It is controversial whether the membranous (M) cells of the Peyer's patches represent a separate cell line or develop from enterocytes under the influence of lymphocytes on the domes. To answer this question, the crypts that produce the dome epithelial cells were studied and the distribution of M cells over the domes was determined in mice. The Ulex europaeus agglutinin was used to detect M cells in mouse Peyer's patches. Confocal microscopy with lectin-gold labeling on ultrathin sections, scanning electron microscopy, and laminin immuno-histochemistry were combined to characterize the cellular composition and the structure of the dome-associated crypts and the dome epithelium. In addition, the sites of lymphocyte invasion into the dome epithelium were studied after removal of the epithelium using scanning electron microscopy. The domes of Peyer's patches were supplied with epithelial cells that derived from two types of crypt: specialized dome-associated crypts and ordinary crypts differing not only in shape, size, and cellular composition but also in the presence of M cell precursors. When epithelial cells derived from ordinary crypts entered the domes, they formed converging radial strips devoid of M cells. In contrast to the M cells, the sites where lymphocytes invaded the dome epithelium were not arranged in radial strips, but randomly distributed over the domes. M cell development is restricted to specialized dome-associated crypts. Only dome epithelial cells that derive from these specialized crypts differentiate into M cells. It is concluded that M cells represent a separate cell line that is induced in the dome-associated crypts by still unknown, probably diffusible lymphoid factors.

BACKGROUNDVascular endothelial growth factor (VEGF)‐A and angiopoietin (Ang)‐1 and Ang‐2 are key factors in angiogenic signaling. In this study the expression of these factors was identified in cartilage tumors. As interleukin (IL)‐1β has been found to be an indispensable factor in angiogenic signaling, we further analyzed the effect of IL‐1β on the expression of VEGF‐A, Ang‐1, and Ang‐2 using a previously established cell culture model.METHODSSurgical specimens of enchondromas, conventional chondrosarcomas, and dedifferentiated chondrosarcomas were obtained from 72 patients. VEGF‐A, Ang‐1, and Ang‐2 mRNA expression was detected by conventional and quantitative reverse transcription polymerase chain reaction (PCR). VEGF‐A expression was also detected by immunohistochemistry or Western blot.RESULTSDifferential expression of VEGF‐A, Ang‐1, and Ang‐2 was clearly demonstrated in cartilage tumors. VEGF‐A expression was positively correlated with the tumor type. Higher VEGF‐A expression levels were detected in conventional chondrosarcomas Grades II and III (using a 3‐tier grading system) than in dedifferentiated chondrosarcomas (P < .05). A typical pattern of VEGF‐A isoforms was identified, including VEGF121, VEGF145, VEGF165, and VEGF189. Ang‐1 presented as a low‐level transcript with slightly elevated levels in chondrosarcomas (P < .05). Highly variable Ang‐2 expression levels were detected in solitary cases of conventional chondrosarcomas. IL‐1β regulated VEGF‐A and Ang‐1 expressions in a dose‐dependent manner. Whereas low IL‐1β concentrations increased VEGF‐A and Ang‐1 transcription, high IL‐1β concentrations had the opposite effect. IL‐1β did not activate Ang‐2 expression.CONCLUSIONSAngiogenic signaling in cartilage tumors is variable and at least partly regulable by IL‐1β. The findings are of therapeutic relevance, either as a desired effect or a side effect in medical treatment. Cancer 2006. © 2006 American Cancer Society.

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Brush cells are specialised epithelial cells that are assumed to represent chemoreceptors of the digestive tract. They comprise a small population of the epithelial cells lining the intestine, possess a unique ultrastructure and, in many aspects, resemble the receptor cells of taste buds. To characterise glycoconjugates possibly involved in a sensory function, we investigated brush cells in the small intestine of three species using lectin histochemistry in confocal light and thin-section electron microscopy. Brush cells of rats were selectively labelled by the sialic acid-specific lectin Maackia amurensis agglutinin, those of guinea-pigs by the D-galactose-specific lectin Bandeiraea simplicifolia agglutinin, isolectin B 4 and those of mice by the L-fucose-specific lectin Ulex europaeus agglutinin lectin I. Lectin binding sites were consistently located in the glycocalyx of the apical membrane and in that of cytoplasmic vesicles. In vivo lectin labelling revealed that the glycoconjugates of the apical membrane are accessible under physiological conditions, that brush cells do not endocytose and that they probably possess a high membrane turnover rate. The results show that specialisations exist in the composition of glycoconjugates forming the glycocalyx of brush cells in all species investigated. The presence of brush cell-specific glycoconjugates would be in accordance with the current hypothesis of a receptive function of brush cells. Differences in the specific glycosylation patterns among rats, guinea-pigs and mice indicate that species-specific adaptations exist.