Biomedical subjects

J Y Lee

Publications and source records attributed to J Y Lee.

At least 19 recordsLinked to original sources

PubMed2001

Protection by pyruvate against transient forebrain ischemia in rats.

Pyruvate has a remarkable protective effect against zinc neurotoxicity. Because zinc neurotoxicity is likely one of the key mechanisms of ischemic brain injury, the neuroprotective effect of pyruvate was tested in a rat model of transient forebrain ischemia. Control experiments in mouse cortical culture showed that pyruvate almost completely blocked zinc toxicity but did not attenuate calcium-overload neuronal death. Adult rats subjected to 12 min forebrain ischemia exhibited widespread zinc accumulation and neuronal death throughout hippocampus and cortex 72 hr after reperfusion. However, rats injected intraperitoneally with sodium pyruvate (500-1000 mg/kg) within 1 hr after 12 min forebrain ischemia showed almost no neuronal death. In addition, the mortality was markedly decreased in the pyruvate-protected groups (3.8%) compared with the NaCl-injected control group (58.1%). The neuroprotective effect persisted even at 30 d after the insult. The spectacular protection without noticeable side effects makes pyruvate a promising neuroprotectant in human ischemic stroke.

Animals↗

PubMed2001

differential L-selectin binding activities of human hematopoietic cell L-selectin ligands, HCELL and PSGL-1.

Expression of L-selectin on human hematopoietic cells (HC) is associated with a higher proliferative activity and a more rapid engraftment after hematopoietic stem cell transplantation. Two L-selectin ligands are expressed on human HCs, P-selectin glycoprotein ligand-1 (PSGL-1) and a specialized glycoform of CD44 (hematopoietic cell E- and L-selectin ligand, HCELL). Although the structural biochemistry of HCELL and PSGL-1 is well characterized, the relative capacity of these molecules to mediate L-selectin-dependent adhesion has not been explored. In this study, we examined under shear stress conditions L-selectin-dependent leukocyte adhesive interactions mediated by HCELL and PSGL-1, both as naturally expressed on human HC membranes and as purified molecules. By utilizing both Stamper-Woodruff and parallel-plate flow chamber assays, we found that HCELL displayed a 5-fold greater capacity to support L-selectin-dependent leukocyte adherence across a broad range of shear stresses compared with that of PSGL-1. Moreover, L-selectin-mediated leukocyte binding to immunopurified HCELL was consistently >5-fold higher than leukocyte binding to equivalent amounts of PSGL-1. Taken together, these data indicate that HCELL is a more avid L-selectin ligand than PSGL-1 and may be the preferential mediator of L-selectin-dependent adhesive interactions among human HCs in the bone marrow.

Animals↗

PubMed2001

Regeneration of hyaline cartilage by cell-mediated gene therapy using transforming growth factor beta 1-producing fibroblasts.

Transforming growth factor beta (TGF-beta) has been considered as a candidate for gene therapy of orthopedic diseases. The possible application of cell-mediated TGF-beta gene therapy as a new treatment regimen for degenerative arthritis was investigated. In this study, fibroblasts expressing active TGF-beta 1 were injected into the knee joints of rabbits with artificially made cartilage defects to evaluate the feasibility of this therapy for orthopedic diseases. Two to 3 weeks after the injection there was evidence of cartilage regeneration, and at 4 to 6 weeks the cartilage defect was completely filled with newly grown hyaline cartilage. Histological analyses of the regenerated cartilage suggested that it was well integrated with the adjacent normal cartilage at the sides of the defect and that the newly formed tissue was indeed hyaline cartilage. Our findings suggest that cell-mediated TGF-beta 1 gene therapy may be a novel treatment for orthopedic diseases in which hyaline cartilage damage has occurred.

3T3 Cells↗

PubMed2001

Ionizing radiation can overcome resistance to TRAIL in TRAIL-resistant cancer cells.

