Biomedical subjects

K H Choi

Publications and source records attributed to K H Choi.

At least 91 records · Page 5Linked to original sources

PubMed1998

Recurrent parosteal osteosarcoma of the talus in a 2-year-old child.

Parosteal osteosarcoma is an uncommon, low-grade malignant bone tumor and is found in an older age group than conventional osteosarcoma. We present a talar parosteal osteosarcoma that recurred twice in a 2-year-old child. To our knowledge, this is the youngest patient reported with a parosteal osteosarcoma. The talus is an unusual site for parosteal osteosarcoma. Inadequate resection due to a diagnosis of juxtacortical chondroma resulted in recurrence of the tumor. The age of the patient, the thick cartilaginous cap, and well-differentiated trabecular bone all contributed to the critical erroneous diagnosis.

Bone Neoplasms↗

PubMed1998

Effects of niacin deficiency on the levels of soluble proteins and enzyme activities in various tissues of Japanese quail.

The effects of niacin deficiency on the levels of soluble proteins and enzyme activities of Japanese quail have been investigated. SDS-polyacrylamide gel electrophoresis revealed that in the pectoral muscle the soluble proteins with molecular masses corresponding to 181, 128, 93, 76, 72, 62, 56, 43, 41, 28 and 20 kDa were present in lower amounts but those of 60, 50 and 37 kDa were present in higher amounts. In the heart the soluble proteins with a molecular mass of 181 kDa were present in lower amounts and in the brain those of 43 kDa were present in lower amounts but those of 221 kDa were present in higher amounts. In the intestine the soluble proteins with molecular masses corresponding to 181, 102, 83, 74, 72, 44 and 40 kDa were present in lower amounts but those of 41 kDa and 18 kDa were present in higher amounts. There was a marked reduction in the level of NAD and NADPH in the pectoral muscle of niacin deficient quail but not in other tissues. The specific activity of glyceraldehyde-3-phosphate dehydrogenase decreased markedly both in the liver and pectoral muscle of niacin deficient quail whereas that of 6-phosphogluconate dehydrogenase and malic enzyme decreased markedly in the liver or pectoral muscle, respectively. In contrast, the specific activity of acetylcholinesterase and carboxypeptidase increased markedly in the liver or the pectoral muscle, respectively. The results suggest that a severe niacin deficiency exerted specific effects on levels of some soluble proteins particularly in the pectoral muscle and intestine and on activities of certain enzymes in the liver and the pectoral muscle.

Animals↗

PubMed1998

In-vitro and in-vivo antibacterial activity of CFC-222, a new fluoroquinolone.

CFC-222 is a novel fluoroquinolone with potent and broad-spectrum antibacterial activity. The in-vitro and in-vivo activities of CFC-222 were compared with those of ciprofloxacin, ofloxacin, lomefloxacin and sparfloxacin. Against gram-positive bacteria such as Staphylococcus aureus (quinolone-susceptible and quinolone-resistant), Staphylococcus epidermidis, Streptococcus pneumoniae and Enterococcus faecalis, CFC-222 was more active than ciprofloxacin and similar to sparfloxacin. Against gram-negative bacteria, including Enterobacteriaceae, the in-vitro activity of CFC-222 was similar to that of sparfloxacin, but less than that of ciprofloxacin. However, it was less active than ciprofloxacin and sparfloxacin against Pseudomonas aeruginosa. In mouse systemic infection caused by S. aureus Smith or S. aureus TMS 33, CFC-222 demonstrated an activity similar to that of ciprofloxacin and sparfloxacin, but better than that of ofloxacin. The compound was more effective than ciprofloxacin and sparfloxacin in murine infection caused by Streptococcus pyogenes ATCC 8668. Against Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae infections, the efficacy of CFC-222 was similar to those of ciprofloxacin, ofloxacin and sparfloxacin. The activity of CFC-222 was similar to those of ciprofloxacin and sparfloxacin against P. aeruginosa MB4-16 in the same infection model. These results suggest that CFC-222 may be a promising therapeutic agent for the treatment of various bacterial infections.

