bluuebunny/crossref_metadata_2025 huggingface dataset:
Potassium-induced relaxation in vascular smooth muscle of ground squirrels and rats
Authors: Harker C. T. , Webb R. C.
Published: December 2017

This study was designed to assess differences in potassium-induced relaxation in two rodents, the Sprague-Dawley albino rat and the 13-lined ground squirrel, Citellus tridecimlineatus. Femoral arteries from both species were cut into helical strips for isometric force recording. After norepinephrine-induced contraction in potassium-free solution, the arterial strips relaxed in response to the introduction of potassium (0.25-20 mM) into the bath. Potassium-induced relaxation was greater in rat than ground squirrel arteries. The concentrations required to induce half-maximal relaxation were approximately 2.5 mM for both species. Potassium-induced relaxation varied with the duration of incubation in potassium-free solution, and with the contractile magnitude induced by varying norepinephrine concentrations. Ouabain inhibited potassium-induced relaxation, with the ground squirrel showing greater sensitivity to the cardiac glycoside than did the rat. Acute cooling (from 37 to 17 degrees C) caused a reduction of the contractile response to norepinephrine in rat arteries, whereas those taken from ground squirrels maintained contractions at, or above, those attained at 37 degrees C. In addition, potassium-induced relaxation in ground squirrel vessels was more sensitive to inhibition by cold than it was in those from the rat. The results show that the characteristics of potassium-induced relaxation (ouabain and temperature sensitivity, magnitude of response, etc.) are species related (ground squirrel vs. rat).
Increased synthesis and release of atrial peptide during DOCA escape in conscious dogs
Authors: Metzler C. H. , Gardner D. G. , Keil L. C. , Baxter J. D. , Ramsay D. J.
Published: December 2017

The escape from the sodium-retaining effects of prolonged mineralocorticoid treatment in animals and humans was first noted over 40 yr ago, but despite intense study the mechanisms responsible for the escape phenomenon have not been identified. Putative “natriuretic hormones” have been proposed to account for the escape phenomenon. To determine whether atrial natriuretic peptides (ANP) could participate in the escape phenomenon, the mineralocorticoid deoxycorticosterone acetate (DOCA) was administered to conscious dogs for 14 days. Escape was accompanied by a doubling of plasma ANP concentration and four- to sevenfold increases in cardiac ANP messenger RNA. There were also significant increases in mean arterial blood pressure during the last 8 days of DOCA treatment. Thus increases in the synthesis and secretion of ANP and increases in atrial pressure may represent mechanisms that contribute to the escape from mineralocorticoid-induced sodium retention.
Fragility and composition of growing rat bone after one week in spaceflight
Authors: Patterson-Buckendahl P. , Arnaud S. B. , Mechanic G. L. , Martin R. B. , Grindeland R. E. , Cann C. E.
Published: December 2017

To gain some insight into the early effects of spaceflight on skeletal metabolism, we quantified the major chemical constituents and a noncollagenous protein, osteocalcin, in the third-lumbar vertebrae and humeri from 8-wk-old rats that were part of the 7-day NASA Spacelab 3 flight experiments. The ratio of calcium to hydroxyproline in the humeral diaphysis increased from 8.5 in preflight to 9.8 in ground simulation control and only to 8.9 in flight bones. There was no demonstrable change in the fraction of nonmineralized collagen. Osteocalcin content was reduced in the humerus and vertebra. Reduced accumulation of mineral and osteocalcin with no associated decrease in collagen in flight animals suggests that both mineralization and collagen metabolism are impaired in growing animals during spaceflight within a few days after launch. Strength tests of the humeri of flight rats showed substantial deficits that appeared to be related, not only to the reduced bone mass, but also to the composition and quality of new bone formed.
Restricted daily feeding during nursing period resets circadian locomotor rhythm of infant rats
Authors: Honma S. , Honma K. , Hiroshige T.
Published: December 2017

Phase setting of the circadian rhythm by restricted daily feeding (RF) was examined in rat pups. Feeding of virgin, pregnant, and nursing rats together with pups was restricted to 4 h at a fixed time of the day. Phases of the circadian rhythm developed in neonatally blinded pups were measured on the day of weaning to evaluate the effect of RF on phase setting. The activity onset and offset of the locomotor rhythm were used for the phase reference. In blinded pups born and raised under ad libitum feeding, the phase at weaning was a function of the free-running period measured after weaning and located in a narrow range (control zone). When RF was imposed from 2 wk prior to the conception (C) until weaning (3w), the pups phases were located outside the control zone and related to the feeding time. To identify the period in which the phase setting is effective, RF was imposed during 5 different periods (C-0w, C-1w, C-2w, 2-6w, and 3-6w). The circadian rhythm of all pups in the C-2w group and some in the C-1w was phase set, but those in other groups were not affected. It is concluded that RF imposed during the early nursing period is capable of phase setting the circadian system of blinded infant rats.x
Time course of radiolabeled 2-deoxy-D-glucose 6-phosphate turnover in cerebral cortex of goats
Authors: Pelligrino D. A. , Miletich D. J. , Albrecht R. F.
Published: December 2017

