bluuebunny/crossref_metadata_2025 huggingface dataset:
Total body electrical conductivity measurements: effects of body composition and geometry
Authors: Fiorotto M. L. , Cochran W. J. , Funk R. C. , Sheng H. P. , Klish W. J.
Published: December 2017

This study used an animal model to analyze the effect of body geometry and chemical composition on the calibration of a total body electrical conductivity (TOBEC) instrument developed to measure the body composition of human infants. The TOBEC signal (adjusted for length) of infant miniature pigs from 10 to 33 days of age correlated highly with their chemically analyzed fat-free mass (FFM; r = 0.998) and total body water contents (TBW; r = 0.998); 95% prediction intervals (approximately +/- 2 SEE) for individual measurements were +/- 0.16 kg FFM and +/- 0.12 liter water. These values were significantly improved (+/- 0.08 kg and +/- 0.06 liter, respectively) by accounting for individual variability in weight/length2. The effect of variations in the composition of FFM on the TOBEC measurements was evaluated by comparing the response of the infant piglets with that of adult rabbits of similar size. The differences in composition, primarily TBW and Na content, were insufficient to alter the electrical properties of FFM appreciably. Thus the TOBEC used under the conditions defined in this study accurately predicted the FFM and TBW content of infant miniature pigs. The calibration derived from the piglets will be applicable to the interpretation of the TOBEC measurements of human infants provided their FFM is of comparable shape to that of the piglets. Differences in composition are likely to be of consequence only if the proportion of fat within the FFM and the FFM density are widely divergent. This, however, does not appear to be the case.
Effect of stimulation of afferent renal nerves on plasma levels of vasopressin
Authors: Caverson M. M. , Ciriello J.
Published: December 2017

Experiments were done in alpha-chloralose-anesthetized, paralyzed and artificially ventilated cats with vagus, cervical sympathetic, aortic depressor, and carotid sinus nerves cut bilaterally to investigate the effect of afferent renal nerve (ARN) stimulation on circulating levels of vasopressin (AVP). Electrical stimulation of ARN elicited a pressor response that had two components, a primary (1 degree) component locked in time with the stimulus and a secondary (2 degree) component that had a long onset latency and that outlasted the stimulation period. The 1 degree and 2 degree components of the pressor response were largest at stimulation frequencies of 30 and 40 Hz, respectively. Autonomic blockade with hexamethonium bromide and atropine methylbromide abolished the 1 degree component. Administration of the vasopressin V1-vascular receptor antagonist d(CH2)5VAVP during autonomic blockade abolished the 2 degree component. Plasma concentrations of AVP measured by radioimmunoassay increased from control levels of 5.2 +/- 0.9 to 53.6 +/- 18.6 pg/ml during a 5-min period of stimulation of ARN. Plasma AVP levels measured 20-40 min after stimulation (13.6 +/- 7.0 pg/ml) were not significantly different from control values. Plasma osmolality was not altered during the course of the experiment. These data demonstrate that sensory information originating in the kidney alters the release of vasopressin from the neurohypophysis and suggest that ARN are an important component of the neural circuitry involved in homeostatic mechanisms controlling arterial pressure.
Quaternary ammonium sulfanilamide: a membrane-impermeant carbonic anhydrase inhibitor
Authors: Henry R. P.
Published: December 2017

A novel carbonic anhydrase (CA) inhibitor, quaternary ammonium sulfanilamide (QAS), was tested for potency as a CA inhibitor and for its ability to be excluded from permeating biological membranes. Inhibitor titration plots of QAS vs. pure bovine CA II and CA from the gills of the blue crab, Callinectes sapidus, yielded Ki values of approximately 15 microM; thus QAS is a relatively weak but effective CA inhibitor. Permeability of the QAS was directly tested by two independent methods. The inhibitor was excluded from human erythrocytes incubated in 5 mM QAS for 24 h as determined using an 18O-labeled mass spectrometer CA assay for intact cells. Also QAS injected into the hemolymph of C. sapidus (1 or 10 mM) did not cross the basal membrane of the gill. The compound was cleared from the hemolymph by 96 h after injection, and at no time during that period could the QAS be detected in homogenates of gill tissue. Total branchial CA activity was only slightly reduced following the QAS injection. These data indicate that QAS is a CA inhibitor to which biological membranes are impermeable and that can be used in vivo or in vitro in the study of membrane-associated CA.
Activation of neurosecretory cells by osmotic stimulation of anteroventral third ventricle
Authors: Honda K. , Negoro H. , Higuchi T. , Tadokoro Y.
Published: December 2017

Extracellular action potentials of paraventricular neurosecretory cells were obtained from urethan-anesthetized rats during microinjection of a hyper- or hypotonic solution into the anteroventral third ventricle (AV3V), third ventricle, or the vicinity of the recording site. The injection of a 0.2-microliter NaCl solution with a concentration range from 0.16 to 0.8 M into the AV3V excited most of the neurons tested. However, the magnitude of the response was dose related. In most cases, arterial blood pressure recorded simultaneously with the excitatory response of the neuron did not change after the injection. Distilled water (0.2 microliter) was injected into the AV3V after the intraperitoneal injection of a 1.5 M NaCl solution (1 ml), which decreased the firing rate in 67% of the neurons tested. The small volume (0.2 microliter) of hypertonic saline, which was effective when injected into the AV3V, excited none of the neurons tested when injected into the third ventricle or the vicinity of the recording site. These results strongly suggest that the AV3V is sensitive to the osmotic stimulus within a physiological range and that the region plays an important role as an osmoreceptor site for the osmoregulation of paraventricular neurosecretory cells.
Alpha-adrenergic receptor subtypes in the cerebral circulation of newborn piglets
Authors: Wagerle L. C. , Delivoria-Papadopoulos M.
Published: December 2017

