Biomedical subjects

Wei Li

Publications and source records attributed to Wei Li.

At least 127 records · Page 7Linked to original sources

PubMed2006

Detection of known thalassemia point mutations by snapback single-strand conformation polymorphism: the feasibility analysis.

OBJECTIVES: To explore if snapback single-strand conformation polymorphism (snapback SSCP) can be applied to the detection of known thalassemia point mutations. DESIGN AND METHODS: We examined 13 types of known thalassemia point mutations by using snapback SSCP. RESULTS: These 13 different thalassemia point mutations could be identified by snapback SSCP. CONCLUSIONS: Snapback SSCP can be applied to the detection of known thalassemia point mutations. The advantages of snapback SSCP are (1) it is simple as compared to PCR-ASO; (2) snapback SSCP is specific and stable once the conditions of snapback SSCP are optimized; (3) samples can be checked at any time without the limit of half-life of radioactive isotope; and (4) since PCR products used in snapback SSCP can be checked by using 2% agarose gel before snapback SSCP, misdiagnoses caused by false positive or false negative PCR can be reduced significantly in snapback SSCP.

Base Sequence↗

PubMed2006

Microcystin-RR-induced apoptosis in tobacco BY-2 cells.

Our previous studies showed that microcystin-RR could induce oxidative damage in plant cells as they do with animal cells. However, whether microcystin can induce plant cell apoptosis is still unknown. In this study, the morphological changes of tobacco BY-2 suspension cells exposed to microcystin-RR were observed under light microscopy and transmission electron microscopy, and apoptosis was clearly distinguished by intense perinuclear chromatin margination, condensation of nuclear chromatin after 6d exposure of 50mg/L (about 50microM) microcystin-RR. We also found that microcystin-RR can induce tobacco cell apoptosis in a dose- and time-dependent manner with flow cytometry analysis. Our study provides the first evidence that microcystins can induce plant cell apoptosis.

Apoptosis↗

PubMed2006

Brownian dynamics simulation of directional sliding of histone octamers caused by DNA bending.

Chromatin-remodeling complexes such as SWI/SNF and RSC of yeast can perturb the structure of nucleosomes in an ATP-dependent manner. Experimental results prove that this chromatin remodeling process involves DNA bending. We simulate the effect of DNA bending, caused by chromatin-remodeling complexes, on directional sliding of histone octamers by Brownian dynamics simulation. The simulation results show that, after a DNA loop being generated at the side of a nucleosome, the histone octamer slides towards this DNA loop until the loop disappears. The DNA loop size is an important factor affecting the process of directional sliding of the histone octamer.

Anisotropy↗

PubMed2006

Highly efficient photoactivation of Mn-depleted photosystem II by imidazole-liganded manganese complexes.

The oxygen-evolving complex (OEC) of Mn-depleted photosystem II (PSII) can be reconstituted in the presence of exogenous Mn or a Mn complex under weak illumination, a process called photoactivation. Synthetic Mn complexes could provide a powerful system to analyze the assembly of the OEC. In this work, four mononuclear Mn complexes, [(terpy)2Mn(II)(OOCH3)] x 2 H2O (where terpy is 2,2':6',2''-terpyridine), Mn(II)(bzimpy)2, Mn(II)(bp)2(CH3CH2OH)2 [where bzimpy is 2,6-bis(2-benzimidazol-2-yl)pyridine] and [Mn(III)(HL)(L)(py)(CH3OH)]CH3OH (where py is pyridine) were used in photoactivation experiments. Measurements of the photoreduction of 2,6-dichorophenolindophenol and oxygen evolution demonstrate that photoactivation is more efficient when Mn complexes are used instead of MnCl2 in reconstructed PSII preparations. The most efficient recoveries of oxygen evolution and electron transport activities are obtained from a complex, [Mn(III)(HL)(L)(py)(CH3OH)]CH3OH, that contains both imidazole and phenol groups. Its recovery of the rate of oxygen evolution is as high as 79% even in the absence of the 33-kDa peptide. The imidazole ligands of the Mn complex probably accelerate P680*+ reduction and consequently facilitate the process of photoactivation. Also, the strong intermolecular hydrogen bond probably facilitates interaction with the Mn-depleted PSII via reorganization of the hydrogen-bonding network, and therefore promotes the recovery of oxygen evolution and electron transport activities.

