bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal responses to parathyroid hormone in young chickens
Authors: Feng J. Q. , Clark N. B.
Published: December 2017

Renal clearance studies were performed in chicks 1, 5, and 9 days after hatching. Calcium gluconate was infused to block endogenous parathyroid hormone (PTH) secretion, whereas ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) was infused to stimulate endogenous PTH secretion. PTH, dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP), or vehicle was administered intravenously. In 9-day-old birds, urinary cAMP and inorganic phosphate excretion fell dramatically after calcium loading and rose significantly after PTH, DBcAMP, or EGTA administration. These manipulations had no significant effect on excretion of calcium or inorganic phosphate in 1-day-old hatchlings. Five day-old-chicks gave an intermediate response. All three age groups, as well as 15-day-embryos, showed sharp increases in urinary cAMP values after PTH administration. Thus the adult response pattern to PTH appears to develop gradually during the first week after hatching or to be suppressed during the perinatal period, whereas the second-messenger response to the hormone, indicating hormone-receptor interaction, is present from late embryogenesis onward.
Interactive effects of growth hormone and exercise on muscle mass in suspended rats
Authors: Grindeland R. E. , Roy R. R. , Edgerton V. R. , Grossman E. J. , Mukku V. R. , Jiang B. , Pierotti D. J. , Rudolph I.
Published: December 2017

Measures to attenuate muscle atrophy in rats in response to stimulated microgravity [hindlimb suspension (HS)] have been only partially successful. In the present study, hypophysectomized rats were in HS for 7 days, and the effects of recombinant human growth hormone (GH), exercise (Ex), or GH+Ex on the weights, protein concentrations, and fiber cross-sectional areas (CSAs) of hindlimb muscles were determined. The weights of four extensor muscles, i.e., the soleus (Sol), medial (MG) and lateral (LG) gastrocnemius, and plantaris (Plt), and one adductor, i.e., the adductor longus (AL), were decreased by 10-22% after HS. Fiber CSAs were decreased by 34% in the Sol and by 17% in the MG after HS. In contrast, two flexors, i.e., the tibialis anterior (TA) and extensor digitorum longus (EDL), did not atrophy. In HS rats, GH treatment alone maintained the weights of the fast extensors (MG, LG, Plt) and flexors (TA, EDL) at or above those of control rats. This effect was not observed in the slow extensor (Sol) or AL. Exercise had no significant effect on the weight of any muscle in HS rats. A combination of GH and Ex treatments yielded a significant increase in the weights of the fast extensors and in the CSA of both fast and slow fibers of the MG and significantly increased Sol weight and CSA of the slow fibers of the Sol. The AL was not responsive to either GH or Ex treatments. Protein concentrations of the Sol and MG were higher only in the Sol of Ex and GH + Ex rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Phorbol ester-induced prostaglandin production in piglet cortical astroglia
Authors: Thore C. R. , Nam M. , Busija D.
Published: December 2017

We examined effects of phorbol 12,13-dibutyrate (PDB), which activates protein kinase C (PKC), on prostaglandin and leukotriene production in piglet cultured glia derived from cerebral cortex and white matter. Levels of prostaglandins were determined using enzyme immunoassay. Baseline levels in media for prostaglandin F2 alpha (PGF2 alpha) were 730 +/- 116 pg/ml and increased to 1,551 +/- 196 pg/ml at 10(-8) M PDB (P < 0.05) and to 2,182 +/- 190 pg/ml at 10(-6) M PDB (P < 0.05) (n = 16). Little or no 6-keto-prostaglandin F1 alpha, prostaglandin E2, or leukotrienes C4/D4 were produced. PGF2 alpha levels in media did not increase in the presence of the vehicle for PDB (dimethyl sulfoxide) or 4 alpha-phorbol 12,13-didecanoate (PDD; a phorbol ester that does not activate protein kinase C) or when indomethacin (10 micrograms/ml), quinacrine (10(-6) M), or isoquinolinylsulfonylmethyl piperazine (10(-4) M) (an inhibitor of PKC activation) was coadministered with PDB. We conclude that glia can be important contributors of prostaglandins to extracellular-cerebrospinal fluids where they could influence cerebrovascular tone, and that PDB probably increases prostaglandin production via liberation of arachidonic acid by PKC-induced activation of phospholipase A2.
Interactions between cellular respiration and thermoregulation in the paramecium
Authors: Malvin G. M. , Havlen P. , Baldwin C.
Published: December 2017

An important adaptation to hypoxia is a regulated reduction in body temperature because it lowers metabolic rate when oxygen supply is limited. Although this beneficial response occurs in organisms ranging from protozoans to mammals, little is known of the cellular mechanisms responsible for the hypoxia-induced reduction in temperature. Using the unicellular protozoan, Paramecium caudatum, we showed that inhibition of oxidative phosphorylation with sodium azide (NaN3) under normoxic conditions mimics the thermoregulatory effects of hypoxia, causing this species to select a lower temperature in a thermal gradient (P < 0.0001). Under control conditions, selected temperature (Tsel) was 28.3 +/- 0.3 degrees C. NaN3 concentrations of 0.1 mM and above significantly reduced Tsel (P < 0.0001). Ten millimolar NaN3 produced the maximal reduction in Tsel, 11.4 degrees C, and the dose that produced 50% of the maximal response was 0.7 mM. The reduction in temperature was beneficial because both O2 consumption and survival were significantly less affected by NaN3 at lower temperatures. These results suggest that O2 does not directly affect thermoregulation in the paramecium. Rather, the hypoxia-induced reduction in Tsel results from inhibition of oxidative phosphorylation.
24-hour control of body temperature in rats. I. Integration of behavioral and autonomic effectors
Authors: Gordon C. J.
Published: December 2017

