Lorraine T. Miller

Microbiological Assay of Vitamin B-6 in Blood and Urine

Although new, more precise techniques have been developed for the determination of vitamin B-6, the microbiological assay of this vitamin in blood and urine is still an important and valuable method. The assay organism used in our laboratory to measure vitamin B-6 is the yeast, Saccharomyces uvarum (formerly, S. carlsbergensis). Vitamin B-6 determination with this organism is simple, convenient, reproducible, and sensitive. In this paper, we will present the background for our choice of this organism and our procedure for determining plasma and urinary vitamin B-6.

Vitamin B-6 status of children undergoing continous ambulatory peritoneal dialysis

Abstract The purpose of this study was to evaluate the vitamin B-6 status of children undergoing continuous ambulatory peritoneal dialysis (CAPD) and to determine the renal and peritoneal clearance of vitamin B-6 in these children. Eight children, mean age 12 years, were included in the first study. Urine, dialysate and plasma were analyzed for total vitamin B-6 and pyridoxal 5′-phosphate (PLP). Dialysate total protein and serum alkaline phosphatase were also measured and a three day dietary record was obtained. Plasma PLP was measured in six subjects one year following the first study after they had been receiving daily pyridoxine supplements for one year. Mean plasma total vitamin B-6 and PLP were 304 and 25.5 nM, respectively, in the first study. The mean ratio of plasma PLP/total vitamin B-6 was 0.146. Mean plasma PLP in supplemented subjects was 60.4nM. Renal and dialysate clearance of vitamin B-6 was 0.41 and 0.90 mls/min, respectively. Mean dietary intake of vitamin B-6 was 59% of the RDA. CAPD treated children appear to be deficient in vitamin B-6 although dialysate losses are minimal. Pyridoxine supplements of at least 2mg/day are necessary to increase plasma PLP to normal concentrations in these children.

Vitamin Retention During Home Drying of Vegetables and Fruits

The effect of home drying on the retention of several vitamins was measured in some foods commonly dried. Little vitamin C was retained in dried green beans and tomatoes, while more was retained in dried zucchini squash, raspberries, and boysenberries. Retention of carotene (measured only in dried green beans and tomatoes) was almost negligible. Except for blanched green beans, the retention of free folacin was higher than that of total folacin in the dried products. From 60 to 96 percent of vitamin B6 was retained during drying.