bluuebunny/crossref_metadata_2025 huggingface dataset:
Dissociation of renal interstitial hydrostatic pressure and natriuresis of atrial natriuretic factor
Authors: Khraibi A. A. , Heublein D. M. , Burnett J. C. , Knox F. G.
Published: December 2017

The objective of these experiments was to test the hypothesis that renal interstitial hydrostatic pressure (RIHP) plays an important role in the natriuretic effect of atrial natriuretic factor (ANF) in anesthetized Wistar rats. Three groups of male Wistar rats were used in this study. Two groups were infused with different doses of ANF, and the third group was a time control. In all groups, one kidney was acutely decapsulated, and the contralateral kidney was used as control. Renal decapsulation was used to control RIHP. In one group, 3 micrograms.kg-1.h-1 of synthetic ANF were infused intravenously (iv) and produced a plasma level of ANF (PANF) of 810 +/- 186.5 pg/ml. This pharmacological dose of ANF produced a significant increase in RIHP of the control kidney from 9.5 +/- 0.8 to 11.1 +/- 1.3 mmHg (P less than 0.05) but not in the decapsulated kidney [from 7.1 +/- 0.6 to 8.1 +/- 0.9 mmHg, not significant (NS)]. However, the changes in fractional excretion of sodium (FENa) and urine flow rate (V) as a result of ANF infusion were similar in both kidneys. In the decapsulated kidney, FENa and V increased by 1.53 +/- 0.41% and 26.21 +/- 5.98 microliters/min, respectively, from control to ANF infusion periods. In the control kidney, FENa and V increased by 1.60 +/- 0.28% and 31.61 +/- 5.87 microliters/min, respectively, from control to ANF infusion periods. In the second group, 1 microgram.kg-1.h-1 iv of synthetic ANF was infused and produced 165.2 +/- 29.3 pg/ml of PANF.(ABSTRACT TRUNCATED AT 250 WORDS)
Vascular effects of kinins in trout and bradykinin metabolism by perfused gill
Authors: Lipke D. W. , Oparil S. , Olson K. R.
Published: December 2017

In the preceding studies we have shown that elements of a kallikrein-kinin system (KKS) are present in trout. The present study examines the cardiovascular effects of intra-arterial kinin injection and the ability of perfused gills or gill homogenates to metabolize bradykinin or the pressor substance generated in trout plasma by glandular kallikrein (T60K). Bradykinin (BK), t-kinin, kallidin, and Met-kallidin produced pressor responses in vivo. BK responses were unaffected by alpha-adrenergic blockade or cyclooxygenase inhibition. Perfused gills extracted approximately 40% of a [3H]BK bolus, however, metabolites were not recovered from the effluent perfusate. Gill homogenates completely metabolized [3H]BK and inactivated the pressor substance T60K. Captopril reduced BK and T60K metabolism by gill homogenates. The present study demonstrates that kinins have pressor effects in trout that are not mediated through adrenergic or prostanoid-derived mechanisms. The results also suggest that trout do not release endothelium-derived relaxing factors in response to kinin injection. The gill is able to metabolize BK and T60K, although, with respect to BK, this process appears to involve intracellular hydrolysis and may be only partially dependent on angiotensin-converting enzyme. Inactivation of BK by gill tissue may be fundamentally different from kinin metabolism by the mammalian lung.
Life in a frozen state: adaptive strategies for natural freeze tolerance in amphibians and reptiles
Authors: Storey K. B.
Published: December 2017

Winter survival for various species of amphibians and reptiles that hibernate on land depends on freeze tolerance, the ability to survive for long periods of time with up to 65% of total body water as extracellular ice. Freeze tolerance has been described for four species of frogs, one salamander, and hatchlings of the painted turtle. A very limited tolerance also occurs in garter snakes. Studies of freeze tolerance in vertebrates have primarily focused on the wood frog Rana sylvatica and have assessed the regulation of cryoprotectant synthesis, cryoprotectant action in freezing preservation of isolated cells and tissues, metabolism and energetics under the ischemic conditions imposed by freezing, and the role of ice-nucleating agents in blood. The adaptations that preserve life at subzero temperatures for these animals illustrate the principles of vertebrate organ cryopreservation and may have important applications in the development of technology for the freezing preservation of transplantable human organs.
Pentobarbital anesthesia alters renal actions of alpha-hANP in dogs
Authors: Madwed J. B. , Wang B. C.
Published: December 2017

The magnitude of the natriuretic response to an infusion of alpha-human atrial natriuretic peptide (alpha-hANP) has varied considerably in different studies. The greatest renal responses to alpha-hANP infusion have been observed in barbiturate-anesthetized dogs. We therefore examined the renal, hormonal, and cardiovascular responses to alpha-hANP infusion in eight female dogs, once awake and again anesthetized with pentobarbital sodium (25 mg/kg body wt). After a 20-min control period, alpha-hANP was infused at a rate of 25 ng.kg-1.min-1 for 60 min. In dogs when awake, infusion of alpha-hANP produced a significant increase in sodium excretion from a control value of 39 +/- 7 to 73 +/- 13 and 89 +/- 15 mu eq/min after 40 and 60 min. In dogs when anesthetized, infusion of alpha-hANP produced an increase in sodium excretion from 21 +/- 3 to 105 +/- 12 and 143 +/- 21 mu eq/min after 40 and 60 min. The increase in sodium excretion was significantly greater in dogs when anesthetized than when awake. We also investigated the role of the renal sympathetic nerves on these responses in six dogs after chronic bilateral renal denervation. In dogs with denervated kidneys when awake, infusion of alpha-hANP did not change sodium excretion significantly. In dogs with denervated kidneys when anesthetized, infusion of alpha-hANP significantly increased sodium excretion; however, the increase was significantly attenuated when compared with anesthetized dogs with intact kidneys. We conclude that the natriuretic response to an infusion of alpha-hANP is enhanced in dogs when anesthetized. Also, the natriuretic response was attenuated by renal denervation in dogs when anesthetized.
Ingestion rate as an independent variable in the behavioral analysis of satiation
Authors: Kaplan J. M. , Spector A. C. , Grill H. J.
Published: December 2017