The in vivo dephosphorylation rate of 2-deoxy-D-glucose 6-phosphate (DGP) in the cerebral cortex of goats injected intravenously with radiolabeled 2-deoxy-D-glucose (DG) was investigated. Serial rapidly frozen samples of parietal cortical gray tissue were obtained at regular intervals over time periods from 45 min to 3 h in awake goats or in paralyzed and artificially ventilated goats maintained under 70% N2O or pentobarbital sodium anesthesia. The samples were analyzed for glucose content and separate DG and DGP activities. The rate parameters for phosphorylation (k3*) and dephosphorylation (k4*) were estimated in each animal. The glucose phosphorylation rate (PR) was calculated over the intervals 3-5 (or 6), 3-10, 3-20, 3-30, and 3-45 min, assuming k4* = 0. As the evaluation period was extended beyond 10 min, the calculated PR became increasingly less when compared with that calculated over the 3- to 5- (or 6) min interval (PRi). Furthermore, as metabolic activity decreased, the magnitude of the error increased such that at 45 min pentobarbital-anesthetized goats underestimated the PRi by 46.5% compared with only 23.1% in N2O-anesthetized goats. This was also reflected in the greater than twofold higher k4*/k3* ratio in the pentobarbital vs. N2O-anesthetized group. It is concluded that when using the DG method in the goat, DGP dephosphorylation cannot be ignored when employing greater than 10-min evaluation periods.
Acid-base balance in ducks (Anas platyrhynchos) during involuntary submergence
Authors: Shimizu M. , Jones D. R.
Published: December 2017

Measurements of all the major independent variables [arterial CO2 tension (PaCO2); strong-ion difference ([SID]), and total protein content, which approximate total weak acid concentration in plasma] are essential for understanding changes in acid-base balance in plasma. During involuntary submergence of 1, 2, or 4 min, PaCO2 in ducks increased and arterial pH (pHa) decreased. During 1-min dives there were no significant changes in any strong ions. In both 2- and 4-min dives, there was a significant increase in [lactate-], but because of an increase in equal magnitude of [Na+], [SID] did not change. During recovery from all dives the plasma remained acidotic for several minutes, although PaCO2 fell below predive levels in less than 1 min. [Lactate-] increased in the recovery period. There were no changes in total protein content during submergence or recovery. Breathing 100% O2 before 2-min dives caused a reduction in [lactate-] production and release during and after the dive, although due to a marked increased in PaCO2, pHa fell as low as in 4-min dives after breathing air. After 1 min of recovery, pHa returned to normal along with the restoration of the predive level of PaCO2. We conclude that the acidosis during involuntary submergence is due solely to an increase in PaCO2, whereas in recovery it is caused by decreased [SID].
Atrial natriuretic peptide blocks renin response to renal hypotension
Authors: Scheuer D. A. , Thrasher T. N. , Quillen E. W. , Metzler C. H. , Ramsay D. J.
Published: December 2017

We have reported that the renin response to systemic hypotension is inhibited in the presence of elevated atrial pressure and that elevations in atrial pressure of similar or larger magnitude cause graded increases in plasma atrial natriuretic peptide (ANP). Therefore we tested the hypothesis that comparable increments in plasma ANP can inhibit renal hypotension-induced increases in plasma renin activity (PRA) in conscious dogs. Renal perfusion pressure was controlled using cuffs implanted around the abdominal aorta just above the renal arteries. Reducing renal perfusion pressure by 10 or 30% of control caused graded increases in PRA (P less than 0.01). Infusion of 1-28 rat ANP (5 ng X kg-1 X min-1), which increased plasma ANP by 34.8 +/- 7.5 (SE) pg/ml, eliminated increases in PRA in response to a 10% reduction in renal perfusion pressure and markedly inhibited the response to a 30% pressure reduction (P less than 0.01). These results indicate that increments in plasma ANP which reproduce endogenous release inhibit renal hypotension-induced stimulation of PRA. Furthermore, the results provide an explanation for the inhibition of the renin response to renal hypotension during elevated atrial pressure.
Distribution of antithrombin III in rabbits: role of host and protein
Authors: Regoeczi E.
Published: December 2017

Unlike in the case of some other species, the plasma curve of iodine-labeled antithrombin III (I-AT-III) in rabbits requires fitting with a three-term exponential function for obtaining reliable estimates of the catabolic rate and distribution of I-AT-III among various body compartments (Carlson, Atencio, and Simon. J. Clin. Invest. 74: 191-199, 1984). To decide whether this phenomenon is referable to the host or the protein, the behavior of rabbit and human I-AT-III was comparatively analyzed in rabbits. Data obtained with rabbit I-AT-III confirmed the findings by Carlson and co-workers. Human I-AT-III assumed a distribution that closely paralleled that of homologous I-AT-III, thus suggesting that the pattern of distribution is determined by the host species rather than its AT-III. Rabbits metabolized human I-AT-III 1.61 times faster than homologous I-AT-III by an unknown mechanism not involving immune response; a facet that may prove useful for the identification of the sites of catabolism of AT-III. The exponent of the body weight was calculated for the relationship between species size and AT-III turnover. A value of 0.5 was obtained that is distinctly lower than the exponents found earlier for some other plasma proteins.
Resistance to diet-induced obesity: food intake, pancreatic sympathetic tone, and insulin
Authors: Levin B. E. , Triscari J. , Hogan S. , Sullivan A. C.
Published: December 2017

