bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation and selectivity of splenic sympathetic nerve electrical activity response to bacterial endotoxin
Authors: MacNeil B. J. , Jansen A. H. , Greenberg A. H. , Nance D. M.
Published: December 2017

Regulatory interactions and neuroanatomic pathways have been described between the sympathetic nervous system and the immune system. It is not clear whether these pathways are activated during immune responses and if target specificity provides selective regulation of immune organs. The present study examined whether systemic injection of endotoxin [lipopolysaccharide (LPS)] induces sympathetic outflow to an immune organ (spleen). Sympathetic nerve activity was recorded from either the splenic or renal nerve of adult male rats after intravenous injections of LPS. Splenic nerve activity increased in a dose-dependent manner up to 175% of control after injection of LPS, with an onset time of 17.1-23.5 min. In contrast, renal nerve recordings showed a significantly slower onset time of 37.1-52.6 min at similar doses. In addition, splenic nerve recordings of 8/8 rats responded to 10 micrograms of LPS, whereas only 4/11 positive renal nerve responses were observed at this dose. The magnitude of the responses of both splenic and renal nerves were comparable. These data suggest that the splenic nerve responds to and is more sensitive to LPS-stimulated sympathetic activation in terms of latency and frequency of responses. Thus sympathetic outflow can be directed to an immune organ in response to a stimulus known to activate the immune system.
Simulations of light effects on the human circadian pacemaker: implications for assessment of intrinsic period
Authors: Klerman E. B. , Dijk D. J. , Kronauer R. E. , Czeisler C. A.
Published: December 2017

The sensitivity of the human circadian system to light has been the subject of considerable debate. Using computer simulations of a recent quantitative model for the effects of light on the human circadian system, we investigated these effects of light during different experimental protocols. The results of the simulations indicate that the nonuniform distribution over the circadian cycle of exposure to ordinary room light seen in classical free-run studies, in which subjects select their exposure to light and darkness, can result in an observed period of approximately 25 h, even when the intrinsic period of the subject's endogenous circadian pacemaker is much closer to 24 h. Other simulation results suggest that accurate assessment of the true intrinsic period of the human circadian pacemaker requires low ambient light intensities (approximately 10-15 lx) during scheduled wake episodes, desynchrony of the imposed light-dark cycle from the endogenous circadian oscillator, and a study length of at least 20 days. Although these simulations await further experimental substantiation, they highlight the sensitivity to light of the human circadian system and the potential confounding influence of light on the assessment of the intrinsic period of the circadian pacemaker.
A comparative study of different means of assessing long-term energy expenditure in humans
Authors: Rosenbaum M. , Ravussin E. , Matthews D. E. , Gilker C. , Ferraro R. , Heymsfield S. B. , Hirsch J. , Leibel R. L.
Published: December 2017

We compared three independent techniques for measurement of total energy expenditure (TEE) in human subjects: 1) weight-maintaining energy intake (dietTEE), 2) 24-h chamber calorimetry (chamberTEE), and 3) differential elimination rates 2H2O and H(2)18O (isotopeTEE). Twenty-three healthy adult in-patients [19 never obese (NO), 2 obese (OB), and 2 formerly-obese (RO); 9 female, 14 malel] ingested a liquid formula diet (40% of calories as fat, 45% carbohydrate, 15% protein), the volume of which was adjusted until body weight was stable for at least 14 days. Body composition was then determined by hydrodensitometry, isotope dilution, and dual photon beam absorptiometry (DXA). The thermic effect of feeding (TEF) and resting energy expenditure [REE; measured before arising (dietREE) and after arising (chamberREE)] were determined by indirect calorimetry. Non-resting energy expenditure (NREE) was calculated as NREE = TEE - (REE + TEF). Subjects then gained or lost 10% of their body weight and were restudied as described above. All measures of TEE were significantly correlated (dietTEE vs. chamberTEE r2 = 0.75; dietTEE vs. isotopeTEE r2 = 0.88; isotopeTEE vs. chamberTEE r2 = 0.73; P < 0.0001). ChamberTEE (mean +/- SE = 2,107 +/- 64 kcal/day) was approximately 20% lower than either dietTEE (2,536 +/- 94 kcal/day, P < 0.0001) or isotopeTEE (2,564 +/- 83 kcal/day, P < 0.0001). When data were normalized to metabolic mass, weight gain of 10% was associated with significant increases in dietTEE (P < 0.005) and isotopeTEE (P < 0.05) but not chamberTEE; weight loss of 10% was associated with significant reductions in dietTEE (P < 0.005) and isotopeTEE (P < 0.05) but not chamberTEE. We conclude that measures of energy expenditure obtained in a highly controlled environment by caloric titration (dietTEE) or differential excretion rates of 2H2O and H(2)18O (isotopeTEE) are not significantly different and that measurements of TEE obtained in a respiratory chamber (chamberTEE) are significantly lower than dietTEE or isotopeTEE, probably largely due to limitations on physical activity in the chamber.
Control of acid secretion in cultured gas gland cells of the European eel Anguilla anguilla
Authors: Pelster B. , Pott L.
Published: December 2017

