bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors influencing pulmonary and cutaneous arterial blood flow in the toad, Bufo marinus
Authors: West N. H. , Burggren W. W.
Published: December 2017

In the conscious, undisturbed toad, Bufo marinus, pulmonary arterial blood flow increased during periods of lung ventilation and decreased in intervening periods of pulmonary apnea. In unidirectionally ventilated, anesthetized toads, lung inflation produced by increasing the outflow resistance to pulmonary gas flow to 3 cmH2O caused a significant increase in pulmonary arterial blood flow and a significant decrease in cutaneous arterial blood flow. Changes in flow were associated with reciprocal changes in calculated vascular resistance. Mean pulmocutaneous pressure and cardiac frequency did not change significantly. Thus lung inflation (in the absence of changes in the composition of intrapulmonary gases) increased the proportion of total pulmocutaneous flow routed to the lungs and decreased the proportion directed to the skin. Unidirectional ventilation with air + 5% CO2 at constant lung volume produced a significant decrease in pulmonary arterial blood flow, an increase in calculated pulmonary arterial flow resistance, and a small increase in the flow to the cutaneous artery. Concomitant mild hypoxia potentiated the effects of pulmonary hypercapnia, although hypoxia alone was less effective than hypercapnia alone in decreasing pulmonary flow. Pulmonary arterial blood flow was decreased by infusion of acetylcholine into the pulmocutaneous artery, but epinephrine had no effect on either the pulmonary or cutaneous artery at doses below those that produced systemic effects. Atropine blocked all changes in pulmonary arterial blood flow. This and other evidence suggest that calculated arterial resistance changes are due to reflex changes in the tone of vascular smooth muscle. Intrapulmonary CO2-sensitive mechanoreceptors possess appropriate response characteristics to mediate the afferent limb of the reflex.
Diet-dependent hyperplastic growth of adipose tissue in hypothalamic obese rats
Authors: Faust I. M. , Miller W. H. , Sclafani A. , Aravich P. F. , Triscari J. , Sullivan A. C.
Published: December 2017

Accelerated production of fat cells is often seen in dietary obesity in rats but not in obesity occurring in response to damage to the medial area of the hypothalamus (MH). The basis for this difference was examined. MH damage (MHD) was produced in rats by either electric current or small knife cuts. Rats were then fed either chow or a high-fat high-sugar diet (HFS) for up to 6 mo. Fat cell production did not accelerate during the 1st 16 wk after MHD in rats fed only chow, but acceleration clearly occurred in rats fed HFS during only 4 wk. At 18 wk after MHD rats fed only chow showed evidence of accelerated fat cell production. However, there was greater acceleration after MHD in HFS-fed rats held to the same weight gain as chow-fed rats. Rats allowed to freely eat HFS for 6 mo after MHD showed extremely large increases in body weight and fat cell number. The plateau in body weight often seen in rats fed only chow after MHD did not occur. Because HFS-feeding promoted unimpeded production of fat cells, accelerated weight gain induced by MHD could continue indefinitely. These findings suggest that enlargement of fat cells and components of the diet act synergistically in the promotion of adipocyte hyperplasia in adult rats and also suggest that accelerated weight gain after MHD is not due to elevation of a set point for body weight or body fat.
Accelerated functional recovery of isolated rat kidney with ATP-MgCl2 after warm ischemia
Authors: Sumpio B. E. , Chaudry I. H. , Clemens M. G. , Baue A. E.
Published: December 2017

Isolated rat kidneys were subjected to 45, 60, and 90 min of normothermic ischemia. Kidneys reperfused with a saline solution after ischemia had very low initial whole kidney inulin clearances (Cin), urine flow rates (V), renal perfusate flow rates (RPF), and fractional absorption of sodium values that remained depressed throughout the 110 min of reperfusion. Kidneys subjected to 45 min of warm ischemia and reperfused with a solution containing 0.3 mM ATP-MgCl2 had higher initial Cin and attained complete recovery of Cin by 75 min of perfusion. Fractional absorption of sodium and water were also improved, and RPF, V, and tissue ATP levels returned to control values after 110 min of perfusion. Kidneys subjected to 60 min of ischemia and reperfused with a solution containing 0.3 mM ATP-MgCl2 also had higher initial Cin values and attained 50% recovery of Cin after 110 min of perfusion. RPF also improved, and V reached control levels. Kidneys subjected to 90 min ischemia showed no improvement in renal function even with 2 mM ATP-MgCl2. Because, even in isolated kidneys, administration of ATP-MgCl2 after 45 and 60 min of ischemia results in an early recovery of renal function, the beneficial effects of ATP-MgCl2 are exerted directly on the kidney and are not mediated via systemic effects.
Insulin increases body fat despite control of food intake and physical activity
Authors: Torbay N. , Bracco E. F. , Geliebter A. , Stewart I. M. , Hashim S. A.
Published: December 2017