The purpose of this study was to identify the alpha-adrenergic receptor subtype mediating cerebral vasoconstriction during sympathetic nerve stimulation in the newborn piglet. The effect of alpha 1- and alpha 2- antagonists prazosin and yohimbine on the cerebrovascular response to unilateral electrical stimulation (15 Hz, 15 V) of the superior cervical sympathetic trunk was studied in 25 newborn piglets. Regional cerebral blood flow was measured with tracer microspheres (15 +/- 1 micron). Sympathetic stimulation decreased blood flow to the ipsilateral cerebrum hippocampus, choroid plexus, and masseter muscle by 15 +/- 2, 10 +/- 2, 51 +/- 5, and 94 +/- 5%, respectively. alpha 1-Adrenergic receptor blockade with prazosin (0.5 mg/kg, n = 10) inhibited the sympathetic vasoconstriction in the cerebrum, hippocampus, and masseter muscle (7 +/- 2, 4 +/- 3, and 55 +/- 9%, respectively) and abolished it in the choroid plexus. alpha 2-Adrenergic receptor blockade with yohimbine (0.5 mg/kg, n = 6 and 1.0 mg/kg, n = 5) had no effect. Following the higher dose of yohimbine, however, blood flow to all brain regions was increased by approximately two-fold, possibly due to enhanced cerebral metabolism. These data demonstrate that vascular alpha 1-adrenergic receptors mediate vasoconstriction to neuroadrenergic stimulation in cerebral resistance vessels in the newborn piglet.
Nonisotonicity of simian eccrine primary sweat induced in vitro
Authors: Sato K. , Sato F.
Published: December 2017

Na+, K+, Cl-, and HCO-3 concentrations were determined in both methacholine (MCh)-induced and isoproterenol (ISO)-induced primary sweat collected directly from isolated and cannulated rhesus monkey palm eccrine secretory coils in vitro. Na+ concentration [( Na+]) of MCh-induced sweat was higher than that of the bathing medium by 4.2 mM, i.e., 155.4 vs. 151.2 mM. Sweat [Cl-] was consistently higher than that of the medium by 13.7 and 11.2 mM in both MCh- and ISO-induced primary fluid, respectively. The sweat-to-bath Cl- gradient increased as [Cl-] in the bath was lowered by substituting with less-permeable anions. In contrast sweat [HCO-3] was much lower in both MCh- and ISO-induced sweat than that of the bathing medium, i.e., approximately 6 mM in sweat vs. 25 mM in the bath. [K+] in MCh-induced primary sweat (mean of 6.63 mM) was consistently higher than that of the bathing medium (5 mM). Furthermore, [K+] tended to be the highest in the first sweat sample after MCh stimulation, reaching as high as 9 mM. In sharp contrast ISO-induced primary sweat showed [K+] that was almost always less than 5 mM with the mean of 4.03 mM. These electrolyte profiles of the primary fluid have been discussed relative to the transport model generally applied for Cl- secretory epithelia.
Changes in blood volume and plasma sodium concentration after water intake in rats
Authors: Nose H. , Sugimoto E. , Okuno T. , Morimoto T.
Published: December 2017

Changes in blood volume (BV) and Na+ concentration of plasma ([Na+]) were measured continuously during recovery from thermal dehydration in rats. At least 5 days prior to the experiments rats were cannulated into both the jugular vein and the descending aorta. After thermal dehydration (DBT: 36 degrees C, RH: 20%) amounting to approximately 6% of body wt, catheters were connected to a system for continuous monitoring of BV and [Na+]. Water was made available and water intake, BV, and [Na+] were recorded at 30-s intervals for 4 h. The rats took 2-3 ml of water/100 g of body wt in the first 10 min and then drank 1 ml at 30- to 60-min intervals to reach equilibrium in 2-3 h. The relations between water intake and delta BV and between delta[Na+] were analyzed for 2 h after the start of water supply. BV was unchanged until 18.9 +/- 3.6 min after access to water, whereas [Na+] started to decrease after 3.6 +/- 0.6 min. The retention ratio of ingested fluid in the vascular space was 20.8 +/- 2.8%, and the decrease of [Na+] was 1.5 +/- 0.2 meq X l-1 X ml ingested fluid-1 X 100 g body wt-1. These results indicate that drinking causes the change of [Na+] more rapidly than that of blood volume.
Differential effect of stimulation of nucleus ambiguus on atrial and ventricular rates
Authors: Thompson M. E. , Felsten G. , Yavorsky J. , Natelson B. H.
Published: December 2017

Acute experiments were performed on open-chest male mongrel dogs that were anesthetized with thiopental sodium and respired. An average of 10 penetrations per side was used to explore the rostral-caudal organization of the nucleus ambiguus (NA) and the area ventrolateral to it. Atrial pacing was performed on some trials to clarify the occurrence of atrioventricular (AV) block. In addition, the vagi were sectioned in some animals to confirm the peripheral pathway of the observed effects. Finally, the twin-pulse technique was used to classify the neurons underlying the observed effects according to their refractory periods. Stimulation in the area of the NA and lateral to it produced bradycardia and bradyarrhythmias without altering blood pressure. Stimulation of either the left or right NA produced slowing of both atrial and ventricular rates. However, slowing of the atrial rate was greatest with right NA stimulation, whereas slowing of the ventricular rate was predominant with left-side stimulation. The presence of AV block was evident from dropped QRS complexes with and without pacing. Vagotomy demonstrated that these effects were conducted by ipsilateral but not contralateral nerves. Measurement of the refractory periods showed that the neurons underlying both atrial and ventricular slowing were characteristic of B-fibers.
High-affinity substance P binding sites in rat esophagus plexus submucosus
Authors: Wiedermann C. J. , Sertl K. , Pert C. B.
Published: December 2017

