Méthode de sélection de lacs de référence dans le cadre d'une étude Before-After Control-Impact (BACI) évaluant les effets des coupes forestières sur le zooplancton des lacs de la forêt boréale

Plusieurs approches tentent de mesurer l'impact des perturbations anthropiques sur les écosystèmes. L'approche BACI (Before-After Control-Impact) consiste à suivre deux groupes de sites (contrôle et impact), avant et après une perturbation, afin de mesurer l'effet de cette dernière sur les écosystèmes. Les études BACI permettent de contrôler la variabilité naturelle entre les groupes de sites, par le suivi des mêmes sites d'impact avant et après la perturbation, tout en minimisant la variabilité naturelle entre les années grâce au suivi de sites de contrôle échantillonnés également avant et après la perturbation. Puisque la variation naturelle entre les années dans les sites d'impact est estimée à partir de celle des sites de contrôle, il est nécessaire de sélectionner des sites de contrôle dont les caractéristiques limnologiques sont semblables à celles des sites d'impact. Ceci est essentiel pour une bonne application de l'approche BACI, afin de s'assurer que les sites naturels et perturbés répondent de la même façon aux variations naturelles interannuelles dans l'environnement et que les différences observées dans les sites d'impact avant et après la perturbation soient attribuables à celle-ci.Cet article propose une méthode de sélection des sites de contrôle dans le cadre d'une étude BACI portant sur l'impact des coupes forestières sur le zooplancton des lacs de la forêt boréale au Québec. Le zooplancton de 16 lacs de la forêt boréale a été échantillonné un an avant (2000) et deux ans après (2001-2002) des coupes forestières sur le bassin versant de certains lacs. Six lacs ont subi des coupes importantes sur 44 à 77 % du bassin versant (lacs de coupe: DA2, DF2, DF7, DF9, K4, K8) et 10 lacs sont restés à l'état naturel ou n'ont subi que des coupes négligeables sur moins de 2 % du bassin versant (lacs de référence: K2, AB34, AB35, AB40, CSL5, DA4, DF4, N35, N89, N43). Parmi ces dix lacs de référence, nous avons sélectionné les six lacs les plus semblables aux lacs de coupe, à l'aide d'analyses en composantes principales (ACP) basées sur la similarité des variables morphométriques, de la qualité de l'eau et du zooplancton avant la coupe (2000). De plus, les variables ayant la plus grande contribution à la variation totale au niveau de ces trois groupes de variables ont été déterminées. Quatre lacs ont été exclus (K2, N89, AB35, AB40) et six lakes (AB34, CSL5, DA4, DF4, N35, N43) ont été sélectionnés comme référence. Finalement, la validité du choix des six lacs de référence a été testée par des analyses de redondance (RDA) avec une variable binaire qui permettait de distinguer les lacs de coupe des lacs de référence sélectionnés. Les analyses de redondance ont montré que les variables de la morphométrie, de la qualité de l'eau et du zooplancton des lacs de référence sélectionnés ne différaient pas significativement de celles des lacs de coupe avant la perturbation. En conséquence, les différences observées après la perturbation dans les six lacs de coupe, relativement aux variations naturelles dans les six lacs de référence sélectionnés, devraient être attribuables à l'effet de la coupe forestière. La méthode de sélection développée dans le cadre de cette étude peut être utilisée pour évaluer à l'aide d'une approche BACI les effets de toute perturbation anthropique sur les écosystèmesSeveral designs can be used to assess the effects of human perturbations on ecosystems. However, the main difficulty is to isolate natural sources of variation from the variation induced by the perturbation. Several studies have shown that the natural differences between the reference and the impacted sites may influence their responses to the perturbation. In a comparative design comparing the conditions at the reference sites and the impacted sites after the perturbation, it is not possible to control for the natural sources of variation between these two groups of sites that occurred before the perturbation. This natural variation among sites is taken into account in a Before-After design in which the same sites are monitored before and after perturbation, but the natural sources of variation among years cannot be separated from the variation induced by the perturbation. In this study, we used a BACI (Before-After Control-Impact) design to measure the effect of a perturbation on an ecosystem by following two groups of sites (control and impacted) before and after the perturbation. A BACI design is the only one that allows controlling for the natural variability