Biology subjects

Hall, M. E.

Publications and source records attributed to Hall, M. E..

5 recordsLinked to original sources

bioRxiv2025

The Effect of Resistance Training Volume on Individual-Level Skeletal Muscle Adaptations: A Novel Replicated Within-Participant Unilateral Trial

PurposeThere is growing emphasis on investigating heterogeneity in resistance training (RT) outcomes, likely motivated by observations of substantial gross variability in training effects. However, gross variability does not necessarily represent true inter-individual response variation (IRV) and can be obscured by measurement error, sampling variance, and biological variability. Appropriate study design and statistical analysis are required to distinguish IRV from these confounding sources of within-participant variation. Methods16 recreationally trained participants completed a novel replicated within-participant unilateral design across two 11-week training phases separated by a 6-8 week washout. Lower limbs were randomized to a low volume ([~]8 sets/week) or high volume ([~]16 sets/week) training protocol in each phase. We assessed both general (GEN; average response across conditions) and condition-specific (CON; difference between volumes) IRV for vastus lateralis cross-sectional area and leg press one-repetition maximum using a multi-stage statistical approach. ResultsHigher weekly set volumes demonstrated a detectable advantage for muscle hypertrophy (1.8 cm{superscript 2} [95% HDI: 0.29, 3.41]; 98.77% posterior probability) but not maximal strength (3.48 kg [95% HDI: -5.1, 12.15]; 80.01% posterior probability). Despite substantial gross variability, we failed to detect irrefutable evidence of meaningful IRV. Integrated methods revealed stronger evidence for GEN versus CON IRV, with correlation coefficients ranging from 0.67 to 0.7 for GEN versus 0.04 to 0.06 for CON. ConclusionsOur findings clearly illustrate that gross variability in training outcomes does not necessarily indicate true inter-individual differences, a distinction critical for both research and practice. KEY POINTSO_LIGross variability in resistance training outcomes is commonly interpreted as evidence of meaningful inter-individual response variation (IRV), but this variability often reflects confounding sources of within-participant variation rather than true inter-individual differences. C_LIO_LIUsing a novel replicated within-participant unilateral design, we investigated the effects of different weekly set volumes on changes in muscle size and maximal strength, as well as the inter-individual variation thereof. C_LIO_LIAt the group level, higher weekly set volumes produced modest but detectable benefits for muscle hypertrophy but not maximal strength. At the individual level, we failed to reveal irrefutable evidence of true IRV for either primary outcome, though there was stronger support for variability in training responses independent of weekly set volume (i.e., general IRV) compared to differential responses between volume conditions (i.e., condition-specific IRV). C_LIO_LIWhile this study has limitations, it highlights that appropriate study design and statistical analysis are essential for investigating IRV in resistance training. Our findings, along with the broader research in multiple disciplines (i.e., medicine, nutrition science, and exercise physiology), demonstrate that gross variability can purely reflect confounding sources of within-participant variation (e.g., sampling variance, measurement error, biological variability) rather than true inter-individual differences--a distinction critical for both research and practice. C_LI

physiology↗

bioRxiv2022

Enhanced photosynthetic efficiency for increased carbon assimilation and woody biomass production in hybrid poplar INRA 717-1B4

Increasing CO2 levels in the atmosphere and the resulting negative impacts on climate change have compelled global efforts to achieve carbon neutrality or negativity. Most such efforts focus on carbon sequestration through chemical or physical approaches. We aim to harness the power of synthetic biology to enhance plants natural ability to draw down and sequester carbon, thereby positively affecting climate change. Past decades of scientific progress have shed light on strategies to overcome the intrinsic limitations of carbon drawdown and fixation through photosynthesis, particularly in row crops in hopes of improving agricultural productivity for food security. Incorporating a photorespiration bypass in C3 plants has shown promising results of increased biomass and grain yield. Despite their globally dominant role in atmospheric carbon flux, the drawdown rates of most trees are currently limited by their C3 photosynthetic metabolism, and efforts to improve the photosynthetic capacity of trees, such as by reducing energy loss in photorespiration, are currently lacking. Here, we selected a photorespiration bypass pathway and tested its effectiveness on photosynthetic enhancement in hybrid poplar INRA717-IB4. The design includes a RNAi strategy to reduce the transportation of the photorespiration byproduct, glycolate, out of chloroplast and a shunt pathway to metabolize the retained glycolate back to CO2 for fixation through the Calvin-Benson cycle. Molecular and physiological data collected from two repeated growth experiments indicates that transgenic plants expressing genes in the photorespiration bypass pathway have increased photosynthetic efficiency, leading to faster plant growth and elevated biomass production. One lead transgenic event accumulated 53% more above-ground dry biomass over a five month growth period in a controlled environment. Pilot projects with photosynthesis-enhanced trees in the field are in progress. Our results provide a proof-of-concept for engineering trees to help combat climate change.

