bluuebunny/crossref_metadata_2025 huggingface dataset:
Systemic arterial pressor responses induced by potassium in dogfish, Squalus acanthias
Authors: Opdyke D. F. , Carroll R. G. , Keller N. E.
Published: December 2017

Intravascular injection of small doses of potassium (0.025-0.5 meq) into dogfish results in dose-related dorsal aortic pressor responses. The responses are blocked by phentolamine, an alpha-adrenergic blocking agent. Assays of plasma catecholamines before and after injection of potassium (K+) showed that plasma levels of epinephrine (E) and norepinephrine (NE) had increased significantly (E, 314%; NE, 233%) 1 min after injection. The pressor responses were initiated 40-90 s after K+ injection at which time plasma E and NE levels were already significantly elevated. Experiments on isolated dogfish arterial strips showed that phentolamine cannot block the increase in vascular smooth muscle tension that occurs after direct exposure to small increases (0.003 meq/ml) in K+ concentration. Because phentolamine effectively blocks the pressor response to even higher doses of K+ in vivo, it is thought that, in addition to any direct vasoconstrictor effect or K+, the adrenergic stimulation provided by catecholamine release is required to produce the observed pressor response.
Comparative physiology of insect renal function
Authors: Phillips J.
Published: December 2017

Transport mechanisms and their control in various segments of insect excretory systems are reviewed and compared to those of vertebrate nephrons, exocrine glands, and hindguts. Formation of the primary urine in most insect Malpighian tubules (MT) is by isosmotic secretion, which is driven by an apical cation (K+) pump rather than by Na+-K+-ATPase. Unlike the glomerular filtrate of vertebrates, insect MT fluid is very different from the blood in composition, often having very high K+-to-Na+ ratios, and urine-to-plasma values much less than unity for most other solutes. The total surface area of insect MT is some 20 times that of vertebrate glomeruli per unit body weight. Secretion of MT fluid is regulated by neuropeptides over a wide range of rats, similar to glomerular filtration rate values for many vertebrate kidneys. Several secretory mechanisms for selected solutes are probably common to insect and vertebrate tubules. Unlike vertebrates, insects usually reabsorb most of the filtered water, ions, and metabolites in the rectum, which has a small surface area relative to the MT. The rectum is also where ionic and osmotic composition of the excreta is finally adjusted, under the control of neuropeptide hormones. In the rectum, insect excreta can become as hyperosmotic as mammalian urine, even though a countercurrent multiplier system is not present. Active transport of Cl- predominates in both locust rectum and the thick ascending limb of Henle's loop, but the characteristics of the anion transfer process are quite different in these two epithelia.xs
Muscle enzyme profile, diet, and flight in South American bats
Authors: Yacoe M. E. , Cummings J. W. , Myers P. , Creighton G. K.
Published: December 2017

Activities of four catabolic enzymes (citrate synthase, hexokinase, 3-hydroxyacyl-CoA dehydrogenase, and phosphorylase) were measured in the pectoralis muscles of 10 species of South American bats, representing four families. The pattern of enzyme activities in these tissues suggests that these muscles differ qualitatively with other mammalian and avian muscles in two respects. First, the muscles of all 10 bat species were much more highly oriented toward fat metabolism and away from glucose metabolism than in any previously measured skeletal muscle. Second, the species were divided into two major groups with respect to hexokinase activity. Primarily frugivorous species had hexokinase activities about 2-3 times as high as insectivorous species. It is suggested that the weight restrictions of flight limit glycogen storage and thus bias muscle metabolism toward fat. However, the extent to which pectoralis muscles have the capacity for glucose oxidation appears to be dependent on the intake of dietary glucose.
Estimation of whole-body capillary transport parameters from osmotic transient data
Authors: Wolf M. B.
Published: December 2017

A mathematical model has been developed of short-term, extrarenal, whole-body fluid volume regulation. The Kedem and Katchalsky equations are used to describe rapid movements of crystalloid and colloid solutes and water between five fluid compartments. Simulation results showing rapid cell volume changes following a hyperosmotic crystalloid infusion demonstrated the necessity of considering the effect of cellular water shifts in osmotic transient experiments. From measurements of plasma volume and osmolality in acutely nephrectomized dogs subjected to isosmotic and hyperosmotic NaCl infusions and with the model, six parameters related to capillary membrane transport of water and NaCl were estimated. The mean capillary filtration capacity from six experiments was estimated as 0.01 ml.min-1.mmHg-1.100 g-1 of dog. This increased about threefold due to the hyperosmolality. Mean values of capillary diffusion capacity and osmotic reflection coefficient for NaCl were 0.37 cm3.s-1.100 g-1 and 0.087, respectively. These results support the use of the osmotic transient approach and a mathematical model to study the role of microvascular transport in whole-body fluid volume regulation.
Renal and endocrine response to water deprivation in dog
Authors: Zucker A. , Gleason S. D. , Schneider E. G.
Published: December 2017

Plasma and urine sodium, potassium, osmolality, aldosterone, and plasma renin activity (PRA) were measured in time controls and during control dehydration and rehydration periods in conscious dogs fed a 50 mmol NaCl diet. During 4 days of water restriction, plasma sodium and osmolality and PRA were elevated, whereas plasma potassium and aldosterone were not affected. Urinary potassium excretion was elevated above intake levels during the entire dehydration period, whereas Na excretion was only elevated during the first 2 days of dehydration. Unrestricted rehydration was associated with a marked fall in plasma sodium and osmolality, a decrease in PRA, and no change in plasma potassium or aldosterone. In addition, during the 1st day of rehydration, there was marked retention of sodium and potassium. Thus, in the dog, dehydration and subsequent rehydration cause significant alterations in sodium and potassium balance and marked alterations in PRA that are not associated with changes in either plasma aldosterone concentration or urinary aldosterone excretion.
Central dipsogenic effect of vasopressin
Authors: Szczepanska-Sadowska E. , Sobocinska J. , Sadowski B.
Published: December 2017

