The mortality from leukaemia and other cancers among patients with Down's syndrome (mongols) and among their parents

Bleomycin-induced chromosomal aberrations and sister chromatid exchanges in Down lymphocyte cultures

Peripheral blood lymphocytes from three patients with Down syndrome (DS; trisomy 21; aged 5-6 years) and three age-matched control children were studied for the induction of chromosomal aberrations and sister chromatid exchanges (SCEs). Cells in G0 were exposed to bleomycin (20-100 micrograms/ml) for 3 h, and then cultured in medium containing 5-bromodeoxyuridine and phytohemagglutinin for 66 h. By the sister chromatid differential staining method, chromosome analyses were performed on metaphase cells that had divided one, two, or three or more times after treatment. The results indicate that DS cells exposed to bleomycin are hypersensitive to the production of dicentric and ring chromosomes compared to normal cells. Bleomycin also led to a dose-related increase in the frequency of SCEs, but no difference was found between the SCE frequencies in DS or normal lymphocytes exposed to bleomycin.

Alzheimer's disease: genetic aspects and associated clinical disorders

Genetic aspects and associated clinical disorders were studied in a consecutive series of 68 men and women in whom Alzheimer's disease appeared at or before age 70. Secondary cases of dementia were found in 17 (25%) of the families, affecting 22 of the probands' siblings and parents. The cumulative incidence of Alzheimer's disease in these relatives was approximately 14% at age 75. An increased frequency of Down's syndrome was observed among relatives of the probands: a rate of 3.6 per 1,000, as compared with an expected rate of 1.3 per 1,000. A history of thyroid disease was established in 9 (19.6%) of the 46 female probands, a frequency greater than that reported in the general population. There was no excess of hematological malignancies among the blood relatives, and parental age at the time of birth of the probands did not differ from the norm. The results of this study indicate that early-onset Alzheimer's disease is associated with a genetic factor manifested in a substantial familial aggregation of dementia, a probable excess of Down's syndrome in the probands' relatives, and a possible association with thyroid dysfunction in women with this form of dementia.

Spindle disturbances in mammalian cells. I. Changes in the quantity of free sulfhydryl groups in relation to survival and C-mitosis in V79 Chinese hamster cells after treatment with colcemid, diamide, carbaryl and methyl mercury

Asynchronously growing V79 Chinese hamster cells were treated with colcemid, diamide, carbaryl and methyl mercury, which are all known to be spindle disturbing agents. For each compound the dose response for c-mitosis, survival and level of free sulfhydryl groups was investigated under comparable conditions. Diamide, carbaryl and methyl were all found to give a significant increase of c-mitosis at a dose giving a decrease of non-protein sulfhydryl groups (NPSH, mainly glutathione) of 30-40% suggesting that a decrease of this magnitude may have a predictive value for spindle disturbances. Despite this similarity at concentrations close to the respective thresholds it was found that the c-mitotic activity at higher concentrations was not a simple function of average NPSH decrease. Diamide, which rapidly oxidizes glutathione to glutathione disulfide, was a less efficient c-mitotic agent than carbaryl and methyl mercury in relation to average NPSH decrease at higher concentrations. Protein bound sulfhydryl groups (PSH) were not significantly affected with diamide and carbaryl at their lowest c-mitotic concentrations while methyl mercury caused a significant decrease already at concentrations below the lowest c-mitotic concentration. With colcemid a significant decrease of average NPSH (14%) and PSH (12%) was observed only with concentrations giving close to 100% c-mitotic cells. Concentrations giving more than 20% c-mitosis gave a pronounced decrease of survival with carbaryl, diamide and methyl mercury while no toxic effects were obtained with colcemid, not even with concentrations giving close to 100% c-mitosis. Carbaryl, diamide and methyl mercury caused increased glutathione peroxidase activity indicating that these compounds cause increased lipid peroxidation. The possible connection between peroxidative damage of membranes and c-mitosis is discussed.

Leukemia and other cancers, anomalies and infections as causes of death in Down's syndrome in the United States during 1976

All 995 persons with Down's syndrome who died in the United States during 1976 and whose death certificates listed Down's syndrome as the underlying or a contributing cause of death were identified. This allowed the underlying causes of death of 793 affected persons to be analysed and compared to deaths in the whole US population for that year. Mortality ratios provided evidence that the excess risk of leukemia mortality continues into adulthood and that deaths from other hematopoietic malignancies also occur excessively among Down's syndrome adults. Congenital anomalies of all kinds in infancy and congenital defects of the heart in infancy and later were also excessive. Respiratory tract infections and pneumonia showed persistently high ratios. Diabetes was raised only at ages 24 to 34 years. Ischemic heart disease, non-hematopoietic cancers, accidents, suicides and violence were under-represented among the causes of death. Methodological limitations of proportional mortality analysis are discussed.

