. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INHIBITORS OF PROTEIN SYNTHESIS addition of emetine relaxed with time (Fig. 3A), and a second addition of the same amount of emetine at 12 h reduced incorporation slightly further (Fig. 2A). However, following prolonged incubation in the presence of eme- tine, the addition of chloramphenicol 3 h before labeling led to significantly lower levels of incorporation, partic- ularly at 24 h and 48 h following the addition of emetine (Figs. 2A, 3A). Therefore, some of the apparent relaxation of inhibition by emetine may be due to a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. INHIBITORS OF PROTEIN SYNTHESIS addition of emetine relaxed with time (Fig. 3A), and a second addition of the same amount of emetine at 12 h reduced incorporation slightly further (Fig. 2A). However, following prolonged incubation in the presence of eme- tine, the addition of chloramphenicol 3 h before labeling led to significantly lower levels of incorporation, partic- ularly at 24 h and 48 h following the addition of emetine (Figs. 2A, 3A). Therefore, some of the apparent relaxation of inhibition by emetine may be due to an increase in the proportion of protein synthesis attributable to contami- nating chloramphenicol-sensitive prokaryotes. This is likely to be the result of bacterial growth on the emetine- treated larvae themselves, as these larvae become weaker, although rifampicin ( (iAf) was present throughout. The inhibitory effect of a single addition of anisomycin (200 pM) persisted longer than that caused by 9 eme- tine (Figs. 2B, 3B), and a second addition 12 h after the first did not reduce the incorporation of [3H]leucine fur- ther (Fig. 2B). In the presence of anisomycin, the addition of chloramphenicol 3 h before pulse-labeling did not lead to significantly lower levels of incorporation up to 24 h (Figs. 2B, 3B). Much of the inhibition of protein synthesis by a single addition of anisomycin was reversed between 24 and 48 h (Fig. 3B). This late apparent relaxation was blocked by chloramphenicol (Fig. 3B), suggesting that it was due to an increase in prokaryotic incorporation. Effects of emetine and anisomycin on RNA synthesis To test whether emetine affects RNA synthesis, larvae were pulsed with [3H]uridine both in the presence and absence of 10 6 M GABA (added 30 min following the addition of emetine). No significant inhibition of RNA synthesis was observed except at 6 h in the presence of both GABA and 9 nM emetine (Fig. 4A). The presence of emetine (9 ) may have a stimu
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