Biomedical subjects

C H Chen

Publications and source records attributed to C H Chen.

At least 19 recordsLinked to original sources

PubMed1995

Dynamic three-dimensional echocardiographic assessment of intracardiac blood flow jets.

Transthoracic dynamic 3-dimensional reconstruction of the heart with tissue depiction has been proved to be feasible when using various methods of data acquisition. The same method can theoretically be applied to color Doppler flows to generate dynamic 3-dimensional images of intracardiac blood flow jets. To explore the feasibility of this approach, we studied 41 patients with various valvular disorders or intracardiac shunts. We acquired sequential 2-dimensional images along with color Doppler information using rotational scanning from a transthoracic or a subcostal window. Images were digitized and processed for 3-dimensional reconstruction using dedicated software. After adequate segmentation, the flow jets were displayed in 3 dimensions in a gray scale format. With use of this approach, 3-dimensional reconstruction of color Doppler flows was possible in all but 1 patient. Still frames allowed immediate appreciation of the shape of the jets, their location in the cardiac chambers, and their size related to that cavity. Dynamic display was even more striking by showing the flow in real time. Dynamic 3-dimensional images enabled visualization of flow jets in projections not available in conventional color flow Doppler, looking directly at the views of shunt and regurgitant flows, and also permitted 3-dimensional delineation of flow convergence zones. We conclude that dynamic visualization of various intracardiac flows in 3 dimensions using transthoracic echocardiography is possible. It provides a better understanding of the shape and size of the jets, and can potentially aid in flow quantification by displaying the actual shape of flow convergence regions.

Adolescent↗

PubMed1995

Radiation-induced apoptosis: effects of cell age and dose fractionation.

The cell cycle dependence of radiation-induced apoptosis was measured using mitotically synchronized REC:myc(ch1) and Rat1:mycb cells. Cells in S and G2 phases were more susceptible; the apoptotic fraction was about 0.7-0.8 as compared to about 0.4 for G1 cells at a dose of 10 Gy. Two-dimensional cytofluorimetric analysis of cells, pulsed-labeled with bromodeoxyuridine and then irradiated with 10 Gy, showed both G1 and G2 blocks (6-8 h) for REC:myc(ch1) cells but only G2 block for Rat1:mycb cells. Consistent with these results, wild-type p53 and WAF1 (or p21), known to play a role in G1 delay, was induced by radiation in REC:myc(ch1) but not in Rat1:mycb cells. The cell cycle dependence of radiation-induced apoptosis and the absence of a G1 block for Rat1:mycb cells led to the prediction and observation of the novel "inverse split-dose effect," i.e., a radiation dose given in two equal halves separated by a few hours yielded a higher level of apoptosis relative to that resulting from the same total dose given all at once. This effect is due to cell cycle progression from G1 to the more sensitive S-G2 phase during the interval between the split doses. In contrast, the inverse split-dose effect for apoptosis is absent for REC:myc(ch1), due presumably to the radiation-induced G1 delay. Parallel split-dose experiments, but using clonogenic survival as end points, show recovery for REC:myc(ch1) cells but not for Rat1:mycb cells, reflecting the influence of split-dose, radiation-induced apoptosis.

Animals↗

PubMed1995

Cigarette smoking in China. Prevalence, characteristics, and attitudes in Minhang District.

