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Biomedical subjects

J W Chen

Publications and source records attributed to J W Chen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Constructing parton convolution in effective field theory.

Parton convolution models have been used extensively in describing the sea quarks in the nucleon and explaining quark distributions in nuclei (the EMC effect). From the effective field theory point of view, we construct the parton convolution formalism which has been the underlying conception of all convolution models. We explain the significance of scheme and scale dependence of the auxiliary quantities such as the pion distributions in a nucleon. As an application, we calculate the complete leading nonanalytic chiral contribution to the isovector component of the nucleon sea.

Journal Article↗
PubMed2001

Influence of cholesterol on the biophysical properties of the sphingomyelin/DOPC binary system.

The influence of cholesterol on the sphingomyelin (SM)/dioleoylphosphatidylcholine (DOPC) binary system was investigated in various respects. Electron spin resonance (ESR) measurements reveal that the order parameter of 5DS (5-doxyl stearic acid) in SM/DOPC bilayers increases notably when the concentration of cholesterol is over 30 mol%. Membrane potential measurements indicate that the K+ permeability of the SM/DOPC bilayer decreases steeply at 40 mol% cholesterol concentration. Both these experiments suggest that cholesterol reduces the motion amplitude of hydrocarbon chains abruptly above 30 mol%. In contrast to the ordering effects on the hydrocarbon chains, (31)P-NMR results indicate that cholesterol slightly increases the motion of phosphate groups of the lipids. (31)P-NMR also raises the possibility of domain formation in the presence of cholesterol. Fluorescence-quenching experiments verified that solid domains appear in the binary system when cholesterol is present, and percolation threshold occurs at 50 mol% cholesterol concentration. The solid domains bear the properties of liquid ordered phase, which is the basic structure of caveolae and functional rafts. So this work provides an artificial model for the study of rafts and caveolae on biological membranes.

Animals↗
PubMed2001

Measuring the P-odd pion-nucleon coupling h((1))(piNN) in pi(+)-photoproton production near threshold.

We show that gamma-->p-->pi(+)n in the threshold region is an excellent candidate for measuring the leading parity-violating pion-nucleon coupling h((1))(piNN) to an uncertainty of 20% if it has a natural size from dimensional analysis. The conclusion is based on a large unpolarized cross section, a new low-energy theorem for the photon polarization asymmetry at the threshold A(gamma)/(th) = square root of 2 f(pi)(mu(p)-mu(n))h((1))(piNN)/g(A)m(N) approximately h((1))(piNN)/2, and its strong dominance at forward and backward angles in the threshold region.

Journal Article↗
PubMed2001

Salvianolic acid B attenuates VCAM-1 and ICAM-1 expression in TNF-alpha-treated human aortic endothelial cells.

Attachment to, and migration of leukocytes into the vessel wall is an early event in atherogenesis. Expression of cell adhesion molecules by the arterial endothelium may play a major role in atherosclerosis. It has been suggested that antioxidants inhibit the expression of adhesion molecules and may thus attenuate the processes leading to atherosclerosis. In the present study, the effects of a potent water-soluble antioxidant, salvianolic acid B (Sal B), and an aqueous ethanolic extract (SME), both derived from a Chinese herb, Salvia miltiorrhiza, on the expression of endothelial-leukocyte adhesion molecules by tumor necrosis factor-alpha (TNF-alpha)-treated human aortic endothelial cells (HAECs) were investigated. When pretreated with SME (50 and 100 microg/ml), the TNF-alpha-induced expression of vascular adhesion molecule-1 (VCAM-1) was notably attenuated (77.2 +/- 3.2% and 80.0 +/- 2.2%, respectively); and with Sal B (1, 2.5, 5, 10, and 20 microg/ml), 84.5 +/- 1.9%, 78.8 +/- 1.2%, 58.9 +/- 0.4%, 58.7 +/- 0.9%, and 57.4 +/- 0.3%, respectively. Dose-dependent lowering of expression of intercellular cell adhesion molecule-1 (ICAM-1) was also seen with SME or Sal B. In contrast, the expression of endothelial cell selectin (E-selectin) was not affected. SME (50 microg/ml) or Sal B (5 microg/ml) significantly reduced the binding of the human monocytic cell line, U937, to TNF-alpha-stimulated HAECs (45.7 +/- 2.5% and 55.8 +/- 1.2%, respectively). SME or Sal B significantly inhibited TNF-alpha-induced activation of nuclear factor kappa B (NF-kappaB) in HAECs (0.36- and 0.48-fold, respectively). These results demonstrate that SME and Sal B have anti-inflammatory properties and may explain their anti-atherosclerotic properties. This new mechanism of action of Sal B and SME, in addition to their previously reported inhibition of LDL, may help explain their efficacy in the treatment of atherosclerosis.

