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排序方式: 共有259条查询结果,搜索用时 15 毫秒
1.
J L Bowtell K Gelly M L Jackman A Patel M Simeoni M J Rennie 《Journal of applied physiology》2000,88(5):1529-1536
Seven untrained male subjects participated in a double-blind, crossover study conducted to determine the efficacy of different carbohydrate drinks in promoting carbohydrate storage in the whole body and skeletal muscle during recovery from exhaustive exercise. The postabsorptive subjects first completed an exercise protocol designed to deplete muscle fibers of glycogen, then consumed 330 ml of one of three carbohydrate drinks (18.5% glucose polymer, 18.5% sucrose, or 12% sucrose; wt/vol) and also received a primed constant infusion of [1-(13)C]glucose for 2 h. Nonoxidative glucose disposal (3.51 +/- 0.28, 18.5% glucose polymer; 2.96 +/- 0.32, 18.5% sucrose; 2.97 +/- 0.16, 12% sucrose; all mmol. kg(-1). h(-1)) and storage of muscle glycogen (5.31 +/- 1.11, 18.5% glucose polymer; 4.07 +/- 1.05, 18.5% sucrose; 3.45 +/- 0.85, 12% sucrose; all mmol. kg wet wt(-1). h(-1); P < 0.05) were greater after consumption of the glucose polymer drink than after either sucrose drink. The results suggest that the consumption of a glucose polymer drink (containing 61 g carbohydrate) promotes a more rapid storage of carbohydrate in the whole body, skeletal muscle in particular, than an isoenergetic sucrose drink. 相似文献
2.
Human cyclins B1 and B2 are localized to strikingly different structures: B1 to microtubules, B2 primarily to the Golgi apparatus. 总被引:23,自引:3,他引:20
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We have raised and characterized antibodies specific for human cyclin B2 and have compared the properties of cyclins B1 and B2 in human tissue culture cells. Cyclin B1 and B2 levels are very low in G1 phase, increase in S and G2 phases and peak at mitosis. Both B-type cyclins associate with p34cdc2; their associated kinase activities appear when cells enter mitosis and disappear as the cyclins are destroyed in anaphase. However, human cyclins B1 and B2 differ dramatically in their subcellular localization. Cyclin B1 co-localizes with microtubules, whereas cyclin B2 is primarily associated with the Golgi region. In contrast to cyclin B1, cyclin B2 does not relocate to the nucleus at prophase, but becomes uniformly distributed throughout the cell. The different subcellular locations of human cyclins B1 and B2 implicate them in the reorganization of different aspects of the cellular architecture at mitosis and indicate that different mitotic cyclin-cyclin-dependent kinase complexes may have distinct roles in the cell cycle. 相似文献
3.
We describe a sensitive specific and simple high pressure liquid chromatographic procedure for determining 3,4-dihydroxyphenylethylene glycol (DHPG) in both plasma and tissue. DHPG is extracted from plasma or tissue extracts by adsorption onto alumina. DHPG in the alumina eluate is detected electrochemically following chromatography on a C18 reverse phase column. The method is sensitive enough to detect approximately 20 pg/ml of plasma DHPG. Both clonidine (100 μg/kg) and desmethylimipramine (2.5 mg/kg) when administered to rabbits for 3 days induced significant falls in both cardiac and plasma DHPG concentrations. These experiments indicate that both tissue and plasma DHPG concentrations may be of value in assessing both the release and re-uptake of norepinephrine at peripheral sympathetic nerve endings in vivo. 相似文献
4.
