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Biomedical subjects

M Wang

Publications and source records attributed to M Wang.

At least 271 records · Page 15Linked to original sources

Functional characterization of zinc-finger motif in redox regulation of RPA-ssDNA interaction.

The 70-kDa subunit of eukaryotic replication protein A (RPA) contains a conserved four cysteine-type zinc-finger motif that has been implicated in regulation of DNA replication and repair. Unlike other zinc-finger proteins, RPA zinc-finger motif is not a DNA-binding component, and deletion of the zinc-finger had very little effect on its ssDNA binding activity. Recently, we described a novel function for the zinc-finger motif in regulation of RPA's ssDNA binding activity through reduction-oxidation (redox). In this study, we carried out a detailed analysis of wild-type RPA and zinc-finger mutants in redox regulation of their ssDNA binding activity. Any mutation at a zinc-finger cysteine abolished its redox role in regulation of RPA-ssDNA interaction, suggesting that all four zinc-finger cysteines are required for redox regulation. Reactivity of cysteine residues to 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) indicated that wild-type RPA contained 8.2 reactive thiols/molecule including all four cysteines in the zinc-finger motif. Zinc-finger cysteines slowly reacted to DTNB as compared to others. Zn(II) was not only essential but also uniquely qualified for redox regulation of RPA-ssDNA interaction, suggesting that Zn(II)-cysteine coordination is crucial for the zinc-finger function. Redox status significantly affected initial interaction of RPA with ssDNA but had no effect after RPA formed a stable complex with DNA. Together, our results suggest that the zinc-finger motif mediates the transition of RPA-ssDNA interaction to a stable RPA-ssDNA complex in a redox-dependent manner.

Biosensing Techniques↗

Ternary early-transition-metal palladium pnictides Zr3Pd4P3, Hf3Pd4P3, HfPdSb, and Nb5Pd4P4.

Several ternary palladium pnictides of the early transition metals have been prepared by arc-melting of the elemental metals and the binary pnictides ZrP, HfP, HfSb2, or NbP, and their structures have been determined by X-ray diffraction methods. The phosphides M3Pd4P3 (M = Zr, Hf) adopt a new structure type (Pearson symbol oP40), crystallizing in the orthorhombic space group Pnma with Z = 4 and unit cell parameters of a = 16.387(2), b = 3.8258(5), and c = 9.979(1) A for Zr3Pd4P3 and a = 16.340(2), b = 3.7867(3), and c = 9.954(1) A for Hf3Pd4P3. The antimonide HfPdSb was identified by powder X-ray diffraction (orthorhombic, Pnma, Z = 4, a = 6.754(1) A, b = 4.204(1) A, and c = 7.701(2) A) and confirmed to be isostructural to ZrPdSb, which adopts the TiNiSi-type structure. The phosphide Nb5Pd4P4 adopts the Nb5Cu4Si4-type structure, crystallizing in the tetragonal space group I4/m with Z = 2, a = 10.306(1) A, and c = 3.6372(5) A. Coordination geometries of pentacapped pentagonal prisms for the early transition metal, tetracapped distorted tetragonal prisms for Pd, and tricapped trigonal prisms for the pnicogen are found in the three structures; tetracapped tetragonal prisms for Nb are also found in Nb5-Pd4P4. In common with many metal-rich compounds whose metal-to-nonmetal ratio is equal or close to 2:1, the variety of structures formed by these ternary palladium pnictides arises from the differing connectivity of pnicogen-filled trigonal prisms. Pnicogen-pnicogen bonds are absent in these structures, but metal-metal bonds (in addition to metal-pnicogen bonds) are important interactions, as verified by extended Hückel band structure calculations on Zr3Pd4P3.

Journal Article↗

Nitrogen Adsorption Studies of PAN-Based Activated Carbon Fibers Prepared by Different Activation Methods.

Polyacrylonitrile (PAN)-based activated carbon fibers (ACFs) prepared by various activation methods were characterized using low-temperature nitrogen adsorption over a wide relative pressure from 10(-6) to 1. Nitrogen adsorption is a standard tool for determination of porous structure parameters. In the present work, we carried out extensive adsorption studies of a series of PAN-ACFs activated by different methods. It was shown that the high-resolution alpha(S) plot provided valuable information about structural properties of samples under study. The pore size distributions of samples under study were calculated by employing the regularization method according to density functional theory. By these analyses, the pore development and the dominant pores of samples prepared by different methods can be clearly observed. Moreover, the adsorption measurement could provide profound insight into the structural heterogeneity of the ACFs. Copyright 2000 Academic Press.

