bluuebunny/crossref_metadata_2025 huggingface dataset:
Newborn northern fur seals (Callorhinus ursinus)--do they suffer from cold?
Authors: Blix A. S. , Miller L. K. , Keyes M. C. , Grav H. J. , Elsner R.
Published: December 2017

Several hundred thousand northern fur seals (C. ursinus) are born each summer during July at St. Paul Island in the Bering Sea. The weather in the area is usually cold, wet, and windy during the breeding season. At birth the pups are small (5--6 kg) and insulated only by a partly wettable pelt and a 2- to 4-mm layer of blubber. In air, the pups' lower critical temperature appears to be below the 6 degrees C 50-yr record low July temperature for the islands. During rainy weather much of the insulative value of the pelt is lost, and the pups, which already have a high resting metabolic rate of 3.5 W.kg-1, must increase heat production by shivering and/or nonshivering thermogenesis to maintain deep body temperature. The high level of metabolism (up to 18 W.kg-1) is supported by a very rich milk. The pups will, nevertheless, become hypothermic if their insulation is not improved through peripheral vasoconstriction and shedding of water from the pelt by periodic shudder. Even with these protections the newborn and very young pups are brought close to their limit of tolerance during rainy and windy days. Unfit pups are likely to succumb under such circumstances.
Aortic wavelength as a determinant of the relation between heart rate and body size in mammals
Authors: Milnor W. R.
Published: December 2017

Measurements of aortic input impedance in the rat, dog, and man suggest a new hypothesis to explain the inverse correlation between rate and body size: that pulse wavelength and arterial length are matched in a way that minimizes cardiac work. The optimal rate is fast enough to avoid the high impedances produced by reflections at relatively low frequencies, yet slow enough to permit orderly excitation and recovery of the myocardium.
Influence of hypothalamic and ambient temperatures on sleep in kangaroo rats
Authors: Sakaguchi S. , Glotzbach S. F. , Heller H. C.
Published: December 2017

Unanesthetized, unrestrained kangaroo rats (Dipodomys) were studied to examine the changes in the frequency and duration of sleep states caused by long-term manipulations of hypothalamic temperature (Thy) at a thermoneutral (30 degrees C) and a low (20 degrees C) ambient temperature (Ta). A cold stimulus present in either the hypothalamus or the skin decreased both the total sleep time (TST) and the ratio of paradoxical sleep (PS) to TST. At a low Ta, TST, but not the PS-to-TST ratio, was increased by raising Thy, indicating that a cold peripheral stimulus could differentially inhibit PS. At a thermoneutral Ta, cooling Thy decreased both TST and the PS/TST. Changes in the amount of PS were due largely to changes in the frequency, but not the duration, of individual episodes of PS, suggesting that the transition to PS is partially dependent on the thermoregulatory conditions existing during slow-wave sleep (SWS). These results are consistent with the recent findings that the thermoregulatory system is functional during SWS but is inhibited or inactivated during PS.
Forum on osmosis. II. A criticism of "solvent tension" in osmosis
Authors: Hildebrand J. H.
Published: December 2017

Concepts about the liquid state that are inconsistent with the facts are noted, and solvent under tension is one of them. Osmosis is not present in a solution: it is a process in the presence of a semipermeable membrane that can be quantified by the operation of applying a hydrostatic pressure. The classical derivation of the van't Hoff equation from Raoult's law is reviewed. The soundness of the early views of G. H. Lewis has not changed.
Forum on osmosis. IV. More on osmosis and diffusion
Authors: Soodak H. , Iberall A.
Published: December 2017

A brief summary is presented of the Gibbsian view of chemical drives and of its mechanical interpretation, including a description of the “diffusion force” that arises from an interplay between fluctuations and dissipation. Osmotic flows are shown to be driven by diffusion forces acting at the membrane interface, and not by the effects of Hammel and Scholander's “solvent tension.”
A two-dimensional transient mathematical model of human thermoregulation
Authors: Kuznetz L. H.
Published: December 2017

Current models of human thermoregulation are limited in that they fail to account for temperature distribution in any spatial direction other than radially outward from the body centerline. They are therefore incapable of accounting for nonuniform environmental conditions or nonuniform heat generation from muscles or organs within the body. However, for many situations, these nonuniform conditions are commonplace and lead to disparate skin temperatures and heat loss rates on different sides of the same body compartement. A new mathematical model of human thermoregulation that has been developed and is presented here has the capability of predicting transient temperature variations in two spatial dimensions, both radially and angularly, as measured from the body centerline. In so doing, the model accounts for nonuniform environments and internal heat generation rates. Typical results from the model are demonstrated, and comparisons with available experimental data are also presented.
General systems theory, brain organization, and early experiences
Authors: Denenberg V. H.
Published: December 2017

