bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of thyroid hormone replacement on beta-adrenergic responsiveness of food-deprived rats
Authors: Barney C. C. , Wuertz K. E. , Katovich M. J.
Published: December 2017

Thyroid hormone levels and beta-adrenergic responsiveness after stimulation with the beta-adrenergic agonist isoproterenol were studied in four groups of male rats. The groups used were control rats, rats deprived of food for 72 h, rats administered 50 micrograms thyroxine (T4)/kg daily for 4 days, and rats deprived of food for 72 h and administered 50 micrograms T4/kg daily for 4 days. Food deprivation significantly decreased serum T4 and triiodothyronine (T3) levels, and administration of T4 significantly increased serum T4 and T3 levels in both fed and food-deprived rats. Administration of T4 led to lower body weights in both fed and food-deprived rats. Administration of isoproterenol led to increases in colonic and tail skin temperatures and heart rate. Food deprivation significantly attenuated the increased body temperatures and heart rate induced by isoproterenol, and administration of T4 to food-deprived rats returned these adrenergic responses to control levels. Administration of T4 to fed rats significantly increased the thermal and cardiac responses to isoproterenol above those of the control rats. Administration of isoproterenol also increased plasma glucose levels. Food deprivation significantly decreased both postsaline- and isoproterenol-stimulated glucose levels. However, administration of T4 was without effect on either the postsaline- or isoproterenol-stimulated glucose levels of either the fed or food-deprived rats. The decreases in T4 and T3 that accompany food deprivation may thus be responsible for some, but not all, of the reductions in beta-adrenergic responsiveness observed in food-deprived rats.
Respiratory phase locking during mechanical ventilation in anesthetized human subjects
Authors: Graves C. , Glass L. , Laporta D. , Meloche R. , Grassino A.
Published: December 2017

The coupling patterns between the rhythm of a mechanical ventilator and the rhythm of spontaneous breathing were studied in enflurane-anesthetized adult human subjects. The spontaneous breathing pattern was altered in response to different frequencies and amplitudes of forced lung inflations. A 1:1 phase locking (the frequency of the mechanical ventilator is matched by the frequency of spontaneous breathing with a fixed phase between the 2 rhythms) was observed in a range of up to +/- 40% of some of the subject's spontaneous breathing frequencies. During 1:1 phase locking, there were marked changes in the expiratory duration as measured from the electromyogram of the diaphragm. The phase relationship between onset of inflation and onset of inspiration depended on the frequency and amplitude of mechanical inflation. At ventilator settings that did not give 1:1 phase locking, other simple phase-locked patterns, such as 1:2 and 2:1, or irregular non-phase-locked patterns were observed. Reflexes arising from lung inflation, which may underlie the entrainment, are discussed in the context of these results.
Control of food intake by fatty acid oxidation
Authors: Scharrer E. , Langhans W.
Published: December 2017

The role of fatty acid oxidation in the control of food intake was studied using mercaptoacetate (MA), an inhibitor of fatty acid oxidation. Food intake, plasma free fatty acids (FFA) and ketone bodies, and blood glucose were measured. Rats were fed either a low-fat (LF, 3.33% fat) or a medium-fat (MF, 18% fat) diet. At the onset of the dark phase of the lighting cycle, MA did not affect food intake in LF rats but increased it 74% in MF rats in comparison to control. Four hours after the injection the effect of MA on food intake disappeared. In the middle of the bright phase of the lighting cycle, MA increased food intake in MF rats approximately 120% up to 6 h postinjection. After MA, plasma FFA concentration was elevated, and plasma 3-hydroxybutyrate concentration was lowered, indicating that fatty acid oxidation had been successfully reduced. MA did not affect blood glucose. These results indicate fatty acid oxidation is involved in the control of food intake, at least when the dietary fat level is relatively high.
Ventricular efficiency predicted by an analytical model
Authors: Burkhoff D. , Sagawa K.
Published: December 2017

Based on the recent data from the literature, we derived analytic expressions for ventricular stroke work (SW), ventricular O2 consumption, and the ratio of the former to the latter, defined as ventricular efficiency, in terms of ventricular contractile properties and arterial afterloading properties. The ventricular properties were quantified by Ees and V0, the slope and volume axis intercept, respectively, of the linear end-systolic pressure-volume relationship. Ventricular afterload was represented by the effective arterial elastance (Ea), a parameter that is dependent on aortic input impedance parameters. O2 consumption was assessed by estimating ventricular pressure-volume area, which has been shown to be linearly related to O2 consumption. Model analysis indicated that SW is maximum when Ea = Ees, the afterload that results in the greatest efficiency is always less than that which provides the maximum SW, the SW and efficiency of a weak heart are more sensitive to changes in afterload than in a strong heart, and there is a sigmoidal relation between ventricular efficiency and end-diastolic volume that reaches its maximum at volumes outside the upper limit of the physiological range. Further analysis of the model indicated that under physiological conditions ventricular and arterial properties may be adjusted more toward optimization of efficiency than SW.
Norepinephrine turnover in brown adipose tissue is stimulated by a single meal
Authors: Glick Z. , Raum W. J.
Published: December 2017

