Epidermal thickness

Only one animal study was located. In this investigation, guinea pigs exhibited considerable erythema, edema, and increased epidermal thickness following an imcovered dermal exposure to imdiluted trichloroethylene three times a day for 3 days (Anderson et al. 1986). 

J. Sandby-M0ller, T. Poulsen, and H. C. Wulf. Epidermal Thickness at different body sites Relationship to age, gender, pigmentation, blood content, skin type and smoking habits. Acta Derm. Venereol. 83 41C)—413 (2003). 

FIGURE 2.2 A diagram of human skin. Epidermal thickness depends upon body site being thickest on the palms and soles (-1500 pm) and thinnest around the eyes (-10 pm). The stratum corneum is the only layer composed of anucleated, terminally differentiated kerati-nocyte cells called corneocytes. All other epidermal layers contain nucleated keratinocytes. The dermis is composed primarily of the structural proteins collagen and elastin. 

Fig. 12.2. Quantitative measurements of skin. Routine measurements of skin, in late anagen in this figure, include interfollicular epidermal thickness (circled area), hair follicle length (L), dermal thickness (D), hypodermal fat layer thickness (H, normally varies with the hair cycle), and full thickness (FT) from the surface of the stratum corneum to the top of the panniculus carnosus muscle.

Fig. 12.3. Epidermal measurements, mitotic figures, and apoptotic keratinocytes in a chronic proliferative dermatitis mutant (Sharplncpdm/Sharplncpdm) mouse. Routine hematoxylin- and eosin-stained paraffin histologic sections can be used to determine proliferation rates based on mitotic index (number of mitotic figures, circled in the figure, in the stratum basale per 1000 cells) or the presence and numbers of apoptotic epidermal keratinocytes (dotted arrows) when present. Epidermal thickness can be measured at high dry magnification (40x) to include the malpigian, living cell, layer (M), the stratum corneum thickness (SC), or the full thickness of the epidermis (M+SC).

Dithranol in combination with urea is widely used in psoriasis to improve the clinical efficacy, to minimize the dithranol concentration, to achieve the desired effect, to shorten the contact, to get a better hydration of the stratum corneum, and to decrease the proliferation rate of the keratinocytes. Gabard and Bieli showed an increased keratolytical effect of salicylic acid by adding 10% urea.54 Hagemann and Proksch55 showed in 10 patients with psoriasis under a 2-week treatment with a 10% urea ointment increased stratum corneum hydration, a small decrease in TEWL, a reduction in epidermal thickness (-29%), and a decreased epidermal proliferation (-51%). The altered expression of involucrin and cytokeratins as marker for epidermal proliferation was partially reversed.55... 

Bernstein, E.F. et al., Citric acid increases viable epidermal thickness and glycosaminoglycan content of sun-damaged skin, Dermatol. Surg., 23, 689, 1997. 

In vivo studies have been conducted in man and in several species to compare absorption fates of numerous compounds. Percutaneous absorption rates in the rat and rabbit were generally higher than in human while the skin permeability of monkeys and swine more closely resembles humans. Although these differences are not predicted by any single factor, such as epidermal thickness, they are not unexpected in light of differences in skin characteristics. There are interspecies differences in routes of excretion of some chemicals as well. This may be due in part to metabolism of the... 

TABLE 35.1. Comparative Stratum Corneum Thickness, Epidermal Thickness, and the Number of Epidermal Cell Layers in the Ventral Abdomen (VAB) and at the Thoracolumbar Junction (TLJ) of Several Species (H E, Paraffin Sections)... 

Bullough, W. S., The Control of Epidermal Thickness, Brit. J. Dermatol. 

The data shown in Figures 12 and 13 are based on measurements made on the backs of adult males having epidermal thickness of 80 pm. The time to produce burns can be significantly shorter for areas having thinner epidermis (e.g., eyelids), and for children and older adults. To prevent burns in at-risk... 

Recent studies by Christophers and Braun-Falco (C5) indicate that at the edge of lesions there is increased epidermal thickness and mitotic... 

Is the increased epidermal thickness accompanied by an increase in size of the epidermal cell (hypertrophy) Or are there just more cells (hyperplasia) Despite histologic (H2) and electron microscopic (B36) impressions to the contrary, biochemical evidence indicates that the cell size in the psoriatic lesion is no different than normal. This conclusion is based on measurements indicating that both normal and psoriatic epidermis contain approximately two-thirds water by weight (H2, M15, S17) and, therefore, have the same wet dry weight ratio in conjunction with DNA measurements which have been made in normal and psoriatic skin. 

Measurements op Epidermal Thickness in Psoriasis and Normal Skin ... 

Dermal exposure to white spirits (three times daily for 3 days) resulted in skin irritation in guinea pigs as evidenced by an increase in mean epidermal thickness, visible redness, palpable induration, and evident swelling (Anderson et al. 1986). 

Table 1.1 Epidermal Thickness, Stratum Corneum Thickness, and Number of Cell Layers from the Back and Abdomen of Nine Species...

Therkildsen, R, Hasdersdal, M., Lock-Andersen, J., Olivarisu, F. dF., Poulsen, T., Wulf, H.C., 1998. Epidermal thickness measured by light microscopy a methodological study. Skin Res. Technol. 4, 174—179. 

Increase of epidermal thickness (increased turn over)... 

---