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There is no report on the fine structure of three types of olfactory organs in Xenopus laevis. Their functional assignments in olfaction are not yet established. The fine structure of three types of olfactory organs, olfactory epithelium (OE), vomeronasal organ (VNO), and middle chamber epithelium (MCE), was examined in Xenopus laevis by light and electron microscopy. The olfactory cells of the OE and the sensory cells of the VNO were equipped with cilia and microvilli, respectively, similar to terrestrial animals that possess both the OE and the VNO. On the other hand, the sensory cells of the MCE were classified into two types, the sensory cells with cilia and the sensory cells with microvilli, like those of the OE in fish. These findings suggest that the OE and the VNO in Xenopus laevis detect different kinds of odoriferous molecules in air, whereas the MCE is involved in the perception of odorants in water.

ABSTRACT. Differential maturation of three types of olfactory organs, the olfactory epithelium (OE), the vomeronasal organ (VNO) and the septal olfactory organ of Masera (MO), was examined immunohistochemically in embryonic and newborn rats by the use of antiprotein gene product 9.5 (PGP 9.5) serum. These olfactory organs were derived in common from the olfactory placode as neuroepithelia. In the OE, PGP 9.5-immunopositive olfactory cells first appeared at 13 days of gestation. The OE maturated completely, and showed the same cytological features as in the adult at 20 days of gestation. The MO first appeared as a dense mass of PGP 9.5-immunopositive sensory cells on the most ventrocaudal part of the nasal septum at 15 days of gestation and was evidently isolated from the OE by the decrease of immunopositive cells in the intercalated epithelium between the OE and the MO at 20 days of gestation. However, even at 7 days after birth, the MO did not complete its development and contained sensory cells aggregating in the mass. The VNO was separated from the nasal cavity at 13 days of gestation as a tubular structure of a neuroepithelium including PGP 9.5-immunopositive sensory cells. These cells gradually increased in number in the sensory epithelium of the VNO and extended their dendritic processes to the free surface at 7 days after birth. These findings clarified the differential maturation of these olfactory organs. That is, the OE completes its development before birth, while the MO and VNO after birth. KEY WORDS: development, olfactory epithelium, protein gene product 9.5, septal olfactory organ of Masera, vomeronasal organ.J. Vet. Med. Sci. 63 (7): [759][760][761][762][763][764][765] 2001 In mammals can occur three different types of olfactory organs, the olfactory epithelium (OE), the vomeronasal organ (VNO) and the septal olfactory organ of Masera (MO) [12,24,29,32]. These olfactory organs were reported to be derived in common from the embryonic olfactory placode as neuroepithelia during their ontogenetic development to take part in different kinds of olfaction [6, 9, 10-13, 26, 34, 36]. The OE responds to general and volatile odorants and takes charge of the usual olfactory function, while the VNO is thought to be specialized for the perception of pheromonal and non-volatile substances and involved in reproductive and/or social behaviors [1,3,4,7,13,19,22,28,40,41]. On the other hand, the MO appears as a small part of the primitive OE in the later embryonic stage and is separated from the OE by the non-sensory (respiratory) epithelium during the course of embryonic development, and finally becomes an isolated small patch of sensory epithelium located on the ventrocaudal part of the nasal septum in the adult [11]. As for its function, Kratzing [20] suggested that the MO could act to monitor the airflow in a quiet respiration, while Marshall and Maruniak [23] revealed electrophysiologically that the MO shows higher chemical sensitivity to some odorants such as pentyl-acetate and butanol than the OE.These o...

Benzbromarone, a uricosuric drug, reportedly causes hepatic hypertrophy accompanied by proliferation of peroxisomes in rats. To elucidate the mechanisms underlying induction of peroxisome proliferation by benzbromarone, we examined binding affinity for peroxisome proliferator-activated receptor α (PPARα) and γ (PPARγ), and effects on the binding activity of PPARs with peroxisome proliferation-responsive element (PPRE) and expression of the PPARs target protein. Binding affinity of benzbromarone for PPARα and PPARγ was examined by reporter gene assay. Binding activity of PPARs with PPRE was determined by electric mobility shift assay, and expression of lipoprotein lipase (LPL) and acyl-CoA synthetase (ACS) by Western blot method. Benzbromarone displayed affinity for PPARα and PPARγ, and promoted binding of PPARs to PPRE. Furthermore, cultured cells with benzbromarone added showed upregulated expression of LPL and ACS. These results suggest that benzbromarone induces peroxisome proliferation in hepatocytes by binding to PPARs, and controls expression of proteins related to lipid metabolism.