Biomedical subjects

Yan Li

Publications and source records attributed to Yan Li.

At least 361 records · Page 20Linked to original sources

PubMed2005

Expression of recombinant small hydrophobic protein for serospecific detection of avian pneumovirus subgroup C.

The small hydrophobic (SH) gene of the avian pneumovirus (APV) Colorado isolate (CO), which belongs to subgroup C (APV/C), was expressed with a baculovirus vector. The recombinant SH protein was evaluated as a potential subgroup-specific diagnostic reagent in order to differentiate infections resulting from APV/C from those induced by APV/A, APV/B, and human metapneumovirus (hMPV). When the recombinant baculovirus was used to infect insect cells, a 31- to 38-kDa glycosylated form of the SH protein was produced and subsequently tested for reactivity with antibodies specific for APV/A, APV/B, APV/C, and hMPV. Western blot analysis showed that the expressed recombinant SH protein could only be recognized by APV/C-specific antibodies. This result was consistent with sequence analysis of the APV/C SH protein, which had very low (24%) amino acid identity with the corresponding protein of hMPV and no discernible identity with the SH protein of APV/A or APV/B. A recombinant SH protein-based enzyme-linked immunosorbent assay (ELISA) was developed, and it further confirmed the lack of reactivity of this protein with antisera raised to APV/A, APV/B, and hMPV and supported its designation as a subgroup-specific antigen. This finding indicated that the recombinant SH protein was a suitable antigen for ELISA-based detection of subgroup-specific antibodies in turkeys and could be used for serologically based differential diagnosis of APV and hMPV infections.

Amino Acid Sequence↗

PubMed2005

Involvement of a short interspersed element in epigenetic transcriptional silencing of the amoebapore gene in Entamoeba histolytica.

Transcriptional silencing of an amoebapore (ap-a) gene occurred in Entamoeba histolytica following the transfection of plasmids containing a DNA segment (473 bp) homologous to the 5' upstream region of the gene (R. Bracha, Y. Nuchamowitz, and D. Mirelman, Eukaryot. Cell 2:295-305, 2003). This segment contains the promoter region of the ap-a gene, a T-rich stretch, followed by a truncated SINE1 (short interspersed element 1) that is transcribed from the antisense strand. Transfection of plasmids containing truncated SINE1 sequences which lack their 3' regulatory elements upstream of the ap-a gene was essential for the downstream silencing of the ap-a gene while transfection with plasmids containing the entire SINE1 sequence or without the T-rich stretch promoted the overexpression of the ap-a gene. Both the T-rich stretch and sequences of the 5' SINE1 were essential for the transcription of SINE1. RNA extracts from gene-silenced cultures showed small amounts of short (approximately 140-nucleotide), single-stranded molecules with homology to SINE1 but no short interfering RNA. Chromatin immunoprecipitation analysis with an antibody against methylated K4 of histone H3 showed a demethylation of K4 at the domain of the ap-a gene, indicating transcriptional inactivation. These results suggest the involvement of SINE1 in triggering the gene silencing and the role of histone modification in its epigenetic maintenance.

Animals↗

PubMed2005

Solution structure of the carbon storage regulator protein CsrA from Escherichia coli.

The carbon storage regulator A (CsrA) is a protein responsible for the repression of a variety of stationary-phase genes in bacteria. In this work, we describe the nuclear magnetic resonance (NMR)-based structure of the CsrA dimer and its RNA-binding properties. CsrA is a dimer of two identical subunits, each composed of five strands, a small alpha-helix and a flexible C terminus. NMR titration experiments suggest that the beta1-beta2 and beta3-beta4 loops and the C-terminal helix are important elements in RNA binding. Even though the beta3-beta4 loop contains a highly conserved RNA-binding motif, GxxG, typical of KH domains, our structure excludes CsrA from being a member of this protein family, as previously suggested. A mechanism for the recognition of mRNAs downregulated by CsrA is proposed.

Amino Acid Sequence↗

PubMed2005

Human coronavirus NL-63 infections in children: a 1-year study.