Electron Transport↗

PubMed2006

Determination of omeprazole in rat plasma by high-performance liquid chromatography without solvent extraction.

A HPLC method without solvent extraction and using ultraviolet detection at 302 nm for the determination of omeprazole in rat plasma has been validated. Plasma samples after pretreatment with acetonitrile to effect deproteinization were dried under N(2) at 40 degrees C and reconstituted with mobile phase. The standard calibration curve for omeprazole was linear (r(2)=0.9999) over the concentration range of 0.02-3 microgml(-1). The intra- and inter-day assay variability range was 4.8-9.2% and 5.2-10.3% individually. This method has been successfully applied to a pharmacokinetic study of omeprazole in rats.

Animals↗

PubMed2006

Transforming growth factor-alpha: a major human serum factor that promotes human keratinocyte migration.

In unwounded skin, human keratinocytes (HKs) are in contact with a plasma filtrate. In an acute wound, HKs come in contact with serum for the first time. Because human serum (HS), but not plasma, promotes HK migration, we speculated that a major HK pro-motility factor in vivo comes from serum. In this study, we compared all of the published growth factors (GFs), reported to promote HK migration, with HS. No single GF could duplicate the HK pro-motility activity in HS. Among these GFs, transforming growth factor-alpha [corrected] showed the highest HK pro-motility activity, reaching approximately 80% of the activity in HS. The order of potency was: TGFalpha > insulin > EGF > heparin binding (HB)-EGF > IGF-1 > basic fibroblast growth factor >IL-8 > HGF > IL-1 > KGF>TGFbeta. Interestingly, the combination of TGFalpha and insulin could duplicate the HK pro-motility activity in HS, although only the TGFalpha, but not insulin, levels increase in serum over plasma. Addition of neutralizing antibodies against TGFalpha to serum or depletion of TGFalpha from serum by immunoprecipitation significantly abolished its HK pro-motility activity. Plasma with added TGFalpha stimulated HK migration that reached more than 80% of the serum stimulation. Since insulin levels are identical between plasma and serum, we propose that TGFalpha is the physiologic HK pro-motility factor in HS.

Cell Movement↗

PubMed2006

Enhancement of NKT cells and increase in regulatory T cells results in improved allograft survival.

BACKGROUND: Natural killer T (NKT) cells can serve as regulatory cells important in peripheral tolerance. In an experimental colitis model, it was shown that FK506 enhances the tolerizing effect of regulatory NKT cells induced by oral tolerance. We explored whether a subtherapeutic dose of FK506 could enhance the tolerizing effect of NKT cells induced by oral administration of donor spleen cells (SCs) in the pre-transplant period to prolong heart allograft survival. METHODS: Heterotopic heart transplantation was performed from BALB/c to B6 mice. The B6 recipients were pre-treated with either BALB/c SCs (2 x 10(7)/mouse), or FK506 (1.0 mg/kg/d), or BALB/c SCs + FK506 by gavage every other day for a total of five feedings before transplantation. RESULTS: Heart allograft survival was only significantly prolonged in the BALB/c SC + FK506 pre-fed mice. This was associated with a marked increase of NKT cells in both the liver and spleen of the recipients, and most importantly, 7 days after transplantation, an increase in CD25+CD4+ T cells expressing CTLA4 in the spleen. CONCLUSIONS: In our model it appears that a subtherapeutic dose of FK506 enhanced the tolerizing effect of NKT cells induced by oral tolerance, prolonging allograft survival by generating CD25+CD4+ CTLA4 T cells. This appears to be an excellent in vivo model to generate regulatory T cells to allospecific transplant antigens.

Animals↗

PubMed2006

Inhibitory effect of medroxyprogesterone acetate on human liver cytochrome P450 enzymes.

