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Biomedical subjects

K Lee

Publications and source records attributed to K Lee.

At least 379 records · Page 21Linked to original sources
PubMed1998

The DNA binding domains of the WT1 tumor suppressor gene product and chimeric EWS/WT1 oncoprotein are functionally distinct.

The t(11;22)(p13;q12) translocation associated with desmosplastic small round cell tumor results in a chimeric molecule fusing the amino terminal domain (NTD) of the EWS1 gene to three of the four carboxy-terminal zinc fingers of the WT1 tumor suppressor gene. Since the DNA binding domains of WT1 and EWS/WT1 are structurally different, we have assessed the functional consequences of the EWS/WT1 fusion. We find that the EWS/WT1 protein has a higher binding affinity for a given recognition target than the WT1 product. This is unlike other fusion products involving translocation of the NTD of EWS to DNA binding domains in which DNA binding specificity and affinity is not changed. We demonstrate that EWS/WT1 is a nuclear protein and that the NTD of EWS contains (a) nuclear localization signal(s). We also find that the integrity of a domain within the WT1 zinc fingers, responsible for mediating interaction between WT1 and the transcriptional repressor par-4, is disrupted in the EWS/WT1 fusion product. Deletion analysis of the NTD of EWS indicated that integrity of the entire domain was necessary to achieve full transactivation potential.

Animals↗
PubMed1998

Genetic and hematological studies in a group of 114 adult patients with SC sickle cell disease.

The clinical and biological heterogeneity of sickle cell hemoglobin (Hb) C disease (SC disease) is similar to sickle cell anemia, but has a much milder course. The effect of genetic factors such as alpha thalassemia or beta-globin gene haplotype has been analyzed in a limited number of cases. In this work, we report about 114 adult SC patients, aged 15 to 65 years (M/F = 0.93). The frequency of deletional alpha thalassemia (alpha(-3.7)) was found to be about 35%. The coinheritance of an alpha-thalassemia trait with SC disease had no effect on the hemoglobin level but hemolysis was significantly reduced. In these patients, as described for homozygous Hb S individuals, the Hb F level was higher in females than in males and in individuals carrying the beta(s)-Senegal haplotype. This haplotype involves the presence of an Xmnl site 5' to Ggamma, which is considered responsible for an increased Ggamma/Agamma ratio. Our survey showed that some genetic factors may modulate hematological parameters in SC disease.

Adolescent↗
PubMed1998

Control of cytoskeletal architecture by the src-suppressed C kinase substrate, SSeCKS.

Activation of protein kinase C (PKC) in many cell types results in cytoskeletal reorganization associated with cell proliferation. We previously described a new cell cycle-regulated myristylated PKC substrate, SSeCKS (pronounced essex), that interacts with the actin cytoskeleton [Lin et al., 1995, 1996]. SSeCKS shares significant homology with Gravin, which encodes kinase scaffolding functions for PKC and PKA [Nauert et al., 1997]. This article describes the cellular effects of ectopically expressing SSeCKS in untransformed NIH3T3 fibroblasts. Because the constitutive overexpression of SSeCKS is toxic [Lin et al., 1995], we developed cell lines with tetracycline (tet)-regulated SSeCKS expression. The induction of SSeCKS (removal of tet) caused significant cell flattening and the elaboration of an SSeCKS-associated cortical cytoskeletal matrix resistant to Triton X-100 extraction. Flattened cells were growth-arrested and marked by the formation of cellular projections and the temporary loss of actin stress fibers and vinculin-associated adhesion plaques. SSeCKS overexpression did not affect steady-state levels of actin, vinculin, or focal adhesion kinase (FAK) but did increase integrin-independent FAK tyrosine phosphorylation. Stress fiber loss was coincident with induced SSeCKS expression, strongly suggesting a direct effect. Cytochalasin, and to a lesser extent nocodazole, inhibited SSeCKS-induced cell flattening, however, only cytochalasin affected the shape of pre-flattened cells, suggesting a greater dependence on microfilaments, rather than microtubules. By contrast, only nocodazole caused retraction of the filopodia-like processes. These data indicate a role for SSeCKS in modulating both cytoskeletal and signaling pathways. Thus, we propose to expand SSeCKS scaffolding functions to include the ability to control actin-based cytoskeletal architecture, as well as mitogenic signal pathways.