Single cells and cell clusters isolated from the swimbladder epithelium of the European eel Anguilla anguilla attached to collagen S-coated petri dishes and proliferated in a modified Dulbecco's modified Eagle's medium, supplemented with 0.5% fetal calf serum. At a temperature of 20-22 degrees C, the growing colonies reached confluence typically within 6-8 days. Activities of glycolytic and pentose phosphate shunt enzymes remained stable or increased only slightly during the first 10 days of primary culture. Incubated in a defined medium providing glucose as a fuel, gas gland cells in primary culture produced and released lactic acid. The rate of acid secretion of cultured gas gland cells measured with a cytosensor microphysiometer was not influenced by cholinergic stimulation. Similarly, the Ca2+ ionophore A-23187 had no effect. Adrenergic stimulation with epinephrine or the beta-agonist isoproterenol also did not increase the rate of acid secretion, indicating that in gas gland cells the metabolic activity cannot be stimulated via beta-adrenergic stimulation followed by an increase in adenosine 3',5'-cyclic monophosphate (cAMP). Artificially increasing the intracellular concentration of cAMP by incubation with forskolin or the cAMP analogue 8-(4-chlorophenylthio)-cAMP even resulted in a marked reduction in the rate of acid secretion. The results demonstrate that primary cell culture provides a useful means for the analysis of metabolic control and of ion transfer processes in swimbladder gas gland cells.
Converting enzyme inhibitors cause pressure-independent resetting of baroreflex control of sympathetic outflow
Authors: Heesch C. M. , Crandall M. E. , Turbek J. A.
Published: December 2017

The current study was performed to determine whether baroreflex resetting after acute administration of converting enzyme inhibitors (CEIs) was dependent on the concomitant decrease in mean arterial pressure (MAP). Reflex changes in lumbar sympathetic nerve activity (LSNA) due to increases and decreases in MAP [i.v. phenylephrine (PE) and nitroprusside infusions] were determined in normotensive and renal hypertensive (1-kidney, 1-clip) anesthetized WKY rats 1) before (control), 2) 15 min after intravenous captopril (2 mg/kg) or enalaprilat (300 micrograms), and 3) 15 min after MAP was returned to pre-CEI levels with intravenous PE. CEIs decreased MAP and caused a leftward shift of the MAP-LSNA curve toward a lower operating pressure range in all hypertensive and in one group of normotensive rats. The baroreflex curve remained shifted to the left even after MAP was restored to pre-CEI levels by infusion of PE. Thus CEIs cause a pressure-independent resetting of baroreflex control of sympathetic outflow within 15 min. This effect of CEIs is most likely due to elimination of a central nervous system effect of circulating angiotensin II and could contribute to the antihypertensive actions of this class of compounds.
Deterministic and probabilistic control of the behavior of rats ingesting liquid diets
Authors: Davis J. D.
Published: December 2017

The probability distributions of bouts of licking and pauses between them in rats ingesting sucrose solutions were studied to determine if the durations of these ingestive and noningestive acts were controlled by a deterministic or probabilistic decision rule in the central nervous system. The duration of the bouts of licking could be modeled by a Poisson process, indicating that these bouts were terminated by a probabilistic rule. Three different types of pauses terminated the bouts of licking. Each averaged 0.3, 1.5, or 50-60 s in duration. The two longer pauses could be modeled by a Poisson process, indicating that their termination was also probabilistic in nature. The shorter pauses averaging 0.3 s could not and are more likely deterministically controlled.
Exercise and recovery in frog muscle: metabolism of PCr, adenine nucleotides, and related compounds
Authors: Krause U. , Wegener G.
Published: December 2017

The effects of exercise (swimming), fatigue, and recovery on the intracellular pH (pHi), energy-rich phosphates, and related metabolites were studied in the gastrocnemius muscle of common frogs (Rana temporaria) at 20 degrees C. Exercise caused a rapid decrease in the content of phosphocreatine (PCr) and a corresponding increase in that of Pi. The ATP level remained virtually constant for 1 min; its precipitous decrease during the following minute was associated with a rise in the contents of inosine 5'-monophosphate (IMP) and NH4+, indicating a marked activation of AMP deaminase. Five minutes of swimming caused severe fatigue, which was correlated with decreases in muscle PCr (-85%), ATP (-42%), and pHi (-0.8 units). Recovery appeared almost complete within 2 h, and the frogs were then induced to swim again. During the initial 10 s of this second exercise, ATP synthesis was as high as in the first exercise, but the rate decreased more rapidly between 10 and 60 s, thus indicating that repeated exercise caused increased metabolic stress. IMP formation in working muscle was not strictly correlated with the pHi or the tissue contents of Pi, AMP and ADP, although from studies in vitro AMP deaminase is known to be modulated by these parameters.
Moderate exercise triggers both priming and activation of neutrophil subpopulations
Authors: Smith J. A. , Gray A. B. , Pyne D. B. , Baker M. S. , Telford R. D. , Weidemann M. J.
Published: December 2017

We investigated how moderate exercise affects neutrophil microbicidal activity and whether exercise-induced responses are associated with changes in growth hormone (GH) secretion. Biological fluctuations were controlled for and GH secretion was manipulated by glucose ingestion. In eight men, 1 h of moderate exercise increased intracellular H2O2 generation in response to phorbol 12-myristate 13-acetate stimulation by threefold (P = 0.025) and complement receptor expression by 20% (P = 0.045). These responses were accompanied by a twofold increase in the plasma concentration of elastase, a marker of neutrophil activation in vivo. The plasma concentration of GH increased 10-fold after exercise, but this was reduced to 3-fold by glucose ingestion (P < 0.001), which also blunted elastase release (P < 0.001). Although the magnitude of H2O2 generation increased in proportion to the increase in plasma GH concentration, it declined progressively once this exceeded 20 ng/ml. The net response of neutrophils to exercise may represent a balance between the individual responses of subpopulations that are unaffected, primed, or fully activated by circulating mediators that respond to exercise and to dietary glucose intake.
Gastrin regulates growth of human pancreatic cancer in a tonic and autocrine fashion
Authors: Smith J. P. , Shih A. , Wu Y. , McLaughlin P. J. , Zagon I. S.
Published: December 2017

