The intraspecific diversity of Norwegian Arctic charr (Salvelinus alpinus (L.)): An examination of repeatability and life history

Across Arctic charr’s Holearctic distribution we see repeated patterns where multiple ecotypes diverge along ecological resource gradients. Arctic charr occur in both anadromous and lacustrine forms. Furthermore, lacustrine ecotypes are seen repeatedly specializing their morphology, trophic ecology, and life history along a benthic pelagic axis and along the depth gradient. Typically, a pelagic ecotype cooccurs with a profundal benthivorous ecotype. With increasing intraspecific diversity, a third piscivorous ecotype may also occur. These patterns of ecotype divergence occur in multiple lakes, therefore I studied if ecotypes occur in a random manner or if there is evidence for repeatability in their phenotypes. Life history was studied among five lakes to assess the repeatability of life history traits finding that variation in traits may be related to the number of ecotypes. The next study examined the repeatability and correlations among habitat use, diet, morphology, and life history. As these traits were found to be correlated differently in the ecotypes and at differing levels of intraspecific diversity, I propose the presence of an adaptive trait syndrome in Arctic charr ecotypes. Finally, in the anadromous Arctic charr I developed a method to quantify the number of marine migrations performed by an individual. These estimates of marine experience were discussed in relation to their influence on trophic ecology where there is increasing specialization with successive migrations. We also report an estimate of the number of marine migrations required for maturity in Arctic charr. This work demonstrates the importance of developing new methods and of studying diversity at a multi-trait level to improve our understanding of biodiversity and ability to manage and conserve species in accelerating climate change

Lifelong divergence of growth patterns in Arctic charr life history strategies: implications for sustainable fisheries in a changing climate

Arctic charr (Salvelinus alpinus Linnaeus, 1758) are phenotypically variable with multiple life history strategies including anadromous and freshwater resident individuals. The mechanism determining life history is believed to be set early in life. Anadromous individuals show greater seasonality in growth and feeding after the first seaward migration relative to resident conspecifics. We used otolith growth increment measurements to estimate lifelong growth patterns for 355 individuals with anadromous or resident life history from four populations within Cumberland Sound, Nunavut. Using a general and a generalized linear model, we discovered a linear increase (estimate = 0.006) in growth for both Arctic charr life histories between 1990 and 2016. Resident Arctic charr have lower annual growth (estimate = −0.176) and show a decrease in the annual proportion of summer growth as they age (estimate = −0.042), whereas their anadromous counterparts maintain a higher seasonality in their growth patterns with age. This suggests that growth is indeed important in life history trajectory for Arctic charr and that seasonal growth patterns differ among life histories. The results highlight the importance of improving our understanding of mechanisms influencing life history trajectory in Arctic charr to ensure sustainability of harvested Arctic charr populations in a changing climate

Salmon-lice as a potential threat to anadromous Arctic charr populations

Salmon-lice have the potential to change the behaviour and growth of their salmonid host species. Here, the baseline infection levels of salmon-lice of post-smolts (n = 815) and veteran migrants (n = 875) of sea-run Arctic charr (Salvelinus alpinus Linnaeus, 1758) were monitored over two successive years in a sub-Arctic Norwegian fjord without farming of salmonids. All Arctic charr were collected after the seamigration period from a trap placed in the river, ascending to their overwintering freshwater habitat (Lake Laksvatn). The sea-lice infection showed a stable infection across the 2 years while increasing through the migration period and with the size of the wild sea-run Arctic charr. The prevalence of sea-lice infection was intermediate to high, and the intensities of sea-lice infections observed were generally modest, although some individuals had high infections. The relatively high infection of salmonlice highlights the potential detrimental effects these parasites can have at both the individual and population level of such endangered sub-Arctic life-history strategies. A comparative study should be performed in fjords with aquaculture activity as focal points for salmon-lice, to investigate the impact farming have on sea-run Arctic charr populations

A thermal‐gradient approach to variable‐temperature measurements resolved in space

