Biology subjects

Ahmadi, H.

Publications and source records attributed to Ahmadi, H..

15 recordsLinked to original sources

bioRxiv2026

Genetic Architecture of Perivascular Space Morphology in the Pediatric Brain

IntroductionPerivascular spaces (PVS) support brain homeostasis through metabolite delivery and waste clearance, yet the genetic determinants of PVS morphology during childhood remain unknown. Here, we leveraged cross-sectional Adolescent Brain Cognitive Development Study data (N = 6,600; ages 9-10), including genomics and 3T structural MRI. MethodsLinear mixed-effects models examined associations between 45 single nucleotide polymorphisms (SNPs) previously linked to adult PVS structure or function and PVS count and volume fraction (VF) across six macroregions and 28 Desikan-Killiany subregions. ResultsFifteen SNPs demonstrated significant associations with PVS macroregion morphology, predominantly VF; 21 SNPs demonstrated associations with subregion morphology. Variants near SLC13A3 showed the strongest, most widespread associations with PVS VF. Additional replicated variants implicated Wnt signaling, cell adhesion, apoptosis, and glymphatic function. ConclusionThese findings suggest genetic associations with PVS morphology are detectable in childhood, while highlighting developmental and regional specificity. Longitudinal studies are now needed to determine whether childhood PVS genetic architecture predicts trajectories of glymphatic maturation and associated cognitive outcomes. Key PointsO_LIPerivascular space morphology, mapped across 28 white matter subregions, displays substantial regional and interindividual variability during childhood. C_LIO_LISix genetic associations with perivascular morphology were only detectable at subregion resolution, demonstrating that lobar averaging can obscure spatially restricted signals. C_LIO_LINearly 50% of adult-identified perivascular space risk variants replicated in 9-10 year-olds, with anatomically patterned associations reflecting patterns of neurovascular complexity and neurodevelopmental timing. C_LI

neuroscience↗

bioRxiv2026

Developmental Differences in White Matter Microarchitecture in Youth with ADHD: Longitudinal Findings from the ABCD Study

BackgroundAttention-deficit/hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder and is a risk factor for later brain disorders. Here, we characterize the relationship between ADHD status and white matter cellularity across development and examine associations with medication, using a novel biophysical diffusion MRI model in youth aged 9 to 14 years. Methods: The ABCD Study(R) is a longitudinal cohort study with three biennial waves of brain MRI collection. Twenty-seven white matter tracts were delineated using multi-shell diffusion-weighted imaging (DWI) and tractography. Intracellular isotropic (RNI) and directional (RND) diffusion were quantified using the Restriction Spectrum Imaging (RSI) model. Longitudinal linear mixed-effect models characterize the effects of ADHD status and medication use on white matter cellularity across three waves. Results: By wave: 9,426 participants at baseline (mean [SD] age: 9.92 [0.63] years; 48.7% Female; 12.2% with ADHD), 6745 participants at 2-year (11.95 [0.65] years; 46.8% Female; 11.3% with ADHD), and 2,483 participants at 4-year (14.07 [0.69] years; 46.0% Female; 11.8% with ADHD). ADHD was associated with decreased RNI in 20 tracts at age 9, with evidence of developmental trajectory differences suggesting attenuation over early adolescence. We found enduring ADHD-associated decreases in RND of 16 tracts spanning ages 9 to 14 years, with methylphenidate effects on 2 tracts. Low-motion sensitivity analyses confirmed robust RNI findings, but not RND findings. ConclusionsADHD was associated with reductions in isotropic diffusion in white matter tracts, and possibly with complementary reductions in directional diffusion of select tracts. Isotropic diffusion findings suggest atypical glial cellularity in white matter during late childhood.

neuroscience↗

bioRxiv2026

Prefrontal working memory activity partially mediates link between enriched neighborhood environments and episodic memory among 9-13-year-olds

