bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of sodium uptake in freshwater animals: a comparison of ion-exchange and proton pump hypotheses
Authors: Potts W. T.
Published: December 2017

Sodium uptake has been shown to follow saturation kinetics in many freshwater species of animals, and in the presence of hydrogen ions uptake appears to show competitive inhibition. These characteristics are compatible with the hypothesis that uptake occurs via a carrier-mediated exchange of sodium ion for hydrogen ion. However, recently it has been shown that in frog skin, sodium uptake is driven by an electrogenic pump not directly linked to sodium, and evidence is accumulating that a similar pump may occur in other freshwater animals. A mathematical model is developed that shows that a proton pump would also produce saturation kinetics and mimic carrier-mediated competitive inhibition. It would also account for the linkage between sodium influx and efflux observed in several species.
Measurement of circulating blood volume in vivo after trauma-hemorrhage and hemodilution
Authors: Wang P. , Ba Z. F. , Lu M. C. , Ayala A. , Harkema J. M. , Chaudry I. H.
Published: December 2017

Although cardiac output (CO) and other hemodynamic variables are used to assess the adequacy of fluid resuscitation after hemorrhage, it is not known whether there is any correlation between restoration of CO and circulating blood volume (CBV). To determine this, rats underwent a midline laparotomy (i.e., trauma induced) and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximum bleedout volume was returned in the form of Ringer lactate (RL). The animals were then resuscitated with four or five times the volume of maximum bleedout in the form of RL. CO and hepatocellular function were measured using an in vivo hemoreflectometer. CBV was monitored by using in vivo indocyanine green clearance. A good correlation between the values of blood volume obtained by this method and the 125I-albumin method indicates that the indocyanine green method is also a reliable technique for measuring CBV. Results indicate that resuscitation after hemorrhage improved the decreased CBV but did not restore it to control levels despite the fact that CO was restored and central venous pressure was more than doubled. A good correlation between depressed CBV and hepatocellular dysfunction was also observed under such conditions. Thus measurement of CBV appears to be useful for evaluating the adequacy of fluid resuscitation after trauma-hemorrhage and hemodilution.
Postingestive alliesthesia produced by exogenous cholecystokinin and blocked by abdominal vagotomy
Authors: Cabanac M. , Zhao C.
Published: December 2017

Facial consummatory responses reflecting ingestive and aversive perceptions were studied and quantified in rats chronically implanted with oral catheters. A gustatory stimulus of 50 microliters of 1.75 M sucrose was injected into the mouth every 5 min during 65 min. At 5 min, 2 micrograms/kg exogenous cholecystokinin (CCK) was injected intraperitoneally. Typical ingestive facial consummatory responses were observed in response to sweet stimuli before the load. Aversive consummatory responses were observed in response to sweet stimuli after the intraperitoneal exogenous CCK (negative alliesthesia). Control intraperitoneal injection of saline was not followed by negative alliesthesia in response to sweet oral stimuli. In the last part of the experiment rats were vagotomized or underwent sham operation. When the vagotomized rats were again subjected to the same gustatory sessions, the intraperitoneal exogenous CCK was not followed by negative alliesthesia in response to sweet stimuli, whereas sham-operated rats presented a strong negative alliesthesia. These results in rats suggest that CCK mediates duodenal preabsorptive signal for alimentary alliesthesia. They also suggest that the effect is peripheral, with the vagus nerve as afferent pathway.
Induction of low-T3 syndrome in exercising women occurs at a threshold of energy availability
Authors: Loucks A. B. , Heath E. M.
Published: December 2017

To investigate the relationship between energy availability (dietary energy intake minus energy expended during exercise) and thyroid metabolism, we studied 27 untrained, regularly menstruating women who performed approximately 30 kcal.kg lean body mass (LBM)-1.day-1 of supervised ergometer exercise at 70% of aerobic capacity for 4 days in the early follicular phase. A clinical dietary product was used to set energy availability in four groups (10.8, 19.0, 25.0, 40.4 kcal.kg LBM-1.day-1). For 9 days beginning 3 days before treatments, blood was sampled once daily at 8 A.M. Initially, thyroxine (T4) and free T4 (fT4), 3,5,3'-triiodothyronine (T3) and free T3 (fT3), and reverse T3 (rT3) were in the normal range for all subjects. Repeated-measures one-way analysis of variance followed by one-sided, two-sample post hoc Fischer's least significant difference tests of changes by treatment day 4 revealed that reductions in T3 (16%, P < 0.00001) and fT3 (9%, P < 0.01) occurred abruptly between 19.0 and 25.0 kcal.kg LBM-1.day-1 and that increases in fT4 (11%, P < 0.05) and rT3 (22%, P < 0.01) occurred abruptly between 10.8 and 19.0 kcal.kg LBM-1.day-1. Changes in T4 could not be distinguished. If energy deficiency suppresses reproductive as well as thyroid function, athletic amenorrhea might be prevented or reversed by increasing energy availability through dietary reform to 25 kcal.kg LBM-1.day-1, without moderating the exercise regimen.
Glucose turnover after a mixed meal in dogs: glucoregulation without change in arterial glycemia
Authors: Strack T. R. , Poussier P. , Marliss E. B. , Albisser A. M.
Published: December 2017