Three hypothetical brain processes--interhemispheric coupling, hemispheric activation, and interhemispheric inhibition--are derived from an equation characterizing general systems theory. To investigate these processes, experimental rats were reared under differing early experience conditions. When adult, they had their right or left neocortex lesioned, had a sham operation, or were left undisturbed. Interhemispheric coupling was measured by means of a correlation coefficient between the right and left hemispheres. The presence of a significant positive correlation is taken as evidence of a negative feedback loop between the hemispheres. In one experimental population, in which rats did not receive any extra stimulation in infancy, the correlation was not significantly different from zero, thus implying that the two hemispheres were operating independently. In another population, in which rats had received handling stimulation in infancy, the correlation coefficient was significant (0.543), indicating that the hemispheres were coupled in a systems arrangement. The processes of hemispheric activation and interhemispheric inhibition were assessed by comparing the mean performance of the two unilateral lesion groups and the group with intact brain. The two rat populations had different forms of brain organizations as measured by these processes. These analyses show that the behavior of the isolated hemisphere cannot be directly extrapolated to the behavior of the connected hemisphere. If there is hemispheric coupling via a negative feedback loop or if there is interhemispheric inhibition, then the disconnected hemisphere may show behaviors that are not evident in the normal connected condition.
Ion exchanges through respiratory and chloride cells in freshwater- and seawater-adapted teleosteans
Authors: Girard J. P. , Payan P.
Published: December 2017

The present study discusses the respective roles of the chloride and respiratory cells in branchial ion exchange in freshwater- and seawater-adapted teleosts. In the gill, two distinct epithelia are defined according to their blood irrigation and cellular characteristics: the primary lamellar epithelium containing mostly chloride cells is functionally connected to the venous compartment; the secondary lamellar epithelium consisting of respiratory cells is irrigated by the arterioarterial circulation. The fundamental reorganization occurring in the chloride cells during adaptation to seawater consists of the appearance of leaky ultrastructure related to an increase in the ionic and nonelectrolyte permeabilities of the primary lamellar epithelium. The physiological functions of respiration, excretion, and the maintenance of acid-base balance occur through the secondary lamellar epithelium both in freshwater and seawater fish. The increase of the exchange diffusion across the secondary lamellar epithelium on seawater adaptation is directly related to the increase in the external salinity. The study of adrenergic control in the teleost gill emphasizes the functional advantage to the fish during adaptation to seawater of the anatomic separation of the osmoregulatory primary lamellar epithelium.
Functional reinnervation and development of supersensitivity to NE after renal denervation in rats
Authors: Kline R. L. , Mercer P. F.
Published: December 2017

The time course for functional reinnervation and development of supersensitivity to norepinephrine (NE) in the denervated rat kidney was studied using an in situ kidney preparation perfused at constant flow. Changes in perfusion pressure were measured during renal nerve stimulation (RNS, 1-10 Hz) and after administration of NE (1-50 ng, ia) up to 8 wk after unilateral renal denervation or a sham operation. During the first 2 wk after denervation, supersensitivity to NE was present, but there was no response to RNS. Between 24 and 32 days after denervation, RNS produced responses averaging 40% of control in denervated kidneys and supersensitivity to NE was still present. A fluorescence assay was used to determine that the NE concentration in kidneys 24-32 days after denervation was less than 30% of that found in control kidneys. At 8 wk, average responses to RNS in denervated kidneys were not significantly different from innervated kidneys, while supersensitivity to NE was still present. These results indicate that functional reinnervation of the renal vasculature begins to occur between 14 and 24 days after denervation, and that complete return of function may occur by 8 wk. The response to RNS during reinnervation appears to be due to a combination of regeneration of nerve fibers and denervation supersensitivity to NE.
Mathematical model of steroidogenesis in rat and rabbit testes
Authors: Becker S. , Chubb C. , Ewing L.
Published: December 2017

The purpose of this study was to develop a mathematical model of testicular steroidogenesis which could not only predict steroid secretion but also could be implemented to test the validity of assumptions used in studies of testicular testosterone biosynthesis in rats and rabbits. Since the two predominant fates of testicular steroids are metabolism and secretion, we hypothesized that the data for construction of the model could be observed testicular steroid secretions and that these data could then be used to elucidate intratesticular steroid conversions. Equations based on steroid secretion by testes perfused in vitro were developed to estimate transition probabilities corresponding to steroid secretion or conversion. The model was tested by comparing the predicted steroid secretion rates with those observed for control testes perfused in vitro. In addition, the transition probabilities determined by the model were used to indicate the predominant series of reactions for converting pregnenolone to testosterone. The results presented herein confirm the capability of the model to predict steroid secretion rates and to predict preferred pathways for testosterone biosynthesis in maximally stimulated testes perfused in vitro. Moreover, the model construction required only algebra and steady-state measurements.
Optimal and adaptive control in canine postural regulation
Authors: Schuster D. , Talbott R. E.
Published: December 2017

For analytic purposes, dogs trained to stand quietly on an oscillating platform can be likened to a fixed-length inverted pendulum with a point mass. Describing function analysis permitted derivation of torque and error values as functions of phase and gain relative to platform movement. A phase criterion was determined for minimization of either control torque at a given error amplitude or error at a given control torque amplitude. Describing functions for dogs with and without vision approached optimal phase. Stretch reflex control involving proportional-plus-rate feedback is not sufficient to account for the approach to optimal phase. Blindfolded labyrinthectomized dogs did not exhibit optimal behavior and the phase constraint for stretch reflex control was satisfied at most frequencies. The observed behavior is best accounted for by a model involving both otolith and visual feedforward (pursuit-precognitive) control processes. Reductions in phase lag by blindfolded dogs during the first few cycles of platform motion provide evidence of adaptive control.
Pharmacologic responsiveness of isolated single eccrine sweat glands
Authors: Sato K. , Sato F.
Published: December 2017

