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and P e d i a t r i c s , New Haven. Inherited methylmalonicacidemia (MM-emia) due t o d e f i c i e n t a c t i v i t y of methylmalonyl-CoA mutase may be caused by an abnormal mutase apoenzyme or by reduced holoenzyme a c t i v i t y secondary t o impaired synthesis of t h e mutase-requiring coenzyme, 5'-deoxyadenosylcobalamin (Ado-Cbl).. We studied Ado-Cbl synthesis i n 5 f i b r o b l a s t l i n e s from unrelated p a t i e n t s who have MM-emia due t o defective cobalamin (vitamin B12) metabolism. Their whole c e l l s i n c u l t u r e f a i l t o synthesize Ado-Cbl but make normal amounts of t h e other cobalamin coenzyme, methy lcobalamin.After breaking t h e c e l l s t o define t h e s t e p s i n Ado-Cbl synthesis, we assayed t h e f i n a l s t e p which combines the reduct i o n of cob(1I)alamin t o cob(1)alamin and the adenosylation of cob(1)alamin. Subcellular f r a c t i o n a t i o n s t u d i e s localized t h i s a c t i v i t y t o mitochondria. I n crude broken c e l l e x t r a c t s , enzyme a c t i v i t y was d e f i c i e n t or absent i n 3 of t h e 5 mutant c e l l l i n e s (4,0,0 pg Ado-~bl/mg protein/30 min;control l i n e s , 23 + 8). The other two MM-emia l i n e s had normal a c t i v i t i e s (23 and 17). These r e s u l t s e s t a b l i s h deficiency of Ado-Cbl synthesizing enzyme a s one cause of abnormal cobalamin metabolism and MM-emia. The two MM-emia l i n e s t h a t had normal enzyme a c t i v i t y suggest t h e r e i s f u r t h e r heterogeneity within the disorders of cobalamin metabolism a s well a s i n the MM-emia phenotype.IS CYSTINE ESSENTIAL FOR PREMATURE INFANTS? John I . Malone, John S. Curran, and Lewis A. Barness. Univ. of S. Fla. and Tampa General Hospital, Dept. of P e d i a t r i c s , Tampa 33620.Growth i n i n f a n t s (weight 1000-200f gms, 26-32 wks gestation) fed a commercially a v a i l a b l e low c y s t i n e formulawas not s i g n i f i c a n t l y d i f f e r e n t from those fed a formulation cont a i n i n g twice t h e d i e t a r y cystine. The formulas were i d e n t i c a l with t h e exception of p r o t e i n qua1ity;the low cystine formula contained 13mg/100ml and t h e high cystine formula 24mg/100ml. There was no s i g n i f i c a n t difference i n growth r a t e of i n f a n t s , i n t h e serum concentration o r t h e t i s s u e l e v e l s (glutathione) of c y s t i n e i n t h e two groups. Cystathionase act i v i t y i n t h e l i v e r has been reported t o be absent i n premature i n f a n t s . These r e s u l t s i n d i c a t e t h a t t h e low c y s t i n e formula contains adequate c y s t i n e f o r normal growth of premature inf a n t s & provides normal serum & t i s s u e l e v e l s of t h i s amino acid. W e have postulated (APS-SPR, Apr. '72) t h a t s h o r t and/or medium chain f a t t y acid accumulation i s important i n t h e pathogenesis of RS, causing mitochondria1 swelling. c e r e b r a l edema, hypoglycemia and f a t t y viscera. This study r e p o r t s gas chromatographic q u a n t i t a t ...

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Dosages of 20 and 10 ppm methylmercury were toxic to rabbits while 1 ppm did not produce clinical signs or death. Serum alkaline phosphatase levels were elevated in all rabbits exposed to methylmercury. Methylmercury-exposed rabbits challenged to A/PR8 influenza virus had hemagglutination inhibition titers as much as four times lower than those of controls. Histopathologic lesions were found in the cerebellum of rabbits that died. The most significant features of this study were that methylmercury chloride suppressed the humoral immune system and resulted in increased serum alkaline phosphatase levels, which may aid in diagnosis when methylmercury poisoning is suspected.