bluuebunny/crossref_metadata_2025 huggingface dataset:
Circulating osteocalcin in rats is inversely responsive to changes in corticosterone
Authors: Patterson-Buckendahl P. E. , Grindeland R. E. , Shakes D. C. , Morey-Holton E. R. , Cann C. E.
Published: December 2017

Decreased bone formation in rats during spaceflight may be attributable to corticosteroid excess induced by environmental factors other than weightlessness that are associated with spaceflight experiments. To determine whether decreased osteocalcin, which may reflect altered bone formation rate, could be associated with corticosteroid excess, we measured serum osteocalcin in rats after injection of corticosterone or in response to various environmental stimuli. Exogenous steroid elicited a time- and dose-related decrease in serum osteocalcin, which was significant within 1 h of administration and maximally 25% below controls 1.5 h after injection of 3.3 mg corticosterone/kg body wt, the highest dose we tested. Adrenalectomy resulted in a 38% increase in osteocalcin. Exposure to environmental stressors lasting from 1.5 h to 3 wk also resulted in decreased osteocalcin levels, which showed a strong negative correlation (P less than 0.001) with serum corticosterone levels and adrenal mass after 1-3 wk of chronic cold exposure. Changes in serum osteocalcin were maximally about +/- 40% after 3 wk of chronic exposure to steroid excess or depletion. The response of osteocalcin to the well-defined adrenal hormone system implies an important role for corticosteroids in the control of serum osteocalcin.
Determination of sulfobromophthalein excretion in rabbits
Authors: Quale J. M. , Bergasa N. V. , Mandel L. J.
Published: December 2017

The excretion of sulfobromophthalein (BSP) is determined by hepatic uptake (storage capacity) and secretion (transport maximum). We calculated the BSP excretion data in six rabbits by measuring the rate of rise of BSP at various infusion rates. The relative storage capacity was determined to be 0.34 +/- 0.13 mg.mg-1.dl-1.kg-1. The transport maximum was calculated to be 0.91 +/- 0.12 mg.min-1.kg-1. These results compare closely with previously reported results using more direct measurements that require anesthesia and surgical cannulation of the biliary tree. Repeated studies were easily performed. Our method provides a reliable and simple technique to study the effects of various conditions or substances on BSP excretion in conscious, unanesthetized rabbits.
Cholecystokinin decreases sucrose intake in chronic decerebrate rats
Authors: Grill H. J. , Smith G. P.
Published: December 2017

The capacity of chronic decerebrate rats to reduce their intake of an orally infused sucrose solution in response to peripherally administered cholecystokinin octapeptide (CCK-8) was investigated. The sucrose intake of both 24-h food-deprived chronic decerebrate rats and pair-fed control rats was reduced by CCK-8 relative to the intake after desulfated CCK-8. The intake-reducing effect of CCK-8 in the chronic decerebrate rat provides compelling evidence that the caudal brain stem is of sufficient neural complexity to mediate this response. Although others have hypothesized that connections between the caudal brain stem and forebrain are required to mediate this effect(s) of CCK-8, our results demonstrate that these pathways are not necessary.
Membrane lipid composition and overwintering strategy in thermally acclimated crayfish
Authors: Pruitt N. L.
Published: December 2017

The membrane lipid composition of hepatopancreas tissue was analyzed from two phylogenetically related species of crayfish after thermal acclimation to either 5 or 20 degrees C. One species overwinters in a quiescent state (Orconectes propinquus) and the other remains active throughout the winter (Cambarus bartoni). Both species significantly decreased the level of saturates in the major phosphatides, phosphatidylcholine (PC) and phosphatidylethanolamine (PE; difference not significant in C. bartoni), and both winter-active and winter-quiescent animals tended to be enriched in n-3 acids in PC. Orconectes animals tended to be enriched in n - 3 acids in PC. Orconectes accumulated n - 6 acids in PE at low temperature, whereas Cambarus lost n - 6 acids in this lipid, a change that was offset by the accumulation of monoenes. Cardiolipin became more saturated with cold acclimation in both species. The fatty acid content of the triacylglycerol fraction showed little change with acclimation history, although O. propinquus did accumulate n - 3 acids in triglycerides at low temperature. In O. propinquus, head-group composition was not significantly altered by temperature, but in C. bartoni, cold temperature increased the relative amounts of PE, sphingomyelin, and phosphatidylinositol at the expense of PC. Adaptations to temperature in membrane composition of poikilotherms are related to the overwintering strategy of the animal.
Radio-frequency vs. electrolytic VMH lesions: differential effects on plasma hormones
Authors: King B. M. , Dallman M. F. , Esquerre K. R. , Frohman L. A.
Published: December 2017

