bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal secretion of amino acids in ophidian reptiles
Authors: Benyajati S. , Dantzler W. H.
Published: December 2017

Net renal tubular secretion of endogenous beta-amino acids (taurine, beta-alanine, beta-aminoisobutyric acid) and their endogenous analogue (L-cysteic acid) was revealed in the olive sea snake, Aipysurus laevis, and in the garter snake, Thamnophis sirtalis, by renal clearance methods. The net secretory rates ranged from 16 to 795 nmol X kg-1 X h-1, with taurine being secreted at the highest rates. These rates of secretion are comparable to those observed in marine fish, the only other group of vertebrates exhibiting renal tubular secretion of L-amino acids under physiological conditions. However, only some snakes (8-58%) demonstrated net tubular secretion; the others (0-58%) showed net tubular reabsorption of these amino acids. Net tubular secretion was consistently observed whenever the filtered load of the amino acid was low, and net reabsorption was apparent whenever the filtered load was high; the two variables being significantly correlated. An analysis of the net amino acid transport rates, both secretory and reabsorptive, as a function of the filtered load suggests that in snakes the beta-amino acids are reabsorbed and secreted at discrete tubular sites, with the secretory sites located beyond the major reabsorptive sites. Taurine, beta-alanine, and L-cysteic acid appear to share a common transport system in the snake renal tubule cells.
Sympathetic nervous system and blood pressure maintenance in the Brattleboro DI rat
Authors: Williams J. L. , Johnson M. D.
Published: December 2017

Experiments were performed to determine the functional role of the sympathetic nervous system (SNS) in blood pressure regulation in Brattleboro diabetes insipidus (DI) rats and to determine the effects of synthetic arginine vasopressin (AVP) on sympathetic function in DI rats. The experiments were conducted in male age-matched Long-Evans (LE) and DI rats in the conscious unstressed state. Mean arterial pressure (MAP) and heart rate were similar in conscious unstressed LE and DI rats, but basal plasma concentrations of norepinephrine (NE) and epinephrine (E) were elevated in DI rats compared with LE rats. An intra-arterial bolus injection of hexamethonium (30 mg/kg) resulted in greater reductions of MAP in DI rats (-62 +/- 5 mmHg) than in LE rats (-42 +/- 7 mmHg; P less than 0.05). Administration of AVP to DI rats by osmotic minipump reduced plasma NE concentration in DI rats to a level not different from that in LE rats, but E concentration remained elevated. AVP administration to DI rats also reduced the hexamethonium-induced fall in MAP in these animals (-47 +/- 7 mmHg) to a level not different from that in LE rats. We conclude that the SNS plays a greater role in blood pressure maintenance in conscious DI rats than in LE rats and that AVP administration can normalize plasma NE concentration and the contribution of the SNS to blood pressure maintenance in these animals.
Development of bronchiolar epithelium in rats
Authors: Massaro G. D. , Massaro D.
Published: December 2017

We used ultrastructural and morphometric means to examine aspects of the regulation of the maturation of rat bronchiolar Clara cells and the development of the epithelium of small conducting airways in the perinatal period. We found the nuclear numerical density per cubed centimeter (Nvn) of Clara cells fell and the Nvn of ciliated cells increased from birth to age 60 days, the prenatal administration of a glucocorticosteroid (dexamethasone) to dams caused a 35% decrease in the Nvn of ciliated cells present at birth but did not alter the Nvn of Clara cells, the administration of dexamethasone to pups from postnatal days 1 to 6 did not alter the Nvn of bronchiolar Clara or ciliated cells present at age 7 days but did diminish the total number of lung cells as assessed by measurements of lung DNA, the administration of dexamethasone to dams from gestation days 18 to 20 or from gestation days 20 to 22 did not alter the volume density of Clara cell glycogen, secretory granules, rough endoplasmic reticulum, or mitochondria of pups at gestation day 21.5 or on the day of birth, and glucagon, epinephrine, and 8-bromoadenosine 3',5'-cyclic monophosphate resulted in a decrease of Clara cell glycogen when individually incubated in vitro for 4 h with bronchiolar tissue from rat fetuses 21.5 days of age.
Control of ingestion in 6-day-old rat pups: termination of intake by gastric fill alone?
Authors: Phifer C. B. , Sikes C. R. , Hall W. G.
Published: December 2017

Six-day-old rat pups, tested away from the dam, vigorously ingested orally infused milk for up to 90 min when the ingested milk was allowed to drain through a gastric fistula. Total intake in pups with unplugged fistulas was more than double that consumed by littermates with plugged fistulas. This persistent feeding could not be due to the absence of postgastric cues because blocking movement of the milk into the intestine with a closed pyloric noose resulted in less intake than when the noose was open. Furthermore, a 5% body weight gastric preload of milk or nonnutritive saline suppressed intake in pups with either open or closed pyloric nooses by an amount equal to the preload. Regardless of noose or preload condition, ingestion stopped when stomach content reached approximately 6.5% of body weight. Thus level of gastric fill appeared critical for intake control. When gastric fistulas were unplugged after pups had ingested milk until they stopped, vigorous ingestion followed, with total intakes of up to 20% body weight. Intake termination in young rat pups thus appears to be controlled exclusively by gastric fill level; pregastric signals alone appear insufficient, and postgastric signals appear unnecessary for termination of intake.
Peripheral circulatory responses to 96 h of hypoxia in conscious sinoaortic-denervated sheep
Authors: Krasney J. A. , Miki K. , McAndrews K. , Hajduczok G. , Curran-Everett D.
Published: December 2017

