bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental study of adipose cellularity in lateral hypothalamic-lesioned Zucker obese rats
Authors: Milam K. M. , Keesey R. E. , Storlien L. H. , Stern J. S.
Published: December 2017

Ten-week-old lean and obese Zucker rats were sham lesioned or received bilateral, electrolytic lesions of the lateral hypothalamus (LH). They were maintained on a wet mash diet until killing at 15 or 32 wk of age; control lean and obese rats were also killed at 6 and 10 wk. Body composition analyses were performed and adipocyte cellularity of epididymal, retroperitoneal, and subcutaneous depots were calculated. Changes in body composition of LH-lesioned rats, though similar in the two genotypes on an absolute basis, differed on a percentage basis due to the extreme adiposity of the obese rats. Retarded development of protein depots in both lesioned lean and obese rats was apparent at 15 but not 32 wk. Relative to genotypic controls, lesioned lean and obese rats had smaller adipose depots by 32 wk due to decreased adipocyte size in lean rats and reduced adipocyte number in the obese. This genotype-specific response was probably due to the chronic hyperplasia of adipocytes unique to the obese rats. This distinctive developmental pattern of the epididymal depot is discussed.
Entrainment of the circadian rhythm from the eye of Aplysia: role of serotonin
Authors: Corrent G. , Eskin A. , Kay I.
Published: December 2017

The finding that serotonin (5-HT) treatments as short as 1.5 h in duration produce phase shifts in a circadian rhythm from the isolated eye of Aplysia suggested that release of 5-HT was part of an ocular entrainment pathway. Since light cycles entrain this rhythm, we compared phase shifting by 5-HT and by light. The similarity in the shapes of the phase-response curves for 5-HT and light pulses indicates that 5-HT treatments are capable of entraining the rhythm. Also, "skeleton" 5-HT treatments phase shift as well as continuous 5-HT treatments. However, 5-HT does not appear to mediate the phase shifts produced by light, since 1) treatments that should block transmitter release do not change the phase shifts produced by light pulses; 2) the response curves of 5-HT and light pulses are displaced by 12 h relative to one another on the phase axis of the response curve; and 3) light-induced phase shifts are apparent almost immediately, whereas 5-HT-induced phase shifts become evident only about 24 h after 5-HT treatment. The eye appears to contain two independent entrainment pathways, one for light and one utilizing 5-HT.
Chloride secretion and conductance of teleost opercular membrane: effects of prolactin
Authors: Foskett J. K. , Machen T. E. , Bern H. A.
Published: December 2017

Effects of prolactin on transport properties of opercular membranes from seawater-adapted tilapia, Sarotherodon mossambicus, have been examined. These membranes are high conductance (average Gt approximately 4 mS.cm-2) tissues with short-circuit currents (I) equal to net chloride secretion. Despite high Gt, nonlinear current-voltage relationships suggest that opercular membranes cannot be classified as "leaky" tissues. Variability among membranes is reflected in a linear relationship between I and Gt with a slope equal to 26 mV and the zero-current Gt intercept equal to 0.45 mS.cm-2. Prolactin injections decrease I and Gt in a dose-dependent manner. Phosphodiesterase inhibition, without effect on I in untreated fish, often partially reverses these prolactin effects. Gt-I data from prolactin-treated fish yield a slope of 18 mV and a Gt intercept of 0.10 mS.cm-2. The effects of prolactin are discussed in terms of conventional equivalent circuit analysis. Discrepancies between predictions based on this model and the actual data indicate that an alternative interpretation, based on a heterogeneous cell population, is more accurate. Analysis of this circuit suggests that the ratio of paracellular to active transport pathway conductances associated with chloride cells is constant and that differences in Gt and I are due to parallel changes in these conductances. Prolactin may effectively "remove" chloride cells from these membranes as well as inhibit (reversible by elevated cellular cAMP levels) active transport pathway conductance of remaining cells.
Evidence for a direct action of thyroid hormone in specifying muscle properties
Authors: Nwoye L. , Mommaerts W. F. , Simpson D. R. , Seraydarian K. , Marusich M.
Published: December 2017

Thyroidal trophic effects on slow-twitch skeletal muscle properties were compared in normally innervated and denervated soleus of rats maintained at different thyroid states. Hypothyroidism caused fast to slow changes in fiber type composition (99% decrease in proportion of type II fibers), ATPase activities (down 20-30%), myosin light chain pattern (54% less fast light chains), calcium uptake by SR (down 60%), LDH activity (down 11%), and isozyme pattern (9% decrease in M-subunits). Changes of similar magnitude but opposite in direction were induced by thyrotoxicosis. Denervations reversed, to varying degrees, the fast to slow transformations observed in hypothyroidism. However the slow to fast changes found in hyperthyroidism were facilitated rather than inhibited by denervation. These latter results clearly show that the hormone effect can be elicited in the absence of motor innervation. Furthermore, denervation alone caused slow to fast changes in euthyroid muscles. From these results, it is proposed that denervation and dysthyreosis alter muscle properties by independent mechanisms. Our data favor a direct action of thyroid hormone over a neurally mediated mechanism.
Computer simulation of energy metabolism in acidotic cardiac ischemia
Authors: Achs M. J. , Garfinkel D.
Published: December 2017

