IRM-2近交系小鼠的G-显带核型和自发畸变率的研究

目的阐明新型IRM-2近交系小鼠G-显带核型和自发畸变率.方法采用小鼠骨髓制备和G-显带法.结果从20只小鼠的50个G-显带细胞中,10个G-显带细胞被选作模型分析.根据特有带型来识别各号染色体,描述了带型特征,测量了相对长度和标准差,绘制了模式图.对于1、6与X,4与5,9、13与14等带型较相似的染色体提出了一些识别要点.此外,用常规Giemsa染色分析了1200个中期细胞,发现染色体断裂为0.33%,无着丝粒畸变和不平衡易位均为0.08%,自发畸变率很低.结论新型IRM-2近交系小鼠G-显带的识别为结构异常、辐射效应、肿瘤研究和基因作图提供了科学依据.     

中国地鼠山医群体近交系E繁殖性状的遗传力估计

目的对中国地鼠山医群体近交系E的一些繁殖性状进行遗传力估计分析。方法采用平均信息约束最大似然法（AIREML）,利用WOMBAT软件进行处理。结果产仔数、离乳数、胎间隔2-1和胎间隔3-2的遗传力均较低,分别为0.05、0.096、0.182和0.116。结论中国地鼠山医群体近交系E繁殖性状的遗传力均属于低遗传力。     

自发NIDDM中国地鼠血液相关酶及蛋白的变化研究

本研究测定了自发NIDDM 近交系中国地鼠的血液相关酶的六项指标及蛋白变化的2项指标,并于正常对照近交系进行了对比,结果显示:血液相关酶的五项指标及总蛋白的变化明显高于正常对照近交系。(P< 0-01) 。提示:自发NIDDM 近交系中国地鼠发病以后,糖代谢、蛋白代谢出现异常。     

小鼠G显带核型

分析了4个自交系小鼠和1个杂交系小鼠的54个骨髓细胞G显带核型,各系小鼠G显带标本均能观察到显示大带和小带的两种带型细胞。大带细胞带少、清晰、恒定,根据其带型能鉴别各号染色体。各系小鼠大带带型相同。本文还描述了各号染色体大带带型特征,并绘制了小鼠G带核型模式图,提出了带型相似的6,8;1,X;9,13;及17,18等染色体识别要点。     

小细胞肺癌患者和重度吸烟者体细胞染色体畸变的类型和断点

应用G显带方法,分析了17名重度吸烟者的小细胞肺癌(SCLC)患者骨髓和外周血细胞的180和172个核型;16名健康吸烟者和20名健康非吸烟者外周血淋巴细胞的367和336个核型。详细记载了畸变的类型和断点,不仅发现吸烟能引起很高的染色体结构和数目畸变,而且看到畸变的染色体片段和断点主要涉及1、2、3、9和11号染色体的某些区域,如1q,3p14—pter,11q13等。许多染色体断裂部位与目前已知的、并描绘在染色体模式图上的癌基因,染色体脆性部位和个体瘤细胞中发现的染色体重排的断点(癌断点)的位置重合或接近,本工作对3组人染色体畸变率和重排类型的分析,发现SCLC患者几乎都是对香烟烟雾作用敏感的个体。     

