Unbiased counting of neurons in the cochlea of developing gerbils

Richter, Claus Peter; Kumar, Gagan; Webster, Erica; Banaś, Sławomir; Whitlon, Donna S.

doi:10.1016/j.heares.2011.02.003

Cited by 16 publications

(17 citation statements)

References 41 publications

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“…Total SGNs and type II SGNs from WT, ephrin-A5 À / À or EphA4 EGFP/EGFP P2 mice were quantified using a stereological reconstruction method 54 . Data were statistically analysed using a Student's t-test.…”

Section: Methodsmentioning

confidence: 99%

Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells

et al. 2013

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Hearing requires an optimal afferent innervation of sensory hair cells by spiral ganglion neurons in the cochlea. Here we report that complementary expression of ephrin-A5 in hair cells and EphA4 receptor among spiral ganglion neuron populations controls the targeting of type I and type II afferent fibres to inner and outer hair cells, respectively. In the absence of ephrin-A5 or EphA4 forward signalling, a subset of type I projections aberrantly overshoot the inner hair cell layer and invade the outer hair cell area. Lack of type I afferent synapses impairs neurotransmission from inner hair cells to the auditory nerve. By contrast, radial shift of type I projections coincides with a gain of presynaptic ribbons that could enhance the afferent signalling from outer hair cells. Ephexin-1, cofilin and myosin light chain kinase act downstream of EphA4 to induce type I spiral ganglion neuron growth cone collapse. Our findings constitute the first identification of an Eph/ephrin-mediated mutual repulsion mechanism responsible for specific sorting of auditory projections in the cochlea.

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Section: Methodsmentioning

confidence: 99%

Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells

et al. 2013

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“…Whitlon et al (2006) reported counts slightly higher than the median of published values, which is approximately 8041, and this may be accounted for by their method of counting every cell and the outbred strain CD-1. Richter et al (2011), using the same methods of counting and staining as Whitlon et al, observed much higher populations. This may have to do with differences in animal age or strain.…”

Section: Discussionmentioning

confidence: 69%

“…Additionally, a single section is unlikely to reveal abnormalities present in other regions of the cochlea. The reader is referred to Richter et al (2011) for recommendations relevant to analyzing specific cochlear locations.…”

Section: Discussionmentioning

confidence: 99%

“…Spiral ganglion neurons (SGNs) of the cochlea are indispensable in relaying auditory information from hair cells to the auditory brainstem, and studying their survival and degeneration provides insight into the physiological basis for the progression of hearing loss. Despite decades of research, techniques for quantifying the number of SGNs in a cochlea remains quite varied across studies (Richter et al, 2011). …”

Section: Introductionmentioning

confidence: 99%

“…Certain methods will be most practical for a particular study. Counting all neurons within Rosenthal’s canal using unbiased techniques will undoubtedly result in the most accurate data (Richter et al, 2011). The total number of SGNs is often not the only measure of interest, but rather one of a number of anatomical and functional measures within a study.…”

Section: Introductionmentioning

confidence: 99%

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The efficiency of design-based stereology in estimating spiral ganglion populations in mice

Schettino

Lauer

2013

Hearing Research

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Accurate quantification of cell populations is essential in assessing and evaluating neural survival and degeneration in experimental groups. Estimates obtained through traditional two-dimensional counting methods are heavily biased by the counting parameters in relation to the size and shape of the neurons to be counted, resulting in a large range of inaccurate counts. In contrast, counting every cell in a population can be extremely labor-intensive. The present study hypothesizes that design-based stereology provides estimates of the total number of cochlear spiral ganglion neurons (SGNs) in mice that are comparable to those obtained by other accurate cell-counting methods, such as a serial reconstruction, while being a more efficient method. SGNs are indispensable for relaying auditory information from hair cells to the auditory brainstem, and investigating factors affecting their degeneration provides insight into the physiological basis for the progression of hearing dysfunction. Stereological quantification techniques offer the benefits of efficient sampling that is independent of the size and shape of the SGNs. Population estimates of SGNs in cochleae from young C57 mice with normal-hearing and C57 mice with age-related hearing loss were obtained using the optical fractionator probe and traditional two-dimensional counting methods. The average estimated population of SGNs in normal-hearing mice was 7009, whereas the average estimated population in mice with age-related hearing loss was 5096. The estimated population of SGNs in normal-hearing mice fell within the range of values previously reported in the literature. The reduction in the SGN population in animals with age-related hearing loss was statistically significant. Stereological measurements required less time per section compared to two-dimensional methods while optimizing the amount of cochlear tissue analyzed. These findings demonstrate that design-based stereology provides a practical alternative to other counting methods such as the Abercrombie correction method, which has been shown to notably underestimate cell populations, and labor-intensive protocols that account for every cell individually.

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Acute Damage Threshold for Infrared Neural Stimulation of the Cochlea: Functional and Histological Evaluation

Goyal¹,

Rajguru²,

Matic³

et al. 2012

The Anatomical Record

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This article provides a mini review of the current state of infrared neural stimulation (INS), and new experimental results concerning INS damage thresholds. INS promises to be an attractive alternative for neural interfaces. With this method, one can attain spatially selective neural stimulation that is not possible with electrical stimulation. INS is based on the delivery of short laser pulses that result in a transient temperature increase in the tissue and depolarize the neurons. At a high stimulation rate and/or high pulse energy, the method bears the risk of thermal damage to the tissue from the instantaneous temperature increase or from potential accumulation of thermal energy. With the present study, we determined the injury thresholds in guinea pig cochleae for acute INS using functional measurements (compound action potentials) and histological evaluation. The selected laser parameters for INS were the wavelength (k ¼ 1,869 nm), the pulse duration (100 ls), the pulse repetition rate (250 Hz), and the radiant energy (0-127 lJ/pulse). For up to 5 hr of continuous irradiation at 250 Hz and at radiant energies up to 25 lJ/pulse, we did not observe any functional or histological damage in the cochlea. Functional loss was observed for energies above 25 lJ/pulse and the probability of injury to the target tissue resulting in functional loss increased with increasing radiant energy. Corresponding cochlear histology from control animals and animals exposed to 98 or 127 lJ/pulse at 250 Hz pulse repetition rate did not show a loss of spiral ganglion cells, hair cells, or other soft tissue structures of the organ of Corti. Light microscopy did not reveal any structural changes in the soft tissue either. Additionally, microcomputed tomography was used to visualize the placement of the optical fiber within the cochlea.

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Unbiased counting of neurons in the cochlea of developing gerbils

Cited by 16 publications

References 41 publications

Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells

Ephrin-A5/EphA4 signalling controls specific afferent targeting to cochlear hair cells

The efficiency of design-based stereology in estimating spiral ganglion populations in mice

Acute Damage Threshold for Infrared Neural Stimulation of the Cochlea: Functional and Histological Evaluation

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