Journal Article↗

Use of allochimeric proteins to mitigate graft-versus-host and host-versus-graft immune responses to rat small bowel allografts.

BACKGROUND: We aimed to identify the polymorphic epitopes that mitigate graft-versus-host disease (GvHD) and host-versus-graft response (HvGR) toward rat small bowel allografts in rats. METHODS: We tailored class I major histocompatibility complex (MHC) allochimeric antigens encoding 10 al-helical (alpha(1h)l58-80-RT1.Aa) or 4 (alpha(1h)l/u62-69-RT1.Aa) polymorphic amino acids. In the GvHD model, ACI (RT1a) donors were pretreated (day -14) with an intrathymic injection of alpha(1h)l58-80-RT1.Aa, alpha(1h)l/u62-69-RT1.Aa, or RT1.Al protein, with or without simultaneous intravenous injection of anti-T-cell receptor R73 monoclonal antibodies. Wistar-Furth (WF; RT1u) donors were tested with a similar protocol. In the HvGR model, ACI recipients were treated with a protocol designed to induce transplantation tolerance toward WF heart allografts: a portal vein injection of alpha(1h)l/u62-69-RT1.Aa protein and cyclosporine (4 mg/kg, intramuscular; days 0-6). RESULTS: GvHD was prevented in all (ACI x LEW) F1 recipients (RT1a/l) by pretreating ACI donors with R73 monoclonal antibody and recipient RT1.Al or alpha(1h)l58-80-RT1.Aa protein. Similarly, pretreatment of WF donors with RT1.Aa protein also prevented GvHD in (ACI x WF) F1 recipients. However, in a combined GvHD/HvGR model, ACI recipient perioperative treatment designed to prevent HvGR only modestly prolonged WF small bowel allograft survival (27.7+/-5.3 days compared to 17.4+/-4.6 days in the cyclosporine-alone group). In contrast, application of the two protocols significantly prolonged WF allograft survival (55.6+/-34.6 days), with two of seven recipients surviving more than 100 days. CONCLUSION: Simultaneous inhibition of GvHD and HvGR significantly prolongs small bowel allograft survival.

Animals↗

A link between basic fibroblast growth factor (bFGF) and EWS/FLI-1 in Ewing's sarcoma cells.

The EWS/FLI-1 fusion gene is characteristic of most cases of Ewing's sarcoma and has been shown to be crucial for tumor transformation and cell growth. In this study we demonstrate a drastic down-regulation of the EWS/FLI-1 protein, and a growth arrest, following serum depletion of Ewing's sarcoma cells. This indicates that growth factor circuits may be involved in regulation of the fusion gene product. Of four different growth factors tested, basic fibroblast growth factor (bFGF) was found to be of particular significance. In fact, upon treatment of serum-depleted cells with bFGF, expression of the EWS/FLI-1 protein and growth of the Ewing's sarcoma cells were restored. In addition, a bFGF-neutralizing antibody, which was confirmed to inhibit FGF receptor (FGFR) phosphorylation, caused down-regulation of EWS/FLI-1. Experiments using specific cell cycle blockers (thymidine and colcemide) suggest that EWS/FLI-1 is directly linked to bFGF stimulation, and not indirectly to cell proliferation. We also demonstrated expression of FGFRs in several tumor samples of Ewing's sarcoma. Taken together, our data suggest that expression of FGFR is a common feature of Ewing's sarcoma and, in particular, that the bFGF pathway may be important for the maintenance of a malignant phenotype of Ewing's sarcoma cells through up-regulating the EWS/FLI-1 protein. Oncogene (2000) 19, 4298 - 4301

Adenocarcinoma↗

Influence of alternatively and classically activated macrophages on fibrogenic activities of human fibroblasts.

