced in pigeons by food deprivation
Authors: Graf R. , Krishna S. , Heller H. C.
Published: December 2017

The daily body temperature (Tb) cycle of pigeons is altered by food deprivation in that Tb falls to lower and lower levels on consecutive nights after the onset of deprivation, whereas the Tb levels during corresponding days remain nearly unchanged. Manipulations of spinal cord temperature, a major feedback parameter in the avian thermoregulatory system, reveal that episodes of nocturnal hypothermia are regulated. The spinal cord threshold temperature for inducing increases in metabolic heat production falls to progressively lower levels each night and returns to normal euthermic levels during the day.
Renal denervation alters forebrain hexokinase activity in neurogenic hypertensive rats
Authors: Simon J. K. , Zhang T. X. , Ciriello J.
Published: December 2017

The effect of afferent renal nerve transection (tARN) on the metabolic activity of forebrain structures the activity of which was altered after aortic depressor nerve transection (tADN) was studied using the hexokinase (HK) histochemical method in the rat. In tADN-sham (s) ARN rats, increases in HK activity were observed in the medial septum (MS), median preoptic nucleus (MnPO), subfornical organ, supraoptic nucleus, nucleus circularis (Nc), magnocellular, and dorsal and medial (mpPVH) parvocellular components of paraventricular nucleus, the anterior, lateral, and dorsomedial (DMH) hypothalamus, and in the central and medial nuclei of the amygdala. In addition, a decrease in HK activity was seen in the dorsal arcuate nucleus (dArc). Similarly, increases in HK activity were seen in sADN-tARN rats in all the above structures except MS, Nc, and DMH, where no changes were observed, and dArc, where an increase in HK activity was noted. The bed nucleus of the stria terminalis, lateral preoptic nucleus (POA), and ventral (v) Arc also showed elevated HK activity. In contrast, the increased HK activity after either tADN or tARN alone was returned to levels not different from sADN-sARN rats in all structures in the tADN-tARN rats, except MnPO, mpPVH, and dArc, where the level of HK activity was only attenuated, and MS, POA, and vArc, where it remained elevated. These data suggest that similar forebrain structure are associated with the hypertension after tADN and are involved in the integration of ARN information and that these sites of interaction are involved in the maintenance and the reversal of the neurogenic hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
Arginine vasopressin mediates cardiovascular responses to hypoxemia in fetal sheep
Authors: Perez R. , Espinoza M. , Riquelme R. , Parer J. T. , Llanos A. J.
Published: December 2017

Acute hypoxemia results in hypertension, bradycardia, and cardiac output redistribution in fetal sheep. The blood flow redistribution is produced by differential changes in vascular resistance of various fetal organs. alpha-Adrenergic activity is one of the few vasoconstrictor mechanisms thus far identified in the hypoxemic fetal sheep. Arginine vasopressin (AVP) is a potent vasoconstrictor in adults. Since AVP administration to the normoxic fetus mimics some of the fetal cardiovascular responses to hypoxemia and fetal plasma AVP levels increase with hypoxemia, we examined the hypothesis that AVP modifies the fetal cardiovascular response to hypoxemia by changing the vascular resistance of some fetal vascular beds. To test this we determined fetal systemic arterial pressure and fetal cardiac output and its distribution during hypoxemia with and without the V1 AVP antagonist d(CH2)5-Tyr(Me)AVP. Fourteen fetal sheep (0.79-0.90 of gestation) were chronically catheterized. Five days after surgery fetal hypoxemia was induced by introducing a mixture of 95% N2-5% CO2 (10-20 l/min) into a maternal tracheal catheter. The hypoxemia was maintained for 40 min. Fetal heart rate, systemic arterial blood pressure, and combined ventricular output and its distribution (radiolabeled microspheres) were measured before hypoxemia, at 20 min of hypoxemia alone, and at 20 min of hypoxemia plus either AVP antagonist (n = 5) or NaCl 0.9% (n = 5, controls). Fetal hypertension and bradycardia were partially reversed after the AVP antagonist administration during hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)
Total translation of vasopressin and oxytocin in neurohypophysis of rats
Authors: Robinson A. G. , Roberts M. M. , Evron W. A. , Janocko L. E. , Hoffman G. E.
Published: December 2017

