An exploration of Board of Trustees' perceptions of their impact on student learning

The radical changes within the Tomorrow’s Schools reforms came to fruition in 1989 amid much debate about the ideology that underpinned the change and the capability and roles of boards of trustees. The roles of boards have evolved from a primary focus on compliance to the current focus on student achievement. This has raised the question of whether trustees, individually or collectively, have an impact on student learning through their governance roles. This small-scale study sets out to explore the perceptions of a small group of trustees. It uses a qualitative framework, based on data from semi-structured interviews with ten trustees across five primary schools. The interview data was supplemented with school and sector-based documentation. The study sought of trustees their perceptions of their impact on student learning through an analysis of the data, and with consideration given to participants’ context. The literature review provides an historical review of Tomorrow’s Schools and outlines how boards are enabled, or constrained, by aspects of the governance model. The findings of the study suggest that trustees perceived that they had both a direct and indirect impact on student learning. It identified challenges for trustees related to the governance-management model, and how trustees understood student learning. It highlighted a perceived lack of support for trustees and a need for improved quality and quantity of trustee training, as well as noting the influence of compliance on trustees’ thinking. This study raises questions about the support that the current governance model provides for student learning and concludes with a range of recommendations for policy-makers and for future research. It suggests that, in relation to student learning, Nash’s (1989) comment that the ‘jury is still out’ about the effectiveness of the model may still be valid

Polymer Induced Bundling of F-actin and the Depletion Force

The inert polymer polyethylene glycol (PEG) induces a "bundling" phenomenon in F-actin solutions when its concentration exceeds a critical onset value C_o. Over a limited range of PEG molecular weight and ionic strength, C_o can be expressed as a function of these two variables. The process is reversible, but hysteresis is also observed in the dissolution of the bundles, with ionic strength having a large influence. Additional actin filaments are able to join previously formed bundles. Little, if any, polymer is associated with the bundle structure. Continuum estimates of the Asakura-Oosawa depletion force, Coulomb repulsion, and van der Waals potential are combined for a partial explanation of the bundling effect and hysteresis. Conjectures are presented concerning the apparent limit in bundle size

Nucleotide-dependence of G-actin conformation from multiple molecular dynamics simulations and observation of a putatively polymerisation-competent superclosed state

The assembly of monomeric G-actin into filamentous F-actin is nucleotide dependent: ATP-G-actin is favored for filament growth at the “barbed end” of F-actin, whereas ADP-G-actin tends to dissociate from the “pointed end.” Structural differences between ATP- and ADP-G-actin are examined here using multiple molecular dynamics simulations. The “open” and “closed” conformational states of G-actin in aqueous solution are characterized, with either ATP or ADP in the nucleotide binding pocket. With both ATP and ADP bound, the open state closes in the absence of actin-bound profilin. The position of the nucleotide in the protein is found to be correlated with the degree of opening of the active site cleft. Further, the simulations reveal the existence of a structurally well-defined, compact, “superclosed” state of ATP-G-actin, as yet unseen crystallographically and absent in the ADP-G-actin simulations. The superclosed state resembles structurally the actin monomer in filament models derived from fiber diffraction and is putatively the polymerization competent conformation of ATP-G-actin

The vertebrate muscle Z-disc: sarcomere anchor for structure and signalling

The Z-disc, appearing as a fine dense line forming sarcomere boundaries in striated muscles, when studied in detail reveals crosslinked filament arrays that transmit tension and house myriads of proteins with diverse functions. At the Z-disc the barbed ends of the antiparallel actin filaments from adjoining sarcomeres interdigitate and are crosslinked primarily by layers of α-actinin. The Z-disc is therefore the site of polarity reversal of the actin filaments, as needed to interact with the bipolar myosin filaments in successive sarcomeres. The layers of α-actinin determine the Z-disc width: fast fibres have narrow (~30–50 nm) Z-discs and slow and cardiac fibres have wide (~100 nm) Z-discs. Comprehensive reviews on the roles of the numerous proteins located at the Z-disc in signalling and disease have been published; the aim here is different, namely to review the advances in structural aspects of the Z-disc

Insulin-like growth factor-I (IGF-I) and IGF binding protein-5 in Schwann cell differentiation

Schwann cells (SCs) are the myelin producing cells of the peripheral nervous system. During development, SCs cease proliferation and differentiate into either a myelin-forming or non-myelin forming mature phenotype. We are interested in the role of insulin-like growth factor-I (IGF-I) in SC development. We have shown previously SCs proliferate in response to IGF-I in vitro. In the current study, we investigated the role of IGF-I in SC differentiation. SC differentiation was determined by morphological criteria and expression of myelin proteins. Addition of 1 mM 8-bromo cyclic AMP (cAMP) or growth on Matrigel matrix decreased proliferation and induced differentiation of SCs. IGF-I enhanced both cAMP and Matrigel matrix-induced SC differentiation, as assessed by both morphological criteria and myelin gene expression. Cultured SCs also express IGF binding protein-5 (IGFBP-5), which can modulate the actions of IGF-I. We examined the expression of IGFBP-5 during SC differentiation. Both cAMP and Matrigel matrix treatment enhanced IGFBP-5 protein expression and cAMP increased IGFBP-5 gene expression five fold. These findings suggest IGF-I potentiates SC differentiation. The concomitant up-regulation of IGFBP-5 may play a role in targeting IGF-I to SCs and thus increase local IGF-I bioavailability. J. Cell. Physiol. 171:161–167, 1997. © 1997 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34438/1/6_ftp.pd

Conformational Dynamics of Actin: Effectors and Implications for Biological Function

Actin is a protein abundant in many cell types. Decades of investigations have provided evidence that it has many functions in living cells. The diverse morphology and dynamics of actin structures adapted to versatile cellular functions is established by a large repertoire of actin-binding proteins. The proper interactions with these proteins assume effective molecular adaptations from actin, in which its conformational transitions play essential role. This review attempts to summarise our current knowledge regarding the coupling between the conformational states of actin and its biological function