Trypsin-dissociated cells from the muscle tissue of 9-day-old chick embryos were employed to investigate the effects of cycloheximide and a puromycin-cycloheximide mixture on cell aggregation, protein synthesis and respiratory metabolism.

Cycloheximide when introduced at a concentration of 10 µg/ml into a suspension of cells in Eagle's MEM inhibited aggregation by 25% at 24 h. At this time an inhibition of 40% was apparent in the presence of a mixture of cycloheximide and puromycin both at a concentration of 10 µg/ml.

Both cycloheximide and the cycloheximide-puromycin mixture arrested protein synthesis of rotated cells by 90% within 15 min of introducing the antibiotics into cell suspensions. The antibiotics retained their inhibitory effects on protein synthesis for the 24-h period of rotation.

Cycloheximide inhibited cellular oxygen uptake and carbon dioxide evolution of rotated cells by 25% at the end of the 24-h experimental period. At this time an inhibition of 30% was observed in the presence of the cycloheximide-puromycin mixture. The release of radioactive carbon dioxide by cycloheximide-treated cells was inhibited by 46% at 24 h. In the presence of the antibiotic mixture, 14CO2 release was inhibited by 30% at 4 h, but after 8 h very little further 14CO2 was evolved.

As a control, puromycin (10 µg/ml) inhibited cell aggregation and respiration to an extent similar to that previously reported.

The results are discussed in terms of puromycyl peptides producing a metabolic effect on cell aggregation. It is considered that this is additional to the effect of puromycin inhibiting aggregation through the arrest of protein synthesis.

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