The purpose of the present study was to investigate the possible role of vasopressin (ADH) in the control of thirst. With this aim spontaneous water intake (WI) was examined in conscious dogs after 1) electric stimulation in the basal forebrain causing release of ADH, 2) injection of 0.03, 0.05, 0.10, 0.15, 0.30, and 3.00 mU of ADH into the third cerebral ventricle (3rd V), 3) injection of 0.3, 3.0, and 30 mU of ADH into the lateral cerebral ventricle (LV) and injection of 5.0 and 10.0 mU of ADH into the carotid artery (CA). Stimulation through 10 of 16 electrodes located in various structures of the limbic system caused a significant increase in blood ADH, decrease of urine output, increase in renal free-water reabsorption, nonstimulus-bound drinking, positive water balance, and decrease in plasma osmolality (Posmol). Injection of ADH to the 3rd V caused a significant increase in WI. The maximum WI was observed after injection of 0.10-0.15 mU of ADH. Elevation of WI caused a significant decrease in Posmol 1 h after injection of ADH to the 3rd V. Insignificant increases or no changes in WI were observed when ADH was injected into the LV and CA, respectively. The results suggest that ADH may exert central dipsogenic effects.
Energy utilization by Limulus telson muscle at different sarcomere and A-band lengths
Authors: Davidheiser S. , Davies R. E.
Published: December 2017

Phosphorylargnine utilization (delta PArg) was determined in isolated Limulus telson muscle during isometric and isovelocity contractions at long, intermediate, and short lengths when thick filaments were either long and staggered, long and aligned, or shortened. Muscles developed 30% of maximum force at a length of 0.5 Lo (Lo 7 micrometers sarcomere length) during isometric tetani of 5, 15, and 30 s; however, the rate of delta PArg was the same in both the 0.5 Lo and Lo groups. External force and delta PArg were both less during isometric tetani at lengths of 1.7 and 2.0 Lo compared with the values at Lo, as expected due to a reduction in thick-thin filament overlap. However, at lengths of 0.6 and 0.3 Lo delta PArg was the same as at Lo despite a decrease in external isometric tension. No significant delta PArg was measured when telson muscles shortened rapidly (0.8 Vmax) at long or short lengths indicating the thick filament shortening per se required little, if any, energy expenditure. The overall chemical efficiency of telson muscles for performing external work during slow isovelocity contractions was 31% in groups shortening equivalent distances (0.5 Lo) from starting lengths of 1.6 and 1.3 Lo and 15% in the group shortening from 1.1 Lo.
Cholecystokinin suppresses food intake by inhibiting gastric emptying
Authors: Moran T. H. , McHugh P. R.
Published: December 2017

In a search for the physiological mechanisms that could mediate and characterize a satiety function for the hormone cholecystokinin (CCK), we examined in Macaca mulatta the effect of intraperitoneal injections (0.1-0.8 microgram/kg) and intravenous infusions (60-240 ng.kg-1.h-1) of the C-terminal octapeptide of CCK on gastric emptying of saline test meals. Within these dose ranges, gastric emptying was inhibited by this hormone to a degree comparable with that produced by intraintestinal nutrient. The onset of the inhibition is rapid and its effect brief. At the doses of CCK that produce gastric inhibition, CCK would not affect feeding in a fasted monkey unless the stomach was filled with saline. This result suggests that a satiety influence of circulating CCK is an indirect one. The satiety effect depends upon inhibition of gastric emptying, which then leads to gastric distention with further food injection. CCK thus can be considered a link in a chain of physiological elements producing the short-term satiety that leads to the appropriate interruption of a meal or bout of feeding behavior.
Excretion-retention diagram to evaluate gas exchange properties of vertebrate respiratory systems
Authors: Zwart A. , Luijendijk S. C.
Published: December 2017

Excretion [E = (PE - PI)/(PV - PI)] and retention [R = (Pa - PI)/(PV -PI)]are completely model-free defined variables which describe the dual input-output black-box representation of vertebrate respiratory systems under steady-state conditions. In the excretion-retention diagram (E-R diagram), E is plotted as a function of R. The application of the principle of mass conservation confines the possible combinations of E and R for a gas with a blood-gas partition coefficient, lambda, in a respiratory system with an overall ventilation, VT, and an overall perfusion, QT, to E = (lambda QT/VT) (1 - R). In general, E can be described as a continuous function of R. The mathematical formulation of this function depends on the configuration of the respiratory system. Easily recognizable curvatures are obtained for counter-cross, and cocurrent systems with and without parallel inhomogeneities. Visual inspection of actual E and R data displayed in an E-R diagram therefore allows the correct choice of the configuration of the respiratory system to be eventually used for further parameter estimation schemes. The E-R diagram is also a powerful tutorial tool for visualizing the complex relationships between the gas exchange of agents with different physical properties and the consequences of changes in ventilation and perfusion distribution within the respiratory system on gas transport.
Sex differences in the circadian control of hamster wheel-running activity
Authors: Davis F. C. , Darrow J. M. , Menaker M.
Published: December 2017

