Search PubMed⌕ Search

Biomedical subjects

Y M Lee

Publications and source records attributed to Y M Lee.

At least 19 recordsLinked to original sources
PubMed2003

Effect of 5-methoxypsoralen (5-MOP) on cell apoptosis and cell cycle in human hepatocellular carcinoma cell line.

The chemopreventive role of 5-methoxypsoralen (5-MOP) in the human hepatocellular carcinoma (HCC) cell line was investigated by studying the regulation of proliferation and apoptosis in HCC (J5) cells. Morphological analysis, cell viability assay, DNA analysis and cell-cycle analysis suggest that there are at least three modes of the suppressive effects shown by 5-MOP: (a) kills J5 cells directly; (b) induces apoptosis by arresting J5 cells at the G2/M phase in the cell cycle; (c) induces apoptosis through an independent pathway with cell-cycle arrest at 24-72 h of exposure. Further immunoblot analysis demonstrated that inhibition of cyclin B1 by 5-MOP may play an important role in G2/M arrest of J5 cells and provides an additional way to prevent cells from entering the M phase and undergoing apoptosis. 5-MOP therefore appears to exert its anticarcinogenic properties by cytotoxic effect, inducing apoptosis and inhibiting proliferation in the human hepatocellular carcinoma cell line.

5-Methoxypsoralen↗
PubMed2002

Prophylactic lamivudine prevents hepatitis B reactivation in chemotherapy patients.

BACKGROUND: Chronic hepatitis B virus carriers receiving chemotherapy develop a high hepatitis B virus reactivation rate (38-53%) with a high mortality (37-60%). Few studies have characterized the efficacy of lamivudine in the treatment of chemotherapy-induced hepatitis B virus reactivation. AIM: To determine whether lamivudine prophylaxis reduces chemotherapy-induced hepatitis B virus reactivation and mortality. METHODS: The medical records of all hepatitis B surface antigen-positive patients with malignancy treated with chemotherapy since 1995 at the National University Hospital of Singapore were identified, and divided into those who received lamivudine prophylaxis before chemotherapy (P) and those who did not (NP). The parameters examined included gender, age, malignancy type, steroid usage, number of chemotherapy courses and regimens, follow-up duration and hepatitis B virus status. The outcome measures were hepatitis B virus reactivation (abrupt rise of serum alanine aminotransferase to > 200 IU/L) and reactivation death. Patients with primary hepatoma or liver metastasis were excluded. RESULTS: Thirty-five patients were identified: 16 in the P group and 19 in the NP group. The baseline characteristics of the two groups were similar. Seven of the 19 patients in the NP group and none of the 16 patients in the P group developed reactivation (36.8% vs. 0%, P=0.009). Six of the seven patients in the NP group who developed reactivation received lamivudine at that time, but five died (mortality, 71.4%), whilst no patient in the P group died from reactivation (P=0.064). CONCLUSIONS: Prophylactic lamivudine appears to prevent hepatitis B virus reactivation and its associated mortality in patients treated with chemotherapy. This should be confirmed with prospective studies.

Adult↗
PubMed2002

Antithrombotic effect of PMC, a potent alpha-tocopherol analogue on platelet plug formation in vivo.

Platelet thrombi formation was induced by irradiation of mesenteric venules with filtered light in mice pretreated intravenously with fluorescein sodium. PMC (2, 2, 5, 7, 8-pentamethyl-6-hydroxychromane; 20 microg/g, i.v.) significantly prolonged the latent period of inducing platelet plug formation in mesenteric venules. When fluorescein sodium was given at 10 microg/kg, PMC (20 microg/g) delayed occlusion time by about 1.7-fold. Furthermore, aspirin (250 microg/g) also showed similar activity in delaying the occlusion time. On a molar basis, PMC was about 14-fold more potent than aspirin at delaying the occlusion time. PMC was also effective in reducing the mortality of ADP-induced acute pulmonary thromboembolism in mice when administered intravenously at doses of 5 and 10 microg/g. In addition, intravenous injection of PMC (5 microg/g) significantly prolonged bleeding time by about 1.6-fold compared with normal saline in severed mesenteric arteries of rats. Continuous infusion of PMC (1 microg/g/min) significantly increased the bleeding time by about 1.6-fold and the bleeding time was also significantly prolonged for up to 90 min after cessation of PMC infusion. These results suggest that PMC has an effective antiplatelet effect in vivo and may be a potential therapeutic agent for arterial thrombosis, but must be assessed further for toxicity.

