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Biomedical subjects

C H Chen

Publications and source records attributed to C H Chen.

At least 217 records · Page 12Linked to original sources
PubMed1999

Characterization of the binding and phosphorylation of cardiac calsequestrin by epsilon protein kinase C.

In this study, we report the cloning of the rat cardiac isoform of calsequestrin on the basis of its interaction with an epsilonprotein kinase C-unique sequence (epsilonV1) derived form the epsilonprotein kinase C regulatory domain. Calsequestrin binds activated epsilonprotein kinase C holoenzyme better than the inactive enzyme and nearly three times better than other protein kinase C isozymes. The interaction between epsilonprotein kinase C and calsequestrin is mediated by sequences in both the regulatory and kinase domains of the epsilonprotein kinase C. Finally, we show that calsequestrin is an epsilonprotein kinase C substrate in vitro and protein kinase C phosphorylation of calsequestrin leads to a decreased binding of epsilonprotein kinase C to calsequestrin.

Amino Acid Sequence↗
PubMed1999

Chemical cleavage sequencing of DNA using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

In this paper, we report for the first time use of laser desorption mass spectrometry for measurement of chemical cleavage sequencing products of DNA. In this method, the target DNA was labeled with biotin and subjected to chemical modification and cleavage according to the Maxam-Gilbert sequencing protocol. The biotin-containing fragments were captured by streptavidin-coated magnetic beads and separated from the other fragments. The captured fragments were released by hot ammonia treatment, and the released fragments were analyzed by mass spectrometry. Potential applications of this method in resolving sequence ambiguities and sequencing repeat sequences as well as in the analysis of DNA-protein interactions are discussed.

Amino Acid Sequence↗
PubMed1999

Process control procedures to augment quality control of leukocyte-reduced red cell blood products.

Quality control of leukocyte-reduced packed red cell units (LRprc) produced in blood facilities must conform to regulatory criteria, which state that units may not contain more than 1 x 10(6) to 5 x 10(6) white blood cells (WBC) per unit. The post-filtration WBC content of a total of n = 386 LRprc units was counted with a Nageotte chamber to model the probability that a unit would not meet the regulatory criteria. The distribution of the residual leukocyte counts is close to a negative binomial distribution (NBD) and is independent of the packed red cell volume filtered. The observed probability that a unit of blood has a residual WBC greater than 5 x 10(6) is 2.6 +/- 2.6 x 10(-3). A power analysis of the two-sample Kolmogorov-Smirnov (KS) test in this application shows that a sample size of 20 is sufficient for determining that the process is in control when an out of control process has a k NBD parameter greater than or equal to that of the in control process. The three out of control processes observed to date appear to have this property. A sample of size 80 may be necessary for confirming that process validation data sets conform to the larger 'reference' database (n = 386) for processes that are out of control in such a way that their k NBD parameter is less than the k parameter of the in control process.

Blood Component Removal↗
PubMed1999

Snt309p modulates interactions of Prp19p with its associated components to stabilize the Prp19p-associated complex essential for pre-mRNA splicing.

The SNT309 gene was identified via a mutation that causes lethality of cells in combination with a prp19 mutation. We showed previously that Snt309p is a component of the Prp19p-associated complex and that Snt309p, like Prp19p, is associated with the spliceosome immediately after or concomitantly with dissociation of U4 from the spliceosome. We show here that extracts prepared from the SNT309-deleted strain (DeltaSNT309) were defective in splicing but could be complemented by addition of the purified Prp19p-associated complex. Isolation of the Prp19p-associated complex from DeltaSNT309 extracts indicated that the complex was destabilized in the absence of Snt309p and dissociated on affinity chromatography, suggesting a role of Snt309p in stabilization of the Prp19p-associated complex. Addition of the affinity-purified Prp19p-Snt309p binary complex to DeltaSNT309 extracts could reconstitute the Prp19p-associated complex. Genetic analysis further suggests that Snt309p plays a role in modulating interactions of Prp19p with other associated components to facilitate formation of the Prp19p-associated complex. A model for how Snt309p modulates such interactions is proposed.

Cell Division↗
PubMed1999

Conformational alteration in serum albumin as a carrier for pyridoxal phosphate: a distinction from pyridoxal phosphate-dependent glutamate decarboxylase.