OBJECTIVE: To determine the prevalence, pattern, and financial implications of cigarette smoking and the attitudes toward and knowledge of the health effects of tobacco use in a population in China. DESIGN: A two-stage, stratified cluster survey using door-to-door interviews. SETTING: Minhang District, China (near Shanghai), with a population of 506,000. PARTICIPANTS: A total of 3423 males and 3593 females aged 15 years and older. MAIN OUTCOME MEASURES: Smoking prevalence, age of initiation of smoking, reasons for smoking, knowledge of tobacco hazards, and costs of smoking. RESULTS: A total of 2279 males (67%) but only 72 females (2%) smoke. Many males initiate smoking in adulthood. A total of 1156 males (50.7%) began smoking between 20 and 24 years of age, and 666 (29.2%) began between 25 and 39 years of age. Among all respondents, 6202 (88.4%) believe smoking is harmful for both the smoker and those exposed passively to the smoke. Only 332 (14.1%) of all male smokers reported a desire to quit smoking. Current smokers spent an average of 3.65 yuan daily on cigarettes or 1332 yuan yearly (8.5 yuan per US dollar), which represents 60% of personal income and 17% of household income. CONCLUSIONS: The survey reveals a dangerous health situation that in all likelihood will worsen. More than two thirds of men smoke, and people in successive age cohorts start smoking at earlier ages. Smokers spend a substantial proportion of their income on cigarettes. There is a low rate of quitting and a low desire to quit despite high awareness of the health hazards. Tobacco control measures need to be implemented urgently in China.

Adolescent↗

PubMed1995

Analysis of polymerase chain reaction-amplified DNA products by mass spectrometry using matrix-assisted laser desorption and electrospray: current status.

Recent advances in molecular biology are making it possible to diagnose genetic diseases and identify pathogens through the analysis of DNA. As clinical applications for molecular diagnosis increase, rapid, reliable methods for determination of DNA size will be needed. Mass spectrometry offers the potential of analyzing amplified DNA quickly and reliably, without the need for gel-based separation and sample labeling steps that are conventionally employed. Both electrospray ionization and matrix-assisted laser desorption/ionization have been evaluated for the size analysis of DNA using both synthetic oligonucleotides and PCR-amplified samples corresponding to bases 1626 to 1701 of the cystic fibrosis transmembrane conductance regulator gene. Both technologies have been demonstrated to have mass range and sensitivity required for the analysis of PCR-amplified DNA in this size range using minimal sample preparation. Steps required to incorporate either ionization technique into a reliable analytical scheme for the rapid, routine analysis of DNA are outlined.

Base Sequence↗

PubMed1995

Population-based study of insulin, C-peptide, and blood pressure in Chinese with normal glucose tolerance.

Insulin resistance may play a role in the pathogenesis of essential hypertension. The purpose of the present study was to examine the relations of fasting serum insulin or C-peptide levels with hypertension and blood pressure (BP) in a stable homogeneous southern Chinese population with normal glucose tolerance. This community-based survey of adults aged > or = 30 years in Kin-Chen, Kinmen, was conducted by the Yang-Ming Crusade in 1992 and 1994. Data of fasting serum insulin and C-peptide from a total of 1,447 men and 1,800 women (mean age 46.7 years) were analyzed. Both continuous (by multiple regression) and categorical analyses (by analysis of covariance) were used. Fasting insulin concentrations (as independent variables) were significantly associated with log systolic BP (as outcome variables, coefficient = 0.000081, p = 0.0035) and log diastolic BP (as outcome variables, coefficient = 0.000098, p = 0.0006) after accounting for age, sex, body mass index, and waist-to-hip ratio. Similarly, fasting C-peptide concentrations were significantly associated with log systolic BP (coefficient = 0.023304, p = 0.0001) and log diastolic BP (coefficient = 0.032971, p = 0.0001). In categorical analyses, both fasting insulin and C-peptide concentrations were significantly different (insulin p = 0.01010, and C-peptide p = 0.0004) between hypertensive and normotensive subjects when the similar set of covariates were accounted for. In conclusion, both fasting serum insulin and C-peptide concentrations are significantly associated with BP in this homogeneous Chinese population with normal glucose tolerance.

Adult↗

PubMed1995

R-loop stability as a function of RNA structure and size.

