The APS Journal Legacy Content is the corpus of 100 years of historical scientific research from the American Physiological Society research journals. This package goes back to the first issue of each of the APS journals including the American Journal of Physiology, first published in 1898. The full text scanned images of the printed pages are easily searchable. Downloads quickly in PDF format.

Abstract— —Glutamic acid, glutamine, GABA and aspartic acid exhibited postnatal increases in the developing mouse brain at the same time that the other amino acids, both essential and non‐essential, of the pool decreased. The most significant decreases were observed in the concentrations of taurine, phosphoethanolamine, glycine and alanine. The period of rapid accumulation of the members of the glutamic acid family in the mouse brain was concurrent with dramatic increases and decreases in brain weight and water content, respectively.

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THE broad objective of the present investigation was to study the distribution and changes in easily extractable (free) amino acids and other ninhydrin-positive substances in the rat brain during development. These data are needed to provide basic information on the metabolic factors operative during structural and functional maturation of the brain and to lead to a better understanding of the correlation between the changes in amino acid metabolism and specific structural features at various developmental stages. The rat is particularly useful for such an investigation since its brain is unmyelinated at birth (WAELSCH, SPERRY and STOYANOFF, 1941). Myelination begins at about 12 days and is completed at about 40 days in this species.With the development of a more refined technique of column chromatography (SPACKMAN, STEIN and MOORE, 1958) for the separation and identification of amino acids and their peptides, it has become possible to determine with precision and accuracy their concentration in biological extracts. Column chromatographic studies of TALLAN, MOORE and STEIN (1954) showed the presence of a large number of ninhydrin-positive compounds in the cat brain. FRIEDBERG and GREENBERG (1947) reported that rat brain has a high concentration of free amino acids, second only to that in kidney. Although the physiological significance of the high amino acid content in the brain is not yet clearly understood, studies of GMTONDE and RICHTER (1955RICHTER ( , 1956 with isotopically labelled amino acids revealed that free amino acids are rapidly incorporated into the brain proteins. Recent studies Of SHAW and HIENE(I965) established the presence of fifty-eight ninhydrin positive substances, including nine unknown peaks in four different areas of the rat brain with the column chromatographic methods of PIEZ and MORRIS (1960) and of HAMILTON (1963).In the present study the changes in free amino acid pool of the rat brain have been investigated during ontogeny. An attempt was made to correlate the variation in amino acid pool with the chemical and physiological maturation of the brain. METHODS A N D MATERIALSAlbino rats of the Wistar strain bred in our animal colony and reared under the same standards of management and nutrition were used throughout this experiment. These animals received Wayne Lab Blocks ration and were handled from birth by various workers. No attempt was made to control the environment beyond temperature control which is held at 72°F. The environment hence was rich in sensory stimuli. The whole brains were analysed at the following ages: 0, 1, 7, 14, 21,30,60,% 120 days after birth, and adult. For each age group the number of animals empIoyed was varied to obtain sufficient material for analysis (the numbers of animals in each age group are shown in Table 2). In any age group the average value of three determinations represents brains drawn from several litters. The rats were not starved for this series of experiments since HAKKINEN and KULONEN (1963) established that fasting itself does not have any...