Cyclic movement frequency is associated with muscle typology in athletes.

There is a continuing research interest in the muscle fiber type composition (MFTC) of athletes. Recently, muscle carnosine quantification by proton magnetic resonance spectroscopy (1 H-MRS) was developed as a new non-invasive method to estimate MFTC. This cross-sectional study aims to better understand estimated MFTC in relation to (a) different disciplines within one sport; (b) cyclic sport exercise characteristics; (c) within-athlete variability; and (d) athlete level. A total of 111 elite athletes (74 runners, 7 triathletes, 11 swimmers, 14 cyclists and 5 kayakers) and 188 controls were recruited to measure muscle carnosine in gastrocnemius and deltoid muscle by 1 H-MRS. Within sport disciplines, athletes were divided into subgroups (sprint-, intermediate-, and endurance-type). The controls were used as reference population to allow expression of the athletes' data as Z-scores. Within different sports, endurance-type athletes systematically showed the lowest Z-score compared to sprint-type athletes, with intermediate-type athletes always situated in between. Across the different sports disciplines, carnosine content showed the strongest significant correlation with cyclic movement frequency (R = 0.86, P = 0.001). Both within and between different cyclic sports, estimated MFTC was divergent between sprint- and endurance-type athletes. Cyclic movement frequency, rather than exercise duration came out as the most determining factor for the optimal estimated MFTC in elite athletes.

Discriminant musculo-skeletal leg characteristics between sprint and endurance elite Caucasian runners.

Excellence in either sprinting or endurance running requires specific musculo-skeletal characteristics of the legs. This study aims to investigate the morphology of the leg of sprinters and endurance runners of Caucasian ethnicity. Eight male sprinters and 11 male endurance runners volunteered to participate in this cross-sectional study. They underwent magnetic resonance imaging and after data collection, digital reconstruction was done to calculate muscle volumes and bone lengths. Sprinters have a higher total upper leg volume compared to endurance runners (7340 vs 6265 cm3 ). Specifically, the rectus femoris, vastus lateralis, and hamstrings showed significantly higher muscle volumes in the sprint group. For the lower leg, only a higher muscle volume was found in the gastrocnemius lateralis for the sprinters. No differences were found in muscle volume distribution, center of mass in the different muscles, or relative bone lengths. There was a significant positive correlation between ratio hamstrings/quadriceps volume and best running performance in the sprint group. Sprinters and endurance runners of Caucasian ethnicity showed the greatest distinctions in muscle volumes, rather than in muscle distributions or skeletal measures. Sprinters show higher volumes in mainly the proximal and lateral leg muscles than endurance runners.

An insight into the antibiofilm properties of Costa Rican stingless bee honeys.

OBJECTIVE: There is an increasing search for antibiofilm agents that either have specific activity against biofilms or may act in synergy with antimicrobials. Our objective is to examine the the antibiofilm properties of stingless bee honeys. METHOD: Meliponini honeys from Costa Rica were examined along with Medihoney as a reference. All honeys were submitted to a screening composed of minimum inhibitory concentration, inhibition of biofilm formation and biofilm destruction microplate-based assays against a Staphylococcus aureus biofilm forming strain. Dialysis led to the isolation of an antibiofilm fraction in Tetragonisca angustula honeys. The honey antibiofilm fraction was evaluated for protease activity and for any synergistic effect with antibiotics on a Staphylococcus aureus biofilm. The active fraction was then separated through activity guided isolation techniques involving SDS-PAGEs, anion exchange and size exclusion fast protein liquid chromatographies. The fractions obtained and the isolated antibiofilm constituents were tested for amylase and DNase activity. RESULTS: A total of 57 Meliponini honeys from Costa Rica were studied in this research. The honeys studied belonged to the Tetragonisca angustula (n=36) and Melipona beecheii (n=21) species. Costa Rican Tetragonisca angustula honeys can inhibit the planktonic growth, biofilm formation, and are capable of destroying a Staphylococcus aureus biofilm. The antibiofilm effect was observed in the protein fraction of Tetragonisca angustula honeys. The biofilm destruction proteins allowed ampicillin and vancomycin to recover their antimicrobial activity over a Staphylococcus aureus biofilm. The antibiofilm proteins are of bee origin, and their activity was not due to serine, cysteine or metalloproteases. There were 2 proteins causing the antibiofilm action; these were named the Tetragonisca angustula biofilm destruction factors (TABDFs). TABDF-1 is a monomeric protein of approximately 50kDa that is responsible of the amylase activity of Tetragonisca angustula honeys. TABDF-2 is a protein monomer of approximately 75kDa. CONCLUSION: Tetragonisca angustula honeys from Costa Rica are a promising candidate for research and development of novel wound dressings focused on the treatment of acute and chronic Staphylococcus aureus biofilm wound infections.

