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Biomedical subjects

Yi Chen

Publications and source records attributed to Yi Chen.

At least 109 records · Page 6Linked to original sources
PubMed2005

IL-23 drives a pathogenic T cell population that induces autoimmune inflammation.

Interleukin (IL)-23 is a heterodimeric cytokine composed of a unique p19 subunit, and a common p40 subunit shared with IL-12. IL-12 is important for the development of T helper (Th)1 cells that are essential for host defense and tumor suppression. In contrast, IL-23 does not promote the development of interferon-gamma-producing Th1 cells, but is one of the essential factors required for the expansion of a pathogenic CD4(+) T cell population, which is characterized by the production of IL-17, IL-17F, IL-6, and tumor necrosis factor. Gene expression analysis of IL-23-driven autoreactive T cells identified a unique expression pattern of proinflammatory cytokines and other novel factors, distinguishing them from IL-12-driven T cells. Using passive transfer studies, we confirm that these IL-23-dependent CD4(+) T cells are highly pathogenic and essential for the establishment of organ-specific inflammation associated with central nervous system autoimmunity.

Animals↗
PubMed2005

Deficiency of inducible nitric oxide synthase exacerbates hepatic fibrosis in mice fed high-fat diet.

The role of inducible nitric oxide synthase (iNOS) in the progression of fibrosis during nonalcoholic steatohepatitis remains to be elucidated. This study examined the role of iNOS in the progression of fibrosis during steatohepatitis by comparing iNOS knockout (iNOS(-/-)) and wild-type (iNOS(+/+)) mice that were fed a high-fat diet. Severe fatty metamorphosis developed in the liver of iNOS(+/+) and iNOS(-/-) mice. Fibrotic changes were marked in iNOS(-/-) mice. Gelatin zymography showed that pro MMP-2 and pro MMP-9 protein expressions were more highly induced in iNOS(+/+) mice than in iNOS(-/-) mice. Active forms of MMP-2 and MMP-9 were clearly present only in the liver tissue of iNOS(+/+) mice. In situ zymography showed strong gelatinolytic activities in the liver tissue of iNOS(+/+) mice, but only spotty activity in iNOS(-/-)mice. iNOS may attenuate the progression of liver fibrosis in steatohepatitis, in part by inducing MMP-2 and MMP-9 expression and augmenting their activity.

Animals↗
PubMed2005

Chiral ion-exchange capillary electrochromatography of arylglycine amides with dextran sulfate as a pseudostationary phase.

A low-cost tunable chiral ion-exchange capillary electrochromatographic method has been developed for the separation of arylglycine amide racemic mixtures with dextran sulfate (DS) as an anionic and chiral pseudostationary phase and Tris-tartrate as a buffer system. The concentrations of DS and Tris had opposite influences on retention and resolution and could serve as ideal factors to finely tune the running speed and chiral resolution. Tartrate and pH largely impact the separation but pH should be confined within 3.0-5.5, only suitable for coarse tuning, while tartrate was preserved as the key buffering reagent, normally maintained at 40 mmol/L. With a working system composed of 0.1-1.0% DS, 20-60 mmol/L Tris, and 40 mmol/L tartrate at pH 3.50-4.50, the enantioresolution of arylglycine amides was shown to be dependent on their chemical structure: The chiral resolution increased when the hydrogen at the alpha-amino group or at the p-position of phenyl ring was replaced by other larger group(s) but the resolution decreased when the group at the o- or m-site on the phenyl ring was enlarged. Further, the electronegative substitute of -Cl had larger resolution increment than methyl or methoxy at the position p- of phenyl ring but much lower increment at position m-. It is possible to well explain the resolution variation phenomenon by considering the group resistance and the variation of hydrogen-bonds formed inside the amino amides and between the solutes and DS. The amido group was shown irreplaceable to have chiral resolution with DS alone as an ionic and chiral pseudostationary phase.

Buffers↗
PubMed2005

A novel rearrangement in electrospray ionization multistage tandem mass spectrometry of amino acid ester cyclohexyl phosphoramidates of AZT.

Several amino acid ester cyclohexyl phosphoramidates of AZT as anti-HIV prodrugs were synthesized and investigated by electrospray ionization tandem mass spectrometry (ESI-MS(n)). A novel methoxy group migration from the carbonyl group to the phosphoryl group was observed in ESI-MS2. This migration is believed to be a general pathway for ions with a methyl ester moiety at the gamma-position to a phosphoric acid moiety, which is assisted with metal ions such as Li(+), Na(+) and K(+). Coordination between metal ions with both the carbonyl oxygen and phosphoryl oxygen might be a key factor responsible for this migration.

