bluuebunny/crossref_metadata_2025 huggingface dataset:
Divergence in proportional fat intake in AKR/J and SWR/J mice endures across diet paradigms
Authors: Smith Brenda K. , Andrews P. Kyle , York David A. , West David B.
Published: December 2017

These experiments were designed to test the hypothesis that the contrasting patterns of macronutrient selection described previously in AKR/J (fat preference) and SWR/J (carbohydrate preference) mice are not dependent on a single diet paradigm. The effect of mouse strain on proportional fat intake was tested in naive mice by presenting two-choice diets possessing a variety of physical, sensory, and nutritive properties. In three separate experiments, AKR/J mice preferentially selected and consumed a higher proportion of energy from the high-fat diet than SWR/J mice. Specifically, this phenotypic difference was observed with 1) fat-protein vs. carbohydrate-protein diets, independent of fat type (vegetable shortening or lard), 2) isocaloric, high- vs. low-fat liquid diet preparations, and 3) high- vs. low-fat powdered-granular diets. These results confirm our previous observation of a higher proportional fat intake by AKR/J compared with SWR/J mice using the three-choice macronutrient selection diet and show that this strain difference generalizes across several diet paradigms. This strain difference is due largely to the robust and reliable fat preference of the AKR/J mice. In contrast, macronutrient preference in SWR/J mice varied across paradigms, suggesting a differential response by this strain to some orosensory or postingestive factor(s).
Effect of capsaicin on the micturition reflex in normal and chronic spinal cord-injured cats
Authors: Cheng Chen-Li , Liu Jiang-Chuan , Chang Sun-Yran , Ma Cheng-Ping , de Groat William C.
Published: December 2017

The effect of capsaicin (10–80 mg/kg sc) on reflex activity of the urinary bladder was examined in anesthetized normal as well as anesthetized and awake chronic spinal cord-injured (SCI) cats. In normal cats, capsaicin elicited a transient increase in the frequency of isovolumetric bladder contractions and reduced the volume threshold for inducing micturition, but did not depress the amplitude of bladder contractions or the reflex firing on bladder nerves. In anesthetized SCI cats, capsaicin depressed reflex bladder activity and firing on bladder nerves. In awake SCI cats, capsaicin initially decreased the volume threshold for inducing micturition; however, after a delay of 3–6 h the volume threshold increased and intravesical voiding pressure decreased. This effect persisted for 4–12 days. It is concluded that capsaicin-sensitive C fiber bladder afferents are not involved in initiating reflex micturition in normal cats, but play an essential role in triggering automatic micturition in chronic SCI cats. The results are consistent with the clinical data indicating that C fiber bladder afferents contribute to bladder hyperactivity and incontinence in patients with neurogenic bladder dysfunction.
Organization of rat circadian rhythms during daily infusion of melatonin or S20098, a melatonin agonist
Authors: Pitrosky B. , Kirsch R. , Malan A. , Mocaer E. , Pevet P.
Published: December 2017

Daily administration of melatonin or S20098, a melatonin agonist, is known to entrain the free-running circadian rhythms of rats. The effects of the duration of administration on entrainment were studied. The animals demonstrated free-running circadian rhythms (running-wheel activity, body temperature, general activity) in constant darkness. Daily infusions of melatonin or S20098 for 1, 8, or 16 h entrained the circadian rhythms to 24 h. Two daily infusions of 1 h (separated by 8 h) entrained the activity peak within the shorter time interval. The entraining properties of melatonin and S20098 were similar and were affected neither by pinealectomy nor by infusion of 1- or 8-h duration. However, with 16-h infusion, less than half of the animals became entrained. Once entrained, the phase angle between the onset of infusion and the rhythms (onset of activity or acrophase of body temperature) increased with the duration of infusion. Before entrainment, the free-running period increased with the duration of infusion, an effect that was not predictable from the phase response curve.
Use of recombinant human soluble TNF receptor in anorectic tumor-bearing rats
Authors: Torelli Giovanni F. , Meguid Michael M. , Moldawer Lyle L. , Edwards Carl K. , Kim Hyune-Ju , Carter Janna L. , Laviano Alessandro , Fanelli Filippo Rossi
Published: December 2017

With progression of tumor growth, rats demonstrate anorexia and reduced food intake, a function of meal number and meal size. Tumor necrosis factor-α (TNF-α), a recognized anorectic agent, reacts with two different receptors (type I: 55 kDa; type II: 75 kDa). We used a dimeric, pegylated 55-kDa TNF receptor construct to test its effects on food intake, meal number, and meal size, which were continuously measured with a rat eater meter in 16 Fischer 344 male rats injected with 106 viable methylcholanthrene cells. When anorexia developed, rats received a subcutaneous injection of either 0.25 mg/kg body wt of soluble TNF receptor construct (study) or vehicle (tumor-bearing control). Before TNF inhibitor injection, no differences were observed in food intake, meal number, or meal size between the two groups. After the TNF inhibitor injection, study vs. control rats significantly improved food intake as a result of an increase in meal number and meal size. Rats also showed a significant improvement in body weight. These data suggest that TNF-α, in addition to other cytokines, contributes to the anorexia of tumor growth, probably mediated via the hypothalamus.
Acute reduction in whole cell conductance in anoxic turtle brain
Authors: Ghai H. S. , Buck L. T.
Published: December 2017

