Ageing Effect Evaluation on HD-sEMG Signals Using CCA Approach

ObjectivesThe objective of the proposed study is to exploit the technology of high-density surface electromyography (HD-sEMG), in order to evaluate the muscle activation in young and elderly subjects during a daily life gesture, namely, Sit To Stand (STS), using wireless connected ambulatory equipment (TMSi©) and Blind Source Separation (BSS) approach with Canonical Correlation Analysis (CCA).Materials and methodsSixteen subjects participated (50% females) divided into two categories (‘H1’: young (30.62 yrs ±5.92, 23.95 kg/m² ±3.08), versus ‘H2’: old (61.87 yrs ±7.98, 23.4 kg/m² ±3.38)), in the recording of HD-sEMG signals, using 32-electrodes square grids (4×8), during Sit To Stand (STS) motion, three times at spontaneous speed. The studied muscle is the Rectus Femoris (RF) muscle. The recorded HD-sEMG signals were analyzed with CCA approach to extract correlation coefficient sets according to two age categories (young versus old), in order to evaluate its discriminating power with ageing. Statistical tests (t-test) were used to evaluate the discrimination for these two categories.ResultsThe calculation of CCA correlation coefficients showed a significant difference between young and old category concerning the mean CCA correlation coefficient (P<0.001***) and also the standard deviation of the CCA correlation coefficients (P<0.0001****).ConclusionThe obtained results are promising and indicate a clear difference between the obtained source variability using CCA method between the young and the old tested subjects during daily life motion. Furthermore, these estimated sources seem to be impacted by both anatomical and functional modifications with ageing.     

The citrus plant pathogen Xanthomonas citri has a dual polyamine-binding protein

ATP-Binding Cassette transporters (ABC transporters) are protein complexes involved in the import and export of different molecules, including ions, sugars, peptides, drugs, and others. Due to the diversity of substrates, they have large relevance in physiological processes such as virulence, pathogenesis, and antimicrobial resistance. In Xanthomonas citri subsp. citri, the phytopathogen responsible for the citrus canker disease, 20% of ABC transporters components are expressed under infection conditions, including the putative putrescine/polyamine ABC transporter, PotFGHI. Polyamines are ubiquitous molecules that mediate cell growth and proliferation and play important role in bacterial infections. In this work, we characterized the X. citri periplasmic-binding protein PotF (XAC2476) using bioinformatics, biophysical and structural methods. PotF is highly conserved in Xanthomonas sp. genus, and we showed it is part of a set of proteins related to the import and assimilation of polyamines in X. citri. The interaction of PotF with putrescine and spermidine was direct and indirectly shown through fluorescence spectroscopy analyses, and experiments of circular dichroism (CD) and small-angle X-ray scattering (SAXS), respectively. The protein showed higher affinity for spermidine than putrescine, but both ligands induced structural changes that coincided with the closing of the domains and increasing of thermal stability.     

Effect of spatial and temporal patterns of stress and disturbance intensities in a sub-Mediterranean grassland

Abstract

The present study examined a sub-Mediterranean pastoral system in the central Apennines (Italy) with a long history of grazing, where winter cold stress is alternated with summer drought stress. The research goals were to ascertain whether different floristic structures correspond to different stress conditions (xeric and semimesic), and whether peculiar functional plant traits (such as avoidance and tolerance mechanisms) respond to stress/disturbance intensities, and understand how vegetation reacts to changeable livestock pressure (through floristic and plant trait variations). Cluster analysis indicated that separate communities develop under different stress intensities. Other analyses highlighted how avoidance strategies predominate within the pastoral system. Observations of grazed and ungrazed patches conducted in 10-m transects revealed spiny cushion formation in semimesic grassland, where a brief period of overgrazing occurs in late summer, causing variations in plant community structure. All these results confirm the importance of historical grazing and current land use, showing how small disturbances and stress variations cause ecosystem responses. Best practices for management were identified. In xeric conditions, it is advisable that the intensity of disturbance be lessened, while in semimesic grassland overgrazing should be forbidden during the dry period, because it could facilitate the development of spiny patches, and subsequent spread of Brachypodium rupestre.     