Longevity and mortality in Down's syndrome

The life span of individuals with DS has gradually increased since the 1920s. The DS individual now has an average life expectancy of 35 years. Despite advances in the health care of the retarded and improvements in the quality of institutional care, the overall mortality rate remains elevated by five-fold. Specific mortality rates from respiratory diseases (particularly pneumonia), infectious diseases, congenital heart disease, leukaemia and neurological disorders are still substantially increased. Disorders of immunological functioning, particularly T-cell mediated, appear related to this increased vulnerability, although further research is necessary. The periods of highest risk are during infancy, when congenital heart disease, leukaemia and respiratory diseases are most lethal, and late adulthood, when Alzheimer-type dementia and declining immunological function appear to be significant factors.

The implications of S-phase exchanges for the mechanisms of radiosensitivity in trisomy 21

Human lymphocytes obtained from four patients with Down syndrome and from two normal individuals were irradiated with X-rays during their S phase and examined for chromatid type aberrations. It is suggested that the significantly increased frequency of asymmetrical chromatid interchanges found in trisomic cells is related to an altered DNA repair system. This altered repair system is probably responsible for the increased frequency of chromosome aberrations that can be induced in these cells by x-rays and the increased tendency for leukemia observed in Down syndrome as well.

Genes coding for sensitivity to interferon (IfRec) and soluble superoxide dismutase (SOD-1) are linked in mouse and man and map to mouse chromosome 16

By using 12 hamster-mouse hybrids segregating a mouse T(16;17)Bnr Robertsonian translocation chromosome in conjunction with 10 similar hybrids segregating normal mouse chromosomes, we have shown that the loci that control cellular sensitivity to interferon (IfRec) and code for the soluble enzyme superoxide dismutase (SOD-1) (superoxide:superoxide oxidoreductase; EC 1.15.1.1) are syntenic in the mouse and map to mouse chromosome 16. IfRec and SOD-1 are also syntenic in man. They have previously been assigned to the distal segment of the long arm of human chromosome 21, trisomy for which causes Down syndrome. Because both IfRec and SOD-1 map to mouse chromosome 16, it will now be possible to use mice trisomic for this chromosome to determine whether certain aspects of the Down syndrome phenotype in man are caused by an altered dosage of IfRec and SOD-1.

SV40 T-antigen expression in cultured fibroblasts from patients with Down syndrome and their parents

Expression of simian papovavirus 40 (SV40) T-antigen following in vitro infection was studied in skin fibroblasts from patients with Down syndrome (DS) and their parents to determine whether the increased susceptibility to SV40 infection reflected the cytogenetic defect or the leukemia risk associated with this syndrome. As a group, fibroblasts from patients with DS showed elevated T-antigen expression 72 hrs after infection compared to that of a healthy control population. However, among 24 patients tested, the cell lines of only 11 showed statistically significant increases in T-antigen expression. A cell line from a patient with concurrent DS and acute myelogenous leukemia had a normal value. T-antigen expression did not correlate with the percentage of cells trisomic for chromosome 21 in 18 cell lines examined or with the number of copies of this chromosome in disomic and trisomic cell strains cloned from three mosaic patients.Collectively, cell lines from parents of trisomy 21 patients also showed increased susceptibility to SV40 infection; however, in five families tested, a consistent pattern of genetic transmission of elevated T-antigen expression from parent to offspring was not observed. Q-banding of cell lines in one family showed that elevated T-antigen expression is not a marker of parental nondisjunction. Variation in susceptibility to human interferon, an antiviral agent, did not account for variation in T-antigen levels among these cell lines. Thus, the abnormalities of T-antigen expression in DS appear independent of the hyperdiploid state and are not a sensitive indicator of cancer risk.

Family studies in acute leukaemia in childhood: a possible association with autoimmune disease

Medical histories of themselves and their first-degree relatives were obtained from parents of 82 leukaemic children (54 acute lymphoblastic (ALL), 28 acute myeloblastic (AML)) and from control couples matched for age. The possibility of a primary familial immunological abnormality as an aetiological factor in childhood leukaemia was suggested by binding some infections significantly more frequently reported in parents than in controls, but more strongly supported by the finding of a significantly (P less than 0.02) increased prevalence of disorders associated with autoimmunity (but not of other conditions such as peptic ulceration, infective hepatitis, tuberculosis or malignancy) amongst members of ALL families compared to those of controls. Analogy with Down's syndrome and the strain of NZB mice, in which diminished T-cell function is associated with autoimmune disease and lymphoid neoplasia, is discussed. Varicella and herpes zoster occurred respectively in 2 ALL mothers during their pregnancies involving the patients and in none of the other 388 pregnancies here reported. This supports previous evidence that antenatal varicella infections may be of aetiological importance in some cases of ALL.