The circadian pacemaker that underlies the wheel-running activity of hamsters was studied in males and females. Sex differences were found in the mechanism by which the pacemaker entrains to light-dark cycles and in the timing of activity onset. When exposed to a light-dark cycle with a period of 24.75 h (with 1 h of light/cycle), males show a greater ability to maintain entrainment than do females. This difference in the upper limit of entrainment appears due to a sex difference in the magnitude of light-induced phase shifts. A small difference in free-running period may also contribute to the sex difference in entrainment. Two weeks after castration of adults, the sex difference in entrainment is not affected, indicating that the difference does not depend on circulating gonadal steroids or on estrous cyclicity of the female. However, castration of females at an early age increases their ability to entrain, whereas long-term castration of males seems to reduce entrainment ability. During entrainment to a 24-h light-dark cycle (LD 14:10), females were found to begin their daily activity before males and before castrated females. This difference is consistent with a sex difference in the magnitude of light-induced phase shifts and in entrainment of the pacemaker. However, evidence is given that the sex difference in activity onset might also be caused by a sex difference in the relationship of locomotor activity to the pacemaker in intact males and females.
Effect of hypercapnia and cerebral perfusion pressure on cerebrospinal fluid production in cat
Authors: Heisey S. R. , Adams T. , Fisher M. J. , Dang W.
Published: December 2017

Brain ventricles of anesthetized cats were perfused with an artificial cerebrospinal fluid (CSF) containing inulin (or [14C]dextran) and 3H-labeled sucrose while each animal respired in turn either room air or an 8-11% CO2-in-air gas mixture. Perfusion inflow (Vi) and outflow (Vo) rates and concentrations of the test molecules were measured to calculate steady-state CSF production (Vf), CSF absorption (Va), and ependymal sucrose permeability (Ksuc). During respiratory acidosis Vf varied inversely as a function of normocapnic Vf, Ksuc increased, and Va was the same as during normocapnia. Vf increased with cerebral perfusion pressure (CPP) during normocapnia but was inversely related to it during hypercapnia. When a normocapnic animal's CPP is high in the range 70-105 Torr, its Vf will also be high, but it will increase its Vf little or not at all during hypercapnia. In the same range, if its CPP is low, its Vf will also be low, but its Vf will increase predictably fourfold or more when it breathes CO2. CPP is an influential determinant of Vf at any level of acid-base balance, possibly due to variations in blood flow at CSF production sites.
Altered sympathetic activity during development of diet-induced obesity in rat
Authors: Levin B. E. , Triscari J. , Sullivan A. C.
Published: December 2017

Sprague-Dawley rats developed diet-induced obesity (DIO) after 3 mo on a high-fat, high-sucrose diet (DIO diet), with associated increases in total body and interscapular brown adipose tissue (IBAT) lipid content. After 7 days on the DIO diet, rats had increased levels of tyrosine hydroxylase (TH; 34%), norepinephrine (NE; 34%), and NE turnover (94%; estimated by alpha-methyl-p-tyrosine inhibition of TH) in their IBAT compared with chow-fed controls. After 3 mo on the DIO diet, NE levels and/or turnover were reduced by 27–50% in aortas, hearts, and pancreata in obese rats. While IBAT NE turnover was normal, TH inhibition failed to increase the lipid content of IBAT in obese rats as it did in controls, suggesting a postsynaptic defect in basal NE-stimulated lipolysis in this thermogenically active tissue. When obese rats were switched from the DIO diet to rat chow for 3 days, NE levels remained depressed in their hearts (25%) and aortas (14%) but were increased by 36–45% in IBAT, pancreata, and white adipose tissue. NE turnover rates and/or constants were increased by 37–110% in hearts, aortas, pancreata, and IBAT of these obese rats while there were increased IBAT TH (20%) and dopamine-beta-hydroxylase (87%) activities compared with chow-fed controls. Therefore, sympathetic activity varied markedly as a function of both dietary composition and relative body weight during the development of DIO.
Metabolic organization of muscle and brown fat of normal and dystrophic hamsters
Authors: Wickler S. J. , Horwitz B. A.
Published: December 2017

The thermogenic response to catecholamines, i.e., regulatory nonshivering thermogenesis (NST), is significantly reduced in dystrophic hamsters (BIO 14.6) compared with age-matched normals. The possibility that this reduction reflects, in part, lower levels of enzymes in those tissues implicated in NST has been examined by assaying citrate synthase (CS), beta-hydroxyacyl CoA dehydrogenase (HOAD), and phosphofructokinase (PFK), enzymes whose activity reflect the potential flux of substrates through the tricarboxylic acid cycle, beta-oxidation, and glycolysis, respectively. Each enzyme was assayed in brown fat, heart, gastrocnemius, and semitendinosus of 3-mo-old normal (n = 15) and dystrophic (n = 18) hamsters. Brown fat masses from interscapular, cervical, and scapular-axillary regions of dystrophics averaged only 50% those of normals (424 vs. 890 mg). Additionally, markers of aerobic metabolism (CS and HOAD) were significantly reduced in the brown fat from dystrophic animals. (CS activities averaged 59% of normal, whereas HOAD activities averaged 75% of normal). In dystrophic animals CS and HOAD levels were similar to those of normals in cardiac tissue but were significantly elevated in skeletal muscle samples. Tissue PFK activities were reduced only in cardiac tissue of the more affected dystrophics. Thus decreased NST capacity in dystrophic hamsters is accompanied by reduced masses and CS values in brown fat but not by decreases in the aerobic markers in skeletal or cardiac muscle.
Renal response to central volume expansion in humans is attenuated at night
Authors: Krishna G. G. , Danovitch G. M.
Published: December 2017

