bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of dependence on oxygen in embryo salamanders
Authors: Adolph E. F.
Published: December 2017

Survival times in anoxia and hypoxia were measured at various stages of development in Ambystoma embryos and larvae of two species. Survival times in anoxia at 20 degrees C shifted from more than 30 h at 2 days after fertilization to 20 h at 10 days of age, to only 4--2 h at 14 days of age. In hypoxia (oxygen pressure equivalent to 3.8% oxygen) similar shifts of survival times appeared about 7 days of age later. During anoxia heart rates decreased, less at younger stages than at older. At older stages the heart stopped beating, sometimes irreversibly. In hypoxia also, hearts at all stages whether in situ or isolated decreased their rates of beat. Oxygen uptakes of larvae diminished in oxygen pressures even as high as 11% oxygen. This critical oxygen pressure did not change between early stages without blood flow and later stages with blood flow. Oxygen uptake was probably not limited by oxygen delivery but presumably by properties of cellular masses. No oxygen debts were paid off. Some parallel changes of tolerances to anoxia in embryo birds and mammals are noted.
Vasopressin release and drinking induced by intracranial injection of angiotensin II in monkey
Authors: Simonnet G. , Rodriguez F. , Fumoux F. , Czernichow P. , Vincent J. D.
Published: December 2017

The effects of intracerebral injection of angiotensin II (AII) on both water intake and arginine-vasopressin (AVP) release were tested on unanesthetized rhesus monkeys (Macaca mulatta). Injection of 10(-10) mol of peptide was administered with a cannula microinjection system stereotaxically implanted into different diencephalic structures. The preoptic area, anterior part of third ventricle, caudate nucleus, and septum appeared to be the injection sites most effective in eliciting both drinking behavior and AVP release when the animal did not have access to water. On the contrary, when water was presented, AVP release was blocked after AII microinjections in the preoptic area and the third ventricle. No drinking was observed after microinjection in the supraopticus nucleus although AVP release was stimulated. These data suggest that AII might be effective in the regulation of water balance by centrally controlling both the input (drinking) and the output (ADH secretion) of water.
Renin and aldosterone secretions during hypovolemia in rats: relation to NaCl intake
Authors: Stricker E. M. , Vagnucci A. H. , McDonald R. H. , Leenen F. H.
Published: December 2017

Plasma renin activities (PRA) and aldosterone concentrations increased in parallel over a wide range of plasma volume deficits produced in unanesthetized rats by extravascular administration of polyethylene glycol (PEG) solution. When PEG-treated rats were given water to drink, their intakes were proportional to PRA; when given water and 0.5 M NaCl, PRA and the steroid concentrations diminished concurrently in association with sodium consumption. Aldosterone concentrations and NaCl intakes were markedly enhanced after PEG treatment in rats maintained on a sodium-deficient diet for 4 days. On the other hand, a clear relation between PRA and water intake, and between circulating aldosterone levels and sodium intake, was not suggested by other experiments in this series. For example, bilateral nephrectomy abolished the rise in PRA during hypovolemia yet rats drank water normally. Moreover, aldosterone concentrations were substantially elevated by PEG treatment in the nephrectomized rats yet sodium appetite was abolished. These and other findings suggest that neither angiotensin nor aldosterone plays a prominent role in stimulating water and saline intakes during hypovolemia.
Independence of brain and body temperatures in flying American kestrels, Falco sparverius
Authors: Bernstein M. H. , Curtis M. B. , Hudson D. M.
Published: December 2017

Brain and body temperatures were measured via small thermocouples implanted in the anterior hypothalami and colons, respectively, of five adult American kestrels (F. sparverius, mean mass 119 g) during descending flights in a wind tunnel at angles of 4 and 6 degrees below horizontal, at 10 m.s-1 air speed, and at 23 degrees C air temperature. For comparison, temperatures were recorded from resting birds at 22.5-36.1 degrees C air temperatures. Colonic (Tc) and hypothalamic (Th) temperatures both increased after the onset of flight; steady-state levels were attained after 1 min in the hypothalamus and after 5 or more min in the colon. The steady-state difference (delta T = Tc - Th) averaged 1.2 degrees C, higher by 0.5 degrees C than delta T in resting kestrels. The establishment of delta T during flight may be correlated with increased respiratory and corneal evaporation. The response apparently confines most stored body heat to noncranial regions, thus protecting brain tissue from thermal extremes.
Computer simulation of metabolism in pyruvate-perfused rat heart. IV. Model behavior
Authors: Achs M. J. , Kohn M. C. , Garfinkel D.
Published: December 2017

The behavior of a computer model of energy metabolism was determined for perfused rat hearts utilizing pyruvate as sole exogenous fuel and subjected to a rapid increase in work load. Computer-generated metabolite profiles, which are solutions of the differential equations for 1 min elapsed time, closely match 12 experimental curves (involving 120 concentration measurements) and exhibit the following properties. The computed cytosolic pyruvate level oscillates due to large changes in the rates of the processes that produce and consume this metabolite. Cytosolic Mg2+ seems to act as a coordinated controller of glycolytic enzymes; its transient increase permits a transient increase of glycolysis without an accumulation of glucose 6-phosphate. Lactate is exported to the interstitium by a lactate permease and then reimported and oxidized. As a result, the malate-aspartate shuttle reverses direction, and the Krebs cycle is “unspanned.”
Regulation of cardiac output during rapid volume loading
Authors: Barnes G. E. , Chevis B. C. , Granger H. J.
Published: December 2017

