Biology subjects

Valenzuela, P.

Publications and source records attributed to Valenzuela, P..

3 recordsLinked to original sources

bioRxiv2026

Environmental and spatiotemporal drivers of marine microbial communities from Antarctic and Subantarctic water masses

The Southern Ocean harbors diverse marine microbial communities shaped by both local oceanographic conditions and dispersal limitations. However, this knowledge is mainly based on coastal Antarctic sites, whereas circumpolar Antarctic open sea and subantarctic ecosystems remain poorly explored. Here, we characterize marine microbial communities (using 16S rDNA high-throughput sequencing) and marine oceanographic data across two regions: the Subantarctic, involving two localities (the Magellan Strait and the Beagle Channel), and Antarctic open sea, involving two localities (Eastern Indian and Central South Pacific). We found extensive differences across regions and localities, characterized by distinct taxonomic patterns, alpha diversity, microbial composition, and enriched taxa profiles. Despite these differences, Clade Ia, Amylibacter, NS5 marine group, and NS2b marine group exhibited high prevalence across regions. Oceanographic parameters had variable relationships with microbial alpha diversity across regions: Sea surface temperature and salinity had a negative and positive correlation, respectively, in the Magellan Strait during 2024. In the Antarctic region, dissolved oxygen displayed a negative correlation in the Indian Ocean during 2024, whereas salinity displayed a more variable relationship in the Indian Ocean: positively correlated during 2024, while negatively correlated during 2025. Collectively, our results highlight a strong microbiological biogeographic structure in the Southern Ocean, both across broad scales (between Subantarctic and Antarctic regions) and within regions. Furthermore, our results show dynamic relationships between oceanographic variables and marine microbial diversity across Antarctic and Subantarctic regions.

microbiology↗

bioRxiv2024

alpha-Actinin-3 deficiency protects from the effects of acute cold exposure through altered skeletal muscle Ca2+ and OXPHOS signaling.

Summary / AbstractA nonsense polymorphism in the ACTN3 gene (R577X, rs1815739) results in the loss of the fast skeletal muscle fiber protein -actinin-3 in an estimated 1.5 billion humans worldwide. Homozygosity for this common polymorphism (ACTN3 577XX) does not cause disease but is detrimental to sprint performance in elite athletes. Recently, we reported that ACTN3 577XX humans and Actn3 knockout mice show improved cold tolerance. This was not due to an increase in brown adipose tissue activity or a greater muscle shivering response, but was associated with an increased abundance of slow myosin heavy chain muscle fibers in XX individuals, which in turn increased muscle tone to improve cold tolerance. Using the Actn3 knockout mouse we have now analyzed the molecular and physiological impacts of acute cold exposure (4{degrees}C, for 5 hours) on skeletal muscle. In addition, we used statistical inference of publicly available archaic (Neanderthal and Denisovan) and modern human DNA data to estimate the age of the ACTN3 X-allele and to identify a novel haplotype associated with this variant that provides support for genetic selection in some populations of modern humans. Our results indicate that skeletal muscle of Actn3 knockout mice exhibit higher mitochondrial oxidative phosphorylation abundance and activity than wild-type controls. Following acute cold exposure, we identified reductions in gene ontology pathways associated with metabolism and protein breakdown, which impact muscle mass loss and improved muscle fatigue resistance. Together this provides further evidence for improved cold tolerance in Actn3 knockout mice and ACTN3 577XX individuals. Furthermore, we confirm that the X-allele first appeared in modern humans [~]135,000 years ago, with this variant increasing in frequency in European and Asian populations from as early as 42,000 years ago, which aligns with modern human migration out of Africa. Taken together these data provide additional molecular and functional evidence for a protective advantage of -actinin-3 deficiency following cold exposure, highlighting the importance of skeletal muscle in mammalian thermogenesis and its potential role in the evolution of modern-day humans.

cell biology↗

bioRxiv2019

Physiological predictors of competitive performance in CrossFit(R) athletes

The aim of this study was to determine which physiological variables could predict performance during a CrossFit competition. Fifteen male CrossFit athletes (35 {+/-} 9 years) participated and performed a series of tests (incremental load test for full squat and bench press, jump tests, incremental running test, and Wingate test) that were used as potential predictors of CrossFit performance. Thereafter, they performed the five Workouts of the Day (WODs) corresponding to the CrossFit Games Open 2019, and the relationship between each variable and CrossFit performance was analyzed. Overall Crossfit performance (i.e., final ranking considering all WODs) was significantly related to jump ability, mean and peak power output during the Wingate test, relative maximum strength for the full squat and the bench press, and maximum oxygen uptake and maximum speed during an incremental running test (all p<0.05, r=0.58-0.75), although the relationship of most markers varied depending on the analyzed WOD. Multiple linear regression analysis showed that the combination of maximum oxygen uptake, squat jump ability, and reactive strength index accounted for 81% of the variance in overall CrossFit performance (p=0.0003). CrossFit performance seems dependent on a variety of power-, strength-, and aerobic-related markers, which reflects the complexity of this sport. Improvements in aerobic capacity may help people and athletes in CrossFit performance and well-being. Also, focus on lower body power could be the key to obtain better performance markers.

physiology↗