Biomedical subjects

T H Chen

Publications and source records attributed to T H Chen.

At least 37 records · Page 2Linked to original sources

PubMed2001

Clinicopathologic and prognostic differences between patients with hepatitis B- and C-related resectable hepatocellular carcinoma.

BACKGROUND AND PURPOSE: Hepatitis B and C viral infections are important factors in the development of hepatocellular carcinoma (HCC). This study examined the clinicopathologic and prognostic differences in patients with hepatitis B- and C-related resectable HCC. METHODS: A total of 270 HCC patients who underwent hepatic resection were enrolled. Among these patients, 211 were positive for hepatitis B surface antigen (HBsAg) and 59 were positive for anti-hepatitis C virus antibody (anti-HCV). The clinical manifestations, pathologic features, and treatment outcomes were compared between the HBsAg-positive and anti-HCV-positive groups. RESULTS: Compared to anti-HCV-positive patients, HBsAg-positive patients were significantly younger, had a higher familial incidence of HCC, larger tumor size, and a higher incidence of multiple tumors. HCC patients who were anti-HCV positive had worse liver function and a higher incidence of history of blood transfusion. DNA flow cytometric analysis revealed significantly more proliferative activity in the non-tumor part of the liver in HBsAg-positive HCC patients. The 1-, 3-, and 5-year overall survival rates of HBsAg-positive patients were 79%, 57%, and 48%, respectively, and for anti-HCV-positive patients were 91%, 75%, and 62%, respectively. HBsAg-positive patients had a significantly lower overall survival rate than anti-HCV-positive patients (p = 0.018). CONCLUSIONS: HBsAg-positive patients with resectable HCC had a less favorable survival rate after tumor resection than anti-HCV-positive HCC patients. This survival difference might have been related to the relatively advanced stage of disease and the higher proliferative activity of the non-tumor part of the liver in HBsAg-positive HCC patients.

Adult↗

PubMed2001

The in vitro inhibitory effect of flavonoid astilbin on 3-hydroxy-3-methylglutaryl coenzyme A reductase on Vero cells.

BACKGROUND: Epidemiological studies have shown that hypercholesterolemia is a major risk factor for coronary heart disease. In clinical trials of lipid lowering therapy, 3-hydroxy-3-methylglutaryl Coenzyme A (HMG-CoA) reductase inhibitor has been shown to decrease cardiac events and mortality. Flavonoids are polyphenolic natural antioxidants existing in vegetables, fruits and beverages such as tea and wine. Previous studies have shown that some antioxidants had hypocholesterolemic effect, and flavonoid intake was associated with the decrease of mortality from coronary artery disease. The aim of this study was to evaluate the inhibitory effect of flavonoids on HMG-CoA reductase. METHODS: The methods for analysis of specific inhibitors of mevalonate biosynthesis have been well-established, using Vero cells, a cell line obtained from kidneys of African green monkeys. Flavonoids isolated from different traditional Chinese herbs were dissolved in DMSO and incubated with Vero cells with or without the addition of 1 mM mevalonate or 5 mM sodium acetate in order to observe cell growth for 24 h. RESULTS: Concentrations of 1 mM mevalonate or 5 mM sodium acetate were added into culture medium in order to observe the effect on cell growth. Different concentrations of pravastatin to inhibit cell growth were used as a positive control. About 40 flavonoid compounds were used for study, only one compound, astilbin (belonging to the flavonol group), showed significant inhibition of Vero cell growth. CONCLUSIONS: This study shows that one flavonoid compound, isolated from traditional medicinal herbs, may be an effective HMG-CoA reductase inhibitor which might be developed into a new hypocholesterolemic agent.

Animals↗

PubMed2001

Bedside pericardiocentesis under the guidance of transesophageal echocardiography in a 13-month-old boy.