The sequence-specific formation of R-loops can be assayed using RNAs which overlap a HindIII cleavage site in a 3.5 kb plasmid. Chemical modification of the displaced DNA strand has permitted stabilization of these R-loops and allowed a systematic investigation of the dependence of these triple-stranded structures on the chain length and structure of the input RNA. RNAs as short as 50 nt form stable R-loops if 5-allylamine uridines (Uaa-RNA) are used in place of normal uridines; normal RNAs must be 100 nt long to form R-loops quantitatively. Since acetic anhydride decreases the hybridization efficiency of Uaa-RNAs, the positive charge of the RNAs must diminish the electrostatic repulsion of the three negatively charged phosphodiester backbones. The dependence of R-loop stability on the length of RNA can be stimulated with a random walk model, which also applies to strand migration within Holiday junctions. R-loop hybridization provides a versatile method to generate single-stranded DNA in a sequence-selective manner.

DNA↗

PubMed1995

Double stranded scission of DNA directed through sequence-specific R-loop formation.

R-loop formation with short (100 nt) RNAs provides a highly flexible and stringent method to achieve sequence-specific separation of target DNA at any given sequence. After stabilization of R-loops with glyoxal and removal of the RNA through RNase treatment the remaining single-stranded DNA bubble provides a highly favorable substrate for attenuated micrococcal nuclease. We investigated this method for sequence-specific scission of double-stranded DNA and achieved quantitative scission of 3-5 kb plasmids. The applicability to larger size DNA is demonstrated through specific excision of the intervening segment between two R-loops from a P1 plasmid of approximately 120 kb.

Base Sequence↗

PubMed1995

Relation between diurnal variation of blood pressure and left ventricular mass in a Chinese population.

In western populations, patients with hypertension who have a nocturnal decrease in blood pressure (BP) may have less left ventricular (LV) hypertrophy and cardiovascular morbidity than those without a diurnal variation in BP. To further examine this association between nocturnal BP reduction and LV mass index, we studied 720 normotensives (< 140/90 mm Hg), 380 borderline hypertensives (140 to 159/90 to 94 mm Hg), and 582 hypertensives (> or = 160/95 mm Hg) from Taiwan and Quemoy island by using 24-hour ambulatory BP monitoring and 2-dimensional echocardiography to obtain LV mass index during a community-based cardiovascular survey. After controlling for age, sex, height, weight, daytime BP, and daytime heart rate, the nocturnal reduction of systolic BP was found to associate weakly with LV mass index, for the whole population (partial correlation coefficient = -0.06, p < 0.05), as well as for the patients with hypertension (partial correlation coefficient = -0.09, p < 0.05), but these associations were eliminated when 24-hour BP and heart rate were accounted for. The average and percent nocturnal decrease of systolic BP (mean +/- SD; mm Hg, [%]) of 3.2 +/- 5.9 (2.7 +/- 4.8%); 3.3 +/- 7.3 (2.4 +/- 5.4%); and 4.6 +/- 9.0 (3.0 +/- 6.1%) in normotensives, borderline hypertensives, and hypertensives, respectively, was smaller than that found in previous studies. Hence, in this large Chinese population, a small nocturnal BP drop was found and it was only weakly associated with LV mass index. These results emphasize the general need for ambulatory BP reference values based on internal controls.

Adult↗

PubMed1995

Structure-functional effects of a series of alcohols on acetylcholinesterase-associated membrane vesicles: elucidation of factors contributing to the alcohol action.

Structure-functional effects of a series of alcohols on acetylcholinesterase (AChE) derived from Torpedo californica were investigated. No significant effect on the soluble form of the enzyme was observed, but a marked biphasic effect on the activity of the membrane-associated form of the enzyme was found: it increased to maxima of 115 +/- 2% at 40 mM ethanol, 123 +/- 2% at 10 mM propanol, and 114 +/- 2% at 10 mM t-butanol; declined with further increases in alcohol concentration; and then leveled off. Significantly, no increase was observed with n-butanol. The effect on membrane-associated AChE activity was in the order of propanol > t-butanol > ethanol > n-butanol, suggesting that the site of action of alcohol was small and could not accommodate straight-chain alcohols longer than propanol. Comparison of the results for soluble AChE and membrane-associated AChE activity indicated the involvement of the membrane in alcohol action. Fluorescence steady-state polarization (P) measurements of Torpedo membrane vesicles showed that membrane fluidity increased with increasing [alcohol], as indicated by a decrease in polarization (delta P = -0.010 +/- 0.003, -0.062 +/- 0.0003, -0.017 +/- 0.002, and -0.011 +/- 0.002 in the presence of 60 mM ethanol, propanol, n-butanol, and t-butanol, respectively). Alcohol-induced increase in membrane fluidity was in the order propanol > n-butanol > t-butanol, ethanol, suggesting that both lipid solubility and molecular size of alcohols could be important if alcohols must fit into membrane lipid domains in order to affect membrane fluidity. The biphasic effect of alcohol action on membrane-associated AChE activity is discussed in terms of membrane fluidity, lipid solubility, molecular size of alcohol, enzyme-lipid interaction, site of alcohol action, and a direct interaction of alcohol with the enzyme.