BackgroundEnriched environments support neurodevelopment. The pathways linking enrichment to cognitive processes such as episodic memory among youth remain unclear. This study examined whether brain function and structure in episodic memory-implicated neurocircuitry mediate the relationship between neighborhood enrichment and episodic memory performance. MethodsWe analyzed data from the Adolescent Brain Cognitive Development Study (n = 9,028) at two timepoints (baseline: 9-11-years-old and two-year follow-up: 11-13-years-old). Neighborhood enrichment was estimated at the childs primary residential address proxied by the Child Opportunity Index 2.0 (COI). Episodic memory was assessed using the Picture Sequence Memory Test (PSMT). A multimodal neuroimaging approach examined task-based working memory-related functional activity, brain volume, and resting-state intrinsic activity in 26 bilateral brain regions, segmented using the Desikan-Killiany atlas, implicated in episodic memory. Following FDR-corrected linear mixed effects models, controlling for sociodemographic, neuroimaging factors, and site-related variability, two sets of mediation analyses were conducted per time point. ResultsGreater neighborhood enrichment (i.e., higher COI scores) was directly associated with better episodic memory, prefrontal cortex (PFC) task-based functional activity, and larger PFC and medial temporal lobe volume across timepoints. PFC task-based functional activity, but not brain volume or intrinsic activity, partially mediated these relationships. Specifically, PFC task-activity in the left and right caudal and rostral middle frontal gyri, and left pars opercularis, accounted for [~]2-7% of the mediated effect. ConclusionOur findings contribute to a rapidly growing body of literature linking environmental influences on neurocognitive outcomes during development. Given childhood and adolescence represent sensitive periods for neurodevelopment, interventions aimed at increasing neighborhood access to enriching experiences such as educational opportunities, cognitively stimulating activities, and social support may have lasting benefits for neurocognitive development.

neuroscience↗

bioRxiv2025

Sex and gender differences in perivascular space in early adolescence

Perivascular spaces (PVS) surrounding cerebral blood vessels play an important role in the blood-brain barrier and glymphatic system. Although it was once thought that PVS were either absent or too small to be seen or quantified during healthy development with MRI, recent studies have found visible, quantifiable PVS exist throughout the white matter of the cerebrum in childhood and adolescence. As a result, researchers have begun to explore individual differences, including potential sex-based variations in developing PVS. Meta-analyses in adults have shown that PVS are larger on average in males than in females, and several studies have shown a similar relationship in children. In contrast, no studies to date have examined the association between gender and PVS at any age. This cross-sectional study examined 6,538 youths from a large, nationwide sample of 9- to 11-year-olds in the U.S. to examine the relationship between sex, felt-gender, and PVS count and volume. Using a model-building approach, we conducted a series of linear mixed-effects models to determine the maximum variance explained in PVS count and volume, including age, pubertal development status, race, parent education, BMI z-score, and regional white matter volume, while also adjusting for MRI scanner and site. BMI z-score, age, and parent education were significant predictors of both PVS volume and count. Adding sex to the model improved model fit in all regions, and the further addition of felt-gender significantly improved model fit for PVS count in 5/6 regions of interest. Moreover, we found increases in PVS volume and count were associated with reduced executive function, learning, and memory. As the first study to report an association between felt-gender and PVS, our findings demonstrate the importance of considering gender in addition to sex as a potential source of structural variance in PVS in adolescents.

neuroscience↗

bioRxiv2025

Estimating individual-level changes in functional brain connectivity and correspondence with topology changes

With the rise of precision medicine and large neuroimaging datasets, measuring brain changes on an individual level becomes more possible and more important. However, functional connectivity has some mathematical and conceptual quirks that make estimating individual-level changes more complicated than, for example, estimating structural brain changes. Here, we compared six different change scores, i.e., metrics for quantifying change in functional connectivity, using a large sample with two time points, roughly 2 years apart, of low-motion data from the ABCD Study (N=2,719, ages 9-13 years). First, we compared distributions and potential interpretations of each metric. Then, we assessed how well different metrics captured topology change estimates by comparing them to individual-level changes in clustering coefficient, betweenness centrality, and network strength. As multivariate metrics may be more reliable than single connections and researchers often interpret connectivity changes in topological terms, this offers additional insight into the implications of change score choice. Overall, our analyses revealed widely different distributions between change scores that conferred vastly different results and interpretations of functional connectivity changes between time points. Thus, we provide recommendations for each change score and its optimal (or suboptimal) use cases, depending on the population, study design, and research question.

