bluuebunny/crossref_metadata_2025 huggingface dataset:
Ontogeny of diet-induced obesity in selectively bred Sprague-Dawley rats
Authors: Ricci Matthew R. , Levin Barry E.
Published: March 2015

Outbred Sprague-Dawley rats selectively bred for their propensity to develop diet-induced obesity (DIO) become heavier on low-fat diet than those bred to be diet resistant (DR) beginning at ∼5 wk of age. Here we assessed the development of metabolic and neural functions for insights into the origins of their greater weight gain. From week 5 to week 10, chow-fed DIO rats gained 15% more body weight and ate ∼14% more calories but had only slightly greater adiposity and plasma leptin than DR rats. From day 3 through week 10, DIO and DR rats had similar mRNA expression of arcuate nucleus neuropeptide Y, proopiomelanocortin, agouti-related peptide, and all splice variants of the leptin receptor (OB-R). When fed a high-energy (HE; 31% fat) diet, 7-wk-old DIO rats had a 240% increase in plasma leptin levels after only 3 days. Despite this early leptin rise, they maintained a persistent hyperphagia and became more obese than chow-fed DIO rats and DR rats fed chow or HE diet. Their failure to reduce caloric intake, despite high levels of leptin, suggests that selectively bred DIO rats might have reduced leptin sensitivity similar to that seen in the outbred DIO parent strain.
Thermoregulatory and metabolic changes during fever in young and old rats
Authors: Buchanan Jessica B. , Peloso Elizabeth , Satinoff Evelyn
Published: March 2015

We injected old and young rats with lipopolysaccharide (LPS; 50 μg/kg ip) at two ambient temperatures ( Ta; 21 and 31°C). Young rats mounted equivalent fevers at both Tas [peak body temperatures ( Tb) of 38.3 and 38.7°C, respectively]. The Tbof old rats was not different from baseline (37.3°C) after LPS at Ta21°C, whereas, at 31°C, their Tbrose to a mean peak of 38.4°C. We also measured the associated thermoregulatory responses by use of calorimetry. At 21°C, young rats developed a fever by increasing both O2consumption and heat conservation. Old rats did not become febrile, and O2consumption fell by 15%. Heat loss was the same in old and young rats. At 31°C, young and old rats developed similar fevers with similar increases in heat production and conservation. Our results suggest that the lack of LPS fever in old rats at 21°C is due mainly to the lowered metabolic rate.
Synergy between angiotensin and aldosterone in evoking sodium appetite in baboons
Authors: Shade R. E. , Blair-West J. R. , Carey K. D. , Madden L. J. , Weisinger R. S. , Denton D. A.
Published: March 2015

The synergy between ANG II and aldosterone (Aldo) in the induction of salt appetite, extensively studied in rats, has been tested in baboons. ANG II was infused intracerebroventricularly at 0.5 or 1.0 μg/h; Aldo was infused subcutaneously at 20 μg/h. Separate infusions over 7 days had no significant effect on the daily intake of 300 mM NaCl. Concurrent infusions, however, increased daily NaCl intake ∼10-fold and daily water intake ∼2.5-fold. In addition, the combined infusions caused 1) a reduction in daily food intake, 2) changes in blood composition indicative of increased vasopressin release, and 3) changes of urinary excretion rates of cortisol and Aldo indicative of increased ACTH release. Arterial blood pressure, measured in two baboons, rose during concurrent ANG II and Aldo treatment. These results indicate a potent synergy between central ANG II and peripheral Aldo in stimulating salt appetite in baboons. At the same time, other ANG II-specific brain mechanisms concerned with water intake, food intake, vasopressin release, ACTH release, and blood pressure regulation appear to have been activated by the same type of synergy. These central enhancement processes have never been previously demonstrated in primates.
Compensatory role of NO in cerebral circulation of piglets chronically treated with indomethacin
Authors: Zhang Yifan , Leffler C. W.
Published: March 2015

We hypothesize that inhibitory effects exist between prostanoids and nitric oxide (NO) in their contributions to cerebral circulation. Piglets (1–4 days old) were divided into three chronically treated (6–8 days) groups: control piglets, piglets treated with indomethacin (75 mg/day), and piglets treated with Nω-nitro-l-arginine methyl ester (l-NAME, 100 mg · kg−1· day−1). Pial arterioles dilated in response to hypercapnia similarly among the three groups (41 ± 4, 40 ± 6, and 45 ± 11%). Cerebrospinal fluid cAMP increased in control piglets, while cGMP increased in indomethacin-treated piglets. l-NAME, but not 7-nitroindazole, inhibited the response to hypercapnia only in indomethacin-treated piglets (40 ± 6 vs. 17 ± 5%). Topical sodium nitroprusside or iloprost restored dilation in response to hypercapnia. Similar results were obtained when the dilator was bradykinin. Pial arterioles of control and l-NAME-treated piglets constricted in response to ACh (−24 ± 3%). However, those of indomethacin-treated piglets dilated in response to ACh (15 ± 2%). This dilation was inhibited by l-NAME. NO synthase activity, but not endothelial NO synthase expression, increased after chronic indomethacin treatment. These data suggest that chronic inhibition of cyclooxygenase can increase the contribution of NO to cerebrovascular circulatory control in piglets.
Suppression of fever at near term is associated with reduced COX-2 protein expression in rat hypothalamus
Authors: Mouihate A. , Clerget-Froidevaux M-S. , Nakamura K. , Negishi M. , Wallace J. L. , Pittman Q. J.
Published: March 2015

