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FIG. 1. Scheme of the biosynthetic pathway for bile acid synthesis from cholesterol indicating the position in the pathway of known inborn errors in bile acid synthesis. pathways in bile acid synthesis. In particular, these data indirectly serve to support the concept that side-chain oxidation can precede the nuclear changes in the synthesis of bile acids and that these alternative pathways have particular relevance in early life. For example, 6a-hydroxylation and lp-hydroxylation of the steroid nucleus are important pathways in the fetu~~~.~' and account for a high proportion of the biliary bile acids. The presence of many tetrahydroxylated bile acids in the rneconi~ m~~.~ bnd urinez4 of healthy newborns shows that these pathways persist beyond birth (Fig. 2). This is also evident from studies of the biliary bile acid composition of the gastric aspirate of newborn infants with high intestinal bl~ ckage,~~.~~ in whom the …