Recent theory predicts that the fitness of pioneer populations can decline when species expand their range, due to high rates of genetic drift on wave fronts making selection less efficient at ...purging deleterious variants. To test these predictions, we studied the fate of mutator bacteria expanding their range for 1650 generations on agar plates. In agreement with theory, we find that growth abilities of strains with a high mutation rate (HMR lines) decreased significantly over time, unlike strains with a lower mutation rate (LMR lines) that present three to four times fewer mutations. Estimation of the distribution of fitness effect under a spatially explicit model reveals a mean negative effect for new mutations (-0.38%), but it suggests that both advantageous and deleterious mutations have accumulated during the experiment. Furthermore, the fitness of HMR lines measured in different environments has decreased relative to the ancestor strain, whereas that of LMR lines remained unchanged. Contrastingly, strains with a HMR evolving in a well-mixed environment accumulated less mutations than agar-evolved strains and showed an increased fitness relative to the ancestor. Our results suggest that spatially expanding species are affected by deleterious mutations, leading to a drastic impairment of their evolutionary potential.
Horizontal gene transfer (HGT) plays a key role in bacterial evolution, especially with respect to antibiotic resistance. Fitness costs associated with mobile genetic elements (MGEs) are thought to ...constrain HGT, but our understanding of these costs remains fragmentary, making it difficult to predict the success of HGT events. Here we use the interaction between P. aeruginosa and a costly plasmid (pNUK73) to investigate the molecular basis of the cost of HGT. Using RNA-Seq, we show that the acquisition of pNUK73 results in a profound alteration of the transcriptional profile of chromosomal genes. Mutations that inactivate two genes encoded on chromosomally integrated MGEs recover these fitness costs and transcriptional changes by decreasing the expression of the pNUK73 replication gene. Our study demonstrates that interactions between MGEs can compromise bacterial fitness via altered gene expression, and we argue that conflicts between mobile elements impose a general constraint on evolution by HGT.
To the Editor:
In their review, Ginsburg et al. (March 21 issue)
1
highlight the promising potential of wearable digital health technologies (DHTs) to empower patients and provide them with a greater ...sense of control over their disease management. However, concerns regarding the potential drawbacks associated with constant self-monitoring, which could inadvertently contribute to coerced healthism, were not discussed justly. Many digitized health-promotion strategies tend to focus solely on individual responsibility for health, overlooking the broader social, cultural, and political dimensions of digital technology use.
2,3
Coercion can manifest in various contexts, such as employer wellness programs linking incentives to the use . . .
Although designed as a consumer product to help motivate individuals to be physically active, Fitbit activity trackers are becoming increasingly popular as measurement tools in physical activity and ...health promotion research and are also commonly used to inform health care decisions.
The objective of this review was to systematically evaluate and report measurement accuracy for Fitbit activity trackers in controlled and free-living settings.
We conducted electronic searches using PubMed, EMBASE, CINAHL, and SPORTDiscus databases with a supplementary Google Scholar search. We considered original research published in English comparing Fitbit versus a reference- or research-standard criterion in healthy adults and those living with any health condition or disability. We assessed risk of bias using a modification of the Consensus-Based Standards for the Selection of Health Status Measurement Instruments. We explored measurement accuracy for steps, energy expenditure, sleep, time in activity, and distance using group percentage differences as the common rubric for error comparisons. We conducted descriptive analyses for frequency of accuracy comparisons within a ±3% error in controlled and ±10% error in free-living settings and assessed for potential bias of over- or underestimation. We secondarily explored how variations in body placement, ambulation speed, or type of activity influenced accuracy.
We included 67 studies. Consistent evidence indicated that Fitbit devices were likely to meet acceptable accuracy for step count approximately half the time, with a tendency to underestimate steps in controlled testing and overestimate steps in free-living settings. Findings also suggested a greater tendency to provide accurate measures for steps during normal or self-paced walking with torso placement, during jogging with wrist placement, and during slow or very slow walking with ankle placement in adults with no mobility limitations. Consistent evidence indicated that Fitbit devices were unlikely to provide accurate measures for energy expenditure in any testing condition. Evidence from a few studies also suggested that, compared with research-grade accelerometers, Fitbit devices may provide similar measures for time in bed and time sleeping, while likely markedly overestimating time spent in higher-intensity activities and underestimating distance during faster-paced ambulation. However, further accuracy studies are warranted. Our point estimations for mean or median percentage error gave equal weighting to all accuracy comparisons, possibly misrepresenting the true point estimate for measurement bias for some of the testing conditions we examined.
