bluuebunny/crossref_metadata_2025 huggingface dataset:
Amniotic fluid volume and fetal swallowing rate in sheep
Authors: Tomoda S. , Brace R. A. , Longo L. D.
Published: December 2017

To investigate amniotic fluid (AF) dynamics and volume regulatory mechanisms, we measured the concentration of radioiodinated (125I) serum albumin (RISA), 51Cr-labeled red blood cells (Cr-RBC), and 103Ru-labeled microspheres after injection into the amniotic cavity and determined AF volume and fetal swallowing rate in 22 singleton pregnant sheep. Under normal conditions 2-3 h were required for complete mixing of RISA and Cr-RBC within AF; however, when the fetus was dead only 3-5 h were required. AF volume of 17 sheep on the 5th postoperative day averaged 975 +/- 128 ml by RISA and 986 +/- 130 ml by Cr-RBC. AF volume determined with RISA and Cr-RBC correlated well. In contrast, AF volume measurement with microspheres produced erratic results. The disappearance rate of the labels in 17 ewes on the 5th postoperative day averaged 4.9 +/- 0.7%/h for RISA and 5.5 +/- 0.7 for Cr-RBC, and the calculated rates of fetal swallowing were 935 +/- 78 ml/day by RISA and 1,085 +/- 102 by Cr-RBC. In dead fetuses the disappearance rates were almost zero, suggesting that the labels disappear mainly by swallowing. Absolute volume swallowed and swallowed volume per fetal weight correlated with gestational age. AF volume correlated with fetal weight. Radiolabeled albumin or red blood cells may be used to simultaneously measure amniotic fluid volume and the rate of fetal swallowing. Furthermore it appears that fetal swallowing increases with gestational age.
Time-dependent effect of insulin in suprachiasmatic nucleus on blood glucose
Authors: Mori T. , Nagai K. , Hara M. , Nakagawa H.
Published: December 2017

Studies were made on the effects of insulin (30 or 300 microU) injected into the suprachiasmatic nucleus (SCN) of the hypothalamus on the plasma glucose and insulin concentrations in pentobarbital-anesthetized rats, which had been kept under 12:12 light-dark conditions. Insulin injection caused a decrease in the plasma glucose concentration in the light period but an increase in the dark period, these changes being significant within 2 min after injection. Insulin injection also caused a decrease in plasma insulin concentration in the light period but a tendency for its increase in the dark period. Intraperitoneal injection of insulin at the same dose did not affect the plasma glucose or insulin concentration in either the light or dark period. Insulin injection into the SCN decreased glycogen phosphorylase a activity but increased glycogen synthase I activity in the liver in the light period, but the insulin injection did not affect the activities of these enzymes in the dark period. Lesions including bilateral SCN completely eliminated the responses of the plasma glucose and insulin concentrations to insulin injection both in the light and dark periods. These findings suggest that insulin injection into the SCN causes time-dependent changes in plasma glucose through changes in activities of glycogen metabolizing enzymes in the liver in the light period but through other mechanisms in the dark period.
Recovery of lipid mass after removal of adipose tissue in ground squirrels
Authors: Dark J. , Forger N. G. , Stern J. S. , Zucker I.
Published: December 2017

Male golden-mantled ground squirrels subjected to surgical removal of substantial portions of inguinal, retroperitoneal, and epididymal adipose tissue [lipectomy (Lipx)] or to sham lipectomy (Sham) during the early prehibernatory fattening phase did not differ in body mass 4 mo later at the time of their annual body weight peaks. Body mass restoration by Lipx squirrels was achieved without compensatory increases in food intake. There was little or no regeneration of epididymal adipose tissue, complete regeneration of the retroperitoneal depot, and an increase in mass of subcutaneous fat of Lipx animals. Epididymal and retroperitoneal adipocytes were equivalent in size in Sham and Lipx squirrels; adipocytes in subcutaneous fat were 20% larger in Lipx than in Sham animals. Generation of the annual body mass cycle of this ground squirrel involves active regulation of the lipid mass.
Control of ACTH and vasopressin in neurohypophysectomized conscious dogs
Authors: Raff H. , Merrill D. , Skelton M. , Cowley A. W.
Published: December 2017

Adrenocorticotropin (ACTH), cortisol, and vasopressin responses to clamped decreases in blood pressure (MAP) and to ovine corticotropin-releasing factor (CRF) infusion (20 ng X kg-1 X min-1) in intact and neurohypophysectomized (NHX) conscious dogs were examined. Mean arterial blood pressure was decreased 28 mmHg by a controlled infusion of sodium nitroprusside. Hypotension induced large increases in ACTH (peak 164 +/- 25 pg/ml), cortisol (peak 12.5 +/- 2.5 micrograms/dl), and vasopressin (peak 221 +/- 64 pg/ml) in intact (n = 7) dogs. NHX (n = 7) significantly attenuated these responses to hypotension. CRF infusion induced increases in ACTH similar in intact (n = 4) and NHX (n = 4) dogs. However, cortisol responses were significantly attenuated by NHX. Interestingly, CRF infusion induced small but significant increases in vasopressin from 3.0 +/- 1.1 to 8.1 +/- 2.0 pg/ml. We conclude that NHX attenuates ACTH and vasopressin responses to hypotension and cortisol responses to CRF-induced increases in ACTH. CRF seems to stimulate vasopressin release.
Area postrema mediates tumor effects on food intake, body weight, and learned aversions
Authors: Bernstein I. L. , Treneer C. M. , Kott J. N.
Published: December 2017

