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Journal of Experimental Biology 40,493-516 (1963)
Published by Company of Biologists 1963

Some Observations on the Actions of Steroids on the Metaplasia of the Amoeba, Naegleria Gruberi

JANET L. PEARSON ¹ and E. N. WILLMER ¹

¹ Physiological Laboratory, Cambridge

1. The age of the culture of Naegleria gruberi, i.e. the time since the last subculture, is of little importance in determining the numbers of cells which turn flagellate when placed in the extremely dilute buffer solutions used.

2. Between 17° and 21° C. there is a very great decrease in the time which the amoebae require in order to become flagellate when placed in buffer solution.

3. There is no evidence that the amoeba, as such, differentiates between solutions of KC1 or NaCl. On the other hand, the flagellate form is somewhat more reactive to KC1 than to NaCl, and fewer flagellates are found in KC1 solutions.

4. The metaplasia is affected by the presence of steroids in the medium.

5. The more interesting actions of the steroids tested may be summarized as follows. At high concentrations, progesterone and deoxycorticosterone, when applied to the amoeba, prevent the change to the flagellate form. When applied to the flagellate, progesterone has little action, but deoxycorticosterone encourages the return to the amoeboid form, especially in the presence of K+. In lower concentrations both steroids favour the change from amoeba to flagellate and also from flagellate to amoeba. Other steroids have characteristic effects.

6. While the dose/response curves indicate qualitatively different effects of concentration of progesterone and deoxycorticosterone they only show quantitatively different effects with oestradiol and androsterone.

7. Progesterone acts on amoebae at concentrations which are comparable with those at which it acts in the human body.

8. When both progesterone and oestradiol are applied together at concentrations which suppress the flagellate form the effects are additive. The same applies to mixtures of testosterone and oestradiol. An activating concentration of progesterone has not yet been tested in combination with an inhibiting dose of oestradiol.