bluuebunny/crossref_metadata_2025 huggingface dataset:
Potentiated cortisol response to paired hemorrhage: role of angiotensin and vasopressin
Authors: Lilly M. P. , DeMaria E. J. , Bruhn T. O. , Gann D. S.
Published: December 2017

Potentiated adrenocorticotropin (ACTH) and cortisol responses occur after the second of two small hemorrhages (hems) spaced 24 h apart in the dog. To test whether increased responses of other hormones might be associated with this effect, we examined plasma renin activity (PRA), angiotensin II (ANG II), and vasopressin after paired 10% hem (H1 and H2) spaced 5 h apart in chronically prepared conscious dogs. Cortisol secretion increased after each hem, and the response to H2 was larger (P less than 0.05; H1 peak at 6.8 +/- 1.3 micrograms/min vs. H2 peak at 18.3 +/- 5.3 micrograms/min). ACTH did not change after H1 but increased after H2, and the H2 response was larger (P less than 0.01). Vasopressin increased after each hem, and the H2 response was larger (P less than 0.01). The time courses of ACTH and vasopressin responses were similar after H2 (significant increases by 8 min). PRA and ANG II increased by 4 min after each hem, and although the difference was small the early PRA and ANG II responses were greater after H2. Blood volume and hem volume did not differ between hems. Hemodynamic responses to the hems were not different. We conclude that, although the PRA and ANG II respond rapidly enough after hem to influence pituitary responses, the slightly greater responses of these factors to H2 are not responsible for greatly increased pituitary-adrenal responses to H2. On the other hand, the markedly potentiated vasopressin response to H2, which parallels that of ACTH, suggests that vasopressin may mediate the increased ACTH responses to H2.
Acute-phase response to endogenous pyrogen in rabbit: effects of age and route of administration
Authors: Martin L. W. , Deeter L. B. , Lipton J. M.
Published: December 2017

Aspects of host defense, collectively called the acute phase response (APR), can be induced by central actions of cytokines. To determine whether aging alters this response, aged and young rabbits were given endogenous pyrogen (EP), a crude preparation containing interleukin 1 and other cytokines, via an intracerebroventricular cannula. Arterial blood was sampled before EP administration and 2, 4, and 24 h later. Measurements were made of changes in body temperature, white blood cells, neutrophils, concentration of antipyretic, anti-inflammatory peptide alpha-melanocyte stimulating hormone (alpha-MSH), corticosterone, and C-reactive protein (CRP) concentrations. EP caused greater fever and increases in corticosterone and CRP in young rabbits. EP-induced changes in circulating neutrophils did not show age-related differences. There was no significant change in alpha-MSH in either age group; thus only certain aspects of APR induced by central actions of EP were altered with aging. To determine whether changes in APR caused by peripherally administered cytokines are similar to those after central injection, young female rabbits were given EP by both routes. Although administration caused greater fever, increases in alpha-MSH and corticosterone concentrations and in neutrophil counts were greater after intravenous administration, perhaps the result of a combined influence on peripheral and central receptors. The EP-induced increase in circulating alpha-MSH is a new finding that indicates that this antipyretic and anti-inflammatory peptide is rapidly available to modulate host responses after challenge.
Baroreflex inhibition during coronary occlusion is mediated by prostaglandins
Authors: Zucker I. H. , Panzenbeck M. J. , Hackley J. F. , Haiderzad K.
Published: December 2017

The present study was undertaken to determine whether the baroreflex control of renal sympathetic nerve activity (RSNA) was attenuated by an acute coronary artery occlusion and if so, what was the role played by cardiac prostaglandins in this attenuation. Arterial pressure was lowered with an infusion of sodium nitroprusside before and during a 5- to 10-min occlusion of the left circumflex coronary artery. The protocol was repeated 30 min after indomethacin (5 mg/kg) had been given. In addition, this study was carried out in a group of vagotomized dogs and in a group of thoracic-sympathectomized dogs. In intact dogs, coronary occlusion reduced the slope of the mean arterial pressure-RSNA relationship by 75% from -7.7 +/- 1.8% change in RSNA per millimeter Hg before indomethacin treatment. After indomethacin, there was no inhibition of the baroreflex slope during coronary occlusion. The reduction in the slope during coronary occlusion was abolished in dogs that were vagotomized but preserved in thoracic-sympathectomized dogs. In this latter group, indomethacin inhibited the attenuation of the slope during coronary occlusion. These data provide strong support for the notion that some cyclooxygenase product (most likely a prostaglandin) is released during coronary ischemia and stimulates or sensitizes cardiac vagal afferent endings, which, in turn, attenuate the baroreflex-mediated increase in RSNA during lowered arterial pressure.
Effects of synaptic blockade on thermosensitive neurons in rat diencephalon in vitro
Authors: Dean J. B. , Boulant J. A.
Published: December 2017

To identify the distribution of inherently thermosensitive and conditionally (i.e., synaptically dependent) thermosensitive neurons in the rat diencephalon, single-unit recordings (n = 88) were made in horizontal tissue slices during localized thermal stimulation before, during, and after reversible synaptic blockade. Inherently warm-sensitive neurons (n = 17) were found in 10 nuclei, the largest number occurring in the preoptic area-anterior hypothalamus (POAH). Inherently cold-sensitive neurons (n = 5) were encountered in three nuclei, with the highest number in the posterior hypothalamus (PH) and mammillary body (MB). Fifty-nine percent of the inherently thermosensitive neurons showed a change in spontaneous activity and/or thermosensitivity during synaptic blockade, indicating that these neurons undergo synaptic modulation. Conditionally warm-sensitive neurons (n = 14) were found in six nuclei with the majority of these neurons located in the accumbens nucleus, diagonal band of Broca, and PH-MB. Two conditionally cold-sensitive neurons were found in the POAH and one in the MB. Temperature-insensitive neurons (n = 49) were rarely affected by synaptic blockade. Thus inherently and conditionally thermosensitive neurons are found in many locations in the diencephalon. These thermosensitive neurons may belong to the neuronal networks responsible for thermo-regulation and the other homeostatic systems that are influenced by temperature.
Cold-induced changes in uncoupling protein and GDP binding sites in brown fat of ob/ob mice
Authors: Milner R. E. , Trayhurn P.
Published: December 2017

