References: Hair growth and hair loss
cvm.tamu.edu
The effects of hypothyroidism on canine skin were determined by comparing morphologic, morphometric, and hair cycle differences in skin biopsy samples from 3 groups of age- and gender-matched Beagle dogs: (1) euthyroid dogs; (2) dogs made hypothyroid by administration of 131I; and (3) dogs made hypothyroid and maintained in a euthyroid state by treatment with synthetic thyroxine. After 10 months of observation, there was slower regrowth of hair 2 months after clipping in the untreated-hypothyroid dogs. Untreated-hypothyroid dogs had a greater number of follicles in telogen and fewer hair shafts (ie, a greater number of hairless telogen follicles) than did the control group. The control dogs had a greater number of telogen follicles but the same number of hair shafts as the treated-hypothyroid group. Treated-hypothyroid dogs had the greatest number of follicles in the growing stage of the hair cycle (anagen). This study suggests that, at least in Beagles, induced hypothyroidism does not affect the pelage as dramatically as has been described in naturally occurring disease. This is because normal Beagles retain hair shafts in follicles for long periods, and the alopecia of hypothyroidism appears to evolve slowly because of the prolongation of this haired telogen stage. The evaluation of thyroxine-treated hypothyroid dogs demonstrates that thyroid hormone supplementation of Beagle dogs with induced hypothyroidism stimulates hair growth.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11817058&dopt=Abstract
Lab Anim. 2002 Jan;36(1):61-7.
Atrichia with papular lesions resulting from mutations in the rhesus macaque (Macaca mulatta) hairless gene.
Ahmad W, Ratterree MS, Panteleyev AA, Aita VM, Sundberg JP, Christiano AM.
Department of Dermatology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
Atrichia with papular lesions (APL) is a rare form of hair loss with an autosomal recessive mode of inheritance that is characterized by the absence of normal hair follicles, and formation of intradermal cystic structures. Mutations in the hairless (hr) gene in mice and humans have been implicated in the development of this phenotype. Hairless is a putative transcription factor containing a single zinc-finger DNA binding domain, with restricted expression in brain and skin. Here, we describe the complete hr cDNA sequence from the rhesus macaque (Macaca mulatta) and report the identification of a compound heterozygous mutation in a hairless rhesus macaque born from unrelated parents. Cutaneous biopsy samples from the affected macaque revealed abnormalities, including the replacement of normal hair follicles with dermal cysts and comedones, reminiscent of the skin phenotype observed in hairless mice and humans with APL.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11831740&dopt=Abstract
Dermatology. 2002;204(1):33-6.
Perception of baldness and hair density.
Vecchio F, Guarrera M, Rebora A.
DiSEM, Section of Dermatology, University of Genoa, Italy.
BACKGROUND: Androgenetic alopecia needs to be scored precisely. OBJECTIVE: A possible measure is the ratio between the hair density in the parietal area and that in the occipital area which, being not affected by baldness, supposedly has a 'normal' density. METHODS: On the vertex and just below the occipital protuberance of 109 men, two 1-cm(2) areas were identified. In both areas, hairs were clipped short and photographed by a videomicroscope. Hairs were then counted within a 30-mm(2)-wide central square section. RESULTS: In the occipital area, the average count was 127/cm(2), without differences among the Hamilton/Norwood classes. In the parietal area, the average density significantly diminished from 138 to 47/cm(2). A main difference was found between classes 1-3 vertex and classes 4-6. CONCLUSIONS: The parietal/occipital ratio decreased significantly only when baldness was clinically manifest. The parietal/occipital ratio cannot be a better measure of baldness severity than the rough Hamilton/Norwood scale. The perception of early baldness does not depend on the diminished hair density, but also on the progressive thinning of the hair shafts. Copyright 2002 S. Karger AG, Basel
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11834847&dopt=Abstract
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