bluuebunny/crossref_metadata_2025 huggingface dataset:
Norepinephrine elevation in the fetal lamb: oxygen consumption and cardiac output
Authors: Lorijn R. H. , Longo L. D.
Published: December 2017

In an effort to determine if placental diffusion reserves exceed fetal O2 requirements, we increased fetal O2 consumption (VO2) by infusing 1.7-11.5 microgram of norepinephrine (NE) . min-1. After 50 min of infusion VO2 rose 25% to 10.2 from 8.2 ml . min-1 . kg fetal wt-1. Placental CO diffusing capacity remained essentially unchanged from control, 0.49 +/- 0.05 (SE) ml . min-1. Torr-1 . kg-1, During the first 5 min of NE infusion fetal arterial blood pressure increased 29%, while heart rate decreased 15%. In addition, coronary, pulmonary, and umbilical blood flow, expressed per kilogram of fetal weight as determined by use of labeled microspheres, increased 50, 162, and 25%, respectively (P less than 0.05), although fetal cardiac output remained constant at 538 +/- 23 (SE) ml . min-1 . kg-1. Finally, we determined the NE-blood pressure dose-response relations for the fetus; Blood pressure increased with doses up to 1 microgram . min-1 . kg-1, but failed to rise further with higher doses. We conclude that 1) fetal VO2 increases with NE infusion 2) the placental reserve for O2 diffusion exceeds normal requirements, and 3) NE infusion is associated with increased blood pressure, bradycardia, and a redistribution of blood flows to the heart, lungs, and placenta despite a constant cardiac output.
Time course of peripheral heterothermy in a homeotherm
Authors: Brown R. T. , Baust J. G.
Published: December 2017

The integrity of the peripheral heterothermic response was monitored in adult Sprague-Dawley rats during cold acclimation. Subcutaneous peripheral temperature gradients were simultaneously recorded in the hindlimbs. One limb was exposed to room temperature (22 +/- 2 degrees C) while the contralateral limb was gradually cooled to 0 +/- 1 degrees C. Noncontrols were acclimated at 5 +/- 1 degrees C for periods up to 35 days. Controls responded to the cooling regimen (25 to 0 degrees C at 0.5 degrees C . min-1) in a "poikilothermic" manner indicating local cold-induced vasoconstriction (CIVC). CIVC was not released until tissue temperatures reached 22,3 +/- 2.5 degrees C whereupon nonpatterned limb temperature fluctuations, Lewis' hunting response, were often initiated. The hunting response occurred synchronously in the contralateral warmed limb despite its elevated temperature. The experiments revealed a progressive decrease in the intensity of heterothermy indicative of an earlier onset of cold-induced vasodilation as well as increased resistance to tissue cooling with increasing acclimation time. Following 21 days at 5 degrees C, limb exposure to 0 degrees C resulted in a 2-4 degrees C drop in tissue temperature. The time course of the diminution in peripheral heterothermy is discussed. In addition, evidence supporting the hypothesis of a central component in the regulation of the hunting response is presented.
Hamsters through time's window: temporal structure of hamster locomotor rhythmicity
Authors: Davis F. C. , Menaker M.
Published: December 2017

The temporal patterns of running-wheel locomotor activity of a group of 15 golden hamsters (Mesocricetus auratus) are described in detail. The temporal patterns of activity and the behavior of activity bouts in these animals provide the basis for a hypothetical multioscillator framework underlying locomotor activity. The framework consists of a pacemaker that controls the transitions between two continuous states, activity time and rest time, each composing approximately half of the circadian cycle. Activity time appears as a "window" during which the expression of locomotor bouts controlled by additional circadian oscillators is permitted. In our model, whether or not locomotor activity is expressed as well as its detailed temporal pattern are functions of the phase relationships between the window pacemaker and bout oscillators.
Persistence of impaired heat tolerance from artificially induced miliaria rubra
Authors: Pandolf K. B. , Griffin T. B. , Munro E. H. , Goldman R. F.
Published: December 2017

Ten volunteers were heat acclimatized to 48.9 degrees C (Ta), 20% rh for 7 days to complete a 100-min walk on a level treadmill (1.56 m x s-1). Subjects were then divided into experimental (n = 6) and control (n = 4) groups. Miliaria rubra (heat rash) was then induced on the experimental subjects by wrapping them for 3 days in polyethylene plastic. All six developed marked miliaria with involvement of 40-70% of the total body surface area. All subjects were reexposed to walking in the heat on the 7th day after unwrapping, by which time rash was clinically indetectable, and again 14 days after unwrapping. On the first test (day 7) only one of the rashed group, and on the second test (day 14) only two could complete the 100-min walk; the control group finished without difficulty on both days. Body heat storage for the rash group was 2.5 times that of the control group on day 7 and 1.5 as great on day 14; measurements of mean body temperature (Tb) on the rash group indicated a much greater heat stress when compared to their own prerash-acclimatized values or those of the control group. These data demonstrate the potential of "healed" miliaria in the etiology of clinical heat illness.
Circadian control of oviposition activity in Ostrinia nubilalis
Authors: Skopik S. D. , Takeda M.
Published: December 2017