The acute and chronic effects of cold exposure on the thermogenic activity and capacity of brown fat of obese (ob/ob) and lean mice have been examined. After 1 h at 13 degrees C, mitochondrial GDP binding increased in warm-acclimated (28 degrees C for 3 wk) lean mice, and increases in mitochondrial mass and the specific mitochondrial concentration of uncoupling protein were evident at 24 h. Long-term cold exposure led to further progressive increases in the specific mitochondrial concentration and total tissue content of uncoupling protein. The acute increase in GDP binding was due to an unmasking of binding sites on the protein and was accompanied by a parallel increase in the acetate-induced swelling of the mitochondria. In contrast to lean animals, ob/ob mice did not exhibit an increase in GDP binding or unmasking of binding sites during the first 24 h of cold exposure; unmasking was, however, evident by 3 days. A delay in the stimulation by cold of both the specific mitochondrial concentration of uncoupling protein (not increased until 3 days) and the mitochondrial content of brown fat (not increased until 8 days) occurred in the obese mice. Acute warm exposure (28 degrees C) of cold-acclimated (13 degrees C for 3 wk) mice led to a reduction in GDP binding in both lean and obese animals because of a rapid masking of binding sites. Mitochondrial content and the specific mitochondrial concentration of uncoupling protein fell progressively in both groups of mice with continued warm exposure.(ABSTRACT TRUNCATED AT 250 WORDS)
Electrophysiological study of micturition reflexes in rats
Authors: Mallory B. , Steers W. D. , De Groat W. C.
Published: December 2017

Electrophysiological techniques were used to examine the asynchronous and evoked activity on postganglionic nerves to the urinary bladder in the urethananesthetized rat. Distension of the bladder (0.4-0.6 ml) evoked reflex contractions of the bladder (mean intravesical pressure 28 cmH2O) and efferent firing on postganglionic nerves. Electrical stimulation of afferent and efferent axons in the pelvic nerve elicited short-latency (0.3-11 ms) responses and long-latency (45-170 ms) reflexes on the nerves. The short-latency responses consisted of nonsynaptic axonal volleys with conduction velocities ranging from 0.5 to 11 m/s and synaptic responses with latencies of 6-11 ms. Stimulation of the pelvic nerve elicited late supraspinal reflexes (mean latency 122 +/- 28 ms) in 60% of normal rats and an early reflex (mean latency 56 +/- 5 ms) in 25% of those animals in which a late reflex was also identified. Early reflexes (mean latency 50 +/- 9 ms) were elicited in 100% of chronic spinal animals. The conduction time for the afferent and efferent limbs of the reflexes was calculated to be 7 and 58 ms, respectively, with a central delay of 57 ms for the late and less than 5 ms for the early reflex. It is concluded that sacral parasympathetic input to the urinary bladder of the rat is mediated by supraspinal and spinal reflex pathways. It is likely that in normal animals the late-occurring supraspinal reflex mediates micturition. The significance of the spinal reflex in the normal animals is uncertain; however, this reflex is essential for the generation of automatic micturition in chronic spinal preparations.
Organic anion and cation transport in crab urinary bladder
Authors: Miller D. S. , Smith P. M. , Pritchard J. B.
Published: December 2017

Crab urinary bladder, a simple, flat-sheet epithelium, is structurally and functionally analogous to vertebrate renal proximal tubule. Like proximal tubule, crab bladder plays an important role in the excretion of potentially toxic, charged metabolites and xenobiotics. Bladders from Cancer borealis secrete monovalent, organic anions and cations in vivo and in vitro. For organic cations, secretion is a two-step process, with mediated and energetically downhill uptake into cells at the serosal membrane and uphill exit at the luminal membrane. The uptake step may be driven by the electrical potential difference across the serosal membrane, the luminal step by organic cation-proton exchange. Monovalent organic anions are also secreted by a separate two-step process. Recent experiments with intact bladder tissue and isolated membrane vesicles show that (as in mammalian proximal tubule) uphill serosal uptake can be coupled indirectly to the Na+ gradient. Organic anion (p-aminohippurate; PAH) uptake is driven by exchange for certain divalent organic anions, e.g., glutarate and alpha-ketoglutarate. The divalent anion gradient (in greater than out) is in turn maintained by Na+-coupled divalent uptake. The PAH exist step at the luminal membrane is mediated and downhill; it may involve anion exchange.
Brush-border amino acid transport mechanisms in carnivorous eel intestine
Authors: Storelli C. , Vilella S. , Romano M. P. , Maffia M. , Cassano G.
Published: December 2017

