RESUMO
Based on immunohistochemical techniques against connexins and the intercellular flux of staining molecules, it has previously been shown that electrotonic communication occurs among endothelial and vascular smooth muscle cells, this due to the presence of myoendothelial gap junctions. The aim of this study was to evaluate the density of myoendothelial contacts in the left coronary and internal mammary arteries as well as in the left saphenous vein by means of electron microscopy, the distance between both cells participating in an myoendothelial contact with a semi-automatic image analysis system and the presence of homocellular and heterocellular gap junctions between endothelial and smooth muscle cells by using the immunohistochemical technique and confocal microscopy in thoracic aorta were also analyzed. The results are that all blood vessels studied present myoendothelial contacts, while density studies show that they are more abundant in the saphenous vein. The myoendothelial contact distance is constant and in no case the cytoplasmic processes reach the plasma membrane of the partner cell toward which they are advanced. Homocellular gap junctions were found between smooth muscle cells and between endothelial cells. Heterocellular gap junctions were absent, evidencing the possibility that signaling molecules between endothelial and smooth muscle cells may be transferred through plasma membranes as was once thought and not necessarily by electrotonic communication.
Assuntos
Comunicação Celular , Endotélio Vascular/metabolismo , Junções Comunicantes/metabolismo , Músculo Liso Vascular/fisiologia , Transdução de Sinais/fisiologia , Animais , Aorta Torácica/citologia , Aorta Torácica/fisiologia , Vasos Coronários/citologia , Vasos Coronários/fisiologia , Endotélio Vascular/fisiologia , Junções Comunicantes/fisiologia , Imuno-Histoquímica , Masculino , Artéria Torácica Interna/citologia , Artéria Torácica Interna/fisiopatologia , Microscopia Confocal , Microscopia Eletrônica , Músculo Liso Vascular/citologia , Ratos , Ratos Sprague-Dawley , Veia Safena/citologia , Veia Safena/fisiologiaRESUMO
The distribution of the cation-independent mannose 6-phosphate and 78 kDa receptors was studied in postnuclear subcellular fractions from two rat liver cell lines. ELISA assays revealed that the mannose 6-phosphate receptor is enriched in the light buoyant Percoll fractions that contain Golgi structures and early endosomes. Most of the 78 kDa receptor is localized in a heavy fraction at the bottom of the Percoll gradient and smaller amounts in the endosomal fractions. The high-density compartment is denser than lysosomes, contains LAMP2 but not LIMPII or acid hydrolases, and is not disrupted with glycyl-l-phenylalanine 2-naphthylamide, a substrate for cathepsin C that selectively disrupts lysosomes. Immunofluorescence microscopy studies indicate no colocalization of the 78 kDa receptor with the mannose 6-phosphate receptor or LIMPII. Mannose 6-phosphate-independent endocytosed beta-glucuronidase was found in the lysosomal, the early and late endosomal fractions. These fractions were immunoadsorbed in columns containing antibodies against the 78 kDa receptor. Only the endocytosed beta-glucuronidase present in the early and late endosomal fractions is associated to immunoadsorbed vesicles. In these vesicles, LAMP2 was detected but no LIMPII or the mannose 6-phosphate receptor. Results obtained suggest that the 78 kDa receptor is found along the endocytic pathway, but in vesicles different from the cation-independent mannose 6-phosphate receptor.
Assuntos
Hepatócitos/metabolismo , Fígado/metabolismo , Lisossomos/enzimologia , Manosefosfatos/metabolismo , Receptor IGF Tipo 2/metabolismo , Frações Subcelulares/metabolismo , Animais , Fracionamento Celular , Linhagem Celular , Centrifugação com Gradiente de Concentração , Técnica Indireta de Fluorescência para Anticorpo , Hepatócitos/ultraestrutura , Fígado/ultraestrutura , Peso Molecular , Povidona , Ratos , Receptor IGF Tipo 2/isolamento & purificação , Dióxido de SilícioRESUMO
Se estudió el desarrollo de placas ateros-clerósicas en conejos Nueva Zelanda alimentados con una dieta rica en colesterol. Para ello se comparó el contenido sérico de lípidos y glucosa en conejos sanos y conejos alimentados con 1 y 10 por ciento de colesterol por 10 semanas. Además, se hicieron estudios histológicos de las aortas de dichos animales para evaluar las lesiones ateromatosas. En los animales que recibían una dieta con 10 por ciento de colesterol, los niveles séricos de éste aumentaron significativamente de 26.3 ñ 8.1 mg/dL a 1485 ñ 26.8 mg/dL (p < 0.05). El colesterol asociado con LDL también se incrementó, de 15.9 ñ 5.9 a 1383.8 ñ 58.9 (p < 0.5); y los triglicéridos de 88.3 ñ 35.6 a 411 ñ 154.5. Se encontraron lesiones ateros-clerósicas solamente en los conejos alimentados con 10 por ciento de colesterol. Este modelo es reproducible y puede ser útil en el estudio de la aterosclerosis per se y de la aterogénesis asociada con enfermedades como la diabetes mellitus
Assuntos
Animais , Coelhos , Arteriosclerose/induzido quimicamente , Hipercolesterolemia/induzido quimicamente , Projetos de Pesquisa , Colesterol na Dieta/efeitos adversos , Lipoproteínas/efeitos adversosRESUMO
Smooth muscle cells from thoracic aortas of 12-week-old rats were cultured on elastin membranes for up to 21 days. The cell cultures were examined using light microscopy, trasmission and scanning electron microscopy. The contractile phenotype characteristic for resident arterial wall muscle cell changed to the synthetic phenotype. In the synthetic state, the muscle cells contain few filaments, but a substantial amount of orgenelles are involved with synthesis. The cells grown on elastin substrates showed a multilayered pattern with the formation of nodules. Cell degeneration was present from dayeight and increased with time. At the end of the experiment, the center of the multilayered areas showed degenerative changes with numerous foam cells of smooth muscle origin, areas of necrosis and a considerable amount of calcium deposit. Our experimental model would be valuable in the investigation of the pathological changes associated with smooth muscle cell proliferation in vessels
Assuntos
Ratos , Animais , Aorta Torácica/citologia , Células Cultivadas/fisiologia , Meios de Cultura/metabolismo , Elastina/fisiologia , Histocitoquímica/tendências , Microscopia Eletrônica de Varredura/métodos , Músculo Liso Vascular/crescimento & desenvolvimento , Ratos Sprague-Dawley/cirurgiaRESUMO
The variation in mechanical stress to which the aortic wall is subjected requires that forces be transmited between its components by means of relatively strong but compliant attachments. We have used transmission electron microscopy in order to study the cell to stroma contacts (smooth muscle cell-elastic fiber contact) in the tunica media of normotensive and hypertensive aortas of Sprague-Dawley rats. Hypertension was produced with a silver clip positioned around the left renal artery and the vessels were fexed by intravital perfusion at normal and elevated pressure. In ultrathin sections, the density of cell to stroma contacts per 100 µm cell perimeter and per 100 cell profiles were determined using an image analysis computer. In the hypertensive group the density of cell to stroma contacts fell considerably when compared with the control group. This research provides insights into the conditions under which high blood pressure may produce medial injuries and, perhaps, be a factor in the precipitation of dissections