Ultraviolet-stimulated thymidine incorporation in xeroderma pigmentosum lymphocytes / Peter G. Burk Marvin A. Lutzner Donald D. Clarke and Jay H. Robbins Bethesda, Md and Bronx, N.Y. From the Dermatology Branch, National Cancer Institute, National Institutes of Health and the Chemistry Department, Fordham University

Autoradiographic and liquid scintillation counting techniques were utilized to measure the ultraviolet (UV)-stimulated incorporation of radioactive thymidine during repair replication of the UV-damaged deoxyribonucleic acid (DNA) of irradiated peripheral blood lymphocytes from 4 patients w ith xeroderma pigmentosum (XDP) and from normal donors. Lymphocytes from 3 of the 4 patients had a markedly decreased rate of incorporation soon after irradiation in comparison with the rate obtained with normal donors\u27 lymphocytes. However, the duration of incorporation into these 3 patients\u27 lymphocytes was prolonged, so that XDP lymphocytes appear eventually to incorporate as much total thymidine as normal lymphocytes. Lymphocytes from the fourth patient had a rate and duration of thymidine incorporation after irradiation similar to normal lymphocytes. This patient, therefore, may have a different genetic and biochemical defect from the other XDP patient