Philip T. Bladon

Effect of crude coal tar in the mouse-tail model of psoriasis

SummaryA histological comparison was made between normal mouse tails and those treated with crude coal tar, and the effect of crude coal tar on the keratin profile of the living cells of treated animals was examined. The prophylactic effect of crude coal tar on the neonatal mouse tail is described. The variation in the anatomical site of prekeratin of the dorsal and tail epidermis of the mouse is reported. These results are discussed with reference to the use of the mouse tail as a model for screening drugs for the treatment of psoriasis.

Isolation, characterization and comparison of mammalian epidermal prekeratins

1. The lower living layers of mammalian epidermis contain a cytoplasmic tonofilament protein, prekeratin, believed to be the precursor of the keratin which is found in the outer dead cell layer or stratum corneum. 2. Prekeratin is distinguished by its property of being extractable from epidermis homogenized in the presence of citric acid trisodium citrate buffer pH 2.65. 3. In the present study we have compared the epidermal prekeratins from ten mammalian species and have shown them to be of similar amino acid composition. 4. Conditions have been established for studying the immunology of these insoluble proteins and examination of their immunological properties has shown that they are similar to one another but that their antigenic determinants are different from those of callus keratin. 5. The SDS polyacrylamide gel electrophoretic patterns of these proteins differ widely and we have also demonstrated anatomical site variation by this method.

The composition of prekeratin and keratin from psoriatic epidermis [Abstract]

A photographic technique has been developed to measure fluorescence in skin. This has been used to measure stratum corneum (SC) turnover rate and to assess the transfer of topically applied fluorescent agents through the SC in vivo. Measurement of fluorescence is made from density measurements of photographic negatives exposed to the fluorescence, which is quantifled by reference to a standard fluorescence scale photographed with the site studied. Dansyl chloride has been used as a fluorescent marker in the assessment of SC turnover time, but subjective assessment of the end point of fluorescence has been diflicult. After applying dansyl chloride for 24 h, daily measurements of fluorescence were taken and a precise end point could be calculated. By applying fluorescent agents topically and measuring the degree of fluorescence at different levels of Sellotape stripping we have been able to measure the movement of topically applied fluorescent agents through the SC in vivo. A proflle ofthe diffusion characteristics of dansyl chloride within the SC has been constructed by comparing the degree of fluorescence at strip levels o, 3, 6, 9 and 12, at times 5, 30, 60, 90 and 120 min. By applying various topical agents beforehand and repeating this proflle we are able to assess changes in barrier function. If DMSO 50% is applied for 20 min before dansyl chloride application, the 60 min proflle is profoundly altered, but occlusion ofthe area beforehand has little effect. The development of this technique therefore provides a new non-invasive method for assessing SC turnover time at different sites and allows a new method for quantifying changes in barrier function.