Bacteria isolated from the gut of different developmental stages of Phlebotomus duboscqi Neveu-Lemaire, 1906 belonged almost all to aerobic or facultatively anaerobic gram-negative rods. In females, the highest bacterial counts were observed two days after bloodfeeding; seven days after bloodfeeding the bacterial counts returned to pre-feeding levels. Most isolates were identified phenotypically as Ochrobactrum sp. The distinctiveness and homogeneity of the phenotypic and genotypic characteristics of Ochrobactrum isolates indicated that they belonged to a single strain (designated AK). This strain was acquired by larvae from food and passaged transtadially: it was isolated from the guts of fourth-instar larvae shortly before pupation, from pupae as well from newly emerged females. Most other bacteria found in females were acquired from the sugar solution fed to adults. To determine if the midgut lectin activity may serve as antibacterial agent females were membrane-fed on blood with addition of inhibitory carbohydrates. No significant differences in bacterial infections were found between experimental and control groups and we suppose that the lectin activity has no effect on gram-negative bacteria present in sandfly gut.
Physico-chemical properties and carbohydrate-binding specificity of hemagglutination activity (HA) were compared in tissue lysates and haemolymph of unfed and bloodied females of five sandfly species. Sandfly gut lectins were found to be heat-labile, sensitive to dithiotreitol treatment, freezing/thawing procedures and were affected by divalent cations. The pH optimum of HA ranged between 7.0-7.5. Specificity of gut HA of all species studied was directed towards aminosugars and some glycoconjugates, mainly lipopolysaccharide from Escherichia coli K-235, heparin and fetuin. Gut HA of Phlebotomus papatasi (Scopoli, 1786) was strongly inhibited by lipophosphoglycan (LPG) from Leishmania major promastigotes. In females, that took blood, the HA was higher but the carbohydrate-binding specificity remained the same; this suggests that the same lectin molecule was present, at different levels, both in unfed and fed flies. High HA was found in ovaries of fed females of Lutzomyia longipalpis (Lutz et Nieva, 1912), P. papatasi and P. duhoscqi Neveu-Lemaire, 1906. In P. papatasi and P. duboscqi the HA was present also in the haemolymph and head lysates of both fed and unfed females. Carbohydrate-binding specificity of HA present in these tissues was similar with the gut lectin.
Sandfly females, while feeding on the host, excrete urine to concentrate proteins of the bloodmeal and restore weight and water balance. This process, analogous to prediuresis in mosquitoes, was observed in 100% of Phlebotomus papatasi (Scopoli) and 85% of P. duboscqi Neveu-Lemaire females studied. Individual females, however, differed in duration of prediuresis and in the number of ejected urine droplets. In both species the prediuresis generally started 1-2 min after the commencement of feeding and the variation in urine production was positively correlated with the length of feeding. The first one or two droplets were opaque whitish while the remaining ones were clear. Erythrocytes were found sporadically in first droplets of some females. Representative prediuresis in P. duboscqi included 27 droplets, i.e., about 325 nl urine in total, ejected during 8 min of feeding. The study revealed prediuresis in P. papatasi and P. duboscqi as a regular physiological process which may have consequences in transmission of infective diseases.
In this paper, studies on zoonotic cutaneous leishmaniasis (ZCL) are reviewed that were performed during the last ten years largely by scientists of the Martsinovsky Institute of Medical Parasitology and Tropical Medicine. New data on the taxonomy of Leishmania circulating in populations of Rhombomys opimus, their main host, and the results of field and laboratory studies allowed revision of certain concepts generally accepted in epidemiology and epizootology of ZCL in Central Asia.
Targeting polyamines of parasitic protozoa in chemotherapy has attracted attention because polyamines might reveal novel drug targets for antiparasite therapies (Müller et al. 2001). The biological function of the triamine spermidine in parasitic protozoa has not been studied in great detail although the results obtained mainly imply three different functions, i.e., cell proliferation, cell differentiation, and biosynthesis of macromolecules. Sequence information from the malaria genome project databases and inhibitor studies provide evidence that the current status of spermidine research has to be extended since enzymes of spermidine metabolism are present in the parasite (Kaiser et al. 2001). Isolation and characterisation of these enzymes, i.e., deoxyhypusine synthase (EC 1.1.1.249) (DHS) and homospermidine synthase (EC 2.5.1.44) (HSS) might lead to valuable new targets in drug therapy. Currently research on spermidine metabolism is based on the deposition of the deoxyhypusine synthase nucleic acid sequence in GenBank while the activity of homospermidine synthase was deduced from inhibitor studies. Spermidine biosynthesis is catalyzed by spermidine synthase (EC 2.5.1.16) which transfers an aminopropyl moiety from decarboxylated S-adenosylmethionine to putrescine. Spermidine is also an important precursor in the biosynthesis of the unusual amino acid hypusine (Wolff et al. 1995) and the uncommon triamine homospermidine in eukaryotes, in particular in pyrrolizidine alkaloid-producing plants (Ober and Hartmann 2000). Hypusine is formed by a two-step enzymatic mechanism starting with the transfer of an aminobutyl moiety from spermidine to the ε-amino group of one of the lysine residues in the precursor protein of eukaryotic initiation factor eIF5A by DHS (Lee and Park 2000). The second step of hypusinylation is completed by deoxyhypusine hydroxylase (EC 1.14.9929) (Abbruzzese et al. 1985). Homospermidine formation in eukaryotes parallels deoxyhypusine formation in the way that in an NAD+-dependent reaction an aminobutyl moiety is transferred from spermidine. In the case of homospermidine synthase, however the acceptor is putrescine. Thus the triamine homospermidine consists of two symmetric aminobutyl moieties while there is one aminobutyl and one aminopropyl moiety present in spermidine. Here, we review the metabolism of the triamine spermidine with particular focus on the biosynthesis of hypusine and homospermidine in parasitic protozoa, i.e., Plasmodium, Trypanosoma and Leishmania, compared to that in prokaryotes i.e., Escherichia coli, a phytopathogenic virus and pyrrolizidine alkaloid-producing plants (Asteraceae) and fungi.
In our previous work we established a T7 polymerase-driven Tetracycline-inducible protein expression system in Leishmania mexicana (Biagi, 1953). We used this system to analyse gene expression profiles during development of L. mexicana in procyclic and metacyclic promastigotes and amastigotes. The transcription of the gene of interest and the T7 polymerase genes was significantly reduced upon cell differentiation. This regulation is not locus-specific. It depends on untranslated regions flanking open reading frames of the genes analysed. In this paper, we report that the previously established conventional inducible protein expression system may not be suitable for studies on differentiation of species of Leishmania Ross, 1903 and protein expression systems might have certain limitations., Aygul Ishemgulova, Natalya Kraeva, Drahomíra Faktorová, Lucie Podešvová, Julius Lukeš, Vyacheslav Yurchenko., and Obsahuje bibliografii