Some studies suggest that the nocturnal elevation in core temperature (Tc) of the rat is mediated by an elevation in the set point. The role of set point can be assessed if behavioral effectors are measured simultaneously with other thermoregulatory effectors and Tc over a 24-h period. Selected ambient temperature (STa) and motor activity (MA) were measured in rats housed in a temperature gradient system with a 12:12-h photoperiod (lights on 0600 h). Tc and heart rate (HR) were monitored by telemetry. During the light phase, STa, Tc, HR, and MA were relatively stable with values 29.0 degrees C, 37.1 degrees C, 310 beats/min, and 1-2 m/h, respectively. During the light-to-dark transition there were abrupt elevations in Tc, HR, and MA but no change in STa. STa decreased during the dark phase and reached a nadir of 23 degrees C at 0500 h. All variables recovered to basal levels within 3-4 h after the onset of the light phase. Overall, autonomic effectors control the elevation in Tc during the onset of the dark phase while behavioral effectors have little if any role. Behavioral thermoregulation is important in two ways: 1) the selection of cooler Ta values at night to prevent an excess elevation in Tc and 2) a preference for cooler Ta values before the light phase to facilitate the recovery of Tc.
Resistance exercise and growth hormone as countermeasures for skeletal muscle atrophy in hindlimb-suspended rats
Authors: Linderman J. K. , Gosselink K. L. , Booth F. W. , Mukku V. R. , Grindeland R. E.
Published: December 2017

Unweighting of rat hindlimb muscles results in skeletal muscle atrophy, decreased protein synthesis, and reduced growth hormone (GH) secretion. Resistance exercise (ladder climbing) and GH treatment partially attenuate skeletal muscle atrophy in hypophysectomized hindlimb-suspended rats. It was hypothesized that a combination of multiple bouts of daily resistance exercise and GH (1 mg.kg-1.day-1) would prevent skeletal muscle atrophy in growing nonhypophysectomized hindlimb-suspended rats. Hindlimb suspension decreased the absolute (mg/pair) and relative (mg/100 g body wt) weights of the soleus, a slow-twitch plantar flexor, by 30 and 21%, respectively, and the absolute and relative weights of the gastrocnemius, a predominantly fast-twitch plantar flexor, by 20 and 11%, respectively (P < 0.05). Exercise did not increase soleus mass but attenuated loss of relative wet weight in the gastrocnemius muscles of hindlimb-suspended rats (P < 0.05). Hindlimb suspension decreased gastrocnemius myofibrillar protein content and synthesis (mg/day) by 26 and 64%, respectively (P < 0.05). The combination of exercise and GH attenuated loss of gastrocnemius myofibrillar protein content and synthesis by 70 and 23%, respectively (P < 0.05). Results of the present investigation indicate that a combination of GH and resistance exercise attenuates atrophy of unweighted fast-twitch skeletal muscles.
Differential relationships among the 10-Hz rhythmic discharges of sympathetic nerves with different targets
Authors: Gebber G. L. , Zhong S. , Barman S. M. , Paitel Y. , Orer H. S.
Published: December 2017

Partial coherence analysis was used to remove the influences of the central circuits controlling a sympathetic nerve (as reflected by its discharges) on the coherence of the 10-Hz discharges of other sympathetic nerves in unanesthetized decerebrate or urethan-anesthetized cats. In many cases, partialization reduced but did not eliminate the sharp peak near 10 Hz in the coherence functions relating the discharges of sympathetic nerve pairs. This observation implies that the central sources of the 10-Hz rhythmic discharges of any nerve are not identical to those responsible for the rhythm recorded from any other nerve. Partial coherence analysis also revealed differential relationships among the 10-Hz rhythmic discharges of sympathetic nerves with different targets. Importantly, the pattern of differential relationships observed in one experiment could be the reverse of that in the next. Although the basis for the differential relationships is not yet clear, nonuniform coupling of multiple brain stem 10-Hz oscillators and/or nonuniform cross talk between spinal circuits controlling different sympathetic nerves may be involved.
Aortic baroreceptors play a predominant role in the regulation of hindlimb vascular resistance in rats
Authors: Machado B. H. , Bonagamba L. G. , Castania J. A. , Menani J. V.
Published: December 2017

In previous studies using bilateral carotid occlusion in conscious freely moving rats we suggested that aortic baroreceptors may play a more important role in the regulation of hindlimb than in renal and mesenteric vascular resistances. In the present study we performed electrical stimulation of the aortic baroreceptor nerve and analyzed the changes in mean arterial pressure and in hindlimb, renal, and mesenteric vascular resistances. All the experiments were performed under urethan anesthesia. Unilateral electrical stimulation (3 V, 2 ms, 50 Hz) of the aortic baroreceptor nerve produced a fall in arterial pressure (-27 +/- 3 mmHg) and an important reduction in hindlimb vascular resistance (-43 +/- 5%), with an increase in renal (+3 +/- 14%) and mesenteric (+48 +/- 12%) vascular resistances. Similar changes in arterial pressure as well as in the resistance of the three vascular beds studied were also observed during electrical stimulation of the aortic baroreceptor nerve in rats with bilateral carotid baroreceptor denervation or in rats treated with methylatropine. The data obtained with electrical stimulation indicated that aortic baroreceptors play a more important role in the regulation of blood flow in hindlimb than in renal and mesenteric vascular beds.
Comparative studies on tryptophan binding to hepatic nuclear envelopes in Sprague-Dawley and Lewis rats
Authors: Sidransky H. , Verney E.
Published: December 2017