Substance P receptors were investigated in rat esophagus using 125I-Bolton-Hunter substance P as a labeling probe. Autoradiographic studies show that esophageal submucosa contains clusters of high-affinity substance P binding sites [maximum binding (Bmax) 4.2 +/- 0.28 fmol/mg protein; dissociation constant (Kd) 0.1 +/- 0.01 X 10(9) M]. The receptor distribution pattern is typical for submucous neurons. These data suggest that substance P may act as a neurotransmitter in rat esophagus.
Circadian pacemaker interferes with sleep onset at specific times each day: role in insomnia
Authors: Strogatz S. H. , Kronauer R. E. , Czeisler C. A.
Published: December 2017

The human circadian pacemaker modulates our desire and ability to fall asleep at different times of day. To study this circadian component of sleep tendency, we have analyzed the sleep-wake patterns recorded from 15 free-running subjects in whom the sleep-wake cycle spontaneously desynchronized from the circadian rhythm of body temperature. The analysis indicates that the distribution of sleep onsets during free run is bimodal, with one peak at the temperature trough and, contrary to previous reports, a second peak 9-10 h later. Furthermore, there are two consistent zones in the circadian temperature cycle during which normal subjects rarely fall asleep. We hypothesize that this bimodal rhythm of sleep tendency, revealed under free-running conditions, maintains the same fixed phase relation to the circadian temperature cycle during 24-h entrainment. This would imply that normally entrained individuals should experience a peak of sleep tendency in the midafternoon and a zone of minimal sleep tendency approximately 1-3 h before habitual bedtime. Our temporal isolation data thereby account quantitatively for the timing of the afternoon siesta and suggest that malfunctions of the phasing of the circadian pacemaker may underlie the insomnia associated with sleep-scheduling disorders.
Effects of corticosterone on neurons of reticular formation in rats
Authors: Avanzino G. L. , Ermirio R. , Ruggeri P. , Cogo C. E.
Published: December 2017

The effects of microelectrophoretic application of corticosterone (CS) on single neurons of the brain stem reticular formation (RF) were investigated and then compared with the effects produced on the same neurons by intravenous administration of CS. The experiments were done in two groups of rats, one anesthetized with urethan and the other with pentobarbital sodium because these anesthetics cause different increases of basal concentration of plasma CS. Microelectrophoretic application of CS to neurons in the caudal portion of RF caused primarily excitatory effects, whereas inhibitory effects were observed in neurons of the rostral portion of the RF. The intravenous injection of CS (5 micrograms/100 g body wt) always produced the same effects as microelectrophoretic application. Under our experimental conditions the increase in plasma CS concentration produced by the intravenous injection of CS was found to be within the physiological range for the rat. The different anatomical distribution of units within the RF responding with either excitation or inhibition may be related to functional differences of the two RF areas.
Cholesterol content and water and solute permeabilities of kidney membranes from aging rats
Authors: Pratz J. , Ripoche P. , Corman B.
Published: December 2017

The influence of the age-related increase in cholesterol content of kidney brush-border membranes on their water and solute permeabilities was studied in 10- and 24-mo-old male Wistar rats. These permeabilities were determined from the rate of shrinkage and swelling of brush-border vesicles using a stopped-flow apparatus coupled to a light transmission recording. Despite a 20% rise in total cholesterol per milligram proteins, the osmotic water permeabilities of the vesicles were unchanged between 10 (287 +/- 40 micron/s) and 24 mo (270 +/- 31 micron/s). In contrast, passive diffusions of NaCl and KCl, but not of urea, thiourea, and glycerol, were reduced by 35% between 10 and 24 mo. These results suggest that an increase in cholesterol content of kidney brush-border membrane decreases its salt permeabilities without altering the water pathways.
Cardiovascular and metabolic responses to temperature in Coluber constrictor
Authors: Stinner J. N.
Published: December 2017

The cardiovascular adjustments associated with elevated metabolic demand caused by rising body temperature were investigated in Coluber constrictor. From 16 to 35 degrees C, O2 consumption increased roughly ninefold. Systemic blood flow, determined by the Fick method, increased approximately 4.5-fold and arteriovenous O2 difference increased approximately 2-fold. Heart rate steadily increased over the temperature range examined. At the cooler temperatures stroke volume also increased but, above approximately 25 degrees C, stroke volume declined with rising temperature. The changes in stroke volume may result from the direct effect of temperature on myocardial contractility. The thermal dependence of blood convection requirement in C. constrictor is similar to changes in air convection requirement determined in a previous study. Consequently the minute ventilation-to-perfusion ratio appears to be independent of temperature, at least from 20 to 35 degrees C. Systemic arterial blood pressure increases with rising body temperature due to the rise in cardiac output, whereas vascular resistance declines. Blood pressure in snakes disturbed by the investigator is roughly two times higher than in resting animals at all temperatures studied. This marked change in blood pressure suggests an "alarm reaction" mediated by the sympathetic nervous system.
Effect of stimulation of trigeminal ganglion on regional cerebral blood flow in cats
Authors: Goadsby P. J. , Duckworth J. W.
Published: December 2017

