Página 16 dos resultados de 1181 itens digitais encontrados em 0.004 segundos

‣ Lean thinking: Glass Wall Management

Calatróia, Pedro Miguel Pereira
Fonte: Instituto Politécnico de Lisboa Publicador: Instituto Politécnico de Lisboa
Tipo: Dissertação de Mestrado
Publicado em /05/2013 Português
Relevância na Pesquisa
17.239934%
Sendo os desperdícios “Waste” associados à atividade industrial em Portugal e nos mercados globais e os seus custos inerentes, uma das maiores preocupações a todos os níveis de gestão empresarial, a filosofia “Lean” nasce como ajuda e encaminhamento na solução desta problemática. O conceito “Lean”, no que se refere à indústria, desde sempre e até aos dias de hoje, tem uma enorme ênfase, com a adoção deste conceito.Verificam-se bons resultados ao nível da redução de custos, melhoria da qualidade geral dos artigos produzidos, no controlo da produção em geral e é uma poderosa ferramenta no estreitamento da relação entre os diferentes intervenientes da cadeia de valor de determinado produto, sobretudo com fornecedores e com clientes. Com “Lean Management” e “Glass Wall Management”, em ambientes onde as empresas mais avançadas estão a procurar melhorar a sua competitividade através de uma gestão transparente (“Glass Wall Management”), a partir da qual, “toda informação relevante é compartilhada de maneira a que todos entendam a situação”(Suzaki, K, 1993), ganha cada vez mais importância a existência de uma estrutura organizacional que permita esta transparência e a consequente maturidade das empresas. Neste trabalho foram descritos alguns processos de gestão transparente desenvolvidos nos últimos dois anos numa PME portuguesa...

‣ A 31P MR spectroscopy study on rat models of liver disease

Severo, Frederico Ribeiro da Silva
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2014 Português
Relevância na Pesquisa
17.239934%
Tese de mestrado integrado em Engenharia Biomédica e Biofísica, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2014; O objectivo deste projecto assenta no desenvolvimento e optimização de técnicas de Espectroscopia por Ressonância Magnética com Fósfoto-31 (31P MRS), para a avaliação do conteúdo metabólico e descoberta de biomarcadores em modelos de patologia hepática. A Espectroscopia por Ressonância Magnética é uma técnica não invasiva utilizada para estudos metabólicos, qualitativos e quantitativos. Esta técnica permite, especificamente no caso do Fósforo-31, a avaliação e quantificação de metabolitos cuja composição contenha Fósforo, como é caso da Fosfocreatina, Adenosinatrifosfato ou o Fosfato Monosódico. Através da avaliação qualitativa e quantitativa destes metabolitos há como objectivo a asserção de diversas patologias e alterações metabólicas de forma consistente, segura e não invasiva. O estudo tem como base a optimização de sequências pré-existentes, como ISIS (Image Selected In-Vivo Spectroscopy), CSI (Chemical Shift Imaging) e SPULS (Single Pulse and 1D acquire), assim como o desenvolvimento de uma sequência de localização 1D sem auxílio de gradientes. Esta sequência...

‣ O potencial dos sites de redes sociais no desempenho das pequenas e médias empresas da região do Algarve

Belo, Ana
Fonte: Universidade do Algarve Publicador: Universidade do Algarve
Tipo: Dissertação de Mestrado
Publicado em //2011 Português
Relevância na Pesquisa
17.239934%
Dissertação de mest., Economia da Inovação e Empreendedorismo, Faculdade de Economia, Univ. do Algarve, 2011; A evolução da internet com a web 2.0 criou novas oportunidades para as PME, entre as quais se destacam os sites de redes sociais. O objectivo da presente dissertação é analisar o potencial destas redes como ferramenta de desempenho das PME da região do Algarve, tendo sido efectuado um questionário para o efeito. O estudo empírico realizado revela que os dados recolhidos (de 70 empresas) possuem boas qualidades psicométricas. Foi validado que já existe por parte de algumas empresas uma estratégia integrada com as redes sociais, bem como um grupo de pessoas dentro da empresa responsáveis pelo seu envolvimento nestas redes. Os dados mostram que as actividades mais beneficiadas são: comunicar com os clientes, estar mais perto de possíveis clientes e marketing. Contudo, ficou demonstrado que as empresas utilizam as redes sociais para outras actividades como: analisar a concorrência, padrões de comportamento, conhecer tendências, cooperação, fidelização, internacionalização, lançamento de concursos, de novos produtos, notoriedade da marca, novos negócios, pedido de opinião, pesquisa, procurar ideias...