After 15 wk on a moderately high-calorie high-fat (CM) diet, 43% of 40 3-mo-old male Sprague-Dawley rats developed diet-induced obesity (DIO) (29% more weight gain), whereas 57% of diet-resistant (DR) rats gained no more weight than 20 chow-fed controls. When switched to chow for another 7 wk, DR rats ate 13% less, gained 55% less weight, and had 49% lower food efficiency, whereas DIO rats ate 4% less but had comparable weight gain and efficiency to controls. DIO rats had 29% more carcass lipid (percent of carcass weight). DIO rat retroperitoneal white adipose pads had 65% more cells that were the same size as those in chow-fed pads; DR rat cells were similar to controls. Both DR and DIO rats increased norepinephrine turnover in their interscapular brown adipose pads by greater than 90%. DIO rats also had 40% lower pancreatic turnover; their plasma insulin levels were 327% of controls after 15 wk on the CM diet and 188% after 7 wk on chow. DR levels were the same as controls at both times. Therefore, regulation of caloric intake, pancreatic sympathetic tone, and plasma insulin levels were three important differences between rats that resisted and those that developed DIO on high-energy diets.
Inhibition of renal nerve sympathetic activity by spinal stimulation in rat
Authors: Schramm L. P. , Livingstone R. H.
Published: December 2017

We determined the physiological and anatomical properties of systems mediating renal nerve inhibition elicited by electrical and chemical stimulation of the cervical dorsolateral funiculus of the anesthetized spinally transected rat. Stimulus-response characteristics suggested that this system was well suited for a role in tonic inhibition of sympathetic activity. Inhibition was elicited from a region of the cervical spinal cord extending from a lateral position near the accessory nerve to the dorsal columns. Inhibition could not be elicited by spinal stimulation before lesions had been placed rostral to stimulation sites in the lateral funiculi. Inhibition was blocked by similarly placed lesions caudal to stimulation sites. Therefore, this system may course in the lateral funiculus, and it may be tonically active in intact rats. Renal sympathetic activity could be inhibited by electrical stimulation caudal to large, chronic, spinal lesions. Therefore, some component of the inhibitory system was either antidromically activated or propriospinal. Glutamate applied to the dorsolateral surface of the cervical spinal cord elicited inhibition indistinguishable from that elicited by electrical stimulation, which suggested that neurons with somas located superficially at cervical levels may be responsible for some component of the spinally elicited inhibition.
Does a decrease in cortisol negative feedback efficacy precede ovine parturition?
Authors: Wood C. E.
Published: December 2017

In sheep and other ruminants parturition is stimulated by increased secretion of fetal cortisol. The mechanism of this increased fetal adrenal activity is not known, but may be dependent on a decreased fetal hypothalamopituitary sensitivity to the negative feedback inhibition by cortisol. Seven fetal sheep (129-142 days gestation), chronically prepared with vascular catheters, were infused with cortisol (10 micrograms/min; n = 5) or vehicle (n = 4) for 5 h. Cortisol infusion increased fetal plasma cortisol to 50.8 +/- 4.3 ng/ml, approximately 33 ng/ml above the corresponding plasma cortisol concentration in the vehicle-infused fetuses. One hour after the end of the cortisol or vehicle infusion, infusion of sodium nitroprusside (50 micrograms/min, iv) increased fetal plasma adrenocorticotropin hormone (ACTH) concentration in both groups of fetuses. Results of another study (15) demonstrated that increases in fetal plasma cortisol of only 1.7 ng/ml for 5 h in younger (117-131 days gestation) fetuses completely blocked the fetal ACTH response to the same dose of nitroprusside. The results indicate that the preparturient rise in fetal ACTH is accompanied by a decrease in cortisol negative feedback.
Arterial baroreceptor and vagal inputs to sympathoexcitatory neurons in rat medulla
Authors: Sun M. K. , Guyenet P. G.
Published: December 2017

Lumbar sympathetic nerve discharge and unit activity of reticulospinal sympathoexcitatory (SE) neurons located in nucleus paragigantocellularis lateralis (PGCL) were recorded in rats. The sympathoinhibition produced by low-frequency stimulation of vagal afferents was abolished by bilateral microinjections of 20 pmol of bicuculline methiodide (BIC, a GABA-receptor antagonist) into PGCL and was converted into a pressor response by injections of 100 pmol. These BIC injections also inhibited the arterial baroreflex in a dose-dependent manner. In contrast the sympathoexcitation produced by high-frequency stimulation of vagal afferents was selectively blocked by bilateral injections of kynurenic acid (KYN, a Glu-receptor antagonist) into PGCL. Convergence of vagal excitatory, vagal inhibitory, and arterial baroreceptor inputs was detected in all SE neurons recorded. Single-pulse stimulation of vagal afferents produced up to two peaks of excitation of SE neurons, both blocked by iontophoretic applications of KYN and at least one inhibitory period selectively blocked by iontophoresis of BIC. The results emphasize the importance of SE neurons and surrounding area in integrating the brain vasomotor output to spinal preganglionic neurons.
A rapid bioassay for quantification of atrial natriuretic polypeptides
Authors: Matsui K. , Kimura T. , Ota K. , Shoji M. , Inoue M. , Iitake K. , Yoshinaga K.
Published: December 2017

A quantitative bioassay for the detection and quantification of atrial natriuretic polypeptides (ANPs) was developed in a pentobarbital-anesthetized rat. Ten percent mannitol in 0.9% saline was infused to achieve stable diuresis. The conductivity of the urine, urine flow, and blood pressure were continuously recorded. A bolus injection of synthetic alpha-human atrial natriuretic polypeptide (alpha-hANP) elicited dose-dependent increases in the urine conductivity, sodium excretion, and urine volume. Changes in the urine conductivity correlated significantly with the increase in sodium excretion. By use of changes in urine conductivity, biological ANP activity of crude rat atrial extract was determined. Atrial contents of ANP in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were 25.5 +/- 1.2 microgram per atrium (n = 4) and 25.1 +/- 0.8 (n = 5) in euhydration. They were increased to 27.0 +/- 1.1 micrograms (n = 4) and 29.3 +/- 1.3 (n = 5, P less than 0.05), after 5-day water deprivation, respectively. This assay procedure provides a good tool for rapid and quantitative determination of ANPs.
Homeostatic control of manganese excretion in the neonatal rat
Authors: Ballatori N. , Miles E. , Clarkson T. W.
Published: December 2017

