bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissociation of adrenal corticosteroid production from ACTH in water-restricted female rats
Authors: Doell R. G. , Dallman M. F. , Clayton R. B. , Gray G. D. , Levine S.
Published: December 2017

These experiments were undertaken to investigate the mechanism whereby a precipitous drop in plasma corticosterone concentration is brought about following drinking in rats on a restricted water schedule. No alteration in adrenocorticotrophic hormone (ACTH) output was found, nor was catabolism of corticosterone sufficient to account for the drop. It is concluded that corticosterone level is controlled under these conditions by a mechanism independent of ACTH concentration.
Regional neurohypophyseal blood flow and its control in adult sheep
Authors: Page R. B. , Funsch D. J. , Brennan R. W. , Hernandez M. J.
Published: December 2017

Regional neurohypophyseal and cerebral blood flows were measured by the radiolabeled microsphere technique in 30 adult sheep under light barbiturate anesthesia. Regional blood flows were determined under basal conditions. The responses of regional blood flow to alterations in arterial PCO2 and to changes in arterial blood pressure wee also determined. In addition, the relationship between regional neurohypophyseal blood flow and neurosecretory activity as judged by plasma arginine vasopressin levels was assessed. Under basal conditions median eminence blood flow averaged 461 ml.100 g-1.min-1 and did not significantly differ from neural lobe blood flow (436 ml.100 g-1.min-1). Blood flow in the neurohypophysis was about 8 times cortical and 16 times white matter blood flow in these animals. Median eminence and neural lobe blood flow proportionately increased far less than regional cortical or white matter blood flow under conditions of hypercarbia. With alteration of arterial blood pressure, regional neurohypophyseal blood flow remained constant beyond the limits of cerebral autoregulation. The neurohypophysis demonstrates a degree of blood flow homeostasis that exceeds that of any other brain area studied. Although the neurohypophysis is a diverticulum of the brain, its vascular system forms a unique functional as well as a unique anatomic unit.
Effect of methacholine on Na+ pump activity and ion content of dispersed avian salt gland cells
Authors: Hootman S. R. , Ernst S. A.
Published: December 2017

The effects of the cholinergic agonist methacholine chloride (MCh) on cellular ion content and Na+ pump activity of dissociated duck salt gland cells were studied. Dispersed salt gland cells regulate intracellular ion levels in a ouabain-sensitive manner. MCh (0.5 mM) caused no detectable change in cell Na+ levels over the first 10 min of exposure of cells to the agonist but elicited decreases of 23 and 13%, respectively, in intracellular Cl- and K+ content. The rate of turnover of salt gland cell plasmalemmal Na+ pumps, as measured by [3H]ouabain binding to the dissociated cells, was markedly stimulated by 0.5 mM MCh, although the total number of binding sites at equilibrium remained unchanged. Replacement of medium Na+ with choline abolished the MCh-stimulated increase in ouabain binding but had no effect on the rate of glycoside binding in the absence of the agonist. Substitution of Cl- in the medium by NO3-, SO42-, or benzene sulfonate- reduced the stimulated component of Na+ pump turnover by 85-90%. Addition of 1 mM furosemide to the medium abolished the increase in ouabain binding and ouabain-sensitive oxygen consumption observed after exposure of salt gland cells to MCh. These data are consistent with the hypothesis that cholinergic stimulation of salt gland cells triggers a Cl--dependent uptake of Na+, which elicits a compensatory increase in Na+ pump turnover. In addition, the decrease in cellular Cl- content caused by MCh suggests that the agonist either directly or indirectly mediates an efflux of Cl- from the cells.
Circannual renal function and plasma electrolytes of the marmot
Authors: Zatzman M. L. , South F. E.
Published: December 2017

Studies with unanesthetized active (non-lethargic) marmots demonstrated circannual rhythms of renal function (clearances of p-aminohippurate, creatinine, and inulin), plasma osmolality, and plasma sodium and potassium concentrations. Effective renal plasma flow, glomerular filtration rate, the clearance of creatinine, and plasma potassium were highest in spring and lowest in the fall and winter. Plasma osmolality and plasma sodium concentrations tended to be highest during the winter months and lowest in the spring and summer. p-Aminohippurate excretion was shown to be a Tm-limited system.
Comparison of the "mammal machine" and the "reptile machine": energy use and thyroid activity
Authors: Hulbert A. J. , Else P. L.
Published: December 2017

Oxygen consumption of tissue slices of liver, kidney, and brain were measured at 37 degrees C to assess in vitro metabolism of tissues of Amphibolurus nuchalis and Mus musculus (a reptile and mammal with same weight and body temperature). “Sodium transport” metabolism was also assessed (with use of ouabain) in these tissues. The mammal had an in vitro tissue metabolism that was two to five times that of the reptile and its sodium transport metabolism was four- to ninefold greater. Growth of reptile young and mammal young at the same body temperature was measured and the mammal showed a growth rate that was an order of magnitude greater than the reptile. Thyroid activity was assessed in the reptile and mammal by measurement of thyroidal uptake and release of 125I and serum thyroxine concentration. All parameters indicated a greater thyroid activity in the mammal. These findings are discussed in relation to the action of the thyroid hormones, the paleoecology of mammals and reptiles and the evolution of endothermy.
Dark pulses affect the circadian rhythm of activity in hamsters kept in constant light
Authors: Ellis G. B. , McKlveen R. E. , Turek F. W.
Published: December 2017

