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Biomedical subjects

Y K Choi

Publications and source records attributed to Y K Choi.

At least 91 records · Page 5Linked to original sources
PubMed2000

Suppression of immunoglobulin E-mediated anaphylactic reaction by Alpinia oxyphylla in rats.

We investigated the effect of Alpinia oxyphylla water extract (AOWE) on immunoglobulin E (IgE)-mediated anaphylaxis activated by anti-dinitrophenyl (DNP) IgE antibody. AOWE dose-dependently suppressed passive cutaneous anaphylaxis (PCA) when intraperitoneally or orally administered. On the other hand, it showed weak suppressive activity when administered intravenously. AOWE dose-dependently suppressed anaphylactic histamine release from rat peritoneal mast cells (RPMC) activated by anti-DNP IgE antibody. However, AOWE had a significant augmenting effect on anti-DNP IgE antibody-induced tumor necrosis factor-alpha secretion from RPMC. These results indicated that AOWE may possess strong antianaphylactic action and also suggest that differential activity following administration routes may be caused by difference of bioavailability.

Animals↗
PubMed2000

A toxoplasmic uveitis case of a 60-year-old male in Korea.

A toxoplasmic uveitis case was reported on the focus of impairment of pathological findings and serological antibody titers after chemotherapy. A chief complaint of a 60-year-old male was a decreased and blurred vision in his right eye for 2 weeks after experiencing tremendous stress and fatigue. A steroid therapy for 3 weeks was not effective and the retinal lesion became necrotic. Anti-Toxoplasma gondii antibody titer was checked to be a strong positive by both ELISA and indirect latex agglutination assay (ILA). He was treated with Fansidar F for 8 weeks. His vision improved as the necrotic lesion healed by scarring, but the antibody titers still remained very high without any signs of negative conversion. It is suggested to be a recurrent case of the past asymptomatic infection by presumed immune suppression caused by excessive stress.

Animals↗
PubMed2000

A virtual reality system for hand acupuncture.

A virtual reality system for the hand acupuncture treatment is proposed. The hand acupuncture, called sujichim, is mostly conducted at home and many people try to learn and apply it to the health care of their family. Using our system, a novice can easily perform the acupuncture by himself to improve his body condition. According to the experiments, our system is proved to be very effective and easy to use.

Acupuncture Points↗
PubMed1999

Development of new adherent mutant from human myeloma-derived cell line: in vitro model of anaplastic transformation of myeloma.

Anaplastic myeloma is a rare but distinct, biologically aggressive variant of myeloma which usually results from dedifferentiation or anaplastic transformation of the myeloma cells. The molecular mechanisms that determine the biologic behavior of anaplastic myeloma and effective treatment modalities have not been well known due to lack of in vitro models. In the present study, we have developed an anaplastically transformed mutant from a human myeloma-derived cell line. In the process of long-term culture of the myeloma-derived IM-9 cell line in low serum and nutrient conditions, an adherent mutant line was developed and named IM-9/AD. This mutant cell line displayed several characteristics resembling anaplastic myeloma such as: 1, large cells with large vesicular nucleus and prominent nucleolus, multinuclearity and high mitotic figures; 2, loss of leukocyte-associated antigens; and 3, higher tumorigenecity in scid mice than its parental cell line. This newly developed mutant cell line may serve as a readily available in vitro model to investigate the biology of anaplastic myeloma.

Animals↗
PubMed1999

New biodegradable polymers for injectable drug delivery systems.

Many biodegradable polymers were used for drug delivery and some are successful for human application. There remains fabrication problems, such as difficult processability and limited organic solvent and irreproducible drug release kinetics. New star-shaped block copolymers, of which the typical molecular architecture is presented, results from their distinct solution properties, thermal properties and morphology. Their unique physical properties are due to the three-dimensional, hyperbranched molecular architecture and influence microsphere fabrication, drug release and degradation profiles. We recently synthesized thermosensitive biodegradable hydrogel consisting of polyethylene oxide and poly(L-lactic acid). Aqueous solution of these copolymers with proper combination of molecular weights exhibit temperature-dependent reversible sol-gel transition. Desired molecular arrangements provide unique behavior that sol (at low temperature) form gel (at body temperature). The use of these two biodegradable polymers have great advantages for sustained injectable drug delivery systems. The formulation is simple, which is totally free of organic solvent. In sol or aqueous solution state of this polymer solubilized hydrophobic drugs prior to form gel matrix.

