We report a method for quantitative analysis of erythema and pigmentation using a videomicroscope interfaced with a computer. The analysis was carried out by examining the brightness intensity of every picture element, composed of an image picked up from each band of red, green, and blue, and by deriving the quasi-absorbance value (absorbance index) from the mean brightness for each band. In assessments of UV-induced erythema and tanning, excellent linear correlations were found between the results obtained with our system and those with a narrow-band reflectance spectrometer. Moreover, the absorbance indices of haemoglobin and melanin solutions showed linear relationships with their concentrations in in vitro examination. As the monitored picture becomes out of focus if incorrect pressure is exerted on the skin, and as regions of interest can be chosen from a magnified image, this system offers excellent interobserver reproducibility, and is suitable for the evaluation of erythema or pigmented lesions which are too small or irregular to quantify by conventional methods such as colorimetry.

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This system may be a useful tool for demonstrating the relationship between skin color and the amount and distribution of major cutaneous chromophores.

Differentiation of the hair was examined in the head skin of rat embryos aged from days 12.5 to 18.5 of gestation. In 12.5-day-old embryos, the skin consisted of single layered epidermis and underlying loose connective tissue. On day 17.5 of gestation, the epidermis appeared to have a two or three layered epithelium, and the subepidermal connective tissue gave rise to an overlying dense tissue, into which blood capillaries arose from the deeper layer. The epidermis showed partial thickenings, where basal cells were arranged perpendicular to the surface of the epidermis. Beneath the epidermal thickenings, a number of connective tissue cells appeared to have accumulated and occasionally were accompanied by blood capillaries. In sequential development of the skin, the thickenings protruded as cords to the underlying dermal tissue and formed hair follicles covered with a connective tissue sheath. Skin obtained from 12.5-day-old embryos was transplanted singly or with cerebral cortex into the third ventricle of adult male rats. Thirty days after the transplantation, hairs and sebaceous glands had developed from the grafted skin. Hair growth tended to be more prominent in the cotransplanted skin grafts. However, no nerve fibers immunoreactive for substance P or calcitonin gene-related peptide (CGRP) were found in the grafted skin, although these fibers appeared in the dermis at the end of gestation in vivo. These results showed that the skin of 12.5-day-old embryos was able to induce hair growth in the third ventricle without accompanying peripheral neuronal fibers or blood capillaries, although the effects of connective tissue cells could not be ruled out.

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