References: Hair growth and hair loss
Br J Dermatol. 1999 Jun;140(6):1100-4.
Androgen-induced delay of hair growth in the golden Syrian hamster.
Mezick JA, Gendimenico GJ, Liebel FT, Stenn KS.
Johnson & Johnson Consumer Products Worldwide, Grandview Road, Skillman, NJ 08558-9418, USA.
The golden Syrian hamster flank organ has been used to study the stimulatory effect of androgens on sebaceous glands and hair. Androgens cause the sebaceous glands and hair follicles in this organ to grow. We have made the novel observation that exogenously administered androgen, testosterone propionate (TP), suppresses hair growth in the area surrounding the flank organ. When given in a time-release (systemic) subcutaneous dosage form (pellet), 25 mg TP inhibited the regrowth of clipped hair in peri-flank organ skin for up to 21 days; however, by 28 days hair grew back to the same extent as in controls. The peak serum level of testosterone in TP-treated animals occurred at 14 days, and declined thereafter. When two separate TP pellets (25 mg/pellet) were administered 14 days apart in order to maintain high serum levels for 28 days, the amount of hair regrowth after 35 days was identical to animals receiving a single TP pellet or placebo. This suggests that the systemic level of testosterone was not the only factor in hair regulation. Hair growing within the flank organ appeared to be unaffected by TP administration. In the golden Syrian hamster, androgen, as in humans, can exert stimulatory and inhibitory effects on hair growth depending on the body site. We conclude that this animal model could serve as a useful system to investigate the mechanisms responsible for the opposing effects of androgen on hair growth.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10354077&dopt=Abstract
J Invest Dermatol. 2001 Dec;117(6):1357-62.
Melanocyte-associated T cell epitopes can function as autoantigens for transfer of alopecia areata to human scalp explants on Prkdc(scid) mice.
Gilhar A, Landau M, Assy B, Shalaginov R, Serafimovich S, Kalish RS.
Skin Research Laboratories, Flieman Medical Center and Rappaport Faculty of Medicine, Technion Institute of Technology, Haifa, Israel.
Alopecia areata is a tissue restricted autoimmune condition affecting the hair follicle, resulting in hair loss. The goal of this study was to test the hypothesis that the autoantigen of alopecia areata is melanocyte associated. Potential autoantigens were tested in the human scalp explant/Prkd(scid) CB-17 mouse transfer system. Scalp T cells from lesional (bald) alopecia areata scalp were cultured with antigen-presenting cells, and antigen, along with interleukin-2. The T cells were then injected into autologous lesional scalp grafts on SCID mice, and hair regrowth was measured. Hair follicle homogenate was used as an autoantigen control. T cells cultured with melanoma homogenate induced statistically significant reduction in hair growth (p <0.01 by ANOVA). HLA-A2-restricted melanocyte peptide epitopes were then tested with lesional scalp T cells from HLA-A2-positive alopecia areata patients. Melanocyte-peptide-activated T cells significantly reduced the number of hairs regrowing in two experiments with six patients (p <0.001 by ANOVA). Injected scalp grafts showed histologic and immunochemical changes of alopecia areata. The most consistent peptide autoantigens were the Gp100-derived G9-209 and G9-280 peptides, as well as MART-1 (27-35). Melanocyte peptide epitopes can function as autoantigens for alopecia areata. Multiple peptides were recognized, suggesting epitope spreading.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11886495&dopt=Abstract
Comp Med. 2001 Jun;51(3):239-44.
Evaluation of fentanyl transdermal patches in rabbits: blood concentrations and physiologic response.
Foley PL, Henderson AL, Bissonette EA, Wimer GR, Feldman SH.
Center for Comparative Medicine, University of Virginia, Charlottesville 22908, USA.
In the study reported here, we sought to evaluate transdermal fentanyl patches for their ability to achieve detectable plasma concentrations with minimal adverse effects in New Zealand White rabbits. Fentanyl patches were applied to the dorsum after removing hair either by clipping or by application of a depilatory agent. Blood samples were collected every 12 h for a total of 96 h (24 h after patch removal) for determination of plasma fentanyl concentration. At those times, rabbits were assessed for changes in body temperature, heart rate, respiratory rate, and body weight. In rabbits with clipped hair, where rapid hair re-growth was not a mitigating factor, mean plasma fentanyl concentration reached a mean (+/- SEM) peak of 1.11 +/- 0.32 ng/ml at 24 h, decreased to 0.77 +/- 0.21 ng/ml at 72 h, and was negligible at 96 h. In rabbits with depilated hair, peak concentration was obtained at 12 h (6.7 +/- 0.57 ng/ml) and decreased gradually to 0.27 +/- 0.06 ng/ml at 72 h. In a second group of fentanyl-treated rabbits in which hair started growing back within 24 h, plasma fentanyl concentration was not detectable. Control and fentanyl-treated rabbits with clipped hair had no effect from the experimental manipulations other than slight loss in body weight. In the depilatory group, two rabbits appeared moderately sedated during the initial 12-h period, and had decreased respiratory rate for 24 h. In conclusion, rabbits tolerate the transdermal fentanyl patch well. Hair regrowth in rabbits may present a complicating factor that impedes dermal absorption of fentanyl. The application of a depilatory agent lead to early and rapid absorption of fentanyl causing undue sedation in some rabbits and lack of sustained plasma concentrations for the desired three-day period.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11924779&dopt=Abstract
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