Comparative analyses in biology rely on the quality of available data. Methodological differences among studies may introduce variation in results that obscure patterns. In the field of ...eco-immunology, functional immune assays such as antimicrobial capacity assays are widely used for among-species applications. Sample storage time and animal handling time can influence assay results in some species, but how sample holding time prior to freezing influences assay results is unknown. Sample holding time can vary widely in field studies on wild animals, prompting the need to understand the implications of such variation on assay results. We investigated the hypothesis that sample holding time prior to freezing influences assay results in six species (Leiocephalus carinatus, Iguana iguana, Loxodonta africana, Ceratotherium simum, Columba livia, and Buteo swainsoni) by comparing antibacterial capacity of serum with varying processing times prior to snap-freezing. Blood was collected once from each individual and aliquots were placed on ice and assigned different holding times (0, 30, 60, 180, and 240 min), after which each sample was centrifuged, then serum was separated and snap-frozen on dry ice and stored at -80ºC for 60 days prior to assaying. For each aliquot, we conducted antibacterial capacity assays with serial dilutions of serum inoculated with E. coli and extracted the dilution at 50% antibacterial capacity for analysis. We found a decrease in antibacterial capacity with increased holding time in one of the six species tested (B. swainsoni), driven in part by complete loss of antibacterial capacity in some individuals at the 240-min time point. While the majority of species' antibacterial capacity were not affected, our results demonstrate the need to conduct pilot assays spanning the anticipated variation in sample holding times to develop appropriate field protocols.
Terrestrial mammals span 7 orders of magnitude in body size, ranging from the < 2 g pygmy shrew (Suncus etruscus) to the > 3900 kg African elephant (Loxodonta africana). Although body size profoundly ...affects the behavior, physiology, ecology, and evolution of species, how investment in immune defenses changes with body size across species is unknown. Comparative immunology studies are often limited because of reagents or because assays are calibrated for a specific species. We developed a novel 12‐point dilution‐curve approach to compare complement‐mediated antibacterial capacity against 3 diverse bacterial species (Escherichia coli, Salmonella enterica, Micrococcus luteus) among >160 terrestrial species of mammals. We tested published predictions about the scaling of immune defenses, focusing on the Safety Factor Hypothesis, which predicts that broad, early‐acting immune defense should scale hypermetrically with body mass. Multivariate linear mixed models using Markov chain Monte Carlo techniques demonstrate that antibacterial activity across mammals exhibited isometry (scaling coefficient = 0), regardless of the bacterial species used in the challenge. For example, the antibacterial ability of a specific dilution scaled isometrically when serum was tested against E. coli(b95% Credible Intervals =‐0.144 : 0.044), S. enterica (b = ‐0.102 : 0.061), and M, luteus (b = ‐0.401 : 0.177). Therefore, body size was unrelated to killing capacity across species. Intriguingly, these results indicate that the serum of large mammals was less hospitable to bacteria than would be predicted by their metabolic rates. That is, if metabolic rates restrict the rate of organismal reactions as postulated by the Rate of Metabolism Hypothesis, large species should have disproportionately lower antibacterial capacity than small species, but they do not. These results have direct implications for effectively modeling the evolution of immune defenses and identifying potential reservoir hosts of zoonotic pathogens. This work was supported by the National Science Foundation (award numbers IOS 1656551 to C.J.D. and IOS 1656618 to L.B.M), and the authors have no competing interests to declare.
Terrestrial mammals span seven orders of magnitude in body size, ranging from the <2-g Etruscan pygmy shrew (Suncus etruscus) to the >3,900-kg African elephant (Loxodonta africana). Although body ...size profoundly affects the behavior, physiology, ecology, and evolution of species, how investment in functional immune defenses changes with body size across species is unknown. Here, we (1) developed a novel 12-point dilution curve approach to describe and compare antibacterial capacity against three bacterial species among >160 terrestrial species of mammals and (2) tested published predictions about the scaling of immune defenses. Our study focused on the safety factor hypothesis, which predicts that broad, early-acting immune defenses should scale hypermetrically with body mass. However, our three statistical approaches demonstrated that antibacterial activity in sera across mammals exhibits isometry; killing capacity did not change with body size across species. Intriguingly, this result indicates that the serum of a large mammal is less hospitable to bacteria than would be predicted by its metabolic rates. In other words, if metabolic rates underlie the rates of physiological reactions as postulated by the metabolic theory of ecology, large species should have disproportionately lower antibacterial capacity than small species, but they do not. These results have direct implications for effectively modeling the evolution of immune defenses and identifying potential reservoir hosts of pathogens.
