bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractal properties in fetal breathing dynamics
Authors: Szeto H. H. , Cheng P. Y. , Decena J. A. , Cheng Y. , Wu D. L. , Dwyer G.
Published: December 2017

The dynamic pattern of fetal breathing was studied in 17 fetal lambs with chronically implanted electromyographic electrodes in the diaphragm. The instantaneous breathing rate time series appeared similar on different time scales, with clusters of faster breathing rates interspersed with periods of relative quiescience, suggesting self-similarity. Distribution histograms of the interbreath intervals (IBIs) showed log-normal distribution for IBIs less than 1 s and inverse power-law distribution for IBIs greater than 1 s. The ratio of log-normal distribution to power-law distribution varied from approximately 2 at 102 days to approximately 30 by 130 days of gestation. Fast Fourier transform of the breathing rate time series revealed 1/f beta power spectra for all animals, with beta increasing linearly from 0.43 to 0.88 between 102 and 139 days. Studies in the newborn lamb showed further maturation in both the distribution characteristics of the IBIs, as well as in the 1/f power spectra, with beta approaching 1.0 at 2 days after birth. The inverse power-law relationship in the distribution of the IBIs, together with the 1/f beta power spectra, indicate scale invariance and suggest that fractal mechanisms are involved in the regulation of fetal breathing.
Properties and localization of endothelin-1-specific receptors in rat testicles
Authors: Sakaguchi H. , Kozuka M. , Hirose S. , Ito T. , Hagiwara H.
Published: December 2017

The characterization and localization of rat testicular endothelin receptors were studied. Receptor binding assay with radiolabeled members of the endothelin family revealed that endothelin-1-specific receptors were present in rat testes; a maximal binding capacity of 250 +/- 62 fmol/mg protein and a dissociation constant value of 0.35 +/- 0.06 nM were calculated from the Scatchard plot. The affinities for endothelin analogues were endothelin-1 = endothelin-2 much greater than endothelin-3 much greater big endothelin-1 for the membrane-bound receptors. Receptors of endothelin-1 were localized in peritubular myoid cells and interstitial cells of rat testis by 125I-labeled endothelin-1 autoradiography; the receptors were undetectable in spermatogenic cells. The presence of endothelin-1 receptors in the rat testis raises the possibility that one or more of the endothelins may play a physiological role in the regulation of testicular function.
Healing of intestinal anastomoses in adrenalectomized rats given corticosterone
Authors: Matsusue S. , Walser M.
Published: December 2017

To determine the effect of physiological variations in glucocorticoid levels on wound healing, adrenalectomized rats, implanted with corticosterone pellets of varying concentrations, and sham-operated rats were subjected to ileal transection followed by end-to-end anastomosis. Adrenalectomized animals with plasma corticosterone levels less than 2.5 micrograms/dl suffered 25% mortality. In rats surviving 1 wk, bursting pressure of the anastomotic site was measured as an index of wound healing. At plasma corticosterone levels of 3.9-7.4 micrograms/dl, which approximate normal physiological levels, bursting pressure was not significantly different from that in sham-adrenalectomized animals. In adrenalectomized rats with lower or higher corticosterone levels, bursting pressure was significantly reduced. Thus a narrow range of plasma corticosterone is required for optimal wound healing in this model; higher values tend to impair healing, as do subnormal values, perhaps because of slower protein turnover; low values also lead to high mortality.
Composition and mechanics of mesenteric resistance arteries from pregnant rats
Authors: Mackey K. , Meyer M. C. , Stirewalt W. S. , Starcher B. C. , McLaughlin M. K.
Published: December 2017

We tested the hypothesis that the systemic resistance vasculature of the rat is remodeled during pregnancy as evidenced by significant alterations in the passive mechanical properties and extracellular matrix proteins in mesenteric arteries. Mechanical characteristics were determined for arteries from 20-day pregnant rats (n = 6) and age-matched controls (n = 5). Lumen diameter and wall thickness were measured in pressurized arteries (250-microns diameter) using a dimension analyzing system. Distensibility (the relative change in diameter per unit change in pressure) was less in the arteries from the pregnant rats (P less than 0.01). The calculated stress-strain relationships and elastic moduli indicated that the arteries were less stiff by late gestation (P less than 0.05). Ultramicro amino acid analysis and radioimmunoassay were used to measure hydroxyproline, desmosine, and leucine as indicators of collagen, elastin, and total protein, respectively, in similar-sized arteries. Hydroxyproline/leucine (index of collagen) and desmosine/leucine (elastin concentration) decreased 19 and 15% by late gestation (P less than 0.05). The significant alterations in passive mechanics and in extracellular protein content support the concept that arterial wall remodeling in the peripheral vasculature may be one component of the cardiovascular adaptations during pregnancy.
Midbrain central gray: influence on medullary sympathoexcitatory neurons and the baroreflex in rats
Authors: Verberne A. J. , Guyenet P. G.
Published: December 2017

