Mitotic Activity in Cells of the Wool Follicle Bulb

Abstract

Mitotic activity in the cells of the germinative region of wool follicle bulbs was quantified by using small (0 '1-0; 5 ml) intradermal doses of colchicine and selective staining of the metaphase-blocked nuclei using either crystal violet, iodine and eosin or haematoxylin and eosin. The number of metaphase nuclei present 3 h after colchicine administration increased with colchicine dose from 0 to 1 p,g and thereafter remained relatively constant up to 200 p,g colchicine. The accumulation of metaphase nuclei was linear for up to 6 h after intradermal colchicine. The metaphase-blocking effect of intradermal colchicine was confined to a radius of less than 5 cm from the injection site, allowing a number of estimates of mitotic rates to be made over a small area of skin. Such estimates revealed little variation in mitotic activity over the midside region of the sheep, although there were substantial differences in follicle activity at different sites over the body. The technique is simple, allows serial or concurrent estimates of mitotic activity to be made in the same animal, and eliminates problems associated with intravenous colchicine administration. It was used to derive the relationship between follicle activity and fibre production after nutritional changes, and to define the time course of mitotic events after administration of the antimitotic defleecing agent cyclophosphamide.

Biology of the wool follicle: an excursion into a unique tissue interaction system waiting to be re‐discovered

“…In Merino sheep the cell lineages that form the layers of the follicle do not include the medulla. It has been calculated that up to 80% of the proliferating cells differentiate to form the inner root sheath (IRS) instead of fibre shaft (43). From the practical viewpoint of producing more wool it would be advantageous if the follicle could be manipulated to direct more cells of the proliferating and differentiating bulb cells away from the lineage for the IRS to differentiate into cortex and cuticle.…”

Eclipta alba extract with potential for hair growth promoting activity

“…Various species of animals such as mice (Chase, 1954;Hattori and Ogawa, 1983), rats (Johnson and Ebling, 1964), sheep (Hynd et al, 1986), monkeys (Uno, 1991) have been used, and the mouse model is most widely reported for hair growth promotion studies due to availability of large data base and specific mutants such as nude, hairless, rhino, and severe combined immunodeficient mice (Sundberg and King, 1996). The periodic intervals of rodent hair cycles, particularly the duration of the anagen phase are much more consistent and less susceptible to iatrogenic influences (Mori and Uno, 1990).…”

The use of high‐energy electrons to depilate the breech of sheep

“…Skin biopsies (1 cm diameter) were taken under local anaesthesia from the breech region of the five, electron-treated sheep at regular intervals. Four hours after treatment a small part of the treated area was injected intradermally with colchicine (0.1 ml of 500pg/ml) in order to arrest cell division in metaphase (Hynd et al 1986). Two hours later, skin sections were taken and these were fixed in Zenker-acetic acid mixture, washed, iodized, blocked in paraffin, sectioned in the longitudinal plane of the follicles at 8pm and stained with haemotoxylin and eosin (Hynd et al 1986).…”

“…Four hours after treatment a small part of the treated area was injected intradermally with colchicine (0.1 ml of 500pg/ml) in order to arrest cell division in metaphase (Hynd et al 1986). Two hours later, skin sections were taken and these were fixed in Zenker-acetic acid mixture, washed, iodized, blocked in paraffin, sectioned in the longitudinal plane of the follicles at 8pm and stained with haemotoxylin and eosin (Hynd et al 1986). The sections were viewed at a magnification of 400x and bulbs with visible dermal papilla were scored as having 0,1,2 ,........, n mitotic cells.…”