bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of ganglionic blockade on catecholamine secretion in exercised dogfish
Authors: Opdyke D. F. , Bullock J. , Keller N. E. , Holmes K.
Published: December 2017

A brief bout of vigorous exercise results in significant increases in plasma epinephrine (E) and norepinephrine (NE) in the dogfish, Squalus acanthias. Since the presence of a functioning sympathetic nervous system in dogfish is in doubt, experiments were undertaken to show whether or not exercise-induced catecholamine (CA) secretion is under autonomic neurogenic control. Changes in plasma E and NE in a control group of exercised fish were compared with changes in fish exercised while under the influence of ganglionic blockade. Ganglionic blockade was induced in dogfish by hexamethonium infusion before exercise. CA secretion in response to a subsequent bout of exercise was significantly reduced without impairment of the ability of the fish to exercise. The pattern of systemic arterial pressure response to exercise and recovery (initial decrease during exercise followed by a prompt recovery to control level) was not significantly altered by ganglionic blockade. It is concluded that in dogfish some fraction of CA secretion capacity is possibly or potentially under neurogenically related control. Apparently the fraction of CA secretion under such control is not essential for performing exercise. The pattern of CA secretion accompanying the events of exercise and recovery in dogfish suggests that CA may play a more important role in recovery from exercise than in its performance.
Anisotropic diffusion of oxygen in slices of rat muscle
Authors: Homer L. D. , Shelton J. B. , Dorsey C. H. , Williams T. J.
Published: December 2017

The diffusion coefficient of oxygen (D) and the fluorescence quenching coefficient (K') of pyrenebutyric acid (PBA) were measured in sections of rat hamstring muscles. Values of D and K' at temperatures (Tc) of 20, 30, and 40 degrees C were determined and referred to the values in water. In sections cut parallel to the muscle fibers, D = DH2O (0.380 +/- 0.038), whereas in sections cut across the grain of the fibers, D = DH2O (0.985 +/- 0.039). Oxygen diffuses along the length of a muscle fiber over twice as rapidly as it diffuses in directions perpendicular to the long axis of the fiber. This suggests that fibers, myofibrils, or myofilaments offer substantial barriers to the diffusion of oxygen, whereas extracellular space and spaces around fibers or myofibrils or myofilaments offer no more resistance than water to the diffusion of oxygen. Corresponding estimates for K' were K' = K'H2O[0.14 (1 + 0.25 Tc)] and K' = K'H2O[0.21 (1 + 0.25 Tc)] for slices cut parallel to the long axis of muscle fibers and across the long axis, respectively. Standard deviations of K' were 9%.
Effects of photoperiod and gonadectomy on food intake, body weight, and body composition in Siberian hamsters
Authors: Wade G. N. , Bartness T. J.
Published: December 2017

Two experiments examined the effects of gonadectomy, photoperiod, and melatonin treatment on food intake, body weight, and carcass composition in male and female Siberian hamsters (Phodopus sungorus sungorus). Gonadectomy caused small decreases in body weight in both sexes but did not affect food intake. In males the weight reduction was due to small (nonsignificant) decreases in all carcass components. Ovariectomy caused a significant reduction in carcass lipid but did not affect lean body mass. A short photoperiod (8 h light, 16 h dark, LD 8:6) caused significant weight losses in all animals except ovariectomized females. Daily melatonin injections (12.5 micrograms sc, 3 h before lights-out) also reduced body weight in males and females housed in a long photoperiod (LD 16:8). The photoperiod- and melatonin-induced weight losses were almost entirely due to decreases in carcass lipid; lean body mass was unaffected by either treatment. Although short photoperiods and melatonin treatments decreased food intake, these changes were preceded by a significant loss of body weight. Thus photoperiod induced changes in food intake may be a consequence of the changes in body weight, rather than vice versa. These findings indicate that photoperiod and melatonin have important effects on adipose tissue mass in both Siberian and Syrian hamsters, even though one species gains weight (Syrian) and the other loses weight (Siberian) in short photoperiods.
Left ventricular size, output, and structure during guinea pig pregnancy
Authors: Morton M. , Tsang H. , Hohimer R. , Ross D. , Thornburg K. , Faber J. , Metcalfe J.
Published: December 2017

We investigated left ventricular (LV) hemodynamics, pressure-volume relations, and morphometry to determine what cardiac changes characterize pregnancy in the guinea pig. Time-bred virgin guinea pigs were paired by weight with unbred controls. Hemodynamic studies and LV pressure-volume relations were obtained on days 59-68 of the 68-day gestation. Weight of control sows increased from 817 to 902 g (P less than 0.01) and pregnant sows from 810 to 1,251 g (P less than 0.01). LV weights were not different. When indexed for maternal weight minus uterus and contents, pregnancy produced increases in O2 consumption, +48% (P less than 0.01); cardiac output, +32% (P less than 0.05); and stroke volume, +46% (P less than 0.025). Passive LV pressure-volume curves (dP/dV) were shifted to the right (P less than 0.025), but dP/dV at constant pressure was unchanged. Using a thin-walled spherical model, elastic modulus at constant stress was not different. The percent LV inter- and intracellular volumes and myocyte myofibril and organelle volumes were unchanged during pregnancy. In the guinea pig, pregnancy increases LV output, stroke volume, and size without changes in LV mass, morphometry, or elastic modulus.
Effects of sleep deprivation on thermoregulation during exercise
Authors: Sawka M. N. , Gonzalez R. R. , Pandolf K. B.
Published: December 2017