The fever response is blunted at near term. As the enzyme cyclooxygenase-2 (COX-2) plays a critical role in fever development, we measured its expression in rat hypothalamus during pregnancy and lactation. Western blot analysis revealed a 72-kDa COX-2-immunoreactive band in non-immune-challenged, pregnant rats at day 15 of pregnancy. In contrast, it was almost undetectable at near term and at lactation day 5. COX-2 was significantly induced at the 15th day of pregnancy and at the 5th lactating day after intraperitoneal lipopolysaccharide (50 μg/kg). However, this COX-2 induction was significantly reduced at near term compared with values before and after term. The protein levels of the EP3 receptor in the hypothalamus, one of the prostaglandin E2(PGE2) receptors suggested to be a key receptor for fever induction, were unaffected throughout the pregnancy and lactation in both non-immune-challenged and lipopolysaccharide-treated rats. These data suggest that suppression of fever at near term is associated with a significantly reduced induction of COX-2 by lipopolysaccharide, resulting in a reduced production of PGE2. Altered expression of the EP3 receptor does not seem to be involved in this fever refractoriness at near term.
HPA-axis responses during experimental colitis in the rat
Authors: Kojima Kensaku , Naruse Yoshihisa , Iijima Norio , Wakabayashi Naoki , Mitsufuji Shoji , Ibata Yasuhiko , Tanaka Masaki
Published: March 2015

We investigated the responses of the hypothalamic-pituitary-adrenal (HPA) axis during experimental colitis induced by intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid in the rat. On days 3 and 7 after induction of colitis, the corticotropin-releasing hormone (CRH) mRNA level in the parvocellular paraventricular nucleus (pPVN) of the hypothalamus was reduced, the plasma ACTH level remained at the basal level, and the plasma corticosterone (Cort) level was high. Induction of colitis on day 3 after adrenalectomy with Cort pellet replacement (ADX + Cort) resulted in a marked increase in CRH mRNA on day 7 after induction of colitis compared with noncolitic ADX + Cort animals. Pair feeding to match the food intake of the colitic animals resulted in no significant change in CRH mRNA in the pPVN, plasma ACTH, and Cort compared with healthy control animals. These findings indicated that CRH mRNA expression in the pPVN was inhibited by glucocorticoid feedback during this experimental colitis, and the decrease in food intake during colitis was not simply responsible for the expression of CRH mRNA. It is inferred that the HPA axis including the CRH level in the pPVN is altered in patients with inflammatory bowel disease.
Gene transcription of brain voltage-gated potassium channels is reversibly regulated by oxygen supply
Authors: Prentice Howard M. , Milton Sarah L. , Scheurle Daniela , Lutz Peter L.
Published: March 2015

Voltage-dependent potassium channels (Kv channels) are important determinants of brain electrical activity. Hypoxia may be an important modifier, because several voltage-gated K+channels are reversibly blocked by acute hypoxia and are thought to act as oxygen sensors. Here we show, using the anoxia-tolerant turtle brain ( Trachemys scripta) as a model, that brain Kv1 channel transcription is reversibly regulated by oxygen supply. We found that in turtle brains exposed to 4-h anoxia Kv1 transcripts were reduced to 18.5% of normoxic levels. Kv1 channel mRNA levels were restored to normal within 4 h of subsequent reoxygenation. Our results provide clear evidence that brain Kv channel expression is sensitive to oxygen supply and indicate an important mechanism that matches brain activity to oxygen supply.
Differential expression of cold- and diet-specific genes encoding two carp liver Δ9-acyl-CoA desaturase isoforms
Authors: Polley S. D. , Tiku P. E. , Trueman R. T. , Caddick M. X. , Morozov I. Y. , Cossins A. R.
Published: March 2015

Carp respond to cold by the upregulated expression of Δ9-acyl-CoA desaturase. Here we report the cloning and characterization of Cds2, a second Δ9-acyl CoA-desaturase expressed in carp liver. Both Cds1and Cds2 complemented the ole1 mutation in Saccharomyces cerevisiae, permitting the synthesis of Δ9-monounsaturates, confirming their identity as Δ9-desaturases. We demonstrate that under a standard feeding regime it is the Cds2, and not Cds1, transcript that is transiently upregulated during the first few days of cooling from 30°C to 10°C, the period when cold-induced membrane restructuring occurs. Cds2 exists as two differentially spliced transcripts, differing by a small segment from the 3′-untranslated region, the ratio of which varies with temperature. Feeding a diet enriched in saturated fats produced a fourfold increase in Cds1 transcript levels, which was blocked by cooling to 15°C. Cds2 transcript levels, however, showed no substantial response to the saturated diet. Thus carp liver uniquely expresses two isoforms of Δ9-acyl CoA desaturase, possibly formed by a recent duplication event, that are differentially regulated by cooling and dietary treatment.
Method for measuring ATP production in isolated mitochondria: ATP production in brain and liver mitochondria of Fischer-344 rats with age and caloric restriction
Authors: Drew Barry , Leeuwenburgh Christiaan
Published: March 2015