Is the whole more than the sum of its parts? Evolutionary trade-offs between burst and sustained locomotion in lacertid lizards.

Trade-offs arise when two functional traits impose conflicting demands on the same design trait. Consequently, excellence in one comes at the cost of performance in the other. One of the most widely studied performance trade-offs is the one between sprint speed and endurance. Although biochemical, physiological and (bio)mechanical correlates of either locomotor trait conflict with each other, results at the whole-organism level are mixed. Here, we test whether burst (speed, acceleration) and sustained locomotion (stamina) trade off at both the isolated muscle and whole-organism level among 17 species of lacertid lizards. In addition, we test for a mechanical link between the organismal and muscular (power output, fatigue resistance) performance traits. We find weak evidence for a trade-off between burst and sustained locomotion at the whole-organism level; however, there is a significant trade-off between muscle power output and fatigue resistance in the isolated muscle level. Variation in whole-animal sprint speed can be convincingly explained by variation in muscular power output. The variation in locomotor stamina at the whole-organism level does not relate to the variation in muscle fatigue resistance, suggesting that whole-organism stamina depends not only on muscle contractile performance but probably also on the performance of the circulatory and respiratory systems.

Why the long face? A comparative study of feeding kinematics of two pipefishes with different snout lengths.

This study showed that the mouth of Doryrhamphus dactyliophorus, a species with a relatively long snout, travels a greater distance compared with Doryrhamphus melanopleura, a species with a considerably shorter snout, allowing it to strike at prey that are farther away from the mouth. The long-snouted species also tended to reach significantly higher linear velocities of the mouth approaching the prey. On the other hand, D. melanopleura needed less time to capture its prey. A striking difference in prey-capture success was observed between species: D. melanopleura and D. dactyliophorus had a prey-capture success of 91 and 31%, respectively. The small prey size and the relatively large distance between eyes and prey are potential reasons why directing the mouth accurately to the prey is difficult in D. dactyliophorus, hence possibly explaining the lower prey-capture success in this long-snouted species.

Experimentally generated footprints in sand: Analysis and consequences for the interpretation of fossil and forensic footprints.

Fossilized footprints contain information about the dynamics of gait, but their interpretation is difficult, as they are the combined result of foot anatomy, gait dynamics, and substrate properties. We explore how footprints are generated in modern humans. Sixteen healthy subjects walked on a solid surface and in a layer of fine-grained sand. In each condition, 3D kinematics of the leg and foot were analyzed for three trials at preferred speed, using an infrared camera system. Additionally, calibrated plantar pressures were recorded. After each trial in sand, the depth of the imprint was measured under specific sites. When walking in sand, subjects showed greater toe clearance during swing and a 7 degrees higher knee yield during stance. Maximal pressure was the most influential factor for footprint depth under the heel. For other foot zones, a combination of factors correlates with imprint depth, with pressure impulse (the pressure-time integral) gaining importance distally, at the metatarsal heads and the hallux. We conclude that footprint topology cannot be related to a single variable, but that different zones of the footprint reflect different aspects of the kinesiology of walking. Therefore, an integrated approach, combining anatomical, kinesiological, and substrate-mechanical insights, is necessary for a correct interpretation.

