ORCID Profile
0000-0002-9180-2919
Current Organisation
Queen's University
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Publisher: The Company of Biologists
Date: 15-09-2013
DOI: 10.1242/JEB.089136
Abstract: Thyroid hormone (TH) is a universal regulator of growth, development and metabolism during cold exposure in mammals. In zebrafish (Danio rerio), TH regulates locomotor performance and metabolism during cold acclimation. The influence of TH on locomotor performance may be via its effect on metabolism or, as has been shown in mammals, by modulating muscle phenotypes. Our aim was to determine whether TH influences muscle phenotypes in zebrafish, and whether this could explain changes in swimming capacity in response to thermal acclimation. We used propylthiouracil and iopanoic acid to induce hypothyroidism in zebrafish over a 3-week acclimation period to either 18 or 28°C. To verify that physiological changes following hypothyroid treatment were in fact due to the action of TH, we supplemented hypothyroid fish with 3,5-diiodothryronine (T2) or 3,5,3′-triiodothyronine (T3). Cold-acclimated fish had significantly greater sustained swimming performance (Ucrit) but not burst speed. Greater Ucrit was accompanied by increased tail beat frequency, but there was no change in tail beat litude. Hypothyroidism significantly decreased Ucrit and burst performance, as well as tail beat frequency and SERCA activity in cold-acclimated fish. However, myofibrillar ATPase activity increased in cold-acclimated hypothyroid fish. Hypothyroid treatment also decreased mRNA concentrations of myosin heavy chain fast isoforms and SERCA 1 isoform in cold-acclimated fish. SERCA 1 mRNA increased in warm-acclimated hypothyroid fish, and SERCA 3 mRNA decreased in both cold- and warm-acclimated hypothyroid fish. Supplementation with either T2 or T3 restored Ucrit, burst speed, tail beat frequency, SERCA activity and myosin heavy chain and SERCA 1 and 3 mRNA levels of hypothyroid fish back to control levels. We show that in addition to regulating development and metabolism in vertebrates, TH also regulates muscle physiology in ways that affect locomotor performance in fish. We suggest that the role of TH in modulating SERCA1 expression during cold exposure may have predisposed it to regulate endothermic thermogenesis.
Publisher: The Company of Biologists
Date: 15-05-2014
DOI: 10.1242/JEB.088880
Abstract: The evolution of endothermy is one of the most intriguing and consistently debated topics in vertebrate biology, but the proximate mechanisms that mediated its evolution are unknown. Here, we suggest that the function of thyroid hormone in regulating physiological processes in response to cold is key to understanding the evolution of endothermy. We argue that the capacity of early chordates to produce thyroid hormone internally was the first step in this evolutionary process. Selection could then act on the capacity of thyroid hormone to regulate metabolism, muscle force production and cardiac performance to maintain their function against the negative thermodynamic effects of decreasing temperature. Thyroid-mediated cold acclimation would have been the principal selective advantage. The actions of thyroid hormone during cold acclimation in zebrafish are very similar to its role during endothermic thermogenesis. The thyroid-mediated increases in metabolism and locomotor performance in ectotherms eventually resulted in sufficient heat production to affect body temperature. From this point onwards, increased body temperature per se could be of selective advantage and reinforce thyroid-induced increases in physiological rates. Selection for increased body temperature would promote those mechanisms that maximise heat production, such as increased Na+/K+-ATPase activity, futile cycling by SERCA, and mitochondrial uncoupling, all of which are regulated by thyroid hormone. The specific end point of this broader evolutionary process would be endothermic thermoregulation. However, considering the evolution of endothermy in isolation is misleading because the selective advantages that drove the evolutionary process were independent from endothermy. In other words, without the selective advantages of thyroid-mediated cold acclimation in fish, there would be no endotherms.