The influence of the central gray (CG) of the midbrain on the activity of 19 barosensitive sympathoexcitatory neurons of the rostral ventrolateral medulla (RVLM) and on the sympathetic vasomotor baroreflex was studied in halothane-anesthetized rats. Eighteen RVLM barosensitive units were readily activated by train stimulation of the CG, although twin-pulse stimulation was less effective (10 of 19 neurons responded). Inhibition of neurons within the RVLM by bilateral microinjection of the GABA-mimetic drug muscimol abolished the pressor responses to CG stimulation, while the accompanying lumbar nerve sympathoexcitation was converted to sympathoinhibition. In baroreceptor-denervated vagotomized animals, unilateral microinjection of muscimol into the RVLM ipsilateral or contralateral to the site of CG stimulation resulted in approximately equal attenuation of the CG sympathoexcitatory and pressor responses. In contrast, the sympathoexcitatory response to electrical stimulation of the sciatic nerve was reduced more effectively by inhibition of the RVLM contralateral to the site of stimulation. Electrical stimulation of the CG lateral and ventrolateral to the aqueduct produced sympathoexcitation [increased discharge of the greater splanchnic and lumbar sympathetic nerves (SSN and LSN)] with an increase in mean arterial blood pressure. Activation of the SSN by CG stimulation was greater than that observed for the LSN (n = 5 rats). This differential influence of the CG on the sympathetic outflow was not a result of a differential influence of the baroreflex. Electrical stimulation of the CG produced elevations of the gain and the cut-off pressure of the baroreflex for both the SSN and LSN.(ABSTRACT TRUNCATED AT 250 WORDS)
Adrenergic regulation of neonatal brown fat adenylyl cyclase and Gs alpha activity
Authors: Chaudhry A. , Granneman J. G.
Published: December 2017

Norepinephrine (NE)-stimulated adenylyl cyclase (AC) activity increases during the perinatal period in rat brown adipose tissue (BAT), and this increase is associated with changes in the activities of both the catalytic subunit (C) and Gs alpha, the GTP-binding protein that mediates activation of C. The present study examined the role of the sympathetic nervous system in the postnatal sensitization of AC. The sympathetic innervation of BAT increased 7- to 13-fold after birth, and this increase was temporally correlated with the postnatal enhancement of AC responsiveness. 6-hydroxydopamine (6-HDA) treatment of neonates reduced tyrosine hydroxylase levels by greater than 90%. This treatment greatly reduced the perinatal increase in NE- and NaF-stimulated AC and completely abolished the increase in forskolin-Mn(2+)-stimulated activity. However, sympathectomy did not alter the postnatal increase in Gs alpha-specific activity and did not prevent the postnatal reduction in Gs alpha levels. These results demonstrate that the sympathetic innervation of BAT develops fully after birth and is essential for the postnatal increase in the activity of C but not of Gs alpha.
Endothelium-derived relaxing factor in pulmonary and renal circulations during hypoxia
Authors: Perrella M. A. , Edell E. S. , Krowka M. J. , Cortese D. A. , Burnett J. C.
Published: December 2017

The pulmonary and renal vasculatures, in contrast to the systemic vasculature, constrict during hypoxia. The endothelium has been implicated in mediating these vascular responses to acute hypoxia via the production of endothelium-derived vasoactive factors. The present study, performed in anesthetized dogs, was designed to investigate the role of endothelium-derived relaxing factor (EDRF) to attenuate the vasoconstrictor response of the pulmonary and renal circulations during acute hypoxia. In response to hypoxia, pulmonary (2.2 +/- 0.3 to 4.5 +/- 0.6 mmHg.l-1.min) and renal (0.60 +/- 0.07 to 0.90 +/- 0.14 mmHg.ml-1.min) vascular resistances increased. Inhibition of endogenous EDRF with NG-monomethyl-L-arginine resulted in similar increases in pulmonary (3.0 +/- 0.1 to 4.8 +/- 0.4 mmHg.l-1.min) and renal (0.67 +/- 0.07 to 0.90 +/- 0.09 mmHg.ml-1.min) vascular resistances as in hypoxia. However, in the presence of both hypoxia and EDRF inhibition, an exaggerated pulmonary vascular response was observed (2.2 +/- 0.2 to 7.4 +/- 0.9 mmHg.l-1.min), in contrast to the renal vascular response to EDRF inhibition during hypoxia (0.61 +/- 0.05 to 0.95 +/- 0.10 mmHg.ml-1.min), which was not different from hypoxia or EDRF inhibition individually. The endothelium-derived contracting factor endothelin, which modestly increased during hypoxia (11.7 +/- 1.9 to 15.6 +/- 2.4 pg/ml), may also contribute to this vasoconstrictive response to hypoxia. This study suggests in the intact animal that EDRF serves to oppose the pulmonary vasoconstrictor response to hypoxia and further characterizes the role of endothelium-derived factors in the regulation of vascular function during hypoxia.
Divergent effects of intravenous GSH and cysteine on renal and hepatic GSH
Authors: Aebi S. , Lauterburg B. H.
Published: December 2017

There is a growing interest in the therapeutic use of sulfhydryls. To assess the effect of glutathione (GSH) and cysteine on the cellular thiol status, thiols were administered intravenously to rats in doses ranging from 1.67 to 8.35 mmol/kg with and without pretreatment with 4 mmol/kg buthionine-[S,R]-sulfoximine (BSO), an inhibitor of GSH synthesis. One hour after administration of 1.67 mmol/kg GSH, the concentration of GSH rose from 5.2 +/- 1.0 to 8.4 +/- 0.9 mumol/g and from 2.5 +/- 0.5 to 3.7 +/- 0.7 mumol/g in liver and kidneys, respectively. After 8.35 mmol/kg, hepatic GSH did not increase further, but renal GSH rose to 6.7 +/- 1.8 mumol/g. Infusion of cysteine increased hepatic GSH to the same extent as intravenous GSH, but renal GSH did not increase after 1.67 mmol/kg and even significantly decreased to 0.6 +/- 0.2 mumol/g after 8.35 mmol/kg. In the presence of BSO, GSH resulted in a significant increase in renal but not hepatic GSH, suggesting that the kidneys take up intact GSH and indicating that the increment in hepatic GSH was due to de novo synthesis. The present data show that hepatic GSH can be markedly increased in vivo by increasing the supply of cysteine. Measurements of hepatic cysteine indicate that up to a concentration of approximately 0.5 mumol/g cysteine is a key determinant of hepatic GSH, such that the physiological steady-state concentration of GSH in the liver appears to be mainly determined by the availability of cysteine. At higher concentrations GSH does not increase further, possibly due to feedback inhibition of GSH synthesis or increased efflux.(ABSTRACT TRUNCATED AT 250 WORDS)
Bile is essential for lipid assimilation in Leach's storm petrel, Oceanodroma leucorhoa
Authors: Place A. R.
Published: December 2017