Since Lewis rats are susceptible to many inflammatory diseases and have been used in an experimental model of the eosinophilia-myalgia syndrome, we investigated whether Lewis rats would respond to L-tryptophan as have Sprague-Dawley rats reported earlier. In this comparative study using females of both strains, we observed a decrease in the affinity of in vitro L-tryptophan binding to hepatic nuclei and nuclear envelopes of Lewis rats compared with Sprague-Dawley rats. However, in vivo stimulatory effects of administering L-tryptophan on hepatic polyribosomal aggregation, protein synthesis, and nuclear RNA release were similar in both strains. In vitro [3H]tryptophan binding to hepatic nuclear envelopes, using L-tryptophan implicated in cases of the eosinophilia-myalgia syndrome, revealed less specific binding than when using nonimplicated L-tryptophan in both strains. The possible significance of the quantitative difference in the binding affinity of L-tryptophan to hepatic nuclei of Lewis rats compared with those of Sprague-Dawley rats is as yet undetermined.
Effects of gonadectomy on sexually dimorphic antidiuretic action of vasopressin in conscious rats
Authors: Wang Y. X. , Crofton J. T. , Liu H. , Brooks D. P. , Share L.
Published: December 2017

The present study examined whether the antidiuretic response to vasopressin is affected by the estrous cycle and by gonadectomy in conscious, chronically instrumented hydrated rats. Infusion of vasopressin (10-100 pg.min-1.kg body wt-1) resulted in a dose-dependent antidiuresis. Urine volume and free water clearance decreased and urinary osmolality increased with no significant changes in mean arterial blood pressure, heart rate, osmolar clearance, and urinary sodium and potassium excretion. The antidiuretic response to vasopressin was significantly greater in intact male and estrous female rats than in intact female rats in the other phases of the estrous cycle. Thus the calculated doses of vasopressin to reduce urine flow and free water clearance, as well as to increase urinary osmolality 50% from their control values, were significantly higher in nonestrous females than in males and estrous females. Gonadectomy was without effect on the antidiuretic potency of vasopressin in males, but in gonadectomized females the antidiuretic response to vasopressin was enhanced to a level similar to that observed in intact males. These data indicate that the antidiuretic activity of vasopressin is affected not only by gender but also by phase of the estrous cycle and that the ovarian hormone(s) may modulate the antidiuretic action of vasopressin.
2-deoxy-D-glucose suppresses food intake through activation of hypothalamic histamine in rats
Authors: Sakata T. , Tamari Y. , Kang M. , Yoshimatsu H.
Published: December 2017

The aim of this experiment was to demonstrate whether brain histamine contributes to delayed suppression of food intake after administration of 2-deoxy-D-glucose (2-DG). Food intake decreased significantly for 48 h after infusion of 2-DG into the rat third cerebroventricle. This delayed decrease in food intake was abolished by depletion of neuronal histamine by intraperitoneal pretreatment with alpha-fluoromethylhistidine (160 mumol/rat), a suicide inhibitor of a histamine-synthesizing enzyme. Intracerebroventricular infusion of 24 mumol 2-DG accelerated turnover rate of hypothalamic histamine. These results indicate that the delayed feeding suppression by 2-DG is modulated through histaminergic neurons in the hypothalamus. This histaminergic response may be related, at least in part, to homeostatic control of energy metabolism in the brain.
Dopamine DA1 receptors on vascular smooth muscle cells are regulated by glucocorticoid and sodium chloride
Authors: Yasunari K. , Kohno M. , Yokokawa K. , Horio T. , Takeda T.
Published: December 2017

The modulation of dopamine DA1 receptors of cultured rat renal arterial smooth muscle cells by glucocorticoid and sodium chloride was studied. At a concentration of 10 nM, the synthetic glucocorticoid dexamethasone increased maximum receptor binding but had no effect on the dissociation constant. However, the maximum binding of [3H]Sch-23390 in cells treated with 100 mM sodium chloride did not change. However, the dissociation constant for DA1 receptor was increased by adding sodium chloride. The glucocorticoid effect on DA1 of arterial smooth muscle cells became apparent after hours of incubation in the presence of the steroid and was significantly inhibited by cycloheximide (10 micrograms/ml) or by the glucocorticoid receptor antagonist RU-38486, indicating that the effect required protein synthesis through glucocorticoid receptors. Treatment of cells with 1 microM dexamethasone for 24 h increased basal and DA1-stimulated adenylate cyclase activity. Basal adenylate cyclase was decreased by sodium chloride in a dose-dependent manner. These results suggest differential control of DA1 receptors on vascular smooth muscle cells by glucocorticoid or sodium chloride.
The effect of intracarotid vasopressin infusion on ACTH release in neurohypophysectomized, conscious dogs
Authors: Raff H. , Papanek P. E. , Liard J. F. , Cowley A. W.
Published: December 2017

Neurohypophysectomy (NHX) attenuates the adrenocorticotropic hormone (ACTH) response to arterial hypotension but not corticotropin-releasing hormone (CRH) or insulin-induced hypoglycemia in conscious dogs. The purpose of the present study was to determine if increasing vasopressin (AVP) in the cephalic circulation by carotid infusion normalizes the ACTH response to hypotension attenuated by NHX. Five male, conditioned dogs underwent controlled, acute decreases in arterial pressure (by approximately 25 mmHg) by infusion of sodium nitroprusside (NP) before and > 4 wk after selective NHX. ACTH increased from 40 +/- 3 to 242 +/- 79 pg/ml during NP in the intact state. This response was greatly attenuated after NHX (peak ACTH 81 +/- 15 pg/ml). Simultaneous intravenous infusion of AVP (12.5 ng/min) had a small, augmenting effect on the ACTH response to NP (peak ACTH 120 +/- 27 pg/ml). Intracarotid AVP (12.5 ng/min) greatly augmented the ACTH response to NP (peak ACTH 202 +/- 26 pg/ml) such that it was no longer different from the intact response. Neither intravenous nor intracarotid AVP infusion per se had a great effect on ACTH. A normal ACTH response to hypotension requires an intact neurohypophysis and is mediated by a cephalic action of magnocellular AVP.
Nocodazole inhibition of organic anion secretion in teleost renal proximal tubules
Authors: Miller D. S. , Pritchard J. B.
Published: December 2017