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.096602
Abstract: Limitations to oxygen transport reduce aerobic scope and thereby activity at thermal extremes. Oxygen transport in fish is facilitated to a large extent by cardiac function so that climate variability may reduce fitness by constraining the performance of the heart. In zebrafish (Danio rerio), thyroid hormone (TH) regulates skeletal muscle function and metabolism in response to thermal acclimation. Here we aimed to determine whether TH also regulates cardiac function during acclimation. We used propylthiouracil and iopanoic acid to induce hypothyroidism in zebrafish over a 3-week acclimation period to either 18 or 28°C. We found that cold-acclimated fish had higher maximum heart rates and sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) activity than warm acclimated fish. Hypothyroid treatment significantly decreased these responses in the cold acclimated fish, but it did not affect the warm-acclimated fish. TH did not influence SERCA gene transcription, nor did it increase metabolic rate, of isolated whole hearts. To verify that physiological changes following hypothyroid treatment were in fact due to the action of TH, we supplemented hypothyroid fish with 3,5-diiodothryronine (T2) or 3,5,3′-triiodothyronine (T3). Supplementation of hypothyroid fish with T2 or T3 restored heart rates and SERCA activity to control levels. We also show that in zebrafish changes in cardiac output in response to warming are primarily mediated by heart rate, rather than by stroke volume. Thus changes in heart rate are important for the overall aerobic capacity of the fish. In addition to its local effects on heart phenotype, we show that TH increases sympathetic tone on the heart at rest and during maximum exercise. Our findings reveal a new pathway through which fish can mitigate the limiting effects of temperature variability on oxygen transport to maintain aerobic scope and promote thermal tolerance.
Publisher: Canadian Science Publishing
Date: 03-2023
Abstract: Female-biased mortality has been consistently reported in Pacific salmon during their adult upriver migration. We collected coho salmon ( Oncorhynchus kisutch (Walbaum, 1792)) upon arrival at their spawning grounds to test whether females are more prone to cardiac oxygen limitations following exercise stress. We used a surgical approach to periodically s le arterial and venous blood over 48 h following recovery from a chase protocol to induce maximum metabolic rate. We found no significant differences in arterial or venous partial pressures of O 2 between males and females. Female salmon had significantly elevated plasma cortisol levels but there were no effects of sex on either plasma lactate or K + . Our data show that female coho salmon do not suffer oxygen limitations to the spongy myocardium after a single exercise event at moderate temperatures (14 °C)—at least not when arriving to their spawning grounds. This study found no clear support for a cardiac oxygen limitation underlying elevated female mortality in Pacific salmon. Neither, however, does our study design nor specific findings allow us to rule out cardiac limitations in these fish. Future work should address whether potential oxygen limitations to the spongy myocardium at high temperatures or oxygen limitations to the compact myocardium via coronary blood flow contribute to female-biased mortality earlier on the migratory route.
Publisher: Elsevier BV
Date: 10-2018
DOI: 10.1016/J.CBPB.2017.11.005
Abstract: Cytochrome c oxidase (COX), the terminal enzyme of the electron transport system, is central to aerobic metabolism of animals. Many aspects of its structure and function are highly conserved, yet, paradoxically, it is also an important model for studying the evolution of the metabolic phenotype. In this review, part of a special issue honouring Peter Hochachka, we consider the biology of COX from the perspective of comparative and evolutionary biochemistry. The approach is to consider what is known about the enzyme in the context of conventional biochemistry, but focus on how evolutionary researchers have used this background to explore the role of the enzyme in biochemical adaptation of animals. In synthesizing the conventional and evolutionary biochemistry, we hope to identify synergies and future research opportunities. COX represents a rare opportunity for researchers to design studies that span the breadth of biology: molecular genetics, protein biochemistry, enzymology, metabolic physiology, organismal performance, evolutionary biology, and phylogeography.
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.214841
Abstract: Female-biased mortality has been repeatedly reported in Pacific salmon during their upriver migration in both field studies and laboratory-holding experiments, especially in the presence of multiple environmental stressors, including thermal stress. Here we used coho salmon (Oncorhynchus kisutch) to test whether females exposed to elevated water temperatures (18°C) i) suppress circulating sex hormones (testosterone, 11-ketotestosterone, and estradiol), owing to elevated cortisol levels, ii) have higher activities of enzymes supporting anaerobic metabolism (e.g., lactate dehydrogenase), iii) lower activities of enzymes driving oxidative metabolism (e.g., citrate synthase CS), in skeletal and cardiac muscle, and iv) have more oxidative stress damage and reduced capacity for antioxidant defense (lower catalase activity CAT). We found no evidence that a higher susceptibility to oxidative stress contributes to female-biased mortality at warm temperatures. We did, however, find that females had significantly lower cardiac LDH and that 18°C significantly reduced plasma levels of testosterone and estradiol, especially in females. We also found that relative gonad size was significantly lower in the 18°C treatment regardless of sex, whereas relative liver size was significantly lower in females held at 18°C. Further, relative spleen size was significantly elevated in the 18°C treatments across both sexes, with larger warm-induced increases in females. Our results suggest that males may better tolerate bouts of cardiac hypoxia at high temperature, and that thermal stress may also disrupt testosterone- and estradiol-mediated protein catabolism, and the immune response (larger spleens) in migratory female salmon.