Adenosine Diphosphate↗
PubMed2002

Diagnosing deep vein thrombosis in the lower extremity: correlation of clinical and duplex scan findings.

OBJECTIVE: To identify factors that predict a positive duplex scan examination result in patients with suspected deep vein thrombosis of the lower extremity. DESIGN: Retrospective study. SETTING: Vascular laboratory in a university teaching hospital. PATIENTS AND METHODS: The results of 345 lower extremity duplex venous scans performed between August 1994 and November 1998 were reviewed. All patients were in-patients referred from different specialties due to clinical suspicion of lower extremity deep vein thrombosis. Positive duplex scans were correlated with patients' demographic data (sex, age), medical history (history of malignancy, deep vein thrombosis, and pulmonary embolism) and clinical features (leg swelling, venous insufficiency, calf pain, and leg ulcer). Univariate analysis was performed using the Chi squared test. RESULTS: A total of 345 scans were performed for 313 patients. The mean age was 55 years (range, 19-92 years). Sixty-three patients (49 male, 14 female) had a positive scan, giving a yield of 18.3%. Four factors had a significant association with a positive scan: male sex (P=0.0102), history of malignancy (P=0.0040), history of deep vein thrombosis (P=0.0001), and history of pulmonary embolism (P=0.0265). CONCLUSIONS: Common presenting clinical features do not predict the result of ultrasonographic investigation for deep vein thrombosis. The chance of having a positive scan is significantly higher in male patients and those with a history of malignancy, deep vein thrombosis, or pulmonary embolism.

Adult↗
PubMed2001

Human kinesin superfamily member 4 is dominantly localized in the nuclear matrix and is associated with chromosomes during mitosis.

In a previous study, we identified the human counterpart of murine kinesin superfamily member 4 (KIF4), a microtubule-based motor protein [Oh, Hahn, Torrey, Shin, Choi, Lee, Morse and Kim (2000) Biochim. Biophys. Acta 1493, 219-224]. As an initial step to understand the function(s) of human KIF4, its subcellular localization in HeLa cells was examined by using immunocytochemical and subcellular fractionation methods, and it was found that most KIF4 is localized in the nucleus. Since murine KIF4 is known to transport cytoplasmic vesicles, dominant nuclear localization of the human counterpart was somewhat surprising. Subsequent subnuclear fractionation revealed predominant association of KIF4 with the nuclear matrix. These results clearly indicate that human KIF4 is, at least, a nuclear protein. In further confirmation of this conclusion, the hexapeptide PKLRRR (amino acids 773-778) in the molecule was found to function as a nuclear localization signal. During the mitotic phase of the cell cycle, human KIF4 was associated with the chromosomes, suggesting that human KIF4 might be a microtubule-based mitotic motor, with DNA as its cargo.

Adenocarcinoma↗
PubMed2001

The activation of PI 3-K and PKC zeta in PMA-induced differentiation of HL-60 cells.

The human myelocytic leukemia cell line HL-60 is a useful model for the study of cellular differentiation. Phorbol 12-myristate 13-acetate (PMA) induces the monocyte/macrophage-like differentiation of HL-60 cells and results in growth arrest, increasing adherence. In PMA-induced differentiation of HL-60 cells, phosphoinositide 3-kinase (PI 3-K) activity was measured as phosphatidylinositol3P recovery from phosphatidylinositol by in vitro kinase assay. PI 3-K activity was increased in HL-60 cells that were stimulated by 20 nM PMA and the activity was inhibited by pretreatment with 20 microM LY294002, a specific inhibitor of PI 3-K. Members of the protein kinase C (PKC) family have been suggested to be one of the downstream targets of PI 3-K. PKC zeta is one of the atypical PKCs, non-diacylglycerol-responsive PKCs, and the activity was measured by the ability of phosphorylation onto myelin basic protein. PMA also induced the activation of PKC zeta during monocytic differentiation of HL-60 cells, and LY294002-pretreated cells failed to induce PKC zeta activation. The activity of PI 3-K is essential for PKC zeta activation, and LY294002 blocks both monocytic differentiation of HL-60 cells and activation of PKC zeta during PMA-induced cell differentiation. This implies that activated PI 3-K subsequently stimulates the PKC zeta in the process of PMA-induced monocytic differentiation.