Previous studies in neonatal and suckling animals showed that immature animals have a greatly diminished capacity to excrete manganese and therefore were considered to be unable to regulate tissue manganese concentrations. In contrast, the present studies indicate that suckling rats have the capacity to excrete excess manganese at rates nearly comparable to those of adults. Eight- to 10-day-old rats given a tracer dose of 54MnCl2 (essentially carrier free), either via gavage or by intraperitoneal injection showed little elimination of the 54Mn until the 18-19th day of life, when there was an abrupt increase in the rate of the metal's excretion. However, when manganese was given in doses of 1 and 10 mg/kg, the young animals excreted from 30-70% of the dose in only 4 days, at which time a new rate of excretion was achieved. This enhanced rate of excretion remained constant until the 18-19th day of life, when it was again accelerated. Biliary excretion of manganese, the primary route for the elimination of the metal, was only 30-60% lower in 14-day-old rats compared with adults at doses ranging from tracer to 10 mg 54Mn/kg. For both the 14-day-old and adult rats, an apparent biliary transport maximum was reached at a dose of 10 mg Mn/kg. These studies indicate that the excretory pathways for manganese are well developed in the neonatal rat. The avid retention of tracer quantities of manganese by the neonate may be a consequence of the scarcity of this essential trace metal in its diet.
Acute effects of dietary protein on food intake, tissue amino acids, and brain serotonin
Authors: Peters J. C. , Harper A. E.
Published: December 2017

Male rats (100 g) previously adapted to a 20% casein diet were fed diets containing from 0 to 55% of casein and were killed after 20, 60, 150, 240, or 330 min. Food intake of rats fed a protein-free diet or a diet containing greater than 35% of casein was depressed within 20 min and remained depressed for up to 5.5 h. Depressed food intake of rats fed protein-free diets was accompanied by a rapid reduction in plasma and brain total concentrations of free indispensable amino acids (IAA). Food intake depression among groups fed diets containing in excess of 35% casein was associated with elevated plasma and brain total IAA concentrations, compared with those of animals fed diets containing 15-20% of casein. No consistent relationships were observed between food or protein intakes and whole-brain concentrations of 5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, or their sum. Our results suggest that in animals fed a single diet, food intake is depressed if the total concentration of free IAA in brain either falls below a certain critical minimum or exceeds some maximum tolerable level.
Matching of vertebrate cardiac energy demand to energy metabolism
Authors: Driedzic W. R. , Sidell B. D. , Stowe D. , Branscombe R.
Published: December 2017

Concentrations of high-energy phosphates and activities of key enzymes of energy metabolism were assessed in hearts from species with differing levels of cardiac power output. Positive correlations were found between resting power output and the total adenylate pool and between citrate synthase activity and the total adenylate pool. Maximum in vitro activity levels of enzymes from energy metabolism were compared with calculated resting cardiac power output and maximal cardiac power output (as reflected by total oligomycin-insensitive adenosine-triphosphatase activity). Three indexes of carbohydrate metabolism (hexokinase, pyruvate kinase, and L-lactate dehydrogenase) all plateau at relatively low levels of energy demand. In contrast, enzymes required for aerobic fatty acid metabolism, (carnitine palmitoyltransferase and 3-hydroxyacyl-CoA dehydrogenase) and for tricarboxylic acid and electron transport (citrate synthase and cytochrome-c oxidase) show consistent increases as ATP demand is elevated. It appears that as capacity for power development by vertebrate hearts, increases across taxa, the elevated demand for ATP is met by expansion of fatty acid based aerobic metabolism and not carbohydrate metabolism.
Beta-endorphin, ACTH, and cortisol response to hemorrhage in conscious pigs
Authors: O'Benar J. D. , Hannon J. P. , Peterson J. L. , Bossone C. A.
Published: December 2017

Some of the interrelations of neuroendocrine changes associated with hypovolemia were investigated in a model simulating an arterial hemorrhage. beta-Endorphin, adrenocorticotropin hormone (ACTH), and cortisol levels were measured by radioimmunoassay before, during, and after controlled bleeding of conscious splenectomized pigs. All animals showed significant (P less than 0.05) increases in the three neuroendocrine substances during hemorrhage. beta-Endorphin values initially were 55 +/- 7 pg/ml (+/- SE) and rose to a peak of 386 +/- 44 pg/ml at the nadir of blood pressure (mean arterial pressure = 47.5 mmHg). ACTH showed a similar pattern, increasing from 49 +/- 10 to a peak of 518 +/- 56 pg/ml. Cortisol values reached their peak of 18.2 +/- 2.5 micrograms % during the recovery phase. beta-Endorphin values displayed a close inverse correlation to blood pressure during hemorrhage, but returned to basal levels more rapidly than blood pressure during the recovery period. Plasma ACTH levels rose significantly more slowly than beta-endorphin as the hemorrhage progressed. An equimolar ratio of ACTH and beta-endorphin returned only as levels declined following the hemorrhagic insult. In awake pigs therefore an arterial hemorrhage is accompanied by endorphin release proportional to the decrement in blood pressure, a somewhat retarded buildup of ACTH, and a still later cortisol peak during recovery.
Thermogenic activity and capacity of brown fat in fasted and refed golden hamsters
Authors: Levin I. , Trayhurn P.
Published: December 2017

