Biomedical subjects
Publications and source records attributed to D K Park.
We report two cases of lipoma of the parotid gland which present as a non-tender, freely movable and intraparotid mass. Lipomas are common soft tissue neoplasms but found very rarely in the parotid gland, and so are often not considered in the initial differential diagnosis of parotid gland tumor. We believe that these tumors are cured by simple excision, and thus superficial parotidectomy is enough for treatment.
Ser-49 located at the exposed surface loop of subtilisin J was replaced with Asp and Arg. Proteinase activity of the Asp-49 mutant was similar to that of wild-type, but the Arg mutant was inactivated. At 37 degrees C, mature subtilisin J protein of the Asp-49 mutant rapidly degraded, and specific breakdown products were accumulated. These proteins were analyzed by SDS-PAGE, and the N-terminal sequences were determined for the mature and deleted protein. We identified the autoproteolytic cleavage site in the mature Asp-49 mutant protein from sequencing data.
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A cell line derived from a normal beagle embryo was treated in vitro with various levels of N-methyl-N'-nitro-N-nitrosoguanidine or dimethyl sulfoxide (control). Cells treated only with the carcinogen underwent morphologic alteration in vitro, and one of these altered cell lines produced tumors subcutaneously when injected into NIH nude mice. The tumorigenic transformed line formed larger cell aggregates and grew in this aggregate form when suspended in liquid growth medium above an agar base.
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A variety of experiments of endothelial cell seeding on artificial vessels have been performed. To improve endothelialization, one or two extracellular matrix components have been used as an underlying matrix. Although these methods have succeeded in in vitro experiments, they have not performed well in vivo. In this study, the authors used the whole extracellular matrix (ECM) excreted from fibroblasts as an underlying matrix. Fetal human fibroblasts were cultured on a polyurethane (PU) sheet. After confluence was attained, the cytoskeleton and the nuclei of the fibroblasts were destroyed using Triton-X, mitomycin, and irradiation. Omental microvascular endothelial cells from adult humans were seeded on various supports. After 12 days in culture, the cells were counted. The authors found that the ECM treated by irradiation had the highest cell number. In addition, the cells on this support exhibited the best morphologic appearance. Finally, the authors performed preliminary animal experiments. The PU vessels (inner diameter: 1.5 mm) treated with ECM were implanted in the arteries of rats. After the vessels had been implanted for 5 weeks, the authors found that the surface of the PU vessels were completely covered with endothelial cells. On the basis of these results, the authors conclude that the whole ECM makes a better underlying substrate for the endothelialization of small diameter artificial vessels.