Electrolytic lesions of the ventromedial hypothalamus (VMH) result in marked hyperphagia and obesity, but several studies have found the excess food intake and weight gain to be greatly reduced when lesions are produced by electrocauterization with radio-frequency current. Unlike electrolytic lesions, radio-frequency lesions leave few or no deposits of metallic ions that can potentially stimulate adjacent tissue. In the present experiment, weight gain and several endocrine responses previously associated with the VMH syndrome were compared in female rats given either electrolytic, radio-frequency, or sham VMH lesions. Both groups with VMH lesions became obese, but rats with radio-frequency lesions displayed only 63.2% of the weight gain of animals with irritative lesions (120.0 vs. 189.8 g in 20 days). Only rats with electrolytic lesions displayed elevated plasma insulin levels during an initial period of food restriction, but both groups with lesions were hyperinsulinemic when allowed to overeat. Plasma growth hormone levels were decreased by electrolytic lesions but unaffected by radio-frequency lesions. Morning corticosterone levels were elevated in both VMH groups, but only the rats with electrolytic lesions were found to have elevations in plasma adrenocorticotropin. It is concluded that some of the endocrine dysfunctions resulting from electrolytic VMH lesions are due to irritative stimulation rather than to tissue ablation.
Spatial map of salts and saccharides on dog tongue
Authors: Garvin J. L. , Robb R. , Simon S. A.
Published: December 2017

Front and rear regions of dog tongue were tested for spatial heterogeneity with respect to monovalent chloride salts (NaCl, KCl, and NH4Cl) and sweet tastants (sucrose, D-glucose, and L-glucose) by placing them in Ussing chambers where the open-circuit potential, Voc, and short-circuit current, Isc, were measured. The responses of Voc and Isc to 0.5 M NaCl were greater in the front of the tongue than in the rear, whereas the responses of Voc and Isc to 0.5 M sucrose were greater in the rear of the tongue than in the front. These results are similar to those of published neurophysiological measurements from the chorda tympani nerve and thalamus. These data suggest that the spatial heterogeneities seen in higher taste centers are present in the isolated lingual epithelium where primary taste transduction events occur.
Satiating effect of fat in diabetic rats: gastrointestinal and postabsorptive factors
Authors: Edens N. K. , Friedman M. I.
Published: December 2017

Streptozotocin-diabetic rats decrease food intake more than normal animals in response to a fat test meal. To determine the physiological basis of this differential response, we examined the effects of an ingested corn oil meal on food intake, gastrointestinal fill, and plasma triglycerides, glycerol, and ketone bodies. Hyperphagic diabetic rats decreased intake of a high-carbohydrate, low-fat stock diet starting 2-4 h after the fat meal, whereas normal rats did not. Gastric emptying was accelerated and intestinal mass and contents were increased in diabetic rats. The fat meal reduced gastric emptying and increased stomach contents in diabetic and normal rats starting within 2 h of ingestion. Intestinal fill decreased in diabetic animals after the oil meal. Triglycerides and glycerol increased transiently after fat ingestion in normal and diabetic rats, whereas ketone body concentrations rose only in diabetic rats starting 1-3 h after fat ingestion. The results indicate that the differential effect of a fat meal on food intake in normal and diabetic rats is related to differences in the postabsorptive metabolism of the ingested fat rather than to effects of fat feeding on gastrointestinal fill or clearance.
Measurement of 2H2O by IR absorbance in doubly labeled H2O studies of energy expenditure
Authors: Karasov W. H. , Han L. R. , Munger J. C.
Published: December 2017

The energy expenditure of animals in their natural surroundings can be determined by measuring the turnover in body water of isotopes of oxygen and hydrogen. We evaluated the use of infrared spectrophotometry for measuring 2H2O in small (20-microliters) water samples also labeled with 18O. For 2H2O over the enrichment range of 0.1-1 atom%, there was a linear relationship between infrared absorbance and 2H2O enrichment. 2H2O enrichments could be measured with a precision and accuracy of less than or equal to 1%, using this relationship. The presence of 18O in water samples in enrichments of up to 1 atom% had no significant effect on measurement of 2H2O by infrared absorbance. We measured the simultaneous turnover rates of 2H2O and 3H in mice and turtles also labeled with 18O. Our results validated the use of infrared absorbance in doubly labeled water measures of energy expenditure and indicated that the fractionation factors in vivo for 2H2O and 3H do not differ.
Proposal for APS-IUPS convention for diagraming physiological mechanisms
Authors: Allweis Cecil
Published: December 2017

Pages R717–R726: Cecil Allweis. “Proposal for APS-IUPS convention for diagraming physiological mechanisms.” Page R721: an arrow was omitted from the second diagram in the left-hand column. The correct diagram follows

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H+ homeostasis, osmolality, and body temperature during controlled NaCl and H2O intake
Authors: Anderson J. W. , Jennings D. B.
Published: December 2017

Arterial PCO2, arterial [H+] ([H+]a), electrolytes, and osmolality, as well as rectal temperature (Tre), were monitored in six awake dogs over sequential 12- or 13-day periods in which their NaCl intake was first less than 5 meq/day, then approximately 120 meq/day, and finally less than 5 meq/day. Water intake was maintained constant at 77 ml.kg-1.day-1 throughout. During low-NaCl periods, decreases in body and plasma water, indicated by weight loss did not prevent lower arterial [Na+] ([Na+]a), arterial [Cl-] ([Cl-]a), and osmolality relative to the high-NaCl period. During high dietary NaCl, the arterial strong ion difference [[SID]a = ([Na+]a + [K+]a) - (arterial [lactate-] + [Cl-]a)] was lower. From physicochemistry, this lowered [SID]a results in a higher [H+]a. However, independent of NaCl intake, [H+]a was positively correlated with plasma osmolality; moreover, [H+]a, relative to plasma osmolality, was higher at lower Tre than at higher Tre. We speculate that this spectrum of plasma osmolality and body temperature may contribute to the creation of an appropriate protein pK to match plasma [H+]a. We also found that the difference between plasma [protein] (measured by the biuret test) and [ATOT]a (an estimation of plasma protein as total weak acid from physicochemistry) was related to plasma osmolality, [SID]a, and [Na+]a. These latter relations may reflect the effect of plasma water concentration (osmolality) and strong ions on the pK of plasma proteins.
Ingestive behavior in preweanling rats: emergence of postgastric controls
Authors: Phifer C. B. , Hall W. G.
Published: December 2017

