Long-wave Ultraviolet Light Irradiation Research Articles

Assessment of fungal viability after long-wave ultraviolet light irradiation combined with riboflavin administration

Corneal collagen cross-linking (CXL), a technique that combines riboflavin administration with long-wave ultraviolet light irradiation, was primarily developed to increase the biomechanical strength of collagen fibrils of the cornea to avoid the progression of keratoconus. Recently, this method has been proposed to treat selected cases of infectious keratitis. To test the protocol used for progressive keratoconus in infectious keratitis, Candida albicans, and Fusarium solani, strains were exposed to irradiation using a wavelength of 365 nm at a power density of 3 mW/cm(2) for 30 min in the presence of riboflavin photosensitizer. All experiments were performed in triplicate. Qualitative and quantitative measurements of fungal viability used plate cultures and an automated trypan blue dye exclusion method respectively. Fungal cell diameter was also assessed in all groups. Statistical analyses were performed using the triplicate values of each experimental condition. Experimental findings of photodynamic therapy applied to the cell inactivation of both yeasts and filamentous fungi were compared with control groups. Qualitative results were corroborated with quantitative findings which showed no statistical significance between challenged samples (experimental groups) and the control group (p-value = 1). In comparison with a control group of live cells, statistical significance was observed when riboflavin solution alone had an effect on the morphologic size of filamentous fungi, while ultraviolet light irradiation alone showed a slight decrease in the cell structure of C. albicans. The impact of long-wave ultraviolet combined with riboflavin photosensitizer showed no antifungal effect on C. albicans and F. solani. The significant decrease in cell morphology of both filamentous fungi and yeasts submitted to photosensitizing riboflavin and exposure to ultraviolet light, respectively, may be promising in the development and standardization of alternatives for fungal cell inactivation, because of their minimal cytotoxic effects on the corneal surface. The methodological improvement in the preparation and application of individual chemical compounds, such as riboflavin, or physical systems, such as a long-wave light source, as antifungal agents may also assist in establishing promising therapeutic procedures for keratomycosis.

Inhibition of Substance-P-Induced Histamine Release from Rat Peritoneal Mast Cells by 8-Methoxypsoralen Plus Long-Wave Ultraviolet Light Irradiation: Decreased Intracellular Calcium as a Possible Mechanism

Rat peritoneal mast cells purified on a Percoll gradient were activated by substance P (SP) and the effect of 8-methoxypsoralen (8-MOP) plus long-wave ultraviolet light (UVA) irradiation (8-MOP/UVA) on SP-induced histamine release from the cells was investigated. At a concentration of 10^–5 M SP caused a significant histamine release. 8-MOP or UVA irradiation alone at the doses used in the present study neither induced a histamine release nor had any significant effects on SP-induced histamine release from mast cells. On the other hand, 8-MOP/UVA inhibited SP-induced histamine release; this inhibition was dependent on the UVA doses (0.5–3.0 J/cm²) and was accompanied by a reduction in the rise in intracellular calcium concentrations ([Ca²⁺]_i). These data suggest that 8-MOP/UVA inhibits histamine release from SP-activated rat peritoneal mast cells by suppressing the rise in [Ca²⁺]_i.

８‐メトキシソラレンと長波長紫外線（ＵＶＡ）併用（ＰＵＶＡ）によるサブスタンスＰ刺激ラット腹腔肥満細胞からのヒスタミン遊離抑制

８‐メトキシソラレンと長波長紫外線（ＵＶＡ）併用（ＰＵＶＡ）によるサブスタンスＰ刺激ラット腹腔肥満細胞からのヒスタミン遊離抑制

Photochemotherapy of oral lichen planus: A cotrolled study

Photochemotherapy with 8-methoxypsoralen and long-wave ultraviolet light (PUVA) has become a useful alternative in dermatologic therapy. PUVA therapy has been successfully used in the treatment of severe psoriasis and cutaneous lichen planus. The aim of this investigation was to use PUVA in the treatment of oral lichen planus (OLP). Eighteen patients with long-standing, bilateral, and severe OLP of the buccal mucosa participated in the investigation. A dose of 0.6 mg/kg 8-methoxypsoralen was administered orally 2 hours before long-wave ultraviolet light irradiation was done. The patients were randomly assigned to treatment of the left or right side of the buccal mucosa. The irradiation therapy was given 12 times at intervals of 2 to 3 days, and the patients received a total average dosage of 16.5 J/cm2. The results showed that 13 treated sites compared with six control sites responded significantly favorable to PUVA therapy. Two patients dropped out because of side effects that were similar to those seen after whole-body irradiation PUVA treatment. The follow up times was 12 months. The conclusion of this study is that PUVA seems to be effective in the treatment of OLP and should be considered in severe cases of OLP.

