bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic contribution of CO2 to the "group effect"
Authors: Schlenker E. H. , Carlson D. , Herreid C. F.
Published: December 2017

Metabolic rates (VCO2) were determined in 22 mice. Subsequently 11 of the mice were placed into separate metabolic chambers. Each chamber was connected to one other metabolic chamber containing one mouse. The metabolic rates of the 11 “donor” and the 11 “'recipient” mice were measured. Afterwards the direction of airflow was reversed so that the previous donor became the recipient mouse and the previous recipient became the donor. Again VCO2 was measured. When the mice were donors, VCO2 = 2.75 +/- 1.0 ml CO2 . g-1 . h-1, whereas when recipients, VCO2 = 1.9 +/- 1.0 ml CO2 . g-1 . h-1 (P less than 0.01). Eleven of the mice were then made anosmic using an intranasal instillation of 5% ZnSO4. Anosmia was confirmed behaviorally. The metabolic rates of the anosmic and control mice were again determined when each was a donor and a recipient. VCO2 dropped from 3.1 to 1.8 ml CO2 . g-1 . h-1 from donor status to recipient status. Finally, VCO2 was determined when all 22 mice were exposed to 0.05% CO2 or 0.2% CO2 in air (the level of CO2 in the exhaust air of donor mice). VCO2 dropped from 3.0 +/- 0.38 on 0.05% CO2 to 1.7 +/- 1.01 on 1.01 ml CO2 . g-1 . h-1 on 0.2% CO2 in the anosmic group and from 2.9 +/- 0.29 to 1.91 +/- 0.51 ml CO2 . g-1 . h-1 in the control group when exposed to the same gases. These experiments suggest that the airborne factor emanating from the donor chambers was acting systematically and not via the olfactory system. This factor may be a low level of CO2.
Baroreceptor control of heart rate in the conscious toad Bufo marinus
Authors: Smith D. G. , Berger P. J. , Evans B. K.
Published: December 2017

Perivascular balloons were used to elicit heart rate (HR) responses to imposed changes in mean arterial pressure (Pa) in conscious unrestrained toads (Bufo marinus). It is clear that functional baroreceptors lie in the pulmocutaneous arteries of B. marinus, and that these can elicit compensatory heart rate responses to perturbations of blood pressure. Functional baroreceptors were not present in the carotid circulation and are probably absent from the lateral aortae and conus arteriosus as well. Normalized gain of the baroreceptor-heart rate reflex (delta HR%/delta Pa) in five toads was 13%/kPa, which is considerably less than that found in other vertebrates to date.
Spontaneous obesity in maturing squirrel monkeys fed semipurified diets
Authors: Ausman L. M. , Rasmussen K. M. , Gallina D. L.
Published: December 2017

The squirrel monkey is usually a lean primate (5-10% fat) until the onset of the pubertal growth spurt at about 3 yr of age. This characteristic is generally maintained thereafter for animals fed commercial monkey biscuits. Animals fed semipurified diets containing a moderate amount of fat and sucrose continue to gain weight, however, until a frank obesity is developed. Conventionally, an animal is labeled obese when the body weight is greater than 1,200 and 800 g for males and females, respectively. By 6 yr of age, practically 100% of the animals satisfy these criteria. The carcass composition from a subset of obese animals showed that fat content ranged from 18 to 40%, and that weight gain in males heavier than 800 g represents increasing proportions of fat. The annual weight cycling ascribed to sexual activity appeared to remain superimposed on the “basal” obesity. Food intake monitoring showed a significant hyperphagia associated with rapid weight gain. A major interaction between the neuroendocrine setting and a very palatable diet in the development of this syndrome is implied.
Thermosensitive single-unit activity of in vitro hypothalamic slices
Authors: Kelso S. R. , Perlmutter M. N. , Boulant J. A.
Published: December 2017

Single-unit activity was recorded in vitro from tissue slices of rat preoptic area-anterior hypothalamus. The thermosensitivity of 139 units was determined by their changes in firing rate in response to changes in slice temperature. Of these neurons, 30% were warm sensitive, 10% were cold sensitive, and 60% were temperature insensitive. These proportions are similar to results obtained in whole-animal studies, indicating that this is a viable preparation. It also suggests that hypothalamic neuronal thermosensitivity is not dependent on peripheral afferent input. All units had low firing rates (less than 10 imp/s) at 37 degrees C, and 83% of the warm-sensitive units were most thermosensitive above 37 degrees C. This supports the concept that afferent input determines the level of firing rate and range of thermosensitivity of warm-sensitive neurons. The cold-sensitive units also displayed maximal thermosensitivity above 37 degrees C, which would be expected if cold-sensitive neurons received inhibitory synaptic input from nearby warm-sensitive neurons.
Drug entry into and distribution within brain and cerebrospinal fluid: [14C]urea pharmacokinetics
Authors: Rapoport S. I. , Fitzhugh R. , Pettigrew K. D. , Sundaram U. , Ohno K.
Published: December 2017

