Showing papers by "Iris E. C. Sommer published in 1995"
TL;DR: The aggregation of actin along groove/ridge boundaries is a primary driving event in determining fibroblast orientation on microgrooved substrata and the Curtis and Clark theory that cells react to topography primarily at lines of discontinuity in the substratum by actin nucleation is supported.
Abstract: The role of the cytoskeleton and cell attachments in the alignment of baby hamster kidney fibroblasts to ridge and groove substratum topography was investigated using confocal scanning microscopy. This was carried out with normal cells and cells treated with the cytoskeleton modifiers cytochalasin D, colcemid, and taxol. Actin was localised with fluorescent phalloidin. Tubulin, vinculin, and intracellular adhesion molecule-1 were visualised by indirect immunofluorescence. The spreading, elongation, and orientation of the cells after 24 h of culture in these conditions were measured on grooves of 5, 10, and 25 microns width and 0.5, 1, 2, and 5 microns depth. We have also observed events over the first 30 min of cell attachment. Five minutes after cell attachment, F-actin condensations were seen close to the intersection of groove wall and ridge top, that is, at a topographic discontinuity. The condensations were often at right angles to the groove edge and showed a periodicity of 0.6 microns. Vinculin arrangement at the early stages of cell spreading was similar to that of actin. Organisation of the microtubule system followed later, becoming obvious at about 30 min after cell plating. The Curtis and Clark theory (that cells react to topography primarily at lines of discontinuity in the substratum by actin nucleation) is supported by these results. The use of cytoskeletal poisons did not entirely abolish cell reaction to grooves. Colcemid increased cell spreading and reduced cell orientation and elongation. Cytochalasin D reduced cell spreading, orientation, and elongation. Taxol reduced cell elongation but did not affect cell spreading and orientation. We conclude that the aggregation of actin along groove/ridge boundaries is a primary driving event in determining fibroblast orientation on microgrooved substrata.
163 citations
TL;DR: A bibliographical review of the effects of Mexico City's waste water land application on soil fertility and heavy metal accumulation is presented in this paper, showing that Pb, Cd, Cu, and Zn levels in soils and crops at present do not represent risks, but there is a clear tendency for these metals to accumulate in the upper layers of soils.
Abstract: Waste water from Mexico City metropolitan area has been used to irrigate the Mezquital Valley since 1912. This zone is nowadays the largest area under this situation. Mexico City's drainage is a water mixture emanating from different sources: household, industries, commerce, rain, and runoff. Waste waters used in the valley have greatly increased crop yields. Owing to the increase in the country's industrial development, since the seventies several studies have been carried out in this area, especially related to metal content in water, soils, and crops. The aim of this paper is to present a bibliographical review of the effects of Mexico City's waste water land application on soil fertility and heavy metal accumulation. Pb, Cd, Cu, and Zn levels in soils and crops at present do not represent risks, but there is a clear tendency for these metals to accumulate in the upper layers of soils. Salt content in waste water is intensifying soil salinization in impeded drainage areas. The local conditions of soil,...
20 citations