bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic rate, respiratory exchange ratio, and apneas during meditation
Authors: Kesterson J. , Clinch N. F.
Published: December 2017

We tested the hypothesis that a drop in metabolic rate (MR) causes the apneas observed in some subjects during transcendental meditation (TM). We measured O2 consumption (VO2) and CO2 production (VCO2) in three groups of experienced meditators and one group of nonmeditating controls. Measurements were made before, during, and after TM for the meditators and before, during, and after eyes-closed relaxation for the nonmeditating controls. The three groups of meditators consisted of 1) those showing little change in the frequency of ventilation (f) with meditation, 2) those showing a marked decline in f, and 3) those showing numerous apneas and a marked fall in f. There were significant trial effects but no group or interaction effects for the decline in VO2. Thus we concluded that a drop in MR is not the cause of the apneas. However, there were significant trial and interaction effects for the changes in VCO2 and the respiratory exchange ratio (R), with a significant drop in R for the meditators but not for the controls. We report additional evidence and speculate that the drop in R is a consequence of mild hypoventilation.
Administering triazolam on a circadian basis entrains the activity rhythm of hamsters
Authors: Van Reeth O. , Turek F. W.
Published: December 2017

A single injection of the short-acting benzodiazepine, triazolam, can induce permanent phase shifts in the circadian rhythm of locomotor activity in free-running hamsters, with the direction and magnitude of the phase shifts being dependent on the circadian time of treatment. The shape of the "phase-response curve" to triazolam injections is totally different from that for light pulses. These findings raise the possibility that repeated injections of triazolam on a circadian basis might be capable of entraining the circadian pacemaker underlying the activity rhythm of hamsters and that the entrainment pattern might differ from that observed in animals entrained to light pulses. To test this hypothesis, blind hamsters received intraperitoneal injections of triazolam (or vehicle) every 23.34, 23.72, 24.00 or 24.66 h for 19-20 days, and the effect of these injections on the period of the rhythm of wheel-running behavior was determined during and after treatment. Repeated injections of 0.1 mg triazolam at these time intervals resulted in the entrainment of the activity rhythm in 36 of 40 animals, whereas 0 of 40 animals entrained to vehicle injections. Importantly, the phase relationship between triazolam injections and the circadian activity rhythm was dependent on the period of drug treatment and could be predicted from the phase-response curve to single injections of triazolam. These phase relationships are dramatically different from those observed between the activity rhythm and 1-h light pulses presented at similar circadian intervals.(ABSTRACT TRUNCATED AT 250 WORDS)
Determinants of arterial pressure after chronic spinal transection in rats
Authors: Osborn J. W. , Taylor R. F. , Schramm L. P.
Published: December 2017

The present study was conducted to determine whether sympathetic vasoconstrictor activity is a determinant of mean arterial pressure (MAP) hours and days after cervical spinal transection (CST) in unanesthetized rats. MAP on the 2 days before CST was 107.2 +/- 3.6 and 103.3 +/- 3.0 mmHg, respectively, and fell to 77.7 +/- 1.1 mmHg on day 1 after CST. MAP returned to control levels over the course of the study and, by day 9 after CST, was not statistically different from control (98.6 +/- 3.4 mmHg). Neither autonomic ganglionic blockade nor alpha-adrenergic blockade affected MAP the 1st day after CST. Similarly, alpha-adrenergic blockade was without effect on days 3, 5, and 7 after CST. Administration of a vasopressin V1-antagonist had no effect on MAP on day 1 or day 8 after CST. However, blockade of angiotensin-converting enzyme with captopril decreased arterial pressure both on day 1 (-22.1 +/- 2.6 mmHg) and day 8 (-23.3 +/- 2.9 mmHg) after CST. We conclude that neither sympathetic nor vasopressin vasoconstrictor activity affected MAP within the 1st wk after CST. Although the vasoconstrictor actions of angiotensin II were important, these effects were not responsible for the normalization of MAP observed after CST.
Effects of chronic icv infusion of vasopressin on sleep-waking cycle of rats
Authors: Arnauld E. , Bibene V. , Meynard J. , Rodriguez F. , Vincent J. D.
Published: December 2017

The effect of arginine vasopressin (AVP) on the duration and the relative proportion of sleeping and wakeful periods has been investigated. Vigilance states were determined by visual scoring of polygraphic recordings from unrestrained rats. Animals were implanted with a cannula into the third ventricle through which AVP or related drugs, dissolved in artificial cerebrospinal fluid, were infused at a constant rate by an osmotic pump. Polygraphic data were collected 24 h/day from day 4 to day 9. Recordings were continued for 3 additional days during AVP recovery. AVP infusions significantly increased the amount of time spent in waking compared with control or recovery periods (12%). This effect was mimicked by an AVP agonist (2-phenylalanine, 8-ornithine oxytocin). Oxytocin, a peptide structurally close to AVP, induced a mild change in waking time. The infusion of an AVP antagonist, 1-desaminopenicillamine-2-(O-methyl)tyrosine-arginine vasopressin (dPTyr(Me)AVP), or of anti-AVP antibodies significantly decreased duration of waking. The infusion of antioxytocin antibodies did not modify the duration of waking. The effects of structural analogues of AVP relatively specific for each type of peripheral AVP receptor indicated the participation of a V1-like AVP receptor in the action of AVP on waking time. During infusion of anti-AVP antibodies and dPTyr(Me)AVP and during the first days of recovery from AVP infusion, the ultradian rhythmic distribution of sleep and wakefulness was still present, but the amplitude of the circadian rhythm was reduced.
Comparison of intracerebroventricular and intracarotid infusions of PGE2 in conscious sheep
Authors: Breuhaus B. A. , Demarest K. T. , Chimoskey J. E.
Published: December 2017

