bluuebunny/crossref_metadata_2025 huggingface dataset:
Critical role of food amount for prefeeding corticosterone peak in rats
Authors: Honma K. I. , Honma S. , Hiroshige T.
Published: December 2017

The effects of food on plasma corticosterone levels were examined in rats under restricted daily feeding or prolonged food deprivation. High hormone levels before feeding were observed when the daily meal was restricted to 2 h at a fixed time of day, but it was not detected when food availability was extended to 6 h. The amount of food intake under the latter condition was comparable to that in 24 h of ad libitum feeding. After the termination of restricted feeding, the prefeeding hormone peak was maintained in rats fasted subsequently but disappeared when rats were returned to ad libitum feeding. Food deprivation for 10 days increased plasma corticosterone levels in the light period, resulting in abolition of the circadian rhythm. A subsequent meal decreased the hormone level such that the 24-h mean hormone level after food ingestion was inversely related to the amount of food intake. When rats were allowed to feed for 6 h after prolonged food deprivation, the prefeeding hormone peak observed at the second meal disappeared at the fourth meal. The amount of food consumption in these rats increased and reached a level comparable to that with ad libitum feeding at the third meal. It is concluded that the amount of food intake is critical for the development and maintenance of the prefeeding hormone peak under restricted feeding; prolonged fasting.
Body temperature control of rat tail blood flow
Authors: Raman E. R. , Roberts M. F. , Vanhuyse V. J.
Published: December 2017

Tail blood flow (BF) and heat flow (HF) were measured in five albino rats during transients in rectal temperature (Tre) caused by body heating at rest. During heating, tail temperature (Tt) was kept at 15, 20, 25, 30, 35, or 42 degrees C by enclosing the tail in a water-perfused tube. Thermal conductance (K) was computed as HF/(Tre-Tt). BF was measured by venous occlusion plethysmography. Heating caused a rise in Tre that was accompanied by proportional increases in both K and BF. The ratio R = K/BF represents conductance per unit BF and reflects the amount of heat exchange for a given BF. R can thus be used to estimate the distribution of BF within the tail. R was independent of Tre at all Tt, indicating that BF distribution is controlled by the tail. R was low at low Tt and rose at higher Tt. This suggests that at low Tt, blood flows primarily in central veins of the tail and at higher Tt blood flows in peripheral tail veins.
Temporal self-organization in biochemical systems: periodic behavior vs. chaos
Authors: Goldbeter A. , Decroly O.
Published: December 2017

The patterns of temporal self-organization in regulated biochemical systems are examined. Simple periodic oscillations are the most frequent type of such organization, as exemplified by glycolytic oscillations in yeast and muscle and by the periodic synthesis of adenosine 3',5'-cyclic monophosphate in Dictyostelium discoideum amoebas. These phenomena originate, respectively, from the periodic operation of the product-activated phosphofructokinase and adenylate cyclase reactions. The analysis of a model for a multiply regulated biochemical system shows more complex oscillatory phenomena, e.g., the coexistence between two stable periodic regimes for the same set of parameter values (birhythmicity) and chaos. The latter phenomenon of aperiodic oscillations occurs in a narrow range of parameter values and is much less frequent than simple or complex periodic behavior. It is suggested that a sufficient condition for the occurrence of birhythmicity and chaos in a regulated biological system subjected to a constant environment (i.e., in the absence of periodic forcing) may be the simultaneous presence and interaction of two mechanisms capable of producing oscillations.
Lateralization of function in rats
Authors: Denenberg V. H.
Published: December 2017

Research findings during the past several years have shown that the rat's brain is lateralized for a number of behavioral functions. Neurochemical and anatomical asymmetries have also been found and, in some instances, have been associated with the behavioral asymmetries. It has also been found that extra stimulation in early life can enhance existing asymmetries or can induce asymmetries where none previously existed.
Atypical amino acids inhibit histidine, valine, or lysine transport into rat brain
Authors: Tews J. K. , Harper A. E.
Published: December 2017

Transport of histidine, valine, or lysine into rat brain slices and across the blood-brain barrier (BBB) was determined in the presence of atypical nonprotein amino acids. Competitors of histidine and valine transport in slices were large neutral amino acids including norleucine, norvaline, alpha-aminooctanoate, beta-methylphenylalanine, and alpha-aminophenylacetate. Less effective were aromatic amino acids with ring substituents; ineffective were basic amino acids and omega-amino isomers of norleucine and aminooctanoate. Lysine transport was moderately depressed by homoarginine or ornithine plus arginine; large neutral amino acids were also similarly inhibitory. Histidine or valine transport across the BBB was also strongly inhibited by large neutral amino acids that were the most effective competitors in the slices (norvaline, norleucine, alpha-aminooctanoate, and alpha-aminophenylacetate); homoarginine and 8-aminooctanoate were ineffective. Homoarginine, ornithine, and arginine almost completely blocked lysine transport, but the large neutral amino acids were barely inhibitory. When rats were fed a single meal containing individual atypical large neutral amino acids or homoarginine, brain pools of certain large neutral amino acids or of arginine and lysine, respectively, were depleted.
Genetic variation, chronic stress, and the central and peripheral noradrenergic systems
Authors: Blizard D. A. , Freedman L. S. , Liang B.
Published: December 2017