The production of ATP is vital for muscle contraction, chemiosmotic homeostasis, and normal cellular function. Many studies have measured ATP content or qualitative changes in ATP production, but few have quantified ATP production in vivo in isolated mitochondria. Because of the importance of understanding the energy capacity of mitochondria in biology, physiology, cellular dysfunction, and ultimately, disease pathologies and normal aging, we modified a commercially available bioluminescent ATP determination assay for quantitatively measuring ATP content and rate of ATP production in isolated mitochondria. The bioluminescence assay is based on the reaction of ATP with recombinant firefly luciferase and its substrate luciferin. The stabilities of the reaction mixture as well as relevant ATP standards were quantified. The luminescent signals of the reaction mixture and a 0.5 μM ATP standard decreased linearly at rates of 2.16 and 1.39% decay/min, respectively. For a 25 μM ATP standard, the luminescent signal underwent a logarithmic decay, due to intrinsic deviations from the Beer-Lambert law. Moreover, to test the functionality of isolated mitochondria, they were incubated with 1 and 5 mM oligomycin, an inhibitor of oxidative phosphorylation. The rate of ATP production in the mitochondria declined by 34 and 83%, respectively. Due to the sensitivity and stability of the assay and methodology, we were able to quantitatively measure in vivo the effects of age and caloric restriction on the ATP content and production in isolated mitochondria from the brain and liver of young and old Fischer-344 rats. In both tissues, neither age nor caloric restriction had any significant effect on the ATP content or the rate of ATP production. This study introduces a highly sensitive, reproducible, and quick methodology for measuring ATP in isolated mitochondria.
Protein-free phospholipid emulsion treatment improved cardiopulmonary function and survival in porcine sepsis
Authors: Goldfarb Roy D. , Parker Thomas S. , Levine Daniel M. , Glock Dana , Akhter Imran , Alkhudari Azzam , McCarthy Robert J. , David Eric M. , Gordon Bruce R. , Saal Stuart D. , Rubin Albert L. , Trenholme Gordon M. , Parrillo Joseph E.
Published: March 2015

Lipoprotein phospholipid (PL) plays a major role in neutralization of endotoxin. This study tested the hypothesis that prophylactic administration of a PL-enriched emulsion (PRE), which augments PL content of serum lipoproteins and neutralizes endotoxin in vitro, would preserve cardiovascular function and improve survival in porcine septic peritonitis. A control group was compared with low-, mid-, and high-dose treatment groups that received PRE by primed continuous infusion for 48 h. A fibrin clot containing live Escherichia coli 0111.B4 was implanted intraperitoneally 30 min after the priming dose. Survival increased in a dose-dependent manner and was correlated with serum PL. Infused PL was associated with high-density lipoprotein in the low-dose group and all serum lipoproteins at higher doses. Treatment significantly lowered serum endotoxin and tumor necrosis factor (TNF)-α, preserved cardiac output and ejection fraction, and attenuated increases in systemic and pulmonary vascular resistances. This study demonstrated that augmentation of lipoprotein PL via administration of PRE improved survival and offered a novel therapeutic approach to sepsis.
Novel mechanism for high-altitude adaptation in hemoglobin of the Andean frogTelmatobius peruvianus
Authors: Weber Roy E. , Ostojic Hrvoj , Fago Angela , Dewilde Sylvia , Van Hauwaert Marie-Louise , Moens Luc , Monge Carlos
Published: March 2015

In contrast to birds and mammals, no information appears to be available on the molecular adaptations for O2transport in high-altitude ectothermic vertebrates. We investigated Hb of the aquatic Andean frog Telmatobius peruvianus from 3,800-m altitude as regards isoform differentiation, sensitivity to allosteric cofactors, and primary structures of the α- and β-chains, and we carried out comparative O2-binding measurements on Hb of lowland Xenopus laevis. The three T. peruvianus isoHbs show similar functional properties. The high O2affinity of the major component results from an almost complete obliteration of chloride sensitivity, which correlates with two α-chain modifications: blockage of the NH2-terminal residues and replacement by nonpolar Ala of polar residues Ser and Thr found at position α131(H14) in human and X. leavis Hbs, respectively. The data indicate adaptive significance of α-chain chloride-binding sites in amphibians, in contrast to human Hb where chloride appears mainly to bind in the cavity between the β-chains. The findings are discussed in relation to other strategies for high-altitude adaptations in amphibians.
Angiotensin II injures the arterial wall causing increased aortic stiffening in apolipoprotein E-deficient mice
Authors: Tham Doris M. , Martin-McNulty Baby , Wang Yi-Xin , Da Cunha Valdeci , Wilson Dennis W. , Athanassious Christian N. , Powers Andrew F. , Sullivan Mark E. , Rutledge John C.
Published: March 2015

Cardiovascular diseases, such as atherosclerosis and hypertension, are associated with arterial stiffening. Previous studies showed that ANG II exacerbated atherosclerosis and induced hypertension and aneurysm formation in apolipoprotein E-deficient (apoE-KO) mice. The aim of the present study was to examine the effects of chronic treatment of ANG II on the arterial elastic properties in apoE-KO mice. We hypothesized that ANG II will injure the arterial wall resulting in increased arterial stiffening. Male apoE-KO mice were infused with either ANG II (1.44 mg · kg−1 · day−1) or vehicle (PBS) for 30 days. ANG II treatment accelerated atherosclerosis in the carotid artery by sixfold ( P < 0.001) and increased blood pressure by 30% ( P < 0.05). Additionally, our data demonstrated that ANG II increased arterial stiffening using both in vivo and in vitro methods. ANG II significantly increased pulse wave velocity by 36% ( P< 0.01) and decreased arterial elasticity as demonstrated by a more than 900% increase in maximal stiffening (high strain Young's modulus) compared with vehicle ( P < 0.05). These functional changes were correlated with morphological and biochemical changes as demonstrated by an increase in collagen content (60%), a decrease in elastin content (74%), and breaks in the internal elastic lamina in the aortic wall. In addition, endothelium-independent vasorelaxation to sodium nitroprusside was impaired in the aortic rings of ANG II-treated mice compared with vehicle. Thus, the present data indicate that ANG II injures the artery wall in multiple ways and arterial stiffening may be a common outcome of ANG II-induced arterial damage.
Frequency modulation of mesenteric and renal vascular resistance
Authors: Grisk Olaf , Stauss Harald M.
Published: March 2015