The renal response to central volume expansion induced by head-out water immersion was examined in 10 normal, salt-replete subjects studied during the day (0900–1300) and during the night (0000–0400). Sodium excretion in the hour preceding the study was 155 +/- 21 mueq/min and 120 +/- 14 mueq/min, respectively. During the day, immersion was followed by a natriuresis, which reached a mean peak level of 293 +/- 46 mueq/min during the 2nd h of immersion and which was maintained for the remainder of the immersion. During the night, there was no significant increase in sodium excretion from prestudy values during the first 3 h of immersion. Values rose significantly in the 4th h and reached a mean peak level of 211 +/- 20 mueq/min. Potassium excretion rose during the day (from 61 +/- 12 mueq/min to 126 +/- 16 mueq/min) but was unaltered at night. Neither glomerular filtration rate nor plasma levels of aldosterone differed between day and night. To exclude the possibility that the blunted nocturnal natriuresis could be explained by a lesser degree of central fluid translocation induced by immersion at night six normal salt-replete subjects received a 2-liter infusion of normal saline administered over 4 h during the day and during the night. The blunting of the nocturnal natriuresis was again observed. We conclude that, in addition to well-described diurnal variations in electrolyte excretion, there are diurnal variations in the responsivity of volume regulatory mechanisms.
Effects of sucrose, caffeine, and cola beverages on obesity, cold resistance, and adipose tissue cellularity
Authors: Bukowiecki L. J. , Lupien J. , Follea N. , Jahjah L.
Published: December 2017

Rats consuming Coca-Cola and Purina chow ad libitum increased their total energy intake by 50% without excess weight gain. Their resistance to cold was markedly improved. These phenomena were characterized by significant increases in interscapular brown adipose tissue weight (IBAT) (91%), cellularity (59%), triglyceride content (52%), protein content (94%), and cytochrome oxidase activity (167%). In contrast, Coca-Cola consumption did not significantly affect the cellularity or triglyceride content of parametrial white adipose tissue (PWAT), although it slightly augmented PWAT weight. The effects of Coca-Cola on cold resistance, IBAT cellularity, and composition were entirely reproduced by sucrose, but not caffeine, consumption. Although caffeine also increased IBAT cellularity and composition, it significantly decreased the rate of body weight gain, PWAT weight, and adipocyte size. Moreover, it markedly inhibited adipocyte proliferation in PWAT thereby mimicking the effects of exercise training and food restriction (Bukowiecki et al., Am. J. Physiol. 239 (Endocrinol. Metab. 2): E422-E429, 1980). It is concluded a) that sucrose and Coca-Cola consumption improve the resistance of rats to cold, most probably by increasing brown adipose tissue cellularity, and b) that moderate caffeine intake might be useful for inhibiting proliferative activity in white adipose tissue, thereby preventing obesity.
Cerebroventricular sites for enkephalin inhibition of the central actions of angiotensin
Authors: Summy-Long J. Y. , Keil L. C. , Sells G. , Kirby A. , Chee O. , Severs W. B.
Published: December 2017

The effect of leucine5-enkephalin (Leu-enkephalin) administered into the lateral (LV) or fourth (4V) cerebroventricle on angiotensin II (ANG II)-stimulated increase in blood pressure, plasma vasopressin concentration ([AVP]), and drinking behavior was determined in conscious rats. Leu-enkephalin (20, 50, or 100 micrograms) was injected into the LV (5 microliters) or 4V (2 microliters) less than or equal to 15 s before ANG II (50 or 500 ng, LV). LV and 4V administration of Leu-enkephalin (100 or 50 micrograms) significantly (P less than 0.05) delayed the drinking onset, decreased the number of animals drinking, and reduced the volume consumed (100 micrograms, 30 min) in response to ANG II (50 ng). ANG II-stimulated increases in plasma [AVP] and blood pressure were inhibited by 50 or 100 micrograms, respectively, of Leu-enkephalin administered into LV but not 4V. Decreased motor activity occurred after Leu-enkephalin (100 micrograms) administration into LV and 4V, whereas head shakes were more consistent after the former. Fast green dye administered into 4V did not reach anterior periaqueductal, third, or lateral cerebroventricular sites. Thus opioid peptide receptors inhibiting ANG II-stimulated drinking, vasopressin release, and pressor response are postulated to be in brain structures accessible from lateral or third cerebroventricles. Opiate receptors inhibitory to drinking are also reached from peri-4V sites.
Physiological conflict in humans: fatigue vs. cold discomfort
Authors: Cabanac M. , Leblanc J.
Published: December 2017

Six male human subjects were placed in a situation of physiological conflict, fatigue vs. cold discomfort. Dressed in swim suits and shoes they walked at 3 km X h-1 on a treadmill placed in a climatic chamber. The slope of the treadmill was varied from 0 to 24% and the ambient temperature (Ta) from 25 to 5 degrees C. The subjects could choose Ta when slope was imposed or the converse. They rated pleasure and displeasure of Ta and exercise. Deep body temperature and heart rate were monitored. The results show that the subjects adjusted their behavior to maintain approximatively steady deep body temperature and to limit heart rate below 120 beats X min-1. The physiological compromise was thus correlated to the drive for maximal pleasure-minimal displeasure in the two sensory dimensions fatigue and discomfort.
Role of calcium in osmotic and nonosmotic release of vasopressin from rat organ culture
Authors: Ishikawa S. , Schrier R. W.
Published: December 2017