Publisher: University of Chicago Press
Date: 05-2020
DOI: 10.1086/708673
Publisher: CRC Press
Date: 19-12-2017
DOI: 10.1201/B20420
Publisher: Elsevier
Date: 2018
DOI: 10.1016/BS.VH.2017.06.004
Abstract: Thyroid hormone (TH) plays important signaling roles in mammalian growth, development, and thermogenesis. Traditionally its actions were thought to be regulated predominately through modulation of free plasma concentrations, intracellular breakdown by deiodinase enzymes and nuclear processing by thyroid receptors. In the past decade, however, there has been some departure from this classical model, whereby regulatory changes at different levels of organization simultaneously modulate its bioavailability and bioactivity. Here I review the recent literature to emphasize how subtle changes at these various levels of regulation can underlie tissue-specific and temporal (development and disease) changes in mammalian systems. For instance, it has become increasingly clear that TH acts both centrally to control sympathetic output and peripherally to regulate metabolism in target tissues. An interesting caveat is that central actions by TH may simultaneously alter its effects at peripheral tissues. In addition to T3, other TH derivatives (e.g., rT
Publisher: Springer Science and Business Media LLC
Date: 09-04-2016
DOI: 10.1007/S00360-016-0984-2
Abstract: Thyroid hormone (TH) regulates many physiological processes that differ between tissues, developmental stages and in response to specific environmental cues. It can therefore play very different signaling roles depending on specific physiological contexts. Much progress has been made in resolving mechanisms for TH signaling over the past 2 decades, and there has been increasing emphasis on the role of peripheral levels of regulation in determining ultimate TH action. This progress has revealed a complex regulatory network, where TH bioavailability and bioactivity are peripherally regulated by sometimes subtle mechanisms at various levels of organization, including membrane receptors and transporters on the cell surface, intracellular deiodinase enzymes, thyroid receptor isoforms and cytosolic thyroid hormone binding proteins, and via accessibility and subtypes of thyroid hormone response elements in the promoters of target genes. The majority of this research comes from disease models, and so the biological relevance of each of these regulatory levels has not been comprehensively explored. This review synthesizes what is known of these local levels of TH regulation, with particular focus on their functional roles in regulating animal response to environmental cues. While thorough analysis for all of these regulatory levels in any one study is currently unrealistic, an appreciation for their collective importance is necessary to frame comparative analyses in a relevant context. This is important because common biomarkers for TH action can have very different meanings, not only for different tissues, but also for in iduals, populations and species from different developmental or environmental backgrounds.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2013
Publisher: Springer Science and Business Media LLC
Date: 19-08-2019
DOI: 10.1038/S41559-019-0951-X
Abstract: Extreme events, such as tropical cyclones, are destructive and influential forces. However, observing and recording the ecological effects of these statistically improbable, yet profound 'black swan' weather events is logistically difficult. By anticipating the trajectory of tropical cyclones, and s ling populations before and after they make landfall, we show that these extreme events select for more aggressive colony phenotypes in the group-living spider Anelosimus studiosus. This selection is great enough to drive regional variation in colony phenotypes, despite the fact that tropical cyclone strikes are irregular, occurring only every few years, even in particularly prone regions. These data provide compelling evidence for tropical cyclone-induced selection driving the evolution of an important functional trait and show that black swan events contribute to within-species ersity and local adaptation.
Publisher: Springer Science and Business Media LLC
Date: 21-01-2021
DOI: 10.1186/S12915-020-00942-W
Abstract: Thermal plasticity is pivotal for evolution in changing climates and in mediating resilience to its potentially negative effects. The efficacy to respond to environmental change depends on underlying mechanisms. DNA methylation induced by DNA methyltransferase 3 enzymes in the germline or during early embryonic development may be correlated with responses to environmental change. This developmental plasticity can interact with reversible acclimation within adult organisms, which would increase the speed of response and could alleviate potential mismatches between parental or early embryonic environments and those experienced at later life stages. Our aim was to determine whether there is a causative relationship between DNMT3 enzyme and developmental thermal plasticity and whether either or both interact with short-term acclimation to alter fitness and thermal responses in zebrafish ( Danio rerio ). We developed a novel DNMT3a knock-out model to show that sequential knock-out of DNA methyltransferase 3a isoforms (DNMT3aa −/− and DNMT3aa −/− ab −/− ) additively decreased survival and increased deformities when cold developmental temperatures in zebrafish offspring mismatched warm temperatures experienced by parents. Interestingly, short-term cold acclimation of parents before breeding rescued DNMT3a knock-out offspring by restoring survival at cold temperatures. DNMT3a knock-out genotype interacted with developmental temperatures to modify thermal performance curves in offspring, where at least one DNMT3a isoform was necessary to buffer locomotion from increasing temperatures. The thermal sensitivity of citrate synthase activity, an indicator of mitochondrial density, was less severely affected by DNMT3a knock-out, but there was nonetheless a significant interaction between genotype and developmental temperatures. Our results show that DNMT3a regulates developmental thermal plasticity and that the phenotypic effects of different DNMT3a isoforms are additive. However, DNMT3a interacts with other mechanisms, such as histone (de)acetylation, induced during short-term acclimation to buffer phenotypes from environmental change. Interactions between these mechanisms make phenotypic compensation for climate change more efficient and make it less likely that thermal plasticity incurs a cost resulting from environmental mismatches.