Pericardial effusion is a common sequel to cardiac surgery. Urgent pericardiocentesis is required in the case of cardiac tamponade. In adult patients, most pericardiocentesis is accomplished using transthoracic echocardiographic imaging. However, transthoracic echocardiographic imaging may interfere with the procedure field in children. We report the case of a 13-month-old boy who developed cardiac tamponade resulting in heart failure after surgical repair of tetralogy of Fallot. Urgent pericardiocentesis was safely performed at the bedside under transesophageal echocardiographic guidance. Transesophageal echocardiographic monitoring during pericardiocentesis in children has the advantages of better imaging of pericardial effusion without procedure-field interference.

Echocardiography, Transesophageal↗

PubMed2000

Amino acids in the second and third intracellular loops of the parathyroid Ca2+-sensing receptor mediate efficient coupling to phospholipase C.

To determine the role of amino acids in the second and third intracellular (IC) loops of the Ca(2+)-sensing receptor (CaR) in phospholipase C (PLC) activation, we mutated residues in these loops either singly or in tandem to Ala and assessed PLC activity by measuring high extracellular [Ca(2+)] ([Ca(2+)](o))-induced inositol phosphate accumulation and protein expression by immunoblotting and immunocytochemistry in human embryonic kidney 293 cells. Two CaR constructs in the second IC loop, F707A CaR and to a lesser extent L704A CaR, demonstrated reduced activation of PLC, despite levels of protein expression comparable with the wild-type (wt) CaR. Substitution of Tyr or His for Phe-707, but not Leu, Val, Glu, or Trp, partially restored the ability of high [Ca(2+)](o) to activate PLC. Eight residues in the third IC loop were involved in PLC signaling. The responses to high [Ca(2+)](o) in cells expressing CaRs with Ala substitutions at these sites were <35% of the wt CaR. The L798A, F802A, and E804A CaRs were dramatically impaired in their responses to [Ca(2+)](o) even up to 30 mm. Substitutions of Leu-798 with other hydrophobic residues (Ile, Val, or Phe), but not with acidic, basic, or polar residues, produced reduced responses compared with wt. Phe-802 could be replaced with either Tyr or Trp with partial retention of the ability to activate PLC. Glu-804 could only be substituted with Asp or Gln and maintain its signaling capacity. Cell surface expression of the CaRs mutated at Leu-798 and Phe-802 appeared normal compared with wt CaR. Cell surface CaR expression was, however, reduced substantially in cells expressing several mutants at position Glu-804 by confocal microscopy. These studies strongly implicate specific hydrophobic and acidic residues in the second and third IC loops of the parathyroid CaR (and potentially larger stretches of the third loop) in mediating efficient high [Ca(2+)](o)-induced PLC activation and or CaR expression.

Amino Acid Sequence↗

PubMed2000

Evaluation of a population-based screening for type 2 diabetes: a community-based screening project in Puli, Taiwan.

BACKGROUND: A Markov method incorporating the relationships between prevalence, incidence, and mortality with respect to type 2 diabetes was used to assess a population-based screening for this disease. METHODS: Data from a population-based screening project for residents of Puli, Taiwan, over 30 years of age (n= 1,219) were used to estimate the annual incidence of asymptomatic type 2 diabetes, the prevalence to incidence (P/I) ratio, and the hazard rate of death due to type 2 diabetes. These parameters were employed to develop a Markov process to evaluate the effects of early detection of type 2 diabetes on the risk of death from this disease in a simulated population (n= 10,000) receiving biennial, 5-year interval, or no screening. RESULTS: The estimated annual incidence, average duration from asymptomatic to symptomatic type 2 diabetes (P/I ratio), and hazard rate for death from this disease were 0.86% (95% CI 0.50-1.48), 10 years (95% CI 7.69-14.01), and 1.1% per year, respectively. This yields an optimal screening interval of 5 years. Simulation of a 5-year interval screening regimen versus no screen ing yielded a relative risk reduction of 31% (95% CI 12-46%). A similar value was found for a biennial screening regime. CONCLUSIONS: The results suggest that early detection of type 2 diabetes via a community-based screening project in developing countries with high prevalence is worthwhile.

