Ultraviolet light

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

Fungicidal effects of chemical disinfectants, UV light, desiccation and heat on the amphibian chytrid, Batrachochytrium dendrobatidis

Abstract: The efficacy of a number of disinfection treatments was tested on in vitro cultures of the fungus Batrachochytrium dendrobatidis, the causative agent of chytridiomycosis in amphibians The aim was to evaluate the fungicidal effects of chemical disinfectants, sterilising ultraviolet (UV) light, heat and desiccation, using methods that were feasible for either disinfection in the field, in amphibian husbandry or in the laboratory The chemical disinfectants tested were: sodium chloride, household bleach (active ingredient: sodium hypochlorite), potassium permanganate, formaldehyde solution, Path-XTM agricultural disinfectant (active ingredient: didecyl dimethyl ammonium chloride, DDAC), quaternary ammonium compound 128 (DDAC), Dithane, Virkon, ethanol and benzalkonium chloride In 2 series of experiments using separate isolates of B dendrobatidis, the fungicidal effect was evaluated for various time periods and at a range of chemical concentrations The end point measured was death of 100% of zoospores and zoosporangia Nearly all chemical disinfectants resulted in 100% mortality for at least one of the concentrations tested However, concentration and time of exposure was critical for most chemicals Exposure to 70% ethanol, 1 mg Virkon ml–1 or 1 mg benzalkonium chloride ml–1 resulted in death of all zoosporangia after 20 s The most effective products for field use were Path-XTM and the quaternary ammonium compound 128, which can be used at dilutions containing low levels (eg 0012 or 0008%, respectively) of the active compound didecyl dimethyl ammonium chloride Bleach, containing the active ingredient sodium hypochlorite, was effective at concentrations of 1% sodium hypochlorite and above Cultures did not survive complete drying, which occurred after <3 h at room temperature B dendrobatidis was sensitive to heating, and within 4 h at 37°C, 30 min at 47°C and 5 min at 60°C, 100% mortality occurred UV light (at 1000 mW m–2 with a wavelength of 254 nm) was ineffective at killing B dendrobatidis in culture

The isolation, genetics and survival characteristics of ultraviolet light-sensitive mutants in yeast

Abstract: 96 mutants of yeast have been isolated which were more sensitive than wild-type to ultraviolet irradiation. Genetic analysis showed that many are inherited as single mendelian recessive mutations, and that they occupy at lest 22 different loci. Survival curves show that in all the mutants the low UV-dose shoulder characteristic of the survival curve of wild-type yeast is absent or very reduced, but that the slopes vary from one mutant to the next and are often complex. 5 mutants are also more sensitive to ionising radiation than wild-type and 5 reduce the ability of yeast to sporulate.

Photochemical kinetics of corneal cross-linking with riboflavin.

Abstract: Purpose To model the photochemical kinetics of corneal cross-linking with riboflavin (Rf) and confirm the model through measured oxygen concentration experiments under varying energy input conditions by UV-A irradiance and temperature modulation in ex vivo porcine cornea. Methods A theoretical model was developed to describe the corneal cross-linking photochemical kinetics of Rf. After instillation with drops of Rf solution in distilled water, de-epithelialized porcine corneas were exposed to 365-nm ultraviolet light (UV-A) under varying irradiance and temperature. Oxygen concentration in the cornea at a known depth was monitored during UV-A illumination with a dissolved oxygen fiberoptic microsensor. Data from the oxygen experiments were used to confirm the model. Results On the basis of the known chemical reactions and diffusion rates of Rf and oxygen into the cornea, the authors developed a theoretical model consistent with corneal oxygen consumption experimental results during UV-A irradiation under different conditions. Oxygen concentration in the cornea is modulated by UV-A irradiance and temperature and quickly decreased at the beginning of UV-A exposure. The time-dependence of both Type-I and Type-II photochemical mechanisms in corneal cross-linking with Rf are discussed. Conclusions Using a chemical kinetics modeling approach, the authors developed a simple model that is in agreement with their experimental results on oxygen consumption in the cornea during corneal cross-linking with Rf. It is suggested that the main photochemical kinetics mechanism is the direct interaction between Rf triplets and reactive groups of corneal proteins, which leads to the cross-linking of the proteins mainly through radical reactions.

Radiation-stimulated dna synthesis in cultured mammalian cells

Abstract: A type of DNA synthesis in mammalian cells that is stimulated by ultraviolet light has been studied by means of radioautography and density gradient centrifugation. The characteristics of this synthesis are: (a) it is not semiconservative; (b) it is enhanced by the presence of 5-bromodeoxyuridine in the DNA molecule; (c) the degree of stimulation is dose dependent; (d) there is less variability in the rate of incorporation of H3-thymidine during this synthesis than during normal DNA synthesis; (e) it occurs in cells that are not in the normal DNA synthesis phase (G1 and G2 cells). This kind of synthesis has been found in cultured cell lines from five different species; however, in some strains, the presence of bromouracil in the DNA is required before it can be demonstrated by radioautography.