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Biomedical subjects

I A Magnus

Publications and source records attributed to I A Magnus.

17 recordsLinked to original sources
PubMed1979

Clinical, genetic and DNA repair studies on a consecutive series of patients with xeroderma pigmentosum.

We report clinical, genetic and biochemical findings in 13 families with the photosensitive genodermatosis, xeroderma pigmentosum. All patients had a defect in repair of DNA damage provoked by ultraviolet radiation. Eleven patients and their three affected sibs were defective in the excision repair of UVR induced DNA lesions while the other two were defective in post-replication repair. One in the former group was diagnosed prior to the development of permanent skin abnormalities and preventive measures succeeded for almost five years in maintaining a normal appearing skin. In addition, two cases were diagnosed prenatally and aborted therapeutically. Some patients' parents showed slightly reduced repair of UVR induced DNA damage. In xeroderma pigmentosum (XP), the defect in the excision of DNA lesions appears to be due to homozygosity for one of at least seven different mutations and, accordingly, XP patients can be assigned to seven so-called complementation groups, A to G. Of these, groups A, C and D are the most common. Somatic cell fusion allowed three of the families reported here to be assigned to group A, four to group C and four to group D. Fibroblasts of patients from these three groups were shown to differ not only in the degree and kinetics of their residual DNA repair but also in the kinetics with which their defect is complemented by fusion with normal or XP cells of other groups. This confirms that mutations of different genes play a role in XP and provides a basis for understanding how such genes interact to secure repair of DNA lesions in normal cells. We discuss the phenotype of XP from different complementation groups in relation to the severe neurological abnormalities which may develop and must be considered in genetic counselling. We also discuss the biochemical anomalies of XP and the cellular effects of physical and chemical agents which damage DNA. In the practical management of XP, the importance of early differential diagnosis and prompt initiation of treatment is emphasized. Lastly we review the relationship between DNA repair and skin cancer in XP.

Adolescent↗
PubMed1979

The effect of environmental lighting on porphyrin hepatic metabolism in the rat.

It has been shown that light may stimulate hepatic porphyria in the rat. This is evidently due to a neuro-endocrine pathway involving retina, nerve pathways in the brain and including the sympathetic chain, the pineal gland and the gonads. This light effect in porphyria appears to be via a circadian rhythm in the liver.

5-Aminolevulinate Synthetase↗
PubMed1978

Skin porphyrin assay in porphyria.

The analysis of skin porphyrins in biopsies in patients with porphyria cutanea tarda has been achieved by high pressure liquid chromatography. Porphyrins were determined as their methyl ester copper-chelates and 2-,4-,5-,6-,7- and 8-carboxylic porphyrins distinguished and quantified.

Adult↗
PubMed1978

Description and application of a personal ultraviolet dosimeter: a review of preliminary studies.

Preliminary work on a dosimeter suitable for measuring UVR exposure on individual persons is described. It is based on the use of polysulfone film which, on exposure, shows a change in absorbance that is determined spectrophotometrically. The results of studies of groups of persons with vastly different degrees of solar exposure, e.g., outdoor and indoor workers and geriatric patients, and psychiatric patients with photosensitivity from phenothiazine drugs are presented. We consider the dosimeter may also be suitable for epidemiologic studies in sunlight-induced skin cancer.

Antipsychotic Agents↗
PubMed1977

Effects of radiation on the visual appearance and mechanical properties of mouse skin.

A study of the long term effects of radiation on the visual appearance and mechanical properties of mouse skin is presented. The effects associated with the hair follicle (greying and alopecia) increase monotonically with exposure. Other effects (load, extension and stress at rupture and scarring of the skin) all show a reversal at the highest exposures. The skin thickness changes little with exposure, while the skin stiffness exhibits a shoulder on the response curve. Possible mechanisms underlying these effects are discussed.

Alopecia↗
PubMed1976

The sunburn cell in mouse skin: preliminary quantitative studies on its production.

Quantitative studies on sunburn cell (SBC) production in mouse epidermis are reported. Ultraviolet radiation (UVR), 260-300 nm, produced a dose related effect with respect to SBC formation. Maximal spectral reactivity was at wavelengths shorter than 300 nm. In 8-methoxypsoralen (8-MOP) photosensitization, SBCs were also produced and this response is dose related with respect to long wave UVR dose. In fluorescein photosensitization, provoked by 487 nm light, SBCs were not produced. The response in 8-MOP photosensitization and 254 nm UVR (given alone) differed in respect of time course, but it is considered that both may perhaps to initiated by a DNA lesion.

Animals↗
PubMed1975

Skin porphyrin and photosensitivity in the porphyric rat.

Skin porphyrin assays and photobiological studies in normal and porphyric rats suggest that in the latter, skin photosensitivity to 400 nm radiation is associated with raised uroporphyrin and 7-carboxylic porphyrin in the skin.

Animals↗