Human coronavirus NL63 (HCoV-NL63), a newly discovered coronavirus, has been associated with acute respiratory tract infections (ARI). Important questions pertaining to the contribution of HCoV-NL63 to ARI and its impact on public health remain. We reviewed HCoV-NL63 in specimens collected from 13 November 2002 to 31 December 2003 from the Stollery Children's Hospital on patients of <17 years of age to assess the role of this virus in ARI in children. Twenty-six of 1,240 specimens (2.1%) from seven outpatients and 19 inpatients aged 7 days to 9.5 years tested positive for HCoV-NL63 by reverse transcription-PCR. The majority of outpatients (86%) had upper respiratory tract infections, while the majority of inpatients (58%) had bronchiolitis. Peak HCoV-NL63 activity occurred in March. These results provide further evidence of the importance of HCoV-NL63 in ARI in children.

Alberta↗

PubMed2005

Evidence for NF-kappaB- and CBP-independent repression of p53's transcriptional activity by human T-cell leukemia virus type 1 Tax in mouse embryo and primary human fibroblasts.

The human T-cell leukemia virus type 1 (HTLV-1) Tax oncoprotein can repress the transcriptional activity of the tumor suppressor protein p53. However, it remains controversial whether Tax requires NF-kappaB factors/activity and/or p300/CBP in order to inactivate p53 function. To address this issue, we have investigated Tax's effect on p53's transcriptional activation in IkappaB-kinase-deficient mouse embryonic fibroblasts (MEFs); some of which are entirely silent for Tax-induced NF-kappaB activity. We found that, in IKKalpha-/-, IKKbeta-/-, and IKKgamma-/- MEFs, p53 activation of a prototypic responsive plasmid (pG13-luciferase) was repressed by wild-type Tax. Curiously, p53's activity in MEFs was also repressed by a p300/CBP-binding deficient Tax protein. Our results highlight the complex nature of Tax-mediated repression of p53- activity, which requires further investigation.

Animals↗

PubMed2005

Phase transition of nanostructure zirconias doped with rare earth elements.

Nanostructure zirconias doped with rare earth elements were obtained by coprecipitation. The morphology, structure, and phase transition of the as-prepared samples were studied. According to transmission electron microscopy, the particles appear in near spherical shape and have a mean particle sizes of about 150 nm without change with the rare earth elements. From laser Raman and X-ray diffraction results, it is known that the tetragonal phase of zirconia is stabilized by a certain concentration of the rare earth dopants, and the cubic phase is obtained if enough dopants are added. The crystal lattice increases with the increase of dopant concentration. Moreover, the heavy rare earths are better than the light ones in stabilizing effect. According to our study, laser Raman is more sensitive than X-ray diffraction in monitoring the phase transition.

Crystallization↗

PubMed2005

Racial differences in the progression of cognitive decline in Alzheimer disease.

OBJECTIVE: Alzheimer disease (AD) is the leading cause of dementia in older persons, but little is known about racial differences in its clinical manifestations. The purpose of the current study was to examine the association of race with rate of cognitive decline in AD. METHODS: Older persons with clinically diagnosed AD were recruited from healthcare settings. At 6-month intervals for up to 4 years, they completed a battery of nine cognitive tests from which a previously established measure of global cognition was derived. Follow-up data were available on 452 participants (27.6% African American, 68.8% women), 88.1% of those eligible. RESULTS: A growth curve approach was used to estimate individual paths of change in global cognition. In a model that controlled for age and education, African Americans had a lower level of global cognition at baseline than non-African Americans, but declined at a 25% slower rate on average. In additional models, there was no indication that the association of race with cognitive decline varied by age, gender, or education. CONCLUSION: The rate of cognitive decline in AD appears to be slower in African Americans than non-African Americans.

Adult↗

PubMed2005

Isolation of a human intestinal bacterium that transforms mangiferin to norathyriol and inducibility of the enzyme that cleaves a C-glucosyl bond.

