Use of the method of mixed substrates to study the specificity of tRNA methylases

The absence of summation of the rate of methylation of positionally analogous cytidine residues in tRNA1Val, tRNAPhe, and tRNAMet in the case of simultaneous presence of two substrates in the incubation mixture was demonstrated by the method of mixed substrates. The same result was also obtained in the methylation of A19 (counting from the 3' end of the molecule) in tRNA1Val, tRNAPhe, tRNAfMet, tRNASer, and tRNAGlu individually and in the case of their mixing in pairs. These data are evidence that positionally analogous nucleotides in different RNAs are attacked by the same enzyme. Yeast tRNASer, already possessing a methyl group at the cytidine residue studied, proved to be an effective inhibitor of methylase, forming m5C with valine and phenylalanine tRNAs. The results obtained are evidence that differences in the primary and secondary structures at the site of methylation are not the deciding factors in the interaction of tRNA with methylases.     

A new quinoline-carbamate aphicide

We found that it was nearly impossible to apply the quinoline-carbamate aphicide per os by means of synthetic diets, owing to its high feeding-deterrent-effect. After application via the roots of the host plant, this systemic compound is deposited on the leaf surface. The results suggest that the toxic effect is not the result of the oral uptake of phloem sap, but of the tarsal contact with the toxicant. Sensitivity of aphids to this compound and LD50-values were determined after topical applications.     

Oxygen intake and walking speed before and after total hip replacement

The objective of the study was to evaluate the walking ability and the energy cost of walking in patients before and after total hip replacement. The oxygen intake and the maximum walking speed were measured immediately before and 6 months after operation in 25 patients. Although the oxygen intake did not change significantly in most patients it was decreased in those patients who before surgery had had the worst walking capacity. The average maximum walking speed almost doubled in the 25 patients.