Clear and Dark Basal Keratinocytes in Human Epidermis

Abstract

Standardized techniques of stereologic cytology were applied to normal human epidermis, in order to comparatively describe the suprabasal and the dark and clear basal keratinocytes. The results, expressed mainly in surface and volume densities of epidermal components, showed that some important stereologic parameters of dark basal keratinocyte constituents exhibited values which could be interpreted as intermediate between those of the clear basal keratinocytes and those of the suprabasal keratinocytes. Although the degenerative nature of dark cells cannot be ruled out, the stereologic characterization of their cell architecture also could indicate that dark basal cells are already differentiating keratinocytes still remaining in the basal layer.

Modelling effective dielectric properties of materials containing diverse types of biological cells

“…These volume fraction limits are often exceeded in tissues since cells often do not have spherical or ellipsoidal geometry and are tightly packed. For example in the basal layer of the human epidermis the volume fraction of cells is f = 0.83 [16]. Deviations from the spherical shapes clearly have an impact on the dielectric spectra.…”

The Basal Layer of the Epidermis: A Mathematical Model for Cell Production Under a Surface Density Constraint

“…The detachment rate \= \eta P of proliferating cells is set to zero to simulate a normal, nonpathological epidermis in which cell proliferation is essentially confined to the basal layer. For the parameters \chi and p of the function \theta (N ), the assumed values (\chi = 0.95 and p = 3) allow a surface cell density in agreement with the close-packing of basal cells [25]. It appears reasonable that cell-to-cell mechanical interactions can affect cell proliferation only over some threshold of cell crowding.…”

“…This suggests a down-concavity of the function \theta (N ) for N small and motivates the choice of p = 3. Measurements of the volume of basal cells have found values in the range of 600 to 700 \mu m 3 [1] (see also [25]). Then the maximal surface density N max was computed assuming the basal layer as formed by a monolayer of cubic cells having edge length of 8.5 \mu m (and cell volume of 614.125 \mu m 3 ), so obtaining the value of 0.0138 cells\cdot \mu m - 2 .…”