among sites by following the same impacted sites before and after the perturbation. This approach also takes into account the natural variability among years by monitoring concomitantly the control sites before and after the perturbation. Since the natural variability among years at the impacted sites is estimated by the variability measured at the control sites, it is essential to select control sites that are the most similar to the impacted sites with respect to their limnological characteristics. This is a requirement for the good use of the BACI design, to make sure that control and impacted sites have the same responses towards year-to-year natural variations in their environment and to ensure that the differences observed at the impacted sites before-after the perturbation are caused by it.This paper proposes a method for the selection of control sites in a BACI design to study the impact of forest harvesting on zooplankton communities in lakes of the boreal forest in Québec. Zooplankton in 16 lakes was sampled one year before (2000) and two years after (2001-2002) forest harvesting in the watersheds of some lakes. Six lakes were impacted by important harvesting on 44 to 77% of their watershed (cut lakes: DA2, DF2, DF7, DF9, K4, K8) and ten lakes were considered as natural lakes with forest harvesting on less than 2% of their watershed (reference lakes: K2, AB34, AB35, AB40, CSL5, DA4, DF4, N35, N89, N43). Among these ten natural lakes, we selected the six reference lakes that had limnological features most similar to the cut lakes, based on the morphometry, water quality and zooplankton variables before forest harvesting (2000). We used principal component analyses (PCA) to compare the lakes (10 natural lakes and six lakes to be impacted by watershed harvesting) using ordination biplots. A PCA was done for each group of variables. Lake volume, maximal depth, and area and the slope of the watershed were the variables having the most important contributions to the total variation in morphometry. Positive correlations were found between the slope of the watershed and the maximal depth of the lake and between the lake area and the lake volume. This PCA allowed us to eliminate two reference lakes that had higher values in lake volume and area for one lake (K2) and in lake volume and maximal depth for the other one (AB35), compared to the cut lakes. When comparing water quality variables, total phosphorus (TP), total nitrogen (TN), dissolved organic carbon (DOC), Secchi depth, Ca2+, Mg2+, alkalinity (ALK) and pH contributed more to the total variation than other variables. Among these variables, DOC, TP and TN were positively correlated together whereas they were negatively correlated to water transparency (Secchi). Two reference lakes (AB35, N89) had higher transparency and lower values in DOC, TP and TN and one reference lake (AB40) had lower values in pH, ALK, Ca2+ and Mg2+ compared to cut lakes. Since one of these three lakes had previously been eliminated on the basis of its morphometric variables, we had a total of four reference lakes excluded from the study. The PCA on zooplankton variables revealed that only the largest class of zooplankton (>500 µm) contributed significantly to zooplankton total variation. In general, reference lakes and cut lakes had a similar distribution on the ordination biplot so no lake was eliminated with respect to zooplankton variables. Finally, four reference lakes were excluded (K2, N89, AB35, AB40) and six reference lakes were selected (AB34, CSL5, DA4, DF4, N35, N43).The validation of the selection of the six reference lakes was made using redundancy analyses (RDA) with a binary variable discriminating between the six cut lakes and the six reference lakes selected in the PCAs. Multivariate methods such as RDA have the advantage of testing if the two groups of lakes are different with respect to many variables and not just one, as would be the case when using a univariate method. Redundancy analyses showed that the morphometric, water quality and zooplankton variables in the six selected reference lakes were not significantly different from those in the six cut lakes before harvesting. The RDA results supported the selection of the six reference lakes based on the ordination biplots from the three PCA made on the three groups of variables. We could then presume that any difference observed after the perturbation in the cut lakes, relative to the natural variation among years in the six reference lakes, could be attributed to the effect of forest harvesting. Finally, this method of selection of control sites could be used for any BACI study testing the effects of human perturbation on ecosystems