The gastrointestinal peptides gastrin and cholecystokinin (CCK) stimulate growth of human pancreatic cancer through a CCK-B/gastrin- like receptor. In the present study we evaluated whether growth of human pancreatic cancer is endogenously regulated by gastrin. Immunohistomical examination of BxPC-3 cells and tumor xenografts revealed specifc gastrin immunoreactivity. Gastrin was detected by radioimmunoassay in pancreatic cancer cell extracts and in pancreatic cancer cell extracts and in the growth media. With use of reverse-transcriptase polymerase chain reaction gastrin gene expression was detected in both cultured BxPC-3 cancer cells and transplanted tumors, as well as seven addition human pancreatic cancer cell lines. Growth of BxPC-3 human pancreatic cancer cell in serum-free medium was inhibited by the addition of the CCK-B/gastrin receptor antagonist L-365,260, and gastrin treatment reversed the inhibitory effect of the antagonist. A selective gastrin antibody (Ab repressed growth of BxPC-3 cells. Gastrin immunoreactivity was detected in fresh human pancreatic cancer specimens but not in normal human pancreatic tissue. These data provide the first evidence that growth of a human pancreatic cancer is tonically stimulated by the autocrine production of gastrin. Evidence for the ubiquity of this system was provided by the detection of gastrin gene expression in multiple human pancreatic cancer cell lines and detection of gastrin in cell lines and fresh pancreatic tumors.
K+ balance during exercise and role of beta-adrenergic stimulation
Authors: Hallen J. , Saltin B. , Sejersted O. M.
Published: December 2017

Infusion of the beta 2-adrenoceptor agonist terbutaline will cause an activation of the Na(+)-K+ pump that leads to lowering of plasma K+ concentration and intracellular Na+ concentration. The present study examines whether these changes will affect the K+ homeostasis during subsequent exercise. Two-legged knee-extension exercise was carried out at low (40 W) and high (75 W) power for 8 min in six healthy, male subjects before (control) and during intravenous infusion of terbutaline (priming dose 500 micrograms, sustained dose 4.1 micrograms/min). Catheters in the femoral vein and artery allowed blood sampling and continuous recording of femoral venous plasma K+ concentration ([K+]fv) by means of a pliable, K(+)-sensitive electrode. Leg blood flow was measured by bolus injections of indocyanine green. Terbutaline decreased arterial K+ concentration by 0.83 mmol/l. The femoral veno-arterial concentration difference for K+ and loss rates of K+ were not significantly affected by terbutaline, but leg blood flow during steady-state exercise increased by approximately 0.5 l/min (P < 0.05). However, at cessation of exercise terbutaline significantly attenuated the rate of fall of [K+]fv at high power from 63 +/- 6 to 38 +/- 6 micromol. l-1.s-1, indicating a reduced reuptake rate of K+. The loss rate of K+ from the leg peaked after around 40 s of exercise, pointing to a rapid activation of reuptake rate of K+. We conclude that, during terbutaline infusion, the reuptake rate of K+ in exercising muscles is attenuated.
Effect of cross-reinnervation on the expression of GLUT-4 and GLUT-1 in slow and fast rat muscles
Authors: Johannsson E. , Waerhaug O. , Bonen A.
Published: December 2017

We determined whether the twitch-velocity phenotype or the metabolic phenotype of a muscle influences the content of GLUT-4 and GLUT-1 proteins. The soleus (Sol) and extensor digitorum longus (EDL) muscles were cross-reinnervated (X-Sol, X-EDL). After 3 mo the X-EDL had become enriched in slow-twitch oxidative (SO) fibers (70.5% SO) compared with its control (3.8% SO), whereas the X-Sol became enriched in fast-twitch oxidative-glycolytic (FOG) fibers (78.6% FOG) compared with its control (10% FOG). Thus the twitch phenotype of X-Sol shifted to fast-twitch muscle, whereas X-EDL shifted to a slow-twitch muscle. In the X-EDL, the oxidative nature of the X-EDL was increased to 97% oxidative fibers compared with 43% oxidative fibers in the normal EDL. In the Sol the oxidative nature of the X-Sol was retained at 100%. GLUT-4 content was increased 1.6-fold in the X-EDL (P < 0.05) but was not changed in the X-Sol (P > 0.05). GLUT-1 content was increased fourfold in X-EDL but was not altered in the X-Sol. We conclude that GLUT-4 and GLUT-1 content in muscle is related to the oxidative phenotype of the muscle rather than the twitch-velocity phenotype.
Regulation of DNA synthesis of myocardial and epicardial cells in developing rat heart by [Met5]enkephalin
Authors: McLaughlin P. J.
Published: December 2017

