Biomedical subjects

Y Kim

Publications and source records attributed to Y Kim.

At least 235 records · Page 13Linked to original sources

PubMed2000

Thermodynamic modulation of light chain amyloid fibril formation.

To obtain further insight into the pathogenesis of amyloidosis and develop therapeutic strategies to inhibit fibril formation we investigated: 1) the relationship between intrinsic physical properties (thermodynamic stability and hydrogen-deuterium (H-D) exchange rates) and the propensity of human immunoglobulin light chains to form amyloid fibrils in vitro; and 2) the effects of extrinsically modulating these properties on fibril formation. An amyloid-associated protein readily formed amyloid fibrils in vitro and had a lower free energy of unfolding than a homologous nonpathological protein, which did not form fibrils in vitro. H-D exchange was much faster for the pathological protein, suggesting it had a greater fraction of partially folded molecules. The thermodynamic stabilizer sucrose completely inhibited fibril formation by the pathological protein and shifted the values for its physical parameters to those measured for the nonpathological protein in buffer alone. Conversely, urea sufficiently destabilized the nonpathological protein such that its measured physical properties were equivalent to those of the pathological protein in buffer, and it formed fibrils. Thus, fibril formation by light chains is predominantly controlled by thermodynamic stability; and a rational strategy to inhibit amyloidosis is to design high affinity ligands that specifically increase the stability of the native protein.

Amino Acid Sequence↗

PubMed2000

Low-density lipoprotein-induced expression of interleukin-6, a marker of human mesangial cell inflammation: effects of oxidation and modulation by lovastatin.

Low-density lipoprotein (LDL) may contribute to the pathogenesis of glomerulosclerosis by stimulating a mesangial cell inflammatory response. Interleukin-6 (IL-6) is a marker of active inflammation and ongoing glomerular injury. Therefore, we investigated the effects of native and oxidized LDL on human mesangial cell production of IL-6 and a possible modulation of this inflammatory response by lovastatin, which has been shown to ameliorate experimental glomerulosclerosis. Human mesangial cells were exposed for 6 or 24 h to culture medium containing either native LDL alone or a LDL mixture containing 5 or 20% oxidized LDL. We found that native LDL stimulated 6 h mRNA expression and secretion of IL-6. This effect was further enhanced, in a dose-related manner, when mesangial cells were exposed to increasing concentrations of oxidized LDL. Lovastatin markedly inhibited mesangial cell expression of IL-6 mRNA and reduced IL-6 secretion. The inhibitory effects of lovastatin were overridden at least partially by exogenous mevalonate. We conclude that LDL, and particularly oxidized LDL, might contribute to the pathogenesis of glomerular disease by modulating the inflammatory response of human mesangial cells, as assessed by the stimulation of IL-6 expression. Moreover, this inflammatory response can be prevented by lovastatin, providing a potential direct anti-inflammatory mechanism by which HMG-CoA reductase inhibitors may attenuate lipid-induced glomerular injury.

Base Sequence↗

PubMed2000

Requirement of Rbp9 in the maintenance of Drosophila germline sexual identity.

Drosophila germline sex determination is controlled by a group of genes expressed at early stages of oogenesis (ovo, otu, bam, and Sxl, etc.). Mutations in these genes cause not only sex transformation of female germ cells, but also ovarian tumors. Although mutations at the Rbp9 locus also cause an ovarian tumor phenotype, Rbp9 has been shown to function during later developmental stages than do other ovarian tumor-causing genes. To test whether Rbp9 is also required for germline sex determination, we examined the sex transformation process of female germ cells in Rbp9 mutant flies. The detection of Sxl male transcripts and other male germline markers in Rbp9 mutant ovaries revealed that the Rbp9 mutation caused a partial germline sex transformation. Therefore, sex determination signals that persist throughout oogenesis appear to be required for proper maintenance of germline sexual identity.

Animals↗

PubMed2000

The tertiary structure of full-length bovine adrenodoxin suggests functional dimers.

