Fig. 2. Conditions of anoxia (filled squares), low pH (6.4; filled triangles), anoxia plus low pH (+ symbols) or anoxia plus 1.5 mmol l^-1 ATP (open diamonds) in organello cause decreased transcription in A. franciscana embryos compared to controls (filled circles; normoxic, pH 6.4).Incorporation of ³²P-UTP was followed by scintillation counting of TCA-precipitated RNA. Mitochondria were incubated at room temperature with 100 µg ml^-1 actinomycin D to measure RNA synthesis under conditions identical to those used to assess mRNA half-life. All values are means ± S.E.M. (N=3).