ABSTRACT
Powered flight has evolved several times in vertebrates and constrains morphology and physiology in ways that likely have shaped how organisms cope with infections. Some of these constraints ...probably have impacts on aspects of immunology, such that larger fliers might prioritize risk reduction and safety. Addressing how the evolution of flight may have driven relationships between body size and immunity could be particularly informative for understanding the propensity of some taxa to harbor many virulent and sometimes zoonotic pathogens without showing clinical disease. Here, we used a comparative framework to quantify scaling relationships between body mass and the proportions of two types of white blood cells – lymphocytes and granulocytes (neutrophils/heterophils) – across 63 bat species, 400 bird species and 251 non-volant mammal species. By using phylogenetically informed statistical models on field-collected data from wild Neotropical bats and from captive bats, non-volant mammals and birds, we show that lymphocyte and neutrophil proportions do not vary systematically with body mass among bats. In contrast, larger birds and non-volant mammals have disproportionately higher granulocyte proportions than expected for their body size. Our inability to distinguish bat lymphocyte scaling from birds and bat granulocyte scaling from all other taxa suggests there may be other ecological explanations (i.e. not flight related) for the cell proportion scaling patterns. Future comparative studies of wild bats, birds and non-volant mammals of similar body mass should aim to further differentiate evolutionary effects and other aspects of life history on immune defense and its role in the tolerance of (zoonotic) infections.
Motor competence is important for lifelong physical activity (PA). The current study aimed to examine associations between PA and motor competence. In total, 43 children aged 7–12 years with ...intellectual disabilities and/or autism spectrum disorder completed anthropometric measures, the Bruininks-Oseretsky Test of Motor Proficiency-2, and wore a wrist accelerometer to capture total PA, moderate-to-vigorous PA (MVPA), average acceleration, and intensity gradient. No significant associations were found between PA outcomes and motor competence. Motor competence performance was commonly ‘below average’ or ‘average’. The weakest subtests were upper limb coordination and strength. The strongest subtest was running speed and agility. Total weekly MVPA was 336.1 ± 150.3 min, higher than UK recommendations of 120-180 per week for disabled children and young people. Larger scale studies are needed to better understand the relationship between PA and motor competence. Future research should also consider the influence of environmental factors on PA in this group.
PURPOSEThis study aimed to provide a means for calibrating raw acceleration data from wrist-worn accelerometers in relation to past estimates of children’s moderate-to-vigorous physical activity ...(MVPA) from a range of cut points applied to hip-worn ActiGraph data.
METHODSThis is a secondary analysis of three studies with concurrent 7-d accelerometer wear at the wrist (GENEActiv) and hip (ActiGraph) in 238 children age 9–12 yr. The time spent above acceleration (ENMO) thresholds of 100, 150, 200, 250, 300, 350, and 400 mg from wrist acceleration data (≤5-s epoch) was calculated for comparison with MVPA estimated from widely used children’s hip-worn ActiGraph MVPA cut points (Freedson/Trost, 1100 counts per minute; Pate, 1680 counts per minute; Evenson, 2296 counts per minute; Puyau, 3200 counts per minute) with epochs of ≤5, 15, and 60 s.
RESULTSThe optimal ENMO thresholds for alignment with MVPA estimates from ActiGraph cut points determined from 70% of the sample and cross validated with the remaining 30% were as followsFreedson/Trost = ENMO 150+ mg, irrespective of ActiGraph epoch (intraclass correlation ICC ≥ 0.65); Pate = ENMO 200+ mg, irrespective of ActiGraph epoch (ICC ≥ 0.67); Evenson = ENMO 250+ mg for ≤5- and 15-s epochs (ICC ≥ 0.69) and ENMO 300+ mg for 60-s epochs (ICC = 0.73); Puyau = ENMO 300+ mg for ≤5-s epochs (ICC = 0.73), ENMO 350+ mg for 15-s epochs (ICC = 0.73), and ENMO 400+ mg for 60-s epochs (ICC = 0.65). Agreement was robust with cross-validation ICC = 0.62–0.71 and means within ∣7.8∣% ± 4.9% of MVPA estimates from ActiGraph cut points, except Puyau 60-s epochs (ICC = 0.42).
CONCLUSIONIncremental ENMO thresholds enable children’s acceleration data measured at the wrist to be simply and directly compared, at a group level, with past estimates of MVPA from hip-worn ActiGraphs across a range of cut points.