‣ Os determinantes da rendibilidade das KIBS

Almeida, Rita Susana Martins de
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2013 Português
Relevância na Pesquisa
17.239934%
Na literatura internacional, o estudo da rendibilidade das empresas tem sido tema de investigação em diversas áreas da Economia. O presente estudo tem como objetivo principal analisar os possíveis determinantes da rendibilidade das Pequenas e Médias Empresas (PME) consideradas como Knowledge Intensive Business Services (KIBS). Para responder a este objetivo, foram utilizados modelos de dados em painel estáticos e dinâmicos, com o recurso a uma amostra de 68 PME KIBS portuguesas, sob o período temporal compreendido entre 2004 e 2009. Como possíveis determinantes da rendibilidade das empresas alvo do nosso estudo, considerámos a dimensão, a idade, a liquidez, o endividamento de longo prazo, as despesas em Investigação e Desenvolvimento (I&D) e o risco das PME. Os resultados alcançados mostram que a dimensão, a liquidez, o endividamento de longo prazo e as despesas em I&D influenciam positivamente a rendibilidade das PME KIBS, destacando-se o determinante relativo à intensidade em I&D, ao apresentar um forte impacto na rendibilidade. O risco apresenta um impacto negativo, e a idade não revela qualquer influência sobre a rendibilidade das PME KIBS. Por último, os resultados obtidos mostram que a rendibilidade do período anterior se relaciona positivamente com a rendibilidade do período atual da empresa.

‣ Osteotomias do processo coracoide: um estudo anatômico

Terra,Bernardo Barcellos; Figueiredo,Eduardo Antônio de; Marczyk,Carlos Stanislaw Fleury; Monteiro,Gustavo Cará; Pochini,Alberto de Castro; Andreoli,Carlos Vicente; Ejnisman,Benno
Fonte: Sociedade Brasileira de Ortopedia e Traumatologia Publicador: Sociedade Brasileira de Ortopedia e Traumatologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 Português
Relevância na Pesquisa
17.239934%
OBJETIVO: Estudar as principais estruturas tendinosas e ligamentares inseridas no processo coracoide, correlacionando com diversos níveis de osteotomia e relatando as estruturas envolvidas no fragmento distai osteotomizado. MÉTODOS: Trinta ombros de 15 cadáveres (10 masculinos e cinco femininos) frescos foram dissecados. O processo coracoide com as principais estruturas anatômicas inseridas foram dissecados e cinco níveis de osteotomias (1,0; 1,5; 2,0; 2,5; 3,0cm) foram realizadas a partir do ápice e anotadas as principais estruturas inseridas no fragmento distal osteotomizado. RESULTADOS: Nas osteotomias de 1,0cm, em 100% dos casos houve envolvimento somente do tendão conjunto (TC). Nas osteotomias de 1,5cm, em 63,33% houve envolvimento do TC e peitoral menor (PMe), em 20% apenas do TC e em 16,66% do TC, PMi e ligamento coracoumeral (LCU). Nas osteotomias de 2,0cm, em 80% dos ombros, as osteotomias abrangeram o TC, PMe e o LCU e em 20% houve apenas envolvimento de TC e PMe. Nas osteotomias de 2,5cm, em 100% dos casos houve envolvimento do TC, PMe e LCU. Nas osteotomias de 3,0cm, em seis casos (20%) houve lesão do ligamento trapezoide e em 100% destas osteotomias, o fragmento distal osteotomizado abrangia o TC, PMe, LCU e em 90% envolvia também totalmente o ligamento coracoacromial. CONCLUSÃO: O conhecimento das estruturas anatômicas inseridas e envolvidas nos cortes das osteotomias do processo coracoide é de fundamental importância no manejo das osteotomias realizadas nas técnicas que utilizam o processo coracoide como enxerto ou referência anatômica. Nas osteotomias de 3...

