Salivary glands of Drosophila hydei recovering from an anaerobic treatment show a significant increase in apparent Vmax. of mitochondrial NADH dehydrogenase. This increase in Vmax. is based on an increase in enzyme molecules resulting from synthesis de novo in the cytoplasm, as indicated by the inhibition by cycloheximide of both the increase in apparent Vmax. and the increase in amino acid incorporation into enzyme fractions. The increase in enzyme activity is also inhibited by actinomycin D, which is in support of previous data indicating a casual relationship between transcription in puff 4-81B in the polytene chromosomes and an increase in apparent Vmax. of the enzyme. Gel electrophoresis of mitochondrial protein extracts revealed three protein fractions with NADH dehydrogenase activity. All three fractions showed increased activity as well as increased amino acid labelling in glands recovering from anaerobiosis compared with control glands. The data suggest that the increase in mitochondrial NADH dehydrogenase activity in salivary glands recovering from an anaerobic treatment depends on increased gene transcription.

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