Regional cerebral blood flow was studied in the cat, with and without trigeminal ganglion stimulation, by the intravenous injection of the tracer [14C]iodoantipyrine and subsequent regional brain dissection. Electrical activation of the trigeminal ganglion led to a selective increase in regional blood flow in the frontal and parietal cortex that was bilateral without change in the posterior cortex, deep cerebral nuclei, white matter, or brain stem. Unilateral intracranial section of the facial nerve blocked the response in the ipsilateral frontal and parietal cortex, whereas bilateral facial nerve section blocked the contralateral frontal cortical response. The contralateral parietal cortical increase in blood flow was not affected by facial nerve section and may thus represent the result of metabolic activation of sensory cortex.
Effects of photoperiod on hibernation in castrated Turkish hamsters
Authors: Goldman B. D. , Darrow J. M.
Published: December 2017

Hibernation and circulating reproductive hormones [luteinizing hormone, follicle-stimulating hormone, and prolactin (LH, FSH, and PRL)] were studied for greater than 40 wk in castrated male Turkish hamsters (Mesocricetus brandti) housed in either a long-day cold or short-day cold environment. A significantly greater percentage of short-day animals hibernated than did long-day animals, indicating that short-day exposure can predispose Turkish hamsters to enter hibernation and that this photoperiodic effect cannot be explained entirely by the inhibitory influence of short days on testicular endocrine activity. Long-day castrates showed no significant changes in LH or FSH levels during the experiment. In the short-day castrates serum LH, FSH, and PRL levels were reduced after 4-9 wk and increased again after 18-23 wk of short-day exposure. The hibernation season ended after 30-34 wk on short days, several weeks later than in testis-intact males studied previously. These results indicate that gonadal factors are not required for the termination of hibernation but may influence its timing. The resumption of FSH secretion occurred no later during short-day exposure in castrated hibernators than in the preceding study of testis-intact, short-day males hibernating in the cold or those held at room temperature. Thus the endogenous timing mechanism regulating the reactivation of the hypothalamopituitary axis toward the end of the winter season is apparently gonad independent and is little affected by the low body temperatures experienced during hibernation.
Why do total-body decay curves of iodine-labeled proteins begin with a delay?
Authors: Regoeczi E.
Published: December 2017

The initial delay that occurs in total-body radiation curves reaching their single-exponential slopes was analyzed from 106 experiments involving several mammalian species (guinea pig, mouse, rabbit, and rat) and plasma proteins (alpha 1-acid glycoprotein, antithrombin III, fibrinogen, immunoglobulin G, and transferrin) in 14 different combinations. The time interval (Td) between injection and the intercept of the slope with the full-dose value was adopted as a measure of curve nonideality. The overall mean Td was 6.6 h, but individual values showed a significant correlation to protein half-lives, whereby proteins of unequal metabolic properties exhibited different mean Td values. Targeting protein to the liver abolished delay. Choice of the isotope (125I or 131I) and size of the labeled protein had no influence on the magnitude of delay. Whole-body radiation curves of animals that received [125I]iodotyrosines, Na131I, or 131I-polyvinylpyrrolidone exhibited no initial delays. These results do not support the earlier notion that delay is caused by a redistribution of the labeled protein in the body to radiometrically more favorable sites. However, they are compatible with the assumption that delayed passage of a protein dose through the extracellular matrix and/or retarded transfer of proteolytic products from extravascular catabolic sites to plasma may be responsible for the phenomenon.
Hypothalamus and sodium-potassium pump activity in skeletal muscles of DOCA-hypertensive rats
Authors: Katafuchi T. , Oomura Y. , Maruyama T. , Akaike N.
Published: December 2017

The effects of hypothalamic lesions on Na+ and K+ content ([Na+]i and [K+]i) in both slow tonic muscle [soleus (SOL)] and fast-twitch muscle [extensor digitorum longus (EDL)] were investigated in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. In DOCA-treated rats, [Na+]i was increased and [K+]i decreased in both SOL and EDL muscles compared with controls. Cellular K+ loss and Na+ accumulation in SOL were restored after tibial nerve sectioning (delta [Na+]i, -14.2 +/- 2.6 and delta [K+]i, 13.9 +/- 2.6 mmol/l fiber water (FW), n = 18, P less than 0.01) or bilateral lesioning of the ventromedial hypothalamic nucleus (VMH) (delta [Na+]i, -15.5 +/- 1.5 and delta [K+]i, 17.4 +/- 4.6 mmol/l FW, n = 6, P less than 0.01 and P less than 0.05). On the other hand, the anomalous electrolyte content in EDL was counteracted by lesions of anteroventral portion of the third ventricle (AV3V) (delta [Na+]i, -8.8 +/- 1.6 and delta [K+]i, 5.2 +/- 1.2 mmol/l FW, n = 6, P less than 0.01 and P less than 0.05) or paraventricular hypothalamic nucleus (PVN) (delta [Na+]i, -6.8 +/- 0.6 and 5.7 +/- 1.2 mmol/l FW, n = 6, P less than 0.01 and P less than 0.05), but aggravated by denervation (delta [Na+]i, 13.4 +/- 1.8 and delta [K+]i, -9.6 +/- 1.8 mmol/l FW, n = 18, P less than 0.01). These results suggest that there are at least two hypothalamic mechanisms of suppression of muscle Na-K pump activity in DOCA-hypertensive rats; i.e., neurally mediated inhibition in SOL by the VMH and, presumably, humorally mediated inhibition originating from the AV3V or PVN with greater influence in EDL.
Drinking, oropharyngeal signals, and inhibition of vasopressin secretion in dogs
Authors: Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