Male rats from two inbred strains genetically selected for variation in response to stress were exposed for 9 consecutive days to 50 min of intermittent foot shock and killed 24 h after the last stress session. Maudsley Nonreactive (MNRA/Har) rats, genetically selected for decreased reactivity to stress, exhibited a significantly greater elevation (114% above control levels) in tyrosine hydroxylase activity in the locus ceruleus after chronic stress than Maudsley Reactive (MR/Har) animals (63% above control levels), genetically selected for heightened reactivity to stress. In the peripheral noradrenergic system, chronic stress produced an increase in norepinephrine (NE) content of small intestine and submaxillary gland of MNRA/Har rats, whereas chronic stress had no effect on NE content of these same tissues in MR/Har animals. These results are consistent with the proposition that genetic selection for variation in susceptibility to stress has altered the capacity of the central and peripheral noradrenergic system to adapt to chronic stress.
Carbohydrate feeding speeds reversal of enhanced glucose uptake in muscle after exercise
Authors: Young J. C. , Garthwaite S. M. , Bryan J. E. , Cartier L. J. , Holloszy J. O.
Published: December 2017

Muscle contractile activity results in an increase in glucose uptake rate that can persist for hours. This study was undertaken to determine the effect of carbohydrate repletion on reversal of an exercise-induced increase in glucose uptake. Rats were exercised by swimming. In rats studied 60 min after exercise, muscle glycogen content was 75% depleted and glucose uptake rate was increased. The effect of exercise on glucose uptake was reversed, and glycogen concentration had increased 44 mumol/g muscle, within 18 h in rats fed carbohydrate. In rats fed a carbohydrate-free diet, muscle glycogen increased only 11 mumol/g, and glucose uptake rate had returned only 50% of the way to base line 18 h after exercise. The rate of 3-methylglucose accumulation in muscles was increased sixfold 60 min after exercise. This increase in permeability to sugar was reversed within 18 h in rats fed carbohydrate. In rats fed a carbohydrate-free diet the rate of 3-methylglucose accumulation was still threefold above base line 18 h after exercise. Our results provide evidence that decreased availability of carbohydrate slows reversal of an exercise-induced increase in permeability of muscle to sugar
Parabrachial units responding to stimulation of buffer nerves and forebrain in the cat
Authors: Cechetto D. F. , Calaresu F. R.
Published: December 2017

Spontaneously firing units in the region of parabrachial nuclei (PB) and Kolliker-Fuse nuclei (KF) of 19 chloralose-anesthetized cats were monitored for changes in firing frequency during electrical stimulation of carotid sinus (CSN) and aortic depressor (ADN) nerves, of central nucleus of the amygdala (ACE), and of paraventricular nuclei of the hypothalamus (PVH). In the ipsilateral PB 64 of 189 and in the contralateral PB 9 of 103 units responded to CSN stimulation; 18 of 185 ipsilaterally and 7 of 97 contralaterally responded to ADN stimulation. Responses were primarily excitatory, and units were located primarily in the ventrolateral portion of the PB. Only 9 of 267 units responded to stimulation of both CSN and ADN. Stimulation of the ACE and PVH antidromically activated 9 and 7 units, respectively, in PB and approximately half of these also responded to buffer nerve stimulation. In the ipsilateral PB 56 of 207 and in the contralateral PB 11 of 103 units responded orthodromically to ACE stimulation, and 23 of 177 ipsilaterally and 2 of 103 contralaterally responded orthodromically to PVH stimulation with primarily excitatory responses and were located primarily in the ventrolateral portion of the PB and KF. Of these units approximately half also responded to buffer nerve stimulation. These results suggest an important role for PB-KF in mediating ascending and descending cardiovascular and respiratory control signals.
Uterine blood flow in relation to endogenous hormones during estrous cycle and early pregnancy
Authors: Roman-Ponce H. , Caton D. , Thatcher W. W. , Lehrer R.
Published: December 2017

To evaluate the extent to which endogenous hormones in peripheral blood can account for uterine blood flow (UBF), rates of blood flow and concentrations of estrone (E1), estradiol (E2), and progesterone (P4) were measured simultaneously in four sheep during the estrous cycle and the first 3 wk of pregnancy. During the estrous cycle, UBF was inversely related to the concentration of P4 (P less than 0.01) and directly related to (E1 + E2)/P4 (P less than 0.01). There was no animal in which UBF was related to estrogen alone. No statistically significant relationship between endogenous hormones and UBF was detected in any ewe during the first 3 wk of pregnancy. Data support the idea that UBF varies during the estrous cycle in relation to peripheral concentrations of P4 and (E1 + E2)/P4 but leaves open the nature of the relationship in early pregnancy.
Light-dark masking of circadian temperature and activity rhythms in squirrel monkeys
Authors: Gander P. H. , Moore-Ede M. C.
Published: December 2017

In addition to the synchronizing effects of light-dark cycles on the circadian timing system, light per se can have a direct masking effect on the rhythmic variables monitored as indicators of the circadian system. To evaluate the masking action of light on the rest-activity and body temperature rhythms of squirrel monkeys (Saimiri sciureus), animals were exposed to cycles of 2 h of light alternating with 2 h of darkness (LD 2:2). There was evidence of phase-dependent masking responses in both rhythms, with the light-induced elevation of activity levels and temperature greatest around the times of the circadian maxima of the respective rhythms. The temporal distribution of activity was more strongly affected by the masking action of the 2:2 cycle than was the temporal pattern of temperature variation. The increase in activity observed during lights on was evidently a major factor contributing to the corresponding increase in temperature.
Adrenalectomy and food restriction in the genetically obese (ob/ob) mouse
Authors: Saito M. , Bray G. A.
Published: December 2017

