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611.
Training-induced alterations of carbohydrate metabolism in women: women respond differently from men 总被引:4,自引:0,他引:4
Friedlander Anne L.; Casazza Gretchen A.; Horning Michael A.; Huie Melvin J.; Piacentini Maria Francesca; Trimmer Jeffrey K.; Brooks George A. 《Journal of applied physiology》1998,85(3):1175-1186
We examined the hypothesis that glucose flux wasdirectly related to relative exercise intensity both beforeand after a 12-wk cycle ergometer training program [5days/wk, 1-h duration, 75% peakO2 consumption(O2 peak)] inhealthy female subjects (n = 17; age23.8 ± 2.0 yr). Two pretraining trials (45 and 65% of O2 peak)and two posttraining trials [same absolute workload (65% of oldO2 peak)and same relative workload (65% of new O2 peak)] wereperformed on nine subjects by using a primed-continuous infusion of[1-13C]- and[6,6-2H]glucose.Eight additional subjects were studied by using[6,6-2H]glucose.Subjects were studied postabsorption for 90 min of rest and 1 h ofcycling exercise. After training, subjects increased O2 peak by 25.2 ± 2.4%. Pretraining, the intensity effect on glucose kinetics wasevident between 45 and 65% ofO2 peak with rates ofappearance (Ra: 4.52 ± 0.25 vs. 5.53 ± 0.33 mg · kg1 · min1),disappearance (Rd: 4.46 ± 0.25 vs. 5.54 ± 0.33 mg · kg1 · min1),and oxidation (Rox: 2.45 ± 0.16 vs. 4.35 ± 0.26 mg · kg1 · min1)of glucose being significantly greater(P 0.05) in the 65% thanin the 45% trial. Training reducedRa (4.7 ± 0.30 mg · kg1 · min1),Rd (4.69 ± 0.20 mg · kg1 · min1),and Rox (3.54 ± 0.50 mg · kg1 · min1)at the same absolute workload (P 0.05). When subjects were tested at the same relative workload,Ra,Rd, andRox were not significantlydifferent after training. However, at both workloads after training,there was a significant decrease in total carbohydrate oxidation asdetermined by the respiratory exchange ratio. These results show thefollowing in young women: 1)glucose use is directly related to exercise intensity;2) training decreasesglucose flux for a given power output;3) when expressed asrelative exercise intensity, training does not affect the magnitude ofblood glucose flux during exercise; but4) training does reduce totalcarbohydrate oxidation. 相似文献
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613.
Gretchen F. Sassenrath-Cole Robert W. Pearcy Scott Steinmaus 《Photosynthesis research》1994,41(2):295-302
The mechanisms regulating transient photosynthesis by soybean (Glycine max) leaves were examined by comparing photosynthetic rates and carbon reduction cycle enzyme activities under flashing (saturating 1 s lightflecks separated by low photon flux density (PFD) periods of different durations) and continuous PFD. At the same mean PFD, the mean photosynthetic rates were reduced under flashing as compared to continuous light. However, as the duration of the low PFD period lengthened, the CO2 assimilation attributable to a lightfleck increased. This enhanced lightfleck CO2 assimilation was accounted for by a greater postillumination CO2 fixation occurring after the lightfleck. The induction state of photosynthesis, ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco), fructose 1,6-bisphosphatase (FBPase) and ribulose 5-phosphate kinase (Ru5P kinase) activities all responded similarly and were all lower under flashing as compared to constant PFD of the same integrated mean value. However, the fast phase of induction and FBPase and Ru5P kinase activities were reduced more than were the slow phase of induction and rubisco activity. This was consistent with the role of the former enzymes in the fast induction component that limited RuBP regeneration. Competition for reducing power between carbon metabolism and thioredoxin-mediated enzyme activation may have resulted in lower enzyme activation states and hence lower induction states under flashing than continuous PFD, especially at low lightfleck frequencies (low mean PFD).Abbreviations FBPase
fructose 1,6-bisphosphatase (EC 3.1.3.11)
- LUE
lightfleck use efficiency
- P-glycerate
3-phosphoglycerate
- PICF
post-illumination CO2 fixation
- Ru5P kinase
ribulose 5-phosphate kinase (EC 2.7.1.19)
- RuBP
ribulose 1,5-bisphosphate
- rubisco
ribulose 1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39)
- SBpase
sedoheptulose 1,7-bisphosphatase (EC 3.1.3.37) 相似文献
614.
