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E Chen

Publications and source records attributed to E Chen.

At least 181 records · Page 10Linked to original sources
PubMed1993

Molecular characterization of glucose-6-phosphate dehydrogenase (G6PD) deficiency in patients of Chinese descent and identification of new base substitutions in the human G6PD gene.

The underlying DNA changes associated with glucose-6-phosphate dehydrogenase (G6PD)-deficient Asians have not been extensively investigated. To fill this gap, we sequenced the G6PD gene of 43 G6PD-deficient Chinese whose G6PD was well characterized biochemically. DNA samples were obtained from peripheral blood of these individuals for sequencing using a direct polymerase chain reaction (PCR) sequencing procedure. From these 43 samples, we have identified five different types of nucleotide substitutions in the G6PD gene: at cDNA 1388 from G to A (Arg to His); at cDNA 1376 from G to T (Arg to Leu); at cDNA 1024 from C to T (Leu to Phe); at cDNA 392 from G to T (Gly to Val); at cDNA 95 from A to G (His to Arg). These five nucleotide substitutions account for over 83% of our 43 G6PD-deficient samples and these substitutions have not been reported in non-Asians. The substitutions found at cDNA 392 and cDNA 1024 are new findings. The substitutions at cDNA 1376 and 1388 account for over 50% of the 43 samples examined indicating a high prevalence of these two alleles among G6PD-deficient Chinese. Our findings add support to the notion that diverse point mutations may account largely for much of the phenotypic heterogeneity of G6PD deficiency.

Asian↗
PubMed1993

Continuous-wave quantum yields of various cobalamins are influenced by competition between geminate recombination and cage escape.

Quantum yields of photolysis of the cobalt-carbon bond for three cobalamin compounds were measured with a continuous-wave laser at 442 nm under both aerobic and anaerobic conditions. Aerobically, the initial homolysis product, Co(II) cobalamin, is trapped by oxygen to form aquocobalamin. Use of an excess of the radical trapping reagent 2,2,6,6-tetramethyl-1-piperidinyloxyl, under anaerobic conditions, scavenges the carbon radical and allows detection of the cobalt(II) photoproduct. Quantum yields measured under anaerobic conditions for 5'-deoxyadenosylcobalamin (phi (Co-C alpha),442 = 0.20 +/- 0.03) and methylcobalamin (phi (Co-C alpha),442 = 0.35 +/- 0.03) are in agreement with the values obtained under aerobic conditions (phi (Co-C alpha),442 = 0.19 +/- 0.04 and phi (Co-C alpha),442 = 0.36 +/- 0.04, respectively). Additionally, the quantum yield values for 5'-deoxyadenosylcobalamin and its base-off derivative (phi (Co-C alpha),442 = 0.045 +/- 0.015) match those obtained on a nanosecond time scale [Chen, E., & Chance, M. R. (1990) J. Biol. Chem. 256, 12987-12994]. A comparison of quantum yields obtained anaerobically for 5'-deoxyadenosylcobalamin and methylcobalamin in H2O versus ethylene glycol shows a 4-fold decrease for the former cobalamin and no change for the latter. These quantum yields are evaluated in terms of time-independent radical separation distances.

Aerobiosis↗
PubMed1993

Genomic structure and chromosomal localization of the human deoxycytidine kinase gene.

Deoxycytidine kinase (NTP:deoxycytidine 5'-phosphotransferase, EC 2.7.1.74) is an enzyme that catalyzes phosphorylation of deoxyribonucleosides and a number of nucleoside analogs that are important in antiviral and cancer chemotherapy. Deficiency of this enzyme activity is associated with resistance to these agents, whereas increased enzyme activity is associated with increased activation of such compounds to cytotoxic nucleoside triphosphate derivatives. To characterize the regulation of expression of this gene, we have isolated genomic clones encompassing its entire coding and 5' flanking regions and delineated all the exon/intron boundaries. The gene extends over more than 34 kilobases on chromosome 4 and the coding region is composed of 7 exons ranging in size from 90 to 1544 base pairs (bp). The 5' flanking region is highly G+C-rich and contains four regions that are potential Sp1 binding sites. A 697-bp fragment encompassing 386 bp of 5' upstream region, the 250-bp first exon, and 61 bp of the first intron was demonstrated to promote chloramphenicol acetyltransferase activity in a T-lymphoblast cell line and to have > 6-fold greater activity in a Jurkat T-lymphoblast than in a Raji B-lymphoblast cell line. Our data suggest that these 5' sequences may contain elements that are important for the tissue-specific differences in deoxycytidine kinase expression.