Matriptase regulates c-Met mediated proliferation and invasion in inflammatory breast cancer.

The poor prognosis for patients with inflammatory breast cancer (IBC) compared to patients with other types of breast cancers emphasizes the need to better understand the molecular underpinnings of this disease with the goal of developing effective targeted therapeutics. Dysregulation of matriptase expression, an epithelial-specific member of the type II transmembrane serine protease family, has been demonstrated in many different cancer types. To date, no studies have assessed the expression and potential pro-oncogenic role of matriptase in IBC. We examined the functional relationship between matriptase and the HGF/c-MET signaling pathway in the IBC cell lines SUM149 and SUM190, and in IBC patient samples. Matriptase and c-Met proteins are localized on the surface membrane of IBC cells and their expression is strongly correlated in infiltrating cancer cells and in the cancer cells of lymphatic emboli in patient samples. Abrogation of matriptase expression by silencing with RNAi or inhibition of matriptase proteolytic activity with a synthetic inhibitor impairs the conversion of inactive pro-HGF to active HGF and subsequent c-Met-mediated signaling, leading to efficient impairment of proliferation and invasion of IBC cells. These data show the potential of matriptase inhibitors as a novel targeted therapy for IBC, and lay the groundwork for the development and testing of such drugs

Uptake and Retention of Nanoplastics in Quagga Mussels

Here, a set of experiments to assess the feasibility of using an invasive and widespread freshwater mussel (Dreissena rostrformis bugensis) as a sentinel species for nanoplastic detection is reported. Under laboratory experimental conditions, mussels ingest and retain fluorescent polystyrene (PS) beads with carboxylic acid (COOH) termination over a size range of 200- 2000 nm. The number of beads the mussels ingested is quantified using fluorescence spectroscopy and the location of the beads in the mussels is imaged using fluorescence microscopy. PS beads of similar size (1000- 2000 nm) to mussels’ preferred food are trafficked in the ciliated food grooves of the gills. Beads of all sizes are observed in the mussels’ digestive tracts, indicating that the mussels do not efficiently reject the beads as unwanted foreign material, regardless of size. Fluorescence microscopy shows all sizes of beads are concentrated in the siphons and are retained there for longer than one month postexposure. Combined atomic force microscopy- infrared spectroscopy and photothermal infrared spectroscopy are used to locate, image, and chemically identify the beads in the mussel siphons. In sum, these experiments demonstrate the potential for using mussels, specifically their siphons, to monitor environmental accumulation of aquatic nanoplastics.Can quagga mussels (Dreissena rostriformis bugensis), a widespread and invasive freshwater species that alters local ecosystems, act as a sentinel species for detecting nanoplastics? In the laboratory, mussels ingest and retain 200- 2000 nm fluorescent polystyrene beads, which are in the size range for the mussels’ preferred food and are trafficked like food in the ciliated grooves of the gills.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155884/1/gch2201800104-sup-0001-SuppMat.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155884/2/gch2201800104.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155884/3/gch2201800104_am.pd

Gender Differences in Head Impacts Sustained by Collegiate Ice Hockey Players

Purpose—This study aims to quantify the frequency, magnitude, and location of head impacts sustained by male and female collegiate ice hockey players over two seasons of play. Methods—Over two seasons, 88 collegiate athletes (51 female, 37 male) on two female and male NCAA varsity ice hockey teams wore instrumented helmets. Each helmet was equipped with 6 single-axis accelerometers and a miniature data acquisition system to capture and record head impacts sustained during play. Data collected from the helmets were post-processed to compute linear and rotational acceleration of the head as well as impact location. The head impact exposure data (frequency, location, and magnitude) were then compared across gender. Results—Female hockey players experienced a significantly lower (p \u3c 0.001) number of impacts per athlete exposure than males (female: 1.7 ± 0.7; male: 2.9 ± 1.2). The frequency of impacts by location was the same between gender (p \u3e 0.278) for all locations except the right side of the head, where males received fewer impacts than females (p = 0.031). Female hockey players were 1.1 times more likely than males to sustain an impact less than 50 g while males were 1.3 times more likely to sustain an impact greater than 100 g. Similarly, males were 1.9 times more likely to sustain an impact with peak rotational acceleration greater than 5,000 rad/s2 and 3.5 times more likely to sustain an impact greater than 10,000 rad/s2. Conclusions—Although the incidence of concussion has typically been higher for female hockey players than male hockey players, female players sustain fewer impacts and impacts resulting in lower head acceleration than males. Further study is required to better understand th

Thirty Years After Michael E. Porter: What Do We Know About Business Exit?

Although a business exit is an important corporate change initiative, the buyer’s side seems to be more appealing to management researchers than the seller’s because acquisitions imply growth, i.e., success. Yet from an optimistic viewpoint, business exit can effectively create value for the selling company. In this paper we attempt to bring the relevance of the seller’s side back into our consciousness by asking: What do we know about business exit? We start our exploration with Porter (1976), focusing on literature that investigates the antecedents of, barriers to, and outcomes of business exit. We also include studies from related fields such as finance and economics.1 Through this research we determine three clusters of findings: factors promoting business exit, exit barriers, and exit outcomes. Overall, it is the intention of this paper to highlight the importance of business exit for research and practice. Knowing what we know about business exits and their high financial value we should bear in mind that exit need not mean failure but a new beginning for a corporation

