The flipflop orphan genes are required for limb bud eversion in the Tribolium embryo

Abstract Background Unlike Drosophila but similar to other arthropod and vertebrate embryos, the flour beetle Tribolium castaneum develops everted limb buds during embryogenesis. However, the molecular processes directing the evagination of epithelia are only poorly understood. Results Here we show that the newly discovered genes Tc-flipflop1 and Tc-flipflop2 are involved in regulating the directional budding of appendages. RNAi-knockdown of Tc-flipflop results in a variety of phenotypic traits. Most prominently, embryonic limb buds frequently grow inwards rather than out, leading to the development of inverted appendages inside the larval body. Moreover, affected embryos display dorsal closure defects. The Tc-flipflop genes are evolutionarily non-conserved, and their molecular function is not evident. We further found that Tc-RhoGEF2, a highly-conserved gene known to be involved in actomyosin-dependent cell movement and cell shape changes, shows a Tc-flipflop-like RNAi-phenotype. Conclusions The similarity of the inverted appendage phenotype in both the flipflop- and the RhoGEF2 RNAi gene knockdown led us to conclude that the Tc-flipflop orphan genes act in a Rho-dependent pathway that is essential for the early morphogenesis of polarised epithelial movements. Our work describes one of the few examples of an orphan gene playing a crucial role in an important developmental process

Magnetic tweezers optimized to exert high forces over extended distances from the magnet in multicellular systems

Magnetic tweezers are mainly divided into two classes depending on the ability of applying torque or forces to the magnetic probe. We focused on the second category and designed a device composed by a single electromagnet equipped with a core having a special asymmetric profile to exert forces as large as 230 pN–2.8 μm Dynabeads at distances in excess of 100 μm from the magnetic tip. Compared to existing solutions our magnetic tweezers overcome important limitations, opening new experimental paths for the study of a wide range of materials in a variety of biophysical research settings. We discuss the benefits and drawbacks of different magnet core characteristics, which led us to design the current core profile. To demonstrate the usefulness of our magnetic tweezers, we determined the microrheological properties inside embryos of Drosophila melanogaster during the syncytial stage. Measurements in different locations along the dorsal-ventral axis of the embryos showed little variation, with a slight increase in cytoplasm viscosity at the periphery of the embryos. The mean cytoplasm viscosity we obtain by active force exertion inside the embryos is comparable to that determined passively using high-speed video microrheology

Fe atom exchange between aqueous Fe \u3c sup\u3e 2+ \u3c/sup\u3e and magnetite

The reaction between magnetite and aqueous Fe2+ has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe2+ with magnetite (Fe3O4) results in the structural incorporation of Fe2+ and an increase in the bulk Fe2+ content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe 2+, as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe2+ and magnetite by reacting isotopically normal magnetite with 57Fe-enriched aqueous Fe2+. The extent of Fe atom exchange between magnetite and aqueous Fe2+ was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with 56Fe2+ indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co2+Fe23+O4) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite. © 2012 American Chemical Society

Fe Atom Exchange between Aqueous Fe²⁺ and Magnetite

The reaction between magnetite and aqueous Fe²⁺ has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe²⁺ with magnetite (Fe₃O₄) results in the structural incorporation of Fe²⁺ and an increase in the bulk Fe²⁺ content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe²⁺, as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe²⁺ and magnetite by reacting isotopically “normal” magnetite with ⁵⁷Fe-enriched aqueous Fe²⁺. The extent of Fe atom exchange between magnetite and aqueous Fe²⁺ was significant (54–71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with ⁵⁶Fe²⁺ indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co²⁺Fe₂³⁺O₄) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite

Challenges and Opportunities for Emergency Department Sepsis Screening at Triage

Feasibility of ED triage sepsis screening, before diagnostic testing has been performed, has not been established. In a retrospective, outcome-blinded chart review of a one-year cohort of ED adult septic shock patients (“derivation cohort”) and three additional, non-consecutive months of all adult ED visits (“validation cohort”), we evaluated the qSOFA score, the Shock Precautions on Triage (SPoT) vital-signs criterion, and a triage concern-for-infection (tCFI) criterion based on risk factors and symptoms, to screen for sepsis. There were 19,670 ED patients in the validation cohort; 50 developed ED septic shock, of whom 60% presented without triage hypotension, and 56% presented with non-specific symptoms. The tCFI criterion improved specificity without substantial reduction of sensitivity. At triage, sepsis screens (positive qSOFA vital-signs and tCFI, or positive SPoT vital-signs and tCFI) were 28% (95% CI: 16–43%) and 56% (95% CI: 41–70%) sensitive, respectively, p 0.05, and specificities were 97% (95% CI: 96–97%) and 95% (95% CI: 95–96%), p < 0.001. ED patients who developed septic shock requiring vasopressors often presented normotensive with non-specific complaints, necessitating a low threshold for clinical concern-for-infection at triage

