Understanding the functions of titin and nebulin

AbstractIndividual molecules of the giant muscle proteins titin and nebulin span large distances in the sarcomere. Approximately one-third of the titin molecule forms elastic filaments linking the ends of thick filaments to the Z-line. The remainder of the molecule is probably bound to the thick filament where it may regulate assembly of myosin and the other thick filament proteins. This region also contains a sequence similar to catalytic domains in protein kinases. Nebulin appears to be associated with thin filaments and may regulate actin assembly

Roles of Titin in the Structure and Elasticity of the Sarcomere

The giant protein titin is thought to play major roles in the assembly and function of muscle sarcomeres. Structural details, such as widths of Z- and M-lines and periodicities in the thick filaments, correlate with the substructure in the respective regions of the titin molecule. Sarcomere rest length, its operating range of lengths, and passive elastic properties are also directly controlled by the properties of titin. Here we review some recent titin data and discuss its implications for sarcomere architecture and elasticity

Reintroduciendo actividades etnomatemáticas maoríes en el aula: conceptos tradicionales maoríes de orientación espacial

Māori mathematical practices were excluded from schooling in Aotearoa/New Zealand for over 150 years as a result of explicit policies precluding the use of the Indigenous language and culture. As a consequence of the range of assimilationist policies, by the 1970s, the Māori language was considered endangered. In response to the perilous state of the language, Māori communities set up their own schools, initially outside of the state system, to support the revitalisation of the language and culture. However, the reintroduction of the cultural knowledge in areas such as mathematics has not matched language revitalisation efforts. Many original ethnomathematical practices are no longer in general use in the Indigenous community and the practices valued by the European majority remain the norm in the state-mandated school curricula. Spatial orientation is an example of the mathematics curricula content that is based on Western mathematical perspectives. To provide a Māori perspective, this paper draws on interviews with elders and historical data to examine Māori spatial orientation terms and the spatial frames of references that they are derived from. Students in a Māori-medium school were tested on their understanding of this traditional knowledge. As a consequence, a series of learning activities based on Māori spatial orientation concepts were developed and trialled. The outcomes of these learning activities showed some increased understandings about Māori spatial orientation concepts

Dynamics of semi-flexible polymer solutions in the highly entangled regime

We present experimental evidence that the effective medium approximation (EMA), developed by D.C. Morse [Phys. Rev. E {\bf 63}, 031502, (2001)], provides the correct scaling law of the macroscopic plateau modulus $G^{0}\propto\rho^{4/3}L^{-1/3}_{p}$ (where $\rho$ is the contour length per unit volume and $L_{p}$ is the persistence length) of semi-flexible polymer solutions, in the highly entangled concentration regime. Competing theories, including a self-consistent binary collision approximation (BCA), have instead predicted $G^{0}\propto\rho^{7/5}L^{-1/5}_{p}$. We have tested both the EMA and BCA scaling predictions using actin filament (F-actin) solutions which permit experimental control of $L_p$ independently of other parameters. A combination of passive video particle tracking microrheology and dynamic light scattering yields independent measurements of the elastic modulus $G$ and $L_{p}$ respectively. Thus we can distinguish between the two proposed laws, in contrast to previous experimental studies, which focus on the (less discriminating) concentration functionality of $G$.Comment: 4 pages, 6 figures, Phys. Rev. Lett. (accepted

Te Reo Tātai: The Development of a Mathematics Register for Māori-Medium Schooling

This thesis investigates the development of a lexicon and register to facilitate the teaching of mathematics in the medium of te reo Māori. This sociolinguistic development is situated within the wider Māori language revitalisation movement in Aotearoa/New Zealand, of which Māori-medium education is a central component. Lexication of a language is a subdomain of corpus planning. Corpus, status and language-in-education planning are considered the three major interconnected domains of language planning and policy (LPP). For decades, the primary focus of LPP research has been on the activities of states and their agencies at the macro (national) level. The significance of this study is that it addresses this gap in the research, by investigating the development of LPP at the meso/micro-level—in this case, with respect to the development of a mathematics register for an endangered indigenous language, te reo Māori. The thesis draws on two major participant data sources. The first is the narratives of key individuals at the forefront of lexical development for Māori-medium mathematics who recounted their experiences. The second is interviews with principals and teachers from two Māori-medium case study schools to examine their own learning and usage of the standardised pāngarau lexicon. Two complementary theoretical frameworks were used to investigate the topic. First, an LPP theoretical framework was applied to investigate the complex relationships between the various levels of LPP that have impacted on the evolution of te reo Māori and Māori-medium schooling. Second, a linguistic framework, systemic functional linguistics (SFL), was used to investigate the linguistic and pedagogical issues. Thesis findings show that the status of te reo Māori was variously affected by linguistic ideologies such as assimilation, which in turn led to such policies as English only in schooling. As a consequence, at the micro-level of LPP, Māori-medium mathematics development went into a hiatus for over 100 years, and at the macro-level, considerable language shift occurred to English, causing te reo Maori to become endangered. In response to language revitalisation efforts, the (re) vernacularisation of te reo Māori over the past 30 years has exhibited a complex combination of both bottom-up and top-down LPP. Within this, early pāngarau lexical developments were largely driven by local schools and their communities, which sometimes centred on the maintenance of their tribal dialects, often in conflict with later LPP agency language goals. Subsequently, lexication for pāngarau was influenced by macro-level sociolinguistic beliefs such as linguistic purism, which in turn have influenced the technical approach to creating terms and may have created particular pedagogical issues, such as a lack of intertranslatability between te reo Māori and English at the higher levels of mathematics study. While Māori-medium schooling has contributed significantly to language revitalisation in the past 30 years, its development has been very ad hoc. In the absence of a “formal” language plan for Māori-medium education, policy has been significantly driven by national education (English-medium) imperatives since the late 1970s to the present day. On the other hand, these policies have favoured mathematics education and directly supported the development of the Māori-medium specialised lexicon and register