Adult↗

PubMed2000

Peripheral nerve regeneration using silicone rubber chambers filled with collagen, laminin and fibronectin.

A 10 mm gap of rat sciatic nerve was created between the proximal and distal nerve stumps, which were sutured into silicone rubber tubes filled with an extracellular gel containing collagen, laminin and fibronectin. Empty silicone rubber tubes were used as controls. Six weeks after implantation, all extracellular elements were completely degraded and absorbed, and 90% of the animals from the extracellular gel group exhibited regeneration across the nerve gaps, whereas only 60% in the control group. Both qualitative and quantitative histology of the regenerated nerves revealed a more mature ultrastructural organization with 28% larger cross-sectional area and 28% higher number of myelinated axons in the extracellular gel group than the controls. These results showed that the gel mixture of collagen, laminin and fibronectin could offer a suitable growth medium for the regeneration of axons.

Action Potentials↗

PubMed2000

The effect of posterior capsulorrhaphy in primary total hip arthroplasty: a prospective randomized study.

Between 1994 and 1997, 180 cases of primary total hip arthroplasty (THA) were performed with the posterior (Moore) approach for a variety of indications and studies prospectively. The cases were separated randomly into 2 groups to evaluate the effect of posterior capsulorrhaphy in the prevention of postoperative dislocation. In group 1 (96 cases), closure of the arthroplasty was performed with a posterior capsulorrhaphy; in group 2 (84 cases), closure was performed without capsulorrhaphy. The follow-up period was 38 months (range, 12-60 months). No dislocations occurred in group 1, whereas 2 dislocations (2.3%) occurred in group 2. Although the factors affecting dislocation in primary THA are many, a posterior capsulorrhaphy may be helpful in the prevention of posterior dislocation of primary THA performed with a posterior approach.

Arthroplasty, Replacement, Hip↗

PubMed2000

Mechanisms of AVP-induced glucagon release in clonal alpha-cells in-R1-G9: involvement of Ca(2+)-dependent and -independent pathways.

1. The mechanisms underlying AVP-induced increase in [Ca(2+)](i) and glucagon release in clonal alpha-cells In-R1-G9 were investigated. 2. AVP increased [Ca(2+)](i) and glucagon release in a concentration-dependent manner. After the administration of AVP, glucagon was released within 30 s, quickly reached the maximum within 2 min, and maintained a steady-state concentration for at least 15 min. 3. In Ca(2+)-containing medium, AVP increased [Ca(2+)](i) in a biphasic pattern; a peak followed by a sustained plateau. In Ca(2+)-free medium, the Ca(2+) response to AVP became monophasic with lower amplitude and no plateau. Both the basal and AVP-induced glucagon releases were lower in the absence than in the presence of extracellular Ca(2+). When [Ca(2+)](i) was stringently deprived by BAPTA, a Ca(2+) chelator, AVP still significantly increased glucagon release. 4. Pretreatment with thapsigargin, a microsomal Ca(2+) ATPase inhibitor, abolished both the Ca(2+) peak and sustained plateau. 5.AVP increased intracellular concentration of IP(3). 6. U-73122 (8 microM), a phospholipase C inhibitor, abolished AVP-induced increases in [Ca(2+)](i), but only reduced AVP-induced glucagon release by 39%. 7. Pretreatment with nimodipine, an L-type Ca(2+) channel blocker failed to alter AVP-induced glucagon release or increase in [Ca(2+)](i). 8. The results suggest that AVP causes glucagon release through both Ca(2+)-dependent and -independent pathways. For the Ca(2+)-dependent pathway, the G(q) protein activates phospholipase C, which catalyzes the formation of IP(3). IP(3) induces Ca(2+) release from the endoplasmic reticulum, which, in turn, triggers Ca(2+) influx. Both Ca(2+) release and Ca(2+) influx may contribute to AVP-induced glucagon release.

