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C H Chen

Publications and source records attributed to C H Chen.

At least 73 records · Page 4Linked to original sources
PubMed2001

Solid-state structures of group 1 and group 2 metal 1,5-naphthalenedisulfonates: systematic investigation of lamellar three-dimensional networks constructed by metal arenedisulfonate.

Seven Group 1 and Group 2 1,5-naphthalenedisulfonates (1,5-nds) have been synthesized and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy and thermal gravimetric analysis. For Group 1 metal complexes, with M = Li(+) (1), Na(+) (2) and K(+) (3), all crystallize in the same space group (P2(1)/c) with the same composition, [M(2)(1,5-nds)(H(2)O)(2)]. They adopt similar three-dimensional packing arrangements with the metal-sulfonate inorganic layers pillared by naphthalene rings. However, the coordination behavior of three metal cations toward the SO(3)(-) group and water molecule are different, resulting in different architectures for the inorganic portion. For Group 2 complexes with M = Mg(2+) (4), Ca(2+) (5), Sr(2+) (6) and Ba(2+) (7), Mg(2+) shows no direct coordination by the SO(3)(-) group while Ca(2+) is coordinated by four SO(3)(-) groups and a two-dimensional network is formed. Complexes (6) and (7) are isostructural, adopting the same three-dimensional, inorganic-organic pillared framework as seen for (1)-(3). The coordination behavior of the metal cations in these structures neatly illustrates the increase in coordination strength with decreasing charge/radius ratio for Group 1 and Group 2 metal cations with large organic anions.

Journal Article↗
PubMed2001

Inhibition of plant vacuolar H(+)-ATPase by diethylpyrocarbonate.

Treatment of the tonoplast H(+)-ATPase from mung bean seedlings (Vigna radiata L.) with histidine-specific modifier, diethyl pyrocarbonate (DEP), caused a marked loss of the ATP hydrolysis activity and the proton translocation in a concentration-dependent manner. The reaction order of inhibition was calculated to be 0.98, suggesting that at least one histidine residue of vacuolar H(+)-ATPase was modified by DEP. The absorbance of the vacuolar H(+)-ATPase at 240 nm was progressively increased after incubation with DEP, suggesting that N-carbethoxyhistidine had been formed. Hydroxylamine, which could break N-carbethoxyhistidine, reversed the absorbance change and partially restored the enzymic activity. The pK(a) of modified residues of vacuolar H(+)-ATPase was kinetically determined to be 6.73, a value close to that of histidine. Thus, it is assuredly concluded that histidine residues of the vacuolar H(+)-ATPase were modified by DEP. Kinetic analysis showed that V(max) but not K(m) of vacuolar H(+)-ATPase was decreased by DEP. This result is interpreted as that the residual activity after DEP inhibition was primarily due to the unmodified enzyme molecules. Moreover, simultaneous presence of DEP and DCCD (N,N'-dicyclohexyl-carbodiimide), an inhibitor modified at proteolipid subunit of vacuolar H(+)-ATPase, did not induce synergistic inhibition, indicating their independent effects. The stoichiometry studies further demonstrate that only one out of four histidine residues modified was involved in the inhibition of vacuolar H(+)-ATPase by DEP. Mg(2+)-ATP, the physiological substrate of vacuolar H(+)-ATPase, but not its analogs, exerted preferentially partial protection against DEP, indicating that the histidine residue involved in the inhibition of enzymatic activity may locate at/or near the active site and directly participate in the binding of the substrate.

Adenosine Triphosphate↗
PubMed2001

Deletion mapping of chromosome 16q24 in hepatocellular carcinoma in Taiwan and mutational analysis of the 17-beta-HSD gene localized to the region.

