Ectopic mineralized cartilage formation in human undifferentiated pancreatic adenocarcinoma explants grown in nude mice

Mineralized as well as nonmineralized cartilage-like structures enclosing cells resembling chondrocytes were found in human-derived undifferentiated but not in poorly differentiated pancreatic adenocarcinoma explants grown in nude mice. The structures reacted with anti-mouse IgG but not with antibodies against human cytokeratin 19, indicating that the newly formed tissue was of mouse origin. High activity of alkaline phosphatase was found in cell layers surrounding the structures and in cells embedded in the matrix. The extracellular matrix was strongly positive after Sirius red staining, reacted with anti-collagen type II antibodies, and the presence of proteoglycans was demonstrated with Alcian blue staining and by metachromasia after Giemsa staining. Electron microscopic inspection revealed the presence of bundles of both thick collagenous fibrils with low levels of fine filamentous material and thin collagenous fibrils with high concentrations of filamentous components. The majority of both types of matrices was found to be partially or completely calcified. The mean area density of the cartilage-like structures in the undifferentiated tumors was 0.31%. The frequent formation of the cartilage-like structures in the rapidly growing undifferentiated explants and its absence in the slowly growing, more differentiated explants suggest that low oxygen tensions in combination with altered levels of growth factors, such as members of the transforming growth factor beta superfamily, create conditions that induce differentiation of fibroblasts to chondrocytes. It is concluded that these human tumors grown in nude mice can be used as an in vivo model to study ectopic formation of mineralized cartilag

Intra-specific morphological variation of the spermatheca in the simultaneously hermaphroditic land snail Helix aperta

In the majority of internally fertilizing animals, females are equipped with sperm storage organs where they store the sperm received during copulation. In many simultaneously hermaphroditic pulmonates, these organs consist of complex spermathecae that show inter- and intra-specific variation in their structure. This variability is theoretically predicted by postcopulatory sexual selection in the context of sperm competition and cryptic female choice. In this study, the variation in the structure of the spermatheca was investigated in the land snail Helix aperta from four natural populations near Bejaia in northern Algeria. The populations were different in local snail density, probably also reflecting the intensity of sperm competition. We tested whether the spermatheca showed differences that are predicted by sperm competition theory. In addition, we tested whether the spermathecal structure depends on the shell size and/or is correlated with other reproductive organs that are thought to be affected by sexual selection. We found that the fertilization pouch of H. aperta consists of a simple fertilization chamber and 3–9 spermathecal tubules. The four populations did not differ significantly in the mean number of these tubules. However, significant differences were found in the length of the main tubule, the length of the fertilization chamber, and the average length of lateral tubules. In addition, strong associations were detected between the lengths of these structures and the local snail density, while no effect of shell size or reproductive organs was found. Our results indicate that the intensity of sperm competition may not affect the total number of spermathecal tubules, but may increase their lengths. This increase in spermathecal length may reflect an improved sperm storage capacity that is probably beneficial in situations of high sperm competitions intensity