References: Hair growth and hair loss
Schweiz Arch Tierheilkd. 1997;139(2):78-83.
[Histochemical and biochemical studies of the circannual aspects of carbohydrate-dependent energy metabolism of the hair follicles of Turkish Angora goats]
[Article in German]
Meyer W, Saglam M, Tanyolac A, Schwarz R, Hetzel U.
Institut fur Zoologie, Tierarztlichen Hochshule, Hannover.
Based on biopsy material, the study describes circannual variations of the accumulation of glycogen and organic carbon in the hair follicles. The results have been obtained by histochemical and biochemical methods. The histochemical-densitometric analysis of glycogen contents in the cells of the outer epithelial root sheath of the hair follicles exhibited a clear circannual course, with maxima in May/June and December, and minima in March and August. The content of organic carbon of the hair follicles was 7.61 micrograms/mg (max. 21.56 micrograms/mg) DW on average, with a corresponding annual cycle. The findings are discussed with regard to the energy metabolism of the hair follicle, especially in view of the fact that a biphasic cycle of hair growth becomes obvious in the Turkish Angora goat, a phenomenon that is obscured by other methods.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9381110&dopt=Abstract
J Anim Sci. 2000 Aug;78(8):2113-20.
Genetic analysis of litter size in Targhee, Suffolk, and Polypay sheep.
Rao S, Notter DR.
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
Data on litter size, weaning weights at 60, 90, and 120 d, postweaning gains from weaning to 120 or 365 d of age, fleece weight, and fiber diameter from Targhee, Suffolk, and Polypay flocks participating in the U.S. National Sheep Improvement Program were used to estimate genetic parameters for litter size and genetic relationships between early-life traits and future litter size. Records on 7,591 lambings by 3,131 Targhee ewes, 10,295 lambings by 5,038 Suffolk ewes, and 6,061 lambings by 2,709 Polypay ewes were used. Heritability estimates for litter size ranged from .09 to .11 across breeds; repeatability ranged from .09 to .13. Additive genetic effects on litter size were generally positively, and occasionally significantly, correlated with animal additive genetic effects on weaning weights and postweaning gains. Genetic correlations (r(a)) ranged from .08 to .48 in Targhee and from .17 to .43 in Suffolk but were close to 0 in Polypay (-.14 to .09). Additive maternal effects on weaning weight were positively associated with litter size in Suffolk and Polypay; this correlation was negative (-.23 to -.35), but not significant, in Targhee. Fleece weight was not strongly associated with litter size; (r(a) = -.09 to .21). However, fiber diameter had a significant undesirable correlation with litter size (.30) in Targhee. Estimates of phenotypic correlations of litter size with early-life traits were uniformly small (-.02 to .08). Thus, although occasional genetic antagonisms between litter size and early-life traits were observed in these data, none appeared large enough to prevent simultaneous genetic improvement in both traits.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10947097&dopt=Abstract
virginia.edu
BACKGROUND: The frizzled (fz) gene of Drosophila encodes the founding member of the large family of receptors for the Wnt family of signaling molecules. It was originally studied in the adult epidermis, where it plays a key role in the generation of tissue polarity. Mutations in components of the fz signal transduction pathway disrupt tissue polarity; on the wing, hairs normally point distally but their polarity is altered by these mutations. RESULTS: We devised a method to induce a gradient of fz expression with the highest levels near the distal wing tip. The result was a large area of proximally pointing hairs in this region. This reversal of polarity was seen when fz expression was induced just before the start of hair morphogenesis when polarity is established, suggesting that the gradient of Fz protein acted fairly directly to reverse hair polarity. A similar induction of the dishevelled (dsh) gene, which acts cell autonomously and functions downstream of fz in the generation of tissue polarity, resulted in a distinct tissue polarity phenotype, but no reversal of polarity; this argues that fz signaling was required for polarity reversal. Furthermore, the finding that functional dsh was required for the reversal of polarity argues that the reversal requires normal fz signal transduction. CONCLUSIONS: The data suggest that cells sense the level of Fz protein on neighboring cells and use this information in order to polarize themselves. A polarizing signal is transmitted from cells with higher Fz levels to cells with lower levels. Our observations enable us to propose a general mechanism to explain how Wnts polarize target cells.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9382848&dopt=Abstract
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