bluuebunny/crossref_metadata_2025 huggingface dataset:
Anorexia induced in rat by D-glucosamine deoxidized at C-1
Authors: Fujimoto K. , Sakata T. , Shiraishi T. , Kurata K. , Terada K. , Etou H.
Published: December 2017

The effects of D-glucosamine (2-amino-2-deoxy-D-glucose), an endogenous glucose analogue, and 1-deoxy-D-glucosamine on feeding behavior were clarified. Test solutions (24 mumol) were infused into the third cerebroventricle of the rat. Glucosamine induced a feeding episode within 30 min after infusion and then prolonged the ensuing postprandial intermeal interval for the first 4 h of the dark period, while glucose suppressed feeding by decreasing meal size. Ventricular injection of 1-deoxyglucosamine potently suppressed feeding in a dose-related manner by affecting all meal parameters, and oral administration of 2,400 mumol also induced anorexia. Changes in activity of glucose-sensitive neurons in the lateral hypothalamus and glucoreceptor neurons in the ventromedial hypothalamus after electrophoretic application of glucosamine and 1-deoxyglucosamine were compatible with behavior changes. The results indicate that replacement of a hydroxyl group by an amino group at C-2 of the glucose molecule affects feeding behavior and deoxidation of C-1 potently induces anorexia.
Effects of atriopeptin and chicken heart extract in Gallus domesticus
Authors: Gregg C. M. , Wideman R. F.
Published: December 2017

Effects of Ser-Leu-Arg-Arg-atriopeptin III (ANP) and chicken heart extract (CHE) were compared during unilateral renal portal infusion in anesthetized Single Comb White Leghorn chickens. The purpose was to determine whether renal effects were glomerular and/or tubular. Both CHE and ANP caused substantial decreases in mean arterial pressure but had different renal actions. ANP caused small but significant increases in both absolute and fractional sodium excretion, but these effects were modest compared with those reported in mammals. Although there was a tendency for higher fractional sodium excretion in the portal infused kidney, the difference was not significant (0.1 less than P greater than 0.05). ANP also increased glomerular filtration rate (GFR), urine flow rate (UFR), and osmolal clearance and decreased estimated renal vascular resistance. In contrast, CHE decreased GFR and increased resistance. In contrast, CHE decreased GFR and increased fractional potassium excretion in the infused kidney. After CHE infusion was stopped, GFR and UFR increased, and there was a further transient kaliuresis. No natriuretic effects were ever seen with CHE. Chickens apparently lack potent mammalian-type cardiac natriuretic factor(s) and/or have a limited capacity for natriuresis in response to mammalian ANP. Because hypotension was the most prominent avian response to both CHE and ANP, endogenous vasoactive factor(s) in chicken hearts may function to regulate blood pressure rather than blood volume.
Area postrema lesions: cause of overingestion is not altered visceral nerve function
Authors: Edwards G. L. , Ritter R. C.
Published: December 2017

Rats with lesions of the area postrema and the immediately subjacent nucleus of the solitary tract (AP lesions) ingest greater quantities of palatable foods than intact rats. Because AP lesions destroy some abdominal vagal sensory terminals and may damage vagal motor neurons as well, it is possible that lesion-induced alteration of vagal function causes overingestion of palatable foods. To test this hypothesis, we have examined ingestion of a highly palatable solid food by AP- and sham-lesioned rats with total subdiaphragmatic vagotomies and examined ingestion of a highly palatable sucrose solution by AP- and sham-lesioned rats with open gastric fistulas (sham feeding). Vagotomy in sham-lesioned rats failed to cause overingestion of palatable food. Furthermore, vagotomy in AP-lesioned rats did not abolish their overingestion of palatable food, although AP lesion-induced overingestion was attenuated by vagotomy. Finally, sham-feeding AP-lesioned rats consumed significantly more sucrose solution than sham-lesioned rats. These results indicate that overingestion of palatable foods and solutions by AP-lesioned rats is not due to impaired abdominal visceral afferent function and probably is not due to altered vagal efferent function. The data are consistent with our previous suggestion that overingestion by AP-lesioned rats results from a primary change in responsiveness to orosensory cues.
Environment and hamster reproduction: responses to phase-specific starvation during estrous cycle
Authors: Morin L. P.
Published: December 2017

Reproductive capacity of female hamsters, as estimated by the ovulatory response, is particularly susceptible to interference by food deprivation. Previous studies showed that hamsters generally fail to ovulate if deprived of food for one or two estrous cycles. The present work demonstrates that starvation which is specific to the 2 days immediately after ovulation will block the next expected ovulation in approximately 80% of the animals. Such phasic starvation also resulted in significantly smaller ovarian follicle sizes. When placed with vigorous males, anovulatory animals failed to show lordosis behavior unless exogenous estradiol benzoate (EB) was supplied. With EB provided, all animals showed short-latency lordosis. These bioassay data suggested that poorly developed follicles were secreting insufficient estradiol for the facilitation of lordosis. Exogenous luteinizing hormone (LH) given 6 h before lights off on cycle day 4 failed to elicit ovulation, further suggesting that the follicles were not mature. Radioimmunoassay of LH and follicle-stimulating hormone (FSH) levels during the ovulatory gonadotropin surge showed that LH was vastly reduced, whereas FSH was in the low-to-normal range. Estradiol levels, assayed immediately before the gonadotropin surge, were low compared with controls, whereas progesterone levels were higher than normal. The results suggest that ovulatory failure in response to phasic food deprivation is a joint function of absence of an ovulatory LH surge and a set of immature follicles.
K+-H+ exchange and volume homeostasis in brown adipose tissue mitochondria
Authors: DiResta D. J. , Kutschke K. P. , Hottois M. D. , Garlid K. D.
Published: December 2017