Activated macrophages regulate fibrogenesis by providing cytokines and growth factors that modulate the proliferation and collagen synthesis of fibroblasts. However, macrophages can be activated in a classical pathway induced by LPS or IFN-gamma and an alternative pathway induced by IL-4 or glucocorticoid. Differently activated macrophages display distinct biological features. To clarify the difference between these two subsets of macrophages in the regulatory mechanisms controlling fibrogenesis, human peripheral blood monocytes were used as the source of macrophages and cocultivation of differently activated macrophages and a fibroblast cell line, WI-38, was performed. Alternatively activated macrophages increased the proliferation index and collagen synthesis of cocultivated WI-38 cells in comparison to untreated monocytes, while classically activated macrophages markedly reduced collagen production of cocultivated WI-38 cells. Additionally, mRNA expression and protein production of TGF-beta(1), PDGF-AA, and PDGF-BB were elevated in alternatively activated macrophages in parallel to their profibrogenic effects. In contrast, expression and production of TNF-alpha, as well as MMP-7, were enhanced in classically activated macrophages. These findings suggested that alternatively activated macrophages enhance fibrogenesis of fibroblasts by providing profibrogenic factors, while classically activated macrophages inhibit fibrogenesis of fibroblasts by releasing antifibrogenic or fibrolytic factors.

Cell Division↗

Characterization of nicotinic acetylcholine receptor-mediated noradrenaline release from the isolated rat stomach.

We characterized nicotinic acetylcholine receptor-mediated noradrenaline release from the isolated, vascularly perfused rat stomach. The stomach was perfused via the coeliac artery with Krebs-Ringer solution at a constant flow rate of 4 ml per minute. Endogenous noradrenaline released into the perfusate was electrochemically measured using high-performance liquid chromatography. Nicotinic receptor agonists were applied once into the perfusion medium for 2 min and nicotinic receptor antagonists were administered throughout the experiments. The (-)-nicotine (3x10(-5) M)-induced noradrenaline release was abolished by tetrodotoxin and hexamethonium and partially blocked by dihydro-beta-erythroidine (up to 10(-5) M) (a relatively selective antagonist of alpha4beta2 nicotinic receptors) and abolished by mecamylamine (10(-5) M) (a relatively selective antagonist of alpha3beta4 nicotinic receptors), but not influenced by alpha-bungarotoxin (3x10(-7) M) or alpha-conotoxin ImI (10(-6) M) (antagonists of alpha7 nicotinic receptors). (+/-)-Epibatidine (3x10(-7) M) (a very potent, but non-selective agonist) and (-)-cytisine (3x10(-4) M) (an agonist of beta4 nicotinic receptors) effectively evoked the release of noradrenaline, while (E)-N-methyl-4-(3-pyridinyl)-3-butene-1-amine (RJR-2403) (up to 10(-4) M) (an agonist of alpha4beta2 nicotinic receptors) had no effect. The potency of these agonists was as followed; (+/-)-epibatidine>>(-)-nicotine>(-)-cytisine>>>RJR -2403. These results are compatible with the published view that alpha3beta4 nicotinic receptors are predominant in other parts of the autonomic nervous system. These receptors (probably located on the gastric sympathetic ganglia) are involved in the release of noradrenaline from the rat stomach.

Animals↗

FIN219, an auxin-regulated gene, defines a link between phytochrome A and the downstream regulator COP1 in light control of Arabidopsis development.

Light signals perceived by photoreceptors are transduced to negatively regulate COP1, a key repressor of photomorphogenic development. To identify genes involved in light inactivation of COP1, a genetic screen was employed to identify extragenic modifier mutations of a temperature-sensitive cop1 allele. One suppressor mutation isolated also exhibited a far-red-specific long hypocotyl phenotype in a wild-type background. Further phenotypic analyses of this new mutation, named fin219, suggested that it defines a novel phytochrome A signaling component. Genetic analysis indicated that FIN219 interacts closely with another phytochrome A signaling component, FHY1. Molecular characterization of FIN219 indicated that it encodes a cytoplasmic localized protein highly similar to the GH3 family of proteins and its expression is rapidly induced by auxin. In contrast to its loss-of-function mutant phenotype, overexpression of FIN219 results in a far-red-specific hyperphotomorphogenic response. Our data suggest that FIN219 may define a critical link for phytochrome A-mediated far-red inactivation of COP1 and a possible cross-talk juncture between auxin regulation and phytochrome signaling.

