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Effects of fluorocarbon propellants on respiratory flow and ECG.

Valić, F; Skurić, Z; Bantić, Z; Rudar, M; Hećej, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1977 Português
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Ten subjects were exposed to the propellants freon 11, freon 12, freon 114, to two mixtures of freon 11 and 12 and to a mixture of freon 12 and 114. The length of exposure was 15, 45 or 60 seconds. Maximum expiratory flow-volume (MEF) curves and ECG were recorded before, and intermittently up to 1 hour after, exposure. Breathing level concentrations of propellants during exposure were determined by gas chromatography. All freons induced biphasic reduction of ventilatory capacity on inhalation. The first fall occurred within a few minutes of exposure while the second was delayed 13-30 minutes after exposure. The effects of mixtures were greater than those of individual freons. The relative fall in MEF 75% was more pronounced than that in MEF 50%. No clear-cut pathological changes in ECG were found. Nevertheless, most subjects developed variations in heart rate exceeding those noted before exposure. In a few cases inversion of the T wave, and in one case atrioventricular block, were observed.

Analysis of fumonisin B1-induced apoptosis.

Jones, C; Ciacci-Zanella, J R; Zhang, Y; Henderson, G; Dickman, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/2001 Português
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Fumonisins are mycotoxins produced by Fusarium moniliforme, a prevalent fungus that infects corn and other cereal grains. Fumonisin B1(FB1 is the most common mycotoxin produced by F. moniliforme, suggesting it has toxicologic significance. The structure of FB1 resembles sphingoid bases, and it inhibits ceramide synthase. Because sphingoid bases regulate cell growth, differentiation, transformation, and apoptosis, it is not surprising to find that FB1 can alter growth of certain mammalian cells. Previous studies concluded FB1-induced apoptosis, or cell cycle arrest, in African green monkey kidney fibroblasts (CV-1). In this study we have identified genes that inhibit FB1 induced apoptosis in CV-1 cells and two mouse embryo fibroblasts (MEF). A baculovirus gene, inhibitor of apoptosis (CpIAP), protected these cells from apoptosis. CpIAP blocks apoptosis induced by the tumor necrosis factor (TNF) pathway as well as other mechanisms. Further support for the involvement of the TNF signal transduction pathway in FB1 induced apoptosis was the cleavage of caspase 8. Inhibition of caspases by the baculovirus gene (italic)p35 also inhibited FB1-induced apoptosis. The tumor suppressor gene p53 was not required for FB1 induced apoptosis because p53-/- MEF undergo apoptosis following FB1 treatment. Furthermore...

Prevalence and Molecular Genetics of Macrolide Resistance among Streptococcus pneumoniae Isolates Collected in Finland in 2002

Rantala, M.; Huikko, S.; Huovinen, P.; Jalava, J.;
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/2005 Português
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The prevalence and mechanisms of macrolide resistance among 1,007 clinical pneumococcal isolates collected in Finland were investigated. Of these, 217 (21.5%) were resistant to erythromycin and 11% to clindamycin. Among the erythromycin-resistant isolates, mef(E) was present in 95 isolates (44%), mef(A) was present in 12 isolates (6%), and erm(B) was present in 90 isolates (41%). A double mechanism, mef(E) and erm(B), was detected in five isolates (2%). Ribosomal mutation was detected in 14 (6%) macrolide-resistant isolates in which no other determinant was found. Based on the telithromycin MICs, two groups of isolates were formed: 83.3% of the isolates belonged to a major group for which the telithromycin MIC range was ≤0.008 to 0.063 μg/ml, and 16.7% belonged to a minor group for which the telithromycin MIC range was 0.125 to 8 μg/ml. All except three isolates in the minor population carried a macrolide resistance gene.