The effect of experimentally induced hyperinsulinemia on body composition was studied in rats with food intakes precisely controlled by intragastric feeding and physical activity manipulated by sedation with chlordiazepoxide (CDP). Male Sprague-Dawley rats (n = 38) were fitted surgically with gastrostomy tubes. After 8 days the animals were divided into four groups. Group 1 received daily injections of protamine-zinc insulin; group 2 received daily injections of saline; group 3 received the same insulin doses as group 1 plus daily administration of CDP mixed with the diet; group 4 received daily injections of saline plus CDP in the diet. All groups were tubefed identical amounts of semiliquid diet via gastrostomy. Physical activity was measured by electronic monitor. After 4 wk the rats were killed. The insulin-treated groups (1 and 3) had significantly larger fat depots and larger mean fat cell size than the noninsulin-treated groups (2 and 4). This increase in fat occurred concurrently with a decrease in carcass protein and water. Physical activity, as measured, was unaltered by insulin but was significantly reduced by CDP. Treatment with CDP only increased the dorsal fat depot and liver weight but had no significant effect on total dissected fat depots and had a reductive effect on carcass protein. In conclusion insulin treatment enhanced the efficiency of conversion of energy intake into fat energy stores.
Postrenal modification of urine in birds
Authors: Anderson G. L. , Braun E. J.
Published: December 2017

The role of the cloaca and lower intestine in the postrenal modification of urine was studied in conscious normally hydrated desert quail. The birds were studied for a period of 12 days during which they were in intake-output balance. It was calculated that of the combined mixture of urine-feces entering the lower intestine, 47% water, 62% sodium, and 49% potassium were reabsorbed. If this material is considered as coming from the ureteral urine, then the composition of the ureteral urine entering the lower intestine was changed as follows: 77% water, 72% sodium, and 82% potassium were reabsorbed. For urate, 68% of the total present in ureteral urine was degraded in the lower intestine. In terms of the filtered load produced by the kidneys, the lower intestine reabsorbed 1.5% filtered water, 0.4% filtered sodium, and 46% filtered potassium. The total filtered loads reabsorbed by the combined efforts of the kidney and lower intestine were 99.5% water, 99.8% sodium, and 88% potassium. It appears that the cloaca and lower intestine of birds may serve a similar function to that of the distal nephron in mammals, making the fine adjustments in water and sodium reabsorption from the urine.
Impaired drinking responses of rats with lesions of nucleus medianus: circadian dependence
Authors: Gardiner T. W. , Stricker E. M.
Published: December 2017

The drinking behavior of rats with electrolytic lesions of ventral nucleus medianus (vNM) was examined during acute hyperosmolality and hypovolemia. The brain-damaged animals were impaired in their drinking responses to systemic treatment with hypertonic saline or polyethylene glycol solution when they were tested during the day. However, apparently normal drinking responses to both dipsogenic challenges were observed when the same animals were pretreated with the stimulant drug, caffeine, or when they were tested at night. These results suggest that lesions of vNM may produce complex alterations in the control of drinking behavior rather than the destruction of sensory receptors. The lesions appear to disrupt both circadian influences on drinking and activational components of drinking that normally serve to facilitate the behavioral response. The present results, together with similar findings for rats given lesions of the subfornical organ, support recent proposals that periventricular tissue bordering the rostral wall of the third cerebral ventricle plays an important role in the central control of drinking.
Brown adipose tissue lipectomy leads to increased fat deposition in Osborne-Mendel rats
Authors: Moore B. J. , Inokuchi T. , Stern J. S. , Horwitz B. A.
Published: December 2017

Inter- and subscapular brown adipose tissue depots were removed from nine female Osborne-Mendel rats. These lipectomized animals and nine sham-operated controls recovered from surgery for 7 days at 25 degrees C and were then placed on a highly palatable liquid diet. All animals were maintained for a 2nd wk at 25 degrees C before being switched to 8 degrees C. After 9 wk in the cold, animals were killed, and the brown adipose tissue was dissected from scapular, cervical, thoracic, perirenal, and axillary regions. Total brown fat pad mass, protein content, brown adipocyte number, citrate synthase activity, and beta-hydroxyacyl CoA dehydrogenase activity in each of the dissected brown fat depots were significantly less than those of the sham-operated controls. Thus there was incomplete metabolic compensation in the remaining brown fat depots after the removal of the scapular brown fat in the lipectomized rats. The mass and lipid content of the retroperitoneal white adipose depot were significantly increased in the lipectomized rats as was their carcass fat content (up 14%). Food intake of the lipectomized rats was slightly but significantly decreased. These data indicate that a reduction in the amount of functional brown fat is accompanied by increased body fat accretion and are thus consistent with the hypothesis that decreased brown adipose thermogenesis can lead to altered energy balance and increased white fat deposition.
Organization of sympathetic responses to distension of urinary bladder
Authors: Weaver L. C.
Published: December 2017

Distension of the urinary bladder can cause reflex pressor responses, which appear to be mediated by increased sympathetic activity. However, preganglionic upper thoracic sympathetic activity is excited inconsistently by bladder distension in intact and spinal animals. The objective of this investigation was to determine if any of the postganglionic nerves originating from thoracic and lumbar spinal segments are consistently excited by vesical afferent nerves. Responses of external carotid, renal, and splenic sympathetic nerves to distension of the urinary bladder were evaluated in chloralose-anesthetized cats. In addition, the potential preferential spinal segmental distribution of vesico-sympathetic reflexes was assessed by comparing the magnitudes of external carotid, renal, and splenic nerve responses. Distension of the urinary bladder with 5–35 ml saline initiated vesical contractions to pressures of 45–90 cmH2O and caused inconsistent changes in arterial pressure and activity of renal and splenic sympathetic nerves. External carotid nerves were excited by this stimulus. Vesical distension with 12–50 ml saline caused contractions to vesical pressures of 135–175 cmH2O and produced consistent increases in arterial pressure and activity of all three nerves. Thus activation of vesical afferent nerves by high pressure produced excitation of upper thoracic vasomotor neurons and of two major components of splanchnic and lumbar sympathetic outflow. The magnitudes of external carotid, renal, and splenic sympathetic responses were not different, illustrating that propriospinal circuits thought to mediate vesicosympathetic responses are not organized segmentally.
Effect of stimulation of nucleus raphe dorsalis on carotid blood flow. II. The cat
Authors: Goadsby P. J. , Piper R. D. , Lambert G. A. , Lance J. W.
Published: December 2017

