Comparaison entre la végétation du Mackenzie et du Nord québécois à l’Holocène

Le Québec-Labrador et la région de la vallée inférieure du Mackenzie ont en commun quelques traits phytogéographiques, mais leur histoire végétale postglaciaire est largement différente. Les caractéristiques structurales et floristiques de la toundra arbustive, de la toundra forestière et de la taïga se ressemblent fortement. On trouve aussi des clones disjoints et isolés de Populus balsamifera dans les deux régions. Les bioclimats sont différents sous quelques rapports, notamment les précipitations annuelles, les caractéristiques de la couverture de neige, le régime annuel des températures et la saison de croissance. Toutefois, le déroulement et la chronologie de la déglaciation ont été les facteurs qui ont déterminé les différences les plus importantes entre les deux régions en ce qui a trait à l'histoire de la végétation. La région occidentale, libérée des glaces vers 15 000 BP, a été dominé par une toundra herbeuse pendant les deux millénaires qui ont suivi. Vers 13 000-12 000 BP, les toundras arbustives (Betula glandulosa, Ericales, Salix) se sont étendues, puis les forêts de Populus, d'abord, et de Picea, ensuite, se sont succédé de 10 000 à 9000 BP. Au début de l'Holocène, la moyenne de rayonnement solaire estival a atteint son maximum et la limite septentrionale de la zone forestière s'est déplacée au nord. Par la suite, vers 6000-4000 BP, l'aulne (Alnus) s'est établi et la pessière a laissé place à une toundra arbustive, et ce, jusqu'à nos jours. Par contre, la partie centrale du Nouveau-Québec est demeurée englacée jusque vers 6500 BP et la colonisation initiale a été remplacée par les arbres (Picea, Larix) et les arbustes (Alnus). Les différences entre les deux régions s'expliquent par l'âge de la déglaciation, l'influence de la calotte résiduelle sur le climat, la proximité du stock floristique disponible et les voies de migration des plantes.Northern Québec-Labrador and the Lower Mackenzie region have several phytogeographic characteristics in common, but their postglacial vegetation histories are distinctly different. The structural and floristic features of the shrub tundra, forest-tundra, and northern boreal forest are basically similar in the two regions. Isolated stands of Populus balsamifera beyond the northern forest limit are found in both areas. The bioclimates differ in several respects: annual precipitation, snow cover, continentality and length of the growing season. However, the sequence and chronology of déglaciation was the most important factor that determined the differences between the two regions in vegetation history. The landscapes of the western region were free of glacial ice by 15,000 yr. BP when a herb tundra prevailed for almost two millennia. Shrub tundra (Betula glandulosa, Ericales, Salix) expanded about 13,000 to 12,000 yr. BP, and then forests of first Populus and later Picea succeeded at 10,000 to 9000. At that time, the beginning of the Holocene, solar radiation in summer was at maximum values for the Holocene, and the northern limit of the forest zone was farther north. Later, alder (Alnus) expanded about 6000 to 4000 yr. BP, and the spruce forest was replaced in the north by forest-tundra. By contrast, the central part of Nouveau-Québec remained ice-covered until about 6500 yr. BP, and the initial colonisation was effected by trees (Picea, Larix) and later (Alnus). The regional differences can be explained by the differences in the timing of déglaciation, the influence of the residual ice sheet on the general climate, and the proximity of floristic source populations and their migration routes.Québec-Labrador und die Gegend des unteren Mackenzie-Tals haben einige phytogeographische Merkmale gemeinsam, aber ihre postglaziale Vegetationsgeschichte ist sehr verschieden. Die struktur- und pflanzlichbedingten Charakteristika der Busch-Tundra, der WaId-Tundra und der Taiga âhneln einander stark. Man findet auch gelockerte und insolierte klone von Populus balsamifera in beiden Gebieten. Die Bioklimas sind in mancher Hinsicht verschieden, vor allem die jâhrlichen Niederschlàge, die Charakteristika der Schneedecke, die jâhrlichen Temperaturverhàltnisse und die Wachstumsperiode. Indessen waren der Ablauf und die Chronologie der Eisabschmelzung die bestimmenden Faktoren fur die wichtigsten Unterschiede zwischen den beiden Gebieten, was die Geschichte der Vegetation betrifft. Das westliche Gebiet, das urn 15 000 BP vom Eis befreit wurde, war wâhrend der zwei folgenden tausend Jahre durch eine Gras-Tundra beherrscht. Gegen 13 000-12 000 BP haben sich die Busch-Tundras (Betula glandulosa, Ericales, Salix) ausgebreitet, dann sind zuerst die Populus-und danach die Picea-Wàlder von 10 000 bis 9000 v.u.Z. aufeinander gefolgt. Am Beginn des Holozàn hat die durchschnittliche Sommer-Sonnen-Bestrahlung ihren Hohepunkt erreicht und die nôrdliche Grenze der Baumzone hat sich nach Norden verschoben. Anschliepend, gegen 6000-4000 BP, hat sich die Erie (Alnus) ausgebreitet und die Rottanne ist der Busch-Tundra gewichen und das bis heute. Hingegen blieb das Zentrum von Nouveau-Québec vereist bis gegen 6500 BP und die ursprijngliche Vegetation wurde durch Baume (Picea, Larix) und Busche (Alnus) ersetzt. Die Unterschiede zwischen den beiden Gebieten lassen sich durch das Alter der Eisabschmelzung, den Einflufi der Restkalotte auf das Klima, die Nàhe des zur Verfùgung stehenden pflanzlichen Bestands und die Migrationswege der Pflanzen erklàren

