Skeletal muscle regeneration depends on the correct expansion of resident quiescent stem cells (satellite cells), a process that becomes less efficient with aging. Here, we show that mitochondrial ...dynamics are essential for the successful regenerative capacity of satellite cells. The loss of mitochondrial fission in satellite cells—due to aging or genetic impairment—deregulates the mitochondrial electron transport chain (ETC), leading to inefficient oxidative phosphorylation (OXPHOS) metabolism and mitophagy and increased oxidative stress. This state results in muscle regenerative failure, which is caused by the reduced proliferation and functional loss of satellite cells. Regenerative functions can be restored in fission-impaired or aged satellite cells by the re-establishment of mitochondrial dynamics (by activating fission or preventing fusion), OXPHOS, or mitophagy. Thus, mitochondrial shape and physical networking controls stem cell regenerative functions by regulating metabolism and proteostasis. As mitochondrial fission occurs less frequently in the satellite cells in older humans, our findings have implications for regeneration therapies in sarcopenia.
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•Mitochondrial fission increases in satellite cells (SCs) after muscle injury•Mitochondrial fission boosts SC proliferation by inducing OXPHOS and proteostasis•DRP1 loss in SCs (genetically or during aging) impairs muscle regeneration•Normalizing mitochondrial dynamics in aged SCs restores muscle regeneration
Hong et al. illustrate that mitochondrial dynamics are required for tissue regeneration. Mitochondrial fission facilitates stem cell function via OXPHOS and mitophagy regulation. The genetic (or aging-related) loss of the mitochondrial fission regulator DRP1 in muscle stem cells blunts their proliferation and regenerative capacity, whereas DRP1 re-establishment rescues these defects.
The particle size of the food resource strongly determines the structure and dynamics of food webs. However, the ecological implications of carcass size variation for scavenging networks structure ...and functioning have been largely overlooked. Here we investigate differences in scavenging patterns due to carcass size in a complex vertebrate scavenger community, Hluhluwe‐iMfolozi Park, South Africa, while taking into account seasonality. We monitored the consumption of three types of experimental carcasses: ‘small’ (< 10 kg), ‘medium’ (10–100 kg) and ‘large’ (> 100 kg). We employed general lineal models to explore the influence of carcass size on 1) scavenging network structure (scavenger species richness per carcass) and 2) functioning (carcass detection time, consumption time, consumption rate and percentage of carrion consumed). We also tested whether the structure of the scavenging network of each carcass size was nested, i.e. whether the scavenging assemblage in species‐poor carcasses was a subset of the assemblage consuming species‐rich carcasses. We found strong evidence indicating that carcass size is a major factor governing the associated scavenger assemblage. Scavenger species richness per carcass and carcass consumption time and rate increased with carcass size, while carcass detection time and percentage of carrion biomass consumed were negatively related to carcass size. Strikingly, most of the carrion biomass was consumed by facultative scavengers, represented by large mammalian carnivores, rather than by obligate scavengers (i.e. vultures). Scavenging network nestedness tended to be higher at larger carcasses, and nestedness was sensitive to the removal of the most connected species in the network (spotted hyena) rather than vultures. When comparing scavenging and predation assemblages, crucial size‐dependent differences emerge. Also, we identified a traditionally ignored mechanism by which hunting large prey could be relatively less profitable for predators, namely the costs associated with competition from scavengers and decomposers.
Loss of skeletal muscle mass and function is a hallmark of aging. This phenomenon has been related to a dysregulation of mitochondrial function and proteostasis. Calorie restriction (CR) has been ...demonstrated to delay aging and preserve function until late in life, particularly in muscle. Recently, we reported the type of dietary fat plays an important role in determining life span extension with 40% CR in male mice. In these conditions, lard fed mice showed an increased longevity compared to mice fed soybean or fish oils. In this article, we analyze the effect of 40% CR on muscle mitochondrial mass, autophagy, and mitochondrial dynamics markers in mice fed these diets. In CR fed animals, lard preserved muscle fibers structure, mitochondrial ultrastructure, and fission/fusion dynamics and autophagy, not only compared to control animals, but also compared with CR mice fed soybean and fish oils as dietary fat. We focus our discussion on dietary fatty acid saturation degree as an essential predictor of life span extension in CR mice.
