E coli Accumulation behind an Obstacle

This paper describes our findings regarding the accumulation of motile bacteria at the rear of a confined obstacle and the physical description of the mechanisms at play. We found that the modification of flow due to the presence of the obstacle produces vorticity that favor the diffusion of bacteria towards the downstream stagnation point. By testing different flow rates, we determined the range in which bacteria accumulate. More interestingly, we observe that hydrodynamic interaction between the bacteria and the top and bottom surface of the microfluidic chip maintain the bacteria in the region where the flow velocity is lower than their own velocity. In the case of non-motile bacteria, this effect is not observed because bacteria follow the streamlines as passive tracers do.

Preliminary Evaluation of Biocontrol Agents against Maize Pathogens <i>Exserohilum turcicum</i>and <i>Puccinia sorghi</i>in Field Assays

Exserohilum turcicum and Puccinia sorghi cause foliar fungal diseases that affect maize crop in Argentina. These diseases, northern leaf blight and common rust respectively, are presented each year with different levels of severity affecting significantly the yield in susceptible hybrids. Disease control usually consists in the use of resistant cultivars and chemical control. Biological control as a preventive method is a viable alternative to evaluate. The aims of this study were to evaluate the natural incidence of both foliar diseases in maize after application of two antagonists, to determine the survival of the antagonists in the maize phyllosphere and to evaluate the effect of inoculation on grain yield at harvest. Plants treated with both biological control agents showed significant reductions in the incidence of both foliar diseases. In northern leaf blight the reduction was higher than 50% during 40 days in plants treated with Bacillus spp. Moreover, grain yield was significantly higher as compared to control treatments.

E-Cadherin Dysfunction and Cancer

E-cadherin molecules are cell-cell molecular connectors, but also act attaching cell surface to the cytoskeleton through catenin’s and additional partner proteins. Its main function is to regulate cellular adhesion and motility, and therefore acts as an invasion suppressor system. Its role is crucial in the induction and maintenance of cell polarity and differentiation, and in the organization and maintenance of tissue architecture. Downregulation or loss of its function is associated with an invasive and aggressive phenotype in many types of human cancers. In alterations of animal development, E-cadherin dysfunction influence in premature lethality or epidermal barrier and immunity defects. However, new hypothesis over its promoter role in tissue invasion is on focus. In addition to its tumor suppressor role, E-cadherin is a guiding molecule in collective cell migration increasing the metastasis risk during in vivo tumorigenesis. This E-cadherin function explains the retention of the functional E-cadherin expression, and that the epithelial-mesenchymal transition (EMT) is not required for the metastasis occurrence. However, like a switch, in some tumoral environments E-cadherin post-translational modifications may cause cell cluster migration. Like in development, in certain in vivo tumoral contexts, E-cadherin apparently involves signaling rather than cell contact formation. In this report, we explore the possibility of a novel role of thyroid hormones (THs) in the signal via E-cadherin-catenins, this not only should be involved in development and homeostasis, but also in cancer susceptibility of gastrointestinal tract.

PUB16 gene expression under abiotic stress and their putative role as an ARM repeat protein in <i>Arabidopsis thaliana</i>self-pollination pathway

The armadillo repeat super-family proteins (ARM repeat super-family proteins) possess tandem armadillo repeats and have been postulated to play different roles in plant development, morphogenesis, defense, cell death, and signal transduction through hormone signalling. In The Arabidopsis Information Resource (TAIR), we found 113 loci closely related to ARM repeat family proteins. This extensive group of proteins was studied in flowers tissues by western blot using antibodies directed against the most conserved region of the ARM repeat family proteins. The amino acid residues sequences from TAIR were aligned and the resulting phylogenetic tree allows us to inferring their evolutionary relationships. The main finding was the high similarity between the gene product of PUB16 (At5g01830, A. thaliana) and ARC1 (Brassica napus). In order to search a possible role for PUB16 we carried out stress bioassays using hormonal and saline approaches. Gene expression using RT-PCR showed that some of the ARM repeat super-family proteins are expressed both under salt or hormonal stress conditions. Particularly these studies allowed to detect and semi-quantify PUB16 gene expression in normal or stress growth conditions. In this approach it was revealed that, only in presence of GA, the expression of mRNA-PUB16 became evident. To morphologically verify the increasing number of germinated pollen grain in gibberellins treated flowers, we used epi-fluorescence microscopy assay. These results suggest that PUB16 may participate in GA signaling pathway favoring self-pollination.

