Base de dados : LILACS
Pesquisa : A11.284.149.165.570 [Categoria DeCS]
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Id: lil-470360
Autor: Corrêa, José R; Atella, Georgia C; Vargas, Camila; Soares, Maurilio J.
Título: Transferrin uptake may occur through detergent-resistant membrane domains at the cytopharynx of Trypanosoma cruzi epimastigote forms
Fonte: Mem. Inst. Oswaldo Cruz;102(7):871-876, Nov. 2007. ilus, graf.
Idioma: en.
Resumo: Uptake of transferrin by epimastigote forms of the protozoan Trypanosoma cruzi occurs mainly through a cytostome/ cytopharynx, via uncoated endocytic vesicles that bud off from the bottom of the cytopharynx. We have here examined whether detergent-resistant membrane (DRM) domains might be involved in this process. Purified whole cell membrane fractions were assayed for cholesterol levels and used in dot blot analyses. Detergent-resistant membrane markers (cholera B toxin and anti-flotillin-1 antibody) presented positive reaction by dot blots in cholesterol-rich/ protein-poor membrane sub-fractions. The positive dot blot fraction was submitted to lipid composition analysis, showing composition similar to that of raft fractions described for other eukaryotic cells. Immunofluorescence assays allowed the localization of punctual positive signal for flotillin-1, matching the precise cytostome/ cytopharynx location. These data were confirmed by immunofluorescence assays with the co-localization of flotillin-1 and the transferrin uptake site. Our data suggest that DRM domains occur and are integrated at the cytostome/ cytopharynx of T. cruzi epimastigotes, being the main route for transferrin uptake.
Descritores: Colesterol/metabolismo
Detergentes/farmacologia
Microdomínios da Membrana/metabolismo
Microtúbulos/metabolismo
Transferrina/metabolismo
Trypanosoma cruzi/metabolismo
-Imunofluorescência
Microscopia Eletrônica de Transmissão
Trypanosoma cruzi/efeitos dos fármacos
Trypanosoma cruzi/ultraestrutura
Limites: Animais
Tipo de Publ: Research Support, Non-U.S. Gov't
Responsável: BR1.1 - BIREME


  2 / 6 LILACS  
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Id: lil-467602
Autor: Sesso, Antonio.
Título: Pitfalls in the use of electron microscopy to study the mitochondrial membrane permeability transition in apoptotic cells and pellets: where do we stand in relation to the incidence of mitochondrial swelling in apoptosis?
Fonte: Braz. j. morphol. sci = Rev. bras. ciênc. morfol;23(1):57-74, jan.-mar. 2006. ilus.
Idioma: en.
Resumo: The importance of apoptosis as a form of programmed cell death was recognized in the 1980s, whereas the central role of mitochondria in controlling this process was identifi ed in the mid-1990s. An important event in apoptosis is the collapse of the mitochondrial transmembrane potential (ÃØm), with the ensuing loss of the selective permeability of the inner membrane resulting in swelling of the hyperosmolar mitochondrial matrix. This event is known as the mitochondrial permeability transition (MPT). After swelling of the intermembrane space, the outer membrane ruptures, exposing the permeable inner membrane. An increasingly swollen matrix covered by the inner membrane eventually herniates into the cytoplasm through the breach formed in the outer membrane (OM). The increase in surface area of the inner mitochondrial membrane (IMM) involves the unfolding of membrane stored in the cristae. This membrane movement is osmotically driven since the cytoplasm has a lower osmolality. The proteins partly embedded in the inner membrane are thus exposed to the cytoplasm. In nine out of ten electron microscopy studies of isolated mitochondria expressing the permeability transition, the existing ruptures of the OMM were overlooked. The MPT can also be recognized in individual mitochondria by using fl uorescent probes that are not retained in these organelles once the ÃØm is lost. In cases in which there is no rupture of the OMM, cytochrome c must be released from mitochondria with impermeable inner membranes. Examination of several hundred of the more than 61,000 published papers on programmed cell death revealed that the key signaling events of apoptosis, such as the onset of the MPT, mitochondrial swelling and cytochrome c release to the cytoplasm, are infl uenced by factors such as the cell type and presence of apoptogenic agents...
Descritores: Apoptose
Permeabilidade da Membrana Celular
Citocromos c
Microscopia Eletrônica de Transmissão
Membranas Mitocondriais
Membrana Celular/ultraestrutura
Membranas Mitocondriais/ultraestrutura
Membranas/citologia
-Membrana Celular
Mitocôndrias
Microdomínios da Membrana/ultraestrutura
Tipo de Publ: Revisão
Responsável: BR734.1 - Biblioteca Central Cesar Lattes - BCCL


