Restoration of pharyngeal dilator muscle force in dystrophin-deficient (mdx) mice following co-treatment with neutralizing interleukin-6 receptor antibodies and urocortin-2

New Findings: What is the central question of this study? We previously reported impaired upper airway dilator muscle function in the mdx mouse model of Duchenne muscular dystrophy (DMD). Our aim was to assess the effect of blocking interleukin-6 receptor signalling and stimulating corticotrophin-releasing factor receptor 2 signalling on mdx sternohyoid muscle structure and function. What is the main finding and its importance? The interventional treatment had a positive inotropic effect on sternohyoid muscle force, restoring mechanical work and power to wild-type values, reduced myofibre central nucleation and preserved the myosin heavy chain type IIb fibre complement of mdx sternohyoid muscle. These data might have implications for development of pharmacotherapies for DMD with relevance to respiratory muscle performance. The mdx mouse model of Duchenne muscular dystrophy shows evidence of impaired pharyngeal dilator muscle function. We hypothesized that inflammatory and stress-related factors are implicated in airway dilator muscle dysfunction. Six-week-old mdx (n = 26) and wild-type (WT; n = 26) mice received either saline (0.9% w/v) or a co-administration of neutralizing interleukin-6 receptor antibodies (0.2 mg kg−1) and corticotrophin-releasing factor receptor 2 agonist (urocortin 2; 30 μg kg−1) over 2 weeks. Sternohyoid muscle isometric and isotonic contractile function was examined ex vivo. Muscle fibre centronucleation and muscle cellular infiltration, collagen content, fibre-type distribution and fibre cross-sectional area were determined by histology and immunofluorescence. Muscle chemokine content was examined by use of a multiplex assay. Sternohyoid peak specific force at 100 Hz was significantly reduced in mdx compared with WT. Drug treatment completely restored force in mdx sternohyoid to WT levels. The percentage of centrally nucleated muscle fibres was significantly increased in mdx, and this was partly ameliorated after drug treatment. The areal density of infiltrates and collagen content were significantly increased in mdx sternohyoid; both indices were unaffected by drug treatment. The abundance of myosin heavy chain type IIb fibres was significantly decreased in mdx sternohyoid; drug treatment preserved myosin heavy chain type IIb complement in mdx muscle. The chemokines macrophage inflammatory protein 2, interferon-γ-induced protein 10 and macrophage inflammatory protein 3α were significantly increased in mdx sternohyoid compared with WT. Drug treatment significantly increased chemokine expression in mdx but not WT sternohyoid. Recovery of contractile function was impressive in our study, with implications for Duchenne muscular dystrophy. The precise molecular mechanisms by which the drug treatment exerts an inotropic effect on mdx sternohyoid muscle remain to be elucidated

Inspiratory pressure-generating capacity is preserved during ventilatory and non-ventilatory behaviours in young dystrophic mdx mice despite profound diaphragm muscle weakness

Diaphragm dysfunction is recognized in the mdx mouse model of muscular dystrophy, however there is a paucity of information concerning the neural control of dystrophic respiratory muscles. In young adult (8 weeks of age) male wild‐type and mdx mice, we assessed ventilatory capacity, neural activation of the diaphragm and external intercostal (EIC) muscles and inspiratory pressure‐generating capacity during ventilatory and non‐ventilatory behaviours. We hypothesized that respiratory muscle weakness is associated with impaired peak inspiratory pressure‐generating capacity in mdx mice. Ventilatory responsiveness to hypercapnic hypoxia was determined in conscious mice by whole‐body plethysmography. Diaphragm isometric and isotonic contractile properties were determined ex vivo. In anaesthetized mice, thoracic oesophageal pressure, and diaphragm and EIC electromyogram (EMG) activities were recorded during baseline conditions and sustained tracheal occlusion for 30–40s. Despite substantial diaphragm weakness, mdx mice retain the capacity to enhance ventilation during hypercapnic hypoxia. Peak volume‐ and flow‐related measures were also maintained in anaesthetized, vagotomized mdx mice. Peak inspiratory pressure was remarkably well preserved during chemoactivated breathing, augmented breaths, and maximal sustained efforts during airway obstruction in mdx mice. Diaphragm and EIC EMG activities were lower during airway obstruction in mdx compared with wild‐type mice. We conclude that ventilatory capacity is preserved in young mdx mice. Despite profound respiratory muscle weakness and lower diaphragm and EIC EMG activities during high demand in mdx mice, peak inspiratory pressure is preserved, revealing adequate compensation in support of respiratory system performance, at least early in dystrophic disease. We suggest that a progressive loss of compensation during advancing disease, combined with diaphragm dysfunction, underpins the development of respiratory system morbidity in dystrophic diseases

N-acetylcysteine decreases fibrosis and increases force-generating capacity of mdx diaphragm

Respiratory muscle weakness occurs due to dystrophin deficiency in Duchenne muscular dystrophy (DMD). The mdx mouse model of DMD shows evidence of impaired respiratory muscle performance with attendant inflammation and oxidative stress. We examined the effects of N-acetylcysteine (NAC) supplementation on respiratory system performance in mdx mice. Eight-week-old male wild type (n = 10) and mdx (n = 20) mice were studied; a subset of mdx (n = 10) received 1% NAC in the drinking water for 14 days. We assessed breathing, diaphragm, and external intercostal electromyogram (EMG) activities and inspiratory pressure during ventilatory and non-ventilatory behaviours. Diaphragm muscle structure and function, cytokine concentrations, glutathione status, and mRNA expression were determined. Diaphragm force-generating capacity was impaired in mdx compared with wild type. Diaphragm muscle remodelling was observed in mdx, characterized by increased muscle fibrosis, immune cell infiltration, and central myonucleation. NAC supplementation rescued mdx diaphragm function. Collagen content and immune cell infiltration were decreased in mdx + NAC compared with mdx diaphragms. The cytokines IL-1β, IL-6 and KC/GRO were increased in mdx plasma and diaphragm compared with wild type; NAC decreased systemic IL-1β and KC/GRO concentrations in mdx mice. We reveal that NAC treatment improved mdx diaphragm force-generating capacity associated with beneficial anti-inflammatory and anti-fibrotic effects. These data support the potential use of NAC as an adjunctive therapy in human dystrophinopathies

