Biomedical subjects
Publications and source records attributed to T Schaap.
Hunter disease in Israel occurs among Ashkenazi, Oriental, and Sephardic Jews and is by far more frequent than Hurler disease. None of the other mucopolysaccharidoses has been diagnosed in Ashkenazi Jews. The possibility of Hunter disease being a "Jewish" disease is discussed.
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A total of 1,319 chromosomal breaks and rearrangements, induced in human lymphocytes by mitomycin C, was investigated. Patterns of "preference" and "avoidance" among the partners of chromosomal rearrangements were easily discerned. The centromeric regions of chromosomes 1, 9, and 16 were most frequently involved in rearrangements that tended to occur between homologs. The acrocentric chromosomes prefer rearrangements within their own group, including homologs, and avoid involvement with the centromeric region of chromosome No. 9 (9c). Regions designated as "rarely rearranging" avoid the centromeres of 1 and 9 and prefer rearrangements within their own groups. No correlation could be demonstrated between the frequency of open breaks and rearrangements in the same chromosomal region.
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Chromosomal breakage in peripheral lymphocytes, cultured fibroblasts and long-term lymphoblastoid cell lines was investigated in five hitherto undescribed patients with ataxia telangiectasia (AT). Increased chromosomal instability was observed in lymphocytes and fibroblasts, and clones possessing a Dq+ marker were observed. Breakage rates were significantly higher in the fibroblasts than in the lymphocytes of AT patients or in similar tissues from patients with Bloom syndrome or Fanconi anemia. However, chromosome breakage in lymphoblastoid lines established from these five AT patients and six others did not differ from controls. These observations suggests that selection pressures, in vivo or in vitro, or both, act differently on the expression of chromosomal instability in these various cell types.
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The Papillon-Lefèvre syndrome (PLS) is segregating in a large kindred of a Jewish isolate originating from Cochin, India. The frequency of the gene responsible for PLS among the Cochin Jews, 0.1, was estimated from the number of unrelated carriers in the isolate who married into the kindred. The obvious discrepancy between this apparently high gene frequency and the total absence of PLS in other kindreds of the isolate suggests that the syndrome may not behave as a simple autosomal recessive trait.
The offspring of 214 otosclerotic x normal couples were investigated, and within these sibships, the segregation of otosclerosis is compatible with autosomal dominant inheritance. However, the overall sex ratio is approximately 0.73, with otosclerosis being approximately 1.8 times more frequent in female offspring. These observations are interpreted as the consequence of selection against males carrying the otosclerosis gene. Elimination of such males occurs only in certain sibships. The remaining families demonstrate a sex ratio approximating unity with similar rates of otosclerosis in both sexes. This selection operates mainly, and possibly only, prenatally.
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The graphic representation of family data for the computation of the coefficients of inbreeding [F] and relationship [r] can be replaced by an algebraic method. The organization of family data is facilitated by a data form which can be easily, thoroughly, and correctly completed, even by a layman. The computation of the coefficients is practically automatic and greatly reduces the possibility of error.
A family is described in which both a father and son are affected with Ebstein's anomaly, while several other family members manifest different cardiac malformations. Five additional instances of familial Ebstein's anomaly were found in the literature and compared with our family. Inspection of possible modes of inheritance in this group of families suggests that Ebstein's anomaly is probably inherited as a polygenic character with a threshold phenomenon.
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Lymphoblastoid cell lines from fragile X patients and amniotic cells from fragile X embryos, when cultured with methotrexate (MTX) or fluorodeoxyuridine (FUdR), showed a significant increase in endoreduplication and polyploidy. This phenomenon was not observed in fragile X lymphocytes or in lymphoblastoid cell lines and amniotic cells of normal control individuals. The relationship between the inducible fragile site at Xq27.3 and the inducible endoreduplication is discussed. The induction of endoreduplication and polyploidy in fragile X lymphoblasts and amniocytes is evaluated as a possible diagnostic test.
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