Pharmacologic responsiveness of the eccrine sweat gland has never been studied under well-defined in vitro experimental conditions. Using isolated cannulated single monkey palm eccrine sweat glands, the dose response to both cholinergic and alpha- and beta-adrenergic agents and the effects of various antagonists on agonists were studied. The maximal sweat rate was highest after stimulation with cholinergic agonists, was lower with the beta-adrenergic agonist, and was least with the alpha-adrenergic agonist. Each secretory response was inhibited by its specific antagonist. Attempts to demonstrate the spare receptor, if any, by means of preincubation of the glands with N-(2-chlorethyl)dibenzylamine (Dibenamine) were unsuccessful. From the hyperbolic dose-response curves the values for KA and KB, dissociation constants for agonists and antagonists, respectively, were thus tentatively estimated according to Clark's classical receptor theory. Schild plots for each agonist-antagonist interaction produced straight lines with slopes of near unity, indicating the adequacy of the methodology. It was concluded that the isolated eccrine sweat glands retain their pharmacologic viability in vitro and show responsiveness to cholinergic as well as both alpha- and beta-adrenergic stimulations.
Role of aldosterone in sodium retention of pregnancy in the rat
Authors: Churchill S. , Bengele H. H. , Melby J. C. , Alexander E. A.
Published: December 2017

The purpose of this study was to test whether the absence or inhibition of aldosterone would alter the Na retention of pregnancy in the rat. We performed metabolic balance studies during the last 2 wk of the 3-wk rat pregnancy in the following four groups of saline-drinking rats: nonpregnant, sham adrenalectomized; pregnant, sham adrenalectomized; nonpregnant, adrenalectomized; and pregnant, adrenalectomized. Significant net Na retention was not found during the 2nd wk in any of the groups. During the final week, however, both pregnant groups retained between 8 and 11 meq Na more than their respective control groups. In addition, we measured plasma aldosterone concentration in these rats at term. The mineralocorticoid was not detectable in the nonpregnant adrenalectomized rats but was present in the pregnant adrenalectomized rats at a concentration of about 50% of that found in the pregnant sham-adrenalectomized rats. Serial measurements revealed that aldosterone was measurable by day 18 and nondetectable by 2 days postpartum in these pregnant adrenalectomized rats. Comparable balance studies were also performed in three groups of water-drinking rats: nonpregnant, pregnant, and pregnant rats that received large daily doses of spironolactone. During the 3rd wk both pregnant groups were in significant positive Na balance. Net Na retention for untreated pregnant rats was 8.4 meq and for the spironolactone treated, 6.9 meq, values that were not significantly different. We conclude that is is unlikely that aldosterone plays a critical role in the Na retention found during rat pregnancy.
Cycloheximide-induced phase shifting of circadian clock of Neurospora
Authors: Nakashima H. , Perlman J. , Feldman J. F.
Published: December 2017

Cycloheximide (CHX), an inhibitor of cytosolic (80S) protein synthesis in eucaryotes, causes phase shifts of the circadian clock of Neurospora crassa when administered as 4-h pulses to cultures in liquid medium. Differential effects of the pulses at different phases of the circadian cycle were observed and plotted as a phase-response curve (PRC). Nearly all phase shifts observed were phase advances, with maximum sensitivity in the middle of the subjective day. Inhibition of protein synthesis by CHX was the same at both phases of the cycle. The PRC was the same at 20 and 25 degrees C. Dose-response curves for the effects of CHX on phase shifting and inhibition of protein synthesis were determined and showed a striking parallel in the responses of these two phenomena to CHX. These results support the view that synthesis of one or more proteins at specific phases of the circadian cycle is necessary for the normal operation of the circadian clock of Neurospora.
Cardiac output distribution before and after endotoxin challenge in the rooster
Authors: Merrill G. F. , Russo R. E. , Halper J. M.
Published: December 2017

Cardiac output and its distribution to selected organs was studied using radiolabeled microspheres in unanesthetized, restrained white Leghorn roosters before and 3 h after an Escherichia coli endotoxin challenge. Cardiac output was not significantly altered in either control or endotoxin-treated animals, nor was there a difference in cardiac output between the two groups. Systemic arterial pressure decreased by 37% in the endotoxin group from 187 +/- 14 to 117 +/- 9 mmHg, thus reflecting a marked reduction in total peripheral resistance. The fraction of cardiac output perfusing the heart, adrenals, and liver (hepatic arterial) was not altered by the challenge. Conversely, the percent of total blood flow received by the kidneys, pancreas, and gut (proventriculus and duodenum) was significantly (P less than 0.05) reduced during endotoxemia. Absolute flow to the brain was also decreased. These findings demonstrate that in the rooster endotoxin-induced systemic arterial hypotension is a sufficient stress to cause a redistribution of blood flow, and that the brain in this species (unlike its counterpart in mammals) probably regulates its blood supply passively during periods of hypotension. Conversely, the reduced blood supply to such organs as the gut, pancreas, and kidney following the endotoxin challenge is similar to changes seen in the more commonly studied mammals during experimental endotoxemia.
Brain receptor binding and central actions of angiotensin analogs in rats
Authors: Mann J. F. , Schiller P. W. , Schiffrin E. L. , Boucher R. , Genest J.
Published: December 2017

