Effect of fibronectin on the Crithidia luciliae test for anti-double-stranded DNA antibodies.
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The various tests for anti-double-stranded DNA antibodies do not always agree. Plasma fibronectin specifically binds DNA, is a component of immune complexes, and shows variations in concentration with disease activity in systemic lupus erythematosus. It may therefore interfere with the detection of DNA autoantibodies. This possibility was examined in a series of studies using the Crithidia luciliae test. Studies were based on serum samples received during one year (250 samples). Serum samples from 50 patients which were positive or weakly positive in the C luciliae test were used. In blocking experiments fibronectin was added either to the wells or to the serum. In a second series of experiments fibronectin was depleted by affinity chromatography from six serum samples with weak anti-DNA staining. Preincubation of wells with fibronectin or addition of fibronectin to serum invariably blocked the interaction of anti-DNA antibodies with the C luciliae kinetoplast. When fibronectin was removed from serum the intensity of staining was increased. These results indicate that fibronectin influences the detection of anti-double-stranded DNA antibodies using C luciliae and may explain the disparity between the results of different tests for DNA antibodies. Furthermore, the unmasking of positive reactivity when fibronectin is removed from serum has implications for the diagnosis and treatment of systemic lupus erythematosus. (+info)
Host modulation of parasite competition in multiple infections.
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Probing mixed-genotype infections II: high multiplicity in natural infections of the trypanosomatid, Crithidia bombi, in its host, Bombus spp.
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Inhibitors of ergosterol biosynthesis and growth of the trypanosomatid protozoan Crithidia fasciculata.
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Six nitrogen-, sulfur- and cyclopropane-containing derivatives of cholestanol were examined as inhibitors of growth and sterol biosynthesis in the trypanosomatid protozoan Crithidia fasciculata. The concentrations of inhibitors in the culture medium required for 50% inhibition of growth were 0.32 microM for 24-thia-5 alpha,20 xi-cholestan-3 beta-ol (2), 0.009 microM for 24-methyl-24-aza-5 alpha,20 xi-cholestan-3 beta-ol (3), 0.95 microM for (20,21),(24,-25)-bis-(methylene)-5 alpha,20 xi-cholestan-3 beta-ol (4), 0.13 microM for 22-aza-5 alpha,20 xi-cholestan-3 beta-ol (5), and 0.3 microM for 23-azacholestan-3-ol (7). 23-Thia-5 alpha-cholestan-3 beta-ol (6) had no effect on protozoan growth at concentrations as high as 20 microM. Ergosterol was the major sterol observed in untreated C. fasciculata, but significant amounts of ergost-7-en-3 beta-ol, ergosta-7,24(28)-dien-3 beta-ol, ergosta-5,7,22,24(28)-tetraen-e beta-ol, cholesta-8,24-dien-3 beta-ol, and, in an unusual finding, 14 alpha-methyl-cholesta-8,24-dien-3 beta-ol were also present. When C. fasciculata was cultured in the presence of compounds 2 and 3, ergosterol synthesis was suppressed, and the principal sterol observed was cholesta-5,7,24-trien-3 beta-ol, a sterol which is not observed in untreated cultures. The presence of this trienol strongly suggests that 2 and 3 specifically inhibit the S-adenosylmethionine:sterol C-24 methyltransferase but do not interfere with the normal enzymatic processing of the sterol nucleus. When C. fasciculata was cultured in the presence of compounds 5 and 7, the levels of ergosterol and ergost-7-en-3 beta-ol were suppressed, but the amounts of the presumed immediate precursors of these sterols, ergosta-5,7,22,24(28)-tetraen-3 beta-ol and ergosta-7,24-(28)-dien-3 beta-ol, respectively, were correspondingly increased. These findings suggest that 5 and 7 specifically inhibit the reduction of the delta 24(28) side chain double bond. When C. fasciculata was cultured in the presence of compound 4, ergosterol synthesis was suppressed, but the sterol distribution in these cells was complex and not easily interpreted. Compound 6 had no significant effect on sterol synthesis in C. fasciculata. (+info)
Seasonal variability of prevalence and occurrence of multiple infections shape the population structure of Crithidia bombi, an intestinal parasite of bumblebees (Bombus spp.).
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