In the present study the role of calcium (Ca) in the stimulation of arginine vasopressin (AVP) release from the cultured rat hypothalamoneurohypophyseal complex (HNC) was examined in response to three different stimuli, 56 mM potassium chloride, an increase in medium osmolality from 290 to 310 mosmol/kg H2O, or 1 X 10(-6) M angiotensin II (ANG II). With all three stimuli AVP release from rat HNC explants was enhanced by increasing Ca concentration in the medium from 0 to 1.8 mM Ca. However, high concentrations of Ca (8 mM) inhibited the response of AVP release to either hyperosmolality or angiotensin II. Chemically dissimilar blockers of cellular Ca uptake, verapamil (5.2 X 10(-6) or 5.2 X 10(-5) M) or nifedipine (5.8 X 10(-6) or 5.8 X 10(-5) M), completely abolished AVP release from rat HNC explants in response to the three different stimuli in 1.8 mM Ca. In a normal concentration of medium Ca (1.8 mM) a Ca ionophore, A23187 (3.8 X 10(-5) M), significantly enhanced the osmotic and nonosmotic (ANG II-stimulated) release of AVP from rat HNC explants compared with controls without Ca ionophore. This effect of Ca ionophore to enhance AVP release was more evident in a lower Ca medium (0.9 mM Ca in the hyperosmolality study and 0.3 mM Ca in the ANG II study). These results therefore indicate that cellular Ca uptake is an important modulator of osmotic and nonosmotic AVP release from the intact rat hypothalamoneurohypophyseal system. The influence of extracellular Ca on the osmotic and nonosmotic release of AVP is also demonstrated.
Changes in beta-adrenergic receptors in dog livers during endotoxic shock
Authors: Liu M. S. , Ghosh S.
Published: December 2017

The effects of endotoxin administration on beta-adrenergic receptors in dog liver plasma membranes were studied using [3H]dihydroalprenolol as a radioactive ligand. The Scatchard analysis revealed a one-component binding characteristic both in control and endotoxin-injected dogs. The Kd (dissociation constant) value was increased by 60% (4.2 +/- 0.5 nM for control vs. 6.7 +/- 0.5 nM for endotoxic; P less than 0.01) and the Bmax (maximum binding capacity) was decreased by 38% (600 +/- 60 and 370 +/- 70 fmol/mg protein for control and endotoxic, respectively; P less than 0.01) 2 h following endotoxin administration. The competitive inhibition studies show that the apparent Kd values for (-)-isoproterenol, (-)-epinephrine, and (-)-norepinephrine were increased by 14, 51, and 5 times, respectively, 2 h postendotoxin. In addition, endotoxin in vitro had a dose-dependent inhibitory effect on the specific binding of [3H]dihydroalprenolol, and it also reduced the number of beta-receptors. These data demonstrate that endotoxin, both in vivo and in vitro, decreased the binding affinity and the number of beta-adrenergic receptors in dog liver plasma membranes. A modification of the beta-adrenergic receptors in dog livers induced by endotoxin administration may play an important role in the development of hepatic glucose dyshomeostasis during shock.
Role of luminal acidity in the pathogenesis of stress-induced gastroduodenal disease
Authors: Natelson B. H. , Tapp W. N.
Published: December 2017

Infusion of progressively more acidic fluids into the stomachs of rats stressed by immobilization had disparate effects on gastric erosive disease despite their producing a stepwise fall in venous pH. At the highest concentration infused, disease was exacerbated. However, at lower concentrations, disease was ameliorated. The acidity of the infusate altered the incidence but not the magnitude of the duodenal disease that accompanies stress. When bicarbonate was given parenterally, systemic pH was normalized but gastric disease still developed. Thus the level of mucosal pH does not reliably predict whether or not gastric disease will develop. When a series of progressively more basic fluids was infused into the stomachs of stressed rats, gastric disease was lessened in only those rats infused with the highest concentration of bicarbonate. Increasing the pH of the infusate in a stepwise fashion produced a stepwise diminution of duodenal disease incidence with no effect on duodenal disease severity. When the stressed rat's mucosa was stimulated to secret acid by the parenteral injection of secretagogues, gastric disease severity was the same as in control animals given saline. Although secretagogue infusion did not affect the incidence of stress-induced duodenal disease, it significantly exacerbated the magnitude of the elicited disease. These experiments suggest that luminal acid plays a negligible role in the onset of stress-induced gastric disease but may be important in determining the severity of the gastric disease once it has begun. Conversely the amount of luminal acid correlates with the incidence of stress-induced duodenal disease but does not seem to play a role in determining the severity of the duodenal disease after it has begun.
Arterial pressure-urinary output relationship in DOCA-saline hypertensive rats
Authors: Sugai T. , Nakagawa Y. , Takeda K. , Imai S.
Published: December 2017

To know the role played by the kidney in the genesis of deoxycorticosterone acetate (DOCA)-saline hypertension, the arterial pressure-urinary output (AP-UO) relationship was compared in unanesthetized, unrestrained uninephrectomized (1-K) control and normal Wistar-Imamichi (W-I) rats according to the method of Norman et al. [Am. J. Physiol. 234 (Regulatory Integrative Comp. Physiol. 3): R98-R103, 1973]. The gradient of AP-UO relationship was slightly decreased in 1-K control rats compared with that in W-I rats. However, the AP-UO relationship of DOCA-saline hypertensive rats underwent only a parallel shift to higher blood pressure ranges compared with that of 1-K control rats. There was no significant change in the urinary volume, urinary sodium excretion, and urinary osmolarity. Furthermore, the AP-UO relationship was shifted back to the lower pressure range under the influence of hydralazine, a preferential renal arteriolar dilator, suggesting that constriction of the renal artery caused the rise of the arterial pressure in DOCA-saline hypertensive rats.
Renal glomerular filtration rate and hepatic blood flow during voluntary diving in Weddell seals
Authors: Davis R. W. , Castellini M. A. , Kooyman G. L. , Maue R.
Published: December 2017

