Mothers of children with attention deficit/hyperactivity disorder: relationship among parenting stress, parental practices and child behaviour

This study focuses on mothers of children diagnosed with attention deficit/hyperactivity disorder (ADHD) and sets out (1) to characterize dimensions of both parental functioning (parenting stress and parental practices) and child characteristics (behaviour) and (2) to determine predictors of parenting stress, namely parental rearing practices or perceived behaviour of the child, in order to plan intervention with the families. Fifty-two mothers of children diagnosed with ADHD and aged 6-12 years participated in the study. The Portuguese versions of the Parenting Stress Index (Abidin and Santos 2003), EMBU-P (Canavarro and Pereira 2007) and Child Behaviour Checklist (Albuquerque et al. 1999) were used. Results showed that mothers of children with ADHD experience higher levels of parenting stress (emerging essentially from the child's characteristics) and report more behavioural problems in their children (for girls and boys), but use parental practices similar to those of the mothers of the Portuguese validation sample. Results also indicate that child behaviour (both internalized and externalized) and parental practices dominated by rejection predict parenting stress. These findings have implications for intervention with children diagnosed with ADHD and their families.     

Probing DNA conformational changes with high temporal resolution by tethered particle motion

The tethered particle motion (TPM) technique informs about conformational changes of DNA molecules, e.g. upon looping or interaction with proteins, by tracking the Brownian motion of a particle probe tethered to a surface by a single DNA molecule and detecting changes of its amplitude of movement. We discuss in this context the time resolution of TPM, which strongly depends on the particle-DNA complex relaxation time, i.e. the characteristic time it takes to explore its configuration space by diffusion. By comparing theory, simulations and experiments, we propose a calibration of TPM at the dynamical level: we analyze how the relaxation time grows with both DNA contour length (from 401 to 2080 base pairs) and particle radius (from 20 to 150 nm). Notably we demonstrate that, for a particle of radius 20 nm or less, the hydrodynamic friction induced by the particle and the surface does not significantly slow down the DNA. This enables us to determine the optimal time resolution of TPM in distinct experimental contexts which can be as short as 20 ms.     

The recombination landscape in Arabidopsis thaliana F2 populations

Recombination during meiosis shapes the complement of alleles segregating in the progeny of hybrids, and has important consequences for phenotypic variation. We examined allele frequencies, as well as crossover (XO) locations and frequencies in over 7000 plants from 17 F(2) populations derived from crosses between 18 Arabidopsis thaliana accessions. We observed segregation distortion between parental alleles in over half of our populations. The potential causes of distortion include variation in seed dormancy and lethal epistatic interactions. Such a high occurrence of distortion was only detected here because of the large sample size of each population and the number of populations characterized. Most plants carry only one or two XOs per chromosome pair, and therefore inherit very large, non-recombined genomic fragments from each parent. Recombination frequencies vary between populations but consistently increase adjacent to the centromeres. Importantly, recombination rates do not correlate with whole-genome sequence differences between parental accessions, suggesting that sequence diversity within A. thaliana does not normally reach levels that are high enough to exert a major influence on the formation of XOs. A global knowledge of the patterns of recombination in F(2) populations is crucial to better understand the segregation of phenotypic traits in hybrids, in the laboratory or in the wild.     

Molecular Plasticity of E-Cadherin and Sialyl Lewis X Expression,in Two Comparative Models of Mammary Tumorigenesis

Background

The process of metastasis involves a series of steps and interactions between the tumor embolus and the microenvironment. Key alterations in adhesion molecules are known to dictate progression from the invasive to malignant phenotype followed by colonization at a distant site. The invasive phenotype results from the loss of expression of the E-cadherin adhesion molecule, whereas the malignant phenotype is associated with an increased expression of the carbohydrate ligand-binding epitopes, (e.g. Sialyl Lewis ^x/a) that bind endothelial E-selectin of the lymphatics and vasculature.

Methodology

Our study analyzed the expression of two adhesion molecules, E-cadherin and Sialyl Lewis x (sLe^x), in both a canine mammary carcinoma and human inflammatory breast cancer (IBC) model, using double labelled immunofluorescence staining.

Results

Our results demonstrate that canine mammary carcinoma and human IBC exhibit an inversely correlated cellular expression of E-cadherin and sLe^x within the same tumor embolus.

Conclusions

Our results in these two comparative models (canine and human) suggest the existence of a biologically coordinated mechanism of E-cadherin and sLe^x expression (i.e. molecular plasticity) essential for tumor establishment and metastatic progression.     

Antigen-Specific Th17 Cells Are Primed by Distinct and Complementary Dendritic Cell Subsets in Oropharyngeal Candidiasis

Candida spp. can cause severe and chronic mucocutaneous and systemic infections in immunocompromised individuals. Protection from mucocutaneous candidiasis depends on T helper cells, in particular those secreting IL-17. The events regulating T cell activation and differentiation toward effector fates in response to fungal invasion in different tissues are poorly understood. Here we generated a Candida-specific TCR transgenic mouse reactive to a novel endogenous antigen that is conserved in multiple distant species of Candida, including the clinically highly relevant C. albicans and C. glabrata. Using TCR transgenic T cells in combination with an experimental model of oropharyngeal candidiasis (OPC) we investigated antigen presentation and Th17 priming by different subsets of dendritic cells (DCs) present in the infected oral mucosa. Candida-derived endogenous antigen accesses the draining lymph nodes and is directly presented by migratory DCs. Tissue-resident Flt3L-dependent DCs and CCR2-dependent monocyte-derived DCs collaborate in antigen presentation and T cell priming during OPC. In contrast, Langerhans cells, which are also present in the oral mucosa and have been shown to prime Th17 cells in the skin, are not required for induction of the Candida-specific T cell response upon oral challenge. This highlights the functional compartmentalization of specific DC subsets in different tissues. These data provide important new insights to our understanding of tissue-specific antifungal immunity.