Muscle architecture and passive lengthening properties of the gastrocnemius medialis and Achilles tendon in children who idiopathically toe-walk

Children who idiopathically toe-walk (ITW) habitually operate at greater plantarflexion angles and thus, at shorter muscle-tendon unit (MTU) lengths than typically developing (TD) children. Therefore, it is often assumed that habitual use of the gastrocnemius muscle in this way will cause remodelling of the muscle-tendon architecture compared to TD children. However, the gastrocnemius muscle architecture of children who ITW has never been measured. It is essential that we gain a better understanding of these muscle-tendon properties, to ensure that appropriate clinical interventions can be provided for these children. Five children who ITW (age 8 ± 2 years) and 14 TD children (age 10 ± 2 years) participated in this study. Ultrasound was combined with isokinetic dynamometry and surface electromyography, to measure muscle architecture at common positions and passive lengthening properties of the gastrocnemius muscle and tendon across full range of motion. Regardless of which common condition groups were compared under, both the absolute and normalised to MTU muscle belly and fascicle lengths were always longer, and the Achilles tendon length was always shorter in children who ITW than TD children (p 0.05); however, passive joint stiffness was greater in children who ITW at maximum dorsiflexion (p = 0.001) and at a joint moment common to all participants (p = 0.029). Consequently, the findings of this pilot study indicate a remodelling of the relative MTU that does not support the concept that children who ITW commonly experience muscle shortening. Therefore, greater consideration of the muscle and tendon properties are required when prescribing clinical interventions that aim to lengthen the MTU, and treatments may be better targeted at the Achilles tendon in children who ITW

Bacterial biodiversity in deep-sea sediments from two regions of contrasting surface water productivity near the Crozet Islands, Southern Ocean

The relationship between surface-derived particulate organic matter (POM) and deep-sea sediment bacterial abundance, community structure and composition was investigated in two different sediment layers from two zones of contrasting surface water productivity in the southern Indian Ocean. Bacterial sediment communities from high chlorophyll (HC) and low chlorophyll (LC) sites were characterized and compared using direct counts, clone library construction, denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH). Of the 1566 bacterial clones generated from the sediment communities, 1010 matched published 16 S rDNA sequences at ?97% identity. A comparison of surface sediment clone libraries showed that at least one third of all identified operational taxonomic units (OTUs) were common to both HC and LC sites. DGGE community profiles were consistent (82% similar) and evenness of the major phylogenetic groups was 96% similar between surface sediment communities, where gamma- and alpha-Proteobacteria were dominant. Sediment communities shared similarly high biodiversity, while species richness was marginally higher at the LC site. Intra-site shifts in bacterial abundance and composition were observed with increasing sediment depth. Despite the differences in organic matter input between sites, the consistency observed between HC and LC sediment communities pointed to 1) the extent of remineralisation by mega and meio-fauna was a factor affecting the quantity and quality of POM available to sediment bacteria, 2) sampling during the early ‘nutrient assimilation phase’ of the bacterial response to freshly deposited POM or 3) the action of bacteria in the water column could affect the quantity and quality of POM available to sediment bacteria. Although factors other than these may explain the observed similarities, this first comparison of deep-sea sediment communities in relation to surface-derived productivity may be useful in further elucidating the role of sediment bacteria in carbon remineralisation in the deep-sea environment

Genetic variance and genotype reaction norms in response to larval food manipulation for a trait important in scorpionfly sperm competition.

Engqvist L. Genetic variance and genotype reaction norms in response to larval food manipulation for a trait important in scorpionfly sperm competition. Functional Ecology. 2008;22(1):070915213639001-???Sperm competition is an important attribute of many mating systems. Examining the genetic and environmental factors influencing male sperm competition success is essential in order to understand variation in reproductive success. In the scorpionfly Panorpa cognata, male success in sperm competition is influenced by the number of sperm transferred during copulation. This will be determined by copulation duration and the sperm transfer rate of males. Sperm transfer rate is a trait which shows considerable phenotypic variance. Here, I use a full-sib split-brood design in order to investigate both to what extent this trait is heritable and the influence of larval food availability on male sperm transfer rate. The results demonstrate considerable genetic variance underlying the phenotypic expression of sperm transfer rate. Heritability estimates were slightly larger, but not significantly so, for offspring reared at low food availability. In contrast, there was no straightforward evidence that larval food availability had an effect on the sperm transfer rate of males. However, a significant family x treatment interaction provided evidence of a genotype x environment effect on male sperm competitive ability. These results demonstrate different reaction norms for sperm transfer rate in response to larval treatment for individuals with different genetic background