Base Sequence↗
PubMed1993

Restricted cytokine expression in rheumatoid arthritis.

OBJECTIVE: To determine the cytokine profile of the phenotypically activated T cell in rheumatoid arthritis (RA) synovium. METHODS: Interleukin-2 (IL-2), IL-2 receptor (IL-2R), IL-6, IL-4, and interferon-gamma (IFN gamma) gene expression was examined in T cells from freshly isolated synovial fluids (SF) and synovial tissues (ST) from patients with RA. Estimates of baseline expression were determined using unstimulated peripheral blood (PB) T cells from healthy individuals. The corresponding positive controls were phytohemagglutinin-activated tonsil T cells. RESULTS: In studies of paired PB and SF T cell samples from 17 RA patients, IL-2 messenger RNA (mRNA) levels in only 1 PB and 3 SF samples were more than 2 standard deviations above the mean of levels in unstimulated PB from healthy donors. Similarly, only 5 PB and 7 SF samples exhibited elevated IL-2R mRNA levels. IFN gamma gene expression was not detected in any of the paired RA PB or SF samples. Fractionated T cells from 12 RA ST were screened with similar results: Only 1 of 12 samples exhibited IL-2 mRNA levels more than 2 standard deviations above levels in baseline controls. IL-2R mRNA levels were low or not detected, and IFN gamma mRNA was absent. Subsequent studies showed that IL-4 and IL-6 gene expression levels were also low in RA tissues compared with tonsil T cell-positive controls. CONCLUSION: These data provide evidence for restricted cytokine expression in the T cell population in RA tissues.

Actins↗
PubMed1993

Inhibition of cytochrome oxidase and blue-light damage in rat retina.

The activity of cytochrome oxidase, outer nuclear layer thickness, and edema were quantitatively evaluated in the blue-light exposed rat retina. Dark-adapted or cyclic-light reared rats were exposed to blue light with a retinal dose of 380 kJ/m2. Immediately, 1, 2, and 3 day(s) after exposure, the retinas of six rats from each adaptation group were examined. There was no difference between the dark-adapted and cyclic-light reared rats. Immediately after light exposure, cytochrome oxidase activity decreased. The activity in the inner segments remained low at day 1, while severe edema was observed in the inner and outer segments. The outer nuclear layer thickness decreased 1-3 days after exposure. The blue-light exposure inhibited cytochrome oxidase activity and caused retinal injury. Similarity of the injury process in the dark-adapted and cyclic-light reared retinas suggests that rhodopsin was not involved. The inhibition of cytochrome oxidase could be a cause of retinal damage.

Animals↗
PubMed1993

Regulation of human deoxycytidine kinase expression.

The human deoxycytidine kinase gene is a single copy gene and is comprised of seven exons that are spread over more than 34 kb of the genome. The 5'-flanking region is highly G/C rich and does not contain CAAT or TATA boxes. This region, when cloned into a recorder gene construct containing the chloramphenicol acetyltransferase gene, is capable of mediating CAT activity in human lymphoid cell lines and appears to have greater activity in human T, as compared to B, lymphoblast cell lines. The expression of the gene at the mRNA level does not appear to be cell-cycle regulated in that the levels of mRNA in human peripheral blood T lymphocytes remain constant as the cells progress from a resting to a proliferating state. Since this enzyme catalyzes the conversion of a number of chemotherapeutic agents to their corresponding monophosphate form and is thus essential for their activation, it will be important to define further the genetic elements which regulate the expression of this gene.

Cell Division↗
PubMed1993

Aromatase gene is amplified in MCF-7 human breast cancer cells.

