Spontaneous and fertilization-induced Ca2+ oscillations in mouse immature germinal vesicle-stage oocytes.

Mouse germinal vesicle (GV)-stage oocytes not only show Ca2+ oscillations in response to fertilization but also exhibit spontaneous Ca2+ oscillations during meiotic maturation in vitro. Spontaneous Ca2+ oscillations were entirely suppressed by microinjection of heparin (25 microM final intracellular concentration), an antagonist of inositol trisphosphate (IP3) receptor, whereas fertilization-induced Ca2+ oscillations were only partially inhibited by heparin even at a high dosage of 600 microM. Inhibition of endogenous IP3 generation by antagonizing phospholipase C using U73122 (20 microM final concentration) also failed to suppress the generation of fertilization-induced Ca2+ transients, suggesting that the two types of Ca2+ oscillations do not have the same dependence on IP3-induced Ca2+ release. In addition, spontaneous Ca2+ oscillations require the presence of intact GV whereas fertilization-induced Ca2+ oscillations are independent of the GV but require cytoplasm, since enucleation eliminated only spontaneous Ca2+ oscillations but not fertilization-induced Ca2+ oscillations. These results suggest that IP3-induced Ca2+ release is the primary mechanism responsible for spontaneous Ca2+ oscillations. Sperm-induced Ca2+ oscillations, however, may employ more complex mechanisms during fertilization.

[Analgesic effect and gastro-intestinal motility inhibitory action of 3-hydroxy-4-methoxy-acetophenone from Cynanchum paniculatum (Bunge) Kitagawa].

3-Hydroxy-4-methoxy-acetophenone (HMA) isolated from Cynanchum paniculatum was found to have analgesic effect and inhibitory action on the gastro-intestinal motility. The effect and action were equivalent to that of paeonol, HMA displayed a very low degree of antibacterial activity against Escherichia coli and Shigella flexneri.

A comparison of intracellular changes in porcine eggs after fertilization and electroactivation.

The experiments compare intracellular changes in porcine eggs induced by electrical activation with those induced by sperm penetration. Adequate electrostimulation induces changes in both cortical granule exocytosis and protein synthesis similar to those induced by sperm during fertilization. However, ionic changes induced by electrostimulation differ markedly from those initiated at fertilization. Thus, dynamic video imaging using Fura-2 as a Ca2+ probe provides evidence that parthenogenetic activation induced by electrostimulation is initiated by a single sharp rise in the concentration of intracellular free calcium ([Ca2+]i) in the egg. The intracellular Ca2+ transient increase is triggered by an influx of extracellular Ca2+ immediately after electrostimulation. The amplitude of the intracellular Ca2+ transient increase is a function both of the extracellular Ca2+ concentration and of electric field parameters (field strength and pulse duration). Imaging demonstrates further that a single electrical pulse can only induce a single Ca2+ transient which usually lasts three to five minutes; no further Ca2+ transients are observed unless additional electrical stimuli are applied. By contrast, sperm-induced activation is characterised by a series of Ca2+ spikes which continue for at least 3 hours after sperm-egg fusion. The pattern of Ca2+ spiking after fertilization is not consistent during this period but changes both in frequency and amplitude. Overall, the results demonstrate that, although electrostimulation induces both cortical granule exocytosis and protein reprogramming in porcine eggs, it does not reproduce the pattern of [Ca2+]i changes induced by sperm entry at fertilization.