Toxoplasma gondii: detection of MIC10 antigen in sera of experimentally infected mice.

We developed a sandwich ELISA for the detection of circulating Toxoplasma gondii MIC10 antigens. In T. gondii culture supernatant, MIC10 was detected in a growth dependent manner. Mice were infected with a lethal dose of either a virulent RH strain, an avirulent Beverley strain or a sub-lethal dose of a PLK strain of T. gondii. MIC10 appeared 2 days after infection and increased gradually in the sera of RH-infected mice. A detectable but significantly lower amount of MIC10 was observed in the sera of mice infected intraperitoneally with Beverley tachyzoites. In contrast, the MIC10 antigen in mice sera following oral infection with Beverley cysts was below detectable levels during the course of the experiment. In sera of PLK-infected mice, MIC10 was predominantly observed between late acute and early chronic phase. Our data show that the kinetics of circulating MIC10 differs depending on the strain and route of infection.

Effects of exposure to a 50 Hz electric field on plasma levels of lactate, glucose, free Fatty acids, triglycerides and creatine phosphokinase activity in hind-limb ischemic rats.

We previously reported that extremely low frequency electric fields (ELF-EFs) affect energy metabolism in stressed conditions. To further confirm this, the effect of exposure to ELF-EFs on the experimental ischemic rat was examined. The test was based on a comparison of rats treated with EF alone, ischemic surgery alone, the combination of EF with ischemic surgery, or no treatment (double sham). The EF condition used in this study was an alternating current of 50 Hz EF at 17 500 V/m intensity for 15 min per day. The exposure to EF in ischemic rats significantly decreased plasma levels of free fatty acids and triglycerides, compared to those of the no treatment or EF alone group. The plasma lactate levels of two ischemic groups peaked on experimental day-4 and gradually decreased until the end of the study. The changes in the lactate levels induced by ischemia did not show any difference between rats treated with ischemia alone or a combination of ischemia with an EF. Any changes in plasma levels of glucose and creatine phosphokinase activity were not influenced by EF treatment. These results indicate that the EF effect on glycolysis parameters, plasma lactate or glucose levels, does not appear in a highly stressed condition and that EF effects varied dependent on the condition of organism but ELF-EF used in this study have impact on lipid metabolism parameter in a hind-limb ischemic rat. However, further studies are needed to elucidate the association of ELF-EF with the lipid metabolism system.

Alpha1-receptor or adenosine A1-receptor dependent pathway alone is not sufficient but summation of these pathways is required to achieve an ischaemic preconditioning effect in rabbits.

1. It is reported that alpha1-receptors and adenosine A1-receptors are involved in the ischaemic preconditioning (PC) effect on infarct size (IS). However, it is still unclear to what extent alpha1-receptors and adenosine A1-receptors contribute to the mechanism of PC. Therefore, we investigated the extent of the contribution of alpha1-receptors and adenosine A1 receptors to the PC effect on IS and examined the relationship between these receptors and protein kinase C. 2. Infarct size was measured in rabbits subjected to 30 min ischaemia and 48 h reperfusion. Tyramine (Tyr) was intravenously administered before 30 min ischaemia in the absence or presence of bunazosin (BN, alpha1-receptor blocker) and staurosporine (ST), a protein kinase C inhibitor, respectively. R(-)N6-(2-phenylisapropyl)-adenosine (PIA), a selective adenosine A1 agonist, was intravenously administered before 30 min ischaemia in the absence or presence of 8-p-sulphophenyltheophylline (8SPT), an adenosine blocker and ST, respectively. In the PC groups, BN, BN + PIA, 8SPT, 8SPT + Tyr or placebo saline was injected before or during PC. 3. Both Tyr and PIA reduced the IS, which was blocked by BN and 8SPT, respectively. The IS-reducing effect of Tyr or PIA was blocked by ST. The IS-reducing effect of PC was completely blocked by BN and 8SPT, respectively. The blocking effect of BN on the IS-reducing effect of PC was abolished by adding PIA during PC ischaemia. The blocking effect of 8SPT on the IS-reducing effect of PC was abolished by adding Tyr before PC ischaemia. 4. These data suggest that an alpha1-receptor dependent pathway exists and an adenosine A1-receptor dependent pathway, stimulation of both of which activates protein kinase C, then reduces the IS. However, exclusive stimulation of a single alpha1-receptor dependent pathway or a single adenosine A1-receptor dependent pathway alone is not sufficient but the summation of these pathways is required to achieve a PC effect on IS in rabbits.

Cross-talk among noradrenaline, adenosine and protein kinase C in the mechanisms of ischemic preconditioning in rabbits.

To date, there are two pathways discussed as a mechanism of ischemic preconditioning. Activation of protein kinase C by ischemic preconditioning increases adenosine release. The increased adenosine further activates protein kinase C through adenosine A1 receptors, and activated protein kinase C induces an infarct size-reducing effect through the opening of K(ATP) channels (pathway I). Meanwhile, activation of the alpha1b-adrenoceptor through increased interstitial noradrenaline by ischemic preconditioning is also associated with the ischemic preconditioning effect. However, the exact pathway of this is unknown, although it is postulated that protein kinase C and adenosine are cross-talking. Myocardial interstitial noradrenaline levels were measured in Japanese white rabbits using a microdialysis technique. Ischemic preconditioning was elicited by a single episode of 5 min ischemia and 5 min reperfusion. The infarct size was measured in rabbits subjected to 30 min ischemia and 48 h reperfusion. An increase in interstitial noradrenaline by ischemic preconditioning was not inhibited by an adenosine A1 receptor blocker (1,3-dipropyl-8-cyclopentylxanthine), but was inhibited by an adenosine A2 receptor blocker (3,7-dimethyl-1-(2-propynyl) xanthine) or protein kinase C inhibitors (staurosporine and polymyxin B). Interstitial noradrenaline was increased by an adenosine A2 receptor agonist (CGS21680) and the increase was inhibited by a protein kinase C inhibitor. The infarct size-reducing effect of ischemic preconditioning was inhibited by a selective alpha1b-adrenoceptor blocker (chloroethylclonidine) or a protein kinase C inhibitor, and that of tyramine, an inducer of noradrenaline, was inhibited by protein kinase C inhibitor. This suggests the presence of pathway II, indicating ischemic preconditioning --> activation of protein kinase C --> adenosine release --> pre-synaptic adenosine A2 receptors --> activation of protein kinase C in sympathetic nerve --> noradrenaline --> alpha1b-adrenoceptor --> activation of protein kinase C in myocytes --> infarct size-reducing effect. In addition, the ischemic preconditioning effect on infarct size was not inhibited by 1,3-dipropyl-8-cyclopentylxanthine, but was inhibited by 3,7-dimethyl-1-(2-propynyl) xanthine or chloroethylclonidine, suggesting the greater importance of pathway II compared with pathway I. Thus, pathway II plays an important role in the pathogenesis of the infarct size-reducing effect in ischemic preconditioning.