PubMed Health⌕ Search

Biomedical subjects

Y J Lee

Publications and source records attributed to Y J Lee.

At least 19 recordsLinked to original sources
PubMed1996

Dual effect of 1 alpha,25-dihydroxyvitamin D3 on hsp28 and PKC beta gene expression in phorbol ester-resistant human myeloid HL-525 leukemic cells.

We investigated the effect of 1 alpha-25-dihydroxyvitamin D3 [1,25-(OH)2D3] on the expression of the 28-kDa heat shock protein gene (hsp28) and the protein kinase C beta gene (PKC beta) in the human myeloid HL-60 leukemic cell variant HL-525, which is resistant to phorbol ester-induced macrophage differentiation. Northern and western blot analysis showed little or no hsp28 gene expression in the HL-60 cell variant, HL-205, which is susceptible to such differentiation, while a relatively high basal level of hsp28 gene expression was observed in the HL-525 cells. However, both cell lines demonstrated heat shock-induced expression of this gene. During treatment with 50-300 nM 1,25-(OH)2D3, a marked reduction of hsp28 gene expression along with an induction of PKC beta gene expression was observed in HL-525 cells. A gel mobility-shift assay demonstrated that the 1,25-(OH)2D3-induced alteration of hsp28 gene expression was associated with decreased binding activity to the vitamin D3 receptor-vitamin D3 response element (VDR-VDRE), whereas binding to the heat shock transcription factor-heat shock element (HSF-HSE) was not altered. Our results suggest that the dual effect of 1,25-(OH)2D3 on hsp28 and PKC beta gene expression is due to the different sequence composition of the vitamin D response element in the promoter region as well as an accessory factor for each gene or that 1,25-(OH)2D3 increases PKC beta gene expression, which, in turn, negatively regulates the expression of the hsp28 gene or vice versa.

Calcitriol↗
PubMed1996

Cooperativity and segregation of function within the Ig-alpha/beta heterodimer of the B cell antigen receptor complex.

The B cell antigen receptor complex contains heterodimers of Ig-alpha and Ig-beta. The cytoplasmic tails of each of these chains contain two conserved tyrosines, phosphorylation of which initiates the signal transduction cascades activated by the receptor complex. Although the cytoplasmic domains of Ig-alpha and Ig-beta have been expressed individually and demonstrated to be competent signal transduction units, we postulated that within the context of a heterodimer, Ig-alpha and Ig-beta could have new, complementary or even synergistic functions. Therefore we developed a system to compare the signal transducing capacities of dimers of Ig-alpha/Ig-alpha, Ig-beta/Ig-beta, or Ig-alpha/Ig-beta. This was done by fusing the extracellular and transmembrane domains of either human platelet-derived growth factor receptor (PDGFR) alpha or beta to the cytoplasmic tail of either Ig-alpha or Ig-beta. Three cell lines expressing PDGFRbeta/Ig-alpha, PDGFRbeta/Ig-beta, or PDGFRalpha/Ig-beta together with PDGFRbeta/Ig-alpha were established in the murine B cell line A20 IIA1.6. While aggregation of each dimer by itself could induce the tyrosine phosphorylation of cellular substrates, only aggregation of the heterodimer induced the phosphorylation of substrates similar in range and intensity to that induced by the endogenous B cell antigen receptor complex. Interestingly, Ig-beta remarkably enhanced the rapidity (Tmax decreased from 5 to 1 min) and intensity (greater than 10-fold enhancement) of Ig-alpha phosphorylation. Conversely, the phosphorylation of Ig-beta was reduced to undetectable levels when co-aggregated with Ig-alpha. The enhancement of Ig-alpha phosphorylation by Ig-beta correlated with a lowering of the stimulation threshold for tyrosine kinase activation.

Amino Acid Sequence↗
PubMed1996

Hypoglycemia-induced AP-1 transcription factor and basic fibroblast growth factor gene expression in multidrug resistant human breast carcinoma MCF-7/ADR cells.