Other than for measures of steps in adults with no limitations in mobility, discretion should be used when considering the use of Fitbit devices as an outcome measurement tool in research or to inform health care decisions, as there are seemingly a limited number of situations where the device is likely to provide accurate measurement.
Protocells and RNA Self-Replication Joyce, Gerald F; Szostak, Jack W
Cold Spring Harbor perspectives in biology,
09/2018, Letnik:
10, Številka:
9
Journal Article
Recenzirano
Odprti dostop
The general notion of an "RNA world" is that, in the early development of life on the Earth, genetic continuity was assured by the replication of RNA, and RNA molecules were the chief agents of ...catalytic function. Assuming that all of the components of RNA were available in some prebiotic locale, these components could have assembled into activated nucleotides that condensed to form RNA polymers, setting the stage for the chemical replication of polynucleotides through RNA-templated RNA polymerization. If a sufficient diversity of RNAs could be copied with reasonable rate and fidelity, then Darwinian evolution would begin with RNAs that facilitated their own reproduction enjoying a selective advantage. The concept of a "protocell" refers to a compartment where replication of the primitive genetic material took place and where primitive catalysts gave rise to products that accumulated locally for the benefit of the replicating cellular entity. Replication of both the protocell and its encapsulated genetic material would have enabled natural selection to operate based on the differential fitness of competing cellular entities, ultimately giving rise to modern cellular life.
With the significant decrease in physical activity rates, the importance of intervention programs in the schools, where children spend a significant part of the day, has become indisputable. The ...purpose of this review is to systematically examine the possibility of school-based interventions on promoting physical activity and physical fitness as well as preventing obesity. A systematic approach adopting PRISMA statement was implemented in this study. Three different databases (2010-2019) were screened and primary and secondary school-based intervention programs measuring at least one variable of obesity, physical activity, or physical fitness were included. The risk of bias was assessed using the validated quality assessment tool for quantitative studies. Among 395 potentially related studies, 19 studies were found to meet the eligibility criteria. A general look at the studies examined reveals that among the outcomes, of which most (18/19) were examined, a significant improvement was provided in at least one of them. When the program details are examined, it can be said that the success rate of the physical activity-oriented programs is higher in all variables. School-based interventions can have important potential for obesity prevention and promotion of physical activity and fitness if they focus more on the content, quality, duration and priority of the physical activity.
Keywords Tendon; Descending inhibition; Diffuse noxious inhibitory control; Methodology Objectives Our primary objective was to report the presence of a conditioned pain modulation (CPM) effect in ...people with localised mid-portion Achilles tendinopathy and whether changes occur over a 12-week period. Our secondary objectives were to quantify the proportion of participants who present for tendinopathy research with previous interventions or co-morbidities, which may impact the CPM-effect and investigate modulating factors. Design Prospective, observational cohort pilot study. Method 215 participants presented for this Achilles tendinopathy research and were screened for inclusion with nine being included. Included participants had the CPM-effect (cold-pressor test) assessed using pressure pain thresholds at the Achilles tendon and quantified as absolute, relative and meaningful change at baseline and 12-week follow-up. Results The most common reasons for exclusion were failure to meet a load-related diagnosis for Achilles tendinopathy (15.5%), presence of confounding other injury (14.1%) and previous injection therapy (13.6%). All participants had a meaningful CPM-effect at baseline and 12-week follow-up. The mean (SD, n) baseline relative CPM effect (reduction in PPTs) was -40.5 (32.7, 9) percent. Moderators of the CPM-effect as well as follow-up changes were not statistically analysed due to a small sample size. Conclusion Based on these data, we would suggest that