Five fit men completed a practice, control, and sleep deprivation exercise test. Two nights of normal sleep preceded the control test, and 33 h of wakefulness preceded the sleep deprivation test. These tests consisted of 20 min of rest followed by 40 min of cycle-ergometer exercise (50% of peak O2 uptake, VO2) in a temperate (ambient temperature, 28 degrees C; relative humidity, 30%)-environment. Esophageal temperature (Tes), local sweat rate (mds), and chest thermal conductance (kch) were continuously measured. During exercise a 0.7 and 0.5 degrees C rise in Tes was found for the sleep deprivation and control tests, respectively. This increase in Tes values from rest to the end of exercise was greater (P = 0.08) for the sleep deprivation than control test. Total body sweat rate, calculated from Potter balance measurements, was 27% less (P less than 0.01) for the sleep deprivation than the control test. Both mds and kch values were lower (P less than 0.05) during the final 20 min of exercise for the sleep deprivation than control test. Final exercise mds values were 19% lower (P less than 0.05) for the sleep deprivation than control test. An asynchronous rather than a normal synchronous mds pattern was frequently observed during the sleep deprivation test. During the sleep deprivation test, the mds sensitivity (delta mds X delta Tes-1) was 38% lower (P less than 0.01) and kch sensitivity (delta kch X delta Tes-1) was 42% lower (P less than 0.05) than during the control test. These data indicate that sleep deprivation decreases evaporative and dry heat loss during moderate-intensity exercise.
Oral glucose is the prime elicitor of preabsorptive insulin secretion
Authors: Grill H. J. , Berridge K. C. , Ganster D. J.
Published: December 2017

Seven sugars, two sugar alcohols, and a nonnutritive sweetener were orally administered to naive rats with and without gastric drainage fistulas. Although all taste solutions were ingested, only glucose evoked a statistically significant elevation of insulin levels. This rise was independent of a rise in glycemia. The preeminence of oral glucose as an elicitor of preabsorptive insulin secretion is especially striking, considering that glucose is neither the most intense (as measured electrophysiologically) nor the most palatable (as measured by behavioral preference tests) taste stimulus tested. These results suggest the existence of a gustatory and/or gastrointestinal chemoreceptor that is most responsive to glucose.
Allometric scaling in comparative biology: problems of concept and method
Authors: Smith R. J.
Published: December 2017

Allometric scaling, a widely used comparative approach for studying the relationship between size, shape, and function in organisms, is examined in both concept and application. The general adoption of an “allometric method” with several standardized conventions has inhibited the creative study of size-correlated phenomena and has falsely simplified a complex area of research. Discussed here are some of the consequences of using a power function (and the resulting logarithmic transformation of data) to describe allometric trends, the dependence on correlation coefficients as a measure of strength of association, and the assumptions underlying use of empirical data to determine the relative size of structures. Several alternative methods for data analysis are suggested.
Effect of bilateral vagotomy on the ventilatory responses of the water snake Nerodia sipedon
Authors: Gratz R. K.
Published: December 2017

The effects of bilateral vagotomy on pulmonary ventilation, O2 consumption, and heart rate were determined for the water snake, Nerodia sipedon, breathing room air at 15, 25, and 30 degrees C and breathing 5.2% CO2 in air at 25 degrees C. At all body temperatures, vagotomy resulted in a four- to sevenfold increase in tidal volume in snakes breathing room air. At the same time, ventilatory frequency decreased such that pulmonary ventilation was unchanged after vagotomy. Heart rate increased approximately 1.5 times after vagotomy, but O2 uptake was unchanged. The air convection requirement decreased similarly with increasing body temperature in both intact and vagotomized snakes. Arterial pH values were similar to those of intact snakes measured in a previous study and decreased by -0.013 U/degrees C. Since this occurs despite elimination of peripheral chemoreceptor input, it is suggested that the temperature compensation is a centrally controlled process. In intact snakes, breathing CO2 resulted in a fourfold increase in ventilation. Elimination of peripheral receptor input by vagotomy resulted in a loss of this ventilatory response to CO2 breathing. This means that peripheral receptors are required for a response to changes in arterial CO2 partial pressure and pH. Snakes thus differ from turtles and mammals in that central chemoreceptors alone are unable to produce the ventilatory response to inspired CO2.
A theory for phase locking of respiration in cats to a mechanical ventilator
Authors: Petrillo G. A. , Glass L.
Published: December 2017

A mathematical model describing the Hering-Breuer reflexes in mechanically ventilated cats is developed. There is good agreement between the properties of the model and experimental studies performed over a wide range of frequencies and volumes of the mechanical ventilator. There is a correspondence between the model and a periodically forced nonlinear oscillator, similar to the van der Pol equation. Brain stem mechanisms underlying the entrainment are discussed.
Effect of exposure to low temperature on normal and iron-deficient subjects
Authors: Martinez-Torres C. , Cubeddu L. , Dillmann E. , Brengelmann G. L. , Leets I. , Layrisse M. , Johnson D. G. , Finch C.
Published: December 2017