Amides↗
PubMed2005

Effect of Weikangfu granule on the physiopathologic figure of precancerosis of gastric mucosa in patients of chronic gastritis with Pi-deficiency syndrome.

OBJECTIVE: To study the physiopathologic basis of Weikangfu Granule (WKFG) in treating precancerosis of gastric mucosa in patients of chronic gastritis with Pi-deficiency syndrome (CG-PDS). METHODS: One hundred and fifteen patients of CG-PDS who suffered from intestinal metaplasia (IM) and atypical hyperplasia (ATHP) of gastric mucosa, were divided into two groups. The treated group (n = 61) was treated by WKFG with its ingredients modified according to the syndrome type of patients. The control group (n = 54) was treated with Weishu granule. The histopathological and subcellular ultrastructural changes were detected by optical microscope, screening electronic microscope, transmission electronic microscope and histochemical staining; the nuclear and mitochondrial ultrastructure of gastric mucosa were analyzed with energy dispersion X-ray analyser and image analysis system. And the changes of cAMP, lipid peroxide (LPO), superoxide dismutase (SOD) before and after treatment in the treated group were measured and compared with those of the health control group consisting of 15 volunteers. RESULTS: The symptomatic and pathological therapeutic effect in the treated group were significantly superior to those in the control group (P < 0.05). The contents of Zn, Cu, cAMP, SOD and (3)H-TdR LCT in gastric mucosa of the treated group before treatment were all lower than those of the healthy control group, yet all these indexes markedly increased after treatment, while serum LPO level, which increased before treatment was lowered after treatment. All the changes showed statistical significance (P < 0.05 or P < 0.01). CONCLUSION: WKFG can reverse IM and ATHP in patients of CG-PDS, and the effect may be realized by way of increasing the level of Zn, Cu, cAMP and SOD in gastric mucosa, promoting cell differentiation, enhancing cellular immunity and reducing oxygen free radicals and lipid peroxidation.

Adult↗
PubMed2005

[A new rat model of cerebral infarction based on the injury of vascular endothelial cell].

OBJECTIVE: A new rat model of cerebral infarction was developed to elucidate the contribution of vascular endothelial cell during focal cerebral infarction formation. METHODS: Forty-eight Sprague-Dawley (SD) rats were randomly divided into the model group, sham operation group, and control group for indexes observation of triphenyltetrazolium chloride (TTC) dyeing, neurological deficit, plasma tissue-type plasminogen activator (tPA) activity, plasminogen activator inhibitor (PAI) activity, thromboxane B(2) (TXB(2)) content, and 6-keto-prostaglandin (6-keto-PGF(1alpha)) content. RESULTS: (1) The highest neurological score appeared at 6 h after operation, descending significantly at sequential time. (2) Using TTC dyeing and optical microscope technique, pathological changes in brains were observed. (3) Compared with control group and sham operation groups, there was a decrease in tPA activity of model rats at the initial 12 h after injection of sodium laurate (P < 0.05), PAI activity decreased markedly in the model group at 24 h after injection of sodium laurate. (4) In plasma TXB(2) concentration reached the highest level compared at 6 h after injection of sodium laurate, but there were not obvious differences in plasma 6-keto-PGF(1alpha) concentration among all groups (P > 0.05). CONCLUSION: Focal cerebral infarction in rats could be induced by some sodium laurate, showing ischemic cerebrum necrosis, function disorder of vascular endothelium-platelet, fibrinolysis abnormality. This model could play an important role in researching the contribution of vascular endothelial cell during cerebral infarction development, preventing and curing by traditional Chinese medicine.

Animals↗
PubMed2005

Adsorption isotherms on nicotinamide-imprinted polymer stationary phase.

The molecular-imprinted technique is applied for the preparation of a polymer selector by using methacrylic acid as functional monomer, ethyleneglycol dimethacrylate as the cross-linker, 2,2'-azobisisobutyronitrile as the initiator, and nicotinamide as the template. The adsorption isotherms of nicotinamide and nicotinic acid and the competitive adsorption isotherms of nicotinamide and nicotinic acid on the imprinted stationary phase are determined using rectangular pulse frontal analysis and static method. Aqueous solution is used as the mobile phase in frontal analysis. It is found that the adsorption data fit well to both Langmuir and Freundlich isotherm models.