The possible physiological importance of brain receptors for angiotensin was investigated. Structure-activity relationships were established for 12 fragments and analogs of angiotensin II (ANG II). 1) Affinities of the peptides were determined in an in vitro assay of rat brain angiotensin receptors. 2) Blood pressure (BP) and water intake following intracerebroventricular administration of the peptides to conscious rats were monitored. In vitro, ANG II and [des-Asp1]ANG II displayed the highest affinities. [Trp1]ANG II and [Trp8]ANG II had one-eighth and one-ninth the affinity of ANG II, respectively. Multiple substitutions in positions 1, 4, and 8 produced a 1,000-fold fall in binding affinity. Excellent correlation was found between the in vitro binding affinities and the in vivo central activities of the peptides on BP (r = 0.975) and on water intake (r = 0.900). The results suggest that the biochemically characterized brain angiotensin receptors may be physiologically relevant to BP and body fluid homeostasis. The brain angiotensin receptors mediating BP and thirst have very similar structural requirements.
Metabolic concomitants of glucagon-induced suppression of feeding in the rat
Authors: Geary N. , Langhans W. , Scharrer E.
Published: December 2017

The suppression of food intake elicited in rats by injection of pancreatic glucagon and the accompanying changes in energy metabolite flux were investigated. Glucagon injections, 120-360 micrograms ip, were made as rats began the first meal of the dark phase after food deprivation during the light phase. Glucagon-injected rats terminated their meals sooner and ate smaller meals than vehicle-injected rats. For metabolic assays, rats were identically treated and killed just at meal onset or 15 min later. Portal vein blood glucose increased similarly in all rats allowed to feed, whereas plasma nonesterified fatty acid and D-(-)-3-hydroxybutyrate levels decreased during feeding. In contrast, hepatic vein and aorta blood glucose levels increased more after glucagon than after vehicle injections. Liver glycogen content decreased after glucagon injections. The highest glucagon dose only had slight lipolytic and ketogenic effects. It was concluded the glycogenolytic and hyperglycemic action of glucagon may generate a satiety signal sufficient to cause premature termination of meals. Changes in ketone and lipid fluxes do not appear necessary for this behavioral effect.
Oxygen consumption and locomotor activity during restricted feeding and realimentation
Authors: Boyle P. C. , Storlien L. H. , Harper A. E. , Keesey R. E.
Published: December 2017

Both the resting rate of O2 consumption and the heat increment in response to an intubated meal were measured in male rats following periods of food restriction and during realimentation. In one experiment, resting rates of O2 consumption were significantly reduced below control values after food consumption had been restricted and during a substantial part of an 11-day period of controlled realimentation. In a second experiment, the heat increment in response to an intubated meal was also significantly less following an interval of food restriction and during the early stages of realimentation. The reduction in O2 consumption was not related to reduced locomotor activity. These results obtained whether O2 consumption was measured in absolute amount or was referenced to an estimate of the animal's metabolically active tissue (kg body wt0.75). It is suggested that these metabolic adaptations contribute significantly to the enhanced efficiency of food utilization reported in food-restricted animals during controlled realimentation.
Rat muscle structure and metabolism in relation to age and food intake
Authors: McCarter R. J. , Masoro E. J. , Yu B. P.
Published: December 2017

Age changes in oxygen consumption and the structural composition of the lateral omohyoideus muscle were studied in adult male rats. The rate were either fed ad libitum (group A) or 60% of the ad libitum intake (group R). An age-related loss in muscle mass did not occur even at advanced ages in group A or group R rats. Muscle fiber diameter decreased with age in both groups but a concomitant increase in the number of fibers prevented a change in muscle mass. The muscles of group R rats contained the same number of fibers as those of group A rats at all ages. The muscles of group A rats showed a progressive loss in rate of resting oxygen consumption until 18 mo of age. A similar but less marked loss in oxygen consumption occurred in the muscles of group R rats. These results provide further evidence that life-prolonging food restriction modulates physiological changes associated with the aging process.
Rhythmic contractions of the teat sphincter in bovines: an expulsion mechanism
Authors: Lefcourt A. M.
Published: December 2017

Spontaneous and induced rhythmic contractions of the teat sphincter muscle were measured in conscious bovines using a pressure transponding device. Contractions were induced or the frequency of contractions was increased by intravenous injection of phenylephrine. Epinephrine, isoxsuprine, and phentolamine inhibited contractions and prior administration of phentolamine blocked the response to phenylephrine. Contractions in adjacent teats were asyncronous and the frequency of spontaneous contractions (0-20/min) increased with time after milking, presumably due to the effect of the increased muscle tension that resulted from the accumulation of milk within the gland cistern and the teat cistern. Furthermore, the contractions were found to be peristaltic in nature. Squeezing the tip of the teat was found to induce one or more contractions, whereas squeezing the teat elsewhere had no effect. It was hypothesized that peristaltic contractions in response to irritation of the tip of the teat might represent an expulsion mechanism.
Circulatory mechanoreceptors in the pond turtle Pseudemys scripta
Authors: Faraci F. M. , Shirer H. W. , Orr J. A. , Trank J. W.
Published: December 2017

