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Análise de estabilidade de contenções, via MEF, considerando a interação solo-estrutura.; Analysis of stability of retaining walls, via MEF, regarding the soil-structure interaction.

Nascimento, Alessandro Lugli
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/11/2011 Português
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Este trabalho tem a finalidade de estudar a influência da parede de concreto na análise de estabilidade de contenções atirantadas bem como discutir sobre segurança nestas análises. Para isto foram elaborados modelos em estado plano de deformação por meio do método dos elementos finitos, MEF, para análise. A parede de concreto foi modelada com variações de rigidez e modelos reológico, com o fim de se entender sua influência no fator de segurança. Por fim foi realizado um breve estudo sobre a utilização dos métodos estatísticos na análise de estabilidade de contenções.; This work has the purpose of study the influence of the concrete wall in the stability analysis of tieback retaining walls and to discuss these safety analysis. Models were developed using plane strain state via the finite element method, FEM, for analysis. The concrete wall was modeled with variations of stiffness and rheological models, in order to bore its influence on the safety factor. Finally a brief study was conducted on the use of statistical methods in stability analysis of retaining walls.

Método dos elementos de contorno aplicado na análise do escorregamento de estacas.; Boundary element method applied in pile slip analysis.

Vick, Guilherme Basílio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/04/2014 Português
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Neste trabalho apresenta-se um modelo numérico para a análise de problemas tridimensionais envolvendo a interação mecânica estaca-solo, acoplando-se o Método dos Elementos de Contorno (MEC) ao Método dos Elementos Finitos (MEF). O solo é modelado com o MEC utilizando-se as soluções fundamentais de Mindlin, assumindo um meio semi-infinito, homogêneo, isotrópico e elástico-linear. As estacas, modeladas com o MEF, consistem em um elemento único, com quatro nós e 14 parâmetros nodais (três deslocamentos em cada nó e mais duas rotações no topo da estaca). Cada uma das estacas é levada em consideração no MEC como uma linha de carga. Considera-se o escorregamento das estacas em relação ao maciço, empregando modelos de aderência para a definição da evolução das tensões tangenciais ao longo do comprimento das estacas. São empregados, como funções de forma, polinômios do quarto grau para os deslocamentos horizontais, cúbicos para os deslocamentos verticais e tensões horizontais ao longo do fuste e quadráticos para as tensões verticais do fuste e escorregamento. A reação da ponta da estaca é calculada assumindo tensão constante na base.; This work presents a method for tri-dimensional pile-soil interaction problems...

Identification of the Conjugative mef Gene in Clinical Acinetobacter junii and Neisseria gonorrhoeae Isolates

Luna, Vicki A.; Cousin, Sydney; Whittington, William L. H.; Roberts, Marilyn C.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /09/2000 Português
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The mef gene, originally described for gram-positive organisms and coding for an efflux pump, has been identified in clinical isolates of Acinetobacter junii and Neisseria gonorrhoeae. These strains could transfer the mef gene at frequencies ranging from 10−6 to 10−9 into one or more of the following recipients: gram-negative Moraxella catarrhalis, Neisseria perflava/sicca and Neisseria mucosa and gram-positive Enterococcus faecalis. Three Streptococcus pneumoniae strains could transfer the mef gene into Eikenella corrodens, Haemophilus influenzae, Kingella denitrificans, M. catarrhalis, Neisseria meningitidis, N. perflava/sicca, and N. mucosa at similar frequencies. The mef gene can thus be transferred to and expressed in a variety of gram-negative recipients.

Dissemination of Macrolide-Resistant Streptococcus pneumoniae Isolates Containing Both erm(B) and mef(A) in South Korea

Waites, Ken B.; Jones, Kellie E.; Kim, Kyung Hyo; Moser, Stephen A.; Johnson, Crystal N.; Hollingshead, Susan K.; Kang, Eun-Suk; Hong, Ki Sook; Benjamin, William H.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /12/2003 Português
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Macrolide resistance was detected in 64 of 77 (83.1%) Streptococcus pneumoniae isolates from South Korea. Seven (10.9%) isolates contained only mef(A), 32 (50%) contained only erm(B), and 25 (39.1%) contained mef(A) and erm(B). Nineteen isolates containing mef(A) and erm(B) belonged to serotype 19F, and seven isolates were identical to the Taiwan19F-14 clone.