Animals↗
PubMed1999

Antitumor effect of GnRH agonist in epithelial ovarian cancer.

OBJECTIVE: The effects of the gonadotropin releasing hormone (GnRH) agonist (D-Trp(6)) were examined in two human ovarian cancer cell lines and in severe combined immune deficiency (SCID) mice to evaluate its potential as a cytocidal, cytostatic, or differentiating antitumor agent. METHODS: We treated the human ovarian cancer cell lines OVCAR-3 and SKOV-3 for 5 or 7 days and sex-matched SCID mice with GnRH agonist for 29 days. The antitumor effect of GnRH agonist were studied in various aspects. To confirm the antiproliferative effect, we used 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyltetrazolium bromide colorimetric assay, in vitro, and a serial measurement of tumor growth in vivo. The disturbances of progression in the cell cycle and the changes of cyclin-dependent kinase 1 following treatment with GnRH agonist were evaluated with flow cytometric analysis in vitro. The induction of apoptosis following treatment with GnRH agonist was studied using in situ terminal deoxyribonucleotidyl transferase (Tdt) and further quantitated with ELISA in vitro. The presence of telomerase activity following treatment with GnRH agonist was measured by PCR-based telomeric repeat amplification protocol and ELISA detection in cell lines and xenografts in vitro and in vivo. RESULTS: Continuous exposure of cell lines and xenografts to GnRH agonist resulted in growth inhibition of cancer cells in a dose- and time-dependent manner. In cultured cells, the GnRH agonist blocked cell cycle progression in G0/G1 phase and thus reduced the number of cells in S and G2/M phases. The phenomenon of apoptosis was documented in cultured cells treated with GnRH agonist by in situ Tdt assay. The frequency of apoptotic cells in the in situ Tdt assay was 5-6% compared with control, 4-5%. Apoptosis quantified by ELISA revealed a high incidence in cultured cells treated with GnRH agonist. The activities of telomerase in cell lines and xenografts were not decreased by GnRH agonist. There were not any significant changes of expression of CA-125 by flow cytometry and of the cellular morphology observed with light microscopy. CONCLUSIONS: Our results indicate that the antiproliferative effect of GnRH agonist in epithelial ovarian cancer cells may be mainly attributed to cytostatic activities resulting in blocking of cell cycle progression in the G0/G1 phase and minimally related to the induction of apoptosis.

Animals↗
PubMed1999

Effect of nodularin on the expression of glutathione S-transferase placental form and proliferating cell nuclear antigen in N-nitrosodiethylamine initiated hepatocarcinogenesis in the male Fischer 344 rat.

The tumor-promoting effect of nodularin during carcinogenesis was investigated. Male Fischer 344 rats were injected with nodularin for 10 weeks from week 3 after N-nitrosodiethylamine initiation without partial hepatectomy. Rats were further maintained for 10 weeks after the cessation of nodularin and were periodically killed. In contrast to the minimal foci in the DEN and nodularin alone groups, treatment with DEN and nodularin produced four kinds of nodules with eosinophilic, clear, mixed and basophilic cells. After the cessation of nodularin, the maximally increased number, but not the area, of glutathione S-transferase placental form-positive [GST-P(+)] nodules at week 12 decreased significantly and the appearance of two types of hyperplastic nodules was noted by GST-P immunostaining; homogeneously stained dense nodules (DN) and heterogeneously stained pale nodules (PN), which appeared only after the cessation of nodularin. DN were well circumscribed by enzyme-altered cells, as opposed to poorly in PN. Moreover, normal-appearing hepatocytes replaced the enzyme-altered cells in PN. In contrast to the higher PCNA index in GST-P(+) DN, the background level returned to that of the control at week 15. PCNA indices in DN were significantly higher than in PN, which were still higher than the control, indicating that nodularin affected the PCNA index differentially in the altered and unaltered hepatocytes. However, nodularin without DEN initiation significantly increased the PCNA index through initial cell death and subsequent hepatocyte proliferation. These results suggest that: (i) nodularin has a promoting effect by inducing hepatocyte proliferation in both enzyme-altered hyperplastic nodules and the surrounding parenchyma; (ii) proliferation is transient in background cells but not in enzyme-altered hepatocytes; (iii) GST-P(+) DN can be regarded as progressive and GST-P(+) PN as regressive, revealed by both immunohistochemistry and PCNA index.

