Same resource,different benefits: hermit crab shell structure advantages owners,but not intruders in agonistic interactions

Resources may confer advantages by enhancing their owners’ fighting ability (resource holding potential; RHP). While the resource-correlated RHP hypothesis has been recognized as a determinant of agonistic success in different taxa, this has mostly been based on assessment of either the intruder or the owner, but only rarely in both contestants. We tested whether the internal structure of shells affects hermit crabs’ RHP, both as owners defending the shell against eviction and as intruders attempting to gain access to an occupied shell. We conducted contests (n?=?60) to compare the success in shell eviction by intruders in intact shells vs. in shells with the columella artificially reduced, and the success of shell retention by owners in intact shells vs. shells with the columella reduced. The internal configuration of the shell showed different resource-correlated RHP effects depending on the individual’s role in the fight. The presence of a columella in the intruder’s shell did not affect the likelihood that they would evict their opponents. However, owners resisted more evictions in shells with intact columella than those in shells with reduced columella. Our results demonstrate that the same resource can offer different RHP advantages to owners and intruders during an agonistic interaction.

     

Expression and functional analysis of an Entamoeba histolytica truncated adhesin in tomato plants

Several antigens from Entamoeba histolytica the agent causing human amoebiasis have been identified as potential vaccine candidates. One of them is the EhADH112 adhesin, which plays an important role during trophozoite adherence to and phagocytosis of target cells. We report here the expression of the EhADH112 carboxy-terminus of the gene (Adh240) in tomato plants. A 28 kDa band is recognized by specific antibodies in total proteins from transformed tomatoes. The plant-based adhesin conserves the ability to inhibit trophozoite adherence and phagocytosis of target cells by an average of 32.8 and 44.75% respectively.     

Growth patterns of <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> trees along altitudinal gradients in Tierra del Fuego,Argentina

The influence of ecological factors resulting from altitude on growth characteristics of Nothofagus pumilio was analyzed. N. pumilio forests grow in the southern Andes from near sea level to 600 m.a.s.l. Eight study sites were selected in the southwestern area of Tierra del Fuego, on north- and south-facing slopes, and distributed along an altitudinal gradient (200–600 m.a.s.l.). Growth cycles throughout time were identified. The correlation between climate and tree growth was determined. Tree diameter and height decreased whereas stand density increased towards tree-line. South-facing slopes showed higher values in common growth variability, probably because of stronger climatic controlling factors. Climate-growth correlation models revealed long-term temperature influences on growth variability, and showed variations among the different plots. Differences were detected in the spectral power component of the chronologies throughout the altitudinal profile. The series had a significant spectral peak at frequencies around 7 years, possibly related to mast seeding cycles. This signal became weaker as the altitude increased probably due to lower seed production. These results suggest a strong altitudinal component in growth variability of N. pumilio in Tierra del Fuego.     

Type II arginine methyltransferase PRMT5 regulates gene expression of inhibitors of differentiation/DNA binding Id2 and Id4 during glial cell differentiation

PRMT5 is a type II protein arginine methyltranferase that catalyzes monomethylation and symmetric dimethylation of arginine residues. PRMT5 is functionally involved in a variety of biological processes including embryo development and circadian clock regulation. However, the role of PRMT5 in oligodendrocyte differentiation and central nervous system myelination is unknown. Here we show that PRMT5 expression gradually increases throughout postnatal brain development, coinciding with the period of active myelination. PRMT5 expression was observed in neurons, astrocytes, and oligodendrocytes. siRNA-mediated depletion of PRMT5 in mouse primary oligodendrocyte progenitor cells abrogated oligodendrocyte differentiation. In addition, the PRMT5-depleted oligodendrocyte progenitor and C6 glioma cells expressed high levels of the inhibitors of differentiation/DNA binding, Id2 and Id4, known repressors of glial cell differentiation. We observed that CpG-rich islands within the Id2 and Id4 genes were bound by PRMT5 and were hypomethylated in PRMT5-deficient cells, suggesting that PRMT5 plays a role in gene silencing during glial cell differentiation. Our findings define a role of PRMT5 in glial cell differentiation and link PRMT5 to epigenetic changes during oligodendrocyte differentiation.     