A novel intake testing paradigm, allowing explicit adjustment of the rate of sucrose ingestion via intraoral delivery, was used to investigate the effects of ingestion rate on ingestion duration and amount consumed. In experiment I, 12 rats were tested under each of three sucrose concentrations (0.1, 0.3, and 1.0 M) delivered at each of four rates (0.5, 1.0, 1.5, and 2.0 ml/min). For each stimulus concentration, intraoral intake varied as a decreasing linear function of ingestion rate (infusion rate). In experiment II, a second (part B) infusion (0.5, 1.0, or 1.5 ml/min) was initiated 30 s after an initial (part A) infusion (0.5, 1.0, or 1.5 ml/min) of the same stimulus was rejected. Amount consumed during the part B infusion was substantial only when the part B infusion rate was lower than that of part A. Quantitative analysis of experiment II indicated that across sessions with common part B infusion rates, total session intake remained stable regardless of 1) whether the part A ingestion rate was greater than or equal to that of part B, 2) systematic differences in part A intake and duration, 3) differences in total session duration, and 4) differences in average ingestion rate for the session (total session intake/total session duration). The behavioral results are discussed in relation to the analysis of satiety under traditional intake testing paradigms and to gastric and postgastric theories of satiety.
Measurements of core temperature in spontaneously hypertensive rats by radiotelemetry
Authors: Berkey D. L. , Meeuwsen K. W. , Barney C. C.
Published: December 2017

Spontaneously hypertensive (SH) rats have been shown to have elevated colonic temperatures when compared with normotensive Wistar-Kyoto (WKY) rats. In the present study, core temperatures of SH and WKY rats were compared using radiotelemetry temperature sensors implanted in the abdominal cavity. At an ambient temperature (Ta) of 25 degrees C, SH and WKY rats showed no significant difference in core temperature over a 24-h period. After 1 h exposures to Ta values of 5, 15, 25, or 35 degrees C, there were no significant differences between core temperatures of SH and WKY rats, but at 40 degrees C the SH rats had a significantly higher core temperature than the WKY rats. Handling and moderate restraint also led to significantly higher core temperatures in the SH rats. Core temperature was also significantly increased in the SH rats compared with the WKY rats when a temperature probe was either inserted intermittently or inserted and left in place. The results of this study indicate that nonstressed SH rats do not have an elevated core temperature but that stress such as heat exposure, handling, restraint, or even the presence of a colonic temperature probe can cause significant increases in core temperature in these rats.
Angiotensin II binding sites in aortic endothelium of domestic fowl
Authors: Stallone J. N. , Nishimura H. , Nasjletti A.
Published: December 2017

In domestic fowl, angiotensin II (ANG II) produces a unique vasodepressor response in vivo and endothelium-dependent relaxation of aortic rings in vitro that appear to be a direct effect on vascular smooth muscle mediated through vascular angiotensin receptors. To explore the possible role of the endothelium in ANG II-induced vasodilation, ANG II binding to aortic membrane fractions and intact endothelium and prostaglandin (PG) production were examined in fowl aortas. 125I-[Ile5]ANG II binding by endothelium-intact aortic membrane fractions was consistently higher than binding by identically prepared endothelium-deleted membrane fractions at virtually all concentrations of ligand (10 pM-0.20 microM). Incubation of intact aortic rings with 125I-[Ile5]ANG II (0.50 nM) resulted in specific endothelial binding that increased linearly with time from 5.5 +/- 1.7 (SE) fmol/mg protein at 5 min to 13.7 +/- 1.8 at 30 min. Endothelial ANG II binding increased linearly with the dose of ligand, from 2.7 +/- 0.3 fmol/mg protein at 0.1 nM to 21.0 +/- 2.2 at 1.0 nM. Specific ANG II binding to aortic endothelium was competitively displaced 73 +/- 11% by unlabeled ANG II (0.1 microM) but not by bradykinin (0.1 microM). Incubation of intact aortic rings with [14C]arachidonic acid resulted in the formation of radioactive metabolites that comigrated in thin-layer chromatography with authentic PGE2 but not with 6-keto-PGF1 alpha. PGE2 production by aortic rings (44.4 +/- 4.5 ng.mg dry tissue-1.h-1) was not stimulated by addition of ANG II. These results suggest that specific receptors for ANG II exist in fowl aortic endothelium and that PGs are not involved in ANG II-induced vasodilation of the fowl aorta.
Light and target distance interact to control pupil size
Authors: Myers G. A. , Barez S. , Krenz W. C. , Stark L.
Published: December 2017

