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PubMed1997

Expression of the microfilarial sheath protein 2 (shp2) of the filarial parasites Litomosoides sigmodontis and Brugia malayi.

The microfilarial sheaths of the filarial parasites Brugia malayi, Brugia pahangi, and Litomosoides sigmodontis consist of several parasite proteins, probably ranging between 7 and 10. The gene encoding sheath protein 2 (shp2), which is the object of this study, is transcribed in embryos and in the uterine epithelium; at least in B. malayi, it is translated in both tissues. Apparently, shp2 is synthesized as a monomer, exported by the respective cells, and integrated into the microfilarial sheath. In the sheath, it exists as a highly polymerized molecule cross-linked by cysteine formation and other covalent bonds, presumably epsilon-(gamma-glutamyl)-lysine links.

Animals↗
PubMed1997

Ivermectin-induced killing of microfilariae in vitro by neutrophils mediated by NO.

Rat neutrophil granulocytes isolated after intraperitoneal casein injection of the donors exhibit high cytotoxic efficacy in vitro against microfilariae of Litomosoides carinii in the presence of ivermectin. Optimum effects of 80-90% killing of microfilariae were obtained with 100 ng ivermectin per milliliter and a microfilariae: cell ratio of 1:100. Spleen cells killed approximately 30% of the microfilariae under these conditions. Cytotoxic effects were independent of any adherence of the cell to the larvae. In contrast to the effects of spleen cells, cytotoxicity of neutrophils completely abrogated when cells and targets were separated by a membrane impermeable for the cells, suggesting a very short-living mediator in the latter case. Correspondingly, cytotoxic effects of neutrophils were completely inhibited by the addition of the arginine analogues NG-monomethyl-L-arginine and L-canavanine, indicating the involvement of reactive nitrogen intermediates. The nitric oxide scavenger hemoglobin also protected the microfilariae. Several compounds which are known to interfere with reactive oxygen intermediates were ineffective. An excess of ferrous ions in the medium in the presence of a reducing agent significantly reduced the cytotoxic efficacy of neutrophils.

Animals↗
PubMed1997

Development of a rapid, nonradioactive, oligonucleotide-based assay for the detection of Setaria digitata.

Setaria species are filarial parasites which inhabit the peritoneal cavity of cattle and other ungulates. The parasite is generally considered to be nonpathogenic in its natural hosts, but the transmission of the infective larvae through mosquito vectors to its abnormal hosts (goats, sheep, or horses) can result in a serious and often fatal neuropathological disorder commonly referred to as cerebrospinal nematodiasis. We have previously described the cloning and characterization of a repetitive DNA sequence of Setaria digitata that could be used as a diagnostic probe to detect the parasite in host and vector populations. Here we report the development of a rapid nonradioactive hybridization assay using an oligonucleotide probe based on the above cloned repetitive sequence.

Animals↗
PubMed2000

Litomosoides sigmodontis: dynamics of the survival of microfilariae in resistant and susceptible strains of mice.

Litomosoides sigmodontis in the BALB/c mouse is the only model of filariasis which allows the observation of the complete development in an immunocompetent mouse. In this study, we injected microfilariae (mf) intravenously, as well as into the pleural cavity, the site of natural release of mf from adult female worms, and followed the kinetics of elimination within the host. In susceptible BALB/c mice, mf circulated at high levels in the blood. In contrast, in C57BL/6 mice, which are refractory to full development, mf were eliminated rapidly from the peripheral blood. However, 6 days after intrapleural injection, viable larvae could be found in the pleural cavity and lung capillaries of both susceptible and resistant strains. The numbers of mf in the pleural cavity and lung capillaries in individual mice were significantly correlated, but not dependent on strain or peripheral microfilaraemia. Thus, although C57BL/6 mice showed enhanced production of nitric oxide by pleural exudate cells and a faster change in the numbers of circulating leukocytes after injection, rapid killing of mf by cell or nitric oxide-mediated mechanisms were not the reason for the different outcome. Furthermore, 3 h after iv injection, only a small percentage of mf could be recovered from the peripheral circulation, indicating the presence of a reservoir for mf containment. In conclusion, injected mf showed disparate dynamics of persistence within susceptible and resistant hosts, which is similar to the disparate outcome of natural infections with L. sigmodontis. This difference became obvious within 1 day after injection. The lung capillary system plays obviously a crucial part in regulation of microfilaremia. Our model also provides a possible means to explain frequent cases of occult infections in human filariasis.

Animals↗
PubMed2001

Influence of intercodon and base frequencies on codon usage in filarial parasites.

Base frequency, codon usage, and intercodon identity were analyzed in five filarial parasite species representing five Onchocercidae genera. Wucheria bancrofti, Brugia malayi, Onchocerca volvulus, Acanthocheilonema viteae, and Dirofilaria immitis gene sequences were downloaded from NCBI, and analysis was performed using locally designed computer programs and other freely available applications. A clear sequence bias was observed among the nematode species examined. At the nucleotide level, AT basepairs were present in gene sequences at higher frequencies than GC. In addition, codons ending in A or T were used proportionately more than those with G or C in the third-codon position. In addition, the amino acids used most often corresponded to codons ending in AT basepairs. Intercodon base proportion was biased in that A was found most often at N4, second only to T in certain specific cases. Since all of these sequence biases were observed in a relatively consistent fashion among all of the organisms studied, we conclude that sequence bias is a genetic characteristic, which is associated with multiple filarial genera.

Animals↗
PubMed2000

Differential diagnosis of human lymphatic filariasis using PCR-RFLP.

Filariasis is still a public health problem in tropical countries. The most common causative agents of human filariasis are Wuchereria bancrofti and Brugia malayi. Traditional methods used to detect filarial parasites in human, animal and vector populations are tedious, time consuming, and confer little guarantee of sensitivity and species specificity. We have developed a rapid and specific method to detect filarial parasite DNAs in blood and mosquito samples using the polymerase chain reaction (PCR) technique. The primers used are MF/F and MF/R which amplify a 1.5 kb glutathione peroxidase gene of filarial worms. Using the restriction fragment length polymorphism (RFLP) technique, these PCR products will be further digested with restriction enzymes either Hpa I, Pst I, Alu I or Hinf I to differentiate the genus of filaria. This PCR-RFLP technique can be apply to use in diagnosis and to differentiate between species of filaria in humans the reservoir host and the mosquito vector in endemic areas

Animals↗
PubMed1977

Setaria cervi: enzymes of glycolysis and PEP-succinate pathway.

Setaria cervi, the filarial parasite inhabiting the Indian water buffalo (Bubalus bubalis Linn.) contained almost all the enzymes involved in glycogen degradation. Significant activities of glycogen phosphorylase, glucokinase, phosphoglucomutase, phosphoglucose isomerase, phosphofructokinase, FDP-aldolase, glyceraldehyde-3-phosphate dehydrogenase, phosphopyruvate hydratase, pyruvate kinase, lactate dehydrogenase glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were detected in cell-free extracts of whole worms. The presence of PEP-carboxykinase, malate dehydrogenase, fumarase and fumarate reductase revealed the functioning of the PEP-succinate pathway in addition to phosphorylating glycolysis and pentose phosphate pathway in the parasite. Excepting fumarate reductase all other enzymes were localized in the particulate-free cytosol fraction, although small amounts of glycogen phosphorylase, aldolase and lactate dehydrogenase were also detected in the mitochondrial fraction.

Animals↗