The effects of different food deprivation regimens on the thermogenic activity and capacity of brown adipose tissue in the golden hamster have been investigated. Thermogenesis in the tissue was assessed by measurements of tissue cytochrome-c oxidase activity, mitochondrial GDP binding, and the specific mitochondrial concentration of uncoupling protein. The thermogenic activity and capacity of brown adipose tissue were found to be markedly reduced in fasted or underweight hamsters. Measurements of cytochrome-c oxidase activity indicate that the reductions were caused exclusively by a loss in mitochondrial mass, uncoupling protein concentration and GDP binding to mitochondria remaining unchanged. The decrease in brown adipose tissue thermogenesis was associated with a reduction in the capacity for nonshivering thermogenesis in the whole animal. Hamsters recovered from weight losses without increasing their food intake, and the recovery was accompanied by a normalization in mitochondrial mass in brown adipose tissue. Mitochondrial mass was, however, restored only after 10 days of ad libitum refeeding. These results suggest that the reduction in energy expenditure in the fasted hamster could relate to a decrease in brown adipose tissue thermogenesis, in addition to the previously reported decreases in resting metabolic rate and locomotor activity. Reductions in thermogenesis may also represent a further mechanism by which energy stores recover in the golden hamster without postfast hyperphagia.
Myocardial adaptation to endurance exercise training in diabetic rats
Authors: Paulson D. J. , Kopp S. J. , Peace D. G. , Tow J. P.
Published: December 2017

The purpose of this study was to determine whether exercise training would prevent the progressive functional decline in pump function of hearts from diabetic rats. Four groups were studied: sedentary control, trained control, sedentary diabetic, and trained diabetic. Trained rats were adapted to the treadmill prior to induction of diabetes in half of the group streptozotocin injected (50 mg/kg). Thereafter the duration, speed, and grade were then progressively increased until the trained rats could run for 60 min at 27 m/min, 5% grade (wk 8). Cardiac output and work were measured in isolated working hearts perfused at various left atrial filling pressures and with buffer containing the concentrations of glucose and fatty acids found in vivo. Sedentary diabetic rats had lowered body weight, elevated plasma glucose, triacylglycerol, and cholesterol. Exercise training of diabetic rats lowered plasma triacylglycerol levels. Training increased plantaris muscle cytochrome oxidase activity significantly in both the trained control and trained diabetic groups. Cardiac pump function was impaired in hearts from the sedentary diabetic rats perfused with either normal or diabetic substrate conditions, but the impairment was larger under diabetic conditions. Training of diabetic rats prevented this depression. Myocardial carnitine content was decreased in hearts from sedentary diabetic rats. Exercise training increased carnitine content in both control and diabetic rats. This training protocol did not affect cardiac pump function of the trained control group. These results suggest that exercise training may limit the myocardial contractile dysfunction associated with diabetes mellitus.
Solvent flow in osmosis and hydraulics: network thermodynamics and representation by bond graphs
Authors: Atlan H. , Thoma J.
Published: December 2017

A tutorial introduction to network thermodynamics and bond graphs as a modeling technique for any physiochemical system is presented with a particular emphasis on reaction diffusion systems. It combines the generality of nonequilibrium thermodynamics with the advantages of a graph theory. It is applied to the representation of osmotic and hydraulic flows across a semipermeable membrane on the basis of the solvent diffusion theory of osmosis. This theory allows for an easy derivation of the van't Hoff law of osmotic pressure from the Fick law of diffusion. Molar flows and volume flows are transformed into one another by transducers, the modulus of which is the partial molar volume of water, in such a way that power is conserved by a reciprocal transformation between the chemical potential and the pressure. Osmotic and hydraulic resistances are calculated, and their dependence on pore size is estimated.
Effects of daily melatonin injections on activity rhythms of rats in constant light
Authors: Chesworth M. J. , Cassone V. M. , Armstrong S. M.
Published: December 2017

Although from pinealectomy studies the pineal body does not appear to participate in the generation of circadian rhythms of mammals, daily injections of the pineal hormone melatonin entrain free-running locomotor activity rhythms of rats in constant darkness. The aim of the present study was to determine whether rats whose circadian activity and drinking rhythms were disrupted in constant light (LL) could be synchronized by daily melatonin administration. Rats were subjected to a regime of gradually increasing photoperiod until they were maintained in LL. Rats whose rhythms became disrupted or showed intact free-running rhythms were injected daily with either melatonin (1 mg/kg) or vehicle (ethanol-saline) solution. Daily melatonin injections either synchronized or partly synchronized disrupted circadian patterns of activity. In contrast to previous findings from experiments conducted in constant darkness, melatonin did not entrain but only partly synchronized intact free-running rhythms. Results are interpreted in terms of melatonin acting on the coupling or phase relationships between oscillators generating circadian locomotor activity rhythms.
Adaptation of circadian rhythmicity to shift in light-dark cycle accelerated by a benzodiazepine
Authors: van Reeth O. , Turek F. W.
Published: December 2017

