bluuebunny/crossref_metadata_2025 huggingface dataset:
Disordered drinking in developing spontaneously hypertensive rats
Authors: Kraly F. S. , Coogan L. A. , Specht S. M. , Trattner M. S. , Zayfert C. , Cohen A. , Goldstein J. A.
Published: December 2017

Eating and drinking in spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats were measured at 5-17 wk of life. The SHR drank significantly more water in 24 h than WKY as early as wk 9, spilled more dry food than did WKY, and exhibited an inverse relation between 24-h water intake and dry food spilled. When eating a meal of dry food after 12 h food deprivation, SHR drank earlier and drank more in a 1-h test than WKY rats. Moreover, SHR exhibited (as early as wk 7) a striking pattern of interrupting eating to drink. This pattern was not present when SHR ate liquid food, and it was attenuated by infusion of water through a cheek fistula. Adult SHR (22 wk) salivated less than WKY in response to intraperitoneal 3.25 mg/kg pilocarpine nitrate. When developing SHR and WKY were maintained on liquid and solid food, SHR gained disproportionately more weight than WKY during development. When young SHR were permitted to drink no more water than WKY rats, the development of hypertension was retarded, and body weight gain was slowed. Because restricted access to food, which produced an equivalent slowing of body weight gain as did restricted access to water, also retarded development of hypertension, it appears that restricted access to water retards development of hypertension due to delayed growth. These results demonstrate that hyperdipsia, apparently caused by deficient salivary function, is not necessary for the development of hypertension in SHR.
Glucose transport in intestinal epithelia of winter flounder
Authors: Thompson K. A. , Kleinzeller A.
Published: December 2017

D-Glucose (Glc) transport was studied in stripped intestinal epithelial sheets of the winter flounder Pseudopleuronectes americanus. At 1 mM Glc and 15 degrees C, Glc uptake did not occur against a concentration gradient (free cell Glc 0.78 +/- 0.06 mM) but was inhibited by 0.5 mM phlorizin or ouabain. [U-14C]-Glc oxidation to 14CO2 was also depressed by these agents or the absence of Na+ and was saturable (Km 3.3 +/- 1.2 mM Glc; maximal velocity at saturating substrate concentration (Vmax) 4.0 +/- 2.0 mumol X g wet wt-1 X h-1]. No electrical transcellular manifestations of the Na-Glc cotransport system were seen in regular media. In the absence of Cl-, Glc and nonmetabolizable Glc analogs (alpha-methyl-D-glucopyranoside or 3-O-methyl-D-glucose) added mucosally elicited an increase in a serosally directed short-circuit current that was inhibitable by 0.5 mM mucosal phlorizin or 0.1 mM serosal ouabain and dependent on the external sugar concentration [Km 2.3 +/- 1.8 mM (range 0.6 to 6.1); Vmax 2.4 +/- 1.1 microA X cm-2 (range 0.8-4.2)]. Vmax for L-leucine transport was fivefold greater [13.4 +/- 7.3 microA X cm-2 (range 4.6-20.7)]. These results indicate the presence of a mucosal Na+-linked Glc absorptive system and reflect the paucity of transport sites for Glc relative to leucine.
Effect of intracerebroventricular vasopressin on body temperature and endotoxin fever of macaque monkey
Authors: Lee T. F. , Mora F. , Myers R. D.
Published: December 2017

In the adult monkey (Macaca fasicularis) acclimated to a primate restraint chair, intracerebroventricular (ICV) cannulas were stereotaxically implanted bilaterally in the lateral cerebral ventricle. During an experiment, colonic and skin temperatures were continuously recorded, and in selected cases heart and respiratory rates as well as O2 consumption were similarly monitored. Arginine vasopressin (AVP) was infused ICV in a volume of 500 microliter in one of six doses ranging from 16 to 4,240 ng. The results showed that AVP in all doses infused failed to alter the resting core and skin temperatures of the monkey or other recorded physiological responses. After a fever was produced in the monkey by 1/10–1/100 dilution of Escherichia coli endotoxin infused ICV, AVP at doses of 16–260 ng did not augment the febrile response. Further, AVP infused in the same range of doses caused only a negligible and inconsistent antipyretic action; i.e., the 65-ng dose of AVP lowered the mean core temperature of the febrile monkey by only 0.5 degrees C. This was in marked contrast to the antipyretic effect of dipyrone administered systemically. In addition, no reproducible changes occurred in respiratory, heart, or metabolic rates after ICV infusion of AVP. These results indicate that AVP does not affect the normal thermoregulatory function of this species of monkey and, in contrast to other species, a febrile response is neither enhanced nor antagonized in the monkey by a central action of AVP. Although AVP thus does not appear to be an endogenous antipyretic in the monkey, anatomic investigations will be required to substantiate this conclusion in the subhuman primate.
Abdominal vagus and regulation of ingestive behavior and body weight in golden hamsters
Authors: Miceli M. O.
Published: December 2017