3T3 Cells↗
PubMed1998

Analysis of two transcription activation elements in the promoter of the developmentally regulated con-10 gene of Neurospora crassa.

The con-10 gene of Neurospora crassa is activated during conidiation. CRS-B (conidiation response sequence-B) and CGE (con-10 general enhancer) elements have been proposed to function as sites of transcriptional activation and as possible elements that confer developmental regulation to con-10. In a specific analysis of the roles of these elements we found that two CRS-B elements are necessary for full activation of con-10 during macroconidiation, whereas two CGE elements are functionally redundant, such that a single CGE is sufficient for maximal expression. However, CRS-B and CGE elements are not sufficient for developmental activation of a reporter gene. The CRS-B element was further dissected and one of the CRS-B elements appears to function in repression as well as activation. con-10 is also highly expressed during microconidiation, a different form of asexual sporulation, but we show here that CRS-B elements do not play a significant role in con-10 expression during microconidiation. Both CRS-B elements contribute to basal con-10 expression during mycelial growth. con-10 is also regulated by light, and CRS-B and CGE elements may play minor roles in controlling con-10 expression in response to light.

Base Sequence↗
PubMed1998

Tissue-specific repression of starvation and stress responses of the Neurospora crassa con-10 gene is mediated by RCO1.

The Neurospora crassa con-10 gene is weakly expressed in mycelia but is induced approximately 1000-fold during macroconidiation. Studies of the promoter elements and trans-acting factors that regulate con-10 expression are needed to gain a detailed understanding of developmental regulation. The rco-1 mutant displays a 10-fold elevated basal level of expression of con-10. In contrast to the wild type, con-10 expression in mycelia of the rco-1 mutant was rapidly induced to high levels by starvation for carbon or nitrogen and by heat shock. Although con-10 is developmentally induced late in conidiation, con-10 was inducible by heat shock shortly after exposure of the wild-type mycelium to air. These findings support the view that RCO1 is a cell type-specific repressor of con-10. We propose that inactivation of RCO1 allows developing conidiophores to adjust the timing of con-10 induction in response to stress.

Amino Acid Sequence↗
PubMed1998

Dietary taurine supplementation reduces plasma and liver cholesterol and triglyceride levels in rats fed a high-cholesterol or a cholesterol-free diet.

The effects of dietary taurine supplementation on plasma and hepatic lipid levels and phospholipid profiles were evaluated in rats fed a high-cholesterol or a cholesterol-free diet. Four groups of male rats were fed one of the following diets for 5 weeks: cholesterol-free diet (CFD); high cholesterol diet (HCD); high cholesterol, high taurine diet (HCHTD); or high taurine diet (HTD). Rats fed a HCHTD had significantly lower plasma levels of total cholesterol (32% reduction), LDL-cholesterol (37% reduction) and triglyceride (43% reduction) than rats fed a HCD alone. Plasma concentrations of total cholesterol, LDL-cholesterol and triglyceride were also significantly reduced in rats fed a HTD compared to rats fed a CFD. Taurine supplementation to the HCD significantly reduced hepatic cholesterol (50% decrease) and triglyceride (30% decrease) levels in rats. Taurine supplementation to the CFD also significantly reduced the hepatic triglyceride concentration (43% decrease) and elevated hepatic free fatty acid levels (77% increase) compared to rats fed only a CFD. These results suggest that dietary taurine supplementation is both hypocholesterolemic and hypotriglyceridemic in rats whose body cholesterol status is high or normal.

Animals↗
PubMed1998

Antitumor activity of paclitaxel and epirubicin in human breast carcinoma, R-27.

The antitumor effect of paclitaxel, epirubicin, and both in combination was tested using R-27, an estrogen receptor-positive human breast carcinoma. In an in vivo study using nude mice both drugs showed an additive effect, whereas they showed a supraadditive pattern in in vitro MTT assay. The combination of paclitaxel and epirubicin may enhance the antitumor effect on breast carcinoma.