Adsorption↗
PubMed2005

Community attitudes toward HIV prevention for injection drug users: findings from a cross-border project in southern China and northern Vietnam.

Success of HIV prevention projects for injection drug users (IDUs) depends on the support of the communities in which they are implemented. This article presents data from cross-sectional community surveys of HIV knowledge and attitudes toward peer-based HIV prevention interventions for injection drug users in a border area of Lang Son Province, Vietnam and Ning Ming County, Guangxi Province, China. Analysis of these surveys at baseline and 18 months reveals generally high or improving levels of HIV knowledge and positive attitudes toward the interventions in both Vietnam and China. Levels of knowledge and positive attitudes tended to be higher in Vietnam than in China. Interviews with staff and peer educators suggest that the project's community education efforts have increased support for the interventions and contributed to their smooth implementation. However, the community surveys also reveal some continuing deficits in HIV knowledge and understanding of the interventions, including perceptions that provision of new needles/syringes will result in increased drug use. Additional education, including dissemination of countervailing project data, is necessary to address these deficits and further increase community support for the interventions.

Adult↗
PubMed2005

11,11'-dideoxy-verticillin: a natural compound possessing growth factor receptor tyrosine kinase-inhibitory effect with anti-tumor activity.

11,11'-dideoxy-verticillin, a compound of the novel epidithiodioxopiprazine structural class, is isolated from the traditional Chinese medicinal herb Shiraia bambusicola. The present study demonstrated for the first time that 11,11'-dideoxy-verticillin has potent tyrosine kinase-inhibitory and anti-tumor activities. In the cell-free ELISA tyrosine kinase assay, 11,11'-dideoxy-verticillin significantly inhibited the activities of epidermal growth factor receptor (EGFR), vascular endothelial growth factor receptor-1/fms-like tyrosine kinase-1 (VEGFR-1/Flt-1) and human epidermal growth factor receptor-2 (HER2/ErbB-2), with relative specificity on EGFR and VEGFR-1 with IC50s of 0.136+/-0.109 and 1.645+/-0.885 nM, respectively. Exposure of 11,11'-dideoxy-verticillin for 1 h to EGFR-overexpressed MDA-MB-468 human breast carcinoma cells and HER2-overexpressed SK-OV-3 human ovarian adenocarcinoma cells resulted in obvious inhibition of EGF-induced phosphorylation of EGFR and HER2. In addition, 11,11'-dideoxy-verticillin also inhibited the EGF-induced phosphorylation of Erk1/2, but had no effect on the phosphorylation of AKT in both tumor cell lines. Moreover, 11,11'-dideoxy-verticillin has potent anti-tumor activity. In vitro cytotoxicity assay showed that 11,11'-dideoxy-verticillin potently inhibited the proliferation of four human breast tumor cell lines with an average IC50 value of 0.2 microM. In vivo, 11,11'-dideoxy-verticillin exhibited remarkable efficacy against mice sarcoma 180 and hepatoma 22 after daily i.p. administration of 0.5 or 0.75 mg/kg with inhibition rates ranging from 45.0 to 72.4%. Treated with 11,11'-dideoxy-verticillin at 0.5-2.0 microM for 36 h, MB-MB-468 cells exhibited significant apoptotic morphological changes. At low concentrations (0.0625-0.5 microM) for 24 h, 11,11'-dideoxy-verticillin induced a dose-dependent accumulation of MDA-MB-468 cells in the G2/M phase of the cell cycle. These results indicate that 11,11'-dideoxy-verticillin is a naturally derived growth factor receptor tyrosine kinase inhibitor with potent anti-tumor activity.

Animals↗
PubMed2005

Unsaturated phosphatidylcholine and its application in surgical adhesion.