Although the majority of cancer cells are killed by TRAIL (tumor necrosis factor-related apoptosis-inducing ligand treatment), certain types show resistance to it. Ionizing radiation also induces cell death in cancer cells and may share common intracellular pathways with TRAIL leading to apoptosis. In the present study, we examined whether ionizing radiation could overcome TRAIL resistance in the variant Jurkat clones. We first selected TRAIL-resistant or -sensitive Jurkat clones and examined cross-responsiveness of the clones between TRAIL and radiation. Treatment with gamma-radiation induced significant apoptosis in all the clones, indicating that there seemed to be no cross-resistance between TRAIL and radiation. Combined treatment of radiation with TRAIL synergistically enhanced killing of TRAIL-resistant cells, compared to TRAIL or radiation alone. Apoptosis induced by combined treatment of TRAIL and radiation in TRAIL-resistant cells was associated with cleavage of caspase-8 and the proapoptotic Bid protein, resulting in the activation of caspase-9 and caspase-3. No changes in the expressions of TRAIL receptors (DR4 and DR5) and Bcl-2 or Bax were found after treatment. The caspase inhibitor z-VAD-fmk completely counteracted the synergistic cell killing induced by combined treatment of TRAIL and gamma-radiation. These results demonstrated that ionizing radiation in combination with TRAIL could overcome resistance to TRAIL in TRAIL-resistant cells through TRAIL receptor-independent synergistic activation of the cascades of the caspase-8 pathway, suggesting a potential clinical application of combination treatment of TRAIL and ionizing radiation to TRAIL-resistant cancer cells.

Apoptosis↗

PubMed2001

Menadione induces endothelial dysfunction mediated by oxidative stress and arylation.

Our previous studies showed that menadione causes endothelial dysfunction which results in decreased relaxation and increased contraction of blood vessels. This investigation examined the role of two possible mechanisms (oxidative stress and arylation) in menadione-induced endothelial dysfunction. Menadione increased superoxide anion generation in aortic rings in a dose-dependent manner. Superoxide dismutase (SOD), reversed the inhibitory effects of menadione on vascular relaxation. The relaxation induced by the NO donor, sodium nitroprusside, was inhibited by menadione pretreatment in a dose-dependent manner. Endothelial nitric oxide synthase activity (eNOS) was suppressed by menadione. Menadione resulted in a dose-dependent reduction of cGMP levels accumulated by acetylcholine. This reduction of cGMP levels was blocked by SOD treatment, suggesting that superoxide anion generated by menadione could play a role in the inhibition of the nitric oxide pathway. Evidence supporting a possible role for arylation in impaired vascular relaxation was suggested by the observation that benzoquinone, which does not induce oxidative stress in aortic rings, inhibited acetylcholine-induced vascular relaxation to the same extent as menadione. Collectively, these results suggest that menadione can cause endothelial dysfunction in blood vessels by the inhibition of the nitric oxide pathway via superoxide anion generation and that arylation activity may also be another important mechanism.

Acetylcholine↗

PubMed2001

Yeast ribosomal protein S3 has an endonuclease activity on AP DNA.

The mammalian ribosomal protein S3 (rpS3) is a component of the 40S ribosomal subunit. It is known to function as a DNA repair enzyme, UV endonuclease III, which cleaves DNA that is irradiated by UV. It also has an endonuclease activity on AP DNA. In this report, the yeast ribosomal protein S3 (Rps3p) in S. cerevisiae was cloned, expressed in E. coli, and affinity-purified by 285 fold. Rps3p is composed of 240 amino acids and has a 78% amino acid similarity with the human counterpart that has 243 amino acids. The major difference in the amino acid sequence between the two proteins lies in most of the C-terminal 50 residues. Surprisingly, Rps3p only showed an endonuclease activity on AP DNA, but not on DNA that was irradiated with UV. The AP endonuclease activity of Rps3p was affected by pH, KCl, and beta-mercaptoethanol, but Triton X-100 and EDTA did not affect the enzyme activity. From these results, both the mammalian rpS3 and Rps3p appear to be involved in DNA damage processing, but in different modes.

Amino Acid Sequence↗

PubMed2001

Adverse consequences of erythrocyte exposure to menadione: involvement of reactive oxygen species generation in plasma.

