bluuebunny/crossref_metadata_2025 huggingface dataset:
Lipoprotein lipase in white and brown adipose tissues of exercised rats fed a high-fat diet
Authors: Deshaies Y. , Arnold J. , Lalonde J. , Richard D.
Published: December 2017

The combined effects of a high-fat-supplemented diet and exercise training on serum lipids as well as on lipoprotein lipase activity in white and brown adipose tissues of the rat were evaluated. Male Wistar rats were fed ad libitum either a stock diet or the stock diet supplemented with food items rich in fat. Half of each dietary group was submitted to daily treadmill running for 35 days. Food intake and final body weight were raised by the high-fat-supplemented diet and lowered by exercise training. Postprandial serum triglycerides were not affected by diet or exercise, whereas the latter decreased total cholesterol in the high-fat group only (14%, P less than 0.01). Total lipoprotein lipase activity in white adipose tissue was elevated (120%, P less than 0.01) by high-fat feeding, and this increase was greatly reduced by concomitant exercise training. In brown adipose tissue, however, the large elevation (104%, P less than 0.01) in enzyme activity brought by the high-fat diet was unaltered by concomitant training. Thus a high-fat-supplemented diet increased lipoprotein lipase activity in both an energy-storing and a heat-producing tissue, and exercise training was able to counteract this effect in white, but not in brown, adipose tissue. These findings support the notion that the regulation of lipoprotein lipase is tissue specific.
Effect of teleost GnRH on reinitiation of oocyte meiosis in goldfish, in vitro
Authors: Habibi H. R. , Van der Kraak G. , Bulanski E. , Peter R. E.
Published: December 2017

The effects of native and an agonist analogue of teleost gonadotropin-releasing hormone (GnRH) [(D-Arg6, Trp7, Leu8, Pro9-NHEt)-GnRH; tGnRH-A] on the hormone-induced meiotic maturation of goldfish oocytes were investigated. Incubation of follicle-enclosed goldfish oocytes with either carp gonadotropin (GtH) or meiogenic progestogens, including 17 alpha-hydroxyprogesterone (HP) and 17 alpha,20 beta-dihydroxyprogesterone (DHP), reinitiated oocyte meiosis in vitro, as indicated by germinal vesicle dissolution (GVD). Addition of tGnRH-A (10(-7) M) significantly attenuated the GVD response to GtH, HP, and DHP in a dose-related fashion; tGnRH-A reduced the magnitude of progestogen-induced GVD response without significantly affecting the sensitivity of the oocytes to the meiogenic steroids. Similarly, administration of native teleost GnRH (tGnRH) significantly attenuated GtH-induced GVD response, although the 50% maximal response of the native peptide was significantly higher than that of tGnRH-A (380.9 +/- 125 and 2.72 +/- 0.94 nM, respectively). The present results provide the first demonstration of an inhibitory action of a GnRH agonist on the process of progestogen-induced oocyte meiosis and support the hypothesis that GnRH or a GnRH-like peptide might play a modulating role in the control of oocyte meiosis at the ovarian level in goldfish.
Atrial natriuretic peptide inhibits postural release of renin and vasopressin in humans
Authors: Williams T. D. , Walsh K. P. , Lightman S. L. , Sutton R.
Published: December 2017

The effects of infusions of atrial natriuretic peptide (ANP) on the hormonal and hemodynamic responses to head-up tilt were investigated in six healthy adults. Head-up tilt at 45 degrees for 2 h during placebo saline infusion caused a 7% fall in blood volume accompanied by increases in plasma renin activity (PRA) and plasma arginine vasopressin (AVP) of 112 and 175%, respectively. Head-up tilt was repeated during an infusion of ANP producing a four- to sixfold increase in plasma ANP concentrations. This resulted in an 18% fall in plasma volume, yet despite this greater fall in plasma volume, PRA did not change. Two subjects experienced vasovagal symptoms toward the end of the ANP infusions accompanied by large increases in plasma AVP. In the other four subjects, plasma AVP remained unchanged during ANP infusions. Both procedures resulted in similar increases in plasma norepinephrine levels and in heart rate. Infusion of ANP prevents the posturally stimulated release of renin and AVP.
Effects of meal frequency on energy utilization in rats
Authors: Hill J. O. , Anderson J. C. , Lin D. , Yakubu F.
Published: December 2017

The effects of differences in meal frequency on body weight, body composition, and energy expenditure were studied in mildly food-restricted male rats. Two groups were fed approximately 80% of usual food intake (as periodically determined in a group of ad libitum fed controls) for 131 days. One group received all of its food in 2 meals/day and the other received all of its food in 10-12 meals/day. The two groups did not differ in food intake, body weight, body composition, food efficiency (carcass energy gain per amount of food eaten), or energy expenditure at any time during the study. Both food-restricted groups had a lower food intake, body weight gain, and energy expenditure than a group of ad libitum-fed controls. In conclusion, these results suggest that amount of food eaten, but not the pattern with which it is ingested, has a major influence on energy balance during mild food restriction.
Effects of hemorrhage on vasopressin and Met-Enk releases in blood and cerebrospinal fluid in dogs
Authors: Ota K. , Kimura T. , Matsui K. , Iitake K. , Shoji M. , Inoue M. , Yoshinaga K.
Published: December 2017

