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The molecular mechanism of neural induction is still unknown and the identity of the natural inducer remains elusive. It has been suggested that both the protein kinase C and cAMP signal transduction pathways may be involved in mediating its action. Here we provide evidence that Ca2+ is implicated in the process of transduction of the neuralizing signal. We(More)
Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were(More)
Plasma membrane-bound voltage-dependent calcium channels may couple the perception of an initial stimulus to a regulated pathway for calcium influx. The activities of these channels have been shown to be very low and highly unstable but may be recruited by large-predepolarizing pulses, according to a process referred to as recruitment. By combining(More)
Using Nicotiana plumbaginifolia constitutively expressing the recombinant bioluminescent calcium indicator, aequorin, it has been previously demonstrated that plant cells react to cold-shock by an immediate rise in cytosolic calcium. Such an opportune system has been exploited to address the regulatory pathway involved in the calcium response. For this(More)
Meiosis reinitiation has been triggered via electrophoretic driving of Ca++ into the cortex of Xenopus laevis oocytes freed from functional follicle cells by collagenase treatment. Mg++ could not be substituted for Ca++. Ca++ induced maturation resembles progesterone induced maturation in so far both are inhibited by cycloheximide, give rise to amplifiable(More)
Mercuric chloride (HgCl2) induces T helper 2 (Th2) autoreactive anti-class II T cells in Brown Norway rats. These cells produce interleukin (IL)-4 and induce a B cell polyclonal activation that is responsible for autoimmune disease. In Brown Norway rats, HgCl2 triggers early IL-4 mRNA expression both in vivo and in vitro by T cells, which may explain why(More)
In intact Xenopus embryos, an increase in intracellular Ca(2+) in the dorsal ectoderm is both necessary and sufficient to commit the ectoderm to a neural fate. However, the relationship between this Ca(2+) increase and the expression of early neural genes is as yet unknown. In intact embryos, studying the interaction between Ca(2+) signaling and gene(More)
In contrast to the situation found in the bivalves Barnea candida and Spisula solidissima, prophase-arrested oocytes of Ruditapes philippinarum cannot be fertilized when removed from the ovary. They must first undergo germinal vesicle breakdown under the influence of the neurohormone serotonin (5-HT), which drives them to a second block occurring in(More)
In amphibia, noggin, one of the neural inducers expressed in the Spemann organizer, acts by neutralizing the effects of bone morphogenetic protein-4 (BMP-4). It is shown that noggin is able to activate L-type calcium channels. The fos proto-oncogene is known to be induced within minutes by calcium signaling. Here it is reported that in animal cap explants(More)