The hypothesis was tested that low-frequency vasomotions in individual vascular beds are integrated by the cardiovascular system, such that new fluctuations at additional frequencies occur in arterial blood pressure. In anesthetized rats ( n = 8), the sympathetic splanchnic and renal nerves were simultaneously stimulated at combinations of frequencies ranging from 0.075 to 0.8 Hz. Blood pressure was recorded together with mesenteric and renal blood flow velocities. Dual nerve stimulation at low frequencies (<0.6 Hz) caused corresponding oscillations in vascular resistance and blood pressure, whereas higher stimulation frequencies increased the mean levels. Blood pressure oscillations were only detected at the individual stimulation frequencies and their harmonics. The strongest periodic responses in vascular resistance were found at 0.40 ± 0.02 Hz in the mesenteric and at 0.32 ± 0.03 Hz ( P < 0.05) in the renal vascular bed. Thus frequency modulation of low-frequency vasomotions in individual vascular beds does not cause significant blood pressure oscillations at additional frequencies. Furthermore, our data suggest that sympathetic modulation of mesenteric vascular resistance can initiate blood pressure oscillations at slightly higher frequencies than sympathetic modulation of renal vascular resistance.
Protein kinase-dependent and Ca2+-independent cAMP inhibition of ANP release in beating rabbit atria
Authors: Cui Xun , Wen Jin Fu , Jin Jing Yu , Xu Wen Xie , Kim Sung Zoo , Kim Suhn Hee , Lee Ho Sub , Cho Kyung Woo
Published: March 2015

Regulation of atrial release of atrial natriuretic peptide (ANP) is coupled to changes in atrial dynamics. However, the mechanism by which mechanical stretch controls myocytic ANP release must be defined. The purpose of this study was to define the mechanism by which cAMP controls myocytic ANP release in perfused, beating rabbit atria. The cAMP-elevating agents forskolin and 3-isobutyl-1-methylxanthine (IBMX) inhibited myocytic ANP release. The activation of adenylyl cyclase with forskolin inhibited ANP release, which was a function of an increase in cAMP production. Inhibitors for L-type Ca2+channels and protein kinase A (PKA) attenuated a minor portion of the forskolin-induced inhibition of ANP release. Gö-6976 and KN-62, which are specific inhibitors for protein kinase C-α and Ca2+/calmodulin kinase, respectively, failed to modulate forskolin-induced inhibition of ANP release. The nonspecific protein kinase inhibitor staurosporine blocked forskolin-induced inhibition of ANP release in a dose-dependent manner. Staurosporine but not nifedipine shifted the relationship between cAMP and ANP release. Inhibitors for L-type Ca2+channels and PKA and staurosporine blocked forskolin-induced accentuation of atrial dynamics. These results suggest that cAMP inhibits atrial myocytic release of ANP via protein kinase-dependent and L-type Ca2+-channel-dependent and -independent signaling pathways.
Burn-induced changes in IGF-I and IGF-binding proteins are partially glucocorticoid dependent
Authors: Lang Charles H. , Nystrom Gerald J. , Frost Robert A.
Published: March 2015

The purpose of the present study was to determine whether burn-induced changes in various components of the insulin-like growth factor (IGF) system are mediated by the actions of endogenous glucocorticoids or tumor necrosis factor (TNF). To address this aim, a 30% total body surface area full-thickness scald burn was produced in anesthetized rats, and the animals were studied 24 h later. Separate groups of time-matched control and burned rats were pretreated with either an antagonist to glucocorticoids (RU-486) or to TNF (TNF-binding protein; TNFBP). Thermal injury decreased the plasma concentration of IGF-I (38%) as well as the IGF-I mRNA abundance in muscle and kidney (31 and 48%, respectively). While RU-486 prevented the burn-induced decrease in plasma IGF-I, it did not ameliorate the reduction in tissue IGF-I mRNA. Burn increased the plasma concentration of IGF-binding protein (IGFBP)-1 as well as the mRNA content of IGFBP-1 in liver and kidney (15- to 20-fold). These burn-induced increases were partially or largely prevented by RU-486. In contrast, burn decreased the plasma concentration of IGFBP-3 (30%). Burn concomitantly decreased hepatic IGFBP-3 mRNA abundance (42%) but increased IGFBP-3 mRNA in kidney and muscle (50% and 10-fold, respectively). RU-486 largely prevented the burn-induced changes in IGFBP-3 mRNA in kidney and muscle but failed to attenuate the decreases in plasma and liver. Finally, burn injury decreased hepatic acid-labile subunit (ALS) mRNA by 80% and increased the mRNA content of IGFBP-related protein-1 (mac25) in liver by twofold, and these changes were not modified by pretreatment with RU-486. The above-mentioned changes in the IGF system were associated with a burn-induced decrease in muscle protein content that was prevented by RU-486. TNFBP failed to completely ameliorate any of the burn-induced changes in the IGF system. These results demonstrate that glucocorticoids, but not TNF, mediate many but not all of the burn-induced changes in the IGF system.
Importance of the renal medullary circulation in the control of sodium excretion and blood pressure
Authors: Mattson David L.
Published: March 2015