Conscious sheep chronically prepared with nonocclusive indwelling vascular and cerebroventricular catheters were used to compare hemodynamic, hematologic, hormonal, and behavioral responses of intracarotid (ic) prostaglandin E2 (PGE2) to intracerebroventricular (ivt) PGE2. PGE2 had less potent hemodynamic effects when infused ivt than when infused ic. Intracarotid PGE2, 100 ng.kg-1.min-1, increased arterial pressure and heart rate 31 mmHg and 26 beats/min, respectively (P less than 0.01), whereas ivt PGE2, 300 ng.kg-1.min-1, did not alter heart rate and increased arterial pressure 9 mmHg (P less than 0.01). Both ic and ivt PGE2 increased packed cell volume 3% (P less than 0.01). Neither ic nor ivt PGE2 caused changes in plasma concentrations of epinephrine or norepinephrine. Despite ivt PGE2S less potent hemodynamic effects, ivt administration of PGE2 decreased plasma osmolality 2 mosmol/kg (P less than 0.05) and sodium concentration 2 meq/l (P less than 0.01) and increased plasma vasopressin concentration 2.5-fold (P less than 0.05). Intracerebroventricular PGE2 also caused some physical and behavioral changes that were not observed during ic PGE2 administration or during ivt infusion of vehicle. These changes included pupillary constriction, vocalization, and coughing. We conclude that PGE2 given ivt may not reach the same sites in the brain as does ic PGE2 or that ivt PGE2 may reach the same sites in different concentrations.
Evidence for a regenerative capacity in adult mammalian cardiac myocytes
Authors: Butler R.
Published: December 2017

Cardiac muscle does not contain a copopulation of myogenic cells and is mitotically inactive; hence, any regenerative capacity of the myocardium most likely originates from viable fragments of damaged cells rather than mitogenic activity. To assess the extent of such tissue recovery, single doses of the drug bupivacaine were used to induce degeneration of rat ventricular myocytes, and histological evidence for tissue recovery was sought. Up to 1 wk posttreatment, extensive degeneration was found around the injection site. At 2 wk, evidence of regeneration could be seen, and at 3 wk posttreatment, some relatively normal looking tissue was found.
Swallowing reflex elicited by water and taste solutions in humans
Authors: Shingai T. , Miyaoka Y. , Ikarashi R. , Shimada K.
Published: December 2017

We investigated whether water and taste solutions are adequate stimuli for elicitation of the swallowing reflex from the pharyngolaryngeal region in humans. Subjects were five healthy males. Small amounts of water and taste solutions were applied to the posterior tongue of the subject as he reclined on a dental chair. The latency between the onset of application of the stimuli and the occurrence of swallowing was measured. Water was a most effective stimulus for elicitation of the swallowing reflex. The stimulatory effect was altered by anions, particularly Cl-, added to the water. Gustatory factors affected the latency of swallowing. The results suggest that humans have water-sensitive receptors in the pharyngolaryngeal region and that these receptors are responsible for initiation of the swallowing reflex by water.
Control of phosphate transport in flounder renal proximal tubule primary cultures
Authors: Gupta A. , Renfro J. L.
Published: December 2017

Unidirectional mucosal-to-serosal (Jm----s) and serosal-to-mucosal (Js----m) transepithelial phosphate fluxes across monolayers of flounder (Pseudopleuronectes americanus) renal proximal tubule cells in primary culture were examined for effects of diacylglycerols, phorbol ester, A23187, forskolin, and extracellular phosphate availability. Tissues were cultured on floating collagen rafts and studied short circuited in Ussing chambers. Transepithelial electrical properties were continuously monitored and were unaffected by any of the treatments compared with paired controls. Under usual conditions (phosphate = 0.4 mM) tissues invariably displayed net phosphate reabsorption [Js----m = 2.3 +/- 0.52; Jm----a = 7.1 +/- 1.77; Jnet = 4.9 +/- 1.45 (SE) nmol.cm-2.h-1]. Acute elevation of bath phosphate concentration above 0.5 mM stimulated net secretion. Exposure to 100 microM 1,2-dihexanoyl-sn-glycerol stimulated net phosphate secretion within 30 min, the result of a fivefold increase in Js----m. Phorbol-12,13-didecanoate stimulated net phosphate secretion by increasing Js----m and decreasing Jm----s. The inactive diacylglycerol, 1,3-didecanoyl-rac-glycerol (100 microM), had no effect on phosphate fluxes. A23187 stimulated net phosphate secretion; Jm----s was reduced almost fourfold while Js----m was increased threefold. Forskolin (10 microM) stimulated net reabsorption more than threefold after a long latency (2 h). These data indicate that renal phosphate secretion and reabsorption may be regulated by several putative intracellular messengers. In addition, extracellular phosphate availability may modulate renal phosphate handling.
Beat-to-beat regulation of left ventricular function in the intact cardiovascular system
Authors: Slinker B. K. , Glantz S. A.
Published: December 2017