Twenty-one Venezuelan peasants were segregated into three groups on the basis of measurements of iron status: seven normal subjects, six iron-deficient subjects with normal hemoglobin and eight iron-deficient subjects with a hemoglobin concentration of less than 9 g/dl. All subjects were placed in a water bath at an initial temperature of 36 degrees C. The water temperature was then rapidly lowered to 28 degrees C, and observations were made over the period of 1 h. Mean oral temperature of the first group fell 0.2, the second group 0.5, and the third group 0.9 degrees C. Mean plasma norepinephrine levels in both groups of iron-deficient subjects were significantly higher at 36 degrees C and during cold exposure compared with control subjects. Oxygen consumption was also significantly increased in both groups of iron-deficient subjects after cold exposure.
An illustration of the experimental range of variation of blood pressure
Authors: Iberall A. S.
Published: December 2017

The nominal uniformity of long-term mean pressure (approximately 100 mmHg at heart level) for all mammalian species belies the broad nature of its variance, which is found at many time scales. Such variations should be a useful index of physiologically normal and pathological processes. However, it is dubious whether a scientifically meaningful determination of central blood pressure at its many process scales can be achieved from a few isolated measurements: to cite a common and highly significant instance, measurement made by a physician on a patient during one or two office visits. The data presented here are far from exhaustive (a few reports in the literature and detailed longitudinal data on 1 subj), but they serve to illustrate a protocol and a sample of the physiological results that might be expected if data were gathered for larger populations. The basic scales of interest lie in the lower-frequency domain, involving periods of fluctuations longer than tens of minutes.
A distributed model of peritoneal-plasma transport: theoretical considerations
Authors: Flessner M. F. , Dedrick R. L. , Schultz J. S.
Published: December 2017

Transport of water-soluble substances between the peritoneal cavity and the plasma was modeled with a distributed approach. The model includes diffusion and convection through tissue as well as membrane transport across blood capillaries, which are assumed to be distributed uniformly in the tissue. Lymphatic uptake via the diaphragm is also included. Transport in the remainder of the body is modeled by a system of compartments. The resulting system of mass balances and rate equations is solved numerically to provide predictions of peritoneal volume and concentrations in plasma, peritoneal fluid, and tissue surrounding the cavity. The model sensitivity is explored by varying key parameters to determine whether the changes would have a significant effect on model output. Key parameters include peritoneal surface area, tissue diffusivity, capillary permeability, tissue void fraction, and hydrostatic and osmotic pressures in the capillaries and interstitium.
Identification and quantification of mitochondria-rich cells in transporting epithelia
Authors: Karnaky K. J. , Degnan K. J. , Garretson L. T. , Zadunaisky J. A.
Published: December 2017

Fluorescent dyes specific for mitochondria have become important tools in the study of transporting epithelia. These dyes permit the localization and quantification of mitochondria-rich (MR) cells in these epithelia. To determine the specificity of the dye, dimethylaminostyrylmethylpyridiniumiodine ( DASPMI ), we combined fluorescence microscopy of this dye with the ultrastructural localization of the mitochondrial enzyme, cytochrome oxidase. Labeled cells were traced from the fluorescence-microscopic to the electron-microscopic level by devising several novel technical procedures. This new methodology assures a critical assessment of the specificity of fluorescent mitochondrial dyes in heterogeneous epithelia. Confirmation of DASPMI specificity allows the unequivocal identification of MR chloride cells in two epithelia in the head region of Fundulus heteroclitus and validates linear regression analysis of chloride cell number and short-circuit current in this species. In addition, this method provides a permanent, flat whole mount of labeled cells for morphological studies with the light microscope and with the scanning and transmission electron microscopes.
Regulation of calcium metabolism in streptozotocin-induced diabetes
Authors: Wood R. J. , Allen L. H. , Bronner F.
Published: December 2017

Sixty-nine-day-old female Wistar rats that had been made diabetic 9 days earlier by an intraperitoneal injection of streptozotocin were studied by a combination radioisotope and balance technique that evaluates calcium absorption, excretion, and bone calcium deposition and resorption rates. Streptozotocin-induced diabetes was associated with a marked drop in calcium absorption and a threefold rise in urinary calcium excretion, changes that greatly exceeded the expected effects from the hyperphagia and increased calcium intake of the experimental animals. Bone calcium deposition was halved in the diabetic rats, with bone resorption unchanged and ewqual to the deposition rate. As a result, the bone and body calcium balances were zero in the experimental animals. To maintain plasma calcium near normal under these circumstances, the diabetic animals turned over their skeletal calcium in relationship to the central pool much more rapidly than the controls. Although the skeleton in the normal animals serves as both storehouse and regulator of the plasma calcium, in short-term streptozotocin-induced diabetes there is no calcium storage in bone, with the skeleton only playing the role of regulator of calcium homeostasis.
Antidiuresis and vasopressin release with hypoxemia and hypercapnia in conscious dogs
Authors: Rose C. E. , Anderson R. J. , Carey R. M.
Published: December 2017

