References: Hair growth and hair loss
utdallas.edu
The purpose of this study was to test the hypothesis that differences exist in the amount of protection provided by prior sound conditioning with continuous vs. interrupted, moderate-level noise. Differences were determined by monitoring the changes that occurred in cubic (2f1-f2) distortion product otoacoustic emission (DPOAE) amplitude growth functions subsequent to a traumatizing noise exposure (105 dB SPL, 1.0-2.0 kHz octave band noise presented 24 h per day for 3 days) in guinea pigs which had been conditioned with either continuous (89 dB SPL, 1.0-2.0 kHz octave band noise presented 24 h per day for 11 days) or interrupted noise (95 dB SPL, 1.0-2.0 kHz octave band noise presented on a 6-h 'on'/18-h 'off' schedule for 11 days) of equal acoustic energy. Results suggest that there are significant differences in the degree of protection provided by prior sound conditioning with the continuous and interrupted schedules of moderate-level noise used in this study. Specifically, the interrupted conditioning protocol afforded some degree of protection against the damaging effects of the traumatizing noise exposure, limited to frequencies above the noise exposure band. Conversely, there was a lack of any consistent and sizable protective effect found across the entire test frequency range for the continuous sound conditioning protocol.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9508025&dopt=Abstract
Mech Dev. 1998 Jan;70(1-2):181-92.
Distinct roles for the actin and microtubule cytoskeletons in the morphogenesis of epidermal hairs during wing development in Drosophila.
Turner CM, Adler PN.
Biology Department and Cancer Center, University of Virginia, Charlottesville 22903, USA.
We have found that the actin and microtubule cytoskeletons have overlapping, but distinct roles in the morphogenesis of epidermal hairs during Drosophila wing development. The function of both the actin and microtubule cytoskeletons appears to be required for the growth of wing hairs, as treatment of cultured pupal wings with either cytochalasin D or vinblastine was able to slow prehair extension. At higher doses a complete blockage of hair development was seen. The microtubule cytoskeleton is also required for localizing prehair initiation to the distalmost part of the cell. Disruption of the microtubule cytoskeleton resulted in the development of multiple prehairs along the apical cell periphery. The multiple hair cells were a phenocopy of mutations in the inturned group of tissue polarity genes, which are downstream targets of the frizzled signaling/signal transduction pathway. The actin cytoskeleton also plays a role in maintaining prehair integrity during prehair development as treatment of pupal wings with cytochalasin D, which inhibits actin polymerization, led to branched prehairs. This is a phenocopy of mutations in crinkled, and suggests mutations that cause branched hairs will be in genes that encode products that interact with the actin cytoskeleton.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9510034&dopt=Abstract
Acta Anat (Basel). 1997;159(1):15-24.
Development of lung, kidney and skin in the brushtail possum, Trichosurus vulpecula.
Buaboocha W, Gemmell RT.
Department of Anatomical Sciences, University of Queensland, Brisbane, Australia.
The thyroid gland is not present at birth in marsupials and thyroid function begins during the latter half of pouch life. The hormonal output of the thyroid gland is important for normal development. In this study the structure of the lung, kidney and skin of the developing possum was examined and the structural development of these three organs was described. The lung of the newborn brushtail possum was functional and continued to develop during pouch life, alveolar formation beginning at day 39 and concluding at day 113 postpartum. The mesonephric kidneys of the newborn possum degenerated and were replaced by the metanephric kidneys, the nephrogenic zone of the metanephric kidney being present from 35 to 96 days postpartum. No new nephrons were formed after day 96. After the completion of nephrogenesis, the kidney increases in size through glomerular and tubular growth. The sequence of steps in the development of the possum skin was identical to that observed in other marsupials. The epidermis of the possum was thickest at 60 microns on about day 28 postpartum and as development proceeded the epidermis gradually decreased in thickness. A sparse number of primordia of hair follicles were observed at day 10 and the possum had a good covering of hair by day 129 postpartum. Correlation between the development of the lung, kidney and skin with the previously published plasma thyroxine concentration in the young possum suggests that thyroxine from the mother and from the young is important in the development of these three organs.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9522893&dopt=Abstract
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