Wrapping Up The Summaries

As I was choosing which articles I'll use for my outline, I realized that I have several articles I read and forgot to summarize. Here they are!

Mechanisms of noise-induced hearing loss indicate multiple methods of prevention. Colleen G Le Prell et al. Hearing Research (2007)
This article outlines a lot of different methods for prevention of noise-induced hearing loss, including studies of antioxidants, steroids, and vasodilators (among others I couldn't understand). Although most of the article was beyond my comprehension level, I did gather that scientists are coming close to finding prevention methods for noise-induced hearing loss both immediately and up to weeks after exposure.
In terms of antioxidants, the idea came after Halliwell, Gutteridge, and Evans discovered "...that intense metabolic activity alters cellular redox state and drives the formation of free radicals... In excess, [free radicals] damage cellular lipids, proteins, and DNA, and upregulate apoptotic pathways." So essentially, the noise is over-energizing the metabolic activity which causes breakdown of the auditory system. Using an antioxidant helps to reduce or eliminate the permanent threshold shift in a noise-exposed system. Interestingly enough, the temporary threshold shift is not affected by use of antioxidants.
I found it fascinating that the authors explained, "The finding that dietary supplements reduce NIHL is of particular interest given their easy over-the-counter accessibility; however, therapy with any single micronutrient may need to be initiated days to week in advance of noise exposure to obtain clinically meaningful results." That's alright! We should all be getting more nutrients to begin with. I never thought that vitamins could reduce the effects of harmful noise. No wonder our society is becoming more affected by noise pollution; we're getting less healthy, too! This is an important factor to keep in mind for young children whose diets are still determined by their parents.
It's not directly related to the topic of this research, but the authors made the point that, "...[Neurotropic factors] have been shown to be extremely effective at preserving neural survival in the absence of surviving hair cells." This screams cochlear implant application to me and would be a good point to remember when that time comes in class!


Effect of Long-Term Noise Exposure on the Developing and Developed Ear in the Rat. Sharon Freeman, et, al. Audiology & Neuro-Otology (1999)
This article was fascinating! I have always thought that young ears are more sensitive than fully-developed and 'toughened' ears. This article (and its sources) proved that idea to be false. As the authors wrote, "...exposure caused greater long-term changes in hearing in the adult compared to the young noise-exposed rats, although histology showed greater damage to hair cells in the younger animals." This floored me! What causes less functional loss but more cellular damage? Is the younger ear just more able to adjust and compensate?
Also blowing my preconceptions out of the water was the response to the idea that babies in the womb are protected from sound. The authors wrote, "...more recent measurements in humans and sheep, using a hydrophone, showed that lower frequencies were not attenuated at all and may even be enhanced by about 5 dB, whilst higher frequency sounds are attenuated by 10-20 dB only." Very interesting!


More to come this evening. I hit a wall!