Using 137 Cs as a tool for the assessment and the management of erosion/sedimentation risks in view of the restoration of the Rainbow Smelt (Osmerus mordax) fish population in the Boyer River basin (Québec, Canada)

The Boyer River (Québec, Canada) drains a 217 km 2 watershed that is under cultivation at 60%. The last 2 km of the river bed has always been used as a spawning ground by Rainbow Smelts (Osmerus mordax). This fish population, which plays an important ecological role in the St.Lawrence River estuary, has dramatically declined over the last decades. Siltation and excessive algal growth in the spawning area were identified as the most probable causes of the fish population decline; suggesting that soil erosion, nutrient and sediment transport are major factors underlying the environmental problem . In this context, 137Cs provides an effective tool for investigating the magnitude and spatial distribution of long-term soil redistribution taking place in the watershed. Sampling of cultivated fields, riverbanks, bottom sediments and forested sites were thus undertaken to help understand the erosive behaviour of the watershed. Results obtained so far suggest in-field erosion rates of up to 13 t ha-1 yr-1 with net outputs reaching 11 t ha-1 yr-1. These results agree well with estimates obtained from the USLE. The 137Cs data indicate that fields located in the upstream half of the basin produce smaller sediment loadings than those in the downstream portion, despite higher soil erodibilities and more frequent ose for annual crops. They also suggest that more than 75% of the sediment deposited in the spawning area originates from cultivated fields, and less than 25% from streambanks

Using 137 Cs as a tool for the assessment and the management of erosion/sedimentation risks in view of the restoration of the Rainbow Smelt (Osmerus mordax) fish population in the Boyer River basin (Québec, Canada)

The Boyer River (Québec, Canada) drains a 217 km 2 watershed that is under cultivation at 60%. The last 2 km of the river bed has always been used as a spawning ground by Rainbow Smelts (Osmerus mordax). This fish population, which plays an important ecological role in the St.Lawrence River estuary, has dramatically declined over the last decades. Siltation and excessive algal growth in the spawning area were identified as the most probable causes of the fish population decline; suggesting that soil erosion, nutrient and sediment transport are major factors underlying the environmental problem . In this context, 137Cs provides an effective tool for investigating the magnitude and spatial distribution of long-term soil redistribution taking place in the watershed. Sampling of cultivated fields, riverbanks, bottom sediments and forested sites were thus undertaken to help understand the erosive behaviour of the watershed. Results obtained so far suggest in-field erosion rates of up to 13 t ha-1 yr-1 with net outputs reaching 11 t ha-1 yr-1. These results agree well with estimates obtained from the USLE. The 137Cs data indicate that fields located in the upstream half of the basin produce smaller sediment loadings than those in the downstream portion, despite higher soil erodibilities and more frequent ose for annual crops. They also suggest that more than 75% of the sediment deposited in the spawning area originates from cultivated fields, and less than 25% from streambanks

Predictors of residential stability among homeless young adults : a cohort study.

Abstract : BACKGROUND: Homelessness episodes have been shown to be associated with serious health outcomes among youth. This study was undertaken to estimate the probability of reaching residential stability over time and to identify predictors of residential stability among homeless young adults aged 18 to 25 years. METHODS: A prospective cohort study was carried out in Montréal, Canada, between April 5(th) 2006 and January 21(th) 2009. Interviews conducted every three months included questions on life conditions and social and mental health factors that are known to influence residential trajectories. Residential status was determined, starting on the first day after recruitment; each follow-up day was classified as a homeless day or a housed day. A period of 90 days was used to define residential stability; therefore the main study outcome was the occurrence of the first consecutive 90 housed days during the follow-up period. Kaplan-Meier and Cox proportional-hazards regression analyses were conducted. RESULTS: Of the 359 participants, 284 reached 90 days of residential stability over the study period, representing an annual probability of 80.5 %. In multivariate analysis, youth who had a high school degree, had a formal sector activity, and those who had sought psychological help were more likely to reach residential stability. Being a man, injecting substances, and having an informal sector activity were associated with a decreased probability to reach residential stability. CONCLUSION: Exposure to factors related to opportunities that promote social integration increases the chance of reaching residential stability. On the other hand, factors related to high level of street entrenchment seem to interfere with stabilization. Maximum efforts should be made to prevent chronic homelessness among youth, targeting not only individual impairments but also hinging on services adapted to foster social connections among the youth

Translational Control through eIF2alpha Phosphorylation during the Leishmania Differentiation Process

The parasitic protozoan Leishmania alternates between an invertebrate and a mammalian host. Upon their entry to mammalian macrophages, Leishmania promastigotes differentiate into amastigote forms within the harsh environment of the phagolysosomal compartment. Here, we provide evidence for the importance of translational control during the Leishmania differentiation process. We find that exposure of promastigotes to a combined elevated temperature and acidic pH stress, a key signal triggering amastigote differentiation, leads to a marked decrease in global translation initiation, which is associated with eIF2α phosphorylation. Interestingly, we show that amastigotes adapted to grow in a cell-free medium exhibit lower levels of protein synthesis in comparison to promastigotes, suggesting that amastigotes have to enter a slow growth state to adapt to the stressful conditions encountered inside macrophages. Reconversion of amastigotes back to promastigote growth results in upregulation of global translation and a decrease in eIF2α phosphorylation. In addition, we show that while general translation is reduced during amastigote differentiation, translation of amastigote-specific transcripts such as A2 is preferentially upregulated. We find that A2 developmental gene regulation is triggered by temperature changes in the environment and that occurs mainly at the level of translation. Upon elevated temperature, the A2 transcript is stabilized through its association with polyribosomes leading to high levels of translation. When temperature decreases during amastigote to promastigote differentiation, the A2 transcript is not longer associated with translating polyribosomes and is being gradually degraded. Overall, these findings contribute to our better understanding of the adaptive responses of Leishmania to stress during its development and highlight the importance of translational control in promastigote to amastigote differentiation and vice-versa

Development and Evaluation of a PCR Method for Detection of the Clostridium difficile Toxin B Gene in Stool Specimens

A PCR assay detecting Clostridium difficile toxin B gene in stool specimens was compared to the cytotoxicity assay as the reference standard for the diagnosis of C. difficile antibiotic-associated diarrhea (CDAD). Overall, 118 stool samples were tested. All of the specimens that were negative by the cytotoxicity assay (59 out of 118) were also negative by the PCR method (specificity of 100%). Of the 59 cytotoxin-positive samples, 54 were PCR positive (sensitivity of 91.5%). This PCR method is promising for rapid diagnosis of CDAD