Oviposition activity in the European corn borer, Ostrinia nubilalis, is under circadian control. Light cycles entrain the rhythm, and the system free-runs in constant darkness (DD) with a circadian period (tau). The lability of tau is evident in the DD free runs following entrainment to various light cycles. Oviposition activity is strongly suppressed in constant light but a circadian rhythm is initiated upon transfer to DD. The phase-response curve (PRC) for 1-h light pulses is type 1, not type 0 as predicted by Beck's dual system theory. The PRC can be used to predict entrained steady states in non-24-h light cycles (T's). Predicted phase relationships between the light component of the cycle and the rhythm in T19 and T26 are in close agreement with the observed peaks of oviposition. Symmetric skeleton photoperiods (two 1-h light pulses per cycle) also entrain the rhythm to the shorter of the two alternatives that are possible in these regimes.
Effects of pressure on cerebrospinal fluid formation: nonsteady-state measurements in dogs
Authors: Sklar F. H. , Reisch J. , Elashvili I. , Smith T. , Long D. M.
Published: December 2017

Effects of pressure on cerebrospinal fluid (CSF) formation were studied in dogs with a recirculatory spinal perfusion tracer clearance technique that does not require steady-state conditions. The data permit statistical analysis of the relationship between the rate of CSF formation and pressure for individual animals. Most animals showed no statistical relationship between CSF formation and intracranial pressure (ICP) and/or cerebral perfusion pressure (CPP). In this study, a disturbance of cerebral blood flow (CBF) autoregulation may have been present in five animals on the basis of CPP reductions, and four of this latter group showed formation to decrease with increasing ICP. It is suggested that CSF formation is normally pressure insensitive. With impaired autoregulation of CBF, formation may follow CBF and CPP passively.
Membrane potentials and chloride activities in epithelial cells of Aplysia intestine
Authors: Gerencser G. A. , White J. F.
Published: December 2017

Microelectrodes were used to measure the potential difference across the mucosal membrane (psi m) of cells lining the mucosa of isolated Aplysia californica intestine. In glucose-free sodium chloride seawater medium psi m was -68.2 +/- 2.2 mV, the cell interior negative relative to the mucosal bathing medium. Simultaneously, the transmural potential difference (psi m leads to s) was recorded and its value averaged -0.4 +/- 0.1 mV (serosa negative). The addition of D-glucose to the mucosal compartment depolarized psi m to -62.1 +/0 2.5 mV and hyperpolarized psi m leads to s to -1.5 +/- 9.1 mV. Intracellular chloride activity (aCli) was also determined in Aplysia intestinal cells using single-barreled ion-exchange microelectrodes. In the absence of D-glucose the mean aCli was 10.1 +/- 0.5 mM, whereas after mucosal glucose addition the paired mean aCli increased significantly to 14.2 +/- 0.6 mM. Both aCli values were less than those predicted by the electrochemical equilibrium for chloride across the mucosal membrane. An active chloride transport mechanism located in the lateral-serosal membrane of the surface epithelial cells is proposed to explain these observations.
Properties of body fluids influencing salt gland secretion in Pekin ducks
Authors: Hammel H. T. , Simon-Oppermann C. , Simon E.
Published: December 2017

Pekin ducks were reared and maintained on 620 mosmol NaCl/kg H2O to enhance the secretory capability of their salt glands. When a control solution of 1,000 mosmol NaCl/kg H2O was infused intravenously at 0.2, 0.4, or 0.6 ml/min for 60-90 min, the infused loads were secreted in approximately equal quantities, indicating that the amount of NaCl in the extracellular fluid (ECF) before and after each infusion did not change. Salt and water secreted in response to experimental infusions of hyposmotic saline or blood were less than the solute and water infused. Thus, ECF volume increased and the Na+ concentration decreased. Infusions of control solution followed these experimental infusions. The salt and water secreted again equaled the amounts infused, indicating that the threshold concentration of Na+ ([Na+]th) for salt gland secretion was decreased by the increase in ECF volume. When the colloid dextran was added to the control solution, its infusion increased the colloid osmotic pressure of the blood and decreased nasal secretion. Because dextran increased the intravascular volume while the interstitial fluid volume (ISFV) decreased, we conclude that the [Na+]th was inversely correlated with ISFV.
Vasopressin, fluid, and electrolyte response to chronic angiotensin II infusion
Authors: Cowley A. W. , Switzer S. J. , Skelton M. M.
Published: December 2017

The chronic interrelationships between blood-borne angiotensin (AII), plasma arginine vasopressin (AVP), fluid and electrolyte balance, and mean arterial pressure (AP) were studied in mongrel dogs by continuous intravenous infusion of AII for 7 days. Two groups of dogs were infused: group 1 and group 2 received 5.0 and 20.0 ng AII . kg-1 . min-1, respectively, and each were studied first on ad lib H2O intake and then several weeks later with “fixed” water intake. Plasma AVP was determined utilizing a sensitive radioimmunoassay procedure described herein, Group 1 (5.0 ng AII): AP rose to a steady-state level nearly 20 mmHg above control by the 3rd day of AII infusion with both ad lib and “fixed” H2O intake. With ad lib H2O, AVP was chronically unchanged while with fixed H2O a significant decrease had occurred by the 2nd day of AII infusion. Plasma [Na] and osmolality were not significantly changed in either state. Group 2 (20.0 ng AII): AP rose nearly 40 mmHg above control by the 3rd day of infusion with both ad lib and fixed water intake. AVP did not change significantly from a control of 0.8 microU/ml throughout AII infusion with ad lib H2O intake but drinking was more than doubled. With fixed H2O intake, plasma AVP rose from a control of 0.8 microU/ml to an average of 1.3 microU/ml over the last 4 days of AII infusion. A negative correlation was obtained between the “cumulative H2O balance” and plasma AVP obtained during AII infusion. We conclude first that circulating AII is not directly involved in the long-term control of AVP secretion and, second, neither AVP nor enhanced drinking contributes significantly to AII-induced hypertension.
One why of the warmth of warm-bodied fish
Authors: Stevens E. D. , Carey F. G.
Published: December 2017