Growth of a Leydig cell [LTW (m)] tumor in rats is associated with the development of significant hypophagia and severe aversions to the available diet. Lesions of the area postrema and nearby caudal medial area of the solitary tract were found to block or greatly attenuate the anorexia and food aversions that typically accompany the growth of this tumor. Thus these tumor-induced symptoms may be associated with the detection of blood-borne chemicals by cells located in or near the area postrema.
Vascular basis for regulation of nasal heat exchange in reindeer
Authors: Johnsen H. K. , Blix A. S. , Jorgensen L. , Mercer J. B.
Published: December 2017

A hypothesis for the operation and control of nasal heat exchange in reindeer is presented that originated from studies of the nasal vascular anatomy and has been supported by physiological measurements as well as test experiments on a physical prototype model of the reindeer nose. A central theme of our hypothesis is that the nasal mucosa possesses arterial and venous retia that communicate by way of capillaries and arteriovenous anastomoses. During heat conservation the blood runs countercurrent in these retia, whereby a temperature gradient along the nasal mucosa can be maintained. During heat dissipation, however, the retia are perfused unidirectionally in the anterior direction, whereby the temperature gradient along the nasal mucosa is reduced and heat loss facilitated. In this situation cooled venous blood, routed by way of the dorsal nasal vein, may be distributed either to the caval veins directly, for general body cooling, or, by way of the cavernous sinus that encases the carotid rete, for selective cooling of the brain.
Selective destruction of renal afferent versus efferent nerves in rats
Authors: Lappe R. W. , Webb R. L. , Brody M. J.
Published: December 2017

Previous anatomic studies demonstrated that afferent projections from the left kidney of the rat passed predominantly through the dorsal roots of spinal segments T10-L1. Selective destruction of renal afferent nerves, without damaging renal efferent nerves, was attempted by severing the dorsal roots carrying the afferent fibers. In anesthetized rats, the dorsal left side of the spinal cord was exposed through a partial laminectomy at vertebral sections T10-L1; and the dorsal roots were carefully isolated and cut. Four to ten days after surgery, arterial pressure and hindquarter vascular resistance were maximally reduced by 14 +/- 2 mmHg and 42 +/- 1%, respectively, during electrical stimulation of renal afferent fibers in sham-operated rats. In rats with selective dorsal rhizotomy no significant changes in arterial pressure or hindquarter vascular resistance were observed after renal afferent nerve stimulation. Renal vasoconstrictor responses to electrical stimulation of the left greater splanchnic nerve or posterior hypothalamic area were not different between sham and rhizotomized rats. These data demonstrate that severing dorsal roots T10-L1 cause a functional afferent denervation of the kidney, without impairing renal efferent nerve function.
Estimate of muscle-shortening rate during locomotion
Authors: Lindstedt S. L. , Hoppeler H. , Bard K. M. , Thronson H. A.
Published: December 2017

All skeletal muscle can produce roughly the same maximal cross-sectional force; however, the power (energy X time-1) required to develop and maintain that force increases with increasing contraction velocity. Thus the rate of muscle tension development may be of primary importance in setting the energy demand of contracting muscle. We have estimated the rate of muscle shortening during terrestrial locomotion in mammals as a function of body mass. The rate of muscle shortening of the knee extensors is much faster in small than large mammals, scaling in proportion to the -0.23 power of mass. This exponent suggests a constant body size-independent relation among skeletal muscle: O2 consumption, mitochondria content, myosin ATPase activity, and in vivo shortening velocity.
Corticosteroids and plasma restitution after hemorrhage and hypothalamic lesions
Authors: Bealer S. L.
Published: December 2017

The effects of electrolytic ablation of the anteroventral portion of the third ventricle (AV3V) on plasma volume (PV) restitution and adrenal corticosteroid responses after hemorrhage were determined. After recovery from AV3V ablation or control surgeries, animals were implanted with a catheter in the femoral artery. PV was determined before and either 2 or 24 h after moderate hemorrhage (1.4% body wt for controls; 1.3% body wt for AV3V lesion) by calculating dilution of 125I-labeled serum albumin. Other rats with AV3V lesions and control animals were used to measure concentrations of renin, aldosterone, and corticosterone 0.5 or 2 h after similar hemorrhage. The percent of shed PV restored was similar in rats with AV3V lesions and control-operated animals both 2 and 24 h after hemorrhage. Furthermore, the restitution of plasma protein mass was not different. Rats with AV3V lesions showed a similar increase in plasma renin concentration after hemorrhage, but they showed a smaller increase in the concentration of plasma aldosterone and no increase in the concentration of plasma corticosterone. These data demonstrate that electrolytic ablation of AV3V periventricular tissue does not alter either the short- or long-term phase of PV restitution, even though concentrations of plasma corticosterone are not increased.
Prostaglandin E2 and muscle proteolysis: effect of burn injury and cycloheximide
Authors: McKinley C. J. , Turinsky J.
Published: December 2017