  3 / 6 LILACS  
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Texto completo SciELO Chile
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Id: lil-437388
Autor: Vergara, Julio L; Difranco, Marino.
Título: Modulation by caffeine of calcium-release microdomains in frog skeletal muscle fibers
Fonte: Biol. Res;39(3):567-581, 2006. ilus.
Idioma: en.
Projeto: National Institutes of Health; . Muscular Dystrophy Association.
Resumo: The effects of caffeine on the process of excitation-contraction coupling in amphibian skeletal muscle fibers were investigated using the confocal spot detection technique. This method permits to carefully discriminate between caffeine effects on the primary sources of Ca2+ release at the Z-lines where the triads are located and secondary actions on other potential Ca Release sources. Our results demonstrate that 0.5 mM caffeine potentiates and prolongs localized action-potential evoked Ca2+ transients recorded at the level of the Z-lines, but that 1mM only prolongs them. The effects at both doses are reversible. At the level of the M-line, localized Ca2+ transients displayed more variability in the presence of 1 mM caffeine than in control conditions. At this dose of caffeine, extra-junctional sources of Ca2+ release also were observed occasionally.
Descritores: Cafeína/farmacologia
Cálcio/metabolismo
Estimulantes do Sistema Nervoso Central/farmacologia
Fibras Musculares Esqueléticas
Contração Muscular/fisiologia
Músculo Esquelético/efeitos dos fármacos
-Eletrofisiologia
Microdomínios da Membrana
Potenciais da Membrana
Microscopia de Fluorescência
Fibras Musculares Esqueléticas
Músculo Esquelético/metabolismo
Rana catesbeiana
Fatores de Tempo
Limites: Animais
Responsável: BR1.1 - BIREME


  4 / 6 LILACS  
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Texto completo SciELO Brasil
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Id: lil-364486
Autor: Hakomori, Senitiroh.
Título: Glycosynapses: microdomains controlling carbohydrate-dependent cell adhesion and signaling
Fonte: An. acad. bras. ciênc;76(3):553-572, Sept. 2004. ilus, tab, graf.
Idioma: en.
Resumo: O conceito de microdomínios em membrana plasmática foi desenvolvido há mais de duas décadas, após a observação da polaridade da membrana baseada no agrupamento de componentes específicos da membrana. Microdomínios envolvidos na adesão celular dependente de carboidrato, com transdução de sinal que afeta o fenótipo celular são denominados "glicosinapses". Três tipos de glicosinapse foram observados: "tipo 1" que possue glicoesfingolipídio associado com transdutores de sinal (proteínas G pequenas, cSrc, cinases da família Src) e proteolipídios; "tipo 2" que possue glycoproteínas O-ligadas tipo mucina associadas com cinases da família Scr; e "tipo 3" que possue receptor de integrina, com glycanas N-ligadas, complexado com tetraspanina e gangliosídio. Tipos celulares diferentes são caracterizados pela presença de tipos específicos de glicosinapse ou suas combinaçäes, cuja adesão induz transdução de sinal para facilitar ou inibir a sinalização. Ex., a sinalização através da glicosinapse tipo 3 inibe mobilidade celular e a diferenciação. Glicosinapses são distintas dos microdomínios conhecidos classicamente como "caveolas", "membrana caveolar", ou mais recentemente "rafts lipídicos", os quais não estão envolvidos na adesão celular dependente de carboidrato. Glicosinapses tipo 1 e tipo 3 são resistentes a regentes que se ligam ao colesterol, enquanto a estrututa e função de "membrana caveolar" ou "rafts lipídicos" são sensíveis a esses reagentes. Vários dados sugerem um papel funcional para as glicosinapses durante a diferenciação, o desenvolvimento e a transformação oncogênica.
Descritores: Carboidratos
Microdomínios da Membrana
Transdução de Sinais
Sinapses
-Adesão Celular
Limites: Humanos
Responsável: BR1.1 - BIREME


