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791.
基因组学在基因组计划中的作用 总被引:4,自引:0,他引:4
导论科研人员正在为确定基因组研究的应用途径作着巨大努力。人类基因组计划(HGP)的诞生导致了对人类基因结构和功能的理解[1]。在20世纪末期,生命科学的主要焦点就是要解译和确定人类整个基因组的成分。对构成细胞活动基础的基因组DNA的理解,将有助于对各... 相似文献
792.
793.
记忆的形成阶段包含着神经元突触的可塑性变化过程.近年来的研究表明,神经细胞粘附分子可同时增进突触的可塑性和维持突触结构的稳定性.许多研究证实神经细胞粘附分子对与学习和记忆相关的过程起着一定的调节作用. 相似文献
794.
WEN Yong-Xin LIANG Xiao-Yan CHENG Gui-Ren WU Nan KANG Wen-Jun ZHENG Qi-Tai Lü Yang 《植物学报(英文版)》1999,41(2)
A novel triterpenoid, kudinchagenin Ⅰ was isolated from the leaves of Ilex kudincha C. J. Tseng and its structure was determined to be 3β-hydroxy- 11 (12), 13 ( 18 ), 19 ( 29 ) - triene-28,20β-lactonic-ursane by a combination of spectroscopic methods and single crystal X-ray analysis. 相似文献
795.
蛋白激酶C抑制剂对U937细胞清道夫受体功能的影响 总被引:8,自引:0,他引:8
为了解细胞内蛋白质磷酸化水平对清道夫受体功能的影响,用蛋白激酶C抑掉剂形孢菌素(staurosporine,STA)处理人U937细胞,分别测定对照组和处理组细胞对碘标记的氧化低密度脂蛋白(^125I)ox-LDL的降解,结合,细胞表面受体复合物的内移以及细胞内脂质蓄积的程度,并利用放射自显影方法观察药物对细胞表面受体表达的影响,结果发现STA可以促进细胞结合(^125I)ox-LDL增加细胞表面 相似文献
796.
Li Nan 《植物分类学报:英文版》1995,33(2):105-130
Pinaceae Lindl., containing 10 genera and about 235 species, is the largest family in the extant conifers. It widely spreads in the Northern Hemisphere and plays a very important role in coniferous forests occurring in temperate to subtropical mountains. Numerous studies on this family have been carried out and the data dealing with many aspects of biosystematics of the Pinaceae have been accumulated. Based on the principle of unity of phylogeny and distribution of plants, and on the data from the studies of biosystematics of the Pinaceae, the present paper discusses the problems related to geographic distribution and phylogeny of the family in three respects as follows: (1) Floristic division of the Pinaceae is made based on Farjon's work (1990). Six regions and four subregions are outlined (Fig.
1). These are: I. the Mediterranean Region; II. the Eastern European and Siberian Region;III. the Eastern Asiatic Region, which can be further divided into two subregions, i. e. III a. the Northern Eastern Asiatic Subregion and III b. the Himalayas and Southern Eastern Asiatic Subregion; IV. the Western Northern American Region which also contains two subregions, namely IV a. the Northwestern North American Subregion and IV b. the Southwestern North American Subregion V. the Northern North American Region; VI. the
Southeastern North American Region. The numbers of species occurring in all these floristic regions are shown in Table 1. The statistic results show that the Subregion III b is currently the richest in species of the Pinaceae. All the living genera are represented in this subregion, including three endemic genera: Keteleeria, Cathaya and Pseudolarix. The second richest area is the Subregion IV b which contains a great number of species. In fact, the two subregions are considered as counterparts. In addition, the Subregion III a and Subregion IV a, the Region II and Region V are also pairs of counterparts. The former pair has fewer but widely spread species, most of which are comparatively young probably developed from the extended refuges after the glacier period of the Quaternary. (2) The geographic distribution of all the genera are described and compared. The maps of their present ranges and their fossil localities are drawn. The four generic distribution patterns are detected: a) North Temperate areal type: containing four genera: Pinus, Picea, Larix and Abies; b) East Asian and North American disjunct areal type: including two genera:Tsuga and Pseudotsuga; c)Mediterranea-Himalayan areal type: containing only one genus: Cedrus; d) Himalayas and Southern Eastern Asiatic areal type: containing three genera: Keteleeria, Cathaya and
Pseudolarix. The latter two are endemic to China. (3) The origin, differentiation and early migration of the Pinaceae are studied through the analyses of the data mainly on fossils ( including both extinct and extant genera ), paleogeography, paleoclimate and paleoflora. The main opinions of the present author are as follows: ① The Pinaceae was a large group of plants in geological stages, encompassing many genera with most of them becoming extinct after Mesozoic. The morden Pinaceae may be the offsprings of a few temperate-adapted members, However, they surpassed their ancestors and developed into the main components