Antioxidants↗
PubMed2001

Seroprevalence and demographic characteristics of HTLV-I among blood donors in Taiwan: 1996-1999.

Screening for the human T-cell lymphotropic virus type I (HTLV-I) and-II in blood donors was implemented in Taiwan beginning in February 1996. The purpose of the present study was to investigate the changes in HTLV-I seroprevalence in all unpaid blood donors in Taiwan during the period from February 1996 to December 1999 and to determine the influence of age and sex on the HTLV-I seropositivity of donors. HTLV-I and HTLV-II screening was performed using combined HTLV-I/II immunoassay. Repeated reactive samples were confirmed by Western blot analysis. Of a total of 3,701,087 donors in all 6 blood centers in Taiwan, 2,311 (0.058%) were seropositive for HTLV-I. The HTLV-I seropositivity was 0.130%, 0.063%, 0.044%, and 0.032% in the years 1996, 1997,1998, and 1999, respectively. There was a linear increase of HTLV-I seropositivity with advancing age. The HTLV-I carrier rate for female donors was twice that for the male donors. Ninty-seven percent of HTLV-I seropositive results came from first-time donors. Our findings suggest that Taiwan is a low-prevalence nonendemic area for HTLV-I infection. The large-scale HTLV-I screening program has decreased HTLV-I seropositivity among blood donors and is useful for preventing HTLV-I transmission via blood transfusion.

Adolescent↗
PubMed2001

Effect of cholesterol on the formation of an interdigitated gel phase in lysophosphatidylcholine and phosphatidylcholine binary mixtures.

We previously reported that 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) forms an interdigitated gel phase in the presence of 1-palmitoyl-sn-glycero-3-phosphocholine (16:0LPC) at concentrations below 30 mol%. In the present investigation, fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH), X-ray diffraction, and differential scanning calorimetry (DSC) were used to investigate the effect of cholesterol on the phase behavior of 16:0LPC/DPPC binary mixtures. At 25 degrees C, 30 mol% 16:0LPC significantly decreases the DPH fluorescence intensity during the transition of DPPC from the L(beta') phase to the L(betaI) phase. However, the addition of cholesterol to 16:0LPC/DPPC mixtures results in a substantial increase in fluorescence intensity. The changes in DPH fluorescence intensity reflect the probe's redistribution from an orientation parallel to the acyl chain to the center of the bilayer, suggesting a bilayer structure transition from interdigitation to noninterdigitation. The normal repeat period of small angle X-ray diffraction patterns can be restored and a reflection appears at 0.42 nm with a broad shoulder around 0.41 nm in wide angle X-ray diffraction patterns when 10 mol% cholesterol is incorporated into 30 mol% 16:0LPC/DPPC vesicles, indicating that the mixtures are in the gel phase (L(beta')). Moreover, DSC results demonstrate that 10 mol% cholesterol is sufficient to significantly decrease the main enthalpy, cooperativity and lipid chain melting of 30 mol% 16:0LPC/DPPC binary mixtures, which are L(betaI), indicating that the transition of the interdigitated phase is more sensitive to cholesterol than that of the noninterdigitated phase. Our data imply that the interdigitated gel phase induced by 16:0LPC is prevented in the presence of 10 mol% cholesterol, but unlike ethanol, an increasing concentration of 16:0LPC is not able to restore the interdigitation structure of the lipid mixtures.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2001

Hepatocellular carcinoma: US-guided percutaneous microwave coagulation therapy.