‣ Plano Municipal de Educação e a afirmação de princípios para a educação local

Werle,Flávia Obino Corrêa; Barcellos,Jorge Alberto Soares
Fonte: Fundação CESGRANRIO Publicador: Fundação CESGRANRIO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2008 Português
Relevância na Pesquisa
17.239934%
O texto discute um elemento de política pública, o Plano Municipal de Educação (PME) da cidade de Porto Alegre, Rio Grande do Sul, Brasil. Analisa o Plano em suas diferentes partes e a tramitação no Legislativo e no Conselho Municipal de Educação de Porto Alegre. Considera os atores envolvidos nos diferentes momentos do processo, os discursos afirmados e os negados, ideologias e visões de mundo. O conteúdo do texto é importante, pois sugere elementos para avaliar o PME como um documento de política educacional numa perspectiva reflexiva. Indica como são sustentados/articulados os discursos no PME, a forma ambígua com que os atores registram sua presença/escrita e responsabilizam-se pelo PME em suas diferentes fases. O Plano Nacional de Educação como um paradigma dilui e abafa uma possível abordagem cognitivo-interpretativa mais peculiar do mundo que o PME possa representar no âmbito do município.

‣ An Increase in Pectin Methyl Esterase Activity Accompanies Dormancy Breakage and Germination of Yellow Cedar Seeds1

Ren, Chengwei; Kermode, Allison R.
Fonte: American Society of Plant Physiologists Publicador: American Society of Plant Physiologists
Tipo: Artigo de Revista Científica
Publicado em /09/2000 Português
Relevância na Pesquisa
17.239934%
Pectin methyl esterase (PME) (EC 3.1.1.11) catalyzes the hydrolysis of methylester groups of cell wall pectins. We investigated the role of this enzyme in dormancy termination and germination of yellow cedar (Chamaecyparis nootkatensis [D. Don] Spach) seeds. PME activity was not detected in dormant seeds of yellow cedar but was induced and gradually increased during moist chilling; high activity coincided with dormancy breakage and germination. PME activity was positively correlated to the degree of dormancy breakage of yellow cedar seeds. The enzyme produced in different seed parts and in seeds at different times during moist chilling, germination, and early post-germinative growth consisted of two isoforms, both basic with isoelectric points of 8.7 and 8.9 and the same molecular mass of 62 kD. The pH optimum for the enzyme was between 7.4 and 8.4. In intact yellow cedar seeds, activities of the two basic isoforms of PME that were induced in embryos and in megagametophytes following dormancy breakage were significantly suppressed by abscisic acid. Gibberellic acid had a stimulatory effect on the activities of these isoforms in embryos and megagametophytes of intact seeds at the germinative stage. We hypothesize that PME plays a role in weakening of the megagametophyte...

‣ Structural Insights into the Target Specificity of Plant Invertase and Pectin Methylesterase Inhibitory Proteins

Hothorn, Michael; Wolf, Sebastian; Aloy, Patrick; Greiner, Steffen; Scheffzek, Klaus
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /12/2004 Português
Relevância na Pesquisa
17.239934%
Pectin methylesterase (PME) and invertase are key enzymes in plant carbohydrate metabolism. Inhibitors of both enzymes constitute a sequence family of extracellular proteins. Members of this family are selectively targeted toward either PME or invertase. In a comparative structural approach we have studied how this target specificity is implemented on homologous sequences. By extending crystallographic work on the invertase inhibitor Nt-CIF to a pectin methylesterase inhibitor (PMEI) from Arabidopsis thaliana, we show an α-helical hairpin motif to be an independent and mobile structural entity in PMEI. Removal of this hairpin fully inactivates the inhibitor. A chimera composed of the α-hairpin of PMEI and the four-helix bundle of Nt-CIF is still active against PME. By contrast, combining the corresponding segment of Nt-CIF with the four-helix bundle of PMEI renders the protein inactive toward either PME or invertase. Our experiments provide insight in how these homologous inhibitors can make differential use of similar structural modules to achieve distinct functions. Integrating our results with previous findings, we present a model for the PME-PMEI complex with important implications.

‣ Mammalian protein methylesterase. Physical and enzymic properties.