K+-H+ exchange activity in hamster brown adipose tissue mitochondria is activated following depletion of matrix Mg2+ with the divalent cation ionophore A23187. Quinine inhibits K+-H+ exchange reversibly with an I50 of 22 microM, whereas mild treatment with N,N'-dicyclohexylcarbodiimide (DCCD) inhibits this activity irreversibly. In an attempt to label and identify the K+-H+ antiporter protein, brown adipose tissue mitochondria were incubated with [14C]DCCD and subjected to denaturing polyacrylamide gel electrophoresis and fluorography. We observed a labeled band of relative mol wt, 78,000, which satisfies criteria established in rat liver mitochondria for the identification of this carrier (W. H. Martin et al., J. Biol. Chem. 259: 2062-2065, 1984). Thus Mg2+ and quinine each protect the K+-H+ exchanger against both inhibition and binding by DCCD. Volume homeostasis in brown adipose tissue mitochondria, as in other mitochondria, requires a balance between K+ influx and efflux. We propose that regulation of the K+-H+ antiporter, the primary K+ efflux mechanism, plays a major role in this process.
Effects of alkalosis on skeletal muscle metabolism and performance during exercise
Authors: Spriet L. L. , Lindinger M. I. , Heigenhauser G. J. , Jones N. L.
Published: December 2017

This study examined the effects of extracellular alkalosis on the metabolism and performance of perfused rat hindlimb muscles during electrical stimulation. Three acid-base conditions were used: control (C, normal acid-base state), metabolic alkalosis (MALK, increased bicarbonate concentration), and respiratory alkalosis (RALK, decreased PCO2). A one-pass system was used to perfuse the hindlimb via the femoral artery for 20 min at rest and during 5 min of tetanic stimulation via the sciatic nerve. The isometric tension generated by the gastrocnemius-plantaris-soleus muscle group was recorded. Arterial and venous perfusates were periodically sampled for substrate and metabolite measurements, and muscle samples were taken pre- and postperfusion. Peak isometric tensions in C, MALK, and RALK were similar: 3,367 +/- 107, 3,317 +/- 110, and 3,404 +/- 69 g, respectively. The rate of tension decay was also unaffected by alkalosis and represented 78 and 55% of the peak tension following 2 and 5 min of stimulation, respectively. Muscle O2 uptake, glycogen utilization, and total lactate (La-) production were similar following 5 min of stimulation in all conditions. However, alkalosis resulted in an enhanced La- release from working muscle (peak La- release: C, 15.5 +/- 1.1; MALK, 19.7 +/- 1.6; RALK, 18.3 +/- 2.2 mumol/min), and a 15-20% reduction in intramuscular La- accumulation. Alkalosis had no effect on muscle creatine phosphate and ATP concentrations. Thus, in the perfused rat hindlimb, alkalosis was not associated with changes in tetanic force or glycolysis, but La- release from the working muscle was enhanced by increased extracellular pH and bicarbonate.
Modeling the contractility of urinary bladder smooth muscle using isometric contractions
Authors: van Mastrigt R. , Koopal J. W. , Hak J. , van de Wetering J.
Published: December 2017

In the course of developing a clinical contractility index, isometric contractions of pig urinary bladder smooth muscle were analyzed in terms of phase plots (a plot of the rate of change of a variable, in this case force, as a function of the variable itself). The straight line describing the major part of the phase plots is characterized by the two parameters Fiso (the horizontal intercept) and c (the slope) of the line. It was found that changes in the geometry of the tissue sample and changes in extracellular calcium grossly influence Fiso, but not c, whereas changes in prestimulus rest time influence c, but not Fiso. It is concluded that Fiso is related to the number of available contractile units, and c is related to the limiting rate constant in the excitation-contraction coupling, which is probably determined by the release of intracellular calcium. The existence of the calcium paradox and the interpretation of the concept of facilitation or potentiation in this type of smooth muscle are discussed.
Commentary on the mutual interaction model of McCarley and Massaquoi for REM-NREM cycle
Authors: Daan S. , Beersma D. G.
Published: December 2017

McCarley and Massaquoi successfully simulated human REM-NREM cycle characteristics by extending the McCarley-Hobson model with two sets of assumptions, one creating limit cycle behavior, the other introducing two sources of circadian variation. We argue that the limit cycle assumptions, due to freedom in choosing parameter values, suffice to explain variation in REM across the night. Nonmonotonic circadian variation in REM latency requires a circadian cycle dependence only of initial conditions at sleep onset.
Effects of hypertonic saline infusion and water drinking on atrial peptide
Authors: Salazar F. J. , Granger J. P. , Joyce M. L. , Burnett J. C. , Bove A. A. , Romero J. C.
Published: December 2017

