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We have previously reported1 the isolation of a specific aldolase (NANaldolase) which reversibly cleaves two of the sialic acids as follows (Keg, 0.1 M): N-acylneuraminic acid = N-acyl-D-mannosamine + pyruvate. While the enzyme catalyzes the synthesis of N-acetyl and N-glycolyl sialic acids, at low substrate concentrations the equilibrium favors cleavage. Further, despite the wide distribution of NANaldolase in animal tissues,2 we have been unable to detect significant activity in those tissues that secrete sialic acid containing mucins. For these reasons, alternate pathways were sought for the biosynthesis of the neuraminic acids.Such a pathway has recently been reported by Warren and Felsenfeld.3 These authors demonstrated the synthesis of N-acetylneuraminic acid (NAN) by protein fractions obtained from rat liver when incubated with N-acetyl-D-mannosamine, PEP, ATP, Mg, DPN, and TPN. Although free NAN was isolated, the data indicated that: (a) NANaldolase was not involved; (b) several steps were probably required for the over-all reaction; (c) one step appeared to be the phosphorylation of N-acetyl-D-mannosamine. The accompanying paper describes the data on the kinase reaction obtained in this laboratory; the product is N-acetv]-D-mannosamine 6-phosphate.It appeared possible that one of the steps in the new system might be a condensation reaction between PEP and either N-acetyl-D-mannosamine or the corresponding 6-phosphate ester. We had previously considered such a condensation but failed to demonstrate it.' Our experiments had been based on the analogy in structure between the sialic acids (2-keto-3-deoxy-nonulosaminic acids), and the known 2-keto-3-deoxy-heptonic and -octonic acids. The latter compounds are enzymatically formed by condensation of PEP with the corresponding tetrose-or pentose-phosphate.4 5 A re-examination of our previous experiments, using the mild homogenization techniques emphasized by Warren and Felsenfeld,3 has now led to the isolation of an enzyme from pig submaxillary gland extracts which catalyzes the following

In this article we set up a mathematical model to represent the effects of the forces which operate during the rowing of racing shells. The analysis is conducted in terms of eights, but could apply equally well to fours, pairs and double or quad sculls, and even (with obvious verbal changes) to single sculls. McMahon as well as McMahon and Bonner have previously considered various numbers of rowers in racing shells, and reached conclusions suggesting that consideration of an eight is representative of all possible combinations of rowers.

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