A four-compartment model was derived to analyze drug exchange among cerebral capillary plasma, cerebrospinal fluid (CSF), and the brain extracellular and intracellular (or bound) compartments. Equations that were derived incorporated the factor of cerebral blood flow. They were fit by nonlinear least squares to measured brain, plasma, and CSF (when available) concentrations of [14C]urea in the rat, in response to a step increase in plasma concentration, to intravenous infusion, or to a bolus injection of tracer. Best-fit values for the transfer constants were consistent among the three administrative regimens and agreed with published values, when available. Expressions also were derived and numerically evaluated for the lower limit of the brain extracellular space, for half times of brain [14C]urea uptake, and for the steady-state brain/plasma distribution volume. The model should make it possible to use transfer constants obtained for a given drug from one study (e.g., constant plasma concentration) to predict brain concentrations from measured plasma concentrations in other acute or chronic studies.
Chemical maturation in growing guinea pigs
Authors: Sheng H. P. , Huggins R. A. , Garza C.
Published: December 2017

Twenty-seven guinea pigs were analyzed chemically for total body water (TBW), fat, nitrogen (N), calcium (Ca), and sodium (Na); 26 were analyzed for potassium (K). Body weights ranged between 82 and 877 g. The data were analyzed by regression analysis. If the slope of a regression line did not differ significantly from zero (P less than 0.05), the mean and standard deviation were calculated. The slopes of the regression lines were significant for Na [meq/100 g fat-free wet weight (FFWW)] on body weight in grams, K in milliequivalents on FFWW in grams, and total body fat (TBF) (g) on body weight in grams. The means and standard deviations for the remaining constituents were in g/100 g FFWW; 76.0 +/- 2.5 for TBW and 2.52 +/- 0.28 for N, and in meq/100 g FFWW Ca 58.26 +/- 7.35 and K 6.35 +/- 0.74, and % TBF 8.57 +/- 3.44. The values for the following ratios were: K/N 2.609 +/- 0.247; K/TBW 0.087 +/- 0.011; and N/TBW 0.033 +/- 0.004 (K is in meq, N and H2O in g). The suggestion that the lower figure for TBW reported by earlier investigators compared to the present data could be the result of a systematic methodological error is discussed.
Physiological mechanisms for thirst in the nonhuman primate
Authors: Wood R. J. , Rolls E. T. , Rolls B. J.
Published: December 2017

The relationship between body fluid deficits and drinking has been investigated in a nonhuman primate. Intravenous sodium chloride infusions (0.93-3.25 M) given to rhesus monkeys caused drinking correlated with increases in plasma osmolality and sodium concentrations. Sucrose infusions (0.3 M in 0.15 M NaCl) also caused drinking while equiosmolal urea infusions did not. It was found that the drinking threshold corresponded to a 2.3% increase in plasma osmolality. Water deprivation for 24 h caused significant cellular dehydration, as indicated by a 5.8% elevation in plasma osmolality that exceeded the threshold for thirst, and a significant hypovolemia as indicated by elevated plasma protein and hematocrit values. Intravenous water preloads decreased plasma osmolality and produced a dose-related decrease in subsequent drinking. Infusions that restored plasma osmolality to predeprivation values, reduced intake by 85%. Intravenous isotonic saline preloads which abolished the hypovolemia did not have a consistent effect and reduced mean water intakes by only 3.2%. Thus in the rhesus monkey, cellular dehydration is an effective stimulus for thirst, and it is the primary determinant of drinking after water deprivation, used as an example of a natural thirst stimulus. In contrast to findings in nonprimates, the extracellular deficit contributes very little to drinking after water deprivation.
Perfused rat hindlimb wound model: lambda-carrageenan induced
Authors: O'Connor J. A. , Scott R. L. , Mellick P. W. , Caldwell M. D.
Published: December 2017

We established an isolated perfused rat hindlimb wound model using intramuscular injections of lambda-carrageenan. Wound and control hindlimbs of 24-h fasting anesthetized (phenobarbital sodium, 5 mg/100 g body wt) rats were perfused for 60 min (10 ml/min) with media containing 10 mM glucose and physiological levels of amino acids. Analysis of perfusate showed a significant increase in glucose clearance and lactate production from the wounded hindlimb but no significant difference in tissue adenine nucleotide levels. Alterations in net amino acid release were measured over a 60-min period; all amino acids were released in greater concentration from wounded hindlimbs. Comparison of amino acid release, normalized for phenylalanine concentration, suggested the following alterations in amino acid metabolism by the wounded tissue: depressed threonine, glycine serine and alanine release, and increased release of the branched chain amino acids (BCAA), leucine, isoleucine, and valine. The increased release and intracellular concentration of BCAA was supported by decreased BCAA transaminase activity in the wounded muscle tissue. This result may explain the decreased alanine release from the wounded hindlimbs.
Peptidergic regulation of stress-induced eating
Authors: Morley J. E. , Levine A. S. , Murray S. S. , Kneip J. , Grace M.
Published: December 2017

By use of the model of stress-induced (mild tail pinch) eating we have examined the interrelationships of peptides and monoamines responsible for regulating this behavior. We have shown that the synthetic opiate analog, D-Ala2-Met-enkephalinamide (1 microgram), when administered intracerebroventricularly (icv) reverses the suppressive effects of the serotonin agonist, quipazine (40 micrograms icv), the beta-agonist, isoproterenol (40 micrograms icv), and the alpha-antagonist, phentolamine (150 micrograms icv), and partially reversed the effects of atropine (2.5 mg/kg sc) and the dopamine antagonist haloperidol (0.5 mg/kg sc). The opiate antagonist naloxone (10 mg/kg sc) suppressed tail-pinch-induced eating, and this effect could not be reversed by the GABA-agonist muscimol (500 ng icv) nor norepinephrine (20 micrograms icv). The putative satiety hormones cholecystokinin-octapeptide (5 micrograms/kg sc) and bombesin (5 micrograms/kg sc) suppressed stress-induced eating. The suppressive effect of these substances was reversed by a number of known appetite stimulants viz., D-Ala2-Met-enkephalinamide, diazepam, muscimol, and propanolol. Norepinephrine reversed the suppressive effect of bombesin but not that of cholecystokinin. Based on these results we present a hypothetical model to partially explain the peptidergic-monoamine regulation of stress-induced eating.
Circadian timing of sleepiness in man and woman
Authors: Winfree A. T.
Published: December 2017

