bluuebunny/crossref_metadata_2025 huggingface dataset:
Thromboxane receptor-mediated bronchial and hemodynamic responses in ovine endotoxemia
Authors: Kuhl P. G. , Bolds J. M. , Loyd J. E. , Snapper J. R. , FitzGerald G. A.
Published: December 2017

The role of thromboxane A2 in sheep endotoxemia, an animal model of the adult respiratory distress syndrome, was investigated by a combined biochemical and pharmacological approach. Endogenous thromboxane biosynthesis was assessed by gas chromatographic-mass spectrometric analysis of urinary (thromboxane B2, 2,3-dinor-thromboxane B2) and plasma (11-dehydrothromboxane B2) metabolites that demonstrated a significant stimulation by endotoxin. The functional relevance of thromboxane A2 was probed with a specific thromboxane-prostaglandin endoperoxide receptor antagonist, SQ 29548. The antagonist significantly blunted the increase in pulmonary arterial pressure, pulmonary vascular resistance, lung lymph flow, and lymph protein clearance induced by endotoxin. Whereas the reduction in lung compliance caused by endotoxin was abolished, the augmented airway resistance was unaffected. From the simultaneous increase in thromboxane biosynthesis and effects of receptor blockade, it was concluded that thromboxane A2 mediates the early pathophysiological changes of sheep endotoxemia. Thromboxane receptor antagonism may offer a potential therapeutic approach to patients at risk of the adult respiratory distress syndrome.
NH4+ transport in acid-secreting insect epithelium
Authors: Thomson R. B. , Thomson J. M. , Phillips J. E.
Published: December 2017

The relationship between ammonia secretion (JAmm), hydrogen ion secretion (JH), and intracellular pH (pHi) was investigated in isolated locust (Schistocerca gregaria) rectal epithelia mounted as flat sheets in specially designed Ussing chambers. In the absence of exogenous CO2 and ammonia, the rectum is capable of net acid and ammonia secretion into the lumen against pH gradients of up to 1.8 U. JAmm was dependent on the presence of luminal amino acids and Na+ and it was relatively unaffected by K+ removal or changes in membrane potential. JAmm and pHi remained fairly constant over a luminal pH range of 7-5, whereas JH decreased linearly to zero over the same pH range. Mucosal addition of 1 mM amiloride reduced JAmm by 60%. This study demonstrates that the locust rectum secretes significant quantities of endogenously produced ammonia preferentially into the lumen as NH+4 rather than NH3. Moreover, the results suggest that the ammonia crosses the apical membrane via an amiloride-inhibitable Na+-NH+4 exchange mechanism.
Comparison of IR thermography and thermocouple measurement of heat loss from rabbit pinna
Authors: Mohler F. S. , Heath J. E.
Published: December 2017

The temperature of the pinnae of male New Zealand White rabbits was measured by use of infrared thermography. At ambient temperatures of 15, 20, and 25 degrees C, the average pinna temperatures were 23.0, 28.7, and 36.2 degrees C, respectively. From these temperatures, average heat loss from the total pinna surface area was calculated to be 2.8, 3.3, and 4.4 W, respectively. Preoptic temperature changes also affect the vasomotor state of the rabbit. At an ambient temperature of 20 degrees C, cooling the preoptic area of the rabbit by approximately 1 degree C resulted in an average pinna temperature of 26.5 degrees C and a heat loss of 2.4 W. Heating the preoptic area by approximately 1 degree C resulted in an average pinna temperature of 33.5 degrees C and a heat loss of 5.4 W. Finally, pinna temperatures were measured by use of a thermocouple and infrared thermography simultaneously. When the pinnae were vasodilated, the thermocouple measurements were consistently higher than the pinna surface temperatures measured thermographically. When the pinnae were vasoconstricted, the thermocouple measurements were consistently lower than the pinna surface temperatures measured thermographically. The discrepancy between the two methods of measurement is discussed.
Striatal dopamine release and metabolism in sinoaortic-denervated rats by in vivo microdialysis
Authors: Alexander N. , Nakahara D. , Ozaki N. , Kaneda N. , Sasaoka T. , Iwata N. , Nagatsu T.
Published: December 2017

The purpose of this study was to provide new evidence favoring the hypothesis that cardiovascular information from arterial baroreceptors is integrated with the nigrostriatal system that contributes to regulation of motor activity. Samples of extracellular striatal dopamine (DA) and its metabolites, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), were collected by the technique of in vivo microdialysis and analyzed by high-performance liquid chromatography-electron capture detection. Rats were prepared with a guide tube placed in the caudate-putamen for subsequent insertion of microdialysis probes. During the 1st wk after sinoaortic denervation (SAD) or sham operation (SO), a microdialysis probe was inserted and perfused with Ringer solution at the rate of 2 microliter/min in the freely moving rats. Samples were collected every 20 min before and after injection of pargyline, 100 mg/kg ip. The results showed that SAD rats have approximately 50% less extracellular striatal DA, DOPAC, and HVA than SO rats (P less than 0.01). After blockade of monoamine oxidase activity with pargyline, striatal DA accumulated three times faster in SO than SAD rats suggesting DA synthesis is reduced in SAD rats. These data provide further evidence that the arterial baroreceptor system affects dopaminergic metabolism in the nigrostriatal system possibly as a means for integration of cardiovascular and motor activity.
Hormonal and renal responses to water drinking in moderately trained and untrained humans
Authors: Freund B. J. , Claybaugh J. R. , Hashiro G. M. , Dice M. S.
Published: December 2017

