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Biomedical subjects

Y Wu

Publications and source records attributed to Y Wu.

At least 487 records · Page 27Linked to original sources
PubMed1999

Facilitated antigen presentation by B cells expressing IgD when responding T cells express IgD-receptors.

In vitro studies have confirmed that cognate interactions between T and B cells are required to demonstrate enhanced helper activity using T cells with upregulated IgD-receptors (IgD-Rs). We studied the mechanism by which IgD-R+ T cells facilitate antibody responses by examining whether T cells also benefit from their expression of IgD-R. Experiments were designed to determine whether upregulation of IgD-R on T cells facilitates antigen presentation by IgD+ B cells. Goat Ig-primed splenic T cells from BALB/c mice were tested for their ability to respond to antigen-presenting B cells treated with goat anti-mouse (GAM) IgM or GAM IgD. T cell responses to GAM IgM and GAM IgD presented by B cells were significantly higher when goat Ig-primed cells were induced to express IgD-R by exposure to oligomeric IgD compared with goat Ig-primed control T cells. This effect was inhibited when monomeric IgD was added to the cultures. No differences in T and IgD-R+ T cell responses were seen using adherent cells as APCs. B cells from IgD-/- mice were also tested. Such B cells present antigen to IgD-R+ T cells without promoting enhanced responses compared with B cells from heterozygous IgD+/- mice. These studies suggest that IgD may play a costimulatory role during antigen presentation. We conclude that when T cells are induced to express IgD-R, these lectin-like receptors can ligate B cell membrane IgD during antigen presentation to facilitate responses of each of the cells engaged in cognate interaction, yielding enhanced antigen-specific T cell and B cell responses.

Animals↗
PubMed1999

Signal transduction pathways mediated by glycoprotein Ia/IIa in human platelets: comparison with those of glycoprotein VI.

Human platelets were activated either by glycoprotein (GP) Ia/IIa agonist (rhodocytin) or by a GPVI agonist (collagen-related peptide, CRP), and the intracellular signal transduction pathways were compared in the presence of various inhibitors. Rhodocytin isolated from Calloselasma rhodostoma venom was verified as a GPIa/IIa agonist, based on the inhibitory effects of three mAbs directed against GPIa. Platelet activation mediated by GPIa/IIa led to overt platelet aggregation, elevation of intracellular Ca2+, and tyrosine phosphorylation of several proteins, similar to that of GPVI. p72(syk) and phospholipase Cgamma2 (PLCgamma2) tyrosine phosphorylation were also observed with GPIa/IIa-mediated platelet aggregation, although they peaked slightly later than that of GPVI. In contrast to GPVI-mediated platelet activation, most of these phenomena induced by GPIa/IIa activation were markedly suppressed by acetylsalicylic acid (ASA) or cytochalasin D. These findings suggest that the requirements for thromboxane A2 (TXA2) production and actin polymerization, which are the characteristics of collagen-induced platelet activation, are derived from the GPIa/IIa-mediated signal transduction, but not from that of GPVI.

Antibodies, Monoclonal↗
PubMed1999

Identification of 1 alpha,25-dihydroxyvitamin D3 response elements in the human transforming growth factor beta 2 gene.

Transforming growth factor-beta (TGF-beta) is one of the most abundant growth factors secreted by bone cells, and regulation of TGF-beta expression is crucial for bone development and growth. Previous studies from our laboratory demonstrated that 1 alpha, 25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) inhibits human osteoblast and keratinocyte growth by increasing TGF-beta2 secretion and synthesis. To examine the mechanism by which 1 alpha,25(OH)2D3 regulates TGF-beta 2 transcription in osteoblasts, we ligated segments of the human TGF-beta 2 promoter 5' of a growth hormone reporter gene in a growth hormone reporter plasmid and examined the effects of 1 alpha,25(OH)2D3 administration on the expression of growth hormone in cells transfected with such chimeric promoter-reporter plasmids. The promoter region extending from -973 to +68 bp of the transcription start site elicited a 7-fold increase in reporter gene activity in transiently transfected osteoblasts after 1 alpha,25(OH)2D3 treatment, whereas the region from -553 to +68 bp of the transcription start site showed no response following 1 alpha,25(OH)2D3 treatment. Transfection of osteoblasts with reporter plasmids containing TGF-beta 2 promoter DNA from -869 to -658 bp revealed a 3.8-fold increase in reporter gene activity. DNA fragments from this region (-743 to -676 bp and -786 to -728 bp) ligated into reporter plasmids also showed increases in reporter activity. Gel retardation assay experiments showed that DNA fragments from -774 to -735 bp and -714 to -675 bp both formed a DNA-protein complex with bacterially expressed human retinoic acid X receptor alpha (RXR alpha) and vitamin D receptor (VDR) and with nuclear extracts from human bone cells. Addition of a vitamin D receptor antibody to reactions containing the aforesaid DNA fragments and bone cell nuclear extract resulted in further retardation of the mobility of the DNA-protein complex (super-shifting). Removal of two putative direct repeat DNA fragments in this region abolished VDR-RXR alpha-vitamin D response element complex formation. The TGF-beta 2 promoter contains two imperfect direct repeat DNA sequences: TGTAGAACAAGTAGA and AATGAAGTTGGTGGA that mediate the effect of 1 alpha,25(OH)2D3.