Animals↗
PubMed1998

Current status of anti-HBV chemotherapy.

In the past decade, significant progress has been achieved in the battle against hepatitis B virus. In addition to the immunomodulating agents such as interferon-alpha and thymosin, many novel antiviral agents have been discovered, among which nucleoside analogues are the mainstay. New-generation compounds such as 3TC and famciclovir have shown promise in the treatment of patients chronically infected by this virus, and are on the line for approval. However, viral rebound after cessation of therapy still remains a major problem. Additionally, the reports on the drug resistance to these antiviral agents suggest that combination therapy will be the eventual strategy (Bartholomew et al., 1997; Tipples et al., 1996). Therefore, developments of safe and effective antiviral agents which do not cross-resist with currently available antiviral drugs are still much needed.

Animals↗
PubMed1998

Possible implication for an indirect interaction between basic fibroblast growth factor and (Na,K)ATPase.

The (Na,K)ATPase is responsible for generating the ionic gradients and membrane potentials by the exchange of intracellular Na+ for K+. It has been recently shown that (Na,K)ATPase is involved in the exocytic pathway of basic fibroblast growth factor (bFGF), although it is not known that bFGF is secreted to the outside of cell through direct interaction with (Na,K)ATPase. To understand the role for (Na,K)ATPase in the secretory pathway of bFGF, we have sought to identify the cytoplasmic domains of the alpha 1 isoform of (Na,K)ATPase interacting with bFGF by yeast two-hybrid system. We have also investigated the interaction between the alpha 2 isoform of (Na,K)ATPase and bFGF to find out whether the interaction is isoform-specific. We found that none of the cytoplasmic domains of (Na,K)ATPase isoforms interacted with bFGF. The result suggests that the interaction between bFGF and (Na,K)ATPase might be indirect, thus requiring other proteins which are involved in the formation of protein complexes for the interaction, although we cannot exclude the possibility that the interaction requires the element of the whole alpha subunit structure that was not present in the isolated alpha subunit cytoplasmic domains.

Blotting, Western↗
PubMed1998

Nucleotide and deduced amino acid sequences of rat myosin binding protein H (MyBP-H).

The complete nucleotide sequence of the cDNA clone encoding rat skeletal muscle myosin-binding protein H (MyBP-H) was determined and amino acid sequence was deduced from the nucleotide sequence (GenBank accession number AF077338). The full-length cDNA of 1782 base pairs(bp) contains a single open reading frame of 1454 bp encoding a rat MyBP-H protein of the predicted molecular mass 52.7 kDa and includes the common consensus 'CA__TG' protein binding motif. The cDNA sequence of rat MyBP-H show 92%, 84% and 41% homology with those of mouse, human and chicken, respectively. The protein contains tandem internal motifs array (-FN III-Ig C2-FN III-Ig C2-) in the C-terminal region which resembles to the immunoglobulin superfamily C2 and fibronectin type III motifs. The amino acid sequence of the C-terminal Ig C2 was highly conserved among MyBPs family and other thick filament binding proteins, suggesting that the C-terminal Ig C2 might play an important role in its function. All proteins belonging to MyBP-H member contains 'RKPS' sequence which is assumed to be cAMP- and cGMP-dependent protein kinase A phosphorylation site. Computer analysis of the primary sequence of rat MyBP-H predicted 11 protein kinase C (PKC) phosphorylation site, 7 casein kinase II (CK2) phosphorylation site and 4 N-myristoylation site.

Amino Acid Sequence↗
PubMed1998

Acute and chronic fluoxetine treatment decreases the sensitivity of rats to rewarding brain stimulation.

The effects of fluoxetine on rewarding brain stimulation were determined in eight Wistar rats using a rate-independent discrete-trial threshold measure. Rats were implanted with bipolar, stainless steel electrodes either into the ventral tegmental area (VTA) or medial forebrain bundle (MFB). Acute administration of fluoxetine significantly raised the reward threshold (decreased sensitivity) at doses of 2.5, 5.0, 10.0, and 20.0 mg/kg, i.p., without altering latency of response. There were no significant differences between VTA and MFB groups. To determine the effects of chronic treatment, daily injections of 5.0 mg/kg fluoxetine were administered to rats for 21 days. Chronic treatment of fluoxetine continued to significantly elevate reward thresholds with no evidence of tolerance. The results of these experiments suggest that fluoxetine does not possess abuse potential and that serotonin produces an inhibitory effect on the mesolimbic dopaminergic reward system. Furthermore, these results suggest that the antidepressant effects of fluoxetine are not the direct result of excitation of brain reward systems, at least in the same manner as abused substances, for example, cocaine.

