L-茶氨酸对H2O2致L02细胞损伤的保护作用及其机制研究

研究L-茶氨酸对肝细胞损伤的保护作用及其机制。利用H2O2诱导的LO2肝细胞损伤模型,分别用MTT法检测细胞存活率、测定LDH、流式细胞术检测细胞凋亡率、Western blot法检测Caspase-3和PARP蛋白表达7LBax／Bcl-2比值的变化,评价L-茶氨酸是否能保护H2O2诱导的肝细胞损伤。结果表明,L-茶氨酸能提高H2O2损伤的L02细胞存活率,减少LDH的渗漏,降低肝细胞凋亡,且L-茶氨酸通过抑制caspase-3的激活和PARP的切割及Bax／Bcl-2比值的升高而发挥抗凋亡的作用。L-茶氨酸对肝细胞损伤有一定的治疗和保护作用。     

成年沙田柚树试管嫁接及微繁殖的研究

分别以两类沙田柚侧芽为接穗、酸柚为砧木进行了试管嫁接,结果表明:不同嫁接方式、接穗大小以及不同激素处理均直接影响到试管嫁接成活率.对大田侧芽而言,接穗大小以茎尖为宜,1.0mg/LGA3或0.5mg/L6-BA处理效果较佳,嫁接成活率分别达50%和30%;对侧枝沙培萌发的侧芽而言,接穗大小以茎尖 1个节间为宜,2.0mg/LGA3或0.5mg/L6-BA处理效果较佳,嫁接成活率分别达90%和80%.在相同条件下,后者的嫁接成活率一般明显高于前者.两种沙田柚嫁接苗的试管微繁殖没有明显区别,在MS 6-BA0.1mg/L培养基上均可分化不定芽,继代的嫁接成活率可达90%以上.     

海藻酸-SiO2杂化凝胶固定化洋葱伯克霍尔德茵脂肪酶的研究

利用四乙氧基硅烷（TEOS）原位水解法将SiO2掺杂于海藻酸（ALG）凝胶中,通过双交联制备出新型ALG—SiO2杂化凝胶以固定化洋葱伯克霍尔德菌脂肪酶。结果表明,固定化酶的最优条件：质量分数为2．0％的ALG、0．2mol／LCaCl2、V（ALG）／V（TEOS）为5、加酶量为1gALG加100mg酶粉、固定化60min、采用直径为0．8mm的针头滴定、真空冷冻干燥。在此条件下,酶蛋白的包埋率可达100％,酶活回收率可达91％。固定化酶的最适pH为8．0,最适作用温度为50℃,重复使用8次后,酶活性仍能保持80％以上。ALG—Si02杂化凝胶的场扫描电镜（FESEM）观察发现凝胶的整体构造仍然是海藻酸凝胶骨架;与ALG凝胶平滑的内部相比较,杂化凝胶仍具有完整的网络结构,但内部更为粗糙,结构更为致密。     

2000年诺贝尔生理学／医学奖与神经科学发展

20 0 0年 1 0月 9日 ,ＫａｒｏｌｉｎｓｋａＩｎｓｔｉｔｕｔｅｔ诺贝尔委员会决定将 2 0 0 0年诺贝尔生理学 /医学奖授予ＡｒｖｉｄＣａｒｌｓｓｏｎ ,ＰａｕｌＧｒｅｅｎｇａｒｄ和ＥｒｉｃＫａｎｄｅｌ三位科学家 ,作为对他们在“神经系统信号转导”方面至关重要发现的奖励[1] 。人大脑中有超过一千亿个神经元 ,他们通过极其复杂的神经网络彼此相连。从一个神经元发出的信息通过不同的化学神经递质传递给另一个神经元 ,这一过程发生在神经元间相接的特殊位点 ,称为“突触” ,一个神经元可以有数以千计这样的突触和其它神经元接触。三位诺…     

Arabidopsis DEMETER-LIKE proteins DML2 and DML3 are required for appropriate distribution of DNA methylation marks