The conformation of bovine serum albumin (BSA), a pyridoxal phosphate (pyridoxal-P) carrier, was investigated by using uv/visible spectrophotometry, fluorescence spectroscopy, circular dichroism, and differential scanning microcalorimetry. Upon interacting with pyridoxal-P, the uv/visible absorption spectrum of BSA exhibits peaks at 330 and 392 nm due to the formation of a Schiff base. Pyridoxal-P quenches the fluorescence emission intensity (excited at 295 or 280 nm) by 24% and enhances fluorescence steady-state polarization of BSA by 20%. These observations suggest a conformational change in BSA when it interacts with pyridoxal-P. However, this conformational change appears to be small since circular dichroism showed only a 2-4% decrease in the alpha-helical content of BSA and no change in the beta-sheet content, and differential scanning microcalorimetry yielded only a 10% change in the enthalpy of thermal unfolding of BSA. 2-Aminoethylisothiouronium bromide, an antioxidant, causes no effect on either uv/visible absorption spectrum or fluorescence emission intensity of BSA, suggesting that BSA lacks sensitive sulfhydryl groups. To help in understanding BSA as a carrier for pyridoxal-P, the results were compared with those for glutamate decarboxylase (GAD), a pyridoxal-P-dependent protein, which requires pyridoxal-P as the cofactor for activity. Although BSA and GAD exhibit comparable molecular weights (66430 versus 65300), numbers of amino acid residues (582 versus 585), and binding affinity (>10(6) M-1), distinct conformational alterations occur between the two proteins upon interacting with pyridoxal-P: a small conformational change for BSA versus a large conformational change for GAD. In contrast to the case of BSA, AET causes significant effects on both the uv/visible spectrum and fluorescence emission intensity of GAD, because GAD contains sensitive sulfhydryl groups. Factors such as disulfide bond and active site sequence were discussed to understand BAS as a carrier for pyridoxal-P and a pyridoxal-P-independent protein.

Amino Acid Sequence↗
PubMed1999

Cef1p is a component of the Prp19p-associated complex and essential for pre-mRNA splicing.

The Prp19p protein of the budding yeast Saccharomyces cerevisiae is an essential splicing factor and is associated with the spliceosome during the splicing reaction. We have previously shown that Prp19p is not tightly associated with small nuclear ribonucleoprotein particles but is associated with a protein complex consisting of at least eight protein components. By sequencing components of the affinity-purified complex, we have identified Cef1p as a component of the Prp19p-associated complex, Ntc85p. Cef1p could directly interact with Prp19p and was required for pre-mRNA splicing both in vivo and in vitro. The c-Myb DNA binding motif at the amino terminus of Cef1p was required for cellular growth but not for interaction of Cef1p with Prp19p or Cef1p self-interaction. We have identified a small region of 30 amino acid residues near the carboxyl terminus required for both cell viability and protein-protein interactions. Cef1p was associated with the spliceosome in the same manner as Prp19p, i.e. concomitant with or immediately after dissociation of U4. The anti-Cef1p antibody inhibited binding to the spliceosome of Cef1p, Prp19p, and at least three other components of the Prp19p-associated complex, suggesting that the Prp19p-associated complex is likely associated with the spliceosome and functions as an integral complex.

Amino Acid Sequence↗
PubMed1999

Plasma carotenoids, glutathione S-transferase M1 and T1 genetic polymorphisms, and risk of hepatocellular carcinoma: independent and interactive effects.

This study was conducted to assess the role of carotenoid and glutathione S-transferase (GST) M1 and T1 genetic polymorphisms in the development of hepatocellular carcinoma (HCC). A total of 84 incident cases of HCC and 375 matched controls selected from a cohort of 7,342 men (4,841 chronic hepatitis B carriers and 2,501 noncarriers) who were recruited between 1988 and 1992 in Taiwan were studied. Neither GST M1/T1 polymorphisms nor plasma levels of various carotenoids were independently associated with HCC, but they modulated smoking- and/or drinking-related HCC risk. Cumulative exposure to tobacco smoke significantly increased HCC risk in a dose-dependent manner among subjects with low plasma beta-carotene levels (p for trend = 0.047) but not among those with high levels. A statistically significant effect of habitual alcohol drinking on HCC risk was observed only for those with low plasma levels of beta-carotene, alpha-carotene, or lycopene and for GST M1 null subjects. There was evidence suggesting an interaction between the GST M1/T1 genotype and certain carotenoids in HCC associated with smoking and drinking. The strongest effect of smoking and drinking was noted among GST M1 null subjects with low plasma levels of beta-carotene (smoking: adjusted odds ratio (OR) = 3.54, 95% confidence interval (CI) 1.06-11.83; drinking: OR = 8.28, 95% CI 2.40-28.61).

