Actin in Xenopus yolk platelets: a peculiar and debated presence.

Yolk platelets in Xenopus oocytes maintain an acidic internal pH which may be essential for sodium accumulation

Yolk platelets constitute an embryonic endocytic compartment that stores maternally synthesized nutrients. The pH of Xenopus yolk platelets, measured by photometry on whole oocytes which had endocytosed FITC-vitellogenin, was found to be acidic (around pH 5.6). Experiments on digitonin-permeabilized oocytes showed that acidification was due to the activity of an NEM- and bafilomycin A1-sensitiv...

Changes in yolk platelet pH during Xenopus laevis development correlate with yolk utilization. A quantitative confocal microscopy study.

The variations of the pH in Xenopus yolk platelets have been estimated by fluorescence confocal microscopy and computer image processing. For pH measurements in vitellogenic oocytes, the pH-sensitive fluorescent dye, DM-NERF, was coupled to vitellogenin, and the DM-NERF-vitellogenin was taken up by oocytes via receptor-mediated endocytosis. Dual emission ratio measurements of internalized DM-NE...

A biochemical and ultrastructural study of RNA in yolk platelets of Xenopus gastrulae.

Yolk platelets from Xenopus gastrulae were isolated in a sucrose-polyvinyl pyrrolidone medium, washed, centrifuged four times, and portions of each pellet were prepared for electron microscopy. Electron microscopy revealed isolated platelets to be free of cytoplasmic contamination with progressive disruption of the superficial layer after each washing. Each washing and the final pellet were ext...

The utilization of yolk platelets by tissues of Xenopus embryos studied by a safranin staining method.

Xenopus laevis lectin is localized at several sites in Xenopus oocytes, eggs, and embryos

The endogenous lectin of Xenopus laevis oocytes, unfertilized eggs, and blastula-stage embryos was immunohistochemically localized using a highly specific antiserum. Each tissue was examined with several techniques, including paraformaldehyde or glutaraldehyde fixation, frozen or plastic sections, and immunofluorescence or immunoperoxidase staining. In oocytes and unfertilized eggs, lectin was ...