Human chromosome band 16q24 commonly undergoes loss of heterozygosity (LOH) in human hepatocellular carcinoma (HCC). To further localize the region of deletion on 16q24 and to evaluate the genetic role of 17-beta-HSD, which is near 16q24, in HCC, we examined the pattern of loss of heterozygosity in 88 HCC patients. DNAs from 88 pairs of HCCs and corresponding non-tumor parts were prepared. Loss of heterozygosity on chromosomes 16q24 was investigated by 11 sets of microsatellite markers. Mutation analysis of type II 17-beta-HSD was performed by automatic sequencing. LOH on 16q24 for at least 1 locus was found in 43 of the 88 tumor DNAs (49%). Three non-overlapping regions of frequent LOH were defined in these 43 tumors with partial deletions. The first region was between D16S516 loci and D16S507, encompassed by a 1-cM region, defined by the D16S504. The second region was defined by the 17HSDB2 locus between D16S505 and D16S422, encompassed approximately by a 1-cM region. The third region was between D16S520 and D16S413, defined by D16S3048, encompassed approximately by a 4-cM region. Homozygous deletions of any exons in 17HSDB2 gene were identified in 7 of 27 cases (26%). Automated sequencing analysis of 17HSDB2 failed to demonstrate mutations in any of these specimens. Our data suggest that the 17HSDB2 locus is a frequent target of deletion in HCC but the inactivation of 17HSDB2 may not involve sequence mutations. Furthermore, the presence of the other 2 frequent LOH regions suggest that the putative tumor suppressor genes at these locations might be involved in the development of HCC.

17-Hydroxysteroid Dehydrogenases↗
PubMed2001

Affinity chromatography of proteins on non-porous copolymerized particles of styrene, methyl methacrylate and glycidyl methacrylate.

Non-porous particles having an average diameter of 2.1 microm were prepared by co-polymerization of styrene, methyl methacrylate and glycidyl methacrylate, which was abbreviated as P(S-MMA-GMA). The particles were mechanically stable due to the presence of benzene rings in the backbone of polymer chains, and could withstand high pressures when a column packed with these particles was operated in the HPLC mode. The polymer particles were advantaged by immobilization of ligands via the epoxy groups on the particle surface that were introduced by one of the monomers, glycidyl methacrylate. As a model system, Cibacron Blue 3G-A was covalently immobilized onto the non-porous copolymer beads. The dye-immobilized P(S-MMA-GMA) particles were slurry packed into a 1.0 cm x 0.46 cm I.D. column. This affinity column was effective for the separation of turkey egg white lysozyme from a protein mixture. The bound lysozyme could be eluted to yield a sharp peak by using a phosphate buffer containing 1 M NaCl. For a sample containing up to 8 microg of lysozyme, the retained portion of proteins could be completely eluted without any slit peak. Due to the use of a shorter column, the analysis time was shorter in comparison with other affinity systems reported in the literature. The retention time could be reduced significantly by increasing the flow-rate, while the capacity factor remained at the same level.

Chromatography, Affinity↗
PubMed2001

Disrupting the transforming activity of shrimp ras(Q(61)K) by deleting the CAAX box at the C-terminus.

BALB/3T3 cells were transformed by transfection with DNA encoding the mutated ras(Q(61)K) from shrimp Penaeus japonicus. Ras transcription and protein levels had increased significantly in the cells transfected with the S-ras plasmid, compared to cells transfected with a control plasmid pcDNA3.1. The bacterially expressed GTP-locked S-Ras(Q(61)K) is successfully prenylated by rat protein geranylgeranyltransferase I (PGGTase I) and then polymerized with tubulin, in agreement with findings for GTP-locked mammalian K(B)-Ras(Q(61)K) in vitro. Shrimp protein farnesyltransferase (PFTase) of shrimp did not prenylate the GTP-locked shrimp S-Ras(Q(61)K) (Lin and Chuang. 1998. J Exp Zool 281:565-573), whereas rat PFTase efficiently catalyzed the farnesylation of GTP-locked S-Ras(Q(61)K). To investigate the effect of geranylgeranylation on cellular transformation, we generated S-ras(Q(61)K) mutants with deletion of the CAAX box [S-ras(Q(61)K)(-caax)] or replacement of the CAAX box [S-ras(Q(61)K)(Kcaax)] or replacement of the arginine-rich domain [S-ras(Q(61)K)(K-Lys)] with corresponding sequences from rat K(B)-ras(Q(61)K). BALB/3T3 cells transfected with DNA encoding S-ras(Q(61)K), S-ras(Q(61)K)(KCAAX), S-ras(Q(61)K)(K-Lys) were transformed successfully, but S-ras(Q(61)K)(-CAAX) was defective in its ability to transform. Thus, prenylation at CAAX is required for transformation. Either the geranylgeranylated or the farnesylated S-Ras(Q(61)K) was endowed with abilities to transform. The arginine-rich region in S-Ras or the lysine-rich clusters from the rat K(B)-Ras appear not essential for activity to transform.

