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- Title
XERODERMA PIGMENTOSUM: Abnormal Monochromatic Action Spectrum and Autoradiographic Studies.
- Authors
Cripps, Derek J.; Ramsay, Colin A.; Ruch, Donald M.
- Abstract
Xeroderma pigmentosum (XP) is characterized by sensitivity to sunlight and absent or reduced repair replication of DNA. In this study, the action spectrum to determine the minimal erythema dose (MED) was compared in one subject with XP and 10 controls, using a prism-grating monochromator in the wavelength range of 250-350 nm. The action spectrum in XP differed in several ways from the standard erythema curve of 19 controls. In XP erythema was delayed and peak intensity for all wavelengths occurred at 72 hours, with the most effective wavelengths at 293 nm (MED 1.1 mW sec/cm2). In XP the MED's for all wavelengths at 72 hours had not been visible at 24 hours, at which time the most effective wavelength for the controls was 250 nm. In XP erythema could be produced with longer wavelengths up to 340 nm whereas in the controls no reaction occurred over 320 nm. The MED for most wavelengths in the patient with XP was lower than normal although at 250 mn this was within the standard deviation of controls. A comparison of the effect of 250 and 300 nm radiation on DNA synthesis was made by autoradiography using <em>in vitro</em> exposure to tritiated thymidine. The percentage of heavy labeled epidermal nuclei in unirradiated sites in XP was 1.5% and in 4 controls, 1.8%-2.8%. At 24 hours after irradiation with 250 and 300 nm (with 3 MED), there was no change in XP (1.6%), in contrast to controls (2.1-5.9%) which showed individual increases of heavy labeling (DNA replication phase of cell cycle). A significantly increased number of sparsely labeled nuclei in the epidermis of controls was observed either immediately or 1 ¼ hours after <em>in vivo</em> and <em>in vitro</em>. UV radiation of skin (mean 48.8 and 69.3% respectively). Sparse labeling thought to represent unscheduled DNA synthesis was not observed to the same degree in the patient with XP after <em>in vitro</em> radiation (9.1%). In XP the persistent and delayed UV erythema may be related to the reduced unscheduled DNA synthesis and also a reduction in the DNA replication phase of the cell cycle.
- Subjects
XERODERMA pigmentosum; AUTORADIOGRAPHY; DNA replication; PHOTOSENSITIVITY disorders; RADIOGRAPHY; SUNSHINE
- Publication
Journal of Investigative Dermatology, 1971, Vol 56, Issue 4, p281
- ISSN
0022-202X
- Publication type
Article
- DOI
10.1111/1523-1747.ep12261015