Rats were subjected to a single hindlimb scald, and 3 days later soleus muscles from the burned and contralateral unburned hindlimbs were studied in vitro. Burned limb muscle released 354% more prostaglandin E2 (PGE2) and 119% more tyrosine than the contralateral uninjured counterpart. Neither the rate of net proteolysis in the uninjured muscle nor the stimulated net proteolysis in the burned limb muscle could be reduced by 90% inhibition of PGE2 production with aspirin or indomethacin. Inhibition of tissue protein synthesis with 5 X 10(-5) M cycloheximide stimulated tyrosine release by soleus muscles of both hindlimbs, but the increment in the burned limb muscle was 167% greater than in the contralateral uninjured counterpart. Concomitantly, cycloheximide decreased PGE2 releases by injured and uninjured muscles 90 and 73%, respectively. This previously unrecognized action of cycloheximide was investigated in soleus muscles of normal uninjured rats. It was found that 1 X 10(-6) M cycloheximide produces a 70% inhibition of muscle PGE2 release and increasing the concentration of inhibitor up to 500-fold does not further decrease PGE2 production. Cycloheximide acts by reducing the availability of endogenous arachidonic acid for PGE2 synthesis.
Interaction between CRF and angiotensin II in control of ACTH and adrenal steroids
Authors: Keller-Wood M. , Kimura B. , Shinsako J. , Phillips M. I.
Published: December 2017

These experiments were designed to test for interactions between plasma angiotensin II (ANG II) and corticotropin-releasing factor (CRF) in the control of plasma adrenocorticotropin (ACTH), aldosterone, and corticosteroids, mean arterial pressure (MAP), and heart rate (HR) in conscious dogs. Five trained dogs with exteriorized carotid arteries were studied. Each dog was infused with saline and with CRF at three rates (2.5, 5, and 10 ng X kg-1 X min-1) and ANG II at three rates (5, 10, and 20 ng X kg-1 X min-1) for 60 min. The same animals were also coinfused with 10 ng X kg-1 X min-1 ANG II at each rate of CRF infusion and with 10 ng CRF X kg-1 X min-1 at each rate of ANG II infusion. Infusion of ANG II alone caused dose-related increases in aldosterone, corticosteroids, and MAP but did not alter ACTH or HR. Infusion of CRF alone increased ACTH, aldosterone, and corticosteroids but not MAP or HR. Coinfusion of CRF and ANG II caused ANG II dose-related ACTH responses but did not alter the sensitivity of the ACTH responses to CRF. Thus it appears that ANG II alone does not stimulate ACTH release but requires increased CRF concentrations to effect ACTH release.
Absence of fast negative feedback control of ACTH and renin in fetal and adult sheep
Authors: Wood C. E.
Published: December 2017

Fetal adrenocorticotropin (ACTH) and renin secretion are increased by a variety of stimuli and decreased by cortisol negative feedback inhibition. However, the time courses of these interactions are unknown. The present studies were designed to test for rapid feedback negative suppression of ACTH and renin secretion in fetal and adult sheep. In chronically catheterized fetal sheep, ACTH and renin secretion were stimulated by intravenous infusion of sodium nitroprusside, a vasodilator drug. Vehicle or cortisol, infused at rates of 1, 2, or 4 micrograms/min for 2 min before and during the infusion of nitroprusside did not significantly alter the fetal ACTH or renin responses to nitroprusside. In five nonpregnant ewes, chronically prepared with skin loops containing the carotid arteries, nitroprusside (20 micrograms X kg-1 X min-1) was infused beginning 2 min after infusion of vehicle or cortisol (3.5 or 7 micrograms X kg-1 X min-1). Cortisol infusion produced a rising plasma cortisol concentration similar to that after stress but did not alter the magnitude of the ACTH response to nitroprusside. The results indicate that cortisol-induced suppression of ACTH secretion does not occur rapidly in the fetal or adult sheep and that the cortisol-induced suppression of fetal plasma renin activity is a slow process.
Regulation of hepatic glucose output during exercise by circulating glucose and insulin in humans
Authors: Jenkins A. B. , Furler S. M. , Chisholm D. J. , Kraegen E. W.
Published: December 2017

We have tested the hypothesis that hepatic glucose output (Ra) during exercise in humans is subject to feedback control by circulating glucose within a control range that is determined by the circulating insulin concentration. Three exercise protocols based on 60-min cycle ergometer exercise at 55% maximal O2 consumption were used: 1) control, 2) insulin infusion with a euglycemic clamp, and 3) insulin infusion with a fixed-rate glucose infusion. Ra was measured using a constant infusion of [3H]glucose. During the glucose clamp there was no Ra response to exercise. There were significant inverse relationships between Ra and plasma glucose during control exercise (r = -0.73, P less than 0.001) and exercise with fixed-rate glucose and insulin infusion (r = -0.96, P less than 0.001). During the fixed-rate glucose and insulin infusion, plasma glucose fell from the commencement of exercise but stabilized at a lower level. These results are interpreted in terms of a simple difference controller where Ra is proportional to the deviation of plasma glucose from a defined set point. Insulin affects Ra and regulates the steady-state glucose level by altering the sensitivity of this control system.
Diffusion permeability of cyanocobalamin in human placenta
Authors: Willis D. M. , O'Grady J. P. , Faber J. J. , Thornburg K. L.
Published: December 2017