Colon Adenocarcinoma Diagnosis in Human Samples by Multicontrast Nonlinear Optical Microscopy of Hematoxylin and Eosin Stained Histological Sections

Combined multimodal nonlinear optical (NLO) microscopies were used to detect and quantify morphological changes associated with stroma and epithelial transformation in colon cancer. Our findings provide complementary information about tissue microstructure, displaying distinctive patterns between normal and malignant human colon. Additionally, we have demonstrated the usefulness of using fixed tissues for the disease diagnostic and prognostic.?The present work provides a framework for using NLO techniques as a clinical diagnostic tool for human colon cancer. NLO metrics could be applied to other disorders, which are characterized by abnormal cell proliferation and collagen assembly.

Driving factors of tree biomass and soil carbon pool in xerophytic forests of northeastern Argentina

Background The conversion of forests into agricultural lands can be a threat because the forests carbon stored could be a source of emissions. The capacity to improve the predictions on the consequences of land use change depends on the identification of factors that influence carbon pools. We investigated the key driving factors of tree biomass and soil carbon pools in xerophytic forests in northeastern Argentina. Based on analyses of forest structure variables and abiotic factors (topography and soil properties) from 18 mature forests, we evaluated carbon pools using uniand multivariate (redundancy analysis) methods. Results The total carbon pool was estimated at 102.4 ± 24.0 Mg ha−1. Soil organic carbon storage is the single largest carbon pool relative to tree biomass, representing 73.1% of total carbon. Tree canopy cover and basal area were positively correlated with biomass carbon pool (r = 0.77 and r = 0.73, p < 0.001, respectively), proving to be significant drivers of carbon storage in this compartment. Slope, soil clay content and cation-exchange capacity had a better explanation for the variability in soil carbon pools, and all showed significant positive correlations with soil carbon pools (r = 0.64, 0.60 and 0.50;p < 0.05, respectively). The vertisols showed a 27.8% higher soil carbon stock than alfisols. Conclusions The relevance of our study stems from a dearth of information on carbon pools and their drivers in xerophytic forests, and in particular, the importance of this ecosystems’ type for Argentina, because they cover 81.9% of native forest area. Basal area and tree canopy cover exert a strong effect on the carbon pool in tree biomass but not in the soil. The results suggests that there is a potentially major SOC accumulation in forests located in slightly sloping areas and soils with higher topsoil clay content, such as vertisols. This could provide an important reference for implementing forestry carbon sink projects.

Impacts of brood parasitism by shiny cowbird Molothrus bonariensis on the breeding success of a small host, the black-backed water tyrant Fluvicola albiventer

The shiny cowbird Molothrus bonariensis parasitizes many species with different life-history traits and has a detrimental effect on the survival of the progeny of the hosts.In response,hosts have developed numerous antiparasitic defenses.Here,we examined the effects of brood parasitism by shiny cowbird on the clutch and brood sizes(83 nests)in a small host,the black-backed water tyrant Fluvicola albiventer.We also studied whether the death of parasite nestlings was related to the care of the foster parents and whether the host had any antiparasitic defense against the shiny cowbird.Our results indicate that brood parasitism significantly decreased the host hatching and fledging successes.The majority of nest failures(57%)were caused by brood parasitism.Shiny cowbird parasitism occurred in 52%of nests and the intensity of parasitism was 1.23±0.53 eggs per parasitized nest.Of the total host eggs,54%were damaged.During the incubation stage,20 nests(47%)were abandoned because of egg punctures by shiny cowbirds females.Only two parasitic fledglings were recorded,while the remaining nestlings either died from starvation(n=12)or predation(n=3).Foster parents abandoned parasitic nestlings between 5 and 10 days old.Our findings demonstrate that the shiny cowbird has very low rates of fledging success when parasitizing black-backed water tyrant.Also,parasitism had a high reproductive cost in the black-backed water tyrant because a very low proportion(7%)of the parasitized nests(n=43)were successful.