Ingestion of water leads to a rapid fall in plasma levels of vasopressin in 24-h water-deprived dogs. The rapid inhibition of vasopressin secretion is not due to absorption of water and dilution of plasma nor is it due to gastric distension. Blood pressure rises sharply during drinking, and this may provide the afferent signal leading to inhibition of vasopressin secretion. Other possibilities include a generalized increase in oropharyngeal motor activity or simply the sight of water. To test these hypotheses, 24-h water-deprived dogs were given either phenylephrine, to mimic the rise in blood pressure observed during drinking, offered canned meat, to induce oropharyngeal motor activity and swallowing, or presented with a bowl of water that was placed just out of reach. Administration of phenylephrine, ingestion of food, and the presence of water all caused increases in blood pressure, which were similar to the rise in blood pressure during drinking. However, none of these paradigms caused a fall in plasma vasopressin. In contrast, ingestion of water consistently led to a significant fall in plasma vasopressin, which was detectable within 3 min of drinking and well before changes in plasma osmolality. Therefore we conclude that the mechanism by which ingestion of water causes rapid inhibition of vasopressin secretion in dehydrated dogs cannot be dependent on a rise in blood pressure, a nonspecific increase in oropharyngeal motor activity, or the presence of water.
Effects of endogenous atrial natriuretic peptide released by rapid atrial pacing in dogs
Authors: Walsh K. P. , Williams T. D. , Canepa-Anson R. , Pitts E. , Lightman S. L. , Sutton R.
Published: December 2017

The relationships between the hemodynamic, renal, and endocrine changes induced by rapid atrial pacing were studied in seven chloralose-anesthetized greyhounds paced from the right atrial appendage for 60 min at 250 beats/min. Pacing increased mean pulmonary wedge pressure, decreased cardiac output, and decreased mean arterial pressure. Systemic vascular resistance did not change significantly. Coronary sinus atrial natriuretic peptide (ANP) concentrations rose maximally within 5 min of commencing pacing. The corresponding increase in arterial ANP concentrations during this time was only 44% of its maximum value after 30 min of pacing. Plasma concentrations of arginine vasopressin were unchanged. Plasma renin activity decreased during pacing and showed a marked rebound increase at 60 min postpacing. Plasma norepinephrine levels did not change significantly during pacing. Urine flow increased during the latter 30 min of pacing. There was no significant change in sodium clearance despite high sustained concentrations of ANP. The lack of significant natriuretic and systemic vasodilator effects in association with high arterial plasma concentrations of endogenous ANP, in the absence of antagonistic mechanisms, suggests that the natriuretic and vascular effects of ANP may not be its major physiological actions.
Cholecystokinin and gastric distension activate oxytocinergic cells in rat hypothalamus
Authors: Renaud L. P. , Tang M. , McCann M. J. , Stricker E. M. , Verbalis J. G.
Published: December 2017

Systemic administration of cholecystokinin octapeptide (CCK-8) prompts an abrupt increase in circulating levels of oxytocin (OXY) but not vasopressin (VP) in rats. The present study determined whether CCK-8 selectively stimulated OXY-secreting neurons in the hypothalamic supraoptic nucleus of pentobarbital-anesthetized male rats. Antidromically identified neurosecretory neurons were categorized into putative OXY- and VP-secreting cells on the basis of their firing patterns and response to peripheral baroreceptor activation. Of 36 OXY-secreting cells studied, 30 demonstrated a 50-200% increase in firing frequency within 2 min of administering CCK-8 by intravenous or intraperitoneal injection, whereas none of the eight VP-secreting neurons studied was activated. In related experiments, 4-10 ml of air were used to inflate an intragastric balloon in rats; 20 of 22 OXY-secreting neurons displayed an abrupt and readily reversible increase in firing frequency, whereas only 2 of 17 VP-secreting cells were activated. Gastric distension similarly elevated plasma OXY levels in unanesthetized rats with indwelling gastric cannulas. Together with previous findings that the effects of CCK-8 on OXY release were attenuated by gastric vagotomy, these observations clearly demonstrate the existence of a sensitive neural link between the stomach and the neurohypophysis in the rat.
Delayed recycling of plasma FFA in mice: revised model of turnover and oxidation
Authors: Baker N. , Gan-Elepano M. , Guthrie B. A. , Mead J. F.
Published: December 2017

We have reexamined the concept of the irreversible disposal rate (IDR) or fractional catabolic rate (FCR) in relation to the oxidation of a major metabolic fuel, plasma free fatty acids (FFA), in mice. We measured the disappearance of intravenously injected [1-14C]palmitate complexed to mouse serum albumin from the circulation of normal mice fed ad libitum and fasted approximately 4 h before tracer injection. We also measured the appearance of expired 14CO2 in the breath. Using multicompartmental analyses (SAAM) we found that, in contrast to earlier studies in this and other mammals where the estimated IDR has always been two to three times greater than the oxidative rate, the IDR (FCR) corresponded closely to the fractional rate of plasma FFA oxidation to CO2. This rate could be estimated accurately in a study of 10- to 15-min duration. In an extended study (5-h duration) we obtained kinetic evidence of a major transport pathway that involves delayed recycling of FFA through at least several unidentified relatively slowly turning compartments.
Vasoactive intestinal peptide stimulates ion transport in avian salt gland
Authors: Lowy R. J. , Schreiber J. H. , Ernst S. A.
Published: December 2017