Interactions between heart rate (HR) and the Frank-Starling mechanism in augmenting cardiac output (CO) during acute volume loading were studied in dogs under varying conditions. In normal conscious dogs with low HRs of 70--90 beats/min, end-diastolic diameter (EDD) was maximal and CO was increased reflexly by cardioacceleration. By contrast, anesthetized open-chest dogs with high HRs ranging from 140 to 160 beats/min, responded with bradycardia and CO was adjusted solely by increasing stroke volume (SV). In anesthetized open-chest dogs with low HRs, EDD was less than maximal and increases in both HR and SV contributed to augment CO. These data show that both the cardioacceleration reflex and the Frank-Starling mechanism are important determinants of the cardiac response to elevated preload. Although the relative contribution of each control mechanism varies with initial conditions, their interplay extends the range of cardioregulation beyond that attainable by either loop operating alone.
Effects of jejunoileal bypass on meal patterns in genetically obese and lean rats
Authors: Kissileff H. R. , Nakashima R. K. , Stunkard A. J.
Published: December 2017

Jejunoileal bypass surgery, designed to reproduce the human operation (long bypass) was contrasted with a short bypass of only a few centimeters of ileum in both genetically obese rats and their lean littermates. In comparison with the short-bypassed rats, long-bypassed rats of both genotypes lost weight and reduced food intake. When adjustments were made for group differences before surgery, no significant differences were detected in the effectiveness of the operation on the two genotypes. The reduction in food intake was accomplished by a decrease in meal size and an increase in intermeal interval. Food intake gradually returned in the long-bypassed rats toward its level in the short-bypassed rats. This increase was accomplished by an increase in meal size alone. Intermeal intervals remained prolonged. In the long-bypassed rats, compared with the short, meal duration was initially elevated and gradually increased more than did meal size, indicating a great slowing of eating rate. Water intake was unaffected, but water-to-food ratio was elevated initially and gradually declined in the long-bypassed rats. Learned food aversion, dehydration, and gastrointestinal and metabolic alterations due to malabsorption are mentioned as possible contributors to the reduction in food intake, but none of these alone can account for all the changes in meal pattern by which intake reduction is accomplished.
Static and kinetic properties of the dolphin pupil
Authors: Dawson W. W. , Adams C. K. , Barris M. C. , Litzkow C. A.
Published: December 2017

In dim illumination, adult human pupil area becomes asymptotic at about 51 mm2 whereas the dolphin pupil achieves an area of about 70 mm2 under equivalent conditions. At moderate illumination levels (greater than 100 lx), the dolphin pupil becomes a horizontally oriented ellipse and develops a pronounced central constriction with additional light. The relative relationship between pupil area and illumination copmares closely with published human data. Rates of pupil response to step increments in illumination are very similar for the two species. Although the pupil has been proposed as a mechanism for correction of the dolphins' high aerial myopia, correlation of the laboratory findings on static and kinetic pupil properties with visually controlled aerial behaviors disclosed no special interdependence.
Fat-free mass, total body water, and intracellular water in the aged rat
Authors: Lesser G. T. , Deutsch S. , Markofsky J.
Published: December 2017

Total body water (TBW) and intracellular water (ICW = TBW minus extracellular water), when related to fat-free body mass (FFB), were recently observed to remain stable in healthy aged men and women. To expand these findings, a group of male Sprague-Dawley rats was followed from weaning to death. The design minimized several perturbations common to aging studies. At about 100-day intervals from 297 to 888 days, representative animals were killed for chemical studies. TBW/FFB was stable from 362 to 715 days, then significantly higher at 800 and 888 days. Extracellular water content of the fat-free body (ECW/FFB) increased significantly during middle life (362--579 days), then remained stable through 888 days. Changes of ICW/FFB were not significant. Aside from a uniquely higher value at 638 days, protein content did not differ significantly at any age. The stability of these major constituents suggested approximate maintenance of cell mass in healthy rats at late ages, a conclusion supported by additional observations of this colony and of an aged human population. We are unable to confirm the hypothesis that loss of FFB is part of the normal aging process.
Reconstruction of the gill from single-cell suspensions of the eel, Anguilla japonica
Authors: Naito N. , Ishikawa H.
Published: December 2017

Minute gill arches, about 2 mm in length and with 17-20 pairs of filaments, were reconstructed from single-cell suspensions of the adult eel gill. Mixed populations of the dissociated cells were cultured with growth medium (pH 7.2-7.4) either in a Rose chamber or in a roller tube at 20 degrees C. Single cells began to aggregate within 1 h into small cell clusters, which increase in size with selective adhesion of free cells. Melanin cells were frequently observed in the aggregates. Cell aggregates containing melanin cells transformed progressively into a gill barlike structure, and then, filamentlike structures grew from the bar. Secondary lammelalike structures were observed on the filaments. With growth of the gill bar, the filaments increased in both number and length, and after about 1-2 wk minute gill arches were reconstructed with original histological properties and circulatory system.
Accessory cells in teleost branchial epithelium
Authors: Hootman S. R. , Philpott C. W.
Published: December 2017