Previous studies have indicated that the termination of intake in very young rat pups is controlled almost exclusively by the level of gastric fill; nutritive cues from diet have no effect on intake. In the present series of experiments, we investigated the ontogeny of postgastric nutritive controls of intake in rat pups ingesting independent of their dam. In 6-day-old pups, the level of gastric fill required to terminate ingestion was not affected by the presence or absence of post-gastric nutritive cues, but by 15 days of age a greater level of gastric fill was required to stop ingestion when postgastric cues were eliminated by a closed pyloric noose. This emergent post-gastric contribution to the inhibition of intake in 15-day-old pups does not depend on preexisting gastric fill signals, as sham-feeding pups (open gastric fistula) with nutrients in their intestines ingested less than pups without intestinal nutrients. These results provide evidence that postgastric controls of ingestive behavior mature during the postnatal period and just shortly before they are required at weaning.
Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light
Authors: Thomas E. M. , Armstrong S. M.
Published: December 2017

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.
Effect of starvation and food intake on sympathetic activity
Authors: Sakaguchi T. , Arase K. , Fisler J. S. , Bray G. A.
Published: December 2017

These studies have examined the effect of fasting and nutrient loads on sympathetic firing rate in three groups of rats that develop widely divergent degrees of obesity when eating a high-fat diet. Starvation of Sprague-Dawley rats for 24 or 48 h was associated with a decrease in basal sympathetic activity of nearly 25% in the first 24 h and of slightly greater than 30% in 48 h. This decline in sympathetic activity paralleled the loss of body weight and reduction in adipose tissue mass. After starvation for 48 h, Osborne-Mendel rats, which readily develop obesity when eating a high-fat diet, showed a greater decrease in basal sympathetic activity than did the diet-resistant S 5B/P1 rats. A single liquid 36-kcal intragastric meal was associated with an acute 30% increase in sympathetic firing rate in the overnight-fasted Sprague-Dawley rats. The values 3 h after the meal had returned halfway to normal, and by 6 h they were more than 85% of the way to normal. An intravenous injection of glucose produced a greater rise in sympathetic activity in diet-resistant S 5B/P1 rats than in the diet-sensitive Osborne-Mendel rats. These data are consistent with the hypotheses that sympathetic activity is positively related to nutrient status, that it varies between strains of rats, and that it can be acutely increased by an intragastric meal or by intravenous glucose.
Correlation between catecholamine release and degree of acidotic stress in trout
Authors: Tang Y. , Boutilier R. G.
Published: December 2017

Exhaustive exercise in freshwater (FW) and seawater (SW) rainbow trout resulted in a marked and acute increase of plasma catecholamines. Immediately after exercise, epinephrine and norepinephrine concentrations in FW trout were 69 and 15 times the resting level, respectively; in SW trout, they were 46 and 11 times the resting value, respectively. Over the 1st h of recovery, the magnitude of the catecholamine surge in FW animals was about twice that of their SW counterparts. Correlated with this was an extracellular pH disturbance in FW trout, which was approximately twice as severe as in SW trout. Indeed, both the magnitudes and time courses of the plasma catecholamine responses were matched to those of the acid-base disturbances. Linear correlations were found to exist between the immediate depression of blood pH and the corresponding increases in plasma epinephrine and norepinephrine. We conclude that catecholamines are released into the plasma in proportion to the magnitude of the acid-base disturbance. The higher postexercise levels of plasma catecholamines in FW trout vs. SW appear to be a response to the greater acid-base disturbance in the FW animals.
Enhanced ANG II activity in anterior pituitary cell aggregates from hypertensive rats
Authors: Robberecht W. , Denef C.
Published: December 2017

Pituitary cell reaggregates from 14-day-old and adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were cultured in serum-free, chemically defined medium supplemented with the thyroid hormone triiodothyronine and the glucocorticoid dexamethasone. After 1 wk in culture, aggregates were transferred into a perifusion system, and the effect of angiotensin II (ANG II) on prolactin (PRL) and growth hormone (GH) release was studied. In aggregates from adult SHR, ANG II displayed a significant and dose-dependent GH releasing activity, whereas a negligible effect or no effect was seen in aggregates from adult WKY. In contrast, no difference in the stimulation of PRL release by ANG II was found. To exclude the possibility that the enhanced GH responsiveness was secondary to longstanding hypertension, aggregates from animals in the prehypertensive stage were studied. Both the GH and PRL responses to ANG II were significantly higher in aggregates from 14-day-old SHR than in aggregates from 14-day-old WKY. These data indicate that abnormal GH and PRL responses to ANG II exist in pituitary cell aggregates from SHR long before hypertension develops. Because these differences were found in pituitary cells maintained in culture for 1 wk, they do not seem to be secondary to changes in brain regulation of pituitary function but rather are caused by factors intrinsic to the pituitary.
Strain differences in taste reactivity to NaCl
Authors: Grill H. J. , Bernstein I. L.
Published: December 2017