There is a paucity of information about total translation rate of vasopressin and oxytocin. Because the site of synthesis of the neurohypophysial hormones is anatomically separate from the site of storage, we were able to measure total translation by blocking transport of newly synthesized hormone and measuring accumulation in the areas of synthesis in the hypothalamus. Colchicine administered into the third ventricle in doses as low as 3.5 micrograms/rat blocked transport for 18 h. The linear increase in vasopressin and oxytocin content over 18 h indicated a stable rate of synthesis, which was 1.2 and 1.9 pmol/h for vasopressin and 1.4-2.5 pmol/h for oxytocin. The molar correlation for synthesis of total neurophysin to total hormone was 1.16. Infusion of oxytocin and vasopressin into rats indicated that this level of synthesis of hormone was essential under steady-state conditions to maintain plasma levels in the low physiological range of approximately 3 pg/ml for oxytocin and 1 pg/ml for vasopressin. The data on total synthesis of the neurohypophysial hormones provide a reference for studies in which physiological replacement is required and also provide the technique and base-line data to determine how translation of vasopressin and oxytocin is regulated when neurohypophysial function is altered.
Effects of hypoxia and hypocapnia on brain redox balance in ducks
Authors: Bickler P. E. , Koh S. O. , Severinghaus J. W.
Published: December 2017

Low arterial CO2 tension (PaCO2) experienced by birds during high-altitude flight may result in cerebral vasoconstriction with reduced cerebral O2 delivery. To test this, brain redox balance and blood volume were studied during severe hypocapnia (PaCO2 11-20 mmHg) in ducks. Cerebrocortical redox balance, measured as relative [NADH], and blood volume were measured simultaneously with a fiber-optic fluorometer-reflectometer. Cerebrocortical blood volume (an index of blood flow) fell nearly linearly with PaCO2 during severe hypocapnia, even during severe hypoxemia. Cerebrocortical redox balance was shifted toward reduction of NADH ([NADH] increased) by both hypoxemia and hypocapnia. If hypocapnia causes similar changes in brain blood flow during high-altitude flight, tissue hypoxia will be exacerbated. Tolerance of brain tissue hypoxia during flight may be an important adaptation in high-flying birds.
Bright light can delay human temperature rhythm independent of sleep
Authors: Drennan M. , Kripke D. F. , Gillin J. C.
Published: December 2017

New evidence suggest that the phase of human circadian (approximately 24 h) rhythms can be reset by exposures to bright artificial light. This study explored the value of 5 h of bright 3,800-6,000 lx light in resetting human circadian rhythm phases among healthy volunteers. Nine subjects were exposed to 3-5 h bright light for three evenings and to control dim light for an equivalent time, in counterbalanced orders. Electroencephalogram sleep recordings, overnight rectal temperature measurements, and mood scales were obtained. Compared with control dim light, bright light delayed the body temperature rhythm approximately 3 h; however, sleep latency was delayed only 9 min. This suggests that bright light shifted the phase of the human circadian temperature rhythm independent of its effects on sleep phase. Resetting rhythms with bright light may prove useful in treatment of psychiatric disorders.
Atrial natriuretic peptide response to rapid atrial pacing in cardiac-denervated dogs
Authors: Williams T. D. , Walsh K. P. , Canepa-Anson R. , Noble M. I. , Drake-Holland A. J. , Sutton R. , Lightman S. L.
Published: December 2017

The effects of rapid atrial pacing on central hemodynamics, plasma hormones, and renal function were investigated in eight control and nine cardiac-denervated dogs under chloralose anesthesia. Pacing at approximately 250 ppm for 60 min caused similar increases in pulmonary wedge and right atrial pressures, systemic vascular resistance, and plasma atrial natriuretic peptide (ANP) in both groups. In control dogs, pacing produced a fall in both plasma vasopressin (AVP) and plasma renin activity (PRA) and a rise in urine flow rate associated with an increase in free water but not sodium clearance. In contrast, in cardiac-denervated dogs, both plasma AVP and PRA increased during pacing; urine flow rate did not change, and marked sodium retention occurred. This study supports the concept that the increase in urine flow during rapid atrial pacing is mediated by inhibition of renin and AVP secretion through intact cardiac nerves. The secretion of ANP is unaffected by cardiac denervation. The natriuretic and vasodilator actions of high plasma ANP concentrations during rapid atrial pacing can be inhibited either by neurally mediated cardiorenal effects in normal animals or by stimulation of the renin-angiotensin system after cardiac denervation.
Role of the renin-angiotensin system in hypertension during reduced uteroplacental perfusion pressure
Authors: Woods L. L. , Brooks V. L.
Published: December 2017