Publisher: The Company of Biologists
Date: 2016
DOI: 10.1242/JEB.143529
Abstract: Thyroid hormone is a key regulator of metabolism, and in zebrafish hypothyroidism decreases sustained and burst swimming performance. These effects are accompanied by decreases in both metabolic scope and the activity of sarco-endoplasmic reticulum ATPase (SERCA) in zebrafish. Our aim was to determine whether thyroid hormone affects skeletal muscle contractile function directly and whether these effects are mediated by influencing SERCA activity. We show that hypothyroidism reduces sustained locomotor performance but not sprint performance in carp (Cyprinus carpio). We accept our hypothesis that hypothyroidism reduces force production in isolated skeletal muscle, when compared to T2, but we reject the hypothesis that this effect is mediated by influencing SERCA activity. Blocking SERCA activity with thapsigargin reduced muscle fatigue resistance, but hypothyroidism had no effect on fatigue. Hence, thyroid hormone plays a role in determining isolated skeletal muscle mechanics, but its effects are more likely to be mediated by other mechanisms than affecting SERCA activity.
Publisher: Springer Science and Business Media LLC
Date: 07-10-2022
DOI: 10.1038/S41390-021-01738-6
Abstract: Preterm birth is associated with the development of acute and chronic disease, potentially, through the disruption of normal gut microbiome development. Probiotics may correct for microbial imbalances and mitigate disease risk. Here, we used licon sequencing to characterise the gut microbiome of probiotic-treated premature infants. We aimed to identify and understand variation in bacterial gut flora from admission to discharge and in association with clinical variables. Infants born weeks gestation and g, and who received probiotic treatment, were recruited in North Queensland Australia. Meconium and faecal s les were collected at admission and discharge. All s les underwent 16S rRNA short licon sequencing, and subsequently, a combination of univariate and multivariate analyses. 71 admission and 63 discharge s les were collected. Univariate analyses showed significant changes in the gut flora from admission to discharge. Mixed-effects modelling showed significantly lower alpha ersity in infants diagnosed with either sepsis or retinopathy of prematurity (ROP) and those fed formula. In addition, chorioamnionitis, preecl sia, sepsis, necrotising enterocolitis and ROP were also all associated with the differential abundance of several taxa. The lower microbial ersity seen in infants with diagnosed disorders or formula-fed, as well as differing abundances of several taxa across multiple variables, highlights the role of the microbiome in the development of health and disease. This study supports the need for promoting healthy microbiome development in preterm neonates. Low ersity and differing taxonomic abundances in preterm gut microbiota demonstrated in formula-fed infants and those identified with postnatal conditions, as well as differences in taxonomy associated with preecl sia and chorioamnionitis, reinforcing the association of the microbiome composition changes due to maternal and infant disease. The largest study exploring an association between the preterm infant microbiome and ROP. A novel association between the preterm infant gut microbiome and preecl sia in a unique cohort of very-premature probiotic-supplemented infants.
Publisher: The Royal Society
Date: 2015
DOI: 10.1098/RSOS.140251
Abstract: The shape of performance curves and their plasticity define how in iduals and populations respond to environmental variability. In theory, maximum performance decreases with an increase in performance breadth. However, reversible acclimation may counteract this generalist–specialist trade-off, because performance optima track environmental conditions so that there is no benefit of generalist phenotypes. We tested this hypothesis by acclimating in idual mosquitofish ( Gambusia holbrooki ) to cool and warm temperatures consecutively and measuring performance curves of swimming performance after each acclimation treatment. In iduals from the same population differed significantly in performance maxima, performance breadth and the capacity for acclimation. As predicted, acclimation resulted in a shift of the temperature at which maximal performance occurred. Within acclimation treatments, there was a significant generalist–specialist trade-off in responses to acute temperature change. Surprisingly, however, there was also a trade-off across acclimation treatments, and animals with greater capacity for cold acclimation had lower performance maxima under warm conditions. Hence, cold acclimation may be viewed as a generalist strategy that extends performance breadth at the colder seasons, but comes at the cost of reduced performance at the warmer time of year. Acclimation therefore does not counteract a generalist–specialist trade-off and, at least in mosquitofish, the trade-off seems to be a system property that persists despite phenotypic plasticity.