Animals↗
PubMed1998

Effects of intravenous immunoglobulin on plasma interleukin-10 levels in Kawasaki disease.

Kawasaki disease is an acute febrile disease in children and many inflammatory cytokines are known to be involved in its pathogenesis. Interleukin-10 (IL-10) is an anti-inflammatory cytokine and previous reports have shown blood IL-10 levels were elevated during the acute phase of Kawasaki disease. In this study, we endeavoured to clarify the effects of i.v.IG on plasma IL-10 levels and to verify by RT-PCR, using specific primers, whether viral IL-10 or human IL-10 was responsible for high plasma IL-10. T-cells and B-cells were separated using magnetic beads, and IL-10 mRNA expressions were tested in both cell types. The mean plasma IL-10 levels were significantly decreased from 125.037 +/- 111.161 pg/ml, before i.v.IG treatment, to 32.437 +/- 54.716 pg/ml, after i.v.IG treatment, in subjects with Kawasaki disease. The levels of patients before i.v.IG treatment were significantly higher than those of the acute febrile patients (mean 26.956 +/- 13.316 pg/ml) and the normal controls (mean 16.042 +/- 5.088 pg/ml). RT-PCR was performed using specific primers to distinguish whether viral IL-10 (BCRF-1) or human IL-10 was produced in Kawasaki disease. Viral IL-10 (BCRF-1) mRNA expression was not detected in any groups and only human IL-10 mRNA transcripts were detected in PBMCs of Kawasaki patients as well as in those of acute febrile patients and normal controls. Human IL-10 mRNA transcripts were detected in both CD3+ T-cells and CD19+ B-cells. Elevated IL-10 levels during the acute phase of Kawasaki disease decreased immediately after i.v.IG administration, coincidentally with rapid improvement of inflammatory symptoms. Elevated plasma IL-10 in Kawasaki disease was transcripted from the human IL-10 gene and IL-10 mRNA expressions were detected in both T- and B-cells. Therefore, this study suggests that plasma IL-10 levels may be useful in the early identification and discrimination of the acute phase of Kawasaki disease from other febrile diseases. However, i.v.IG effects on IL-10 production still needs further investigation.

B-Lymphocytes↗
PubMed1998

Family planning policies and programmes in eight low-income countries: a comparative policy analysis.

The extent to which family planning programmes are successful at reducing fertility remains a major debate among population scholars. A comparative policy analysis of four pairs of low-income countries (Bangladesh/Pakistan, Thailand/Philippines, Tunisia/Algeria and Zimbabwe/Zambia) was carried out to understand why some countries develop appropriate and effective programmes, while other countries do not. The study found that the formation of coalitions among policy elites, spread of policy risk, and institutional and financial stability were factors which supported or inhibited the adoption of strong population policies and family planning programmes.

Developing Countries↗
PubMed1998

Characterization of the mechanism of action of tachykinins in rat striatal cholinergic interneurons.

The mechanism by which substance P depolarizes cholinergic interneurons in the rat striatum was studied using whole-cell recording techniques. In all cases the effects of substance P were mimicked by the neurokinin1 receptor agonist [Sar9, Met(O2)11] substance P and were antagonized by the neurokinin1 receptor antagonist SR140333. [Sar9, Met(O2)11] substance P was found to depolarize cholinergic interneurons by the induction of a calcium-activated inward current at -60 mV. This inward current was irreversibly potentiated by photolysis of caged GTPgammaS within neurons implicating the involvement of a G-protein. The [Sar9, Met(O2)11] substance P-induced inward current was inhibited by the phospholipase C inhibitor U-73122, and by the inclusion of the inositol-1,4,5-triphosphate receptor antagonist heparin in the electrode solution. These findings suggest that neurokinin1 receptors depolarize cholinergic interneurons in the rat striatum primarily through a phosphoinositide signalling pathway.

