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Biomedical subjects

J Choi

Publications and source records attributed to J Choi.

At least 235 records · Page 13Linked to original sources
PubMed1985

Long-term follow-up of concomitant band ligation and sclerotherapy for internal hemorrhoids.

From 1978 to 1983, 111 patients with symptomatic internal hemorrhoids were treated as outpatients by a modification of the Barron ligation technique. Each ligated hemorrhoid was injected with a sclerosant. Follow-up, available for 94 of the patients, ranged from 2 to 60 months (mean 18 months). Presenting symptoms were bleeding in 75 (80%) of the 94 patients, pain in 46 (49%), pruritus in 22 (23%) and prolapse in 24 (26%). Results were excellent in 51 (54%) patients, good in 20 (21%) and fair in 9 (10%). Fourteen (15%) patients had unsatisfactory results; only 4 of these required hemorrhoidectomy. The other 10 had residual symptoms but did not require further treatment. Nine patients had minor complications, which included pain lasting 24 to 72 hours in seven, bleeding in one and syncope in one. The addition of sclerotherapy to traditional band ligation for the management of internal hemorrhoids has the advantages of exciting a greater inflammatory reaction between the mucosa and submucosa and preventing premature slipping of the band. The authors conclude that this method of therapy is effective for symptomatic hemorrhoids and that surgical hemorrhoidectomy is seldom indicated.

Adult↗
PubMed1984

DNA elimination in Tetrahymena: a developmental process involving extensive breakage and rejoining of DNA at defined sites.

Elimination of specific DNA sequences occurs during macronuclear development in the ciliate Tetrahymena thermophila. Recombinant DNA clones containing a segment of micronuclear (germinal) DNA involved in elimination and the corresponding segment of macronuclear (somatic) DNA produced after elimination were isolated. Detailed comparisons of the cloned DNAs, as well as the genomic DNAs, by hybridization indicated that DNA elimination is accompanied by specific DNA rearrangements. In this 9.5 kb region three defined DNA segments are deleted and the remaining sequences are linked together as one contiguous piece in the macronucleus. Specific DNA rearrangement of this kind occurs widely in the genome. Analysis of 20 randomly selected DNA clones suggests that there are more than 5000 such rearrangement sites in the genome. Thus specific breakage and rejoining of DNA occurs extensively during development, and might play an essential role in nuclear differentiation.

Animals↗
PubMed1983

Purification of protein methylase II from human erythrocytes.

Protein methylase II (S-adenosylmethionine:protein-carboxyl O-methyltransferase, EC. 2.1.1.24) which methyl esterifies free carboxyl groups of protein substrate using S-adenosyl-L-methionine as the methyl donor, has been purified from human erythrocytes approximately 13000-fold with a yield of 12%. The purified enzyme was over 95% pure as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A bulk of hemoglobin present in the erythrocyte lysate, which severely limited the use of affinity chromatography for purification, was effectively removed by ammonium sulfate precipitation and by the subsequent salt washing of the precipitates followed by molecular sieve chromatography on Sephadex G-75. This preparation can be further purified by affinity chromatography, in which S-adenosyl-L-homocysteine is covalently linked to Sepharose-4B, followed by Sephadex G-75 chromatography to yield an enzyme with an activity of 27000 pmol methyl group transferred/mg/min at 37 degrees C.

Chromatography, Affinity↗
PubMed1981

A mutant of Chinese hamster ovary cells resistant to alpha-methyl- and alpha-difluoromethylornithine.

We describe a mutant of Chinese hamster ovary cells which is resistant to elevated levels of alpha-methylornithine and alpha-difluoromethylornithine, reversible and enzyme-activated irreversible inhibitors, respectively, of the enzyme ornithine decarboxylase (ODC). The mutant cells have significantly elevated levels of enzyme activity compared to wild-type cells, but several of the physical parameters of the enzyme are completely normal: Michaelis-Menten parameter, Km, affinity for the analog, and half-life. The temporal regulation of this activity in synchronized cells is not perturbed, and the suppression of ODC activity by the addition of putrescine is still observed. Indirect experiments suggest increased concentrations of ODC mRNA in the mutant cells.

