Investigating the mechanical behaviour at a core-sheath interface in peripheral nerves

Published without an abstract

Force transmission across a core-sheath interface in peripheral nerves [poster presentation]

No abstract - poster presentation

Characterization of novel pollen-expressed transcripts reveals their potential roles in pollen heat stress response in Arabidopsis thaliana

Key message: Arabidopsis pollen transcriptome analysis revealed new intergenic transcripts of unknown function, many of which are long non-coding RNAs, that may function in pollen-specific processes, including the heat stress response. Abstract: The male gametophyte is the most heat sensitive of all plant tissues. In recent years, long noncoding RNAs (lncRNAs) have emerged as important components of cellular regulatory networks involved in most biological processes, including response to stress. While examining RNAseq datasets of developing and germinating Arabidopsis thaliana pollen exposed to heat stress (HS), we identified 66 novel and 246 recently annotated intergenic expressed loci (XLOCs) of unknown function, with the majority encoding lncRNAs. Comparison with HS in cauline leaves and other RNAseq experiments indicated that 74% of the 312 XLOCs are pollen-specific, and at least 42% are HS-responsive. Phylogenetic analysis revealed that 96% of the genes evolved recently in Brassicaceae. We found that 50 genes are putative targets of microRNAs and that 30% of the XLOCs contain small open reading frames (ORFs) with homology to protein sequences. Finally, RNAseq of ribosome-protected RNA fragments together with predictions of periodic footprint of the ribosome P-sites indicated that 23 of these ORFs are likely to be translated. Our findings indicate that many of the 312 unknown genes might be functional and play a significant role in pollen biology, including the HS response

A low-background γγ-coincidence spectrometer for radioisotope studies

The performance of a new, low-background NaI(Tl) spectrometer, based on γγ-coincidence counting, is discussed. We present experimental coincidence efficiencies, timing resolutions, background count rates, and minimum detectable activities. The spectrometer has been simulated using Geant4, and the results are used for estimating coincidence efficiencies for volume sources. To test the device, we measured the cosmogenic 26Al activity in a small (17.7 g) meteorite fragment. We find a value of 52.9±7.8dpm∕kg, in agreement with the activity measured previously in a much larger fragment of the same meteorite using a HPGe detector

A population-scale temporal case–control evaluation of COVID-19 disease phenotype and related outcome rates in patients with cancer in England (UKCCP)

Patients with cancer are at increased risk of hospitalisation and mortality following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, the SARS-CoV-2 phenotype evolution in patients with cancer since 2020 has not previously been described. We therefore evaluated SARS-CoV-2 on a UK populationscale from 01/11/2020-31/08/2022, assessing case-outcome rates of hospital assessment(s), intensive care admission and mortality. We observed that the SARS-CoV-2 disease phenotype has become less severe in patients with cancer and the non-cancer population. Case-hospitalisation rates for patients with cancer dropped from 30.58% in early 2021 to 7.45% in 2022 while case-mortality rates decreased from 20.53% to 3.25%. However, the risk of hospitalisation and mortality remains 2.10x and 2.54x higher in patients with cancer, respectively. Overall, the SARS-CoV-2 disease phenotype is less severe in 2022 compared to 2020 but patients with cancer remain at higher risk than the non-cancer population. Patients with cancer must therefore be empowered to live more normal lives, to see loved ones and families, while also being safeguarded with expanded measures to reduce the risk of transmission

Investigating the mechanical shear-plane between core and sheath elements of peripheral nerves

The mechanical architecture of rat sciatic nerve has been described as a central core surrounded by a sheath, although the way in which these structures contribute to the overall mechanical properties of the nerve is unknown. We have studied the retraction responses of the core and sheath following transection, together with their tensile properties and the interface between them. Nerves were harvested and maintained at their in situ tension and then either transected entirely, through the sheath only, or through an exposed section of the core. The retraction of each component was measured within 5 min and again after 45 min. Post mortem loss of retraction was tested 0 min or 60 min after excision. For fresh nerves, immediate retraction was 12.68% (whole nerve), 5.35% (sheath) and 4% (core), with a total retraction of 15%, 7.21% and 5.26% respectively. For stored nerves, immediate retraction was 5.33% (whole nerve) and 5.87% (sheath), with an extension of 0.78% for core, and a total retraction of 6.71% and 7.87% and an extension of 1.74%, respectively. Tensile extension and pullout force profiles were obtained for the sheath, the core and the interface between them. These showed a consistent hierarchy of break strengths that would, under increasing load, result in failure of the interface, then the core and finally the sheath. These data reflect the contributions of material tension and fluid swelling pressure to total retraction, and the involvement of an energy-dependent process that runs down rapidly post mortem. This study increases our understanding of the composite nature of peripheral nerve tissue architecture and quantifies the material properties of the distinct elements that contribute to overall mechanical function

Analysis of mechanical interactions between distinct intraneural regions of the rat sciatic nerve, and their restoration after damage and repair

Abstract can be reached at the URL

Investigation of mechanical interactions between intraneural elements of the rat sciatic nerve after repair

The development of tissue engineered conduits for the surgical repair of peripheral nerves has raised important questions with regard to the mechanical aspects of neuroanatomy. Restoration of the ability of a repaired nerve to accommodate the movements required during limb movement is an important consideration in the design of repair strategies. A model has been developed for use alongside existing experimental assays of nerve function to explore the restoration of mechanical features in the regenerating rat sciatic nerve. This is based on the presence of a distinct core and sheath with an interface at the level of the innermost perineurial cell layer. The core and sheath can be separated experimentally using tensile testing equipment which allows quantification of the force required. This force has been shown to be consistent in control nerves from unoperated animals, providing a reference for the subsequent investigation of the interaction between these neural regions after repair. In this investigation, the left sciatic nerves in 18 Wistar rats were transected and immediately repaired using epineurial sutures. Animals were sacrificed 2, 4, 8 and 12 weeks post-repair and the nerves underwent mechanical testing to measure the force required for separation of the core and sheath. Controls were unoperated contralateral sciatic nerves from animals in the experimental group. The ability to separate the endoneurial core from the nerve sheath depends on the maximal force required being less than the break-strength of either region. 4 weeks after primary repair, separation of core and sheath was possible and required a greater force than controls. At the other time points the endoneurial core failed before separation from the sheath could take place, suggesting that the strength of the interface was greater than the strength of the endoneurial core. These data provide an insight into the mechanical changes that occur following primary repair in the rat sciatic nerve. Knowledge of such changes provides an additional means by which to compare alternative approaches to nerve regeneration in this animal model with a view to developing implantable devices which restore mechanical integrity along with conductional functionality