This study was undertaken to characterize cardiovascular receptors in the turtle, Pseudemys scripta, with particular attention being given to neural activity changes associated with alterations in blood pressure. Vagal afferent nerve traffic, synchronous with heart contractions, was recorded in anesthetized artificially ventilated turtles. Action potentials, from receptors that fired regularly during each heart cycle, occurred during ventricular systole. Mechanical probing and vascular occlusion indicated that these receptors were located in the proximal common pulmonary artery including the bulbus cordis region. Bolus injections of saline into the ventricle or the common pulmonary artery caused immediate but transient increases in cardiac synchronous traffic. Prolonged elevation of arterial and ventricular blood pressure, by either saline injection or arterial occlusion, caused increases in receptor discharge of the same duration as the pressure increases. Although these receptors could participate in the regulation of the systemic and the pulmonary circulation, the physiological role for them is presently unknown.
Splenic afferents and some of their reflex responses
Authors: Herman N. L. , Kostreva D. R. , Kampine J. P.
Published: December 2017

Afferent nerve activity was recorded from the distal ends of cut splenic nerves in pentobarbital- (35 mg/kg) anesthetized mongrel dogs (15-20 kg). Increases in splenic venous pressure (SVP) produced either by manual compression of discrete portions of the spleen or splenic contraction produced by injection of epinephrine (100 micrograms) into the splenic artery or vein of an occluded spleen produced significant increases in SVP and splenic afferent nerve activity. Increases in splenic afferent nerve activity were linearly related to increases in SVP. Histological sections of nerves from which afferent recordings were obtained demonstrated that all afferents were unmyelinated C-fibers. Electrical stimulation of the cut central end of splenic nerves resulted in marked reflex increases in both renal and cardiopulmonary sympathetic efferent nerve activity that remained elevated throughout the stimulation period. Reflex increase in cardiopulmonary sympathetic efferent nerve activity was associated with increases in right (22-45%) and left (11-19%) ventricular contractile force measured with Brodie-Walton strain gauge transducers, in heart rate (5-15 beats/min), and in blood pressure (5-10 mmHg). This study is the first to demonstrate both the existence of low-pressure baroreceptors in the spleen and that these splenic afferents can reflexly alter cardiopulmonary and renal sympathetic efferent nerve activity, heart rate, ventricular contractile force, and systemic blood pressure.
Intraspecies allometry: correlation between kidney weight and glomerular filtration rate vs. body weight
Authors: Hackbarth H. , Buttner D. , Gartner K.
Published: December 2017

Allometric equations of the form of Y = a*BWb were calculated between body weight (BW) on the one hand and either kidney weight (KW) or glomerular filtration rate (GFR) on the other. By using strain and sex means obtained from 24 different inbred strains of adult mice or F1-hybrids environmental and genetical influences could be separated statistically. Thus, allometric equations reported in this study describe exclusively genetic influence. The parameters for intraspecies allometric equations obtained in these studies were compared to those in the literature presenting interspecies relationships. The double logarithmic regressions of KW vs. BW gave results different from the interspecies equation. The difference between intra- and interspecies results of allometric relationships may be due to the experimental exclusion of environmental influences. The regression parameters for GFR vs. BW obtained for the inbred strains, however, agreed very well with those of the empirical equation for interspecies relationship and also with the theoretically expected value. The dependence of GFR on BW was found to be GFR = 0.036*BW0.74 +/- 0.15, where GFR is measured in ml/min and BW in g. The exponent of 0.74 seems to be a valid biological constant that is genetically determined within and across species lines.
Substrate metabolism in seasonally acclimatized American goldfinches
Authors: Marsh R. L. , Dawson W. R.
Published: December 2017

Concentration of ([Glc]) and turnover (Ro) of plasma glucose, concentration of free fatty acids in plasma ([FFA]), and concentration of glycogen in muscle and liver were measured in freshly captured summer- and winter-acclimatized American goldfinches (Carduelis tristis). These birds were acutely exposed to one of three thermal regimes: 1) “thermoneutral,” 30 degrees C in air, 2) “cold,” -15 degrees C in air, and 3) “severe cold,” 0 degrees C in 79% He and 21% O2. Additionally, the activities of citrate synthase (CS), phosphofructokinase (PFK), and beta-hydroxyacyl-CoA dehydrogenase (HOAD) were measured in pectoralis and leg muscles of winter and summer birds. Ro for goldfinches at 30 degrees C is unchanged between winter and summer, whereas it is 25% lower at -15 degrees C in winter than in summer birds, even though rates of heat production are similar. Additionally, winter animals depleted muscle glycogen at slower rates than summer individuals when exposed to “cold” or “severe cold.” [Glc] and [FFA] for each test regime did not vary between seasons. The activity of the beta-oxidative enzyme HOAD is the pectoralis muscle (the main thermogenic tissue) increases by 50% from summer to winter, but the activities of PFK and CS remain essentially constant. We conclude that the ability to restrict carbohydrate use under cold stress is a component of the winter acclimatization process in the American goldfinch. One mechanism which might foster this ability in the increase in beta-oxidative capacity of the flight muscles, permitting a greater reliance on fatty acids by winter animals during cold-induced thermogenesis.
Vasomotion in chicken foot: dual innervation of arteriovenous anastomoses
Authors: Hillman P. E. , Scott N. R. , van Tienhoven A.
Published: December 2017