We tested the effect of anoxia, a “mimic” turtle artificial cerebrospinal fluid (aCSF) consisting of high Ca2+and Mg2+concentrations and low pH and adenosine perfusions, on whole cell conductance ( Gw) in turtle brain slices using a whole cell voltage-clamp technique. With EGTA in the recording electrode, anoxic or adenosine perfusions did not change Gwsignificantly (values range between 2.15 ± 0.24 and 3.24 ± 0.56 nS). However, perfusion with normoxic or anoxic mimic aCSF significantly decreased Gw. High [Ca2+] (4.0 or 7.8 mM) perfusions alone could reproduce the changes in Gwfound with the mimic perfusions. With the removal of EGTA from the recording electrode, Gwdecreased significantly during both anoxic and adenosine perfusions. The A1-receptor agonist N6-cyclopentyladenosine reduced Gwin a dose-dependent manner, whereas the A1-receptor specific antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked both the adenosine- and anoxic-mediated changes in Gw. These data suggest a mechanism involving A1-receptor-mediated changes in intracellular [Ca2+] that result in acute changes in Gwwith the onset of anoxia.
GLP-1 slows solid gastric emptying and inhibits insulin, glucagon, and PYY release in humans
Authors: Näslund Erik , Bogefors Jesper , Skogar Staffan , Grybäck Per , Jacobsson Hans , Holst Jens Juul , Hellström Per M.
Published: December 2017

The aim of the present study was to assess the effect of glucagon-like peptide-1 (GLP-1) on solid gastric emptying and the subsequent release of pancreatic and intestinal hormones. In eight men [age 33.6 ± 2.5 yr, body mass index 24.1 ± 0.9 (means ± SE)], scintigraphic solid gastric emptying during infusion of GLP-1 (0.75 pmol ⋅ kg−1 ⋅ min−1) or saline was studied for 180 min. Concomitantly, plasma concentrations of C- and N-terminal GLP-1, glucose, insulin, C-peptide, glucagon, and peptide YY (PYY) were assessed. Infusion of GLP-1 resulted in a profound inhibition of both the lag phase (GLP-1: 91.5, range 73.3–103.6 min vs. saline: 19.5, range 10.2–43.4 min) and emptying rate (GLP-1: 0.34, range 0.06–0.56 %/min vs. saline: 0.84, range 0.54–1.33 %/min; P< 0.01 for both) of solid gastric emptying. Concentrations of both intact and total GLP-1 were elevated to supraphysiological levels. Plasma glucose and glucagon concentrations were below baseline during infusion of GLP-1 in contrast to saline infusion, where concentrations were elevated above baseline (both P< 0.001). The insulin and C-peptide responses were lower during infusion with GLP-1 than with saline ( P < 0.004 and P < 0.001, respectively). Plasma PYY concentrations decreased below baseline during GLP-1 infusion in contrast to saline, where concentrations were elevated above baseline ( P = 0.04). Infusion of GLP-1 inhibits solid gastric emptying with secondary effects on the release of insulin, C-peptide, and glucagon, resulting in lower plasma glucose concentrations. In addition, the release of PYY into the circulation is inhibited by GLP-1 infusion, suggesting a negative feedback of GLP-1 on the function of the L-cell.
Anesthetics can alter subsequent in vitro assessment of contractility in slow and fast skeletal muscles of rat
Authors: Lapointe Benoît M. , Côté Claude H.
Published: December 2017

Anesthetic agents can interfere with measurement of skeletal muscle contractility in vivo or in situ. Data obtained in vitro are however believed to be unaffected by such drugs. Our objective was to compare in vitro contractile measurements of fast- and slow-twitch muscles dissected from rats anesthetized with pentobarbital sodium (PS, 50 mg/kg ip) or with a mixture of ketamine and xylazine (KX, 87.5:12.5 mg/kg ip). The soleus (Sol) and extensor digitorum longus (EDL) muscles were precisely dissected 10 and 20 min after induction of anesthesia and equilibrated for 20 min in vitro before measuring contractile properties. All data obtained from PS rats were comparable with published values obtained under similar conditions. In EDL, maximum tetanic tension (Po) in KX rats was significantly decreased at both times compared with that in PS muscles. In the Sol, only the muscles exposed for 20 min to KX showed a decreased Po. These results clearly emphasize the need for investigators assessing skeletal muscle contractility in vitro to take into account the type of anesthetics used and the time of in vivo exposition to the drug.
Activation of antilipolytic α2-adrenergic receptors by epinephrine during exercise in human adipose tissue
Authors: Stich Vladimir , de Glisezinski Isabelle , Crampes Francois , Suljkovicova Hana , Galitzky Jean , Riviere Daniel , Hejnova Jindra , Lafontan Max , Berlan Michel
Published: December 2017

The involvement of the antilipolytic α2-adrenergic pathway and the specific role of epinephrine in the control of lipolysis during exercise in adipose tissue (AT) were investigated in healthy male subjects (age: 24.1 ± 2.2 yr; body mass index: 23.0 ± 1.6). An in vitro study carried out on isolated adipocytes showed that the weak lipolytic effect of epinephrine was potentiated after blockade of α2-adrenergic receptor (AR) by an α2-AR antagonist and reached that of isoproterenol, a β-AR agonist. The effect of the nonselective α2-AR antagonist phentolamine on the response of the extracellular glycerol concentration (EGC) in AT during two successive bouts of aerobic exercise (50% maximum O2uptake, 60 min duration) was evaluated using the microdialysis method. The metabolic responses measured in perfused probes with Ringer solution were compared with those obtained in perfused probes with Ringer plus 0.1 mmol/l phentolamine. Plasma norepinephrine level was not different during the two exercise bouts, whereas that of epinephrine was 2.5-fold higher during the second exercise. EGC in AT was twofold higher in the second compared with the first exercise, and the same response pattern was found for plasma glycerol. The exercise-induced increase in EGC was higher in the probe perfused with phentolamine compared with the control probe in both bouts of exercise. However, the potentiating effect of phentolamine on EGC was significant during the second exercise bout but did not reach a significant level during the first. These results suggest that epinephrine is involved in the control of lipid mobilization through activation of antilipolytic α2-AR in human subcutaneous AT during exercise.
Enantioselectivity of odor perception in squirrel monkeys and humans
Authors: Laska Matthias , Liesen Anne , Teubner Peter
Published: December 2017