After adrenalectomy in obese mice the rate of weight gain parallels that in lean controls and falls progressively behind that in intact ob/ob mice. Food intake was reduced to normal, but the body temperature of adrenalectomized ob/ob mice was similar to that of intact ob/ob mice and remained below that of control lean mice. After exposure to an ambient temperature of 6 degrees C the body temperature in adrenalectomized ob/ob mice fell at the same rate as in intact ob/ob mice. The increase in tail length, brain weight, spleen weight, and muscle weight after adrenalectomy in ob/ob mice could not be duplicated by reducing the weight gain of ob/ob mice to that of the adrenalectomized mice. Similarly the induction of obesity with gold thioglucose significantly increased the weight of the gastrocnemius muscle and spleen rather than lowering it to levels found in ob/ob mice. Treatment of adrenalectomized ob/ob mice with cortisone acetate, but not with deoxycorticosterone acetate (DOCA), reduced muscle weight, spleen weight, brain weight, and the growth in tail length. Both cortisone and DOCA increased food intake, liver weight, growth rate, and the weight of the adipose tissue in ob/ob mice. These effects are significantly greater than observed in comparably treated lean animals and suggest that glucocorticoids of adrenal origin play an integral role in the phenotypic expression of genetic obesity. These data also indicate that the hypothermia is not a sufficient cause of the obesity in the ob/ob mice, since hypothermia persists in the adrenalectomized mice, but when food intake falls to normal there is no progression of the obesity.
Erythrocyte phosphates and hemoglobin function in monotremes and some marsupials
Authors: Isaacks R. , Nicol S. , Sallis J. , Zeidler R. , Kim H. D.
Published: December 2017

Hematologic values, red blood cell (RBC) organic phosphate composition, hemoglobin function, and hemoglobin composition have been determined on blood from the monotremes, the duckbill platypus and the echidna, and three species of marsupials, the Tasmanian devil, the wallaby, and the brush-tail possum. Blood from the platypus had a RBC count of 8.63 X 10(6)/mm3, a mean corpuscular volume of 49.1 millemicron3, and a white blood cell count of 26.0 X 10(3)/mm3. The RBCs from the monotremes and the three marsupials exhibited hemoglobin polymorphism, each with three hemoglobin components. Addition of ATP, 2,3-bisphosphoglycerate (2,3-P2-glycerate), or inositol pentakisphosphate (inositol-P5) to phosphate-free hemoglobin from each species decreased hemoglobin oxygen affinity; the order of effect of these compounds was ATP less than 2,3-P2-glycerate less than inositol-P5. The RBCs of all species had concentrations of 2,3-P2-glycerate ranging from 6.02 mumol/ml RBCs in the wallaby to 10.39 mumol/ml RBCs in the possum. The RBCs from the three species of marsupials had concentrations of ATP ranging from 0.24 mumol/ml RBCs in the possum to 0.80 mumol/ml RBCs in the Tasmanian devil. The level of ATP in RBCs of the platypus and echidna were 0.06 and 0.03 mumol/ml RBCs, respectively.
Raphe neurons with sympathetic-related activity: baroreceptor responses and spinal connections
Authors: Morrison S. F. , Gebber G. L.
Published: December 2017

We have previously used spike-triggered averaging to identify cat medullary raphe neurons with activity locked to the 2- to 6-cycles/s rhythm in sympathetic nerve discharge (SND) [Am. J. Physiol. 243 (Regulatory Integrative Comp. Physiol. 12): R49-R59, 1982]. In the present study, we classified such cat raphe neurons on the bases of their spinal connections and responses to baroreceptor reflex activation. Type I neurons, comprising 139 of 190 raphe units with activity related to inferior cardiac SND, were excited when carotid sinus pressure was elevated. The majority of these neurons were located in nucleus raphe pallidus. A time-controlled collision test for antidromic activation revealed that the axons of approximately one-third of type I neurons terminated in the sympathetic intermediolateral nucleus (IML) after coursing through the dorsolateral funiculus (DLF) of the spinal cord. The axons of the remaining type I neurons did not project to the spinal cord. It is suggested that type I raphe neurons are involved in mediating sympathoinhibition at spinal and supraspinal levels. Importantly, type I unit discharge remained locked to SND when the phase relationship between baroreceptor afferent and sympathetic efferent activities was disrupted. Thus type I neurons are not simple interneurons in the afferent limb of the baroreceptor reflex arc. Apparently they also receive input from the generator of the 2- to 6-cycles/s rhythm in SND. Type II raphe neurons (n = 51) were inhibited when carotid sinus pressure was elevated. Although the axons of these neurons coursed through the spinal DLF, they did not terminate in IML. Whether type II neurons subserve a sympathoexcitatory function remains to be determined.
Pulmonary transit time and diffusing capacity in mammals
Authors: Lindstedt S. L.
Published: December 2017

Allometry is used as a tool to explain the apparent mismatch of oxygen consumption and diffusing capacity in the mammalian lung. By combining equations for pulmonary capillary volume and cardiac output, it is apparent that erythrocyte transit time through the lung must scale disproportionately to body mass. This inequality is a consequence of physical and mechanical properties setting optimal cardiac and respiratory frequencies. Because of much shorter transit times, the mean alveolar-capillary oxygen pressure difference increases as body size decreases. The time course of oxygen binding to hemoglobin may limit maximum oxygen consumption in the smallest mammals. To assure carbon dioxide diffusion equilibrium, levels of carbonic anhydrase are much higher in small than in large mammals. Because of the differences in transit time, the pulmonary diffusing capacity must scale linearly to body mass to assure adequate oxygen delivery in all mammals.
Fitting physiological models to data
Authors: Garfinkel D. , Fegley K. A.
Published: December 2017