A single meal stimulates brown adipose tissue (BAT) thermogenesis in rats. In the present study the role of norepinephrine in this thermogenic response was assessed from the rate of its turnover in BAT after a single test meal. For comparison, norepinephrine turnover was determined in the heart and spleen. A total of 48 male Wistar rats (200 g) were trained to eat during two feeding sessions per day. On the experimental day, one group (n = 24) was meal deprived and the other (n = 24) was given a low-protein high-carbohydrate test meal for 2 h. The synthesis inhibition method with alpha-methyl-p-tyrosine was employed to determine norepinephrine turnover from its concentration at four hourly time points after the meal. Tissue concentrations of norepinephrine were determined by radioimmunoassay. Norepinephrine concentration and turnover rate were increased more than threefold in BAT of the meal-fed compared with the meal-deprived rats (P less than 0.001 and P less than 0.005 for concentration and turnover, respectively). Neither were significantly altered by the meal in the heart or spleen. Other measures of turnover kinetics, turnover time and rate constant, were not significantly affected in any of the tissues examined. Our data suggest that norepinephrine mediates a portion of the thermic effect of meals that originate in BAT.
Pressure-volume characteristics of aortas of harbor and Weddell seals
Authors: Rhode E. A. , Elsner R. , Peterson T. M. , Campbell K. B. , Spangler W.
Published: December 2017

The mechanical properties of the radially enlarged proximal segment of the aorta of diving marine mammals was studied on 15 excised aortas of harbor seals and five aortas of Weddell seals. This was done by recording static pressure-volume relationships for the whole thoracic aorta, the aortic bulb, and the descending thoracic aorta and passive length-tension measurements of aortic strips. Aortic bulb volume distensibility was found to be much greater than that of the descending thoracic aorta or of an equivalent aortic segment of terrestrial mammals. The consequences were that the total potential energy and volume that may be stored within the aortic bulb is very large, with a capacity for storage of the stroke work of more than two normal heart beats and a volume of more than three times normal stroke volume. The aortic bulb has an average radius and wall thickness twice that of the descending aorta, but at any level of distension the wall stress (g/cm2) is the same throughout. The static mechanical properties of aortic strips from the bulb and descending thoracic aortas were not markedly different, so that the differences in the pressure-volume relationships are explained by differences in geometry of the two sections. The expanded aortic bulb functions through energy and volume storage actions and through uncoupling actions to maintain arterial pressures and stroke volume at near predive levels during a dive.
Partition of heat loss in resting and exercising winter- and summer-insulated reindeer
Authors: Folkow L. P. , Mercer J. B.
Published: December 2017

Partition of heat loss was performed in resting (standing) and exercising (running; 9.2 km . h-1 for 40 min) winter- (W) and summer- (S) insulated conscious reindeer (Rangifer tarandus tarandus) in a climatic chamber set to an ambient temperature (Ta) of -30, 0, or 25 degrees C. Heat loss and production were determined using indirect calorimetry. The relative importance of radiant heat loss was greatest during rest at low Ta's, both during winter and summer (44-58% at Ta's -30 and 0 degrees C). At high Ta's, especially during exercise, a large proportion of total heat loss occurred through evaporation [45% at Ta 25 degrees C during rest and 47% at Ta 0 degrees C during exercise (W); 38% at Ta 25 degrees C during exercise (S)]. The proportion of heat lost through convection during rest and exercise was 38-52 and 46-72%, respectively, depending on Ta and season. The legs were found to represent an important avenue for radiant heat loss, particularly in heat stress situations. Their importance for convective heat loss was even greater, especially during exercise.
Food intake, feeding rhythm, and body mass regulation in Svalbard rock ptarmigan
Authors: Stokkan K. A. , Mortensen A. , Blix A. S.
Published: December 2017

Food intake (FI), feeding activity (FA), and body mass (BM) were recorded continuously throughout a 13-mo period in Svalbard rock ptarmigan kept under natural conditions of light and ambient temperature at Svalbard (79 degrees N). FI was persistently high from March until August, including the period when daylight is continuous, whereas it was low from November until January, when it is permanently dark. From August until November, BM doubled, while FI dropped to one-third. BM fell rapidly from mid-November until April despite a doubling of FI from February until March. From August until mid-November and from February until mid-April FA occurred mainly during the light period of the day. From late November until February and from mid-April until August intermittent FA occurred continuously. It is suggested that the seasonal changes in BM are not determined by FI alone but depend heavily on seasonal changes in locomotor activity as reflected in FA.
Effects of dietary protein and tyrosine on behavior of diabetic rats
Authors: Bellush L. L. , Rowland N. E.
Published: December 2017

Streptozotocin-diabetic and nondiabetic control male rats were fed synthetic diets varying in macronutrient content (experiment 1) or diets with or without added tyrosine (experiments 2 and 3). All rats were evaluated for stereotyped behaviors after administration of apomorphine (1 mg/kg) and amphetamine (3 and 5 mg/kg). At the end of experiments 2 and 3, rates of tyrosine hydroxylation in hypothalamus, nucleus accumbens, and striatum were determined by measuring L-3,4-dihydroxyphenylalanine concentrations after decarboxylase inhibition. In experiment 3 the ratios of tyrosine to dopamine were also measured in striatum and nucleus accumbens. Diabetic rats fed a standard high-carbohydrate diet showed decreased stereotypy relative to controls. Neither systematic alterations of fat or protein content of the diet nor selective tyrosine enrichment affected this attenuation of stereotypy in diabetics. L-3,4-dihydroxyphenylalanine concentration in nucleus accumbens was increased by dietary tyrosine enrichment in experiment 2 but not in experiment 3. However, brain tyrosine levels were elevated in rats fed tyrosine-enriched diets. These results argue against a significant contribution of precursor elevation to catecholamine function and behavior in experimental diabetes.
Electrical stimulation in subfornical organ increases plasma vasopressin concentrations in the conscious rat
Authors: Ferguson A. V. , Kasting N. W.
Published: December 2017

