144 research outputs found
Fearful No More: Teachers Amplifying Culturally and Linguistically Diverse Familial Voices in Technological Spaces
Based on field research and observations, this work challenges existing assumptions about using technology to support learner engagement and recommends tech-rich instructional strategies made possible when teachers engage critical consciousness and reflection to create equitable learning spaces
Myosin and tropomyosin stabilize the conformation of formin-nucleated actin filaments
The conformational elasticity of the actin cytoskeleton is
essential for its versatile biological functions. Increasing
evidence supports that the interplay between the structural and
functional properties of actin filaments is finely regulated by
actin-binding proteins, however, the underlying mechanisms and
biological consequences are not completely understood. Previous
studies showed that the binding of formins to the barbed end
induces conformational transitions in actin filaments by making
them more flexible through long-range allosteric interactions.
These conformational changes are accompanied by altered
functional properties of the filaments. To get insight into the
conformational regulation of formin-nucleated actin structures,
in the present work we investigated in detail how binding
partners of formin-generated actin structures, myosin and
tropomyosin, affect the conformation of the formin-nucleated
actin filaments, using fluorescence spectroscopic approaches.
Time-dependent fluorescence anisotropy and temperature-dependent
Forster-type resonance energy transfer measurements revealed
that heavy meromyosin, similarly to tropomyosin, restores the
formin-induced effects and stabilizes the conformation of actin
filaments. The stabilizing effect of heavy meromyosin is
cooperative. The kinetic analysis revealed that despite the
qualitatively similar effects of heavy meromyosin and
tropomyosin on the conformational dynamics of actin filaments,
the mechanisms of the conformational transition is different for
the two proteins. Heavy meromyosin stabilizes the formin-
nucleated actin filaments in an apparently single-step reaction
upon binding, while the stabilization by tropomyosin occurs
after complex formation. These observations support the idea
that actin-binding proteins are key elements of the molecular
mechanisms that regulate the conformational and functional
diversity of actin filaments in living cells
Relations between assemblages of carpological remains and modern vegetation in a shallow reservoir in southern Poland
This paper explores relations between assemblages of carpological remains and vegetation in and around a small, shallow reservoir in southern Poland. The study was conducted from 2006 to 2008. Quantity and distribution of species in the reservoir were recorded annually during the growing season. In October 2008, 40 samples of surface sediment (top 2 cm) were collected along transects at 10 m intervals. Samples of 100 cm3 were prepared for analysis of plant macroremains. Assemblages of carpological remains generally reflect local vegetation well. In some cases, however, even analysis of numerous samples failed to fully capture the species composition or reflect plant ratios in the parent phytocenosis. Reasons for this include factors that affect seed production, transport and fossilization, which differ among species. Among the best-represented macroremains were plants of the rush phytocenosis. In analysed samples, macroremains of 68.8 % of extant rushes were identified. Sixty percent of submerged and floating-leaf taxa were found in carpological samples, whereas 26.7 % of the trees and bushes were represented in sediment deposits. Species composition of phytocenoses in the reservoir and in surrounding areas was best reflected by macroremains from the nearby reed bed. Numbers of diaspores of Mentha aquatica, Hippuris vulgaris and Carex reflected well their relative abundance in phytocenoses. Chara sp., Juncus inflexus and Eupatorium cannabinum were overrepresented, whereas Typha latifolia and Sparganium minimum were poorly represented in relation to contemporary plant cover. There were no diaspores of Phragmites australis, which dominates the contemporary reed bed. Besides the shape of a reservoir, the key factor influencing diaspore numbers is distribution of plant cover. In many cases, single diaspores (Potentilla erecta, Myosotis scorpioides, Lythrum salicaria, Scutellaria galericulata), or higher concentrations (Hippuris vulgaris, Mentha aquatica, Eleocharis palustris, Schoenoplectus tabernaemontani, Chara sp.) reflected well the location of parent vegetation. The findings indicate that carpological remains in sediments can be an important source of information about plants in and around lakes. They generally reflect well local vegetation and in some cases may be used to identify taxa that dominated in the past
DAAM is required for thin filament formation and Sarcomerogenesis during muscle development in Drosophila.
During muscle development, myosin and actin containing filaments assemble into the highly organized sarcomeric structure critical for muscle function. Although sarcomerogenesis clearly involves the de novo formation of actin filaments, this process remained poorly understood. Here we show that mouse and Drosophila members of the DAAM formin family are sarcomere-associated actin assembly factors enriched at the Z-disc and M-band. Analysis of dDAAM mutants revealed a pivotal role in myofibrillogenesis of larval somatic muscles, indirect flight muscles and the heart. We found that loss of dDAAM function results in multiple defects in sarcomere development including thin and thick filament disorganization, Z-disc and M-band formation, and a near complete absence of the myofibrillar lattice. Collectively, our data suggest that dDAAM is required for the initial assembly of thin filaments, and subsequently it promotes filament elongation by assembling short actin polymers that anneal to the pointed end of the growing filaments, and by antagonizing the capping protein Tropomodulin
Institutional investors and corporate governance
We provide a comprehensive overview of the role of institutional investors in corporate governance with three main components. First, we establish new stylized facts documenting the evolution and importance of institutional ownership. Second, we provide a detailed characterization of key aspects of the legal and regulatory setting within which institutional investors govern portfolio firms. Third, we synthesize the evolving response of the recent theoretical and empirical academic literature in finance to the emergence of institutional investors in corporate governance. We highlight how the defining aspect of institutional investors – the fact that they are financial intermediaries – differentiates them in their governance role from standard principal blockholders. Further, not all institutional investors are identical, and we pay close attention to heterogeneity amongst institutional investors as blockholders
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