The taste reactivity test was used to determine whether strain differences in response to NaCl revealed by preference tests were attributable to taste or postoral factors. Taste reactivity data revealed significant differences between sodium-replete Fischer 344 (F-344) and Wistar strains in response to NaCl for both aversive and ingestive oral motor behaviors. Because the taste reactivity test analyzed the immediate response to orally applied chemical stimuli, these data support a strain difference based on taste factors. Taste reactivity data also indicate strain differences in ingestive but not aversive scores to other normally ingested chemical stimuli, water, and two sucrose concentrations. In response to normally avoided quinine, F-344 and Wistar strains did not differ in either ingestive or aversive score. To investigate whether strain differences revealed when rats were tested while sodium replete would persist in the sodium-deficient state, both strains were treated with the diuretic furosemide. Taste reactivity tests revealed that in response to sodium deficiency both F-344 and Wistar strains shift their oral motor response profile to NaCl; strains did not differ in either ingestive or aversive score when sodium deficient. NaCl intake and preference measures also support the fact that both strains demonstrate a sodium appetite. Interpretive limitations based on ceiling and floor effects within taste reactivity and preference data were discussed.
Plasma angiotensin II levels at moment of drinking during angiotensin II intravenous infusion
Authors: Anke J. , Van Eekelen M. , Phillips M. I.
Published: December 2017

Angiotensin II (ANG II) was infused intravenously within an apparent physiological dose range of 10-200 ng.kg-1.min-1 to induce a drinking response in rats. To determine the plasma ANG II level at the moment of drinking, blood samples were collected from the femoral artery at the onset of the drinking response. Control blood samples were obtained in a similar way before infusion. The lowest dose of ANG II did not evoke drinking. Variable water intake in response to 25, 50, and 75 ng ANG II.kg-1.min-1 after a relatively long latency to drink (40-65 min) was observed. All animals showed a drinking response when 100 ng ANG II.kg-1.min-1 or higher doses of ANG II were infused. The latencies to drink were inversely correlated to the dose of ANG II and were as short as 8 min with 200 ng ANG II.kg-1.min-1. Measurement of ANG II in the plasma of drinking rats showed that all concentrations were similar with an average of 458 +/- 58.1 pg/ml. This dipsogenic plasma ANG II level is equivalent to plasma ANG II after 48 h of dehydration. The results show that drinking in response to exogenous intravenous ANG II requires a threshold level to be reached that is equivalent to levels produced by the endogenous renin-angiotensin system when dehydration is prolonged. This suggests that intravenous ANG II is not involved in moment-to-moment fluid homeostasis but operates only when dehydration is severe.
Is there a Cl- pump?
Authors: Gerencser G. A. , White J. F. , Gradmann D. , Bonting S. L.
Published: December 2017

Three universally accepted mechanisms of Cl- transport across plasma membranes exist and they are 1) anion-coupled antiport, 2) cation-coupled symport, and 3) coupling to primary active ion transport through electrical and/or chemical processes. No unequivocal direct evidence has been provided for primary active Cl- transport (Cl- pump) despite numerous reports of cellular Cl- -stimulated adenosinetriphosphatase (ATPases) and of Cl- transport that cannot be accounted for by the three well-documented Cl- transport processes. It has been demonstrated that Cl- -stimulated ATPase activity is localized to both mitochondrial and microsomal aspects of the cellular apparatus. However, one group ascribes microsomal localization of Cl- -stimulated ATPase activity to mitochondrial contamination of that membrane fraction. Therefore, no Cl- pump could ever exist naturally in any plasma membrane. The other group simply states that there is plasma membrane localization of Cl- -stimulated ATPase activity that could function as a Cl- pump. Both arguments are logically advanced and their conclusions are consistent with their respective premises. Resolution to the question Is there a Cl- pump? rests with each reader's critique and objective evaluation.
Localization of vagal preganglionic somata controlling sinoatrial and atrioventricular nodes
Authors: Plecha D. M. , Randall W. C. , Geis G. S. , Wurster R. D.
Published: December 2017

Canine cardiac vagal ganglia in the region of the inferior vena cava and inferior left atrium (IVC-ILA) and at the junction of the right pulmonary veins and left atrium (PVFP) control atrioventricular conduction and heart rate, respectively. After retrograde transport of horseradish peroxidase (HRP) injected separately into these ganglia in different dogs, the left and right and longitudinal distributions of brain stem somata terminating in these ganglia were compared with functional dominance of left and right vagal control of heart rate and atrioventricular conduction. Labeled somata innervating these ganglia had quite similar longitudinal distribution patterns. Although functional dominance of heart rate was found to be in either the right vagus or bilaterally in both vagi, a corresponding difference in somata innervating the PVFP ganglia was not found. Functional vagal dominance of atrioventricular conduction was found to be either right, bilateral, or left with correspondence between left-right distributions of somata after HRP injection into the IVC-ILA region. However, these results should be cautiously interpreted because these ganglia mediate other cardiac functions.
Effects of chronic sinoaortic denervation on central vasopressin and catecholamine systems
Authors: Alexander N. , Morris M.
Published: December 2017