A series of experiments was undertaken to examine the role of the vagus nerve in body weight regulation and the control of ingestive behavior in Syrian hamsters. Body weight, food and water intake, and feeding responsiveness to the putative satiety hormone cholecystokinin (CCK) were studied in hamsters with total subdiaphragmatic or selective gastric vagotomy. Body weight and food intake during ad libitum feeding were unaffected by either type of vagotomy. However, hamsters with total subdiaphragmatic or gastric vagotomy could better maintain body weight during intermittent food access. Vagotomy blocked feeding suppression after low-dose (4.0 micrograms/kg) systemic injections of CCK octapeptide (CCK-8). This blocking effect was specific to feeding suppression in response to CCK-8, because vagotomized hamsters remained responsive to other putative satiety hormones (bombesin, calcitonin, and thyrotropin-releasing hormone). Hamsters with either type of vagotomy were, however, responsive to high doses (greater than or equal to 8.0 micrograms/kg) of CCK-8, thus indicating that extravagal (possibly central nervous system) sites of CCK action may also be relevant to the control of feeding. The results are discussed in relation to normal vagal function in hamsters and vagal control of ingestive behavior in other species.
Cardiovascular function and fluid compartments in newborn canine hemorrhagic shock
Authors: Horton J. W. , Coln D.
Published: December 2017

Hemorrhage in the adult disrupts cellular function, resulting in a redistribution of fluids and electrolytes. There is little data about the effects of hemorrhage on body fluids in the neonate. The purpose of this study was to determine the effects of hemorrhage on cardiovascular function, coronary blood flow, red blood cell mass (RBCM), plasma volume (PV), and extracellular fluid (ECF) volume in newborn dogs. Group 1 consisted of 88 dogs, 1–20 days old, and group 2 was 81 dogs, 3–6 wk old. There is a significantly higher ECF volume in younger (256 +/- 10 ml/kg) compared with older puppies (121 +/- 5 ml/kg). A 40% hemorrhage caused ECF to fall less in the younger (-27%) than in the older puppies (-51%), whereas PV and RBCM decreased to a similar extent in both groups. After returning shed blood, PV and RBCM returned to prehemorrhage values, but there was a 12% deficit in functional ECF volume in both groups. A similar degree of bradycardia, myocardial depression, and acidosis occurred in both groups during shock and after returning shed blood. Cardiac output and coronary blood flow, measured only in group 2, fell significantly in shock (-60 and -50%, respectively; P less than 0.05) and remained below control values after returning shed blood. Our data indicate that inadequate perfusion of the myocardium and persistent acidosis impairs cardiac function in newborn shock.
Glucose and lactate kinetics in American eel Anguilla rostrata
Authors: Cornish I. , Moon T. W.
Published: December 2017

Simultaneous infusion of [6-3H]glucose and [U-14C]lactate was used to calculate the turnover rate of glucose, the irreversible replacement rate of lactate, and the rates of the exchange of carbon atoms between glucose and lactate in free-swimming American eels (Anguilla rostrata) fed or food deprived for 6, 15, and 36 (maturing) mo. The mean turnover rate of glucose in fed animals averaged 1.0 mg X min-1 X 100 g-1, while the lactate irreversible replacement rate was approximately 4.0 micrograms X min-1 X 100 g-1. The conversion of 35% of lactate carbon to glucose implied a substantial Cori cycle activity, but this amounted to less than 1% of total glucose production. Food deprivation for 6 mo altered few kinetic patterns, except for an increased lactate irreversible replacement rate and a minor increase in gluconeogenesis from lactate. After a 15-mo fast, glucose turnover decreased to 0.09 +/- 0.02 mg X min-1 X 100 g-1. Plasma lactate concentrations and production rates continuously increased during the experiment. Maturing eels that had been food deprived for 36 mo maintained glucose and lactate concentrations and kinetics similar to values in animals food deprived for only 6 mo. This study stresses the importance of carbohydrate in the metabolism of this species under fed and food-deprived conditions and further supports the tolerance of Anguillid species to food deprivation.
Energy expenditure is reduced in preobese 2-day Zucker fa/fa rats
Authors: Moore B. J. , Armbruster S. J. , Horwitz B. A. , Stern J. S.
Published: December 2017

The rate of oxygen consumption was measured in 2-day Zucker preobese (fa/fa), homozygous (Fa/Fa) lean, and lean rats of unknown genotype (Fa/?) over the ambient temperature range of 26-35 degrees C. Significant differences in body mass were found among the three groups at this early age, the preobese pups having the greatest body mass. To account for body mass differences, the oxygen consumption data were expressed in terms of metabolic body size (ml O2 consumed X g body mass-2/3 X h-1). This mass-independent rate of oxygen consumption was significantly lower in the preobese pups than in the homozygous lean (Fa/Fa) pups at both thermoneutral (33-34 degrees C) and cold (26-27 degrees C) ambient temperatures at which, respectively, minimal and maximal rates of oxygen consumption were observed. This reduction in energy expenditure occurs before the establishment of hyperphagia or decreased levels of activity in the preobese pups. These data support the view that attenuated energy expenditure is a significant contributor to the early development of obesity in the Zucker fatty rat and point to the possibility of defective brown adipose tissue-mediated thermogenesis in the preobese pup.
Roles of right versus left vagal sensory nerves in cardiopulmonary reflexes of conscious dogs
Authors: Barron K. W. , Bishop V. S.
Published: December 2017

