Exposure to aminoglycoside antibiotics and loud noises are two common causes of deafness. Aminoglycoside antibiotics are ototoxic to hair cells. Loud noises overstimulate the hair cells of the inner ear, leading to their eventual death. Mammals cannot regenerate lost hair cells. Hair cells of sea anemones are similar to mammalian hair cells in morphology and function. However, hair cells of sea anemones self-repair after extensive damage. Hair cells of the sea anemone, Nematostella vectensis, were exposed to streptomycin (an aminoglycoside antibiotic), cytochalasin D (CD, a drug that depolymerizes actin), and calcium-free seawater (mimics overstimulation). Streptomycin causes a significant decrease in the abundance of hair bundles. Streptomycin causes a significant decrease in labeling of mitochondria using a vital dye that labels normal mitochondria and causes a significant increase in cell turnover within the epithelium of tentacles. CD causes a loss of normal morphology and a decrease in the abundance of hair bundles. The abundance of hair bundles recovers within 3 hours after exposure to CD. CD exposure reveals the presence of two populations of hair bundles on tentacles of sea anemones: a CD-resistant population that appears to be uninvolved in vibration-dependent discharge of nematocysts and a CD-sensitive population that is involved in vibration-dependent discharge of nematocysts. Exposure to calcium-free seawater significantly decreases the abundance of hair bundles. A partial recovery occurs within 3 hours of exposure to calcium-free seawater, followed by a full recovery of abundance within 24 hours. This partial recovery is prevented by inhibitors that block the activity of Rho G-proteins. Widening at the tips of hair bundles and lengthening of stereocilia normally occur during spontaneous recovery from exposure to calcium-free seawater. Rho inhibitors block the lengthening of stereocilia. Rho G-proteins are required for recovery of hair bundles. These studies confirm the resiliency of the hair cells of sea anemones to multiple types of damage and suggest that sea anemones may constitute a useful model system for studying recovery of hair cells following damage.
|Advisor:||Watson, Glen M.|
|Commitee:||Moon, Brad, Chlan, Caryl A., Mire, Patricia L., Greenwood, Paul G.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||DAI-B 81/2(E), Dissertation Abstracts International|
|Keywords:||Aminoglycosides, Cytochalasin G, Hair bundles, Hair cells, Nematostella vectensis, Rho G-proteins|
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