Abstract
Extract: The incorporation of L-phenylalanine-14C into protein of several brain areas and into liver of the miniature pig has been studied in vivo. A sequential decrease (approximately 50%) in incorporation of labeled phenylalanine occurred during the first day of life in all brain regions (fig. 1). There was no important difference in degree of incorporatn ioin the three brain regions examined. Labeling of liver protein was roughly threefold higher than in brain protein. A considerably smaller postnatal decrease of labeling of liver protein occurred in proportion to the total initial count.
Premature delivery by hysterectomy at two different conceptual ages resulted in a similar reduction of labeling of brain protein fractions, suggesting that birth rather than the conceptual age of the animal was the relevant factor (figs. 2 and 3).
Radioactivity in the trichloracetic acid-soluble fraction (free amino acids) of all brain areas increased during the first day of life, suggesting that the decreased incorporation of labeled amino acid was not a function of failure of the tracer to enter into brain substance (fig. 4).
Expression of the radioactivity of protein in the brain regions as a function of radioactivity of liver protein established that while there is some postnatal decrease of incorporation into liver protein, there is a relatively greater decrease of incorporation into various brain regions (table I).
Speculation: The timing of the abrupt decrease of amino acid incorporation into brain protein that occurs postnatally may be an important factor in determining subsequent development of the central nervous system. Prematurely induced birth apparently is associated with a premature decrease of incorporation rate. This may have significance in regard to the high incidence of neurological complications found in prematurely born human infants.
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Schain, R., Carver, M. & Copenhaver, J. Postnatal Changes in Protein Metabolism of Brain: I. Studies in Newborn Miniature Pigs at Varying Conceptual Ages. Pediatr Res 3, 135–139 (1969). https://doi.org/10.1203/00006450-196903000-00005
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DOI: https://doi.org/10.1203/00006450-196903000-00005
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