Transcriptomes of parents identify parenting strategies and sexual conflict in a subsocial beetle

This work was funded by UK NERC grants to M.G.R. and A.J.M. an NERC studentship to D.J.P. the University of Georgia and a US NSF grant to A.J.M. and M.G.R.Parenting in the burying beetle Nicrophorus vespilloides is complex and, unusually, the sex and number of parents that can be present is flexible. Such flexibility is expected to involve specialized behaviour by the two sexes under biparental conditions. Here, we show that offspring fare equally well regardless of the sex or number of parents present. Comparing transcriptomes, we find a largely overlapping set of differentially expressed genes in both uniparental and biparental females and in uniparental males including vitellogenin, associated with reproduction, and takeout, influencing sex-specific mating and feeding behaviour. Gene expression in biparental males is similar to that in non-caring states. Thus, being ‘biparental’ in N. vespilloides describes the family social organization rather than the number of directly parenting individuals. There was no specialization; instead, in biparental families, direct male parental care appears to be limited with female behaviour unchanged. This should lead to strong sexual conflict.Publisher PDFPeer reviewe

Presentation, Prognostic Factors and Patterns of Failure in Adult Rhabdomyosarcoma

Purpose: The purpose of our study is to retrospectively review our institutional experience with adult rhabdomyosarcoma (RMS) to determine presentation, prognostic factors and patterns of failure in this disease

Model-based lamotrigine clearance changes during pregnancy: clinical implication

Objective: The objective of the study was to characterize changes in the oral clearance (CL/F) of lamotrigine (LTG) over the course of pregnancy and the postpartum period through a model-based approach incorporating clinical characteristics that may influence CL/F, in support of developing clinical management guidelines. Methods: Women receiving LTG therapy who were pregnant or planning pregnancy were enrolled. Maternal blood samples were collected at each visit. A pharmacokinetic analysis was performed using a population-based, nonlinear, mixed-effects model. Results: A total of 600 LTG concentrations from 60 women (64 pregnancies) were included. The baseline LTG CL/F was 2.16 L/h with a between-subject variability of 40.6%. The influence of pregnancy on CL/F was described by gestational week. Two subpopulations of women emerged based on the rate of increase in LTG CL/F during pregnancy. The gestational age-associated increase in CL/F displayed a 10-fold higher rate in 77% of the women (0.118 L/h per week) compared to 23% (0.0115 L/h per week). The between-subject variability in these slopes was 43.0%. The increased CL/F at delivery declined to baseline values with a half-life of 0.55 weeks. Interpretation The majority of women had a substantial increase in CL/F from 2.16 to 6.88 L/h by the end of pregnancy, whereas 23% of women had a minimal increase. An increase in CL/F may correspond to decreases in LTG blood concentrations necessitating the need for more frequent dosage adjustments and closer monitoring in some pregnant women with epilepsy. Postpartum doses should be tapered to preconception dose ranges within 3 weeks of delivery

Comparison of plasma cortisol and corticosterone in the dexamethasone suppression test for melancholia