The C-glucosyl bond of C-glucosides generally tolerates acid and enzymatic hydrolysis. Many C-glucosides are cleaved by human intestinal bacteria. We isolated the specific bacterium involved in the metabolism of mangiferin (2-beta-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone), C-glucosyl xanthone, from a mixture of human fecal bacteria. The anaerobic Bacteroides species named MANG, transformed mangiferin to the aglycone, norathyriol, suggesting cleavage of a C-glucosyl bond. However, B. sp. MANG cleaved C-glucosyl in a dose- and time-dependent manner only when cultivated in the presence of mangiferin. Cleavage was abolished by inhibitors of RNA and protein syntheses, such as rifampicin and chloramphenicol, respectively, indicating that the enzyme that cleaves C-glucosyl is induced by mangiferin. In contrast, mangiferin did not affect bacterial alpha- and beta-glucosidase activities under any conditions. The C-glucosyl-cleavage in cell-free extracts was not altered by potent glucosidase inhibitors such as 1-deoxynojirimycin and gluconolactone. Therefore, the C-glucosyl-cleaving enzyme substantially differs from known glucosidases that cleave O-glucosides. This is the first description of a specific intestinal bacterium that is involved in the metabolism of mangiferin and which produces a novel and inducible C-glucosyl-cleaving enzyme.

Antiviral Agents↗

PubMed2005

Blood pressure reduction and cardiovascular prevention: an update including the 2003-2004 secondary prevention trials.

In a meta-analysis published in June 2003, we reported that new and old classes of antihypertensive drugs had similar long-term efficacy and safety. Furthermore, we observed that in clinical trials in hypertensive or high-risk patients gradients in systolic blood pressure (SBP) accounted for most differences in outcome. To test whether our previous conclusions would hold, we updated our quantitative overview with new information from clinical trials published before 2005. To compare new and old antihypertensive drugs, we computed pooled odds ratios from stratified 2 x 2 contingency tables. In a meta-regression analysis, we correlated these odds ratios with corresponding between-group differences in SBP. We then contrasted observed odds ratios with those predicted from gradients in SBP. The main finding of our overview was that reduction in SBP largely explained cardiovascular outcomes in the recently published actively controlled trials in hypertensive patients and in placebo-controlled secondary prevention trials. The published results suggested that dihydropyridine calcium-channel blockers might offer a selective benefit in the prevention of stroke and inhibitors of the renin-angiotensin system in the prevention of heart failure. For prevention of myocardial infarction, the published results were more equivocal, because of the benefit of amlodipine over placebo or valsartan in 2 trials, whereas other placebo-controlled trials of calcium-channel blockers or angiotensin converting enzyme inhibitors did not substantiate the expected benefit with regard to cardiac outcomes. In conclusion, the hypothesis that new antihypertensive drugs might influence cardiovascular prognosis over and beyond their antihypertensive effect remains unproven. Our overview emphasizes the need of tight blood pressure control, but does not allow determining to what extent blood pressure must be lowered for optimal cardiovascular prevention.

Antihypertensive Agents↗

PubMed2005

DNA sequence comparative analysis of the 3pter-p26 region of human genome.

Most proterminal regions of human chromosomes are GC-rich and gene-rich. Chromosome 3p is an exception. Its proterminal region is GC-poor, and likely to lose heterozygosity, thus causing a number of fatal diseases. Except one gap left in the telomeric position, the proterminal region of human chromosome 3p has been completely sequenced. The detailed sequence analysis showed: (i) the GC content of this region was 38.5%, being the lowest among all the human proterminal regions; (ii) this region contained 20 known genes and 22 predicted genes, with an average gene size of 97.5 kb. The previously mapped gene Cntn3 was not found in this region, but instead located in the 74 Mb position of human chromosome 3p; (iii) the interspersed repeats of this region were more active than the average level of the whole human genome, especially (TA)n, the content of which was twice the genome average; (iv) this region had a conserved synteny extending from 104.1 Mb to 112.4 Mb on the mouse chromosome 6, which was 8% larger in size, not in accordance with the whole genome comparison, probably because the 3pter-p26 region was more likely to lose nucleotides and its mouse synteny had more active interspersed repeats.

Animals↗

PubMed2005

The impact of NiO on microstructure and electrical property of solid oxide fuel cell anode.