PURPOSE: To evaluate the use of percutaneous microwave coagulation therapy for hepatocellular carcinoma, particularly with tumor nodules larger than 2 cm in diameter. MATERIALS AND METHODS: Fifty patients with 107 hepatocellular carcinoma nodules (mean diameter, 2.7 cm +/- 1.5 [SD]; range, 0.8-6.4 cm) were treated with percutaneous microwave coagulation therapy. Single electrode insertion was used in 46 nodules (43.0%) 2 cm or smaller, whereas multiple electrode insertion was applied in 61 (57.0%) nodules larger than 2 cm. RESULTS: At 1 month after therapy, technical success for tumors 2 cm or smaller and those larger than 2 cm was achieved in 45 (98%) and 56 (92%) nodules, respectively. After follow-up of 9 months or longer, local recurrence was found in one nodule (2%) sized 1.8 cm and in five nodules (8%) larger than 2 cm. At the end of the study, 26 (52%) of 50 patients were free of disease, and disease-free survival rates at 1 and 2 years were 55% and 41%, respectively. Overall survival rates at 1, 2, and 3 years were 96%, 83%, and 73%, respectively. CONCLUSION: Percutaneous microwave coagulation therapy is an effective and safe therapeutic modality for hepatocellular carcinoma. A multiple electrode insertion technique can enhance the effectiveness of this therapy in tumors 6 cm or smaller.

Adult↗
PubMed2001

Coronary artery calcium determined by electron beam computed tomography for predicting angiographic coronary artery disease in moderate- to high-risk Chinese patients.

The aim of this study was to evaluate the prevalence of coronary calcification among moderate- to high-risk Chinese patients and to evaluate the ability of the coronary calcium score determined by electron beam computed tomography (EBCT) to predict angiographic coronary artery disease in this population. We enrolled 163 consecutive patients and analyzed their cardiovascular risk factors, coronary calcium scores and coronary angiogram results. One hundred and twenty-five patients (76.7%) had a positive EBCT scan result (coronary calcium score >0). The prevalence of calcification and the calcium scores showed a graded relation to the number of cardiovascular risk factors and age (p < 0.001 for trend). Coronary calcium scores showed statistically significant differences between patients with angiographic evidence of coronary artery disease and patients with normal coronary angiography (p < 0.05), but could not differentiate between patients with significant and insignificant coronary artery disease. Receiver operating characteristic curve analysis showed that a coronary calcium score >5 predicted angiographic coronary artery disease with 93% sensitivity and 86% specificity (area under the curve 0.95 +/- 0.019). Multivariate analysis showed a coronary calcium score >5 to be the strongest independent predictor of angiographic coronary artery disease (odds ratio 120.7, 95% confidence interval 21.7-671.4; p < 0.001). Coronary calcium score determined by EBCT appears to have a similar predictive value in Chinese patients as it does in other ethnic populations that have been reported to date.

Adult↗
PubMed2001

Differential coronary calcification on electron-beam CT between syndrome X and coronary artery disease in patients with chronic stable angina pectoris.