This study examined the relative roles of the right vs. left vagi in mediating the inhibitory influence of vagal sensory input on sympathetic outflow to the cardiovascular system. This objective was pursued through examination of responses to 1) interruption of tonic vagal input and 2) intracoronary administration of veratridine (Bezold-Jarisch effect). Bilateral vagal cold block (BVB) (n = 16) increased arterial pressure 25 +/- 3 mmHg and heart rate 66 +/- 7 beat/min, whereas right vagal cold block (RVB) and left vagal cold block (LVB) increased arterial pressure 13 +/- 2 and 4 +/- 2 mmHg, respectively. The relative differences in the change in mean arterial pressure were independent of heart rate since similar changes in arterial pressure were observed with preelevation of heart rate with atropine. Sinoaortic baroreceptor denervation augmented the pressure responses approximately fourfold, with the relative pressure changes produced by BVB, RVB, or LVB remaining proportionally the same. Intracoronary administration of veratridine (0.1 g/kg) produced a hypotension action (-44 +/- 6 mmHg), bradycardia (-48 +/- 8 beat/min), and a negative intropic effect (-482 +/- 68 mmHg/s, left ventricular (LV) (dP/dt)max. During RVB the depressor effect of veratridine was reduced to -18 +/- 5 mmHg, and changes in heart rate or LV (dP/dt)max were abolished. Veratridine administration during LVB decreased arterial pressure (-39 +/- 6 mmHg), heart rate (-22 +/- 6 beat/min), and LV (dP/dt)max (-250 +/- 60 mmHg). We conclude that in the conscious dog the tonic inhibitory influence of vagal afferent nerves on vasomotor outflow is predominantly associated with the right vagus as in Bezold-Jarisch effect.
Central chemical control of ventilation and response of turtles to inspired CO2
Authors: Hitzig B. M. , Allen J. C. , Jackson D. C.
Published: December 2017

The role of central chemosensors in the overall ventilatory response of freshwater turtles (Chrysemys scripta elegans) to the addition of CO2 in inspired gas was measured. Centrally mediated ventilatory responses were isolated in the unanesthetized animal by combining CO2 breathing and brain ventricular perfusion with mock cerebrospinal fluid (CSF) of varying acid-base status. Breathing 4.5% CO2 resulted in increases in both ventilatory frequency (f) and tidal volume (VT), with increases in VT providing most of the overall ventilatory change. Alterations in the acid-base status of the perfusate produced highly significant changes in f. VT changes were divorced from the acid-base status of the mock CSF perfusate. We therefore conclude that ventilatory changes in turtles, mediated by central chemosensors, are primarily affected by alterations in f. VT changes, associated with acid-base homeostatic mechanisms, are mediated by receptors outside the blood-brain barrier in these animals. On the basis of these data, we hypothesize that the increase in f observed when turtles breathe 4.5% CO2 is primarily mediated by the central chemosensors.
Nycthemeral rhythms and sodium chloride appetite in rats
Authors: Rowland N. E. , Bellush L. L. , Fregly M. J.
Published: December 2017

Adrenalectomized rats maintained on a 12:12 light-dark cycle drank large amounts of 0.3 M NaCl solution during the night. They showed virtually no NaCl appetite during the day. As a result of their high day natriuresis, the adrenalectomized rats sustained a negative Na+ balance during the day about three times that of controls. This was offset by a correspondingly higher positive Na+ balance at night. In a second experiment in intact rats, the latency to exhibit NaCl appetite during polyethylene glycol-induced hypovolemia was shorter when the treatment was administered in the evening than in the morning. This again demonstrates a relative facilitation of NaCl intake at night and suggests a major nycthemeral interaction with putative physiological stimuli of NaCl appetite.
Fat and lean chickens: prefattening period and in vivo sensitivity to insulin, atropine, and propranolol
Authors: Simon J. , Leclercq B.
Published: December 2017

Fat (FL) or lean (LL) chickens have been obtained by divergent selection. In previous studies, FL chickens were consistently hypoglycemic (slightly) and had high plasma levels of insulin in response to glucose or refeeding from 5 to 8 wk of age. In these, at 12–13 days of age before any difference in fattening can be demonstrated, FL chickens exhibit a better glucose tolerance pattern and enhanced glucose-induced insulin levels but normal insulin levels during refeeding. Plasma levels of alpha-NH2 nonprotein nitrogen, uric acid, free fatty acids, and potassium were neither consistent nor significantly different between lines. Atropine, at high dose, blocked the absorption of glucose and at low dose had no major effect on glucose-induced insulin release in either line. At 8 wk, sensitivity to and disappearance of exogenous insulin were normal in FL birds. Propranolol slightly decreased plasma glucose and inhibited the hypokalemic effect of exogenous insulin to the same extent in both lines. Cerebrospinal fluid glucose level and liver glycogen content were similar in both lines in the fasting or the fed state, but liver glycogen was restored faster after refeeding in the FL, at least in older birds.
Resynchronization patterns for urinary rhythms in rats after light-dark shifts
Authors: Poulis J. , Roelfsema F. , van der Heide D. , Smeenk D.
Published: December 2017

Diurnal urinary rhythms during a fixed 12:12 light-dark cycle were studied in male and female rats. After a control period of 9 days the light-dark cycle was shifted either +6 or -6 h by delaying or advancing the light period, respectively. Subsequently the resynchronization process was studied for 19–21 days. In both male and female rats an asymmetry effect was present: resynchronization was more rapid after a -6-h shift than after a +6-h shift. However, female rats exhibited a rate of resynchronization slower than male rats. During the process of resynchronization a state of transient internal dissociation was found for all urinary constituents. These results probably point to different control systems rather than to different circadian pacemakers. Further analysis of the role of sex steroid hormones is required in view of the sex variations reported.
Sympathetic rhythms during hyperventilation-induced apnea
Authors: Connelly C. A. , Wurster R. D.
Published: December 2017