Endogenous opioids serve as negative growth factors in neural and nonneural tissues in addition to being neuromodulators. This study investigated the hypothesis that native opioid peptides are inhibitory growth factors in heart development. DNA synthesis of ventricular myocardial and epicardial cells in 1-day-old rats was examined. Administration of a variety of opioids and peptides revealed that [Met5]enkephalin had the greatest inhibitory effect on DNA synthesis; peptides related to mu-, delta-, kappa-, epsilon-, and sigma-receptors had no influence on cell proliferation, even at concentrations as high as 10 mg/kg. [Met5]enkephalin, also termed opioid growth factor (OGF), depressed DNA synthesis at 1 and 10 mg/kg but not at 0.01 or 0.1 mg/kg. The effects of OGF were noted within 1 h of treatment, persisted for as long as 22 h after drug administration, and could depress DNA synthesis in myocardial and epicardial cells to 43 and 36%, respectively, of control values. The effect of OGF on DNA synthesis of heart cells was opioid receptor-mediated. Organ culture experiments revealed that opioids acted directly on developing cardiac cells. Both OGF and its receptor, zeta, were detected in heart cells of 1-day-old rats by immunocytochemistry. mRNA for preproenkephalin, the precursor to OGF, was observed in 1-day-old rat heart. These results indicate that an autocrine- or paracrine-produced endogenous opioid peptide (i.e., OGF) and its receptor (i.e., zeta) are present in the developing heart and govern DNA synthesis, with OGF acting directly as a tonic negative regulator of cell generation.
Ciliary neurotrophic factor is catabolic and shares with IL-6 the capacity to induce an acute phase response
Authors: Espat N. J. , Auffenberg T. , Rosenberg J. J. , Rogy M. , Martin D. , Fang C. H. , Hasselgren P. O. , Copeland E. M. , Moldawer L. L.
Published: December 2017

Ciliary neurotrophic factor (CNTF), a member of the interleukin-6 (IL-6) superfamily, has recently been shown to induce several inflammatory responses when administered to healthy animals, including induction of fever and a hepatic acute phase protein response. In the present report, 250 micrograms.kg body wt-1.day-1 of recombinant rat CNTF or murine IL-6 were repeatedly administered to healthy mice over a 7-day period in an effort to compare biological responses. In addition to its in vivo capacity to elicit a hepatic acute phase response, administration of CNTF, but not IL-6, produced profound anorexia and lean tissue wasting in mice. In C57B1/6 mice, 7 days of CNTF administration led to a 21% loss in carcass protein content, resulting from carcass protein breakdown rates being increased 218% over freely fed controls (both P < 0.01). Protein synthesis rates in carcass protein were also increased in CNTF-treated mice compared with both freely fed animals and mice pair-fed equivalent quantities of food. In contrast, administration of equivalent quantities of murine IL-6 had no effect on food intake or body weight in mice, although IL-6 produced a similar hepatic acute phase response, as determined by increases in serum amyloid P and seromucoid fraction and increases in total hepatic protein synthesis. However, when CNTF was coincubated with extensor digitorum longus muscles from juvenile rats in vitro, rates of total muscle and myofibrillar protein degradation and muscle protein synthesis were unchanged. We conclude that CNTF can regulate in vivo both skeletal muscle remodeling as well as the distant anorexia and hepatic acute phase protein responses. In the case of skeletal muscle, these actions are both indirect and independent of the associated anorexia. These properties of CNTF are distinct from IL-6, which when administered to the mouse at these doses is neither anorexigenic nor cachexia producing.
Circadian rhythms in the human pupil and eyelid
Authors: Loving R. T. , Kripke D. F. , Glazner L. K.
Published: December 2017

The human eye was studied to investigate its use as a noninvasive marker of circadian phase state. Subjects were measured every 30 min over 24 h to observe bilateral changes in pupil size and palpebral fissure. Twelve males and twelve females (ages 18-29 yr, mean = 21.6 yr) were studied around the clock while they remained within a light-controlled facility (< 100 lux). The acrophases (maximums) for pupil diameters and palpebral fissure distances were estimated using a cosine curve-fitting technique applied to each 24-h data set. Pupil diameter acrophases occurred randomly throughout the day. The data demonstrated a significant circadian rhythm for both resting and maximum palpebral fissure values. However, palpebral fissure acrophases were widely distributed, with the largest portion of the peaks occurring between 10:00 A.M. and 10:00 P.M.. These data did not support the hypotheses that sympathetic innervation to the pineal is paralleled in the eye, and results do not demonstrate any applicability of human eye measurements as circadian markers.
Clearance receptors and endopeptidase 24.11: equal role in natriuretic peptide metabolism in conscious sheep
Authors: Charles C. J. , Espiner E. A. , Nicholls M. G. , Richards A. M. , Yandle T. G. , Protter A. , Kosoglou T.
Published: December 2017

Although many studies have examined the effects of administering natriuretic peptide receptor C (NPR-C) ligands and endopeptidase 24.11 (EP 24.11) inhibitors on clearance and bioactivity of atrial natriuretic peptide (ANP), none have systematically compared their effects on the endogenous levels of both ANP and brain natriuretic peptide (BNP) under physiological conditions. Accordingly, we examined the hemodynamic, hormonal, and renal actions of an EP 24.11 inhibitor, SCH-32615, and an NPR-C ligand, C-ANP-(4-23), both alone and in combination in eight normal conscious sheep. NPR-C blockade and EP 24.11 inhibition induce similar rises in plasma ANP, BNP, and guanosine 3',5'-cyclic monophosphate (cGMP). Synergistic increments in plasma ANP, BNP, and cGMP observed during combined administration are likely to be due to the reduced clearance of C-ANP-(4-23) in the setting of EP 24.11 inhibition, leading to increased inhibition of the receptor pathway. Combined administration was also associated with enhanced hemodynamic actions and diuretic and natriuretic effects. Our findings show that both enzymatic and receptor clearance pathways contribute equally to natriuretic peptide clearance and induce potentially important hemodynamic and renal effects in normal conscious sheep.
Dopaminergic receptors and angiotensinogen gene expression in opossum kidney cells
Authors: Wang T. T. , Lachance S. , Delalandre A. , Carriere S. , Chan J. S.
Published: December 2017