The dorsal raphe nucleus (DRN) and surrounding midbrain of 74 cats were stimulated both electrically and chemically, and carotid flows were measured with electromagnetic flow probes. Stimulation of the DRN caused a frequency-dependent decrease in common carotid vascular resistance, which was abolished by bilateral section of the facial nerve intracranially. Injection of DL-homocysteic acid into the DRN reproduced the effect of electrical stimulation, indicating that the responses arose from excitation of cell bodies within the DRN, not from fibers of passage. The responses were mediated entirely within the brain stem since they remained intact after high spinal cord section. The vasodilator response was blocked by the intravenous administration of the nicotinic ganglion blocker hexamethonium but not by the alpha-adrenoceptor blocker phentolamine. The responses were unaffected by intravenous administration of methysergide but were markedly reduced after depletion of central serotonin by pretreatment with the serotonin depletor, p-chlorophenylalanine. A poststimulus constrictor response was mediated by release of catecholamines from the adrenal medulla and was blocked by the alpha-adrenoceptor antagonist phentolamine. No response involved supracollicular mechanisms since they persisted after decerebration.
Alteration of adipocyte calcium homeostasis by Escherichia coli endotoxin
Authors: Nelson K. M. , Spitzer J. A.
Published: December 2017

The present study evaluated calcium homeostasis in rat adipocytes after either in vivo or in vitro exposure to Escherichia coli endotoxin. Fat cells from endotoxin-treated rats showed an enhanced uptake of 45Ca. In an attempt to differentiate between 45Ca binding to the cell surface and intracellular 45Ca accumulation, adipocytes were exposed to 5 mM LaCl3. The amount of 45Ca remaining associated with lanthanum-treated adipocytes was taken to be located intracellularly and was increased in adipocytes from endotoxin-treated rats. The amount of 45Ca displaced by lanthanum was also increased in adipocytes from endotoxin-treated rats. This suggested that the endotoxin-induced increase of 45Ca accumulation included both cell surface and intracellular binding sites. Compartmental analysis of the exchange kinetics of cell-associated 45Ca with 40Ca in the medium indicated a 77% increase in the size of the cell surface compartment of adipocytes from endotoxin-treated rats compared with controls. In addition, endotoxin treatment altered the flux of calcium from the cells to the medium. In vitro exposure of freshly prepared adipocytes to 250 or 750 micrograms endotoxin/ml did not produce a perturbation of adipocyte calcium homeostasis. The results indicate that endotoxin induces alterations in the ability of adipocytes to regulate calcium translocations, suggesting that some metabolic and hormonal aspects of endotoxins' actions may be mediated through perturbation of cellular calcium homeostasis.
Multiple-objective criteria for optimal experimental design: application to ferrokinetics
Authors: Nathanson M. H. , Saidel G. M.
Published: December 2017

Optimal experimental design is used to predict the experimental conditions that will allow the "best" estimates of model parameters. A variety of criteria must be considered before an optimal design is chosen. Maximizing the determinant of the information matrix (D optimality), which tends to produce the most precise simultaneous estimates of all parameters, is commonly considered as the primary criterion. To complement this criterion, we present another whose effect is to reduce the interaction among the parameter estimates so that changes in any one parameter can be more distinct. This new criterion consists of maximizing the determinant of an appropriately scaled information matrix (M optimality). These criteria are applied jointly in a multiple-objective function. To illustrate the use of these concepts, we develop an optimal experimental design of blood sampling schedules using a detailed ferrokinetic model.
Short-latency tachycardia evoked by stimulation of muscle and cutaneous afferents
Authors: Gelsema A. J. , Bouman L. N. , Karemaker J. M.
Published: December 2017

The short-latency effect on heart rate of peripheral nerve stimulation was studied in decerebrate cats. Selective activation (17-40 microA, 100 Hz, 1 s long) of low-threshold fibers in the nerves to the triceps surae muscle yielded isometric contractions of maximal force that were accompanied by a cardiac cycle length shortening within 0.4 s from the start of stimulation. This effect was abolished by pharmacologically induced neuromuscular blockade. The cardiac cycle length shortening during paralysis reappeared after a 6- to 10-fold increase of the stimulation strength. Cutaneous (sural) nerve stimulation (15-25 microA, 100 Hz, 1 s long) elicited reflex contractions in the stimulated limb, which were also accompanied by a cardiac acceleration with similar latency. Paralysis prevented the reflex contractions and reduced the cardiac response in some cats and abolished it in others. The response reappeared in either case after a 5- to 10-fold increase of the stimulus strength. It is concluded that muscle nerve and cutaneous nerve activity both cause a similar cardiac acceleration with a latency of less than 0.4 s. The response to muscle nerve stimulation is elicited by activity in group III afferents. It is excluded that the cardiac response to nerve stimulation is secondary to a change in the respiratory pattern.
Adrenal corticoids in hamsters: role in circadian timing
Authors: Albers H. E. , Yogev L. , Todd R. B. , Goldman B. D.
Published: December 2017