This study was undertaken to define the changes in plasma levels of atrial natriuretic peptide (ANP) induced by hypertonic saline infusion followed by spontaneous water drinking and to determine whether these changes in ANP are correlated with changes in right atrial pressure (RAP) and plasma levels of vasopressin (AVP). Conscious dogs (n = 5) were infused with hypertonic saline (6%) at a rate of 1.4 ml/min for 4 h. Water was withheld for the first 2 h and administered ad libitum for the final 2 h. Hypertonic saline infusion induced increases (P less than 0.05) in plasma osmolality (posM), pAVP, mean arterial pressure (MAP), and RAP (1.9 +/- 0.6 to 3.1 +/- 0.7 mmHg). These changes were accompanied by an increase of pANP (68 +/- 14 to 120 +/- 33 pg/ml, P less than 0.05). Spontaneous water drinking (1,410 +/- 127 ml) returned posM and pAVP to control levels and produced a further and significant increment in RAP (150%) and pANP (100%). During the water-drinking phase MAP was not further altered, and hematocrit decreased by 11.1% (P less than 0.05). A positive linear correlation (P less than 0.001) was found between increases in RAP and pANP. The administration of an AVP vasopressor antagonist in a similar protocol, and before hypertonic saline infusion, inhibited the increase of MAP, but it did not alter the changes of posM, hematocrit, RAP, nor pANP. These results suggest that changes in the release of ANP during increases in posM and after spontaneous water drinking are predominantly controlled by changes in RAP.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenal medullary responses to repeated hemorrhage in conscious dogs
Authors: Lilly M. P. , Engeland W. C. , Gann D. S.
Published: December 2017

Potentiated adrenal responses to the second of two identical hemorrhages spaced 24 h apart are seen in the pentobarbital sodium-anesthetized dog. Although pentobarbital effectively reduces environmental influences, barbiturates affect hemodynamic and hormonal responses and preclude normal daily feeding and activity patterns. To determine the role of anesthesia in these earlier results, we prepared awake trained dogs with chronic adrenal venous catheters. Animals were bled 8.7-21.8% of measured blood volume [131] over 3 min, and peripheral and adrenal blood was sampled. Blood was reinfused 1 h later, and the dogs were fed. The protocol was repeated 24 h later. Dogs with small hemorrhage (11.6 +/- 2.3% blood vol; n = 9) showed no difference in catecholamine secretion on the 2 days. Dogs with large hemorrhage (18.9 +/- 2.1% blood vol; n = 9) showed a greater epinephrine and norepinephrine secretory response to hemorrhage on day 2. No differences were detected in the hemodynamic response to bleeding on the 2 days. Whereas potentiation was seen in epinephrine and norepinephrine responses to a second 10% hemorrhage in anesthetized dogs, larger hemorrhage was needed to elicit this effect in awake dogs. Thus potential adrenal medullary responses to repeated hemorrhage occur in both awake and pentobarbital-anesthetized dogs, but important differences in the threshold and manifestation of this effect are seen.
Pituitary-adrenal responses to repeated small hemorrhage in conscious dogs
Authors: Lilly M. P. , Engeland W. C. , Gann D. S.
Published: December 2017

Potentiated pituitary-adrenocortical responses to the second of two identical small hemorrhages, spaced 24 h apart, are seen in the pentobarbital sodium-anesthetized dog. To investigate the role of pentobarbital anesthesia in these results and to better define the range of the effect, we studied awake trained dogs with chronic adrenal venous catheters. Each dog was bled an amount between 8.7 and 21.8% of measured blood volume [131I] (MBV) over 3 min, and peripheral and adrenal blood were sampled. Blood was reinfused 1 h later, and the dogs were fed. The same hemorrhage and experimental protocol were repeated 24 h later. Steroids were assayed by high-performance liquid chromatography-ultraviolet (HPLC-UV) and adrenocorticotropic hormone (ACTH) by radioimmunoassay (RIA). Secretory rates of cortisol were calculated using measured adrenal blood flow rates. Maximal secretion of cortisol was determined after injection of 100 mU ACTH following each experiment. Dogs whose day 1 cortisol secretion after hemorrhage was submaximal (hem volume = 14.8 +/- 3.7% MBV; n = 7) showed a greater cortisol secretory response to the same hemorrhage on day 2 (P less than 0.005). This increased cortisol response on day 2 was accompanied by an increased ACTH presentation rate (APR) (P less than 0.025) and by increased adrenal sensitivity to ACTH (P less than 0.025). The increased APR was caused by both an increased venous ACTH and by an increased adrenal blood flow. If posthemorrhage cortisol secretion was maximal on day 1, ACTH, APR, and ABF were not different on the 2 days. No hemodynamic differences were seen to explain these findings. These results confirm and extend our previous results.(ABSTRACT TRUNCATED AT 250 WORDS)
Hepatic portal glucose infusions decrease food intake and increase food preference
Authors: Tordoff Michael E. , Friedman Mark I.
Published: December 2017

Page 192: Michael E. Tordoff and Mark I. Friedman. “Hepatic portal glucose infusions decrease food intake and increase food preference.” Page R195: first paragraph, the first four sentences should read

In addition to the theoretical implications of these results, several practical implications are apparent. The data suggest that repeated tests of the same subject must be interpreted with caution, because the response during later tests may well be determined by previous infusions. It is interesting to note in this regard that several previous studies finding no change in feeding after hepatic portal glucose infusion have used daily tests according to counterbalanced designs (Refs. 2, 13, and 17–20 and perhaps Refs. 26, 27, and 29).
Puberty in female rats: relative effect of exercise and food restriction
Authors: Bronson F. H.
Published: December 2017

Reproductive development in relation to growth and fat deposition was compared in three groups of female rats: a group that was allowed to grow only slowly by requiring them to work hard on a running wheel for their food; a group in which the same slow rate of growth was imposed by restricting their food intake, but without an exercise requirement; and a normally growing, nonexercising, ad libitum-fed, control group. Animals forced to run for their food experienced vaginal opening at a significantly lower body weight than either of the other two groups. The same trend was apparent for the first ovulation, but not significant. Thus the present results suggest that, under some conditions, intense exercise may actually accelerate rather than decelerate reproductive development, at least relative to body weight. With the possible exception of body weight, none of the whole-body parameters measured in this experiment (body weight, growth rate, or amount of fat) were found to be critically related to the first ovulation when all three groups of females were considered as a unit. Thus the present results also argue against some of the current hypotheses, all developed using dietary manipulation, that the onset of fertility is somehow dependent on one of these factors.
Morphology and development of an apoeccrine sweat gland in human axillae
Authors: Sato K. , Leidal R. , Sato F.
Published: December 2017

