Sex specific retinoic acid signaling is required for the initiation of urogenital sinus bud development

The mammalian urogenital sinus (UGS) develops in a sex specific manner, giving rise to the prostate in the male and the sinus vagina in the embryonic female. Androgens, produced by the embryonic testis, have been shown to be crucial to this process. In this study we show that retinoic acid signaling is required for the initial stages of bud development from the male UGS. Enzymes involved in retinoic acid synthesis are expressed in the UGS mesenchyme in a sex specific manner and addition of ligand to female tissue is able to induce prostate-like bud formation in the absence of androgens, albeit at reduced potency. Functional studies in mouse organ cultures that faithfully reproduce the initiation of prostate development indicate that one of the roles of retinoic acid signaling in the male is to inhibit the expression of Inhba, which encodes the βA subunit of Activin, in the UGS mesenchyme. Through in vivo genetic analysis and culture studies we show that inhibition of Activin signaling in the female UGS leads to a similar phenotype to that of retinoic acid treatment, namely bud formation in the absence of androgens. Our data also reveals that both androgens and retinoic acid have extra independent roles to that of repressing Activin signaling in the development of the prostate during fetal stages. This study identifies a novel role for retinoic acid as a mesenchymal factor that acts together with androgens to determine the position and initiation of bud development in the male UGS epithelia.     

Enteropathogenic E. coli effectors EspG1/G2 disrupt microtubules,contribute to tight junction perturbation and inhibit restoration

Enteropathogenic Escherichia coli (EPEC) uses a type 3 secretion system to transfer effector proteins into the host intestinal epithelial cell. Several effector molecules contribute to tight junction disruption including EspG1 and its homologue EspG2 via a mechanism thought to involve microtubule destruction. The aim of this study was to investigate the contribution of EspG‐mediated microtubule disruption to TJ perturbation. We demonstrate that wild type EPEC infection disassembles microtubules and induces the progressive movement of occludin away from the membrane and into the cytosol. Deletion of espG1/G2 attenuates both of these phenotypes. In addition, EPEC infection impedes barrier recovery from calcium switch, suggesting that inhibition of TJ restoration, not merely disruption, prolongs barrier loss. TJs recover more rapidly following infection with ΔespG1/G2 than with wild type EPEC, demonstrating that EspG1/G2 perpetuate barrier loss. Although EspG regulates ADP‐ribosylation factor (ARF) and p21‐activated kinase (PAK), these activities are not necessary for microtubule destruction or perturbation of TJ structure and function. These data strongly support a role for EspG1/G2 and its associated effects on microtubules in delaying the recovery of damaged tight junctions caused by EPEC infection.     

Vertebrate Decomposition Is Accelerated by Soil Microbes

Carrion decomposition is an ecologically important natural phenomenon influenced by a complex set of factors, including temperature, moisture, and the activity of microorganisms, invertebrates, and scavengers. The role of soil microbes as decomposers in this process is essential but not well understood and represents a knowledge gap in carrion ecology. To better define the role and sources of microbes in carrion decomposition, lab-reared mice were decomposed on either (i) soil with an intact microbial community or (ii) soil that was sterilized. We characterized the microbial community (16S rRNA gene for bacteria and archaea, and the 18S rRNA gene for fungi and microbial eukaryotes) for three body sites along with the underlying soil (i.e., gravesoils) at time intervals coinciding with visible changes in carrion morphology. Our results indicate that mice placed on soil with intact microbial communities reach advanced stages of decomposition 2 to 3 times faster than those placed on sterile soil. Microbial communities associated with skin and gravesoils of carrion in stages of active and advanced decay were significantly different between soil types (sterile versus untreated), suggesting that substrates on which carrion decompose may partially determine the microbial decomposer community. However, the source of the decomposer community (soil- versus carcass-associated microbes) was not clear in our data set, suggesting that greater sequencing depth needs to be employed to identify the origin of the decomposer communities in carrion decomposition. Overall, our data show that soil microbial communities have a significant impact on the rate at which carrion decomposes and have important implications for understanding carrion ecology.     

