Protective effect of basic fibroblast growth factor on auditory hair cells after noise exposure.

The purpose of this study was to observe the protective effects of basic fibroblast growth factor (bFGF) on the cells of the inner ear using in vivo experiments. The studies were carried out using guinea pigs in which bFGF or artificial perilymph was perfused into the cochlea. The compound action potential (CAP) was measured before and after exposure to a sound simulating an explosion. The difference in CAP was significant between the bFGF-perfused group and the control group (p < 0.01, t = 3.896) and between the bFGF-perfused group and the artificial perilymph-perfused group (p < 0.05, t = 2.520). The cochleae were removed and hair cell loss estimated from surface preparations. Acoustic trauma caused loss of outer hair cells in the first and second turns of the cochlea in the bFGF-perfused group and the artificial perilymph-perfused group and partial loss of inner hair cells in the control group. Treatment with bFGF reduced the loss of inner hair cells compared to that of control animals. Our results demonstrate that treatment with bFGF protects the hair cells from acoustic trauma and may facilitate the recovery of hearing.

Stereo morphology of temporal bone and ear.

BACKGROUND: The temporal bone has the most complicated anatomic feature among the whole human body, which always challenges otolaryngologists. This study was to study three-dimensional (3D) morphology of the temporal bone and the ear by means of a computer image processing technique, for the purpose of providing a 3D image to help in pathological, diagnostic and surgical procedures. METHODS: Forty sets of temporal bone celloidin serial sections with reference points were prepared and the contours of selected structures and reference points were entered into a graphics programme. The technique of computer-aided 3D reconstruction was applied to obtain 3D images and parameters of the temporal bones and the ears. Stereo views of the ossicles (n = 5), the facial nerves (n = 11), the posterior tympanic sinuses (n = 11), the posterior ampullary nerves (n = 4), the endolymphatic ducts and sacs (n = 5), and the bony and membranous labyrinth (n = 1) were reconstructed. RESULTS: Three-dimensional images, including the cochlea, the ossicles, the nerves, the tendons and the endolymphatic fluid system in the temporal bone, were obtained. Stereo picture pairs and 3D parameters of spatial dimensions, angle and volume for these reconstructed structures were calculated. The arrangement of the ossicles, spatial relationship of the bony and membranous labyrinth, the whole course of the facial nerves, the endolymphatic sac and posterior tympanic cavity were clearly observable. Stereo picture pairs made the spatial relationships among the above-mentioned structures much clearer. The operation of the posterior ampullary nerve transection was designed and simulated on the graphic computer based on 3D anatomic investigations. CONCLUSION: The technique of computer-aided 3D reconstruction provides a new tool to observe the morphology of the temporal bone and thus may allow design and study of new surgical approaches.

[Simultaneously optical recording of membrane potential in population vestibular ganglion neurons].

AIM: To investigate membrane electro-physiological features in vestibular ganglion neuronal population using a voltage-sensitive dye and optical recording technique. METHODS: Dissociated and cultured mouse vestibular ganglion neurons were stained with an absorption voltage-sensitive dye, RH 155, and were imaged in 16 x 16 elements Photodiode arrays (PDA) optical recording system. RESULTS: When the cells were depolarized during perfusion with 150 mmol/L potassium solution, optical absorption of the dye that bound to the external surface of neuron membranes increased. The relative ratio (delta I/I) of optical absorption change was 0.23% +/- 0.08% (x +/- s, n = 28). These optical responses were wavelength dependent. Under our experimental conditions, photo toxicity and pharmacological effects of the dye were either absent or insignificant. CONCLUSION: Our results suggest that optical recording provides a new, practical and less toxic method to simultaneously monitor changes in membrane potential from several cultured vestibular ganglion cells.