With use of a conditioning paradigm, the ability of six squirrel monkeys to distinguish between 10 pairs of enantiomers, i.e., odorants that are identical except for chirality, was investigated. As a group, the animals were only able to discriminate between the optical isomers of α-pinene, carvone, limonene, and fenchone, whereas they failed to distinguish between the (+) and (−) forms of β-citronellol, menthol, rose oxide, 2-butanol, α-terpineol, and camphor. With use of a triple forced-choice procedure, 10 human subjects were tested for their ability to discriminate between the same enantiomeric odor pairs in parallel and, with the exception of fenchone, showed a very similar pattern of performance compared with the squirrel monkeys. These findings support the assumption that human and nonhuman primates may share common principles of odor quality perception. Furthermore, the results suggest that, in both species, enantioselective molecular odor receptors may only exist for some, but not all volatile enantiomers and thus that chiral recognition of odorants is not a general phenomenon, but may be restricted to some substances.
Effect of hepatic glucose infusion on glucose intake and licking microstructure in deprived and nondeprived rats
Authors: Baird John-Paul , Grill Harvey J. , Kaplan Joel M.
Published: December 2017

The effects of hepatic-portal glucose or saline infusions on intake and the temporal distribution of licking (lick microstructure) were evaluated in nondeprived and in 20.5-h food-deprived rats. Rats received portal infusions of isotonic glucose or saline (0.1 ml/min) for 2 h before and then throughout a 90-min period of access to a spout that delivered 12.5% glucose. Overall, a significant treatment-related intake suppression was obtained in nondeprived but not in deprived groups. For both groups, however, there was a significant positive linear relationship between the amount individual rats consumed under the saline (baseline) infusion condition and the extent to which portal glucose infusion suppressed intake. The linear fit for the deprived group was similar in slope, but right shifted, relative to the best fit for the nondeprived group. The individual-subject and group differences in response to portal glucose infusion are discussed in relation to the inconsistent literature on this treatment’s short-term intake effects. We focused analysis of the licking pattern on those rats for which a prominent portal glucose infusion effect was obtained (i.e., nondeprived rats with higher than average baseline intakes). Features of the lick pattern associated with taste evaluation (1st min lick rate; lick burst duration) were not significantly affected by portal glucose infusion. Rather, the minute-by-minute rate of ingestion under glucose infusion declined more rapidly than under baseline tests, indicating that portal glucose infusion enhanced the inhibitory influence of the accumulating postingestive load.
Emergence of altered circadian timing in a cholinergically supersensitive rat line
Authors: Ferguson Sally A. , Kennaway David J.
Published: December 2017

Mammalian circadian rhythms are controlled by the suprachiasmatic nuclei (SCN) in concert with light information. Several neurotransmitters and neural pathways modulate light effects on SCN timing. This study used a line of rat with an upregulated cholinergic system to investigate the role of acetylcholine in rhythmicity. With the use of a selective breeding program based on the thermic response to a cholinergic agonist, we developed a supersensitive (Sox) and subsensitive (Rox) rat line. The Sox rats showed an earlier onset time of melatonin rhythm under a 12:12-h light-dark photoperiod from generation 3 (3 ± 0.5 h after dark) compared with Rox rats (4.5 ± 0.1 h) and an earlier morning decline in temperature (0.9 ± 0.3 h before lights on) compared with Rox animals (0.1 ± 0.1 h). Furthermore, the Soxanimals displayed a significantly shorter free-running period of temperature rhythm than Rox rats (23.9 ± 0.04 and 24.3 ± 0.1 h, respectively, P < 0.05). The results suggest that the altered circadian timing of the Sox rats may be related to the cholinergic supersensitivity, intimating a role for acetylcholine in the circadian timing system.
Optical imaging of the ventral medullary surface across sleep-wake states
Authors: Richard C. A. , Rector D. M. , Harper R. K. , Harper R. M.
Published: December 2017

We hypothesized that spontaneous activity declines over widespread areas of the cat ventral medullary surface (VMS) during rapid eye movement (REM) sleep. We assessed neural and hemodynamic activity, measured as changes in reflected 660- and 560-nm wavelength light, from the VMS during sleep and waking states in five adult, unrestrained cats and in two control cats. Relative to quiet sleep, overall activity declined, and variability, assessed by standard deviation, increased by 25% during REM sleep. Variability in activity during waking also increased by 45% over quiet sleep, but mean activity was unchanged. REM sleep onset was preceded by a reduction in the hemodynamic signal from 5 to 60 s before neural activity decline. The activity decline during REM sleep, previously noted in the goat rostral VMS, extends to intermediate VMS areas of the cat and differs from most neural sites, such as the cortex, hippocampus, and thalamus, which increase activity during REM sleep. The activity decline during REM sleep has the potential to modify VMS responsiveness to baroreceptor and chemoreceptor challenges during the REM state.
Pressure and volume overloads are associated with ventricular hypertrophy in male rainbow trout
Authors: Clark Raymond J. , Rodnick Kenneth J.
Published: December 2017

