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Since micro-organisms were first visualised by Robert Hooke and Antoni van Leeuwenhoek, bacteria and protists were quickly categorised as either primary producers or consumers and thus forming the base of the marine food web. New conceptual understanding sees this traditional dichotomy between autotrophs and heterotrophs in the marine food web replaced by one that recognises that mixotrophy is widespread. Many "phytoplankton" eat, while 50% of "microzooplankton" perform photosynthesis. This mixotrophic behaviour affects the cycling of nutrients, enhances primary production, biomass transfer to higher trophic levels, and the marine sequestration of atmospheric CO2. Moreover, the mixotrophic behaviour of many toxic protists could also be partly responsible for their ecological success and the occurrence of Harmful Agal Blooms (HABs).While science requires a tool to measure the contributions of phototrophy and heterotrophy in plankton to help in biogeochemical modelling, my colleagues and I have already shown that hydrogen (H) isotopic signature (i.e. d2H) of lipids is uniquely sensitive to the expression of heterotrophy relative to photosynthesis in terrestrial plants and bacteria. This presentation will discuss groundwork experiments performed with Chlorella sorokiniana, Prymnesium parvum and Emiliania huxleyi that had for objective to explore whether d2H values of diverse compounds produced by protists are similarly sensitive to their central metabolic pathway. Hydrogen isotope analyses performed on organic compounds from these experiments, using an isotope ratio mass spectrometer (IRMS) coupled to a gas chromatograph (GC), suggest that H isotopic signature of lipids is indeed sensitive to the level of heterotrophic growth in diverse protists.If this relation can be confirmed and calibrated, compound specific hydrogen isotope analyses could provide a powerful means to study the role of mixotrophy on the global carbon cycle, the cycling of nutrients and the occurrences of HABs.

BackgroundAmyotrophic lateral sclerosis (ALS) is a disabling and rapidly progressive neurodegenerative disorder. Increasing age is an important risk factor for developing ALS, thus the societal impact of this devastating disease will become more profound as the population ages. A significant hurdle to finding effective treatment has been an inability to accurately quantify cerebral degeneration associated with ALS in humans. Advanced magnetic resonance imaging (MRI) techniques hold promise in providing a set of biomarkers to assist in aiding diagnosis and in efficiently evaluating new drugs to treat ALS.MethodsThe Canadian ALS Neuroimaging Consortium (CALSNIC) was founded to develop and evaluate advanced MRI-based biomarkers that delineate biological heterogeneity, track disease progression, and predict survival in a large and heterogeneous sample of ALS patients.FindingsCALSNIC has launched two studies to date (CALSINC-1, CALSNIC-2), acquiring multimodal neuroimaging, neurological, neuropsychological data, and neuropathological data from ALS patients and healthy controls in a prospective and longitudinal fashion from multiple centres in Canada and, more recently, the United States. Clinical and MRI protocols are harmonized across research centres and different MR vendors.InterpretationCALSNIC provides a multicentre platform for studying ALS biology and developing MRI-based biomarkers.FundingCanadian Institutes of Health Research, ALS Society of Canada, Brain Canada Foundation, Shelly Mrkonjic Research Fund

In many neoplasms, lymphography is a reliable method with which lymph node metastases are demonstrated, but its accuracy in Stage IB cancer of the uterine cervix remains to be more firmly established. One hundred patients with Stage IB cancer of the uterine cervix underwent lymphography before radical hysterectomy with pelvic lymphadenectomy was contemplated. All the lymphographic findings were reviewed without knowledge of the pathologic parameters of the patients and were classified as being either positive (five cases), suspicious (15 cases), or negative (80 cases). The pathologic studies revealed lymph node metastases in 18 patients—in five with positive lymphographic findings, in three with suspicious findings, and in 10 with negative ones. The five true positive cases were compared to the 13 false negative or suspicious lymphographic results. It appears that the former have a greater number of involved lymph nodes and a greater mean size of the metastases. Thus, in Stage IB cancer of the uterine cervix, lymphography demonstrates an excellent specificity (100%) but a low sensitivity (27.8%).