2-Amino-5-phosphonovalerate↗
PubMed1998

Association of chronotropic incompetence with echocardiographic ischemia and prognosis.

OBJECTIVES: This study sought to examine the prognostic importance of chronotropic incompetence among patients referred for stress echocardiography. BACKGROUND: Although chronotropic incompetence has been shown to be predictive of an adverse prognosis, it is not clear if this association is independent of exercise-induced myocardial ischemia. METHODS: Consecutive patients (146 men and 85 women; mean age 57 years) who were not taking beta-adrenergic blocking agents and were referred for symptom-limited exercise echocardiography were followed for a mean of 41 months. Chronotropic incompetence was assessed in two ways: (1) failure to achieve 85% of the age-predicted maximum heart rate and (2) a low chronotropic index, a heart rate response measure that accounts for effects of age, resting heart rate and physical fitness. RESULTS: The primary end point, a composite of death, nonfatal myocardial infarction, unstable angina and late (>3 months after the exercise test) myocardial revascularization, occurred in 41 patients. Failure to achieve 85% of the age-predicted maximum heart rate was predictive of events (relative risk [RR] 2.47, 95% confidence interval [CI] 1.28 to 4.79, p=0.007); similarly, a low chronotropic index was predictive (RR 2.44, 95% CI 1.31 to 4.55, p=0.005). Even after adjusting for myocardial ischemia and other possible confounders, failure to achieve 85% of age-predicted maximum heart rate was predictive (adjusted RR 2.20, 95% CI 1.11 to 4.37, p=0.02). A low chronotropic index also remained predictive (adjusted RR 1.85, 95% CI 0.98 to 3.47, p=0.06). CONCLUSIONS: Chronotropic incompetence is predictive of an adverse cardiovascular prognosis even after adjusting for echocardiographic myocardial ischemia.

Echocardiography↗
PubMed1998

A prospective randomized trial of suture of the patellar tendon defect after harvesting.

In a rabbit model, we studied the long-term biomechanical and biochemical effects of leaving the patellar tendon unsutured, or closing the defect with absorbable sutures, after harvesting one third. Using a prospective randomized design, after harvest of its central third, the patellar tendon was either sutured side to side with absorbable sutures, or left unsutured in 112 skeletally mature rabbits. The rabbits were killed at 2 and 6 weeks, and 6 and 9 months postoperatively. After an initial increase in both groups (.001 < P < .019), water content decreased from 2 weeks to 9 months after the operation (.02 < P < .0045), and remained significantly greater than in the control contralateral limb at all times (.00 1 < P < .003). Collagen content showed no significant differences between the two experimental groups. The operated tendons always showed a decreased collagen content at all time periods (.012 < P < .049). Failure load, ultimate stress, stiffness, and energy absorbed before failure tended to gradually return to normal over 9 months after a significant initial drop. There were no significant differences between the two experimental groups in failure load, ultimate stress stiffness, and energy absorbed before failure. At 9 months, the operated patellar tendon was significantly thicker (.0016 < P < .03) and had a greater cross-sectional area (.01 < P < .03) than the contralateral control regardless of whether it had been sutured or left open. After removal of the central third, closing the tendon gap with absorbable sutures or leaving it open makes little difference on the biomechanical and biochemical properties of the remaining patellar tendon.

Animals↗
PubMed1998

Structural modification of an orally active thrombin inhibitor, LB30057: replacement of the D-pocket-binding naphthyl moiety.

An amidrazonophenylalanine derivative LB30057 (2) was identified as a potent (Ki = 0.38 nM), selective, and orally active thrombin inhibitor. As a continuation of studies into benzamidrazone-based thrombin inhibitors, we have structurally modified compound 2 by replacing the naphthyl group with a variety of hydrophobic moieties. This study led to discovery of several compounds with significantly enhanced potency in thrombin inhibition without sacrificing selectivity against trypsin and oral absorption. The highest activity was obtained with compound 23 (Ki = 0.045 nM).

Administration, Oral↗