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155923/1/jcr2te5056.pd

Tractostorm 2 : Optimizing tractography dissection reproducibility with segmentation protocol dissemination

The segmentation of brain structures is a key component of many neuroimaging studies. Consistent anatomical definitions are crucial to ensure consensus on the position and shape of brain structures, but segmentations are prone to variation in their interpretation and execution. White-matter (WM) pathways are global structures of the brain defined by local landmarks, which leads to anatomical definitions being difficult to convey, learn, or teach. Moreover, the complex shape of WM pathways and their representation using tractography (streamlines) make the design and evaluation of dissection protocols difficult and time-consuming. The first iteration of Tractostorm quantified the variability of a pyramidal tract dissection protocol and compared results between experts in neuroanatomy and nonexperts. Despite virtual dissection being used for decades, in-depth investigations of how learning or practicing such protocols impact dissection results are nonexistent. To begin to fill the gap, we evaluate an online educational tractography course and investigate the impact learning and practicing a dissection protocol has on interrater (groupwise) reproducibility. To generate the required data to quantify reproducibility across raters and time, 20 independent raters performed dissections of three bundles of interest on five Human Connectome Project subjects, each with four timepoints. Our investigation shows that the dissection protocol in conjunction with an online course achieves a high level of reproducibility (between 0.85 and 0.90 for the voxel-based Dice score) for the three bundles of interest and remains stable over time (repetition of the protocol). Suggesting that once raters are familiar with the software and tasks at hand, their interpretation and execution at the group level do not drastically vary. When compared to previous work that used a different method of communication for the protocol, our results show that incorporating a virtual educational session increased reproducibility. Insights from this work may be used to improve the future design of WM pathway dissection protocols and to further inform neuroanatomical definitions.Peer reviewe

Brain

We report a composite extreme phenotype design using distribution of white matter hyperintensities and brain infarcts in a population-based cohort of older persons for gene-mapping of cerebral small vessel disease. We demonstrate its application in the 3C-Dijon whole exome sequencing (WES) study (n = 1924, nWESextremes = 512), with both single variant and gene-based association tests. We used other population-based cohort studies participating in the CHARGE consortium for replication, using whole exome sequencing (nWES = 2,868, nWESextremes = 956) and genome-wide genotypes (nGW = 9924, nGWextremes = 3308). We restricted our study to candidate genes known to harbour mutations for Mendelian small vessel disease: NOTCH3, HTRA1, COL4A1, COL4A2 and TREX1. We identified significant associations of a common intronic variant in HTRA1, rs2293871 using single variant association testing (Pdiscovery = 8.21 × 10-5, Preplication = 5.25 × 10-3, Pcombined = 4.72 × 10-5) and of NOTCH3 using gene-based tests (Pdiscovery = 1.61 × 10-2, Preplication = 3.99 × 10-2, Pcombined = 5.31 × 10-3). Follow-up analysis identified significant association of rs2293871 with small vessel ischaemic stroke, and two blood expression quantitative trait loci of HTRA1 in linkage disequilibrium. Additionally, we identified two participants in the 3C-Dijon cohort (0.4%) carrying heterozygote genotypes at known pathogenic variants for familial small vessel disease within NOTCH3 and HTRA1. In conclusion, our proof-of-concept study provides strong evidence that using a novel composite MRI-derived phenotype for extremes of small vessel disease can facilitate the identification of genetic variants underlying small vessel disease, both common variants and those with rare and low frequency. The findings demonstrate shared mechanisms and a continuum between genes underlying Mendelian small vessel disease and those contributing to the common, multifactorial form of the disease

COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study

Background: The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms. Methods: International, prospective observational study of 60 109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms. Results: ‘Typical’ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (≤ 18 years: 69, 48, 23; 85%), older adults (≥ 70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each P < 0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country. Interpretation: This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men

Profil radial discriminatif du propagateur de diffusion de faisceaux de la matière blanche du cerveau

