52 research outputs found
Achilles tendon (3D): Do the mechanical properties of tendon change in response to exercise?
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recor
Selectivity and functional diversity in arbuscular mycorrhizas of co-occurring fungi and plants from a temperate deciduous woodland
1 The arbuscular mycorrhizal (AM) fungi colonizing plants at a woodland site in North Yorkshire (UK) have been characterized from the roots of five plant species (Rubus fruticosus agg. L., Epilobium angustifolium L., Acer pseudoplatanus L., Ajuga reptans L. and Glechoma hederacea L.), and identified using small-subunit rRNA (SSUrRNA) gene amplification and sequencing. 2 Interactions between five plant species from the site and four co-occurring glomalean fungi were investigated in artificial one-to-one AM symbioses. Three of the fungi were isolated from the site; the fourth was a culture genetically similar to a taxon found at the site. Phosphorus uptake and growth responses were compared with non-mycorrhizal controls. 3 Individual fungi colonized each plant with different spatial distribution and intensity. Some did not colonize at all, indicating incompatibility under the conditions used in the experiments. 4 Glomus hoi consistently occupied a large proportion of root systems and outperformed the other fungi, improving P uptake and enhancing the growth of four out of the five plant species. Only G. hoi colonized and increased P uptake in Acer pseudoplatanus, the host plant with which it associates almost exclusively under field conditions. Colonization of all plant species by Scutellospora dipurpurescens was sparse, and beneficial to only one of the host plants (Teucrium scorodonia). Archaeospora trappei and Glomus sp. UY1225 had variable effects on the host plants, conferring a range of P uptake and growth benefits on Lysimachia nummularia and T. scorodonia, increasing P uptake whilst not affecting biomass in Ajuga reptans and Glechoma hederacea, and failing to form mycorrhizas with A. pseudoplatanus. 5 These experimental mycorrhizas show that root colonization, symbiont compatibility and plant performance vary with each fungus-plant combination, even when the plants and fungi naturally co-exist. 6 We provide evidence of physical and functional selectivity in AM. The small number of described AM fungal species (154) has been ascribed to their supposed lack of host specificity, but if the selectivity we have observed is the general rule, then we may predict that many more, probably hard-to-culture glomalean species await discovery, or that members of species as currently perceived may be physiologically or functionally distinct
The genomes of two key bumblebee species with primitive eusocial organization
Background: The shift from solitary to social behavior is one of the major evolutionary transitions. Primitively eusocial bumblebees are uniquely placed to illuminate the evolution of highly eusocial insect societies. Bumblebees are also invaluable natural and agricultural pollinators, and there is widespread concern over recent population declines in some species. High-quality genomic data will inform key aspects of bumblebee biology, including susceptibility to implicated population viability threats. Results: We report the high quality draft genome sequences of Bombus terrestris and Bombus impatiens, two ecologically dominant bumblebees and widely utilized study species. Comparing these new genomes to those of the highly eusocial honeybee Apis mellifera and other Hymenoptera, we identify deeply conserved similarities, as well as novelties key to the biology of these organisms. Some honeybee genome features thought to underpin advanced eusociality are also present in bumblebees, indicating an earlier evolution in the bee lineage. Xenobiotic detoxification and immune genes are similarly depauperate in bumblebees and honeybees, and multiple categories of genes linked to social organization, including development and behavior, show high conservation. Key differences identified include a bias in bumblebee chemoreception towards gustation from olfaction, and striking differences in microRNAs, potentially responsible for gene regulation underlying social and other traits. Conclusions: These two bumblebee genomes provide a foundation for post-genomic research on these key pollinators and insect societies. Overall, gene repertoires suggest that the route to advanced eusociality in bees was mediated by many small changes in many genes and processes, and not by notable expansion or depauperation
Turning points nella storia della lessicografia umanistica
Mechanical loading of the Achilles tendon during isolated
eccentric contractions could induce immediate and
region-dependent changes in mechanical properties.
Three-dimensional ultrasound was used to examine the
immediate effect of isolated eccentric exercise on the
mechanical properties of the distal (free tendon) and
proximal (gastrocnemii) regions of the Achilles tendon.
