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Biomedical subjects

K M Lee

Publications and source records attributed to K M Lee.

At least 127 records · Page 7Linked to original sources
PubMed1999

Phase II trial of a paclitaxel and carboplatin combination in Asian patients with metastatic nasopharyngeal carcinoma.

PURPOSE: An earlier phase II trial of paclitaxel in patients with metastatic nasopharyngeal carcinoma (NPC) demonstrated a response rate of 22%. Hence we proceeded to study the combination of paclitaxel and carboplatin in these patients. PATIENTS AND METHODS: The 21-day regimen was as follows: i.v. paclitaxel 175 mg/m2 over three hours preceded by standard premedications, followed by i.v. carboplatin dosed at AUC of six infused over one hour. Only chemotherapy-naive patients with histological diagnoses of undifferentiated carcinoma of the nasopharynx, systemic metastases and radiologically measurable lesions were eligible. RESULTS: Thirty-two patients were accrued to this study. Twenty patients (62%) had at least two sites of metastasis. The main grade 3-4 toxicity was neutropenia (31%). Nine patients (28%) developed neutropenic sepsis, which caused the demise of one of them. Twenty-four patients (75%) responded to treatment, with one (3%) attaining a complete response. The median time to progression of disease was seven months and the median survival was 12 months. At one year, 52% of the patients were alive. CONCLUSIONS: The combination of paclitaxel and carboplatin is an active regimen in NPC. Its convenience of administration and good tolerability make it an attractive alternative regimen to consider for patients with metastatic disease.

Adult↗
PubMed1999

Economic analysis of erythropoietin use in orthopaedic surgery.

The aim was to assess the cost-effectiveness of erythropoietin (EPO) to reduce patients' exposure to perioperative allogenic blood products in orthopaedic surgery. The use of EPO was assessed for EPO used alone and for EPO, to augment preoperative autologous donation (PAD). A decision analytical model was designed incorporating (i) the risk of receiving allogeneic blood, (ii) the costs of blood products, (iii) the likelihood of developing transfusion-related diseases, (iv) the costs of transfusion-related diseases, (v) the impact of transfusion-related diseases on patient morbidity and mortality and (vi) the effect of EPO upon the probability of transfusion. The efficacy of EPO was derived from data from a meta-analysis of published randomized trials. Estimates for the other parameters were obtained by a systematic review of the literature. EPO alone led to only modest incremental benefit compared to no intervention for orthopaedic surgery (0.000024 life-years gained per patient). As an augmentation to PAD, EPO also led to modest benefits (0.000006 life-years gained per patient). For EPO compared to no intervention, the incremental cost per life-year gained was $66 million (Canadian). For EPO to augment PAD, the incremental cost per life-year gained was $329 million (Canadian). Detailed sensitivity analysis did not reveal any circumstances in which the cost-effectiveness ratios reached a level generally considered attractive. On the basis of cost-effectiveness, the use of EPO to reduce perioperative allogeneic transfusions in orthopaedic surgery did not meet criteria conventionally considered acceptable.

Blood Transfusion↗
PubMed1999

Molecular cloning and functional properties of two early-stage encapsulation-relating proteins from the coleopteran insect, Tenebrio molitor larvae.

Encapsulation is a major defensive reaction against foreign materials that are too large to be phagocytosed by individual hemocytes; however, the biochemical process of encapsulation is still obscure. To isolate and characterize the early-stage encapsulation-relating protein (ERP), we used the coleopteran insect, Tenebrio molitor larvae, injecting three differing kinds of bead or inserting pieces of surgical suture into the abdomen of T. molitor larvae. The resulting proteins from the injected beads or the inserted pieces of surgical suture were recovered 10 min after injection or insertion, and were analyzed on SDS/PAGE under reducing conditions. Four different proteins (86, 78, 56 and 48 kDa) were enriched compared with the crude hemolymph. Among them, we purified 56-kDa and 48-kDa ERPs to homogeneity and raised polyclonal antibodies against each protein. Immunoblotting analysis showed that the affinity-purified antibodies of the 56-kDa and 48-kDa ERPs cross-reacted with the 48-kDa and 56-kDa ERPs, respectively. Analysis of the cDNA of 56-kDa ERP consisted of 579 amino acid residues and showed a novel glutamine-rich protein. Positive clones of the 48-kDa ERP showed the same DNA sequence as 56-kDa ERP. Interestingly, the chemically determined N-terminal amino acid sequence and the three partial amino acid sequences of the 48-kDa protein were found in the 56-kDa ERP, suggesting that the 48 kDa ERP was produced by the cleavage of Arg101-Gly102 of the 56-kDa ERP by a limited proteolysis. Western blotting analysis showed that these ERPs were detected exclusively on membrane fractions of hemocytes. Also, when the early-stage encapsulated beads were coated with both the 56-kDa and 48-kDa ERP antibodies and re-injected into larvae, no further encapsulation reaction was observed. However, when the early-stage encapsulated beads were incubated with 56-kDa ERP antibody, 48-kDa ERP antibody or nonimmunized rabbit IgG and re-injected into larvae, further encapsulation did occur.

