Molecular Evolution of Ultraspiracle Protein (USP/RXR) in Insects

Ultraspiracle protein/retinoid X receptor (USP/RXR) is a nuclear receptor and transcription factor which is an essential component of a heterodimeric receptor complex with the ecdysone receptor (EcR). In insects this complex binds ecdysteroids and plays an important role in the regulation of growth, development, metamorphosis and reproduction. In some holometabolous insects, including Lepidoptera and Diptera, USP/RXR is thought to have experienced several important shifts in function. These include the acquisition of novel ligand-binding properties and an expanded dimerization interface with EcR. In light of these recent hypotheses, we implemented codon-based likelihood methods to investigate if the proposed shifts in function are reflected in changes in site-specific evolutionary rates across functional and structural motifs in insect USP/RXR sequences, and if there is any evidence for positive selection at functionally important sites. Our results reveal evidence of positive selection acting on sites within the loop connecting helices H1 and H3, the ligand-binding pocket, and the dimer interface in the holometabolous lineage leading to the Lepidoptera/Diptera/Trichoptera. Similar analyses conducted using EcR sequences did not indicate positive selection. However, analyses allowing for variation across sites demonstrated elevated non-synonymous/synonymous rate ratios (dN/dS), suggesting relaxed constraint, within the dimerization interface of both USP/RXR and EcR as well as within the coactivator binding groove and helix H12 of USP/RXR. Since the above methods are based on the assumption that dS is constant among sites, we also used more recent models which relax this assumption and obtained results consistent with traditional random-sites models. Overall our findings support the evolution of novel function in USP/RXR of more derived holometabolous insects, and are consistent with shifts in structure and function which may have increased USP/RXR reliance on EcR for cofactor recruitment. Moreover, these findings raise important questions regarding hypotheses which suggest the independent activation of USP/RXR by its own ligand

International Society of Sports Nutrition Position Stand: Nutritional recommendations for single-stage ultra-marathon; training and racing

Background. In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by following an individualized and periodized strategy, comprising a varied, food-first approach; ii) Athletes should plan and implement their nutrition strategy with sufficient time to permit adaptations that enhance fat oxidative capacity; iii) The evidence overwhelmingly supports the inclusion of a moderate-to-high carbohydrate diet (i.e., ~60% of energy intake, 5 – 8 g⸱kg−1·d−1) to mitigate the negative effects of chronic, training-induced glycogen depletion; iv) Limiting carbohydrate intake before selected low-intensity sessions, and/or moderating daily carbohydrate intake, may enhance mitochondrial function and fat oxidative capacity. Nevertheless, this approach may compromise performance during high-intensity efforts; v) Protein intakes of ~1.6 g·kg−1·d−1 are necessary to maintain lean mass and support recovery from training, but amounts up to 2.5 g⸱kg−1·d−1 may be warranted during demanding training when calorie requirements are greater; Recommendations for Racing. vi) To attenuate caloric deficits, runners should aim to consume 150 - 400 kcal⸱h−1 (carbohydrate, 30 – 50 g⸱h−1; protein, 5 – 10 g⸱h−1) from a variety of calorie-dense foods. Consideration must be given to food palatability, individual tolerance, and the increased preference for savory foods in longer races; vii) Fluid volumes of 450 – 750 mL⸱h−1 (~150 – 250 mL every 20 min) are recommended during racing. To minimize the likelihood of hyponatraemia, electrolytes (mainly sodium) may be needed in concentrations greater than that provided by most commercial products (i.e., >575 mg·L−1 sodium). Fluid and electrolyte requirements will be elevated when running in hot and/or humid conditions; viii) Evidence supports progressive gut-training and/or low-FODMAP diets (fermentable oligosaccharide, disaccharide, monosaccharide and polyol) to alleviate symptoms of gastrointestinal distress during racing; ix) The evidence in support of ketogenic diets and/or ketone esters to improve ultra-marathon performance is lacking, with further research warranted; x) Evidence supports the strategic use of caffeine to sustain performance in the latter stages of racing, particularly when sleep deprivation may compromise athlete safety

Capturing hotspots of fresh submarine groundwater discharge using a coupled surface–subsurface model