Amino Acid Sequence↗

A study of postoperative radiotherapy in patients with non-small-cell lung cancer: a randomized trial.

PURPOSE: To study the value of postoperative radiotherapy for non-small-cell lung cancer (NSCLC) with positive regional lymph metastases (NI or N2) after radical surgery. MATERIALS AND METHODS: From February 1982 to October 1995, 366 patients with NSCLC and N1 or N2 disease were randomized into postoperative radiotherapy (S + R) (183 patients) and no further treatment (S alone) (182 patients). Postoperative radiotherapy (RT) was administrated 3-4 weeks after radical operation. Irradiated fields covered the bronchial stump, ipsilateral hilum, and most of the mediastinum. The midplane dose was 6000 cGy/30 fractions/6 weeks, with the spinal cord limited to 4000 cGy/20 fractions/4 weeks or less. One hundred thirty-four patients in S + R group and 162 patients in S alone group were evaluated. Clinical data were comparable in both arms, except for the numbers of N2 patients. RESULTS: The 3-year and 5-year overall survival rates were 51.9% and 42.9% in the S + R group and 50.2% and 40.5% in the S alone Group (p = 0.56). The 3-year and 5-year disease-free survival rates were 50.7% +/- 4.7% and 42.9% +/- 5.2% in the S + R group vs. 44.4% +/- 4.3% and 38.2% +/- 4.5% in the S alone group (p = 0.28), respectively. In the patients with NI or T3-4 tumors, there was a trend toward improved survival in the S + R group, especially in the patients with T3-4N1M0. These patients demonstrated 20% improvement in overall survival (p = 0.092) and greater than 20% better disease-free survival (p = 0.057). Postoperative RT reduced local recurrence but had no impact on distant metastases. CONCLUSION: Postoperative RT significantly reduced local relapses, but did not improve overall survival, due to a high frequency of distant metastases in this patient group.

Carcinoma, Non-Small-Cell Lung↗

Exonic deletion mutations of the Parkin gene among sporadic patients with Parkinson's disease.

Exonic deletions of the Parkin gene are common in the autosomal recessive form of juvenile parkinsonism. Here we report Parkin gene mutations among apparently sporadic Parkinson's disease (PD) patients. We screened 200 patients with PD (103 women and 97 men). The age of onset was 54.2+/-10.3years (mean+/-S.D.).Four out of the 200 patients had homozygous exonic deletions in the Parkin gene. The clinical features of these four patients were essentially the same as those of idiopathic PD. The age of onset was consistently younger (33, 38, 47 and 48years, respectively). On medication, all of them were at Hoehn and Yahr stage II or III even after 12-16years from the onset of the disease.Thus 2% of apparently sporadic PD patients in Japan have homozygous Parkin gene mutations. This positive rate was 6.3% among the patients with the age of onset below 50. Our study suggests that the prevalence of the carrier state of Parkin gene may be more than that we expected. Our study warrants further studies on Parkin gene mutations in apparently sporadic PD patients.

Journal Article↗

Brain phospholipase A(2)-arachidonic acid cascade is involved in the activation of central sympatho-adrenomedullary outflow in rats.

The present experiments were designed to explore the role of the brain phospholipase A(2)-arachidonic acid cascade in the activation of central sympatho-adrenomedullary outflow in rats, using melittin (an activator of phospholipase A(2)) and arachidonic acid. Intracerebro-ventricularly administered melittin (2.5, 10, and 25 microg/animal) or arachidonic acid (75, 150, 300 microg/animal) effectively and dose dependently elevated plasma levels of adrenaline and noradrenaline. The elevation of both catecholamines induced by melittin (10 microg/animal) was abolished by centrally administered mepacrine (an inhibitor of phospholipase A(2)), but not by neomycin (an inhibitor of phospholipase C). However, mepacrine had no effect on the increase induced by arachidonic acid (150 microg/animal). Indomethacin (an inhibitor of cyclooxygenase) abolished all responses induced by melittin and arachidonic acid. Furegrelate (an inhibitor of thromboxane A(2) synthase) abolished the elevation of adrenaline induced by melittin and arachidonic acid, but had no effect on the elevation of noradrenaline induced by these compounds. These results suggest that activation of the brain phospholipase A(2)-arachidonic acid cascade facilitates the central sympatho-adrenomedullary outflow in rats. Brain thromboxane A(2) is involved in the activation of central adrenomedullary outflow and an active metabolite of arachidonic acid other than thromboxane A(2) may be involved in activation of the central sympathetic outflow.