A tritium-labeled glycerol triether was tested as a non-absorbable lipid marker for studies of neutral lipid absorption in normal and cholestryamine-induced steatorrhic chicks of Leach's storm petrel (Oceanodroma leucorhoa). Absorption of triacylglycerol and wax ester (96 +/- 4.2 and 94 +/- 2.1%, respectively) in normal chicks was indistinguishable. Absorption of neutral lipids decreased with increasing quantities of resin, and with the highest dosage (14% wt/wt) less than 30% of dietary lipids were assimilated. The concentration of bile salts (greater than 500 mM) in the gallbladder of Leach's storm petrel is among the highest recorded. The bile salts are predominantly taurine conjugates of chenodeoxycholate and cholate. Biliary cholesterol levels are within the range observed in humans although biliary phospholipid levels are lower and triglyceride levels are higher. Extensive retrograde movement of duodenal contents and biliary secretions to the gizzard and proventriculus were found. Although similarities in fat and bile salt assimilation exist between seabirds and mammals, there do exist differences that make non-polar lipid assimilation (i.e., wax esters) more efficient in seabirds.
Baroreflex control of arterial blood pressure during involuntary diving in ducks (Anas platyrhynchos var.)
Authors: Smith F. M. , Jones D. R.
Published: December 2017

The dynamic role of arterial baroreceptors in control of mean arterial blood pressure (MAP), heart rate (HR), cardiac output (CO), hindlimb vascular (HLVR) and total peripheral (TPR) resistance responses to forced dives was investigated in acutely and chronically barodenervated ducks. To activate the baroreflex, the proximal end of one aortic nerve was stimulated electrically with bipolar electrodes that had been implanted under pentobarbital sodium anesthesia. Predive nerve stimulation caused CO to fall (by reducing HR; stroke volume remained constant), producing a decrease in MAP to half the prestimulation level. During diving (for 2.5-min periods) nerve stimulation did not affect HR and MAP after the first minute of submersion. Neither HLVR nor TPR contributed to the fall in MAP during aortic nerve stimulation before or during diving. The effects of nerve stimulation on HR and MAP were maintained to the end of dives in animals given 100% O2 to breathe before diving. In separate experiments, increasing arterial chemoreceptor input by perfusing one vascularly isolated carotid body with venous blood caused a reduction in the effects of aortic nerve stimulation on MAP. Arterial baroreceptors may thus act on HR to alter MAP early in the dive, but as the dive progresses the baroreflex is attenuated by an increase in peripheral chemoreceptor drive.
Stress in birds due to routine handling and a technique to avoid it
Authors: Le Maho Y. , Karmann H. , Briot D. , Handrich Y. , Robin J. P. , Mioskowski E. , Cherel Y. , Farni J.
Published: December 2017

The stress that might result in animals from the routine handling that most experimental studies involve, e.g., weighing, injecting, and blood sampling, is usually assumed to be minimal when the animals look quiet. However, the intensity of this stress remains largely ignored. We have developed a system that allows blood samples to be taken from freely behaving geese without entering the animal room. In these entirely undisturbed geese, the humoral indexes of stress, i.e., blood levels of catecholamines, corticosterone, and lactate, were as low or even lower than the lowest values previously reported for birds. Remarkably, the mean basal values for epinephrine and norepinephrine were 90-fold and 5-fold, respectively, below the lowest values in the literature. Stress-induced variations in pH that would have concealed detection of nutrition-induced changes in pH were eliminated. In contrast, even though the birds looked quiet during a short 5-min routine handling procedure, to which they had been accustomed for weeks, there was a dramatic increase in the level of humoral indexes of stress. These increased severalfold within only 2 min, and the return to initial values could take up to 1 h. Acid-base balance was also disrupted. Thus, in studies on animals, the absence of stress cannot be deduced from only behavioral observations. Only a system for taking blood without human interference may enable stress-free investigations.
Cerebrovascular and coronary effects of endothelin-1 in the goat
Authors: Dieguez G. , Garcia J. L. , Fernandez N. , Garcia-Villalon A. L. , Monge L. , Gomez B.
Published: December 2017

In vivo and in vitro effects of endothelin-1 (ET-1) on cerebral and coronary vasculature of goats were examined and compared. In six anesthetized goats intravenous injections of ET-1 (0.1-0.8 nmol) increased arterial pressure, did not change the middle cerebral (MCA) and left anterior descending or left circumflex coronary (LCC) arterial blood flows (electromagnetically measured), and increased cerebral and coronary vascular resistances. In four other anesthetized goats intra-arterial injections of ET-1 (0.01-0.3 nmol) decreased the MCA flow less than the LCC flow (maximal reduction was 20 and 80%, respectively) and only the highest dose increased arterial pressure. In isolated segments from large arteries ET-1 (10(-11) to 10(-7) M) caused concentration-dependent isometric contractions, the concentration causing 50% of the maximal effect and the maximal contraction being lower in cerebral arteries than in coronary arteries. The in vitro reactivity of both arteries was unaffected by endothelium removal or by indomethacin (10(-5) M). Therefore ET-1 produces cerebral and coronary vasoconstriction in vivo and in vitro, probably by acting directly on vascular musculature. Although the sensitivity is higher in isolated cerebral arteries than in coronary arteries, the reactivity in vivo could be lower in the cerebral circulation than in the coronary circulation to this endothelium-derived peptide.
Interleukin-1 stimulates aldosterone secretion: involvement of renin, ACTH, and prostaglandins
Authors: Bataillard A. , del Rey A. , Klusman I. , Arditi G. M. , Besedovsky H. O.
Published: December 2017

