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Biomedical subjects

J Wu

Publications and source records attributed to J Wu.

At least 361 records · Page 20Linked to original sources
PubMed2001

[Diagnosis and treatment of paragangliomas in the central nerve system].

OBJECTIVE: To explore the diagnosis and treatment of paragangliomas in the central nerve system. METHODS: 17 patients with paragangliomas in the central nerve system over a 20-year period (1976-1999) were analyzed retrospectively. They included 11 patients with glomus jugular tumors, 1 with carotid body tumor, 1 with supersellar paraganglioma, 2 with spinal involvement, and 2 with superficial hemisphere involvement. RESULTS: Neoplasm was completely resected in 11 patients, subtotally in 3, and partial in 3. The postoperative mortality was 1/17. One patient remained severe disability, yet the others had excellent long-time outcome. CONCLUSIONS: Both the characteristic clinical presentation and neuroradiological manifestation were useful for preoperative diagnosis. Total resection is ideal for paragangliomas. Preoperative embolization should be used routinely to control intraoperative bleeding, and postoperative radiation-therapy would be valuable to control the recurrence of the remaining tumor.

Adult↗
PubMed2000

A mechanistic study of the antibacterial effect of silver ions on Escherichia coli and Staphylococcus aureus.

To investigate the mechanism of inhibition of silver ions on microorganisms, two strains of bacteria, namely Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus), were treated with AgNO(3) and studied using combined electron microscopy and X-ray microanalysis. Similar morphological changes occurred in both E. coli and S. aureus cells after Ag(+) treatment. The cytoplasm membrane detached from the cell wall. A remarkable electron-light region appeared in the center of the cells, which contained condensed deoxyribonucleic acid (DNA) molecules. There are many small electron-dense granules either surrounding the cell wall or depositing inside the cells. The existence of elements of silver and sulfur in the electron-dense granules and cytoplasm detected by X-ray microanalysis suggested the antibacterial mechanism of silver: DNA lost its replication ability and the protein became inactivated after Ag(+) treatment. The slighter morphological changes of S. aureus compared with E. coli recommended a defense system of S. aureus against the inhibitory effects of Ag(+) ions.

Anti-Bacterial Agents↗
PubMed2000

A practical synthesis of a COX-2-specific inhibitor.

A number of synthetic strategies to the Cox-2 specific inhibitor 1 have been described. These studies have led to the identification of a novel pyridine construction using annulation of ketone 2 using a vinamidinium species 29 and ammonia in 97% assay yield. Three approaches to the synthesis of ketone 2 are described that allow for its preparation in large quantities in >65% overall yield from methyl 6-methylnicotinate.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2000

Complexation of trivalent lanthanide cations by inositols in the solid state: crystal structure and an FT-IR study of PrCl3.myo-inositol.9 H2O.

The title compound, PrCl3.C6H12O6.9 H2O crystallized in the monoclinic space group P2(1)/n with cell dimensions a = 15.8293(3), b = 8.67750(10), c = 16.2292(3) A, beta = 107.0788(8) degrees, V = 2130.92(6) A3 and Z = 4. Each Pr ion is coordinated to nine oxygen atoms, two from the inositol and seven from water molecules, with Pr-O distances from 2.4729 to 2.6899 A; the other two water molecules are hydrogen-bonded. No direct contacts exist between Pr and Cl. There is an extensive network of hydrogen bonds formed by hydroxyl groups, water molecules, and chloride ions. The IR spectra of Pr-, Nd-, and Sm-inositol complexes are similar, which shows that the three metal ions have the same coordination mode. The IR results are consistent with the crystal structure.

Crystallization↗
PubMed2000

Global histone acetylation and deacetylation in yeast.

Histone acetyltransferases and deacetylases can be targeted to promoters to activate or repress genes. For example, the histone acetyltransferase GCN5 is part of a yeast multiprotein complex that is recruited by the DNA-binding activator protein GCN4 (refs 1-3). The histone deacetylase RPD3 complex is recruited to DNA by the repressor UME6 (refs 4, 5); similar mechanisms exist in other eukaryotes. However, deletion of RPD3 also increases expression of the PHO5 gene that is repressed by nucleosomes, and regulated by GCN5 (ref. 10) but not by UME6. We have determined whether acetylation and deacetylation are promoter specific at PHO5, by using antibodies against acetylated lysine residues and chromatin immunoprecipitation to examine the acetylation state of a 4.25-kilobase region surrounding the PHO5 gene. Here we show that this region is acetylated extensively by ESA1 and GCN5 and deacetylated by HDA1 and RPD3, and that widespread histone modification affects three separate chromosomal regions examined, which total 22kb. Our data indicate that targeted modification occurs in a background of global acetylation and deacetylation that not only reduces basal transcription, but also allows a rapid return to the initial state of acetylation when targeting is removed.