Ni-Ce(0.8)Sm(0.2)O(1.9) (Ni-SDC) cermet was selected as anode material for reduced temperature (800 degrees C) solid oxide fuel cells in this study. The influence of NiO powder fabrication methods for Ni-SDC cermets on the electrode performance was investigated so that the result obtained can be applied to make high-quality anode. Three kinds of NiO powder were synthesized with a fourth kind being available in the market. Four types of anode precursors were fabricated with these NiO powders and Ce(0.8)Sm(0.2)O(1.9) (SDC), and then were reduced to anode wafers for sequencing measurement. The electrical conductivity of the anodes was measured and the effect of microstructure was investigated. It was found that the anode electrical conductivity depends strongly on the NiO powder morphologies, microstructure of the cermet anode and particle sizes, which are decided by NiO powder preparation technique. The highest electrical conductivity is obtained for anode cermets with NiO powder synthesized by NiCO(3).2Ni(OH)(2).4H(2)O or Ni(NO(3))(2).6H(2)O decomposition technique.

Electric Impedance↗

PubMed2005

Inhibition of superoxide generation and associated nitrosative damage is involved in metallothionein prevention of diabetic cardiomyopathy.

The mechanisms of metallothionein prevention of diabetic cardiomyopathy are largely unknown. The present study was performed to test whether inhibition of nitrosative damage is involved in metallothionein prevention of diabetic cardiomyopathy. Cardiac-specific metallothionein-overexpressing transgenic (MT-TG) mice and wild-type littermate controls were treated with streptozotocin (STZ) by a single intraperitoneal injection, and both developed diabetes. However, the development of diabetic cardiomyopathy, revealed by histopathological and ultrastructural examination, serum creatine phosphokinase, and cardiac hemodynamic analysis, was significantly observed only in the wild-type, but not in MT-TG, diabetic mice 2 weeks and 6 months after STZ treatment. Formations of superoxide and 3-nitrotyrosine (3-NT), a marker for peroxynitrite-induced protein damage, were detected only in the heart of wild-type diabetic mice. Furthermore, primary cultures of cardiomyocytes from wild-type and MT-TG mice were exposed to lipopolysaccharide/tumor necrosis factor-alpha for generating intracellular peroxynitrite. Increases in 3-NT formation and cytotoxicity were observed in wild-type, but not in MT-TG, cardiomyocytes. Either urate, a peroxynitrite-specific scavenger, or Mn(111) tetrakis 1-methyl 4-pyridyl porphyrin pentachloride (MnTMPyP), a superoxide dismutase mimic, significantly inhibited the formation of 3-NT along with a significant prevention of cytotoxicity. These results thus suggest that metallothionein prevention of diabetic cardiomyopathy is mediated, at least in part, by suppression of superoxide generation and associated nitrosative damage.

Animals↗

PubMed2005

[Development of rAAV2-GAD-Ig for IDDM gene therapy].

AIM: To develop rAAV2 containing cDNA of GAD-Ig fusion gene [GAD-Ig fusion gene is constructed by inserting glutamic acid decarboxylase(GAD) into N-terminal of murine IgG3 heavy chain(Ig)], and to study whether rAAV2 mediated GAD-Ig fusion gene expression could induce specific tolerance in IDDM animal model-nonobese diabetic (NOD) mice. METHODS: GAD-Ig cDNA was amplified by PCR from the plasmid BSSK-GAD-Ig and inserted into an eukaryotic expression plasmid pSNAV to construct a recombinant expression plasmid pSNAV/GAD-Ig. Plasmid pSNAV-GAD-Ig was then transfected into the rAAV2 packaging cell-BHK-21 cells using LipofectAMINE TM 2000 to produce rAAV-GAD-Ig. Target gene expression in BHK-21 cells infected by rAAV-GAD-Ig was confirmed by RT-PCR, Western blot and ELISA respectively. Then rAAV-GAD-Ig was injected into intramuscularly NOD mice. Antigen-specific tolerance in NOD mice was detected by specific lymphocytic proliferation reaction to GAD antigen. RESULTS: GAD-Ig gene was inserted into the genome of target cells. Target cells transfected by rAAV2-GAD-Ig could secret GAD-Ig. rAAV2-GAD-Ig induced specific tolerance in NOD mice. CONCLUSION: rAAV2-GAD-Ig was obtained, which can be used in IDDM gene therapy in NOD mice.

Animals↗

PubMed2005

[Construction and expression of anti-human CD3 chimeric antibody gene and preliminary study of expressed product].

