The purpose of this study was to investigate the incidence of parakeratotic stratum corneum cells on the cheek skin surface from 335 healthy subjects and the changes of them according to their ages. We also studied the quantitative levels of parakeratotic cells in various regions of face. Stratum corneum cells were collected by tape-stripping method and observed with hematoxyrin-eosin stain after formalin fixation. In our results, parakeratotic cells were observed in 68.4% of the total subjects, 64.4% of them were women and 72.7% of them were men. They were observed at about 80% in second and third decades of women and decreased as the age advanced. On the other hand, they were observed at about 80% after the first decade in men. Quantity of parakeratotic cells was the highest in upper cheek and followed by the forehead and nose. They were seldom observed below the cheek and chin. It was suggested that the parakeratotic cells were appeared in the stratum corneum cells in face, because our facial skin is always exposed to many external stimulations such as ultraviolet rays and so on and turn over of epidermis was accelerated. Moreover, we strongly suggested that sebum is one of the factor causing parakeratosis. Because parakeratotic cells were observed more frequently in the region where sebum level was high and most of them were observed around the pore of the hairs. Appearance of parakeratotic cells on skin surface implied the loss of skin barrier function and was important problem to the beauty and healthinèss of skin.
Using noninvasive measurement techniques, parameters representing skin characteristics were measured in a total of 117 Japanese females ranging in age from 3 to 65 years. The parameters measured were sebum secretion rate, transepidermal water loss, skin surface conductance, skin color, skin surface temperature, corneocyte surface area, and skin surface microtopography. Measurements were taken twice for each subject, once in the summer (July) and again in the winter (December). Polynomial regression analysis was used to quantitatively assess age-related trends associated with changes in shin parameters. Also, to evaluate the progression of the aging phenomena in adults (i.e., physiological aging), multiple regression analysis was carried out with age as the criterion variable and the above parameters as predictor variables. The results of these analyses established the following facts: Most physiological skin parameters undergo changes that can be characterized by curves which attain peak values during the third decade of life, whereas morphological parameters tend to vary linearly with age. Until the third dacade of life, the physiological functions of female skin remain in the developmental phase and are extremely prone to fluctuations. However, during the third decade, the physiological development of the skin reaches a stage of completion and becomes comparatively stable, and thereafter commences a gradual transition to senescence concomitant with chronological aging. The degree of skin aging can be estimated by a quantiative assessment of age-related physiological phenomena and a comprehensive analysis of the relevant data.
Physiological and morphological changes in the facial skin were investigated in relation to aging in British, French, American (caucasian), and Japanese women to clarify racial differences. The following parameters were measured; sebum secretion rate, transepidermal water loss, skin surface conductance, skin surface microtopography, corneocyte surface area, and skin color. In any ethnic group it was shown that sebum secretion rate was highest in the 20's to 30's, after which it declined with aging. However, Japanese women showed most remarkable age-associated change. Transepidermal water loss was inclined to decrease with increasing age and no racial difference was recognized. Skin conductance was low in young age group, and then it increased with aging until 30's or 40's. Caucasian people had higher conductance in every age group examined than Japanese. Skin surface microstructure was considerably changed during the aging process, showing that pore size and irregularity of furrows incresed with aging. From the change in these parameters it was appeared that the skin texture of Japanese women is finer than that of caucasian. British and Japanese women showed almost the same change in corneocyte surface area with aging and so, it was considered that there is little racial difference in the age-related change of turnover time of stratum corneum. It was also found that skin color changes from reddish to yellow and value decreases.
The surface configuration of the skin characterized by surface furrows and rises is known to change with aging and skin condition. And there have heen many attempts to analyse the surface configration in order to evaluate the effect of skin care products. However the systems proposed up to now are insufficient to obtain three-dimensiomal informations. We developed a new system of analysis based on image analysis and the Fourier transform so we can make a quick and quantitative analysis of the three-dimensional surface configuration of the skin, applying the new method to measure changes in the surface configuration caused by aging and clarify the effects of cosmetic cream. As a result of measuring changes caused by aging, it was found that the furrows become less pronounced, the texture gets coarse and irregular, and the furrows become uniform in one direction as women from 20 through 60s grow in years. This findings are believed to correspond to the fact that the skin's metabolic and moisturizing functions deteriorate as a result of aging. By measuring changes in the surface configuration before and after application of the cream, it was found that the furrows become more conspicuous and the texture becomes finer in the surface configuration after the application of the cream. This is believed to be attributable to plumpness of the epidermal rise caused by the moisturizing effect of the cream.