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Publisher Summary This chapter discusses a study for comparison of serum vitamin B12 (cobalamin) determination by two isotope-dilution methods and by euglena assay. A microbiological assay was compared with two isotope-dilution assay, one using coated charcoal and the other a solid-phase technique for separation of free and bound cobalamin. Emphasis was laid on samples having low and borderline values of cobalamin in an attempt to clarify which method has the highest power to differentiate between a pathological and a normal cobalamin status. In the microbiological assay, Euglena gracilis of the z strain is used as the test organism. Cyanocobalamin standards were prepared by diluting stock solutions in water. The solid-phase assay used in the study was a commercially available version of the radiosorbent assay of Wide and Killander. In coated-charcoal assay used, an intrinsic factor preparation from hog pyloric mucosa is used as binding protein, and bound and free cobalamin are separated with hemoglobin-coated charcoal. The results showed that the microbiological method gives the lowest results and the radiosorbent method the highest ones. The correlation between all methods is good; the best correlation is obtained between the coated-charcoal and the microbiological method. |