Utero-placental ischemia is known to cause systemic hypertension in various species, but the mechanisms are unknown. These studies were designed to test the hypothesis that the increased systemic arterial pressure that occurs during reduced utero-placental perfusion pressure is mediated by the renin-angiotensin system, possibly due to release of renin or angiotensin from the ischemic gravid uterus. In trained, chronically instrumented pregnant dogs (gestational age 47 +/- 2 days, term = 60 days) maintained on a normal Na+ intake (approximately 80 meq/day), uterine perfusion pressure was reduced to 60 mmHg with an inflatable aortic occluder positioned distal to the renal arteries but proximal to the uterine arteries and was servo-controlled at this level for 1 h. Systemic arterial pressure rose by 14 +/- 2 mmHg, from 96 +/- 7 to 110 +/- 8 mmHg. Plasma renin activity and angiotensin II levels did not change significantly. On another day in the same animals, the activity of the renin-angiotensin system was fixed by infusing captopril and sufficient angiotensin II to restore arterial pressure to normal (2-5 ng.kg-1.min-1 iv). Reduction of uterine artery pressure to 60 mmHg caused systemic arterial pressure to increase by 10 +/- 2 mmHg with the renin-angiotensin system fixed, a response not different from that in the control experiments. These data suggest that the increase in systemic arterial pressure during reduced uteroplacental perfusion pressure is independent of the renin-angiotensin system.
Axon destruction and adrenergic systems mediate pressor responses after AV3V lesions
Authors: Bealer S. L. , Van Huysse J. W.
Published: December 2017

These studies investigated the neural tissue and peripheral mechanism mediating the transient pressor response following electrolytic ablation of the periventricular tissue surrounding the anteroventral third ventricle (AV3V) of the rat. Arterial blood pressure was monitored in conscious animals for 2 h following either microinjection of kainic acid (AV3V-KA) or electrolytic lesions (AV3V-X) in the AV3V region or control procedures (Cont). Blood pressure did not change in AV3V-KA (4 +/- 3 mmHg) or Cont rats but significantly increased in AV3V-X animals (20 +/- 4 mmHg). The pressor response following AV3V-X was not altered by pretreatment with MK-422 (converting-enzyme inhibitor), TMe-AVP (vasopressin antagonist), or hexamethonium (ganglionic blocker). However, intravenous administration of prazosin (alpha-adrenergic blocker) or bilateral adrenalectomy abolished the increase in blood pressure. Furthermore, plasma concentrations of norepinephrine were significantly higher in AV3V-X rats (1,125 +/- 150 pg/ml) compared with Cont animals (322 +/- 83 pg/ml) following treatment. These data indicate that the acute hypertensive response following AV3V-X is caused by the destruction of fibers of passage and results from circulating catecholamines of adrenal origin.
Urethral responses to sacral stimulation in chronic spinal dog
Authors: Walter J. S. , Wheeler J. S. , Robinson C. J. , Khan T. , Wurster R. D.
Published: December 2017

Urethral activity was investigated in the awake chronic spinal-injured canine using urodynamic recordings, video cystofluoroscopy, and urethral pressure recordings without anesthesia. Bladder contractions and voiding were induced by electrical stimulation with epidural electrodes inserted into the sacral canal. Urethral pressure remained elevated during stimulation and for 1-3 s afterward. Poststimulation voiding occurred with three different patterns: 1) pulsatile voiding in which squirting of urine was associated with contractions in the membranous urethra; 2) "on and off" voiding in which pulsatile flow was interrupted for brief periods of time; and 3) steady-stream voiding in which nonpulsatile flow was followed by pulsatile flow. Viewing these voiding patterns with fluoroscopy indicated that the proximal membranous urethra was important in all of the patterns. We conclude that in the chronic spinal-injured canine the skeletal muscle within the membranous urethra (rhabdosphincter) is involved in responses to sacral stimulation and various voiding patterns.
Interstitial and intravascular pressures in conscious dogs during head-out water immersion
Authors: Miki K. , Klocke M. R. , Hong S. K. , Krasney J. A.
Published: December 2017

