The contribution of cytokines and chemokines to resistance and susceptibility to African trypanosomiasis remains controversial. In the present study, the levels of type I and type II cytokines and of the MCP-1 chemokine were compared during the early and late stages of Trypanosoma congolense infection in susceptible BALB/c and resistant C57BL/6 mice. Moreover, the status of macrophage activation was compared in these animals by analyzing the inducible nitric oxide synthase-arginase balance, tumor necrosis factor secretion, and expression of the FIZZ1 and YM genes. Data show that changing from a predominant type I cytokine environment in the early stage of infection to a predominant type II cytokine environment and an enhanced MCP-1 secretion in the late stage of infection correlates with resistance to T. congolense. Concomitantly, macrophage activation evolves from a classical to a predominant alternative phenotype. We further confirmed that the simultaneous occurrence of type I/type II cytokines in the early stage of infection in susceptible BALB/c mice, reflected by the presence of macrophages exhibiting a mixed classical/alternative activation phenotype, is associated with uncontrolled parasite growth and early death. Interleukin-4 (IL-4) and IL-13 signaling did not influence the susceptibility of BALB/c mice to T. congolense infection and interestingly were not the main trigger to alternative macrophage activation. In T. congolense-resistant C57BL/6 mice, our results corroborated the induction of FIZZ1 and YM gene expressions with the alternative pathway of macrophage activation. In susceptible BALB/c mice, however, YM but not FIZZ1 induction reflected the emergence of alternatively activated macrophages. Hence, the FIZZ1 and YM genes may be useful markers to discriminate between distinct populations of alternatively activated macrophages.

The liquid-phase adsorption of C 5 -C 24 linear alkanes in zeolite 5A at room temperature was studied using the configurational bias Monte Carlo molecular modeling technique and the batch experimental method. Up to C 16 , a highly discontinuous variation of the saturation capacity with the carbon number occurred. Whereas the shortest chains remain as a whole within the cage, longer chains are distributed in a more bent configuration over adjacent cages or even adopt highly coiled configurations within one cage. For alkanes greater than C 16 , a sharp, unexpected drop in adsorption capacity with a minimum at C 18 -C 19 was observed experimentally. The almost complete exclusion of these alkanes was not observed in the molecular simulation under equilibrium conditions and is explained by an extremely slow diffusion of C 18 -C 19 because of "cage nestling", i.e., an imperturbable adsorption of tightly fitting highly coiled n-alkanes in the first supercage they enter. The competitive adsorption and counterdiffusion of alkane mixtures is strongly affected by the differences in adsorption mechanism for alkanes of different chain length.

The adsorption behavior of the butene isomers on NaY zeolite is studied experimentally and compared with quantum chemical predictions. The adsorption experiments were carried out with the pulse chromatographic method, the calculations were performed both on the HF as on the DFT-B3LYP level in combination with the 6-31G* and the 6-311+G** basis set. The results of the calculations are in line with the experimental ones for the cation-butene isomer interaction in the gas phase; the same adsorption trend in the zeolite cluster, however, could not be recovered. The calculated interaction energies for a Na + zeolite cluster are close to the experimental ones with a magnitude of deviation of only 2 kcal/mol, showing the reliability of the model chosen. The trends obtained are discussed in the framework of the HSAB principle and purely electrostatic and inductive interactions.

In the adsorption of linear C1-C8 alkanes, alkenes and alcohols on zeolite chabazite, molecules smaller than 6.7 A are adsorbed in significant amounts, whereas longer chains are almost fully excluded from the micropores.