Dynamic shoulder dynamometry: a way to develop delay onset muscle soreness in shoulder muscles

A dynamic shoulder dynamometer has been designed to develop a vertical downward force over a measured range of motion, i.e. scapular elevation. The dynamometer is force-controlled to apply a required force within the range of motion. Calibration procedures were performed to assess the reliability of the force and displacement measurements. The system is designed to operate in isometric or eccentric conditions. For eccentric exercise the dynamometer has, for the first time, provided possibilities to elicit delay onset muscle soreness in shoulder muscles. In future, the apparatus will enable investigations of sensory-motor interactions in the shoulder region.     

Morphological evidence for neural interactions between leptin and orexin in the hypothalamus

Both leptin and orexin have been recently discovered as peptides involved in feeding regulation. The morphological evidence of neural interaction between leptin and orexin, one considered to inhibit food intake and the other to stimulate it in the central nervous system (CNS), was studied by use of double immunostaining method. The leptin receptor-like immunoreactive (LR-LI) neurons in the hypothalamic arcuate nucleus and ventromedial nucleus were innervated by orexin-like immunoreactive (OX-LI) neurons. The distribution of LR-LI neurons in the hypothalamus was very similar to that of OX-LI neurons. These results may suggest that leptin and orexin are intimately correlated with each other and that they reciprocally regulate feeding at the hypothalamic level.     

Dynamic modeling of complex biological systems: a link between metabolic and macroscopic description

In this study, a class of dynamic models based on metabolic reaction pathways is analyzed, showing that systems with complex intracellular reaction networks can be represented by macroscopic reactions relating extracellular components only. Based on rigorous assumptions, the model reduction procedure is systematic and allows an equivalent 'input-output' representation of the system to be derived. The procedure is illustrated with a few examples.     

Analysis of the effects of modulatory agents on a modeled bursting neuron: Dynamic interactions between voltage and calcium dependent systems

In a computational model of the bursting neuron R15, we have implemented proposed mechanisms for the modulation of two ionic currents (I _R andI _SI) that play key roles in regulating its spontaneous electrical activity. The model was sufficient to simulate a wide range of endogenous activity in the presence of various concentrations of serotonin (5-HT) or dopamine (DA). The model was also sufficient to simulate the responses of the neuron to extrinsic current pulses and the ways in which those responses were altered by 5-HT or DA. The results suggest that the actions of modulatory agents and second messengers on this neuron, and presumably other neurons, cannot be understood on the basis of their direct effects alone. It is also necessary to take into account the indirect effects of these agents on other unmodulated ion channels. These indirect effects occur through the dynamic interactions of voltage-dependent and calcium-dependent processes.     

Electronic structure and stabilities of Ni-doped germanium nanoclusters: a density functional modeling study

The present study reports the geometry, electronic structure, growth behavior and stability of neutral and ionized nickel encapsulated germanium clusters containing 1–20 germanium atoms within the framework of a linear combination of atomic orbital density functional theory (DFT) under a spin polarized generalized gradient approximation. In the growth pattern, Ni-capped Ge_n and Ni-encapsulated Ge_n clusters appear mostly as theoretical ground state at a particular size. To explain the relative stability of the ground state clusters, variation of different parameters, such as average binding energy per atom (BE), embedding energy (EE) and fragmentation energy (FE) of the clusters, were studied together with the size of the cluster. To explain the chemical stability of the clusters, different parameters, e.g., energy gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO gap), ionization energy (IP), electron affinity (EA), chemical potential (μ), chemical hardness (η), and polarizability etc. were calculated and are discussed. Finally, natural bond orbital (NBO) analysis was applied to understand the electron counting rule applied in the most stable Ge₁₀Ni cluster. The importance of the calculated results in the design of Ge-based superatoms is discussed.

Resilience in a two-population system: interactions between Allee effects and connectivity

Resilience in ecosystems and resistance to regime shifts has been a major focus in ecological research. How migration and general network dynamics affect the resilience of populations or induce regime shift cascades is a particularly challenging open question in theoretical ecology. We focus on regime shifts in populations with variable-strength Allee effects to demonstrate the effect of migration on resilience in two-population systems with critical transitions. The result is a mathematical model that justifies the assumption that resilience can be averaged across connected populations and suggests several management strategies to either avoid or induce regime shift cascades.     