We compared the effects of light pulses in constant darkness (DD) and dark pulses in constant light (LL) on the free-running rhythm of locomotor activity in male golden hamsters. Light pulses yielded advances, delays, or no change in the rhythm of activity. These data conform to a typical phase-response curve; this curve was unaffected by pinealectomy. Dark pulses occurring either late in the subjective night or early in the subjective day had little effect. In contrast, dark pulses occurring either late in the subjective day or early in the subjective night altered the rhythm in one of three ways: advance of the rhythm; splitting into two components; or induction of a new component, in phase with the pulse. Because dark pulses in LL perturb the circadian system in a different manner than do light pulses in DD, they may have value in identifying heretofore unknown aspects of circadian systems. As such, the use of dark pulses to perturb circadian rhythmicity will be a useful tool in examining the formal properties of circadian systems.
Free amino acids in the blood of fetal and maternal Weddell seals
Authors: Murphy B. J. , Hochachka P. W. , Zapol W. M. , Liggins G. C.
Published: December 2017

The content of free amino acids in whole blood was measured in near-term gravid female Weddell seals (Leptonychotes weddelli) and compared with fetal amino acid profiles during rest and during experimental diving. With the exception of taurine and glutathione, Ninhydrin-reactive components of acid extracts of blood occurred in higher concentrations on the fetal side of the placenta than on the maternal side. Compared with humans the Weddell seal displayed higher ratios of fetal arterial to maternal arterial levels for aspartate, glycine, alanine, valine, tyrosine, phenylalanine, and total branched-chain amino acids. In the resting state the total free amino acid concentration in maternal blood was only about 70% as large as the total amino acid concentration in fetal blood, compared with a value of over 80% for humans. Only modest changes in the concentrations of specific amino acids occurred during simulated awake diving, but the overall maternal pools of glycine, glutamate, and glutamine were augmented, creating favorable conditions for uptake by the fetus.
Myocardial blood flow and metabolism in the diving seal
Authors: Kjekshus J. K. , Blix A. S. , Elsner R. , Hol R. , Amundsen E.
Published: December 2017

The adaptations of myocardial metabolism to diving asphyxia have been studied in 12 harbor seals (Phoca vitulina). Unanesthetized animals were submerged for periods of 10-16 min. Heart rate decreased from 135 to 12 beats/min. Myocardial blood flow decreased to an average of 10% of predive values and remained constant during the dive. The progressive reduction in arterial O2 content was associated with an increase in myocardial lactate and hydrogen ion production, but no change in glucose or free fatty acid extraction occurred. After restoration of breathing a reactive myocardial hyperemia and an immediate return to myocardial uptake of lactate were observed. Despite increased glycogenolytic activity throughout the dive, coronary flow distribution was fully controlled, and no evidence of ischemic dilatation of the left ventricle or S-T segment elevation in the electrocardiogram was observed. These adaptations to diving asphyxia in the seal myocardium permit a reduction of coronary blood flow comparable to that observed in the infarcted dog myocardium and therefore have relevance for therapeutic approaches to reduction of myocardial ischemic injury in humans.
Catecholamine release and blood pressure changes induced by exercise in dogfish
Authors: Opdyke D. F. , Carroll R. G. , Keller N. E.
Published: December 2017

Plasma norepinephrine (NE), epinephrine (E), and potassium (K+) were measured before, during a 3-min bout of exercise, and at intervals after exercise in Squalus acanthias. The dorsal aortic pressure response following 1 min of exercise was observed in another series of experiments. Plasma E, NE, and K+ increased significantly and progressively during the exercise period and for 2 min after exercise. Plasma E increased significantly during the 1st min; NE during the 2nd min; but K+ did not increase significantly until the 3rd min of exercise. Blood pressure decreased significantly during 1 min of exercise but increased over control level within 4 min after the end of exercise coincident with the peak of plasma E and NE concentrations. Plasma NE, E, and blood pressure decreased slowly in parallel fashion during the 37-min postexercise period of observation. Increased plasma K+ from skeletal muscle is probably not the primary stimulus for early catecholamine release in exercising dogfish, but increased plasma K+ does contribute to releasing and maintaining plasma NE and E levels in the postexercise period. This results in a sustained pressor effect that promotes blood flow and aids in metabolic recovery.
Central and peripheral adrenergic modulation of carotid sinus-induced renin release
Authors: Schultz H. D. , Zehr J. E. , Livnat A.
Published: December 2017

To study central and peripheral mechanisms that regulate the level of circulating renin during activation of the carotid sinus baroreflex, both carotid sinuses were isolated and perfused at constant flow in chloralase-anesthetized dogs. Sinus pressure was controlled by an adjustable reservoir while systemic pressure was stabilized using an external chamber. Arterial renin activity, measured by radioimmunoassay, was increased during sinus hypotension only if systemic pressure was held constant. The renin response was eliminated by either sinus or renal denervation. Administration of propranolol (iv) or phentolamine directly into the renal artery totally blocked the increase in renin during activation of the reflex. Perfusion of a beta-adrenergic blocker (propranolol) or an alpha-adrenergic blocker (phentolamine) through the third and fourth cerebroventricles had no effect on the increase in renin during sinus hypotension, whereas centrally administered clonidine, and alpha-agonist, blocked the response. We conclude that the sinus reflex arc affecting renin release involves not only activation of peripheral alpha- and beta-adrenergic receptors in the kidney but also inhibition of central alpha-adrenergic receptors. No evidence for central beta-involvement was found.
Toward a concept of the functional unit of mammalian skeletal muscle
Authors: Bloch E. H. , Iberall A. S.
Published: December 2017

