Cited by 888
Queens College, CUNY
Publishes on Trypanosoma species research and implications, Protist diversity and phylogeny, Microbial Community Ecology and Physiology. 149 papers and 5.3k citations.
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SUMMARY. An improved assay of vitamin B 12 is described. The z strain of Euglena gracilis , which grows more vigorously than the bacillaris strain previously used, is recommended. The pattern of B 12 specificity of the two strains appears to be the same. A new medium containing sucrose, aspartic acid, glutamic acid, and glycine at pH 3.6 is well buffered and allows luxuriant growth. Vigorous utilization of sugar appears to depend on readily available nitrogen and a Krebs‐cycle component; these requirements are well met by aspartic acid (or asparagine) and glutamic acid. The proposed procedure is especially suitable for the measurement of B 12 in blood serum because rise in pH and precipitation of serum proteins during incubation are minimized. Like bacillaris , the z strain allows the distinction between “combined” and “uncombined” B 12 in serum. Serum may be an appropriate test material to tell whether such phagotrophs as Peranema can better utilize bound forms of vitamins than can the related osmotrophs. Patterns of B 12 requirements and occurrence are discussed as phylogenetic markers.
alpha-Difluoromethylornithine (RMI 71,782), a specific irreversible inhibitor of the first step in polyamine biosynthesis, that is, the formation of putrescine from ornithine by ornithine decarboxylase, cures mice infected with a virulent, rodent-passaged strain of Trypanosoma brucei brucei. This parasite is closely related to the trypanosomes that cause human sleeping sickness. The drug, which is remarkably nontoxic, was effective when administered in drinking water or by intubation. The ability of the compound to inhibit ornithine decarboxylase in vitro was demonstrated by the reduced amounts of putrescine synthesized from tritiated ornithine in Trypanosoma brucei suspensions. These observations direct attention to polyamine metabolism as a target for chemotherapy of parasitic diseases.
Abstract A microbiologic method based on Lactobacillus casei for assaying folic acid activity in serum is presented. The assay correlates directly with the clinical diagnosis. Comparison with formimino-L-glutamic acid determinations and other microbiologic assay methods shows the assay here described to yield a more dependable estimate of the folic acid status in humans.