Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.

Polymerizable biodegradable polymers including carbonate or dioxanone linkages

Abstract: Water-soluble macromers including at least one hydrolysable linkage formed from carbonate or dioxanone groups, at least one water-soluble polymeric block, and at least one polymerizable group, and methods of preparation and use thereof are described. The macromers are preferably polymerized using free radical initiators under the influence of long wavelength ultraviolet light or visible light excitation. Biodegradation occurs at the linkages within the extension oligomers and results in fragments which are non-toxic and easily removed from the body. The macromers can be used to encapsulate cells, deliver prophylactic, therapeutic or diagnostic agents in a controlled manner, plug leaks in tissue, prevent adhesion formation after surgical procedures, temporarily protect or separate tissue surfaces, and adhere or seal tissues together.

Caries Prevention in Pits and Fissures Sealed with an Adhesive Resin Polymerized by Ultraviolet Light: A Two-Year Study of a Single Adhesive Application

Abstract: Examinations were made to determine the protection from caries 1½ and two years after the sealing of 200 pits and fissures of deciduous and permanent teeth surfaces with an adhesive resin polymerized by ultraviolet light. After two years, a single application of the adhesive to the surfaces of permanent teeth had resulted in a 99% caries reduction; there was an 87% reduction of caries in the pits and fissures of the occlusal surfaces of the deciduous teeth. Adhesive sealing could be useful in preventive dentistry because it is intended for the caries-susceptible areas that are least benefited by fluoride.

Synthesis and Photocatalytic Activities of NaNbO3 Rods Modified by In2O3 Nanoparticles

Abstract: NaNbO3 rods modified by In2O3 nanoparticles (In2O3/NaNbO3) were successfully synthesized by an improved coprecipitation method, and they were found to be advantageous for photocatalytic H2 evolution under visible light irradiation and pure water splitting under ultraviolet light irradiation. The composites were characterized by X-ray diffraction, UV−vis diffuse reflectance spectrometry, Brunauer−Emmett−Teller measurement, scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy. With use of the electrochemical and valence band X-ray photoelectron spectroscopy analysis, the improvement of the photocatalytic activity was attributed to the promoted transportation of photoexcited holes in the composite.

Direct Photoaffinity Labeling of Tubulin With Taxol

Abstract: Background Taxol is a potent inhibitor of the replication of eukaryotic cells and has significant antitumor activity in human malignancies. The drug induces the formation of bundles of stable microtubules and blocks cells in the mitotic phase of the cell cycle. In vitro, taxol enhances the polymerization of tubulin to microtubules that are resistant to depolymerization. Although it is evident that taxol interacts with the tubulin-microtubule system, no information has been available on the binding site for the drug on the microtubule. Purpose Our purpose was to determine if taxol binds to one or both of the tubulin subunits. Methods In the absence of a photoaffinity-labeled analogue of taxol, [3H]taxol was used directly to photolabel tubulin. A complex of microtubule protein and [3H]taxol was irradiated by ultraviolet light and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results and conclusions The radiolabeled drug preferentially binds covalently to the beta-subunit of tubulin, and the binding can be competed with unlabeled taxol. Implications This observation is the first step in a study to determine the binding site for taxol on the microtubule.

Biochemical characterization of programmed cell death in NGF-deprived sympathetic neurons.

Abstract: Young sympathetic neurons die when deprived of nerve growth factor (NGF). Under such circumstances, cell death is appropriate to the developing nervous system and requires RNA and protein synthesis. We have hypothesized the existence of an endogenous death program within neurons that is suppressed by trophic factors. The extent and timing of required changes in the synthetic events that comprise the death program are unknown. In an effort to characterize the biochemical events that mediate the death program further, we performed several experiments on embryonic rat sympathetic neurons in vitro. The death program was blocked with cycloheximide when total protein synthesis was inhibited ≥80%. When protein synthesis was inhibited within 22 ± 4 h of NGF deprivation, death was prevented in half the neurons. Hence, we define the commitment point for protein synthesis to be 22 ± 4 h. Analogously, the commitment point for RNA synthesis was 26 ± 4 h and that for NGF rescue, 24 ± 4 h. We tested the ability of a wide variety of chemicals to interfere with the death program. Most compounds tested were unable to prevent neuronal death. Some treatments, however, did save NGF-deprived neurons and were subsequently characterized. These included ultraviolet light and agents that raise intracellular concentrations of cAMP. Finally, we looked for the neuronal expression in vitro and in vivo of genes that have been associated with programmed death in other cell types, including TRPM-2/SGP-2, polyubiquitin, TGFβ-1, c-fos, and c-myc. None of these genes showed significant activation associated with neuronal death. © 1992 John Wiley & Sons, Inc.