The objective of this study was to determine whether chronic arterial baroreceptor deficit induces time-related changes in central vasopressin (AVP) and catecholamine systems. Groups of sinoaortic-denervated (SAD) and sham-operated (SO) rats were studied 1, 3, 4, 7, and 14 days after surgery. Supraoptic (SON), paraventricular (PVN) and arcuate (ARC) nuclei, median eminence (ME) region, and A1 region of medulla were obtained by micropunch from frozen brain sections and assayed for AVP, tyrosine hydroxylase (TH) activity, catecholamines, and their metabolites, dihydroxyphenylethyleneglycol (DOPEG) and 2,5-dihydroxyphenylacetic acid (DOPAC). AVP concentration in SON and PVN was increased in 1-day-SAD rats, reduced in 3- and 4-day-SAD rats, equal and above control values in 7- and 14-day-SAD rats, respectively. TH activity was increased in SON and reduced in ME and ARC of 1- and 7-day-SAD rats. In SON, DOPEG was increased, whereas in ME all catecholamines and DOPEG and DOPAC were reduced in 1-day-SAD rats. ME catecholamines returned toward control levels in 3- to 4-day-SAD rats. These studies show that the chronic absence of arterial baroreceptor input produces time-related, regionally specific central changes of vasopressin and regionally associated catecholamines.
Effects of melatonin on long-day responses in short-day housed adult Siberian hamsters
Authors: Bartness T. J. , Goldman B. D.
Published: December 2017

Testis growth is stimulated when short photoperiod-regressed Siberian hamsters are exposed to a lengthening photoperiod, an effect presumably mediated by the pineal gland through a decrease in the peak nocturnal duration of secretion of its hormone melatonin (MEL)(D. S. Carter and B. D. Goldman, Endocrinology 113: 1268-1273, 1983). We examined this stimulatory or "progonadal" effect of MEL in short photoperiod-regressed, adult male Siberian hamsters that were pinealectomized (PINX) and given timed daily subcutaneous 1) injections of MEL (1 or 10 micrograms/day) or saline or 2) infusions of MEL that were "long day-like" (4 h, 10 or 100 ng/day), "short day-like" (10 h, 10 ng/day), or control saline infusions (4 h/day). Photoregressed sham PINX hamsters were transferred to long days at this time. After 5 wk of treatment, 1-microgram MEL-injected hamsters and both groups of 4-h MEL-infused hamsters had stimulatory responses that mimicked those of the long-day-exposed, sham PINX group [i.e., increased testes, body, and epididymal white adipose tissue (EPIWAT) weights, total body fat, EPIWAT lipoprotein lipase activity, and serum prolactin and follicle-stimulating hormone levels]. These effects were not observed in 10-micrograms MEL- or saline-injected and 10-h MEL- or saline-infused hamsters. Thus the peak nocturnal duration of serum MEL is the critical parameter of the MEL secretion profile for stimulating a variety of photoperiodic responses when photoregressed hamsters are exposed to lengthening daylengths.
Immune activation and psychoneurogenic stress modulate corticosterone-releasing effects of lymphokines and ACTH
Authors: Torres-Aleman I. , Barasoain I. , Borrell J. , Guaza C.
Published: December 2017

Possible modulatory effects of psychoneurogenic stress and endotoxin-induced immune activation on the in vitro corticosterone-releasing effects of lymphokine-containing supernatants (LCS) and adrenocorticotropic hormone (ACTH) were studied in rats. We have found that activation of the immune system by endotoxin increases the in vitro sensitivity of the adrenocortical cells to LCS and ACTH. In addition, we found that psychoneurogenic stress not only produced an increase of in vitro adrenal sensitivity to ACTH, but it also enhanced the release of corticosterone after perfusion of LCS. A synergistic interaction between ACTH and LCS was observed in all experimental groups of animals studied. An increased adrenal sensitivity to LCS and ACTH after stress or immune activation might have a functional significance, since the adrenal cortex is a major site in the response of the organism to alterations in the homeostatic balance. On the other hand, the temporal pattern of in vitro corticosterone release after LCS was different in all groups under study compared with that observed after ACTH challenge. LCS elicited a more rapid corticosterone response that lasted for a shorter time than after giving ACTH. These latter results suggest that different mechanisms may underlie the effects of LCS and ACTH on adrenal corticosteroidogenesis. In conclusion, the present findings further reinforce the existence of possible physiologically relevant interactions between the immune system and the pituitary-adrenal axis.
Fetal cerebral responses to ventilation and oxygenation in utero
Authors: Gleason C. A. , Jones M. D. , Traystman R. J. , Notter R. H.
Published: December 2017