Acetylation↗
PubMed2000

Epidermal growth factor-induced phosphatidylinositol 3-kinase activation and DNA synthesis. Identification of Grb2-associated binder 2 as the major mediator in rat hepatocytes.

In previous work we showed that the phosphatidylinositol 3-kinase (PI3-kinase), not the mitogen-activated protein kinase, pathway is necessary and sufficient to account for insulin- and epidermal growth factor (EGF)-induced DNA synthesis in rat hepatocytes. Here, using a dominant-negative p85, we confirmed the key role of EGF-induced PI3-kinase activation and sought to identify the mechanism by which this is effected. Our results show that EGF activates PI3-kinase with a time course similar to that of the association of p85 with three principal phosphotyrosine proteins (i. e. PY180, PY105, and PY52). We demonstrated that each formed a distinct p85-associated complex. PY180 and PY52 each constituted about 10% of EGF-activated PI3-kinase, whereas PY105 was responsible for 80%. PY105 associated with Grb2 and SHP-2, and although it behaved like Gab1, none of the latter was detected in rat liver. We therefore cloned a cDNA from rat liver, which was found to be 95% homologous to the mouse Grb2-associated binder 2 (Gab2) cDNA sequence. Using a specific Gab2 antibody, we demonstrated its expression in and association with p85, SHP-2, and Grb2 upon EGF treatment of rat hepatocytes. Gab2 accounted for most if not all of the PY105 species, since immunoprecipitation of Gab2 with specific antibodies demonstrated parallel immunodepletion of Gab2 and PY105 from the residual supernatants. We also found that the PI3-kinase activity associated with Gab2 was totally abolished by dominant negative p85. Thus, Gab2 appears to be the principal EGF-induced PY protein recruiting and activating PI3-kinase and mitogenesis.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Medium-chain acyl-coenzyme A dehydrogenase bound to a product analogue, hexadienoyl-coenzyme A: effects on reduction potential, pK(a), and polarization.

2,4-Hexadienoyl-coenzyme A (HD-CoA) has been used to investigate the redox and ionization properties of medium-chain acyl-CoA dehydrogenase (MCAD) from pig kidney. HD-CoA is a thermodynamically stabilized product analogue that binds tightly to oxidized MCAD (K(dox) = 3.5 +/- 0.1 microM, pH 7.6) and elicits a redox potential shift that is 78% of that observed with the natural substrate/product couple [Lenn, N. D., Stankovich, M. T., and Liu, H. (1990) Biochemistry 29, 3709-3715]. The midpoint potential of the MCAD.HD-CoA complex exhibits a pH dependence that is consistent with the redox-linked ionization of two key glutamic acids as well as the flavin adenine dinucleotide (FAD) cofactor. The estimated ionization constants for Glu376-COOH (pK(a,ox) approximately 9.3) and Glu99-COOH (pK(a,ox) approximately 7.4) in the oxidized MCAD.HD-CoA complex indicate that while binding of the C(6) analogue makes Glu376 a stronger catalytic base (pK(a,ox) approximately 6.5, free MCAD), it has little effect on the pK of Glu99 (pK(a,ox) approximately 7.5, free MCAD) [Mancini-Samuelson, G. J., Kieweg, V., Sabaj, K. M., Ghisla, S., and Stankovich, M. T. (1998) Biochemistry 37, 14605-14612]. This finding is in agreement with the apparent pK of 9.2 determined for Glu376 in the human MCAD.4-thia-octenoyl-CoA complex [Rudik, I., Ghisla, S., and Thorpe, C. (1998) Biochemistry 37, 8437-8445]. The pK(a)s estimated for Glu376 and Glu99 in the reduced pig kidney MCAD.HD-CoA complex, 9.8 and 8.6, respectively, suggest that both of these residues remain protonated in the charge-transfer complex under physiological conditions. Polarization of HD-CoA in the enzyme active site may contribute to the observed pK(a) and redox potential shifts. Consequently, the electronic structures of the product analogue in its free and MCAD-bound forms have been characterized by Raman difference spectroscopy. Binding to either the oxidized or reduced enzyme results in localized pi-electron polarization of the hexadienoyl C(1)=O and C(2)=C(3) bonds. The C(4)=C(5) bond, in contrast, is relatively unaffected by binding. These results suggest that, upon binding to MCAD, HD-CoA is selectively polarized such that partial positive charge develops at the C(3)-H region of the ligand, regardless of the oxidation state of the enzyme.