Spatial and temporal effects of free-air CO2 enrichment (POPFACE) on leaf growth,cell expansion,and cell production in a closed canopy of poplar

Leaf expansion in the fast-growing tree, Populus x euramericana was stimulated by elevated [CO(2)] in a closed-canopy forest plantation, exposed using a free air CO(2) enrichment technique enabling long-term experimentation in field conditions. The effects of elevated [CO(2)] over time were characterized and related to the leaf plastochron index (LPI), and showed that leaf expansion was stimulated at very early (LPI, 0-3) and late (LPI, 6-8) stages in development. Early and late effects of elevated [CO(2)] were largely the result of increased cell expansion and increased cell production, respectively. Spatial effects of elevated [CO(2)] were also marked and increased final leaf size resulted from an effect on leaf area, but not leaf length, demonstrating changed leaf shape in response to [CO(2)]. Leaves exhibited a basipetal gradient of leaf development, investigated by defining seven interveinal areas, with growth ceasing first at the leaf tip. Interestingly, and in contrast to other reports, no spatial differences in epidermal cell size were apparent across the lamina, whereas a clear basipetal gradient in cell production rate was found. These data suggest that the rate and timing of cell production was more important in determining leaf shape, given the constant cell size across the leaf lamina. The effect of elevated [CO(2)] imposed on this developmental gradient suggested that leaf cell production continued longer in elevated [CO(2)] and that basal increases in cell production rate were also more important than altered cell expansion for increased final leaf size and altered leaf shape in elevated [CO(2)].     

Mechanism for increased leaf growth in elevated CO2

The effect of exposure to elevated CO₂ on the processes of leafcell production and leaf cell expansion was studied using primaryleaves of Phaseolus vulgaris L. Cell division and expansionwere separated temporally by exposing seedlings to dim red lightfor 10 d (when leaf cell division was completed) followed byexposure to bright white light for 14 d (when leaf growth wasentirely dependent on cell expansion). When plants were exposedto elevated CO₂ during the phase of cell expansion, epidermalcell size and leaf area development were stimulated. Three piecesof evidence suggest that this occurred as a result of increasedcell wall loosening and extensibility, (i) cell wall extensibility(WEx, measured as tensiometric extension using an Instron) wassignificantly increased, (ii) cell wall yield turgor (V, MPa)was reduced and (iii) xyloglucan endotransglycosylase (XET)enzyme activity was significantly increased. When plants wereexposed to elevated CO₂ during the phase of cell division, thenumber of epidermal cells was increased whilst final cell sizewas significantly reduced and this was associated with reducedfinal leaf area, WEx and XET activity. When plants were exposedto elevated CO₂ during both phases of cell division and expansion,leaf area development was not affected. For this treatment,however, the number of epidermal cells was increased, but cellexpansion was inhibited, despite exposure to elevated CO₂ duringthe expansion phase. Assessments were also made of the spatialpatterns of WEx across the expanding leaf lamina and the datasuggest that exposure to elevated CO₂ during the phase of leafexpansion may lead to enhanced extensibility particularly atbasal leaf margins which may result in altered leaf shape. The data show that both cell production and expansion were stimulatedby elevated CO₂, but that leaf growth was only enhanced by exposureto elevated CO₂ in the cell expansion phase of leaf development.Increased leaf cell expansion is, therefore, an important mechanismfor enhanced leaf growth in elevated CO₂, whilst the importanceof increased leaf cell production in elevated CO₂ remains tobe elucidated. Key words: Phaseolus vulgaris L., dwarf beans, elevated CO², biophysics of cell expansion, xyloglucan endotransglycosylase, XET, water relations     

Variable domains and a VpreB-like molecule are present in a jawless vertebrate

Immunoglobulins (Igs) and T cell antigen receptors (TCRs) that undergo somatic diversification have not been identified in the two extant orders of jawless vertebrates, which occupy essential positions in terms of understanding the evolution of the emergence of adaptive immunity. Using a single motif-dependent PCR-based approach coupled with a vector that allows selection of cDNAs encoding secretion signal sequences, four different genes encoding Ig V-type domains were identified in the sea lamprey (Petromyzon marinus). One of the predicted proteins encoded by these genes shares structural characteristics with mammalian VpreB molecules, including the absence of a recognizable transmembrane region, a relatively high proportion of charged amino acids in its C-terminal tail and distinctive features of its secretion signal peptide. This is the first indication of a molecule related to the B cell receptor (BCR) complex in a species that diverged prior to the jawed vertebrates in which RAG-mediated adaptive immunity is first encountered.Sequences described in this paper have been deposited in GenBank, with accession numbers AY576797–AY576800.     