Light and target distance stimuli were presented to normal human subjects, and their pupillary responses were measured. A homeomorphic computer model of the pupillary control system is presented in which the form of interaction of controller signals due to light and target distance was investigated. The error remaining when model parameters were optimized to fit experimental pupil size (area or diameter) was smaller for the linear interaction hypothesis than for either power law or logical law interaction. A generalized second-order nonlinear model with six parameters (vs. 3 for each of the other models) yielded somewhat lower residual error. With the use of a modified Akaike information criterion, the value (in an information theoretic sense) of the improved fit afforded by the three additional parameters in the generalized nonlinear model was shown to be small, and thus the generalized second-order nonlinear model was rejected in favor of the simpler and more parsimonious linear model.
Different effects of sodium or chloride depletion on angiotensin II receptors in rats
Authors: Ray P. E. , Castren E. , Ruley E. J. , Saavedra J. M.
Published: December 2017

We studied the effects of selective chronic sodium or chloride depletion (0.005% in diet) on central and peripheral angiotensin II receptors in young rats. Chloride depletion produced the most significant increase in plasma renin activity and extracellular fluid volume contraction. In the brain, subfornical organ angiotensin II receptor concentration was decreased by sodium depletion and increased by chloride depletion. There were no significant changes in angiotensin II binding in the paraventricular nucleus. When sodium-depleted rats were water deprived for 3 days, subfornical organ angiotensin II receptor concentration increased, showing that normal sodium intake was not essential for increased numbers of angiotensin II receptors during dehydration. In the adrenal gland, chloride depletion decreased angiotensin II receptors in the medulla and zona glomerulosa. Conversely, sodium depletion increased angiotensin II receptors in the zona glomerulosa. In the kidney glomeruli and medulla, angiotensin II receptors were decreased by either sodium or chloride depletion. These results suggest different roles for sodium and chloride in the regulation of the peripheral and central renin-angiotensin system in young rats.
Altered sensitivity of osmotically stimulated vasopressin release in quadriplegic subjects
Authors: Wall B. M. , Williams H. H. , Presley D. N. , Crofton J. T. , Schneider E. G. , Share L. , Cooke C. R.
Published: December 2017

Osmoregulation of vasopressin release was studied in 15 quadriplegic subjects (Quad) and 7 healthy control subjects (Con). Hypertonic NaCl (0.85 M) was infused intravenously (0.05 ml.kg-1.min-1) over 90 min in studies on supine subjects and in comparable studies on the same subjects erect (sitting). Erect posture in Quad, but not in Con, was accompanied by orthostatic reductions in arterial blood pressure and by significantly increased plasma aldosterone (P less than 0.001) and cortisol (P less than 0.001) concentrations and increased plasma renin activity (P less than 0.025). Changes in plasma arginine vasopressin concentration (PAVP) during hypertonic NaCl infusions were also greater in erect than in supine Quad (P less than 0.005), despite identical changes in plasma osmolality (Posm). Linear regression analysis of the PAVP/Posm relationship during hypertonic NaCl infusions showed highly significant correlations (P less than 0.0002) in both Quad and Con. Mean slope values for regression lines, however, were significantly higher in erect than in supine Quad (P less than 0.005) but did not differ in relation to posture in Con. Differences in posture were not associated with differences in abscissal intercepts in either Quad or Con. These studies show significant alterations in the sensitivity of osmotically stimulated vasopressin release related to differences in posture in Quad, characterized by enhanced sensitivity in erect posture due to nonosmotic stimuli not evident in Con.
Circadian variation of thermoregulatory responses during exercise in rats
Authors: Tanaka H. , Yanase M. , Kanosue K. , Nakayama T.
Published: December 2017

Rats exercised on a treadmill at daytime lows and nighttime highs of circadian change in body temperature at two different work intensities [40 and 60% of maximal oxygen uptake (VO2max)] with the ambient temperature (Ta) at 24 degrees C. Immediately before exercise at 60% VO2max, rectal temperature (Tre) was 0.7 degrees C higher at night than during the day. During the exercise, Tre rose more during the day than at night, and Tre at the end of exercise was the same in the day as at night. Threshold Tre for tail vasodilation did not differ between day and night. Similar tendencies of Tre change and tail vasomotor response were observed at a work intensity of 40% VO2max, except that the rise in Tre was smaller than at the higher work intensity. On the other hand, threshold Tre for tail vasodilation spontaneously occurring in resting rats in a warm environment (Ta of 28 degrees C) was 0.7 degrees C higher at night than during the day. In conclusion, exercise in rats attenuates the differences in deep body temperature and threshold Tre for tail vasodilation seen between day and night.
Vasopressinergic augmentation of cardiac baroreceptor reflex in conscious rats
Authors: Brizzee B. L. , Walker B. R.
Published: December 2017

