As an important step in the nuclear transfer (NT) procedure, we evaluated the effect of three different treatments for oocyte activation on the in vitro and in vivo developmental capacity of bovine reconstructed embryos: (1) strontium, which has been successfully used in mice but not yet tested in cattle; (2) ionomycin and 6-dimethylaminopurine (6-DMAP), a standard treatment used in cattle; (3)...

Secretion of cytokines by T cells in vitro can be influenced by the methods chosen for T cell activation. However, the awareness of this fact appears insufficient. Two of the most widely applied methods for activation of T cells are phorbol 12-myristate 13-acetate (PMA) together with Ionomycin or anti-CD3/anti-CD28 stimulation. We analyzed production of IL-4, IFN-γ, IL-17 and IL-10 by a panel o...

In the porcine renal epithelial cell line, LLC-PK1, activation of the cAMP-dependent signal transduction pathway induces the urokinase-type plasminogen activator (uPA) gene. We show here that the cAMP response is enhanced when the intracellular calcium concentration is increased. When LLC-PK1 cells were treated with the calcium ionophore ionomycin alone, there was no uPA mRNA accumulation. Howe...

Sequential stimulation and washout procedures were employed to examine the kinetics and reversibility of pharmacologically manipulated second messenger signals mediating phenotypic changes and proliferative activation of resting human T lymphocytes. Phorbol dibutyrate (PDBu) was used to stimulate protein kinase C (Ca2+/phospholipid-dependent enzyme) while ionomycin was used to manipulate intrac...

PURPOSE Cortical cataract in humans is associated with Ca2+ overload and protein loss, and although animal models of cataract have implicated Ca2+-activated proteases in this process, it remains to be determined whether the human lens responds in this manner to conditions of Ca2+ overload. The purpose of these experiments was to investigate Ca2+-induced opacification and proteolysis in the orga...

Whereas signalling pathways involved in transcriptional control have been studied extensively, the pathways regulating mRNA turnover remain poorly understood. We are interested in the role of mRNA stability in cell activation and oncogenesis using PB-3c mast cells as a model system. In these cells the short-lived interleukin-3 (IL-3) mRNA is stabilized by ionomycin treatment and following oncog...

Protein tyrosine kinases, which are highly expressed in the central nervous system, are implicated in many neural processes. However, the relationship between protein tyrosine kinases and neurotransmitter release remains unknown. In this study, we found that ionomycin, a Ca²⁺ ionophore, concurrently induced asynchronous neurotransmitter release and phosphorylation of a non-receptor protein tyro...

We previously reported an enhanced peak response of intracellular free Ca2+ to thrombin in platelets of spontaneously hypertensive rats in comparison with normotensive Wistar-Kyoto rats. In the present study, we compared the platelet intracellular Ca2+ response to the receptor-linked agonist thrombin with the response to the Ca2+ ionophore ionomycin. Basal intracellular Ca2+ was higher in hyper...

The role of calcium in the regulation of GnRH gene expression and the mechanism for its effects were examined in the present study. Using the immortalized hypothalamic GT1-7 cell line, which synthesizes and secretes GnRH, we demonstrated by ribonuclease protection assay and Northern blot analysis that these cells respond to treatment with the calcium ionophores ionomycin and A23187 with an inhi...

Background: Oocyte vitrification and assisted oocyte activation have increasingly important implications in assisted reproductive technology. However, an important area of concern with matured oocyte cryobiology is that elements of oocytes intimately involved in metaphase-II arrest may be modified by cryopreservation. In a comparison between different cellular characteristics of unvitrified, vi...