Men and women living contentedly in long-term isolation from the usual time-of-day cues have revealed surprising new regularities about the timing of human sleep/wake alternations. Contemporary effort to ferret out and articulate these regularities in quantitative terms lead to a diversity of mathematical models. If these eventually acquire predictive competence then we may expect practical improvements of therapy for insomnia, jet lag, and some kinds of psychiatric depression.
Sympathetic and thyroid influences on metabolic rate in fed, fasted, and refed rats
Authors: Rothwell N. J. , Saville M. E. , Stock M. J.
Published: December 2017

Twice daily subcutaneous injections of norepinephrine (NE, 25 micrograms/100 g body wt) for 16 days, in adults rats, produced significant increases in resting oxygen consumption (VO2), thermogenic responses to NE, plasma triiodothyrone (T3) levels, interscapular brown fat mass, and hepatic mitochondrial alpha-glycerophosphate dehydrogenase activity. These responses were absent in hypothyroid rats. Rats fasted for 72 h showed significant decreases in VO2 and plasma T3. Refeeding with carbohydrate (CHO, 40 kJ) produced a rapid rise in plasma T3 within 3 h and a delayed rise in VO2 (peak rise at 24 h). Treatment with the beta-adrenergic antagonist propranolol (2 mg/100 g body wt, sc) at the time of the meal blocked the rises in T3 and VO2. Injecting fasted rats with T3 (365 ng/100 g body wt, ip) had no effect on subsequent VO2 but NE (40 micrograms/100 g body wt, sc) produced similar increases in plasma T3 and VO2 to CHO refeeding. The delayed rise in VO2 after CHO refeeding was blocked by propranolol (0.5 mg/100 g body wt, sc) when given 24 h after the meal. These results provide evidence for catecholamine-induced changes in thyroid hormone metabolism and for a sympathetic involvement in thyroid-dependent responses to nutritional manipulations.
Fetal and maternal arterial pressures and heart rates: histograms, correlations, and rhythms
Authors: Lawler F. H. , Brace R. A.
Published: December 2017

We attempted to shed light on the characterization and control of fetal arterial pressure and fetal heart rate in the chronically catheterized fetal lamb. To do this we continuously recorded fetal and maternal arterial pressures and heart rates as well as amniotic fluid pressures using on-line computer techniques. The data were analyzed for histogram distributions, correlations and regressions, and for intrinsic rhythms within each variable. We found the following: 1) neither fetal nor maternal variables are normally distributed because of an exaggerated mode and frequent skewing to the right, 2) there was no correlation between fetal and maternal variables over time periods of 10 min to 24 h, 3) a positive correlation exists between fetal arterial pressure and fetal heart rate, 4) there were no major rhythms in the fetal or maternal variables or in amniotic fluid pressure with cycles between 10 min and 24 h. The data suggest that 1) fetal arterial pressure and heart rate are largely independent of the mother, 2) fetal and maternal variables are well controlled about a physiological set point, and 3) rhythms in fetal arterial pressure and heart rate are not significant under normal laboratory conditions.
Multiprobe monitoring of ionic, metabolic, and electrical activities in the awake brain
Authors: Friedli C. M. , Sclarsky D. S. , Mayevsky A.
Published: December 2017

A new approach for studying brain metabolic, ionic, and electrical activities in the awake animal is described. We developed a multiprobe assembly holding electrodes for extracellular K+, pH, DC potential, electrocorticogram, and temperature as well as a light guide for monitoring intramitochondrial NADH oxidation-reduction state. The assembly was designed so that because of the type of electrodes used and the protection system around them, the same system could be used in many experiments. The results presented here are typical and show the potential use of the multiprobe approach for studying the effects of hypoxia, anoxia, spreading depression, and ischemia on the awake brain. From the results obtained the following conclusions can be drawn. 1) The DC correction for the K+ and H+ measurements is necessary, although it was not as good for the H+ as for the K+ signals. 2) During ischemia (complete or partial) a clear acidification of the brain was found in correlation with the decrease in oxygen availability as evaluated by the NADH fluorescence signal. 3) During brain activation (induced by spreading depression) extracellular K+ was elevated and then actively pumped back into the cells. The NADH showed an oxidation response, and the pH response started with an alkalinization followed by a short acidification.
Sympathetic activity in spontaneously hypertensive rats after spinal transection
Authors: Schramm L. P. , Chornoboy E. S.
Published: December 2017

