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51.
给出群分次环A=Ag的Jacobson根与J(A1)的各种关系,推广群环的相应结论。 相似文献
52.
53.
R. Hardeland 《Cellular and molecular life sciences : CMLS》1993,49(8):614-622
The bioluminescent dinoflagellateGonyaulax polyedra contains various indoleamines, in particular, melatonin and 5-methoxytryptamine, as well as enzymes of their biosynthetic pathway. Melatonin exhibits a high-amplitude circadian rhythm characterized by a dramatic increase shortly after the onset of darkness. The maximum of melatonin is followed by a peak of 5-methoxytryptamine. These 5-methoxylated indoleamines seem to be involved in the mediation of the information darkness.G. polyedra shows a short-day response, which consists in the formation of asexual cysts. Light break experiments demonstrate the photoperiodic nature of this reaction. Cells become sensitive to short days only upon exposure to a lowered temperature (<16°C). Melatonin mimics the short-day effect, but only at decreased temperature. 5-Methoxytryptamine is even a better inducer of cyst formation, acting also at 20°C and in any lighting schedule, including LL. Cyst induction is associated with stimulation of bioluminescence and cytoplasmic acidification. A model on the intracellular pathway of photoperiodic information transduction assumes increased deacetylation of melatonin under cyst-inducing conditions, binding of 5-methoxytryptamine to the membrane of an acidic vacuole, proton transfer to the cytoplasm, and decreased intracellular pH as the stimulus for encystment. Melatonin shows the property of a scavenger of superoxide anions. This reaction, which is efficiently catalyzed by hemin, leads to the formation of a substituted kynuramine (AFMK). Destruction of melatonin by light-induced superoxide anions in the presence of cellular hemin may represent a property which, during evolution, has made this molecule suitable as an indicator of darkness. On the other hand, AFMK, which is formed under illumination, might have become a mediator of the information light. Photoperiodism inGonyaulax shows surprising parallels to that in mammals, but allows the analysis of this phenomenon at an entirely cellular level. 相似文献
54.
新型钛基二氧化铅电极降解苯胺的试验研究 总被引:3,自引:0,他引:3
采用自制钌钛复合氧化物的二氧化铅电极为阳极、石墨为阴极降解苯胺废水,在碱性(pH=9.0)和酸性(pH=3.0)条件下分别达到了85.1%、84、9%、实验表明自制的二氧化铅电极对苯胺废水有良好的催化效果,羟基自由基的生成有利于苯胺的降解。 相似文献
55.
通过建立力竭跑台训练模型,测试大鼠骨骼肌组织超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性、谷胱甘肽过氧化物酶(GSH-Px)活性、丙二醛(MDA)含量和ATP酶活性,探讨沙苑子对力竭跑台训练大鼠骨骼肌组织自由基代谢、ATP酶活性和运动能力的影响.结果显示,与安静组比较,运动力竭组SOD、CAT和GSH-Px活性降低,MDA含量升高;沙苑子组大鼠骨骼肌组织活性显著高于对照组,MDA含量明显低于相应对照组(P<0.01);运动力竭组Na 、K -ATPase和Ca2 、Mg2 -ATPase活性与安静组比较降低,沙苑子组大鼠骨骼肌组织ATPase活性显著高于对照组.沙苑子可显著提高运动大鼠抗氧化的功能,提高运动大鼠骨骼肌组织ATPase活性,具有较强抗氧化能力,使大鼠运动能力有了明显提高. 相似文献
56.
57.
侯波 《河北师范大学学报(自然科学版)》2003,27(1):12-14
通过引入弱g-正则元的概念,对于无单位元分次环R,给出以内部元素刻画的分次Brown-McCoy根BMG(R)。证明了任何分次环都有1个分次Brown-McCoy根,并且当R有1时,BMG(R)即为通常定义的BMgr(R)。另外还证明了BMG(R)具有遗传性。 相似文献
58.
报道了一种合成吡啶基氮氧自由基的新方法,与传统方法对比,缩短了反应时间,提高了产率,是合成吡啶基氮氧自由基的一种简便方法. 相似文献
59.
In renal carcinoma cells (RCC4) hypoxia inducible factor-1 (HIF-1) is constitutively expressed due to a von Hippel Lindau
protein deficiency, but can be degraded by calpain, independently of the 26S proteasome, when exposed to hypoxia/nitric oxide
(NO). In this study we examined molecular mechanisms to explain calpain activation. The inability of hypoxia/NO to degrade
HIF-1α in respiratory-deficient RCC4-ρ0 cells pointed to the requirement for mitochondria-derived reactive oxygen species.
A prerequisite for O
2
−
in combination with NO to destabilize HIF-1α was corroborated in RCC4-p0 cells, when the redox cycler 2,3-dimethoxy-1,4-naphthoquinone
was used as a source of superoxide. Degradation of HIF-1α required intracellular calcium transients and calpain activation.
Using uric acid to interfere with signal transmission elicited by NO/O
2
−
blocked HIF-1α degradation and attenuated a calcium increase. We conclude that an oxidative signal as a result of NO/O
2
−
coformation triggers a calcium increase that activates calpain to degrade HIF-1α, independently of the proteasome.
Received 14 August 2007; received after revision 4 October 2007; accepted 22 October 2007 相似文献
60.
亚甲蓝光敏反应对腹水型肝癌细胞(HepA)DNA合成具有明显的抑制作用,对DNA分子具有明显的降解作用,降解作用随照光时间的延长而加剧,避光组织细胞DNA分子也有一定的降解,但照光组的降解作用明显高于避光组。 相似文献