Educational paper: Abusive Head Trauma Part I. Clinical aspects

Abusive Head Trauma (AHT) refers to the combination of findings formerly described as shaken baby syndrome. Although these findings can be caused by shaking, it has become clear that in many cases there may have been impact trauma as well. Therefore a less specific term has been adopted by the American Academy of Pediatrics. AHT is a relatively common cause of childhood neurotrauma with an estimated incidence of 14–40 cases per 100,000 children under the age of 1 year. About 15–23% of these children die within hours or days after the incident. Studies among AHT survivors demonstrate that approximately one-third of the children are severely disabled, one-third of them are moderately disabled and one-third have no or only mild symptoms. Other publications suggest that neurological problems can occur after a symptom-free interval and that half of these children have IQs below the 10th percentile. Clinical findings are depending on the definitions used, but AHT should be considered in all children with neurological signs and symptoms especially if no or only mild trauma is described. Subdural haematomas are the most reported finding. The only feature that has been identified discriminating AHT from accidental injury is apnoea. Conclusion: AHT should be approached with a structured approach, as in any other (potentially lethal) disease. The clinician can only establish this diagnosis if he/she has knowledge of the signs and symptoms of AHT, risk factors, the differential diagnosis and which additional investigations to perform, the more so since parents seldom will describe the true state of affairs spontaneously

A Gel-Based Proteomic Comparison of Human Cerebrospinal Fluid between Inflicted and Non-Inflicted Pediatric Traumatic Brain Injury

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63392/1/neu.2006.0061.lowlink.pdf_v03.pd

Head injury from falls in children younger than 6 years of age

The risk of serious head injury (HI) from a fall in a young child is ill defined. The relationship between the object fallen from and prevalence of intracranial injury (ICI) or skull fracture is described. Method Cross-sectional study of HIs from falls in children (<6 years) admitted to UK hospitals, analysed according to the object fallen from and associated Glasgow Coma Score (GCS) or alert, voice, pain, unresponsive (AVPU) and CT scan results. Results Of 1775 cases ascertained (median age 18 months, 54.7% boys), 87% (1552) had a GCS=15/AVPU=alert. 19.3% (342) had a CT scan: 32% (110/342) were abnormal; equivalent to 5.9% of the overall population, 16.9% (58) had isolated skull fractures and 13.7% (47) had ICI (49% (23/47) had an associated skull fracture). The prevalence of ICI increased with neurological compromise; however, 12% of children with a GCS=15/AVPU=alert had ICI. When compared to falls from standing, falls from a person's arms (233 children (mean age 1 year)) had a significant relative OR for a skull fracture/ICI of 6.94 (95% CI 3.54 to 13.6), falls from a building (eg, window or attic) (mean age 3 years) OR 6.84 (95% CI 2.65 to 17.6) and from an infant or child product (mean age 21 months) OR 2.75 (95% CI 1.36 to 5.65). Conclusions Most HIs from a fall in these children admitted to hospital were minor. Infants, dropped from a carer's arms, those who fell from infant products, a window, wall or from an attic had the greatest chance of ICI or skull fracture. These data inform prevention and the assessment of the likelihood of serious injury when the object fallen from is known

The Changing Face of Winter: Lessons and Questions From the Laurentian Great Lakes

Among its many impacts, climate warming is leading to increasing winter air temperatures, decreasing ice cover extent, and changing winter precipitation patterns over the Laurentian Great Lakes and their watershed. Understanding and predicting the consequences of these changes is impeded by a shortage of winter-period studies on most aspects of Great Lake limnology. In this review, we summarize what is known about the Great Lakes during their 3–6 months of winter and identify key open questions about the physics, chemistry, and biology of the Laurentian Great Lakes and other large, seasonally frozen lakes. Existing studies show that winter conditions have important effects on physical, biogeochemical, and biological processes, not only during winter but in subsequent seasons as well. Ice cover, the extent of which fluctuates dramatically among years and the five lakes, emerges as a key variable that controls many aspects of the functioning of the Great Lakes ecosystem. Studies on the properties and formation of Great Lakes ice, its effect on vertical and horizontal mixing, light conditions, and biota, along with winter measurements of fundamental state and rate parameters in the lakes and their watersheds are needed to close the winter knowledge gap. Overcoming the formidable logistical challenges of winter research on these large and dynamic ecosystems may require investment in new, specialized research infrastructure. Perhaps more importantly, it will demand broader recognition of the value of such work and collaboration between physicists, geochemists, and biologists working on the world\u27s seasonally freezing lakes and seas