Placental syncytiotrophoblast constitutes a major barrier to vertical transmission of Listeria monocytogenes.

Listeria monocytogenes is an important cause of maternal-fetal infections and serves as a model organism to study these important but poorly understood events. L. monocytogenes can infect non-phagocytic cells by two means: direct invasion and cell-to-cell spread. The relative contribution of each method to placental infection is controversial, as is the anatomical site of invasion. Here, we report for the first time the use of first trimester placental organ cultures to quantitatively analyze L. monocytogenes infection of the human placenta. Contrary to previous reports, we found that the syncytiotrophoblast, which constitutes most of the placental surface and is bathed in maternal blood, was highly resistant to L. monocytogenes infection by either internalin-mediated invasion or cell-to-cell spread. Instead, extravillous cytotrophoblasts-which anchor the placenta in the decidua (uterine lining) and abundantly express E-cadherin-served as the primary portal of entry for L. monocytogenes from both extracellular and intracellular compartments. Subsequent bacterial dissemination to the villous stroma, where fetal capillaries are found, was hampered by further cellular and histological barriers. Our study suggests the placenta has evolved multiple mechanisms to resist pathogen infection, especially from maternal blood. These findings provide a novel explanation why almost all placental pathogens have intracellular life cycles: they may need maternal cells to reach the decidua and infect the placenta

Varying Herbivore Population Structure Correlates with Lack of Local Adaptation in a Geographic Variable Plant-Herbivore Interaction

Local adaptation of parasites to their hosts due to coevolution is a central prediction of many theories in evolutionary biology. However, empirical studies looking for parasite local adaptation show great variation in outcomes, and the reasons for such variation are largely unknown. In a previous study, we showed adaptive differentiation in the arctiid moth Utetheisa ornatrix to its host plant, the pyrrolizidine alkaloid-bearing legume Crotalaria pallida, at the continental scale, but found no differentiation at the regional scale. In the present study, we sampled the same sites to investigate factors that may contribute to the lack of differentiation at the regional scale. We performed field observations that show that specialist and non-specialist polyphagous herbivore incidence varies among populations at both scales. With a series of common-garden experiments we show that some plant traits that may affect herbivory (pyrrolizidine alkaloids and extrafloral nectaries) vary at the regional scale, while other traits (trichomes and nitrogen content) just vary at the continental scale. These results, combined with our previous evidence for plant population differentiation based on larval performance on fresh fruits, suggest that U. ornatrix is subjected to divergent selection even at the regional scale. Finally, with a microsatellite study we investigated population structure of U. ornatrix. We found that population structure is not stable over time: we found population differentiation at the regional scale in the first year of sampling, but not in the second year. Unstable population structure of the herbivore is the most likely cause of the lack of regional adaptation

Eficácia de substâncias químicas auxiliares na instrumentação de canais radiculares Efficiency of chemical auxiliaries in the root canal instrumentation

Comparou-se, mediante a pesagem de dentes humanos, o emprego de dois métodos químicos coadjuvantes da instrumentação de canais radiculares, a saber: Endo PTC alternado com hipoclorito de sódio a 1%, seguindo-se irrigação/aspiração com solução detergente/anti-séptico (grupo A) e hipoclorito de sódio a 1% usado isoladamente (grupo B). Os resultados permitiram as seguintes conclusões: ocorreram diferenças, para os dois grupos estudados, nas três grandezas analisadas. O grupo A propiciou maior diferença de peso quando comparado com o grupo B. Este exigiu menor tempo de instrumentação em relação ao grupo A. Relativamente à diferença de peso por unidade de tempo, o grupo A exibiu valores mais elevados do que o grupo B. Tais diferenças foram estatisticamente significantes (p < 0,05).<br>By weighing human teeth, two auxiliary chemical methods in the instrumentation of root canals were compared as follows: Endo PTC in alternation with 1% sodium hipochlorite followed by irrigation, aspiration with detergent/antisseptic solution (group A) and with 1% sodium hipochlorite alone (group B). Our conclusions indicate that: 1) Differences occured in two of the studied groups in three categories. 2) Group A showed a greater difference of weight when compared to group B (p < 0.01). 3) Group B required a minor time of instrumentation in relation to group A (p < 0.05). 4) Relative to the difference of weight based on time unit, group A presented higher values when compared to group B (p < 0.05)