Correlated morphological and cytochemical investigations of the branchial epithelium of the pinfish, Lagodon rhomboides, have revealed a cell type that is invariably associated with chloride cells. These cells, termed “accessory cells,” have been described previously in the teleost pseudobranch (Dunel and Laurent. J. Microsc. Biol. Cell 16:53-74, 1973) but not in the gill proper. Accessory cells are more numerous in pinfish adapted to seawater than to 33% seawater, and in the former participate with chloride cells in the formation of apical crypts. Although accessory cells are much smaller than chloride cells, they possess numerous mitochondria and display an abbreviated labyrinth of plasma membrane-derived tubules. The labyrinth membranes of accessory cells are essentially unreactive, however, when processed for Na-K-ATPase localization by K-nitrophenylphosphatase cytochemistry, whereas chloride cell membranes exhibit copious, ouabain-sensitive reaction products. The zonulae occludentes between accessory cells and chloride cells also appear to be less extensive than those between either of these cells and the flanking pavement cells. These features suggest that accessory cells represent a population of partially differentiated chloride cells.
Blood-brain barrier transport and cerebral utilization of dopa in living monkeys
Authors: Garnett E. S. , Firnau G. , Nahmias C. , Sood S. , Belbeck L.
Published: December 2017

[18F]fluoro-dopa, DL-3,4-dihydroxy-5-[18F]fluorophenylalanine, a tracer for dopa, was injected intravenously into cynomolgus monkeys anesthetized with enflurane, and the appearance of 18F in the head and the disappearance of 18F from the blood were each measured continuously for 10 min with simple gamma-ray detectors. A three-compartment explanatory model was used to derive fractional rate constants for the forward flux of L-dopa into the endothelium of the brain capillaries from the blood (1.54 +/- 0.37 min-1), the back flux of dopa and/or its metabolites to the blood from the endothelium (0.67 +/- 0.05 min-1), the formation of dopamine from dopa (0.20 +/- 0.04 min-1), and the destruction of dopamine (0.04 +/- 0.02 min-1). It was also shown that only one-fifth of the dopa that entered the endothelium was available for dopamine synthesis in neurons. It was concluded that the technique described could be extended to man and used to investigate the role of dopa and dopamine in the control of mood and locomotion.
Drinking and vasopressin release during ventricular infusions of hypertonic solutions
Authors: Thrasher T. N. , Jones R. G. , Keil L. C. , Brown C. J. , Ramsay D. J.
Published: December 2017

Six dogs were administered third ventricular infusions of artificial cerebrospinal fluid (CSF) (292 mosmol/l) alone or artificial CSF to which neither NaCl, sucrose, glucose, or urea was added to yield a final osmolar concentration of 500 mosmol/l. The volume of water drunk during 45 min of infusion was measured and blood was sampled for determination of plasma vasopressin concentration at 15-min intervals. Artificial CSF made hypertonic by addition of NaCl or sucrose stimulated water intakes of 9.0 +/- 3.2 ml/kg (mean +/- SE) and 7.3 +/- 3.7 ml/kg, respectively. There was no statistical difference in the amounts drunk and the latencies. In contrast, artificial CSF containing glucose, urea, or artificial CSF alone were without effect. Plasma vasopressin concentration increased significantly in response to intraventricular NaCl and sucrose but was not affected by glucose, urea, or artificial CSF alone. These data are compatible with an osmoreceptor mechanism mediating drinking and vasopressin release.
Energy balance in ovariectomized rats with and without estrogen replacement
Authors: Laudenslager M. L. , Wilkinson C. W. , Carlisle H. J. , Hammel H. T.
Published: December 2017

The effect of estrogen replacement on several parameters of energy balance was investigated in ovariectomized rats tested during the dark phase of their diurnal cycle. Estrogen replacement, either as 17 beta-estradiol or beta-estradiol-3-benzoate via subcutaneous Silastic capsules, was associated with elevated rates of heat production and dry heat loss relative to untreated ovariectomized controls. Estrogen treatment reduced body mass and retarded fur growth. The effects of estrogen replacement on heat production and dry heat loss could not be attributed to these differences in body mass and fur growth or locomotor activity. Estrogen replacement had no effect on rate of evaporative heat loss. If estrogen replacement was delayed 75 days following ovariectomy, the increase in heat production and dry heat loss was not observed. There was no effect of the hormone treatment on rectal temperature. It was concluded that either heat production was elevated, with dry heat loss increased to compensate for the additional thermal load, or dry heat loss was accelerated with heat production elevated in compensation.
Postnatal development of the renin-angiotensin system in rats
Authors: Wallace K. B. , Hook J. B. , Bailie M. D.
Published: December 2017

The purpose of this investigation was to correlate the development of the various enzyme activities associated with the renin-angiotensin system with age-related differences in the steady-state concentrations of angiotensin I (AI) and II (AII). Angiotensin was quantified by radioimmunoassay. Plasma renin activity and concentration increased between birth and 3 wk of age, and declined thereafter to adult values. Renal renin content, on the other hand, increased throughout the first 6 wk of postnatal life. The concentration of AII in plasma also increased following birth; however, maximum concentrations were not attained until 5 wk of age. In contrast, plasma AI did not increase between 3 and 6 wk of age. These data suggest that the steady-state concentration of AII in neonatal rat plasma may be partially limited by the low plasma renin substrate concentration. The increase in AII between 3 and 6 wk of age may reflect the increasing converting enzyme activity.
Computer modeling, complex biological systems, and their simplifications
Authors: Garfinkel D.
Published: December 2017

