Isolation of Shigella dysenteriae type 1 and S. flexneri strains from surface waters in Bangladesh: comparative molecular analysis of environmental Shigella isolates versus clinical strains

Bacillary dysentery caused by Shigella species is a public health problem in developing countries including Bangladesh. Although, shigellae-contaminated food and drinks are often the source of the epidemic's spread, the possible presence of the pathogen and transmission of it through environmental waters have not been adequately examined. We analyzed surface waters collected in Dhaka, Bangladesh, for the presence of shigellae by a combination of PCR assays followed by concentration and culturing of PCR-positive samples. Analysis of 128 water samples by PCR assays for Shigella-specific virulence genes including ipaBCD, ipaH, and stx1 identified 14 (10.9%) samples which were positive for one or more of these virulence genes. Concentration of the PCR-positive samples by filtration followed by culturing identified live Shigella species in 11 of the 14 PCR-positive samples. Analysis of rRNA gene restriction patterns (ribotype) showed that the environmental isolates shared ribotypes with a collection of clinical isolates, but in contrast to the clinical isolates, 10 of the 11 environmental isolates were either negative or carried deletions in the plasmid-encoded invasion-associated genes ipaB, ipaC, and ipaD. However, all environmental Shigella isolates were positive for the chromosomal multicopy invasion-associated gene ipaH and all Shigella dysenteriae type 1 isolates were positive for the stx1 gene in addition to ipaH. This study demonstrated the presence of Shigella in the aquatic environment and dispersion of different virulence genes among these isolates which appear to constitute an environmental reservoir of Shigella-specific virulence genes. Since critical virulence genes in Shigella are carried by plasmids or mobile genetic elements, the environmental gene pool may contribute to an optimum combination of genes, causing the emergence of virulent Shigella strains which is facilitated in particular by close contact of the population with surface waters in Bangladesh.     

Leaf and stem physiological responses to summer and winter extremes of woody species across temperate ecosystems

Winter cold limits temperate plant performance, as does summer water stress in drought‐prone ecosystems. The relative impact of seasonal extremes on plant performance has received considerable attention for individual systems. An integrated study compiling the existing literature was needed to identify overall trends. First, we conducted a meta‐analysis of the impacts of summer and winter on ecophysiology for three woody plant functional types (winter deciduous angiosperms, evergreen angiosperms and conifers), including data for 210 records from 75 studies of ecosystems with and without summer drought across the temperate zone. Second, we tested predictions by conducting a case study in a drought‐prone Mediterranean ecosystem subject to winter freezing. As indicators of physiological response of leaves and xylem to seasonal stress, we focused on stomatal conductance (g_s), percent loss of stem xylem hydraulic conductivity (PLC) and photochemical efficiency of photosystem II (F_v/F_m). Our meta‐analysis showed that in ecosystems without summer drought, g_s was higher during summer than winter. By contrast, in drought‐prone ecosystems many species maintained open stomata during winter, with potential strong consequences for plant carbon gain over the year. Further, PLC tended to increase and F_v/F_m to decrease from summer to winter for most functional types and ecosystems due to low temperatures. Overall, deciduous angiosperms were most sensitive to climatic stress. Leaf gas exchange and stem xylem hydraulics showed a coordinated seasonal response at ecosystems without summer drought. In our Mediterranean site subjected to winter freezing the species showed similar responses to those typically found for ecosystems without summer drought. We conclude that winter stress is most extreme for systems without summer drought and systems with summer drought and winter freezing, and less extreme for drought‐prone systems without freezing. In all cases the evergreen species show less pronounced seasonal responses in both leaves and stems than deciduous species.     

Human monoclonal rheumatoid synovial B lymphocyte hybridoma with a new disease-related specificity for cartilage oligomeric matrix protein

Joint-specific self-Ags are considered to play an important role in the induction of synovial T and B cell expansion in human rheumatoid arthritis (RA). However, the nature of these autoantigens is still enigmatic. In this study a somatically mutated IgG2 lambda B cell hybridoma was established from the synovial membrane of an RA patient and analyzed for its Ag specificity. A heptameric peptide of cartilage oligomeric matrix protein (COMP) could be characterized as the target structure recognized by the human synovial B cell hybridoma. The clonotypic V(H) sequences of the COMP-specific hybridoma could also be detected in synovectomy material derived from five different RA patients but in none of the investigated osteoarthritis cases (n = 5), indicating a preferential usage of V(H) genes closely related to those coding for a COMP-specific Ag receptor in RA synovial B cells. Moreover, the COMP heptamer was preferentially recognized by circulating IgG in RA (n = 22) compared with osteoarthritis patients (n = 24) or age-matched healthy controls (n = 20; both p < 0.0001). Hence, the COMP-specific serum IgG is likely to reflect local immune responses toward a cartilage- and tendon-restricted Ag that might be crucial to the induction of tissue damage in RA.     

The human serum amyloid A (SAA)-encoding gene GSAA1: nucleotide sequence and possible autocrine-collagenase-inducer function

We have determined the genomic sequence of the human GSAA1 gene, a member of the family of acute-phase human serum amyloid A (SAA)-encoding genes. This sequence predicts a mature protein of 104 amino acids (aa), several of which differ from residues usually conserved in the sequence of SAA proteins isolated from serum. Despite coding differences, however, the four-exon structure of GSAA1 resembles that of other SAA genes in humans and mice. The N-terminal 25 aa of the mature GSAA1 protein are virtually identical to those of an 'SAA-like' autocrine collagenase inducer produced by rabbit synovial fibroblasts; the latter also differ from the corresponding aa found in SAA in serum. We propose that GSAA1 is the human gene coding for a protein closely related to the SAA, but which is adapted to this important autocrine cytokine function.     

