Attenuation of adverse effects of noise induced hearing loss on adult neurogenesis and memory in rats by intervention with Adenosine A2A receptor agonist.

Hearing loss and cognitive decline are commonly associated with aging and morbidity. Present clinical interest lies in whether peripheral hearing loss promotes cognitive decline and if prophylaxis with selective adenosine receptor agonist CGS21680 effectively mitigates the adverse effects. In the current study, male Sprague Dawley rats weighing 200-250 g m were randomly allocated into three groups: Group 1) rats exposed to 100 dB SPL white noise, 2 h a day for 15 consecutive days, 2) rats supplemented with an adenosine receptor agonist, CGS21680 at 100 µg/kg/day prior to noise exposure and 3) unexposed control rats. Baseline hearing and cognition assessed by auditory brainstem response (ABR) and water maze respectively was undertaken for all the groups. Phalloidin stain and synaptic ribbons count in cochlea, and, Ki67, DCX and NeuN in hippocampus were observed by immunohistochemistry. It was inferred that noise exposed rats showed elevated thresholds of ABR and poorer performances in spatial working memory when compared with controls. On the contrary, CGS21680 administered group exhibited improved ABR and cognitive functions with shorter mean latency and path-length to reach the platform, significant reduction in the noise induced loss of synaptic ribbons count and increased number of Ki67 and doublecortin (DCX) positive cells compared to their noise exposed counterparts. Pharmacologic intervention with selective A2A receptor agonist CGS21680 provided adequate protection from noise by effectively maintaining hearing threshold levels, cell viability in cochlea and hippocampus & functional/intact reference memory.

Distortion product oto-acoustic emission: a superior tool for hearing assessment than pure tone audiometry.

OBJECTIVE: Hearing plays a crucial role in the performance of a soldier and is important for communication and speech processing. Service personnel are constantly exposed to high levels of noise and hence predisposed to occupational health disabilities, principally noise-induced hearing loss (NIHL) and tinnitus. NIHL is a significantly common impairment in the military and can affect the warfare performances. Parochial awareness about the effects of uproarious noise which exacerbates their hearing, acceptance rate of use of hearing protection devices and follow-up audiological tests have become the major drawback for prevention of NIHL and are less pondered upon. METHOD: The present study focuses on the effects of noise on the hearing of service crew operating and maintaining military equipment and explores the efficacy of DPOAE's to substitute pure tone audiometry as a quick, easy to operate and implementable test technique for monitoring of hearing status. RESULTS: The results suggest that DPOAE test is important and more coherent than audiometry alone for the early detection of cochlear injury due to noise from military operations and efficacious for detecting NIHL.

Acquired toxic methaemoglobinaemia.

Eighty Six adult males presented with central cyanosis and constitutional symptoms 2 to 4 hours following ingestion of meal from a common kitchen. On spectrometry methaemoglobin was detected. All recovered fully in 12 to 36 hours on symptomatic treatment. Epidemiological study and toxicological examination revealed that metanil yellow used for colouring the rice was responsible.