Molecular Epidemiology of Multiresistant Streptococcus pneumoniae with Both erm(B)- and mef(A)-Mediated Macrolide Resistance

Farrell, David J.; Morrissey, Ian; Bakker, Sarah; Morris, Louise; Buckridge, Sylvie; Felmingham, David
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /02/2004 Português
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Of a total of 1,043 macrolide-resistant Streptococcus pneumoniae isolates collected from 24 countries as part of PROTEKT 1999-2000, 71 isolates tested positive for both the mef(A) and erm(B) genes. Of 69 isolates subjected to further molecular investigations, all were resistant to tetracycline, 63 (91.3%) were resistant to penicillin, and 57 (82.6%) were resistant to trimethoprim-sulfamethoxazole. One isolate was also fluoroquinolone resistant, and another was resistant to quinupristin-dalfopristin. The ketolide telithromycin retained activity against all of the isolates. Of the 69 of these 71 isolates viable for further testing, 46 were from South Korea, 13 were from the United States, 8 came from Japan, and 1 each came from Mexico and Hungary. One major clonal complex (59 [85.5%] of 69 isolates) was identified by serotyping (with 85.5% of the isolates being 19A or 19F), pulsed-field gel electrophoresis, and multilocus sequence typing. The remaining isolates were less clonal in nature. Representative isolates were shown to carry the mobile genetic elements Tn1545 and mega, were negative for Tn1207.1, had tetracycline resistance mediated by tet(M), and contained the mef(E) variant of mef(A). All isolates were positive for mel, a homologue of the msr(A) efflux gene. These clones are obviously very efficient at global dissemination...

A ubiquitous factor (HF-1a) and a distinct muscle factor (HF-1b/MEF-2) form an E-box-independent pathway for cardiac muscle gene expression.

Navankasattusas, S; Zhu, H; Garcia, A V; Evans, S M; Chien, K R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1992 Português
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Recent studies have identified a conserved 28-bp element (HF-1) within the rat cardiac MLC-2 gene which confers cardiac muscle-specific and inducible expression during myocardial cell hypertrophy. Utilizing a combination of independent experimental approaches, this study characterizes two cardiac nuclear factors which bind to HF-1, a ubiquitous factor (HF-1a), and an A + T-rich binding factor (HF-1b) which is preferentially expressed in differentiated cardiac and skeletal muscle cells. The HF-1a binding site is located in a core region of the 28-bp conserved element, immediately upstream from the A + T-rich HF-1b site, which is homologous to the MEF-2 site found in a number of muscle genes. By a number of separate criteria (gel mobility shift, competition, and mutagenesis studies), HF-1b and MEF-2 appear to be indistinguishable and thus are either identical or closely related muscle factors. Transient assays of luciferase reporter genes containing point mutations throughout the 28-bp HF-1 regulatory element document the importance of both the HF-1a and HF-1b sites in transient assays in ventricular muscle cells. In the native 250-bp MLC-2 promoter fragment, mutations in the single E box had little effect on cardiac muscle specificity...

Macrolide Efflux in Streptococcus pneumoniae Is Mediated by a Dual Efflux Pump (mel and mef) and Is Erythromycin Inducible

