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Biomedical subjects

H M Choi

Publications and source records attributed to H M Choi.

9 recordsLinked to original sources
PubMed2002

Visualization of bubble-fluid interaction by a moving object flow image analyzer system.

This paper deals with interaction between a bubble and fluid around it, visualized by a moving object flow image analyzer (MOFIA) consisting of a three-dimensional (3D) moving object image analyzer (MOIA) and two-dimensional particle image velocimetry (PIV). The experiments were carried out for rising bubbles of various sizes and shapes in stagnant water in a vertical pipe. In the MOFIA employed, 3D-MOIA was used to measure bubble motion and PIV to measure fluid flow. The 3D position and shape of a bubble and the velocity field were measured simultaneously. The experimental results showed that the interaction was characterized by the shape, size and density of a bubble. Concretely, they showed the characteristics of bubble motion, wake shedding, and flow field.

Journal Article↗
PubMed2001

Transcriptional repression of type I procollagen genes during adipocyte differentiation.

Adipocyte differentiation is a very complex process in which whole-cell changes are accompanied. Among them, type I procollagen gene has been shown to specifically decrease during adipocyte differentiation; however, little is known about the molecular mechanism. To examine how type I procollagen gene expression is regulated at the level of transcription during adipocyte differentiation, 3T3-L1 preadipocyte cell line was used as an in vitro model. Northern blot analysis demonstrated that mRNA expression of type I procollagen gene was dramatically reduced during adipocyte differentiation. Time-course analysis indicated that decrease in mRNA expression occurred at early stage of differentiation. Studies on several stable cell lines showed that transcriptional activities of both alpha1 and alpha2 promoters decreased significantly during adipocyte differentiation. Despite extensive deletion-promoter analyses, however, we could not identify the cis-element responsible for the switch-off of type I procollagen gene during adipocyte differentiation, suggesting that the transcriptional repression of this gene occur through general transcription machinery rather than a specific cis-element. In conclusion, down-regulation of type I procollagen mRNA expression during adipocyte differentiation is due to repression of its promoter activity through general transcription machinery.

3T3 Cells↗
PubMed2001

Quantitative analysis of apical root resorption by means of digital subtraction radiography.

OBJECTIVE: This study was performed to assess the diagnostic and quantifying ability of digital subtraction images for simulated apical root resorption, as well as to compare the diagnostic accuracy of conventional intraoral radiographs with digital subtraction images for this condition. STUDY DESIGN: Digital and intraoral radiographs of 10 sound maxillary central incisors and those with simulated apical root resorption were taken with varying horizontal and vertical angulations of the x-ray beam. Paired t tests were used to compare the lengths of the sound teeth on the images with their actual lengths, and the estimated amount of simulated apical root resorption was compared with the actual amount of tooth loss by means of Emago software. The diagnostic accuracy for detecting lesions was also evaluated on conventional intraoral radiographs and digital subtraction images through receiver operating characteristic (ROC) analysis. RESULTS: There were no statistically significant differences between the actual lengths and those measured on the reconstructed images of the sound teeth. The calculated amounts of apical root resorption showed no statistically significant differences in comparison with the actual amounts (P >.05). The diagnostic accuracy of the conventional intraoral radiographs in detecting the lesions was low (ROC area = 0.6446). CONCLUSION: A quantitative analysis of small amounts of apical root resorption can be performed by means of digital subtraction radiography.

Humans↗
PubMed2001

Quantitative analysis of normal major salivary glands using computed tomography.

OBJECTIVES: We sought to calculate the size and the computed tomography (CT) number of normal parotid and submandibular glands and to evaluate their relationship with respect to sex, age, and obesity in the Korean population. STUDY DESIGN: The authors investigated the axial CT images of 42 healthy volunteers. The maximum cross-sectional area (MCSA) was used as an indicator of the size of the gland. Three regions of interest on axial scans were selected to calculate the mean CT number. RESULTS: There was a significant decrease in the mean MCSA of the submandibular gland and the CT number of both glands with age. The MCSA of the submandibular gland in males was larger than that in females. There was a close correlation between the parotid and the submandibular glands with respect to the CT number, as well as between the left and right glands with respect to the MCSA and the CT number. The body mass index was positively correlated with the MCSA of the parotid gland, whereas the body mass indexes and the CT numbers of both glands were negatively correlated. CONCLUSIONS: Both age and obesity are closely correlated with the size and the CT number of the major salivary glands. Moreover, the correlation between the CT numbers of the parotid and the submandibular glands may be used for diagnostic purposes.

Adult↗
PubMed2000

Clinical significance of early diastolic notch depth: uterine artery Doppler velocimetry in the third trimester.