The three-dimensional X-ray crystal structure of full-length oxidized bovine adrenodoxin (Adx) has been determined at 2.5 A resolution by molecular replacement using a structure of a truncated form as a starting model. Crystals of Adx belong to a primitive monoclinic space group P2(1) with four Adx molecules in an asymmetric unit. The unit cell dimensions are a = 59.44 A, b = 77.03 A, c = 59.68 A, and beta = 94.83 degrees. The structure has been refined to an R factor of 23.5%. Structures of the four molecules of full-length Adx (127 amino acids) in the asymmetric unit were compared with each other and also with that of the truncated Adx (4-108). The overall topology of full-length Adx remains the same as described earlier for the truncated protein. Differences that do occur are almost wholly confined to alternate side-chain conformations that reflect differing lattice contacts made by two proteins. Extensive interactions found between molecules 1 and 2 in the full-length Adx asymmetric unit may reflect the ability of Adx to form dimers in vivo and are consistent with hydrodynamic measurements which show that in solution there is an equilibrium between monomeric and dimeric forms of Adx. Dimerization of Adx could explain why the truncated form has greater affinity for the P450 redox partner than the full-length form. From these results it can be considered that the mechanism of electron transfer is not necessarily the same in different mitochondrial P450 systems.

Adrenodoxin↗

PubMed2000

Naphthazarin derivatives (VI): synthesis, inhibitory effect on DNA topoisomerase-I and antiproliferative activity of 2- or 6-(1-oxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquinones.

2- or 6-(1-Hydroxyiminoalkyl)-5,8-dimethoxy-1,4-naphthoquin-one (DMNQ) and 6-(1-propyloxyimino- alkyl)-DMNQ derivatives were synthesized, and their inhibitory effects on DNA topoisomerase-I (TOPO-I) and antiproliferative activities against L1210 cells were examined. In a comparison, it was found that 6-(1-hydroxyiminoalkyl)-DMNQ derivatives exhibited higher potencies in both bioactivities than 2-(1-hydroxyiminoalkyl)-DMNQ analogues, suggesting that the difference in bioactivities between two positional isomers might be due to the steric hindrance of the side chain. It is noteworthy that the optimal size of alkyl group for both bioactivities of 6-(1-hydroxyiminoalkyl)-DMNQ derivatives was pentyl to octyl (IC50, 22-29 microM) for the inhibition of TOPO-I and propyl to nonyl (ED50, 0.12-0.19 microM) for the antiproliferative activity. In addition, a similar potency of bioactivities was expressed by 6-(1-propyloxyiminoalkyl)-DMNQ derivatives, propylation products of the oximes.

Animals↗

PubMed2000

Determination and excretion study of gestrinone in human urine by high performance liquid chromatography and gas chromatography/mass spectrometry.

Gestrinone was studied by HPLC for screening and by GC/MS for confirmation. Three unknown peaks were found by HPLC which are probably the metabolites of gestrinone, and conjugated gestrinone in dosed human urine. The metabolites and gestrinone were excreted as the conjugated forms. The total amounts of metabolite 1 and conjugated gestrinone, recovered after 48 h, were 0.20 and 0.32 mg, respectively. When metabolite 1 was tested by LC/MS and LC/MS/MS, the parent ion was m/z 327, [MH](+), and fragment ions were seen at m/z 309 [MH - H(2)O](+), 291 [MH - 2H(2)O](+), 283, 263 and 239. The TMS-enol-TMS ether derivative of gestrinone has three peaks in the GC/MS chromatogram formed by tautomerism. The reproducibility of the derivatization method was stable and recoveries were over 87% when spiked into blank urine.

Chromatography, Liquid↗

PubMed2000

Determination of the metabolites of gestrinone in human urine by high performance liquid chromatography, liquid chromatography/mass spectrometry and gas chromatography/mass spectrometry.

Gestrinone was studied by high performance liquid chromatography (HPLC) for screening and by gas chromatography/mass spectrometry (GC/MS) for confirmation. When the chromatograms of blank, spiked urine and dosed urine were compared by HPLC, two unknown metabolites were found and these were excreted as the conjugated forms. Metabolites 1 and 2 were tested by LC/MS and LC/MS/MS and both had parent ions at m/z 325. The fragment ion of metabolite 1 was at m/z 263 and ions for metabolite 2 were m/z 307 [MH - H(2)O](+), 289, 279 and 241. LC/MS/MS of m/z 263 as the parent ion of metabolite 1 gave fragment ions at m/z 245 and 217, which were assumed to be [263 - H(2)O](+) and [235 - H(2)O](+), respectively. The trimethylsilyl (TMS)-enol-TMS ether derivative of gestrinone displayed three peaks in its GC/MS chromatogram, formed by tautomerism.