Ambrose, Karita D.; Nisbet, Rebecca; Stephens, David S.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/2005 Português
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Macrolide resistance in Streptococcus pneumoniae due to efflux has emerged as an important worldwide clinical problem over the past decade. Efflux is mediated by the genes of the genetic element mega (macrolide efflux genetic assembly) and related elements, such as Tn1207.1. These elements contain two adjacent genes, mef (mefE or mefA) and the closely related mel gene (msrA homolog), encoding a proton motive force pump and a putative ATP-binding cassette transporter homolog, and are transcribed as an operon (M. Del Grosso et al., J. Clin. Microbiol. 40:774-778, 2004; K. Gay and D. S. Stephens, J. Infect. Dis. 184:56-65, 2001; and M. Santagati et al., Antimicrob. Agents Chemother. 44:2585-2587, 2000). Previous studies have shown that Mef is required for macrolide resistance in S. pneumoniae; however, the contribution of Mel has not been fully determined. Independent deletions were constructed in mefE and mel in the serotype 14 macrolide-resistant strains GA16638 (erythromycin [Em] MIC, 8 to 16 μg/ml) and GA17719 (Em MIC, 2 to 4 μg/ml), which contain allelic variations in the mega element. The MICs to erythromycin were significantly reduced for the independent deletion mutants of both mefE and mel compared to those of the parent strains and further reduced threefold to fourfold to Em MICs of <0.15 μg/ml with mefE mel double mutants. Using quantitative reverse transcription-PCR...

Prevalence and Antibacterial Susceptibility of mef(A)-Positive Macrolide-Resistant Streptococcus pneumoniae over 4 Years (2000 to 2004) of the PROTEKT US Study▿

Farrell, David J.; File, Thomas M.; Jenkins, Stephen G.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Português
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In the United States, approximately 30% of Streptococcus pneumoniae isolates are macrolide (erythromycin [ERY]) resistant (ERSP), most commonly due to expression of the mef(A) gene previously associated with lower-level ERY resistance (ERYr; MIC = 1 to 4 μg/ml). The data from the PROTEKT US surveillance study were analyzed to evaluate the prevalence and antibacterial susceptibility of mef(A)-positive ERSP. In all, 26,634 isolates of S. pneumoniae were collected in the United States between 2000 and 2004 from centers common to all years. ERYr was stable at approximately 29% over the 4 years, but the proportion of ERSP isolates positive for mef(A) alone decreased (year 1 [2000 to 2001], 69.0%; year 4 [2003 to 2004], 60.7%), with the sharpest declines seen in isolates from patients from 0 to 2 years of age. Conversely, the proportion isolates positive for both erm(B) and mef(A) increased over the duration of the present study (year 1, 9.3%; year 4, 19.1%), a change that was again most marked in patients aged ≤2 years. The majority of ERSP isolates expressing mef(A) alone exhibited higher than previously reported levels of ERYr (MIC90 = 16 μg/ml). However, the ketolide antibacterial telithromycin consistently demonstrated in vitro activity against these isolates over the 4 years of the study (MIC90 = 0.5 to 1 μg/ml).

The microRNA miR-1 regulates a MEF-2 dependent retrograde signal at neuromuscular junctions

Simon, David J.; Madison, Jon M.; Conery, Annie L.; Thompson-Peer, Katherine L.; Soskis, Michael; Ruvkun, Gary B.; Kaplan, Joshua M.; Kim, John K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 30/05/2008 Português
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We show that miR-1, a conserved muscle specific microRNA, regulates aspects of both pre- and post-synaptic function at C. elegans neuromuscular junctions. miR-1 regulates the expression level of two nicotinic acetylcholine receptor (nAChR) subunits (UNC-29 and UNC-63), thereby altering muscle sensitivity to acetylcholine (ACh). miR-1 also regulates the muscle transcription factor MEF-2, which results in altered pre-synaptic ACh secretion, suggesting that MEF-2 activity in muscles controls a retrograde signal. The effect of the MEF-2-dependent retrograde signal on secretion is mediated by the synaptic vesicle protein RAB-3. Finally, acute activation of levamisole-sensitive nAChRs stimulates MEF-2-dependent transcriptional responses, and induces the MEF-2-dependent retrograde signal. We propose that miR-1 refines synaptic function by coupling changes in muscle activity to changes in pre-synaptic function.