To test the hypothesis that sympathetic hyperactivity and hyperexcitability in spontaneously hypertensive rats (SHR) is generated at spinal and/or ganglionic levels, we measured integrated renal nerve activity (before ganglionic blockade) and adrenal nerve activity (after ganglionic blockade) in 12- to 14-wk-old SHR and normotensive Wistar-Kyoto rats (WKY). Rats were anesthetized with alpha-chloralose, artificially respired, and paralyzed. Spinal cords were transected at C1 to eliminate normal supraspinal control of sympathetic activity. The effectiveness of descending sympathoexcitatory and sympathoinhibitory pathways was tested by measuring changes in nerve activity elicited by graded spinal stimulation. Spontaneous renal nerve activity was elevated in SHR, but stimulation of descending excitatory pathways caused similar responses in SHR and WKY. Spontaneous adrenal preganglionic nerve activity was similar in SHR and WKY, but excitatory stimulation elicited larger adrenal nerve responses in SHR. We conclude that spinal and/or ganglionic mechanisms may generate a component of the sympathetic hyperactivity exhibited by SHR. The larger adrenal preganglionic nerve responses to excitatory stimulation in SHR suggest that spinal systems may be partially responsible for adrenomedullary hyperexcitability in spontaneous hypertension.
Effects of aldosterone on potassium distribution
Authors: Young D. B. , Jackson T. E.
Published: December 2017

To assess the effects of long-term changes in aldosterone on potassium distribution within the body, two groups of experiments were conducted. In the first, seven normal dogs received continuous infusion of aldosterone at a high physiological rate, 250 micrograms/day. Total exchangeable potassium (Ke) and plasma potassium concentration (KP) were measured before and 4 and 6 days after aldosterone infusion. KP fell by 20% while Ke decreased by 8% after 6 days of infusion; the ratio between extracellular and total body potassium had been altered by the aldosterone infusion. In the second study, 10 adrenalectomized dogs received aldosterone infusion first at 50 micrograms/day, then at 250 micrograms/day. While on each level of aldosterone infusion, three levels of potassium intake were given by iv infusion. When the animals were in electrolyte balance at each level of aldosterone and potassium (after at least 7 days on each level of infusion), Ke (expressed as meq/kg) and KP were measured. The two variables were plotted against each other, Ke being the independent variable. Data taken while the dogs received 50 micrograms/day aldosterone were described by the equation, KP = 0.100Ke + 0.055, while those obtained at 250 micrograms/day were fitted by the equation, KP = 0.057Ke + 1.30. The correlation coefficients for the two were 0.778 and 0.760, respectively. The regressions were significantly different at a level of P less than 0.02. Data from the two groups of experiments are consistent with the hypothesis that aldosterone alters the distribution of potassium between the intra- and extracellular spaces, a greater portion of total potassium being intracellular at higher levels of aldosterone.
Angiotensin does contribute to drinking induced by caval ligation in rat
Authors: Fitzsimons J. T. , Elfont R. M.
Published: December 2017

In small (0.5 mg/kg) subcutaneous doses, the angiotensin-converting enzyme inhibitor, captopril, greatly enhanced drinking in response to caval ligation in the rat. Drinking was not secondary to urinary water loss since the rats developed a substantial positive fluid balance. High (50 mg/kg) subcutaneous doses of captopril reduced drinking to a level below that following caval ligation alone. This effect could be mimicked by giving repeated intracerebroventricular injections of captopril (total amount 110 micrograms) to rats treated with the lower subcutaneous dose of captopril. With this combination, therefore, not only did the lower dose enhancement disappear, the basal caval ligation drinking response was also reduced with a total dose of captopril of less than 2% of the higher subcutaneous dose alone. These results show that, when conversion of angiotensin I to angiotensin II is prevented in the brain as well as systemically, drinking in response to caval ligation is reduced although not entirely prevented. The original report that such drinking is multifactorial, depending on angiotensin as well as nonangiotensin mechanisms, is confirmed.
Effect of cervical vagal stimulation on chicken heart rate and atrioventricular conduction
Authors: Goldberg J. M. , Johnson M. H. , Whitelaw K. D.
Published: December 2017

The effects of supramaximal stimulation of the right and left cervical vagi on heart rate, pacemaker localization, and atrioventricular (AV) conduction were investigated in 15 anesthetized open-chest chickens before and after atropine sulfate. Epicardial bipolar electrograms were recorded from selected atrial sites and right ventricle. A back lead electrocardiogram was also recorded. The effect of stimulation on atrioventricular conduction was evaluated during pacing from one of the right atrial recording sites. Supramaximal stimulation of either cervical vagus produced bradycardia but not cardiac arrest. Heart rate was reduced from an average spontaneous rate of 282 +/- 13 (SE)/min to 161 +/- 13/min with stimulation of the right and left cervical vagus. Pacemaker shifts occurred in over 50% of the vagal stimulations. The most frequent shift occurred to the lower AV node or ventricles. Pacemaker shifts to the AV junctional region producing almost simultaneous activation of the atria and ventricles were not observed. Vagal stimulation during atrial pacing produced minimal prolongation in AV conduction time [right vagus, 13 +/- 3 (SE) ms; left vagus, 8 +/- 2 ms]. Second and third degree heart blocks were not observed during pacing. Vagal stimulation after atropine indicates that the cervical vagi do not contain sympathetic fibers going to pacemaker or AV conduction tissues.
Quantitative histochemistry of rat lumbar vertebrae following spaceflight
Authors: Eurell J. A. , Kazarian L. E.
Published: December 2017