The amount of information defining a biological system, as specified in its genome, is vastly larger than the amount of information the human mind can handle simultaneously in its short-term memory (7 +/- 2 items at most). In such a situation the mind tends to simplify, linearize, and consider only a few of many variables that may be involved. This may be limiting when an experimenter interprets his own experiments without help from theory or modeling as is common in biology. The Michaelis-Menten model, which is very useful although not necessarily valid, and its linearizations are described as an example of this. The social processes and obligations involved in simplifying complex situations are discussed. Computer simulation provides a method for investigating complex nonlinear systems that does not require excessive simplification of the biological system being studied and whose economics are becoming steadily more favorable.
Projections to the hypothalamus from buffer nerves and nucleus tractus solitarius in the cat
Authors: Calaresu F. R. , Ciriello J.
Published: December 2017

In 18 cats anesthetized with chloralose, electrical activity of spontaneously active hypothalamic units was monitored for changes in firing frequency during electrical stimulation of carotid sinus (CSN) and aortic depressor (ADN) nerves and the nucleus tractus solitarius (NTS). Stimulation of the CSN altered the activity of 55% (381/691) of the tested. These responsive units were widely distributed in the ipsi- and contralateral hypothalamus. Of the units tested during stimulation of the ADN only 6% (17/274) changed their firing frequency. Responsive units were located only on the ipsilateral side and primarily in the paraventricular and supraoptic nuclei, Electrical stimulation of the NTS altered the firing frequency of all 84 hypothalamic units previously identified by stimulation of the CSN. NTS stimulation elicited responses that had a significantly shorter latency and followed significantly higher frequencies of stimulation when compared to stimulation of the CSN. These results demonstrate that the two buffer nerves have distinctly different central projections to the hypothalamus and suggest different functional roles for the ADN and CSN in homeostatic regulatory mechanisms mediated by the hypothalamus.
Renal and peripheral vascular responsiveness to arginine vasotocin in bullfrog, Rana catesbeiana
Authors: Pang P. K. , Galli-Gallardo S. M. , Collie N. , Sawyer W. H.
Published: December 2017

Arginine vasotocin (AVT), the amphibian neurohypophysial hormone, has pressor and antidiuretic actions in bullfrogs (Rana catesbeiana). Much higher doses of exogenous AVT were required for the pressor response than those for the antidiuretic response. When bullfrog legs and kidneys were perfused under constant pressure simultaneously, the kidney vasculature was more sensitive to bolus injection of AVT than was the leg vasculature. The same was true when the tissues were perfused with different concentrations of hormone. AVT constricts preglomerular vessels in the bullfrog. We suggest that the preglomerular vasculature of the bullfrog is more sensitive to AVT than is the peripheral vasculature. This may explain in part the antidiuretic action of the hormone at nonpressor doses. Evolutionary speculations are discussed.
Effect of liver denervation on the feeding pattern of rats
Authors: Louis-Sylvestre J. , Servant J. M. , Molimard R. , Le Magnen J.
Published: December 2017

This study was undertaken to assess the role of the hepatic innervation in the short-term regulatory mechanisms of food intake. A liver denervation was performed in male Wistar rats: the liver was entirely freed from the surrounding organs, its vessels (with the exception of the hepatic veins) and the bile ducts were stripped. Controls consisted of two groups of liver-denervated rats in which sympathectomy or vagotomy were carried out. A continuous recording of food intake was performed in a third group. The complete absence of the hyperglycemic response to trauma in adrenalectomized liver-denervated animals was taken as evidence of functional sympathectomy of the liver. The disappearance of a vagovagal reflex--heart rate variation brought about by a glucose injection into the portal vein--was taken as evidence of functional vagotomy. The analysis of the recorded feeding patterns of liver-denervated and sham-operated animals showed that, in rats, this liver denervation did not affect in any way the feeding behavior.
2-Deoxy-D-glucose-induced hypothermia: thermoregulatory pathways in rat
Authors: Shiraishi T. , Mager M.
Published: December 2017

2-Deoxy-D-glucose (2-DG) elicits significant and prolonged hypothermia in a variety of animals when administered either peripherally or centrally. From our current studies it would appear that, in high concentrations (250 mg/kg or more, ip), 2-DG can act directly on peripheral tissues in the rat by competitively interfering with glucose metabolism and consequently with normal heat producing mechanisms. When a low concentration of 2-DG (20 micrograms) is injected centrally, the ensuing glucopenia results in vagal stimulation and subsequent diminution of peripheral heat production. Vagal involvement is concluded from studies with atropine, which demonstrated total inhibition of the usual 2-DG depression of body temperature by administration to the ventral premammillary nucleus (PMV), a site that is normally extremely sensitive to this analog of glucose. Additionally, from studies with PMV-lesioned rats, it was concluded that an intact nucleus is necessary for thermoregulation in a normal, a hot, or a cold environment.
In vivo recording of oviductal contractions in rabbits during the periovulatory period
Authors: Bourdage R. J. , Halbert S. A.
Published: December 2017

