Morphological and histological comparisons of the middle and inner ears.

<p>(A) The bullae of <i>Fgf</i> mice (bottom row) appear white and cloudy with less structural refinement than both <i>Fgf</i> (top row) and <i>Fgf</i> mice (middle row), indicating incomplete ossification. (B) The auditory ossicles are dysplastic in <i>Fgf</i> mice. (C) H&E stained, paraffin sections demonstrate increased vascularization of the bony labyrinth in <i>Fgf</i> mice (arrowheads). (D) The highly-organized laminar structure of the otic capsule, bordering the spiral ligament, is lost in the <i>Fgf</i> genotype. Lines in A and B are orienting lines from the microscope objective.</p

Auditory measurements from <i>Fgf</i> mutant mice.

<p>(A) ABR and (B) DPOAE thresholds demonstrate profound hearing loss at all frequencies in <i>Fgf</i> mice, and moderate hearing loss at high frequencies in <i>Fgf</i> mice. (C) ABR wave I amplitudes appear slightly depressed in <i>Fgf</i> mice but are not statistically differentiable (except at 32 kHz where threshold differences impact magnitude ). ABR amplitudes in <i>Fgf</i> mice are significantly reduced compared to the other genotypes . (D) Threshold adjusted ABR wave I latency measurements demonstrate significant increases in latency in both <i>Fgf</i> and <i>Fgf</i> genotypes when compared to <i>Fgf</i> littermates . Error bars present standard error of the mean.</p

Mid-modiolar cochlear sections from <i>Fgf</i> (left column) and <i>Fgf</i> mice (right column).

<p>(A) Neural populations and gross anatomical structure appear normal in <i>Fgf</i> mice. (B) The stria vascularis (StVas), spiral ligament (SpLig), spiral limbus (SpLim), tectorial membrane (TM) and Reissner's membrane (RM) are similar to <i>Fgf</i> mice. (C) Inner hair cells (IHC), Outer hair cells (OHC), supporting cells (SC) and basilar membrane (BM) are morphologically normal. Sections were embedded in araldite and osmium stained.</p

Morphological comparisons of the otic capsule from (A) <i>Fgf</i>, (B) <i>Fgf</i> and (C) <i>Fgf</i> mice.

<p>All genotypes appear similar but the <i>Fgf</i> cochlea is slightly smaller and whiter. Black lines are orienting lines from the microscope objective.</p

2D and 3D CT reconstructions of bullae from <i>Fgf</i> and <i>Fgf</i> mice.

<p>Each row contains reconstructions from one ear (top row: <i>Fgf</i>, bottom row: <i>Fgf</i>). (A) The otic capsule and bulla show loss of structural refinement and decreased density (arrowheads). (B) In <i>Fgf</i> mice the footplate of the stapes demonstrate thickening (arrowheads). (C) The incus and incudomalleal joint are dysplastic (arrowheads) and the mastoid is under-pneumatized (asterisks). (D) The borders of 3D reconstructed <i>Fgf</i> ossicles are sharp and well-defined while those of <i>Fgf</i> ossicles are blurry due to poor contrast with surroundings, resulting from decreased bone density in the mutant. <i>Fgf</i> ossicles demonstrate reduced structural refinement, particularly in the malleus and incus.</p