Structure of isolated Z-disks from honeybee flight muscle

The Z-disk is a complex structure comprising some 40 proteins that are involved in the transmission of force developed during muscle contraction and in important signalling pathways that govern muscle homeostasis. In the Z-disk the ends of antiparallel thin filaments from adjacent sarcomeres are crosslinked by α-actinin. The structure of the Z-disk lattice varies greatly throughout the animal kingdom. In vertebrates the thin filaments form a tetragonal lattice, whereas invertebrate flight muscle has a hexagonal lattice. The width of the Z-disk varies considerably and correlates with the number of α-actinin bridges. A detailed description at a high resolution of the Z-disk lattice is needed in order to better understand muscle function and disease. The molecular architecture of the Z-disk lattice in honeybee (Apis mellifera) is known from plastic embedded thin sections to a resolution of 7 nm, which is not sufficient to dock component protein crystal structures. It has been shown that sectioning is a damaging process that leads to the loss of finer details present in biological specimens. However, the Apis Z-disk is a thin structure (120 nm) suitable for cryo EM. We have isolated intact honeybee Z-disks from indirect flight muscle, thus obviating the need of plastic sectioning. We have employed cryo electron tomography and image processing to investigate the arrangement of proteins within the hexagonal lattice of the Apis Z-disk. The resolution obtained, ~6 nm, was probably limited by damage caused by the harshness of the conditions used to extract the myofibrils and isolate the Z-disks

Are the adverse effects of glitazones linked to induced testosterone deficiency?

<p>Abstract</p> <p>Background</p> <p>Adverse side-effects of the glitazones have been frequently reported in both clinical and animal studies, especially with rosiglitazone (RGZ) and pioglitazone (PGZ), including congestive heart failure, osteoporosis, weight gain, oedema and anaemia. These led to consideration of an evidence-based hypothesis which would explain these diverse effects, and further suggested novel approaches by which this hypothesis could be tested.</p> <p>Presentation of hypothesis</p> <p>The literature on the clinical, metabolic and endocrine effects of glitazones in relation to the reported actions of testosterone in diabetes, metabolic syndrome, and cardiovascular disease is reviewed, and the following unifying hypothesis advanced: "<it>Glitazones induce androgen deficiency in patients with Type 2 Diabetes Mellitus resulting in pathophysiological changes in multiple tissues and organs which may explain their observed clinical adverse effects</it>." This also provides further evidence for the lipocentric concept of diabetes and its clinical implications.</p> <p>Testing of the hypothesis</p> <p>Clinical studies to investigate the endocrine profiles, including measurements of TT, DHT, SHBG, FT and estradiol, together with LH and FSH, in both men and women with T2DM before and after RGZ and PGZ treatment in placebo controlled groups, are necessary to provide data to substantiate this hypothesis. Also, studies on T treatment in diabetic men would further establish if the adverse effects of glitazones could be reversed or ameliorated by androgen therapy. Basic sciences investigations on the inhibition of androgen biosynthesis by glitazones are also warranted.</p> <p>Implications of the hypothesis</p> <p>Glitazones reduce androgen biosynthesis, increase their binding to SHBG, and attenuate androgen receptor activation, thus reducing the physiological actions of testosterone, causing relative and absolute androgen deficiency. This hypothesis explains the adverse effects of glitazones on the heart and other organs resulting from reversal of the action of androgens in directing the maturation of stem cells towards muscle, vascular endothelium, erythroid stem cells and osteoblasts, and away from adipocyte differentiation. The higher incidence of side-effects with RGZ than PGZ, may be explained by a detailed study of the mechanism by which glitazones down-regulate androgen biosynthesis and action, resulting in a state of androgen deficiency.</p