Renal and hepatic function were studied during voluntary dives in Weddell seals by measuring the clearance rate of inulin and indocyanine green (ICG). Inulin is cleared exclusively by the kidneys and measures renal glomerular filtration rate (GFR). ICG is cleared by the liver and is blood flow dependent at concentrations used. Studies were conducted from a portable hut with a trapdoor placed over an isolated hole in the sea ice near McMurdo Station, Antarctica. An intravertebral extradural catheter was inserted percutaneously under light anesthesia in subadult seals weighing 130-200 kg. When released into the ice hole, the seals made voluntary dives, but always had to return to breathe. Serial blood samples were taken after single injections of inulin and ICG and analyzed within 24 h. The mean half time (t 1/2) for inulin clearance while resting at the surface was 27.3 +/- 13.0 min (n = 43) and the mean t 1/2 for ICG clearance was 18.3 +/- 7.3 min (n = 23). The mean resting GFR was 3.6 ml X min-1 X kg-1 (range 3.2-3.9, n = 3). Inulin and ICG clearance rates did not change from resting levels during dives shorter than the seal's aerobic dive limit (ADL). Inulin clearance decreased over 90% during dives longer than the ADL, but there was no significant reduction in ICG clearance during dives lasting up to 23 min. It appears that normal renal GFR and hepatic blood flow continue during natural aerobic dives. During dives that exceed the ADL, GFR is reduced but hepatic blood flow may be maintained.
Effects of hypotonic, isotonic, and hypertonic fluids on thoracic duct lymph flow
Authors: Brace R. A. , Power G. G.
Published: December 2017

To test whether whole-body lymph flow responses to vascular volume loading depend on osmolality, we measured left thoracic duct lymph flow rate and protein concentration, plasma protein concentration, plasma osmolality, hematocrit, and arterial and venous pressures in pentobarbital-anesthetized, acutely nephrectomized dogs. Hypo- (100 mosmol), iso- (309 mosmol), and hypertonic (600 mosmol) saline, isotonic lactated Ringer solution, and 5% glucose in lactated Ringer solution (580 mosmol) were infused into the jugular vein (20 ml/kg per infusion over 5 min at 30-min intervals). Changes in blood, interstitial, and cellular volumes were calculated from the infused volume and from the hematocrit and plasma osmolality. The hypotonic fluid increased lymph flow about half as much as the isotonic fluid, whereas the hypertonic fluids increased lymph flow about twice as much as the isotonic infusions. Responses appeared independent of the osmotic agent, because hypertonic NaCl was as effective as hypertonic glucose in increasing lymph flow. Responses were not altered appreciably after lowering arterial pressure by 25 mmHg. The major finding of this study is that for every condition we explored, the excess lymph flow over 30 min (ELF in ml X kg-1 X 30 min-1) correlated with the change in interstitial fluid volume (delta ISFV in ml/kg); ELF = 0.076 delta ISFV (r = 0.909). These data suggest that cellular fluid that enters the interstitium is equally effective in increasing thoracic duct lymph flow as is vascular fluid that filters into the interstitium.
Preoptic recess lesions, body fluid compartments, and the renin-aldosterone system
Authors: Bealer S. L. , Schneider E. G.
Published: December 2017

The effects of electrolytic ablation of the periventricular tissue surrounding the anteroventral third ventricle (AV3V) of the rat brain on body fluid distribution and the renin-aldosterone system were determined. Rats underwent either ablation of AV3V periventricular tissue or control surgeries. After recovery, animals were implanted with femoral arterial and jugular venous catheters, and sodium space and plasma volume were measured by calculating the dilution of intravenous injections of 22Na- and 125I-labeled serum albumin, respectively. Total body water was determined in separate groups of rats by desiccation. Other animals with AV3V lesions and control rats were used to measure urinary sodium excretion and plasma renin (Prenin) and aldosterone (Paldo) concentrations while volume replete and after volume depletion. Animals with AV3V lesions had expanded extracellular fluid volume and decreased plasma volume, but total body water was comparable with control-operated rats. Volume-replete and volume-depleted rats with AV3V lesions had significantly higher Prenin than control animals in similar volume states. Although Paldo was not different between groups in the volume-replete state, it was significantly greater in rats with AV3V lesions than in control animals after volume depletion. These data demonstrate that AV3V periventricular ablation results in chronic alterations in the normal body fluid distribution but does not diminish the rats' ability to increase Prenin and Paldo or decrease sodium excretion during volume depletion.
Effects on intravascular pressures of vasopressin and angiotensin II in dogs
Authors: Bie P. , Warberg J.
Published: December 2017

The effects of 30-min intravenous infusions of 8-arginine vasopressin (AVP) and angiotensin-(1,8)-octapeptide (ANG II) to conscious dogs were studied by measurements of systolic (SABP), mean (MABP), and diastolic arterial blood pressures, central venous pressure (CVP), heart rate (HR), and plasma concentrations of vasopressin (pAVP). Infusion of AVP at six rates (0.4-12.8 ng X min-1 X kg-1) raised mean pAVP by 5-490 pg/ml and increased CVP by 2-10 cmH2O. HR decreased and arterial pressures increased with infusion rates of 1.6-12.8 ng X min-1 X kg-1. However, the increase in SABP was only transient. ANG II increased all arterial pressures; however, it barely changed CVP and did not change HR or pAVP. It is concluded that 1) AVP can elevate MABP without changes in SABP, 2) the effects of AVP on arterial pressures are buffered within 5-15 min, 3) CVP can be increased by doses of AVP that do not affect arterial pressures, and 4) the pressor activity is independent of the presence of ANG II. The results confirm that the cardiovascular response to vasopressin is qualitatively different from that elicited by ANG II.
Role of dietary preferences in the weaning pattern of the rat
Authors: Blake H. H. , Okuhara C. T. , Henning S. J.
Published: December 2017