Experiments were performed on conscious, chronically instrumented rats to determine the contribution of V2-receptor activation in augmentation of cardiac baroreceptor reflex (BRR) sensitivity by arginine vasopressin (AVP). At least 1 wk before experimentation, rats were implanted with arterial and venous catheters, as well as with pulsed Doppler flow probes for measurement of cardiac output (CO). An initial set of experiments was performed to determine whether cardiac BRR sensitivity is enhanced by AVP in conscious rats. A series of pressor doses of either AVP or phenylephrine (PE) were administered on separate days (n = 8). The slope of pulse interval (PI) vs. mean arterial blood pressure (MABP) was determined for each experiment by linear regression and used as an index of cardiac BRR sensitivity. The slope of PI vs. MABP was greater in response to AVP than in response to PE in all animals studied. A separate group of animals (n = 7) received either a 40-min infusion of AVP (5 ng/min iv) or a specific V2-antagonist, d(CH2)5[DIle2,Ile4]AVP (20 micrograms/kg iv), 10 min before infusion of AVP. The responses of MABP, CO, and total peripheral resistance to AVP infusion were similar with and without V2-antagonism; however, the bradycardic response to AVP was less with V2-antagonist pretreatment. Furthermore, administration of V2-antagonist reduced delta PI/delta MABP in response to AVP infusion. Additional experiments were performed to test the effect of infusion of a specific V2-agonist, dVDAVP (5 ng/kg iv), on BRR-induced bradycardia in response to a series of pressor PE bolus doses.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of acute and chronic baroreceptor denervation on diving responses in ducks
Authors: Smith F. M. , Jones D. R.
Published: December 2017

To investigate the effects of barodenervation on the cardiovascular responses to forced submersion, we implanted snares around the aortic nerves innervating the baroreceptors in anesthetized (pentobarbital sodium, 35-45 mg/kg) ducks (Anas platyrhynchos). Snares were withdrawn 1 wk after surgery to effect barodenervation in the absence of complications from surgical trauma or anesthesia. After barodenervation, resting heart rate (HR), hind limb vascular resistance (HLVR), and mean arterial pressure (MAP) all increased, with different time courses, over the 16-day observation period. Bradycardia developed during forced submersion in ducks before and after barodenervation, although this response was reduced for 1-3 days after nerve section. The HR response to diving intensified 4-5 days after denervation, and the level of dive bradycardia at 16 days was similar to that before denervation. End-dive MAP fell further, as a proportion of predive MAP, with time after baroreceptor loss. The absolute level of HLVR reached during diving was unaffected by barodenervation. These results show that diving responses develop in the absence of baroreceptors, but MAP in the dive is not maintained as well in barodenervates as in baroreceptor-intact animals.
Direct observation of the phosphate acceptor and phosphagen pool sizes in vivo
Authors: Van Waarde A. , van den Thillart G. , Verhagen M. , Erkelens C. , Addink A. , Lugtenburg J.
Published: December 2017

Earthworms were subjected to environmental anoxia (200 min) and electrical stimulation (5 min, 6 V, 50 Hz). The levels of high-energy phosphate compounds and the intracellular pH were monitored during anoxia, muscular contraction, and recovery by in vivo phosphorus-31 nuclear magnetic resonance (31P-NMR). Several key metabolites were determined by enzymatic analysis and reversed-phase high-performance liquid chromatography of perchlorate extracts. Because lombricine, the phosphagen phosphate acceptor of earthworms, is a phosphodiester, 31P-NMR permitted direct analysis of the extent of phosphorylation of the lombricine pool in vivo. Total lombricine, lombricine phosphate, ATP, and H+ were measured by NMR, and free ADP was calculated from the lombricine kinase equilibrium constant. The ADP concentration was not significantly changed by anoxia, but it rose threefold after stimulation. L-Lactate accumulated on stimulation, whereas multiple end products (L-lactate, alanine, succinate, and glutamine) were formed during environmental anaerobiosis.
Model study of placental water transfer and causes of fetal water disease in sheep
Authors: Faber J. J. , Anderson D. F.
Published: December 2017

The purpose of the computer simulation was to use experimentally measured parameters of placental water transfer to compute conceptual water acquisition during the last third of ovine pregnancy and to evaluate the possible role of each of these parameters in the pathophysiology of polyhydramnios. Total conceptual water at birth was almost insensitive to the value of the placental filtration coefficient. It was more sensitive to fetal and maternal placental blood flows, the concentrations of actively transported or metabolically produced solutes in fetal plasma (bicarbonate, fructose, alpha-amino acids, urea, lactate), and the hydrostatic pressure difference across the placental barrier. It was quite sensitive to the NaCl reflection coefficient and permeability. We conclude that the actively transported or produced solutes in fetal plasma constitute a primary driving force. The opposing diffusion gradient of NaCl, and to a much lesser extent that of glucose, are essential to restrain the process. The causes of polyhydramnios in this species are, in order of probability, an increase in the placental diffusion permeability of NaCl, a decrease in the placental reflection coefficient for NaCl, or an increase in the concentration of an osmotically effective solute in fetal plasma, by active transport or metabolic production.
Pharmacological responsiveness of dissociated native and cultured eccrine secretory coil cells
Authors: Yokozeki H. , Saga K. , Sato F. , Sato K.
Published: December 2017

Methacholine (MCh)- and isoproterenol (Iso)-stimulated 14CO2 production was compared between freshly dissociated rhesus sweat secretory coil cells (mainly clear cells) and cultured cells (grown on a collagen-coated plastic plate) derived from native cells. 14CO2 production was enhanced by MCh and by Iso in native coil cells (but not in ductal cells) in a pharmacologically specific and dose-dependent manner. 14CO2 production in subcultured coil cells (19-45 days in culture) was only one-third to one-fifth that of native cells. MCh-stimulated 14CO2 production was inhibited by ouabain and furosemide in both native and cultured coil cells. A decrease in 14CO2 production, of about one-half, was already evident in primary cells cultured for less than 1 wk. The decreased pharmacological responsiveness of the cultured coil cells was seen, although the cultured cells showed the typical epithelioid appearance, abundant mitochondria, the occasional presence of intercellular lacunae resembling intercellular canaliculi, and the persistence of immunoreactive keratin. We conclude that 1) a primary culture of sweat gland cells can be initiated from dissociated cells; 2) cultured sweat secretory coil cells qualitatively, but not quantitatively, retain the pharmacological responsiveness and transport activity of the native cells as determined by 14CO2 production; 3) collagenase-dissociated cells represent an excellent in vitro system for the study of glandular function at the cellular level; and 4) the decrease in pharmacological responsiveness is not simply due to trypsin treatment during harvesting of cultured cells, because that of organ-cultured, intact, secretory coils also declines with time of culture.
Micturition reflexes in decerebrate and spinalized neonatal rats
Authors: Kruse M. N. , De Groat W. C.
Published: December 2017

