Role of Chk1 in the differentiation program of hematopoietic stem cells

Hematopoietic stem cells (HSC) isolated from umbilical cord blood (UCB) were treated with ionizing radiation (IR) and sensitivity and IR induced checkpoints activation were investigated. No difference in the sensitivity and in the activation of DNA damage pathways was observed between CD133+ HSC and cells derived from them after ex vivo expansion. Chk1 protein was very low in freshly isolated CD133+ cells, and undetectable in ex vivo expanded UCB CD133+ cells. Chk1 was expressed only on day 3 of the ex vivo expansion. This pattern of Chk1 expression was corroborated in CD133+ cells isolated from peripheral blood apheresis collected from an healthy donor. Treatment with a specific Chk1 inhibitor resulted in a strong reduction in the percentage of myeloid precursors (CD33+) and an increase in the percentage of lymphoid precursors (CD38+) compared to untreated cells, suggesting a possible role for Chk1 in the differentiation program of UCB CD133+ HSC.     

Enhancing rice resistance to fungal pathogens by transformation with cell wall degrading enzyme genes from Trichoderma atroviride

Three genes encoding for fungal cell wall degrading enzymes (CWDEs), ech42, nag70 and gluc78 from the biocontrol fungus Trichoderma atroviride were inserted into the binary vector pCAMBIA1305.2 singly and in all possible combinations and transformed to rice plants. More than 1800 independently regenerated plantlets in seven different populations (for each of the three genes and each of the four gene combinations) were obtained. The ech42 gene encoding for an endochitinase increased resistance to sheath blight caused by Rhizoctonia solani, while the exochitinase-encoding gene, nag70, had lesser effect. The expression level of endochitinase but exochitinase was correlated with disease resistance. Nevertheless, exochitinase enhanced the effect of endochitinase on disease resistance when the two genes co-expressed in transgenics. Resistance to Magnaporthe grisea was found in all kinds of regenerated plants including that with single gluc78. A few lines expressing either ech42 or nag70 gene were immune to the disease. Transgenic plants are being tested to further evaluate disease resistance at field level. This is the first report of multiple of expression of genes encoding CWDEs from Trichoderma atroviride that result in resistance to blast and sheath blight in rice.     

Energy input from quasars regulates the growth and activity of black holes and their host galaxies

In the early Universe, while galaxies were still forming, black holes as massive as a billion solar masses powered quasars. Supermassive black holes are found at the centres of most galaxies today, where their masses are related to the velocity dispersions of stars in their host galaxies and hence to the mass of the central bulge of the galaxy. This suggests a link between the growth of the black holes and their host galaxies, which has indeed been assumed for a number of years. But the origin of the observed relation between black hole mass and stellar velocity dispersion, and its connection with the evolution of galaxies, have remained unclear. Here we report simulations that simultaneously follow star formation and the growth of black holes during galaxy-galaxy collisions. We find that, in addition to generating a burst of star formation, a merger leads to strong inflows that feed gas to the supermassive black hole and thereby power the quasar. The energy released by the quasar expels enough gas to quench both star formation and further black hole growth. This determines the lifetime of the quasar phase (approaching 100 million years) and explains the relationship between the black hole mass and the stellar velocity dispersion.     

Esterase polymorphisms in European and American populations of the periwinckle,Littorina littorea (Gastropoda)

Résumé La structure génétique de 7 populations du gastéropode marinLittorina littorea a été étudiée par analyse de phénotypes d'estérases révélés par électrophorèse sur gel de polyacrylamide. Les populations des USA (Maine, Massachusetts), d'origine récente, ont davantage de variation géographique que celles de France, d'origine ancienne. De plus, parmi ces dernières il y a réduction de l'hétérozygotie dans l'échantillon semi-isolé du Golfe du Morbihan.     

Effects of 9.4 GHz microwave exposure on meiosis in mice

Summary Exposure to 9.4 GHz pulsed microwaves at low power densities for 1 h/day during 2 weeks induces in adult male Balb/c mice disturbances in meiosis, consisting in an increase of translocations and the appearance of cells with several chromosome pair remaining univalents at MI.Acknowledgments. Grant No. 30121/120/53674 of the Centre International des Etudiants et Stagiaires to E. Manikowska and grant No. 78-1017/DRED of the Direction des Recherches et Etudes Techniques du Ministère de Défense to B. Servantie accorded by the French Government are gratefully acknowledged. The authors express their thanks to Miss M.R. Morazzani for her technical assistance.