Methods of fitting models to experimental data obtained from biological systems are reviewed. The Michaelis-Menten model is used as the working example of a familiar and well-studied biological model. Criteria for selecting models include goodness of fit, freedom from systematic errors, and simplicity. A given model is usually fitted and the optimal parameters determined by minimization of an objective function, usually the sum of the squared errors. Freedom from systematic errors is best judged graphically. The important mathematical methods of fitting models are derived from the calculus and include linear and quadratic programming. The latter leads to minimization of the sum of squares of errors. Optimal search procedures, which also perform this minimization, are surveyed. Other properties of models, such as the proper number of parameters and whether linearization is appropriate, are discussed. The specialized problems of biological models and data are considered.
Calcium metabolism in birds: computer simulation of response to 1,25-dihydroxycholecalciferol
Authors: Hurwitz S. , Fishman S. , Bar A. , Talpaz H.
Published: December 2017

A simulation model of calcium metabolism in the chick has been used to evaluate the response of the systems that regulate plasma calcium to a continuous input of 1,25-dihydroxycholecalciferol [1,25(OH)2D3] from the intestine. The results of simulation showed that the concentration of the vitamin D metabolite in the intestine increased during the first 24 h and thereafter decreased slightly due to suppression of endogenous hormone production. Metabolite accumulation was accompanied by an increase in calcium absorption, with a lag period of about 4 h. Most of the increase in absorbed calcium was excreted in the urine, with a lesser change in net bone calcium uptake. Plasma calcium increased with time, in proportion to the intake of the exogenous hormone. The validity of the predicted steady-state plasma calcium levels, and bone and kidney calcium flows, is discussed. The results of the simulation demonstrate the importance of the vitamin D-intestinal axis in regulation of plasma calcium.
Excretion of ouabain by Malpighian tubules of Oncopeltus fasciatus
Authors: Meredith J. , Moore L. , Scudder G. G.
Published: December 2017

An in vitro preparation of Malpighian tubules was used to investigate the excretion of the polar cardiac glycoside, ouabain, in Oncopeltus fasciatus. Tubules were found to consist of at least two morphologically and physiologically distinct segments, both of which metabolized ouabain. The distal segment (segment II) secreted primary urine and ouabain. Secretion of ouabain by segment II was not observed to occur against a concentration gradient and increased with increasing fluid secretion. The proximal segment (segment I) reabsorbed fluid and ouabain but not metabolites. Ouabain was reabsorbed against a strong concentration gradient (23-fold), was independent of fluid reabsorption, and increased with increasing fluid secretion by segment II. In rapidly secreting Malpighian tubules (a situation of high cardiac glycoside secretion by segment II), the presence of segment I reduced the excretion of ouabain by 84-93%, mainly by reducing ouabain concentration. It appears excretory loss of cardiac glycosides can be reduced in O fasciatus and thus may be a factor in the sequestration of cardiac glycosides in this insect.
Renal and iliac vascular responses to left ventricular receptor stimulation in conscious dogs
Authors: Gorman A. J. , Cornish K. G. , Zucker I. H.
Published: December 2017

The purpose of the present study was to investigate the relative responses of the renal and iliac vascular beds to the selective chemical stimulation of left ventricular receptors in the conscious dog. Twenty dogs were chronically instrumented to obtain measurements of arterial blood pressure, renal blood flow, and iliac blood flow before and after a bolus intracoronary injection of veratridine (0.4-1.0 micrograms/kg in 0.5-ml vol) with the heart paced. The responses to intracoronary veratridine were a significant reduction in arterial blood pressure averaging 25 mmHg accompanied by a simultaneous reduction in renal blood flow of 25%. Renal resistance did not change throughout the course of the response analyzed (50 s). Iliac blood flow, however, increased, reaching a peak of 35% above control due to a 51% decrease in iliac resistance. After sinoaortic denervation, renal resistance still failed to show a decrease, although the recovery of arterial blood pressure and iliac resistance was prolonged. After a mild hypotensive hemorrhage (20 ml/kg), a greater decrease in iliac resistance occurred with intracoronary veratridine injections, but renal resistance still did not change. The reduction in iliac resistance with intracoronary veratridine was significantly attenuated after phentolamine administration (2 mg/kg iv) but not after atropine alone (0.2 mg/kg iv). A significant cholinergic receptor component of iliac vasodilation was observed only after prior alpha-adrenergic-receptor blockade. The results of this study are consistent with the conclusion that in the conscious dog, left ventricular receptors exert a preferential neural control over skeletal muscle vascular resistance and do not influence renal vascular resistance.
Improved mitochondrial function following ischemia and reflow by ATP-MgCl2
Authors: Chaudry I. H. , Ohkawa M. , Clemens M. G.
Published: December 2017