Growth of segment parameters and a morphological classification for children between 15 and 36 months.

This study is part of a research program that aims at a better understanding of the influence of individual morphological differences and physical growth on development of independent walking in toddlers. As morphometric and segment inertial parameters for toddlers aged between 15 and 36 months are indispensable for the mechanical analyses inherent to this purpose, parameter data were collected. The provided dataset of morphological and segment inertial parameters is a valuable tool for locomotor biomechanical modelling. Analysis of the parameter data showed that there are substantial changes of most segment inertial parameters across body length and body mass. In addition, a classification system was developed to categorize toddlers on the basis of morphometry, reflecting the segment inertial constitution of the child. A principal components analysis (PCA) was applied to define the variance in physique between the children. PCA resulted in three newly composed variables: the 'Axis of chubbiness', the 'Axis of allometric growth' and the 'Axis of relative limb length'. The three axes are plotted against each other, resulting in eight morphological classes. With this classification the morphotype of toddlers between 15 and 36 months can be specified and used for further research on their walking patterns.

Why the semicircular canals are not stimulated by linear accelerations.

Head accelerations are sensed by the vestibular system in the inner ear. Linear accelerations stimulate the otolith organs, while the semicircular canals (SCC) sense angular accelerations. Fluid-structure interaction (FSI) models of the cupula sensor (simulated with finite element method (FEM)) and the endolymph fluid (simulated with computational fluid dynamics (CFD)) in the semicircular canal offer the possibility to investigate why the SCC are not stimulated by linear accelerations. Two hypotheses exist in the literature. The first hypothesis focusses on the density of the cupula sensor in the SCC, while the second is based on the continuous loop of fluid in the semicircular canal. However, neither increasing the cupula density, nor disrupting the continuous fluid circulation substantially increase the cupula deformation under linear head acceleration, thereby rejecting both existing hypotheses. We propose an alternative hypothesis, based on the circular geometry of the semicircular canal. During angular head acceleration, the cupula intersects the body of endolymph and 'pushes' it forward because the cupula seals the semicircular canal like a diaphragm. This results in cupula deflection and neural stimulation. During linear head acceleration, on the other hand, a large part of the canal wall also 'pushes' the endolymph forward, which leads to hardly any cupula deflection.

Influence of M. tibialis anterior fatigue on the walk-to-run and run-to-walk transition in non-steady state locomotion.

The purpose of this study was to examine the influence of muscular fatigue of tibialis anterior (TA) on the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered at different constant accelerations (a=0.01, 0.07 and 0.05 ms(-2)). Twenty women (height: 168.9+/-3.36 cm) performed WRTs and RWTs on a motor-driven treadmill, before and after a protocol inducing muscular fatigue of the TA. WRT-speed decreased after TA fatigue whereas RWT-speed did not change except during the intermediate deceleration. Integrated EMG (iEMG) of the activity burst of TA around heel contact was examined in the last steps before transition, the transition step and the first steps after transition. iEMG increased before WRT, then decreased after transition to running. In the RWT the opposite was observed: iEMG increased after RWT, then decreased with decreasing walking speed. After inducing fatigue in the TA, there was a decrease in iEMG in the WRT whereas no influence of fatigue was found on iEMG in the RWT. As a result of TA fatigue, WRT occurred at a lower speed, probably to avoid over-exertion of the TA. This indicates that the TA is a likely determinant of WRT as previously reported. The RWT, on the other hand, was not altered following TA fatigue, which would indicate that WRT and RWT are determined by different factors.

Kinematics of the transition between walking and running when gradually changing speed.