Acyl Coenzyme A↗
PubMed2000

Solution structure of BmP02, a new potassium channel blocker from the venom of the Chinese scorpion Buthus martensi Karsch.

BmP02 is a 28-amino acid residue peptide purified from the venom of the Chinese scorpion Buthus martensi Karsch, which had been demonstrated to be a weak blocker of apamin-sensitive calcium-activated potassium channels. Two-dimensional NMR spectroscopy techniques were used to determine the solution structure of BmP02. The results show that BmP02 formed a alpha/beta scorpion fold, the typical three-dimensional structure adopted by most short chain scorpion toxins whose structures have been determined. However, in BmP02 this alpha/beta fold was largely distorted. The alpha-helix was shortened to only one turn, and the loop connecting the helix to the first beta-strand exhibited conformational heterogeneity. The instability of BmP02 could be attributed to a proline at position 17, which is usually a glycine. Because the residue at this position makes intense contact with the alpha-helix, it was supposed that the bulky side chain of proline had pushed the helix away from the beta-sheet. This had a significant influence on the structure and function of BmP02. The alpha-helix rotated by about 40 degrees to avoid Pro17 while forming two disulfides with the second beta-strand. The rotation further caused both ends of the helix to be unwound due to covalent restrictions. According to its structure, BmP02 was supposed to interact with its target via the side chains of Lys11 and Lys13.

Amino Acid Sequence↗
PubMed2000

c-Crk, a substrate of the insulin-like growth factor-1 receptor tyrosine kinase, functions as an early signal mediator in the adipocyte differentiation process.

Differentiation of 3T3-L1 preadipocytes into adipocytes is induced by a combination of inducers, including a glucocorticoid, an agent that elevates cellular cAMP, and a ligand of the insulin-like growth factor-1 receptor. Previous studies have implicated protein-tyrosine phosphatase (PTPase) HA2, a homologue of PTPase 1B, in the signaling cascade initiated by the differentiation inducers. Vanadate, a potent PTPase inhibitor, blocks adipocyte differentiation at an early stage in the program, but has no effect on the mitotic clonal expansion required for differentiation. Exposure of preadipocytes to vanadate along with the inducing agents led to the accumulation of pp35, a phosphotyrosyl protein that is a substrate for PTPase HA2. pp35 was purified to homogeneity and shown by amino acid sequence and mass analyses of tryptic peptides to be c-Crk, a known cytoplasmic target of the insulin-like growth factor-1 receptor tyrosine kinase. Transfection of 3T3-L1 preadipocytes with a c-Crk antisense RNA expression vector markedly reduced c-Crk levels and prevented differentiation into adipocytes. Studies with C3G, a protein that binds to the SH3 domain in c-Crk, showed that phosphorylation of c-Crk rendered the SH3 domain inaccessible to C3G. Taken together, these findings indicate that locking c-Crk in the phosphorylated state with vanadate prevents its participation in the signaling system that initiates adipocyte differentiation.

3T3 Cells↗
PubMed2000

Carboxyl methylation of the phosphoprotein phosphatase 2A catalytic subunit promotes its functional association with regulatory subunits in vivo.

The phosphoprotein phosphatase 2A (PP2A) catalytic subunit contains a methyl ester on its C-terminus, which in mammalian cells is added by a specific carboxyl methyltransferase and removed by a specific carboxyl methylesterase. We have identified genes in yeast that show significant homology to human carboxyl methyltransferase and methylesterase. Extracts of wild-type yeast cells contain carboxyl methyltransferase activity, while extracts of strains deleted for one of the methyltransferase genes, PPM1, lack all activity. Mutation of PPM1 partially disrupts the PP2A holoenzyme in vivo and ppm1 mutations exhibit synthetic lethality with mutations in genes encoding the B or B' regulatory subunit. Inactivation of PPM1 or overexpression of PPE1, the yeast gene homologous to bovine methylesterase, yields phenotypes similar to those observed after inactivation of either regulatory subunit. These phenotypes can be reversed by overexpression of the B regulatory subunit. These results demonstrate that Ppm1 is the sole PP2A methyltransferase in yeast and that its activity is required for the integrity of the PP2A holoenzyme.