Endurance exercise training alters the regulation of body fluids. To investigate specifics of these alterations, hormonal, electrolyte, and renal responses to water ingestion (1% of lean body wt) were studied in six moderately trained (T) and 6 untrained (UT) male subjects. No differences between groups for base-line hormonal, electrolyte, or renal measurements were found. After water ingestion, atrial natriuretic factor remained unaltered in both groups. Predrink plasma antidiuretic hormone (ADH) levels of 0.51 +/- (SE) 0.19 (UT) and 0.47 +/- 0.07 microU/ml (T) remained unchanged in the T group but were reduced from min 9 through 90 in the UT group. At 30 min postdrink, UT subjects had lower ADH values than T subjects (0.18 +/- 0.02 vs. 0.33 +/- 0.05 microU/ml), while plasma osmolality was similarly reduced by approximately 3 mosmol/kg in both groups. Urine flow rates increased in both groups from similar values of 0.85 +/- 0.24 (UT) and 0.67 +/- 0.11 ml/min (T) to peak flows of 4.6 +/- 1.6 for UT and 2.7 +/- 1.1 ml/min (T) to peak T, P less than or equal to 0.05) at 60 min postdrink. Urine osmolality was reduced from similar values of 809.1 +/- 62.1 and 867.0 +/- 56.1 mosmol/kg to values of 248.8 +/- 87.6 and 469 +/- 146.1 mosmol/kg for UT and T, respectively (UT vs. T, P less than 0.05), at 60 min. Reduced ADH before reductions in plasma osmolality in the UT but not the T subjects suggests that T subjects have a reduced oropharyngeal inhibition of ADH.(ABSTRACT TRUNCATED AT 250 WORDS)
Renal response to atrial natriuretic factor is modulated by intrarenal angiotensin II
Authors: Showalter C. J. , Zimmerman R. S. , Schwab T. R. , Edwards B. S. , Opgenorth T. J. , Burnett J. C.
Published: December 2017

The present study in anesthetized dogs (n = 8) was designed to test the hypothesis that intrarenal angiotensin II (ANG II) attenuates the increase in sodium excretion in response to atrial natriuretic factor (ANF). To test this hypothesis, renal hemodynamic and excretory responses to systemically administered ANF (0.3 micrograms.kg-1.min-1) were assessed in the presence of ANG II infusion into the left kidney (ANG II K) at a nonpressor dose (1.5 ng.kg-1.min-1) and with an infusion of saline into the right kidney, the latter which served as control (CK). During ANF infusion, absolute increases in urinary sodium excretion (delta + 160.8 +/- 44.7 vs. delta + 369.4 +/- 56.9 mu eq/min, P less than 0.005) and fractional sodium excretion (delta + 2.55 +/- 0.62 vs. delta + 4.26 +/- 0.82%, P less than 0.03) were markedly attenuated in the ANG II K compared with CK. Glomerular filtration rate increased only in the CK. Urine osmolality decreased in both the ANG II K and CK. These studies demonstrate an attenuated natriuresis to ANF in the presence of intrarenally infused ANG II, which is associated with a blunted increase in glomerular filtration rate. These studies support the hypothesis that the renal hemodynamic and excretory responses to ANF are modulated by intrarenal ANG II.
Subfornical organ and cardiovascular influences on identified septal neurons
Authors: Donevan S. D. , Ferguson A. V.
Published: December 2017

We have identified, in urethan-anesthetized male Sprague-Dawley rats, a polysynaptic pathway connecting the subfornical organ (SFO) with the paraventricular nucleus (PVN) with a relay neuron in the medial septum-diagonal band of Broca (MS-DBB). Extracellular recordings were obtained from 136 MS-DBB neurons antidromically identified as projecting to the PVN. SFO stimulation orthodromically activated 79% of these cells (mean latency, 21.2 +/- 0.6 ms; mean duration, 6.0 +/- 0.2 ms), whereas stimulation in the fornix or hippocampal commissure had no effect. Of 35 identified MS-DBB neurons tested with systemic angiotensin II (ANG II), eight showed increases and six decreases in excitability that coincided with the ANG II-induced increase in blood pressure. To determine whether such changes were blood pressure related, 23 of the 35 identified MS-DBB neurons tested with ANG II were tested with systemic epinephrine. In every case the effect of epinephrine was similar to that of ANG II. These findings suggest that neurons in the MS-DBB receive afferent information from the SFO and the cardiovascular system. These cells in turn may activate neurons involved in the control of a variety of autonomic functions.
Immunoreactive atrial natriuretic factor is increased in ovine model of endotoxemia
Authors: Lubbesmeyer H. J. , Woodson L. , Traber L. D. , Flynn J. T. , Herndon D. N. , Traber D. L.
Published: December 2017

A bolus of Escherichia coli endotoxin (1.5 micrograms/kg) was administered to chronically instrumented sheep. Immunoreactive atrial natriuretic factor (IR-ANF) was measured in extracted plasma by radioimmunoassay. There was a thirteenfold increase in IR-ANF 2 h after endotoxin administration, and IR-ANF levels remained significantly elevated during the first 6 h. A marked diuresis and natriuresis occurred between 4 and 6 h. ANF not only affects renal function but is also associated with decreased cardiac output, increased peripheral resistance (in sheep), and decreased capillary absorption (in rats). These renal and hemodynamic changes are also characteristic of the early (first 6 h) response to endotoxin. Therefore ANF should be considered as a potential mediator of renal and hemodynamic changes induced by sepsis. It is difficult to determine if ANF elevation is an epiphenomenon or a causative factor, because no antagonist of ANF is currently available.
Medullary inspiratory activity during opossum development
Authors: Farber J. P.
Published: December 2017

