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Biomedical subjects

Y Wu

Publications and source records attributed to Y Wu.

At least 469 records · Page 26Linked to original sources
PubMed1999

Intracellular IL-1 receptor antagonist is elevated in human dermal fibroblasts that overexpress intracellular precursor IL-1 alpha.

Cultured dermal fibroblasts from systemic sclerosis patients express higher levels of intracellular IL-1 alpha than fibroblasts from healthy controls. In this study, we found that systemic sclerosis dermal fibroblasts also express higher levels of the intracellular isoform of IL-1 receptor antagonist (icIL-1Ra) than normal fibroblasts after stimulation with IL-1 beta or TNF-alpha. A possible relationship between elevated precursor IL-1 alpha (preIL-1 alpha) and elevated icIL-1Ra was investigated by transducing normal dermal fibroblasts to overexpress preIL-1 alpha, preIL-1 beta, or icIL-1Ra. Fibroblasts that overexpressed icIL-1Ra did not have elevated levels of IL-1 alpha. On the other hand, fibroblasts that overexpressed preIL-1 alpha had at least 4-fold higher basal levels of icIL-1Ra than control fibroblasts and 4-fold higher levels of icIL-1Ra after induction with IL-1 beta or TNF-alpha. Fibroblasts overexpressing preIL-1 beta did not exhibit elevated icIL-1Ra. The differences in icIL-1Ra protein levels were reflected in differences in mRNA. In contrast, IL-1-stimulated levels of MCP-1 and IL-6 were not different in control and preIL-1 alpha-transduced fibroblasts. Addition of neutralizing anti-IL-1 alpha Abs to fibroblast cultures did not diminish basal or stimulated levels of icIL-1Ra in the preIL-1 alpha-transduced cells, supporting an intracellular site of action of preIL-1 alpha. This is the first report of an association between intracellular levels of these IL-1 family members. We hypothesize that intracellular preIL-1 alpha participates in the regulation of icIL-1Ra.

Adult↗
PubMed1999

The simultaneous estimation of the number of signals and frequencies of multiple sinusoids when some observations are missing: I. Asymptotics.

The problem of simultaneous estimation of the number of signals and frequencies of multiple sinusoids is considered in the case when some observations are missing. The number of signals is estimated with an information theoretic criterion, and the frequencies are estimated with eigenvariation linear prediction. The strong consistency of the estimates of the number of signals and the frequencies is established and the rate of convergence of these estimates is provided. Besides, the limiting distributions of various estimates are given.

Journal Article↗
PubMed1999

Induction of CD40 on human endothelial cells by Alzheimer's beta-amyloid peptides.

Growing evidence suggests that beta-amyloid (Abeta) peptides play a central role in mediating vascular endothelium dysfunction, but the extent to which immune mechanisms are involved in this process remains unclear. To explore such mechanisms, we incubated cultured human aortic endothelial cells (HAEC) with freshly solublized Abeta and examined expression of a central immunoregulatory molecule, CD40, in these cells using reverse transcriptase-polymerase chain reaction, Western immunoblotting, and Flow cytometry. Our results show that treatment of endothelial cells with Abeta1-40, Abeta1-42 or gamma interferon (IFN-gamma) results in a dose-dependent induction of endothelial CD40 expression. Furthermore, ligation of endothelial CD40 and simultaneous treatment of human endothelial cells with IFN-gamma or Abeta peptides leads to a significant release of interleukin-1beta (IL-1beta), a marker for endothelial cell activation. Since IL-1beta is an important inflammatory response mediator, these findings suggest that the functional role of Abeta-induced endothelial CD40 may be promotion of the inflammatory cascade in vascular endothelial cells.

Alzheimer Disease↗
PubMed1999

Opioid growth factor and organ development in rat and human embryos.