3T3 Cells↗
PubMed2001

MALDI-TOF mass spectrometric method for detection of hybridized DNA oligomers.

Two new approaches for nucleic acid hybridizations by MALDI-TOF mass spectrometry are described. Hybridization using genomic DNA without polymerase chain reaction was demonstrated. Total genomic DNA of bacteriophages bound to charge-modified nylon membranes was identified by the hybridization of species-specific oligonucleotide probes. lambda-Phage DNA and M13 were used for the test with good success. Since MALDI-TOF mass spectrometry can be used to measure the molecular weights of different probes, mass spectrometry can be used for the detection of hybridizations with multiple probes. We demonstrate that multiple-probe hybridization can be resolved by mass spectrometry. Six probes with different mass tag were used for hybridization on a single spot. MALDI-TOF mass spectrometry was successfully used to measure these probes simultaneously. This provides a simple nonradioactive method for multiplex hybridization analysis. It has the potential to drastically increase the speed for microarray hybridization analysis in the future.

Bacteriophage M13↗
PubMed2001

Adenylate cyclase in prothoracic glands during the last larval instar of the silkworm, Bombyx mori.

We have previously reported that the absence of prothoracicotropic hormone (PTTH) signal transduction during the early last larval instar of Bombyx mori plays a role in leading to very low ecdysteroid levels in the hemolymph, inactivation of the corpora allata, as well as larval-pupal transformation. In the present study, adenylate cyclase was characterized in crude preparations of prothoracic gland cell membranes in an effort to localize the cause of refractoriness to PTTH. It was found that cyclase activity of the prothoracic glands from the day 6 last instar showed activation responses to fluoride, a guanine nucleotide analogue, as well as calmodulin (CaM) in dose-dependent fashions. The additive effects of day 5 prothoracic gland adenylate cyclase stimulation by fluoride and CaM imply that there may exist Gs protein-dependent and CaM-dependent forms of adenylate cyclase. For day 1 last instar prothoracic glands, which showed no response to stimulation by PTTH in either cAMP generation or ecdysteroidogenesis, adenylate cyclase activity exhibited far less responsiveness to Ca(2+)/CaM than did that from day 5 glands. These findings suggest that day 1 prothoracic glands may possess some lesions in the receptor-Ca(2+) influx-adenylate cyclase signal transduction pathway and these impairments in PTTH signal transduction may be, at least in part, responsible for decreased ecdysteroidogenesis.

Adenylyl Cyclases↗
PubMed2001

Systematic search for mutations in the human tissue inhibitor of metalloproteinases-3 (TIMP-3) gene on chromosome 22 and association study with schizophrenia.

Several linkage studies have suggested that chromosome 22q12-q13 is a putative region for schizophrenic genes. In this study, the human tissue inhibitor of metalloproteinase-3 (TIMP-3) gene was investigated as positional candidate gene for schizophrenia because of its regulatory function on extracellular matrix proteins, cell adhesion molecules, and neural cell adhesion molecules in the brain. We systematically searched for the nucleotide variants by sequencing all the exons and their flanking intronic sequences in a sample of Chinese schizophrenic patients from Taiwan. Two silent mutations in the exon 3 were identified: c.249T-->C at codon 83 (His) and c.261C-->T at codon 87 (Ser). However, no mutations causing amino acid alteration or aberrant splicing of transcripts were observed. Hence, it is unlikely that the TIMP-3 gene itself may play an important role in the genetic susceptibility to schizophrenia. Further case control association study revealed a significant difference of genotype distribution of the c.249T-->C between schizophrenic patients and control. This finding supports that 22q12 is a schizophrenia susceptible region, and it is likely that there might be other genetic mutations in the neighborhood of the TIMP-3 gene locus that may contribute to the susceptibility of schizophrenia.