Because the dog can respond to a mixed-meal challenge with little or no change in plasma glucose concentration, we used kinetic techniques to quantify the magnitude and duration of changes in glucoregulation. Glucose turnover was measured using [3-3H]glucose and [U-14C]glucose over two 19-h periods in healthy dogs, first during a fast (n = 6) and then throughout the postprandial state (n = 6) after a single mixed meal. Mean arterial glycemia remained constant in the fasted state (7.5 +/- 0.2 mM) and in the fed state (7.6 +/- 0.3 mM). Glucose appearance (Ra), however, increased slowly after the meal from 38 +/- 2 mg/min to a maximum of 79 +/- 8 mg/min after 6 h and stayed elevated until 12 h (P < 0.001). In parallel, glucose disappearance (Rd) rose from 35 +/- 3 to 83 +/- 7 mg/min, closely matching the corresponding Ra. Glucose recycling rose from 25 +/- 8% at baseline to a maximum of 53 +/- 15% (P < 0.05) at 14 h in fed dogs, whereas levels for fasted dogs stayed between 19 +/- 7% at 0 h and 27 +/- 12% at 6 h. Insulin levels rose significantly 30 min after the meal from 67 +/- 7 pM to a peak of 208 +/- 54 pM at 6 h but remained elevated for 12 h. We conclude that 1) the dog was able to maintain postprandial glucoregulation by very precise matching of Ra and Rd such as to maintain glycemia constant.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic lipolysis in guinea pig is not a beta 3-adrenergic response: comparison with human adipocytes
Authors: Carpene C. , Castan I. , Collon P. , Galitzky J. , Moratinos J. , Lafontan M.
Published: December 2017

beta 3-Adrenoceptor agonists are potent lipolytic activators in rats, but they are only weak stimulators in human adipocytes, indicating interspecies differences in the adrenergic regulation of lipid mobilization. Like human but not rat adipocytes, guinea pig fat cells were poorly responsive to the beta 3-agonists BRL-37344, CGP-12177, SR-58611, and ICI-215001, acid metabolite of ICI-D7114. In guinea pigs, the beta 1-agonist dobutamine was more lipolytic than the beta 2-agonist procaterol. Anatomic location of fat deposits was without major influence on the beta-adrenergic responsiveness. Weak responses to beta 3-agonists were found whatever the sex or the age (from 2 days to 16 mo) of the animals. Even in the interscapular brown adipose tissue, which is well known in rats for its beta 3-adrenergic responsiveness, a blunted response to BRL-37344 was observed. The alpha 2-adrenergic antilipolytic effect and receptor number were smaller in guinea pig than in human adipocytes, but the beta-adrenergic receptor number was similar in the two species. Thus guinea pig adipocytes resemble human fat cells when their weak beta 3-adrenergic responsiveness is considered.
Role of central chemoreceptors in behavioral thermoregulation of the toad, Bufo marinus
Authors: Branco L. G. , Wood S. C.
Published: December 2017

We tested the hypothesis that hypercapnia will induce behavioral hypothermia in toads and that central chemoreceptors are involved in this response. Animals were tested in an enclosed temperature gradient supplied with different gas mixtures. Fractional inspired CO2 (FICO2) between 0 and 0.05 had no significant effect on selected body temperature, but FICO2 between 0.06 and 0.10 reduced the selected body temperature from U approximately 28 to 18 degrees C. To determine if the hypercapnia-induced hypothermia is mediated by acidification of central chemoreceptors, the pH of the fourth ventricle was kept constant by perfusion with mock cerebrospinal fluid of pH 7.7 or 7.1 (normal and acidic values, respectively). Ventricular perfusion at pH 7.7 under normocapnic conditions had no effect on body temperature. Hypercapnia (FICO2 0.08) failed to induce hypothermia when the fourth ventricle was kept at pH 7.7 and when hyperoxia was present. Acidic ventricular perfusion under normocapnic conditions decreased selected body temperature from 27 to 25 degrees C, a significant drop but much less than that due to hypercapnia producing the same brain pH, suggesting an important role of peripheral chemoreceptors. The physiological significance of behavioral hypothermia and nature of the peripheral stimulus were evaluated by measuring the effect of hypercapnia on arterial oxygen saturation, PO2, and pH at 15 and 25 degrees C. Arterial oxygen saturation was higher at the lower temperature. Increasing FICO2 decreased oxygen saturation at 25 degrees C but not at 15 degrees C. Arterial PO2 increased with increasing inspired CO2. This increase was greater at 15 degrees C than at 25 degrees C. Arterial pH decreased at both temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)
Central interleukin-1 receptors contribute to suppression of feeding after acute colitis in the rat
Authors: McHugh K. J. , Collins S. M. , Weingarten H. P.
Published: December 2017

Experimental colitis, induced in rats by intrarectal administration of trinitrobenzenesulfonic acid (TNB), results in a suppression of eating for 3 days. Because interleukin-1 (IL-1) is elevated within 24 h after TNB treatment, and because chronic administration of IL-1 leads to a pattern of anorexia similar to that seen after TNB, we evaluated the role of endogenous IL-1 in the anorexia observed in the TNB model. Human recombinant IL-1 receptor antagonist (rhIL-1ra) was administered chronically via osmotic minipump either peripherally or centrally after TNB treatment. Peripheral delivery of 40 micrograms/h rhIL-1ra significantly attenuated TNB-induced anorexia. However, 24 micrograms/h rhIL-1ra attenuated TNB-induced anorexia only when delivered centrally, not peripherally. These findings implicate central IL-1 receptors in the suppression of eating during acute experimental colitis but leave open a possible involvement of peripheral IL-1 receptors.
Evidence for pancreatic pacemaker for insulin oscillations in low-frequency range
Authors: Chou H. F. , Berman N. , Ipp E.
Published: December 2017