M P Jackman M A Parry J Hofsteenge S R Stone 《The Journal of biological chemistry》1992,267(22):15375-15383
Stopped-flow fluorescence spectroscopy has been used to study the reaction of human alpha-thrombin with recombinant hirudin variant 1 (rhir) at 37 degrees C and an ionic strength of 0.125 M. A 35% enhancement in intrinsic fluorescence accompanied formation of the thrombin-rhir complex. Over one third of this enhancement corresponded to a structural change that could be induced by binding of either the NH2-terminal fragment (residues 1-51) or the COOH-terminal fragment (residues 52-65) of rhir. Three kinetic steps were detected for reaction of thrombin with rhir. At high rhir concentrations (greater than or equal to 3 microM), two intramolecular steps with observed rate constants of 296 +/- 5 s-1 and 50 +/- 1 s-1 were observed. By using the COOH-terminal fragment of rhir as a competitive inhibitor, it was possible to obtain an estimate of 2.9 x 10(8) M-1 s-1 for the effective association rate constant at low rhir concentrations. At higher ionic strengths, this rate constant was lower, which is consistent with the formation of the initial complex involving an ionic interaction. The mechanism for the reaction of both the COOH- and NH2-terminal fragments of rhir appeared to involve two steps. When thrombin was reacted with the COOH-terminal fragment at high concentrations (greater than or equal to 6 microM), the bimolecular step occurred within the dead time of the spectrometer and only one intramolecular step, with a rate constant of 308 +/- 5 s-1 was observed. At concentrations of NH2-terminal fragment below 50 microM, its binding to thrombin appeared to be a bimolecular reaction with an association rate constant of 8.3 x 10(5) M-1 s-1. In the presence of saturating concentrations of the COOH-terminal fragment, a 1.7-fold increase in this rate constant was observed. At concentrations of NH2-terminal fragment greater than 50 microM, biphasic reaction traces were observed which suggests a two-step mechanism. By comparing the reaction amplitudes and dissociation constants observed with rhir and its COOH-terminal fragment, it was possible to obtain approximate estimates for the values of the rate constants of different steps in the formation of the rhir-thrombin complex. 相似文献
5.
Effects of chilling on tomato fruit texture 总被引:1,自引:0,他引:1
The effects of chilling on tomato ( Lycopersicon esculentum Mill cv. Caruso) texture were investigated using fruit stored at 22°C (nonchilled) or 5°C (chilled) for 28 days. or at 5°C for 15 days before transfer to 22°C to facilitate ripening during and additional 13 days (prechilled). Prechilled fruit exhibited symptoms of slight chilling injury, i.e. development of mealiness, accelerated softening relative to that of nonchilled fruit and nonuniform surface colour development. The firmness of all fruit decreased during ripening and chilled storage when measured by flat plate compression and puncture, especially during the early stages of ripening of nonchilled and prechilled fruit. The compression firmness of pericarp tissue similarly decreased during ripening of nonchilled and prechilled fruit, but was maintained during chilling. Total moisture content (ca 94%) of tissue, uronide content (32-35% w/w) and extracted β-galactosidase activity did not differ significantly ( P > 0.05) among fruit during ripening and chilled storage. The degree of uronide methyl esterification in ethanol-insoluble solids prepared from pericarp tissue (EIS) was relatively low for all fruit. i.e. <40%. EIS from which greater levels of pectinesterase were extracted (i.e. nonchilled>chilled>prechilled) exhibited decreased levels of uronide methyl esterification. Markedly elevated levels of β-glucosidase activity were extracted from prechilled EIS. Total polygalacturonase activity (mainly as PGI) and autolysis of enzyme-extracted EIS were inversely correlated ( P ≤ 0.05) only with the loss of nonchilled fruit and tissue firmness and prechilled fruit firmness. Results suggest a possible role for β-glucosidase in textural changes of prechilled fruit and tissue (e.g. loss of firmness, development of mealiness) and also implicate loss of skin strength in the softening of whole fruit during chilling. 相似文献
6.
