Conventional histological methods were used to screen for myelinopathy. Samples from representative levels in the neuraxis were examined, including myelinated regions of the brain stem. Special stains for myelin were used in cases showing spongioform change.The HCP content of brain tissue was determined by mass spectrometry after purification of extracts. A cerebral hemisphere sample was examined in each of the 20 infants and a portion of brain stem from five infants. Brain stored in formalin was used since HCP can be recovered from brain after years in formalin and HCP does not leach into the fixative.4 Also Vaterlaus (personal communication), using sensitive quantitative methods, had found no evidence that formalin extracted hexachlorophane from brain in the rat. Half-gram quantities were homogenised in 5 ml 0 4 mol/l phosphate buffer pH 7 5, to which 25 ng HCP (Methylene-14C) had been added. The homogenate was then extracted twice with 2 vol redistilled benzene. The extract was reduced in volume to about 1 ml and acetylated with 0-2 ml pyridine-acetic anhydride (1:1 v/v) for 15 min at 65°C. The acetylation products were chromatographed on a silica gel column 40 x 4 mm. The hexachlorophane diacetate in the residues was 25
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