Infants physiologic considerations

The metabolism of newborn infants during their first week of life is characterized by an increased breakdown of nucleoproteins leading to transient hyperuricemia and hyperuricosuria which is particularly enhanced in infants with hemolytic diseases. Furthermore, there are physiologically considerable changes in the concentration of calcium in the blood of newborns. 

The affected infants have a normal plasma concentration of biotin and excrete normal amounts of biotin in the urine. Skin fibroblasts have extremely low activities of aU four biotin-dependent carboxylases when they are cultured in media containing approximately physiological concentrations of biotin. But, culture with considerably higher concentrations of biotin results in normal activity of aU four carboxylases. The defect is in the affinity of holocarboxylase synthetase for biotin (its is 20- to 70-fold higher than normal). 

Fructose crystallizes well when pure. It is much more soluble and considerably sweeter than common sugar. It is a physiological sugar in every sense of the word. Now that we have analytical methods capable of distinguishing fructose from glucose certainly, it has been shown that fructose is normally present in human blood (71). In embryonic and newborn infants, the level is much higher than in adults (5). Fructose is also the predominant sugar of seminal fluid and its concentration has an important effect upon the motility of spermatozoa (38). 

Short-chain fatty acids (SCFAs) are of considerable importance to the physiological effect of the intestinal microbiota. They are the fermentation product of bacteria in the colon and are therefore an important characteristic feature of the intestinal microbiota (60). Compared to formula-fed infants, the profile of SCFAs differs considerably from that of breastfed infants. On supplementing an infant formula... 

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