bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny of epinephrine-induced anorexia in rats
Authors: Rodriguez-Zendejas A. M. , Chambert G. , Lora-Vilchis M. C. , Epstein A. N. , Russek M.
Published: December 2017

Intraperitoneal or intraportal epinephrine elicits a strong inhibition of food intake in adult rats and dogs but has no effect when injected intramuscularly or intrajugularly, in spite of production of larger hyperglycemia and cardiovascular changes. These facts suggest that the effect of epinephrine on feeding is elicited via the liver. Ontogeny of this adrenergic control of food intake was studied in newborn and weanling rats. Anorexic effect of intraperitoneal epinephrine was clearly observed in dam-deprived 3-day-old neonatal rats (youngest in which it was tested), both when they were offered enriched milk through an anterior oral cannula while they were isolated from their dam and when they were allowed to suckle from her. However, anorectic effect was less in neonatal rats (day 3-13) than in adults. Weanling rats, 21-26 days old, were as sensitive to intraperitoneal epinephrine as adults. In 3- to 4-day-old rats it also reduced water intake, but this effect disappeared by day 12 and was not observed in mildly water-deprived adults. Peripheral adrenergic control of intake appears very early in ontogeny of rats. First, it affects food and water intake equally, but by day 12 it affects only food intake. Increase in sensitivity to epinephrine after weaning is probably due to an increase in number of hepatocytic adrenergic receptors and/or increase in enzymes necessary for hepatic effects of epinephrine.
Renal afferent input to thoracolumbar spinal neurons of the cat
Authors: Ammons W. S.
Published: December 2017

Responses of 65 thoracolumbar spinal neurons to electrical stimulation of the left renal nerves were examined in 19 cats anesthetized with alpha-chloralose. Cells were found primarily in laminae V and VII of the T12-L2 segments on the left side of the spinal cord. Renal nerve stimulation excited 55 and inhibited 10 cells. Excitatory responses were characterized either by short latency or both short and long latency responses (means +/- SE: 13 +/- 1 and 68 +/- 7 ms). Recordings of the compound action potential in the least splanchnic nerve indicated that early responses resulted from A delta-renal afferent input and long latency responses from C-fiber renal input. Maximal responses to A delta-renal input (3.3 +/- 0.5 spikes/stimulus) were significantly greater than maximal responses to C-fiber renal input (1.5 +/- 0.3 spikes/stimulus). Inhibitory responses were best demonstrated by repetitive stimuli; however, responses of five cells to single stimuli showed that these responses had long latencies to onset (36 +/- 6 ms). All cells were excited or inhibited by somatic stimuli. Excitatory somatic receptive fields invariably included the left flank region and lower abdomen, occasionally included the left hindlimb, and in a few cases included the right hindlimb. Thirteen cells had both excitatory and inhibitory somatic receptive fields. The results show that thoracolumbar spinal neurons receive renal A delta- and C-fiber input that converges with input from somatic structures. These cells may participate in renal pain which is referred to somatic structures or reflexes initiated by renal afferent fibers.
Substance P, 5-hydroxytryptamine, and bradykinin stimulate abdominal visceral afferents
Authors: Lew W. Y. , Longhurst J. C.
Published: December 2017

To determine if chemicals produced endogenously within the gastrointestinal system stimulate abdominal visceral sensory endings, we recorded the response of 42 A- and 25 C-fibers in the splanchnic nerve of cats as substance P (10-20 micrograms), 5-hydroxytryptamine (5-HT, 100-200 micrograms), or bradykinin (10 micrograms) was injected into the descending thoracic aorta. Approximately half of the sensory endings responded to each chemical. However, significantly more C- than A-fiber endings responded to 5-HT (64 vs. 39%) and bradykinin (76 vs. 41%). Most C-fiber endings were insensitive to external mechanical stimuli, supporting the concept that these endings are primarily chemosensitive. In contrast, most A-fiber endings were quite sensitive to external mechanical stimuli. Additionally, more A-fiber endings located in contractile (gut or vasculature) than in noncontractile (pancreas, liver, or spleen) regions responded to 5-HT (58 vs. 19%), bradykinin (67 vs. 15%), and substance P (57 vs. 29%), a response that frequently occurred coincident with the development of chemically induced gut contractions. Thus many A-fiber endings are primarily sensitive to mechanical stimuli. However, 15-30% of the A-fiber endings located in noncontractile regions responded to chemicals, although the endings likely were removed from the mechanical effects of these chemicals. Since these A-fiber endings are also quite sensitive to external mechanical stimuli, they may be polymodal in their function. We conclude that abdominal visceral sensory endings are not homogeneous in function and are stimulated by several chemicals produced endogenously within the gastrointestinal system, including substance P, 5-HT, and bradykinin.
Sympathetic activity, lipids accumulation, and arterial wall morphology in rabbits at high altitude
Authors: Fronek K. , Alexander N.
Published: December 2017

The purpose of this study was to investigate the effect of increased sympathetic nervous activity on arterial wall viability as reflected by its response to elevated plasma lipids. Our previous finding that vascular wall viability was reduced by low sympathetic nervous activity indicated that chronically enhanced sympathetic activity should have the opposite effect. In this study rabbits were divided into two groups, both of which received 1% cholesterol in the diet. One group was born and raised at high altitude to induce chronic activation of sympathetic activity, and the other was raised at sea level. Aorta of high-altitude rabbits exhibited significantly less lipid accumulation than aortas of sea-level rabbits. This difference in lipid accumulation was accompanied by elevated norepinephrine turnover and decreased sensitivity to exogenous norepinephrine of high-altitude rabbit arteries. Vascular smooth muscle cells of high-altitude rabbits demonstrated striated increased relative volume density of mitochondria and decreased nucleocytoplasmic ratio, reflecting lower mitotic rate. These results are suggestive that enhanced chronic activity of vascular sympathetic innervation protects smooth muscle from lipid accumulation and exerts a positive effect on vascular viability.
Extraction and metabolism of circulating catecholamines by the trout gill
Authors: Nekvasil N. P. , Olson K. R.
Published: December 2017