Weaning in the rat begins on postnatal day 17 and is completed by day 26. To evaluate the contribution of dietary preferences and/or aversions to weaning progression, choice experiments utilizing isocaloric liquid diets were conducted. In experiment 1, both consumption records and behavioral studies showed that pups choosing between two diets differing only in the nature of the carbohydrate (CHO) (glucose vs. lactose) had a strong preference for the glucose diet. In experiment 2, pups chose between diets differing in the relative proportions of CHO and fat. When the CHO was glucose, the preference was for the high-CHO diet, whereas when the CHO was lactose, the preference was for the low-CHO diet. The sweetness preference and/or lactose aversion of these experiments was present from day 17 onward and therefore cannot explain the gradual transition seen in normal weaning. In experiment 3, behavioral testing showed that pups choosing between suckling from their anesthetized dam or drinking a liquid diet strongly preferred to suckle at day 17 but to drink by day 24. The gradual transition displayed in this experiment suggests that the decline of interest in suckling plays an important role in the process of weaning.
Timing of human sleep: recovery process gated by a circadian pacemaker
Authors: Daan S. , Beersma D. G. , Borbely A. A.
Published: December 2017

A model for the timing of human sleep is presented. It is based on a sleep-regulating variable (S)--possibly, but not necessarily, associated with a neurochemical substance--which increases during wakefulness and decreases during sleep. Sleep onset is triggered when S approaches an upper threshold (H); awakening occurs when S reaches a lower threshold (L). The thresholds show a circadian rhythm controlled by a single circadian pacemaker. Time constants of the S process were derived from rates of change of electroencephalographic (EEG) power density during regular sleep and during recovery from sleep deprivation. The waveform of the circadian threshold fluctuations was derived from spontaneous wake-up times after partial sleep deprivation. The model allows computer simulations of the main phenomena of human sleep timing, such as 1) internal desynchronization in the absence of time cues, 2) sleep fragmentation during continuous bed rest, and 3) circadian phase dependence of sleep duration during isolation from time cues, recovery from sleep deprivation, and shift work. The model shows that the experimental data are consistent with the concept of a single circadian pacemaker in humans. It has implications for the understanding of sleep as a restorative process and its timing with respect to day and night.
Attenuation by prostaglandins of adrenergically induced renal vasoconstriction in anesthetized rats
Authors: Inokuchi K. , Malik K. U.
Published: December 2017

We have investigated the role of prostaglandins (PG) in the modulation of adrenergic neuroeffector events by examining the effect of PGI2 and PGE2 and their precursor, arachidonic acid, on the decrease in renal blood flow elicited by renal nerve stimulation or by injected norepinephrine in pentobarbital-anesthetized rats, with or without pretreatment with the cyclooxygenase inhibitor, sodium meclofenamate. Administration of PGI2 or PGE2 (0.4 micrograms X kg-1 X min-1) or arachidonic acid (5 micrograms X kg-1 X min-1) into the renal artery reduced vascular resistance and inhibited the vasoconstrictor response elicited by renal nerve stimulation or by injected norepinephrine. In contrast, administration of sodium meclofenamate (10 mg/kg iv + 30 micrograms X kg-1 X min-1) into the renal artery increased renal vascular resistance and enhanced the renal vasoconstrictor response to both adrenergic stimuli. In animals pretreated with the cyclooxygenase inhibitor, the ability of arachidonic acid, but not that of either PGE2 or PGI2, to reduce renal vascular resistance and the vasoconstrictor response to either nerve stimulation or injected norepinephrine was abolished. These data indicate that one or more prostaglandins, probably PGE2 or PGI2, formed in the kidney reduce renal vascular tone by their direct action on the vascular smooth muscle and by attenuating the influence of adrenergic stimuli on renal vasculature.
Circadian brain and body temperature rhythms in the squirrel monkey
Authors: Fuller C. A.
Published: December 2017

This study examines the hypothalamic temperature rhythm and its relationship with the colonic temperature rhythm of squirrel monkeys in 24-h light-dark cycles (LD 12:12) at four different ambient temperatures (Ta). The waveforms and phases of both temperature rhythms were similar in all TaS. The rhythm amplitudes were, however, reduced as Ta increased. The 24-h means also showed systematic decreases at higher TaS. The hypothalamic temperature was regulated over a narrower range than the colonic temperature and was higher than colonic temperature at all TaS except the warmest. Further, the mean nighttime temperatures were influenced more by Ta than were the mean daytime temperatures. In summary, the hypothalamic and colonic temperature rhythms are very similar in their circadian regulation. However, the mean temperature levels of these rhythms are controlled differentially. Thus these rhythms are the integrated response of both the circadian and thermoregulatory control systems.
Comparison of a class of regression equations
Authors: Jackson T. E.
Published: December 2017