The 24-h patterns of circulating cortisol and corticosterone were determined in male hamsters housed under a 14:10 light-dark cycle. Corticoid levels varied significantly over the 24-h sampling period with peak levels of both hormones occurring near the onset of the daily dark phase. The ratio of cortisol to corticosterone changed dramatically during the day. Corticosterone levels were significantly higher than cortisol during the early part of the light phase; however, cortisol levels became significantly higher than corticosterone when both hormones began their daily rise. To examine whether the circadian rhythm of cortisol secretion could be involved in the physiological control of hamster circadian organization, cortisol was infused at approximately physiological levels into adrenalectomized hamsters either continuously or in a 24-h rhythm. No significant differences were observed in the timing of circadian wheel-running rhythms in hamsters housed in LD 16:8, LD 14:10, or LL when cortisol was infused continuously, in a 24-h rhythm that mimicked the cortisol rhythm of intact hamsters, or in a 24-h rhythm several hours out of phase with the rhythm of intact hamsters. Provision of cortisol in a 24-h rhythm appeared to promote the survival of adrenalectomized hamsters since hamsters receiving a 24-h pattern of cortisol survived the experimental protocol significantly longer than those receiving the same dose of cortisol continuously.
Recovery from energy deficit in golden hamsters
Authors: Borer K. T. , Allen E. R. , Smalley R. E. , Lundell L. , Stockton J.
Published: December 2017

Hamsters feeding at greater than 2-h intermeal intervals (IMI) lose weight but recover from weight losses without hyperphagia if they are allowed to feed at 2-h IMIs (Am. J. Physiol. 236 (Endocrinol. Metab. Gastrointest. Physiol. 5): E105-E112, 1979). To determine the relative importance of changes in energy expenditure and fat synthesis in their energy regulation, measurements were made of resting metabolic rate, respiration by brown adipose tissue (BAT), locomotion, fecal energy content, and insulin and hepatic lipogenic enzyme responses to feeding in underweight hamsters allowed to feed at 2- or 5-h IMIs. Energy deficit suppressed the resting metabolic rate and general locomotor activity and increased the activity of fatty acid synthetase (FAS). Heat production by BAT increased in underweight hamsters. Increase in IMIs blocked the postprandial insulin release, reduced plasma insulin concentration and FAS activity, and increased malic enzyme activity. Thus ad libitum feeding hamsters recover from energy deficit by reducing energy expenditure, whereas failure to add additional meals and impaired insulin and changed lipogenic responses to feeding produce energy deficits in infrequently feeding hamsters.
Level of satiety: fatty acid and glucose metabolism in three brain sites associated with feeding
Authors: Kasser T. R. , Harris R. B. , Martin R. J.
Published: December 2017

Two experiments were conducted to determine if the level of satiety alters fatty acid and glucose metabolism in selected brain areas. Rats received 150, 100, or 50% of normal intake by gastric intubation for 7 days. Thus the impetus for spontaneous feeding would be impaired in 150% fed rats (anoretic), potentiated in 50% fed rats (hungry), and maintained in 100% fed (control) rats. In vitro metabolism of glucose and palmitate was examined in liver, cortex, ventrolateral hypothalamus (VLH), ventromedial hypothalamus (VMH), and area postrema nucleus of the solitary tract. The VLH of hungry (50%) rats had a 40% increase in palmitate oxidation and a 9% decrease in glucose oxidation compared with controls (100%). The VLH of anoretic rats (150%) had a 36% decrease in palmitate oxidation and a 20% increase in glucose oxidation compared with controls. Hepatic metabolic differences were similar to those seen in VLH. Total fatty acid synthesis was 37% higher in anoretic and 29% lower in hungry compared with control rats. Recognition of excess, sufficient, or deficient peripheral energy status may be a process that monitors both VLH energy utilization and VMH energy storage in an attempt to depict metabolic adaptations of the periphery.
Primary role of volume expansion in stimulation of rectal gland function
Authors: Solomon R. , Taylor M. , Sheth S. , Silva P. , Epstein F. H.
Published: December 2017

Chloride secretion by the in vivo rectal gland of the shark is stimulated by the intravascular infusion of salt solutions of varying osmolar and sodium concentration. In a cross-perfused and denervated rectal gland, the infusion of a small amount of a hypertonic salt solution raises plasma osmolality but does not increase plasma volume in the donor fish. Under these conditions, rectal gland chloride secretion is not stimulated. A subsequent infusion of isotonic shark Ringer solution increases plasma volume 50%, decreases plasma osmolality, and produces a fourfold increase in chloride secretion and a threefold decrease in vascular resistance within the gland. Both the vasodilatory and secretory responses also follow the infusion of a hypotonic shark Ringer solution. The data further support the hypothesis that the rectal gland of the shark is involved in the regulation of intravascular volume rather than in osmoregulation.
Osmoregulation and vasopressin secretion during pregnancy in Brattleboro rats
Authors: Barron W. M. , Dürr J. , Stamoutsos B. A. , Lindheimer M. D.
Published: December 2017

