Changes in muscle mass may result from changes in protein turnover, reflecting the balance between protein synthesis and protein degradation, and changes in cell turnover, reflecting the balance ...between myonuclear accretion and myonuclear loss. Myonuclear accretion, i.e. increase in the number of myonuclei within the muscle fibers, takes place via proliferation and fusion of satellite cells, myogenic stem cells associated to skeletal muscle fibers and involved in muscle regeneration. In developing muscle, satellite cells undergo extensive proliferation and most of them fuse with myofibers, thus contributing to the increase in myonuclei during early postnatal stages. A similar process is induced in adult skeletal muscle by functional overload and exercise. In contrast, satellite cells and myonuclei may undergo apoptosis during muscle atrophy, although it is debated whether myonuclear loss occurs in atrophying muscle. An increase in myofiber size can also occur by changes in protein turnover without satellite cell activation, e.g. in late phases of postnatal development or in some models of muscle hypertrophy. The relative role of protein turnover and cell turnover in muscle adaptation and in the establishment of functional muscle hypertrophy remains to be established. The identification of the signaling pathways mediating satellite cell activation may provide therapeutic targets for combating muscle wasting in a variety of pathological conditions, including cancer cachexia, renal and cardiac failure, neuromuscular diseases, as well as aging sarcopenia.
Understanding the impacts of agricultural intensification and extensification on soil biota communities is useful in order to preserve and restore biological diversity in agricultural soils and ...enhance the role of soil biota in agroecosystem functioning. Over four consecutive years, we investigated the effects of agricultural intensification and extensification (including conversion of grassland to arable land and vice versa, increased and decreased levels of mineral fertilization, and monoculture compared to crop rotation) on major soil biota group abundances and functional diversity. We integrated and compared effects across taxonomic levels to identify sensitive species groups.
Crops with reduced requirement for nitrogen (N) fertilizer would have substantial benefits in developed nations, while improving food security in developing nations. This study employs the functional ...structural plant model SimRoot to test the hypothesis that variation in the growth angles of axial roots of maize (Zea mays L.) is an important determinant of N capture.
Six phenotypes contrasting in axial root growth angles were modelled for 42 d at seven soil nitrate levels from 10 to 250 kg ha(-1) in a sand and a silt loam, and five precipitation regimes ranging from 0·5× to 1·5× of an ambient rainfall pattern. Model results were compared with soil N measurements of field sites with silt loam and loamy sand textures.
For optimal nitrate uptake, root foraging must coincide with nitrate availability in the soil profile, which depends on soil type and precipitation regime. The benefit of specific root architectures for efficient N uptake increases with decreasing soil N content, while the effect of soil type increases with increasing soil N level. Extreme root architectures are beneficial under extreme environmental conditions. Extremely shallow root systems perform well under reduced precipitation, but perform poorly with ambient and greater precipitation. Dimorphic phenotypes with normal or shallow seminal and very steep nodal roots performed well in all scenarios, and consistently outperformed the steep phenotypes. Nitrate uptake increased under reduced leaching conditions in the silt loam and with low precipitation.
Results support the hypothesis that root growth angles are primary determinants of N acquisition in maize. With decreasing soil N status, optimal angles resulted in 15-50 % greater N acquisition over 42 d. Optimal root phenotypes for N capture varied with soil and precipitation regimes, suggesting that genetic selection for root phenotypes could be tailored to specific environments.
