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Selected AbstractsExercise training in late middle-aged male Fischer 344 × Brown Norway F1-hybrid rats improves skeletal muscle aerobic functionEXPERIMENTAL PHYSIOLOGY, Issue 7 2008Andrew C. Betik The Fischer 344 × Brown Norway F1-hybrid (F344BN) rat has become an increasingly popular and useful strain for studying age-related declines in skeletal muscle function because this strain lives long enough to experience significant declines in muscle mass. Since exercise is often considered a mechanism to combat age-related declines in muscle function, determining the utility of this strain of rat for studying the effects of exercise on the ageing process is necessary. The purpose of this study was to evaluate the plasticity of skeletal muscle aerobic function in late middle-aged male rats following 7 weeks of treadmill exercise training. Training consisted of 60 min per day, 5 days per week with velocity gradually increasing over the training period according to the capabilities of individual rats. The final 3 weeks involved 2 min high-intensity intervals to increase the training stimulus. We used in situ skeletal muscle aerobic metabolic responses and in vitro assessment of muscle mitochondrial oxidative capacity to describe the adaptations of aerobic function from the training. Training increased running endurance from 11.3 ± 0.6 to 15.5 ± 0.8 min, an improvement of ,60%. Similarly, distal hindlimb muscles from trained rats exhibited a higher maximal oxygen consumption in situ (23.2 ± 1.3 versus 19.7 ± 0.8 ,mol min,1 for trained versus sedentary rats, respectively) and greater citrate synthase and complex IV enzyme activities in gastrocnemius (29 and 19%, respectively) and plantaris muscles (24 and 28%, respectively) compared with age-matched sedentary control animals. Our results demonstrate that skeletal muscles from late middle-aged rats adapt to treadmill exercise by improving skeletal muscle aerobic function and mitochondrial enzyme activities. This rat strain seems suitable for further investigations using exercise as an intervention to combat ageing-related declines of skeletal muscle aerobic function. [source] Regional sympathetic denervation affects the relation between canine local myocardial blood flow and oxygen consumptionEXPERIMENTAL PHYSIOLOGY, Issue 3 2007David J. C. Alders Myocardial blood flow and oxygen consumption are heterogeneously distributed. Perfusion and myocardial oxygen consumption are closely correlated in the normal heart. It is unknown how this metabolism,perfusion relation is influenced by sympathetic denervation. We investigated this question in seven chloralose-anaesthetized dogs, 3,4 weeks after regional sympathetic denervation of the left circumflex coronary artery area of supply of the left ventricle. Measurements were made of local myocardial blood flow (MBF, in ml min,1 (g dry wt),1), measured with microspheres, and myocardial oxygen consumption (, in ,mol min,1 (g dry wt),1) in the same location, calculated from the 13C spectrum of tissue extracts after intracoronary infusion of 3,13C-lactate. Since both innervated and denervated regions are subject to the same arterial pressure, lower blood flow indicates higher resistance. Mean MBF was 5.56 ml min,1 (g dry wt),1 (heterogeneity of 3.47 ml min,1 (g dry wt),1) innervated, 7.48 ml min,1 (g dry wt),1 (heterogeneity of 3.62 ml min,1 (g dry wt),1) denervated (n.s.). Significant linear relations were found between MBF and of individual samples within the innervated and denervated regions. The slopes of these relations were not significantly different, but the adjusted mean was significantly higher in the denervated regions (+1.92 ml min,1 (g dry wt),1, an increase of 38% of the mean MBF at the pooled mean , P= 0.028, ANCOVA). The ratio (in ml ,mol,1) was significantly higher, being 0.296 ± 0.167 ml ,mol,1 in the denervated region compared with the innervated region, 0.216 ± 0.126 ml ,mol,1, P= 0.0182, Mann,Whitney U test. These results indicate that sympathetic tone under chloralose anaesthesia imposes a moderate vasoconstrictive effect in the myocardium that is not detected by comparison of the mean blood flow or resistance. [source] Presence of a Na+ -stimulated P-type