Blood exits the foot of the domestic chicken via two major venous routes: a counter-current network surrounding the major incoming artery and a large collateral vein. Between these two routes are numerous large collateral vein. Between these two routes are numerous anastomotic veins. Both venous routes drain capillaries and arteriovenous anastomoses (AVAs). Blood flow through the foot was measured on unanesthetized hens. Flow varies with ambient temperature: 0.2 ml/min at 5 degrees C, 2.2 ml/min at thermoneutrality, and 5.4 ml/min at 36 degrees C; the AVAs contribute 8, 26, and 63% to this flow, respectively. Flow through capillaries is reduced by alpha-adrenergic agonists and is increased by beta-adrenergic agonists. Blocking nerve conduction to the foot at thermoneutrality releases alpha-adrenergic tone and increase AVA flow. Faradic stimulation of foot nerves after adrenergic blockage increases AVA flow, but not capillary flow, suggesting active vasodilation of the AVAs. Such AVA vasodilation normally occurs during body heating, since AVA flow decreases after denervation. Dopaminergic or beta-adrenergic nerves are not involved in active vasodilatation, however, purinergic nerves may play a role. Thus AVAs have a functional dual innervation.
2-Deoxy-D-glucose and insulin modify release of norepinephrine from rat hypothalamus
Authors: McCaleb M. L. , Myers R. D.
Published: December 2017

Both 2-deoxy-D-glucose (2-DG) and insulin, administered systemically, evoke spontaneous feeding in the satiated animal. To determine whether hypothalamic norepinephrine (NE) could be involved in this eating response, we examined the effect of the two compounds on the kinetics of NE release from this structure in the unrestrained rat. An individual site in the hypothalamus of the rat was radiolabeled by 1.0-2.0 microCi of [14C]NE microinjected in a volume of 0.5-1.0 microliters through a permanently implanted guide cannula. Then 30 min later, the NE-labeled tissue was perfused, by means of push-pull cannulas, with an artificial cerebrospinal fluid at a rate of 25 microliters/min. The duration of each perfusion was 5.0 min with a 5.0-min interval between successive perfusions. After two base-line samples were collected, a saline control injection or either 40 mg/kg 2-DG or 20 U/kg insulin was given intraperitoneally; then the perfusion sequence was continued for an additional 1-h period. Aliquots of the collected samples of perfusate were analyzed by combined scintillation spectrometry and high-pressure liquid chromatography. 2-DG enhanced the release of NE at sites in the medial hypothalamus, whereas insulin generally caused a suppression of catecholamine efflux particularly at sites within the lateral hypothalamic area. The changes in NE efflux were morphologically specific. Taken together with the differences in amine release, these results suggest that 2-DG and insulin modify feeding by independent neurochemical mechanisms that may involve noradrenergic neurons at the hypothalamic level.
Cycle of lordosis behavior in female hamsters whose circadian activity rhythm has split into two components
Authors: Swann J. , Turek F. W.
Published: December 2017

Within 75 days of exposure to constant light (LL), the circadian activity rhythm of 21 of 32 hamsters had dissociated or "split" into two distinct components. These components were labeled either evening (E) or morning (M) depending on whether they appeared to be derived from the E or M portion of the activity phase prior to the occurrence of "splitting." Both regular (i.e., 4-day) and irregular (i.e., non-4-day) cycles in lordosis behavior were observed in all of the animals with an intact activity rhythm and in 18 of the 21 animals with a split rhythm of activity. The onset of behavioral estrus always occurred near the time of the onset of locomotor activity in animals with an intact activity rhythm. Among the females with a split activity rhythm, seven showed lordosis onsets only near the onset of the E component whereas five others began lordosis behavior only near the onset of the M component. Importantly, in five animals the onset of lordosis was associated on different days with either the E or M component. These results indicate that cycles in lordosis behavior persist even after the circadian rhythm of activity has dissociated into two components, and that at least one component of the estrous cycle, onset of lordosis behavior, can be coupled to either of two oscillators that underlie the circadian rhythm of locomotor activity in hamsters.
Increased cardiac output following occlusion of the descending thoracic aorta in dogs
Authors: Stene J. K. , Burns B. , Permutt S. , Caldini P. , Shanoff M.
Published: December 2017

Occlusion of the thoracic aorta (AO) in dogs with a constant volume right ventricular extracorporeal bypass increased cardiac output (Q) by 43% and mean arterial pressure by 46%, while mean systemic pressure (MSP) was unchanged. We compared AO with occlusion of the brachiocephalic and left subclavian arteries (BSO) which decreased cardiac output by 5%, increased mean arterial pressure by 32%, and increased MSP by 11%. We feel these results confirm that AO elevates preload by transferring blood volume from the splanchnic veins to the vascular system drained by the superior vena cava. If the heart is competent to keep right arterial pressure at or near zero, this increase in preload will elevate Q above control levels. Comparing our data with results of other authors who have not controlled right atrial pressure, emphasizes the importance of a competent right ventricle in allowing venous return to determine Q.
Endurance training attenuates stress hormone responses to exercise in fasted rats
Authors: Winder W. W. , Beattie M. A. , Holman R. T.
Published: December 2017