We investigated whether ventricular hypertrophy in reproductively mature male trout ( Oncorhynchus mykiss) is associated with elevated hemodynamic loads. We measured ventral aortic blood pressure, pulse pressure dynamics, and blood volume in cannulated, unanesthetized trout with a wide range of relative ventricle masses (RVM, 0.076–0.199% of body wt). We also investigated in vitro pressure-volume dynamics in the bulbus arteriosus taken from trout with a wide range of RVMs. RVM was positively correlated with peak systolic pressure (SBP), mean blood pressure, and pulse pressure. Diastolic pressure and the absolute duration of arterial systole were similar among all animals, but a lower heart rate and a smaller relative duration of arterial systole were correlated with increasing RVM. Blood volume was expanded up to 34% as ventricles enlarged, and clearance of Evans blue dye was greater at higher SBP. Mass, maximal volume, and the pressure-volume dynamics of the bulbus were similar among all animals, suggesting that the bulbus did not compensate for ventricular enlargement. This conclusion was supported by the elevated maximal rates of arterial pressure development (+d P/d t) and decay (−d P/d t) observed as RVM increased. We conclude that 1) mature trout are hypertensive and hypervolemic, 2) the dynamics of the bulbus may contribute to increased afterload, and 3) these changes in hemodynamic load may promote ventricular hypertrophy.
Leptin inhibits insulin secretion induced by cellular cAMP in a pancreatic B cell line (INS-1 cells)
Authors: Ahrén Bo , Havel Peter J.
Published: December 2017

The effect of leptin on insulin secretion is controversial due to conflicting results in the literature. In the present study, we incubated insulin-producing rat insulinoma INS-1 cells for 60 min and examined the effects of recombinant murine leptin (20 nmol/l). We found that leptin (0.1–100 nmol/l) did not affect the insulin response to glucose (1–20 mmol/l). However, when cells were incubated with agents that increase the intracellular content of cAMP, i.e., glucagon-like peptide-1 (100 nmol/l), pituitary adenylate cyclase activating polypeptide (100 nmol/l), forskolin (2.5 μmol/l), dibutyryl-cAMP (1 mmol/l), or 3-isobutyl-1-methylxanthine (100 μmol/l), leptin significantly reduced insulin secretion (by 34–58%, P < 0.05–0.001). In contrast, when insulin secretion was stimulated by the cholinergic agonist carbachol (100 μmol/l) or the phorbol ester 12- O-tetradecanoylphorbol 13-acetate (1 μmol/l), both of which activate protein kinase C, leptin was without effect. We conclude that leptin inhibits insulin secretion from INS-1 cells under conditions in which intracellular cAMP is increased. This suggests that the cAMP-protein kinase A signal transduction pathway is a target for leptin to inhibit insulin secretion in insulin-producing cells.
Cardiovascular and renal responses produced by central orphanin FQ/nociceptin occur independent of renal nerves
Authors: Kapusta Daniel R. , Kenigs Velga A.
Published: December 2017

The present study investigated the role of the renal nerves in mediating the cardiovascular and renal responses produced by the central administration of the opioid-like peptide orphanin FQ/nociceptin (OFQ/N) in conscious Sprague-Dawley rats. In conscious rats, OFQ/N (10 μg icv) produced a transient bradycardia and hypotension (nadir 20 min). Although renal sympathetic nerve activity (RSNA) initially remained unchanged, a delayed renal sympathoinhibitory response occurred after recovery (30 min) of blood pressure. By 30 and 70 min postinjection, RSNA decreased to 75 and 66% of control, respectively. Coinciding with the decrease in RSNA, central OFQ/N elicited a diuresis and antinatriuresis that occurred independent of changes in renal hemodynamics. In other studies, intracerebroventricular OFQ/N produced similar cardiovascular and renal excretory responses in bilaterally renal-denervated rats. Finally, in conscious sinoaortic deafferentiated rats, intracerebroventricular OFQ/N produced a rapid decrease in RSNA (55% of control, 10 min; 38% of control, 20 min) that paralleled the onset of the hypotension and bradycardia. These studies demonstrate that in conscious rats, intracerebroventricular OFQ/N produces a centrally mediated inhibition of RSNA which, due to activation of baroreflex mechanisms, is temporally dissociated from the hypotensive and bradycardia responses. As revealed in renal-denervated rats, the cardiovascular and renal excretory responses produced by central OFQ/N occur by a pathway that is independent of intact renal nerves or changes in renal hemodynamics.
Possible role of aldosterone and T3in development of amiloride-blockable SCC across frog skin in vivo
Authors: Takada Makoto , Shiibashi Michio , Kasai Miyoko
Published: December 2017

There are inconsistencies between the in vitro and in vivo effects of thyroid hormone and aldosterone (Aldo) on the development of an amiloride-blockable short-circuit current (SCC) across bullfrog skin [Takada, M., H. Yai, and K. Takayama-Arita. Am. J. Physiol. 268 ( Cell Physiol. 37): C218–C226, 1995]. To address this issue, tadpoles were raised in Aldo + T3. An amiloride-blockable SCC developed across the skin before forelimbs appeared. Noise analysis of the characteristics (single-channel current, blocking and unblocking rate coefficients, and apparent dissociation constant) of this amiloride-blockable Na+channel showed that it really was of the adult type. A similar SCC developed at stage XIX in the skin of tadpoles raised with Aldo alone. These results strongly support our hypothesis that the crucial hormone in the development of this SCC is Aldo but that a suppression mechanism attenuates its effect on SCC development until it is removed by the increase in the serum concentration of thyroid hormone (which starts at stages XVIII–XIX in vivo).
Total body catecholamine kinetics before and after birth in spontaneously hypoxemic fetal lambs
Authors: Smolich Joseph J. , Esler Murray D.
Published: December 2017