Tunas are unusual among fish in that they are warm bodied. In the present essay we argue that one adaptive advantage to being warm is that the warmth increases the rate of delivery of oxygen from the cell boundary to the mitochondria by myoglobin. This argument is supported by the following. 1) Tuna have extremely high rates of oxygen uptake, much higher than other fish and close to the rates achieved by mammals. 2) Tuna have an extraordinary capacity to maintain high cruising speeds for a long time. 3) Tuna have much red muscle that contains a high concentration of myoglobin. 4) The effect of temperature on simple diffusion of oxygen is very small whereas the potential affect on facilitated diffusion by myoglobin is large.
Sites and action spectra for encephalic photoreception in the Japanese quail
Authors: Glass J. D. , Lauber J. K.
Published: December 2017

Sexually mature Japanese quail, Coturnix coturnix japonica, were transferred to short environmental photoperiod for 20 days, during which they received encephalic illumination via surgically implanted optic fibers. White light delivered to discrete sites in the basal hypothalamus induced photogonadal response for testicular maintenance. There was also a strong positive response to monochromatic red, green, or blue light delivered to these areas, and this response was of equal magnitude regardless of wavelength. Illumination of sites in the median eminence and pars nervosa was also effective in inducing photogonadal response. White light delivered to the optic chiasma was effective, whereas green or blue light to this structure had no effect. Illumination of the preoptic hypothalamus or the dorsal cortex was also without effect. Our data indicate that there are photoreceptive sites in and near the basal hypothalamus that, when illuminated directly, are capable of responding to a broad range of visible wavelengths.
A modeling study of the effect of fasting on bilirubin kinetics in Gilbert's syndrome
Authors: Okolicsanyi L. , Orlando R. , Venuti M. , Dal Brun G. , Cobelli C. , Ruggeri A. , Salvan A.
Published: December 2017

The mechanism of fasting hyperbilirubinemia (FH) is not fully understood. We investigated basal bilirubin kinetics in 20 Gilbert's patients and in 7 healthy volunteers. The study was repeated in seven of these Gilbert's patients after 48-h fasting. A two-compartment model proved to be adequate for interpreting crystalline bilirubin kinetics in these individuals. The parameters of bilirubin kinetics were estimated by employing a maximum likelihood parameter estimation technique. Consistency of the model and uniqueness of the estimated parameter values (from the covariance matrix) were shown. Our results confirmed previous observations regarding impaired bilirubin kinetics in Gilbert's patients as compared to controls. The main results obtained from kinetic studies in Gilbert's patients after fasting were i) no modification in the bilirubin clearance, and ii) a more than twice increase of bilirubin turnover. These data indicate that FH is related to an increased bilirubin production (mainly intrahepatic). Furthermore, evidence arises from this study that the bilirubin tolerance test is a useful diagnostic test for Gilbert's syndrome.
Sympathetic-related activity of brain stem neurons in baroreceptor-denervated cats
Authors: Gebber G. L. , Barman S. M.
Published: December 2017

A search was initiated in baroreceptor-denervated cats for brain stem neurons with activity patterns related to inferior cardiac sympathetic nerve discharge (SND). Neurons whose spontaneous discharges were followed by increases or decreases in SND fell into two categories. S unit discharges were related to SND but not electroencephalogram (EEG) activity. The activity of SE units was related to SND and EEG activity. The anatomic distribution of S and SE units was similar to that previously reported [Barman and Gebber, Am J. Physiol. 240 (Regulatory Integrative Comp. Physiol. 9): R335-R347, 1981] for units with activity patterns related to SND in baroreceptor-innervated cats. Autocorrelograms of S unit discharges and SND contained the same rhythm (2-6 cycles/s). This rhythm was different from that contained in SE unit discharges and EEG activity in experiments in which SND and cortical activity were not related. In other experiments, sympathetic nerve and cortical rhythms were locked to each other. SE units but no S neurons were located in these cats, and the rhythm contained within the autocorrelograms of their discharges was the same as that observed in SND and EEG activity. A model of brain stem networks, which govern the discharges of sympathetic nerve, is presented on the basis of these data.
Optimal control evaluation of left ventricular systolic dynamics
Authors: Livnat A. , Yamashiro S. M.
Published: December 2017

A model of the contracting left ventricle was developed, in which the left ventricle was represented as a time-varying compliance. The vascular load included the nonlinear (Bernoulli) resistance of the aortic valve, blood inertance, and a Windkessel model of the arterial tree. Owing to the obligatory aerobic nature of the heart, oxygen consumption can be used to characterize the energy utilized by the myocardium. An adaptive control law was developed for determining the systolic time course of ventricular pressure and volume that minimizes cardiac oxygen consumption. Three main determinants of myocardial oxygen consumption were included in the integral criterion function: developed wall tension, inotropic state, and external (mechanical) work. The optimal control problem was solved using the Pontryagin maximum principle. The model could predict, in good agreement with experimentally obtained data, systolic time course of ventricular pressure and volume, as well as directional changes in the duration of isovolumic contraction and ejection phase under various conditions of end-diastolic volume, mean aortic pressure, and inotropic state.
Stress-induced eating in rats
Authors: Levine A. S. , Morley J. E.
Published: December 2017

