Uptake and incorporation of myo-inositol by bovine preimplantation embryos from two-cell to early blastocyst stages

The uptake of myo-inositol and its incorporation into the phosphoinositides and inositol phosphates of the phosphatidylinositol (PtdIns) signal transduction system by in vivo preimplantation cattle embryos was investigated using [(3)H] myo-inositol. Uptake of inositol was examined in two-cell and four-cell embryos (day 2 after insemination), morulae (day 6) and early blastocysts (day 7). Uptake in all stages examined was largely sodium-dependent indicating the presence of a sodium-dependent inositol transporter. Uptake of inositol did not vary significantly from two-cell to early blastocyst stages when expressed either on a per embryo or a per microg of protein basis. Incorporation of inositol into the three phosphoinositides, PtdIns, PtdInsP, and PtdInsP(2), was detectable at all stages examined. In contrast, incorporation of inositol into inositol phosphates was not detected until blastocyst formation at day 7. The second messenger, Ins(1,4,5)P(3), was first detected in day 7 blastocysts.     

Layilin,A Novel Talin-binding Transmembrane Protein Homologous with C-type Lectins,is Localized in Membrane Ruffles

Changes in cell morphology and motility are mediated by the actin cytoskeleton. Recent advances in our understanding of the regulators of microfilament structure and dynamics have shed light on how these changes are controlled, and efforts continue to define all the structural and signaling components involved in these processes. The actin cytoskeleton-associated protein talin binds to integrins, vinculin, and actin. We report a new binding partner for talin that we have named layilin, which contains homology with C-type lectins, is present in numerous cell lines and tissue extracts, and is expressed on the cell surface. Layilin colocalizes with talin in membrane ruffles, and is recruited to membrane ruffles in cells induced to migrate in in vitro wounding experiments and in peripheral ruffles in spreading cells. A ten–amino acid motif in the layilin cytoplasmic domain is sufficient for talin binding. We have identified a short region within talin''s amino-terminal 435 amino acids capable of binding to layilin in vitro. This region overlaps a binding site for focal adhesion kinase.     

Fungal network responses to grazing

Mycelial networks operate on scales from microscopic to many m² and naturally persist for extended periods. As fungi exhibit highly adaptive development, it is important to test behavioural responses on natural substrata with realistic nutrient levels across a range of spatial scales and extended time periods. Here we quantified network responses over 7.5 months in large (57 × 57 cm) microcosms to test whether grazing shifts the network to a more resilient architecture. Resource limitation constrained any ability to respond at all, with both grazed and ungrazed networks gradually thinning out over time. Added resources sustained further exploratory growth, but only transiently increased cross-connectivity and network resilience, when tested by simulated damage in silico. Grazed networks were initially weaker and emergence of new exploratory growth was curtailed. However, increased interstitial proliferation led to new cross-links, consolidating the existing mycelial network and increasing the resilience of the network to further attack.     

Biological solutions to transport network design

Transport networks are vital components of multicellular organisms, distributing nutrients and removing waste products. Animal and plant transport systems are branching trees whose architecture is linked to universal scaling laws in these organisms. In contrast, many fungi form reticulated mycelia via the branching and fusion of thread-like hyphae that continuously adapt to the environment. Fungal networks have evolved to explore and exploit a patchy environment, rather than ramify through a three-dimensional organism. However, there has been no explicit analysis of the network structures formed, their dynamic behaviour nor how either impact on their ecological function. Using the woodland saprotroph Phanerochaete velutina, we show that fungal networks can display both high transport capacity and robustness to damage. These properties are enhanced as the network grows, while the relative cost of building the network decreases. Thus, mycelia achieve the seemingly competing goals of efficient transport and robustness, with decreasing relative investment, by selective reinforcement and recycling of transport pathways. Fungal networks demonstrate that indeterminate, decentralized systems can yield highly adaptive networks. Understanding how these relatively simple organisms have found effective transport networks through a process of natural selection may inform the design of man-made networks.