Transparency improves concealment in cryptically coloured moths

Predation is a ubiquitous and strong selective pressure on living organisms. Transparency is a predation defence widespread in water but rare on land. Some Lepidoptera display transparent patches combined with already cryptic opaque patches. A recent study showed that transparency reduced detectability of aposematic prey with conspicuous patches. However, whether transparency has any effect at reducing detectability of already cryptic prey is still unknown. We conducted field predation experiments with free avian predators where we monitored and compared survival of a fully opaque grey artificial form (cryptic), a form including transparent windows and a wingless artificial butterfly body. Survival of the transparent forms was similar to that of wingless bodies and higher than that of fully opaque forms, suggesting a reduction of detectability conferred by transparency. This is the first evidence that transparency decreases detectability in cryptic terrestrial prey. Future studies should explore the organization of transparent and opaque patches in animals and their interplay on survival, as well as the costs and other potential benefits associated with transparency on land.     

Four millennia of vegetation and environmental history above the Hyrcanian forest,northern Iran

Vegetation History and Archaeobotany - Past vegetation, fire, and climate dynamics, as well as human impact, have been reconstructed for the first time in the highlands of the Gilan province in the...     

8,000 years of climate,vegetation, fire and land-use dynamics in the thermo-mediterranean vegetation belt of northern Sardinia (Italy)

Vegetation History and Archaeobotany - Knowledge about the vegetation history of Sardinia, the second largest island of the Mediterranean, is scanty. Here, we present a new sedimentary record...     

Generation of a novel decay accelerating factor (DAF) knock-out rat model using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9), genome editing

Decay accelerating factor (DAF), a key complement activation control protein, is a 70 kDa membrane bound glycoprotein which controls extent of formation of the C3 and C5 convertases by accelerating their decay. Using clustered regularly-interspaced short palindromic repeats, (CRISPR)/associated protein 9 (Cas9) genome editing we generated a novel DAF deficient (Daf^?/?) rat model. The present study describes the renal and extrarenal phenotype of this model and assesses renal response to complement-dependent injury induced by administration of a complement-fixing antibody (anti-Fx1A) against the glomerular epithelial cell (podocyte). Rats generated were healthy, viable and able to reproduce normally. Complete absence of DAF was documented in renal as well as extra-renal tissues at both protein and mRNA level compared to Daf^+/+ rats. Renal histology in Daf^?/? rats showed no differences regarding glomerular or tubulointerstitial pathology compared to Daf^+/+ rats. Moreover, there was no difference in urine protein excretion (ratio of urine albumin to creatinine) or in serum creatinine and urea levels. In Daf^?/? rats, proteinuria was significantly increased following binding of anti-Fx1A antibody to podocytes while increased C3b deposition was observed. The DAF knock-out rat model developed validates the role of this complement cascade regulator in immune-mediated podocyte injury. Given the increasing role of dysregulated complement activation in various forms of kidney disease and the fact that the rat is the preferred animal for renal pathophysiology studies, the rat DAF deficient model may serve as a useful tool to study the role of this complement activation regulator in complement-dependent forms of kidney injury.

     

Developing Motion Picture Appreciation

Abstract

A well-dressed art viewer (who appears to be affluent and highly educated) is observed gazing at several contemporary works in an art museum gallery. Out of this gentleman's view, in an adjacent gallery, a blue-collar worker enters carrying a new and attractive, but ordinary-looking door that he quickly but carefully places on the floor, leaning it against a wall near several artworks. The worker exits the gallery just as the art viewer enters it. With great concentration, the viewer contemplates all of the artworks he sees. His attention is immediately drawn to the door left behind by the workman. The viewer is intrigued by the door, which he obviously mistakes for a work of art. The door is studied intensively and at length by the viewer who seems to be searching for layers of meaning. That deep intellectual pursuit is interrupted abruptly, however, when the worker reenters the gallery, picks up the door, and carries it away. Evidently, the worker's job is to install the door elsewhere in the museum, no doubt where it will not be mistaken for a work of art. Had he been asked to comment on the art viewer's encounter with the door, the worker would surely have expressed some degree of puzzlement and criticism because—from the worker's viewpoint—anyone with even a small measure of common sense (something the “expert” art viewer apparently lacks) knows the difference between a door and a work of art, no matter how finely crafted the door may be.     

