Vitamin E-inspired multi-scale imaging agent

The production and use of multi-modal imaging agents is on the rise. The vast majority of these imaging agents are limited to a single length scale for the agent (e.g. tissues only), which is typically at the organ or tissue scale. This work explores the synthesis of such an imaging agent and discusses the applications of our vitamin E-inspired multi-modal and multi-length scale imaging agents TB-Toc ((S,E)-5,5-difluoro-7-(2-(5-((6-hydroxy-2,5,7,8-tetramethylchroman-2-yl) methyl) thiophen-2-yl) vinyl)-9-methyl-5H-dipyrrolo-[1,2-c:2’,1’-f][1,3,2]diazaborinin-4-ium-5-uide). We investigate the toxicity of TB-Toc along with the starting materials and lipid based delivery vehicle in mouse myoblasts and fibroblasts. Further we investigate the uptake of TB-Toc delivered to cultured cells in both solvent and liposomes. TB-Toc has low toxicity, and no change in cell viability was observed up to concentrations of 10?mM. TB-Toc shows time-dependent cellular uptake that is complete in about 30?min. This work is the first step in demonstrating our vitamin E derivatives are viable multi-modal and length scale diagnostic tools.     

Divergence with gene flow is driven by local adaptation to temperature and soil phosphorus concentration in teosinte subspecies (Zea mays parviglumis and Zea mays mexicana)

Patterns of genomic divergence between hybridizing taxa can be heterogeneous along the genome. Both differential introgression and local adaptation may contribute to this pattern. Here, we analysed two teosinte subspecies, Zea mays ssp. parviglumis and ssp. mexicana, to test whether their divergence has occurred in the face of gene flow and to infer which environmental variables have been important drivers of their ecological differentiation. We generated 9,780 DArTseqTM SNPs for 47 populations, and used an additional data set containing 33,454 MaizeSNP50 SNPs for 49 populations. With these data, we inferred features of demographic history and performed genome wide scans to determine the number of outlier SNPs associated with climate and soil variables. The two data sets indicate that divergence has occurred or been maintained despite continuous gene flow and/or secondary contact. Most of the significant SNP associations were to temperature and to phosphorus concentration in the soil. A large proportion of these candidate SNPs were located in regions of high differentiation that had been identified previously as putative inversions. We therefore propose that genomic differentiation in teosintes has occurred by a process of adaptive divergence, with putative inversions contributing to reduced gene flow between locally adapted populations.     

Monitoring attributes for ecological restoration in Latin America and the Caribbean region

Ecological restoration is becoming mainstreamed worldwide but target ecosystems' responses to restorative interventions are not sufficiently monitored, in terms of the wide range of ecological, social, and economic attributes available. In order to highlight and better understand this problem, we conducted a literature review of the ecological, social, and economic attributes cited in the scientific literature used for monitoring the success of ecological restoration projects in Latin America and the Caribbean region, where no regional study of this kind has previously been conducted. In 84 of the 91 articles retained for the study, ecological indicators were evaluated, while only seven articles included measurements of socioeconomic indicators. Regarding the Society for Ecological Restoration Primer attributes of restored ecosystems, we only found indicators measuring attributes 1–6, with attribute 1 (species assemblages) predominating (73%), followed by physical conditions (54%) and ecological functions (51%). Brazil was the country in the region where most monitoring was being carried out (51% of the articles), and tropical rainforest (33%) and tropical dry forest (25%) were the ecosystem types where ecological restoration was most frequently monitored. Highly vulnerable ecosystems such as mangroves and paramos were underrepresented. Attributes related to ecosystem stability or to governance and education of communities were not monitored at all. More real long‐term monitoring, instead of chronosequences, is needed, especially where understanding socioeconomic implications of, and barriers to, effective ecological restoration is a top priority.     

Disentangling conformational states of macromolecules in 3D-EM through likelihood optimization

Although three-dimensional electron microscopy (3D-EM) permits structural characterization of macromolecular assemblies in distinct functional states, the inability to classify projections from structurally heterogeneous samples has severely limited its application. We present a maximum likelihood-based classification method that does not depend on prior knowledge about the structural variability, and demonstrate its effectiveness for two macromolecular assemblies with different types of conformational variability: the Escherichia coli ribosome and Simian virus 40 (SV40) large T-antigen.     

A switch from α‐helical to β‐strand conformation during co‐translational protein folding

Cellular proteins begin to fold as they emerge from the ribosome. The folding landscape of nascent chains is not only shaped by their amino acid sequence but also by the interactions with the ribosome. Here, we combine biophysical methods with cryo‐EM structure determination to show that folding of a β‐barrel protein begins with formation of a dynamic α‐helix inside the ribosome. As the growing peptide reaches the end of the tunnel, the N‐terminal part of the nascent chain refolds to a β‐hairpin structure that remains dynamic until its release from the ribosome. Contacts with the ribosome and structure of the peptidyl transferase center depend on nascent chain conformation. These results indicate that proteins may start out as α‐helices inside the tunnel and switch into their native folds only as they emerge from the ribosome. Moreover, the correlation of nascent chain conformations with reorientation of key residues of the ribosomal peptidyl‐transferase center suggest that protein folding could modulate ribosome activity.     