Spaceflight has been shown to cause alterations in bone mineral content, bone growth, and resorption. In this study, the effects of return to gravity immediately and 6 and 29 days following spaceflight on bone of rat vertebral bodies were histochemically analyzed. Immediately postflight, there was no significant change in calcium salt content of the vertebrae, but 6 days later it was significantly decreased (P less than 0.05). By 29 days postflight, the calcium salt content had returned to normal. Postflight collagen content was not significantly altered. Keratosulfate was significantly higher (P less than 0.05) in trabecular bone of rats immediately postflight and 6 days postflight. Chondroitin sulfate was increased in vertebral bone on days 6 and 29 postflight. The histochemical patterns observed in this study suggest that bone turnover slows in vertebrae during spaceflight allowing bone ageing. The results support the contention that a form of osteolysis begins, immediately upon return to gravity, to remove components of old bone at which time mineral levels do decrease and levels of chondroitin and keratosulfates shift. The osteolysis phase is quickly followed by new bone replacement which is completed before 29 days postspaceflight.
Effect of spaceflight on the non-weight-bearing bones of rat skeleton
Authors: Simmons D. J. , Russell J. E. , Winter F. , Tran Van P. , Vignery A. , Baron R. , Rosenberg G. D. , Walker W. V.
Published: December 2017

Male Wistar rats prelabeled with tetracycline to mark surfaces of bone and tooth formation-mineralization were placed into orbit for 18.5 days aboard the Soviet COSMOS-1129 Biosatellite. They were injected with tetracycline for a second and third time on the 6th and 27th days, respectively, after recovery of the Biosatellite. Spaceflight did not alter the rate of periosteal bone formation in the non-weight-bearing ribs and regions of the mandibles, which were covered by masticatory muscles. Bone formation-calcification rates were impaired at those sites in the jaw that had no contiguous muscle (molar region). The remodeling activity on the alveolar bone around the buccal roots of the molar teeth was significantly reduced but without creating a negative balance between formative and resorptive activities. Total Ca, P, and hydroxyproline concentrations in the jaws, incisors, and ribs were normal after spaceflight, but gravity density fractionation studies indicated that in the jaws alone, O-G conditions caused a delay in the maturation of bone mineral and matrix. A 29-day postflight recovery period at earth's gravity was sufficient to fully correct these anomalies. Relative to tooth formation, relatively normal circadian and infradian biorhythmic periodicities of Ca and P in dentin and enamel were maintained during spaceflight. We conclude that most of the non-weight-bearing bones of the rat skeleton are at risk to the effects of hypogravity.
Effects of weightlessness on body composition in the rat
Authors: Pitts G. C. , Ushakov A. S. , Pace N. , Smith A. H. , Rahlmann D. F. , Smirnova T. A.
Published: December 2017

Five male rats were exposed to 18.5 days of weightlessness in the Soviet mission COSMOS 1129 (flight group) and killed after reentry. They were immediately dissected into three major body subdivisions: musculoskeletal system, skin, and pooled viscera analyzed for fat, water, solids, and six elements. These results, expressed as percentages of the fat-free body or its components, were compared with two groups of terrestrial controls: one subjected to a flight simulation in a spacecraft mock-up and the other under standard vivarium conditions. Relative to the control groups the flight group showed 1) a reduced fraction of total body water, 2) a net shift of body water from skin to viscera, 3) a marked diminution in fraction of extracellular water in the fat-free body, 4) a marked reduction in fraction of bone mineral, 5) no change in the quantity of stored fat or adrenal masses, and 6) a net increase in total muscle mass as indicated by total body creatine, protein, and body cell mass.
Atlantic hagfish cardiac muscle: metabolic basis of tolerance to anoxia
Authors: Hansen C. A. , Sidell B. D.
Published: December 2017

Oxygen tensions in the major venous inputs to the systemic and portal-vein hearts of normoxic Atlantic hagfish (12.3 +/- 1.7 and 11.0 +/- 1.6 mmHg, respectively) are low compared with typical vertebrate values. Anoxia and poisoning with cyanide and azide do not significantly affect in situ performance of the systemic heart. Idoacetate poisoning, however, results in a significant decrease in cardiac performance of the systemic heart to 12% of the initial value after 3 h. Activities of mitochondrial enzymes of hagfish ventricle suggest a small potential for aerobic metabolism compared with those in the aerobic ventricle of Atlantic cod. Activities of enzymes of carbohydrate metabolism indicate similar anaerobic capacity in hagfish and cod ventricle. The ratio of pyruvate kinase to cytochrome c oxidase, an index of anaerobic to aerobic capacity, is 5.6 times greater in hagfish than cod ventricle. Metabolite concentrations in freeze-clamped ventricles of normoxic and hypoxic hagfish indicate hypoxia-induced activation of glycogenolysis, enhanced substrate flow across 6-phosphofructokinase, and an apparent secondary constriction of glycolysis at the level of glyceraldehyde-phosphate dehydrogenase. Carbohydrate utilization via the glycolytic pathway appears essential for maintenance of cardiac performance in both normoxic and anoxic hagfish. Under conditions of severe hypoxia, ATP provision is probably met by anaerobic glycolysis.
Human vascular tissues produce thromboxane as well as prostacyclin
Authors: Mehta J. , Roberts A.
Published: December 2017

