Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0849640 (skin damage)
 1,516 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Light fractionation with dark periods of the order of hours has been shown to considerably increase the efficacy of 5-aminolevulinic acid-photodynamic therapy (ALA-PDT). Recent investigations have suggested that this increase may be due to the resynthesis of protoporphyrin IX (PpIX) during the dark period following the first illumination that is then utilized in the second light fraction. We have investigated the kinetics of PpIX fluorescence and PDT-induced damage during PDT in the normal skin of the SKH1 HR hairless mouse. A single illumination (514 nm), with light fluences of 5, 10 and 50 J cm-2 was performed 4 h after the application of 20% ALA, to determine the effect of PDT on the synthesis of PpIX. Results show that the kinetics of PpIX fluorescence after illumination are dependent on the fluence delivered; the resynthesis of PpIX is progressively inhibited following fluences above 10 J cm-2. In order to determine the influence of the PpIX fluorescence intensity at the time of the second illumination on the visual skin damage, 5 + 95 and 50 + 50 J cm-2 (when significantly less PpIX fluorescence is present before the second illumination), were delivered with a dark interval of 2 h between light fractions. Each scheme was compared to illumination with 100 J cm-2 in a single fraction delivered 4 or 6 h after the application of ALA. As we have shown previously greater skin damage results when an equal light fluence is delivered in two fractions. However, significantly more damage results when 5 J cm-2 is delivered in the first light fraction. Also, delivering 5 J cm-2 at 5 mW cm-2 + 95 J cm-2 at 50 mW cm-2 results in a reduction in visual skin damage from that obtained with 5 + 95 J cm-2 at 50 mW cm-2. A similar reduction in damage is observed if 5 + 45 J cm-2 are delivered at 50 mW cm-2. PpIX photoproducts are formed during illumination and subsequently photobleached. PpIX photoproducts do not dissipate in the 2 h dark interval between illuminations.
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PMID:Topical 5-aminolevulinic acid-photodynamic therapy of hairless mouse skin using two-fold illumination schemes: PpIX fluorescence kinetics, photobleaching and biological effect. 1114 Feb 68

Photodynamic therapy using methylated 5-aminolevulate (MAL-PDT) appears to have an effect on non-neoplastic skin diseases, for example acne vulgaris and rosacea, for which antibiotics are sometimes used, and a possible antibiotic effect of PDT has previously been suggested. It does, however, also cause local immunosuppression and post-treatment barrier defects, which may promote infection. At the same time, PDT-induced therapeutic skin damage is sometimes confused with secondary bacterial infection by non-dermatologists. The possible changes in bacterial flora associated with MAL-PDT were therefore studied in 47 patients undergoing treatment. Skin swabs were taken immediately before applying the MAL and instantly after light irradiation. Bacterial growth was identified in 18 cases. No statistically significant changes were seen, either in the specific species found or the estimated bacterial density on the skin surface. The observations do not support the notion that routine MAL-PDT affects the bacterial flora of the skin in a clinically significant manner. Therefore, the possible antibacterial effect of routine MAL-PDT is probably not the main explanation of its apparent effect on non-neoplastic skin disease.
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PMID:The bacterial flora of the skin surface following routine MAL-PDT. 1697 16