Animals↗
PubMed1981

Microsome-dependent methylation of erythrocyte proteins by dimethylnitrosamine.

The precarcinogen, N-[methyl-14C]dimethylnitrosamine, rat liver microsomes and NADPH were incubated in the presence of intact human erythrocytes. Uptake of radioactivity into erythrocytes was time-dependent and analysis of an acid hydrolysate of the erythrocyte proteins showed several radioactive peaks which were identified as 3-N-methyl- and 1-N-methyl-histidine, S-methyl-cysteine. Since no binding occurs in the absence of microsomes, the alkylating species from dimethylnitrosamine metabolism can clearly penetrate the erythrocyte plasma membrane.

Amino Acids↗
PubMedDate not supplied

Recent advances in polyhydroxyalkanoate production by bacterial fermentation: mini-review.

Poly(3-hydroxybutyrate) [P(3HB)] and other polyhydroxyalkanoates (PHAs) have been drawing much attention as biodegradable substitutes for conventional nondegradable plastics. For the economical production of P(3HB), various bacterial strains, either wild-type or recombinant, and new fermentation strategies were developed for the production of P(3HB) with high concentration and productivity. To reduce the cost of carbon substrate, several processes for P(3HB) production from cheap carbon sources were also developed. P(3HB) can now be produced to a content of 80% of cell dry weight with the productivity greater than 4 g/l per h. Fermentation strategy was also developed for the efficient production of medium chain length PHA by high cell density culture. With all these advances, P(3HB) and PHAs can be produced by bacterial fermentation at a cost (ca. $2/kg) similar to that of other biodegradable polymers under development.

Bacteria↗
PubMedDate not supplied

Role of computed tomographic arterial portography and intraoperative ultrasound in the evaluation of patients for resectability of hepatic lesions.

Computed tomographic arterial portography (CTAP) has been shown to be the most sensitive preoperative test for determining resectability of hepatic lesions but we have shown it to have low specificity. Intraoperative ultrasound (IOUS) evaluation of the liver has also been proposed as an accurate means of assessing resectability. We sought to compare the effectiveness of the two modalities. Fifty-six patients who had been deemed candidates for liver resection based on CTAP findings underwent systematic exploration, liver mobilization, and IOUS examination. Ultrasound findings were compared with results of CTAP. In 46 patients the IOUS findings were in complete agreement with those of CTAP. In 10 patients CTAP lesions could not be verified by IOUS and these patients did not undergo resection. Follow-up of these 10 patients revealed eight who did not have progression of malignancy at the CTAP-predicted site (CTAP false positive). Two patients did have progression at a CTAP-positive IOUS-negative site (IOUS false negative). Sensitivity for CTAP and IOUS was 100% and 96%, respectively. Specificity for IOUS was 100%. These findings demonstrate the high sensitivity of CTAP and the high sensitivity and specificity of IOUS. CTAP may "overcall" hepatic lesions but IOUS can correctly identify these false positives in most instances. Because CTAP is useful for determining which patients might benefit from surgical exploration, we conclude that the two modalities are complementary for the assessment of resectability of hepatic lesions. The false positive rate for CTAP implies that caution must be used when declining to operate on patients on the basis of this test.

Adult↗
PubMedDate not supplied

Molecular piracy of Kaposi's sarcoma associated herpesvirus.

Kaposi's Sarcoma associated Herpesvirus (KSHV) is the most recently discovered human tumor virus and is associated with the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and Multicentric Casttleman's disease. KSHV contains numerous open reading frames with striking homology to cellular genes. These viral gene products play a variety of roles in KSHV-associated pathogenesis by disrupting cellular signal transduction pathways, which include interferon-mediated anti-viral responses, cytokine-regulated cell growth, apoptosis, and cell cycle control. In this review, we will attempt to cover our understanding of how viral proteins deregulate cellular signaling pathways, which ultimately contribute to the conversion of normal cells to cancerous cells.

Animals↗
PubMedDate not supplied

Upregulated surface expression of intracellularly sequestered Igepsilon receptors (FcepsilonRII/CD23) following activation in human peripheral blood eosinophils.

