On the Dynamical Behavior of the Cysteine Dioxygenase‐l‐Cysteine Complex in the Presence of Free Dioxygen and l‐Cysteine

In this work, viable models of cysteine dioxygenase (CDO) and its complex with l ‐cysteine dianion were built for the first time, under strict adherence to the crystal structure from X‐ray diffraction studies, for all atom molecular dynamics (MD). Based on the CHARMM36 FF, the active site, featuring an octahedral dummy Fe(II) model, allowed us observing water exchange, which would have escaped attention with the more popular bonded models. Free dioxygen (O₂) and l ‐cysteine, added at the active site, could be observed being expelled toward the solvating medium under Random Accelerated Molecular Dynamics (RAMD) along major and minor pathways. Correspondingly, free dioxygen (O₂), added to the solvating medium, could be observed to follow the same above pathways in getting to the active site under unbiased MD. For the bulky l ‐cysteine, 600 ns of trajectory were insufficient for protein penetration, and the molecule was stuck at the protein borders. These models pave the way to free energy studies of ligand associations, devised to better clarify how this cardinal enzyme behaves in human metabolism.     

Effects of external and surgically implanted dummy radio transmitters on mortality, swimming performance and physiological status of juvenile masu salmon Oncorhynchus masou

The effects of external and surgically implanted radio transmitters on juvenile masu salmon Oncorhynchus masou were examined. External attachment of transmitters significantly decreased the survival of fish and caused a decreased critical swimming speed compared with surgical implantation. Although plasma cortisol, plasma glucose and haematocrit values did not differ significantly among groups, it appeared that the most suitable transmitter attachment method for juvenile O. masou may be surgical implantation.     

A microtitre chemiluminescence sensor for detection of pyrethroids based on dual‐dummy‐template molecularly imprinted polymer and computational simulation

The residues of pyrethroids in foods of animal origin are dangerous to the consumers, so this study presented a chemiluminescence sensor for determination of pyrethroids in chicken samples. A dual‐dummy‐template molecularly imprinted polymer capable of recognizing 10 pyrethroids was synthesized. The results of computation simulation showed that the specific 3D conformations of the templates had important influences on the polymer' recognition ability. The polymer was used to prepare a sensor on conventional 96‐well microplates, and the sample solution was added into the wells for direct absorption. The absorbed analytes were initiated with the bis(2,4,6‐trichlorophenyl)oxalate–H₂O₂–imidazole system, and the chemiluminescence intensity was used for analyte quantification. Results showed that one assay was finished within 12 min, and this sensor could be reused four times. The limits of detection for the 10 analytes were in the range o0.3–6.0 pg/ml, and the recoveries from the standards of fortified blank chicken samples were in the range 70.5–99.7%.     

Estimating predation pressure in ecological studies: controlling bias imposed by using sentinel plasticine prey

Sentinel plasticine prey has been increasingly used to estimate predation pressure. The use of plasticine prey may, however, bias the results, as this method was originally designed to account for predation by organisms that can visually recognize the shapes and colors of their prey. To evaluate the limitations of using sentinel plasticine prey, we compared predator attack rates between real prey – dead and live mealworms, Tenebrio molitor L. (Coleoptera: Tenebrionidae) – and plasticine models in a monsoonal tropical rainforest of southeastern China. The attack rates by invertebrates were highest on dead prey followed by live prey and plasticine models, whereas the attack rates by vertebrates were lowest on dead prey, and did not differ between live prey and plasticine models. These results confirm that bias imposed by using the plasticine models is affected by the type of predators. In addition, we tested the validity and generality of the premise that predators can distinguish the shapes of plasticine model prey and preferentially attack a caterpillar-like shape over other shapes. To test this hypothesis, we conducted three independent experiments in China, Papua New Guinea, and Finland. In the two latter localities, predation rates on plasticine caterpillars were higher than on models of other shapes, whereas in China, these differences were not significant. Taken together, our study suggests that plasticine models may underestimate the predation by invertebrates to a greater extent than predation by vertebrates, and the preference of model shape by predators may be locality-specific, presumably due to differences in the composition of the predator community. We propose that predation be estimated on both live and plasticine prey in future studies to measure the potential bias imposed by using plasticine models and its variation among various habitats and predator groups.     

Instrumented hip implants: Electric supply systems

Instrumented hip implants were proposed as a method to monitor and predict the biomechanical and thermal environment surrounding such implants. Nowadays, they are being developed as active implants with the ability to prevent failures by loosening. The generation of electric energy to power active mechanisms of instrumented hip implants remains a question. Instrumented implants cannot be implemented without effective electric power systems. This paper surveys the power supply systems of seventeen implant architectures already implanted in-vivo, namely from instrumented hip joint replacements and instrumented fracture stabilizers. Only inductive power links and batteries were used in-vivo to power the implants. The energy harvesting systems, which were already designed to power instrumented hip implants, were also analyzed focusing their potential to overcome the disadvantages of both inductive-based and battery-based power supply systems. From comparative and critical analyses of the methods to power instrumented implants, one can conclude that: inductive powering and batteries constrain the full operation of instrumented implants; motion-driven electromagnetic energy harvesting is a promising method to power instrumented passive and active hip implants.     