Adult↗
PubMed2001

Catalytic growth and characterization of gallium nitride nanowires.

The preparation of high-purity and -quality gallium nitride nanowires is accomplished by a catalytic growth using gallium and ammonium. A series of catalysts and different reaction parameters were applied to systematically optimize and control the vapor-liquid-solid (VLS) growth of the nanowires. The resulting nanowires show predominantly wurtzite phase; they were up to several micrometers in length, typically with diameters of 10-50 nm. A minimum nanowire diameter of 6 nm has been achieved. Temperature dependence of photoluminescence spectra of the nanowires revealed that the emission mainly comes from wurtzite GaN with little contribution from the cubic phase. Moreover, the thermal quenching of photoluminescence was much reduced in the GaN nanowires. The Raman spectra showed five first-order phonon modes. The frequencies of these peaks were close to those of the bulk GaN, but the modes were significantly broadened, which is indicative of the phonon confinement effects associated with the nanoscale dimensions of the system. Additional Raman modes, not observed in the bulk GaN, were found in the nanowires. The field emission study showing notable emission current with low turn-on field suggests potential of the GaN nanowires in field emission applications. This work opens a wide route toward detailed studies of the fundamental properties and potential applications of semiconductor nanowires.

Journal Article↗
PubMed2001

Expressions of cancer-testis antigens in human hepatocellular carcinomas.

Though regular sonographic examination can early detect small hepatocellular carcinoma, the therapeutic results remains unsatisfactory. Antigen-specific immunotherapy is an alternative approach for controlling tumors. The prerequisite for antigen-specific cancer immunotherapy is the identification of appropriate tumor antigens. Recently, a new category of tumor-specific shared antigens, called cancer-testis antigens, has been identified. The cancer-testis antigens have been found in a variety of cancers. However, the expression of cancer-testis antigens in human hepatocellular carcinomas is unknown. The aim of this current study is to investigate the expression of cancer-testis antigens in human hepatocellular carcinomas. Reverse-transcription polymerase chain reaction (RT-PCR) was used to investigate the expression of the SSX-1,-2,-4,-5, SCP-1, NY-ESO-1 genes in tumorous and corresponding non-tumorous liver tissues. In the 30 hepatocellular carcinomas studied, SSX-1,-2,-4,-5, SCP-1, and NY-ESO-1 mRNA expressions were detected in 24 (80%), 14 (46.7%), 22 (73.3%), 10 (33.3%), 2 (6.7%), and 11 (36.7%), respectively. Expressions of these genes were detected in few non-tumor liver tissues. The cancer-testis antigens are expressed in a high percentage of hepatocellular carcinomas. These cancer-testis antigen gene products are potential targets for antigen-specific immunotherapy of hepatocellular carcinoma.

Adult↗
PubMed2001

Patients with Alzheimer's disease have reduced activities in midlife compared with healthy control-group members.

The development of Alzheimer's disease (AD) later in life may be reflective of environmental factors operating over the course of a lifetime. Educational and occupational attainments have been found to be protective against the development of the disease but participation in activities has received little attention. In a case-control study, we collected questionnaire data about 26 nonoccupational activities from ages 20 to 60. Participants included 193 people with probable or possible AD and 358 healthy control-group members. Activity patterns for intellectual, passive, and physical activities were classified by using an adaptation of a published scale in terms of "diversity" (total number of activities), "intensity" (hours per month), and "percentage intensity" (percentage of total activity hours devoted to each activity category). The control group was more active during midlife than the case group was for all three activity categories, even after controlling for age, gender, income adequacy, and education. The odds ratio for AD in those performing less than the mean value of activities was 3.85 (95% confidence interval: 2.65-5.58, P < 0.001). The increase in time devoted to intellectual activities from early adulthood (20-39) to middle adulthood (40-60) was associated with a significant decrease in the probability of membership in the case group. We conclude that diversity of activities and intensity of intellectual activities were reduced in patients with AD as compared with the control group. These findings may be because inactivity is a risk factor for the disease or because inactivity is a reflection of very early subclinical effects of the disease, or both.