НАПРАВЛЕНИЯ СОВЕРШЕНСТВОВАНИЯ ОБРУДОВАНИЯ ДЛЯ ФЛОТАЦИОННОГО ОБОГАЩЕНИЯ ТОНКОДИСПЕРСНыХ МАТЕРИАЛОВ

Проблема и ее связь с научными и практическими задачами. В связи с тем, что в поступающем на обогатительные фабрики сырье содержится до 30% ма-териала крупностью менее 1 мм, роль процесса флотации существенно возрас-тает. Этому способствует и возможность создания достаточно простых замкну-тых водно-шламовых схем, включающих флотацию в качестве основного эле-мента очистки оборотных вод. Многими исследованиями, которые проводились ранее и продолжают выполняться и в настоящее время, установлены направле-ния совершенствования этого достаточно сложного физико-химического про-цесс

Response to Comments on "Productivity Is a Poor Predictor of Plant Species Richness"

Pan et al. claim that our results actually support a strong linear positive relationship between productivity and richness, whereas Fridley et al. contend that the data support a strong humped relationship. These responses illustrate how preoccupation with bivariate patterns distracts from a deeper understanding of the multivariate mechanisms that control these important ecosystem properties

Plant species' origin predicts dominance and response to nutrient enrichment and herbivores in global grasslands

Exotic species dominate many communities; however the functional significance of species’ biogeographic origin remains highly contentious. This debate is fuelled in part by the lack of globally replicated, systematic data assessing the relationship between species provenance, function and response to perturbations. We examined the abundance of native and exotic plant species at 64 grasslands in 13 countries, and at a subset of the sites we experimentally tested native and exotic species responses to two fundamental drivers of invasion, mineral nutrient supplies and vertebrate herbivory. Exotic species are six times more likely to dominate communities than native species. Furthermore, while experimental nutrient addition increases the cover and richness of exotic species, nutrients decrease native diversity and cover. Native and exotic species also differ in their response to vertebrate consumer exclusion. These results suggest that species origin has functional significance, and that eutrophication will lead to increased exotic dominance in grasslands

Predicting invasion in grassland ecosystems: is exotic dominance the real embarrassment of richness?

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the native community or, alternatively, dominance by a single exotic species. Here, we used a globally replicated study to quantify relationships between exotic richness and abundance in grass-dominated ecosystems in 13 countries on six continents, ranging from salt marshes to alpine tundra. We tested effects of human land use, native community diversity, herbivore pressure, and nutrient limitation on exotic plant dominance. Despite its widespread use, exotic richness was a poor proxy for exotic dominance at low exotic richness, because sites that contained few exotic species ranged from relatively pristine (low exotic richness and cover) to almost completely exotic-dominated ones (low exotic richness but high exotic cover). Both exotic cover and richness were predicted by native plant diversity (native grass richness) and land use (distance to cultivation). Although climate was important for predicting both exotic cover and richness, climatic factors predicting cover (precipitation variability) differed from those predicting richness (maximum temperature and mean temperature in the wettest quarter). Herbivory and nutrient limitation did not predict exotic richness or cover. Exotic dominance was greatest in areas with low native grass richness at the site- or regional-scale. Although this could reflect native grass displacement, a lack of biotic resistance is a more likely explanation, given that grasses comprise the most aggressive invaders. These findings underscore the need to move beyond richness as a surrogate for the extent of invasion, because this metric confounds monodominance with invasion resistance. Monitoring species’ relative abundance will more rapidly advance our understanding of invasions.This is the publisher’s final pdf. The published article is copyrighted by John Wiley & Sons Ltd and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2486

Development and Validation of a Multiplex Microsphere-Based Assay for Detection of Domestic Cat (Felis catus) Cytokines ▿

Cytokines are essential signaling molecules that mediate the innate immune response, and therefore their presence can be of diagnostic, prognostic, and pathogenic significance. Microsphere-based immunoassays allow rapid and accurate evaluation of cytokine levels in several species, including humans, dogs, and mice; however, technology to evaluate domestic cat (Felis catus) cytokines has been limited to single-analyte enzyme-linked immunosorbent assays (ELISAs). Microsphere-based immunoassays provide an attractive alternative technology for detecting and quantifying multiple analytes in a single assay using as little as 50 μl of sample. We describe the development and validation of a microsphere-based assay for three commonly analyzed domestic cat cytokines (gamma interferon, interleukin-10, and interleukin-12/interleukin-23 p40) using reagents from commercially available ELISAs. The assay was optimized for capture and detection antibody concentrations, streptavidin-phycoerythrin concentration, and number of microspheres. The validated lower and upper quantitation limits were 31 and 1,000 pg/ml for gamma interferon, 63 and 2,000 pg/ml for interleukin-10, and 39 and 625 pg/ml for interleukin-12/interleukin-23 p40. Cytokine concentrations in peripheral blood mononuclear cell supernatants were measured, and results obtained by the microsphere assay were correlated with values obtained with commercially available ELISA kits. This technology is a convenient and reproducible assay to evaluate domestic cat cytokine responses elicited by a variety of diseases