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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
The melanocytes and associated keratinocytes form a structural and functional unit, the “epidermal melanin unit”. It is this concept which aids in explaining the variations in skin color based on four fundamental biological processes: the synthesis and melanization of melanosomes in the melanocyte, the attachment of melanocytes to the keratinocytes, the transfer of melanosomes, and the degradation of melanosomes within the keratinocyte.90,91
Basic Science
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
The quantity of melanin and the degree of epidermal melanization are the most important determinants of skin color. Melanin synthesis occurs in the cytoplasmic organelle, “melanosomes” within the melanocyte. The entire process of epidermal melanization occurs in epidermal melanin units. The distribution of these units throughout the skin surface eventually determines the quantity and quality of melanization, which results in the baseline skin and hair color within an individual. At any given time, an individual's skin color has two components: Constitutive skin color: Biological potentiality of epidermal melanin units, under the control of cellular genetic program, independent of UV exposure and other relevant factors (as given in Figure 4.2a).Facultative skin color: Affected by UV exposure, hormones, nutrients, chemicals, environmental factors (as given in Figure 4.2b and Figures 4.3 through 4.5).
Microdermabrasion and Dermabrasion
Published in Antonella Tosti, Maria Pia De Padova, Gabriella Fabbrocini, Kenneth R. Beer, Acne Scars, 2018
Annie Chiu, Deirdre Hooper, Katherine O. Brag
To reduce the appearance of acne scars, more than six treatments are generally needed [2,30]. Tsai et al. found that patients required an average of nine treatments when using aluminum oxide crystal devices to reduce the appearance of all kinds of facial scarring [36]. However, to obtain good-to-excellent results, the study found acne scar patients needed an average of 15 treatments and some patients needed as many as 40 treatments to see results [36]. Another study by El-Domyati and colleagues investigated the clinical and histologic impact of microdermabrasion on melasma, acne scars, and striae distensae after eight treatment sessions [31]. In the melasma group, mild-to-moderate improvement in dyspigmentation was noted clinically and decreased melanization and more regular distribution of melanosomes was noted histologically [31]. In the acne scar group, patients with superficial erythematous acne scars showed the greatest improvement compared with patients with rolling, ice pick, or boxcar scars [31]. Histologically, these patients had more regular collagen bundle arrangement and increased collagen density, but no change in elastic fiber density or arrangement [31]. In the striae distensae group, erythematous lesions responded better than hypopigmented lesions; there was no statistically significant difference in epidermal thickness but again, these patients had more regular collagen bundle arrangement and increased collagen density [31].
Evaluation of needling/microneedling as an adjunct to phototherapy in the treatment of stable acral vitiligo: a comparative clinical and immunohistochemical study
Published in Journal of Dermatological Treatment, 2022
Samia Esmat, Magda I. Assaf, Riham Mohye Eldeen, Heba I. Gawdat, Dina G. Saadi
In NB-UVB monotherapy-treated patches, there was a statistically insignificant quantitative increase in melanocyte counts assessed by Melan-A immunostaining (p = .670) (Figure 5). The most notable change was observed in the transitional zone between the depigmented and pigmented skin, where the melanocyte count rose from a mean of 2.94 ± 2.48 SD to 4.89 ± 5.17 SD (p = .186). Increased melanocyte density, dendricity and melanization was observed.