A variety of regulatory mechanisms have evolved to control the heart's pump function because the cardiovascular system must continually adapt to the changing demands that body functions place on it. This regulation takes place through many physiological systems; however, fine adjustments in cardiac pumping probably require adaptations more quickly than external control mechanisms (such as the autonomic nervous system) can compensate. Thus cardiac pumping is also regulated by mechanisms intrinsic to the heart. To better understand these intrinsic control mechanisms, we studied the beat-to-beat response of left ventricular function to continually varying changes in loading conditions produced by transiently occluding the pulmonary artery, venae cavae, and aorta. We used multiple linear regression to identify and quantify the important beat-to-beat determinants of left ventricular systolic function, quantified as stroke work. We could not adequately explain or predict beat-to-beat changes in stroke work with traditional determinants of ventricular function, preload, afterload, and heart rate, because a large systematic error remains after taking these traditional determinants of function into account. To eliminate this systematic error, we had to include some function of previous beat stroke volume and end-systolic size and pressure. This additional information significantly improved both our ability to model the observed transient changes in left ventricular stroke work and to predict additional observations that were not used to develop our model. We conclude that previous beat contraction history is an important determinant of left ventricular function and implies an important regulatory mechanism whereby the left ventricle can fine tune its function from beat to beat in response to continually changing loading conditions.
Mechanisms of fetal blood volume restoration after slow fetal hemorrhage
Authors: Brace R. A.
Published: December 2017

Previous studies have shown that blood volume returns to normal within 24-48 h after hemorrhage in the adult of several species, whereas vascular volume restoration occurs within 3-4 h after a 2-h hemorrhage of the sheep fetus. The purpose of the present study was to determine whether an increase in fetal osmolality and/or circulating plasma protein mass contribute to the rapid volume restoration in the fetus. Nine chronically catheterized fetal sheep at 132 +/- 2 days gestation (term = 145-150 days) were hemorrhaged 30.9 +/- 2.2% of their initial blood volume over 2 h. Blood volume returned to normal 3 h after the hemorrhage. No change in fetal osmolality or in the fetal-maternal osmotic gradient occurred during or after the hemorrhage. However, there was a near-perfect correlation between blood volume and circulating plasma protein mass during and after the hemorrhage. Thus the present study provides no evidence for either a fetal cellular or transplacental source of fluid during fetal posthemorrhage volume restoration because osmolality was unchanged. Instead it appears that a rapid redistribution of proteins and fluid from the fetal interstitial space most likely mediates the vascular volume restoration.
Regional alterations in hexokinase activity within rat brain during dehydration and rehydration
Authors: Krukoff T. L. , Vincent D. H.
Published: December 2017

Histochemical localization and photodensitometric quantification of the metabolic enzyme, hexokinase (HK), were used to study changes in brain metabolic activity that occur during the development of (5 days) and recovery from (7 days) dehydration. In water-deprived (WD) rats, HK activity increased after 2 days in the subfornical organ (SFO, 22%), nucleus circularis (NC, 36%), parvo- and magnocellular divisions of the paraventricular nucleus (pPVH, 17%; mPVH, 46%) and supraoptic nucleus (SON, 46%). Activity in SFO declined to control levels at 3 days but increased again thereafter. In pPVH, mPVH, and SON, activity was elevated until the end of the experiment. In NC, activity returned to control levels within 2 days of drinking by the rats. In salt-loaded (2% NaCl in water) rats, changes were similar to those of WD rats up to 2 days of dehydration (SFO, 25%; NC, 20%; pPVH, 16%; mPVH, 38%; SON, 50%). Activity in SFO and pPVH returned to control levels after 3 days and remained unchanged. In mPVH, SON, and NC, activity remained elevated and declined to control levels when salt-free water was provided. Results confirm that water deprivation is a stronger dehydrating stimulus than salt loading. In addition, metabolic activity, as measured by HK activity, varies daily during periods of dehydration and rehydration. These changes cannot always be predicted from results obtained only at the end of a period of dehydration. It is concluded that it is necessary to study dehydration-induced changes in brain metabolism on a daily basis to more fully understand the roles of discrete brain regions in the regulation of body fluids.
Vasomotor responses of the umbilical circulation in fetal sheep
Authors: Adamson S. L. , Morrow R. J. , Bull S. B. , Langille B. L.
Published: December 2017

The effects of vasoactive agents on the distribution of vascular resistance within the umbilical circulation of fetal sheep in utero has been assessed under general anesthesia. Under control conditions, 37% of the arterial to venous pressure drop occurred across the umbilical arteries and their major tributaries, 8% occurred across umbilical veins, and the remaining 55% occurred across the cotyledons. Isoproterenol had no significant effect on these resistances. Norepinephrine and angiotensin II both dramatically increased placental vascular resistance, but the distribution of resistances was altered in different ways. Angiotensin caused a 13-fold increase in the umbilical arterial resistance, whereas there were no changes in cotyledon or venous resistances. Norepinephrine also had no effect on cotyledon vascular resistance but it constricted downstream vessels (6-fold increase). These results suggest that norepinephrine and angiotensin II regulate fetal placental blood flow and that they can independently control pressure in placental exchange vessels. As a consequence, these agents may play an important role in controlling fetal-maternal fluid transport.
Autonomic modulation of ultradian blood pressure and heart rate oscillations in dogs
Authors: Broten T. P. , Zehr J. E.
Published: December 2017

Autonomic receptor modulation of ultradian oscillations of blood pressure and heart rate was studied in telemetered free-running dogs. Data, analyzed for their harmonic content by fast Fourier transform (FFT) methods, indicated that ultradian and circadian oscillations of 22.9 +/- 2.5 and 10.5 +/- 0.9 (SD) mmHg, respectively, were present. The average principal frequency for the ultradian oscillations in 12 dogs was 0.760 +/- 0.11 cycles/h for arterial pressure and 0.808 +/- 0.10 for heart rate. Atropine had no effect on periodicity of either arterial pressure or heart rate. Metoprolol, a beta 1-antagonist, or hexamethonium, a ganglionic blocker, significantly reduced the power of both arterial pressure and heart rate (P less than 0.05), whereas the primary frequencies of both were unchanged. Prazosin, an alpha 1-blocker, sharply reduced arterial pressure power (P less than 0.05) and increased the power of heart rate (P less than 0.05), demonstrating that it is possible to uncouple arterial pressure oscillations from influences of heart rate. We conclude that the sympathetic limb of the autonomic nervous system is primarily responsible for these oscillations and that vagal influences on the heart partially dampen these rhythms.
Cholecystokinin-induced anorexia depends on serotoninergic function
Authors: Stallone D. , Nicolaidis S. , Gibbs J.
Published: December 2017