Electrical stimulation in the subfornical organ (SFO) of conscious freely moving rats was found to increase plasma vasopressin concentrations from control values of 1.43 +/- 0.32 to poststimulation values of 22.32 +/- 4.9 pg/ml (P less than 0.01). Similar stimulation in immediately adjacent brain regions including the medial septum and hippocampal commissure caused no significant changes in plasma concentrations of this peptide hormone. These data indicate that activation of SFO neurons in conscious rats causes increased release of vasopressin from the posterior pituitary. Such data corroborate previous electrophysiological findings demonstrating that in anesthetized animals electrical stimulation in SFO results in increased excitability of antidromically identified vasopressin-secreting neurons in the supraoptic and paraventricular nuclei of the hypothalamus.
Hematocrit variation during sleep apnea in elephant seal pups
Authors: Castellini M. A. , Costa D. P. , Huntley A.
Published: December 2017

Hematocrit (Hct) levels were found to increase throughout long-duration sleep apnea in the northern elephant seal pup. Breath holds ranging from 4 to greater than 11 min were sampled. Blood collected from the extradural intravertebral vein showed an increase in Hct from 55.6 to 63.1% with the peak value occurring within 1 min of the end of apnea. Plasma lactate did not change throughout the breath hold. Previous observations of changing Hct levels in seals were made on animals diving naturally, and consequently the effects of exercise could not be separated from those of apnea. The results of this study demonstrate that the rise in Hct is produced quickly upon apnea, occurs without significant levels of hypoxic metabolism, and does not depend on exercise.
Renin-angiotensin system, converting-enzyme inhibition and kidney function in aging female rats
Authors: Corman B. , Michel J. B.
Published: December 2017

The age-related changes in the renin-angiotensin system were investigated in normotensive 3-, 10-, 20-, and 30-mo-old female Wistar rats. Plasma renin concentration and immunofluorescent renal renin index remained constant from 3 to 10 mo, then decreased as the animals become older, whereas plasma concentration of renin substrate diminished slightly between 10 and 20 mo and plasma converting-enzyme activity was not modified with age. Acute inhibition of converting-enzyme activity by intravenous administration of 0.1 mg/100 g body wt S 9780 (the diacid form of S 9490) was followed by a 7- to 8-mmHg decrease in arterial pressure and a concomitant 10-12% increase in inulin and p-aminohippuric acid (PAH) clearance in the 10- and 20-mo-old rats. On the other hand, neither glomerular filtration rate, PAH clearance nor arterial blood pressure were affected by converting-enzyme inhibition in the 30 mo-old rats. These results indicate that the activity of the renin-angiotensin system is progressively reduced with age and suggest that angiotensin II does not play an important role in the maintenance of blood pressure and kidney hemodynamics in normotensive female senescent rats.
Mechanisms of endotoxin-induced impairment in Na+-Ca2+ exchange in canine myocardium
Authors: Liu M. S. , Xuan Y. T.
Published: December 2017

Effects of endotoxin administration on the Na+-Ca2+ exchange in canine cardiac sarcolemma were characterized. In addition, roles of phospholipase A2 and phosphorylation on the endotoxin-induced impairment in Na+-Ca2+ exchange were investigated. The results show that intravesicular sodium (Nai+)-dependent 45Ca2+ uptake was decreased by 39-66% (P less than 0.05) and extravesicular sodium (Nao+)-induced 45Ca2+ efflux was decreased by 36-52% (P less than 0.05) at 2 h following endotoxin administration. Ca2+o-induced 45Ca2+ efflux in the absence of Ko+ was not affected, but Ca2+o-induced 45Ca2+ efflux in the presence of Ko+ was significantly reduced by endotoxin administration. The stoichiometry of Na+-Ca2+ exchange was altered from 3 Na+ for 1 Ca2+ for the control to 2 Na+ for 1 Ca2+ for the endotoxin-treated dogs. The ATP-dependent 22Na+ uptake and Na+-Ca2+ exchange in inside-out vesicles remained unchanged after endotoxin injection. Digestion of control heart sarcolemmal vesicles with exogenous phospholipase A2 (0.02-0.06 unit/500 micrograms protein) inhibited Na+-Ca2+ exchange activity measured as Nai+-dependent 45Ca2+ uptake, and the inhibition was concentration dependent. Lysophosphatidylcholine addition to the control cardiac sarcolemma had no effect on Na+-Ca2+ exchange. The inhibition of Na+-Ca2+ exchange caused by phospholipase A2 digestion in the control heart sarcolemma was completely reversible by the addition of phosphatidylcholine (0.1 mM). The inhibition of Na+-Ca2+ exchange caused by the in vivo administration of endotoxin was completely reversible by the addition of phosphatidylcholine (0.1-0.15 mM).(ABSTRACT TRUNCATED AT 250 WORDS)
Liver glycogenolysis during exercise in adrenodemedullated male and female rats
Authors: Winder W. W. , Loy S. F. , Burke D. S. , Hawkes S. J.
Published: December 2017