Conscious sheep exposed to 4 days of eucapnic hypoxia (arterial PO2 40 Torr, arterial PCO2 33 Torr) respond with sustained increases in heart rate, cardiac output, and coronary, cerebral, and respiratory muscle blood flows (Respir. Physiol. 59: 197-211, 1985). In the present investigation, seven adult ewes were studied during similar levels of hypoxia (arterial PO2 40 Torr, 4 days) after chronic section of the carotid sinus and aortic depressor nerves to determine the contribution of the arterial chemoreceptors to these responses. Ventilation and arterial PCO2 did not change, indicating that ventilatory acclimation did not occur. O2 consumption decreased by 24%. Cardiac output (thermodilution) increased by 12% for only 24 h, heart rate increased by 44-69% above normoxic levels for only 72 h, and stroke volume was unchanged. Systemic arterial pressure was unchanged, whereas pulmonary arterial pressure rose by 56%. Coronary flow (radio-labeled microspheres) increased from 155 +/- 50.4 (SE) to 299 +/- 81 ml X min-1 X 100 g-1 at 24 h and then declined to normoxic levels by 96 h. Cerebral flow rose from 62 +/- 6.5 to between 85 +/- 14.4 and 124 +/- 43.5 ml X min-1 X 100 g-1 for 96 h. These results indicate that the arterial chemoreflexes or reflexes secondary to increased ventilation are responsible for the continued elevation of heart rate, cardiac output, and coronary flow during eucapnic hypoxia.
Changes in blood pressure and extracellular fluid with taurine in DOCA-salt rats
Authors: Fujita T. , Sato Y.
Published: December 2017

The effect of taurine, a sulfur amino acid, on blood pressure and extracellular fluid volume in deoxycorticosterone acetate (DOCA)-salt hypertensive rats was studied. Uninephrectomized rats showed average systolic pressure of 175 +/- 3 mmHg after the 28 days of treatment with DOCA while receiving 1% NaCl solution to drink. The supplementation of 1 and 3% taurine could prevent the development of DOCA-salt hypertension in a dose-related fashion: average pressures on day 28 after these dosages were 126 +/- 2 and 104 +/- 2 mmHg, respectively. Exchangeable body sodium (sodium "space") at week 4 was significantly increased in DOCA-salt rats compared with that of the vehicle-injected control rats. Furthermore, the taurine supplement increased sodium space significantly in the DOCA-salt rats. Overall, there was a negative correlation between the systolic blood pressure and sodium space at week 4 in the taurine-supplemented DOCA-salt rats (r = -0.492, P less than 0.02), although there was a positive correlation between systolic pressure and sodium space in the DOCA-salt rats and the vehicle-injected control rats (r = 0.036, P less than 0.001). The results suggest that taurine loading may attenuate the rise in blood pressure associated with fluid retention during the DOCA-salt treatment and that the fall in blood pressure with its consequence for the renal circulation may be the cause of fluid retention.
Dietary obesity: brown fat denervation fails to alter development or recovery
Authors: Cox J. E. , Lorden J. F.
Published: December 2017

We assessed the effect of scapular brown adipose tissue (BAT) denervation on dietary obesity in adult female Sprague-Dawley rats. In rats maintained for 32 days on an obesity-inducing regimen, BAT denervation produced significant reductions in food intake (83.4 vs. 94.4 kcal/day), weight gain (66.0 vs. 103.5 g), and carcass fat (19.3 vs. 27.6%). A subgroup of denervates consuming as many calories as controls (94.1 kcal/day) failed to gain more weight (92.2 g) or accumulate more fat (25.4%) than controls. In rats developing obesity for 32 days followed by 8 days on laboratory chow, weight change was unaffected by denervation during either weight gain (89.4 vs. 87.1 g for controls) or weight loss (21.2 vs. 22.1 g) phases, as was carcass fat (21.0 vs. 20.4%). BAT norepinephrine utilization was unchanged in nondenervated obese rats and those recovering from obesity. We did not, therefore, find evidence that under these experimental conditions sympathetic activation of BAT countered obesity during overconsumption or contributed to recovery from obesity.
Renal opiate receptor mediation of renin secretion to renal nerve stimulation in the dog
Authors: Koyama S. , Hosomi H.
Published: December 2017

The present study was designed to evaluate renal opiate receptor mediation of the renin secretion response to electrical stimulation of the renal nerves in the pentobarbital sodium-anesthetized dog by use of the opiate agonist leucine-enkephalin (Leu-enk) and the opiate antagonist naloxone. In all animals studied, left kidneys were pump perfused at a constant renal blood flow. Renal perfusion pressure (RPP) and glomerular filtration rate (GFR) were unaltered at a stimulation frequency of 1.0 Hz; however, renin secretion rate (RSR) increased significantly in the nontreated group. High-frequency renal nerve stimulation (10 Hz) increased RPP and decreased GFR. RSR at the high-frequency stimulation was significantly augmented in the nontreated group. Renal arterial infusion of either Leu-enk (25 micrograms X kg-1 X min-1) or naloxone (7 micrograms X kg-1 X min-1) did not alter base-line levels of renal hemodynamics and RSR and did not produce significant changes in these variables even when renal nerves were stimulated at the low frequency; however, Leu-enk inhibited RPP and RSR responses to the high-frequency stimulation, and naloxone augmented these responses. Phentolamine (13 micrograms X kg-1 X min-1) prevented renal hemodynamic responses to the renal nerve stimulation, whereas RSR responses to the stimulation were unaffected. Propranolol (8 micrograms X kg-1 X min-1) resulted in decreases in RSR at the renal nerve stimulation despite the presence of changes in renal hemodynamics similar to the other groups. The results indicate that intrarenal opiate receptors may participate in inhibiting renal secretion of renin mediated by the renal nerves when renal vasoconstriction and reduction of GFR occurred at the high-frequency stimulation.
Comparative facilitated transport of oxygen
Authors: Gonzalez-Fernandez J. M. , Atta S. E.
Published: December 2017