The purpose of this study was to examine kinematics of the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered with a constant acceleration of 0.1 m s(-2), respectively -0.1 m s(-2). Thirteen women (height: 168.9+/-3.36 cm) performed gait transitions on a motor-driven treadmill. WRT-speed was 2.16+/-0.12 m s(-1), RWT-speed 2.19+/-0.12 m s(-1). Kinematics were examined in the range from eight steps before to eight steps after transition in order to identify the possible occurrence of a transition process to facilitate the actual realization of transition. A transition step in which the main changes from one gait to another are realized is present in WRT and RWT. Despite this clear discontinuity, a transition process also appeared in both transitions. In the WRT, transition was prepared and kinematic adaptations were found in the last swing before transition leading to altered landing conditions. During RWT posttransition changes were observed and RWT was only completed after reorientation of the trunk in the first walking stride after transition. A noteworthy finding was that spatiotemporal (presence of a flight phase), kinematic (knee flexion) and energetic (kinetic and gravitational potential energy fluctuating in-phase versus out-of-phase) criteria to define transition stride correspond to each other. Furthermore, a functional interlimb asymmetry was recognized as a unique characteristic of the transition stride, offering a fourth way of identifying the transition stride.

Polysulfone-ZrO(2) surface interactions. The influence on formation, morphology and properties of zirfon-membranes.

The interaction between polysulfone and ZrO(2) particles is studied as a function of the particle sintering temperature in order to understand the role of ZrO(2) on the formation, morphology, and properties of organo-mineral composite membranes. The adsorption between the sintered ZrO(2) and the constituents of polysulfone, 2,2-diphenylpropane and diphenyl sulfone, is investigated using high-pressure liquid chromatography. The influence of the polymer-ZrO(2) interaction on the flow behavior of the casting suspension is registered via viscoelastic measurements. The organo-mineral composite membranes are formed by immersion precipitation in water, and the resulting membrane morphology is analyzed using high-resolution SEM. The zirconia concentration in the top-layer of the composite structure is determined by XPS. Finally, the link between the polymer-filler interactions, the membrane formation process, and the resulting membrane structure and properties is established.

Spatiotemporal characteristics of the walk-to-run and run-to-walk transition when gradually changing speed.

The purpose of this study was to examine spatiotemporal parameters of the walk-to-run transition (WRT) and run-to-walk transition (RWT) when speed is altered with different constant accelerations. Twenty women (height: 168.9+/-3.36cm) performed three accelerations (0.05, 0.07 and 0.1ms(-2)) and three decelerations (-0.05, -0.07 and -0.1ms(-2)) on a motor-driven treadmill. The transition step in the WRT (first step with a flight phase) and RWT (first step with a double stance phase) occurred at the same speed for all accelerations but these did not occur in the same way. The most striking difference was the presence of a transition step with specific spatiotemporal characteristics in the WRT, whereas this was not observed in the RWT. The transition is not a sudden one-step-event. WRT occurred before transition and consisted of a "pre-transition period" and the transition step whereas RWT occurred after transition and consisted of the transition step and a "post-transition period". Both transition periods were characterized by an exponential evolution of step frequency and step length. Step frequency and step length showed a linear evolution before and after transition. The flight phase of the transition step in the WRT reached a minimum with comparable duration of the last flight phase in the RWT. The flight phase could be considered as an intrinsic dynamical factor of transition. Further research in kinematics, the trajectory of the body centre of mass and energy fluctuations will give more insight in these transitions.

Environment-dependent prey capture in the Atlantic mudskipper (Periophthalmus barbarus).

