Effects Of Ultraviolet Exposure Research Articles

Enhanced keratinocyte prostaglandin synthesis after UV injury is due to increased phospholipase activity.

The possibility that increased eicosanoid synthesis in skin after ultraviolet light irradiation is due to enhanced phospholipase activity was examined. [3H]arachidonic acid-labeled human keratinocyte cultures exposed to 30 mJ/cm2 ultraviolet (UV) B were studied 6 h after injury. Bradykinin-stimulated release of [3H]arachidonic acid was increased 1.8-fold over release from control cultures by prior irradiation. In unlabeled cultures, prior irradiation produced a threefold increase in bradykinin-stimulated prostaglandin (PG) E2 synthesis as measured by immunoassay. The relative contribution of increased phospholipase vs. cyclooxygenase activity was therefore examined using stable isotope mass measurements of PGE2. By this method, prior irradiation increased bradykinin-stimulated phospholipase activity 3.5-fold, while no change in total cellular cyclooxygenase activity was observed. The effects of irradiation on phospholipase activity were then assessed in more detail. The activities of phospholipase A2, arachidonoyl-CoA synthetase, and arachidonoyl-CoA lysophosphatide acyltransferase in cell homogenates were determined. No effect of UV exposure on the activity of these enzymes was observed. These results suggest that the increase in prostaglandin synthesis produced after UV irradiation is due to increased phospholipase activity, thus enhancing arachidonate release.

No N-ras mutations in human uveal melanoma: the role of ultraviolet light revisited

cases (Van't Veer et al., 1989). The primary tumours of these 7 patients were exclusively located on continuously sunexposed body sites. These mutations were all near dipyrimidine sites, suggesting an active role for ultraviolet (UV) radiation in the induction of the mutations. Shukla et al. (1989) found in one out of 22 tested primary cutaneous melanomas N-ras mutation in codon 61, but no details of sun exposure were available. Melanoma of the uvea (iris, ciliary body and choroid) is the most common primary intraocular malignancy in adults (Cutler & Young, 1975). The incidence of uveal melanoma in whites is eight times the incidence in blacks and threefold greater than in certain Asian groups (Hakulinen et al., 1987). In the Caucasian population individuals with light irides have three times the risk of developing uveal melanoma compared to persons with brown eyes (Gallagher et al., 1985). Early life exposures to sunlight have been found to be especially important in the development of intra-ocular melanoma. (Tucker et al., 1985). Recent epidemiological studies have reported an elevated risk for Northern European ancestry, light skin colour, the presence of 10 or more cutaneous naevi, use of sunlamps a-nd intense sun exposure (Seddon et al., 1990). Holly et al. (1990) found an increased risk of developing uveal melanoma for the apparent effects of UV exposure (severe eye burn, snow blindness), and for host factors, like light eye colour and a propensity to burn rather than tan. These findings implicate sunlight as an environmental risk factor for this disease. The colour of the iris is determined by the degree of pigmentation; limited pigmentation leads to a blue or grey iris and high concentrations of melanin are present in brown irides. Melanin can absorb UV as well as visible light. To investigate possible UV mediated activation of N-ras

The effect of ultraviolet exposure on thermoluminescent CaF 2:Mn

After an ultraviolet exposure of read out thermoluminescent powder CaF 2:Mn a second reading can be obtained. Some experiments have been carried out to find a relationship between the previous and the u.v. induced response. This u.v. exposure offers possibilities for repeated readings and there is a difference between the response due to gamma rays, and that due to heavy particles.

The effect of ultraviolet exposure upon succinic dehydrogenase activity.

The effect of ultraviolet exposure upon succinic dehydrogenase activity.