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Approach:

Amoebae were cultured and subcultured, placed in a buffer and fed paramecium. Five units of 24 chambers, each divided into three 5 ml compartments containing either amoebae, paramecium, or fixative were prepared two days before launch. Amoebae were screened and counted as they were selected for chambers. After loading, chambers were filled with a glycine buffer, with a small airspace left. An attempt was made to determine if there was a normal growth pattern or progression of food vacuole digestion, accomplished by both fixing and feeding in space after variable periods of starvation by means of an activated piston. At recovery, all live organisms were counted and examined for the presence of mitotic forms. Food vacuoles were counted and graded, and the general external morphology of the cell was described.

Results:

Amoebae fed normally while in orbit, and specimens fixed in orbit retained the ordinary heteropodial shape. Growth rates of orbited amoebae, both fed and starved, were slower than controls following reentry and recovery procedures. In continuously fed organisms there was little or no effect of flight detectable in growth rate or actual number of divisions. Electron micrographs showed no abnormalities and few differences between flight and control organisms. Cytochemical data indicate that little or no difference on various digestive processes was produced by weightlessness, acceleration or vibration. Food vacuole data, though, were collected improperly, and little significance can be drawn from them. Growth rates in flight amoebae, although somewhat reduced during flight, appeared to accelerate around the time of reentry. Results suggest that the weightless environment did not produce any gross irreversible alterations in the normal physiologic processes of the amoebae.

++ -- Measurements Continue Launch/Start Date Landing/End Date Duration

09/07/1967 09/09/1967 2 days