In addition to neurotransmission, the native opioid peptide, [Met5]enkephalin, is a tonically active inhibitory growth molecule that is termed opioid growth factor (OGF). OGF interacts with the zeta (zeta) opioid receptor to influence cell proliferation and tissue organization. We now identify OGF and the zeta receptor in embryonic derivatives including ectoderm, mesoderm, and endoderm of the rat on gestation day 20. Messenger RNA for preproenkephalin (PPE), the precursor of OGF, was detected in the developing cells, suggesting an autocrine production of this peptide. Acute exposure of the pregnant female to OGF resulted in a decrease in DNA synthesis in cells of organs representing all three germ layers, and did so in a receptor-mediated fashion. The influence of OGF was direct, as evidenced in organ culture studies. Blockade of endogenous opioid interaction using naltrexone (NTX) produced an increase in DNA synthesis, indicating the constitutive and functional nature of opioid activity on growth during prenatal life. Human fetal cells contained OGF and the zeta receptor. These data support the hypothesis that endogenous opioid modulation of organ development is a fundamental principle of mammalian embryogenesis, and that OGF has a profound influence on ontogeny. Irregularities in the role of opioids as growth regulators in relationship to the more than 500,000 newborns suffering from birth defects each year in the US needs to be examined.

Animals↗
PubMed1999

Redox regulation of cell signaling by selenocysteine in mammalian thioredoxin reductases.

The intracellular generation of reactive oxygen species, together with the thioredoxin and glutathione systems, is thought to participate in redox signaling in mammalian cells. The activity of thioredoxin is dependent on the redox status of thioredoxin reductase (TR), the activity of which in turn is dependent on a selenocysteine residue. Two mammalian TR isozymes (TR2 and TR3), in addition to that previously characterized (TR1), have now been identified in humans and mice. All three TR isozymes contain a selenocysteine residue that is located in the penultimate position at the carboxyl terminus and which is encoded by a UGA codon. The generation of reactive oxygen species in a human carcinoma cell line was shown to result in both the oxidation of the selenocysteine in TR1 and a subsequent increase in the expression of this enzyme. These observations identify the carboxyl-terminal selenocysteine of TR1 as a cellular redox sensor and support an essential role for mammalian TR isozymes in redox-regulated cell signaling.

Amino Acid Sequence↗
PubMed1999

Bcr: a negative regulator of the Bcr-Abl oncoprotein.

Chronic myelogenous leukemia is typically characterized by the presence of the Philadelphia chromosome (Ph) in which 5' portions of the BCR gene are fused to a large portion of the ABL gene. Our studies and those of others indicate that Bcr sequences within the Bcr-Abl oncoprotein are critically involved in activating the Abl tyrosine kinase and actively participate in the oncogenic response, which is generated by the Bcr-Abl oncoprotein. We investigated the role of the Bcr protein in the oncogenic effects of Bcr-Abl. Reduction of the level of the Bcr protein by incubating cells with a 3' BCR anti-sense oligodeoxynucleotide increased the growth rate and survival of hematopoietic cell lines expressing Bcr-Abl. Also, enforced expression of Bcr in Bcr-Abl cell lines strongly reduced transformation efficiency. Induction of Bcr expression drastically reduced the phosphotyrosine content of Bcr-Abl in Rat-1 fibroblasts transformed by P185 BCR-ABL and in hematopoietic cells expressing P210 Bcr-Abl within days following induction of Bcr. Rat-1/P185 cells maintained for three weeks after Bcr induction had dramatically reduced amounts of phosphotyrosine proteins compared to cells in which Bcr expression was repressed by the addition of Tet. In contrast Bcr expression did not decrease the phosphotyrosine content of either v-Src or activated Neu tyrosine kinase. Importantly, the phosphotyrosine content of total P160 BCR (induced plus endogenous) was strongly reduced by inducing expression of Bcr, indicating that the induced Bcr protein was not a target of the tyrosine kinase activity of Bcr-Abl but instead functioned as an inhibitor of Bcr-Abl. These results show that the Bcr protein can function as a negative regulator of Bcr-Abl, but that the inhibitory effects of Bcr are dependent on achieving an elevated level of Bcr expression relative to Bcr-Abl.

Animals↗
PubMed1999

Improved mutation detection in GC-rich DNA fragments by combined DGGE and CDGE.