The current concepts for the functional unit of mammalian skeletal muscle are reviewed and shown to lack components that are required for determining the unit. To secure a definition for the functional unit, requisite criteria were selected, and the manner by which these criteria were used to define the functional unit are discussed. For deriving a definition of the unit the following values were obtained: the unit is associated with the total length of the muscle fiber, which may achieve a maximum length of 60 cm; it exhibits an average diameter of 40 micrometers/fiber; it is associated with a capillary net whose length (arteriole to venule) is about 750-1,000 micrometers max; the net exhibits a capillary-to-fiber ratio for long capillaries of approximately 1-1.5:1, with a transverse capillaries occurring approximately every 150 micrometers; and it has a fiber-to-motor end plate ratio of 1:1. The correlation between anatomic data and functional data indicate that a functional unit of muscle is delimited by about 1 mm2 of the cross-sectional area of a muscle bundle, since this is the maximum area under autonomic control of its particular arteriolar blood supply, the metabolic throttle that determines the power being expended by the muscle bundle.
Role of the small bowel in regulating food intake in rats
Authors: Atkinson R. L. , Whipple J. H. , Atkinson S. H. , Stewart C. C.
Published: December 2017

This study tested the hypothesis that exposure of the lower intestine to nutrients decreases subsequent food intake. Eight male Sprague-Dawley rats underwent jejunoileal bypass surgery with 8 cm of proximal jejunum anastomosed to 5 cm of terminal ileum in an end-to-side fashion. Eight control rats had sham bypass surgery with similar intestinal incisions that were reanastomosed in normal continuity. Another group of eight rats underwent ileal transposition (IT). A 10-cm segment of terminal ileum was transected, leaving the mesentery and blood supply intact, and transposed to the jejunum 8 cm from the ligament of Treitz. Thus total intestinal length was intact. Eight control rats had similar intestinal transections reanastomosed in normal continuity. A similar pattern of decreased food intake in the first 1-2 wk occurred in both bypass and IT rats. The values were significantly different from the respective sham surgery control groups. Body weights decreased, but the fall was greater in bypass rats. These data suggest that partially digested food in the lower intestine decreases food intake.
Reduction of cerebrovascular reactivity during hypercapnia
Authors: Lopez de Pablo A. L. , Gonzalez M. C. , Dieguez G. , Gomez B. , Lluch S.
Published: December 2017

The effects on cerebral blood flow of alpha- or beta-adrenergic receptor stimulation of cerebral vessels were examined in 13 unanesthetized goats before and during hypercapnia produced by inhalation of 10% CO2 in air. This procedure increased the PCO2 from 34 to 52 and was accompanied by a fall in pH from 7.39 to 7.26. Electrical stimulation of the cervical sympathetic nerve and injections of norepinephrine and tyramine into the internal maxillary artery produced reductions in cerebral blood flow that were abolished or reduced in hypercapnia. The increase in cerebral blood flow in response to beta-adrenergic stimulation with isoproterenol was also reduced. Hypercapnia caused a similar depression of the constrictor and dilatory effects of the nonadrenergic drugs vasopressin and diazoxide. The results show a decreased response of cerebral vessels to adrenergic and nonadrenergic stimuli in hypercapnia. The findings do not suggest any difference between the refractoriness of cerebral vessels in hypercapnia and that described in other vascular beds.
Effect of chronic altitude hypoxia on hematologic and glycolytic parameters
Authors: Clench J. , Ferrell R. E. , Schull W. J.
Published: December 2017

The physiological effect of chronic exposure to altitude hypoxia on the glycolytic intermediates, adenosine triphosphate and 2,3-diphosphoglyceric acid, and the hematologic parameters, hemoglobin, hematocrit, and mean cell hemoglobin concentration, has been examined in an indigenous population, the Aymara, of the Departamento de Arica, Chile. This population normally resides at three altitudes: the coast (0-500 m), the sierra (2,500-3,500 m), and the altiplano (above 4,200 m). After isolation of altitude from other environmental factors (age, sex, body build, ethnicity, smoking, and residential permanence), an increase in 2,3-diphosphoglycerate and a decrease in adenosine triphosphate was observed. Both hemoglobin and hematocrit increased as expected, but mean cell hemoglobin concentration declined. It is proposed that a decline in the activity of a single enzyme, pyruvate kinase, can account for these observed changes and suggests a pivotal role for pyruvate kinase in the physiological adaptation to altitude hypoxia.
Uridine regulation by the isolated rat liver: perfusion with an artificial oxygen carrier
Authors: Monks A. , Cysyk R. L.
Published: December 2017

The isolated rat liver was used to investigate the role of the liver in the regulation of circulating uridine concentrations. A synthetic blood substitute (Fluosol-43) was utilized as an alternative oxygen-carrying perfusion medium to a simplified blood preparation and produced no apparent hepatotoxicity within the perfusion period. The isolated rat liver excreted uridine into a circulating perfusion medium achieving concentrations similar to those found in rat plasma (1.4 +/- 0.6 microM). The mean output of uridine over 2 h was 107 nmol.h-1.g liver-1, but if the perfusate was recirculated the net output of uridine was reduced to 12.7 nmol.h-1.g-1. The rate of depletion of nonphysiological concentrations of circulating uridine was found to be concentration dependent up to 25 microM. At a steady state of circulating uridine, a radioactive uridine spike was cleared with a half-life of 7.4 min and an elimination constant of 0.094 min-1; 30% of the radioactivity appeared in the perfusate as metabolites of uridine within 40 min. Thus the perfused rat liver acts to maintain circulating uridine concentrations similar to those measured in plasma.
Dissociation of dipsogenic and pressor responses to chronic central angiotensin II in rats
Authors: Di Nicolantonio R. , Mendelsohn F. A. , Hutchinson J. S. , Takata Y. , Doyle A. E.
Published: December 2017