The effect of hyperventilation-induced apnea on the respiratory rhythmicity of sympathetic nerve activity was determined using spectral analysis of sympathetic nerve frequencies. Left phrenic, external intercostal, and inferior cardiac sympathetic nerves were recorded in alpha-chloralose-anesthetized, vagotomized, paralyzed, artificially ventilated cats. The respiratory modulation of sympathetic activity during normoventilation was indicated by spectral peaks of sympathetic activity coinciding with respiratory frequencies determined from the phrenic nerve activity of each cat. The spectral peaks of respiratory-related sympathetic activity disappeared during hyperventilation-induced apnea and then reappeared with the return of phrenic nerve activity when normoventilation was resumed. Although sympathetic activity lost its respiratory modulation during hyperventilation, baroreceptor-mediated bilateral carotid occlusion responses and electrocardiogram (R wave)-triggered computer summation of cardiac related sympathetic activity were unaffected. Hence central respiratory inputs on sympathetic pathways in the central nervous system best explain the origin of respiratory-related sympathetic rhythms. Independent sympathetic rhythms of apparent nonrespiratory origin may be due to artificial ventilator influences, baroreflex-autonomic oscillation loops, or Mayer waves.
Role of histidine-related compounds to intracellular buffering in fish skeletal muscle
Authors: Abe H. , Dobson G. P. , Hoeger U. , Parkhouse W. S.
Published: December 2017

Histidine-related compounds (HRC) were analyzed in fish skeletal muscle as a means of identifying their precise role in intracellular buffering. Fish muscle was used because it contains two functionally and spatially distinct fiber types, red and white. Two fish species, rainbow trout (Salmo gairdneri) and the Pacific blue marlin (Makaira nigricans), were studied because these species demonstrate widely different activity patterns. Marlin red and white muscle buffer capacity was two times higher than trout with white muscle, buffering being two times greater than red in both species. Buffer capacity was highest in the 6.5–7.5 pH range for all tissues, which corresponded to their high anserine levels. The titrated HRC buffering was greater than the observed HRC buffering, which suggested that not all HRC were available to absorb protons. The HRC contribution to total cellular buffering varied from a high of 62% for marlin white to a low of 7% for trout red. The other principal buffers were found to be phosphate and protein with taurine contributing within red muscle in the 7.0–8.0 pH range. HRC were found to be dominant in skeletal muscle buffering by principally accounting for the buffering capacity differences found between the species and fiber types.
Distribution of ventilation in American alligator Alligator mississippiensis
Authors: Bickler P. E. , Spragg R. G. , Hartman M. T. , White F. N.
Published: December 2017

The regional distribution of ventilation in the multicameral lung of spontaneously ventilating alligators (Alligator mississippiensis) was studied with 133Xe scintigraphy. Frequent gamma camera images of 133Xe washin and washout were obtained and processed to allow evaluation of regional ventilation. Washin of 133Xe to equilibrium occurred in three to four breaths in anterior, central, and posterior compartments. Washin was most rapid in the posterior compartment and slowest in the anterior. The structure of the lungs and distribution of ventilation of inspired gas is consistent with the rapid radial spread of gas through a parallel arrangement of lung units surrounding the central intrapulmonary bronchus. Washout to equilibrium of 133Xe from all compartments occurred within three to four breaths. This rapid washin and washout of gas to all parts of the lung stands in contrast to the lungs of turtles and snakes, in which the caudal air sacs are relatively poorly ventilated.
Transplacental diffusion and blood flow of gravid bovine uterus
Authors: Reynolds L. P. , Ferrell C. L. , Ford S. P.
Published: December 2017

Electromagnetic blood flow transducers and uterine arterial, uterine venous, umbilical venous, fetal femoral arterial, and fetal femoral venous catheters were implanted in 11 cows on day 161 +/- 4 of gestation. Antipyrine (0.66 M) plus NaCl (0.16 M) dissolved in deuterium oxide (D2O), or H2O, was infused at a constant rate into the fetal femoral vein catheter. Concentrations of antipyrine and D2O in uterine arterial and venous blood and antipyrine in fetal arterial and umbilical venous blood, as well as middle uterine arterial blood flow (electromagnetic transducer), were determined. Antipyrine and D2O gave similar estimates (steady-state diffusion method) of gravid uterine blood flow. In addition, the slope of the regression of D2O on antipyrine estimates was not different (P greater than 0.10) from one. Electromagnetic transducers gave estimates of uterine blood flow that were 32-42% of those obtained with steady-state diffusion but were correlated (P less than 0.05) with estimates obtained by use of both antipyrine and D2O. The transplacental clearance rate of antipyrine was similar (per kg placenta) to that observed in ewes. It was suggested that the maternal and fetal microvasculatures of the bovine placenta could have a concurrent arrangement with vascular shunts or maldistribution of flows, as has been suggested for the ewe.
Effect of adrenalectomy and corticosterone replacement on meal patterns of Zucker rats
Authors: Freedman M. R. , Castonguay T. W. , Stern J. S.
Published: December 2017

