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At least 847 records · Page 47Linked to original sources
PubMed1981

Pyrimidine dimers induced in Escherichia coli DNA by ultraviolet radiation present in sunlight.

Escherichia coli DNA was irradiated with various wavelengths of monochromatic UV light from 254 to 320 nm, and the relative yields of the different cyclobutane pyrimidine dimers determined. Cytosine-thymine dimers (C mean value of T) were more frequent than thymine dimers (T mean value of T) at low fluences of 300 and 313 nm light, whereas the reverse was true at either longer or shorter wavelengths. Thus, in the solar UV range deemed responsible for skin cancer (i.e. 295-315 nm), C mean value of T are probably more important than T mean value of T.

DNA, Bacterial↗
PubMed1995

Sunlight exposure, pigmentation factors, and risk of nonmelanocytic skin cancer. II. Squamous cell carcinoma.

INTRODUCTION AND DESIGN: Squamous cell carcinoma of the skin (SCC), a common cancer in white populations, is related to sunshine exposure; however, relatively little information is available on how timing and character of exposure affect the relationship. The purpose of this study was to investigate the nature of the relationship of SCC to individual solar UV exposure after control for phenotype and pigmentary factors. All newly diagnosed cases of SCC were in men aged 25 through 79 years, ascertained in the province of Alberta from January 1, 1983, through December 31, 1984, who were approached for participation; 80% completed a standardized etiologic interview that was conducted in their homes by a trained interviewer. Control subjects were chosen at random from the Alberta Health Care Insurance Plan subscribers list, matched only by sex (male) and age (within a 5-year age group). The response rate among controls was 71%. RESULTS: Subjects with pale skin and red hair had an elevated risk of SCC. Subjects whose mother was of southern European ancestry had a reduced risk of SCC. After accounting for pigmentary factors, no association was seen between risk of SCC and cumulative lifetime sun exposure. However, a strong trend toward increasing risk was seen with increasing chronic occupational sun exposure in the 10 years prior to diagnosis. CONCLUSION: The results suggest that recent sun exposure (in the 10 years prior to diagnosis) may be important in accounting for individual risk of SCC.

Adult↗
PubMed1995

[Effect of sunlight on the skin--what have we learned?].

Ultraviolet radiation (UVR) exerts a variety of effects on the skin, most of which are inimical. Best known is the effect of UVB radiation which readily burns unprotected skin, but we now know that even UVA radiation may exert penetrating effects on the skin, as well as causing DNA damage and increased risk of cancer. The markedly increased incidence of basal cell and squamous cell carcinoma and malignant melanoma among fair-skinned Caucasians in industrialised countries is attributed to increased exposure to UVR. Sunscreen creams may have exacerbated the situation. Effective phototherapy is a useful product of photomedical research, and it can be further improved. Recently new perspectives were opened up in basic research into UVR, when it was found that repair of DNA lesions via different pathways orchestrates a series of cellular phenomena such as oncogene expression, acid radical defence, immunomodulation, apoptosis and pigmentation induction.

Cytokines↗
PubMed1994

Responses of the skin over the dorsum to sunlight in hairless descendants of Mexican hairless dogs.

Responses of the skin over the dorsum to solar UV irradiation (2 hours/d for 6 consecutive days) were investigated in hairless descendants of Mexican hairless dogs. Assessment of skin color changes, using a spectrophotometer, indicated that luminance values began to decrease from the third day of UV irradiation, reached the minimal value at 3 weeks, and almost recovered 12 weeks after completion of UV irradiation. The number of the dihydroxyphenylalanine-positive melanocytes increased significantly (P < 0.01) from the third day of UV irradiation, reached its maximal value at 2 weeks, and recovered to normal at 12 weeks after completion of UV irradiation. On the second day of UV irradiation, the epidermis became focally thick, with disarrangement of component cells that had degenerative changes. In addition, a few so-called sunburn cells with pyknotic nuclei were seen in the epidermis. On the third day of UV irradiation, apparent suntan reaction developed, and a large number of epithelial cells in the epidermis were heavily pigmented with melanin granules. At 12 weeks after completion of UV irradiation, the epidermis appeared almost normal. On the other hand, significant changes were not detected in the dermis throughout the study.

Animals↗