Construction and fit to experimental data of a computer model of glycolysis, the tricarboxylic acid cycle, and related metabolism in the perfused rat heart involving 63 enzyme submodels is described. The experimental preparation simulated is a rat heart perfused with Krebs bicarbonate solution containing glucose and insulin whose pH was lowered to 6.6 by equilibration with 35% CO2-65% O2. The glycolytic rate falls sharply and ischemia results, becoming apparent after 3.5 min. The model initially ascribes the fall in glycolysis largely to inhibition of hexokinase by accumulated glucose 6-phosphate and inactivation of phosphofructokinase by the low pH and subsequently to cytoplasmic glucose depletion owing to limitation of glucose uptake by the external acidosis. At the same time there is insufficiently deep hypoxia to trigger substantial mobilization of endogenous fuels (e.g., glycogenolysis or fatty acid mobilization, so that these hearts become ischemic primarily owing to a shortage of metabolic fuel.
Hyperdynamic severe intravascular sepsis depends on fluid administration in cynomolgus monkey
Authors: Carroll G. C. , Snyder J. V.
Published: December 2017

A new model of high cardiac output septic shock in primates is presented that includes hemodynamic and metabolic effects of separate and combined infusions of normal saline and live Escherichia coli. In monkeys receiving ketamine anesthesia, cardiac output (QT) increased with saline loading but not significantly with bacterial infusion, and bacterial infusion without saline never significantly increased QT. Depressed oxygen consumption (VO2) was reversed with saline loading. In spite of continuing E. coli infusion, radiolabeled microspheres showed no increase in systemic anatomic shunt when QT was elevated. It is perceived that the tissue dysfunction associated with sepsis, which is called septic shock, and elevation of cardiac output are related only indirectly. High cardiac output only reflects an adequate volume status in a stressed individual; some of the afferent stress signals can be related to the septic state, but no specific or direct relationship is involved. In general, shock as indicated by a depression of VO2 does not appear to occur when QT is increased.
Analysis of the actions of angiotensin on the central nervous system of conscious dogs
Authors: Reid I. A. , Brooks V. L. , Rudolph C. D. , Keil L. C.
Published: December 2017

Angiotensin II (ANG II) acts on the brain to elevate blood pressure (BP), stimulate drinking, increase the secretion of vasopressin and corticotropin (ACTH), and inhibit the secretion of renin. The present studies were designed to evaluate the possible physiological significance of these effects. The experiments were performed in conscious dogs with small catheters chronically implanted in both carotid and both vertebral arteries. ANG II was infused into both carotid or both vertebral arteries in doses of 0.1, 0.33, 1.0, and 2.5 ng.kg-1.min-1. Intravertebral ANG II produced dose-related increases in BP that were generally accompanied by increases in heart rate. Intracarotid angiotensin also increased BP but did not change heart rate. Intracarotid ANG II stimulated drinking and, at the highest dose only, increased the secretion of vasopressin, ACTH, and corticosteroids. Intravertebral and intracarotid ANG II suppressed plasma renin activity (PRA). In a parallel series of experiments, the effects of intravenous ANG II, in doses of 2, 5, 10, and 20 ng.kg-1.min-1, were studied. These infusions produced dose-related increases in BP and water intake and suppressed PRA. Only the highest dose of ANG II increased vasopressin or corticosteroid secretion. Analysis of these results in terms of calculated or measured changes in plasma ANG II concentration indicate that the central cardiovascular and dipsogenic actions of angiotensin, as well as the suppression of PRA, can be elicited by concentrations of the peptide that are within the physiological range. On the other hand high, probably supraphysiological, levels of ANG II are required to increase vasopressin or ACTH secretion.
Functional anatomy of the lung of the snake Pituophis melanoleucus
Authors: Stinner J. N.
Published: December 2017

The respiratory system in Pituophis melanoleucus is composed of a trachea, a single bronchial lung containing the pulmonary vasculature, and a large membranous caudal air sac. Total air volume (VL) in a 1-kg snake is 97.5 ml and varies with size (M) according to the equation VL = 0.388 M0.80 where VL is in milliliters and M is in grams. These air volumes are similar to those measured in many lizards and turtles. Relative volumes of the trachea, vascular lung, and air sac in Pituophis are about 4, 20, and 76%, respectively. The respiratory tissue is composed of a honeycomb network of capillary-bearing partitions, which collectively forms the gas exchange surface. This respiratory tissue is confined to the proximal 20% of the lung. Total respiratory surface area (SA) in a 1-kg snake is 2.00 x 10(3) cm2 and varies with size according to the equation SA = 3.03 M0.94 where SA is in square centimeters. Total SA/VL within the bronchial lung is large, being approximately 101 cm2/ml. Gradients in respiratory surface area and lung air volume are reversed so that SA/VL is highest near the cranial tip of the lung and decreases towards the air sac. Harmonic mean thickness of the air-blood barrier was found to be 0.46 +/- 10(-4) cm with the result that the anatomic diffusion factor, or ratio of respiratory surface area to mean diffusion distance, for a 1-kg snake is 0.44 x 10(8) cm. This index of diffusion capacity is very close to that reported for two lungs of a turtle.
Acute effects of hypoxia on renal and endocrine function in normal humans
Authors: Heyes M. P. , Farber M. O. , Manfredi F. , Robertshaw D. , Weinberger M. , Fineberg N. , Robertson G.
Published: December 2017