BACKGROUND: It has been confirmed that surface-active phospholipid (SAPL), or surfactant, lines the surface of peritoneum and serves as a release and lubricating agent. The most important component in SAPL is phosphatidylcholine. A previous animal study showed that a saturated phosphatidylcholine, dipalmitoyl-phosphatidylcholine, reduced the formation of surgical adhesion. Latest studies have indicated that the dominant SAPL species at some sites outside the lung are not saturated phosphatidylcholine but, rather, are unsaturated phosphatidylcholine. METHODS: High performance liquid chromatography was used to analyse the phosphatidylcholine profile of dialysate samples obtained from peritoneal dialysis patients. Friction tests were performed on dipalmitoyl-phosphatidylcholine and selected unsaturated phosphatidylcholine. RESULTS: It was discovered that unsaturated phosphatidylcholine was the dominant SAPL species inside the peritoneal cavity. They are palmitoyl-linoleoyl-phosphatidylcholine, palmitoyl-oleoylphosphatidylcholine and stearoylarachidonoylphosphatidylcholine. Most interestingly, there was no dipalmitoyl-phosphatidylcholine detected from these dialysate samples. The coefficients of static and dynamic friction from palmitoyllinoleoyl-phosphatidylcholine and palmitoyloleoyl-phosphatidylcholine were measured and found to be lower than that of dipalmitoyl-phosphatidylcholine. CONCLUSION: The results from the current study reveal that unsaturated phosphatidylcholine is the endogenous species inside the peritoneal cavity. This discovery offers further evidence that the dominant SAPL species at non-lung sites are unsaturated phosphatidylcholine, not saturated phosphatidylcholine, strongly indicating the difference between phosphatidylcholine species distribution at lung and non-lung sites. Unsaturated phosphatidylcholine has better anti-friction and lubrication properties than dipalmitoyl-phosphatidylcholine. Unsaturated phosphatidylcholine-based SAPL pharmaceutical products should be developed and evaluated.

Chromatography, High Pressure Liquid↗
PubMed2005

Induction of Epstein-Barr virus lytic replication by recombinant adenoviruses expressing the zebra gene with EBV specific promoters.

The latent Epstein-Barr virus (EBV) is found in the cells of many tumors. For example, EBV is detectable in almost all cases, and in almost all tumor cells, of non-keratinizing nasopharyngeal carcinoma. Activating the latent virus, which will result in its lytic replication and the death of tumor cells, is a potential approach for the treatment of EBV-associated cancers. In this study, three recombinant adenoviruses were constructed to express the Zebra gene, an EBV gene responsible for switching from the latent state to lytic replication. EBV-specific promoters were used in order to limit Zebra expression in EBV-positive cells, and reduce the potential side effects. The EBV promoters used were Cp, Zp and a dual promoter combining both promoters, CpZp. The Zebra protein was detected in HEK293 cells as well as the EBV-positive D98-HR1 cells infected with recombinant viruses. An EBV lytic replication early antigen, EA-D, was also detected in infected D98-HR1, implying the initiation of lytic replication. In the cell viability assay, Zebra-expressing adenoviruses had little effect on EBV-negative HeLa cells, while significantly reducing the cell viability and proliferation of D98-HR1 cells. The results indicate that EBV virus promoters can be used in adenovirus vectors to express the Zebra gene and induce EBV lytic replication in D98-HR1 cells.

Adenoviridae↗
PubMed2005

PldB, a putative phospholipase D homologue in Dictyostelium discoideum mediates quorum sensing during development.

Quorum sensing, also known as cell-density sensing in the unicellular eukaryote Dictyostelium discoideum, is required for efficient entry into the differentiation and development segment of its life cycle. Quorum sensing is accomplished by simultaneously secreting and sensing the glycoprotein Conditioned Medium Factor, or CMF. When the density of starving cells is high, CMF levels are high, which leads to aggregation followed by development. Here, we describe the role of pldB, a gene coding for a putative phospholipase D (PLD) homologue, in quorum sensing. We find that in submerged culture, adding butanol, an inhibitor of PLD-catalyzed phosphatidic acid production, allows cells to bypass the requirement for CMF mediated quorum sensing and aggregate at low cell density. Deletion of pldB mimics the presence of butanol, allowing cells to aggregate at low cell density. pldB- cells also initiate and finish aggregation rapidly. Analysis of early developmental gene expression in pldB- cells reveals that the cyclic AMP receptor cAR1 is expressed at higher levels earlier than in wild-type cells, which could explain the rapid aggregation phenotype. As would be predicted, cells overexpressing pldB are unable to aggregate even at high cell density. Adding CMF to these pldB- overexpressing cells does not rescue aggregation. Both of these phenotypes are cell autonomous, as mixing a small number of pldB- cells with wild-type cells does not cause the wild-type cells to behave like pldB- cells.