Amino Acid Sequence↗
PubMed1999

The prediction of interferon-alpha therapeutic effect by sequence variation of the HCV hypervariable region 1.

Interferon-alpha (IFN-alpha) has been used to treat hepatitis C virus (HCV)-induced hepatitis, but it has been effective in only about half of the treated patients, with recurrence appearing in the other half. As a consequence of the possible complications associated with IFN-alpha and the high cost of treatment, it has become extremely important to select the proper patients for IFN-alpha treatment. In our previous study, we found that the quasispecies in the hypervariable region (HVR) 1 of HCV were various and that a new quasispecies can appear in non-responders and/or lead to deterioration in the patients' condition. The preliminary data we obtained in the process of our previous research led us to believe that the quasispecies of HVR 1 has something to do with the effect of IFN-alpha. Thus, in this investigation, we tried to determine the predictive factors of IFN-alpha therapy. Thirty patients with HCV infection were treated with IFN-alpha. Among them, 15 patients recovered after six months IFN-alpha treatment, but the remaining 15 patients showed no response after six months IFN-alpha treatment. We cloned HVR 1 DNA by reverse transcription-polymerase chain reaction (RT-PCR) and examined the quasispecies of HVR 1. As the quasispecies of HVR 1 in non-responders varied more than in the complete remission group, we concluded that the sequence variation in HVR 1 of HCV can be used to predict the effect of IFN-alpha.

Adult↗
PubMed1998

Molecular basis of T cell inactivation by CTLA-4.

CTLA-4, a negative regulator of T cell function, was found to associate with the T cell receptor (TCR) complex zeta chain in primary T cells. The association of TCRzeta with CTLA-4, reconstituted in 293 transfectants, was enhanced by p56(lck)-induced tyrosine phosphorylation. Coexpression of the CTLA-4-associated tyrosine phosphatase, SHP-2, resulted in dephosphorylation of TCRzeta bound to CTLA-4 and abolished the p56(lck)-inducible TCRzeta-CTLA-4 interaction. Thus, CTLA-4 inhibits TCR signal transduction by binding to TCRzeta and inhibiting tyrosine phosphorylation after T cell activation. These findings have broad implications for the negative regulation of T cell function and T cell tolerance.

Abatacept↗
PubMed1998

Molecular cloning of cDNA for pro-phenol-oxidase-activating factor I, a serine protease is induced by lipopolysaccharide or 1,3-beta-glucan in coleopteran insect, Holotrichia diomphalia larvae.