Interleukin-1 (IL-1), a cytokine produced during infection and inflammation, mediates some of the endocrinological alterations that parallel these processes. The purpose of this study was to determine whether human recombinant IL-1 (hrIL-1) affects aldosterone output as well as renin and adrenocorticotropic hormone (ACTH) release, two key factors in the regulation of mineralocorticoid secretion. We observed that intravenous administration of hrIL-1 into conscious unrestrained rats elicited a marked and rapid rise in aldosterone plasma levels in a dose-dependent manner. The hrIL-1-induced increase in aldosterone levels was associated with enhanced renin activity and increased ACTH levels in plasma. Furthermore, aldosterone levels of IL-1-injected rats were positively correlated with plasma renin activity (PRA), suggesting that the renin-angiotensin system contributes to the changes observed in the levels of the mineralocorticoid hormone. ACTH seems also to be implicated in the aldosterone response to hrIL-1 because the profile of the kinetic curves of changes in the levels of the pituitary hormone and aldosterone was similar. Pretreatment with the cyclooxygenase inhibitor indomethacin markedly reduced the increase in aldosterone plasma levels and PRA induced by IL-1, indicating that prostaglandins are involved in these effects of the cytokine. These results suggest that IL-1 may play an important role in the control of homeostasis during infectious and inflammatory diseases.
Membrane and synaptic activity during anoxia in the isolated turtle cerebellum
Authors: Perez-Pinzon M. A. , Chan C. Y. , Rosenthal M. , Sick T. J.
Published: December 2017

Electrical depression in the turtle brain during anoxia has been suggested as a strategy for sparing energy and promoting the extraordinary survival capacity of this tissue. The present study was aimed toward defining the changes in membrane properties during anoxia that may underlie such electrical depression. Studies were conducted in isolated cerebellum from turtle brain. Anoxia caused transmembrane potentials (TMP) to become relatively less polarized in most Purkinje cells. In no cell, however, was TMP depolarized to levels associated with the complete loss of transmembrane ion gradients produced by tissue superfusion with iodoacetate during anoxia. Sodium (and likely calcium) spike thresholds were increased, postsynaptic responses from the major afferent input pathways to Purkinje cells were depressed, and input resistance decreased significantly during anoxia. These changes likely contribute to the sparing of energy needed for ion transport and perhaps other functions that may be directly related to cell survival.
Role of right heart receptors in the control of renin, vasopressin, and cortisol secretion in dogs
Authors: Carr D. H. , Jennings D. B. , Thrasher T. N. , Keil L. C. , Ramsay D. J.
Published: December 2017

We have reported that increased left heart pressure inhibits increases in plasma renin activity (PRA), arginine vasopressin (AVP), and cortisol during arterial hypotension. The goal of this study was to determine whether increases in right heart pressure also inhibited hormonal responses to hypotension. Seven dogs were chronically instrumented with inflatable cuffs around the ascending aorta (AA), the pulmonary artery (PA), and the thoracic inferior vena cava (IVC), as well as with catheters in both atria, the abdominal aorta, and vena cava. The IVC, the PA, and the AA cuffs were inflated on different days to cause step reductions in mean arterial pressure (MAP) of 5, 10, 20, and 30% below control MAP. Graded constriction of the AA caused large increases in left atrial pressure and plasma atrial natriuretic peptide (ANP), but had no effect on plasma AVP or cortisol and caused only a small increase in PRA at the maximal reduction of MAP. Constriction of the IVC reduced both atrial pressures and plasma ANP, but stimulated increases in PRA, AVP, and cortisol. Constriction of the PA increased right atrial pressure and plasma ANP and caused increases in plasma AVP and cortisol that were similar to responses during IVC constriction, but the PRA response was only half (P < 0.05). These results indicate that increasing pressure on the right side of the heart can attenuate the PRA response to hypotension, and suggest that the inhibition is mediated by the rise in plasma ANP.
Metabolic adaptation of fetal hindlimb to severe, nonlethal hypoxia
Authors: Boyle D. W. , Meschia G. , Wilkening R. B.
Published: December 2017

To test the hypothesis that an important aspect of the fetal response to severe, nonlethal hypoxia is a relatively large reduction in oxidative metabolism and small increase in lactate production by organs whose O2 supply is selectively reduced, net fluxes of O2, glucose, pyruvate, lactate, and CO2 derived from fetal plasma lactate carbon [(CO2)PL] were measured across the hindlimb and umbilical circulations in six sheep fetuses before and at 200-260 min of hypoxia. During hypoxia, blood lactate reached a high but steady level (15.2 +/- 2.2 vs. 1.7 +/- 0.2 mM; P < 0.001). Hypoxia was induced by reducing uterine blood flow. Limb O2 uptake and (CO2)PL decreased (P < 0.01) and lactate output increased (P < 0.05) (-83.1 +/- 13.9, -28.6 +/- 5.0, and +35.7 +/- 13.7 nmol.min-1 x g-1, respectively), while pyruvate and glucose uptakes remained similar to control. The increase in limb glycolysis was approximately 10% of the value that would compensate for the decrease in oxidative energy metabolism. The ratio of limb O2 uptake to fetus O2 uptake decreased significantly (0.247 +/- 0.029 vs. 0.447 +/- 0.036; P < 0.01). In contrast to fetal limb (CO2)PL, fetal (CO2)PL did not decrease. During severe, nonlethal hypoxia, fetal survival depends on uneven and counterbalancing organ O2 uptake and lactate metabolism.
Systemic injection of TNF-alpha attenuates fever due to IL-1 beta and LPS in rats
Authors: Long N. C. , Morimoto A. , Nakamori T. , Murakami N.
Published: December 2017