Veeraragavan, K; Gagnon, C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/1989 Português
Relevância na Pesquisa
17.239934%
Protein methylesterase (PME) amino acid composition and substrate specificity towards methylated normal and deamidated protein substrates were investigated. The enzyme contained 23% acidic and 5% basic residues. These values are consistent with a pI of 4.45. The product formed from methylated protein by PME was confirmed as methanol by h.p.l.c. The kcat. and Km values for several methylated protein substrates ranged from 20 x 10(-6) to 560 x 10(-6) s-1 and from 0.5 to 64 microM respectively. However, the kcat./Km ratios ranged within one order of magnitude from 11 to 52 M-1.s-1. Results with the irreversible cysteine-proteinase inhibitor E-64 suggested that these low values were in part due to the fact that only one out of 25 molecules in the PME preparations was enzymically active. When PME was incubated with methylated normal and deamidated calmodulin, the enzyme hydrolysed the latter substrate at a higher rate. The Km and kcat. for methylated normal calmodulin were 0.9 microM and 31 x 10(-6) s-1, whereas for methylated deamidated calmodulin values of 1.6 microM and 188 x 10(-6) s-1 were obtained. The kcat./Km ratios for methylated normal and deamidated calmodulin were 34 and 118 M-1.s-1 respectively. By contrast, results with methylated adrenocorticotropic hormone (ACTH) substrates indicated that the main difference between native and deamidated substrates resides in the Km rather than the kcat. The Km for methylated deamidated ACTH was 5-fold lower than that for methylated native ACTH. The kcat./Km ratios for methylated normal and deamidated ACTH were 43 and 185 M-1.s-1 respectively. These results indicate that PME recognizes native and deamidated methylated substrates as two different entities. This suggests that the methyl groups on native calmodulin and ACTH substrates may not be on the same amino acid residues as those on deamidated calmodulin and ACTH substrates.

‣ In vivo and in vitro hepatic phosphorus-31 magnetic resonance spectroscopy and electron microscopy in chronic ductopenic rejection of human liver allografts

Taylor-Robinson, S; Sargentoni, J; Bell, J; Thomas, E; Marcus, C; Changani, K; Saeed, N; Hodgson, H; Davidson, B; Burroughs, A; Rolles, K; Foster, C; Cox, I
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1998 Português
Relevância na Pesquisa
17.239934%
Background—In vivo hepatic phosphorus-31 magnetic resonance spectroscopy (MRS) provides non-invasive information about phospholipid metabolism. 
Aims—To delineate MRS abnormalities in patients with chronic ductopenic rejection (CDR) and to characterise spectral changes by in vitro MRS and electron microscopy. 
Patients and methods—Sixteen liver transplant recipients (four with CDR; 12 with good graft function) and 29 controls (23healthy volunteers; six patients with biliary duct strictures) were studied with in vivo 31P MRS. Peak area ratios of phosphomonoesters (PME) and phosphodiesters (PDE), relative to nucleotide triphosphates (NTP) were measured. In vitro MRS and electron microscopy were performed on biopsy specimens from five patients with CDR, freeze clamped at retransplantation. Phosphoethanolamine (PE), phosphocholine (PC), glycerophosphorylethanolamine (GPE), and glycerophosphorylcholine (GPC) concentrations were measured. 
Results—The 12 patients with good graft function displayed no spectral abnormalities in vivo; the four patients with CDR showed significantly elevated PME:NTP (p<0.01) and PDE:NTP ratios (p<0.005). Patients with biliary strictures had significant differences in PME:NTP (p<0.01) from patients with CDR...

‣ Overexpression of Pectin Methylesterase Inhibitors in Arabidopsis Restricts Fungal Infection by Botrytis cinerea1[C][W]

Lionetti, Vincenzo; Raiola, Alessandro; Camardella, Laura; Giovane, Alfonso; Obel, Nicolai; Pauly, Markus; Favaron, Francesco; Cervone, Felice; Bellincampi, Daniela
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Publicado em /04/2007 Português
Relevância na Pesquisa
17.239934%
Pectin, one of the main components of plant cell wall, is secreted in a highly methylesterified form and is demethylesterified in muro by pectin methylesterase (PME). The action of PME is important in plant development and defense and makes pectin susceptible to hydrolysis by enzymes such as endopolygalacturonases. Regulation of PME activity by specific protein inhibitors (PMEIs) can, therefore, play a role in plant development as well as in defense by influencing the susceptibility of the wall to microbial endopolygalacturonases. To test this hypothesis, we have constitutively expressed the genes AtPMEI-1 and AtPMEI-2 in Arabidopsis (Arabidopsis thaliana) and targeted the proteins into the apoplast. The overexpression of the inhibitors resulted in a decrease of PME activity in transgenic plants, and two PME isoforms were identified that interacted with both inhibitors. While the content of uronic acids in transformed plants was not significantly different from that of wild type, the degree of pectin methylesterification was increased by about 16%. Moreover, differences in the fine structure of pectins of transformed plants were observed by enzymatic fingerprinting. Transformed plants showed a slight but significant increase in root length and were more resistant to the necrotrophic fungus Botrytis cinerea. The reduced symptoms caused by the fungus on transgenic plants were related to its impaired ability to grow on methylesterified pectins.