The effects of hypoxia upon renal and endocrine function are unclear. Normal water-loaded subjects were exposed to hypoxia for 1 h (inspired PO2 = 74 Torr) in a decompression chamber (5,100 m, n = 8) or by breathing 10.5% oxygen at ambient pressure (n = 4). In four of eight subjects exposed to hypobaric hypoxia: urine flows (V) decreased (mean = 56%), urine osmolality increased (340%), plasma arginine vasopressin (AVP) increased (2,700%), plasma cortisol increased (256%), and mean blood pressure (BP) decreased (18%). V correlated inversely with AVP (r = 0.71, P less than 0.01) while AVP increases correlated with falls in mean BP (r = 0.72, P less than 0.05). Similar results were observed in the subjects exposed to normobaric hypoxia. Plasma aldosterone fell in the four subjects who maintained V on exposure to hypobaric hypoxia, but plasma renin activity did not change. In both groups prolactin levels were variable and solute and creatinine excretion were unchanged. No changes were observed in controls or in subjects exposed to hypobaria alone. Acute hypoxic exposure may produce significant hypotension with consequent increased AVP secretion resulting in diminished V.
Extra- and intracellular water spaces in muscles of man at rest and with dynamic exercise
Authors: Sjogaard G. , Saltin B.
Published: December 2017

A method was established to analyze the extracellular water space (H2Oe) in small muscle tissue samples as [3H]inulin distribution space. After initial experiments on rats, the method was applied on 13 men and 6 women. Muscles with different fiber compositions (soleus, S; vastus lateralis, (VL; gastrocnemius, G; triceps brachii, TB) were studied at rest. The total water content was the same for all muscles, 320 (313-330) ml/100 g dry wt. However, differences were demonstrated for H2Oe, with 26-34 ml/100 g dry wt in VL and 38-54 ml/100 g dry wt in S, (P less than 0.05); the values for G and TB were in between those for VL and S. The differences in H2Oe were not related to the fiber composition of the muscles. During 3 x 3 min of intense bicycle exercise demanding about 120% VO2 max (6 men), total water content increased in VL from 313 to 359 ml/100 g dry wt and H2Oe increased from 34 to 60 ml/100 g dry wt (P less than 0.05), In TB, which is relatively inactive during bicycle exercise, no such changes occurred. The calculated intracellular lactate concentration increased in VL from 5.7 to 30.6 mmol/l H2Oi. The extracellular lactate concentration amounted to 13.6 mmol/l H2Oe at the end of exercise. The concentration gradient for lactate of 2 from intra- to extracellular space favored a flux of water to the intracellular space. The relative large increase in H2Oe may then be caused by a hydrostatic rather than an osmotic factor.U
Brain potassium ion homeostasis, anoxia, and metabolic inhibition in turtles and rats
Authors: Sick T. J. , Rosenthal M. , LaManna J. C. , Lutz P. L.
Published: December 2017

Microelectrode measurements of tissue oxygen tension (PtO2) and extracellular potassium ion concentration ([K+]o) and dual wavelength spectrophotometric measurements of the reduction/oxidation state of cytochrome aa3 were used to compare the resistance of turtle and rat brain to anoxia in vivo. In both species, respiration with 100% N2 resulted in a decrease of tissue oxygen tension to near 0 mmHg and reduction of cytochrome aa3. However, N2 respiration resulted in only moderate elevation of [K+]o in turtle bran while [K+]o in rat brain was elevated to levels greater than 50 mM. In addition, N2 respiration in turtles had no effect on the rate of recovery of [K+]o, which was elevated by direct electrical stimulation of the brain. Electrocorticographic activity (ECoG) of the turtle brain was only moderately depressed during N2 respiration for up to 4 h whereas the ECoG of rat brain became isoelectric within 1 min. Inhibition of glycolysis with iodoacetate (IAA) resulted in rapid elevation of [K+]o in turtle brain during anoxia, but IAA had little effect on [K+]o during normoxia. These results indicate that the remarkable resistance of the diving turtle to anoxia does not result from continued provision of oxygen to the brain either by redistribution of systemic blood flow or from blood O2 storage. In addition, the turtle brain does not rely on cellular stores of high-energy compounds for maintenance of ionic homeostasis. We conclude that potassium ion homeostasis in the anoxic turtle brain must result from increased glycolytic ATP production and from decreased energy utilization.
Obesity in Osborne-Mendel and S 5B/Pl rats: effects of sucrose solutions, castration, and treatment with estradiol or insulin
Authors: Schemmel R. A. , Teague R. J. , Bray G. A.
Published: December 2017

S 5B/Pl rats were tested for their susceptibility to develop obesity when 1) ovariectomized, 2) given injections of insulin, and 3) given a sucrose solution to drink instead of water. The results obtained in Osborne-Mendel rats susceptible to dietary obesity when fed a high-fat diet were compared to those obtained in the S 5B/Pl rats not susceptible to dietary obesity. When tested at the end of 10 wk, ovariectomized rats of both strains had gained 22% more weight than sham-operated controls. Replacement estradiol injections suppressed food intake in both strains with a concomitant loss in body weight. Osborne-Mendel rats tolerated at least 40 U of U-100 protamine zinc insulin/day and rapidly gained weight whereas S 5B/Pl rats given more than 2 U U-100 protamine zinc insulin/day died. Compared to female Osborne-Mendel rats drinking water, rats drinking a sucrose solution accumulated more body fat and had higher levels of serum immunoreactive insulin and lower levels of serum free fatty acids. The substitution of a sucrose solution for plain drinking water suppressed weight gain in S 5B/Pl rats.
Ontogeny of blood-brain barrier permeability to, and cerebrospinal fluid sink action on, [14C]urea
Authors: Parandoosh Z. , Johanson C. E.
Published: December 2017