Chronic intracerebroventricular (icv) infusion of angiotensin II (ANG II) (6 micrograms/h) in rats resulted in a sustained 70-mmHg rise in blood pressure during 7 days of treatment. A marked dipsogenic response preceded the maximal rise in blood pressure, peaked at 24 h, and returned to control by the 5th day. Urinary sodium excretion rose on the 1st day of infusion but thereafter was not different from that of vehicle-infused rats. ANG II-infused rats showed a small but significant kaliuresis, a fall in serum osmolality (5.5 mosmol/kg), but no change in plasma Na+, K+, or glucose. Rats infused with the same dose of ANG II intravenously showed a small, 8-mmHg rise in blood pressure, but none of the changes noted after icv ANG II. Plasma renin activity was suppressed in rats infused with ANG II by both routes. We conclude that the pressor, dipsogenic, and renal excretory effects of icv ANG II are mediated centrally and cannot be explained by leakage of the peptide into the systemic circulation. Furthermore, the pressor and dipsogenic effects of ANG II become clearly dissociated during chronic icv infusion.
Action of preoptic injections of beta-endorphin on temperature regulation in rabbits
Authors: Rezvani A. H. , Gordon C. J. , Heath J. E.
Published: December 2017

Male New Zealand White rabbits, Oryctolagus cuniculus, were stereotaxically implanted with a guide tube above the preoptic/anterior hypothalamus area (PO/AH) for the injection of the opioid peptide, beta-endorphin (beta-E), naloxone, sodium salicylate, or physiological saline. PO/AH and ear temperature, oxygen consumption, and evaporative heat loss (EHL) were recorded in free-moving rabbits before and after injection of saline followed with beta-E, naloxone, or sodium salicylate at ambient temperatures (Ta) of 2-31 degrees C. A 5-micrograms injection of beta-E promoted a rapid reduction in ear temperature followed by a prolonged rise in PO/AH (body) temperature. Preinjection with an isovolumetric amount of the opiate antagonist, naloxone, inhibited the thermoregulatory effects of beta-E. The beta-E-induced rise in body temperature was directly correlated with Ta. beta-E had no effect on oxygen consumption at Ta's of 5 and 27 degrees C. When measured 30 min after injection, beta-E demonstrated a significant inhibition of EHL at Ta's of 27 and 31 but not 5 degrees C. The beta-E-induced rise in body temperature was not antagonized with preinjections of sodium salicylate in the PO/AH. These data indicate that beta-E promotes a regulated increase in body temperature. The mechanism of activation appears to be distinct from that of an infectious fever.
PAH secretion in the urinary bladder of a crab Cancer borealis
Authors: Miller D. S. , Holliday C. W.
Published: December 2017

Uptake of 10 microM p-aminohippuric acid (PAH) by sections of Cancer borealis urinary bladder was concentrative, saturable (Km 67 microM, Vmax 1.7 nmol.mg tissue-1.h-1), inhibitable by other organic anions, and dependent on medium Na and glycolytic metabolism. Bladders mounted in flux chambers exhibited net secretory transport of PAH, with serosa-to-lumen fluxes (Js leads to l) being about 4 times lumen-to-serosa fluxes (Jl leads to s). In 60-min flux chamber studies, tissue-to-medium ratios exceeded unity with serosal, but not luminal, PAH. Initial (10 min) fluxes and tissue accumulations (Ac) were measured in the absence and presence of 1-5 mM BCG (bromocresol green; competitor organic anion). With serosal PAH, serosal BCG (1 mM) reduced serosa-to cell flux (Js leads to c), Ac, and Jc leads to l by 60-75%. With luminal PAH, luminal BCG (1 mM) had no effect on Jl leads to c, Ac, or Jc leads to s; increasing the luminal BCG concentration to 5 mM reduced Jl leads to c, Ac, and Jc leads to s by 40-50%. The data are consistent with a model featuring an inwardly directed pump on the serosal membrane, cellular accumulation, and a facilitated carrier on the luminal membrane.
Baroreflex control of heart rate in humans during nitroprusside-induced hypotension
Authors: Chen R. Y. , Fan F. C. , Schuessler G. B. , Chien S.
Published: December 2017