Denaturing gradient gel electrophoresis (DGGE) has proven to be a powerful pre-screening method for the detection of DNA variants. If such variants occur, however, in DNA fragments that are very rich in G and C, they may escape detection. To overcome this limitation, we tested a novel gel system which combines DGGE and constant denaturant gel electrophoresis (CDGE), as it might have the advantages of both methods. Indeed, this combination had the advantages of both methods, good separation of hetero-duplex molecules and prevention of total strand dissociation, and it proved successful in the detection of DNA variants in several GC-rich fragments.

Base Sequence↗
PubMed1999

Structure-activity relationships of pyrroloquinazolines as thrombin receptor antagonists.

A series of pyrroloquinazolines has been discovered that represent novel small molecule inhibitors of the intramolecular ligand of the thrombin receptor. Analogs were prepared to study the structure-activity relationships of substitution at the N 1, N3, and N7 positions of the heterocycle. Compounds 4e and 4f have been identified with IC50's of 56 and 52 nM, respectively.

Drug Evaluation, Preclinical↗
PubMed1999

Studies of peptide binding to allyl amine and vinyl acetic acid-modified polymers using matrix-assisted laser desorption/ionization mass spectrometry.

Previous studies have shown that increases in surface-peptide binding affinity result in decreases in peptide matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) ion signals. The present work demonstrates that, with appropriate corrections for peptide ionization efficiency under MALDI conditions, relative surface-peptide binding affinities can be assayed using the MALDI MS methodology. Peptides with a range of pI values are allowed to interact with amine-modified and carboxylic acid-modified polymer surfaces (produced by pulsed radio-frequency plasma polymerization of allyl amine and vinyl acetic acid) in buffered solutions of neutral pH. Because of the net positive and negative charges associated with the peptides and surfaces in solution, both electrostatic and hydrophilic interactions play a role in the surface-peptide interaction. Consistent with expectations, the peptide MALDI ion signals for peptides with net negative charges in solution are smaller than those for peptides with net positive charges in solution when the peptides are allowed to interact with positively charged surfaces. A reversal of the relative peptide MALDI ion signal intensities is observed when the same peptides are allowed to interact with negatively charged surfaces. Cumulatively, the results demonstrate that even modest changes in surface-peptide interactions can be comparatively probed by MALDI mass spectrometry.

Amines↗
PubMed1999

Effect of ion modification of commonly used orthopedic materials on the attachment of human bone-derived cells.

Biomaterials which combine optimum properties of strength and biocompatibility are desirable in improving the long-term performance of implantable medical devices. Our study is aimed at developing technology designed to alter the outer atomic layers of a material to give the desired compatibility with the tissue while retaining the properties of the bulk substratum. Materials used in this study were titanium vanadium alloy (Ti-6Al-4V) and cobalt chromium molybdenum alloy (Co-Cr). Soda lime glass discs and polyethylene terephthalate (PET) acted as controls. A cathode of either Ti-6Al-4V or Co-Cr was used to simultaneously deposit and implant identified substrata. The attachment of human bone-derived cells (HBDC) to various materials was determined using radiolabeling or colorimetric assays. Results show that HBDC adhere preferentially to the unmodified surfaces of Ti-6Al-4V and Ti-6Al-4V on glass compared to the unmodified Co-Cr surfaces and to that of the Co-Cr on glass. Depositing Ti-6Al-4V on Co-Cr gives significantly better attachment of HBDC than when depositing Co-Cr onto Ti-6Al-4V. While cellular attachment to the created surfaces reflects that of the cathodic materials, it is not identical to these materials. Ion deposition/implantation is capable of creating permanent surfaces which reflect the adhesion of source materials not bulk substrata.

Alloys↗
PubMed1999

Molecular weights of CTLA-4 and CD80 by sedimentation equilibrium ultracentrifugation.