Cell Differentiation↗
PubMed2001

Locating the metal ion in calcium-binding proteins by using cerium(III) as a probe.

The detection and assignment of NMR spectroscopic signals of carbon atoms from carbonyl and carboxylate groups in the loop hosting the Ce(III) ion was performed for the cerium-substituted calcium-binding protein calbindin D9k. This provided a tool to characterize in solution the first coordination sphere of the metal ion. Due to the well-documented possibility of replacing calcium with metal ions of the Ln(III) series, this approach turns out to be extremely efficient for characterizing in solution the coordination of calcium ions in proteins, independently of the availability of X-ray crystal structures. The present approach completes the structural characterization of lanthanide-substituted calcium-binding proteins, for which the role of long-range constraints arising from hyperfine interaction and self-orientation has already been assessed.

Calbindins↗
PubMed2001

Magnolol reduces myocardial ischemia/reperfusion injury via neutrophil inhibition in rats.

The accumulation of oxygen-free radicals and activation of neutrophils are strongly implicated as important pathophysiological mechanisms mediating myocardial ischemia/reperfusion injury. It has been proven that various antioxidants have cardioprotective effects. Magnolol, an active component extracted from the Chinese medicinal herb Magnolia officinalis, possesses potent antioxidant and free radical scavenging activities. In this study, the cardioprotective activity of magnolol was evaluated in an open-chest anesthetized rat model of myocardial ischemia/reperfusion injury. The results demonstrated that pretreatment with magnolol (0.2 and 0.5 microg/kg, i.v. bolus) at 10 min before 45 min of left coronary artery occlusion, significantly suppressed the incidence of ventricular fibrillation and mortality when compared with the control group. Magnolol (0.2 and 0.5 microg/kg) also significantly reduced the total duration of ventricular tachycardia and ventricular fibrillation. After 1 h of reperfusion, pretreatment with magnolol (0.2 and 0.5 microg/kg) caused a significant reduction in infarct size. In addition, magnolol (0.2 microg/kg) significantly reduced superoxide anion production and myeloperoxidase activity, an index of neutrophil infiltration in the ischemic myocardium. In addition, pretreatment with magnolol (0.2 and 0.5 microg/kg) suppressed ventricular arrhythmias elicited by reperfusion following 5 min of ischemia. In vitro studies of magnolol (5, 20 and 50 microM) significantly suppressed N-formylmethionyl-leucyl-phenylalanine (fMLP; 25 nM)-activated human neutrophil migration in a concentration-dependent manner. It is concluded that magnolol suppresses ischemia- and reperfusion-induced ventricular arrhythmias and reduces the size of the infarct resulting from ischemia/reperfusion injury. This pronounced cardioprotective activity of magnolol may be mediated by its antioxidant activity and by its capacity for neutrophil inhibition in myocardial ischemia/reperfusion.

Animals↗
PubMed2001

Szygium aromaticum (L.) Merr. Et Perry (Myrtaceae) flower bud induces apoptosis of p815 mastocytoma cell line.

This study was conducted to investigate SAFB-induced apoptosis of mast cells as it pertains to both its basic drug mechanism and the potential therapeutics of the pathologic conditions accompanying mast cell proliferation. SAFB induced many apoptotic manifestations as evidenced by changes in cell morphology, generation of DNA fragmentation, activation of caspase 3, and DNA hypoploidy. The reduction of mitochondrial membrane potential and the release of cytochrome c to cytosol were also demonstrated. However, reduction of mitochondrial membrane potential and cytochrome c release were not prevented by caspase inhibitor zVAD-fmk or PTP blockers such as bongkrekic acid and cyclosporin A. Expression levels of Bcl-2 and Fas remained unchanged following SAFB treatment. This results suggest that the clinical effect of SAFB may depend on the pharmacological mechanism regulating the demise of mast cells.

