Prospectives

Tiré de: Prospectives, vol. 10, no 5, déc. 1974Titre de l'écran-titre (visionné le 24 janv. 2013

Comparing the behavioural thermoregulation response to heat stress by Atlantic salmon parr ( Salmo salar ) in two rivers

Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon (Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (Tonset = 28.3°C) than in the LSWM (Tonset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R2 = 0.61 & 0.65; P50 = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies

Response of the Ha! Ha! River to the flood of July 1996 in the Saguenay region of Quebec: Large-scale avulsion in a glaciated valley.

Modifications to valley form due to extreme flooding in the lower 34 km of the Ha! Ha! River were analyzed. Heavy regional precipitation in July 1996 triggered extreme runoff and the catastrophic drainage of Ha! Ha! Lake, producing discharges of 1100 m³/s, 8 times the 100‐year flood. Dominant valley modifications, revealed by comparing preflood and postflood topographies derived photogrammetrically, were related to two large‐scale avulsions; in particular, a deep retrogressive incision which bypassed the 30‐m‐high Perron Falls, exporting 6 × 10⁶ m³ of glacial stratified drift from a 2‐km section of valley and producing massive sedimentation in the reach downstream. Reconstructed maximum flow power values support the existence of a 300 W/m² threshold for major scouring of the alluvial valley bottom. The evidence highlights the potential for massive scour and fill and reorganization of the long profile, with potentially catastrophic effects on infrastructure, during extreme floods in glaciated valley settings

Rheumatoid arthritis specific anti-Sa antibodies target citrullinated vimentin

Antibodies directed to the Sa antigen are highly specific for rheumatoid arthritis (RA) and can be detected in approximately 40% of RA sera. The antigen, a doublet of protein bands of about 50 kDa, is present in placenta and in RA synovial tissue. Although it has been stated that the Sa antigen is citrullinated vimentin, experimental proof for this claim has never been published. In this study, we investigated the precise nature of the antigen. Peptide sequences that were obtained from highly purified Sa antigen were unique to vimentin. Recombinant vimentin, however, was not recognized by anti-Sa reference sera. In vivo, vimentin is subjected to various post-translational modifications, including citrullination. Since antibodies to citrullinated proteins are known to be highly specific for RA, we investigated whether Sa is citrullinated and found that Sa indeed is citrullinated vimentin. Anti-Sa antibodies thus belong to the family of anticitrullinated protein/peptide antibodies. The presence of the Sa antigen in RA synovial tissue, and the recent observation that vimentin is citrullinated in dying human macrophages, make citrullinated vimentin an interesting candidate autoantigen in RA and may provide new insights into the potential role of citrullinated synovial antigens and the antibodies directed to them in the pathophysiology of RA

Novel HIV-1 Recombinant Forms in Antenatal Cohort, Montreal, Quebec, Canada

Near full-length genomes of 4 unclassified HIV-1 variants infecting patients enrolled in an antenatal cohort in Canada were obtained by sequencing. All 4 variants showed original recombination profiles, including A1/A2/J, A1/D, and A1/G/J/CRF11_cpx structures. Identification of these variants highlights the growing prevalence of unique recombinant forms of HIV-1 in North America

HIV-1 Genetic Diversity in Antenatal Cohort, Canada

Non-B HIV-1 was consistent with patients’ area of origin

F.A.R.O.G. FORUM, Vol. 6 No. 4

https://digitalcommons.library.umaine.edu/francoamericain_forum/1065/thumbnail.jp