Submarine groundwater discharge (SGD) contributes to the physical and chemical characters of coastal waters by discharging nutrients and contaminants, significantly impacting regional marine ecosystems and contributing to ocean chemical budgets. However, such groundwater discharge varies dramatically across scales and is often not comparable due to different model assumptions and field designs. We used a hydrologic model with integration of fundamental surface and subsurface processes to simulate the coastline level fresh SGD for the Crete Island in the Mediterranean Sea. The modeled hydrological processes suggested that fresh SGD substantially contributes to water flow entering the Mediterranean Sea (2.3 × 108 m3/yr), amounting to 31% of river discharge and 14% of precipitation. Spatially, fresh SGD varied from 2.4 m3/yr/m to 13.4 × 104 m3/yr/m, with an average of 2.6 × 103 m3/yr/m. The local maxima were commonly associated with river mouths reflecting larger hydraulic gradients and higher permeable structures. Temporally, fresh SGD was impacted by episodic precipitation in a delayed and prolonged pattern. We found that fresh SGD variability at the coastline segment level was compared to point measurements and fresh SGD magnitudes summered up to the catchment level were consistent with global products. Our results suggest the coupled surface–subsurface hydrologic modeling approach is a promising strategy to quantify and partition large-scale water budgets down to point observations that typically do not capture the full range of fresh SGD dynamics

Modeling Soil Aggregation at the Early Pedogenesis Stage from the Parent Material of a Mollisol Under Different Agricultural Practices

Soil aggregation and development of soil structure play a crucial role in determining soil functions and ecosystem services in Earth's Critical Zone. Soil organic matter (SOM) is the main constituent that binds mineral particles together into larger-sized aggregates. Many theoretical concepts have been proposed to explain soil aggregation and SOM accrual processes, but quantification of the processes remains lacking. We observed changes in aggregate size mass distribution and aggregate carbon content in 2 discrete years from an 8-year field experiment, which was conducted to determine how to speed up soil development and restoration with different agricultural practices. The 2-year data showed that the proportion of macroaggregates (> 250 μm) increased with the decreasing proportions of microaggregates (53–250 μm) and soil texture units (< 53 μm) and increasing proportion of particulate organic matter occluded in the macroaggregates. This aggregation process was more noticeable in the field treatments with higher organic carbon input. By using these data, we successfully calibrated the recently developed CAST mathematical model, which assumes that primary macroaggregates are first formed around plant-derived organic matter and primary microaggregates are then formed within the macroaggregates as the occluded organic materials are decomposed. The secondary microaggregates and macroaggregates are assumed to form after the breakdown of primary macroaggregates. The calibration processes separated the plant growth season from the frozen winter season. Some calibrated parameters were the same for all of the field treatments, and these parameters included the first-order rate constants of the fragmentation and decomposition of plant litter within the macroaggregates, the decomposition rates of organic matter incorporated and protected in microaggregates, and organic carbon associated with the free soil texture units. Other calibrated parameter values were affected by the field treatments, and the parameters were the first-order decay rate constants of the plant-derived organic matter in nonaggregated soils and in the secondary macroaggregates, the least carbon sources for the formation of the secondary macroaggregates, and the correction factor to adjust carbon with the mass flow of the soil texture units. The differences in the calibrated parameter values suggested that the rates of the primary macroaggregation and the secondary microaggregation were likely controlled by the intrinsic properties of the parent material rather than by the land use and agricultural practices, whereas the rates of the secondary macroaggregation process were likely affected by land use through controlling plant litter quality and quantity and by agricultural practices, such as soil tillage, and to a less extent by fertilizers that control organic input and then carbon and mass content of the soil texture units and microaggregates. The model results were consistent with measured changes over time of the aggregate mass distribution by size class, the total organic matter content, and the SOM bound in aggregates. However, the CAST model did not reproduce particularly well the mass of the soil texture units within different aggregate size classes nor the relative contribution of carbon stocks from different carbon pools within aggregates. The gap between observations and model results points the way forward to develop further the detailed process descriptions in the CAST modeling approach, for example, to consider primary microaggregation directly from basic soil texture units. Nevertheless, this study demonstrates that the CAST model is very powerful to predict the dynamics of soil aggregation and concurrent SOM change in response to changes in land use and soil management

Position sense and reaction angle after eccentric exercise: the repeated bout effect.

The purpose of the present investigation was to examine the effects of a repeated eccentric exercise on position sense and muscle reaction angle. Fourteen healthy women underwent an isokinetic exercise session on their knee flexors, which was repeated after 4 weeks. Muscle damage indices, position sense and joint reaction angle of the knee were examined before, immediately after, as well as at 1, 2, 3, 4 and 7 days after exercise. The second exercise bout induced significantly lesser effects in all muscle damage indices as well as lesser disturbances in position sense and reaction angle when compared to the first one. The main finding of this study is that position sense and joint reaction angle to release of the lower limbs may adapt in response to a repeated bout of eccentric exercise, leading to less disturbances in position sense and reaction angle after the second bout of exercise