Extraction and metabolism of [3H]-norepinephrine (NE) and [3H]epinephrine (E) by the respiratory (efferent branchial) and filamental (venous) vasculature of the trout gill were examined using an isolated perfused arch technique in which outflow from the two circulations was separated. Deaminated and O-methylated metabolites in the effluent were identified by ion-exchange chromatography. Metabolism by tissue homogenates was also measured. Gill homogenates deaminate catecholamines (CAs) faster than homogenates of liver, kidney, and skeletal muscle; branchial O-methylation was comparable to that of liver and kidney. The perfused gill extracted 60% of a NE pulse and 47% of an E pulse. During continuous CA perfusion the gill removed greater than 30% of the NE from the circulation through extraction and metabolism; only 7% of the E was removed. The gill venous system extracts and metabolizes more CAs than the efferent. NE is the preferred substrate for extraction and metabolism. A mechanism is proposed whereby high circulating CA levels, common during stress, are maintained through CA-induced reduction in venous blood flow. After the stress is alleviated, CA levels begin to fall, flow to the venous pathway increases, and the rate of inactivation of circulating CAs increases.
Angiotensin extraction by trout tissues in vivo and metabolism by the perfused gill
Authors: Olson K. R. , Kullman D. , Narkates A. J. , Oparil S.
Published: December 2017

Plasma clearance and tissue accumulation of 125I-angiotensin I, [Asp1, Ile5]ANG I, and [14C]sucrose, an inert volume reference, were measured after a bolus injection into the dorsal aorta of rainbow trout, Salmo gairdneri. Retention and metabolism of ANG I to angiotensin II (ANG II) and their constituent 1-4 peptide by the gill were examined using an isolated perfused arch preparation in which outflow from the respiratory and central filamental (venous) pathways was separated. Clearance of ANG I from plasma is multiexponential, reflecting dilution and tissue extraction. Liver, bile, gonads, corpuscles of Stannius, and white skeletal muscle accumulate more 125I than 14C; gill tissue accumulates less 125I than 14C. ANG I and II are retained by the perfused gill longer than the inert vascular marker sucrose, even though the distribution volumes of the former are less. The gill respiratory pathway converts ANG I to ANG II whereas the venous pathway metabolizes either ANG I or II to the 1-4 peptide and other metabolites. The gill respiratory pathway is in series with the systemic vasculature, has a large blood-cell contact area, and, like the mammalian lung, is ideally suited to activate ANG I. The gill venous pathway is in parallel with the systemic vasculature and removes ANG II from the circulation. During stress, elevated plasma catecholamines may reduce venous perfusion and thereby help maintain elevated circulating ANG II levels through reduced venous metabolism.
Glucagon-induced inhibition of feeding is impaired by hepatic portal alloxan injection
Authors: Ritter S. , Weatherford S. C. , Stone S. L.
Published: December 2017

Subdiabetogenic doses of alloxan injected into the hepatic portal vein of rats abolished glucagon-induced inhibition of feeding (glucagon satiety) both in daytime tests using a palatable food and in nighttime tests using their standard pelleted diet. In contrast, inhibition of food intake by cholecystokinin and epinephrine and stimulation of feeding by 2-deoxy-D-glucose were not impaired by alloxan. Alloxan-induced deficits in glucagon satiety did not appear to result from generalized hepatocellular necrosis, because satiety deficits outlasted histological signs of toxicity and because furosemide, which produced a similar degree of hepatotoxicity, did not impair glucagon satiety. In addition, alloxan's effects were not associated with impaired glycogen storage or mobilization. Recovery of glucagon satiety occurred in some animals but not until 3-6 mo after alloxan. The degree of recovery was inversely related to alloxan dose. Our results indicate that, when administered into the hepatic portal vein, alloxan may be a relatively specific toxin for cells involved in the mediation of glucagon satiety. The specificity of the deficit and the time course of recovery suggest that the alloxan-sensitive cells may be hepatic vagal neurons.
Osmotic blood-brain barrier opening to IgM monoclonal antibody in the rat
Authors: Neuwelt E. A. , Minna J. , Frenkel E. , Barnett P. A. , McCormick C. I.
Published: December 2017

Pharmacokinetic parameters of iodinated monoclonal antibody (MAb) delivery to normal rat brain were examined. The mean cerebrovascular permeability-surface area (PA; permeability X capillary surface area) to immunoglobulin M (IgM) MAb (mol wt 1,000,000) 10 min after infusion was 0.40 X 10(-6) S-1. When osmotic blood-brain barrier (BBB) disruption is utilized, the PA increased to 8.36 X 10(-6) S-1. Neither intravenous nor intracarotid MAb administration significantly affected delivery to brain. However, osmotic BBB opening significantly (P less than 0.0005) increased MAb uptake independent of the route of administration. After BBB opening and intracarotid MAb the maximum concentration in brain at 1 h was 0.72% per gram of the total administered dose. For 6 h postdisruption, ipsilateral brain levels were 25- to 100-fold greater than in the contralateral hemisphere or nonbarrier-disrupted controls. MAb concentration in brain slightly decreased over 72 h (P less than 0.05). Antibody recovered from disrupted brain retained 90% of its immunological reactivity for at least 24 h. MAb delivery to ipsilateral brain after BBB disruption was linear over a dose of 0.5-5.0 micrograms IgM, whereas the percentage of the total administered dose remained unchanged. After osmotic treatment, barrier opening was maximal to MAb delivery for 1 min with delivery declining rapidly thereafter. The type of anesthesia used and the administration of a thyroid-blocking agent were found to affect brain MAb levels after BBB disruption.
Independent osmoregulatory control of central and systemic angiotensin II concentrations in dogs
Authors: Simon-Oppermann C. , Gray D. A. , Simon E.
Published: December 2017