To study the effect of fetal hypoxemia on perinatal norepinephrine and epinephrine total body kinetics, 13 near-term fetal lambs were instrumented with vascular catheters under general anesthesia. One week later, norepinephrine and epinephrine kinetics were measured in normoxemic ( n = 7) or spontaneously hypoxemic fetuses ( n = 6) with isotope dilution methodology. Hypoxemic fetuses had lower body ( P < 0.02) and placental ( P = 0.01) weights and a threefold elevation in plasma norepinephrine ( P< 0.005) and epinephrine ( P < 0.025) associated with correspondingly higher total body norepinephrine ( P < 0.005) and epinephrine ( P < 0.05) spillovers. After birth, total body norepinephrine and epinephrine spillover increased 45% and 3.2-fold, respectively, in normoxemic animals (both P < 0.001). However, in the hypoxemic group, norepinephrine total body spillover was unchanged between fetal and 1-h lambs and then fell in 4-h lambs ( P < 0.005). In addition, total body epinephrine release rose postnatally ( P < 0.05) but less than in the normoxemic group ( P < 0.02). No differences in norepinephrine or epinephrine total body clearance occurred between normoxemic and hypoxemic groups in either fetal or newborn lambs. These findings indicate that in hypoxemic and growth-restricted fetuses 1) elevated circulating norepinephrine and epinephrine levels are related to increased sympathoadrenal activity and 2) birth is associated with an initial maintenance and subsequent decline in global sympathetic activity but a blunting of adrenal medullary activation.
Circannual changes in free thyroxine, prolactin, testes, and relative food intake in woodchucks, Marmota monax
Authors: Concannon Patrick W. , Castracane V. Daniel , Rawson Richard E. , Tennant Bud C.
Published: December 2017

Woodchucks ( n = 12–14/group) with circannual cycles entrained to northern versus southern hemisphere photoperiods were assessed monthly for 16 mo. Changes in serum total triiodothyronine (TT3), free thyroxine (T4), total thyroxine (TT4), and prolactin were determined in a subset of five animals per group. Metabolic hormone results were examined in relation to changes in body weight, food intake, and serum testosterone ( n = 12–14/group). Seasonal changes in each parameter were similar in both groups as were nadir and peak TT3 (162 ± 6 and 392 ± 12 ng/ml, respectively), free T4 (19 ± 2 and 86 ± 7 ng/ml, repectively), TT4 (3.2 ± 0.2 and 8.0 ± 0.5 ng/ml, respectively), and prolactin (0.6 ± 0.1 and 14 ± 2 ng/ml, respectively). In late winter and early spring, simultaneous increases in both free T4 and prolactin were associated with 1) a large increase in food intake, 2) a decline in body weight to nadir values, 3) a corresponding negative energy balance, 4) a peak and decline in serum testosterone, and 5) a modest increase in TT4 and large decline in serum TT3. Low levels of free T4 and prolactin were observed in summer when energy balance was very positive. The results demonstrate that, in woodchucks, serum T4 and prolactin undergo seasonal changes during annual cycles entrained by photoperiod. The results suggest that changes in free T4, acting as a calorigenic hormone, and changes in both T4and prolactin, potentially acting as lipolytic, antilipogenic, and/or orectic hormones, are likely involved in the mechanisms underlying the corresponding seasonal changes in food intake, fat metabolism, and energy balance in this species. Their potential roles in gonadal regression and recrudescence are less clear.
Adenosine-induced renal vasoconstriction in diabetes mellitus rats: role of prostaglandins
Authors: Pflueger Axel C. , Gross Jennifer M. , Knox Franklyn G.
Published: December 2017

We investigated the role of prostaglandins in the renal vascular response to exogenous and endogenous adenosine in control and streptozotocin (STZ) diabetic rats. Exogenous adenosine (0.01–100 nmol) injected into the abdominal aorta decreased renal blood flow (RBF) in a dose-dependent manner to a much greater extent in STZ rats than in control rats ( P < 0.001). Inhibition of prostaglandin synthesis with indomethacin (Indo; 10 mg/kg iv) potentiated the adenosine-induced renal vasoconstriction in control rats but not in STZ rats. In control rats, Indo shifted the dose response curve of exogenous adenosine-induced RBF reductions to the left by a factor of 10 (ED50: from 5.5 ± 0.51 to 0.55 ± 0.07 nmol adenosine, n = 6, P < 0.001) and in STZ rats only by a factor of two (ED50: from 0.32 ± 0.03 to 0.16 ± 0.02 nmol adenosine, n = 6, P > 0.05). The renal response to endogenous adenosine was assessed by the magnitude of the postocclusive reduction of RBF (POR), an adenosine-mediated phenomenon. POR was greater in STZ rats (−65.3 ± 5.2%, P < 0.001) compared with control rats (−36.2 ± 3.5%). Indo markedly enhanced POR in control rats (−20.3 ± 3.7%) but not in STZ rats (−4.5 ± 2.7%). Renal cortical and medullary PGE2microdialysate concentrations and urinary PGE2excretions were clearly not lower in STZ (cortex: 169 ± 61 pg/ml; medulla: 640 ± 88 pg/ml, urine: 138 ± 25 pg/min) compared with control rats (cortex: 99 ± 12 pg/ml; medulla: 489 ± 107 pg/ml; urine: 82 ± 28 pg/min). Indo significantly decreased renal cortical, medullary, and urinary excretion of PGE2in STZ and control rats. These findings demonstrate that the adenosine-induced renal vasoconstriction is increased in the presence of Indo in control rats but not in STZ rats. The observations suggest that the diabetic renal vasculature may have a diminished vasodilatory capacity in response to prostaglandins to counteract adenosine-induced renal vasoconstriction.
Effects of a three-day head-down tilt on renal and hormonal responses to acute volume expansion
Authors: Mauran Pierre , Sediame Saïd , Traon Anne Pavy-Le , Maillet Alain , Carayon Alain , Barthelemy Christiane , Weerts Guillaume , Guell Antonio , Adnot Serge
Published: December 2017

