Biomedical subjects

Qingjun Ma

Publications and source records attributed to Qingjun Ma.

16 recordsLinked to original sources

PubMed2005

Ubiquitination and degradation of the Arg tyrosine kinase is regulated by oxidative stress.

The c-Abl and Arg nonreceptor tyrosine kinases are activated in the response of cells to oxidative stress. The present studies demonstrate that treatment of cells with 0.1 mM H2O2 is associated with increased tyrosine phosphorylation of Arg and little effect on Arg levels. By contrast, exposure to 1.0 mM H2O2 decreased Arg phosphorylation. Treatment with 1.0 mM H2O2 was also associated with ubiquitination and degradation of Arg. The results show that Arg is stabilized in response to 0.1 mM H2O2 by autophosphorylation of Y-261, consistent with involvement of the Arg kinase function in regulating Arg levels. The results further demonstrate that c-Abl-mediated phosphorylation of Arg on Y-261 similarly confers Arg stabilization. In concert with these results, phosphorylation of Arg on Y-261 blocked H2O2-induced ubiquitination and thereby Arg degradation and inactivation. These findings demonstrate that Arg phosphorylation and degradation are differentially regulated by the degree of oxidative stress, and that Arg stability is conferred by phosphorylation of Y-261.

Arginine↗

PubMed2005

Characterization of a monoclonal antibody that antagonizes the function of human endostatin.

Endostatin, a 20-kDa proteolytic fragment of collagen XVIII, is a potent inhibitor of angiogenesis and tumor growth. The anti-angiogenic effects of endostatin include inhibition of endothelial cell migration and proliferation, and inhibition of the activity of MMP2. Structure-function analysis of endostatin that implies this contravention function buried in separate fragments of endostatin introduces new issues into the understanding of the structure-function relationship of endostatin. We developed and characterized a novel murine MAb, 4E7, to human endostatin, which antagonizes the function of endostatin. As we show here, MAb 4E7 blocks the anti-migration/adhesion effects of endostatin in vitro and the anti-angiogenesis effect of endostatin in vivo, but the inhibition effect of endostatin on endothelial cell proliferation is not affected by MAb4E7. These results suggest that the anti-migration and anti-proliferation functions of endostatin may have distinct structural foundations.

Animals↗

PubMed2004

Alkali burn causes aldehyde dehydrogenase 3A1 (ALDH3A1) decrease in mouse cornea.

PURPOSE: Aldehyde dehydrogenase 3A1 (ALDH3A1) is the most abundant soluble protein component in the mouse cornea, produced mainly by corneal epithelial cells. High levels of ALDH3A1 in cornea contribute to maintenance of a stable an d transparent corneal structure. Alkali burn is a common damage to the corneal surface, which produces an alkaline hydrolysis of matrix proteins and induces an inflammatory reaction. Our study was intended to detect changes in ALDH3A1 expression after corneal alkaline burn. METHODS: To address this issue we employed RTQ-PCR to monitor the transcriptional change of ALDH3A1 after alkali burn. We used zymography to test enzyme activity changes of ALDH3A1 in the alkali burn cornea; And SDS-PAGE and mass spectrometry technology were used to verify protein content changes and to identify ALDH3A1 protein. RESULTS: Using zymography, ALDH3A1 enzymic activity was observed to decrease immediately after corneal alkali burn and the levels recovered following healing. Proteins extracted from alkali burned corneas, when run on SDS-PAGE, showed the same sized band (about 54 kDa, which is the molecular weight of ALDH3A1) but in much smaller quantity, compared to normal corneas. This result was further verified by mass spectrometry fingerprinting of the in-gel lysis product. An immediate decrease of ALDH3A1 transcription after alkali burning of the cornea was also found using RTQ-PCR. This level of transcription was gradually restored during healing. CONCLUSIONS: Alkali burn of the corneal surface caused a rapid decrease of ALDH3A1 in the corneal at both the RNA and protein levels, which leads to the loses of the protective component of the corneal surface and makes it vulnerable to further damage. The ALDH3A1 level in the cornea gradually recovered during the healing process. Use of an anti-oxidation reagent as a treatment ingredient for alkali burn of the corneal surface could compensate for the decrease of anti-oxidation protection potential caused by ALDH3A1 loss.

Aldehyde Dehydrogenase↗

PubMed2004

A seven-membered aluminum sulfur allenyl heterocycle arising from the conversion of an aluminacyclopropene with CS2.