Adverse responses of Cabera pusaria caterpillars to high dietary manganese concentration

The adaptation of insects to environmental changes can constitute a crucial factor in their development and activity. The response of Cabera pusaria L. (Lepidoptera: Geometridae) caterpillars to high manganese (Mn) concentrations in the diet was studied. Birch leaves were treated by dipping in MnCl₂·4H₂O solutions, thereby achieving Mn contents of 370 (T0), 695 (T1), 3 198 (T2), and 6 302 mg kg⁻¹ (T3). The reactions were determined by observing caterpillar mortality, development time, food consumption, and pupal weight. Manganese concentrations in larval excrement, pupae, and food were determined. Manganese in the diet at unnaturally increased concentrations caused great stress for caterpillars. All individuals in the treatment with the highest Mn concentration (T3) died during rearing and successful pupation occurred in only four individuals in T2. Even in the case of caterpillars from T1 (twofold higher than T0) a negative reaction (increased food consumption and prolonged development) was recorded. We also determined significantly increased Mn concentration in pupae from T1 (T2 and T3 were not included in this evaluation due to mortality) and excrement (T1‒T3) compared with T0 having a natural Mn concentration. Caterpillars were seen to eliminate negatively acting dietary Mn by its translocation to excrement. However, the highest mortality rate in T2 and T3 and negative reactions of individuals in T1 very likely demonstrate energy insufficiency and the high energy requirements of Mn elimination mechanisms.     

Paleofloristic diversity and paleoenvironmental interpretation of new Cisuralian localities in the south-central sector of the Anticlinorium of Huayacocotla,Hidalgo, Mexico

The Anticlinorium of Huayacocotla has several outcrops of geological and paleontological importance. However, reports of localities with paleoflora have been scarce so far. In this study, we report three new localities in the Cisuralian, the diversity and composition of which lead us to propose that the paleoflora may have been derived from vegetation that grew in an arid environment with seasonal wetness. The plant remains from the localities of Papaxtla and Calnali are highly transported and their diversity indicates the presence of several groups of plants that were shared with the La Virgen locality, which yielded the best preserved plant fossils. Changes in paleoenvironmental conditions indicate that the preservation of the flora was affected by the tectonic evolution of the region associated with sea level changes. The data presented here increase our knowledge of both the Cisuralian fossil flora and paleoenvironment in the south-central region of the Huayacocotla Anticlinorium, Hidalgo state.     

Molecular insights into the mechanisms of cation-type specific stability and denaturation of poly-l-glutamate: a simulation study

Cation-induced conformational changes of peptide as a guide to developing insights into human diseases-related proteins have received a lot of attention. The interactions between poly-l-glutamate (PGA) and different cations, including Na⁺, K⁺ and Mg²⁺, respectively, are studied in solvent at a concentration of 1 M, and the behaviours of peptide with different cations are investigated. For Na⁺, an oscillatory stabilising process to α-helix PGA is found, in accordance with the uniform free-energy landscape, whereas for K⁺, an extended α-helix structure is formed by the terminal turns, suggesting a weaker attraction to charged head groups. For Mg²⁺, the bridged charged side chains are responsible for the maximum probability of helix state. These distinct structural changes can be attributed to the different interactions between charged head groups and cations. Both Na⁺ and K⁺ are mainly attracted around head groups by direct ion binding while Mg²⁺ is centrally trapped among adjacent charged head groups. In addition, a surprising shift of the backbone hydrogen bond, from intact state to intermediate state, is observed. This is opposite to the stabilising effect of Na⁺ around negatively charged head groups.     

Ultrafast molecular dynamics of biofuel extraction for microalgae and bacteria milking: blocking membrane folding pathways to damaged lipid-bilayer conformations with nanomicelles

Cell milking is a 100% renewable green energy for CO₂ by extraction of biofuels inside the cytosol of photosynthetic micro-organisms as microalgae and bacteria. The cells are exposed to a hydrophobic solvent forming holes and cracks through their membranes from which the biofuels can leak out. In protein folding, the goal would be to find pathways to the unique functional protein conformer. However, in the lipid-bilayer interaction with the solvent for milking, the objective is to block the pathways for damaged membrane conformations of low free energy with undesired nanostructures, using the solvent properties, as shown with an ab initio structural bioinformatic model. Statistical thermodynamics is used to compute the free energy (including entropy) from the molecular dynamics trajectory of the biomolecular system with many conformational changes. This model can be extended to the general problem of biomolecules folding as for proteins and nucleic acids. Using an adaptation of the Einstein diffusion law, the conformational change dynamics of the lipid bilayer depends on the two diffusion coefficients of the solvent: D₁ before the irreversible folding transition time and the much smaller D₂ thereafter. In contrast to the n-hexane and n-heptane hydrocarbons of smaller size, the residual D₂?=?4.7?×?10^?7?cm²/s of the n-decane solvent, with the highest partition coefficient among the three extractors, is the only to present a D₂ value that is significantly below the critical threshold of 10^?6?cm²/s. Therefore, the membrane would resist to long hydrocarbons and the exposed cells would remain viable for milking.     

