116 



HAROLD KOEiNIG 



_h h K. 



Rt. temporal lobe 



^MA/n/j/i.v'Y^ 



Ll. temporal lobe 



Transverse temporal 



Fig. 10. EEG 6 days after 12 mg FUR into right temporal lobe. Note seizure ac- 

 tivity. Pentobarbital anesthe.sia. 



acid, the natural precursor of pyriniidiiies in the nervous system. These 

 studies have disclosed that FO is efficiently converted into the followina, acid- 

 soluble nucleotides in nervous tissue: fluorouridine monophosphate, diphos- 

 phate, and triphosphate: fluorouridine diphosphate-2,lucose and diphosphate- 

 acetyl2,lucosamine, and fluorocytidine monophosphate (Fig. 11). FO is in- 

 corporated into RNA as fluorouridine monophosphate, but is not incorporated 

 into DNA. Unlike FO, 5-fluorouracil (FU), is not conxerted efficiently into 

 acid-soluble and RNA nucleotides in the feline neiuaxis. Uracil itself also is 

 poorly metabolized by this tissue. 



These observations suggest that nucleoside phosphorylase, the enzyme 

 which converts pyrimidine bases to their ribosides, is present in scanty 

 amounts in the central nervous system of the cat. Poor anabolic conversion 



