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Biomedical subjects

K M Lee

Publications and source records attributed to K M Lee.

At least 109 records · Page 6Linked to original sources
PubMed2000

Proto-oncogene Raf-1 as an autoantigen in Meniere's disease.

The 28 kd protein extracted from the guinea pig inner ear membranous fraction, which reacted with sera from patients with Meniere's disease, has been subjected to microsequencing. Nineteen amino acids were obtained (IVQQFGFQRRASDDGKLTQ). A protein data bank search showed that this sequence corresponded to residues 41 to 60 of human Raf-1 protein. Sera from 16 of 27 patients with Meniere's disease showed reactivity to the recombinant purified glutathione-S-transferase-Raf-1 protein. These results support the hypothesis that a subgroup of patients who suffer from Meniere's disease, as well as some other kinds of autoimmune inner ear diseases, have an autoantibody against Raf-1 protein.

Amino Acid Sequence↗
PubMed2000

Generalized low areal and volumetric bone mineral density in adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) may be associated with generalized low bone mineral status. The bone mineral density (BMD) of 75 girls of 12-14 years of age and diagnosed as having AIS were compared with 94 age-matched female control subjects. Areal BMD (aBMD) of the lumbar spine (L2-L4) and the bilateral proximal femur were measured using-energy X-ray absorptiometry (DEXA), and volumetric BMD (vBMD) of the nondominant distal radius and bilateral distal tibias was measured with peripheral quantitative computer tomography (pQCT). Relevant anthropometric parameters and the severity of the spinal deformity (Cobb's angle) also were evaluated and correlated with the BMD measurements. Results revealed the presence of a generalized lower bone mineral status in AIS patients. Detailed analysis showed that the aBMD and vBMD measured at the bilateral lower extremities were significantly lower in AIS patients when compared with the same in the normal controls. The most significant effect was seen in the trabecular BMD (tBMD) of the distal tibias. Of all the AIS girls, 38% of the aBMD and 36% of the vBMD were below -1 SD of the normal. BMD was found to correlate better with "years since menarche" (YSM) than with chronological age. When the BMD was evaluated for the 3 YSM groups, aBMD of the proximal femur and tBMD of distal tibias were found to be significantly lower in the AIS patients. Neither the aBMD nor the vBMD of AIS patients was found to be associated with the severity of spinal deformity. In addition, anthropometric measurements showed significantly longer arm span and lower extremities in the AIS girls. We concluded that the AIS girls had generalized lower aBMDs and vBMDs.

Adolescent↗
PubMed2000

Cost effectiveness of epoetin-alpha to augment preoperative autologous blood donation in elective cardiac surgery.

OBJECTIVE: The objective of this study was to assess the cost effectiveness of using epoetin-alpha (erythropoietin) to augment preoperative autologous donation (PAD) of blood prior to elective cardiac surgery. DESIGN AND SETTING: We designed a decision-analytic model incorporating the risk of receiving allogeneic blood, the costs of blood products, the likelihood of developing transfusion-related diseases, the costs of transfusion-related diseases and their impact on life expectancy, and the effect of epoetin-alpha on the probability of transfusion. INTERVENTIONS: The efficacy of epoetin-alpha was derived from data from a meta-analysis of published randomised trials comparing the use of epoetin-alpha to augment PAD with the use of PAD alone. Estimates for the other parameters were obtained by a systematic review of the literature. MAIN OUTCOME MEASURES AND RESULTS: The use of epoetin-alpha reduced the proportion of patients receiving allogeneic transfusions by 60% (from 31.6 to 12.7%). However, this led to only a modest benefit of 0.000035 life years gained per patient and an incremental cost per life year gained of $Can44.6 million (1998 Canadian dollars). A detailed sensitivity analysis confirmed that the cost-effectiveness ratio was larger than that which is generally considered acceptable. CONCLUSIONS: Our study indicates that the use of epoetin-alpha to reduce perioperative allogeneic transfusions in cardiac surgery is not cost effective.

Blood Transfusion, Autologous↗
PubMed2000

Cortical areas differentially involved in multiplication and subtraction: a functional magnetic resonance imaging study and correlation with a case of selective acalculia.