The reaction of an aluminacyclopropene LAl[eta2-C2(SiMe3)2] (1, L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) with CS2 in the temperature range from -78 degrees C to room temperature affords the first seven-membered aluminum sulfur-containing heterocyclic compound [LAl]2(mu-S)[eta2-SC(SiMe3)=C=C(SiMe3)] (2) bearing an allenyl group. The structural characterization of 2 and the analogous compound LAl[OC(O)C2(SiMe3)2] (3) of the proposed intermediate A and the variable-temperature 1H NMR kinetic study of this reaction may give a better understanding on this unusual conversion.

Aluminum↗

PubMed2004

Mapping of a substrate binding site in the protein disulfide isomerase-related chaperone wind based on protein function and crystal structure.

The protein disulfide isomerase (PDI)-related protein Wind is essential in Drosophila melanogaster, and is required for correct targeting of Pipe, an essential Golgi transmembrane 2-O-sulfotransferase. Apart from a thioredoxin fold domain present in all PDI proteins, Wind also has a unique C-terminal D-domain found only in PDI-D proteins. Here, we show that Pipe processing requires dimeric Wind, which interacts directly with the soluble domain of Pipe in vitro, and we map an essential substrate binding site in Wind to the vicinity of an exposed cluster of tyrosines within the thioredoxin fold domain. In vitro, binding occurs to multiple sites within the Pipe polypeptide and shows specificity for two consecutive aromatic residues. A second site in Wind, formed by a cluster of residues within the D-domain, is likewise required for substrate processing. This domain, expressed separately, impairs Pipe processing by the full-length Wind protein, indicating competitive binding to substrate. Our data represent the most accurate map of a peptide binding site in a PDI-related protein available to date and directly show peptide specificity for a naturally occurring substrate.

Amino Acid Sequence↗

PubMed2004

Antibody responses against SARS-coronavirus and its nucleocaspid in SARS patients.

BACKGROUND: SARS-Cov is the etiologic agent of severe acute respiratory syndrome. An understanding of the antibody responses to the viral components is very important for diagnosis and vaccine development. OBJECTIVE: The spectrum of SARS-specific antibody profiles in SARS patients was investigated from 7 to 210 days after the onset of the symptoms. STUDY DESIGN: Serial serum samples from 14 SARS patients were isolated from 7 to 210 days after the onset of the symptoms, and were tested for anti-viral IgG and IgM by indirect immunofluorescence tests (IFA), anti-nucleocaspid antibody by ELISA tests and viral neutralization. RESULTS: Anti-viral (IgG) and anti-nucleocaspid antibodies were observed in 13 of 14 patients at 14 days after the onset of symptoms, and in all 14 patients at 30-210 days thereafter. Anti-viral antibody (IgM) was detected maximally at 30 days, later than that for the IgG class. IgM antibody declined and became undetectable between 60 to 180 days after the onset of the symptoms. Neutralizing viral antibodies were demonstrated in the sera from all of the patients with SARS symptoms. CONCLUSIONS: Anti-viral IgG, IgM, and anti-nucleocaspid antibodies were detected 7-30 days in patients after the onset of SARS symptoms. Anti-viral IgM antibodies disappeared earlier than IgG. Viral neutralization was demonstrated in the sera from the convalescent patients.

Adult↗

PubMed2004

Profile of antibodies to the nucleocapsid protein of the severe acute respiratory syndrome (SARS)-associated coronavirus in probable SARS patients.

Profiles of antibodies to the nucleocapsid protein of the severe acute respiratory syndrome (SARS)-associated coronavirus in 445 probable SARS patients and 3,749 healthy people or non-SARS patients were analyzed by antigen-capturing enzyme-linked immunosorbent assay. Antinucleocapsid antibodies were elucidated in 17.5% of the probable SARS patients 1 to 7 days after the onset of symptoms and in 80% of the patients 8 to 14 days after the onset. About 90% of the probable SARS patients were positive 15 or more days after illness. Antibody titers increased up to 70 days, and high antibody titers were maintained at least for another 3 months. Of the healthy people and non-SARS patients, only seven (0.187%) were weakly positive.

Adult↗

PubMed2003

Simvastatin induces osteoblastic differentiation and inhibits adipocytic differentiation in mouse bone marrow stromal cells.

To clarify the mechanism of the stimulatory effect of statins on bone formation, we investigated the effect of simvastatin, a widely used statin, on osteoblastic and adipocytic differentiation in primary cultured mouse bone marrow stromal cells (BMSCs). Simvastatin treatment enhanced the expression level of mRNA for osteocalcin and protein for osteocalcin and osteopontin, and increased alkaline phosphatase activity significantly (p<0.05). After BMSCs were exposed to an adipocyte differentiation agonist, Oil Red O staining, fluorescence activated cell sorting, and decreased expression level of lipoprotein lipase mRNA showed that treatment with simvastatin significantly inhibits adipocytic differentiation compared to controls that did not receive simvastatin (p<0.05). Lastly, we found that simvastatin induces high expression of BMP(2) in BMSCs. These observations suggested that simvastatin acts on BMSCs to enhance osteoblastic differentiation and inhibits adipocytic differentiation; this effect is at least partially mediated by inducing BMP(2) expression in BMSCs.