neuroscience↗

bioRxiv2025

Ambient Pollution Components and Sources Associated with Hippocampal Architecture and Memory in Pre-Adolescents

BackgroundAmbient air pollution poses significant risks to brain health. The hippocampus may be particularly vulnerable, yet the extent to which it is impacted in children remains unclear. MethodsUsing partial least squares correlation, we cross-sectionally analyzed air pollution, brain, and cognitive data from the Adolescent Brain Cognitive Development Study to examine how multi-pollutant exposure influences hippocampal structure and memory in 9-11-year-olds (n= 7,940). Annual average air pollution exposures included PM2.5 (total mass, 15 components, and 6 source factors), NO2, and 8-hour maximum O3. Hippocampal outcomes included microstructure measured using Restriction Spectrum Imaging and hippocampus longitudinal-axis (i.e., head, body, tail) volumes. We examined hippocampal-dependent list-learning using the Rey Auditory Verbal Learning Test. Models were adjusted for demographic, socioeconomic, and neuroimaging factors. FindingsPM2.5 total mass was associated with hippocampal microstructure, but not long-axis volume or list-learning ability. Component and source analyses provided greater specificity: higher bromine, sulfate, and vanadium exposure was related to microstructure (72% shared variance), while higher copper and zinc exposure correlated with smaller left head and right body and tail volumes (75% shared variance). Source models implicated biomass burning and traffic pollution in microstructure (61% and 32% shared variance) and industrial and traffic sources in smaller hippocampal volumes (77% shared variance). Higher exposure to several components were also linked to poorer list-learning (67% shared variance). DiscussionCo-exposure to multiple pollutants is linked to differences in hippocampal structure and memory, showing that associations are driven not only by PM2.5 total mass but also by specific components and sources. This evidence underscores the necessity of targeting source-specific (e.g., biomass burning, traffic, and industrial emissions) and constituent components (e.g., metals) of air pollution during critical developmental windows to safeguard brain health.

neuroscience↗

bioRxiv2025

Sleep duration and efficiency moderate the effects of prenatal and childhood ambient pollutant exposure on global white matter microstructural integrity in adolescence

BackgroundAir pollution is a ubiquitous neurotoxicant associated with alterations in structural connectivity. Good habitual sleep may be an important protective lifestyle factor due to its involvement in the brain waste clearance and its bidirectional relationship with immune function. Wearable multisensory devices may provide more objective measures of sleep quantity and quality. We investigated whether sleep duration and efficiency moderated the relationship between prenatal and childhood pollutant exposure and whole-brain white matter microstructural integrity at ages 10-13 years. MethodsWe used multi-shell diffusion-weighted imaging data collected on 3T MRI scanners and objective sleep data collected with Fitbit Charge 2 from the 2-year follow-up visit for 2178 subjects in the Adolescent Brain Cognitive Development Study(R). White matter tracts were identified using a probabilistic atlas. Restriction spectrum imaging was performed to extract restricted normalized isotropic (RNI) and directional (RND) signal fraction parameters for all white matter tracts, then averaged to calculate global measures. Sleep duration was calculated by summing the time spent in each sleep stage; sleep efficiency was calculated by dividing sleep duration by time spent in bed. Using an ensemble-based modeling approach, air pollution concentrations of PM2.5, NO2, and O3 were assigned to each childs residential addresses during the prenatal period (9-month average before birthdate) as well as at ages 9- 10 years. Multi-pollutant linear mixed effects models assessed the associations between global RNI and RND and sleep-by-pollutant interactions, adjusting for appropriate covariates. ResultsSleep duration interacted with childhood NO2 exposure and sleep efficiency interacted with prenatal O3 exposure to affect RND at ages 10-13 years. Longer sleep duration and higher sleep efficiency in the context of higher pollutant exposure was associated with lower RND compared to those with similar pollutant exposure but shorter sleep duration and lower sleep efficiency. ConclusionsLow-level air pollution poses a risk to brain health in youth, and healthy sleep duration and efficiency may increase resilience to its harmful effects on white matter microstructural integrity. Future studies should evaluate the generalizability of these results in more diverse cohorts as well as utilize longitudinal data to understand how sleep may impact brain health trajectories in the context of pollution over time.