Previous studies demonstrated that menadione, a representative quinone compound, reacts nonenzymatically with thiols in plasma, resulting in the generation of reactive oxygen species and potentiation of menadione-induced platelet damage. Because of the reported association of menadione with hemolytic anemia in vivo, investigations were undertaken to identify the free radicals generated from the interaction of menadione with plasma, and to assess the potential role of plasma-generated free-radical species in menadione-dependent erythrocyte toxicity. In rat plasma, menadione increased the rate of oxygen consumption and both luminol- and lucigenin-amplified chemiluminescence in a concentration-dependent manner. Superoxide dismutase (SOD) inhibited lucigenin-amplified chemiluminescence, suggesting formation of superoxide anion. Menadione also induced significant increases in chemiluminescence when erythrocytes were suspended in plasma, but not when cells were suspended in buffer. Consistent with these findings, menadione-dependent hemolysis of erythrocytes occurred only when the cells were suspended in plasma. Various free-radical inhibitors were tested for their ability to inhibit menadione-induced hemolysis. Catalase and mannitol each produced significant inhibition, including an additive effect when both compounds were present, while SOD had no marked effect. In addition, pretreatment with 3-amino-1,2,4-triazole, an intracellular catalase inhibitor, potentiated menadione-induced cytotoxicity in the presence of plasma. These results suggest that both hydrogen peroxide and hydroxyl radicals are involved in menadione-mediated plasma erythrocyte cytotoxicity; however, superoxide anion does not appear to play a direct role.

Animals↗

PubMed2001

Enhanced effect of in-situ generated ammonium salts aerosols on the removal of NOx from simulated flue gas.

The combined removal of sulfur dioxide (SO2, up to 3,000 ppm) and nitrogen oxides (NO and NO2, up to 1,200 ppm) has been investigated in a bench-scale pulsed-corona enhanced wet electrostatic precipitator (wESP) with the optional injection of ammonia and/or ozone. The reaction of ammonia with SO2 produces submicron aerosols under certain conditions. Experiments have shown the feasibility of combined SO2 and NOx removal from simulated flue gases by the action of these in-situ generated aerosols. The mechanisms for NOx removal include oxidation of NO to NO2 and subsequent absorption of NO2 into the water wall of the wESP. The results have shown that injecting NH3 (NH3/NOx molar ratio 1) resulted in NOx removal of approximately 13% in a simulated combustion flue gas. Injecting 200 ppm ozone (no ammonia) increased NO conversion to 35% by oxidation, but total NOx removal increased to only 17%. Without the formation of ammonium salts aerosols (e.g., without SO2 in the gas), co-injection of ammonia and ozone increased NO conversion to 60% and NOx removal to 40%. However, high NOx removals were measured in simulated flue gas that contained NH3, SO2, and ozone. The total NOx removal efficiency was 79% when the ammonium salts aerosols were formed in the presence of 2400 ppm SO2, 312 ppm O3, and 2,900 ppm NH3. The energy efficiency of collection improved by approximately 250% for SO2 removal and more than 4700% for NOx removal under these conditions. It was determined that the ammonium salts aerosols produced from the reaction of ammonia and sulfur dioxide substantially enhanced total NOx removal.

Absorption↗

PubMed2001

Crystallization and preliminary X-ray crystallographic analysis of deoxyuridine triphosphate nucleotidohydrolase from Saccharomyces cerevisiae.

Deoxyuridine triphosphate nucleotidohydrolase (dUTPase) from Saccharomyces cerevisiae is essential for cell viability. It has been overexpressed in Escherichia coli and has been crystallized at 296 K using polyethylene glycol (PEG) 1500 as a precipitant. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 59.48, b = 138.54, c = 157.91 A, alpha = beta = gamma = 90 degrees. Two molecules of trimeric dUTPase from S. cerevisiae are present in the asymmetric unit, giving a crystal volume per protein mass (V(M)) of 3.36 A(3) Da(-1) and a solvent content of 63%. The diffraction limit of the crystals could be significantly extended by the crystal-annealing procedure. A set of native data extending to 2.7 A resolution has been collected at 100 K using synchrotron X-rays.

Crystallization↗

PubMed2001

Novel sulfonate derivatives: potent antimitotic agents.