Page R29: W. M. Barron, J. Dürr, B. A. Stamoutsos, and M. D. Lindheimer. “Osmoregulation and vasopressin secretion during pregnancy in Brattleboro rats.” Page R29: Abstract, line 18—PAVPshould be defined as plasma arginine vasopressin.
Characterization of muscles from aspartic acid obese rats
Authors: Burbach J. A. , Schlenker E. H. , Goldman M.
Published: December 2017

This study was undertaken to determine whether changes in muscle mass, muscle fiber diameter, or shifts in fiber type occur in the aspartic acid-injected rat, an animal model of hypothalamically induced obesity. We found that diaphragm, gastrocnemius, and soleus muscle mass was 140, 149, and 171% greater, respectively, in control compared with aspartic acid-injected rats. No differences were noted in heart weights. Significant reductions in mean fiber diameter of aspartic compared with control rats were present in each skeletal muscle. Furthermore, significant size reductions were noted for each fiber type in the diaphragm, with fast-glycolytic fibers showing the greatest reduction compared with controls at both 7 and 12 mo. Fiber type composition within the diaphragm did not differ between groups but showed a change with age. These results are compared with genetic models of obesity, the Zucker rat and the ob/ob mouse, as well as the ventromedial hypothalamic lesioned rat and the gold thioglucose mouse. Based on these results, the aspartic rat appears more similar to the two genetic models of obesity and also mimics some of the effects of malnutrition in rodents.
Monosaccharide transport into hemocytes of a sipunculan worm Themiste dyscrita
Authors: Ingermann R. L. , Hall R. E. , Bissonnette J. M. , Terwilliger R. C.
Published: December 2017

The hemerythrin-containing blood cells, or hemocytes, of the sipunculan worm Themiste dyscrita were found to have a stereospecific and nonconcentrative monosaccharide transport system. The transport system transferred both D-glucose and 3-O-methyl-D-glucose (3-OMG), and transport into cells by this system was rapid, reaching 50% equilibrium in approximately 20 s at 10 degrees C with an initial concentration gradient of 0.1 mM; the contribution to total uptake by simple diffusion was very small. 3-OMG uptake showed saturation kinetics with a low half-saturation constant (Km less than or equal to 0.1 mM). The uptake of labeled 3-OMG by the hemocytes was strongly inhibited by unlabeled 3-OMG, 2-deoxy-D-glucose, alpha- and beta-D-glucose, D-galactose, and D-mannose. It was moderately inhibited by D-xylose, only slightly by alpha-methyl-D-glucoside and D-fructose, and uninhibited by sucrose, L-glucose, or D-sorbitol. Phloretin was more potent than phloridzin in blocking entry of 3-OMG. Cytochalasin B did not bind tightly to the T. dyscrita transporter and was not a potent inhibitor of transport; it half-maximally inhibited 3-OMG transport at 0.1 mM. Therefore, despite some differences the data suggest functional similarities in the mechanism of monosaccharide transport into blood cells of mammals and this invertebrate.
Insulin and central regulation of spontaneous fattening and weight loss
Authors: Melnyk R. B. , Martin J. M.
Published: December 2017

Insulin binding to receptors in a partially purified hypothalamic membrane preparation is altered by prolonged starvation. To define further the relationship between hypothalamic insulin binding and energy balance, we studied the Richardson's ground squirrel, a hibernator that exhibits spontaneous 6- to 8-mo body weight cycles when kept in constant conditions. Isolated pancreatic islets from squirrels killed during the weight gain phase had greater glucose-stimulated insulin secretion than those from weight loss phase animals, and adipocytes showed significantly greater glucose incorporation into total lipid in response to insulin. Differences in lipogenesis were not attributable to changes in insulin-binding capacity. Hypothalamic tissue from weight gain phase animals bound more insulin than that from weight loss phase animals. Maximal binding was correlated with pancreatic islet responsiveness and maximal insulin-stimulated lipogenesis. The strong positive correlation between peripheral metabolic events associated with spontaneous alterations in energy balance and the binding kinetics of hypothalamic insulin receptors suggests that insulin may play an important role in the central regulation of body weight.
Subfornical organ and supraoptic nucleus connections with septal neurons in rats
Authors: Ferguson A. V. , Bourque C. W. , Renaud L. P.
Published: December 2017

Extracellular single unit recordings obtained in pentobarbital-anesthetized male Sprague Dawley rats were utilized to examine the electrophysiology of connections of medial septum-diagonal band of Broca (MS-DBB) neurons with the subfornical organ (SFO), hippocampal commissure (HC), and supraoptic nucleus (SON). Of the 119/216 cells tested that demonstrated antidromic activation from SON, many (60%) were orthodromically excited by SFO stimulation, whereas most (68%) were unresponsive to stimulation in the adjacent HC. Separate populations of MS-DBB neurons that displayed antidromic activation from the SFO (11/140 cells tested) or HC (24/78 tested) were orthodromically excited by SON stimulation. Three cells were activated antidromically from both the SFO and SON. These observations reveal some possible interconnections between these three brain regions and point to the existence of an indirect pathway whereby the SFO can influence SON neurons through an influence on MS-DBB neurons.
Influence of central chemoreceptor afferent inputs on respiratory muscle activity
Authors: Haxhiu M. A. , Mitra J. , van Lunteren E. , Prabhakar N. R. , Cherniack N. S.
Published: December 2017