We investigated the regulation, secretion, and surface expression of the low-affinity FcepsilonRII receptor (CD23) in eosinophils isolated from human blood using multiple monoclonal antibodies (mAbs) directed at different epitopes of human CD23. Substantial surface expression of CD23 was not demonstrated in the resting state. Mean fluorescence intensity (MFI) measured by flow cytometry was 7. 1 +/- 0.8 for 9P25 mAb (p = NS) and 15.7 +/- 3.8 for BU38 mAb (p <. 04) versus 5.3 +/- 1.0 for IgG1 isotype control Ab. By contrast, MFI using BU38 mAb was 154 +/- 18 for JY-B lymphocytes (p <.0001 versus eosinophils). Despite weak surface expression, eosinophil permeabilization demonstrated substantial intracellular expression of CD23; MFI was 33.6 +/- 5.2 for 9P25 mAb versus 4.4 +/- 0.43 for IgG control (p <.001). Western blot analysis using both positive and negative controls demonstrated immunological identity with CD23 on JY-B lymphocytes. Activation of eosinophils caused rapid translocation of CD23 to the surface membrane (160 +/- 33 MFI; p <. 005), which was maximal within 30 sec. Secretory CD23 was detected within the perfusate also at 30 sec and was fully reinternalized at 10 min. This is the first demonstration of the presence of intracellular CD23 in human eosinophils. Our data indicate that eosinophils rarely express CD23 on their surface but are capable of transient high-level expression and secretion with rapid reuptake of intracellular stores of CD23.

Cells, Cultured↗
PubMedDate not supplied

Production and characterization of monoclonal antibodies specific to atrazine group compounds: effects of coating ligand structure on the variation of sensitivity and specificity.

Hybridoma cells were prepared by immunizing mice with carboxylic derivatives of atrazine conjugate to bovine serum albumin. After the screening of culture supernatant of hybridomas, five cell lines producing monoclonal antibodies were established and 1.8-5.3 ml of ascitic fluid per mouse was obtained from each cell line. The protein A affinity purification yielded 0.35-0.65 mg per ml of ascitic fluid from each cell line. The characterization studies in terms of sensitivity and specificity indicate that MAb 2F9 and MAb 4B9 showed the best responses with atrazine and its group of ametryne and cyanazine, using microtiter plate coated with simazine derivative of 6-amino hexanoic acid; no cross-reactivity was shown with simazine and cyanuric chloride.

Animals↗
PubMedDate not supplied

A DBMS-based medical teleconferencing system.

This article presents the design of a medical teleconferencing system that is integrated with a multimedia patient database and incorporates easy-to-use tools and functions to effectively support collaborative work between physicians in remote locations. The design provides a virtual workspace that allows physicians to collectively view various kinds of patient data. By integrating the teleconferencing function into this workspace, physicians are able to conduct conferences using the same interface and have real-time access to the database during conference sessions. The authors have implemented a prototype based on this design. The prototype uses a high-speed network test bed and a manually created substitute for the integrated patient database.

Computer Graphics↗
PubMedDate not supplied

Doppler study on pulmonary venous flow in the human fetus.

OBJECTIVES: The fetal pulmonary circulation is different from the postnatal circulation: the flow is small. The arterial pressure is almost systemic, and the vascular resistance is high. Moreover, lungs are collapsed in the fetus. However, the pulmonary venous flow in the fetus has not been studied. The aims of this study were to look at flow patterns of pulmonary venous system in the fetus and to see whether there are any changes in Doppler parameters with fetal growth. METHODS: The pulmonary venous flow velocity was analyzed in 56 normal human fetuses. The fetal gestational age ranged from 17 to 37 weeks. Pulsed-Doppler echocardiography was used to investigate the right upper pulmonary vein in four-chamber view. After the pulmonary venous signal was obtained, by enlarging the sample size, the pulmonary arterial signal was superimposed for timing. Heart rate velocities at systolic peak (S), at diastolic peak (D), at nadir between S and D (O), and at nadir between D and the next S (X) and velocity-time integral were measured. RESULTS: The pulmonary venous signal showed basically continuous flow from pulmonary vein toward left atrium through all the cardiac cycles, and it had biphasic peaks: one during the systolic and the other during the diastolic phase. The systolic peak of pulmonary vein occurred slightly earlier or later than the systolic upstroke of pulmonary arterial waveforms. The systolic peak of pulmonary vein was higher than the diastolic peak in 45 out of 56 cases. Velocities of systolic and diastolic peaks and velocity-time integral of the pulmonary vein have significantly increased with fetal growth. CONCLUSIONS: In the fetus, the flow pattern of the pulmonary vein was similar to that of the postnatal pattern with the exception of absence of atrial reversal. Lower velocities may reflect a decreased pulmonary flow volume.