Circulating insulin concentrations oscillate in regular fashion, with periods that fall into a high-frequency (period of 5-17 min) or low-frequency (period of 50-150 min) range. Only the high-frequency oscillations have so far been reported in vitro, suggesting that these derive from a primary pancreatic source. This study tested whether the low-frequency insulin oscillations could also be identified in vitro. Rat islets of Langerhans were perifused for 20 h using RPMI medium with 5.5 mM glucose. Perifusate fractions were collected at 9.9-min intervals. Mean insulin concentrations at the outset were 21.4 +/- 2.9 microU/ml, increased to 32.5 +/- 4.6 (P < 0.05) between 13 and 17 h after the start of perifusion, and then either leveled off or decreased to baseline. Superimposed on this general trend, we found sustained insulin oscillations with a period of 50-100 min. The mean amplitude was 14.2 +/- 4.2 microU/ml, and the amplitude/mean ratio was 64.6 +/- 12%. Spectral analysis revealed significant peaks at periods that were close to either 50 or 100 min and a smaller peak at 24-37 min. These data, using in vitro methodology and constant glucose concentrations, indicate the presence of sustained, spontaneous, low-frequency, ultradian insulin oscillations in the pancreatic islets. This provides evidence for a pancreatic component that may participate in the previously described in vivo ultradian insulin oscillations. This finding may also provide a mechanism for the apparent escape from glucose entrainment of serum insulin oscillations in non-insulin-dependent diabetes mellitus.
Insulin binding and receptor tyrosine kinase activity in skeletal muscle of carnivorous and omnivorous fish
Authors: Parrizas M. , Planas J. , Plisetskaya E. M. , Gutierrez J.
Published: December 2017

We characterized the insulin receptors in skeletal muscle from several fish species with different nutritional preferences: brown trout (Salmo trutta fario), gilthead sea bream (Sparus aurata), tilapia (Tilapia mossambica), and carp (Cyprinus carpio), semipurified by affinity chromatography (wheat germ agglutinin-agarose). Total specific binding and number of receptors per unit weight of piscine white skeletal muscle were lower than those values found in mammalian skeletal muscle. The same parameters in carp muscle receptor preparations were severalfold higher than in trout muscle (binding capacity 440 +/- 47 fmol/mg glycoprotein in carp and 82 +/- 23 fmol/mg glycoprotein in trout). Piscine insulin receptors phosphorylated exogenous substrate poly(Glu,Tyr) but less so than mammalian receptors. Tyrosine kinase activity of receptors, calculated as percent of 32P incorporated into substrate in the presence of insulin compared with basal incorporation, was also highest in carp (210 +/- 4%) and lowest in trout (150 +/- 2%). In both trout and carp deprived of food for 15 days, specific binding of insulin decreased. Nevertheless, differences between the two species were retained. Our results demonstrate that particular properties of insulin receptors in fish skeletal muscle may be related to nutritional preferences. This finding coincides with the phenomenon of differential glucose tolerance in fish: carnivorous fish, such as trout, are less tolerant, whereas omnivorous fish, such as carp, readily utilize a carbohydrate-rich diet.
Taurine, betaine, and inositol share a volume-sensitive transporter in skate erythrocyte cell membrane
Authors: Goldstein L. , Davis E. M.
Published: December 2017

Our previous study [J. K. Haynes and L. Goldstein. Am. J. Physiol. 265 (Regulatory Integrative Comp. Physiol. 34): R173-R179, 1993] showed that skate erythrocytes have a volume-sensitive amino acid transporter that passes amino acids across the cell membrane in a size-related nonstereospecific manner. The aim of the present study was to determine whether representatives of other groups of organic osmolytes (polyols, trimethylamines) could be transported by this same system. Volume-sensitive transport was assayed by measuring Na(+)-independent uptake of osmolytes into erythrocytes. Hypotonic stress stimulated uptake of the polyol myo-inositol and the trimethylamine betaine severalfold. There was little or no competition between osmolytes for transport. However, inhibitor studies indicated that both betaine and inositol are transported by the same pathway as amino acids. Inhibitors of the anion exchanger band 3 and a variety of chloride channel inhibitors blocked the hypotonically stimulated uptake of betaine, inositol, and taurine in a quantitatively similar manner. These results show that different chemical classes of organic osmolytes share a common volume-sensitive transporter.
Anoxia and adenosine induce increased cerebral blood flow rate in crucian carp
Authors: Nilsson G. E. , Hylland P. , Lofman C. O.
Published: December 2017

The crucian carp (Carassius carassius) has the rare ability to survive prolonged anoxia, indicating an extraordinary capacity for glycolytic ATP production, especially in a highly energy-consuming organ like the brain. For the brain to be able to increase its glycolytic flux during anoxia and profit from the large liver glycogen store, an increased glucose delivery from the blood would be expected. Nevertheless, the effect of anoxia on brain blood flow in crucian carp has never been studied previously. We have used epireflection microscopy to directly observe and measure blood flow rate on the brain surface (optic lobes) during normoxia and anoxia in crucian carp. We have also examined the possibility that adenosine participates in the regulation of brain blood flow rate in crucian carp. The results showed a 2.16-fold increase in brain blood flow rate during anoxia. A similar increase was seen after topical application of adenosine during normoxia, while adenosine was without effect during anoxia. Moreover, superfusing the brain with the adenosine receptor blocker aminophylline inhibited the effect of anoxia on brain blood flow rate, clearly suggesting a mediatory role of adenosine in the anoxia-induced increase in brain blood flow rate.
Time course of adaptation to a high-fat diet in obesity-resistant and obesity-prone rats
Authors: Pagliassotti M. J. , Knobel S. M. , Shahrokhi K. A. , Manzo A. M. , Hill J. O.
Published: December 2017

