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Peripheral lymphocytes of three Fanconi's anemia (FA) patients and of five heterozygotes have been tested for their susceptibility to chromosomal breakage and sister chromatid exchange (SCE) induction by diepoxybutane (DEB). As previously shown, DEB dramatically increases the chromosomal breakage level in both homozygotes and heterozygotes. Slightly, but significantly, reduced spontaneous levels of SCE were found in cultures from FA patients and FA gene carriers as compared with controls. SCE rates were not enhanced in lymphocytes grown in the presence of DEB, irrespective of the time at which it had been added to the culture, and were comparable in cells of FA patients and FA heterozygotes. This was in contrast with SCE rates in control cells, which showed increases positively related to the length of DEB treatment.

Report is given of a mentally retarded and dysmorphic patient with a partial monosomy 8q, resulting from a de novo translocation t(4;8)(q13;q213). Oetermination of erythrocyte glutathione reductase (E-GSR) activity in the proposita shows activity in the normal range. Previous evidence for of the assignment of E-GSR locus to the short arm of chromosome 8 is confirmed.

A male patient with mental retardation and typical clinical features of 10p trisomy syndrome was found to have a duplication of the short arm of chromosome 10 attached to the short arm of the Y chromosome. Quantitative evaluation of nine red cell enzymes showed significantly increased activity levels of HK1 and, to a lesser extent, of PK, PGI, 6PGD, and G6PD. It is suggested that the HK1 locus may be in the 10pter leads to p12 region. The increased levels of HK1 could affect other erythrocyte metabolic pathways slowing down the physiological rate of cellular senescence and result in increased activity levels of other cell-age-dependent enzymes.

A case of partial trisomy 9 is described in a mentally retarded and dysmorphic child, confirming that this chromosome unbalance results in a characteristic clinical entity. This trisomy arose through aberrant segregation of translocation chromosome during meiosis in the patient's mother, who is a balanced heterozygote for a complex translocation involving chromosomes 9, 21 and 22. The phenotypically normal sister of the proposition is also carrier of the same complex translocation.

Peripheral blood lymphocytes from eight Fanconi anemia (FA) patients, 14 FA heterozygotes, and nine normal subjects have been tested for their susceptibility to chromosomal breakage induction by diepoxybutane (DEB) and by two peroxides. In addition, the effect of five antioxidants was investigated in standard cultures and in cultures stressed either with DEB or with butylhydroperoxide (BHP) or with hydrogen peroxide (H2O2). DEB, BHP, and H2O2 dramatically increased the chromosomal breakage levels in homozygous and heterozygous FA cells. A partial correction of chromosomal instability was obtained by treating the patients' lymphocytes with antioxidants. A "protective" effect was also noted in the DEB or peroxide-stressed lymphocytes of patients and heterozygotes, grown in the presence of antioxidants.

Partial trisomy 9p and a 13/14 translocation occurred in the daughter of a t(5;9)(p15;p12) mother and a t(13;14)(p11;q11) father. Two additional offspring displayed a normal karyotype and a translocation trisomy 13 respectively. Two first cousins, selected for chromosome analysis because of a spontaneous abortion, were found to have an identical translocation t(14;21)(p11;q11). Their second pregnancy was monitored by midtrimester amniocentesis and disclosed a balanced fetus. The different zygotic chromosome constitutions and the counselling problems in the marriages between two balanced translocation carriers are discussed.

Centric fission of chromosome No. 4 was found in the healthy mother of two children with trisomy 4p. The two telocentrics derived are stable and show no evidence of fusing again. The 2:3 ratio of unbalanced offsprings born to the proposita indicates that, contrary to the evidence emerging from studies in other species, the risk for the production of unbalanced gametes is high.

Duchenne muscular dystrophy (DMD) is a lethal sex-linked degenerative disorder of the muscle in man. Generalized cell membrane abnormalities seem to be involved in the pathogenesis of the disease; in particular, the impairment of lymphocyte capping capacities has been repeatedly confirmed. To clarify whether capping impairment is a consequence of factors related to the activity of the disease or an expression of an intrinsic cellular defect, we have investigated the capping capacities of DMD EBV-transformed cell lines. The results indicate a significant impairment of capping capacity in cultured cell lines, providing evidence for an intrinsic cell deficiency in DMD.