Φm46.1, the Main Streptococcus pyogenes Element Carrying mef(A) and tet(O) Genes▿

Brenciani, Andrea; Bacciaglia, Alessandro; Vignaroli, Carla; Pugnaloni, Armanda; Varaldo, Pietro E.; Giovanetti, Eleonora
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Φm46.1, the recognized representative of the most common variant of mobile, prophage-associated genetic elements carrying resistance genes mef(A) (which confers efflux-mediated erythromycin resistance) and tet(O) (which confers tetracycline resistance) in Streptococcus pyogenes, was fully characterized. Sequencing of the Φm46.1 genome (55,172 bp) demonstrated a modular organization typical of tailed bacteriophages. Electron microscopic analysis of mitomycin-induced Φm46.1 revealed phage particles with the distinctive icosahedral head and tail morphology of the Siphoviridae family. The chromosome integration site was within a 23S rRNA uracil methyltransferase gene. BLASTP analysis revealed that the proteins of Φm46.1 had high levels of amino acid sequence similarity to the amino acid sequences of proteins from other prophages, especially Φ10394.4 of S. pyogenes and λSa04 of S. agalactiae. Phage DNA was present in the host cell both as a prophage and as free circular DNA. The lysogeny module appears to have been split due to the insertion of a segment containing tet(O) (from integrated conjugative element 2096-RD.2) and mef(A) (from a Tn1207.1-like transposon) into the unintegrated phage DNA. The phage attachment sequence lies in the region between tet(O) and mef(A) in the unintegrated form. Thus...

Myocyte-Specific M-CAT and MEF-1 Elements Regulate G-Protein Gamma 3 Gene (γ3) Expression in Cardiac Myocytes

McWhinney, Charlene; Robishaw, Janet D.
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
Publicado em /07/2008 Português
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Little is known regarding the mechanisms that control the expression of G-protein α, β, and γ subtypes. We have previously shown that the G-protein γ3 gene is expressed in the heart, brain, lung, spleen, kidney, muscle, and testis in mice. We have also reported that the G-protein γ3 subunit is expressed in rat cardiac myocytes, but not in cardiac fibroblasts. Other studies have shown that the γ3 subunit couples to the angiotensin A1A receptor in portal vein myocytes, and has been shown to mediate β-adrenergic desensitization in cardiac myocytes treated with atorvastatin. In the present study, we evaluated G-protein γ3 promoter-luciferase reporter constructs in primary myocytes to identify key regulatory promoter regions. We identified two important regions of the promoter (upstream promoter region [UPR] and downstream promoter region [DPR]), which are required for expression in cardiac myocytes. We observed that removal of 48 bp in the UPR diminished gene transcription by 75%, and that the UPR contains consensus elements for myocyte-specific M-CAT and myocyte enhancer factor 1 (MEF-1) elements. The UPR and DPR share transcription factor elements for myocyte-specific M-CAT element. We observed that cardiac myocyte proteins bind to γ3 oligonucleotides containing transcription factor elements for myocyte-specific M-CAT and MEF-1. Myocyte-specific M-CAT proteins were supershifted with transcriptional enhancer factor-1 (TEF-1) antibodies binding to the γ3 M-CAT element...

Immortalization of MEF is characterized by the deregulation of specific miRNAs with potential tumor suppressor activity

Rizzo, Milena; Evangelista, Monica; Simili, Marcella; Mariani, Laura; Pitto, Letizia; Rainaldi, Giuseppe
Fonte: Impact Journals LLC Publicador: Impact Journals LLC
Tipo: Artigo de Revista Científica
Publicado em 11/07/2011 Português
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The life span (Hayflick limit) of primary mouse embryo fibroblasts (MEF) in culture is variable but it is still unclear if the escape of the Hayflick limit is also variable. To address this point MEF were expanded every fifteen days (6T15) instead of every three days (6T3) until they became immortal. With this protocol MEF lifespan was extended and immortalization accordingly delayed. By testing a panel of genes (p19ARF, p16, p21) and miRNAs (miR-20a, miR-21, miR-28, miR-290) related to primary MEF senescence, a switch of p21 from up to down regulation, the down regulation of specific miRNAs as well as a massive shift from diploidy to hyperdiploidy were observed in coincidence with the resumption of cell proliferation. Collectively, these data indicate that the inactivation of genes and miRNAs, important in controlling cell proliferation, might be determinant for the escape from the Hayflick limit. In support of this hypothesis was the finding that some of the down regulated miRNAs transfected in immortalized MEF inhibited cell proliferation thus displaying a tumor suppressor-like activity.