The purpose of the present study was to characterize the time course of adaptation (i.e., circulating metabolites and hormones, fat pad mass, lipoprotein lipase) to a high-fat diet in obesity-prone (OP) and obesity-resistant (OR) male Wistar rats. Delineation of OP and OR was based on body weight gain (upper tertile for OP; lower tertile for OR) after 1 wk on a high-fat diet (60% of kcal from corn oil). Rats were killed after 1, 2, or 5 wk of the dietary period. Increased body weight and percent body fat in OP rats at 1 wk could not be accounted for by increased retroperitoneal or epididymal fat pad weight. Plasma nonesterified fatty acids and triglycerides, as well as blood concentrations of glucose, lactate, and glycerol, were similar throughout the study. Plasma insulin was significantly greater in OP vs. OR rats and low-fat diet (LFD; 20% of kcal from corn oil) controls at 5 wk only, and blood beta-hydroxybutyrate (mM) was significantly higher in OR compared with OP and LFD rats at 1, 2, and 5 wk. Lipoprotein lipase mRNA and activity were significantly greater in epididymal fat pad and significantly lower in gastrocnemius muscle of OP vs. OR rats at 1 wk. Results suggest that early (i.e., 1 wk) differences in body weight and fat weight between OP and OR rats are not due to fat deposition in retroperitoneal or epididymal fat depots, and tissue-specific changes in LPL (increase in epididymal fat pad and decrease in gastrocnemius muscle) that occur in OP compared with OR rats after 1 wk on a high-fat diet provide a metabolic environment favoring fat storage.
Organization of vestibular inputs to nucleus tractus solitarius and adjacent structures in cat brain stem
Authors: Yates B. J. , Grelot L. , Kerman I. A. , Balaban C. D. , Jakus J. , Miller A. D.
Published: December 2017

The vestibular system is involved in maintaining stable blood pressure and respiration during changes in posture and is essential for eliciting motion sickness-related vomiting. Because the nucleus tractus solitarius (NTS) participates in the regulation of sympathetic and inspiratory outflow and the triggering of emesis, we tested the hypothesis that this region receives vestibular inputs in cats. In one set of experiments, microinjections of the tracer Phaseolus vulgaris leucoagglutinin into the medial and inferior vestibular nuclei labeled projections to the middle and lateral regions of the NTS. In electrophysiological experiments, electrical stimulation of the vestibular nerve modified the firing rates of neurons located in the same regions. Some neurons with vestibular inputs received convergent signals from the abdominal vagus nerve and could potentially mediate motion sickness-related vomiting. Others received convergent baroreceptor inputs and could act as a substrate for some components of vestibulosympathetic reflexes. In contrast, inspiratory neurons in the dorsal respiratory group received little vestibular input, suggesting that vestibulorespiratory reflexes are mediated by cells located elsewhere.
Differential effects of bright light and social cues on reentrainment of human circadian rhythms
Authors: Honma K. , Honma S. , Nakamura K. , Sasaki M. , Endo T. , Takahashi T.
Published: December 2017

Reentrainment of human circadian rhythm to an 8-h advanced schedule of sleep and social contacts was assessed under two different conditions: with and without bright light (4,000-6,000 lx). Subjects spent 15 days without knowing the natural day-night alternation. On the fourth day, the social schedule was phase-advanced by 8 h. In one experiment, a bright light pulse of 3-h duration was given in every subjective morning, and in the other no light pulse was applied. Plasma melatonin and rectal temperature rhythms were measured. Seven of nine subjects showed an orthodromic phase shift, the rate of which was significantly larger with bright light pulses than without them. The maximum phase-advance shift by three consecutive light pulses was observed when the first pulse was applied approximately 4 h after the onset of melatonin rise. By contrast, the maximum phase shift of a similar extent was detected at 1 h after the onset of melatonin rise, when ordinary room light (300-500 lx) at the time corresponding to bright light was regarded as a dim light pulse. It is concluded that bright light accelerates the reentrainment of human circadian rhythm, and bright light and social schedule have differential effects on the reentrainment.
Responses of single neurons in amygdala to interoceptive and exteroceptive stimuli in conscious cats
Authors: Knuepfer M. M. , Eismann A. , Schutze I. , Stumpf H. , Stock G.
Published: December 2017

The amygdala is critical for behavioral arousal and must therefore integrate a wide variety of inputs. We examined sensory inputs and the degree of convergence to single neurons in the amygdala in conscious freely moving cats. A pressor stimulus elicited responses, predominantly inhibitory, in one-half of the amygdalar neurons tested. Most neurons in the central and basal nuclei responded to carotid chemoreceptor activation typically with an excitation. Almost one-half of all amygdalar neurons tested, particularly in the central nucleus, received orthodromic input from the locus ceruleus, the substantia nigra, and/or the contralateral central nucleus of the amygdala. Exteroceptive sensory stimulation with optic, acoustic, tactile, and olfactory stimuli elicited responses in 33, 55, 39, and 59% of amygdalar neurons, respectively. Two-thirds of the neurons tested with more than one external stimulus modality responded in the same manner to the various stimuli (usually excitation), demonstrating a convergence of exteroceptive stimuli on single amygdalar neurons, particularly in the basal nucleus. Spontaneous and induced behavioral arousal elicited responses in 92 and 86% of neurons, respectively. Most neurons responded to multimodal exteroceptive stimuli and behavioral arousal in the same manner. We suggest that amygdalar inputs are highly varied and, in many cases, relatively nonspecific and that the amygdala integrates a large number of external and internal sensory modalities to regulate autonomic and behavioral responsiveness to various stimuli.
Thyroxine affects ventilation, lung morphometry, and necrosis of diaphragm in dystrophic hamsters
Authors: Schlenker E. H. , Burbach J. A.
Published: December 2017

