SUMMARY An imbalance of potassium in cardiac muscle causes an alteration of heart function. The distribution and concentration of potassium in rat papillary heart muscle was studied using cryofixation and X‐ray microanalysis. Freeze‐dried cryosections and sections of freeze‐dried, embedded tissue were analysed. Bulk frozen specimens were freeze‐dried either in a vacuum or by a new technique using liquid propane as a cryodehydration medium. These two methods of freeze‐drying were tested for elemental retention in other specimens, with comparable results. A potassium concentration of 120 mmol/l was measured in normal myocytes of cardiac papillary muscle compared to 80 mmol/l in myocytes of animals stressed by a temperature of 45°C for 1 h. The presumed physiological significance of the findings is discussed.

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Biologically important elements: K, Na, Mg, Ca, Cl, P, and S were analyzed in Acanthamoeba castellanii. A higher potassium content, as compared with other cations, was detected. Total content of the cation-forming elements: K, Na, Mg, and Ca was ca. 360 mmoles/kg dry weight of the cells. Phosphorus content was estimated as 492 mmoles/kg dry weight. Content of chlorine, a basic cellular anion, was 173 mmoles/kg dry weight. The low level of chlorine appears not the be sufficient to balance all the cations in Acanthamoeba. Distribution of potassium in Acanthamoeba cells was nonuniform and similar to that of phosphorus as shown by X-ray microanalysis technique. Quantitative correlation between phosphorus and potassium as well as the similar distribution of these elements suggests that in Acanthamoeba phosphorus is an essential anion which, being nonuniformly distributed in the cell, determines also a nonuniform distribution of potassium.

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In egg vesicles of Galleria mellonella (Lepidoptera) electron microprobe analysis reveals calcium in concentrations of 9 and 3 mmoles per 1,000 g tissue wet weight in oocyters and accompanying trophic cells, respectively. This high average level of calcium characterizes both pre- and postvitellogenic oocytes, but the distribution of calcium is not uniform. In postvitellogenic vesicles the central area of the ooplasm shows a higher content of Ca than peripheral one, what may be correlated with the distribution of mature yolk platelets within the ooplasm.