To ascertain the ontogeny of CSF sink action on a small hydrophilic solute, we investigated the rate and extent of uptake of [14C]urea by lateral ventricle choroid plexus (CP), cisternal cerebrospinal fluid (CSF), cerebral cortex, and cerebellum in 0.5- to 4-wk-old etherized nephrectomized rats. Five hours after ip injection, radiourea penetrated the entire H2O of tissue and CSF in 1-wk-old brain; moreover, for animals 1-4 wk old there was a marked inverse relationship between age and magnitude of steady-state [14C]urea space in all regions. However, there was lack of progression (with advancing age) in distribution times to steady state, undoubtedly a reflection of the complexity of maturational factors (CSF secretion, barrier permeability, biphasic changes in cerebral blood flow, etc.) that affect solute penetration into central nervous system. Analysis of [14C]urea uptake curves for various regions at different stages of development (1 vs. 2 wk) revealed half times (slow component) that were significantly greater at 1 wk (1.2-1.4 h) than at 2 wk (0.5-0.8 h). Steady-state concentration gradients for tracer urea, plasma to CP to CSF, indicated negligible molecular sieving of urea by CP 1 wk after birth; however, after the 2nd postnatal wk CSF sink action on urea became manifest due to development of CSF secretion and molecular sieving at the blood-CSF and blood-brain barriers.
Evaluation of reaction rate enhancement by reduction in dimensionality
Authors: Wiegel F. W. , DeLisi C.
Published: December 2017

The paths followed by ligands as they react with or dissociate from cell surface receptors may include weak association with nonreceptor portions of the surface followed by lateral diffusion in the plane of the membrane to a receptor. The change in dimensionality of the diffusion process by utilization of these nonspecific paths has been invoked by a number of investigators as a mechanism for enhancing reaction rate in biological systems. This paper extends our previous work on the calculation of diffusive rate constants for ligand-receptor paths. We find that they have little effect on rate constants unless the number of free receptors per cell has been reduced to less than or equal to 10(2). This number represents better than 90% occupancy for most eukaryotes, suggesting that the dimensional change mechanism is of limited consequence. We show further that when the free receptor number is low enough for rate enhancement, then the primary parameter of consequence is D'K*/D, where D' and D are the two- and three-dimensional diffusion coefficients, respectively, and K* the nonspecific affinity. A 10-fold rate enhancement with 100 free receptors requires that this parameter be of order 10(-3). This value is barely within the lower limit imposed by currently available experimental information, casting doubt on the relevance of nonspecific paths in cellular systems.
Plasma catecholamines during hypoxemia in fetal lamb
Authors: Cohen W. R. , Piasecki G. J. , Jackson B. T.
Published: December 2017

Changes in peripheral plasma catecholamines were studied during varying degrees of hypoxemia in fetal lambs of 95–140 days gestation. Epinephrine and norepinephrine concentrations were measured by radioenzymatic assay in plasma obtained simultaneously from the distal aorta and inferior vena cava in 15 chronically catheterized fetuses with the mother breathing 20, 10, or 8% oxygen mixtures. Levels of both epinephrine and norepinephrine increased significantly after 5 min of hypoxemia and showed a strong inverse exponential correlation with PO2 (P less than 0.001). Plasma norepinephrine always exceeded epinephrine concentrations (P less than 0.01). Resting arterial and venous catecholamine levels were not different, but during hypoxemia arterial levels of both epinephrine and norepinephrine exceeded venous levels significantly, suggesting the adrenal medulla as a major source of these substances. Hypoxemia led to fetal bradycardia, the degree of which moderated somewhat with extremely low oxygen tensions and associated very high catecholamine levels. Fetal blood pressure increased initially in proportion to norepinephrine levels but reached a plateau at concentrations higher than 10 ng/ml. Although concentrations of catecholamines were lower in the earlier gestation fetuses studied, similar qualitative relations between catecholamines and PO2 were evident at all gestational ages.
Role of central and peripheral chemoreceptors in diving responses of ducks
Authors: Jones D. R. , Milsom W. K. , Gabbott G. R.
Published: December 2017

Using techniques of vascular isolation and subsequent perfusion we have investigated the effects of altering blood gas tensions, in the cerebral and carotid body circulations, on some cardiovascular responses to diving in unanesthetized ducks. After denervating the right carotid body, perfusion of the innervated left carotid body with hyperoxic blood significantly reduced diving bradycardia and reduced the increase in hindlimb vascular resistance (HLVR) in 1-min dives compared with dives in which the innervated carotid body was autoperfused. Denervation of systemic arterial baroreceptors reduced the fall in heart rate (HR) and increased the rise in HLVR in all dives. Cross-perfusion of the head, from a donor with blood of normal blood gas tensions, did not significantly affect HR or HLVR in 2-min dives compared with dives in which the head was autoperfused. however, cross-perfusing the cerebral circulation with blood of elevated PaCO2 caused significantly greater increases in HLVR than when high PaCO2 only affected the peripheral circulation. We conclude that peripheral chemoreceptors cause virtually all the bradycardia in the later stages of a dive but only about one-half the increase in HLVR, a significant contribution comes from the stimulation of central chemoreceptors with blood of high PaCO2.
Ventilatory reflexes originated from carotid and extracarotid chemoreceptors in rats
Authors: Cardenas H. , Zapata P.
Published: December 2017

