Models of dynamic extraction of lipid tethers from cell membranes

When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this processes by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that they can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers.Comment: 16 pages, 7 figure

Biological and environmental rhythms in (dark) deep-sea hydrothermal ecosystems

During 2011, two deep-sea observatories focusing on hydrothermal vent ecology were up and running in the Atlantic (Eiffel Tower, Lucky Strike vent field) and the Northeast Pacific Ocean (NEP) (Grotto, Main Endeavour Field). Both ecological modules recorded imagery and environmental variables jointly for a time span of 23 days (7–30 October 2011) and environmental variables for up to 9 months (October 2011–June 2012). Community dynamics were assessed based on imagery analysis and rhythms in temporal variation for both fauna and environment were revealed. Tidal rhythms were found to be at play in the two settings and were most visible in temperature and tubeworm appearances (at NEP). A  ∼  6 h lag in tidal rhythm occurrence was observed between Pacific and Atlantic hydrothermal vents, which corresponds to the geographical distance and time delay between the two sites.info:eu-repo/semantics/publishedVersio

Europe counts marine life

Over 500 marine scientists are working together within the framework of MarBEF - a European network of excellence, which started in March 2004. Of all the seas, the European seas are among the most studied in the world. By bringing this expertise and knowledge together, MarBEF aims at a better understanding of long-term and large-scale distribution patterns and functionalities of biodiversity across marine ecosystems. To inventory this wealth of marine life, the European Register of Marine Species (ERMS), at this moment containing nearly 30,000 species names, is adopted and will serve as the reference list and taxonomic backbone within MarBEF. ERMS has been put into a relational database and will be maintained and regularly updated online by a consortium of taxonomic experts. The taxonomic register will be supplemented with biogeographic, ecological and socio-economic information, together with species illustrations, original descriptions and vernacular names. When available, links will be provided with other online species information systems. EurOBIS, the European node of the Ocean biogeographic Information System, is a distributed system that integrates individual datasets on biogeographic information into one large consolidated database and provides the end-user with a fully searchable geographic interface. EurOBIS already captures and freely communicates over 350,000 distribution data from 14,000 species, online. When combining these data with biological, physical, chemical and geologic data, our understanding of the ecosystem will greatly improve, resulting in better ecosystem-based management plans. The Flanders Marine Institute is taking a leading role in these major European data integrating projects within MarBEF and has recently developed online tools for ERMS and EurOBIS (http://www.marbef.org/data)

Eosinophil adhesion under flow conditions activates mechanosensitive signaling pathways in human endothelial cells

Leukocyte transmigration can be affected by shear stress; however, the mechanisms by which shear stress modulates transmigration are unknown. We found that adhesion of eosinophils or an eosinophilic cell line to intereukin 4–stimulated endothelial cells led to a shear-dependent increase in endothelial cell intracellular calcium and increased phosphorylation of extracellular signal-regulated kinase (ERK) 2, but not c-Jun NH2-terminal kinase or p38 mitogen-activated protein kinase. Latex beads coated with antibodies were used to characterize the role of specific endothelial cell surface molecules in initiating signaling under shear conditions. We found that ligation of either vascular cell adhesion molecule–1 or E-selectin, but not major histocompatibility complex class I, induced a shear-dependent increase in ERK2 phosphorylation in cytokine-stimulated endothelial cells. Disassembly of the actin cytoskeleton with latrunculin A prevented ERK2 phosphorylation after adhesion under flow conditions, supporting a role for the cytoskeleton in mechanosensing. Rapid phosphorylation of focal adhesion kinase and paxillin occurred under identical conditions, suggesting that focal adhesions were also involved in mechanotransduction. Finally, we found that Rho-associated protein kinase and calpain were both critical in the subsequent transendothelial migration of eosinophils under flow conditions. These data suggest that ligation of leukocyte adhesion molecules under flow conditions leads to mechanotransduction in endothelial cells, which can regulate subsequent leukocyte trafficking