The existence of a relationship between cholecystokinin (CCK)-induced satiety and the serotoninergic system was evaluated. The food intake of 3-h-fasted male rats was studied after treatment with the COOH-terminal octapeptide of CCK (CCK-8) alone or in combination with one of two blockers of serotonin (5-HT) receptors, metergoline (MET; 1.0 or 0.06 mg/kg), active in both the periphery and brain, or xylamidine tosylate (XYL; 1.5 mg/kg), active only in the periphery. CCK-8 reduced food intake in the 30 min after food presentation by 37% at 2 micrograms/kg, 68% at 4 micrograms/kg, and 80% at 8 micrograms/kg compared with controls. Both doses of MET attenuated CCK-8-induced satiety, increasing food intake of rats treated with all doses of CCK-8 to control values. Food intake was significantly increased over base line by the 1.0-mg/kg dose of MET alone but unaffected by the 0.06-mg/kg dose of MET alone. XYL had no effect either given alone or in combination with CCK-8. These results indicate that the inhibitory action of CCK-8 on food intake is dependent on intact functioning of the serotoninergic system, probably at central sites.
Thermal sensitivity of reptilian melatonin rhythms: "cold" tuatara vs. "warm" skink
Authors: Firth B. T. , Thompson M. B. , Kennaway D. J. , Belan I.
Published: December 2017

Daily rhythms in plasma melatonin levels were compared in two ecologically diverse reptilian species under natural environmental conditions in autumn. The nocturnal, cold temperature-adapted tuatara (Sphenodon punctatus) had a melatonin rhythm of much lower amplitude than did the diurnal desert-adapted sleepy lizard (Tiliqua rugosa). Experiments in controlled laboratory environments showed that, although both species are capable of attaining a comparable melatonin peak (approximately 750 pmol/l), the threshold temperature at which a significant daily rhythm occurs is approximately 15 degrees C in S. punctatus compared with approximately 25 degrees C in T. rugosa. This difference probably reflects the disparate thermoregulatory adaptations of the two species, S. punctatus favoring mean activity temperatures of 11.5 degrees C and T. rugosa, 32.5 degrees C. In ectotherms such as reptiles, therefore, species-typical thermoregulatory behavior may provide thermal cues that interact with photoperiod to provide the appropriate melatonin signal for the regulation of annual physiological cycles.
Glucocorticoid inhibition of Na-SO4 transport by chick renal brush-border membranes
Authors: Renfro J. L. , Clark N. B. , Metts R. E. , Lynch M. A.
Published: December 2017

To examine the effect of glucocorticoids on sulfate transport by the chick (domestic Gallus gallus) renal tubule we dosed 3-wk-old animals with 60 micrograms dexamethasone/100 g body wt at 24 and 6 h before isolation of renal brush-border (BBM) and basolateral membranes (BLM). Dexamethasone treatment significantly reduced Na-dependent sulfate transport by BBM and had no effect in paired membranes on bicarbonate, proton, or electrical gradient-driven sulfate transport. The glucocorticoid treatment had no statistically significant effect on HCO3-SO4 exchange in the BLM. Kinetic analysis of the dexamethasone effect on the Na-SO4 transport process showed that apparent Vmax was significantly decreased to almost one-half that seen in controls (from 676 to 348 pmol.mg protein-1.5 s-1). The Km in control BBM was 0.40 +/- 0.095 mM and was not significantly different in dexamethasone-treated membranes (0.53 +/- 0.094 mM). To determine whether the dexamethasone-induced decrease in Na-SO4 transport by BBM was indirectly caused by stimulation of Na-H exchange and more rapid dissipation of the initial Na gradient used to drive sulfate uptake, we examined the effect of 0.1 mM amiloride on Na-SO4 uptake by BBM. With amiloride present, dexamethasone treatment caused Vmax to significantly drop from 1,102 to 660 pmol.mg protein-1.5 s-1. Amiloride had no statistically significant effect on the Km. The extent to which amiloride increased Na-SO4 transport and blocked 22Na uptake by BBM did not appear to be related to hormone treatment. The data indicate that glucocorticoids may participate in the regulation of sulfate excretion.
Intraventricular CCK inhibits food intake and gastric emptying in baboons
Authors: Figlewicz D. P. , Sipols A. J. , Porte D. , Woods S. C. , Liddle R. A.
Published: December 2017

To evaluate the role of cholecystokinin (CCK) as a physiological regulator of meal size and gastric emptying in the baboon, we measured plasma CCK bioactivity during 30-min meals alone and after intravenous or intraventricular infusions of CCK COOH-terminal octapeptide (CCK-8). Both intravenous (2 micrograms/kg) and intraventricular (1 microgram/kg) CCK-8 administration resulted in plasma CCK elevations comparable with normal prandial CCK levels: peak plasma levels were 4.1 +/- 0.9, 7.1 +/- 1.1, and 4.9 +/- 2.2 pM for pooled intravenous and intraventricular control, intravenous, and intraventricular conditions. Also, both treatments appeared to reduce gastric emptying as indicated by a significant suppression of postprandial plasma insulin and glucose levels. However, only intraventricular CCK reliably reduced meal size (percent of control meal size was 91 +/- 5% or 43 +/- 19% with intravenous or intraventricular CCK). We conclude that circulating endogenous CCK is a potent postprandial endocrine regulator of gastric emptying. However, the ability of CCK to decrease meal size may require direct interaction with the central nervous system.
Maternal responses to long-term hypoxemia in sheep
Authors: Kitanaka T. , Gilbert R. D. , Longo L. D.
Published: December 2017