Sorafenib is the unique accepted molecular targeted drug for the treatment of patients in advanced stage of hepatocellular carcinoma. The current study evaluated cell signaling regulation of ...endoplasmic reticulum (ER) stress, c‐Jun‐N‐terminal kinase (JNK), Akt, and 5′AMP‐activated protein kinase (AMPK) leading to autophagy and apoptosis induced by sorafenib. Sorafenib induced early (3–12 hr) ER stress characterized by an increase of Ser51P‐eIF2α/eIF2α, C/EBP homologous protein (CHOP), IRE1α, and sXBP1, but a decrease of activating transcription factor 6 expression, overall temporally associated with the increase of Thr183,Tyr185P‐JNK1/2/JNK1/2, Thr172P‐AMPKα, Ser413P‐Foxo3a, Thr308P‐AKt/AKt and Thr32P‐Foxo3a/Foxo3a ratios, and reduction of Ser2481P‐mammalian target of rapamycin (mTOR)/mTOR and protein translation. This pattern was related to a transient increase of tBid, Bim
EL, Beclin‐1, Bcl‐xL, Bcl‐2, autophagy markers, and reduction of myeloid cell leukemia‐1 (Mcl‐1) expression. The progressive increase of CHOP expression, and reduction of Thr308P‐AKt/AKt and Ser473P‐AKt/AKt ratios were associated with the reduction of autophagic flux and an additional upregulation of Bim
EL expression and caspase‐3 activity (24 hr). Small interfering‐RNA (si‐RNA) assays showed that Bim, but not Bak and Bax, was involved in the induction of caspase‐3 in sorafenib‐treated HepG2 cells. Sorafenib increased autophagic and apoptotic markers in tumor‐derived xenograft model. In conclusion, the early sorafenib‐induced ER stress and regulation of JNK and AMPK‐dependent signaling were related to the induction of survival autophagic process. The sustained drug treatment induced a progressive increase of ER stress and PERK‐CHOP‐dependent rise of Bim
EL, which was associated with the shift from autophagy to apoptosis. The kinetic of Bim
EL expression profile might also be related to the tight balance between AKt‐ and AMPK‐related signaling leading to Foxo3a‐dependent BIM
EL upregulation.
The early sorafenib‐induced endoplasmic reticulum (ER) stress and regulation of JNK and AMPK‐dependent signaling were related to the induction of survival autophagic process. The sustained drug treatment induced a progressive increase of ER stress and PERK‐CHOP‐dependent rise of BimEL, which was associated with the shift from autophagy to apoptosis.
A few studies have assessed the observed fibrosis progression between serial liver biopsies (LB) in human immunodeficiency virus (HIV) / hepatitis C virus (HCV)‐coinfected patients. Approximately ...half of the patients progressed at least one fibrosis stage over a short period of time. The risk factors for this fast progression need clarification. Because of this, we evaluated the observed fibrosis progression rates of HIV/HCV‐coinfected patients and the risk factors for accelerated progression. Overall, 135 HIV‐infected patients with positive serum HCV RNA, without other possible causes of liver disease, who underwent two LB, separated at least by 1 year, were included in this retrospective cohort study. The median (Q1‐Q3) time between both LBs was 3.3 (2.0‐5.2) years. Patients showed the following changes in fibrosis stage: regression ≥1 stage: 23 (17%), no change: 52 (39%), progression 1 stage: 38 (28%), and progression ≥2 stages: 22 (16%). Seventeen (13%) patients had cirrhosis in the second biopsy. Factors independently associated with progression ≥1 stage were undetectable plasma HIV RNA during the follow‐up (relative risk RR 95% confidence interval, 95% CI 0.61 0.39‐0.93, P = 0.03), moderate‐to‐severe lobular necroinflammation (1.77 1.16‐2.7, P = 0.009), time between biopsies (1.11 1.08‐1.2, P = 0.01), and end of treatment response to anti‐HCV therapy (0.41 0.19‐0.88, P = 0.02). Conclusion: Fibrosis progresses with high frequency in HIV/HCV‐coinfected patients over a period of time of 3 years. Absent‐to‐mild lobular necroinflammation at baseline, achievement of response with anti‐HCV treatment, and effective antiretroviral therapy are associated with slower fibrosis progression. (HEPATOLOGY 2009.)
•Spatial mismatches between ecosystem services supply and demand increase over time due to urban sprawl and population growth.•Maps of supply-demand mismatches provide insights for land-use planning ...beyond administrative boundaries.•High-resolution quantitative methods of ecosystem services mapping facilitate multiscale land-use planning.