RAX, the PKR activator, sensitizes cells to inflammatory cytokines, serum withdrawal, chemotherapy, and viral infection

Bennett, Richard L.; Blalock, William L.; Abtahi, Dean M.; Pan, Yu; Moyer, Sue A.; May, W. Stratford
Fonte: The American Society of Hematology Publicador: The American Society of Hematology
Tipo: Artigo de Revista Científica
Publicado em 01/08/2006 Português
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While the interferon (IFN)–inducible double-stranded RNA (dsRNA)–dependent protein kinase PKR is reported to initiate apoptosis in some instances, the mechanism by which diverse stress stimuli activate PKR remains unknown. Now we report that RAX, the only known cellular activator for PKR, initiates PKR activation in response to a broad range of stresses including serum deprivation, cytotoxic cytokine or chemotherapy treatment, or viral infection. Thus, knock-down of RAX expression by 80% using small interfering RNA (siRNA) prevents IFNγ/tumor necrosis factor α (TNFα)–induced PKR activation and eIF2α phosphorylation, IκB degradation, IRF-1 expression, and STAT1 phosphorylation, resulting in enhanced murine embryonic fibroblast (MEF) cell survival. In contrast, expression of exogenous RAX, but not of the nonphosphorylatable, dominant-negative RAX(S18A) mutant, sensitizes cells to IFNγ/TNFα, mitomycin C (MMC), or serum deprivation in association with increased PKR activity and apoptosis. Furthermore, RAX(S18A) expression in Fanconi anemia complementation group C–null MEF cells not only prevents PKR activation but also blocks hypersensitivity to IFNγ/TNFα or mitomycin C that results in enhanced apoptosis. In addition, reduced RAX expression facilitates productive viral infection with vesicular stomatitis virus (VSV) and promotes anchorage-independent colony growth of MEF cells. Collectively...

KIN-29 SIK regulates chemoreceptor gene expression via an MEF2 transcription factor and a class II HDAC

van der Linden, Alexander M; Nolan, Katherine M; Sengupta, Piali
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
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The expression of individual chemoreceptor (CR) genes in Caenorhabditis elegans is regulated by multiple environmental and developmental cues, possibly enabling C. elegans to modulate its sensory responses. We had previously shown that KIN-29, a member of the salt-inducible kinase family, acts in a subset of chemosensory neurons to regulate the expression of CR genes, body size and entry into the alternate dauer developmental stage. Here, we show that KIN-29 regulates these processes by phosphorylating the HDA-4 class II histone deacetylase (HDAC) and inhibiting the gene repression functions of HDA-4 and an MEF-2 MADS domain transcription factor. MEF-2 binds directly to the CR gene regulatory sequences, and is required only to repress but not activate CR gene expression. A calcineurin phosphatase antagonizes the KIN-29/MEF-2-regulated pathway to modulate levels of CR gene expression. Our results identify KIN-29 as a new regulator of MEF2/HDAC functions in the nervous system, reveal cell-specific mechanisms of action of this pathway in vivo and demonstrate remarkable complexity in the regulation of CR gene expression in C. elegans.

Molecular Epidemiology of Macrolide and Tetracycline Resistances in Commensal Gemella sp. Isolates▿

Zolezzi, Paula Cerdá; Cepero, Pilar Goñi; Ruiz, Joaquim; Laplana, Leticia Millán; Calvo, Carmen Rubio; Gómez-Lus, Rafael
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
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The epidemiologic relatedness of 29 erythromycin-resistant Gemella sp. strains from normal flora, characterized previously, were evaluated by pulsed-field gel electrophoresis (PFGE). Three isolates carried the tet(O) gene and the tet(M) gene. The msr(A) gene was found in two Gemella morbillorum strains in combination with the erm(B) or mef(E) gene. The sequences of the mef(A/E), erm(B), and msr(A) genes showed a high similarity to the corresponding sequences of other gram-positive cocci. All the strains harboring the mef(A/E) gene and the msr(D) gene possessed open reading frame 3 (ORF3)/ORF6. The 16 G. morbillorum isolates represented 15 distinct DNA profiles. Four clusters were identified (≥80% genetic relatedness). The 12 Gemella haemolysans strains belonged to different PFGE types. The clonal diversity found suggests that horizontal transfer may be the main route through which erythromycin resistance is acquired.

Application of a model to explore interspecies differences in acetylcholine M-receptor-stimulated gastric acid secretion.