Publisher: American Physiological Society
Date: 06-2010
DOI: 10.1152/PHYSIOLGENOMICS.00015.2010
Abstract: Vertebrate mitochondrial cytochrome c oxidase (COX) possesses 10 nuclear-encoded subunits. Six subunits have paralogs in mammals, but the origins and distribution of isoforms among vertebrates have not been analyzed. We used Bayesian phylogenetic analysis to interpret the origins of each subunit, inferring the roles of gene and genome duplications. The paralogous ancestries of five genes were identical throughout the major vertebrate taxa: no paralogs of COX6c and COX7c, two paralogs of COX4 and COX6a, and three paralogs of COX7a. Two genes had an extra copy in teleosts (COX5a, COX5b), and three genes had additional copies in mammals (COX6b, COX7b, COX8). Focusing on early vertebrates, we examined structural ergence and explored transcriptional profiles across zebrafish tissues. Quantitative transcript profiles revealed dramatic differences in transcript abundance for different subunits. COX7b and COX4 transcripts were typically present at very low levels, whereas COX5a and COX8 were in vast excess in all tissues. For genes with paralogs, two general patterns emerged. For COX5a and COX8, there was ubiquitous expression of one paralog, with the other paralog in lower abundance in all tissues. COX4 and COX6a shared a distinct expression pattern, with one paralog dominant in brain and gills and the other in muscles. The isoform profiles in combination with phylogenetic analyses show that vertebrate COX isoform patterns are consistent with the hypothesis that early whole genome duplications in basal vertebrates governed the isoform repertoire in modern fish and tetrapods, though more recent lineage-specific gene/genome duplications also play a role in select subunits.
Publisher: Elsevier BV
Date: 02-2015
DOI: 10.1016/J.ENVPOL.2014.12.003
Abstract: Bisphenol A (BPA) is a ubiquitous pollutant around the globe, but whether environmental concentrations have toxic effects remains controversial. BPA interferes with a number of nuclear receptor pathways, including several that mediate animal responses to environmental input. Because thermal acclimation is regulated by these pathways in fish, we hypothesized that the toxicity of BPA would change with ambient temperature. We exposed zebrafish (Danio rerio) to ecologically relevant and artificially high concentrations of BPA at two acclimation temperatures, and tested physiological responses at two test temperatures that corresponded to acclimation temperatures. We found ecologically relevant concentrations of BPA (20 μg l(-1)) impair swimming performance, heart rate, muscle and cardiac SERCA activity and gene expression. We show many of these responses are temperature-specific and non-monotonic. Our results suggest that BPA pollution can compound the effects of climate change, and that its effects are more dynamic than toxicological assessments currently account for.
Publisher: Wiley
Date: 28-08-2014
Publisher: Wiley
Date: 27-11-2018
DOI: 10.1111/NEP.13520
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.MVR.2019.04.005
Abstract: The link between in utero and early life insults and the development of chronic illness remains to be fully understood, but there is increasing data to indicate that microvasculature pathology plays an important mechanistic role. Currently available data indicate that retinal microvasculature changes are detectable in children as young as six years of age, however, there are no data for younger children. We present retinal microvasculature measurement from the first two years of life. Retinal images suitable for analysis were available from 18 infants in our proof-of-concept study. The mean and standard deviation (SD) for birth weight and gestation was 3410 (384) g and 39.1(1.4) weeks, respectively. Retinal vessel calibres were summarized as the mean(SD) central retinal arteriolar equivalent (CRAE) at six months of age was 156 (32) μm, increased to 175 (75) μm by 12 months and a slightly declined by 24 months of age to 168 (50) μm. In a similar pattern, mean(SD) central retinal venular equivalent (CRVE) at six months was 211 (19) μm, increased to 238 (25) μm by 12 months of age followed by a slight decline at 24 months of age to 222 (36) μm. The arterio-venous ratio and tortuosity index remained the same at 6, 12 and 24 months. Findings from this study could help future investigators better understand early microvasculature changes and adaptation that occur early in life.
