Biomedical subjects

J H Woo

Publications and source records attributed to J H Woo.

At least 19 recordsLinked to original sources

PubMed2006

Magnocellular and parvocellular visual pathways have different blood oxygen level-dependent signal time courses in human primary visual cortex.

PURPOSE: The magnocellular and parvocellular pathways (M and P pathways) are the major pathways of the visual system, with distinct histologic and physiologic properties that may also have different metabolic characteristics. We hypothesize that the differences of the 2 visual pathways would also manifest as differences in the signal time course of blood oxygen level-dependent functional MR imaging (BOLD fMRI). The differences in BOLD signal time course may provide insight into the metabolic requirements of the 2 pathways. METHODS: Eleven fMRI sessions on 6 subjects were performed using stimuli that preferentially activated the 2 pathways. Regions commonly activated by both the M and P stimuli in the primary visual cortex (V1) were determined, and the contrast elicited by the stimulus, time-to-peak (TTP), and the full width at half maximum (FWHM) of the BOLD signal time course were measured. RESULTS: The functional stimuli activated cortical regions described previously in the literature, such as V1, V4, and V5. Within V1, the TTP of the signal time course of the 2 stimuli were statistically different, with the P stimulus generating TTPs that were on average 12% faster than the M stimulus (P = .0037). CONCLUSION: We have demonstrated the ability to functionally differentiate the M and P stimuli in a commonly activated anatomic region. Because the BOLD response is dependent on the ratio of oxyhemoglobin and deoxyhemoglobin in the blood, the difference in the BOLD time course between the 2 stimuli suggests that the oxygen demand of the 2 pathways may be different.

Brain Mapping↗

PubMed2005

A study on the treatment of antifouling paint waste from shipyard.

A study on the treatment of antifouling paint waste from shipyards, including sandblast waste and ship hull washing wastewater, was performed. The sandblast waste could be effectively detoxified by heat treatment, and the efficiency was affected by the temperature of the heating vessel and treatment time. The removal efficiency of total organotin compounds from the sandblast waste was over 99% at 1000 degrees C and treatment for 1 h. For the treatment of ship hull washing wastewater by the solvent extraction, ship diesel was a good solvent for the tributyltin (TBT) extraction, and the proper amount of solvent was about 10 mL for TBT extraction from 1L of wastewater. The extraction efficiency of TBT was significantly affected by the agitation intensity. The TBT in the wash wastewater was rapidly extracted within 1 h. The level of the TBT residual in the wastewater extracted for 1h was 2.8 microg L(-1), and this was further decreased to 0.8 after 5 h extraction.

Gasoline↗

PubMed2003

Resistance to extended-spectrum cephalosporins and mortality in patients with Citrobacter freundii bacteremia.

BACKGROUND: This study was performed to characterize the clinical features and to identify the risk factors for resistance to extended-spectrum cephalosporins (ESCs) and for mortality in patients with Citrobacter freundii bacteremia. PATIENTS AND METHODS: 105 patients (aged > or = 15 years) with C. freundii bacteremia in 1991-2000 were retrospectively analyzed. RESULTS: Nosocomial acquisition was identified in 78.1% of the patients. Hepatic, biliary and pancreatic disease was the most common underlying disease (65.7%) and the biliary tract was the most common site of infection (50.5%). The overall resistance rate to ESCs was 59.0% and was significantly associated with hepatic, biliary and pancreatic disease, recent surgery and procedure, biliary drainage catheter and previous antibiotic therapy in univariate analysis. However, only previous antibiotic therapy with ESCs (OR = 5.0, 95% CI 1.6-15.7, p = 0.006) and recent surgery or procedure (OR = 3.1, 95% CI 1.1-8.4, p = 0.03) were strong, independent risk factors in multivariate analysis. Mortality directly related to C. freundii bacteremia was 21.9% and there was no difference between cases with resistance and susceptibility to ESCs (19.4% vs 25.6%; p = 0.45). Mortality was significantly associated with rapidly fatal or ultimately fatal underlying disease, a solid tumor, septic shock and polymicrobial bacteremia in univariate analysis. Among patients who had therapeutic surgical procedures, mortality was lower (4.5%, p = 0.04). Multivariate analysis revealed rapidly or ultimately fatal disease, septic shock and polymicrobial bacteremia as independent prognostic factors. CONCLUSION: Biliary infection was the leading cause of C. freundii bacteremia. Previous antibiotic therapy, especially with ESCs, frequently predisposed for resistance to these antibiotics. However, resistance to ESCs was not associated with increased mortality.