Welsh, N. J.; Shankley, N. P.; Black, J. W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/1995 Português
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1. Concentration-effect curves were obtained, in the absence and presence of histamine H2-receptor blockade, to 5-methylfurmethide (5-MeF) and McN-A 343, high efficacy and low efficacy acetylcholine (ACh) M-receptor agonists, respectively, in isolated stomach preparations from the mouse and immature rat and guinea-pig. 2. In the immature guinea-pig assay, the responses to 5-MeF and McN-A 343 were abolished by histamine H2-receptor blockade suggesting that the responses were totally dependent upon gastric mucosal histamine. However, in the mouse and immature rat assays, although the histamine H2-receptor antagonists produced small but significant rightward shifts and, in some cases, depression of the maximum of the agonist concentration-effect curves, a significant secretory response remained, presumed to be due to direct stimulation of oxyntic cells. 3. Previously, by assuming that the histamine H2-receptor blockade alters the mode of agonist-stimulated acid secretion from mainly an indirect action mediated by histamine release to direct stimulation of the oxyntic cell, we applied an operational model of agonism to similar data obtained in the mouse preparation. In that study we were able to account for the behaviour of 5-MeF and McN-A 343 by assuming that the agonists expressed 6 fold higher efficacy...

Serotypes, Clones, and Mechanisms of Resistance of Erythromycin-Resistant Streptococcus pneumoniae Isolates Collected in Spain▿

Calatayud, Laura; Ardanuy, C.; Cercenado, E.; Fenoll, A.; Bouza, E.; Pallares, R.; Martín, R.; Liñares, J.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
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The aim of this study was to analyze the distributions of antibiotic susceptibility patterns, serotypes, phenotypes, genotypes, and macrolide resistance genes among 125 nonduplicated erythromycin-resistant Streptococcus pneumoniae clinical isolates collected in a Spanish point prevalence study. The prevalence of resistance to macrolides in this study was 34.7%. Multiresistance (to three or more antimicrobials) was observed in 81.6% of these strains. Among 15 antimicrobials studied, cefotaxime, moxifloxacin, telithromycin, and quinupristin-dalfopristin were the most active drugs. The most frequent serotypes of erythromycin-resistant isolates were 19F (25%), 19A (17%), 6B (12%), 14 (10%), and 23F (10%). Of the 125 strains, 109 (87.2%) showed the MLSB phenotype [103 had the erm(B) gene and 6 had both erm(B) and mef(E) genes]. Sixteen (12.8%) strains showed the M phenotype [14 with mef(E) and 2 with mef(A)]. All isolates were tested by PCR for the presence of the int, xis, tnpR, and tnpA genes associated with conjugative transposons (Tn916 family and Tn917). Positive detection of erm(B), tet(M), int, and xis genes related to the Tn916 family was found in 77.1% of MLSB phenotype strains. In 16 strains, only the tndX, erm(B), and tet(M) genes were detected...

DIFFERENTIATION OF CLOSELY RELATED CELLS BY A VARIANT OF POLIOVIRUS, TYPE 2, MEF1 STRAIN

Murphy, William H.; Armstrong, Raymond
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 30/09/1959 Português
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By application of a variant of poliovirus, Type 2, MEF1 strain, as a selective agent it was possible to distinguish among stable parent strains of epithelial cells and their clonal derivatives by their differential morphologic response to infection. The variant of poliovirus grew in a number of cell strains without induction of observable cytopathogenic changes. Other strains of cells reacted to viral infection by manifesting partial or complete degeneration. Parent HeLa cells and virus underwent simultaneous serial propagation in the absence of homotypic antiserum to virus. The stability of the virus-cell relationship was established by results from replicate experiments conducted over a period of years. Some cell strains of common origin maintained in different laboratories did not react similarly to the cytopathogenic effect of virus. Representative experiments revealed that the morphologic response of HeLa cells to MEF virus infection was not influenced by the presence or absence of pleuropneumonia-like organisms. The differential morphologic response of cells to infection was confirmed by efficiency-of-plating experiments which revealed differences in the capacity of MEF virus to form plaques in the test cell strains. Serial passages of MEF virus in cell strains demonstrated differences in their selection for cytopathogenic "mutants" of virus.

