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S R Plastow

Publications and source records attributed to S R Plastow.

6 recordsLinked to original sources
PubMed1991

Sunscreens with low sun protection factor inhibit ultraviolet B and A photoaging in the skin of the hairless albino mouse.

We examined the chronic effect of long daily suberythemal, fluorescent solar-stimulated radiation (FSSR; ultraviolet B (UVB)+A(UVA)) and UVA alone on female Skh-1 hairless albino mouse skin. Mice were dorsally irradiated 8 h every weekday for 16 weeks with FSSR or UVA, or 32 weeks with UVA alone. Various topical, low concentration, UVB and/or UVA sunscreens were applied before irradiation. Damage was assessed by skin-fold thickness, histology and biochemically by changes in the proportion of type III collagen. All FSSR-exposed mice showed increased skin thickening, elastic fibre hyperplasia, collagen damage and an increased proportion of type III collagen. Application of the UVB sunscreen (2.00%) resulted in marked protection for all nonbiochemical endpoints. There was no obvious advantage of adding 0.75% UVA sunscreen to the UVB sunscreen, but adding 2.00% UVA sunscreen reduced biochemical changes and connective tissue damage. Sixteen weeks of UVA irradiation caused skin thickening and laxity but the histology and biochemistry were indistinguishable from the controls. The mice irradiated with UVA for 32 weeks showed slight elastic fibre hyperplasia and collagen damage histologically, and increased skin thickening and laxity; these changes were unmodified by the 0.75% UVA sunscreen. These mice showed a significant increase in the proportion of type III collagen against which the UVA sunscreen offered protection. Our data suggest that UVA may be important in photoaging and that the use of low sun protection factor UVB+ UVA sunscreens on a day-to-day basis may offer some protection from solar photoaging.

Administration, Cutaneous↗
PubMed1990

Phototumorigenesis studies of 5-methoxypsoralen in bergamot oil: evaluation and modification of risk of human use in an albino mouse skin model.

The skin of the female hairless albino mouse (Skh 1) was used to study the enhancement of solar simulated radiation (SSR) tumorigenesis by 5-methoxypsoralen (5-MOP) in model perfumes that contain bergamot oil. This work was done in association with yeast mutagenicity studies and human skin phototoxicity studies. Analyses of time-to-onset of tumour observation with 5-MOP at 0, 5, 15 and 50 ppm show a highly significant 5-MOP dose effect and the data indicate that 5-MOP has phototumorigenic potential even at 5 ppm. The addition of 0.5% UVB and 0.5% UVA sunscreens significantly reduces the tumorigenicity associated with the vehicle (i.e. 5-MOP at 0 ppm) and 5-MOP at all concentrations. Pairwise comparisons of 5-MOP (at 5 or 15 ppm) plus sunscreens with vehicle plus sunscreens show that the sunscreens afford total protection at the lower 5-MOP concentrations. Additional studies show that a 5-6 h delay between 5-MOP application and SSR exposure defers the time-to-onset of tumours as does intermittent 5-MOP and SSR treatment. A comparison of 5-MOP at 50 ppm in bergamot oil with 5-MOP at 50 ppm prepared from pure 5-MOP crystals shows identical results, indicating that the active phototumorigenic agent in bergamot oil is 5-MOP and not other related compounds, which may be present at greater concentrations. Analyses of tumour histology at death show, in general, similar patterns of malignancy for all groups. Thus although it is possible to delay tumorigenesis by various strategies, the tumours that eventually develop are just as likely to be malignant, if not more so, when compared with non-delayed groups.

5-Methoxypsoralen↗
PubMed1990

Measurement techniques for melanoma: a statistical comparison.

Inter- and intra-observer variation in measuring the depth of invasion of malignant melanomas was assessed using three different techniques: eye-piece graticule, stage Vernier, and projection image analysis. Significant variation was found for all methods but was least pronounced with the stage Vernier. It is recommended that this should be the preferred technique for routine use.

Analysis of Variance↗
PubMed1988

Early changes in dermal collagen of mice exposed to chronic UVB irradiation and the effects of a UVB sunscreen.

Our previous studies have shown that hairless albino mice receiving chronic UVB irradiation show an increase in type III collagen, in the irradiated skin, after 12-36 weeks treatment. In this study we wished to find the earliest time at which such collagen changes were detectable and also to ascertain whether a topically applied UV-B sunscreen could prevent such changes. Groups of 10 hairless albino mice were irradiated, dorsally, with a daily dose of 62 mJcm-2 UVB for 3, 6, 9, and 12 weeks. Three parallel groups were used. They received a) no topical treatment, b) sunscreen vehicle alone, and c) sunscreen (containing 2-ethylhexyl 4'-methoxy-cinnamate) applied dorsally at 2 microliter cm-2. Dorsal and ventral (non-irradiated) skin samples were taken and the types I and III collagen quantified densitometrically after cyanogen bromide digestion and polyacrylamide gel electrophoresis. The ratio of dorsal/ventral type III collagen (D/V III) was determined for each mouse. The topical treatments caused no change in D/V III in the non-irradiated animals. In the non-topically treated group the irradiated animals showed a considerable increase in D/V III, compared with controls, at 12 weeks (P less than 0.001). The group treated with sunscreen vehicle alone also showed a significant increase in D/V III at week 12 (P less than 0.01). Both these groups showed a slight elevation in D/V III at week 6. The group treated with sunscreen showed no significant difference in D/V III between irradiated and control animals at any time.

Animals↗
PubMed1987

UVB-induced collagen changes in the skin of the hairless albino mouse.

Biochemical techniques have been used to measure ultraviolet-B (UVB)-induced changes in dermal collagen composition. Hairless albino mice were irradiated dorsally with a daily dose of 62 mJ/cm2 UVB for 12, 24, 30, and 36 weeks. Nonirradiated controls were housed under identical conditions. Additional groups were irradiated for similar periods and kept for a further 6-24 weeks without irradiation. Skin samples were taken from dorsal and ventral (nonirradiated) surfaces and types I and III collagen were quantified densitometrically after cyanogen bromide digestion and polyacrylamide gel electrophoresis. Type III collagen was expressed as a percentage of the total types I and III collagen and the ratio of dorsal/ventral type III (D/V III) was determined for each mouse. The ratio increased significantly in irradiated animals whereas it decreased in the corresponding period in control animals. In irradiated mice withdrawn from UV exposure the ratio D/V III tended to revert to control levels. These data are in agreement with those of our previous human studies, which showed an increase in type III collagen in sun-exposed skin when compared with covered sites.

Albinism↗