A patient with an intracranial hemorrhage showed differential impairment among arithmetic types (impaired in multiplication but not in subtraction). A functional magnetic resonance imaging (fMRI) experiment using normal volunteers also revealed a differential activation between the two arithmetic types. The fMRI result could account for the selective acalculia of the patient in that the lesion shown by structural MRI included the region with multiplication-higher activation and spared subtraction-higher regions. These findings suggest that the cognitive mechanism and neural substrates differ among the simple arithmetic operations.

Adult↗
PubMed1999

Identification of genes controlled by quorum sensing in Pseudomonas aeruginosa.

Bacteria communicate with each other to coordinate expression of specific genes in a cell density-dependent fashion, a phenomenon called quorum sensing and response. Although we know that quorum sensing via acyl-homoserine lactone (HSL) signals controls expression of several virulence genes in the human pathogen Pseudomonas aeruginosa, the number and types of genes controlled by quorum sensing have not been studied systematically. We have constructed a library of random insertions in the chromosome of a P. aeruginosa acyl-HSL synthesis mutant by using a transposon containing a promoterless lacZ. This library was screened for acyl-HSL induction of lacZ. Thirty-nine quorum sensing-regulated genes were identified. The genes were organized into classes depending on the pattern of regulation. About half of the genes appear to be in seven operons, some seem organized in large patches on the genome. Many of the quorum sensing-regulated genes code for putative virulence factors or production of secondary metabolites. Many of the genes identified showed a high level of induction by acyl-HSL signaling.

4-Butyrolactone↗
PubMed1999

Prognostic factors in 677 patients in Singapore with nondisseminated nasopharyngeal carcinoma.

BACKGROUND: The objective of the current study was to describe the survival of nasopharyngeal carcinoma (NPC) patients in Singapore, verify the prognostic value of the revised 1997 TNM staging system, and develop a multivariate prognostic model for NPC. In addition, the authors also examined the prognostic value of characteristics of lymph node spread and parapharyngeal involvement. METHODS: A prospectively maintained database containing clinical and computed tomography scan data was used to reclassify 677 NPC patients treated between 1992 and 1994 according to the new staging system. Records were linked with the death registry to ascertain the patient's vital status and date of death. Overall and stage specific survival were analyzed using the Kaplan-Meier method and the log rank test. Univariate and multivariate Cox proportional hazards regression analysis were used to obtain prognostic models. RESULTS: Two hundred seventy-four deaths (40.5%) occurred. The 5-year survival rate was 56.6% (95% confidence interval [95% CI], 52.3%, 60.7%). The stage specific 5-year survival rates were: Stage I, 88%; Stage IIA, 75%; Stage IIB, 74%; Stage III, 60%; Stage IVA, 35%; and Stage IVB, 28%. TNM stage was found to be a statistically significant prognostic factor (P < 0.0001). Cranial nerve (hazard ratio [HR]: 2.77), orbit (HR: 5.71), and intracranial involvement (HR: 2.46) conferred a particularly bad prognosis in univariate analysis. Independently significant prognostic factors were age; lymph node status; and paraoropharyngeal, cranial nerve, orbit, and nasal involvement. Among lymph node positive patients, independently significant prognostic lymph node characteristics were Ho level and laterality. Although parapharyngeal involvement appeared to be prognostically unimportant, paraoropharyngeal involvement distinguished a subgroup with a poorer prognosis (HR: 1.84; 95% CI, 1.45, 2.34; P < 0.0001). Lateral spread to the medial infratemporal fossa and beyond also was found to confer a poorer prognosis. CONCLUSIONS: The results of the current study show that the revised 1997 TNM staging system is prognostically useful. Subdivision into paraoropharyngeal involvement and using the medial infratemporal fossa to delineate prognostically significant lateral spread should be considered in future revisions.

Adolescent↗
PubMed1999

Concurrent chemoradiotherapy followed by adjuvant chemotherapy in Asian patients with nasopharyngeal carcinoma: toxicities and preliminary results.