Fe(II)-Catalyzed Recrystallization of Goethite Revisited

Results from enriched ⁵⁷Fe isotope tracer experiments have shown that atom exchange can occur between structural Fe in Fe­(III) oxides and aqueous Fe­(II) with no formation of secondary minerals or change in particle size or shape. Here we derive a mass balance model to quantify the extent of Fe atom exchange between goethite and aqueous Fe­(II) that accounts for different Fe pool sizes. We use this model to reinterpret our previous work and to quantify the influence of particle size and pH on extent of goethite exchange with aqueous Fe­(II). Consistent with our previous interpretation, substantial exchange of goethite occurred at pH 7.5 (≈ 90%) and we observed little effect of particle size between nanogoethite (average size of 81 × 11 nm; ≈ 110 m²/g) and microgoethite (average size of 590 × 42 nm; ≈ 40 m²/g). Despite ≈90% of the bulk goethite exchanging at pH 7.5, we found no change in mineral phase, average particle size, crystallinity, or reactivity after reaction with aqueous Fe­(II). At a lower pH of 5.0, no net sorption of Fe­(II) was observed and significantly less exchange occurred accounting for less than the estimated proportion of surface Fe atoms in the particles. Particle size appears to influence the amount of exchange at pH 5.0 and we suggest that aggregation and surface area may play a role. Results from sequential chemical extractions indicate that ⁵⁷Fe accumulates in extracted Fe­(III) goethite components. Isotopic compositions of the extracts indicate that a gradient of ⁵⁷Fe develops within the goethite with more accumulation of ⁵⁷Fe occurring in the more easily extracted Fe­(III) that may be nearer to the surface

Amnioserosa cell constriction but not epidermal actin cable tension autonomously drives dorsal closure

Tissue morphogenesis requires coordination of multiple force-producing components. During dorsal closure in fly embryogenesis, an epidermis opening closes. A tensioned epidermal actin/MyosinII cable, which surrounds the opening, produces a force that is thought to combine with another MyosinII force mediating apical constriction of the amnioserosa cells that fill the opening. A model proposing that each force could autonomously drive dorsal closure was recently challenged by a model in which the two forces combine in a ratchet mechanism. Acute force elimination via selective MyosinII depletion in one or the other tissue shows that the amnioserosa tissue autonomously drives dorsal closure while the actin/MyosinII cable cannot. These findings exclude both previous models, although a contribution of the ratchet mechanism at dorsal closure onset remains likely. This shifts the current view of dorsal closure being a combinatorial force-component system to a single tissue-driven closure event

Agricultural landscape structure and invasive species : The cost-effective level of crop field clustering

Invasive pests in agricultural settings may have severe consequences for agricultural production, reducing yields and the value of crops. Once an invader population has established, controlling it tends to be very expensive. Therefore, when the potential impacts on production may be great, protection against initial establishment is often perceived to be the most cost-effective measure. Increasing attention in the ecological literature is being given to the possibility of curbing invasion processes by manipulating the field and cropping patterns in agricultural landscapes, so that they are less conducive to the spread of pests. However, the economic implications of such interventions have received far less attention. This paper uses a stochastic spatial model to identify the key processes that influence the vulnerability of a fragmented agricultural landscape to pests. We explore the interaction between the divergent forces of ecological invasion pressure and economic returns to scale, in relation to the level of clustering of crop fields. Results show that the most cost-effective distances between crop fields in terms of reducing food production impacts from an invasive pest are determined by a delicate balance of these two forces and depend on the values of the ecological and economic parameters involved. If agricultural productivity declines slowly with increasing distance between fields and the dispersal range of the potential invader is high, manipulation of cropping structure has the potential to protect against invasion outbreaks and the farmer can gain benefit overall from maintaining greater distances between fields of similar crops

Fe(II)-catalyzed recrystallization of goethite revisited

© 2014 American Chemical Society. Results from enriched 57Fe isotope tracer experiments have shown that atom exchange can occur between structural Fe in Fe(III) oxides and aqueous Fe(II) with no formation of secondary minerals or change in particle size or shape. Here we derive a mass balance model to quantify the extent of Fe atom exchange between goethite and aqueous Fe(II) that accounts for different Fe pool sizes. We use this model to reinterpret our previous work and to quantify the influence of particle size and pH on extent of goethite exchange with aqueous Fe(II). Consistent with our previous interpretation, substantial exchange of goethite occurred at pH 7.5 (≈ 90%) and we observed little effect of particle size between nanogoethite (average size of 81 × 11 nm; ≈ 110 m2/g) and microgoethite (average size of 590 × 42 nm; ≈ 40 m2/g). Despite ≈90% of the bulk goethite exchanging at pH 7.5, we found no change in mineral phase, average particle size, crystallinity, or reactivity after reaction with aqueous Fe(II). At a lower pH of 5.0, no net sorption of Fe(II) was observed and significantly less exchange occurred accounting for less than the estimated proportion of surface Fe atoms in the particles. Particle size appears to influence the amount of exchange at pH 5.0 and we suggest that aggregation and surface area may play a role. Results from sequential chemical extractions indicate that 57Fe accumulates in extracted Fe(III) goethite components. Isotopic compositions of the extracts indicate that a gradient of 57Fe develops within the goethite with more accumulation of 57Fe occurring in the more easily extracted Fe(III) that may be nearer to the surface