Modélisation spatiale des stocks en carbone, azote et phosphore des tourbières laurentiennes

Les tourbières ont accumulé des quantités importantes de matière organique (tourbe) depuis le début de l’Holocène. La tourbe séquestre des quantités de carbone (C), d’azote (N) et de phosphore (P) substantielles à l’échelle globale. Cependant, très peu d’études ont estimé les stocks de ces nutriments à l’échelle régionale. De plus, les estimations actuelles sont souvent obtenues sans considérer la variabilité des profondeurs de tourbe et les variables biophysiques et physiques qui dictent la capacité de stockage en nutriments. Ce mémoire vise à estimer les stocks en C, N et P des tourbières d’une région du sud du Québec en modélisant les variations de profondeurs de tourbe et en identifiant quelles variables biophysiques et physiques expliquent la capacité de stockage en nutriments des différents types de tourbières. Le sondage manuel des sites d’études a révélé des différences significatives de profondeurs de tourbe entre les types de tourbières. La profondeur moyenne de tourbe obtenue pour les tourbières ombrotrophes était de 4,4 m alors que celles des tourbières minérotrophes et forestières étaient respectivement de 2,3 et 2,0 m. Les profondeurs ont été modélisées par interpolation spatiale pour chaque bassin d’accumulation de tourbe. La relation entre la superficie des tourbières et les stocks en C était significativement différente entre les tourbières ombrotrophes et les tourbières minérotrophes et forestières. Aucune variable étudiée ne permettait de discriminer les stocks en N et P selon le type de tourbière. Les stocks en C, N et P de la tourbe ont été extrapolés pour la région en utilisant la superficie des tourbières et estimés à 5,65 Tg C, 230,5 Gg N et 21,8 Gg P. Mes travaux ont démontré que l’hétérogénéité du bassin d’accumulation et les caractéristiques de surface influencent les stocks en C, N et P contenus dans la tourbe.Peatlands have accumulated important amounts of organic matter since the beginning of the Holocene. This organic matter accumulation is described as peat, that globally stores large amounts of carbon (C), nitrogen (N), and phosphorus (P). Regional estimations of C and nutrients stocks have seldom been quantified. Moreover, peat depth variability and biophysical and physical variables are often not included in actual peat C, N, and P pool size estimations. The goal of this thesis is to provide an estimation of peat C, N, and P pool sizes for a regional county of southern Quebec by modeling peat depth variations and by using biophysical and physical variables to discriminated peat C, N, and P storage among peatland types. Manual peat depth probing showed significant differences in peat depth among peatland types. Mean peat depth of bogs was 4.4 m, while fens and forested peatlands mean peat depths were of 2.3 and 2.0 m, respectively. Modeling of peat accumulation basin by spatial interpolation took these peat depth variations into account, among peatland types. The relationship between peatland area and peat C stocks was statistically different between bogs and fens, and bogs and forested peatlands. Peat N and P content among peatland types were not discriminated by the biophysical and physical variables considered in this study. Peat C, N, and P stocks were extrapolated within the study region using peatland area and estimated at 5.65 Tg C, 230.5 Gg N et 21.8 Gg P. This study has shown that peat accumulation basin heterogeneity and peatland geometric shape influenced peat C, N, and P stocks at the regional scale

Physiological markers of challenge and threat mediate the effects of performance-based goals on performance

Manuscript "in press", Journal of Experimental Social PsychologyWe predicted that adopting a performance-approach vs. performance-avoidance goal would lead to physiological responses characteristic of psychological states of challenge vs. threat appraisals, respectively. Furthermore, we predicted that these states would mediate the effects of goals on performance. Twenty-seven undergraduate females performed a task described as identifying either exceptionally strong performers (performance-approach goal) or exceptionally weak performers (performance-avoidance goal). Participants' cardiovascular reactivity (CVR) was recorded while they performed the task. As predicted, participants in the performance-approach goal condition performed better on the task than did those in the performance-avoidance goal condition. Also as predicted, those in the former condition exhibited a challenge pattern of CVR whereas those in the latter condition exhibited a threat pattern of CVR. Furthermore, physiological responses mediated the effects of performance-based goals on performance