The aim of this study was to assess the physical activity (PA) patterns of youth with intellectual disabilities (ID). PA was monitored for 7 days in 70 participants, 5-15 years old, using ...accelerometers. There were 32 participants included in the final analysis. Habitual PA and the number of continuous bouts accrued for a range of bout lengths (5-600 s) for light (LPA), moderate (MPA), and vigorous (VPA) PA were calculated. Multivariate analysis of covariance was used to assess differences in the number of continuous bouts by sex, age, and ID group and between week and weekend days. Participants exhibited short sporadic bursts of activity. The number of continuous bouts decreased as the intensity and duration increased. Few differences in PA patterns were reported by sex, ID group, and age group and between week and weekend days, possibly due to the generally low PA levels in this population.
The benefits of physical activity and active play for children and young people are well established. However, there is a lack of physical activity research involving children and young people with ...intellectual disabilities. This study investigated habitual physical activity and recess play behaviour in 70 5- to 15-year-old participants with intellectual disabilities using objective methods (accelerometers) and systematic observation techniques. Results showed that few children were active enough to benefit their physical health (23% of the cohort). No differences in habitual physical activity, sedentary behaviour, or recess play behaviours were observed between boys and girls. Participants spent most of their recess time alone or playing in small groups, with no participants engaging in large group play. Older participants spent more recess time playing in small groups rather than playing alone and participants with Autistic Spectrum Disorder spent more time engaged in active pursuits and less time standing than non-Autism Spectrum Disorder participants. Positive correlations were observed between time spent alone and physical activity. These findings contrast with those typically observed in a mainstream school setting. In conclusion, interventions designed from formative research are needed to promote physical activity within this population. Implications for school psychologists are discussed.
The ability to compare published group-level estimates of objectively measured moderate-to-vigorous physical activity (MVPA) across studies continues to increase in difficulty. The objective of this ...study was to develop conversion equations and demonstrate their utility to compare estimates of MVPA derived from the wrist and hip. Three studies of youth (N = 232, 9-12yrs, 50% boys) concurrently wore a hip-worn ActiGraph and a wrist-worn GENEActiv for 7-days. ActiGraph hip count data were reduced using four established cutpoints. Wrist accelerations were reduced using the Hildebrand MVPA 200 mg threshold. Conversion equations were developed on a randomly selected subsample of 132 youth. Equations were cross-validated and absolute error, absolute percent error, and modified Bland-Altman plots were evaluated for conversion accuracy. Across equations R2adj was 0.51-0.56 with individual-level absolute error in minutes ranging from 7 (wrist-to-hip Puyau) to 14.5 minutes (wrist-to-hip Freedson 3MET) and absolute percent differences ranging from 13.9%-24.5%. Group-level cross-validation to convert hip-to-wrist MVPA resulted in average absolute percent errors ranging from 3.1%-4.9%. Conversion of wrist-to-hip MVPA resulted in average absolute percent errors ranging from 3.0%-10.0%. We recommend the use of these equations to compare published estimates of MVPA between the wear-site cut-point combinations presented.
ObjectiveGross motor competence is essential for daily life functioning and participation in physical activities. Prevalence of gross motor competence in children with intellectual disabilities (ID) ...and/or autism is unclear. This systematic review aimed to identify appropriate assessments for children with ID and/or autism.Design & data sourcesAn electronic literature search was conducted using the EBSCOhost platform searching MEDLINE, Education Research Complete, ERIC, CINAHL Plus and SPORTDiscus databases.Eligibility criteriaIncluded studies sampled children with ID and/or autism aged between 1 and 18 yrs, used field-based gross motor competence assessments, reported measurement properties, and were published in English. The utility of assessments were appraised for validity, reliability, responsiveness and feasibility.ResultsThe initial search produced 3182 results, with 291 full text articles screened. 13 articles including 10 assessments of motor competence were included in this systematic review. There was limited reporting across measurement properties, mostly for responsiveness and some aspects of validity. The Bruininks–Oseretsky Test of Motor Proficiency-2 followed by The Test of Gross Motor Development-2 demonstrated the greatest levels of evidence for validity and reliability. Feasibility results were varied, most instruments required little additional equipment (n=8) and were suitable for a school setting, but, additional training (n=7) was needed to score and interpret the results.ConclusionThis review found the BOT-2 followed by the TGMD-2 to be the most psychometrically appropriate motor competency assessments for children with ID and/or autism in field-based settings. Motor competence assessment research is limited for these cohorts and more research is needed.PROSPERO registration numberCRD42019129464.
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