The suppression of plasma corticosterone (B), measured by radioimmunoassay (RIA), was compared to simultaneous suppression of plasma cortisol (F), measured as total corticoids by a competitive protein binding (CPB) assay, in the overnight dexamethasone suppression test (DST). Baseline plasma B concentrations in IO control subjects were 4.04 +/- 1.07 ng/ml (X +/- S.D.) at 0800 hr and 1.51 +/- 0.68 ng/ml at 1600 hr. Post-dexamethasone 1600 hr B levels in the controls were 0.46 +/- 0.29 ng/ml. An early escape of plasma B (> 1.2 ng/ml), like that of F (> 5 [mu]g/dl), during the overnight 24 hr 1.0 mg dose DST was noted in patients with melancholia (endogenous depression).Half-hourly catheter samples in a normal subject stimulated to escape from dexamethasone suppression showed that in general, plasma B concentrations parallel plasma F concentrations over a 12 hr period. Repeated weekly DSTs on two patients with different psychiatric diagnoses resulted in B: F correlations of 0.74 and 0.60. Overall agreement between B- and F-DST outcomes in all categories tested at 1600 and 2300 hr was 93%; the agreement in the melancholic and non-endogenous depressed groups was 100%.Post-dexamethasone, both B and F were suppressed 55-60% below the criterion level in controls. In those patients who escaped from dexamethasone suppression, the percentage increase in plasma B above the criterion level was significantly greater (+ 55%) than the corresponding percentage change in plasma F. Most patients with borderline abnormal F-DSTs (3.5-4.9 [mu]g/dl) exhibited clearly abnormal B-DSTs (> 1.2 ng/ml). We conclude that the use of dexamethasone suppression of plasma B (using 1.2 ng/ml as the abnormal criterion value) is an additional indicator of an abnormal DST in depressed patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24951/1/0000378.pd

Regional differences in brain monoamine oxidase subtypes in an animal model of geriatric depression: effects of olfactory bulbectomy in young versus aged rats

Abstract Geriatric depression is often associated dysregulation of the hypothalamus-pituitary-adrenal (HPA) axis, and with poor responsiveness to antidepressants that work through inhibition of monoamine reuptake; accordingly, it has been suggested that MAO inhibitors may represent a therapeutic alternative in this group. In the current study, we evaluated expression of MAO subtypes in brain regions of young and aged rats subjected to olfactory bulbectomy (OBX), a procedure that reproduces many of the biochemical and functional changes associated with human depression. Activities of both MAO A and B were elevated in aged rats as compared to young rats in most regions, but not in the midbrain, and the OBX lesion failed to produce any change in this pattern. These results stand in contrast to the differential effects of glucocorticoids, which reduce brain MAO in young animals but induce activity in aged rats. Our results support the view that the aged brain possesses biochemical characteristics that distinguish its monoamine biochemistry from that of young brain, and that these distinctions may work in conjunction with HPA axis dysregulation to influence the etiology and therapy of geriatric depression. The use of appropriate animal models for depression and for disruption of HPA axis function can allow for the testing of potential human biomarkers (such as platelet MAO) that may serve to predict treatment outcome

Connective tissue activation

Alpha- and beta-adrenergic blocking agents and imipramine inhibit the increased hyaluronate synthesis that may be induced in human synovial cultures by connective tissue activating peptide (CTAP). Considerations of drug concentration requirements, actions of analogues, and time studies all indicate that the adrenergic blockers do not act in this circumstance as conventional blockers of alpha or beta receptor sites. It is suggested that the membrane-stabilizing properties of these agents may be the important determinant for their limited “antiactivation” effect. Ethacrynic acid, a potent and more complete inhibitor of connective tissue activation, appears to act via a different mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37727/1/1780180504_ftp.pd

Kidney volume to GFR ratio predicts functional improvement after revascularization in atheromatous renal artery stenosis