STUDY OBJECTIVES: The differential diagnosis of syndrome X and coronary artery disease (CAD) in patients with evidence of myocardial ischemia may be difficult. The possible difference in coronary calcium detected by electron-beam CT (EBCT) between syndrome X and CAD is rarely evaluated, especially in aged patients with chronic, stable angina. DESIGN AND SETTINGS: Prospective, controlled study at a tertiary referral medical center. PATIENTS AND MEASUREMENTS: Forty patients with syndrome X (85% male) and 53 patients with CAD (89% male) were enrolled. Ten control subjects (90% male) with negative exercise treadmill test results and normal coronary angiographic findings served as control subjects. EBCT determined the coronary calcium scores (CCSs), and standard cardiovascular risk factors of all study subjects were analyzed. RESULTS: The 93 study patients had CCSs that ranged from 0 to 1,857. Coronary calcification was seen in 2 of the 10 control subjects (20%), 21 of the 40 syndrome X patients (52.5%), and 51 of the 53 CAD patients (96.2%) [p < 0.01]. The CCS (median [range]) was significantly lower in syndrome X patients than in CAD patients: 1 (0 to 117) vs 202 (0 to 1,857) [p < 0.001]. Receiver operating characteristic curve analyses also demonstrated that coronary calcification differentiated syndrome X from CAD (area under curve, 0.891; 95% confidence interval, 0.806 to 0.947). Of the CAD patients whose CCSs were < 117 and overlapped with CCSs of syndrome X, multivariate analyses determined CCS > 5 (odds ratio, 13.1; 95% confidence interval, 2.86 to 59.7), hypertension (odds ratio, 6.4; 95% confidence interval, 1.5 to 27.4), and hypercholesterolemia (odds ratio, 6.7; 95% confidence interval, 1.5 to 30.5) to be independent discriminators to differentiate CAD from syndrome X. Patients with CAD had more frequent hypertension than patients with syndrome X. CONCLUSIONS: The coronary calcium detected noninvasively by EBCT was different, though with some overlapping, between patients with syndrome X and CAD. In addition to standard cardiovascular risk factors, CCS determined by EBCT (especially > 117 or = 0) could differentiate between syndrome X and CAD in patients with chronic, stable angina with evidence of myocardial ischemia. Larger trials would be useful to validate CCS on EBCT as a predictor of clinical outcome in these patients.

Adult↗
PubMed2001

Differential coronary artery calcification detected by electron beam computed tomography as an indicator of coronary stenosis among patients with stable angina pectoris.

BACKGROUND: The detection of coronary artery calcification by electron beam computed tomography (EBCT) has been suggested as an indicator of atherosclerosis and coronary artery disease (CAD). There is no consensus on the correlation between coronary calcification and angiographically significant stenosis on an artery-by-artery basis. OBJECTIVE: To examine the relationship between coronary calcification score (CCS) and the presence of significant CAD on an artery-by-artery basis in patients with stable angina pectoris. METHODS AND RESULTS: EBCT and coronary angiogram (CAG) were evaluated in 71 patients with stable angina and in nine control subjects. The CCSs of each of the four major coronary arteries were highest in patients with significant CAD (n=43), followed by patients with insignificant CAD (n=5), patients with syndrome X (n=23) and control subjects, respectively. Calcification scores of the four major coronary arteries appeared to have different predictive power for significant stenosis on the same vessel. For left main (LM) and left anterior descending (LAD) coronary arteries, CCSs of vessels with significant stenoses were not different from those without significant stenoses (values expressed as medians: LM 0 versus 1; LAD 98.5 versus 70; not significant). Calcification scores of left circumflex (LCX) and right coronary arteries (RCA) were significantly higher in vessels with significant stenosis (LCX 49.5 versus 0; RCA 53 versus 1; P<0.05). CCSs appeared to be moderately useful to predict significant stenoses in these two vessels (areas under receiver operating characteristic curves: LCX 0.68+/-0.08, 95% CI 0.52 to 0.81; RCA 0.71+/-0.08, 95% CI 0.55 to 0.84). CONCLUSIONS: The CCSs of RCA and LCX arteries, but not those of LM and LAD arteries, may predict significant angiographic stenosis on an artery-by-artery basis among patients with stable angina pectoris.

Aged↗
PubMed2001

Intrafamilial transmission and risk assessment of HTLV-I among blood donors in southern Taiwan.