The effect of tumor necrosis factor-alpha (TNF-alpha) on the febrile response to interleukin-1 beta (IL-1 beta) was investigated in rats. While both of these substances are capable of causing fever when injected into rats, an earlier study showed that the injection of antiserum against TNF-alpha enhanced endotoxin [lipopolysaccharide (LPS)] fever, suggesting that physiological levels of circulating TNF may act to limit the magnitude of fever. In the present study, the intraperitoneal injection of 1 microgram/kg of TNF-alpha significantly attenuated the fever due to the intraperitoneal injection of 10 micrograms/kg of IL-1 beta. Higher doses of TNF-alpha (10 and 50 micrograms/kg injected ip) slightly lowered the febrile response to this dose of IL-1 beta, but these changes were not significant. None of these doses of TNF-alpha alone significantly altered body temperature. The injection of 1 microgram/kg of TNF-alpha also significantly lowered the febrile response to the intraperitoneal injection of 10 micrograms/kg of LPS. The febrile responses to the preoptic area (POA) or intraperitoneal injection of IL-1 beta were not changed when a nonpyrogenic dose of TNF-alpha was simultaneously injected into the POA. Further studies are needed, however, before we can conclude that TNF does not act in the central nervous system to control the febrile response. These data support the hypothesis that nonpyrogenic levels of TNF act in the systemic circulation to suppress the development of fever.
Intestinal secretion after jejunal bypass in the ground squirrel
Authors: Carey H. V. , Cooke H. J.
Published: December 2017

The preceding paper [H. V. Carey, Am. J. Physiol. 263 (Regulatory Integrative Comp. Physiol. 32): R1202-R1208, 1992] demonstrated that a 3-day fast or the extended fast of hibernation enhanced the chloride secretory responses to a variety of agonists in the ground squirrel jejunum. Here we examined the effect of jejunal bypass on intestinal secretory capacity in squirrels that either remained active and continued to feed (ACT), or were induced to hibernate (HIB). Mucosal wet weights were reduced in jejunal segments that had little or no exposure to the luminal stream (all segments from HIB and bypassed segments from ACT) compared with segments in contact with luminal contents (sham and in continuity segments of ACT). Tissue conductances were greater in those segments not exposed to luminal contents. Short-circuit current (Isc) responses to electrical stimulation of submucosal neurons, or to serosal carbachol, were greater in segments not exposed to luminal contents when responses were normalized to serosal surface area. Normalization of secretory responses to crypt area produced a similar pattern. Isc responses to mucosal alanine, which reflect electrogenic Na+ absorption, were greatest in segments with little or no exposure to luminal contents. Tissue wet weights, conductances and secretory responses of bypassed segments of HIB and ACT squirrels were always similar. These results suggest that luminal contents directly influence jejunal secretory capacity.
Normobaric hypoxia stimulates endothelin-1 gene expression in the rat
Authors: Elton T. S. , Oparil S. , Taylor G. R. , Hicks P. H. , Yang R. H. , Jin H. , Chen Y. F.
Published: December 2017

The current study tested the hypothesis that exposure to hypoxia enhances endothelin-1 (ET-1) gene expression and elevates circulating ET-1 levels in the rat. Rats were exposed to normobaric hypoxia (10% O2) or room air for 24 or 48 h. ET-1 in arterial blood was measured by radioimmunoassay. ET-1 gene transcript levels were measured by the slot blot technique on total RNA isolated from lung, right and left atria, right and left ventricles, kidney, spleen, liver, brain, main trunk of pulmonary artery, and thoracic aorta. Blots were probed with a 0.5 kb rat prepro ET-1 cDNA that does not cross-hybridize with mRNA for ET-2 or ET-3. Plasma ET-1 levels were increased significantly at 24 (10.03 +/- 2.33 pg/ml) and 48 h (14.02 +/- 3.44 pg/ml) of hypoxia compared with air controls (4.14 +/- 0.66 pg/ml). ET-1 mRNA levels were increased significantly (2-fold) in lung and right atrium after 48 h of hypoxia; no change was seen in organs perfused by the systemic vascular bed. These findings suggest that the hypoxia-induced increase in circulating ET-1 levels is mainly of pulmonary origin. A paracrine effect of ET-1 produced by lung endothelial cells could account for hypoxic pulmonary hypertension.
Cerebral anoxia tolerance in turtles: regulation of intracellular calcium and pH
Authors: Bickler P. E.
Published: December 2017

To investigate mechanisms of cerebral anoxia tolerance, cerebrocortical intracellular calcium ([Ca2+]i) and pH (pHi) regulation were compared in turtles (Trachemys scripta) and laboratory rats. [Ca2+]i and pHi in living 200 to 300-microns-thick cortical brain slices were measured with the fluorescent indicators fura-2/acetoxymethyl ester (AM) and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein during exposure to anoxia. Within 5 min, [Ca2+]i increased to > 1,000 nM in rat brain slices exposed to anoxia but [Ca2+]i was normal even after 5 h of anoxia in turtles. ATP levels remained normal in anoxic turtle brain but fell rapidly in rats. During anoxia, pHi fell by 0.25 +/- 0.08 pH units in rats but only 0.10 +/- 0.04 in turtles (P < 0.05). Inhibition of glycolysis in anoxic turtle brain with iodoacetate resulted in large increases in [Ca2+]i but prior exposure of slices to anoxia resulted in greatly attenuated calcium entry. The reduction in calcium flux was greater with increasing exposure to anoxia, suggesting progressive arrest of calcium channel activity. Tolerance of cerebral anoxia in turtles may be related to anaerobic ATP production, arrest of calcium channels, and attenuation of changes in pHi.
Eicosanoids in third ventricular cerebrospinal fluid of fetal and newborn sheep
Authors: Jones S. A. , Adamson S. L. , Bishai I. , Lees J. , Engelberts D. , Coceani F.
Published: December 2017