determine the effects of acute blood gas derangements on renal water and solute excretion and vasopressin secretion, six unanesthetized mongrel dogs were studied during 1) combined acute hypoxemia and hypercapnic acidosis [arterial O2 partial pressure (PaO2) 36 +/- 1 Torr, arterial CO2 partial pressure (PaCO2) 54 +/- 2 Torr, pH 7.18 +/- 0.01], 2) acute hypoxemia (PaO2 33 +/- 2 Torr, PaCO2 33 +/- 1 Torr, pH 7.34 +/- 0.01), and 3) acute hypercapnic acidosis (PaO2 83 +/- 3 Torr, PaCO2 53 +/- 1 Torr, pH 7.19 +/- 0.02). Combined acute hypoxemia and hypercapnic acidosis increased (P less than 0.05) mean arterial pressure, but renal hemodynamic function deteriorated with decreased (P less than 0.05) glomerular filtration rate and increased (P less than 0.05) renal vascular resistance. Moreover free water clearance became more negative (P less than 0.05) and urine osmolality increased (P less than 0.05). During acute hypoxemia or acute hypercapnic acidosis alone, mean arterial pressure and renal hemodynamic function were unchanged but free water clearance became more negative (P less than 0.05). During acute hypoxemia, urine osmolality increased (P less than 0.05) comparably with values observed during combined acute hypoxemia and hypercapnic acidosis. Plasma vasopressin concentrations increased profoundly (P less than 0.05) during combined hypoxemia and hypercapnic acidosis and during acute hypoxemia alone and were significantly elevated (P less than 0.05) above the increased plasma vasopressin concentrations observed during acute hypercapnic acidosis. We conclude that acute hypoxemia and hypercapnic acidosis result in impairment of renal water excretion, probably mediated through vasopressin secretion.
Characterization of the renin-angiotensin system in the turtle Pseudemys scripta
Authors: Cipolle M. D. , Zehr J. E.
Published: December 2017

Studies were conducted in freshwater turtles Pseudemys scripta to define some characteristics of the renin-angiotensin system in this reptile. Dialyzed acid-treated kidney extract (1 g tissue per ml water) produced a prolonged pressor response in unanesthetized turtles, which was eliminated by boiling the extract or by pretreating the turtle with [Sar1, Ile8]angiotensin II. A rat pressor assay was employed because turtle angiotensin (ANG) was bound poorly by the anti-[Asp1, Ile5, His9]ANG I used in our radioimmunoassay. Kidney extract incubated with homologous plasma (pH 5.5 and 25 degrees C) produced a time-dependent pressor response in rats. The pressor activity of the product was eliminated by dialysis or by pretreating the rats with [Sar1, Ile8]ANG II. The pressor response in anesthetized turtles to ANG I was significantly reduced by captopril, whereas the ANG II response remained unchanged, thus demonstrating the presence of ANG-converting enzyme activity in these animals. We determined the velocity of turtle ANG formation at various dilutions of enzyme (kidney extract) or substrate (plasma). Turtle kidney extract incubated with homologous plasma displayed typical Michaelis-Menten kinetics. Finally we conducted experiments to determine whether a portion of turtle plasma renin exists in an inactive form. Trypsinization caused a slight increase in plasma renin activity (PRA), whereas acidification to pH 3.3 yielded a fourfold increase in PRA.
Effects of theophylline and cAMP on intestinal allosteric chloride transport in freshwater prawns
Authors: Ahearn G. A. , Kullama L. K.
Published: December 2017

Active transmural Cl- transport across the intestine of the freshwater prawn Macrobrachium rosenbergii and the transmural potential difference resulting from the net movements of this ion and Na+ are significantly reduced or abolished in the presence of 10 mM theophylline or 1 mM dibutyryl adenosine 3',5'-cyclic monophosphate (DB-cAMP). The locus of theophylline or DB-cAMP action appears to be at the epithelial apical membrane where increased intracellular cAMP or other cyclic nucleotide such as guanosine 3',5'-cyclic monophosphate (cGMP) may interact directly or through another agent, such as the divalent cation Ca2+, to reduce or eliminate coupled Na+-Cl- influx into the cell from the gut lumen. Under control conditions, cotransport of Na+ and Cl- across the epithelial apical membrane of prawn intestine occurs by an allosteric carrier protein exhibiting sigmoidal influx kinetics for the two monovalent ions. Exogenous Ca2+ is a third binding ligand for this multisubunit protein, with the divalent cation serving as an allosteric activator of the transport system. Bilateral intestinal incubation with 10 mM theophylline abolished Cl- influx (control, 0.71 +/- 0.23; theophylline treated, 0.03 +/- 0.03 mumol X cm-2 X h-1). Addition of 1 mM DB-cAMP to intestinal incubation saline significantly (P less than 0.01) reduced the maximal Cl- influx velocity from 0.76 +/- 0.08 to 0.33 +/- 0.05 mumol X cm-2 X h-1 without altering the anion affinity constant (control, 102 +/- 5; DB-cAMP, 96 +/- 19 mM). In addition, the cyclic nucleotide had no effect on the Hill interaction coefficient of the transfer mechanism (control, 3.22 +/- 0.12; DB-cAMP, 3.42 +/- 0.68).(ABSTRACT TRUNCATED AT 250 WORDS)
Ethosecretogram: relation of behavior to plasma corticosterone in freely moving rats
Authors: Shiraishi I. , Honma K. , Honma S. , Hiroshige T.
Published: December 2017

An ethosecretogram, which illustrates the phase relation between animal behavior and plasma hormone levels, was constructed in conscious rats. A catheter was placed into the right atrium in male rats 2 days before blood sampling. Plasma corticosterone levels were monitored individually through the catheter every 5 min over a period of several hours under freely moving conditions on an Animex, which records spontaneous locomotor activity. The results showed that the bursts of locomotor activity were temporally correlated with those of plasma corticosterone level, the peak of the former preceding the hormone peak by 15 min. Regarding the type of locomotor activity, feeding and grooming were significantly correlated with the subsequent hormone elevation, whereas drinking was not. In a separate series of experiments, effects of feeding and drinking on plasma corticosterone levels were examined in conscious rats that had been fasted or water deprived for 24 or 48 h. In both cases, feeding induced a more pronounced elevation than drinking, although locomotor activity counts per se increased more sharply in the latter. It is concluded that in the ethosecretogram specific types of locomotor activity such as feeding and grooming induce a phase-locked elevation of plasma corticosterone under freely moving conditions.
Nature of the light stimulus producing Aschoff's intensity effect and anovulation
Authors: Ferraro J. S. , McCormack C. E.
Published: December 2017