OBJECTIVE: Our purpose was to evaluate the usefulness of early diastolic notch depth in predicting adverse perinatal outcome. STUDY DESIGN: Uterine artery Doppler velocimetry is widely applied in predicting pregnancy outcomes. Recent studies of uterine artery early diastolic notch have demonstrated its usefulness as a marker for fetal well-being. The early diastolic notch represents the reflected blood flow of uteroplacental circulation. This study was carried out under the hypothesis that when early diastolic notch is present evaluating its depth plays a significant role in predicting poor pregnancy outcomes. Its ability to predict adverse perinatal outcomes was evaluated in 198 pregnant women with early diastolic notch after 28 weeks' gestation. RESULTS: The incidence of adverse perinatal outcome (5-minute Apgar score <7, cesarean delivery because of fetal distress, admission to neonatal intensive care unit, fetal growth restriction, or perinatal death) was 90.5% when the notch index was </=0.70. When the notch index range was 0.70 to 0.79, 0.80 to 0.89, and >/=0.90, the respective incidences were 72.3%, 46. 9%, and 28.1%. CONCLUSION: This study suggests that evaluating notch depth in the presence of early diastolic notch on uterine artery velocimetry during the third trimester would be a useful method for predicting adverse perinatal outcomes.

Apgar Score↗
PubMed1996

Combined cis-platinum and alpha interferon therapy of advanced hepatocellular carcinoma.

To evaluate the clinical efficacy of alpha-interferon(IFN-alpha) plus cis-platinum in hepatocellular carcinoma(HCC). 56 inoperable patients with HCC were divided into IFN-alpha plus cis-platinum treated group (n = 30) and no antitumor therapy group (n = 26). The survival of IFN-alpha plus cis-platinum treated patients was significantly better than that of patients who received no antitumor therapy (p = 0.001). Median survival time was 33 weeks and 14.0 weeks, respectively. The cumulative estimated survival rates of our IFN-alpha plus cis-platinum treated group (93.5% at 3mo, 75.0% at 6mo) were for longer than that of the no antitumor therapy group (84.6% at 3mo, 57.7% at 6mo). Objective tumor regression, greater than 50% was observed in 13.3% (4 of 30) of patients receiving IFN-alpha plus cis-platinum. By the univariate analysis, the absence of portal vein thrombus (p < 0.05), alkaline phosphatase lesser than 280 U/L (p = 0.001), total bilirubin less than 2.0 mg% (p < 0.05), serum triglyceride less than 155 mg/dl (p < 0.05) were shown to be the factors most significantly favoring a better survival. By the multivariate analysis, using Cox proportional hazards model, IFN-alpha plus cis-platinum treated group (p = 0.0001), alkaline phosphatase less than 280 mg/dl (p = 0.005), the absence of portal vein thrombus (p = 0.020) were independent favorable prognostic factors. We conclude that IFN-alpha plus cis-platinum is useful in patients with inoperable HCC and the above favorable prognostic factors may also be useful in the design and analysis of future clinical trials of systemic chemotherapy for HCC.

Adult↗
PubMed1993

Oil sorption behavior of various sorbents studied by sorption capacity measurement and environmental scanning electron microscopy.

Oil sorption capacities of various natural and man-made fibrous sorbents were compared in a simulated seawater bath containing oil. Natural sorbents such as milkweed, kapok, cotton, and wool showed higher sorption capacities than man-made sorbents such as polyester, polypropylene, viscose rayon, nylon 6, nylon 66, and acetate. Sorption capacities of the natural sorbents were over 30 g oil/g fiber. No definite advantages were observed using man-made bicomponent and biconstituent fibers over regular man-made fibers with respect to their sorption capacity. Analyses of sorption mechanisms using an environmental scanning electron microscope revealed that an oil deposit disappeared from the fiber surface after a certain time interval in milkweed, kapok, and cotton. This suggested that the sorption of oil in these fibers occurred through capillary action, probably due to their hollow lumens. Contrarily, adsorption, a surface phenomenon, would be the most prominent mechanism for oil sorption of wool fibers due to large amounts of surface wax, irregular scaly surfaces, and crimp. Effects of both adsorption and absorption were shown in the oil sorption of man-made fibers, depending upon the type and shape of the sorbent. Dumbbell-like oil deposits were seen on the fiber surface in certain oleophilic man-made fibers, because of a partial wetting of oil on the fiber surface. For some hydrophilic man-made fibers such as polyvinylalcohol and copolymer of isobutylene-maleic anhydride, the physical configuration of the fiber was a decisive factor in determining oil sorpton capacity of the sorbents.

Capillary Action↗
PubMed1986

Cutaneous metastatic adenocarcinoma of stomach--nodular and inflammatory carcinoma.

A 65-year-old male patient presented multiple cutaneous nodules on trunk and an erythematous inflammatory lesion resembling erysipelas on left side of neck. Result of skin biopsies disclosed groups of metastatic adenocarcinoma cells in the dermis, subcutaneous tissue, and lumina of the lymphatic vessels. Histopathologic examination of the stomach, along with the gastroscope, established that the cutaneous metastasis was of stomach origin.

Adenocarcinoma↗