Biomedical subjects

Jing Chen

Publications and source records attributed to Jing Chen.

337 records · Page 19Linked to original sources

PubMed2002

[Primary study on establishment of namalwa 12/MTX resistant cell strain and its mechanism].

BACKGROUND & OBJECTIVE: Methotrexate has been used to treat malignant tumor for 50 years. Different mechanisms of methotrexate resistance has been known in various kinds of leukemias. Because of individualized chemotherapy according to different drug metabolism in different leukemia patients, the treatment became more reasonable and scientific and the treatment effect has been gradually improved. However, there was few report about its drug resistance mechanism in lymphoma. This study was designed to establish Burkitt's lymphoma methotrexate resistant cell strain--Namlwa 12/MTX and study its resistant mechanism. METHODS: Namlwa 12/MTX resistant cell strain was established by repeated impulsed exposure to methotrexate. The difference of the methotrexate effect on Namlwa 12/MTX and Namlwa cell strains were evaluated with MTT method. The level of dihydrofolate reductase (DHFR) mRNA expression was assayed with RT-PCR. The function of the reduced folate carrier (RFC) were tested with 3H-MTX labeling and counted with beta-liquid scintillation counter. The capacity to form the polyglutamate methotrexate (MTXPG) in these cell strains was assayed with 3H-MTX labeling and high pressure liquid chromatography (HPLC) separation. RESULTS: More than 20 times methotrexate resistance was found in Namalwa 12/MTX cell strain in comparison with the Namalwa cell strain. This resistance was not associated with the dysfunction of the RFC, but was closely associated with the amount of MTXPG formed. The amount of total MTXPG (MTXPG1-6) formed in these 2 cell strains was (1583 +/- 26) pmol/10(9) tumor cells and (4453 +/- 236) pmol/10(9) tumor cells, respectively (P < 0.05), while the amount of long chain MTXPG (MTXPG4-6) formed only accounted for 5.5% and 25.4% of the MTXPG1-6, respectively (P < 0.05). The level of DHFR mRNA expression was gradually increased with the formation of the drug resistance in Namalwa 12/MTX. CONCLUSION: Synthesizing difficulty of MTXPG and over-expression of DHFR mRNA level result in methotrexate resistance in Namalwa 12/MTX cell strain.

Antimetabolites, Antineoplastic↗

PubMed2002

[Capillary zone electrophoresis for determination of thymulin in human plasma].

AIM: To establish a capillary zone electrophoresis (CZE) method for determination of thymulin in human blood plasma. Thymulin is a nonapeptide produced by the thymic epithelium. METHODS: The uncoated capillary used was 75 microns ID x 57 cm (50 cm effective length). The experimental conditions were as follows: the running buffer was phosphate-borate buffer containing 50 mmol.L-1 Na2B4O7-10 mmol.L-1 Na2HPO4 (pH 9.10); running voltage was 12 kV; operated temperature was 25 degrees C; running time was 13 minutes, detective wavelength was 200 nm. RESULTS: The linear range of the thymulin standard curve was 1-10 micrograms.mL-1, gamma = 0.9990, the average recovery was 70.97% with RSD of 3.32%, the RSD of reproducibility was 3.05%. CONCLUSION: The method of CZE for determination of thymulin in human plasma is simple and reliable.

Child, Preschool↗

PubMed2002

[Formation of the third phase and spectroscopic research of the loading organic phases in the gold extraction].

The formation of the third phase during the gold extraction from cyanide solution by quaternary ammonium, tetradecyldimethylbenzylammonium chloride (TDMBAC) was studied by 198Au tracer method. The microstructure of the organic phases was investigated by FTIR, 31P-NMR. With the increasing of gold concentration, aggregations were formed in the gold-loaded organic phase. With the further increasing of gold concentration, the organic phase turned into two layers. Gold, water, and tri-n-butyl phosphate (TBP) were mainly in the down organic phase. In the down layer, distinct O-H stretching vibration peak was found by FTIR; the frequency of P=O stretching vibration shifted to the low frequency; 31P-NMR chemical shift was markedly shifted to the high frequency field. The radius of aggregation was measured by the dynamic laser scattering (DLS) method.

English Abstract↗

PubMed2002

[Chromosome analysis of Chongqing thermo-photo sensitive male sterile wheat].

Seed gliadin acid-polyacrylamide-gel-electrophoresis (APAGE) and chromosome C-banding techniques were used to identify chromosome constitution of Chongqing thermo-photo sensitive male sterile wheat. Results showed that 1BS of the male sterile lines was substituted by 1RS of rye. They were 1B/1R wheat with Triticum aestivum cytoplasm.