Ventilatory responses to transient stimulation and inhibition of arterial chemoreceptors--by hypoxia and hyperoxia, respectively--were studied in 10 pentobarbitone-anesthetized rats. N2 tests and intravenous injections of NaCN provoked transient increases in tidal volume and respiratory frequency, while O2 tests elicited decreases of these parameters. After bilateral carotid neurotomy, ventilatory responses to N2 and NaCN were still present although reduced in all rats, while ventilatory depression in response to O2 tests was observed in 60% of these rats. Further bilateral sectioning of main vagus, aortic, and superior laryngeal nerves immediately below the nodose ganglia abolished the ventilatory responses to NaCN in only one of the five rats subjected to this procedure, the remaining animals showing moderate hyperventilation in response to large doses of this drug. Mild ventilatory depression in response to hyperoxia, indicative of a persistent peripheral chemosensory drive, was still present in two of these rats. It is concluded that, although the carotid bodies constitute the main source of ventilatory chemoreflexes in rats, other vagally and nonvagally innervated chemoreceptors (presumably thoracic and abdominal) may elicit ventilatory reflexes in this species.
Diffusion of oxygen in slices of rat brain
Authors: Homer L. D. , Shelton J. B. , Williams T. J.
Published: December 2017

A new method for the joint determination in tissue slices of the diffusion coefficient of oxygen (D) and the fluorescence-quenching coefficient (K') of pyrenebutyric acid (PBA) is introduced. Values of D and K' in rat brain at temperatures (Tc) from 20 to 40 degrees C were determined and referred to the values in water. D = DH2O (0.72 - 0.0074 Tc) +/- 0.079 X 10(-5) cm2/s for 80-microns slices. D = DH2O (1.01 – 0.0074 Tc) +/- 0.12 X 10(-5) cm2/s for 160-microns slices. K' = K'H2O (0.72 + 0.025 Tc) +/- 0.56 X 10(-4) mmHg-1. The temperature dependence of both these parameters in tissue is different from their temperature dependence, and comparison with parameter values obtained with other methods leads us to conclude that factors affecting the diffusion of oxygen in tissue are heterogenous rather than homogenous. The variation in the different parameters, D and K', probably exceeds a twofold range.
Angiotensin II and bradykinin: interactions between two centrally active peptides
Authors: Lewis R. E. , Hoffman W. E. , Phillips M. I.
Published: December 2017

Two neuropeptides, bradykinin (BK) and angiotensin II (ANG II), produce an increase in blood pressure when injected into the brain ventricles. This study is an example of central peptide-peptide interaction and was carried out to determine if BK and ANG II share a common mechanism in the brain to control blood pressure and drinking in rats. Prior injection of saralasin [10 micrograms intraventricularly (ivt)] was found to enhance the pressor response to ivt BK (5 micrograms) by 44%. The same dose of saralasin attenuated the pressor response to ivt ANG II (200 ng) by 55%. 50 ng ANG II and 5 micrograms BK given together ivt did not significantly alter blood pressure or urine conductance compared to 50 ng ANG II alone. Drinking to ivt infusions of ANG II (14 ng/min) was significantly attenuated when combined with BK (0.7 micrograms or 2.8 micrograms/min). Pretreatment with 10 micrograms indomethacin ivt diminished the pressor response to 5 micrograms ivt BK. Prostaglandin E2 (1.4 micrograms/min), but not prostaglandin A2, inhibited drinking to 14 ng/min ivt infusions of ANG II. The results suggest that ANG II and BK share an interrelationship with respect to their central actions: ANG II inhibits the BK pressor response and BK acts to inhibit drinking induced by ANG II. Prostaglandins of the E series may mediate these central actions of bradykinins.
Lability and diversity of circadian rhythms of cotton rats Sigmodon hispidus
Authors: Johnston P. G. , Zucker I.
Published: December 2017

Cotton rats (Sigmodon hispidus) were maintained from birth in constant LD 14:10 photoperiods and temperatures. Wheel running was diurnal for 6 of 13 juvenile rats and nocturnal for most others. Most diurnal rats eventually added nocturnal activity components. In constant darkness the activity rhythms of adult rats free-ran with a period of 23.2 +/- 0.3 h; in constant illumination the period was 24.7 +/- 0.1 h, in conformation to Aschoff's rule for nocturnal rodents. Some previously nocturnal adult rats eventually adopted stable diurnal activity cycles and other were successively nocturnal, diurnal for 6 mo, and then nocturnal again while maintained in the LD 14:10 photoperiod. The existence of multiple activity types, as well as the spontaneous inversions from nocturnal to diurnal status substantiate and extend field observations of this species. Seasonal inversions from nocturnal to diurnal activity, previously attributed to fluctuating environmental conditions, may also be subject to regulation by endogenous processes. It is suggested that spontaneous phase reversals in activity reflect changes in entrainment of circadian pacemakers by the light-dark cycle or altered relations between such pacemakers and the overt activity rhythm.
Sodium chloride absorption across the body surface: frog skins and other epithelia
Authors: Kirschner L. B.
Published: December 2017

Sodium chloride transfer across isolated frog skin is described by the well-known Koefoed Johnsen-Ussing (KU) model, the central features of which are 1) a two-step, active, inward transport of Na+, and 2) passive cotransfer of Cl-, which is coupled electrically to Na+ movement under open-circuit conditions. However, NaCl absorption by the frog skin in vivo involves active inward transport of both ions by completely independent systems. Electrical neutrality is maintained by countertransfer of H+ (exchanged for Na+) and HCO-3 (exchanged for Cl-). This behavior is called the Krogh (KR) model. The KU and KR models share some features, notably amiloride sensitivity and participation of the Na+-K+-ATPase in Na+ transport, but the differences between them are fundamental. The latter appear to be due to the use of different experimental conditions. Intact frogs are usually studied in dilute (approximatley 1 mM) external solutions, while Ringer solution is used in most work on isolated skins. The skin is virtually impermeable to Cl- in dilute external media but permeable in Ringer solution. This concentration-dependent change in PCl can explain most of the differences between KU and KR models. Regulation of blood NaCl concentration in freshwater aquatic animals requires active uptake of both Na+ and Cl-. Data on representatives of four phyla show that the KR model describes the transport behavior in all of them. Such similarities in unrelated animals suggest that the transport mechanisms evolved very early in marine ancestors of modern freshwater forms. The implications of this suggestion are considered.
Aerobic response to exercise of the fastest land crab
Authors: Full R. J. , Herreid C. F.
Published: December 2017