Respiratory activity can be substantially affected by perturbations confined to the superficial areas of the ventrolateral surface of the medulla, the putative site of central chemoreceptors. In this study we compared the effect of thermal and pharmacological interventions that are known to alter respiration on the electrical activity of the rib cage muscles, diaphragm, and abdominal muscles. With cooling of the intermediate areas to 20 degrees C, tidal volume decreased 50%. The electrical activity of the diaphragm decreased less than the other muscles (diaphragm less than inspiratory intercostal less than expiratory intercostal). Abdominal muscle activity was depressed as much as expiratory intercostal activity but reappeared with further cooling to 10 degrees C if cooling was prolonged and the vagi were intact. gamma-Aminobutyric acid (GABA) and its agonist muscimol, like cooling, reduced expiratory and inspiratory intercostal activity more than diaphragm activity. Nicotine, a respiratory stimulant, applied to the intermediate areas increased inspiratory intercostal activity more than the diaphragm. The results suggest that under the conditions of the experiments the rib cage musculature, and probably the abdominal muscles as well, are more responsive than the diaphragm to depression or excitation of chemosensitive elements in the superficial regions of the medulla.
Afferent renal nerve stimulation excites supraoptic vasopressin neurons
Authors: Day T. A. , Ciriello J.
Published: December 2017

Single-unit recording experiments were performed in pentobarbital-anesthetized rats to investigate the effects of afferent renal nerve (ARN) stimulation on the activity of neurosecretory vasopressin cells of the supraoptic nucleus (SON). Neurosecretory SON cells were identified by antidromic invasion from the neurohypophysis and classified either as vasopressin (AVP) or oxytocin (OXY) secreting on the basis of their spontaneous activity patterns and response to activation of arterial baroreceptors. Fifty-three spontaneously active units were identified bilaterally in the SON: 40 putative AVP and 13 putative OXY neurons. Most putative AVP neurons (14/14 contralateral, 18/26 ipsilateral) were excited by ARN stimulation (mean onset latency 189 +/- 5 ms, mean response duration 237 +/- 17 ms). In contrast, ARN stimulation had no effect on the firing frequency of the 13 putative OXY neurons. These data indicate that sensory information originating in the kidney selectively alters the activity of SON AVP neurons and suggest that afferent information from the kidney is important in the coordination of neural and hormonal activity concerned with body fluid balance and the regulation of arterial pressure.
Absence of sodium chloride preference in Fischer-344 rats
Authors: Midkiff E. E. , Fitts D. A. , Simpson J. B. , Bernstein I. L.
Published: December 2017

Preference for NaCl solutions as a function of concentration was examined in three inbred strains of rats (Munich-Wistar, Buffalo, and Fischer-344) and outbred Wistar rats. Fischer-344 rats were found to differ markedly from the other strains in that they failed to prefer any concentration of NaCl solution to water. This difference did not appear to be due to an insensitivity to the taste of NaCl since they significantly avoided solutions at concentrations (greater than 0.7%) that were strongly preferred by other rat strains. Differences between Fischer-344 and other rat strains also did not appear to be due to a generally anomalous taste system since their intake and preference for prototypes of other basic tastes (sweet, sour, and bitter) were generally similar to those of other strains. Although Fischer-344 rats were somewhat slower than Wistar to excrete a sodium load, it is unlikely that this difference can provide a direct explanation of the aversion of Fischer-344 rats for NaCl.
Rete mirabile of goat: its flow-damping effect on cerebral circulation
Authors: Lluch S. , Dieguez G. , Garcia A. L. , Gomez B.
Published: December 2017

This work was designed to characterize in anesthetized goats the hemodynamic response of the carotid rete during pharmacologically induced changes in systemic blood pressure or blood flow to the brain. Under control conditions, mean blood pressure in the middle cerebral artery (distal to rete) was 18% lower than that measured in the internal maxillary artery (proximal to rete). Pressure gradient and calculated resistance across the rete were unchanged when systemic arterial pressure was increased or decreased by intravenous administration of norepinephrine or isoproterenol, respectively. Hypercapnia or injections of isoproterenol and acetylcholine into the internal maxillary arteries increased blood flow and decreased middle cerebral arterial pressure, whereas injections of norepinephrine decreased blood flow and increased postrete pressure. Calculated resistance across the rete was unchanged. These observations indicate that the response of the carotid rete to the substances tested is negligible; they also suggest that the carotid rete may have a flow-damping effect by maintaining resistance to blood flow when a change in the caliber of brain vessels occurs.
Bicarbonate-chloride exchange in gill plasma membranes of blue crab
Authors: Lee S. H. , Pritchard J. B.
Published: December 2017

The uptake of chloride was studied in gill plasma membrane vesicles from low-salinity-adapted blue crabs (Callinectes sapidus). Cl- uptake was not Na+ dependent. However, when a HCO-3 gradient (in greater than out) was imposed across the membrane, a transient overshoot of about 2.5-fold was produced. Approximately 90% of the Cl- uptake reflected entry into the osmotically active intravesicular space. Cl- itself, nitrate, hydroxyl, and sulfite could substitute for HCO-3. The HCO-3/Cl- exchange process appeared to saturate at higher concentrations of either HCO-3 or Cl-. The apparent Km for Cl- was 15 mM. HCO-3-dependent Cl- uptake was significantly inhibited by 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid and thiocyanate but not by amiloride, furosemide, or ouabain. Alterations in membrane potential had no effect on Cl- uptake. Addition of Cl- or HCO-3 to the external medium also accelerated efflux of 36Cl- and H14CO-3 from preloaded vesicles. These results indicate that the uptake of Cl- by the crab gill plasma membrane is a carrier-mediated Na+-independent anion exchange process.
Gut-derived endotoxin elicits hepatotrophic factor secretion for liver regeneration
Authors: Cornell R. P.
Published: December 2017

