1,505 research outputs found
The relative effects of pace of life-history and habitat characteristics on the evolution of sexual ornaments: A comparative assessment
Selection may favor greater investment into sexual ornaments when opportunities for future reproduction are limited, for example, under high adult mortality. However, predation, a key driver of mortality, typically selects against elaborate sexual ornaments. Here, we examine the evolution of sexual ornaments in killifishes, which have marked contrasts in life-history strategy among species and inhabit environments that differ in accessibility to aquatic predators. We first assessed if the size of sexual ornaments (unpaired fins) influenced swimming performance. Second, we investigated whether the evolution of larger ornamental fins is driven primarily by the pace of life-history (investment into current vs. future reproduction) or habitat type (a proxy for predation risk). We found that larger fins negatively affected swimming performance. Further, males from species inhabiting ephemeral habitats, with lower predation risk, had larger fins and greater sexual dimorphism in fin size, compared to males from more accessible permanent habitats. We show that enlarged ornamental fins, which impair locomotion, evolve more frequently in environments that are less accessible to predators, without clear associations to life-history strategy. Our results provide a rare link between the evolution of sexual ornaments, effects on locomotion performance, and natural selection on ornament size potentially through habitat differences in predation risk
Looking our limitations in the eye: A call for more thorough and honest reporting of study limitations
The replication crisis and subsequent credibility revolution in psychology have highlighted many suboptimal research practices such as p‐hacking, overgeneralizing, and a lack of transparency. These practices may have been employed reflexively but upon reflection, they are hard to defend. We suggest that current practices for reporting and discussing study limitations are another example of an area where there is much room for improvement. In this article, we call for more rigorous reporting of study limitations in social and personality psychology articles, and we offer advice for how to do this. We recommend that authors consider what the best argument is against their conclusions (which we call the “steel‐person principle”). We consider limitations as threats to construct, internal, external, and statistical conclusion validity (Shadish et al., 2002), and offer some examples for better practice reporting of common study limitations. Our advice has its own limitations — both our representation of current practices and our recommendations are largely based on our own metaresearch and opinions. Nevertheless, we hope that we can prompt researchers to write more deeply and clearly about the limitations of their research, and to hold each other to higher standards when reviewing each other's work
Bridging the gap, how interprofessional collaboration can support emergency preparedness for children with disabilities and their families: an exploratory qualitative study
Background: Children with disabilities and their families are at higher risk during emergencies and disasters, which is often attributed to the lack of disability inclusion in emergency response as well as disparities in preparedness. This disparity speaks to a need for emergency preparedness that centers children with disabilities and their families. The purpose of this study was to elicit the perspectives of health professionals (nurses, occupational therapists, social workers), disability advocates, and public safety personnel (e.g., fire fighters, police officers, emergency management administrators) on what would enable these types of professionals to support family-centered emergency preparedness for families who care for children with disabilities. One goal of this research is to provide recommendations for practice and policy to improve safety outcomes for children with disabilities and their families in emergency situations. Methods: This study consisted of 46 qualitative interviews with nurses, occupational therapists, social workers, public safety personnel, and advocacy organization representatives about their role in emergency preparedness for families of children with disabilities. Qualitative content analysis was used to identify themes from participants’ responses. Results: Participants expressed interest in family-centered emergency preparedness, and stated that greater awareness, more education and training, increased networking between professions, and institutional support would enable their involvement. Conclusions: These findings have implications for the importance of interprofessional collaboration in supporting family-centered emergency preparedness for families of children with disabilities. Stronger interprofessional networks would help overcome many of the barriers identified by participants, and advocacy groups appear to be well-positioned to bridge the gap between these professionals and their areas of expertise
Dynamic space utilization for lame and non-lame gestating sows estimated by the lying-standing sequence
peer-reviewedThe objective of this study was to estimate the dynamic space utilization for lame and non-lame sows using their lying-standing postural sequence profile. Eighty-five sows (parity 0.9 ± 1.14; range 0 to 4) were used. Sows were moved to a pen on 30, 60 and 90 days of gestation and a ceiling mounted camera was installed above the pen to record one lying-standing event per sow. Observations ceased when the sow lied and stood, or 2.5 h elapsed from recording commencement. Additionally, each sow was evaluated for walking lameness while moving from their gestation stall to the pen. Still frames were captured from the sows’ lying and standing sequences and were combined into a single image and measured by counting pixels from contouring the sows’ body (CONTOUR), overlaying a grid on the sow image and counting any square including any part of the sow (FULL-GRID) and only counting any square that was half full or more (HALF-GRID). The space utilized while turning around was calculated by measuring the sows’ length from snout to the base of the tail and using that length as the diameter of a circle (D-PIVOT), or as the radius of a circle (R-PIVOT). Parity was re-classified as 0, 1, and 2+. There were no observed differences in the dynamic space utilized to lie, stand or turn around between lame and non-lame sows (P > 0.05). On average, sows used 1.2 ± 0.47 m2 to lie and 1.3 ± 0.46 m2 to stand. There was no difference between the CONTOUR and HALF-GRID methods (P > 0.05); however, using the FULL-GRID sows required 0.3 m2 more floor area to lie and stand compared with the other measuring methods (P < 0.05). Space used to turn around differed between measuring method (P < 0.05). Sows required 1.9 ± 0.18 m2 for D-PIVOT and 7.3 ± 0.18 m2 for R-PIVOT to turn around. Space utilized to lie-down and stand-up increased as gestation progressed (P < 0.05). Under the conditions of this study, lameness did not influence dynamic space utilization; however, lameness recorded was relatively mild and might not have been sufficiently severe to significantly affect the results. These results could be important in decision-making process for housing specifications regarding US sow gestation housing
Regionally Strong Feedbacks Between the Atmosphere and Terrestrial Biosphere
The terrestrial biosphere and atmosphere interact through a series of feedback loops. Variability in terrestrial vegetation growth and phenology can modulate fluxes of water and energy to the atmosphere, and thus affect the climatic conditions that in turn regulate vegetation dynamics. Here we analyze satellite observations of solar-induced fluorescence, precipitation, and radiation using a multivariate statistical technique. We find that biosphere-atmosphere feedbacks are globally widespread and regionally strong: they explain up to 30 of precipitation and surface radiation variance. Substantial biosphere-precipitation feedbacks are often found in regions that are transitional between energy and water limitation, such as semi-arid or monsoonal regions. Substantial biosphere-radiation feedbacks are often present in several moderately wet regions and in the Mediterranean, where precipitation and radiation increase vegetation growth. Enhancement of latent and sensible heat transfer from vegetation accompanies this growth, which increases boundary layer height and convection, affecting cloudiness, and consequently incident surface radiation. Enhanced evapotranspiration can increase moist convection, leading to increased precipitation. Earth system models underestimate these precipitation and radiation feedbacks mainly because they underestimate the biosphere response to radiation and water availability. We conclude that biosphere-atmosphere feedbacks cluster in specific climatic regions that help determine the net CO2 balance of the biosphere
mtDNA depletion confers specific gene expression profiles in human cells grown in culture and in xenograft
<p>Abstract</p> <p>Background</p> <p>Interactions between the gene products encoded by the mitochondrial and nuclear genomes play critical roles in eukaryotic cellular function. However, the effects mitochondrial DNA (mtDNA) levels have on the nuclear transcriptome have not been defined under physiological conditions. In order to address this issue, we characterized the gene expression profiles of A549 lung cancer cells and their mtDNA-depleted ρ<sup>0 </sup>counterparts grown in culture and as tumor xenografts in immune-deficient mice.</p> <p>Results</p> <p>Cultured A549 ρ<sup>0 </sup>cells were respiration-deficient and showed enhanced levels of transcripts relevant to metal homeostasis, initiation of the epithelial-mesenchymal transition, and glucuronidation pathways. Several well-established HIF-regulated transcripts showed increased or decreased abundance relative to the parental cell line. Furthermore, growth in culture versus xenograft has a significantly greater influence on expression profiles, including transcripts involved in mitochondrial structure and both aerobic and anaerobic energy metabolism. However, both <it>in vitro </it>and <it>in vivo</it>, mtDNA levels explained the majority of the variance observed in the expression of transcripts in glucuronidation, tRNA synthetase, and immune surveillance related pathways. mtDNA levels in A549 xenografts also affected the expression of genes, such as <it>AMACR </it>and <it>PHYH</it>, involved in peroxisomal lipid metabolic pathways.</p> <p>Conclusion</p> <p>We have identified mtDNA-dependent gene expression profiles that are shared in cultured cells and in xenografts. These profiles indicate that mtDNA-depleted cells could provide informative model systems for the testing the efficacy of select classes of therapeutics, such as anti-angiogenesis agents. Furthermore, mtDNA-depleted cells grown culture and in xenografts provide a powerful means to investigate possible relationships between mitochondrial activity and gene expression profiles in normal and pathological cells.</p
Fluctuations and differential contraction during regeneration of Hydra vulgaris tissue toroids
We studied regenerating bilayered tissue toroids dissected from Hydra
vulgaris polyps and relate our macroscopic observations to the dynamics of
force-generating mesoscopic cytoskeletal structures. Tissue fragments undergo a
specific toroid-spheroid folding process leading to complete regeneration
towards a new organism. The time scale of folding is too fast for biochemical
signalling or morphogenetic gradients which forced us to assume purely
mechanical self-organization. The initial pattern selection dynamics was
studied by embedding toroids into hydro-gels allowing us to observe the
deformation modes over longer periods of time. We found increasing mechanical
fluctuations which break the toroidal symmetry and discuss the evolution of
their power spectra for various gel stiffnesses. Our observations are related
to single cell studies which explain the mechanical feasibility of the folding
process. In addition, we observed switching of cells from a tissue bound to a
migrating state after folding failure as well as in tissue injury.