In 14 dogs angiotensin (ANG II)-like immunoreactivity was analyzed in simultaneously collected samples of cerebrospinal fluid (CSF) from the anterior part of the third cerebral ventricle and of plasma. Plasma and CSF ANG II were not different in euhydrated conscious dogs (29.3 +/- 2.7 and 30.8 +/- 2.8 pg X ml-1, means +/- SE). During anesthesia CSF ANG II was not significantly altered, but plasma ANG II was more than doubled in comparison with conscious animals. In conscious dogs 24 h of dehydration with sodium-rich food significantly increased ANG II concentration in the plasma (to 59.8 +/- 16.5 pg X ml-1) and CSF (to 71.8 +/- 20.1 pg X ml-1). Subsequent rehydration by drinking caused no consistent changes in plasma ANG II within 90 min but reduced CSF ANG II significantly. Salt loading by infusion of 5% saline in seven conscious dogs produced a small but consistent decrease in plasma ANG II by 20%, on average, whereas CSF ANG II rose in five animals. The directions of changes in concentration of central ANG II compared with plasma ANG II suggest that central endogenous ANG II may function as a central osmoregulatory mediator independent from systemic ANG II.
Postnatal development of micturition reflex in rats
Authors: Maggi C. A. , Santicioli P. , Meli A.
Published: December 2017

The postnatal development of the micturition reflex and factors related to its initiation have been investigated by means of cystometric techniques under urethan anesthesia. In rats less than 10 days of age, micturition is not elicited in response to bladder distension. In these animals voiding is triggered by application of a somatic stimulus in the perineal area. In rats greater than or equal to 15 days of age the response to bladder filling is similar to that observed in adults. In rats 10-15 days of age an intermediate pattern is frequently observed; i.e., bladder filling elicited micturition at high values of pressure threshold. The myogenic (tetrodotoxin insensitive) contractile activity of the bladder is absent at birth and developed postnatally, similar to that described in the isolated organ [C. A. Maggi, P. Santicioli, and A. Meli. Am. J. Physiol. 247 (Regulatory Integrative Comp. Physiol. 16): R972-R978, 1985]. The ability of topical capsaicin to induce tetrodotoxin-sensitive contractions of rat bladder (micturition reflex) appeared at day 10 and increases thereafter in parallel with ability of the bladder to respond to distension. These findings demonstrate that peripheral factors, such as myogenic contractile activity and sensory innervation, which are involved in the initiation of bladder voiding undergo a postnatal development in rats.
Effect of intracerebroventricular calcitonin on renal hydromineral excretion in sheep
Authors: Appelgren B. H. , Arver S. , Sagulin G. B.
Published: December 2017

The localization of calcitonin in hypothalamic tissue and cerebrospinal fluid and calcitonin binding sites in circumventricular organs suggests involvement in neural mechanisms, possibly hydromineral balance. Therefore, we compared the effects of intracerebroventricular and intravenous infusions of porcine calcitonin (0.04-0.05 mU X kg-1 X min-1) on renal water, Ca, Mg, Na, and K excretions. The intracerebroventricular administration of calcitonin for 60 min induced a pronounced increase (P less than 0.01) in free water clearance, from a preinfusion value of -0.73 +/- 0.45 to +3.02 +/- 1.15 ml/min at the end of the infusion. In contrast, the free water clearance was unaltered during the intravenous infusion of calcitonin. Renal Ca excretion fell significantly (53%) 40 min after the end of the intracerebroventricular infusion of calcitonin, whereas the corresponding intravenous infusion of calcitonin did not change (P greater than 0.05) urinary Ca excretion. Renal Mg excretion was increased (P less than 0.01) during the intracerebroventricular infusion of calcitonin but was not altered during intravenous infusion of calcitonin. Urinary excretions of Na and K were not affected by either intracerebroventricular or intravenous administration of calcitonin. It is concluded that calcitonin can act centrally to modify renal water, Ca, and Mg excretions.
Behavioral fever and therapy in a rickettsia-infected Orthoptera
Authors: Louis C. , Jourdan M. , Cabanac M.
Published: December 2017

Gryllus bimaculatus were infected with an intracellular prokaryote, Rickettsiella grylli, then reared either at fixed temperatures or in a temperature gradient (22-36 degrees C) where they could select the temperature they preferred. Only 50% of the infected insects reared at 28 degrees C or less survived after 20 days, against 75% of those reared at 30 degrees C or more and 90% of those in the temperature gradient. Examination of smears of insect tissue showed that all (100%) of the infected insects reared between 23 and 29 degrees C had developed a strong rickettsial infection. Only 20% of the insects reared in a gradient of temperature showed signs of strong infection. Body temperature of crickets in the temperature gradient, recorded using thin thermocouples, was 33 degrees C in infected crickets and 26.6 degrees C in controls. It is concluded that thermoregulatory behavior was used by the insects to produce a fever when infected with Rickettsiella grylli. This protected them and increased survival capacity.
Chemoreflexive responses to hypoxia and NaCN in longnose gar: evidence for two chemoreceptor loci
Authors: Smatresk N. J. , Burleson M. L. , Azizi S. Q.
Published: December 2017

