References: Hair growth and hair loss
Plant J. 1997 Nov;12(5):1035-43.
The maize actin-depolymerizing factor, ZmADF3, redistributes to the growing tip of elongating root hairs and can be induced to translocate into the nucleus with actin.
Jiang CJ, Weeds AG, Hussey PJ.
School of Biological Sciences, University of London, Egham, Surrey, UK.
The maize actin depolymerizing factor, ZmADF3, binds G- and F-actin, and increases in vitro actin dynamics. Polyclonal antibodies have been raised against ZmADF3 and these detect a single band of approximately 17 kDa in all maize tissues examined, with the exception of pollen. In the development of root hairs, the distribution of ZmADF3 is related to actin reorganization. In the early stages of hair development, ZmADF3 is distributed throughout the cytoplasm. As the hair emerges and the microfilament bundles redirect to the outgrowth there is a simultaneous redistribution of ZmADF3 which now concentrates at the tip of the emerging hair and remains in this position as elongation proceeds. These observations show that ZmADF3 localizes to a region where actin is being remodelled during tip growth. After cytochalasin D treatment which disrupts actin filaments, short rods of ZmADF3 and actin appear in the nucleus suggesting that ZmADF3 may function by guiding actin to sites of actin polymerization.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9418045&dopt=Abstract
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The extrauterine development of marsupial pouch young (northern brown bandicoot Isoodon macrourus) has facilitated the study of the effects of murine epidermal growth factor (mEGF) on pattern formation in skin. Hair follicle initiation and development, which in the mouse would occur from about Days 13-14 of gestation onward, occurs postnatally. In the present study the effect in vivo of mEGF on developing skin corresponding to mouse gestational ages from Day 13 onward was examined. Subcutaneous injections of mEGF (0.5, 1.0 and 2.0 microg g[-1] body weight) or equivalent volumes of saline (0.9% w/w) were administered daily, before and during hair follicle initiation and development. Murine EGF inhibited the formation of hair follicles, hair follicle sweat glands, sebaceous glands and dermal papillae. The pattern of follicle initiation was perturbed. The characteristic trio follicle grouping was absent, and follicle rudiment densities (no. per mm2 skin surface) were significantly lower in animals treated with mEGF, whereas follicle diameters were increased. These data may reflect a role for the epidermal growth factor (EGF) receptor in epidermal pattern formation. The EGF receptor and its potential ligands (such as EGF, transforming growth factor (TGF-alpha) or other yet-to-be-discovered ligands) perhaps act as parts of a pattern-forming system in vertebrate skin.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9418978&dopt=Abstract
Radiat Res. 1998 Jan;149(1):11-8.
Radiation sensitivity of human hair follicles in SCID-hu mice.
Kyoizumi S, Suzuki T, Teraoka S, Seyama T.
Department of Radiobiology, Radiation Effects Research Foundation, Hiroshima, Japan.
We developed an experimental model for studying the growth and epilation of the human hair follicle by implanting human scalp tissue onto immunodeficient C.B-17 scid/scid mice. The skin grafts showed continuous growth of black human hairs for at least 1 year and maintained the normal histological structure of a human hair follicle and other tissues associated with the skin. Using this in vivo model, we evaluated the effect of irradiation on the function of human hair follicles. Localized X irradiation (1 to 6 Gy) induced hair loss dose-dependently and synchronously in the third week after irradiation. The hairs undergoing epilation showed a gradual decrease in width toward the root. The minimum width at the thinnest portion of the surviving hair 4 weeks after irradiation suggested that epilation resulted from the breaking of hairs when the hair width decreased to less than 20 microm. After the highest-dose irradiation, the normal structure of the hair bulb was totally abrogated, and long and narrow epithelial tissues associated with regressed papillary cells remained. The surviving epithelia were morphologically similar to the outer epithelial sheath of the follicle associated with palisadic basal cell layers. In the third week some cells in the basal layers of the surviving epithelium in each follicle expressed proliferating cell nuclear antigen. By about 9 weeks after irradiation, the complete structure of the follicle regenerated, with hair growth activity even in the grafts irradiated at the highest dose, although about 30% of the hairs did not regrow. These findings suggest that follicular stem cells that survive high-dose exposure in the sheath-like epithelial tissue can reproduce the complete follicle structure. This animal model can be used to assess the effects of radiation exposure on human skin and to identify and characterize human follicular stem cells.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9421149&dopt=Abstract
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