Photo-dermatology最新文献

More potent narrow-band UV sources need to be developed to determine the in vivo action spectra of long-term UV effects, such as photocarcinogenesis. This article describes the development of a potent, narrow-band UVB source, an Oriel solar simulator modified by the use of newly developed all-dielectric interference (ADI) filters. The sharp cut-off edges and high levels of transmission are unique features of these filters. Further, they can be produced as long-wave-pass or short-wave-pass filters with maximum transmittance at any given wavelength. The simulator is equipped with up to 4 ADI filters and potentially emits narrow UV bands. The filter combinations for narrow bands allow transmission of up to 80% of the incoming radiation. There was a homogeneous intensity area of 25 X 25 cm at a distance of 150 cm from the source in the centre of the irradiation field. The average intensity of UV available in narrow bands of UV (with a minimum half-band width of 11 nm) was 140 mW/m2. These values are sufficient to determine action spectra in groups of live animals (mice).

A narrow-band UV light source with emission peaks at 292, 300, 307, 317, and 336 nm was developed and used to irradiate whole cages of hairless mice. The purpose was to obtain experimental information on the action spectrum for photocarcinogenesis and dermal elastosis. Groups of 20 mice were irradiated with 500 J/m2 daily, 5 times per week during one year. The total dose was 130 kJ/m2. All mice irradiated with 292 nm and 300 nm developed squamous cell carcinomas. None in the other groups developed malignant skin tumors. Elastosis was estimated quantitatively. The elastic fibers covered 3% of a representative microscopic section of dermis in the control group. In the groups irradiated with peaks at 336 nm, 317 nm, 307 nm, 300 nm, and 292 nm the corresponding percentages were 6%, 13%, 28%, 32%, and 36%, respectively. The shorter the wavelengths the more pronounced was a subepidermal zone replacing the elastotic tissue to the deeper dermis. This zone stained corresponding to a content of glycosaminoglycans (GAG), sulphated GAG, hyaluronic acid, mature collagen, and new reticulin.

UV radiation can induce definitive ultrastructural and biochemical alterations in the dermis of the human skin that are independent of the aging process. We present observations on the solubility of collagen and the ratio of type III/type I collagen in skin protected from the sun (abdomen/axilla) and exposed to the sun (neck/face) in 15 subjects, together with histological and immunohistochemical data on the same subjects. The solubility of collagen in acetic acid was similar for protected and exposed skin and solubility in the pepsin-digestable fraction was not significantly altered by chronic sun damage. This indicates that UV radiation does not affect synthesis or cross-link formation of the collagen chains of the human skin in vivo. Further studies indicated that the proportion of type III collagen in pepsin-soluble fraction was not increased in actinic damage. These findings were in line with immunohistochemical studies using antibodies to type III procollagen.

Since free radicals are probably involved in the induction of erythema following ultraviolet (UV) irradiation, a study was conducted to investigate the influence of a topical application of methimazole (a free radical scavenger), before and at different times up to 2 h, after exposure to UV radiation. Seven subjects took part and erythema was assessed 6 h after exposure by a quantitative reflectance technique. Erythema was reduced at the sites that received methimazole 15 min prior to exposure and, although the trend was towards a decrease in erythema at the sites where methimazole was applied after exposure, the mean differences in these cases were not significant. It is believed that methimazole may have a useful role in the reduction of erythema following UV irradiation.

We have determined the ability of a chemical sunscreen with a sun protection factor (SPF) of 15 to protect human skin from ultraviolet (UV) radiation-induced DNA damage. The DNA damage was susceptible to cleavage by Micrococcus luteus UV endonuclease, which recognizes pyrimidine dimers in DNA. An alkaline agarose gel electrophoresis method was used to quantify the number of pyrimidine dimers in nonradioactive DNA from skin biopsies of 5 individuals irradiated with UV from a solar simulator. After exposure to an equivalent dose of UV, the number of pyrimidine dimers was 0.8 per 10(7) bases in sunscreen-treated skin as compared with 32 dimers per 10(7) bases in untreated skin. This assay provides a means of determining the efficacy of sunscreens in protecting skin from UV-induced DNA damage.

The photodegradation of 4-aminobenzoic acid, 2-ethylhexyl N,N-dimethyl 4-aminobenzoate (Escalol 507) and 1-glyceryl 4-aminobenzoate (Escalol 106), resulting from irradiation by sun lamps, was examined by UV spectroscopy. 2-ethylhexyl N,N-dimethyl 4-aminobenzoate showed the longest half-life, indicating the highest photostability.

The exposure to grenz rays of office personnel handling a grenz ray unit working with 10 kV voltage was investigated for different treatment situations. Scattered and leakage radiation, and primary radiation at some distance from the grenz ray unit were measured. Air absorption was found to be most important. Direct exposure of the operator to the primary grenz ray beam at a distance of 4 m was practically nil. At a distance of 2 m from the unit, the operator is permitted to be exposed 100 h per year; at a distance of 1 m, the permitted exposure of the direct beam is 3 h per year. Scattered and leakage radiation from the unit was of no importance and certain clothing was demonstrated to promote absorption.