OBJECTIVE: Medroxyprogesterone acetate (MPA), frequently used in contraception and chemotherapy, was involved in a report of drug-drug interaction (DDI) when co-administrated with phenytoin, doxifluridine and cyclophosphamide. In order to clarify the mechanism of such interaction, an in vitro study was undertaken to evaluate MPA's potential to inhibit cytochrome P450 (CYP) enzymes. METHODS: Inhibitory effects of MPA on seven CYPs, including CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2D6, CYP2E1 and CYP3A4, were conducted in human liver microsomes. Time- and NADPH-dependent inhibitions were also tested. DDI potential was predicted according to the [I]/K ( i ) value. RESULTS: MPA was found to inhibit CYP2C9 and CYP3A4; half inhibition concentration (IC(50)) was 16.1 microM and 31.5 microM, respectively. Slight inhibition was observed on CYP1A2, CYP2A6, CYP2C8 and CYP2D6 with IC(50) of more than 100 microM. MPA exhibited activation rather than inhibition on CYP2E1. Further study revealed that MPA showed a noncompetitive inhibition on CYP2C9 and a competitive inhibition on CYP3A4 with K ( i ) of 9.0 microM and 36 microM, respectively. In addition, MPA was not a mechanism-based inhibitor to any of seven isoforms tested. By using predicted concentration of MPA in liver, [I]/K ( i ) was estimated to be 0.24 and 0.06 for CYP2C9 and CYP3A4, respectively. The concentration of phenytoin co-administrated with MPA was calculated to increase by 24%. CONCLUSION: Based on our results, MPA can possibly cause clinically relevant DDI via the inhibition of CYP2C9.

Adult↗

PubMed2006

Molecular cloning and expression analysis of a hepcidin antimicrobial peptide gene from turbot (Scophthalmus maximus).

Antimicrobial peptides (AMPs) are regarded as important components of the host innate immune system and play crucial roles in host defence against microbial invasion. A small number of hepcidin AMPs have been isolated from teleosts. Here, we report the isolation of a hepcidin gene from the liver of turbot (Scophthalmus maximus) (GenBank accession numbers: and ). In the 1037 bp-long genomic sequence, three exons and two introns were identified. The full-length cDNA is 778bp long and contains an ORF of 273bp encoding a prepropeptide of 90 amino acid residues. The predicted prepropeptide consists of three domains: a signal peptide (24 amino acids), a prodomain (40 amino acids) and a mature peptide (26 amino acids). RT-PCR demonstrated that hepcidin transcripts were highly abundant in liver, abundant in heart, head kidney, spleen, skin and gill, less abundant in blood cell, gonad and intestine, and undetectable level in muscle. The level of the hepcidin mRNA in embryos gradually increases during embryogenesis from 2 h (2 cell stage) to 95 h (larva stage) after fertilisation. Challenge of turbot with pathogenic bacteria, Listonella anguillarum, significantly elevated hepcidin mRNA levels in liver and spleen in a time-dependent fashion. The hepcidin transcripts were detected in turbot embryonic cell line (TEC). Challenge of TEC cells with the pathogenic bacteria significantly elevated hepcidin mRNA levels.

Amino Acid Sequence↗

PubMed2006

Desymmetrization of diols by a tandem oxidation/Wittig olefination reaction.

Diols are desymmetrized by a tandem oxidation/Wittig olefination to give alpha,beta-unsaturated hydroxy esters without the requirement for protecting group strategies; the alpha,beta-unsaturated hydroxy esters are transformed into dienyl diesters using a second oxidation/Wittig olefination sequence using PCC.

Alkenes↗

PubMed2006

Screening of single-chain variable fragments against TSP50 from a phage display antibody library and their expression as soluble proteins.

A novel gene, testes-specific protease 50 (TSP50), is abnormally activated and differentially expressed in most patients with breast cancer, suggesting it as a novel biomarker for this disease. The possibility that TSP50 may be an oncogene is presently under investigation. In this study, the single-chain variable fragments (scFvs) against TSP50 were panned from a phage display antibody library using TSP50-specific peptide, pep-50, as a target antigen. After 4 rounds of panning, 3 clones (A1, A11, and C8) from the library were verified to show strong binding affinities for TSP50 by enzyme-linked immunosorbent assay (ELISA) and to contain the variable region genes of the light and heavy chains of scFv antibodies but different complementary determining regions by sequencing. The genes of scFv-A1 and scFv-A11 were cloned into expression vector pPELB and successfully expressed as a soluble protein inEscherichia coli Rosetta. The yields of expressions were about 4.0 to 5.0 mg of protein from 1 L of culture. The expressed proteins were purified by a 2-step procedure consisting of ion-exchange chromatography, followed by immobilized metal affinity chromatography. The purified proteins were shown a single band at the position of 31 KDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Sandwich ELISA demonstrated that the expressed scFv proteins were able to specifically react with pep-50, laying a foundation for the investigation of the function of TSP50 in the development and treatment of breast cancer.