The human T-lymphotropic virus type I (HTLV-I) is one of the important etiological agents of adult T-cell leukemia/lymphoma and of HTLV-I associated myelopathy or tropical spastic paraparesis. There is still a lack of data concerning HTLV-I transmission by seropositive carriers in Taiwan. We investigated the patterns of HTLV-I intrafamilial transmission in HTLV-I seropositive blood donors and assessed the risk factors of HTLV-I transmission in relatives of HTLV-I carriers in Taiwan. A total of twenty HTLV-I seropositive donors and their 103 relatives were enrolled. Among those 103 relatives, 40 (38.8%) were seropositive for HTLV-I. Their ages ranged from one to 70 years old with a mean age of 31.0 +/- 1.65 year-old. Three of the ten wives of male carriers were HTLV-I seropositive. However, none of the six husbands of female carriers were HTLV-I seropositive. Mother-to-child vertical transmission was found in nine of 48 (18.8%) tested. Significant risk factors of HTLV-I transmission among relatives of HTLV-I carriers were hospital admission, previous transfusion, breast feeding, anti-HCV seropositivity and female relatives of age >/= 30 with odds ratio (OR) of 9.73, 8.64, 4.36, 8.86 and 4.91, respectively (all p < 0.05). Nonsignificant risk factors of HTLV-I transmission were sharing needles, operation history, HBsAg seropositivity and male relatives of age >/= 30. Our findings suggest that mother-to-child and husband-to-wife transmissions are the important forms of intrafamilial transmission of HTLV-I in Taiwan. Screening for HTLV-I in family members of HTLV-I seropositive blood donors may be warranted.

Adult↗
PubMed2001

[Construction of eukaryotic expression plasmid for mouse myogenic regulatory factor MyoD gene].

OBJECTIVE: To construct eukaryotic expression plasmid of mouse myogenic regulatory factor MyoD gene for further study on MyoD gene function in molecular regulatory mechanism in skeletal muscle repair. METHODS: The plasmids PEMMBC2 beta 5 containing full cDNA length of MyoD inserted in EcoRI restriction site, were first propagated in Escherichia coli DH5a, then extracted and purified with the Wizard Plus Minipreps DNA Purification System (Promega, USA). The coding sequence of MyoD in PEMMBC2 beta 5 was confirmed by agarose gel electrophoresis and DNA sequence analysis. After plasmids PEMMBC2 beta 5 and plasmids pcDNA3-neo were prepared by digestion with EcoRI, the MyoD cDNA fragment was inserted into EcoRI site in pcDNA3-neo eukaryotic expression vector, and pcDNA3/MyoD was formed. The pcDNA3/MyoD, digested with restriction enzymes, was found to contain the MyoD cDNA sequence by agarose gel electrophoresis analysis. RESULTS: The extracted and purified PEMMBC2 beta 5 contained the correct nucleotide sequence for the full length of MyoD cDNA fragment. The MyoD cDNA fragment had been inserted into the eukaryotic expression plasmid pcDNA3-neo, which formed the pcDNA3/MyoD. CONCLUSION: The pcDNA3/MyoD, a eukaryotic expression plasmid, for MyoD is constructed successfully.

Animals↗
PubMed2000

1-Cys peroxiredoxin, a bifunctional enzyme with glutathione peroxidase and phospholipase A2 activities.

This report provides definitive evidence that the protein 1-Cys peroxiredoxin is a bifunctional ("moonlighting") enzyme with two distinct active sites. We have previously shown that human, rat, and bovine lungs contain an acidic Ca(2+)-independent phospholipase A(2) (aiPLA(2)). The cDNA encoding aiPLA(2) was found to be identical to that of a non-selenium glutathione peroxidase (NSGPx). Protein expressed using a previously reported E. coli construct which has a His-tag and 50 additional amino acids at the NH(2) terminus, did not exhibit aiPLA(2) activity. A new construct which contains the His-tag plus two extra amino acids at the COOH terminus when expressed in Escherichia coli generated a protein that hydrolyzed the sn-2 acyl chain of phospholipids at pH 4, and exhibited NSGPx activity with H(2)O(2) at pH 8. The expressed 1-Cys peroxiredoxin has identical functional properties to the native lung enzyme: aiPLA(2) activity is inhibited by the serine protease inhibitor, diethyl p-nitrophenyl phosphate, by the tetrahedral mimic 1-hexadecyl-3-trifluoroethylglycero-sn-2-phosphomethanol (MJ33), and by 1-Cys peroxiredoxin monoclonal antibody (mAb) 8H11 but these agents have no effect on NSGPx activity; NSGPx activity is inhibited by mercaptosuccinate and by 1-Cys peroxiredoxin mAb 8B3 antibody which have no effect on aiPLA(2) activity. Mutation of Ser(32) to Ala abolishes aiPLA(2) activity, yet the NSGPx activity remains unaffected; a Cys(47) to Ser mutant is devoid of peroxidase activity but aiPLA(2) activity remains intact. These results suggest that Ser(32) in the GDSWG consensus sequence provides the catalytic nucleophile for the hydrolase activity of aiPLA(2), while Cys(47) in the PVCTTE consensus sequence is at the active site for peroxidase activity. The bifunctional catalytic properties of 1-Cys peroxiredoxin are compatible with a simultaneous role for the protein in the regulation of phospholipid turnover as well as in protection against oxidative injury.