Adolescent↗

PubMed2002

Retrospective analysis of clinical and microbiological aspects of Klebsiella oxytoca bacteremia over a 10-year period.

From 1991 to 2000, 125 sporadic cases of Klebsiella oxytoca bacteremia were analyzed retrospectively to review clinical features and to identify the risk factors associated with resistance to extended-spectrum cephalosporins and fatal outcome. Bacteremia was acquired nosocomially in 52% of the patients. Almost all patients (97%) had an underlying disease, with biliary and pancreatic disease occurring most frequently (55%). The biliary tract was the most common site of infection (44%). Resistance to extended-spectrum cephalosporins was identified in 22 of the 125 (18%) Klebsiella oxytoca blood isolates and resistance to ciprofloxacin in 9 (7%). Only previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia ( P=0.009). The mortality rate was 24% and was higher in patients infected with isolates resistant to extended-spectrum cephalosporins (41% vs. 20%; P=0.04). In multivariate analysis, fatal outcome was independently associated with septic shock, deteriorated mental status, polymicrobial bacteremia, and solid tumor. Surgical therapy had a protective effect (OR, 0.06; 95% CI, 0.005-0.7; P=0.03). In conclusion, Klebsiella oxytoca bacteremia was most commonly associated with biliary tract infection. Previous antibiotic therapy was strongly associated with resistance to extended-spectrum cephalosporins in patients with Klebsiella oxytoca bacteremia.

Adolescent↗

PubMed2002

Risk factors for penicillin resistance and mortality in Korean adults with Streptococcus pneumoniae bacteremia.

A retrospective analysis was performed to measure the incidence of pneumococcal bacteremia and to identify risk factors for penicillin resistance and prognostic factors for outcome in adults. A total of 151 cases of pneumococcal bacteremia were identified from 149 adults during the period 1996-2000. The overall rate of penicillin resistance was 49%, ranging from 54.2% in 1996 to 48.5% in 2000 (P=0.93). Rates of resistance to ceftriaxone, clindamycin, erythromycin, and trimethoprim-sulfamethoxazole were 21.6%, 51%, 62%, and 44.7%, respectively. Multidrug resistance was documented in 47.7% of the cases. Penicillin resistance was significantly associated with solid tumor, biliary drainage catheter, and previous beta-lactam therapy in the univariate analysis. However, the associations were not as significant as independent risk factors in the multivariate analysis. Mortality was 23.8% and did not change significantly during the study period (P=0.06). Mortality rates in cases caused by penicillin-susceptible Streptococcus pneumoniae and penicillin-resistant Streptococcus pneumoniae were 23% and 24.7%, respectively (P=0.81). Mortality was not significantly influenced by penicillin resistance, even high-level resistance (24.4% vs. 20%; P=0.64). Multivariate analysis revealed that antineoplastic chemotherapy, respiratory failure, and acute renal failure were independent prognostic factors for mortality. In conclusion, the rate of penicillin resistance among pneumococcal blood isolates was high in the late 1990s, but penicillin resistance, and even high-level penicillin resistance, was not significantly associated with increased mortality in adults with pneumococcal bacteremia.

Adolescent↗

PubMed2001

Immune response induced by immunization with Hepatitis B virus core DNA isolated from chronic active hepatitis patients.

There are many mutations in the gene encoding Hepatitis B virus (HBV) core antigen of chronic active hepatitis patients, and such mutations are most likely to be related to the severity of disease. Here, we constructed plasmids containing wild-type and deletion type of HBV core gene (HBc) to develop an experimental DNA vaccine and to compare immunogenicity of two types of HBc vaccine. Twenty-nine wild-types and seven deletion types of HBc were detected in sera of 32 Korean patients with chronic active hepatitis. Four wild-types (W1, W2, W4, W6) and two deletion types (D3, D4) of HBc were cloned into the pcDNA3 vector. Intramuscular immunization with wild-type HBc efficiently increased serum anti-HBc antibody response in a dose-dependent manner. Anti-HBc antibody response in mice injected with W6 increased 14 days after immunization, and peaked after 30 days and was maintained at least up to 50 days. W6 immunization induced a specific cytotoxic T lymphocyte response to W6-transfected 3LL (3LL-W6), and reduced the sizes of tumor mass of mice challenged with 3LL-W6 or 3LL transfected with D4. However, intramuscular immunization with D3 and D4 did not show antibody response at all. D3 and D4 have 157 bp (from 331 to 491 bp) and 122 bp (from 327 to 448 bp) gene deletion, respectively, and these encode class II MHC-restricted T-cell epitope. Altogether, these results suggest that mutant virus that has deleted HBc gene may evade immune systems due to loss of T-cell epitope.

