hair growth, stop hair loss



References: Hair growth and hair loss








Planta. 1997 Dec;203(4):495-505.
Root hair growth in Arabidopsis thaliana is directed by calcium and an endogenous polarity.

Bibikova TN, Zhigilei A, Gilroy S.

Department of Biology, Pennsylvania State University, University Park 16802, USA.

Tip growth of plant cells has been suggested to be regulated by a tip-focused gradient in cytosolic calcium concentration ([Ca2+]c). However, whether this gradient orients apical growth or follows the driving force for this process remains unknown. Using localized photoactivation of the caged calcium ionophore Br-A23187 we have been able to artificially generate an asymmetrical calcium influx across the root hair tip. This led to a change in the direction of tip growth towards the high point of the new [Ca2+]c gradient. Such reorientation of growth was transient and there was a return to the original direction within 15 min. Root hairs forced to change the direction of their growth by placing a mechanical obstacle in their path stopped, reoriented growth to the side, and grew past the mechanical blockage. However, as soon as the growing tip had cleared the obstacle, growth returned to the original direction. Confocal ratio imaging revealed that a tip-focused [Ca2+]c gradient was always centered at the site of active growth. When the root hair changed direction the gradient also reoriented, and when growth returned to the original direction, so did the [Ca2+]c gradient. This normal direction of apical growth of Arabidopsis thaliana (L.) Heynh, root hairs was found to be at a fixed angle from the root of 85 +/- 6.7 degrees. In contrast, Tradescantia virginiana (L.) pollen tubes that were induced to reorient by touch or localized activation of the caged ionophore, did not return to the original growth direction, but continued to elongate in their new orientation. These results suggest that the tip-focused [Ca2+]c gradient is an important factor in localizing growth of the elongating root hair and pollen tube to the apex. However, it is not the primary determinant of the direction of elongation in root hairs, suggesting that other information from the root is acting to continuously reset the growth direction away from the root surface.

online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9421933&dopt=Abstract




Cancer Res. 1998 Jan 1;58(1):89-94.
Disruption of the mouse xeroderma pigmentosum group D DNA repair/basal transcription gene results in preimplantation lethality.

de Boer J, Donker I, de Wit J, Hoeijmakers JH, Weeda G.

Medical Genetics Center, Department of Cell Biology and Genetics, Erasmus University, Rotterdam, The Netherlands.

The xeroderma pigmentosum (XP) group D (XPD) gene encodes a DNA helicase that is a subunit of the transcription factor IIH complex, involved both in nucleotide excision repair of UV-induced DNA damage and in basal transcription initiation. Point mutations in the XPD gene lead either to the cancer-prone repair syndrome XP, sometimes in combination with a second repair condition; Cockayne syndrome; or the non-cancer-prone brittle-hair disorder trichothiodystrophy. To study the role of XPD in nucleotide excision repair and transcription and its implication in human disorders, we isolated the mouse XPD gene and generated a null allele via homologous recombination in embryonic stem cells by deleting XPD helicase domains IV-VI. Heterozygous cells and mice are normal without any obvious defect. However, when intercrossing heterozygotes, homozygous XPD mutant mice were selectively absent from the offspring. Furthermore, we could not detect XPD-/- embryos at day 7.5 of development. In vitro growth experiments with preimplantation-stage embryos obtained from heterozygous intercrosses showed a significantly higher fraction of embryos that died at the two-cell stage, compared to wild-type embryos. These results establish the essential function of the XPD protein in mammals and in cellular viability and are consistent with the notion that only subtle XPD mutations are found in XP, XP/Cockayne syndrome, and trichothiodystrophy patients.

online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9426063&dopt=Abstract




Plast Reconstr Surg. 1998 Jan;101(1):12-9.
Bone morphogenetic protein-2 induces scar formation and skin maturation in the second trimester fetus.

Stelnicki EJ, Longaker MT, Holmes D, Vanderwall K, Harrison MR, Largman C, Hoffman WY.

Fetal Treatment Center, University of California San Francisco, USA.

Fetal mammals heal skin wounds through the second trimester of development without evidence of scar. We have investigated the role of bone morphogenetic protein 2 (BMP-2), which is a member of the TGF-beta superfamily, in normal skin development and fetal wound healing. We first used RNA in situ hybridization to demonstrate that BMP-2 was expressed at low levels in the developing hair follicles and in the epidermis of normal human fetal skin. We then created an in vivo model to test how exogenous BMP-2 would affect fetal skin development and wound healing. Fifty micrograms of BMP-2 was implanted into the subcutis of five 70-day-old fetal lambs through a full-thickness linear incision. The BMP-2 was placed beneath the right half of the wound, whereas the left half served as an untreated control. In two of the five animals 1 microgram of TGF-beta was placed into the same position in addition to the 50 micrograms of BMP-2. Twenty days later (90 days gestation, term = 140 days) all the fetal wounds were examined for evidence of cellular hyperproliferation and scar formation. BMP-2 induced massive dermal and epidermal growth when compared with controls. This finding was characterized by marked epidermal thickening and keratinization, a dramatic increase in the number of hair follicles, and more than 50 percent thickening of the dermis. The dermal thickening was the result of both increased cellularity and deposition of large irregular collagen bundles. Wounds treated with both BMP-2 and TGF-beta healed also with an adult-like pattern of scar formation. Surprisingly, the wounds with BMP-2 alone healed with an equal pattern of scar, indicating that there was not an additive effect of combining BMP-2 and TGF-beta. We conclude that BMP-2 is a pleomorphic growth factor that induces cellular growth, maturation, and fibroplasia in both the dermis and epidermis. Further analysis of this growth factor in both fetal and adult wound healing may lead to important discoveries regarding the control of scar formation and fibrosis in many adult tissues.

online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9427911&dopt=Abstract





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