Proteins that are heavily glycosylated pose unique challenges in their biophysical characterization. In particular, molecular weight analysis is exacerbated by such glycosylation. For example, glyoproteins are refractory to careful mass spectrum analysis and often give anomalous retention times using size exclusion chromatography. We combine several approaches to characterize the molecular weights of the extracellular domains of the glycoproteins CTLA-4 and CD80 using carbohydrate analysis, electrospray mass spectrometry, size exclusion chromatography, and analytical ultracentrifugation. In addition, we have applied a method described previously, using sedimentation equilibrium analysis to calculate the contribution of carbohydrates to the molecular masses of CTLA-4 and CD80. It is important to understand the oligomeric states of these protein domains because the interaction between these lymphocyte receptors plays an important costimulatory role in the Th-cell antigenic response. It is thought that extracellular interactions between these receptors may regulate both the self-association of these receptor proteins and the oligomeric state of the heterocomplex; this regulation has important consequences for potentiating the signaling mechanism between Th-cells and antigen-presenting cells.

Abatacept↗
PubMed1999

Glutamine-enriched total parenteral nutrition preserves respiratory immunity and improves survival to a Pseudomonas Pneumonia.

BACKGROUND: Addition of 2% glutamine (GLN), a specific lymphocyte fuel, prevents deleterious effects of TPN on gut-associated lymphoid tissue and IgA while preserving IgA-mediated upper respiratory immunity to influenza virus. We examined whether a 2% GLN-enhanced TPN solution preserves respiratory immunity to a lethal and clinically relevant pneumonia challenge. MATERIALS AND METHODS: Male ICR mice were randomized to chow (n = 20), TPN (n = 20), or an isonitrogenous, isocaloric TPN-2% GLN solution (n = 17). All groups were immunized 10 days before surgery with Pseudomonas polysaccharide-containing liposomes (LIP) to confer immunity except for a nonimmune chow-fed LIP control group (n = 21) which received LIP without Pseudomonas. Mice received 5 days of diet and then were given an LD90 dose of 1.2 x 10(8) intratracheal Pseudomonas bacteria, and mortality was recorded. RESULTS: Immunization reduced mortality compared with LIP alone. TPN impaired immunity and reduced survival while GLN maintained immunization effectiveness. CONCLUSIONS: Pseudomonas immunization reduces mortality to Pseudomonas pneumonia, but this immunity is lost with TPN. Addition of 2% GLN to TPN preserves immunity in the respiratory tract and reduces mortality to a lethal bacterial challenge compared with standard TPN.

Animals↗
PubMed1999

Radiation-induced assembly of Rad51 and Rad52 recombination complex requires ATM and c-Abl.

Cells from individuals with the recessive cancer-prone disorder ataxia telangiectasia (A-T) are hypersensitive to ionizing radiation (I-R). ATM (mutated in A-T) is a protein kinase whose activity is stimulated by I-R. c-Abl, a nonreceptor tyrosine kinase, interacts with ATM and is activated by ATM following I-R. Rad51 is a homologue of bacterial RecA protein required for DNA recombination and repair. Here we demonstrate that there is an I-R-induced Rad51 tyrosine phosphorylation, and this induction is dependent on both ATM and c-Abl. ATM, c-Abl, and Rad51 can be co-immunoprecipitated from cell extracts. Consistent with the physical interaction, c-Abl phosphorylates Rad51 in vitro and in vivo. In assays using purified components, phosphorylation of Rad51 by c-Abl enhances complex formation between Rad51 and Rad52, which cooperates with Rad51 in recombination and repair. After I-R, an increase in association between Rad51 and Rad52 occurs in wild-type cells but not in cells with mutations that compromise ATM or c-Abl. Our data suggest signaling mediated through ATM, and c-Abl is required for the correct post-translational modification of Rad51, which is critical for the assembly of Rad51 repair protein complex following I-R.

Ataxia Telangiectasia Mutated Proteins↗
PubMed1999

Calmodulin kinase inhibition prevents development of the arrhythmogenic transient inward current.