neuroscience↗

bioRxiv2024

Effects of one-night partial sleep deprivation on perivascular space volume fraction: Findings from the Stockholm Sleepy Brain Study

Increased waste clearance in the brain is thought to occur most readily during late-stage sleep (stage N3). Sleep deprivation disrupts time spent in deeper sleep stages, fragmenting the clearance process. Here, we have utilized the publicly available Stockholm Sleepy Brain Study to investigate whether various sleep-related measures are associated with changes in perivascular space (PVS) volume fraction following a late-night short-sleep experiment. Our sample consisted of 60 participants divided into old (65-75 years) and young (20-30 years) age groups. We found that partial sleep deprivation was not significantly associated with major PVS changes. In the centrum semiovale, we observed an interaction between percentage of total sleep time spent in N3 and sleep deprivation status on PVS volume fraction. In the basal ganglia, we saw an interaction between N2 (both percentage of total sleep time and absolute time in minutes) and sleep deprivation status. However, the significance of these findings did not survive multiple comparisons corrections. This work highlights the need for future longitudinal studies of PVS and sleep, allowing for quantification of within-subject morphological changes occurring in PVS due to patterns of poor sleep. Our findings here provide insight on the impacts that a single night of late-night short-sleep has on the perivascular waste clearance system. Statement of SignificanceSleep issues have been known to be associated with a variety of health risks. Recent research has shown the importance of sleep for brain clearance, with increases in brain clearance occurring during sleep. PVS seen on MRI are known to represent both influx and efflux pathways for the exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) in the brain parenchyma, a key process underlying the waste clearance system.1 Numerous recent studies have found links between sleep disruption and PVS volume changes. However, no study to date has been able to examine within-subject changes in PVS resulting from experimental manipulation of sleep. Our study represents the first within-subject study looking at the effects of partial sleep deprivation on PVS volume fraction using an automated PVS segmentation technique.

neuroscience↗

bioRxiv2024

Amygdala Subregion Volumes and Apportionment in Preadolescents -- Associations with Age, Sex, and Body Mass Index

The amygdala, a key limbic structure, is critical to emotional, social, and appetitive behaviors that develop throughout adolescence. Composed of a heterogeneous group of nuclei, questions remain about potential differences in the maturation of its subregions during development. In 3,953 9- and 10-year-olds from the Adolescent Brain Cognitive DevelopmentlZI Study, the CIT168 Amygdala Atlas was used to segment nine amygdala subregions. Linear mixed-effects models were used to examine the effects of age, sex, pubertal stage, and body mass index z-score (BMIz) on subregion volumes and their relative apportionment within the amygdala. Distinct associations were observed between age, sex, and BMIz and whole amygdala volume, subregion volumes, and subregion apportionment. Pubertal stage was not related to amygdala subregion volumes. Age was associated with near-global expansion of amygdala subregions during this developmental period. Female sex was linked to smaller volumes in most amygdala subregions, with larger relative apportionment in the dorsal subregions and smaller apportionment in the basolateral ventral paralaminar subregion. Higher BMIz was associated with smaller volumes in large basolateral subregions, with increased relative apportionment in smaller subregions. These findings provide a foundational context for understanding how developmental variables influence amygdala structure, with implications for understanding future risk for brain disorders. HighlightsO_LISegmentation of amygdala subregions in nearly 4,000 preadolescents. C_LIO_LIAge, but not puberty, was associated with a near-global expansion of the amygdala. C_LIO_LISex differences exist in preadolescent amygdala apportionment. C_LIO_LIChildhood obesity is linked to differences in the basolateral amygdala. C_LI

neuroscience↗

bioRxiv2024

More similarity than difference: comparison of within- and between-sex variance in early adolescent brain structure