Avian salt glands are considered to be under the control of cholinergic nerve fibers. Here we report evidence that vasoactive intestinal peptide (VIP) also regulates ion transport. Nerve fibers stained immunocytochemically with anti-VIP were distributed throughout the tissue within the peritubular connective tissue and were in close proximity to the secretory tubules. VIP applied to primary cultures of the secretory cells elicited active ion transport as assayed by short-circuit current (Isc) analysis. The mucosal-to-serosal positive Isc was produced in a dose-dependent fashion [(EC50) = 3.1 X 10(-9) M], was potentiated by theophylline, and was inhibited by either ouabain or furosemide. This Isc was independent of activation by cholinergic agonists. VIP also increased ouabain-sensitive respiration 14-18% in acutely isolated cells from salt-stressed and unstressed animals. These data demonstrate for the first time that VIP is present in the avian salt gland and can act as a secretagogue by directly affecting the secretory cells. In addition, the results provide evidence for direct control of ion transport by an adenosine 3',5'-cyclic monophosphate-linked neurohormone in both adult unstressed and fully salt-stressed animals.
Angiotensin II sensitization of aldosterone responsiveness to plasma sodium in conscious dogs
Authors: Merrill D. C. , Skelton M. M. , Cowley A. W.
Published: December 2017

Studies were performed to quantify the interaction of angiotensin II (ANG II) and plasma sodium (Na+) on the adrenal gland's ability to secrete aldosterone (Aldo). Two groups of normal conscious dogs were used in which plasma Na+ was independently elevated in the face of differing background levels of ANG II. In group 1 (n = 6), plasma Na+ was increased progressively over a 1-h period (from 143 +/- 1 to 152 +/- 1.2 meq/l), whereas plasma K+ was maintained at a constant level by intravenous infusion. With low background levels of ANG II (0.5 ng.kg-1.min-1), plasma Aldo remained unchanged with the increase in plasma Na+. With high ANG II (20.0 ng.kg-1.min-1), plasma Na+ changed in a similar manner (143.1 +/- 1.2 to 154.3 +/- 0.7 meq/l), whereas plasma Aldo decreased progressively from 35.3 +/- 2.3 to 27.9 +/- 3.8 ng/dl (P less than 0.05). In group 2 (n = 5), plasma Na+ was increased abruptly (144.9 +/- 0.6 to 152.1 +/- 0.5) and maintained at the elevated level for 3 h, and plasma K+ was held constant. Again, at low steady-state levels of ANG II (0.5 ng.kg-1.min-1), plasma Aldo levels remained unchanged. But, at intermediate levels of ANG II (5.0 ng-kg-1.min-1), producing plasma ANG II levels similar to those seen with dietary NaCl restriction, plasma Aldo decreased from 20.4 +/- 4.3 to 9.0 +/- 1.3 ng/dl (P less than 0.05). This rate of infused ANG II has been shown to result in plasma ANG II levels similar to that seen with dietary NaCl restriction. At the highest dose of ANG II (20 ng.kg-1.min-1), the ability of plasma Na+ to lower plasma Aldo was blunted to the extent that the decrease from 27.5 +/- 2.2 to 21.3 +/- 1.6 was not statistically significant. These studies indicate that physiological elevation of ANG II appears to sensitize the adrenal aldosterone responsiveness to changes in plasma Na+.
Effects of hypoxia and hypercapnia on VT, f, and VI of nestling and adult bank swallows
Authors: Colby C. , Kilgore D. L. , Howe S.
Published: December 2017

The effects of hypoxia, hypercapnia, and hypoxic hypercapnia on ventilation, and breathing pattern in adult and nestling bank swallows (Riparia riparia) were assessed. The CO2 threshold above which inhaled minute volume (VI) increased significantly in adults and nestlings was 0.045. At each level of fractional concentration of inspired CO2 (FICO2), ventilation in nestlings was lower than that in adults. At a FICO2 of 0.09, VI of adults increased by 284%, whereas VI in nestlings changed 238%. Adult bank swallows also showed a blunted ventilatory response to hypoxia, and the nestling's response was similar to other birds. Adults exhibited greater changes in VI at all levels of hypoxic hypercapnia compared with nestlings. Combined hypoxic and hypercapnic stimuli had an additive effect on ventilation in both groups. Chronic exposure of nestlings to the hypercapnia and hypoxia within burrows seems to significantly alter their ventilatory response to these respiratory stimuli.
Circulating interleukin 1 and tumor necrosis factor during inflammation
Authors: Moldawer L. L. , Gelin J. , Schersten T. , Lundholm K. G.
Published: December 2017

It is proposed that interleukin 1 (IL 1) and tumor necrosis factor (TNF) alpha play central roles in the host's response to inflammation. Yet circulating concentrations have not been frequently measured in many inflammatory states. Serum levels of IL 1 and TNF were evaluated in mice with a tumor, sterile inflammation, endotoxinemia, or generalized peritonitis where an acute-phase protein response was documented. In tumor-bearing mice, no IL 1 or TNF could be detected despite marked increases in the serum concentration of the acute-phase reactant protein, amyloid P. In mice with peritonitis, induced by cecal ligation and perforation, or a turpentine-induced subcutaneous abscess, IL 1 but not TNF could be detected in the serum. Only expansion of the reticuloendothelial system with Corynebacterium parvum and subsequent challenge with endotoxin resulted in serum TNF appearance. The failure to observe IL 1 or TNF in any of the disorders could not be explained by inhibitors. Rather, the data suggest that a hepatic acute-phase protein response can occur during inflammatory states without the appearance of either IL 1 or TNF in the circulation. Circulating levels of both monokines do not appear to be a universal finding in inflammation.
Cat diencephalic neurons with sympathetic nerve-related activity
Authors: Varner K. J. , Barman S. M. , Gebber G. L.
Published: December 2017

