T H E amphibian egg bears a cortex as the periphery of its cytoplasm. The interpretation by Dalcq & Pasteels (1937) of experiments performed by Pasteels (1938, 1940, 1941), in which fertile eggs of Rana fusca were centrifuged or inverted, led to the suggestion that the cortex possesses properties which control the course of development to some degree. It appeared that the properties of the cort...

Chloride is the most abundant permeable anion in the cell, and numerous studies in the last two decades highlight the great importance and broad physiological role of chloride currents mediated anion transport. They participate in a multiplicity of key processes, as for instance, the regulation of electrical excitability, apoptosis, cell cycle, epithelial secretion and neuronal excitability. In...

Die wêreldwye indringerpadda, die gewone platanna Xenopus laevis (Anura: Pipidae), toon duidelike filogeografiese verskille tussen sy verskillende bevolkings in suidelike Afrika, natuurlike gebied. Dit het direk tot hoë genetiese variasie sommige van indringerbevolkings bygedra. Nietemin is daar nog geen sekerheid oor hoe stamme gebied met mekaar verband hou nie. Daarbenewens en geografi ese ve...

The amiloride-sensitive Na + /H + antiporter in defolliculated oocytes of Xenopus laevis was characterized by measurements of H Na + influx and apparent H + efflux. Uptake of ^Na"" was linear over a 90-min incubation period and was inhibited approximately 80% with 5xlO~moll~ amiloride. Amiloride-sensitive sodium uptake was reduced following collagenase treatment or oocyte aging. Ko 5 for amilor...

Cell polarity is manifest along the animal/vegetal axis in eggs of the frog, Xenopus laevis. Along this axis, maternal cytoplasmic components are asymmetrically distributed and are thought to underlie specification of distinct cell fates. To ascertain the molecular identities of such cytoplasmic components, we have used a monoclonal antibody that specifically stains the vegetal hemisphere of Xe...

Microinjection of Xenopus laevis oocytes followed by thin-sectioning electron microscopy (EM) is an excellent system for studying nucleocytoplasmic transport. Because of its large nucleus and high density of nuclear pore complexes (NPCs), nuclear transport can be easily visualized in the Xenopus oocyte. Much insight into the mechanisms of nuclear import and export has been gained through use of...

We have isolated Xenopus laevis cDNA and genomic clones encoding the neuropeptide Y (NPY) mRNA and gene using a probe from the human NPY gene. The longest open reading frame in the cDNA encodes a peptide 76% identical to human prepro-NPY and 73% identical to rat prepro-NPY. The putative mature Xenopus NPY (XNPY) peptide is 94% identical to both human and rat peptides. A genomic clone containing...

The germ cell nuclear factor (GCNF) is a nuclear orphan receptor and a putative regulator of the pluripotent state of cells. Although it was first described in mouse germ cells, GCNF is also expressed in mouse and Xenopus embryos. By means of 5'RACE we have identified a novel isoform of Xenopus laevis GCNF that is predominantly expressed in germ cells, whereas both the oocyte and embryonic form...

Fragments of amplified Xenopus laevis DNA, coding for 18S and 28S ribosomal RNA and generated by EcoRI restriction endonuclease, have been linked in vitro to the bacterial plasmid pSC101; and the recombinant molecular species have been introduced into E. coli by transformation. These recombinant plasmids, containing both eukaryotic and prokaryotic DNA, replicate stably in E. coli. RNA isolated ...