Blood Flow Velocity↗
PubMedDate not supplied

In vivo crypt surface hyperproliferation is decreased by butyrate and increased by deoxycholate in normal rat colon: associated in vivo effects on c-Fos and c-Jun expression.

BACKGROUND: Studies on colon carcinogenesis suggest that the short-chain fatty acid butyrate may be protective, whereas the secondary bile acid deoxycholate may promote tumor development. Crypt surface hyperproliferation is regarded as a biomarker of colon cancer risk and can be modulated in vitro by the differentiation inducer butyrate and the tumor promoter deoxycholate. We hypothesized that butyrate decreases and deoxycholate increases crypt surface proliferation in vivo and that these effects are mediated by changes in the expression of the protooncogenes c-Fos and c-Jun, which are known to regulate proliferation and differentiation. METHODS: Twenty-five adult Sprague-Dawley rats underwent colonic isolation and 24-hour intraluminal instillation of 10 mmol/L sodium chloride, 10 mmol/ L sodium butyrate, or 10 mmol/L sodium deoxycholate. Proliferation of the whole crypt and five crypt compartments from base to surface was assessed by proliferating cell nuclear antigen immunohistochemistry. The øh value, an index of "premalignant" hyperproliferation, was calculated as the ratio of labeled cells in the two surface compartments divided by the labeled cells in the entire crypt. Expression of c-Fos and c-Jun was evaluated by Western blot. RESULTS: Crypt surface proliferation and the øh value were significantly decreased by butyrate and increased by deoxycholate. Butyrate increased colonic expression of c-Jun, whereas deoxycholate significantly induced c-Fos. CONCLUSIONS: The in vivo effects on surface proliferation are consistent with a potential protective [corrected] role for butyrate and a promotive role for deoxycholate in colon carcinogenesis. The concurrently observed effects on colonic c-Jun and c-Fos expression represent a novel finding and suggest that direct or indirect modulation of protooncogene expression may be the mechanism by which these dietary byproducts regulate proliferation in vivo.

Animals↗
PubMedDate not supplied

Determination of fluoroquinolone residues in animal tissues using Escherichia coli as indicator organism.

Three strains of Escherichia coli (ATCC 128, 10536, and 25922) and one strain of Bacillus subtilis (ATCC 3491) were compared as indicator microorganisms in microbial inhibition tests for their ability to detect fluoroquinolone residues. E. coli strains 128 and 10536 were most susceptible to fluoroquinolone residues, with detection limits of 35-50 micrograms/kg for enrofloxacin. Of the 2 strains, E. coli 10536 was slightly less susceptible. Ciprofloxacin was detected consistently by E. coli 128 at 30 micrograms/kg. Other fluoroquinolone drugs of veterinary interest detected by E. coli 128 were sarafloxacin and difloxacin at 100-250 micrograms/kg concentration. E. coli 25922 yielded 100% sensitivity in detection of enrofloxacin only at the 250 micrograms/kg concentration, and ciprofloxacin and sarafloxacin at 200 micrograms/kg. B. subtilis detected only enrofloxacin 100% of the time at 250 micrograms/kg. The E. coli strains tested were insensitive to other antibacterials commonly used in animals, with the exception of ceftiofur which was detected by E. coli 128 and 10536 at 500 micrograms/kg. The B. subtilis strain was not effective in detecting the fluoroquinolone drugs, whereas the E. coli strains were selective for the fluoroquinolones. E. coli 128 was 100% effective in detecting enrofloxacin and ciprofloxacin in spiked diaphragm homogenate samples at 50 micrograms/kg. Of the microorganisms tested, E. coli strain ATCC 128 was highly suitable as an indicator microorganism in a microbial inhibition assay for selective detection of fluoroquinolone antibacterial residues in animal tissues.

Animals↗