How should species phylogenies be inferred from sequence data?

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Dog pancreatic duct epithelial cells: Long-term culture and characterization

Epithelial cells, isolated front a normal dog pancreatic duct, were grown on collagen-coated culture inserts suspended above a feeder layer of myofibroblasts. The cells were examined by transmission electron microscopy, immunohistochemistry, cytogenetics, and flow cytometry. In addition, the constitutive and agonist-stimulated mucin secretion of these cells was studied using a [3H]N-acetyl-D-glucosamine labeling assay, and the stimulation of intracellular cAMP was measured. Cells grown on inserts with a feeder layer developed into confluent monolayers consisting of strictly polarized columnar epithelial cells with prominent microvilli, intercellular junctions, and normal chromosomal characteristics. They could be passaged repeatedly without a detectable alteration in their morphology. The cells could also be grown on organotypic cultures, resulting in further differentiated cells simulating in vivo morphology. Immunohistochemistry demonstrated the presence of carbonic anhydrase II in these cells. Cells treated with vasoactive intestinal peptide, epinephrine, and dibutyryl-cAMP demonstrated a marked increase in mucin secretion compared with controls. In parallel experiments, VIP and epinephrine significantly increased intracellular cAMP. In conclusion we have developed a pancreatic epithelial cell preparation with morphology, cytokinetics, chromosomal, and DNA analyses characteristic of normal cells. Similar to normal columnar epithelial cells, these pancreatic duct cells secreted mucin constitutively and responded to agonist by increasing secretion via a cAMP-mediated pathway. They also contained carbonic anhydrase, which indicates that the cells are capable of secreting bicarbonate.link_to_subscribed_fulltex

Modified mincut supertrees

A polynomial time supertree algorithm could play a key role in a divide-and-conquer strategy for assembling the tree of life. To date only a single such method capable of accommodate conflicting input trees has been proposed, the MinCutSupertree algorithm of Semple and Steel. This paper describes this algorithm and its implementation, then illustrates some weaknesses of the method. A modification to the algorithm that avoids some of these problems is proposed. The paper concludes by discussing some practical problems in supertree construction