References: Hair growth and hair loss
Ann Dermatol Venereol. 2002 May;129(5 Pt 2):793-9.
[Genetic dissection of retinoic acid function in epidermis physiology]
[Article in French]
Ghyselinck NB, Chapellier B, Calleja C, Kumar Indra A, Li M, Messaddeq N, Mark M, Metzger D, Chambon P.
Institut de Genetique et de Biologie Moleculaire et Cellulaire, CNRS/INSERM/ULP, College de France, BP 10142, 67404 Illkirch Cedex, CU de Strasbourg, France.
The active metabolite of vitamin A (retinoic acid, RA) acts through the nuclear receptors RARalpha, beta and gamma and RXRalpha, beta and gamma. These receptors form RAR/RXR heterodimers, which bind to genetic regulatory DNA sequences and activate transcription of RA target genes. As RXR form heterodimers with a number of other nuclear receptors, such as the vitamin D3 receptor (VDR) and are involved in several signaling pathways. In the skin, RARgamma and RXRalpha predominate, but RARalpha and RXRbeta are also expressed. To elucidate the role of RA in skin physiology, we produced mutant mouse lines null for RAR or RXR. On the one hand, null mutations for RARa or RXRbeta have no effect on the skin, whereas a RARgamma-null mutation induces alterations in the granular cell layer. On the other, genetic inactivation of RXRa leads to embryonic lethality before epidermal development. Consequently, to determine the role of RXRa in adult mice, studies were performed using conditional somatic mutagenesis (permitting inactivation of a given gene in a specific tissue and in a time-dependent manner). Using this novel genetic approach, mutant mice were obtained in which RXRalpha was not expressed in the skin. These mice developed hair follicle degeneration, then alopecia, similar to that observed in VDR-null mutants, suggesting that hair follicle homeostasis depends on RXRalpha/VDR heterodimers. A similar genetic approach applied to the RARgamma locus demonstrated that topical administration of RA on the skin activates RARgamma/RXR heterodimers in suprabasal cells, and induces expression of a paracrine growth factor (HB-EGF) in these cells which, in turn, stimulates the proliferation of basal cells.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12223961&dopt=Abstract
J Eur Acad Dermatol Venereol. 2002 Jul;16(4):361-6.
Scleroderma 'en coup de sabre' and progressive facial hemiatrophy. Is it possible to differentiate them?
Orozco-Covarrubias L, Guzman-Meza A, Ridaura-Sanz C, Carrasco Daza D, Sosa-de-Martinez C, Ruiz-Maldonado R.
The aim was to be able to evaluate the diagnosis of two diseases by a consensus of clinical opinion used in the Department of Dermatology of the National Institute of Paediatrics in Mexico City. To differentiate between scleroderma 'en coup de sabre' (SCS) and progressive facial hemiatrophy (PFH), colour slides of 13 patients diagnosed as SCS and nine as PFH were examined by two dermatologists and microscopic slides by two pathologists. In both cases, the slides were randomly presented and no clinical information was given. The clinical and histopathological findings were statistically compared with two-tailed tests and alpha = 0.05. Kappa coefficients were obtained to evaluate the concordance between dermatologists, pathologists, and in terms of the consensus diagnosis. The usefulness of photographic assessment is limited by the inability to palpate the consistency of lesions. The most important clinical feature that differentiated both conditions was cutaneous sclerosis present in eight of 13 patients with SCS and in none of the PFH patients (P < 0.005). Other clinical features more frequently found in SCS were cutaneous hyperpigmentation and alopecia. The more frequent clinical features in PFH were total hemifacial involvement and ocular changes. Statistically significant histopathological features were: connective tissue fibrosis present in all cases with SCS and two of nine patients with PFH (P < 0.0002); adnexal atrophy present in 11 of 13 patients with SCS, and in three of nine with PFH (P < 0.02), and mononuclear cell infiltrates in all patients with SCS cf. six with PFH (P < 0.05). Our results suggest that in most cases it is possible to differentiate SCS from PFH based on clinicopathological findings.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12224693&dopt=Abstract
Eksp Med Morfol. 1975;14(2):83-91.
[Studies on the differences between the skin of nude mice and bald skin in man]
[Article in Bulgarian]
Kadanov D.
The author carried out studies and established that in contrast to the bald skin of a man the elastic fibres in the skin of naked mice were completely normal and the small arteries and arterioles were with normal structure, because of which they could not be considered as a cause of degeneration of hair follicles, falling of hairs and of their irreplaceability with hairs grown externaly in these animals (fig. 4 a and b, fig. 5 a and b). The processes, occuring in the skin of the mice, are determined genetically and their manifestations represent changes in features, which, induced by mutation, are inherited.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1222703&dopt=Abstract
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