Adult↗
PubMed1999

Improved left ventricular mechanics from acute VDD pacing in patients with dilated cardiomyopathy and ventricular conduction delay.

BACKGROUND: Ventricular pacing can improve hemodynamics in heart failure patients, but direct effects on left ventricular (LV) function from varying pacing site and atrioventricular (AV) delay remain unknown. We hypothesized that the magnitude and location of basal intraventricular conduction delay critically influences pacing responses and that single-site pacing in the delay-activated region yields similar or better responses to biventricular pacing. METHODS AND RESULTS: Aortic and LV pressures were measured in 18 heart failure patients (mean+/-SD: LV ejection fraction, 19+/-7%; LV end-diastolic pressure, 25+/-8 mm Hg; QRS duration, 157+/-36 ms). Data under normal sinus rhythm were compared with ventricular pacing (VDD) at varying sites and AV delays (randomized order). Right ventricular (RV) apical or midseptal pacing had negligible contractile/systolic effects. However, LV free-wall pacing raised dP/dtmax by 23.7+/-19.0% and pulse-pressure by 18.0+/-18.4% (P<0.01). Biventricular pacing yielded less change (+12.8+/-9.3% in dP/dtmax, P<0.05 versus LV). Pressure-volume analysis performed in 11 patients consistently revealed minimal changes with RV pacing but increased stroke work and lower end-systolic volumes with LV pacing. Optimal AV intervals averaged 125+/-49 ms, and within this range, AV delay had less influence on LV function than pacing site. Basal QRS duration positively correlated with %DeltadP/dtmax (P<0.005), but pacing efficacy was not associated with QRS narrowing. Conduction delay pattern generally predicted pacing sites with most effect. CONCLUSIONS: VDD pacing acutely enhances contractile function in heart failure patients with intraventricular conduction delay. Single-site pacing at the site of greatest delay achieves similar or greater benefits to biventricular pacing in such patients. These data clarify pacing-effect mechanisms and should help in candidate identification for future studies.

Adult↗
PubMed1999

Efficacy of media enriched with nonlactate-generating substrate for organ preservation: in vitro and clinical studies using the cornea model.

BACKGROUND: Using a rabbit cornea model, our recent study demonstrated that Chen Medium (CM), an isotonic media enriched with nonlactate-generating high-energy substrates, is very effective for organ preservation. In the present study, the efficacy of CM is further evaluated with human corneas METHODS: The effectiveness of CM and Optisol for preserving the endothelial integrity of human corneas in vitro was evaluated by scanning electron microscopy. Clinical efficacy was evaluated in a total of 83 patients: 10 patients with keratoconus grafted randomly with either CM- or Optisol-stored cornea of the same donor, and 73 patients with various conditions grafted with CM-stored corneas. After surgery, visual acuity and quality of the graft were monitored for up to 4.6 years. RESULTS: The scanning electron microscopic study revealed that after 11-day storage at 4 degrees C, the CM-stored cornea had only marginal disruptive changes, 9.4+/-1.1%, in endothelial cells, as opposed to 42.4+/-4.6% of the Optisol-stored cornea. All 78 CM-stored corneas, including 67 with 12.2- to 17.7-hr death-to-storage time, 3-7.6 days of storage time, and initial marginal quality before storage, were successfully transplanted. These grafts were thin and clear, with an excellent epithelial integrity and without significant changes in endothelial cell density. Five Optisol-stored corneas were also successfully grafted; one of them, however, was edematous for about 4 weeks, and all the grafts were slightly thicker with substantial endothelial cell loss. CONCLUSION: Using a cornea model, present and recent studies show that CM is very effective for preserving tissue viability and endothelial integrity. Previous study revealed that CM-stored tissues maintained high levels of ATP and metabolic function, with suppression of lactate formation and accumulation. Thus, these findings support the concept that preservation of tissue viability is closely associated with the ability of the tissues to retain metabolic activity, to generate ATP efficiently, and to prevent acidosis effectively during storage.

Adenosine↗
PubMed1999

Correlation of fasting serum C-peptide and insulin with markers of metabolic syndrome-X in a homogenous Chinese population with normal glucose tolerance.