Muscular activity of the oviductal isthmus was recorded in intact awake rabbits with an extraluminal optoelectronic transducer. Telemetered data were collected continuously during the periovulatory period to relate changes in contraction frequency to oviductal transport function. Mean frequencies during estrus ranged from 11.7 to 18.7 contractions/min. Animals stimulated to ovulate either by luteinizing hormone (LH) or by mating showed equivalent responses. Within 2 h following the stimulus, the frequency increased rapidly and remained elevated more than 50% above the estrous control level for approximately 10 h. Thereafter, the frequency declined slowly to reach a second plateau, 30% below the control level, which was maintained throughout the 2nd and 3rd poststimulus days. Subsequently, the activity returned to the prestimulus level. The periods of elevated and depressed activity correspond closely in time to the periods of rapid preovulatory transport of sperm and slow postovulatory transport of ova through the isthmus, suggesting the possibility of regulation of gamete transport by the oviductal musculature.
Forebrain control of fluid and electrolyte homeostasis and angiotensin sensitivity in rabbit
Authors: Fink G. D. , Bryan W. J.
Published: December 2017

A small discrete area near the optic recess of the anterior ventral third ventricle (AV3V) in the rat brain has been shown to be an important mediator of cardiovascular and dipsogenic response to angiotensin II and osmotic stimuli and to be involved in normal day-to-day regulation of water and electrolyte balance. However, no attempt has been made until now to explore the function of the AV3V in species other than the rat. In the present study, rabbits subjected to electrolytic lesion of the AV3V exhibited expanded plasma volume and plasma sodium concentration, and significantly attenuated pressor responses to angiotensin II and hypertonic sodium chloride solutions injected via the lateral ventricles. Resting arterial pressure, plasma potassium concentration, extracellular fluid volume, and pressor responses to intravenous angiotensin II were not changed by lesioning. Thus, the effects of AV3V lesions in rabbits are similar, but not identical, to those previously observed in rats. Rabbits should be a suitable species in which to carry out studies aimed at distinguishing central and peripheral cardiovascular effects of angiotensin II.
Hypothermia in iron deficiency due to altered triiodothyronine metabolism
Authors: Dillman E. , Gale C. , Green W. , Johnson D. G. , Mackler B. , Finch C.
Published: December 2017

Iron-deficient rats become hypothermic and have an excessive catecholamine response when exposed to an ambient temperature of 4 degrees C. This is not due to changes in body insulation, since thickness is unaltered, since differences persist after removal of hair, and since cutaneous vasoconstriction is intact. On the other hand, oxygen consumption of iron-deficient animals at 4 degrees C is reduced, 39 +/- 3 ml . kg-1 . min-1 compared to 63 +/- 2 in control animals. Thyroxine (T4) values at 4 degrees C were 4.34 +/- 0.20 microgram/dl sera as compared to control values of 3.6 +/- 0.32. Triiodothyronine (T3) values of iron-deficient animals in the cold were 48 +/- 6.8 ng/dl as compared to 72 +/- 5.6 in control animals. Treatment of iron-deficient animals with iron was shown to normalize the plasma T3 response at 4 degrees C within 6 days. Thyroidectomized iron-deficient animals injected with T3 did not show hypothermia at 4 degrees C, whereas thyroidectomized iron-deficient animals injected with T4 showed hypothermia, increased catecholamines, and decreased T3 levels as compared to non-iron-deficient animals similarly treated. It is proposed that iron deficiency impairs conversion of T4 to T3 and that this is primarily responsible for the hypothermia observed.
Intralamellar blood flow patterns in fish gills
Authors: Farrell A. P. , Sobin S. S. , Randall D. J. , Crosby S.
Published: December 2017

The dimensions of the lamellar vascular sheet in ling cod gills were examined over a range of transmural pressures (delta Plam). The mean vascular sheet thickness (h) increased linearly with delta Plam over the range 30-60 cmH2O, where h = 8.36 + 0.07 delta Plam. The vascular space-to-tissue ratio, however, was unchanged over the pressure range examined. Thus sheet flow equations, formerly derived for the interalveolar wall of the mammalian lungs, can be used to describe blood flow through the lamellae. Predictions were made on the distribution of blood flow within the lamella. When delta Plam and flow are raised, blood flow is redistributed away from the base of the lamella, since regional variations exist in the thickness and the vascular compliance of the lamellar sheet. Variations in the pattern of intralamellar blood flow are likely to affect gas transfer in the gills.
Amino acid incorporation in medial hypothalamic nuclei: circadian, perikarya, and neuropil variations
Authors: Van den Pol A. N.
Published: December 2017