To view the aerobic response to exercise, the ghost crab Ocypode guadichaudii was run in a treadmill respirometer at three velocities (0.13, 0.19, and 0.28 km/h) while oxygen consumption (VO2) was monitored. A steady-state VO2 that increased linearly with velocity was attained. VO2 transient periods at the beginning and end of exercise were extremely rapid with half times from 50 to 150 s. The magnitude of oxygen deficit and debt were small and both showed increases with an increase in velocity. Oxygen debt was measured at each velocity after 4-, 10-, and 20-min exercise bouts. No change in the magnitude of oxygen debt was observed with respect to exercise duration. Maximal VO2 was 11.9 times the average resting VO2. Oxygen uptake kinetics have shown only very sluggish and reduced rates in five other more sedentary crab species previously tested. The aerobic response pattern observed in the present study is more comparable to that of exercising mammals and highly aerobic ectothermic vertebrates. This suggests that the ghost crab meets the energy demand of sustained exercise by aerobic ATP production in contrast to many other crab species.
Scaling of osmotic regulation in mammals and birds
Authors: Calder W. A. , Braun E. J.
Published: December 2017

Allometric equations provide a means of summarizing and relating the components of renal structure and function in water balance and osmotic regulation. These summary equations also serve as base lines for evaluating adaptations to stressful environments and for comparisons of kidney designs and osmotic strategies of ureotelic mammals and uricotelic birds. Many of the functions can be quantitatively related to the M3/4 scaling of metabolic rates.
Suppression of afferent activity of the hepatic vagus nerve by anomers of D-glucose
Authors: Niijima A. , Fukuda A. , Taguchi T. , Okuda J.
Published: December 2017

Afferent discharges were recorded from the nerve filaments dissected from the hepatic branch of the vagus nerve in the guinea pig. Recordings were made in isolated and perfused liver preparations and in vivo to study the effect of alpha and beta anomers of D-glucose on the afferent discharge rate. Infusions of these anomers (30 mg or 50 mg dissolved in 10 ml glucose-free Ringer solution) into the portal vein in perfused liver preparations and intraportal injections of these anomers (50 mg/kg dissolved in 0.2 ml saline) in vivo partially suppressed the afferent activity. However, the effect of suppression by the beta anomer was stronger than that of the alpha anomer. Results indicate the existence of anomeric stereospecificity of D-glucose action to the hepatic "glucose sensors."
Response of single units in the amygdala to stimulation of buffer nerves in cat
Authors: Cechetto D. F. , Calaresu F. R.
Published: December 2017

Electrical activity of spontaneously active units in the amygdala of 19 chloralose-anesthetized cats was monitored for changes in firing frequency during electrical stimulation of the carotid sinus (CSN) and aortic depressor (ADN) nerves. Stimulation of the CSN altered the firing frequency of 30% (73/241) of the units on both sides of the amygdala. Of these units, 47% were excited and 53% were inhibited. Stimulation of the ADN elicited a change in firing frequency of 20% (50/251) of ipsi- and contralateral units. Of these, 68% were excited and the remainder were inhibited. The average latency for all CSN responses (53 +/- 4.0 ms) was significantly longer than the average latency for ADN responses (35 +/- 3.3 ms). The majority of the responsive units were located in the central and lateral nuclei of the amygdala. Spontaneously firing units responding to both CSN and ADN stimulation were found infrequently (7%, 14/188). These results indicate that the two buffer nerves project to specific regions within the amygdala, but the CSN and the ADN follow separate pathways probably involved in reflex arcs mediating different physiological responses.
Effects of thyroxine supplementation on metabolic rate and aerobic capacity in a lizard
Authors: John-Alder H. B.
Published: December 2017

Effects of thyroxine (T4) on standard and maximal rates of O2 consumption and on citrate synthase activity, an index of mitochondrial oxidative capacity, were examined in the lizard Dipsosaurus dorsalis. Two weeks of daily injections of 200 ng T4/g body mass resulted in significant increases in standard (+60%) and maximal (+15%) rates of O2 consumption. Citrate synthase activity in liver and in red iliofibularis and gastrocnemius muscles was significantly higher than in controls. Correlational analyses indicate that intraspecific differences in standard metabolic rate may be partially attributable to fundamental differences in tissue metabolic capacities and that thyroxine injections lead to a general increase in aerobic capacities. Similar increases in aerobic capacities may occur in response to high thyroid activity during Spring in temperate-zone lizards. The injection protocol used in this study, taken from previous authors, results in suppression of natural thyroid secretory activity and in a 24-h average plasma T4 level of 95 ng/ml compared with 2.5 ng/ml in controls.
Macronutrient self-selection in three forms of hypothalamic obesity
Authors: Sclafani A. , Aravich P. F.
Published: December 2017