The impact of the microtubule-disrupting drug nocodazole on renal tubular secretion of organic anions was examined in vitro using proximal tubular masses from teleost fish. Nocodazole reversibly inhibited 20-30% of the tubular accumulation of two model organic anions, p-aminohippurate and fluorescein (FL), by winter flounder tubular masses. However, the drug had no effect on the initial rate of organic anion uptake. Thus it did not reduce transport into the cells at the basolateral membrane, either directly by affecting basolateral organic anion transport proteins or indirectly by altering metabolism or ion gradients. Instead, epifluorescence video microscopy and digital image analysis of killifish tubules showed that nocodazole greatly reduced luminal accumulation of FL and had a smaller effect on cellular dye accumulation. Luminal FL accumulation returned to control levels when tubules were incubated in drug-free medium. Confocal fluorescence microscopy confirmed the marked reduction in luminal FL concentration and demonstrated that intracellular punctate FL accumulation was also markedly reduced. Finally, immunohistochemistry with an anti-tubulin antibody showed that the concentrations of nocodazole used in the above experiments reversibly disrupted microtubules within renal epithelial cells. These data indicate that a component of organic anion secretion in teleost proximal tubule is dependent on an intact microtubular network.
Effects of sinoaortic baroreceptor denervation on depletion-induced salt appetite
Authors: Thunhorst R. L. , Lewis S. J. , Johnson A. K.
Published: December 2017

This study examined the effects of denervation of the carotid sinus and aortic arch baroreceptors on sodium depletion-induced salt appetite in rats. Depletion of extracellular fluid began with two injections of furosemide (10 mg/kg sc), 30 min apart, and removal of all ambient sodium from the cages. Water and sodium-deficient chow were available overnight. The next morning, access to 0.3 M NaCl was provided, and intakes of water and saline were measured every 30 min for 2 h and again at 24 h. Three such tests were administered. Groups of sham and sinoaortic baroreceptor-denervated (SAD) rats had equivalently negative water and sodium balances before access to saline the next morning. Sham-denervated rats drank sufficient saline in 2 h to achieve positive sodium balance and subsequently ingested sodium in excess of need for another 22 h. SAD rats drank half as much saline as sham-denervated rats by 2 and 24 h and remained in negative balance at 2 h. Sham-denervated rats increased their intakes of saline solution with repeated tests, but SAD rats did not. These findings suggest that arterial baroreceptors provide critical neural input for the normal expression of salt appetite.
Involvement of capsaicin-sensitive nerves in regulation of insulin secretion and glucose tolerance in conscious mice
Authors: Karlsson S. , Scheurink A. J. , Steffens A. B. , Ahren B.
Published: December 2017

The impact of sensory nerves in glucose-stimulated insulin secretion and glucose tolerance was investigated in conscious mice treated neonatally with either capsaicin (Cap) or vehicle (Veh). At 10-12 wk after Cap, both the early (1 min) insulin secretory response to intravenous glucose (2.8 mmol/kg) (by 67%) and glucose elimination were potentiated (P < 0.05). In contrast, basal insulin, glucagon, and glucose were not affected by Cap. Plasma norepinephrine and epinephrine levels did not differ between Cap- and Veh-treated animals, whereas the increase in plasma insulin levels normally induced by alpha-adrenoceptor blockade by phentolamine was absent after Cap treatment. In isolated islets, the insulin secretory response to glucose (20 mmol/l), carbachol (0.1 mmol/l), or phentolamine (0.5 mmol/l) was not affected after Cap. It is concluded that sensory denervation by Cap results in increased glucose tolerance, which is in part because of a potentiated early insulin response to glucose. This potentiation does not seem secondary to altered plasma catecholamine levels or to altered islet secretory capacity. The results suggest rather that Cap-sensitive nerves, by a local effector function and/or as the afferent loop of a neural reflex, exert inhibitory influences on insulin secretion.
Freeze tolerance in turtles: visual analysis by microscopy and magnetic resonance imaging
Authors: Rubinsky B. , Hong J. S. , Storey K. B.
Published: December 2017

Two visual techniques were used to analyze the patterns of natural freezing and thawing in freeze-tolerant hatchling painted turtles Chrysemys picta marginata. Directional solidification plus light microscopy of liver, heart, and skeletal muscle slices was used to compare freezing at -4 degrees C (a survivable temperature in vivo) and -20 degrees C (not survivable). At -4 degrees C tissues showed large amounts of ice in expanded extracellular and vascular spaces, occupying 36% (liver) and 61% (muscle) of total tissue volume. Cells at -4 degrees C were shrunken, but intracellular water remained; at -20 degrees C, however, cells showed little evidence of free water. Liver micrographs showed novel spherical shells of water associated with intracellular particles (apparently glycogen granules) suggesting that a noncolligative method of cell water retention was employed. Proton magnetic resonance imaging was used for noninvasive analysis of freezing and thawing in the intact animal. Images showed that freezing propagated in a directional manner through the body with ice formed first in extraorgan spaces (e.g., abdominal cavity, brain ventricles). However, thawing occurred uniformly throughout the body core, and organs melted more rapidly than the extraorgan ice surrounding them.
A functional model of the circadian system based on the degree of intercommunication in a complex system
Authors: Diez-Noguera A.
Published: December 2017