Four different types of human blood vessels were examined for spontaneous and arachidonate-stimulated release of prostacyclin (PGI2) and thromboxane A2 (TXA2). Spontaneous PGI2 release was umbilical veins greater than umbilical arteries greater than saphenous veins greater than internal mammary arteries. With stimulation, PGI2 release by all four different vessels increased significantly (P less than 0.001) and was similar. Spontaneous release of TXA2 was also identified from all vessels examined and was similar. With stimulation, TXA2 release from all vessels increased significantly (P less than 0.001). Internal mammary artery released more TXA2 than other vessels on stimulation. The identity of TXA2 was confirmed by similar displacement of TXB2 antibody by TXB2 standards and by multiple dilutions of supernates. Treatment of vessels with aspirin inhibited PGI2 as well as TXA2 release, whereas treatment with OKY 1581 (TXA2 synthetase inhibitor) inhibited TXA2 release only. Two-dimensional thin-layer chromatography showed [14C]arachidonate conversion to PGI2 and TXA2 similar to that measured by radioimmunoassay. These data suggest that TXA2 is synthesized by human vessels. In older vessels when PGI2 generation is decreased, TXA2 production may by of pathophysiological significance.
Individual variations in structure and function of human eccrine sweat gland
Authors: Sato K. , Sato F.
Published: December 2017

The mechanisms underlying variations in perspiration rate at the glandular level are still poorly understood. Human eccrine sweat glands were dissected from the back of 12 adults, cannulated, and stimulated in vitro with methacholine (Mch). The maximal sweat rate and pKA for Mch determined from the dose-response curve for each individual were compared with the anatomic dimensions of the isolated secretory tubules. There was significant correlation between Mch sensitivity (pKA) and the size of the sweat gland, sweat rate per gland, sweat rate per unit length of the secretory tubule, and sweat rate per unit glandular volume. The sweat glands from individuals judged to be poor sweaters exhibited smaller size, lower secretory activity both in vivo and in vitro, and decreased Mch sensitivity compared with glands from physically fit individuals. We conclude that the increased Mch sensitivity and glandular hypertrophy are the two important features of functionally active sweat glands and infer that these parameters could improve as a result of acclimatization to physical exercise and/or heat.
Angiotensin II in the renal excretory response to behavioral stress in conscious dogs
Authors: Koepke J. P. , Obrist P. A.
Published: December 2017

The effects of inhibition of the renin-angiotensin system on the decreased renal excretion of sodium and water resulting from behavioral stress (shock avoidance) were examined in conscious saline-infused (4-5 ml/min) dogs. During saline infusion alone in six dogs, avoidance decreased sodium excretion (64% from 329 mueq/min) and urine flow (63% from 1.9 ml/min). During converting enzyme inhibition with captopril in the same dogs, the decreases in sodium excretion (35% from 464 mueq/min) and urine flow (35% from 2.6 ml/min) during avoidance were attenuated. Similarly, in six other dogs, avoidance decreased sodium excretion (41% from 361 mueq/min) and urine flow (43% from 2.1 ml/min) with saline infusion alone. During angiotension II (ANG II) receptor antagonism with saralasin, decreases in sodium excretion (29% from 417 mueq/min) and urine flow (27% from 2.2 ml/min) were attenuated. These mean changes in excretion during inhibition of the renin-angiotensin system were significantly (P less than 0.05) less than during saline alone. Whereas decreases in fractional sodium and water excretion were attenuated by renin-angiotensin inhibition, decreases in glomerular filtration rate and effective renal blood flow and increases in mean arterial pressure were not affected. These results indicate that ANG II contributes to the renal excretory response to avoidance.
Seasonal acclimatization in American goldfinches: the role of the pectoralis muscle
Authors: Yacoe M. E. , Dawson W. R.
Published: December 2017

The present study attempts to assess whether the marked seasonal changes in the capacity for shivering thermogenesis in American goldfinches (Carduelis tristis) involve adjustments of metabolic pathways of the pectoralis muscles similar to those observed in mammalian muscle in response to endurance training, i.e., changes favoring increased reliance on fatty acid oxidation and decreased utilization of carbohydrate reserves. Analysis of seasonal changes in enzyme profile of the pectoralis muscle revealed that winter-acclimatized birds have significantly greater (P less than 0.05) activities of phosphorylase, phosphofructokinase, and beta-hydroxy-acyl-CoA dehydrogenase than do birds in other seasons. The activities of citrate synthase and hexokinase do not vary seasonally. These results differ fundamentally from the pattern of changes in enzyme activities associated with endurance adaptation in mammals. Furthermore no seasonal changes were observed in capacities for the oxidation of fatty acids (palmitate and linoleate) or pyruvate in either crude homogenates or isolated mitochondria of goldfinch pectoralis muscles. The oxidation of pyruvate by isolated pectoralis muscle mitochondria was inhibited (greater than 90%) by the oxidation of palmitoyl carnitine at palmitoyl carnitine concentrations as low as 50 microM. These data agree with physiological observations indicating little use of glucose by this tissue during steady-state shivering. However, the extent of this inhibition does not vary seasonally. Therefore the present study fails to document any significant seasonal change in the catabolic pathways of the pectoralis muscle that would link observed seasonal changes in capacity for shivering thermogenesis with a shift in the balance of substrate use by this tissue.
Multisegmental spinal sympathetic reflexes originating from the heart
Authors: Weaver L. C. , Fry H. K. , Meckler R. L. , Oehl R. S.
Published: December 2017