Abstract. This is the first article of branchiobdellidans on blue crabs, Callinectes sapidus , in Chesapeake Bay, MD, USA. The ectosymbionts consisted of sympatric populations of Cambarincola mesochoreus and Cambarincola pamelae living on the ventral body surface and in the gill chambers of blue crabs. The occurrence of branchiobdellidans in the upper bay region was documented at ten sites during August and late September 2003. Branchiobdellidans were found on blue crabs following a rainy summer when salinity levels fell below 3 ppt. The blue crabs move into the freshwater estuaries during the summer, where they enter the habitats of crayfishes; however, the mechanism of transfer from one crustacean host to another is not known. 相似文献
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618.
The ascidian sperm reaction, Which involves swelling, migration, and loss of the single large mitochondrion, can be triggered in vitro by raising the seawater pH to 9.3 or lowering Na+ to 20 mM, but only if the sperm are allowed to attach to a suitable Substate. Mitochondrial translocation does not usually occur in the absence of sperm attachment. Extracellular Ca2+ is necessary for triggering the reaction with low Na+ but not high pH; however, the intrecellular Ca2+ blocker, TMB-8, inhibits high pH-induced mitochondrial movement in the absence of extracellular Ca2+. After swelling, the mitochondrion fluoresces in the presence of chlortetracycline, suggesting that Ca2+ becomes membranebound after activation. Elevated cAMP and theophylline both inhibit mitochondrial move ment but not sperm motility. The antiactin drug cytochalasin B(10μM) and the calmodulinblocking drugs TFP (1 μM) and W-13 (10 μM) block mitochondrial movement, suggesting roles for actin and calmodulin in mitochondrial movement. A model is proposed relating intracellular alkalinization, Ca2+ influx, actin, myosin, and calmodulin in mitochondrial translocation. 相似文献
619.
Calycogonium formonense, a new species, is here described from the floristically diverse Massif de la Hotte of southern Haiti. It is compared to
C. hispidulum, to which it is likely related. Although the genus Calycogonium is not monophyletic, C. formonense and C. hispidulum are probably related to other species, e.g., C. calycopteris, C. heterophyllum, and C. reticulatum, that exhibit reduced inflorescences and 4-merous flowers having hypanthia with four conspicuous lobes separated by longitudinal
grooves and external calyx lobes that are flattened parallel to the floral radii. These distinctive species may form a clade.
Calycogonium formonense is distinguished from C. hispidulum by its smaller leaves with the tertiary veins not raised on the abaxial surface, with entire margins (i.e., margin without
elongate multicellular hairs), and usually solitary flowers. 相似文献
620.
Gretchen H. Stein Vjekoslav Duli 《BioEssays : news and reviews in molecular, cellular and developmental biology》1995,17(6):537-543
Human diploid fibroblasts have a finite proliferative lifespan in culture, at the end of which they are ararrested with G1 phase DNA contents. Upon serum stimulation, senescent cells are deficient in carrying out a subset of early signal transduction events such as activation of protein kinase C and induction of c-fos. Later in G1, they uniformly fail to express late G1 genes whose products are required for DNA synthesis, implying that they are unable to pass the R point. Failure to pass the R point may occur because senescent cells are unable to phosphorylate the retinoblastoma protein, owing to the accumulation of inactive complexes of cyclin E/Cdk2 and possibly cyclin D/Cdk4. Senescent cells contain high amounts of p21, a potent cyclin-dependent kinase inhibitor whose levels are also elevated in cells arrested in G1 following DNA damage, suggesting that both arrests might share a common mechanism. Cell aging is accompanied by a progressive shortening of chromosomal telomeres, which could be perceived by the cells as a form of DNA damage that gives rise to the signals that inactivate the cell cycle machinery. 相似文献