Animals↗

PubMed1998

Nonossifying fibroma: characteristics at MR imaging with pathologic correlation.

PURPOSE: To correlate the findings of nonossifying fibroma at magnetic resonance (MR) imaging with those at pathologic examination. MATERIALS AND METHODS: In 19 patients (age range, 8-25 years; mean age, 14 years) with pathologically proved nonossifying fibroma, MR images were analyzed for signal intensity and patterns of contrast enhancement. Findings at MR imaging and biopsy were correlated. RESULTS: On T1-weighted images, all nonossifying fibromas had low signal intensity compared with that of skeletal muscle. On T2-weighted images, 15 lesions (79%) were hypointense and four (21%) were hyperintense. On gadolinium-enhanced images, intense contrast enhancement was seen throughout 15 lesions (heterogeneous pattern in 12 and homogeneous in three) and in the margins and septa in four. Extensive hypercellular fibrous tissue and hemosiderin seen at pathologic examination were depicted with low signal intensity on T2-weighted MR images. CONCLUSION: The distinguishing features of nonossifying fibroma included hypointensity and septation on T2-weighted images. Signal intensity on T1- and T2-weighted MR images and the patterns of contrast enhancement were dependent on the amounts of hypercellular fibrous tissue, hemosiderin, hemorrhage, collagen, foamy histiocytes, and bone trabeculae.

Adolescent↗

PubMed1998

Membranoproliferative glomerulonephritis associated with HCV infection in native kidneys and renal allograft.

Hepatitis C viral infection occurs relatively low in Korea compared to hepatitis B. However, it progresses into chronic hepatitis and cirrhosis more frequently than HBV. It may be associated with cryoglobulinemia and glomerulonephritis, both in native and transplanted kidneys. We report three cases of membrano-proliferative glomerulonephritis type I in anti-HCV positive, but cryoglobulin-negative patients, presenting massive proteinuria, two in native kidneys and one in an allograft. HCV-RNA was positive in sera of two patients. Two were cirrhotic and ALT was mildly elevated in two. In addition to the characteristic membranoproliferative feature, two native kidneys overlapped with features of diabetic nephropathy. Immunofluorescence demonstrated mainly IgM and C3 deposits along the peripheral capillary walls. Subendothelial electron dense deposits were present in the glomeruli of all three cases with subepithelial and intramembranous deposits in two. HCV-RNA was associated not only with a greater amount of immune deposits but also with subepithelial and intramembranous deposits, indicating the role of active infection.

Adult↗

PubMed1998

Hepatitis G virus infection in hemodialysis and continuous ambulatory peritoneal dialysis patients.

To determine the prevalence and clinical relevance of HGV infection in dialysis patients, we performed a cross-sectional study of 61 HD patients and 79 Continuous Ambulatory Peritoneal Dialysis (CAPD) patients. HGV-RNA was identified by reverse-transcription (RT) polymerase chain reaction (PCR) assay with primers from the 5'-untranslated region of the viral genome. The prevalence of HGV infection was similar in HD and CAPD patients (9.8% vs. 12.7%), while that of HCV infection was significantly higher in HD patients compared to CAPD patients (16.4% vs. 1.3%, p < 0.05). The mean age (49.2 +/- 13.4 vs. 46.7 +/- 13.0 years), male to female ratio (2.4:1 vs. 1.3:1), history of transfusion (62.3% vs. 49.4%), history of hepatitis (27.9% vs. 26.6%), mean ALT level during the previous 6 months (22.4 +/- 37.9 vs. 14.0 +/- 7.4 IU/L), and the prevalence of HBsAg (8.2% vs. 6.3%) showed no difference between HD and CAPD patients. In both HD and CAPD patients, the presence of HGV RNA was not related to age, sex, duration of dialysis, history of transfusion, history of hepatitis, or to the presence of HBV or HCV markers. There was no significant difference in the clinical and biochemical data between patients with isolated HGV infection (n = 12) and patients without viremia (n = 106). The clinical feature of patients coinfected with HGV and HBV (n = 2), or HGV and HCV (n = 2) seemed to be similar to those of patients with isolated HBV (n = 8) or HCV (n = 9) infection. In conclusion, the prevalence of HGV infection was not different between HD and CAPD patients, and HGV infections did not seem to be associated with clinically significant hepatitis. The routes of HGV transmission, other than transfusion or contamination during HD procedure, were suspected.

