Biomedical subjects

Simon Walker

Publications and source records attributed to Simon Walker.

7 recordsLinked to original sources

PubMed2026

Six weeks of isometric resistance training led to evidence of corticospinal but not reticulospinal adaptation in previously untrained adult males.

The latest hypothesis regarding the source of enhanced neural activation from resistance training is the reticulospinal rather than the corticospinal tract, based on invasive animal and emerging human data. The present study employed a six-week isometric resistance training intervention in a randomized controlled design to address this knowledge gap. Thirty-nine healthy, untrained males (age ~23 y, sustained contraction group n = 13, explosive contraction group n = 9, control group n = 17) underwent neuromuscular and electrophysiological testing and completed all study requirements. Maximal isometric torque (MVC) and rate of torque development (RTD) were measured during a familiarization session as well as before and after the six-week period. Transcranial magnetic stimulation was used to assess motor-evoked potential (MEP) area and silent period duration while subjects contracted to 10% of MVC. Loud sound (120 dB) was used to modulate MEP area and reaction time to visual stimuli during the StartReact test. Only the intervention groups demonstrated significant improvements in MVC (27%) and RTD (60%) (both P < 0.01), along with reduced MEP area (- 21%) and silent period duration (- 23%) (both P < 0.01). The sustained contraction group showed reduced modulation of reaction time and increased MEP suppression due to loud sound. Short-term resistance training seemed to reduce cortical inhibition and corticospinal excitability in both training groups. The study showed conflicting changes in measures purported to evaluate reticulospinal functioning. It is recommended to examine different forms of resistance training and longer training exposure in future.

Humans↗

PubMed2026

Age-related differences in motor unit behaviours and maximal strength: A systematic review and meta-analysis.

Ageing is associated with a decline in strength; however, the neural mechanisms underpinning these changes remain poorly understood. Motor unit discharge rate (MUDR) and recruitment threshold (MURT) regulate the magnitude of motoneuron output through rate coding and orderly recruitment, while discharge rate variability (MUDRV) reflects the steadiness of motoneuron output. Yet, age-related differences in these properties remain inconsistent across the literature. Therefore, this systematic review and meta-analysis quantified age-related differences in motor unit behaviours and their contribution to maximal isometric strength. Electronic databases (Medline, Embase, Scopus, PsycINFO, Ovid Emcare, CENTRAL, and Web of Science) were searched up to May 2025, yielding 1493 records; of these, 48 studies met the inclusion criteria. Standardised mean differences (SMDs) were calculated using random-effects models to compare older and younger adults, and methodological quality was assessed using the AXIS tool. Older adults exhibited markedly lower maximal strength than younger adults (SMD = -1.01; 95% CI -1.22, -0.79). MUDR was lower in older adults across all contraction intensities, with greater reductions at high forces (> 60% maximal voluntary contraction (MVC): SMD = -0.65; 95% CI -0.96, -0.34) compared to low forces (< 30% MVC: SMD = -0.34; 95% CI -0.50, -0.18). Discharge rate variability was greater (SMD = 0.44; 95% CI 0.15, 0.72), whereas recruitment thresholds relative to MVC were lower (SMD = -0.42; 95% CI -0.80, -0.03) in older adults. Collectively, these findings suggest that age-related alterations in motor unit discharge behaviour may contribute, at least in part, to reduced maximal strength in older adults.

Aging↗

PubMed2026

STABIX: summary-statistic-based GWAS indexing and compression.

MOTIVATION: Genome-wide association studies (GWAS) are widely used to investigate the role of genetics in disease traits, but the resulting file sizes from these studies are large, posing barriers to efficient storage, sharing, and querying. This issue is especially important for biobanks like the UK Biobank that publish GWAS for thousands of traits, increasing the volume of data that must be effectively managed. Current compression and query methods reduce file sizes and allow for quick genomic position-based queries but do not provide utility for quickly finding loci based on their summary statistics. For example, finding all SNVs in a particular p-value range would require decompressing and scanning the whole file. We propose a new tool, STABIX, which introduces summary-statistic-based queries and improves upon the standard bgzip compression and Tabix query tool in both compression ratio and decompression speed. RESULTS: When applied to 10 GWAS files from PanUKBB, STABIX created smaller compressed data and indices than Tabix for all files, where bgzip and tbi files were an average of 1.2 times the size of STABIX compressed files and indexes. In the same 10 files, STABIX per gene decompression was, on average 7× faster than Tabix per gene decompression, and achieved faster per gene decompression times for over 99% of nearly 20,000 genes. AVAILABILITY AND IMPLEMENTATION: Software freely available for download at GitHub: https://github.com/kristen-schneider/stabix/.