Base Sequence↗
PubMed1999

JunB forms the majority of the AP-1 complex and is a target for redox regulation by receptor tyrosine kinase and G protein-coupled receptor agonists in smooth muscle cells.

To understand the role of redox-sensitive mechanisms in vascular smooth muscle cell (VSMC) growth, we have studied the effect of N-acetylcysteine (NAC), a thiol antioxidant, and diphenyleneiodonium (DPI), a potent NADH/NADPH oxidase inhibitor, on serum-, platelet-derived growth factor BB-, and thrombin-induced ERK2, JNK1, and p38 mitogen-activated protein (MAP) kinase activation; c-Fos, c-Jun, and JunB expression; and DNA synthesis. Both NAC and DPI completely inhibited agonist-induced AP-1 activity and DNA synthesis in VSMC. On the contrary, these compounds had differential effects on agonist-induced ERK2, JNK1, and p38 MAP kinase activation and c-Fos, c-Jun, and JunB expression. NAC inhibited agonist-induced ERK2, JNK1, and p38 MAP kinase activation and c-Fos, c-Jun, and JunB expression except for platelet-derived growth factor BB-induced ERK2 activation. In contrast, DPI only inhibited agonist-induced p38 MAP kinase activation and c-Fos and JunB expression. Antibody supershift assays indicated the presence of c-Fos and JunB in the AP-1 complex formed in response to all three agonists. In addition, cotransfection of VSMC with expression plasmids for c-Fos and members of the Jun family along with the AP-1-dependent reporter gene revealed that AP-1 with c-Fos and JunB composition exhibited a higher transactivating activity than AP-1 with other compositions tested. All three agonists significantly stimulated reactive oxygen species production, and this effect was inhibited by both NAC and DPI. Together, these results strongly suggest a role for redox-sensitive mechanisms in agonist-induced ERK2, JNK1, and p38 MAP kinase activation; c-Fos, c-Jun, and JunB expression; AP-1 activity; and DNA synthesis in VSMC. These results also suggest a role for NADH/NADPH oxidase activity in some subset of early signaling events such as p38 MAP kinase activation and c-Fos and JunB induction, which appear to be important in agonist-induced AP-1 activity and DNA synthesis in VSMC.

Acetylcysteine↗
PubMed1999

Multinuclear solid-state three-dimensional MRI of bone and synthetic calcium phosphates.

Multinuclear three-dimensional solid-state MRI of bone, tooth, and synthetic calcium phosphates is demonstrated in vitro and in vivo with a projection reconstruction technique based on acquisition of free induction decays in the presence of fixed amplitude magnetic field gradients. Phosphorus-31 solid-state MRI provides direct images of the calcium phosphate constituents of bone substance and is a quantitative measurement of the true volumetric bone mineral density of the bone. Proton solid-state MRI shows the density of bone matrix including its organic constituents, which consist principally of collagen. These solid-state MRI methods promise to yield a biological picture of bone richer in information concerning the bone composition and short range-crystalline order than the fluid-state images provided by conventional proton MRI or the density images produced by radiologic imaging techniques. Three-dimensional solid-state projection reconstruction MRI should be readily adaptable to both human clinical use and nonmedical applications for a variety of solids in materials science.

Bone and Bones↗
PubMed1999

[Mutations of the fibroblast growth factor receptor 3 gene in achondroplasia].

