Critical analysis of the topology and rooting of the parabasalian 16S rRNA tree

Between 20% and 60% of the population of most countries are infected with the protozoan Toxoplasma gondii . Subjects with clinically asymptomatic life-long latent toxoplasmosis differ from those who are Toxoplasma free in several behavioral parameters. Case–control studies cannot decide whether these differences already existed before infection or whether they were induced by the presence of Toxoplasma in the brain of infected hosts. Here, we searched for such morphological differences between Toxoxoplasma -infected and Toxoplasma -free subjects that could be induced by the parasite (body weight, body height, body mass index, waist–hip ratio), or could rather correlate with their natural resistance to parasitic infection (fluctuating asymmetry, 2D : 4D ratio). We found Toxoplasma -infected men to be taller and Toxoplasma -infected men and women to have lower 2D : 4D ratios previously reported to be associated with higher prenatal testosterone levels. The 2D : 4D ratio negatively correlated with the level of specific anti- Toxoplasma antibodies in Toxoplasma -free subjects. These results suggest that some of the observed differences between infected and noninfected subjects may have existed before infection and could be caused by the lower natural resistance to Toxoplasma infection in subjects with higher prenatal testosterone levels.     

The role of salivary androgen-binding protein in reproductive isolation between two subspecies of house mouse: Mus musculus musculus and Mus musculus domesticus

Previous behavioural studies using inbred lines have suggested that the gene ( Abpa ) for the alpha subunit of salivary androgen-binding protein (ABP) plays a role in prezygotic isolation between house mouse Mus musculus subspecies. We tested this hypothesis in animals from wild allopatric (121 individuals from four samples) and parapatric (320 animals from 15 samples) populations sampled on the Czech–Bavarian transect across the hybrid zone between M. m. domesticus and M. m. musculus . The study did not reveal a consistent statistically significant trend of homosubspecific preferences in individual allopatric and parapatric populations. Nonetheless, the whole pattern of preference was skewed toward homosubspecific preference mostly on the M. m. musculus side of the hybrid zone. The pattern of homosubspecific preferences was stronger for the time spent sniffing than it was for the first choice of the signal (the ratio of homosubspecific vs. heterosubspecific preferences for both sexes was 6 : 2 in allopatric and 21 : 9 in parapatric populations, while the same rates were 4 : 4 and 16 : 14 for the first choice). To the extent that Y-maze tests reflect preference under wild conditions, we suggest that this slight preference may not in itself be sufficient to impede gene flow between the two subspecies and thus act as a reproductive barrier. ABP most probably participates in a complex system of subspecies-specific recognition in the hybrid zone, but the picture is far too complex at this time to allow a conclusive evaluation of the importance of this role.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 349–361.     

Behavior and Pathogenicity of Tritrichomonas foetus in Chick Liver Cell Cultures*

SYNOPSIS. Clones of Tritrichomonas foetus, referred to as strains KV-1, DK-2, and UT-1, which were judged by subcutaneous mouse assay to differ in pathogenicity, had different effects on trypsin-dispersed liver cell cultures prepared from 3 lines (Light Brown Leghorn, Massachusetts Brown, Massachusetts Low Growth) of chicks. The general pattern of parasite-cell interaction was similar in all cell cultures, but the intensity of certain responses of the cultures to trichomonads, reflected best in the levels of macrophage activity, depended on the line of chicks. The mild UT-1 strain was readily engulfed and digested by the macrophages, caused very little damage to the epithelial cells and fibroblasts, and had a minimal inhibitory effect on the division rate of the latter. Many abnormal changes were seen, however, in the cytoplasm and nucleil of fibroblasts and epithelial cells in cultures exposed to strains of high (KV-1) and intermediate (DK-2) pathogenicity or to cell-free filtrates of rich active cultures (henceforth referred to as filtrates) of these strains. The changes included retraction of cytoplasm which caused cell-free spaces to appear in the sheets of fibroblasts and around the epithelial islands; the islands became detached from the surrounding fibroblast sheets and tended to form multilayered cell mounds. The flagellates and filtrates of KV-1 strain greatly inhibited fibroblast division, and similar, but less pronounced, inhibitory effects were exerted by DK-2 strain and its filtrates. Trichomonads of all 3 strains did not attach themselves to fibroblasts and epithelial cells. Thus the abnormal changes in cultures infected with KV-1 and DK-2 parasites apparently were caused by some toxic substances produced by the trichomonads, which had to be responsible also for the identical changes in cultures exposed to filtrates of these strains. KV-1 and DK-2 strains inhibited the phagocytic activity of the macrophages in the early stages of infection, the former causing stronger and longer lasting inhibition. Trichomonads of KV-1 strain multiplied actively within the phagocytes which developed degenerative changes and ultimately burst, releasing healthy parasites into the medium. DK-2 flagellates, altho incapable of dividing inside the macrophages, usually were not digested and caused degeneration of the cells which contained them.     