Global trends in land-use changes, including urbanization and abandonment of rural areas, have important repercussions for the supply and demand of ecosystem services (ES). In this study, we assessed and mapped the supply and demand of three ES (water provision, climate regulation, and outdoor recreation) along an urban-rural gradient in the Madrid region (Spain) from 1990 to 2012. We mapped ES supply, based on land use/land cover (LULC) data, using InVEST models and complementary methods, and ES demand, using population density and demand indicators. Then, we explored spatial supply-demand mismatches at a municipality spatial scale. Despite an increase in ES supply in some areas, a general increase in ES demand led to increasing dependence by the Madrid metropolitan area on outlying areas. We found that the number of municipalities that exhibited mismatches between the supply and demand in ES increased throughout the study period, due mainly to urban sprawl. Our results suggest the need for comprehensive land-use planning at the regional scale, taking into account that many ES flows reach beyond municipality boundaries. Finally, we discuss the utility of analyzing spatial mismatches in the supply and demand of ES for land-use planning and decision-making.
The effect of fire on soil organic matter—a review González-Pérez, José A.; González-Vila, Francisco J.; Almendros, Gonzalo ...
Environment International,
08/2004, Letnik:
30, Številka:
6
Book Review, Journal Article
Recenzirano
The extent of the soil organic carbon pool doubles that present in the atmosphere and is about two to three times greater than that accumulated in living organisms in all Earth's terrestrial ...ecosystems. In such a scenario, one of the several ecological and environmental impacts of fires is that biomass burning is a significant source of greenhouse gases responsible for global warming. Nevertheless, the oxidation of biomass is usually incomplete and a range of pyrolysis compounds and particulate organic matter (OM) in aerosols are produced simultaneously to the thermal modification of pre-existing C forms in soil. These changes lead to the evolution of the OM to “pyromorphic humus”, composed by rearranged macromolecular substances of weak colloidal properties and an enhanced resistance against chemical and biological degradation. Hence the occurrence of fires in both undisturbed and agricultural ecosystems may produce long-lasting effects on soils' OM composition and dynamics. Due to the large extent of the C pool in soils, small deviations in the different C forms may also have a significant effect in the global C balance and consequently on climate change. This paper reviews the effect of forest fires on the quantity and quality of soils' OM. It is focused mainly on the most stable pool of soil C; i.e., that having a large residence time, composed of free lipids, colloidal fractions, including humic acids (HA) and fulvic acids (FA), and other resilient forms. The main transformations exerted by fire on soil humus include the accumulation of new particulate C forms highly resistant to oxidation and biological degradation including the so-called “black carbon” (BC). Controversial environmental implications of such processes, specifically in the stabilisation of C in soil and their bearing on the global C cycle are discussed.
Deep learning is nowadays at the forefront of artificial intelligence. More precisely, the use of convolutional neural networks has drastically improved the learning capabilities of computer vision ...applications, being able to directly consider raw data without any prior feature extraction. Advanced methods in the machine learning field, such as adaptive momentum algorithms or dropout regularization, have dramatically improved the convolutional neural networks predicting ability, outperforming that of conventional fully connected neural networks. This work summarizes, in an intended didactic way, the main aspects of these cutting-edge techniques from a medical imaging perspective.
Childhood obesity has reached epidemic levels and is a serious health concern associated with metabolic syndrome, nonalcoholic fatty liver disease, and gut microbiota alterations. Physical exercise ...is known to counteract obesity progression and modulate the gut microbiota composition. This study aims to determine the effect of a 12-week strength and endurance combined training program on gut microbiota and inflammation in obese pediatric patients. Thirty-nine obese children were assigned randomly to the control or training group. Anthropometric and biochemical parameters, muscular strength, and inflammatory signaling pathways in mononuclear cells were evaluated. Bacterial composition and functionality were determined by massive sequencing and metabolomic analysis. Exercise reduced plasma glucose levels and increased dynamic strength in the upper and lower extremities compared with the obese control group. Metagenomic analysis revealed a bacterial composition associated with obesity, showing changes at the phylum, class, and genus levels. Exercise counteracted this profile, significantly reducing the Proteobacteria phylum and Gammaproteobacteria class. Moreover, physical activity tended to increase some genera, such as Blautia, Dialister, and Roseburia, leading to a microbiota profile similar to that of healthy children. Metabolomic analysis revealed changes in short-chain fatty acids, branched-chain amino acids, and several sugars in response to exercise, in correlation with a specific microbiota profile. Finally, the training protocol significantly inhibited the activation of the obesity-associated NLRP3 signaling pathway. Our data suggest the existence of an obesity-related deleterious microbiota profile that is positively modified by physical activity intervention. Exercise training could be considered an efficient nonpharmacological therapy, reducing inflammatory signaling pathways induced by obesity in children via microbiota modulation.
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