Evidence is presented that in adult human axillae there exists a third type of sweat gland tentatively designated as the apoeccrine sweat gland. This type of gland shows a segmental or diffuse apocrinelike dilatation of its secretory tubule but has a long and thin duct which does not open into a hair follicle. The electron microscopy of its dilated segment is often indistinguishable from that of the classical apocrine gland. The less remarkably dilated segment of the apoeccrine gland tends to retain intercellular canaliculi and/or dark cells. These apoeccrine glands are consistently present in adult human axillae regardless of sex or race. In the axillae of the two 6-yr-old subjects, both classical apocrine and eccrine glands were present but no apoeccrine glands were found. Between 8–14 yr of age, the number of large eccrine glands with or without partial segmental dilatation gradually increased. At 16–18 yr of age, the number of apoeccrine glands increased to as high as 45% of the total axillary glands. The data support the notion that apoeccrine glands develop during puberty in the axillae from eccrine or eccrinelike sweat glands.
Na+-H+ exchange and Na+-dependent transport systems in streptozotocin diabetic rat kidneys
Authors: el-Seifi S. , Freiberg J. M. , Kinsella J. , Cheng L. , Sacktor B.
Published: December 2017

The streptozotocin-induced diabetic rat was used to test the hypothesis that Na+-H+ exchange activity in the proximal tubule luminal membrane would be increased in association with renal hypertrophy, altered glomerular hemodynamics, enhanced filtered load and tubular reabsorption of Na+, and stimulated Na+ pump activity in the basolateral membrane, previously reported characteristics of this experimental animal model. Amiloride-sensitive H+ gradient-dependent Na+ uptake and Na+ gradient-dependent H+ flux were increased in brush-border membrane vesicles from the streptozotocin-treated animals. Na+ gradient-dependent uptakes of phosphate, D-glucose, L-proline, and myoinositol were decreased in the drug-induced diabetic animals. These membrane transport alterations were not found when the streptozotocin-diabetic animals were treated with insulin.
Stress-induced blood pressure responses in SHR: effect of dietary calcium
Authors: Hatton D. C. , Huie P. E. , Muntzel M. S. , Metz J. A. , McCarron D. A.
Published: December 2017

To assess the influence of dietary calcium on stress-induced blood pressure responses, spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were placed on low Ca2+ (0.1%) and Na+ (0.25%), intermediate Ca2+ (1.0%) and Na+ (0.45%), or high Ca2+ (2.0%) and Na+ (1.0%) diets for 13 wk prior to measuring blood pressure (BP) responses in an aversive classical conditioning paradigm. Forty-eight hours prior to testing, catheters were placed in a femoral artery under halothane anesthesia for recording direct pressure. On recovery the rats were classically conditioned to a 10-s tone followed by a brief electric shock using a discrimination paradigm. After 24 reinforced trials, SHRs on a low diet had significantly larger pressor responses to the conditioned tones than rats in the high diet condition. SHRs on the intermediate diet exhibited pressor responses midway between the low and high diet groups. In the WKY strain there was no significant dietary effect on conditioned BP response. In both strains the low diets resulted in significantly elevated base-line blood pressure levels. The data confirm earlier reports of elevated BP in SHRs and WKYs following dietary calcium restriction and provide suggestive evidence that the elevation in base-line BP may be related to diet-induced changes in BP reactivity in the SHR.
Effect of parathyroid hormone on transport by toad and turtle bladder
Authors: Sabatini S. , Kurtzman N. A.
Published: December 2017

We recently demonstrated that parathyroid hormone (PTH) inhibited both vasopressin- and cyclic AMP-stimulated water transport in the toad bladder. This was associated with an increase in calcium uptake by isolated epithelial cells. We postulated that PTH exerts its action on H2O transport by directly stimulating calcium uptake. The current study was designed to compare the effects of PTH and the calcium ionophore, A23187, on H2O and Na transport and H+ secretion in toad and turtle bladders. In toad bladder, PTH and A23187 decreased arginine vasopressin (AVP)-stimulated H2O flow and short-circuit current (SCC) after 60 min serosal incubation. In turtle bladder A23187 decreased SCC to 79.3 +/- 3.6% of base line (P less than 0.05), and significantly decreased RSCC as well. PTH had no effect on SCC or H+ secretion in turtle bladders. Both PTH and A23187 increased 45Ca uptake in toad bladder epithelial cells; only A23187 increased 45Ca uptake in the turtle bladder. The different action of PTH in these two membranes, compared with that of the calcium ionophore, illustrates the selectivity of PTH on membrane transport. PTH increases calcium uptake and decreases transport only in a hormone-sensitive epithelium, whereas the ionophore works in virtually all living membranes. The mode of action of these two agents to increase calcium uptake is, therefore, likely different.
Changes in pituitary growth hormone cells prepared from rats flown on Spacelab 3
Authors: Grindeland R. , Hymer W. C. , Farrington M. , Fast T. , Hayes C. , Motter K. , Patil L. , Vasques M.
Published: December 2017