1-Butanol↗

PubMed1995

Ceramide reverses brefeldin A (BFA) resistance in BFA-resistant cell lines.

We have found that C6 ceramide, a cell-permeable ceramide analog, partially restored the brefeldin A (BFA) sensitivity in a BFA-resistant mutant of Vero cells (BER-40) and in the naturally BFA-resistant Madin-Darby canine kidney (MDCK) cells. Incubation of BER-40 and MDCK cells with low concentrations of C6 ceramide resulted in (i) a pronounced increase in BFA cytotoxicity as measured by the inhibition of [3H]thymidine incorporation and the inhibition of colony formation by BFA, (ii) a significant protection by BFA against ricin cytotoxicity, and (iii) an inhibition of bulk protein secretion by BFA in BER-40 and MDCK cells. Related sphingolipids including sphingosine, sphingomyelin, and lactosylceramide and other unrelated lipid second messengers such as arachidonic acid and 1,2-diacylglycerol did not elicit the protection of BER-40 and MDCK cells against ricin cytotoxicity by BFA. C6 ceramide was the most effective among the ceramides with different acyl chain lengths. Interestingly, dihydro-C6 ceramide, which lacks the trans double bond in the sphingoid base, had no effect. On the other hand, C6 ceramide did not enhance BFA sensitivity in BFA-sensitive Vero cells. The LD50 of C6 ceramide were similar in Vero and BER-40 cells. Fluorescence microscopic studies revealed that C6 ceramide induced the redistribution of beta-COP from the Golgi membranes to a more dispersed localization in both BFA-sensitive and BFA-resistant cell lines, mimicking the effect of BFA. Suboptimal concentration of C6 ceramide also restored the effect of BFA on the beta-COP distribution in BER-40 and MDCK cells. These results indicate that C6 ceramide restores the BFA sensitivity in BFA-resistant BER-40 and MDCK cells.

Animals↗

PubMed1995

A population-based epidemiological study on cardiovascular risk factors in Kin-Chen, Kinmen.

We conducted a population survey of cardiovascular risk factors in Kin-Chen, Kinmen (Quemoy), an island under military control for 40 years and the focal point of confrontation between mainland China and Taiwan. During the period 1992-1994, all residents > or = 30 years of age in Kin-Chen, the largest township in Kinmen, were invited to participate. The response rate was 60.3% (3826/6346). The prevalence of hypertension (> or = 160/95 mmHg and/or under treatment) was 25.2% in men and 17.6% in women. The rate for smoking was 41.5% in men and 2.9% in women. The prevalence of diabetes was 6.7% in men and 6.4% in women. Mean values for systolic blood pressure, diastolic blood pressure, total cholesterol, triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol were 135.3 mmHg, 85.5 mmHg, 5.3 mmol/l, 1.1 mmol/l, 3.5 mmol/l and 1.4 mmol/l in men; and 128.0 mmHg, 79.5 mmHg, 5.2 mmol/l, 1.0 mmol/l, 3.3 mmol/l and 1.5 mmol/l in women, respectively. The unexpectedly high prevalence of hypertension in Kin-Chen male may reflect the effect of more than 40 years of military control and discipline. The high serum cholesterol level in Kin-Chen relative to mainland China and the low triglyceride level relative to Taiwan and Beijing, suggest further study of the contributions of diet and other psychosocial or environmental factors.

