Increased App expression in a mouse model of Down's syndrome disrupts NGF transport and causes cholinergic neuron degeneration

Degeneration of basal forebrain cholinergic neurons (BFCNs) contributes to cognitive dysfunction in Alzheimer's disease (AD) and Down's syndrome (DS). We used Ts65Dn and Ts1Cje mouse models of DS to show that the increased dose of the amyloid precursor protein gene, App, acts to markedly decrease NGF retrograde transport and cause degeneration of BFCNs. NGF transport was also decreased in mice expressing wild-type human APP or a familial AD-linked mutant APP; while significant, the decreases were less marked and there was no evident degeneration of BFCNs. Because of evidence suggesting that the NGF transport defect was intra-axonal, we explored within cholinergic axons the status of early endosomes (EEs). NGF-containing EEs were enlarged in Ts65Dn mice and their App content was increased. Our study thus provides evidence for a pathogenic mechanism for DS in which increased expression of App, in the context of trisomy, causes abnormal transport of NGF and cholinergic neurodegeneration.     

Income and body mass index in Europe

The problem of obesity is alarming public health authorities around the world. Therefore, it is important to study its determinants. In this paper, we explore the empirical relationship between household income and body mass index (BMI) in nine European Union countries. Our findings suggest that, in general, the association is negative for women and nonexistent for men. Moreover, once we decompose household income into “own labor earnings” and “other household income”, we find that the different relationship for men and women appears to be driven by the negative relationship between BMI and “own labor earnings” for women.     

SKIP is required for TGF-β1-induced epithelial mesenchymal transition and migration in transformed keratinocytes

Transforming growth factor-β1 (TGF-β1) potently induces the epithelial-mesenchymal transition (EMT) during tumoral progression. Although Sky-interacting protein (SKIP) regulates TGF-β1-induced Smad activation, its role in the induction of cell malignance remains uncertain. We found that TGF-β1 increases SKIP expression in PDV cells. In cells stably transfected with SKIP antisense, AS-S, Smad3 activation decreased, along with an inhibition of TGF-β1-induced EMT, and the cells were sensitized to the TGF-β1-dependent inhibition of proliferation. Also, AS-S cells showed a weaker migration and invasion response. Moreover, TGF-β1-induced urokinase-type plasminogen activator expression was inhibited, concomitantly with a TGF-β1-independent increment of the plasminogen-activator inhibitor-1 expression. Thus, these results suggest that SKIP is required for EMT and invasiveness induced by TGF-β1 in transformed cells.     

The integral membrane protein p16.7 organizes in vivo phi29 DNA replication through interaction with both the terminal protein and ssDNA

Remarkably little is known about the in vivo organization of membrane-associated prokaryotic DNA replication or the proteins involved. We have studied this fundamental process using the Bacillus subtilis phage phi29 as a model system. Previously, we demonstrated that the phi29-encoded dimeric integral membrane protein p16.7 binds to ssDNA and is involved in the organization of membrane-associated phi29 DNA replication. Here we demonstrate that p16.7 forms multimers, both in vitro and in vivo, and interacts with the phi29 terminal protein. In addition, we show that in vitro multimerization is enhanced in the presence of ssDNA and that the C-terminal region of p16.7 is required for multimerization but not for ssDNA binding or interaction with the terminal protein. Moreover, we provide evidence that the ability of p16.7 to form multimers is crucial for its ssDNA-binding mode. These and previous results indicate that p16.7 encompasses four distinct modules. An integrated model of the structural and functional domains of p16.7 in relation to the organization of in vivo phi29 DNA replication is presented.     

Thermodynamic analysis of the structural stability of the shiga toxin B-subunit

The conformational stability of Shiga toxin B-subunit (STxB), a pentameric protein from Shigella dysenteriae has been characterized by high sensitivity differential scanning calorimetry and circular dichroism spectroscopy under different solvent conditions. It is shown that the thermal folding/unfolding of STxB is a reversible process involving a highly cooperative transition between folded pentamer and unfolded monomers. The conformational stability of STxB is pH dependent and because of its pentameric nature is also concentration dependent. STxB is maximally stable in the pH range from 5 to 9 (Delta G upon unfolding is close to 13 kcal per mol of monomer at 25 degrees C), and its stability decreases both at lower and at higher pH values. The pH dependence of the Gibbs energy of stabilization between pH 2.5 and 5 is consistent with the change in the ionizable state of an average of four groups per monomer upon unfolding. Structural thermodynamic calculations show that the stabilization of the STxB pentamer is primarily due to the interactions established between monomers rather than intramonomer interactions. The folding of an isolated monomer into the conformation existing in the pentamer is unfavorable and expected to be characterized by a free-energy change upon folding in the order of 2.5 kcal mol(-1) at 25 degrees C. On the average, intersubunit interaction induced upon oligomerization of folded monomers should contribute close to -13.4 kcal per mol of monomer to bring the overall Gibbs energy to the experimentally determined value at this temperature.     