Female↗

PubMed1998

Interleukin-1 beta, -6 and interferon-gamma productions in patients undergoing continuous ambulatory peritoneal dialysis.

In order to investigate cytokine productions in patients undergoing continuous ambulatory peritoneal dialysis (CAPD), we studied the production of interleukin (IL)-1 beta, -6 and interferon (IFN)-gamma by cultured peripheral blood mononuclear cells (PBMC) in peritonitis-free CAPD patients. The correlation of cytokine production with plasma parathyroid hormone (PTH) and albumin levels was also evaluated. While the release of IL-1 beta was not markedly different from controls release of IL-6 from 24-hour cultured PBMCs was significantly greater than that of controls, (Mean +/- S.D., IL-6: 2186.8 +/- 1217.9 pg/ml, vs 1516.3 +/- 767.9, p < 0.05). The addition of lipopolysaccharide (LPS, 10 micrograms/ml, significantly stimulated IL-1 beta and -6 production of PBMCs in CAPD patients and controls, compared to an unstimulated condition. The LPS-induced IL-1 beta production was also not markedly different from controls, whereas LPS-induced IL-6 production was significantly higher than controls (IL-6: 13,220.7 +/- 7177.4 vs 7411.4 +/- 1236.9, p < 0.05). However, the percentage increases of IL-6 production stimulated with LPS in CAPD patients were not significantly different from controls (p > 0.05). No difference of baseline IFN-gamma was detected between CAPD patients controls, but phytohemagglutinin (PHA, 10 micrograms/ml)-stimulated IFN-gamma release was significantly higher in CAPD patients than controls (2425.9 +/- 1565.0 pg/ml vs 1364.0 +/- 755.1, p < 0.05). There was no significant correlation between PTH and, IL-1 beta, serum albumin level and LPS-stimulated IL-6 production (r = 0.54, p < 0.05). In conclusion, CAPD seems to partly induce activation of PBMCs with an enhanced release of IL-6 and IFN-gamma, and CAPD patients with higher serum albumin levels tend to show higher IL-6 production in immune response.

Adult↗

PubMed1998

HIV prevention among Asian and Pacific Islander American men who have sex with men: a critical review of theoretical models and directions for future research.

Nationally, the incidence of AIDS is increasing at a higher rate among Asian and Pacific Islander American men who have sex with men (API MSM) than among white MSM. Furthermore, current HIV prevention efforts are inadequate to slow the rapidly rising HIV epidemic in the gay API community, and little attention has been paid to the applicability of existing behavior change models to APIMSM. This paper reviews the five major models of health behavior change used in HIV prevention for the MSM population: the health belief model, theory of reasoned action, social learning theory, diffusion theory, and the AIDS risk reduction model. Although some of these models have been useful in designing risk reduction programs for API MSM, recent empirical data suggest that the models do not adequately address environmental influences affecting API MSM and limit our choices in prevention strategies to the level of the individual. We propose an ecological model for health promotion as a potentially useful theoretical framework, and suggest prevention strategies directed at the individual, the family, the general API community, and the mainstream gay community to reduce HIV risk among API MSM.

Asian↗

PubMed1997

Tetracycline-mediated suppression of gene expression with a new dicistronic retroviral vector.

Since the first description of the helper-free retrovirus vector by Mann et al. (1983), many improvements have been introduced to the system to increase titer, or to achieve better expression of the transduced genes in cells of different lineage. The typical form of recombinant retrovirus vector utilizes its 5' long terminal repeat (LTR) as a promoter unit for the transcription of the inserted gene(s), which allows only the constitutive expression of the inserted gene(s) in target cells. Although constitutive expression of the delivered gene(s) in target cells may be sufficient for some purposes, controlled expression of gene(s) in target cells or tissues would be favorable in many basic and clinical applications. To circumvent these problems, we developed a new retroviral vector that allows controlled expression of the inserted genes. With these new retroviral vectors, the expression level of the inserted genes can be controlled up to 200-fold in the presence of a minimum amount of tetracycline. We think these new retroviral vectors will be useful in regulating the expression of the genes delivered in vivo.