Activities of Daily Living↗
PubMed2001

[Effects of di-zhen granules on catecholamine transmitter and gonadotropin of clamacteric rats with deficiency of yin brings about the interior heat-syndrome].

Fifteen-month-old Sprague-Dawley rats were given with some kinds of hot property of herb to produce model of Deficiency of yin brings about the interior heat-syndrome. The weight, water drinking volume, and body temperature of model rats were observed at the process of producing model and the treatment of di-zhen granules. Hypothalamic NE, DA and plasma NE, E concentration were determined by high-performance liquid chromatography, and serum E2, FSH, LH levels were determined by radioimmunoassay. The results were that after having been given the hot property of herbs for 2 weeks, the model rats increased water drinking volume and body temperature, which is similar to the appearance of patients with Deficiency of yin brings about the interior heat syndrome, and after having been treated with di-zhen granules, the water drinking volume and temperature of model rats decreased significantly (P < 0.01). The hypothalamic NE, DA, plasma NE, E, and the serum FSH, LH of the group treated with di-zhen granules were significantly lower than that of the model group and the normal group(P < 0.01). The results show that our model mentioned above possesses some characteristic features of the human climacteric syndrome which exhibits Deficiency of yin brings about the interior heat-syndrome. Di-zhen granules may regulate the function of GnRH neurons and other neurotic nucleus in hypothalamus, and then rectify the endocrine disorders of climacteric.

Animals↗
PubMed2001

Functional mutation in the promoter region of thrombomodulin gene in relation to carotid atherosclerosis.

Thrombomodulin is an important endothelial anticoagulant protein that decreases thrombin activity and activates protein C. Our recent study has shown that the G-33A promoter mutation of thrombomodulin gene is associated with coronary artery disease. This study was conducted to determine whether the G-33A mutation in the promoter region of thrombomodulin gene is a genetic risk factor for ischemic stroke or carotid atherosclerosis. The functional significance of this mutation was also evaluated. We recruited 333 patients (mean age 64 years, 59% male) with ischemic stroke and 257 age- and sex-matched controls. In all study participants, carotid atherosclerosis was assessed by Duplex scanning, and thrombomodulin G-33A promoter mutation was detected by single-strand conformation polymorphism. Luciferase reporter gene assay was used to assess the influence of this mutation on thrombomodulin promoter activity. There was no significant difference in the thrombomodulin G-33A mutation frequency (GA+AA genotypes) between the stroke and the control groups (18.3 vs. 24. 1%, P=0.105). The G-33A mutation frequency was also similar between the study participants with and without carotid atherosclerosis (22.2 vs. 19.8%, P=0.550). When only younger subjects (age </=60 years) were included in the analysis, however, we found the mutation occurred more frequently in participants with carotid atherosclerosis (33.3 vs. 17.3%, odds ratio [OR]=2.38, 95% confidence interval [CI]=1.16-4.90, P=0.027). Multiple logistic regression analyses showed that only diabetes mellitus (OR=3.11, 95% CI=1.33-7.30, P=0.009) and G-33A mutation (OR=2.46, 95% CI=1.14-5.29, P=0.021) were associated independently with carotid atherosclerosis in younger subjects. As assessed by luciferase reporter gene assays, the contructs bearing the G-33A mutation showed a significant decrease (36+/-12%) in transcriptional activity in comparison with the wild type constructs. Our findings suggest that G-33A mutation reduces the thrombomodulin promoter activity and is associated with carotid atherosclerosis in younger subjects.

Aged↗
PubMed2001

Nonresonant MALDI of oligonucleotides: mechanism of ion desorption.