Previous studies have shown that cerebral oxygen consumption (CMRO2) increases by nearly 50% at birth. The perinatal factors responsible for this increase are unknown; however, one possibility is that fetal CMRO2 is constrained by the normal intrauterine arterial PO2 (PaO2) of approximately 20 mmHg. We investigated this possibility in seven near-term chronically instrumented fetal sheep (131-138 days gestation) in which we inserted vascular catheters and an endotracheal tube. After 1-3 days recovery, we measured cerebral blood flow (CBF) with radiolabeled microspheres and calculated CMRO2. Measurements were made in utero under three conditions for each fetus: 1) nonventilated control; 2) ventilation with 3% O2-5% CO2-92% N2; and 3) ventilation with an inspired oxygen concentration sufficient to raise fetal PaO2 to normal newborn levels (mean 73 mmHg). A calf lung surfactant extract (CLSE) was instilled into the endotracheal tube of the fetus before ventilation to ensure adequate levels of alveolar surfactant and to maintain stable pH and arterial PCO2. The results showed that increasing fetal arterial PO2 to postnatal levels did not consistently increase CMRO2. CBF decreased as arterial O2 content (CaO2) rose, with an inverse hyperbolic response similar to that previously found to relate CBF to CaO2 during fetal hypoxic hypoxia. This indicates that the normally low intrauterine PaO2 does not intrinsically limit CMRO2 and implies that the rapid increase in CMRO2 at birth reflects the activation of specific cellular and physiological processes at (or near) this unique developmental event.
Ontogeny of alpha- and beta-adrenergic anorexia in rats
Authors: Lora-Vilchis M. C. , Chambert G. , Rodriguez-Zendejas A. M. , Soto-Mora L. M. , Russek M. , Epstein A. N.
Published: December 2017

The anorectic action of alpha- (phenylephrine) and beta- (isoproterenol) adrenergic agonists was studied in mildly deprived neonatal, weanling, prepubescent, and adult rats. Intraperitoneal phenylephrine produced a reduction of food intake at all ages but with reduced potency and with a maximum of 50% in neonates. Contrary to intramuscular epinephrine that has no effect on feeding at any age, intramuscular phenylephrine was as effective as intraperitoneal in neonates, probably because it is not as rapidly destroyed in tissues as epinephrine. However, in weanlings and adults intramuscular phenylephrine was much less anorectic than intraperitoneal, suggesting that this effect is exerted via the liver. Isoproterenol did not reduce milk intake at any age before adulthood. Lactate had no effect on milk intake before the age of 40 days. Thus catecholamine anorexia is a purely alpha-adrenergic effect in young rats and appears before the metabolic effect of lactate. beta-Adrenergic anorexia, on the other hand, can be obtained only after puberty, suggesting that the mechanism mediating it matures after the preparatory action of the sexual hormones.
Acylation of lysophosphatidylcholine in liver microsomes of thermally acclimated trout
Authors: Livermore R. C. , Hazel J. R.
Published: December 2017

The specificity of acyl-coenzyme A (CoA): lysophosphatidylcholine acyltransferase (LPCAT; EC 2.3.1.23) was determined for a range for acyl-CoA substrates differing with respect to chain length and degree of unsaturation in liver microsomes of thermally acclimated (5 and 20 degrees C) rainbow trout, Salmo gairdneri. Absolute levels of oleate incorporation into phosphatidylcholine (PC) were determined at substrate concentrations in the physiological range (12 microM) and higher (64 microM). The specificity of LPCAT was determined by the extent to which competing substrates decreased the incorporation of oleate. LPCAT specificity was significantly influenced by both assay and acclimation temperature at total substrate concentrations of both 72 and 256 microM. A clear preference for 14- and 16-carbon monoenes was exhibited by LPCAT from 20 but not 5 degrees C-acclimated trout. Furthermore, LPCAT from 5 degrees C-acclimated trout preferentially incorporated long chain and polyunsaturated fatty acids (eicosadienoyl, arachidonoyl, erucoyl) and excluded 18-carbon unsaturates at an assay temperature of 5 degrees C compared with 20 degrees C; at 20 degrees C, 18-carbon unsaturates were incorporated more readily than 20-carbon species. Linolenic acid (18:3N3) was generally excluded from incorporation, reflecting a possible mechanism by which this precursor of docasahexaenoic acid (22:6N3, n - 3) remains available for modification. These results indicate that trout liver LPCAT preferentially incorporates fatty acids into PC on the basis of both chain length and degree of unsaturation in a manner consistent with the temperature-induced restructuring of membrane phospholipids.
Effects of cimaterol, a beta-adrenergic agonist, on energy metabolism in ob/ob mice
Authors: Walker H. C. , Romsos D. R.
Published: December 2017

Cimaterol when added to the diets for 3 or 9 wk stimulated whole animal energy expenditure and brown adipose tissue thermogenic activity comparably in genetically obese (ob/ob) and lean mice; however, ob/ob mice fed diets containing 140 or 280 micrograms cimaterol/kcal failed to increase energy intake as much as lean mice. Consequently, the efficiency of energy retention was actually lower in ob/ob mice fed diets containing cimaterol than in similarly treated lean mice. Cimaterol stimulated skeletal muscle gain in ob/ob mice, although at no point did final hindlimb muscle weight of ob/ob mice equal that of lean mice. Hyperinsulinemia was abolished in ob/ob mice fed diets containing cimaterol even though plasma corticosterone concentrations remained elevated. We conclude that cimaterol has greater effects on energy balance and plasma insulin, but not on skeletal muscle accretion, in ob/ob mice than in lean mice.
Direct cardiac stimulation by arginine vasotocin in bullfrogs (Rana catesbeiana)
Authors: Sham J. S. , Sawyer W. H. , Pang P. K.
Published: December 2017