Publisher: American Physiological Society
Date: 09-2016
DOI: 10.1152/AJPREGU.00148.2016
Abstract: Central pathways regulate metabolic responses to cold in endotherms to maintain relatively stable internal core body temperatures. However, peripheral muscles routinely experience temperatures lower than core body temperature, so that it would be advantageous for peripheral tissues to respond to temperature changes independently from core body temperature regulation. Early developmental conditions can influence offspring phenotypes, and here we tested whether developing muscle can compensate locally for the effects of cold exposure independently from central regulation. Muscle myotubes originate from undifferentiated myoblasts that are laid down during embryogenesis. We show that in a murine myoblast cell line (C2C12), cold exposure (32°C) increased myoblast metabolic flux compared with 37°C control conditions. Importantly, myotubes that differentiated at 32°C compensated for the thermodynamic effects of low temperature by increasing metabolic rates, ATP production, and glycolytic flux. Myotube responses were also modulated by the temperatures experienced by “parent” myoblasts. Myotubes that differentiated under cold exposure increased activity of the AMP-stimulated protein kinase (AMPK), which may mediate metabolic changes in response cold exposure. Moreover, cold exposure shifted myosin heavy chains from slow to fast, presumably to overcome slower contractile speeds resulting from low temperatures. Adjusting thermal sensitivities locally in peripheral tissues complements central thermoregulation and permits animals to maintain function in cold environments. Muscle also plays a major metabolic role in adults, so that developmental responses to cold are likely to influence energy expenditure later in life.
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.217075
Abstract: Intra-group social stability is important for the long-term productivity and health of social organisms. We evaluated the effect of group size on group stability in the face of repeated social perturbations using a cooperatively breeding fish, Neol rologus pulcher. In a laboratory study, we compared both the social and physiological responses of in iduals from small versus large groups to the repeated removal and replacement of the most dominant group member (the breeder male), either with a new male (treatment condition) or with the same male (control condition). In iduals living in large groups were overall more resistant to instability but were seemingly slower to recover from perturbation. Members of small groups were more vulnerable to instability but recovered faster. Breeder females in smaller groups also showed greater physiological preparedness for instability following social perturbations. In sum, we discover both behavioral and physiological evidence that living in larger groups helps to d en the impacts of social instability in this system.
Publisher: Frontiers Media SA
Date: 04-08-2017
Publisher: The Company of Biologists
Date: 12-2015
DOI: 10.1242/JEB.129049
Abstract: Locomotion facilitates behaviour and its underlying physiological mechanisms may therefore impact behavioural phenotypes. Metabolism is often thought to modulate locomotion and behaviour, but empirical support for this suggestion is equivocal. Muscle contractile function is directly associated with locomotion. Here, we test the hypotheses that muscle mechanics determine locomotor performance and activity in zebrafish (Danio rerio) and thereby also affect risk-taking behaviour. We show that there is a mechanistic link between muscle performance and behaviour by manipulating muscle contractile properties, which caused proportional changes in critical sustained swimming performance and, in an open arena, voluntary swimming speed, the proportion of time fish were active, and the latency to move. We modelled the relationships between muscle contractile properties, swimming performance, activity and behaviour with a partial least-squares path model. The latent variable ‘muscle’, formed by isolated muscle force production, stress, fatigue resistance and activation and relaxation rates, had a significant positive effect on swimming performance (‘swim’ reflected in sustained and sprint speeds). Together, muscle and swim had a significant positive effect on activity, and explained 71.8% of variation in the distance moved, time active and maximum voluntary speed in an open field. Activity had a significant positive effect on boldness, explaining 76.0% of variation in latencies to move and to approach a novel object. Muscle contractile function determines voluntary movement and we suggest that exploration and dispersal are functions of physiological and mechanical optimisation. Boldness therefore may be partly explained by the greater likelihood of faster fish to move further and encounter novel objects and conspecifics more quickly as a result.
Publisher: Springer Science and Business Media LLC
Date: 15-04-2020
DOI: 10.1007/S00467-020-04554-Y
Abstract: We carried out a study to determine the impact of prematurity on kidney development in the first 2 years of life. In this prospective study, extremely preterm neonates (gestation 28 weeks) were recruited and underwent assessments at 6, 12, and 24 months of age. A cohort of neonates born term were also recruited and followed up for 24 months. The primary outcomes measured in this study were total kidney volume (TKV) and estimated glomerular filtration rate (eGFR) albuminuria and blood pressure measurements (all provided as mean (standard deviation)) were the secondary outcomes. Fifty-three premature and 31 term neonates (control) were recruited. At the age of 24 months (corrected age), infants born preterm had significantly smaller TKV (56.1 (9.4) vs. 64.8 (10.2) mL P = 0.006). There was no difference in eGFR. These preterm infants were smaller (11.25 (1.53) vs. 12.9 (1.8) kg P = 0.002) and shorter (83.8 (3.0) vs. 86.3 (3.4) cm P = 0.02) when compared with the control group. At 6, 12, and 18 months respectively, preterm infants had, relative to their height, significantly smaller kidney volumes (0.54 (0.1) vs. 0.59 (0.1) mL/cm, P = 0.05 0.61 (0.1) vs.0.71 (0.1) mL/cm, P = 0.003 and 0.67 (0.1) vs.0.76 (0.1) mL/cm, P = 0.006). Relative to body length, TKV in premature infants is smaller. Since length reflects adult body proportions more accurately than BSA, TKV to height ratio may be a more important measure in the child. Despite smaller TKV (and therefore fewer nephrons), infants born prematurely achieve similar eGFRs in the first 24 months of life, probably due to single-nephron hyperfiltration.