The interplay between density- and trait-mediated effects in predator-prey interactions: a case study in aphid wing polymorphism

Natural enemies not only influence prey density but they can also cause the modification of traits in their victims. While such non-lethal effects can be very important for the dynamic and structure of prey populations, little is known about their interaction with the density-mediated effects of natural enemies. We investigated the relationship between predation rate, prey density and trait modification in two aphid-aphid predator interactions. Pea aphids (Acyrthosiphon pisum, Harris) have been shown to produce winged dispersal morphs in response to the presence of ladybirds or parasitoid natural enemies. This trait modification influences the ability of aphids to disperse and to colonise new habitats, and hence has a bearing on the population dynamics of the prey. In two experiments we examined wing induction in pea aphids as a function of the rate of predation when hoverfly larvae (Episyrphus balteatus) and lacewing larvae (Chrysoperla carnea) were allowed to forage in pea aphid colonies. Both hoverfly and lacewing larvae caused a significant increase in the percentage of winged morphs among offspring compared to control treatments, emphasising that wing induction in the presence of natural enemies is a general response in pea aphids. The percentage of winged offspring was, however, dependent on the rate of predation, with a small effect of predation on aphid wing induction at very high and very low predation rates, and a strong response of aphids at medium predation rates. Aphid wing induction was influenced by the interplay between predation rate and the resultant prey density. Our results suggests that density-mediated and trait-mediated effects of natural enemies are closely connected to each other and jointly determine the effect of natural enemies on prey population dynamics.     

Multiplicity of interactions between dromedary hemoglobin and solvent components. A structural and functional study

The interaction of dromedary hemoglobin with various solvent components [2-(p-chlorophenoxy)-2-methylpropionic acid (CFA), 2,3-bisphospho-D-glycerate (glycerate-2,3-P2) and chloride] has been studied. 1. CFA greatly lowers the oxygen affinity of dromedary hemoglobin. 2. The oxygen-linked CFA binding sites are probably located in the deoxy derivative at the alpha cleft, while in the oxy form and in the presence of two other effectors (glycerate-2,3-P2 and chloride) additional, structurally and possibly functionally relevant binding site(s) should be considered. 3. Both CFA and glycerate-2,3-P2 stabilize the deoxy-like tertiary structure in the oxy derivative. 4. Chloride appears to be fundamental to obtain quaternary structural changes. 5. Interaction energy, retained in the protein when the three ligands (CFA, glycerate-2,3-P2 and chloride) are bound to the oxy form, favours intermediates not stable if only one or two allosteric effector(s) is (are) present on the protein. 6. The oxygen affinity appears to be related to both tertiary and quaternary structural changes, while cooperatively is largely invariant with solvent conditions. In conclusion, the functional properties of dromedary hemoglobin do not depend in any simple way on the variety of stabilized conformations.     

A density functional theory study on the hydrogen bonding interactions between luteolin and ethanol

Ethanol is one of the most commonly used solvents to extract flavonoids from propolis. Hydrogen bonding interactions play an important role in the properties of liquid system. The main objective of the work is to study the hydrogen bonding interactions between flavonoid and ethanol. Luteolin is a very common flavonoid that has been found in different geographical and botanical propolis. In this work, it was selected as the representative flavonoid to do detailed research. The study was performed from a theoretical perspective using density functional theory (DFT) method. After careful optimization, there exist nine optimized geometries for the luteolin ? CH₃CH₂OH complex. The binding distance of X ? H···O, and the bond length, vibrational frequency, and electron density changes of X ? H all indicate the formation of the hydrogen bond in the optimized geometries. In the optimized geometries, it is found that: (1) except for the H2’, H5’, and H6’, CH₃CH₂OH has formed hydrogen bonds with all the hydrogen and oxygen atoms in luteolin. The hydrogen atoms in the hydroxyl groups of luteolin form the strongest hydrogen bonds with CH₃CH₂OH; (2) all of the hydrogen bonds are closed-shell interactions; (3) the strongest hydrogen bond is the O3’ ? H3’···O in structure A, while the weakest one is the C3 ? H3···O in structure E; (4) the hydrogen bonds of O3’ ? H3’···O, O ? H···O4, O ? H···O3’ and O ? H···O7 are medium strength and covalent dominant in nature. While the other hydrogen bonds are weak strength and possess a dominant character of the electrostatic interactions in nature.     

A density functional theory study on the interactions between dibenzothiophene and tetrafluoroborate-based ionic liquids

The interactions between dibenzothiophene (DBT) and N-butyl-N-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), N-butyl-N-methylmorpholinium tetrafluoroborate ([Bmmorpholinium][BF₄]), N-butyl-N-methylpiperdinium tetrafluoroborate ([BMPiper][BF₄]), N-butyl-N-methylpyrrolidinium tetrafluoroborate ([BMPyrro][BF₄]), and N-butylpyridinium tetrafluoroborate ([BPY][BF₄]) were investigated using density functional theory approach. Geometric, electron, and topological properties were analyzed using natural bond orbital, atoms in molecules theory, and noncovalent interaction methods in order to understand intermolecular interactions between DBT and ionic liquids. The result shows that hydrogen bond and van der Waals interactions are widespread in all the ionic liquids-DBT systems. Ion-π interactions between DBT and cation or anion are also observed, while π⁺-π interactions are only found in the [BMIM][BF₄]-DBT and [BPY][BF₄]-DBT systems. The order of interaction energy is [BPY][BF4]-DBT > [BMIM][BF₄]-DBT >> [BMPiper][BF₄]-DBT > [BMPyrro][BF₄]-DBT > [BMmorpholinum][BF₄]-DBT. The energies between DBT and the two ionic liquids containing aromatic cations are significantly higher.     