BackgroundAdolescent neuroimaging studies of sex differences in the human brain predominantly examine mean differences between males and females. This focus on between-groups differences without probing relative distributions and similarities may contribute to both conflation and overestimation of sex differences and sexual dimorphism in the developing human brain. MethodsWe aimed to characterize the variance in brain macro-and micro-structure in early adolescence as it pertains to sex at birth using a large sample of 9-11 year-olds from the Adolescent Brain Cognitive Development (ABCD) Study (N=7,723). Specifically, for global and regional estimates of gray and white matter volume, cortical thickness, and white matter microstructure (i.e., fractional anisotropy and mean diffusivity), we examined: within-and between-sex variance, overlap between male and female distributions, inhomogeneity of variance via the Fligner-Killeen test, and an analysis of similarities (ANOSIM). For completeness, we examined these sex differences using both uncorrected (raw) brain estimates and residualized brain estimates after using mixed-effects modeling to account for age, pubertal development, socioeconomic status, race, ethnicity, MRI scanner manufacturer, and total brain volume, where applicable. ResultsThe overlap between male and female distributions was universally greater than the difference (overlap coefficient range: 0.585 -0.985) and the ratio of within-sex and between-sex differences was similar (ANOSIM R range: -0.001 -0.117). All cortical and subcortical volumes showed significant inhomogeneity of variance, whereas a minority of brain regions showed significant sex differences in variance for cortical thickness, white matter volume, fractional anisotropy, and mean diffusivity. Inhomogeneity of variance was reduced after accounting for other sources of variance. Overlap coefficients were larger and ANOSIM R values were smaller for residualized outcomes, indicating greater within-and smaller between-sex differences once accounting for other covariates. ConclusionsReported sex differences in early adolescent human brain structure may be driven by disparities in variance, rather than binary, sex-based phenotypes. Contrary to the popular view of the brain as sexually dimorphic, we found more similarity than difference between sexes in all global and regional measurements of brain structure examined. This study builds upon previous findings illustrating the importance of considering variance when examining sex differences in brain structure. HighlightsO_LIHigh male/female overlap is ubiquitous across all brain features in early adolescence C_LIO_LIMale variance exceeded female variance for global and regional brain volumes C_LIO_LIBetween-and within-sex differences were similar in magnitude for all features C_LI Plain English SummaryBrain imaging research has consistently revealed differences between males and females in the shape and size of adolescent brains. Studies usually compare the average male brain to the average female brain. However, brain structure varies greatly among individuals, even within the same sex. Without looking at both the variability within people of the same sex, and the degree of similarity between the sexes, it is unclear if separating adolescent brains into male and female categories will help us understand brain development. In this study, we looked at the overlap in brain structure among male and female youths (ages 9 to 11 years). We also compared variability between sexes and within each sex. Overall, we found that, there was more similarity than difference between male and female brains. The difference between any given male and any given female was similar to the difference between two individuals of the same sex. These findings suggest that, despite some small average differences, the brains of early adolescent males and females are more alike than different at ages 9-11 years.

neuroscience↗

bioRxiv2024

Spatiotemporal patterns in cortical development: Age, puberty, and individual variability from 9 to 13 years of age