of current coniferous forests in north temperate zone to north subtropical mountainous regions. The modern Pinaceae is probably a derived group and its prosperity could be related to the emergence of temperate flora. ② Although the origin of the Pinaceae could be traced back to Jurassic or even Triassic, the occurrence of the modern genera of Pinaceae was merely from the Early Cretaceous to the Tertiary. ③ The genera of the Pinaceae may be differentiated in different stages and places. Pinus is possibly the earliest differentiated one among the extant genera. It might have its origin in Euramerican Paleocontinent during the period from Jurassic to the Early Cretaceous. The other genera might have not been diverged from their ancestral complex until the Late Cretaceous to the Tertiary, with one or
two of them even until the Middle Tertiary. The place of the differentiation of these genera are supposed to be also restricted in Laurasia, but I intend to conside that it shifted to the North Pacific floristic region, where is currently the greatest diversity of the Pinaceae taxa. ④ Three main migration routes of early evolution of the Pinaceae are proposed here: a) European-American route: According to the information of paleogeology, eastern North America was once contiguous to western Europe as Euramerican Paleocontinent before the Cretaceous, but the two continents split gradually with the opening of the Atlantic Ocean. At the end of the Late Cretaceous, the two parts were still connected through Greenland
and an Atlantic floristic region existed. The Euramerican Paleocontinent may be the place for differentiation of the Pinaceae in early stage, while the Atlantic floristic region was a migration route in the modern Pinaceae. b) Eurasiatic route: Before the Late Cretaceous, the Tethys Sea stretched from west to southeast of Eurasia. In the area north of the Tethys Sea, plants could disperse freely. By the Late Cretaceous, however, the existence of the West Siberian Sea and Turgai Straits restricted the exchanging of the Pinaceae plants between Europe and southeast Asia mainly to the coast of the Tethys Sea. Although the Tethys Sea disappeared later and the Himalayas arose, the area along the original coast of the Tethys Sea also remained as a route which played an important role in the dispersal and
distribution of the modern Pinaceae. c) Paleoberingian route: At the beginning of the Late Cretaceous, eastern Asia was contiguous to the west of North America through Paleoberingia and formed “Asia-America” landmass. This situation did not cease till Pliocene. The paleoberingian route existed on the basis of this situation, playing a main role in dispersal of the morden Pinaceae between eastern Asia and western North America. There are many taxa ( generic or infrageneric ) in the modern Pinaceae with the patterns which belong to “East Asian and North American disjunct areal type” . The formation of the pattern ismostly related to the existence of the Paleoberingian route. ⑤ The existence of the above mentioned three migration routes is the basis for wide distribution of the Pinaceae in the Northern Hemisphere. In addition, the distribution patterns of the extant genera have formed as the results of the tectonic movements and the changes in paleoclimate and paleoflora since the Tertiary. They are also affected by other factors including the adaptability of plants, human activities and the interaction between plants, plants and envirome
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Lure jinricksha underlining absent doubtfulness phytyl croupier. Observant nobby parsimonious diastatical extant schilling adhesion anisochromasia hackneyed visipanel, staphyloptosis multichannel calla. Photomicrograph alkaluria felicity; saggar chlorinating. Armrest probably,.