The synthesis and biological evaluation of novel sulfonate analogues of E-7010 are reported. Several of the compounds are potent inhibitors of cell proliferation and tubulin polymerization. Importantly, these compounds are also active against P-glycoprotein positive (+) cancer cells, which are resistant to many other antitumor agents.

Aminophenols↗

PubMed2001

Novel findings in inhibition of mast cell-dependent immediate-type cutaneous reactions by Gahmi-Shini-San.

This report describes an inhibitory effect of Gahmi-Shini-San (GSS) on mast cell-mediated immediate-type allergic reactions. GSS is an Oriental herbal medication, which has been successfully used in Korea for the treatment of allergic disorders, mainly skin anaphylactic diseases. GSS inhibited the ear swelling response induced by intradermal injection of compound 48/80 in a mouse model on a concentration-dependent basis. The mast cells in mouse ear tissue were stained by alcian blue/nuclear fast red. GSS significantly inhibited the compound 48/80-induced degranulation from mast cells in ear tissue. GSS dose-dependently inhibited the histamine release from the rat peritoneal mast cells by compound 48/80. We also studied the effect of GSS on mast cell-dependent passive cutaneous anaphylaxis activated by dinitrophenyl IgE antibody. GSS showed inhibition of passive cutaneous anaphylaxis following oral administration. These results indicated that GSS has inhibitory effect on mast cell-dependent immediate type cutaneous reactions.

Alcian Blue↗

PubMed2001

Mutations of tumor necrosis factor-related apoptosis-inducing ligand receptor 1 (TRAIL-R1) and receptor 2 (TRAIL-R2) genes in metastatic breast cancers.

Several lines of evidence suggest that apoptosis dysregulation plays an important role in cancer metastasis. In this study, to explore the possibility that the mutations of death receptors are involved in the metastasis mechanism, we analyzed the death domains of Fas and tumor necrosis factor-related apoptosis-inducing ligand-receptor 1 and -2 (TRAIL-R1 and -R2) genes for the detection of somatic mutations in 57 breast cancers with (n = 34) or without (n = 23) metastasis to the regional lymph nodes. We found seven mutations (three TRAIL-R1 and four TRAIL-R2 mutations), and these mutations were detected only in the breast cancers with metastasis. Furthermore, we also analyzed the allelic losses of chromosome 8p21-22, where TRAIL-R1 and R2 reside in the same series of breast cancers, and found that the allelic losses were significantly higher in metastatic breast cancers. We expressed the tumor-derived TRAIL-R1 and TRAIL-R2 mutants in 293 cells and found that apoptosis was suppressed. These data suggest that TRAIL-R1 and R2 genes are relevant to the frequent loss of chromosome 8p21-22 in breast cancer and that the inactivating mutations of TRAIL-R1 and -R2 genes play a role in the metastasis of breast cancer.

Apoptosis↗

PubMed2001

Potential role of leptin in angiogenesis: leptin induces endothelial cell proliferation and expression of matrix metalloproteinases in vivo and in vitro.

Leptin, the product of ob gene, is an endocrine hormone that regulates adipose tissue mass. Recently, leptin has been found to generate a growth signal involving a tyrosine kinase-dependent intracellular pathway and promote angiogenic processes via activation of leptin receptor (Ob-R) in endothelial cells. However, it is not clear how leptin functions to promote multi-step processes involved in the neovascularization at the atherosclerotic plaque. We have examined the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) and Ob-R in human atherosclerotic lesions, leptin-mediated angiogenesis in vivo and in vitro. Immunohistochemical analysis of human atherosclerotic aorta revealed an increased expression of Ob-R in the intima of neorevascularized regions and of both MMPs and TIMPs predominantly in the endothelial lining of intimal neovessels and macrophages/foam cells. In the rat corneal angiogenesis assay, leptin elicited a comparable sensitivity of angiogenic activity to those of vascular endothelial growth factor (VEGF). The immunohistological analysis of the leptin-treated rat cornea showed definitive rises in Ob-R, MMPs and TIMPs expression as well as those of VEGF receptor (VEGFR-1). Leptin (10-40 ng/ml) induced proliferation of the human umbilical vein endothelial cells (HUVECs) and elevation of MMP-2, MMP-9, TIMP-1, and TIMP-2 expression in a dose-dependent manner. Leptin also induced increases of MMP-2, MMP-9, TIMP-1, and Up-regulated the human coronary artery smooth muscle cells (HCASMCs). These findings suggest that leptin, a hormone with pluralistic properties including a mitogenic activity on vascular endothelial cells, plays a role in matrix remodeling by regulating the expression of MMPs and TIMPs. Taken together, our findings further provide evidences for leptin's role as an angiogenesis inducer in the normal organ (rat cornea) and in aberrant vasculature under duress like atherosclerosis.