The control of renal medullary perfusion and the impact of alterations in medullary blood flow on renal function have been topics of research interest for almost four decades. Many studies have examined the vascular architecture of the renal medulla, the factors that regulate renal medullary blood flow, and the influence of medullary perfusion on sodium and water excretion and arterial pressure. Despite these studies, there are still a number of important unanswered questions in regard to the control of medullary perfusion and the influence of medullary blood flow on renal excretory function and blood pressure. This review will first address the vascular architecture of the renal medulla and the potential mechanisms whereby medullary perfusion may be regulated. The known extrarenal and local systems that influence the medullary vasculature will then be summarized. Finally, this review will present an overview of the evidence supporting the concept that selective changes in medullary perfusion can have a potent influence on sodium and water excretion with a long-term influence on arterial blood pressure regulation.
Regulation of MRP2-mediated transport in shark rectal salt gland tubules
Authors: Miller David S. , Masereeuw Rosalinde , Karnaky Karl J.
Published: March 2015

We examined endothelin-1 (ET-1) regulation of the xenobiotic efflux pump, multidrug resistance-associated protein isoform 2 (MRP2), in intact dogfish shark rectal salt gland tubules using a fluorescent substrate sulforhodamine 101 and confocal microscopy. Subnanomolar to nanomolar concentrations of ET-1 rapidly reduced the cell-to-lumen transport of sulforhodamine 101. These effects were prevented by an ETBreceptor antagonist but not by an ETAreceptor antagonist. Immunostaining with an antibody to mammalian ETBreceptors showed specific localization to the basolateral membrane of the shark rectal gland epithelial cells. ET-1 effects on transport were blocked by a protein kinase C (PKC)-selective inhibitor, implicating PKC in ET-1 signaling. A protein kinase A (PKA)-selective inhibitor had no effect. Forskolin reduced luminal accumulation of sulforhodamine 101, but inhibition of PKA did not block the forskolin effect. Consistent with this observation, a cAMP analog that does not activate PKA reduced luminal accumulation of sulforhodamine 101. These results indicate that shark rectal gland transport on MRP2 is regulated by ET acting through an ETBreceptor and PKC. In addition, cAMP affects transporter function through a PKA-independent mechanism, possibly by competition for transport.
Regional, metabolic, and circadian specificity of lateral hypothalamic orexin A feeding stimulation
Authors: Thorpe Andrew J. , Mullett Mary A. , Wang Chuanfeng , Kotz Catherine M.
Published: March 2015

Orexin A (OX-A) administered in the lateral hypothalamus (LH) increases feeding in a dose-dependent manner. The LH is a relatively large neural structure with a heterogeneous profile of neural inputs, efferent projections, and orexin receptor distribution. We sought to determine the LH region most sensitive to the feeding stimulatory effect of OX-A injection. Fifty-six male Sprague-Dawley rats were fitted with cannulas 1 mm above four separate LH regions ∼1 mm apart in the rostral-caudal direction. There were 14–16 animals/LH region. After recovery, animals received either artificial cerebrospinal fluid or OX-A (250, 500, or 1,000 pmol). To determine whether there is a circadian effect of LH OX-A on the feeding response, we performed injections at 0200, 0900, 1400, and 2100. Food intake was measured at 1, 2, and 4 h after injection. The most rostral extent of the LH was the only region in which injection of OX-A significantly stimulated feeding. Within this region, feeding was increased at all times of the day, although the most robust and only significant feeding response occurred after the afternoon injection (1400) of OX-A. To determine the extent to which the metabolic status of the rat contributed to the circadian specificity of orexin-induced feeding, animals were placed on a restricted diet and injected with OX-A in the most rostral region of the LH. Under these conditions, OX-A significantly increased feeding and more robustly when compared with animals on a nonrestricted diet. These data suggest that the rostral LH is the only region of the LH sensitive to the injection of OX-A, and the metabolic status of the animal at the time of injection may influence the feeding response to OX-A.
Melatonin in mice: rhythms, response to light, adrenergic stimulation, and metabolism
Authors: Kennaway D. J. , Voultsios A. , Varcoe T. J. , Moyer R. W.
Published: March 2015

There has been relatively little research conducted on pineal melatonin production in laboratory mice, in part, due to the lack of appropriate assays. We studied the pineal and plasma rhythm, response to light, adrenergic stimulation, and metabolism of melatonin in CBA mice. With the use of a sensitive and specific melatonin RIA, melatonin was detected in the pineal glands at all times of the day >21 fmol/gland in CBA mice but not in C57Bl mice. Both plasma and pineal melatonin levels peaked 2 h before dawn in a 12:12-h light-dark photoperiod (162 ± 31 pM and 1,804 ± 514 fmol/gland, respectively). A brief light pulse (200 lx/15 min), 2 h before lights on, suppressed both plasma and pineal melatonin to near basal levels within 30 min. Exposure to light pulses 4 h after lights off or 2 h before lights on resulted in delays and advances, respectively, in the early morning decline of plasma and pineal melatonin on the next cycle. Administration of the β-adrenergic agonist isoproterenol (20 mg/kg) 2 and 4 h after lights on in the morning resulted in a fivefold increase in plasma and pineal melatonin 2.5 to 3 h after the first injection. In the mouse, unlike the rat, melatonin was shown to be metabolized almost exclusively to 6-glucuronylmelatonin rather than 6-sulphatoxymelatonin. These studies have shown that the appropriate methodological tools are now available for studying melatonin rhythms in mice.
Feeding melatonin enhances the phase shifting response to triazolam in both young and old golden hamsters
Authors: Kolker Daniel E. , Losee Olson Susan , Dutton-Boilek Jeanette , Bennett Katherine M. , Wallen Edward P. , Horton Teresa H. , Turek Fred W.
Published: March 2015