Mild tail pinch (TP) in rats resulted in 72% of animals displaying ingestive behavior with 20% demonstrating gnawing behavior without food ingestion and 8% demonstrating licking behavior only. The animals ate steadily over 5 min with a maximum rate occurring at 1 min (0.5 +/- 0.2 g). There was a circadian rhythm of TP-induced behavior with the peak food ingestion occurring at 24 h. A mild increase in blood glucose occurred 120 s after commencement of TP (115 +/- 4 mg/dl). Common satiety signals such as stomach distension and glucose decreased food ingestion. Parenteral administration of glucagon, cholecystokinin-octapeptide, bombesin, and thyrotropin-releasing hormone resulted in suppression of TP-induced food ingestion. Chronic TP (12 5-min TP periods/day) resulted in a fall in spontaneous food intake with the total intake remaining similar to food intake prior to the chronic TP period. We suggest that TP serves as an excellent model for eating behavior because 1) it correlates well with starvation-induced eating; 2) it precludes the necessary deprivation of food and water to adrenalectomized animals; and 3) animals subjected to TP continue chewing in the face of decreased food intake allowing one to exclude the possibility that the effects of an anorectic are secondary to nausea.
Comparative properties of tobacco hornworm, Manduca sexta, carbonic anhydrases
Authors: Jungreis A. M. , Barron N. D. , Johnston J. W.
Published: December 2017

Comparative properties of midgut, fat body and integumentary carbonic anhydrases (CAs) were measured as functions of CA-catalyzed CO2 hydration or p-nitrophenylacetate (pNPA) hydrolysis in feeding larvae and pharate pupae. Alkali metal cations fully reverse the halide anion inhibition of CA catalyzed CO2 hydration during the larval but not the pharate pupal stages in development. Concentrations of acetazolamide required to inhibit 50% of tissue-specific CA-catalyzed CO2 hydration (I50) were approximately 10(-8) M. The activity profiles between pH 6.0 and 9.0 had well-defined optima around pH 8.0 with activity declining dramatically above the optima. When CA-catalyzed pNPA hydrolysis was measured between 4 and 37 degrees C, insect enzymes failed to exhibit positive Q10 values between 25 and 37 degrees C. The affinities of the hornworm CAs toward pNPA were determined with stage- and tissue-specific Km ranging from 0.42 to 8.0 X 10(-3) M. It is concluded that tissue and stage-specific CAs exist in M. sexta, whose properties appear to differ markedly with those previously reported for mammalian enzymes.
Thermal balance in ketamine-anesthetized rhesus monkey Macaca mulatta
Authors: Hunter W. S. , Holmes K. R. , Elizondo R. S.
Published: December 2017

A partitional calorimetry study compared thermoregulatory responses of unanesthetized adult rhesus monkeys (4 female, 1 male) to those anesthetized with ketamine HCl and exposed to ambient temperature (Ta) of 18, 29, 38 degrees C. Steady-state metabolic heat production (M), mean skin temperature (Tsk), rectal temperature (Tre), respiratory evaporative heat loss (Eres), and total evaporative heat loss (Etot) were measured at each Ta. Average Tre of anesthetized animals was reduced by approximately 1 degree C at Ta 18 degrees C, but thermal balance in anesthetized and control animals was maintained by reflexly decreased tissue conductance and shivering. For anesthetized animals, the average M increased 1.8 times over the lowest value of 40.13 W/m2 at Ta 29 degrees C, compared to a 1.5-fold increase for controls. Responses for both groups were not different at Ta 29 degrees C, both groups regulated body temperatures by vasodilation and increased sweating, but with ketamine sweating was reduced (35%). Effective tissue thermal conductance (K) was lowest at Ta 18 (10.8 W/m2 . degrees C) and increased to 39.4 W/m2 . degrees C at Ta 38 degrees C. No significant difference in K was found between ketamine and control groups at other Ta's.
Effect of hemorrhagic shock on hepatic transmembrane potentials and intracellular electrolytes, in vivo
Authors: Sayeed M. M. , Adler R. J. , Chaudry I. H. , Baue A. E.
Published: December 2017

Page R211: M. M. Sayeed, R. J. Adler, I. H. Chaudry, and A. E. Baue. “Effect of hemorrhagic shock on hepatic transmembrane potentials and intracellular electrolytes, in vivo.” Page R211: R. J. Adler should read R. C. Adler.
Role of sodium concentration of the cerebrospinal fluid in the salt appetite of sheep
Authors: Weisinger R. S. , Considine P. , Denton D. A. , Leksell L. , McKinley M. J. , Mouw D. R. , Muller A. F. , Tarjan E.
Published: December 2017

The role of sodium concentration of the cerebrospinal fluid (CSF[Na]) in the initiation and/or satiation of Na appetite of Na-deplete or Na-replete sheep was investigated. Slow infusion (1 ml/h) into a lateral brain ventricle of an artificial sheep CSF solution was begun 0-60 min prior to and continued until the end of the Na access period (30-120 min). In Na-deficient sheep, increasing CSF[Na] caused a decrease in Na intake. In both Na-deficient and Na-replete sheep, decreasing CSF[Na] caused an increase in Na intake. The appetite was observed within 25 min of beginning infusion, which represents the most rapid induction of Na appetite yet observed. In Na-replete sheep, the appetite induced by decreasing CSF[Na] was predominantly for Na-containing solutions. A decrease in CSF[Na] of only 4-6 mmol/l was sufficient to induce Na appetite. The results derived by use of different Na, saccharide, or urea containing artificial CSF solutions suggest that there are sensors within the neuropil that respond to change of [Na] and influence salt appetite. They can be accessed by inducing change in [Na] of cerebroventricular CSF.
On comparing regression lines with unequal slopes
Authors: Zerbe G. O. , Archer P. G. , Banchero N. , Lechner A. J.
Published: December 2017