Variation in Sexual Expression in Jacaratia mexicana (Caricaceae) in Southern Mexico: Frequency and Relative Seed Performance of Fruit-Producing Males

Dioecy, the segregation of male and female structures among individuals, is widespread in tropical plants, encompassing 10–30 percent of species in some sites. In many cases, interindividual sex separation is not complete, as individual plants, although nominally dioecious, may produce both types of reproductive structures. A common form of this sexual variation is the production of female structures in otherwise male individuals, commonly referred to as fruiting males. Here we report the existence of fruiting males in the dioecious tropical tree Jacaratia mexicana (Caricaceae). We show that fruiting males can constitute up to 45 percent of all males in some populations of a tropical forest in Southern Mexico. In order to determine the functional significance of fruiting males for the breeding system of J. mexicana , we compared the relative performance of male- and female-borne seeds. Our results show that seeds from fruiting males are three times less likely to germinate and survive than seeds from female trees. Based on relative seed fitness data, and sex ratios in natural populations, we estimate that 6–15 percent of the genes contributed by fruiting males to the next generation are transmitted via ovules, meaning that morphological variation in gender is at least partially accompanied by functional gender variation. Finally, our seed fitness estimates for fruiting males suggest that fruiting males will not replace female plants in natural populations.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp .     

Antioxidant responses of cortex neurons to iron loading

Brain cells have a highly active oxidative metabolism, yet they contain only low to moderate superoxide dismutase and catalase activities. Thus, their antioxidant defenses rely mainly on cellular reduced glutathione levels. In this work, in cortical neurons we characterized viability and changes in reduced and oxidized glutathione levels in response to a protocol of iron accumulation. We found that massive death occurred after 2 days in culture with 10 microM Fe. Surviving cells developed an adaptative response that included increased synthesis of GSH and the maintenance of a glutathione-based reduction potential. These results highlight the fundamental role of glutathione homeostasis in the antioxidant response and provide novel insights into the adaptative mechanisms of neurons subjected to progressive iron loads.     

Differential effects of strength training leading to failure versus not to failure on hormonal responses, strength, and muscle power gains.

The purpose of this study was to examine the efficacy of 11 wk of resistance training to failure vs. nonfailure, followed by an identical 5-wk peaking period of maximal strength and power training for both groups as well as to examine the underlying physiological changes in basal circulating anabolic and catabolic hormones. Forty-two physically active men were matched and then randomly assigned to either a training to failure (RF; n = 14), nonfailure (NRF; n = 15), or control groups (C; n = 13). Muscular and power testing and blood draws to determine basal hormonal concentrations were conducted before the initiation of training (T0), after 6 wk of training (T1), after 11 wk of training (T2), and after 16 wk of training (T3). Both RF and NRF resulted in similar gains in 1-repetition maximum bench press (23 and 23%) and parallel squat (22 and 23%), muscle power output of the arm (27 and 28%) and leg extensor muscles (26 and 29%), and maximal number of repetitions performed during parallel squat (66 and 69%). RF group experienced larger gains in the maximal number of repetitions performed during the bench press. The peaking phase (T2 to T3) after NRF resulted in larger gains in muscle power output of the lower extremities, whereas after RF it resulted in larger gains in the maximal number of repetitions performed during the bench press. Strength training leading to RF resulted in reductions in resting concentrations of IGF-1 and elevations in IGFBP-3, whereas NRF resulted in reduced resting cortisol concentrations and an elevation in resting serum total testosterone concentration. This investigation demonstrated a potential beneficial stimulus of NRF for improving strength and power, especially during the subsequent peaking training period, whereas performing sets to failure resulted in greater gains in local muscular endurance. Elevation in IGFBP-3 after resistance training may have been compensatory to accommodate the reduction in IGF-1 to preserve IGF availability.     

Differences in the Detection of BrdU/EdU Incorporation Assays Alter the Calculation for G1, S,and G2 Phases of the Cell Cycle in Trypanosomatids

Trypanosomatids are the etiologic agents of various infectious diseases in humans. They diverged early during eukaryotic evolution and have attracted attention as peculiar models for evolutionary and comparative studies. Here, we show a meticulous study comparing the incorporation and detection of the thymidine analogs BrdU and EdU in Leishmania amazonensis, Trypanosoma brucei, and Trypanosoma cruzi to monitor their DNA replication. We used BrdU‐ and EdU‐incorporated parasites with the respective standard detection approaches: indirect immunofluorescence to detect BrdU after standard denaturation (2 M HCl) and “click” chemistry to detect EdU. We found a discrepancy between these two thymidine analogs due to the poor detection of BrdU, which is reflected on the estimative of the duration of the cell cycle phases G1, S, and G2. To solve this discrepancy, we increase the exposure of incorporated BrdU using different concentrations of HCl. Using a new value for HCl concentration, we re‐estimated the phases G1, S, G2 + M, and cytokinesis durations, confirming the values found by this approach using EdU. In conclusion, we suggest that the studies using BrdU with standard detection approach, not only in trypanosomatids but also in others cell types, should be reviewed to ensure an accurate estimation of DNA replication monitoring.