The levels of the aromatase gene and its expression in MCF-7 human breast cancer cells and seven additional cultured cells were investigated. Using normal human foreskin fibroblasts as the control, the aromatase gene appeared to be amplified in MCF-7 cells as shown by Southern and DNA slot blot analyses utilizing human placental aromatase cDNA as the probe. However, the promoter I.1 and the first exon of the aromatase gene were not amplified in MCF-7 cells based on results obtained from DNA slot blot analysis using oligonucleotide probes having sequences derived from those regions of human aromatase gene. Aromatase was expressed at a very low level in this cell line as indicated by Northern blot analysis to measure the level of aromatase mRNA, immunoprecipitation analysis to measure the level of aromatase protein, and aromatase activity measurement. Furthermore, nucleotide sequence analysis of the aromatase cDNA obtained from MCF-7 cells by PCR techniques, revealed no sequence difference from that of the enzyme expressed in placenta. These results lead us to conclude that the expression of aromatase in MCF-7 cells is under the control of an unusual promoter and aromatase gene expression is repressed at the transcriptional level in these cells.

Aromatase↗
PubMed1993

Optimal antithrombotic therapy following aortocoronary bypass: a meta-analysis.

To evaluate the role of antithrombotic therapy, on preserving graft patency, we performed a meta-analysis of randomized clinical trials involving aspirin (ASA), dipyridamole (D), anticoagulants (AC) and placebo or nontreatment controls (P). Manual literature searches were performed supplemented by computerized MEDLINE listings complete to July 1991. Saphenous vein graft occlusion was determined by angiography (patients with > or = 1 distal anastomotic occlusion). The trial data were aggregated with the methods of Mantel and Haenszel. The results are reported as odds ratios (OR) +/- 95% confidence intervals (CI). Seventeen trials were evaluated. Aspirin strongly influenced graft occlusion [ASA +/- D vs P: OR 0.60, 95% CI 0.51, 0.71, P < 0.0001], but dipyridamole provided no additional benefit [ASA+D vs ASA: OR 0.94, 95% CI 0.72, 1.24, P = 0.71]. Anticoagulants reduced graft occlusion [AC vs P: OR 0.56, 95% CI 0.33, 0.93, P = 0.025] and the results were similar to that achieved with aspirin [ASA vs AC: OR 0.95, 95% CI 0.62, 1.44, P = 0.87]. The combination of aspirin and anticoagulants was superior to anticoagulants alone in two limited trials [ASA+AC vs AC: OR 0.55, 95% CI 0.33, 0.88, P = 0.01]. A low (100 mg) to medium (325 mg) daily aspirin dosage was more effective than a high dose (975 mg). Early postoperative treatment (< or = 6 h) strongly influenced graft occlusion while preoperative administration provided no additional benefit. No mortality advantage was identified for any antithrombotic therapy. Aspirin or anticoagulants enhance saphenous vein graft patency following aortocoronary bypass surgery, and a combination thereof deserves further investigation in a trial large enough to detect the effects of these treatments with respect to clinical events.

Anticoagulants↗
PubMed1993

A common lens nuclear area in Scheimpflug photographs.

Scheimpflug photography has been proven to be a useful method for documentation of opacification of the lens nucleus. In the present study, a common lens nuclear area (CNA) is established for photometry of nuclear cataract on Scheimpflug photographs. Using the established method, one measurement for one photograph, and one photograph for each subject is enough for the photometry of nuclear density. Further, this method allows detection of a 10% change in nuclear density between two occasions with a group of at least 7 subjects, and for independent groups with at least 95 subjects in each group (alpha = 0.05, beta = 0.10). It is anticipated that the CNA will provide a useful tool for quantitative determination of nuclear cataract.

Aged↗
PubMed1993

Does coronary endarterectomy adversely affect the results of bypass surgery?

Coronary endarterectomy (TEA) is performed infrequently during coronary artery bypass graft (CABG) surgery due to the impression that it results in higher rates of myocardial infarction (MI), operative mortality (OM), and poor long-term outcome. To assess the effectiveness of TEA, 1,228 patients undergoing isolated CABG between 1982 and 1989 were evaluated. The incidence of OM (3.2%) and MI (6.0%) following TEA was similar to conventional CABG (OM = 3.8%, MI = 5.5%, p = NS). The incidence of low output syndrome (LOS, 15.1%) and intraaortic balloon pump insertion (IABP, 4.5%) following TEA was similar to conventional CABG (LOS = 12.6%, IABP = 6.0%, p = NS). The highest level of the cardiac specific isoenzyme (CK-MB) released following surgery was similar for the TEA group (46 +/- 49) and conventional CABG group (42 +/- 44, p = NS). Ventricular dysfunction, urgent surgery, left main stenosis, advanced age, and reoperative surgery were similar in the TEA and conventional CABG groups. At a mean follow-up of 4.2 years, 65.6% of all TEA patients were free of angina, 44.4% were gainfully employed, and 62% were in New York Heart Association Class I. The incidence of late myocardial infarction was 5.4%. The 5-year actuarial survival was 90%. Patients with double TEA and limited TEA ( < or = 3 cm TEA specimens) tended to have a lower 5-year survival. With strict criteria for selection of TEA patients and with significant technical experience, the short- and long-term results of TEA are comparable to conventional CABG.

