A murine model was used to study the histopathological aspects and cytokine expression levels in skeletal muscle provoked by the infection with Mexican TcI strains. BALB/c mice were inoculated with the virulent Querétaro strain and the nonvirulent Ninoa strain. Parasite numbers were counted in blood and skeletal muscle at different times post-infection, and real time-PCR expression levels of the cytokines IL-12, IL-4, IL-10, IFN-γ, and TNF-α were evaluated. In the acute phase of infection, a high parasitic load, both in blood and skeletal muscle, was detected. The histopathological analyses showed an exacerbated inflammation and granulomatous-like infiltrate with the Querétaro strain. Interestingly, extensive calcification areas were observed in the skeletal muscle surrounded by inflammatory infiltrates. TNF-α and IL-10 expression exhibited a significant increase at the peak of infection. In summary, Querétaro strain, a Mexican TcI strain, is virulent enough to induce high inflammation and calcification in skeletal muscle of the hind limbs, which could be related to high expression levels of TNF-α.

An 84 base pair sequence of the Streptococcus mutans virulence factor, known as dextranase, has been obtained from 10 individuals from the Bronze Age to the Modern Era in Europe and from before and after the colonization in America. Modern samples show four polymorphic sites that have not been found in the ancient samples studied so far. The nucleotide and haplotype diversity of this region have increased over time, which could be reflecting the footprint of a population expansion. While this segment has apparently evolved according to neutral evolution, we have been able to detect one site that is under positive selection pressure both in present and past populations. This study is a first step to study the evolution of this microorganism, analysed using direct evidence obtained from ancient remains.

Shrews of the Cryptotis mexicanus group (Mammalia, Soricidae) are closely associated with the humid mountain forest north of the Neotropics. Within this group, phylogenetic studies have defined a monophyletic group composed of 3 species: C. nelsoni as sister of the clade C. obscurus -C. mexicanus. The pattern of morphological variation and estimates of potential distribution suggests that its evolution is tightly associated with the altitudinal changes induced by the last glacial-interglacial cycles. In this study, we analyzed 70 mitochondrial sequences of the Cytochrome b for this clade using phylogeographic and phylogenetic analyses to test whether the valleys, canyons, and plains along the distribution of this group could be promoting its genetic structure and differentiation. The results indicate 4 genetic groups, partially congruent with previous studies; one corresponds to C. nelsoni, while the other 3 appear within the clade C. obscurus -C. mexicanus. The genetic divergence observed among the 4 groups suggests the influence of some geographical barriers, from valleys and canyons to volcanoes, which through the last glacial-interglacial cycles could have shaped the current genetic pattern variation. Our findings also suggest that the taxonomy between C. obscurus and C. mexicanus is not yet resolved.

No abstract

We present the complete mitochondrial genome of Tzotzilthelphusa villarosalensisVillalobos & Álvarez, 2013, a freshwater crab from Mexico. This is the first mitochondrial genome reported for the superfamily Pseudothelphusoidea. We performed a de novo assembly from genome skimming reads. The mitochondrial genome of T. villarosalensis has a length of 17,203 bp and its gene topology is similar to other freshwater and marine families, e.g., the position of the cytochrome oxidase complex subunits and ATA synthetase, even the order of nad3, nad5, nad4, nad4L, nad6, and cytb. By contrast, the order and organization of genes like the 16S, 12S, and nad1 are different depending on the phylogenetic group with which they are compared. The phylogenetic analyses placed T. villarosalensis as a sister group of all freshwater crabs reported until now and as part of the subsection Heterotremata. This complete mitochondrial genome could be a reference for further genomic studies of the family Pseudothelphusidae and other primary freshwater crabs.