Eugene Roberts

Changes with Age in Amino Acid Composition of Arterial Elastin.

Summary Comparative analyses of elastin from young and old aortas reveal a pattern of characteristic age changes consisting of increase in specific gravity, calcium, and free carboxyl groups. There is an underlying shift in relative amino acid composition. In contrast to the aorta, the pulmonary artery shows minimal age changes.

gamma Aminobutyric acid content and glutamic decarboxylase activity in developing mouse brain.

Summary Brain weights, content of γ−aminobutyric acid, and the activity of glutamic acid decarboxylase were determined in brains of mice at various stages of postpartum development. All of the quantities studied increased greatly during postnatal development, attaining their maximal levels at 90 days. The increase in decarboxylase activity was slower during the first two weeks than that of the weight and the γ−aminobutyric acid. A cytological study revealed that the period of greatest increase in glutamic acid decarboxylase activity is correlated with the period of greatest increment in features which are related to maturation of the central nervous system. Examination of selected samples of nervous tissues of the cat, dog, and rabbit showed that the glutamic decarboxylase-γ−aminobutyric acid system is present chiefly in the gray matter of the central nervous system. The results of the present study were correlated with relevant data from the literature.

Amino Acids of Nervous Tissue

Summary The pattern of free amino acids in mouse brain, as shown by 2-dimensional paper chromatography, does not reflect the amino acid composition of the brain as a whole. The brains of mice of several strains and various parts of the nervous system of the rabbit were studied. Free glutamic and aspartic acids, γ-aminoibutyric acid, taurine, glutamine, cystine, serine, glycine, alanine, valine, and the leucines were detected consistently. The variations in these constituents with age, sex, and strain in mice are discussed. The sciatic nerve in the rabbit had considerably smaller quantities of detectable constituents than the various parts of the central nervous system. A transplantable neuroblastoma in mice had a pattern of free amino acids which was similar to that found in other malignant tissues and in brains of 15-day embryos and significantly different from that found in all of the other samples of mouse brain examined. The suitability of the chromatographic method for the study of changes in the free amino acids of brain homogenates is indicated.

Influence of cortisone on free hydroxyproline in the developing chick embryo.

Summary A chromatographic examination was made of the free amino acids of tissues of normal and cortisone-injected chick embryos. The content of free hydroxyproline was increased markedly in the tissues of the cortisone-treated embryos. The results were confirmed by a colorimetric procedure. With the exception of glycine, in which increases were noted in some instances, the other amino acids showed no consistent changes as a result of the injection of cortisone. The injection of Δ 1 -17 α-hydroxy progesterone produced slight decreases in free hydroxyproline content.

Influence of Administration of ACTH on Urinary Amino Acids

Summary Typical results are presented showing the influence of ACTH a dministration in the human on the urinary excretion of nitrogenous substances. The hormone evoked notable increases in the excretion of amino acids, ammonia, urea, uric acid, and some undetermined nitrogenous constituents. Twodimensional chromatograms revealed some of the detailed changes in the excretion of both free and bound amino acids. Microbiological determination of some of the amino acids gave results which were concordant with the chromatographic findings. All of the urinary nitrogenous constituents returned to normal levels shortly after cessation of the treatment. The possible significance of some of the findings is indicated.

Inhibition of utilization of glutamic acid by Lactobacillus arabinosus.

Summary 1. Ten compounds were tested for inhibition of utilization of glutamic acid and glutamine by Lactobacillus arabinosus. 2. DL-α-methylglutamic acid and one of the diastereoisomeric racemates of β-hydroxyglutamic acid were potent competitive inhibitors of glutamic acid utilization. None of the compounds tested was a glutamine inhibitor. 3. The results indicated that the two active compounds prevented the synthesis of glutamine from glutamic acid by the bacteria. 4. Experiments in which the time-course of growth was followed showed that under certain conditions the inhibition by α-methylglutamic acid could be overcome. A possible explanation was suggested for this finding and the importance of taking readings at several time intervals was emphasized.

Studies of transamination.

Abstract 1. 1. In addition to previously described transaminations, it has been found that acetone powders of brain, liver, Escherichia coli , and Aspergillus fumigatus can catalyze the transamination of δ-aminovaleric acid and α,γ-diaminoglutaric acid with α-ketoglutarate. 2. 2. The extent of transamination with α-ketoglutarate of the 3–6-carbon straight-chain ω-amino monocarboxylic acids was compared with the corresponding α,ω-amino acids, and the results were discussed.

Amino Acids of Turnip Yellow Mosaic Virus.

Summary 1. The amino acids of the protein of crystalline turnip yellow mosaic virus were studied by paper chromatographic and microbiological technics. 2. Virtually all the protein was accounted for by microbiological assay for 18 amino acids performed on hydrolysates of the protein. 3. The protein was characterized by the presence of large amounts of serine, threonine, and proline. Hydroxyproline was not detected.

Amino Acids of Bence-Jones Protein

Summary 1. Hydrolysates of a sample of Bence-Jones protein isolated from the urine of a patient with multiple myelomatosis were examined by paper chromatography. Quantitative estimations of 18 amino acids were also made by microbiological methods. 2. The protein was characterized by a very low content of methionine (0.12%) and by relatively large amounts of serine, threonine, and proline. No evidence of the presence of hydroxyproline was obtained. 3. The analyses accounted for 93% of the nitrogen present in the protein.

Inhibition of utilization of aspartic acid for growth of Leuconostoc mesenteroides P-60.

Summary β-DL-Aspartylhydrazide and a-DL-methylaspartic acid were found to be good inhibitors of the utilization of L-aspartic acid for the growth of L. mesenteroides P-60. The specificity of the inhibition was shown by the finding that the corresponding analogues of glutamic acid were much less active.