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PubMed1982

Adenine nucleotides of the organ of Corti under metabolic stress.

The purpose of the reported experiments was to measure the concentrations of adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP) in the organ of Corti in order to arrive at estimates of three commonly used adenylate ratios. Under normal conditions the concentrations of ATP, ADP, and AMP amounted to 15.8, 3.9, and 0.53 mmoles/kg dry weight, respectively. Of the three substances, AMP is the most sensitive indicator of metabolic stress, since ischemia of 65 seconds leads to an increase of 155%. Under normal conditions the adenylate energy charge, the energy status, and the phosphorylation state amounted to 0.83, 4.1, and 2.5 gram wet weight/mumole, respectively. Within 10 minutes of ischemia the energy charge had declined by 26%, the energy status by 50%, and the phosphorylation state by 76%. The apparent equilibrium constant of adenylate kinase of the organ of Corti was found to be 0.55. The potential significance of these data and their relationship to the situation in the stria vascularis are discussed.

Adenosine Diphosphate↗
PubMed2003

New tunes from Corti's organ: the outer hair cell boogie rules.

The amplification of acoustic stimuli is a feature of hair cells that evolved early on in vertebrates. Though standard stereocilia mechanisms to promote such amplification may persist in the mammal, an additional mechanism evolved to enhance high frequency sensation. Only in mammals, a special cell type, the outer hair cell, arose that possesses a remarkably fast somatic mechanical response, which probably endows the passive cochlea with a boost in sensitivity by a factor of 100 (40dB), at least. Experiments conducted over the past few years have shed light on many aspects of outer hair cell electromotility, including the molecular identification of the motor, the effects of a knockout, and underlying mechanisms of action. A review of this remarkable progress is attempted.

Acoustic Stimulation↗
PubMedDate not supplied

A note on development of Corti's organ.

The structure and postnatal transformation of Kölliker's organ in the cat were studied by means of both light and electron microscopes. Kölliker's organ, which is located in the inner sulcus area of the cochlear duct during embryonic development of the kitten, appeared to undergo a major transformation during the first 30 days after birth. On the level of the organ as a whole the possible nature of this transformation is briefly discussed. On the cellular level, the transformation of this organ was found to involve a process of cellular autophagocytosis. Kölliker's organ consists of numerous tightly packed, tall columnar cells filling the inner sulcus. Autophagic vacuoles containing cell organelles were observed in these cells in all stages of transformation of the organ. Cellular autophagocytosis reduced the number of cells present in each section from approximately 50 in the newborn, to approximately 12 in the 30-day-old kitten. The apparent transformation of Kölliker's organ was observed as progressing from base to apex and from the limbus to the inner hair cell. The relationship of the tectorial membrane to Kölliker's organ and that of the tectorial membrane to the area in and around the inner hair cells are discussed.

Animals↗
PubMed2001

Experimental studies of vibratory trauma of Corti's organ. II. Scanning electron microscopy.

In the first part of this study, the authors presented the results of cochlear microphonics measurements in guinea pigs subjected to long-term whole-body vibration. In animals undergoing vibration over 30, 90, and 180 days, a statistically significant lowering of voltage over the range up to 2 kHz was seen. In accordance with cochlear-frequency position, this pointed to possible formation of sensory epithelium damages in the fourth and third turning. In the present study an attempt was made to verify electrophysiological measurements with a scanning electron microscope. In all, 80 cochleae were examined, 20 in each group of animals: one control and three experimental groups. The healthy animals showed a correct picture of the sensory epithelium in each case, whereas its damage was ascertained in all the study groups. The damage advanced with a longer duration of the experiment and was most often seen in the outer hair cell region of the apex, where it gradually spread towards the base of the cochlea. The damage of cells decreased from the circumference to the modiolus, and the inner hair cells showed considerably greater resistance to vibration. The results of the study demonstrate the harmful effect of mechanical vibration on the inner ear. According to the observed pattern of damage, one can expect an increasing hearing impairment in the low and medium frequency range in persons exposed to whole-body vibration.

Animals↗
PubMed2002

[Adenovirus-mediated NT3 gene transfer protects spiral ganglion neurons from degeneration after noise trauma].

Numerous studies have shown that the health of spiral ganglion neurons is highly important for hearing. As a trophic factor of spiral ganglion neurons, neurotrophin 3 (NT3) is a potential candidate for prevention of spiral ganglion neuron degeneration in human. In our experiments, efficient transduction and long term expression of foreign gene of cochlea cells has been found with adenovirus carried lacZ gene (Ad-lacZ). A model of guinea pig deafness was made by intense noise exposure, which destroyed the entire organ of Corti in the middle part of the cochlea. Seven days after noise exposure, the animals were anesthetized and 1 10(8) recombinant adenoviral particles were injected into the scala tympani through the round window membrane. Animals inoculated with neurotrophin 3 adenovirus(Ad-NT3) were designated as the experimental group, animals inoculated with Ad-lacZ vector served as the control group. Four weeks after the inoculation of the virus, NT3 immunoreactivity was observed in the Ad-NT3 inoculated group. HE histochemical staining results showed that in the Ad-lacZ injected group, the neuronal degeneration was severer and the density of spiral ganglion neurons was significantly lower than those in the Ad-NT3 injected group. Our results demonstrate that with adenovirus-mediated overexpression NT3 may be developed into a new treatment to prevent secondary spiral ganglion degeneration following the damage to Corti organ.

Adenoviridae↗