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Biomedical subjects

Y W Choi

Publications and source records attributed to Y W Choi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Subaortic left innominate vein: radiologic findings and consideration of embryogenesis.

To propose a hypothesis about the embryogenesis of the subaortic left innominate vein, the authors reviewed the radiologic features of 14 patients diagnosed with subaortic left innominate vein made by computed tomography or magnetic resonance imaging scan. The authors retrospectively analyzed the level of the aortic arch, associated aortic arch anomalies, and the presence or absence of obliteration of the prevascular space. A high aortic arch was seen in 10 patients, five with a cervical, two with a right and, one with a double aortic arch. The prevascular space was occupied by the aortic arch, the great arteries, or both in all 10 patients with a high arch. In the remaining four patients with a normal aortic arch, the prevascular space was preserved, but abnormal elongation of the aortic segment between the left common carotid artery and the left subclavian artery was seen in three. The authors postulate that precardinal anastomosis can develop in any pathway where there is the available space. In the presence of abnormal elongation of the aortic arch and resultant widening of the subaortic space, the chance of the development of a subaortic left innominate vein increases.

Adult↗
PubMed1999

Mucormycosis of the central airways: CT findings in three patients.

Computed tomographic (CT) findings are described in three diabetic patients with central airways mucormycosis. The CT findings of the tracheobronchial mucormycosis include enhancing areas of mural thickening (n = 3), luminal narrowing (n = 3), intramural air (n = 3), low-attenuation nonenhancing bronchial wall thickening (n = 2), and bronchonodal fistula formation (n = 1). These CT features in a diabetic patient should raise a high index of suspicion for tracheobronchial mucormycosis, particularly when typical radiographic features of pulmonary tuberculosis are absent.

Aged↗
PubMed1999

Comparative enzymatic hydrolysis of phytate in various animal feedstuff with two different phytases.

Bacillus amyloliquefaciens DS11 phytase (DS11 phytase) and Aspergillus ficuum phytase (AF phytase) activities were investigated by measuring the release of phosphate from phytate in animal feedstuff such as wheat bran, corn meal, soybean meal and rice flour at pH 5 and 7. In all the tested feedstuff, the enzymatic activity of DS11 phytase was more active at pH 7, but that of AF phytase was more active at pH 5. From these results, the phytate in the gastrointestinal tract could be degraded in the small intestine or stomach by DS11 or AF phytase, respectively. In conclusion, the results presented in this paper indicated that different combination ratios of DS11 and AF phytase, depending on the kind of feedstuff, might effectively induce more enzymatic activity both in the stomach and small intestine in terms of the pH of the gastrointestinal tract.

6-Phytase↗
PubMed1998

Stable lipiodolized emulsions for hepatoma targeting and treatment by transcatheter arterial chemoembolization.

We attempted to develop lipiodolized emulsions that remain in the tumour for a long period, release drug in a sustained release pattern, and thus improve the conventional treatment of hepatocellular carcinoma (HCC) [1]. Polyoxyethylene derivatives of hydrogenated castor oil (HCO) were the most suitable emulsifiers in stabilizing emulsions containing Lipiodol as an oil phase. The length of ethylene oxide coupled to HCO rather than the hydrophilic-lipophilic balance (HLB) values was an important factor in preparing stable emulsions and in achieving sustained-release characteristics. When distilled water was replaced with Iopamiro, a heavy water soluble contrast medium with a specific gravity of 1.335, more stable lipiodolized emulsions with longer sustained release behaviour could be prepared with smaller amount of HCO. To study the in vivo stability of the w/o Lipiodol emulsion and the sustained-release characteristics of doxorubicin from the emulsion, the pharmacokinetic study was performed with normal dogs using transcatheter arterial chemoembolization technique. The area under the plasma concentration-time curve for the first eight hours (AUC0-8) and AUCtotal values of the stabilized emulsion were three to four times higher than those of the coarse emulsion prepared lacking HCO 60. From the in vitro and in vivo studies, Lipiodol based water in oil emulsion with HCO 60 containing doxorubicin showed higher stability and released doxorubicin in a sustained fashion.

Animals↗
PubMed1998

Programmed removal of chondrocytes during endochondral fracture healing.