  5 / 6 LILACS  
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Texto completo SciELO Chile
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Id: lil-323337
Autor: Bender, Florent; Montoya, Margarita; Monardes, Virginia; Leyton, Lisette; Quest, Andrew F. G.
Título: Caveolae and caveolae-like membrane domains in cellular signaling and disease: identification of downstream targets for the tumor suppressor protein caveolin-1
Fonte: Biol. Res;35(2):151-167, 2002. ilus, tab, graf.
Idioma: en.
Projeto: FONDECYT; . FONDAP; . ICGEB; . CONICYT.
Resumo: Caveolae are small, flask-shaped invaginations of the plasma membrane present on a large number of mammalian cells. Recent results obtained with knock-out mice for the gene caveolin-1 demonstrate that expression of caveolin-1 protein is essential for caveolae formation in vivo. Caveolae are implicated in a wide variety of cellular events including transcytosis, cholesterol trafficking and as cellular centers important in coordinating signalling events. Caveolae share this role and the property of detergent insolubility with plasma membrane assemblies rich in glycosphingolipids and cholesterol, often called lipid rafts, but preferably referred to here as caveolae-like membrane domains. Due to such widespread presence and usage in cellular function, caveolae and related domains are implicated in human diseases, including cancer. In particular, the protein caveolin-1 is suggested to function as a tumor suppressor protein. Evidence demonstrating such a role for caveolin-1 in human colon carcinoma cells will be discussed together with data from microarray experiments seeking to identify caveolin-1 target genes responsible for such behavior
Descritores: Cavéolas
Caveolinas
Microdomínios da Membrana
Transdução de Sinais
Proteínas Supressoras de Tumor/fisiologia
-Caveolinas
Transformação Celular Neoplásica
Neoplasias do Colo
Doença
Camundongos Knockout
Camundongos Nus
Limites: Humanos
Animais
Camundongos
Tipo de Publ: Revisão
Research Support, Non-U.S. Gov't
Responsável: BR1.1 - BIREME


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Id: lil-323334
Autor: Magee, Tony; Pirinen, Niina; Adler, Jeremy; Pagakis, Stamatis N; Parmryd, Ingela.
Título: Lipid rafts: cell surface platforms for T cel signaling
Fonte: Biol. Res;35(2):127-131, 2002.
Idioma: en.
Projeto: UK Medical Research Council; . Swedish Medical Research Council; . Wellcome Trust; . Swedish Cancer Fund.
Resumo: The Src family tyrosine kinase Lck is essential for T cell development and T cell receptor (TCR) signaling. Lck is post-translationally fatty acylated at its N-terminus conferring membrane targeting and concentration in plasma membrane lipid rafts, which are lipid-based organisational platforms. Confocal fluorescence microscopy shows that Lck colocalizes in rafts with GPI-linked proteins, the adaptor protein LAT and Ras, but not with non-raft membrane proteins including the protein tyrosine phosphatase CD45. The TCR also associates with lipid rafts and its cross-linking causes coaggregation of raft-associated proteins including Lck, but not of CD45. Cross-linking of either the TCR or rafts strongly induces specific tyrosine phosphorylation of the TCR in the rafts. Remarkably, raft patching alone induces signalling events analogous to TCR stimulation, with the same dependence on expression of key TCR signalling molecules. Our results indicate a mechanism whereby TCR engagement promotes aggregation of lipid rafts, which facilitates colocalization of signaling proteins including Lck, LAT, and the TCR, while excluding CD45, thereby potentiating protein tyrosine phosphorylation and downstream signaling. We are currently testing this hypothesis as well as using imaging techniques such as fluorescence resonance energy transfer (FRET) microscopy to study the dynamics of proteins and lipids in lipid rafts in living cells undergoing signaling events. Recent data show that the key phosphoinositide PI(4,5)P2 is concentrated in T cell lipid rafts and that on stimulation of the cells it is rapidly converted to PI(3,4,5)P3 and diacylglycerol within rafts. Thus rafts are hotspots for both protein and lipid signalling pathways (AU)#S
Descritores: Microdomínios da Membrana
Transdução de Sinais
Linfócitos T
-Lipídeos
Proteína Tirosina Quinase p56(lck) Linfócito-Específica
Proteínas ras
Receptores de Antígenos de Linfócitos T
Limites: Humanos
Animais
Tipo de Publ: Revisão
Research Support, Non-U.S. Gov't
Responsável: BR1.1 - BIREME



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