Amino acid, [3H]lysine, incorporation was examined with autoradiographic techniques in four nuclei of the medial hypothalamus during four consecutive 6-h periods. Rats which had previously been maintained under 12:12 light-dark conditions were kept in constant darkness during the day of [3H]lysine administration to prevent any direct influence of light on hypothalamic activity. Forty-five minutes after intraperitoneal injection of the tritiated amino acid, animals were killed. After autoradiography processing, grain counting revealed that the suprachiasmatic and magnocellular paraventricular nuclei showed a statistically significant circadian variation in the number of grains over neural perikarya. A time-of-day effect was also found in the grain count over neuropil of the arcuate, ventromedial, and paraventricular nuclei. A corresponding behavioral study found that feeding continued to occur primarily during the 12 h of night, even with lights out for 24 h. These data suggest an endogenous circadian variation in one or more factors that influence amino acid uptake and protein synthesis in some hypothalamic neurons. When [3H]lysine uptake was analyzed in terms of grains/100 micrometer 2 of cell area, the arcuate and paraventricular nuclei showed a significantly greater (double) uptake of [3H]lysine than did the suprachiasmatic or ventromedial nuclei. Four times more grains were counted over somata than over an equal area of cell-free neuropil.
Depressor responses to stimulation of sympathetic afferents in monkeys and dogs
Authors: Kostreva D. R. , Hopp F. A. , Kampine J. P.
Published: December 2017

In dogs and monkeys anesthetized with pentobarbital sodium, stimulation of the cut central ends of the stellate cardiac nerve, the left and right anterior ansae subclavia, and the stellate ganglia resulted in a depressor response when stimulating fibers with conduction velocities in the range of 2.5-10 m/s. These afferents are in the A delta-fiber-type range. Pressor responses could be elicited by stimulating afferent fibers with conduction velocities in the range of 0.5-3.0 m/s. These fibers are in the C-fiber-type range. Stimulation of the abdominal sympathetic afferents always resulted in a depressor response regardless of the conduction velocities of the fibers. No changes in heart rate were observed. Bilateral cervical vagotomy did not alter the pressor or depressor responses.
Mechanism of reduced water intake in rats at high altitude
Authors: Jones R. M. , Terhaard C. , Zullo J. , Tenney S. M.
Published: December 2017

Water intake was reduced during the 1st day of hypobaric hypoxia (inspired O2 pressure of 75 Torr) to 35-40% of the normoxic level in both normal rats (N) and rats with diabetes insipidus (DI). Analysis of water intake under graded saline loads at several inspired O2 levels (inspired O2 fractional concentrations of 0.105, 0.120, and 0.2095) indicated that hypoxia increased the threshold for osmotic stimulation of drinking without changing the sensitivity of the response in both N and DI rats. Nephrectomized N rats reduced water intake during hypoxia to 33% of the nephrectomized normoxic level of intake, and nephrectomized DI rats reduced intake to 47% of the nephrectomized normoxic intake. From these results it is concluded that reduced angiotensin II formation was not the factor responsible for reduced water intake during hypoxia. Polyethylene glycol-induced hypovolemia resulted in increased water intake during normoxia, but during hypoxia it was reduced to 29% of the normoxic rate. Reduced body temperature and hyperventilation were not the source of hypoxic attenuation of thirst. The mechanism may reside beyond the central integration of osmotic and nonosmotic information, or at the osmotic sensing mechanism itself.
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

In this study we investigated in vivo changes in hepatic cellular electrolytes and resting transmembrane potentials (Em) during hemorrhagic shock. Hepatic Na-K transport and cell volume regulation were assessed in vitro. Rats were bled and the ensuing hypotension (40 mmHg) was maintained by returning 25-30% (intermediate-shock, IS) or 55-60% (late-shock, LS) of the shed blood. We resuscitated IS rats by reinfusion of all of the remaining shed blood and Ringer's lactate solution. Hepatic cellular Na and Cl increased and K decreased progressively with shock. Resuscitation of IS rats restored cell K and Cl but not Na to preshock levels. Em decreased from the control average value of -40 (mV) to -31 in IS and -19 in LS. Em was partially restored (-36 mV) after resuscitation. We evaluated changes in relative membrane permeability to Na and K (PNa/PK) with shock by assuming Em either to be a Na-K exchange diffusion potential or due to an unequally coupled movement of Na and K. These evaluations show a lack of effect of shock (IS, with or without resuscitation) on PNa/PK. Our observations are compatible with failure of an electrogenic Na pump in shock. This may be related to loss of hepatic cell volume regulation in shock.
Sodium metabolism during acclimation to water restriction by wild mice, Mus musculus
Authors: McKenna T. M. , Haines H.
Published: December 2017

Changes in sodium and potassium balance and urinary aldosterone excretion (free plus “acid labile”) were surveyed in house mice acclimating initially to 1/2 the ad libitum water ration and later to 1/4 of ad libitum. Each water restriction caused negative sodium and potassium balance, followed by conservation of both ions. At the first water restriction, negative balance was produced by natriuresis and kaliuresis, at successive water restriction, a negative balance was due to a decrease in food consumption. Aldosterone excretion doubled at the 1/2 ad libitum restriction, and then generally remained at control levels thereafter. Fractional intestinal absorption of both ions showed a persistent increase after the 3rd day of water restriction. The Na:K ratio in urine and feces declined as mice responded to each water restriction and returned to control levels in acclimated animals.
Brain stem neuronal types with activity patterns related to sympathetic nerve discharge
Authors: Barman S. M. , Gebber G. L.
Published: December 2017