Brush-border membrane vesicles (BBMV) were prepared from European eel (Anguilla anguilla) intestinal epithelium by a magnesium-ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) precipitation technique. Amino acid transport by these purified vesicle preparations was investigated using either radiolabeled substrates or the voltage-sensitive fluorescent dye 3,3'-diethylthiadicarbocyanine iodide [DiSC2(5)]. All amino acids tested exhibited carrier-mediated, Na+-dependent and Na+-independent transfer processes plus diffusion. The only exceptions were glutamic acid and proline, which displayed Na+ dependency and diffusion but did not appear to be transported by Na+-independent agencies. Carrier-mediated transport kinetic constants (Kapp and Jmax) for several amino acids are reported. Cis-inhibition experiments suggested the presence of at least four distinct Na+-dependent transport systems in eel intestinal BBMV: 1) an anionic transport process for glutamic and aspartic acids; 2) a cationic mechanism for lysine and arginine; 3) a relatively specific neutral amino acid carrier for proline and alpha-(methylamino)isobutyric acid; and 4) a nonspecific neutral amino acid system for most other substrates of this group. This scheme for carnivorous fish intestine most closely approximates that reported for mammalian gut with minor dissimilarities that may relate to metabolic differences or specific dietary requirements of the two vertebrate groups.
Role of endogenous atrial natriuretic peptide in congestive heart failure
Authors: Awazu M. , Imada T. , Kon V. , Inagami T. , Ichikawa I.
Published: December 2017

Effects of purified rabbit anti-rat 25-amino acid atrial natriuretic peptide (ANP) immunoglobulin G (IgG) on renal sodium excretion and glomerular filtration rate were studied in a rat model of congestive heart failure (CHF) having high circulating ANP levels. Bolus injection of anti-ANP into anesthetized rats with surgically induced myocardial infarction (MI) significantly and markedly depressed both absolute and fractional urinary excretion of sodium without affecting mean arterial pressure or glomerular filtration rate. By contrast, anti-ANP failed to affect these renal functions in normal or acutely water-deprived rats. Nonimmune IgG did not affect renal function in MI rats. These results indicate that high circulating ANP plays an important role in sodium homeostasis of congestive heart failure: by promoting sodium excretion, ANP opposes the tendency of sodium retention characteristic of CHF.
Regional changes in adipose tissue blood flow and metabolism in rats after a meal
Authors: West D. B. , Prinz W. A. , Greenwood M. R.
Published: December 2017

Adipose tissue blood flow was measured in five depots, and plasma concentrations of glucose, insulin, and triglyceride were measured at 0, 15, 30, and 45 min after the start of a meal in unanesthetized, freely moving rats. In addition, adipose tissue lipoprotein lipase activity was measured in four depots before and 45 min after the start of a meal. Plasma glucose was significantly elevated only at the 15-min time point, and while plasma triglyceride increased these changes did not reach significance. Plasma insulin was significantly elevated at all time points after a meal. Feeding resulted in a consistent decrease of adipose tissue blood flow expressed per gram wet weight of tissue. This decrease was maximal at 30 min after the start of feeding. The decrease in adipose tissue blood flow averaged 45% at 45 min after the start of feeding for the five depots evaluated. Lipoprotein lipase activity significantly increased in the retroperitoneal and mesenteric fat depots at 45 min after the meal start, but did not change in the epididymal or dorsal subcutaneous fat depots. These results suggest that a decrease in adipose tissue blood flow is a normal result of a meal in the rat. The regional specificity of changes in adipose tissue lipoprotein lipase activity supports the concept of regional specificity of function for adipose tissue and suggests that the mesenteric and retroperitoneal depots are particularly important for the storage of triglycerides immediately after a meal.
Nonshivering thermogenesis and adaptation to fasting in king penguin chicks
Authors: Duchamp C. , Barre H. , Delage D. , Rouanet J. L. , Cohen-Adad F. , Minaire Y.
Published: December 2017

The ability to develop nonshivering thermogenesis (NST) and the effect of fasting on thermogenic response to cold were studied in winter-acclimatized king penguin chicks. Metabolic rate (MR) and integrated electrical muscle activity were measured at different ambient temperatures. In cold-acclimatized (5 degrees C) fed chicks, shivering threshold temperature (STT) was 9.4 degrees C lower than lower critical temperature (LCT), indicating that NST (0.7 W/kg) occurs at moderate cold, whereas in control chicks fed and reared at 25 degrees C for 3 wk, LCT and STT were similar. Chicks reared in the cold and fasting for 3 wk or 4-5 mo (natural winter fast) developed an NST of 0.8 and 2.4 W/kg, respectively, despite the fast. In fasting chicks, the intercept of the metabolic curve with the abscissa at zero MR was far below body temperature, contrasting with the classic model for heat loss. Their low LCT indicates the capacity of a large reduction in convective conductance characteristic of diving animals and allows energy sparing in moderate cold. Below LCT, conductance reincreases progressively, leading to a steeper than expected slope of the metabolic curve and allowing preservation of a threshold temperature in the shell. These results show for the first time in a wild young bird the development of NST after cold acclimatization. Further, at the temperature of cold acclimatization, an energy-sparing mechanism is shown in response to long-term fast adaptation.
Renal calyceal and pelvic contraction rhythms
Authors: Yamaguchi O. A. , Constantinou C. E.
Published: December 2017