Animals↗

PubMed2006

A fragment energy assembler method for Hartree-Fock calculations of large molecules.

We present a fragment energy assembler approach for approximate Hartree-Fock (HF) calculations of macromolecules. In this method, a macromolecule is divided into small fragments with appropriate size, and then each fragment is capped by its neighboring fragments to form a subsystem. The total energy of the target system is evaluated as the sum of the fragment energies of all fragments, which are available from conventional HF calculations on all subsystems. By applying the method to a broad range of molecules, we demonstrate that the present approach could yield satisfactory HF energies for all studied systems.

Journal Article↗

PubMed2006

Separation of phospholipids by capillary zone electrophoresis with indirect ultraviolet detection.

A simple method for separation of different anionic and zwitterionic phospholipid classes by capillary zone electrophoresis (CZE), using indirect UV detection with adenosine monophosphate (AMP) as background electrolyte and the UV-absorbing additive, was successfully developed in this study. The separation conditions including apparent pH (pH*) of running buffer, concentration of AMP, organic solvent, applied voltage and capillary temperature were systematically optimized. The application of this method to human blood sample was also briefly examined.

Adenosine Monophosphate↗

PubMed2006

Activation of individual alphaIIbbeta3 integrin molecules by disruption of transmembrane domain interactions in the absence of clustering.

We used laser tweezers-based force spectroscopy to measure the binding strength between fibrinogen molecules covalently bound to latex beads and either wild-type alphaIIbbeta3 molecules or alphaIIbbeta3 molecules containing the transmembrane domain mutations beta3 G708N or alphaIIb G972N expressed on Chinese hamster ovary cells. As we demonstrated previously for alphaIIbbeta3 on agonist-stimulated platelets and for purified alphaIIbbeta3 molecules incubated with Mn(2+), two regimes of rupture forces were present when wild-type alphaIIbbeta3 was activated by the monoclonal antibody PT25-2: rupture forces of 20-60 pN with an exponentially decreasing probability of detection and rupture forces in the range of 60-150 pN with a maximum at approximately 70-80 pN. Both rupture force regimes were specific for fibrinogen binding to the activated conformation of alphaIIbbeta3 because they were inhibited by alphaIIbbeta3-specific antagonists. Identical rupture force regimes were present constitutively when cells expressing the alphaIIb and beta3 transmembrane domain mutants were studied, confirming that these mutations induced an active alphaIIbbeta3 conformation. Moreover, there were no significant differences in the yield strength of the low-to-moderate and strong force regimes when alphaIIbbeta3 was activated by PT25-2 or the transmembrane domain mutations, implying that there was no fundamental difference in the way these forms of activated alphaIIbbeta3 interacted with fibrinogen. Thus, the two-step pathway of the interaction of alphaIIbbeta3 with fibrinogen we have identified appears to be a fundamental property of the high-affinity state of alphaIIbbeta3 and is identical regardless of whether this affinity state is achieved by intracellular, extracellular, or membrane-associated events.

Animals↗

PubMed2006

Transcriptional regulatory networks downstream of TAL1/SCL in T-cell acute lymphoblastic leukemia.

Aberrant expression of 1 or more transcription factor oncogenes is a critical component of the molecular pathogenesis of human T-cell acute lymphoblastic leukemia (T-ALL); however, oncogenic transcriptional programs downstream of T-ALL oncogenes are mostly unknown. TAL1/SCL is a basic helix-loop-helix (bHLH) transcription factor oncogene aberrantly expressed in 60% of human T-ALLs. We used chromatin immunoprecipitation (ChIP) on chip to identify 71 direct transcriptional targets of TAL1/SCL. Promoters occupied by TAL1 were also frequently bound by the class I bHLH proteins E2A and HEB, suggesting that TAL1/E2A as well as TAL1/HEB heterodimers play a role in transformation of T-cell precursors. Using RNA interference, we demonstrated that TAL1 is required for the maintenance of the leukemic phenotype in Jurkat cells and showed that TAL1 binding can be associated with either repression or activation of genes whose promoters occupied by TAL1, E2A, and HEB. In addition, oligonucleotide microarray analysis of RNA from 47 primary T-ALL samples showed specific expression signatures involving TAL1 targets in TAL1-expressing compared with -nonexpressing human T-ALLs. Our results indicate that TAL1 may act as a bifunctional transcriptional regulator (activator and repressor) at the top of a complex regulatory network that disrupts normal T-cell homeostasis and contributes to leukemogenesis.