PURPOSE: Nasopharyngeal carcinoma (NPC) is endemic in Singapore. Nearly 60% of the patients diagnosed with NPC will present with locally advanced disease. The North American Intergroup study 0099 reported improved survival outcome in patients with locally advanced NPC who received combined chemoradiotherapy when compared to radiotherapy alone. Hence we explored the feasibility and efficacy of a similar protocol in our patients. METHODS AND MATERIALS: Between June 1996 and December 1997, 57 patients were treated with the following schedule as described. Radical radiotherapy (RT) of 66-70 Gy to the primary and neck with cisplatin (CDDP) 25 mg/m2 on days 1-4 given by infusion over 6-8 hours daily on weeks 1, 4, and 7 of the RT. This is followed by a further 3 cycles of adjuvant chemotherapy starting from week 11 from the first dose of radiation (CDDP 20 mg/m2/d and 5-fluorouracil [5-FU] 1 gm/m2/d on days 1-4 every 28 days). RESULTS: The majority of patients (68%) had Stage IV disease. About 54% of patients received all the intended treatment; 75% received all 3 cycles of CDDP during the RT phase and 63% received all three cycles of adjuvant chemotherapy. The received dose intensity of CDDP and 5-FU of greater than 0.8 was achieved in 58% and 60% of the patients respectively. Two treatment-related deaths due to reactivation of hepatitis B and neutropenic sepsis respectively, were encountered. At median follow-up of 16 months, 14 patients had relapsed, 12 systemically and 2 loco-regionally. CONCLUSION: Due to the acceptable tolerability of such a protocol in our cohort of patients, we have embarked on a Phase III study to confirm the results of the 0099 Intergroup study in the Asian context.

Adult↗
PubMed1999

Antifungal activities of recombinant antifungal protein by conjugation with polyethylene glycol.

Tenecin 3, an antifungal protein isolated from coleopteran insect Tenebrio molitor larvae, inhibited growth of the fungus Candida albicans. We have previously reported that tenecin 3 has a propensity of random structure with very loose turn-like elements by circular dichroism (CD) analysis and 2D nuclear overhauser effect spectroscopy [Lee et al. (1999)]. However, the antifungal mechanism of tenecin-3 has not yet been studied due to its very low availability from natural sources. As an initial step to study the antifungal mechanism of tenecin 3, recombinant tenecin 3 (RT-3) obtained from an expression system in Escherichia coli showed antifungal activity against C. albicans as did natural tenecin 3. To elucidate the antifungal mechanism of RT-3 and to explore the possibility of preparing polyethylene glycol (PEG) conjugated derivative, we synthesized PEG conjugated RT-3 (RT-3-PEG) and examined its antifungal activity against C. albicans in vitro. RT-3-PEG showed greater antifungal activity against C. albicans than RT-3 alone at the same dose. When C. albicans was treated with RT-3-PEG in vitro, K+ in the C. albicans cell was leaked out rapidly compared to the C. albicans treated with RT-3 alone. When the morphological change of RT-3-PEG treated C. albicans was examined by scanning electron microscopy, string-like substances, which may have been derived from the fungus, were stacked around the cell whose wall was damaged. Also, no appreciable hemolysis of mouse erythrocytes was detected under conditions in which 1% melittin caused 100% hemolysis. These results suggested that the RT-3-PEG derivative probably does not interact with mammalian cell appreciably, although it has antifungal activity.

Animals↗
PubMed1999

hSWI/SNF disrupts interactions between the H2A N-terminal tail and nucleosomal DNA.

We have employed a site-specific core histone-DNA cross-linking approach to investigate the mechanism of hSWI/SNF remodeling of a nucleosome. Remodeling results in the complete loss of canonical contacts between the N-terminal tail of H2A and DNA while new interactions are detected between this domain and DNA near the center of the original nucleosome. The data are consistent with a model in which remodeling results in the unraveling of a region of DNA from the edge of the nucleosome, leading to a repositioning of the H2A/H2B dimer to a noncanonical position near the center of the remodeled complex. Additionally, we find that prior cross-linking of the H2A N-terminal region to nucleosomal DNA does not restrict hSWI/SNF remodeling of the remainder of the nucleosome. Thus, disruption of both H2A-DNA interactions near the edge of the nucleosome is not an obligatory step in remodeling of the remainder of the complex.