To clarify whether exposure to 6° head-down tilt (HDT) leads to alterations in body fluid volumes and responses to a saline load similar to those observed during space flight we investigated eight healthy subjects during a 4-day, 6° HDT and during a time-control ambulatory period with cross-over. Compared with the ambulatory period, HDT was associated with greater urinary excretion of water and sodium (UV, UNaV) from 0 to 12 h (cumulated UV 1,781 ± 154 vs. 1,383 ± 170 ml, P < 0.05; cumulated UNaV 156 ± 14 vs. 117 ± 9 mmol, P < 0.05), and with higher plasma atrial natriuretic factor (ANF) at 4 h. Hemoglobin and hematocrit increased over the first 24 h, and blood and plasma volumes were decreased after 48 h of HDT ( P< 0.05). Plasma renin activity (PRA) and aldosterone did not differ between the two groups. With prolongation of HDT, UV and UNaV returned close to baseline values. On the fourth HDT day, a 30-min infusion of 20 ml/kg isotonic saline was performed, while a large oral water load maintained a high urine output. The ambulatory period experiment was done with the subjects in the acute supine posture. Sodium excreted within 4 h of loading was 123 ± 8 mmol during HDT vs. 168 ± 16 mmol during the ambulatory period ( P < 0.05). The increase in plasma ANF and decrease in PRA were greater during HDT than during the ambulatory period (ANF 30 ± 5 vs. 13 ± 4 pg/ml, P < 0.05; PRA −1.4 ± 0.4 vs. −0.5 ± 0.2 ng ⋅ ml−1 ⋅ h−1, P < 0.05). Our data suggest that after a 3-day HDT period, thoracic volume receptor loading returns to the level seen in the upright position, leading to blunted responses to volume expansion, compared with acute supine control.
Tachyphylaxis to PACAP-27 after inhibition of NO synthesis: a loss of adenylate cyclase activation
Authors: Whalen Erin J. , Johnson Alan Kim , Lewis Stephen J.
Published: December 2017

The vasodilator effects of pituitary adenylate cyclase activating polypeptide (PACAP-27) are subject to tachyphylaxis in rats treated with the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME). This study examined whether this tachyphylaxis is due to the loss of vasodilator potency of cAMP generated by activation of the Gsprotein-coupled PACAP receptors. Five successive treatments with PACAP-27 (2 nmol/kg iv) produced pronounced vasodilator responses in saline-treated rats that were not subject to tachyphylaxis. The first injection of PACAP-27 (2 nmol/kg iv) in l-NAME (50 μmol/kg iv)-treated rats produced vasodilator responses of similar magnitude to those in saline-treated rats, whereas four subsequent injections produced progressively and markedly smaller responses. The hemodynamic effects of the membrane-permeable cAMP analog 8-(4-chlorophenylthiol)-cAMP (8-CPT-cAMP; 5–15 μmol/kg iv) were similar inl-NAME-treated rats and inl-NAME-treated rats that had received the five injections of PACAP-27. In addition, five injections of 8-CPT-cAMP (10 μmol/kg iv) produced pronounced vasodilator responses in saline- andl-NAME-treated rats that were not subject to the development of tachyphylaxis. These results suggest that a loss of biological potency of cAMP is not responsible for tachyphylaxis to PACAP-27 inl-NAME-treated rats. This tachyphylaxis may be due to the inability of the Gsprotein-coupled PACAP receptor to activate adenylate cyclase.
Medullary lateral tegmental field: an important synaptic relay in the baroreceptor reflex pathway of the cat
Authors: Orer Hakan S. , Barman Susan M. , Gebber Gerard L. , Sykes Shannon M.
Published: December 2017

This study was designed to test the hypothesis that the medullary lateral tegmental field (LTF) is an important synaptic relay in the baroreceptor reflex pathway controlling sympathetic nerve discharge (SND) of urethan-anesthetized cats. We determined the effects of blockade of excitatory amino acid-mediated neurotransmission in the LTF on three indexes of baroreceptor reflex function: cardiac-related power in SND, strength of linear correlation (coherence value) of SND to the arterial pulse (AP), and inhibition of SND during increased arterial pressure produced by abrupt obstruction of the abdominal aorta. Bilateral microinjection ofd-(−)-2-amino-5-phosphonopentanoic acid, an N-methyl-d-aspartate (NMDA) receptor antagonist, abolished cardiac-related power and coherence of SND to the AP, and it prevented inhibition of SND during aortic obstruction. These data support the view that NMDA receptor-mediated neurotransmission in the LTF is critical for baroreceptor reflex control of SND. Bilateral microinjection of 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzo-[ f]-quinoxaline-7-sulfonamide, a non-NMDA receptor antagonist, decreased cardiac-related power and total power in the 0- to 6-Hz band of SND; however, the AP-SND coherence value remained high, and inhibition of SND during aortic obstruction was preserved. These data imply that non-NMDA receptor-mediated neurotransmission in the LTF is involved in setting the level of excitatory drive to sympathetic nerves.
Relationship between the daily rhythms of locomotor activity and body temperature in eight mammalian species
Authors: Refinetti Roberto
Published: December 2017

The relationship between the daily rhythms of locomotor activity and body temperature was studied by telemetry in four nocturnal and four diurnal mammalian species. The results showed that the two rhythms are very closely synchronized, as they 1) ascend past the daily mean at the same time, 2) reach the daily acrophase at the same time, and 3) are best correlated at time lags approaching zero. The rhythms of nocturnal animals crossed the daily mean at the transition between the light and dark phases of the light-dark cycle and reached their acrophases during the dark phase, whereas the rhythms of diurnal animals crossed the daily mean at the transition between the dark and light phases and reached their acrophases during the light phase. Despite the close synchrony of the two rhythms, the results indicate that the temperature rhythm is not a byproduct of the activity rhythm, as body temperature during the active phase of the daily cycle was higher than body temperature during the inactive phase in all species irrespective of the activity level prevailing during each phase.
Phosphorylation state of red and white muscle in tilapia during graded hypoxia: an in vivo31P-NMR study
Authors: van Ginneken V. J. T. , van den Thillart G. E. E. J. M. , Muller H. J. , van Deursen S. , Onderwater M. , Visée J. , Hopmans V. , van Vliet G. , Nicolay K.
Published: December 2017

