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991.
目的:本研究旨在探讨低糖低氧对大鼠神经干细胞增殖和代谢的影响。方法:实验采用不同葡萄糖浓度的培养基以及不同的氧浓度进行处理:高糖(4.5g/L)、低糖(1.4g/L);常氧(20%O2)、低氧(3%O2);神经干细胞(NSCs)来自孕13.5d的大鼠中脑,在不同糖浓度下培养至第三代进行低氧处理,分为低糖常氧(L+N)、低糖低氧(L+H)、高糖常氧(H+N)、高糖低氧(H+H)组。神经干细胞在上述四种条件下分别培养1、3、5d后,利用CCK-8检测神经干细胞的增殖情况;生化分析仪测定细胞培养上清液中葡萄糖、乳酸、丙酮酸浓度;RT-PCR方法检测葡萄糖转运蛋白4(GluT4)、葡萄糖激酶(GK)、丙酮酸激酶(PK)和乳酸脱氢酶(LDH)的表达变化。结果:在低糖低氧条件下培养3d时NSCs的数量增加最为明显;低糖低氧条件下,葡萄糖浓度降低最为显著;而丙酮酸浓度在低糖处理组均高于高糖处理组;同样地,在低糖低氧处理组培养上清中乳酸含量增加的幅度最大;此外,在低糖或低氧时Glut4和PK的表达也明显高于对照组。结论:低氧能促进NSCs的增殖,而以低氧和低糖共同作用时更为明显;在低氧低糖条件下,神经干细胞的代谢发生变化,葡萄糖的利用明显增加,主要通过糖酵解途径代谢产能。 相似文献
992.
993.
Urate oxidase (EC 1.7.3.3) of Chlamydomonas reinhardii cells grown on purines and purine derivatives has been partially characterized. Crude enzyme preparations have a pH optimum of 9.0, require O2 for activity, have an apparent Km of 12 μ M for urate, and are inhibited by high concentrations of this substrate. Enzyme activity was particularly sensitive to metal ion chelating agents like cyanide, cupferron, diethyldithiocarbamate and o -phenanthroline, and to structural analogues of urate like hypoxanthine and xanthine. Chlamydomonas cells grow phototrophically on adenine, guanine, hypoxanthine, xanthine, urate, allantoin or allantoate as sole nitrogen source, indicating that in this alga the standard pathway of aerobic degradation of purines of higher plants, animals and many microorganisms operates. As deduced from experiments in vivo , urate oxidase from Chlamydomonas is repressed in the presence of ammonia or nitrate. 相似文献
994.
David R. Thomas Azis Araffin M.Noh Hj Jalil Bob C.S. Yong Robert J. Cooke Clifford Wood 《Phytochemistry》1981,20(6):1241-1244
Carnitine increases chlorophyll production in greening barley leaves. [Methyl-14C]carnitine fed to greening leaves was not utilized as a carbon sou 相似文献
995.
Paul L. Wood 《Peptides》1983,4(5):595-601
Biochemical measurements of DOPAC, HVA, DA and 3-MT allow the assessment of both DA metabolism in nerve endings and DA release into the synaptic cleft. Using these biochemical indices of DA neuronal activity, we have examined the actions of mu, delta and kappa opiate receptor agonists on the nigrostriatal pathway. These studies indicate that delta and mu2 isoreceptors regulate activity in the nigrostriatal pathway of the rat, mouse, gerbil and hamster. In general, increased DA metabolism is observed; however, increased DA release is only evident in pathways devoid of a presynaptic clamping action. As indicated with enkephalinase inhibitors, these enkephalinergic inputs to dopaminergic neurons possess a phasic ongoing activity. 相似文献
996.
997.
A reconstituted glycolytic system has been established from individually purified enzymes to simulate the conversion of glucose to ethanol plus CO2 by yeast. Sustained and extensive conversion occurred provided that input of glucose matched the rate of ATP degradation appropriately.ATPase activity could be replaced by arsenate, which uncoupled ATP synthesis from glycolysis. The mode of uncoupling was investigated, and it was concluded that the artificial intermediate, 1-arseno-3-phosphoglycerate, has a half-life of no more than a few milliseconds. Arsenate at 4 mM concentration could simulate the equivalent of 10 μmol ml?1 min?1 of ATPase activity.The reconstituted enzyme system was capable of totally degrading 1 M (18% w/v) glucose in 8 h giving 9% (w/v) ethanol. The levels of metabolites during metabolism were measured to detect rate-limiting steps.The successful operation of the reconstituted enzyme system demonstrates that it is possible to carry out complex chemical transformations with multiple enzyme systems in vitro. 相似文献
998.