Micturition in neonatal rats is mediated by a spinal reflex pathway activated by the mother licking the perineum (the perineal-to-bladder reflex, P-Bld). Micturition in adult rats is mediated by a spinobulbospinal reflex pathway activated by bladder distension (the bladder-to-bladder reflex, Bld-Bld). This study examines the postnatal development of the Bld-Bld reflex in decerebrate or spinalized unanesthetized and urethan-anesthetized rat pups 2-26 days of age. Urethan anesthesia depressed both the Bld-Bld and P-Bld micturition reflexes. Bld-Bld micturition reflexes (peak intravesical pressures of 13 +/- 6 cmH2O and durations of 35 +/- 11 s) were noted in 54% of 2-day-old decerebrate pups and in all of the 6- and 9-day-old decerebrate pups but in none of the 2- or 9-day-old spinalized pups. We conclude that a weak supraspinal Bld-Bld reflex is present during the early postnatal period; however, the P-Bld reflex is the primary mediator of micturition in the neonatal rat.
Sodium-coupled organic anion transport by Cancer borealis urinary bladder
Authors: Smith P. M. , Miller D. S. , Pritchard J. B.
Published: December 2017

Recently, p-aminohippurate (PAH) transport by rat renal basolateral membrane (BLM) vesicles was shown to be coupled indirectly to the Na+ gradient through PAH-glutarate exchange and Na(+)-glutarate cotransport. We have examined the mechanism of PAH transport in Cancer borealis urinary bladder, a simple flat-sheet epithelium that is functionally analogous to vertebrate renal proximal tubule. These experiments indicate that crab bladder is capable of both Na(+)-coupled glutarate uptake and PAH-glutarate exchange and that PAH uptake may be coupled to Na+ in the intact tissue. First, glutarate uptake by intact bladder was lithium sensitive, Na(+) dependent, and inhibited by other dicarboxylates. In flux chambers, the bladder exhibited net glutarate secretion and tissue accumulation occurred primarily from the basolateral side. Furthermore, both BLM and brush-border membrane (BBM) vesicles also exhibited lithium-sensitive Na(+)-coupled glutarate uptake. Second, imposition of an in greater than out glutarate gradient markedly stimulated PAH uptake by bladder BLM vesicles, demonstrating PAH-glutarate exchange. In contrast, exchange was absent in BBM vesicles. Third, in intact bladder tissue, external glutarate increased the steady-state tissue-to-medium ratio for PAH from 14 +/- 1 to 19 +/- 1.5. This increase was both lithium inhibitable and Na+ dependent. Thus not only do bladder BLM show all the elements needed for indirect coupling of PAH transport to the Na+ gradient, but indirect coupling to Na+ can also drive uphill PAH transport in the intact epithelium.
Underlying mechanisms of atrophic state of brown adipose tissue in obese Zucker rats
Authors: Seydoux J. , Benzi R. H. , Shibata M. , Girardier L.
Published: December 2017

The mechanisms involved in brown adipose tissue (BAT) atrophy in obese rats were investigated. In urethan-anesthetized adult obese (fa/fa) and lean (Fa/?) rats, colonic temperature (Tc), interscapular BAT (IBAT) temperature (TIBAT), and the TIBAT-Tc gradient were measured after microknife cut in the prepontine region and during norepinephrine (NE) infusion. The knife cut tests the neural control of IBAT since it suppresses a tonic inhibition of thermogenesis revealing a sustained reflex stimulation of BAT. The NE infusion tests the metabolic capacity of BAT. In 22 degrees C-acclimated lean rats, the cut induced marked hyperthermia, TIBAT that rose faster than Tc, and a reversed temperature gradient. By contrast, in the obese rat, the cut had practically no effect, and NE infusion caused only slight increases in Tc and TIBAT. In cold-acclimated obese rats, an almost complete response to NE infusion and a partial response to knife cut were observed. After adrenalectomy, the responses were similar in lean and obese rats. An operational model to account for these results and for the deficit in diet-induced thermogenesis in fa/fa rats is proposed.
Thermal acclimation and muscle contractile properties in cyprinid fish
Authors: Johnston I. A. , Fleming J. D. , Crockford T.
Published: December 2017

After several weeks of cold acclimation, the swimming performance of some fish is increased at low temperatures and decreased at high temperatures. The temperature compensation of locomotory activity involves changes in central patterns of muscle fiber recruitment and in the properties of the peripheral nervous system and muscle tissues. In some freshwater fish belonging to the family Cyprinidae, including the goldfish (Carassius auratus), the common carp (Cyprinus carpio), and the roach (Rutilus rutilus), the intrinsic contractile properties of muscles are modified by thermal acclimation. Parameters that can be altered by temperature acclimation in both fast and slow muscle fibers include isometric twitch contraction time, maximum force production, and unloaded shortening speed. The molecular mechanisms responsible for these changes in contractility are discussed.
Thermal dependence of locomotor capacity
Authors: Bennett A. F.
Published: December 2017