English Abstract↗

PubMed2000

CEK2, a Novel MAPK from Candida albicans Complement the Mating Defect of fus3/kss1 Mutant.

A novel MAPK(mitogen-activated protein kinase) gene, CEK2(Candida albicans extracellular signal-regulated kinase 2), was isolated by screening the Candida albicans library based on oligonucleotide probe hybridization and degenerated PCR. The CEK2 gene is 1 119 bp in length, and coding for a 373 aa protein. The CEK2 shares 56% homology with CEK1 from Candida albicans, 55 % homology with FUS3 from S. cerevisiae. From the deduced amino acid sequence, the Cek2 protein contains a conserved ATP binding site and a Ser/Thr kinase activity signal and a conserved TEY sequence was located at L(12) region. In vitro kinase activity assay showed Cek2 could phosphorylate MBP(myelin bovine protein) but not histone H1. CEK2 gene could complement the fus3/kss1 mutant and underwent mating signal induction by a tester strain, but CEK1 gene could not complement with the fus3/kss1 mutant. CEK2 is therefore a FUS3 homolog in Candida albicans.

Journal Article↗

PubMed2000

Molecular Cloning of MAPK Gene Family Using Degenerate PCR.

MAPK(Mitogen-activated protein kinase) pathways play an important role in morphorgenesis of Candida albicans. According to the conserved amino acid sequence of the known MAPKs, two degenerate primers attaching to subdomain VIB and IX were designed to screen novel MAPKs in C. albicans. The PCR was performed under non-strigent conditons. 100 PCR fragments were sequenced and among 25 novel gene fragments, two novel MAPK gene fragments were obtained. Using these two PCR fragments as probes to screen a Candida albicans genomic DNA library, two novel MAPK genes designated CSK1(Candida albicans sporulation-related MAP kinase1) and CEK2(Candida albicans extracellular signal-regulated kinase 2) were cloned. These two genes share high similarity with three cloned MAPK genes CEK1 and MKC1 and CaHOG1. The CSK1 gene is 1 193 bp in length, containing a 92 bp intron, coding for a 367 aa protein. The CSK1 shares highest similarity with SMK1, with homology 55.3% in nucleotide sequence and 50% in amino acid sequence. SMK1 encodes a MAPK involved in the sporulation pathway in S. cerevisiae. In vitro kinase activity assay showed that the Csk1 kinase exhibited a phosphorylation ability when using MBP as a substrate but not histone H1.

Journal Article↗

PubMed2000

[Effect of Methotrexate on Cell Growth of Human Monocyte-like Cell Line U937 and Its Induction of Apoptosis]

Acute myeloid leukemia (AML) is considered to be a malignancy that is intrinsically resistant to methotrexate (MTX). As compared to acute lymphoblastic leukemia (ALL) blasts, AML blasts, except those of acute monocytic leukemia (AML-M(5)), form fewer amounts of long chain polyglutamate of MTX (MTXPG), when incubated with MTX, thus providing an explanation for their lack of responsiveness to MTX. To explore the novel approach of treatment in patients with AML-M(5), the U937 cell line, which has the monocytic characters, was used. Cell growth inhibition was mearsured by XTT assay after 24 and 48 hours in the continuous presence of various concentrations of MTX ranging from 1 nmol/L to 100 micro mol/L. After 24 hours MTX treatment, the IC(50) value for U937 cells was 0.04 micro mol/L. After 48 hours treatment, the IC(50) was 0.037 micro mol/L and IC(90) was 0.39 micro mol/L. To understand the mechanism of MTX cytotoxicity, the process of cell death was analyzed. A variety of assays, including trypan blue exclusion, flow cytometry, light microscopy (Wright's staining) and DNA fragment electrophoresis, were performed. There were no significant apoptotie changes after shorter exposure of MTX (4 and 6 hours). After 8 hours at various concentrations of MTX treatment ranging from 5 nmol/L to 10 micro mol/L, the percentage of the cells in the pre-G(1) (apoptotic) was 3.2% at 0.1 micro mol/L and it reached a peak of 18.2% at 5.0 micro mol/L. The DNA synthesis in S-phase was inhibited from 41.2% (0.01 micro mol/L) to 19.1% (10 micro mol/L). DNA ladder band, a feature of apoptosis, was observed. The arrest of cell growth and apoptotic properties induced by MTX have lead to its evaluation as a potentially therapeutic agent in the treatment of AML-M(5).