Water immersion (WI) causes an increase in plasma volume in humans and dogs. To determine the mechanism for this fluid movement, the transmission of external water hydrostatic pressure to the interstitial and vascular compartments was studied in six conscious dogs. Systemic arterial, central venous, peripheral arterial (ulnar artery) and venous (cephalic vein), pleural, intra-abdominal, and interstitial fluid hydrostatic (by Guyton's capsule and wick catheter method) pressures and external reference water pressure were measured at three different levels of WI: 1) extremities only, 2) midchest, and 3) midcervical levels at 37 degrees C. There was a significant linear relationship between interstitial fluid hydrostatic pressure (X) and external water pressure (Y): (Y = 0.86X + 1.4, r = 0.93 by Guyton's capsule; Y = 0.85X + 2.4, r = 0.93 by wick catheter. However, vascular pressures did not change when dogs were immersed at the level of the extremities. These pressures increased only during WI at the midchest and midcervical levels. Therefore the pressure gradient that develops between the interstitial and intravascular compartments is probably the major reason for the transcapillary fluid shift during WI.
Ontogeny of neuronally released norepinephrine on renin secretion in sheep
Authors: Nakamura K. T. , Klinkefus J. M. , Smith F. G. , Sato T. , Robillard J. E.
Published: December 2017

The role of renal nerves and norepinephrine release on renin secretion during fetal and postnatal maturation has not been studied. Experiments were performed to determine the effect of veratridine, a substance known to promote norepinephrine release from nerve terminals, on active and inactive renin secretion from renal cortical slices of fetal (134-138 days gestation; term is 145 days), newborn (4-9 days of age), and adult nonpregnant sheep. Veratridine (10-300 microM) significantly increased active renin secretion and produced a small but nonsignificant rise in inactive renin secretion in all three groups of animals (P less than 0.05). The percent rise in active renin secretion during veratridine stimulation was similar among all groups. Veratridine-stimulated (300 microM) active renin secretion was antagonized by tetrodotoxin (0.5 and 5.0 microM) and DL-propranolol (1 microM) in fetal renal cortical slices. However, neither tetrodotoxin nor propranolol completely inhibited the stimulatory effect of veratridine on active renin secretion. These results suggest that 1) norepinephrine released from nerve terminals may regulate active renin secretion early during development; 2) the effect of veratridine on active renin secretion was similar in fetal, newborn, and adult sheep; 3) veratridine had no significant effect on inactive renin secretion; and 4) active renin secretion due to depolarization of nerve terminals in fetal sheep is dependent on activation of beta-adrenoceptors as it is in adults.
An explanation for decreased ketogenesis in the liver of the obese Zucker rat
Authors: Azain M. J. , Ontko J. A.
Published: December 2017

These studies were undertaken to further characterize and explain the differences in hepatic fatty acid metabolism between lean and obese Zucker rats. It was shown that the rate of palmitate or octanoate oxidation and the inhibition of palmitate oxidation by malonyl CoA in mitochondria isolated from lean and obese Zucker rats were similar. Cytochrome oxidase activity was similar in lean and obese rat livers. It was found that the addition of cytosol from the obese rat liver inhibited palmitate oxidation by 20-30% in mitochondria isolated from lean or obese rat livers and thus reproduced the conditions observed in the intact cell. Increased concentrations of metabolites such as malonyl CoA and glycerophosphate in the liver of the obese rat are likely contributors to this inhibitory effect. These results are extrapolated to the intact cell and suggest that decreased hepatic fatty acid oxidation in the obese rat can be accounted for by cytosolic influences on the mitochondria. The decreased rate of fatty acid oxidation observed in the intact hepatocyte or perfused liver cannot be explained by a defect in the capacity of mitochondria to oxidize substrate or by a decrease in mitochondrial number in the obese rat liver.
Species differences in regulation of alpha-adrenergic receptor function
Authors: Shen Y. T. , Vatner D. E. , Gagnon H. E. , Vatner S. F.
Published: December 2017

