Many dipteran and hymenopteran insects use near-field sound caused by wing beat for conspecific communications. One of the most sophisticated sound communications is seen in the waggle dance of honeybee workers. Behavioral studies have collectively suggested that Johnston’s organ (JO) in the second segment of the antennae is a primary sensor to detect air-particle movements caused by the waggle dance. As a first step to elucidate central processing of the dance language, we recently investigated sensory subgroups in JO and their central projections in the honeybee. The comparison of the projection patterns in the honeybee with those in the fruitfly, mosquitoe revealed that axons of the sensory neurons in these species project extensively to the antennal mechanosenory center in the deutocerebrum, the posterior region of the protocerebrum (visuo-motor center) and the subesophageal ganglion, but some species-specific features were evident. The projections of the JO neurons in the cockroach were devoid of axon terminals in the protocerebrum, indicating that the projection to the visuo-motor center is an innovation in flying, holometabolous insects. The possible roles of extensive termination fields of JO afferents in parallel processings of mechanosensory signals are discussed.

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Sound arriving at the tympanic membrane is transmitted via ossicles from the middle ear to the cochlea. Each structure of the middle ear and the cochlea has an effect on the incoming sound. However, the details of the vibration of the human auditory system have not been clarified because in direct observation, the positions at which measurement is possible are limited. The finite element method (FEM) is a powerful tool for analyzing the vibrations of the auditory system because the complicated shapes of the middle ear and the cochlea can be modeled in detail. In this study, the FEM models of the middle ear and the cochlea were constructed to simulate sound transmission in human auditory system. The models presented in this report suggest that the middle ear acts as a moderate bandpass filter which passes vibration around 1 kHz with changing its vibration mode. Each part of the basilar membrane in the cochlea has a characteristic frequency, and the cochlea performs frequency analysis of transmitted vibration from the middle ear.

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Recently, in situ reverse transcription (RT)-PCR has been developed to detect weak mRNA signals on histological sections by amplifying the relevant molecular mRNA, because RT-PCR allows one mRNA to be amplified a billionfold. This method was performed using rTth DNA polymerase that transcripts cDNA to mRNA, and amplifying the cDNA. We applied this technique to detect prohormone convertases PC1 and PC2 in the rat pituitary gland, and vascular endothelial growth factor (VEGF) in the developing pituitary gland, where these mRNAs were not detectable usual in situ hybridization techniques. Therefore, this in situ RT-PCR method is useful for identifying specific cells expressing weak signals in histological sections.

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