The antidiuretic and vasopressor effects of arginine vasotocin (AVT) in bullfrogs have been well documented. However, the direct cardiac stimulatory effects of AVT have not been previously reported. We found that AVT stimulates significant increases in heart rate, pulse pressure, and the maximal time derivative of ventricular pressure in anesthetized bullfrogs after the beta-adrenergic and muscarinic receptors in the heart were blocked by atropine and propranolol. In spontaneously beating isolated frog atria, AVT increased the beating rate by 20% and the contractile force by 100%. The inotropic effect of AVT was also demonstrated in electrically driven atria and ventricles. Propranolol was ineffective in blocking these cardiac responses in vitro. The Hill coefficients of the concentration-response curves did not differ from unity. In conclusion, AVT possesses both positive chronotropic and inotropic effects in bullfrogs, Rana catesbeiana, probably by direct stimulation of its specific receptors in the heart.
Morphological dynamics of ureteral transport. I. Shape and volume of constituent urine fractions
Authors: Ohlson L.
Published: December 2017

Ureteral transport was studied in 50 urinary systems by urography with video recording in the upright and recumbent positions using low-osmolality and high-osmolality contrast media. Morphometry and volumetry were applied to right urinary systems in which the urine-filled segments had a circular cross section at maximum peristaltic distension. The filling of the lumbar segment was composed of four fractions, each entering that segment by a specific mechanism: 1) the residual urine left behind by the preceding contraction ring, 2) the postcontraction injection from the pyelocalyceal system, 3) the extraperistaltic flow, and 4) the peristaltic injection produced by the pyelocalyceal contraction rings. The variations in the precontraction filling by fractions 1-3 and in the volume of fraction 4 gave rise to four types of transport. The junction between the lumbar and pelvic segments constituted a constant point of resistance to flow that prevented fractions 1-3 from entering the pelvic segment, the peristaltic injection into that segment being determined solely by the resistance at the junction and the volume of the bolus in the lumbar segment. Extraperistaltic flow to the bladder constituted a separate type of transport.
Central action of acidic fibroblast growth factor in feeding regulation
Authors: Hanai K. , Oomura Y. , Kai Y. , Nishikawa K. , Shimizu N. , Morita H. , Plata-Salaman C. R.
Published: December 2017

A phasic increase in activity similar to that of acidic fibroblast growth factor (aFGF) was detected in the cerebrospinal fluid of rats after feeding or after an intraperitoneal injection of glucose. This FGF-like activity in the cerebrospinal fluid was bioassayed in two systems: depression of the feeding response of Hydra and DNA synthesis-stimulating activity in BALB/c 3T3 cells after fractionation on a heparin affinity column. Dynamic feeding-related changes in activity of aFGF, basic FGF, and other growth factors were detected by both bioassay systems. Intracerebroventricular microinfusion of aFGF suppressed food intake in rats. Central infusion of inactivated aFGF, or peripheral administration of aFGF, in doses equivalent to or higher than those administered centrally was without effect. Electrophoretically applied aFGF specifically suppressed the activity of glucose-sensitive neurons in the lateral hypothalamus. Glucose-insensitive neurons were only slightly affected. The results suggest that aFGF may participate in the regulation of feeding at the level of the central nervous system.
Morphological dynamics of ureteral transport. II. Peristaltic patterns in relation to flow rate
Authors: Ohlson L.
Published: December 2017

To study in the human the conditions for the flow regimes inherent in urinary systems with a dependence of the contraction interval on urine flow rate (boluses-in-contact, leaky-bolus, and open-tube flow regimes), 50 urinary systems were examined at low and high flow rates. Morphometry and volumetry were applied to eight urinary systems. The bolus frequently contacted the preceding contraction ring but the mechanisms differed categorically from that conventionally postulated. Thus the contraction interval proved independent of flow rate, leading to boluses in contact not only at high but also at low flow rates, which is impossible in flow-dependent urinary systems. Likewise, contact proved possible with small as well as large boluses. Furthermore, the contact was invariably interrupted at the points of resistance to flow, the total contact period being only 4% of the ureteral transit. Leaky-bolus flow and open-tube flow were absent. The flow regimes as conventionally defined thus proved to be absent from and inconsistent with normal human urinary transport.
Cerebral oxygenation and blood flow in infant and young adult rats
Authors: Kreisman N. R. , Olson J. E. , Horne D. S. , Holtzman D.
Published: December 2017

In vitro cerebral oxidative metabolism undergoes dramatic increases in infant rats between 10 and 20 days of age. To determine this was also the case in vivo, comparisons were made of cerebral blood flow (CBF) and oxygenation in rats at 10, 20, and 60-90 days of age, under pentobarbital sodium anesthesia. Measurements were made of CBF, arterial and venous O2 content, cerebral PO2 distributions, and the oxidation state of cytochrome-c oxidase (cytochrome aa3). CBF, O2 delivery, and O2 consumption all increased progressively with maturation. In contrast, cerebral PO2, cytochrome aa3 oxidation state, and O2 extraction fraction were higher in 20-day-old rats than in either 10-day-old or adult rats. We attribute this difference primarily to the high density of cerebral capillaries in the 20-day-old rat. We conclude that cerebral tissue PO2 and the oxidation state of cytochrome aa3 are determined by the density of perfused capillaries in addition to the more commonly accepted factors of cerebral O2 delivery and consumption.
Breathing and upper airway CO2 in reptiles: role of the nasal and vomeronasal systems
Authors: Coates E. L. , Ballam G. O.
Published: December 2017

