环境因子和生物因子对黄河三角洲滨海湿地土壤呼吸的影响

采用Li-8150多通道土壤呼吸自动测量系统对黄河三角洲滨海湿地土壤呼吸进行全年连续测定,同步测量了温度、土壤含水量、地上生物量以及叶面积指数等环境因子和生物因子.结果表明: 土壤呼吸日动态在全年尺度上多呈单峰型,但在受到土壤封冻和地表积水干扰时,土壤呼吸日动态呈多峰型.土壤呼吸具有明显的季节动态特征,总体呈单峰型,年平均土壤呼吸速率为0.85 μmol CO₂·m^-2·s^-1,生长季平均土壤呼吸速率为1.22 μmol CO₂·m^-2·s^-1.在全年尺度上,土壤温度是滨海湿地土壤呼吸的主要控制因子,可解释全年土壤呼吸87.5%的变化.在生长季尺度上,土壤含水量和叶面积指数对土壤呼吸的协同影响达到85%.     

小鼠成纤维细胞凋亡与bcl-2结合蛋白

为检测细胞凋亡过程中bcl-2基因的结合蛋白,用PCR技术扩增小鼠bcl-2基因(mbcl-2)调控区,经亚克隆后的序列分析证实其准确性.用5-氟尿嘧啶(5-Fu)诱导小鼠成纤维细胞(C3H 10 T1/2 Cl 8)凋亡,以此PCR产物作探针,对上述细胞的核蛋白质粗提物进行迁移位移法(EMSA)与DNA-蛋白质印迹分析.结果表明,细胞核内一分子质量为53 ku的结合蛋白与mbcl-2调控区的结合信号在5-Fu刺激12 h后明显增强,而一种100 ku的DNA结合蛋白与该区的结合信号在5-Fu刺激12 h后明显减弱.因而,p53蛋白有可能是bcl-2的负转录因子,100 ku的DNA结合蛋白有可能是bcl-2的正转录因子.     

DNA损伤与细胞周期调控

DNA损伤和损伤后修复可引起细胞周期阻滞,这一事件由三个阶段组成：损伤的识别,损伤信号的传递以及细胞周期阻滞.在某些情况,这种细胞周期阻滞会失效.     

光质、光强和光期对水母雪莲愈伤组织生长和黄酮生物合成的影响

白光、蓝光、红光和远红光等不同光质照射及不同的白光强度对水母雪莲愈伤组织生长、苯丙氨酸氨基裂解酶（ＰＡＬ） 活性及黄酮合成有不同的影响。红光明显促进愈伤组织的生长,但强烈抑制ＰＡＬ活性和黄酮的合成。蓝光对愈伤组织生长无明显影响,但显著提高ＰＡＬ 活性和黄酮的合成。白光的作用介于红光和蓝光之间。远红光的作用与蓝光相似,但作用比较弱。每天１６ ｈ 蓝光加８ ｈ 白光和８ ｈ 蓝光加１６ ｈ 白光的组合产生最高的黄酮含量和黄酮生产率。     

脓毒血症大鼠心肌II型磷脂酶A_2活性变化及其调控

观察了脓毒血症大鼠心肌ＩＩ型ＰＬＡ２ 活性、蛋白质含量及其ｍ ＲＮＡ 的变化。结果发现, 脓毒血症早期与晚期心肌ＩＩ型ＰＬＡ２ 活性较对照组分别降低２５ ．０ ％ （Ｐ ＜ ０ ．０５）及增高４７．６ ％ （Ｐ ＜ ０ ．０１）,ＩＩ型ＰＬＡ２ 蛋白质含量分别降低２７．０％ 及增高４８ ．０ ％（ 均Ｐ ＜ ０ ．０１）; 心肌ＩＩ型ＰＬＡ２ ｍ ＲＮＡ合成率与含量呈现类似的双相变化, 在脓毒血症早、晚期ｍＲＮＡ 合成率分别降低４５．０％ 和升高７０．０ ％ （均Ｐ ＜ ０ ．０１）,ｍＲＮＡ含量分别降低３４．１ ％ 和增加１５７ ．０％ （均Ｐ＜ ０ ．０１） 。脓毒血症早、晚期心脏ＩＩ型ＰＬＡ２ ｍ ＲＮＡ半衰期无显著变化（Ｐ ＞ ０．０５） 。实验结果表明大鼠脓毒血症发生过程中心肌ＩＩ型ＰＬＡ２ 活性呈现出先下降后升高的变化, 这一变化受其ｍＲＮＡ 转录水平的调节。     