Aging alters many aspects of circadian rhythmicity, including responsivity to phase-shifting stimuli and the amplitude of the rhythm of melatonin secretion. As melatonin is both an output from and an input to the circadian clock, we hypothesized that the decreased melatonin levels exhibited by old hamsters may adversely impact the circadian system as a whole. We enhanced the diurnal rhythm of melatonin by feeding melatonin to young and old hamsters. Animals of both age groups on the melatonin diet showed larger phase shifts than control-fed animals in response to an injection with the benzodiazepine triazolam at a circadian time known to induce phase advances in the activity rhythm of young animals. Thus melatonin treatment can increase the sensitivity of the circadian timing system of young animals to a nonphotic stimulus, and the ability to increase this sensitivity persists into old age, indicating exogenous melatonin might be useful in reversing at least some age-related changes in circadian clock function.
“Drink at least eight glasses of water a day.” Really? Is there scientific evidence for “8 × 8”?
Authors: Valtin Heinz ,   (With the Technical Assistance of Sheila A. Gorman)
Published: March 2015

Despite the seemingly ubiquitous admonition to “drink at least eight 8-oz glasses of water a day” (with an accompanying reminder that beverages containing caffeine and alcohol do not count), rigorous proof for this counsel appears to be lacking. This review sought to find the origin of this advice (called “8 × 8” for short) and to examine the scientific evidence, if any, that might support it. The search included not only electronic modes but also a cursory examination of the older literature that is not covered in electronic databases and, most importantly and fruitfully, extensive consultation with several nutritionists who specialize in the field of thirst and drinking fluids. No scientific studies were found in support of 8 × 8. Rather, surveys of food and fluid intake on thousands of adults of both genders, analyses of which have been published in peer-reviewed journals, strongly suggest that such large amounts are not needed because the surveyed persons were presumably healthy and certainly not overtly ill. This conclusion is supported by published studies showing that caffeinated drinks (and, to a lesser extent, mild alcoholic beverages like beer in moderation) may indeed be counted toward the daily total, as well as by the large body of published experiments that attest to the precision and effectiveness of the osmoregulatory system for maintaining water balance. It is to be emphasized that the conclusion is limited to healthy adults in a temperate climate leading a largely sedentaryexistence, precisely the population and conditions that the “at least” in 8 × 8 refers to. Equally to be emphasized, lest the message of this review be misconstrued, is the fact (based on published evidence) that large intakes of fluid, equal to and greater than 8 × 8, are advisable for the treatment or prevention of some diseases and certainly are called for under special circumstances, such as vigorous work and exercise, especially in hot climates. Since it is difficult or impossible to prove a negative—in this instance, the absence of scientific literature supporting the 8 × 8 recommendation—the author invites communications from readers who are aware of pertinent publications.
Thirst and salt appetite responses in young and old Brown Norway rats
Authors: Thunhorst Robert L. , Johnson Alan Kim
Published: March 2015

Male Brown Norway rats aged 4 mo (young) and 20 mo (old) received a series of experimental challenges to body fluid homeostasis over ∼3 mo. Water was available for drinking in some tests, and both water and 0.3 M NaCl were available in others. The series included three episodes of extracellular fluid depletion (i.e., furosemide + 20 h of sodium restriction), two tests involving intracellular fluid depletion (i.e., hypertonic saline: 1 or 2 M NaCl at 2 ml/kg body wt sc), one test involving overnight food and fluid restriction, and testing with captopril adulteration of the drinking water (0.1 mg/ml) for several days. Old rats were significantly heavier than young rats throughout testing. Old rats drank less water and 0.3 M NaCl after sodium deprivation than young rats, in terms of absolute and body weight-adjusted intakes. Old rats drank only half as much water as young rats in response to subcutaneous hypertonic NaCl when intakes were adjusted for body weight. Old rats drank less 0.3 M NaCl than young rats after overnight food and fluid restriction when intakes were adjusted for body weight. In response to captopril adulteration of the drinking water, young rats significantly increased daily ingestion of 0.3 M NaCl when it was available as an alternative to water and significantly increased daily water intakes when only water was available, in terms of absolute and body weight-adjusted intakes. Old rats had no response to captopril treatment. These results add important new information to previous reports that aging rats have diminished thirst and near-absent salt appetite responses to regulatory challenges.
The respiratory metabolism of a lizard (Lacerta vivipara) in supercooled and frozen states
Authors: Voituron Yann , Verdier Bruno , Grenot Claude
Published: March 2015

We investigated the respiratory metabolism of the overwintering lizard Lacerta vivipara while in either supercooled or frozen states. With a variable pressure and volume microrespirometer and a chromatograph, we show that the oxygen consumption of the supercooled animals showed a nonlinear relationship with temperature and an aerobic metabolism demand between 0.5 and −1.5°C. A significant increase in the respiratory quotient (RQ) values indicated an increasing contribution by the anaerobic pathways with decreasing temperature. In the frozen state, two phases are easily detectable and are probably linked to the ice formation within the body. During the first 5–6 h, the animals showed an oxygen consumption of 3.52 ± 0.28 μl · g−1 · h−1 and a RQ value of 0.52 ± 0.09. In contrast, after ice equilibrium, oxygen consumption decreased sharply (0.55 ± 0.09 μl · g−1 · h−1) and the RQ values increased (2.49 ± 0.65). The present study confirms the fact that supercooled invertebrates and vertebrates respond differently to subzero temperatures, in terms of aerobic metabolism, and it shows that aerobic metabolism persists under freezing conditions.
Interleukin-10 concentration determined by sandwich enzyme-linked immunosorbent assay is unrepresentative of bioactivity in murine blood
Authors: Hillyer L. M. , Woodward Bill
Published: March 2015