Interactions between internal and external O2 stimulus levels were assessed by measuring the ventilatory and cardiovascular responses to varying water (PWO2) and air bladder (PabO2) O2 levels and intravascular NaCN in anesthetized spontaneously ventilating Lepisosteus osseus. As PWO2 fell, air-breathing frequency (fab) increased. Buccal pressure amplitude (Pb) also increased as PWO2 fell from hyperoxia to normoxia, but hypoxic water depressed Pb. The PO2 in the ventral aorta (VA) fell as PabO2 fell, which stimulated fab and Pb when the gar was in normoxic or hyperoxic water. Thus gill ventilation and air breathing were normally controlled by both internal and external O2 levels, but aquatic hypoxia uniformly depressed gill ventilation regardless of changes in PabO2 levels. Heart rate and blood pressure were unaffected by these changes. NaCN stimulated hypoxic reflexes and bradycardia more quickly when given into the VA or conus than when given into the dorsal aorta. The animals appear to possess internal chemoreceptors that set the level of hypoxic drive and external chemoreceptors that inhibit gill ventilation and shift the ventilatory emphasis from water to air breathing.
Effect of endotoxic shock on kinetics of system A amino acid transport in rat soleus muscle
Authors: Karlstad M. D. , Sayeed M. M.
Published: December 2017

This study evaluated the kinetics of system A amino acid transport in soleus muscle during endotoxic shock. Fasted male rats (80-100 g) were killed by decapitation 5 h after the intravenous injection of saline (control) or 20 mg/kg Salmonella enteritidis endotoxin. Soleus muscles (40 mg) from control or endotoxic rats were incubated in oxygenated Krebs-Ringer-bicarbonate buffer (pH 7.4) at 37 degrees C for 20, 40, or 60 min. Initial rates of entry of alpha-aminoisobutyric acid (AIB) into the inulin-inaccessible space of muscles were measured over a wide range of AIB concentrations (0.1-20.0 mM). Initial rates of AIB transport were separated into two parallel transport processes, a saturable carrier-mediated component and a nonsaturable passive diffusive process. The diffusion constant for the nonsaturable process in the endotoxic muscles (0.36 h-1) was 38% greater than control muscles (0.26 h-1). The maximum rate of AIB transport decreased from 55.6 +/- 3.3 nmol . g dry wt-1 . min-1 in controls to 18.3 +/- 1.9 nmol . g dry wt-1 . min-1 in endotoxic muscles. The apparent Km for saturable AIB transport was not different between control (1.68 +/- 0.12 mM) and endotoxic muscles (1.64 +/- 0.19 mM). Alterations of system A amino acid transport in endotoxic soleus muscles were due to an increase in passive AIB diffusion and a decrease in the number and/or activity of existing carriers and not to a change in carrier affinity for AIB. These results elucidate the mechanism for the decreased amino acid transport (system A) by soleus muscle in endotoxic shock.
Lesions in lateral parabrachial nucleus enhance drinking to angiotensin II and isoproterenol
Authors: Ohman L. E. , Johnson A. K.
Published: December 2017

The lateral parabrachial nucleus (LPBN) has been shown to be anatomically linked to a number of forebrain nuclei and medullary structures implicated in the control of body fluid balance and cardiovascular regulation. Although these connections suggest a role for the LPBN in body fluid homeostasis, there is currently little or no physiological or behavioral data to support this notion. The purpose of the present series of experiments was to determine the importance of the ventrolateral region of the LPBN (VLLPBN) in the behavioral response to various thirst challenges. Rats with electrolytic lesions of the VLLPBN and control rats were studied after administration of angiotensin II (ANG II) (1.5 and 3.0 mg/kg), isoproterenol (30 and 100 micrograms/kg), polyethylene glycol (20%) and hypertonic saline (4 and 12%). It was found that rats with lesions drank more in response to ANG II and isoproterenol administration than did control animals.
Cardiac input to medullary reticular formation: neuronal responses to CAO
Authors: Blair R. W.
Published: December 2017

Responses of 46 medullary reticular neurons to coronary arterial occlusions (CAO) of the left anterior descending (LAD) and left circumflex (CX) coronary arteries were determined in chloralose-anesthetized cats paralyzed with pancuronium. Extracellular potentials were recorded from individual neurons, in the medial reticular formation, responsive to electrical stimulation of cardiopulmonary sympathetic afferents. CAO responses were characterized by one of three patterns. Cell activity changed during myocardial ischemia (IS response). Fifteen neurons were excited during ischemia (9 +/- 2.8 to 15 +/- 3.2 spikes/s for CX occlusion and 10 +/- 3.0 to 17 +/- 4.7 spikes/s for LAD occlusion), and two were inhibited (8 +/- 3.0 to 4 +/- 3.0 spikes/s). Cell activity changed at the onset or release of occlusion and rapidly adapted (ON response). Four cells were excited at the onset of LAD occlusion (2 +/- 1.4 to 10 +/- 6.0 spikes/s), 9 cells were excited at onset of CX occlusion (5 +/- 2.5 to 16 +/- 5.6 spikes/s), and 1 cell decreased its rate at onset of CX occlusion. A combination of ON and IS responses occurred in five cells (ON-IS response). Overall, 24 neurons exhibited at least one of these responses, and 22 cells were unaffected by CAO. Thirty neurons were tested for responses to CAO of CX and LAD; neurons most often exhibited different patterns of responses to CAO of each artery. Thirty-one of 34 cells tested exhibited qualitatively, but often not quantitatively, similar responses to cardiac ischemia and to application of bradykinin to epicardium of free wall of left ventricle. Results indicate that medullary neurons often respond differentially to occlusion of different coronary arteries.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiac input to medullary reticular formation: neuronal responses to mechanical stimuli
Authors: Blair R. W.
Published: December 2017