Adult↗
PubMed1993

Evaluation of gray scale steps on Scheimpflug photographs.

A method for the calibration of gray scale density in a Scheimpflug photograph was established. Based on the result of statistical analysis, it was found that variability in the film emulsion was insignificant if the measuring area > or = 0.01 mm2. Each lens image should be calibrated with the reference gray scale in the same photograph. Photometric readings of the lens image was converted to gray scale levels. This conversion can be obtained from fitting photometric readings of the gray scale as a function of gray scale steps with a third order polynomial. Adopting this calibration procedure, 95% of estimated nuclear densities are within +/- 3-5% of the real value.

Analysis of Variance↗
PubMed1993

BCR-ABL and v-abl oncogenes induce distinct patterns of thymic lymphoma involving different lymphocyte subsets.

The human BCR-ABL oncogenes encoded by the Philadelphia chromosome (Ph) affect the pathogenesis of diverse types of leukemia and yet are rarely associated with T-lymphoid leukemia. To determine whether BCR-ABL kinases are inefficient in transforming T lymphocytes, BCR-ABL-expressing retroviruses were injected intrathymically into mice. Thymomas that expressed BCR-ABL kinase developed after a relatively long latent period. In most thymomas, deletion of 3' proviral sequences resulted in loss of tk-neo and occasionally caused expression of kinase-active carboxy-terminally truncated BCR-ABL oncoprotein. In contrast, deletion of 3' proviral sequences was not observed in thymomas induced with Abelson murine leukemia virus (A-MuLV). BCR-ABL viruses induced distinct patterns of disease and involved different thymocyte subsets than A-MuLV and Moloney murine leukemia virus (Mo-MuLV). While Mo-MuLV only induced Thy-1+ thymomas, v-abl- and BCR-ABL-induced thymomas often contained mixed populations of B220+ and Thy-1+ lymphocytes in the same tumor. In most v-abl and BCR-ABL tumors, Thy-1+ lymphoid cells expressed CD8 and a continuum of CD4 ranging from negative to positive. Conversely, Mo-MuLV thymomas contained distinct populations of CD4+ cells that were either CD8+ or CD8-. A-MuLV-transformed T-lymphoid cells did not express the CD3/T-cell receptor complex, while BCR-ABL tumors were CD3+. Thus, BCR-ABL viruses preferentially induce somewhat more differentiated T lymphocytes than are transformed by A-MuLV. Furthermore, rare B220+ lymphocytes may represent preferred v-abl and BCR-ABL transformation targets in the thymus.

Animals↗
PubMed1993

Differential expression of Rel family members in human T-cell leukemia virus type I-infected cells: transcriptional activation of c-rel by Tax protein.

The Tax protein of the human T-cell leukemia virus type I (HTLV-I) has been shown to induce nuclear expression of Rel family NF-kappa B-binding proteins. However, under different experimental conditions, different J. H. Kim, Y. Daitoku, and W. G. Greene, J. Virol. 65:6892-6899, 1991). In this study, using specific immunological reagents capable of distinguishing individual members of the Rel family proteins, we show that only c-Rel, not NF-kappa B p50 or p65, is induced in HTLV-I-infected cells. Preferential c-rel induction by HTLV-I infection was detected at the protein and RNA levels as well as in the nuclear NF-kappa B-binding form. Induced c-rel expression was also detected in cells stably transfected with tax cDNA, further correlating the c-rel induction with viral Tax expression. An increase in c-rel mRNA was detected within 3 h after induction of Tax expression, suggesting that this effect is at least partially regulated at the level of transcription. Furthermore, using a particle bombardment method for gene cotransfection, we show that Tax can transcriptionally activate the c-rel promoter in a T-cell line, Jurkat.