Previous studies have shown that adrenodemedullation has no effect on the rate of liver glycogenolysis during exercise in male rats. Mature female rats have been reported to have a higher hepatic beta-adrenergic receptor activity than do male rats of the same age. The present study was undertaken to determine the role of plasma epinephrine in stimulating liver glycogenolysis during exercise in female rats. Both male and female rats were adrenodemedullated or sham operated. Three weeks later rats were run for 60 min at 21 m/min up a 15% grade. The rate of liver glycogenolysis during exercise was not affected by adrenodemedullation in either female rats or male rats. Hepatic adenosine 3',5'-cyclic monophosphate increased to approximately the same extent in sham operated as in adrenodemedullated female rats during exercise. Adrenodemedullation caused a significant reduction in the amount of glycogen utilized by the soleus muscle and in the degree of hyperglycemia during exercise. We conclude that epinephrine is unessential for stimulation of liver glycogenolysis during exercise in either male or female rats.
Micturition in rats: a chronic model for study of bladder function and effect of anesthetics
Authors: Yaksh T. L. , Durant P. A. , Brent C. R.
Published: December 2017

The volume-evoked micturition reflex (VEMR) and the effects of anesthetics on the VEMR were studied in a chronic unanesthetized rat model. The bladder catheter was implanted chronically through a laparotomy and externalized percutaneously. An intrathecal (IT) catheter was implanted chronically in animals scheduled for an IT injection. By 2 days after implantation, infusion of saline (200 microliter/min) in the bladder reliably resulted in a low base-line pressure (BP) followed by a transient increase in bladder pressure, an opening of the sphincter (bladder opening pressure, BOP) corresponding to expression of urine (volume of urination, V), then a further rise in pressure (peak pressure, PP) and a subsequent return to base line. Seven days after implantation, values (means +/- SE) for BP, BOP, PP, and V were 10 +/- 0.3, 30 +/- 2, 67 +/- 6 cmH2O, and 1.0 +/- 0.1 ml, respectively. Residual volumes were reliably less than 2-4% of the expressed volume. The VEMR was reliably evoked up to 28 days after implantation. V values in unimplanted and implanted animals were not different. In implanted animals, VEMR parameters were not different during infusion or during spontaneous urination after oral fluid load. Administration of pentobarbital sodium (50 mg/kg ip), alpha-chloralose (130 mg/kg ip), ketamine (100 mg/kg im), halothane (in air 2%), and local anesthetics (2-chloroprocaine 3% or bupivacaine 0.75%, 10 microliter IT) produced a complete blockade of the VEMR and overflow incontinence at pressures significantly higher than BOP values. To compare overflow pressures and passive compliance of the bladder, unanesthetized animals were decapitated.(ABSTRACT TRUNCATED AT 250 WORDS)
Localization of efferent function in the dorsal motor nucleus of the vagus
Authors: Laughton W. B. , Powley T. L.
Published: December 2017

To investigate the spatial organization of the vagal preganglionic neurons that control gastric acid, insulin and glucagon secretion, as well as bradycardia, these variables were simultaneously monitored before, during, and after monopolar stimulation (50 microA, 1 ms, 50 Hz) through semimicroelectrodes (tip 25-50 microns) in urethan-chloralose-anesthetized rats. Gastric acid, insulin, and glucagon secretion were elicited by stimulation of the dorsal motor nucleus of the vagus (DMV), whereas heart rate, mean arterial blood pressure, and plasma glucose were not affected. Post hoc analyses were used to characterize the viscerotopic patterns within the DMV. For each of the three positive responses, the “center of gravity” (centroid) of 205 stimulation sites was located within the DMV at approximately the midanterioposterior extent of the nucleus. Vectors of response effectiveness around the centroids as well as comparisons of different groups of DMV electrodes established that effective sites were found throughout the full rostrocaudal extent of the DMV. Comparisons of left vs. right DMV sites indicated that gastric acid, insulin, and glucagon secretion are influenced equally by the two sides of the brain stem. The differences in response strength observed in the DMV were best described in terms of the discrete medial and lateral longitudinal columns of the DMV. The centroid point for gastric acid was in the medial DMV, and the points for insulin and glucagon were in the lateral DMV. Further, medial placements were significantly more effective than lateral ones in eliciting gastric acid secretion; lateral placements were more effective than medial ones in eliciting insulin secretion. Although the effect was not significant in the case of glucagon, the trend paralleled the pattern for insulin.
CRF initiates biological actions within the brain that are observed in response to stress
Authors: Lenz H. J. , Raedler A. , Greten H. , Brown M. R.
Published: December 2017