To investigate whether expression of the renal angiotensinogen gene is regulated by dopaminergic receptors, we used opossum kidney (OK 27) cells with a fusion gene containing the 5'- flanking regulatory sequence of the rat angiotensinogen gene fused with a human growth hormone (hGH) gene as a reporter [pOGH, angiotensinogen nucleotide (N) -1498/+18], permanently integrated into their genomes. The level of expression of pOGH (angiotensinogen N-1498/+18) in OK 27 was evaluated by the amount of immunoreactive hGH (ir-hGH) secreted into the culture medium. In the absence of 3-isobutyl-1-methylxanthine (IBMX), addition of dopamine (10(-13) to 10(-5)M) had minimal effect on the expression of the pOGH (angiotensinogen N-1498/+18) in OK 27 cells. In the presence of IBMX, addition of low concentrations (10(-13) and 10(-7) M) of dopamine stimulated the expression of pOGH angiotensinogen N-1498/+18) in OK 27 cells in a dose-dependent manner, whereas high concentrations (i.e., > 10(-7) M) had minimal effect. The stimulatory effect of dopamine on the expression of pOGH (angiotensinogen N-1498/+18) was inhibited by the presence of SCH-23390 (D1-dopaminergic receptor antagonist) and spiperone (D2-dopaminergic receptor antagonist), but not by ketanserin (5 HT2/5HT1c-serotonergic receptor antagonist). Moreover, the stimulatory effect of dopamine was inhibited by the presence of U-73122 (an inhibitor of phospholipase C and phospholipase A2) or staurosporine (an inhibitor of protein kinase C) or (R)-p-adenosine 3',5'-cyclic monophosphorothioate (Rp-cAMP[S]; an inhibitor of cAMP-dependent protein kinase AI and II). Addition of low concentrations (10(-13) to 10(-9)M) of SKF-82958 (D1-dopaminergic receptor agonist) or PPHT (D2-dopaminergic receptor agonist) also stimulated the expression of pOGH (angiotensinogen N-1498/+18). The stimulatory effect of SKF-82958 was inhibited by the presence of SCH-23390 or Rp-cAMP[S], whereas the effect of PPHT was inhibited by the presence of spiperone or staurosporine. These studies demonstrate that the expression of pOGH (angiotensinogen N-1498/+18) in OK 27 cells is modulated by dopaminergic receptor agonists.
Oxidative damage and antioxidants in Rana sylvatica, the freeze-tolerant wood frog
Authors: Joanisse D. R. , Storey K. B.
Published: December 2017

Freeze-tolerant wood frogs (Rana sylvatica) must endure prolonged ischemia on freezing. Reperfusion on thawing brings with it the potential or oxidative damage due to reactive oxygen species formation, a well-known consequence of mammalian ischemia-reperfusion. To determine whether oxidative damage occurs during thawing and how frogs deal with this, we examined oxidative damage and antioxidant and prooxidant systems in tissues of Rana sylvatica and a nonfreezing relative, Rana pipiens. Glutathione status indicated little oxidative stress in tissues during freezing or thawing; an increase of the glutathione pool in the oxidized form was observed during freezing only in Rana sylvatica kidney (by 85%) and brain (by 33%). Oxidative damage to tissue lipids, measured as the levels of thiobarbituric acid-reactive substances and/or by an Fe(III)-xylenol orange assay, did not increase above control values pver a freeze-thaw time course. Correlative data showing increased activities of some antioxidant enzymes during freezing, notably glutathione peroxidase (increasing 1.2- to 2.5-fold), as well as constitutively higher activities of antioxidant enzymes and higher levels of glutathione in the freeze-tolerant species compared with Rana pipiens, suggest that antioxidant defenses play a key role in amphibian freeze tolerance.
Branchial and systemic roles of adenosine receptors in rainbow trout: an in vivo microscopy study
Authors: Sundin L. , Nilsson G. E.
Published: December 2017

The purinergic branchial vasomotor control in rainbow trout (Oncorhynchus mykiss) was studied using an epi-illumination microscope equipped with a water-immersion objective. Cardiac output (Q), heart rate, and dorsal (PDA) and ventral (PVA) aortic pressures were recorded simultaneously. Prebranchial injection of adenosine or the A1-receptor agonist N6-cyclopentyl-adenosine (CPA) constricted the distal portion of the filament vasculature, which coincided with an increase of PVA. The A2-receptor agonist PD-125944 was without effect. After adenosine and CPA injection, an overflow of blood to the secondary system was repeatedly observed unless blood flow came to a complete stop. The lack of a concomitant reduction of Q suggested a redistribution of blood to the secondary system and to more proximal parts of the filament. The branchial effects of adenosine and CPA were completely blocked by the unspecific adenosine receptor antagonist amino-phylline and the specific A1-receptor antagonist N6-cyclopen-tyltheophylline. The results suggest that A1-receptors alone mediate the branchial vasoconstriction observed. Thus the responses of the branchial vasculature to adenosine include a vasoconstriction of the filament vasculature mediated via specific A1 receptors and a redistribution of blood flow to the secondary system and to proximal parts of the filament. Additional cardiovascular effects of adenosine included decreased systemic vascular resistance and heart rate.
The CNS site of glucocorticoid negative feedback during LPS- and psychological stress-induced fevers
Authors: Morrow L. E. , McClellan J. L. , Klir J. J. , Kluger M. J.
Published: December 2017