To assess whether hemorrhagic shock causes simultaneous release of methionine enkephalin-like substance (MELS) and arginine vasopressin (AVP) both in cerebrospinal fluid (CSF) and circulating blood, continuous bleeding at a rate of 1 ml.kg-1.min-1 was undertaken for 40 min in anesthetized dogs (n = 6) and mean arterial pressure and heart rate were measured. In a time control study (n = 6), hemorrhage was omitted. Plasma AVP and MELS concentrations did not differ from CSF AVP and MELS in the control period in either the hemorrhage or the control groups. In the hemorrhage group, plasma AVP increased at 20 min and thereafter during the hemorrhagic shock, and plasma MELS increased at 30 and 40 min. No changes in AVP and MELS in the CSF occurred during hemorrhage, except a rise in AVP at 40 min. In the control group, AVP and MELS in the plasma and CSF did not change during the study, except for a rise in CSF AVP at 40 min. MELS was found in three forms: its large-molecular-weight form, methionine enkephalin, and metabolite; but the large-molecular-weight form was only observed in the CSF. These results showed that hemorrhage increases circulating MELS and AVP, but not MELS and AVP in the CSF, except for a slight rise in AVP during severe hypotension.
CRF activates autonomic nervous system and reduces natural killer cytotoxicity
Authors: Irwin M. , Hauger R. L. , Brown M. , Britton K. T.
Published: December 2017

Corticotropin-releasing factor (CRF) acts within the brain to elicit changes in neuroendocrine, autonomic, and behavioral activity similar to those observed after stress. A reduction of immune function has also been described following central administration of CRF. In this study, we examined whether autonomic nervous system activation plays a role in CRF-induced suppression of natural killer (NK) cytotoxicity. synthetic rat CRF (1.0 microgram) microinjected into the lateral ventricle significantly increased plasma concentrations of norepinephrine and reduced splenic NK cell activity in the rat. Pretreatment of the animals with the ganglionic-blocking agent chlorisondamine completely abolished the CRF-induced increase in plasma norepinephrine levels and reduction in NK activity. However, CRF-induced elevations in plasma levels of adrenocorticotropic hormone and corticosterone were not affected by chlorisondamine. The results of this study suggest that activation of the sympathetic nervous system plays a role in CRF-induced suppression of NK cytotoxicity.
Effect of vasopressin on adrenal steroidogenesis
Authors: Schneider E. G.
Published: December 2017

The direct effect of vasopressin on adrenal steroidogenesis and its effect on angiotensin II- and adrenocorticotropic hormone (ACTH)-stimulated steroidogenesis was evaluated by using an isolated perfused canine adrenal gland preparation. Infusions of vasopressin alone (50, 100, or 250 pg/ml perfusate) had no significant effect on the secretion of either aldosterone or cortisol. Infusions of vasopressin at 75 or 250 pg/ml perfusate during stimulation of steroidogenesis by angiotensin II or by ACTH did not cause a consistent increase in aldosterone secretion. In contrast, infusion of 250 but not 75 pg vasopressin/ml perfusate caused a consistent enhancement of ACTH-stimulated cortisol secretion. The infusion of a vasopressin V1-receptor agonist, but not of either a vasopressin V2-receptor agonist or oxytocin, also caused a significant enhancement of ACTH-stimulated cortisol secretion. These results suggest that the sensitivity of fasciculata cells to vasopressin is greater than that of glomerulosa cells. Finally, levels of vasopressin reported to occur in plasma during severe hemorrhage appear to be capable of enhancing cortisol secretion by a direct action on the adrenal gland via a V1-receptor mechanism.
Vole infant development is influenced perinatally by maternal photoperiodic history
Authors: Lee T. M. , Zucker I.
Published: December 2017

Vole pups were maintained from the time of conception in the same short-day (SD) photoperiod (10 h light/day, LD 10:14); groups differed only with respect to SD photoperiodic histories of dams before gestation, which simulated those experienced by dams breeding in autumn (SD-2, 2 wk of short days), midwinter (SD-21), or late winter (SD-26). Compared with SD-2 pups, offspring born to SD-26 dams matured more rapidly with respect to body size and reproductive status. Several other somatic and behavioral measures indicated that winter preparedness was greatest in pups whose dams had experienced 2 wk and least in those that had experienced 26 wk of SD treatment before conception. A cross-fostering design, in which pups gestated in long (LD 14:10) or short photoperiods were reared postnatally in the same or opposite day length, indicated that several photoresponsive traits are influenced predominantly by prenatal photoperiod, others by postnatal day length, and others by both photoregimens. Information is communicated to fetuses about the length of time dams have been exposed to short day lengths before mating as well as about the day length prevailing during gestation. The changes induced by the mother in her pups pre- and postnatally likely facilitate adaptation of newly weaned voles to seasonally varying environmental conditions.
An analysis of residual NaCl taste response after amiloride
Authors: Formaker B. K. , Hill D. L.
Published: December 2017

The identity of the residual taste response to NaCl after lingual application of the sodium transport blocker, amiloride, was studied by electrophysiological recordings from the rat chorda tympani nerve. Stimulation of the anterior tongue with salt solutions resulted in responses to halogenated sodium salts that were not eliminated by amiloride; approximately 30% of the halogenated sodium salt response remained after amiloride. In contrast, responses to nonhalogenated sodium salts were reduced to less than 4% of the original response after amiloride. To further learn of characteristics relating to the residual NaCl response, binary mixture and cross-adaptation experiments were accomplished. Responses to mixtures of sodium acetate or sodium bicarbonate with choline chloride were similar to responses elicited by equimolar concentrations of NaCl before and after amiloride. Moreover, NaCl and NaBr cross-adapted with choline chloride after, but not before, lingual application of amiloride. These experiments indicate that the residual response to halogenated sodium salts (e.g., NaCl) is related to the halogen itself, and from findings presented here, we propose one pathway for sodium taste transduction.
Insulin secretion and substrate homeostasis in prolonged hypothermia in rats
Authors: Hoo-Paris R. , Jourdan M. L. , Wang L. C. , Rajotte R.
Published: December 2017