We investigated the effect of hypoglycemic treatment on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in multidrug resistant human breast carcinoma MCF-7/ADR cells. Northern blot and gel mobility shift assays showed that hypoglycemic treatment induced c-jun and c-fos gene expression, AP-1 binding activity, as well as bFGF gene expression. Moreover, transfected cells expressing high levels of abnormal c-Jun protein exhibited a reduction in the bFGF protein levels compared to parental cells. A potent protein kinase C (PKC) inhibitor, H-7 (60 micrograms/ml) suppressed the stress-induced bFGF gene expression. Our study also demonstrated that H-7 did not facilitate the decay of bFGF mRNA. Thus, the suppression of bFGF gene expression by treatment with H-7 was due to the effect of the drug on the synthesis of bFGF mRNA rather than the stability of bFGF mRNA. Our data suggest that hypoglycemia-induced bFGF gene expression is mediated through the activation of PKC and the AP-1 transcription factors.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

Thermal response in murine L929 cells lacking alpha B-crystallin expression and alpha B-crystallin expressing L929 transfectants.

We investigated the role of alpha B-crystallin expression in the development of thermotolerance in murine L929 cells. An initial heat-shock of 10 min at 45 degrees C induced thermotolerance in these cells to a heat challenge at 45 degrees C administered 24 h later. The thermotolerance ratio at 10(-1) isosurvival was 1.7. Expression of alpha B-crystallin gene was not detected during the 24 h incubation at 37 degrees C following heat shock by either northern or western blots. In contrast, inducible HSP70 synthesis was observed during this time period. Thus, this cell line provided an unique system in which to examine the effects of transfected alpha B-crystallin on thermoresistance and thermotolerance. Cells stably transfected with alpha B-crystallin under the control of an inducible promoter did not show a significant increase in the ability to develop thermotolerance. However, a stably transfected L929 clone expressing high levels of constitutive alpha B-crystallin exhibited an approximately 50% increase in thermal resistance over parental and control cells. Though expression of alpha B-crystallin is not requisite for the development of thermotolerance in L929 cells, overexpression of transfected alpha B-crystallin can contribute to increased thermoresistance.

3T3 Cells↗
PubMed1996

Structure and expression of the tenecin 3 gene in Tenebrio molitor.

A genomic DNA fragment encoding tenecin 3, an antifungal protein was cloned from the genomic DNA library of Tenebrio molitor. The DNA sequence analysis showed that the coding region is divided into two exons by an intron of 49 bp in the middle of the putative leader peptide coding region. Southern blot analysis suggests that the gene is present as a single copy. The transcription initiation site was determined by primer extension analysis and S1 mapping. The TATA box and CCAAT box sequences were found at -30, and -121, respectively, from the transcription initiation site. Tenecin 3 mRNA is abundantly expressed in larvae and adults, while little was detected in RNAs from pupae, suggesting that the expression of the tenecin 3 gene is developmentally regulated.

Amino Acid Sequence↗
PubMed1996

Excess protein in nuclei isolated from heat-shocked cells results from a reduced extractability of nuclear proteins.