Previously, we identified two pro-phenol oxidase-activating factors, named PPAF-I and PPAF-II, directly involved in the activation of the purified pro-phenol oxidase (pro-PO) from the hemolymph of the coleopteran, Holotrichia diomphalia larvae [Lee, S. Y., Kwon, T. H., Hyun, J. H., Choi, J. S., Kawabata, S. I., Iwanga, S, & Lee, B. L. (1998) Eur. J. Biochem. 254, 90-97]. Here, we report molecular cloning of cDNA for PPAF-I. Based on the sequence of the cloned cDNA, the PPAF-I gene appears to encode a member of serine protease zymogen consisting of 365 amino acid residues with a molecular mass of 40193 Da. The 109 amino acid residues preceding the amino-terminus Ile residue of the mature protein seem to constitute a prepro-sequence. The mature protein is a serine protease composed of 256 amino acids with a calculated molecular mass of 28009 Da. The overall structure is highly similar to that of Drosophila easter serine protease (42.9% identity), an essential serine protease zymogen for pattern formation in normal embryonic development. The locations of disulfide linkages in the pro-segment of PPAF-I were similar to those of Tachypleus proclotting enzyme and the mammalian neutrophil-derived defensin. Furthermore, [3H]diisopropylphosphate (iPr2P)-labeled PPAF-I was specifically produced from the crude preparation of PPAF-I zymogen by incubation with lipopolysaccharide or 1,3-beta-glucan, whereas [3H]iPr2P-labeled PPAF-I was not produced under the same conditions in the absence of these microbial polysaccharides. These results indicate that the pro-PO-activation system in H. diomphalia larvae may proceed with the activation of PPAF-I zymogen by microbial polysaccharides.

Amino Acid Sequence↗
PubMed1998

Linker DNA and H1-dependent reorganization of histone-DNA interactions within the nucleosome.

We have employed a site-directed photochemical cross-linking procedure to precisely map interactions between nucleosomal DNA and the C-terminal tail of core histone H2A. We find that this tail has the potential to contact multiple sites within the nucleosome and that these contacts are dependent upon the configuration of the complex. This tail contacts DNA near the dyad axis within nucleosome core particles but rearranges to a site near the edge of the nucleosomal DNA when linker DNA is present. Moreover, in the presence of linker histone H1 the contacts near the edge of the nucleosome but not at the dyad are further rearranged. In addition, we present further evidence for the suggestion that the binding of linker histone causes a subtle but global change in core histone-DNA interactions within the nucleosome [Usachenko, S. I., Gavin, I. M., and Bavykin, S. G. (1996) J. Biol. Chem. 271, 3831-3836].

Animals↗
PubMed1998

(1,4,7-trimethyl-1,4,7-triazacyclononane)iron (III)-mediated cleavage of DNA: detection of selected protein-DNA interactions.

A new reagent for the oxidative cleavage of DNA, (1,4,7-trimethyl-1, 4,7-triazacyclononane)iron(III) chloride was recently introduced. We have determined the utility of this reagent for detecting protein-DNA interactions within two types of complexes. Interestingly, we find that the rates of DNA cleavage by this reagent are differentially affected by the two classes of protein-DNA interactons studied. We find that the rate of DNA cleavage by this reagent is relatively unaffected by the non-sequence-specific histone-DNA interactions within a nucleosome complex. Conversely, a clear footprint pattern is obtained with two different DNA sequence-specific protein-DNA complexes. The results suggest that (1,4,7-trimethyl-1,4,7-triazacyclononane)iron(III) chloride will be a useful reagent to probe trans -acting-factor-DNA interactions within a chromatin environment. Differences between these two types of protein-DNA interactions, which might account for this observation, are discussed.

Bacterial Proteins↗
PubMed1998

Physiologically based pharmacokinetic model for chronic inhalation of 2-butoxyethanol.

2-Butoxyethanol (2BE) is used extensively in the production of cleaning agents and as a general solvent. It is primarily metabolized in the liver to 2-butoxyacetic acid (2BAA), which is excreted in urine. The objective of this study was to develop a physiologically based pharmacokinetic (PBPK) model describing the toxicokinetic behavior of 2BE and 2BAA in different species following repeated, long-term exposures. The PBPK model was first developed for short-term 2BE exposure to male rats. Allometric scaling was employed to estimate physiological and biochemical model parameters based on body weight. To accommodate differences in 2BE toxicokinetics in female rats, a higher Vmax for 2BE metabolism to 2BAA, higher plasma protein binding sites for 2BAA, and lower Vmax for 2BAA excretion through the kidney were incorporated into the model. For mice, a higher Vmax for 2BE metabolism to 2BAA for both sexes and higher plasma protein binding sites for 2BAA for female mice were also incorporated into the model. Subsequently, the model was expanded to simulate 2BE and 2BAA toxicokinetics for long-term, repeated exposures by incorporating time-dependent changes in model parameters. To reflect physiological/biochemical changes in animals during a chronic exposure, parameters for cardiac output, body composition, metabolic capacity, protein binding, or capacity of renal excretion were adjusted over time depending on species and sex. Sensitivity analysis was performed to better understand how sensitive model responses were to uncertainties in input parameters. The resulting PBPK model was used to simulate toxicokinetic data acquired during a 2-year inhalation toxicity and carcinogenicity study in male and female F344/N rats and B6C3F1 mice.