3T3 Cells↗

PubMed1997

Structure and expression of the AWI 31 gene specifically induced by wounding in Arabidopsis thaliana.

Differential screening of an Arabidopsis cDNA library constructed from the plant tissues harvested 1 h after wounding resulted in the isolation of wound-inducible cDNA clones (Kim et al., 1994). The cDNA clones could be broadly classified into two groups according to the expression time of their transcripts. Nine clones from the 10 different wound-inducible cDNAs were rapidly induced, reaching a maximum level in approximately 1-1.5 h and then were progressively reduced after wounding. The cDNA clone AWI 31 showed steady accumulation of the transcripts and reached the maximum value at a later time point of 2.5 h and then started to decline. The corresponding gene of the AWI 31 in which the coding region was interrupted by an intron, had an open reading frame that predicted a protein of 386 amino acids. However, the gene product did not show any significant homology to other known proteins in the database. Northern hybridization study using the cDNA probe revealed that the gene was not regulated by other environmental stresses such as drought, high salt, low temperature, or a DPE herbicide treatment, indicating that the cDNA clone AWI 31 was specifically induced by wounding.

Amino Acid Sequence↗

PubMed1997

Overexpression of arylsulfate sulfotransferase as fusion protein with glutathione S-transferase.

A procedure has been developed for the overexpression and purification of milligram quantities of the Klebsiella K-36 arylsulfate sulfotransferase (ASST). The structural gene was amplified by means of a polymerase chain reaction (PCR) technique and inserted into the plasmid vector pGEX-3X. The plasmid pGEX-100, carrying the Klebsiella K-36 astA structural gene under the control of the Escherichia coli tac promoter, was transformed into the E. coli strain BL21 (DE3). The ASST was produced in E. coli as a fusion with glutathione S-transferase. Conditions for protein production, isolation on glutathione Sepharose 4B, and Xa cleavage to generate active ASST were developed. The purification yielded approximately 0.7 mg of pure enzyme per liter of bacterial culture. Kinetic analysis of the overexpressed enzyme indicated that it had kinetic properties almost the same as those of the enzyme purified from Klebsiella K-36 cells. The purification procedure was very rapid and is suitable for obtaining considerable amounts of enzyme at a relatively high yield compared with its purifying method from the culture of the Klebsiella K-36 strain.

Amino Acid Sequence↗

PubMed1997

MRI of mesenchymal chondrosarcoma of the orbit: case report and review of the literature.

Extraskeletal mesenchymal chondrosarcoma is a relatively uncommon entity, an orbital location being extremely rare. A review of the literature revealed 16 reported cases of primary orbital mesenchymal chondrosarcoma demonstrated by plain film and CT. To the best of our knowledge, the MRI features of orbital extraskeletal mesenchymal chondrosarcoma have not been previously reported. We present the case of an 18-year-old man with a 2-year history of progressive proptosis of the right eye who underwent CT, dynamic CT, MRI without and with gadolinium enhancement, and magnetic resonance angiography of the orbits. CT of orbital mesenchymal chondrosarcoma demonstrates a well-defined mass with multiple areas of fine and coarse calcification and shows moderate contrast enhancement. The noncalcified portions of the mass demonstrate signal intensity lower than or equal to gray matter on T1-weighted images and are isointense to the gray matter on T2-weighted images. Dynamic CT reveals delayed contrast enhancement. MRI has proven to be a valuable diagnostic tool in the diagnosis and differentiation of well-defined intraorbital masses. By a combination of CT and MRI, it appears mesenchymal chondrosarcoma can be differentiated from other intraorbital lesions, such as cavernous hemangioma, hemangiopericytoma, orbital amyloidosis and fibrous histiocytoma.