Novel Cell Type–Specific Antiviral Mechanism of Interferon γ Action in Macrophages

Presti, Rachel M.; Popkin, Daniel L.; Connick, Megan; Paetzold, Susanne; Virgin, Herbert W.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 19/02/2001 Português
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Interferon (IFN)-γ and macrophages (Mϕ) play key roles in acute, persistent, and latent murine cytomegalovirus (MCMV) infection. IFN-γ mechanisms were compared in embryonic fibroblasts (MEFs) and bone marrow Mϕ (BMMϕ). IFN-γ inhibited MCMV replication in a signal transducer and activator of transcription (STAT)-1α–dependent manner much more effectively in BMMϕ (∼100-fold) than MEF (5–10-fold). Although initial STAT-1α activation by IFN-γ was equivalent in MEF and BMMϕ, microarray analysis demonstrated that IFN-γ regulates different sets of genes in BMMϕ compared with MEFs. IFN-γ inhibition of MCMV growth was independent of known mechanisms involving IFN-α/β, tumor necrosis factor α, inducible nitric oxide synthase, protein kinase RNA activated (PKR), RNaseL, and Mx1, and did not involve IFN-γ–induced soluble mediators. To characterize this novel mechanism, we identified the viral targets of IFN-γ action, which differed in MEF and BMMϕ. In BMMϕ, IFN-γ reduced immediate early 1 (IE1) mRNA during the first 3 h of infection, and significantly reduced IE1 protein expression for 96 h. Effects of IFN-γ on IE1 protein expression were independent of RNaseL and PKR. In contrast, IFN-γ had no significant effects on IE1 protein or mRNA expression in MEFs...

Distribution of Pneumococcal Surface Protein A Families 1 and 2 among Streptococcus pneumoniae Isolates from Children in Finland Who Had Acute Otitis Media or Were Nasopharyngeal Carriers▿

Melin, Merit M.; Hollingshead, Susan K.; Briles, David E.; Hanage, William P.; Lahdenkari, Mika; Kaijalainen, Tarja; Kilpi, Terhi M.; Käyhty, Helena M.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
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PspA is a structurally variable surface protein important to the virulence of pneumococci. PspAs are serologically cross-reactive and exist as two major families. In this study, we determined the distribution of PspA families 1 and 2 among pneumococcal strains isolated from the middle ear fluid (MEF) of children with acute otitis media and from nasopharyngeal specimens of children with pneumococcal carriage. We characterized the association between the two PspA families, capsular serotypes, and multilocus sequence types (STs) of the pneumococcal isolates. MEF isolates (n = 201) of 109 patients and nasopharyngeal isolates (n = 173) of 49 children were PspA family typed by whole-cell enzyme immunoassay (EIA). Genetic typing (PCR) of PspA family was done for 60 isolates to confirm EIA typing results. The prevalences of PspA families 1 and 2 were similar among pneumococci isolated from MEF (51% and 45%, respectively) and nasopharyngeal specimens (48% each). Isolates of certain capsule types as well as isolates of certain STs showed statistical associations with either family 1 or family 2 PspA. Pneumococci from seven children with multiple pneumococcal isolates appeared to express serologically different PspA families in different isolates of the same serotype; in three of the children the STs of the isolates were the same...

Mice lacking protein phosphatase 5 are defective in ATM-mediated cell cycle arrest

Yong, Weidong; Bao, Shideng; Chen, Hanying; Li, Dapei; Sánchez, Edwin R.; Shou, Weinian
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Eukaryotic cells have evolved cell cycle checkpoints to maintain genomic stability and integrity. Protein phosphatase 5 (Ppp5), a tetratricopeptide repeat domain protein, has been implicated in multiple cellular functions, including cellular proliferation, migration, differentiation and survival, and cell cycle checkpoint regulation via the ATM/ATR signal pathway. However, the physiological functions of Ppp5 have not been reported. To confirm the role of Ppp5 in cell cycle checkpoint regulation, we generated Ppp5-deficient mice and isolated mouse embryonic fibroblast (MEF) cells from Ppp5-deficient and littermate control embryos. Although Ppp5-deficient mice can survive through embryonic development and postnatal life and MEF cells from the Ppp5-deficient mice maintain normal replication checkpoint induced by hydroxyurea, Ppp5-deficient MEF cells display a significant defect in G2/M DNA damage checkpoint in response to ionizing radiation (IR). To determine whether this defect in IR induced-G2/M checkpoint is due to altered ATM-mediated signaling, we measured ATM kinase activity and ATM-mediated downstream events. Our data demonstrated that IR-induced ATM kinase activity is attenuated in Ppp5-deficient MEFs. Phosphorylation levels of two known ATM substrates...