For the situation in which the slopes of two regression lines may differ, procedures are discussed for the comparison of the lines at a single X, simultaneous comparison at several values of X, and determination of the range of X for which the difference between the lines is large enough to be statistically significant. These useful procedures have previously been discussed but do not seem to be well known. Their usefulness in the analysis of physiological data is demonstrated with data arising from a study of pulmonary response to hypoxia.
Neural control of vasomotion in rabbit ear is impaired during desynchronized sleep
Authors: Franzini C. , Cianci T. , Lenzi P. , Guidalotti P. L.
Published: December 2017

In a warm environment the skin vessels of the rabbit ear, dilated during synchronized sleep (SS), reduce their caliber during desynchronized sleep (DS). In a cold environment the ear skin vessels, constricted during SS, increase their caliber during DS. These vascular changes contrast with thermoregulatory homeostasis. They can be accounted for by the decrease in both local transmural pressure and sympathetic vasoconstrictor discharge accompanying the DS phase. A decrease in local transmural pressure prevails in a warm environment and a decrease in sympathetic discharge in a cold environment. Accordingly, the vessel caliber decreases in the heat and increases in the cold. The results of the sympathetic denervation of the ear and of the alpha-receptor blockade confirm the passive nature of vascular changes in the rabbit ear during DS.
Sympathetic activity in thyroid-treated Zucker rats
Authors: Levin B. E. , Triscari J. , Sullivan A. C.
Published: December 2017

Treatment of lean and obese 3- to 4-mo-old male Zucker rats with 0.03% thyroid powder (TP) for up to 41 days produced a decreased weight gain and carcass lipid content in obese but not lean rats, without reduction in food intake. Improved thermogenesis in TP-treated obese rats was evidenced by increased basal rectal temperatures and improved cold tolerance, although TP did not alter the lower stress-evoked levels of plasma norepinephrine (NE) or epinephrine of the obese rats. Levels of NE and/or NE turnover were lower in hearts, aortas, pancreata, interscapular brown adipose, and epididymal white adipose pads of obese compared with lean rats. Both NE levels and turnover were increased in the hearts and aortas of TP-treated obese rats, suggesting increased sympathetic activity in these organs. Basal but not stress-evoked hyperglycemia, hyperinsulinemia, and hyperglycerolemia in the obese rats were partly or totally corrected by TP treatment as was defective in vivo utilization of fatty acids. Therefore 0.03% TP administration had a selective effect on the obese Zucker rat compared with the lean and led to decreased weight gain associated with improved thermogenesis. These effects appeared to be related in part to increased sympathetic function in some organs and improved utilization of fatty acids.
Coulometric microrespirometry
Authors: Heusner A. A. , Hurley J. P. , Arbogast R.
Published: December 2017

Capacitive coulometry is based on the automatic quantitative replacement of O2 consumed by an animal in a closed system with electrolytic O2, produced by discharging a capacitor through a CuSO4 solution. The sensitivity of the device is better than 0.1 nl. The unit volume of O2 produced (1 nl) is both accurate and precise within 1% in a temperature range from 2.8 to 40 degrees C. The upper limit of recordable O2 consumption is 1 ml/h. The microrespirometer can be autoclaved, making the technique ideally suited for metabolic studies in microbiology, cell and organ cultures, and comparative physiology.
Effect of Na+ and ATP on peritubular Ca transport by the marine teleost renal tubule
Authors: Renfro J. L. , Dickman K. G. , Miller D. S.
Published: December 2017

Ca uptake rates and efflux rate coefficients were determined in isolated renal tubules of the winter flounder, Pseudopleuronectes americanus. Na-free medium and 10(-4) M ouabain depressed while 0.2 mM dinitrophenol stimulated Ca efflux. The effects on Ca movement appeared to be associated with the adenosine triphosphate (ATP) concentration of the tubular fluid space (TFS), rather than the bath-to-tissue Na gradient. Elevation of the ATP concentration of TFS by incubation of tissue in external ATP more than doubled Ca uptake rate. Inhibition of Ca uptake by lanthanum and stimulation by Ca ionophore A23187 suggested that ATP altered plasma membrane Ca transport. Incubation in external phosphate had no effect. Plasma membrane vesicles (PMV) prepared from flounder tubules showed saturable Ca uptake inhibited by Mg, unaffected by Na gradients, and stimulated by intravesicular but not extravesicular ATP. ATP appeared to stimulate PMV Ca uptake by increasing membrane Ca binding. We concluded that Ca uptake across the peritubular membranes was not directly linked to the serosal Na gradient but was greatly influenced by the intracellular ATP concentration.
Biological fluid membrane generates triggering cycle and homeostasis
Authors: Schiffmann Y.
Published: December 2017

A working engine has to operate in cycles, and at completion of a work cycle it should revert to its initial state. The ubiquitous unit cycle in medicine and physiology is characterized by a rapid upstroke followed by a plateau, which is in turn followed by a quick restoration to a resting state. So far, such cycles could not be derived from the basic laws of chemistry, in particular from the law of mass action; but within the context of a new biochemical control theory, which replaces the notion of conformational change by redistribution in the membrane, such a cycle can be derived from the law of mass action if the system is two dimensional, namely if the biochemical reactions are restricted to an optimally fluid membrane which is an open nonequilibrium system. The failure of this universal mechanism for triggering cycle is suggested to be a universal cause of disease. This failure involves abnormal membrane fluidity and leakage of enzyme and receptor from the membrane.
Negative and positive feedback of central nervous system temperature in thermoregulation of pigeons
Authors: Schmidt I. , Simon E.
Published: December 2017