Endurance exercise training produces major adaptations in hormonal and metabolic responses to exercise. This study was designed to determine whether the differences in hormone response persist in the fasted condition when liver glycogen is depleted. Rats were run on a motor-driven rodent treadmill 5 days/wk for periods up to 2 h/day for 10 wk. Trained and nontrained rats were then fasted 24 h and were run for periods ranging from 0- to 60 min. At the end of 60 min of exercise muscle glycogen was higher in trained rats (2.9 +/- 0.3 vs. 1.1 +/- 0.1 mg/g). Blood glucose was maintained at higher levels in trained rats throughout the course of the exercise (3.2 +/- 0.1 vs. 2.3 +/- 0.1 mM after 60 min). Plasma concentrations of glucagon and epinephrine increased in both groups during the exercise but were significantly lower in trained animals. Differences between trained and nontrained animals in stress hormone responses to exercise persist in the fasted state and appear to be a consequence of the capacity of trained animals to maintain higher blood glucose levels.
Model of the kinetics of ketone bodies in humans
Authors: Cobelli C. , Nosadini R. , Toffolo G. , McCulloch A. , Avogaro A. , Tiengo A. , Alberti K. G.
Published: December 2017

The kinetics of ketone bodies was studied in normal humans by giving a combined bolus intravenous injection of labeled acetoacetate ([14C]AcAc) and D(--)-beta-hydroxybutyrate (beta-[14C]-OHB) to seven subjects after an overnight fast, on two different occasions, and by collecting frequent blood samples for 100 min. Kinetic data were analyzed with both noncompartmental and compartmental modeling techniques. A four-compartment model, representing AcAc and beta-OHB in blood and two equilibrating ketone body compartments, inside the liver and extrahepatic tissues, was chosen as the most reliable mathematical representation; it is physiologically plausible and was able to accurately fit the data. The model permitted evaluation of the in vivo rate of ketone body production in the liver, the individual plasma clearance rates of AcAc and beta-OHB, their initial volumes of distribution, and the transfer rate parameters among the four ketone body compartments. Moreover, the model provided estimates of the components of the rates of appearance of AcAc and beta-OHB in plasma due to newly synthesized ketone body from acetyl-CoA in the liver, and to interconversion and recycling in the liver and extrahepatic tissues. The model also was used to evaluate other methodologies currently employed in the analysis of ketone body turnover data: the conventional approach based on use of the combined specific activity of AcAc and beta-OHB required assumptions not satisfied in vivo, leading to substantial errors in key parameter estimates.
Lack of enhanced nocturnal growth hormone release in tethered cynomolgus monkeys
Authors: Bunner D. L. , McNamee G. A. , Dinterman R. E. , Wannemacher R. W.
Published: December 2017

To determine spontaneous 24-h patterns of growth hormone (GH) plasma levels in unsedated and unrestrained nonhuman primates, a jacket and tethering system were used to study six cynomolgus monkeys. Hourly blood samples were collected, and body temperatures were recorded over 24-h periods. Measurements of GH were made on all samples. In one 24-h study cortisol levels were also measured as well to document a normal circadian rhythm. GH was released at mean intervals of 4.5 +/- 0.47 h (mean +/- SE) over the 24-h studies. There were no day-to-night differences in either the mean interval of GH release (day, 4.6 +/- 0.66 h; night, 4.4 +/- 0.51) or the mean GH values (day, 9.8 +/- 1.7 mU/l; night, 7.9 +/- 0.8). An apparent midday peak in GH in the 24-h studies followed feeding. As expected, body temperature was higher during the day than night, documenting a normal circadian rhythm. Plasma cortisol also showed a normal circadian variation with a low point midday and a progressive rise during the night in the one 24-h cycle in which it was measured. GH in unsedated, unrestrained cynomolgus monkeys was released in 4- to 5-h cycles both day and night without increased nighttime release. This contrasts sharply with the known nocturnal sleep release of GH seen in humans.
Glucoprivic feeding is impaired by lateral or fourth ventricular alloxan injection
Authors: Ritter S. , Murnane J. M. , Ladenheim E. E.
Published: December 2017

Feeding and blood glucose responses to insulin and 2-deoxy-D-glucose (2-DG) were examined in rats previously given lateral or fourth ventricular injections of the diabetogenic agents, alloxan and streptozotocin. Although streptozotocin (120, 200, and 400 micrograms) was ineffective, lateral ventricular alloxan injections (40 micrograms in 5 microliters) reduced feeding to 45% of control after 350 mg/kg 2-DG (sc), 33% of control after 150 mg/kg 2-DG, and 65% of control after insulin (2 U/kg). Fourth ventricular alloxan injections produced greater deficits, reducing feeding to 19, 7, and 46% of control, respectively. The sympathoadrenal response to glucoprivic agents was normal after alloxan treatment; however, blood glucose levels fell more rapidly during fasting than in controls. Alloxan-induced deficits did not appear to result from damage to catecholamine neurons, since neither regional concentrations nor glucoprivation-induced elevation of catecholamine turnover was altered by alloxan pretreatment. We conclude that cells involved in the glucoprivic control of feeding can be selectively and permanently damaged by intracerebroventricular alloxan administration. Such cells appear to reside in the hindbrain, to be noncatecholaminergic, and to function independently of glucoreceptors mediating sympathodrenal discharge.
Effects of DDAVP and AVP on sodium and water balance in conscious rat
Authors: Gross P. A. , Anderson R. J.
Published: December 2017