L’architecture fibreuse de la matière blanche rend possible la reconstruction virtuelle de celle-ci à partir de données d'imagerie par résonance magnétique de diffusion. Par contre, la complexité de cette structure amène des défis qui font encore l’objet d’études. La plupart des méthodes utilisées pour analyser les fibres de la matière blanche se divisent en deux familles, une qui se concentre surtout sur l’orientation de celles-ci et l’autre plutôt sur leur microstructure. Or, une technique combinant l’information d’orientation et de microstructure pourrait s’avérer concluante afin de surpasser les obstacles que pose l’estimation de la structure de ce tissu du cerveau. Ainsi, l’hypothèse selon laquelle des éléments de microstructure différenciant les orientations des faisceaux de fibres sont détectables à l’aide du propagateur de diffusion est posée et examinée dans ce mémoire. Des observations, sur des données de haute qualité, de type clinique et simulées, montrent le potentiel d’une nouvelle méthode d’analyse qui utilise l’aspect radial et angulaire des récents schémas d’acquisition. De plus, les résultats obtenus semblent démontrer que le propagateur de diffusion est un outil assez sensible pour distinguer des populations de fibres correspondant à différents faisceaux. L’expérimentation sur des données simulées donne également des pistes sur les paramètres de diffusivité qui font varier le propagateur. Ces avancées posent les préliminaires pour des études de microstructure spécifiques à des faisceaux de fibres à l’aide du propagateur de diffusion et peuvent contribuer à différentes applications telles que la tractométrie et la connectivité

Accès aux services de santé en français et gouverne en réseau : différentes représentations et stratégies d’action

Au Canada, l’enjeu de l’amélioration de l’accès aux services de santé en français, surtout dans les provinces hors Québec, s’inscrit dans des relations complexes entre différents acteurs qui poursuivent des objectifs variés. En 2008, au Nouveau-Brunswick, l’État a remplacé les huit régies régionales existantes par deux nouvelles régies, soit la Régie régionale de la santé A (Réseau de santé Vitalité) et la Régie régionale de la santé B (Réseau de santé Horizon). Plus tard, il a été établi que Vitalité fonctionnerait en français et Horizon en anglais, et que les réseaux assureraient la prestation des services de santé dans la langue officielle du choix des citoyens. Ainsi, l’objectif général de la recherche était de comprendre l’influence des dynamiques entre les acteurs d’une gouverne en réseau sur le traitement de l’enjeu que représente l’accès aux services de santé en français. Une méthode qualitative comprenant notamment des entretiens semi-directifs (n=26) a été retenue. Les résultats montrent que, d’une part, l’offre de services dans la langue du choix des citoyens, qui est conditionnée par le cadre juridique sur les droits linguistiques, pousse les acteurs à mobiliser des stratégies axées sur la qualité et la sécurité. D’autre part, l’accès révèle une dimension symbolique, puisqu’il est associé aux notions d’équité et de gouvernance. L’accès aux services de santé en français est un sujet délicat pour l’État, qui demeure en retrait par rapport à celui-ci. Afin de mieux répondre aux besoins en santé des citoyens, cet acteur doit faire émerger des liens de confiance et formuler des objectifs clairs.In Canada, the issue of improving access to French-language health services, especially in provinces outside of Quebec, lies within a complex relational dynamic between different actors who pursue various objectives. In 2008, the Government of New Brunswick merged the eight existing regional health authorities into two, Regional Health Authority A (Vitalité Health Network) and Regional Authority B (Horizon Health Network). Later, it was determined that Vitalité would operate in French and Horizon, in English, while ensuring the delivery of health services in the citizens’ official language of choice. The general objective of the research was to understand how the dynamics between the actors of a network governance influence the way the issue of access to health services in French is managed. The research was based on a qualitative method and included semi-structured interviews (n=26). The results show that the legal framework of language rights’ requirement to offer services in the language of choice pushes the actors to mobilize strategies focused on quality and security. The notion of access also has a symbolic dimension, as it is associated with notions of equity and governance. Access to health services in French is a sensitive issue for the government, which tends to steer clear of it. To better address the health needs of citizens, this actor must build trust and set clear objectives