References: Hair growth and hair loss
J Invest Dermatol. 1996 Dec;107(6):804-7.
Human hair follicle regeneration following amputation and grafting into the nude mouse.
Jahoda CA, Oliver RF, Reynolds AJ, Forrester JC, Horne KA.
Department of Biological Sciences, University of Durham, U.K.
In this study we investigated the capacity of the human hair follicle to regenerate a fiber-forming bulb after its amputation. We removed the bases from terminal follicles from a variety of sites and transplanted the follicles onto athymic mice, either still attached to a skin graft or as subcutaneous implants of individual follicles. External hair growth was observed on the skin grafts, and histology of the follicles revealed restoration of dermal papillae and follicle bulb structures. This result suggests that the capacity of hair follicles to regenerate their lower structures after removal, which was first demonstrated on whisker follicles, may be a general phenomenon. It emphasizes the importance of specific cellular subpopulations within the follicle and the role of dermal-epidermal interactions in adult follicle activities.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8941664&dopt=Abstract
Hear Res. 1995 Oct;90(1-2):31-43.
Secretion of a new basal layer of tectorial membrane following gentamicin-induced hair cell loss.
Epstein JE, Cotanche DA.
Department of Anatomy and Neurobiology, Boston University School of Medicine, MA 02118, USA.
Scanning electron microscopy (SEM) and video-enhanced DIC light microscopy were used to assess morphological changes in the chick tectorial membrane (TM) following gentamicin-induced hair cell loss. Gentamicin was administered (100 mg/kg/day for 3 days) and isolated and in-situ TMs were examined in both fixed and unfixed preparations at days 5 and 10 after the initial injection. Although this protocol induced hair cell damage extending up to 75% of the length of the basilar papilla, there was no apparent damage to the TM itself. However, the ejection of damaged hair cells appeared to sever the filamentous attachments between the TM and the apical surface of the basilar papilla. In SEM preparations this detachment caused the TM to shrink back toward the superior edge. Interestingly, despite the lack of TM damage, gentamicin treatment did reveal the secretion of a new basal layer of TM. Secretion of this new basal layer had begun by day 5 and it was well organized by day 10. This new layer formed attachments to both the recovering basilar papilla and the overlying original TM, a step thought to be necessary for the restoration of auditory function in the regenerating cochlea.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8975003&dopt=Abstract
Proc Natl Acad Sci U S A. 1996 Dec 24;93(26):15469-74.
Regeneration of broken tip links and restoration of mechanical transduction in hair cells.
Zhao Y, Yamoah EN, Gillespie PG.
Department of Physiology, Johns Hopkins University, Baltimore, MD 21205, USA.
A hair cell's tip links are thought to gate mechanoelectrical transduction channels. The susceptibility of tip links to acoustic trauma raises questions as to whether these fragile structures can be regenerated. We broke tip links with the calcium chelator 1,2-bis(O-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid and found that they can regenerate, albeit imperfectly, over several hours. The time course of tip-link regeneration suggests that this process may underlie recovery from temporary threshold shifts induced by noise exposure. Cycloheximide does not block tip-link regeneration, indicating that new protein synthesis is not required. The calcium ionophore ionomycin prevents regeneration, suggesting regeneration normally may be stimulated by the reduction in stereociliary Ca2+ when gating springs rupture and transduction channels close. Supporting the equivalence of tip links with gating springs, mechanoelectrical transduction returns over the same time period as tip links; strikingly, adaptation is substantially reduced, even 24 hr after breaking tip links.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8986835&dopt=Abstract
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