To determine whether infused ATP-MgCl2 affects mitochondrial adenine nucleotide translocase (ANT) activity, free fatty acids (FFAs), and Ca2+ levels, total hepatic ischemia in rats was produced for 90 min after which blood flow was allowed to return to the liver. Immediately on reflow, the animals received intravenously 0.5 ml of either saline, ATP-MgCl2 (12.5 mumol), or dopamine (6 mg/kg). Three hours after ischemia and reflow, hepatic mitochondrial FFAs and Ca2+ levels increased; however, ATP-MgCl2 infusion significantly lowered FFAs and restored Ca2+ levels. The depressed mitochondrial ANT activity was somewhat improved but not restored by circulatory support with dopamine; however, ATP-MgCl2 infusion following ischemia restored that activity. Thus the present results suggest that the improved organ function that occurs with ATP-MgCl2 infusion following ischemia may be mediated through an improvement in ischemia-induced mitochondrial function.
Ultradian oscillations in blood pressure and heart rate in free-running dogs
Authors: Livnat A. , Zehr J. E. , Broten T. P.
Published: December 2017

A long-term (14
24 h) telemetry recording of mean arterial pressure (MAP) and heart rate (HR) was obtained from conscious unrestrained dogs (n = 9) maintained in a closed environment. MAP and HR records were analyzed for their harmonic content by the fast Fourier transform method. The power spectral density functions of MAP and HR clearly revealed the existence of coherent ultradian rhythms of MAP and HR with a period of 1-2 h. HR and MAP are in phase and sustained during a 24-h period. To elucidate the nature of these rhythms, two additional studies were conducted (n = 4) in which clonidine (200 micrograms/kg) was administered systemically. In series I, a 7-h control period preceded the administration of clonidine, whereas in series II the order was reversed. Control (series I) and recovery (series II) periods were compared with a 0- to 7-h postinjection period. The results show that clonidine drastically and significantly reduces the amplitude of both MAP and HR oscillations for an average period of 7 h. This response was very consistent in both series and in all four dogs. These results implicate the central nervous system as the origin of these rhythms.
Vascular recovery following hemorrhage in the dogfish shark Squalus acanthias
Authors: Carroll R. G. , Opdyke D. F. , Keller N. E.
Published: December 2017

Cardiovascular regulatory systems were examined in the dogfish shark after hemorrhage of 1% of body weight. An immediate 45% decrease in mean dorsal aortic pressure and delayed increases in plasma epinephrine concentration and plasma norepinephrine concentration were noted. During the recovery period following hemorrhage, the catecholamine levels peaked (epinephrine 203% of control, norepinephrine 148% of control) and then returned toward control values. Hematocrit, however, continued to decline as blood pressure recovered. Phentolamine pretreatment, which in itself caused a 55% decrease in dorsal aortic pressure, did not prevent the recovery of blood pressure after hemorrhage. This study indicates that 1) hemorrhage causes an increase in circulatory catecholamine concentration, possibly by a baroreceptor reflex; 2) volume recruitment, as indicated by the drop in hematocrit, is a major mechanism contributing to the recovery of dorsal aortic pressure after hypotension; and 3) alpha-adrenergic receptors are not necessary for the recovery of dorsal aortic pressure after hemorrhage.
Circannual rhythms of body weight in pallid bats
Authors: Beasley L. J. , Pelz K. M. , Zucker I.
Published: December 2017

Body weights of pallid bats collected in the field were substantially greater during October and December than between April and September. When maintained in the laboratory under constant conditions of photoperiod and temperature, bats manifested circannual rhythms in body weight. These endogenous cycles were observed in adult and juvenile individuals of both sexes and in bats housed in long or short photoperiods (14 or 10 h of light/day). The period of the cycle averaged 10 mo. Photoperiod influenced the timing and magnitude of the body weight cycle; bats kept in short photoperiods achieved peak body weights earlier than animals housed in long day lengths. We propose that day length is one of the proximate factors for synchronization of circannual cycles of pallid bats.
Regional blood flow in rats after a single low-protein, high-carbohydrate test meal
Authors: Glick Z. , Wickler S. J. , Stern J. S. , Horwitz B. A.
Published: December 2017

It was previously observed that a single low-protein, high-carbohydrate test meal results in increased in vitro thermic activity of brown adipose tissue. In the present study, we have examined whether such a meal increases the in vivo thermic activity, estimated from measurement of the rate of blood flow. With radioactively labeled microspheres, blood flows into brown fat and several other tissues were determined in meal-deprived (n = 11) and meal-fed (n = 11) rats. The microspheres were injected into the heart of anesthetized animals about 2-2.5 h after the test meal, one injection in the resting state and one during maximal norepinephrine stimulation. In the resting state, blood flow per gram tissue more than doubled in the brown fat (P less than 0.05) and was increased more than 50% in the heart (P less than 0.01) of the fed group. Blood flows into liver and retroperitoneal white fat were reduced by 40 (P less than 0.01) and 30%, respectively, in the fed group. During norepinephrine infusion, significant meal-associated increases in blood flow were evident only in brown fat (P less than 0.05) and the soleus muscle (P less than 0.05), whereas a significant decrease was observed in the liver (P less than 0.05). No statistically significant meal-associated changes in norepinephrine-stimulated blood flow were found in the other tissues examined (i.e., heart, gastrocnemius, and diaphragm muscles, kidneys, white fat, spleen, and adrenals). Our in vivo data thus support the view that brown fat plays a role in the thermic effect of a meal.
Localization of the central pressor action of bradykinin to the cerebral third ventricle
Authors: Lewis R. E. , Phillips M. I.
Published: December 2017