‣ Phosphorus metabolism during growth of lymphoma in mouse liver: a comparison of 31P magnetic resonance spectroscopy in vivo and in vitro.

Thomas, C. P.; Dixon, R. M.; Tian, M.; Butler, S. A.; Counsell, C. J.; Bradley, J. K.; Adams, G. E.; Radda, G. K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1994 Português
Relevância na Pesquisa
17.239934%
Large phosphomonoester (PME) signals are detected in the phosphorus magnetic resonance spectra (31P MRS) of many neoplastic and rapidly dividing tissues. In addition, alterations in phosphodiester (PDE) signals are sometimes seen. The present study of a murine lymphoma growing in liver showed a positive correlation between the hepatic PME/PDE ratio measured in vivo by 31P MRS at 4.7 T and the degree of lymphomatous infiltration in the liver, quantified by histology. High-resolution 31P MRS of liver extracts at 9.7 T showed that the PME peak consists largely of phosphoethanolamine (PE) and to a lesser extent of phosphocholine (PC). The concentration of both PE and PC increased positively with lymphomatous infiltration of the liver. In vivo, the PDE peak contains signals from phospholipids (mostly phosphatidylethanolamine and phosphatidylcholine) and the phospholipid breakdown products glycerophosphoethanolamine (GPE) and glycerophosphocholine (GPC). Low levels of GPE and GPC were detected in the aqueous extracts of the control and infiltrated livers; their concentrations remained unchanged as the infiltration increased. The total concentration of phospholipids measured by 31P MRS of organic extracts decreased about 3-fold as the infiltration increased to 70%. Thus...

‣ Phosphorus-31 metabolism of post-menopausal breast cancer studied in vivo by magnetic resonance spectroscopy.

Twelves, C. J.; Porter, D. A.; Lowry, M.; Dobbs, N. A.; Graves, P. E.; Smith, M. A.; Rubens, R. D.; Richards, M. A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1994 Português
Relevância na Pesquisa
17.239934%
We have studied the metabolism of 31P-containing metabolites of post-menopausal breast cancers in vivo using magnetic resonance spectroscopy (MRS) and a 5.5 cm surface coil. Spectra were acquired from 23 diameter. The spectra of the 19 previously untreated tumours had significantly higher phosphomonoester (PME) 31P relative peak areas than the normal breasts of eight post-menopausal women (11.7% and 7.7% respectively, P = 0.002). Although an increased PME relative peak area was characteristic of malignancy, PME relative peak area is similarly raised in lactating breast and, therefore, not a specific feature of cancer. An apparently lower nucleotide triphosphate (NTP) relative peak area in tumours than healthy postmenopausal breast was secondary to the differences in PME relative peak area; contamination by signal from chest wall muscle probably accounts for the ostensibly higher phosphocreatine (PCr) relative peak area of the tumours. Spectroscopy was repeated following chemotherapy in six women. An increase in PCr relative peak area was seen in all five patients who responded, but again this may represent increased contamination secondary to changes in tumour size. A fall in PME relative peak area was noted in four responders, but also one non-responder...

‣ Human primary brain tumour metabolism in vivo: a phosphorus magnetic resonance spectroscopy study.

Cadoux-Hudson, T. A.; Blackledge, M. J.; Rajagopalan, B.; Taylor, D. J.; Radda, G. K.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em /09/1989 Português
Relevância na Pesquisa
17.239934%
Magnetic resonance spectroscopy was used to study intracellular pH and compounds which contain phosphorus in normal human brain and primary brain tumours non-invasively. In normal subjects (n = 7) intracellular pH (pHi) of the brain was 7.03 +/- 0.02 (mean +/- s.e.m.). The pHi did not vary between superficial (2 cm, majority grey matter) and deep brain (5 cm, majority white matter). The relative concentrations of phosphocreatine (PCr) and phosphomonoesters (PME) to ATP were also constant with depth. The relative concentration of phosphodiesters (PDE) increased from superficial to deep in normal brain. The astrocytomas (n = 7, grade II-IV) were significantly more alkaline (pHi = 7.08 +/- 0.03), and contained more PCr and PME, with respect to ATP, than normal brain at similar depth. The meningiomas (n = 4) were also more alkaline (pHi = 7.19 +/- 0.02) with a raised PME level but reduced PCr. The reduction in meningioma PCr may be due to the significant necrosis (greater than 20%) seen in the surgical biopsies. No significant necrosis was seen in the gliomas. Previous in vitro studies suggest that increased PME may be due to accumulation of phosphoethanolamine (PE), a phospholipid precursor. These results suggest that human primary brain tumours characteristically are more alkaline with increased PME than normal brain.