The molecular weight of cyanocobalamin is well suited to distinguish the two patterns of size discrimination found in the hemochorial and epitheliochorial placentas. The concentrations of cyanocobalamin that were used ensured that nondiffusional transport was negligible, and experiments on guinea pigs confirmed that the diffusion permeabilities measured with cyanocobalamin were the same as those expected for inert hydrophilic substances of similar molecular weight. All human studies were performed on volunteers who were scheduled for elective cesarean section under spinal or epidural anesthesia. Endogenous plasma concentrations of cobalamin were measured in 10 pregnant volunteers and their newborns. Ten additional volunteers were given 1 mg of cyanocobalamin by intramuscular injection 44 min before delivery. Placental permeability, calculated as the ratio of fetal uptake and the concentration-time integral between maternal and fetal plasmas, was 14.3 microliter X min-1 X g placental wt-1. The permeability of the human placenta parallels that of the histologically similar guinea pig placenta, at a slightly higher level, up to molecular weights of 1,355.
Enhanced noradrenergic activity in kidney of Brattleboro rats with diabetes insipidus
Authors: Kline R. L. , Patel K. P. , Mercer P. F.
Published: December 2017

The possibility that sympathetic nervous system activity may be altered in Brattleboro rats with diabetes insipidus (DI) was studied using the norepinephrine (NE) turnover technique. Female DI and Long-Evans rats were used. NE turnover in peripheral organs was calculated by measuring the decline in tissue [NE] after inhibition of tyrosine hydroxylase with alpha-methyltyrosine. NE turnover was increased significantly in the kidney of DI rats but was not significantly altered in other peripheral organs examined (heart, duodenum, skeletal muscle). Both NE and epinephrine concentrations in the adrenal gland were significantly higher in the DI rats. Treatment of DI rats for 7 days with vasopressin tannate (Pitressin, 100 mU/100 g) or 1-deamino-[8-D-arginine] vasopressin (DDAVP, 250 ng X kg-1 X day-1) reversed the changes in renal NE turnover and also decreased the turnover in other tissues. The results of these studies suggest that, compared with Long-Evans rats, DI rats have a selective increase in NE turnover in the kidney and the potential to release more catecholamines from the adrenal glands. The apparently nonspecific effect of antidiuretic therapy on NE turnover in DI rats is probably mediated by the epithelial receptor for vasopressin, because both Pitressin and DDAVP produced similar results.
Renal proximal tubule of flounder. I. Physiological properties
Authors: Beyenbach K. W. , Petzel D. H. , Cliff W. H.
Published: December 2017

The proximal segment of the winter flounder, Pseudopleuronectes americanus, was investigated. Isolated tubules net secrete fluid, although at low rates, 37 pl X min-1 X mm-1. The dominant ions in secreted fluid are Na and Cl, with [Cl] significantly higher than in the bath. Mg and SO4 concentrations in secreted fluid are more than 10-fold greater than in the bath. The transepithelial voltage (-1.9 mV) and resistance (26 omega X cm2) indicate an electrically leaky epithelium, and transepithelial diffusion potentials suggest the Na selectivity of the paracellular pathway. Transepithelial electrochemical potentials point to active transport of Mg, SO4, and probably also Cl and to transepithelial equilibrium of Na. Failure to observe any secretory transport in tubules perfused in vitro at the commonly used perfusion rates illustrates the necessity of low, preferably subnanoliter, perfusion rates in detecting and studying low-capacity epithelial transport systems by the method of Burg.
Physical and metabolic correlates of sexual inactivity in aged male mice
Authors: Bronson F. H. , Desjardins C.
Published: December 2017

The object of this study was to identify specific syndromes of sexual loss in aged male mice. Emphasis was placed on uncovering syndromes that involve physical as opposed to motivational deterioration. To this end, 30-mo-old CBF1 male mice were subjected to a large battery of tests, each of which was designed to detect sensory, neuromuscular, metabolic, or sexual deficits. Over 50 measures were obtained on each of 63 males. A group of 23 6-mo-old males were studied simultaneously to establish base lines of normal performance. Old males routinely showed evidence of deterioration in some tests but not in others. Some old males actually performed as well as young males in some tests, including an exhaustive test of sexual capacity. Ten nonsexual measures were significantly correlated with sexual activity. Further analyses then suggested seven distinct syndromes of reproductive loss, each with its own specific cause and unique manifestation. Six of these syndromes manifested themselves as behavioral deficits; one was related to a failure to eject sperm. Our data also suggest the possible existence of two more syndromes, but these remain to be verified more fully. Although additional syndromes undoubtedly will be found in male mice, the present testing paradigm can be exploited to isolate and study the functional bases of each of these specific facets of reproductive loss.
Circannual variations in circadian rhythms of ground squirrels
Authors: Lee T. M. , Carmichael M. S. , Zucker I.
Published: December 2017

There was a circannual rhythm in the times of activity onset (psi o) and activity termination (psi T) and in the duration of the active phase (alpha) in female ground squirrels (Spermophilus lateralis) maintained in a light-dark (LD) 14:10 photoperiod for 22 mo. Activity onset occurred 2.3 h after light onset in the 4 mo before estrus, 0.5 h before light onset during the month encompassing estrus, and progressively later during each of the ensuing 4 mo. Termination of activity occurred later during the month of estrus than in the 4 mo preceding estrus; alpha nearly doubled during the month of estrus and decreased gradually over the next 3 mo. The psi o and psi T remained entrained to the daily illumination cycle, but the phase angles of activity onset and offset and the duration of the active phase varied seasonally and recurred with a circannual period of 9-11 mo. The LD 14:10 photoperiod entrained the circadian activity rhythm throughout the year; however, circannual variations in activity as well as in estrus and body mass were not entrained by this photoperiod but free-ran with periods of less than 12 mo.
Effects of exercise training on regional adipose tissue metabolism in pregnant rats
Authors: Savard R. , Palmer J. E. , Greenwood M. R.
Published: December 2017