Few vertebrates capture prey in both the aquatic and the terrestrial environment due to the conflicting biophysical demands of feeding in water versus air. The Atlantic mudskipper (Periophthalmus barbarus) is known to be proficient at feeding in the terrestrial environment and feeds predominately in this environment. Given the considerable forward flow of water observed during the mouth-opening phase to assist with feeding on land, the mudskipper must alter the function of its feeding system to feed successfully in water. Here, we quantify the aquatic prey-capture kinematics of the mudskipper and compare this with the previously described pattern of terrestrial feeding. Prior to feeding in the aquatic environment, the gill slits open, allowing water to be expelled through the gill slits. The opposite happens in terrestrial feeding during which the gill slits remain closed at this point. In water, the expansive movements of the head are larger, amounting to a larger volume increase and are initiated slightly later than in the terrestrial environment. This implies the generation of strong suction flows when feeding in water. Consequently, the kinematic patterns of the hydrodynamic tongue during terrestrial feeding and aquatic suction feeding are similar, except for the amplitude of the volume increase and the active closing of the gill slits early during the terrestrial feeding strike. The mudskipper thus exhibits the capacity to change the kinematics of its feeding apparatus to enable successful prey capture in two disparate environments.

C1-inhibitor prevents PEG fractionation-induced, EDTA-resistant activation of mouse complement.

Fractionation of mouse serum by precipitation with a critical amount of polyethylene glycol 6000 (PEG; 11% w/v) results in a classical and alternative pathway-independent activation of the terminal complement route. The activation can take place after the separation of an activating principle together with the terminal route components from a natural regulator. The isolation and identification of the regulatory component preventing this activation in serum, is subject of this paper. The regulator was purified by fractionated PEG-precipitation (15-25%), followed by heparin-Sepharose affinity, Mono Q anion-exchange, and Superose 12 gel filtration chromatography. The regulator appeared to be a single-chain protein with a Mr of 96 k. A protein with similar activity purified from human serum had a Mr of 104 k and was functionally and antigenically indistinguishable from C1-INH. The mouse 96 k protein inhibited C1-esterase activity indicating that this protein is indeed C1-INH. Mouse C1-INH regulates the PEG fractionation-induced bypass activation of complement, but does not interfere with the assembly or the lytic activity of membrane attack complexes. alpha 2-Macroglobulin appeared also to be capable of inhibiting the PEG-precipitation-induced activation process, but with lower efficiency.

Mechanoreceptor distribution in stag beetle jaws corresponds to the material stress in fights.

Male stag beetles (Lucanidae) use their extremely elongated jaws to pinch their rivals forcefully in male-male battles. The morphology of these jaws has to be a compromise between robustness (to withstand the bite forces), length and weight. Cyclommatus metallifer stag beetles circumvent this trade-off by reducing their bite force when biting with their slender jaw tips. Here we describe the functional mechanism behind the force modulation behaviour. Scanning Electron Microscopy and micro CT imaging show large numbers of small sensors in the jaw cuticle. We find a strong correlation between the distribution of these sensors and that of the material stress in the same jaw region during biting. The jaw sensors are mechanoreceptors with a small protrusion that barely protrudes above the undulating jaw surface. The sensors stimulate dendrites that extend from the neuronal cell body through the entire thickness of the jaw exoskeleton towards the sensors at the external surface. They form a sensory field that functions in a feedback mechanism to control the bite muscle force. This negative feedback mechanism enabled the stag beetles to evolve massive bite muscles without risking overloading their valuable jaws.

Bovine Staphylococcus aureus Secretes the Leukocidin LukMF' To Kill Migrating Neutrophils through CCR1.