Humans and nonhuman primate studies suggest that timing and tempo of cortical development varies neuroanatomically along a sensorimotor-to-association (S-A) axis. Prior human studies have reported a principal S-A axis across various modalities, but largely rely on cross-sectional samples with wide age-ranges. Here, we investigate developmental changes and individual variability in cortical organization along the S-A axis between the ages of 9-13 years using a large, longitudinal sample (N = 2487-3747, 46-50% female) from the Adolescent Brain Cognitive Development Study (ABCD Study(R)). This work assesses multiple aspects of neurodevelopment indexed by changes in cortical thickness, cortical microarchitecture, and resting-state functional fluctuations. First, we evaluated S-A organization in age-related changes and, then, computed individual-level S-A alignment in brain changes and assessing differences therein due to age, sex, and puberty. Varying degrees of linear and quadratic age-related brain changes were identified along the S-A axis. Yet, these patterns of cortical development were overshadowed by considerable individual variability in S-A alignment. Even within individuals, there was little correspondence between S-A patterning across the different aspects of neurodevelopment investigated (i.e., cortical morphology, microarchitecture, function). Some of the individual variation in developmental patterning of cortical morphology and microarchitecture was explained by age, sex, and pubertal development. Altogether, this work contextualizes prior findings that regional age differences do progress along an S-A axis at a group level, while highlighting broad variation in developmental change between individuals and between aspects of cortical development, in part due to sex and puberty. Significance StatementUnderstanding normative patterns of adolescent brain change, and individual variability therein, is crucial for disentangling healthy and abnormal development. We used longitudinal human neuroimaging data to study several aspects of neurodevelopment during early adolescence and assessed their organization along a sensorimotor-to-association (S-A) axis across the cerebral cortex. Age differences in brain changes were linear and curvilinear along this S-A axis. However, individual-level sensorimotor-association alignment varied considerably, driven in part by differences in age, sex, and pubertal development.

neuroscience↗

bioRxiv2023

Sex, gender diversity, and brain structure in children ages 9 to 11 years old

There remains little consensus about the relationship between sex and brain structure, particularly in childhood. Moreover, few pediatric neuroimaging studies have analyzed both sex and gender as variables of interest - many of which included small sample sizes and relied on binary definitions of gender. The current study examined gender diversity with a continuous felt-gender score and categorized sex based on X and Y allele frequency in a large sample of children ages 9-11 years-old (N=7693). Then, a statistical model-building approach was employed to determine whether gender diversity and sex independently or jointly relate to brain morphology, including subcortical volume, cortical thickness, gyrification, and white matter microstructure. The model with sex, but not gender diversity, was the best-fitting model in 75% of gray matter regions and 79% of white matter regions examined. The addition of gender to the sex model explained significantly more variance than sex alone with regard to bilateral cerebellum volume, left precentral cortical thickness, as well as gyrification in the right superior frontal gyrus, right parahippocampal gyrus, and several regions in the left parietal lobe. For mean diffusivity in the left uncinate fasciculus, the model with sex, gender, and their interaction captured the most variance. Nonetheless, the magnitude of variance accounted for by sex was small in all cases and felt-gender score was not a significant predictor on its own for any white or gray matter regions examined. Overall, these findings demonstrate that at ages 9-11 years-old, sex accounts for a small proportion of variance in brain structure, while gender diversity is not directly associated with neurostructural diversity. HighlightsO_LISex-related variance in regional human brain structure is widespread at ages 9-11 C_LIO_LITogether, sex and gender diversity accounted for more variance in only a few regions C_LIO_LIFelt-gender diversity itself was not significantly related to any outcome at ages 9-11 C_LIO_LIEffect sizes for sex and felt-gender estimates were small C_LI

neuroscience↗

bioRxiv2023

Prediction of SARS-CoV-2 spike protein mutations using Sequence-to-Sequence and Transformer models