Male dystrophic hamsters (DH) were treated with pellets containing thyroxine (T hamsters) or placebo (P hamsters) for 8 wk. O2 consumption, ventilation, and ventilation in response to 8% CO2 in O2 and 10% O2 in N2 were evaluated 1 and 8 wk after treatment began. O2 consumption was elevated in T hamsters at 1 and 8 wk, whereas ventilation was similar in the two groups on the first week. By 8 wk, ventilation and ventilatory responses to hypoxic and hypercapnic challenges were 100% greater in T than in P hamsters (P < 0.05). Morphometric evaluations at the end of the treatment period indicated that air space surface density, tissue volume density, and surface density-to-air space volume ratio of the lung parenchyma were greater (P < 0.05) in T than in P hamsters. In contrast, chord length within the lung parenchyma was shorter and necrosis in the diaphragm and tongue, but not in the heart, was lower (P < 0.05) in T than in P hamsters. Taken together, these results suggest that T treatment of DH for 8 wk affects O2 consumption, ventilation, lung architecture, and skeletal muscle without increasing triiodothyronine levels.
Central ANG II-receptor antagonists impair cardiovascular and vasopressin response to hemorrhage in rats
Authors: Lee W. J. , Yang E. K. , Ahn D. K. , Park Y. Y. , Park J. S. , Kim H. J.
Published: December 2017

The role of brain angiotensin II (ANG II) in mediating cardiovascular, vasopressin, and renin responses to hemorrhage was assessed in conscious spontaneously hypertensive rats (SHR) and in normotensive Wistar-Kyoto (WKY) and Wistar rats. Intracerebroventricular administration of losartan (10 micrograms) and saralasin (1 microgram.microliter-1.min-1) produced a markedly greater fall in blood pressure and a reduced tachycardia during and after hemorrhage (15 ml/kg) compared with the artificial cerebrospinal fluid control in SHR and Wistar rats but not in WKY rats. Vasopressin release after hemorrhage was also impaired, but renin release was enhanced by intracerebroventricular ANG II antagonists in SHR and Wistar rats but not in WKY rats. Losartan and saralasin produced remarkably similar effects on the cardiovascular, vasopressin, and renin responses to hemorrhage. These data suggest that brain ANG II acting through AT1 receptors plays an important physiological role in mediating rapid cardiovascular regulation and vasopressin release in response to hemorrhage. The relative importance of brain angiotensin system may vary in different strains of rate.
Thermal dehydration-induced thirst in rats: role of body temperature
Authors: Barney C. C. , Folkerts M. M.
Published: December 2017

Male Sprague-Dawley rats were used to study the possible role of hyperthermia in the thirst associated with thermal dehydration. Rats were exposed to 40 degrees C for 4 h and then allowed access to water at different times after they were transferred to 25 degrees C. Delaying the time prior to allowing the rats to drink did not significantly alter either water intake or percent rehydration even though core temperature decreased during the first 1.5 h after removal from the heat. Exposing thermally dehydrated rats to 5 degrees C for 30 min prior to allowing them access to water also failed to significantly affect water intake or percent rehydration. Thermally dehydrated rats allowed to drink while remaining in the heat did not show a significant increase in water intake during the first hour or percent rehydration over rats drinking at 25 degrees C. Nondehydrated rats did show significant increases in water intake and percent rehydration when allowed to drink in the heat. Hyperthermia does not play a role in drinking in thermally dehydrated rats but can stimulate drinking in water-replete rats.
Blockade of beta-adrenoceptor in control of blood pressure in fowl
Authors: Kamimura K. , Nishimura H. , Bailey J. R.
Published: December 2017

Several avian species show elevated blood pressure (BP) and spontaneous atherogenesis in the aorta and other large arteries. The BP appears to be influenced by age, sex (higher in males), environment, and diet in some species. We reported previously that mean aortic pressure and heart rate, but not plasma renin activity (PRA), of conscious female domestic fowl were markedly reduced by propranolol. In the present study, we aimed to determine in conscious roosters whether 1) hypotension evoked by atenolol or practolol, which selectively inhibit cardiac beta-receptors in mammals, is more potent than that evoked by propranolol, and 2) the renin-angiotensin (ANG) system and/or catecholamines are involved in beta-adrenoceptor antagonist-induced hypotension. Mean arterial pressure (171.2 +/- 3.5 mmHg) and heart rate (281 +/- 4 beats/min) of chronically cannulated roosters (n = 38) were markedly reduced by acute infusion or repeated injections (14 days) of propranolol, atenolol, or practolol, but not by SQ-14,225 (ANG-converting enzyme inhibitor) or [Sar1, Thr8]ANG II (nonselective ANG receptor antagonist). None of the beta-adrenoceptor blockers, however, showed cardioselectivity. The resting PRA of conscious roosters (1.27 +/- 0.09 ng.ml-1.h-1, n = 38) was low and did not change significantly after chronic or acute treatment with beta-adrenoceptor blockers except for a slight decrease induced by practolol. PRA increased after SQ-14,225. The plasma levels (pg/ml) of norepinephrine (701.9 +/- 76.0), epinephrine (337.2 +/- 57.1), and dopamine (299.1 +/- 39.0) of conscious roosters were further increased by propranolol. Practolol also increased dopamine significantly.(ABSTRACT TRUNCATED AT 250 WORDS)
Alterations of energy and substrate metabolism in rats with large and sustained changes in daily food intake
Authors: Wang J. F. , Koopmans H. S.
Published: December 2017