Two experiments were performed, each using six male and six female C57BL/6J mice collectively ranging from 4 wk to 17 mo of age. Blood was obtained following CO2anesthesia, and the IL-10 concentration of each serum sample was determined both by sandwich enzyme-linked immunosorbent assay (ELISA) and by bioassay. In the first experiment, mean serum IL-10 immunoactivity was 9.3 pg/ml while the mean bioactivity was 700 times greater, i.e., 6.5 ng/ml. However, the bioassay required sample dilution, which might have released bound cytokine that the ELISA could also detect. In the second experiment, therefore, the ELISA was applied to samples diluted to 20% as for the bioassay. Nevertheless, the immunoassay continued to detect only a small fraction of the serum IL-10 identified by the bioassay (mean values: 32.4 pg/ml vs. 2.6 ng/ml). Although currently the preferred method, the sandwich ELISA is inappropriate for quantification of blood IL-10 concentrations. Moreover, studies of the actions of IL-10 are needed at the concentrations revealed in the blood by bioassay and currently considered supraphysiological.
Neural factors account for strength decrements observed after short-term muscle unloading
Authors: Deschenes Michael R. , Giles Jennifer A. , McCoy Raymond W. , Volek Jeff S. , Gomez Ana L. , Kraemer William J.
Published: March 2015

Strength decrements observed after extended (4–6 wk) periods of muscle unloading are associated with significant atrophy. Because early (up to 2 wk) strength gains from resistance exercise are related to improved neural recruitment, we hypothesized that the loss of strength resulting from 2 wk of muscle unloading [unilateral lower limb suspension (ULLS)] was due to impaired neural activation of the affected muscle. Blood samples, muscle biopsy specimens, muscle function data, and electromyography (EMG) recordings were analyzed before and after 14 days of muscle unloading. Pre- to postunloading data showed significant ( P ≤ 0.05) decrements in peak torque and total work performed by knee extensors and flexors. This was coupled with decreased EMG activity, but no change in neuromuscular efficiency (total torque/EMG). Resistance to muscle fatigue was enhanced after ULLS. The 14-day intervention failed to alter the size or fiber type distribution of muscle samples. However, resting plasma cortisol levels were significantly increased after muscle unloading, suggesting an endocrine environment favorable to muscle atrophy. Our data confirm that the diminution in muscle function displayed after 2 wk of unloading is mainly due to neural, rather than contractile, disturbances.
Central nervous system effects of caffeine and adenosine on fatigue
Authors: Davis J. Mark , Zhao Zuowei , Stock Howard S. , Mehl Kristen A. , Buggy James , Hand Gregory A.
Published: March 2015

Caffeine ingestion can delay fatigue during exercise, but the mechanisms remain elusive. This study was designed to test the hypothesis that blockade of central nervous system (CNS) adenosine receptors may explain the beneficial effect of caffeine on fatigue. Initial experiments were done to confirm an effect of CNS caffeine and/or the adenosine A1/A2 receptor agonist 5′- N-ethylcarboxamidoadenosine (NECA) on spontaneous locomotor activity. Thirty minutes before measurement of spontaneous activity or treadmill running, male rats received caffeine, NECA, caffeine plus NECA, or vehicle during four sessions separated by ∼1 wk. CNS caffeine and NECA (intracerebroventricular) were associated with increased and decreased spontaneous activity, respectively, but caffeine plus NECA did not block the reduction induced by NECA. CNS caffeine also increased run time to fatigue by 60% and NECA reduced it by 68% vs. vehicle. However, unlike the effects on spontaneous activity, pretreatment with caffeine was effective in blocking the decrease in run time by NECA. No differences were found after peripheral (intraperitoneal) drug administration. Results suggest that caffeine can delay fatigue through CNS mechanisms, at least in part by blocking adenosine receptors.
The natriuretic peptide system in eels: a key endocrine system for euryhalinity?
Authors: Takei Yoshio , Hirose Shigehisa
Published: March 2015

The natriuretic peptide system of a euryhaline teleost, the Japanese eel ( Anguilla japonica), consists of three types of hormones [atrial natriuretic peptide (ANP), ventricular natriuretic peptide (VNP), and C-type natriuretic peptide (CNP)] and four types of receptors [natriuretic peptide receptors (NPR)-A, -B, -C, and -D]. Although ANP is recognized as a volume-regulating hormone that extrudes both Na+and water in mammals, ANP more specifically extrudes Na+in eels. Accumulating evidence shows that ANP is secreted in response to hypernatremia and acts to inhibit the uptake and to stimulate the excretion of Na+but not water, thereby promoting seawater (SW) adaptation. In fact, ANP is secreted immediately after transfer of eels to SW and ameliorates sudden increases in plasma Na+concentration through inhibition of drinking and intestinal absorption of NaCl. ANP also stimulates the secretion of cortisol, a long-acting hormone for SW adaptation, whereas ANP itself disappears quickly from the circulation. Thus ANP is a primary hormone responsible for the initial phase of SW adaptation. By contrast, CNP appears to be a hormone involved in freshwater (FW) adaptation. Recent data show that the gene expression of CNP and its specific receptor, NPR-B, is much enhanced in FW eels. In fact, CNP infusion increases22Na uptake from the environment in FW eels. These results show that ANP and CNP, despite high sequence identity, have opposite effects on salinity adaptation in eels. This difference apparently originates from the difference in their specific receptors, ANP for NPR-A and CNP for NPR-B. VNP may compensate the effects of ANP and CNP for adaptation to respective media, because it has high affinity to both receptors. On the basis of these data, the authors suggest that the natriuretic peptide system is a key endocrine system that allows this euryhaline fish to adapt to diverse osmotic environments, particularly in the initial phase of adaptation.
Determinants of leptin gene expression in fat depots of lean mice
Authors: Zhang Yiying , Guo Kai-Ying , Diaz Patricia A. , Heo Moonseong , Leibel Rudolph L.
Published: March 2015