The thermal dependence of locomotor performance capacity, particularly speed and endurance, in vertebrate ectotherms is examined. Most studies have found an optimal speed for performance at relatively high body temperatures, close to upper lethal limits. These performance capacities decrease markedly at low body temperatures and may be compensated by increments in aggressive or evasive behaviors. Relative ranking of performance is maintained among individuals across body temperatures. Acclimation of performance capacities is generally incomplete or entirely absent: most animals compensate locomotor performance rather poorly to cold exposure. Locomotor performance in different groups has been shown to possess the attributes (e.g., variability, repeatability, heritability, and differential survivorship) necessary for evolutionary adaptation, but interpretation of comparative data is complicated by phylogenetic differences among species studied. Controlled studies show partial but incomplete adaptation to environmental temperature.
Development of circadian cycle of core temperature in juvenile rats
Authors: Nuesslein B. , Schmidt I.
Published: December 2017

To find out whether or not juvenile rats can sustain circadian rhythms of core temperature (Tc) in the absence of diurnal cues, we continuously recorded Tc for 12 days in isolated pups artificially reared in continuous dim light. Possible effects of uncontrolled environmental 24-h cycles were excluded by simultaneously studying pups born on the same day to two mothers entrained to 12:12 h light-dark cycles 180 degrees out of phase. Age-dependent changes were discriminated from the effects of sustained isolation by comparing Tc records between pups isolated from 10 or from 4 days of age (late- or early-isolated pups). Both groups of pups showed Tc cycles in phase with the light cycle in the colony of origin and with highest amplitudes from 10 to 13 days of age. Tc cycles with a period length close to 24 h could be seen through the 12th day of artificial rearing for early-isolated pups but only until the 6th day for late-isolated pups. In the third postnatal week the rhythm faded gradually. Self-sustained circadian Tc rhythms observed in isolated 1- to 2-wk-old pups demonstrate a functional endogenous clock in the juvenile rat.
Physiological correlates of schedule-induced activities in rats
Authors: Mittleman G. , Brener J. , Robbins T. W.
Published: December 2017

Oxygen consumption and heart rate as well as a range of behavior variables were tracked continuously as rats adapted to a schedule of food delivery. Over 15 days of observation a majority of the subjects developed characteristic patterns of schedule-induced polydipsia (SIP) in which bouts of drinking reliably followed food delivery. Variations in food tray entries, oxygen consumption, heart rate, and, in the final stage of the experiment, rates of general activity were also time locked to food delivery in both rats exhibiting SIP and nondrinkers. However, the patterns of variation in these measures differed consistently between these two groups. Oxygen consumption varied over a wider range and reached higher levels in drinkers than nondrinkers. Additionally, heart rate was lower in the drinkers, which, in the final stage of the experiment, also exhibited depressed rates of food tray entries and general activity relative to the nondrinkers. Each of these between-subject differences was paralleled by differences within the drinking group between trials on which drinking occurred and trials on which it did not occur. The implications of these results on the utility of unidimensional energetic constructs are discussed.
Regulation of renal pelvic pressure by diuresis and micturition
Authors: Djurhuus J. C. , Frokjaer J. , Munch Jorgensen T. , Knudsen L. , Pham T. , Constantinou C. E.
Published: December 2017

The influence of the voiding cycle and diuresis on the hydrodynamic pressures of the renal pelvis in the multicalyceal kidney of miniature pigs has been examined. Identification of the pressure patterns characteristic of the renal pelvis with an undisturbed pelviureteric and ureterovesical junction was emphasized. The frequency and amplitude of contractions in the renal pelvis were measured bilaterally. The patterns of renal pelvic pressure changes were interpreted during bladder filling and emptying and diuresis to evaluate the mechanisms facilitating the pressure isolation of the upper urinary tract. These studies were undertaken in the awake pig equipped with a long-term radiotelemetry implant transmitting renal pelvic and urinary bladder pressure. The results show that renal pelvic contractions are low-pressure events having an amplitude of 10.3 +/- 4.2 cmH2O and a frequency of 6.6 +/- 0.7 contractions/min. During basal hydration, the process of renal pelvic filling and emptying is active, with rhythmic pelvic contractions. The left and right renal pelvis demonstrate approximately equal frequency, 1.04:1.00, but are not synchronous. Furosemide-stimulated diuresis produces radical changes in the renal pelvis by transforming emptying from an active to passive mode and facilitating the transmission of voiding pressures and spontaneous bladder pressures to the kidney.
Role of central mineralocorticoid binding sites in development of hypertension
Authors: Janiak P. C. , Lewis S. J. , Brody M. J.
Published: December 2017