An experimental study of the porcine multicalyceal pacemaker system was undertaken. In particular, the characteristic rhythmicities of in situ calyces were examined as well as rhythmicities between the calyceal system and the renal pelvis using pig kidneys perfused ex vivo via the renal artery. The temporal and spatial organization of calyceal and renal pelvic contraction rates were evaluated by simultaneously recording pressure from the renal pelvis and from three calyces. The results obtained from 15 kidneys indicate that the upper, middle, and lower calyces contract rhythmically at the essentially equal rates of 12.8 +/- 2.4, 14.0 +/- 1.6, and 13.06 +/- 2.3 min-1. The interaction between the activities of different calyces was analyzed by measuring the phase of individual calyceal contractions. Phase locking, coordination of contraction and phase oscillation, systematic fluctuations, or divergence of phase were obtained in most preparations, indicating the existance of a mechanism of coherent intercalyceal coupling. During periods in which phase locking occurred, pelvic contractions were related to all of the observed calyceal regions. When phase oscillation was present, the region of calyceal system evidencing a higher frequency was associated with pelvic contraction, whereas in the absence of calyceal coupling renal pelvic contractions could not be correlated to calyceal activity.
Intrapreoptically microdialyzed and microinjected norepinephrine evokes different thermal responses
Authors: Quan N. , Blatteis C. M.
Published: December 2017

Norepinephrine (NE) microdialyzed into the medial preoptic area (MPO) evokes a core temperature (Tco) fall in contrast to the rise when it is microinjected. Because prostaglandin E2 (PGE2) is a contaminant of the microinjection procedure per se, we determined whether it might account for these differential thermal responses. NE (1 microgram/microliter) was bilaterally microinjected into the MPO of conscious guinea pigs treated 20 min prior with a PG synthetase inhibitor, indomethacin (Indo, 10 mg/kg, im). Under these conditions, the latency of the NE-induced Tco rise was prolonged (138 +/- 18 min). When Indo was administered both 20 min before and 20 min after NE microinjection, NE was hypothermizing. NE (10 micrograms/microliter at 2 microliters/min for 3 h) microdialyzed into the MPO, lateral septum, or anterior hypothalamus caused Tco falls, whereas it induced no Tco change when dialyzed into the lateral preoptic area, indicating site specificity. PGE2 (1 microgram/microliter) caused a Tco rise when it was dialyzed intra-MPO. Microdialysis of PGE2 and NE together neutralized each other's effects. Indo given at the end of intra-MPO NE dialysis blocked the usual recovery of Tco from its lowered value. These results indicate that NE and PGE2 in the MPO may reciprocally influence the Tco of guinea pigs. The data further suggest that PGE may account for the different responses to microinjected and microdialyzed NE.
Platelet-activating factor: an endogenous mediator of mesenteric ischemia-reperfusion-induced shock
Authors: Mozes T. , Braquet P. , Filep J.
Published: December 2017

The role of platelet-activating factor (PAF) in circulatory shock of intestinal origin was investigated in anesthetized dogs by measuring PAF levels in the superior mesenteric vein during reperfusion after 2-h occlusion of the superior mesenteric artery; by monitoring the effects of BN 52021, a specific PAF receptor antagonist; and by studying the circulatory effects of exogenous PAF injected into the superior mesenteric vein. PAF was measured by a platelet-aggregation assay. Identity of PAF-like bioactivity was ascertained by thin-layer chromatography, high-pressure liquid chromatography, and alkaline treatment. Removal of the superior mesenteric artery occlusion caused an immediate dramatic decrease in mean arterial blood pressure with concomitant increase in mean portal venous pressure and hematocrit values. PAF concentration in the superior mesenteric vein increased from 0.2 +/- 0.1 to 2.8 +/- 0.4 ng/ml (n = 4, P less than 0.05) within the first 5 min of reperfusion. Administration of exogenous PAF (0.1 microgram/kg) injected into the superior mesenteric vein produced similar hemodynamical effects. Pretreatment of the animals with BN 52021 (4 mg/kg), a specific PAF receptor antagonist, prevented the circulatory collapse. The present results suggest that PAF release during intestinal ischemia may play an important role in the development of circulatory collapse caused by mesenteric artery occlusion.
Renal sympathetic nerve activity and plasma catecholamines during eating in cats
Authors: Matsukawa K. , Honda T. , Ninomiya I.
Published: December 2017

We measured renal sympathetic nerve activity (RNA) and arterial plasma concentration of norepinephrine (NE) and epinephrine (EPI) before, during, and after eating in six conscious cats. Eating continued for a period of 5 min. RNA, heart rate (HR), and arterial blood pressure (AP) increased almost simultaneously with the onset of eating and reached a maximum value of 192%, 221 beats/min, and 121 mmHg at 2.5-5 min after the onset of eating, respectively. The plasma NE level increased significantly (P less than 0.05) during eating from the control value of 0.56 ng/ml and reached a maximum value of 1.33 ng/ml at 4.5-5 min, whereas the plasma EPI level did not change significantly from the control value of 0.12 ng/ml. The plasma levels of NE and EPI were unaffected by the blood samplings. The relationship between the changes in RNA and the plasma NE level during eating had a significant (P less than 0.05) positive correlation (r = 0.52). The result suggests that plasma NE concentration tends to increase with the rise in RNA during eating.
Responses to dehydration and rehydration during heat exposure in young and older men
Authors: Miescher E. , Fortney S. M.
Published: December 2017