To determine the maternal cardiovascular responses to long-term hypoxemia, we studied three groups of animals: 1) pregnant ewes (n = 20) at 110-115 days gestation subjected to hypoxia for up to 28 days; 2) pregnant ewes (n = 4) that served as normoxic controls; and 3) nonpregnant ewes (n = 6) subjected to hypoxemia for up to 28 days. We measured mean arterial pressure, heart rate, uterine blood flow, and uterine vascular resistance continuously for 1 h/day while the ewe was exposed to an inspired O2 fraction of 12-13% for at least 17 days. Arterial PO2, O2 saturation, hemoglobin, arteriovenous O2 difference, and uterine O2 uptake were measured daily while blood volume and erythropoietin concentration were measured weekly. In the pregnant hypoxic group arterial PO2 decreased from a control value of 101.5 +/- 5.1 to 59.2 +/- 5.1 Torr within a few minutes, where it remained throughout the study. The hemoglobin concentration increased from 8.9 +/- 0.5 to 10.0 +/- 0.5 g/dl within 24 h where it remained, whereas erythropoietin concentration increased from 16.6 +/- 2.1 to 39.1 +/- 7.8 mU/ml at 24 h but then returned to near-control levels. Arterial glucose concentration, mean arterial pressure, and cardiac output decreased slightly but insignificantly. In contrast, body weight, heart rate, blood volume, uterine blood flow, uterine O2 flow, uteroplacental O2 uptake, and the concentrations of catecholamines and cortisol remained relatively constant. Thus both pregnant and nonpregnant sheep experience relatively minor cardiovascular and hematologic responses in response to long-term hypoxemia of moderate severity.
Interaction of CCK-8 and somatostatin-14 in control of food intake in dogs
Authors: Kalogeris T. J. , Reidelberger R. D. , Mendel V. E. , Solomon T. E.
Published: December 2017

interactions of cholecystokinin COOH-terminal octapeptide (CCK-8) and somatostatin-14 (SS-14) on food intake in dogs were examined by administration of graded doses of these peptides alone and in combination. In animals fasted 19 h, SS-14 (2,000 or 20,000 pmol.kg-1.h-1) had no effect on food intake. In animals fasted 4 h, food intake was not affected by 40 or 400 pmol.kg-1.h-1 SS-14 but was significantly (P less than 0.05) increased by 20% after 4,000 pmol.kg-1.h-1 SS-14. Feeding responses to simultaneous infusions of CCK-8 (50 or 400 pmol.kg-1.h-1) and SS-14 (40, 400, or 4,000 pmol.kg-1.h-1) were determined in animals fasted 4 h. Given alone, the high dose of CCK-8 (400 pmol.kg-1.h-1) significantly (P less than 0.01) depressed food intake by 55%. This effect was blocked by all doses of SS-14. In the absence of CCK-8, SS-14 had no effect except at the highest dose (4,000 pmol.kg-1.h-1), which significantly (P less than 0.01) stimulated food intake by 57%. This effect was blocked by both doses of CCK-8. Simultaneous infusion of lower doses of SS-14 (40 and 400 pmol.kg-1.h-1) and CCK-8 (50 pmol.kg-1.h-1) had no effect on food intake. These results suggest that plasma levels of CCK and SS-14 after a meal are not sufficient alone or in combination to produce satiety.
Mechanism of inhibition of renin response to hypotension by atrial natriuretic factor
Authors: Scheuer D. A. , Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

We have reported that infusion of atrial natriuretic factor (ANF) inhibited the rise in plasma renin activity (PRA) in response to constriction of the abdominal aorta to cause a reduction in renal perfusion pressure (RPP). To evaluate the effect of ANF on neural control of renin release, acute thoracic inferior vena caval constriction (TIVCC) was performed in conscious dogs to reduce arterial pressure by 25% of control and stimulate PRA by a reflex increase in renal nerve activity and a reduction in RPP. Propranolol was used to block neural stimulation of renin release. TIVCC caused significant increases in PRA, plasma aldosterone, arginine vasopressin (AVP), and adrenocorticotropic hormone (ACTH) concentrations. The increase in PRA was significantly reduced by the infusion of either ANF at 20 ng.kg-1.min-1 or propranolol. The combined infusion of ANF and propranolol produced an additive and complete inhibition of the renin response to TIVCC; therefore the effect of ANF is independent of neural stimulation of renin release. ANF at 20 ng.kg-1.min-1 also inhibited increases in aldosterone, AVP, and ACTH, but ANF at 5 ng.kg-1.min-1 only affected the aldosterone response to TIVCC. Therefore ANF inhibits angiotensin II-stimulated aldosterone synthesis and/or secretion at very low doses and at higher doses attenuates reflex increases in AVP and ACTH caused by hypotension.
Suprachiasmatic nuclei influence torpor and circadian temperature rhythms in hamsters
Authors: Ruby N. F. , Ibuka N. , Barnes B. M. , Zucker I.
Published: December 2017