An excellent correlation has been established between the quantity of protein associated with nuclei isolated from heat-shocked cells and the level of hyperthermic cell killing. However, controversy remains about whether increases in nuclear-associated protein result from a heat-induced migration of cytoplasmic proteins into the nucleus or because hyperthermia reduces the solubility of nuclear proteins in the detergent buffers commonly used to isolate nuclei. To address this controversy, the nuclear protein content was measured in whole and detergent-extracted cells before and following hyperthermia. It was found that hyperthermia caused no significant change in the nuclear protein content of whole, unextracted cells, and when fluorescently labeled proteins were microinjected into the cytoplasm no gross change in the selective permeability of the nuclear membrane to soluble proteins was observed during or following hyperthermia. Measurements in extracted cells showed that the detergent buffers removed protein from both the nucleus and cytoplasm of control, nonheated cells and that hyperthermia reduced the extractability of both nuclear and cytoplasmic proteins. The amount of protein found in nuclei isolated from heated cells approached that observed in nuclei within nonheated whole cells as the hyperthermic exposure was increased. Thus, the dose-dependent, two- to threefold increase in the protein content of nuclei isolated from heated cells represents a heat-induced reduction in the extractability of proteins normally present within cell nuclei and does not result from a mass migration of cytoplasmic proteins into the nucleus, although some specific proteins (e.g., the 70 KDa heat shock protein) do migrate to the nucleus following heat shock. Differential scanning calorimetry (DSC) measurements of whole cells, isolated nuclei, cytoplasts, and karyoplasts supported these conclusions and suggested that most of the detergent-insoluble proteins remaining in the nuclei and cytoplasm of heated cells are in their native state. Thus, a relatively small amount of denatured protein may be sufficient to initiate and sustain insoluble protein aggregates comprised of mostly native proteins. Analyses of the DSC data also implied that the previously identified critical target proteins, predicted to have a Tm of 46.0 degrees C, are present in both the nucleus and cytoplasm.

3T3 Cells↗
PubMed1996

Homocysteine and neural tube defects.

It is now well established that folic acid, when taken periconceptionally, can prevent many neural tube defects. It is also becoming clear that folic acid does not work by correcting a nutritional deficiency in pregnant women. Rather, it appears that a metabolic defect is responsible for these neural tube defects and that this defect or defects can be corrected by a sufficiently large dose of folic acid. Our recent work demonstrates that homocysteine metabolism is likely to be the critical pathway affected by folic acid. We have demonstrated significantly higher homocysteine levels in women carrying affected fetuses than in control women. These findings indicate that one of the enzymes responsible for homocysteine metabolism is likely to be abnormal in affected pregnancies. Animal studies suggest that the conversion of homocysteine to methionine could be the critical step. Rat embryos in culture require methionine for neural tube closure. Methionine synthase, cystathionine synthase, and 5,10 methylene tetrahydrofolate reductase are all important in the metabolism of homocysteine in humans. If methionine synthase is the critical enzyme, it would raise the interesting public health issue that vitamin B-12 might be able to stimulate the abnormal enzyme as folic acid does. Adding vitamin B-12 might make it possible to reduce the dose of folic acid required in fortified food, thus allaying concerns about overexposure to folic acid.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1996

Major causes of diabetic death at one hospital.

Death certificates filed between 1987 and 1990 at the Kaohsiung Medical College Hospital (KMCH) were reviewed to investigate causes of diabetic death. During this period, 1,383 patients expired at KMCH, of which 151 had diabetes mellitus. The major causes of death in these 151 diabetic patients were infection in 25.8%, cardiovascular disease in 18.5%, cerebrovascular disease in 11.3%, uremia in 8.6% and diabetic ketoacidosis in 1.3%, while diabetes was reported as the contributory or underlying cause of death. Malignancy in 12.0%, liver disease in 5.3%, trauma in 1.3% and upper gastroenteral bleeding in 0.7%, likewise, were among the leading causes of death irrespective of underlying diabetes. However, cause of death in 15.2% of these diabetic patients was undetermined. Our analysis revealed that infection and cardiocerebrovascular disease were the leading problems contributing to diabetic death. Therefore, reducing the risk of infection by strict glycemic control, intensive medical intervention in infection and the proper prevention of diabetic angiopathy-related risk factors and complications are imperative for the reduction of diabetic mortality in our patients.

Cardiovascular Diseases↗
PubMed1996

Hypercholesterolemia in undiagnosed non-insulin-dependent diabetes in southern Taiwan.