Body temperature, plasma responses, and subjective ratings of thirst and hotness were studied in 5 older men (OM, 61-67 yr) and 6 younger men (YM, 21-29 yr) during 180-min thermal dehydration and subsequent 60-min rehydration (45 degrees C, 25% relative humidity). Rectal temperature (Tre) increased more rapidly and to a greater magnitude in OM, while average total body sweat rates and chest sweat rates were not significantly different. During dehydration, both OM and YM lost similar body weight (1.52 +/- 0.11 vs. 1.55 +/- 0.22%, mean +/- SE). However, in OM, plasma volume (Pv) decreased (-11.3 +/- 2.8 vs. -4.9 +/- 2.9%), and plasma osmolality (Posm) increased to a greater extent (+5.0 +/- 0.32 vs. 1.1 +/- 0.24 mosmol/kg) compared with YM. On rehydration, OM and YM similarly replaced water debt (46.6 +/- 4.9 vs. 49.0 +/- 3.0%). Within 30 min of drinking, YM had restored Pv and Posm, whereas OM showed slower responses, restoring Posm after 60 min and Pv only after a subsequent 30 min at 25 degrees C. Despite a higher Tre and greater change in Pv and Posm, OM rated themselves less thirsty and not significantly hotter than YM. These findings suggest that aging results in decreased ability to maintain Tre during heat stress and that the mechanisms comprise a combination of alterations in body fluid distribution and perception.
Atrial natriuretic peptide and pressure natriuresis: interactions with the renin-angiotensin system
Authors: Mizelle H. L. , Hall J. E. , Hildebrandt D. A.
Published: December 2017

The aim of this study was to quantitate the effects of increases in atrial natriuretic peptide (ANP), within the pathophysiological range, on the acute pressure natriuresis mechanism and the role of the renin-angiotensin system (RAS) in modulating these effects. Renal hemodynamics and electrolyte excretion were measured in anesthetized dogs while renal perfusion pressure (RPP) was controlled at three levels (120-122, 100, and 75 mmHg) with and without intrarenal infusion of ANP at 5 ng.kg-1.min-1. Sodium excretion was significantly higher during ANP infusion at RPP of 122 +/- 3 mmHg, averaging 55.8 +/- 13.7 during control and 113.3 +/- 23.3 mueq/min during ANP infusion. AT RPP of 101 +/- 1 mmHg, sodium excretion was 51.8 +/- 17.4 during control and 93.0 +/- 17.6 mueq/min during ANP infusion, but at RPP of 75 +/- 0 mmHg there was no difference in sodium excretion between control and ANP infusion. In a second set of dogs, angiotensin II (ANG II) formation was blocked with captopril (20 micrograms.kg-1.min-1), circulating (5 ng.kg-1.min-1), and the above protocol was repeated. When the RAS was fixed, the renal responses to ANP infusion were abolished, even at the higher pressure levels. These data indicate that ANP increases the slope of pressure natriuresis; at higher levels of RPP, ANP potentiates pressure natriuresis but not at lower pressures. In addition, part of this effect may be due to suppression of the RAS, because the ANP-induced shift in the pressure natriuresis relationship was abolished when circulating ANG II was maintained constant.
Vascular pressure-volume relationships in pregnant and estrogen-treated guinea pigs
Authors: Davis L. E. , Hohimer A. R. , Giraud G. D. , Paul M. S. , Morton M. J.
Published: December 2017

We investigated the relationship between mean circulatory filling pressure (MCFP) and blood volume in nonpregnant (NP), estrogen-treated (E), and pregnant (P) guinea pigs. Reversible circulatory arrest was produced by rapid ventricular pacing or acetylcholine in unanesthetized animals remote from surgery. MCFP (mmHg) was higher for E (7.1 +/- 0.3) than for NP (5.8 +/- 0.5) or P (5.3 +/- 0.4). The gradient for venous return, the difference between MCFP and right atrial pressure (mmHg), did not differ in NP- (6.0 +/- 0.5), P- (5.8 +/- 0.5), or E- (5.8 +/- 0.4) treated animals. Capacitance, the blood volume (ml/kg) at an MCFP of 6 mmHg, was increased in P (84 +/- 6) and E (89 +/- 7), compared with NP (64 +/- 5) animals. Compliance, the ratio of the change in volume to change in pressure in the range of 6-12 mmHg (ml.kg-1.mmHg-1), was greater in P (4.4 +/- 0.3) than NP (3.5 +/- 0.3) animals. Hexamethonium blockade did not affect MCFP, capacitance, or compliance. We conclude that the effect of blood volume expansion on the circulation in pregnancy cannot be predicted from knowledge of MCFP-blood volume relationships in the nonpregnant animal, because capacitance and compliance are altered. Estrogen administration to nonpregnant animals reproduces some of these effects.
Cerebral oxidative metabolism in lambs during perinatal period: relationship to electrocortical state
Authors: Richardson B. S. , Carmichael L. , Homan J. , Gagnon R.
Published: December 2017

Cerebral oxidative metabolism and regional blood flow were studied, with changes in behavioral state over the immediate perinatal period, to determine the change in cerebral metabolism at birth and the relationship to behavioral activity. Nine unanesthetized fetal sheep (139-142 days gestation) were each studied during a period of high-voltage and low-voltage electrocorticogram (ECOG) activity and then again after cesarean delivery at 2 h of age while awake and at 24 h of age while awake and during a period of high-voltage ECOG sleep. Preductal arterial and sagittal vein blood samples were analyzed for O2 content, blood gases, and pH. Blood flow was measured with a radioactive microsphere technique. Cerebral oxidative metabolism showed no significant perinatal change, although a coupling to behavioral state was evident with significant increases during both the perinatal low-voltage ECOG state and the awake state at 24 h. Blood flow to the brain showed a significant perinatal decrease after birth and state-related increases during both the prenatal low-voltage ECOG state and the awake state at 24 h consistent with the tight coupling of flow and/or O2 delivery to metabolic needs reported for normal brain tissue. The cerebral metabolic rate of the prenatal low-voltage ECOG state suggested a level of functional excitation comparable with that of the awake state after birth, supporting the importance of the rapid-eye-movement (REM) state mechanism as a source of endogenous stimulation during the perinatal period of brain growth and development.
Dynamics of apical membrane responses to ADH in amphibian bladder
Authors: Wade J. B.
Published: December 2017