Genetics of neoplasia--impact of ecogenetics on oncogenesis. A review

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White cell function in Down's syndrome

Neutrophil function was studied in 25 patients with Down's syndrome at a mental subnormality hospital and compared with 26 normal controls. In vitro killing of Candida albicans was significantly lower in the Down's group, but there was no difference in the percentage of cells actively involved in phagocytosis or in the phagocytic index. The spontaneous nitroblue tetrazolium reduction was increased in 10 patients, but no abnormality of peroxidase activity or leucocyte alkaline phosphatase activity was found.

DNA repair and frequency of x-ray and u.v.-light induced chromosome aberrations in leukocytes from patients with Down's syndrome

DNA-repair and the frequency of chromosome aberration after u.v. and X-ray irradiation was studied on leukocytes from patients with Down's syndrome. The u.v.-induced DNA-repair synthesis was followed by the incorporation of [3H]thymidine in the presence of hydroxyurea. Similar dose-response curves were established for Down's syndrome leukocytes and controls. The cells from patients with Down's syndrome incorporated 70-75% of the activity of control cells at the various doses (32-196 erg/mm.2). This difference was significant for the two highest u.v.-doses (P less than 0-01). The yield of dicentric chromosomes after X-ray exposure (150 rad.) was 35% higher in Down's syndrome leukocytes than in the control cells (P less than 0-001). Combined u.v. and X-ray irradiation caused a twofold increase in the frequency of dicentric chromosomes in control cells, while the increase was only 27% in Down's syndrome leukocytes. This synergistic effect of u.v. and X-ray irradiation on the yield of dicentric chromosomes suggests that healing of X-ray and u.v.-induced DNA lesions may partly utilize the same repair enzymes. The results also indicate that DNA repair mechanisms are impaired in leukocytes from patients with Down's syndrome, which may contribute to the increased incidence of leukemia and the susceptibility to X-ray irradiation in this disorder.

Leukemia in twins: antenatal and postnatal factors

Two factors emerged from a search for obstetric phenomena that might explain concordance of leukemia in both members of a twin pair within days or months of each other: antenatal exposure to ionizing radiation; and antenatal cojoined intrauterine circulation. In addition, antenatal tumor metastasis and chromosomal changes, antenatal or postnatal, may be contributory. Continued observation of reports should be carried out.

[Clastogenic effect of trenimon on in vitro chromosomes of phemotypically healthy subjects with morphologically abnormal caryotype]

The effect of a given concentration of Trenimon (6 xpe was analysed in vitro. The research included 6 subjects with balanced translocations, one of them with a centric fusion. Of the remaining 5 subjects, 2 had a duplication in the paracentric region, 1 showed an inversion, and 2 had a marker chromosome. In the group with morphologically abnormal chromosomes a higher sensibility to the influence of Trenimon was found as compared with a control group with morphologically normal karyotype. The subjects with an atypical karyotype had 36 to 65% aberrations, the control group 28%. A localization of the breaks showed no increased aberration rates in the morphologically abnormal chromosomes.

Down's syndrome and acute leukaemia: a cytogenetic study

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DNA polymerase activity as an index of lymphocyte stimulation: studies in Down's syndrome

The ability of peripheral blood lymphocytes to respond to phytohemagglutinin (PHA) in vitro was studied in patients with Down's syndrome. The response was measured by the increase in DNA polymerase activity and the rate of incorporation of tritiated thymidine by the cultured lymphocytes. These activities were significantly lower in PHA-stimulated lymphocytes from patients with Down's syndrome compared with age- and sex-matched, mentally retarded patients without Down's syndrome from the same institution and the normal healthy volunteers. The impairment in response to PHA does not seem to be related to the presence of Australia antigen in patients with Down's syndrome or to institutionalization itself. In contrast to DNA polymerase activity and thymidine-(3)H uptake, there was no significant difference in the percentage of blast transformation in the three groups studied. The poor response of the lymphocytes from patients with Down's syndrome to a mitogenic stimulus could reflect an impairment of cellular immune functions in these patients which may be one of the factors contributing to the vulnerability of these patients to repeated or persistent infections.