Numerical solutions were obtained for a model of facilitated transport of O2. The dependence of the facilitated flow on the concentrations of O2 at the two boundaries of the transport path was studied. The numerical values of the parameters correspond to the adult Ascaris lumbricoides and to vertebrate red striated muscle. A global control principle is formulated. This states that for every fixed O2 concentration at the low concentration boundary there exists an O2 concentration at the high concentration boundary for which the facilitated flow is maximum. The collection of these maxima makes possible the existence of a global adjustment of the facilitated transport in contradistinction to the mere presence of a local maximum. The ranges of the pairs of boundary O2 concentrations thus defined and for which the facilitated flow is within 70% of its attainable maximum were found to coincide with the physiological ranges of boundary O2 concentrations for the Ascaris and vertebrate striated muscle. This phenomenon has the character of a graded compensatory mechanism to hypoxia. It is an intrinsic property of the carrier transport system and does not depend on sensors for hypoxia.
Reduced running endurance in gluconeogenesis-inhibited rats
Authors: John-Alder H. B. , McAllister R. M. , Terjung R. L.
Published: December 2017

The functional significance of gluconeogenesis in prolonging endurance during submaximal activity was assessed in untrained and endurance-trained rats. Gluconeogenesis was inhibited at the phosphoenolpyruvate carboxykinase reaction by 3-mercaptopicolinic acid (3-MPA). Endurance was significantly reduced by 3-MPA in untrained (-32%; P less than 0.005) and in trained rats (-26%; P less than 0.001). Metabolic correlates of fatigue were examined in trained rats. At exhaustion, 3-MPA-treated rats had only 3% of resting hepatic glycogen, 46% of resting white quadriceps glycogen, and 37% of resting blood glucose. All of these substrates were at higher levels in sham-injected controls after the same duration of running (130 min). Glycogen levels in red quadriceps, blood lactate levels, and blood glycerol levels were not different between groups. Plasma free fatty acid levels were elevated to the same extent in both groups after 90 min of activity, remained high at 130 min in controls, but had returned to resting levels in the severely hypoglycemic 3-MPA-treated rats at exhaustion. The results indicate that gluconeogenesis is important for maintaining blood glucose levels and for prolonging endurance time during submaximal activity.
Increased left ventricular pressure attenuates the baroreflex in unanesthetized dogs
Authors: Holmberg M. J. , Zucker I. H.
Published: December 2017

To determine whether stimulation of left ventricular mechanoreceptors alters the baroreflex control of heart rate (HR), dogs were instrumented with a vascular occluder around the ascending aorta and appropriate instrumentation for the recording of left ventricular pressure (LVP), aortic pressure, left atrial pressure, HR, and left ventricular dP/dt. Baroreflex sensitivity (pulse interval or HR vs. aortic systolic pressure linear-regression slopes to infusions of phenylephrine or nitroprusside) was determined in the conscious state a minimum of 7 days postoperatively. After control responses were determined with both phenylephrine and nitroprusside, the experiment was repeated during inflation of the ascending aortic occluder so as to significantly raise left ventricle systolic pressure from 127.9 +/- 8.4 to 178.5 +/- 11.3 mmHg (P less than 0.01) and left ventricle end-diastolic pressure from 3.5 +/- 0.7 to 8.9 +/- 1.0 mmHg (P less than 0.01). There were no changes in mean arterial blood pressure, pulse pressure, or HR during elevation of LVP. The baroreflex sensitivity was reduced only during the infusion of nitroprusside from a control of 11.03 +/- 1.9 to 4.80 +/- 1.2 ms/mmHg (P less than 0.01) for the pulse interval relationship and from -2.51 +/- 0.53 to -1.14 +/- 0.32 beats . min-1 . mmHg-1 (P less than 0.05) for the HR relationship. Cholinergic blockade with atropine abolished the depression in the baroreflex sensitivity during nitroprusside infusion when LVP was increased. beta 1-Adrenergic blockade with metoprolol did not significantly reduce the baroreflex sensitivity during increased LVP.(ABSTRACT TRUNCATED AT 250 WORDS)
Cecal degradation of uric acid in Gambel quail
Authors: Campbell C. E. , Braun E. J.
Published: December 2017

In birds, urine enters the lower gastrointestinal tract from paired ureters and can be moved in a retrograde fashion into the colon and digestive ceca. As a major constituent of urine, uric acid is carried into these regions of the gastrointestinal tract. In these locations the chemical composition of the urine, including uric acid, could be altered. To examine this possibility the postrenal degradation of uric acid in the hindgut (ceca, colon, and ileum) of the Gambel quail (Callipepla gambelii) was investigated in vitro to determine the location of activity and the possible source of uricolytic enzymes. Significant breakdown of uric acid was observed in all cecal preparations; only minor amounts were degraded in the ileum and colon. The cecal degradation amounted to 15-49% of the uric acid estimated to be produced by the quail. Attempts to demonstrate uric acid decomposition by bacteria cultured from ceca gave inconclusive results.
Relationship between autonomic and behavioral thermoregulation in the golden hamster
Authors: Gordon C. J. , Fehlner K. S. , Long M. D.
Published: December 2017