Studying the collective motions of the adenosine A2A receptor as a result of ligand binding using principal component analysis

Abstract

Adenosine receptors (ARs) belong to family A of GPCRs that are involved in many diseases, including cerebral and cardiac ischemic diseases, immune and inflammatory disorders, etc. Thus, they represent important therapeutic targets to treat these conditions. Computational techniques such as molecular dynamics (MD) simulations permit researchers to obtain structural information about these proteins, and principal component analysis (PCA) allows for the identification of collective motions. There are available structures for the active form (3QAK) and the inactive form (3EML) of A2AR which permit us to gain insight about their activation/inactivation mechanism. In this work, we have proposed an inverse strategy using MD simulations where the active form was coupled to the antagonist caffeine and the inactive form was coupled to adenosine agonist. Moreover, we have included four reported thermostabilizing mutations in the inactive form to study A2AR structural differences under different conditions. Some observations stand out from the PCA studies. For instance, the apo structures showed remarkable similarities, and the principal components (PCs) were rearranged in a ligand-dependent manner. Additionally, the active conformation was less stable compared to the inactive one. Some PCs inverted their direction in the presence of a ligand, and comparison of the PCs between 3EML and 3EML_ADN showed that adenosine induced major changes in the structure of A2AR. Rearrangement of PCs precedes and drives conformational changes that occur after ligand binding. Knowledge about these conformational changes provides important insights about the activity of A2AR.     

Computational study of conformational changes in human 3-hydroxy-3-methylglutaryl coenzyme reductase induced by substrate binding

Abstract

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is mainly involved in the regulation of cholesterol biosynthesis. HMGR catalyses the reduction of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonate at the expense of two NADPH molecules in a two-step reversible reaction. In the present study, we constructed a model of human HMGR (hHMGR) to explore the conformational changes of HMGR in complex with HMG-CoA and NADPH. In addition, we analysed the complete sequence of the Flap domain using molecular dynamics (MD) simulations and principal component analysis (PCA). The simulations revealed that the Flap domain plays an important role in catalytic site activation and substrate binding. The apo form of hHMGR remained in an open state, while a substrate-induced closure of the Flap domain was observed for holo hHMGR. Our study also demonstrated that the phosphorylation of Ser872 induces significant conformational changes in the Flap domain that lead to a complete closure of the active site, suggesting three principal conformations for the first stage of hHMGR catalysis. Our results were consistent with previous proposed models for the catalytic mechanism of hHMGR.

Communicated by Ramaswamy H. Sarma     

The effect of immersion cleansers on gloss,colour and sorption of acetal denture base material

doi: 10.1111/j.1741‐2358.2012.00657.x The effect of immersion cleansers on gloss, colour and sorption of acetal denture base material Objective: To study the effect of peroxide and hypochlorite cleansers on gloss, colour and sorption of acetal denture resins. Materials and methods: Pink acetal and thermoplastic acrylic resins were evaluated. Thirty‐five specimens 39 × 39 × 1.8 mm of each resin were prepared. Each group of specimens (n = 7) was then immersed into cleansers for 100 days. Group I immersed in tap water, Group II in Corega Extradent for 5 min, Group III in Corega Extradent for 8 h, Group IV in NitrAdine? Seniors for 15 min and Group V in NaOCl 5.25%. Gloss, colour and weight measurements were taken initially and after 100 days. Data subjected to two‐way anova and Tukey’s test at α = 0.05. Results: Acrylic resin showed reductions of glossiness from ?5 to ?15 and acetal from ?0.2 to ?6. Colour changes (ΔΕ*) ranged from 2.64 to 7.64 for acrylic and 2.77 to 26.54 for acetal resin. Sorption for acrylic ranged from 11.64 to 17.06 μg/mm³ and 9.18 to 24.79 μg/mm³ for acetal resin. The results of (ΔΕ*) and sorption showed an interaction between denture resins and cleansers. Conclusions: The gloss of acetal resin was less affected by water, peroxides and NaOCl 5.25% compared with acrylic resin. Acetal resin showed clinically acceptable (ΔΕ*) whereas acrylic resin unacceptable ones for water and peroxide solutions. The immersion of acetal resin in NaOCl 5.25% showed clinically unacceptable (ΔΕ*) and higher sorption and should be avoided or should be managed with care.