Impact of the placental cytokine-chemokine balance on regulation of cell-cell contact-induced human immunodeficiency virus type 1 translocation across a trophoblastic barrier in vitro

Cells constituting the placental barrier secrete soluble factors that may participate in controlling human immunodeficiency virus type 1 (HIV-1) transmission from the mother to the fetus. In this study, we asked whether placental soluble factors (PSF) could limit cell-cell contact inducing HIV-1 production that occurs after inoculation of HIV-1-infected peripheral blood mononuclear cells (HIV-1+ PBMCs) onto trophoblast-derived BeWo cells grown as tight and polarized barriers in a two-chamber system. The activity of recombinant chemokines and cytokines expressed by placental tissue and of factors secreted by either early or term placentae of HIV-1-negative women, was analyzed. We identified chemokines (RANTES and MIP-1beta) and cytokines (tumor necrosis factor alpha and interleukin-8) that decreased and increased, respectively, viral production in trophoblast barrier cells inoculated with HIV-1+ PBMCs. Unexpectedly, factors secreted by either early or term placentae of HIV-1-negative women enhanced viral production. Nevertheless, the same PSF did not favor infection of trophoblastic barriers with cell-free HIV-1 and strongly reduced viral production in PBMCs infected with cell-free HIV-1. Moreover, PSF contained chemokines (RANTES and MIP-1beta) and a cytokine, leukemia inhibitory factor, exhibiting a strong anti-HIV-1 activity in our model of cell-to-cell infection. Together these data suggested that at the maternal interface the global activity of PSF is related to the synergistic action of several soluble factors with a balance in favor of an enhancing activity on the passage of viruses across the trophoblast barrier. This could explain the presence of viral sequences in trophoblasts in all placentae of HIV-1-infected women.     

An ER‐resident membrane protein complex regulates nicotinic acetylcholine receptor subunit composition at the synapse

Nicotinic acetylcholine receptors (nAChRs) are homo‐ or heteropentameric ligand‐gated ion channels mediating excitatory neurotransmission and muscle activation. Regulation of nAChR subunit assembly and transfer of correctly assembled pentamers to the cell surface is only partially understood. Here, we characterize an ER transmembrane (TM) protein complex that influences nAChR cell‐surface expression and functional properties in Caenorhabditis elegans muscle. Loss of either type I TM protein, NRA‐2 or NRA‐4 (n icotinic r eceptor a ssociated), affects two different types of muscle nAChRs and causes in vivo resistance to cholinergic agonists. Sensitivity to subtype‐specific agonists of these nAChRs is altered differently, as demonstrated by whole‐cell voltage‐clamp of dissected adult muscle, when applying exogenous agonists or after photo‐evoked, channelrhodopsin‐2 (ChR2) mediated acetylcholine (ACh) release, as well as in single‐channel recordings in cultured embryonic muscle. These data suggest that nAChRs desensitize faster in nra‐2 mutants. Cell‐surface expression of different subunits of the ‘levamisole‐sensitive’ nAChR (L‐AChR) is differentially affected in the absence of NRA‐2 or NRA‐4, suggesting that they control nAChR subunit composition or allow only certain receptor assemblies to leave the ER.     