Amino Acid Sequence↗
PubMed2000

Hyperglycemia-induced mitochondrial superoxide overproduction activates the hexosamine pathway and induces plasminogen activator inhibitor-1 expression by increasing Sp1 glycosylation.

The hexosamine pathway has been implicated in the pathogenesis of diabetic complications. We determined first that hyperglycemia induced a decrease in glyceraldehyde-3-phosphate dehydrogenase activity in bovine aortic endothelial cells via increased production of mitochondrial superoxide and a concomitant 2.4-fold increase in hexosamine pathway activity. Both decreased glyceraldehyde-3-phosphate dehydrogenase activity and increased hexosamine pathway activity were prevented completely by an inhibitor of electron transport complex II (thenoyltrifluoroacetone), an uncoupler of oxidative phosphorylation (carbonyl cyanide m-chlorophenylhydrazone), a superoxide dismutase mimetic [manganese (III) tetrakis(4-benzoic acid) porphyrin], overexpression of either uncoupling protein 1 or manganese superoxide dismutase, and azaserine, an inhibitor of the rate-limiting enzyme in the hexosamine pathway (glutamine:fructose-6-phosphate amidotransferase). Immunoprecipitation of Sp1 followed by Western blotting with antibodies to O-linked GlcNAc, phosphoserine, and phosphothreonine showed that hyperglycemia increased GlcNAc by 1.7-fold, decreased phosphoserine by 80%, and decreased phosphothreonine by 70%. The same inhibitors prevented all these changes. Hyperglycemia increased expression from a transforming growth factor-beta(1) promoter luciferase reporter by 2-fold and increased expression from a (-740 to +44) plasminogen activator inhibitor-1 promoter luciferase reporter gene by nearly 3-fold. Inhibition of mitochondrial superoxide production or the glucosamine pathway prevented all these changes. Hyperglycemia increased expression from an 85-bp truncated plasminogen activator inhibitor-1 (PAI-1) promoter luciferase reporter containing two Sp1 sites in a similar fashion (3.8-fold). In contrast, hyperglycemia had no effect when the two Sp1 sites were mutated. Thus, hyperglycemia-induced mitochondrial superoxide overproduction increases hexosamine synthesis and O-glycosylation of Sp1, which activates expression of genes that contribute to the pathogenesis of diabetic complications.

Acetylglucosamine↗
PubMed2000

Arsenite induces apoptosis of murine T lymphocytes through membrane raft-linked signaling for activation of c-Jun amino-terminal kinase.

Because of its dual roles in acute toxicity and in therapeutic application in cancer treatment, arsenic has recently attracted a renewed attention. In this study, we report NaAsO(2)-induced signal cascades from the cell surface to the nucleus of murine thymic T lymphocytes that involve membrane rafts as an initial signal transducer. NaAsO(2) induced apoptosis through fragmentation of DNA, activation of caspase, and reciprocal regulation of Bcl-2/Bax with the concomitant reduction of membrane potential. We demonstrated that NaAsO(2)-induced caspase activation is dependent on curcumin-sensitive c-Jun amino-terminal kinase and barely dependent on SB203580-sensitive p38 kinase or PD98059-sensitive extracellular signal-regulated kinase. Additionally, staurosporine, which severely inhibited the activation of mitogen-activated protein (MAP) family kinases and c-Jun, partially blocked the NaAsO(2)-mediated signal for poly(ADP-ribose) polymerase (PARP) degradation. Potentially as the initial cell surface event for intracellular signaling, NaAsO(2) induced aggregation of GPI-anchored protein Thy-1 and superoxide production. This Thy-1 aggregation and subsequent activation of MAP family kinase and c-Jun and the degradation of PARP induced by NaAsO(2) were all inhibited by DTT, suggesting the requirement of interaction between arsenic and protein sulfhydryl groups for those effects. beta cyclodextrin, which sequestrates cholesterol from the membrane rafts, inhibited NaAsO(2)-induced activation of protein tyrosine kinases and MAP family kinases, degradation of PARP, and production of superoxide. In addition, beta cyclodextrin dispersed NaAsO(2)-induced Thy-1 clustering. These results suggest that a membrane raft integrity-dependent cell surface event is a prerequisite for NaAsO(2)-induced protein tyrosine kinase/c-Jun amino-terminal kinase activation, superoxide production, and downstream caspase activation.

Animals↗
PubMed2000

Gating of inward rectifier K+ channels by proton-mediated interactions of N- and C-terminal domains.