The effects of alpha-adrenergic receptor stimulation with norepinephrine and phenylephrine after beta-adrenergic and muscarinic receptor blockades were compared in conscious baboons, calves, dogs, and rats in which left ventricular (LV) pressure. LV maximum rate of pressure development (dP/dt), and heart rate were measured. Autonomic receptor density was examined in crude sarcolemmal preparations from the hearts. The major physiological differences were observed in rats, where alpha 1-adrenergic receptor stimulation resulted in the greatest (P less than 0.05) increases in LV dP/dt (29 +/- 2%) in response to phenylephrine, 5.0 micrograms/kg, in comparison with responses in dogs (12 +/- 4%), calves (3 +/- 3%), and baboons (1 +/- 2%). This was associated with the greatest (P less than 0.05) alpha 1-adrenergic receptor density in the rat heart (73 +/- 5 fmol/mg) compared with values in the baboon (6 +/- 1 fmol/mg), calf (21 +/- 3 fmol/mg), or dog (10 +/- 3 fmol/mg) myocardium. Thus there are major differences among mammalian species in alpha-adrenergic receptor density and physiological responsiveness to alpha-adrenergic agonists.
Short photoperiod and cold activate brown fat lipoprotein lipase in the Djungarian hamster
Authors: Klingenspor M. , Klaus S. , Wiesinger H. , Heldmaier G.
Published: December 2017

Activation of lipoprotein lipase (LPL) in brown fat of the Djungarian hamster ensures substrate supply for nonshivering thermogenesis. Cold acclimation [5 degrees C ambient temperature (Ta)] in long photoperiod [light-dark (LD) 16:8] increased brown fat LPL activity from 4.7 to 22.7 nmol oleate.mg-1.min-1 within 1 day. Slight reduction of this high LPL activity was observed during prolonged cold exposure for up to 4 wk. Deacclimation (transfer from 5 to 23 degrees C Ta) caused total inactivation of brown fat LPL within 4 days. Short photoperiod (LD 8:16) also stimulates brown fat LPL activity. Its effect can be summarized by three different observations. At thermoneutrality short photoperiod elevated LPL activity to 7.1 instead of 4.7 nmol.mg-1.min-1 observed in long photoperiod. Second, at low ambient temperature short photoperiod reinforces the effect of cold acclimation. Maximum LPL activity of cold-exposed Djungarian hamsters averaged 23.7 nmol.mg-1.min-1 in long photoperiod and was elevated to 35.5 nmol.mg-1.min-1 in short photoperiod. Third, inactivation of LPL during deacclimation was delayed in short photoperiod. These results demonstrate that photoperiod as well as ambient temperature may be cooperatively used as environmental cues for seasonal acclimation of brown fat substrate supply for nonshivering thermogenesis.
Influence of preweaning food intake on body composition of young adult baboons
Authors: Lewis D. S. , Bertrand H. A. , McMahan C. A. , McGill H. C. , Carey K. D. , Masoro E. J.
Published: December 2017

The hypothesis that infant overnutrition increases fat cell number and promotes obesity in the young adult primate was tested. Newborn baboons were fed similar volumes of Similac formulas with caloric densities of 40.5 (underfed, n = 8), 67.5 (normally fed, n = 12), and 94.5 (overfed, n = 12) kcal/100 g formula until 4 mo of age. Afterwards all baboons were fed the same diet until they were young adults. At 5 yr of age body composition, mean fat cell size, and total fat cell number were measured. Infant food intake did not significantly influence body composition or fat cell number in the 5-yr-old male baboons. Five-year-old female baboons, overfed as infants, had significantly greater body fat mass, percent of body mass that was fat, and mean fat cell volume compared with females that were underfed or normally fed as infants. There was no difference in total fat cell number between the obese baboons that were overfed as infants and the lean baboons that were underfed or normally fed as infants. Fat cell number was not associated with body fat content; males had more fat cells than did females. These results demonstrate that infant overnutrition in a primate species promotes obesity in young adult females by increasing primarily fat cell size and not fat cell number.
Electrophysiological and cable parameters of perfused beetle malpighian tubules
Authors: Isaacson L. C. , Nicolson S. W. , Fisher D. W.
Published: December 2017

Isolated perfused Malpighian tubules of the desert beetle Onymacris plana (Coleoptera: Tenebrionidae) have been subjected to cable analysis under the following conditions: control, adenosine 3',5'-cyclic monophosphate (cAMP), corpora cardiaca homogenate (CCH), and high ambient K (130 mM). In addition, we investigated possible effects of perfusate composition on proximal transtubular potential (Vo) by reducing K, Na, or Cl or by adding ouabain, furosemide, or dinitrophenol. The effects of cAMP, CCH, and high K on Vo and cable parameters were consistent with increased fluid secretion, i.e., diminished input and core resistances and increased virtual short-circuit current, length constant, and luminal diameter. They differed in that CCH had variable effects on Vo and high K did not reduce transepithelial resistance. In terms of their effects on the parameters of a simple equivalent electrical circuit, the responses to cAMP, CCH, and a high ambient K concentration appear to be mediated by different mechanisms. Alterations in perfusate composition were almost without effect.
Effects of prolonged hyperinsulinemia on erythropoiesis in fetal sheep
Authors: Stonestreet B. S. , Goldstein M. , Oh W. , Widness J. A.
Published: December 2017