The ventilatory response of the garter snake, Thamnophis sirtalis, to 2% CO2 delivered to the upper airways (UA) was measured before and after the olfactory or vomeronasal nerves were transected. The UA (nasal cavities and mouth) were isolated from the gas source inspired into the lungs by inserting an endotracheal T tube into the glottis. CO2 was administered to the UA via a head chamber. The primary ventilatory response to UA CO2 was a significant decrease in ventilatory frequency (f) and minute ventilation. The decrease in f was caused by a significant increase in the pause duration. Tidal volume, expiratory duration, and inspiratory duration were not altered with UA CO2. The f response to UA CO2 was abolished with olfactory nerve transection, whereas vomeronasal nerve transection significantly increased the magnitude of the f depression. These results indicate that CO2-sensitive receptors are located in the nasal epithelium and that the olfactory nerves must be intact for the UA CO2 f response to be observed. In addition, the vomeronasal system appears to modulate the ventilatory response to UA CO2.
Lateral parabrachial lesions attenuate ingestive effects of area postrema lesions
Authors: Edwards G. L. , Ritter R. C.
Published: December 2017

Lesions of the area postrema and adjacent nucleus of the solitary tract (AP lesions) cause rats to consume increased amounts of palatable food in short duration tests. Because the lateral parabrachial nucleus (lPBN) receives a prominent afferent projection from the AP and adjacent nucleus of the solitary tract, it is possible the lPBN plays a role in the altered ingestive behaviors observed in AP-lesioned rats. The present study examines the role of the lPBN in overingestion of highly palatable foods subsequent to AP lesions. We found that lesions of the lPBN alone did not cause rats to consume increased amounts of palatable food. Rather, when lPBN lesions were produced before AP lesions, increased intake of highly palatable food did not occur. Moreover, when AP-lesioned rats received subsequent lPBN lesions, the previously established overingestion of palatable foods was abolished. These results indicate that the lPBN is necessary in the pathogenesis of AP lesion-induced overingestion of highly palatable foods.
Coronary autoregulation and metabolism in hypothermic rat and ground squirrel hearts
Authors: Burlington R. F. , Dean M. S. , Jones S. B.
Published: December 2017

An isovolumic Langendorff preparation was used to perfuse rat and ground squirrel (Spermophilus tridecemlineatus) hearts at 37, 27, 17, and 7 degrees C. Perfusion pressure (PP) was randomly increased or decreased (40, 60, 70, 110, 120, or 140 mmHg) from a control PP of 90 mmHg. Coronary flow (CF) was measured immediately after each PP change (initial CF) and after stable flow was observed (final CF). Compared with initial flow, final CF was decreased at high PPs or increased at low PPs (autoregulation) in hearts from both species, but rat hearts did not autoregulate CF or develop left ventricular systolic pressure (LVSP) at 7 degrees C. Squirrel hearts generated LVSP at all temperatures and perfusion pressures. LVSP and initial CF were proportional to PP in both species, but squirrel heart LVSP was independent of PP at 7 degrees C. Myocardial O2 consumption (MVO2) was highly correlated with CF in all hearts at 37 degrees C but not at lower temperatures. Squirrel hearts were more efficient (MVO2 vs. HR X LVSP) than rat hearts at low temperatures but less efficient at 37 degrees C. The intrinsic temperature adaptations displayed by squirrel hearts would support continued myocardial function when body temperature and blood pressure fluctuate throughout the stages of hibernation.
Sleep changes in emperor penguins during fasting
Authors: Dewasmes G. , Buchet C. , Geloen A. , Le Maho Y.
Published: December 2017

The proportion and the distribution over 24 h of the different arousal stages characterized in emperor penguins [wakefulness (W), drowsiness (D), slow-wave sleep (SWS), and paradoxical sleep (PS)] were studied under natural ambient conditions in four subjects that were first fed and then deprived of food for 7-18 days. In both fed and fasting states, each arousal stage was distributed through numerous episodes of short duration. The fasting state provoked only a slight increase in D. There was, however, a large increase in SWS, which increased from 37.5 to 55.4%/day, mainly at the expense of W, which fell from 42.7 to 21.9%/day, in close relation to the first two fasting phases when proteins were saved and when most of the energy was derived from lipids. PS proportions were lower during fasting (from 5.7 to 2.4%/day). These changes in the arousal stages in emperor penguins are examined for their implications in sleep mechanisms and energy saving. Their possible consequences, due to the reduced alertness, are also discussed.
Stress can enhance the renin response to reduced renal perfusion pressure
Authors: Porter J. P.
Published: December 2017

It was recently reported that electrical stimulation of the hypothalamus could enhance the renin response to reductions in renal perfusion pressure. However, electrical stimulation of brain sites may activate neural pathways that never function physiologically. In the present investigation an external stress in the form of a jet of air to the face was applied to achieve a more physiological activation of the sympathetic nervous system. Conscious restrained rats, instrumented with pneumatic occluding cuffs around the aorta proximal to the renal arteries, were used to determine the relationship between renal perfusion pressure (RPP) and plasma renin activity (PRA) in the control state and in the presence of the stress. The jet of air produced a rightward shift in the relationship between RPP and PRA and also increased the slope, suggesting an enhanced sensitivity. Both the rightward shift and the increase in slope were absent in animals with bilateral renal denervation. In animals with adrenal enucleation, the rightward shift was still present but there was no significant increase in the sensitivity. These data suggest that an external activation of the central nervous system (by a stress) has the potential to modulate the responsiveness of the kidney to nonneural stimuli for renin secretion.