Reduced ex vivo chemokine production by polymorphonuclear cells after in vivo exposure of normal humans to endotoxin

Monocytes from patients with sepsis have a reduced capacity to produce cytokines, a state referred to as immunoparalysis. To determine whether polymorphonuclear leukocytes (PMNL) can be rendered hyporesponsive, PMNL from 6 healthy volunteers intravenously challenged with lipopolysaccharide (LPS; 4 ng/kg) were stimulated ex vivo with heat-killed bacteria or LPS, and the release of the CXC chemokines interleukin-8, epithelial-derived neutrophil attractant-78, and growth-related oncogen-alpha was measured. At 1 and 2 h after LPS administration in vivo, PMNL produced fewer CXC chemokines after stimulation with bacteria or LPS (all P <.05). Serum obtained 2 h after in vivo administration of LPS did not influence chemokine production by PMNL from 6 healthy volunteers not previously exposed to LPS. Thus, intravenous injection of LPS induces a refractory state of PMNL that is not caused by soluble factors produced in response to in vivo exposure to LP

E-research support services: responding to a challenge facing the South African research and information communities

Opportunities for researchers to interact with their global counterparts have improved dramatically since the advent of the knowledge era. To ensure that South Africa continues to meet international standards, the South African national research and development strategy, published in 2002, invited role players to find ways of increasing economic growth and improve the quality of life of all South Africans. Many relatively small, disconnected information projects with various funding streams were initiated to meet this e-Research challenge. However, the authors see a threat to sustainability and the need for a coherent information and knowledge support system and therefore propose a 'Team South Africa' approach, with high-level participation and commitment, to overcome certain current disparities in e-research support across the system and disciplines, that will be to the benefit of all researchers and research groups.

Dynamic simulation of the carbon-in-pulp and carbon-in-leach processes

Carbon-in-leach and carbon-in-pulp are continuous processes that use activated carbon in a cascade of large agitated tanks, which have been widely used to recover or concentrate precious metals in gold extraction plants. In the carbon-in-pulp process adsorption occurs after the leaching cascade section of the plant, and in the carbon-in-leach process leaching and adsorption occur simultaneously. In both processes the activated carbon is moved from one tank to another in countercurrent with the ore pulp until the recovery of the loaded carbon in the first tank. This paper presents a dynamic model that describes, with minor changes, the carbon-in-leach, the carbon-in-pulp, and the gold leaching processes. The model is numerically solved and calibrated with experimental data from a plant and used to perform a study of the effect of the activated carbon transfer strategy on the performance of the adsorption section of the plant. Based on the calculated values of the gold loss in the liquid and of the gold recovered in the loaded activated carbon that leaves the circuit, the results indicate that strategies in which a significant amount of activated carbon is held in the first tank and the contact time between the carbon and the pulp is longer are the best carbon transfer strategies for these processes