Fertilization in sea urchins, Strongylocentrotus purpuratus, is the result of a series of interactions between the egg and sperm. Microfilament formation has been implicated in both the acrosomal process formation and the entry of the sperm into the egg. Changes in internal calcium concentrations have been linked to exocytosis reactions that occur in both the egg and the sperm. Therefore, the d...

To determine the role of the adenylate cyclase system in potentiation of enzyme secretion, we used cholera toxin to activate adenylate cyclase before examining the effects of agents on chief cell cAMP and pepsinogen secretion. Dispersed chief cells were obtained from guinea pig stomach by fractionation of mucosal cells on a Percoll gradient. Incubation of cells with 100 nM cholera toxin for 90 ...

Trypanosoma cruzi, the protozoan responsible for Chagas disease, employs distinct strategies to invade mammalian host cells. In the present work we investigated the participation of calcium ions on the invasion process using primary cultures of embryonic mice cardiomyocytes which exhibit spontaneous contraction in vitro. Using Fura 2-AM we found that T. cruzi was able to induce a sustained incr...

The mechanism by which palmitic and oleic acids modify calcium sequestration by sarcoplasmic reticulum vesicles was investigated by examining the effects of these fatty acids on calcium -dependent ATPase activity, on the phosphoenzyme intermediates found during calcium sequestration reactions, and on passive membrane permeability to calcium. The calcium sequestered in the presence of these fatt...