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141.
It has been shown that a stretch of uridines (U's) near the 5' end of the virion RNA of influenza A virus is the polyadenylation site for viral mRNA synthesis. In addition, the RNA duplex made up the 3' and 5' terminal sequences adjacent to the U stretch is also involved in polyadenylation. We have further characterized the polyadenylation signal of influenza virus RNA with a ribonucleoprotein transfection system. We found that the optimal length of the U stretch is 5 to 7 uridine residues. We also showed that the upstream sequence at the 5' end is not involved in polyadenylation and that the optimal distance between the 5' end and the U stretch is 16 nucleotides. The combination of these features defines the polyadenylation site and differentiates this signal from other U stretches scattered throughout the genomes of influenza viruses. 相似文献
142.
Procedures have been developed which allow the preparation of highly pure endoplasmic reticulum and plasma membrane from tendrils ofBryonia dioica. These and further membrane fractions were used to study vanadate-sensitive ATPase activity as well as Mg2+ATP-driven transport of45Ca2+. Calcium-translocating ATPases were detected in the endoplasmic reticulum, the plasma membrane and the mitochondrial fraction and characterized kinetically and with respect to the effects of various inhibitors. The endoplasmic-reticulum Ca2+-translocating ATPase was stimulated by KCl and was calmodulin-dependent. The plasma-membrane enzyme was not affected by these agents. These, as well as the inhibitor data, show that the Ca2+-translocating ATPases of the endoplasmic reticulum and the plasma membrane are distinctly different enzymes. Upon mechanical stimulation, the activities of the vanadate-sensitive K+, Mg2+-ATPase and the Ca2+-translocating ATPase(s) increased rapidly and transiently, indicating that increasing transmembrane proton and calcium fluxes are involved in the early stages of tendril coiling.Abbreviations CAM
calmodulin
- CCCP
carbonylcyanidem-chlorophenylhydrazone
- IC50
concentration giving 50% inhibition
- PM
plasma membrane
- rER
rough endoplasmic reticulum
- sER
smooth endoplasmic reticulum
- FC
fusicoccin
- U3+U3
the two PM-rich upper phases obtained after phase partitioning of microsomal membranes
The authors wish to thank the Deutsche Forschungsgemeinschaft, Bonn, Germany, and the Fonds der Chemischen Industrie, Frankfurt, Germany (literature provision) for financial support. 相似文献
143.
144.
比较研究几种兼性和专一性CAM植物材料的PEPC同工酶表明:经自然干旱诱导,兼性CAM植物露花(Mesembryanthemumcordifolium)、长药景天(Sudumspectabile)有新的PEPC同工酶的出现,诱导前后各同工酶的天然分子量变化不大;而土三七(Sedumaizoon)则没有新的PEPC同工酶出现,但诱导后其同工酶的天然分子量有所增大。以上几种兼性CAM植物的PEPC同工酶酶谱无明显昼夜变化。专一性CAM植物的PEPC酶谱和天然分子量均较一致,亦无昼夜差异。 相似文献
145.
胎盘型谷胱甘肽S-转移酶基因在胃癌中的表达 总被引:1,自引:0,他引:1
用Dig-GST-πcDNA探针分子杂交方法,检测了正常胃组织,胃癌及相应癌旁正常组织中GST-πDNA和GST-πRNA水平,发现GST-πDNA水平没有明显变化,而GST-πRNA在8例胃癌组织中有6例高于正常胃组织,在12例低分化腺癌中有7例癌旁正常组织高于相应癌组织,表明GST-π基因表达增加与胃癌有关,而且早于细胞形态的变化。 相似文献
146.
巨大螺旋藻光合放氧和超微结构的研究 总被引:4,自引:0,他引:4
选用常温下培养的巨大螺旋藻为材料,对其光合放氧与超微结构进行了观察和研究。结果表明:1)巨大螺旋藻具有较强的放氧能力;2)巨大螺旋藻细胞内存在有含量极丰富的类囊体,气泡,藻胆体及羧化体等特写结构与其光合放氧特性相适应;3)类囊体膜片层在细胞的部分区域已趋于重叠,且封闭成一独立系统存在,具类似真核生物叶绿体的结构;4)从进化角度来看,巨大螺旋藻类囊体膜存在的方式可以作为叶绿体系统演化的证据之一,即真 相似文献
147.
几种环境因素对玉米叶切块光诱导的影响 总被引:1,自引:1,他引:0
利用液相氧电极研究了暗处理、光强、CO2水平、缺钾和干旱对玉米叶切块光诱导的影响。发现长时间的暗处理、高光强、低CO2浓度、缺钾和干旱均使光合诱导期拉长。影响光合诱导期的外界逆境如低CO2浓度、缺钾和干旱也使玉米叶片的净光合速率下降,并对这些结果产生的原因作了分析。 相似文献
148.
Cecilia Del Casino Yi-Qin Li Alessandra Moscatelli Monica Scali Antonio Tiezzi Mauro Cresti 《Biology of the cell / under the auspices of the European Cell Biology Organization》1993,79(2):125-132
Summary— The distribution of microtubules was investigated in Nicotiana tabacum pollen tubes at different stages of tube growth by immunofluorescence microscopy. Using specific antibodies, the presence of microtubules consisting of different tubulin isoforms was tested. α-, β- and tyrosinated α-tubulin were present within the tube, whereas the acetylated form was lacking. The presence of tubulin subunits in pollen tube extracts was also investigated by immunoblotting analyses. The use of a confocal laser scanning microscope integrated with computer-assisted imaging, allowed a detailed visualization of the microtubule distribution and organization. Cytoplasmic microtubules organized as short bundles with various orientations were detected at the apex of long tubes. 相似文献
149.
Abstract This paper deals with alternative hosts of an egg parasitoid. Trichogramma dendrolimi Matsumura in three habitats: mixed forest, pure stand and sparse wood. The experiment was conducted in Liuyan County which is located in the eastern part of Hunan Province. The results suggested that there are 103 species of alternative Lepidopteran hosts for T. dendrolimi . There were two critical periods throughout the year when there were no eggs of Dendrolimus punctatus Walker and few eggs of alternative hosts available for ovipsition by the parasitoids. 相似文献
150.
腹腔注射链脲佐霉素(65mg/kg)诱发Wistar大鼠糖尿病。糖尿病发病4周后,向饲料中加尼群地平(30mg·kg-1·d-1)。结果表明,糖尿病4周时大鼠心室舒张功能首先受损,8周后心室舒张和收缩功能均明显受累。尼群地平处理对糖尿病大鼠的心肌收缩性有一定的改善作用。提示尼群地平对大鼠糖尿病性心肌病有一定有益作用。 相似文献