Preferred ambient temperature (Ta) of male golden hamsters (Mesocricetus auratus) was measured repeatedly by placing the animals in a temperature gradient for 80 min. A total of 180 observations were made during the last 20 min of treatment in the gradient. The mean preferred Ta was 28.2 +/- 0.2 degrees C. In another experiment the same animals were placed in a temperature-controlled chamber for 80 min while metabolic rate, evaporative water loss, thermal conductance, and colonic temperature were measured at Ta's of 14-34 degrees C. The lower critical Ta, the Ta below which metabolic rate increased above the resting level, was 28 degrees C. This Ta corresponds closely to the mean preferred Ta of the hamster when placed in the temperature gradient. Evaporative water loss was minimal at Ta's of 14 and 16 degrees C and increased gradually with increasing Ta. Thermal conductance was minimal between Ta's of 14 and 28 degrees C and then increased sharply with increasing Ta. The data from the hamster are qualitatively similar to the mouse in that the preferred Ta corresponds with the lower critical Ta. It appears that, for these rodents, the control of preferred Ta is critically related to the animal's metabolic requirements.
Characteristics of myocardial beta-adrenergic receptors during endotoxicosis in the rat
Authors: Romano F. D. , Jones S. B.
Published: December 2017

The effects of in vivo endotoxin administration on beta-adrenergic receptors in rat ventricle membranes were studied using [3H]dihydroalprenolol as a radioligand. Nonlinear regression analysis of saturation binding indicated one-site binding of antagonist in both control and endotoxic tissues. There was no change in maximum binding or dissociation constant of [3H]dihydroalprenolol at 0.5 or 3 h after endotoxin administration or when the rats were in the agonal stage of shock. Isoproterenol competition studies revealed that there was an increase in the slope of the curve from endotoxic tissues at the agonal stages (0.6 +/- 0.06 vs. 0.91 +/- 0.12, control and endotoxic, respectively, P less than 0.05) and that there was a decrease in affinity for isoproterenol binding. Control binding modeled to a two-state fit, whereas binding to endotoxin-exposed membranes modeled to one state of lower affinity. These data suggest that there is an alteration in receptor-adenylate cyclase coupling, which may account for an attenuation of agonist-stimulated cyclase activity. A modification in the beta-adrenergic receptor may contribute to the decrease in myocardial performance during shock.
Atrial natriuretic peptide levels during acute and chronic saline loading in conscious dogs
Authors: Salazar F. J. , Romero J. C. , Burnett J. C. , Schryver S. , Granger J. P.
Published: December 2017

The purpose of the present study was to determine if acute and chronic increases in sodium intake by isotonic saline infusion are accompanied by changes in plasma concentrations of atrial natriuretic peptide (PANP). Acute saline loading (5% body wt) over a 30-min period in seven conscious chronically instrumented dogs produced a significant increase in PANP (48 +/- 5 to 119 +/- 24 pg/ml, P less than 0.05). However, chronic and progressive increments of sodium intake from 5 to 75 to 300 meq/day for 7 days, each by isotonic saline infusion, were examined in the same group of dogs and had no significant effect on PANP. PANP's were 37 +/- 7, 39 +/- 8, and 33 +/- 5 pg/ml when sodium intake was changed from 5 to 75 to 300 meq/day, respectively. The increase of sodium intake from 5 to 75 meq/day produced decreases of plasma renin activity (PRA) (2.5 +/- 0.5 to 1.5 +/- 0.4 ng angiotensin I X ml-1 X h-1, P less than 0.05), plasma aldosterone concentration (PAC) (19.3 +/- 5.4 to 2.9 +/- 0.4 pg/ml, P less than 0.05), and urinary excretion of prostaglandin E2 (760 +/- 131 to 320 +/- 58 pg/min, P less than 0.05). Further increase of sodium intake to 300 meq/day induced decreases of PRA and PAC to undetectable levels and an increase of urinary excretion of 6-ketoprostaglandin F1 alpha (649 +/- 95 to 1,056 +/- 148 pg/min, P less than 0.05). Before the completion of the study, sodium intake was decreased from 300 to 75 meq/day.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of adrenodemedullation on metabolic responses to high-intensity exercise
Authors: Marker J. C. , Arnall D. A. , Conlee R. K. , Winder W. W.
Published: December 2017

To determine the role of epinephrine in glycogenolysis during high-intensity exercise, rats were adrenodemedullated (ADM) or sham operated (SHAM) and run for either 30 min at 38 m/min or for 5 min at 27, 38, or 48 m/min up a 15% grade. At the end of exercise the rats were anesthetized by intravenous injection of pentobarbital sodium. Liver, blood, and muscle samples were obtained. Plasma epinephrine values were 5.9 and 0.3 nM for SHAM and ADM animals, respectively, after 30 min of exercise. Liver glycogen decreased by 16 and 21 mg/g in the SHAM and ADM groups, respectively, and liver cAMP increased significantly in both groups. Glycogen in the soleus muscle decreased 80% in the SHAM but only 43% in the ADM animals after 30 min of exercise. The exercise-induced hyperglycemia observed in the SHAM animals was not present in the ADM animals. The responses of cyclic AMP, soleus glycogen, and blood glucose were similar in both the 5- and 30-min exercise groups. During intense exercise, epinephrine is unessential for stimulating liver glycogenolysis but does play an important role in stimulating glycogenolysis in the soleus muscle and in establishing exercise-induced hyperglycemia.
Endocrine mechanisms regulating sodium excretion during water deprivation in dogs
Authors: Metzler G. H. , Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