Animals↗

The presence and subcellular localization of caspase 3-like proteinases in plant cells.

Caspases play a very important role in initiating and executing apoptotic processes in animal cells. In this study we show that plant mitochondria were able to initiate the activation of caspase 3 in a Xenopus cell free system. Caspase 3-like activity was found to be present in plant cells and could only be inhibited by the specific caspase 3 inhibitor N-acetyl-Asp-Glu-Val-Asp-fluoromethylketone (Ac-DEVD-fmk) and not by cysteine protease inhibitors. By micro-injection of the caspase 3 substrate in living Chara cells we showed that caspase 3-like activity was mainly present in the cytosol rather than in the vacuole. This is the first time that in vivo caspase 3-like activity has been demonstrated in plants.

Animals↗

Absence of specific mucosal antibody responses in HIV-exposed uninfected sex workers from the Gambia.

OBJECTIVES: Specific antibodies to HIV envelope that inactivate virus at the mucosal surfaces involved in sexual contact are of interest for the design of a vaccine against HIV-1. It has been suggested that, in frequently HIV-exposed but uninfected individuals, HIV-specific mucosal antibody responses may exist and play a role in resistance against HIV. This study investigated HIV-1 envelope specific mucosal antibody responses in HIV-resistant sex workers in west Africa. METHODS: A group of 26 exposed uninfected female commercial sex workers from the Gambia, who have had repeated exposures to HIV-1 and HIV-2 were studied. We assessed the presence of vaginal IgA and IgG in vaginal swabs against a range of HIV-1 and HIV-2 envelope presentations and performed HIV-1 neutralization assays. RESULTS: No significant vaginal IgA or IgG responses against HIV-1 or HIV-2 were detected, and none of the vaginal secretions tested displayed any HIV-1 neutralizing activity. CONCLUSION: Vaginal antibody responses against HIV were not found in Gambian sex workers who resist HIV infection. Resistance against HIV infection can therefore occur in the absence of specific antibodies against HIV at the genital mucosa. A protective role for HIV-envelope specific IgA in resistance against HIV-1 infection in exposed uninfected individuals as reported in the literature is uncertain.

Antibody Formation↗

RPA stabilizes the XPA-damaged DNA complex through protein-protein interaction.

The xeroderma pigmentosum group A complementing protein (XPA) and eukaryotic replication protein A (RPA) are among the major damage-recognition proteins involved in the early stage of nucleotide excision repair (NER). XPA and RPA are able to bind damaged DNA independently, although RPA interaction stimulates XPA binding to damaged DNA [Li, L., Lu, X., Peterson, C. A., and Legerski, R. J. (1995) Mol. Cell. Biol. 15, 5396-5402 (1); Stigger, E., Drissi, R., and Lee, S.-H. (1998) J. Biol. Chem. 273, 9337-9343 (2)]. In this study, we used surface plasmon resonance (SPR) analysis to investigate the interaction of XPA and RPA with two major types of UV-damaged DNA: the (6-4) photoproduct and the cis-syn cyclobutane dimer of thymidine. Both XPA and RPA preferentially bind to (6-4) photoproduct-containing duplex DNA over cis-syn cyclobutane dimer-containing DNA. The binding of XPA to (6-4) photoproduct was weak (K(D) = 2.13 x 10(-)(8) M), whereas RPA showed a very stable interaction with (6-4) photoproduct (K(D) = 2. 02 x 10(-)(10) M). When XPA and RPA were incubated together, the stability of the XPA-damaged DNA interaction was significantly enhanced by wild-type RPA. On the other hand, mutant RPA (RPA:p34Delta33C) defective in its interaction with XPA failed to stabilize XPA-damaged DNA complex. Taken together, our results suggest that a role for RPA in UV-damage recognition is to stabilize XPA-damaged DNA complex through protein-protein interaction.

Base Sequence↗

14-3-3 proteins interact with a 13-lipoxygenase, but not with a 9-lipoxygenase.