Glucocorticoids exert negative feedback in the anterior hypothalamus (AH) during lipopolysaccharide (LPS)-induced fevers, but the central location of their negative feedback during psychological stress-induced fever has not been determined. To confirm that glucocorticoid modulation of LPS fever occurs in the AH, adrenalectomized animals were injected intrahypothalamically with either 0.25 ng of corticosterone or vehicle followed by 50 micrograms/kg LPS intraperitoneally. Animals pretreated with corticosterone developed significantly smaller fevers (P = 0.007) than animals given vehicle. To determine if glucocorticoid modulation during psychological stress-induced fever may occur in the hippocampus, the fornix was transected to block hippocampal communication with the AH. This resulted in significantly larger psychological stress-induced fevers (P = 0.02) compared with sham-operated animals. There were no differences between these groups for LPS-induced fevers (P = 0.92). To determine where in the hippocampus glucocorticoids might exert their negative feedback during psychological stress, rats were microinjected with either 1 ng RU-38486 (a type II glucocorticoid receptor antagonist) or vehicle into the dentate gyrus prior to exposure to the open field. There were no differences between the psychological stress-induced fevers of the RU-38486- and vehicle-injected groups, supporting the hypothesis that these fevers are modulated elsewhere in the hippocampus. Our data support the hypothesis that glucocorticoids modulate LPS-induced fever in the AH and do not involve the hippocampus, and that psychological stress-induced fevers are modulated by neural connections between the hippocampus and the hypothalamus. The precise sites of action of glucocorticoid negative feedback on stress-induced fevers in the hippocampus (or other brain regions) are not yet known.
Gastric volume rather than nutrient content inhibits food intake
Authors: Phillips R. J. , Powley T. L.
Published: December 2017

To evaluate the separate contributions of distension and nutrient stimulation of the stomach to the inhibition of short-term food intake and, particularly, to reassess previous analyses based on the inflatable gastrointestinal cuff, four experiments were performed. Rats equipped with pyloric cuffs and indwelling gastric catheters consumed a liquid diet ad libitum. Their consumption during short-term (30 min) feeding bout was measured after gastric infusions on cuff-open and cuff-closed trials. Animals taking meals (approximately 5 ml) with cuffs closed immediately after receiving intragastric infusions of 2.5, 5, 7.5, or 10 ml of normal saline exhibited both suppression at the smallest infusion and a dose-dependent reduction across the other volumes (experiment 1). Additionally, when the test diet concentration was varied, animals with their cuffs closed consumed a constant volume, not a constant number of calories (experiment 2). Furthermore, cuff-closed animals exhibited no more suppression to 5-ml intragastric infusions of nutrients (including, on different trials, 50 and 100% Isocal diet; 10, 20, and 40% glucose; and 40% sucrose and 40% fructose) than to the same volume of saline (experiments 3 and 4). In contrast, on cuff-open trials in which gastric contents could empty into the duodenum, these same nutrient loads were more effective (except fructose) than saline in producing suppression of food intake. In summary, although both limited gastric distension with the pylorus occluded and intestinal nutrient stimulation with the cuff open effectively reduced intake, cuff-closed gastric loads of mixed macronutrients or carbohydrate solutions of 2-8 kcal, pH from 5.8 to 6.7, and osmolarities between 117 and 2,294 mosM/kg produced only the distension-based suppression generated by the same volume of saline.
Convergent carotid sinus nerve and superior laryngeal nerve afferent inputs to neurons in the NTS
Authors: Mifflin S. W.
Published: December 2017

A population of 43 neurons in the nucleus of the solitary tract (NTS) was identified in pentobarbital sodium anesthetized, paralyzed, and artificially ventilated cats that received convergent inputs from carotid sinus nerve (CSN) and superior laryngeal nerve (SLN) afferents. In 21 neurons, electrical stimulation of the CSN and SLN each evoked an excitatory postsynaptic potential (EPSP; mean onset latency +/- SE of CSN-evoked input = 7.2 +/- 0.8 ms, range 2.1-14.1 ms; of SLN-evoked input = 10.3 +/- 2.1 ms, range 2.8-46.8 ms). In 22 neurons, electrical stimulation of either the CSN or SLN evoked an EPSP/ inhibitory postsynaptic potential (IPSP) sequence (CSN-evoked input = 6.7 +/- 0.6 ms, range 2.1-12.2 ms; SLN-evoked input = 8.4 +/- 0.8 ms, range 3.0-19.4 ms). Spatial interactions (facilitation, summation, occlusion) and time-dependent inhibitory interactions were observed between the convergent inputs. Natural stimulation of specific receptors indicated that 14 cells received a convergent excitatory input from carotid sinus baroreceptors and laryngeal mechanoreceptors, 10 received a convergent excitatory input from carotid body chemoreceptors and laryngeal mechanoreceptors, and 5 received a convergent excitatory input from baroreceptors, chemoreceptors, and laryngeal mechanoreceptors. The interactions and various patterns of convergence suggest a significant integration of convergent inputs from disparate afferent sources by these neurons.
AT1 and TxA2/PGH2 receptors maintain hypertension throughout 2K,1C Goldblatt hypertension in the rat
Authors: Wilcox C. S. , Cardozo J. , Welch W. J.
Published: December 2017