The time course and mechanism of the natriuresis that accompanies 24 h of water, but not food, deprivation were studied in eight chronically catheterized dogs. Dogs were fed a controlled diet containing 35 meq of sodium, 110 meq of potassium, and 107 ml of water at 9:00 A.M. every day (time 0), and urine and blood samples were taken at 0, 2, 4, 6, 8, 10, 12, 16, 20, and 24 h after feeding on 3 consecutive days: the control, dehydration, and recovery days. Twenty-four hours of water deprivation decreased body weight by 880 g, increased plasma sodium by 7.2 meq, and increased plasma osmolality by 22.5 mosmol/kg. Cumulative daily sodium excretion increased from 30.4 +/- 2.8 meq on the control day to 50.7 +/- 5.7 meq on the dehydration day (P less than 0.01) and resulted in significant negative sodium balance that developed during the last half of the dehydration day. Cumulative sodium excretion during the first half of the dehydration day was not different from the corresponding period of the control day. Cumulative potassium excretion also increased from 91.9 +/- 4.5 meq during the control day to 123.0 +/- 6.7 meq during the dehydration day (P less than 0.01). Significant and progressive increases in plasma vasopressin concentration and renin activity were observed during water deprivation, but plasma aldosterone did not change from control levels. Furthermore, there was no correlation between the rate of sodium excretion and plasma vasopressin or aldosterone concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Plasma volume changes during head-out water immersion in conscious dogs
Authors: Miki K. , Hajduczok G. , Hong S. K. , Krasney J. A.
Published: December 2017

Blood volume (51Cr-erythrocyte dilution method), hematocrit, and arterial (Pa), central venous (Pv), plasma colloid osmotic (IIpl), and interstitial fluid hydrostatic (Pcps, Guyton's capsule method) pressures were measured continuously to determine the kinetics of the transvascular fluid shift during 100 min of water immersion (WI) at 37 degrees C in six splenectomized dogs. Urine flow increased by 180% above control levels (P less than 0.05) by 30 min of WI. Plasma volume (PV) started to increase at 5 min of WI and rose by 7.2% (P less than 0.05) above control levels by 35 min of WI, and then it decreased gradually. PV returned to control levels immediately after WI. Plasma protein concentration and IIpl decreased significantly by 0.2 g/100 ml and 1.2 mmHg, respectively, at 35 min of WI, while plasma osmolality and Na+ concentration were constant. Pa and Pv increased (P less than 0.05) by 25 and 12 mmHg, respectively. Mean capillary pressure, which was calculated from Pa, Pv, and an estimated pre-to-postcapillary resistance ratio of 5-12, increased by 13-14 mmHg while Pcps increased (P less than 0.05) by 17 and 26 mmHg at upper hindlimb and lower forelimb, respectively. The changes in mean capillary pressure and IIpl tend to promote capillary filtration in WI; however, the greater elevation of Pcps more than offsets these forces and leads to a net transvascular shift into the plasma compartment.
Cardiac receptors, vasopressin, and corticosteroid release during arterial hypotension in dogs
Authors: Lee M. E. , Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

The relative roles of cardiopulmonary and sinoaortic baroreceptors in the regulation of vasopressin and corticosteroid release were evaluated in conscious dogs. The dogs were prepared with inflatable cuffs around either the ascending aorta, proximal to the brachiocephalic trunk, or the pulmonary artery. Inflation of the cuffs was adjusted to cause a reduction of mean systemic arterial pressure (MAP) of 0, 5, 10, 20, or 30% of control for 1 h in separate experiments. In spite of the profound systemic hypotension caused by constriction of the ascending aorta, plasma vasopressin failed to increase and corticosteroids increased only in response to a 30% decrease in MAP. In contrast, a 5% reduction in MAP during pulmonary arterial constriction increased plasma vasopressin and corticosteroid concentrations significantly. The apparent paradox in these results is correlated with different effects of the two maneuvers on left atrial pressure. Left atrial pressure increased dose dependently during inflation of the ascending aortic cuff but decreased during inflation of the pulmonary arterial cuff. In contrast, graded inflation of the pulmonary arterial cuff caused dose-dependent increases in right atrial pressure, plasma vasopressin, and corticosteroids. Therefore, we conclude that powerful inhibitory signals, arising from the left heart, can inhibit vasopressin and hypotension release in response to systemic hypotension.
Circadian principles and design of rotating shift work schedules
Authors: Turek F. W.
Published: December 2017

Circadian rhythms may be disrupted when shift workers rotate from one work schedule to another. It has been suggested that in order to minimize the time needed to readjust circadian rhythms to a new work schedule the work time of shift workers should be rotated in a delaying rather than an advancing direction. However, delaying or advancing the work time does not imply that the sleep-wake cycle is also shifted in a similar manner. Indeed, after a complete rotation between the day, evening, and night shifts the sleep time will be advanced once, delayed once, and not shifted once, regardless of whether the workers are on a delaying or an advancing work rotation schedule. Thus circadian rhythms are likely to be perturbed in a similar manner whether the work schedule is rotated in a delaying or an advancing direction.
Trout vascular and renal responses to atrial natriuretic factor and heart extracts
Authors: Duff D. W. , Olson K. R.
Published: December 2017