Animals↗

PubMed2001

Group B streptococcal bacteremia in nonpregnant adults with hepatic disease in Korea.

Sixty-seven cases of group B streptococcal bacteremia in adults were retrospectively reviewed during the period 1991-2000. Not one case occurred in pregnant women. The mean age of the patients was 57 years, and 67.2% were men. Of the 67 cases of illness, 25.4% were hospital acquired and 11.9% were polymicrobial. Common predisposing diseases included hepatic disease (55.2%), diabetes mellitus (28.4%), malignancy (20.9%), and cardiovascular diseases (17.9%). Primary bacteremia, peritonitis, bone and joint infections, and skin and soft tissue infections accounted for most presentations. Peritonitis was a more common presentation in patients with hepatic disease (P<0.001), whereas skin and soft tissue infection was more common in patients with non-hepatic disease (P=0.008). More patients with hepatic disease had polymicrobial bacteremia than did patients with nonhepatic disease (P=0.018). Death occurred in 9.8% of cases, and mortality did not differ between patients with hepatic disease and those with nonhepatic disease. Hepatic disease was found to be an important predisposing condition in adults with group B streptococcal bacteremia. However, mortality for patients with hepatic disease was similar to that for patients with nonhepatic disease.

Adult↗

PubMed2001

Bcl-2 overexpression attenuates resveratrol-induced apoptosis in U937 cells by inhibition of caspase-3 activity.

Resveratrol has been shown to induce anti-proliferation and apoptosis of human cancer cell lines. In the present study, we determined the effect of high intracellular levels of the anti-apoptosis protein Bcl-2 on caspase-3 activation, PLC-gamma1 degradation and cytochrome c release during resveratrol-induced apoptosis. For this, we used U937/vector and U937/Bcl-2 cells, which were generated by transfection of the cDNA of the Bcl-2 gene. As compared with U937/vector, U937/Bcl-2 cells exhibited a 4-fold greater expression of Bcl-2. Treatment with 60 or 100 microM resveratrol for 24 h produced morphological features of apoptosis and DNA fragmentation in U937/vector cells, respectively. This was associated with caspase-3 activation and PLC-gamma1 degradation. In contrast, resveratrol-induced caspase-3 activation and PLC-gamma1 degradation and apoptosis were significantly inhibited in U937/Bcl-2 cells. Bcl-2 overexpressing cells exhibited less cytochrome c release and sustained expression levels of the IAP proteins during resveratrol-induced apoptosis. In addition, these findings indicate that Bcl-2 inhibits resveratrol-induced apoptosis by a mechanism that interferes with cytochrome c release and activity of caspase-3 that is involved in the execution of apoptosis.

Apoptosis↗

PubMed2001

Improved binding of a bivalent single-chain immunotoxin results in increased efficacy for in vivo T-cell depletion.

Anti-CD3 immunotoxins exhibit considerable promise for the induction of transplantation tolerance in pre-clinical large animal models. Recently an anti-human anti-CD3epsilon single-chain immunotoxin based on truncated diphtheria toxin has been described that can be expressed in CHO cells that have been mutated to diphtheria toxin resistance. After the two toxin glycosylation sites were removed, the bioactivity of the expressed immunotoxin was nearly equal to that of the chemically conjugated immunotoxin. This immunotoxin, A-dmDT390-sFv, contains diphtheria toxin to residue 390 at the N-terminus followed by VL and VH domains of antibody UCHT1 linked by a (G(4)S)(3) spacer (sFv). Surprisingly, we now report that this immunotoxin is severely compromised in its binding affinity toward CD3(+) cells as compared with the intact parental UCHT1 antibody, the UCHT1 Fab fragment or the engineered UCHT1 sFv domain alone. Binding was increased 7-fold by adding an additional identical sFv domain to the immunotoxin generating a divalent construct, A-dmDT390-bisFv (G(4)S). In vitro potency increased 10-fold over the chemically conjugated immunotoxin, UCHT1-CRM9 and the monovalent A-dmDT390-sFv. The in vivo potency of the genetically engineered immunotoxins was assayed in the transgenic heterozygote mouse, tgepsilon 600, in which the T-cells express human CD3epsilon as well as murine CD3epsilon. T-cell depletion in the spleen and lymph node observed with the divalent construct was increased 9- and 34-fold, respectively, compared with the monovalent construct. The additional sFv domain appears partially to compensate for steric hindrance of immunotoxin binding due to the large N-terminal toxin domain.

