References: Hair growth and hair loss
virginia.edu
The adult cuticular wing of Drosophila is covered by an array of distally pointing hairs that reveals the planar polarity of the wing. We report here that mutations in dachsous disrupt this regular pattern, and do so by affecting frizzled signaling. dachsous encodes a large membrane protein that contains many cadherin domains and dachsous mutations cause deformed body parts. We found that mutations in dachsous also result in a tissue polarity phenotype that at the cellular level is similar to frizzled, dishevelled and prickle, as many cells form a single hair of abnormal polarity. Although their cellular phenotype is similar to frizzled, dishevelled and prickle, dachsous mutant wings display a unique and distinctive abnormal hair polarity pattern including regions of reversed polarity. The development of this pattern requires the function of frizzled pathway genes suggesting that in a dachsous mutant the frizzled pathway is functioning - but in an abnormal way. Genetic experiments indicated that dachsous was not required for the intracellular transduction of the frizzled signal. However, we found that dachsous clones disrupted the polarity of neighboring wild-type cells suggesting the possibility that dachsous affected the intercellular signaling function of frizzled. Consistent with this hypothesis we found that frizzled clones in a dachsous mutant background displayed enhanced domineering non-autonomy, and that the anatomical direction of this domineering non-autonomy was altered in regions of dachsous wings that have abnormal hair polarity. The direction of this domineering nonautonomy was coincident with the direction of the abnormal hair polarity. We conclude that dachsous causes a tissue polarity phenotype because it alters the direction of frizzled signaling.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9449678&dopt=Abstract
Histochem Cell Biol. 1997 Dec;108(6):489-94.
Complementary expression of glutamine synthetase and carbamoylphosphate synthetase I in ornithine carbamoyltransferase-deficient mouse liver (spf-ash mouse).
Shiojiri N, Ohta T, Ogawa K, Gebhardt R.
Department of Biology, Shizuoka University, Oya, Japan.
Glutamine synthetase and carbamoylphosphate synthetase I expression was examined immunohistochemically in livers of spf-ash homozygous and hemizygous mice, in which one of the urea cycle enzymes (ornithine carbamoyltransferase) is deficient and hyperammonemic disorders are obvious. In the mutant adult mouse liver, only hepatocytes lining central veins expressed glutamine synthetase. In contrast, other hepatocytes expressed carbamoylphosphate synthetase I but not glutamine synthetase. This complementary expression pattern is similar to that seen in wild-type mouse liver. In the liver of mutant young mice, which showed severe retarded growth and abnormal hair and skin development, the developmental expression pattern of both enzymes was also similar to that of the corresponding wild-type liver. However, suppression of carbamoylphosphate synthetase I expression in the pericentral hepatocytes occurred later in the mutant than in wild-type liver. These results show that high plasma concentrations of ammonium ions, which are one of the substrates for both the enzymes, do not change their complementary expression. Instead they support the idea that factor(s) associated with central veins rather than humoral factors direct pericentral hepatocytes to express glutamine synthetase and to suppress carbamoylphosphate synthetase I expression.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9450631&dopt=Abstract
Arch Dermatol Res. 1997 Nov;289(12):698-704.
Cultured dermal papilla cells of the rat vibrissa follicle. Proliferative activity, adhesion properties and reorganization of the extracellular matrix in vitro.
Almond-Roesler B, Schon M, Schon MP, Blume-Peytavi U, Sommer C, Loster K, Orfanos CE.
Department of Dermatology, University Medical Center Benjamin Franklin, Free University of Berlin, Germany.
The dermal papilla of the mammalian hair follicle plays an important role in regulating and controlling the hair cycle. Distinct functional stages of dermal papilla cells (DPC) are involved in this process, thus suggesting that the dermal papilla is a highly specialized suborgan of the pilosebaceous unit. The aim of the present study was to investigate the functional properties of cultured DPC in various assays and to compare their functional properties with those of dermal fibroblasts (DFB). In monolayer cell cultures DPC showed an aggregative growth pattern, different to that of DFB, and lower proliferation rates, as compared to the controls. Adhesion assays performed using a 51[Cr]labeling method showed strong adhesion of both cell populations to collagen types I and IV, fibronectin and laminin, but DPC in vitro showed significantly higher adhesiveness to collagen type IV, a major component of the basement membrane of dermal papillae in vivo. The capacity of DPC to reorganize extracellular matrix components, as measured by gel contraction with three-dimensional collagen type I lattices, proved to be significantly lower than that of DFB and, moreover, DPC lysed the collagen lattices completely after 48 h in culture. The functional differences between DPC and DFB were paralleled by higher surface expression and synthesis levels of the beta 1, alpha 1, and alpha 5 chains of integrin adhesion receptors in DPC, as detected by fluorescence-activated cell-sorter analysis and radioimmunoprecipitation. These findings provide evidence that DPC are a highly specialized cell population, which clearly differs from another mesenchymal cell type, DFB. After their isolation and cultivation in vitro, DPC still preserve functional properties related to important steps of cell-matrix interaction involved in the hair cycle.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9452891&dopt=Abstract
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