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Biomedical subjects

W Keijzer

Publications and source records attributed to W Keijzer.

9 recordsLinked to original sources
PubMed1979

A seventh complementation group in excision-deficient xeroderma pigmentosum.

Cells from a xeroderma pigmentosum patient XP2BI who has reached 17 years of age with no keratoses or skin tumours constitute a new, 7th complementation group G. These cells exhibit a low residual level of excision repair, 2% of normal after a UV dose of 5 J/m2 and an impairment of post-replication repair characteristic of excision-defective XPs. They are also sensitive to the lethal effects of UV and defective in host-cell reactivation of UV-irradiated SV40 DNA.

Adolescent↗
PubMed1979

Prenatal diagnosis of xeroderma pigmentosum (group C) using assays of unscheduled DNA synthesis and postreplication repair.

The analysis of DNA repair processes is described in two pregnancies at risk for xeroderma pigmentosum. In both cases, excision repair (measured by unscheduled DNA synthesis) and postreplication repair were analyzed. An affected and an unaffected fetus were identified within 3 weeks after amniocentesis. The cells from the affected fetus were found to be deficient in excision DNA repair, whereas the PRR patterns were intermediate between those of normal and PRR deficient cells. This indicates the possibility of prenatal diagnosis of PRR deficient XP patients (XP variants).

Amniotic Fluid↗
PubMed1977

Induction of sister chromatid exchanges in xeroderma pigmentosum cells after exposure to ultraviolet light.

The role of DNA repair mechanisms in the induction of sister chromatid exchanges (SCE) after exposure to ultraviolet radiation was investigated in xeroderma pigmentosum cells. Cells from different excision-deficient XP strains, representing the 5 complementation groups in XP, A, B, C, D and E, and from excision-proficient XP variant strains were irradiated with low doses of UVR (0-3.5 J/m2). The number of SCE was counted after two cycles in the presence of BUdR. In cells of the complementation groups A, B, C and D the number of SCE was significantly higher than in UV-exposed control cells. The frequencies of SCE in group E cells and in XP varient cells were not different from those in control cells. Treatment with caffeine (0-200 microgram/ml) did not result in a different response of variant cells compared with normal cells. A simple correlation between SCE frequency and residual excision-repair activity was not observed. The response of the excision-repair deficient cells suggest that unrepaired damage, produced by UVR is involved in the production of SCE.

Caffeine↗
PubMed1977

Repair of ultraviolet light damage in a variety of human fibroblast cell strains.

Postreplication repair of DNA damage after ultraviolet light irradiation has been examined in a wide variety of human fibroblast strains. The donors were patients with xeroderma pigmentosum (XP) of different complementation groups or other hereditary disorders with indications of radiosensitivity, or with light sensitivity or multiple cancers. The defect in postreplication repair previously found in XP variants (excision-proficient XP's) has now been observed in a total of five XP variants and a less severe defect in postreplication repair has been found in excision-defective XP's in Complementation Groups A, B, C, and D. Complementation Group E and all other cell strains studied showed a response that was not significantly different from that of cells from normal donors. Excision repair was also measured in some of these cell strains and was found to be defective only in XP cells. Ultraviolet cell survival characteristics have been obtained for may of the cell strains. The most sensitive were cells from the excision-deficient XP's and from a sun-sensitive child (11961); the latter had no measurable defect in either excision or postreplication repair. The rest of the survival curves lay in a band limited by normal cell strains on the one hand and the slightly more sensitive excision-proficient XP variant XP30RO. Only in the case of the variants XP30RO and XP7TA were we able to demonstrate any influence of caffeine on cell survival.

Caffeine↗
PubMed1975

Five complementation groups in xeroderma pigmentosum.

A collaborative study was undertaken to determine the relationship between the three DNA repair complementation groups in xeroderma pigmentosum found at Erasmus University, Rotterdam, and the four groups found at the National Institutes of Health, Bethesda. The results of this study reveal that there are five currently known complementation groups in xeroderma pigmentosum.

Cell Fusion↗