Ultrastructural Changes in Primary Endings of Deaf White Cats

Huchton, David M.; Pongstaporn, Tan; Niparko, John K.; Ryugo, David K.

doi:10.1016/s0194-59989770262-6

Otolaryngol.--head neck surg.

1997

DOI: 10.1016/s0194-59989770262-6

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Ultrastructural Changes in Primary Endings of Deaf White Cats

David M. Huchton

Tan Pongstaporn

John K. Niparko

et al.

Abstract: Changes in brain structure occur as a consequence of altered experience. During maturation of the auditory nervous system, sensory deprivation is known to cause cell loss, abnormal axonal projections, and synaptic alterations. These animal data may be relevant to clinical observations that cochlear implants provide superior benefit for individuals who become deaf postlingually compared with those who become deaf prelingually. That is, implantation appears most efficacious if it occurs after functional connecti… Show more

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Cited by 4 publications

References 38 publications

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Cochlear nucleus cell size changes in the dalmatian: Model of congenital deafness

Niparko

Finger²

1997

Otolaryngology - Head and Neck Surgery

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We assessed cellular changes in one population of neurons of the cochlear nucleus associated with a form of genetic deafness in deaf dalmatians. Spheric cells from deaf dalmatians and age-matched control (hearing) dogs were analyzed morphometrically. The somatic silhouette of these cells was reduced by 22.1% to 38.1%. The effect on cell size was greater with increased duration of deafness. Because the deaf dalmatian exhibits progressive degeneration of the auditory periphery, shrinkage of spheric cells may reflect the initial influence of attenuated activity of auditory nerve fibers, and sensorineural degeneration with longer periods of deafness.

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Cochlear nucleus cell size changes in the dalmatian: Model of congenital deafness

Niparko

Finger²

1997

Otolaryngology - Head and Neck Surgery

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Dodson

Charalabapoulou

2001

Journal of Neurocytology

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Homozygous deafwaddler mice (dfw/dfw) have a mutation in the gene encoding plasma membrane Ca2+ATPase isoform 2 (Pmca2). They walk with a hesitant and wobbly gait, display head bobbing and are deaf. Light microscopy and transmission electron microscopy were used to evaluate the nature and relationship of morphological changes in the cochlea, spiral ganglion cells and spherical cells of the cochlear nucleus in homozygous and heterozygous mice of different ages and controls. Ultrastructural findings showed that in 7 week old homozygous (dfw) mice, inner hair cells and their afferent terminals were present although outer hair cells appeared apoptotic. Stereocilia were absent from the second and third rows of outer hair cells. Ganglion cells were also present although abnormal in appearance. In older homozygous mutants there was a loss of hair cells and spiral ganglion cells. Remaining ganglion cells in this group contained very few cytoplasmic organelles apart from a few hypertrophied mitochondria. In the anteroventral cochlear nucleus, spherical cell soma size was smaller in all homozygous (dfw) mutants than in heterozygous mice and controls. The ultrastructural appearance of the end bulbs of Held in homozygous mutants was abnormal compared with controls, and in the younger group were seen to be swollen, with less distinct synaptic densities and containing large numbers of small synaptic vesicles arranged in clumps. In the older group these synapses were distorted and contained hypertrophied mitochondria and no synaptic densities could be seen, suggesting that these synapses may be non-functional. This study has shown that in homozygous (dfw) mice structural abnormalities occurred not only in cochlear hair cells but also in the spiral ganglion neurones and spherical cells in the cochlear nucleus. It seems likely that these changes are the result of the Pmca2 mutation and the subsequent accumulation of toxic levels of calcium that may lead to alterations in their functional integrity.

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Activity Influences on Neuronal Connectivity Within the Auditory Pathway

Niparko

1999

The Laryngoscope

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Impulse traffic is a critical factor in the interaction between the ear and central auditory stations and appears necessary for the maintenance of key synapses. As hearing disorders with impaired comprehension may be modeled by studies of auditory deafferentation, these observations extend the possibility that changes in central neuronal connections underlie reduced capabilities for processing restored auditory input.

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Ultrastructural Changes in Primary Endings of Deaf White Cats

Cited by 4 publications

References 38 publications

Cochlear nucleus cell size changes in the dalmatian: Model of congenital deafness

Cochlear nucleus cell size changes in the dalmatian: Model of congenital deafness

Untitled

Activity Influences on Neuronal Connectivity Within the Auditory Pathway

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