Adult↗

PubMed2000

Effects of enzyme inducers and inhibitor on the pharmacokinetics of intravenous 2-(allylthio)pyrazine, a new chemoprotective agent, in rats.

In order to find what types of hepatic cytochrome P450 (CYP) isozymes are involved in the metabolism of 2-(allylthio)pyrazine (2-AP) in rats, enzyme inducers, such as phenobarbital, 3-methylcholanthrene, dexamethasone, or isoniazid, and an enzyme inhibitor, such as SKF 525-A were pretreated. After 1-min intravenous administration of 2-AP, 50 mg/kg, to rats pretreated with SKF 525-A (a non-specific CYP inhibitor in rats), the plasma concentrations were significantly higher, and the area under plasma concentration-time curve from time zero to time infinity (AUC) was significantly greater (1365 compared with 1034 microg min/mL) as a result of significantly slower total body clearance (Cl) (36.6 compared with 48.3 mL/min/kg) than those in control rats, indicating that 2-AP was metabolized by CYP isozymes. After 1-min intravenous administration of 2-AP, 50 mg/kg, to rats pretreated with dexamethasone (an inducer of CYP3A in rats), phenobarbital (an inducer of CYP2B1/2, 2C6, 2C7, and 3A1/2 in rats), and 3-methylcholanthrene (an inducer of CYP1A1/2 and 2A1 in rats), the plasma concentrations were significantly lower, and AUC was significantly smaller (27, 41 and 60% decrease, respectively, compared with respective control rats) owing to faster Cl [37 (p>0.05), 70 (p<0.001), and 150% (p<0.001) increase, respectively, compared with respective control rats].

Amines↗

PubMed2000

Effects of enzyme inducers or inhibitors on the pharmacokinetics of intravenous parathion in rats.

In order to find what form of hepatic cytochrome P450 (CYP) is involved in the metabolism of parathion to form paraoxon, rats were pretreated with the enzyme inhibitors, such as SKF 525-A and ketoconazole or enzyme inducers, such as dexamethasone, isoniazid, phenobarbital, and 3-methylcholanthrene. Parathion, 3 mg/kg, was infused in 1 min via the jugular vein. In rats pretreated with SKF 525-A or ketoconazole, nonspecific CYP inhibitors, the area under the plasma concentration-time curve from time zero to time infinity (AUC) and total body clearance (Cl) of parathion were significantly greater and slower, respectively, than those in respective control rats, suggesting that parathion was metabolized by CYPs. In rats pretreated with dexamethasone (CYP3A23 inducer), the AUC was significantly smaller (41.5 compared with 52.5 microg min/mL), Cl was significantly faster (72.2 compared with 57.1 mL/min/kg), and the amounts and/or tissue-to-plasma ratios of parathion was significantly (or tended to be) smaller than those in control rats. However, the pharmacokinetic parameters of parathion were not significantly different after pretreatment with other enzyme inducers compared with respective control rats. The above data suggested that parathion was metabolized to paraoxon by dexamethasone-inducible CYP3A23, the induction of which was confirmed by Western blot analysis. This was supported by in vitro intrinsic clearance (Cl(int)) of parathion to form paraoxon in hepatic microsomal fraction; the Cl(int) in rats pretreated with dexamethasone was significantly faster (0.0900 compared with 0.0290 mL/min/mg protein) than that in control rats.

Animals↗

PubMed2000

Genetically distinct cardial cells within the Drosophila heart.