The dynamic insertion and retrieval of membrane at the apical surface plays an important role in the action of antidiuretic hormone (ADH). The addition of membrane with water channels is a crucial event in initiating the water permeability response. ADH-stimulated bladders display distinctive differentiations in the apical membrane that represent sites where intracellular vesicles carrying intramembrane particle aggregates have fused with the apical surface. In the absence of an osmotic gradient these fusion sites appear to be relatively stable structures, but in the presence of an osmotic gradient there seems to be continuous addition and retrieval of membrane during sustained exposure to ADH. It is now clear that a dynamic feedback process is present, such that the water permeability of the apical membrane is adjusted by retrieval or addition of membrane depending on the magnitude of the transepithelial osmotic gradient. Removal of ADH leads to a striking retrieval of apical membrane, and intact aggregates have been demonstrated in the membrane of the vesicles that form in the apical cytoplasm after reversal of the response. Structure-function analysis has provided unique information, demonstrating that membrane dynamics is central to the mechanism whereby ADH regulates osmotic permeability in the toad urinary bladder.
Heart rate spectral analysis of fasting-induced bradycardia of cattle
Authors: Clabough D. L. , Swanson C. R.
Published: December 2017

The autonomic mechanisms of fasting-induced bradycardia of cattle were studied using heart rate spectral analysis. This was performed on digitized, lead II, surface electrocardiograms from conscious, fed, and 48-h-fasted adult cows. Fasting resulted in a significant (P less than 0.05) decrease in resting heart rate and a significant (P = 0.0041) increase in low frequency (0-90 mHz) power spectral area. Administration of atropine sulfate (0.02 mg/kg iv) in either the fed or fasted state resulted in a significant (P less than 0.001) decrease in both low-frequency and high-frequency (100-400 mHz) power spectral areas. Significant (P less than 0.05) increases in serum total bilirubin, inorganic phosphorus, and total protein were associated with fasting. Significant decreases were seen in fasting serum aspartate aminotransferase and potassium values. Manual evacuation of the rumen of seven steers with chronic rumen fistulae resulted in a mean percent decrease in heart rate of 22 +/- 0.9% (mean +/- SE). These results indicate that in normal cattle a decrease in ruminorecticular fill results in a reflex slowing of the heart rate, due predominantly to an increase in parasympathetic tone.
In vitro reactivity of dog cavernous carotid artery to stretch and adrenergic stimulation
Authors: Valle J. , Garcia-Villalon A. L. , Nava-Hernandez E. , Garcia J. L. , Santamaria L. , Gomez B. , Dieguez G.
Published: December 2017

The reactivity of the dog cavernous carotid artery to stretch, field electrical stimulation, and norepinephrine was studied using arterial segments under isometric conditions. Light microscopy revealed that this artery is of muscular type and its external surface is covered by venous endothelium, and fluorescence microscopy showed a dense adrenergic innervation. On stretch, arteries exhibited an immediate, transient contraction (phasic response) and a late, maintained contraction (tonic response) that were unaffected by tetrodotoxin (10(-6) M) or endothelium removal but were reduced by the inhibitors of cyclooxygenase indomethacin (10(-6) M), acetylsalicylic acid (3 x 10(-5) M), or meclofenamate (10(-5) M). Electrical stimulation (0.5-4 Hz) contracted the arteries in a frequency-dependent manner, and the response was reduced by tetrodotoxin, phentolamine, (10(-6) M), or the inhibitors of cyclooxygenase used but was unaffected by endothelium removal. Norepinephrine (10(-9)-3 x 10(-4) M) caused dose-dependent contraction that was blocked by phentolamine and by the inhibitors of cyclooxygenase but was not modified by endothelium removal. The results indicate that the dog cavernous carotid artery develops myogenic tone on stretch and contracts on adrenergic stimulation. They also suggest that in these responses prostaglandins but not the endothelium are involved. Therefore, the cavernous carotid artery, because of its location and reactivity, could be of relevance in regulating blood flow or pressure within the cerebral circulation when arterial pressure or adrenergic activity increases.
Effects of 2-deoxy-D-glucose on sympathetic nerve activity to interscapular brown adipose tissue
Authors: Egawa M. , Yoshimatsu H. , Bray G. A.
Published: December 2017

The effects on firing rate of sympathetic nerves to interscapular brown adipose tissue were measured after induction of intracellular glycopenia by peripheral or central administration of 2-deoxy-D-glucose (2-DG). Injection of 2-DG (250 mg/kg body wt) into the jugular vein rapidly suppressed the sympathetic activity, which declined 84% within 10 min after the injection. This suppression persisted for at least 40 min. Hyperglycemia did not affect the sympathetic activity but partially inhibited the suppressive effect of 2-DG injection. Acute vagotomy failed to block the suppressive effect of 2-DG. Injection of 2-DG (2.5 mg/rat) into the third cerebral ventricle suppressed the sympathetic activity. This suppression was followed by gradual recovery. Saline injection did not affect the sympathetic activity. We conclude that cellular glycopenia induced by injecting 2-DG peripherally or into the third cerebral ventricle suppresses the sympathetic activity to brown adipose tissue. The results are consistent with the hypothesis that an acute energy shortage decreases the thermogenesis in interscapular brown adipose tissue by suppressing sympathetic neural activation of this tissue.
Ion leakage is reduced during anoxia in turtle brain: a potential survival strategy
Authors: Chih C. P. , Rosenthal M. , Sick T. J.
Published: December 2017