‣ School achievement in 14-year-old youths prenatally exposed to marijuana

Goldschmidt, Lidush; Richardson, Gale A.; Willford, Jennifer A.; Severtson, Stevan G.; Day, Nancy L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.239934%
The relation between prenatal marijuana exposure (PME) and school achievement was evaluated in a sample of 524 14-year-olds. Women were recruited during pregnancy and assessed, along with their offspring, at multiple phases from infancy to early adulthood. The sample represents a low-income population. Half of the adolescents are male and 55% are African American. School achievement was assessed with the Wechsler Individual Achievement Test (WIAT) Screener (Psychological Corporation, 1992). A significant negative relation was found between PME and 14-year WIAT composite and reading scores. The deficit in school achievement was mediated by the effects of PME on intelligence test performance at age 6, attention problems and depression symptoms at age 10, and early initiation of marijuana use. These findings suggest that the effects of PME on adolescent achievement are mediated by the earlier negative effects of PME on child characteristics. The negative impact of these characteristics on adolescent achievement may presage later problems in early adulthood.

‣ Demethylesterification of Cell Wall Pectins in Arabidopsis Plays a Role in Seed Germination1[W][OA]

Müller, Kerstin; Levesque-Tremblay, Gabriel; Bartels, Sebastian; Weitbrecht, Karin; Wormit, Alexandra; Usadel, Bjoern; Haughn, George; Kermode, Allison R.
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.239934%
The methylesterification status of cell wall homogalacturonans, mediated through the action of pectin methylesterases (PMEs), influences the biophysical properties of plant cell walls such as elasticity and porosity, important parameters for cell elongation and water uptake. The completion of seed germination requires cell wall extensibility changes in both the radicle itself and in the micropylar tissues surrounding the radicle. In wild-type seeds of Arabidopsis (Arabidopsis thaliana), PME activities peaked around the time of testa rupture but declined just before the completion of germination (endosperm weakening and rupture). We overexpressed an Arabidopsis PME inhibitor to investigate PME involvement in seed germination. Seeds of the resultant lines showed a denser methylesterification status of their cell wall homogalacturonans, but there were no changes in the neutral sugar and uronic acid composition of the cell walls. As compared with wild-type seeds, the PME activities of the overexpressing lines were greatly reduced throughout germination, and the low steady-state levels neither increased nor decreased. The most striking phenotype was a significantly faster rate of germination, which was not connected to altered testa rupture morphology but to alterations of the micropylar endosperm cells...

‣ Wound-induced pectin methylesterases enhance banana (Musa spp. AAA) susceptibility to Fusarium oxysporum f. sp. cubense

Ma, Li; Jiang, Shuang; Lin, Guimei; Cai, Jianghua; Ye, Xiaoxi; Chen, Houbin; Li, Minhui; Li, Huaping; Takáč, Tomáš; Šamaj, Jozef; Xu, Chunxiang
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.239934%
Recent studies suggest that plant pectin methylesterases (PMEs) are directly involved in plant defence besides their roles in plant development. However, the molecular mechanisms of PME action on pectins are not well understood. In order to understand how PMEs modify pectins during banana (Musa spp.)–Fusarium interaction, the expression and enzyme activities of PMEs in two banana cultivars, highly resistant or susceptible to Fusarium, were compared with each other. Furthermore, the spatial distribution of PMEs and their effect on pectin methylesterification of 10 individual homogalacturonan (HG) epitopes with different degrees of methylesterification (DMs) were also examined. The results showed that, before pathogen treatment, the resistant cultivar displayed higher PME activity than the susceptible cultivar, corresponding well to the lower level of pectin DM. A significant increase in PME expression and activity and a decrease in pectin DM were observed in the susceptible cultivar but not in the resistant cultivar when plants were wounded, which was necessary for successful infection. With the increase of PME in the wounded susceptible cultivar, the JIM5 antigen (low methyestrified HGs) increased. Forty-eight hours after pathogen infection...