To investigate the effects of intense exercise training on maternal adiposity and fetal development, normal lean Zucker (Fa/Fa) rats were divided into three groups: control nonpregnant (CNP), control pregnant (CP), and exercise-trained pregnant (TRP). Trained rats swam three continuous hours per day, 6 days/wk, throughout pregnancy. Food efficiency increased with pregnancy, the highest values being observed during the last trimester of the gestation period. On day 21, pup number, weight, and body composition were similar for CP and TRP. By day 21 of gestation, in both TRP and CP rats, inguinal adipose tissue weight, cell size, and lipoprotein lipase (LPL) activity increased; although TRP values were smaller (P less than 0.05). In CP rats, parametrial and retroperitoneal adipose tissue weights, cell size, and LPL activities increased throughout pregnancy, whereas TRP values were similar to CNP (P less than 0.05). Parametrial fat cell lipolysis showed, however, no effect of training. These results indicate that the extensive energy expenditure occurring during endurance training selectively reduced the dams' adiposity in a regionally specific fashion without any apparent alteration in pup development. The increased substrate utilization required by training during pregnancy did not, however, modify fat cell lipolysis but rather prevented lipid filling through suppression of LPL activity of some depots.
Ionic requirements of peritubular taurine transport in Fundulus kidney
Authors: Wolff N. A. , Perlman D. F. , Goldstein L.
Published: December 2017

A peritubular mechanism for active taurine uptake, similar to that previously found in the flounder, was demonstrated in killifish (Fundulus heteroclitus) teased renal tubules. Other beta-amino acids and glycine inhibited taurine transport. Uptake exhibited a nearly absolute requirement for external Na+. The stoichiometric relationship between Na+ and taurine was found to be 2:1. Medium Cl- markedly stimulated the Na+-dependent taurine uptake, but none of the other small monovalent anions tested (NO3-, Br-, SCN-) could substitute for Cl- in activating taurine transport. Cl- replacement resulted in a significant decrease in V max, whereas the affinity of the carrier for taurine appeared to be unaffected. In the absence of Cl- the Na+ dependence of taurine influx was reduced to a stoichiometric relationship of 1.4 Na+:1 taurine, indicating an effect of Cl- on the binding of Na+ to the transport system. A model for Na+ -Cl- -taurine cotransport is presented.
Medullary lesions eliminate ACTH responses to hypotensive hemorrhage
Authors: Darlington D. N. , Shinsako J. , Dallman M. F.
Published: December 2017

The adrenocorticotropin (ACTH) response to hemorrhage (15 ml . kg-1 . 3 min-1) before and 30 min or 4 days after placement of bilateral electrolytic lesions of the nucleus tractus solitarius (NTS) were examined in anesthetized and in conscious rats. Two groups of rats were anesthetized with pentobarbital sodium (45 mg/kg). Femoral arterial and venous cannulas were placed acutely in the anesthetized group and chronically in the conscious group. Each rat received a hemorrhage 30 min before and 30 min after NTS lesions (in the anesthetized group) and 1 day before and 4 days after NTS lesions (in the conscious group). Plasma ACTH was determined before and 20 min after hemorrhage, and mean arterial blood pressure and heart rate were measured throughout. The baroreceptor reflex (bradycardia caused by a phenylephrine-induced rise in MABP) was determined 5 min before hemorrhage (in the anesthetized group) and 1 day before hemorrhage (in the conscious group) to assess the effectiveness of lesion. Hexamethonium was given to rats that developed hypertension postlesion and to sham-lesioned controls. Plasma ACTH did not increase after hemorrhage 30 min or 4 days after NTS lesions when compared with the other groups (sham, sham with hexamethonium, and missed lesion) and to prelesion controls. Also, lesions of the NTS had no effect on resting ACTH levels 4 days later. Mean arterial pressure and heart rate decreased during hemorrhage to similar extents before and after lesions in all groups. This study demonstrates that lesions of the NTS eliminate the ACTH response to hemorrhage immediately and 4 days after the lesions but have no effect on resting ACTH levels. The result suggests that the NTS is an essential part of the neural pathway for ACTH release after hemorrhage.
Effect of synthetic atrial natriuretic factor on aldosterone secretion in the rat
Authors: Vari R. C. , Freeman R. H. , Davis J. O. , Villarreal D. , Verburg K. M.
Published: December 2017

Direct in vivo measurements of aldosterone secretion were made before and after infusion of synthetic rat atrial natriuretic factor (ANF) into anesthetized rats with markedly different levels of plasma renin activity. Infusion of ANF peptide at 350 ng . kg-1 . min-1 significantly decreased aldosterone secretion by 32% and plasma renin activity by 55% in rats that had been maintained on a normal-sodium diet. Similar reductions in aldosterone secretion and plasma renin activity were observed in hyperreninemic rats after chronic sodium restriction. Infusion of ANF at 350 ng . kg-1 . min-1 into anephric rats with low circulating levels of renin did not significantly decrease the secretion of aldosterone. Increasing the ANF peptide infusion dose fivefold in these anephric rats did result in a significant reduction in aldosterone secretion, but this higher dose also produced significant decreases in blood pressure not observed with the lower dose of ANF. These results demonstrate that infusion of synthetic ANF decreases the secretion rate of aldosterone in the rat, but the ability of ANF to decrease aldosterone secretion is attenuated when circulatory levels of renin and hence angiotensin II are very low. The data suggest that although ANF can exert a direct inhibitory effect on the adrenal glomerulosa in larger doses that also produce systemic cardiovascular effects, one physiological mechanism by which ANF suppresses aldosterone secretion may be related indirectly to the inhibition of renin release.
Changes in forebrain hexokinase activity after aortic baroreceptor denervation
Authors: Turton W. E. , Ciriello J. , Calaresu F. R.
Published: December 2017