In hypothermia, impairment of metabolic substrate mobilization and utilization may be a factor limiting survival. By use of a newly developed technique, substrate profiles and their regulation by insulin were examined in hypothermic rats (body temperature 19 degrees C) over 24 h. Plasma glucose concentrations increased to approximately 300 mg/dl during cooling and remained high throughout the period of hypothermia. Free fatty acid (FFA) concentration was not altered during cooling or during the first 10 h of hypothermia (approximately 700 mu eq/l) but progressively decreased thereafter, reaching 420 mu eq/l by 20 h. Plasma insulin decreased dramatically during cooling and remained very low (9 +/- 2 microU/ml) during the whole period of hypothermia, reflecting the suppression of insulin secretion by isolated islets at low temperatures. To test he hypothesis that suppression of endogenous insulin secretion may hamper glucose utilization and thus limit survival in hypothermia, exogenous insulin was administered. At doses of 0.1, 0.5, and 1 U/kg intravenously, insulin slowly decreased plasma glucose and FFA. However, at 0.1 and 1 U/kg intraperitoneally, insulin resulted in a dose-dependent decrease in survival time in the hypothermic rat. It is possible that the antilipolytic effect of insulin may have outweighed any beneficial effect of improving glucose utilization in hypothermia.
Effect of paraventricular nucleus lesions on drinking and pressor responses to ANG II
Authors: Gutman M. B. , Jones D. L. , Ciriello J.
Published: December 2017

Experiments were done to investigate the contribution of cells of the paraventricular nucleus of the hypothalamus (PVH) to the drinking and pressor responses elicited by microinjection of angiotensin II (ANG II) into the subfornical organ (SFO) in the awake unrestrained rat. Microinjection of ANG II (5 eta g in 0.2 microliter) elicited drinking (7.1 +/- 0.7 ml in 15 min, n = 18) and pressor (19 +/- 1 mmHg, n = 17) responses. Bilateral lesions of the PVH by the administration of kainic acid (KA; 0.2 microgram in 0.2 microliter of phosphate buffer) resulted in the abolition of the drinking response (before, 7.8 +/- 1.8 ml in 15 min; after, 0 ml in 15 min, n = 6) and significant (P less than 0.05) attenuation of the pressor response (before, 15 +/- 1 mmHg; after, 5 +/- 2 mmHg, n = 5). Administration of 0.2 microliter of the phosphate buffer vehicle bilaterally into the PVH and KA into regions adjacent to the PVH had no significant effect on the drinking or pressor responses. KA injections into the PVH resulted in the loss of 70-80% of parvocellular cells in the posterodorsal component of the PVH compared with animals with KA injections into adjacent non-PVH tissue (n = 7) or vehicle injection into the PVH (n = 5). These results suggest that parvocellular cells of the PVH are an important component of the neural circuitry that mediates the drinking and pressor response to ANG II acting at the SFO.
Behavioral evidence for cholecystokinin-opiate interactions in neonatal rats
Authors: Weller A. , Blass E. M.
Published: December 2017

In adult mammals, cholecystokinin (CCK)-opiate interactions are complex and task dependent. Specifically, CCK antagonizes opiate effects in some cases, yet acts similarly to opiate agonists in others. The present study used behavioral measures to determine how CCK interacts with opiates in neonatal rats. CCK, at doses of 1 microgram/kg and higher, markedly reduced isolation-induced distress vocalization in rat pups. Moreover, CCK selectively prevented naltrexone antagonism of opiate-mediated reduction in distress vocalization in 3- and 11-day-old rats. Yet CCK did not affect opiate-induced analgesia, as measured by the hot-plate paw-lift response. Thus CCK either did not interact with opiates or did so agonistically, with the same (low) dose range, and within subjects. These findings suggest independence of stress and pain systems in neonatal rats and demonstrate a functional interaction between CCK and opioid systems.
Low-dose fourth ventricular bombesin selectively suppresses food intake
Authors: Ladenheim E. E. , Ritter R. C.
Published: December 2017

Bombesin (BBS) administered into the lateral cerebral ventricles suppresses food intake. Suppression of food intake, however, is accompanied by arousal of competing behaviors such as grooming and increased locomotion, which are atypical of normal satiety. We have found that BBS infused into the fourth cerebral ventricle in rats reduces food intake at doses one-tenth to one-hundredth of those required via the lateral ventricle. In addition, the lowest fourth ventricular dose that significantly reduced food intake did not increase locomotor activity. These data suggest that the hindbrain may be a more sensitive site for BBS-induced suppression of feeding than forebrain sites and that feeding and locomotor effects of BBS may involve dissociable neural substrates.
Effects of atrial natriuretic factor on isolated arteries and perfused organs of trout
Authors: Olson K. R. , Meisheri K. D.
Published: December 2017