Adult↗

PubMed1995

Detection of delta F508 mutation of the cystic fibrosis gene by matrix-assisted laser desorption/ionization mass spectrometry.

The most common mutation of the cystic fibrosis gene is characterized by the deletion of three nucleotides that code phenylalanine in the 508 position of the cystic fibrosis transmembrane conductance regulator. We report the first measurements by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry for the delta F508 mutation in cystic fibrosis carriers and patients. Furthermore, in a blind test, results from the normal and delta F508 mutant alleles in 30 clinical samples based on MALDI mass spectrometry and on conventional gel analysis of the DNA were in total agreement. These results demonstrate the utility of MALDI mass spectrometry in the molecular diagnosis of mutant alleles and point to its potential use for ultra-fast detection in large-scale screening of DNA mutations.

Base Sequence↗

PubMed1995

Relations between joint torque, motion, and electromyographic patterns at the human elbow.

Voluntary movements may be considered kinematic actions resulting from the neural control patterns that activate the motoneuron pools. One school of thought proposes that specific features of the intended kinematic trajectory such as the duration of acceleration are used by the central nervous system to plan muscle activation patterns. Our own experience suggests that it is the intended force trajectory that is directed by muscle activation patterns. Although under many circumstances these two approaches lead to indistinguishable behavior patterns, examples of movements that are incompatible with the former but not the latter approach are presented in this manuscript.

Biomechanical Phenomena↗

PubMed1995

Basic fibroblast growth factor reverses atherosclerotic impairment of human coronary angiogenesis-like responses in vitro.

The influence of atherosclerosis on vascular growth in humans was evaluated in an in vitro model of angiogenesis. Coronary artery intima-media explants from patients (n = 10) with coronary artery disease (CAD) (in all cases Stary type V lesions) and patients without CAD (n = 10) were cultured in a collagen matrix containing serum-free medium. Endothelial cell growth from explants was organized as capillary-like microtubes (CLM); the sum of their lengths was morphometrically quantitated as an index of angiogenesis. CLM growth was suppressed in CAD explants (n = 120), the index values at two weeks averaging only 20% +/- 3% of non-CAD explants (n = 120, P < 0.001). Addition of exogenous basic fibroblast growth factor (bFGF) (10 ng/ml) stimulated CLM growth substantially more in the CAD than in the non-CAD group, whereas bFGF-neutralizing antibodies nearly abolished growth in both. Endothelial cells isolated from non-CAD coronary arteries exhibited in culture typical endothelial characteristics, including cobblestone appearance, staining for von Willebrand factor, CLM formation on Matrigel substrate, and sensitivity to bFGF and to bFGF-neutralizing antibody. Inhibition of cell replication by oxidized low-density lipoprotein (OxLDL) was reversed by bFGF. We conclude that human atherosclerosis is associated with impairment of angiogenesis-like endothelial growth and that decreased bFGF availability contributes to the impairment.

Cell Count↗

PubMed1995

Quantitative detection of hepatitis B virus DNA in human sera by branched-DNA signal amplification.

Serum samples from 116 patients with hepatitis B surface antigen (HBsAg), from 7 patients without detectable HBsAg and from 71 healthy blood donors were tested by a branched DNA signal amplification (bDNA) method. Hepatitis B virus (HBV) DNA was detected in 39 (34%) of the 116 samples with HBsAg, including 19 (70%) of the 27 patients who were also positive for hepatitis B e antigen (HBeAg). In contrast, one of the 7 patients without HBsAg and none of the 71 blood donors were positive for HBV DNA. The titers of serum HBV DNA did not correlate with the serum alanine aminotransferase levels. All the samples positive by the bDNA assay were positive by the polymerase chain reaction (PCR). However, 59% of the PCR-positive samples were bDNA-negative. None of the PCR-negative samples was positive by the bDNA method. Although the sensitivity of bDNA method is not entirely satisfactory, it showed excellent specificity and reproducibility. Thus it may be considered as an alternative for quantitative detection of HBV DNA in serum samples of patients with relatively high titers of HBV viremia.