The influence of exogenous endotoxin pretreatment on liver regeneration after partial hepatectomy was evaluated. Partial hepatectomy was performed by 67% liver resection of ether-anesthetized rats with midline laparotomy and liver manipulation as the sham control. Animals were pretreated with endotoxin at a dose of 33 micrograms/100 g sc or iv 24 h before surgery and then fasted. Liver regeneration was quantified after partial hepatectomy by [3H]thymidine incorporation into hepatic DNA, and plasma levels of hepatotrophic factors were measured by radioimmunoassay or radioreceptor assay. Systemic endotoxemia occurred after exogenous endotoxin administration as well as after partial hepatectomy due to absorption of exogenous endotoxin from the gut into the portal circulation as determined by quantitative chromogenic lysate assay of perchloric acid-extracted plasma samples. Alterations in putative hepatotrophic factors, including insulin, glucagon, epidermal growth factor, vasopressin, and triiodothyronine, were remarkable similar in response to endotoxemia by exogenous endotoxin administration and by endogenous endotoxin absorption from the gut after partial hepatectomy. Our hypothesis purports that gut-derived systemic endotoxemia elicits hepatotrophic factor secretion for liver regeneration after partial hepatectomy and that endotoxin pretreatment expedites the hepatotrophic factor response, thus accelerating DNA synthesis in the proliferating liver after 67% resection.
Urinary concentrating ability: insights from comparative anatomy
Authors: Bankir L. , de Rouffignac C.
Published: December 2017

It appears difficult to build a coherent picture of the concentrating system of the mammalian renal medulla. This may be due to the diversity of the factors involved and to considerable interspecies differences. Several morphological adaptations that may be critical in the improvement of water conservation are described. They include variations in the length of the papilla, number of nephrons, percentage of long-looped nephrons, nephron heterogeneity, development of pelvic fornices, confluence of collecting ducts, vascular bundles in the inner stripe of the outer medulla, thin descending limb epithelium, and relative development of the three medullary zones. The organization of the medullary circulation is described; the medulla includes several functionally different compartments favoring preferential exchanges by the juxtaposition of certain tubules and vessels. This may improve the efficiency of certain recycling routes and hence the insulation of the different compartments. As discussed in section III, a better inner medullary insulation may be key, not (or not only) in achieving a high urine concentration but mainly in reducing the time required to reach this high concentration. This overview of the multiple interspecies variations in medullary organization underlines the importance, among other factors, of the inner stripe architecture and of the internephron differences in the process of urine concentration.
Phase shifting two coupled circadian pacemakers: implications for jet lag
Authors: Gander P. H. , Kronauer R. E. , Graeber R. C.
Published: December 2017

Flights across time zones produce an abrupt displacement of the environmental time cues (zeitgebers), and the endogenous circadian timing system resynchronizes only gradually to the new schedule. A coupled two-oscillator model can simulate the human circadian system in temporal isolation and in artificial zeitgeber cycles. The model is here shown to explain the major features of resynchronization of circadian rhythms after time zone shifts, i.e., the rate of adjustment depends on the rhythm being measured, the number of time zones crossed, the flight direction (eastward or westward), and the strength of the zeitgebers in the new time zone. Investigations of the contribution of different model parameters to system performances suggest that intersubject differences in pacemaker periods may be a major factor in the observed variability in the effects of time zone shifts on circadian rhythms. With individualized period estimate the models can simulate case studies in which four subjects recorded their sleep-wake and core body temperature rhythms throughout simple and complex patterns of transmeridian flights.
Vascular smooth muscle responsiveness in a hibernator: effects of season and temperature
Authors: Miller V. M. , Miller W. L. , South F. E.
Published: December 2017

To determine the effects of season, acclimation state, and hibernation on the reactivity of vascular smooth muscle from a hibernant species, strips of thoracic aorta, renal and femoral arteries, and portal vein obtained from adult woodchucks, Marmota monax, were suspended for isometric tension measurements in physiological salt solution. These blood vessels exhibited no seasonal variation in resting tension, connective tissue content, or maximum tension developed to norepinephrine. However, the concentration-response curves to norepinephrine in both aortic and portal vein strips from animals tested in May and June were shifted to the left of those from animals tested in either August or November through February. This increased sensitivity to the catecholamine was seen also in renal vessels from hibernating compared with nonhibernating animals. Decreasing organ bath temperature from 37 to 28 degrees C increased tension developed in response to norepinephrine in aortic and renal strips, whereas that of the femoral artery was unchanged. With further cooling to 17 degrees C, the responses to norepinephrine in aortic and renal strips were similar to the responses at 37 degrees C. The contraction developed to 40 mM KCl was diminished in all tissues at 28 degrees C. Blockade of beta-adrenergic receptors did not augment the response to norepinephrine at 37 degrees C. Contractions of the woodchuck aorta in calcium-free medium were sustained longer than comparable tissue obtained from a rabbit. These data suggest that receptor-mediated processes are modulated in hibernating animals. This modulation varies among vascular beds and may act to maintain or divert perfusion of the tissue through entry, during, and arousal from hibernation.
Photic cues induce multiple neuroendocrine adjustments in testicular function
Authors: Blank J. L. , Desjardins C.
Published: December 2017