Neurons in the medullary reticular formation were tested for responses to mechanical stimuli applied to the heart in cats anesthetized with chloralose and paralyzed with pancuronium. In most experiments baroreceptors were denervated. Aortic occlusion excited 15 neurons (19%) and decreased the mean discharge rates of five neurons (6%). Discrete probing of the heart elicited one to three spikes from 18 of 27 neurons tested. Thirteen of these cells had defined cardiac receptive fields; fields were large, often encompassing most of the left ventricle. Of 12 neurons tested for responses during fibrillation, 8 were excited, 2 were inhibited, and 2 were unaffected. Neurons often exhibited different sensitivities to these mechanical stimuli, as well as to ischemia produced during coronary arterial occlusion. Neurons were more likely to respond to stimuli that affected a large mass of myocardium. In addition to cardiac input, 98% of neurons in this study also received input from at least one additional sensory modality, and 39 cells were excited by somatic, auditory, and visual stimuli. Results indicate that medullary reticular neurons are responsive to mechanical events in the heart as well as to myocardial ischemia and respond to other sensory modalities.
Hypotension induced by passive head-up tilt: endocrine and circulatory mechanisms
Authors: Sander-Jensen K. , Secher N. H. , Astrup A. , Christensen N. J. , Giese J. , Schwartz T. W. , Warberg J. , Bie P.
Published: December 2017

Circulatory changes and arterial plasma hormone concentrations were measured in seven healthy young adults during 30 and 60 degrees passive head-up tilt with the subjects supported by a saddle. The 30 degrees tilt induced a decrease in pulse pressure (Pp) from 45 +/- 2 to 35 +/- 4 (mean +/- SE) mmHg concomitant with an increase in heart rate (HR) from 58 +/- 4 to 78 +/- 8 beats/min and a marginal increase in mean arterial pressure (MAP). Norepinephrine increased from 180 +/- 20 to 310 +/- 40 pg/ml, aldosterone increased fivefold, and angiotensin II increased from 8 +/- 2 to 22 +/- 7 pg/ml. The 60 degrees tilt initially produced changes, which were qualitatively similar to the 30 degrees tilt. However, after 19 +/- 3 min sudden decreases were seen in MAP (94 +/- 3 to 50 +/- 8 mmHg), in Pp (38 +/- 5 to 18 +/- 4 mmHg), and in HR (90 +/- 7 to 57 +/- 6 beats/min). Concomitantly, epinephrine doubled while norepinephrine remained unchanged; the vagally controlled hormone pancreatic polypeptide increased from 29 +/- 3 to 51 +/- 8 pmol/l, vasopressin from 4 +/- 1 to 126 +/- 58 pg/ml, and angiotensin II from 23 +/- 9 to 35 +/- 12 pg/ml. The hypotensive bradycardiac episode was immediately reversible on termination of the head-up tilt.(ABSTRACT TRUNCATED AT 250 WORDS)
Alterations in cardiac [14C]deoxyglucose uptake induced by two renal afferent stimuli
Authors: Herman N. L. , Kostreva D. R.
Published: December 2017

The reflex effects of renal afferents on the heart were studied in pentobarbital-anesthetized rats (400-425 g) using 2-[14C]deoxyglucose (DG). Three groups of rats were given a single bolus injection of DG (100 mu Ci/kg) 1) six controls, 2) four with periodic electrical stimulation of the proximal end of a cut renal nerve (2 Hz, 0.5-ms width) and 1-mA current, and 3) six with intermittent renal venous occlusion (unilateral). Forty-five minutes after injection the heart was removed, cooled quickly, and frozen-sectioned. Sections 20 micron thick were exposed to film for 12 days. The resulting autoradiographs were scanned using a computerized densitometer, and these densities were converted to relative glucose utilization (GlU, mumol X 100 g-1 X min-1) using the lumped constant for rat brain. Both renal venous occlusion and renal afferent nerve stimulation resulted in a decrease in blood pressure of 6.7 +/- 0.6 mmHg (P less than 0.001) and 7.3 +/- 0.7 mmHg (P less than 0.001) and heart rate-blood pressure product of 5.6 +/- 0.7% (P less than 0.001) and 8.8 +/- 0.8% (P less than 0.001), respectively, and afferent renal nerve stimulation induced a decrease in heart rate of 7.2 +/- 0.9 beats/min (P less than 0.01). However, when compared with control, renal venous occlusion induced a significant increase in GlU in left ventricular myocardium (LV myo, P less than 0.05), endocardium (LV endo, P less than 0.001), and papillary muscle (LV pap, P less than 0.001), whereas afferent renal nerve stimulation induced a significant increase in GlU in LV endo (P less than 0.05) and LV pap (P less than 0.002) only. This study shows both a reflex increase in GlU for the rat heart and a decrease in heart rate with either renal vein occlusion or afferent renal nerve stimulation.
Hyperoxia reversibly suppresses development of bronchiolar epithelium
Authors: Massaro G. D. , McCoy L. , Massaro D.
Published: December 2017