The light-dark cycle is the major synchronizing agent for circadian rhythms in animals. After an abrupt shift in the light-dark cycle, it usually takes many days for circadian rhythms to resynchronize. A single injection of the short-acting benzodiazepine, triazolam, to hamsters subjected to an 8-h advance of the light-dark cycle resulted in an approximately 50% reduction in the time taken for the circadian locomotor activity rhythm to be resynchronized to the new lighting schedule. These results suggest that it may be possible to use drugs to facilitate the resynchronization of human circadian rhythms following an abrupt change in environmental time.
Potassium secretion by nasal salt glands of desert lizard Sauromalus obesus
Authors: Shuttleworth T. J. , Thompson J. L. , Dantzler W. H.
Published: December 2017

Potassium secretion by the nasal salt glands of the herbivorous desert lizard Sauromalus obesus was determined in vivo by a new technique. Intraperitoneal injection of KCl rapidly increased the potassium secretion rate from 0.28 to 15.35 mumol X 100 g-1 X h-1. A second identical intraperitoneal injection, given 15 h after the first, further increased potassium secretion to 50.09 mumol X 100 g-1 X h-1. This was associated with a doubling of plasma K+ concentration and salt gland Na+-K+-adenosinetriphosphatase (ATPase) activity. Neither salt gland weight or residual (Mg2+) ATPase activity were affected. In an isolated perfused head preparation, potassium secretion from the nasal salt glands was stimulated from 0.99 to 10.76 mumol X 100 g-1 X h-1 by methacholine and to 14.68 mumol X 100 g-1 X h-1 by forskolin. In this perfused preparation, simultaneous determination of salt gland perfusion flow (using radiolabeled microspheres) and the rate of potassium secretion revealed that the secreting glands removed 68% of the perfusing potassium ions. Calculations indicated that secretion at the maximal rate observed in vivo would necessitate a fourfold increase in the rate of blood flow to the gland.
Comparison of corticotropin-releasing factor and acetylcholine on catecholamine secretion in dogs
Authors: Engeland W. C. , Lilly M. P. , Bruhn T. O. , Gann D. S.
Published: December 2017

To test whether corticotropin-releasing factor (CRF) is a secretagogue for adrenal secretion of catecholamines, a preparation was developed that permits measurement of adrenal venous output in response to in vivo arterial injection into the dog adrenal gland. Dogs were prepared with catheters in the lumboadrenal vein for monitoring adrenal blood flow and secretion rate of epinephrine and norepinephrine and in the lumboadrenal and inferior phrenic arteries for adrenal injection. Under pentobarbital anesthesia 48 h after surgery, dogs received a series of intra-adrenal injections that included acetylcholine (0.2-200 nmol), CRF (2.0-20.0 nmol), and diluent. There was a log dose-response relationship before epinephrine secretion and norepinephrine secretion to acetylcholine. Adrenal injection of CRF stimulated epinephrine and norepinephrine secretion at the highest dose tested (20 nmol). The response observed was equivalent to the response to 0.2 nmol acetylcholine. A similar dose of CRF given systemically produced hypotension without stimulating catecholamine responses. Adrenal catecholamine responses to acetylcholine were not augmented by addition of CRF. These findings show that arterial injection of CRF into the intact dog adrenal stimulates secretion of epinephrine and norepinephrine. However, the low potency of CRF relative to that of acetylcholine, the lack of a synergistic effect of CRF on catecholamine responses to acetylcholine, and the high dose of CRF required to achieve a response suggest that CRF does not function in the adrenal medulla as a physiologically important secretagogue for catecholamines.
Role of cardiac nerves in response to head-out water immersion in conscious dogs
Authors: Hajduczok G. , Miki K. , Hong S. K. , Claybaugh J. R. , Krasney J. A.
Published: December 2017

The circulatory, renal, and hormonal responses during 100 min of thermoneutral (37 degrees C) head-out water immersion (WI) were investigated in conscious intact (INT) and cardiac-denervated (CD) dogs. In the INT group, both left and right atrial and aortic transmural distending pressures and left ventricular contractile performance (LV dP/dtmax) increased, and total peripheral resistance remained unchanged. Cardiac output (QCO) increased in association with an increase in heart rate and LV dP/dtmax. Urine flow (V), sodium excretion (UNaV), and osmolal clearance (Cosmol) all increased, whereas glomerular filtration rate, as indicated by creatinine clearance (CCr), remained constant. The diuresis and natriuresis occurred in the absence of any significant changes in plasma levels of antidiuretic hormone (ADH), aldosterone, or plasma renin activity. The CD animals showed a similar hemodynamic response except that the increase in QCO was now associated with an increase in stroke volume and no change in heart rate or LV dP/dtmax. Although the increase in V was similar in both magnitude and time course of the INT animals, there was no significant change in UNaV. Thus there is a striking change in the character of the response of the denervated group in that the natriuresis is abolished and, instead, a water diuresis occurred. Free water clearance increased, but no significant changes in Cosmol or CCr were observed. In addition plasma ADH levels significantly declined during WI in the CD group. These data indicate that cardiac receptors are important in determining the nature of the renal response to WI.
A role for the ventral surface of the medulla in regulation of nasal resistance
Authors: Haxhiu M. A. , Strohl K. P. , Norcia M. P. , van Lunteren E. , Deal E. C. , Cherniack N. S.
Published: December 2017