槲皮素对中国地鼠肺成纤维细胞、小鼠骨髓细胞和小鼠睾丸精母细胞染色体影响的初步研究

目的:研究槲皮素对中国地鼠肺成纤维细胞、小鼠骨髓细胞和小鼠睾丸精母细胞染色体的影响.方法:采用80、40、20、10、5μg/mL 5个剂量组的槲皮素在有或无代谢活化条件下处理体外培养的中国地鼠肺成纤维细胞(CHL)3小时后更换新鲜培养液,恢复生长21小时后收获细胞制片.体内试验以10000、5000、2500mg/kg剂量的槲皮素给ICR小鼠灌胃后取股骨骨髓、两侧睾丸进行制片.观察槲皮素对三种哺乳动物细胞染色体的影响.结果:在有或无代谢活化条件下槲皮素在浓度>10μg/mL均能够诱导CHL细胞染色体断裂和交换等,染色体细胞畸变率显著增加(P<0.01);而槲皮素各剂量组未引起小鼠骨髓细胞染色体断片、交换、畸变细胞率显著增加,亦未引起小鼠睾丸精母细胞染色体断片、易位、畸变细胞率、常染色体单价体、性染色体单价体显著增加.结论:在本试验条件下槲皮素对体外哺乳动物细胞显示出明显致突变性,存在潜在的遗传毒性,对体内哺乳动物体细胞及生殖细胞染色体无明显损伤作用.     

山医群体中国地鼠近交E家系RAPD分析

目的　分析山医群体中国地鼠E家系的遗传纯度。方法　应用经过筛选的 3 1条随机引物对中国地鼠E家系 12只个体基因组DNA进行RAPD扩增 ,计算近交个体间的相似系数。结果　所有样品的相似系数0 943 1到 0 9978之间变动 ,平均相似系数为 0 9749,聚类分析得到了这些个体的同源树资料。结论　山医群体E家系有较高的遗传纯度     

山医群体近交系中国地鼠(Cricetulus griseus)的研究——Ⅰ、驯养与繁殖

经过12年工作,将野生中国地鼠驯养和近亲交配,繁育成山医群体,其中A-30家系已繁殖到22代。经遗传监测,证明20代鼠已育成近交系。文中对饲养条件、繁殖方法、近交系的建立等进行了讨论。     

平阳霉素诱发人精子染色体畸变—评价化学物质致断性的一种离体测试系统*

人精子经已知的致断剂平阳霉素处理后与去透明带地鼠卵受精,继而制备人精子染色体进行核型分析。平阳霉素20μg, 40μg, 60μg/ml各剂量组均诱发出了多种类型的染色体结构畸变;其畸变精子率依次为39%、44%, 52.4%,其断裂均数依次为1.90, 2.70, 3.86,与对照组的畸变精子率4%和断裂均数0.07分别进行比较,差异非常显著(P<0.01)并存在明显的剂量依赖关系。本研究为检测化学物质对人精子中染色体的致断作用提供了一种新的离体测试系统。     

肿瘤染色体畸变分析方法新进展

摘要: 肿瘤的发生多与染色体畸变有关, 确定染色体畸变与肿瘤的关系, 必然离不开染色体畸变的检测分析。文章简要综述几种常用染色体畸变的检测方法及其新进展, 包括G显带、荧光原位杂交(FISH )、光谱核型分析(SKY)、多色荧光原位杂交(M-FISH)、多色显带分析技术(Rx-FISH)、比较基因组杂交(CGH)和微阵列比较基因组杂交(Array CGH), 以及这些方法在肿瘤诊断和研究方面的应用。     

丝裂霉素C诱发中国仓鼠体外培养细胞姐妹染色单体互换的研究

本文对不同年龄中国仓鼠各种组织的体外培养细胞姐妹染色单体互换(SCE)频率进行了比较研究。实验结果表明,体外培养细胞的自发SCE频率与动物年龄无关,相同组织细胞经MMC处理后,老龄仓鼠SCE频率比幼龄仓鼠SCE频率明显低。心脏和皮肤细胸的SCE频率高于肺和尾的SCE频率。     

Identification of a chromosome that controls malignancy in Chinese hamster cells.

A chromosome that controls malignancy in Chinese hamster cells has been identified by analysis of the Giemsa banding pattern of a malignant cell line transformed by simian virus 40 (SV40), non-malignant revertants from this line, segregants from the revertants that were again malignant and a cell line transformed by methylcholanthrene. The malignant cell line transformed by SV40 was near diploid and had gained additional material of chromosome 3. Revertants with a suppression of malignancy and malignant revertants from which they were derived. Malignancy of these cells was associated with the ability to form colonies in agar. Cells of a line transformed by methylcholanthrene were malignant, formed almost no colonies in agar and the only chromosome change from the normal diploid chromosome banding complement was the addition of a long arm of chromosome 3. The results indicate that chromosome 3 carriers gene(s) that control malignancy in Chinese hamster cells in cell lines transformed by a viral or a chemical carcinogen and that malignancy was induced in both cell types by an increase of these genes.     