Anterior pituitaries from “small” (250 g) and “large” (400 g) rats flown on the 7-day Spacelab 3 mission were pooled and trypsinized into two single-cell suspensions. Compared with ground-based controls, flight cells appeared to contain more intracellular growth hormone (GH) but release less GH over a 6-day culture period. After implantation into hypophysectomized rats, both sets of flight cells released only 50% of the GH compared with the control cells. Glands from large flight rats contained 44% somatotrophs compared with 37% for controls; small animals showed no difference. There were no striking differences in somatotroph ultrastructure between cells in the four groups. Western blot analysis indicated that there were no major differences in immunoactive GH variants. High-performance liquid chromatography fractionation of culture media indicated that small flight cells released much less of a high-molecular weight variant rich in GH bioactivity. The results suggest that GH cells from rats exposed to microgravity may experience secretory dysfunction. The possibility that this occurs directly at the pituitary cell level is discussed.
Histomorphometric analysis of rat skeleton following spaceflight
Authors: Wronski T. J. , Morey-Holton E. R. , Doty S. B. , Maese A. C. , Walsh C. C.
Published: December 2017

Male Sprague-Dawley rats were placed in orbit for 7 days aboard the space shuttle. Bone histomorphometry was performed in the long bones and lumbar vertebrae of flight rats and compared with data derived from ground-based control rats. Trabecular bone mass was not altered during the 1st wk of weightlessness. Strong trends were observed in flight rats for decreased periosteal bone formation in the tibial diaphysis, reduced osteoblast size in the proximal tibia, and decreased osteoblast surface and number in the lumbar vertebra. For the most part, histological indexes of bone resorption were normal in flight rats. The results indicate that 7 days of weightlessness are not of sufficient duration to induce histologically detectable loss of trabecular bone in rats. However, cortical and trabecular bone formation appear to be diminished during the 1st wk of spaceflight.
Suppressed serum prolactin in sinoaortic-denervated rats
Authors: Alexander N. , Melmed S. , Morris M.
Published: December 2017

We investigated the effect of arterial baroreceptor deafferentation on serum and pituitary prolactin (PRL) and on catecholamines in median eminence (ME) and anterior and posterior pituitaries. Male Wistar rats were sinoaortic denervated (SAD) or sham operated (SO). Three days after surgery serum prolactin, measured by radioimmunoassay, was suppressed in SAD rats (-54%, P less than 0.05), and dopamine (DA) and norepinephrine (NE) concentrations, measured by radioenzymatic or high-performance liquid chromatography electron capture methods, were significantly reduced in ME of SAD rats (NE, -54% P less than 0.005 and DA, -56% P less than 0.001). Simultaneously, anterior pituitary of SAD rats had significant increases in both catecholamines, whereas posterior pituitary showed no changes. Four hours after surgery serum PRL was also reduced (-40%, P less than 0.05) in SAD rats, but no changes in ME catecholamines were found. Mean arterial pressure (MAP) and heart rate were measured before and after injection of bromocriptine (0.5 mg/kg ip) in SAD and SO rats 3 days after surgery. Bromocriptine markedly suppressed serum PRL in both groups and reduced MAP from 144 +/- 10 to 84 +/- 5 and from 116 +/- 2 to 99 +/- 3 in SAD and SO rats, respectively; heart rate was reduced in SAD rats. We conclude that the SAD rat is a model of hypertension with suppressed serum PRL and that interruption of arterial baroreceptor nerves suppresses PRL secretion probably by modulating tuberoinfundibular turnover of catecholamines.
Responses to converting-enzyme inhibition and hemorrhage in newborn lambs and adult sheep
Authors: Rose J. C. , Block S. M. , Flowe K. , Morris M. , South S. , Sundberg D. K. , Zimmerman C.
Published: December 2017

We compared the cardiovascular and hormonal responses to angiotensin converting enzyme inhibition and hemorrhage of 20% of blood volume in chronically instrumented unanesthetized newborn lambs and adult sheep. Administration of the nonsulfhydryl-containing converting-enzyme inhibitor enalapril reduced mean arterial pressure in the newborn but not in the adult animals. Blood pressure fell in both age groups after hemorrhage, and the hemorrhage-induced fall in blood pressure, integrated over the period of hypovolemia, was more pronounced when converting-enzyme inhibition was present in the lambs. This was not observed in the adults. Cardiac output fell following hemorrhage in both age groups, and the fall was greater when enalapril was present in the lambs, but this was not the case in the adults. Hemorrhage increased plasma renin activity in both groups, and enalapril augmented this increase. Plasma concentrations of vasopressin and catecholamines increased following hemorrhage within and between groups. Taken together these data suggest that the renin-angiotensin system plays a more important role in the maintenance of cardiovascular homeostasis in newborn lambs than it does in adult sheep, and catecholamine and vasopressin responses to volume loss can occur in the presence of blockade of the renin-angiotensin system.
Diet, lighting, and food intake affect norepinephrine turnover in dietary obesity
Authors: Yoshida T. , Fisler J. S. , Fukushima M. , Bray G. A. , Schemmel R. A.
Published: December 2017