Activation of cardiac sympathetic afferent nerves can initiate excitatory cardiocardiac reflexes through pathways that are exclusively spinal. In addition, stimulation of the same nerves also causes lower thoracic and lumbar sympathetic excitation, but the contribution of spinal pathways to these reflexes is unknown. Therefore experiments were performed to compare cardiac, splenic, and renal sympathetic responses to cardiac sympathetic afferent stimulation before and after cervical spinal cord transection in anesthetized, vagotomized, sinoaortic-denervated cats. Electrical stimulation of afferent cardiac sympathetic nerves produced excitatory responses in cardiac and renal nerves before transection but only cardiac nerve responses after transection. In contrast, afferent stimulation by epicardially applied bradykinin excited cardiac, renal, and splenic nerves before and after cord transection. Splenic nerve responses were greater than renal nerve responses in intact and spinal cats. These results demonstrate that spinal reflexes initiated by activation of cardiac sympathetic afferent nerves are not limited to cardiocardiac pathways. The similarity of patterns of responses in intact and spinal cats suggests that spinal pathways contribute significantly to the reflex excitation observed in intact animals.
Relationship between sympathetic activity and diet-induced obesity in two rat strains
Authors: Levin B. E. , Triscari J. , Sullivan A. C.
Published: December 2017

Chronic diet-induced obesity developed in 50-60% of male Sprague-Dawley rats fed a relatively high-calorie diet for 90 days. The remaining rats decreased their caloric intake and resisted the development of obesity. All male Fischer F-344 rats fed this diet for 85 days became obese but to only half the degree of the obese Sprague-Dawley rats. The development of chronic obesity in both rat strains was associated with decreased norepinephrine (NE) levels in hearts and aortas and decreased NE turnover in aortas compared with chow-fed controls. However, 40-50% of the Sprague-Dawley rats did not become obese on this diet, yet showed similar findings suggesting an effect of dietary composition on sympathetic function. The more profoundly obese Sprague-Dawley rats additionally showed decreased or absent NE turnover in their hearts and pancreases. Since sympathetic function in both strains of rats with diet-induced obesity was either depressed or normal, it appears unlikely that the initial enhancement of sympathetic activity seen during short-term overfeeding plays an important continuing role in combating more chronic states of obesity in the rat.
Vasopressin in blood and third ventricle CSF of dogs in chronic experiments
Authors: Simon-Oppermann C. , Gray D. , Szczepanska-Sadowska E. , Simon E.
Published: December 2017

A device for chronic implantation was developed that allowed sampling of cerebrospinal fluid (CSF) from the anterior part of the third cerebral ventricle (A3V) of dogs in repeated experiments for up to 4 mo. Osmolalities, electrolyte concentrations, and concentrations of arginine vasopressin (AVP) measured with a radioimmunoassay were determined in repeated experiments on the chronically prepared animals under conditions of normal hydration, both in the conscious state and during inhalation anesthesia. In conscious dogs, AVP concentrations in plasma and CSF were 3.3 +/- 0.4 and 21.8 +/- 2.5 pg X ml-1, respectively. During anesthesia without surgical interference, the AVP concentrations in plasma and CSF were increased twofold above the levels obtained in conscious dogs. During the time of observation (180 min) all measured parameters remained constant. The AVP concentrations in plasma and CSF samples collected during the surgical procedure of device implantation were about 10-fold higher than in the samples collected during the conscious state. Thus, in each experimental condition, AVP concentration in the CSF collected from the A3V was consistently higher than that in the simultaneously collected blood samples.
Naturalistic studies of human light exposure
Authors: Okudaira N. , Kripke D. F. , Webster J. B.
Published: December 2017

For 24 h, 10 volunteers wore an apparatus that recorded their exposure to light at eye level and at the wrist. Activity was also recorded from the head, both wrists, and an ankle. Most of the subjects were exposed to daylight illumination intensities for only brief and scattered episodes during the 24 h. Some experienced the brightest illumination in the morning and others in the evening. Illuminations at eye level and at the wrist were correlated 0.76, while eye-level illumination was correlated 0.25, 0.44, 0.39, and 0.44 with head, wrists, and ankle activity, respectively. Because human biologic rhythms are probably well synchronized only by illumination approaching daylight intensities, inadequate illumination could be a source of sleep disturbance, chronobiologic disorders, or depression.
Interspecies pharmacokinetic scaling and the Dedrick plots
Authors: Boxenbaum H. , Ronfeld R.
Published: December 2017

Interspecies variations in pharmacokinetics are frequently the consequence of organisms living in different time domains. Whereas species' parameter values differ when referenced to chronological time, scaling of data with respect to active mass (ergosomes) and to ideal (mathematical) pharmacokinetic space time (mesochrons, kallynochrons, or apolysichrons) removes the astronomical time dependency. A theory of pharmacokinetic similarities is presented which states that both physiological and pharmacokinetic processes are biologically interrelated and governed by a master synchronization mechanism; consequently interspecies pharmacokinetic events frequently may be expressed as invariant values; e.g., hexobarbital disposition half-life is approximately the duration of 1,680 gut beats (time standard) regardless of mammalian species. The depletion theory hypothesis of aging that each mammalian organism of set mass is genetically endowed with a set total energy or metabolism (lebenszeitliche Kraft) is found to be adaptable at the microscopic pharmacokinetic level; thus it is hypothesized that each mammalian organism has a genetically determined and finite quantity of phase I hepatic pharmacokinetic stuff (activity) to expend during a lifetime and that this pharmacokinetic stuff (ml cleared X kg-1 X maximum life-span potential-1) is a constant. The rate at which this pharmacokinetic stuff is utilized (comparative pharmacokinetics) is presumed to be regulated by a pharmacokinetic clock, which may undergo either acute or chronic perturbations having either a genetic or environmental origin.
Control of extracellular ions in skate brain during osmotic disturbances
Authors: Cserr H. F. , Bradbury M. W. , Mackie K. , Moody E. J.
Published: December 2017