Siberian hamsters were maintained in a short-day photoperiod (8 h light-day) at 15 degrees C; body temperature (Tb) and locomotor activity were telemetrically recorded at 10-min intervals over the course of 5 mo. Animals manifesting repeated torpor bouts (Tb less than 30 degrees C for several hours) were subjected to lesions of the suprachiasmatic nuclei (SCN), pinealectomy, or sham operations. In the 15 wk after surgery, none of the animals with bilateral lesions of the SCN exhibited torpor; circadian Tb and locomotor activity rhythms, as determined by cosinor and power spectral analysis, also were absent in SCN-lesioned hamsters. Pinealectomized animals and brain-lesioned hamsters with intact SCN had normal circadian temperature and activity rhythms and showed torpor for at least 4 wk postsurgically. Expression of torpor and circadian rhythms of Tb and activity are dependent on intact SCN and persist for several weeks in the absence of pineal secretory activity.
Aldosterone binding sites along nephron of Xenopus and rabbit
Authors: Gnionsahe A. , Claire M. , Koechlin N. , Bonvalet J. P. , Farman N.
Published: December 2017

Distal segment of several amphibians exhibits aldosterone-modulated ion transport properties. On the other hand, A6 cells, derived from Xenopus laevis (XL) kidney, are aldosterone sensitive. We examined the distribution of aldosterone binding sites in isolated tubules of XL compared with rabbit. After incubation with 2 nM [3H]aldosterone, microdissected tubular segments from proximal (PT), distal straight segment (DST), and flask cell collecting (CT) tubules from XL and from rabbit cortical thick ascending limb (CTAL), connecting (CNT), and collecting (CCD) tubules were processed for dry film autoradiography. In XL, specific nuclear labeling of type I (mineralocorticoid) sites was restricted to DST. Labeling of type II (glucocorticoid) sites was present all along the tubule. No specific cytoplasmic labeling was observed, except for type II sites in PT. In the rabbit, aldosterone binds to both type I and type II sites in the three tubular segments studied. In these segments, the binding was about fourfold higher than in DST of XL. These results bring direct evidence in designating the distal tubule of amphibians as a target epithelium for aldosterone. In addition, they suggest that A6 cell line may derive from DST of the Xenopus nephron.
Excitatory and inhibitory effects of gastrin peptides on gastric motility in sheep
Authors: McLeay L. M. , Wong M. H.
Published: December 2017

In conscious sheep, tetragastrin, pentagastrin, and synthetic human gastrin I, injected either subcutaneously or intravenously in doses of 156-5,200 pmol/kg body wt, inhibited the vagally dependent cyclical motility of the reticulum and rumen, whereas in vitro pentagastrin (10(-12) to 10(-6) M) had no demonstrable inhibitory or excitatory effects on intrinsically active or quiescent muscle of the reticulum, rumen, and omasal leaves. In vitro pentagastrin (10(-18) to 10(-4) M) stimulated quiescent and intrinsically active longitudinal and circular muscles of the body of the omasum and the body and antrum of the abomasum and potentiated contractile responses of antral muscle to electrical stimulation of intramural cholinergic nerves. Responses in the presence of hexamethonium, atropine, and tetrodotoxin indicated that the excitatory effects on mixed nerve-muscle preparations of omasal and abomasal tissue were mediated both through stimulation of cholinergic neurones and by direct actions on the muscle. In vitro the ovine stomach shows marked regional differences in both its response and sensitivity to gastrin peptides, and their inhibitory effects on reticuloruminal motility in vivo appear to be other than direct.
Baroreceptor activation or glutamate coinjection facilitates depressor responses to ANF microinjection into NTS
Authors: McKitrick D. J. , Calaresu F. R.
Published: December 2017

As microinjection of atrial natriuretic factor (ANF) into the nucleus of the solitary tract (NTS) has been shown to elicit depressor responses [D. J. McKitrick and F. R. Calaresu. Am. J. Physiol. 255 (Regulatory Integrative Comp. Physiol. 24): R182-R187, 1988], we investigated the possibility that these responses might be facilitated either by electrical stimulation of arterial baroreceptor fibers in the aortic depressor nerve (ADN) or by simultaneous microinjection of L-glutamate (Glu) into the same sites in the NTS. Male Wistar rats (n = 51) were anesthetized with urethan (1.4 g/kg ip), artificially ventilated, and the dorsal medulla was exposed. The ADN was isolated, cut distally, and the central end was placed on bipolar stimulating electrodes. Threshold doses of 10(-7) M ANF microinjected into the NTS were combined with threshold electrical stimulation of the ADN (n = 37) or threshold doses of 0.13-0.5 M Glu (n = 14) microinjected into the NTS. There was a significant interaction between ANF microinjection and ADN stimulation in producing changes in mean arterial pressure (MAP) and heart rate [HR; P less than 0.05; -20.2 +/- 2.3 (SE) mmHg and -30.8 +/- 6.9 (SE) beats/min, respectively; n = 18]. There was also a significant interaction between ANF and Glu in producing changes in MAP and HR [P less than 0.05; -16.3 +/- 1.8 (SE) mmHg and -15.0 +/- 3.0 (SE) beats/min, respectively; n = 8]. These results indicate that ANF influences neurons in the NTS, which are also influenced by activation of arterial baroreceptors, and ANF and Glu interact in the NTS to produce facilitated cardiovascular responses.
Control of canine ACTH by corticosteroids: an integral feedback effect of steroids
Authors: Keller-Wood M.
Published: December 2017