Atrial natriuretic factor (ANF) increases blood pressure when injected into conscious trout [Duff and Olson, Am. J. Physiol. 251 (Regulatory Integrative Comp. Physiol. 20): R639-R642, 1986]. The effects and mechanisms of action of ANF on trout vessels in vitro were examined in the present study using isolated celiacomesenteric arterial rings, perfused gill arches, and a two-artery perfused trunk preparation. In all experiments, ANF alone either relaxed trout vessels or had no effect. ANF inhibited contractions of arterial rings produced by a variety of agonists in part through inhibition of intracellular calcium release. In perfused gills, ANF attenuated epinephrine (EPI) alpha-mediated vasoconstriction but had no effect on beta-stimulated increases in water permeability. ANF only slightly lowered an EPI-induced increase in resistance in either pathway of the perfused trunk. These results indicate that the vascular effects and mechanism of action of ANF are similar in fish and mammals and that the pressor response to ANF injection in vivo is mediated through central or secondary effects.
Paraventricular stimulation with glutamate elicits bradycardia and pituitary responses
Authors: Darlington D. N. , Miyamoto M. , Keil L. C. , Dallman M. F.
Published: December 2017

The excitatory neurotransmitter, L-glutamate (0.5 M, pH 7.4), or the organic acid, acetate (0.5 M, pH 7.4), was microinjected (50 nl over 2 min) directly into the paraventricular nuclei (PVN) of pentobarbital sodium-anesthetized rats while arterial blood pressure and heart rate and plasma adrenocorticotropic hormone (ACTH), vasopressin, and oxytocin were measured. Activation of PVN neurons with L-glutamate led to increases in plasma ACTH, vasopressin, and oxytocin and a profound bradycardia (approximately 80 beats/min) with little change in arterial blood pressure. Microinjection of acetate had no effect on the above variables. The decrease in heart rate was shown to be dependent on the concentration of glutamate injected and the volume of injectate. The bradycardia was mediated through the autonomic nervous system because ganglionic blockade (pentolinium tartrate) eliminated the response; atropine and propranolol severely attenuated the bradycardia. The bradycardia was greatest when L-glutamate was microinjected into the caudal PVN. Injections into the rostral PVN or into nuclei surrounding the PVN led to small or nonsignificant decreases in heart rate. Focal electric stimulation (2-50 microA) of the PVN also led to decreases in heart rate and arterial blood pressure. These data suggest that activation of PVN neurons leads to the release of ACTH, vasopressin, and oxytocin from the pituitary and a bradycardia that is mediated by the autonomic nervous system.
Relationship between respiratory state and intracardiac shunts in turtles
Authors: White F. N. , Hicks J. W. , Ishimatsu A.
Published: December 2017

Injection of radioactively labeled microspheres and blood O2 analysis from central vascular sites was utilized to assess intracardiac shunts in the unanesthetized and unrestrained turtle, Pseudemys scripta, at 15 degrees C. Both methods indicated a simultaneously occurring right-to-left (R-L) and left-to-right (L-R) shunt during ventilation and apnea. During ventilation, the O2 method estimated a R-L shunt of 24%. In contrast, injection of microspheres during ventilation estimated a R-L shunt of 65%, which was significantly greater than the value determined from the O2 method. During apnea, both methods indicated a significantly larger R-L shunt. Estimates of the R-L shunt from O2 analysis were between 60 and 90% of the venous return. The R-L shunt estimated from the O2 content of left aortic arch blood was significantly greater than the value determined from right aortic arch blood. During apnea, the microsphere method estimated a R-L shunt of 79%, which was in the intermediate range calculated by the O2 method using two aortic arches. Our results verify previous reports of significant differences in R-L shunt levels between ventilation and apnea during the normal ventilatory cycle of turtles.
Retinyl esters in the vertebrate neuroretina
Authors: Rodriguez K. A. , Tsin A. T.
Published: December 2017

High-performance liquid chromatography (HPLC) was employed to measure retinyl esters in the vertebrate retina. Both retina and retinal pigment epithelium (RPE) from frog, chicken, and bovine eyes were studied. In comparison to the RPE, the retina possessed a significant level of 11-cis and all trans retinyl palmitate. Using a sensitive radioassay, we also detected the presence of retinyl ester hydrolase (REH) activity in homogenates prepared from both retina and RPE. The rate of retinyl ester hydrolysis in these retinas was sufficiently high to supply retinal chromophores for the metabolic renewal and for the regeneration of visual pigments. In comparison to retinyl esters in the RPE, retinyl esters in the retina are located much closer to the sites of visual pigment synthesis and regeneration. Hence it is possible that these retinyl esters play a more important role in the visual cycle than those in the RPE.
Prolactin stimulates food intake in a dose-dependent manner
Authors: Gerardo-Gettens T. , Moore B. J. , Stern J. S. , Horwitz B. A.
Published: December 2017

Lactation in the rat is marked by pronounced hyperphagia and suppression of brown fat (BAT) thermogenic capacity. We previously examined the possibility that elevated prolactin levels mediate these changes. The present study evaluated the effect of varying prolactin levels on food intake, BAT mitochondrial GDP binding, and carcass adiposity. Female rats were injected daily for 10 days with ovine prolactin at one of three doses: high = 3.0, medium = 1.0, or low = 0.3 micrograms/g body wt. Controls were injected with 0.9% NaCl. A group of uninjected rats served as an additional control. Cumulative food intake was significantly elevated in a dose-dependent manner in the prolactin-treated animals relative to the saline-injected and uninjected controls. Compared with the saline controls, the mean cumulative food intake was greatest at the high dose (20% increase), intermediate at the medium dose (17%), and smallest at the low dose (12%). Prolactin-treated rats gained significantly more weight during the experiment than did controls. Despite the hyperphagia in the prolactin-treated rats, no significant differences in BAT mitochondrial GDP binding were observed among the five groups. These data indicate that elevated prolactin levels stimulate food intake in a dose-dependent manner and that this hyperphagia is not accompanied by an increase in BAT mitochondrial GDP binding.
Brown fat thermogenesis during hibernation and arousal in Richardson's ground squirrel
Authors: Milner R. E. , Wang L. C. , Trayhurn P.
Published: December 2017