Discharge properties of medullary neurons associated with inspiration were assessed during opossum development. Location of these neurons and projections to the spinal cord were also evaluated. Studies were performed on suckling opossums, from 15-20 days of age to weaning (approximately 100 days), as well as adult animals, anesthetized with Inactin. Most cells either discharged during inspiration (I cells) or were phase-spanning between late expiration and inspiration (EI cells). Number of spikes per breath for I and EI cells significantly increased as the animal matured. For younger opossums (up to approximately 60 days of age), bulbospinal I and EI cells discharged an average of 1.9 spikes per breath, with a minimum interspike interval of 59 ms. Their conduction velocities, determined by use of antidromic stimulation, were in the unmyelinated range (less than 2 m/s). The occurrence of few spikes per breath with long interspike interval, in bulbospinal cells of the younger opossums, suggests that inspiration is not subject to fine feedback control and that rate of high-frequency motor bursts is relatively slow.
Effect of weaning on accuracy of doubly labeled water method in infants
Authors: Roberts S. B. , Coward W. A. , Ewing G. , Savage J. , Cole T. J. , Lucas A.
Published: December 2017

Variations in background 2H and 18O abundances in body water influence the accuracy and precision of the 2H218O method for determination of energy expenditure. To investigate the effect of weaning during infancy on background 2H and 18O abundances, urine samples from 44 breast- or formula-fed infants aged 5-16 wk were analyzed. 2H and 18O abundances were significantly higher (P less than 0.001) in breast- than in formula-fed infants. The relationship between 2H and 18O abundances was linear and independent of diet [slope, 4.16 +/- 0.43 (SE)]. By use of this information, the effect of weaning on the accuracy of the 2H218O method was evaluated, taking into account the effect of 2H-18O abundances in the isotope loading dose. In infants weaned completely from breast milk to formula during the measurement, energy expenditure can be overestimated by 18.0%, even if 2H-18O abundances in the isotope dose equal the ratio of naturally occurring background changes. However, this error can be reduced to less than 3.0% by manipulating the study duration and isotope dose. During gradual weaning, the overestimation of energy expenditure is only 0.3-2.0%.
Osmoregulation of thirst and vasopressin during normal menstrual cycle
Authors: Vokes T. J. , Weiss N. M. , Schreiber J. , Gaskill M. B. , Robertson G. L.
Published: December 2017

Changes in osmoregulation during normal menstrual cycle were examined in 15 healthy women. In 10 women, studied repetitively during two consecutive menstrual cycles, basal plasma osmolality, sodium, and urea decreased by 4 mosmol/kg, 2 meq/l, and 0.5 mM, respectively (all P less than 0.02) from the follicular to luteal phase. Plasma vasopressin, protein, hematocrit, mean arterial pressure, and body weight did not change. In five other women, diluting capacity and osmotic control of thirst and vasopressin release were assessed in follicular, ovulatory, and luteal phases. Responses of thirst and/or plasma vasopressin, urine osmolality, osmolal and free water clearance to water loading, and infusion of hypertonic saline were normal and similar in the three phases. However, the plasma osmolality at which plasma vasopressin and urine osmolality were maximally suppressed as well as calculated osmotic thresholds for thirst and vasopressin release were lower by 5 mosmol/kg in the luteal than in the follicular phase. This lowering of osmotic thresholds for thirst and vasopressin release, which occurs in the luteal phase, is qualitatively similar to that observed in pregnancy and should be taken into account when studying water balance and regulation of vasopressin secretion in healthy cycling women.
Basal and insulin-stimulated skeletal muscle sugar transport in endotoxic and bacteremic rats
Authors: Westfall M. V. , Sayeed M. M.
Published: December 2017

Membrane glucose transport with and without insulin was studied in soleus muscle from 5-h endotoxic rats (40 mg/kg Salmonella enteritidis lipopolysaccharide), and in soleus and epitrochlearis muscles from 12-h bacteremic (Escherichia coli, 4 X 10(10) CFU/kg) rats. Glucose transport was measured in muscles by evaluating the fractional efflux of 14C-labeled 3-O-methylglucose (14C-3-MG) after “loading” muscles with 14C-3-MG. Basal 3-MG transport was elevated in soleus muscles from endotoxic as well as in soleus and epitrochlearis muscles from bacteremic rats compared with time-matched controls. Low insulin concentrations stimulated 14C-3-MG transport more in bacteremic and endotoxic rat muscles than in controls. However, sugar transport in the presence of high insulin dose was attenuated in soleus and epitrochlearis muscles from bacteremic rats and soleus muscles from endotoxic rats compared with controls. Analysis of the dose-response relationship with ALLFIT revealed that the maximal transport response to insulin was significantly decreased in both models of septic shock. Sensitivity to insulin (EC50) was increased in endotoxic rat muscles, and a somewhat similar tendency was observed in bacteremic rat soleus muscles. Neural and humoral influences and/or changes in cellular metabolic energy may contribute to the increase in basal transport. Shifts in insulin-mediated transport may be due to alterations in insulin-receptor-effector coupling and/or the number of available glucose transporters.
Morphology and cell dynamics of adipose tissue in hypothalamic obese mice
Authors: Ochi M. , Sawada T. , Kusunoki T. , Hattori T.
Published: December 2017

Morphological and cell kinetic characteristics of the epididymal adipose tissue of obese mice, induced by monosodium glutamate (MSG), were examined in comparison to those of normal mice. Mice treated with MSG for 5 postnatal days became obese after 8 wk of age; adipocytes of the MSG-treated mice were larger than those of normal mice. Heterogeneity was noted in components of the adipose tissue in the obese mice after 24 wk; various-sized adipocytes appeared, and the connective tissue elements increased; necrosis of adipocytes was observed by 36 wk; and mononuclear cells and macrophages infiltrated around the necrotic adipocytes. Such changes were not seen in normal mice. Autoradiographic study with continuous and pulse labeling with [3H]thymidine showed that half the fat cells were replaced in 150-200 days in normal mice and that the turnover rate of adipocytes was more rapid in the obese mice than in the normal mice. In the obese mice, cell death and cell renewal were found to occur more actively.
Effects of food and light on norepinephrine turnover
Authors: Yoshida T. , Bray G. A.
Published: December 2017