The role of sirtuins in modulating redox stressors

For much of the time since their discovery, the sirtuin family of deacetylase enzymes has been associated with extension of life span. This longevity-promoting capacity in numerous model systems has enabled the sirtuins to gain "celebrity status" in the field of aging research. However, the mechanisms underpinning these changes remain incompletely defined. A general phenotype long associated with aging is the dysregulation of biological systems, which partly occurs via the accumulation of damage over time. One of the major sources of this damage is oxidative stress, which can harm both biological structures and the mechanisms with which they are repaired. It is now becoming clear that the beneficial life-span effects of sirtuins, along with many of their other functions, are closely linked to their ability to regulate systems that control the redox environment. Here we investigate the links between sirtuins and their oxidative/redox environment and review the control mechanisms that are regulated by the activity of sirtuin deacetylase proteins.     

FMRI Effective Connectivity and TMS Chronometry: Complementary Accounts of Causality in the Visuospatial Judgment Network

Background

While traditionally quite distinct, functional neuroimaging (e.g. functional magnetic resonance imaging: fMRI) and functional interference techniques (e.g. transcranial magnetic stimulation: TMS) increasingly address similar questions of functional brain organization, including connectivity, interactions, and causality in the brain. Time-resolved TMS over multiple brain network nodes can elucidate the relative timings of functional relevance for behavior (“TMS chronometry”), while fMRI functional or effective connectivity (fMRI EC) can map task-specific interactions between brain regions based on the interrelation of measured signals. The current study empirically assessed the relation between these different methods.

Methodology/Principal Findings

One group of 15 participants took part in two experiments: one fMRI EC study, and one TMS chronometry study, both of which used an established cognitive paradigm involving one visuospatial judgment task and one color judgment control task. Granger causality mapping (GCM), a data-driven variant of fMRI EC analysis, revealed a frontal-to-parietal flow of information, from inferior/middle frontal gyrus (MFG) to posterior parietal cortex (PPC). FMRI EC-guided Neuronavigated TMS had behavioral effects when applied to both PPC and to MFG, but the temporal pattern of these effects was similar for both stimulation sites. At first glance, this would seem in contradiction to the fMRI EC results. However, we discuss how TMS chronometry and fMRI EC are conceptually different and show how they can be complementary and mutually constraining, rather than contradictory, on the basis of our data.

Conclusions/Significance

The findings that fMRI EC could successfully localize functionally relevant TMS target regions on the single subject level, and conversely, that TMS confirmed an fMRI EC identified functional network to be behaviorally relevant, have important methodological and theoretical implications. Our results, in combination with data from earlier studies by our group (Sack et al., 2007, Cerebral Cortex), lead to informed speculations on complex brain mechanisms, and TMS disruption thereof, underlying visuospatial judgment. This first in-depth empirical and conceptual comparison of fMRI EC and TMS chronometry thereby shows the complementary insights offered by the two methods.     

MOS11: a new component in the mRNA export pathway

Nucleocytoplasmic trafficking is emerging as an important aspect of plant immunity. The three related pathways affecting plant immunity include Nuclear Localization Signal (NLS)-mediated nuclear protein import, Nuclear Export Signal (NES)-dependent nuclear protein export, and mRNA export relying on MOS3, a nucleoporin belonging to the Nup107-160 complex. Here we report the characterization, identification, and detailed analysis of Arabidopsis modifier of snc1, 11 (mos11). Mutations in MOS11 can partially suppress the dwarfism and enhanced disease resistance phenotypes of snc1, which carries a gain-of-function mutation in a TIR-NB-LRR type Resistance gene. MOS11 encodes a conserved eukaryotic protein with homology to the human RNA binding protein CIP29. Further functional analysis shows that MOS11 localizes to the nucleus and that the mos11 mutants accumulate more poly(A) mRNAs in the nucleus, likely resulting from reduced mRNA export activity. Epistasis analysis between mos3-1 and mos11-1 revealed that MOS11 probably functions in the same mRNA export pathway as MOS3, in a partially overlapping fashion, before the mRNA molecules pass through the nuclear pores. Taken together, MOS11 is identified as a new protein contributing to the transfer of mature mRNA from the nucleus to the cytosol.     

Identification of potent,selective and orally bioavailable phenyl ((R)-3-phenylpyrrolidin-3-yl)sulfone analogues as RORγt inverse agonists

An X-ray crystal structure of one of our previously discovered RORγt inverse agonists bound to the RORγt ligand binding domain revealed that the cyclohexane carboxylic acid group of compound 2 plays a significant role in RORγt binding, forming four hydrogen bonding and ionic interactions with RORγt. SAR studies centered around the cyclohexane carboxylic acid group led to identification of several structurally diverse and more potent compounds, including new carboxylic acid analogues 7 and 20, and cyclic sulfone analogues 34 and 37. Notably, compounds 7 and 20 were found to maintain the desirable pharmacokinetic profile of 2.