Heme-induced Trypanosoma cruzi proliferation is mediated by CaM kinase II.

Trypanosoma cruzi, the etiologic agent of Chagas disease, is transmitted through triatomine vectors during their blood-meal on vertebrate hosts. These hematophagous insects usually ingest approximately 10mM of heme bound to hemoglobin in a single meal. Blood forms of the parasite are transformed into epimastigotes in the crop which initiates a few hours after parasite ingestion. In a previous work, we investigated the role of heme in parasite cell proliferation and showed that the addition of heme significantly increased parasite proliferation in a dose-dependent manner [1]. To investigate whether the heme effect is mediated by protein kinase signalling pathways, parasite proliferation was evaluated in the presence of several protein kinase (PK) inhibitors. We found that only KN-93, a classical inhibitor of calcium-calmodulin-dependent kinases (CaMKs), blocked heme-induced cell proliferation. KN-92, an inactive analogue of KN-93, was not able to block this effect. A T. cruzi CaMKII homologue is most likely the main enzyme involved in this process since parasite proliferation was also blocked when Myr-AIP, an inhibitory peptide for mammalian CaMKII, was included in the cell proliferation assay. Moreover, CaMK activity increased in parasite cells with the addition of heme as shown by immunological and biochemical assays. In conclusion, the present results are the first strong indications that CaMKII is involved in the heme-induced cell signalling pathway that mediates parasite proliferation.

Effect of electroacupuncture on physical performance of young men and responses to exercise

Chinese Medicine uses acupuncture points K-3 (Taixi), Li-3 (taichong), S-36 (Zusanli), Ren-4 (Guanyuan)and Ren-6 (Qihai) to enhance the individual's general energy, improving capacity to physical efforts, and the body threshold to fadigue. We studied the influence of these specific points on physical performance capacity (PPC) and physiological responses to excercise (PRE). Material - We assigned 27 healthy men at random to three groups: acupuncture (A), acupuncture sham (S) and control group (no acupuncture (N). Methods - Performance was determined through of a spiroergometric test was carried out at the beginning and at the end of five sucessive daily sessions, consisting of 20 minutes of electroacupuncture (EA) of the selected points. They performed a continuous incremental (25 watts/min) test until exhaunstion in bicycle ergometer (Cibex the Bike). Respiratory and metabolic variables were calculated every 20s during excercise by a computerized spiroergometric system (Vista CX). The heart was obtained by telemetry (Polar), The rate of perceived exertion (RPE) was measured by the Borg's revised scale. Results - The results before and after treatment were compared in these conditions: rest (R); moderate exercise (M); at the anaerobic threshold (AT); intense exercise (I); maximal exercise (MX) and recovery (RC). The subjects from group A didn't increase the maximal performance capacity neither the PPC at AT. Respiratory, cardiovascular responses and movement economy in M, AT, I and MX didn't improve in these group. We detected a positive effect of EA only in RPE during M. There was no differences between tests in groups S an N. Conclusion - These results suggest that the EA in studied conditions isn't effective to increase PPC or improve PRE.