The possibility that central mineralocorticoid binding sites are involved in the development of mineralocorticoid hypertension was examined using chronic blockade of these sites with a specific mineralocorticoid receptor antagonist RU 28318 administered by intracerebroventricular (icv) infusion. The antagonist significantly attenuated the development of deoxycorticosterone acetate (DOCA)-salt hypertension, but the development of one-kidney, one-clip renal hypertension was not affected. This antihypertensive action was attributable to a central action, since intraperitoneal infusion of the same dose of mineralocorticoid antagonist did not alter the peak development of DOCA-salt hypertension. The icv infusion of RU 28318 did not change either the increase of fluid intake induced by DOCA-salt treatment or the pressor reactivity to centrally or peripherally injected arginine vasopressin and angiotensin II and peripherally administered phenylephrine. The antihypertensive action of icv infusion of the mineralocorticoid antagonist was associated with a reduction of neurogenic vasomotor tone and a restoration of impaired arterial baroreflexes. We conclude that functional integrity of central mineralocorticoid binding sites is required for the full development of DOCA-salt hypertension.
Role of renal sympathetic nerves in response of the ovine fetus to volume expansion
Authors: Smith F. G. , Sato T. , McWeeny O. J. , Klinkefus J. M. , Robillard J. E.
Published: December 2017

To investigate the role of renal sympathetic nerves in the fetal response to hypervolemia, studies were carried out in conscious, chronically instrumented fetal sheep aged 137-142 days of gestation. Bilateral renal denervation (n = 9) or sham surgery (n = 8) was carried out under halothane anesthesia 3-6 days before experiments. Bilateral renal denervation did not alter basal fetal renal hemodynamics, glomerular filtration rate (GFR), or Na+ excretion. Volume expansion with 6% Dextran 70 (18 ml/kg) was associated with a fall in fetal hematocrit, a sustained increase in mean arterial blood pressure, and a sustained diuresis and natriuresis. There was no significant change in GFR during fetal hypervolemia from control levels of 4.51 +/- 0.74 ml/min (intact) and 4.43 +/- 0.43 ml/min (denervated). Atrial natriuretic factor increased from 144 +/- 34 to 464 +/- 134 pg/ml, and plasma renin activity decreased from 5.15 +/- 1.7 to 3.04 +/- 1.0 ng.ml-1.h-1 in intact animals, within 30 min of completion of the dextran infusion. Similar changes occurred in denervated fetuses. Plasma aldosterone levels remained constant in intact and denervated fetuses during hypervolemia at control levels of 40.8 +/- 5.4 and 59.3 +/- 8.4 pg/ml, respectively. These findings suggest that renal sympathetic nerves do not influence basal renal hemodynamics or function and do not appear to play an important role in the natriuretic response to volume expansion during fetal life. This can be explained by a low tonic renal nerve activity before birth.
Net basolateral potassium flux and short-circuit current in ouabain-treated frog skin
Authors: Cox T. C. , Woods R. E.
Published: December 2017

A new technique has been developed to correlate K loss from cells (JK) across the basolateral membrane into a K-free ouabain Ringer solution and short-circuit current (Isc) for a model Na-transporting epithelium, the frog skin. Distinct differences were observed when the tissue was bathed in sulfate or chloride Ringer. In sulfate Ringer, K-free ouabain treatment caused both JK and Isc to decline in a nearly parallel fashion with time. JK-Isc was approximately 1 microA/cm2. In sulfate Ringer, isoproterenol caused parallel increases, whereas amiloride (apical side) caused parallel decreases in JK and Isc. In chloride Ringer, K-free ouabain treatment caused Isc to decline at a slightly faster rate than JK.JK-Isc was approximately 8 microA/cm2. Bumetanide decreased JK with very little effect on Isc. Barium caused small parallel changes in both Isc and JK. Amiloride decreased Isc with very little effect on JK. These experiments show that after ouabain treatment changes in JK from the cells across the basolateral membrane can largely account for changes in Isc. However, JK also occurs via neutral mechanisms and perhaps from cells not related to the transport pathway, demonstrating that there is not always a tight coupling of K loss at the basolateral membrane with Na entry across the apical membrane.
Effect of arginine vasopressin on CSF composition and bulk flow in hyperosmolar state
Authors: Szmydynger-Chodobska J. , Szczepanska-Sadowska E. , Chodobski A.
Published: December 2017

To find out whether central arginine vasopressin (AVP) plays a role in regulation of cerebrospinal fluid (CSF) composition and of CSF bulk flow (CSFbf) in acute hyperosmolar state, the experiments were performed on 16 anesthetized cats in which the ventriculocisternal system was perfused either with artificial CSF (aCSF; 8 control experiments) or with aCSF containing AVP (10 microU/min, 8 experiments) before, during, and after intravenous infusion of 5% NaCl. In both series, hyperosmotic infusion significantly increased CSF osmolality (CSFosmol) and sodium (CSFNa) and potassium (CSFK) concentration and reduced CSFbf. Administration of AVP significantly influenced the dynamics of changes in CSFNa and slightly affected changes in CSFK concentration induced by infusion of hyperosmotic saline, while it did not modify changes in CSFosmol) and CSFbf. In control experiments, CSFbf was significantly related to plasma and CSF osmolalities and sodium concentrations, whereas in AVP experiments these relationships were markedly suppressed. The results suggest that during acute hyperosmolar state AVP significantly influences sodium handling in CSF and may play a role in adaptation of the brain to hyperosmolality.
Comparative effects of hypoxia on behavioral thermoregulation in rats, hamsters, and mice
Authors: Gordon C. J. , Fogelson L.
Published: December 2017

