Gilles Charpentier

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The slow inward Na current observed during sustained depolarization of the Xenopus oocyte membrane is due to a complex mechanism described as the induction of the channels. The present work investigates the role of protein phosphorylation in Na channel function. Injection of alkaline phosphatase in the oocytes decreased inward current. Therefore, the(More)
Masculinizing effect of testes on developing rat ovaries was shown in vitro by culturing testes from 17.5-day-old fetuses in contact with female genital tracts from 14.5-day-old rat fetuses. The testes induced the differentiation of epithelial cells staining for cytokeratin in the ovarian blastema. These cells formed seminiferous cord-like structures(More)
In neurons, voltage-gated Ca(2+) channels and nuclear Ca(2+) signaling play important roles, such as in the regulation of gene expression. However, the link between electrical activity and biochemical cascade activation involved in the generation of the nuclear Ca(2+) signaling is poorly understood. Here we show that depolarization of Aplysia neurons(More)
It remains unclear how different intracellular stores could interact and be recruited by Ca(2+)-releasing messengers to generate agonist-specific Ca(2+) signatures. In addition, refilling of acidic stores such as lysosomes and secretory granules occurs through endocytosis, but this has never been investigated with regard to specific Ca(2+) signatures. In(More)
Ca(2+) signalling is one of the most important means in mammalian cells of relaying the action of hormones and neurotransmitters. The great diversity of agonist-induced Ca(2+) signatures, visualized by optical imaging techniques, can be explained by the production of intracellular messengers triggering Ca(2+) release from internal stores and/or by different(More)
Protein phosphorylation by protein kinase C (PKC) has recently been shown to be a key event in the induction of the slow inward Na current observed during sustained depolarization of the Xenopus oocyte membrane. The present work investigates the possible pathways leading to PKC activation. PKC is activated by a series of phospholipid metabolites, such as(More)
Many physiological processes are controlled by a great diversity of Ca2+ signals. Within cell, Ca2+ signals depend upon Ca2+ entry and/or Ca2+ release from internal Ca2+ stores. The control of Ca2+-store mobilization is ensured by a family of messengers comprising inositol 1,4,5 trisphosphate, cyclic ADP-ribose and nicotinic acid adenine dinucleotide(More)
Xenopus oocytes injected with rat cerebellar mRNA expressed functional voltage-dependent Ca channels detected as an inward Ba current (IBa). The pharmacological resistance to dihydropyridines and omega-conotoxin together with the blockade obtained with Agelenopsis aperta venom suggest that these channels could be somehow assimilated to P-type Ca channels.(More)
An unusual inward current which is slowly elicited in the Xenopus oocyte membrane during sustained depolarization is reportedly carried by Na+. It is thought that Na+ selective channels are in some way induced to become voltage-sensitive by the depolarization. Earlier studies report that the induction process involves a phospholipase C and a protein kinase(More)
The membrane of immature Xenopus oocytes is known to possess a peculiar type of sodium channels, which are not activatable unless the membrane has been depolarized for some time. Once induced by a long-lasting depolarization, the channels behave like voltage-dependent channels, but they slowly activate and apparently do not inactivate. In addition, these(More)