Animals↗
PubMed1999

High-dose-rate brachytherapy for primary carcinomas of the oral cavity and oropharynx.

OBJECTIVE: Local control for patients treated with primary radiation therapy for tumors of the oral cavity is improved using low-dose-rate brachytherapy. Oropharyngeal carcinomas have also been treated with brachytherapy. The few reports in the literature regarding high-dose-rate brachytherapy (HDRBT) for head and neck cancer involve small numbers of patients and often contain a mix of palliative and curative cases. The purpose of this study is to evaluate the feasibility of HDRBT in the largest reported cohort of primary head and neck cancer patients treated with primary radiation therapy. STUDY DESIGN: This is a prospective nonrandomized study. METHODS: Fifty-five patients with primary untreated squamous cell carcinomas of the oral cavity and oropharynx were analyzed. There were 16 patients with T1, 26 with T2, 8 with T3, and 5 with T4 tumors. All patients received external-beam radiotherapy (EBRT) followed by HDRBT. Thirty-eight patients received hyperfractionated (twice daily) EBRT followed by HDRBT two or three times daily. Patients with cervical adenopathy also received hyperthermia and an electron boost to the site(s) of positive nodes. Median follow-up was 2.7 years. Toxicity and local control were analyzed. Data were analyzed by the Kaplan-Meier life-table method with statistical significance determined by the X2 and log-rank tests. RESULTS: High-dose-rate brachytherapy was extremely well tolerated. Only 9 patients (16%) developed a complication. Four patients developed osteoradionecrosis, and five developed soft tissue necrosis, all of which healed with conservative medical management. No complication required surgical intervention or hospitalization. Actuarial 2-year local control for the entire cohort was 79%. Local control was 87% for patients with T1 (15/16) and T2 (22/26) tumors versus 47% for T3 (5/8) and T4 (2/5) tumors (P < .01). CONCLUSIONS: High-dose-rate brachytherapy is feasible as a boost for patients with primary squamous cell carcinomas of the oral cavity and oropharynx. Patients with T1 and T2 tumors fared exceptionally well; those with advanced tumors may require more aggressive treatment, such as higher radiation doses, surgical resection, or systemic chemotherapy. The use of HDRBT both shortens the overall treatment time and limits the volume of tissue exposed to high doses of radiation therapy. In the future, as more patients treated with HDRBT are evaluable, we hope to identify potential factors that predict for local control so that we may select patients optimally for this treatment.

Adult↗
PubMed1999

Fatal measles virus infection in Japanese macaques (Macaca fuscata).

An outbreak of natural measles virus infection occurred in a group of Japanese macaques (Macaca fuscata). Over a period of 4 months, 12 of 53 Japanese macaques died following a 2-23-day history of anorexia, diarrhea, and dermatitis. The monkeys were kept in outdoor exhibits but had been moved temporarily into indoor caging and then transferred to new outdoor exhibits. Ten monkeys died while they were in temporary caging, and two monkeys died after they were moved to new outdoor exhibits. The diagnoses were made based on the results of histopathology, immunohistochemistry (IHC), in situ hybridization (ISH), and electron microscopy. Measles virus antigens were detected in the lung, stomach, skin, salivary gland, spleen, and lymph nodes. Tangled, tubular nucleocapsids compatible with paramyxovirus were noted in the lung tissue. As a result of immunosuppression following measles virus infection, various secondary infections including disseminated cytomegalovirus infection, adenoviral and bacterial pneumonia, and Candida albicans-associated gingivitis and esophagitis were noted. The primary infective source or the mode of infection could not be determined in this outbreak, but measles virus may have been transmitted to the monkeys from human visitors while the monkeys were on exhibit.

Animals↗
PubMed1999

Effect of cilostazol on the neuropathies of streptozotocin-induced diabetic rats.