Basic Helix-Loop-Helix Proteins↗

PubMed2006

Identification of CD36 as a new surface marker of marginal zone B cells by transcriptomic analysis.

Follicular (FO) B cells and marginal zone (MZ) B cells belong to the mature B cell population in spleen of mice. To identify new surface markers of these mature B cell subsets, we compared gene expression profiles of FO and MZ B cells by DNA microarray using FACS-sorted mouse FO and MZ B cells. From 14,000 mouse genes, 27 membrane proteins were expressed mainly in MZ B cells while another 22 membrane proteins expressed largely in FO B cells. Using FACS analysis, we identified that CD36, CD68, and CD49e were expressed on MZ B cells but not on FO B cells. In addition, using semi-quantitative PCR, we found that the mRNA of CD131 were much more abundant in MZ B cells. These results revealed new phenotypic properties of MZ and FO B cells, and would facilitate further studies in the differentiation and functions of these mature B cells.

Animals↗

PubMed2006

Bipolar cell pathways for color and luminance vision in a dichromatic mammalian retina.

The mammalian retina is fundamentally dichromatic, with trichromacy only recently emerging in some primates. In dichromats, an array of short wavelength-sensitive (S, blue) and middle wavelength-sensitive (M, green) cones is sampled by approximately ten bipolar cell types, and the sampling pattern determines how retinal ganglion cells and ultimately higher visual centers encode color and luminance. By recording from cone-bipolar cell pairs in the retina of the ground squirrel, we show that the bipolar cell types sample cone signals in three ways: one type receives input exclusively from S-cones, two types receive mixed S/M-cone input and the remaining types receive an almost pure M-cone signal. Bipolar cells that carry S- or M-cone signals can have a role in color discrimination and may contact color-opponent ganglion cells. Bipolar cells that sum signals from S- and M-cones may signal to ganglion cells that encode luminance.

Animals↗

PubMed2006

Elicited antibodies in baboons exposed to tissues from alpha1,3-galactosyltransferase gene-knockout pigs.

BACKGROUND: This study investigates anti-nonGal antibodies (Abs) in baboons after alpha1,3-galactosyltransferase gene-knockout (GalT-KO) pig heart transplantation (Tx). METHODS: Four baboons underwent pig heart Tx under chronic immunosuppression, which was discontinued after graftectomy. During follow-up, one baboon also received a pig splenocyte infusion. Hearts and splenocytes were from GalT-KO pigs (n = 3) or pigs with low Gal expression (Gal-low, n = 2), all of swine leukocyte antigen (SLA) dd haplotype. Several weeks after graftectomy, sera were tested by flow cytometry and cytotoxicity assay on porcine peripheral blood mononuclear cells (PBMC) for elicited anti-nonGal Abs. Sera were adsorbed on a Gal immunoaffinity matrix, and tested for SLA haplotype specificity using PBMC from SLA aa, cc, and dd haplotypes. RESULTS: Before heart Tx, no baboon had anti-nonGal Abs demonstrable by binding or cytotoxicity to GalT-KO PBMC. All four baboons developed anti-nonGal Abs after Tx, demonstrable by flow cytometry, and three sera from baboons showed cytotoxicity to GalT-KO PBMC of SLA(dd) haplotype. After adsorption of anti-Gal Abs, the elicited anti-nonGal Abs showed similar binding to PBMCs from pigs of all three haplotypes (SLA(dd), SLA(aa), SLA(cc)). CONCLUSIONS: Anti-nonGal Abs developed after GalT-KO pig heart Tx into baboons. The most potent of these antibodies appeared to detect antigens shared by the three pig haplotypes tested. It remains unclear whether these antibodies are directed towards shared SLA determinants or other pig antigens, and whether antibodies with specificity for allelic SLA determinants are also present, but at lower titer.

Alleles↗