Assessment of intraspecific mtDNA variability of European Ixodes ricinus sensu stricto (Acari: Ixodidae).

The Ixodes ricinus complex is composed of 14 species distributed worldwide. Some members of this complex are involved in the transmission of a number of diseases to animals and humans, in particular Lyme borreliosis, tick-borne encephalitis, ehrlichiosis and babesiosis. While the phylogenetic relationships between species of the I. ricinus complex have been investigated in the past, still little is known about the genetic structure within the species I. ricinus sensu stricto. We have investigated the intraspecific variability among 26 I. ricinus s.s. ticks collected in various European countries, including Switzerland, Italy, Austria, Denmark, Sweden, and Finland by using five mitochondrial gene fragments corresponding to the control region, 12S rDNA, cytb, COI, and COII. The five genes considered here showed a low genetic variability (1.6-5%). Our results based on both statistical parsimony (applied to the COI + COII + cytb + 12S + CR data set, for a total of 3423 bp) and maximum parsimony (applied to the COI + COII + cytb + 12S data set, for a total of 2980 bp) did not provide any evidence for a correlation between the identified haplotypes and their geographic origin. Thus, the European I. ricinus s.s. ticks do not seem to show any phylogeography structure.

Phylogeny of the scathophagidae (Diptera, calyptratae) based on mitochondrial DNA sequences.

The family Scathophagidae constitutes, together with members of the families Muscidae, Fannidae, and Anthomyiidae, the Muscoidea superfamily. The species Scathophaga stercoraria has been used extensively to investigate questions in animal ecology and evolution, particularly as a model system for studies of sperm competition and life history evolution. However, no phylogenetic studies have ever been performed on the Scathophagidae and the relationships within this family remain unclear. This study represents a molecular approach aimed at uncovering the phylogenetic relationships among 61 species representing 22 genera of Scathophagidae. A fragment of the terminal region of the mitochondrial gene COI (subunit I of the cytochrome oxidase gene) was sequenced in scathophagid species covering a wide geographic area, as well as a diverse spectrum of ecological habitats. Several clades grouping different genera and species have been identified, but the resolution power of the COI was insufficient to establish the exact relationships between these clades. The molecular data confirm the existence of a group consisting of the genera Delina, Chylizosoma, and Americina, which could represent the subfamily Delinae. Concerning the controversial position of the genus Phrosia, our data clearly suggest that it should be removed from the Delinae and placed within the genus Cordilura. Monophyly of most genera was confirmed, except for the genus Scathophaga, which should be divided into several different taxa.

Mechanism of metronidazole resistance in Helicobacter pylori: comparison of the rdxA gene sequences in 30 strains.

The rdxA gene of 30 independently isolated Helicobacter pylori strains was sequenced. A comparison of the rdxA sequences revealed a higher percentage of amino acid substitutions in the corresponding protein than in other housekeeping genes. Out of 122 point mutations, 41 were missense and 4 were nonsense. A resistant strain with a nucleotide insertion in the rdxA sequence was also found. With the exception of the point mutations and the insertion generating a stop signal, no particular nucleotide mutation or amino acid substitution could be associated to metronidazole resistance. Moreover, phylogenetic analysis of the 30 nucleotide sequences did not demonstrate specific clusters associated with the resistance phenotype.

Phylogenetic relationships among muscoidea (Diptera: calyptratae) based on mitochondrial DNA sequences.

