排序方式: 共有28条查询结果,搜索用时 15 毫秒
21.
By allowing dimethyl peroxide (10?4M) to decompose in the presence of nitric oxide (4.5 × 10?5M), nitrogen dioxide (6.5 × 10?5M) and carbon tetrafluoride (500 Torr), it has been shown that the ratio k2/k2′ = 2.03 ± 0.47: CH3O + NO → CH3ONO (reaction 2) and CH3O + NO2 → CH3ONO2 (reaction 2′). Deviations from this value in this and previous work is ascribed to the pressure dependence of both these reactions and heterogeneity in reaction (2). In contrast no heterogeneous effects were found for reaction (2′) making it an ideal reference reaction for studying other reactions of the methoxy radical. We conclude that the ratio k2/k2′ is independent of temperature and from k1 = 1010.2±0.4M?1 sec?1 we calculate that k2′ = 109.9±0.4M?1 sec?1. Both k2 and k2′ are pressure dependent but have reached their limiting high-pressure values in the presence of 500 Torr of carbon tetrafluoride. Preliminary results show that k4 = 10.9.0±0.6 10?4.5±1.1/ΘM?1 sec?1 (Θ = 2.303RT kcal mole?1) and by k4 = 108.6±0.6 10?2.4±1.1/ΘM?1 sec?1: CH3O + O2 → CH2O + HO2 (reaction 4) and CH3O + t-BuH → CH3OH + (t-Bu) (reaction 4′). 相似文献
22.
23.
24.
25.
26.
ABSTRACT: BACKGROUND: Cell therapy is a potential therapeutic approach for several neurodegenetative disease, including Huntington Disease (HD). To evaluate the putative efficacy of cell therapy in HD, most studies have used excitotoxic animal models with only a few studies having been conducted in genetic animal models. Genetically modified animals should provide a more accurate representation of human HD, as they emulate the genetic basis of its etiology. RESULTS: In this study, we aimed to assess the therapeutic potential of a human striatal neural stem cell line (STROC05) implanted in the R6/2 transgenic mouse model of HD. As DARPP-32 GABAergic output neurons are predominately lost in HD, STROC05 cells were also predifferentiated using purmorphamine, a hedgehog agonist, to yield a greater number of DARPP-32 cells. A bilateral injection of 4.5x105 cells of either undifferentiated or predifferentiated DARPP-32 cells, however, did not affect outcome compared to a vehicle control injection. Both survival and neuronal differentiation remained poor with a mean of only 161 and 81 cells surviving in the undifferentiated and differentiated conditions respectively. Only a few cells expressed the neuronal marker beta-III-tubulin. CONCLUSIONS: Although the rapid brain atrophy and short life-span of the R6/2 model constitute adverse conditions to detect potentially delayed treatment effects, significant technical hurdles, such as poor cell survival and differentiation, were also sub-optimal. Further consideration of these aspects is therefore needed in more enduring transgenic HD models to provide a definite assessment of this cell line's therapeutic relevance. However, a combination of treatments is likely needed to affect outcome in transgenic models of HD. 相似文献
27.
28.
u: A→H(I), I ε J], and let x: Q→S be the equalizer of ηS and Sη. 相似文献