Nasal resistance is known to be affected by changes in nasal blood volume and hence to depend on sympathetic discharge to nasal blood vessels. Structures located superficially near the ventrolateral surface of the medulla significantly affect respiratory and sympathetic activity and the tone of the trachea. To assess the importance of these structures on nasal patency, we measured transnasal pressure at a constant flow and examined the change in pressure produced by topically applied N-methyl-D-aspartic acid (NMDA). Experiments were performed in chloralose-anesthetized, paralyzed, and artificially ventilated cats. NMDA administered on the intermediate area of the ventral surface of the medulla decreased transnasal pressure and increased phrenic nerve activity. The response to NMDA could be diminished or abolished by application to the ventral medullary surface of the NMDA antagonist 2-amino-5-phosphonovalerate (2-APV) or the local anesthetic lidocaine. Carotid sinus denervation and posthypothalamic decerebration did not alter the nasal and phrenic nerve responses to NMDA; however, cervical sympathetic denervation decreased these responses, both in intact and in bilaterally adrenalectomized animals. Therefore, activation of NMDA receptors on structures near the ventral surface of the medulla increases tone in the nasal vasculature and leads to a response pattern that includes changes in not only phrenic nerve activity and blood pressure but also nasal patency.
Cortical control of thermogenesis induced by lateral hypothalamic lesion and overeating
Authors: De Luca B. , Monda M. , Pellicano M. P. , Zenga A.
Published: December 2017

Increased O2 consumption was found in rats after bilateral lesions of the lateral hypothalamus (LH) or during voluntary overeating. This phenomenon appears to be mediated by the sympathetic nervous system (SNS) in both conditions, since it is blocked by the beta-blocker propranolol administration. In the first experiment we showed that the brain cortex is involved in the thermogenesis induced by LH lesion and this effect is mediated by SNS, since bilateral functional decortication induced by cortical-spreading depression (CSD) impaired the increase of O2 consumption to the same extent as administration of propranolol. In the second experiment the role played by the cerebral cortex on thermogenesis in rats during voluntary overeating of "cafeteria" diet and in control rats was investigated. Cafeteria rats showed a significantly higher colonic temperature, brown adipose tissue temperature (Tbat), and rate of O2 consumption than control animals. CSD led to a significant decrease of Tbat and O2 consumption in cafeteria rats but not in controls. On the basis of the results obtained in the two experiments, the possibility that the cerebral cortex could be involved in the metabolic responses for reduction of body weight to the "set-point" is hypothesized.
Distribution of glycolysis and gluconeogenesis in perfused chicken kidney
Authors: Yorita K. , Yamano T. , Ikeda K. , Kobayashi T. , Shiota M. , Sugano T.
Published: December 2017

Regional metabolism of glucose in chicken kidneys was studied in kidneys perfused with either an arterial system or a portal system. Provided that kidneys were perfused with oxygenated buffer solution at a flow rate of 5 ml/min per gram of kidney in both perfusion systems, oxygenation of the kidney was achieved, as judged by the rates of O2 uptake and the formation of lactate, gluconeogenesis, and the ratio of lactate to pyruvate. The rate of formation of lactate and pyruvate during glucose metabolism, in the presence or absence of KCN, was markedly higher with the arterial system than with the portal system. The rate of gluconeogenesis was equal with both perfusion systems but the rate was modulated by the type of substrate used. With succinate as substrate, ouabain inhibited glucose production and O2 uptake in both perfusion systems. With lactate and pyruvate as substrate, ouabain had no effect on glucose production in both perfusion systems, whereas the inhibition of O2 uptake by ouabain was greater with the arterial system than with the portal system. From the viewpoint of the accepted morphological components of the blood supply, these results suggest that chicken renal gluconeogenesis occurs in the cortex and that glycolysis occurs in medullary structures.
Pulsatile secretion of growth hormone and insulin in relation to feeding in rats
Authors: Even P. , Danguir J. , Nicolaidis S. , Rougeot C. , Dray F.
Published: December 2017

In unrestrained male Wistar rats chronically implanted with intracardiac catheters, blood samples were taken every 20 min throughout the 24 h of the diurnal cycle. Plasma concentrations of growth hormone (GH), insulin, and glucose were measured. The pattern of food intake was continuously monitored. The existence of 3-h pulsatile cycles of GH secretion was confirmed. In addition, short bursts of insulin secretion were observed in the middle of every second GH peak-to-peak interval. Food intake appeared to be enhanced during short periods that corresponded with GH release into the blood and was reduced during the GH peak-to-peak periods in which the bursts of insulin secretion were observed. From these observations this study draws a schematic relationship between the rhythmicity of the secretion of GH and insulin and the probability of occurrence of feeding. We speculate that the rhythmic endocrine activity may be causally related to feeding.
Role of atrial natriuretic peptide in natriuresis in volume-expanded rats
Authors: Kaneko K. , Okada K. , Ishikawa S. , Kuzuya T. , Saito T.
Published: December 2017

Continuous intravenous infusion of rat atrial natriuretic peptide (rANP) was carried out for 60 min in urethan-anesthetized rats. Plasma rANP (PANP) levels during 0, 12.5, and 50 ng/min rANP infusion reached 20.9 +/- 3.4, 61.2 +/- 12.3, and 228 +/- 30.6 pg/ml, respectively. Urinary sodium excretion (UNaV) remained unchanged during the 0 and 12.5 ng/min rANP infusion. In contrast, the 50 ng/min rANP infusion resulted in a 5.6-fold increase in UNaV without significant changes in plasma aldosterone levels and glomerular filtration rate. Isotonic saline infusion (116 microliter/min for 60 or 120 min) caused a significant increase in UNaV. UNaV in an experimental model of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was 5.0 times greater than in control animals. PANP levels in 60- or 120-min saline-infused and SIADH rats were 46.3 +/- 6.7, 39.0 +/- 9.0, and 35.6 +/- 3.2 pg/ml, respectively. These values were significantly higher than control values but failed to achieve a level at which natriuresis occurred during the infusion of rANP. These results suggest that endogenous ANP may not play a critical role in the induction of acute natriuresis in volume-expanded states, although it could be partially involved in such a natriuretic response.
Calcium transport in turtle bladder
Authors: Sabatini S. , Kurtzman N. A.
Published: December 2017

