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Montréal, Canada

Leysi-Derilou Y.,Laval University | Duchesne C.,Laval University | Garnier A.,Laval University | Pineault N.,Hema Quebec
Differentiation | Year: 2012

Several fundamental questions regarding cell growth and development can be answered by recording and analyzing the history of cells and their progeny. Herein, long-term and large-field live cell imaging was used to study the process of megakaryopoiesis at the single cell level (n=9300) from human CD34 + cord blood (CB) in the presence of thrombopoietin (TPO) or the cytokine cocktail BS1 with or without nicotinamide (NIC). Comparative analyses revealed that the cocktail BS1 increased the mitotic and proplatelet rate of diploid and polyploid cells, respectively. Conversely, only NIC treatment increased the endomitotic rate of megakaryocytes (MKs) leading to the formation of CB-MKs with ploidy level frequently observed with BM-MKs. However, NIC failed to enhance platelet production. Rather, a 7- and 31-fold reduction in proplatelet formation was observed in tetraploid and octaploid CB-MKs, respectively, and ex vivo platelet production output was reduced by half due to a reduction in MK output in NIC cultures. Unexpectedly, a significant fraction of di- and polyploid CB-MKs were seen to undergo complete proplatelet regression. Though rare (<0.6%), proplatelet reversal led to the formation of regular round cells that could at times resume normal development. The cell tracking data was then used to investigate the impact of "developmental fate" and ploidy on cell cycling time, and to identify potential developmental patterns. These analyses revealed that cell fate and ploidy level have major impacts on the cell cycling time of the cells, and that four recurrent cell lineage patterns could be identified for CD34 + cells undergoing MK differentiation. © 2012 International Society of Differentiation. Source


Conner M.,University of Leeds | Godin G.,Laval University | Sheeran P.,University of Sheffield | Germain M.,Hema Quebec
Health Psychology | Year: 2013

Objective: The present research assessed the simultaneous effects of four attitude variables (cognitive attitudes, affective attitudes, anticipated negative affective reactions, and anticipated positive affective reactions) in the context of the theory of planned behavior (TPB) on blood-donation intentions and behavior. Methods: Experienced blood donors (N = 1108) completed questionnaires measuring attitude variables plus components of the TPB and a measure of attitudinal ambivalence in relation to giving blood again in the next six months. Records were used to assess whether participants subsequently donated blood again in the six months after completing the questionnaire. The main outcome measures were objectively assessed blood donation and intentions to make an additional donation of blood. Results: Confirmatory factor analysis supported a distinction between cognitive attitudes about giving blood, affective attitudes about giving blood, anticipated negative affective reactions about not giving blood, and anticipated positive affective reactions about giving blood. Multiple regression analyses indicated that perceived behavioral control, anticipated negative affective reactions, cognitive attitude, anticipated positive affective reactions and subjective norms were significant simultaneous predictors of intentions to donate blood. Logistic regression analyses indicated that intentions, perceived behavioral control, and anticipated positive affective reactions were significant, simultaneous predictors of blood donation. Attitudinal ambivalence significantly moderated the effects of cognitive attitudes on intentions, and the effects of anticipated negative affective reactions on both intentions and donation behavior. Conclusion: The findings point to the value of considering different types of attitudes, and anticipated negative affective reaction in particular, for predicting health behaviors. © 2012 American Psychological Association. Source


Robert A.,Hema Quebec | Boyer L.,Hema Quebec | Pineault N.,Hema Quebec | Pineault N.,Laval University
Stem Cells and Development | Year: 2011

