Cytogenetics study in severely mentally retarded patients.

OBJECTIVE: To study the frequency of chromosomal abnormalities in severely mentally retarded Iraqi patients. Secondly, to determine the types of chromosomal abnormalities that play a major role in the causation of mental retardation and to compare our results with those reported elsewhere. METHODS: Twenty one patients with severe mental retardation were subject to chromosomal analysis. The lymphocyte culture was carried out according to standard methods. RESULTS: Fourteen of the subjected mentally retarded patients had chromosomal abnormalities, 13 autosomal abnormalities, and only one had sex chromosomal abnormalities. However, structural autosomes were found to be the most prominent abnormalities and only 2 patients were demonstrated to have diagnosable syndrome. CONCLUSION: Chromosomal abnormalities are an important cause of mental retardation and its frequency increased with the severity of mental retardation. We concluded that chromosomal studies in mentally retarded patients help in accurate diagnosis and proper prognosis followed by genetic counseling and management rehabilitation.

Chromosome studies in male patients suffering from infertility.

OBJECTIVE: The goal was to estimate the contribution of chromosome anomalies in the Iraqi infertile males. METHODS: Sixty-four male patients were included in the present study. Blood culture and chromosomal harvesting were conducted according to standard methods. RESULTS: The percentage of normal karyotype was 87.5%. The number of abnormal karyotypes constitute about 12.5%. In our azoospermic patients, about 11% of patients stated to have abnormal karyotype comparing to 15% in oligospermic patients. On the other hand, sex chromosomal anomalies were detected in 4 patients with azoospermia. No autosomal anomalies were found in this group. Meanwhile, 3 patients with sex chromosomal anomalies were recorded in oligospermic patients. The unique autosomal anomaly was detected in one oligospermic patient. CONCLUSION: Karyotyping of subfertile males will still be important not only from a diagnostic viewpoint, but even more importantly, in order to gain a better understanding of gametogenic impairment, which is associated with chromosomal abnormalities. Moreover, the value of cytogenetic screening is emphasized since this group of chromosomally abnormal patients can be excluded from conventional treatment.

Metaphase acrocentric associations in metally retarded patients.

OBJECTIVE: The metaphase of 21 severely mentally retarded patients were studies to assess the role of satellite association in the etiology of mental retardation. METHODS: Peripheral blood culture, chromosome harvesting and study scoring were conducted according to standard methods. RESULTS: Considered as a whole the results indicate that there is a significant increase in the frequency of satellite association among the mentally retarded. CONCLUSION: The present study concluded that satellite association may play a role in the etiology of mental retardation and may explain to some extent the presence of normal karyotype in some mental retardation patients.

Cytogenetics study in severely mentally retarded patients.

OBJECTIVE: To study the frequency of chromosomal abnormalities in severely mentally retarded Iraqi patients. Secondly, to determine the types of chromosomal abnormalities that play a major role in the causation of mental retardation and to compare our results with those reported elsewhere. METHODS: Twenty-one patients with severe mental retardation were subject to chromosomal analysis. The lymphocyte culture was carried out according to standard methods. RESULTS: Fourteen of the subjected mentally retarded patients had chromosomal abnormalities, 13 autosomal abnormalities, and only one had sex chromosomal abnormalities. However, structural autosomes were found to be the most prominent abnormalities and only 2 patients were demonstrated to have diagnosable syndrome. CONCLUSION: Chromosomal abnormalities are an important cause of mental retardation and its frequency increased with the severity of mental retardation. We concluded that chromosomal studies in mentally retarded patients help in accurate diagnosis and proper prognosis followed by genetic counseling and management rehabilitation.

Evidence for indirect involvement of thymidine kinase in excision repair processes in mouse cell lines.

Wild-type cells and thymidine kinase-deficient clones from two mouse lymphoma cell lines, P388 and L5178Y, were compared for sensitivity to killing by the mutagens, ultraviolet irradiation (UV), ethyl methane sulfonate (EMS), and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Two out of three thymidine kinase-deficient P388 clones showed significantly enhanced sensitivity to killing by all three mutagens. This increased sensitivity to killing was also reflected in increased mutagenesis by the three mutagens. In the L5178Y cell line, wild-type cells showed little difference to two thymidine kinase-deficient clones in terms of mutagen sensitivity. This indicates that thymidine kinase may be significant for DNA repair processes in P388 but not in L5178Y cells. Unscheduled DNA synthesis (UDS) experiments were carried out on P388 and L5178Y wild-type cells and wild-type Friend leukemia cells (which are mutagen-sensitive when deficient in thymidine kinase). The UDS experiments showed the L5178Y cells were low in excision repair abilities relative to the P388 cells and the Friend cell clone. This indicates that the increased mutagen sensitivity in thymidine kinase-deficient P388 and clone 707 Friend cells may be due to thymidine kinase playing an indirect role in DNA excision repair, a process which is of little significance in the L5178Y cell line.

Hypersensitivity of thymidine kinase-deficient Friend leukaemia cells to the induction of cytogenetic aberrations by mitomycin C.

Clone 707 of the Friend leukaemia cell line was compared with the hypermutable thymidine kinase deficient subclone 707 BUF for sensitivity to the induction of cytogenetic aberrations by mitomycin C (MMC). Two 16-h doses of MMC were utilized, namely 0.1 and 0.15 microgram ml-1. Following removal of MMC from the cultures, metaphase spreads were prepared after 15, 29 and 43 h growth in non-selective medium. Thirteen types of aberrations were scored. The thymidine kinase deficient subclone showed considerably increased sensitivity to the induction of aberrations, with the aberrations also persisting longer. In light of these and earlier reported results, the significance of thymidine kinase for accurate DNA repair is discussed.

Cytogenetic evidence for hemizygosity at the thymidine kinase locus in P388 mouse lymphoma cells.

A detailed cytogenetic investigation was carried out on P388 mouse lymphoma cells. The cells have a mean chromosome number of 36.86 with a mode and median of 37 chromosomes. G-banding analysis of 12 spreads revealed a total of 15 marker chromosomes with chromosome 11, the determinant of thymidine kinase, being present only in single copy per cell. It is therefore concluded that the P388 cell line is hemizygous at the thymidine kinase locus. Thymidine kinase activities were assayed in P388 cells and two other malignant cell lines, clone 707 Friend mouse leukaemia cells and L5178Y mouse lymphoma cells. No clear relationship was observed between enzyme activity and gene dosage.