This study analysed the suramin sensitivity of 29 stocks of Trypanosoma evansi isolated from Egypt, Sudan, and Indonesia and compared the results with the isoenzyme banding patterns of 20 soluble ...enzymes in these stocks of T. evansi. The results showed that the type VII banding pattern of malic enzyme was found only in T. evansi stocks which were highly resistant to suramin.
Tawe, W., Walter, R. D., and Henkle-Dührsen, K. 2000. Onchocerca volvulus superoxide dismutase genes: Identification of functional promoters for pre-mRNA transcripts which undergo trans-splicing. ...Experimental Parasitology94, 172–179. The genes encoding three forms of superoxide dismutase, the cytosolic and extracellular CuZn superoxide dismutases and the mitochondrial Mn superoxide dismutase, were isolated from an Onchocerca volvulus λ fix II genomic library. Genomic Southern blot analyses indicate single-copy genes in the O. volvulus genome. The O. volvulus cytosolic and extracellular CuZnSOD genes (Ov-sod-1 and Ov-sod-2) are separated by 0.8 kb of sequence and are convergently transcribed. Since the transcripts from all three sod genes are trans-spliced, the transcription start point of each gene was determined in a heterologous system that lacks trans-splicing machinery by in vitro transcription using Drosophila embryo nuclear extracts, followed by primer extension experiments. The ability of the 5′ flanking region of the genes encoding the three Ov-SODs to promote transcription was further examined in transient transfections of Chinese hamster ovary cells. In firefly luciferase reporter assays, the Ov-sod-1 and -2 and the MnSOD (Ov-sod-3) gene promoters showed minimal, strong, and moderate levels of activity in these cells, respectively. Both Ov-sod-2 and -3 gene promoter regions showed an initial increase in activity in response to 5′ deletions. The results from the in vitro transcription experiments and the luciferase reporter assays were consistent and suggest the presence of Inr-like elements in the promoter regions of the Ov-sod genes.
Transmission of malaria parasites occurs by relatively few species of mosquitoes. One proposed mechanism of refractoriness is an inability of certain Plasmodium spp. to cross the peritrophic matrix ...(PM) in the midgut of an incompatible mosquito. We have tested this hypothesis by studying sporogonic development of Plasmodium gallinaceum in susceptible (Aedes aegypti and Anopheles gambiae G3) and refractory (Anopheles stephensi) mosquito species in the presence and absence of the PM. In the presence of the PM the number of oocysts that developed in A. gambiae G3 was about 20% of that in A. aegypti, whereas no oocysts developed in A. stephensi. To disrupt PM formation we added, to an infectious bloodmeal, either exogenous fungal chitinase or polyoxin D, the latter being a potent inhibitor of chitin synthase. The absence of the PM did not increase the susceptibility of A. aegypti and A. gambiae nor did it make A. stephensi susceptible to P. gallinaceum infection. The data indicate that the PM is not the primary determinant of P. gallinaceum compatibility in these mosquitoes and suggest that determinant(s) of refractoriness occurs after the parasite crosses the mosquito PM.
Wimmer, M., Schmid, B., Tag, C., and Hofer, H. W. 1998.Ascaris suum:Protein phosphotyrosine phosphatases in oocytes and developing stages.Experimental Parasitology88, 139–145. Protein tyrosine ...phosphatases were analyzed in oocytes ofAscaris suum. Phosphatases dephosphorylating modified acidic lysozyme were present in high-molecular-weight form (Mt>600,000) and as a 50-to 55-kDa protein in the soluble fraction. The low-molecular-weight form of the phosphatase cross-reacted with the antiserum raised against human T-cell protein tyrosine phosphatase and was not distinguishable from the 50- to 55-kDa protein tyrosine phosphatase previously described in the muscular layer of the adult worms (B. Schmidet al.1996,Molecular and Biochemical Parasitology77,183–192). The low-molecular-weight form was also present on immunoblots of high-molecular-weight protein tyrosine phosphatase preparations after denaturing electrophoresis. The same or a similar form of the tyrosine phosphatase was also found in detergent extracts from the pelletal fraction. In addition, another tyrosine phosphatase of 180 kDa molecular mass that dephosphorylated myelin basic protein was also found in extracts from the soluble compartment as well as detergent extracts from the pelletal fraction. It showed no cross-reactivity with antisera raised against soluble mammalian phosphatases and was resistant to inhibition by vanadate. While the activities of the myelin basic protein-dephosphorylating protein phosphatase remained fairly constant during early development of the oocytes, the activity of the enzyme dephosphorylating modified lysozyme in the pelletal fraction decreased to less than 10% of the initial activity between days 3 and 28 of incubation. Immuncytochemical studies of unfertilized and developingascariseggs revealed association of protein tyrosine kinase and protein tyrosine phosphatase with the egg shell, in addition to their presence in the neighborhood of mitochondria. The amount of enzyme changed with the stage of development. In the larval stage (21 days) protein tyrosine kinase had increased in the chitin layer of the shell and in the nuclei while the relative amount of tyrosine phosphatase decreased in accordance with the biochemical data.