These experiments were designed to test whether the pattern of change in plasma corticosteroid or the total corticosteroid dose is important in determining the degree of inhibition of adrenocorticotropic hormone (ACTH) responses to stress by corticosteroid intermediate-delayed feedback. Five conscious dogs were studied. The ACTH response to induced hypoglycemia was measured after no prior corticosteroid feedback signal or after a corticosteroid feedback signal produced by infusion, two bolus injections, or three bolus injections of cortisol and corticosterone. The total corticosteroid dose (45 micrograms/kg) and the total interval of steroid treatment (60-30 min before hypoglycemia) were the same in all three cases of corticosteroid treatment. Changes in plasma glucose concentration during induced hypoglycemia were not altered by corticosteroid treatment. The plasma ACTH response to hypoglycemia was inhibited by all three patterns of treatment with corticosteroids. The inhibition of ACTH response was not significantly altered among the patterns of treatment with corticosteroids. The data suggest that the integrated (total) or the mean change in plasma corticosteroid concentration over time determines the degree of inhibition of stimulated ACTH in this time domain.
Measurement of hepatocellular function, cardiac output, effective blood volume, and oxygen saturation in rats
Authors: Hauptman J. G. , DeJong G. K. , Blasko K. A. , Chaudry I. H.
Published: December 2017

The available techniques do not permit the measurement of hepatocellular function, cardiac output, effective blood volume, and oxygen saturation in small animals without the need of blood or tissue sampling. We present methodology that permits us to measure the above variables in the rat. Multiple doses of indocyanine green (ICG; 0.16-2.6 mg/kg) were given to pentobarbital-anesthetized rats, and [ICG] was continuously measured by an in vivo hemoreflectometer. Initial velocity of clearance (Vo) was determined from the [ICG] vs. time plot for each dose by nonlinear regression. The maximal velocity of clearance (Vmax; indicating hepatocellular function) was calculated. Vmax was 1) accurately determined using two, three, or four doses of ICG; 2) it was 1.09 +/- 0.16 mg.kg-1.min-1, not different from the Vo of the near-saturating dose of 25 mg/kg; and 3) it decreased after partial hepatectomy. Cardiac output was 41.89 +/- 1.46 ml.100 g-1.min-1, effective blood volume was 6.12 +/- 0.34 ml/100 g, and oxygen saturation was 92 +/- 2%. These methodologies may prove useful in the evaluation of hepatocellular dysfunction and hemodynamic parameters in the rat during and after various diseased states.
Mechanisms of integumental amino acid transport in marine bivalves
Authors: Wright S. H. , Pajor A. M.
Published: December 2017

The marine bivalve integument accumulates amino acids from seawater at rates that can significantly supplement other nutritional strategies. Reviewed here are studies that used both intact bivalve gill tissue and membranes isolated from gills to examine the mechanism of integumental transport. The evidence supports a model for secondary active transport in which an inward flux of Na+ down its electrochemical gradient provides the energy to support uptake of amino acids. Indeed, the Na+-cotransport paradigm appears to be a ubiquitous strategy by which animal cells energize uphill transport of organic solutes. What appears to distinguish integumental processes from others are the conditions under which they must routinely work: exposed to ambient concentrations of substrate of less than 1 microM and to cytoplasmic concentrations that exceed 0.1 M, transport of amino acid occurs against gradients that can exceed 10(6) to 1! Somewhat paradoxically, these transporters, which are characterized by an extremely high affinity for amino acid (Kt values of congruent to 5 microM), work so well because they have a low affinity for Na+; low cytoplasmic Na+ concentrations prevent the system from acting as an avenue for efflux, whereas the very high concentrations of Na+ in seawater are adequate to fully activate the influx mode of operation. The combination of these kinetic characteristics results in a class of transporters that makes efficient use of the scarce nutritional resource represented by dissolved organic material in near-shore waters.
Sarcoplasmic reticulum, potassium, and cardiac force in rainbow trout and plaice
Authors: el-Sayed M. F. , Gesser H.
Published: December 2017

The role played by the sarcoplasmic reticulum in force development and in cellular Ca2+ balance and its dependence on extracellular K+ were examined in heart ventricular tissue of rainbow trout and plaice. Compared with the steady-state twitch at a stimulation rate of 0.2 Hz, a 30-s rest led to a similar increase in twitch force in trout heart, regardless of whether [K+] was 2.5 or 5 mM. At 5 mM (but not at 2.5 mM) post-rest potentiation increased with increasing rest periods (from 30 to 900 s). These post-rest potentiations were removed or transformed into a loss of force by 10 microM ryanodine or 8 mM caffeine. In the plaice heart, where the sarcoplasmic reticulum is claimed to be sparse, the post-rest potentiation and the influence of ryanodine were small. The Ca2+ uptake measured during 5 min with 45Ca in the trout heart was higher in 5 than in 2.5 mM K+, regardless of the concomitant stimulation rate. This effect of K+ was removed by 10 microM ryanodine. The twitch force after 5 min of rest correlated significantly with the Ca2+ uptake, whereas the twitch force developed at a rate of 0.2 or 1.0 Hz did not. In conclusion, an elevation of K+ appears to stimulate the Ca2+ uptake of the sarcoplasmic reticulum. The twitch force after prolonged rest seems to relate to the Ca2+ contained in this organelle, whereas this does not apply to the twitch force developed at more physiological rates (0.2 or 1 Hz).
Physiological role of HMG-CoA reductase in regulating egg production by Schistosoma mansoni
Authors: Vandewaa E. A. , Mills G. , Chen G. Z. , Foster L. A. , Bennett J. L.
Published: December 2017