The baroreflex control of heart rate was investigated on 10 informed human subjects during light halothane anesthesia (0.3-0.5%, inspired concentration). The relationship of systolic pressure (SP) to the succeeding pulse interval (PI) was evaluated on a beat-to-beat basis during the entire course of sodium nitroprusside (SNP) depressor test. The initial slope of SP-PI plot (dPI/dSP) was used as an index of the sensitivity of baroreflex control of heart rate. Following an injection of SNP (4-6 micrograms/kg), dPI/dt was related directly to dPI/dSP, whereas the latter was inversely correlated with dSP/dt. The recovery of PI lagged behind that of SP, and there was a hysteresislike loop on the SP-PI plot. The time lag of PI recovery and the loop of SP-PI plot were markedly decreased by propranolol treatment and significantly increased by atropine. The slopes of SP-PI plot were significantly decreased by atropine but relatively unaffected by propranolol. These results indicate that SNP-induced hypotension in man during halothane anesthesia is associated with a withdrawal of parasympathetic inhibition and an enhancement of sympathetic activity. The autonomic control of heart rate in response to rapid changes in arterial pressure induced by SNP is dominated by parasympathetic influence; the more persistent sympathetic activity only becomes evident when the parasympathetic influence subsides quickly as the arterial pressure stays relatively constant at a new level. The slope of SP-PI plot (dPI/dSP) and the ratio of dPI/dt to dSP/dt during the decreasing pressure phase of SNP test can be used as indices for the sensitivity of baroreflex control of heart rate.
High sensitivity of Xenopus gustatory receptors to amino acids and bitter substances
Authors: Yoshii K. , Yoshii C. , Kobatake Y. , Kurihara K.
Published: December 2017

The gustatory nerve responses of the aquatic toad Xenopus laevis to salts, acids, amino acids, and bitter substances were recorded. 1) The gustatory receptors were sensitive to amino acids and bitter substances. The thresholds were 10(-7) M for Arg, 3 X 10(-9) M for strychnine, and 3 X 10(-8) M for quinine, 200-20,000 times lower than the thresholds for the respective stimuli in the bullfrog. 2) The basic and the neutral amino acids were effective whereas the acidic ones were not. Relations between the responses and log stimulus concentrations for the basic amino acids were linear in a wide concentration range whereas those for the neutral ones were of S shape. Cross-adaptation did not occur among pairs of a basic amino acid and a neutral one. 3) Responses to the basic amino acids and the basic bitter substances were suppressed by the addition of salts to the stimulating solutions, while those to the neutral and the acidic substances were not suppressed.
Appetite suppressant activity in plasma of rats after intestinal bypass surgery
Authors: Atkinson R. L. , Brent E. L.
Published: December 2017

Male Sprague-Dawley rats with a jejunoileal bypass ate 32% less in the 1st h of refeeding after an overnight fast than did sham-bypass rats. Fasted recipients injected intraperitoneally with 6-7 ml of bypass plasma also ate 32% less (P less than 0.001) during the 1st h of refeeding than did recipients of sham-bypass plasma, but subsequent intake was not significantly different. Rectal temperature, hematocrit, white blood cell count, and percent polymorphonuclear leukocytes were not different between bypass and sham-bypass rats. A test for aversive conditioning suggested that the effect of bypass plasma was not due to illness or discomfort. These data suggest that intestinal bypass produces a transferable humoral factor that suppresses food intake and that the effect is not due to illness or discomfort. If the decreased food intake in humans after intestinal bypass is due to a similar mechanism, the possibility exists that this humoral appetite-suppressant factor may be clinically useful in the treatment of morbid obesity.
Alpha-methyl-p-tyrosine shifts circadian temperature rhythms
Authors: Cahill A. L. , Ehret C. F.
Published: December 2017

alpha-Methyl-p-tyrosine shifts the acrophase (time of highest temperature) of the circadian temperature rhythm of the rat to earlier or later times of day depending on the phase of the circadian cycle at which the drug is administered. When alpha-methyl-p-tyrosine methyl ester HCl is injected intraperitoneally at a dose of 100 mg/kg late in the projected 8-h light phase, the acrophase of the intraperitoneal temperature rhythm is delayed by up to 3 h. However, when the same dose of drug is given 9-10 h into the projected 16-h dark phase of the daily cycle, the acrophase of the temperature rhythm occurs about 2 h earlier than expected. The times of alpha-methyl-p-tyrosine administration leading to maximal phase delays or advances are correlated with the times of minimal and maximal turnover of norepinephrine in the hypothalamus. These results suggest that changing rates of norepinephrine turnover in the hypothalamus may regulate the circadian temperature rhythm in rats. The results also emphasize the fact that the effects of drugs may vary as a function of the time of administration. This fact must be taken into account in pharmacologic testing.
Incorporation of polyunsaturated fatty acids into lipids of rainbow trout hepatocytes
Authors: Sellner P. A. , Hazel J. R.
Published: December 2017

Hepatocytes from 5- or 20 degrees C-acclimated rainbow trout (Salmo gairdneri) were incubated with [1-14C]oleic, -linoleic, or -linolenic acid. Both acclimation groups demonstrated greater incorporation of derivatives from linolenic and linoleic acids into phospholipids when assayed at 5 and 20 degrees C; few derivatives of oleic acid were formed. Cells from cold-acclimated trout, when assayed at 5 degrees C with linolenic acid, incorporated a large proportion of radioactivity into free fatty acids. Analysis of each lipid fraction revealed a relatively specific incorporation of certain fatty acids. For example, "dead end" elongation products of the three substrates were preferentially incorporated into neutral lipids, while delta 6 desaturation products of the three acids were retained in the free fatty acid fraction. Twenty-carbon acid derivatives of linoleic and linolenic acids were directed into the phospholipid fraction. Incorporation of the delta 5 desaturation products was temperature sensitive in cells from cold-acclimated but not warm-acclimated trout. The results suggest that selectivity of incorporation of specific fatty acids into phospholipids may be of importance in restructuring membranes of poikilotherms during thermal adaptation.
Comparison of the response of muskrat, rabbit, and guinea pig heart muscle to hypoxia
Authors: McKean T. , Landon R.
Published: December 2017

