Phytohemagglutinin Induces Delays in Oral Regeneration in the Ciliate Stentor coeruleus1

Abstract

Regenerating Stentor, exposed to the plant lectin phytohemagglutinin, are significantly delayed in completing oral regeneration. All of the delays are restricted to the earliest stages of regeneration prior to stage 3. The effects of phytohemagglutinin are reversible once the drug is removed. The addition of the presumed sugar receptor for phytohemagglutinin, N-acetylgalactosamine, at the start of oral regeneration could not reverse the effects of phytohemagglutinin, but the addition of excess (10 mM) extracellular calcium could. When the addition of the excess calcium was delayed for various times after phytohemagglutinin exposure, the effectiveness of the calcium in reversing the phytohemagglutinin-induced delays was reduced. Based on the mechanism of action of PHA in other cells, these results suggest that membrane proteins may be involved in controlling oral regeneration, possibly through mechanisms involving Cat+.PON the loss of its oral feeding apparatus, the ciliate Sten-

Concanavalin a inhibits oral regeneration in Stentor coeruleus through a mechanism involving binding to the cell surface

“…The same effect of extracellular calcium is also observed with PHA (Maloney, 1984). These results suggest that Con A is not stimulating calcium influx as it does in lymphocyte mitogenesis since one would predict that the excess extracellular calcium should increase the delays if this were true.…”

“…Based on these results with Con A and the earlier results from this lab with PHA (Maloney, 1984) and local anesthetics (Maloney, 19801, there is clearly some relationship between calcium metabolism, membrane disturbance and oral regeneration. In almost all cases the presence of excess extracellular calcium can negate the effects of a particular agent on oral regeneration, suggesting the necessity of extracellular calcium for normal oral regeneration.…”

“…That Con A is binding to glycosylated membrane proteins in Stentor is indicated by the fact that exogenously added a-MM, which prevents the effects of Con A in other systems (Brown and Hunt, 1978;Ofer et al, 1976;Scott and Hufnagel, 1983;Novogrodsky et al, 1978), completely prevents the effects of Con A even when added after Con A first attaches to the cells (Table 3) and prevents the binding of FITC-Con A to Stentor. PHA also delays oral regeneration in a manner similar to Con A (Maloney, 1984) and Nilsson and Waxdal (1978) have recently demonstrated that Con A and PHA bind to identical sets of cell surface glycoproteins, further supporting the binding of Con A to the cell surface.…”

“…Thus her results have clearly demonstrated the involvement of the cell surface in the control of oral development. Pharmacological experiments using various chemical membrane probes have confirmed this hypothesis by indicating that various membrane perturbations can also affect oral development (Maloney, 1980(Maloney, , 1984. The actual means by which the cell surface regulates oral development is uncertain, though one possible mechanism could involve glycosylated membrane proteins.…”

“…As early as 1966 Zech (1966) showed that PHA could affect cell division in Stentor. Recently it has been shown that PHA can also affect oral regeneration in Stentor (Maloney, 1984) tentatively suggesting the involvement of glycosylated membrane proteins there. However, the binding of the lectin to the cell surface could not be conclusively demonstrated and the preparations used were not as homogeneous as is the case with other lectins, particularly Con A.…”