Animals↗
PubMed2001

Molded porous poly (L-lactide) membranes for guided bone regeneration with enhanced effects by controlled growth factor release.

The aim of this study was to develop platelet-derived growth factor (PDGF-BB) loaded moldable porous poly (L-lactide) (PLLA)-tricalcium phosphate (TCP) membranes for guided bone regeneration (GBR) therapy. The membranes were designed to fit various types of bone defect sites. PDGF-BB-dissolved PLLA-TCP in methylene chloride-ethyl acetate solution was cast on a dome shaped metallic mold to fabricate a model membrane. The release rate of PDGF-BB, the osteoblast attachment test, and guided bone regeneration potential were evaluated with PDGF-BB-loaded PLLA-TCP membranes. Regular pores were generated throughout the membrane mainly due to phase inversion of PLLA-methylene chloride-ethyl acetate solution. A therapeutic amount of PDGF-BB was released from the membrane. The release rate could be controlled by varying the initial loading content of PDGF-BB. A significant amount of cells attached onto the PDGF-BB-loaded membrane rather than onto the unloaded membrane. Dome shaped bone formation was achieved in rabbit calvaria at 4 weeks. This indicated that restoration of bone defects to the bone's original shape can be made possible by using molded membranes, which guide bone regeneration along with providing sufficient spaces. Bone forming efficiency was increased remarkably due to PDGF-BB release from PLLA-TCP membranes. These results suggested that the PDGF-BB releasing molded PLLA-TCP membrane may potentially improve GBR efficiency in various types of bone defects.

Animals↗
PubMed2001

Magnetic susceptibility tensor anisotropies for a lanthanide ion series in a fixed protein matrix.

The full series of lanthanide ions (except the radioactive promethium and the S-state gadolinium) has been incorporated into the C-terminal calcium binding site of the dicalcium protein calbindin D(9k). A fairly constant coordination environment is maintained throughout the series. At variance with several lanthanide complexes with small chelating ligands investigated in the past, the large protein moiety provides a large number of NMR signals whose hyperfine shifts can be exclusively ascribed to pseudocontact shifts (PCS). The chemical shifts of 1H and 15N backbone and side chain amide NH groups were accurately measured through HSQC experiments. 1097 PCS were estimated from these by subtracting the diamagnetic contributions measured on HSQC spectra of either the 4f(0) lanthanum(III) or the 4f(14) lutetium(III) derivatives and used to define a quality factor for the structure. The differences in diamagnetic chemical shifts between the two diamagnetic blanks were relatively small, although some were not negligible especially for the nuclei closest to the metal center. These differences were used as a tolerance for the PCS. The magnetic susceptibility tensor anisotropies for each paramagnetic lanthanide ion were obtained as the result of the solution structure determination performed by using the NOEs of the cerium(III) derivative and the PCS of all lanthanides simultaneously. This set of reliable magnetic data permits an experimental assessment of Bleaney's theory relative to the magnetic properties for an extended series of lanthanide complexes in solution. All of the obtained tensors show some rhombicity, as could be expected from the lack of symmetry of the protein environment. The directions of the largest magnetic susceptibility component for Ce, Pr, Nd, Sm, Tb, Dy, and Ho and of the smallest magnetic susceptibility component for Eu, Er, Tm, and Yb were found to be all within 15 degrees from their average (within 20 degrees for Sm), confirming the essential similarity of the coordination environment for all lanthanides. Bleaney's theory is in excellent qualitative agreement with the observed pattern of axial anisotropies. Its quantitative agreement is substantially better than that suggested by previous analyses performed on more limited sets of PCS data for small lanthanide complexes, the so-called crystal field parameter varying only within +/-30% from one lanthanide to another. These variations are even smaller (+/-15%) if a reasonable T(-3) correction is taken into consideration. A knowledge of magnetic susceptibility anisotropy properties of lanthanides is essential in determining the self-orienting properties of lanthanide complexes in solution when immersed in magnetic fields.

Algorithms↗
PubMed2001

Detection of Kaposi sarcoma-associated herpesvirus in bone marrow biopsy samples from patients with multiple myeloma.