A method to serially sample cerebrospinal fluid (CSF) from the third ventricle of chronically catheterized fetal and newborn sheep was developed. Either sampling cannulas of preset lengths (“fixed-probe” technique) or a single cannula that could be positioned at the desired depth (“roving-probe” technique) was used. The roving probe proved superior because free CSF flow was obtained in seven of ten animals after surgery compared with two of nine animals implanted with a fixed probe. CSF (5 animals) and plasma (7 animals) was collected serially from 2 wk before to 2 wk after birth, including the time around labor. Prostaglandin E2 (PGE2) levels (means +/- SE) were significantly higher in CSF (366 +/- 120 pg/ml; n = 5) and plasma (520 +/- 69 pg/ml; n = 7) before the day of delivery than in the same animals after birth. During labor, CSF and plasma PGE2 levels increased significantly to 1,428 +/- 643 pg/ml in CSF and to 2,015 +/- 414 pg/ml in plasma. However, by 1 h after birth, PGE2 had fallen to 366 +/- 165 pg/ml in CSF and to 338 +/- 106 pg/ml in plasma; levels similar to those observed in the fetus before labor. PGE2 continued to decrease precipitously and, at 24 h of age, levels were significantly less than those observed in the fetus. PGE2 levels were near the limit of detection of the assay in CSF (< 5 pg/ml) and were 49 +/- 10 pg/ml in plasma. In contrast, CSF thromboxane B2 (n = 2) and total peptidoleukotriene content (n = 4) showed little change during labor or after birth.(ABSTRACT TRUNCATED AT 250 WORDS)
Food deprivation- and palatability-induced microstructural changes in ingestive behavior
Authors: Davis J. D. , Perez M. C.
Published: December 2017

The effects of 17 h food deprivation and stimulation by five concentrations (0.05-0.8 M) of sucrose solutions on the licking behavior of rats were investigated. Food deprivation increased the intake of the three lowest concentrations (0.05, 0.1, and 0.2 M) but had no effect on the volume ingested of the two highest concentrations (0.4 and 0.8 M). Food deprivation had no significant effect on the duration of the meals of any of the sucrose solutions; rather it affected the rate of ingestion. In those cases where food deprivation did affect volume intake, it did so by increasing the initial rate of ingestion. Although food deprivation had no effect on the volume ingested of the two strongest concentrations of sucrose, it nevertheless affected the ingestive behavior by increasing the duration of the sustained periods of bursts of licking and decreasing their number. Deprivation also significantly decreased the rate of licking within these sustained bouts of licking. The results indicate that food deprivation can affect the ingestive behavior of rats in ways that are not revealed by measuring volumetric intake alone. The data also support the view that food deprivation increases the palatability of the test solutions.
Autonomic regulation of heart rate and blood pressure in hemorrhaged toads
Authors: Michalicek J. , Campbell G.
Published: December 2017

Mean arterial blood pressure (P(a)) and heart rate (HR) were studied in normal conscious cane toads (Bufo marinus) or in autonomically blocked animals treated variously with bretylium, atropine, phentolamine, and propranolol. Partial or total autonomic blockade had no effect on resting values of the variables tested, with the exception that atropine treatment of bretylium-treated toads caused an increase of heart rate by 5.3 +/- 1.3 beats/min. In graded hemorrhage, aliquots of blood (1.68 ml/100 g body wt) were removed at 60-min intervals. There was extensive plasma recruitment, and blood could be removed up to 10.08 ml/100 g without inducing cardiovascular shock. Each hemorrhage caused an initial transient decrease in P(a) and increase in HR followed by recovery toward prehemorrhage values. Repeated hemorrhage caused a progressive rise in basal HR and fall in basal P(a). The effects of drug treatments suggest that transient increases in HR may be caused by the release of adrenal catecholamines. In addition, hemorrhage may increase sympathetic tone so that basal HR becomes elevated, which, together with sympathetic vasoconstriction, limits the progressive fall of basal P(a).
Regulation of renal hemodynamics after protein feeding: effects of proximal and distal diuretics
Authors: Woods L. L. , Smith B. E. , De Young D. R.
Published: December 2017

The purpose of these studies was to compare the effects of proximally and distally acting diuretics on the renal hemodynamic response to protein feeding to determine the importance of the proximal tubule in postprandial renal vasodilation. In chronically instrumented conscious dogs, a meat meal (10 g/kg raw beef) caused glomerular filtration rate (GFR) to increase from 63 +/- 5 to 87 +/- 10 ml/min and effective renal plasma flow (ERPF) to increase from 189 +/- 20 to 249 +/- 20 ml/min, while plasma alpha-amino nitrogen levels rose from 4.0 +/- 0.1 to 6.8 +/- 0.4 mg/dl. Administration of amiloride (0.2 mg/kg + 0.003 mg.kg-1.min-1) or potassium canrenoate (1.76 mg/kg + 1.76 mg.kg-1.h-1), diuretics that act in the distal tubule, had no effect on the renal hemodynamic responses to a meat meal. However, the normal renal hemodynamic responses to protein feeding were abolished during administration of a diuretic that acts in the proximal tubule, acetazolamide (20 mg/kg + 20 mg.kg-1.h-1), although plasma alpha-amino nitrogen levels increased after the meat meal in all experiments. These data suggest that normal proximal tubular sodium reabsorptive function is necessary for acute protein-stimulated renal vasodilation and are consistent with the hypothesis that a tubuloglomerular feedback mechanism may mediate postprandial renal vasodilation.
Hemodynamic changes induced by low blood oxygen affinity in dogs
Authors: Liard J. F. , Kunert M. P.
Published: December 2017