Animals↗

PubMed2001

Systems analysis of functional magnetic resonance imaging data using a physiologic model of venous oxygenation.

The authors revisit a simple mathematical model, presented in previous work, that characterizes the response of cerebral venous oxygenation to changes in blood flow and oxygen consumption. This physiologically based model can qualitatively duplicate the results of several recent empirical studies in which other authors have tested the hypothesis of linearity in the functional magnetic resonance imaging (fMRI) response to task activation, in that the experimentally found nearly linear behavior of the system and also its subtle departures from linearity are both predicted by simulations of the model. The model is simple enough that its equations can be explicitly solved. Moreover, an amended model that incorporates a varying cerebral blood volume parameter is found to have similar if not better consistency with the empirical data; indeed, this "extended" model is shown to be solvable by the same differential equation as the authors' simple one, wherein the volume is fixed as a constant. These investigations lend further indirect support to the blood oxygen level-dependent hypothesis of venous deoxyhemoglobin as the primary mechanism for fMRI signal changes during task activation, as well as for the authors' simple system as a useful physiologic model thereof. Although the authors' mathematical model does not formally represent a linear system with respect to the flow input, its underlying linear character may help partially explain the "nearly" linear behavior of the fMRI response.

Blood Flow Velocity↗

PubMed2001

A case of disseminated Trichosporon beigelii infection in a patient with myelodysplastic syndrome after chemotherapy.

Trichosporonosis is a potentially life-threatening infection with Trichosporon beigelii, the causative agent of white piedra. The systemic infection by this fungus has been most frequently described in immunocompromised hosts with neutropenia. Here, we report the first patient with disseminated infection by T. beigelii in Korea, acquired during a period of severe neutropenia after chemo-therapy for myelodysplastic syndrome. The patient recovered from the infection after an early-intensified treatment with amphotericin B and a rapid neutrophil recovery. The disseminated infection by T. beigelii is still rare, however, is an emerging fatal mycosis in immunocompromised patients with severe neutropenia.

Adult↗

PubMed2000

Retinoic acid and its geometrical isomers block both growth and fusion of L6 myoblasts by modulating the expression of protein kinase A.

All-trans retinoic acid (RA) and its geometrical isomers, such as 9-cis RA, 13-cis RA, and 9,13-di-cis RA, strongly inhibited both growth and fusion of L6 myoblasts. However, illumination of white light diminished their inhibitory activity on membrane fusion with little effect on cell growth. During myogenic differentiation, the intracellular level of cAMP decreased whereas the total activity of protein kinase A as well as the protein level of its regulatory subunit Ialpha (RIalpha) and catalytic subunit (Calpha) increased. RAs raised the intracellular level of cAMP by over 3-fold, but decreased the total activity of protein kinase A. Like RAs, dibutyryl-cAMP inhibited myoblast fusion and reduced the expression of both RIalpha and Calpha subunits. These results suggest that RAs negatively modulate the differentiation of L6 myoblasts by increasing the intracellular level of cAMP, which may in turn down-regulate the expression of protein kinase A and hence its activity.

Animals↗

PubMed2000

Expression of an anti-CD3 single-chain immunotoxin with a truncated diphtheria toxin in a mutant CHO cell line.

ADP-ribosylating immunotoxins are generally expressed in Escherichia coli and then refolded in vitro. Because the efficiency of the in vitro refolding process decreases with the number of protein domains and internal disulfide bonds, these immunotoxins have been generally limited to single-chain monovalent structures. We now show that using the hamster cell line CHO K1 RE1.22c (J. M. Moehring and T. J. Moehring, 1979, Somat. Cell Genet. 5, 453-468) that has been mutated to ADP-ribosylation insensitivity, a level of 4 microg/ml of a truncated anti-T cell immunotoxin, DT390-scFvUCHT1, can be secreted into the medium. This immunotoxin is glycosylated at the two potential N-linked glycosylation sites in the toxin moiety: positions 16-18 in the A chain and residues 235-237 in the B chain. The glycosylated immunotoxin is relatively nontoxic (IC(50) 4.8 x 10(-10) M). Removal of the N-linked oligosaccharides by N-glycosidase F treatment or mutations at the two N-linked glycosylation sites results in a highly active immunotoxin with an IC(50) of 4 x 10(-12) M toward CD3(+) Jurkat cells. This is a 12-fold increase in toxicity over the same immunotoxin harvested from E. coli periplasm without refolding. A single Asn(235) Ala mutation that removed the B chain glycosylation was nearly as toxic as the double mutant. This suggests that B chain glycosylation is the major cause for the loss of toxicity.

