Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.9.3.1 (cytochrome oxidase)
 8,822 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binaural and monaural ossicle ablation in neonate rats before the time of onset of auditory input resulted in hearing deficits as detected by behavioural responses to sound stimuli in these rats as young adults. Cochlear disruption at the same neonatal age similarly resulted in the absence of startle reflexes in many of the rats. When the middle and inner ears of the rats were analysed postmortem in serial sections, it was observed that most ears after neonatal ossicle ablation contained only small remnants of the malleus-incus unit, separated from the stapes; in other ears an apparent continuity of ossicles had been restored. The rats with blind-ending ear canals and ossicle atrophy were those that had shown little response to sound stimuli. In the cochlear-disrupted rats, those with modiolar damage and loss of most spiral ganglion cells had shown substantial impairment of sound perception, even in some rats with only monaural modiolar loss. The chronic conduction deficit caused by neonatal ossicle removal did not result in detectable differences in relative cytochrome oxidase activity in the dorsal cochlear nuclei and central nucleus of the inferior colliculus. For monaurally ossicle-ablated rats, quantitation of the average intensity of enzyme reaction product in sections of dorsal or ventral cochlear nuclei, or central nucleus, did not reveal a difference between operated and non-operated sides. However, in binaurally ossicle-ablated rats, the relative enzyme activity in the anteroventral cochlear nuclei was reduced in comparison to this nucleus in control rats. The volume of the anteroventral cochlear nucleus in rats that had had neonatal binaural cochlear disruption was reduced relative to the volume in control rats or in rats that had had binaural ossicle ablation (P < 0.001); the latter procedure did not result in a statistically significant difference from controls in AVCN volume. In cochlear-operated rats with monaural modiolar damage, the AVCN contralateral to the damaged cochlea had a lower mean level of cytochrome oxidase activity in its neurons measured individually than that for neurons in the ipsilateral AVCN. These results suggested the importance during development of input from contralateral cochlear neurons.
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PMID:Auditory behaviour and brainstem histochemistry in adult rats with characterized ear damage after neonatal ossicle ablation or cochlear disruption. 838 69

Conductive hearing loss (CHL) restricts auditory input to an intact peripheral auditory system. Effects of deprivation on the central auditory system (CAS) have been debated, although a number of studies support the hypothesis that CHL can cause modification of CAS structure and function. The present study was designed to test the hypothesis that unilateral CHL results in a decrease in cytochrome oxidase (CO) activity in CAS nuclei that receive major afferent input from the affected ear. Gerbils at postnatal day 12 (P21) or 6-8 weeks underwent left unilateral CHL (malleus removal), cochlear ablation, or a sham surgical procedure. After a survival time of 48 hours or 3 weeks, animals were sacrificed and tissue was processed for cytochrome oxidase histochemistry. Optical density (OD) measurements were made from individual neurons in the anteroventral cochlear nucleus (AVCN) and from medial and lateral dendritic fields in the medial superior olivary nucleus (MSO), the lateral superior olivary nucleus, and the inferior colliculus. The width of the CO-stained neuropil in MSO was also measured as an estimate of dendritic length. OD measures were corrected to neutral areas of the brain. Cochlear ablation caused significant decreases in CO activity in left lower brainstem nuclei, particularly in adult animals. Following CHL, a significant decrease in CO activity was observed in the ipsilateral AVCN and a significant increase was observed in the contralateral AVCN. Cochlear ablation resulted in decreased width of MSO neuropil containing dendrites that receive primary input from the ablated ear. CHL resulted in a significant increase in the width of MSO neuropil on both sides of the brain in the P21 animals that survived 3 weeks but not in P21 animals that survived only 48 hours or in the adult animals. Unilateral CHL is associated with changes in CO activity in the AVCN and may affect MSO dendritic length in younger animals.
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PMID:Conductive hearing loss results in changes in cytochrome oxidase activity in gerbil central auditory system. 1208 27