AIM: To construct and express anti-human CD3 chimeric antibody. METHODS: The genes of variable regions of the light chain (V(L)) and heavy chain (V(H)) were cloned respectively into the expression vectors (V(L) Express, V(H) Express), and co-transfected into COS-7 cells. Expression level of the chimeric antibody in culture supernatant was detected by ELISA. The antibody was purified through protein A affinity chromatography and identified by Western blot. Binding activity of the chimeric antibody to the antigen was determined by FACS. Biological activity of the chimeric antibody was determined by mixed T-lymphocyte culture test. RESULTS: The expression vectors were constructed and the anti-human CD3 chimeric antibody was expressed and purified successfully. Western blot showed that the purified antibody was human-mouse chimeric antibody. FACS result showed that the chimeric antibody had antigen-binding activity. Mixed T-lymphocyte culture test showed that the chimeric antibody could suppress proliferation of T lymphocytes. CONCLUSION: The anti-human CD3 chimeric antibody has been constructed and expressed successfully, which lays the foundation for its further study.

Animals↗

PubMed2005

[Preparation of monoclonal antibodies against multiple antigens].

OBJECTIVE: To prepare monoclonal antibodies (mAbs) against multiple antigens by single cell fusion. METHODS: BALB/c mice were immunized with the multiple antigens, namely alpha fetoprotein (AFP), carcinoembryonic antigen (CEA), HBsAgiHBcAg and HBeAg, and hybridomas were employed using PEG as the fusing agent. The hybridoma cells were respectively screened with AFP, CEA, HBsAg, HBcAg and HBeAg by enzyme-linked immunosorbent assay and limited dilution. The mAbs were purified by protein G affinity chromatography, its subtype was identified, the affinity constants (K(a)) were determined and the specificity was analyzed by Western blotting. RESULTS: Twenty hybridoma cell lines were obtained by single cell fusion, including 5 cell lines against AFP, 6 against CEA, 3 against HBsAg, 4 against HBcAg, and 2 against HBeAg. The subtypes of some hybridoma cell lines positive for the mAbs were identified as the immunoglobulin G1 (IgG1), with K(a) ranging from 1x10(9) M(-1) to x10(11) M(-1). Western blot analysis showed that all the mAbs strongly and specifically bound to their respective antigens. CONCLUSION: The mAbs against multiple antigens have been obtained by single cell-fusion, which increases the production of mAbs and reduces the time of preparation.

Animals↗

PubMed2005

[Correlation of matrix metalloproteinase-3 polymorphism to genetic susceptibility and lymph node metastasis of non-small cell lung cancer].

BACKGROUND & OBJECTIVE: Matrix metalloproteinases (MMPs) might be involved in invasion and metastasis of tumors by degrading extracellular matrix (ECM) and basement membrane (BM). The 5A or 6A single nucleotide polymorphism (SNP) at the -1 171 bp site of promoter region of MMP-3 may modify the transcription and local expression of MMP-3. This study was to investigate correlation of the MMP-3 SNP with genetic susceptibility and lymph node metastasis of non-small cell lung cancer (NSCLC). METHODS: Genotypes of the MMP-3 SNP of 173 NSCLC patients and 350 healthy controls were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: Distributions of the MMP-3 genotypes in both NSCLC patients and healthy controls were accorded with Hardy-Weinberg equilibrium (P>0.05). Frequencies of the 6A/6A, 5A/6A, and 5A/5A genotypes were 65.3%, 30.6%, and 4.1% in NSCLC patients, and 67.7%, 30.0%, and 2.3% in healthy controls, whereas frequencies of the 6A and 5A alleles were 79.3% and 20.7% in NSCLC patients, and 82.7% and 17.3% in healthy controls. The overall genotype and allelotype distributions among NSCLC patients and healthy controls were similar (P>0.05). However, stratified analysis found that frequency of the 5A allele was significantly higher in smoking patients than in healthy smokers (21.0% vs. 12.9%, P=0.03). Therefore, smokers with the 5A/6A or 5A/5A genotype have higher risk of developing NSCLC [age and sex adjusted odds ratio (OR) =2.07, 95% confidence interval (CI) =1.13-3.78]. When stratified by pathologic types, no significant difference in MMP-3 genotype or allelotype distribution between adenocarcinoma patients, squamous carcinoma patients and healthy controls was shown. When further stratified by lymphatic metastasis status, frequencies of the 5A allele and the 5A/5A genotype were significantly higher in NSCLC patients with lymphatic metastasis than in NSCLC patients without lymphatic metastasis (22.8% vs. 11.8%, P=0.02u 8.6% vs. 0%, P=0.02). Thus, NSCLC patients with the 5A/5A genotype have higher risk of lymphatic metastasis than NSCLC patients with the 6A/6A genotype (OR=12.38, 95% CI=0.76-202.13). CONCLUSIONS: The 5A allele of MMP-3 might be associated with the increased susceptibility to NSCLC among smokers. The 5A homozygote might increase the risk of lymphatic metastasis in NSCLC patients.

