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R Dohmen

Publications and source records attributed to R Dohmen.

8 recordsLinked to original sources
PubMed1995

High pH prevents retinoic acid-induced teratogenesis.

Exogenously applied retinoic acid is known to cause teratogenic effects in a variety of animal systems. We examined whether the formation of teratogenic effects may be influenced by the electrical charge of retinoic acid. The pKa of retinoic acid ranges from 6 to 8, indicating that it is electrically neutral in a pH5 medium and is negatively charged in a pH9 medium. With this idea in mind, embryos of the pond snail Lymnaea stagnalis were pulse-treated with retinoic acid and cultured in media of different pH. The percentage of embryos with retinoic acid-induced eye defects was 6-fold lower in the pH9 medium as compared to the pH5 medium. In contrast, the apical plate defects induced by retinoic acid were not pH-dependent. The observation that high pH prevents eye defects but not apical plate defects can be explained by taking into account an electrophoretic redistribution of retinoic acid resulting from the voltage gradients that are generated by the Lymnaea embryo.

Animals↗
PubMed1993

Polar ionic currents around embryos of Lymnaea stagnalis during gastrulation and organogenesis.

Embryos of Lymnaea stagnalis generate ionic currents which can be measured with the vibrating probe. Here we investigated the presence and origin of the currents during late embryonic development. During gastrulation the current pattern correlates with the animal-vegetal polarity and during organogenesis it is correlated to the newly formed antero-posterior axis. The origin of the ionic currents was studied by inhibition of the Na+/K(+)-pump with ouabain and by enzyme-cytochemical detection of the Ca(2+)-pump. Ouabain treatment resulted in a reduced current density around the embryo, indicating that the Na+/K(+)-pump contributes significantly to the net current. The Ca(2+)-pump was found to be localized in the vegetal blastomeres during gastrulation and in the larval kidney during organogenesis. It seems likely that this Ca(2+)-pump renders only a minor contribution to the net current in late embryonic development. Ionic currents have now been described in Lymnaea from the uncleaved egg up to the juvenile snail. During this period the overall current pattern changes only twice, demonstrating that the voltage gradient generated by the embryo remains stable during prolonged periods in development.

Animals↗