Oligonucleotide ions have been detected using matrix-assisted laser desorption/ionization (MALDI) under nonresonant laser irradiation of the sample. When mass resolution was not limited by adduct attachment to the analyte ions, the nonresonant MALDI spectra demonstrated better resolution than the spectra acquired with resonant ultraviolet irradiation. We found that preparation of thin-film samples on absorbing substrate surfaces was critical for the success of NR-MALDI. The possible acoustic mechanisms of ion formation and desorption are discussed.

Oligonucleotides↗
PubMed2001

Determination of urine catecholamines by capillary electrophoresis with dual-electrode amperometric detection.

Demonstrated in this study is that without pretreatment and preconcentration nanomolar-level catecholamines in human urine samples can be quantitatively determined with ease by utilizing capillary electrophoresis coupled with amperometric detection. The detector employs a parallel-opposed dual-electrode scheme assembled with an on-capillary electrode and a disk electrode and takes advantage of the redox cycling of analytes between the two working electrodes to improve the limit of detection. The matrix effect of urine samples significantly decreases the detection sensitivity from that obtained in standard solutions. Therefore, calibration curves derived from standard solutions cannot be used in quantitative determination of catecholamines. Methods of standard addition and internal standard have been studied. The results suggest that isoproterenol is a good internal standard to facilitate the measurements of dopamine, epinephrine, and norepinephrine in human urine samples.

Catecholamines↗
PubMed2001

Identification and characterization of two novel components of the Prp19p-associated complex, Ntc30p and Ntc20p.

The yeast Saccharomyces cerevisiae Prp19p protein is an essential splicing factor and a spliceosomal component. It is not tightly associated with small nuclear RNAs (snRNAs) but is associated with a protein complex consisting of at least eight proteins. We have identified two novel components of the Prp19p-associated complex, Ntc30p and Ntc20p. Like other identified components of the complex, both Ntc30p and Ntc20p are associated with the spliceosome in the same manner as Prp19p immediately after or concurrently with dissociation of U4, indicating that the entire complex may bind to the spliceosome as an intact form. Neither Ntc30p nor Ntc20p directly interacts with Prp19p, but both interact with another component of the complex, Ntc85p. Immunoprecipitation analysis revealed an ordered interactions of these components in formation of the Prp19p-associated complex. Although null mutants of NTC30 or NTC20 showed no obvious growth phenotype, deletion of both genes impaired yeast growth resulting in accumulation of precursor mRNA. Extracts prepared from such a strain were defective in pre-mRNA splicing in vitro, but the splicing activity could be restored upon addition of the purified Prp19p-associated complex. These results indicate that Ntc30p and Ntc20p are auxiliary splicing factors the functions of which may be modulating the function of the Prp19p-associated complex.

Antibodies↗
PubMed2001

A study comparing precision of the maximum multipoint heterogeneity LOD statistic to three model-free multipoint linkage methods.

This study compared the performance of the maximum lod (MLOD), maximum heterogeneity lod (MHLOD), maximum non-parametric linkage score (MNPL), maximum Kong and Cox linear extension (MKC(lin)) of NPL, and maximum Kong and Cox exponential extension (MKC(exp)) of NPL as calculated in Genehunter 1.2 and Genehunter-Plus. Our performance measure was the distance between the marker with maximum value for each linkage statistic and the trait locus. We performed a simulation study considering: 1) four modes of transmission, 2) 100 replicates for each model, 3) 58 pedigrees (with 592 subjects) per replicate, 4) three linked marker loci each having three equally frequent alleles, and 5) either 0% unlinked families (linkage homogeneity) or 50% unlinked families (linkage heterogeneity). For each replicate, we obtained the Haldane map position of the location at which each of the five statistics is maximized. The MLOD and MHLOD were obtained by maximizing over penetrances, phenocopy rate, and risk-allele frequencies. For the models simulated, MHLOD appeared to be the best statistic both in terms of identifying a marker locus having the smallest mean distance from the trait locus and in terms of the strongest negative correlation between maximum linkage statistic and distance of the identified position and the trait locus. The marker loci with maximum value of the Kong and Cox extensions of the NPL statistic also were closer to the trait locus than the marker locus with maximum value of the NPL statistic.

Bias↗