Pathological lesions observed in humans infected with Schistosoma mansoni are due to the eggs produced by the female parasite. Mevinolin, a potent inhibitor of the enzyme hydroxymethylglutaryl-CoA (HMG-CoA) reductase, blocks egg production by this parasite. In this report, we demonstrate that cholesterol precursors, mevalonate and farnesol, stimulate egg production by the female parasite and that these precursors can reverse the mevinolin-induced inhibition of egg production. Because the parasite cannot synthesize cholesterol, we incubated parasites in a culture media containing radiolabeled acetate with and without mevinolin. We isolated nonsterol lipids from the parasite and observed that mevinolin dramatically reduced the conversion of acetate into the polyisoprenoid (dolichols) lipids of the parasite. Dolichols and other nonsterol lipids did not stimulate egg production. HMG-CoA reductase activity was observed in homogenates of the parasite and was inhibited by mevinolin (Ki = 52 nM), but its activity was tripled when the parasite was chronically exposed to low doses of the drug. Parasites with increased reductase activity produced five to six times more eggs. Lastly, chronic administration of large doses of mevinolin to infected mice resulted in a marked reduction of the pathology associated with the infection. These results suggest that egg production in S. mansoni is associated with the parasite's HMG-CoA reductase activity and that a nonsterol lipid produced in the biochemical pathway regulated by this enzyme stimulates egg production.
Blood volume restitution after hemorrhage in the newborn lamb
Authors: Block S. M. , Pixley J. E. , Wray A. H. , Ray D. , Barnes K. D. , Engstrom P. C. , Rose J. C.
Published: December 2017

Blood volume restitution after hemorrhage was investigated in lambs in the first week of life. Two groups of nonsplenectomized lambs were bled 10 and 20% of their blood volume at 2%/min while being suspended horizontally in a sling with their legs dependent, and a third group was bled 20% while lying down. Blood pressure fell 8% in the lambs bled both 10 and 20% while lying down and 44% in those bled 20% while being suspended. Blood volume was completely restored in all three groups by 5 h after the hemorrhage, the rate of restitution being equal among the groups. The initial phase of restitution was slower when the lambs were bled while lying down. Vasopressin levels were increased only in the lambs bled 20% of their blood volume while being suspended. Plasma renin activity increased similarly in all groups. Hemorrhage increased plasma glucose but did not change plasma protein and serum osmolality. We conclude that lambs bled up to 20% of blood volume restitute relatively quickly at a rate independent of the volume shed. The position of the animal affects the degree of hypotension, the levels of vasopressin, and the rate of the initial phase of volume restoration.
Dependent effect of drinking volume on vasopressin but not atrial peptide in humans
Authors: Williams T. D. , Seckl J. R. , Lightman S. L.
Published: December 2017

The act of drinking causes a fall in plasma arginine vasopressin (AVP) concentration that precedes changes in plasma osmolality. To investigate the specificity of this drinking stimulus on hormone secretion, six volunteers (5 male, 1 female, aged 22-39 yr) were water deprived for 36 h and then drank 15 ml/kg water at 10-12 degrees C using 15-20 swallowing actions/min over 3.5 +/- 0.5 min (mean +/- SE). This caused a fall in plasma AVP from 4.5 +/- 0.7 to 3.2 +/- 0.5 pmol/l (P less than 0.05) and in thirst (by 5.7 +/- 0.6 on a 10-cm linear analog scale) (P less than 0.05) 5 min after drinking. No significant changes occurred in mean arterial pressure, heart rate, or plasma atrial natriuretic peptide (ANP) concentration. A second study was undertaken to determine whether the reflex inhibition of AVP secretion is activated simply by the act of swallowing regardless of the volume of liquid consumed. The six volunteers were water deprived for 36 h and then sipped and swallowed 1 ml/kg water at 10-12 degrees C using 15-20 swallowing actions/min over 3.0 +/- 0.1 min. There was no change in plasma AVP concentration, although thirst was reduced by 2.3 +/- 0.6 (P less than 0.05) at 5 min. Plasma AVP 10 min after sipping and swallowing (4.2 +/- 0.8 pmol/l) was significantly greater than at 10 min after drinking 15 ml/kg (2.8 +/- 0.5 pmol/l) (P less than 0.05) despite the fact that plasma osmolality at this stage was similar in both studies. We conclude that the drinking-mediated reflex inhibition of AVP secretion in humans is dependent on swallowing an adequate volume and is not accompanied by changes in hemodynamics or in plasma ANP concentration.
Role of the ventral surface of medulla in the generation of Mayer waves
Authors: Haxhiu M. A. , van Lunteren E. , Deal E. C. , Cherniack N. S.
Published: December 2017

The regions adjacent to the ventrolateral medullary surface (VMS) play critical roles in the regulation of respiratory and cardiovascular function. Furthermore, these areas seem to be important sites for the integration of afferent inputs from certain sensory organs and the source of excitatory inputs to preganglionic sympathetic and parasympathetic neurons. To determine whether the VMS contributes to the generation of nonrespiratory-related periodic oscillations of arterial blood pressure (Mayer waves), excitatory substances, such as N-methyl-D-aspartate (NMDA), cholinergic agonists, and neuropeptides (substance P, neurokinin A, neurotensin), were applied topically to the intermediate area of VMS in anesthetized cats. In addition, the effects of application of lidocaine and inhibitory substances (benzodiazepines) on Mayer waves were studied. After application of excitatory substances to the VMS, we observed oscillations of arterial blood pressure, recurring with a period of 17.8 +/- 10 (SE) s, which had similar characteristics as the Mayer waves recorded during hypercapnia or hypoxia. In addition, cyclic changes in phrenic nerve activity and tracheal tone occurred with the same periodicity as arterial blood pressure oscillation. Application of lidocaine or benzodiazepines on the intermediate area of the VMS abolished Mayer waves observed during hypercapnia, hypoxia, or application of excitatory substances. These findings show for the first time that the VMS can be considered as one of several synaptic relays involved in the generation of arterial blood pressure oscillation, as well as the cyclic changes in phrenic nerve activity and tracheal smooth muscle tone that occur simultaneously.