Genome-Wide Association Study↗

PubMed2006

PI(3)Kgamma has an important context-dependent role in neutrophil chemokinesis.

The directional movement of cells in a gradient of external stimulus is termed chemotaxis and is important in many aspects of development and differentiated cell function. Phophoinositide 3-kinases (PI(3)Ks) are thought to have critical roles within the gradient-sensing machinery of a variety of highly motile cells, such as mammalian phagocytes, allowing these cells to respond quickly and efficiently to shallow gradients of soluble stimuli. Our analysis of mammalian neutrophil migration towards ligands such as fMLP shows that, although PtdIns(3,4)P(2) and PtdIns(3,4,5)P(3) accumulate in a PI(3)Kgamma-dependent fashion at the up-gradient leading-edge, this signal is not required for efficient gradient-sensing and gradient-biased movement. PI(3)Kgamma activity is however, a critical determinant of the proportion of cells that can move, that is, respond chemokinetically, in reaction to fMLP. Furthermore, this dependence of chemokinesis on PI(3)Kgamma activity is context dependent, both with respect to the state of priming of the neutrophils and the type of surface on which they are migrating. We propose this effect of PI(3)Kgamma is through roles in the regulation of some aspects of neutrophil polarization that are relevant to movement, such as integrin-based adhesion and the accumulation of polymerized (F)-actin at the leading-edge.

Actins↗

PubMed2006

Which patients would prefer to walk to theatre?

INTRODUCTION: Increasing patient autonomy in the pre-operative period may help to lessen the anxiety associated with under-going a surgical procedure, and may enhance patient satisfaction. This study seeks to explore patients' preferences for mode of travel to the operating theatre. PATIENTS AND METHODS: A questionnaire survey was undertaken with all patients having an in-patient or day-case surgical procedure over a 4-week period at one hospital. Results were analysed with respect to the patients' age, gender and surgical specialty. RESULTS: In all, 171 patients completed the questionnaire, 118 day-cases and 53 in-patients. In both sexes and in all age groups, the majority of patients expressed a preference to walk to theatre. The only sub-group which demonstrated an equal preference for a trolley transfer compared with walking were gynaecology patients. CONCLUSIONS: These results suggest that a high proportion of patients would prefer to walk to theatre for their operation if given the choice. If the policy of offering choice were adopted, it would enhance patient autonomy and may reduce delays in transferring patients to theatre. It may also release portering resources for other purposes.

Ambulatory Surgical Procedures↗

PubMed2002

Postnatal growth and circulating ACTH and cortisol concentrations during the first month of life in cloned lambs.

Recent studies have indicated that there is a decrease in perinatal survival of apparently normal animals produced by somatic-cell nuclear transfer. Here we report that the cortisol and adrenocorticotrophic hormone (ACTH) profiles of cloned lambs in the first 4 weeks of life are significantly different to that of control lambs. The growth of cloned lambs however was not different to controls. These findings demonstrate that endocrine development may be altered in apparently "normal" clones.

Adrenocorticotropic Hormone↗

PubMedDate not supplied

NADPH oxidases in cardiovascular health and disease.

Increased oxidative stress plays an important role in the pathophysiology of cardiovascular diseases such as hypertension, atherosclerosis, diabetes, cardiac hypertrophy, heart failure, and ischemia-reperfusion. Although several sources of reactive oxygen species (ROS) may be involved, a family of NADPH oxidases appears to be especially important for redox signaling and may be amenable to specific therapeutic targeting. These include the prototypic Nox2 isoform-based NADPH oxidase, which was first characterized in neutrophils, as well as other NADPH oxidases such as Nox1 and Nox4. These Nox isoforms are expressed in a cell- and tissue-specific fashion, are subject to independent activation and regulation, and may subserve distinct functions. This article reviews the potential roles of NADPH oxidases in both cardiovascular physiological processes (such as the regulation of vascular tone and oxygen sensing) and pathophysiological processes such as endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, angiogenesis, and vascular and cardiac remodeling. The complexity of regulation of NADPH oxidases in these conditions may provide the possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the disease process.

Animals↗