Energy expenditure was measured in one-way crossed-intestine rats by use of indirect calorimetry to examine the role of energy metabolism in body weight control. The intestinal surgery was done according to Koopmans (Brain Res. Bull. 14: 595-603, 1985). The food-losing rats increased daily food intake from 70.8 to 126.3 g/day, whereas their partners decreased intake from 67.1 to 38.7 g/day (P < 0.001). Compared with levels before surgery, the food-losing rats showed slightly increased O2 consumption (1.31 vs. 1.28 1.h-1.kg-1) and metabolic rate (6.62 vs. 6.39 kcal.h-1.kg-1) and largely increased CO2 production (1.31 vs. 1.22 l.h-1.kg-1, P < 0.01), whereas in their food-gaining partners O2 consumption (1.12 vs. 1.25 l.h-1.kg-1, P < 0.01) and metabolic rate (5.76 vs. 6.26 kcal.h-1.kg-1) were significantly decreased. Respiratory quotients were higher in the food-gaining rats than in their partners (1.076 vs. 0.999, P < 0.01), indicating more fatty acid synthesis. These results suggest that daily food intake and energy expenditure increase and decrease together, despite the fact that about the same amount of food has been absorbed from the intestines of each rat.
Imaging of VMS activity during blood pressure challenges in awake and anesthetized goats
Authors: Harper R. M. , Gozal D. , Forster H. V. , Ohtake P. J. , Pan L. G. , Lowry T. F. , Rector D. M.
Published: December 2017

We examined scattered-light changes in a rostral ventral medullary surface (VMS) area from five goats after blood pressure challenges during waking and halothane anesthesia. Reflected 660-nm images were digitized at 1/s after baseline; intravenous saline; 5, 10, or 15 micrograms/kg phenylephrine administration; or sodium nitroprusside infusion sufficient to lower blood pressure by 50%. Phenylephrine elicited a dose-dependent, blood pressure elevation during both states and a substantial transient reflectance increase (interpreted as activity decline) during anesthesia, but only a minimal, long-latency, slow-reflectance decrease activity increase) during waking. Sodium nitroprusside elicited lowering of blood pressure and decreased reflectance in the rostral site during anesthesia. The magnitude of the reflectance change to depressor challenge increased 30%, and the onset latency shortened during waking. Isolated regions of enhanced reflectance changes appeared during both challenges. Activity in this rostral VMS site differentially responds to blood pressure elevation or lowering, and state markedly alters the responses. We speculate that VMS responses to depressor challenge represent reflex activation of respiratory regions.
Selective regulation of myofiber differentiation by energy status during postnatal development
Authors: Harrison A. P. , Rowlerson A. M. , Dauncey M. J.
Published: December 2017

The role of energy status in postnatal regulation of porcine skeletal muscle development has been determined in littermate animals kept for 3-4 wk on a high (H) or low (L) energy intake (H = 2L), at a thermally neutral [26 degrees C (26H and 26L, respectively)] or low [10 degrees C (10H and 10L, respectively)] environmental temperature. A variety of skeletal muscles was assessed at 7 wk of age for changes in myofiber hypertrophy and differentiation. In contrast with findings in adult humans and rats, there was no selective preservation of type I slow-oxidative fiber size during energy restriction. However, differentiation between mature skeletal myosin heavy-chain isoforms was markedly affected by energy status, and in rhomboideus there were particularly striking effects of both nutrition and temperature: proportions of type I fibers from the four groups 26H, 26L, 10H, and 10L were 34 +/- 2, 50 +/- 4, 73 +/- 2, and 72 +/- 3 (P < 0.005 for diet at 26 degrees C; P < 0.001 for temperature). These changes may have been induced by alterations in both thyroid status and contractile activity. They support the hypothesis of a key role for rhomboideus muscle in thermoregulation and demonstrate the plasticity of skeletal muscle differentiation to environmental change during postnatal life.
Effects of food deprivation on induction of neural progestin receptors by estradiol in Syrian hamsters
Authors: Du Y. , Wade G. N. , Blaustein J. D.
Published: December 2017

Food deprivation, as well as treatment with metabolic inhibitors, suppress steroid hormone-induced estrous behavior in ovariectomized (OVX) Syrian hamsters. Previous work indicates that 48 h of food deprivation decreases the number of detectable estrogen receptor immunoreactive (ERIR) cells in the ventromedial hypothalamus (VMH) and the area just lateral to it (VLH), increases the number of ERIR cells in the medial preoptic area (MPO), and has no effect on the number of ERIR cells in the nucleus of the solitary tract in OVX hamsters. The present study examined the effects of food deprivation on neural progestin receptor binding using an in vitro binding assay and on progestin receptor immunoreactivity (PRIR) in estradiol-primed, OVX hamsters. Parallel behavior tests for sexual behavior were also performed in both experiments. OVX hamsters received 2.5 micrograms estradiol benzoate and were fed ad libitum or food deprived at the same time. Forty-eight hours later, animals were killed in preparation for the immunocytochemistry or progestin receptor assay. Binding assays indicated that 48-h food deprivation decreased progestin receptor levels in the preoptic area and had no effect in the mediobasal hypothalamus, an area that includes the VMH and the arcuate nucleus (ARH). Immunocytochemical analysis confirmed these findings. Food deprivation caused a decrease in sexual receptivity and in the number of detectable PRIR cells in the MPO and medial amygdala but had no effect on the number of detectable PRIR cells in the VMH/VLH, the ARH, or the anteroventral periventricular nucleus. These results suggest that food deprivation modulates progestin receptor binding and PRIR in a site-specific manner. In addition, the effects of food deprivation on neural ERIR and PRIR are significantly different.
NTS neurons with carotid chemoreceptor inputs arborize in the rostral ventrolateral medulla
Authors: Koshiya N. , Guyenet P. G.
Published: December 2017

