Continuous-flow automation of the Lactobacillus casei serum folate assay

Microbiological analysis of 5-formyltetrahydrofolic acid and other folates using an automatic 96-well plate reader

The growth of auxotrophic bacteria remains the method of choice for the determination of biologically active folate metabolites in plasma. This report describes a microbiological assay for folates adapted to use disposable 96-well plates and an automatic plate reader. The modifications in the assay decreased reagent costs and made the analysis of hundreds of samples per day possible with a sensitivity limit of 10 fmol of (6S)-5-formyltetrahydrofolic acid. This limit compares favorably with that of previously reported, more laborious methods. The unnatural 6R diastereomer of 5-formyltetrahydrofolic acid did not interfere with the microbiological assay of the natural 6S diastereomer.

Anaemia in patients with myelomatosis

Twenty-four untreated patients with myelomatosis were studied in order to characterize their anaemia, using standard haematological and ferrokinetic techniques, together with measurements of circulating erythropoietin, erythropoietin sensitivity of marrow cultures and in vitro measurements of haem synthesis. There is a reduction in total erythroid output by the marrow, together with a minor degree of plasma expansion. In patients with normal renal function there is an appropriate increase in erythropoietin in response to anaemia, but in a few cases there may be reduced response of CFU-E to the hormone in vitro. No abnormality of iron status or haem synthesis was found. One case of folate deficiency was discovered.

Aminoacid infusion induced depression of serum folate after cholecystectomy

Aminoacid solutions were given to cholecystectomy patients for a period of 48 h starting 24 h after the operation. Infusion of the aminoacid component of parenteral nutrition regimens, without calorie source, frequently led to an acute fall in the serum folate concentration. The degree of depression varied with different commercial aminoacid solutions. (Aminoplex 14 = c.60%, Vamin = 30%, Aminosol = c.0%). The folate depression by Vamin infusion was unaffected by supplementation with L-methione but was alleviated by the addition of glycine. As a consequence of surgical operation itself, folate values fell by 37% during the 24 h following cholecystectomy. This seems likely to increase the risk of haematological toxicity (i.e. acute leukopenia and thrombocytopenia) in patients given folate-free parenteral nutrition after a surgical operation.