Emergence and Spread of Streptococcus pneumoniae with erm(B) and mef(A) Resistance

Farrell, David J.; Jenkins, Stephen G.; Brown, Steven D.; Patel, Manish; Lavin, Bruce S.; Klugman, Keith P.
Fonte: Centers for Disease Control and Prevention Publicador: Centers for Disease Control and Prevention
Tipo: Artigo de Revista Científica
Publicado em /06/2005 Português
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Streptococcus pneumoniae isolates (N = 31,001) were collected from patients with community-acquired respiratory tract infections during the PROTEKT US surveillance study (2000–2003). While the macrolide (erythromycin) resistance rate remained stable at ≈29%, the prevalence of resistant isolates containing both erm(B) and mef(A) increased from 9.7% in year 1 to 16.4% in year 3, with substantial regional variability. Almost all (99.2%) dual erm(B)+mef(A) macrolide-resistant isolates exhibited multidrug resistance, whereas 98.6% and 99.0% were levofloxacin- and telithromycin-susceptible, respectively. These strains were most commonly isolated from the ear or middle-ear fluid of children. Of 152 representative erm(B)+mef(A) isolates, >90% were clonally related to the multidrug-resistant international Taiwan19F-14 clonal complex 271 (CC271). Of 366 erm(B)+mef(A) isolates from the PROTEKT global study (1999–2003), 83.3% were CC271, with the highest prevalence seen in South Africa, South Korea, and the United States. This study confirms the increasing global emergence and rapidly increasing US prevalence of this multidrug-resistant pneumococcal clone.

The transcription factors myeloid elf-1-like factor (MEF) and distal-less homeobox 5 (Dlx5) inversely regulate the differentiation of osteoblasts and adipocytes in bone marrow

Baek, Kyunghwa; Baek, Jeong-Hwa
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em 01/01/2013 Português
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In bone marrow, the differentiation of osteoblasts and adipocytes is reciprocally regulated. This inverse regulation occurs mainly through complex signaling crosstalk between transcriptional factors such as peroxisome proliferator-activated receptor-γ (PPARγ) and runt-related transcription factor 2 (Runx2). This commentary addresses the role of myeloid elf-1 like factor (MEF) and distal-less homeobox 5 (Dlx5) in the lineage commitment of bone marrow mesenchymal stem cells into adipocytes and osteoblasts, respectively. MEF suppresses osteoblastogenesis by preventing Runx2 from binding to the promoters of target genes and enhancing adipogenesis via transactivation of PPARγ expression. Conversely, Dlx5 enhances osteoblastogenesis through upregulation of the expression of Runx2 and osteoblast marker genes while suppressing adipogenesis through the downregulation of PPARγ expression by sequestering the cAMP response element binding protein and CCAAT/enhancer-binding protein α. Studies designed to examine the effects of physiological and pathologic signals on the expression of MEF and Dlx5 will provide further insight to the function of these transcription factors in vivo.

MEF promotes stemness in the pathogenesis of gliomas

Bazzoli, Elena; Pulvirenti, Teodoro; Oberstadt, Moritz C.; Perna, Fabiana; Wee, Boyoung; Schultz, Nikolaus; Huse, Jason T.; Fomchenko, Elena I.; Voza, Francesca; Tabar, Viviane; Brennan, Cameron W.; DeAngelis, Lisa M.; Nimer, Stephen D.; Holland, Eric C.;
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 07/12/2012 Português
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High-grade gliomas are aggressive and uniformly fatal tumors, composed of a heterogeneous population of cells that include many with stem cell-like properties. The acquisition of stem-like traits might contribute to glioma initiation, growth and recurrence. Here we investigated the role of the transcription factor myeloid Elf-1 like factor (MEF, also known as ELF4) in glioma. We found that MEF is highly expressed in both human and mouse GBMs and its absence impairs gliomagenesis in a PDGF-driven glioma mouse model. We show that modulation of MEF levels in both mouse neural stem cells and human glioblastoma cells, has a significant impact on neurosphere formation. Moreover, we identify Sox2 as a direct downstream target of MEF. Taken together, our studies implicate MEF as a previously unrecognized gatekeeper gene in gliomagenesis by promoting stem cell characteristics through Sox2 activation.

