Search

Growth hormone (GH) and ? agonists increase muscle mass, but the mechanisms for this response are unclear and the magnitude of response is thought to vary with age of animal. To investigate the mechanisms driving the muscle response to these agents, we examined the effects of short-term (6 day) administration of GH or cimaterol (a ?2-adrenergic agonist, BA) on skeletal muscle phenotype in both young (day 60) and mature (day 120) lambs. Expression of myosin heavy chain (MyHC) isoforms were measured in Longissimus dorsi (LD), Semitendinosus (ST) and Supraspinatus (SS) muscles as markers of fibre type and metabolic enzyme activities were measured in LD. To investigate potential mechanisms regulating the changes in fibre type/metabolism, expression or activity of a number of signalling molecules were examined in LD. There were no effects of GH administration on MyHC isoformexpression at either the mRNA or protein level in any of the muscles. However, BA treatment induced a proportional change in MyHC mRNA expression at both ages, with the %MyHCI and/or IIA mRNA being significantly decreased in all three muscles and % MyHCIIX/IIB mRNA significantly increased in the LD and ST. BA treatment induced de novo expression of MyHCIIB mRNA in LD, the fastest isoform not normally expressed in sheep LD, as well as increasing expression in the other two muscles. In the LD, theincreased expression of the fastest MyHC isoforms (IIX and IIB) was associated with a decrease in isocitrate dehydrogenase activity, but no change in lactate dehydrogenase activity, indicating a reduced capacity for oxidative metabolism. In both young and mature lambs, changes in expression of metabolic regulatory factors were observed that might induce these changes in musclemetabolism/fibre type. In particular, BA treatment decreased PPAR-? coactivator-1? mRNA and increased receptor-interacting protein 140 mRNA. The results suggest that the two agents work via different mechanisms or over different timescales, with only BA inducing changes in muscle mass and transitions to a faster, less oxidative fibre type after a 6-day treatment.

Fat infiltration within muscle is one of a number of features of vitamin D deficiency, which leads to a decline in muscle functionality. The origin of this fat is unclear, but one possibility is that it forms from myogenic precursor cells present in the muscle, which transdifferentiate into mature adipocytes. The current study examined the effect of the active form of vitamin D3, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), on the capacity of the C2C12 muscle cell line to differentiate towards the myogenic and adipogenic lineages. Cells were cultured in myogenic or adipogenic differentiation media containing increasing concentrations (0, 10−13, 10−11, 10−9, 10−7 or 10−5 M) of 1,25(OH)2D3 for up to 6 days and markers of muscle and fat development measured. Mature myofibres were formed in both adipogenic and myogenic media, but fat droplets were only observed in adipogenic media. Relative to controls, low physiological concentrations (10−13 and 10−11 M) of 1,25(OH)2D3 increased fat droplet accumulation, whereas high physiological (10−9 M) and supraphysiological concentrations (≥10−7 M) inhibited fat accumulation. This increased accumulation of fat with low physiological concentrations (10−13 and 10−11 M) was associated with a sequential up-regulation of PPARγ2 (PPARG) and FABP4 mRNA, indicating formation of adipocytes, whereas higher concentrations (≥10−9 M) reduced all these effects, and the highest concentration (10−5 M) appeared to have toxic effects. This is the first study to demonstrate dose-dependent effects of 1,25(OH)2D3 on the transdifferentiation of muscle cells into adipose cells. Low physiological concentrations (possibly mimicking a deficient state) induced adipogenesis, whereas higher (physiological and supraphysiological) concentrations attenuated this effect.

Tropical forest ecosystems are hotspots for biodiversity and represent one of the largest terrestrial carbon stocks, making their role in climate change mitigation (CCM) programmes increasingly important (e.g. REDD+). In Latin America these ecosystems suffer from high land use pressures that have resulted in a dramatic biodiversity loss. Little is known about how CCM options may impact on biodiversity and how this in turn may affect ecosystem carbon storage. Within this context, the FP7 ROBIN (Role Of Biodiversity In climate change mitigatioN) project developed a framework for multi-scale integrated analysis of the impacts that land use change may have on the ecological and social-economic processes of these ecosystems. The framework represents a continuous feedback loop in which changes in CCM options modify land use, that results in biodiversity change, affecting ecosystem functions, leading to changes in ecosystem services that affect human outcomes and societal behaviour, and which then affect the main drivers and pressures on biodiversity and ecosystems, and so on. We have constructed an indicator framework that allows to quantify, link and assess these interactions at three spatial scales: regional (Central and South America), national (Bolivia, Brazil, Guyana and Mexico) and sub-national (study sites representing multifunctional landscapes). Indicators are selected through a demand-driven approach, by directing modelling and assessment efforts towards end-user relevant issues using stakeholder participatory processes. Indicator values are grounded on field data, statistics and model outputs. The framework provides a basis for understanding potential tipping points and unexpected consequences that may arise from the implementation of climate change mitigation policies, or management options (e.g. reducing deforestation and burning, or expansion of areas of biofuel crops in illegal areas). An illustrative example, showing how the framework helps to identify the appropriate indicators to synthesise the impacts of afforestation (one of the CCM options) across the ecological and socio-ecological processes and regions is presented

International audience; The contractile and associated metabolic characteristics of muscles are determined by their myosin heavy chain (MHC) isoform expression. In large mammals, the level of MHCIIB expression, which is associated with fast glycolytic-type muscle fibers, has not been fully characterized. In this study, quantitative reverse transcription-PCR and SDS-PAGE methodologies were developed for the analyses of adult ovine MHC isoform expression and used to characterize MHC expression in 3 skeletal muscles [LM, semitendinosus, and supraspinatus) from 66-d-old lambs. Three MHC isoforms (MHCI, MHCIIA, and MHCIIX) were detected at both the protein and messenger RNA levels in all 3 muscles, with greater proportions of type II than type I MHC. The expression of MHCIIB could not be detected at the protein level in any of the muscles and was detectable (in semitendinosus muscle) only at the messenger RNA level by using semiquantitative reverse transcription-PCR, indicating that MHCIIX is the predominant fast glycolytic fiber type in the sheep muscles studied. The methodologies developed are suitable for studying fiber type transformations at the molecular level, as well as allowing analyses of very small samples, including biopsies, when histochemical analysis may not be possible.

Although existing LR(1) or U(1) parser generators suffice for many language recognition problems, writing a straightforward grammar to translate a complicated language, such as C++ or even C, remains a non-trivial task. We have often found that adding translation actions to the grammar is harder than writing the grammar itself. Part of the problem is that many languages are context-sensitive. Simple, natural descriptions of these languages escape current language tool technology because they were not designed to handle semantic information. In this paper, we introduce predicated LR (k) and LL (k) parsers as a solution. Predicates provide a general, practical means to utilize semantic tests in parsers. Used in conjunction with k >1 lookahead sets, a predicated parser simplifies the task of writing real translators. Our approach differs from previous work in that (i) we allow multiple predicates to be placed arbitrarily within a production, (ii) we describe the construction of predicated LR (k) parsing tables, (iii) we automatically hoist predicates in an LL(k) parser from one production to aid in the recognition of another, and (iv) we have implemented predicate handling in a public-domain parser generator that offers k-token lookahead - The Purdue Compiler Construction Tool Set (PCCTS)