Biomedical subjects
P Hamernyik
Publications and source records attributed to P Hamernyik.
Ascorbic acid in lymphocytes: cell preparation and liquid-chromatographic assay.
Measurements of ascorbic acid concentration in leukocytes by "high-performance" liquid chromatography (HPLC) provides better nutritional assessment, leading to better management, particularly of presymptomatic and critically ill patients. This procedure includes a simple, reproducible cell-separation technique that requires no more than 2 mL of whole blood. Cell populations are separable with greater than 95% purity and greater than 99% viability. Ascorbic acid is assayed by HPLC. The vitamin can be reproducibly quantified in concentrations as low as 0.1 microgram/mL of cell extract. The chromatographic procedure is very rapid, analysis being completed within 15 min after specimen preparation. The assay is suitable also for urine and protein-free filtrates of plasma and of other biological materials. Reference intervals for plasma, mononuclear leukocytes, and polymorphonuclear leukocytes were established. A preliminary clinical evaluation revealed that hospital patients were at a greater risk of ascorbic acid deficiency than expected.
Inherited deficiency of delta-aminolevulinic acid dehydratase.
Delta-aminolevulinic acid dehydratase (ALA-D) is the second enzyme in the porphyrin-heme pathway and converts delta-aminolevulinc acid (ALA) to porphobilinogen (PBG). A family is reported with an inherited deficiency of red cell ALA-D activity occurring over three generations in an autosomal dominant pattern. Intial experiments support the hypothesis that the mutation in this family may affect a regulatory gene, but enzyme purification and further study are required. Although no clinical manifestations of deficient ALA-D activity have been found in affected persons, families such as this may be at increased risk for the serious consequences of lead poisoning, which produces marked inhibition of ALA-D activity.
Modified erythrocyte uroporphyrinogen I synthase assay, and its clinical interpretation.
Assay of erythrocyte uroporphyrinogen I synthase is an accepted diagnostic test for acute intermittent porphyria, particularly in those individuals who are asymptomatic or in whom the disease is not biochemically manifested by excretion of excess porphyrin precursor. The assay described is based upon a coupled-enzyme procedure in which added delta-aminolevulinic acid and its dehydratase present in erythrocytes are used to generate porphobilinogen as substrate for uroporphyrinogen synthase. Zinc and dithiothreitol are added with preincubation to give maximum activity and reproducibility. These agents also prevent inhibition by lead. Healthy young women had a mean activity of 40 nmol of porphyrin formed per milliliter of erythrocytes per hour, men and activity of 38 nmol/ml/h. Preparation of control specimens is described. This assay gave within-day CVs ranging from 1.9 to 2.8%. Precautions in interpretation of results are discussed.
Erythrocyte uroporphyrinogen I synthase activity in diagnosis of acute intermittent porphyria.
Measurement of the activity of uroporphyrinogen I synthase provides an excellent laboratory aid in the diagnosis of acute intermittent porphyria, particularly in those patients who are asymptomatic or in whom the disease is not biochemically manifested by porphyrin precursor excretion. We describe here a simplified fluorometric method for measuring the activity of this enzyme in whole blood. The assay is based upon a coupled-enzyme procedure in which added delta-aminolevulinic acid and the dehydratase that is present in erythrocytes are used to generate porphobilinogen as substrate for uroporphyrinogen synthase. After appropriate incubation the protein is removed we sensitivity, specificity, and precision of the assay compare well with previously described procedures. Activity in nonporphyric male subjects was 31 (SD, 6.0) nmol of porphyrin formed per milliliter of erythrocytes per hour at 37 degrees C. Application of the method for identifying gene carriers of acute intermittent porphyria is demonstrated in three generations of an affected family.
Coordination of university and private hospital educational programs.
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