Alleles↗

PubMed2005

[Changes in content of plasma brain natriuretic peptide in dilated cardiomyopathy in rabbits].

OBJECTIVE: To determine the changes in plasma brain natriuretic peptide (BNP) in adriamycin-induced dilated cardiomyopathy (DCM) in rabbit, and to evaluated the significance. METHODS: Twenty-two rabbits were randomly divided into control group (n=10) and model group(n=12). The DCM model was reproduced by injecting adriamycin via ear vein for 8 weeks. Echocardiogram was performed and plasma BNP were measured before administration, and at 8 th and 11 th week after the challenge. Indexes of hemodynamics and pathological changes were observed. RESULTS: Indexes of echocardiogram and hemodynamics of model group were consistent with pathologic changes of DCM. Plasma levels of BNP of the model group were increased significantly after administration of the drug(all P<0.01), though the values before the drug administration were approximately the same as in the control group. Plasma BNP levels were significantly higher in DCM group at the 11 th week than at the 8 th week (P<0.05). Plasma levels of BNP were positively correlated with and left ventricular end-diastolic volume(LVEDV), left ventricular end-systolic volume (LVESV), left ventricular end-diastolic pressure(LVEDP) and negatively correlated with left ventricular systolic pressure(LVSP), and left ventricular ejection fraction (LVEF). CONCLUSION: Administration of intravenous adriamycin to rabbits results in DCM which in suitable for the conduction of research of neuroendocrine abnormality of heart. Overload of the left ventricle and increasing tension of left ventricular wall are key factors for regulating BNP excretion. Plasma BNP level is a good marker for evaluating degree of severity of cardiac function in DCM.

Animals↗

PubMed2005

[Experimental study of adoptive immunotherapy using CD3AK cells].

AIM: To analyze the immunological properties and biological activity of a monoclonal antibody (mAb) against CD3 molecule(yCD3), and to observe the tumor-suppressive activity of CD3AK cells in vitro and in vivo. METHODS: FCM was used to test the specificity of yCD3 and the immunological phenotype and cytokine production of CD3AK. 3H-TdR assay was used to measure the transformation of lymphocytes activated by yCD3. LDH assay was used to analyze the cytotoxic activity of CD3AK in vitro. Mice bearing tumors were used to observe the anti-tumor effect of CD3AK cells. RESULTS: yCD3 could bind specifically to T cells. 5 microg yCD3 could competitively inhibit 70% of standard anti-CD3 antibody to bind with CD3 molecules on cell membrane. 8 microg/L of yCD3 stimulated the proliferation of peripheral blood lymphocytes, which could be further boosted by IL-2 or anti-CD28 antibodies. Among activated CD3AK cells, CD3+, CD8+, and CD25+ cells increased. IL-2 and IFN-gamma producing CD3+ cells were also increased, to 3.29- and 2.47- fold, respectively, under the co-stimulation of anti-CD28 antibody. When the ratio of effective cells and target cells was 80:1, 57.54% target cells were killed. As compared with control, the percent of tumor inhibition in CD3AK cells treated tumor-bearing mice was 33.17%, and the inhibition rate of lung metastasis was 39.70%. The CD3AK cells treatment was more effective when combined with LAK cells. CONCLUSION: yCD3 could activate T cells and significantly induce the tumor-suppressive activity of CD3AK cells in vitro and in vivo, which lays a foundation for adoptive immunotherapy against tumors in clinical medicine.

Animals↗