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Transfer RNAs from liver and brain of young and old BC3F1 mice were compared in regard to extent of aminoacylation and cochromatographic profiles of isoaccepting tRNA species on reversed-phase columns. Homologous synthetase preparations and optimal aminoacylation conditions were employed, having been determined for each amino acid and found to be the same for those from old and young mice. Small differences were found between tRNAs from young and old mice in the extent of acceptance for arginine and tyrosine in the liver and for aspartic acid in the brain. There were no differences observed between preparations from young and old mice in any of the cochromatographic profiles for the amino acids examined in this study, which included arginyl-, aspartyl-, glutamyl-, histidyl-, leucyl-, lysyl-, phenylalanyl-, seryl-, and tyrosyl-tRNAs from liver and arginyl-, aspartyl-, histidyl-, leucyl-, lysyl-, and seryl-tRNAs from brain. Comparisons of tRNA preparations from fetal and neonatal liver with those from adult liver did reveal both qualitative and quantitative differences. These results suggest that the postulated accumulation of errors as a result of age-related alterations in the translational mechanism does not occur in tRNA or aminoacyl-tRNA synthetases of these two tissues.

The tRNA synthesized by Escherichia coli during chloramphenicol treatment has altered chromatographic properties, as analyzed by reversed-phase chromatography. The data suggest that most of the tRNAs synthesized in the presence of chloramphenicol are immature, chromatographically distinct forms, capable of being converted to mature forms upon removal of chloramphenicol. Methylation of tRNA during chloramphenicol treatment appears to be quantitatively and qualitatively normal. The tRNA synthesized during chloramphenicol treatment differs from normal tRNA mainly in that it contains 60–70% less 4-thiouridine and dihydrouridine. Preliminary experiments indicate that these two minor bases are not required for normal aminoacylation. Phenylalanyl-, valyl-, isoleucyl- and lysyl-tRNAs from untreated and chloramphenicol-treated cells are equally functional in an in vitro hemoglobin-synthesizing system.

Transfer ribonucleic acid (tRNA) profiles in human lymphocytes stimulated by various mitogens have been compared with profiles from nonstimulated cells and from leukemic cells using reversed-phase chromatography. Comparisons of (/sup 3/H)- or (/sup 11/C)uridine- or (/sup 32/P)phosphate-labeled tRNAs showed that the greatest changes in tRNA composition upon phytohemagglutinin (PHA) stimulation occurred in the first 8 h after mitogen addition. Stimulation of lymphocytes by pokeweed mitogen, anti-human immunoglobulin, or bacterial lipopolysaccharide resulted in tRNA species which showed distinct differences from each other and also from the tRNAs produced by phytohemagglutinin stimulation. Leukemic lymphocyte tRNAs showed the most extensive differences in profile when compared with chromatograms from non-neoplastic cells stimulated by a variety of mitogens. Specific isoaccepting species of tyrosyl-, aspartyl-, and phenylalanyl-tRNAs were also compared in PHA-stimulated and resting lymphocytes and no differences were found. When these same species were studied in leukemic cells, tyrosyl-tRNA profiles were shifted to elute at a lower salt concentration, while the aspartyl-tRNA profile showed a new peak not present in noncancerous cells.