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UV-B Light (uv-b + light)
Selected AbstractsPhotochemistry and Phototoxicity of Fluocinolone 16,17-Acetonide,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Giorgia Miolo ABSTRACT Fluocinolone 16,17-acetonide is a corticosteroid used topically to treat various inflammatory skin diseases. Its photoreactivity was studied under UV-A and UV-B light in aqueous buffer in the presence of oxygen. This drug is photolabile under UV-B light and, to a lesser extent, under UV-A light, which is absorbed far less. In phosphate buffer, approximately 80% of fluocinolone acetonide decomposes after 5 J/cm2 of UV-B irradiation, whereas under 30 J/cm2 of UV-A light approximately only 20% decomposes. Both the drug and its photoproducts have been evaluated through a battery of in vitro studies and found to cause photohemolysis and induce photodamage to proteins (erythrocyte ghosts, bovine serum albumin) and linoleic acid. In addition, one of the photoproducts (the 17-hydroperoxy derivative) is highly toxic in the dark. Therefore, both loss of therapeutic activity and light-induced adverse effects may be expected when patients expose themselves to sunlight after drug administration. A major mechanism for phototoxicity involves radicals forming from drug breakdown, at least under UV-B, although reactive oxygen species may play a role, particularly under UV-A. [source] UV Absorption and Photoisomerixation of p -Methoxycinnamate Grafted Silicone,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2004Supason Pattanaargson ABSTRACT p -Methoxycinnamate moieties, UV-B-absorptive chromophores of the widely used UV-B filter, 2-ethylhexyl p -methoxycinnamate (OMC), were grafted onto the 7 mol% amino functionalized silicone polymer through amide linkages. Comparing with OMC, the resulting poly [3(p -methoxycinnamido)(propyl)(methyl)-dimethyl] siloxane copolymer (CAS) showed less E to Z isomerization when exposed to UV-B light. The absorption profiles of the product showed the maximum absorption wavelength to be similar to that of OMC but with less sensitivity to the type of solvent. Poly (methylhydrosiloxane) grafted with 10 mol%p -methoxycinnamoyl moieties was prepared through hydrosilylations of 2-propenyl- p -methoxycinnamate, in which the resulting copolymer showed similar results to those of CAS. [source] In Vitro Phototoxic Properties of Triamcinolone 16,17-acetonide and Its Main Photoproducts,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2003Giorgia Miolo ABSTRACT The phototoxicity of triamcinolone 16,17-acetonide has been estimated through a panel of,in vitro tests. The main target involved in phototoxicity induced by triamcinolone appeared to be the cell membrane. Oxygen-independent photohemolysis was observed. A photochemical study in water and buffered solutions supported the conclusion that this is related to the action of radicals formed upon UV irradiation (in particular UV-B) by Norrish Type-I fragmentation of the C-20 ketone group. Peroxy radicals were formed in the presence of oxygen and were the active species in that case. Three photoproducts, isolated from the photodegradation of the drug, were submitted to the same toxicity tests. Two of them were proved to possess toxic or phototoxic properties on erythrocytes, primarily induced by UV-B light, and may participate in the photosensitizing activity of triamcinolone 16,17-acetonide. Our in vitro results suggest that the drug can elicit weak photosensitizing properties in vivo. [source] Identification of regulatory elements involved in expression and induction by sucrose and UV-B light of the Arabidopsis thaliana COX5b-2 gene, encoding an isoform of cytochrome c oxidase subunit 5bPHYSIOLOGIA PLANTARUM, Issue 3 2009Raúl N. Comelli The promoter sequences required for expression of the Arabidopsis thaliana COX5b-2 gene, encoding an isoform of cytochrome c oxidase subunit 5b, were analyzed using plants transformed with deleted and mutagenized forms of the promoter fused to gus. A 1000-bp promoter fragment produces expression in root and shoot meristems, leaf and cotyledon tips, and anthers. Deletion analysis indicated the presence of positive and negative regulatory elements. A regulatory element located between ,660 and ,620 from the translation start site was identified as a G-box by mutagenic analysis. Mutation of the G-box, that is present within the coding region of the preceding gene in the genome, increases expression of COX5b-2 in cotyledon and leaf lamina and abolishes induction by ultraviolet-B (UV-B) light, which presumably acts through the removal of an inhibitory factor. Identified positive regulatory elements include a site II element (TGGGCC), a related element with the sequence TGGGTC and four initiator elements (YTCANTYY) that completely abolish expression when mutated in combination. Site II elements are also involved in the response to sucrose. The results imply that the COX5b-2 gene has retained expression characteristics presented by most respiratory chain component genes, but its expression mechanisms have diverged from those employed by COX5b-1, the other gene encoding cytochrome c oxidase subunit 5b in Arabidopsis. [source] The effect of drought and ultraviolet radiation on growth and stress markers in pea and wheatPLANT CELL & ENVIRONMENT, Issue 12 2001V. Alexieva Abstract It emerged recently that there is an inter-relationship between drought and ultraviolet-B (UV-B) radiation in plant responses, in that both stresses provoke an oxidative burst. The purpose of this investigation was to compare the effects and interaction of drought and UV-B in wheat and pea. The absence of changes in relative leaf water content (RWC) after UV-B treatments indicate that changes in water content were not involved. RWC was the main factor resulting in reduced growth in response to drought. Increases in anthocyanin and phenols were detected after exposure to UV-B. The increases do not appear to be of sufficient magnitude to act as a UV-B screen. UV-B application caused greater membrane damage than drought stress, as assessed by lipid peroxidation as well as osmolyte leakage. An increase in the specific activities of antioxidant enzymes was measured after UV-B alone as well as after application to droughted plants. Proline increased primarily in drought-stressed pea or wheat. Proline may be the drought-induced factor which has a protective role in response to UV-B. The physiological and biochemical parameters measured indicate the UV-B light has stronger stress effectors than drought on the growth of seedlings of both species. The two environmental stresses acted synergistically to induce protective mechanisms in that pre-application of either stress reduced the damage caused by subsequent application of the other stress. [source] The effects of UV-B stress on the production of terpenoid indole alkaloids in Catharanthus roseus hairy rootsBIOTECHNOLOGY PROGRESS, Issue 3 2009Bernard Y. K. Binder Abstract In nature, plants generate protective secondary metabolites in response to environmental stresses. Such metabolites include terpenoid indole alkaloids (TIAs), which absorb UV-B light and serve putatively to protect the plant from harmful radiation. Catharanthus roseus plants, multiple shoot cultures, and cell suspension cultures exposed to UV-B light show significant increases in the production of TIAs, including precursors to vinblastine and vincristine, which have proven effective in the treatment of leukemia and lymphoma. Here, the effect of UV-B light on C. roseus hairy roots was examined. Analysis of alkaloid concentrations up to 168 h after UV-B exposure shows significant increases in the concentrations of lochnericine and significant decreases in the concentration of hörhammericine over time (ANOVA, P < 0.05). Our results also indicate that increasing UV-B exposure time up to 20 min caused significant increases in lochnericine, serpentine, and ajmalicine and a decrease in hörhammericine (t-test, p < 0.05). © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source] | ||||||||||