Unidirectional 45Ca fluxes were measured in the turtle bladder under open-circuit and short-circuit conditions. In the open-circuited state net calcium flux (JnetCa) was secretory (serosa to mucosa) and was 388.3 +/- 84.5 pmol.mg-1.h-1 (n = 20, P less than 0.001). Ouabain (5 X 10(-4) M) reversed JnetCa to an absorptive flux (serosal minus mucosal flux = -195.8 +/- 41.3 pmol.mg-1.h-1; n = 20, P less than 0.001). Amiloride (1 X 10(-5) M) reduced both fluxes such that JnetCa was not significantly different from zero. Removal of mucosal sodium caused net calcium absorption; removal of serosal sodium caused calcium secretion. When bladders were short circuited, JnetCa decreased to approximately one-third of control value but remained secretory (138.4 +/- 54.3 pmol.mg-1.h-1; n = 9, P less than 0.025). When ouabain was added under short-circuit conditions, JnetCa was similar in magnitude and direction to ouabain under open-circuited conditions (i.e., absorptive). Tissue 45Ca content was approximately equal to 30-fold lower when the isotope was placed in the mucosal bath, suggesting that the apical membrane is the resistance barrier to calcium transport. The results obtained in this study are best explained by postulating a Ca2+-ATPase on the serosa of the turtle bladder epithelium and a sodium-calcium antiporter on the mucosa. In this model, the energy for calcium movement would be supplied, in large part, by the Na+-K+-ATPase. By increasing cell sodium, ouabain would decrease the activity of the mucosal sodium-calcium exchanger (or reverse it), uncovering active calcium transport across the serosa.
Ion fluxes during tetanic stimulation in isolated perfused rat hindlimb
Authors: Lindinger M. I. , Heigenhauser G. J.
Published: December 2017

The present study examined the relationships between changes in intra- and extracellular concentrations of strong ions, the appearance of nonvolatile acid (NVA) in venous perfusate, and skeletal muscle fatigue during intense electrical stimulation. A one-pass system was used to perfuse an isolated rat hindlimb during 5 min of intermittent tetanic contractions. Initial isometric tensions averaged 2.85 kg/hindlimb and declined by 45% during 5 min. During stimulation, intracellular lactate concentration ([La-]i) increased by 2, 13, 15, and 21 meq/l of intracellular fluid in the soleus, plantaris, and red and white gastrocnemius. This was associated with a proportionate decrease in intracellular K+ ([K+]i) and Mg2+([Mg2+]i) concentrations and increased intracellular Na+ ([Na+]i) and Cl-([Cl-]i) concentrations. A stoichiometrically equivalent uptake of Na+ and Cl- from the perfusate peaked at 8.5 mu eq.min-1.g-1 at the end of the 5th min. The increase in plasma [K+] during the last 4 min of stimulation was constant at 0.5 mu eq.min-1.g-1. A significant reduction in intracellular strong ion difference of all muscles contributed directly to an increase in [H+] during stimulation. After the 1st min of stimulation the rate of appearance of NVA in venous perfusate exceeded that of the increase in venous plasma [La-] by 12-fold; this decreased to 2.7-fold at the end of 5 min. La- release and NVA appearance in venous perfusate was maximal at 3.1 and 9.7 mu eq.min-1.g wet wt-1 during the 4th min of stimulation. It is concluded that the changes in the intracellular concentrations of strong ions during intense contractile activity are the primary factors contributing to skeletal muscle fatigue.
Effect of atriopeptin II on isolated opercular epithelium of Fundulus heteroclitus
Authors: Scheide J. I. , Zadunaisky J. A.
Published: December 2017

The effect of atriopeptin II (ANF) on the in vitro opercular epithelium was investigated by use of short-circuit current techniques. Serosal addition of ANF stimulates chloride secretion (short-circuit current) 19% above control values with a 7% increase in tissue conductance. Mucosal addition of ANF to the opercular epithelium was without effect. The ANF stimulation of the current was dose dependent with a maximum at 10(-7) M. The addition of ANF had no effect on the current or the conductance of opercular epithelia bathed in Cl--free Ringer. The opercular current could be stimulated above the ANF response by isoproterenol (10(-6) M). Pretreatment of the opercular epithelium with propranolol (10(-5) M) did not inhibit the stimulation of the short-circuit current by ANF but did inhibit the isoproterenol response indicating that the ANF stimulatory activity was independent of the beta-adrenergic receptors. The ANF-stimulated short-circuit current was found in operculi pretreated with tetrodotoxin (10(-6) or 10(-5) M) or diltiazem (10(-4) M) indicating the ANF response was not due to nerve stimulation. Pretreatment of opercular tissue with dibutyryl adenosine 3',5'-cyclic monophosphate, 8-bromoadenosine 3',5'-cyclic monophosphate, or 8-bromoguanosine 3',5'-cyclic monophosphate (10(-4) M) had no effect on the ANF stimulatory response. Opercular epithelia from short-term freshwater-adapted killifish also showed the ANF-induced response. The stimulation of chloride secretion in Fundulus heteroclitus chloride cells by ANF may have a role in teleost ion regulation.