Bradykinin injected into the lateral ventricle produces a rise in blood pressure. Cream plugs selectively localized to discrete regions of the ventricular system were used to block drug access to periventricular sites. Third ventricular plugs blocked the pressor response to lateral ventricular injections of 5 micrograms bradykinin (27 +/- 5 before vs. 5 +/- 5 mmHg after plug, n = 7) and 100 ng angiotensin II (22 +/- 3 before vs. 4 +/- 2 mmHg after plug, n = 5). Third ventricular plugs also suppressed the drinking response to angiotensin II (3.7 +/- 0.6 before vs. 0.9 +/- 0.6 ml after plug, n = 5). However, plugs that occluded the fourth ventricle failed to suppress the central bradykinin pressor response (27 +/- 8 before vs. 35 +/- 9 mmHg after plug, n = 5). The data suggest that the central bradykinin pressor response has a site of action similar to that of angiotensin II in the ventral third ventricle.
Oxygen delivery to the heart and brain during hypoxia: Pekin duck vs. bar-headed goose
Authors: Faraci F. M. , Kilgore D. L. , Fedde M. R.
Published: December 2017

To investigate mechanisms that may allow birds to tolerate extreme high altitude, we acutely exposed unanesthetized bar-headed geese (Anser indicus) and Pekin ducks (Anas platyrhynchos) to 0.21, 0.10, and 0.05 inspired fractional concentrations of O2 (FIO2). In both birds, arterial O2 partial pressure (PaO2) was about 95 Torr at 0.21 FIO2, 45 Torr at 0.10 FIO2, and 28 Torr at 0.05 FIO2. Hyperventilation occurred at both levels of hypoxia, with PaCO2 decreasing to about 7 Torr at 28 Torr PaO2. At 28 Torr PaO2, arterial O2 content (CaO2) in geese (10.4 vol%) was significantly higher than in ducks (4.1 vol%). As PaO2 declined from about 95 to 28 Torr, both cerebral and coronary blood flow (determined by using the radioactive microsphere method) increased more than fivefold in ducks but less than threefold in geese. At both levels of hypoxia, O2 delivery (flow X CaO2) to the heart and brain of geese was the same as or higher than that of ducks. The unique control of cerebral and coronary O2 delivery exhibited by both species of birds may be related to their remarkable tolerance to severe hypocapnic hypoxia.
Sodium balance and aldosterone during dehydration and rehydration in the dog
Authors: Thrasher T. N. , Wade C. E. , Keil L. C. , Ramsay D. J.
Published: December 2017

The regulation of sodium metabolism and the renin-angiotensin-aldosterone system was evaluated during 24 h of water, but not food, deprivation and during rehydration in the dog. Dehydration caused increases in plasma concentrations of sodium (6.0 +/- 0.7 meq/l), protein (0.8 +/- 0.1 g/dl), vasopressin (5.3 +/- 0.9 pg/ml), and renin activity (3.5 +/- 1.1 ng AI X ml-1 X 3 h-1). Plasma aldosterone was unchanged and plasma potassium fell slightly (0.2 +/- 0.1 meq/l). During dehydration, food, and thus sodium intake fell by more than 10% in 12 of 19 dogs, but urinary sodium excretion increased significantly, leading to a negative sodium balance (1.9 +/- 0.2 meq/kg). Sodium retention was observed after rehydration and sodium balance; plasma electrolytes, vasopressin, and plasma renin activity (PRA) returned turned to control levels after the 1st day of recovery. However, plasma aldosterone was slightly elevated at this time, returning to control after the 2nd day of recovery. The dehydration-induced natriuresis could not be accounted for by a fall in plasma aldosterone. However, sodium retention following rehydration could be aldosterone dependent, because additional studies showed a threefold rise in plasma levels of the hormone 1 h after drinking. The acute rise in aldosterone correlated closely (r = 0.82) with the fall in plasma sodium after drinking but not with changes in adrenocorticotrophic hormone, PRA, or plasma potassium. It is concluded that natriuresis is a homeostatic response to dehydration as a means of ameliorating the rise in body fluid osmolality.(ABSTRACT TRUNCATED AT 250 WORDS)
Seasonal obesity in Syrian hamsters: effects of age, diet, photoperiod, and melatonin
Authors: Wade G. N. , Bartness T. J.
Published: December 2017

Two experiments examined the effects of photoperiod, melatonin, and diet on body weight in female Syrian hamsters (Mesocricetus auratus). In experiment 1, daily injections of 25 micrograms melatonin increased body weight when given 3 h before lights-out but not when given at the midpoint of the light phase, in a 16-h light-8-h dark cycle (LD 16:8). Ten micrograms of melatonin, given 3 h before lights-out, were sufficient to increase body weight and fat content, to increase interscapular brown adipose tissue weight, to decrease uterine weight, and to interrupt estrous cyclicity. However, 2.5 micrograms of melatonin increased body weight and fat content without affecting brown adipose tissue weight or reproductive function. In experiment 2, melatonin treatment, exposure to a short photoperiod (LD 8:16), and feeding a high-fat diet increased body weight gain in weanling (25-day-old) female hamsters. When melatonin treatment or high-fat diet were withdrawn, hamsters reduced their food intake, and their body weight and fat content returned to control levels. After 15-17 wk in the short photoperiod, hamsters also began to undereat, and their body weight and fat content returned to control levels. These findings suggest several conclusions. 1) As with the changes in reproductive function, melatonin is effective at increasing body weight only when given at certain times of day. 2) Not all end points are equally responsive to melatonin, suggesting that they are independent of one another. 3) Weanling hamsters respond to photoperiod, melatonin, and diet just as adults do. 4) The striking obesities induced by these manipulations are completely reversible.
Blood-brain barrier transport and brain sequestration of propranolol and lidocaine
Authors: Pardridge W. M. , Sakiyama R. , Fierer G.
Published: December 2017