BACKGROUND: Kaposi sarcoma-associated herpesvirus (KSHV) recently has been identified in the bone marrow (BM) dendritic cell of multiple myeloma (MM) patients. However, whether or not KSHV is associated with MM remains controversial because many studies have failed to detect the presence of KSHV DNA sequences in the BM of their MM patients. METHODS: We have assayed for KSHV DNA sequences in the BM biopsy samples from 49 patients with MM and from 8 patients with normal BM, using nested polymerase chain reaction and dot blot analysis. The polymerase chain reaction product of KSHV was further determined by single-strand conformation polymorphism and sequence analyses. RESULTS: KSHV DNA was detectable in 22 of 49 patients (44.9%) with MM but was not detectable in normal BM cells. Single-strand conformation polymorphism and sequence analyses showed that there were interpatient specific mutations. Sixteen out of 22 KSHV DNA sequences belonged to a previously defined subgroup, and the other 6 remain unclassified and may represent distinct strains of KSHV in Taiwan. CONCLUSIONS: Data strongly supported that KSHV infection did exist in the BM of the current study patients with MM. However, the role of KSHV in the pathogenesis of multiple myeloma remains to be determined.

Adult↗
PubMed2001

Attomole level protein sequencing by Edman degradation coupled with accelerator mass spectrometry.

Edman degradation remains the primary method for determining the sequence of proteins. In this study, accelerator mass spectrometry was used to determine the N-terminal sequence of glutathione S-transferase at the attomole level with zeptomole precision using a tracer of (14)C. The transgenic transferase was labeled by growing transformed Escherichia coli on [(14)C]glucose and purified by microaffinity chromatography. An internal standard of peptides on a solid phase synthesized to release approximately equal amounts of all known amino acids with each cycle were found to increase yield of gas phase sequencing reactions and subsequent semimicrobore HPLC as did a lactoglobulin carrier. This method is applicable to the sequencing of proteins from cell culture and illustrates a path to more general methods for determining N-terminal sequences with high sensitivity.

Carbon Radioisotopes↗
PubMed2001

Importance of leucine zipper domain of mi transcription factor (MITF) for differentiation of mast cells demonstrated using mi(ce)/mi(ce) mutant mice of which MITF lacks the zipper domain.

The mi transcription factor (MITF) is a basic helix-loop-helix leucine zipper (bHLH-Zip) transcription factor that is important for the development of mast cells. Mast cells of mi/mi genotype express normal amount of abnormal MITF (mi-MITF), whereas mast cells of tg/tg genotype do not express any MITFs. Mast cells of mi/mi mice show more severe abnormalities than those of tg/tg mice, indicating that the mi-MITF possesses the inhibitory function. The MITF encoded by the mi(ce) mutant allele (ce-MITF) lacks the Zip domain. We examined the importance of the Zip domain using mi(ce)/mi(ce) mice. The amounts of c-kit, granzyme B (Gr B), and tryptophan hydroxylase (TPH) messenger RNAs decreased in mast cells of mi(ce)/mi(ce) mice to levels comparable to those of tg/tg mice, and the amounts were intermediate between those of +/+ mice and those of mi/mi mice. Gr B mediates the cytotoxic activity of mast cells, and TPH is a rate-limiting enzyme for the synthesis of serotonin. The cytotoxic activity and serotonin content of mi(ce)/mi(ce) mast cells were comparable to those of tg/tg mast cells and were significantly higher than those of mi/mi mast cells. The phenotype of mi(ce)/mi(ce) mast cells was similar to that of tg/tg mast cells rather than to that of mi/mi mast cells, suggesting that the ce-MITF had no functions. The Zip domain of MITF appeared to be important for the development of mast cells. (Blood. 2001;97:2038-2044)

Animals↗
PubMed2001

Inhibitory effect on natural killer activity of microphthalmia transcription factor encoded by the mutant mi allele of mice.