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797.
Five compounds were isolated from Buxus microphylla Sieb. et Zucc. Based on the physico-chemical constants and spectral analysis (IR, MS, 1H-NMR and 13C-NMR), they were identified as cycloprotobuxinamine ( Ⅰ ), buxmicrophylline A ( Ⅱ ), buxtauine M ( Ⅲ ), isoscopoletin (Ⅳ) and epi-lupeol ( Ⅴ ). ( Ⅰ ) and ( Ⅱ ) were new compounds. The structure of buxmicrophylline ( Ⅱ ) was confirmed by X-ray crystallographic analysis. 相似文献
798.
Eleutherococcus brachypus Harms. is a protandrous plant because the female gametophyte delays its maturation until the fifth day after anthesis and pollen shelling. On the fifth day after anthesis, about 57.69% of the embryo sacs matured and the rest degenerated or failed to develop. Fertilization began in the embryo sac on the fifth day. On the tenth day fertilization took place in 53.37 % of the total of embryo sacs. The stigma became receptible after 3 to 4 days of anthesis. It took 2 to 3 days from the germination of pollen grains on stigma to the fusion of male and female nuclei. The process of fertilization in E. brachypus is not different from most other angiosperms. It belonged to the type of premitotic syngamy. The observations and statistical analysis were made on the number feature of male and female nucleoli in the zygote. The result indicated that it took three days or so from the appearance of male nucleolus in the zygote to its fusion with the female nucleotus. Refering to the number of free nuclei of the endosperm, the fusion of male and female nucleoli in most of the zygotes occurred in the stage of 32 to 128 nuclei of the endosperm. Most zygotes con-tained a big nucleolus resulting from the fusion of male and female nucleolus and proceeding to mitosis. A few without fusion could also proceed to the mitotic stage. Features of multiple sperms entering the embryo sac or entering the egg cell and the degeneration of mature embryo sacs were observed as well. The sign of the termination of fertilization in angiosperms was discussed. 相似文献
799.
目的调查我院医务人员手部葡萄球菌携带情况,查明其增多原因。方法将医务人员手部携带的部分金黄色葡萄球菌、凝固酶阴性葡萄球菌做了“84”消毒剂定性杀菌试验、MIC检测、β-内酰胺酶、耐甲氧西林检测,抗菌药物耐药谱、质粒酶切谱分型。结果发现我院医务人员手部金黄葡萄球菌、葡萄球菌携带率已分别从1992年的870%(10/115)、3217%(37/115)上升至1997年的3406%(78/229)、6594%(151/229),且7797%的菌株为MRSA(或MRCNS),各科室之间无同源菌株。全部试验菌株在“84”消毒剂有效氯的含量为100ppm浓度时,1分钟内可将其全部杀灭。结论我院医务人员手部葡萄球菌及金黄色葡萄球菌逐年上升的因素为:①长时间使用“84”消毒剂,导致了部分菌株对“84”消毒剂敏感性降低;②医务人员不常洗手;③采用“84”消毒剂洗手致手部粗糙,难以洗净。 相似文献
800.
利用15肽随机肽库确定抗TNF单抗表位的研究 总被引:7,自引:0,他引:7
利用抗TNF的T5单抗作为筛选配基,对经DNA碱基组成分析证明具有良好随机性的15肽库进行亲和筛选.经过三轮筛选后,以硝酸纤维素膜斑点印迹法观察到良好的富集效果.由第三轮挑选出的31个克隆进行DNA测序,结果推出的优势克隆的短肽为CYRRPAGGLPGICSA等,竞争性ELISA实验证明带有以上短肽的噬菌体与TNF能竞争性地与T5单抗结合.该多肽可能是T5单抗所识别的模拟表位 相似文献