Publisher: Elsevier BV
Date: 04-2019
DOI: 10.1016/J.HLC.2018.03.008
Abstract: Anti-myosin antibodies (AMAs) are often formed in response to myocardial infarction (MI) and have been implicated in maladaptive cardiac remodelling. We aimed to: (1) compare AMA formation in patients with Non-ST-Elevation MI (NSTEMI) and ST-Elevation MI (STEMI) (2) evaluate factors predicting autoantibody formation and, (3) explore their functional significance. Immunoglobulin M (IgM) and Immunoglobulin G (IgG) AMA titres were determined in serum s les collected at admission, 3 and 6 months post MI. The relationship between demographic and clinical data, and antibody formation, was investigated to determine factors predicting antibody formation and functional significance. Forty-three (43) patients were consecutively recruited 74.4% were positive for IgM at admission, compared with 23.3% for IgG. Mean IgG levels increased by 1.24% (±0.28) at 3 months, and 13.55% (±0.13) at 6 months post MI. Mean antibody levels were significantly higher in the NSTEMI cohort at both follow-up time points for IgG (p<0.001, p<0.0001), but not IgM (p=0.910, p=0.066). A moderately positive correlation between infarct size and increase in mean IgM concentration was observed at 3 months (r(98)=0.455 p=0.015). Anti-myosin antibody formation was not associated with an unfavourable outcome at follow-up. Anti-myosin antibodies are formed in a significant proportion of patients following MI, particularly among those with NSTEMI. While IgM levels fall after infarction, IgG levels increase and persist beyond 6 months of follow-up. This raises the possibility that they may contribute to long-term myocardial damage and dysfunction. Future research should focus on the specific epitopes that are targeted by these antibodies, and their functional significance. This may result in the emergence of novel therapies to attenuate cardiac dysfunction in MI patients.
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.YMPEV.2010.04.022
Abstract: Billfishes (Scombroidei) and tunas (Scombridae), both considered part of the suborder Scombroidei, have long been studied by biologists largely because of their remarkable physiological and anatomical muscular adaptations associated with regional endothermy and continuous swimming. These attributes, combined with analyses of other morphological and molecular data, have led to a general perception that tunas and billfishes are close relatives, though this hypothesis has been vigorously debated. Using Bayesian phylogenetic analysis of nine mitochondrial and three nuclear loci (>7000bp), we show that billfishes are only distantly related to tunas, but rather share strong evolutionary affinities with flatfishes (Pleuronectiformes) and jacks (Carangidae). This phylogenetic relationship is striking because of the marked variation in phenotype and niche across these trans-ordinal groups of fishes. Billfishes and flatfishes have each evolved radically ergent morphological and physiological features: elongated bills and extraocular heater organs in billfishes, and cranial asymmetry with complete eye migration during ontogenetic development in flatfishes. Despite this ergence, we identify synapomorphies consistent with the hypothesis of a common billfish/flatfish/jack ancestor.
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.TREE.2019.04.009
Abstract: Rigorously evaluating of the ecological impacts of cyclones is logistically challenging. Here we issue a call-to-action to organize a global collaboration initiative to advance cyclone ecology. If successful, this will allow the international community to pose some of the most exciting questions in ecology and provide definitive answers.
