(15,16).
RESULTSVitamin A supplementation resulted in prominence of lipocytes without significantly altering the light microscopic appearance of paraffin-embedded material. The total amount of collagen estimated by determination of hepatic hydroxyproline was the same in rats supplemented with vitamin A and rats not supplemented, the collagen concentration increasing in CC14-treated animals from 1.00 mg to 1.71 mg of hydroxyproline per g of dried, defatted tissue at the end of 6 weeks, and from 1.17 mg to 5.03 mg of hydroxyproline after 12 weeks. Light and electron microscopy After 1 or 2 weeks' duration of the experiments, the livers displayed centrolobular necrosis with steatosis in the surrounding parenchyma. The necrotic area contained, besides macrophages, conspicuous numbers of lipocytes, as shown by many Phosphin-3R-positive fat droplets imparting a fading vitamin A autofluorescence. Lipocytes were also recognized in 1 ,um thick sections and under the electron microscope. They were far more conspicuous, and indeed presented a striking appearance, after vitamin A supplementation (Fig. 1), when the cells appeared larger and contained a greater number of fat droplets, the latter imparting a strong vitamin A autofluorescence. They were intermixed with pigmented macrophages containing granules giving a yellow, nonfading autofluorescence, presumably of lipofuscin. Fibroblasts were not conspicuous in the necrotic area in the first 2 weeks.In animals treated for longer periods, connective tissue septa linking central zones with each other were observed after 6 weeks; after 12 and 24 weeks, the septa extended to the portal
Spectrophotofluorometric micromethods for the determination of phenylalanine and tyrosine on 25 µl of serum are described. These methods were applied to detect phenylketonuria among homozygotes and heterozygotes and in the newborn population. The data presented agree with those previously reported. (1) Phenylketonurics have markedly elevated serum phenylalanine and lower serum tyrosine than the controls. (2) The heterozygotes have a higher fasting serum phenylalanine and, after a standard oral phenylalanine test, show a higher and more prolonged rise of serum phenylalanine than the controls. There was a lesser increase of serum tyrosine after phenylalanine loading in the heterozygotes than the controls. (3) Premature infants of low birth weight have higher serum phenylalanine and tyrosine levels than normal birth weight infants, presumably due to enzyme immaturity. Simultaneous determinations of serum phenylalanine and tyrosine will differentiate newborn infants who are suspected to be phenylketonurics from the homozygotes (phenylketonurics).
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