Offspring of diabetic mothers have an increased incidence of neonatal polycythemia, decreased oxygen tension in cord blood at delivery, and elevated plasma erythropoietin levels at birth. Experimental fetal hyperinsulinemia has been associated with reduced fetal oxygen content and increased erythropoietin concentration. To test the hypothesis that prolonged fetal hyperinsulinemia results in increased fetal erythropoiesis and red cell volume during gestation, we infused insulin or placebo for 11 +/- 0.2 (+/- SE) days into chronically catheterized fetal sheep, beginning at 124 days of gestation. Indices of fetal erythropoiesis, red cell and blood volume were measured before and during the infusions. Insulin infusion resulted in increased plasma insulin, decreased plasma glucose, and decreased oxygen saturation values. The nucleated red blood cell (RBC) and RBC counts were significantly higher in the insulin- compared with the placebo-treated fetal sheep after 6-8 and 9-12 days of infusion, respectively. Although erythropoietin concentration did not differ between the groups, red cell volume expressed as a change from the base-line value was significantly higher in the insulin-treated group. We conclude that prolonged fetal hyperinsulinemia augmented erythropoiesis and red cell volume during late gestation in fetal sheep.
Protein phosphorylation in isolated hepatocytes of septic and endotoxemic rats
Authors: Deaciuc I. V. , Spitzer J. A.
Published: December 2017

The purpose of this study was to investigate possible alterations induced by sepsis and endotoxicosis in the late phase of Ca2+-dependent signaling in rat liver. Hepatocytes isolated from septic or chronically endotoxin (ET)-treated rats were labeled with [32P]H3PO4 and stimulated with various agents. Proteins were resolved by one-dimensional polyacrylamide gel electrophoresis and autoradiographed. Vasopressin (VP)- and phenylephrine (PE)-induced responses were attenuated in both septic and ET-treated rats for cytosolic and membrane proteins compared with their respective controls. Glucagon and 12-O-myristate phorbol-13-acetate (TPA) affected only the phosphorylation of membrane proteins. Glucagon-induced changes in the phosphorylation of membrane proteins were affected by both sepsis and endotoxicosis, whereas TPA-stimulated phosphorylation was lowered only in endotoxicosis. Response to the Ca2+ ionophore A23187 was depressed in septic rats for cytosolic proteins. The phosphorylation of two cytosolic proteins, i.e., 93 and 61 kDa (previously identified as glycogen phosphorylase and pyruvate kinase, respectively), in response to VP, PE, and A23187 was severely impaired by endotoxicosis and sepsis. TPA did not affect the phosphorylation state of these two proteins. The results show that sepsis and endotoxicosis produce perturbations of the phosphorylation step in Ca2+ transmembrane signaling. Such changes can explain alterations of glycogenolysis and gluconeogenesis associated with sepsis and endotoxicosis.
Turtle urinary bladder: regulation of ion transport by dynamic changes in plasma membrane area
Authors: Stetson D. L.
Published: December 2017

Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.
Peripheral arterial chemoreceptors and reflex control of sodium and water homeostasis
Authors: Honig A.
Published: December 2017

In response to acute exposure to moderate high-altitude hypoxia, mammals increase their blood hemoglobin concentration very rapidly by reducing their plasma volume. This phenomenon is caused not only by a redistribution of the body fluid volumes but also by a suppression of voluntary sodium and water intake as well as an inhibition of renal tubular sodium reabsorption with natriuresis and diuresis. This article reviews the role of the peripheral arterial chemoreceptors within the framework of the reflex mechanisms that might cause the changes in sodium and water metabolism in acute arterial hypoxia. The evidence that the peripheral arterial chemoreceptors do also influence sodium and water homeostasis in normoxia is presented. The interrelations between carotid body structure and arterial chemoreceptor reflex effects on the one hand and primary systemic hypertension on the other are discussed.
Regional differences in fat pad responses to short days in Siberian hamsters
Authors: Bartness T. J. , Hamilton J. M. , Wade G. N. , Goldman B. D.
Published: December 2017