The relationships among the spontaneous activity of single neurons in the cat medulla and inferior cardiac sympathetic nerve discharge (SND), electroencephalogram (EEG) activity, phrenic nerve activity, and the R wave of the electrocardiogram were studied with the methods of spike-triggered averaging and postevent interval analysis. Three categories of neurons (SR, SE, and S) with activity patterns related to SND wee identified. The activity of SR units was related in time to SND and the R wave but not to EEG activity. SE unit discharges were related to SND and EEG activity but not to the R wave. S unit activity was related only to SND. Each of the three categories of neurons could be subdivided into two groups depending on whether their discharges were followed by an increase or a decrease in SND. All unit types exhibited respiratory-related discharge patterns. These data are discussed with regard to the problems associated with the identification of neurons in brain stem networks that govern the discharges of sympathetic nerves.
Exchange diffusion, active transport, and diffusional components of transbranchial Na and cl fluxes
Authors: Kirschner L. B. , Howe D.
Published: December 2017

Sodium efflux across the gills of the sculpin Leptocottus armatus average about 900 mumol.100 g-1.h-1 in seawater (SW). When external Na+ was replaced by Tris [tris(hydroxymethyl)aminomethane] the efflux dropped about 35% and the voltage across the gill (TEP) decreased from +20.3 to -2.3 mV. The electrical change accounted, almost exactly, for the diminution of efflux, suggesting that most, if not all, of the Na+ efflux in this fish is diffusive. Chloride efflux in SW was about 300 mumol.100 g-1.h-1. When external Cl- was replaced by gluconate, efflux fell to about one-half the SW value. This could not be due to a change in TEP and is therefore attributed to exchange diffusion. Injection of thiocyanate further reduced the efflux to about 15% of the SW rate. This fraction of the total efflux is active extrusion. The remaining efflux (exchange and active transport eliminated) is diffusive. It is also shown that substitution of gluconate for chloride reduces the activity coefficient for Na+. A small decrease in TEP, noted in this substitution, can be explained by the activity change. A few experiments with isethionate suggest that it does not have this effect and hence is a better chloride substitute in single-ion replacement experiments.
Distinctions among three sugars in their effects on gastric emptying and satiety
Authors: Moran T. H. , McHugh P. R.
Published: December 2017

We have studied in Macaca mulatta both the gastric emptying of glucose, D-xylose, and fructose and the effects of these sugars on feeding. Glucose and D-xylose empty in the same fashion, i.e., linearly and more slowly with increasing concentration so that the delivery of solute to the small intestine is constant at 0.1 g/min over time and across concentrations. Fructose empties exponentially and more rapidly than the other sugars. When solutions of each of these sugars (37.5 g in 150 ml) preceded the monkey's daily 4-h feeding period there was a similar total reduction in food intake for each. However, fructose inhibited food intake in the first 2 h of feeding less than did the other sugars just as it inhibited gastric emptying less. D-Xylose, although mimicking glucose in both gastric emptying and feeding on the experimental day, produced, as it is poorly metabolized, a caloric deficit replaced by overeating on the subsequent control day. We conclude from the similarities between glucose and xylose that the stomach, while emptying nutrients, influences feeding and can be at least one source of signals for preabsorptive satiety and caloric homeostasis. The results with fructose require that other sites must be active to permit a similar regulation of feeding to occur despite differing gastric emptying characteristics.
Bradykinin effects on adrenergic transmission in the canine kidney: relation to prostaglandins
Authors: Susic H. , Nasjletti A. , Malik K. U.
Published: December 2017

We studied the action(s) of bradykinin at the renal vascular neuroeffector junction, and its relation to prostaglandin synthesis, by investigating the effect of the peptide on the renal venous output of the neurotransmitter and on the renal vasoconstrictor responses elicited by sympathetic nerve stimulation and by norepinephrine in pentobarbital-anesthetized dogs. Renal arterial infusion of bradykinin at 10 ng . kg-1 . min-1 increased blood flow to the kidney and inhibited the vasoconstrictor effect of renal nerve stimulation (1-8 Hz) and injected norepinephrine (0.06-0.5 micrograms). However, bradykinin did not alter the rise in venous output of norepinephrine elicited by nerve stimulation. Infusion of another vasodilatory peptide, substance P (2 ng . kg-1 . min-1) into the renal artery also increased blood flow to the kidney but failed to alter the vasoconstriction produced by either adrenergic stimulus. Pretreatment of dogs with an inhibitor of prostaglandin synthesis, either sodium meclofenamate or indomethacin (5 mg/kg), abolished the inhibitory effect of the kinin on renal vasoconstriction produced by adrenergic stimuli. These data suggest that bradykinin acts on postjunctional sites to reduce adrenergically induced vasoconstriction in the canine kidney by a mechanism dependent on prostaglandin synthesis.
Isoproterenol-induced thirst: renal and extrarenal mechanisms
Authors: Rettig R. , Ganten D. , Johnson A. K.
Published: December 2017