OBJECTIVE: To evaluate whether mutation in the exon 10 of the fibroblast growth factor receptor 3(FGFR3) gene in common in Chinese patients with achondroplasia. METHODS: Genomic DNA from seven sporadic cases of achondroplasia was studied by using PCR-SSCP and restriction enzymes. RESULTS: All patients carried the same glycine-to-arginine mutation at codon 380(G380R) of the transmembrane domain of FGFR3. CONCLUSION: The results suggest that the G380R mutation of FGFR3 is also a frequent mutation causing achondroplasia in Chinese. Detecting FGFR 3 gene mutation with PCR-SSCP and restriction enzymes analysis is a convenient, rapid and reliable molecular diagnostic assay for prenatal and early diagnosis of achondroplasia.

Achondroplasia↗
PubMed1999

The human KDR/flk-1 gene contains a functional initiator element that is bound and transactivated by TFII-I.

KDR/flk-1, the receptor for vascular endothelial growth factor, is required for normal vascular development. KDR/flk-1 is a TATA-less gene, containing four upstream Sp1 sites and a single transcription start site, although analysis of the start site sequence discloses only weak similarities with the consensus initiator element (Inr) sequence. In vitro transcription assays, however, demonstrate that the region from -10 to +10 relative to the start site contains Inr activity that is orientation- and position-dependent, and mutagenesis of the KDR/flk-1 Inr reduces promoter activity to 28% of the wild-type promoter in transient transfection assays. Gel shift assays confirm that nuclear proteins specifically bind the Inr, and competition experiments demonstrate that TFII-I, a multifunctional Inr-binding nuclear protein, is a component of these DNA-protein complexes. TFII-I transactivates the wild-type KDR/flk-1 promoter, but not a promoter containing a mutated Inr, in transient transfection assays. Immunodepletion of TFII-I from nuclear extracts prior to in vitro transcription assays abolishes transcription from the KDR/flk-1 Inr, an effect that can be rescued by adding back purified TFII-I, reflecting the importance of TFII-I in KDR/flk-1 Inr activity. These experiments demonstrate that the KDR/flk-1 gene contains a functional Inr that is bound by TFII-I and that both the functional Inr and TFII-I activity are essential for transcription.

Animals↗
PubMed1999

Relation of calcium, vitamin D, and dairy food intake to ischemic heart disease mortality among postmenopausal women.

To investigate whether greater intakes of calcium, vitamin D, or milk products may protect against ischemic heart disease mortality, the authors analyzed data from a prospective cohort study of 34,486 postmenopausal Iowa women 55-69 years old and without a history of ischemic heart disease who completed a dietary questionnaire in 1986. Through 1994, 387 deaths due to ischemic heart disease were documented (International Classification of Diseases, Ninth Revision, codes 410-414, 429.2). The multivariate-adjusted relative risks for the highest versus the lowest quartiles of total calcium, vitamin D, and milk product intakes were as follows: 0.67 (95% confidence interval (CI) 0.47-0.94; p for trend = 0.09) for calcium, 1.41 (95% CI 0.93-2.15; p for trend = 0.12) for vitamin D, and 0.94 (95% CI 0.66-1.35; p for trend = 0.68) for milk products. The relative risk was 0.63 (95% CI 0.40-0.98) for high dietary calcium but no supplemental calcium intake and 0.66 (95% CI 0.36-1.23) for high supplemental calcium but low dietary calcium intake. These results suggest that a higher intake of calcium, but not of vitamin D or milk products, is associated with reduced ischemic heart disease mortality in postmenopausal women, and reduced risk may be achievable whether the higher intake of calcium is attained by diet, supplements, or both.

Aged↗
PubMed1999

Effects of protein-surface interactions on protein ion signals in MALDI mass spectrometry.

The influence of polymer surface-protein binding affinity on protein ion signals in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is examined. The surfaces of poly(vinylidene fluoride) and poly(ethylene terephthalate) polymer substrates are modified by pulsed rf plasma deposition of allylamine. By varying the on/off duty cycle of the pulsed rf plasma, the polymer substrate surfaces are coated with thin films having varying densities of surface amine groups. The varying surface amine density is shown to lead to systematic changes in the surface binding affinity for the 125I-radiolabeled peptides angiotensin I and porcine insulin. Unlabeled angiotensin I and porcine insulin are then deposited on the pulsed rf plasma-modified substrates and analyzed by MALDI mass spectrometry. The experimental approach involves applying the peptide to the modified polymer surface in an aqueous phosphate-buffered saline solution and allowing the peptide solution to dry completely under ambient conditions. Subsequently, the MALDI matrix alpha-cyano-4-hydroxycinnamic acid in methanol and 10% trifluoroacetic acid in water are added to the peptide-coated modified polymer surfaces. The results of these studies demonstrate that, for the sample preparation method employed, increases in the surface peptide binding affinity lead to decreases in the peptide MALDI ion signal.

