The System Of Mouse Otomicrosurgery Instruments And The Establishment Of Endocochlear Potential Measurement

Objective:To develop a series of instruments for microsurgery on the mouse, and establish a stable and safty methods for endocochlear potential measurement, and introduce their application on the hearing research.Methods:By self research and development, we made up a series of instruments which are suitable for microsurgery on the mouse. The instrument include the magnetic base retractor, the magnetic base head fixator, the magnetic limbs and tail fixator, the roatable electric heat homeothermia operating table, the highlight illuminator adaptor for zoom stereo microsurgery, and the microsurgery tool shelf.The magnetic base retractor consists of one magnet, one screw, two screw nuts, and a hook made of dental stainless wire. The screw attached to the magnet with magnetic force, and these assembles the so-called magnetic base, then the hook is clamped by two screw nuts on the screw, and these makes up of the retractor at last. The height of the retractor can be adjusted by rotating the two wing nuts on the screw. The orientation of the traction force as well as the strength can be adjusted by moving the magnetic retractor on the operating table. The magnetic base can also be made up a head fixtator for mouse by adding a custom crocodile clip on the screw. A hole at the tip of the crocodile clip was made by drilling, so the upper incisors can be placed in the hole and the upper jaw can be clamped by the crocodile clip. The magnetic base can fix the tail of the mouse on the operating table for body fixation by adding a custom screw nut on the bottom of the magnetic base. The custom screw nut was rasped to get a nick on one surface of it in advance, so the limbs or tail of the mouse can be placed under the nick of the screw nut and fixed by the magnetic fixator on the operative table.Using the custom instruments, we established a new way to exposure the otocyst of the mouse, and an effective way for mouse endocochlear potential measurement.Results:The retractor can retract many tissues such as muscles, vessels and nerves quickly to target position and obtain a well exposed operative site in most operation. The advantages of the magnetic retractor are shown below in detail:The most important advantage of the technique is that the retractor can reduce trauma to the animal with high postoperative survival rate owing to small skin incision with less damage on the muscle and vessels or nerves. The minimal length of the skin incision could be as short as 3 mm according to the diameter of the dental stainless wire. There can be several retractors work together on the same operative site owing to the retractors take few spaces in the operative site. Secondly, it is a kind of self retaining retractor, maintaining the opening steadily and allowing the user to work freely without an assistant. It can avoid the complication caused by retractor accident. Thirdly, it can retract certain object to target position quickly within about 3 seconds, so it will take less time to do the operation, and lessen the opportunity of suffering from infection owing to airborne exogenous microorganisms with better postoperative recovery. Fourthly, the gravity's effect on the retractor is negligible, so the posture of the subject can be slanted ad libitum by rotating the operating table to get a better visual field for the operation under dissecting microscope or to get a suitable posture for draining of airway secretions. Fifthly, it can retract tissues asymmetrically with three or more retractors work together to get a polygonal operative field, so it can suits and outline the target organ much more better than ordinary symmetric retractor which exerts force equally on each sides no matter which side should be retracted. Sixthly, it is easy to accommodate the height of the retractor steplessly, so it can be applied to different sizes of animals as well as different kinds of operation.The magnetic base head fixator with the tail fixator can fix the head, the limbs and the tail of the mouse on the operating table well, and made the microsurgery on the otocyst easily and the measurement of endocochlear potential stable.The roatable electric heat homeothermia operating table is a useful device for mouse microsurgery, it can maintain the temperature of the mouse at 37 centigrade degree, and allow the magnetic base retracator et al fix on the operating table by magnetic force. It can made the posture of the subject slanted ad libitum by rotating the operating table to get a better visual field for the operation under dissecting microscope or to get a suitable posture for draining of airway secretions.The highlight illuminator adaptor for zoom stero microscope can supply enough light for microsurgery. It is a small but powerful device which can make the common zoom stereo microscope into a dissecting microscope without a fibre optic illuminator.The microsurgery tool shelf can supply a well place for arrangement of different kinds of microsurgery tool, such as the fine needle, fine forceps, scissors, syringe, operating scalpel and the magnetic base retractor. It can make the operator find and get the tool quickly, shorten the operation time and the anesthesia duration at lastThe new way of the otocyst exposure with the assistance of the magnetic base retractor is a minimally invasive microsurgery. It is a good way for measurement of the endocochlear potential. The tympanic membrane and the ossicular chain of the mouse can be reserved completely in the operationConclusions:The novel retractor should be a simple but useful minimally invasive tool for mouse microsurgery. The instrument system is suitable to timeconsuming microsurgery on the mouse. The new way of the otocyst exposure and the endocochlear potential measurement are safe and repeatable. Objective:Introduce a special method of illumnation in the microdissection of the mice inner ear using the zoom-stereo microscope.Methods:Using the fibre optic illuminator, with the light enter into the lateral of the flat plate,and the reflect light from the specimen will enter into the optic system of the zoom-stereo microscope;To compare the effect of the lateral illumination with the traditionary illuminations, the falling-illumination and the transillumination.Results:The effect of the lateral illumination is better than the traditionary illuminations. with less background interference.Conclusion:Using the lateral illumination can improve the microdissection of the inner ear. Objective:To establish the mice model of AHL, and investigate the relationship between AHL and the cytoactive of cochlear hair cell in C57BL/6J mice.Methods:C57BL/6J mice were divided into 6 experimental groups by age. Auditory function of C57 mice were measured with ABR, the stimulus was click and toneburst (6 kHz and 8 kHz).3 months later, the ABR of group C and group G was test again, as group E and group H, respectively. After ABR test have taken, the cytoactive of the hair cells was detected by succinate dehydrogenase staining and surface preparation technic from two mice of each group except the group C and group G.Results:The ABR threshold of the mice was increased with the age, and the marked change of the cocholea was the degeneration of the cytoactive of cochlear hair cell, especially the outer hair cell. At first, the basement of the basal membrane suffered from degeneration of mitochondrion of the outer hair cell. Then it spread towards the top region. At last, the the inner hair cell was involved.Conclusion:The C57BL/6J mice was a typic animal model for the AHL, and the main change of the cochlea was the degeneration of the hair cell, especially the outer hair cell.Thus, the C57BL/6J mice should be a suitable animal model for sensory presbycusis.