Animals↗
PubMed1999

Cdc2 activation in fission yeast depends on Mcs6 and Csk1, two partially redundant Cdk-activating kinases (CAKs).

Cyclin-dependent kinases (Cdks) are fully active only when phosphorylated by a Cdk-activating kinase (CAK) [1]. Metazoan CAK is itself a Cdk, Cdk7, whereas the CAK of Saccharomyces cerevisiae is a distinct enzyme unrelated to Cdks [1]. The Mcs6-Mcs2 complex of Schizosaccharomyces pombe is a putative CAK related to the metazoan enzyme [2] [3]. Although the loss of Mcs6 is lethal, it results in a phenotype that is inconsistent with a failure to activate Cdc2, the major Cdk in S. pombe [3]. We therefore tested the ability of Csk1, a putative regulator of Mcs6 [4], to activate Cdk-cyclin complexes in vitro. Csk1 activated both the monomeric and the Mcs2-bound forms of Mcs6. Surprisingly, Csk1 also activated Cdc2 in complexes with either Cdc13 or Cig2 cyclins. When a double mutant carrying a csk1 deletion and a temperature-sensitive mcs6 allele was incubated at the restrictive temperature, Cdc2 was not activated and the cells underwent a cell division arrest prior to mitosis. Cdc2-cyclin complexes isolated from the arrested cells could be activated in vitro by recombinant CAK, whereas complexes from wild-type cells or either of the single mutants were refractory to activation. Thus, fission yeast contains two partially redundant CAKs: the Mcs6-Mcs2 complex and Csk1. Inactivation of both CAKs is necessary and sufficient to prevent Cdc2 activation and cause a cell-cycle arrest. Mcs6, which is essential, may therefore have required functions other than Cdk activation.

Adenosine Triphosphate↗
PubMed1999

The pro-phenoloxidase of coleopteran insect, Tenebrio molitor, larvae was activated during cell clump/cell adhesion of insect cellular defense reactions.

To characterize the proteins involved in cell clump/cell adhesion of insect cellular defense reactions, we induced the cell clump/cell adhesion reaction in vitro with the hemolymph of larvae of the coleopteran insect, Tenebrio molitor. The 72 kDa protein was specifically enriched in the residues of cell clump/cell adhesion and was purified to homogeneity. A cDNA clone for the 72 kDa protein was isolated. We found that the 72 kDa protein was an activated phenoloxidase from Tenebrio pro-phenoloxidase. We suggest that activated phenoloxidase is involved in the cell clump/cell adhesion reaction as well as in the synthesis of melanin.

Amino Acid Sequence↗
PubMed1999

Regulation of cytotoxic T lymphocyte-associated molecule-4 by Src kinases.

Cytotoxic T lymphocyte-associated molecule-4 (CTLA-4) is a cell surface receptor expressed on activated T cells that can inhibit T cell responses induced by activation of the TCR and CD28. Studies with phosphorylated peptides based on the CTLA-4 intracellular domain have suggested that tyrosine phosphorylation of CTLA-4 may regulate its interactions with cytoplasmic proteins that could determine its intracellular trafficking and/or signal transduction. However, the kinase(s) that phosphorylate CTLA-4 remain uncharacterized. In this report, we show that CTLA-4 can associate with the Src kinases Fyn and Lck and that transfection of Fyn or Lck, but not the unrelated kinase ZAP70, can induce tyrosine phosphorylation of CTLA-4 on residues Y201 and Y218. A similar pattern of tyrosine phosphorylation was found in pervanadate-treated Jurkat T cells stably expressing CTLA-4. Phosphorylation of CTLA-4 Y201 in Jurkat cells correlated with cell surface accumulation of CTLA-4. CTLA-4 phosphorylation induced the association of CTLA-4 with the tyrosine phosphatase SHP-2, but not with phosphatidylinositol 3-kinase. In contrast, Lck-induced phosphorylation of CD28 resulted in the recruitment of phosphatidylinositol 3-kinase, but not SHP-2. These findings suggest that phosphorylation of CD28 and CTLA-4 by Lck activates distinct intracellular signaling pathways. The association of CTLA-4 with Src kinases and with SHP-2 results in the formation of a CTLA-4 complex with the potential to regulate T cell activation.