Neuroendocrine responses were evaluated in an outbred population of deer mice (Peromyscus maniculatus nebrascensis) after exposure to an inhibitory photoperiod (8:16 light-dark) for 10 wk. Deer mice were chosen as an animal model for this study because they are typical of naturally selected species that rely on environmental factors to signal the onset or cessation of annual reproductive effort. Short photoperiods induced multiple neuroendocrine adjustments as judged by three types of spermatogenic responses: normal, intermediate, and azoospermic individuals. Plasma concentrations of luteinizing hormone and testosterone coincided with gradations in spermatogenic activity. In contrast, plasma concentrations of follicle-stimulating hormone were unaffected. Prolactin secretion was lowered in all mice exposed to short day lengths, regardless of sperm count. These results demonstrate that short photoperiods engage at least three types of neuroendocrine adjustments: 1) a suppression in luteinizing hormone and testosterone secretion accompanying spermatogenic arrest, 2) a reduction in prolactin secretion independent of changes in testicular function, and 3) a null response in gonadotrophic hormone secretion in which spermatogenesis is unimpaired by short day lengths. The neuroendocrine subsets identified in this model provide new evidence that photic cues induce three types of adjustments in pituitary-testicular function. These subsets are readily identified, and they can be easily exploited to dissect and manipulate the suite of neural, endocrine, and metabolic adaptations triggered by environmental lighting among mammals with annual reproductive strategies.
Interference with central actions of angiotensin II suppresses sodium appetite
Authors: Weiss M. L. , Moe K. E. , Epstein A. N.
Published: December 2017

We have proposed that sodium appetite is aroused by a synergy in the brain of angiotensin II and aldosterone. This hypothesis was tested with 1) chronic intracerebroventricular infusion of captopril, which blocks the conversion of angiotensin I to angiotensin II, or 2) intracerebroventricular injection of eight-substituted analogues of angiotensin II, which block its receptors. Both treatments resulted in a suppression of the sodium appetite induced by sodium deficiency. The suppression was specific for the deficiency-induced appetite, because spontaneous ingestive behaviors were not changed nor was sodium excretion. In addition, the rats continued to express a sodium appetite aroused by pharmacological doses of deoxycorticosterone acetate when they received the highest dose of chronic intracerebroventricular captopril. These results offer compelling evidence for the idea that angiotensin II action in the brain is necessary for expression of sodium appetite.
Interaction of osmotic and volume stimuli in regulation of neurohypophyseal secretion in rats
Authors: Stricker E. M. , Verbalis J. G.
Published: December 2017

Adult male rats were injected subcutaneously with polyethylene glycol (PEG) solution, which causes hypovolemia by progressive isosmotic leaching of plasma fluid into a local edema. Plasma levels of arginine vasopressin (AVP) were found to increase exponentially in response to induced plasma volume deficits up to 40%. However, plasma AVP was reduced to basal levels when the rats were given either free access to drinking water or intragastric water loads that diluted plasma osmolality by only 3-6% despite continued hypovolemia. Administration of hypertonic NaCl stimulated AVP secretion as well. However, combined PEG and hypertonic NaCl treatments produced plasma AVP levels greater than expected from simple additivity of the independent effects of hypovolemia and osmotic concentration. Oxytocin secretion similarly was stimulated by treatment with either PEG solution or hypertonic NaCl, it was especially pronounced when both treatments were given, and it was inhibited by osmotic dilution despite marked hypovolemia. These effects are analogous to those seen when hypovolemia stimulates water intake but subsequent osmotic dilution inhibits thirst in PEG-treated rats.
Oxygen equilibrium curve shape and allohemoglobin interaction in sheep whole blood
Authors: Maginniss L. A. , Olszowka A. J. , Reeves R. B.
Published: December 2017

Adult sheep (Ovis aries) exhibit hemoglobin heterogeneity controlled by two autosomal alleles with codominant expression (Hb AA, AB, BB). Isoelectric points for Hb A and Hb B were 6.94 and 7.15, respectively; for Hb AB animals, the two allohemoglobins were present in equimolar concentrations (Hb A = 52%, Hb B = 48%). Dynamic O2 equilibrium curves (O2ECs) were generated for sheep whole blood at 39 degrees C using thin-film techniques. Half-saturation PO2 values (P50) at pH 7.50 were 31.3, 35.7, and 40.7 Torr for Hb AA, AB, and BB, respectively. CO2 Bohr coefficients at saturation (S) = 0.5 (delta log P50/delta pH) were similar for all phenotypes, ranging from -0.38 to -0.40. The Bohr slopes were also saturation independent between 0.2 and 0.8 S. Standard O2ECs for each phenotype were accurately fitted to three-constant third-order polynomial expressions. Sheep equilibrium curves were not isomorphic with other mammalian O2ECs (e.g., human and dog); sheep curves exhibited greater sigmoidicity. Furthermore, allohemoglobin interaction was not detected in heterozygous sheep. The blood O2 binding characteristics (P50, curve shape, and delta log PO2/delta pH) for Hb AB sheep and an experimental blood mixture containing equal proportions of Hb AA and Hb BB erythrocytes were equivalent.