RESUMEN
The aim of this study was to evaluate the effect of different specimens dimensions on the mechanical properties of a commercial microfilled resin composite by using a modified ISO 4049 standard protocol, that generally provides specimen dimensions of 25 mm length × 2 mm width × 2 mm height; these standard dimensions are not clinically realistic considering the teeth diameter and length average. Furthermore, the overlapping irradiations required lead to specimens that are not homogeneous with the presence of some flaws due to packaging steps. For this reason, a miniflexural test was employed in this work both to simulate clinically realistic dimensions and to concentrate fewer defects. The flexural tests were performed at varying span length, in the range between 18.5 mm as stated by the ISO 4049 flexural test (IFT) and 10.5 mm according to the miniflexural test (MFT), at the increasing of layers with a 1 mm buildup multilayering technique. The results evidenced the impact of specimen dimensions on mechanical performances and consequently stability of resin-based composite with the formation of an asymmetrical structure which possesses higher stiffness and strength at increasing layering steps.
RESUMEN
Neutrophils are traditionally thought of as terminal effectors of inflammatory reaction, but experimental studies suggest that they play a direct role in the inflammatory angiogenesis of tumors. Thus, further evidence in humans is required regarding the mechanisms by which neutrophils induce tumor angiogenesis. In this study, 4 cases of human gastric carcinomas with massive neutrophil infiltration were studied by light and electron microscopy, focusing on the inflammatory angiogenesis in the tumor stroma. At light microscopy, the tumors were advanced gastric carcinomas in which various degrees of tubular differentiation were present. Under an electron microscope, pericytes exhibited two major differentiated states with distinct ultrastructural features: a contractile phenotype and a synthetic phenotype. The contractile phenotype was characterized by abundant microfilaments. Synthetic pericytes contained abundant rough endoplasmic reticulum, lipid bodies, and numerous membrane-bound vesicles. These ultrastructural findings extend concept of contractile/synthetic phenotype modulation, originally described in smooth muscle cells, to tumor microvascular pericytes. Tumor microvasculature was also characterized by abortive or slit-like lumina, endothelial cell mitoses, and replicating basement membranes. These qualitative and observational transmission electron microscopy findings provide additional morphological evidence of active inflammatory angiogenesis in gastric carcinomas with massive neutrophil infiltration.
Asunto(s)
Adenocarcinoma/ultraestructura , Inflamación/inmunología , Neovascularización Patológica/inmunología , Infiltración Neutrófila/inmunología , Neoplasias Gástricas/ultraestructura , Adenocarcinoma/irrigación sanguínea , Adenocarcinoma/inmunología , Anciano , Humanos , Inflamación/patología , Microscopía Electrónica de Transmisión , Persona de Mediana Edad , Neovascularización Patológica/patología , Neoplasias Gástricas/irrigación sanguínea , Neoplasias Gástricas/inmunologíaRESUMEN
Ultrastructural findings in three cases of gastric carcinoma with coagulative necrosis are reviewed with special emphasis on microvascular changes. Intratumoral microvasculature revealed more or less stabilized vessels. Some were characterized by a close association between pericytes and endothelial cells, whereas others showed laminated basement membrane, with a loose association between pericytes and endothelial cells. Some mural cells exhibited ultrastructural signs of regressive changes, including lipofuscin granules, swollen mitochondria, and cytoplasmic lucency. These findings are discussed in relationship to a number of recent studies of the microvascular injury caused by hypoxia and reoxygenation, in humans and animals.