Amino Acid Sequence↗
PubMed2005

Characterization of electrospray ionization mass spectrometry for N-diisopropyloxyphosphoryl dipeptide methyl esters.

A systematic study of the fragmentation pattern of N-diisopropyloxyphosphoryl (DIPP) dipeptide methyl esters in an electrospray ionization (ESI) tandem mass spectrometry (MS/MS) was presented. A combination of accurate mass measurement and tandem mass spectrometry had been used to characterize the major fragment ions observed in the ESI mass spectrum. It was found that the alkali metal ions acted as a fixed charge site and expelled the DIPP group after transferring a proton to the amide nitrogen. For all the N-phosphoryl dipeptide methyl esters, under the activation of a metal ion, the rearrangement product ion at m/z 163 was observed and confirmed to be the sodium adduct of phosphoric acid mono-isopropyl esters (PAIE), via a specific five-membered penta-co-ordinated phosphorus intermediate. However, no rearrangement ion was observed when a beta-amino acid was at the N-terminal. This could be used to develop a novel method for differentiating isomeric compounds when either alpha- or beta-amino acid are at the N-terminus of peptides. From the [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters (DIPP Xaa1 Xaa2 OMe), the peaks corresponding to the [M+Na Xaa1 C3H6]+ were observed and explained. The [M+Na]+ ESI-MS/MS spectra of N-phosphoryl dipeptide methyl esters with Phe located in the C-terminal, such as DIPPValPheOMe, DIPPLeuPheOMe, DIPPIlePheOMe, DIPPAlaPheOMe and DIPPPhePheOMe, had characteristic fragmentation. Two unusual gas-phase intramolecular rearrangement mechanisms were first proposed for this fragmentation. These rearrangements were not observed in dipeptide methyl ester analogs which did not contain the DIPP at the N-terminal, suggesting that this moiety was critical for the rearrangement.

Cations↗
PubMed2005

Estimation of hymenopteran parasitism in cereal aphids by using molecular markers.

Polymerase chain reaction (PCR) primers were designed and tested for identification of immature parasitoids in small grain cereal aphids and for estimation of parasitism rates. PCR technique was evaluated for 1) greenhouse-reared greenbugs, Schizaphis graminum (Rondani), parasitized by Lysiphlebus testaceipes Cresson and 2) aphids collected from winter wheat fields in Caddo County, Oklahoma. For greenhouse samples, parasitism frequencies for greenbugs examined by PCR at 0, 24, and 48 h after removal of L. testaceipes parasitoids were compared with parasitism frequencies as determined by greenbug dissection. PCR was unable to detect parasitism in greenbugs at 0 and 24 h postparasitism, but it was able to detect parasitoids 48 h after parasitoid removal at frequencies that were not significantly different from dissected samples. Field-collected samples were analyzed by rearing 25 aphids from each sample and by comparing parasitoid frequencies of mummies developed and PCR performed on another 50 aphids. Aphid samples included corn leaf aphids, Rhopalosiphum maidis (Fitch); bird cherry-oat aphids, Rhopalosiphum padi (L.); English grain aphids, Sitobion avenae (F.); and greenbugs. Mummies were isolated until adult emergence, whereupon each parasitoid was identified to species (L. testaceipes was the only parasitoid species found). Parasitism detection frequencies for PCR also were not statistically different from parasitism frequencies of reared aphids. These results indicate that PCR is a useful tool for providing accurate estimates of parasitism rates and especially for identification of immature parasitoids to species.

Animals↗
PubMed2005

[Niche of the mosses on floor in Shanghai City].

The mosses on the floor of 22 sites at 20 main parks and 2 chemical plants in Shanghai were sampled, and 75 moss species were recorded. Their niche breadths were calculated by Levins equation. The results indicated that most moss species had rather narrow niche breadth, 68% of them with a niche breadth less than 0.1. The relationship between species number (N) and their niche breadth (B) followed the model N = 0.344 x e(-0.0377B), R = 0.9684. The niche overlaps of 39 main moss species (important value > 0.1) were calculated by Wang's equation. Based on their niche overlaps, the ordination plot of Principal Axes Analysis (PAA) and the Minimal Spanning Tree (MST) were drawn. The results showed that five ecological groups of the 39 moss species related to different habitats could be identified.

Bryophyta↗