ATPase in the plasma membrane of the alkaliphilic halotolerant cyanobacterium Aphanothece halophyticaFEMS MICROBIOLOGY LETTERS, Issue 1 2007Kanjana Wiangnon Abstract Aphanothece cells could take up Na+ and this uptake was strongly inhibited by the protonophore, carbonyl cyanide m -chlorophenylhydrazone (CCCP). Cells preloaded with Na+ exhibited Na+ extrusion ability upon energizing with glucose. Na+ was also taken up by the plasma membranes supplied with ATP and the uptake was abolished by gramicidin D, monensin or Na+ -ionophore. Orthovanadate and CCCP strongly inhibited Na+ uptake, whereas N, N, -dicyclohexylcarbodiimide (DCCD) slightly inhibited the uptake. Plasma membranes could hydrolyse ATP in the presence of Na+ but not with K+, Ca2+ and Li+. The Km values for ATP and Na+ were 1.66±0.12 and 25.0±1.8 mM, respectively, whereas the Vmax value was 0.66±0.05 ,mol min,1 mg,1. Mg2+ was required for ATPase activity whose optimal pH was 7.5. The ATPase was insensitive to N -ethylmaleimide, nitrate, thiocyanate, azide and ouabain, but was substantially inhibited by orthovanadate and DCCD. Amiloride, a Na+/H+ antiporter inhibitor, and CCCP showed little or no effect. Gramicidin D and monensin stimulated ATPase activity. All these results suggest the existence of a P-type Na+ -stimulated ATPase in Aphanothece halophytica. Plasma membranes from cells grown under salt stress condition showed higher ATPase activity than those from cells grown under nonstress condition. [source] Antioxidants in aerial parts of Hypericum sampsonii, Hypericum japonicum and Hypericum perforatumINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 11 2009Chung Li Chen Summary Antioxidants contents and antioxidative enzymes and their activities in fresh aerial tissues of Hypericum sampsonii (Sampson's St John's Wort), Hypericum japonicum (Japanese St John's Wort) and Hypericum perforatum were investigated. Hypericum sampsonii contained more total ascorbate [34.33 ,mol g,1 fresh weight (FW)] than H. perforatum (57% less) and H. japonicum (82% less). It also contained more thiol and phenolics than two other species. Hypericum japonicum had highest superoxide dismutase (SOD) activity (8.74 mmol min,1 g,1 FW), followed by H. sampsonii (2% less) and H. perforatum (37% less). Hot-air dried H. perforatum materials contained more thiol [208.7 ,mol g,1 dry weight (DW)] and phenolics (352.82 mg g,1 DW) than freeze-dried and fresh materials. Both drying treatments decreased the activities of antioxidative enzymes in aerial tissues of H. perforatum. However, freeze-dried H. perforatum contained the highest SOD activity (5.42 mmol min,1 g,1 DW) among the antioxidative enzymes measured from both freeze-dried and hot-air dried tissues (ranged from 0.02 to 2.65 ,mol min,1 g,1 DW). [source] Production, purification and thermal characterisation of invertase from a newly isolated Fusarium sp. under solid-state fermentationINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2008Iram Shaheen Summary Production of invertase employing a newly isolated Fusarium sp. under solid-state fermentation was optimised. Different process parameters were optimised. The maximum enzyme activity under optimum conditions was 47.23 ± 2.12 U gds,1 with nitrogen additives. The enzyme was purified by ammonium sulphate precipitation, diethylaminoethyl cellulose ion-exchange chromatography and Sephadex gel filtration. This protocol gave 20.25-fold purification and 5.53% recovery. The optimum pH and temperature for activity were 5.0 and 50 °C. The Km and Vmax values for the enzyme were 8.33 mm and 21.48 ,mol min,1, respectively. A detailed kinetic study of thermal inactivation has been carried out. Enthalpy of activation (,H*) decreased when entropy (,S*) of activation increased at higher temperatures. Moreover, free energy of denaturation (,G*) increased at higher temperature making the enzyme thermally stable. A possible explanation for the thermal inactivation of invertase at higher temperatures is also discussed. [source] Reciprocal regulation of human soluble and particulate guanylate cyclases in vivoBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2006M Madhani Background & purpose: We demonstrated previously that reciprocal regulation of soluble (sGC) and particulate (pGC) guanylate cyclases by NO and natriuretic peptides coordinates cyclic cGMP-mediated vasodilatation in vitro. Herein, we investigated whether such an interaction contributes to vascular homeostasis in mice and humans in vivo. Experimental approach: Mean arterial blood pressure (MABP) changes in anaesthetized mice were monitored in response to i.v. administration of cGMP- and cAMP-dependent vasodilators in wild-type (WT), endothelial NO synthase (eNOS) and natriuretic peptide receptor (NPR)-A knockout mice. Forearm blood flow (FBF) in response to intra-brachial infusion of ANP (25, 50, 100, 200 pmol min -1) in the absence and presence of the NOS inhibitor NG -methyl-L-arginine (L-NMA; 4 ,mol min -1) and the control constrictor noradrenaline (240 pmol min -1) was assessed in healthy volunteers. Key results: Sodium nitroprusside (SNP; NO-donor) and atrial natriuretic peptide (ANP) produced dose-dependent reductions in MABP in WT animals that were significantly enhanced in eNOS KO mice. In NPR-A K mice, SNP produced a dose-dependent reduction in MABP that was significantly greater than that in WT mice. Responsiveness to the cAMP-dependent vasodilator epoprostenol was similar in WT, eNOS KO and NPR-A KO animals. ANP caused vasodilatation of the forearm resistance vasculature that was significantly greater in individuals lacking endothelium-derived NO (i.e. L-NMA treated). Conclusions & implications: These data demonstrate that crosstalk occurs between the NO-sGC and ANP-pGC pathways to regulate cGMP-dependent vasodilatation in vivo in both mice and humans. These findings have implications for understanding the link between natriuretic peptide activity and cardiovascular risk. British Journal of Pharmacology (2006) 149, 797,801. doi:10.1038/sj.bjp.0706920 [source] Enzymatic properties of phenoloxidase from Pieris rapae (Lepidoptera) larvaeINSECT SCIENCE, Issue 4 2006CHAO-BIN XUE Abstract The kinetic parameters of partially purified phenoloxidase (PO, EC. 1.14.18.1) from the 5th instar larvae of Pieris rapae (Lepidoptera) were determined, using L-3, 4-dihydroxyphenylalanine (L-DOPA) as substrate. The optimal pH and temperature of the enzyme for the oxidation of L-DOPA were determined to be at pH 7.0 and at 42°C, respectively. The enzyme was stable between pH 6.5 and 7.4 and at temperatures lower than 37°C. At pH 6.8 and 37°C, the Michaelis constant (Km) and maximal velocity (Vm) of the enzyme for the oxidation of L-DOPA were determined to be 0.80 ,mol/L and 1.84 ,mol/ L/min, respectively. Tetra-hexylresorcinol and 4-dodecylresorcinol effectively inhibited activity of phenoloxidase and this inhibition was reversible and competitive, with the IC50 of 1.50 and 1.12 ,mol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47 ,mol/L, respectively. [source] The correlation between cerebral glucose metabolism and benzodiazepine receptor density in the acute vegetative stateEUROPEAN JOURNAL OF NEUROLOGY, Issue 6 2002J. Rudolf This paper compares the results of parallel positron emission tomography (PET) studies of regional cerebral glucose metabolism with the radiotracer 18F-fluorodeoxyglucose (FDG) and benzodiazepine receptor (BZR) density by PET using the BZR ligand 11C-flumazenil (FMZ), a tracer of neuronal integrity, in nine patients with acute vegetative state (AVS, duration <1 month). Overall glucose utilization was significantly reduced in AVS in comparison with age-matched controls (global metabolic rate for glucose 26 ,mol/100 g/min in AVS vs. 31 ,mol/100 g/min in controls). FMZ-PET demonstrated a considerable reduction of BZR binding sites in all cortical regions that grossly corresponded to the extent of reduction of cerebral glucose metabolism assessed with FDG-PET, whilst the cerebellum was spared from neuronal loss. In controls, cortical relative flumazenil binding was not lower than five times the average white matter activity, whilst in AVS, nearly all values were below this threshold. There was no relevant overlap of the data of relative flumazenil binding between both groups. The comparison of FDG- and FMZ-PET findings in AVS demonstrates that alterations of cerebral glucose consumption do not represent mere functional inactivation, but irreversible structural brain damage. [source] | |||||||||||||