Lipophilic amine drugs such as propranolol and lidocaine are actively sequestered by tissues via saturable cytoplasmic binding systems. The present studies were designed to characterize the kinetics of drug transport and sequestration in rat brain in vivo by using the carotid injection technique. Both propranolol and lidocaine are sequestered by brain, and the half time (t 1/2) of clearance of the drugs from brain to blood is 6-7 min. The t 1/2 of propranolol association and dissociation reactions with the brain sequestration system are 0.38 +/- 0.03 and 1.33 +/- 0.20 min, respectively. The blood-brain barrier transport of propranolol and lidocaine is inhibited by acid pH, and drug transport is mediated by a low-affinity, high-capacity saturable transport system [propranolol half-saturation constant (Km) = 9.8 +/- 1.2 mM, maximal rate of saturable transport (Vmax) = 5.7 +/- 0.7 mumol X min-1 X g-1, and nonsaturable transport constant (KD) = 0.061 +/- 0.012 ml X min-1 X g-1). These studies indicate that in addition to cerebral blood flow, the distribution of lipophilic amines in brain is a function of plasma pH and of the activity of brain sequestration systems. The latter may represent high-capacity cytoplasmic drug-binding proteins that normally bind endogenous ligands in brain.
Elevated postprandial insulin levels do not induce satiety in normal-weight humans
Authors: Woo R. , Kissileff H. R. , Pi-Sunyer F. X.
Published: December 2017

To determine whether an elevated insulin level contributes to satiety, two experiments were conducted using a covert system of monitoring food intake. Normal-weight volunteers received intravenous infusion of either 0.15 M saline or a mixture of glucose and insulin during a single-course meal. In the first group, the glucose-insulin infusion (0.03 U insulin X kg-1 X h-1 and 0.25 g glucose X kg-1 X h-1) was begun 30 min before the start of the test meal and ended 15 min after subjects had voluntarily stopped eating. Plasma insulin was raised threefold, and glucose increased 20 mg/dl above preinfusion base line at time of eating. In the second group, the glucose-insulin mixture (insulin bolus of 12 mU/kg plus 0.03 U insulin X kg-1 X h-1 and 0.125 g glucose X kg-1 X h-1) was delivered 12 min after an appetizer was served and just as the test meal began. This infusion was stopped 12 min after the end of the meal. Serum insulin was fourfold higher than saline infusion levels at onset of eating, but glucose remained the same. The changes induced in these studies by the glucose-insulin infusions mimicked normal insulin and glucose levels seen shortly before satiation is complete in a meal. No effect on meal size or duration was observed. Therefore normal postprandial elevation of insulin is unlikely to signal satiety in humans.
Mechanism of training-induced attenuation of postexercise ketosis
Authors: Beattie M. A. , Winder W. W.
Published: December 2017

We have examined the roles of liver glycogen and malonyl coenzyme A (CoA) in determining the degree of postexercise ketosis in endurance-trained and nontrained rats. Three groups of rats were run on a treadmill for 90 min: trained (2 h/day, 6 wk) and food restricted to 5.5 g/100 g body wt the night before the 90-min exercise bout (group 1), nontrained fed ad libitum (group 2), and nontrained food restricted (same as trained) (group 3). Liver glycogen was 34 +/- 5, 24 +/- 2, and 7 +/- 2 mg/g in groups 1, 2, and 3, respectively, at the end of exercise. At the end of exercise and during the postexercise period the blood 3-hydroxybutyrate concentration in group 3 was significantly higher than in groups 1 or 2. No difference was observed between groups 1 and 2 in blood 3-hydroxybutyrate. Hepatic malonyl CoA was decreased to the same extent in all rats during exercise but remained depressed only in the glycogen-depleted group 3 rats in the postexercise period. These data suggest that the differences in degree of ketonemia in the postexercise period (but not during exercise) were due to lower hepatic malonyl CoA in group 3 rats.
Activation of afferent renal nerves by intrarenal bradykinin in conscious rats
Authors: Smits J. F. , Brody M. J.
Published: December 2017

Bradykinin was infused intravenously and into the right renal artery of conscious rats that were chronically instrumented with catheters and miniaturized pulsed-Doppler flow probes. The effects on regional hemodynamics were compared with those in animals in which the infused kidney was denervated as well as in animals anesthetized with pentobarbital sodium. In intact rats bradykinin (1 microgram/min) caused an immediate increase in mean arterial blood pressure (MAP, 27 +/- 4 mmHg), heart rate (HR, 67 +/- 11 beats/min), mesenteric resistance (MR, 32 +/- 10%), and both right (RRR, 42 +/- 14%) and left renal resistance (LRR 21 +/- 8%). These effects were significantly different from those during intravenous infusion of the same dose of bradykinin (MAP, 6 +/- 3 mmHg; HR, 31 +/- 7 beats/min; MR, -21 +/- 5%; RRR, 8 +/- 4%; LRR, 6 +/- 3%). Pentobarbital greatly attenuated the responses to intrarenal bradykinin. In conscious animals denervation of the infused kidney completely abolished the cardiovascular effects of intrarenal bradykinin. In a separate group of animals, chlorisondamine (7.5 mg/kg iv) completely blocked the increases in MAP and HR during intrarenal bradykinin (1 microgram/min). It is concluded that selective renal administration of bradykinin alters afferent renal nerve activity and that this results in hemodynamic changes consistent with efferent sympathetic activation.
Salt gland and kidney responses to intracerebral osmotic stimulation in salt- and water-loaded ducks
Authors: Gerstberger R. , Simon E. , Gray D. A.
Published: December 2017