The development of culture processes for hematopoietic progenitors could lead to the development of a complementary source of platelets for therapeutic purposes. However, functional characterization of culture-derived platelets remains limited, which raises some uncertainties about the quality of platelets produced in vitro. The aim of this study was to define the proportion of functional platelets produced in cord blood CD34+ cell cultures. Toward this, the morphological and functional properties of culture-derived platelet-like particles (PLPs) were critically compared to that of blood platelets. Flow cytometry combined with transmission electron microscopy analyses revealed that PLPs formed a more heterogeneous population of platelets at a different stage of maturation than blood platelets. The majority of PLPs harbored the fibrinogen receptor αIIbβ3, but a significant proportion failed to maintain glycoprotein (GP)Ibα surface expression, a component of the vWF receptor essential for platelet functions. Importantly, GPIbα extracellular expression correlated closely with platelet function, as the GPIIb+ GPIbα+ PLP subfraction responded normally to agonist stimulation as evidenced by α-granule release, adhesion, spreading, and aggregation. In contrast, the GPIIb+ GPIbα- subfraction was unresponsive in most functional assays and appeared to be metabolically inactive. The present study confirms that functional platelets can be generated in cord blood CD34+ cell cultures, though these are highly susceptible to ectodomain shedding of receptors associated with loss of function. Optimization of culture conditions to prevent these deleterious effects and to homogenize PLPs is necessary to improve the quality and yields of culture-derived platelets before they can be recognized as a suitable complementary source for therapeutic purposes. © 2011, Mary Ann Liebert, Inc. Source


Godin G.,Laval University | Germain M.,Hema Quebec | Conner M.,University of Leeds | Delage G.,Hema Quebec | Sheeran P.,University of Sheffield
Health Psychology | Year: 2014

Objective: This study tested key variations in the question- behavior effect against a control condition or an implementation intention condition on returning to give blood among lapsed donors (individuals who had not given blood in the past 2 years). Design: At baseline, 7,000 lapsed donors were randomized to 1 of 6 experimental conditions or to a control condition. Participants in the experimental conditions were asked to complete a 6-item postal questionnaire assessing intentions only, interrogative intention, moral norm plus intention, anticipated regret plus intention, positive self-image plus intention, or implementation intentions. Objective measures of behavior were obtained 6 and 15 months later. The frequency of registrations to give blood over the next 6 and 15 months was measured. Results: Intention-to-treat analysis of the frequency of registrations (GENMOD procedure, Poisson distribution) indicated main effects for condition (experimental vs. control) at both 6 months, χ2(1) = 4.64, p < .05, and 15 months, Χ2(1) = 5.88, p < .05. Positive self-image and implementation intention interventions outperformed the control condition at 6 months. At 15 months, standard intention, interrogative intention, and regret plus intention conditions showed more frequent registrations compared with control and were just as effective as implementation intention formation. Moderation analysis showed that the moral norm and positive self-image conditions were significant for first-time (1 previous donation) but not repeat (2 or more previous donations) donors. Conclusion: The question- behavior effect can be used to reinvigorate blood donation among lapsed donors, and can be as effective as forming implementation intentions. © 2013 American Psychological Association. Source


Neron S.,Hema Quebec | Neron S.,Laval University | Roy A.,Hema Quebec | Dumont N.,Hema Quebec
PLoS ONE | Year: 2012

Polyclonal preparations of therapeutic immunoglobulins, namely intravenous immunoglobulins (IVIg), are essential in the treatment of immunodeficiency and are increasingly used for the treatment of autoimmune and inflammatory diseases. Currently, patients' accessibility to IVIg depends exclusively upon volunteer blood donations followed by the fractionation of pooled human plasma obtained from thousands of individuals. Presently, there are no in vitro cell culture procedures allowing the preparation of polyclonal human antibodies. All in vitro human therapeutic antibodies that are currently generated are based on monoclonal antibodies, which are mostly issued from genetic engineering or single cell antibody technologies. Here, we describe an in vitro cell culture system, using CD40-CD154 interactions, that leads to a 1×106-fold expansion of switched memory B lymphocytes in approximately 50 days. These expanded cells secrete polyclonal IgG, which distribution into IgG1, IgG2, IgG3 and IgG4 is similar to that of normal human serum. Such in vitro generated IgG showed relatively low self-reactivity since they interacted moderately with only 24 human antigens among a total of 9484 targets. Furthermore, up to one liter of IgG secreting cells can be produced in about 40 days. This experimental model, providing large-scale expansion of human B lymphocytes, represents a critical step toward the in vitro production of polyclonal human IgG and a new method for the ex vivo expansion of B cells for therapeutic purposes. © 2012 Néron et al. Source

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