Administration, Inhalation↗
PubMed1998

Toxicokinetics of inhaled 2-butoxyethanol and its major metabolite, 2-butoxyacetic acid, in F344 rats and B6C3F1 mice.

2-Butoxyethanol (2BE) is used extensively in the production of cleaning agents and solvents. It is primarily metabolized in the liver to 2-butoxyacetic acid (2BAA), which is believed to be responsible for 2BE toxicities associated with hemolysis of red blood cells. The objective of the study was to characterize the systemic disposition of 2BE and 2BAA in rats and mice during 2-year 2BE inhalation toxicity studies. Male and female F344 rats and B6C3F1 mice (6-7 weeks old) were exposed to target 2BE concentrations of 0, 31.2, 62.5, or 125 ppm (rats), or 0, 62.5, 125, or 250 ppm (mice), by whole-body inhalation for 6 h/day, 5 days/week for up to 18 months. Postexposure blood samples were collected after 1 day, 2 weeks, and 3, 6, 12, and 18 months of exposure. Postexposure 16-h urine samples were collected after 2 weeks and 3, 6, 12, and 18 months of exposure. A separate set of mice was kept in the control chamber and exposed to 2BE for 3 weeks when they were approximately 19 months old. Postexposure blood samples were collected after 1 day and 3 weeks of exposure and 16-h urine samples were collected after 2 weeks of exposure from these aged mice. Blood samples were analyzed for both 2BE and 2BAA and urine samples were analyzed for 2BAA using GC/MS, and their kinetic parameters were estimated through the curve-fitting method using SAS. Systemically absorbed 2BE was rapidly cleared from blood (t1/2-RAT < 10 min; t1/2-MOUSE < 5 min after the 1-day exposure) independent of exposure concentration. Proportional increases in AUC2BE relative to increases in exposure concentration indicated linear 2BE kinetics. In contrast, the rate of 2BAA elimination from blood decreased as the exposure concentration increased. Nonproportional increases in AUC2BAA also indicated that 2BAA is eliminated following dose-dependent, nonlinear kinetics. Overall, mice eliminated both 2BE and 2BAA from blood faster than rats. Sex-related differences in 2BAA elimination were most significant with rats, in that females were less efficient in clearing 2BAA from the blood. Differences in renal excretion of 2BAA are possibly responsible for the sex-related difference in the 2BAA blood profiles in rats. As exposure continued, the rates of elimination for both 2BE and 2BAA decreased in both species, resulting in longer residence times in the blood. When 19-month-old naive mice were exposed to 125 ppm, 2BE was rapidly cleared from the systemic circulation, exhibiting clearance profiles similar to young mice. However, old mice eliminated 2BAA from blood > 10 times slower than young mice after 1-day of exposure. This delayed elimination of 2BAA in old mice was less obvious after 3 weeks of exposure, suggesting that there might be other factors in addition to the age of animals that could influence the apparent difference in 2BAA kinetics between old and young mice. It was concluded that the elimination kinetics of 2BE and 2BAA following repeated 2BE exposure appear to be dependent on species, sex, age, time of exposure, as well as the exposure concentration.

Administration, Inhalation↗
PubMed1998

Chromosome spatial order in human cells: evidence for early origin and faithful propagation.

