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In leukocytes a dynamic relationship between the reduced form of ascorbic acid (AA) and its oxidized product dehydro-AA has been described. It is therefore important to know which form of the vitamin predominates when choosing a methodology. The purpose of this study was to find out if the majority of ascorbate in human leukocytes isolated by centrifugation through Percoll is in the reduced AA form by measuring reduced AA by HPLC and comparing the values to those obtained by using the 2,4-dinitrophenylhydrazine (DNPH) method which measures total ascorbate, and quantifying the reduced and oxidized forms of the vitamin in leukocytes using a modification of the DNPH method. There was no significant difference (P greater than .05) between the HPLC and DNPH values for 12 individuals and 87% of the AA was found to be in the reduced form. These results support the assumption that the majority of AA found in a mixed leukocyte population isolated through Percoll is in the reduced form and that both methods can be used for AA measurements.

Rapid, convenient and non-isotopic nucleic-acid hybridization methods are needed for this technology to have practical use in clinical diagnostic tests. A method for hybridization of RNA with a DNA probe in solution followed by capture and measurement of the hybrid is described. DNA probes complementary to 23S rRNAs from Escherichia coli and Bacillus subtilis were labeled with a photoactivable biotin reagent. Hybridization of the biotinylated probes with rRNA was complete in less than 5 min. The resultant hybrids were allowed to bind simultaneously to succinylated avidin immobilized on latex and to beta-galactosidase-labeled Fab' fragments of a monoclonal antibody-specific for DNA:RNA. Finally, beta-galactosidase associated with the captured hybrids was measured colorimetrically. The hybridization method can detect less than 1000 bacteria per assay and has broad specificity to permit detection of the various genera of bacteria that infect the urinary tract.

Erythrocyte fractions of varying density were isolated by discontinuous density gradient centrifugation of washed erythrocytes of five subjects (three adults and two cord bloods). Free and total carnitine concentrations were determined in each gradient fraction to compare the carnitine content of less dense with more dense erythrocytes. Erythrocyte, leukocyte, and reticulocyte counts and hemoglobin were measured on all fractions of each gradient. The density gradient studies showed that the highest proportion of reticulocytes were associated with the least dense gradient fractions of all five subjects. Linear regression analyses revealed significant positive correlations (r = 0.94 to 0.99, P less than 0.02 to P less than 0.001) between the number of reticulocytes per fraction and the total or free carnitine concentrations per fraction for all subjects. No correlation was found between free or total carnitine and hemoglobin, number of erythrocytes, or number of leukocytes per fraction. It appears that erythrocyte carnitine is localized in circulating reticulocytes which have mitochondria and carnitine-dependent fatty acid metabolism.

Six of the human minisatellites detected by DNA fingerprint probes have been localized by in situ hybridization to human metaphase chromosomes. These hypervariable loci are not dispersed at random in the human genome, but show preferential, though not exclusive, localization to terminal G-bands of human autosomes. Two of the proterminal minisatellites are very closely linked to other variable loci. Sequence analysis of one of these additional minisatellites suggests that the two linked minisatellites arose by independent amplification of different repeat units. The proterminal regions of human autosomes may therefore be rich in minisatellites, analogous to the pseudoautosomal terminal pairing region of human sex chromosomes that is similarly abundant in hypervariable minisatellites.