A model of the circadian system is presented. It was developed initially for rats, but after introducing several modifications, we consider that it may be extended to many other living systems. It was not the purpose of the study to develop an oversimplified model of the circadian system but rather to explore the elements and rules that govern the dynamics of a complex circadian system, assuming its multioscillatory nature. The formulation of the model is based on the concept of intercommunication in a population of autonomous oscillators. Most environmental effects (including rhythm entrainment) can be simulated with the model simply by controlling the degree of intercommunication. The model introduces the concept of neutral elements (probably glial cells in real systems) that shorten or lengthen the period in response to changes in illumination intensity as a consequence of their presence. Feedback in the system facilitates the emergence of split patterns. By defining the oscillatory units to have similar intrinsic period and a relatively low level of internal coupling, it is possible to obtain complex circadian patterns, maintaining stable phases among their components, which resemble ultradian rhythms. A computer program was developed allowing experimentation with a variety of different definitions and environmental conditions. Although the computer implementation of the model has required the formulation of the model in mathematical terms, the strength of the model (and its functional properties) lies more in the conceptual definition than in its formal aspects.
LDH-B enzyme expression: the mechanisms of altered gene expression in acclimation and evolutionary adaptation
Authors: Segal J. A. , Crawford D. L.
Published: December 2017

The temperature-dependent expression of lactate dehydrogenase-B (LDH-B) was compared between two environmentally distinct populations of Fundulus heteroclitus acclimated to 10 degrees C and 20 degrees C. The variability in LDH-B protein expression both within and between populations is consistent with a model of thermal compensation. The northern population from the colder environment expresses a twofold greater amount of LDH-B protein than the warmer southern population at both acclimation temperatures. Correspondingly, both populations have 1.3-fold greater levels of the enzyme at an acclimation temperature of 10 degrees C in comparison to 20 degrees C. In 20 degrees C-acclimated individuals there is a similar twofold difference between populations for LDH-B mRNA concentrations, and LDH-B protein and mRNA are highly correlated (r = 0.81). After acclimation to 10 degrees C, this difference between populations is not seen and in the northern population there is no relationship between LDH-B mRNA and protein levels. Thus the molecular mechanism regulating LDH-B enzyme expression changes in response to temperature acclimation and is different between populations.
Cholecystokinin suppresses food intake by a nonendocrine mechanism in rats
Authors: Reidelberger R. D. , Varga G. , Liehr R. M. , Castellanos D. A. , Rosenquist G. L. , Wong H. C. , Walsh J. H.
Published: December 2017

A cholecystokinin monoclonal antibody (CCK MAb) was used to immunoneutralize CCK to test the hypothesis that CCK produces satiety by an endocrine mechanism. We first characterized the effects of CCK MAb on pancreatic secretion. Conscious rats with jugular vein and bile-pancreatic duct cannulas received CCK MAb or control antibody intravenously 30 min before a 2-h maximal dose of CCK-8 (200 pmol.kg-1.h-1 i.v.) or access to food. CCK MAb caused dose-related inhibition of amylase secretion. CCK MAb (2 mg/kg) completely blocked the response to CCK-8 and inhibited the response to food by 89%. In feeding experiments, rats with free access to food received CCK MAb or control antibodies (2 mg/kg iv) 2 h after lights off. CCK MAb had no effect on 1.5- or 3.5-h food intake. Another group of rats received CCK MAb (4 mg/kg i.v.) or a combined injection of type A and type B CCK receptor antagonists devazepide and L-365,260 (1 mg/kg each i.v.). CCK MAb had no effect on feeding, whereas the receptor antagonists stimulated 1-, 2-, 3-, and 4-h intake by 62, 45, 43, and 29%. These results suggest that endogenous CCK stimulates pancreatic enzyme secretion at least partially by an endocrine mechanism and produces satiety by a nonendocrine mechanism.
Increased plasma osmolality stimulates peripheral and central vasopressin release in male and female rats
Authors: Ota M. , Crofton J. T. , Liu H. , Festavan G. , Share L.
Published: December 2017

It has been demonstrated that the neurohypophysial hormones can be released intrahypothalamically by the paraventricular (PVN) and supraoptic nuclei. The present experiments were undertaken to determine whether a physiological stimulus for vasopressin release, increased plasma osmolality, will stimulate the release of vasopressin by the PVN into the surrounding interstitial fluid, and whether the responses are affected by gender. Intravenous infusion of 2.5 M NaCl for 60 min (0.1 ml.kg-1.min-1) in conscious rats resulted in an increased vasopressin concentration in the dialysate from a microdialysis probe adjacent to the PVN. This response was greater in nonestrous females than in males. On the other hand, the rise in the plasma vasopressin concentration was greater in males than in nonestrous females. Mean arterial blood pressure increased and heart rate decreased, but these responses were not affected by gender. The role of centrally released vasopressin in the control of the peripheral release of vasopressin is conjectural, but both responses may be modulated by the gonadal steroid hormones.
The uncoupling protein thermogenin during acclimation: indications for pretranslational control
Authors: Jacobsson A. , Muhleisen M. , Cannon B. , Nedergaard J.
Published: December 2017