Nonhomologous DNA end rejoining in chromosomal aberration formation

The role of recombination of nonhomologous DNA ends in chromosomal aberration formation was investigated in Chinese hamster ovary cells. Restriction enzymes that produce blunt, 3′ overhanging, or 5′ overhanging DNA double-strand breaks were electroporated into cells in various combinations, and chromosomal aberrations were analyzed at metaphase. For all enzyme combinations tested, there was a significant increase in the frequency of aberrations whose formation requires two breaks in the DNA over the sum obtained when each of the enzymes was tested separately and the aberration frequencies were totaled. No such pattern existed for terminal deletions, which presumably require only one DNA break. The extent of interaction did not depend on the homology in the overhanging sequences or on the combination of ends used, although the largest effect was seen with a combination of two blunt ends. This study shows that nonhomologous DNA double-strand breaks can interact to increase chromosomal aberration formation significantly.     

Cytogenetic characterization of Chinese hamster-sheep somatic cell hybrids

The methods used to characterize cytogenetically Chinese hamster x sheep somatic cell hybrids have been reported. G and C banding patterns on hybrid metaphases allowed the discrimination between hamster and sheep chromosomes, and in addition to establish the unidirectional loss of sheep chromosomes in hybrid cells.     

Measurement of micronuclei by cytokinesis-block method in cultured Chinese hamster cells: comparison with types and rates of chromosome aberrations

The cytokinesis-block method of Fenech and Morley (1985) has been tested for the enumeration and characterization of micronuclei in exponentially growing Chinese hamster cells in culture. The consistent dose-response relations were obtained in cultures treated with mitomycin C, caffeine and colcemid. Comparison with the chromosome aberration frequencies indicated that approximately 30% of the acentric chromosomes are expressed as micronuclei in the mitomycin C and caffeine treated cells. The size distribution of the micronuclei suggested that the base-line frequency of micronuclei is mainly a reflection of mitotic dysfunctions rather than chromosome structural aberrations.     

Characterization of p53 in Chinese hamster cell lines CHO-K1, CHO-WBL, and CHL: implications for genotoxicity testing.

Since the p53 gene function is critical to how a cell responds to DNA damage, we investigated the p53 status in Chinese hamster cell lines commonly used in genotoxicity tests for cytogenetic damage around the world. These included: Chinese hamster ovary K1 (CHO-K1), Chinese hamster ovary WBL (CHO-WBL), and Chinese hamster lung (CHL) cells. The results of DNA sequencing, protein analysis, and cell cycle analysis demonstrate that the CHO-K1 and CHO-WBL cell lines have mutant p53 sequence [a mutation in codon 211 in exon 6 resulting in a change from Thr (ACA) to Lys (AAA)], mutant protein (high spontaneous levels that are non-inducible after X-irradiation), and mutant function (lack of G1 checkpoint). Interestingly, the CHL cell line has a completely wild-type p53 DNA sequence. However, the CHL cells have an abnormally high spontaneous level of wild-type p53 protein expression that is not inducible after X-irradiation, yet there is some evidence of G1 delay after irradiation. The protein data suggests that p53 in CHL cells is not being regulated normally, and thus is probably not functioning normally. The mechanism leading to this abnormal regulation of p53 in CHL cells clearly does not involve mutation in the p53 gene. Overall, the CHL cell line may be similar to the CHO cell lines, in that they all appear to have abnormal p53 function. Further work is needed to determine whether the presence of spontaneously high levels of wild-type p53 in CHL cells results in a difference in response to DNA damage (quantitatively or qualitatively) compared to the p53 mutant CHO cell lines.     