Male obese and lean Zucker rats were adrenalectomized (ADX) or sham-operated at 10 wk of age. Approximately 16 wk later, patterns of food intake were monitored by computer-interfaced top loading balances. Data were collected from ADX rats before, during, and after access to a corticosterone-supplemented saline solution (20 micrograms/ml). Although total food intake during the precorticosterone treatment period was not different between ADX and sham controls, ADX resulted in attenuation of light cycle food intake, primarily via decreased meal frequency. With steroid replacement, light cycle meal frequency and food intake increased. Despite comparable self-administered dose (20.33 +/- 0.89 vs. 17.05 +/- 1.2 mg corticosterone/period, obese vs. lean), obese ADX rats were more responsive to steroid than were lean ADX rats. This increased responsiveness was reflected by a 30% increase in food intake and 60% increase in body weight gain of obese ADX rats during replacement. Lean ADX rats exhibited no change in total food intake or weight gain with replacement. Further, during corticosterone treatment, obese ADX rats increased meal frequency, total food intake, and consumption of large meals (greater than or equal to 4 g) during the dark cycle. Significant postprandial correlations were found only in obese ADX rats, both with and without replacement during the dark cycle. These results suggest adrenal glucocorticoids have a minimal effect on food intake and meal patterns in lean Zucker rats but significantly alter intake and meal patterns in obese rats.
Fever-specific changes in central MSH and CRF concentrations
Authors: Holdeman M. , Khorram O. , Samson W. K. , Lipton J. M.
Published: December 2017

Page R125: M. Holdeman, O. Khorram, W. K. Samson, and J. M. Lipton. “Fever-specific changes in central MSH and CRF concentrations.” Page R127: line 16 should read: The identity of the IRCRF detected in the tissue extracts using this assay and antibody was determined previously (J. H. Moltz, J. K. McDonald, M. D. Lumpkin, C. P. Fawcett, and W. K. Samson, personal communication). Page R128: Reference 27 should not appear in the reference list.
Fetal auditory brain stem response: external and intrauterine auditory stimulation
Authors: Plessinger M. A. , Woods J. R.
Published: December 2017

Singleton fetuses from five pregnant ewes of 120-129 days gestation (term = 145 days) were tested for fetal auditory brain stem responses (ABR) generated by earphones placed on the maternal abdomen and compared with ABRs generated by an earphone secured in the fetal lamb's ear. To conduct these studies a cesarean section was performed on the pregnant ewe at 105-110 days gestation in order to implant stainless steel electrodes in the fetal scalp and a hearing aid receiver in the fetal external ear canal. The fetus was returned to the uterus, and the pregnancy was allowed to continue. Comparison of the externally elicited fetal ABR with the internally elicited fetal ABR indicates similar response patterns with delayed peak latencies observed in ABR responses from external stimulation. This new method of generating fetal ABRs by an external sound source documents the neurological response of the fetal auditory end organ and the fetal brain stem in the pregnant nonstressed animal model and may have applications in developmental studies of the fetal auditory system.
Microcomputer-assisted metabolic studies of voluntary diving of Weddell seals
Authors: Guppy M. , Hill R. D. , Schneider R. C. , Qvist J. , Liggins G. C. , Zapol W. M. , Hochachka P. W.
Published: December 2017

Utilizing a microprocessor-controlled peristaltic withdrawal pump, arterial blood samples were obtained from Weddell seals (Leptonychotes weddelli) while diving voluntarily under the sea ice at McMurdo Sound, Antarctica. Plasma concentrations of glucose, lactate, free fatty acids, urea, and amino acids were determined in seals at various times during rest, diving, and recovery. In addition, radiolabeled palmitate, glucose, lactate, p-aminohippurate, inulin, galactose, and cholate were injected into the descending aorta of seals in the resting state or during voluntary diving at sea. Sequential plasma samples were collected, and the kinetics of wash-in and clearance of each component were determined. Under resting conditions, the change in specific activity of palmitate, glucose, and lactate after bolus injection followed smooth multiexponential decay kinetics as in terrestrial animals. Similar decay curves for the clearance of organ-specific compounds were also obtained in seals at rest. If, during voluntary diving, Weddell seals were analogous to exercising animals, the wash-in and clearance kinetics of all metabolites and organ-specific compounds would be qualitatively similar to those observed at rest. In contrast, wash-in and clearance appeared to be qualitatively and quantitatively modified in a way consistent with utilization of the classical Scholander diving response in both short and long dives.
Can cultured teleost hepatocytes show temperature acclimation?
Authors: Koban M.
Published: December 2017

Hepatocytes were prepared from 15 degrees C acclimated catfish (Ictalurus punctatus) and maintained in primary culture for 20 days on biomatrix at 7, 15, and 25 degrees C without hormones or serum to determine if cells can directly adapt to temperature. Specific activities of cytochrome-c oxidase, NADH-cytochrome c reductase, citrate synthase, and glucose-6-phosphate dehydrogenase showed acclimatory rate compensation (7 greater than 15 greater than 25 degrees C cultured); 6-phosphogluconate dehydrogenase had activity changes of 15 greater than 7 greater than 25 degrees C cultured; activity of lactate dehydrogenase occurred in the series 7 greater than 15 = 25 degrees C. Protein synthesis of freshly isolated hepatocytes from catfish acclimated to the three temperatures exhibited acclimatory rate compensation. In contrast, protein synthesis of cultured hepatocytes occurred in the series 15 greater than 25 greater than 7 degrees C cultured. Protein degradation was highest at 25 degrees C followed by cells at 15 and 7 degrees C. Cultured hepatocytes showed incomplete temperature acclimation in vitro by way of enzyme activity changes and of protein synthesis. This suggests that some factor(s), such as hormones, is probably necessary to mediate the full temperature-acclimation process.
Renin, ACTH, and adrenocortical function during hypoxia and hemorrhage in conscious rats
Authors: Raff H. , Sandri R. B. , Segerson T. P.
Published: December 2017