We found a supra-cellular actin ring assembled along the toroid's inner edge.
Its contraction can lead to the observed folding dynamics as we could confirm
by finite element simulations. This actin ring in the inner cell layer is
assembled by myosin- driven length fluctuations of supra-cellular
{\alpha}-actin structures (myonemes) in the outer cell-layer.Comment: 19 pages and 8 figures, submitted to New Journal of Physic
Sympatric and allopatric Alcolapia soda lake cichlid species show similar levels of assortative mating
Characterising reproductive barriers such as mating preferences within rapid evolutionary radiations is crucial for understanding the early stages of speciation. Cichlid fishes are well-known for their adaptive radiations and capacity for rapid speciation and as such we investigate assortative mating among Alcolapia species; a recent (<10,000 years), small adaptive radiation, endemic to the extreme soda lakes, Magadi (one species) and Natron (three species), in East Africa. In seminatural aquarium conditions, we observed both courtship and mate choice (tested by microsatellite paternity analysis) to be significantly assortative among the three sympatric Natron species in a three-way choice experiment. This was also the case between allopatric species from Natron and Magadi, as found in a two-way choice experiment. However, the proportion of disassortative matings was substantial in both of these experiments, with hybrids comprising 29% of offspring in sympatric species and 11.4% in allopatric species comparisons. . Previous work suggests that the Natron/Magadi split might not be much older than the radiation within Natron, so the similar rate of hybridisation in the allopatric comparison is surprising and inconsistent with predictions of reinforcement theory, which predicts a faster rate of accumulation of premating isolation in sympatry. The relatively weak assortative mating in sympatry suggests that additional reproductive barriers, such as microhabitat preferences or spatial structuring may contribute to genetic isolation in nature
The Effect of Nitrate Supplementation on Cycling Performance in the Heat in Well-Trained Cyclists
Purpose:
The aim of this study was to determine the effect of NO₃⁻ consumption on measures of perception, thermoregulation and cycling performance in hot conditions.
Methods:
Using a randomised, double-blind, crossover-design, 8 well-trained cyclists (mean ± SD: age: 25 ± 8 y, V̇O2peak: 64 ± 5 ml·kg⁻¹·min⁻¹) performed 2 separate trials, in hot (35°C, 60% relative humidity) environments, having ingested either 140 ml NO3--rich beetroot juice ~8 mmol NO₃⁻ (NIT), or placebo (PLA), daily for 3-days with a 7-day washout period separating trials. Trials consisted of 2 × 10 min bouts at 40 and 60% peak power output (PPO) to determine physiological and perceptual responses in the heat, followed by a 4 km cycling time-trial.
Results:
Basal [nitrite] was substantially elevated in NIT (2.70 ± 0.98 μM) vs PLA (1.10 ± 0.61 μM) resulting in a most likely (ES = 1.58 ± 0.93) increase after 3-days. There was a very likely trivial increase in rectal temperature [Tᵣₑ] in NIT at 40% (PLA;37.4 ± 0.2°C vs NIT;37.5 ± 0.3°C, 0.1 ± 0.2°C) and 60% (PLA;37.8 ± 0.2°C vs NIT;37.9 ± 0.3°C, 0.1 ± 0.2°C) PPO. Cycling performance was similar between trials (PLA;336 ± 45 W vs NIT;337 ± 50 W, CV±95%CL; 0.2 ± 2.5%). Outcomes for heart rate, and perceptual measures were unclear across the majority of time-points.
Conclusions:
Three days of NO₃⁻ supplementation, resulted in small increases in Tᵣₑ during low- to moderate-intensity exercise, however this did not appear to influence 4 km cycling time-trial performance in hot climates
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