The aim of this study was to measure the energetic consequences of hypoxia in different types of skeletal muscle within a single tilapia species ( n = 5). To that aim, 81.0 MHz31P-nuclear magnetic resonance (NMR) spectra were collected, alternately, from three surface coils placed adjacent to the tissues of interest (dorsal white muscle, ventral white muscle, and lateral red muscle) during a graded hypoxia load over 6 h followed by a 5-h recovery period. The fish were contained in a flow cell, enabling us full control of the oxygen content of the bathing medium. The intracellular pH and the concentrations of ATP, phosphocreatine (PCr), and Piwere determined from the NMR spectra. For normoxia, biochemical differences for [γ-ATP], [PCr], and [sugar phosphates] (SP) were observed between all three locations, especially between the red and white muscle. During hypoxia stress, loss of phosphorylated compounds (PCr+Pi+SP) was observed at all locations but was the most severe in red muscle. When the aerobic (respirometry) and anaerobic (31P-NMR) ATP production via an energy balance are compared, flexible metabolic depression is demonstrated during anaerobioses. It is concluded that control of the aerobic and anaerobic component of metabolism during metabolic depression is independent of each other.
Biochemical and functional evidences for a GLUT-4 homologous protein in avian skeletal muscle
Authors: Thomas-Delloye Véronique , Marmonier Florence , Duchamp Claude , Pichon-Georges Béatrice , Lachuer Joël , Barré Hervé , Crouzoulon Gabriel
Published: December 2017

The characteristics and modulation of glucose transport were investigated in skeletal muscles of 5-wk-old Muscovy ducklings ( Cairina moschata). Glucose uptake by sarcolemmal vesicles isolated from gastrocnemius muscle followed typical Michaelis-Menten kinetics with a Kmvalue (17 mM) similar to that described in equivalent mammalian preparations. Western blot analysis of duckling sarcolemma using antibodies directed against rat GLUT-4 transporter revealed an immunoreactive protein of similar molecular mass (45 kDa) to that present in rats. When ducklings were killed in the postabsorptive state, GLUT-4 homologous protein was located predominantly (80%) in intracellular membranes. Insulin stimulation of a perfused leg muscle preparation in vitro led to the translocation of GLUT-4 homologous proteins from intracellular pools to the sarcolemma, with a subsequent increase in glucose uptake by sarcolemmal vesicles and perfused muscles. Glucose transport was positively controlled by the metabolic needs of skeletal muscle as reflected by the increased glucose uptake of sarcolemmal vesicles isolated from cold-acclimated ducklings. Present results, therefore, demonstrate, for the first time in an avian species, the existence in skeletal muscle of a glucose transporter showing molecular and functional homologies with the mammalian GLUT-4 transporter.
Adaptation to high-fat diet reduces inhibition of gastric emptying by CCK and intestinal oleate
Authors: Covasa Mihai , Ritter Robert C.
Published: December 2017

Rats maintained on low-fat (LF) or high-fat (HF) diets were fitted with gastric cannulas and duodenal catheters. Intraperitoneal injection of 0.250–2.0 μg/kg cholecystokinin (CCK) significantly inhibited gastric emptying of a 5-ml NaCl load in LF rats by 26.2–55.1% compared with emptying after vehicle injection. By contrast, CCK-induced inhibition of gastric emptying was significantly less in HF rats given the same CCK doses (10.0–31.7% inhibition over the same CCK dose range). A 20-min intraduodenal infusion of oleate (0.03 or 0.06 kcal/ml) also resulted in significant inhibition of gastric emptying in LF rats (24 and 89%, respectively). Oleate-induced inhibition of gastric emptying was significantly attenuated in rats maintained on the HF diet (2 and 56%, respectively). Unlike CCK injections or oleate infusion, intraduodenal maltotriose infusion inhibited gastric emptying to a similar degree in LF and HF rats (77 and 78%, respectively). These results indicate that feeding HF diets diminishes the enterogastric inhibition of gastric emptying by intestinal oleate and diminishes the ability of CCK to inhibit gastric emptying.
Identification of the conjugated linoleic acid isomer that inhibits milk fat synthesis
Authors: Baumgard Lance H. , Corl Benjamin A. , Dwyer Debra A. , Saebø A. , Bauman Dale E.
Published: December 2017

Conjugated linoleic acids (CLA) are octadecadienoic fatty acids that have profound effects on lipid metabolism. Our previous work showed that CLA (mixture of isomers) markedly reduced milk fat synthesis. In this study, our objective was to evaluate the effects of specific CLA isomers. Multiparous Holstein cows were used in a 3 × 3 Latin square design, and treatments were 4-day abomasal infusions of 1) skim milk (control), 2) 9,11 CLA supplement, and 3) 10,12 CLA supplement. CLA supplements provided 10 g/day of the specific CLA isomer ( cis-9, trans-11 or trans-10, cis-12). Treatments had no effect on intake, milk yield, or milk protein yield. Only the 10,12 CLA supplement affected milk fat, causing a 42 and 44% reduction in milk fat percentage and yield, respectively. Milk fat composition revealed that de novo synthesized fatty acids were extensively reduced. Increases in ratios of C14:0to C14:1and C18:0to C18:1indicated the 10,12 CLA supplement also altered Δ9-desaturase. Treatments had minimal effects on plasma concentrations of glucose, nonesterified fatty acids, insulin, or insulin-like growth factor-I. Overall, results demonstrate that trans-10, cis-12 CLA is the isomer responsible for inhibition of milk fat synthesis.
Defense of body weight against chronic caloric restriction in obesity-prone and -resistant rats
Authors: Levin Barry E. , Dunn-Meynell Ambrose A.
Published: December 2017