During ageing skeletal muscles undergo a process of structural and functional remodelling that leads to sarcopenia, a syndrome characterized by loss of muscle mass and force and a major cause of ...physical frailty. To determine the causes of sarcopenia and identify potential targets for interventions aimed at mitigating ageing-dependent muscle wasting, we focussed on the main signalling pathway known to control protein turnover in skeletal muscle, consisting of the insulin-like growth factor 1 (IGF1), the kinase Akt and its downstream effectors, the mammalian target of rapamycin (mTOR) and the transcription factor FoxO. Expression analyses at the transcript and protein level, carried out on well-characterized cohorts of young, old sedentary and old active individuals and on mice aged 200, 500 and 800 days, revealed only modest age-related differences in this pathway. Our findings suggest that during ageing there is no downregulation of IGF1/Akt pathway and that sarcopenia is not due to FoxO activation and upregulation of the proteolytic systems. A potentially interesting result was the increased phosphorylation of the ribosomal protein S6, indicative of increased activation of mTOR complex1 (mTORC1), in aged mice. This result may provide the rationale why rapamycin treatment and caloric restriction promote longevity, since both interventions blunt activation of mTORC1; however, this change was not statistically significant in humans. Finally, genetic perturbation of these pathways in old mice aimed at promoting muscle hypertrophy via Akt overexpression or preventing muscle loss through inactivation of the ubiquitin ligase atrogin1 were found to paradoxically cause muscle pathology and reduce lifespan, suggesting that drastic activation of the IGF1-Akt pathway may be counterproductive, and that sarcopenia is accelerated, not delayed, when protein degradation pathways are impaired.
We recently reported that skeletal muscle fibers of obscurin knockout (KO) mice present altered distribution of ankyrin B (ankB), disorganization of the subsarcolemmal microtubules, and reduced ...localization of dystrophin at costameres. In addition, these mice have impaired running endurance and increased exercise-induced sarcolemmal damage compared with wild-type animals. Here, we report results from a combined approach of physiological, morphological, and structural studies in which we further characterize the skeletal muscles of obscurin KO mice. A detailed examination of exercise performance, using different running protocols, revealed that the reduced endurance of obscurin KO animals on the treadmill depends on exercise intensity and age. Indeed, a mild running protocol did not evidence significant differences between control and obscurin KO mice, whereas comparison of running abilities of 2-, 6-, and 11-mo-old mice exercised at exhaustion revealed a progressive age-dependent reduction of the exercise tolerance in KO mice. Histological analysis indicated that heavy exercise induced leukocyte infiltration, fibrotic connective tissue deposition, and hypercontractures in the diaphragm of KO mice. On the same line, electron microscopy revealed that, in the diaphragm of exercised obscurin KO mice, but not in the hindlimb muscles, both M-line and H-zone of sarcomeres appeared wavy and less defined. Altogether, these results suggest that obscurin is required for the maintenance of morphological and ultrastructural integrity of skeletal muscle fibers against damage induced by intense mechanical stress and point to the diaphragm as the skeletal muscle most severely affected in obscurin-deficient mice.
Interactions at the aboveground-belowground interface provide important feedbacks that regulate ecosystem processes. Organisms within soil food webs are involved in processes of decomposition and ...nutrient mineralization, and their abundance and activity have been linked to plant ecophysiological traits such as species identity and the quality and quantity of plant tissue. We tested aboveground-belowground diversity relationships in a naturally developed plant community of native tallgrass prairie by taking soil samples from beneath naturally established grass tillers of chosen characteristics (e.g., homogeneous vs. heterogeneous plant combinations or C4vs. C3photosynthetic pathway) without imposing any disturbances to existing plant-soil relationships. The goal of this study was to elucidate the consequences, for soil microbiota (microflora phospholipid fatty acids, protozoa, and nematode functional groups) and for C and N mineralization, of plant community properties such as species richness, resource quality, resource heterogeneity, species identity, and presence of exotics. None of the biotic or abiotic soil variables was related to plant resource heterogeneity. Protozoa were not responsive to any of the plant community traits. Some bacterial and nematode groups were affected by plant characteristics specific to a particular plant species, but no uniform pattern emerged. Invasive and native plants generally were similar with respect to soil variables tested in this study. The lack of clear responses of soil variables to plant community traits indicates that idiosyncratic effects dominate both at the plant and soil biotic level and that generalized plant and soil diversity effects are hard to predict.
