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Propionic acidaemia (PCCD) or deficiency of propionyl-CoA carboxylase (PCC) is one of the most common organic acidaemias. Recent studies have suggested that this disease can cause somatic or cognitive deterioration even in patients without ketosis or metabolic acidosis, or in cases with unusually late onset. This suggests that for this disease a sensitive yet practical screening procedure is required to achieve early treatment. We conducted a pilot study of gas chromatographic-mass spectrometric screening of 12,000 newborns for PCCD using eluates from dried filter-paper urine collected at 4-7 days of age. Methylcitrate (MC) was targeted for PCCD. For bulk screening, 2-hydroxyundecanoate was used as internal standard; for quantification, stable-isotope-labelled MC was used. Urease pretreatment without fractionation allowed satisfactory recovery and reproducibility of the highly polar MC. We detected an asymptomatic male infant with distinctly elevated MC: the creatinine-corrected level relative to 2-hydroxyundecanoate was 4.8 SD above the normal mean. The MC concentration calculated using the stable-isotope-labelled internal standard was 70.6 mmol/mol creatinine 14.7 SD above the normal mean of 3.70. Parallel analysis of the dried blood spot at 4 days of age by tandem MS showed only borderline elevation of propionylcarnitine. The activity of PCC in lymphocytes was 7% of control. Gene analysis revealed that a single missense mutation, TAT to TGT, resulting in Y435C in the beta chain was present in a homozygous form. Dietary treatment including carnitine supplementation decreased this infant's MC level and to date (at 13 months of age), he shows no neurological or somatic abnormalities.

Ornithine decarboxylase has been measured in midterm mouse placentas by a simple inexpensive method. The reaction vessel was a special plastic scintillation vial. The 14CO2 liberated from dl -1-14C-ornithine was absorbed by a Hyamine hydroxide impregnated blotting paper disc cemented into the vial's cap. This was released into the toluene fluor of another scintillation vial by transfer of the cap after loosening the paper disc. The incubation vial was further adapted by predrilling a hole in its side to permit addition of acid to stop incubation and drive 14CO2 out of solution. This hole was kept sealed with tape. The preference of Hyamine over ethanolamine/2-methoxyethanol mixture (2:1) was established. Also the protective value of EDTA and dithiothreitol and the deleterious effect of freezing and thawing on this enzyme were studied. Mouse placentas contain a relatively large amount of ornithine decarboxylase. This method of assay should be suitable for quantification of other decarboxylases whenever suitable carboxyl-labeled substrates are available.

A comparative examination of Patho-Tec reagent-impregnated paper strips and the corresponding classical biochemical tests for the identification of Enterobacteriaceae was made. Patho-Tec papers appeared to be reliable for the cytochrome-oxidase and phenylalanine-deaminase tests. The urease test papers gave false negative reactions inCitrobacter andEnterobacter isolates, but never inProteus strains. The lysine-decarboxylase test papers gave too many false positive results. These shortcomings of the strips interfere with fast and reliable identification ofSalmonella-like Enterobacteriaceae.