Antioxidants↗
PubMed2000

Optical intrinsic signal imaging in a rodent seizure model.

The authors studied seizure activity with optical intrinsic signal (OIS) imaging in a rat seizure model. OIS, which measures vascular and metabolic effects associated with neuronal activity, showed significant cortical reflectance changes from penicillin-induced seizures, and correlated well with EEG epileptiform discharges. Furthermore, OIS changes often preceded initial EEG spikes. These observations suggest that OIS is well coupled with seizure activity, and may provide sensitive cues for seizure detection.

Animals↗
PubMed2000

Characterization of optical intrinsic signals and blood volume during cortical spreading depression.

Cortical spreading depression (CSD) was imaged in vivo in a rodent model with optical intrinsic signals (OIS). This is the first study to identify a triphasic OIS response and to characterize the rate and timing of the response. The initial OIS phase had a highly uniform wavefront, which spread at a rate characteristic of CSD, 3.5 mm/min. Later phases were more diffuse and inhomogeneous. Blood volume changes, measured with intravascular fluorescent dye, correlated in time and location with the later phases of OIS response. This suggests that the inhomogeneity of the late OIS response may be due to complex residual hemodynamic contributions, as opposed to underlying cortical circuitry.

Animals↗
PubMed2000

Impaired forearm reactive hyperemia is related to late restenosis after coronary stenting.

To investigate whether systemic endothelial function on forearm resistance vessels is related to angiographic restenosis after coronary stenting, 47 men who underwent elective coronary stenting were divided into 2 groups according to the presence (n = 20) or absence (n = 27) of in-stent restenosis 6 months after the procedure. Another 19 risk factor-matched men with normal coronary angiograms served as the control group. Forearm blood flow was assessed by venous occlusive plethysmography. Basal forearm blood flow was similar between restenosis, nonrestenosis, and control groups (2.63 +/- 0.19, 2.58 +/- 0.14, and 3.23 +/- 0.13 ml/100 ml forearm tissue per minute, respectively). In all 3 groups, forearm blood flow increased significantly during reactive hyperemia (5.75 +/- 0.7, 11. 32 +/- 1.23, and 14.52 +/- 1.36 ml/100 ml forearm tissue per minute, p <0.05, respectively) and remained unchanged after sublingual administration of nitroglycerin. The percentage change of forearm blood flow during reactive hyperemia was significantly lower in the restenosis group (117.3 +/- 18.3%) than in the nonrestenosis group (354.2 +/- 46.5%, p <0.01). This difference was still present after sublingual nitroglycerin (37.6 +/- 21.2% vs 226.4 +/- 40.5%, p <0. 01). In contrast, percentage change of hyperemic forearm blood flow was significantly lower in patients with angina (117.5 +/- 49.5%) than in those without angina (290.1 +/- 37.4%, p <0.05) at follow-up. In all patients, the angiographic loss index was correlated negatively to the percentage change of hyperemic forearm blood flow (r = -0.33, p <0.01) and positively to the percentage change of forearm vascular resistance during reactive hyperemia (r = 0.33, p <0.01). In patients with angiographic restenosis after coronary stenting, forearm reactive hyperemia was more impaired compared with those without angiographic restenosis. Systemic endothelial dysfunction might be either a marker or one of the confounding factors in the development of late restenosis after coronary stenting.

Aged↗