We surveyed 1447 men and 1800 women aged 30 years (mean 46.7 years) with normal glucose tolerance in Kin-Chen, Kinmen. Correlations of fasting serum insulin and C-peptide with various clinical and biochemical parameters were analyzed by multiple linear regression analysis. Women had significantly higher levels of insulin than men (98+/-43 vs. 91+/-43 pM, p<0.0001), yet they also had a more favorable cardiovascular risk profile. Insulin was positively associated with the female sex, height, body mass index, waist-to-hip ratio, serum triglyceride, total cholesterol, uric acid, and fasting plasma glucose, and was negatively associated with age, smoking, and high-density lipoprotein cholesterol. Independent correlates for C-peptide were similar to those of insulin, except for the addition of mean blood pressure and the exclusion of age and total cholesterol. Significant interaction of sex-body mass index (coefficient = -0.0051, p = 0.0232) was detected for C-peptide only. In conclusion, both fasting serum insulin and C-peptide are quantitatively associated with cardiovascular risk factors in this homogeneous Chinese population with normal glucose tolerance. The female sex is independently associated with higher insulin and C-peptide levels, and the strength of the positive association between the female sex and C-peptide reduces when the body mass index increases.

Adult↗
PubMed1999

Obesity induces expression of uncoupling protein-2 in hepatocytes and promotes liver ATP depletion.

Uncoupling protein 2 (UCP2) uncouples respiration from oxidative phosphorylation and may contribute to obesity through effects on energy metabolism. Because basal metabolic rate is decreased in obesity, UCP2 expression is predicted to be reduced. Paradoxically, hepatic expression of UCP2 mRNA is increased in genetically obese (ob/ob) mice. In situ hybridization and immunohistochemical analysis of ob/ob livers demonstrate that UCP2 mRNA and protein expression are increased in hepatocytes, which do not express UCP2 in lean mice. Mitochondria isolated from ob/ob livers exhibit an increased rate of H+ leak which partially dissipates the mitochondrial membrane potential when the rate of electron transport is suppressed. In addition, hepatic ATP stores are reduced and these livers are more vulnerable to necrosis after transient hepatic ischemia. Hence, hepatocytes adapt to obesity by up-regulating UCP2. However, because this decreases the efficiency of energy trapping, the cells become vulnerable to ATP depletion when energy needs increase acutely.

Adenosine Triphosphate↗
PubMed1999

Bilateral cortical representation of the intrinsic lingual muscles.

Motor potentials of the intrinsic lingual muscles were recorded by surface electrode in a patient with left hypoglossal neuropathy. Electrical stimulation of the right hypoglossal nerve had contralateral lingual muscle potentials representing the crosstalk volume conducted electromyography signals. Magnetic stimulation of either cerebral hemisphere yielded motor responses on the right half of the tongue with more contribution from the crossed corticobulbar fibers. Follow-up studies showed an improvement of dysphagia and left lingual motor potentials.

Electric Stimulation↗
PubMed1999

Peroxisome proliferation, adipocyte determination and differentiation of C3H10T1/2 fibroblast cells induced by humic acid: induction of PPAR in diverse cells.

Humic acid, a high-molecular-weight polyphenolic compound, exists abundantly in soil, natural water, and various terrestrial and aquatic environments. Humic acid causes peroxisome proliferation in mouse liver and induces the expression of peroxisome proliferator activated receptor (PPAR) in BNL CL.2 cells. Both cytotoxicity and flow cytometry show that humic acid inhibits the growth of C3H10T1/2 cells at G1 phase. C3H10T1/2 fibroblast cells express PPARgamma and the adipocyte P2 (aP2) genes which convert into adipocytes after being treated with humic acid. Our findings may provide a unique model for studying the molecular control of determination and differentiation of mesodermal cell lineages.

Adipocytes↗
PubMed1999

Comparison of empirical strategies to maximize GENEHUNTER lod scores.

We compare four strategies for finding the settings of genetic parameters that maximize the lod scores reported in GENEHUNTER 1.2. The four strategies are iterated complete factorial designs, iterated orthogonal Latin hypercubes, evolutionary operation, and numerical optimization. The genetic parameters that are set are the phenocopy rate, penetrance, and disease allele frequency; both recessive and dominant models are considered. We selected the optimization of a recessive model on the Collaborative Study on the Genetics of Alcoholism (COGA) data of chromosome 1 for complete analysis. Convergence to a setting producing a local maximum required the evaluation of over 100 settings (for a time budget of 800 minutes on a Pentium II 300 MHz PC). Two notable local maxima were detected, suggesting the need for a more extensive search before claiming that a global maximum had been found. The orthogonal Latin hypercube design was the best strategy for finding areas that produced high lod scores with small numbers of evaluations. Numerical optimization starting from a region producing high lod scores was the strategy that found the highest maximum observed.

Alcoholism↗
PubMed1999

Mitochondrial proteins that regulate apoptosis and necrosis are induced in mouse fatty liver.