Papillary muscles were removed from anesthetized muskrats and rabbits and mounted in a muscle chamber maintained at 29 degrees C. Muscles were stimulated at a rate of 12/min and subjected to 30 min of hypoxia followed by 30 min of reoxygenation. Peak tension in muskrats declined less than peak tension in rabbits during oxygen deprivation. During reoxygenation, peak tension in muskrats rapidly returned to control levels and then exceeded control, whereas peak tension in rabbits never recovered. Time to peak tension was largely unaffected in muskrats during hypoxia and decreased in rabbits. During reoxygenation, time to peak tension increased in muskrats and returned to control in rabbits. Hearts from muskrats and guinea pigs were removed under ether anesthesia and perfused retrograde with a physiological saline solution. Developed tension, heart rate, coronary blood flow, and lactate dehydrogenase (LDH) output were monitored. During 30 min of hypoxia, muskrat hearts developed a profound bradycardia compared to guinea pigs. Coronary flow increased in both species but less so in muskrats. Guinea pig hearts developed contracture whereas muskrat hearts relaxed. During reoxygenation heart rate and coronary blood flow returned toward normal but cells released large amounts of LDH, indicating cell damage. It is concluded that the isolated heart of the muskrat, a diving mammal, is better able to deal with hypoxia than the heart of the nondividing guinea pig and rabbit.
Blood metabolites and feeding during postinsulin hypophagia
Authors: Geary N. , Grotschel H. , Scharrer E.
Published: December 2017

Physiological changes accompanying a period of voluntary hypophagia in male Sprague-Dawley rats after insulin-induced hyperphagia and body weight gain were investigated. Postinsulin hypophagia was manifested as a reduction in meal duration diurnally and nocturnally (Geary et al., Behav. Neural Biol. 31: 435-442, 1981). Gastrointestinal transit of 14C-labeled nutrients was unchanged in hypophagic rats, suggesting a postabsorptive mechanism controlled the hypophagia. Basal blood glucose and plasma nonesterified fatty acids, 3-hydroxybutyrate, glycerol, and some amino acids were elevated during hypophagia, while liver glycogen content was reduced. Hypophagic rats' arteriovenous blood glucose differences and glucose oxidation rates, however, were not different from controls. After nutrient repletion blood glucose and plasma glycerol remained elevated in hypophagic rats in comparison to controls, while differences in other plasma metabolites were reduced. Liver glycogen accumulated faster in hypophagic rats. These data were related to the lipostatic and other hypotheses how energy balance status affects hunger and satiety.
Computer simulation of metabolism of glucose-perfused rat heart in a work-jump
Authors: Achs M. J. , Garfinkel D. , Opie L. H.
Published: December 2017

A computer model of glycolysis, the tricarboxylic acid cycle, and related amino acid metabolism, is described for a glucose-perfused experimental rat heart preparation suddenly switched from low work load (Langendorff perfusion) to high work load (left atrial perfusion). Glycolytic intermediate measurements suggest activation of phosphofructokinase within a few seconds. This activation, and also that of other glycolytic enzymes, is calculated as due to a sharp increase in cytoplasmic Mg2+ level, which overcomes the inhibitory effects of a rapid fall in cytoplasmic pH to 6.77 (calculated from a rapid fall in creatine phosphate). Increased glycolytic substrate is initially supplied by glycogenolysis mediated by phosphorylase b (activated by an early rise in cytoplasmic AMP), followed by increased glucose uptake from the perfusate. Testable predictions are made by the model, especially that lactate production rate should peak early. Additional experiments are described that verify these predictions and fill gaps in the original measurements. The role of modeling in interpreting such experiments is discussed.
Obesity-inducing hypothalamic knife cuts: effects on lipolysis and blood insulin levels
Authors: Bray G. A. , Sclafani A. , Novin D.
Published: December 2017

The effect of two experimental manipulations designed to mobilize lipids from adipose tissue have been investigated in rats with parasagittal knife cuts in the ventromedial hypothalamus (VMH). Those animals which displayed hyperphagia during the initial 5 days VMH knife cuts were then restricted in food intake to reduce body weights to levels comparable to that of the sham-operated controls. Two weeks following the knife-cut lesions, or sham operations, animals in the first experiment were exposed to the cold for 60 min, and those in the second experiment were injected with 2-deoxy-D-glucose (2-DG). The injections of 2-DG increased the level of glycerol in the control animals but not in the animals with VMH knife cuts. Both groups showed a rise in glucose. Plasma insulin and triglycerides were the same in both groups. Exposure to the cold increased the level of glycerol in both groups. The insulin levels were lower in the corresponding groups with knife cuts. These studies show that VMH knife cuts do not produce hyperinsulinemia in pair-gained rats.
Relationships between maternal hormones and weight of newborn sheep
Authors: Caton D. , Kalra P. S. , Wilcox C. J.
Published: December 2017

Intact and ovariectomized mixed-breed sheep were studied in chronic experiments during the last weeks of pregnancy. Measurements were made of the rate of uterine blood flow (ml/min and ml X min-1 X kg-1, combined weight of fetus, uterus, and placenta) and of arterial and uterine venous concentrations of progestagens, estrone, and estradiol. The birth weight of the lamb was directly related to mean maternal concentrations of estrone and estradiol and to the rate of progestagen release by the uterus and its contents (ng X ml-1 X kg-1), calculated by taking the product of the rate of blood flow and the arteriovenous progestagen difference. Ovariectomy altered the relationship between birth weight and progestagen release. Data suggest that rates of progestagen release both by the fetoplacental unit and by the ovary are proportional to the birth weight of the lamb.
Chemiosmotic potassium ion pump of insect epithelia
Authors: Harvey W. R. , Cioffi M. , Wolfersberger M. G.
Published: December 2017