Increased tissue oxygen delivery may play a role in the increased vascular resistance that develops in volume-expanded hypertension. This hypothesis was tested by decreasing the affinity of hemoglobin for oxygen in dogs to increase unloading of oxygen to the tissues. Six chronically instrumented dogs were studied before and for 7 days after partial exchange transfusion with red blood cells modified by incorporation of inositol hexaphosphate, which, 1 h after exchange, increased the PO2 value at which hemoglobin is half-saturated with oxygen (P50) to 38.8 +/- 2.1 mmHg from a control value of 31 +/- 1.5 mmHg. Cardiac output (electromagnetic flowmeter) fell to 92.5 +/- 7.4 ml.kg-1.min-1 after 2-4 h from control values between 120.2 +/- 5.7 and 125.8 +/- 4.6 ml.kg-1.min-1. One day later, cardiac output was still significantly decreased to 104.0 +/- 5.9 ml.kg-1.min-1. As P50 returned to control over the next few days, so did cardiac output. Two to four hours after exchange, total peripheral resistance was increased to 1,144 +/- 73 mmHg.l-1.kg.min from control values between 762 +/- 26 and 790 +/- 32 mmHg.l-1.kg.min. It was still increased to 993 +/- 51 mmHg.l-1.kg.min after 1 day. Oxygen consumption did not change significantly. Cardiac output and peripheral resistance changes were significantly different from those measured in a control group of six dogs receiving exchange transfusion with sham-shifted red blood cells without significant P50 changes. These results suggest that an increase in tissue oxygen delivery can raise total peripheral resistance in dogs in the absence of primary changes in fluid volumes, blood flow, or blood pressure.
Nonuniform regional sympathetic nerve responses to hyperinsulinemia in rats
Authors: Morgan D. A. , Balon T. W. , Ginsberg B. H. , Mark A. L.
Published: December 2017

The insulin hypothesis of hypertension proposes that hyperinsulinemia increases sympathetic nerve activity (SNA) and raises arterial pressure. The goals of this study were 1) to determine if hyperinsulinemia produces regionally uniform or nonuniform increases in SNA and 2) to test the hypothesis that spontaneously hypertensive rats (SHR) have exaggerated sympathoadrenal responses to hyperinsulinemia. We measured plasma insulin, blood glucose, mean arterial pressure, and adrenal, renal, and lumbar SNA in alpha-chloralose-anesthetized SHR and normotensive Wistar-Kyoto (WKY) rats before and during infusion of two doses of insulin for 60 min each while maintaining euglycemia. In WKY rats, graded increases in plasma insulin from 27 +/- 5 (SE) to 200 +/- 29 microU/ml increased lumbar SNA from 100% to 285 +/- 26% but failed to significantly increase adrenal or renal SNA. In SHR rats, similar increases in plasma insulin from 27 +/- 4 to 213 +/- 33 microU/ml caused significant increases in adrenal (100% to 174 +/- 16%) and lumbar (100% to 307 +/- 26%) SNA but not in renal SNA. Despite increases in SNA, mean arterial pressure did not increase significantly in either group of rats. We conclude that 1) hyperinsulinemic euglycemic clamp produces regionally nonuniform increases in sympathetic nerve activity, and 2) there is a potentiated increase in adrenal SNA in SHR compared with WKY rats during hyperinsulinemia, whereas lumbar SNA responses were similar in the two strains, and renal SNA did not increase in either strain.
Temperature sensitivity of neurons in slices of the rat PO/AH hypothalamic area: effect of calcium
Authors: Schmid H. A. , Pierau F. K.
Published: December 2017

The temperature sensitivity of spontaneously active neurons in slices of the preoptic and anterior hypothalamic areas (PO/AH) of rats was assessed by extracellular recording during sinoidal temperature displacements. Classifying cells according to their temperature coefficients (TC, impulses.s-1.degree C-1) revealed that 48% of the 177 cells tested were warm sensitive, 5% were cold sensitive, and 47% were temperature insensitive. Increasing the calcium concentration ([Ca2+]) of the artificial cerebrospinal fluid (aCSF) from 0.9 to 1.5 mM Ca2+ decreased the firing rate (FR) and TC of PO/AH neurons. Decreasing extracellular [Ca2+], however, elicited concentration-dependent increases in both parameters. This means in physiological terms that the number and temperature sensitivity of PO/AH neurons is strongly dependent on the extracellular [Ca2+]. Furthermore, these results suggest that caution is warranted when comparing numbers and temperature sensitivities of PO/AH neurons. After blocking synaptic transmission by superfusing the slice with aCSF containing reduced [Ca2+] and elevated [Mg2+], 8 out of 35 neurons ceased their spontaneous activity within 6 min, and 27 remained spontaneously active in low [Ca2+]-high [Mg2+] solution, but displayed unstable spontaneous activity and temperature sensitivity. It is concluded that aCSF with reduced [Ca2+] and elevated [Mg2+] is not a suitable tool to discriminate between inherent and synaptically mediated thermosensitivity.
Biochemical bases for difference in oxygen affinity of maternal and fetal red blood cells of rattlesnakes
Authors: Ragsdale F. R. , Ingermann R. L.
Published: December 2017