Fatty liver is common in nonalcoholic, obese individuals and in lean people who consume alcohol chronically. Although fatty liver is typically benign, a subset of individuals with steatosis develop steatohepatitis and eventually cirrhosis. The disparate outcomes of fatty liver suggest that it reflects a generally beneficial, adaptive response to obesity or alcohol-related stress, but may also increase hepatocyte vulnerability to other challenges. Thus, both protective factors (e.g., Bcl-2 and Bcl-xL) and factors that promote hepatocyte death by apoptosis (e.g., Bax) or necrosis (e.g., UCP2) may be increased in fatty livers. To evaluate this possibility, hepatocyte apoptosis, necrosis, and the expression of factors that regulate cellular viability were assessed in two models of fatty liver (i.e., genetically obese [ob/ob] mice and ethanol [EtOH]-fed lean mice). Findings in mice with fatty livers were compared with lean, control mice that did not have hepatic steatosis. Immunohistochemistry showed striking induction of hepatocyte proteins that promote (e.g., Bax) and inhibit (e.g., Bcl-2 and Bcl-xL) apoptosis in both groups with fatty liver. Both models of fatty liver also increased hepatic transcripts for UCP2, a mitochondrial uncoupling protein, and the protein itself was induced in ob/ob hepatocytes. Despite the up-regulation of factors that threaten cell viability, hepatocyte death was not increased in either ob/ob or EtOH-fed mice, confirming that the liver's protective responses were sufficient under the conditions studied. However, if UCP2 induction reduces the efficiency of adenosine triphosphate (ATP) synthesis, this initially harmless response might enhance the vulnerability of hepatocytes to necrosis.

Animals↗
PubMed1999

Effect of transcutaneous electrical nerve stimulation for pain relief on patients undergoing hemorrhoidectomy: prospective, randomized, controlled trial.

PURPOSE: Posthemorrhoidectomy pain control remains a challenging problem. Transcutaneous electrical nerve stimulation is known to be effective in the treatment of many diseases. Our aim was to investigate the effect of transcutaneous electrical nerve stimulation on pain relief in patients undergoing hemorrhoidectomy. METHODS: Sixty patients with symptomatic hemorrhoids were randomly allocated into two groups, the acupoint group (n = 30) and the nonpoint control group (n = 30). Transcutaneous electrical nerve stimulation was applied to those patients who received hemorrhoidectomy, and patient-controlled analgesia was achieved by injection of morphine through ambulatory infusion pumps. The dependent measures in this study were pain score from 0 (no pain) to 10 (agonizing pain), analgesic doses administrated through patient-controlled analgesia, and postoperative complications. RESULTS: The subjective pain scores evaluated 8, 12, 16, and 24 hours after hemorrhoidectomy in the control group and the acupoint group were 5.9 +/- 0.5 and 4.1 +/- 0.5, 5.7 +/- 0.5 and 3.5 +/- 0.4, 4.1 +/- 0.4 and 2.3 +/- 0.3, and 3.2 +/- 0.4 and 1.9 +/- 0.2, respectively (two-way analysis of variance; P < 0.05). There was a significant difference between treatment groups in morphine use, with 11.6 +/- 2.2 mg in the control group and 6.2 +/- 1.3 mg in the acupoint group (P < 0.05). The acupoint group tended to have less postoperative acute urinary retention (Fisher's exact probability test; P = 0.145) and less need for analgesics than the control group (P = 0.112, Fisher's exact test). CONCLUSION: Transcutaneous electrical nerve stimulation is effective for pain relief in patients receiving hemorrhoidectomy. Its efficacy and safety could assist outpatient pain management after hemorrhoidectomy.

Analgesia, Patient-Controlled↗
PubMed1999

Arthroscopic posterior cruciate ligament reconstruction with quadriceps tendon-patellar bone autograft.

Surgical reconstruction of the posterior cruciate ligament (PCL) is indicated in the PCL-deficient knee with symptomatic instability and multiple ligamentous injury. However, the choice of graft tissues continues to be controversial. We describe an arthroscopic PCL reconstruction technique using the quadriceps tendon-patellar bone autograft. From March through September 1996, this autograft was used in 12 patients with PCL injuries. After 1-1.5 years' follow-up, the clinical outcome has been encouraging. In addition, the quadriceps tendon-patellar autograft has the advantage of being self-available. Furthermore, the technique is easy to perform and has comparable anatomic and biomechanical qualities to other available techniques. Quadriceps tendon-patellar autograft is a reasonable alternative choice for PCL reconstruction.

Adult↗