John H. Pazur Yoshio Tominaga Charles W. DeBrosse Lloyd M. Jackman 《Carbohydrate research》1978,61(1):279-290
The formation of 1,6-anhydro-β-d-glucopyranose and several d-glucosyl oligosaccharides has been observed during the action of a purified, fungal glucosyltransferase (EC 2.4.1.24) on maltose. Such products are synthesized by a transglucosylation mechanism involving the formation of a d-glucosyl-enzyme complex and the displacement of the d-glucosyl group by appropriate acceptor-substrates. The formation of the 1,6-anhydro bond is a novel type of transfer reaction and occurs by displacement of the enzyme from the d-glucosyl-enzyme complex by the proton of the primary hydroxyl group of the same glucosyl group. This reaction is characterized by inversion of configuration at the position of glucosidic bond-cleavage of the substrate. Synthesis of the d-glucosyl oligosaccharides occurs by displacement of the d-glucosyl groups from the enzyme by suitable acceptor-substrates. In these cases, the reactions are characterized by retention of configuration of the d-glucosidic bonds of the substrate. The list of oligosaccharides produced from maltose includes nigerose, kojibiose, isomaltose, maltotriose, panose, isomaltotriose, and 6-O-d-glucosyl-panose. The identity of these compounds has been established by methylation analysis and enzymic hydrolysis. d-Glucose is also a product of the reaction and arises from both the reducing and the non-reducing groups of maltose. 相似文献
7.
J. Earl Jackman 《American anthropologist》1961,63(6):1337-1338
8.
Christopher I Keeling Macaire MS Yuen Nancy Y Liao T Roderick Docking Simon K Chan Greg A Taylor Diana L Palmquist Shaun D Jackman Anh Nguyen Maria Li Hannah Henderson Jasmine K Janes Yongjun Zhao Pawan Pandoh Richard Moore Felix AH Sperling Dezene P W Huber Inanc Birol Steven JM Jones Joerg Bohlmann 《Genome biology》2013,14(3):R27
9.
Ishan Agarwal Sayantan Biswas Aaron M. Bauer Eli Greenbaum Todd R. Jackman Anslem De Silva 《分类学与生物多样性》2013,11(5):427-439
We evaluated the status of 16 of 22 recognized Sri Lankan Cnemaspis Strauch species, and flagged overlooked diversity with two mitochondrial (cyt b & ND2) and two nuclear markers (RAG1 & PDC) totalling 2829 base pairs. A fossil-calibrated timetree and sampling of other South Asian Cnemaspis provide insights into the diversification of the genus in peninsular India and Sri Lanka. Phylogenetic analyses consistently inferred two broad clades within South Asian Cnemaspis, with Sri Lankan species in two clades, which we call the podihuna and kandiana clades. Each Sri Lankan clade as a whole is sister to Indian taxa and nested within Indian lineages. Cnemaspis modigliani Das from Indonesia is a member of the kandiana clade. This suggests a minimum of two dispersal events between India and Sri Lanka and one between Sri Lanka/India and South-east Asia. South Asian Cnemaspis date back to at least the Eocene, in Sri Lanka to the early Miocene, with late Miocene diversification in the kandiana clade. All but one of the named species we sampled is likely to be valid, and 10 divergent unnamed lineages may warrant specific recognition. A resolution of Sri Lankan Cnemaspis taxonomy will require thorough sampling and the use of both morphological and molecular data. 相似文献
10.
Alfred J. Lewy MD. PhD Jonathan S. Emens Bryan J. Lefler Krista Yuhas Angela R. Jackman 《Chronobiology international》2013,30(6):1093-1106
The specific circadian role proposed for endogenous melatonin production was based on a study of sighted people who took low pharmacological doses (500 µg) of this chemical signal for the “biological night”: the magnitude and direction of the induced phase shifts were dependent on what time of day exogenous melatonin was administered and were described by a phase‐response curve that turned out to be the opposite of that for light. We now report that lower (physiological) doses of up to 300 µg can entrain (synchronize) free‐running circadian rhythms of 10 totally blind subjects that would otherwise drift later each day. The resulting log‐linear dose‐response curve in the physiological range adds support for a circadian function of endogenous melatonin in humans. Efficacy of exogenous doses in the physiological range are of clinical significance for totally blind people who will need to take melatonin daily over their entire lifetimes in order to remain entrained to the 24 h day. Left untreated, their free‐running endocrine, metabolic, behavioral, and sleep/wake cycles can be almost as burdensome as not having vision. 相似文献