Proteins↗
PubMed1999

Route of nutrition influences intercellular adhesion molecule-1 expression and neutrophil accumulation in intestine.

HYPOTHESIS: The levels of intestinal interleukin 10 and interleukin 4, inhibitors of intercellular adhesion molecule-1 (ICAM-1) expression, decline with total parenteral nutrition (TPN). These cytokine changes induced by lack of enteral nutrition may increase ICAM-1 expression, resulting in polymorphonuclear neutrophil accumulation in intestine. DESIGN: Prospective randomized experimental trials. SETTING: Laboratory. MATERIALS: Male mice. INTERVENTIONS: Sixty-three mice were randomized to chow, intravenous TPN, or intragastric TPN. MAIN OUTCOME MEASURES: Experiment 1: After diet manipulation, iodine 125-labeled anti-ICAM-1 antibody and iodine 131-labeled nonbinding antibody were injected to quantify ICAM-1 expression on endothelial cells in the lung, liver, kidney, and small intestine. Measurement of myeloperoxidase was used to quantify polymorphonuclear neutrophil accumulation in the organs. Experiment 2: Intestine was harvested for both ICAM-1 and myeloperoxidase levels after chow refeeding of mice in the intravenous TPN group. RESULTS: In experiment 1, uninjured mice fed intravenous TPN showed significantly increased intestinal ICAM-1 expression and polymorphonuclear neutrophil accumulation with no significant changes in the lung, liver, or kidney. No changes occurred in mice fed chow or intragastric TPN. In experiment 2, reinstitution of enteral feeding returned intestinal ICAM-1 and myeloperoxidase levels to normal. CONCLUSION: Gut changes associated with lack of enteral feeding induce endothelial changes and an immunologic response, which may influence subsequent responses to injury.

Animals↗
PubMed1999

Collision-induced dissociation of protonated MK-0991: novel ring opening of a cyclic hexapeptide in the gas phase.

Electrospray ionization tandem mass spectrometry was applied to probe the collision-induced dissociation (CID) of protonated MK-0991 {(4R,5S)-5-[(2-aminoethyl)amino]-N(2)-(10, 12-dimethyl-1-oxotetradecyl)-4-hydroxy-L-ornithyl-L-threonyl-trans -4- hydroxy-L-prolyl-(S)-4-hydroxy-(4-hydroxyphenyl)-L-threonyl-threo-3-h ydroxy-L-or-nithyl-trans-3-hydroxy-L-proline cyclic (6-1)-peptide} in the gas phase; MK-0991 is a newly developed, broad-spectrum pneumocandin antifungal drug. The study showed that protonated MK-0991 (m/z 1094) undergoes specific ring opening under the CID conditions to form two protonated linear peptides at m/z 1076 and 1034. This is different from the commonly observed ring opening of a cyclic peptide that occurs by the cleavage of the N-acyl bonds in many places on the peptide backbone. The structures of the two linear peptides were elucidated on the basis of their tandem mass spectra. The results strongly indicate that the specific ring opening of MK-0991 is affected by the ethylenediamine side-chain formed from the modification of one of the ornithine amino acids in this cyclic hexapeptide.

Anti-Bacterial Agents↗
PubMed1999

Microsatellite instability during the immortalization and transformation of human breast epithelial cells in vitro.

The objective of this study was to determine whether microsatellite instability (MSI) and loss of heterozygosity (LOH) are involved in the immortalization of human breast epithelial cells (HBECs) in vitro and in the early stages of their transformation by benzo[a]pyrene (BP) and 7,12-dimethylbenz[a]anthracene (DMBA). We performed a genome-wide analysis of a total of 466 microsatellite DNA polymorphism loci along the X chromosome and the 22 pairs of human autosomes. MSI was found in the immortalized MCF-10F cells at the following loci: D11S1392 (on chromosome 11p13) and D17S849 (at 17p13.3), D17S796 (at 17p13.1), D17S513 (at 17p13.1), TP53 (at 17p13.1), D17S786 (at 17p13.1), and D17S520 (at 17p12) on chromosome 17. The BP-transformed cells exhibited MSI in the same loci and also in locus D11S912 (at 11q25). The more transformed BP1E cells also exhibited MSI on chromosome 13q12-13 at D13S260 and D13S289, markers known to flank the breast cancer susceptibility gene BRCA2. In the DMBA-transformed D3 and D3-1 cells, MSI was observed at the locus D13S260 in addition to the previously reported locus D16S285 (at 16q12.1). No LOH was observed on any of the chromosomes tested in these cells. These observations led us to conclude that the immortalization and transformation of HBECs may involve defects in mechanisms responsible for the cell's genomic stability, such as DNA replication and DNA mismatch repair.

