Expression of integrin subunits αv and β3 in acute lung inflammation

Integrin subunits v and 3 form a dimer, v3, which is expressed on normal neutrophils and endothelium. We investigated the expression of integrin subunits v and 3 in acute lung inflammation in Sprague-Dawley rats (n=5 each) following intratracheal challenge with Escherichia coli or Streptococcus pneumoniae, which induce neutrophil recruitment through different mechanisms. Control rats (n=5) were given endotoxin-free saline. Both bacterial challenges induced similar levels of recruitment of neutrophils in lungs. Western blots showed lower expression of integrin subunits v and 3 in lungs challenged with E. coli compared to those given S. pneumoniae. Immunohistochemistry and immunogold electron microscopy localized both integrin subunits in neutrophils and endothelium in the control and treated rat lungs. Quantitative immunohistochemistry showed that E. coli-challenged rat lungs contained a lower percentage of neutrophils expressing integrin subunits v and 3 compared to those challenged with S. pneumoniae (P<0.05). We conclude that E. coli infection decreased the percentage of neutrophils expressing integrin subunits v and 3 compared to S. pneumoniae infection. These data lay the foundation for further characterization of these integrin subunits in neutrophil migration specifically in S. pneumoniae infection that utilizes molecules other than 2 integrins for neutrophil recruitment.     

The imbalanced supertree of flowering-plant phylogeny

Two contrasting approaches have been used to construct the overall tree of life from molecular data: one involves the analysis of single large datasets, while the other involves joining many independent smaller analyses into a supertree. A recent study uses the latter approach to produce the most complete phylogeny yet of flowering plant families.     

Geographic distribution of the muscle-dwelling nematode Parelaphostrongylus odocoilei in North America, using molecular identification of first-stage larvae

Molecular identification of dorsal-spined larvae (DSL) from fecal samples indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than has been previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule deer (Odocoileus hemionus hemionus), and black-tailed deer (O. h. columbianus). The DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and they were not recovered from any of the bighorn sheep populations that we examined. In total, DSL were recovered from 20 locations in the United States and Canada (Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California). The DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. The ITS2 sequences were markedly different between Parelaphostrongylus and other protostrongylid genera. Smaller fixed differences served as diagnostic markers for the 3 species of Parelaphostrongylus. The ITS2 sequences (n = 60) of P. odocoilei were strongly conserved across its broad geographic range from California to Alaska. Polymorphism at 5 nucleotide positions was consistent with multiple copies of the ITS2 within individual specimens of P. odocoilei. This work combines extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to describe comprehensively the host associations and geographic distribution of a parasitic helminth.     

Distinctive expression of the T4 antigen in normal and stimulated lymphocytes

Correlated light scatter and fluorescence flow cytometric analysis of human peripheral blood lymphocytes showed that the expression of the T4 antigen was higher in the larger lymphocytes than in the smaller lymphocytes. A similar expression pattern was observed for HLA Class I antigens but not for T3 and T8, whose expression was independent of cell size. Results with lymphocytes from spleen, lymph node, and tonsil were comparable to those of peripheral blood. Thymocytes, however, were smaller and expressed less T4 and T8 than peripheral lymphocytes. In studies of lymphocytes stimulated in vitro with allogeneic cells or pokeweed mitogen, two populations of T4-positive cells were observed: one of large cells expressing high amounts of T4 and one of small cells expressing low amounts of T4. Similar patterns were seen with T8, although less consistently. In contrast, the expression of T3 was the same in both large and small cells. The large cells expressing high amounts of T4 were not restricted to cells engaged in DNA synthesis or mitosis. This was established by selectively analyzing cells in the G0G1 phases of the cell cycle and by studying stimulated lymphocytes no longer undergoing proliferation. Taken together, these results suggest that immature T lymphocytes are small and express low amounts of T4 and T8. We postulate that as they differentiate, cell size and T4 expression increase proportionally, both parameters increasing even further after antigenic or mitogenic stimulation. The quantitative expression of T4, and probably of T8 but not of T3, is therefore intimately related to maturation and activation of lymphocytes, a fact that may conceivably be related to a functional role of these surface molecules.