Comparison of phosphorus deficiency indices during a spring phytoplankton bloom in a eutrophic reservoir

1. Phosphorus limitation was studied along the eutrophic, canyon-type ?ímov reservoir (Czech Republic) during a spring phytoplankton bloom. Concentration of soluble reactive phosphorus (SRP), C:P molar ratio in seston, extracellular alkaline phosphatase activity (APA), and P limitation (bioassay) were used as indices for phosphorus deficiency in the phytoplankton. 2. SRP, C:P, APA, and P limitation indicated a moderate P deficiency in the downstream, but not upper, part of the reservoir. 3. Significant correlations between these parameters were found in the downstream part. Chlorophyll a concentration correlated with APA and P limitation in the upper part. 4. APA was significantly enhanced in the phosphorus-deficient phytoplankton. However, APA was apparently not related to total biomass or species composition of the phytoplankton. 5. Generally, APA was closely correlated with pH in the reservoir. However, extracellular alkaline phosphatases, with a pH optimum above 9.0, were induced and active only during the phytoplankton bloom, whereas low background activity of extracellular phosphatases was found at low chlorophyll a concentrations (winter, clear-water phase).     

Quantitative trait loci meta-analysis of Plum pox virus resistance in apricot (Prunus armeniaca L.): new insights on the organization and the identification of genomic resistance factors

Plum pox virus (PPV) is responsible for sharka disease, one of the most detrimental stone fruit diseases affecting Prunus trees worldwide. Only a few apricot cultivars have been described as resistant, most originating from North American breeding programmes. Several PPV resistance quantitative trait loci (QTLs) have been mapped in various progenies, consistently highlighting the contribution to the resistance of the upper part of linkage group 1 (LG1). However, to date, no consensus has been reached on the precise number of QTLs linked to the resistance to PPV in apricot and P. davidiana or on their accurate position on the genetic linkage map. In the present study, the quantitative resistance of cultivar 'Harlayne' was analysed over five growth periods in a large F1 population. Four QTLs were identified, three mapping on LG1, explaining between 5% and 39% of the observed phenotypic variance. In an effort to further this analysis of PPV resistance in apricot, these results were merged in a single QTL meta-analysis with those of five other PPV resistance analyses available in the literature. Three consensus QTL regions were identified on LG1 and a putative fourth region on LG3. QTL meta-analysis also revealed the contribution of each resistant cultivar to metaQTLs, providing interesting comparative data on the resistance factors shared between the resistance sources used in the various studies. Finally, it was shown that one of the metaQTLs co-localizes with the eukaryotic translation initiation factor eIF4E , thus providing new hypotheses on the mechanisms of PPV resistance in apricot.     

Cloning and Characterization of New Repetitive Sequences in Field Bean (Vicia fabaL.)

Five new repetitive sequences have been isolated from theViciafabagenome, by cloning bands visible on agarose gel electrophoresisafter digestion of genomic DNA with various restriction enzymes.The sequences were 109 to 584 bp long, their abundance rangingfrom 5x10⁴to 5x10⁵copies per haploid genome. Southern blot andinsituhybridization revealed that four of five newly isolatedrepeats were dispersed in theV. fabagenome. One of the repeats(TIII15) showed tandem organization with several major hybridizationspots on mitotic chromosomesin situ.These sites were distributedin euchromatic as well as in heterochromatic chromosomal regions,and in several loci they were simultaneously localized withpreviously describedFokI repeated elements. The sequence ofTIII15 comprises four 26–27 bp subrepeats, but sharesno homology toFokI elements which have similar sequence organization.All newly described sequences were highly specific forV. faba,withlittle or no hybridization to DNA of otherViciaspecies, andno hybridization to DNA of other legumes tested.Copyright 1999Annals of Botany Company Vicia faba, field bean, repeated DNA sequences, FISH, PRINS, genome organization, copy number.     

In Vitro Induced Anaerobic Resistance to Metronidazole In Trichomonas Vaginalis

ABSTRACT. Resitance to metronidazole detectable under anaerobic conditions was induced in two Trichomonas vaginalis strains (TV 10-02 and MRP-2) by cultivation at gradually increasing pressure of the drug (1-100 μ/ml) for 12 to 21 months. the resistant derivatives reproduced in anaerobic trypticase-yeast-extract-maltose medium at 100 μ/ml metronidazole and showed very high values of minimal lethal concentration for metronidazole in anaerobic in vitro assays (556-1,600 μ/ml at 48-h exposure to the drug). Stepwise selection was necessary to develop the resistance in either strain. Attempts to induce resistance by prolonged maintenance of trichomonads with constant, low or moderate drug concentrations (3-10 μ/ml) were unsuccessful. Freshly developed resistance to high concentrations of metronidazole was unstable in absence of drug pressure as well as after cryopreservation. Development of stable resistance required further cultivation at 100 μ/ml metronidazole. Unstable substrains did not revert to original susceptibility. They retained a moderate level of resistance, being able to grow at 10 μ/ml metronidazole. the strains with fully developed resistance had no activity of the hydrogenosomal enzymes pyruvate: ferredoxin oxidoreductase and hydrogenase and ceased uptake of [¹⁴C]-metronidazole. These findings indicate that the pyruvate oxidizing pathway responsible for metronidazole activation was inactivated and metabolism of the drug stopped.     

Helicosporidium parasiticum Keilin Infection in the Caterpillar of a Hepialid Moth in Argentina

SYNOPSIS A case of infection by Helicosporidium parasiticum Keilin, 1921, in a hepialid caterpillar from Argentina is described. The pathogen produces deep proliferation starting from a cuticular callus, with numerous cysts occluded by multiple fibrous layers of connective tissue. Other cysts encapsulated in layers of lymphocytes and cysts in the lobes of the fat body are present in different parts of the body. Centers of melanization occur in most cysts. The pathway of infection, the reaction of the host and some structural features of the parasite are typical for fungus infections. Transfer of the genus Helicosporidium from Protozoa to primitive Ascomycetes, Saccharomycetaceae, is proposed.