Participants (n = 14) underwent two testing sessions in
which tendon measurements were made at rest and
during a 30% and 70% isometric plantar flexion contractions
immediately before and after either: (a) 3 × 15
eccentric heel drops or (b) 10-min rest. There was a significant
time-by-session interaction for free tendon length and strain for all loading conditions (P < 0.05). Pairwise
comparisons revealed a significant increase in free tendon
length and strain at all contraction intensities after eccentric
exercise (P < 0.05). There was no significant time-bysession
interaction for the gastrocnemii (medial or lateral)
aponeurosis or tendon for any of the measured parameters.
Immediate changes in Achilles tendon mechanical
properties were specific to the free tendon and consistent
with changes due to mechanical creep. These findings
suggest that the mechanical properties of the free tendon
may be more vulnerable to change with exercise compared
with the gastrocnemii aponeurosis or tendon
Introduzione
Obst, SJ ORCiD: 0000-0003-4299-9628This study investigated the accuracy of phantom volume and length measurements and the reliability of
in vivo Achilles tendon (AT) volume, length and cross-sectional area measurements obtained using freehand 3-D
ultrasound. Participants (n = 13) were scanned on consecutive days under active and passive loading conditions.
In vivo AT length was evaluated using a two-point method and an approach that accounted for AT curvature
(centroid method). Three-dimensional ultrasound provided accurate measures of phantom volume and length
(mean difference = 0.05 mL and 0.2 mm, respectively) and reliable in vivo measures of AT volume, length and
average cross-sectional area, with all intra-class correlations coefficients greater than 0.98. The mean minimally
detectable changes for in vivo AT volume, two-point length and centroid length were 0.2 mL, 1.5 mm and
2.0 mm, respectively. Two-point AT length underestimated centroid AT length by 0.7 mm, suggesting that the effect
of curvature on in vivo AT length is negligible
Three-dimensional deformation of the Achilles tendon during load in people with unilateral mid-portion Achilles tendinopathy
The author’s clinical experiences suggest that current road bicycle
designs and configurations are sub-optimal for those of average
female height and smaller, and that further research in the area
is necessary to help improve injury and performance outcomes
in this group. The author proposes that the use of proportionally
sized cranks facilitates a more optimal fitting process with positive
effects on both injury and performance. Bike handling and safety
may, however, be negatively affected by the use of lengths deviating
substantially from that which a given frame was designed around.
Such concerns may be resolved with frames based on proportional
crank lengths and wheel sizes
Three-dimensional morphology and volume of the free Achilles tendon at rest and under load in people with unilateral mid-portion Achilles tendinopathy
Obst, SJ ORCiD: 0000-0003-4299-9628Mid-portion Achilles tendinopathy (MAT) adversely affects free Achilles tendon (AT) structure and composition. However, it is not known how these pathological alterations associated with MAT change the normal three-dimensional (3-D) morphology of free AT at rest and under load throughout the entire free tendon length. Here, we used 3-D ultrasound to examine the effect of unilateral MAT on free tendon 3-D morphology [length, cross-sectional area (CSA), anteroposterior (AP) diameter and mediolateral (ML) diameter] and volume at rest and during a submaximal (50%) voluntary isometric plantarflexion contraction bilaterally in individuals with unilateral MAT (n = 10) compared with a matched healthy control group (n = 10). The tendinopathic free AT had a greater CSA relative to the control tendons along the entire tendon length, which was mainly driven by a greater tendon AP diameter. Under load, the tendinopathic tendon experienced greater longitudinal and transverse strains than the control tendons. In contrast to the control tendons, which experienced a reduction in tendon CSA and ML diameter, bulged along the AP axis and behaved isovolumetrically under load, the tendinopathic tendon experienced a reduction in tendon CSA, AP diameter and ML diameter and an overall volume reduction. Overall, these findings suggest that the magnitude of longitudinal strain and volume change and the corresponding magnitude and direction of transverse strain under load are altered in MAT compared with normal tendon. These findings are indicative of a fundamental reorganizationofthetendonmatrixandalterationsintendonfluidcontentanddistributionunder loadintendinopathictendon
Recovery of human Achilles tendon three-dimensional deformation following conditioning
Obst, SJ ORCiD: 0000-0003-4299-9628Objectives: The tendon conditioning effect is transient, but the time course of recovery from conditioning is not known. This study examined the time-course recovery of three-dimensional (3D) Achilles tendon (AT) deformation immediately following a standardised AT conditioning protocol.