Neurons that were excited by hypoxic stimulation of carotid chemoreceptors were recorded in the caudal portion of the nucleus of the solitary tract (cNTS) of urethan-anesthetized, vagotomized, aortic-deafferented, artificially ventilated rats (n = 23). The focus of the study is on 26 chemosensitive neurons (classified as early- and late-response cells) that were tonically activated by chemoreceptor stimulation and never fired in bursts synchronized with the phrenic nerve discharge (PND) cycle. The discharge of early-response cells (n = 14) started up to 2.5 s before the onset of PND activation, whereas the discharge of late-response cells (n = 14) started 1.5-5 s after onset of PND response. Four early-response cells were antidromically activated from the rostral ventrolateral medulla (RVLM; latencies: 7-13 ms), and two had axenal collaterals in the region of the nucleus ambiguus. Four late-response neurons were antidromically activated from the RVLM (latencies: 6-12 ms), but no collateral was found in this area. The basal discharge of early- and late-response cells ranged from 0 to 10 and 0 to 30 spikes/s, respectively, but most of them had a very low spontaneous firing rate (median: 0.2 and 0.6 spikes/s, respectively). Neither type was excited by baroreceptor stimulation. The cNTS also contained neurons that were firing in bursts synchronized with the PND cycle. These cells were activated by chemoreceptor stimulation and were not antidromically activated from the RVLM. Chemosensitive neurons made up 33% of cNTS neurons antidromically activated from the RVLM (8/24). In conclusion, a population of cNTS chemosensitive neurons devoid of respiratory modulation projects through the RVLM and arborizes in this region.
Potency of naloxone's anorectic effect in rats is dependent on diet preference
Authors: Glass M. J. , Grace M. , Cleary J. P. , Billington C. J. , Levine A. S.
Published: December 2017

Modulation of feeding behavior by neuropeptide Y (NPY) and opioids is well established, but the possibility that these neural influences provoke specific appetites, NPY for carbohydrate and opioids for fat, has also been considered. In other studies, intake of standard chow after NPY stimulation can be blocked by naloxone, indicating an interaction between these systems in the regulation of feeding. The present experiments examined the nature of NPY-opioid interactions in diet selection. Rats were administered NPY and naloxone concurrently, then chose between high-fat and high-carbohydrate diets. Subcutaneous administration of naloxone (0.01-0.3 mg/kg) potently reduced intake of the preferred diet, but not the nonpreferred diet. A similar pattern of selection was seen in a separate experiment where the same doses of naloxone were administered after 24-h food deprivation. These data support the idea that the opioid system mediates the “rewarding” aspects of feeding.
Lactate distribution and metabolism during and after anoxia in the turtle, Chrysemys picta bellii
Authors: Jackson D. C. , Toney V. I. , Okamoto S.
Published: December 2017

To determine the fate of lactate during and after prolonged anoxia, 14C-labeled lactate was injected into turtles after 2 h of a 6-h submergence at 20 degrees C. 14C activities of plasma and chamber water were tested at intervals during anoxia and also in expired air during 39 h of recovery. Partitioning of label in major body compartments [extracellular fluid (ECF), intracellular fluid (ICF), and shell] and 14C activity and glycogen in selected tissues (heart, liver, and muscle) were measured after anoxia (n = 7) and after recovery (n = 6). Shell 14C and [lactate] were extensively measured on six anoxic turtles. During anoxia all 14C remained in the animal indicating no urine production. At 6 h of anoxia 47% of recovered 14C, presumably still as lactate, was in the ECF, 27% in the ICF, and 30% in the shell. During recovery, plasma [lactate] fell from 35 to 5 meq, but surrounding water and expired air accounted for only 9 and 8%, respectively, of recovered label. The ICF portion grew to 41%, associated with a recovery in tissue glycogen. The shell still had 22% of total label. We conclude that, during recovery from anoxia, lactate is predominantly resynthesized to glycogen, and only a small fraction is directly oxidized. During anoxia, however, lactate is widely distributed in the body, and a surprisingly large and functionally significant fraction resides in the shell.
Distinct expression of heat shock and acute phase genes during regional hepatic ischemia-reperfusion
Authors: Gingalewski C. , Theodorakis N. G. , Yang J. , Beck S. C. , De Maio A.
Published: December 2017

