Overexpression of Mouse D-Type Cyclins Accelerates G(1) Phase in Rodent Fibroblasts

Mammalian D-type cyclins are growth factor-regulated, delayed early response genes that are presumed to control progression through the G1 phase of the cell cycle by governing the activity of cyclin-dependent kinases (cdks). Overexpression of mouse cyclin D1 in serum-stimulated mouse NIH-3T3 and rat-2 fibroblasts increased their rates of G0 to S- and G1- to S-phase transit by several hours, leading to an equivalent contraction of their mean cell generation times. Although such cells remained contact inhibited and anchorage dependent, they manifested a reduced serum requirement for growth and were smaller in size than their normal counterparts. Ectopic expression of cyclin D2 in rodent fibroblasts, either alone or together with exogenous cdk4, shortened their G0- to S-phase interval and reduced their serum dependency, but cyclin D2 alone did not alter cell size significantly. When cells were microinjected during the G2 interval with a monoclonal antibody specifically reactive to cyclin D1, parental rodent fibroblasts and derivatives overexpressing this cyclin were inhibited from entering S phase, but cells injected near the G1/S phase transition were refractory to antibody-induced growth suppression. Thus, cyclin D1, and most likely D2, are rate limiting for G1progression

The Aminopeptidase CD13 Induces Homotypic Aggregation in Neutrophils and Impairs Collagen Invasion.

Aminopeptidase N (CD13) is a widely expressed cell surface metallopeptidase involved in the migration of cancer and endothelial cells. Apart from our demonstration that CD13 modulates the efficacy of tumor necrosis factor-α-induced apoptosis in neutrophils, no other function for CD13 has been ascribed in this cell. We hypothesized that CD13 may be involved in neutrophil migration and/or homotypic aggregation. Using purified human blood neutrophils we confirmed the expression of CD13 on neutrophils and its up-regulation by pro-inflammatory agonists. However, using the anti-CD13 monoclonal antibody WM-15 and the aminopeptidase enzymatic inhibitor bestatin we were unable to demonstrate any direct involvement of CD13 in neutrophil polarisation or chemotaxis. In contrast, IL-8-mediated neutrophil migration in type I collagen gels was significantly impaired by the anti-CD13 monoclonal antibodies WM-15 and MY7. Notably, these antibodies also induced significant homotypic aggregation of neutrophils, which was dependent on CD13 cross-linking and was attenuated by phosphoinositide 3-kinase and extracellular signal-related kinase 1/2 inhibition. Live imaging demonstrated that in WM-15-treated neutrophils, where homotypic aggregation was evident, the number of cells entering IL-8 impregnated collagen I gels was significantly reduced. These data reveal a novel role for CD13 in inducing homotypic aggregation in neutrophils, which results in a transmigration deficiency; this mechanism may be relevant to neutrophil micro-aggregation in vivo.This work was funded by a Medical Research Council Research Training Fellowship to CAF (G0900329), Addenbrooke’s Charitable Trust (ACT), CUHNHSFT, Papworth Hospital NHS Foundation Trust and the NIHR Cambridge Biomedical Research Centre. CAF received a Raymond and Beverly Sackler Studentship.This is the final version of the article. It first appeared from the Public Library of Science via http://dx.doi.org/10.1371/journal.pone.016010

Continued evaluation of post-fire recovery and treatment effectiveness for validation of the ERMiT erosion model

The use and cost of post-fire emergency stabilization treatments continues to grow. To help maximize the impact of these treatments, many assessment teams use the Erosion Risk Management Tool (ERMiT) erosion model to predict postfire erosion and mitigation effects. However, despite several completed JFSP projects, the long-term effects of these treatments remain unknown, and the ERMiT model has not been validated. Long-term post-fire erosion and runoff data on a variety of mulches and erosion barriers were collected using 12 existing sites throughout the Western U.S. The agricultural straw and wood strand mulch treatments were very effective at reducing erosion and runoff. The contour-felled log treatment was effective at reducing runoff and erosion for small storms, but was not effective for larger events. The hydromulch formulations tested in this study were not effective at reducing runoff or sediment yields. Numerous presentations, field trips, and Burned Area Emergency Response (BAER) trainings were conducted. These activities provided much-needed information about the effectiveness of stabilization treatments

Evaluating Post-fire Salvage Logging Effects on Erosion

Legal challenges have delayed numerous post-fire salvage logging operations, which often results in lost economic value of the burned timber and unrecovered legal expenses. The scientific literature has shed little light on the additive effect of salvage logging operations on post-fire runoff, erosion, flooding, and sedimentation. Hence, there is an urgent need to better understand the impacts of post-fire salvage operations so that land managers can evaluate the relative and cumulative effects of different salvage logging practices. Intensive, multi-scale studies are needed because the effects of post-fire logging are superimposed on the effect of wildfires; rates and processes change according to the spatial and temporal scales of the investigation; and the studies to date indicate tremendous variability in the effects of post-fire salvage logging with the type and extent of the logging, site characteristics, and climatic conditions. To address this need, the current project was established in the Northern Rockies to integrate experiments at the hillslope and small watershed scale that focus on erosion processes. Replicated plots were used to measure sediment production rates from burned and unlogged plots, logged areas, tracked areas due to ground-based logging, and tracked areas with added slash as an erosion control treatment. Measured erosion rates were related to detailed measurements of site characteristics including ground cover, rilling, water repellency, amount of area disturbed due to salvage logging operations, number of passes of logging equipment, soil compaction, and the number and type of erosion mitigation practices (e.g., application of logging slash, mulch, and water bars). Runoff and sediment yield data were collected from two pairs of small watersheds to determine how salvage logging affects runoff, peak flow, and erosion rates, and whether the erosion estimates from the hillslope plots can be extrapolated to the small watershed scale. Rill simulation studies were conducted on three sites affected by ground-based salvage logging to evaluate the various types of equipment and identify site factors that affect runoff and erosion rates

Inhibition of cell proliferation by the Mad1 transcriptional repressor.

Mad1 is a basic helix-loop-helix-leucine zipper protein that is induced upon differentiation of a number of distinct cell types. Mad1 dimerizes with Max and recognizes the same DNA sequences as do Myc:Max dimers. However, Mad1 and Myc appear to have opposing functions. Myc:Max heterodimers activate transcription while Mad:Max heterodimers repress transcription from the same promoter. In addition Mad1 has been shown to block the oncogenic activity of Myc. Here we show that ectopic expression of Mad1 inhibits the proliferative response of 3T3 cells to signaling through the colony-stimulating factor-1 (CSF-1) receptor. The ability of over-expressed Myc and cyclin D1 to complement the mutant CSF-1 receptor Y809F (containing a Y-to-F mutation at position 809) is also inhibited by Mad1. Cell cycle analysis of proliferating 3T3 cells transfected with Mad1 demonstrates a significant decrease in the fraction of cells in the S and G2/M phases and a concomitant increase in the fraction of G1 phase cells, indicating that Mad1 negatively influences cell cycle progression from the G1 to the S phase. Mutations in Mad1 which inhibit its activity as a transcription repressor also result in loss of Mad1 cell cycle inhibitory activity. Thus, the ability of Mad1 to inhibit cell cycle progression is tightly coupled to its function as a transcriptional repressor