We studied the effect of chronic hypoxia on the renin, adrenocorticotropin (ACTH), aldosterone, and corticosterone responses to acute hemorrhage in conscious male rats with chronic femoral arterial catheters. Rats were exposed to 21, 12.5, or 10% O2 (n = 7 per group). At 42 h of exposure, animals underwent a rapid 6 ml/kg hemorrhage. O2 at 12.5 and 10% led to significant hypoxemia (arterial PO2 = 52 +/- 1 and 43 +/- 1 Torr, respectively) and respiratory alkalosis. Significant increases in plasma sodium to 145 +/- 2 meq/l and decreases in plasma potassium to 3.53 +/- 0.12 meq/l were also observed during hypoxia. Hypoxia per se had no significant effect on blood pressure, plasma renin activity, ACTH, and corticosterone. O2 at 12.5% led to a significant reduction in aldosterone levels (0.9 +/- 0.8 ng/dl) compared with normoxia (4.2 +/- 0.9 ng/dl). The mean arterial pressure, plasma renin activity, and aldosterone responses to hemorrhage were unaltered by hypoxia. ACTH and corticosterone responses to hemorrhage were potentiated by exposure to 10% O2. We conclude that chronic exposure to severe hypoxia augments the pituitary-adrenal but not the renin-aldosterone response to hemorrhage.
Diluting segment in avian kidney. I. Characterization of transepithelial voltages
Authors: Nishimura H. , Imai M. , Ogawa M.
Published: December 2017

Renal tubules from the Japanese quail, Coturnix coturnix, were perfused in vitro to characterize the transepithelial voltage (Vt). The thick limb (TL) of the mammalian-type (MT) nephron showed Vt positive in the lumen (+9.1 +/- 0.7 mV, n = 35). The Vt decreased with increases in hydrostatic perfusion pressure. Furosemide (lumen), Na cyanide (bath), and ouabain (bath) reversibly reduced Vt. Removal of Cl or Na from the perfusate and the bath decreased Vt of the TL from +10.3 +/- 3.0 to -0.3 +/- 0.3 (n = 5) and from +7.4 +/- 1.5 to +1.2 +/- 0.2 mV (n = 8), respectively. The distal tubule of the reptilian-type (RT) nephron showed two types of Vt: a lumen-negative Vt in the late segment and a lumen-positive Vt in the early segment that is in close contact with the parent glomerulus. Both voltages were reversibly reduced by ouabain and Na cyanide. These results suggest that in quail the TL of the MT nephron resembles the thick ascending limb of the mammalian kidney with both Na and Cl required for generation of luminal positivity and the distal tubule of the RT nephron appears functionally heterogeneous.
Stimulating fastigial nucleus pressor region elicits patterned respiratory responses
Authors: Lutherer L. O. , Williams J. L.
Published: December 2017

Electrical stimulation of the ventromedial region of the rostral fastigial nucleus (FN) in the cat produced marked quantifiable changes in respiration that were highly correlated with the concurrently elicited cardiovascular responses. The threshold- and stimulus-response curves were very similar for the two responses. Stimulation at relatively low frequencies produced increases in respiratory rate at all active sites. At approximately half the sites biphasic responses were observed with increases in stimulus frequency. These were characterized by a transient period of apnea beginning with onset of the stimulus, followed by an increased respiratory rate. At the remaining sites respiratory rate increased at all stimulation frequencies tested. Inspiratory duration decreased, and mean inspiratory flow increased. Tidal volume was not significantly altered. Similar changes were also observed when the pressor response was blocked by phenoxybenzamine. These observations, together with the frequent demonstration of expiratory-to-inspiratory and inspiratory-to-expiratory phase switching with short-burst stimulation, suggest that the FN can influence a respiratory central pattern generator. Based on these findings, a possible role for the FN in integrating cardiovascular and respiratory responses is suggested.
Effect of restriction of placental growth on umbilical and uterine blood flows
Authors: Owens J. A. , Falconer J. , Robinson J. S.
Published: December 2017

Endometrial caruncles were excised from sheep (caruncle sheep) before pregnancy. The effect of this on umbilical and uterine blood flows in a subsequent pregnancy was examined. Thirteen caruncle and twelve control sheep with indwelling vascular catheters were studied at 121 and 130 days pregnancy. In caruncle sheep, fetal, placental, and total uterine content weights were significantly lower than in control sheep. Six caruncle sheep carried normal-sized fetuses (weight within +/- 2 SD of mean weight for control fetuses) and seven carried small fetuses (weight greater than +/- 2 SD below mean weight for control fetuses). Mean weights of placentas in these groups were 0.290 +/- 0.067 and 0.156 +/- 0.069 kg, respectively, compared with 0.459 +/- 0.157 kg in control sheep. In small caruncle fetuses, umbilical and uterine blood flows and placental antipyrine clearance were significantly lower than in controls at 121 and 130 days gestation. Only umbilical blood flow was reduced in normal-sized caruncle fetuses. Umbilical blood flow and placental antipyrine clearance increased with gestational age in control sheep but not in sheep with normal-sized or small caruncle fetuses. In all sheep, umbilical and uterine blood flows and antipyrine clearance correlated with placental weight. Umbilical blood flow per kilogram of placenta but not uterine blood flow per kilogram of placenta correlated inversely with placental weight. Fetal weight at 130 days generally correlated with placental weight, umbilical and uterine blood flows, and antipyrine clearance in a curvilinear fashion such that fetal weight was not greatly restricted until these variables were less than or equal to 65% of control values.
Osmotic regulation of plasma vasopressin and oxytocin after sustained hyponatremia
Authors: Verbalis J. G. , Baldwin E. F. , Robinson A. G.
Published: December 2017