Non-polar interactions between cholesterol and phospholipids: a molecular dynamics simulation study

A 15-ns molecular dynamics simulation of the fully hydrated dimyristoylphosphatidylcholine-cholesterol (DMPC-Chol) bilayer containing approximately 22 mol% Chol was carried out. An 8-ns trajectory was analysed to investigate the effect of Chol on the chain packing in the bilayer core. While the packing of DMPC chains on the smooth alpha-face side of the Chol ring is similar to that in the pure DMPC bilayer, the packing on the rough beta-face side is less regular and less tight. Two methyl groups located on the Chol beta-face disturb the packing; in effect, van der Waals (vdW) interactions between Chol rings and DMPC chains are weaker than the ones between sole DMPC chains. VdW interactions between an alkyl chain of DMPC and an isooctyl tail of Chol are similarly strong as those between two DMPC chains.     

Dynamic interactions between transposable elements and their hosts

Transposable elements (TEs) have a unique ability to mobilize to new genomic locations, and the major advance of second-generation DNA sequencing has provided insights into the dynamic relationship between TEs and their hosts. It now is clear that TEs have adopted diverse strategies - such as specific integration sites or patterns of activity - to thrive in host environments that are replete with mechanisms, such as small RNAs or epigenetic marks, that combat TE amplification. Emerging evidence suggests that TE mobilization might sometimes benefit host genomes by enhancing genetic diversity, although TEs are also implicated in diseases such as cancer. Here, we discuss recent findings about how, where and when TEs insert in diverse organisms.     

Early medication use in new-onset rheumatoid arthritis may delay joint replacement: results of a large population-based study

IntroductionUse of disease-modifying anti-rheumatic drugs (DMARDs) in rheumatoid arthritis (RA) may prevent joint damage and potentially reduce joint replacement surgeries. We assessed the association between RA drug use and joint replacement in Quebec, Canada.MethodsA cohort of new-onset RA patients was identified from Quebec’s physician billing and hospitalization databases from 2002–2011. The outcome was defined using procedure codes submitted by orthopedic surgeons. Medication use was obtained from pharmacy databases. We used alternative Cox regression models with time-dependent variables measuring the cumulative effects of past use during different time windows (one model focussing on the first year after cohort entry) for methotrexate (MTX), and other DMARDs. Models were adjusted for baseline sociodemographics, co-morbidity and prior health service use, time-dependent cumulative use of other drugs (anti-tumor necrosis factor [anti-TNF] agents, other biologics, cyclooxygenase-2 inhibitors [COXIBs], nonselective nonsteroidal antiinflammatory drugs [NSAIDs], and systemic steroids), and markers of disease severity.ResultsDuring follow-up, 608 joint replacements occurred among 11,333 patients (median follow-up: 4.6 years). The best-fitting model relied on the cumulative early use (within the first year after cohort entry) of MTX and of other DMARDs, with an interaction between MTX and other DMARDs. In this model, greater exposure within the first year, to either MTX (adjusted hazard ratio, HR = 0.95 per 1 month, 95 % confidence interval, 95 % CI 0.93-0.97) or other DMARDs (HR = 0.97, 95 % CI 0.95-0.99) was associated with longer time to joint replacement.ConclusionsOur results suggest that longer exposure to either methotrexate (MTX) or other DMARDs within the first year after RA diagnosis is associated with longer time to joint replacement surgery.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0713-3) contains supplementary material, which is available to authorized users.     

Beyond Mg2+: functional interactions between RNA and transition metals

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Competitive interactions between an exotic and a native ladybeetle: a field cage study

We conducted field‐cage studies on the direct interactions between a coccinellid species native to North America, Coleomegilla maculata De Geer, and a species introduced from Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). We compared the mortality and weight gain of larvae of both species in field cages that enclosed one or both species with corn plants containing high or low aphid numbers. We did not find a significant effect of the presence of H. axyridis on the survival or weight gain of C. maculata, but H. axyridis larvae weighed more when kept with C. maculata for 5 days than when kept with equal numbers of conspecifics. This suggests that intraspecific competition was stronger for H. axyridis than the interspecific competition with C. maculata. The spatial distribution of C. maculata over the plants differed between single‐species and two‐species treatments in a manner that suggested that this species avoided interactions with H. axyridis.     

Dynamic proteomics in modeling of the living cell. Protein-protein interactions

This review is devoted to describing, summarizing, and analyzing of dynamic proteomics data obtained over the last few years and concerning the role of protein-protein interactions in modeling of the living cell. Principles of modern high-throughput experimental methods for investigation of protein-protein interactions are described. Systems biology approaches based on integrative view on cellular processes are used to analyze organization of protein interaction networks. It is proposed that finding of some proteins in different protein complexes can be explained by their multi-modular and polyfunctional properties; the different protein modules can be located in the nodes of protein interaction networks. Mathematical and computational approaches to modeling of the living cell with emphasis on molecular dynamics simulation are provided. The role of the network analysis in fundamental medicine is also briefly reviewed.