To analyze the regulation of the content of the uncoupling protein thermogenin in brown adipose tissue, we have selected a physiological transition phase during which to investigate the relationship between the level of mRNA and the level of the ensuing protein product. Mice preacclimated to 28 degrees C were transferred to 4 degrees C. Cold acclimation led to the expected increases in brown fat total protein and RNA content. Two recruited proteins were analyzed: the cytosolic glycerol-3-phosphate dehydrogenase and the mitochondrial uncoupling protein thermogenin. The activity of the dehydrogenase acutely followed the level of the corresponding mRNA, indicating pretranslational control. However, for thermogenin there was a marked time delay between the establishment of the fully recruited level of thermogenin mRNA (after only approximately 4 h of cold exposure) and that of thermogenin itself (after > 3 wk). By reiterative computer simulation, it was investigated whether a model only involving pretranslational regulation could be invoked for either system. For glycerol-phosphate dehydrogenase, a plausible model could be constructed, provided the protein half-life was shorter than approximately 24 h. Despite the long time delay between full thermogenin mRNA recruitment and full thermogenin protein recruitment, a plausible pretranslational control model could also be constructed, provided that the protein half-life was approximately 5 days. This computed value was in good agreement with the half-life obtained from independent thermogenin half-life studies. It is implied that pretranslational control may suffice to explain the regulation of thermogenin content in brown adipose tissue during a warm-to-cold transition period.
Novel angiotensin receptor subtypes in fowl
Authors: Nishimura H. , Walker O. E. , Patton C. M. , Madison A. B. , Chiu A. T. , Keiser J.
Published: December 2017

We reported previously that blood vessels of domestic fowl contain angiotensin (ANG) receptors on 1) endothelium, mediating vasorelaxation via endothelium-derived relaxing factor and guanosine 3',5'-cyclic monophosphate; 2) vascular smooth muscles, mediating neither relaxation nor contraction; and 3) presumably adrenergic nerve endings, transmitting vasopressor action via a release of norepinephrine. We aimed in the present study to determine fowl vascular ANG receptor subtypes and relate them to function. [Val5]ANG II (native fowl ANG II) increased mean arterial pressure of anesthetized, ganglion-blocker-treated fowl. The dose-pressor response curve for fowl ANG II was not altered by pretreatment (i.v.) with the ANG receptor subtype 1 (AT1) antagonist Dup-753 (losartan, 10 mg/kg) or the subtype 2 (AT2) antagonist PD-123319 (10 mg/kg). Furthermore, cumulative doses (1-20 mg/kg) of losartan or PD-123319 did not selectively inhibit ANG II-induced pressor responses. In reserpine- and prazosin-treated anesthetized fowl, [Val5]ANG II caused dose-dependent vasodepressor actions inhibited by neither losartan (10 mg/kg) nor PD-123319 (10 mg/kg). Likewise, [Val5]ANG II-induced vasorelaxation of fowl aortic rings in vitro was not inhibitable by PD-123319 or losartan (10(-5) M). Specific binding of 125I-labeled ANG II to the aortic endothelium was markedly displaced by ANG II, but not selectively by PD-123319 or losartan. Specific binding of 125I-ANG II ligand to the membrane fraction of aortic smooth muscles was displaced (50% inhibitory concentration) by [Val5]ANG II (3.3 x 10(-8) M) and slightly by PD-123319 (3.7 x 10(-5) M), but not by losartan or EXP-3174, an active metabolite of losartan.(ABSTRACT TRUNCATED AT 250 WORDS)
Thromboxane A2 receptor antagonism prevents hormonal and cardiovascular responses to mineral acid infusion
Authors: Cudd T. A. , Wood C. E.
Published: December 2017

Small infusions of strong acid create large elevations in heart rate (HR), mean arterial pressure (MAP), adrenocorticotropic hormone (ACTH), cortisol, and thromboxane A2 (TxA2). We hypothesized that TxA2 is responsible for these hormonal and hemodynamic responses. Conscious sheep received HCl (1 N, 1 ml/min for 30 min) with or without receiving SQ-29548 [a TxA2/prostaglandin (PG) H2 receptor antagonist]. HCl increased TxB2 from 133 +/- 44 to 1,213 +/- 531 (SE) pg/ml while SQ-29548 + HCl increased TxB2 from 141 +/- 41 to 1,051 +/- 518 pg/ml. HCl decreased pH (7.464 +/- 0.015 to 7.413 +/- 0.011), arterial PCO2 (31.6 +/- 1.3 to 25.9 +/- 1.8 mmHg), and arterial PO2 (98.0 +/- 2.2 to 90.5 +/- 3.2 mmHg), and increased MAP (75 +/- 2 to 88 +/- 5 mmHg), HR (72 +/- 4 to 93 +/- 8 beats/min), hematocrit (25 +/- 1 to 29 +/- 2%), ACTH (154 +/- 41 to 549 +/- 217 pg/ml), and aldosterone (25 +/- 1 to 151 +/- 74 pg/ml) while these responses were prevented by SQ-29548. SQ-29548 reduced but did not prevent the cortisol response to HCl (9 +/- 2 to 23 +/- 10 ng/ml compared with 6 +/- 2 to 17 +/- 4 pg/ml after SQ-29548). K+ and aldosterone also increased after the end of SQ-29548 + HCl treatment (4.0 +/- 0.1 to 4.5 +/- 0.1 meq/l and 53 +/- 21 to 147 +/- 61 pg/ml, respectively). We conclude that TxA2 mediates the blood gas, MAP, HR, ACTH, and aldosterone responses to HCl infusion.(ABSTRACT TRUNCATED AT 250 WORDS)
Ingestion, gastric fill, and gastric emptying before and after withdrawal of gastric contents
Authors: Kaplan Joel M. , Siemers William , Grill Harvey J.
Published: December 2017

