The norpurpureine alkaloid from inhibits human platelet activation in vitro.

Background: The leaves of have yielded several alkaloids with anti-aggregation activities against rabbit platelets. This is promising in the search for agents that might act against platelets and reduce the incidence of cardiovascular diseases. Since significant differences in platelet function have been reported between human and animal platelets, a study focusing on the effect of extracts against human platelet activation is necessary.

Dissecting the Ca²⁺ entry pathways induced by rotavirus infection and NSP4-EGFP expression in Cos-7 cells.

Rotavirus infection modifies Ca(2+) homeostasis provoking an increase in Ca(2+) permeation, cytoplasmic Ca(2+) concentration ([Ca(2+)](cyto)), total Ca(2+) pools and, a decrease of Ca(2+) response to agonists. These effects are mediated by NSP4. The mechanism by which NSP4 deranges Ca(2+) homeostasis is not yet known.

Expression of nonstructural rotavirus protein NSP4 mimics Ca2+ homeostasis changes induced by rotavirus infection in cultured cells.

Rotavirus infection modifies Ca(2+) homeostasis, provoking an increase in Ca(2+) permeation, the cytoplasmic Ca(2+) concentration ([Ca(2+)](cyto)), and total Ca(2+) pools and a decrease in Ca(2+) response to agonists. A glycosylated viral protein(s), NSP4 and/or VP7, may be responsible for these effects. HT29 or Cos-7 cells were infected by the SA11 clone 28 strain, in which VP7 is not glycosylated, or transiently transfected with plasmids coding for NSP4-enhanced green fluorescent protein (EGFP) or NSP4.

Silencing of rotavirus NSP4 or VP7 expression reduces alterations in Ca2+ homeostasis induced by infection of cultured cells.

Rotavirus infection of cells in culture induces major changes in Ca(2+) homeostasis. These changes include increases in plasma membrane Ca(2+) permeability, cytosolic Ca(2+) concentration, and total cell Ca(2+) content and a reduction in the amount of Ca(2+) released from intracellular pools sensitive to agonists. Various lines of evidence suggest that the nonstructural glycoprotein NSP4 and possibly the major outer capsid glycoprotein VP7 are responsible for these effects.

Intracellular disassembly of infectious rotavirus particles by depletion of Ca2+ sequestered in the endoplasmic reticulum at the end of virus cycle.

Rotavirus infection is characterized by a number of Ca(2+) dependent virus-cell interactions. The structure of rotavirus triple-layered particles (TLP) is dependent on Ca(2+) concentration. Acquisition of the capsid outer layer requires a high Ca(2+) concentration inside the ER.