Short-term pathophysiologic changes and histopathologic findings of the auditory pathway after closed head injury, using a rabbit model.

Hearing impairment is a well-known consequence of closed head injury (CHI). The aim of this study was to elucidate the pathogenesis of CHI-induced hearing loss, using a rabbit model. Twelve New Zealand white rabbits were divided into two groups of 6. In the first group, CHI was induced mechanically, whereas the rabbits of the second group served as controls. Baseline distortion product otoacoustic emissions (DPOAEs), contralateral suppression (CS) of the DPOAEs and auditory brainstem response (ABR) were obtained. The same measurements were performed in the first group after CHI. Three hours later, the animals were sacrificed and their brain was excised and subjected to histopathologic examination. Mean I-III ABR latencies were increased and DPOAE amplitudes and CS values were reduced in the trauma group after CHI, at a statistically significant level. Histopathologic examination of the temporal lobe and brainstem showed multiple hemorrhagic and necrotic areas, with edema in the surrounding region. The vestibulocochlear nerve was severely damaged at its emerging site at the brainstem. In conclusion, both peripheral and central involvement of the auditory pathway was found after CHI. Otoacoustic emissions in conjunction with ABR may provide significant information on both peripheral and central auditory function.

Comparison of angiogenic activities after urethral reconstruction using free grafts in rabbits.

OBJECTIVE: To determine the most suitable type of graft-free penile skin grafts or mucosal grafts from bladder or buccal regions - for urethral reconstruction in an animal model, as evaluated on the basis of angiogenic activity. METHODS: Twenty-two male White New Zealand rabbits were randomly divided into four groups. In the control group (group O, n=4) a simple urethrotomy and closure was performed, whereas a ventral urethral defect was created in groups A, B, and C and then bridged using the following onlay patches: free penile skin (group A, n=6), buccal mucosal graft (group B, n=6), and bladder mucosal graft (group C, n=6). On the 21st postoperative day, the animals were sacrificed and the retrieved implants were subjected to macroscopic and microscopic analysis. The angiogenic activity was assessed with immunohistochemistry, using the anti-CD31 MoAb and the phosphatase antialkaline phosphatase procedure. The native vascularity of penile skin as well as buccal and bladder mucosa was assessed in rabbits from group O (n=3). Statistical analysis was performed using the one-way ANOVA. RESULTS: The angiogenesis in a magnification of x200 in groups O, A, B, and C was 34.1+/-4.1 (mean+/-SD), 61.7+/-6.4, 94.3+/-6.4, and 91.5+/-7.2 vessels per optical field, respectively. There were, statistically significant differences (p<0.001) between groups A and B and between groups A and C, but not (p>0.05) between groups B and C. The native vascularity of penile skin, buccal mucosa and bladder mucosa was 23.3+/-3.0, 24.6+/-3.7 and 17.0+/-2.6 vessels per optical field, respectively. CONCLUSION: The viability of mucosal grafts from bladder or buccal regions is better than that of a free penile graft because of higher angiogenic activity. Although the mucosal grafts showed the same angiogenic activity, the buccal mucosa graft is preferable because of its easier harvesting.