Pedersen PL 《Journal of bioenergetics and biomembranes》2007,39(1):1-12
This introductory article to the review series entitled “The Cancer Cell’s Power Plants as Promising Therapeutic Targets”
is written while more than 20 million people suffer from cancer. It summarizes strategies to destroy or prevent cancers by
targeting their energy production factories, i.e., “power plants.” All nucleated animal/human cells have two types of power
plants, i.e., systems that make the “high energy” compound ATP from ADP and P
i
. One type is “glycolysis,” the other the “mitochondria.” In contrast to most normal cells where the mitochondria are the
major ATP producers (>90%) in fueling growth, human cancers detected via Positron Emission Tomography (PET) rely on both types
of power plants. In such cancers, glycolysis may contribute nearly half the ATP even in the presence of oxygen (“Warburg effect”).
Based solely on cell energetics, this presents a challenge to identify curative agents that destroy only cancer cells as they
must destroy both of their power plants causing “necrotic cell death” and leave normal cells alone. One such agent, 3-bromopyruvate
(3-BrPA), a lactic acid analog, has been shown to inhibit both glycolytic and mitochondrial ATP production in rapidly growing
cancers (Ko et al., Cancer Letts., 173, 83–91, 2001), leave normal cells alone, and eradicate advanced cancers (19 of 19)
in a rodent model (Ko et al., Biochem. Biophys. Res. Commun., 324, 269–275, 2004). A second approach is to induce only cancer
cells to undergo “apoptotic cell death.” Here, mitochondria release cell death inducing factors (e.g., cytochrome c). In a
third approach, cancer cells are induced to die by both apoptotic and necrotic events. In summary, much effort is being focused
on identifying agents that induce “necrotic,” “apoptotic” or apoptotic plus necrotic cell death only in cancer cells. Regardless
how death is inflicted, every cancer cell must die, be it fast or slow. 相似文献
999.
Caparrós-Martín JA Reiland S Köchert K Cutanda MC Culiáñez-Macià FA 《Plant molecular biology》2007,63(4):505-517
We have isolated two Arabidopsis thaliana genes, AtGpp1 and AtGpp2, showing homology with the yeast low molecular weight phosphatases GPP1 and GPP2, which have a high specificity for dl-glycerol-3-phosphate, and moreover homology with DOG1 and DOG2 that dephosphorylate 2-deoxyglucose-6-phosphate. Using a comparative
genomic approach, the corresponding genes were identified as conceptual translated haloacid dehalogenase-like hydrolase proteins.
AtGpp1 (gi 18416631) and AtGpp2 (gi 18423981), encode proteins that share 95% identity, with a predicted Mw of 33 and 27 kDa and a pI of 7.8 and 5.6, respectively.
Both isoforms have a high specificity for dl-glycerol-3-phosphate, pH optima at 7.0, and K
m in the range of 3.5–5.2 mM. AtGpp1 and AtGpp2 are expressed throughout development in all plant organs, most strongly in siliqua, and expression is not affected by osmotic,
ionic or oxidative stress. A putative chloroplast transit peptide cTP-containing sequence is appended to the AtGpp1 N-terminus
while AtGpp2, devoid of this tail, is predicted to be in the extraplastidial cytosol; this compartmenting was further confirmed
by subcellular fractionation. An immunohystochemical localization study, using anti-AtGpp2 antibodies, indicates that the
AtGpp proteins are mainly restricted to the meristem of immature flower and vascular elements of the root, shoot, leave, siliqua
and developing embryo. Considerable immunoreaction was observed in the cytoplasm as well as in plastid compartments of distinct
cells types from different heterotrophic Arabidopsis tissues, and particularly localised within phloem companion cells. Transgenic Arabidopsis plants, with gain of AtGpp2 function, show altered phosphatase activity rates and improved tolerance to salt, osmotic and oxidative stress. 相似文献
1000.
Methanomicrococcus blatticola is an obligately anaerobic methanogen that derives the energy for growth exclusively from the reduction of methylated compounds to methane with molecular hydrogen as energy source. Competition for methanol (concentration below 10 microM) and H(2) (concentration below 500 Pa), as well as oxidative stress due to the presence of oxygen are likely to occur in the peripheral region of the cockroach hindgut, the species' normal habitat. We investigated the ecophysiological properties of M. blatticola to explain how it can successfully compete for its methanogenic substrates. The organism showed affinities for methanol (K(m)=5 microM; threshold<1 microM) and hydrogen (K(m)=200 Pa; threshold <0.7 Pa) that are superior to other methylotrophic methanogens (Methanosphaera stadtmanae, Methanosarcina barkeri) investigated here. Thermodynamic considerations indicated that 'methanol respiration', i.e. the use of methanol as the terminal electron acceptor, represents an attractive mode of energy generation, especially at low hydrogen concentrations. Methanomicrococcus blatticola exploits the opportunities by specific growth rates (>0.2 h(-1)) and specific growth yields (up to 7 g of dry cells per mole of methane formed) that are particularly high within the realm of mesophilic methanogens. Upon oxygen exposure, part of the metabolic activity may be diverted into oxygen removal, thus establishing appropriate anaerobic conditions for survival and growth. 相似文献