LTB4 Is a Signal-Relay Molecule during Neutrophil Chemotaxis

SummaryNeutrophil recruitment to inflammation sites purportedly depends on sequential waves of chemoattractants. Current models propose that leukotriene B4 (LTB4), a secondary chemoattractant secreted by neutrophils in response to primary chemoattractants such as formyl peptides, is important in initiating the inflammation process. In this study we demonstrate that LTB4 plays a central role in neutrophil activation and migration to formyl peptides. We show that LTB4 production dramatically amplifies formyl peptide-mediated neutrophil polarization and chemotaxis by regulating specific signaling pathways acting upstream of actin polymerization and MyoII phosphorylation. Importantly, by analyzing the migration of neutrophils isolated from wild-type mice and mice lacking the formyl peptide receptor 1, we demonstrate that LTB4 acts as a signal to relay information from cell to cell over long distances. Together, our findings imply that LTB4 is a signal-relay molecule that exquisitely regulates neutrophil chemotaxis to formyl peptides, which are produced at the core of inflammation sites

Nanometer Scale Dielectric Fluctuations at the Glass Transition

Using non-contact scanning probe microscopy (SPM) techniques, dielectric properties were studied on 50 nanometer length scales in poly-vinyl-acetate (PVAc) films in the vicinity of the glass transition. Low frequency (1/f) noise observed in the measurements, was shown to arise from thermal fluctuations of the electric polarization. Anomalous variations observed in the noise spectrum provide direct evidence for cooperative nano-regions with heterogeneous kinetics. The cooperative length scale was determined. Heterogeneity was long-lived only well below the glass transition for faster than average processes.Comment: 4 pages, 4 embedded PS figures, RevTeX - To appear in Phys. Rev. Let

Identifying lipid particle sub-types in live Caenorhabditis elegans with two-photon fluorescence lifetime imaging

Fat metabolism is an important modifier of aging and longevity in Caenorhabditis elegans. Given the anatomy and hermaphroditic nature of C. elegans, a major challenge is to distinguish fats that serve the energetic needs of the parent from those that are allocated to the progeny. Broadband coherent anti-Stokes Raman scattering (BCARS) microscopy has revealed that the composition and dynamics of lipid particles are heterogeneous both within and between different tissues of this organism. Using BCARS, we have previously succeeded in distinguishing lipid-rich particles that serve as energetic reservoirs of the parent from those that are destined for the progeny. While BCARS microscopy produces high-resolution images with very high information content, it is not yet a widely available platform. Here we report a new approach combining the lipophilic vital dye Nile Red and two-photon fluorescence lifetime imaging microscopy (2p-FLIM) for the in vivo discrimination of lipid particle sub-types. While it is widely accepted that Nile Red staining yields unreliable results for detecting lipid structures in live C. elegans due to strong interference of autofluorescence and non-specific staining signals, our results show that simple FLIM phasor analysis can effectively separate those signals and is capable of differentiating the non-polar lipid-dominant (lipid-storage), polar lipid-dominant (yolk lipoprotein) particles, and the intermediates that have been observed using BCARS microscopy. An advantage of this approach is that images can be acquired using common, commercially available 2p-FLIM systems within about 10% of the time required to generate a BCARS image. Our work provides a novel, broadly accessible approach for analyzing lipid-containing structures in a complex, live whole organism context