Adolescent↗

PubMed1997

Isolation and characterization of a genomic clone for the gene of an insect molting enzyme, chitinase.

Genomic clones for a chitinolytic enzyme were isolated from a library of Sau 3A digested DNA from the tobacco hornworm, Manduca sexta, using a previously isolated chitinase cDNA clone as a probe [Kramer et al., Insect Biochem. Molec. Biol. 23, 691-701 (1993)]. Restriction enzyme mapping and Southern blot analysis of four genomic clones suggested that these are overlapping clones. Sequence analysis of the genomic clones and Southern blot analysis of total genomic DNA also suggest that the M. sexta genome has only one chitinase gene detectable by the cDNA probe. This gene is organized into at least 11 exons in a region spanning > 11 kb. The sequenced M. sexta chitinase gene has a series of exons corresponding to identifiable structural/functional regions of the protein. Similarities in structure and organization between the M. sexta chitinase gene and chitinase genes from other sources are described.

Amino Acid Sequence↗

PubMed1997

In-vitro and in-vivo activities of DW-116, a new fluoroquinolone.

DW-116 is a novel fluoroquinolone that was two- to four-fold more active than rufloxacin and less active than sparfloxacin, ciprofloxacin and ofloxacin against Gram-positive bacteria in vitro. Against Gram-positive and Gram-negative bacteria, the in-vivo activity of DW-116 was similar or slightly greater than that of rufloxacin and less than that of sparfloxacin, ciprofloxacin and ofloxacin. ED50 (50% effective dose) values for DW-116 did not correlate with in-vitro MICs.

Animals↗

PubMed1997

The effect of anti-hypertensive drugs on DNA synthesis and proliferation of cultured rat aortic smooth muscle cells.

The aim of this study was to elucidate the effects of anti-hypertensive drugs, nifedipine, furosemide, hydrochlorothiazide, captopril, and atenolol on DNA synthesis and proliferation of cultured rat aortic smooth muscle cells induced by fetal calf serum. Aortic smooth muscle cells from Sprague-Dawley rats were isolated, cultured, and seeded in multi-well plates. When confluent, cells were cultured in a conditioned medium without fetal calf serum. After 72 hours, cells were cultured in the medium retaining 10% fetal calf serum with or without anti-hypertensive drugs by increasing the concentration between 10(-8) and 10(-4) M. DNA synthesis was assessed by [3H]-thymidine uptake and proliferation by cell numbers using a hemocytometer. Nifedipine at a concentration of 10(-5) M and 5 x 10(-5) M inhibited serum-induced DNA synthesis significantly by 50.8% and 86.6%, respectively (p < 0.05). The results of cell numbers paralleled those of 3H-thymidine incorporation. Serum-induced DNA synthesis was also reduced by 32.6% at the highest dose of furosemide (10(-4) M), but there was no statistical significance. Hydrochlorothiazide, captopril, and atenolol did not show anti-proliferative effect throughout any of the doses. In conclusion, among the various anti-hypertensive drugs, nifedipine seems to be most beneficial in view of its direct inhibitory effect on DNA synthesis and proliferation of smooth muscle cells, as well as for its anti-hypertensive effect.

Animals↗

PubMed1997

Blunt traumatic rupture of the diaphragm: sonographic diagnosis.

Ultrasonographic features of seven patients with diaphragmatic rupture due to blunt trauma were analyzed. The ruptures occurred at the left hemidiaphragm in four patients and at the right in three. Direct ultrasonographic findings were as follows: disrupted diaphragm in four patients; nonvisualized diaphragm in three patients; floating diaphragm in two patients; and herniation of the liver or bowel loops through the diaphragmatic defect in three patients. Indirect sonographic findings included pleural effusion or subphrenic fluid collection in five patients and splenic laceration in one. Although the number of patients was limited, ultrasonography was very useful for the diagnosis of diaphragmatic rupture.

Adult↗

PubMed1997

Impact of metabolic acidosis on serum albumin and other nutritional parameters in long-term CAPD patients.