Although often viewed as a simple pulsating tube, the Drosophila dorsal vessel is intricate in terms of its structure, cell types, and patterns of gene expression. Two nonidentical groups of cardial cells are observed in segments of the heart based on the differential expression of transcriptional regulators. These include sets of four cell pairs that express the homeodomain protein Tinman (Tin), alternating with groups of two cell pairs that express the orphan steroid hormone receptor Seven Up (Svp). Here we show that these myocardial cell populations are distinct in terms of their formation and gene expression profiles. The Svp-expressing cells are generated by asymmetric cell divisions of precursor cells based on decreases or increases in their numbers in numb or sanpodo mutant embryos. In contrast, the numbers of Tin-expressing cardial cells are unchanged in these genetic backgrounds, suggesting they arise from symmetric cell divisions. One function for Svp in the two pairs of cardial cells is to repress the expression of the tin gene and at least one of its targets, the beta3 tubulin gene. Further differences in the cells are substantiated by the identification of separable enhancers for D-mef2 gene transcription in the distinct cardioblast sets. Taken together, these results demonstrate a greater cellular and genetic complexity of the Drosophila heart than previously appreciated.

Animals↗

PubMed2000

Hydrogen peroxide-induced phospholipase D2 activation in lymphocytic leukemic L1210 cells.

Extracellular hydrogen peroxide (H2O2) has been implicated in the activation of phospholipase D (PLD). However, it was still unclear how this activation occurs and what the molecular identity of the H2O2-stimulated PLD isozyme is. This study shows that H2O2 potently increases the PLD activity in mouse lymphocytic leukemic L1210 cells, which contain exclusively PLD2. In addition, H2O2 increased PLD activity only in PLD2-transfected COS-7 cells and not in PLD1-transfected cells. This suggests that PLD2 is selectively activated by H2O2. Depletion of extracellular Ca2+ with EGTA completely blocked the H2O2-induced PLD activation, indicating that Ca2+ influx is required. Moreover, pretreatment of the cells with the protein kinase C (PKC) inhibitors GF-109203X and RO-31-8220 and down-regulation of PKCalpha by prolonged treatment with 4beta-phorbol 12-myristate 13-acetate inhibited the H2O2-stimulated PLD2 activity, which points to the involvement of PKCalpha. Based on these new findings we suggest that PLD2 activity is specifically up-regulated by H2O2 and that the H2O2-induced PLD2 activation is mediated by Ca2+ influx and PKCalpha activation.

Animals↗

PubMed2000

Phase I trial of carboplatin, paclitaxel, etoposide, and cyclophosphamide with granulocyte colony stimulating factor as first-line therapy for patients with advanced epithelial ovarian cancer.

OBJECTIVES: The goal of this study was to determine the maximally tolerated doses (MTDs) of carboplatin, paclitaxel (Taxol), etoposide, and cyclophosphamide (CTEC) with granulocyte-colony stimulating factor (G-CSF, Filgrastim) support as first-line chemotherapy in women with advanced epithelial ovarian cancer (EOC). METHODS: Newly diagnosed patients with either stage IV EOC, or stage III EOC and any amount of gross residual tumor after surgical debulking were eligible to receive six cycles of CTEC over five different dose levels in this phase I trial (planned 21-day cycle length). Paclitaxel, carboplatin, and cyclophosphamide were administered intravenously on Day 1, and oral etoposide was administered on Days 1, 2, and 3. G-CSF was administered beginning Day 4. RESULTS: Twenty patients received a total of 98 cycles of CTEC over the five dose levels evaluated. Bone marrow suppression was the major toxic effect, with grade 4 neutropenia and thrombocytopenia being observed in 25 and 23% of cycles, respectively. The overall incidence of febrile neutropenia was 10%, and no toxic deaths occurred. No grade IV thrombocytopenia or febrile neutropenia was observed once the carboplatin dose was reduced from AUC of 7 to 5. Nonhematologic toxicity was generally mild (grade 2 or less). Dose-limiting toxicity was not observed at the highest dose level evaluated in this study, preventing assignment of the MTD. The clinical complete response rate was 92%, although 15 of 16 evaluable patients have progressed with a median progression-free interval of 4 months (range, 2-11 months). One patient remains disease-free 9 months from the completion of CTEC. CONCLUSIONS: The CTEC regimen is well tolerated and highly active. Although the MTD was not reached in this study, the short median progression-free interval suggests that this regimen is unlikely to be superior to standard treatment with paclitaxel and carboplatin. Strategies to optimize the development of future combination chemotherapy regimens in the treatment of newly diagnosed ovarian cancer are discussed.

Adult↗

PubMed2000

Increased 8-hydroxyguanine formation and endonuclease activity for its repair in ischemic-reperfused hearts of rats.