Modeling RNA tertiary structure motifs by graph-grammars

A new approach, graph-grammars, to encode RNA tertiary structure patterns is introduced and exemplified with the classical sarcin–ricin motif. The sarcin–ricin motif is found in the stem of the crucial ribosomal loop E (also referred to as the sarcin–ricin loop), which is sensitive to the α-sarcin and ricin toxins. Here, we generate a graph-grammar for the sarcin-ricin motif and apply it to derive putative sequences that would fold in this motif. The biological relevance of the derived sequences is confirmed by a comparison with those found in known sarcin–ricin sites in an alignment of over 800 bacterial 23S ribosomal RNAs. The comparison raised alternative alignments in few sarcin–ricin sites, which were assessed using tertiary structure predictions and 3D modeling. The sarcin–ricin motif graph-grammar was built with indivisible nucleotide interaction cycles that were recently observed in structured RNAs. A comparison of the sequences and 3D structures of each cycle that constitute the sarcin–ricin motif gave us additional insights about RNA sequence–structure relationships. In particular, this analysis revealed the sequence space of an RNA motif depends on a structural context that goes beyond the single base pairing and base-stacking interactions

Physiological markers of challenge and threat mediate the effects of performance-based goals on performance

We predicted that adopting a performance-approach vs. performance-avoidance goal would lead to physiological responses characteristic of psychological states of challenge vs. threat appraisals, respectively. Furthermore, we predicted that these states would mediate the effects of goals on performance. Twenty-seven undergraduate females performed a task described as identifying either exceptionally strong performers (performance-approach goal) or exceptionally weak performers (performance-avoidance goal). Participants’ cardiovascular reactivity (CVR) was recorded while they performed the task. As predicted, participants in the performance-approach goal condition performed better on the task than did those in the performance-avoidance goal condition. Also as predicted, those in the former condition exhibited a challenge pattern of CVR whereas those in the latter condition exhibited a threat pattern of CVR. Furthermore, physiological responses mediated the effects of performance-based goals on performance

A transcriptome-based approach to identify functional modules within and across primary human immune cells

Genome-wide transcriptomic analyses have provided valuable insight into fundamental biology and disease pathophysiology. Many studies have taken advantage of the correlation in the expression patterns of the transcriptome to infer a potential biologic function of uncharacterized genes, and multiple groups have examined the relationship between co-expression, co-regulation, and gene function on a broader scale. Given the unique characteristics of immune cells circulating in the blood, we were interested in determining whether it was possible to identify functional co-expression modules in human immune cells. Specifically, we sequenced the transcriptome of nine immune cell types from peripheral blood cells of healthy donors and, using a combination of global and targeted analyses of genes within co-expression modules, we were able to determine functions for these modules that were cell lineagespecific or shared among multiple cell lineages. In addition, our analyses identified transcription factors likely important for immune cell lineage commitment and/or maintenance

The natural history of epilepsy in tuberous sclerosis complex

Background: Although epilepsy affects most patients with tuberous sclerosis complex (TSC), little is known about the natural history of epilepsy in this genetic disease. Methods: A retrospective chart review of all patients with TSC seen between January 2002 and October 2008. Charts were reviewed for a history of infantile spasms (IS), seizure other than IS, refractory epilepsy, Lennox-Gastaut syndrome (LGS), anticonvulsant medication use, ages of seizure onset, last seizure, last clinic visit, clinical seizure phenotype(s), cognitive impairment, and genetic mutation. Results: Two hundred ninety-one patients were included. Among these patients, 37.8% had a history of IS; 85.2% had a history of seizure; 54.1% developed multiple seizure types, not including IS; 63.2% had seizure onset in the first year of life; and 12.1% of adults without a seizure history developed epilepsy. Of epilepsy patients, 62.5% developed refractory epilepsy and 33.5% achieved epilepsy remission; 37.5% of these patients achieved medication freedom. IS was a risk factor for refractory epilepsy (p<0.0001) and LGS (p<0.0001). History of seizure, IS, age at seizure onset, and refractory epilepsy each correlated with poor cognitive outcome (p<0.0001). Epilepsy remission correlated with better cognitive outcome (p<0.0001). TSC2 was a risk factor for IS and epilepsy; patients without an identified mutation were more likely to achieve remission. Conclusion: Most patients with TSC develop epilepsy and most develop multiple seizure types. Onset typically occurs in the first year of life; however, adults remain at risk. Although refractory epilepsy is common, many patients achieve seizure control. Many features of seizure history are predictive of cognitive and epilepsy outcome