Cytosine DNA methylation is a stable epigenetic mark for maintenance of gene silencing across cellular divisions, but it is a reversible modification. Genetic and biochemical studies have revealed that the Arabidopsis DNA glycosylase domain-containing proteins ROS1 (REPRESSOR OF SILENCING 1) and DME (DEMETER) initiate erasure of 5-methylcytosine through a base excision repair process. The Arabidopsis genome encodes two paralogs of ROS1 and DME, referred to as DEMETER-LIKE proteins DML2 and DML3. We have found that DML2 and DML3 are 5-methylcytosine DNA glycosylases that are expressed in a wide range of plant organs. We analyzed the distribution of methylation marks at two methylated loci in wild-type and dml mutant plants. Mutations in DML2 and/or DML3 lead to hypermethylation of cytosine residues that are unmethylated or weakly methylated in wild-type plants. In contrast, sites that are heavily methylated in wild-type plants are hypomethylated in mutants. These results suggest that DML2 and DML3 are required not only for removing DNA methylation marks from improperly-methylated cytosines, but also for maintenance of high methylation levels in properly targeted sites.     

Abnormal Pelage Color in an Isolated Population of <Emphasis Type="Italic">Alouatta guariba clamitans</Emphasis> Cabrera, 1940 in South Brazil

We located 4 brown howlers (1 adult male, 2 adult females, and 1 juvenile male) showing abnormally lighter pelage in 3 social groups comprising 5, 6, and 9 individuals in a 20 ha-forest fragment in the State of Rio Grande do Sul, Brazil. Two additional groups composed only of normally colored individuals also live in the fragment, which is isolated from nearby fragments by 267–1009 m. They were the only brown howlers with abnormal pelage color out of a total of 386 individuals belonging to 67 groups in 21 fragments in the 5876-ha study area. The isolation of the forest fragment, its high howler density (2.2 individuals⁄ha), and large group size (8.8 ± 2.4 individuals) may decrease the likelihood of successful immigration into the population, leading to an increased probability of inbreeding that may facilitate the expression of rare alleles.     

Microhabitat selection by tadpoles of <Emphasis Type="Italic">Buergeria japonica</Emphasis> inhabiting the coastal area

Microhabitat selection is particularly important to increase the survival rate and reproductive success of animals inhabiting heterogeneous environments. I investigated microhabitat selection of Buergeria japonica tadpoles inhabiting the stream in a coastal area to reveal how animals select their appropriate habitat under heterogeneous and unstable environments on the subtropical Okinawa Island of Japan. Tadpoles are sensitive to subtle environmental changes, and the mouths of streams in coastal areas that have intense environmental fluctuations such as desiccation and sudden changes in current velocity would be risky habitat for tadpoles. Tadpoles of B. japonica can inhabit both lotic and lentic systems. Field observations showed that, among six physical factors (water depth, water temperature, salinity, pH, current velocity, and substrate), current velocity and water temperature were key factors in microhabitat selection by tadpoles. It is likely that tadpoles stay at low current velocity sites to reduce the probability of being washed out to the sea by a sudden squall and that selection of warmer sites would accelerate development of tadpoles so as to escape the heterogeneous aquatic habitat sooner.     

NaCl、Na_2SO_4和Na_2CO_3胁迫对小麦叶片自由基含量及质膜透性的比较研究

分别用浓度为２５ｍｍｏｌ／Ｌ、５０ｍｍｏｌ／Ｌ、１００ｍｍｏｌ／Ｌ和２００ｍｍｏｌ／Ｌ的ＮａＣｌ、Ｎａ２ＳＯ４和Ｎａ２ＣＯ３的营养液培养小麦４ｄ,较之不含盐的营养液,其自由基含量上升,产生速率增加,叶片质膜透性增加。不同盐的影响也不同,在低浓度时,ＮａＣｌ的影响大于Ｎａ２ＳＯ４,高浓度时,ＮａＣｌ影响小于Ｎａ２ＳＯ４,Ｎａ２ＣＯ３的影响最为显著。实验结果也表现出小麦叶片自由基含量和质膜透性呈现较好的相关性。因此可认为,盐胁迫促使自由基含量增加,自由基通过过氧化作用影响质膜透性,从而影响植物的生长。