Morphometric study of the cochlea of the rabbit (<i>Oryctulagus cuniculus</i>)

Ramprashad, Fred; Landolt, Jack P.; Money, K. E.; Laufer, Jerry

doi:10.1139/z84-364

Cited by 4 publications

(3 citation statements)

References 17 publications

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“…Additional, although weaker, evidence for a mitotic inhibitor is provided by the comparison ofgroups SD and GD-P, where inclusion of tissue from a control animal resulted in a 22% reduction in proliferative activity (P < 0.01; Fig. 2B .,N "*A,,- (41,42), suggests that similar mechanisms regulating hair cell production may exist in the mammalian inner ear. Additional investigations should fully isolate and characterize these soluble factors, and determine their influence in the chicken cochlea and the inner ear of other species.…”

Section: Resultsmentioning

confidence: 99%

Diffusible factors regulate hair cell regeneration inthe avian inner ear.

Tsue

Oesterle

Rubel

1994

Proc. Natl. Acad. Sci. U.S.A.

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Damage to the avian inner ear results in up-regulation of mitotic activity resulting in regeneration of hair cells. The objective of this investigation was to determine whether the damaed inner ear epithelium releases a soluble mitogen that is responsible for the up-regulation of proliferation. The sensory epithelium from normal and drug-damaged avian inner ears was cultured alone or in the presence of other cultures. (26,27). This disruption of a putative inhibitory heterophilic coupling could provide a signal directly to neighboring cells to re-enter the cell cycle and proliferate to provide a new hair cell replacement. The regenerative signal would persist until the new hair cell was differentiated enough to express the membrane-bound ligand necessary to reestablish the heterophilic coupling.(ii) The second hypothesis involves a paracrine mechanism, whereby damaged hair cells, scavenging phagocytic cells, and/or loss of receptor neural activity causes the release of a mitogenic substance (26). This mitogen could then diffuse from the damaged region to stimulate progenitor cells. Similarly, sensory epithelial damage could decrease production of an antimitotic factor. In support of the diffusible factor hypothesis, several growth factors have been shown to influence proliferation in the developing inner ear (28-31).Historically, the first step toward identification of mitogenic and differentiation factors has come from studies involving cocultures of stimulating and target tissues (32-35) and/or studies using conditioned medium (36)(37)(38)(39). In the present report we have adopted a similar strategy by examining the ability of regenerating inner ear epithelium to stimulate proliferation in tissue from control animals. Using a culture system known to maintain the hair cell regeneration process in vitro (40) Utricles from control and aminoglycoside-treated postnatal chickens were cultured individually or in groups. The utricles were placed into specifically arranged 50-A4 drops of chicken plasma (Cocalico Biologicals, Reamstown, PA) on Abbreviations: BL, basal layer; LL, luminal layer; SC, single control utricle cultured alone; SD, single streptomycin-damaged utricle cultured alone; GC, group (seven) control utricles cultured together; GD-C, single control utricle cocultured with six streptomycindamaged utricles; GD-P, six streptomycin-damaged utricles cocultured with one single control utricle.*To whom reprint requests should be addressed. 1584The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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Section: Resultsmentioning

confidence: 99%

Diffusible factors regulate hair cell regeneration inthe avian inner ear.

Tsue

Oesterle

Rubel

1994

Proc. Natl. Acad. Sci. U.S.A.

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“…To the best of our knowledge, systematic studies have never been performed to evaluate hair cell densities in the rabbit. Although Ramprashad ( 1984 ) had described the morphometric parameters of the rabbit cochlea, including the morphometric changes along the length of the cochlea of the cross-sectional areas of the scalae vestibuli, scalae tympani, scalae media, and BM, as well as the width and thickness of the BM and the density of the bipolar ganglion cells innervating the organ of Corti, the authors did not report hair cell densities, which is crucial for hearing research.…”

Section: Discussionmentioning

confidence: 99%

Cochlear hair cell densities in the rabbit

et al. 2018

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A typical cochleogram was plotted to investigate hair cell densities as a percentage along the whole length of the basilar membrane (BM) of the rabbit, the length of the BM and the width of the organ of Corti. We generated surface preparations of cochlea from adult, healthy New Zealand White (NZW) rabbits. The numbers of inner hair cells (IHCs) and outer hair cells (OHCs) were counted from images acquired from a digital camera attached to an Olympus light microscope with a scale of 100 μm as a primary unit drawn continuously, and the numbers of IHCs and OHCs were converted to densities at 10% intervals along the length of the cochlea. Meanwhile, the length of the BM and the width of the organ of Corti were calculated. The average length of the cochlea was 14.504 ± 0.403 mm, while the total number of IHCs and the numbers of OHCs in the first, second, and third rows were 1556 ± 13, 1840 ± 47, 1842 ± 46, and 1840 ± 45, respectively, accounting for 21.98%, 26.00%, 26.02%, and 26.00% of the total number of cells, respectively. The densities of each row of OHCs reported in 10% intervals were greater than the densities of the IHCs corresponding to their anatomical locations within the cochlea. The densities of OHCs in each row were distributed uniformly along the BM, while the IHCs densities were not and showed a bimodal distribution with a maximum density at the apex and at 70–80% of the cochlear length from the apex but a lower density in the remaining cochlea. The width of the organ of Corti decreased successively from the apex to the base.

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“…2A) and left in J10. When full insertion is achieved, the 7-mm-long electrode array reaches the characteristic frequency region of ;2 kHz (Ramprashad et al, 1984). The ECAP threshold profile and animal's behavioral response were used to estimate the maximum stimulation levels and expected threshold levels for each electrode assuming a typical electrical dynamic range (6.3 dB or 40 current levels in nucleus devices).…”

Section: Chronic Stimulation With Bilateral Wearable Processorsmentioning

confidence: 99%

Chronic Bilateral Cochlear Implant Stimulation Partially Restores Neural Binaural Sensitivity in Neonatally-Deaf Rabbits

2021

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Cochlear implant (CI) users with a prelingual onset of hearing loss show poor sensitivity to interaural time differences (ITDs), an important cue for sound localization and speech reception in noise. Similarly, neural ITD sensitivity in the inferior colliculus (IC) of neonatally-deafened animals is degraded compared with animals deafened as adults. Here, we show that chronic bilateral CI stimulation during development can partly reverse the effect of early-onset deafness on ITD sensitivity. The prevalence of ITD sensitive neurons was restored to the level of adult-deaf (AD) rabbits in the early-deaf rabbits of both sexes that received chronic stimulation and behavioral training with wearable bilateral sound processors during development. We also found a partial improvement in neural ITD sensitivity in the early-deaf and stimulated rabbits compared with unstimulated rabbits. In contrast, chronic CI stimulation did not improve temporal coding in early-deaf rabbits. The present study is the first report showing functional restoration of ITD sensitivity with CI stimulation in single neurons and highlights the importance of auditory experience during development on the maturation of binaural circuitry.

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Morphometric study of the cochlea of the rabbit (Oryctulagus cuniculus)

Cited by 4 publications

References 17 publications

Diffusible factors regulate hair cell regeneration inthe avian inner ear.

Diffusible factors regulate hair cell regeneration inthe avian inner ear.

Cochlear hair cell densities in the rabbit

Chronic Bilateral Cochlear Implant Stimulation Partially Restores Neural Binaural Sensitivity in Neonatally-Deaf Rabbits

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