The EGL-4 PKG Acts With KIN-29 Salt-Inducible Kinase and Protein Kinase A to Regulate Chemoreceptor Gene Expression and Sensory Behaviors in Caenorhabditis elegans

van der Linden, Alexander M.; Wiener, Scott; You, Young-jai; Kim, Kyuhyung; Avery, Leon; Sengupta, Piali
Fonte: Genetics Society of America Publicador: Genetics Society of America
Tipo: Artigo de Revista Científica
Publicado em /11/2008 Português
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The regulation of chemoreceptor (CR) gene expression by environmental signals and internal cues may contribute to the modulation of multiple physiological processes and behavior in Caenorhabditis elegans. We previously showed that KIN-29, a homolog of salt-inducible kinase, acts in sensory neurons to regulate the expression of a subset of CR genes, as well as sensory behaviors. Here we show that the cGMP-dependent protein kinase EGL-4 acts partly in parallel with KIN-29 to regulate CR gene expression. Sensory inputs inhibit both EGL-4 and KIN-29 functions, and KIN-29 function is inhibited in turn by cAMP-dependent protein kinase (PKA) activation. EGL-4 and KIN-29 regulate CR gene expression by antagonizing the gene repression functions of the class II HDAC HDA-4 and the MEF-2 transcription factor, and KIN-29, EGL-4, and PKA target distinct residues in HDA-4 to regulate its function and subcellular localization. While KIN-29 acts primarily via MEF-2/HDA-4 to regulate additional sensory signal-regulated physiological processes and behaviors, EGL-4 acts via both MEF-2-dependent and -independent pathways. Our results suggest that integration of complex sensory inputs via multiple signaling pathways allows animals to precisely regulate sensory gene expression...

Lithocholic acid down-regulation of NF-κB activity through vitamin D receptor in colonic cancer cells

Sun, Jun; Mustafi, Reba; Cerda, Sonia; Chumsangsri, Anusara; Xia, Yinglin Rick; Li, Yan Chun; Bissonnette, Marc
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Lithocholic acid (LCA), a secondary bile acid, is a vitamin D receptor (VDR) ligand. 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), the hormonal form of vitamin D, is involved in the anti-inflammatory action through VDR. Therefore, we hypothesize that LCA acts like 1,25(OH)2D3 to drive anti-inflammatory signals. In present study, we used human colonic cancer cells to assess the role of LCA in regulation of the pro-inflammatory NF-κB pathway. We found that LCA treatment increased VDR levels, mimicking the effect of 1,25(OH)2D3. LCA pretreatment inhibited the IL-1β-induced IκBα degradation and decreased the NF-κB p65 phosphorylation. We also measured the production of IL-8, a well-known NF-κB target gene, as a read-out of the biological effect of LCA expression on NF-κB pathway. LCA significantly decreased IL-8 secretion induced by IL-1β. These LCA-induced effects were very similar to those of 1,25(OH)2D3. Thus, LCA recapitulated the effects of 1,25(OH)2D3 on IL-1β stimulated cells. Mouse embryonic fibroblast (MEF) cells lacking VDR have intrinsically high NF-κB activity. LCA pretreatment was not able to prevent TNFα-induced IκBα degradation in MEF VDR (−/−), whereas LCA stabilized IκBα in MEF VDR (+/−) cells. Collectively...