UNLABELLED: Although Staphylococcus aureus is best known for infecting humans, bovine-specific strains are a major cause of mastitis in dairy cattle. The bicomponent leukocidin LukMF', exclusively harbored by S. aureus of ruminant origin, is a virulence factor associated with bovine infections. In this study, the molecular basis of the host specificity of LukMF' is elucidated by identification of chemokine receptor CCR1 as its target. Bovine neutrophils, the major effector cells in the defense against staphylococci, express significant cell surface levels of CCR1, whereas human neutrophils do not. This causes the particular susceptibility of bovine neutrophils to pore formation induced by LukMF'. Bovine S. aureus strains produce high levels of LukMF' in vitro. In culture supernatant of the mastitis field isolate S1444, LukMF' was the most important cytotoxic agent for bovine neutrophils. In a fibrin gel matrix, the effects of the in situ secreted toxins on neutrophils migrating toward S. aureus were visualized. Under these physiological ex vivo conditions, bovine S. aureus S1444 efficiently killed approaching neutrophils at a distance through secretion of LukMF'. Altogether, our findings illustrate the coevolution of pathogen and host, provide new targets for therapeutic and vaccine approaches to treat staphylococcal diseases in the cow, and emphasize the importance of staphylococcal toxins in general. IMPORTANCE: This study explains the mechanism of action of LukMF', a bicomponent toxin found in bovine lineages of S. aureus that is associated with mastitis in cattle. At a molecular level, we describe how LukMF' can specifically kill bovine neutrophils. Here, we demonstrate the contribution of toxins in the determination of host specificity and contribute to the understanding of mechanisms of coevolution of pathogen and host. Our study provides new targets that can be used in therapeutic and vaccine approaches to treat staphylococcal diseases in the cow. We also demonstrate the importance of toxins in specific elimination of immune cells, which has broader implications, especially in human infections.

Speed and stamina trade-off in lacertid lizards.

Morphological and physiological considerations suggest that sprinting ability and endurance capacity put conflicting demands on the design of an animal's locomotor apparatus and therefore cannot be maximized simultaneously. To test this hypothesis, we correlated size-corrected maximal sprint speed and stamina of 12 species of lacertid lizards. Phylogenetically independent contrasts of sprint speed and stamina showed a significant negative relationship, giving support to the idea of an evolutionary trade-off between the two performance measures. To test the hypothesis that the trade-off is mediated by a conflict in morphological requirements, we correlated both performance traits with snout-vent length, size-corrected estimates of body mass and limb length, and relative hindlimb length (the residuals of the relationship between hind- and forelimb length). Fast-running species had hindlimbs that were long compared to their forelimbs. None of the other size or shape variables showed a significant relationship with speed or endurance. We conclude that the evolution of sprint capacity may be constrained by the need for endurance capacity and vice versa, but the design conflict underlying this trade-off has yet to be identified.

In vivo anti-complementary activities of the cobra venom factors from Naja naja and Naja haje.

The kinetics of complement (C) depletion and recovery of C levels upon injection of BALB/c mice with cobra venom factors (CVF), from N. naja (C3- and C5-depleting) and N. haje (selectively C3-depleting) were studied. The animals received i.p. or i.v. injections of either of the two preparations. CH50 and hemolytic C3 and C5 levels were followed as parameters of residual complement activity. N. naja CVF turned out to be as efficient in depleting total complement activity as N. haje CVF. Decreased CH50 values could largely be ascribed to C3 depletion. Complement consumption after N. naja CVF, however, lasted longer than after N. haje CVF administration. Estimated functional half-lives of N. naja and N. haje CVF were 11.5 and 4.5 h, respectively. Inhibition ELISAs showed that, after in vivo administration of either of the two CVF preparations, antigenic C3 and C5 kept circulating for days.

Functional assay of C5-activating and nonactivating cobra venom factor preparations in the mouse system.

This paper deals with a new, functional assay of cobra venom factor (CVF) preparations with or without C5-activating property. Existing methods lack sensitivity and use diluted human complement as target of inactivation. An adapted assay using diluted mouse serum as complement source was hampered by underestimation of C3 depletion by bystander lysis and an overvaluation of C5 consumption resulting from C3 inactivation in the reagent used. These disadvantages prompted us to develop the new assay which is based on the incubation of CVF preparations with undiluted mouse serum. After incubation, residual total C activity, as well as functional C3 and C5 are estimated by titration. The procedure permits the assessment of CVF activities with minimal interference from undesired processes. The conditions in the new assay approach the in vivo situation in mice by the use of undiluted serum from the same animal species.