This investigation tested the hypothesis that the removal of chondrocytes during endochondral fracture healing involves an ordered process of programmed cell death. To accomplish this, unilateral closed fractures were created in the femora of 36 Sprague-Dawley rats. The rats were killed in groups of four on days 1, 3, 7, 14, 21, 28, 42, 49, and 56 after fracture. The femora were embedded in paraffin and tested for expression of specific markers of fragmented DNA with use of a terminal deoxyuridyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) technique. To determine the potential for transdifferentiation of chondrocytes to osteoblasts, calluses were also hybridized to detect expression of osteocalcin mRNA. Cell proliferation was assessed by an immunohistochemical detection method for proliferating cell nuclear antigen. A separate group of four rats was killed on day 28 to represent the later stage of the endochondral ossification, and the calluses were examined for cellular morphology with transmission electron microscopy. The results showed a coordination in both time and space of the activities of cellular proliferation and programmed cell death. Cell proliferation was most active in the earlier phases of fracture healing (days 1 through 14), although TUNEL expression was apparent in hypertrophic chondrocytes on day 14 after fracture and persisted until day 28. In the later stages of fracture healing (days 14 through 28), proliferating cell nuclear antigen was no longer synthesized in hard callus (intramembranous bone) and cell removal was the dominant activity in soft callus chondrocytes. Expression of osteocalcin mRNA was detected in osteoblasts but not in hypertrophic chondrocytes or in any other nonosteoblastic cell type. These findings support the hypothesis that the removal of chondrocytes during endochondral fracture healing is part of an ordered transition of tissue types in which the cellular mechanisms are genetically programmed to involve proliferation, maturation, and apoptotic cell death.

Animals↗
PubMed1996

Thin-section CT findings of the lungs: experimentally induced bronchial and pulmonary artery obstruction in pigs.

OBJECTIVE: The purpose of this study was to investigate whether a mosaic pattern of lung attenuation, or lobular low attenuation, is revealed on CT imaging after induction of bronchial and pulmonary artery obstruction in pigs. MATERIALS AND METHODS: Eight anesthetized and ventilated pigs, four for bronchial obstruction and four for pulmonary artery obstruction, were examined with thin-section CT. Bronchial obstruction was induced at the subsegmental level using 2- to 3-mm radiopaque silicon spheres at 14 sites. Pulmonary artery obstruction was induced at 11 sites by dislodging 2- to 3-mm silicon spheres at the level of the superior vena cava. CT scans were obtained at end expiration immediately after the obstruction in all pigs (n = 8) and after 1 day (n = 3), 3 days (n = 5), 7 days (n = 4), 14 days (n = 4), and 28 days (n = 3). RESULTS: Of the 14 sites of bronchial obstruction, six sites (43%) on the immediate scans showed a lobular distribution of low attenuation distal to the spheres, which changed to atelectasis, consolidation, or normal on follow-up CT. Of the four sites that did not show changes in lung attenuation on immediate CT scans, two sites showed lobular low attenuation after 1 day. The mean attenuation value +/- SD for the lobular low attenuation was -737 H +/- 122 and that of the adjacent lung was -522 H +/- 53 (p = .0077). None of the pulmonary artery obstruction sites showed visible change in lung attenuation, and mean attenuation values for obstructed sites and unobstructed sites did not show significant differences when scanned as many as 28 days after the immediate scans. CONCLUSION: Lobular low attenuation on thin-section CT was induced by bronchial obstruction, but we found no change in lung attenuation due to obstruction of the pulmonary arteries as many as 28 days after the immediate scans.

Animals↗
PubMed1995

Sonography of the costal cartilage: normal anatomy and preliminary clinical application.

Costal cartilages of 10 controls and 12 patients with Tietze's syndrome (n = 6), deformed (exaggerated bowing) cartilage (n = 4), focal enlargement (n = 1), and cancer-invaded cartilage (n = 1) were examined with ultrasonography. In controls, ultrasonography detected 237 of 240 costal cartilages (98.8%) and 58 of 105 intercartilage connections (55%) with three variations. Correlation with CT was available in 7 patients (1 Tietze's syndrome, 4 deformities, 1 cartilage enlargement, and 1 cancer) among 8 patients whose CT results were known to the sonographer. Sonography showed normal (n = 4) or marginally blurred (n = 2) cartilages in 6 Tietze's syndromes. Ultrasonography is a promising technique in the examination of costal cartilages.

Adolescent↗
PubMed1995

Thoracic manifestations of Behçet syndrome: radiographic and CT findings in nine patients.

PURPOSE: To evaluate the radiographic and computed tomographic (CT) findings of patients with thoracic Behçet syndrome. MATERIALS AND METHODS: Chest radiographs and CT scans of nine patients with thoracic Behçet syndrome were retrospectively reviewed. Findings were compared. RESULTS: Radiographs of the nine patients showed mediastinal widening in five (56%), air-space consolidation in five (56%), and lung mass in three (33%). CT scans of the nine patients showed that mediastinal widening was due to thrombosis in four (44%) or narrowing of the superior vena cava in one [11%], which caused mediastinal edema; that air-space consolidation (seen on both radiographs and CT scans) was due to pulmonary hemorrhage or infarction in five (56%); and that lung mass was due to aneurysm of the right or left pulmonary artery in three (33%). In addition, CT scans showed hyperinflation in one patient. CONCLUSION: Chest radiographic findings of thoracic Behçet syndrome are variable and nonspecific. CT can be helpful in the assessment of the syndrome by showing thrombosis of the superior vena cava and characteristic aneurysms of the pulmonary arteries.