The notion that satiation signals are derived from the stomach with no additional contribution of postgastric sources (J. A. Deutsch. In: Handbook of Behavioral Neuroscience. Food and Water Intake. 1990, vol. 10, p. 151–182) was evaluated in two experiments. In experiment 1, the gastric contents were withdrawn after the rat met the satiety criterion for an initial intraoral intake test (12.5% glucose delivered at 1.0 ml/min). Ten minutes later, the intraoral infusion was continued until the rat again met the satiety criterion. We found that rats reingested an amount closely corresponding to the amount withdrawn, in agreement with previous studies using spout-licking tests. Despite a lower gastric emptying rate during reingestion than during the initial test, the amount recovered from the stomach (both volume and solute content) after reingestion was significantly less (gastric volume 16% less; gastric glucose 18% less) than that withdrawn initially. In experiment 2, a portion (8 ml) of the gastric contents was removed after the end of an initial intraoral intake test and, after 10 min, rats were again given an opportunity to ingest to satiety. The procedure was repeated for a total of three withdrawals (24 ml) and three reingestion opportunities. Rats accurately replaced the amounts withdrawn such that net intake at the end of the experiment did not differ from that ingested during the initial test. In addition, the amount recovered from the stomach after the terminal test was considerably less (gastric volume 25% less; gastric glucose 29% less) than that recovered at the end of single-test control sessions. Both experiments show that gastric feedback cannot alone account for the termination of intraoral intake. The results suggest that rats defend total intake and do so via the integration of signals derived from postgastric as well as gastric sources.

stomach; satiation

Submitted on November 15, 1993

Accepted on May 12, 1994
Preferential incorporation of sn-2 lysoPC DHA over unesterified DHA in the young rat brain
Authors: Thies F. , Pillon C. , Moliere P. , Lagarde M. , Lecerf J.
Published: December 2017

The uptake and metabolism of [3H]docosahexaenoic acid (DHA) esterified at the sn-2 position of lysophosphatidylcholine (lysoPC DHA) and in the unesterified form, both bound to albumin, was studied in 20-day-old rats. LysoPC DHA was preferentially recovered in the brain (4-5% of the injected radioactivity) over the unesterified form of DHA (0.3-0.4%). Conversely, the lysoPC form was taken up less than or at the same extent as the unesterified form by the liver, heart, and kidney. In the brain, DHA was mainly recovered in phosphatidylethanolamine whether the esterified or the unesterified form was used, although DHA from lysoPC was esterified at the same extent in phosphatidylcholine and phosphatidylethanolamine after 2.5 min. The uptake of labeled palmitic, oleic, linoleic, and arachidonic acids, esterified or not in lysophosphatidylcholine, was also studied in brain, liver, heart, and kidney. Only the brain preferentially incorporated unsaturated (but not saturated) lysoPC, with the uptake increasing with the degree of unsaturation of the fatty acid moiety. These results strongly suggest that the young rat brain specifically utilizes albumin-lysoPC-containing polyunsaturated fatty acids.
A specific role for TRH in release of diacetyl alpha-MSH in tilapia stressed by acid water
Authors: Lamers A. E. , Flik G. , Bonga S. E.
Published: December 2017

After exposure of tilapia for 7 days to low-pH water, plasma thyrotropin-releasing hormone (TRH) levels were elevated, and the melanocyte-stimulating hormone (MSH) cells in the pituitary pars intermedia had increased in size and showed enhanced synthetic and secretory activity. The MSH cells became more sensitive to TRH but not to corticotropin-releasing hormone (CRH). Stimulation by TRH (but not by CRH) of the MSH cells of tilapia exposed to low pH specifically enhanced the release of diacetyl alpha-MSH, the most potent corticotropic form of alpha-MSH. Acute stress imposed by handling and confinement for 1 h elevated the plasma cortisol level but did not affect blood plasma alpha-MSH levels. We conclude that stimulation by TRH is pivotal for an enhanced release of diacetyl alpha-MSH during low-pH adaptation. These results are further evidence of a role for TRH and alpha-MSH in the activation of the hypothalamopituitary-interrenal axis during adaptation to low pH.
Long-term perfusion of the cerebroventricular system of dogs without leakage to the peripheral circulation
Authors: Nitecki S. , Karmeli R. , Harty G. J. , Kamei C. , Yaksh T. L. , Szurszewski J. H.
Published: December 2017

Methods developed previously for studying the effect of cerebroventricular injection or ventriculocisternal perfusion of test substances are unsatisfactory because the test substance is not confined to the central compartment. Most likely the test substance enters the peripheral circulation via the arachnoid villi. The purpose of this paper is to describe a method for perfusing the cerebroventricular system of conscious dogs without passage of test substances to the peripheral circulation. With the method described, the mean (+/- SE) cerebroventricular pressure in conscious dogs was 7.4 +/- 0.8 cmH2O (n = 16), and the mean (+/- SE) production of cerebrospinal fluid (CSF) was 25 +/- 0.3 microliter/min (n = 16). Endogenously occurring migrating myoelectric complexes (MMCs) of the small intestine were recorded in dogs before catheters were implanted in the left and right lateral ventricles and the fourth ventricle and after catheter implantation during cerebroventricular perfusion with artificial CSF alone or with CSF containing sulfated (S-CCK-OP) or nonsulfated cholecystokinin octapeptide (NS-CCK-OP). Only cerebroventricular perfusion with S-CCK-OP (1.2 pmol.kg-1.min-1; n = 20) replaced spontaneously occurring MMCs with a fed-like pattern of myoelectric activity. The results suggest that replacement of the fasting pattern of myoelectric activity with a fed-like pattern in the fasted dog was mediated by CCK-A receptors located in one or more brain nuclei surrounding the third ventricle.
Effects of fat feeding on epinephrine secretion in the rat
Authors: Uemura K. , Young J. B.
Published: December 2017

