• Korean Journal of Fisheries and Aquatic Sciences
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• v.29 no.6
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• pp.856-861
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• 1996

The occurrence of TTX in ciliated protozoa was investigated in order to clarify tetrodotoxin (TTX) accumulation mechanisms in marine organisms. Tissue culture bioassay, HPLC, and GC-MS analyses confirmed the occurrence of TTX in Euplotes mutabilis and also in bacteria isolated from the culture medium. Fluorescently labeled bacteria (FLB) were prepared with those bacteria, and predation by E. mutabilis was observed. The results indicated that TTX in bacteria can be transferred to higher trophic levels through the food chain.

• Korean Journal of Plant Tissue Culture
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• v.25 no.2
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• pp.95-98
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• 1998

Hypocotyl explants of flowering cabbage were cocultured with Agrobacterium tumefaciens LBA4404;;pGA875 harboring proteinase inhibitor II(PI-II) cDNA and then regenerated into plants. Sucessful transcripts of PI-II gene were detected by RNA dot blot analysis. Bioassay was conducted on transgenic flowering cabbage. It was confirmed that insecticidal activities of transformants were much higer than that of control plants. In progeny test of hansformants, 27.4% of T$_1$ seeds was resistant on MS medium containing 20 mg/L kanamycin.

• Macromolecular Research
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• v.11 no.5
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• pp.334-340
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• 2003

In order to fabricate new sustained delivery device of nerve growth factor (NGF), we developed NGF-loaded biodegradable poly(L-lactide-co-glycolide) (PLGA, the mole ratio of lactide to glycolide 75:25, molecular weight: 83,000 and 43,000 g/mole, respectively) film by novel and simple sandwich solvent casting method for the possibility of the application of neural tissue engineering. PLGA was copolymerized by direct condensation reaction and the molecular weight was controlled by reaction time. Released behavior of NGF from NGF-loaded films was characterized by enzyme linked immunosorbent assay (ELISA) and degradation characteristics were observed by scanning electron microscopy (SEM) and gel permeation chromatography (GPC). The bioactivity of released NGF was identified using a rat pheochromocytoma (PC-12) cell based bioassay. The release of NGF from the NGF-loaded PLGA films was prolonged over 35 days with zero-order rate of 0.5-0.8 ng NGF/day without initial burst and could be controlled by the variations of molecular weight and NGF loading amount. After 7 days NGF released in phosphate buffered saline and PC-12 cell cultured on the NGF-loaded PLGA film for 3 days. The released NGF stimulated neurite sprouting in cultured PC-12 cells, that is to say, the remained NGF in the NGF/PLGA film at 37 $^{\circ}C$ for 7 days was still bioactive. This study suggested that NGF-loaded PLGA sandwich film is released the desired period in delivery system and useful neuronal growth culture as nerve contact guidance tube for the application of neural tissue engineering.