A type of oxidative DNA damage, 8-hydroxyguanine (8-OH-Gua) formation, and the activity for its subsequent repair, 8-OH-Gua endonuclease activity, were examined in an ischemia-reperfusion model of isolated rat hearts. The level of 8-OH-Gua in myocardial DNA was measured by a high performance liquid chromatography (HPLC) equipped with an electrochemical detector, and the 8-OH-Gua endonuclease activity was analysed by the endonuclease nicking assay using a synthetic double-stranded oligonucleotide containing an 8-OH-Gua residue as a substrate. The Langendorff-perfused rat hearts were subjected to 30 or 60 min of global ischemia, followed by reperfusion with an oxygenated or a nitrogenated Krebs-Henseleit solution. The 8-OH-Gua content in the DNA of the ischemic hearts reperfused with an oxygenated solution was three to four times higher than that of the control hearts. The levels of 8-OH-Gua did not increase either in the ischemic hearts reperfused with a nitrogenated solution or in the ischemic-reperfused hearts treated with SOD, mannitol or allopurinol. When the myocardial extract was incubated with the 8-OH-Gua-containing oligonucleotide substrate, a specific cleavage at the site of an 8-OH-Gua residue was detected. The endonuclease activity responsible for this cleavage increased two-fold in the ischemic-reperfused hearts, compared to the control. This study demonstrates that the formation of 8-OH-Gua in DNA as well as the level of its repair process, 8-OH-Gua endonuclease activity, increase in the ischemic-reperfused rat hearts in response to oxidative stress due to higher levels of oxygen free radicals.

Animals↗

PubMed2000

Characterization of the pcbE gene encoding 2-hydroxypenta-2,4-dienoate hydratase in Pseudomonas sp. DJ-12.

Nucleotide sequence extending 2,3-dihydroxybiphenyl 1,2-dioxygenase gene (pcbC) and 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoate hydrolase gene (pcbD) of Pseudomonas sp. DJ-12 was previously analyzed and the two genes were present in the order of pcbD-pcbC preceded by a promoter from Pseudomonas sp. DJ-12. In this study, a 3.8-kb nucleotide sequence located downstream of the pcbC gene was analyzed to have three open reading frames (ORFs) that are designated as orf1, pcbE and orf2 genes. All of the ORFs were preceded by each ribosome-binding sequence of 5-GGAXA-3 (X=G or A). However, no promoter-like sequence and transcription terminator sequence were found in the analyzed region, downstream of pcbC gene. Therefore, the gene cluster appeared to be present in the order of pcbD-pcbC-orf1-pcbE-orf2 as an operon, which is unique organization characterized so far in biphenyl- and PCB-degrading bacteria. The orf1 gene was composed of 1,224 base pairs which can encode a polypeptide of molecular weight 44,950 containing 405 amino acid residues. A deduced amino acid sequence of the orf1 gene product exhibited 21-33% identity with those of indole dioxygenase and phenol hydroxylase components. The pcbE gene was composed of 783 base pairs encoding 2-hydroxypenta-2,4-dienoate hydratase involved in the 4-chlorobiphenyl catabolism. The orf2 gene was composed of 1,017 base pairs encoding a polypeptide of molecular weight 37,378 containing 338 amino acid residues. A deduced amino acid sequence of the orf2 gene product exhibited 31% identity with that of a nitrilotriacetate monooxygenase component.

Amino Acid Sequence↗

PubMed2000

Effects of cartap on the early-life stages of medaka (Oryzias latipes).

Explore the source record for details and available documents.

Aging↗

PubMed2000

Morphological changes following experimental intraventricular haemorrhage and intraventricular fibrinolytic treatment with recombinant tissue plasminogen activator.

