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51.
自然免耕下的稻田生态系统 总被引:15,自引:0,他引:15
自然免耕是一种新型的稻田耕作法,通过人为改变地表微地形,建立了一个适合水旱作物复种轮作,鱼、萍、鸭周年共生的稻田生态系统.自然免耕促进了土壤内、外环境的物质、能量和信息交换,水、热、气、肥谐调.并通过环境网络效应,强化了环境与生物区系间的缓冲-调节力.提高了土壤自调能力和土壤有序度. 相似文献
52.
本实验合并应用枸杞有效成份和大蒜有效成份,作用于U_14腹水型宫颈癌小鼠,腹腔注射第四天,发现一般状况改善,取腹水观察,癌细胞破损,DNA、RNA荧光染色强度减弱,有大量白细胞和巨噬细胞围绕;流式细胞分析G_1期细胞堆积,超微结构显示胞质中线粒体肿胀,嵴破坏甚至中空,粗面内质网扩大、脱颗粒,肯定了其作用的效果。此因枸杞有效成分活化巨噬细胞与肿瘤细胞紧密结合而起到溶瘤作用,与大蒜有效成分直接杀伤而作用维持短暂结合起来,可大大提高抗癌作用。 相似文献
53.
ELISPOT技术是目前国外评价疫苗免疫原性和免疫应答机理研究中最常使用的方法。本文用自制的NC膜24孔板为固相支持物,建立了检测小鼠脾细胞中特异性ASCs的ELISPOT技术,在检测方法的特异性、结果的稳定性上均取得了满意的效果。并对该方法的某些实验条件进行了摸索。 相似文献
54.
果树介壳虫寄生蜂资源的研究 总被引:4,自引:0,他引:4
介壳虫是果树的重要害虫,研究利用寄生蜂的自然控制作用是果树介壳虫生物防治和综合治理的重要途径。本论述了果树介壳虫寄生蜂资源的研究,报道了小蜂总科寄生蜂5科25属63种。 相似文献
55.
Molecular and statistical approaches to the detection and correction of errors in genotype databases. 总被引:12,自引:5,他引:7 下载免费PDF全文
L M Brzustowicz C Mrette X Xie L Townsend T C Gilliam J Ott 《American journal of human genetics》1993,53(5):1137-1145
Errors in genotyping data have been shown to have a significant effect on the estimation of recombination fractions in high-resolution genetic maps. Previous estimates of errors in existing databases have been limited to the analysis of relatively few markers and have suggested rates in the range 0.5%-1.5%. The present study capitalizes on the fact that within the Centre d'Etude du Polymorphisme Humain (CEPH) collection of reference families, 21 individuals are members of more than one family, with separate DNA samples provided by CEPH for each appearance of these individuals. By comparing the genotypes of these individuals in each of the families in which they occur, an estimated error rate of 1.4% was calculated for all loci in the version 4.0 CEPH database. Removing those individuals who were clearly identified by CEPH as appearing in more than one family resulted in a 3.0% error rate for the remaining samples, suggesting that some error checking of the identified repeated individuals may occur prior to data submission. An error rate of 3.0% for version 4.0 data was also obtained for four chromosome 5 markers that were retyped through the entire CEPH collection. The effects of these errors on a multipoint map were significant, with a total sex-averaged length of 36.09 cM with the errors, and 19.47 cM with the errors corrected. Several statistical approaches to detect and allow for errors during linkage analysis are presented. One method, which identified families containing possible errors on the basis of the impact on the maximum lod score, showed particular promise, especially when combined with the limited retyping of the identified families. The impact of the demonstrated error rate in an established genotype database on high-resolution mapping is significant, raising the question of the overall value of incorporating such existing data into new genetic maps. 相似文献
56.
Study of mechanisms of electric field-induced DNA transfection. V. Effects of DNA topology on surface binding, cell uptake, expression, and integration into host chromosomes of DNA in the mammalian cell. 下载免费PDF全文
Neumann and coworkers (Neumann, E., M. Schaefer-Ridder, Y. Wang, and P. H. Hofschneider. 1982. EMBO J. 1:841-845) have shown that the efficiency of pulsed electric field (PEF)-induced DNA transfection of mouse L-cells by the thymidine kinase gene is several times higher for the linear DNA than for the closed circular DNA. Transfection of Escherichia coli bacteria by several plasmids indicates that the transfection efficiency was much higher for the closed circular/supercoiled (sc-) and circular/relaxed (cr-) DNA than for the linearized (In-) DNA (Xie, T. D., L. Sun, H. G. Zhao, J. A. Fuchs, and T. Y. Tsong. 1992. Biophys. J. 63:1026-1031). To resolve these conflicting observations, we have systematically examined electrotransfection of NIH3T3 mouse fibroblast by the plasmids, pRSVcat, pRSVneo, and pRSVgpt. Mg(2+)-facilitated surface binding of DNA before, and DNA uptake by 3T3 cells after treatment with PEF, were monitored by 3H-labeled plasmids. Transfection efficiency was evaluated by both the transient expression of chloramphenicol acetyltransferase (cat) activity 2-3 days after, and the permanent expression of neomycin phosphotransferase (neo) and xanthine-guanine phosphoribosyltransferase (gpt) genes in the transformants 2 weeks after the PEF treatment. Our results indicate that cell surface binding and PEF-induced cell uptake of DNA did not depend on the topology of DNA. However, both the transient and the permanent expression of the plasmids were three to five times more efficient for the cr-DNA and the sc-DNA than for the in-DNA.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
57.
58.
Light-regulated and cell-specific expression of tomato rbcS-gusA and rice rbcS-gusA fusion genes in transgenic rice. 总被引:11,自引:4,他引:7 下载免费PDF全文
A previously isolated rice (Oryza sativa) rbcS gene was further characterized. This analysis revealed specific sequences in the 5' regulatory region of the rice rbcS gene that are conserved in rbcS genes of other monocotyledonous species. In transgenic rice plants, we examined the expression of the beta-glucuronidase (gusA) reporter gene directed by the 2.8-kb promoter region of the rice rbcS gene. To examine differences in the regulation of monocotyledonous and dicotyledonous rbcS promoters, the activity of a tomato rbcS promoter was also investigated in transgenic rice plants. Our results indicated that both rice and tomato rbcS promoters confer mesophyll-specific expression of the gusA reporter gene in transgenic rice plants and that this expression is induced by light. However, the expression level of the rice rbcS-gusA gene was higher than that of the tomato rbcS-gusA gene, suggesting the presence of quantitative differences in the activity of these particular monocotyledonous and dicotyledonous rbcS promoters in transgenic rice. Histochemical analysis of rbcS-gusA gene expression showed that the observed light induction was only found in mesophyll cells. Furthermore, it was demonstrated that the light regulation of rice rbcS-gusA gene expression was primarily at the level of mRNA accumulation. We show that the rice rbcS gene promoter should be useful for expression of agronomically important genes for genetic engineering of monocotyledonous species. 相似文献
59.
60.
本文对血清岩藻糖测定方法进行了系统研究。血清用量由200μL减至50μL,显色反应4h内稳定。吸收峰在396nm。岩藻糖浓度40μg/mL内线性良好,批间CV=2.1%。以Sephadex-G200层析,血清岩藻糖主要存在于分子量为500kD的组分中。以本法测得30例健康人血清岩藻糖浓度为588.1±172.0μmol/L。 相似文献