Saltwater-adapted ducks with functioning supraorbital salt glands were chronically implanted with a device for perfusion of the third cerebral ventricle (icv perfusion) with artificial cerebrospinal fluid (CSF) of different tonicities. The osmoregulatory responses to icv stimulation were studied at conditions of salt and water loading in which only the salt glands, both salt glands and urinary fluid excretion, or only urinary fluid excretion were stimulated; in the latter experiments plasma antidiuretic hormone (ADH) was measured with a radioimmunoassay. Hypertonic icv stimulation enhanced salt gland secretion and caused antidiuresis, due to the increase of plasma ADH. Hypotonic icv stimulation inhibited salt gland activity and caused diuresis, due to the decrease of plasma ADH. Salt gland activity, urine formation, and plasma ADH reacted more sensitively to changes of icv tonicity in the hypertonic than in the hypotonic range. The effect of icv hypotonic stimulation could be obtained also with icv perfusion of isosmotic artificial CSF deficient in NaCl content. Perfusion with artificial CSF exceeding plasma tonicity by 50 mosmol X kg-1 or more caused inhibition of salt gland secretion associated with enhanced urinary output in several experiments.
Regulation of net amino acid exchange in sea urchin larvae
Authors: Davis J. P. , Stephens G. C.
Published: December 2017

Bacteria-free larvae of Strongylocentrotus purpuratus remove each of 14 free amino acids (FAA) from very dilute solution in seawater. When larvae are maintained in seawater, influx of radiolabeled FAA and net removal of substrate as determined by high-performance liquid chromatography (HPLC) occur at the same rate in those substrates examined. Exposure of larvae to high concentrations of glutamate, glycine, or serine (greater than 50 microM) produces large increases in these substrates in the internal pool of FAA. After incubation of larvae in high concentrations of serine, the rate of influx of 14C-labeled serine is decreased compared with unincubated controls. Comparison of influx of radiolabeled serine with net change in ambient serine as determined by HPLC indicates that the apparent change in rate of influx is a consequence of an increase in ambient serine with time and the resulting decrease in the specific activity of labeled serine. Analysis of data indicates that abnormally high internal serine leads to carrier-mediated efflux of serine as well as other neutral amino acids. The rate of such efflux is increased in the presence of increased levels of ambient serine.
Food intake and gastric emptying in rats with streptozotocin-induced diabetes
Authors: Granneman J. G. , Stricker E. M.
Published: December 2017

Recent studies suggest that the rate of nutrient transit through the upper gastrointestract may provide cues that are important to the control of food intake. We examined gastrointestinal function in rats with streptozotocin-induced diabetes and related these findings to concomitant changes in food intake. Control and diabetic rats were adapted to one of two isocaloric diets either high in carbohydrate or fat. Control rats ate similar amounts of each diet. In contrast, diabetic animals fed high-carbohydrate diet were hyperphagic, whereas those fed low-carbohydrate diet ate normal amounts of food. Gastric emptying, intestinal mass, disaccharidase activity, and glucose absorption were increased in normophagic diabetic rats fed a low-carbohydrate diet. Feeding diabetic rats high-carbohydrate diet potentiated each of these effects, and food intake was highly correlated with rate of gastric emptying. These and other results indicate that diabetes enhances gastric emptying and intestinal carbohydrate digestion and absorption, even in the absence of hyperphagia. Consequently, the hyperphagia of diabetic rats may be in part a behavioral response to a greatly accelerated clearance of nutrients from the upper gastrointestinal tract that occurs when these animals are fed diets rich in carbohydrate.
Two kinds of timing in circadian incubation rhythm of ring doves
Authors: Gibbon J. , Morrell M. , Silver R.
Published: December 2017

Ring dove males share incubation with females by sitting on the nest for a block of time in the middle of the day. The timing of nest exchanges was studied by experimentally delaying the onset, in the morning, of the male's sitting bout. Such delays induced a concomitant but smaller delay in the offset of the male's sitting bout in the afternoon. The female, however, approached the nest to start her bout of sitting at the usual time in the afternoon even though her previous sitting bout had ended later than usual. These findings, together with data on interactions between the pair at the afternoon exchange, suggest that the behavior of the sitting male reflects an interval timing mechanism initiated with the onset of his sitting bout. In contrast the attempts to regain the nest by the nonsitting female probably reflect a circadian oscillation.
Postnatal development of myogenic contractile activity and excitatory innervation of rat urinary bladder
Authors: Maggi C. A. , Santicioli P. , Meli A.
Published: December 2017

Bladder strips from newborn compared with adult rats exhibited marked differences in both myogenic properties and postganglionic excitatory innervation. In the first 2-wk of life myogenic contractile activity progressively changed from a quiescent state (at birth) to the asynchronous contractile activity typical of bladder strips from adult animals. After birth activation of muscarinic cholinoceptors changed the myogenic contractile activity in a manner similar to that observed at later stages of development. Neurogenic contractions of bladders from newborn animals were atropine sensitive in the whole range of frequencies studied. During the first 2 wk the atropine-resistant component of these contractions increased progressively to reach an adult-like condition, i.e., atropine-resistant contractions account for over 90% and approximately 60% of contractions elicited at 0.1 and 1–20 Hz, respectively.