Interaction of hematopoietic progenitor kinase 1 and c-Abl tyrosine kinase in response to genotoxic stress

The c-Abl protein tyrosine kinase is activated by certain DNA-damaging agents and regulates induction of the stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). The hematopoietic progenitor kinase 1 (HPK1) has also been shown to act upstream to the SAPK/JNK signaling pathway. We report here that exposure of hematopoietic Jurkat T cells to genotoxic agents is associated with activation of HPK1. The results demonstrate that exposure of Jurkat cells to DNA-damaging agents is associated with translocation of active c-Abl from nuclei to cytoplasm and binding of c-Abl to HPK1. Our findings also demonstrate that c-Abl phosphorylates HPK1 in cytoplasm and stimulates HPK1 activity. The functional significance of the c-Abl-HPK1 interaction is supported by the demonstration that this complex regulates SAPK/JNK activation. Overexpression of c-Abl(K-R) inhibits HPK1-induced activation of SAPK/JNK. Conversely, the dominant negative mutant of HPK1 blocks c-Abl-mediated induction of SAPK/JNK. These findings indicate that activation of HPK1 and formation of HPK1/c-Abl complexes are functionally important in the stress response of hematopoietic cells to genotoxic agents.     

Malignant astrocytoma cell attachment and migration to various matrix proteins is differentially sensitive to phosphoinositide 3-OH kinase inhibitors

Phosphoinositide 3-OH kinase (PI3-K) has been shown to play an important role in the signaling pathway necessary for cytoskeletal reorganization in non-astrocytic cells. We investigated the role of PI3-K in U-251 MG human malignant astrocytoma cell adhesion and migration. Attachment of U-251 MG cells to vitronectin, fibronectin, laminin, and collagen was inhibited in a concentration-dependent manner by two specific inhibitors of PI3-K (Wortmannin and LY294002). Attachment to vitronectin, fibronectin, and laminin was more sensitive to inhibition of PI3-K (45% inhibition at 10 nM Wortmannin) than attachment to collagen (25% inhibition at 100 nM Wortmannin). Similarly, migration toward these substrates showed differential sensitivity to inhibition. Attachment of the cells to these matrix proteins resulted in an increase in PI3-K activity, as compared to that of cells in suspension, with attachment to vitronectin resulting in the greatest increase in PI3-K activity. p125 focal adhesion kinase (p125FAK) was found to co-immunoprecipitate with PI3-K from the NP40-soluble cell fraction of a 1% NP40 detergent lysate of cells in the early stages of adhesion to vitronectin and fibronectin, but not during adhesion to collagen. The expression of p125FAK protein and level of phosphorylation were similar on adherence to all three substrates. These data indicate that the sensitivity of U-251MG cell attachment and migration to PI3-K inhibitors is substrate-dependent, and that complex formation of PI3-K and p125FAK correlates with this sensitivity to PI3-K inhibitors. Our data suggest a role for PI3-K and p125FAK complex formation in PI3-K activation.     

太白山大熊猫的分布与保护

该文主要以1993年对太白山大熊猫资源调查和1996年对大熊猫资源调查为基础,对太白山大熊猫的分布与保护进行了分析研究,结果表明:太白山的大熊猫主要分布在秦岭南坡的海棠河、大干沟、小干沟、欠开营河、太白河、龙洞沟和太白山主峰拔仙台东南、秦岭北坡的万泉沟,栖息地面积14?898hm2.分布大熊猫为11只,栖息在海拔1?800～2?900m之间的落叶阔叶林带、桦木林带、巴山冷杉林带下,为我国大熊猫的一块新的栖息地,也是分布的最北界.这块栖息地目前正受到采伐、割竹、旅游、采药等人为活动的干扰和威胁,必须采取保护措施,阻止栖息地的进一步恶化和对大熊猫的干扰.     