Journal Article↗

PubMed1999

Molecular Cloning of MAPK Gene Family Using Synthetic Oligonucleotide Probe.

MAPK(mitogen activated protein kinase) is a kind of Ser/Thr protein kinase. The MAPKs play an important role in several different signal transduction pathways. The MAPKs may also have a role in morphorgenesis of Candida albicans. An oligonucleotide probe was used to screen novel MAPKs in C. albicans. All MAPKs shared high homogeneity in their eleven kinase subdomains, especially subdoman VII and VIII. In subdomain VII, nearly all MAPKs have the same KIDFGLAR sequence, and the two known MAPKs in C. albicans CEK1 and MKC1 have only one different nucleotide in that DNA sequence. This probe was hybridized with C. albicans genomic DNA. Under stringent conditions, the probe could only hybridize with CEK1 and MKC1 gene fragment. But when hybridized at 40 degrees in non-SDS solution, two novel bands appeared. This condition was used to screen SC5314 DNA library, and many positive clones with different hybridization density were obtained. The strongest hybridization clones were identified to contain CEK1 and MKC1 gene. From the stronger positive hybridization clones, two novel genes were identified. The first gene, named CRK1(CDC2-related protein kinase 1), shared high homogeneity to MAPKs, but was not of them. It is closest to SGV1 from S. cerevisiae (with homology 47%) and PITALRE from human (with homology 41%), both of which are CDC2-related protein kinases. The second gene called CEK2(Candida albicans extracelluar signal-regulated kinase 2) is a novel MAPK of Candida albicans, which shares the highest identity with CEK1 and its S. cerevisiae homologs, FUS3 and KSS1, two redundant MAPKs in yeast pheromone response and morphogenesis.

Journal Article↗

PubMedDate not supplied

Prevalence of the metabolic syndrome and overweight among adults in China.

BACKGROUND: The metabolic syndrome and obesity are major risk factors for cardiovascular disease. Little information exists on the prevalence of the metabolic syndrome in China. We aimed to provide up-to-date estimates of the prevalence of the metabolic syndrome and overweight in the general adult population in China. METHODS: We did a cross-sectional survey in a nationally representative sample of 15,540 Chinese adults aged 35-74 years in 2000-01. Metabolic syndrome was defined according to guidelines from the US National Cholesterol Education Program. Overweight was defined as body-mass index of 25.0 kg/m2 or greater. FINDINGS: The age-standardised prevalence of metabolic syndrome was 9.8% (95% CI 9.0-10.6) in men and 17.8% (16.6-19.0) in women. The age-standardised prevalence of overweight was 26.9% (25.7-28.1) in men and 31.1% (29.7-32.5) in women. The prevalence of the metabolic syndrome and overweight was higher in northern than in southern China, and higher in urban than rural residents. INTERPRETATION: Our results indicate that a large proportion of Chinese adults have the metabolic syndrome and that overweight has become an important public health problem in China. These findings emphasise the urgent need to develop national strategies for the prevention, detection, and treatment of overweight and the metabolic syndrome, to reduce the societal burden of cardiovascular disease in China.

Adult↗

PubMedDate not supplied

Subcellular localization of phosducin in rod photoreceptors.

Phosducin (Pd) is a 28-kD phosphoprotein whose expression in retina appears limited to photoreceptor cells. Pd binds to the beta,gamma subunits of transducin (Gt). Their binding affinity is markedly diminished by Pd phosphorylation. While Pd has long been regarded as a candidate for the regulation of Gt, the molecular details of Pd function remain unclear. This gap in understanding is due in part to a lack of precise information concerning the total amount and subcellular localization of rod Pd. While earlier studies suggested that Pd was a rod outer segment (ROS) protein, recent findings have demonstrated that Pd is distributed throughout the rod. In this report, the subcellular distribution and amounts of rat Pd are quantified with immunogold electron microscopy. After light or dark adaptation, retinal tissues were fixed in situ and prepared for ultrathin sectioning and immunogold labeling. Pd concentrations were analyzed over the entire length of the rod. The highest Pd labeling densities were found in the rod synapse. Less intense Pd staining was observed in the ellipsoid and myoid regions, while minimal labeling densities were found in the ROS and the rod nucleus. In contrast with rod Gt, no evidence was found for light-dependent movement of Pd between inner and outer segments. There is a relative paucity of Pd in the ROS as compared with the large amounts of Gt found there. This does not support the earlier idea that Pd could modulate Gt activity by controlling its concentration. On the other hand, the presence of Pd in the nucleus is consistent with its possible role as a regulator of transcription. The functions of Pd in the ellipsoid and myoid regions remain unclear. The highest concentration of Pd was found at the rod synapse, consistent with a suggested role for Pd in the regulation of synaptic function.