Amino Acid Chloromethyl Ketones↗

PubMed2000

An electron microscopic-cytochemical localization of plasma membrane Ca(2+)-ATPase activity in poplar apical bud cells during the induction of dormancy by short-day photoperiods.

Plasma membrane (PM) Ca2+-ATPase activity in poplar apical bud meristematic cells during short-day (SD)-induced dormancy development was examined by a cerium precipitation EM-cytochemical method. Ca2+-ATPase activity, indicated by the status of cerium phosphate precipitated grains, was localized mainly on the interior face (cytoplasmic side) of the PM when plants were grown under long days and reached a deep dormancy. A few reaction products were also observed on the nuclear envelope. When plant buds were developing dormancy after 28 to 42 d of SD exposure, almost no reaction products were present on the interior face of the PM. In contrast, a large number of cerium phosphate precipitated grains were distributed on the exterior face of the PM. After 70 d of SD exposure, when buds had developed a deep dormancy, the reaction products of Ca2+-ATPase activity again appeared on the interior face of the PM. The results seemed suggesting that two kinds of Ca2+-ATPases may be present on the PM during the SD-induced dormancy in poplar. One is the Ca2+-pumping ATPase, which is located on the interior face of the PM, for maintaining and restoring the Ca2+ homeostasis. The other might be an ecto-Ca2+-ATPase, which is located on the exterior face of the PM, for the exocytosis of cell wall materials as suggested by the fact of the cell wall thickening during the dormancy development in poplar.

Calcium-Transporting ATPases↗

PubMed2000

Transformation of Arabidopsis with the codA gene for choline oxidase enhances freezing tolerance of plants.

Arabidopsis thaliana was transformed with the codA gene from Arthrobacter globiformis, which encodes choline oxidase, the enzyme that synthesizes glycinebetaine from choline. The transformation enabled the plants to accumulate glycinebetaine in chloroplasts, and significantly enhanced the freezing tolerance of plants. Furthermore, the photosynthetic machinery of transformed plants was more tolerant to freezing stress than that of wild-type plants. Exogenous application of glycinebetaine also increased the freezing tolerance of wild-type plants, suggesting that the presence of glycinebetaine in transformed plants had enhanced their ability to tolerate freezing stress. Northern blotting analysis revealed that the enhancement of freezing tolerance was not related to the expression of four cold-regulated genes. These results suggest that engineering of the biosynthesis of glycinebetaine by transformation with the codA gene might be an effective method for enhancing the freezing tolerance of plants.

Adaptation, Physiological↗

PubMed2000

Risk factors for leukoplakia and malignant transformation to oral carcinoma: a leukoplakia cohort in Taiwan.

The effects of betel nut chewing, smoking and alcohol on the occurrence of leukoplakia and its malignant transformation to oral carcinoma were quantified in a leukoplakia cohort (n = 435) from one medical centre between 1988 and 1998 in Taiwan. Sixty oral carcinomas were ascertained in this cohort. A case-control study within the leukoplakia cohort was used to study, risk factors. Using the Weibull survival model, the incidence of malignant transformation of leukoplakia was shown to increase with follow-up years. After adjustment for other relevant risk factors, betel nut chewing (adjusted odds ratio (OR) = 4.59; 95% confidence interval (CI) 1.25-16.86) remained a significant risk factor for malignant transformation. Results from the case-control study showed that the adjusted odds ratios for betel nut chewing and smoking on the occurrence of leukoplakia were 17.43 (95% CI 1.94-156.27) and 3.22 (95% CI 1.06-9.78), respectively. Similar findings were observed when daily frequency and duration were taken into account. This implies that cessation of smoking may reduce by 36% leukoplakia cases, while elimination of betel nuts may prevent 62% of leukoplakia and 26% of malignant transformation to oral carcinoma in the underlying population.

Alcohol Drinking↗

PubMed2000

Quantitative trait loci and candidate gene mapping of bud set and bud flush in populus.

