8 METABOLISM IN THE NORMAL FUNCTIONAL STATE 



considered to be guanine. However, not until 1954 was it again 

 confirmed in rat brain (Schmitz et al.y 1954). Subsequently the 

 presence of guanine in the acid-soluble nucleotides of brain was 

 confirmed by Thomas (1957) using Kerr's technique combined 

 with paper partition chromatography, and by Heald (1957^) who 

 isolated and characterized guanosine di- and triphosphates from 

 extracts of guinea pig cerebral cortex and whole ox brain. Of the 

 other nucleotides listed, specific roles for the uridine derivatives 

 have not yet been fully described in brain, though studies on the 

 conversion of ^^C labelled glucose to cerebrosidal galactose (Moser 

 and Karnovsky, 1958) suggest that the mechanism for the con- 

 version of UDP glucose to the galactose derivative (Leloir, 1953) is 

 operative (see also Maxwell et al, 1955; Burton et al., 1958). 

 Uridine derivatives of hexoses, hexuronic acids and amino sugars 

 are known to participate widely in the synthesis of polysaccharides 

 and of mucopolysaccharides in plant and animal tissues (Utter, 

 1958) and may be expected to be similarly involved in cerebral 

 tissues. The formation of these derivatives requires sources of 

 uridine triphosphate and, in the case of the N-acetyl glucosamine 

 derivative, a source of glutamine, ample quantities of which exist 

 in brain (Weil-Malherbe, 1952). Uridine diphospho-N-acetyl 

 glucosamine is readily converted to uridine diphospho-N-acetyl 

 galactosamine by a liver enzyme (Cardini and Leloir, 1957) and a 

 similar conversion is likely in brain. Such a possibility makes the 

 finding of the glucosamine derivative of interest in view of the 

 presence of N-acetyl galactosamine in brain gangliosides (Blix 

 et al., 1952; Svennerholm, 1956^), which are included in strandin 

 (Folch et ai, 1951 ; Svennerholm, 19566), and the accumulation of 

 these lipids in the brain in the Tay-Sachs and Niemann-Pick 

 diseases (see for example Klenk et al., 1957; Thannhauser, 1957). 

 The presence of inosine monophosphate, but not the di- or 

 triphosphate is indicative of its probable mode of formation as a 

 de-amination product of adenosine monophosphate (Kerr, 1942; 

 Muntz, 1953; Weil-Malherbe and Green, 1955) a process which, 

 curiously, requires adenosine triphosphate. Cytidine triphosphate 

 has been shown to be essential in the synthesis of lecithin in brain 

 dispersions (McMurray et al., 1957), while the participation of the 

 di- and triphosphopyridine nucleotides in the oxidation reduction 

 reactions during cerebral respiration is well known and fully 

 documented (Mcllwain, 1957, 1959). Fuller discussions of the 