Angiotension II (ANG II) increases the generation of vasoconstrictor prostaglandin endoperoxides (PGH2) and thromboxane A2 (TxA2). Two-kidney, one-clip (2K,1C) Goldblatt hypertensive rats have an increased plasma renin activity (PRA) and ANG II level during the early, but not the late, phases of hypertension. Therefore, the aim of these studies was to compare the antihypertensive efficacy of an ANG II type I (AT1) and a TxA2/PGH2 receptor antagonist during different phases of 2K,1C hypertension. Rats were maintained on a fixed sodium intake for 3 days before and throughout the period of drug administration. These studies assessed the antihypertensive response to administration of the AT1 receptor antagonist losartan (20 mg.kg-1.day-1), the TxA2/PGH2 receptor antagonist ifetroban (20 mg.kg-1.day-1) or vehicle given for 3 days to rats with early (2-4 wk postclip), intermediate (10-12 wk postclip), and late (36-42 wk post-clip) 2K,1C hypertension and to two control groups of rats corresponding in age to the early or intermediate and the late 2K,1C groups. The mean arterial pressure (MAP) was measured directly with indwelling arterial cannulas. The MAP of sham-operated rats was 109 +/- 5 mmHg. In the early phase of 2K,1C hypertension, the MAP was increased to 143 +/- 6 mmHg, and it was increased further to 162 +/- 5 mmHg during the intermediate and to 179 +/- 4 mmHg during the late phase. The PRA, compared with age-matched controls, was increased during early and intermediate, but not late phase 2K,1C hypertension. Neither drug lowered blood pressure in control rats. However, both drugs significantly reduced the blood pressure in the early, intermediate, and late phases of 2K, 1C hypertension. At the end of 3 days of administration, blood pressure in early 2K, 1C rats given losartan was reduced to levels of control rats, but remained slightly elevated in other groups and in those receiving ifetroban. In conclusion, AT1 and TxA2/PGH2 receptors maintain hypertension throughout the evolution of 2K, 1C hypertension in the rat, despite changes in PRA.
Adenosine causes cAMP-dependent activation of chick embryo red cell carbonic anhydrase and 2,3-DPG synthesis
Authors: Glombitza S. , Dragon S. , Berghammer M. , Pannermayr M. , Baumann R.
Published: December 2017

In late chick embryos, coordinate activation of red cell carbonic anhydrase II (CAII) and 2,3-diphosphoglycerate (2,3-DPG) synthesis is initiated by hypoxia. The effects are mediated by unidentified hormonal effectors resident in chick plasma. In the present investigation, we have analyzed the effect of adenosine receptor stimulation on embryonic red cell CAII and 2,3-DPG synthesis. We find that primitive and definitive embryonic red blood cells from chick have an A2a adenosine receptor. Stimulation of the receptor with metabolically stable adenosine analogues causes a large increase of red cell adenosine 3',5'-cyclic monophosphate (cAMP) and subsequent activation of red cell CAII and 2,3-DPG production in definitive red blood cells and of CAII synthesis in primitive red blood cells. Direct stimulation of adenylyl cyclase with forskolin has the same effect. Analysis of red cell protein pattern after labeling with [35S]methionine shows that stimulation of red cell cAMP levels activates synthesis of several other proteins aside from CAII. Presence of actinomycin D inhibits cAMP-dependent changes of protein synthesis, indicating that cAMP-dependent transcriptional activation is required. In contrast to the stable adenosine receptor analogues, adenosine itself was a very weak agonist, unless its metabolism was significantly inhibited. Thus, besides adenosine, other effectors of the adenylyl cyclase system are likely to be involved in the O2 pressure-dependent regulation of red cell metabolism in late development of avian embryos.
Hyperinsulinemia in rats with obesity-inducing amygdaloid lesions
Authors: King B. M. , Cook J. T. , Dallman M. F.
Published: December 2017

Electrolytic lesions of the posterodorsal aspects of the medial division of the extended amygdala in female rats result in hyperphagia and excessive weight gain. In the present study, the effects of such lesions on plasma insulin, glucose, corticosterone, and adrenocorticotropic hormone were assessed during a period of food restriction and again after a 15-day period of food ad libitum. Compared with control animals, the rats with amygdaloid lesions were hyperinsulinemic under both conditions and gained substantially more weight when fed ad libitum. No difference between groups was observed for the other hormones. It is concluded that damage to the posterodorsal aspects of the medial amygdala results in a primary metabolic dysfunction that accounts, at least in part, for the overeating and excessive weight gain.
Signal transduction, second messenger, and protein kinase responses during freezing exposures in wood frogs
Authors: Holden C. P. , Storey K. B.
Published: December 2017

Changes in the percentage of adenosine 3', 5'-cyclic monophosphate (cAMP)-dependent protein kinase present as the active catalytic subunit (PKAc) and in the levels of the second messengers cAMP, guanosine 3',5'-cyclic monophosphate (cGMP), and D-myo-inositol 1,4,5-trisphosphate (IP3) were quantified in tissues of the freeze-tolerant wood frog Rana sylvatica over the course of freezing at -2.5 degrees C and thawing at 5 degrees C. Freezing exposure rapidly raised liver cAMP concentration and %PKAc (by 2- and 6-fold, respectively) within 2 min postnucleation; both peaked and stabilized between 5 and 60 min postnucleation but declined with longer freezing. Other organs also showed elevated PKAc during freezing, particularly skeletal muscle. By contrast, cGMP concentration was reduced in muscle and kidney after 24 h of freezing but rose after thawing in muscle. Liver also showed a twofold elevation of cGMP during thawing. The protein kinase C (PKC) second messenger, IP3, rose throughout freezing in liver, reaching levels 11-fold higher than control values after 24 h of freezing. IP3 was also elevated in brain after 4 and 8 h of freezing. The different patterns of cAMP, protein kinase A (PKA), and IP3 changes in liver suggest that, whereas cAMP and PKA clearly mediate the rapid activation of glucose output as a cryoprotectant, IP3 and PKC may be involved instead with metabolic responses that deal with the consequences of long-term freezing, such as ischemia resistance or cell volume control.
Sensitization of the colonic response to novel stress after previous stressful experience
Authors: Stam R. , Croiset G. , Akkermans L. M. , Wiegant V. M.
Published: December 2017