Experimental alterations of spinal cord and hypothalamic temperature affecting behavioral and autonomic cold defense were investigated in pigeons under external cold load with access to instrumental heat reinforcement. Warming and cooling spinal cord resulted in negative-feedback effects on both instrumental and autonomic cold defense. Hypothalamic warming produced similar negative-feedback effects, whereas hypothalamic cooling produced either no effect or positive-feedback effects on both kinds of cold defense. As determined in previous studies, hypothalamic temperature displacements under heat-load conditions produced only negative-feedback effects on instrumental heat defense. However, only positive-feedback effects were observed on autonomic heat defense by panting. The diverse response patterns of autonomic and behavioral thermoregulatory effectors to changing hypothalamic temperature under heat- and cold-load conditions could be quantitatively described by a mathematical model that takes into account 1) a greater Q10 for intrahypothalamic transmission of the cold signal input than of the warm signal input, and 2) different weights of extra- and intrahypothalamic temperature signal inputs for the control of different effectors.
Beta-adrenergic blockade inhibits thermogenesis and lipolysis during glucoprivation in humans
Authors: Welle S. L. , Thompson D. A. , Campbell R. G.
Published: December 2017

Glucoprivic stress induced by 2-DG (2-deoxy-D-glucose) is associated with increased oxygen consumption (thermogenesis) and sympathetic nervous system activity, as well as elevations of circulating levels of various hormones and metabolic substrates. To examine the role of beta-adrenergic stimulation in the thermogenic, hyperglycemic, and lipolytic responses to glucoprivation, we administered intravenous infusions of propranolol or normal saline (placebo) during 2-DG challenges in seven healthy males. 2-DG alone produced large increments in plasma catecholamine levels, hyperglycemia, a 3.5-fold increase in plasma free fatty acid (FFA) levels, a 15 beat/min increase in pulse rate, and hypothermia in spite of a 20% increase in oxygen consumption. When propranolol was given, 2-DG produced only a 50% increase in FFA levels, no change in oxygen consumption, and a 17 beat/min fall in pulse rate associated with a 25% increase in mean arterial blood pressure. Propranolol only slightly attenuated the hyperglycemia and hypothermia associated with 2-DG but potentiated the elevations of plasma epinephrine levels. It is concluded that 2-DG-induced thermogenesis and lipolysis are primarily dependent on beta-adrenergic stimulation.
Kinetics of specific food intake and weight gain in rat
Authors: Burkhardt S. S. , Mercer L. P. , Schweisthal M. R. , Cole T. B.
Published: December 2017

We report the expanded application of a recently developed time-invariant analytic function that relates food intake, growth (weight gain), and dietary nutrient concentration in the laboratory rat. Data from seven experiments were utilized, providing analysis of three stages of rat (Sprague-Dawley) growth (weanling, adult, and pregnant) and a variety of nutrients: casein, lactalbumin, amino acid mix, thiamin, and pyridoxine. For each experiment the rats were fed graded levels of a nutrient, ranging from 0% to a percentage well above the recommended amount, in an otherwise nutritionally adequate diet. Weight-specific weight gains and food intakes were calculated for each dietary group and fitted to the Gompertz equation. The resulting rate constants for each group were identical for weight gain and food intake. The rate constants were then fitted as functions of dietary nutrient concentration by the four-parameter mathematical model for physiological responses. Kinetic rate constants could be characterized as functions of the dietary concentration of each nutrient tested. This approach offers new possibilities for the determination and optimization of dietary requirements. With this approach, one may characterize food intake and growth in a single rate constant, which varies as a function of dietary nutrient concentration.
Growth and metabolic alterations after submandibular sialadenectomy in male mice
Authors: Li A. K. , Schattenkerk M. E. , De Vries J. E. , Ford W. D. , Malt R. A.
Published: December 2017

Because the submandibular salivary glands of male mice are rich in growth factors such as epidermal growth factor and nerve growth factor, and because there are sporadic reports of sialadenectomized mice showing growth retardation and endocrine abnormalities, we studied oxidative metabolism and fertility after submandibular sialadenectomy. Despite similar intake of food, male mice (n = 60) deprived of submandibular saliva, either by duct ligation or gland excision, initially weighed 12–13% less than the sham controls and had a slower rate of growth (P less than 0.001). After 5 mo, mice with duct ligation caught up with the sham-operated mice, but the differences compared with submandibular-sialadenectomized mice were still apparent at 32 wk (P less than 0.001). The mean respiratory quotient of submandibular-sialadenectomized and duct-ligated mice was 0.71 instead of 0.88 as in the shams at 10, 20, and 30 wk after operation (P less than 0.01). No effect on fecundity was observed in either male or female mice following submandibular sialadenectomy.
Nystatin studies of the skin of larval Rana catesbeiana
Authors: Cox T. C. , Alvarado R. H.
Published: December 2017

