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The major problem with angiogenesis research is the choice of an appropriate assay. Currently, many in vitro and in vivo techniques are available for research into the functions of endothelial cells during angiogenesis. In this historical review article, we describe and evaluate the methodology and specific features of some of the most frequently used of these assays. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to locate the dendritic cells, a part of the immunocompetent system of dental pulp, in histological samples of normal and irreversibly inflamed human dental pulp, using immunohistochemical staining methods. Material and Methods: In light of the particular character of the connective tissue of human dental pulp, the following antibodies were used: vimentin clone V9, a protein associated with neurofilaments (NFAP), the S 100 protein, and smooth muscle type actin (clone 1A4). Results: The results indicated that human dental pulp has numerous cells with branching cytoplasmic extensions, in areas of inflammatory infiltrate. Based on immunohistochemical staining we consider these to be dendritic cells. Conclusions: The presence of dendritic cells in inflamed human dental pulp is not unexpected, considering the great density of the inflammatory infiltrate, and the role they play in the inflammatory response. The subtype and significance of these cells need to be clarified. [ABSTRACT FROM AUTHOR]

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Summary: Vascular endothelial growth factor A (VEGF-A) is an angiogenic growth factor that is a primary stimulant of the vascularization of solid tumors. In the tumor microenvironment, an upregulation of both VEGF and its receptors occurs, leading to a high concentration of occupied receptors on tumor vascular endothelium. Also, VEGF is involved in the development of the normal vascular network of the thymus. Little is known about VEGF expression in normal and malignant thymic tissue. Our purpose was to study the pattern and localization of VEGF expression in benign conditions of the thymus and thymoma to determine a possible correlation with VEGF receptors VEGFR1, VEGFR2 and microvascular density. All cases were positive for VEGF and VEGFR1, 2 in the epithelial cells, in a cytoplasmic, granular pattern. In the normal thymus, there were positive epithelial cells with subcapsular distribution and Hassall''s corpuscle epithelial cells. In acute thymic involution, the positive fields were correlated with dilation and stasis of blood vessels and lymphocyte depletion. Rare positive cells were found in other types of involution; the myasthenic thymus showed an intense and diffuse reaction in lymphoid follicles of the medulla. A strong reaction for VEGF was observed in type B3 thymomas in neoplastic epithelial cells, normal endothelial cells, plasma within the blood vessels and focally in the stroma adjacent to the tumor. Receptors for VEGF were positive in neoplastic epithelial cells and endothelium. We hypothesized that VEGF acts as an immunoregulatory factor in the normal thymus and as proangiogenic and autocrine factor in thymomas. [Copyright &y& Elsevier]

Summary: The study was conducted on 27 specimens of normal thymus, removed during surgery for cardiovascular malformations. Biopsies were processed using current histological techniques, and the samples were stained using morphological and immunohistochemical methods (cytokeratin profile, vimentin, S100, CD45, CD20, CD3, CD68, CD34 protein, chromogranin A, neuronal-specific enolase, desmin). Microscopic examination focused on the structure and immunohistochemical profile of Hassall corpuscles, beginning from the hypothesis that the epithelial cells of these structures, characteristic for the thymus, participate in the negative and positive selection of thymocytes. Morphological assessment revealed the existence of four different types of Hassall corpuscles: juvenile, immature, mature and senescent. The lymphocyte-rich variant was identified in 25.92% of the cases with ages ranging between 7 days and 12 years. From the immunohistochemical point of view, the following reactions were negative: cytokeratins 7 and 8, vimentin, desmin, CD3, CD68, CD34 and neuron-specific enolase. Isolated positive chromogranin cells were found in two cases, and positive intracorpuscular CD20 cells in one case. Polyclonal cytokeratins were positive in all instances in the epithelial cells of the Hassall corpuscles, with higher intensity in high-molecular weight cytokeratin, strongly expressed in mature corpuscles. All specimens had positive SI00 cells in the corpuscles, distributed among the epithelial cells, with dendritic morphology, in great numbers in juvenile and immature forms. Morphological and immunohistochemical results (corpuscle variants, the presence of positive S100 cells, concentration of positive CD20 and CD3 cells around the corpuscles) suggest the active involvement of epithelial cells of Hassall corpuscles in modulating the differentiation of thymocytes at the medullar level, a process that is mediated by protein S100 positive corpuscular dendritic cells. [Copyright &y& Elsevier]

Summary: The study is concerned with the presence of an unusual lymphocyte-rich type of Hassall body in the normal human thymus. Lymphocyte-rich Hassall bodies are large, they are usually lined by squamous epithelial cells, and contain closely packed lymphocytes in areas with necrotic and hyaline material. Lymphocyte-rich areas of the Hassall bodies do not contain epithelial cells (as demonstrated with cytokeratin 8/18, 7, 34?E12, and MNF116), they were negative for CD20 and S100 protein. Immunoreaction for CD3 was positive in 3 of 4 cases. Our results suggest that this type of Hassall body may be involved in the negative selection of thymocytes. [Copyright &y& Elsevier]