Dorsal aortic pressure (DAP), urine flow rate, and urinary K+, Na+, and Cl- were monitored in chronically catheterized unanesthetized rainbow trout before and after injection of saline, tissue extracts, or synthetic (rat, Ile-26) atrial natriuretic factor (ANF). Synthetic ANF (1.0 and 10.0 micrograms/kg body wt) and extracts from trout atria and ventricles increased DAP, urine flow rate, and electrolyte excretion. Saline, skeletal muscle extracts, and 0.1 microgram/kg body wt synthetic ANF had no effect on DAP and only minor effects on renal water and ion excretion. The slow-onset long-duration pressor response to ANF and heart extracts contrasted with a rapid short-acting pressor effect of epinephrine. Synthetic ANF (10 micrograms/kg body wt) and ventricular extracts produced marked increases in Na+ and Cl- excretion but only a mild diuresis. Much of the increase in urine flow rate appears to be due to solvent injection. These results show that trout hearts contain an ANF-like material and that mammalian and piscine ANF produce hemodynamic and renal effects upon intra-arterial injection.
Fate of labeled albumin and erythrocytes following injection into amniotic cavity of sheep
Authors: Tomoda S. , Brace R. A. , Longo L. D.
Published: December 2017

We have previously described a method to measure the amniotic fluid (AF) volume and fetal swallowing rate in near-term sheep by use of 125I-labeled albumin (RISA) and 51Cr-labeled red blood cells (51Cr-RBC). However, when we measured these volumes on consecutive days, reentry of the radionuclides into the amniotic cavity from fetal urine affected the calculated values of AF volume and swallowing rates. In an attempt to clarify the recirculation problem, we injected RISA and Cr-RBC daily for 9 days into the AF of five chronically catheterized pregnant sheep (124 days gestation on the 1st experimental day). We calculated AF volume and fetal swallowing rate, comparing those values to the values corrected for fetal urine isotopic counts. The mean AF volume and fetal swallowing rate measured by RISA were 808 +/- 48 ml (mean +/- SE) and 559 +/- 29 ml/day, respectively. These values were only slightly different from the corrected volumes, 808 +/- 48 ml and 561 +/- 29 ml/day, respectively, because fetal urine 125I activity reached only 4.8% of AF activity even on the 9th day. In contrast, 51Cr-activity in fetal urine on the 9th day showed 47% of the activity of AF. The mean uncorrected AF volume (785 +/- 44 ml) and swallowing rate (561 +/- 31 ml/day) measured by Cr-RBC were different from the corrected values (790 ml and 570 ml/day, respectively). After the 4th day these differences were particularly conspicuous.(ABSTRACT TRUNCATED AT 250 WORDS)
Intragastric balloon reduces food intake and body weight in rats
Authors: Geliebter A. , Westreich S. , Gage D. , Hashim S. A.
Published: December 2017

To test a less invasive method than gastric surgery for treating obesity, balloons were nonsurgically inserted in the stomachs of adult rats (mean wt = 537 g) for 8 wk. One group received balloons that were inflated with 7 ml of water, a second group had balloons inserted that were deflated, and a third group had no balloons inserted. Rats with inflated balloons ingested 27% less food (P less than 0.0005) during the 8 wk and weighted 16% less (P less than 0.05) at the end of this period than rats with deflated balloons or no balloons. Their food intake was significantly depressed through the 7th wk. The stomachs of the rats with inflated balloons were significantly heavier than the others with a thicker muscularis externa. Body composition was not significantly different among groups. A chronic intragastric balloon significantly reduced food intake and body weight.
Role of carotid sinus and aortic nerves in respiratory control of infant rats
Authors: Hofer M. A.
Published: December 2017

The roles of carotid sinus (CSN) and aortic depressor nerves (ADN) in the maintenance of rhythmic respiration and in the response to airway occlusion were investigated in 8- to 10-day-old infant rats. Cutting the CSN led to a periodic loss of rhythmic respiration with arrhythmic low-amplitude waveforms, frequent end-expiratory pauses, and occasional apneas observed in unanesthetized unrestrained pups studied in their home cage nests by impedance pneumography. Cutting the ADN alone did not have this effect. Sinoaortic denervation (SAD) in which both nerves were cut, produced a more severe disturbance that was not relieved by tracheostomy, indicating that it was not due to upper airway obstruction. Tracheal pressure recordings from anesthetized SAD infants in response to short periods of external airway obstruction showed reduced respiratory efforts and prolonged recovery times, deficits that may play a role in the mortality previously reported after SAD in infant rats.
Blood flow to brown fat in lean and obese adrenalectomized Zucker rats
Authors: Wickler S. J. , Horwitz B. A. , Stern J. S.
Published: December 2017

The Zucker obese rat is characterized by decreased capacity for diet-induced and for nonshivering thermogenesis. This decrease is due, in large part, to reduced thermogenesis in depots of brown adipose tissue, a major source of heat production in rats. Adrenalectomy retards the weight gain observed in the obese rats and also normalizes brown fat guanosine 5'-diphosphate (GDP) binding, an in vitro measure of brown fat thermogenic capacity. This study examined the effect of adrenalectomy on brown fat blood flow, an in vivo measure of the tissue's function, and on norepinephrine-induced O2 consumption (NST) of 11-wk-old obese (fa/fa) and lean (Fa/?) rats. Adrenalectomy had little effect on weight gain, NST, or norepinephrine-stimulated blood flow to brown fat in lean rats. However, adrenalectomy produced profound changes in the obese animals, preventing the weight gain normally occurring in the obese rats and normalizing both NST capacity and norepinephrine-stimulated blood flow to brown fat. These findings provide further support for the importance of brown fat thermogenesis and glucocorticoids in modulating the obesity of the Zucker rat.
Cardiovascular responses to hemorrhage and naloxone in conscious barodenervated rabbits
Authors: Schadt J. C. , Gaddis R. R.
Published: December 2017