The thermogenic activity [mitochondrial guanosine 5'-diphosphate (GDP) binding] and capacity (uncoupling protein concentration, cytochrome oxidase activity) of brown adipose tissue have been investigated at different phases of the seasonally linked hibernation cycle in Richardson's ground squirrel. The amount of axillary brown adipose tissue and the total mitochondrial content of the tissue were substantially greater in hibernating squirrels than in squirrels caught posthibernation in April or May; cold acclimation induced qualitatively similar differences. The specific mitochondrial concentration of uncoupling protein was high under all conditions (compared with other species), differing little between hibernating, posthibernating, and cold-acclimated squirrels. The thermogenic capacity of brown adipose tissue in Richardson's ground squirrels is therefore modulated almost exclusively by changes in the mitochondrial content of the tissue. Mitochondrial GDP binding was increased on cold acclimation, but similar binding levels were observed in hibernating and posthibernation (May) animals. GDP binding and the GDP-sensitive component of acetate-induced mitochondrial swelling were increased during the early stages of arousal from hibernation. These changes, which indicate an activation of the thermogenic proton conductance pathway in arousal, occurred without an alteration in the specific mitochondrial concentration of uncoupling protein. Increased GDP binding during arousal is clearly due to the unmasking of binding sites, reflecting an acute activation of preexisting uncoupling protein.
Anesthetic effects on tonic and reflex renal sympathetic nerve activity in awake cats
Authors: Matsukawa K. , Ninomiya I.
Published: December 2017

Renal sympathetic nerve activity (RNA), arterial blood pressure (AP), and heart rate (HR) were simultaneously measured before and after administration of pentobarbital sodium (PB), chloralose (CHL), or urethan (URE) in conscious cats. We examined the time courses and magnitudes of the changes in RNA, AP, and HR over a period of 5 h under anesthesia with spontaneous or artificial respiration. In both respiratory conditions, PB initially decreased and then increased RNA, AP, and HR; CHL sustainedly increased RNA but had almost no effect on AP and HR. Under artificial respiration, URE transiently decreased RNA but had no effect on AP and HR. To examine the baroreflex response of RNA, AP was increased to 150 mmHg by norepinephrine and decreased to 65 mmHg by nitroprusside. RNA responded inversely to the alterations of AP in both awake and anesthetized states. Compared with the awake state, the inverse AP-RNA relationship curve initially shifted downward and then upward under PB, and the slope of the relation curve was initially decreased. On the other hand, under CHL the relationship curve shifted only upward, and the slope increased. Thus the anesthetic drugs affected differently and time dependently tonic and reflex renal sympathetic nerve activity in the conscious cat.
Neurons of rostral ventrolateral medulla mediate somatic pressor reflex
Authors: Stornetta R. L. , Morrison S. F. , Ruggiero D. A. , Reis D. J.
Published: December 2017

The somatic pressor reflex (SPR) elicited in anesthetized paralyzed rats by electrical stimulation of the sciatic or sural cutaneous afferent nerves produced an increase in arterial pressure ranging from 5 to 40 mmHg. Stimulation of femoral or tibial afferent nerves from muscle produced a depressor response. The SPR was not affected by midpontine transection but was eliminated either by hemisection of the lumbar spinal cord contralateral, but not ipsilateral, to the stimulated nerve or by electrolytic or kainic acid lesion of the contralateral, but not ipsilateral, rostral ventrolateral medulla (RVL). Stimulation of the brachial plexus elicited an SPR that was not eliminated by contralateral lumbar hemisection but was abolished by RVL lesion. RVL lesions consistently overlapped areas containing phenylethanolamine N-methyltransferase-labeled C1 adrenergic neurons. Kainic acid injections into the lateral reticular nucleus (LRN) did not affect the SPR. Neither contralateral nor ipsilateral electrolytic lesions of other autonomic areas including parabrachial nucleus, the nucleus tractus solitarii, the A5 region, or the inferior cerebellar peduncle (output pathway of the LRN) affected the reflex. In axonal transport studies using horseradish peroxidase, afferent terminals of the sciatic nerve were shown to overlap spinoreticular neurons in the dorsal horn retrogradely labeled from tracer injections in the RVL. We conclude that the SPR can be elicited in rats, that it is mediated by spinoreticular afferents traveling in the contralateral spinal cord, and that the C1 adrenergic area of the RVL is a critical region for the integration of the somatic pressor reflex.
Nocturnal patterns of macronutrient intake in freely feeding and food-deprived rats
Authors: Tempel D. L. , Shor-Posner G. , Dwyer D. , Leibowitz S. F.
Published: December 2017

Analyses of rats' feeding behavior at the start and the end of the nocturnal cycle have revealed dramatic alterations in macronutrient intake over time. At dark onset, rats displayed a preference for carbohydrate, with the first meal of the night consisting of approximately 60% of this nutrient. This carbohydrate intake was soon followed by a shift toward protein-predominant meals. Superimposed on this pattern of meal-to-meal shifts in nutrient selection appears to be an additional rhythm in which carbohydrate ingestion was favored at dark onset and protein and fat ingestion were favored during the late dark hours. Differential feeding patterns were also apparent following mild food deprivation. A 2-h period of deprivation at dark onset produced a strong compensatory feeding response, particularly of fat and carbohydrate. This pattern was not observed at the end of the dark, when little compensatory feeding was demonstrated. It is suggested that these feeding patterns may be related to the activity of certain hypothalamic neurotransmitters, e.g., norepinephrine and serotonin, known to be important in modulating temporal feeding patterns and nutrient intake.
Siphon mechanism in collapsible tubes: application to circulation of the giraffe head
Authors: Hicks J. W. , Badeer H. S.
Published: December 2017