To study diurnal differences in norepinephrine turnover, groups of rats were housed in rooms with alternating 12 h light and 12 h dark where half the animals were in a normal light cycle and half were in a reversed light cycle. Norepinephrine turnover was measured in all groups beginning at 1000 by inhibition of tyrosine hydroxylase. When rats are fed ad libitum, the turnover of norepinephrine in interscapular brown adipose tissue and heart was significantly higher in the normal cycle than in the reversed cycle. In addition, there was an interaction between the turnover of norepinephrine and the feeding and lighting schedules. When animals were adapted to eating from 0700 to 1900, the turnover of norepinephrine was somewhat faster when the animals ate in the reversed cycle than when they ate in the normal cycle. Conversely, when the feeding schedule was reversed and animals ate between 1900 and 0700, the turnover of norepinephrine in the absence of food was slightly slower in the animals eating in the reversed cycle than in those eating in the light cycle. This interaction between lighting and food intake observed in both male and female rats was abolished by ventromedial hypothalamic lesions. These data suggest that food intake and lighting conditions interact as controllers of the sympathetic nervous system and that these interactions are modulated by the ventromedial hypothalamus.
Capsaicin challenge, reflex bronchoconstriction, and local action of substance P
Authors: Bergren D. R.
Published: December 2017

Capsaicin was administered as an aerosol to unanesthetized guinea pigs in a whole body plethysmograph and intravenously to anesthetized guinea pigs to investigate its mechanism of action. Capsaicin increased specific airway resistance in the unanesthetized guinea pigs and increased insufflation pressure in anesthetized guinea pigs. To investigate the possible reflex action of capsaicin, an atropine or lidocaine aerosol was administered before the capsaicin aerosol challenge in unanesthetized guinea pigs. Both lidocaine and atropine reduced the effect of capsaicin. However, neither intravenous atropine nor bilateral vagotomy antagonized the effect of injected capsaicin in the anesthetized guinea pigs. To investigate further the possible action of capsaicin, spantide (a substance P receptor antagonist) was administered before capsaicin challenge. Spantide injection in anesthetized guinea pigs attenuated the effects of the intravenous capsaicin challenge. In unanesthetized guinea pigs spantide pretreatment, as an aerosol, did not ameliorate the effects of a capsaicin aerosol challenge. However, intraperitoneal administration of spantide did reduce the effect of the capsaicin aerosol challenge as the specific airway resistance increased. Therefore, capsaicin produced its effects independent of vagal reflexes, although reflex actions of capsaicin could have occurred through other pathways. Reflex actions of capsaicin, however, were demonstrable only in the unanesthetized guinea pig. Because spantide attenuated the effect of capsaicin, increased insufflation pressure and specific airway resistance due to capsaicin challenge in both unanesthetized and anesthetized guinea pigs may be attributed, at least in part, to capsaicin's induction of substance P release or the release of other tachykinins.
Gluconeogenesis in liver and kidney of common murre (Uria aalge)
Authors: Herzberg G. R. , Brosnan J. T. , Hall B. , Rogerson M.
Published: December 2017

Phosphoenolpyruvate carboxykinase (PEPCK) in murre liver occurs in both cytoplasmic and mitochondrial forms. During a 3-day fast, hepatic PEPCK increases from 9.1 U/g with 19% cytosolic to 12.2 U/g with 35% cytosolic. The increase in activity is due almost entirely to increased cytosolic activity. PEPCK in murre kidney was present only in the mitochondrial compartment. Gluconeogenesis in vitro was determined in both hepatocytes and kidney tubules isolated from 3-day-fasted murres. In hepatocytes, lactate was the best substrate, but both pyruvate and alanine were good gluconeogenic substrates. This observation is consistent with the existence of a cytosolic form of PEPCK. In the kidney, glycerol was the best substrate but was only slightly better than lactate. Alanine and pyruvate were not as effective as gluconeogenic precursors, presumably because of the lack of cytosolic PEPCK. We propose that the major site of gluconeogenesis from amino acids in the murre is the liver, since this is a much larger organ than the kidney and has a cytosolic form of PEPCK necessary for gluconeogenesis from oxidized substrates.
Optimal contractility and minimal oxygen consumption for constant external work of heart
Authors: Tanaka N. , Yasumura Y. , Nozawa T. , Futaki S. , Uenishi M. , Hiramori K. , Suga H.
Published: December 2017

We theoretically considered the relation between left ventricular O2 consumption (MVO2) and a contractility index (Emax), searching for an optimal Emax that minimizes MVO2 for a given external mechanical work. We used one equation relating Emax with ventricular pressure and volume and another equation relating MVO2 with pressure-volume area (PVA). PVA is theoretically and experimentally a good predictor of MVO2 with Emax as a parameter. Then we could theoretically show the existence of the optimal Emax. For example, MVO2 was minimized to 8.9 ml O2.min-1.100 g-1 at an Emax of 6.3 mmHg.ml-1.100 g when cardiac output was 1.2 l/min, afterload pressure was 100 mmHg, and heart rate was 150 beats/min. These values can be observed experimentally in a 10- to 15-kg dog. Optimal Emax values for a wide range of external work fall in the middle of the normal working range of Emax. Thus our MVO2-PVA-Emax relationship supports the contemporary concept of the optimal contractility that MVO2 for a given cardiac external work is minimum at a middle level of ventricular contractility.
Effect of induced hypercapnia on anaerobic metabolic rate of anoxic musk turtles
Authors: Jackson D. C. , Wasser J. S. , Silver R. B.
Published: December 2017