Abatacept↗
PubMed1999

Reorganization of myosin and focal adhesion proteins in Swiss 3T3 fibroblasts induced by transforming growth factor beta.

Certain types of cells show a dramatic change in cell morphology cultured in the presence of transforming growth factor beta (TGF-beta). To identify cellular components or factors leading to morphological changes, we investigated if any members of cytoskeletal proteins and cell-adhesion molecules were redistributed in TGF-beta-treated Swiss 3T3 fibroblasts by indirect immunofluorescence and Western-blot analysis. Changes in cell morphology became apparent within 12 h of the addition of TGF-beta and new RNA and protein synthesis was necessitated by the changes. While TGF-beta induced reorganization of microfilaments as reported in earlier studies, one of the actin isoforms, alpha actin of smooth muscle, was induced to form stress fibers in Swiss 3T3 cells. It was observed that myosin light chain was relocated from cell periphery to cytoplasmic filamentous structures by TGF-beta treatment, with an increased amount. In addition, the cell-shape change was accompanied by an increase in the level of vinculin and tyrosine phosphorylation at focal adhesions. These results suggest that new protein synthesis is required for the cell-shape change, and acto-myosin filaments and focal adhesion proteins are involved in the alteration of cell morphology induced by TGF-beta in Swiss 3T3 fibroblasts.

3T3 Cells↗
PubMed1999

Subregions within the supplementary motor area activated at different stages of movement preparation and execution.

Previous studies have provided evidence that the primary motor area (M1) is involved in actual execution of a motor program, while the premotor area (PreMA) and the supplementary motor area (SMA) play a role in its preparation. We have used the high temporospatial resolution of functional magnetic resonance imaging (fMRI) to study the relationship between stages of a motor program and activation of these motor-related cortical areas. Seven normal volunteers performed a delayed-motor task in which the preparation of finger movements was dissociated in time from movement execution, while event-related fMRI was obtained. The M1 and PreMA showed expected activation associated with execution and preparation stages, respectively. Within SMA, subregions with different temporal profiles of activation were identified: The anterior part became activated early in the preparation period, whereas the posterior part only with movement execution. This supports the notion that the classic SMA consists of the pre-SMA and SMA proper each with different functions.

Adult↗
PubMed1999

The kinetic characteristics of K228G mutant horse liver alcohol dehydrogenase.

The kinetic constants and the reaction mechanism of the K228G mutant horse liver alcohol dehydrogenase isoenzyme E (HLADH-E) were compared to the wild-type enzyme. All the Km and Ki constants of the mutant enzyme for NAD+, ethanol, acetaldehyde and NADH were larger than those of the wild-type enzyme. The dissociation constants for the NADH and NAD+ (Kiq and Kia) were greatly increased by 130- and 460-fold, respectively. The product inhibition patterns suggested that the reaction mechanism of the mutant enzyme was changed to Random Bi Bi. These results could attribute to the increase in the dissociation rate of coenzyme with the substitution at Lys-228 residue.

Alcohol Dehydrogenase↗
PubMed1999

Bistage control of pH for improving exopolysaccharide production from mycelia of Ganoderma lucidum in an air-lift fermentor.

It was found that pH control definitely affects mycelial cell growth and exopolysaccharide (EPS) production of the mycelial cultivation of Ganoderma lucidum. Compared to the case of uncontrolled pH cultivation, a culture system whose pH was kept constant at 3 and 6 exhibited improved mycelial cell growth and EPS production, respectively. The bistage pH control technique, that is, shifting the pH from 3 to 6 at the initial phase of the exponential growth, is introduced to improve cell growth and EPS production. This technique can greatly increase EPS production to 20.1 g/l from 4.1 g/l in the case of uncontrolled pH cultivation, without adverse effects on cell growth as in the case of constant maintenance of a high pH. It was also proved that bistage pH control retained the desirable morphologies of the mycelia during cultivation and resulted in low viscosity and yield stress of the culture broth. It will be useful for the application of the culture process to mycelial growth in a large-scale fermentor.

Journal Article↗