Genetic basis of the association of resistance genes mef(I) (macrolides) and catQ (chloramphenicol) in streptococci

Mingoia, Marina; Morici, Eleonora; Brenciani, Andrea; Giovanetti, Eleonora; Varaldo, Pietro E.
Fonte: Frontiers Media S.A. Publicador: Frontiers Media S.A.
Tipo: Artigo de Revista Científica
Publicado em 06/01/2015 Português
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In streptococci mef(I) and catQ, two relatively uncommon macrolide and chloramphenicol resistance genes, respectively, are typically linked in a genetic module designated IQ module. Though variable, the module consistently encompasses, and is sometimes reduced to, a conserved ∼5.8-kb mef(I)-catQ fragment. The prototype IQ module was described in Streptococcus pneumoniae. IQ-like modules have subsequently been detected in Streptococcus pyogenes and in different species of viridans group streptococci, where mef(E) may be found instead of mef(I). Three genetic elements, one carrying the prototype IQ module from S. pneumoniae and two carrying different, defective IQ modules from S. pyogenes, have recently been characterized. All are integrative and conjugative elements (ICEs) belonging to the Tn5253 family, and have been designated ICESpn529IQ, ICESpy029IQ and ICESpy005IQ, respectively. ICESpy029IQ and ICESpy005IQ were the first Tn5253 family ICEs to be described in S. pyogenes. A wealth of new information has been obtained by comparing their genetic organization, chromosomal integration, and transferability. The origin of the IQ module is unknown. The mechanism by which it spreads in streptococci is discussed.

Comparison between the cultures of human induced pluripotent stem cells (hiPSCs) on feeder-and serum-free system (Matrigel matrix), MEF and HDF feeder cell lines

Ghasemi-Dehkordi, Payam; Allahbakhshian-Farsani, Mehdi; Abdian, Narges; Mirzaeian, Amin; Saffari-Chaleshtori, Javad; Heybati, Fatemeh; Mardani, Gashtasb; Karimi-Taghanaki, Alireza; Doosti, Abbas; Jami, Mohammad-Saeid; Abolhasani, Marziyeh; Hashemzadeh-Cha
Fonte: Springer Netherlands Publicador: Springer Netherlands
Tipo: Artigo de Revista Científica
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Human induced pluripotent stem cells (hiPSCs) are a type of pluripotent stem cells artificially derived from an adult somatic cell (typically human fibroblast) by forced expression of specific genes. In recent years, different feeders like inactivated mouse embryonic fibroblasts (MEFs), human dermal fibroblasts (HDFs), and feeder free system have commonly been used for supporting the culture of stem cells in undifferentiated state. In the present work, the culture of hiPSCs and their characterizations on BD Matrigel (feeder-and serum-free system), MEF and HDF feeders using cell culture methods and molecular techniques were evaluated and compared. The isolated HDFs from foreskin samples were reprogrammed to hiPSCs using gene delivery system. Then, the pluripotency ability of hiPSCs cultured on each layer was determined by teratoma formation and immunohistochemical staining. After EBs generation the expression level of three germ layers genes were evaluated by Q-real-time PCR. Also, the cytogenetic stability of hiPSCs cultured on each condition was analyzed by karyotyping and comet assay. Then, the presence of pluripotency antigens were confirmed by Immunocytochemistry (ICC) test and alkaline phosphatase staining. This study were showed culturing of hiPSCs on BD Matrigel...