The bronchiolar epithelium of rats is anatomically immature at birth. We now ask whether postnatal hyperoxia impairs the normal development of bronchiolar epithelium; and, if development is impaired, is the impairment permanent? To answer these questions, we exposed newborn rats to hyperoxia (greater than 95% O2, 1 atm) or air for 7 days and killed the rats at age 7 or 30 days. We used ultrastructural and morphometric means to assess maturation of the bronchiolar epithelium. Hyperoxia substantially diminished the postnatal increase in nuclear numerical density of bronchiolar Clara cells and ciliated cells. Hyperoxia also markedly delayed the rise in volume density of Clara cell secretory granules and rough endoplasmic reticulum but accelerated the increase in volume density of Clara and ciliated cell mitochondria. When rats exposed to hyperoxia from age 1 to 7 days were thereafter allowed to breathe air, by age 30 days all the differences were eliminated that were detected between the air- and O2-breathing groups at age 7 days. We conclude hyperoxia causes a marked but nonpermanent suppression of maturation of the bronchiolar epithelium.
Hepatic contribution to satiation of salt appetite in rats
Authors: Tordoff M. G. , Schulkin J. , Friedman M. I.
Published: December 2017

We examined the influence of hepatic-portal vein infusion of NaCl and of hepatic vagotomy on 3% NaCl solution drinking by sodium-deficient rats. Combined dietary sodium restriction and administration of the natriuretic agent, furosemide (5 mg), produced a vigorous appetite for 3% NaCl solution that was attenuated by portal infusion of NaCl. Whereas infusions (1 ml/30 min) of NaCl into the hepatic-portal vein in concentrations as low as 0.15 M (isotonic) significantly reduced 3% NaCl consumption, a higher concentration (0.6 M) infused into the jugular vein, or portal infusions of KCl (0.6 M) or sucrose (1.2 M), were ineffective. Rats with selective hepatic vagotomy displayed an attenuated appetite for salt whether or not they received hepatic-portal NaCl. This was not due to altered excretion of sodium. Taken together, these results suggest that the liver or portal vein can provide a sodium-specific neural signal capable of attenuating the appetite for salt and this information is transferred to the brain by fibers in the hepatic vagus that fire in reciprocal relationship with portal sodium concentration.
Phase resetting and dysrhythmic responses of the respiratory oscillator
Authors: Paydarfar D. , Eldridge F. L.
Published: December 2017

This study explores resetting of respiratory rhythm by facilitatory perturbations. The midbrain reticular formation and periaqueductal gray matter were electrically stimulated to evoke facilitation of phrenic nerve activity in nine anesthetized, vagotomized, and glomectomized adult cats. The animals were paralyzed and servo-ventilated to keep end-tidal PCO2 constant. Brief midbrain stimuli were given at various times in the respiratory cycle and the times of onset of rescheduled breaths after stimulation were measured. A plot of phase resetting as a function of stimulus strength and time of delivery defined a helicoid surface. The axis of this helicoid identified a unique stimulus which, when given at the inspiratory-expiratory transition, resulted in unpredictable resetting of respiratory rhythm. This stimulus had a strength that was intermediate to that which identified types 1 and 0 resetting. In one experiment, the singular stimulus often initiated a breath having prolonged inspiratory activity; resumption of the normal rhythm was delayed significantly (P less than 0.01). We conclude that the dysrhythmias observed in this study represent the respiratory oscillator''s phase singularity.
Valine entry into rat brain after diet-induced changes in plasma amino acids
Authors: Tews J. K. , Greenwood J. , Pratt O. E. , Harper A. E.
Published: December 2017

Passage of amino acids across the blood-brain barrier is assumed to be modified by amino acid composition of the blood. To gain a better understanding of the effects of protein intake on brain amino acid uptake, we examined associations among diet, plasma amino acid patterns, and the rate of entry of valine into the brain. Rats were fed (8 h/day for 7–10 days) diets containing 6, 18, or 50% casein before receiving one meal of a diet containing 0, 6, 18, or 50% casein. After 4–7 h, they were anesthetized and infused intravenously with [14C]valine for 5 min before plasma and brain samples were taken for determination of radioactivity and content of individual amino acids. As protein content of the meal was increased from 0 to 50% casein, plasma and brain concentrations of valine and most other large neutral amino acids (LNAA) increased severalfold; also the ratio of [14C]valine in brain to that in plasma decreased by greater than 50%, and the rate of valine entry into the brain increased 3.5-fold. The increase in valine flux slowed as plasma levels of LNAA, competitors for valine transport, increased. The results were far more dependent on protein content of the final meal than on that of the adaptation diet; thus changes in protein intake, as reflected in altered plasma amino acid patterns, markedly altered valine entry into the brain.
A possible physiological role of milk epidermal growth factor in neonatal eyelid opening
Authors: Tsutsumi O. , Tsutsumi A. , Oka T.
Published: December 2017

The eyelid opening of newborn mice occurs normally on day 13.9 +/- 1.8 after birth. When newborn mice were injected with anti-epidermal growth factor (EGF) antibody every other day starting on day 1 after birth, the eyelid opening was delayed by approximately 3 days. The effect of anti-EGF became less prominent as the treatment was started at later times: when it was given from day 7, no delay in eyelid opening was observed. On the other hand, eyelid opening was enhanced by approximately 3 days by EGF injection given on day 3 for every other day. This effect of EGF was antagonized by simultaneous administration of the anti-EGF antibody. EGF was present at a concentration of 6.6 ng/ml in the plasma of 1-wk-old pups nursed by their mother, but it was not detectable (less than 0.1 ng/ml) in the plasma of 3-wk-old weaned pups. EGF concentration in the submandibular glands, however, was 17 times greater in 3- than in 1-wk-old pups, i.e., 4.66 and 0.28 ng/mg of wet tissue, respectively. These results suggest that milk EGF may play a physiological role in eyelid opening during the neonatal period.
In vivo metabolic activity of hamster suprachiasmatic nuclei: use of anesthesia
Authors: Schwartz W. J.
Published: December 2017

