血栓素合成酶抑制剂的研究现状和展望

血栓素合成酶抑制剂(TxSI)是一类新型抗血小板药,其显著特点是阻断花生四烯酸(AA)代谢过程中诱聚性及血管收缩性产物血栓素A_2(TxA_2)的形成,而不抑制甚至增加抗聚性及血管扩张性前列环素(PGI_2)的生成。这类药物比环氧酶抑制剂阿司匹林等经典抗血小板药具有更高的特异性作用,可望于心血管疾病的临床应用。     

Secondary structure prediction for the spectrin 106-amino acid segment, and a proposed model for tertiary structure

A collective secondary structure prediction for the human erythrocyte spectrin 106-residue repeat segment is developed, based on the sequences of nine segments that have been reported in the literature, utilizing a consensus of several secondary structure prediction methods for locating turn regions. The analysis predicts a five-fold structure, with three alpha-helices and two beta-strand regions, and differs from previous models on the lengths of the helices and the existence of beta-strand structure. We also demonstrate that this structural motif can be folded into tertiary structures that satisfy the experimental spectrin data and several general principles of protein organization.     

人体小卫星DNA探针的制备

根据人体小卫星DNA核心顺序,化学合成长23碱基寡核苷酸探针,筛选人体基因组文库,旨在获得能用作遗传分析探针的小卫星顺序。结果得到15个含小卫星的阳性重组子。随机取其一(C_(35.9))作探针,试做群体分析。所有个体均可检出多条杂交带。其中某些带具有多态性。在一定检测条件下,检出的DNA图谱在有限的个体内具有个体特异性。结果表明筛选文库得到的小卫星顺序可用于小卫星多态性的检测。其它小卫星探针的筛选和应用性研究正在进行。     

小麦—天兰偃麦草—黑麦三属杂种花粉植株诱导条件的研究

研究表明,三属杂种处于单核中晚期阶段的花粉最适于诱导形成愈伤组织。低温预处理对促进三属杂种花粉愈伤组织的诱导有一定的作用。利用以马铃薯提取物为基础物质的马铃薯-Ⅱ培养基作诱导培养基,其愈伤组织诱导与分化的频率比目前两个较好的合成培养基要高。同一个三属杂种F_1春、秋播种植株之间在形成愈伤组织的能力上有较大的差异,秋播材料形成愈伤组织的能力明显高于春播材料。F_(?)杂种植株诱导愈伤组织和分化植株的频率均比F_1杂种明显提高。     

维西香茶菜的二萜成分

维西香茶菜Rabdosia weisiensis C. Y. Wu产云南西北部海拔2600米沟谷中,其化学成分的研究未见报道。从该植物叶的乙醚提取物中,分得两个二萜成分,一为已知成分trichorabdal A(2),一为新成分,命名为维西香茶菜甲素weisiensin A(1)。 维西香茶菜甲素weisiensin A(1),C_(26)H_(36)O_9,mp 298—300℃,其~(13)C NMR谱显示存在三个CH_3,三个CH_2,八个CH,三个四取代碳,三个Ac,二个烯碳和一个羰基     

A detailed analysis of early events during in-vitro fertilization of bovine follicular oocytes

Bovine follicular oocytes collected at slaughter were matured and fertilized in vitro with in-vitro capacitated spermatozoa. Analysis of 621 penetrated ova fixed at various times after in-vitro insemination led to definition of 6 stages of early development. A time sequence for sperm penetration, sperm head decondensation, male pronucleus formation, the activation of second meiotic division, female chromosome decondensation and pronucleus development was established. First sperm penetration into the ooplasm was recorded 6 h after insemination; 1-2 h was required for the sperm head to decondense and another 4-6 h to develop into the opposing pronucleus stage. Synkaryosis and first cleavage occurred 28 h after fertilization. Examination of the early stages revealed four types of abnormalities, i.e. polyspermy, polygyny, asynchrony between male and female pronucleus development, and preactivation of cytokinesis.     