To evaluate the possible effect of induced hypercapnia on anaerobic metabolic rate during anoxia, musk turtles (Sternotherus odoratus) were submerged in N2-equilibrated water at 10 degrees C for 3 days either with (anoxic hypercapnic) or without (anoxic normocapnic) elevated aquatic PCO2 (30-40 Torr). Control animals had access to air at 10 degrees C. Plasma [lactate] was significantly higher (P less than 0.01) in the normocapnic [59.4 +/- 7.4 (SD) mM; n = 22] than in the hypercapnic (47.4 +/- 8.5 mM; n = 19) anoxic turtles, although the hypercapnic turtles had lower blood pH (P less than 0.05). Plasma ion concentrations (Na, K, Cl, Ca, and Mg), however, were no different in the two groups, although all values other than Na were different from control. In some of the animals, [lactate] and [glycogen] (per g wet wt) of skeletal muscle, heart, and liver were measured in addition to blood acid-base values and lactate. Tissue lactates, although significantly elevated from control, and glycogens, although (with the exception of skeletal muscle) significantly reduced from control, were no different in the two anoxic groups. We suggest that these tissue data are more valid indicators of anaerobic metabolic rate than is plasma lactate and therefore conclude that induced hypercapnia does not significantly depress anaerobiosis in musk turtles at 10 degrees C.
A comparison of cholecystokinin-induced changes in gastric emptying and feeding in rats
Authors: Conover K. L. , Collins S. M. , Weingarten H. P.
Published: December 2017

We have compared the abilities of the cholecystokinin octapeptide (CCK-8) to delay gastric emptying and to influence feeding under similar experimental conditions in the rat. The effect of CCK-8 on gastric emptying was assessed in 6-h-deprived rats receiving 10-ml intragastric test loads of 0.15 M saline or 15% (wt/vol) sucrose. Analysis of half-emptying times indicated that intraperitoneal administration of CCK-8 in doses of 1.4-22.4 micrograms/kg produced a dose-dependent retardation of emptying of both saline and nutrient. Lower doses of CCK-8, 0.01 and 0.1 micrograms/kg, had no effect on gastric emptying. The effect of CCK-8 on feeding was assessed in normally feeding rats tested under the same experimental conditions used in the gastric emptying studies. Doses of CCK-8 capable of retarding gastric emptying also suppressed eating in a dose-dependent manner. These findings provide necessary correlational support for the hypothesis that the satiety produced by CCK-8 may be mediated by inhibition of gastric emptying. However, a further quantitative analysis of the correspondence of the gastric emptying and feeding effects of CCK-8 suggest that retardation of emptying cannot account entirely for the satiety effect of the peptide.
Liver fructose 2,6-bisphosphate in rats running at different treadmill speeds
Authors: Winder W. W. , Yang H. T. , Arogyasami J.
Published: December 2017

To determine the effect of work rate on liver fructose 2,6-bisphosphate (fructose 2,6-P2), rats were run for 5 min on a treadmill up a 15% grade at 16, 21, 26, 31, and 36 m/min. The liver content of fructose 2,6-P2 decreased 25, 42, 50, 62, and 71% from resting values after 5 min of running at these work rates. The time course of the decline in liver fructose 2,6-P2 was also studied in rats run at 16 m/min for times ranging from 5 to 100 min, at 23 m/min for times ranging from 5 to 60 min, and at 31 m/min for times of 5, 10, and 20 min. The hepatic content of fructose 2,6-P2 declined significantly after 5 min in all three groups of rats. The rate of decline was greatest in rats run at 31 m/min. After 100 min of running, fructose 2,6-P2 in livers of rats running at 16 m/min declined to levels seen in rats run at 31 m/min for 20 min. Changes in fructose 2,6-P2 occurred before a detectable decline in liver glycogen and in the absence of any significant change in blood glucose. Liver adenosine 3',5'-cyclic monophosphate (cAMP) was elevated after 5 min of exercise in rats running at 23 and 31 m/min but not in rats running at 16 m/min. By the end of exercise, hepatic cAMP was elevated in rats running at all speeds. The rapid decline in fructose 2,6-P2 probably plays a role in decreasing hepatic glycolysis, thereby ensuring that glucose 6-phosphate derived from glycogenolysis is diverted to blood glucose.
Hemodynamic responses to vasopressinergic antagonism in water-deprived conscious rats
Authors: Brizzee B. L. , Harrison-Bernard L. , Pretus H. A. , Clifton G. G. , Walker B. R.
Published: December 2017