Morphine-induced μ-Opioid Receptor Rapid Desensitization is independent of Receptor Phosphorylation and β-Arrestins

Chu, Ji; Zheng, Hui; Loh, Horace H.; Law, Ping-Yee
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Receptor desensitization involving receptor phosphorylation and subsequent βArrestin (βArr) recruitment has been implicated in the tolerance development mediated by μ-opioid receptor (OPRM1). However, the roles of receptor phosphorylation and βArr on morphine-induced OPRM1 desensitization remain to be demonstrated. Using OPRM1-induced intracellular Ca2+ ([Ca2+]i )release to monitor receptor activation, as predicted, [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO), induced OPRM1 desensitization in a receptor phosphorylation- and βArr-dependent manner. The DAMGO-induced OPRM1 desensitization was attenuated significantly when phosphorylation deficient OPRM1 mutants or Mouse Embryonic Fibroblast (MEF) cells from βArr1 and 2 knockout mice were used in the studies. Specifically, DAMGO-induced desensitization was blunted in HEK293 cells expressing the OPRM1S375A mutant and was eliminated in MEF cells isolated from βArr2 knockout mice expressing the wild type OPRM1. However, although morphine also could induce a rapid desensitization on [Ca2+]i release to a greater extent than that of DAMGO and could induce the phosphorylation of Ser375 residue, morphine-induced desensitization was not influenced by mutating the phosphorylation sites or in MEF cells lacking βArr1 and 2. Hence...

Secreted Proteoglycans Directly Mediate Human Embryonic Stem Cell-FGF2 Interactions Critical for Proliferation

Levenstein, Mark E.; Berggren, W. Travis; Lee, Ji Eun; Conard, Kevin R.; Llanas, Rachel A.; Wagner, Ryan J.; Smith, Lloyd M.; Thomson, James A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Human embryonic stem (ES) cells can be maintained in an undifferentiated state if the culture medium is first conditioned on a layer of mouse embryonic fibroblast (MEF) feeder cells. Here we show that human ES cell proliferation is coordinated by MEF-secreted heparan sulfate proteoglycans (HSPG) in conditioned medium (CM). These HSPG and other heparinoids can stabilize basic fibroblast growth factor (FGF2) in unconditioned medium at levels comparable to those observed in CM. They also directly mediate binding of FGF2 to the human ES cell surface, and their removal from CM impairs proliferation. Finally, we have developed a purification scheme for MEF-secreted HSPG in CM. Utilizing column chromatography, immunoblotting, and mass spectrometry-based proteomic analysis, we have identified multiple HSPG species in CM. The results demonstrate that HSPG are key signaling cofactors in CM-based human ES cell culture.

Metal-enhanced Intrinsic Fluorescence of Proteins on Silver Nanostructured Surfaces towards Label-Free Detection

Ray, Krishanu; Chowdhury, Mustafa H.; Szmacinski, Henryk; Lakowicz, Joseph R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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In recent years metal-enhanced fluorescence (MEF) using silver particles has been reported for a number of fluorophores emitting at visible wavelengths. However it was generally thought that silver particles would always quench fluorescence at shorter wavelengths. We now report the observation of metal-enhanced fluorescence of the tryptophan analogue N-acetyl-L-tryptophanamide (NATA) on silver nano-structured surfaces. NATA is a model for the intrinsic tryptophan emission from proteins. We have also studied the effects of silver nanostructures on the emission of N-acetyl-L-tyrosinamide (NATA-tyr). In the case of NATA we observed increased emission, decrease in fluorescence lifetimes, and increase in photostability when NATA was embedded in 15 nm thick spin-casted poly(vinyl alcohol) film on silver nanostructured surfaces. We have also investigated the effects of silver nanostructures on the emission from thin poly(vilnyl alcohol) films containing NATA-tyr. However, we have observed no increase in fluorescence signal for NATA-tyr on silver nanostructures. To understand these results we performed numerical calculations using the Finite-Difference Time-Domain (FDTD) technique to model a tryptophan-wavelength dipole near a spherical silver particle. Our calculations reveal an enhancement of the power of the radiated emission by the excited-state fluorophore in proximity to a 100 nm silver nanoparticle covering the emission spectra of NATA and NATA-tyr. These calculations show a clear wavelength dependence with the specific spectral region displaying low-enhancement at the shorter NATA-tyr wavelength and higher enhancement at NATA emission wavelength. Our FDTD calculations also reveal that excited fluorophores in the near-field of a 100 nm silver nanoparticle can induce enhancement fields of varying degrees of the intensity of the near-fields around the particle that is dependent on the wavelength of the emission. We believe this enhanced near-fields play a role in our observation of MEF from metal surfaces. The enhanced emission of NATA on silver nanostructures suggests that the extension of MEF to the UV region opens new possibilities to study tryptophan-containing proteins without labeling with longer wavelength fluorophores towards label free detection of biomolecules.