Pregnancy in Crotalus viridis oreganus is associated with an increase in the nucleoside triphosphate (NTP) concentration and a concomitant decrease in the oxygen affinity of the adult red blood cell. However, although the red blood cells of non-pregnant adults and fetuses have indistinguishable NTP concentrations, they have different oxygen affinities. Therefore, red blood cell NTP concentrations alone cannot account for the oxygen-affinity difference between fetal and maternal red blood cells. Hemoglobins from adult and fetal snakes had similar intrinsic oxygen affinities; however, adult hemoglobin was more responsive to organic phosphate modulation compared with fetal hemoglobin. Structural differences, indicated by native gel electrophoresis and electrophoresis of the globins under denaturing conditions at high pH, corroborated functional differences of hemoglobins from fetus and adult. Therefore, the biochemical basis for the oxygen-affinity difference between maternal and fetal red blood cells in this rattlesnake appears to be unique. It appears to be caused by a functionally distinct fetal hemoglobin and the pregnancy-associated rise in red blood cell NTP levels in the mother.
Osmoregulation of the magnocellular system during pregnancy and lactation
Authors: Koehler E. M. , McLemore G. L. , Tang W. , Summy-Long J. Y.
Published: December 2017

We compared the responsiveness of both the vasopressin (VP) and oxytocin (OT) magnocellular systems to osmotic stimulation during pregnancy and lactation to determine if changes in thresholds and sensitivities were similar for both neuropeptides. Virgin, pregnant (day 20), and lactating (day 6) Sprague-Dawley rats were injected with a hypertonic NaCl solution (0.25 M-8.0 M NaCl; 15 ml/kg sc) and decapitated 2 h later. Late in gestation, the apparent osmotic threshold for both VP and OT release was lower by approximately 10 mosmol/kgH2O than that of virgin and lactating animals. The sensitivity (i.e., slope of the linear regression relating plasma osmolality and VP or OT levels) of the magnocellular system to osmoregulation, however, was unchanged in pregnant animals but was significantly attenuated (P < 0.01) for both peptides during lactation (slopes of lactating vs. virgin rats: OT, 1.7 vs. 3.4; VP, 1.1 vs. 1.9). The neural lobe content of VP decreased (P < 0.05) in pregnant rats, whereas OT stores were reduced (P < 0.05) in lactating animals. Thus, during pregnancy, the lower tonicity of plasma is perceived as normal by both VP and OT neuroendocrine systems enabling excretion of an acute sodium or water load.
Effects of the substance P receptor antagonist CP-96,345 on renal sensory receptor activation
Authors: Kopp U. C. , Smith L. A.
Published: December 2017

In anesthetized rats, we examined the effects of the substance P (SP) receptor antagonist CP-96,345 on the renorenal reflex responses to renal mechanoreceptor (MR) stimulation produced by increased ureteral pressure. Renal pelvic administration of SP at 0.16, 0.8, 4.0, 20, and 100 micrograms/ml increased ipsilateral afferent renal nerve activity (ARNA) in a concentration-dependent fashion, 45 +/- 28, 134 +/- 26, 185 +/- 24, 185 +/- 25, and 274 +/- 39%, respectively. Renal pelvic perfusion with CP-96,345 at 0.01, 0.1, and 1.0 mg/ml dose-dependently reduced the ARNA response to 4.0 micrograms/ml SP, by 5 +/- 17, 46 +/- 9, and 72 +/- 12%, respectively. Increasing ureteral pressure three times in the presence of renal pelvic perfusion with vehicle, 1 mg/ml CP-96,345, and vehicle, increased ARNA 77 +/- 21, 29 +/- 13, and 101 +/- 36%, respectively. Thus CP-96,345 produced a reversible blockade of the ARNA responses to renal MR stimulation. Increasing ureteral pressure three times in the presence of renal pelvic perfusion with vehicle, CP-96,345 (1 mg/ml), and CP-96,345 + 25-40 micrograms/ml SP, increased ARNA 108 +/- 15, 43 +/- 14, and 153 +/- 63%, respectively. Thus CP-96,345 produced a competitive blockade of the ARNA responses to renal MR stimulation. The contralateral diuretic and natriuretic responses to increased ureteral pressure were also blocked in a reversible and competitive fashion by CP-96,345. The inactive 2R,3R enantiomer of CP-96,345, CP-96,344 (1 mg/ml). had no effect on the ipsilateral ARNA or the contralateral renal excretory responses to increased ureteral pressure.(ABSTRACT TRUNCATED AT 250 WORDS)
Organ specificity of the dopamine1 receptor/adenylyl cyclase coupling defect in spontaneously hypertensive rats
Authors: Felder R. A. , Kinoshita S. , Ohbu K. , Mouradian M. M. , Sibley D. R. , Monsma F. J. , Minowa T. , Minowa M. T. , Canessa L. M. , Jose P. A.
Published: December 2017

The coupling between the dopamine1 (DA1) receptor and the G protein/adenylyl cyclase (AC) enzyme complex is defective in the proximal convoluted tubule (PCT) of 20-wk-old spontaneously hypertensive rats (SHRs). Because this coupling defect could have been due to desensitization secondary to elevated renal dopamine levels in the adult animal, we studied the interaction between DA1 receptors and AC in PCT of rats as early as 3 wk of age, a time when renal dopamine levels are similar in SHRs and their normotensive controls (Wistar-Kyoto rats, WKYs). Maximum receptor density did not change with age and was similar in WKYs and SHRs in all the age groups studied (3, 8, and 20 wk). Basal-, forskolin-, and guanyl nucleotide-stimulated AC activities were also similar in WKYs and SHRs and did not change with age. However, the DA1 agonist-stimulated AC activity was greater in WKYs than in SHRs and increased with age in WKYs but not in SHRs. Moreover, the ability of a nonhydrolyzable analogue of GTP, Gpp(NH)p, to enhance DA1 agonist (SND-919-C12, 1 microM)-stimulated AC activity increased with age in WKY but not in SHRs. To determine if the defect noted in the PCT of SHRs is due to a defective D1A receptor gene, parallel studies were performed in the striatum, since this receptor is expressed predominantly in the latter tissue. In contrast to the results in PCT, radioligand binding and AC studies in striatum revealed no differences between WKYs and SHRs.(ABSTRACT TRUNCATED AT 250 WORDS)