Animals↗

PubMed2000

Multi-organ failure caused by reactivated coccidioidomycosis without dissemination in a patient with renal transplantation.

OBJECTIVE: The acute respiratory failure caused by pulmonary coccidioidomycosis without dissemination is an extremely unusual event. CASE REPORT: We report a 47-year-old renal transplanted man with a reactivated pulmonary coccidioidomycosis, whose clinical course presented as fulminant respiratory failure, disseminated intravascular coagulation and profound hypotension mimicking bacterial pneumonia and septic shock. Lung biopsy showed conglomerated necrotizing granulomas containing many spherules filled with endospores of Coccidioides immitis. CONCLUSION: Coccidioidomycosis should be included in the differential diagnosis of acute sepsis, particularly in an immunocompromised host who has travelled in an endemic area.

Coccidioidomycosis↗

PubMed2000

Vancomycin-intermediate Staphylococcus aureus in Korea.

Recent reports on some methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin have been a major concern in Korea because of the widespread use of vancomycin due to a high prevalence of MRSA in the country. We describe a 45-year-old man with long-standing pelvic abscess due to MRSA. In spite of vancomycin and teicoplanin treatment for a long period of time, the patient died from MRSA sepsis. The blood culture isolate of MRSA exhibited reduced susceptibility to vancomycin (MIC, 8 microg/ml). This is the first report of a vancomycin-intermediate S. aureus case from Korea.

Abdominal Abscess↗

PubMed2000

Hepatic and small bowel mucormycosis after chemotherapy in a patient with acute lymphocytic leukemia.

Mucormycosis is a rare but invasive opportunistic fungal infection with increased frequency during chemotherapy-induced neutropenia. The clinical infections due to Mucor include rhinocerebral, pulmonary, cutaneous, gastrointestinal and disseminated diseases. The first two are the most common diseases and all entities are associated with a high mortality rate. Still hepatic involvement of Mucor is rarely reported. We experienced a case of hepatic and small bowel mucormycosis in a 56-year-old woman after induction chemotherapy for B-cell acute lymphocytic leukemia. Initial symptoms were a high fever unresponsive to broad spectrum antibiotics and pain in the left lower abdominal quadrant. It was followed by septic shock, deterioration of icterus and progressively elevated transaminase. An abdominal CT demonstrated multiple hypodense lesions with distinct margins in both lobes of liver and pericolic infiltration at small bowel and ascending colon. Diagnosis was confirmed by biopsy of the liver. The histopathology of the liver showed hyphae with the right-angle branching, typical of mucormycosis. The patient was managed with amphotericin B and operative correction of the perforated part of the small bowel was performed. However, the patient expired due to progressive hepatic failure despite corrective surgery and long-term amphotericin B therapy.

Female↗

PubMed1999

The correction of MR images distortion with phantom studies.

In the field of Image Guided surgery, Geometrical accuracy of images acquired from CT and MR is an essential prerequisite for good registration process. In this paper, we present the experiment with MR phantom. We visualize the distortion of MR images in 3-D shape and modify it by surface fitting algorithm using the control Point.

Algorithms↗

PubMed1997

Isolation of the Bacillus subtilis cdd downstream region and analysis of genetic structure around the cdd vicinity.

A 310 bp EcoRI/HindIII fragment downstream of the Bacillus subtilis cdd gene was isolated from pSO52 which harbours the cdd gene and its vicinity, and was inserted into the pDIA5304. The hybrid vector pSO701 was integrated into the targeted locus of the B. subtilis chromosome and the cdd downstream region was rescued by furthermost BamHI walking toward the sigA locus. By sequencing and analyzing the intergenic region between the cdd and p23-dnaG-sigA operon from the selected clone pSO702, the era genes encoding glycyl tRNA synthetase alpha and beta chains with two unknown distal genes at both terminals were identified and mapped. The cdd was separated by 6,964 bp from the p23-dnaG-sigA operon. Combined data with an additional analysis of the cdd upstream from the sequenced 280 kb stretch in GenBank database (accession No. D84432) indicates that the revised gene order like hrcA-grpE-dnaK-dnaJ-phoH-dgk-cdd-era-tRNA( gly) synthetase alpha and beta-p23-dnaG-sigA-cccA with unidentified distal genes was established genetically on a counter clockwise orientation at 225 degrees of the linkage map.

Bacillus subtilis↗