Analysis of the myogenin promoter reveals an indirect pathway for positive autoregulation mediated by the muscle-specific enhancer factor MEF-2.

Edmondson, D G; Cheng, T C; Cserjesi, P; Chakraborty, T; Olson, E N
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1992 Português
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Transcriptional cascades that specify cell fate have been well described in invertebrates. In mammalian development, however, gene hierarchies involved in determination of cell lineage are not understood. With the recent cloning of the MyoD family of myogenic regulatory factors, a model system has become available with which to study the dynamics of muscle determination in mammalian development. Myogenin, along with other members of the MyoD gene family, possesses the apparent ability to redirect nonmuscle cells into the myogenic lineage. This ability appears to be due to the direct activation of an array of subordinate or downstream genes which are responsible for formation and function of the muscle contractile apparatus. Myogenin-directed transcription has been shown to occur through interaction with a DNA consensus sequence known as an E box (CANNTG) present in the control regions of numerous downstream genes. In addition to activating the transcription of subordinate genes, members of the MyoD family positively regulate their own expression and cross-activate one another's expression. These autoregulatory interactions have been suggested as a mechanism for induction and maintenance of the myogenic phenotype, but the molecular details of the autoregulatory circuits are undefined. Here we show that the myogenin promoter contains a binding site for the myocyte-specific enhancer-binding factor...

E-box- and MEF-2-independent muscle-specific expression, positive autoregulation, and cross-activation of the chicken MyoD (CMD1) promoter reveal an indirect regulatory pathway.

Dechesne, C A; Wei, Q; Eldridge, J; Gannoun-Zaki, L; Millasseau, P; Bougueleret, L; Caterina, D; Paterson, B M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1994 Português
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Members of the MyoD family of gene-regulatory proteins (MyoD, myogenin, myf5, and MRF4) have all been shown not only to regulate the transcription of numerous muscle-specific genes but also to positively autoregulate and cross activate each other's transcription. In the case of muscle-specific genes, this transcriptional regulation can often be correlated with the presence of a DNA consensus in the regulatory region CANNTG, known as an E box. Little is known about the regulatory interactions of the myogenic factors themselves; however, these interactions are thought to be important for the activation and maintenance of the muscle phenotype. We have identified the minimal region in the chicken MyoD (CMD1) promoter necessary for muscle-specific transcription in primary cultures of embryonic chicken skeletal muscle. The CMD1 promoter is silent in primary chick fibroblast cultures and in muscle cell cultures treated with the thymidine analog bromodeoxyuridine. However, CMD1 and chicken myogenin, as well as, to a lesser degree, chicken Myf5 and MRF4, expressed in trans can activate transcription from the minimal CMD1 promoter in these primary fibroblast cultures. Here we show that the CMD1 promoter contains numerous E-box binding sites for CMD1 and the other myogenic factors...

ELF4/MEF Activates MDM2 Expression and Blocks Oncogene-Induced p16 Activation To Promote Transformation▿ †

Sashida, Goro; Liu, Yan; Elf, Shannon; Miyata, Yasuhiko; Ohyashiki, Kazuma; Izumi, Miki; Menendez, Silvia; Nimer, Stephen D.
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
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Several ETS transcription factors, including ELF4/MEF, can function as oncogenes in murine cancer models and are overexpressed in human cancer. We found that Elf4/Mef activates Mdm2 expression; thus, lack of or knockdown of Elf4/Mef reduces Mdm2 levels in mouse embryonic fibroblasts (mef's), leading to enhanced p53 protein accumulation and p53-dependent senescence. Even though p53 is absent in Elf4−/− p53−/− mef's, neither oncogenic H-RasV12 nor c-myc can induce transformation of these cells. This appears to relate to the INK4a/ARF locus; both p19ARF and p16 are increased in Elf4−/− p53−/− mef's, and expression of Bmi-1 or knockdown of p16 in this context restores H-RasV12-induced transformation. Thus, ELF4/MEF promotes tumorigenesis by inhibiting both the p53 and p16/Rb pathways.