The deleted in colorectal cancer (DCC) protein mediates attractant responses to netrin during axonogenesis. In the rat trigeminal ganglia (TG), axons must extend toward and grow into the trigeminal nerve to innervate target tissues such as dental pulp. Our present study aimed to investigate the exp- ression of DCC in the TG. Four developmental timepoints were assessed in the experiments: postnatal days 0, 7 and 10 and adulthood. RT-PCR and western blotting revealed that the expression of DCC mRNA and protein does not signi- ficantly change throughout development. Immunohistoche- mistry demonstrated that DCC expression in the TG was detectable in the perikarya region of the ganglion cells du- ring development. Nerve injury at 3 and 5 days after the man- dibular nerve had been cut did not induce altered expression of DCC mRNA in the TG. Moreover, DCC-positive cell bodies also showed similar immunoreactive patterns after a nerve cut injury. The results of this study suggest that DCC constituti- vely participates in an axonogenesis attractant in ways other than expression regulation.

The effects of the an immunosuppressive drug cyclos- porine A (CsA), on the salivary gland are largely unknown, even though clinical trials for the stimulation of salivation using CsA have been attempted. Cyclophilin A (CypA) is known to be a binding protein for CsA. CypA has cell proliferation and tissue matrix change activities. In our present study, the presence of CypA in the gland and effects of CsA on CypA expression were investigated by immu- nohistochemistry, immunoblotting and RT-PCR analyses. CypA was immunohistochemically detected in various kinds of ducts in the submandibular glands of Sprague Dawley rats. The CypA mRNA level was highest at postnatal day 1 and gradually decreased in a time-dependent manner up to adulthood. The expression of CypA increased after a 10 day subcutaneous administration of CsA in postnatal day 1 rats. Surgical sections of the chorda-lingual nerve with impaired salivation showed no changes in CypA expression. A cell proliferation assay using PCNA anti-serum showed inc- reased cell division following CsA treatment. These results suggest that CsA and CypA may act on ductal cells to regulate saliva composition rather than salivation levels.

Tooth development involves bud, cap, bell and hard tissue formation stages, each of which is tightly controlled by regulatory molecules. The aim of this study was to identify genes that are differentially expressed during dental hard tissue differentiation. Sprague-Dawley rats at postnatal days 3, 6 and 9 were used in the analysis. Differential display RT-PCR (DD-PCR) was used to screen differentially expressed genes between the 2nd (root formation stage, during mineralization) and 3rd (cap stage, before minerali-zation) molar germs at postnatal day 9. The DNA detected in the 2nd molar germs showed homology to osteonectin only (GenBank accession no. NM_012656.1). The level of osteonectin mRNA expression was much higher in the 2nd molar germs than in the 3rd molar germs and was found to increase in a time-dependent manner from the early bell stage to the root formation stage in the 2nd molar germs. The pattern of osteonectin protein expression was consistent with these RT-PCR results. Osteonectin protein was found by immunofluorescent analysis to localize in odontoblasts and preodontoblasts rather than the dentin matrix itself. Further studies are needed to validate the involvement of osteonectin in mineralization and root formation.

Matrix metalloproteinases (MMPs) have been implicated in tissue development and re-modeling. Dynamic morphological changes of tooth germs reflect involvement of these enzymes during odontogenesis. The present study was performed to investigate expression and localization of MMP-2 and MMP-9, which have been known to have type IV collagenase activities, in rat tooth germs at different developmental stages. MMP-2 expression was increased gradually in the tooth germs from cap to crown staged germs at both transcription and translation levels. The localization of this molecule was detected in secretory ameloblasts and preameloblasts. The strong immunoreactivities were occasionally seen along the basement membrane between ameloblasts (or preameloblasts) and odontoblasts (preodontoblasts). However, weak reactivity was detected in odontoblasts and reduced enamel epithelium. The level of MMP-9 expression in the tooth germs was higher in cap stage than in crown staged germs at both transcription and translation levels. They were strongly expressed in both ameloblasts and odontoblasts. Even though reduced enamel epithelium after enamel formation and inner enamel epithelium at the cap stage exhibited weak reactivity, strong reactivity was detected in dental follicles and perifollicular tissues surrounding cap staged germs. These results suggested that MMP-2 may involve degradation of the basement membrane during hard tissue formation, whereas MMP-9 might be involved in remodeling of follicular tissues.

In order to provide the basic information on the environmental pollution of Kyungsan province, the contents of Pb, Cd, Cr, Cu, Mn and Zn in soil, stream water, aquatic sediment and groundwater were investigated, and also the values of pH, COD, KMnO4-C, NH3-N, NO2-N, NO3-N and Cl- of stream water and groundwater were determined. The results were as follows. The values of COD, NH3-N, NO2-N and NO3-N of the stream waters were very low. The contents of Pb, Cd, Cr, Cu and Zn in the stream waters were respectively at range of 0.014～0.063 ㎎/ℓ, 0.004～0.007 ㎎/ℓ, 0～0.045 ㎎/ℓ, 0～0.008 ㎎/ℓ and 0.001～0.175 ㎎/ℓ, and these values were much lower than those of contaminated stream water in Korea. The contents of Cd, Cr, Cu and Zn in the soils were respectively at range of 0.12～0.71 ppm, 0.88～2.65 ppm, 2.86～22.33 ppm and 3.89～26.39 ppm, and these values were much lower than those of ordinary polluted areas in Korea. The contents of Cd, Cr, Cu, As, Zn and Mn in the aquatic sediments were respectively at range of 3.05～3.81 ppm, 14.6～70.6 ppm, 13.74～61.59 ppm, 76.8～465.5 ppm, 12.56～190.83 ppm and 333.3～1188.3 ppm. The values of pH, KMnO4-C, NH3-N and NO3-N of the groundwaters were respectively at range of 7.6～8.4, 0～3.95 ㎖, 0.05～0.15 ㎎/ℓ and 0.05～0.42 ㎎/ℓ. The contents of Pb, Cd and Cr in the groundwaters were respectively at range of 0.015～0.061 ㎎/ℓ, 0.006～0.009 ㎎/ℓ and 0.005～0.045 ㎎/ℓ.