Publisher: Oxford University Press (OUP)
Date: 2018
Publisher: Research Square Platform LLC
Date: 19-01-2021
DOI: 10.21203/RS.3.RS-144762/V1
Abstract: Background:The gut microbiome plays a critical role in the healthy development, immunity and metabolism of infants. Preterm birth disrupts microbiome development and can contribute to acute and chronic disease. To promote microbial and infant development, and to mitigate the risk of disease, premature infants may be treated with probiotics. Here we used 16S rRNA high throughout sequencing to characterize the bacterial microbiome of probiotic-supplemented premature infants. The study aimed to identify and understand variation in bacterial gut flora, including changes from admission to discharge, and the effect of several clinical variables using a combination of univariate and mixed effects analyses.Results: Infants born weeks gestation and g were recruited in North Queensland, Australia, with faecal s les collected at admission ( n = 71) and at discharge ( n = 63). Our research builds on previous research and supports significant changes over time in the preterm infant microbiome, and in response to several variables. Univariate analysis showed admission and discharge s les had significantly different microbial populations, with Staphylococcus enriched at admission and Enterobacter , Lactobacillus , Colstridium sensu stricto 1 and Veillonella at discharge. From the mixed effects modeling we observed significantly lower alpha ersity in infants diagnosed with either sepsis or retinopathy of prematurity (ROP), and those that only received formula milk. Chorioamnionitis, preecl sia, sepsis, necrotizing enterocolitis and ROP were also all associated with differential abundance of several taxa.Conclusions:Our study builds on previous research and supports significant changes in the preterm microbiome over time and in association with several factors. The fact that several associations were observed, and some in ways that counter previous work, highlights the complexity of microbiome ecology.
Publisher: American Physiological Society
Date: 15-09-2014
DOI: 10.1152/AJPREGU.00115.2014
Abstract: Previous isolated muscle studies examining the effects of ageing on contractility have used isometric protocols, which have been shown to have poor relevance to dynamic muscle performance in vivo. The present study uniquely uses the work-loop technique for a more realistic estimation of in vivo muscle function to examine changes in mammalian skeletal muscle mechanical properties with age. Measurements of maximal isometric stress, activation and relaxation time, maximal power output, and sustained power output during repetitive activation and recovery are compared in locomotory extensor digitorum longus (EDL) and core diaphragm muscle isolated from 3-, 10-, 30-, and 50-wk-old female mice to examine the early onset of ageing. A progressive age-related reduction in maximal isometric stress that was of greater magnitude than the decrease in maximal power output occurred in both muscles. Maximal force and power developed earlier in diaphragm than EDL muscle but demonstrated a greater age-related decline. The present study indicates that ability to sustain skeletal muscle power output through repetitive contraction is age- and muscle-dependent, which may help rationalize previously reported equivocal results from examination of the effect of age on muscular endurance. The age-related decline in EDL muscle performance is prevalent without a significant reduction in muscle mass, and biochemical analysis of key marker enzymes suggests that although there is some evidence of a more oxidative fiber type, this is not the primary contributor to the early age-related reduction in muscle contractility.
Publisher: Elsevier BV
Date: 06-2012
DOI: 10.1016/J.YMPEV.2012.02.012
Abstract: While endothermy is ubiquitous in birds and mammals, it is not exclusive to these most recently arisen vertebrate classes. The ability to warm specific organs and/or tissues above ambient temperature (regional endothermy) has evolved at least three times in phylogentically discrete fish lineages: lamnid sharks (Lamnidae), tunas (Scombridae) and billfishes (Istiophoridae and Xiphidae). Given the links between endothermy and metabolic rate, we looked for evidence of convergent molecular evolution in mtDNA-encoded cytochrome c oxidase (COX) subunits in each of these discrete lineages. We found no evidence that the endothermic phenotype in fishes is driven or accompanied by molecular convergence. Though we found little evidence for positively-selected sites in any of the lineages in any subunit, the conclusions were sensitive to the choice of maximum-likelihood model. Several sites identified by Naïve Empirical Bayes (NEB) were not found when Bayes Empirical Bayes (BEB) was employed. As well, conclusions were profoundly influenced by taxon-s ling. Several of the putative sites of positive selection in COX II were no longer apparent as we augmented taxon s ling. The lack of convergent molecular evolution in these remarkable taxa, combined with the profound influence of model choice and taxon s ling provide a cautionary note on the use of rates of non-synonymous to synonymous mutations (dN/dS) to explore questions of the evolution of physiological function.
Publisher: Wiley
Date: 24-06-2020
DOI: 10.1111/JFB.14402
Location: Canada
Location: United States of America
Location: United States of America
Start Date: 2019
End Date: 2022
Funder: Australian Research Council
View Funded ActivityStart Date: 2010
End Date: 2013
Funder: University of Sydney
View Funded ActivityStart Date: 2014
End Date: 2016
Funder: Canadian Institutes of Health Research
View Funded ActivityStart Date: 2019
End Date: 2022
Funder: Natural Sciences and Engineering Research Council of Canada
View Funded Activity