When given systemically, isoproterenol will induce water intake in various species. The drug also causes hypotension and renin release from the kidney. Angiotensin II and arterial baroreceptors have been hypothesized to be involved in the mediation of beta-adrenoceptor agonist-induced thirst, but their relative importance has been disputed. In the present series of experiments, isoproterenol was infused intravenously at different rates into nephrectomized and ureteric-ligated rats. Thus, different levels of hypotension could be achieved and maintained while water intake was measured. Also, plasma levels of angiotensin II were determined in ureteric-ligated rats following the intravenous infusion of a dipsogenic dose of isoproterenol. The results indicate that for moderate blood pressure changes a renal-related factor, probably angiotensin II, plays a major role in the mediation of isoproterenol-induced thirst. Under extreme conditions involving a very dramatic drop of arterial blood pressure, extrarenal mechanisms (e.g., arterial baroreceptors) are implicated.
Right atrium mediates a vasomotor reflex
Authors: Munzner R. F. , Ward D. G. , Gann D. S.
Published: December 2017

To examine the role of right atrial receptors in mediating reflex vascular responses we measured, in cats anesthetized with chloralose/urethan, changes in mean arterial pressure (MAP) in response to volume pulsation of the right atrium (+/- 1 ml, 1 Hz). Changes in MAP were measured 1) with pressure in the carotid arteries normal and vagus nerves intact: right atrial pulsation led to a very small and transient fall in MAP; 2) with pressure in the carotid arteries at 75 mmHg and the vagus nerves intact: right atrial pulsation led to a larger and sustained fall in MAP; 3) with pressure in the carotid arteries at 75 mmHg and the vagus nerves cooled or sectioned bilaterally: right atrial pulsation of the right atrium led only to a very small and transient fall in MAP. These data suggest strongly that signals from right atrial receptors traveling in the vagus nerves mediate a reflex change in MAP that is normally masked by signals from carotid receptors.
Effects of adrenergic blockade on glucose kinetics in septic and burned guinea pigs
Authors: Durkot M. J. , Wolfe R. R.
Published: December 2017

We have used the primed-constant infusion of [6-3H]glucose to study the effects of phentolamine, an alpha-adrenergic blocker, and propranolol, a beta-adrenergic blocker, on glucose production and clearance in gastrostomy-fed control, septic (repeated sub-Q Escherichia coli injections), and burned (25-30% BSA) guinea pigs. Hypermetabolism and elevated glucoregulatory hormones were evident in both traumatized models, whereas their glucose kinetic response was different. Basal glucose production and clearance were elevated in the burned group and were depressed in the septic group when compared to control values. Propranolol caused a further increase in glucose production and clearance in the burned group, whereas it depressed glucose production and clearance to an even greater extent in the septic group. Phentolamine also produced an increase in glucose production and clearance in the burned group. In the septic group, phentolamine had no significant effect on glucose production, but clearance was significantly elevated. Thus, although alpha- or beta-adrenergic blockade normalized metabolic rate in both groups with respect to control animals, glucose kinetics remained different despite similar changes in counterregulatory hormones.
Zinc nutrition and salt preference in rats
Authors: Jakinovich W. , Osborn D. W.
Published: December 2017

Zinc-deficient rats have an increased preference for sodium chloride (saltwater). We investigated the possibility that this elevated saltwater preference is due to nonfunctional taste receptors. In experiment I, zinc-deficient rats consumed more saltwater than zinc-sufficient rats at most sodium chloride concentrations tested (0.001-1.0 M). When the zinc-deficient rats were fed a zinc-sufficient diet, the clinical symptoms of zinc deficiency rapidly disappeared. However, the rats still preferred saltwater to a greater extent than rats maintained on the zinc-sufficient diet. In experiment II, rats fed diets supplemented with levels of zinc below the requirement for maximum growth had an increased preference for saltwater (0.15 M NaCl). In experiment III, electrophysiological responses of the taste nerves to various concentrations of sodium chloride, sucrose, quinine . HCl, and hydrochloric acid were the same in both zinc-deficient and zinc-sufficient rats. We conclude that the taste receptor sensitivity of the rat is not impaired by zinc deficiency. The increased salt preference of zinc-deficient rats might be related to some endocrine or central nervous system disorder precipitated by inadequate dietary zinc.
Sympathetic nerve function and vascular reactivity in spontaneously hypertensive rats
Authors: Ekas R. D. , Lokhandwala M. F.
Published: December 2017

Increased neurotransmitter release during sympathetic nerve stimulation may contribute importantly to the maintenance of spontaneous hypertension. Therefore, transmitter release and vascular reactivity were measured in perfused mesenteric vasculature of spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto rats (WKY). Increase in norepinephrine release, measured as total tritium overflow, during periarterial nerve stimulation was significantly greater in SHR than in WKY, as was the vasoconstrictor response. Even after blockade of neuronal uptake with cocaine (10 microM), or of neuronal as well as extraneuronal uptake with cocaine plus metanephrine (20 microM), norepinephrine overflow was still greater in SHR than in WKY. The greater vasoconstrictor response in SHR still persisted following uptake blockade. Phentolamine (5.3 microM) increased transmitter overflow markedly but equally in both SHR and WKY thereby suggesting that increased transmitter release in SHR was not due to alterations in presynaptic alpha-adrenoceptor mechanism. Vascular reactivity not only to periarterial nerve stimulation but also to norepinephrine, vasopressin, and barium chloride was increased in SHR. These results suggest that, in SHR, increases in norepinephrine release as well as vasoconstrictor reactivity contribute to the maintenance of hypertension.