Intraventricular haemorrhage (IVH) occurs in up to 50% of patients with primary intracerebral haemorrhage and aneurysmal subarachnoid haemorrhage. It is a significant and independent contributor to mortality and morbidity in these intracranial haemorrhages. Using a model of isolated IVH, we assessed the morphological changes induced by intraventricular bleeding and investigated the effects of intraventricular fibrinolytic treatment following IVH. IVH was induced in 32 pigs by intraventricular infusion of 10 ml autologous blood along with thrombin. The treatment group received an intraventricular injection of 1.5 mg (1 mg/ml) tissue plasminogen activator (tPA) following the injection of blood. The placebo group received the same volume of normal saline. Morphological examinations of the brains were carried out 7 days and 6 weeks following IVH. The ventricles were incompletely filled with blood and significantly enlarged in the placebo group 7 days after the IVH. In contrast, no residual intraventricular clots were visible in the animals treated with tPA, and the diameters of the lateral ventricles had returned to normal within 7 days. Marked losses of the ependymal covering of the ventricular walls were found in the placebo-treated animals, while the ependymal layer was largely intact in the animals treated with tPA. No haemorrhages induced by tPA were observed. The results indicate that intraventricularly administered tPA significantly enhances the lysis of intraventricular blood clots, accelerates the resolution of acute posthaemorrhagic hydrocephalus, and preserves the integrity of the ependymal layer.

Animals↗

PubMed2000

A co-operative study: clinical characteristics of 334 Korean patients with moyamoya disease treated at neurosurgical institutes (1976-1994). The Korean Society for Cerebrovascular Disease.

A co-operative study was conducted to determine the clinical characteristics of patients with moyamoya disease who were diagnosed and treated at neurosurgical institutes in Korea before 1995. Twenty-six hospitals contributed 505 cases and among them, the clinical characteristics of 334 patients with definite moyamoya disease were evaluated. The number of patients began to increase from the late 1980s, and after that approximately 20 patients were treated each year. There were two age peaks: from six to 15 and from 31 to 40 years of age. Haemorrhagic manifestations occurred in approximately 43% of the patients. The major clinical manifestations were haemorrhage in adults (62.4%) and ischaemia in children (61.2%). Overall 54.5% of the patients experienced decreased consciousness levels, mainly due to intracranial haemorrhage or cerebral infarction. In the patients with ischemic manifestations, the adult patients were more likely to have cerebral infarction than the pediatric patients (80% vs. 39%) and the pediatric patients were more likely to have TIA (61% vs. 25%). Thirty eight percent of the patients underwent bypass surgery and 53% of these procedures were performed bilaterally. Treatment policies, including indications for bypass surgery and commonly used drugs, were somewhat different according to the institution. Overall favorable outcome was 73%, and the most significant factor affecting poor outcome was haemorrhagic manifestation. This article describes the characteristics of 334 patients with moyamoya disease, who were diagnosed and treated at neurosurgical institutes in Korea before 1995.

Adolescent↗

PubMed2000

Expression of the human erythrocyte glucose transporter in transitional cell carcinoma of the bladder.

OBJECTIVES: It has previously been shown that glucose uptake and use is more prevalent in carcinomas than in normal cells and tissues. We hypothesized that human erythrocyte glucose transporter (Glut-1) expression is increased in bladder transitional cell carcinoma (TCC) and that the grade of expression might correlate with the degree of malignancy. METHODS: Immunostaining of Glut-1 protein was studied in normal bladder (5 cases), benign papilloma (10 cases), superficial tumor (48 cases), and invasive tumor (31 cases) tissue. The immunoreactivity grading system used was as follows: absence of immunoreactivity in tumor cell = 0; less than 10% of the tumor cells immunoreactive = 1+; 10% to 50% of the tumor cells immunoreactive = 2+; and greater than 50% of the tumor cells immunoreactive = 3+. RESULTS: Immunostaining of Glut-1 protein was not expressed in the normal bladder or benign papilloma samples, but it was expressed in 63.0% (46 of 73) of the TCC samples. In the pattern of expression of Glut-1 protein, superficial TCC was stained focally, but invasive TCC was stained diffusely in the tumor nests. The grade of Glut-1 protein expression increased more significantly in the invasive TCC than in the superficial TCC samples (P = 0.002) and more significantly in the high nuclear grade than in the low nuclear grade samples (P = 0.007). In the superficial TCC samples, the bladder tumor recurrence rate did not significantly correlate with Glut-1 protein expression (P = 0.40). CONCLUSIONS: Our results suggest that the Glut-1 protein is not expressed in normal bladder mucosa and benign lesions, that Glut-1 protein expression is strongly associated with neoplastic progression in bladder TCC, and that Glut-1 expression does not correlate with the recurrence rate in superficial bladder TCC.

Carcinoma, Transitional Cell↗