The hepatic response to injury is orchestrated by the expression of different gene groups (i.e., heat shock and acute phase). In the present study, the expression of heat shock and acute phase genes was analyzed in the context of a localized injury, regional hepatic ischemia-reperfusion. Left and median liver lobes were subjected to 1 h of ischemia, whereas blood flow was maintained to the remainder of the organ. After the period of ischemia, the organ was reperfused, and samples of the ischemic and nonischemic liver were obtained at different time points during reperfusion. Expression of the heat shock gene, HSP 72, was detected only in the ischemic liver, whereas expression of the acute phase gene, beta-fibrinogen, and the interleukin-6-inducible gene, metallothionein, was maximally induced in the nonischemic liver and attenuated in the ischemic liver. To determine how the heat shock and acute phase responses were reprioritized during stress, expression of beta-fibronogen and HSP 72 was induced simultaneously in the same animal by administration of endotoxin and total body hyperthermia, respectively. Administration of endotoxin did not impede the expression of HSP 72; however, heat shock attenuated, but did not eliminate, the endotoxin-induced expression of beta-fibronogen. These observations suggest that the heat shock and acute phase responses are not mutually exclusive.
A new taste reactivity analysis of the integration of taste and physiological state information
Authors: Grill H. J. , Roitman M. F. , Kaplan J. M.
Published: December 2017

We used conjoint manipulation of taste and physiological state to address the theoretical issue of signal integration. The interaction between taste (glucose concentration) and state (food deprivation) was evaluated using the taste reactivity method in which oral motor responses elicited by direct intraoral infusion are measured. The time frame of the typical taste reactivity paradigm, where observation is limited to the infusion period, was expanded to include the postinfusion interval. In each test session, rats received a series of trials consisting of 15-s intraoral infusions and 45-s postinfusion observation intervals. Two experiments were run in which glucose concentration was varied and rats were run nondeprived and after 24 h food deprivation. In experiment 1, glucose concentrations (0, 3.2, 6.25, 12.5, and 25%) were randomly presented during each test session. In experiment 2, individual glucose concentrations (0, 6.25, or 25%) were presented during separate sessions. For both, a deprivation condition was flanked by nondeprived (baseline) sessions. Concentration-response functions were comparable in both experiments. In each experiment, the shape of the concentration-response function was dramatically different during and after infusions. During infusions, there were no increases in glucose-elicited rhythmic oral responses beyond a very dilute concentration. After infusions, the concentration-response functions appeared linear across the concentration range. In both experiments, deprivation elevated responding only in the after-infusion periods. In experiment 1, the concentration-response function was uniformly elevated (on average, 27%) by deprivation, which if taken at face value would suggest an additive combination of taste and state feedback signals. In experiment 2, however, deprivation increased responding (approximately 30%) for 6.25%, but not for 0 or 25%, suggesting a stimulus specificity of the taste-state integration. Clearly then, the taste-state profiles differed as a function of experimental design. In the GENERAL DISCUSSION, we suggest that the uniform elevation of responding to all glucose concentrations, and to water, seen in experiment 1, may be an artifact of the random presentation of all stimuli during individual sessions. Experiment 2, in which stimuli were presented in a between-sessions design, may provide a truer reflection of the underlying integrative process.
Protein kinase C mediates Ca2(+)-induced cardioadaptation to ischemia-reperfusion injury
Authors: Meldrum D. R. , Cleveland J. C. , Mitchell M. B. , Sheridan B. C. , Gamboni-Robertson F. , Harken A. H. , Banerjee A.
Published: December 2017

Although protein kinase C (PKC)-mediated cardioadaptation to ischemia-reperfusion (IR) is accompanied by increased intracellular Ca2+ concentration, it is unknown whether a preischemia sarcoplasmic reticulum (SR) Ca2+ release affects PKC-mediated post-IR functional protection. To study this, crystalloid-perfused (Langendorff) Sprague-Dawley rat hearts were used to assess the effects of a ryanodine (Ry)-induced preischemia Ca2+ load (Ry, 5 nM/2 min, retrograde coronary) 10 min before global IR (20 min). Ry was administered with and without each of two different PKC inhibitors (20 microM chelerythrine and 150 nM bisindolylmaleimide I-HCl). Ry improved myocardial functional recovery (developed pressure, end-diastolic pressure, coronary flow, and creatine kinase activity), which was eliminated after PKC inhibition. Immunohistochemical staining for PKC isoforms demonstrated that Ry induces specific PKC translocation of alpha-, delta-, and zeta-isoforms. We conclude that 1) a preischemia Ca2+ load from the SR results in post-IR myocardial functional protection 2) Ca(2+)-induced functional protection is PKC regulated via the translocation of specific isoforms, and 3) Ca(2+)-induced cardioadaptation to IR injury may have important therapeutic implications prior to planned ischemic events such as cardiac allograft preservation and cardiac bypass surgery.
Novel regulation of peripheral gustatory function by the immune system
Authors: Phillips L. M. , Hill D. L.
Published: December 2017

Soon after adult rats receive unilateral chorda tympani nerve section in combination with dietary sodium restriction, neural taste responses recorded from the intact, contralateral chorda tympani nerve are substantially reduced. We hypothesized that the immune system is compromised in sodium-restricted rats, which leads to functional alterations in the peripheral taste system after neural injury. Here, immune function was stimulated with a systemic injection of lipopolysaccharide (LPS), and neurophysiological responses were recorded from the uncut chorda tympani 4-10 days after nerve section to determine if normal sodium sensitivity was restored. Rats receiving nerve section, dietary sodium restriction, and LPS exhibited normal sodium responses. In intact rats, injection of LPS alone or LPS injection combined with sodium restriction had no effect on taste responses to sodium stimuli. Surprisingly, combining nerve section, LPS injection, and maintenance of rats on a normal diet induced supersensitive responses to sodium. These findings are the first to demonstrate that the immune system can regulate peripheral gustatory function.