2例染色体易位家系中亲代脆性部位表达的研究

本文对２例新发生的Ｘ—常染色体平衡易位携带者家系进行了染色体脆性部位表达的分析。报道了１例患者核型为４６，Ｘ，ｔ（Ｘ；１９）（ｑ２２；ｐ１２）而其母亲ｆｒａ（Ｘ）（ｑ２２）表达频率较高的家系，及患者核型为４６，Ｘ，ｔ（Ｘ；９）（ｑ２６；ｑ２２）其母ｆｒａ（９）（ｑ２２）有表达的病例。此结果提示，染色体断裂点的产生与亲代脆性部位表达增高，特别是在与断裂点同一位点上的脆性部位表达增高有某种联系     

新生儿染色体畸变及脆性部位的研究

新生儿染色体畸变及脆性部位的研究沈婉英，任东平，童英染色体不稳定性与肿瘤易患性之间关系的研究引起了人们广泛关注，近年来这一领域出现了不同的观点［１，２］，查明染色体不稳定个体在人群的分布状况对于这一研究有着重要意义。国内已有作者曾对不同人群做了研究［...     

大肠癌患者及家族成员染色体脆性部位和癌基因位点的研究

大肠癌患者及家族成员染色体脆性部位和癌基因位点的研究李明烈，程俊，莫善兢近年来，有关染色体不稳定性与癌变机理之间相关性研究、其中尤以肿瘤患者及其易感个体的染色体脆性部位的存在正引起人们极大关注。迄今为止，国内外有关大肠癌及其易感个体的脆性部位研究的报...     

白血病染色体畸变与脆性部位

染色体脆性部位在肿瘤发生中的意义,是当前肿瘤细胞遗传学研究的热门课题之一,而脆性部位与肿瘤特异性畸变断裂点及癌基因位点的定位关系尤其引人注目。目前,对这方面了解最多且较能说明问题的是对白血病、淋巴瘤的研究。本文综述了白血病有关的染色体脆性部位、特异断裂点及癌基因对应关系,对其在白血病发生中的影响进行了讨论。     

习惯性流产夫妇染色体脆性部位分析

本文对习惯性流产夫妇及正常同龄健康夫妇各１５对，行染色体脆性部位分析。发现两组检出的断裂点较弥散。流产组２１６个断裂点，ＦＳ表达率７．２％；对照组４４个断裂，ＦＳ表达率１．４７％。两组有高度显著性差异（Ｐ＜０．０１），断裂点以３Ｐ１４最高。提出凡表达的ＰＳ≥８次者，染色体稳定性差，是导致部分患者胚胎或胎儿异常的原因，孕早期应行产前诊断。     

白血病和淋巴瘤的发生与染色体脆性部位的关系

染色体的不稳定性与肿瘤发生的关系及染色体脆性部位同癌基因、癌特异断点的相关关系，已成为医学遗传学研究的重要课题。染色体的脆性部位就是在接触某些特殊化学物质或体外培养条件下所出现的非随机的染色体裂隙、断裂、缺失、无着丝粒片断或多射体等。近几年的研究结果...     

无精症患者染色体脆性位点的研究

目的：探讨染色体脆性位点在无精症形成过程中的作用,了解其相关因素,为进行病因学研究和采取干预措施打下基础。方法：本文用低叶酸低胸苷的培养基,并用5-氟尿嘧啶脱氧核糖核酸苷（FUDR）和咖啡因双诱导淋巴细胞染色体脆性位点表达。结果：实验组染色体脆性位点的频率为13.20%;对照组为4.85%,两组对比差异非常显著。染色体脆性位点的分布两组基本一致。结论：无精症与染色体脆性位点频率增高有关,与脆性位点分布关系不大。     

Fragile sites and chromosome breakpoints in constitutional rearrangements I. Amniocentesis

Since fragile sites may conceivably predispose to chromosome breakage and rearrangements in meiosis, we examined the locations of 278 breakpoints leading to chromosome rearrangements detected in amniocenteses. Of the 278 breakpoints, 59 (21%) were observed to be in bands containing fragile sites compared to an expectation of 31 (11%), a highly significant difference (P less than 0.001). The tendency for breakpoints to be in bands with fragile sites was independent of origin of the rearrangement or class of fragile site, consistent with the concept that fragile sites predispose to heritable chromosome rearrangements.     

