Adenylyl Cyclase α and cAMP Signaling Mediate Plasmodium Sporozoite Apical Regulated Exocytosis and Hepatocyte Infection

Malaria starts with the infection of the liver of the host by Plasmodium sporozoites, the parasite form transmitted by infected mosquitoes. Sporozoites migrate through several hepatocytes by breaching their plasma membranes before finally infecting one with the formation of an internalization vacuole. Migration through host cells induces apical regulated exocytosis in sporozoites. Here we show that apical regulated exocytosis is induced by increases in cAMP in sporozoites of rodent (P. yoelii and P. berghei) and human (P. falciparum) Plasmodium species. We have generated P. berghei parasites deficient in adenylyl cyclase α (ACα), a gene containing regions with high homology to adenylyl cyclases. PbACα-deficient sporozoites do not exocytose in response to migration through host cells and present more than 50% impaired hepatocyte infectivity in vivo. These effects are specific to ACα, as re-introduction of ACα in deficient parasites resulted in complete recovery of exocytosis and infection. Our findings indicate that ACα and increases in cAMP levels are required for sporozoite apical regulated exocytosis, which is involved in sporozoite infection of hepatocytes

Mercury transformation behavior on a bench scale coal combustion furnace

The mercury release behavior in bituminous coals, and the partitioning rate of mercury in solids and gaseous in flue gases have measured to develop technologies for evaluating the partitioning of mercury in coal combustion process and develop in-situ adsorption and removal technologies using three kinds of experiment equipments - a thermo-balance, a drop-tube furnace (DTF), a bench-scale pulverized coal combustion fumace. The results showed that about 20 to 60% of the mercury in coal was released between 573 K and 673 K, which was the range of temperature in which the release of the volatile matter of coal began. And more than 90% of the mercury was released at 773 K, the temperature at which the release of the volatile matter was completed. The rate of mercury partitioned into bottom ash in a bench-scale pulverized coal combustion furnace was the smallest irrespective of the type of coal. The rate of mercury partitioned into cyclone ash was also low for all types of coal with values generally below 10%. The rest of the mercury was partitioned into mercury in gaseous form, but the rate partitioned into dust, oxidized mercury and elemental mercury varied slightly depending on the flue gas temperature and the type of coal.

Different role of Apaf-1 in positive selection, negative selection and death by neglect in foetal thymic organ culture

Apoptotic protease-activating factor 1 (Apaf-1) is a component of the apoptosome which is required for the activation of procaspase-9. As Apaf-1 knockout (KO) (Apaf-1(-/-)) mice die before birth, the role of Apaf-1 during thymic selection was investigated using 5 day foetal thymic organ culture (FTOC) of thymi obtained at gestational day 15. There was a lower ratio of CD4 single-positive (SP) to CD8 SP cells and decreased apoptosis of CD4(+) CD8(+) (DP) thymocytes from Apaf-1 (-/-) mice compared with wild-type. To determine if these defects resulted in increased production of neglected thymocytes, the Apaf-1 (-/-)mice were crossed with the T-cell receptor (TCR)- alpha-chain KO mice. There was no difference in thymocyte development in the thymi of TCR-alpha (-/-) Apaf-1 (-/-) and TCR-alpha (-/-) Apaf-1 (+/+) mice 5 days after FTOC. To determine if Apaf-1 is involved in apoptosis during death by negative or positive selection, FTOC of the thymus of Apaf-1 D- -/-(b)/HY TCR-alphabeta transgenic (Tg) mice was carried out. There was decreased apoptosis of the HY clonal-specific M33(+) thymocytes and an increased percentage of the autoreactive CD8(+) M33(+) thymocytes in male, but not female Apaf-1 (-/-) D-b/HY TCR Tg mice. Our data suggest that Apaf-1 is not involved in positive selection or death by neglect, but may have a partial role in negative selection during early thymic T-cell development