Although forebrain structures have been implicated in both the development and maintenance of the elevated arterial pressure (AP) after aortic baroreceptor denervation, little is known about the location of central structures involved in the hypertensive process. In the present study, regions of the forebrain whose metabolic activity was altered after aortic baroreceptor denervation were functionally identified using hexokinase (HK) histochemistry in the rat. Three days after bilateral aortic depressor nerve (ADN) transection AP was significantly elevated compared with sham ADN-transected animals (143 +/- 1 and 122 +/- 2 mmHg, respectively). Significant increases in HK activity were observed in the magno- and parvocellular components of the paraventricular nucleus of the hypothalamus, supraoptic nucleus, nucleus circularis, median preoptic nucleus, subfornical organ, and central nucleus of the amygdala in the ADN-transected animals. These data have demonstrated that removal of aortic baroreceptor afferent inputs alters the activity of forebrain structures previously implicated in regulation of body fluid balance and AP and suggest that these structures are involved in the hypertensive process after ADN transection.
Urinary and metabolic clearances of arginine vasopressin in normal subjects
Authors: Moses A. M. , Steciak E.
Published: December 2017

Synthetic arginine vasopressin (AVP) was infused into 11 hydrated normal subjects at five different infusion rates ranging from 10 to 350 microU X kg-1 X min-1. Each infusion rate was continued for 1 h, and urinary determinations were made on the 30- to 60-min specimens during which time there was no further rise in plasma AVP. Urinary AVP concentrations (microU/ml) and excretion rates (microU/min) increased linearly with increasing infusion rates, and the concentration of AVP in urine increased 120 times more rapid than plasma. Urinary and metabolic clearances of AVP also increased linearly with the maximum urinary clearance being 60.6% of the creatinine clearance. The total metabolic clearance of AVP (including urinary clearance) was 17.8 times that of the urinary clearance of AVP alone. These data clarify the relationships between plasma and urinary AVP in normal hydrated subjects during AVP infusion under steady-state conditions and emphasize the potential advantage of measuring urinary AVP as a monitor of endogenous AVP secretion.
Brown fat mediates increased energy expenditure of cold-exposed overfed neonatal rats
Authors: Moore B. J. , Stern J. S. , Horwitz B. A.
Published: December 2017

Genetically lean rat pups, overfed by being raised in small litters of three from day 1 postpartum, rapidly become obese compared with pups raised in standard sized litters of eight. Because of the rapid onset of their obesity, we expected that overfed pups would exhibit defective brown fat thermogenesis as is seen in neonatal genetically obese rodents. O2 consumption (VO2) was measured in 2-, 4-, 6-, and 8-day-old homozygous lean (Fa/Fa) Zucker pups from each treatment. We determined minimum rate of VO2 at thermoneutrality and maximum VO2 in response to progressively colder ambient temperatures. Overfed pups were fatter than standard-fed pups (P less than 0.001). But contrary to our prediction, overfed pups had a significantly increased maximum VO2 in response to acute cold exposure. To test the hypothesis that brown fat mediated the increased VO2 in the overfed pups, scapular brown fat lipectomies were performed on a new group of overfed pups at 2 days of age and compared with sham-operated littermate controls. On day 8, no differences in minimum VO2 were seen at thermoneutrality when brown fat is turned off. But maximum VO2 in response to cold, when brown fat is turned on maximally, was significantly reduced in the lipectomized overfed pups compared with sham-operated overfed littermates. These data suggest that manipulations of diet, accomplished by raising pups in small litters, can increase brown fat thermogenic function. The results of the lipectomy experiment imply that brown adipose tissue is a primary mediator of the increased energy expenditure in response to acute cold exposure in the overfed pups.
Interrelationship of blood flow, juxtaglomerular cells, and hypertension: role of physical equilibrium and Ca
Authors: Fray J. C. , Lush D. J. , Park C. S.
Published: December 2017