Using feedback circuits, light exposure was linked to wheel-running activity in female albino rats. Because the photosensitive portions of the circadian cycle are known to coincide with wheel-running activity, the feedback circuits concentrated light on the photosensitive portions of the cycle. In this type of lighting, the free-running period of locomotor activity was directly proportional to the light intensity (i.e., the Aschoff effect), and at an intensity of 100 1x, cyclic ovulation caused. Both these effects, which were previously thought to result only from exposure to continuous light (LL), occurred even though these rats were exposed to only 4 h of light per circadian cycle. These results indicate that the consequences of LL are not due to the continuity of the light per se but represent the effects of light falling on discrete photosensitive portions of the circadian cycle.
Regeneration may mediate the sparing of VMH obesity observed with prior vagotomy
Authors: Fox E. A. , Powley T. L.
Published: December 2017

The extent to which the vagus nerve is involved in mediating the development of obesity in animals with lesions of the ventromedial hypothalamus (VMH) was determined. Female rats were given either VMH lesions or sham lesions 100 days after they had received vagotomy with pyloroplasty, sham vagotomy with pyloroplasty, or sham vagotomy with sham pyloroplasty. For the first 7 postlesion wk, the animals were fed a wet mash diet, then they were maintained on a high-fat diet for 10 wk, and finally they were fed a highly palatable supermarket diet for 4 wk. VMH-lesioned animals with prior vagotomy and pyloroplasty displayed 65% of the obesity observed in lesioned animals with prior sham vagotomy. This expression was increased to 72% of the full VMH obesity during the supermarket diet phase. Assessment of vagotomy suggested that vagal regeneration and, in some cases, recovery of vagally stimulated insulin secretion had occurred. This reorganization may have contributed to the residual obesity expressed in VMH-lesioned animals with prior vagotomy.
Simulating the action of zeitgebers on a coupled two-oscillator model of the human circadian system
Authors: Gander P. H. , Kronauer R. E. , Czeisler C. A. , Moore-Ede M. C.
Published: December 2017

Our two-oscillator model was originally designed to describe the circadian rhythms of human subjects maintained in temporal isolation. The performance of this model in response to simulated environmental synchronizing cycles (zeitgebers) is examined here. Six distinct types of synchronization are demonstrated between the x oscillator (postulated to regulate the core temperature rhythm), the y oscillator (postulated to regulate the rest-activity rhythm), and z (the zeitgeber). Four types of synchronization are identifiable, if we consider only the periods of the three oscillators. Both x and y may be synchronized by z; either may synchronize with z while the other exhibits a different period; or x, y, and z may each show different periods. Two further classes of synchronization are discernible when phase criteria are taken into account. When either x or y is on the verge of desynchronizing from the other two oscillators, it undergoes periodic phase modulations while retaining the common overall period. The type of synchronization observed depends on the periods of x, y, and z and on the strength of the z drive. The effects of modifying each of these parameters have been systematically investigated by simulation, and model performance is summarized in terms of range of entrainment "maps." These constitute extensive sets of predictions about expected patterns of entrainment of the core temperature and rest-activity rhythms of human subjects exposed to various environmental zeitgebers. Experimental data are available against which model predictions can be tested.
Alterations in hepatic Na+-K+ transport during endotoxemia in rats
Authors: Sayeed M. M.
Published: December 2017

The effects of endotoxemia on overall Na+ and K+ transport in liver cells were studied. Rats were injected with Salmonella enteritidis endotoxin (5 or 10 mg/kg iv), and their blood samples and livers were obtained 4.5 h after injections. The higher, but not the lower, dose of endotoxin induced hypoglycemia and hyperlacticacidemia, which typify the metabolic deteriorations of endotoxic shock. Control (saline-injected) or endotoxemic rat liver slices (0.3 mm thick) were incubated in oxygenated Krebs-Ringer-bicarbonate solution initially at 0.5 degrees C (for 90 min) and then at 37 degrees C (for 60 min) to assess net active Na+ extrusion and K+ reaccumulation. Mean Na+ extrusion and K+ reaccumulation in control rats were 160 and 87 mmol/kg dry wt, respectively. An inhibition of both K+ reaccumulation and Na+ extrusion was seen in liver slices of rats killed 4.5 h after the 10-mg/kg dose of endotoxin. The ATP content of rewarmed (37 degrees C) liver slices of endotoxic (10 mg/kg) rats equaled 80% of the values of corresponding controls. Hepatic membrane permeability to Na+ (PNa+) and K+ (PK+) was calculated using passive cation flux approximations, intracellular [K+] determinations, extracellular [Na+] values, and membrane potential estimations. PNa+ and PK+ values, respectively, were 2.8 and 8.0 X 10(-8) cm X S-1 in control and 4.3 and 7.6 X 10(-8) cm X S-1 in shock rats. These studies indicated a marked inhibition of active Na+-K+ transport and an increased membrane permeability to Na+ with little or no change in permeability to K+ in endotoxic shock rats. Such cation transport derangements in the liver during endotoxic shock could potentially contribute to impairment in hepatic glucose production.
Hemodynamic effects of hemorrhage and subsequent naloxone treatment in conscious rabbits
Authors: Schadt J. C. , McKown M. D. , McKown D. P. , Franklin D.
Published: December 2017