Binding of the lectins concanavalin A (Con A) and limulin to Caenorhabditis elegans wild type resulted in consistent, reproducible, partial inhibition of chemoattraction to sterile filtrates of ...Escherichia coli. Normal chemotaxis resumed within 8 hr following treatment with these lectins. Competitive displacement of Con A or limulin by flooding with the specific sugars resulted in rapid resumption of normal chemotactic behavior. The experimental protocol for Con A applied to three age groups (newly hatched larvae, young adults, and old adults) showed the same response for all groups tested. Two mutant C. elegans with morphological defects in the cephalic chemosensilla showed the same inhibition of chemotactic response after exposure to Con A, and rapidly resumed normal behavior after competitive displacement of the lectin. Limulin and Con A did not affect nematode growth, development, or longevity, demonstrating that the observed results were not attributable to toxic effects. These results and other experimental evidence support the premise that behavioral modification was caused by functional impairments caused by Con A and limulin to chemoreceptors located on sensory dendrites of the cephalic sensilla.
Trager, W., Gill, G. S., Lawrence, C., and Nagel, R. L. 1999.Plasmodium falciparum: Enhanced gametocyte formationin vitroin-reticulocyte-rich blood.Experimental Parasitology91,115–118. Concentrates ...of late stage parasites of the gametocyte-forming clone HB-3 were mixed with blood rich in reticulocytes from anemic patients, or with normal control blood, and kept under culture conditions for 4 days. Significantly more gametocytes were always formed in the reticulocyte-rich blood than in the control. This was true whether the anemic blood supported a larger asexual parasitemia than the control, or a lower one, or the same and without regard to the cause of the anemia. Gametocytes as a percentage of asexual forms were up to 10 times higher in reticulocyte-rich blood than in normal blood.
Strongyloides ratti, kinetics of mast cells and goblet cells at various sites in small intestine of infected rats in relation to worm localization, results suggest that intestinal mastocytosis is ...closely related to presence of worms and that mast cells may play important role in worm expulsion
Regulation of intracellular Ca2+ homeostasis was characterized in epimastigote forms of Trypanosoma cruzi using the fluorescence probe Fura-2. Despite an increase in extracellular Ca2+, Ca2+o, from 0 ...to 2 mM, cytosolic Ca2+, Ca2+i, increased only from 85 +/- 9 to 185 +/- 21 nM, indicating the presence of highly efficient mechanisms for maintaining Ca2+i. Exposure to monovalent Na+ (monensin)-, K+ (valinomycin, nigericin)-, and divalent Ca2+ (ionomycin)-specific ionophores, uncouplers of mitochondrial respiration (oligomycin), inhibitors of Na+/K(+)-ATPase (ouabain), and Ca(2+)-sensitive ATPase (orthovanadate) in 0 or 1 mM Ca2+o resulted in perturbations of Ca2+i, the patterns of which suggested both sequestration and extrusion mechanisms. Following equilibration in 1 mM Ca2+o, incubation with orthovanadate markedly increased Ca2+i, results which are compatible with an active uptake of Ca2+i by endoplasmic reticulum. In contrast, equilibration in 0 or 1 mM Ca2+o did not influence the relatively smaller increase in Ca2+i following incubation with oligomycin, suggesting a minor role for the mitochondrial compartment. In cells previously equilibrated in 1 mM Ca2+o, exposure to monensin or ouabain, conditions known to decrease the Na+o/Na+i gradient, upon which the Na+/Ca2+ exchange pathways are dependent, markedly increased Ca2+i. In a complementary manner, decreasing the extracellular Na+ gradient with Li+ increased Ca2+i in a dose-dependent manner. Finally, the calcium channel blockers verapamil and isradipine inhibited the uptake of Ca2+ by greater than 50%, whereas diltiazem, nifedipine, and nicardipine were ineffective. The results suggest that epimastigote forms of T. cruzi maintain Ca2+i by uptake, sequestration, and extrusion mechanisms, with properties common to eukaryotic organisms.
