164 JOURNAL OF COSMETIC SCIENCE Figure 1. Guinea pig epidermis. Group I (control). Figure 2. Guinea pig epidermis. Group II (gel only).

VITAMIN A AND GLYCOLIC ACID FORMULATIONS 165 Figure 3. Guinea pig epidermis. Group III (gel + vitamin A). with basophilic granules. The horny layer was less thick, and some spinous cells were edematous (Figure 3). Group IV (gel + glycolic acid). The thickness of the epidermis was greatly increased, with larger cells and nuclei of various volumes. The basal and spinous layers also showed increased thickness. The granulosa was thicker, with cells containing rough granules of different sizes. The horny layer was thinner and still retained some nuclei. The limits of the spinous cells were clearly visible, and some of these cells were edematous. The presence of spacing between cells was also evident, possibly due to edema (Figure 4). Group V (gel + vitamin A + glycolic acid). This combination caused a greater thickness of the epidermis than observed in the previous groups. The cells reached the largest volume, and the nuclei, containing clear chromatin, were also more voluminous. The signs of edema were much more visible, both inside and outside the cells. The granulose layer was thicker, and the keratin-hyaline granules were rough, of increased size, and showed signs of fusion. The horny layer was thinner and detached (Figure MORPHOMETRIC RESULTS (KARYOMETRY) The nuclei of the basal layer, when evaluated morphometrically, were greatly increased in the areas treated with the formulations tested, with significantly larger volume, area, and perimeter (Table I). The shape of the cells was unchanged in areas II, III, and IV. As observed histopathologically, the nuclei of the cells of the spinous layer presented significantly increased volume, area, and perimeter, with no changes in shape (Table II).