Treatment of cutaneous ulcers with benzoyl peroxide.
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Benzoyl peroxide, a powerful organic oxidizing agent, was applied topically according to a carefully developed technique to cutaneous ulcers of different types. The healing time was shortened greatly by the rapid development of healthy granulation tissue and the quick ingrowth of epithelium. Exceptionally large pressure ulcers with deep cavities, undercut edges and sinus tracts were sucessfully treated, as were stasis ulcers of long duration resistant to all other therapy. There were only 13 treatment failures among the 133 cases. The slow, sustained release of oxygen by benzoyl peroxide was though to be responsible for the success. The only complications were contact irritant dermatitis in 3% and contact allergic dermatitis in 2% of patients treated. (+info)
The effects of radicals compared with UVB as initiating species for the induction of chronic cutaneous photodamage.
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There is substantial evidence that ultraviolet radiation induces the formation of reactive oxygen species which are implicated as toxic intermediates in the pathogenesis of photoaging. The aim of this study was to determine whether repeated topical treatment with benzoyl peroxide, a source of free radicals, produced the same cutaneous effects as chronic ultraviolet B radiation. Three concentrations of benzoyl peroxide (0.1, 1.5, 5.0% wt/wt) and three cumulative fluences of ultraviolet B radiation (0.9, 2.2, 5.1 J per cm2) used alone and in all combinations along with appropriate controls. Female SKH1 (hr/hr) albino hairless mice were treated 5 d per wk for 12 wk. Extracellular matrix molecules and histologic parameters were assessed. Ultraviolet B radiation induced a fluence-dependent and time-dependent increase in skin-fold thickness. Fluence dependence was seen for epidermal thickness, sunburn cell numbers, dermal thickness, glycosaminoglycan content, mast cell numbers, and skin-fold thickness. Benzoyl peroxide treatment alone caused less marked increases in epidermal and dermal measures compared with ultraviolet B under the conditions used. A benzoyl peroxide concentration-dependent increase was only observed for elastin content, although the highest concentration of benzoyl peroxide increased epidermal thickness and glycosaminoglycan content. A synergistic interaction between ultraviolet B and benzoyl peroxide was not found. These results indicate that repeated administration of benzoyl peroxide produces skin changes in the hairless mouse that qualitatively resemble those produced by ultraviolet B and suggest that common mechanisms may be involved. In addition, any potential synergistic effect of ultraviolet B and benzoyl peroxide was below the level of detection used in this study. (+info)
Effects of UV light and tumor promoters on endogenous vitamin E status in mouse skin.
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Recent reports indicate that both orally administered and topically applied alpha-tocopherol (vitamin E, TH) prevent UVB-induced skin carcinogenesis in mice. Because UVB exposure causes the formation of oxidants associated with tumor promotion, epidermal TH status may be an important determinant of susceptibility to photocarcinogenesis. To test this hypothesis, we studied the status of epidermal TH in C3H mice following exposure to single and repeated UVB exposures at doses typical of chronic photocarcinogenesis protocols. Exposure of mice to a single 13 kJ/m(2) dose over 60 min resulted in no acute depletion of epidermal TH and a modest increase in TH within 6-12 h. Daily exposure to 6.5 kJ/m(2) over 30 min resulted in a gradual increase in epidermal TH, which reached 5-fold after five daily exposures. The increase in epidermal TH was accompanied by an increase in the TH oxidation products alpha-tocopherolquinone (TQ) and alpha-tocopherolhydroquinone (THQ). We also studied the effect of the prooxidant chemical tumor promoter benzoyl peroxide and the prooxidant azo initiators azobis(amidinopropane HCl) and azobis(2, 4-dimethylvaleronitrile). Topical application of these prooxidant chemicals acutely oxidized epidermal TH to TQ and THQ. Topical treatments with the phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) increased epidermal TH levels without producing a significant accumulation of TH oxidation products. The results indicate that UVB and tumor promoting chemicals all exert qualitatively different effects on epidermal TH status and that UVB and TPA trigger an adaptive response involving epidermal TH accumulation. (+info)
Topical therapy for acne.
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Acne is a common problem in adolescents and young adults. The disorder is caused by abnormal desquamation of follicular epithelium that results in obstruction of the pilosebaceous canal. This obstruction leads to the formation of comedones, which can become inflamed because of overgrowth of Propionibacterium acnes. Topical retinoids such as tretinoin or adapalene are effective in many patients with comedonal acne. Patients with inflammatory lesions benefit from treatment with benzoyl peroxide, azelaic acid or topical antibiotics. Frequently, the use of comedonal and antibacterial agents is required. (+info)
Inhibitory effect of a flavonoid antioxidant silymarin on benzoyl peroxide-induced tumor promotion, oxidative stress and inflammatory responses in SENCAR mouse skin.