Fragile Sites in Human and Macaca Fascicularis Chromosomes are Breakpoints in Chromosome Evolution

We have analysed the expression of aphidicolin-induced common fragile sites at two different aphidicolin concentrations (0.1 µmol/L and 0.2 µmol/L) in three female and one male crab-eating macaques (Macaca fascicularis, Cercopithecidae, Catarrhini). A total of 3948 metaphases were analysed: 1754 in cultures exposed to 0.1 µmol/L aphidicolin, 1261 in cultures exposed to 0.2 µmol/L aphidicolin and 933 in controls. The number of breaks and gaps detected ranged from 439 in cultures exposed to 0.1 µmol/L aphidicolin to 2061 in cultures exposed to 0.2 µmol/L aphidicolin. The use of a multinomial FSM statistical model allowed us to identify 95 fragile sites in the chromosomes of M. fascicularis, of which only 16 are expressed in all four specimens. A comparative study between the chromosomes of M. fascicularis and man has demonstrated that 38 human common fragile sites (50%) are found in the equivalent location in M. fascicularis. The analysis of the rearrangements that have taken place during chromosome evolution has revealed that the breakpoints involved in these rearrangements correspond significantly (p < 0.025) to the location of M. fascicularis fragile sites.     

Fragile sites and chromosome breakpoints in constitutional rearrangements II. Spontaneous abortions, stillbirths and newborns

Certain fragile sites may possibly predispose to chromosome breakage and rearrangements in meiosis. To test this hypothesis, we examined 894 breakpoints found in spontaneous abortions, stillbirths and livebirths of which 165 (18.5%) were in bands with fragile sites. Compared to an expectation of 98 (11%), there was a significant excess of breakpoints in fragile site bands (P less than 0.001). Together with data from amniocenteses, there is now evidence suggesting that certain fragile sites may be prone to fragility in meiosis.     

Chromosome abnormalities and rare fragile sites detected in azoospermia patients

Summary We have examined constitutional chromosome abnormalities and fragile sites in 40 patients with azoospermia. Chromosome abnormalities were found in four cases. Three cases showed a deletion of the long arm of the Y chromosome 46,X,del(Yq) and the other case had a ring of G group chromosome 46,XY,r(G). In a rare fragile sites test, four fragile site carriers were detected and three rare autosomal fragile sites were identified; fra(8)(q24.1), fra(11)(p15.1), and fra(17)(p12). The expression of these fragile sites were induced specifically by AT-specific DNA ligands, such as distamycin A and Hoechst 33258. In addition, one patient was found to be the case of double ascertainment of fragile sites, fra(8)(q24.1) and fra(17)(p12). The overall frequency of distamycin A-inducible fragile sites in azoospermia patients appeared to be higher than those reported for Japanese healthy subjects and cancer patients. However, no significant relation among fragile sites, clinical and histological findings has been detected so far.     

Fragile sites in human chromosomes I The effect of methionine on the Xq fragile site

The Xq fragile site found in males having non-specific X-linked mental retardation was studied by varying the chemical and physical parameters of leukocyte cultures. Methionine was shown to be required for marker expression in both medium 199 and MEM. Banding studies indicated that methionine does not function as a stabilizing factor for the fragile site on Xq.     

Chromosome Aberrations and Sister Chromatid Exchange Studies in Patients with Prostate Cancer: Possible Evidence of Chromosome Instability

Cytogenetic studies have been carried out using the G-banding technique in peripheral blood lymphocytes of 24 patients with prostate cancer. Of these, eight belong to stage B, six to stage C/e, three to C/sv, two to Do, and the remaining five to DI stage of carcinoma. Simultaneously, sister chromatid exchanges (SCEs) were also analyzed in the peripheral blood lymphocytes of these patients, along with those of 40 age-matched control subjects. The frequency of aberrant metaphases is significantly higher in patients with prostate cancer (7.32%) than in age-matched controls (2.92%). A large number of chromosome aberrations in lymphocytes of these patients, which are generally constitutional in nature, have also been detected. In stage-B patients, the frequency of cytogenetically abnormal cells is comparatively low with regard to the number of cells scanned, and these abnormalities are generally confined only to single chromosome (except in one metaphase in patient 1, who was diagnosed with bladder carcinoma in addition to cancer of the prostate). Sister chromatid exchanges (SCEs) were also analyzed in the patients and age-matched control subjects. The mean SCE frequencies were 9.24 ± 0.62 (n = 1356) per metaphase and 0.203 per chromosome in patients, whereas in control subjects the frequencies were 5.94 ± 0.25 (n = 4000) per metaphase and 0.129 per chromosome. The SCE frequency in cancer patients was statistically significant (p < 0.001). Our results indicate that the patients with prostate cancer show a degree of chromosomal instability that might be related to a predisposition to neoplasia.     

Fragile 19p13 in a family with mental illness

We describe a family where four brothers show the rare heritable folate sensitive autosomal fragile site (FSAFS) at 19p13 when cells were grown in TC199. Two of the brothers are schizophrenic while one brother is mentally retarded with autistic-like features. The clinical significance of this fragile site however is still unknown.