小熊猫染色体异染色质的显示

以培养的小熊猫外周淋巴细胞为实验材料,结合Ｃ－显带技术及ＣＭＡ３／ＤＡ／ＤＡＰＩ三竽荧光杂色的方法,对小熊猫的染色体组型、Ｃ－带带型及ＣＭＡ３／ＤＡ／ＤＡＰＩ荧光带带型进行了研究,发现：（１）经Ｃ－显带技术处理,可在小熊猫染色体上呈现出一种极为独特的Ｃ－带带型。在多数染色体上可见到丰富的插入Ｃ－带及端粒Ｃ－带。而着丝区仅显示弱阳性Ｃ－带;（２）除着丝粒区外,ＣＭＡ３诱导的大多数强荧光带纹与Ｃ－阳性     

野生朱()的新繁殖地

朱()(Nipponia nippon)是世界极危物种(CR),现只有一个野生种群,数量60只左右,生活在我国陕西省洋县境内,分布范围极其狭小.     

Cytochrome P450c17-expressing Escherichia coli as a first-step screening system for 17alpha-hydroxylase-C17,20-lyase inhibitors

We have designed and synthesized a number of cytochrome P450 17alpha-hydroxylase-C17,20-lyase (P450c17) inhibitors with the aim of inhibiting androgen synthesis. To select the most potent inhibitors, we initially used human testicular microsomes, which have a high level of expression of this enzyme. However, due to lack of availability of human tissue and variability among the samples, we utilized recombinant human enzyme expressed in Escherichia coli. We designed a simple and economical protocol based on the report that recombinant bovine P450c17 can be functionally active in live bacteria. In the assay we report here, we substituted high-performance liquid chromatography product isolation with a rapid biochemical acetic acid releasing assay and utilized intact P450c17-expressing E. coli for the source of the enzyme. Enzymatic parameters of the bacterial system (Km = 5.1 x 10(-7) M, Vmax = 15.0 pmol/min/mg) were similar to those of human testicular microsomes (Km = 4.8 x 10(-7) M, Vmax = 40.0 pmol/min/mg), and our compounds displayed a similar pattern of inhibition in both systems. This new system is a fast, reliable, and reproducible method for screening P450c17 inhibitors. Furthermore, it eliminates our dependence on human tissue and potential data fluctuations caused by variations in enzymatic activity between donors.     

四种昼行性动物取食和贮藏红松种子的行为比较

于2005年10月1~7日,采用全时焦点观察法研究了黑龙江凉水国家级自然保护区19林班原始红松林内松鼠(Sciurus vulgaris)、星鸦(Nucifraga caryocatactes)、花鼠(Eutamias sibiricus)和普通(Sitta europaea)4种昼行性动物取食和贮藏红松种子的行为。结果表明①4种动物的取食和贮藏过程包括找寻、松塔的处理与种子剥食、松塔和种子的搬运、确定贮藏点、掩藏和警戒等6个环节,但它们在6个环节所耗费的时间均存在较大差异;②4种动物的种子消耗量亦存在较大差异(χ2=144.67,df=3,P<0.05),松鼠、星鸦、花鼠和普通每次平均取食红松种子的数量分别为40.0粒、20.9粒、16.7粒和1.3粒。松鼠与星鸦能够在地面和树冠层取食或收获红松松塔及种子,而花鼠与普通则主要在地面取食;③4种动物贮藏种子的能力亦有较大差异(χ2=68.76,df=3,P<0.05Kruskal-Wallis),松鼠、星鸦和普通主要分散贮藏红松种子,松鼠和星鸦的贮藏量最多,而花鼠很少分散贮藏种子,但能将许多红松种子集中贮藏在少数的贮藏点;④取食松籽的种间竞争强烈,在红松林的垂直高度上,松鼠和星鸦具有高度重叠的取食生态位,花鼠和普通因为种群数量大,对地面种子库的消耗量较大。分析结果显示,松鼠与星鸦是红松种子扩散的传播者,普通是种子消耗者兼传播者,而花鼠则近乎是完全的捕食者。     

红腹锦鸡血细胞的光镜和扫描电镜观察

为了探讨红腹锦鸡(Chrysolophus pictus)血细胞的形态特征,为生理学研究提供生物学基础资料,利用光镜和扫描电镜观察了红腹锦鸡血细胞的形态特征。结果表明,红腹锦鸡红细胞呈椭圆形或扁圆形,表面光滑,具核;白细胞为球形,体大,淋巴细胞表面有绒毛状突起,嗜中性粒细胞核一般分2~5叶,嗜酸性粒细胞核一般分2叶,嗜碱性粒细胞核分2~3叶,单核细胞表面粗糙不平,核大,呈肾形或圆形;凝血细胞呈球形或不规则形。