Controversy exists over the principles involved in determining blood flow to the head of a giraffe, specifically over the role of gravity pressure (pgh) in the collapsible jugular vein in facilitating uphill flow in arteries. This study investigated the pressures within vertically oriented models containing both rigid and collapsible tubes. An inverted U tube was constructed (height = 103 cm) of thick rubber tubing in the ascending limb and collapsible dialysis tubing in the descending limb. Water flow was induced by a variable speed pump maintained at the reservoir level such that the descending limb was partially collapsed. Pressure measurements were made at various levels within the U tube by two methods: 1) with the transducer at same level as the tip of the water-filled catheter and 2) with the transducer at the reservoir level. During flow, the pressure at any point was nearly atmospheric along the length of the descending limb. Such methods of obtaining pressure indicated that the pressure gradient within the partially collapsed descending limb was the sum of viscous flow pressure (P1-P2 of Poiseuille) and gravitational pressure (pgh). To study the facilitatory effect of a siphon, the descending limb was compared with a horizontally placed limb (length = 100 cm), and the flow was kept constant. Calculations of hydraulic "work" (pressure x flow) indicated that with a partially collapsed descending limb, work of the pump was reduced by 15% compared with uphill flow to the elevated horizontal position. It is concluded that the siphon mechanism operates in a partially collapsed descending limb of a siphon loop.
Underfeeding and the physiological responses to infused epinephrine in lean women
Authors: Mansell P. I. , Macdonald I. A.
Published: December 2017

Undernutrition leads to a reduction in sympathetic nervous system activity, but it is not established whether whole body responsiveness to catecholamines is also affected. The physiological responses to a 30-min infusion of epinephrine at 25 ng.kg-1.min-1 were studied in seven healthy, lean female subjects who had reduced their daily food intake to 60 kJ/kg ideal body weight for 7 days. Underfeeding led to greater epinephrine-induced increases in blood glycerol [peak increment 0.14 +/- 0.02 (SE) vs. 0.08 +/- 0.01 mmol/l, P less than 0.05] and beta-hydroxybutyrate concentrations (mean increment 0.30 +/- 0.05 vs. 0.13 +/- 0.04 mmol/l, P less than 0.05, analysis of variance). Compared with the normally fed state, in the underfed state epinephrine also caused greater increases in skin temperatures measured over the abdomen (0.94 +/- 0.08 vs. 0.67 +/- 0.06 degrees C, P less than 0.05) and over the thigh (1.00 +/- 0.07 vs. 0.61 +/- 0.12 degrees C, P less than 0.01). Underfeeding did not, however, affect the chronotropic, thermogenic, or other measured responses to epinephrine. Underfeeding therefore caused an enhancement of some but not all physiological responses to infused epinephrine.
Fourth ventricle bombesin injection suppresses ingestive behaviors in rats
Authors: Flynn F. W.
Published: December 2017

Food intake after fourth intracerebroventricular (icv) injections of bombesin (BBS) was measured in intact rats. BBS injections (greater than or equal to 10 ng) reliably suppressed chow intake in 17-h food-deprived rats. Systemic injections of BBS (50 ng) had no effect on food intake. These data indicate that BBS can act directly on caudal brain stem site(s) to inhibit food intake. The behavioral specificity of fourth icv BBS was evaluated by measuring the effects of fourth icv BBS injection on water intake by 17-h water-deprived rats in the presence and absence of food. Fourth icv injections of BBS in doses greater than 10 ng suppressed 30-min and 2-h water intake relative to saline injection when food was available in the home cage. In contrast, when food was not present during the 2-h intake test, fourth icv injections of BBS had no effect on water intake. This suggests that the inhibition of water intake was secondary to the effects of BBS on food intake. Lastly, sucrose (0.1 M) was paired with fourth icv BBS (50 ng), fourth icv saline, and intraperitoneal LiCl (1.5 meq/kg) in three groups of naive rats, and sucrose preference was subsequently measured. Rats that received injections of either saline or BBS preferred sucrose during the 24-h two-bottle test, and their preference ratios were significantly greater than those of the LiCl-injected rats. The role of afferent signals elicited by fourth ventricle BBS administration in the control of food intake is discussed.
Cachectin/TNF or IL-1 alpha induces cachexia with redistribution of body proteins
Authors: Fong Y. , Moldawer L. L. , Marano M. , Wei H. , Barber A. , Manogue K. , Tracey K. J. , Kuo G. , Fischman D. A. , Cerami A. , et al.
Published: December 2017