Canadian paediatric neurology workforce survey and consensus statement

Background: Little knowledge exists on the availability of academic and community paediatric neurology positions. This knowledge is crucial for making workforce decisions. Our study aimed to: 1) obtain information regarding the availability of positions for paediatric neurologists in academic centres; 2) survey paediatric neurology trainees regarding their perceptions of employment issues and career plans; 3) survey practicing community paediatric neurologists 4) convene a group of paediatric neurologists to develop consensus regarding how to address these workforce issues. Methods: Surveys addressing workforce issues regarding paediatric neurology in Canada were sent to: 1) all paediatric neurology program directors in Canada (n=9) who then solicited information from division heads and from paediatric neurologists in surrounding areas; 2) paediatric neurology trainees in Canada (n=57) and; 3) community paediatric neurologists (n=27). A meeting was held with relevant stakeholders to develop a consensus on how to approach employment issues. Results: The response rate was 100% from program directors, 57.9% from residents and 44% from community paediatric neurologists. We found that the number of projected positions in academic paediatric neurology is fewer than the number of paediatric neurologists that are being trained over the next five to ten years, despite a clinical need for paediatric neurologists. Paediatric neurology residents are concerned about job availability and desire more career counselling. Conclusions: There is a current and projected clinical demand for paediatric neurologists despite a lack of academic positions. Training programs should focus on community neurology as a viable career option

Outcome of emergency neurosurgery in patients with refractory and super-refractory status epilepticus: a systematic review and individual participant data meta-analysis

BackgroundRefractory (RSE) and super-refractory status epilepticus (SRSE) are serious neurological conditions requiring aggressive management. Beyond anesthetic agents, there is a lack of evidence guiding management in these patients. This systematic review and individual participant data meta-analysis (IPDMA) seeks to evaluate and compare the currently available surgical techniques for the acute treatment of RSE and SRSE.MethodsA systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Individual Participant Data (PRISMA-IPD). Only patients who underwent surgery while in RSE and SRSE were included. Descriptive statistics were used to compare various subgroups. Multivariable logistic regression models were constructed to identify predictors of status epilepticus (SE) cessation, long-term overall seizure freedom, and favorable functional outcome (i.e., modified Rankin score of 0–2) at last follow-up.ResultsA total of 87 studies including 161 participants were included. Resective surgery tended to achieve better SE cessation rate (93.9%) compared to non-resective techniques (83.9%), but this did not reach significance (p = 0.071). Resective techniques were also more likely to achieve seizure freedom (69.1% vs. 34.4%, p = &lt;0.0001). Older age at SE (OR = 1.384[1.046–1.832], p = 0.023) was associated with increased likelihood of SE cessation, while longer duration of SE (OR = 0.603[0.362–1.003], p = 0.051) and new-onset seizures (OR = 0.244[0.069–0.860], p = 0.028) were associated with lower likelihood of SE cessation, but this did not reach significance for SE duration. Only shorter duration of SE prior to surgery (OR = 1.675[1.168–2.404], p  = 0.0060) and immediate termination of SE (OR = 3.736 [1.323–10.548], p = 0.014) were independently associated with long-term seizure status. Rates of favorable functional outcomes (mRS of 0–2) were comparable between resective (44.4%) and non-resective (44.1%) techniques, and no independent predictors of outcome were identified.ConclusionOur findings suggest that emergency neurosurgery may be a safe and effective alternative in patients with RSE/SRSE and may be considered earlier during the disease course. However, the current literature is limited exclusively to small case series and case reports with high risk of publication bias. Larger clinical trials assessing long-term seizure and functional outcomes are warranted to establish robust management guidelines