We have investigated the origin and nature of chromosome spatial order in human cells by analyzing and comparing chromosome distribution patterns of normal cells with cells showing specific chromosome numerical anomalies known to arise early in development. Results show that all chromosomes in normal diploid cells, triploid cells and in cells exhibiting nondisjunction trisomy 21 are incorporated into a single, radial array (rosette) throughout mitosis. Analysis of cells using fluorescence in situ hybridization, digital imaging and computer-assisted image analysis suggests that chromosomes within rosettes are segregated into tandemly linked "haploid sets" containing 23 chromosomes each. In cells exhibiting nondisjunction trisomy 21, the distribution of chromosome 21 homologs in rosettes was such that two of the three homologs were closely juxtaposed, a pattern consistent with our current understanding of the mechanism of chromosomal nondisjunction. Rosettes of cells derived from triploid individuals contained chromosomes segregated into three, tandemly linked haploid sets in which chromosome spatial order was preserved, but with chromosome positional order in one haploid set inverted with respect to the other two sets. The spatial separation of homologs in triploid cells was chromosome specific, providing evidence that chromosomes occupy preferred positions within the haploid sets. Since both triploidy and nondisjunction trisomy 21 are chromosome numerical anomalies that arise extremely early in development (e.g., during meiosis or during the first few mitoses), our results support the idea that normal and abnormal chromosome distribution patterns in mitotic human cells are established early in development, and are propagated faithfully by mitosis throughout development and into adult life. Furthermore, our observations suggest that segregation of chromosome homologs into two haploid sets in normal diploid cells is a remnant of fertilization and, in normal diploid cells, reflects segregation of maternal and paternal chromosomes.

Adult↗
PubMed1998

House dust mite-induced sensitivity in mice.

Sensitivity induced by house dust mite (HDM) extract in mice was investigated in this study. Sensitized B10.RIII mice (H-2r background) had T-cell proliferative responses to HDM extract in vitro and an HDM-specific IgE response. When mice were immunized by injection and intranasal inhalation with HDM extract, a histologic study showed eosinophils and mononuclear cell infiltration in the lung tissue and bronchial wall. Tcr alphabeta-positive cells were also found in the cell infiltration area of the lung lesions. In the control mice that were immunized by injection or intranasal inhalation (but not both), we did not observe cell accumulation in the lung tissue or in the bronchial wall. Epitope studies suggest that T cells recognize multiple epitopes. Molecular analysis of these HDM-specific T-cell hybridoma clones suggest that T-cell receptor use is restricted to members of the V alpha 8 and Vbeta 6 subfamilies.

Allergens↗
PubMed1998

Cloning and expression of a Clostridium thermocellum xylanase gene in Escherichia coli.

A Clostridium thermocellum xylanase gene, designated xynX, was cloned in Escherichia coli and was categorized a novel gene as a result of the comparison of restriction patterns of the C. thermocellum xylanase genes so far reported. The xynX gene encodes a xylanase having the molecular weight of 105 kilodaltons. A number of smaller truncated proteins with activities towards 4-methylumbelliferyl-beta-D-cellobioside and xylan were also produced. The enzyme hydrolyzed xylan to xylo-oligosaccharide, indicating typical activity of endo-beta-1,4-xylanase. This endoxylanase hydrolyzed carboxymethylcellulose without notable reduction of the viscosity as an exo-beta-1,4-glucanase, even though the enzyme exhibited very low levels of activity against other soluble and insoluble cellulosic substrates.

Carboxymethylcellulose Sodium↗
PubMed1998

Endotoxin-induced alteration in the expression of leptin and beta3-adrenergic receptor in adipose tissue.

Cytokines, such as tumor necrosis factor (TNF) and interleukin-6, may contribute to the anorexia and cachexia of infection, cancer, and AIDS. The present study tests the hypothesis that endotoxin alters the expression of two key fat cell proteins, leptin and beta3-adrenergic receptor (beta3-AR), through a mechanism involving TNF-alpha. Increasing doses of Escherichia coli endotoxin (lipopolysaccharide, LPS) resulted in dose-dependent elevations of plasma leptin (maximal response approximately 7-fold, half-maximal effective dose of approximately 16 microg/100 g body wt) and white fat leptin mRNA in C3/HeOUJ mice. LPS also produced a large decrease in adipose tissue beta3-AR mRNA and a parallel reduction in beta-agonist-induced activation of adenylyl cyclase. Changes in plasma leptin and beta3-AR mRNA were preceded by an approximately threefold increase in white fat TNF mRNA. TNF administration resulted in changes similar to those seen with LPS. We conclude that endotoxemia results in an induction of leptin mRNA and a decrease in beta3-AR mRNA in adipose tissue, an effect that may be mediated by alterations in TNF-alpha.

Adenylyl Cyclases↗