JDP2 (Jun Dimerization Protein 2)-deficient Mouse Embryonic Fibroblasts Are Resistant to Replicative Senescence*S⃞

Nakade, Koji; Pan, Jianzhi; Yamasaki, Takahito; Murata, Takehide; Wasylyk, Bohdan; Yokoyama, Kazunari K.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Publicado em 17/04/2009 Português
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JDP2 (Jun dimerization protein 2, an AP-1 transcription factor) is involved in the regulation of the differentiation and proliferation of cells. We report here that JDP2-deficient mouse embryonic fibroblasts (Jdp2-/- MEF) are resistant to replicative senescence. In the absence of JDP2, the level of expression of p16Ink4a, which is known to rise as normal fibroblasts age, fell significantly when cells were cultured for more than 2 months. Conversely, the overexpression of JDP2 induced the expression of genes for p16Ink4a and p19Arf. Moreover, at the promoter of the gene for p16Ink4a in Jdp2-/- MEF, the extent of methylation of lysine 27 of histone H3 (H3K27), which is important for gene silencing, increased. Polycomb-repressive complexes (PRC-1 and PRC-2), which are responsible for histone methylation, bound efficiently to the promoter to repress the expression of the gene for p16Ink4a. As a result, JDP2-deficient MEF became resistant to replicative senescence. Our results indicate that JDP2 is involved in the signaling pathway for senescence via epigenetic regulation of the expression of the gene for p16Ink4a.

Aluminum Nanostructured Films as Substrates for Enhanced Fluorescence in the Ultraviolet-Blue Spectral Region

Ray, Krishanu; Chowdhury, Mustafa H.; Lakowicz, Joseph R.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Particulate aluminum films of varied thicknesses were deposited on quartz substrates by thermal evaporation. These nanostructured substrates were characterized by scanning electron microscopy (SEM). With the increase of aluminum thickness, the films progress from particulate toward smooth surfaces as observed by SEM images. To date, metal-enhanced fluorescence (MEF) has primarily been observed in the visible–NIR wavelength region using silver or gold island films or roughened surfaces. We now show that fluorescence could also be enhanced in the ultraviolet-blue region of the spectrum using nanostructured aluminum films. Two probes, one in the ultraviolet and another one in the blue spectral region, have been chosen for the present study. We observed increased emission, decrease in fluorescence lifetime, and increase in photostability of a DNA base analogue 2-aminopurine and a coumarin derivative (7-HC) in 10-nm spin-casted poly(vinyl alcohol) film on Al nanostructured surfaces. The fluorescence enhancement factor depends on the thickness of the Al films as the size of the nanostructures formed varies with Al thickness. Both probes showed increased photostability near aluminum nanostructured substrates, which is consistent with the shorter lifetime. Our preliminary studies indicate that Al nanostructured substrates can potentially find widespread use in MEF applications particularly in the UV-blue spectral regime. Furthermore...

The chinchilla microdialysis model for the study of antibiotic distribution to middle ear fluid

Cheung, Belinda W. Y.; Liu, Wei; Ji, Ping; Cartier, Linda L.; Li, Zhihong; Mostafa, Nael; Sawchuk, Ronald J.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em 03/02/2006 Português
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In cases of slow or limited penetration of an antibiotic to the site of infection such as in acute otitis media (the middle ear), plasma levels of the agent may not reflect the concentrations that are relevant in determining clinical outcome. There is a need for a model that allows prediction of the time-course of unbound, pharmacologically active drug levels in middle ear fluid (MEF). This article introduces microdialysis as a sampling tool to measure unbound antibiotic concentrations in the MEF of the chinchilla, and briefly summarizes the results of studies of MEF penetration of a cephalosporin, a macrolide, and a ketolide antibiotic using this technique. The general concurrence of preliminary results of the chinchilla studies with clinical findings suggests that the chinchilla microdialysis model may be useful in predicting efficacy in patients.