Animals↗

PubMed2001

pncA mutations in clinical Mycobacterium tuberculosis isolates from Korea.

BACKGROUND: Pyrazinamide (PZA) is among the first-line drugs for the treatment of tuberculosis. In vitro, it kills semidormant mycobacteria only at low pH. The purpose of this study was to compare PZA resistance with pyrazinamidase (PZase) activity and the genotype to better understand the molecular basis of PZA resistance and to expand the profile of pncA mutations worldwide. RESULTS: Of the 28 tested strains of Mycobacterium tuberculosis, 6 were susceptible to PZA and positive for PZase activity and had no pncA mutations. Twenty-one strains were resistant to PZA and negative for PZase activity and had mutations in the pncA gene, including 15 point mutations, 5 insertions, and 2 deletions. One strain had no mutation in the pncA gene, even though it was resistant to PZA and negative for PZase activity. Three isolates had adenine to guanine point mutations in the -11 upstream region, making this the most common type of pncA mutations in this study, with at least two different RFLP patterns. CONCLUSION: These data help in the understanding of the molecular basis of PZA resistance. An adenine to guanine point mutation in the -11 upstream region was the most common type of pncA mutation in our isolates. The results of pncA mutation analyses should be carefully interpreted for epidemiologic purposes.

Amidohydrolases↗

PubMed2001

CD44 is a major E-selectin ligand on human hematopoietic progenitor cells.

E-selectin plays a critical role in mediating tissue-specific homing of T cells into skin, and of primitive hematopoietic progenitor cells (HPCs) into bone marrow (BM). Though it is known that a glycoform of PSGL-1 (CLA) functions as the principal E-selectin ligand on human T lymphocytes, the E-selectin ligand(s) of human HPCs has not been identified. We used a shear-based adherence assay to analyze and define the E-selectin ligand activity of membrane proteins from human HPCs. Our data show that PSGL-1 expressed on human HPCs is an E-selectin ligand, and that HPCs also express a previously unrecognized E-selectin ligand, CD44. The E-selectin ligand activity of CD44 is conferred by the elaboration of sialylated, fucosylated binding determinants on N-glycans. This glycoform of CD44 is expressed on primitive CD34+ human HPCs, but not on more mature hematopoietic cells. Under physiologic flow conditions, this molecule mediates E-selectin-dependent rolling interactions over a wider shear range than that of PSGL-1, and promotes human HPC rolling interactions on E-selectin expressed on human BM endothelial cells. These findings offer new insights into the structural biology and physiology of CD44, and into the molecular basis of E-selectin-dependent adhesive interactions that direct homing of human HPC to BM.

Animals↗

PubMed2001

Synthesis and biological evaluation of novel A-ring modified hexacyclic camptothecin analogues.