Adrenal medullary activity increases with fasting, although a role for diet in the regulation of epinephrine (Epi) secretion is otherwise unknown. The current studies examined the effects of dietary fat on adrenal medullary function in male CD rats. Addition of lard to a lab chow diet (+50% of chow energy) for 4 days lowered Epi excretion by 14% (P = 0.0005). Two weeks' exposure to diet containing 33% lard (by energy) reduced urinary Epi compared with that in animals fed an isoenergetic amount of chow. Epi levels in plasma obtained by indwelling catheter from unanesthetized unrestrained rats were lower in lard-fed rats than in chow-fed controls. The plasma Epi response to intravenous administration of d-fenfluramine (4 mg/kg), however, was exaggerated in the lard-fed rats. Plasma NE levels also rose after d-fenfluramine, but responses did not differ between diet groups. Urinary Epi was also measured after exposure to other fats. Beef tallow, like lard, suppressed Epi excretion, but safflower, medium-chain triglyceride, coconut, and soybean oils did not. These results suggest that fats of animal origin, in contrast to those derived from plants, suppress adrenal medullary function, possibly via alteration in central serotonergic pathways.
Hyperosmolality and sperm storage in hibernating bats: prolongation of sperm life by dehydration
Authors: Crichton E. G. , Hinton B. T. , Pallone T. L. , Hammerstedt R. H.
Published: December 2017

Osmolalities of epididymal fluids obtained by micropuncture from hibernating species of bats (Myotis lucifugus) rise during sperm storage periods to as high as 1,523 mmol/kgH2O (approximately 5 times that of plasma). In vitro studies establish that hyperosmolality can preserve viability and prevent initiation of progressive motility in bat epididymal spermatozoa as well as induce their quiescence by reducing respiration. Reduction of osmolality (to 500-600 mmol/kgH2O) induces swelling of sperm and allows the initiation of motility and increased metabolic rate; further reduction of osmolality to < 300 mmol/kgH2O compromises permeability barriers and causes loss of motility. We hypothesize that seasonal establishment of hyperosmotic conditions driven by those cells that constitute the limits of the epididymal lumen dehydrates the compliant spermatozoa and thereby minimizes their metabolic needs. A novel form of cell storage dependent on unique adaptations of the epididymal epithelium for solute and water transport is implicated. To date, the operative osmolyte or osmolytes responsible for elevating osmolality in this system remain elusive.
Circadian rhythm of serum and lymph apolipoprotein AIV in ad libitum-fed and fasted rats
Authors: Fukagawa K. , Gou H. M. , Wolf R. , Tso P.
Published: December 2017

The aim of the present study was to determine if there is a circadian rhythm in serum and lymph apolipoprotein (apo) AIV and what factors determine this rhythm. Male Sprague-Dawley rats with chronic right atrial catheter were housed in a room illuminated from 0600 to 1800. With ad libitum feeding, serum apo AIV concentration showed a circadian rhythm concomitant with the feeding pattern. In 24-h fasted rats, the serum apo AIV concentration maintained a circadian rhythm and was high during the dark. With mesenteric lymph diversion, serum apo AIV concentration diminished and the circadian rhythm was abolished. The lymph flow, lymph apo AIV, cholesterol, triacylglycerol, and phospholipid contents all exhibited the same circadian rhythm in fasting, with the levels higher in the dark. These circadian rhythms were abolished after bile diversion. In conclusion, serum apo AIV in ad libitum-fed and fasted rats exhibits a circadian rhythm governed by lymph apo AIV output. Furthermore, bile was an important determinant of the circadian rhythm of lymph flow, lymph apo AIV, triacylglycerol, cholesterol, and phospholipid output.
Renal effects of nitric oxide synthesis inhibition in cirrhotic rats
Authors: Atucha N. M. , Garcia-Estan J. , Ramirez A. , Perez M. C. , Quesada T. , Romero J. C.
Published: December 2017

In the present study, we have characterized the renal response to inhibition of endogenous nitric oxide (NO) synthesis [intravenous NG-nitro-L-arginine methyl ester (L-NAME) for 3 h] in anesthetized cirrhotic rats, with (ASC) and without (CIR) ascites, at doses that do not change blood pressure (BP). Administration of L-NAME induced opposite effects on water (UV) and sodium (UNaV) excretion in cirrhotic and control animals. Infusion of 1 microgram.kg-1.min-1 of L-NAME in CIR (n = 5) decreased renal plasma flow (RPF) at the end of the 3-h period, whereas UV, UNaV, and glomerular filtration rate (GFR) were unaltered. In contrast, infusion of L-NAME at 10 micrograms.kg-1.min-1 in six more CIR increased UV and UNaV significantly by the 1st h, without changes in BP or GFR, and these parameters remained elevated throughout the experiment. Infusion of 1 microgram.kg-1.min-1 in ASC (n = 6) did not change BP or GFR but significantly enhanced UV and UNaV after the 1st h. These effects were prevented by pretreatment with L-arginine (0.1 mg.kg-1.min-1) in another group of ASC infused with 1 microgram.kg-1.min-1 of L-NAME. These results indicate that, in ASC and CIR cirrhotic rats, inhibition of NO synthesis at nonpressor does improves renal excretion of sodium and water via a decrease in tubular reabsorption. NO is an important mediator of the renal excretory and hemodynamic alterations of experimental liver cirrhosis.