Hair Follicle Germ Research Articles

Changes in the Pattern of Cytokeratin Polypeptides in Epidermis and Hair Follicles During Skin Development in Human Fetuses

The cytokeratin polypeptides of microdissected epidermis and hair follicles from human fetuses (from week 10 of pregnancy until birth) have been analysed by two-dimensional gel electrophoresis. Two-layered epidermis in 10-week fetuses contains major amounts of cytokeratin polypeptides typical of simple epithelia (components Nos. 8, 18, and 19 according to Moll et al. [31]). These cytokeratins are gradually reduced in their relative amounts and eventually disappear in the multilayered epidermis of later stages. At advanced stages of development, cytokeratins characteristic of adult epidermis are detected and finally predominate. These include the large and basic epidermal cytokeratin No. 1 (apparent molecular weight 68,000) which is already present in the three-layered epidermis of 13-week fetuses. Hair follicle germ cells of 13-week fetuses differ from fetal epidermal keratinocytes and show a very simple cytokeratin pattern, dominated by only two major polypeptides (Nos. 5 and 17). More developed hair follicles of 20-week fetuses have established a cytokeratin pattern similar to, but not identical with, that of hair follicles from adult skin. Different staining patterns obtained by indirect immunofluorescence microscopy using cytokeratin antibodies with different specificities suggest that, in three-layered epidermis, different cytokeratin patterns might exist in the specific cell layers. Such a differential location might explain the high complexity of polypeptide components found in fetal skin. Possible contributions of peridermal cytokeratins to this complex pattern of fetal epidermis are discussed.

Incorporation of tritiated thymidine into the skin and hair follicles. II. Daily fluctuations in 3 H-TdR and 3 H-UR levels.

ABSTRACTDiurnal fluctuations in incorporation of tritiated uridine and tritiated thymidine are reported for full thickness skin and its two proliferative populations, the epidermal basal layer and the hair follicle germ or matrix. Recently developed techniques whereby these two populations can be studied independently were utilized. Resting (unplucked) skin and skin in the middle of the hair growth cycle (10 days after plucking) was studied. the diurnal fluctuations differed at these two stages of the hair cycle. Generally a single minimum level of activity was observed shortly after the beginning of the dark period of the day, i.e. after 18.00 hours.

Melanocyte precursor cells in the hair follicle germ during the dormat stage (telogen).

Der Ursprung der Melanozyten, die in der Haarwurzel wahrend jedes Haarzyklus erscheinen, ist bisher unbekannt gewesen. Helle dendritische Zellen im ruhenden Haarkeim, welche an der Haarpapilla liegen, die sich wahrend der fruhen Anagen teilen und wahrend Anagen III–IV Farbkorperchen hervorbringen, sind augenscheinlich die Vorlaufer der Haarmelanozyten.