In a companion paper, we demonstrated that hypothalamic or medial thalamic lesions attenuate the reduction in inferior cardiac postganglionic sympathetic nerve discharge (SND) produced by decerebration in the anesthetized cat [Huang et al., Am. J. Physiol. 254 (Regulatory Integrative Comp. Physiol. 23): R249-R256, 1988]. This raised the possibility that these diencephalic regions contain the cell bodies of neurons that contribute to SND. The current study tested this possibility in cats anesthetized with alpha-chloralose. Spike-triggered averaging of inferior cardiac SND revealed the existence of two types of hypothalamic and medial thalamic neurons with sympathetic nerve-related activity. Recordings were made from the soma-dendritic region of these neurons, since an inflection often appeared on the rising phase of the unit action potential. The activity of type 1 neurons was synchronized to an aperiodic spikelike event in SND, whereas that of type 2 neurons was synchronized to a 2- to 6-Hz rhythmic component. Some of the type 2 neurons but none of the type 1 neurons had cardiac-related activity. Microstimulation at type 1 and type 2 unit recording sites increased SND. Our results are consistent with the possibility that hypothalamic and medial thalamic neurons contribute to the rhythmic and aperiodic components of SND in the anesthetized cat.
Locus coeruleus monoaminergic activity and plasma corticotropin after hemorrhage in cats
Authors: Thrivikraman K. V. , Carlson D. E. , Gann D. S.
Published: December 2017

Temporal changes in monoaminergic activity in the locus coeruleus (LC) in response to hemorrhage of 10 or 20% of blood volume were assessed using normal pulse voltammetry in alpha-chloralose-urethan-anesthetized cats. Oxidation current was measured with a carbon microelectrode, and changes at 230 and 450 mV were used as estimates of catecholaminergic and indolaminergic activity, respectively. Plasma adrenocorticotropin (ACTH) was measured by radioimmunoassay. Hemorrhage of 20% blood volume caused a transient increase in the catecholaminergic activity in a compact area in the ventral LC (vLC) that preceded increases in the plasma ACTH. The increase in oxidation current at 450 mV was similar to that at 230 mV, suggesting no significant contribution from indolamines. Dorsal rostral pontine sites outside this area exhibited either sustained decreases in oxidation current or no change in response to hemorrhage. The proportion of sites that exhibited transient increases in oxidation current in the vLC after the 10% blood loss was less than that after the 20% blood loss, suggesting that this response was dependent on the magnitude of hemorrhage. Since the LC was implicated previously in the control of ACTH release, we suggest that hemodynamic signals traversing the LC activate catecholaminergic mechanisms that, in turn, participate in the regulation of ACTH release after hemorrhage.
Homeostatic potassium excretion in fed and fasted sheep
Authors: Rabinowitz L. , Green D. M. , Sarason R. L. , Yamauchi H.
Published: December 2017

In unanesthetized adult sheep, following intake of a daily meal, there was a peak in K excretion. The maximum and minimum rates of K excretion following meals were directly related to meal K content. On days without meals, no peak in K excretion occurred. Changes in K excretion on fed and fast days occurred without changes in the low levels of plasma aldosterone and were poorly correlated with urine or blood pH, urine flow rate, Na excretion, or the filtered load of K, but they correlated well with fractional K excretion. Plasma K did not change on fast days. Plasma K increased on some, but not all, fed days. Increases in plasma K that occurred on fed days were insufficient to account for the concurrent kaliuresis. Infusion of aldosterone or isotonic NaCl failed to alter K excretion in fed or fasted sheep. Infusion of isotonic NaCl + aldosterone hypertonic Na2SO4 + aldosterone increased K excretion in fasted but not fed sheep. Infusion of K in the rumen of fed and fasted sheep elevated rumen K concentration and led to increases in K excretion that could not be explained by increases in plasma K. The mechanisms responsible for the homeostatic changes in K excretion on fed and fast days were not ascertained but may importantly depend on sensors of enteric K content.
Enhanced vascular effects of cyclic GMP in septic rat aorta
Authors: McKenna T. M.
Published: December 2017

The modulation of vascular function by guanosine 3',5'-cyclic monophosphate (cGMP) in sepsis was examined in isolated rat aortas. Basal cGMP content was similar in aortas from sham-operated [3.6 +/- 0.8 (SE) pmol cGMP/mg protein] and from septic (3.2 +/- 1.0) rats. Acetylcholine-induced increases in cGMP content were significantly greater in aortas from sham (109.7 +/- 31.1) than aortas from septic rats (42.1 +/- 10.6). Maximal contractile performance by aortas from septic rats was impaired whether contractions were induced by the alpha 1-receptor agonist norepinephrine (497 +/- 49 mg tension/mg tissue vs. sham 749 +/- 43) or by KCl depolarization (265 +/- 31 vs. sham 613 +/- 79). Aortas from septic rats also exhibited a rightward-shifted dose response to norepinephrine. Inhibition of endogenous cGMP production by myoglobin or methylene blue treatment disproportionally improved responses by aortas from septic rats to both norepinephrine and KCl. In contrast, exposure of aortas to exogenous 8-bromo-cGMP engaged exaggerated vasodilatory responses in tissue from septic animals. Aortas from sham and septic rats contracted equally to stimulation by phorbol 12,13-dibutyrate. These findings indicate that reduced vascular contraction in sepsis is not mediated by altered cGMP levels, but rather that enhanced sensitivity to effects of cGMP may contribute to the disorder.
Enhanced fever following castration: possible involvement of brain arginine vasopressin
Authors: Pittman Q. J. , Malkinson T. J. , Kasting N. W. , Veale W. L.
Published: December 2017

