Chemotactic selection of Tetrahymena pyriformis GL induced with histamine,di-iodotyrosine or insulin

It has been hypothesized that in phylogeny the encounter between potential signalling molecules and the continously changing cell membrane could resul t in the formation of a ligand specific receptor. This chemical (hormonal) imprinting is then transmitted to the progeny generations. It is, however, very difficult to know whether the selection of cells with receptor-like pa tterns or amplification of complete receptor-like patterns led to the forma tion of the receptor-hormone complex. The new technique of chemotactic sele ction' provides a physiological response-guided selection of cells. It also enables the testing of subpopulations with the characteristic selector lig and. We show hers that of three chemotactic ligands (histamine, di-iodotyro sine (T-2) and human insulin), insulin and T-2 selected subpopulations expr ess a significantly high chemotactic response. Since the control medium has a selector capacity itself, we introduced a chemotactic selection coeffici ent (Ch(sel)) which facilitates the comparison of all groups. Using this fa ctor we found that insulin (Ch(sel) = 1.57), functions as a strong selector and T-2 (Ch(sel) = 0.98), was a weak selector. Morphometric evaluation of the cells showed a good correlation between chemotactic responsiveness and morphometric characteristics of subpopulations selected with insulin and hi stamine. T-2 data suggest that the long lasting responsiveness is not gener al, but might be subpopulation specific. (C) 2000 Elsevier Science Inc. All rights reserved.