Experiments were performed on conscious, chronically instrumented rats to determine the role of arginine vasopressin (AVP) on the systemic and regional hemodynamic effects of 48-h water deprivation. Arterial and venous catheters as well as pulsed Doppler flow probes were implanted in rats to measure cardiac output (CO), mesenteric blood flow (MBF), renal blood flow (RBF), or hindquarter blood flow (HQBF). After adequate recovery from surgey, euhydrated animals were administered a specific V1-vasopressinergic antagonist [d(CH2)5Tyr(Me)AVP, 10 micrograms/kg iv], a combined V1, V2-antagonist [d(CH2)5DTyr(Et)VAVP, 30 micrograms/kg iv], or saline vehicle (100 microliter/100 g). Neither antagonist was associated with any change in mean arterial blood pressure (MABP), heart rate (HR), systemic or regional flow or vascular resistance. All animals were subsequently water deprived for 48 h, at which time the experiments were repeated. Dehydration was associated with an increase in plasma AVP levels, hematocrit, and MABP but with a decrease in HR. Administration of either the combined V1, V2-antagonist or vehicle had no effect on any systemic or regional hemodynamic variables measured after 48-h dehydration. In contrast, although MABP, CO, MBF, and RBF were unaffected, V1-antagonism resulted in elevated HR, increased HQBF, and decreased hindquarter vascular resistance. In conclusion, AVP does not have a major effect on systemic hemodynamics in the dehydrated rat. However, certain beds may be affected by the relatively moderate levels of plasma AVP elicited during dehydration.
Hormonal and electrolyte responses of conscious sheep to 96 h of hypoxia
Authors: Curran-Everett D. C. , Claybaugh J. R. , Miki K. , Hong S. K. , Krasney J. A.
Published: December 2017

Hypoxia alters the relationship of aldosterone secretion to plasma renin activity. The potential role plasma electrolytes play in this modification is not clear. This study analyzed the interrelationships among renin, aldosterone, vasopressin (ADH), and plasma electrolytes during 96 h of normobaric hypoxia. Eight ewes were exposed, in discrete experiments, to hypocapnic hypoxia [arterial O2 tension (PaO2) 37-42 mmHg, arterial CO2 tension (PaCO2) 26-28 mmHg] and eucapnic hypoxia (PaO2 40-43 mmHg, PaCO2 28-31 mmHg) by N2 dilution in an environmental chamber. Urine output (24 h) was measured, and arterial plasma samples were collected during the normoxic control period and at 24-h intervals of hypoxia. Plasma Na+, K+, renin, and ADH levels did not change from the normoxic values during either hypocapnic or eucapnic hypoxia. However, urinary aldosterone excretion [critical significance (alpha) less than 0.046] and K+ excretion (alpha less than 0.046) decreased markedly during each type of hypoxia. All sheep developed a pronounced negative K+ balance by 96 h of hypoxia. These data suggest that plasma K+ concentration is preserved by movement of K+ out of the intracellular compartment; this change in K+ distribution may inhibit aldosterone secretion during hypoxia.
A compartmental analysis of solute transfer and exchange across blood-nerve barrier
Authors: Rechthand E. , Smith Q. R. , Rapoport S. I.
Published: December 2017

A three-compartment model was derived to analyze solute exchange among plasma, peripheral nerve epineurium, and endoneurium. The model was fit to measured tibial-nerve epineurial and endoneurial contents of [14C]sucrose after intravenous bolus injection of tracer in pentobarbital sodium-anesthetized rats. The transfer constant (K) for tracer at epineurial vessels approximated 1.1 X 10(-3) ml.s-1.g whole-nerve-1. K at the blood-nerve barrier (BNB) equaled 1.36-1.51 X 10(-5) ml.s-1.g endoneurium-1. The endoneurial uptake data were analyzed also by a simplified two-compartment model incorporating solute exchange between plasma and endoneurium. K at the BNB (1.46 X 10(-5) ml.s-1.g endoneurium-1), determined by multiple uptake time graphic analysis, was only threefold greater than K at the blood-brain barrier. The transfer constant at the perineurium alone was determined in situ and equaled (1 X 10(-6) ml.s-1.g endoneurium-1. Calculated permeability coefficients (X 10(-8) cm/s) equaled 3.2 at the perineurium, 23 at the endoneurial capillaries, and 3.2 at the brain vasculature. The results demonstrate that for hydrophilic nonelectrolytes 1) flux across the perineurium contributes significantly to solute uptake from plasma into the endoneurium; 2) although nerve capillaries are more permeable than brain capillaries, the tissues of the BNB function as a unit to markedly restrict solute diffusion into the endoneurium; and 3) a two-compartment analysis accurately describes hydrophilic solute transfer from plasma into peripheral nerve.
Muscle composition and its relation to sprint running in the lizard Dipsosaurus dorsalis
Authors: Gleeson T. T. , Harrison J. M.
Published: December 2017

Iguanid lizards exhibit considerable intraspecific variation in several aspects of their muscle composition. To determine the relationship of this variation to the variation in locomotor performance, running speeds of 20 male desert iguanas (Dipsosaurus dorsalis) of similar mass were measured from video recordings of animals as they sprinted down a 4.9-m runway maintained at 40 degrees C, the preferred body temperature of Dipsosaurus. Mean sprint speed ranged from 2.2 to 4.2 m/s. Selected muscles from these animals were then analyzed histochemically for fiber type size and composition, and the activities of citrate synthase, pyruvate kinase, and creatine kinase were measured. Muscle fiber cross-sectional areas were highly correlated within individuals, in three leg muscles and across all three fiber types, so that individuals could be characterized as possessing large or small fibers relative to the sample mean. Activities of all three enzymes also covaried within individuals so that individual lizards could be characterized as possessing high or low leg muscle catabolic capacity. There existed a significant and inverse relationship between fiber cross-sectional areas and muscle enzyme activities so that individuals with small muscle fibers tended to have higher catabolic capacities. Approximately 25-30% of the variation in mean sprint running speed could be predicted by variation in muscle fiber areas alone. The use of muscle fiber areas and snout vent length as independent variables in a multiple-regression equation explained approximately 50% of the sprint-running variation.(ABSTRACT TRUNCATED AT 250 WORDS)
Vasoactive intestinal peptide stimulates blood flow and secretion of avian salt glands
Authors: Gerstberger R. , Sann H. , Simon E.
Published: December 2017