Regulation of brain water and osmolytes in osmotic disturbances has been studied in the little skate, Raja erinacea. Free-swimming fish were subjected to seawater plus 125 mM NaCl (hyperosmotic; these also received 10 ml/kg body wt im 4.19 M NaCl in elasmobranch Ringer) or to 50% seawater (hyposmotic). At a set time, fish were killed, and blood and brain (telencephalon and medulla) were analyzed. Brain water was divided into a Cl- and a non-Cl- space. Responses of water and osmolytes to osmotic disturbances were mutually consistent. In telencephalon, there was good regulation of Cl- space, based on Na+ and Cl- shifts in hypo- and hyperosmolality. This control was near perfect at 2- and 4-h hyperosmolality. Regulation of non-Cl- space was minimal at 24-h hyperosmolality, with small K+ uptake. In medulla, Cl- space and ions were unregulated, whereas non-Cl- space was partly controlled in hyposmolality in relation to amino acid loss. Thus in this elasmobranch, regulation of Cl- space and of Na+ and Cl- is effective in telencephalon but is nonexistent in medulla oblongata.
Influence of daily sodium intake on vasopressin secretion and drinking in dogs
Authors: Cowley A. W. , Skelton M. M. , Merrill D. C. , Quillen E. W. , Switzer S. J.
Published: December 2017

Studies were carried out to determine the relationship between daily sodium intake, drinking, and vasopressin (AVP) secretion in normal conscious dogs. Chronic responses to 5-day elevations of daily sodium intake (200 meq/day) and 2-wk decreases in daily sodium intake (5 meq/day) were determined. Dogs were studied with ad libitum drinking and with water intake restricted to the amount drunk during the normal-sodium (30 meq/day) control period. Although acute elevations of plasma AVP occurred after a normal (40 meq Na) gastric load, chronic high-sodium intake resulted in no change of steady-state plasma AVP levels or daily AVP excretion (UAVP) with ad libitum drinking. Total water intake and frequency of drinking, however, increased nearly fourfold. In the absence of excess drinking, plasma AVP and UAVP both exhibited a nearly sixfold increase during the period of high-sodium intake. Despite elevations of plasma AVP, daily urine volume increased and urine osmolality rose only gradually during the 5 days of high-sodium intake. Chronic low-sodium intake also did not alter plasma AVP, but total water intake was reduced 20%. The data indicate that with water available, extracellular osmolality is controlled predominantly by drinking rather than by AVP secretion, that either osmolality or sodium concentration is the predominant controller of drinking and AVP secretion, and that daily water excretion need not be related directly to plasma AVP.
Effects of blockade of brain angiotensin II receptors in conscious, sodium-deprived dogs
Authors: Brooks V. L. , Reid I. A.
Published: December 2017

The present studies were designed to evaluate the physiological significance of the actions of angiotensin II (ANG II) on the brain. The effects of blockade of brain ANG II receptors by intracarotid or intravertebral infusions of saralasin were studied in conscious dogs with high circulating ANG II levels (142 +/- 16 pg/ml) due to a low-sodium diet. Three doses of saralasin were infused into each pair of arteries and intravenously: 0.1, 0.3, and 1.0 micrograms X kg-1 X min-1. Saralasin produced dose-related decreases in arterial pressure during infusion into the carotid or vertebral arteries, confirming that ANG II maintains arterial pressure during sodium deficiency. However, intravenous saralasin administration decreased pressure to a similar degree, suggesting that the hypotensive effect was due to recirculation of saralasin, rather than to blockade of a central action of circulating ANG II. Heart rate was not altered by infusion of saralasin by any route. Saralasin administration also caused a dose-dependent increase in plasma renin activity and plasma ANG II concentration. However, because the increases produced by intracarotid or intravertebral saralasin did not differ from the increase produced by intravenous infusion, these results do not provide evidence that renin release is modulated by a central action of ANG II during sodium deficiency. Plasma corticosteroid levels were reduced (2.4 +/- 0.5 to 1.4 +/- 0.2 micrograms/dl, P less than 0.05) by intravenous infusion of the highest dose of saralasin, but neither intracarotid nor intravertebral saralasin infusion altered plasma corticosteroid concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
Central actions of angiotensin II oppose baroreceptor-induced sympathoinhibition
Authors: Stein R. D. , Stephenson R. B. , Weaver L. C.
Published: December 2017

Angiotensin II causes increased arterial pressure which may be mediated, in part, by effects on central sympathetic neurons or by interference with central or peripheral components of the baroreceptor reflex. This investigation was undertaken to determine actions of angiotensin II on sympathetic splanchnic efferent and carotid sinus afferent activity in chloralose-anesthetized cats. Neural responses during increases in arterial pressure caused by intracarotid or intravenous administration of angiotensin II were compared with responses to equivalent increases in arterial pressure induced by intravenously injected dextran or phenylephrine. Intracarotid injections of angiotensin II caused variable splanchnic sympathetic responses consisting of increased, decreased, or unchanged activity. In contrast, intravenous infusions of dextran or phenylephrine consistently inhibited sympathetic activity. Carotid sinus afferent activity was increased similarly by intracarotid angiotensin II and intravenous dextran or phenylephrine. Sympathetic and baroreceptor afferent responses to intravenously injected angiotensin II were not significantly different from responses to dextran or phenylephrine. These data demonstrate that angiotensin II can act centrally to excite sympathetic outflow or to interfere with inhibitory influences of arterial baroreceptors.