Immunologic aspects of contact dermatitis

Contact dermatitis accounts for up to 40% of all occupationally acquired illnesses, with an incidence conservatively estimated at 70,000 new cases per year in the United States, resulting in a cost, in terms of health care and lost productivity, of $22 million annually. If, as suspected, there is gross underrecording of cases, the true cost may lie in the range of $222 million to $1 billion.1 Atopy is the single greatest risk factor for the development of contact dermatitis; the relative odds of developing occupational skin disease are 13.5 times greater in atopic subjects,2 who account for 93% of lost jobs, 79% of lost workdays, and 88% of compensation payments.3 These figures do not, of course, take into account contact dermatitis occurring outside the workplace; up to 3% of the population may be affected by hand eczema alone.4 The figures also exclude reference to many of the types of plant dermatitis discussed in this issue.Although the majority of contact dermatitis is the result of exposure to irritants, allergic contact dermatitis accounts for a substantial proportion of cases. Despite the clinical importance of allergic contact dermatitis, our knowledge of its pathogenesis—in particular, regarding why a given individual becomes sensitized to a specific contact allergen—remains comparatively restricted. This paper will review what is known about pathologic mechanisms involved in the development of allergic contact dermatitis, incorporating recent information on the immunologie function of normal skin. Recent data on the mechanisms of action of agents that modulate the induction or expression of allergic contact dermatitis, such as topical corticosteroids, mid-range ultraviolet light irradiation (UV-B), and 8-methoxypsoralen plus long-wave ultraviolet light irradiation (PUVA), also will be discussed.

Arrest of chain growth of replicon-sized intermediates by aphidicolin during rat fibroblast cell chromosome replication.

The effect of aphidicolin, a specific inhibitor of DNA polymerase alpha, on size maturation of nascent DNA intermediates was studied in cultured rat fibroblast cells. Results provided the first evidence of DNA synthesis associated with merging of intermediates of larger than replicon size. Aphidicolin at a concentration (1.4 micrograms/ml) causing 90-95% inhibition of [3H]thymidine incorporation, resulted in accumulation of intermediates of nearly the same size as the replicon (2-5 x 10(-7) Da); although the synthesis of short nascent fragments (referred to as Okazaki fragments) continued in the presence of aphidicolin, the rate of their elongation to the replicon size was greatly decreased. On removal of aphidicolin, these accumulated intermediates merged into high-molecular-weight DNA. This merging of the intermediates was associated with DNA synthesis in gaps between adjacent intermediates, as revealed by photolysis of bromodeoxyuridine-DNA leader with long-wave ultraviolet light; when the cells had been pulse-labeled for 5 min with bromodeoxyuridine immediately after removal of the drug, the large DNA arising from aphidicolin-arrested intermediates was cut into fragments of the original size by long-wave ultraviolet light irradiation. The arrest of chain elongation at the replicon-size by aphidicolin might be due to inhibition of this DNA synthesis in gaps, because aphidicolin did not cause degradation of nascent DNAs.

Psoriasis, skin cancer, and PUVA

The article by Stern et al' on PUY A treatment of psoriasis and the risk of developing skin cancer may produce fear in patients and physicians and lead to the premature condemnation of what is an effective alternative in the treatment of this disease . The study does document, perhaps for the first time, the fact that patients with psoriasis are far more prone to develop squamous cell carcinomas of the skin at about 50 years of age than is the general population-but is this due to PUYA? Stern et al carried out a noncontrolled experimental trial in psoriatic patients; i.e ., patients were treated orally with 8-methoxypsoralen followed by long-wave ultraviolet light irradiation. During 2 years of follow-up of 1,373 chronically treated patients, it was noted that thirty developed carcinomas. Since they did not have a control group of psoriatic patients not treated with PUYA, they compared the number and types of cancers occurring in their study group with the number and types of skin cancers an age-matched nonpsoriatic control group might be expected to get. Since their patient group developed 2.6 times as many cancers as the "control" group and since they were predominantly squamous cell cancers rather than basal cell cancers, they concluded that psoriatics being treated with PUYA have more cancers (especially squamous cell cancers of non-sun-exposed skin) than the control nonpsoriatic population. The study suffers from inappropriate controls. An age-matched control of skin cancers in the general population is not a proper control for psoriatics who have been exposed to years of treatments with

An unstable donor-recipient DNA complex in transformation of Bacillus subtilis.

In re-extracted DNA obtained shortly after uptake of transforming DNA by Bacillus subtilis, increased amounts of donor DNA radioactivity banding at the position of donor-recipient DNA complex (DRC) are observed in CsCl gradients, if the cells are irradiated with high doses of UV prior to reextraction of the DNA. Qualitatively, the same phenomenon is observed if lysates of transforming cells are irradiated. UV-irradiation of lysates of competent cells to which single-stranded DNA is added after lysis, does not result in linkage of this DNA to the chromosomal DNA. Two observations argue in favour of the formation of a specific labile complex between donor and resident DNA during transformation. Firstly, heterologous donor DNA from Escherichia coli, although being processed to single-stranded DNA in competent B. subtilis, does not seem to be linked to the recipient chromosome upon UV-irradiation, and secondly, the labile complex of donor and recipient DNA can be stabilized by means of treatment of the lysates of transforming cells with 4, 5(1), 8-trimethylpsoralen in conjuction with long-wave ultra violet light irradiation. This indicates that basepairing is involved in the formation of the complex. On the basis of these results we assume that the unstable complex of donor and recipient DNA is an early intermediate in genetic recombination during transformation.