Corticotropin-releasing factor (CRF) is thought to be an endogenous mediator of adrenocorticotropic hormone release following stress. We examined if CRF initiates further biological actions that are observed in response to stressful events. Male beagle dogs (10–12 kg) were fitted with a chronic intracerebroventricular cannula, intra-arterial and intravenous catheters, as well as a gastric fistula. Synthetic human CRF was microinjected into the third cerebral ventricle in conscious animals. CRF (0.1–1.0 nmol/kg) significantly (P less than 0.01) increased plasma concentrations of epinephrine, norepinephrine, glucagon, and glucose and elevated mean arterial pressure and heart rate. Pretreatment of the animals with the ganglionic blocking agent chlorisondamine completely abolished the increases in plasma catecholamine and glucose concentrations as well as the elevations in blood pressure and heart rate. CRF significantly (P less than 0.01) inhibited gastric acid secretion, but not plasma gastrin concentrations stimulated by an 8% liquid peptone meal. The gastric inhibitory action of CRF was completely prevented by chlorisondamine and, in part, by naloxone and a vasopressin antagonist. In contrast, bilateral truncal vagotomy did not affect the gastric inhibitory action of CRF. The results of this study indicate that CRF acts within the central nervous system to increase plasma glucose and glucagon concentrations, mean arterial pressure, and heart rate by activation of the autonomic nervous system. CRF inhibits meal-stimulated gastric acid secretion by activation of the sympathetic nervous system and, in part, by opiate and vasopressin-dependent pathways and not by inhibition of gastrin release.(ABSTRACT TRUNCATED AT 250 WORDS)
Central angiotensin II and PGE2 act independently to increase blood pressure in conscious sheep
Authors: Breuhaus B. A. , Chimoskey J. E.
Published: December 2017

Conscious adult female sheep chronically prepared with nonocclusive indwelling vascular and cerebroventricular catheters were used to determine whether centrally administered prostaglandin E2 (PGE2) increases blood pressure by activation of the brain renin angiotensin system or whether centrally administered angiotensin II (ANG II) increases blood pressure by stimulating prostaglandin synthesis in the brain. Intracerebroventricular (ivt) ANG II, 50 ng X kg-1 X min-1, increased arterial pressure 23 mmHg (P less than 0.01) 30 min after the start of infusion. Infusion of the ANG II antagonist [Sar1-Thr8]ANG II (sarthran), 1,000 ng X kg-1 X min-1 ivt, had no effect on arterial pressure when given by itself but reduced the ivt ANG II-induced pressor response to 5 mmHg (P less than 0.05) when the two peptides were infused at the same time. Intracerebroventricular infusion of sarthran did not alter the pressor responses to intracarotid (ic) PGE2 or to ivt PGE2. Blood pressure increased 21 mmHg (P less than 0.01) 30 min after the start of PGE2 infusion when PGE2 was given ic by itself, compared with 17 mmHg (P less than 0.01) when PGE2 was given ic at the same time as sarthran was given ivt. Blood pressure increased 14 mmHg (P less than 0.01) 30 min after the start of PGE2 infusion when PGE2 was given ivt by itself, compared with 16 mmHg (P less than 0.01) when PGE2 was given ivt at the same time as sarthran was given ivt. Pretreatment with the cyclooxygenase inhibitors indomethacin, 4 mg/kg sc, or flunixin meglumine, 3 mg/kg iv, did not alter the ivt ANG II-induced pressor response.(ABSTRACT TRUNCATED AT 250 WORDS)
Phase setting of circadian locomotor rhythm of infant rats
Authors: Honma K. , Honma S. , Shirakawa T. , Hiroshige T.
Published: December 2017

Postnatal phase setting of pup circadian rhythm by nursing mother was examined in rats by mother-pup exchange experiments. To know the effect of phase reversal of the nursing mother, pups were exchanged after birth so that a mother rat raised pups, half of which were born to her and the other half which came from a reversed mother, and activity onset and offset of pup locomotor rhythm were measured at weaning. Effects of litter size were also examined. Direct entrainment to light-dark cycles was excluded by blinding pups. In the unexchanged group, a strong positive correlation was detected between the phase of the circadian rhythm at weaning and the free-running period measured after weaning. The area covered by the 99% confidence interval of the regression line was used for the phase reference zone, and the circadian rhythm of an exchanged pup whose phase at weaning was located outside the reference zone was regarded as having been influenced by the nursing mother. The complete phase reversal occurred in two out of seven exchanged pups when litter size was relatively large (n = 5-7) and in 9 out of 11 when litter size was small (n = 2). It is concluded that the nursing mother rat is capable of phase setting the circadian locomotor rhythm of blinded pups. This maternal effect seems to be related to litter size.
Cardiovascular and endocrine response to hemorrhage after alpha 1-blockade in lambs and ewes
Authors: Block S. M. , Rose J. C. , Ernest J. M. , Flowe K. , South S. , Zimmerman C.
Published: December 2017

To evaluate the role of the alpha 1-adrenergic system in the response to hemorrhage during development, lambs and adult sheep were chronically catheterized and hemorrhaged after pretreatment with prazosin or vehicle. The adults became markedly more hypotensive after alpha 1-blockade and hemorrhage than after vehicle and hemorrhage (26.1 +/- 4 vs. 10.7 +/- 2%, P less than 0.0001), whereas the lambs were no more hypotensive when hemorrhaged after prazosin (21.5 +/- 3.2 vs. 23.1 +/- 4.4%, P greater than 0.05). In the adults and the lambs, hemorrhage produced elevations in plasma renin activity and arginine vasopressin. However, after prazosin, the adults had a far greater increase in arginine vasopressin levels than after vehicle treatment (1,970 +/- 820 vs. 320 +/- 273%).
Effect of sympathetic sensitization of baroreceptors on renal nerve activity
Authors: Seagard J. L. , Hopp F. A. , Kampine J. P.
Published: December 2017