Half of Sprague-Dawley rats develop and defend diet-induced obesity (DIO) or diet resistance (DR) when fed a high-energy (HE) diet. Here, adult male rats were made DIO or DR after 10 wk on HE diet. Then half of each group was food restricted for 8 wk on chow to maintain their body weights at 90% of their respective baselines. Rate and magnitude of weight loss were comparable, but maintenance energy intake and the degree of sympathetic activity (24-h urine norepinephrine) inhibition were 17 and 29% lower, respectively, in restricted DR than DIO rats. Restricted DIO rats reduced adipose depot weights, plasma leptin, and insulin levels by 35%. Restricted DR rats reduced none of these. When fed ad libitum, both DR and DIO rats returned to the body weights of their respective chow-fed phenotype controls within 2 wk. This was associated with increased adipose mass and leptin and insulin levels only in DIO rats. Thus DR rats appear to alter primarily their lean body mass, whereas DIO rats primarily alter their adipose mass during chronic caloric restriction and refeeding.
Interleukin-1β deficiency results in reduced NF-κB levels in pregnant mice
Authors: Reznikov Leonid L. , Shames Brian D. , Barton Hazel A. , Selzman Craig H. , Fantuzzi Giamila , Kim Soo-Hyun , Johnson Sylene M. , Dinarello Charles A.
Published: December 2017

Interleukin (IL)-1β-deficient (IL-1β−/−) mice were assessed for cytokine production during pregnancy. A significant reduction in nuclear factor (NF)-κB p65 protein content was observed in the uteri and spleens of pregnant IL-1β−/−mice, as demonstrated by immunohistochemistry and Western immunoblot analysis. In addition, electromobility gel shift assay revealed less DNA binding activity of NF-κB p65-containing complex in pregnant IL-1β−/−mice. To investigate differences in cytokine production regulated by NF-κB, the levels of tumor necrosis factor-α, macrophage inflammatory protein-1α, and interferon-γ were measured in the uterine wall, spleen homogenates, and spleen cell cultures obtained from pregnant mice. Endocervical administration of lipopolysaccharide (LPS) increased cytokine levels in both wild-type (IL-1β+/+) and IL-1β−/−animals, but in IL-1β−/−mice this response was 50–75% lower. Splenocytes from nonpregnant mice exhibited decreased LPS-induced cytokine production when primed in vitro with progesterone. This suppression was 25% greater in IL-1β−/−than in IL-1β+/+mice. These data suggest that constitutive NF-κB p65 protein synthesis is regulated by IL-1β, particularly during pregnancy.
Photoperiod regulates arcuate nucleus POMC, AGRP, and leptin receptor mRNA in Siberian hamster hypothalamus
Authors: Mercer Julian G. , Moar Kim M. , Ross Alexander W. , Hoggard Nigel , Morgan Peter J.
Published: December 2017

Siberian hamsters decreased body weight by 30% during 18 wk in short day (SD) vs. long day (LD) controls. Subsequent imposed food deprivation (FD; 24 h) caused a further 10% decrease. In the hypothalamic arcuate nucleus (ARC), SDs reduced proopiomelanocortin (POMC) gene expression and agouti-related protein (AGRP) mRNA was elevated, changes that summate to reduced catabolic drive through the melanocortin receptors. There was no effect of photoperiod on neuropeptide Y (NPY), melanin concentrating hormone, orexin, or corticotropin-releasing factor mRNAs. Superimposed FD increased AGRP gene expression and caused a localized elevation of NPY mRNA in the ARC. Both adipose tissue leptin and ARC leptin receptor (OB-Rb) mRNAs were downregulated in SDs, whereas FD increased OB-Rb gene expression. Thus OB-Rb mRNA is differentially regulated by acute and chronic changes in plasma leptin in this species. In a separate experiment in LDs, AGRP gene expression was increased by 24 or 48 h FD, whereas POMC mRNA was downregulated in the caudal ARC. AGRP and NPY mRNAs were extensively coexpressed in the ARC, and their differential regulation by photoperiod and FD is suggestive of transcript-specific regulation at the level of individual neurons.
Influence of pontine A5 region on renal sympathetic nerve activity in conscious rabbits
Authors: Maiorov Dmitri N. , Malpas Simon C. , Head Geoffrey A.
Published: December 2017

The effects of inhibiting the neural activity in the pontine A5 region on renal sympathetic responses to baroreflex and/or chemoreflex activation were examined in conscious rabbits. Eight rabbits were chronically instrumented with guide cannulas for bilateral microinjections into the A5 area and an electrode for measuring renal sympathetic nerve activity (RSNA). Baroreflex curves were obtained under conditions of normoxia and hypoxia (10% O2 + 3% CO2) after injections into the A5 region of the GABA receptor agonist muscimol or vehicle solution. Under normoxia, injections of muscimol did not affect resting RSNA or blood pressure but increased the range of the RSNA baroreflex by 24 and 33% at doses of 175 or 875 pmol, respectively, without affecting the reflex gain. Hypoxia alone increased resting RSNA by 63%, as well as the range and gain of the RSNA baroreflex by 53 and 89%, respectively, without affecting blood pressure. However, under hypoxia, muscimol increased resting RSNA by 37 and 47% but decreased the gain of the RSNA baroreflex by 19 and 34% at doses of 175 or 875 pmol, respectively, without affecting the reflex range. The effects of muscimol on RSNA were mediated via changes in the amplitude of the sympathetic bursts, whereas burst frequency remained unaffected. These data suggest that the A5 region has a little tonic influence on RSNA in conscious rabbits but serves to limit the renal sympathetic responses to baroreceptor unloading or chemoreceptor stimulation. The different changes in the baroreflex range and gain evoked by muscimol under normoxia and hypoxia indicate that the A5 modulatory action may depend on the activity of the afferent inputs to this region.