Recent experimental evidence has provided important clues as to the role of electrolytes, particularly Ca, in the regulation of blood flow, renin secretion, and blood pressure. The smooth muscle cells of arterioles in general and the juxtaglomerular cells in the renal afferent arterioles have been shown to have Ca channels sensitive to voltage, hormones, and stretch. This paper reviews a model that utilizes these features along with a fundamental law of physics to point to some plausible explanations for some interesting experimental observations on renal blood flow, renin secretion, and hypertension. The chief features of the model are that in the steady state the arteriole must achieve a stable physical equilibrium in which the forces tending to distend the vessel (transmural pressure) counterbalance the forces tending to prevent distension (wall tension); the wall tension consists of a passive and an active component, the latter of which is sensitive to stretch of the vessel; and stretch activates the opening of stretch-sensitive Ca permeability channels that promote the influx of Ca to trigger active tension development. Thus Ca is the signal that couples stretch to contraction. This latter feature is the so-called myogenic response. Altered equilibrium may be initiated either by a rise in perfusion or tissue pressure to alter the distending force or by a rise in cytosolic Ca to increase active tension development and the constricting force. Several factors may initiate disequilibrium, some of which are discussed. Equilibrium is soon reestablished, however, at a new steady state. The model predicts curves for renal blood flow autoregulation and renin secretion in response to changes in renal perfusion pressure, tissue pressure, extracellular Ca, and blockers and promoters of Ca influx and Ca efflux. These predictions agree well with existing experimental evidence and suggest new experiments. The model provides a theoretical basis for explaining the steady-state blood pressure profile observed in renovascular hypertension and perhaps in other forms of hypertension as well. The model also provides a theoretical basis for understanding the volume-vasoconstriction approach used by some workers and the autoregulation approach used by others in explaining the mechanisms of hypertension.(ABSTRACT TRUNCATED AT 400 WORDS)
Angiotensin and Na appetite of sheep
Authors: Weisinger R. S. , Denton D. A. , McKinley M. J. , Muller A. F. , Tarjan E.
Published: December 2017

The effect of both intravenous (iv; 24 micrograms/h) and intracerebroventricular (ivt; 3.8 micrograms/h) infusion over 1-2 days of angiotensin II (ANG II) on Na intake of both Na-replete and -deplete sheep (i.e., 22 h loss of parotid saliva) was observed. In Na-replete sheep with continuous access to water and 2-h daily access to 0.5 M NaCl solution, both iv and ivt ANG II caused an increase in Na intake. The increase in Na intake caused by iv or ivt ANG II was preceded by a Na deficit due to increased urinary Na excretion. The increase in Na intake was eliminated by the continuous return of urine. In Na-deplete sheep with continuous access to water and 2-h daily access to 0.6 M NaHCO3 solution, iv ANG II caused no change in Na loss but a small increase in Na intake during the 1st day of infusion. The ivt ANG II caused no change in Na loss or in Na intake. The iv ANG II caused a small and inconsistent increase in water intake in Na-replete sheep but did not cause any change in water intake of Na-deplete sheep. The ivt ANG II caused a large increase in water intake in both Na-replete and -deplete sheep. In both Na-replete and -deplete sheep, iv ANG II did not alter cerebrospinal fluid or plasma [Na] or osmolality but decreased plasma [K]. The ivt ANG II decreased both cerebrospinal fluid and plasma [Na] and osmolality. The results of the present experiments are consistent with the proposition that the ANG II-induced Na appetite in sheep is largely due to an ANG II-induced Na loss preceding the development of appetite.
Comparison of four methods of averaging nerve activity
Authors: Hopp F. A. , Seagard J. L. , Kampine J. P.
Published: December 2017

Four methods of averaging nerve activity, moving time average (Analog), integration (Integrated), counting spikes (Spikes), and counting pulses from a voltage-to-frequency converter (VFC), were used to analyze artificial pulse trains and renal, carotid sinus, and vagal nerve activities. Results of the methods were compared using least-squares linear regression and correlation to determine the linearity of each method with respect to changes in frequency, amplitude, and width of pulse trains and the degree of agreement between methods. The methods that respond to total voltage (Analog, Integrated, and VFC) were linear with respect to input pulse train modulations and agreed closely with each other when averaging pulse trains, summating pulses, and nerve activity. Spikes were linear with respect to frequency modulation but not with respect to amplitude changes, pulse width changes, or pulse summations. In general, Spikes did not agree as well with Analog, Integrated, and VFC as these methods agreed with each other when averaging nerve activity. The degree of agreement was a function of the voltage threshold for Spikes and the level of nerve activity. Two methods of minimizing noise and obtaining a zero reference level for nerve activity were compared: setting a voltage threshold, such that noise was below and activity above threshold, was found to shift the base-line activity toward zero and compress phasic changes in activity; and recording the average noise level from a crushed nerve and subtracting it from averaged activity shifted the base-line activity toward zero with no change in the phasic component.
Effect of hypoxemia on plasma catecholamines in intact and immunosympathectomized fetal lambs
Authors: Schuijers J. A. , Walker D. W. , Browne C. A. , Thorburn G. D.
Published: December 2017

Fetal lambs treated with sheep anti-mouse nerve growth factor antibodies (anti-NGF) at 80 days gestation subsequently showed a diminished cardiovascular response to intravenous infusion of tyramine (1 mg/min over 10 min) and no significant change in plasma norepinephrine concentrations as measured by reversed-phase high-pressure liquid chromatography and electrochemical detection. At autopsy at 135 days gestation, catecholamine content of the heart, thyroid, kidney, and ileum was reduced by greater than 70% compared with age-matched control fetuses. The anti-NGF-treated fetuses were thus judged to have impaired sympathetic function. When made hypoxemic (arterial PO2 12-14 Torr) for 1 h at 120 or 130 days gestation, anti-NGF-treated fetuses showed no significant change of arterial pressure, heart rate, or plasma catecholamines, whereas control fetuses showed bradycardia, a 28% increase in arterial pressure, and a 670% increase of plasma norepinephrine concentrations. These results suggest that the increase of arterial pressure that occurs during hypoxemia in fetal lambs between 120 and 135 days gestation is attributable to increased activity of the peripheral sympathetic nervous system. The adrenal medulla appears to contribute to the plasma catecholamine pool at rest, but the lack of increased plasma catecholamines during hypoxia after anti-NGF implies that the adrenal medulla was unable to release catecholamines. Possible reasons for this are discussed.
Sleep regulation in rats: effects of sleep deprivation, light, and circadian phase
Authors: Trachsel L. , Tobler I. , Borbely A. A.
Published: December 2017