The neuromodulatory role of vasoactive intestinal peptide (VIP) in avian salt gland secretion and blood flow was investigated in conscious saltwater-acclimated Pekin ducks. Glandular blood flow was measured by laser-Doppler flowmetry or the radioactive microspheres technique. Osmolal excretion was closely related to salt gland blood flow during salt loading. At threshold conditions of salt gland secretion, VIP infused intracarotidally induced both osmolal excretion and arteriolar vasodilation dose dependently (30-240 pmol.min-1.kg body wt-1). The VIPergic effect on the secretory process for NaCl was enhanced by simultaneous intracarotid application of acetylcholine (5 nmol.min-1.kg body wt-1), whereas the intrinsic vasodilatory potency of acetylcholine appeared to be nonadditive in coinfusion experiments. Ongoing secretion induced by systemic infusion of hypertonic saline could be suppressed by muscarinic antagonists, with salt gland blood flow being sustained at the reduced level of atropine-resistant vasodilation. Subsequent intracarotid infusion of VIP stimulated glandular blood perfusion and also, to a minor extent, osmolal excretion, suggesting an independent, functional VIP system in efferent salt gland control.
Sugar-stimulated ion absorption is not different in seahare and vertebrate intestine
Authors: Moran W. M. , Garretson L. T.
Published: December 2017

We have reexamined the notion that sugars stimulate ion absorption differently in invertebrate and vertebrate intestine. In the seahare intestine, mucosal sugar presumably increases the rate of transcellular Na+ and Cl- absorption, whereas only transcellular Na+ absorption is increased in the vertebrate small intestine. Our data indicate that the seahare intestine responds to mucosal D-galactose like the vertebrate small intestine: namely, the apical membrane electrical potential difference depolarizes, the ratio of the mucosal to serosal membrane resistances decreases, and the short-circuit current (Isc) increases. Because mucosal substitution of tetramethylammonium for Na+ abolished the increased Isc, this stimulation resulted from an increase in rheogenic Na+ absorption. Unidirectional transepithelial Cl- fluxes indicate that mucosal D-galactose had no effect on the net Cl- flux under short-circuit conditions. Further, ion substitution experiments indicate that the apical membrane is K+ conductive rather than Cl- conductive as previously reported. These electrophysiological as well as parallel histological findings indicate that studies previously reported on the seahare intestine were in fact conducted on the esophagus.
Parathyroid hormone-like immunoreactivity in brains of tetrapod vertebrates
Authors: Pang P. K. , Harvey S. , Fraser R. , Kaneko T.
Published: December 2017

Heat-stable nondialyzable immunoreactive (IR) parathyroid hormone (PTH)-like activity, that coelutes with authentic PTH on Sep-Pak C18 columns and reverse-phase high-performance liquid chromatography, was measured in the brain, hypothalamus, and pituitary of amphibian, reptilian, avian, and mammalian species, using two specific antisera raised against the 48-64 region of the intact PTH molecule. In each case the IR PTH concentration was greater than that present in peripheral plasma and in rats was not affected by dietary calcium status. Extracts of muscle, liver, and kidney tissue were without IR PTH activity. These results demonstrate the extraparathyroidal occurrence of PTH-like peptides in nontumorous neuroendocrine tissues of vertebrate species. These findings may have evolutionary significance, since IR PTH was present in the brain and plasma of species that lack encapsulated parathyroid glands.
Differentiation of cardiac baroreflex properties by cuff and drug methods in two rabbit strains
Authors: Weinstock M. , Korner P. I. , Head G. A. , Dorward P. K.
Published: December 2017

Sigmoidal mean arterial pressure (MAP)-heart rate (HR) curves were obtained in two genetically related strains of rabbits (groups I and II). We examined vagal (V) and sympathetic (S) effects on HR using perivascular cuffs and vasoactive drugs to alter MAP, and we studied the effects of intravenous naloxone, which affected only I. With the cuff method, both V and S components of gain were much greater in I than in II, and naloxone greatly reduced the difference. With the drug method, gain was similar in I and II and unaffected by naloxone. With both methods, the V component of HR range between plateaus was greater in I than in II because of more pronounced bradycardia at the lower plateau; naloxone eliminated the latter difference when the reflex was drug induced but not when it was cuff induced. The S component of HR range was similar in I and II; with both methods, the tachycardia plateau was reduced by naloxone. The cuff method alters cardiac load more than the drug method, leading to engagement of different groups of afferents for a given change in MAP (delta MAP). We have derived an input-output model, which suggests that with the drug method, gain is almost entirely determined by the input from the arterial baroreceptors, accounting for the minimal difference between I and II. With the cuff method, gain is determined by a nonlinear interaction involving the arterial and nonarterial baroreceptors, which accentuates the response. The opiate mechanism is associated with the nonarterial baroreceptor input and has amplifying properties, which account for the difference in gain between I and II. The two methods and naloxone provide a novel way of differentiating the effector patterns of the reflex; naloxone serves as a marker of activity in a particular pathway.
Renal interstitial hydrostatic pressure during pressure natriuresis in hypertension
Authors: Khraibi A. A. , Knox F. G.
Published: December 2017