The mouse mi locus encodes a basic-helix-loop-helix-leucine zipper-type transcription factor, microphthalmia transcription factor (MITF). Mice of mi/mi genotype express a mutant form of MITF (mi-MITF), whereas mice of tg/tg genotype have a transgene in the 5' flanking region of the mi gene and do not express MITF. Although the mi/mi mouse is deficient in natural killer (NK) activity, it was found that the tg/tg mouse was normal in this respect. To know the cause, spleen cells of both genotypes were compared. Although the proportion of spleen cells expressing an NK cell marker, NK1.1, was comparable in both mice, the proportion of large granular lymphocytes decreased only in mi/mi mice. The difference between mi/mi and tg/tg mice was reproducible in the culture supplemented with interleukin-2. Moreover, the perforin gene expression was reduced in mi/mi-cultured spleen cells. Wild-type (+) MITF transactivated, but mi-MITF suppressed, the perforin gene promoter through the NF-P motif, a strong cis-acting element. However, neither +-MITF nor mi-MITF bound the NF-P motif. Instead, 2 nuclear factors that bound the NF-P motif were retained in the cytoplasm of mi/mi-cultured spleen cells. In addition, overexpression of mi-MITF resulted in cytoplasmic retention of the 2 NF-P motif-binding factors in cytotoxic T lymphocytes. The presence of mi-MITF rather than the absence of +-MITF appeared to lead to poor transactivation of the NF-P motif by intercepting NF-P motif-binding factors. This inhibitory effect of mi-MITF may cause the deficient cytotoxicity of NK cells in mi/mi mice. (Blood. 2001;97:2075-2083)

Alleles↗
PubMed2001

A strategy for the identification of proteins targeted by thioredoxin.

Thioredoxins are 12-kDa proteins functional in the regulation of cellular processes throughout the animal, plant, and microbial kingdoms. Growing evidence with seeds suggests that an h-type of thioredoxin, reduced by NADPH via NADP-thioredoxin reductase, reduces disulfide bonds of target proteins and thereby acts as a wakeup call in germination. A better understanding of the role of thioredoxin in seeds as well as other systems could be achieved if more were known about the target proteins. To this end, we have devised a strategy for the comprehensive identification of proteins targeted by thioredoxin. Tissue extracts incubated with reduced thioredoxin are treated with a fluorescent probe (monobromobimane) to label sulfhydryl groups. The newly labeled proteins are isolated by conventional two-dimensional electrophoresis: (i) nonreducing/reducing or (ii) isoelectric focusing/reducing SDS/PAGE. The isolated proteins are identified by amino acid sequencing. Each electrophoresis system offers an advantage: the first method reveals the specificity of thioredoxin in the reduction of intramolecular vs. intermolecular disulfide bonds, whereas the second method improves the separation of the labeled proteins. By application of both methods to peanut seed extracts, we isolated at least 20 thioredoxin targets and identified 5-three allergens (Ara h2, Ara h3, and Ara h6) and two proteins not known to occur in peanut (desiccation-related and seed maturation protein). These findings open the door to the identification of proteins targeted by thioredoxin in a wide range of systems, thereby enhancing our understanding of its function and extending its technological and medical applications.

Amino Acid Sequence↗
PubMed2001

Cloning of dimethylglycine dehydrogenase and a new human inborn error of metabolism, dimethylglycine dehydrogenase deficiency.

Dimethylglycine dehydrogenase (DMGDH) (E.C. number 1.5.99.2) is a mitochondrial matrix enzyme involved in the metabolism of choline, converting dimethylglycine to sarcosine. Sarcosine is then transformed to glycine by sarcosine dehydrogenase (E.C. number 1.5.99.1). Both enzymes use flavin adenine dinucleotide and folate in their reaction mechanisms. We have identified a 38-year-old man who has a lifelong condition of fishlike body odor and chronic muscle fatigue, accompanied by elevated levels of the muscle form of creatine kinase in serum. Biochemical analysis of the patient's serum and urine, using (1)H-nuclear magnetic resonance NMR spectroscopy, revealed that his levels of dimethylglycine were much higher than control values. The cDNA and the genomic DNA for human DMGDH (hDMGDH) were then cloned, and a homozygous A-->G substitution (326 A-->G) was identified in both the cDNA and genomic DNA of the patient. This mutation changes a His to an Arg (H109R). Expression analysis of the mutant cDNA indicates that this mutation inactivates the enzyme. We therefore confirm that the patient described here represents the first reported case of a new inborn error of metabolism, DMGDH deficiency.

Adult↗