Breast Neoplasms↗
PubMed1999

Increased risk of hepatocellular carcinoma in male hepatitis B surface antigen carriers with chronic hepatitis who have detectable urinary aflatoxin metabolite M1.

We followed 145 men with chronic hepatitis B virus (HBV) hepatitis for 10 years to determine whether exposure to aflatoxin, or concomitant exposure to hepatitis C virus (HCV), or family history of hepatocellular carcinoma (HCC) increased the risk of developing HCC. We collected 8 monthly urine samples before beginning follow-up and pooled them to detect aflatoxin metabolite M1 (AFM1). AFM1 was detected in 78 (54%) of the subjects. The risk of HCC was increased 3.3-fold (with a 95% confidence interval of 1.2-8.7) in those with detectable AFM1 (above 3.6 ng/L). This relative risk was adjusted for age and for HCV status. The attributable risk from exposure to detectable AFM1 was 0.553 (0.087, 0.94). The relative risk of fatal cirrhosis for those with elevated AFM1 was 2.8 (0.6, 14.3), and the odds of having a persistently elevated alanine transaminase (ALT) were 2.5-fold greater in those with detectable AFM1 (P =.007). Concomitant infection with HCV increased the risk of HCC 5.8-fold (2. 0-17), adjusted for age and AFM1 status. A family history of HCC increased the risk of HCC 5.6-fold, adjusted for age and AFM1. Four men with detectable AFM1 and HCC all had missense mutation in codon 249 of the p53 gene in cancer tissues. This study shows that exposure to AFM1 can account for a substantial part of the risk of HCC in men with chronic HBV hepatitis and adds importantly to the evidence that HCV and family history of HCC increase the risk of HCC in men with chronic HBV hepatitis.

Adolescent↗
PubMed1999

Sustained high-level production of murine chemokine C10 during chronic inflammation.

The murine CC chemokine C10, a macrophage chemoattractant, has been shown to have an unusually restricted expression pattern in cultured cells (LPS non-responsive, IL-4 inducible). Its occurrence in vivo has not been characterized. Here the authors employ immunocytochemistry to demonstrate that C10 is expressed in inflammatory macrophages during irritant peritonitis. In addition, C10 was found to be a constitutive component of eosinophils. Peritoneal inflammation led to the accumulation of sufficient C10 (> 10 nM) to permit detection in exudate fluid. This accumulation did not begin until 24h after challenge, and was sustained through at least day 10 of the inflammation. In contrast, MIP-1alpha gene expression was earlier and transient. These kinetic features are consistent with earlier in vitro findings, suggesting that C10 is not a "first-wave" chemokine and may play a role related to chronic stages of host defence reactions.

Adjuvants, Immunologic↗
PubMed1999

The association of anti-Ro52 autoantibodies with myositis and scleroderma autoantibodies.

The presence of autoantibodies to the Ro52 protein in sera from patients with idiopathic inflammatory myopathies has recently been reported. These antibodies were found predominately in sera with the myositis-specific autoantibody anti-histidyl-tRNA synthetase (anti-Jo-1). In this report, we analysed sera from 216 patients to determine whether anti-Ro52 antibodies are associated with myositis autoantibodies other than anti-Jo-1. These included sera containing antibodies that recognize threonyl- or alanyl-tRNA synthetases, Mi-2, PM-Scl, signal recognition particle (SRP), as well as the systemic sclerosis-related antibodies anti-topoisomerase I (Scl-70) and anti-centromere. A high proportion of sera that contain anti-aminoacyl-tRNA synthetase antibodies, anti-SRP, or anti-PM-Scl antibodies were found to contain antibodies to the Ro52 protein. In contrast, in sera containing anti-Mi-2, anti-Scl-70 or anti-centromere antibodies, anti-Ro52 antibodies were absent or occurred infrequently. In addition, only one serum from 41 rheumatoid arthritis patients was positive for anti-Ro52 autoantibodies. These data indicate that anti-Ro52 antibodies are produced in particular subsets of myositis patients, and are not limited to sera with anti-Jo-1 antibodies.

Amino Acyl-tRNA Synthetases↗