悬浮培养红豆杉细胞活力及存活率与生长周期的关系

用TTC法制定红豆杉细胞活力,用中性红测细胞存活率,探讨生长周期中细胞活力及存活率的变化规律。结果显示延迟期细胞活力最强,对数生长期活力较低,稳定期活力最低;而细胞存活率在整个周期中基本保持在70%-80%。     

Male sterility at extreme temperatures: a significant but neglected phenomenon for understanding Drosophila climatic adaptations

The thermal range for viability is quite variable among Drosophila species and it has long been known that these variations are correlated with geographic distribution: temperate species are on average more cold tolerant but more heat sensitive than tropical species. At both ends of their viability range, sterile males have been observed in all species investigated so far. This symmetrical phenomenon restricts the temperature limits within which permanent cultures can be kept in the laboratory. Thermal heat sterility thresholds are very variable across species from 23 degrees C in heat sensitive species up to 31 degrees C in heat tolerant species. In Drosophila melanogaster, genetic variations are observed among geographic populations. Tropical populations are more tolerant to heat induced sterility and recover more rapidly than temperate ones. A genetic analysis revealed that about 50% of the difference observed between natural populations was due to the Y chromosome. Natural populations have not reached a selection limit, however: thermal tolerance was still increased by keeping strains at a high temperature, close to the sterility threshold. On the low temperature side, a symmetrical reverse phenomenon seems to exist: temperate populations are more tolerant to cold than tropical ones. Compared to Mammals, drosophilids exhibit two major differences: first, male sterility occurs not only at high temperature, but also at a low temperature; second, sterility thresholds are not evolutionarily constrained, but highly variable. Altogether, significant and sometimes major genetic variations have been observed between species, between geographic races of the same species, and even between strains kept in the laboratory under different thermal regimes. In each case, it is easily argued that the observed variations correspond to adaptations to climatic conditions, and that male sterility is a significant component of fitness and a target of natural selection.     

影响4类作物种子寿命的主要贮藏环境因素

为研究利用存活比、影响种子贮藏寿命和生活力的主要贮藏环境因子来预测高粱、苋属、甜荞麦和莴苣种子批的寿命和生活力,3个含水量水平的高粱和苋属的8个种子批被贮藏在20℃、30℃和40℃的贮藏温度下长达810 d。以概率回归和存活比线性回归方法,贮藏试验获得的高粱、苋属及文献报道的甜荞麦、莴苣种子批的发芽率和贮藏时间的成套数据,被用于估算不同种子批的平均贮藏寿命(p50)和种子死亡时间分布的标准差(σ),同时两种回归方程的拟合性也被比较;两种方法估算出的p50和σ则分别被用于对贮藏环境因子:贮藏温度(t)及其平方、种子含水量(m)及其对数(logm)以及t和m的交互作用(t×m和t×logm)作逐步回归分析,结果表明,用存活比来估算p50、σ是可行的,而且估算出的p50和σ较用概率估算的有统计学意义;贮藏温度和种子含水量的交互作用(t×m)是使4类作物种子快速丧失生活力,减少寿命的主要贮藏环境因子,包含这个因子和存活比的数学模型:G i/G0=A-p/10K-CWT(t×m),预测甜荞麦种子批的发芽率较V i=K i-p/10K-CWT(t×m)有更高的准确性;所以,建议用前者来预测初始发芽率是已知的种子的贮藏寿命和生活力,而用后者预测初始发芽率未被测定的种子的寿命和生活力。     

The beta-amyloid peptide of Alzheimer's disease decreases adhesion of vascular smooth muscle cells to the basement membrane

Cerebral amyloid angiopathy (CAA) is a major feature of Alzheimer's disease pathology. In CAA, degeneration of vascular smooth muscle cells (VSMCs) occurs close to regions of the basement membrane where the amyloid protein (Abeta) builds up. In this study, the possibility that Abeta disrupts adhesive interactions between VSMCs and the basement membrane was examined. VSMCs were cultured on a commercial basement membrane substrate (Matrigel). The presence of Abeta in the Matrigel decreased cell-substrate adhesion and cell viability. Full-length oligomeric Abeta was required for the effect, as N- and C-terminally truncated peptide analogues did not inhibit adhesion. Abeta that was fluorescently labelled at the N-terminus (fluo-Abeta) bound to Matrigel as well as to the basement membrane heparan sulfate proteoglycan (HSPG) perlecan and laminin. Adhesion of VSMCs to perlecan or laminin was decreased by Abeta. As perlecan influences VSMC viability through the extracellular signal-regulated kinase (ERK)1/2 signalling pathway, the effect of Abeta1-40 on ERK1/2 phosphorylation was examined. The level of phospho-ERK1/2 was decreased in cells following Abeta treatment. An inhibitor of ERK1/2 phosphorylation enhanced the effect of Abeta on cell adhesion. The studies suggest that Abeta can decrease VSMC viability by disrupting VSMC-extracellular matrix (ECM) adhesion.     

Environmental predictability of taxonomic and functional community composition in high‐latitude streams

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