The hemodynamic and plasma catecholamine response to hypotensive hemorrhage and subsequent opioid receptor blockade with naloxone were evaluated before and after complete sinoaortic denervation (SAD). This study was done to test the general hypothesis that opioid-mediated failure of the baroreflex accounts for the hypotension of hemorrhage. The specific hypothesis we tested was that SAD would abolish the pressor effect of opioid receptor blockade with naloxone. The studies were done in conscious chronically prepared rabbits. Hemorrhage of 12 ml/kg did not change mean arterial blood pressure in intact animals due to a compensatory increase in heart rate and vascular resistance. When blood loss exceeded 12 ml/kg, pressure decreased abruptly due to a decrease in vascular resistance. Plasma norepinephrine (NE) and epinephrine (E) were higher after hemorrhage than before. Plasma E levels increased almost 70 times. After SAD, mean blood pressure began to decrease at the beginning of hemorrhage, the heart rate increase was abolished, and vascular resistance decreased throughout the blood loss. Plasma NE was no different after hemorrhage than before. Plasma E increased, but the increase was only fivefold. Naloxone increased mean arterial blood pressure, vascular resistance, cardiac index, and plasma NE before and after SAD. The increases in blood pressure and plasma norepinephrine were significantly greater after SAD. Therefore the pressor effect of naloxone in this model is not due to increased baroreflex sensitivity. Rather, intact baroreflexes buffer naloxone's effects.
Decreased testosterone levels do not mediate short-photoperiod-induced brown fat changes
Authors: Kott K. S. , Moore B. J. , Horwitz B. A.
Published: December 2017

Previous studies showed that short photoperiod increased brown fat (BAT) mass and reduced gonadal size and gonadal hormone secretion in hamsters. The present study investigated the possibility that the effects on BAT were dependent on reduced levels of gonadal hormones. BAT from male Syrian hamsters exposed to short photoperiod for 10 wk was significantly greater in mass, protein content, and total maximal citrate synthase and beta-hydroxyacyl-CoA dehydrogenase activities than was BAT from long-photoperiod hamsters, These differences between short- and long-photoperiod exposure were observed in hamsters housed at 21 as well as at 8 degrees C. Short photoperiod also increased the total recovered mitochondrial GDP binding, a finding consistent with increased BAT thermogenic capacity. These short-photoperiod effects were neither mimicked by castration of long-photoperiod hamsters nor prevented by high levels of testosterone administered to short-photoperiod animals. Castration did attenuate the effects of short photoperiod on BAT growth if, after surgery and prior to short-photoperiod exposure, the animals were housed at a long photoperiod for 2-3 wk. In contrast, in hamsters immediately placed at short photoperiod after surgery, castration did not inhibit short-photoperiod effects. The present three experiments demonstrate that, in addition to increasing BAT mass, short photoperiod elevates the thermogenic capacity of BAT, and this elevation does not require the absence or a much reduced testosterone level.
Closed ventriculocisternal perfusion to determine CSF production rate and pressure
Authors: Artru A. A. , Hornbein T. F.
Published: December 2017

When the rate of cerebrospinal fluid (CSF) production (Vf) is determined using the classical open ventriculocisternal perfusion technique, it is not possible to observe natural fluctuations in CSF pressure, or the effects of experimental treatments on CSF pressure, or to make inferences about CSF volume or resistance to reabsorption of CSF, because CSF pressure is fixed according to the level of the distal end of the cisternal outflow cannula. In addition, the convention of placing the distal end of the cisternal outflow cannula at the interaural line fixes CSF pressure at a value that may not be usual for the animal, thereby introducing potential causes for error in the determination of Vf. The present study describes and evaluates a method of closed ventriculocisternal perfusion that allows the simultaneous determination of Vf and CSF pressure. With this method the time to tracer equilibration was less, and the volume of distribution of the tracer was smaller than with the classical open perfusion system. CSF pressure tracings were of high fidelity showing both respiratory and cardiovascular variation. During both sedation with nitrous oxide or halothane anesthesia, Vf values using closed perfusion were similar to values previously reported using open perfusion. Vf decreased during halothane anesthesia compared with nitrous oxide sedation. No time-related change in Vf from the first measurable time period (approximately 2 h) to the end of the study (approximately 5 h) was observed.
Insulin and metabolic efficiency in rats. II. Effects of NE and cold exposure
Authors: Bartness T. J. , Billington C. J. , Levine A. S. , Morley J. E. , Rowland N. E. , Brown D. M.
Published: December 2017

The role of insulin in metabolic efficiency (ME, i.e., efficiency of body wt gain) was examined under conditions of maximal energy expenditure in control and diabetic rats. Long-lasting insulin was administered using a protocol that did not affect food intake and increased ME in both groups. Half the animals were injected chronically with norepinephrine (NE). NE alone in controls decreased body weight and ME and increased brown adipose tissue (BAT) growth, thermogenic potential [cytochrome c oxidase activity (COA)], and lipoprotein lipases (LPL) activity; however, in diabetics, body weight, ME, and food intake all decreased and only BAT LPL activity and DNA content increased. The combination of NE and insulin increased BAT protein and COA in diabetics; in controls, all BAT measures were further increased and ME was intermediate to that of either treatment alone. Cold exposure decreased body weight and ME, increased food intake and qualitatively produced similar increases in BAT growth, COA, and LPL activity in both controls and diabetics. In diabetics, combined cold exposure and insulin did not affect the increase in BAT growth or LPL activity resulting from either treatment alone, but in controls this combination decreased BAT growth and COA. It is concluded that, even under conditions of maximal energy expenditure, both extremes of basal insulin status result in decreased BAT growth and thermogenic potential, but have opposite effects on ME.
On comparing regression lines with unequal slopes
Authors: Zerbe Gary O. , Archer Philip G. , Banchero Natalio , Lechner Andrew J.
Published: December 2017