Assembly characteristics of plant keratin intermediate filaments in vitro

After selective extraction and purification, plant keratin intermediate filaments were reassembled in vitro. Scanning tunneling microscope (STM) and transmission electron microscope (TEM) micrographs showed that acidic keratins and basic keratins can assemble into dimers and further into 10 nm filaments in vitro. In higher magnification images, it can be seen that fully assembled plant keratin intermediate filaments consist of several thinner filaments of 3 nm in diameter, which indicates the formation of protofilaments in the assembly processes. One of the explicit features of plant keratin intermediate filaments is a 24—25 nm periodic structural repeat alone the axis of beth the 10 nm filaments and protofilaments. The periodic repeat is one of the fundamental characteristic of all intermediate filaments, and demonstrates the half staggered arrangement of keratin molecules within the filaments.     

Mechanism of Change in the Cation-Induced Excitation Energy Distribution Between PSⅡ and PS Ⅰ in the Chloroplast Membrane from Zostera marina

The interrelations between thylakoid polypeptide components and Mg2+-induced Chl a fluorescence and thylakoid surface charge changes were investigated in Zostera marina chloroplasts treated with Ca2+ and trypsin. It was observed that: 1. The increase of Mg2+- induced PS Ⅱ fluorescence intensity was closely related to the decrease of Mg2+-induced surface charge density of the thylakoid membrane in the normal chloroplast; 2. Removal of the 32～34 kD polypeptides of the thylakoid surface by Ca2+ extraction of the chloroplast did not affect the Mg2+-induced phenomena; 3. If the Ca2+-treated chloroplast was further digested by trypsin to remove the 26 kD polypeptide of the membrane surface, the Mg2+-induced phenomena disappeared completely. These results clearly indicated that the 26 kD polypeptide of thylakoid surface is the specific acting site of the cation that induced these two correlated phenomena in the chloroplast from Zostera marina. The mechanism on the regulating effect of the cation on excitation energy distribution between PS Ⅱ and PS Ⅰ was discussed.     

Mg2+ Induced Fluorescence Change in Relation to Thylakoid Surface Electric Charge in Two Varieties of Soybean Chloroplasts

The effects of Mg2+ concentration on chlorophyll a light-in-duced variable fluorescence and eleetrophoretie velocity of chloroplasts obtained from two varieties of soybean (Ji-Pei No. 1 and Feng-Shou Yellow) were recorded. The light induced variable fluorescence yield and the eleetrophoretie mobility of two kinds of ehloroplasts in the suspending medium containing low level of salt differs from each other. But, the fluorescence yield of chloroplast membranes from two varieties of soybean is relative to that of eleetrophoretic mobility. The pattern of kinetic change of Mg2+ induced variable fluorescence intensity is similar to that of eleetrophoretie mobility. The optimum concentrations of Mg2+ required for the effect on chlorophyll fluorescence and the electrophoretie velocity change are also similar These results indicate that Mg2+ induced excitation energy distribution change between the two photosystems is intimately related to Mg2+-indueed alteration of thylakoil membrane surface eleetrostat.ie property. The possible role of earboxyl group of proteins on Mg2+ induced effects has been discussed in this paper.     

Studies on Photoperiod-sensitive Genic Malesterile Rice in Terms of Developmental Biology

Investigations on the mechanism of fertility alternation and its regulation in photoperiodsensitive genic male-sterile rice (PGMR) have received considerable attention due to the important significance in both basic research of plant developmental biology and PGMR potential value in the development of two line hybrid rice seed programs. The present review described the major achivements of study on PGMR in terms of developmental biology: phytochrome was found to be the photoreceptor involved in photoperiod-modulated fertility alternation in PGMR; chloroplasts played a significant role in the photoperiodic signal transduction; gibberellins and auxin might be the chemical signals for fertility regulation; identifying of special proteins promoted the exploration of specially expressed genes related to fertility regulation in PGMR. The author hypothesized that four main steps of photoperiodic signal transduction were involved in the realization of male sterility-multistage magni-fied injury effects to normal function of PGMR induced by long-day stress. There was defect in the anther development of PGMR, and the resistance of anthers to environmental stress was weakened. The multifactor coaction model for photoperiod regulation in fertility alternation in PGMR was proposed and discussed.