Arginine vasopressin (AVP) is thought to act as an antipyretic in the ventral-septal area (VSA) of the brain. As AVP content of this area has been shown to be virtually eliminated following long-term castration, we have tested the hypothesis that castrated rats would display enhanced fevers. Four months after castration (or sham castration), male Wistar rats were given prostaglandin E1 (200 ng), purified interleukin 1 (25 U), or saline (5 microliters) into a lateral cerebral ventricle. Castrated rats displayed fevers of longer duration, reflected as significantly enhanced thermal indexes, than did age-matched sham-operated controls. Castrated rats also were less able to defend their body temperatures to ambient heat stress but not to ambient cold. AVP content of VSA and lateral septum, but not of hippocampus, of castrated rats was significantly reduced; oxytocin content of the three areas was unchanged following castration. These data support earlier studies concerning effects of castration on septal AVP content and are consistent with the possibility that AVP is an antipyretic in the VSA of the rat.
Renal vascular response to combined hypoxia and hypercapnia in conscious rats
Authors: Walker B. R. , Brizzee B. L.
Published: December 2017

Experiments were performed to test for a possible role of arginine vasopressin (AVP) in the renal vascular responses to the combination of hypoxia and varying levels of CO2 in the conscious rat. Animals were instrumented with pulsed Doppler flow probes on the left renal artery and with arterial and venous catheters. Renal blood flow (RBF) and mean arterial blood pressure (MABP) were determined in conscious, unrestrained rats under the following conditions: 1) hypocapnic hypoxia [arterial PO2 (PaO2) = 26 Torr; arterial PCO2 (PaCO2) = 21 Torr]; 2) isocapnic hypoxia (PaO2 = 34 Torr; PaCO2 = 36 Torr); 3) hypercapnic hypoxia (PaO2 = 42 Torr; PaCO2 = 57 Torr); and 4) room air control (PaO2 = 93 Torr; PaCO2 = 38 Torr). MABP fell from 104 +/- 2 to 83 +/- 5 mmHg during hypocapnic hypoxia but was unaffected by the other stimuli. RBF was significantly reduced by both hypocapnic and hypercapnic hypoxia and unchanged in the other protocols, whereas renal vascular resistance (RVR) was elevated only in the hypercapnic hypoxia group. Additional experiments were performed to test whether activation of V1-vasopressinergic receptors during hypoxia might mediate the observed changes in renal hemodynamics. Experiments were performed as before except that at the midpoint of hypoxic or room air exposure, 10 micrograms/kg of the specific V1 vasopressinergic antagonist d(CH2)5Tyr(Me)AVP was administered. However, administration of the V1 antagonist had no effect on the observed renal hemodynamic responses to hypoxia. Therefore, although intense chemoreceptor stimulation by hypercapnic hypoxia may increase RVR and decrease renal perfusion, these renal hemodynamic responses do not appear to be mediated by increased circulating levels of AVP.
Gastric and nongastric mechanisms for satiety action of cholecystokinin
Authors: Moran T. H. , McHugh P. R.
Published: December 2017

The quantitative relationship between cholecystokinin's (CCK) inhibitory actions on gastric emptying and feeding was examined in rats. CCK (1, 2, 4, or 8 micrograms/kg) inhibited both the gastric emptying (determined by the dye dilution method) and ingestion of a 0.5-kcal/ml glucose solution in a 30-min testing period in 20-h deprived male Sprague-Dawley rats. Comparisons of the inhibitions of gastric emptying and feeding across the dose range of CCK revealed two components of CCK satiety: one defined by a linear relationship between the gastric inhibitory and feeding inhibitory actions of CCK through a dose range of 1-4 micrograms/kg, which accounted for 64% of the variability in the satiety action of CCK, and a second that appeared to be independent of the gastric inhibitory action of CCK.
An analogue of thyrotropin-releasing hormone improves outcome after brain injury: 31P-NMR studies
Authors: McIntosh T. K. , Vink R. , Faden A. I.
Published: December 2017

The effects of a long-acting, centrally active thyrotropin-releasing hormone (TRH) analogue, CG3703, on neurological outcome, survival, and intracellular metabolism were evaluated after experimental fluid-percussion (FP) brain injury (2.0-2.4 atm) in the rat. In control (saline-treated) animals, FP brain injury caused a fall in mean arterial pressure (MAP) and resulted in a 58% mortality rate. Surviving control animals showed a pronounced neurological deficit over the following 4-wk period. Administration of CG3703 at 30 min posttrauma significantly increased MAP (mean increase, 21 mmHg). All animals treated with CG3703 survived and demonstrated significantly improved chronic neurological scores compared with saline-treated controls. In a subpopulation of injured animals, phosphorus magnetic resonance spectroscopy (31P-MRS) was used to evaluate changes in brain intracellular metabolism after trauma in control and CG3703-treated animals. A fall in phosphocreatine-to-inorganic phosphate ratio (PCr/Pi) was observed in all animals after FP injury. The PCr/Pi ratio failed to recover in saline controls but demonstrated significant recovery in CG3703-treated animals. Furthermore, an increased phosphomonoester peak was observed after CG3703 but not after saline administration. These results suggest that the centrally active TRH analogue CG3703 can improve neurological outcome and survival after brain injury, perhaps through direct effects on cerebral metabolism.