Ion channels play an important role in cellular functions, and specific cellular activity can be produced by gating them. One important gating mechanism is produced by intra- or extracellular ligands. Although the ligand-mediated channel gating is an important cellular process, the relationship between ligand binding and channel gating is not well understood. It is possible that ligands are involved in the interactions of different protein domains of the channel leading to opening or closing. To test this hypothesis, we studied the gating of Kir2.3 (HIR) by intracellular protons. Our results showed that hypercapnia or intracellular acidification strongly inhibited these channels. This effect relied on both the N and C termini. The CO(2)/pH sensitivities were abolished or compromised when one of the intracellular termini was replaced. Using purified N- and C-terminal peptides, we found that the N and C termini bound to each other in vitro. Although their binding was weak at pH 7.4, stronger binding was seen at pH 6.6. Two short sequences in the N and C termini were found to be critical for the N/C-terminal interaction. Interestingly, there was no titratable residue in these motifs. To identify the potential protonation sites, we systematically mutated most histidine residues in the intracellular N and C termini. We found that mutations of several histidine residues in the C but not the N terminus had a major effect on channel sensitivities to CO(2) and pH(i). These results suggest that at acidic pH, protons appear to interact with the C-terminal histidine residues and present the C terminus to the N terminus. Consequentially, these two intracellular termini bound to each other through two short motifs and closed the channel. Thus, a novel mechanism for K(+) channel gating is demonstrated, which involves the N- and C-terminal interaction with protons as the mediator.

Amino Acid Motifs↗
PubMed2000

DAP10 and DAP12 form distinct, but functionally cooperative, receptor complexes in natural killer cells.

Many of the activating receptors on natural killer (NK) cells are multisubunit complexes composed of ligand-binding receptors that are noncovalently associated with membrane-bound signaling adaptor proteins, including CD3zeta, FcstraightepsilonRIgamma, DAP12, and DAP10. Because the DAP10 and DAP12 genes are closely linked, expressed in NK cells, and have remarkably similar transmembrane segments, it was of interest to determine the specificity of their interactions with ligand-binding receptors and to examine their signaling properties. Despite their similarities, DAP10, DAP12, FcstraightepsilonRIgamma, and CD3zeta form specific receptor complexes with their ligand-binding partners in NK cells and transfectants. The transmembrane regions of DAP10 and DAP12 are sufficient to confer specific association with their partners. Although cross-linking of either DAP10- or DAP12-associated receptors has been shown to be sufficient to trigger NK cell-mediated cytotoxicity against Fc receptor-bearing cells, substantial synergy was observed in the induction of cytokine production when both receptors were engaged. Activation of the Syk/ZAP70 tyrosine kinases by the immunoreceptor tyrosine-based activation motif-containing DAP12 adaptor and of the phosphatidylinositol 3-kinase pathway by the YxNM-containing DAP10 adaptor may play an important role in the stimulation of NK cells and T cells.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Study of charmless hadronic B meson decays to pseudoscalar-vector final states.

We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.

Journal Article↗
PubMed2000

Fiberoptic ductoscopy for patients with nipple discharge.

BACKGROUND: Breast carcinoma and precancer are thought to start in the lining of the milk duct or lobule, yet until recently, we have not had direct access to this area other than by blindly removing tissue by core biopsy or fine-needle aspiration. Fiberoptic ductoscopy (FDS) is an emerging technique allowing direct visual access to the ductal system of the breast through nipple orifice exploration. METHODS: We applied ductoscopy to 259 women who had nipple discharge, and we analyzed the visual findings, the cytological washings, and the subsequent histopathology. RESULTS: In 92 (36%) of these women, fiberoptic ductoscopy was successful in detecting an intraductal papillary lesion. Of these observed lesions, 68 (74%) were single papilloma, 21 (23%) were multiple discrete papillomas, and 3 (3%) were diffuse intraductal thickening which corresponded to diffuse papillomatosis on histopathological analysis. The overall positive predictive value of FDS screening was 83%. Of the lesions observed, 29.8% were located in the main (segmental) duct, 43.9% lesions in the first branch, 17.5% lesions in the second branch, 7.9% in the third branch, and 0.9% in the fourth branch. These lesions had an overall average distance of 2.7 cm from the nipple orifice. Ductal washings performed at the time of ductoscopy were effective at obtaining representative exfoliated ductal cells which could be evaluated for the presence of clumps (> 50 cells), clumps with atypia or single ductal cells. The presence of clumps with positive FDS increased the positive predictive value to 86%. CONCLUSIONS: Fiberoptic ductoscopy currently offers a safe alternative to ductography in guiding subsequent breast surgery in the treatment of nipple discharge.

Adult↗