Osmoregulatory disturbances induced by the parasitic barnacle Loxothylacus texanus (Rhizocephala) in the crab Callinectes rathbunae (Portunidae)

The osmoregulatory response of the blue crab Callinectes rathbunae parasitized with the rhizocephalan barnacle Loxothylacus texanus, and subjected to sudden salinity changes, was experimentally measured in the laboratory. Parasitized and control crabs were exposed to salinity changes every 3 h and their hemolymph osmolality measured. Two experiments, one with increasing salinity conditions (5‰, 12‰, 19‰, 25‰) and a second one with decreasing salinities (35‰, 25‰, 15‰, 5‰) were conducted. The results show that L. texanus significantly alters the hemolymph osmolality of C. rathbunae maintaining it at lower than normal levels. In the increasing salinity trial, the hypoosmotic hemolymph condition of parasitized crabs was present at all salinities tested, whereas in the decreasing salinity trial a significant effect was found only at salinities of 5‰ and 15‰. Since C. rathbunae is constantly subjected to abrupt salinity changes in the tropical estuaries where it occurs, moving into high salinity areas may be the only way to cope with the impact of L. texanus.     

Palaeolimnology of the Santa Clara Abajo Formation,Triassic of the Cuyana Basin Argentina,inferred from fish taphonomy

The Santa Clara Abajo Formation in the north of Mendoza Province, Argentina, is part of the Triassic Cuyana rift Basin infill and consists of fluvial, deltaic and lacustrine units. The combination of progradational to aggradational stacking pattern plus the identification of a fluctuating profundal facies association suggests the Santa Clara Abajo palaeolake was a balanced‐fill lake system. Lake‐centre sediments (finely laminated mudrock facies) preserve pseudobeaconiid actinopterygian fish represented primarily by bones and scales, generally undeformed and concordant with bedding planes. We propose that variation of articulation degree of these fish combined with sediment features provides insights into palaeolimnological changes in this single lake system over time, primarily water temperature. The fish fossils are sorted into three taphonomic modes: Mode A, isolated and dispersed scales; Mode B, associated but dispersed scales, loosely to well sorted, and low to moderate density; and Mode C, scale patches and articulated fishes. We conclude these modes represent, respectively, warm, fluctuating warm–cold and cold water conditions. Stratigraphical analysis of the taphonomic modes for the balanced‐fill lake model revealed an up‐section pattern of fluctuating water temperatures (cold and warm), to a stable‐cold pattern, to a stable‐warm pattern and to fluctuating thermal conditions (cold and warm) again. This pattern is linked to lake‐level fluctuations resulting in lacustrine intervals that reflect hydrological closure to opening to closure again.     

A new mouse model to explore therapies for preeclampsia

Background

Pre-eclampsia, a pregnancy-specific multisystemic disorder is a leading cause of maternal and perinatal mortality and morbidity. This syndrome has been known to medical science since ancient times. However, despite considerable research, the cause/s of preeclampsia remain unclear, and there is no effective treatment. Development of an animal model that recapitulates this complex pregnancy-related disorder may help to expand our understanding and may hold great potential for the design and implementation of effective treatment.

Methodology/Principal Findings

Here we show that the CBA/J x DBA/2 mouse model of recurrent miscarriage is also a model of immunologically-mediated preeclampsia (PE). DBA/J mated CBA/J females spontaneously develop many features of human PE (primigravidity, albuminuria, endotheliosis, increased sensitivity to angiotensin II and increased plasma leptin levels) that correlates with bad pregnancy outcomes. We previously reported that antagonism of vascular endothelial growth factor (VEGF) signaling by soluble VEGF receptor 1 (sFlt-1) is involved in placental and fetal injury in CBA/J x DBA/2 mice. Using this animal model that recapitulates many of the features of preeclampsia in women, we found that pravastatin restores angiogenic balance, ameliorates glomerular injury, diminishes hypersensitivity to angiotensin II and protects pregnancies.

Conclusions/Significance

We described a new mouse model of PE, were the relevant key features of human preeclampsia develop spontaneously. The CBA/J x DBA/2 model, that recapitulates this complex disorder, helped us identify pravastatin as a candidate therapy to prevent preeclampsia and its related complications. We recognize that these studies were conducted in mice and that clinical trials are needed to confirm its application to humans.