The effects of dietary fat content, lighting cycle, and feeding time on norepinephrine turnover in interscapular brown adipose tissue, heart, and pancreas, and on blood 3-hydroxybutyrate, serum glucose, insulin, and corticosterone have been studied in two strains of rats that differ in their susceptibility to dietary obesity. S 5B/Pl rats, which are resistant to dietary obesity, have a more rapid turnover of norepinephrine in interscapular brown adipose tissue and heart and a greater increase in the concentration of norepinephrine in brown fat when eating a high-fat diet than do Osborne-Mendel rats, which are sensitive to fat-induced obesity. Light cycle and feeding schedule are important modulators of sympathetic activity in heart and pancreas but not in brown fat. Rats of the resistant strain also have higher blood 3-hydroxybutyrate concentrations and lower insulin and corticosterone levels than do rats of the susceptible strain. A high-fat diet increases 3-hydroxybutyrate concentrations and reduces insulin levels in both strains. These studies show, in rats eating a high-fat diet, that differences in norepinephrine turnover, particularly in brown adipose tissue, may play an important role in whether dietary obesity develops and in the manifestations of resistance to this phenomenon observed in the S 5B/Pl rat.
Acute central effects of L-glutamate in pentobarbital-anesthetized dogs
Authors: Chelly J. E. , Doursout M. F. , Buckley J. P.
Published: December 2017

Microinjections of L-glutamate (10(-10) to 2 X 10(-8) mol/kg) into the nucleus of tractus solitarii produced a dose-dependent increase in mean arterial pressure and a decrease in heart rate. L-Glutamate-induced hypertension was prevented by spinal transection and pretreatment with atropine (1 mg/kg iv) reversed the bradycardia. L-Glutamate also produced a dose-dependent increase in mean arterial pressure when injected intravenously and into the cisterna magna, but the dose-effect curves were shifted to the right. Finally, pretreatment with hexamethonium (30 mg/kg iv) abolished the hypertension resulting from intravenous injections of L-glutamate. These data demonstrate that the nucleus of tractus solitarii may play a determinant role in the central pressor effects of L-glutamate. In addition, we demonstrated that this hypertension was due to a central sympathetic stimulation and that the autonomic nervous system also mediated the pressor effects of intravenous L-glutamate.
Glucocorticoid inhibition of neurohypophysial vasopressin secretion
Authors: Raff H.
Published: December 2017

Several lines of evidence have suggested that neurohypophysial vasopressin secretion is under the influence of glucocorticoid negative feedback. Studies in clinical and experimental adrenal insufficiency have suggested that the impaired water excretion accompanying that syndrome may be due to elevated vasopressin levels. Furthermore, both the impaired water excretion and elevated vasopressin levels observed in adrenal insufficiency may be normalized by glucocorticoid treatment. This topic remains controversial, with a considerable body of evidence suggesting that vasopressin is elevated during adrenal insufficiency not because of a loss of central steroid negative feedback but because of alterations in plasma volume osmolality (renal mechanisms). Vasopressin responses to a variety of stimuli (hemorrhage, hypoxia, hypertonic saline) in normal humans and animals appear to be attenuated or eliminated by pretreatment with glucocorticoids. However, the vasopressinergic system appears to be considerably less sensitive to negative feedback than the corticotropin-releasing factor-adrenocorticotropic hormone (ACTH) system. There is evidence that the locus for this inhibitory effect is both directly at the posterior pituitary and within the hypothalamus. It is unlikely that corticosteroid negative feedback closes a direct hypothalamo-neurohypophysial-adrenocortical feedback loop. Since neurohypophysial vasopressin is involved in the control of ACTH secretion, it is more likely that the modulation of neurohypophysial vasopressin by glucocorticoid is an integral part of the overall negative-feedback control of ACTH secretion. The physiological role of glucocorticoid inhibition of vasopressin secretion remains speculative.
Quantitation of phosphorus excretion in sheep by compartmental analysis
Authors: Schneider K. M. , Boston R. C. , Leaver D. D.
Published: December 2017

The control of phosphorus excretion in sheep has been examined by constructing a kinetic model that contains a mechanistic set of connections between blood and gastrointestinal tract. The model was developed using experimental data from chaff-fed sheep and gives an accurate description of the absorption and excretion of phosphorus in feces and urine of the ruminating sheep. Simulation of the response to an intravenous phosphorus infusion by adding an inflow of 2 g/day of phosphorus into the compartment describing blood, predicted values for fecal output of phosphorus lower than found experimentally. However, by alteration of the parameters describing absorption or salivation, the predictions approached experimental values. Similarly simulation of the conditions existing when a liquid diet was infused directly into the abomasum, i.e., a decrease in salivation rate [L(4.1)] and dietary phosphorus entering compartment 5 (abomasum) instead of compartment 4 (rumen), gave incorrect predictions for plasma and urinary phosphorus, but when the parameter for urinary phosphorus was increased the predicted values approached experimental values. These results indicated the main control site for phosphorus excretion in the ruminating sheep was the gastrointestinal tract, whereas for the nonruminating sheep fed the liquid diet, control was exerted by the kidney. A critical factor in the induction of adaptation of phosphorus reabsorption by the kidney was the reduction in salivation, and since this response occurred independently of marked changes in the delivery of phosphorus to the kidney, a humoral factor may be involved in this communication between salivary gland and kidney.
Negative-feedback inhibition of fetal ACTH secretion by maternal cortisol
Authors: Wood C. E.
Published: December 2017

Previous studies in this laboratory have shown that small increases in fetal cortisol (F) decreased basal fetal plasma renin activity (PRA) and completely inhibited the fetal adrenocorticotropin hormone (ACTH) response to hypotension. The present study was designed to quantitate suppression of fetal ACTH and renin secretion by maternal F. Fetal and maternal femoral arteries and veins were chronically catheterized (11 fetuses, 118-129 days gestation). Maternal intravenous infusion of 0, 0.5, 1.0, and 2.0 micrograms F X kg-1 X min-1 (n = 5-6) increased mean maternal and fetal cortisol and suppressed fetal ACTH responses to a subsequent period of hypotension in a dose-related manner. Increases in fetal plasma cortisol to 8.3 ng/ml completely suppressed the fetal ACTH response to hypotension. The results indicate that increases in maternal plasma cortisol concentration sufficient to produce modest increases in fetal plasma cortisol inhibit fetal ACTH secretion.
Correlation between osmoregulation and cell volume regulation
Authors: Lang M. A.
Published: December 2017