The purpose of this study was to investigate the prevalence of hypercholesterolemia among subjects having diabetes and glucose intolerance, according to the guidelines of the National Cholesterol Education Program (Adult Treatment Panel II, ATP II). This survey consisted of 2090 subjects (856 men, 1234 women) aged 30 years or more from the Sun-Ming district of Kaohsiung city. Glucose tolerance status was ascertained for both medical history and a 75-g oral glucose tolerance test according to World Health Organization criteria. Frequency of elevated total cholesterol in female subjects with abnormal glucose tolerance is significantly greater than in those with normal glucose tolerance (NGT). However, only male subjects with undiagnosed NIDDM (UDDM) had a statistically higher rate of hypercholesterolemia than those with NGT. Of UDDM individuals, 68% have total cholesterol level between 200 and 239 mg/dl and two or more risk factors for heart disease or evidence of coronary heart disease or total cholesterol > or = 240 mg/dl or high-density lipoprotein (HDL) cholesterol < or = 35 mg/dl. Such individuals should have their low-density lipoprotein (LDL) cholesterol measured. Using the ATP II, LDL cholesterol levels warranting dietary treatment for hypercholesterolemia would be expected in 76% of UDDM. Due to the high prevalence of coronary heart disease in diabetic patients, investigation of blood lipid levels and coronary heart disease risk factors should be routine in these patients, and treatment strategies should include management of lipid disorders and the many other risk factors. A high frequency of dyslipidemia was found among UDDM group in our study. Early detection of undiagnosed diabetic patients is also very important in decreasing the prevalence of coronary heart disease.

Adult↗
PubMed1995

Effect of ionizing radiation on AP-1 binding activity and basic fibroblast growth factor gene expression in drug-sensitive human breast carcinoma MCF-7 and multidrug-resistant MCF-7/ADR cells.

We studied the effect of ionizing radiation on the activation of the AP-1 transcription factors and the regulation of basic fibroblast growth factor (bFGF) gene expression in drug-sensitive human breast carcinoma (MCF-7) cells and its drug-resistant variant (MCF-7/ADR) cells. Northern blot and gel mobility shift assays showed that 135 cGy of ionizing radiation induced c-jun and c-fos gene expression, AP-1 binding activity, as well as bFGF gene expression in MCF-7/ADR cells. In MCF-7 cells, however, we observed little/no induction of bFGF gene expression and AP-1 binding activity after the stress. Nevertheless, MCF-7 cells transfected with plasmids containing c-jun gene contain high levels of bFGF protein. H-7 (60 micrograms/ml), a potent protein kinase C (PKC) inhibitor, inhibited the stress-induced AP-1 binding activity and bFGF gene expression in MCF-7/ADR cells. Corroborating this observation, overexpression of PKC alpha induced bFGF gene expression in MCF-7 cells. Taken together, these results suggest that stress-induced bFGF gene expression is mediated through the activation of PKC and AP-1 transcription factors. Differences in the levels of PKC activity and AP-1 binding factors may be responsible for differential expression of bFGF among breast cancer cell lines. Although there are large differences in response to ionizing radiation between MCF-7 and MCF-7/ADR cell lines, we observed no significant differences in radiocytotoxicity between them.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1995

Differential effect of 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) on alpha B-crystallin and hsp70 gene expression in murine cell lines.

We studied the effect of isoquinolinesulfonamide derivatives (H-7, H-8, and HA1004) on the expression of two heat shock genes (alpha beta-crystallin and hsp70) in NIH 3T3 and Swiss 3T3 cells after heat shock at 45 degrees for 10 min. Western blots and northern blots showed that H-7 effectively suppressed the accumulation of HSP70 and alpha B-crystallin mRNA as well as the synthesis of their proteins. The degree of suppression was dependent upon the concentration of the drug. Moreover, the expression of the hsp genes was differentially suppressed by H-7. The expression of the alpha B-crystallin gene was more effectively inhibited than that of the hsp70 gene by H-7. Nuclear run-on assay demonstrates that this difference was due to the differential effect of H-7 on the elongation of transcription of different hsp genes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