Animals↗

PubMedDate not supplied

Strategy for discovering chemical inhibitors of human cyclophilin a: focused library design, virtual screening, chemical synthesis and bioassay.

The discovery of cyclophilin A (CypA) inhibitor is now of special interest in the treatment of immunological disorders. In this work, using a strategy integrating focused combinatorial library design, virtual screening, chemical synthesis, and bioassay, a series of novel small molecular CypA inhibitors have been discovered. First, using the fragments taken from our previously discovered CypA inhibitors (Bioorg. Med. Chem. 2006, 14, 2209-2224) as building blocks, we designed a focused combinatorial library containing 255 molecules employing the LD1.0 program (J. Comb. Chem. 2005, 7, 398-406) developed by us. Sixteen compounds (1a-e, 2a-b, 3a-b, and 4a-g) were selected by using virtual screening against the X-ray crystal structure of CypA as well as druglike analysis for further synthesis and bioassay. All these sixteen molecules are CypA binders with binding affinities (K(D) values) ranging from 0.076 to 41.0 microM, and five of them (4a, 4c, and 4e-g) are potent CypA inhibitors with PPIase inhibitory activities (IC(50) values) of 0.25-6.43 microM. The hit rates for binders and inhibitors are as high as 100% and 31.25%, respectively. Remarkably, both the binding affinity and inhibitory activity of the most potent compound increase approximately 10 times than that of the most active compound discovered previously. The high hit rate and the high potency of the new CypA inhibitors demonstrated the efficiency of the strategy for focused library design and screening. In addition, the novel chemical entities reported in this study could be leads for discovering new therapies against the CypA pathway.

Binding Sites↗

PubMedDate not supplied

Pocket v.2: further developments on receptor-based pharmacophore modeling.

A deriving pharmacophore model from the three-dimensional structure of a target protein provides helpful information for analyzing protein-ligand interactions and further improvement of ligand binding affinity. A standalone program, Pocket v.2, has been developed based on the original Pocket module in the de novo drug design program LigBuilder. Pocket v.2 is able to derive a pharmacophore model directly from a given protein-ligand complex structure without human intervention. Key features in the pharmacophore model are automatically reduced to a reasonable number. Pocket v.2 has been applied to several case studies, including cyclin dependent kinase 2, HIV-1 protease, estrogen receptor, and 17beta-hydroxysteroid dehydrogenase. It well reproduced previously published pharmacophore models in all of these cases. One notable feature of Pocket v.2 is that it can tolerate minor conformational changes on the protein side upon binding of different ligands to give a consistent pharmacophore model. For different proteins accommodating the same ligand, Pocket v.2 gives similar pharmacophore models, which opens the possibility to classify proteins with their binding features.

17-Hydroxysteroid Dehydrogenases↗

PubMedDate not supplied

Canadian individual risks of radon-induced lung cancer for different exposure profiles.

BACKGROUND: Indoor radon has been determined to be the second leading cause of lung cancer after tobacco smoking. There is an increasing need among radiation practitioners to have numerical values of lung cancer risks for men and women, ever-smokers and never-smokers exposed to radon in homes. This study evaluates individual risks for the Canadian population exposed to radon in homes at different radon concentrations and for different periods of their lives. METHODS: Based on the risk model developed recently by U.S. Environmental Protection Agency (EPA), individual risks of radon-induced lung cancers are calculated with Canadian age-specific rates for overall and lung cancer mortalities (1996-2000) as well as the Canadian smoking prevalence data in 2002. RESULTS: Convenient tables of lifetime relative risks are constructed for lifetime exposures and short exposures between any two age intervals from 0 to 110, and for various radon concentrations found in homes from 50 to 1000 Bq/m3. CONCLUSIONS: The risk of developing lung cancer from residential radon exposure increases with radon concentration and exposure duration. For short exposure periods, such as 10 or 20 years, risks are higher in middle age groups (30-50) compared especially to the later years. Individuals could lower their risks significantly by reducing radon levels earlier in life. The tables could help radiation protection practitioners to better communicate indoor radon risk to members of the public.

Adolescent↗