Ultraviolet light

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

Spectral and Temporal Sensitivity of Cone-Mediated Responses in Mouse Retinal Ganglion Cells

Abstract: The retina uses two photoreceptor types to encode the wide range of light intensities in the natural environment. Rods mediate vision in dim light, whereas cones mediate vision in bright light. Mouse photoreceptors include only 3% cones, and the majority of these coexpress two opsins (short- and middle-wavelength sensitive, S and M), with peak sensitivity to either ultraviolet (360 nm) or green light (508 nm). The M/S-opsin ratio varies across the retina but has not been characterized functionally, preventing quantitative study of cone-mediated vision. Furthermore, physiological and behavioral measurements suggested that mouse retina supports relatively slow temporal processing (peak sensitivity, ∼2–5 Hz) compared to primates; however, past studies used visible wavelengths that are inefficient at stimulating mouse S-opsin. Here, we measured the M/S-opsin expression ratio across the mouse retina, as reflected by ganglion cell responses in vitro, and probed cone-mediated ganglion cell temporal properties using ultraviolet light stimulation and linear systems analysis. From recordings in mice lacking rod function (Gnat1−/−, Rho−/−), we estimate ∼70% M-opsin expression in far dorsal retina, dropping to

Controlling Legionella in hospital drinking water: an evidence-based review of disinfection methods.

Abstract: Hospital-acquired Legionnaires' disease is directly linked to the presence of Legionella in hospital drinking water. Disinfecting the drinking water system is an effective preventive measure. The efficacy of any disinfection measures should be validated in a stepwise fashion from laboratory assessment to a controlled multiple-hospital evaluation over a prolonged period of time. In this review, we evaluate systemic disinfection methods (copper-silver ionization, chlorine dioxide, monochloramine, ultraviolet light, and hyperchlorination), a focal disinfection method (point-of-use filtration), and short-term disinfection methods in outbreak situations (superheat-and-flush with or without hyperchlorination). The infection control practitioner should take the lead in selection of the disinfection system and the vendor. Formal appraisals by other hospitals with experience of the system under consideration is indicated. Routine performance of surveillance cultures of drinking water to detect Legionella and monitoring of disinfectant concentrations are necessary to ensure long-term efficacy.

Review of the evidence regarding the carcinogenicity of hexavalent chromium in drinking water.

Abstract: Recent analyses have revealed that 38% of municipal sources of drinking water in California have detectable levels of hexavalent chromium. This observation provided new impetus to characterize the carcinogenic risk associated with oral exposure to hexavalent chromium in drinking water. Notwithstanding the well-characterized increases in cancer associated with inhalation exposure to this chemical, the marked reduction of hexavalent chromium to trivalent chromium in the stomach suggests that exposure to hexavalent chromium in drinking water may not pose a carcinogenic risk. A reevaluation of studies that investigated the toxicokinetics, the genotoxicity, and the mechanism of carcinogenicity of hexavalent chromium, as well as the available human and animal cancer studies, was undertaken to determine if there is evidence that exposure to this chemical in drinking water may pose a carcinogenic risk. Mechanistic studies suggest the potential for a carcinogenic response if hexavalent chromium enters cells. Both toxicokinetic and genotoxicity studies indicate that a portion of an orally administered dose of hexavalent chromium is absorbed and gets into cells of several tissues, causing DNA damage. The only lifetime oral study of hexavalent chromium in animals conducted thus far yielded a statistically significant increase in stomach tumors compared to controls. Also, in a limited-term cancer study, co-exposure to hexavalent chromium in drinking water and ultraviolet light produced skin tumors in mice. The only available cancer study of humans exposed to hexavalent chromium in drinking water revealed a statistically significant increase in stomach tumors. Moreover, a meta-analysis of occupational studies also revealed a statistically significant increase in stomach cancers. The increases in stomach tumors in both human and animal studies, along with the toxicokinetic, genotoxic, and mechanistic data, suggest that oral exposure to this agent appears to pose a carcinogenic risk.