Ultraviolet light

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

The developmental capacity of nuclei transplanted from keratinized skin cells of adult frogs.

Abstract: SUMMARY 1. Nuclei from keratinized skin cells of adult Xenopus foot-webs have been transplanted to enucleated eggs of the same species. 2. The cells used to provide donor nuclei were obtained as a monolayer outgrowth from cultured foot-web explants. When explants were cultured without plasma for 3 days, over 99-9 % of the outgrowth cells contained keratin as revealed by the binding of monospecific fluorescent antibody prepared against purified Xenopus keratin. Nuclei were transplanted from cells which had been cultured for 3-| days. 3. None of the first transfer embryos developed as far as tadpoles. Eleven clones of embryos were prepared from the nuclei of partial first-transfer blastulae by use of serial nuclear transplantation. Eight of these clones contained swimming tadpoles with functional muscle and nerve cells, and six clones contained tadpoles with beating hearts, well differentiated eyes, and other organs. 4. To prove that the nuclei of nuclear-transplant tadpoles were derived from the transplanted skin cell nuclei and not from a failure of ultraviolet light to inactivate the recipient egg nucleus, l-nu skin cell nuclei were transplanted to eggs laid by 2-nu frogs. Several advanced tadpoles from six clones were analysed for nucleolar and chromosome number and found to be l-nu diploids. 5. The six clones of advanced tadpoles which were proved to carry the donor nuclear marker represent six first-transfer nuclei in a total sample of 129 skin cell nuclei originally transplanted. The probability that all six nuclei were derived from the 01 % of the donor cell population not proved to contain keratin is less than one in 10 10 . 6. We conclude that cell specialization does not involve any loss, irreversible inactivation or permanent change in chromosomal genes required for development.

Antioxidant Stress is Promoted by Nano-anatase in Spinach Chloroplasts Under UV-B Radiation

Abstract: A proven photocatalyst, titanium dioxide in the form of nano-anatase, is capable of undergoing electron transfer reactions under light. In previous studies, we had proven that nano-anatase could absorb ultraviolet light (UV-B) and convert light energy to stable chemistry energy finally via electron transport in spinach chloroplasts.The mechanisms by which nano-anatase promotes antioxidant stress in spinach chloroplasts under UV-B radiation are still not clearly understood. In the present paper, we investigate the effects of nano-anatase on the antioxidant stress in spinach chloroplasts under UV-B radiation. The results showed that nano-anatase treatment could significantly decrease accumulation of superoxide radicals\({\left( {{\text{O}}^{{ \cdot - }}_{2} } \right)}\), hydrogen peoxide (H2O2), and malonyldialdehyde (MDA) content, and increase activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and elevate evolution oxygen rate in spinach chloroplasts under UV-B radiation. Together, nano-anatase could decrease the oxidative stress to spinach chloroplast caused by UV-B radiation.

TiO2 nanoparticles are phototoxic to marine phytoplankton.

Abstract: Nanoparticulate titanium dioxide (TiO2) is highly photoactive, and its function as a photocatalyst drives much of the application demand for TiO2. Because TiO2 generates reactive oxygen species (ROS) when exposed to ultraviolet radiation (UVR), nanoparticulate TiO2 has been used in antibacterial coatings and wastewater disinfection, and has been investigated as an anti-cancer agent. Oxidative stress mediated by photoactive TiO2 is the likely mechanism of its toxicity, and experiments demonstrating cytotoxicity of TiO2 have used exposure to strong artificial sources of ultraviolet radiation (UVR). In vivo tests of TiO2 toxicity with aquatic organisms have typically shown low toxicity, and results across studies have been variable. No work has demonstrated that photoactivity causes environmental toxicity of TiO2 under natural levels of UVR. Here we show that relatively low levels of ultraviolet light, consistent with those found in nature, can induce toxicity of TiO2 nanoparticles to marine phytoplankton, the most important primary producers on Earth. No effect of TiO2 on phytoplankton was found in treatments where UV light was blocked. Under low intensity UVR, ROS in seawater increased with increasing nano-TiO2 concentration. These increases may lead to increased overall oxidative stress in seawater contaminated by TiO2, and cause decreased resiliency of marine ecosystems. Phototoxicity must be considered when evaluating environmental impacts of nanomaterials, many of which are photoactive.

Treatment of psoriasis. Part 1. Topical therapy and phototherapy.

Abstract: New developments in the topical therapy and phototherapy of psoriasis have greatly improved our ability to safely and effectively treat this debilitating disease. Topical corticosteroids remain the most commonly prescribed agents for psoriasis, but they are frequently prescribed with other agents. Investigations of corticosteroids claiming an improved benefit/risk ratio have yielded promising results, but more work is needed. Use of anthralin and tar has declined with the availability of the noncorticosteroids calcipotriene and tazarotene. Other experimental topical therapies are in various stages of development. Broadband ultraviolet B (UVB) remains the most commonly used phototherapy light source, but many patients are being treated with a new form of ultraviolet light, narrowband UVB. Although PUVA remains one of the most effective psoriasis treatments, its use is declining because of its association with cutaneous malignancies. New radiation sources such as lasers have been added to our armamentarium of available therapies and even newer light source-based treatments are being examined. (J Am Acad Dermatol 2001;45:487-98.) Learning objective: At the conclusion of this learning activity, participants should be familiar with the varying topical treatments for psoriasis as well as the different modalities of phototherapy. Participants should also have a better understanding of side effects associated with each treatment, which should help in determining options for therapy.