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光强转换对不同生长环境下桑树叶片光化学效率的影响 总被引:3,自引:0,他引:3
以桑树品种‘蒙古桑’为试验材料,利用叶绿素荧光技术研究了光强转换对生长在不同光强下的桑树叶片实际光化学效率(ΦPSⅡ)、电子传递速率(ETR)和非光化学淬灭(NPQ)的影响,分析了非光化学淬灭(NPQ)3个组分的变化.结果表明:当光强从黑暗或弱光转换到自然光条件下,自然光桑树叶片的光量子转化效率高于弱光叶片,ΦPSⅡ、ETR诱导平衡较快,NPQ诱导呈先升后降趋势.自然光叶片在强光下状态转换淬灭组分(qT)占NPQ的18%,而弱光叶片qT仅占NPQ的7%.与弱光桑树叶片相比,自然光桑树叶片可以通过较高的光量子转化效率和较强的调节激发能在PSⅠ和PSⅡ之间的分配能力来适应光强的变化. 相似文献
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周期节律是由内在时钟系统介导的多重生物过程的周期循环.周期节律系统是由位于大脑的视神经交叉上核的中央时钟系统和位于外周的几乎存在于所有细胞的外周时钟系统组成的.中央时钟与外周时钟都能够对生物体的生理过程进行调控,如激素的分泌、能量代谢、细胞增殖、DNA损伤修复等.而周期节律基因的表达失调,对其下游靶基因包括细胞周期相关基因的表达,以及细胞抗凋亡能力等产生重要的影响.而这一结果会导致细胞增殖加速及基因组不稳定,并可能促进肿瘤的发生.许多实验证据表明,肿瘤是一种节律相关的生理失调,在许多肿瘤中都发现周期节律遭到破坏,如乳腺癌、前列腺癌、子宫内膜癌等.本文将从周期节律对细胞周期进程及对细胞DNA损伤修复的影响来讨论分子水平上细胞的周期节律与肿瘤发生发展的关系. 相似文献
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Yuliya V. Kucherenko Shefalee K. Bhavsar Valentin I. Grischenko Uwe R. Fischer Stephan M. Huber Florian Lang 《The Journal of membrane biology》2010,235(3):177-189
Excessive glucose concentrations foster glycation and thus premature aging of erythrocytes. The present study explored whether
glycation-induced erythrocyte aging is paralleled by features of suicidal erythrocyte death or eryptosis, which is characterized
by cell membrane scrambling with subsequent phosphatidylserine exposure at the cell surface and cell shrinkage. Both are triggered
by increases of cytosolic Ca2+ concentration ([Ca2+]i), which may result from activation of Ca2+ permeable cation channels. Glycation was accomplished by exposure to high glucose concentrations (40 and 100 mM), phosphatidylserine
exposure estimated from annexin binding, cell shrinkage from decrease of forward scatter, and [Ca2+]i from Fluo3-fluorescence in analysis via fluorescence-activated cell sorter. Cation channel activity was determined by means
of whole-cell patch clamp. Glycation of total membrane proteins, immunoprecipitated TRPC3/6/7, and immunoprecipitated L-type
Ca2+ channel proteins was estimated by Western blot testing with polyclonal antibodies used against advanced glycation end products.
A 30–48-h exposure of the cells to 40 or 100 mM glucose in Ringer solution (at 37°C) significantly increased glycation of
membrane proteins, hemoglobin (HbA1c), TRPC3/6/7, and L-type Ca2+ channel proteins, enhanced amiloride-sensitive, voltage-independent cation conductance, [Ca2+]i, and phosphatidylserine exposure, and led to significant cell shrinkage. Ca2+ removal and addition of Ca2+ chelator EGTA prevented the glycation-induced phosphatidylserine exposure and cell shrinkage after glycation. Glycation-induced
erythrocyte aging leads to eryptosis, an effect requiring Ca2+ entry from extracellular space. 相似文献
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Effects of isotonic solutions of polyethylene (glycol) 1500 (PEG-1500) and sucrose on Ca2+ influx into ATP-depleted red blood cells were studied using the Ca2+ -sensitive fluorescent dye fura-2AM. When incubated in isotonic low ionic strength media (containing 2 mM CaCl2 in addition to sucrose and PEG-1500), the initial rate of Ca2+ influx was higher than that for the cells in physiological (normal ionic strength) medium. After 20 minutes of incubation in the PEG-1500-containing solution, a 10-fold increase of Ca2+ influx was observed, whereas in the sucrose medium the rate of Ca2+ influx decreased compared to that in physiological medium. 1H-NMR data provided no evidence of direct interaction between PEG-1500 and the erythrocyte membrane. Moreover, PEG-1500 did not affect lipid peroxidation (LPO) induction in erythrocyte membranes. We propose that a change in the hydrogen environment of Ca2+ -ATPase of the erythrocytes suspended in the PEG-1500 solution is the primary cause of altered Ca2+ homeostasis in these cells. The activation of the Ca2+ -ATP-ase in sucrose medium may result in an incomplete suppression of the Ca2+-pump activity in ATP-depleted cells, which is accelerated when calmodulin binds with the Ca2+-ATP-ase under the conditions of rapid Ca2+ accumulation. 相似文献
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A mathematical model of electron excitation energy transport between molecular probes sorbed on the polymeric chain in solution was proposed. The kinetics of the process was described in terms of the conception of stochastic changes in macromolecule conformation. The results of computer simulation and the analytical expressions obtained in the framework of the perturbation theory for the cases of low transfer rate and/or fast conformation motion of the macrochain are presented. A channel of nonlinear deactivation as a result of binary annihilation of closely-spaced excited centers was considered. Expressions for the effective rate of mutual quenching and delayed annihilation fluorescence of the probe were obtained. Time dependencies of typical luminescent signals and parameteric curves of relative fluorescence quantum yield are presented. 相似文献
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