In the study of viral epidemics, having information about the structural evolution of the virus can be very helpful in controlling the disease and making vaccines. Various deep learning and natural language processing techniques (NLP) can be used to analyze genetic structure of viruses, namely to predict their mutations. In this paper, by using Sequence-to-Sequence (Seq2Seq) model with Long Short-Term Memory (LSTM) cell and Transformer model with the attention mechanism, we investigate the spike protein mutations of SARS-CoV-2 virus. We make time-series datasets of the spike protein sequences of this virus and generate upcoming spike protein sequences. We also determine the mutations of the generated spike protein sequences, by comparing these sequences with the Wuhan spike protein sequence. We train the models to make predictions in December 2021, February 2022, and October 2022. Furthermore, we find that some of our generated spike protein sequences have been reported in December 2021 and February 2022, which belong to Delta and Omicron variants. The results obtained in the present study could be useful for prediction of future mutations of SARS-CoV-2 and other viruses.

bioinformatics↗

bioRxiv2020

Effect of An Inverted Seated Position with Upper Arm Blood Flow Restriction on Measures of Elbow Flexors Neuromuscular Performance

PurposeThe objective of the investigation was to determine the concomitant effects of upper arm blood flow restriction (BFR) and inversion on elbow flexors neuromuscular responses. MethodsRandomly allocated, 13 volunteers performed four conditions in a within-subject design: rest (control, 1-min upright position without BFR), control (1-min upright with BFR), 1-min inverted (without BFR), and 1-min inverted with BFR. Evoked and voluntary contractile properties, before, during and after a 30-s maximum voluntary contraction (MVC) exercise intervention were examined as well as pain scale. ResultsInversion induced significant pre-exercise intervention decreases in elbow flexors MVC (21.1%, [Formula], p=0.02) and resting evoked twitch (29.4%, [Formula], p=0.03) forces. The 30-s MVC induced significantly greater pre- to post-test decreases in potentiated twitch force ([Formula], p<0.0009) during inversion ({downarrow}75%) than upright ({downarrow}65.3%) conditions. Overall, BFR decreased MVC force 4.8% ([Formula], p=0.05). For upright position, BFR induced 21.0% reductions in M-wave amplitude ([Formula], p=0.04). There were no significant differences for electromyographic activity or voluntary activation as measured with the interpolated twitch technique. For all conditions, there was a significant increase in pain scale between the 40-60 s intervals and post-30-s MVC (upright<inversion, and without BFR<BFR). ConclusionThe concomitant application of inversion with elbow flexors BFR only amplified neuromuscular performance impairments to a small degree. Individuals who execute forceful contractions when inverted or with BFR should be cognizant that force output may be impaired.

physiology↗

bioRxiv2019

Enhanced genome integrity maintenance and few large stress-mitigating changes in Arabidopsis halleri extreme-habitat local adaptation

Heavy metal-rich toxic soils and ordinary soils are both natural habitats of Arabidopsis halleri. The molecular divergence underlying survival in sharply contrasting environments is unknown. Here we comparatively address metal physiology and transcriptomes of A. halleri originating from the most highly heavy metal-contaminated soil in Europe, Ponte Nossa (Noss/IT), and from non-metalliferous (NM) soil. Noss exhibits enhanced hypertolerance and attenuated accumulation of cadmium (Cd), and transcriptomic Cd responsiveness is decreased, compared to plants of NM soil origin. Among the condition-independent transcriptome characteristics of Noss, the most highly overrepresented functional class of "meiotic cell cycle" comprises 21 transcripts with elevated abundance in vegetative tissues, in particular Argonaute 9 (AGO9) and the synaptonemal complex transverse filament protein-encoding ZYP1a/b. Increased AGO9 transcript levels in Noss are accompanied by decreased long terminal repeat retrotransposon expression, and are shared by plants from milder metalliferous sites in Poland and Germany. Expression of Iron-regulated Transporter (IRT1) is very low and of Heavy Metal ATPase 2 (HMA2) strongly elevated in Noss, which can account for its specific Cd handling. In plants adapted to the most extreme abiotic stress, broadly enhanced functions comprise genes with likely roles in somatic genome integrity maintenance, accompanied by few alterations in stress-specific functional networks.

plant biology↗