Many aspects of the physiological adaptation to chronic vasopressin and hypotonic fluid administration remain unclear. We therefore infused vasopressin [either 1-desamino-8-D-arginine vasopressin (DDAVP) at 0.112 ng/h or arginine vasopressin (AVP) at 2.4 mU/h] and hypotonic fluid (0.22% NaCl at 3.1 ml/h) into conscious unrestrained rats for 4–6 days. To determine if a decrease in the hydrosmotic effect of vasopressin occurred, urinary osmolality, flow rate, and free water reabsorption were measured sequentially in vasopressin-treated and control animals (receiving 0.22% NaCl alone). Progressive increases in urine flow and decreases in urine osmolality and free water reabsorption occurred in vasopressin-treated animals. This decreased hydrosmotic effect was noted with both DDAVP and AVP and could be dissociated from hormonal degradation and urinary prostaglandin E2 excretion. Sodium and water balance were measured to assess the determinants of the hypotonic state following chronic vasopressin and hypotonic fluid. In DDAVP-treated animals, sodium balance remained constant and hyponatremia resulted from water retention alone. In AVP-treated animals, a greater degree of hyponatremia was observed and resulted from combined positive water balance and negative sodium balance. The difference in sodium balance observed when DDAVP- and AVP-treated animals were compared could not be attributed to differences in either magnitude of water retention or filtered load of sodium.
Circannual body weight rhythms of ground squirrels: role of gonadal hormones
Authors: Zucker I. , Boshes M.
Published: December 2017

The influence of ovarian and testicular hormones on circannual body weight cycles was assessed in golden-mantled ground squirrels (Spermophilus lateralis), maintained in a LD 14:10 photoperiod at 23 degrees C. Animals were gonadectomized or sham operated at 47 days of age and implanted with empty capsules or capsules filled with estradiol benzoate (EB) or testosterone propionate (TP). Body weight, food intake, and reproductive condition were recorded at weekly intervals. Gonadectomized and intact squirrels of both sexes manifested robust circannual rhythms of body weight; cyclic secretion of gonadal hormones was not necessary for the expression of this circannual cycle. Intact and gonadectomized males weighed substantially more than their female counterparts but only during part of the annual cycle. This sex difference waxed and waned on a circannual basis in the absence of concurrent gonadal hormone secretions. EB phase-delayed attainment of peak body weights in ovariectomized squirrels but did not affect timing of trough body weights. EB increased the amount of food consumed by ovariectomized squirrels particularly during the weight gain phase. TP accelerated attainment of trough body weights in orchidectomized animals. Gonadal hormones modify the magnitude and timing of body weight peaks and troughs but are not necessary for the generation or expression of the circannual body weight cycle or for the sex difference in this cycle.
Impairment and restoration of rat urinary bladder responsiveness following distension
Authors: Carpenter F. G.
Published: December 2017

Micturition and bladder responsiveness in vitro were impaired in rats fed isotonic sucrose, afflicted with diabetes mellitus or diabetes insipidus. Their urinary output which was seven times control, initiated micturition responses at volumes three times control. Nerve-induced contractions by bladders from these rats developed substantially less pressure than control. Contractions elicited at 1 Hz by control and impaired bladders were potentiated equally by tetraethylammonium chloride (TEA) (5 mM) or by carbachol (2 X 10(-7) M). Contractions elicited at 20 Hz by normal bladders were not potentiated, those by impaired bladders were. TEA, by increasing transmitter release, and carbachol, by a postjunctional action, substantially reversed bladder dysfunction. Because control and impaired bladders were equally enhanced by TEA, prejunctional and contractile element (CE) activity at 1 Hz were probably unaffected by distension. However, postjunctional sensitivity was probably reduced. Impaired bladders, more compliant than controls, became less compliant after carbachol without elevating resting pressure. Whereas the action of carbachol to enhance bladder responsiveness did not involve tension development, there may have been cholinoceptor facilitation and shortening of CE.
Role of vasopressin in blood pressure regulation in conscious water-deprived dogs
Authors: Schwartz J. , Reid I. A.
Published: December 2017

The role of vasopressin in the regulation of blood pressure during water deprivation was assessed in conscious dogs with two antagonists of the vasoconstrictor activity of vasopressin. In water-replete dogs, vasopressin blockade caused no significant changes in mean arterial pressure, heart rate, plasma renin activity (PRA), or plasma corticosteroid concentration. In the same dogs following 48-h water deprivation, vasopressin blockade increased heart rate from 85 +/- 6 to 134 +/- 15 beats/min (P less than 0.0001), increased cardiac output from 2.0 +/- 0.1 to 3.1 +/- 0.1 1/min (P less than 0.005), and decreased total peripheral resistance from 46.6 +/- 3.1 to 26.9 +/- 3.1 U (P less than 0.001). Plasma renin activity increased from 12.4 +/- 2.2 to 25.9 +/- 3.4 ng ANG I X ml-1 X 3 h-1 (P less than 0.0001) and plasma corticosteroid concentration increased from 3.2 +/- 0.7 to 4.9 +/- 1.2 micrograms/dl (P less than 0.05). Mean arterial pressure did not change significantly. When the same dogs were again deprived of water and pretreated with the beta-adrenoceptor antagonist propranolol, the heart rate and PRA responses to the antagonists were attenuated and mean arterial pressure decreased from 103 +/- 2 to 91 +/- 3 mmHg (P less than 0.001). These data demonstrate that vasopressin plays an important role in blood pressure regulation during water deprivation in conscious dogs.