The turtle brain maintains ATP levels, ion homeostasis, and some neural function during prolonged anoxia despite significant decreases in the rate of ATP production. To test the hypothesis that reduced ATP production during anoxia was compensated partly by conserving energy through reduced ion leakage, the rate of K+ leakage was measured in normoxic and anoxic turtle brains in which Na(+)-K(+)-adenosinetriphosphatase was inhibited with ouabain. Rates of K+ leakage were significantly lower in brains subjected to 2 h of anoxia than in normoxic brains. These data support the suggestion that reduced ion leakage is an important mechanism for energy conservation during anoxia.
Release of vasopressin and oxytocin by paraventricular stimulation in rats
Authors: Landgraf R. , Malkinson T. , Horn T. , Veale W. L. , Lederis K. , Pittman Q. J.
Published: December 2017

The nucleus tractus solitarius/dorsal motor nucleus of the vagus nerve (NTS/DMV) area was perfused by the push-pull perfusion technique in anesthetized rats, and perfusates were assayed for arginine vasopressin (AVP) and oxytocin (OXT) immunoreactivity. As compared with controls, electrical stimulation of the ipsilateral paraventricular nucleus (PVN) resulted in increased amounts of both AVP (approximately 5-fold) and OXT (approximately 10-fold, P less than 0.05 each) in the perfusates. During the poststimulation perfusion period, peptide concentrations were found to return to control levels. Elevation of circulating AVP and OXT by an osmotic stimulus did not result in increases of AVP and OXT in NTS/DMV perfusates. These data suggest that AVP and OXT are released from NTS/DMV area fiber terminals during electrical stimulation of descending PVN neurons. Furthermore, they are consistent with the view that both peptides are involved as neurotransmitters in autonomic regulation.
Chronic cervical spinal cord injury and autonomic hyperreflexia in rats
Authors: Osborn J. W. , Taylor R. F. , Schramm L. P.
Published: December 2017

Although it is well established that patients with cervical spinal cord injury are prone to acute, marked, hypertensive episodes, i.e., autonomic hyperreflexia, the specific mechanisms mediating this sometimes-fatal phenomenon are not completely understood. In this report, we describe the preparation and characterization of a rat model of chronic cervical spinal cord injury and autonomic hyperreflexia. Adult male Sprague-Dawley rats were chronically instrumented with arterial, venous, and gastric catheters. Beginning the first day after a complete cervical spinal transection (CST) and continuing for 1 wk, acute hypertensive responses to a modest increase of urinary bladder pressure (0-20 mmHg) were studied. Mean arterial pressure increased 25.9 +/- 4.8 mmHg during bladder distension the first day after CST. This response was not significantly different 3, 5, and 7 days after CST (overall average = 18.0 +/- 2.3 mmHg). The pressor response to bladder distension was completely abolished by intravesical lidocaine and autonomic ganglionic blockade (atropine + hexamethonium). Responses to bladder distension were not observed after the administration of chloralose anesthesia. We conclude that after cervical spinal transection the rat exhibits autonomic hyperreflexia similar to that seen in humans with spinal injury. Furthermore, autonomic hyperreflexia is completely established within 24 h after CST in the rat. Finally, some spinal autonomic reflexes are suppressed by chloralose anesthesia in the rat.
Effects of outflow pressure and vascular volume loading on thoracic duct lymph flow in adult sheep
Authors: Brace R. A. , Valenzuela G. J.
Published: December 2017

Studies have shown that lymph flow rate from several tissues depends on the pressure at the outflow end of the lymphatics. The left thoracic lymph duct is the largest lymphatic vessel and it transports a majority of the body's lymph. We varied outflow pressure for the left thoracic lymph duct independent of venous pressure in six unanesthetized, nonpregnant adult ewes with chronic lymphatic and venous catheters. When outflow pressure was negative, the thoracic duct lymph flow rate was independent of outflow pressure and averaged 0.040 +/- 0.004 (SE) ml.min-1.kg body wt-1. Lymph flow began to decrease with increasing outflow pressure only when outflow pressure was significantly greater than venous pressure. Above this breakpoint, lymph flow decreased linearly with outflow pressure and ceased at an outflow pressure of 25.6 +/- 4.2 mmHg. After vascular volume loading with lactated Ringer solution, steady-state thoracic duct lymph flow increased to 351 +/- 54% of control and was independent of outflow pressure when outflow pressure was negative. As outflow pressure was elevated, lymph flow began to decrease at the same breakpoint as before volume loading, and lymph flow ceased at the same outflow pressure as before volume loading. Thus this study shows that there is a plateau where thoracic duct lymph flow rate is independent of outflow pressure. In addition venous pressure under normal or volume-loaded conditions is not an impediment to thoracic duct lymph flow in unanesthetized sheep. Large increases in venous pressure are required to totally block thoracic duct lymph flow.
Extracellular dehydration during pregnancy increases salt appetite of offspring
Authors: Nicolaidis S. , Galaverna O. , Metzler C. H.
Published: December 2017

The propensity to prefer and to consume salty foods varies considerably from person to person, and excessive salt intake has been linked to a number of pathological conditions. Extracellular dehydration occurs in humans after vomiting or diarrhea and is commonly observed during pregnancy. Because the hormonal responses to extracellular dehydration are known to increase salt appetite, we tested the hypothesis that extracellular dehydration during pregnancy increases the propensity of offspring to consume salt. Pregnant rats were treated with polyethylene glycol, which is known to produce extracellular dehydration and to exaggerate sodium appetite. The offspring of these treated pregnant rats showed an increase in salt appetite as compared with the offspring of control untreated dams. These results demonstrate that extracellular dehydration during pregnancy can enhance the natriophilic propensity in offspring and suggest that gravidic vomiting may contribute to the epidemiological factors of hypertension and other pathologies.
Maternal pinealectomy alters the daily pattern of fetal breathing in sheep
Authors: McMillen I. C. , Nowak R. , Walker D. W. , Young I. R.
Published: December 2017