Low doses of alpha particles do not induce sister chromatid exchanges in bystander Chinese hamster cells defective in homologous recombination

We reported previously that the homologous recombinational repair (HRR)-deficient Chinese hamster mutant cell line irs3 (deficient in the Rad51 paralog Rad51C) showed only a 50% spontaneous frequency of sister chromatid exchange (SCE) as compared to parental wild-type V79 cells. Furthermore, when irradiated with very low doses of alpha particles, SCEs were not induced in irs3 cells, as compared to a prominent bystander effect observed in V79 cells [H. Nagasawa, Y. Peng, P.F. Wilson, Y.C. Lio, D.J. Chen, J.S. Bedford, J.B. Little, Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations, Radiat. Res. 164 (2005) 141-147]. In the present study, we examined additional Chinese hamster cell lines deficient in the Rad51 paralogs Rad51C, Rad51D, Xrcc2, and Xrcc3 as well as another essential HRR protein, Brca2. Spontaneous SCE frequencies in non-irradiated wild-type cell lines CHO, AA8 and V79 were 0.33SCE/chromosome, whereas two Rad51C-deficient cell lines showed only 0.16SCE/chromosome. Spontaneous SCE frequencies in cell lines defective in Rad51D, Xrcc2, Xrcc3, and Brca2 ranged from 0.23 to 0.33SCE/chromosome, 0-30% lower than wild-type cells. SCEs were induced significantly 20-50% above spontaneous levels in wild-type cells exposed to a mean dose of 1.3mGy of alpha particles (<1% of nuclei traversed by an alpha particle). However, induction of SCEs above spontaneous levels was minimal or absent after alpha-particle irradiation in all of the HRR-deficient cell lines. These data suggest that Brca2 and the Rad51 paralogs contribute to DNA damage repair processes induced in bystander cells (presumably oxidative damage repair in S-phase cells) following irradiation with very low doses of alpha particles.     

Chromatid repulsion associated with Roberts/SC phocomelia syndrome is reduced in malignant cells and not expressed in interspecies somatic-cell hybrids.

Different cell types from a female patient with Roberts/SC phocomelia syndrome were evaluated quantitatively for the presence of repulsion of heterochromatin and satellite regions of mitotic chromosomes. Whereas EBV-transformed lymphoblasts from an established cell line revealed these phenomena at frequencies equal to those in PHA-stimulated lymphocytes and cultured skin fibroblasts, aneuploid cells from a metastatic melanoma displayed them at 50% lower frequency. Cocultivation of the patient's fibroblasts with either an immortal Chinese hamster cell line or with a human male fibroblast strain carrying a t(4;6)(p14;q21) translocation showed that the phenomenon was not corrected or induced by a diffusible factor or by cell-to-cell contact. In each experiment, only the patient's metaphase spreads revealed chromatid repulsion. In fusion hybrids between the patient's fibroblasts and an established Chinese hamster cell line, the human chromosomes behaved perfectly normally, suggesting that the gene product which is missing or mutant in Roberts/SC phocomelia syndrome is supplied by the Chinese hamster genome.     

The relationship between transformation and somatic mutation in human and Chinese hamster cells

The frequencies of transformations of primary human and Chinese hamster fibroblasts have been compared with the spontaneous and induced frequencies of mutation for resistance to thioguanine and ouabain, and for ability to use fructose, using the carcinogens benzo (alpha) pyrene and urethane. Whereas the rates and frequencies of mutation were similar in the two cell systems, transformations to morphologically altered cells was observed only in hamster cells. The frequency of this latter transformation event in hamster cells was abour 10(3) greater than the frequencies of mutation in these cells. The morphologically altered cells formed in the above transformation process cannot grow in agar (aga-) and do not produce tumors when injected into animals. The frequency of transition of these latter cells to aga+ cells which produce tumors in animals is similar to the mutation-like events.