The role of sympathetic efferent innervation of the carotid sinus on the regulation of baroreceptor sensitivity was examined in thiopental-sodium anesthetized dogs (5 mg X kg-1 X h-1 infusion). Baroreflex sensitivity was defined as the slope of renal sympathetic efferent nerve activity vs. carotid sinus pressure in an isolated, perfused carotid sinus. Slopes were obtained before and after sinus sympathectomy performed by section of the cervical sympathetic trunk. There was no significant differences between baroreflex decreases in renal sympathetic activity due to increases in carotid sinus pressure before and after sympathectomy, but the responses to decreases in carotid sinus pressure after sympathectomy were significantly greater than control. Base-line level of renal sympathetic activity, obtained at a constant perfusion pressure of 115 mmHg, abruptly increased by 11% in response to sinus sympathectomy. The response of baroreceptors to sympathomimetic stimulation was examined by recording carotid baroreceptor afferent nerve activity during ramp changes in carotid sinus pressure after addition of epinephrine (10(-8) to 10(-6) M) to the perfusate of the sympathetically denervated sinus. The slopes of the sinus nerve activity vs. carotid sinus pressure were used as direct indexes of baroreceptor sensitivity. Lower levels of epinephrine (10(-8), 10(-7) M) increased the sensitivity of the baroreceptors and reduced renal nerve activity back toward presympathectomy levels. A higher dose of epinephrine (10(-6) M) did not significantly increase baroreceptor sensitivity. The results of this study suggest that sinus sympathetic fibers produce a tonic sensitization of the baroreceptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Seasonal, sexual, and individual variation in endurance and activity metabolism in lizards
Authors: Garland T. , Else P. L.
Published: December 2017

Amphibolurus nuchalis were collected in central Australia during mid- (January) and late summer (March). Endurance time at 1 km/h on a motorized treadmill is greater in larger lizards, scaling as M0.65. Maximal O2 consumption (VO2max) scales as M0.96; standard metabolic rate (SMR) scales as M0.83. Factorial aerobic scope thus increases ontogenetically (9.4 at 1 g vs. 15 at 50 g). All organ masses scale allometrically; larger lizards have relatively smaller livers, but larger hearts and thigh muscles. Hematocrit and hemoglobin increase during early ontogeny, but are mass independent in adults. Maximal in vitro catalytic rates were determined for citrate synthase (CS) and pyruvate kinase (PK) in liver, heart, and thigh muscle and for lactate dehydrogenase (LDH) (lactate oxidation) in heart. All enzyme activities (expressed per g tissue) scale positively, except CS in heart. Females exhibit lower SMR and heart CS activity. March animals exhibit elevated endurance, VO2max, heart LDH, and thigh CS and PK activities. Individual variation in endurance correlates with individual differences in heart LDH and thigh CS and/or PK activities. Individual differences in VO2max are partly related to variation in hematocrit.
Determination of plasma volume in swine by the enzyme-dilution method
Authors: Holmes M. A. , Weiskopf R. B.
Published: December 2017

Plasma volume of six young swine was determined by simultaneous dilution in the plasma of two purified porcine enzymes, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), and Evans blue dye. Ninety-minute time-activity and time-concentration curves were obtained, and the dilution spaces of each plasma indicator at the time of injection were estimated by extrapolation of data from the first 30 min after injection. Plasma volumes estimated using the two enzymes agreed closely with each other (AST, mean 50.2 ml/kg; ALT, mean 49.8 ml/kg) and were 11% smaller than those determined using Evans blue dye (mean 56.3 ml/kg). Plasma volumes calculated from the AST and ALT activities and Evans blue dye concentration in a sample drawn 5 min after injection very closely approximated those obtained by extrapolation. These values were comparable to previously published estimates of plasma volume for swine of equivalent weight. Endogenous plasma levels of AST and ALT activity were measured in samples drawn from five swine before and after a 40% blood loss. No significant change in AST or ALT activities occurred after hemorrhage.
Ion transport in circulatory and/or septic shock
Authors: Sayeed M. M.
Published: December 2017

This review surveys investigations of membrane ion transport in animals in hemorrhagic, endotoxic, or bacteremic shock. The focus of the review is on ion transport studies in the skeletal muscle and liver. Skeletal muscle Na+-K+ transport alterations have been shown during the induction of shock via hemorrhage, endotoxin, or live Gram-negative bacteria in the rodent, canine, and primate species. These alterations include impairment of active cellular K+ accumulation, increased permeability to Na+ and Cl-, and membrane depolarization. The ion transport alterations in the skeletal muscle are compatible with movement of extracellular fluid into the intracellular compartment. Such fluid movements can potentially lead to decreases in circulating plasma volume and thus to circulatory deficits in shock. Studies in the liver of rats subjected to hemorrhagic or endotoxic shock indicated the failure of electrogenic Na+ pump. Although the hepatic cellular membrane permeability to Na+ relative to permeability to K+ appeared unaltered in hemorrhagic shock, endotoxic shock caused an increase in permeability to Na+. Hepatic cellular Ca+ regulation also appeared to be adversely affected during endotoxic shock. Alterations in hepatic Na+-K+ transport and Ca+ regulation could contribute to impairment in hepatic glucose production during shock. Although mechanisms of altered membrane ion transport during shock states remain unknown, such changes could occur prior to any substantial loss of cellular metabolic energy.
Rats with regenerating adrenals are more hypertensive in the morning than afternoon
Authors: Foulkes R. , Gardiner S. M. , Bennett T.
Published: December 2017