Endogenous pituitary secretion of vasopressin (AVP) and oxytocin (OT) was studied in rats with induced dilutional hyponatremia that was sustained for 2-5 days. Graded infusions of hypertonic saline produced progressive increases in plasma osmolality, but despite large relative increases in osmolality, AVP and OT secretion was not significantly stimulated until plasma [Na+] reached normal ranges. Regression analysis of plasma AVP and OT levels once secretion was stimulated showed no significant shift of the osmotic threshold for neurohypophyseal secretion of either hormone, as well as equivalent slopes of plasma AVP and OT increases per unit increases in plasma osmolality, in the hyponatremic rats relative to normonatremic controls. After a 20-25% decrease in plasma osmolality, total brain water content of hyponatremic rats increased only 3-6%, whereas larger decreases (11-17%) in total brain electrolytes were found. During subsequent hypertonic saline infusions in the hyponatremic rats total brain water content decreased linearly, resulting in brain dehydration below normal total brain water levels before stimulation of AVP and OT secretion occurred. The stability of the osmotic threshold for neurohypophyseal secretion, despite evidence of brain adaptation to chronic hypotonicity, argues that cell volume regulation via solute loss is not a likely cause of resetting of the osmostat. Additionally, brains of hyponatremic rats were found to manifest significantly greater susceptibility to dehydration after hypertonic saline infusions than brains of normonatremic controls, which may be a consequence of brain solute loss from adaptation to chronic hypotonicity.
Reversible dissociation and inactivation of phosphofructokinase in the ischemic rat heart
Authors: Carpenter J. F. , Hand S. C.
Published: December 2017

To determine if shifts in the ratio of active phosphofructokinase (PFK) tetramers to the inactive dimeric form of the enzyme occur in vivo in the ischemic rat heart, we have developed a rocket immunoelectrophoretic (IEP) assay that provides a sensitive means by which to measure relative differences in this ratio among crude heart extracts. In ischemic hearts, in the face of a drop in intracellular pH from 6.95 to 6.25, there is a time-dependent decrease (63%) in the ratio of tetramer to dimer IEP rocket height relative to perfused controls. Concomitant with this hysteretic depolymerization is a 50% loss of PFK catalytic activity. Realkalinizing extracts of ischemic hearts fosters a recovery of 86% of the activity lost during ischemia and a return of the tetramer-to-dinner ratio to near control value. The amount of reactivation is directly dependent on the degree of enzyme dissociation that occurred during ischemia. Importantly, ischemia-induced dimerization is also reversed in vivo by postischemic reperfusion. The data are consistent with those in the previous study [Hand and Carpenter, Am. J. Physiol. 250 (Regulatory Integrative Comp. Physiol. 19): R505-R511, 1986] that characterized the pH-dependent hysteretic dissociation of heart PFK in vitro, and together they represent the first demonstration that this molecular behavior is operative in intact tissue. Other vertebrate muscle systems in which this mechanism might be functioning during pH-dependent glycolytic inhibition are discussed.
Pre- and postabsorptive insulin secretion in chronic decerebrate rats
Authors: Flynn F. W. , Berridge K. C. , Grill H. J.
Published: December 2017

Basal, taste-stimulated (preabsorptive), and postabsorptive insulin secretion and plasma glucose responses were studied in chronic decerebrate rats and their pair-fed neurologically intact controls. In experiment 1, preabsorptive insulin responses (PIR) elicited by oral infusions of glucose solution was measured in chronic decerebrate rats. Oral glucose was ingested and led to a significant short-latency elevation in plasma insulin levels. Plasma glucose levels remained constant during this time. These data show that caudal brain stem mechanisms, in isolation of the forebrain, are sufficient for the neurally mediated PIR elicited by oral glucose stimulation. In experiment 2, effects of decerebration on postabsorptive insulin secretion were measured. During the 3 h immediately after transection there was no effect of decerebration on peripheral plasma insulin or glucose levels. Thereafter, however, basal plasma insulin levels of decerebrate rats were at least twice that of control rats. Plasma glucose levels of both groups remained identical despite the hyperinsulinemia in decerebrate rats. Atropine treatment decreased, and phentolamine administration elicited a greater absolute and percent change increase in insulin levels of decerebrate rats. These data indicate that altered autonomic tone contributes to maintaining the basal hyperinsulinemia in the decerebrate rat. In response to intragastric meals and glucose and intravenous glucose administration, insulin secretion was greater in decerebrate than in control rats. Percent change in insulin levels from base line was similar in both groups after intragastric meals and intravenous glucose. In response to intragastric glucose, however, percent increase in insulin levels was greater in decerebrate rats. Decerebrate rats demonstrated mild glucose intolerance after intragastric and intravenous treatments. These results are contrasted with the known effects of ventromedial hypothalamic lesions on insulin secretion and glucose homeostasis.
Stimulation of ventromedial hypothalamus induces cold defense responses in conscious rabbits
Authors: Morimoto A. , Murakami N. , Ono T. , Watanabe T. , Sakata Y.
Published: December 2017