Associations between lipoxygenases (Lox) and 14-3-3 proteins were demonstrated by two different methods. First, immunoprecipitation experiments, using isoenzyme-specific monoclonal Lox antibodies, showed that 14-3-3 proteins co-precipitate with 13-Lox, but not with the 9-Lox from barley. Second, interactions between 13-Lox and 14-3-3 were established by surface plasmon resonance studies, showing that 13-Lox binds with 14-3-3 proteins in a concentration-dependent manner. The interactions between 14-3-3 proteins and 13-Lox may reveal their role during plant development.

14-3-3 Proteins↗

The aconitase function of iron regulatory protein 1. Genetic studies in yeast implicate its role in iron-mediated redox regulation.

Iron regulatory proteins (IRP) are sequence-specific RNA-binding proteins that mediate iron-responsive gene regulation in animals. IRP1 is also the cytosolic isoform of aconitase (c-aconitase). This latter activity could complement a mitochondrial aconitase mutation (aco1) in Saccharomyces cerevisiae to restore glutamate prototrophy. In yeast, the c-aconitase activity of IRP1 was responsive to iron availability in the growth medium. Although IRP1 expression rescued aco1 yeast from glutamate auxotrophy, cells remained growth-limited by glutamate, displaying a slow-growth phenotype on glutamate-free media. Second site mutations conferring enhanced cytosolic aconitase-dependent (ECA) growth were recovered. Relative c-aconitase activity was increased in extracts of strains harboring these mutations. One of the ECA mutations was found to be in the gene encoding cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDP2). This mutation, an insertion of a Ty delta element into the 5' region of IDP2, markedly elevates expression of Idp2p in glucose media. Our results demonstrate the physiological significance of the aconitase activity of IRP1 and provide insight into the role of c-aconitase with respect to iron and cytoplasmic redox regulation.

Aconitate Hydratase↗

Subcellular differences in post-translational modification of barley 14-3-3 proteins.

Expression and post-translational modification of barley 14-3-3 isoforms, 14-3-3A, 14-3-3B and 14-3-3C, were investigated using isoform-specific antibodies. Although all three isoforms were shown to be present in the cytosolic, the nuclear and the microsomal cell fractions, differences in post-translational modification were identified for the different cell fractions. Germination-related modifications of 14-3-3 proteins were observed in the cytosol and the microsomal fraction, but not in the nucleus. In vitro proteolytic cleavage of 14-3-3 proteins using trypsin suggests that for 14-3-3A this change was caused by proteolytic cleavage of the unconserved C-terminal region.

14-3-3 Proteins↗

An inhibitor of activated thrombin-activatable fibrinolysis inhibitor potentiates tissue-type plasminogen activator-induced thrombolysis in a rabbit jugular vein thrombolysis model.

When activated in vitro, thrombin-activatable fibrinolysis inhibitor (TAFI) slows clot lysis by cleaving the C-terminal lysine and arginine residues from partially degraded fibrin. An inhibitor of carboxypeptidase isolated from potato (CPI) reverses prolongation of clot lysis by inhibiting activated TAFI. We investigated in vivo effect of TAFI inhibition on tissue-type plasminogen activator (t-PA)-induced clot lysis using CPI in a rabbit jugular vein thrombolysis model. It was found necessary to further purify the CPI preparations from commercial sources by HPLC chromatography to remove endotoxin and anti-plasmin activity that would affect the endogenous fibrinolytic system. The effect of intravenous administration of the purified CPI with t-PA was determined by measuring thrombus weight at the end of 90 minutes in six groups of animals. In the control group receiving saline, the median thrombus weight was 116 mg. In the group that received CPI only (0.5 mg/kg bolus injection followed by 0.3 mg/kg/h infusion), the median thrombus weight was 121 mg. In the group that received t-PA at a dose of 10 microg/kg bolus followed by 67 microg/kg/h infusion, the median thrombus weight decreased to 86 mg. When CPI was coadministered with the same regimen of t-PA, the median value further decreased to 58 mg. When animals were given three times higher the dose of t-PA (30 microg/kg bolus followed by 200 microg/kg/h infusion) in the absence or presence of CPI, median thrombus weights were 56 mg and 0 mg, respectively. Our results demonstrate that systemic coadministration of the purified CPI improves clot lysis induced by t-PA.

Animals↗