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21.
血管内皮舒张因子在氧自由基所致慢性缺氧大鼠肺内动... 总被引:1,自引:1,他引:0
The role of endothelium-derived relaxing factor (EDRF) on the effect of oxygen-derived free radicals (generated by xanthine-xanthine oxidase system) on intrapulmonary arterial in chronic hypoxic rats was studied by a microbioassay method. Intrapulmonary artery rings with intact or denuded endothelium of hypoxic (5,000 m, 10 days) and normoxic rats were prepared for observation of oxygen-derived free radicals induced contraction. It was shown that oxygen-derived free radicals induced contractions of intrapulmonary arterial rings with intact endothelium were obviously augmented in hypoxic rats than in normoxic controls. The augmented responses could be further potentiated by the addition of EDRF inactivator reduced hemoglobin (RHb), but diminished or even abolished by applying superoxide dismutase (Cu-Zn SOD). However, no effect on denuded rings was observed when RHb or SOD was added. It is concluded that chronic hypoxia may attenuate the action of EDRF in the enhancement of the reactivity of intrapulmonary artery to oxygen-derived free radicals. 相似文献
22.
In vitro vegetative propagation of Chinese cabbage 总被引:1,自引:0,他引:1
Explants from cotyledons, axillary buds, inflorescence stems and flower buds of Brassica campestris ssp. pekinensis (Lour.) Olsson (Chinese cabbage, cv. Wongbok) were cultured on MS medium with growth regulators. Multiple shoots were obtained from cotyledons, axillary buds and flower buds but not from inflorescence stems. Propagation of shoots from cotyledons was more successful than from axillary buds and flower buds. The vegetative propagation rates varied amongst clones derived from cotyledons of the same cultivar and seed lot. The propagation rates of the cotyledon-derived material followed a normal distribution with an average propagation rate of 2.6 shoots per two weeks subculture when cultured on MS media plus 44.4 m benzyladenine (BA) and 14.8 m -indolebutyric acid (IBA). Shoots from three clones were cultured on MS medium with nine different concentrations of BA. The concentration of BA which promoted the highest rate of shoot propagation varied for the three clones and was in the range 44.4 to 177.6 m. 相似文献
23.
Construction and expression of mouse thymidylate synthase minigenes 总被引:10,自引:0,他引:10
J W DeWille C H Jenh T Deng C J Harendza L F Johnson 《The Journal of biological chemistry》1988,263(1):84-91
Mouse thymidylate synthase minigenes that lack introns were constructed by ligating restriction fragments containing 4.5, 1.0, or 0.25 kilobase pairs (kb) of 5'-flanking DNA of the normal thymidylate synthase gene and as little as 0.25 kb of 3'-flanking DNA to full-length thymidylate synthase cDNA. All three minigenes were expressed at approximately the same levels following transfection into hamster V79 cells that were deficient in thymidylate synthase. S1 nuclease protection assays revealed that the multiple 5' and 3' termini of thymidylate synthase mRNA in cells transfected with these minigenes were at the same positions as those of the normal mRNA in mouse cells. Deletion analysis of the promoter region revealed that minigenes extending to position -150 nucleotides (relative to the AUG codon) were expressed at approximately the same level as those extending to -1 kb. However, minigenes extending to -53 nucleotides were inactive. To determine if the minigenes were capable of being regulated in a cell cycle-dependent manner, thymidylate synthase gene expression was measured in hamster cells that were stably transfected with the largest minigene and synchronized by serum-stimulation. Thymidylate synthase enzyme level and mRNA content increased 3-5-fold as cells progressed from G1 through S phase. 相似文献
24.
25.
团花的种子中有抑制物质,把种子和果实的其它部分分别用有机溶剂提取和分离,所得粗提物经柱层析和薄层层析纯化后,用气相色谱、高效液相色谱、气-质联用等仪器进行测定,并结合生物鉴定,证明种子和果实其它部分中均含有一定量的脱落酸。种子中的含量为11.7μg/g干重,其它部分15.8μg/g干重。 相似文献
26.
27.
Structure and synthesis of histopine, a histidine derivative produced by crown gall tumors 总被引:2,自引:0,他引:2
Histopine, an unusual amino acid derivative of histidine isolated from crown gall tumors of sunflowers (Helianthus annus) inoculated with Agrobacterium tumefaciens strain B6, was previously assigned the gross structure N-(1-carboxyethyl) histidine (2). A diastereomeric mixture containing histopine (2a and 2b) was readily prepared by reductive alkylation of (S)-histidine (1) with pyruvic acid and sodium cyanoborohydride. The individual diastereomers were prepared by reaction of (S)-histidine with (R)- and (S)-2-bromopropionic acid. (R)-N-(1-Carboxyethyl)-(S)-histidine (2a) supports the growth of A. tumefaciens whereas (S)-N-(1-carboxyethyl)-(S)-histidine (2b) is inactive. Therefore, we assign structure 2a to histopine. 相似文献
28.
Sprague-Dawley albino rats or Long-Evans pigmented rats were exposed during the dark phase of the daily light:dark cycle to various intensities of a sunlight-stimulating white fluorescent light (0.022, 0.044, 0.110, 0.220, 0.440 or 2.200 μW/cm2) for 30 min; pineal glands and trunk blood samples were then collected and assayed for melatonin by radioimmunoassay. Albino rats exposed to irradiances of 0.110 μW/cm2 or less had pineal melatonin levels that were not significantly different from those of unexposed animals; higher irradiances significantly (P < 0.001) reduced melatonin levels. In contrast, as little as 0.022 μW/cm2 significantly (P < 0.02) reduced pineal and serum melatonin levels in the pigmented rats. These results suggest that something other than the simple presence or absence of eye pigmentation is the critical factor in determining the sensitivity of the rat's pineal to retinal-mediated photic suppression of melatonin synthesis. 相似文献
29.
用对阿特拉津(Atrazine)除草剂抗性的龙葵生物型B_(12)株系作材料,制备叶绿体DNA。B_(12)株ctDNA(叶绿体DNA)经BamHI酶解,在0.7%琼脂糖凝胶电泳上呈现24条带,其中最大的片段为18.6kb,最小的片段为1kb。用pBR322作为载体,构建B_(12)株ctDNA BamHI片段文库。通过与探针的分子杂交,从中筛选出含有编码叶绿体32kd蛋白质的阿特拉津抗性基因的克隆pSB135和含有ATP合酶α亚单位基因的克隆pSB132。 相似文献
30.
买麻藤根的异常次生生长 总被引:2,自引:0,他引:2
.高信曾;.陈耀堂;.邓岳芬;.宋协志 《武汉植物学研究》1989,7(2):119-122
买麻藤(Cnetum montanum)根的异常次生生长与茎的异常次生生长相似,位于维管束外围的薄壁组织细胞可以形成维管束,以这种方式使根加粗。并且在生长过程中以同样的方式,在维管束的外围不断形成新的维管束。这些新的维管束成环状排列,因此,在老根中呈多圈的维管束。与茎唯一不同的是根的异常次生生长为不均等的,在两个宽大的射线区外侧,没有异常的维管束形成,因此,根主要向着与两条宽大射线相垂直的方向扩展,故外形呈扁圆形。 相似文献