In rats following unilateral nephroadrenalectomy and contralateral adrenal enucleation, adrenocortical tissue regenerates and secretes some steroids in abnormal amounts but with a diurnal rhythmicity. This study investigated whether the level of blood pressure (BP) in these rats also varies with the time of day. Systolic BP was measured by the tail-cuff method twice daily [between 0700 and 1000 h (A.M.) and again between 1400 and 1700 h (P.M.)] in conscious Wistar rats before and after unilateral nephroadrenalectomy and either contralateral adrenal-enucleation (AE) or sham-operation (SO); all rats were given 1% NaCl to drink postoperatively. During the 4th wk after surgery, systolic BP in AE rats was higher than in SO rats at both times of day, but the difference was greater A.M. (SO = 142 +/- 2 mmHg, AE = 176 +/- 4 mmHg) than P.M. (SO = 138 +/- 2 mmHg, AE = 150 +/- 2 mmHg). The hypertension and the A.M.-P.M. changes in BP in AE rats were also seen with intra-arterial recording. These phenomena were not directly associated with changes in plasma volume, plasma Na+ concentration, or in the plasma levels of corticosterone or 18-hydroxydeoxycorticosterone.
Cold-induced changes in Ca2+ transport in duckling skeletal muscle mitochondria
Authors: Barre H. , Nedergaard J.
Published: December 2017

Intermyofibrillar mitochondria were isolated from skeletal muscle (gastrocnemius) of cold-acclimated (4 degrees C) or control (30 degrees C) 4-wk-old ducklings. Ca2+ transport in the mitochondria was studied with the Ca2+-sensitive dye arsenazo III. The mitochondria actively took up Ca2+ but at a lower rate in mitochondria from cold-acclimated than from control ducklings. After addition of the Ca2+ uptake inhibitor ruthenium red, a low rate of Ca2+ release was revealed; this rate was, however, higher in the cold-acclimated than in the control ducklings. Furthermore, these nonmammalian mitochondria were also found to possess a mechanism for Na+-stimulated Ca2+ efflux. This mechanism was specific for Na+ (no effects with choline+ or K+, a small effect with Li+). The effect was maximal with 20 mM Na+, which led to a fourfold increase in rate of Ca2+ efflux. Cold acclimation led to a doubling of the rate of this Na+-stimulated Ca2+ release. Due to these alterations in Ca2+ fluxes caused by cold acclimation, the resultant free extramitochondrial Ca2+ levels were higher in mitochondria from cold-acclimated than from control ducklings. The basal level was doubled (from 0.26 to 0.50 microM) as was the increase in steady-state level caused by 10 mM Na+ (from +0.4 to +0.8 microM). The significance of these alterations for acclimation to cold is discussed.
Relationship between preferred ambient temperature and autonomic thermoregulatory function in rat
Authors: Gordon C. J.
Published: December 2017

This study was designed to elucidate the relationships between behavioral and autonomic thermoregulation in three common strains of the laboratory rat. In one experiment eight adult rats of the Sprague-Dawley (SD), Long-Evans (LE), and Fischer (FCH) strains were repeatedly placed in a longitudinal temperature gradient while their preferred ambient temperature (Ta) was recorded. The mean preferred Ta's (+/- SE) for the SD, LE, and FCH strains were 24.9 +/- 0.4, 19.8 +/- 0.3, and 23.4 +/- 0.3 degrees C, respectively. In another experiment, individual adult rats of the same strains were placed in an environmental chamber thermostabilized at 2 degrees C intervals from 14 to 36 degrees C for 90 min while metabolic rate (MR), evaporative water loss (EWL), thermal conductance (C), and colonic temperature (Tcol) were determined. All three strains exhibited a minimal MR at a Ta of 30 degrees C. As Ta decreased below 30 degrees C, MR increased in a nonlinear fashion. EWL and C were minimal at cool Ta's and increased gradually with an elevation in Ta. All three strains maintained a normal Tcol between Ta's of 14 to 30 degrees C. The FCH strain exhibited the best control of Tcol at Ta's above 30 degrees C. Generally, one would predict that the preferred Ta would be associated with minimal thermoregulatory effort. However, the rat is unusual from other rodents (e.g., mouse, hamster, and guinea pig) in that the preferred Ta is well below the lower critical Ta for elevating MR.
Model of plasma calcium regulation: system oscillations induced by growth
Authors: Hurwitz S. , Fishman S. , Talpaz H.
Published: December 2017

The process of growth was included in a model for simulation of calcium homeostasis in the chick, using data of carcass composition and a model of growth and energy intake. Computer simulations, made for chickens between 0 and 10 wk of age, predicted oscillations in plasma calcium and its major regulatory systems. Analysis of the oscillations indicated a periodicity of approximately 55 h. The oscillations were proportionally dependent on the rate of growth, disappearing almost completely when growth rate was made equal to zero. Subject to the validity of the model, it is suggested that the oscillations in plasma calcium and some of the components of the regulatory systems are induced by a continuous perturbation (growth) resulting in a dual response to the main regulatory hormone, parathyroid hormone, one rapid with a response time of minutes (bone), and one delayed, with a response time of hours (calcium absorption via the metabolism of 1,25-dihydroxychole-calciferol). It is also suggested that some of the normal variance and some of the rhythmicity observed previously in various components of the calcium regulatory system may be the results of spontaneous oscillations.
Sucrose-induced obesity: effect of diet on obesity and brown adipose tissue
Authors: Kanarek R. B. , Aprille J. R. , Hirsch E. , Gualtiere L. , Brown C. A.
Published: December 2017