Biogeography of dinoflagellate cysts in northwest Atlantic estuaries

Few biogeographic studies of dinoflagellate cysts include the near‐shore estuarine environment. We determine the effect of estuary type, biogeography, and water quality on the spatial distribution of organic‐walled dinoflagellate cysts from the Northeast USA (Maine to Delaware) and Canada (Prince Edward Island). A total of 69 surface sediment samples were collected from 27 estuaries, from sites with surface salinities >20. Dinoflagellate cysts were examined microscopically and compared to environmental parameters using multivariate ordination techniques. The spatial distribution of cyst taxa reflects biogeographic provinces established by other marine organisms, with Cape Cod separating the northern Acadian Province from the southern Virginian Province. Species such as Lingulodinium machaerophorum and Polysphaeridinium zoharyi were found almost exclusively in the Virginian Province, while others such as Dubridinium spp. and Islandinium? cezare were more abundant in the Acadian Province. Tidal range, sea surface temperature (SST), and sea surface salinity (SSS) are statistically significant parameters influencing cyst assemblages. Samples from the same type of estuary cluster together in canonical correspondence analysis when the estuaries are within the same biogeographic province. The large geographic extent of this study, encompassing four main estuary types (riverine, lagoon, coastal embayment, and fjord), allowed us to determine that the type of estuary has an important influence on cyst assemblages. Due to greater seasonal variations in SSTs and SSSs in estuaries compared to the open ocean, cyst assemblages show distinct latitudinal trends. The estuarine context is important for understanding present‐day species distribution, the factors controlling them, and to better predict how they may change in the future.     

Requirements for antiribosomal activity of pokeweed antiviral protein

It has been known for some time that pokeweed antiviral protein acts by enzymatically inhibiting protein synthesis on eucaryotic ribosome systems. The site of this action is known to be the ribosome itself. In this paper we show that the pokeweed antiviral protein reaction against ribosomes is a strong function of salt concentrations, where 160 mM K⁺ and 3 mM Mg²⁺ retards the reaction, while 20 mM K⁺ and 2 mM Mg²⁺ allows maximum reaction rate. It is also shown, however, that an unidentified protein in the postribosomal supernatant solution, together with ATP, allows the ribosome to be attacked even in the presence of high salt. Kinetic analysis of the antiviral protein reaction has been carried out under both sets of conditions, and reveals that the turnover number for the enzyme is about 300–400 mol/mol per min. in each case. The K_m for ribosomes is 1 μM in the presence of low salt and 0.2 μM at higher salt in the presence of postribosomal supernatant factors plus ATP. The antiviral protein reaction is also shown to be pH dependent and is controlled by a residue with pK_a value of approx. 7.0, apparently a histidine. Stoichiometric reaction of the enzyme with iodoacetamide results in a significant loss of antiribosomal activity.     

Predicting plant responses to mycorrhizae: integrating evolutionary history and plant traits

We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.     

Testosterone influences renal electrolyte excretion in SHR/y and WKY males

Background

Aldehyde dehydrogenase (ALDH) is a cytosolic enzyme highly expressed in hematopoietic precursors from cord blood and granulocyte-colony stimulating factor mobilized peripheral blood, as well as in bone marrow from patients with acute myeloblastic leukemia. As regards human normal bone marrow, detailed characterization of ALDH⁺ cells has been addressed by one single study (Gentry et al, 2007). The goal of our work was to provide new information about the dissection of normal bone marrow progenitor cells based upon the simultaneous detection by flow cytometry of ALDH and early hematopoietic antigens, with particular attention to the expression of ALDH on erythroid precursors. To this aim, we used three kinds of approach: i) multidimensional analytical flow cytometry, detecting ALDH and early hematopoietic antigens in normal bone marrow; ii) fluorescence activated cell sorting of distinct subpopulations of progenitor cells, followed by in vitro induction of erythroid differentiation; iii) detection of ALDH⁺ cellular subsets in bone marrow from pure red cell aplasia patients.

Results

In normal bone marrow, we identified three populations of cells, namely ALDH⁺CD34⁺, ALDH^-CD34⁺ and ALDH⁺CD34^- (median percentages were 0.52, 0.53 and 0.57, respectively). As compared to ALDH^-CD34⁺ cells, ALDH⁺CD34⁺ cells expressed the phenotypic profile of primitive hematopoietic progenitor cells, with brighter expression of CD117 and CD133, accompanied by lower display of CD38 and CD45RA. Of interest, ALDH⁺CD34^- population disclosed a straightforward erythroid commitment, on the basis of three orders of evidences. First of all, ALDH⁺CD34^- cells showed a CD71^bright, CD105⁺, CD45^- phenotype. Secondly, induction of differentiation experiments evidenced a clear-cut expression of glycophorin A (CD235a). Finally, ALDH⁺CD34^- precursors were not detectable in patients with pure red cell aplasia (PRCA).

Conclusion

Our study, comparing surface antigen expression of ALDH⁺/CD34⁺, ALDH^-/CD34⁺ and ALDH⁺/CD34^- progenitor cell subsets in human bone marrow, clearly indicated that ALDH⁺CD34^- cells are mainly committed towards erythropoiesis. To the best of our knowledge this finding is new and could be useful for basic studies about normal erythropoietic differentiation as well as for enabling the employment of ALDH as a red cell marker in polychromatic flow cytometry characterization of bone marrow from patients with aplastic anemia and myelodysplasia.