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Biomedical subjects

E A de Weerd-Kastelein

Publications and source records attributed to E A de Weerd-Kastelein.

6 recordsLinked to original sources
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

Xeroderma pigmentosum cells with normal levels of excision repair have a defect in DNA synthesis after UV-irradiation.

Cells cultured from most patients suffering from the sunlight-sensitive hereditary disorder xeroderma pigmentosum are defective in the ability to excise ultraviolet light (UV)-induced pyrimidine dimers from their DNA. There is, however, one class of these patients whose cells are completely normal in this excision repair process. We have found that these cells have an abnormality in the manner in which DNA is synthesized after UV-irradiation. The time taken to convert initially low-molecular-weight DNA synthesized in UV-irradiated cells into high-molecular-weight DNA similar in size to that in untreated cells is much greater in these variants than in normal cells. Furthermore, this slow conversion of low to high-molecular-weight newly synthesized DNA is drastically inhibited by caffeine, which has no effect in normal cells. Two cell lines from classes of xeroderma pigmentosum that are defective in excision-repair show intermediate effects, with regard to both the time taken to convert newly synthesized DNA to high molecular weight and the inhibition of this process by caffeine.

Caffeine↗
PubMed1974

Photoreactivation and excision repair of ultraviolet radiation-injured DNA in primary embryonic chick cells.

Primary embryonic chick cells have been evaluated on the basis of their capacity to repair photochemical lesions produced in the deoxyribonucleic acid (DNA) by ultraviolet (UV) radiation. The fate of one prominent class of UV photoproducts, cyclobutane pyrimidine dimers, was monitored by an in vitro enzymatic assay. UV-irradiated cultures were incubated for prescribed times after which their damaged, radioactive-labeled DNA was extracted and exposed to a purified UV endonuclease selectively active toward sites altered by dimer formation. Single-strand scissions specifically introduced by the enzyme treatment and, therefore, the dimer-containing sites remaining in the DNA were quantified retrospectively by velocity sedimentation in alkaline sucrose. When the chick fibroblasts were incubated in black light, essentially all nuclease-susceptible sites rapidly disappeared from the UV-damaged DNA. In sharp contrast, incubation of the irradiated cultures in total darkness severely impeded the metabolic machinery responsible for site elimination. A substantial amount of UV-stimulated DNA repair synthesis was also detected in the chick cells by conventional techniques involving isopyknic centrifugation and autoradiography. However, the UV photoproducts triggering this indicator of excision repair were probably not dimers since incubation of the irradiated cultures in the light rather than in the dark did not lead to a diminution in the extent of repair synthesis. By these criteria of DNA repair, it appears that embryonic chick cells primarily rely on a highly proficient, light-requiring mechanism, presumably enzymatic photoreactivation, for dimer elimination but also possess a light-independent, excision-type process to cope with other, as yet unidentified, photochemical defects.

Carbon Radioisotopes↗