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Abstract: Ionizing radiations induce cell death, causing deterministic or stochastic side-effects. This paper briefly summarizes the biological mechanisms of early and late side-effects of ionizing radiations on healthy tissue. [ABSTRACT FROM AUTHOR]

Abstract: Apoptosis represents a particular form of programmed cell death which appears in all the damaged cells and potentially hazardous. It plays a crucial role in the development of multicellular organisms by assuring and maintaining the cellular homeostasis. Thus, apoptosis intervenes not only in the normal process of organisms’ development but also in immune defence and in cancerous cells detection. Indeed, any blockage in the program of the apoptotic machinery would be responsible of some neurodegenerative and auto-immune diseases and could play a crucial role in different steps of carcinogenesis. Some researchers were very interested in studying apoptosis in hematopoietic stem cells CD34+ which could be intended to be reinfused to patients suffering from malignant diseases. They have noted that kinetic study of apoptosis of the hematopoietic stem cells CD34+ after the process of cryoconservation is also necessary. Such study permits to quantify the real and exact number of the viable hematopoietic stem cells CD34+ and therefore to eliminate such risk which would be associated with the reinfusion of apoptotic cells to patients. In this paper, we describe our contribution to hematopoietic stem cells CD34+ study by flow cytometry before and after cryopreservation by using annexin V as a specific probe allowing detection of phosphatidyl serine, one of the major features of apoptosis. But, we have noted a pronounced induction of apoptosis in peripheral mobilized blood compared to cytapheresis (after cryopreservation: 29.79% of apoptotic HSC CD34+ in peripheral mobilized blood but only 11.67% apoptotic HSC CD34+ in cytapheresis). Besides, we have noticed that hematopoietic stem cells CD34+ have had a statute of viability better than other mononuclear cells. These results put in value the reliability, the simplicity and the efficiency of flow cytometry for the analysis of apoptosis in hematopoietic stem cells CD34+ by following the intensity of fluorescence of annexin V. [Copyright &y& Elsevier]

Abstract: Akt (PKB) plays a central role in the regulation of cellular antiapoptosis and, thus, is a core intracellular survival factor underlying various human neoplastic diseases. Hence, Akt specific inhibitors create an attractive target for anticancer therapy. We have previously demonstrated that proteins of the TCL1 family (a protooncogene underlying human T cell prolymphocytic leukemia) interact with Akt and functions as Akt kinase coactivators. TCL1 coactivate Akt by binding to its pleckstrin homology domain (Akt-PHD). Then, with the aim to develop an Akt kinase inhibitor, we have hypothesized and verified that a peptide, which spans the Akt binding site (the A β-strand of human TCL1), binds to Akt and modulates Akt kinase activity and its downstream biological responses. Nuclear magnetic studies suggested that Akt_in shares a similar binding site with TCL1, but causes remote conformational changes on the variable loop 1 of the PH domain, the locus mediating phosphoinositide binding. In the present paper, we used NMR titration experiments to demonstrate that the binding of Akt-in to Akt-PHD significantly decreases the affinity of the PH domain for IP4, the sugar headgroup of phosphatidyl-inositol phosphate lipids, responsible for the membrane anchorage of the kinase and its subsequent activation. To cite this article: V. Ropars et al., C. R. Chimie 9 (2006) . [Copyright &y& Elsevier]