The utility of a mitochondrial DNA (mtDNA) fragment of about 1100 bp (including partial COI and COII sequences and tRNALeu) for evolutionary studies in Muscoidea is discussed. The species investigated are Scathophaga stercoraria, Microprosopa pallidicauda and Trichopalpus fraterna (family Scathophagidae), Musca domestica (Muscidae), Lasiomma seminitidum (Anthomyiidae) and Fannia armata (Fanniidae). Comparisons were made with published mtDNA sequences of Drosophila, Anopheles and three Calliphoridae species. The molecular phylogeny obtained here matches the classical morphological taxonomy reasonably well. This varies considerably, however, at different taxonomical levels. At a high taxonomic level, there is a clear separation between the Nematocera and the Brachycera, but the Calyptratae-Acalyptratae division is not always supported. At a lower taxonomic level, all species belonging to the same family are well grouped, but at an intermediate level, within the Calyptratae, it is impossible to clearly separate the Muscoidea and Calliphoridae, preventing a firm conclusion on the phylogenetic relationships among Muscoidea families. The entire COI sequence of S. stercoraria, as well as other mtDNA sequences (including the proximal portions of the COI gene, tRNATrp, tRNACys and tRNATyr genes) in Muscoidea species, are also presented and discussed.

Arguments against the involvement of Borrelia burgdorferi sensu lato in Alzheimer's disease.

The involvement of spirochaetes, such as the aetiologic agent of Lyme borreliosis, Borrelia burgdorferi sensu lato, in Alzheimer's disease (AD), a common neuropathology, has been proposed by several groups in the past. In our laboratory, brains from 10 AD patients were analysed for the presence of B. burgdorferi sensu lato by both standard and nested PCR techniques based on various target regions, such as the hbb gene (encoding the histone-like protein HBb), the fla gene (flagellin), the rrl-rrf ribosomal intergenic spacer region and the rrs gene (encoding 16S rRNA). In addition, ELISA and Western blot tests for the detection of antibodies against spirochaetal antigens were performed on 27 sera from clinical AD patients. Using these methods, we did not obtain any evidence of the involvement of B. burgdorferi in Alzheimer's disease.

Tick zoonoses in the southern part of Switzerland (Canton Ticino): occurrence of Borrelia burgdorferi sensu lato and Rickettsia sp.

The diversity and the distribution of tick species and their infection rates by the pathogenic micro-organism Borrelia burgdorferi sensu lato, the etiologic agent of Lyme borreliosis, and Rickettsia sp., were studied in Canton Ticino (the southern part of Switzerland). Ticks specimens collected from animals and humans were classified and analysed for the presence of both pathogens. In particular, PCR analysis was performed for the detection of Borrelia spirochetes in Ixodes ricinus and Ixodes hexagonus, and the hemolymph test was done on Rhipicephalus sanguineus for the detection of Rickettsia sp. PCR assays, performed on 424 of the 989 collected ticks, revealed a low rate of infection (around 2%) of both vectors I. ricinus and I. hexagonus by B. burgdorferi sensu lato. These results are in agreement with the modest number of Lyme borreliosis cases yearly recorded in Ticino. Further, through analysis of DNA sequences, the strains carried by the infected ticks were identified as belonging to the genomic group VS116. The widespread finding of the Mediterranean species Rhipicephalus sanguineus in different locations from July 1994 to October 1995 demonstrates its establishment in Ticino. Of the 210 specimens collected, 70 were analysed and one was infected by Rickettsia sp.

Prednisone effects on postnatal brain development of rats following maternal therapy.

16-beta-Metilprednisone was administered in the last week of pregnancy in order to study its effects on postnatal brain development of the litters. Two groups of pregnant inbred rats were used for the experiments. Group I received 1.25 mg/kg/day 16-beta-metilprednisone. Group II served as untreated controls. The litters were killed either within 24 hr after birth, at 17 days, or at 45 days of age. Treated litters (animals whose mothers received the steroid) had a decreased body weight at 17 days of age. Wet brain weight was decreased in the same group. At 17 and 45 days of life treated rats showed a dry brain weight lower than that of controls. Newborn and 17-day-old rats whose mothers received the steroid showed a decreased content of brain proteins. Total lipids, cholesterol, and phospholipids were reduced in the brain of treated rats at 45 days of life. Brain phospholipids were also decreased in 17-day-old rats. These results show that 16-beta-metilprednisone administration to pregnant rats produces long lasting changes in brain chemical composition.