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Hair

11/03/09

10:42:42 pm, by peterpro

, 353 words, 63 views

Categories: Announcements [A]

Hair

J Invest Dermatol. 1976;67:98-105.

Hair.
Ebling FJ.

The psychologic importance of hair to man is in inverse ratio to its physical function. Except for scalp hair and desultory areas of sexual hair, most of man's hair follicles are vestigial. Three problems of hair regrowth remain to be solved: (1) how the intermittent activity of hair follicles in both animals and man is controlled; (2) how the male hormone alters the hair cycle in human skin; and (3) why larger hairs are produced by testosterone in some areas of the body when in some individuals the hair follicles in the scalp regress. Studies in which skin grafts from rats of different ages were exchanged showed that hair follicles are innately programmed but can be slowly influenced by systemic factors. Steroid hormones, especially estrogens, slow down the moult cycle whereas thyroid hormones accelerate it. What establishes the innate rhythm remains problematical. The fact that plucking out the club hair initiates activity in resting follicles has been explained by the hypothesis that the mitotic inhibitor which accumulates during anagen is normally used up or dispersed during telogen or by wounding. However, contrary to this theory, follicular activity is not prolonged by epilation during anagen. Moreover, if rats are epilated within one or two days of eruption, only club hairs are removed since forceps cannot grasp the tips of the new hairs. Such epilation does not affect the anagen in progress, but remarkedly enough the subsequent resting phase is shortened. Both sexual hair and male-pattern baldness depend on androgenic hormones. Target organs of testosterone convert the hormone to active metabolites, chiefly 5alpha-dihydrotestosterone. In skin, however, 5alpha-dihydrotestosterone may not be the only active tissue androgen. The major metabolite of testosterone incubated with hair roots in androstenedione, and hirsute women without other obvious endocrine abnormality sometimes excrete high levels of androstanediol. Both steroids stimulated the sebaceous glands of hypophysectomized-castrated rats, which, however, showed only a limited response to testosterone. The androgenic steroids, the enzymes that convert them to their active metabolites, and the proteins that bind them are undoubtedly very important to the problems of the growth of sexual hair and male-pattern baldness.

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Capciacin effects on hair follicles
Neurosci Lett. 1987;74(2):139

Classification of aberrant primary afferents in the substantia gelatinosa of the rat following neonatal capsaicin treatment.

Beal JA, Knight DS.

Administration of capsaicin to newborn rats results in a loss of a large percentage of primary afferent C fibers many of which terminate in the substantia gelatinosa (SG). Using the Golgi silver impregnation technique, the present study shows that the loss of C fibers results in an invasion of aberrant myelinated primary afferents in the SG by 10 days after birth. The aberrant afferents, identified on the basis of their distinctive collateral arborizations, are derived from hair follicles and slowly adapting type I mechanoreceptors.
Hair loss due to alopecia areata
J Invest Dermatol. 1985 Dec;85(6):569-72.Links
Expression of HLA-DR by anagen hair follicles in hair loss due to alopecia areata.

Messenger AG, Bleehen SS.

The expression of HLA-DR within hair follicles in hair loss secondary to alopecia areata was studied using an immunoperoxidase method. Scalp biopsies were taken from 12 patients with hair loss due to alopecia areata and from 6 normal control subjects. Frozen sections were stained with a panel of 4 anti-HLA-DR monoclonal antibodies, Leu 2, Leu 3, Leu 4, and T6 antibodies. The expression of DR in normal hair follicles and in most anagen follicles from nonlesional alopecia skin was confined to dendritic cells which were sparse below the level of the arrector pilorum insertion. ..snip... The aberrant expression of DR antigens by hair follicle epithelium provides direct evidence that immune mechanisms are operating in the pathogenesis of alopecia areata- induced hair loss. In a previous study of alopecia areata we found evidence of cell injury confined to the precortical matrix and presumptive cortex in lesional anagen follicles. The relative restriction of epithelial DR expression to the same site suggests that this region of the follicle is of fundamental importance in the disease process.
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Hormones in Hair loss in women
Int J Dermatol. 1992;31(12):858

Hormonal status in postmenopausal androgenetic alopecia.

Georgala S, et al

edited for blog

Androgenetic alopecia or pattern hair loss is thought to be caused by increased androgen action on hair follicles with menopause. Testosterone, estradiol and sex hormone binding globulin (SHBG) serum levels were determined in ten postmenopausal women with pattern hair loss and in ten sex and age matched healthy controls. No statistically significant differences were found in the hormone levels between the patients and the controls. These findings suggest that a genetically determined functional alteration of androgen receptors and/or a metabolic disturbance may exist in the hair follicle keratinocytes in pattern hair loss.