Biology subjects

Ramirez-Garcia, G.

Publications and source records attributed to Ramirez-Garcia, G..

3 recordsLinked to original sources

bioRxiv2025

Repeated subconcussive head impacts compromise white matter integrity: A longitudinal DTI and NODDI study in collegiate football players

ObjectivesTo determine whether repetitive subconcussive impacts in collegiate football are associated with altered white matter microstructure, motor control deficits, and changes in concussion symptoms across a single season. DesignCohort study with non-contact controls and stratification of contact athletes by head-impact exposure. MethodTwenty-two male varsity football players and 27 non-contact controls underwent pre-season diffusion tensor imaging. Tract-specific fractional anisotropy (FA) and mean diffusivity (MD) were derived from commissural and association tracts using probabilistic tractography. Helmet-mounted accelerometers quantified head-impact frequency and gForce over the season, classifying athletes into high (HE) and low-exposure (LE) groups. Football players completed the Kinarm Ball-on-Bar bimanual coordination task and SCAT3 symptom checklist pre- and post-season. ResultsAt pre-season, contact athletes showed altered white matter microstructure versus controls, with higher FA and predominantly lower MD across most tracts. Over the season, HE athletes sustained more total impacts and gForce than LE athletes and showed declining bimanual coordination on the Ball-on-Bar motor task. SCAT3 symptom and severity scores were low and showed no differences in change. ConclusionsRepetitive subconcussive exposure in collegiate football is associated with persisting white matter differences and subtle bimanual motor coordination deficits that are not detected by routine symptom-based tools, supporting the use of advanced neuroimaging and robotic motor assessment to monitor athlete brain health.

neuroscience↗

bioRxiv2025

Functional Connectivity Alterations in Spinocerebellar Ataxia Type 10: Insights from Gray Matter Atrophy

Spinocerebellar ataxia type 10 (SCA10) is a rare, inherited neurological disorder caused by an expansion of the non-coding ATTCT pentanucleotide repeat in the ATAXIN 10 gene. It is characterized by cerebellar ataxia and epilepsy. Previous research has demonstrated extensive white and gray matter degeneration, particularly in the cerebellum. However, the impact of the SCA10 mutation on functional connectivity (FC) remains unexplored. This study aimed to characterize intrinsic FC changes in SCA10 patients and their relationship to clinical manifestations. Structural and resting-state MRIs were obtained from 26 SCA10 patients and 26 control subjects. Voxel-based morphometry (VBM) and seed-ROI and Independent Components Analysis (ICA) were performed to identify cerebral atrophy and FC changes respectively. Additionally, correlation analyses were conducted between FC changes and scores from the Scale for the Assessment and Rating of Ataxia (SARA) and the Montreal Cognitive Assessment (MoCA). In SCA10 patients, VBM analysis revealed extensive gray matter loss in motor cortices and the cerebellum. FC analysis identified significant FC changes originating from seed-ROIs in the right cerebellar VI and left precentral gyrus. Furthermore, group comparison using ICA components showed that SCA10 patients exhibited higher FC in the sensorimotor and cerebellar functional networks. Moreover, the average BOLD signal within the cerebellar network negatively correlated with MoCA scores. In summary, SCA10 patients exhibited enhanced FC in brain regions that displayed gray matter atrophy, underscoring the impact of SCA10 degeneration on resting state networks and induction of potential maladaptive FC compensatory mechanisms.

neuroscience↗

bioRxiv2020

Iron limitation by transferrin promotes simultaneous cheating of pyoverdine and exoprotease in Pseudomonas aeruginosa

Pseudomonas aeruginosa is the main bacterial model to study cooperative behaviors, since it yields exoproducts such as exoproteases and siderophores that act as public goods and can be exploited by selfish non-producers that behave as social cheaters. Non-producers of the siderophore pyoverdine are typically isolated in media with low free iron, mainly casamino acids medium supplemented with transferrin. Nevertheless, using a protein as the iron chelator could additionally select mutants unable to produce exoproteases that degrade the transferrin to facilitate iron release. Here, we investigated the dynamics of pyoverdine and exoprotease production in media in which iron was limited by using either transferrin or a cation chelating resin. Our experiments show that concomitant loss of pyoverdine and exoprotease production readily develops in media with transferrin whereas only lack of pyoverdine emerges in medium treated with the resin. Genomic characterization of the exoprotease- and pyoverdine-less mutants revealed large deletions (13 to 33 Kb) including Quorum Sensing (lasR, rsal and lasl) and flagellar genes. Complementation experiments, PCR and motility tests confirmed the deletions. Our work shows that using transferrin as an iron chelator imposes simultaneous selective pressure for the loss of pyoverdine and exoprotease production. The unintended effect of transferrin observed in our experiment settings can help revisiting or informing the design of similar studies.

microbiology↗