Page R178: Gary O. Zerbe, Philip G. Archer, Natalio Banchero, and Andrew J. Lechner. “On comparing regression lines with unequal slopes.” Page R179: first column, the paragraph after Equation 7 should read

Case II. If A < 0 and D > 0, then the tests will be significant for X's satisfying

(See PDF)
Vasopressin responses to asphyxia and hemorrhage in newborn pigs
Authors: Leffler C. W. , Busija D. W. , Brooks D. P. , Crofton J. T. , Share L. , Beasley D. G. , Fletcher A. M.
Published: December 2017

Vasopressin may be important in maintenance of arterial pressure and redistribution of cardiac output in hypotensive and asphyxiated newborns. We used chronically instrumented, unanesthetized, 4-day-old pigs to investigate the effects of hypotensive hemorrhage and asphyxia on plasma vasopressin concentration and to determine the effects of cyclooxygenase inhibition on these responses. Asphyxia [arterial O2 partial pressure (PaO2) = 40-50 Torr, arterial CO2 partial pressure (PaCO2) = 60-80 Torr) increases plasma lysine vasopressin (LVP) from 2.2 +/- 0.8 to 52.4 +/- 15.0 microU/ml. Neither the baseline nor stimulated plasma LVP was affected by indomethacin (5 mg/kg) or meclofenamate (5 mg/kg). Hemorrhage (30 ml/kg) increased plasma LVP from 2.8 +/- 0.8 to 163.4 +/- 28.1 (20 min) and 135.1 +/- 18.5 microU/ml (60 min). The effects of vehicle and indomethacin (5 mg/kg) 20 min after hemorrhage on plasma LVP 60 min after hemorrhage were not different. Changes in plasma vasopressin caused by asphyxia and hemorrhage in the unanesthetized newborn pig are similar to the responses observed in adults of other species. This study does not suggest that prostanoids are involved in these responses in newborn pigs.
Organic cation secretion by Cancer borealis urinary bladder
Authors: Miller D. S. , Holliday C. W.
Published: December 2017

In the crab, Cancer borealis, initial clearance studies showed a potent renal excretory system for the model organic cation, tetraethylammonium (TEA). TEA clearance averaged 145 +/- 32 ml/day, which was 18 times the paired polyethylene glycol clearance. TEA uptake by slices of urinary bladder was concentrative, saturable, inhibitable by N1-methylnicotinamide chloride, and dependent on glycolytic, but not oxidative, metabolism. When mounted in flux chambers, bladders exhibited a large net secretory flux. For 0.1 mM TEA, the ratio of secretory to reabsorptive fluxes was 65. Urinary bladders from another crab, Cancer irroratus, and a lobster, Homarus americanus, also exhibited net TEA secretion. In C. borealis bladder, secretory transport was concentrative, saturable, and nearly abolished by addition of 1 mM quinine to the serosal bath. Reabsorptive transport was not concentrative and was not reduced by luminal quinine. The data are consistent with a secretory pathway that is transcellular and mediated by carriers at both the serosal and luminal membranes.
Effect of immobilization on collagen synthesis in rat skeletal muscles
Authors: Savolainen Jukka , Väänänen Kalervo , Vihko Veikko , Puranen Jaakko , Takala Timo E. S.
Published: December 2017

Page R883: Jukka Savolainen, Kalervo Väänänen, Veikko Vihko, Jaakko Puranen and Timo E. S. Takala. “Effect of immobilization on collagen synthesis in rat skeletal muscles.” Page R883: second column, ninth line should read “in types I and III collagen (23)”. Page R886: Table 2 title should read “Effect of 3 wk cast immobilization on PH and GGT activities and HYP content on muscle.” Page R888: Reference 17 should read “edited by J. B. Weiss and M. I. V. Jayson.”
Fetal responses to altered maternal oxygenation in rhesus monkey
Authors: Jackson B. T. , Piasecki G. J. , Novy M. J.
Published: December 2017

The purpose of this study was to establish (in the primate) maternal-fetal relations for blood gas parameters and certain related aspects of fetal cardiovascular function with the mother at rest and subjected to a range of altered states of oxygenation. In 10 chronically cannulated rhesus monkey fetuses, with the mother lightly sedated with phencyclidine, on each of two days we studied the effects of maternal hypoxia and hyperoxia [(15, 10, and 100% maternal fractional concentration of inspired O2 (FIO2)] on maternal and fetal pH, PCO2, PO2 and O2 concentration (CaO2) and fetal heart rate, blood pressure, and superior vena caval (SVC) flow distribution. We observed a linear correlation between maternal and fetal pH and PCO2. There was evidence of a fetal metabolic acidosis with 10 but not with 15% hypoxia. Maternal-fetal PO2 and CaO2 correlated in curvilinear and linear fashion, respectively. Maternal-fetal CaO2 difference was maintained within a narrow range (2.7–4.8 vol%) for various states of maternal oxygenation, showing a tendency to expand only with severe (10%) hypoxia. Results indicate that quantitative delivery of O2 to the placenta was of paramount importance as a determinant of O2 transfer to the fetus and are compatible with a “concurrent flow” model of transplacental O2 diffusion. Fetal heart rate decreased progressively with 15 and 10% hypoxia. SVC flow to lungs and placenta varied reciprocally with changes in fetal oxygenation. As indicated by distribution to the heart, shunting of SVC flow through the foramen ovale was modest at rest, with no evident change in response to fetal hypoxemia.