Siberian hamsters exhibit decreased body weight and fat after initial exposure to short photoperiods and increased body weight and fat after extended short photoperiod exposure. The purpose of the present experiments was to determine if uniform changes in white adipose tissue (WAT) pad weights and lipid metabolism correspond to these short photoperiod-induced changes in body fat. Carcass lipid content and testes and fat pad weights [retroperitoneal WAT (RWAT), epididymal WAT (EWAT), and inguinal and dorsal subcutaneous WAT, respectively] were decreased in male hamsters relative to their long day counterparts after 6 and 12 wk of short-day exposure. Moreover, EWAT and RWAT weight, EWAT specific lipoprotein lipase activity, and specific and total lipogenesis were disproportionately decreased relative to the subcutaneous fat pads. The changes in fat pad weight and metabolism were generally reversed coincident with the return to a long-day-like reproductive status after prolonged short-day exposure (24 and 30 wk). In a less detailed experiment, female Siberian hamsters had decreased body, fat pad, and uterine weights after 6 wk of short-day exposure; however, no fat pad-specific changes in weight were observed. The results of these experiments demonstrate that short-day-exposed male Siberian hamsters may be a useful model for examining mechanisms underlying fat pad-specific responses. In addition, gender appears to influence the pattern of short-day-induced lipid depletion in this species.
Basal membrane uptake in potassium-secreting cells of midgut of tobacco hornworm (Manduca sexta)
Authors: Chao A. C. , Koch A. R. , Moffett D. F.
Published: December 2017

Basal membrane voltage (Vb), intracellular K+ activity [(K+)i], and short-circuit current (Isc) were measured in isolated posterior midguts of Manduca sexta wherein Isc is a measured of active secretion of K+ from blood into lumen. When bathed in 32 mM K+ and exposed to 100% O2, average values were Isc = 244 microAmp/cm2, Vb = -33.1 mV, and (K+)i = 88.6 mM. The electrochemical gradient across the basal membrane (d mu) averaged +5.8 mV (a gradient favorable for K+ entry). Exposure to 5% O2 led to a new steady state in which Isc = 71 microAmp/cm2, Vb = -18.7 mV, and (K+)i = 99.4 mM. During hypoxia, d mu averaged -9.9 mV (a gradient unfavorable for K+ entry). When the external bathing solution was 10 mM K+, comparable values were, for 100% O2, Isc = 139 microAmp/cm2, Vb = -56.1 mV, (K+)i = 72.2 mM, and d mu = +3.6 mV, and in 5% O2 the values were Isc = 28.3 microAmp/cm2, Vb = -43.7 mV, (K+)i = 76.1 mM, and d mu = -10.2 mV. The failure of cellular K+ to fall during prolonged hypoxia is evidence for a thermodynamically active basal K+ uptake process.
Effects of day length on sheep neuroendocrine estrogen and progestin receptors
Authors: Bittman E. L. , Blaustein J. D.
Published: December 2017

Gonadal steroid hormone receptors were studied in anterior pituitary, preoptic area, and hypothalamus of ovariectomized ewes. We established that systemic administration of estradiol benzoate elevates levels of nuclear estrogen receptor concentrations and results in the appearance of cytosolic progestin receptor the binding characteristics of which are comparable with that reported in rats and guinea pigs [0.1 nM Kd, binding site density (Bmax) of 111, 22, and 2 fmol/mg protein in pituitary, medial basal hypothalamus, and preoptic area, respectively]. Brain tissues also contained a second, low-affinity progestin binding site. To examine possible effects of photoperiod on neuroendocrine steroid receptors, two groups of sheep were exposed to artificial photoperiods. Ewes experienced alternating periods of long (LD 16:8) or short (LD 8:16) days for 290 days to induce breeding season or anestrous states. Animals were then ovariectomized and given steroid treatments designed to mimic a luteal phase followed by either follicular phase levels of estradiol or withdrawal of all exogenous hormones before determination of neuroendocrine steroid receptor concentrations. Despite the ability of long photoperiods to arrest ovarian cyclicity, magnify negative feedback actions of estradiol upon luteinizing hormone, and reduce the ability of estrogen to trigger behavioral estrus, photoperiod did not influence nuclear estrogen receptor concentrations or the induction of cytosolic progestin receptors in the pituitary, hypothalamus, or preoptic area.