The genetic control of bud phenology in hybrid poplar was studied by mapping quantitative trait loci (QTL) affecting the timing of autumn bud set and spring bud flush. The founders of the mapping pedigree were collected from widely separated latitudes to maximize segregating variation for dormancy-related traits in the F(2) generation-the female Populus trichocarpa parent is from Washington State (48 degrees N) and the male P. deltoides parent is from Texas (31 degrees N). Bud set and bud flush timing were measured on the F(2) generation in a replicated clonal field trial. Using a linkage map constructed of AFLP and microsatellite markers, three QTL controlling bud set and six QTL controlling bud flush were detected. Additionally, five candidate genes believed to be involved in perception of photoperiod (PHYB1, PHYB2) or transduction of abscisic acid response signals (ABI1B, ABI1D, and ABI3) were placed on the QTL map. PHYB2 and ABI1B were found to be coincident with QTL affecting bud set and bud flush.

Base Sequence↗

PubMed2000

A nucleoside-nucleotide mixture may reduce memory deterioration in old senescence-accelerated mice.

We investigated the effects of a mixture of dietary nucleosides and nucleotides (NS + NT) on memory in 1- and 7-mo-old senescence-accelerated mice (SAM). Memory retention was studied with passive avoidance (step-through) and active avoidance (shuttle) tests. For 14 wk, mice in the control groups were fed a 20 g of casein/100 g diet, whereas the NS + NT groups were fed this diet supplemented with a 0.5 g of NS + NT mixture/100 g. All mice were killed at wk 14, and we studied the brain histopathology. Lipofuscin, monovacuoles and multiple vacuoles of various brain regions were measured. Body weight, food intake and ambulatory activity did not differ between the control and NS + NT groups. In old mice, the time of passive avoidance was significantly higher in the NS + NT group than in the control group at d 1 and 7 (P: < 0.05). However, such an effect of NS + NT was not observed in young mice. In the active avoidance test, the incidence of successful avoidance in old mice was higher in the NS + NT group than in the control group at d 1 and 2 (P: < 0.05). The percentages of specific brain cells containing lipofuscin were lower in NS + NT groups than in the control groups in both young and old mice (P: < 0.05). The number of monovacuoles and multiple vacuoles in specific brain regions tended to be lower (P: = 0.1-0.25) in NS + NT than in control groups, with significant differences in the microvacuoles of the middle cortex of young mice and in the multiple vacuoles in the hind cortex of old mice (P: < 0. 05). These results suggest that increased dietary NS + NT may be associated with decreases in the age-induced deterioration of brain morphology and certain memory tasks.

Age Factors↗

PubMed2000

Variations of the cystic artery in Chinese adults.

The origin and course of the cystic artery related to the Calot triangle were studied in 72 autopsies. The cystic artery arises from many possible origins; the right hepatic artery is the most common origin (76.6%). The Calot triangle (hepatocystic triangle), which is an important imaginary referent area for biliary surgery, is bounded by the common hepatic duct (CHD), the cystic duct, and the cystic artery. Of all the cystic arteries, 86.1% coursed through the Calot triangle, and 100% of the cystic arteries originating from the right hepatic artery coursed through the Calot triangle. However, only 54% of the cystic arteries that originated from the left, bifurcation, proper, and common hepatic arteries ran through the triangle. None of the cystic arteries that originated from the gastroduodenal, celiac, superior mesentery, or superior pancreaticoduodenal arteries passed through the triangle. Furthermore, 72.7% of the cystic arteries that originated from the right hepatic artery ran beneath the CHD as they entered the Calot triangle; the others ran anterior to the CHD. Of the cystic arteries that arose from locations other than the right hepatic artery, 29.4% ran posterior to the CHD, and 11.8% ran anterior to the CHD. The current study provides detailed information about anatomic variance in Chinese adults that may help avoid injury during open or laparoscopic cholecystectomies.