To evaluate the effects of metabolic acidosis on serum albumin and other nutritional parameters in long-term continuous ambulatory peritoneal dialysis (CAPD) patients, we undertook a retrospective study involving 106 CAPD patients who had monthly biochemical measurements and urea kinetic studies every 6 months for more than 2 years. The patients were divided into three groups according to their mean total CO2 (tCO2) level of the 2-year follow-up (Group I: mean tCO2 < 22 mmol/L; Group II: 22 mmol/L < or = tCO2 < 26 mmol/L; Group III: mean tCO2 > or = 26 mmol/L), and the clinical, biochemical, and urea kinetic data were compared between the three groups. The mean tCO2 in Groups I, II, and III were 20.62 +/- 1.2 mmol/L, 23.91 +/- 1.1 mmol/L, and 27.3 +/- 0.8 mmol/L, respectively. The percentage of body weight (Bwt) to ideal body weight (IBW) was significantly higher in Group I (113.1 +/- 15.3%) compared to Group II (103.5 +/- 11.5%) and Group III (98.7 +/- 8.0%) (p < 0.05), but the percentage of lean body mass (LBM) to Bwt was not different between the three groups. Compared to Group III, Group I had significantly higher blood urea nitrogen (BUN) (61.1 +/- 14.3 vs 46.1 +/- 7.2 mg/dL, p < 0.05), serum albumin (4.04 +/- 0.31 vs 3.75 +/- 0.39 g/dL, p < 0.05), and normalized protein equivalent to nitrogen appearance (NPNA) (1.02 +/- 0.21 vs 0.88 +/- 0.14 g/kg/day, p < 0.05), and more ultrafiltration volume (1.4 +/- 0.4 vs 1.0 +/- 0.3 L/day, p < 0.05), in spite of comparable dialysis dose and albumin loss into the dialysate. No differences were observed in the three groups in the changes of tCO2, Bwt/IBW, LBM/Bwt, BUN, and albumin from the baseline values after the 2-year follow-up. Using stepwise multiple regression analysis, NPNA, Bwt/IBW, and ultrafiltration volume were independent factors affecting mean tCO2 level. In conclusion, low tCO2 levels in long-term CAPD patients may reflect increased protein intake, and the mild to moderate degrees of metabolic acidosis may not affect the nutritional status of well-dialyzed CAPD patients.

Acidosis↗

PubMed1997

Extremely low awareness of AIDS, sexually transmitted diseases and condoms among Dai ethnic villagers in Yunnan province, China.

OBJECTIVE: To assess the awareness of AIDS, other sexually transmitted diseases (STDs), condoms, sources of health information and HIV-related societal risks among Dai villagers in southern Yunnan Province, China. SUBJECTS AND METHODS: In November-December 1994, a cross-sectional descriptive study, comprising a questionnaire-based survey and focus group discussions, was conducted in three Dai villages in Mengla county; a total of 177 Dai villagers were interviewed in the survey and eight focus group discussions were held. Ethnographic observations provided a composite picture of HIV risks in the area. RESULTS: Only 18% of respondents had heard of AIDS, and only 25 and 28%, respectively, had heard of STDs or condoms. Furthermore, among these more aware groups, the level of knowledge was low and misconceptions were common. An ability to understand the official language (Mandarin) was the most important predictor of awareness of AIDS, other STDs or condoms. The sources of information in the three Dai villages sampled included TV, videos, radio and magazines, but only TV and videos had a large audience. Even so, these media were mostly in Mandarin and were not used in AIDS education. Travel outside of China was frequent; most villagers (77%) had traveled to Laos and 9% had traveled to Thailand. Societal risks of HIV transmission, such as an increasing incidence of STDs and an active sex industry, were observed in this area. CONCLUSIONS: Dai villagers in southern Yunnan Province had an extremely low awareness and knowledge of AIDS, other STDs and condoms. Given the high mobility of ethnic villagers to neighboring countries in Southeast Asia and the societal risks of HIV transmission in this area, there is an urgent need to provide accessible education about AIDS and other STDs. Suggestions regarding such health education and the implications of HIV policy-making are discussed.

Acquired Immunodeficiency Syndrome↗