Transporting epithelia of insects are unlike most vertebrate epithelia in that they lack a serosa and possess septate junctions. The Na+/K+ pump is absent and an electrogenic K+ uniport pump is present in such insect epithelia as lepidopteran midgut, dipteran salivary glands, and many Malpighian tubules. The K+ pump is located in the apical plasma membrane and pumps K+ out of the cells. In midgut the transepithelial K+ transport is against a potential difference (PD) in excess of 120 mV and against a 10-fold K+ concentration difference in vivo. The pump uses a K+-modulated ATPase thought to be located in particles called K+ portasomes, which resemble the F1-F0 ATPase of phosphorylating membranes. Like F1-F0 particles the K+ portasomes are located on the cation input, electronegative, ATP-binding side of the membrane and appear to pump two cations for each MgATP2- hydrolyzed. We propose that in K+-transporting epithelia and in phosphorylating membranes running backwards the portasomes orient the binding of ATP with respect to a cation-gated channel in such a way that when MgATP2- is hydrolyzed P-i is separated from MgADP-; the 2 K+ or 2 H+ ions are no longer neutralized and are repelled from the channel to the opposite side of the membrane. We have isolated the K+ portasome-containing goblet cell apical membrane from larval Manduca sexta midgut and are attempting to isolate the K+ portasomes and K+-ATPase.
Renal and adrenal responses to converting-enzyme inhibition in fetal and newborn life
Authors: Robillard J. E. , Weismann D. N. , Gomez R. A. , Ayres N. A. , Lawton W. J. , VanOrden D. E.
Published: December 2017

The renal and adrenal responses to a continuous infusion of the angiotensin-converting enzyme (ACE) inhibitor captopril were studied in 27 chronically catheterized sheep fetuses (less than 120 days gestation, n = 15, and greater than 130 days gestation, n = 12; term being 145 days) and in 12 newborn lambs between 8 and 21 days of age. Total renal blood flow did not change during ACE inhibition. However, the renal vascular resistance decreased significantly in newborn lambs (-21.8 +/- 5.7%) and in fetuses greater than 130 days (-21.7 +/- 4.7%) but not in fetuses less than 120 days. A significant decrease in filtration fraction (-19.2 +/- 6.5%) was observed in newborn lambs. No changes in urinary kallikrein and prostaglandin excretion rate were observed during ACE inhibition in any group of animals. ACE inhibition produced similar declines in blood pressure in both groups of fetuses (-10.2 +/- 3% in fetuses less than 120 days and -9.5 +/- 4.6% in fetuses greater than 130 days) and in newborn lambs (-13.4 +/- 2.1%). The percent changes in plasma renin activity were similar in all groups of animals. However, a significant decline in plasma aldosterone concentration was observed only in newborn lambs (from 130 +/- 31 to 64 +/- 9 pg/ml). These results suggest that the renin-angiotensin system might have physiological significance during maturation, but that this role seems to be more important in near-term fetuses (greater than 130 days) and postnatally than early in gestation.
Bone resorption and mineral excretion in rats during spaceflight
Authors: Cann C. E. , Adachi R. R.
Published: December 2017

Bone resorption was measured directly in flight and synchronous control rats during COSMOS 1129. Continuous tracer administration techniques were used, with replacement of dietary calcium with isotopically enriched 40Ca and measurement by neutron activation analysis of the 48Ca released by the skeleton. There is no large change in bone resorption in rats at the end of 20 days of spaceflight as has been found for bone formation. Based on the time course of changes, the measured 20–25% decrease in resorption is probably secondary to a decrease in total body calcium turnover. The excretion of sodium, potassium, and zinc all increase during flight, sodium and potassium to a level four to five times control values.
Relationship of trace metals to fever during infection: are prostaglandins involved?
Authors: Tocco R. J. , Kahn L. L. , Kluger M. J. , Vander A. J.
Published: December 2017

Endogenous pyrogen/leukocyte endogenous mediator (EP/LEM) induces, in the host organism, a fever that is thought to be mediated to some extent via the production of prostaglandins. The role of prostaglandins in the EP/LEM-induced fall in plasma iron and zinc is less clear. To study this relationship, rabbits and rats were injected with an antipyretic dose of prostaglandin synthase inhibitors concurrent with heat-killed bacteria or endotoxin. These inhibitors, indomethacin and sodium salicylate, were successful in partially and totally blocking fever in rabbits and rats, respectively; however, they had no effect on the hypoferremia and hypozincemia of infection. We conclude that prostaglandins are probably not involved in the fall in plasma iron and zinc during acute bacterial infection. Further, since hypoferremia and hypozincemia occurred even though fever was blocked, the fall in trace metals due to infection is not dependent on the rise in both temperature.
Feeding after recovery from 2-deoxyglucose injection: cerebral and peripheral factors
Authors: Granneman J. , Friedman M. I.
Published: December 2017