Leishmania amazonensis Promastigotes Present Two Distinct Modes of Nucleus and Kinetoplast Segregation during Cell Cycle

Here, we show the morphological events associated with organelle segregation and their timing in the cell cycle of a reference strain of Leishmania (L.) amazonensis promastigotes, the main causative agent of Tegumentary leishmaniasis in the Americas. We show evidences that during the cell cycle, L. amazonensis promastigotes present two distinct modes of nucleus and kinetoplast segregation, which occur in different temporal order in different proportions of cells. We used DAPI-staining and EdU-labeling to monitor the segregation of DNA-containing organelles and DNA replication in wild-type parasites. The emergence of a new flagellum was observed using a specific monoclonal antibody. The results show that L. amazonensis cell cycle division is peculiar, with 65% of the dividing cells duplicating the kinetoplast before the nucleus, and the remaining 35% doing the opposite or duplicating both organelles concomitantly. In both cases, the new flagellum appeared during S to G2 phase in 1N1K cells and thus before the segregation of both DNA-containing organelles; however, we could not determine the exact timing of flagellar synthesis. Most of these results were confirmed by the synchronization of parasites using hydroxyurea. Altogether, our data show that during the cell cycle of L. amazonensis promastigotes, similarly to L. donovani, the segregation of nucleus and kinetoplast do not follow a specific order, especially when compared to other trypanosomatids, reinforcing the idea that this characteristic seems to be species-specific and may represent differences in cellular biology among members of the Leishmania genus.     

Cytotoxicity of Anthrax Lethal Toxin to Human Acute Myeloid Leukemia Cells Is Nonapoptotic and Dependent on Extracellular Signal-Regulated Kinase 1/2 Activity

In this study, we attempt to target the mitogen-activated protein kinase (MAPK) pathway in acute myeloid leukemia (AML) cells using a recombinant anthrax lethal toxin (LeTx). LeTx consists of protective antigen (PrAg) and lethal factor (LF). PrAg binds cells, is cleaved by furin, oligomerizes, binds three to four molecules of LF, and undergoes endocytosis, releasing LF into the cytosol. LF cleaves MAPK kinases, inhibiting the MAPK pathway. We tested potency of LeTx on a panel of 11 human AML cell lines. Seven cell lines showed cytotoxic responses to LeTx. Cytotoxicity of LeTx was mimicked by the specific mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) inhibitor U0126, indicating that LeTx-induced cell death is mediated through the MEK1/2-extracellular signal-regulated kinase (ERK1/2) branch of the MAPK pathway. The four LeTx-resistant cell lines were sensitive to the phosphatidylinositol 3-kinase inhibitor LY294002. Co-treatment of AML cells with both LeTx and LY294002 did not lead to increased sensitivity, showing a lack of additive/synergistic effects when both pathways are inhibited. Flow cytometry analysis of MAPK pathway activation revealed the presence of phospho-ERK1/2 only in LeTx-sensitive cells. Staining for Annexin V/propidium iodide and active caspases showed an increase in double-positive cells and the absence of caspase activation following treatment, indicating that LeTx-induced cell death is caspase-independent and nonapoptotic. We have shown that a majority of AML cell lines are sensitive to the LF-mediated inhibition of the MAPK pathway. Furthermore, we have demonstrated that LeTx-induced cytotoxicity in AML cells is nonapoptotic and dependent on phospho-ERK1/2 levels.     

Structural and Enzymatic Characterization of the Phosphotriesterase OPHC2 from Pseudomonas pseudoalcaligenes

Background

Organophosphates (OPs) are neurotoxic compounds for which current methods of elimination are unsatisfactory; thus bio-remediation is considered as a promising alternative. Here we provide the structural and enzymatic characterization of the recently identified enzyme isolated from Pseudomonas pseudoalcaligenes dubbed OPHC2. OPHC2 belongs to the metallo-β-lactamase superfamily and exhibits an unusual thermal resistance and some OP degrading abilities.

Principal findings

The X-ray structure of OPHC2 has been solved at 2.1 Å resolution. The enzyme is roughly globular exhibiting a αβ/βα topology typical of the metallo-β-lactamase superfamily. Several structural determinants, such as an extended dimerization surface and an intramolecular disulfide bridge, common features in thermostable enzymes, are consistent with its high T_m (97.8°C). Additionally, we provide the enzymatic characterization of OPHC2 against a wide range of OPs, esters and lactones.

Significance

OPHC2 possesses a broad substrate activity spectrum, since it hydrolyzes various phosphotriesters, esters, and a lactone. Because of its organophosphorus hydrolase activity, and given its intrinsic thermostability, OPHC2 is an interesting candidate for the development of an OPs bio-decontaminant. Its X-ray structure shed light on its active site, and provides key information for the understanding of the substrate binding mode and catalysis.