| Research Abstract |
To elucidate the changes of human sebaceous gland function with aging, forehead sebaceous glands of normal individuals of various ages were examined by computer-stereography and electron microscopy, and their forehead sebum samples were biochemically analyzed. The three-dimensional analysis of sebaceous glands using a computer graphic analysis system (Cosmozone 2SA, Nikon, Tokyo) was performed. In females, the volumes of sebaceous glands were small in subjects of less than 10 years of age, the largest at 20s and became smaller after 50s. In males, although they also reached the maximum at 20s,
they maintained the large sizes until 40s or 50s and began to decrease at 60s. The larger average volumes of sebaceous glands showed the larger standard deviation values. The large sebaceous glands stereographically revealed balloon-like swelling. The increase in volume of sebaceous gland was due to increases in both number and size of sebocytes. Ultrastructurally, in the large sebaceous glands of
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young adults the peripheral sebocytes were cuboid in shape and the mature sebocytes had a large number of lipid droplets of a similar size, whereas in the small ones of children and aged persons the peripheral sebocytes were flat in shape and the mature sebocytes had lipid droplets of various sizes. These morphological and morphometrical data suggest that there are distinct age-related structural changes of human sebaceous glands in both sexes, although there is a difference in their size between the sexes in middle-aged individuals. Sebum samples were obtained from the forehead skin of normal human individuals of various ages by an absorption method. The amount of sebum rapidly increased until 20s in both sexes. It gradually decreased after 40s in females, whereas it was maintained at a high level after 40s in males. Wax esters/[cholesterol + cholesterol esters] (WE/[C+CE]) rations, which may be a good index to express the sebaceous gland activities, in the sebum samples, were measured by thin-layer chromatography. The age-related change of the ratios was similar to that of sebum amounts in females, but it was not in males. The ratios in males decreased after 40s similarly to those in females, although they kept higher levels in males than females. The WE fractions were extracted from the sebum samples and their fatty acid methyl esters were analyzed by gas-liquid chromatography using fused-silica capillary column. The percentages of C_<16:1> in WE also showed age-related changes, corresponding to those of WE/[C+CE] ratios, in both sexes. Urinary androgens were separated from 24 hrs-urine samples of all the individuals, trimethylsilylated and submitted to analysis by gas-liquid chromatography. The amounts of testosterone showed age-related changes positively correlated with those of either WE/[C+CE] ratios or C_<16:1> straight chain fatty acid proportions in sebum in both sexes. The amount of 17-ketosteroid also revealed a positive correlation with these sebum indices in females, but in males it did not show such a correlation except for infancy period. The activity of male sebaceous glands seemed to be controlled principally by testosterone as an intrinsic factor, whereas the female sebaceous glands seemed to be more sensitive to adrenal androgens than male ones. These morphological and biochemical findings may indicate that human sebaceous glands show distinct age-related changes of structures and functions in both sexes, although there are some differences in the patterns of the changes between the sexes especially in middle ages. Less
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