The method described in this paper offers a means of comparing linear regression equations with many parameters by utilizing joint parameter confidence regions. It is useful when comparing sets of data in which each set is represented by a similar regression equation. The method consists of establishing a full-rank linear model with the data sets to be considered and then testing hypotheses concerning parameters of the model. It is conveniently expressed in matrix algebra form and is amenable to computer analysis.
Phase-response and Aschoff illuminance curves for locomotor activity rhythm of the rat
Authors: Summer T. L. , Ferraro J. S. , McCormack C. E.
Published: December 2017

A phase-response curve (PRC) for the circadian rhythm of locomotor activity was constructed for female Sprague-Dawley-derived rats kept in continuous darkness (DD) except when given a 1-h light pulse (150 lx) once each 2 wk. By use of the circadian onset of wheel running as the phase-reference point, the free-running period (tau) in DD was 24.09 h. Maximum phase delays and phase advances occurred in response to light pulses given during the first 5 and last 6 h of activity, respectively. The delay-to-advance ratio (D/A) of the PRC was 1.5. In a separate group of rats exposed to continuous light, tau increased by 1.45 h as illuminance was increased in log steps from 0.1 to 10 lx, thus demonstrating the Aschoff effect in rats. This increase in tau was large, considering the relatively low D/A of the PRC, suggesting that factors in addition to the D/A contribute to the Aschoff effect.
Cardiac output and redistribution of organ blood flow in hypermetabolic sepsis
Authors: Lang C. H. , Bagby G. J. , Ferguson J. L. , Spitzer J. J.
Published: December 2017

Cardiac output (CO) and the distribution of blood flow were studied in chronically catheterized conscious rats during sustained (4 days) sepsis. Septicemia was induced by intraperitoneal administration of a pooled fecal inoculum, and tissue blood flow and CO were determined daily with 15-micron radioactive microspheres. Mean arterial blood pressure (MABP, 113 +/- 2 mmHg), CO (244.5 +/- 11.4 ml X min-1 X kg-1), and total peripheral resistance (TPR, 1.36 +/- 0.07 mmHg X ml-1 X min) were stable in control rats over the 4 days postinoculation. Septic animals showed a consistent tachycardia with MABP significantly reduced only on days 3 and 4 (86 +/- 4 mmHg). A hyperdynamic response to sepsis was indicated by an elevated CO (27%) and similarly reduced TPR on day 2. The calculated stroke volume averaged 0.22 +/- 0.01 ml/beat and did not vary over time or between the two groups. There was a 40-70% increase in blood flow to the heart, spleen, adrenal glands, and small intestine, and a greater than sixfold increase in hepatic arterial blood flow. The sustained elevation of coronary blood flow, observed in septic animals, was independent of myocardial work and is consistent with impaired myocardial function. Pancreas, stomach, and skeletal muscle blood flow was consistently compromised (24, 39, and 52%, respectively) during sepsis. Blood flow in other organs remained unchanged over time. Sepsis-induced changes in the fractional distribution of blood flow to various organs were similar to those described for absolute flow. (ABSTRACT TRUNCATED AT 250 WORDS)
Predominantly beta-adrenergic control of equine sweating
Authors: Bijman J. , Quinton P. M.
Published: December 2017

Single equine sweat glands were found to secrete for more than 1 h in vitro in response to pharmacologic secretagogues. The adrenergic agonists epinephrine and norepinephrine evoked maximal sweat rates of 2.0 nl X gland-1 X min-1. However, the concentration of norepinephrine (10(-5) M) required to evoke the maximal response was 10 times higher than that for epinephrine. Maximal sweat rates also were stimulated with the beta 2-adrenergic agonist terbutaline. This stimulation was blocked by the beta-adrenergic antagonist propranolol. Moderate sweating responses were also obtained with the alpha-adrenergic agonists phenylephrine and methoxamine, but these responses also were blocked by propranolol. Neither the muscarinic blocker atropine nor the alpha-adrenergic antagonist phentolamine inhibited any of the pharmacologically induced sweat responses. Unlike most other mammalian exocrine glands, cholinergic agonists were ineffective in stimulating sweat secretion. Therefore equine sweat glands apparently are under predominantly beta-adrenergic control.
Cardiovascular and respiratory responses to heat in dehydrated dogs
Authors: Baker M. A.
Published: December 2017

The effect of dehydration on rectal temperature, respiratory frequency, upper respiratory evaporation, cardiac output, and common carotid blood flow was studied in large mongrel dogs at rest at ambient temperatures between 25 and 45 degrees C. Measurements were made in animals hydrated ad libitum and when they had been dehydrated by removal of drinking water. In hydrated animals, mean body weight was 31.6 +/- 1.7 (SE) kg and plasma osmolality was 296 +/- 2 mosmol/kg H2O. Dehydration decreased body weight to 28.2 +/- 1.5 kg and increased osmolality to 328 +/- 5 mosmol/kg H2O. At all ambient temperatures, every dehydrated animal had a higher rectal temperature, lower respiratory frequency, lower upper respiratory evaporation, lower cardiac output, and lower common carotid blood flow. Rectal temperature, measured in seven animals, was constant as ambient temperature was raised from 25 to 45 degrees C in both the hydrated and dehydrated state, but was elevated by 0.72 degrees C in dehydrated animals. Hypothalamic temperature, measured in two animals, was elevated less than rectal temperature when they were dehydrated. Upper respiratory evaporation and respiratory frequency, measured in seven animals, increased with increasing ambient temperature in both the hydrated and the dehydrated dogs, but were lower at every ambient temperature in dehydrated animals. Cardiac output, measured in five animals, was lower in dehydrated animals at every ambient temperature.(ABSTRACT TRUNCATED AT 250 WORDS)