The central and peripheral hemodynamic effects of rapid hemorrhage and subsequent opiate receptor blockade were studied in conscious rabbits. With hemorrhage of less than 12 ml/kg, mean arterial blood pressure (BP) was maintained by an increase in total peripheral resistance (TPR). Cardiac output (CO) declined in spite of an increase in heart rate (HR). Blood loss greater than 13 ml/kg resulted in an abrupt decrease in BP that was largely due to a decline in TPR. CO continued to decline gradually as it did early in hemorrhage. HR also decreased at the transition to hypotension. Subsequent opiate receptor blockade with naloxone (3 mg/kg) produced a prompt increase in BP and a decrease in HR. An increase in TPR accounted for the rise in BP. CO did not change significantly after naloxone. Therefore the hypotension associated with hemorrhage results from a decline in peripheral vascular resistance that is reversible by opiate receptor blockade with naloxone. These results are consistent with the involvement of opiate receptors and endogenous opiate peptides centrally and/or peripherally in control of vascular resistance during acute hemorrhagic hypotension.
Differential control of sympathetic nerve discharge by the brain stem
Authors: Barman S. M. , Gebber G. L. , Calaresu F. R.
Published: December 2017

This investigation was designed to test the hypothesis that the brain stem differentially controls the basal discharges of postganglionic sympathetic nerves distributed to different organs. Previous studies have shown that the 2- to 6-Hz activity pattern in sympathetic nerves of the baroreceptor-denervated cat originates in the brain stem. In the current study, autocorrelation and power spectral analyses were used to compare the 2- to 6-Hz frequency components of the simultaneously recorded discharges of postganglionic sympathetic nerve pairs (inferior cardiac and renal; external carotid and renal) in baroreceptor-denervated cats anesthetized with sodium diallylbarbiturate and urethan (Dialurethane). In addition, spike-triggered averaging was used to compare the relative strengths of coupling of the basal discharges of single ventrolateral medullary reticular or medullary raphe neurons to activity in postganglionic sympathetic nerve pairs. The major findings of the study are as follows: 1) the predominant 2- to 6-Hz frequency component in the basal discharges of one sympathetic nerve often was different from that in the discharges of a second nerve, and 2) the activity of approximately one-third of ventrolateral medullary reticular neurons and one-half of medullary raphe neurons (with sympathetic-related activity) was differentially related to the discharges of postganglionic nerve pairs. These results support the view that the brain stem reticular formation and raphe complex exert their influences on different sympathetic nerves in a nonuniform fashion.
Alpha 2-adrenoreceptor stimulation inhibits thermogenesis and food intake during glucoprivation in humans
Authors: Thompson D. A. , Penicaud L. , Welle S. L.
Published: December 2017

Noradrenergic central and peripheral nervous system mechanisms for the control of food intake and thermogenesis, respectively, have been described in rats and, to a lesser extent, in humans. To examine further the role of the sympathetic nervous system in energy balance modulation during glucoprivation, the alpha 2-adrenoreceptor agonist clonidine was given to subjects receiving 2-deoxy-D-glucose, a competitive inhibitor of glucose utilization, which induces sympathetic discharge, ingestive behavior, and thermogenesis by initial actions in the central nervous system. Increases in food intake and thermogenesis in association with activation of descending sympathetic outflow during 2-deoxy-D-glucose-induced glucoprivation were totally abolished by clonidine administration. Neither increases in hunger ratings after 2-deoxy-D-glucose infusions nor basal hunger and food intake after sham infusions were decreased by clonidine treatment, which nevertheless reduced thermogenesis under basal conditions. These results clearly indicate that catecholamine-mediated thermogenesis under both stimulated and basal conditions is inhibited by central or peripheral actions of clonidine, presumably at the level of alpha 2-adrenoreceptors. The reduction in food intake brought about by clonidine treatment in subjects undergoing glucoprivic stress may be the result of potentiation of satiation or reduction of hunger during a test meal rather than decreased hunger before a test meal.
Carotid arterial control of vasopressin secretion in sheep
Authors: Wood C. E. , Keil L. C. , Rudolph A. M.
Published: December 2017

The purpose of this study was to test the role of carotid arterial mechanoreceptors in the control of vasopressin secretion in conscious 6- to 7-wk-old lambs. Bilateral carotid occlusion decreased lingual arterial pressure and stimulated reflex increases in heart rate and femoral arterial blood pressure but did not significantly alter plasma concentrations of vasopressin. Acute vagosympathetic blockade, produced by injection of 2% lidocaine onto the vagosympathetic trunks, did not significantly alter heart rate or blood pressure but did stimulate a slow increase in plasma vasopressin concentration, suggesting that afferent vagal fibers tonically inhibit vasopressin secretion. Bilateral carotid occlusion after vagosympathetic blockade stimulated a brisk increase in plasma vasopressin that was larger than the response to vagosympathetic blockade alone. These results suggest that vasopressin secretion in lambs is partially controlled by arterial mechanoreceptors in the carotid sinus and by extracarotid receptors with vagosympathetic afferent fibers.
Uptake of free amino acids by bacteria-free larvae of the sand dollar Dendraster excentricus
Authors: Davis J. P. , Stephens G. C.
Published: December 2017