plant biology↗

bioRxiv2021

Contrast Solution Properties and Scan Parameters Influence the Apparent Diffusivity of Computed Tomography Contrast Agents in Articular Cartilage

The inability to detect early degenerative changes to the articular cartilage surface that commonly precede bulk osteoarthritic degradation is an obstacle to early disease detection for research or clinical diagnosis. Leveraging a known artifact that blurs tissue boundaries in clinical arthrograms, contrast agent diffusivity can be derived from computed tomography arthrography (CTa) scans. We combined experimental and computational approaches to study protocol variations that may alter the CTa-derived apparent diffusivity. In experimental studies on bovine cartilage explants, we examined how contrast agent dilution and transport direction (absorption vs. desorption) influence the apparent diffusivity of untreated and enzymatically digested cartilage. Using multiphysics simulations, we examined mechanisms underlying experimental observations and the effects of image resolution, scan interval and early scan termination. The apparent diffusivity during absorption decreased with increasing contrast agent concentration by an amount similar to the increase induced by tissue digestion. Models indicated that osmotically induced fluid efflux strongly contributed to the concentration effect. Simulated changes to spatial resolution, scan spacing and total scan time all influenced the apparent diffusivity, indicating the importance of consistent protocols. With careful control of imaging protocols and interpretations guided by transport models, CTa-derived diffusivity offers promise as a biomarker for early degenerative changes.

bioengineering↗

bioRxiv2020

Grapevine microbiota reflect diversity among compartments and complex interactions within and among root and shoot systems

BackgroundWithin an individual plant, different compartments (e.g. roots, leaves, fruits) host distinct communities of microorganisms due to variation in structural characteristics and resource availability. Grafting, which joins the root system of one individual with the shoot system of a second genetically distinct individual, has the potential to bring the microbial communities of different genotypes together. An important question is the extent to which unique root system and shoot system genotypes, when grafted together, influence the microbiota of the graft partner. Our study sought to answer this question by utilizing an experimental vineyard composed of Chambourcin vines growing ungrafted and grafted to three different rootstocks, replicated across three irrigation treatments. We characterized bacterial and fungal communities in roots, leaves, and berries, as well as surrounding soil. Our objectives were to (1) characterize the microbiota of compartments within the root system (roots and adjacent soil) and the shoot system (leaves and berries), (2) determine the influence of rootstock genotypes, irrigation, and their interaction on the microbiota of aboveground and belowground compartments, and (3) investigate the distribution of microorganisms implicated in the late-season grapevine bunch rot disease sour rot (Acetobacterales and Saccharomycetes). ResultsCompartments were significantly differentiated in bacterial and fungal richness and composition. Abundance-based machine learning accurately predicted the compartment and differential abundance analysis showed a large portion of taxa differed significantly across compartments. Rootstock genotypes did not differ significantly in microbial community richness or composition; however, individual microbial taxa exhibited significant differences in abundance based on rootstock and irrigation treatment. The relative abundance of Acetobacterales and Saccharomycetes in the berry was influenced by complex interactions among rootstock genotype and irrigation. ConclusionOur results indicate that grapevine compartments retain distinct core microbiota regardless of the rootstock to which they are grafted. While rootstock genotype generally had a subtle impact on global patterns of microbial diversity, we found associations between rootstock genotypes and specific groups of microorganisms. Further experimental validation is needed in order to understand how associations with these microorganisms impacts a vines susceptibility to sour rot upon damage and whether the characteristics of wine are impacted.

plant biology↗

bioRxiv2019

Epiphytic Microbiome of Grapes Berries Varies Between Phenological Timepoints, Growing Seasons and Regions

Extensive research into the microbial ecology of grapes near harvest, with a primary focus on yeasts, has improved our understanding of some components of variation that influence grapevine terroir. Metagenomic tools enable a broader exploration of the plant microbiome and components of variability due to such factors as year, location, management, and phenological stage. In 2014, to characterize the microbial changes of the grape surface over the course of the growing season in the Finger Lakes region of New York, we examined the epiphytic microbiome of grapes at five key phenological stages: pea-sized, bunch closure, Veraison, 15 Brix and harvest. This experiment was repeated in two subsequent years in the Finger Lakes, New York in 2015, and in Tasmania, Australia in 2016, to examine variability of regional terroir. We found significant shifts in taxa presence and relative taxa abundance between phenological timepoints, and determined that the epiphytic microbiome differed significantly not just between regions but also within a single region from one year to the next. These findings call into question the role of the phytobiome in the expression of terroir, as the phytobiome is dynamically responding to its environment, within and between years and locations. On the berry surface in particular, these dynamics are complicated by weather and management. Understanding that the grape surface microbiome is consistently changing may influence how we manage the berry epiphytic microbiome, potentially affecting disease management and vinification decisions.

microbiology↗