The relationship of leptin gene expression to adipocyte volume was investigated in lean 10-wk-old male C57BL/6J mice. mRNA levels for leptin, insulin receptor, glucocorticoid receptor, and tumor necrosis factor (TNF)-α in inguinal, epididymal, and retroperitoneal adipose tissues were quantified and related to adipocyte volume. Leptin mRNA levels were highly correlated with adipocyte volume within each fat depot. Multiple regression analysis of pooled data from the three depots showed that leptin mRNA levels were strongly correlated with adipocyte volumes (β = 0.84, P < 0.001) and, to a smaller degree, with glucocorticoid receptor mRNA levels (β = 0.36, P < 0.001). Depot of origin had no effect ( P > 0.9). Rates of leptin secretion in vitro were strongly correlated with leptin mRNA levels ( r = 0.89, P < 0.001). mRNA levels for TNF-α, insulin receptor, and glucocorticoid receptor showed no significant correlation with adipocyte volume. These results demonstrate that depot-specific differences in leptin gene expression are mainly related to the volumes of the constituent adipocytes. The strong correlation between leptin gene expression and adipocyte volume supports leptin's physiological role as a humoral signal of fat mass.
Multiple dilator pathways in skeletal muscle contraction-induced arteriolar dilations
Authors: Murrant Coral L. , Sarelius Ingrid H.
Published: March 2015

To determine whether nitric oxide (NO), adenosine (Ado) receptors, or ATP-sensitive potassium (KATP) channels play a role in arteriolar dilations induced by muscle contraction, we used a cremaster preparation in anesthetesized hamsters in which we stimulated four to five muscle fibers lying perpendicular to a transverse arteriole (maximal diameter ∼35–65 μm). The diameter of the arteriole at the site of overlap of the stimulated muscle fibers (the local site) and at a remote site ∼1,000 μm upstream (the upstream site) was measured before, during, and after muscle contraction. Two minutes of 4-Hz muscle stimulation (5–15 V, 0.4 ms) produced local and upstream dilations of 19 ± 1 and 10 ± 1 μm, respectively. N ω-nitro-l-arginine (10−4 M; NO synthase inhibitor), xanthine amine congener (XAC; 10−6 M; Ado A1, A2A, and A2B receptor antagonist), or glibenclamide (Glib; 10−5 M; KATP channel inhibitor) superfused over the preparation attenuated the local dilation (by 29.7 ± 12.7, 61.8 ± 9.0, and 51.9 ± 14.9%, respectively), but only XAC and Glib attenuated the upstream dilation (by 68.9 ± 6.8 and 89.1 ± 6.4%, respectively). Furthermore, only Glib, when applied to the upstream site directly, attenuated the upstream dilation (48.1 ± 9.1%). Neither XAC nor Glib applied directly to the arteriole between the local and the upstream sites had an effect on the magnitude of the upstream dilation. We conclude that NO, Ado receptors, and KATP channels are involved in the local dilation initiated by contracting muscle and that both KATP channels and Ado receptor stimulation, but not NO, play a role in the manifestation of the dilation at the upstream site.
Consequences of load carrying by birds during short flights are found to be behavioral and not energetic
Authors: Nudds Robert L. , Bryant David M.
Published: March 2015

The doubly-labeled water technique and video were used to measure the effect of mass loading on energy expenditure and takeoff performance in zebra finches, Taeniopygia guttata, that were making routine (nonalarm) short flights. Finches that carried 27% additional mass did not expend more energy during flight than unloaded controls. Carrying additional mass, however, led to a reduced body mass and a decreased velocity during takeoffs (by 12%). Calculations of instantaneous mechanical power indicated that energy expended by unloaded and loaded finches at takeoff was similar, due to the observed decrease in velocity by mass-loaded finches and a lowering of their body mass. During routine short flights, zebra finches appear to maintain their metabolic power input and mechanical power output regardless of mass loading. Here, the costs of carrying additional mass during routine short flights were revealed to be behavioral and not energetic.
Dual actions of caffeine on voltage-dependent currents and intracellular calcium in taste receptor cells
Authors: Zhao Fang-Li , Lu Shao-Gang , Herness Scott
Published: March 2015

Although the numerous stimuli representing the taste quality of bitterness are known to be transduced through multiple mechanisms, recent studies have suggested an unpredicted complexity of the transduction pathways for individual bitter stimuli. To investigate this notion more thoroughly, a single prototypic bitter stimulus, caffeine, was studied by using patch-clamp and ratiometric imaging techniques on dissociated rat taste receptor cells. At behaviorally relevant concentrations, caffeine produced strong inhibition of outwardly and inwardly rectifying potassium currents. Caffeine additionally inhibited calcium current, produced a weaker inhibition of sodium current, and was without effect on chloride current. Consistent with its effects on voltage-dependent currents, caffeine caused a broadening of the action potential and an increase of the input resistance. Caffeine was an effective stimulus for elevation of intracellular calcium. This elevation was concentration dependent, independent of extracellular calcium or ryanodine, and dependent on intracellular stores as evidenced by thapsigargin treatment. These dual actions on voltage-activated ionic currents and intracellular calcium levels suggest that a single taste stimulus, caffeine, utilizes multiple transduction mechanisms.