Design: Randomised crossover.
Methods: Ten healthy male adults (age: 24 ± 5 years; height: 175.8 ± 4.1 cm; body mass: 78.4 ± 6.3 kg) attended the laboratory on 6 occasions. ATs were scanned using freehand 3D ultrasound during a 50%maximal voluntary isometric contraction (MVIC) of the plantarflexors immediately prior to and following the conditioning protocol (10 × 25 s plantarflexion contractions at 50% MVIC), and then at either 15, 30, 60, 90 or 120 min post-conditioning, randomised by session.
Results: Free AT longitudinal strain was significantly increased from 3.13 ± 0.19% pre-conditioning to 7.49 ± 0.20% immediately post-conditioning and was accompanied by a corresponding reduction in free AT transverse strain from −5.35 ± 0.48% to −10.16 ± 0.49% (p 0.05).
Conclusions: The free AT undergoes a creep response during conditioning which is recoverable within 2 h following conditioning. Recovery from conditioning has the potential to be a source of error during in vivo measurement of AT mechanical properties. The time window in which the free AT longitudinal and transverse strains could be achieved without a large confounding effect of creep recovery is 0–60 min post-conditioning
Regional three-dimensional deformation of human Achilles tendon during conditioning
Our understanding of in\ua0vivo Achilles tendon (AT) conditioning is limited to two-dimensional ultrasound measures of longitudinal deformation of the whole tendon. This study investigated the regional three-dimensional (3D) deformation of the AT during conditioning. Eighteen ATs were scanned using 3D freehand ultrasound during 10 successive 25\ua0s submaximal (50%) voluntary isometric plantarflexion contractions. Longitudinal strain was assessed for the whole AT, aponeurosis, and free AT and transverse strain was assessed for the proximal-, mid-, and distal-portions of the free AT. Longitudinal conditioning of the whole AT was primarily driven by creep response of the free AT and transverse conditioning was greatest for the mid-portion of the free AT. Whole and free AT longitudinal strain increased up to the third contraction and were accompanied by a corresponding reduction in free AT cross-sectional area (CSA) strain in proximal-, mid-, and distal-portions. No significant changes in aponeurosis strain or tendon volume were detected between contractions. These findings suggest that conditioning alters free AT shape, with increased tendon length attained at the expense of reduction in free AT CSA. Although AT experiences different amounts of strain in different regions, the number of contractions required to reach steady-state strain during conditioning is uniform throughout the tendon
Regional three-dimensional deformation of human Achilles tendon during conditioning
Our understanding of in vivo Achilles tendon (AT) conditioning is limited to two-dimensional ultrasound measures of longitudinal deformation of the whole tendon. This study investigated the regional three-dimensional (3D) deformation of the AT during conditioning. Eighteen ATs were scanned using 3D freehand ultrasound during 10 successive 25 s submaximal (50%) voluntary isometric plantarflexion contractions. Longitudinal strain was assessed for the whole AT, aponeurosis, and free AT and transverse strain was assessed for the proximal-, mid-, and distal-portions of the free AT. Longitudinal conditioning of the whole AT was primarily driven by creep response of the free AT and transverse conditioning was greatest for the mid-portion of the free AT. Whole and free AT longitudinal strain increased up to the third contraction and were accompanied by a corresponding reduction in free AT cross-sectional area (CSA) strain in proximal-, mid-, and distal-portions. No significant changes in aponeurosis strain or tendon volume were detected between contractions. These findings suggest that conditioning alters free AT shape, with increased tendon length attained at the expense of reduction in free AT CSA. Although AT experiences different amounts of strain in different regions, the number of contractions required to reach steady-state strain during conditioning is uniform throughout the tendon
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