Attacks by predators on artificial cryptic and aposematic insect larvae

Colour and colour patterns seem to be especially important visual warning signals for predators, which might have innate or learned ability to avoid aposematic prey. To test the importance of larval colour pattern of the aposematic ladybird Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), an invasive alien species in Europe, we presented the plasticine models of aposematic larvae to wild and naïve birds. We studied the attacks on aposematic larvae of various patterns and colours in nature and in an outdoor aviary. The larvae were cryptic (green), aposematic (resembling those of the H. axyridis larvae), and semi-aposematic (i.e., black but missing the typical orange patches of H. axyridis larvae). We detected attacks on 71 larvae out of 450 (i.e., 2.6% daily predation). Twenty-nine attacks were made by birds, 37 by arthropods, and five by gastropods. Wild birds attacked green and black larvae significantly more often than aposematic larvae. Colour did not have an effect on attacks by arthropods. The experiment with naïve birds was conducted in an outdoor aviary, where naïve great tits, Parus major L., were offered the same artificial larvae as in the first experiment. In total, 57 of 90 exposed larvae were attacked by birds (i.e., 28% daily predation), and green larvae were attacked significantly more than the aposematic larvae (but not more than black larvae). Our results imply that aposematic larvae of H. axyridis are more than 12× less likely to be predated by birds than green larvae in nature. The aposematic pattern represented a more effective signal than the semi-aposematic signal. The ability to reject aposematic prey seemed to be innate in our birds.     

The signaling pathway in histidine kinase and the response regulator complex revealed by X-ray crystallography and solution scattering

The structure of a histidine kinase (ThkA) complexed with a response regulator (TrrA) in the two-component regulatory system from hyperthermophile Thermotoga maritima was determined by a combination of X-ray crystallography at a resolution of 4.2 A and small-angle X-ray scattering (SAXS). The boundary of the three component domains (PAS-sensor, dimerization and catalytic domains) of ThkA and the bound TrrA molecule were unambiguously assigned in the electron density map at 4.2 A resolution. ThkA forms a dimer with crystallographic 2-fold symmetry and two monomeric TrrAs bind to the ThkA dimer. SAXS experiments also confirmed this association state in solution and specific binding between ThkA and TrrA (Kd=8.2x10(-11) M(-2)). The association interface between ThkA and TrrA contains the phosphotransfer His residue in the ThkA, indicative of an efficient receipt of the phosphoryl group. One Per-Arnt-Sim (PAS) domain does not interact with the other PAS domain, but with the catalytic domain of the same polypeptide chain and with one TrrA molecule. Observed inter-domain and inter-molecular interactions reveal a definite pathway of signal transduction in the kinase/regulator complex. In addition, we propose a responsible role of TrrA for the feedback regulation of sensing and/or kinase activities of ThkA.     

Bottom‐up and top‐down effects of tree species diversity on leaf insect herbivory

The diversity of plant neighbors commonly results in direct, bottom‐up effects on herbivore ability to locate their host, and in indirect effects on herbivores involving changes in plant traits and a top‐down control by their enemies. Yet, the relative contribution of bottom‐up and top‐down forces remains poorly understood. We also lack knowledge on the effect of abiotic constraints such as summer drought on the strength and direction of these effects. We measured leaf damage on pedunculate oak (Quercus robur), alone or associated with birch, pine or both in a long‐term tree diversity experiment (ORPHEE), where half of the plots were irrigated while the other half remained without irrigation and received only rainfall. We tested three mechanisms likely to explain the effects of oak neighbors on herbivory: (1) Direct bottom‐up effects of heterospecific neighbors on oak accessibility to herbivores, (2) indirect bottom‐up effects of neighbors on the expression of leaf traits, and (3) top‐down control of herbivores by predators. Insect herbivory increased during the growth season but was independent of neighbor identity and irrigation. Specific leaf area, leaf toughness, and thickness varied with neighbor identity while leaf dry matter content or C:N ratio did not. When summarized in a principal component analysis (PCA), neighbor identity explained 87% of variability in leaf traits. PCA axes partially predicted herbivory. Despite greater rates of attack on dummy caterpillars in irrigated plots, avian predation, and insect herbivory remained unrelated. Our study suggests that neighbor identity can indirectly influence insect herbivory in mixed forests by modifying leaf traits. However, we found only partial evidence for these trait‐mediated effects and suggest that more attention should be paid to some unmeasured plant traits such as secondary metabolites, including volatile organic compounds, to better anticipate the effects of climate change on plant‐insect interactions in the future.     

Can a reduction approach predict reliable joint contact and musculo-tendon forces?

Musculoskeletal models generally solve the muscular redundancy by numerical optimisation. They have been extensively validated using instrumented implants. Conversely, a reduction approach considers only one flexor or extensor muscle group at the time to equilibrate the inter-segmental joint moment. It is not clear if such models can still predict reliable joint contact and musculo-tendon forces during gait.Tibiofemoral contact force and gastrocnemii, quadriceps, and hamstrings musculo-tendon forces were estimated using a reduction approach for five subjects walking with an instrumented prosthesis. The errors in the proximal-distal tibiofemoral contact force fell in the range (0.3–0.9 body weight) reported in the literature for musculoskeletal models using numerical optimisation. The musculo-tendon forces were in agreement with the EMG envelops and appeared comparable to the ones reported in the literature with generic musculoskeletal models.Although evident simplifications and limitations, it seems that the reduction approach can provided quite reliable results. It can be a useful pedagogical tool in biomechanics, e.g. to illustrate the theoretical differences between inter-segmental and contact forces, and can provide a first estimate of the joint loadings in subjects with limited musculoskeletal deformities and neurological disorders.