The euryhaline crab, Callinectes sapidus, behaves both as an osmoregulator when equilibrated in salines in the range of 800 mosM and below and an osmoconformer when equilibrated in salines above 800 mosM. There exists a close correlation between osmoregulation seen in the whole animal in vivo and cell volume regulation studied in vitro. Hyperregulation of the hemolymph osmotic pressure and cell volume regulation both occurred in salines at approximately 800 mosM and below. During long-term equilibration of the crabs to a wide range of saline environments, the total concentration of hemolymph amino acids plus taurine remained below 3 mM. During the first 6 h after an acute osmotic stress to the whole animal, the hemolymph osmotic pressure and Na activity gradually decreased, whereas the free amino acids remained below 3 mM. As the hemolymph osmotic pressure decreased below approximately 850 mosM, the amino acid level began to increase to 17-25 mM. This change was primarily due to increases in glycine, proline, taurine, and alanine. The likely source of the increase in hemolymph free amino acids in vivo is the free amino acid loss from muscle cells observed during cell volume regulation in vitro.
Properties enhancing aerobic capacity of calling muscles in gray tree frogs Hyla versicolor
Authors: Marsh R. L. , Taigen T. L.
Published: December 2017

The muscle features that accommodate the extraordinarily high aerobic respiration during calling by the gray tree frog Hyla versicolor were examined. We compared the muscles used for calling by males (external and internal obliques and laryngeal muscles) with the homologous muscles of females and with the leg muscles of males and females. The leg muscles consisted of 75% by volume fast glycolytic fibers, a composition typical of other muscles described in anuran amphibians. In contrast the calling muscles of males consisted of 100% fast oxidative fibers and had citrate synthase (CS) activities among the highest recorded for ectothermic vertebrates, 65-80 mumol X min-1 X g fresh mass-1. We also noted a strong sexual dimorphism in size and oxidative capacity of these muscles. The external and internal obliques of females weighed an order of magnitude less than the corresponding muscles of males and had CS activities of only 6 mumol X min-1 X g-1. Morphometric measurements of transmission electron micrographs revealed that the calling muscles of males contained high mitochondrial densities (approximately 20% of fiber volume) and capillary densities (approximately 700 mm-2) compared with a representative hindlimb muscle, the sartorius (mitochondrial density, 6% of fiber volume; capillary density, 230 mm-2). These frog muscles, which operate at approximately 20 degrees C, have lower capillary densities per mitochondrial volume than are found in mammalian muscles that function at higher temperatures.
Thermogenin amount and activity in hamster brown fat mitochondria: effect of cold acclimation
Authors: Sundin U. , Moore G. , Nedergaard J. , Cannon B.
Published: December 2017

To investigate the acclimation process in a hibernator, four different parameters of thermogenin amount and activity were investigated in brown adipose tissue mitochondria from cold-exposed and cold-acclimated Syrian hamsters. Hamsters, which are hibernators, have been considered to be "primed" for thermogenesis and thus not to show cold-acclimation effects, but here a significant increase in [3H]GDP-binding capacity was observed (from 0.5 nmol in control to 0.9 nmol GDP/mg in cold-acclimated hamsters), and this increase was paralleled by an increase in thermogenin antigen amount, as measured in an enzyme-linked immunosorbent assay. The transient nature of the effect of cold exposure on [3H]GDP binding, characteristically observed with rat mitochondria, was not observed with hamster mitochondria, and the increase in [3H]GDP binding occurred without a change in the dissociation constant (0.7 microM). The increase in thermogenin amount was paralleled by an increase both in GDP-sensitive Cl- permeability of the mitochondria and in GDP-sensitive respiration. It was established that it is the maximal activity of thermogenin that is rate limiting for thermogenesis in isolated mitochondria, provided that an optimal substrate is used (such as palmitoyl carnitine). Cold acclimation also increased the total amount of mitochondria in the tissue, leading totally to a sixfold increase in thermogenin content of the hamster. It is concluded that (contrary to the general view) hamsters show the expected physiological, pharmacological, and biochemical signs of cold acclimation (i.e., an increased capacity for nonshivering thermogenesis).
Aging changes in renal handling of p-aminohippurate
Authors: Wabner C. L. , Chen T. S.
Published: December 2017

Aging alterations in the renal transport of p-aminohippurate (PAH) were investigated using cortical slices from C57BL/6 mice and standard clearance techniques in 5-ethyl-5-(1-methylpropyl)-2-thiobarbituric acid (Inactin)-anesthetized Fischer 344 rats. Life-span stages were classified as growth, maturity, and aging. PAH uptake was linear from 0 to 20 min with steady state occurring at 30 min in the growing and mature mouse and 20 min in the aging mouse. Km values for PAH uptake in the growing, mature, and aging mouse were 250, 123, and 643 microM, respectively, and maximal rate of uptake values were 0.756, 0.926, and 0.586 mumol X g-1 X 30 min-1, respectively. The efflux half-life (t 1/2) for PAH was similar in all age groups. The PAH acetylation rate was similar in the growing and mature mouse but decreased by 40% in the aging mouse. There were statistically significant correlations between aging (12-27 mo) and renal plasma flow [(RPF) r2 = 0.33, P less than 0.05] and between aging and tubular maximal (Tm) activity for PAH transport (r2 = 0.84, P less than 0.001). Maximal decreases of 25 and 40% were found for RPF and Tm, respectively, in the aging rat. It is concluded that aging affects PAH transport at the receptor level.
Elevated levels of atrial natriuretic peptide during aldosterone escape
Authors: Granger J. P. , Burnett J. C. , Romero J. C. , Opgenorth T. J. , Salazar J. , Joyce M.
Published: December 2017