OBJECTIVES: This study examined the effect of cilostazol, a potent phosphodiesterase inhibitor, on the progression of neuropathies associated with streptozotocin-induced diabetes mellitus in Sprague-Dawley rats. METHODS: Eight weeks after streptozotocin treatment, a pelleted diet containing 0.03% cilostazol (15 mg/kg body weight) was given for four weeks. Body weight, blood glucose level, motor nerve conduction velocity (MNCV), myelinated fiber density and size distribution of sciatic nerves were compared between age-matched normal rats (Group 1), control diabetic rats (Group 2) and cilostazol-treated diabetic rats (Group 3). RESULTS: Body weight was significantly reduced and blood glucose level was significantly increased in diabetic rats (Group 2 and 3) compared to normal rats. MNCV and cAMP content of sciatic nerves were significantly reduced in diabetic rats 12 weeks after streptozotocin treatment. Myelinated fiber size and density were also significantly reduced, and thickening of the capillary walls and duplication of the basement membranes of the endoneural vessels were observed in the diabetic rats. Whereas both body weight and blood glucose level of Group 3 did not differ significantly from those of Group 2, cilostazol treatment significantly increased MNCV and cAMP content of sciatic nerves in Group 3 but not to the levels observed in Group 1. MNCV positively correlated with cAMP content of sciatic nerves (r = 0.86; p < 0.001). Cilostazol treatment not only restored myelinated fiber density and size distribution but reversed some of the vascular abnormalities. CONCLUSION: These findings suggest that a reduced cAMP content in motor nerves may be involved in the development of diabetic neuropathy, and that cilostazol may prevent the progression of diabetic neuropathy by restoring functional impairment and morphological changes of peripheral nerves.

Animals↗
PubMed1998

Over-expression of urokinase receptor in human epidermoid-carcinoma cell line (HEp3) increases tumorigenicity on chorio-allantoic membrane and in severe-combined-immunodeficient mice.

Using chorio-allantoic membranes (CAMs) of chick embryos and severe-combined-immunodeficient (SCID) mice, we investigated the effects of urokinase-type plasminogen-activator receptor (u-PAR) over-expression on the process of invasion and tumorigenicity. By the transfection of u-PAR cDNA, 3 u-PAR-over-expressing clones expressing 1.6- to 4.6-fold more u-PAR mRNA than parent cells were obtained from a human epidermoid-carcinoma cell line, HEp3, that expresses urokinase-type plasminogen activator (u-PA) and u-PAR. All the u-PAR-over-expressing clones showed greater invasiveness (13 to 29%) than that of parent HEp3 cells on CAMs. Immunohistochemistry revealed densely stained u-PAR-positive cells near the margin of the tumor, where a u-PAR-over-expressing clone, designated SM-3, was invading thickened fibrous tissue on CAMs. Three u-PAR-overexpressing clones formed larger tumors (>40 mm3) than did parent HEp3 cells on CAMs. Moreover, when the u-PAR-overexpressing clone (SM-3) was injected s.c. into the back of the SCID mice it produced a larger tumor volume than the control (HEp3) and down-regulated (AS-2) clones and significantly shortened the survival of SCID mice. These results demonstrate that increased u-PAR expression is an important factor in determining the malignant phenotype that makes cancer cells more invasive and tumorigenic.

Allantois↗
PubMed1998

Polyethylene glycol-grafted poly-L-lysine as polymeric gene carrier.

A new series of gene carriers, polyethylene glycol (PEG)-grafted poly-L-lysine (PLL, mol. wt. = 25000) with three different PEG-grafted ratios (5, 10 and 25 mole%, which means 5, 10 and 25% of epsilon-amino group of PLL was modified by PEG), was synthesized. These new gene carriers, named comb-shaped PEG-g-PLL copolymer, showed a 5- to 30-fold increase in transfection efficiency compared to PLL alone on a human carcinoma cell line. It is likely that Hep G2 cells were transfected by plasmid DNA/PEG-g-PLL complexes through an endocytosis mechanism due to the fact that chloroquine increased transfection efficiency. Although Lipofectin, a cationic lipid formulation, showed slightly higher transfection efficiency than PEG-g-PLL in Hep G2 cells, our designed PEG-g-PLL demonstrated lower cytotoxicity, early gene expression and maintenance of gene expression for up to 96 h.

Cell Survival↗
PubMed1997

Cloning and expression of a gene encoding Moraxella sp. CK-1 autolysin.