Sleep states and electroencephalographic (EEG) parameters were determined in unrestrained rats that had been implanted with electrodes under deep pentobarbital sodium anesthesia. Two base-line days with a light-dark cycle (LD) and 2 days under continuous darkness (DD) were followed by 24 h of sleep deprivation (SD) ending in the middle of the circadian activity period and by 2 recovery days in DD. In the base-line LD rest period, the amount of rapid-eye-movement sleep (REMS) and the EEG amplitude of non-REMS (NREMS) were lower than in the corresponding DD period. SD caused an immediate enhancement of REMS, NREMS, the slow-wave sleep (SWS) fraction of NREMS, and NREMS EEG amplitude. Although REMS, NREMS, and SWS showed a second peak at habitual light onset, they did not exceed base line. Subsequently, all parameters exhibited a marked negative rebound. We conclude that REMS and the EEG amplitude of NREMS are suppressed by light, amplitude and frequency parameters of NREMS are differently affected by light as well as by SD, and the short duration of the SD-induced increase of SWS may reflect a circadian influence on sleep homeostasis.
Insulin and metabolic efficiency in rats. I. Effects of sucrose feeding and BAT axotomy
Authors: Bartness T. J. , Billington C. J. , Levine A. S. , Morley J. E. , Brown D. M. , Rowland N. E.
Published: December 2017

The role of insulin and brown adipose tissue (BAT) thermogenesis in metabolic efficiency (ME, the efficiency of body wt gain) was examined in rats with varied basal insulin status. Long-lasting insulin was administered using a protocol that did not alter food intake, yet increased ME in both groups. Half the rats were fed sucrose to stimulate BAT growth and thermogenesis. Insulin overrode the exaggerated decrease in ME in sucrose-fed diabetics, with only partial attenuation in controls. Interscapular BAT (IBAT) lipoprotein lipase activity was decreased in diabetic rats, restored by insulin treatment, and not affected in controls. Sucrose-fed diabetics and controls had their IBAT sham or bilaterally surgically denervated. Insulin decreased the thermogenic potential of BAT [cytochrome oxidase activity (COA)] in intact controls and diabetics; in the latter, insulin restored COA independent of BAT innervation. We conclude that insulin can increase ME without an associated increase in energy intake, regardless of basal insulin status, both insulin deficiency and excess decrease BAT thermogenic potential (COA), and hyperinsulinemia-induced increases in ME may result from decreased BAT mitochondrial proliferation.
Possible mechanism for increased beta-adrenergic dipsogenic response in food-deprived rats
Authors: Yeh L. F. , Baker S. P. , Katovich M. J.
Published: December 2017

The dipsogenic responsiveness to isoproterenol was studied in food-deprived male rats. Unstimulated water intake was similar between control and fasted groups, and parallel dose-response curves for the dipsogenic response induced by isoproterenol (10–50 micrograms/kg) were observed. A twofold elevation in dipsogenic responsiveness was observed in the fasted rats, and this enhanced response was correlated with a dose-dependent increase in plasma renin activity when compared with the control rats after administration of isoproterenol. beta-Adrenergic receptor binding assays were performed on both heart and renal cortical tissues. In the heart the receptor concentration was decreased after food deprivation, whereas the affinity of the receptor for the beta-adrenergic antagonist [125I]CYP remained unchanged. On the other hand, an increased beta-adrenergic receptor concentration without change in affinity was found in renal cortices of fasted rats. Results from these receptor binding studies correlated with the attenuated chronotrophic response and the increased dipsogenic response to beta-adrenergic stimulation in the fasted rat. Therefore stimulation of these increased renal receptors by isoproterenol could result in an enhanced activation of the renin-angiotensin system and thus be a factor responsible for the increased dipsogenic response induced by isoproterenol observed in the fasted rats.
Olfactory bulbectomy prevents anti-gonadal effect of exogenous melatonin in male hamsters
Authors: Pieper D. R. , Stone D. A. , Alexander R. L. , Subramanian M. G.
Published: December 2017

When male Golden hamsters are maintained on short days (less than 12.5 h of light/day) the testes gradually regress. This testicular regression is due to an inhibitory effect of pineal gland melatonin on gonadotropin secretion. A previous report from the author's laboratory has indicated that olfactory bulbectomy (BX) will prevent the testicular regression associated with short photoperiod. The present study examined whether BX would also prevent the testicular regression associated with exogenous melatonin (MEL) injections. Male Golden hamsters were BX or sham (SH) BX at 23–28 days of age and were maintained on 14:10 light-dark cycle. Six weeks following surgery, one half of each surgical group began receiving injections of melatonin (15 micrograms sc), whereas the other half was injected with vehicle at 1600 daily. The testes size of the SH group injected with MEL progressively decreased, whereas the testes of all other groups remained large. These results indicate that BX prevents the testicular regression associated with short photoperiod by interfering with the antigonadotropic effect of melatonin.