The objective of this study was to test the hypothesis that changes in renal perfusion pressure (RPP) are not fully transmitted to the renal interstitium in spontaneous hypertension in comparison with normotensive states. Okamoto spontaneously hypertensive and normotensive Wistar-Kyoto rats were used in this study. Renal interstitial hydrostatic pressure (RIHP) was measured directly and continuously via a polyethylene matrix that was implanted chronically in the left kidney 3 wk before RIHP measurement. When RPP was allowed to increase from 136 +/- 0.5 to 162 +/- 1.3 mmHg in male spontaneously hypertensive rats, RIHP was not significantly changed from 3.7 +/- 0.9 to 4.6 +/- 1.1 mmHg, and fractional excretion of sodium (FENa) increased significantly from 0.26 +/- 0.12 to 0.65 +/- 0.15% (P less than 0.05). When RPP was allowed to change from 104 +/- 0.9 to 127 +/- 1.3 mmHg in male Wistar-Kyoto rats, RIHP increased markedly from 4.0 +/- 0.3 to 7.2 +/- 0.4 mmHg (P less than 0.05), and FENa was significantly elevated from 0.27 +/- 0.08 to 2.02 +/- 0.55% (P less than 0.05). In conclusion, spontaneously hypertensive rats have a blunted increase in RIHP and pressure natriuresis response in comparison with Wistar-Kyoto rats. Thus, in Okamoto spontaneously hypertensive rats, the effect of RPP on RIHP is attenuated, leading to a blunted pressure natriuresis response.
Differential maturation of beta-adrenoceptor-mediated responses in the lamb fetus
Authors: Rawashdeh N. M. , Rose J. C. , Ray N. D.
Published: December 2017

To study the functional maturity of beta-receptor-mediated responses, seven chronically catheterized lamb fetuses, 93-107 days of gestation, and seven fetuses, 116-134 days of gestation, received intravenous randomly sequenced infusions of isoproterenol (ISO) 0.03, 0.06, and 0.125 micrograms.kg-1.min-1 for 10 min separated by 45-min intervals or two saline infusions followed by 0.125 micrograms.kg-1.min-1 ISO after treatment with 0.5 mg/kg propranolol (PRO). Each fetus received the two treatments 24-48 h apart. In immature fetuses, plasma renin activity (PRA) of 2.0 +/- 0.7 ng.ml-1.h-1 did not change with either protocol. In mature fetuses, PRA of 7.5 +/- 2.5 ng.ml-1.h-1 increased two- to three-fold after the infusion of the highest two doses of ISO (P less than 0.003). Propranolol blocked this response. No significant changes were observed after the infusions of the lowest dose of ISO or saline. Both groups showed significant heart rate increases with all doses of ISO. Propranolol injection decreased heart rate significantly and blocked responses to ISO. We conclude that although a cardiac beta-receptor-mediated response is present by 93 days of gestation in the lamb fetus, a renal beta-receptor-mediated response, renin secretion, is absent.
Influence of pregnancy and lactation on Na appetite of BALB/c mice
Authors: McBurnie M. , Denton D. , Tarjan E.
Published: December 2017

The effect of pregnancy and lactation on sodium appetite, water, and food intake of young adult BALB/c mice was studied. Voluntary sodium intake increased fourfold during the last 3 days of gestation. Water and food intake and body weight also increased significantly. During the last 14 days of lactation, sodium intake was increased significantly three- to fivefold, relative to base-line period and a control group. Large significant increase of water and food intake occurred also during lactation. After weaning, intake returned to base line. Calculation of sodium sequestered in young in utero and provided to pups during lactation showed increased voluntary intake in great excess of metabolic need, suggestive of hormonal determination of sodium appetite during reproduction as in wild rabbits.
Inhibitor of protein synthesis phase shifts a circadian pacemaker in mammalian SCN
Authors: Inouye S. T. , Takahashi J. S. , Wollnik F. , Turek F. W.
Published: December 2017

The suprachiasmatic nucleus (SCN) of the hypothalamus contains a circadian pacemaker that regulates many circadian rhythms in mammals. Experimental work in microorganisms and invertebrates suggests that protein synthesis is required for the function of the circadian oscillator, and recent experiments in golden hamsters suggest an acute inhibition of protein synthesis can induce phase shifts in a mammalian circadian pacemaker. To determine whether protein synthesis in the SCN region is involved in the generation of circadian rhythms in mammals, a protein synthesis inhibitor, anisomycin, was microinjected into the SCN region, and the effect on the circadian rhythm of locomotor activity of hamsters was measured. A single injection of anisomycin into the SCN region induced phase shifts in the circadian activity rhythm that varied systematically as a function of the phase of injection within the circadian cycle. These results suggest that protein synthesis may be involved in the generation of circadian rhythms in mammals and that the anatomic site of action of anisomycin is within the hypothalamic suprachiasmatic region.
Inhibition of paraventricular neurons by subfornical organ and AV3V in cats
Authors: Osaka T. , Yamashita H. , Koizumi K.
Published: December 2017

The study was designed to examine, by electrophysiological techniques, influences of rostral periventricular structures on neurons in the hypothalamic paraventricular nucleus (PVN) in a large animal (the cat) in which stimulating and recording sites could be precisely identified. Extracellular single action potentials were recorded from the PVN in pentobarbital sodium-anesthetized and hemispherectomized cats. Of 246 neurons tested, 24-47% were inhibited and 9-21% were excited by electrical stimulation of the subfornical organ (SFO), the nucleus preopticus medianus (POMn), and the organum vasculosum of the lamina terminalis (OVLT). The onset latencies of inhibition (19-26 ms) were shorter than those of excitation (28-80 ms). Responses of both neurosecretory and nonneurosecretory neurons were similar to the stimulation of all sites tested. Among these sites, the POMn had the strongest influence on the PVN in view of the proportion of the responsive neurons. Moreover, antidromically evoked action potentials in the PVN neurons (n = 10) were only observed after stimulation of the POMn. Chemical stimulation of POMn and SFO by microinjection of sodium glutamate (50-100 nl, 0.5 M) also inhibited 16 of 38 PVN cells; the remaining neurons were unaffected. These results suggest that activation of the POMn, OVLT, and the SFO neurons mainly inhibits the PVN neurons in the cat.