Adipocytes↗

PubMed2003

Crystal structure and functional analysis of Drosophila Wind, a protein-disulfide isomerase-related protein.

In the developing Drosophila melanogaster embryo, dorsal-ventral patterning displays an absolute requirement for the product of the essential windbeutel gene, Wind. In homozygous windbeutel mutant flies, dorsal-ventral patterning fails to initiate because of the failure of the Golgi-resident proteoglycan-modifying protein, Pipe, to exit the endoplasmic reticulum, and this leads to the death of the embryo. Here, we describe the three-dimensional structure of Wind at 1.9-A resolution and identify a candidate surface for interaction with Pipe. This represents the first crystal structure of a eukaryotic protein-disulfide isomerase-related protein of the endoplasmic reticulum to be described. The dimeric protein is composed of an N-terminal thioredoxin domain and a C-terminal alpha-helical domain unique to protein-disulfide isomerase D proteins. Although Wind carries a CXXC motif that is partially surface accessible, this motif is redox inactive, and the cysteines are not required for the targeting of Pipe to the Golgi. However, both domains are required for targeting Pipe to the Golgi, and, although the mouse homologue ERp28 cannot replace the function of Wind, exchange of the Wind D-domain with that of ERp28 allows for efficient Golgi transport of Pipe.

Amino Acid Sequence↗

PubMed2003

New synthetic route for organic polyoxometallic clusters: synthetic and structural investigations on the first dumb-bell shaped polyoxozirconium hydroxide with the [Zr9(mu5-O)2(mu3-O)4(mu-O)4(mu-OH)8] core structure.

A new route for organic polyoxometallic clusters describes the first dumb-bell-like organic polyoxozirconium hydroxide [[(Cp*Zr)4(mu5-O)(mu3-O)2(mu-OH)4]2Zr(mu-O)4] x 2C7H8 (2; Cp* = C5Me5) involving the treatment of the Brønsted acidic organozirconium hydroxide [(Cp*Zr)6(mu4-O)(mu-O)4(mu-OH)8] x 2C7H8 (1) with organozirconium compounds.

Journal Article↗

PubMed2003

In-house measurement of the sulfur anomalous signal and its use for phasing.

Five test structures (orthorhombic and trigonal trypsin, cubic and rhombohedral insulin and thaumatin) have been solved by the SAD (single-wavelength anomalous diffraction) method using highly redundant data collected at 100 K with a CCD detector, rotating-anode generator and three-circle goniometer. The very weak anomalous scattering (primarily from sulfur) was sufficient to locate all the anomalous scatterers using the integrated direct and Patterson methods in SHELXD. These positions and occupancies were used without further refinement to estimate phases that were extended to native (in-house) resolution by the sphere of influence algorithm in SHELXE. The final map correlation coefficients relative to the anisotropically refined structures were in the range 0.81-0.97. The use of highly redundant medium-resolution laboratory data for sulfur-SAD phasing combined with high-resolution synchrotron native data for phase expansion and structure refinement clearly has considerable potential.

Algorithms↗

PubMed2003

Diagnosis of severe acute respiratory syndrome (SARS) by detection of SARS coronavirus nucleocapsid antibodies in an antigen-capturing enzyme-linked immunosorbent assay.

Recombinant severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein was employed to establish an antigen-capturing enzyme-linked immunosorbent assay (ELISA). Antinucleocapsid protein antibodies could be detected in 68.4% of probable SARS patients 6 to 10 days after illness and in 89.6% of the patients 11 to 61 days after illness. No false-positive results were observed in 20 non-SARS fever patients, 24 non-SARS respiratory illness patients, and 20 health care workers. Among 940 other non-SARS clinical serum samples, only 1 was found to be weakly positive. This method provides a new, sensitive, and specific approach for SARS diagnosis.

Antibodies, Viral↗

PubMed2003

[Simvastatin induces osteoblastic differentiation of bone marrow stromal cells].