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In this communication, we investigate the preventive effect of a flavonoid antioxidant, silymarin, on free radical-generating skin tumor promoting agent benzoyl peroxide (BPO)-induced tumor promotion, oxidative stress and inflammatory responses in SENCAR mouse skin. Topical application of silymarin at a dose of 6 mg prior to BPO resulted in a highly significant protection against BPO-induced tumor promotion in 7,12-dimethylbenz[a]anthracene-initiated SENCAR mouse skin. The preventive effect of silymarin was evident in terms of a 70% reduction (P < 0.001) in tumor incidence, a 67% reduction (P < 0.001) in tumor multiplicity and a 44% decrease (P < 0.001) in tumor volume/tumor. In oxidative stress studies, topical application of BPO resulted in 75, 87 and 61% depletion in superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX) activities in mouse epidermis, respectively. These decreases in antioxidant enzyme activities were significantly (P < 0.005-0.001) reversed by pre-application of silymarin in a dose-dependent manner. The observed effects of silymarin were 18-66, 32-72 and 20-67% protection against BPO-induced depletion of SOD, catalase and GPX activity in mouse epidermis, respectively. Silymarin pre-treatment also resulted in a dose-dependent inhibition (35-87%, P < 0.05-0. 001) of BPO-induced lipid peroxidation in mouse epidermis. In inflammatory response studies, silymarin showed a strong inhibition of BPO-induced skin edema (62-85% inhibition, P < 0.001), myeloperoxidase activity (42-100% inhibition, P < 0.001) and interleukin-1alpha protein level in epidermis (36-81% inhibition, P < 0.001). These results, together with our other recent studies, suggest that silymarin could be useful in preventing a wide range of carcinogen and tumor promoter-induced cancers. (+info)
Study of resin-bonded calcia investment: Part 1. Setting time and compressive strength.
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This study was carried out to develop a new titanium casting investment consisting of calcia as the refractory material and a cold-curing resin system as the binder. The setting time of the investment was investigated under different N,N-dimethyl-p-toluidine (DMPT) contents in methyl methacrylate monomer (MMA) and benzoyl peroxide (BPO) contents in calcia without any sintering agent. The effects of the sintering agents, which were calcium fluoride (CaF2) and calcium chloride (CaCl2), on the compressive strength of the investments were investigated at room temperature before and after heating to two different temperatures. The shortest setting time (68 minutes) of the investment was obtained at 0.37 DMPT/BPO (1.5 vol% /1.0 mass%) ratio by mass. The highest strength (16.5 MPa) was obtained from the investment which contained 2 mass% CaF2 and was heated to 1,100 degrees C. It was found that the developed calcia investment containing 2 mass% CaF2 has a possibility for use in titanium castings. (+info)
New initiation system for resin polymerization using metal particles and 4-META.
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Fifteen kinds of metal particles were examined to establish whether they could induce the setting of UDMA-based monomer containing BPO without amine under the presence of 4-META at room temperature. FT-IR spectra of the resultant set samples and the monomer were analyzed to see if the setting was caused by the polymerization. The effects of 4-META and BPO concentrations on the setting time were also studied using the metal particles that induced the setting very effectively. As-received Cu, Zn, Mo, Sn, Co, and In particles could initiate the polymerization of the monomer in combination with BPO and 4-META when they were moistened with water. All the three kinds of silver alloy particles examined also could initiate the polymerization, although pure silver metal particles could not. The presence of 4-META drastically shortened the setting time of the mixture of Cu particles and the monomer containing BPO, while higher concentration of BPO in the monomer significantly shortened the setting time. (+info)
Polymerization of UDMA using zinc particles and 4-META with and without BPO.
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The polymerization phenomena of zinc particles moistened with a small amount of water, 4-META, and UDMA without amine in the presence and absence of BPO were investigated. The effects of 4-META and BPO on the setting time and the degree of conversion (DC) were studied. Moreover, the effect of zinc ion amount on the setting time was investigated. As-received zinc particles could induce the polymerization either with or without BPO. A higher concentration of 4-META shortened the setting time and increased DC when BPO was absent. However, the presence of BPO generally retarded the setting time and decreased DC, although its effect was dependent on the 4-META concentration. A higher amount of zinc ion retarded the setting reaction in the presence of 4-META. The zinc particles mixed with 10% zinc sulfate and acetic acid solutions could induce the polymerization of UDMA containing BPO when the amine and 4-META were absent. (+info)