Base Sequence↗
PubMed1993

Bladder capacity as measured at voiding cystourethrography in children: relationship to toilet training and frequency of micturition.

To assess the reliability of a frequently used formula for calculating bladder capacity in children, bladder capacity was measured prospectively at voiding cystourethrography in 274 consecutive healthy infants and children. Bladder volume index (BVI) was then calculated by dividing the measured capacity by the predicted capacity. Bladder capacity increased dramatically after 18 months and reached a plateau between 3 and 4 months of age, after which there was no further significant increase in capacity until approximately 9 years. BVI abruptly increased from 1.03 in children aged less than 18 months to 1.50-1.60 in children aged between 18 months and 4 years (P < or = .0001). Because bladder capacity increases sharply during infancy and early childhood and levels off once toilet training is complete, linear models used to predict bladder capacity on the basis of age alone significantly underestimate bladder capacity in infants and younger children.

Adolescent↗
PubMed1993

Refractive indices of the rat retinal layers.

The refractive indices in various rat retinal layers, based on the total dry mass concentration, ranged from 1.369 to 1.385. The ratios of the refractive indices of neighboring retinal layers were near unity. This finding suggests that light passes through the rat retina without much refraction.

Animals↗
PubMed1993

Inhibition of enzymes by short-wave optical radiation and its effect on the retina.

UNLABELLED: INTRODUCTION AND HYPOTHESES: Exposure to short-wave optical radiation is a potential hazard for vision. In the present study, blue-light damage is studied in rat retina. It was hypothesized that the absorption of blue light by cytochrome oxidase in rat retina inhibits this enzyme, and may reduce the retinal oxidative metabolism. Irreversible inhibition of the oxidative metabolism may decrease the activity of the Na/K-ATPase, hence redistribute ions, increase intracellular osmotic pressure and cause cellular edema. Severe retinal edema may be the cause of retinal degeneration. METHODS: A quantitative histochemical method, a combination of histochemical staining and densitometrical measurement, was established to measure the activity of cytochrome oxidase. The distribution of chlorine and potassium in rat retina was estimated with a nuclear microprobe. Microradiography was adopted for measuring the protein and lipid density, which is an indirect estimation of retinal edema and retinal refractive index. The damage to the photoreceptor cells was estimated from the thickness of the outer nuclear layer. RESULTS AND CONCLUSIONS: Blue light inhibited cytochrome oxidase at a retinal dose of about 110 kJ/m2. This inhibition was reversible, and is probably related to the light regulation of retinal metabolism. At a retinal dose of about 380 kJ/m2, the inhibition of cytochrome oxidase was followed consecutively by a probable redistribution of chlorine and potassium in the inner and outer segments, damage to the mitochondria in the inner segments, edema in the inner and outer segments, and progressive degeneration of photoreceptor cells. Dark adaptation did not increase the blue-light retinal injury. These findings support the hypothesis that inhibition of cytochrome oxidase is one of the causes of blue-light retinal damage. The alteration of enzyme kinetics after in vitro exposure to short-wave optical radiation was estimated using lactate dehydrogenase as a model. The ultraviolet-radiation exposure inhibited lactate dehydrogenase with a significant decrease in maximal velocity, while Michaelis constant remained unchanged.

Animals↗
PubMed1993

Detection of c-mos proto-oncogene expression in human cells.

Although the human c-mos proto-oncogene has been characterized for more than a decade, very little is known about its protein product and its expression in somatic cells. We generated three human c-mos-specific antisera and report here the detection of c-mos protein in a human neuroblastoma cell line, SK-N-BE2 (BE2). Both Western (immuno-) blot and immunoprecipitation analyses detected a p37 as the major form and p40 and p35 as minor forms of the c-mos protein. Using Northern blot analysis, 3.5- and 1.7-kb c-mos messages were detected. Using a highly sensitive method that combines reverse transcription and the polymerase chain reaction (RT-PCR), c-mos RNA was detected in all the human samples examined. With Western blot analysis, we further showed that c-mos proteins are expressed in cervical carcinoma-derived cell lines. This ubiquitous expression of low levels of c-mos suggests a fundamental role for the c-mos proto-oncogene.

Animals↗