The Intermediary Metabolism of Nematode Parasites

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Abstract
The O2 consumption of brei or mince prepared from Nematodirus filicollis, N. spathiger, Ascaridia galli, and Neoaplectana glaseri was stimulated by the addition of pyruvate., a-ketoglutarate, succinate, fumarate, malate, and oxaloacetate. Citrate did not stimulate respiration. Malonate, arsenate, arsenite, pyrophosphate, and azide inhibited respiration. When brei from Nematodirus spp. and Ascaridia galli were fortified with coenzymes, the inhibition due to malonate was decreased by adding intermediates of the tricarboxylic acid cycle, and the accumulation of succinate in the malonate-poisoned brei was increased when fumarate, fumarate plus pyruvate, or citrate was added. When Ca ions were present in the medium in which the brei was suspended, the results indicated that only isolated reactions of the tricarboxylic acid cycle were taking place because succinate failed to decrease malonate inhibition and did not accumulate even when fumarate or pyruvate was added. The characteristic reactions of the whole cycle could be obtained by omitting CaCl from the medium or by adding adenosinetriphosphate, diphosphopyridine nucleotide, and triphosphopyridine nucleotide. On the basis of these results, it is suggested that some form of the tricarboxylic acid cycle functions in the tissues of the parasites.