Adolescent↗
PubMed1993

The liposome partitioning system for correlating biological activities of imidazolidine derivatives.

The partitioning of 10 imidazolidines in various liposome/buffer systems (logK'm) has been determined and compared to partitioning in the n-octanol/buffer system (logP'). The logK'm, which was generally greater than the logP', increased or decreased upon the addition of dicetylphosphate (DCP) or stearylamine (STA), respectively, to dimyristoylphosphatidylcholine (DMPC) liposomes. Quantitative correlations of alpha 2-adrenergic potencies of imidazolidines have been made by regression analyses with logP', logK'm, binding affinity, and intrinsic activity. Both central and peripheral potencies correlated with logK'm but not with logP'. Multiple regressions yielded improved predictable quantification of these potencies. Thus, the liposomal membrane system shows certain advantages over the n-octanol/buffer system for the prediction of biological activities of the imidazolidines.

1-Octanol↗
PubMed1991

A method for production of antibodies to human T-cell receptor beta-chain variable regions.

Mouse T-cell hybridomas bearing human V beta elements were produced by transfection of human/mouse hybrid T-cell receptor beta-chain genes into a mouse T-cell hybridoma lacking an endogenous beta-chain gene. These hybridomas were entirely mouse in origin except for the human V beta region. These cells were used to immunize mice against human V beta elements. Mouse monoclonal antibodies have thus been generated against human V beta 13.1 and -13.2. We expect that the method outlined in this paper will be useful in the production of monoclonal antibodies specific for other human V beta or V alpha elements.

Animals↗
PubMed1991

Characterization of distribution behavior of 2-imidazolines into multilamellar liposomes.

The distribution of 2-imidazolines in neutral dimyristoylphosphatidylcholine (DMPC) liposomes, in negatively charged liposomes containing dicetylphosphate (DCP) or phosphatidylserine (PS), and in positively charged liposomes containing stearylamine (STA), has been investigated. Electrophoretic mobilities of multilamellar liposomes have also been measured as a function of drug concentration. Apparent equilibrium partition coefficients (log K'm) increased as a function of the DCP or PS concentration in DMPC liposomes whereas log K'm decreased with STA concentration, except for lofexidine and clonidine. Similarly, the electrokinetic parameters increased in DMPC liposomes that exhibited a small, positive surface charge, decreased in DMPC/cholesterol/DCP (7:1:2 mole ratio) liposomes, and increased in DMPC/STA (3:1 mole ratio) liposomes, except for clonidine which showed a decrease, as a function of the 2-imidazoline concentration. Surface potential change (delta psi o) due to drug inclusion in the liposomes obtained from theoretical considerations exhibited a positive linear relationship with log K'm. Values of delta psi o were greater but less sensitive to log K'm in negatively charged than in neutral or positively charged liposomes at 1 mM drug concentration. Likewise, surface charge densities varied in the same order as the surface potentials as a function of log K'm of the 2-imidazolines, except for clonidine and lofexidine. These data indicate the relative importance of the membrane surface characteristics on the partitioning behavior, and also possibly the membrane transport behavior, of the 2-imidazoline drugs.

Amines↗
PubMed1990

Residues of the variable region of the T-cell-receptor beta-chain that interact with S. aureus toxin superantigens.

The alpha beta T-cell antigen receptor (TCR) recognizes antigenic peptides in the context of self major histocompatibility complex (MHC) molecules. The specificity of recognition of MHC plus antigen is generally determined by a combination of the variable elements of alpha- and beta-chains of the TCR. Several types of antigen, however, have been identified that, when bound to MHC molecules, stimulate T cells bearing particular variable-region beta-chain (V beta) elements irrespective of the other variable components of the TCR. These have been termed 'superantigens', and here we are concerned with one type of superantigen, the toxins produced by Staphylococcus aureus. T cells have been found that bear closely related members of the same V beta family but respond differently to S. aureus toxins; in particular, cells bearing the human V beta 13.2 element respond to toxin SEC2, whereas cells bearing human V beta 13.1 do not. We have now defined the residues of the V beta element responsible for this difference, and find that they reside in a region thought to lie on the side of the TCR molecule, away from the conventional antigen/MHC-binding site. The evolutionary conservation of this site may be due to its having an important role in some function of the TCR other than the binding of conventional antigen plus MHC.