Weakly acidic pH reduces inflammatory cytokine expression in airway epithelial cells

Background Aspiration lung disease (ALD) is a common cause of respiratory morbidity in children and adults with severe neurodisability (sND). Recent studies suggest that chronic microaspiration of gastric contents is associated with mild rather than low, airway acidification. We investigated inflammatory responses to infection by airway epithelial cells (AECs) exposed to weakly acidic media. Methods Using pH measurements from children with sND at high risk of ALD as a guide, we incubated AECs in weakly acidic (pH5.5–7.4) media alone; in combination with lipopolysaccharide (LPS); or prior to LPS stimulation at normal pH. Interleukin (IL) -6 and IL-8 expression were measured. Results IL-6/8 expression in AECs simultaneously exposed to weakly acidic media and LPS for 4 h was reduced with no effect on cell viability. Pre-incubation of AECs at weakly acidic pH also reduced subsequent LPS-induced cytokine expression. Suppression of inflammation was greatest at lower pHs (pH 5.5–6.0) for prolonged periods (16/24 h), but this also adversely affected cell viability. Conclusion AEC inflammatory responses to bacterial stimuli is markedly reduced in a mildly acidic environment

Aspiration lung disease in children with severe neurodisability

Background: Children with severe neurodisability (ND) commonly suffer with respiratory disease and this is the leading cause of premature death. The nature of this respiratory disease is however, poorly understood. The underlying aetiology is often multifactorial, but aspiration (direct or reflux) is likely to play a key role. Unfortunately, diagnostic tests for reflux or direct aspiration are limited. There is a clinical need for high quality research on children with severe ND to define underlying mechanisms of respiratory disease and guide management. Aims: In this study, the aims were to (i) characterise respiratory symptoms and their relationship with lower airway inflammation in children with severe ND, (ii) explore available bronchial lavage (BAL) biomarkers of reflux aspiration, assessing their validity and their relationship to clinical and airway inflammatory data, (iii) develop a novel assay for the accurate detection/quantification of pepsin in BAL, (iv) investigate the validity of an alpha-amylase assay in paediatric BAL and explore the relationship of alpha-amylase levels with lower airway inflammation and clinical symptoms, and (v) investigate the effects of pH alteration and pepsin exposure on airway epithelial cells (AEC). Methods: Clinical data and BAL samples were collected from children with severe ND at times of stability and respiratory deterioration and also from healthy controls. BAL differential cell counts and cytokine measurements (ELISA) were performed. Lower airway microbial colonisation/infection was assessed. BAL pepsin measurement was attempted using a number of methods, and the feasibility of inhibitor affinity enrichment and LC-MRM-MS techniques to identify and quantify BAL pepsin was explored using SDS PAGE gel and mass spectrometry analysis. BAL alpha-amylase activity was measured using an ethylidene-pNP-G7 based assay. BEAS-2B cells were cultured in monolayer and the cytotoxic/inflammatory effects of pH alteration and pepsin exposure were explored through trypan blue staining and cytokine assays. Results: Children with severe ND have burdensome chronic respiratory symptoms that impact on their quality of life and that of their families’. Symptoms may relate to lower airway inflammatory levels. A trend for greater airway neutrophilia and respiratory symptoms was seen in those with lower airway microbial positivity. Available ‘in house’ pepsin ELISA assays were not robust but Western Blot results indicated a higher frequency of BAL pepsin positivity in ND patients with acute respiratory deterioration. Notably, positivity was also found in some healthy controls, highlighting the need for a quantitative assay. The use of an immobilized inhibitor (pepstatin agarose) to recover pepsin from paediatric BAL samples was shown to be feasible. Subsequent digestion of pepsin and detection by LC-MSMS with selective ion monitoring was demonstrated. Significantly increased BAL alpha-amylase levels were seen in Elective-ND patients compared to healthy controls and furthermore, significant correlations were observed with BAL lower airway inflammatory markers. BEAS-2B cells were sensitive to mild acidification, with up-regulation of TGF Beta-1, IL-6 and IL-8 mRNA expression. A corresponding rise in protein secretion was not necessarily seen and in some cases, was significantly down-regulated. No significant cytotoxicity or decrease in cell viability was observed in any condition. Conclusions: In children with severe ND, chronic respiratory symptoms may be directly related to lower airway inflammation and bacterial colonization. Measurement and quantification of pepsin in BAL (as a marker of reflux aspiration) is difficult. However, an inhibitor affinity enhanced mass spectrometry based technique has potential as a ‘gold-standard’ method for identification and quantification of pepsin in BAL. BAL alpha-amylase activity shows promise as a biomarker of direct aspiration. Mild alterations in airway pH may directly contribute to the pathophysiology of inflammatory airway disease and specifically, reflux-aspiration related lung disease in this group. This requires further study as a potential novel therapeutic target