Macrophage secretory products are suspected to participate in the severe lean tissue wasting related to chronic illness. The protein metabolic effects of chronic, 7-day cachectin/tumor necrosis factor (cachectin) or interleukin 1 alpha (IL-1 alpha) administration in vivo were studied in male Wistar rats that were 1) freely fed, 2) pair fed, 3) total protein and calorie starved, 4) twice daily lipopolysaccharide (LPS) administered, 5) twice daily cachectin administered, and 6) twice daily IL-1 alpha administered. LPS, cachectin, or IL-1 alpha administration produced anorexia; weight loss in these groups was comparable to respective pair-fed animals. However, LPS, cachectin, or IL-1 alpha accelerated peripheral protein wasting while preserving liver protein content, unlike the pattern in the pair-fed or starved animals in which loss of liver proteins and relative preservation of skeletal muscle protein were observed. The decrease in skeletal muscle protein content in LPS- or cytokine-treated animals was associated with coordinate decreases in muscle mRNA levels for the myofibrillar proteins myosin heavy chain, myosin light chain, actin, and in the 18S and 28S subunits of ribosomal RNA. We conclude that chronic exposure to the cytokines, IL-1 alpha or cachectin, can simulate those body and muscle protein changes seen in experimental LPS administration or chronic disease and markedly differ from the pattern of protein redistribution due to caloric restriction.
Central respiratory modulation of medullary sympathoexcitatory neurons in rat
Authors: Haselton J. R. , Guyenet P. G.
Published: December 2017

The central respiratory generator exerts a modulatory influence on sympathetic nerve discharge. In cats the sympathoexcitatory neurons of the rostroventrolateral medulla (RVL) exhibit central respiratory modulation as well. Because RVL sympathoexcitatory neurons are largely responsible for the maintenance of sympathetic vasomotor tone, it is likely that the modulation of these neurons accounts for the central respiratory modulation of sympathetic discharge. In the present study experiments were performed to characterize the pattern of respiratory modulation of lumbar sympathetic nerve discharge (LSND) in the halothane-anesthetized rat. Phrenic-triggered averaging of LSND exhibited a small depression coincident with the onset of the phrenic burst followed by a large peak that was coincident with the cessation of the phrenic burst. Phrenic-triggered histograms of the activity of RVL sympathoexcitatory neurons exhibited three patterns of central respiratory modulation: inspiratory depression (I), inspiratory peak (II), and early inspiratory depression followed by a postinspiratory peak (III), a pattern that was very similar to that seen in LSND. Both nerve recording and single-unit recording experiments were performed in vagotomized rats with or without intact barosensory afferents. A comparison of the results suggested that, in the rat, the baroreflex does not modify or contribute to the central respiratory modulation of sympathetic output. Finally, a comparison was made between presumed nonadrenergic pacemaker-like neurons and putative C1 adrenergic neurons in the RVL. No differences were found in the patterns of central respiratory modulation.
Effects of intraventricular infusion of corticotropin-releasing factor on VMH-lesioned obese rats
Authors: Arase K. , Shargill N. S. , Bray G. A.
Published: December 2017

Corticotropin-releasing factor (CRF) has been administered into the third ventricle of sham-operated and ventromedial hypothalamic (VMH)-lesioned rats in acute and chronic experiments. After a single 5-microgram injection of CRF, there was an acute reduction of food intake in both sham-operated and VMH-lesioned rats that persisted for 3 h. The effect was still present in the VMH-lesioned rats between 3 and 6 h but had dissipated in the sham-operated controls. Guanosine 5'-diphosphate (GDP) binding to mitochondria from interscapular brown adipose tissue was used as an index of thermogenic activity in this tissue. In 21-h food-deprived rats, GDP binding was significantly lower in VMH-lesioned than in sham-operated animals. Although the mean increase in sham-operated animals was increased, this was not significantly different from saline-injected controls. In the VMH-lesioned rats, however, CRF acutely increased GDP binding to values not different than those of the sham-operated controls. Serum corticosterone was significantly lower in the VMH-lesioned rats, but both groups showed a significant stimulation by CRF during a 7-day infusion of CRF (4.8 micrograms/day) into the third ventricle. Food intake was significantly depressed in the VMH-lesioned animals that received CRF, from values of 35 g/day to approximately 25 g/day. Body weight showed a slow steady decrease, having fallen by nearly 15 g at the end of the 7-day infusion period. In contrast the mean value in the VMH-lesioned controls had significantly higher in CRF-infused animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Atrial peptide release after hemorrhage in unanesthetized swine
Authors: Carlson D. E. , DeMaria E. J. , Campbell R. W. , Chrostek C. , Graeber C. T. , Gann D. S.
Published: December 2017

Hemorrhage of 14 ml/kg in 5 min was done in two groups of chronically prepared, splenectomized Yorkshire pigs. Group 1 was studied on post-operative day 4 and was conditioned behaviorally with "active restraint", whereas group 2 was studied on postoperative day 6 and was conditioned with behavioral "shaping." The peak decrease in blood volume occurred by 0.25 h after hemorrhage in both groups. However, plasma atrial natriuretic factor (ANF) as measured by radioimmunoassay did not decrease significantly until 2 h in group 1 and 0.5 h in group 2 even though the recovery of blood volume was significantly more rapid in group 1 than in group 2. The responses of ANF differed significantly between groups, suggesting that ANF release after hemorrhage is influenced by prior handling and the time for recovery from surgery. In both groups, some pigs showed increases in ANF during the 1st h after hemorrhage, and changes in ANF were unrelated to decreases in central venous pressure or absolute right atrial volume determined with a conductance catheter. In contrast, changes in ANF after hemorrhage correlated positively with several variables including atrial rate and changes in vasopressin. Multiple regression suggested that the effect of reduced atrial volume on ANF release was opposed by these latter variables or related factors. Furthermore, known actions of ANF do not appear to account for the observed hemodynamic and hormonal responses to hemorrhage.
ANP and sodium excretion during acute baroreflex hypertension in conscious dogs
Authors: Ehmke H. , Persson P. , Kogler U. , Lang R. , Kirchheim H.
Published: December 2017