Adolescent↗

PubMed1995

Epidemiology of hypertension in Kin-Hu, Kinmen.

Data on the prevalence and predictors of hypertension in Kinmen, an island very close to southern mainland China but under Republic of China administration, would be very helpful to understand the effect of environmental and psychosocial factors on hypertension in a specific ethnic group. In 1991, Kin-Hu residents > or = 30 years of age, living in the second largest township of Kinmen, were invited to participate in this survey incorporating face-to-face interviews with a structured questionnaire, collection of fasting blood samples and oral glucose tolerance test. The response rate for subjects with complete data was 80.3% (3289 of 4097). The prevalence rates for definite hypertension (> or = 160/95 mm Hg and/or under antihypertensive treatment) were 20.1, 14.0, and 16.9% for men, women, and the total population, respectively. Overall awareness, treatment, and control rates of definite hypertension were 46.9, 25.0, and 4.7%, respectively. According to the final logistic regression model, after controlling for all other covariates, the significant predictors for current-definite hypertension were old age, male sex, nonsmoking, obesity, alcohol intake, high waist-to-hip ratio, high serum triglyceride and high serum uric acid levels. In comparison with Chinese in Taiwan and mainland China, the unexpectedly high prevalence of hypertension and distinct set of its predictors in Kin-Hu form the basis for future study.

Adult↗

PubMed1995

Changes in portal hypertensive gastropathy after endoscopic variceal sclerotherapy or ligation: an endoscopic observation.

To determine the effect of endoscopic variceal sclerotherapy or ligation on portal hypertensive gastropathy, 90 cirrhotic patients with esophageal variceal bleeding were randomized to receive sclerotherapy (n = 44) or ligation (n = 46). Follow-up endoscopic observations of the gastric mucosa were recorded at 3-month intervals after variceal eradication. Clinical characteristics in both groups were similar. Probability for a change in the severity of portal hypertensive gastropathy was not related to method of eradication. Most cases of portal hypertensive gastropathy that changed in severity returned to baseline status with time, but the return was faster after ligation than after sclerotherapy. According to the results of multivariate analyses, sclerosant volume was the only factor associated with a significant difference between the group with static gastropathy (n = 15) and that with dynamic change in gastropathy (n = 23) after sclerotherapy. No relevant factors were found in the patients receiving ligation. We conclude that changes in the severity of portal hypertensive gastropathy after endoscopic variceal sclerotherapy or ligation are reversible. Most cases of gastropathy return to baseline status sooner or later.

Esophageal and Gastric Varices↗

PubMed1995

Oligoclonal CD8 lymphocytes from persons with asymptomatic human immunodeficiency virus (HIV) type 1 infection inhibit HIV-1 replication.

CD8 lymphocytes from asymptomatic human immunodeficiency virus (HIV) type 1-infected patients can suppress virus production from infected CD4 cells. Suppressive activity is separate and distinct from cytotoxic T lymphocyte (CTL) reactivities and is likely mediated by a soluble factor(s). The majority of HIV-1 suppression studies have been done in the context of bulk CD8 cell cultures. In this study, viral suppression was characterized by clonal populations of CD8 cells derived from HIV-1-infected patients. Most of the suppressive clones were devoid of detectable CTL reactivity against env-, gag-, pol-, and nef-expressing targets. Among the suppressive clones derived from an individual patient, a marked heterogeneity was evident with respect to phenotypic markers, cytokine production, and T cell receptor V beta expression. These results suggest that noncytolytic virus suppression is oligoclonal in nature. Clones provide tools for future studies aimed at understanding the mechanism of suppression and identifying the suppressive factor.

CD8-Positive T-Lymphocytes↗