The involvement of the ventromedial hypothalamus (VMH) in thermoregulatory responses, which include heat production and heat loss responses, was investigated by the method of electrical stimulation. Electrical stimulation of the VMH caused a rise in rectal temperature, accompanied by the enhancement of heat production: O2 consumption and shivering. In addition, a reduction in heat loss was observed, including decreases in skin temperature (Ts), respiratory rate, and body surface area resulting from a huddled posture. In this study, stimulation of the lateral hypothalamus and other regions near the VMH had no effect on thermoregulatory responses. beta-Blocker (propranolol, 1 mg/kg iv) injected 20 min before stimulation lessened O2 consumption by approximately 10% and attenuated the reduction in Ts during VMH stimulation, whereas alpha-blockade (phentolamine, 1 mg/kg iv) was ineffective. These results indicate that most of the increase in O2 consumption during VMH stimulation was due to the occurrence of shivering but that some component of it could be due to nonshivering thermogenesis. They also indicate that the VMH, either directly or by converging influences, is involved in the activation of thermoregulatory responses to cold stress.
Effects of testosterone, estradiol, and temperature on neurons in preoptic tissue slices
Authors: Silva N. L. , Boulant J. A.
Published: December 2017

Thermosensitive preoptic neurons have been implicated in the regulation of body temperature. Testosterone- and estrogen-sensitive preoptic neurons have been implicated in reproductive behavioral and endocrine responses. In this study, rat preoptic tissue slices were used to examine the specificity of these neurons by determining their individual firing rate responses to both temperature and reproductive steroids. Of the 180 neurons classified according to thermosensitivity, 37% were warm sensitive, 8% were cold sensitive, and 55% were temperature insensitive. Ninety-three neurons were tested for their responses to perfusion media containing either testosterone or estradiol (30 pg/ml). Of the cells tested with both steroids, testosterone or estradiol affected half of the thermosensitive neurons and one-third of the temperature-insensitive neurons. This indicates that the population of temperature-insensitive neurons does not contain the majority of the steroid-sensitive neurons. There was much specificity, however, between the two types of steroid-sensitive neurons; testosterone and estradiol rarely affected the same neuron. Although these findings do not indicate a strong specificity between thermosensitive and steroid-sensitive neurons, they do support previous studies suggesting interactions between thermoregulatory and reproductive systems.
Osmotic and volemic regulation of plasma arginine vasotocin in conscious domestic fowl
Authors: Stallone J. N. , Braun E. J.
Published: December 2017

Recently developed radioimmunoassay methods were utilized to quantitatively characterize secretion of the avian antidiuretic hormone [arginine vasotocin (AVT)] by the hypothalamo-neurohypophyseal system (HNS) of the conscious domestic fowl. The functional characteristics of the osmoreceptor-HNS were evaluated during independent experimental manipulations of extracellular osmolality or volume. Simultaneous measurements of plasma AVT (PAVT) and either plasma osmolality (Posm) or blood volume (BV) in these experiments permitted determination of osmoreceptor sensitivity to independent osmotic or volemic stimuli and set point of the AVT secretory system under conditions of normal hydration. In normally hydrated birds, PAVT and Posm averaged 2.7 +/- 0.2 microU/ml (12.9 +/- 1.0 pg/ml) and 308.1 +/- 0.6 mosmol/kg H2O, respectively (means +/- SE). Characterization of AVT secretion revealed that Posm is a primary determinant of AVT secretion by the HNS of the domestic fowl. Highly correlated and significant relationships between Posm and PAVT exist both above and below the observed basal Posm of normally hydrated birds, with an apparent osmotic threshold for AVT secretion at a Posm of 288.8 mosmol/kg H2O. Analysis of the data also suggested that the HNS is insensitive to changes in BV less than or equal to 10%, because neither isotonic expansion nor reduction of BV altered PAVT. Comparison of past and present avian data with that of the mammalian HNS indicates that 1) the osmotic regulation of antidiuretic hormone secretion is qualitatively and quantitatively similar in birds and mammals, and 2) the volemic regulation of antidiuretic hormone secretion is substantially more important in mammals than in birds.
Proteolytic enzymes in human eccrine sweat: a screening study
Authors: Horie N. , Yokozeki H. , Sato K.
Published: December 2017

Thermally induced human eccrine sweat was collected both by simple scraping (SS) and by a polyethylene sweat collector that covered the Vaseline-coated skin of the back to minimize epidermal contamination (CS, clean sweat). Using synthetic chromogenic Kabi S-series substrates, we demonstrated a variety of proteases in both SS and CS, the former being higher than the latter to varying extents. The higher enzyme activity in SS is mainly due to epidermal contamination because abundant protease activity was eluted from the nonperspiring stripped and unstripped skin in vivo and from the stripped stratum corneum itself. The electrophoretic separation of sweat protein has shown that CS contains at least 7 and SS 15 gelatinolytic proteinases. Although some CS proteinases could be derived from the sweat duct, the sweat secretory coil itself is responsible for at least two proteinases at 78 and 25 kilodaltons. The identity and function of these enzymes remain to be studied.
Critical radius of endotherms
Authors: Porter W. P. , Parkhurst D. F. , McClure P. A.
Published: December 2017

The critical radius effect for insulation, well known in the engineering literature, was used by other authors to explain the lack of insulation on newborn endotherms. If that effect existed in small animals, they would lose less heat if nude than if fur or feathers were present. We show 1) that the previous analysis, although incomplete, yields the same result as a solid insulation model with the required sophistication and 2) that a proper model of fur is a porous media model. Neither of two porous media versions yield a critical radius effect. No critical radius effect occurs because simultaneous heat transfer by conduction and radiation makes it impossible to obtain the required logarithmic increase in thermal resistance with increasing insulation radius in a porous medium.