Rats increased food intake 6 h after peripheral and intracerebroventricular injections of 2-deoxy-D-glucose (2-DG) when plasma glucose concentrations had returned to normal from elevated levels. Rats with adrenal demedullation did not become hyperglycemic after injection of 2-DG and increased food intake more than normal animals after peripheral, but not ventricular, injections of 2-DG. Peripheral injections of 2-DG inhibited gastric emptying in normal, but not adrenal demedullated, rats. Intravenous infusions of epinephrine into normal rats, which mimicked some of the physiological effects of peripheral 2-DG injection, did not increase food intake. The results indicate that a prior disruption of cerebral metabolism is sufficient to elicit feeding in the absence of an adrenomedullary response and that increased gastric fill may restrain the increase in food intake produced by a previous cerebral emergency.
Aphagia and adipsia after kainic acid lesioning of the dorsomedial hypothalamic area
Authors: Bellinger L. L. , Williams F. E.
Published: December 2017

Unlike rats which have electrolytic dorsomedial hypothalamic area lesions and are hypophagic and hypodipsic, the rats of the present study with dorsomedial hypothalamic area, kainic acid lesions (KAL) were postoperatively aphagic and adipsic. Subsequently, KAL rats rejected chow or a high-fat diet but ate a 30% sucrose-chow diet. Similarly the KAL rats were adipsic but drank a 30% sucrose solution. Slowly most of the KAL rats began to eat chow and drink tap water but remained hypophagic and hypodipsic. When tested for glucoprivic-induced feeding using 2-deoxy-D-glucose (200 or 400 mg/kg) the KAL rats, in contrast to the sham-operated controls, did not increase their food intake. During water deprivation the recovered KAL rats that would drink tap water ate, and following it they responded with an adequate increase in water consumption. During food deprivation the KAL rats, whether eating chow or sucrose-chow diet, drank, and subsequently the normally hypophagic rats actually ate more than the controls. Although the growth rate (linear and ponderal) of KAL rats was reduced compared with that of the controls, their body composition by indirect measurement was normal. The present data indicate that most of the dorsomedial hypothalamic syndrome results from damage to DMHA neurons and not to fibers of passage.
Arterial baroreceptor reflex control of heart rate in two species of turtle
Authors: Stephens G. A. , Shirer H. W. , Trank J. W. , Goetz K. L.
Published: December 2017

Attempts were made to stimulate an arterial baroreceptor reflex in anesthetized and conscious pond turtles. In turtles anesthetized with either alpha-chloralose or pentobarbital, occlusion of the ascending or descending aortas produced no reflex heart rate (HR) changes. In pentobarbital-anesthetized turtles, direct electrical or mechanical stimulation of potential baroreceptor sites along the central aortic arches and carotid arteries produced no significant changes in either HR or blood pressure (BP). Occlusion of the common carotid arteries also produced no HR or BP changes. Intravenously administered nitroglycerin lowered BP but caused no reflex tachycardia in anesthetized turtles. Phenylephrine and angiotensin elevated BP in the anesthetized turtle but caused no reflex bradycardia. In conscious turtles phenylephrine increased BP and nitroglycerin decreased BP. Neither response produced a statistically significant HR change, although HR tended to decrease transiently with phenylephrine and increase with nitroglycerin. These HR changes were abolished by atropine. Rapid intra-arterial infusion of 6% dextran transiently raised BP but caused no reflex bradycardia. These experiments suggest that cardiovascular regulation in the turtle is accomplished without a major contribution from arterial baroreceptor reflexes.
Splitting of the locomotor activity rhythm in rats by exposure to continuous light
Authors: Cheung Phyllis W. , McCormack Charles E.
Published: December 2017

Female rats exposed to low intensities (0.1–1.5 lx) of continuous light (LL), displayed regular estrous cycles and free-running circadian rhythms of locomotor activity. In most rats, as the intensity of LL was increased to >2.0 lx, components within the active portion (α) of the locomotor rhythm remained synchronized as the periodicity of the rhythm lengthened. However, in a few rats agr split into two components; one of which free-ran with a period shorter than 24 h, while the other free-ran with a period longer than 24 h. As soon as the two components became maximally separated they spontaneously rejoined. In most rats, estrous cycles ceased shortly after the intensity of LL was increased to >2.0 lx even though the locomotor activity rhythm retained its unsplit free-running nature. These observations suggest that the multiple oscillators that control the rhythms of locomotor activity and the estrous cycle are normally coupled to one another. In certain intensities of LL, these oscillators uncouple and free-run with different periodicities, a condition which causes estrous cycles to cease and sometimes produces a split locomotor activity rhythm.

circadian rhythm; oscillators; estrous cycle

Submitted on November 9, 1981

Accepted on October 11, 1982
Alteration of islet neurotransmitter sensitivity following ventromedial hypothalamic lesion
Authors: Campfield L. A. , Smith F. J.
Published: December 2017

Recent studies suggest that alterations in autonomic neural activity may mediate the obese state observed following ventromedial hypothalamic (VMH) lesion. To assess the role of these alterations in the increased glucose responsiveness of the beta-cell observed in this state, we have determined the sensitivity of insulin secretion to norepinephrine or/and acetylcholine in statically incubated pancreatic islets from rats 30-40 days after VMH lesion. In islets from VMH-lesioned rats compared with islets from sham-operated and intact rats, the acetylcholine dose-response curve was shifted down and to the right, indicating a decreased sensitivity, whereas the norepinephrine dose-response curve was translated to the left, indicating an increased sensitivity. The interaction profile, which summarizes combined neurotransmitter exposure on insulin secretion, was shifted in the direction of net inhibition. Thus it was concluded that, following VMH lesion, autonomic neurotransmitter sensitivity of the pancreatic beta-cell was altered. It is suggested that these alterations play a role in the adaptation of the beta-cell to the experimentally induced obese state.