Photo-dermatology最新文献

Photoallergic dermatitis was induced in the mouse following the systemic administration of quinidine in combination with UVB and UVA. The reaction was recorded as ear wet weight, ear thickness and tail wet weight. Statistical calculations showed ear wet weight to be the most sensitive evaluation technique. By varying the quinidine dose administered in induction (2.5-100 mg/kg) and challenge (10-100 mg/kg), dose-response conditions were established. It was shown that the induction dose necessary to obtain a statistically significant reaction was considerably lower than the minimal challenge dose (25 mg/kg). This method is well suited for studies of the dynamics of the induction and elicitation phases of systemically induced photoallergy.

Exposure of highly purified rat serosal mast cells to UVA (34-340 kJ/m2), in the presence or absence of 8-methoxypsoralen (100 ng/ml), or to UVB (160-640 J/m2), resulted in dose-dependent releases of mast cell preformed mediators, as measured by the release of radioactivity from 3H-serotonin-labeled cells. The net release ranged from 2.3% to 14.2%. The above treatments had no effect on mediator release induced by subsequent incubation with calcium ionophore A23187 (0.4 and 4.0 mumol/l) or with compound 48/80 (1.0 microgram/ml), with the exception that exposure to UVB did suppress the release induced by the latter. These results indicate that under clinically relevant conditions, the direct effect of in vitro ultraviolet radiation on mast cells did not alter the ability of these cells to respond to subsequent stimulation with secretagogues.

This is the first in vivo study of the effects of UV on the epidermal melanocytes in dysplastic nevus syndrome (DNS). Eleven DNS patients and 22 healthy subjects were given total body UVB irradiation 8 times during 17 days and the melanocyte population was estimated in biopsies from shielded and irradiated skin. There was a doubling of the melanocyte counts in irradiated skin and a less pronounced but significant increase in the shielded skin area. The urinary excretion of 5-S-cysteinyldopa (5-S-CD) was measured before, during and after the irradiation period. The 5-S-CD excretion reached a maximum after 2 weeks of irradiation and returned towards the basal value after the irradiation period. We were not able to document any abnormal melanocytic UV response in DNS patients before, during or after the irradiation.

Environmental ultraviolet radiation (UVR) was monitored for one year at Durham (latitude 55 degrees N) using a stationary, horizontal sensor, and a sensor rotating in a vertical plane designed to simulate the random motion of subjects outdoors. From these data it was possible to calculate the personal solar UVR representative of populations living at different geographical locations and experiencing varying patterns of cloud cover. The conclusion was that present monitoring programmes that record ambient solar UVR in a horizontal plane at different locations as input data to studies on the epidemiology of skin cancer are appropriate for obtaining a relative estimate of the population exposure in locations with different climatic conditions, providing, of course, that the outdoor exposure habits of different populations are comparable.

The induction and persistence of cyclobuta-dithymidine (T less than greater than T) photoproducts in human skin samples was measured following exposure to artificial solar radiation. DNA extracted from human epidermis, irradiated with the equivalent of 15 to 120 min of midday sunlight, was analyzed by enzyme-linked immunosorbent assay (ELISA). Heavily pigmented skin required 2- to 4-fold higher doses than non-pigmented skin to produce similar amounts of T less than greater than T photoproducts. These results demonstrate the effectiveness of constitutive epidermal pigmentation in protecting epidermal cell DNA from solar UV-induced damage.

Recent interest in photoimmunology has led to the development of the low-dose model of UVB-induced immunosuppression, an experimental framework in which inhibition of contact hypersensitivity is associated with alterations in the morphology and the antigen-presenting function of Langerhans cells in locally irradiated skin, and with the appearance of hapten-specific T-suppressor cells in systemic circulation. This article reviews the scientific data that has been generated from the utilization of this model. It focuses particular attention on current evidence that identifies distinct epidermal cell populations as key sources of the immunosuppression evoked by low-dose UVB.