中职学生如何有效提高家电维修技术

随着家电在人们生活中普及度的提高,家电维修也成了一门高技术的服务行业,中职学生怎样才能在较短时间内有效提高家电维修技术是本文主要讨论的问题.     

Expression and inhibitory activity analysis of a 25-kD Bowman-Birk protease inhibitor in rice

Bowman-Birk protease inhibitors (BBI), belonging to serine protease inhibitors, are well-studied storage and defense proteins widely existing in both dicoty- ledonous and monocotyledonous plants[1―3]. In dicoty- ledonous plants, the BBIs are about 8-kD p…     

Myotoxic activity of a Gln-49 phospholipase A2 from Agkistrodon blomhoffii ussurensis snake venom

A novel myotoxic protein phospholipase A₂ (PLA₂), denoted as Gln49-PLA₂, has been isolated from snake venom of Agkistrodon blomhoffii ussurensis, which has weak lethal effect and apparent anticoagulant activity, but lacks the PLA₂ and hemorrhagenic activity. Gln49-PLA₂ obviously increases of plasma creatine-kinase (CK) upon intramuscular injection in mice, suggesting that it may induce a dose-dependent myonecrosis. Histological studies also reveal morphological changes in mouse skeletal muscles, including extensive myonecrosis, hemorrhage and neutrophil infiltration in the treated animals. The myotoxic ability induced by Gln49-PLA₂ can be partially inhibited by heparin.     

Determination of copy number for 5S rDNA and centromeric sequence RCS2 in rice by Fiber-FISH

The copy number of 5S rDNA and centromeric sequence RCS2 was determined by extended DNA fiber based fluorescence in situ hybridization (Fiber-FISH) in rice (Oryza sativa ssp. indica cv. Guangluai No. 4) genome. In order to determine the copy number, it is necessary to know the basepair number that a given length DNA fiber contains under a microscope. Therefore, the length of two DNA fragments, in which the basepair number had been already known, was measured. The insert sequence of the tested BAC 38D17 was 136 kb and its extended DNA was 56.4 μm long, 2.41 kb/μm on average, while that of the tested BAC 44B4 was 144.5 kb in total and 55.7 μm long, 2.60 kb/μm on average under the microscope. They were very close to the theoretical value of B-DNA in the Watson-Crick DNA model, which is 2.97 kb/μm. According to the average value of basepair number per μm of the two samples mentioned above, that is, 2.51 kb/μm, it could be estimated that the copy number was about 686 for 5S rDNA and 286-1121 for the centromere sequence RCS2.     

Embryonic stem cell as nuclear donor could promote in vitro development of the heterogeneous reconstructed embryo

The nucleus of a somatic cell could be dedifferentiated and reprogrammed in an enucleated heterogeneous oocyte. Some reconstructed oocytes could develop into blastocysts in vitro, and a few could develop into term normally after transferred into foster mothers, but most of cloning embryos fail to develop to term. In order to evaluate the efficacy of embryonic stem cell as nucleus donor in interspecific animal cloning, we reconstructed enucleated rabbit oocytes with nuclei from mouse ES cells, and analyzed the developmental ability of reconstructed embryos in vitro. Two kinds of fibroblast cells were used as donor control, one derived from ear skin of an adult Kunming albino mouse, and the other derived from a mouse fetus. Three types of cells were transferred into perivitelline space under zona pellucida of rabbit oocytes respectively. The reconstructed oocytes were fused and activated by electric pulses, and cultured in vitro. The developmental rate of reconstructed oocytes derived from embryonic stem cells was 16.1%, which was significantly higher than that of both the adult mouse fibroblast cells (0%-3.1%, P < 0.05) and fetus mouse fibroblast cells (2.1%-3.7%, P < 0.05). Chromosome analysis confirmed that blastocyst cells were derived from ES donor cell. These observations show that reprogramming is easier in interspecific embryos reconstructed with ES cells than that reconstructed with somatic cells, and that ES cells have the higher ability to direct the reconstructed embryos development normally than fibroblast cells.     

水稻愈伤组织根分化过程相关基因的初步筛选

水稻愈伤组织在N6培养基上可以保持稳定的增殖而不分化,而培养在含有ABA的N6培养基上的愈伤组织就可以被诱导分化,进而形成根.根据这种生理学特征,分别提取了生长在两种不同培养基上的愈伤组织的RNA,与水稻cDNA芯片杂交.通过分析两种愈伤组织基因表达的差异,共找到271个与水稻愈伤组织根分化过程相关的cDNA克隆,其中107个基因表达被诱导,164个基因表达被抑制.这些初步结果为进一步研究愈伤组织分化生根的分子机理提供了研究线索.     

涎腺腺样囊性癌银染核仁形成区的定量研究

采用ＡｇＮＯＲ技术对３０例正常涎腺及涎腺良、恶性肿瘤中银染核仁形成区（ＡｇＮＯＲ）进行定量研究，结果显示正常涎腺ＡｇＮＯＲ计数值最低，颗粒较均一；良性肿瘤的ＡｇＮＯＲ计数值低于恶性肿瘤，大颗粒所占的比例较大。筛孔型涎腺腺样囊性癌（ＡＣＣ－Ⅰ）与团块型（ＡＣＣ－Ⅱ）其ＡｇＮＯＲ计数值存在显著性差异（Ｐ＜０．０１），这提示筛孔型ＡＣＣ细胞分化较好，属低度恶肿瘤，预后较好；实性团块型ＡＣＣ细胞分化较差，属高度恶性肿疤，预后较差，ＡｇＮＯＲ染色技术可用为判断涎腺腺样囊性癌（ＡＣＣ）恶性程度的辅助手段。     

高硅铝合金的电脉冲孕育处理与液-固相关性

以液态合金的多相结构模型为基础,对电脉冲作用下高硅铝合金熔体结构变化进行了热力学分析,并研究了电脉冲作用下Al-22%Si合金凝固组织的显微硬度以及凝固相变点的变化.实验结果表明,电脉冲促进了呈"胶体"状态存在的Si粒子在Al-22%Si合金熔体中的分解,提高了熔体的均匀程度,部分消除了来自Si原料的遗传性;电脉冲孕育处理提高了Al-22%Si合金熔体的过冷能力,增加了Si粒子在基体组织中的过饱和度,提高了基体的显微硬度;Al-22%Si合金基体显微硬度值的变化显示熔体对于电脉冲频率的响应比较敏感.