Transport and electrical characteristics of the isolated skin of larval Rana catesbeiana were analyzed using ion substitution and nystatin. When the inner (IBS) and outer (OBS) bathing solutions contained Na Ringer solution the electrical potential (TEP), short-circuit current (SCC), and resistance (R2) were 23.5 +/- 7.0 mV, 2.8 +/- 0.7 microA . cm-2, and 8.00 +/- 0.74 k omega. cm2, respectively (n = 4). When K was substituted for Na in the OBS these values were not changed significantly. When nystatin (120 U.cm-3), a drug that increases the permeability of membranes to small cations, was added to the OBS (Na Ringer) there was a striking increase in the TEP to 52.8 +/- 3.1 mV, SCC to 14.8 +/- 2.0 microA . cm-2, and drop in R2 to 3.75 +/- 0.52 k omega . cm2. The response to nystatin was similar with Na or K Ringer solution in the OBS (Na Ringer in the IBS). With Na Ringer in the OBS and IBS, the increase in SCC induced by low doses of nystatin equaled net Na flux measured isotopically. Plots of transepithelial conductance against SCC after nystatin were linear and provided estimates of shunt resistance (R*sh = 14.6 +/- 1.3 k omega . cm2) and electromotive driving force for ions (E*A = 76 +/- 3 mV). Similar curves were obtained with K Ringer in the OBS. In the presence of nystatin, characteristics of the basolateral membrane were evaluated. It displayed selective permeability to K relative to Na or Tris.
Sodium retention and salt appetite following deoxycorticosterone in hamsters
Authors: Fitts D. A. , Yang O. O. , Corp E. S. , Simpson J. B.
Published: December 2017

Previous research suggests that hamsters 1) fail to retain sodium after mineralocorticoid injections, 2) retain sodium after adrenalectomy equal to controls, and 3) do not develop salt appetite after mineralocorticoid or adrenalectomy. The present studies demonstrate sodium retention, body weight gain, hypernatremia, plasma volume expansion, and reduced fecal sodium excretion after daily injections of deoxycorticosterone acetate (DOCA). Salt appetite appeared after the 3rd and 4th days. Adrenalectomy caused reductions of sodium balance, plasma volume, and food intake, which were reversed by DOCA administration. Mineralocorticoids therefore represent one control of sodium metabolism in hamsters.
Incomplete free fatty acid oxidation by ascites tumor cells under low oxygen tension
Authors: Ookhtens M. , Baker N.
Published: December 2017

We tried to understand why our earlier estimates of fatty acid (FA) oxidation rates under the nearly anaerobic state of the Ehrlich ascites tumor (EAT) in vivo were even greater than those found in vitro under aerobic conditions. Using tracers [1–14C]linoleate, [1–14C]-, and [9,10–3H]palmitate, and NaH14CO3, we estimated essential and nonessential FA oxidation rates to CO2 + H2O by EAT in living mice and in vitro under aerobic and anaerobic conditions. Sequestration of intraperitoneally (ip)-injected 14C-FFA allowed a selective labeling of the tumor versus the host; thus, breath 14CO2 could be used to estimate the maximum rate of FA oxidation in vivo by the tumor. Initially, we measured breath 14CO2 following NaH14CO3 injections and developed a multicompartmental model to simulate the tumor-host HCO-3-CO2 system. This model was integrated with our earlier model for tumor FA turnover. The integrated model was fitted to breath 14CO2 data from mice injected ip with 14C-FFA to compute tumor FA oxidation rates. Both essential and nonessential FA were oxidized to CO2 at similar rates. The maximum rate of total FA oxidation to CO2 was 5–6 nmol FA X min-1 X 7-ml tumor-1, about 5–10 times lower than all previous estimates obtained in vitro and in vivo. To resolve this dilemma we used doubly labeled [1–14C; 9,10–3H]palmitate and found that under aerobic conditions, in vitro, EAT formed 3H2O and 14CO2 at nearly equal rates. These rates were suppressed markedly but unequally at low PO2. Anaerobic suppression of 14CO2 formation greatly exceeded that of 3H2O formation. As a result 3H2O/14CO2 reached a value of congruent to 10 at low PO2. Our data indicate that under the nearly anaerobic conditions of a growing EAT in vivo, the partial beta-oxidation of FA to 2C + H2O takes place at a 5 to 10 times faster rate than the complete oxidation of FA to CO2 + H2O. This finding can account for earlier apparent inconsistencies in the literature, since aerobic studies of 14C-FA oxidation to 14CO2 in vitro and of 3H-FA oxidation to 3H2O under nearly anaerobic conditions would both overestimate greatly the rate of FA oxidation to CO2 by EAT in vivo.
Paraventricular nucleus region controls pituitary-adrenal function in Brattleboro rats
Authors: Baertschi A. J. , Beny J. L. , Makara G. B.
Published: December 2017

To study the role of the paraventricular nucleus and of neurohypophysial hormones in the control of ACTH secretion, the paraventricular nuclei (PV) of Brattleboro diabetes insipidus rats (DI) were lesioned (L) with a knife; sham-lesioned DI (S) served as controls. Four days later, the rats were stressed by ether inhalation, and blood samples were taken during and 30–40 min after stress for the determination of corticosterone. The median eminence (ME) and neural lobe (NL) were homogenized in 50 microliters of 0.1 N HCl and frozen pending bioassay of corticotropin-releasing factor (CRF). PV lesion almost abolished the corticosterone secretion to ether and reduced the ME CRF content three- to sevenfold. The NL CRF content in S was about twice that of ME, and oxytocin accounted for more than 60% of NL CRF. However, PV lesion had no effect on NL CRF activity. Low amounts of oxytocin (2 mU/ml) had no significant CRF activity but potentiated the ME CRF effect in L. The results suggest that 1) PV is one of the most important sites for CRF synthesis or CRF fiber transit in DI; 2) corticosterone secretion to ether stress is governed mainly by ME CRF; and 3) a large proportion of CRF fibers to NL probably originates outside PV.
Food intake and peripheral factors after recovery from insulin-induced hypoglycemia
Authors: Friedman M. I. , Granneman J.
Published: December 2017