Escape from the sodium-retaining effects of aldosterone (ALDO) is thought to occur as a result of natriuretic compensatory mechanisms triggered by extracellular fluid volume expansion. The purpose of the present study was to determine whether increases in plasma levels of atrial natriuretic peptide occur during ALDO escape in conscious dogs (n = 6) maintained on a fixed sodium intake (60 meq/day). Infusion of ALDO at a rate of 15 micrograms X kg-1 X day-1 for 6 days decreased sodium excretion (UNaV) from 59.1 +/- 4.0 to 36.2 +/- 5.7 meq/day on day 1, and then UNaV gradually returned to control levels by day 5 of ALDO infusion. Net cumulative sodium balance progressively increased during ALDO infusion, reaching a peak value of 88.8 +/- 21.3 meq/day on day 5. Mean arterial pressure increased from 85 +/- 3 to 95 +/- 4 mmHg, and plasma renin activity decreased from 1.32 +/- 0.27 to 0.32 +/- 0.07 ng angiotensin (ANG) I X ml-1 X h-1 during ALDO infusion. Plasma levels of atrial natriuretic peptide averaged 67.5 +/- 8.9 pg/ml during control and increased to a peak value of 120 +/- 18 pg/ml by day 4 of ALDO infusion. Three to four days after ALDO infusion was stopped, plasma levels of atrial natriuretic peptide averaged 46 +/- 5 and 50 +/- 6 pg/ml, respectively. In summary, escape from the sodium-retaining effects of ALDO is associated with significant increases in the circulatory levels of atrial natriuretic peptide.
Bicuculline blocks an inhibitory baroreflex input to supraoptic vasopressin neurons
Authors: Jhamandas J. H. , Renaud L. P.
Published: December 2017

The excitability of vasopressin-secreting neurons in the hypothalamic supraoptic nucleus is transiently depressed by an abrupt increase in arterial pressure sufficient to activate peripheral arterial baroreceptors. The present experiments examined the ability of locally applied transmitter antagonists to alter this response. Extracellular data were obtained from 27 supraoptic vasopressin-secreting neurons in pentobarbital-anesthetized male Long-Evans rats. In seven of eight cells tested, bicuculline (100 microM) reversibly abolished or delayed the anticipated cessation in neuronal firing that accompanied a 40- to 60-mmHg increase in arterial pressure induced by a brief intravenous infusion of the alpha-agonist metaraminol. Similar tests applied to the remaining cells revealed that prazosin (10 microM), timolol (20 microM), or strychnine (100 microM) were ineffective. These findings suggest that gamma-aminobutyric acidA receptors mediate the depressant responses observed among supraoptic vasopressin-secreting neurons consequent to peripheral baroreceptor activation.
Partial purification and characterization of cysteine proteinases in eccrine sweat
Authors: Yokozeki H. , Hibino T. , Sato K.
Published: December 2017

Attempts were made to purify and characterize cysteine proteinases in human eccrine sweat and further clarify their origin. Benzoyl-DL-arginine-beta-naphthylamide (BANA) and L-leucine beta-naphthylamide (LeuNA) hydrolases in thermally induced sweat were sequentially purified by Sephacryl S-200 chromatography and chromatofocusing, which yielded two major peaks of BANA hydrolase activity, BANA-I and BANA-II. Both enzymes are cysteine proteinases as evidenced by stimulation of enzymic activity by dithiothreitol and ethylenediaminetetraacetic acid and its inhibition by iodoacetic acid, (PCMB), and trans-epoxysuccinyl-L-leucylamido-(4-guanidino)-butane (E-64). Unlike BANA-II, BANA-I showed an additional aminopeptidase activity, an affinity to concanavalin A-Sepharose but no affinity to organomercurial sepharose and failed to hydrolyze benzyloxycarbonyl-phenylalanyl-arginine 4-methyl 7-coumarylamide (Z-Phe-Arg-NMec), a specific substrate for cathepsin B, which is poorly sensitive to leupeptin [inhibitor constant (Ki) = 1 X 10(-5) M] and relatively heat resistant. These and other characteristics such as its isoelectric points (PI) (= 5.8) and the Km for Arg-NMec (0.1 mM) and BANA (0.71 mM) all support the possibility that BANA-I is closely related to cathepsin H. In contrast, BANA-II is sensitive to Zn2+, leupeptin (Ki = 5.5 X 10(-9) M), is not adsorbed by concanavalin A- (Con-A)Sepharose, but is bound to organomercurial sepharose. It has a specificity to Z-Phe-Arg-NMec but not to Arg-NMec, has the molecular weight of 27, PI of 5.2, the pH optima for BANA (6.0), and the Km for BANA of 3.3 mM and the Km for Z-Phe-Arg-NMec of 0.1 mM. These features resemble those of liver cathepsin B. Leupeptin-sensitive BANA hydrolase was observed in the glandular extract of isolated sweat glands, which was increased after stimulation with methacholine and isoproterenol in vitro. The data are consistent with the notion that cathepsins B- and H-like enzymes are present in eccrine sweat and the former may be derived from the sweat gland.