a homogenous population of patients with chronic, unilateral mid-portion Achilles tendinopathy and no other co-morbidities are likely to exhibit a meaningful CPM-effect. Impairments to endogenous analgesic mechanisms seen in people presenting with mid-portion Achilles tendinopathy may be due to other confounding variables. Author Affiliation: (a) School of Physiotherapy, The University of Notre Dame Australia, Fremantle, WA, Australia (b) SportsMed Subiaco, St John of God Health Care, Subiaco, WA, Australia (c) Sports and Exercise Medicine Research Centre, La Trobe University, Bundoora, VIC, Australia (d) Institute for Health Research, The University of Notre Dame Australia, Fremantle, WA, Australia (e) Exercise Medicine Research Institute & School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia (f) School of Physiotherapy and Exercise Science, Curtin University, Bentley, Australia * Corresponding author at: School of Physiotherapy, The University of Notre Dame Australia, 19 Mouat Street (PO Box 1225), Fremantle, Western Australia, 6959, Australia. Article History: Received 10 July 2020; Revised 13 October 2020; Accepted 19 October 2020 Byline: Myles C. Murphy myles.murphy1@my.nd.edu.au (a,b,*), Ebonie K. Rio (c), Paola Chivers (d,e), James Debenham (a), Sean I. Docking (c), Mervyn Travers (a,f), William Gibson (a)
Understanding how organisms adapt to environmental variation is a key challenge of biology. Central to this are bet-hedging strategies that maximize geometric mean fitness across generations, either ...by being conservative or diversifying phenotypes. Theoretical models have identified environmental variation across generations with multiplicative fitness effects as driving the evolution of bet-hedging. However, behavioral ecology has revealed adaptive responses to additive fitness effects of environmental variation within lifetimes, either through insurance or risk-sensitive strategies. Here, we explore whether the effects of adaptive insurance interact with the evolution of bet-hedging by varying the position and skew of both arithmetic and geometric mean fitness functions. We find that insurance causes the optimal phenotype to shift from the peak to down the less steeply decreasing side of the fitness function, and that conservative bet-hedging produces an additional shift on top of this, which decreases as adaptive phenotypic variation from diversifying bet-hedging increases. When diversifying bet-hedging is not an option, environmental canalization to reduce phenotypic variation is almost always favored, except where the tails of the fitness function are steeply convex and produce a novel risk-sensitive increase in phenotypic variance akin to diversifying bet-hedging. Importantly, using skewed fitness functions, we provide the first model that explicitly addresses how conservative and diversifying bet-hedging strategies might coexist.
ObjectiveDespite decreasing mortality, functional impairments in children with transposition of the great arteries (TGA) are still a concern. This study analyses health-related physical fitness ...(HRPF), arterial stiffness and health-related quality of life (HRQoL) in children with anatomically repaired TGA regarding congenital ventricular septal defect (VSD) and coronary patterns.Patients and methods68 children with anatomically repaired TGA with or without VSD (12.9±3.7 years, 19.1% female) were investigated between August 2014 and October 2017. HRPF was assessed by five tests of the FITNESSGRAM, arterial stiffness was measured by oscillometric measurement using Mobil-O-Graph and HRQoL was analysed with a self-report questionnaire (KINDL-R). All test results were compared with a healthy reference cohort (n=2116, 49.1% female) adjusted for sex and age.ResultsChildren with anatomically repaired TGA had significantly worse HRPF (z-score: −0.58±0.81, p<0.001), increased pulse wave velocity (TGA: 4.9±0.3 m/s vs healthy: 4.8±0.3 m/s, p=0.028) and central systolic blood pressure (TGA: 105.9±5.8 mm Hg vs healthy: 103.3±5.7 mm Hg, p=0.001). No difference was found for HRQoL between the two groups (total HRQoL score: TGA: 76.5±10.2 vs healthy: 75.2±10.1, p=0.315). Neither the coronary pattern nor a congenital VSD resulted in significant differences in all functional outcomes.ConclusionChildren with anatomically repaired TGA exhibit impaired HRPF and increased arterial stiffness whereas their HRQoL is normal. The underlying coronary pattern seems to have no influence on the functional outcome, nor does an accompanied congenital VSD.
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