Characteristics of Five New Photoautotrophic Suspension Cultures Including Two Amaranthus Species and a Cotton Strain Growing on Ambient CO(2) Levels

Suspension cultures of cotton (Gossypium hirsutum), Amaranthus cruentus, A. powellii, Datura innoxia, and a Nicotiana tabacum-N. glutinosa fusion hybrid were adapted to grow photoautotrophically under continuous light. The cotton strain grew with an atmosphere of ambient CO₂ (about 0.06 to 0.07% in the culture room) while the other strains required elevated CO₂ levels (5%). Photoautotrophy was indicated by the requirement for CO₂ and for light for growth. The strains grew with doubling times near 14 days and had from 50 to 600 micrograms of chlorophyll per gram of fresh weight. The cells grew in small to moderate sized clumps with cell sizes from 40 to 70 micrometers (diameter). Like most photoautotrophic cultures described so far the ribulose 1,5-bisphosphate carboxylase (RuBPcase) activity levels were well below those of mature leaves. The phosphoenolpyruvate carboxylase levels were not elevated in the C₄Amaranthus species. The cells showed high dark respiration rates and had lower net CO₂ fixation under high O₂ conditions. Dark CO₂ fixation rates ranged from near 10 to 30% of that in light. Fluorescence emission spectra measurements show that the cell antenna pigments systems of the four strains examined are similar to that of chloroplasts of green plants. The cotton strain which was capable of growth under ambient CO₂ conditions showed the unique properties of a high RuBPcase activation level in ambient CO₂ and a stable ability to show net CO₂ fixation in 21% O₂ conditions.     

异细胞质八倍体小黑麦的获得及其细胞遗传

改变小黑麦细胞质有可能增加减数分裂的稳定性,提高小黑麦的结实率与籽粒饱满度。作者以不同细胞质的“中国春”小麦与黑麦杂交,F_1幼苗用秋水仙素加倍获得双二倍体、或以八倍体小黑麦为父本与F_1杂交,获得异细胞质八倍体小黑麦(Triticale 8x)8个品系。实验结果表明:细胞质不同的“中国春”小麦与黑麦杂交结实率差异显著,出苗率亦不同,F_1株型多为两亲的中间型,花药不开裂,个别组合出现雄蕊雌化现象,有的组合表现生长弱性,减数分裂中期Ⅰ常出现1至数个末端交叉的棒状二价体,其数量在不同组合间差异显著,表明异细胞质对染色体配对有影响。D类细胞质对改进八倍体小黑麦的结实率可能有一定的作用。     

A cell type-specific enhancer drives expression of the chick muscle acetylcholine receptor alpha-subunit gene

The regulation of acetylcholine receptor alpha-subunit gene expression was analyzed by transient expression assays. Using rabbit beta-globin cDNA as a reporter gene, we have confirmed that the 5'-flanking sequence of the chicken acetylcholine receptor alpha-subunit gene directs specific expression in differentiated C2C12 cells, a mouse muscle cell line, but not in undifferentiated C2C12 cells and mouse 3T3 fibroblasts. Testing chimeric plasmids containing Bal31 deletion mutants of the alpha-subunit gene upstream sequence, we found the -116 to -81 region of the alpha-subunit to be responsible for tissue- and stage-specific expression. This 36 bp fragment stimulates the activity of both alpha-subunit and SV40 promoters in a distance- and orientation-independent manner, thus fulfilling the criteria of an enhancer.     

The m gamma delta-1 element, a small gamma delta (Tn1000) derivative useful for plasmid mutagenesis, allele replacement and DNA sequencing.

Transposon gamma delta (Tn1000), a 6-kb member of the Tn3 family, is widely used for plasmid mutagenesis. A 1.8-kb derivative of gamma delta was constructed that contains the kan gene from Tn5 and the resolution (res) site from gamma delta cloned between 40-bp inverted repeats of gamma delta's delta (delta) end. This element, named m gamma delta-1, lacks the genes encoding transposase and resolvase, and therefore depends on its host to supply transposition and resolution functions. Thus, in strains lacking gamma delta, m gamma delta-1 will not transpose. The m gamma delta-1 element is shown to be useful for mutagenesis of plasmids, DNA sequencing, and allele replacement (in Streptomyces avermitilis).