The influence of an acute baroreflex hypertension elicited by common carotid occlusion (CCO) on plasma atrial natriuretic peptide (ANP) and renal sodium excretion was investigated in chronically instrumented, conscious foxhounds receiving a normal-sodium diet. CCO (n = 6) significantly increased mean arterial pressure (from 102 +/- 5 to 144 +/- 3 mmHg; P less than 0.01) and sodium excretion (from 82 +/- 10 to 133 +/- 9 mumol/min; P less than 0.05). No changes in plasma ANP and right atrial pressure were observed during the acute hypertension. In contrast, an acute 20% volume expansion (n = 7) corresponding to 1.8% of body weight raised right atrial pressure (from 1.3 +/- 1.2 to 5.8 +/- 1.2 cmH2O; P less than 0.01) and induced a sustained elevation of plasma ANP (from 39 +/- 8 to 67 +/- 16 pg/ml; P less than 0.05). The natriuresis in response to CCO was eliminated when renal perfusion pressure was regulated at the control level by a renal arterial cuff (n = 4); under these conditions, sodium excretion even tended to decrease during CCO (from 81 +/- 17 to 46 +/- 13 mumol/min; P less than 0.05). In conclusion, an increase in renal perfusion pressure and not an elevated ANP level is important in mediating the natriuresis during CCO in conscious dogs. These results imply that changes in plasma ANP are not essential for the induction and maintenance of a pressure natriuresis.
Characterization of midline medulla role in the trigeminal depressor response
Authors: Clement M. E. , McCall R. B.
Published: December 2017

The purpose of the present investigation was to determine the role of the midline medulla in mediating the trigeminal depressor response. Previously we found that lesions of the midline medulla abolished the decrease in blood pressure resulting from electrical stimulation of the spinal trigeminal complex. Electrical stimulation (5 Hz) of the spinal trigeminal tract elicited a decrease in arterial blood pressure that was associated with an inhibition of sympathetic nerve activity recorded from the inferior cardiac nerve of anesthetized cats. The effect of single shocks applied to the trigeminal complex on sympathetic activity was determined using computer-averaging techniques. Single shock stimulation consistently elicited an excitation of sympathetic activity that was followed by an inhibition of sympathetic nerve discharge. The gamma-aminobutyric acid antagonist picrotoxin blocked the depressor response elicited by electrical stimulation of the midline medulla but not by stimulation of the spinal trigeminal complex. Extracellular recordings of the discharges of midline medullary neurons were made to determine the effects of trigeminal stimulation on sympathoinhibitory, sympathoexcitatory, and serotonin neurons. Sympathoinhibitory and sympathoexcitatory neurons were identified by the relationship between unitary discharges and sympathetic nerve activity and by their response to baroreceptor reflex activation. Serotonin (5-HT) neurons were identified using criteria previously developed in our laboratory. These included 1) a slow regular discharge rate, 2) sensitivity to the inhibitory action of the 5-HT1A agonist 8-OH 8-hydroxy-2-(di-n-propylamino)tetralin, 3) failure to respond to baroreceptor reflex activation, and 4) the discharges of the 5-HT neurons were not related to sympathetic activity. Stimulation of the spinal trigeminal complex typically inhibited the discharges of sympathoinhibitory neurons. In contrast, stimulation of the trigeminal complex consistently excited both sympathoexcitatory and 5-HT neurons. These results are discussed in relationship to the role of the midline medulla in mediating the trigeminal depressor response.
Plasma CCK levels after food intake and infusion of CCK analogues that inhibit feeding in dogs
Authors: Reidelberger R. D. , Kalogeris T. J. , Solomon T. E.
Published: December 2017

To determine whether postprandial plasma levels of cholecystokinin (CCK) are sufficient to produce satiety, we compared CCK levels after food intake and administration of CCK analogues that suppress feeding. Seven beagles were adapted to ad libitum access to solid food for 18 h, which was followed by 4 h of food deprivation and a 1-h test session. Plasma CCK increased from 2.7 +/- 0.2 pM before to a maximum of 5.0 +/- 0.7 pM after ingestion of solid food. Intravenous cholecystokinin octapeptide (CCK-8; 0, 50, 100, 200, 400, 800 pmol.kg-1.h-1), caerulein (0, 25, 50, 100, 200, 400 pmol.kg-1.h-1), and [Thr4,Nle7]CCK-9 (0, 25, 50, 100, 200, 400 pmol.kg-1.h-1), at a rate of 1 dose/day given 15 min before feeding and during a 45-min feeding period, caused similar dose-dependent suppression of feeding at 200 pmol.kg-1.h-1 and greater. On separate days blood samples for peptide assay were collected during infusion of scalar ascending doses of CCK-8 or [Thr4,Nle7]CCK-9 (0, 25, 50, 100, 200, 400 pmol.kg-1.h-1) or caerulein (0, 16.7, 50, and 150 pmol.kg-1.h-1), with each dose being administered for 30 min. Peptide levels were highly correlated with dose (r = 0.94, 0.87, and 0.95 for CCK-8, caerulein, and [Thr4,Nle7]CCK-9, respectively). Peptide levels after minimal effective doses for suppression of feeding were 59 +/- 6, 54 +/- 7, and 70 +/- 5 pM for CCK-8, caerulein, and [Thr4,Nle7]CCK-9. These results suggest that postprandial plasma levels of CCK are not sufficient to produce satiety.