Ullrich congenital muscular dystrophy (UCMD) and Bethlem myopathy (BM) are inherited muscle diseases due to mutations in the genes encoding the extracellular matrix protein collagen (Col) VI. Opening ...of the cyclosporin A-sensitive mitochondrial permeability transition pore (PTP) is a causative event in disease pathogenesis, and a potential target for therapy. Here, we have tested the effect of N-methyl-4-isoleucine-cyclosporin (NIM811), a non-immunosuppressive cyclophilin inhibitor, in a zebrafish model of ColVI myopathy obtained by deletion of the N-terminal region of the ColVI α1 triple helical domain, a common mutation of UCMD. Treatment with antisense morpholino sequences targeting col6a1 exon 9 at the 1-4 cell stage (within 1 h post fertilization, hpf) caused severe ultrastructural and motor abnormalities as assessed by electron and fluorescence microscopy, birefringence, spontaneous coiling events and touch-evoked responses measured at 24-48 hpf. Structural and functional abnormalities were largely prevented when NIM811--which proved significantly more effective than cyclosporin A--was administered at 21 hpf, while FK506 was ineffective. Beneficial effects of NIM811 were also detected (i) in primary muscle-derived cell cultures from UCMD and BM patients, where the typical mitochondrial alterations and depolarizing response to rotenone and oligomycin were significantly reduced; and (ii) in the Col6a1(-/-) myopathic mouse model, where apoptosis was prevented and muscle strength was increased. Since the PTP of zebrafish shares its key regulatory features with the mammalian pore, our results suggest that early treatment with NIM811 should be tested as a potential therapy for UCMD and BM.
We have demonstrated how management of key orchard pests including the insect invasive species Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) can be accomplished using a systems-level approach ...termed IPM-CPR (Integrated Pest Management-Crop Perimeter Restructuring) in apple. We conducted on-farm comparisons of IPM-CPR to standard management program for managing H. halys, Cydia pomonella (L.) (Lepidoptera: Tortricidae), Grapholita molesta (Busck) (Lepidoptera: Tortricidae), and Lygus lineolaris Palisot de Beauvois (Hemiptera: Miridae) in commercial apple orchards in 2014, 2016, and 2017 in New Jersey, Maryland, and Virginia. The presence and abundance of key pests and fruit injury at harvest were used as a measure of success of the program. We compared the amount of insecticide applied for each management program. In majority of instances, there were no differences in the IPM-CPR and the standard management program in terms of H. halys numbers in baited pyramid traps and stink bug injury at harvest. Damage from C. pomonella and G. molesta in the IPM-CPR treatment was significantly lower than the standard management program in 2014 and 2017. Amount of active ingredient used was on average 62.1% lower in the IPM-CPR treatment compared with standard management program. Despite a reduction in insecticide use, there were minimal impacts on beneficial insects. Overall, IPM-CPR in apples successfully managed key orchard pests, including H. halys, and used significantly less insecticide than a standard insecticide-based management program and could be adopted as a systems-level approach for pest population reduction.
Muscle-specific ankyrins 1 (sAnk1) are a group of small ankyrin 1 isoforms, of which sAnk1.5 is the most abundant. sAnk1 are localized in the sarcoplasmic reticulum (SR) membrane from where they ...interact with obscurin, a myofibrillar protein. This interaction appears to contribute to stabilize the SR close to the myofibrils. Here we report the structural and functional characterization of skeletal muscles from sAnk1 knockout mice (KO). Deletion of sAnk1 did not change the expression and localization of SR proteins in 4- to 6-mo-old sAnk1 KO mice. Structurally, the main modification observed in skeletal muscles of adult sAnk1 KO mice (4-6 mo of age) was the reduction of SR volume at the sarcomere A band level. With increasing age (at 12-15 mo of age) extensor digitorum longus (EDL) skeletal muscles of sAnk1 KO mice develop prematurely large tubular aggregates, whereas diaphragm undergoes significant structural damage. Parallel functional studies revealed specific changes in the contractile performance of muscles from sAnk1 KO mice and a reduced exercise tolerance in an endurance test on treadmill compared with control mice. Moreover, reduced Qγ charge and L-type Ca(2+) current, which are indexes of affected excitation-contraction coupling, were observed in diaphragm fibers from 12- to 15-mo-old mice, but not in other skeletal muscles from sAnk1 KO mice. Altogether, these findings show that the ablation of sAnk1, by altering the organization of the SR, renders skeletal muscles susceptible to undergo structural and functional alterations more evident with age, and point to an important contribution of sAnk1 to the maintenance of the longitudinal SR architecture.
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