Rats increased food intake after plasma glucose returned to normal in the wake of an insulin-induced hypoglycemic episode. Whereas increased eating 6–8 h after insulin occurred only when plasma glucose levels fell below 70 mg/dl, intakes were not related to the degree of prior hypoglycemia. Administration of glucose in the first 3 h after insulin prevented increased eating, whereas glucose given 4–6 h after insulin was less effective. Intravenous infusions of fructose given in the first 3 h after insulin injection prevented increased food intake in normal but not hepatic-vagotomized rats. Determination of various metabolic variables in parallel experiments showed that insulin treatment resulted in changes in peripheral metabolism, which persisted at the time feeding tests were conducted, and that administration of glucose or fructose tended to reverse these changes. The results suggest that increased food intake after recovery from hypoglycemia is associated with peripheral metabolic consequences of ongoing or previous counterregulatory responses which occur during hypoglycemia and that alterations in hepatic metabolism are sufficient to inhibit this insulin-induced eating.
Effects of ethanol ingestion on thirst and fluid consumption in humans
Authors: Eisenhofer G. , Johnson R. H.
Published: December 2017

To investigate the effects of ethanol on thirst, fluid intake was measured in 24 normal subjects for 3 h after consumption of 1.0 g/kg ethanol, with or without administration of a vasopressin analogue (DDAVP) before ethanol ingestion. Fluid consumption was reduced in subjects receiving DDAVP, suggesting that thirst after ethanol is largely secondary to dehydration due to inhibition of vasopressin release. Further, the effects of ethanol on salt-load-elicited thirst and fluid consumption in normal subjects were studied using intravenous hypertonic saline infusions. Subjects acted as their own controls and received 0.5 or 1.0 ml/kg ethanol 30 min before infusions on one day and an equal volume of fluid on another day. During infusions after ethanol, subjects experienced thirst later and at higher osmolalities. They also drank less immediately after infusions with prior ethanol ingestion. The relationship between thirst score and plasma osmolality was shifted to higher osmolalities by ethanol. Thus, although ethanol progressively causes thirst secondary to dehydration, it has a direct inhibitory effect on the thirst response to osmotic stimulation.
Aortic and carotid chemoreceptor responses to metabolic acidosis in the cat
Authors: Pokorski M. , Lahiri S.
Published: December 2017

The effect of metabolic acidosis on the activity of aortic chemoreceptor afferents and their responses to hypoxia and hypercapnia were investigated in nine cats anesthetized with alpha-chloralose, paralyzed, and artificially ventilated. This effect was compared with that on simultaneously recorded activity of carotid chemoreceptor afferents in three separate cats. The activity of a single or paucifiber preparation of chemoreceptor afferents was recorded at five steady-state levels of arterial O2 tension (PaO2) at a constant arterial CO2 tension (PaCO2) and at three levels of PaCO2 during hyperoxia (PaO2 greater than 400 Torr) before and after slow injection of 1 M lactic acid in the average dose of 2.6 +/- 0.6 mmol X kg-1. On the average, arterial pH decreased from 7.445 +/- 0.046 to 7.222 +/- 0.041 at PaO2 of 98 +/- 5 Torr and PaCO2 of 34 +/- 1 Torr. This decrease in pHa during normoxia increased the aortic chemoreceptor activity from 0.8 +/- 0.2 to 1.4 +/- 0.3 imp X s-1. Metabolic acidosis increased the excitatory effect of hypoxia and hypercapnia. The stimulatory effect of CO2 for the same increase in arterial [H+] was greater than that of metabolic acidosis, indicating a dominant effect of molecular CO2 on aortic chemoreceptors. Simultaneous measurements of carotid and aortic chemoreceptor activities showed that their responses to metabolic acidosis were qualitatively similar. Quantitatively, the response of aortic chemoreceptor afferents was less than that of carotid chemoreceptors.
Integral as well as proportional adrenal responses to ACTH
Authors: Keller-Wood M. E. , Shinsako J. , Dallman M. F.
Published: December 2017

To characterize adrenal responses to ACTH, conscious dogs were infused for 40 min with normal saline or 20-1,500 ng/min alpha-ACTH. Plasma ACTH and corticosteroid levels were measured during the infusion and for 80 min after the end of the infusion. Half-maximal plateau corticosteroid responses were achieved with ACTH levels of 105 pg/ml (23 pM); a maximal plateau corticosteroid response (10.2 micrograms/100 ml) resulted from ACTH levels greater than 335 pg/ml (74 pM). When levels of ACTH between 335 and 3,000 pg/ml were achieved during the 40-min infusion, the duration of maximal corticosteroid levels was prolonged beyond the duration of the ACTH infusion. Plasma ACTH concentration decreased after the end of the infusion with a half-disappearance time of 3.6 +/- 0.2 min, but plasma corticosteroid concentrations and cortisol and corticosteroid secretory rates remained at or above the plateau secretory rates during the infusion and for about 80 min after the end of an infusion of 1,000 ng ACTH/min. When the total corticosteroid responses to the ACTH infusions were estimated, the relationship between the total corticosteroid response and the logarithm of the ACTH concentration was linear for 80-3,000 pg ACTH/ml.