Adult male Sprague-Dawley rats were divided into three groups and fed diets containing either 10, 20, or 40% protein for 56 days. Half of the rats in each dietary condition were given a 32% sucrose solution plus the standard diet and water. Sucrose intake varied directly as a function of dietary protein levels. Rats fed either the 10 or 20% protein diet and sucrose had higher caloric intakes, gained more weight, were more efficient at using calories for weight gain, and had more adipose tissue than rats given the same diet without sucrose. Rats fed the 40% protein diet and sucrose did not exhibit overeating, excess weight gain, or increased feed efficiency relative to animals fed the 40% diet alone. Animals given sucrose had more interscapular brown adipose tissue (IBAT) and a greater metabolic potential for thermogenesis in IBAT as determined by GDP binding in mitochondria than rats not fed sucrose. These results demonstrate that dietary protein is important in the development of sucrose-induced obesity and that increases in IBAT mass and activity can occur concomitant with increased feed efficiency.
Morphometry, histochemistry, and contractility of dystrophic hamster diaphragm
Authors: Burbach J. A. , Schlenker E. H. , Johnson J. L.
Published: December 2017

Differences in gross and microscopic morphology, fiber-size distribution, and fiber-type composition were present in the diaphragm of 35-, 130-, and 180-day-old dystrophic (Bio 14.6) compared with age-matched control (Bio F1B) hamsters. The dystrophic diaphragm was significantly thicker than the control at 130 and 180 days. Increases in wet-to-dry weight ratios, connective tissue per unit area, and muscle fiber number suggest that increased tissue hydration, fibrosis, and fiber hyperplasia contribute to diaphragm hypertrophy. Marked variations of fiber areas and diameters were evident in each fiber type at each age, but generalized atrophy predominated over hypertrophy, resulting in significant decreases in cross-sectional areas of each fiber type. Significant differences in fiber-type composition were noted in the dystrophic vs. control diaphragm at each age: at 35 days the percentage of slow-oxidative fibers was lower and in fast-oxidative fibers was higher; at 130 days the percentage of fast-oxidative fibers remained elevated; at 180 days the percentage of fast-glycolytic fibers was reduced. In vitro contractility studies of 130-day-old animals showed that twitch and peak tension development were significantly lower in the dystrophic compared with the control diaphragm, whereas optimal length, contraction time, and half-relaxation time were within control limits. Microscopic and physiological abnormalities were also present in the soleus of 130-day-old dystrophic animals. As in the diaphragm, fiber areas were reduced, connective tissue area increased, and peak and twitch tension decreased significantly compared with the control soleus. The histopathological and pathophysiological changes in the diaphragm correlated well with each other and are consistent with the slowly evolving inability of the dystrophic hamster to increase tidal volume and minute ventilation in response to a hypercapnic challenge.
Organ-specific metabolism during freezing and thawing in a freeze-tolerant frog
Authors: Storey K. B.
Published: December 2017

Freeze-tolerant wood frogs, Rana sylvatica, were exposed to three consecutive freeze-thaw cycles. Each 2-day freezing exposure resulted in the breakdown of liver glycogen and an accumulation of high quantities of glucose in all 10 tissues tested; during each 2-day thaw glucose was restored as liver glycogen. The data suggest that frogs do not maintain cryoprotectants throughout the winter in anticipation of freezing but only synthesize and/or maintain glucose during actual freezing episodes. The pattern of glucose accumulation during freezing suggests a peripheral vasoconstriction as freezing progresses, leaving circulation open to central organs (liver, heart, and brain) for as long as possible. Lactate and alanine contents in tissues rose during each freezing exposure and were reduced during each thaw. Based on anaerobic end-product accumulation, organs appeared to vary up to 10-fold in anaerobic energy requirements in the frozen state. Levels of adenylates and fructose-2,6-biphosphate were measured in liver and muscle and provided additional evidence of tissue-specific differences in metabolism in the frozen state.
Retrograde tracer technique for assessment of selective and total subdiaphragmatic vagotomies
Authors: Powley T. L. , Fox E. A. , Berthoud H. R.
Published: December 2017

A new protocol that provides a sensitive, reliable, and practical test for completeness of selective as well as total subdiaphragmatic vagotomies is described. This protocol employs a microscopic inventory of retrogradely labeled neurons in topographically distinct regions of the dorsal motor nucleus to determine which vagal branches have been surgically destroyed. Physiological experiments for validation and observations on the use of the method with 243 rats indicate that the protocol described can assess total as well as at least 11 different types of selective subdiaphragmatic vagotomies, including surgeries for which no assays have existed. Furthermore, the technique can identify cases where a branch is only partially destroyed. Other strengths include the facts that the protocol provides a simultaneous inventory of the different branches in a single test, is not influenced by the general health of the animal, and does not interfere with concurrent behavioral or physiological tests. Limitations include the facts that the tracer inventory requires a minimal survival period, can only be done postmortem, and has low resolution for cuts of the vagal hepatic branch. Aspects of the protocol critical to its implementation, including specifics for using the fluorescent tracer true blue, are discussed. Other tracers with similar diffusion characteristics, such as fluoro-gold and fast blue, can be used with equal effectiveness with this protocol.