Larvae of Dendraster excentricus were produced by collecting gametes and carrying out fertilization under aseptic conditions. Since gametes are free of bacteria in the gonad, bacteria-free (axenic) suspensions of larvae result. Net rates of entry of 14 amino acids and the rate of production of ammonia were simultaneously determined by high-performance liquid chromatography. The net rates of uptake of neutral amino acids were an order of magnitude greater than rates for basic and acidic amino acids. Influx of 14C-labeled leucine, arginine, and glutamate accurately reflects the net entry rate of these substrates. Uptake of amino acids by axenic suspensions of larvae was compared with uptake by suspensions prepared without aseptic precautions. There was no significant difference in net uptake of the 14 amino acids or in the pattern of oxidation and assimilation of [14C]leucine during short-term experiments of 4-h duration or less.
Blood volume changes and high and low pressoreceptor activity in cats
Authors: Tomomatsu E. , Gilmore J. P.
Published: December 2017

Studies were undertaken in the cat to determine if moderate hemorrhage or volume expansion significantly altered carotid sinus and aortic baroreceptor activity. In addition, the experimental design provided the opportunity to compare gain of the two sets of receptors. A 20% blood volume expansion increased mean arterial blood pressure 5.2% and carotid sinus nerve activity 14.7%, whereas a 20% hemorrhage decreased mean arterial blood pressure 10.8% and carotid sinus nerve activity 32.3%. For the aortic baroreceptors, a 20% blood volume expansion increased mean arterial blood pressure 5.9% and nerve activity 10.5%, and a 20% hemorrhage decreased mean arterial blood pressure 8.9% and nerve activity 21.0%. The blood pressure-discharge curves for the carotid sinus and aortic baroreceptors were not different. The well-known high sensitivity of atrial receptors was also documented. We conclude that both high- and low-pressure receptors apprise the central nervous system of the status of intravascular volume and pressure.
Glycogen resynthesis in leg muscles of rats during exercise
Authors: Constable S. H. , Young J. C. , Higuchi M. , Holloszy J. O.
Published: December 2017

This study was undertaken to determine whether glycogen resynthesis can occur in glycogen-depleted muscles in response to glucose feeding during prolonged exercise. Rats were exercised for 40 min with a treadmill running program designed to deplete muscle glycogen. One group was studied immediately after the glycogen-depletion exercise. A second group was given 1 g glucose by stomach tube and exercised for an additional 90 min at a running speed of 22 m/min on a treadmill set at an 8 degree incline; they were given additional 1-g glucose feedings after 30 and 60 min of running. The initial 40-min run resulted in liver glycogen depletion, large decreases in plasma glucose and insulin concentrations, and a marked lowering of muscle glycogen. The glucose feedings resulted in greater than twofold increases in the concentrations of glucose and insulin in plasma, and of glycogen in leg muscles, during the 90 min of running. No repletion of liver glycogen occurred. These results provide evidence that glycogen resynthesis can occur in glycogen-depleted muscle despite continued moderate intensity exercise if sufficient glucose is made available.
Morphometry and calcium contents in appendicular and axial bones of exercised ovariectomized rats
Authors: Pohlman R. L. , Darby L. A. , Lechner A. J.
Published: December 2017

To determine the effects of exercise and ovariectomy on calcium status in selected appendicular and axial bones, female Sprague-Dawley (8-9 mo) rats were assigned to groups based on the following combinations: control (C) or ovariectomized (O); sedentary (S) or exercised (E); and length of treatment (2 or 4 mo). Exercise consisted of treadmill running for 1 h/day, 5 days/wk at a speed of 14.1 m/min and 8 degrees elevation. After death, femurs, tibia-fibula complexes, ribs (T7), and vertebrae (T7) were excised, cleaned, and weighed, and selected morphometrics were measured. Tensile strength was measured for the femurs, and all bones were then acid-hydrolyzed and calcium concentration determined spectrophotometrically. Bone [Ca2+] was significantly greater for CE and OE animals when compared with their sedentary counterparts (CS, OS). Within 4 mo calcium losses were evident in the femur and tibia of the ovariectomized animals, and the moderate exercise program was of insufficient intensity to alter this loss. The average stress to failure for femur from all groups was 1.13 +/- 0.11 N/m2. However, the effects of exercise appeared beneficial in the axial bones where [Ca2+] increased in the ovariectomized animals.
Kinetic model for disposition of 6-mercaptopurine in monkey plasma and cerebrospinal fluid
Authors: Covell D. G. , Narang P. K. , Poplack D. G.
Published: December 2017

The antipurine 6-mercaptopurine (6-MP) is effective in the induction and maintenance of remission in patients with acute lymphocytic leukemia. This report presents a compartmental model that describes the kinetics of 6-MP in the plasma and cerebrospinal fluid (CSF) of the monkey. Analysis is based on simultaneously measured plasma and CSF 6-MP concentrations after intravenous and intraventricular bolus administration. Results indicate that 6-MP administered intraventricularly remains largely in the CSF. Disappearance of 6-MP from CSF is principally due to convective losses at a rate equivalent to CSF turnover. Diffusion of 6-MP across the ependymal surface accounts for only 7% of the 6-MP appearing in the plasma. Conversely the dominant route for entry of 6-MP into the CSF from the plasma is entrainment in choroidally formed CSF. Only 12% of 6-MP in the CSF after intravenous administration can be accounted for by permeation of cerebral capillaries and diffusion through brain parenchyma and across the ependymal surface into CSF. These results indicate that the choroid plexus is not a significant barrier for the transfer of molecules like 6-MP from plasma to CSF.
Plasma corticosterone and volume after preoptic recess lesions and volume depletion
Authors: Bealer S. L. , Schneider E. G.
Published: December 2017