Background: Randomized controlled trials (RCT) have shown no overall benefit of renal revascularization in atherosclerotic renovascular disease (ARVD). However, 25% of patients demonstrate improvement in renal function. We used the ratio of magnetic resonance parenchymal volume (PV) to isotopic single kidney glomerular filtration rate (isoSKGFR) ratio as our method to prospectively identify "improvers" before revascularization. Methods: Patients with renal artery stenosis who were due revascularization were recruited alongside non-ARVD hypertensive CKD controls. Using the controls, 95% CI were calculated for expected PV:isoSK-GFR at given renal volumes. For ARVD patients, “improvers” were defined as having both >15% and >1ml/min increase in isoSK-GFR at 4 months after revascularization. Sensitivity and specificity of PV:isoSK-GFR for predicting improvers was calculated. Results: 30 patients (mean age 68 ±8 years), underwent revascularization, of whom 10 patients had intervention for bilateral RAS. Stented kidneys which manifested >15% improvement in function had larger PV:isoSK-GFR compared to controls (19±16 vs. 6±4ml/ml/min, p = 0.002). The sensitivity and specificity of this equation in predicting a positive renal functional outcome were 64% and 88% respectively. Use of PV:isoSK-GFR increased prediction of functional improvement (area under curve 0.93). Of note, non-RAS contralateral kidneys which improved (n = 5) also demonstrated larger PV:isoSK-GFR (15.2±16.2 ml/ml/min, p = 0.006). Conclusion: This study offers early indicators that the ratio of PV:isoSK-GFR may help identify patients with kidneys suitable for renal revascularization which could improve patient selection for a procedure associated with risks. Calculation of the PV:isoSK-GFR ratio is easy, does not require MRI contrast agent

An evaluation of physics engines and their application in haptic virtual assembly environments

Virtual Reality (VR) applications are employed in engineering situation to simulate real and artificial situations where the user can interact with 3D models in real time. Within these applications the virtual environment must emulate real world physics such that the system behaviour and interaction are as natural as possible and to support realistic manufacturing applications. As a consequence of this focus, several simulation engines have been developed for various digital applications, including VR, to compute the physical response and body dynamics of objects. However, the performance of these physics engines within haptic-enabled VR applications varies considerably. In this study two third party physics engines - Bullet and PhysXtm- are evaluated to establish their appropriateness for haptic virtual assembly applications. With this objective in mind five assembly tasks were created with increasing assembly and geometry complexity. Each of these was carried out using the two different physics engines which had been implemented in a haptic-enabled virtual assembly platform specifically developed for this purpose. Several physics-performance parameters were also defined to aid the comparison. This approach and the subsequent results successfully demonstrated the key strengths, limitations, and weaknesses of the physics engines in haptic virtual assembly environments

Prion infectivity in the spleen of a <em>PRNP</em> heterozygous individual with subclinical variant Creutzfeldt-Jakob disease

Blood transfusion has been identified as a source of human-to-human transmission of variant Creutzfeldt–Jakob disease. Three cases of variant Creutzfeldt–Jakob disease have been identified following red cell transfusions from donors who subsequently developed variant Creutzfeldt–Jakob disease and an asymptomatic red cell transfusion recipient, who did not die of variant Creutzfeldt–Jakob disease, has been identified with prion protein deposition in the spleen and a lymph node, but not the brain. This individual was heterozygous (MV) at codon 129 of the prion protein gene (PRNP), whereas all previous definite and probable cases of variant Creutzfeldt–Jakob disease have been methionine homozygotes (MM). A critical question for public health is whether the prion protein deposition reported in peripheral tissues from this MV individual correlates with infectivity. Additionally it is important to establish whether the PRNP codon 129 genotype has influenced the transmission characteristics of the infectious agent. Brain and spleen from the MV blood recipient were inoculated into murine strains that have consistently demonstrated transmission of the variant Creutzfeldt–Jakob disease agent. Mice were assessed for clinical and pathological signs of disease and transmission data were compared with other transmission studies in variant Creutzfeldt–Jakob disease, including those on the spleen and brain of the donor to the index case. Transmission of variant Creutzfeldt–Jakob disease was observed from the MV blood recipient spleen, but not from the brain, whereas there was transmission from both spleen and brain tissues from the red blood cell donor. Longer incubation times were observed for the blood donor spleen inoculum compared with the blood donor brain inoculum, suggesting lower titres of infectivity in the spleen. The distribution of vacuolar pathology and abnormal prion protein in infected mice were similar following inoculation with both donor and recipient spleen homogenates, providing initial evidence of similar transmission properties after propagation in PRNP codon 129 MV and MM individuals. These studies demonstrate that spleen tissue from a PRNP MV genotype individual can propagate the variant Creutzfeldt–Jakob disease agent and that the infectious agent can be present in the spleen without CNS involvement