References: Hair growth and hair loss
J Invest Dermatol. 1997 Apr;108(4):412-22.
Transgenic mice expressing IFN-gamma in the epidermis have eczema, hair hypopigmentation, and hair loss.
Carroll JM, Crompton T, Seery JP, Watt FM.
Keratinocyte Laboratory, Imperial Cancer Research Fund, London, England, U.K.
To study the role of IFN-gamma in the pathogenesis of inflammatory skin diseases, we used the involucrin promoter to overexpress IFN-gamma in the suprabasal layers of transgenic mouse epidermis. IFN-gamma mRNA and protein were readily detectable in the skin but not in the blood. Mice exhibited striking hypopigmentation of the hair due to a reduced abundance of DOPA-positive melanocytes. Severely affected mice had reddened skin, growth retardation, hair loss, and flaky skin lesions. Keratinocyte proliferation was increased, and there was epidermal thickening with spongiosis and parakeratosis. Suprabasal beta1 integrin expression and induction of keratin 17 in interfollicular epidermis provided evidence of perturbed differentiation. IFN-gamma receptor expression was reduced, and there was induction of ICAM-1 and MHC class II molecules on the surface of transgenic keratinocytes. The skin of severely affected mice was characterized by a dermal infiltrate of T lymphocytes and macrophages/monocytes, but the epidermis was almost devoid of Langerhans cells and T lymphocytes. The number of Langerhans cells in the lymph nodes was increased in the transgenics, and autoantibodies to keratinocytes were produced. Transgenic mice showed an increased contact hypersensitivity reaction to topical application of DNFB. We conclude that constitutive IFN-gamma expression in the epidermis results in a form of eczema resembling contact dermatitis and in a profound contact hypersensitivity reaction.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9077468&dopt=Abstract
J Invest Dermatol. 1997 Apr;108(4):495-500.
Hair cycle stage of the mouse vibrissa follicle determines subsequent fiber growth and follicle behavior in vitro.
Robinson M, Reynolds AJ, Jahoda CA.
Department of Biological Sciences, University of Durham, United Kingdom.
The establishment of culture models representative of all aspects of in vivo hair follicle behavior is an important goal for theoretic and analytic studies. Rodent vibrissa follicles have regular, predictable, and relatively short growth cycles. In this investigation, we took advantage of these properties; we classified mouse vibrissa follicles according to different phases in the hair cycle and then compared fiber growth and morphologic changes in culture. Follicles isolated in the early phase of the growth cycle produced fine growing fibers with an average growth that exceeded 3 mm over 15 d. Even when hair growth had slowed or halted subsequently, histology showed that these follicles retained an anagen-like morphology. By contrast, follicles isolated toward the end of the growing cycle produced thicker fibers for much shorter periods, after which growth ceased and the fibers lifted up from the base of the follicle. Internally, these specimens resembled their telogen counterparts in situ. Follicles isolated in mid-growth demonstrated intermediate fiber growth characteristics. In organ culture, mouse vibrissa follicles therefore closely reflect their in vivo origin in growth characteristics and cycle timing. These data provide new opportunities for studying hair growth cycle mechanisms in vitro, but present a caveat for quantitative studies because there may be a greater growth cycle-related variation than has previously been assumed.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9077480&dopt=Abstract
Mycopathologia. 1998;143(2):77-84.
Degradation of chicken feathers by Chrysosporium georgiae.
el-Naghy MA, el-Ktatny MS, Fadl-Allah EM, Nazeer WW.
Botany Department, Faculty of Science, Minia University, Egypt.
Using a baiting technique, Chrysosporium georgiae was isolated from chicken feathers. Twenty-eight different fungal isolates were evaluated for their ability to produce keratinase enzymes using a keratin-salt agar medium containing either white chicken feathers or a prepared feather keratin suspension (KS). The Chrysosporium species were able to use keratin and grow at different rates. Chrysosporium georgiae completely degraded the added keratin after 9 days of incubation. Degradation of feathers by C. georgiae was affected by several cultural factors. Highest keratinolytic activity occurred after 3 weeks of incubation at 6 and 8 pH at 30 degrees C. Chrysosporium georgiae was able to degrade white chicken feathers, whereas bovine and human hair and sheep wool were not degraded and did not support fungal growth. Addition of 1% glucose to the medium containing keratin improved fungal growth and increased enzyme production. Higher keratin degradation resulted in high SH accumulation and the utilization of the carbohydrate carbon in the medium resulted in high keto-acid accumulation but decreased ammonia accumulation. Supplementation of the keratin-salt medium with minerals such as NH4Cl and MgSO4 slightly increased mycelial growth, but decreased production of extracellular keratinase. Keratinase enzymes were very poorly produced in the absence of keratin, indicating its inducible nature. Analysis of endocellular keratinases in the mycelial homogenate indicated higher activity of intracellular keratinase as compared to the extracellular enzyme in culture filtrates. Chrysosporium georgiae was the most superior for keratinase production among the Chrysosporium species tested in the presence or absence of glucose. It produced more of the intracellular enzymes than the exocellular ones.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10205889&dopt=Abstract
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