Stressful life events may be important causative or precipitating factors for functional gastrointestinal disorders such as the irritable bowel syndrome in humans. In the rat, a single session of foot shocks is known to sensitize the behavioral and hormonal responses to subsequent stress, but intestinal responses have not been investigated. Rats were fitted with bipolar electrodes on proximal colon and exposed to a single session of foot shocks (10 x 6 s in 15 min; preshocked) or no shocks (control). Weight gain after foot shocks was identical to that in controls. Two weeks after foot shocks, basal colonic spike burst frequency did not differ from controls or from that recorded before shock treatment. Unlike controls, however, preshocked rats showed a significant increase in colonic spike burst frequency to a novel stressful challenge in the home cage, an electrified prod. Because the behavioral responses to this challenge did not differ, colonic hyperresponsiveness in preshocked rats may represent a form of stress-induced autonomic sensitization. The model should be a useful tool to study mechanisms and pharmacotherapeutic approaches of the gastrointestinal consequences of traumatic stress.
Metabolic and energy correlates of intracellular pH in progressive fatigue of squid (L. brevis) mantle muscle
Authors: Portner H. O. , Finke E. , Lee P. G.
Published: December 2017

Squid (Lolliguncula brevis) were exercised at increasing swimming speeds to allow us to analyze the correlated changes in intracellular metabolic, acid-base, and energy status of the mantle musculature. Beyond a critical swimming velocity of 1.5 mantle lengths/s, an intracellular acidosis developed that was caused by an initial base loss from the cells, the onset of respiratory acidification, and, predominantly, octopine formation. The acidosis was correlated with decreasing levels of phospho-L-arginine and, thus, supported ATP buffering at the expense of the phosphagen. Monohydrogenphosphate, the actual substrate of glycogen phosphorylase accumulated, enabling glycogen degradation, despite progressive acidosis. In addition to octopine, succinate, and glycerophosphate accumulation, the onset of acidosis characterizes the critical velocity and indicates the transition to a non-steady-state time-limited situation. Accordingly, swimming above the critical velocity caused cellular energy levels (in vivo Gibbs free energy change of ATP hydrolysis) to fall. A minimal value was reached at about -45 kJ/mol. Model calculations demonstrate that changes in free Mg2+ levels only minimally affect ATP free energy, but minimum levels are relevant in maintaining functional concentrations of Mg(2+)-complexed adenylates. Model calculations also reveal that phosphagen breakdown enabled L. brevis to reach swimming speeds about three times higher than the critical velocity. Comparison of two offshore squid species (Loligo pealei and Illex illecebrosus) with the estuarine squid L.brevis indicates that the latter uses a strategy to delay the exploitation of high-energy phosphates and protect energy levels at higher than the minimum levels (-42 kJ/mol) characterizing fatigue in the other species. A more economical use of anaerobic resources and an early reduction in performance may enable L. brevis to tolerate more extreme environmental conditions in shallow estuarine waters and even hypoxic environments and to prevent a fatal depletion of energy stores.
Forebrain angiotensin type 1 receptors and parabrachial serotonin in the control of NaCl and water intake
Authors: Colombari D. S. , Menani J. V. , Johnson A. K.
Published: December 2017

This study investigated the roles of serotonin (5-HT) receptors in the lateral parabrachial nucleus (LPBN) and brain angiotensin type 1 (AT1) receptors in the intake of 0.3 M NaCl and water induced by angiotensin II (ANG II). Rats were implanted with stainless steel cannulas for injections into the subfornical organ (SFO) and into the LPBN. Bilateral LPBN pretreatment with the nonselective serotonergic 5-HT1/5-HT2 receptor antagonist methysergide (4 micrograms/200 nl) markedly enhanced 0.3 M NaCl intake induced by injections of ANG II (20 ng/200 nl) into the SFO. Pretreatment of the SFO with the AT1 receptor antagonist losartan (1 microgram/200 nl) blocked the intake of 0.3 M NaCl induced by ANG II in combination with LPBN methysergide injections. These results suggest that serotonergic mechanisms associated with the LPBN inhibit the expression of salt appetite induced by ANG II injections into the SFO. In addition, the results indicate that the enhanced NaCl intake generated by central administration of ANG II in the presence of LPBN 5-HT blockade is mediated by brain AT1 receptors.
Aging affects development and persistence of feeding-associated circadian rhythm in rat plasma corticosterone
Authors: Honma S. , Katsuno Y. , Abe H. , Honma K.
Published: December 2017

Effects of aging on development and persistence of feeding-associated circadian rhythm were examined with respect to the prefeeding plasma corticosterone peak under restricted feeding. Old (20 mo), middle-aged (12 mo), and young (2.5 mo) male rats were subjected to a restricted feeding schedule for 21 days in which free access to food was limited to 2 h/day in the light phase. Prefeeding corticosterone peak was detected 1 wk after the start of the schedule in the young and 3 wk after in the old and middle-aged rats. After the restricted feeding, a feeding/ fasting cycle composed of 7 days of ad libitum feeding and 3 days of fasting was imposed four times. The persistence of feeding-associated rhythm was evaluated by examining the reappearance of the corticosterone peak at the previous meal time during each fasting period of the feeding/fasting cycle. The corticosterone peak was not detected in the old and middle-aged rats even at the first cycle, but it was still distinct at the third cycle in the young rats. In conclusion, aging impaired the development and persistence of feeding-associated circadian rhythm in rats.