In vivo glucose utilization was measured in the suprachiasmatic nuclei (SCN) of Golden hamsters using the 14C-labeled deoxyglucose technique. A circadian rhythm of SCN metabolic activity could be measured in this species, but only during pentobarbital sodium anesthesia when the surrounding background activity of adjacent hypothalamus was suppressed. Both the SCN's metabolic oscillation and its time-keeping ability are resistant to general anesthesia.
Ammonium ion substitutes for K+ in ATP-dependent Na+ transport by basolateral membrane vesicles
Authors: Towle D. W. , Holleland T.
Published: December 2017

Ion-transporting cells from posterior gills of blue crabs (Callinectes sapidus) acclimated to low salinity were used as starting material for the preparation of microsomal membrane vesicles by density gradient centrifugation. The Na+-K+-adenosinetriphosphatase (ATPase)-enriched basolateral vesicles were loaded with KCl- or NH+4-containing medium by dilution and centrifugation, and initial rates of 22Na+ uptake into the vesicles were measured by a rapid filtration procedure. Varying the extravesicular sucrose concentration altered equilibrium uptake of 22Na+, indicating the existence of osmotically sensitive vesicles. Monensin, a sodium-specific ionophore, enhanced passive uptake of 22Na+ across the vesicle membrane in the absence of ATP. With 100 mM KCl in the intravesicular medium, addition of ATP to the extravesicular medium increased initial rates of 22Na+ uptake 10- to 20-fold over levels measured without ATP. A nonhydrolyzable ATP analog failed to stimulate 22Na+ uptake. Intravesicular K+ could be replaced by NH+4 but not by choline. With NH+4 as counterion, Na+ transport was inhibited by digitoxin, but valinomycin had no effect. A study of the kinetic effects of intravesicular K+ and NH+4 on initial rates of 22Na+ uptake indicated the existence of two classes of binding sites, one responding to counterion concentrations in the millimolar range and a second class responding to counterion concentrations over 50 mM. Our results indicate that ATP-dependent 22Na+ uptake by membrane vesicles from Callinectes sapidus gill, mediated by Na+-K+-ATPase, can utilize either K+ or NH+4 as counterion.
Prolonged alterations in plasma cortisol circadian rhythms following trauma in baboons
Authors: McIntosh T. K.
Published: December 2017

Few studies have been performed concerning alterations in the circadian rhythmicity of adrenocortical function following trauma. The present study examined the effects of surgical trauma of varying severity on the secretory pattern of adrenocorticosteroids in the female baboon (Papio anubus). In 30 baboons, blood samples were obtained every hour for three 96-h periods: 1 wk prior to surgery; beginning 30 min following incision closure; and beginning 7 days following surgery. Animals were divided into three groups: anesthesia/surgical controls, low-trauma group [(LT), laparotomy plus 5-min bowel traction], or high-trauma group [(HT), laparotomy plus 20-min bowel traction]. A postoperative rise in plasma cortisol was observed that persisted up to 10 days postsurgery and could be significantly correlated with severity of trauma. The episodic nature of cortisol secretion was unaffected by surgery. The circadian rhythm of cortisol was phase shifted in the LT group and abolished up to 8 days postsurgery in the HT group. We conclude that the magnitude of posttrauma rise and circadian disruption of plasma cortisol is correlated with magnitude of surgical trauma. However, contrary to previous reports, elevated levels of cortisol may persist for an extended time (10 days) following the primary insult.
Unaltered regulatory thermogenic response to dietary signals in exercise-trained rats
Authors: Arnold J. , Richard D.
Published: December 2017

Thermogenic response to ingestion of high-fat diet was investigated in four groups of male rats, two groups being exercise trained and two remaining sedentary. One sedentary and one trained group each received a high-fat dietary supplement in addition to the stock diet. After 35 days, body energy and protein and fat contents were determined. Results indicate that exercise reduced metabolizable energy (ME) intake by 9 and 18% in stock- and high-fat-fed trained rats, respectively. Compared with stock-fed rats, ME intake was elevated 31 and 18% in sedentary and trained high-fat-fed rats, respectively. Exercise also affected energy gains; trained rats deposited almost 60% less energy than controls. Exercise largely decreased both fat and protein contents of rats, whereas the high-fat supplement enhanced fat deposition. Energy expenditure, excluding exercise cost, was calculated on a mass-independent basis and was revealed to be similar in appropriately matched (diet) trained and sedentary rats. High-fat feeding induced increases in expenditure assumed to be due to enhanced brown adipose tissue (BAT) regulatory diet-induced thermogenesis. Conversely, exercise did not affect further the regulatory thermogenic response of BAT to stimuli originating from high-fat diet. Excluding physical activity, energy expenditure components in sum (expressed mass independently), in high-fat- and stock-fed rats, appear unaltered by exercise training.
Aortic baroreceptor reflexes are mediated by NMDA receptors in caudal ventrolateral medulla
Authors: Gordon F. J.
Published: December 2017

The purpose of this study was to identify central nervous system pathways and synaptic receptors that participate in baroreflex control of arterial pressure. Microinjections of excitatory amino acids into the caudal ventrolateral medulla (CVM) of anesthetized rats evoked depressor responses analogous to baroreceptor reflexes. Functional inactivation of CVM neurons produced by microinjection of the gamma-aminobutyric acid receptor agonist muscimol completely abolished baroreflex-mediated decreases in arterial pressure elicited by electrical stimulation of the aortic nerve and markedly reduced depressor responses produced by the excitatory amino acid L-glutamate. In contrast, selective blockade of N-methyl-D-aspartic acid (NMDA) receptors in the CVM abolished synaptically mediated depressor responses evoked by aortic nerve stimulation but not those elicited by L-glutamate, kainic acid, or quisqualic acid injected at the same site. These results indicate that the CVM contains an obligatory synapse in the central aortic baroreflex pathway; neural transmission of aortic baroreceptor information in the CVM is mediated by activation of NMDA receptors; and the neurotransmitter released at CVM synapses may be an excitatory amino acid.
Continuous resetting of the human carotid baroreceptor-cardiac reflex
Authors: Kasting G. A. , Eckberg D. L. , Fritsch J. M. , Birkett C. L.
Published: December 2017