A gene of Moraxella sp. CK-1 encoding cell wall lytic activity has been cloned and expressed in E. coli. A genomic library of Moraxella sp. CK-1 was constructed in the multifunctional phagemid vector pT7T3 19u, with partial Sau3A digests of Moraxella sp. CK-1 genomic DNA inserted at the BamHI restriction site. Screening of about 5,000 transformants for cell lysis activity in LB agar plates containing Micrococcus Iuteus cells gave one positive clone harboring the 3.7 kb insert (pMXA282). Restriction mapping and deletion analysis of the recombinant plasmid carrying a 3.7 kb insert suggested that the autolysin gene was located within a 1.1 kb BamHI-PstI fragment. Analysis of extracts of E. coli clone harboring recombinant plasmids on renaturing SDS-polyacrylamide gels containing heat-killed Micrococcus luteus cells showed a clear zone around a polypeptide of about 32 kDa. Lytic activity against Micrococcus luteus cell walls by the cloned autolysin was maximum at pH 9.0. Even in conditions of over pH 10.0, this cloned autolysin showed a vigrous lytic activity. Southern blot analysis suggested the existence of other homologous regions in Moraxella sp. CK-1 genome.

Bacteriolysis↗
PubMed1997

Tumors of the orbit. Pitfalls of the surgical approach in 37 children with orbital tumor.

The authors review their experience with 37 children with orbital tumors, summarizing their surgical techniques, the indications applied, and the pitfalls of each surgical approach. Tumors located in the retro-ocular or intraorbital space were surgically excised through a transcranial approach (28 cases), while for tumors in other sites lateral orbitotomy (5 cases), medial orbitotomy (1 case) and biopsy (3 cases) were performed. A transcranial approach was used for tumors with intracranial extension and for those located in the orbital apex and deep medial orbital compartment. Lateral orbitotomy was used for tumors located in the superior, temporal or inferior compartment of the orbit and those in the lateral apex. A medial orbitotomy was used for tumors located medial to the optic nerve. Outcomes of the surgical intervention varied, depending on the pathology, location and extent of the individual tumors. To obtain optimal exposure and minimize functional deficits, the pitfalls of surgical approaches to orbital tumors are discussed.

Adolescent↗
PubMed1997

Peptide-specific CTL induction in HBV-seropositive PBMC by stimulation with peptides in vitro: novel epitopes identified from chronic carriers.

Cytotoxic T lymphocytes (CTL) recognize and destroy virus-infected cells, and it has been established that epitope-based peptides could induce such CTL in vivo as well as in vitro. In this study attempts were made to define the epitopes that are recognized by the CTL, and thus a series of 9- to 10-mer peptides derived from the amino acid sequences of hepatitis B virus (HBV) proteins were synthesized on the basis of the previously described HLA-A2 peptide binding motif. The binding assay of the synthetic peptides using transporter-associated with antigen processing (TAP)-deficient human cell line, T2, showed that eight out of 11 peptides tested enhanced the expression of HLA-A2 molecules on the T2 cell surface. Some of these peptides triggered activation of CTL in peripheral blood mononuclear cells of HBV-seropositive chronic carriers. The activated CTL in turn recognized and killed the T2 cells pulsed with the same peptides. This study shows that novel HLA-A2-restricted epitopes exist in the natural repertoire of immunity against HBV. These findings can be useful in developing peptide-based therapeutics against viral infections.

Carrier State↗
PubMed1997

Oncogenic osteomalacia caused by a phosphaturic mesenchymal tumor of the oral cavity: a case report.

We report a case of oncogenic osteomalacia associated with a phosphaturic mesenchymal tumor in a 31-year-old woman. She was presented with severe generalized bone and muscle pain and was restricted to bed. She lost 20 cm in height over the 8 years since she had first noticed a pain in her thigh. A walnut-sized, hard, soft tissue tumor was found very easily beside her lower molar teeth Radiologic examination revealed a remarkable decrease in bone density and multiple pathologic fractures of spine, femur and phalangeal bones. Severe hypophosphatemia, hyperphosphaturia, low plasma 1,25-dihydroxyvitamin D3 level and high plasma PTH level were disclosed at presentation. Histomorphometric examination revealed an extensive area of unmineralized osteoid and little mineralizing activity. A pharmacologic dose of 1 alpha-hydroxyvitamin D3 or or 1,25-dihydroxyvitamin D3 slightly increased the serum phosphate level and renal tubular reabsorption of phosphate, and slightly decreased plasma PTH level without any symptomatic improvement. Histologic examination of the tumor revealed a mixed connective tissue tumor that consisted of central woven bones and surrounding primitive spindle cells with prominent vascularities. After removal of the tumor, all biochemical, hormonal and radiologic abnormalities disappeared with remarkable symptomatic improvement.

Adult↗