ABSTRACT
Addition of thymidine to culture medium commonly used by laboratories performing medical cytogenetics followed by a release of the block by 2-deoxycitidine increases greatly the mitotic index and the proportion of metaphases suitable for chromosome analysis. The benefit is, however, less evident when the method is applied to culture medium used in laboratories specialized in chromosome aberration dosimetry.
Subject(s)
Chromosome Aberrations , Thymidine/pharmacology , Cell Division/drug effects , Cell Division/radiation effects , Cells, Cultured/cytology , Cells, Cultured/drug effects , Cells, Cultured/radiation effects , Colchicine/pharmacology , Culture Media , Deoxycytidine/pharmacology , Dose-Response Relationship, Drug , Dose-Response Relationship, Radiation , Gamma Rays , Humans , Mitotic Index/drug effects , Mitotic Index/radiation effectsABSTRACT
Lymphocyte cultures from patients affected by retinoblastoma (Rb), with or without a microdeletion of chromosome 13, and Wilms tumor (WT), with a microdeletion of chromosome 11p where exposed to gamma-ray radiation during S and G2 phases. Chromatid and chromosome lesions were scored and compared to those observed in controls. No significant differences were detected, neither between patients and controls, nor between patients carrying or not a microdeletion. This lack of difference was unexpected since the genes for catalase and esterase D, also called S-formyl glutathione hydrolase, which are two detoxication enzymes, are deleted in case of microdeletion of 11p and 13q, respectively.
Subject(s)
Acatalasia , Carboxylesterase , Chromosome Aberrations/genetics , Chromosomes, Human, Pair 11/ultrastructure , Chromosomes, Human, Pair 13/ultrastructure , Eye Neoplasms/genetics , Kidney Neoplasms/genetics , Retinoblastoma/genetics , Wilms Tumor/genetics , Adolescent , Adult , Carboxylic Ester Hydrolases/genetics , Catalase/genetics , Cell Cycle/radiation effects , Chromosome Aberrations/enzymology , Chromosome Deletion , Chromosome Disorders , Eye Neoplasms/enzymology , Female , Gamma Rays , Humans , Kidney Neoplasms/enzymology , Lymphocytes/pathology , Lymphocytes/radiation effects , Male , Radiation Tolerance , Retinoblastoma/enzymology , Wilms Tumor/enzymologyABSTRACT
Chromosome breaks and chromatid-type lesions from a prospective study of more than 1000 lymphocyte karyotypes from each of six controls were analysed. These lesions were more frequent in older (75 years old on average) than in younger (29 years old on average) controls, especially after 72 h cultures. All controls were found to be carriers of fragile sites. The most frequent were 3p14.3 and 16q23, especially in older controls. At least one fra (X) (q27) mitosis was found in each control. Most deletions occurred after breakage in heterochromatin or in late-replicating euchromatin. As almost all radials were either "mitotic chiasmata" or triradials (branched chromosomes), it is concluded that chromatid exchanges between non-homologous segments are very rare, and indicate chromosomal instability syndrome or recent exposure to a mutagen.