Gender and viability selection on morphology in fledgling pied flycatchers

Until recently, analyses of gender-dependent differences in viability selection and the ontogeny of sexual size dimorphism have been plagued by difficulties in determining the sex of nestling birds on the basis of morphology. Recently, this problem was overcome using molecular sex identification to report for the first time body-size-mediated antagonistic selection on the viability of male and female collared flycatchers. We used molecular sex identification to analyse natural selection on fledgling viability, sexual size dimorphism and effects of parasites in relation to gender in a Mediterranean population of the related pied flycatcher Ficedula hypoleuca. There was directional positive selection on fledgling weight but no selection on tarsus length. Fledgling weight was the most important determinant of fledgling survival, with heavier fledglings having increased viability. Although selective trends were of the same sign for both sexes, only among female fledglings were selection differentials and gradients statistically significant. Therefore, similar trends in selection were revealed in analyses of a data set where sex was ignored and in separate analyses using same-sex sibship trait means. Mite nest ectoparasites negatively affected fledgling weight, and the effects were stronger in female than male fledglings. There was no effect of parasitism on the tarsus length in males, as previously reported in retrospective analyses performed without knowledge of sex until recruitment. Overall, selection on fledgling viability on the basis of morphological traits and hatching date was not confounded by an individual's gender.     

Hepatitis a outbreak in a public school in Rio de Janeiro,Brazil

From June 1 to July 1 1999, an outbreak involving 25 cases of hepatitis A occurred in a public school in Rio de Janeiro, Brazil. Since these cases were notified to the State Health Department, the National Reference Center for Hepatitis Viruses (CNRHV) was required to investigate the extent of hepatitis A virus (HAV) dissemination. Blood samples from all students were tested for IgM and total anti-HAV antibodies using a commercial enzyme-linked immunoassay (ELISA). At the same time, a questionnaire was completed in order to identify possible risk factors for HAV infection. The environmental investigation showed that there was no fecal contamination of the water supply. The epidemiological investigation demonstrated that almost 50% of this population was susceptible to HAV infection and probably person-to-person transmission was the principal mode of virus dissemination. In this situation, a massive vaccination campaign could control the HAV infection.     

Acceptor specificity of the human leukocyte alpha3 fucosyltransferase: role of FucT-VII in the generation of selectin ligands

The alpha3 fucosyltransferase, FucT-VII, is one of the key glycosyltransferases involved in the biosynthesis of the sialyl Lewis X (sLex) antigen on human leukocytes. The sialyl Lewis X antigen (NeuAcalpha(2-3)Galbeta(1-4)[Fucalpha(1-3)]GlcNAc-R) is an essential component of the recruitment of leukocytes to sites of inflammation, mediating the primary interaction between circulating leukocytes and activated endothelium. In order to characterize the enzymatic properties of the leukocyte alpha3 fucosyltransferase FucT-VII, the enzyme has been expressed in Trichoplusia ni insect cells. The enzyme is capable of synthesizing both sLexand sialyl-dimeric-Lexstructures in vitro , from 3'-sialyl-lacNAc and VIM-2 structures, respectively, with only low levels of fucose transfer observed to neutral or 3'-sulfated acceptors. Studies using fucosylated NeuAcalpha(2-3)-(Galbeta(1- 4)GlcNAc)3-Me acceptors demonstrate that FucT-VII is able to synthesize both di-fucosylated and tri-fucosylated structures from mono- fucosylated precursors, but preferentially fucosylates the distal GlcNAc within a polylactosamine chain. Furthermore, the rate of fucosylation of the internal GlcNAc residues is reduced once fucose has been added to the distal GlcNAc. These results indicate that FucT-VII is capable of generating complex selectin ligands, in vitro , however the order of fucose addition to the lactosamine chain affects the rate of selectin ligand synthesis.      

A novel statistical test for treatment differences in clinical trials using a response-adaptive forward-looking Gittins Index Rule

The most common objective for response-adaptive clinical trials is to seek to ensure that patients within a trial have a high chance of receiving the best treatment available by altering the chance of allocation on the basis of accumulating data. Approaches that yield good patient benefit properties suffer from low power from a frequentist perspective when testing for a treatment difference at the end of the study due to the high imbalance in treatment allocations. In this work we develop an alternative pairwise test for treatment difference on the basis of allocation probabilities of the covariate-adjusted response-adaptive randomization with forward-looking Gittins Index (CARA-FLGI) Rule for binary responses. The performance of the novel test is evaluated in simulations for two-armed studies and then its applications to multiarmed studies are illustrated. The proposed test has markedly improved power over the traditional Fisher exact test when this class of nonmyopic response adaptation is used. We also find that the test's power is close to the power of a Fisher exact test under equal randomization.