Adult female rats were adapted to a macronutrient self-selection regimen which allowed them ad libitum access to separate sources of protein, carbohydrate, and fat. The rats were then given either ventromedial hypothalamic (VMH) lesions, paraventricular hypothalamic (PVH) lesions, parasagittal knife cuts through the medial hypothalamus (CUT), or sham lesions and their macronutrient selection was studied for 60 days. Following surgery the VMH, PVH, and CUT rats overate and became obese compared with controls. The hyperphagias of the three groups were similar, although the CUT group gained more weight than did the PVH and VMH groups. All groups overate primarily by increasing their carbohydrate intake. The VMH and CUT groups, in addition, increased their protein intake such that their percent protein intake remain unchanged. The PVH group failed to increase its absolute protein intake and thus decreased its percent protein intake. Except for a transient increase, fat consumption was not affected by the lesions or knife cuts. During the 2nd postoperative mo (static phase) the total caloric intakes and the carbohydrate intakes of the VMH, PVH, and CUT groups returned to near normal levels. Rats with misplaced PVH lesions displayed minimal hyperphagia and failed to outgain controls but yet showed the same altered macronutrient selection pattern as did rats with obesity-inducing PVH lesions. Measurements of resting insulin levels at the end of the experiment revealed hyperinsulinemia in the VMH and CUT groups but normal insulin values in the PVH group. These results demonstrate that VMH lesions, PVH lesions, and medial knife cuts produce similar hyperphagia syndromes associated with carbohydrate-specific overeating, but that they differentially affect protein selection and resting insulin levels.
Studies on the mechanism of beneficial effects of ATP-MgCl2 following hepatic ischemia
Authors: Ohkawa M. , Clemens M. G. , Chaudry I. H.
Published: December 2017

Infusion of ATP-MgCl2 following hepatic ischemia significantly improves the survival of animals. To determine the subcellular effects of infused ATP-MgCl2 and whether such effects are mediated through vasodilatation, global hepatic ischemia in rats was produced for 90 min followed by reperfusion. The rats then received iv 0.5 ml of saline, dopamine, papaverine, or ATP-MgCl2. At various intervals following reflow, hepatic mitochondria were isolated. ADP-to-O ratio and respiratory control ratio (RCR) were significantly lower 1 h following reflow, and there was a further decrease in these parameters 3 h after reflow in mitochondria from saline-treated rats. Dopamine and papaverine treatment did not improve RCR, however, ATP-MgCl2 treatment resulted in a progressive and significantly higher ADP/O and RCR following reflow. Hepatic ATP levels in saline, dopamine, and papaverine-treated rats were found to be 50% lower 3 h following reflow, however, treatment with ATP-MgCl2 resulted in significantly higher ATP levels and energy charge. Hepatic blood flow was markedly depressed 1 h following reflow in the saline-treated rats but was significantly higher in the ATP-MgCl2 group. Three hours following reflow, hepatic blood flow decreased further in the saline-treated rats, whereas in the ATP-MgCl2-treated rats there was a progressive increase in flow. Dopamine treatment resulted in an initial restoration in flow, however, this effect was not sustained. Hepatic ultrastructure deteriorated progressively following reflow in the saline-treated rats, however, it was normal in the ATP-MgCl2-treated rats 1 h as well as 20 h following reflow. These results lead us to conclude that infused ATP-MgCl2 improves mitochondrial and cellular functions either directly or by way of long-term improvement in microcirculation but not through vasodilatation.
Mitochondrial ammoniagenesis in liver of the channel catfish Ictalurus punctatus
Authors: Campbell J. W. , Aster P. L. , Vorhaben J. E.
Published: December 2017

Rates of ammonia formation from six amino acids by hepatocytes and liver mitochondria were compared with the rate of ammonia excretion by individual fish. Glutamine and asparagine are the most ammoniagenic substrates for hepatocytes and glutamine and glutamate, for isolated liver mitochondria. The main site of ammonia release is the mitochondrion. Ammonia is formed mainly via deamidation or transdeamination. Relatively small amounts of aspartate are formed from glutamate and glutamine by the fish liver mitochondria. This apparent "uncoupling" of glutamate transamination may represent an adaptation of carnivorous fish to the utilization of amino acids as a major energy source. More than 90% of the ammonia formed from glutamate and glutamine by isolated mitochondria are elaborated into the medium. Exiting ammonia is accompanied by a proton, but the source of this proton appears not to be the electrogenic proton pump or the carboxylate of exiting glutamic acid.
Lowered cerebrospinal fluid sodium antagonizes effect of raised blood sodium on salt appetite
Authors: Muller A. F. , Denton D. A. , McKinley M. J. , Tarjan E. , Weisinger R. S.
Published: December 2017

Moderately Na-deficient sheep (i.e., Na deficit = 300-400 mmol) will correct their deficit when given hypertonic NaHCO3 solution to drink. Access to NaHCO3 was provided by bar press for 2 h only each day following 22 h of salivary loss from a parotid fistula. Each delivery by bar press provided 9 mmol of NaHCO3 and, of the 46.3 +/- 2.5 deliveries made and drunk in 2 h, 80-90% were made in the first 20 min. Ten minutes before access to NaHCO3 commenced an intracarotid infusion of 4 M NaCl at 1.6 ml/min for 30 min was initiated. This infusion reduced intake by approximately 80% and increased both plasma and cerebrospinal fluid sodium concentration (CSF[Na]). Intraventricular (ivt) infusion of 0.7 M mannitol in artificial CSF at 1 ml/h for 3 h begun 1 h before access to Na by bar press lowered CSF[Na] and approximately doubled voluntary Na intake. The combination of the two procedures resulted in NaHCO3 intake similar to base line. That is, the ivt infusion of 0.7 M mannitol counteracted the inhibition of Na appetite produced by the systemic infusion of hypertonic NaCl, and this was associated with attenuation of the effect of the systemic 4 M NaCl infusion on CSF[Na]. The results suggest that the effects of both the ivt and the systemic infusions are mediated via the same sensor system located within the neuropil.
Postgastric satiety in the sham-feeding rat
Authors: Reidelberger R. D. , Kalogeris T. J. , Leung P. M. , Mendel V. E.
Published: December 2017