The effects of extracellular fluid volume depletion on plasma corticosterone concentration (Pcort) and plasma volume in rats were determined after recovery from either electrolytic ablation of the periventricular tissue surrounding the anteroventral third ventricle (AV3V region) or control surgery. Rats received either furosemide injections and sodium-free chow or isotonic saline injections and continued access to sodium-replete food. One week after these injections some animals were decapitated and trunk blood collected for analysis of Pcort by radioimmunoassay. The remainder of the rats were implanted with femoral arterial catheters to obtain blood samples for measurement of plasma and blood volumes by calculating dilution of 125I-labeled serum albumin. Volume-replete rats with AV3V lesions had significantly higher Pcort concentrations and smaller plasma and blood volumes than volume-replete control-operated animals. Furthermore, volume depletion induced by furosemide caused a significant increase in Pcort concentration only in rats with AV3V ablations, whereas plasma and blood volumes were significantly lowered in both groups. These data demonstrate that AV3V periventricular ablation results in a chronic elevation of Pcort in the volume-replete animals and an exaggerated glucocorticoid response to volume depletion. These data show that decreased PV characteristic of animals with AV3V lesions is not due to glucocorticoid insufficiency.
Circadian rhythms of sleep and wakefulness in mice: analysis using long-term automated recording of sleep
Authors: Richardson G. S. , Moore-Ede M. C. , Czeisler C. A. , Dement W. C.
Published: December 2017

Circadian rhythms of wheel-running activity and polygraphically defined wakefulness, rapid-eye-movement (REM) sleep and non-REM (NREM) sleep were continuously observed in ten mice (Mus musculus) under both alternating light-dark (LD 12:12) and continuous darkness (DD) conditions. Sleep-wake state was determined automatically using a computer-based method that allowed continuous recordings of from 60 to 280 days in duration. The sleep-wake state percentages (of the circadian cycle) thus obtained were in substantial agreement with other estimates for this or similar strains and showed no significant difference between LD 12:12 (wake 54.3%, NREM sleep 38.1%, REM sleep 7.6%) and DD (wake 53.1%, NREM sleep 39.9%, REM sleep 7.0%) conditions. All 10 mice exhibited clear circadian rhythms in each of the three states and wheel-running activity under both lighting conditions for the entire duration of observation. Probability functions, computed using stationary sections of data from all 10 mice, showed distinct waveforms for all three states and wheel running. These waveforms were remarkably similar under entrained and free-running conditions. This documentation of sustained circadian rhythmicity in sleep-wake state throughout observations of unprecedented length contradicts the currently common assertion that circadian control of sleep state is weaker than that of activity.
Acute and chronic gastrin-releasing peptide decreases food intake in baboons
Authors: Figlewicz D. P. , Stein L. J. , Woods S. C. , Porte D.
Published: December 2017

Gastrin-releasing peptide (GRP) is a peptide structurally related to bombesin that appears to be localized to the mammalian gastrointestinal tract. This study examined the ability of GRP, when administered on either an acute or chronic basis, to suppress food intake in baboons. When administered at 8 micrograms/kg iv before a morning meal, GRP significantly suppressed both food intake and the postprandial rise of plasma glucose and insulin. GRP at doses of 1, 2, 4, and 8 micrograms/kg stimulated basal insulin secretion. Chronic administration of GRP (q.o.d. for 11 days) at a low dose before the A.M. meal resulted in suppression of the A.M. meal and an initial suppression of total food intake, which recovered before the end of the treatment period. In conclusion, GRP appears to be effective in acute suppression of food intake and stimulation of basal insulin secretion in the nonhuman primate.
Inhibition of H+ secretion by lectins in turtle bladder: role of a cell type on acidification
Authors: Potter D. M. , Arruda J. A.
Published: December 2017

Because certain lectins have been shown to bind to the intercalated cell of the cortical collecting tubule, we investigated the effect of concanavalin A and wheat germ agglutinin on urinary acidification in isolated turtle bladders. After addition to the mucosal but not serosal fluid, concanavalin A and wheat germ agglutinin decreased H+ secretion in a dose-dependent manner, and these effects were specifically inhibited by the competitive antagonists of concanavalin A (alpha-methyl-D-mannoside) and of wheat germ agglutinin (N-acetylglucosamine). Concanavalin A decreased H+ secretion by decreasing both the proton motive force and the active conductance of protons. Although electroneutral HCO3 secretion was not inhibited by either lectin, Na transport was decreased by 18 and 25%, respectively, after concanavalin A and wheat germ agglutinin. Concanavalin A failed to inhibit O2 consumption by the granular cell fraction but significantly inhibited O2 consumption by the carbonic anhydrase rich cell fraction. Morphological studies utilizing peroxidase or fluorescein-labeled concanavalin A showed that concanavalin A stained one cell type and that this staining was specific since it could be blocked by the competitive antagonist alpha-methyl-D-mannoside. Studies utilizing double labeling with fluorescein concanavalin A and acridine orange suggested that both probes stain the same cell type. The data strongly suggest that concanavalin A interacts specifically with the cell responsible for H+ secretion.