Although it is widely accepted that afterdepolarizations initiate arrhythmias when action potentials are prolonged, the underlying mechanisms are unclear. In this study, we tested the hypothesis that action potential prolongation would raise intracellular calcium and thereby activate the arrhythmogenic transient inward current (Iti). Furthermore, given that Iti can be activated by sarcoplasmic reticulum Ca2+ release, we tested the hypothesis that inhibition of calmodulin (CaM) kinase would prevent Iti. Isolated rabbit ventricular myocytes were studied with whole-cell-mode voltage clamp. Stimulation with a prolonged action potential clamp, under near-physiological conditions, increased [Ca2+]i. Iti was reproducibly induced in 60 of 60 cells, but Iti was not seen with the use of a shorter action potential waveform (n=12). Iti was associated with a secondary elevation in [Ca2+]i. When [Ca2+]i buffering was enhanced by dialysis with BAPTA (20 mmol/L, n=9), no Iti was present. The Na+/Ca2+ exchanger was likely responsible for Iti, because Iti was inhibited by the Na+/Ca2+ exchanger inhibitory peptide XIP (10 micromol/L, n=6), but not by an inactive scrambled peptide (10 micromol/L, n=5) or by the Cl- current antagonist niflumic acid (10 to 40 micromol/L, n=9). Activator Ca2+ from the sarcoplasmic reticulum was essential for development of Iti, because it was prevented by pretreatment with ryanodine (10 micromol/L, n=6) or thapsigargin (1 micromol/L, n=6). Two different CaM kinase inhibitory peptides (n=16) and a CaM inhibitory peptide (n=4) completely suppressed Iti. These results are consistent with the hypothesis that CaM kinase plays a role in arrhythmias related to increased [Ca2+]i.

Action Potentials↗
PubMed1999

[Study of NAIP gene in spinal muscular atrophy]

OBJECTIVE: Investigating the correlation between the genotype and spinal muscular atrophy(SMA) clinical phenotype. METHODS: Neuronal apoptosis inhibitory protein(NAIP) gene analysis was performed by PCR amplification of exon 5 in 13 unrelated SMA patients with deletions of SMN gene. RESULTS: Two Type-I patients(2/5, 40%) lacked the NAIP exon 5. CONCLUSION: The results suggest a possible correlation between NAIP gene deletion and the disease severity of SMA.

Journal Article↗
PubMed1999

Defective interleukin (IL)-18-mediated natural killer and T helper cell type 1 responses in IL-1 receptor-associated kinase (IRAK)-deficient mice.

Interleukin (IL)-18 is functionally similar to IL-12 in mediating T helper cell type 1 (Th1) response and natural killer (NK) cell activity but is related to IL-1 in protein structure and signaling, including recruitment of IL-1 receptor-associated kinase (IRAK) to the receptor and activation of c-Jun NH2-terminal kinase (JNK) and nuclear factor (NF)-kappaB. The role of IRAK in IL-18-induced responses was studied in IRAK-deficient mice. Significant defects in JNK induction and partial impairment in NF-kappaB activation were found in IRAK-deficient Th1 cells, resulting in a dramatic decrease in interferon (IFN)-gamma mRNA expression. In vivo Th1 response to Propionibacterium acnes and lipopolysaccharide in IFN-gamma production and induction of NK cytotoxicity by IL-18 were severely impaired in IRAK-deficient mice. IFN-gamma production by activated NK cells in an acute murine cytomegalovirus infection was significantly reduced despite normal induction of NK cytotoxicity. These results demonstrate that IRAK plays an important role in IL-18-induced signaling and function.

Animals↗
PubMed1999

[Study on standards for safe and health-protective zone in firework plant].

A retrospective investigation on technology and situation in the production of fireworks, the cause and hazard consequences of accidents in blossom firework enterprises was carried out. The risk factors and their origins, the potential effects on surrounding environments and residents, the manufacture processes producing special potential energy in these enterprises were summarized and assessed. In addition, the consequences of explosive fire accidents were assessed retrospectively by the principle of explosion mechanics and Hopkinson Scaling Law. The safe and health-protective zone of the blossom firework plant was suggested.

Industry↗