Browsing by Author "Drake, J.C."
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Item Identification of anti-plasmodium falciparum antibodies in human breast milk(Scandinavian Journal of Immunology, 1992) Leke, R.G.F.; Ndansi, R.; Southerland, N.J.; Quakyi, I.A.; Graves, P.M.; Drake, J.C.; Allegra, C.J.Malarial infections are rarely observed in neonates. It has been postulated that some immunity may be passively transferred during nursing, but anti-malarial antibodies (Abs) have not been detected in human milk. In this study milk samples collected 2-14 days after parturition from women at the Central Maternity Hospital, Yaounde were evaluated for total IgG and IgA antibody levels by radial diffusion, protein composition by SDS-PAGE, anti-malarial antibodies using an isotype-specific immunofluorescence assay, and the ability to immunoprecipitate Plasmodium falciparum antigens metabolically labelled with 35S-methionine. Results showed that anti-P. falciparum antibodies were present in breast milk, and that paired milk and serum samples from individual women contained Abs that recognized similar malarial antigens.Item Mechanism of pyrimethamine resistance in recent isolates of plasmodium falciparum(Antimicrobial Agents and Chemotherapy, 1984) McCutchan, T.F.; Welsh, J.A.; Dame, J.B.; Quakyi, I.A.; Graves, P.M.; Drake, J.C.; Allegra, C.J.Clones of Plasmodium falciparum prepared from recent isolates of infected blood were studied to determine the molecular mechanism of naturally occurring pyrimethamine resistance. Total DNA, as well as thymidylate synthetase and dihydrofolate reductase activities, were characterized from these lines. Restriction analysis of DNA from pyrimethamine-susceptible and -resistant lines of the parasite showed no obvious amplification of any DNA fragment. Further, analysis of DNA from resistant and susceptible lines by centrifugation in cesium chloride-ethidium bromide revealed no extrachromosomal amplification in the resistant line. Comparison of the dihydrofolate reductase enzyme activity in the two lines revealed similar K(m)s for substrate but a large difference in the inhibition constant for pyrimethamine. Additionally, the enzyme from the resistant line was considerably more stable in vitro than the corresponding enzyme from the susceptible line. The thymidylate synthetase activity in the two lines was similar and unaffected by pyrimethamine. The mechanism of drug resistance in this isolate involves altered properties of the dihydrofolate reductase conferring both a different affinity for the drug and increased stability.