We have investigated the effect of pinealectomy of the pregnant ewe on the 24-h pattern of fetal breathing activity during late gestation. Fetal breathing movements were recorded during 24-h periods on 18 occasions in 5 pinealectomized ewes and on 24 occasions in 6 pineal-intact ewes between 120 and 145 days gestation. All ewes were fed once daily between 1000 and 1300 h and were kept under a light-dark cycle 12:12 h. There was no significant difference in the mean hourly incidence of fetal breathing movements between the pineal-intact (27.2 +/- 0.5 min/h) and pinealectomized (25.5 +/- 0.6 min/h) groups. However, there was a significant difference in the 24-h profiles of fetal breathing movements in the two groups. The peak incidence of fetal breathing occurred between 1900 and 2000 h in the pineal-intact ewes and between 1200 and 1300 h in the pinealectomized ewes. We conclude that maternal pinealectomy alters the daily pattern of a fetal behavioral pattern and that maternal melatonin may therefore provide the fetus with information about time of day.
Effect of intestinal bypass on the expression of actin mRNA in ileal smooth muscle
Authors: Lai M. , Thomason D. B. , Weisbrodt N. W.
Published: December 2017

In this study, messenger RNAs (mRNAs) for actin isoforms were assessed in longitudinal smooth muscle from the ileum of unoperated rats and from rats that had undergone bypass of the middle 70% of the small intestine. The plasmid clone pGEM 10C, which contains a DNA insert complementary to the 3' untranslated region and the region of mRNA that codes for the synthesis of alpha-smooth muscle actin protein, was used to synthesize two riboprobes. One probe, complementary to the coding region of the insert, hybridizes to most, if not all, actin isoform mRNAs. The second probe, complementary to the 3' untranslated region of the insert, hybridizes only to alpha-smooth muscle actin mRNA. RNA was isolated from animals 4 to 5 days after operation, size fractionated by denaturing gel electrophoresis, transferred to nylon membranes, and exposed to the two 32P-labeled riboprobes. Both probes hybridized to RNA of about 1.3 kilobases long. Longitudinal muscle from both groups of animals contained alpha-smooth muscle actin mRNA as well as mRNA for other actin isoforms. Dot blots of varying amounts of RNA were hybridized to the riboprobes to determine the proportions of actin mRNAs. The content and concentration of mRNAs for all actins, and of mRNA for alpha-smooth muscle actin, were significantly greater in muscle from the functioning ileum of bypassed animals 4-5 days after the operation. Thus the operation induces a rapid, specific activation of these contractile protein genes.
Electrophysiological evidence that systemic angiotensin influences rat area postrema neurons
Authors: Papas S. , Smith P. , Ferguson A. V.
Published: December 2017

Extracellular single-unit recordings from neurons in the area postrema (AP) and the nucleus tractus solitarius (NTS) in anesthetized male rats demonstrated that most cells in these regions have spontaneous activities of 5 Hz or less. Systemic angiotensin (ANG II) (50-500 ng) enhanced the activity of 55% of AP cells tested (n = 76), whereas 53% of tested NTS neurons (n = 62) were inhibited by ANG II. To determine whether these neurons were influenced specifically by circulating ANG II or by the accompanying increase in mean arterial blood pressure (BP), the effects of adrenergic agonists given intravenously on ANG II influenced neurons were also examined. Subsequently two cell types were characterized: cells responding to iv ANG II but not to the adrenergic agonist ("ANG II sensitive") and cells responding in a similar way to both agents ("BP sensitive"). Most ANG II-responsive neurons in the AP (53.5%) and the NTS (65%) were determined to be BP sensitive. These data demonstrate that ANG II influences the activity of AP neurons. In addition, there exists a second population of AP neurons apparently responsive to perturbations of the cardiovascular system. These studies further emphasize the potential roles of the AP in the regulation of body fluid balance.
Enhanced thermogenic response to epinephrine after 48-h starvation in humans
Authors: Mansell P. I. , Fellows I. W. , Macdonald I. A.
Published: December 2017

The effects of 48-h starvation on the physiological responses to a 30-min infusion of epinephrine at 25 ng.min-1.kg body wt-1 were studied in 11 normal-weight healthy young subjects. Starvation led to considerable alterations in basal metabolism including a significant (mean 3.6%) increase in resting metabolic rate. During the infusions, plasma epinephrine concentration rose less in the starved state (+1.47 nmol/l) than in the normally fed state (+1.73 nmol/l) (SE 0.06 nmol/l; P less than 0.05). The maximum increments (mean +/- SE) in heart rate induced by epinephrine were 11.9 +/- 1.3 beats/min in the normally fed state and 20.1 +/- 2.0 beats/min in the starved state (P less than 0.001); the corresponding mean increments in blood glycerol concentration were 0.07 and 0.14 mmol/l (SE 0.01 mmol/l; P less than 0.01). The increase in the metabolic rate above base line during the final 10 min of the epinephrine infusion was 0.58 +/- 0.18 kJ/min in the normally fed state and 0.78 +/- 0.14 kJ/min in the starved state (P less than 0.01). The chronotropic, lipolytic, and thermogenic effects of infused epinephrine were therefore enhanced by prior starvation, despite the lower plasma epinephrine levels.