Recent studies using reptiles and other ectothermic species have shown that hypoxia lowers the set point for the control of body temperature. This is characterized by a preference for cooler ambient (Ta) and deep body temperatures (Tb) when placed in a temperature gradient. To elucidate the presence of this effect in mammals, the selected Ta and Tb of three rodent species (mouse, hamster, and rat) were measured while subjected to graded hypoxia in a temperature gradient. Individual animals were placed in the gradient for 30 min. Oxygen content of air entering the gradient was then reduced to a constant level for a period of 60 min by dilution with nitrogen. Tb was significantly reduced in all species at %O2 levels of 5.5-10%. Selected Ta was significantly reduced in the mouse at %O2 levels of 5.5 and 7.3%. Selected Ta of the hamster and rat were reduced slightly at %O2 levels of 5.8 and 7.4%, respectively; however, the effect was not statistically significant. To clarify the effects of hypoxia in these two species, the sample size of rat and hamster was increased to strengthen statistical analysis, and the animals were exposed for 60 min to %O2 levels of 7.4 and 6.7%, respectively. Both species exhibited a significant reduction in selected Ta during hypoxia concomitant with hypothermia. These data support the hypothesis that hypoxia lowers the set point for the control of body temperature in rodents.
Chemoreception for an insoluble nonvolatile substance: starch taste?
Authors: Ramirez I.
Published: December 2017

Substances that are insoluble in both water and lipids, such as starch, are commonly assumed to be tasteless. Starch was suspended in water with a viscous gum. Rats given a choice of fluid containing starch and the same fluid without starch consistently preferred fluids containing starch. Rats were able to detect as little as 0.5% starch from several species of plants (corn, rice, wheat, and potato). In contrast, rats ignored comparable concentrations of cellulose suspended in water. Rats were also capable of choosing the fluid containing higher levels of starch when given a choice of 1 vs. 2% starch or 0.5 vs. 1% starch. This ability to detect starch did not appear to be mediated by salivary alpha-amylase because 1) raw starch is highly resistant to hydrolysis by salivary amylase, 2) starch preference was not correlated with the susceptibility of the starch to hydrolysis by salivary amylase, and 3) starch preference was not blocked by partial or extensive desalivation. Attempts to extract impurities with either organic solvents or water did not provide any evidence that such impurities contribute to starch preference. These experiments point to a seemingly novel form of chemoreception that could be useful to animals that need to identify starch-rich foods.
Hemodynamic responses to acute volume expansion in Dahl salt-sensitive rats
Authors: Reddy R. S. , Baylis C. , Kotchen T. A.
Published: December 2017

The purpose of this study is to evaluate hemodynamic responses to acute volume expansion in chronically instrumented, conscious Dahl salt-sensitive (Dahl-S) and Dahl salt-resistant (Dahl-R) rats that have been maintained on either 0.45% NaCl, 1% NaCl, or 7% NaCl (5 days) intakes. Total peripheral resistance (TPR), but not arterial pressure, was increased by 5 days of 7% NaCl in Dahl-S (P less than 0.05) but not in Dahl-R. In Dahl-S, but not in Dahl-R, right atrial pressure increased with increasing dietary NaCl (P less than 0.05). On the 0.45% NaCl intake, atrial pressure did not differ in the two strains, whereas on both the 1 and 7% NaCl diets atrial pressure was higher in Dahl-S than in Dahl-R (P less than 0.05). In response to acute extracellular fluid volume expansion, arterial pressure did not change, and cardiac output increased in Dahl-S and in Dahl-R. On the 0.45% NaCl intake, TPR decreased (P less than 0.01) similarly in response to volume expansion in both strains; however, on the 1% NaCl intake TPR decreased in Dahl-R (P less than 0.05) but not in Dahl-S. In contrast, in animals fed 7% NaCl for 5 days, TPR decreased acutely in Dahl-S (P less than 0.01) but not in Dahl-R. These observations suggest that cardiopulmonary baroreflex activity is impaired in Dahl-S on a 1% NaCl intake, possibly as a consequence of elevated right atrial pressure. This alteration of the cardiopulmonary baroreflex may contribute to increased TPR in Dahl-S on a high-NaCl intake.
Effect of hepatic vagotomy on hormonal response to exercise in gluconeogenesis-inhibited rats
Authors: Cardin S. , Lavoie J. M. , Trabelsi F.
Published: December 2017

The liver, through the afferent pathway of the hepatic vagus nerve, has been reported to influence the hormonal response to exercise in adrenodemedullated rats. The present investigation was designed to evaluate the role played by gluconeogenesis in this hepatic influence. To this end, we studied the effects of a selective hepatic vagotomy on the hormonal response to a 30-min treadmill run (26 m/min, 0% grade) in adrenodemedullated rats injected with 3-mercaptopicolinic acid, a gluconeogenic inhibitor. Hepatic vagotomy was associated with small but significant higher (P less than 0.05) elevations of peripheral blood glucose levels at rest and after exercise. No significant differences were observed between hepatic-vagotomized and sham-operated rats in either resting or exercising levels of liver glycogen, portal glucose, portal and peripheral insulin and glucagon, and peripheral epinephrine and norepinephrine. All hormonal responses, with the exception of epinephrine, were either decreased or increased similarly in the two experimental conditions after exercise. These data indicate that contrary to what has been reported in rats with an intact capacity for gluconeogenesis, hepatic-vagotomized and sham-operated rats with an inhibited gluconeogenesis had similar hormonal responses to exercise. It is concluded that gluconeogenesis plays a role in the afferent neural influence exerted by the liver via the hepatic vagus nerve in the regulation of hormonal response to exercise.