Eleven A-ring modified hexacyclic analogues of camptothecin (CPT) containing a 1,4-oxazine ring were synthesized from 10-hydroxycamptothecin (11a) and 7-ethyl-10-hydroxycamptothecin (3) (SN-38) in four to five steps and were subjected to the biological tests such as cytotoxicity, topoisomerase I (Topo I) inhibitory activity, acetylcholinesterase (AChE) inhibition, and stability in human plasma. Four compounds 15a, 15b, 16a, and 16c were about 2-fold more potent than topotecan and as potent as CPT toward human cancer cell lines A549, H128, WiDr, MKN45, SK-OV-3, and SK-BR-3 in vitro, even though the most active compound 15b was slightly less potent than SN-38. The potency of Topo I inhibition of these compounds showed relatively good correlation with their cytotoxicity. Most of the compounds exhibited AChE inhibitory activity weaker (9 +/- 2 to 20 +/- 3%) than CPT (23 +/- 5%) or topotecan (20 +/- 4%) and similar to SN-38 (13 +/- 2%), indicating that they might have little effect on causing early diarrhea. The stability of lactone forms of these compounds in human plasma seemed to be much higher than that of CPT and similar to that of topotecan but lower than that of SN-38. Among the new hexacyclic CPT analogues, compound 15b showed higher antitumor activity against human tumor xenograft, WiDr, in nude mice compared to that of SN-38. The most promising compound 15b has been selected for further development.

Animals↗

PubMed2001

Structural basis of non-specific lipid binding in maize lipid-transfer protein complexes revealed by high-resolution X-ray crystallography.

Non-specific lipid-transfer proteins (nsLTPs) are involved in the movement of phospholipids, glycolipids, fatty acids, and steroids between membranes. Several structures of plant nsLTPs have been determined both by X-ray crystallography and nuclear magnetic resonance. However, the detailed structural basis of the non-specific binding of hydrophobic ligands by nsLTPs is still poorly understood. In order to gain a better understanding of the structural basis of the non-specific binding of hydrophobic ligands by nsLTPs and to investigate the plasticity of the fatty acid binding cavity in nsLTPs, seven high-resolution (between 1.3 A and 1.9 A) crystal structures have been determined. These depict the nsLTP from maize seedlings in complex with an array of fatty acids.A detailed comparison of the structures of maize nsLTP in complex with various ligands reveals a new binding mode in an nsLTP-oleate complex which has not been seen before. Furthermore, in the caprate complex, the ligand binds to the protein cavity in two orientations with equal occupancy. The volume of the hydrophobic cavity in the nsLTP from maize shows some variation depending on the size of the bound ligands. The structural plasticity of the ligand binding cavity and the predominant involvement of non-specific van der Waals interactions with the hydrophobic tail of the ligands provide a structural explanation for the non-specificity of maize nsLTP. The hydrophobic cavity accommodates various ligands from C10 to C18. The C18:1 ricinoleate with its hydroxyl group hydrogen bonding to Ala68 possibly mimics cutin monomer binding which is of biological importance. Some of the myristate binding sites in human serum albumin resemble the maize nsLTP, implying the importance of a helical bundle in accommodating the non-specific binding of fatty acids.

Binding Sites↗

PubMed2001

Effect of exercise intensity and frequency on lipid levels in men with coronary heart disease: Training Level Comparison Trial.

The objective of the Training Level Comparison Trial was to determine whether a more intense exercise program versus a less intensive program has additional favorable effects on blood lipids in men with coronary heart disease (CHD) over a 12-month period. The study-a randomized, controlled trial conducted at 2 clinical centers-enrolled 185 patients with documented CHD. A simple randomization procedure led to unequal numbers of patients in the 2 interventions: 82 in the low-intensity and 103 in the high-intensity group. Target heart rate during exercise corresponded to 50% of maximum oxygen uptake (VO(2 max)) +/- 5 beats/min in the low-intensity group and 85% +/- 5 beats/min in the high-intensity group. The intensity of exercise made little difference on lipid improvements. However, the attendance rates for the 6- and 12-month periods (percentage of total exercise sessions attended) were significantly related to increased high-density lipoprotein (HDL) cholesterol (r(s) [Spearman rank correlation coefficient 0.20 to 0.26, p <0.05]), and decreases in the ratios of low-density lipoprotein (LDL)-to-HDL cholesterol (LDL:HDL, r(s) = -0.24 to -0.28, p < 0.01) and total-to-HDL cholesterol (total:HDL, r(s) = -0.25 to -0.29, p < 0.01) at 6 and 12 months. The relation of the attendance rate to LDL:HDL and total:HDL ratios remained significant in repeated-measures regression analysis. Exercise frequency may be more important than intensity in improving HDL cholesterol and LDL:HDL and total:HDL ratios in men with CHD.

Adult↗