‣ Pectin Methylesterase and Pectin Remodelling Differ in the Fibre Walls of Two Gossypium Species with Very Different Fibre Properties

Liu, Qinxiang; Talbot, Mark; Llewellyn, Danny J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/06/2013 Português
Relevância na Pesquisa
17.239934%
Pectin, a major component of the primary cell walls of dicot plants, is synthesized in Golgi, secreted into the wall as methylesters and subsequently de-esterified by pectin methylesterase (PME). Pectin remodelling by PMEs is known to be important in regulating cell expansion in plants, but has been poorly studied in cotton. In this study, genome-wide analysis showed that PMEs are a large multi-gene family (81 genes) in diploid cotton (Gossypium raimondii), an expansion over the 66 in Arabidopsis and suggests the evolution of new functions in cotton. Relatively few PME genes are expressed highly in fibres based on EST abundance and the five most abundant in fibres were cloned and sequenced from two cotton species. Their significant sequence differences and their stage-specific expression in fibres within a species suggest sub-specialisation during fibre development. We determined the transcript abundance of the five fibre PMEs, total PME enzyme activity, pectin content and extent of de-methylesterification of the pectin in fibre walls of the two cotton species over the first 25–30 days of fibre growth. There was a higher transcript abundance of fibre-PMEs and a higher total PME enzyme activity in G. barbadense (Gb) than in G. hirsutum (Gh) fibres...

‣ Examining the Relationships Between Prenatal Methamphetamine Exposure, Early Adversity, and Child Neurobehavioral Disinhibition

Abar, Beau; LaGasse, Linda L.; Newman, Elana; Smith, Lynne M; Huestis, Marilyn; Neal, Charles; DeRauf, Chris; Shah, Rizwan; Arria, Amelia; Grotta, Sheri Della; Dansereau, Lynne M.; Lester, Barry M.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
17.239934%
Methamphetamine use is a growing problem among pregnant women in the United States. Many negative consequences of methamphetamine use have been documented for the users, but little research has examined the long-term association between prenatal methamphetamine exposure (PME) and childhood outcomes. The current study examined the extent to which PME was predictive of childhood neurobehavioral disinhibition (ND), as well as the extent to which early adversity mediated this relationship. A sample of 320 mother–infant dyads (162 PME) was followed from birth through 6.5 years of age. ND was conceptualized as a two factor model consisting of deficits in (a) behavioral and emotional control, and (b) executive function. PME was associated with behavioral and emotional control at 5 years, which was associated with executive function deficits at 6.5 years. Early adversity (birth through year 3) significantly mediated the relationship between PME and ND. Associations with previous research and implications for prevention are discussed.

‣ Pectinases From Sphenophorus levis Vaurie, 1978 (Coleoptera: Curculionidae): Putative Accessory Digestive Enzymes

Evangelista, Danilo Elton; de Paula, Fernando Fonseca Pereira; Rodrigues, André; Henrique-Silva, Flávio
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 09/02/2015 Português
Relevância na Pesquisa
17.239934%
The cell wall in plants offers protection against invading organisms and is mainly composed of the polysaccharides pectin, cellulose, and hemicellulose, which can be degraded by plant cell wall degrading enzymes (PCWDEs). Such enzymes are often synthesized by free living microorganisms or endosymbionts that live in the gut of some animals, including certain phytophagous insects. Thus, the ability of an insect to degrade the cell wall was once thought to be related to endosymbiont enzyme activity. However, recent studies have revealed that some phytophagous insects are able to synthesize their own PCWDEs by endogenous genes, although questions regarding the origin of these genes remain unclear. This study describes two pectinases from the sugarcane weevil, Sphenophorus levis Vaurie, 1978 (Sl-pectinases), which is considered one of the most serious agricultural pests in Brazil. Two cDNA sequences identified in a cDNA library of the insect larvae coding for a pectin methylesterase (PME) and an endo-polygalacturonase (endo-PG)—denominated Sl-PME and Sl-endoPG, respectively—were isolated and characterized. The quantitative real-time reverse transcriptase polymerase chain reaction expression profile for both Sl-pectinases showed mRNA production mainly in the insect feeding stages and exclusively in midgut tissue of the larvae. This analysis...