Wesley Smith
acoustic trauma, noise-induced hearing loss (NIHL) and oxidative damage
Previous results indicated that reduced hearing response follows exposure to loud stimuli in Drosophila. This is uninformative as to the nature of the assumed damage to Johnston's Organ. Studies in vertebrates have shown that hearing loss is likely attributed to the production of oxidative radical species in the inner ear following exposure to loud noises (Yamashita, et al., 2004). Taking note of this, I treated flies and waited seven days to record from their Johnston's Organ. I additionally had Elena fix sections of the flies' antennae before and after exposure for morphological analysis via electron microscopy. Again, flies heterozygous for the nrv315 mutant allele that were exposed to the super-stimulus had a much reduced response in hearing, even after a week. After reviewing EM images of JO ultrastructure in flies with lowered hearing responses, it will be clearer whether or not there has been damage to JO. Since this damage may have been brought about by oxidative species, looking into genes being upregulated during the period following exposure may be informative as to how the auditory structure deals with free radical species. This can be relevant for future studies, as having another model system for studying NIHL provides the opportunity to look at hearing loss in a different light.
Education: Contact:
Biology major (Neurobiology track) wesley-smith@uiowa.edu
Position:
Undergraduate Research Assistant
Project:
Acoustic trauma in Drosophila
Acoustic Trauma in Drosophila melanogaster
FIGURE 2 The most significant reduction in hearing response after treatment occurs in flies heterozygous for nrv315 (Far right): About 50%. N = 10 for each column.
Acoustic trauma is often used as a tool to perturb auditory systems in vertebrates in order to learn about the physiology of cochlear damage and regeneration. In order to characterize acoustic trauma in an invertebrate model system, I have developed a device that can subject flies to an intense auditory super-stimulus.
Electrophysiological recordings taken from the fly auditory organ (Johnston's Organ), have shown that certain strains of Drosophila display an acute reduction in hearing response when presented with the male courtship song after exposure to the super-stimulus, as compared to control counterparts that have not been exposed to the super-stimulus.
Cryptic phenotypes of flies heterozygous for the mutant allele nrv15
Nrv3 codes for the beta-subunit of Drosophila Na/K ATPase, and is involved in the hearing response; two copies of the mutant allele nrv315 is lethal to flies, but flies heterozygous for the mutant allele appear to have normal electrophysiology under unstressed lab conditions. As an assay for a possible haploinsufficiency, I subjected flies heterozygous for nrv315 to acoustic stress; their response compared to cohorts was much reduced.
FIGURE 1 Both columns are averages of recordings from 20 flies. Treated flies on the right have about a 33% reduction in hearing response. Standard error for each column is shown.
FIGURE 3 The greatest reduction in hearing after seven days was again found in the flies heterozygous for nrv315 (Far right). N = 10 for each column.
