Actinic exposure

Habib and Asker (68) showed that metronidazole solutions decompose more under artificial sunlight [from two 40 W fluorescent sunlamps and fluorescent radiation (from cool white tubes)] in a Atlas HPUV Actinic Exposure Cabinet, than under UV-A radiation, as shown in Table 4. 

In the case of some types of polyesters, the dried treated sheet is very tacky, and must be interleaved with a plastic release film to prevent blocking in the roU prior to use. Certain polyesters and acryhcs can be converted to a gelled state by exposure to actinic radiation. 

Causes of actinic keratosis include prolonged exposure to sun, ultraviolet light from artificial sources and x-radiations. 

Precursor of invasive SCC (actinic keratosis) scaly erythematous macule or papule on areas of chronic sun exposure... 

LEVULAN was approved by the FDA in 1999 for the treatment of actinic keratosis, a precancerous condition of the skin caused by excessive light exposure. The compound has been commercialized by DUSA Pharmaceuticals Inc, Wilmington, MA. www.DUSApharma.com. 

Konno, K., and Morales, M.F. (1985) Exposure of actin thiols by the removal of tightly held calcium ions. Proc. Natl Acad. Sci. USA 82, 7904-7908. 

Fig. 5.2 Immunofluorescent demonstration of smooth muscle actin (FITC, green channel) in the blood vessel wall of the human kidney. Red autofluorescence of erythrocytes, elastic lamellae and kidney tubules was captured with a filter exciting the autofluorescence in red spectrum under a longer exposure than with the filter exciting specific fluorescence in the green spectrum. Nuclei are counterstained with DAPI (blue channel)...

The effect of sequential chemoattractant exposure on neutrophil F-actin polymerization responses may also be evaluated with this technique. The data presented in Fig. 3 were collected from an experiment in which neutrophils were exposed to 10 M LTB4 for 5 min and then exposed to 10 M FMLP for 5 min ( ), and compared with neutrophils exposed only to 10 M FMLP under identical incubation conditions (O). 

Fig. 4. Relative F-actin changes during a 30-s exposure to various concentrations of FMLP.

The reduction of silver chloride by hydrazine shows some points of similarity to the action of hydroxylamine, but also some important points of difference (James, 34). An induction period was obtained with the unnucleated precipitates which, under some conditions, was relatively large. However, exposure of the precipitate to actinic light had only a small effect upon the induction period and upon the subsequent course of the reaction. Previous nucleation of the precipitate by the action of hydroxylamine decreased the induction period without eliminating it, and produced little or no effect upon the subsequent course of the reaction. Addition of the dye, 3,3 -diethyl-9-methylthiacarbocyanine chloride, produced no effect until the surface of the precipitate was more than half covered. Further increase in the amount of dye added produced an irregular decrease in the reaction rate. Gelatin decreased the reaction rate, but to a smaller extent than in the hydroxylamine reaction, and a minimum rate was not attained. As the gelatin concentration increased, more and more reduced silver appeared in colloidal form in the solution. 

Aminolevulinic acid (ALA HCl, Levulan Kerastick) is indicated for the treatment of nonhyperkeratotic actinic keratosis of the face and scalp. It has two components, an alcohol solution vehicle and ALA HCl as a dry solid. The two are mixed prior to application to the skin. When applied to human skin, ALA is metabolized to protoporphyrin, which accumulates and on exposure to visible light produces a photodynamic reaction that generates reactive oxygen species (ROS).The ROS produce cytotoxic effects that may explain therapeutic efficacy. Local burning and stinging of treated areas of skin due to photosensitization can occur. 

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