A sham-feeding model using rats fitted with gastric and duodenal cannulas was employed to investigate the role of postgastric mechanisms of satiety in the short-term control of food intake. When fasted rats sham fed a liquid diet [Vivonex High Nitrogen (VHN), 0.5 kcal/ml], food drained freely from gastric fistulas, and mean first-meal size and 90-min intake increased more than threefold. Varying the rate of duodenal infusion of diet during sham feeding (0.06-0.44 kcal/min) decreased first-meal size and total intake in a dose-dependent manner. First meals ended when mean loads of 2-3 kcal had been delivered. The threshold rate (0.11 kcal/min) decreased meal size and total intake by more than 50%. When fasted rats consumed VHN to satiety with closed gastric fistulas, rate of gastric emptying of diet during feeding averaged 0.32 +/- 0.02 kcal/min and the load emptied by meal termination averaged 3.8 +/- 0.2 kcal. These results indicate that rates of gastric emptying of diet and loads delivered to the small intestine following ingestion of liquid food are sufficient to elicit postgastric satiety in the absence of gastric distension.
Sodium chloride preference of genetically hypertensive and normotensive rats
Authors: Di Nicolantonio R. , Mendelsohn F. A. , Hutchinson J. S.
Published: December 2017

Preference for 0.9% saline was examined, using two-bottle preference tests over 6-7 days, in the spontaneously hypertensive rat (SHR) and normotensive Wistar Kyoto rat (WK) of the Okamoto strain, the genetically hypertensive (GHR) and normotensive rat (NT) of the Smirk strain, and the Sprague-Dawley (SD), Dark Agouti (DA), and hooded Long-Evans or Brattleboro (BB) rat. Only the SHR exhibited a sustained and marked preference for 0.9% saline on each test day. The WK, GHR, NT, and SD preferred saline in the first 24-48 h of testing but thereafter showed neither a preference for, nor aversion to, saline. The BB showed neither a preference for, nor aversion to, saline in the first 24 h of testing and thereafter showed a significant aversion to saline on each test day. Saline preference was further examined in both the SHR and WK offered a choice of water and 0.9%, 2.0, or 2.7% saline. While preference for saline decreased in both SHR and WK with increasing saline concentration, the SHR maintained a significantly greater preference for saline and greater total sodium intake than the WK at each concentration. Hydralazine (5 mg . kg-1 . day-1, po) administered to SHR, while they were offered a choice of water and 0.9% saline, significantly lowered blood pressure over a 4-day period but failed to alter their saline preference significantly. We conclude that of the seven strains of rats examined only the SHR exhibited a preference for saline in extended two-bottle preference tests. Furthermore this preference for saline appears to be maintained independently of the blood pressure of the SHR.
Control of ion transport by Gillichthys mirabilis urinary bladder
Authors: Loretz C. A. , Bern H. A.
Published: December 2017

The columnar epithelial cell region of the goby Gillichthys mirabilis urinary bladder is the region responsible for active Na and Cl reabsorption from bladder urine. In 5% seawater-adapted fish, reabsorption occurs via an electrically silent coupled NaCl transport mechanism. Bladder reabsorption is increased in seawater-adapted fish above that observed in 5% seawater-adapted fish; incremental reabsorption results from an electrogenic Na transport in addition to the neutral component. Hypophysectomy of seawater-adapted fish reduces the electrogenic Na transport (measured as short-circuit current, ISC) and increases the transepithelial resistance (R) to values near those of 5% seawater-adapted fish. Cortisol restores the ISC and R to normal seawater-adapted values and will initiate electrogenic Na transport in 5% seawater-adapted fish. Ovine prolactin will also restore the ISC and R of columnar cell regions of hypophysectomized seawater-adapted fish to normal seawater-adapted levels; this effect appears to be due to contamination or to inherent stimulatory activity of the ovine prolactin preparation, since endogenous prolactin is ineffective in the restoration of ISC or R.
Differential sympathetic responses initiated by angiotensin and sodium chloride
Authors: Tobey J. C. , Fry H. K. , Mizejewski C. S. , Fink G. D. , Weaver L. C.
Published: December 2017

Angiotensin II (ANG II) and NaCl act on central receptors to cause pressor responses that may be mediated in part by the sympathetic nervous system. The inhibitory or excitatory nature of effects on central sympathetic outflow are not well defined. This study was undertaken to evaluate further the potential contribution of the sympathetic nervous system to central actions of angiotensin or hypertonic NaCl. Experiments were performed using anesthetized, sinoaortic denervated, vagotomized cats. Intracarotid injection of NaCl produced increased splenic sympathetic nerve activity and decreased renal sympathetic nerve activity. Intracerebroventricular (icv) administration of NaCl caused slight excitatory responses in splenic nerves and no change in renal nerve activity. Intracarotid injection of ANG II caused significantly greater splenic than renal excitation. Administration of ANG II icv caused excitation of splenic nerve activity and no change in renal nerve activity. These findings illustrate that stimulation of sodium-sensitive and angiotensin-sensitive CNS receptors produces differential responses in sympathetic outflow. These differential sympathetic responses may contribute to the complex cardiovascular responses to increased plasma or brain concentrations of angiotensin or sodium.