Triterpenoid saponins affect the function of P-glycoprotein and reduce the survival of the free-living stages of Heligmosomoides bakeri.

We studied the effect of triterpenoid saponins on the development of free-living stages of Heligmosomoides bakeri, a parasitic nematode of the mouse intestine. We evaluated the effectiveness of oleane-type glucuronides (GlcUAOA) isolated from Calendula officinalis and Beta vulgaris. The rhodamine 123 retention assay was used to detect dysfunctions of the major membrane transporter for xenobiotics, P-glycoprotein (Pgp). Both C. officinals and B. vulgaris GlcUAOA affect the development of the free living stages and function of Pgp in H. bakeri. The GlcUAOA inhibits egg hatching and moulting of larvae and also changes their morphology. These saponin fractions reversed the toxic effect of thiabendazole on the nematode; the function of Pgp was also inhibited.

Macronuclear development in conjugants of Tetrahymena thermophila, which were artificially separated at meiotic prophase.

Conjugant pairs of Tetrahymena thermophila were mechanically separated by vigorous pipetting at the early stages of meiotic prophase. The complete sequence of conjugational nuclear events including the appearance of pronuclei, development of the new macronuclei (postzygotic development), and resorption of the old macronuclei was observed in the separated cells, without pronuclear exchange. The pronuclei in the separated cells were recognised by the presence of components of the extranuclear cytoskeleton, which were labelled with anti-tubulin and anti-fenestrin antibodies in the same way as in undisturbed conjugants. The apical region of the separated conjugants (the post-junction area), corresponding to the junction area of conjugants was labelled with anti-fenestrin antibody and maintained the properties required for the nuclear development. The results of the genetic study were consistent with a hypothesis that cytogamy (pronuclear fusion) was induced in the separated conjugants. Therefore, the lasting cell contact is not necessary for the successful completion of conjugational nuclear events.

Inhibition of oral morphogenesis during conjugation of Tetrahymena thermophila and its resumption after cell separation.

During the early stages of the conjugation of Tetrahymena thermophila, the oral apparatus undergoes partial regression: the deep fiber bundle is resorbed and oral membranelies are partially deciliated. However, further progress of the oral replacement is arrested until cell separation. Only then proliferation of basal bodies for a new oral primordium is unblocked and concomitantly the old oral structures are resorbed. This step is followed by the assembly of new oral membranelies and resorption of the old ones. Thus, the cell separation itself may be the source of an important signal for the cortical morphogenesis. To test this hypothesis we have used micronuclearly defective "✴" cells which separate after conjugation about 2.5 h earlier than normal cells and do not undergo postzygotic nuclear divisions. In the "✴" crosses (the crosses of the "✴" × wt cells) the oral primordium appeared before the cell separation (at the stage of hemikarya) following partial regression of the old oral structures, but only in those pairs in which the separation was already advanced in the separation. Consequently onset of conjugational morphogenesis in the "✴" pairs was correlated with the time of the cell separation, in spite of the differences in the course of nuclear events in the two kinds of pairs.

Induction of cybrid strains of Tetrahymena thermophila by electrofusion.

In this paper, the electrofusion of the ciliated protozoan, Tetrahymena thermophila, is described. Deciliated cells were brought into close membrane contact by dielectrophoresis in a weakly conductive medium. Then cell fusion was induced by application of repeated electric pulses. Up to 20 prestarved, logarithmic or stationary phase cells of the same or different mating types may form a single giant cell. The polykaryons are fully able to regenerate cilia and became motile. After an initial process of partial integration the polykaryons yield viable clones by separation of components. Cytoplasmic exchange between fused components occurs before separation. Cytoplasmically inherited chloramphenicol resistance was transmitted from one strain to another by electrofusion and drug-resistant cybrid strains were generated.