Amino Acid Sequence↗
PubMed1990

The liposome as a model membrane in correlations of partitioning with alpha-adrenoceptor agonist activities.

The apparent partition coefficients of a group of imidazoline alpha-adrenoceptor agonists in liposome/buffer systems (K'm) and in the n-octanol/buffer system (P') have been compared in quantitative structure-activity relationships (QSAR) employing biological activities and receptor binding affinities. A parabolic relationship between log K'm and log P' was found, and log K'm was greater than log P' for all liposome compositions. In liposomes, log K'm decreased in the order, negatively charged greater than neutral greater than positively charged. Overall, hyper- and hypotensive activities of these drugs correlated better with log K'm than with log P'; however, poor correlations were obtained between partition coefficients and in vitro binding affinities. Linear correlations of log K'm with hypotensive activities were obtained with negatively charged liposomes, whereas correlations with hypertensive activities were obtained using positively charged liposomes. Multiple regressions of biological activities with binding affinities showed positive correlations with hypotensive but not hypertensive activities with or without the inclusion of log K'm or log P'. Thus, the liposome represents a more selective model membrane system than a bulk oil phase for predicting the biological activities of imidazoline alpha-adrenoceptor agonists.

1-Octanol↗
PubMed1990

Solubilization of liposomes by weak electrolyte drugs. I. Propranolol.

The solubilization of dimyristoylphosphatidylcholine (DMPC) liposomes by a weak electrolyte drug, propranolol (PPL) hydrochloride, has been studied as a function of pH, [PPL], [DMPC], and temperature. The solubilization of liposomes at 40 degrees C by 0.2 mM PPL occurred at different rates from 2.9 to 14.4 mM DMPC but converged at complete solubilization after 13 hr at pH 12.0. At the same [PPL], solubilization was complete after 18 days at pH 11.0, but incomplete solubilization occurred at pH 10.0 and not at all at lower pH's. In 14.4 mM DMPC liposomes, solubilization was gradual and proportional to the [PPL] from 0.001 to 0.10 mM up to 95 hr, then rapid thereafter. The [PPL] at which the solubilization efficiency began to increase rapidly was determined to be 0.078 mM. The rate of solubilization was also influenced by the fluidity of the bilayers, a sevenfold increase in the time for complete solubilization being observed upon cooling from 40 to 20 degrees C. Surface tension (st) data confirmed a low critical micelle concentration (CMC) and continued decrease in the st above the CMC. It is concluded that the critical ratio of PPL to DMPC for solubilization occurs in localized regions of the bilayers, with total solubilization at different rates depending on the [PPL] and the physical properties of the liposomes. The processes may be used advantageously to prepare small vesicles or to extract lipids or proteins, more efficiently than detergents, from biological membranes.

Dimyristoylphosphatidylcholine↗
PubMed1988

Requirement for the simian virus 40 small tumor antigen in tumorigenesis in transgenic mice.

To examine the role of simian virus 40 (SV40) large T and small t antigens in tumorigenesis in animals, we generated transgenic mice which expressed either both the SV40 large T and small t antigens or the SV40 large T antigen alone under the control of the mouse mammary tumor virus long terminal repeat. The mouse mammary tumor virus long terminal repeat directs the expression of transgenes in ductal epithelial cells of several organs, including the mammary gland, lung, and kidney, and in lymphoid cells. The mice which expressed both the T and t tumor antigens developed lung and kidney adenocarcinomas, while those which expressed large T alone did not. Both types of mice developed malignant lymphomas with similar frequencies and latency periods. Our results show that the SV40 small t antigen cooperates with the large T antigen in inducing tumors in slowly dividing epithelial cells in the lung and kidney.

Animals↗
PubMed1987

The mouse mammary tumor virus long terminal repeat directs expression in epithelial and lymphoid cells of different tissues in transgenic mice.

A series of transgenic mice was developed that contained the simian virus 40 early region genes under the transcriptional control of the mouse mammary tumor virus long terminal repeat, including the promoter and glucocorticoid response elements. These mice all expressed the transgene in the epithelial cells of a number of different organs, such as lungs, kidneys, and prostate, salivary, and mammary glands, and in Leydig and lymphoid cells. Transcription of the chimeric gene was inducible by glucocorticoids, either after transfection into tissue culture cells or in cells cultured from animals carrying the transgene. Many, but not all, tissues which expressed the simian virus 40 sequences, as determined immunologically and by RNA analysis, developed into tumors, although they showed premalignant features. Since the mouse mammary tumor virus long terminal repeat is expressed in a number of different cell types when inherited through the germ line, the lactating mammary gland-specific transcription of endogenous proviruses must require other factors or sequences to achieve this specificity.

Animals↗