Although human baroreflex responses have been studied during night as well as day, there has been no attempt to distinguish circadian changes of baroreflex function from those related to sleep. We measured carotid baroreceptor-cardiac reflex responses serially during a 24-h period in 11 normotensive volunteers who were awake and cooperative during testing. We applied sequences of ramped R-wave-triggered neck chamber pressure changes from +40 to -65 mmHg, during held expiration, at 3-h intervals. Subjects maintained their usual sleep-wake cycles but were awakened for three 30-min periods for night testing. There was no systematic change of baroreflex slope during the 24-h period. There were, however, parallel shifts of the entire sigmoid baroreceptor-cardiac reflex response relation along its R-R interval and arterial pressure axes associated with small, but significant, circadian changes of baseline R-R intervals and arterial pressures. Thus, although our data do not point toward major circadian variability of baro-reflex responsiveness, they provide evidence for an ongoing process of human baroreflex resetting.
Effect of immobilization on collagen synthesis in rat skeletal muscles
Authors: Savolainen J. , Vaananen K. , Vihko V. , Puranen J. , Takala T. E.
Published: December 2017

The activities of prolyl 4-hydroxylase (PH) and galactosylhydroxylysyl glucosyltransferase (GGT), both enzymes of collagen biosynthesis, and the concentration of hydroxyproline (Hyp) were measured in the soleus, gastrocnemius, and tibialis anterior muscles of rats after cast immobilization in the middle position for 1 or 3 wk. The specific activity of PH decreased by 54 and 70-75% (P less than 0.001) in the soleus muscle after 1 and 3 wk, respectively, the corresponding decreases in GGT activity were 43 and 47% (P less than 0.001). A less pronounced decrease in the activities of these enzymes was observed in gastrocnemius and tibialis anterior muscles. The Hyp concentration in the soleus increased during the first week of immobilization but began to decrease thereafter, and the total muscular Hyp content was reduced after immobilization for 3 wk. The results suggest a marked inhibition of muscular collagen synthesis during immobilization. Electrical stimulation of the sciatic nerve partially prevented this disuse atrophy and the decreases in PH, GGT, and Hyp in the tibialis anterior muscle but not in the gastrocnemius or soleus muscles.
Ingestive behavior of rats with ibotenic acid lesions of the dorsomedial hypothalamus
Authors: Bellinger L. L.
Published: December 2017

Rats with electrolytic or kainic acid (KA) lesions of the dorsomedial hypothalamic nucleus area (DMHA-L) are hypophagic, hypodipsic, and have a reduced body weight (BW) compared with controls. In the present study, male Sprague-Dawley rats received bilateral ibotenic acid (IBO) lesions of the DMHA (3 micrograms in 0.3 microliter) or sham (S) operations. During the next 32 days the IBO DMHA-L rats showed reduced (P less than 0.01) food and water intake, BW, and linear growth (P less than 0.03), although having a normal Lee obesity index. After a 24-h fast both groups became hyperphagic (P less than 0.01) with the DMHA-L group eating the most (P less than 0.01) during the 1st h; lost BW was regained at the same rate. In the absence of food, DMHA-L rats took less (P less than 0.01) water (data normalized) than S rats. During 24 h of water deprivation, both groups ate similar amounts of food (data normalized); following deprivation the groups were hyperdipsic. Both groups increased their food intake when given 300 mg/kg of 2-deoxy-D-glucose, which contrasts rats with electrolytic or KA DMHA-L rats. Both groups decreased their food intake when given cholecystokinin (3 micrograms/kg ip), which contrasts rats with electrolytic DMHA-L. The DMHA-L rats were not deficient in plasma glucose, insulin, growth hormone, or plasma Na+ and K+. Histology revealed many, but not all neurons, were destroyed in the DMN after IBO. The data indicate that IBO, electrolytic, or KA lesions of the DMHA produce similar but not identical physiological changes.
Characteristics of lung mechanoreceptors in spotted gar, Lepisosteus oculatus
Authors: Smatresk N. J. , Azizi S. Q.
Published: December 2017

Single unit and whole nerve activity were recorded in situ from pulmonary mechanoreceptors in Lepisosteus oculatus in response to step inflation and ramp or flow through ventilation of the lung with air and varying levels of CO2 in air. Slowly adapting receptors (SAR), rapidly adapting receptors (RAR), and CO2-sensitive SAR were identified. Whole nerve activity was often present when transpulmonary pressure was 0 cmH2O and increased due to recruitment and elevated discharge of already-active fibers as lung volume rose. SAR became tonically active once the lung exceeded their threshold volume and demonstrated a rate-sensitive burst of activity on inflation and a rate-sensitive inhibition of activity after deflation of the lung. RAR responded to lung inflation or deflation with a burst of activity. Six of eleven SAR were inhibited by ventilation of the lung with from 6 to 10% CO2 in air, even when lung pressure and volume were kept constant. These receptor discharge characteristics, which were similar to those found for lungfish and amphibians, may account for the reflex responses of gar to lung volume changes.