Adult↗

PubMed2000

Estimation of sojourn time in chronic disease screening without data on interval cases.

Estimation of the sojourn time on the preclinical detectable period in disease screening or transition rates for the natural history of chronic disease usually rely on interval cases (diagnosed between screens). However, to ascertain such cases might be difficult in developing countries due to incomplete registration systems and difficulties in follow-up. To overcome this problem, we propose three Markov models to estimate parameters without using interval cases. A three-state Markov model, a five-state Markov model related to regional lymph node spread, and a five-state Markov model pertaining to tumor size are applied to data on breast cancer screening in female relatives of breast cancer cases in Taiwan. Results based on a three-state Markov model give mean sojourn time (MST) 1.90 (95% CI: 1.18-4.86) years for this high-risk group. Validation of these models on the basis of data on breast cancer screening in the age groups 50-59 and 60-69 years from the Swedish Two-County Trial shows the estimates from a three-state Markov model that does not use interval cases are very close to those from previous Markov models taking interval cancers into account. For the five-state Markov model, a reparameterized procedure using auxiliary information on clinically detected cancers is performed to estimate relevant parameters. A good fit of internal and external validation demonstrates the feasibility of using these models to estimate parameters that have previously required interval cancers. This method can be applied to other screening data in which there are no data on interval cases.

Aged↗

PubMed2000

Psychosocial and psychiatric risk factors for suicide. Case-control psychological autopsy study.

BACKGROUND: Few studies of suicide have simultaneously examined the individual and combined effects of psychosocial and psychiatric risk factors. AIMS: To do so in a representative sample of suicides. METHOD: A case-control psychological autopsy was conducted among 113 consecutive suicides and 226 living controls matched for age, gender, ethnicity and area of residence in Taiwan. RESULTS: Five major risk factors (loss event, suicidal behaviour in first-degree relatives, ICD-10 major depressive episode, emotionally unstable personality disorder and substance dependence) were found to have independent effects on suicide from multivariate conditional logistic regression analysis. CONCLUSIONS: Effective intervention and management for loss event and major depressive episode among emotionally unstable subjects with a family tendency of suicidal behaviour, frequently also comorbid with alcohol or other substance dependence, may prove to be most effective for suicide prevention in different populations.

Case-Control Studies↗

PubMed2000

Mutagenesis and expression of the E3-19k lumenal domain of adenovirus type 2.

CD8+ T cells recognize viral or tumor antigens of 8-10 residues derived from cytosolic proteins that are bound to the class I molecules of the major histocompatibility complex (MHC). To escape this immune surveillance, adenovirus expresses a protein, E3-19k, that specifically down-regulates the cell surface expression of class I MHC molecules on infected cells. To most effectively manipulate the T-cell response to virus-infected cells, it is essential to understand the mechanism by which viruses, such as adenoviruses, down-regulate the class I MHC function. We have subcloned the lumenal domain of adenovirus E3-19k protein in order to characterize its interactions with the class I MHC molecules. Several point mutations have also been generated on the E3-19k lumenal domain with either the first 96 or 108 amino acids. Attempts to crystallize the complexes between E3-19k and class I MHC molecule had been initiated.

Adenovirus E3 Proteins↗

PubMed2000

Reoperative coronary artery bypass grafting without cardiopulmonary bypass.

Conventional reoperative coronary artery bypass grafting (CABG) is associated with increased surgical risk. The use of less invasive methods to perform myocardial revascularization may, therefore, be more suitable, especially for high-risk patients. In June 1999, we performed three reoperative CABG surgeries, without the use of cardiopulmonary bypass, through unilateral or bilateral thoracotomy. One patient had single-vessel disease and the other two had multiple-vessel disease. All three patients had uneventful postoperative recovery. During early postoperative follow-up, all three patients were angina-free and were in New York Heart Association functional class I. The results of these three cases suggest that minimally invasive reoperative CABG may reduce morbidity compared with conventional reoperative CABG.

Aged↗