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Biomedical subjects

I A Magnus

Publications and source records attributed to I A Magnus.

At least 19 recordsLinked to original sources
PubMed1987

Modification of 5-methoxypsoralen phototumorigenesis by UVB sunscreens: a statistical and histologic study in the hairless albino mouse.

Sunscreen preparations containing 5-methoxypsoralen at 25 micrograms/ml and 50 micrograms/ml, and the appropriate vehicle only, sunscreen only, and 5-methoxypsoralen only controls, were assessed for tumorigenic potential in hairless albino mice exposed to solar simulated radiation for a period of 44-46 weeks. Some animals were observed for a 15 week post-irradiation period. A wide range of statistical analyses has shown that, during the course of irradiation, the inclusion of sunscreens eliminates the enhancement of phototumorigenesis and malignancy that is normally observed with 5-methoxypsoralen. There was, however, some indication of increased risk at the end of the postirradiation follow-up period. Possible reasons for the protective effect of the sunscreens and the relevance of these data to the assessment of human risk are discussed.

5-Methoxypsoralen↗
PubMed1987

Hydroxychloroquine in polymorphic light eruption: a controlled trial with drug and visual sensitivity monitoring.

A double-blind controlled trial of oral hydroxychloroquine (HC) treatment in polymorphic light eruption (PLE) was completed in 13 patients on active treatment and 15 on placebo during June, July and August 1982. HC dose was 400 mg daily for the first month and 200 mg daily thereafter. Exposure to ambient solar ultraviolet radiation (UVR) was monitored throughout the trial by polysulphone film lapel badges. Patients scored their symptoms on a visual analogue scale. Drug concentration was monitored in plasma and hair, and oculotoxicity was assessed by visual contrast sensitivity. Moderate clinical improvement occurred, associated with a statistically significant improvement in skin rash (P less than 0.01).

Adult↗
PubMed1987

Prophylactic PUVA and UVB therapy in polymorphic light eruption--a controlled trial.

A double-blind controlled trial of low-dose prophylactic oral psoralen photochemotherapy (PUVA) and ultraviolet-B (UVB) irradiation therapy was undertaken from April to September 1983 in 42 patients with polymorphic light eruption (PLE). Patients were randomly allocated to three groups, PUVA with oral 8-methoxypsoralen (8-MOP), UVB with oral placebo, and control low-dose UVA with oral placebo. The initial dose given to each active treatment group was a third of the predetermined minimal phototoxic or erythema dose, followed three times weekly for 6 weeks by doses incremented by an eighth on each occasion in the PUVA group and by a seventh in the UVB group. Ultraviolet radiation exposure was monitored throughout with polysulphone film lapel badges. Patients recorded their symptoms on a visual analogue scale. Symptoms of rash and itch in patients treated with PUVA and UVB were significantly less affected by increasing exposure to ultraviolet radiation than were these symptoms in control patients.

Clinical Trials as Topic↗
PubMed1985

The effect on photohaemolysis of variation in the structure of the porphyrin photosensitizer.

A comparison of the photosensitizing ability of a variety of porphyrins for photohaemolysis gives the following order of activity: protoporphyrin greater than deuteroporphyrin, mesoporphyrin, haematoporphyrin dimethyl ester much greater than haematoporphyrin diacetate, haematoporphyrin greater than haematoporphyrin monoacetate, coproporphyrin III, haematoporphyrin derivative, coproporphyrin III tetramethyl ester greater than uroporphyrin I, meso-tetra-(N-methyl-4-pyridinium)porphyrin tetratoluene-p-sulphonate, meso-tetra-(p-carboxyphenyl)porphyrin, protoporphyrin dimethyl ester, meso-tetra-(p-hydroxy-sulphonylphenyl)porphyrin tetrasodium salt, uroporphyrin III, deuteroporphyrin-3,8-disulphonic acid and protohaemin. The results for the metal-free porphyrins are rationalized in terms of solubility and partition properties, and a model is proposed for the incorporation of amphipathic porphyrins into the membrane lipid bilayer. Experiments with erythrocytes from patients with erythropoeitic protoporphyria and with normal erythrocytes to which porphyrin was added in a deuterium oxide medium do not lead to an increase in the rate of photohaemolysis. A possible explanation for this somewhat surprising observation is outlined.

Deuterium↗
PubMed1985

A strain of hairless mouse susceptible to tumorigenesis by TPA alone: studies with 8-methoxypsoralen and solar simulated radiation.

Hairless albino mice were painted with 8-methoxypsoralen (8-MOP) and exposed to solar simulated radiation (SSR) for 0, 3 or 6 weeks and subsequently treated with the promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). TPA was highly tumourigenic in non-pretreated mice. Pretreatment with 8-MOP + SSR did not increase this level of tumorigenesis. It is proposed that 8-MOP + SSR tumour induction was the result of promotion of innate initiated cells and that this mouse strain might be useful as a promoter testing model.

Animals↗
PubMed1985

Late-onset erythropoietic protoporphyria with unusual cutaneous features.

A 68-year-old man with apparently light-exacerbated erythematous cutaneous plaques on his face and on the dorsa of his hands was found to have late-onset erythropoietic protoporphyria, diabetes mellitus, and hyperlipidemia. Extensive deposits of material that stained with periodic acid-Schiff were present in the lesional dermis. Monospecific antibody studies showed this material to be mainly type IV collagen. These findings strongly suggest that the lesions are a manifestation of erythropoietic protoporphyria. The late onset and asymptomatic unusual cutaneous lesions appear to be a new presentation of the disease.

Aged↗
PubMed1984

Low-dose oral chloroquine in the treatment of porphyria cutanea tarda.

Seven patients with porphyria cutanea tarda received a total of ten courses of low-dose oral chloroquine therapy (125 mg chloroquine phosphate twice weekly). Patients were treated for a mean 14.9 months during which time all went into clinical and biochemical remission. Relapse occurred in four patients on a total of six occasions after a mean 17 months. In four patients there was no relapse after a mean 47.3 months. There were no adverse side-effects from the treatment. Low-dose oral chloroquine therapy appears to be a safe, effective and convenient treatment for porphyria cutanea tarda, although relapses may occur requiring further therapy.

Administration, Oral↗
PubMed1983

Cellular hypersensitivity to UV-A: a clue to the aetiology of actinic reticuloid?

Fibroblasts cultured from six patients with actinic reticuloid (AR) showed striking cytopathic changes and inhibition of RNA synthesis after exposure to near-ultraviolet radiation that had no effect on normal and other photosensitive cell strains, such as those of xeroderma pigmentosum and Bloom syndrome. An abnormal pattern of DNA fragmentation was observed after doses insufficient to cause cytopathic effects. These results suggest a cellular defect in the prevention or repair of some damage caused by free radicals and other photoproducts. In order to explain the pathogenesis of AR, it is proposed that a deficiency in the cellular mechanisms dealing with oxygen radicals leads to the establishment of a vicious circle favouring the persistence of a lymphohistiocytic infiltrate and hence the chronic clinical course characteristic of the disease.

Cells, Cultured↗
PubMed1983

A comparison of the phototumorigenic potential of 8-MOP and 5-MOP in hairless albino mice exposed to solar simulated radiation.

Hairless albino mice have been treated with topically applied 8-methoxypsoralen and 5-methoxypsoralen at two concentrations and exposed to solar simulated radiation. Both these compounds significantly increased the incidence of cutaneous tumours when compared with controls irradiated after treatment with vehicle. This effect was related to psoralen concentration and at the two concentrations investigated there was no significant difference between the compounds.

5-Methoxypsoralen↗