OBJECTIVE: To observe the effect of simvastatin on osteoblastic cell differentiation of bone marrow stromal cells in vitro, and to elucidate the mechanisms of anabolic effect of simvastatin on bone formation. METHODS: Bone marrow stromal cells from femur and tibia of adult female BALB-C mice were cultured in vitro, after being treated with different concentrations of simvastatin for 72 h, changes of mRNA level of osteocalcin (OCN) were detected by RT-PCR, change of OCN, and osteopontin (OPN) expression were examined by Western blot, and the changes of cellular alkaline phosphatase activity (ALP) were examined by histochemistry and enzymologic measurement. RESULTS: After bone marrow stromal cells were treated with different concentration of simvastatin for 72 h, level of OCN mRNA increased, and expression of OCN and OPN also increased in a concentration-dependent manner, and cellular ALP activity significantly increased in a concentration-dependent manner. CONCLUSION: Simvastatin can stimulate osteoblastic differentiation, and improve cellular ALPase activity with high expression of osteocalcin and osteopontin in vitro. These may be parts of the mechanism of anabolic effect of simvastatin on bone formation.

Alkaline Phosphatase↗

PubMed2002

Synthesis and structures of [[HC(CMeNAr)(2)]Ge(S)X] (Ar = 2,6-iPr(2)C(6)H(3), X = F, Cl, Me): structurally characterized examples with a formal double bond between group 14 and 16 elements bearing a halide.

Treatment of [{HC(CMeNAr)2}GeX] (Ar = 2,6-iPr2C6H3, X = Cl (1), F (2)), with elemental sulfur at room temperature smoothly afforded the [{HC(CMeNAr)2}Ge(S)X] (X = Cl (3), F (4)). Compound 4 can also be obtained from 3 with the fluorination reagent Me3SnF. Reaction of 3 with MeLi led to the formation of [{HC(CMeNAr)2}Ge(S)Me] (5). Single-crystal X-ray structural analyses indicate compounds 3-5 are monomeric. The germanium centers adopt four coordinated sites and reside in distorted tetrahedral environment. Compounds 3 and 4 are structurally characterized examples with a formal double bond between group 14 and 16 elements bearing a halide.

Journal Article↗

PubMed2002

Expression of human VEGF(121) cDNA in mouse bone marrow stromal cells.

OBJECTIVE: To construct a retroviral vector carrying human vascular endothelial growth factor (hVEGF (121)) cDNA for evaluation of the possibility of VEGF gene therapy in ischemic bone disease. METHODS: hVEGF(121) cDNA was obtained from the plasmid pCDI/VEGF(121) and cloned into retroviral plasmid pLXSN. Recombinant plasmid was transferred to the retro virus packaging cell, PT-67, by lipofectamine mediated gene transfer. Mouse bone marrow stromal cells (MSCs) were transfected by the retrovirus. The integration of the hVEGF(121) cDNA into MSC genomic DNA and expression of the VEGF gene was detected. Proliferation assays of human umbilical vein endothelial cells (HUVECs) by VEGF(121) in culture medium were performed. RESULTS: Recombinant pLXSN/VEGF(121) was correctly constructed and confirmed by restriction endonuclease analysis and DNA sequencing analysis. hVEGF(121) gene was integrated into MSC genomic DNA after transfection, and the VEGF(121) protein was expressed. Proliferation assays showed VEGF(121) in culture medium was a biologically active protein and had a mitogenic effect on HUVEC. CONCLUSIONS: Recombinant retroviral vector carrying hVEGF(121) cDNA was successfully constructed. VEGF (121) protein expressed by MSCs had mitogenic effect biologically. This provides a further foundation for VEGF gene therapy for bone ischemic disease and bone tissue engineering.

Animals↗

PubMed2002

[Construction of adenoviral vector encoding human VEGF(121) cDNA and its expression in vitro].

OBJECTIVE: To construct the adenoviral vector bringing hVEGF(121) cDNA for evaluation of the possibility of VEGF gene therapy in ischemic bone disease. METHODS: Human vascular endothelial growth factor (hVEGF(121)) cDNA obtained from the plasmid pCDI/VEGF(121) was cloned into plasmid pshuttle and further cloned to Adeno-X Viral DNA. The recombinant adenoviral plasmid was identified and then transferred to the adenoviral packaging cell HEK293 by lipofectamine mediated gene transfer method to pack the virus. After titilating the virus, the mouse bone marrow stromal cells (MSC) were transfected by the adenovirus and the expression of VEGF gene was detected. RESULTS: The recombinant Adeno-VEGF(121) was correctly constructed and confirmed by restriction endonuclease analysis and DNA sequencing analysis. After MSCs were tranfected by the virus, RT-PCR showed that hVEGF(121) mRNA was transcripted from the hVEGF(121) gene. Western blot and immune histochemistry showed VEGF(121) protein was expressed in transgene MSCs. CONCLUSION: The recombinant adenoviral vector bringing hVEGF(121) cDNA was successfully constructed and the transgene MSC expressed hVEGF gene in vitro, it provided the further foundation of VEGF gene therapy for bone ischemic diseases.

Adenoviridae↗