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Recent column studies suggest that pesticide fate models could be used to estimate the fate of estrogens in soil. Estrogens are detected in livestock manure which is used as a nutrient source on agricultural land. This is the first study to examine estrogen mineralization in a wide range of agricultural soils at the regional-scale. Soil samples were collected from upper and lower landscape positions of 18 agricultural fields in an area spanning 49–60 °N longitude and 110–120 °W latitude and these samples were used to determine 17β-estradiol mineralization parameters in microcosm experiments. Maximum 17β-estradiol mineralization (Max) ranged from 5.8% to 19.2% and was, on average, significantly (P

Estrogenic compounds in livestock manure are also present in soils because manure is land applied on account of its value as an important nutrient source in agricultural production. This is the first study to compare the sorption of 17β-estradiol, estrone, estriol and equol in a wide range of soils. Specifically, for each of these four estrogens, the soil sorption coefficient (Kd) and the sorption coefficient per unit organic carbon (Koc) were determined in 121 surface soils (0–15 cm) obtained from upper-slopes, mid-slopes, and lower-slopes in agricultural fields across seven ecoregions in the Province of Alberta, Canada. Soil organic carbon content (SOC), texture, pH, carbonate content, electrical conductivity and cation exchange capacity were also determined on the air-dried and sieved (2 mm) soil. Both Kd and Koc values significantly increased in the order of Kd-estriol (23 L kg− 1 soil and 1059 L kg− 1, respectively) = Kd-17β-estradiol (23 L kg− 1 soil and 1082 L kg− 1, respectively)

Rho GTP-binding proteins play a key role as molecular switches in many cellular activities. In response to extracellular stimuli and with the help of regulators (GEF, GAP, Effector, GDI), these proteins serve as switches that interact with their environment in a complex manner. Based on the structure of a published ordinary differential equations (ODE) model, we first present a generic process model for the Rho GTP-binding proteins, and compare it with the ODE model. We then extend the basic model to include the behaviour of the GDI regulators and explore the parameter space for the extended model with respect to biological data from the literature. We discuss the challenges this extension brings and the directions of further research. In particular, we present techniques for modular representation and refinement of process models, where, for example, different Rho proteins with different rates for regulator interactions can be given as instances of the same parametric model.

Actin is the monomeric subunit of actin filaments which form one of the three major cytoskeletal networks in eukaryotic cells. Actin dynamics, be it the polymerisation of actin monomers into filaments or the reverse process, plays a key role in many cellular activities such as cell motility and phagocytosis. There is a growing number of experimental, theoretical and mathematical studies on the components of actin polymerisation and depolymerisation. However, it remains a challenge to develop compositional models of actin dynamics, e.g., by using differential equations. In this paper, we propose compositional process algebra models of actin polymerisation, and present a geometric representation of these models that allows to generate movies reflecting their dynamics.

Phagocytosis through Fcγ receptor (FcγR) or complement receptor 3 (CR) requires Arp2/3 complex-mediated actin polymerization, although each receptor uses a distinct signaling pathway [1]. Rac and Cdc42 are required for actin and Arp2/3 complex recruitment during FcγR phagocytosis, while Rho controls actin assembly at CR phagosomes [2, 3]. To better understand the role of Rho in CR phagocytosis, we tested the idea that a known target of Rho, Rho-kinase (ROK), might control phagocytic cup formation and/or engulfment of particles. Inhibitors of ROK (dominant-negative ROK and Y-27632) and of the downstream target of ROK, myosin-II (ML7, BDM, and dominant-negative myosin-II), were used to test this idea. We found that inhibition of the Rho → ROK → myosin-II pathway caused a decreased accumulation of Arp2/3 complex and F-actin around bound particles, which led to a reduction in CR-mediated phagocytic engulfment. FcγR-mediated phagocytosis, in contrast, was independent of Rho or ROK activity and was only dependent on myosin-II for particle internalization, not for actin cup formation. While myosins have been previously implicated in FcγR phagocytosis [4–6], to our knowledge, this is the first demonstration of a role for myosin-II in CR phagocytosis.

The C. elegans gene ced-12 functions in the engulfment of apoptotic cells and in cell migration, acting in a signaling pathway with ced-2 CrkII, ced-5 DOCK180, and ced-10 Rac GTPase and acting upstream of ced-10 Rac. ced-12 encodes a protein with a pleckstrin homology (PH) domain and an SH3 binding motif, both of which are important for ced-12 function. CED-12 acts in engulfing cells for cell corpse engulfment and interacts physically with CED-5, which contains an SH3 domain. CED-12 has Drosophila and human counterparts. Expression of CED-12 and its counterparts in murine Swiss 3T3 fibroblasts induced Rho GTPase-dependent formation of actin filament bundles. We propose that through interactions with membranes and with a CED-2/CED-5 protein complex, CED-12 regulates Rho/Rac GTPase signaling and leads to cytoskeletal reorganization by an evolutionarily conserved mechanism.

BACKGROUND: beta2 integrins mediate many aspects of the inflammatory and immune responses, including adhesion of leukocytes to the endothelium, complement-mediated phagocytosis in macrophages and neutrophils, and antigen-specific conjugate formation between cytotoxic T cells and their targets. A variety of inflammatory mediators, such as tumor necrosis factor-alpha (TNF-alpha), platelet-activating factor (PAF), and lipopolysaccharide (LPS) and other bacterial products induce the functional activation of beta2 integrins, but the signaling events that link membrane receptors to integrin activation are poorly understood. RESULTS: We report here that expression of the constitutively active small GTPases Rap1 or R-ras, but not Ras or RalA, is sufficient for functional activation of alphaMbeta2, the complement receptor 3 (CR3), in macrophages, allowing phagocytosis of C3bi- opsonized targets. Inhibition of Rap1, but not other Ras-like or Rho- like small GTPases, abolishes activation of alphaMbeta2 induced by phorbol esters, LPS, TNF-alpha or PAF. Finally, Rap1 activation specifically controls the binding properties of alphaMbeta2 towards its physiological ligand, namely the complement-opsonized phagocytic targets. CONCLUSIONS: In macrophages, the Rap1 GTPase regulates activation of the alphaMbeta2 integrin in response to a wide variety of inflammatory mediators

A genetic pathway controlling the removal of apoptotic corpses has now been identified in the nematode. Mammalian homologs of the components of this pathway are already known to have key roles in cell motility and integrin-mediated signaling, suggesting that the three processes are mechanistically related.

We deleted exon 2 in human skeletal beta-tropomyosin (h beta-SK tropomyosin) using an improved adaptation of polymerase chain reaction (PCR) technology. The first PCR product was used to prime the full-length cDNA, leading to an exon 2-deleted h beta-SK tropomyosin. This new protein, des-(39-80)-tropomyosin, could then be expressed in Escherichia coli and purified to homogeneity. At the nucleotide level, the junction between exons 1 and 3 has been precisely made in the PCR product. The mutated protein was purified using high-performance liquid chromatography. Des-(39-80)-tropomyosin revealed new immunological properties but was still recognized by certain antitropomyosin antibodies. Furthermore, the structural characteristics of the mutated tropomyosin fit those of the full-length tropomyosin. This new adaptation of PCR technology appears to be suitable for every kind of mutation inside a cloned DNA molecule, and one mutation primer per mutation is sufficient.

Cell migration and other complex cellular processes involve a variety of signaling molecules and require the integration of multiple signals into a coherent cytoskeletal response. Two papers in the May issue of Molecular Cell now demonstrate that phosphorylation plays a critical role in WASP function as a regulator of Arp2/3-mediated actin polymerization.