Functional Divergence of the Tribolium castaneum engrailed and invected Paralogs.

Engrailed (en) and invected (inv) encode paralogous transcription factors found as a closely linked tandem duplication within holometabolous insects. Drosophila en mutants segment normally, then fail to maintain their segments. Loss of Drosophila inv is viable, while loss of both genes results in asegmental larvae. Surprisingly, the knockdown of Oncopeltus inv can result in the loss or fusion of the entire abdomen and en knockdowns in Tribolium show variable degrees of segmental loss. The consequence of losing or knocking down both paralogs on embryogenesis has not been studied beyond Drosophila. To further investigate the relative functions of each paralog and the mechanism behind the segmental loss, Tribolium double and single knockdowns of en and inv were analyzed. The most common cuticular phenotype of the double knockdowns was small, limbless, and open dorsally, with all but a single, segmentally iterated row of bristles. Less severe knockdowns had fused segments and reduced appendages. The Tribolium paralogs appear to act synergistically: the knockdown of either Tribolium gene alone was typically less severe, with all limbs present, whereas the most extreme single knockdowns mimic the most severe double knockdown phenotype. Morphological abnormalities unique to either single gene knockdown were not found. inv expression was not affected in the Tribolium en knockdowns, but hh expression was unexpectedly increased midway through development. Thus, while the segmental expression of en/inv is broadly conserved within insects, the functions of en and inv are evolving independently in different lineages.

Modeling analyte transport and capture in porous bead sensors.

Porous agarose microbeads, with high surface to volume ratios and high binding densities, are attracting attention as highly sensitive, affordable sensor elements for a variety of high performance bioassays. While such polymer microspheres have been extensively studied and reported on previously and are now moving into real-world clinical practice, very little work has been completed to date to model the convection, diffusion, and binding kinetics of soluble reagents captured within such fibrous networks. Here, we report the development of a three-dimensional computational model and provide the initial evidence for its agreement with experimental outcomes derived from the capture and detection of representative protein and genetic biomolecules in 290 µm porous beads. We compare this model to antibody-mediated capture of C-reactive protein and bovine serum albumin, along with hybridization of oligonucleotide sequences to DNA probes. These results suggest that, due to the porous interior of the agarose bead, internal analyte transport is both diffusion and convection based, and regardless of the nature of analyte, the bead interiors reveal an interesting trickle of convection-driven internal flow. On the basis of this model, the internal to external flow rate ratio is found to be in the range of 1:170 to 1:3100 for beads with agarose concentration ranging from 0.5% to 8% for the sensor ensembles here studied. Further, both model and experimental evidence suggest that binding kinetics strongly affect analyte distribution of captured reagents within the beads. These findings reveal that high association constants create a steep moving boundary in which unbound analytes are held back at the periphery of the bead sensor. Low association constants create a more shallow moving boundary in which unbound analytes diffuse further into the bead before binding. These models agree with experimental evidence and thus serve as a new tool set for the study of bioagent transport processes within a new class of medical microdevices.

Location of biomarkers and reagents within agarose beads of a programmable bio-nano-chip.

The slow development of cost-effective medical microdevices with strong analytical performance characteristics is due to a lack of selective and efficient analyte capture and signaling. The recently developed programmable bio-nano-chip (PBNC) is a flexible detection device with analytical behavior rivaling established macroscopic methods. The PBNC system employs ≈300 µm-diameter bead sensors composed of agarose "nanonets" that populate a microelectromechanical support structure with integrated microfluidic elements. The beads are an efficient and selective protein-capture medium suitable for the analysis of complex fluid samples. Microscopy and computational studies probe the 3D interior of the beads. The relative contributions that the capture and detection of moieties, analyte size, and bead porosity make to signal distribution and intensity are reported. Agarose pore sizes ranging from 45 to 620 nm are examined and those near 140 nm provide optimal transport characteristics for rapid (<15 min) tests. The system exhibits efficient (99.5%) detection of bead-bound analyte along with low (≈2%) nonspecific immobilization of the detection probe for carcinoembryonic antigen assay. Furthermore, the role analyte dimensions play in signal distribution is explored, and enhanced methods for assay building that consider the unique features of biomarker size are offered.

A multifunctional reporter mouse line for Cre- and FLP-dependent lineage analysis.

The Cre/lox and FLP/FRT recombination systems have been used extensively for both conditional knockout and cell lineage analysis in mice. Here we report a new multifunctional Cre/FLP dual reporter allele (R26(NZG)) that exhibits strong and apparently ubiquitous marker expression in embryos and adults. The reporter construct, which is driven by the CAG promoter, was knocked into the ROSA26 locus providing an open chromatin domain for consistent expression and avoiding site-of-integration effects often observed with transgenic reporters. R26(NZG) directs Cre-dependent nuclear-localized beta-galactosidase (beta-gal) expression, and can be converted into a Cre-dependent EGFP reporter (R26(NG)) by germline excision of the FRT-flanked nlslacZ cassette. Alternatively, germline excision of the floxed PGKNEO cassette in R26(NZG) generates an FLP-dependent EGFP reporter (R26(ZG)) that expresses beta-gal in FLP-nonexpressing cells. Finally, by the simultaneous use of both Cre and FLP deleters, R26(NZG) allows lineage relationships to be interrogated with greater refinement than is possible with single recombinase reporter systems.

Shall We Focus on the Eosinophil to Guide Treatment with Systemic Corticosteroids during Acute Exacerbations of COPD?: PRO.

In an era of precision medicine, it seems regressive that we do not use stratified approaches to direct treatment of oral corticosteroids during an exacerbation of chronic obstructive pulmonary disease (COPD). This is despite evidence suggesting that 40% of COPD patients have eosinophilic inflammation and this is an indicator of corticosteroid response. Treatments with oral corticosteroids are not always effective and not without harm, with significant and increased risk of hyperglycemia, sepsis, and fractures. Eosinophils are innate immune cells with an incompletely understood role in the pathology of airway disease. They are detected at increased levels in some patients and can be measured using non-invasive methods during states of exacerbation and stable periods. Despite the eosinophil having an unknown mechanism in COPD, it has been shown to be a marker of length of stay in severe hospitalized exacerbations, a predictor of risk of future exacerbation and exacerbation type. Although limited, promising data has come from one prospective clinical trial investigating the eosinophil as a biomarker to direct systemic corticosteroid treatment. This identified that there were statistically significant and clinically worsened symptoms in patients with low eosinophil levels who were prescribed prednisolone, demonstrating the potential utility of the eosinophil. In an era of precision medicine our patients' needs are best served by accurate diagnosis, correct identification of maximal treatment response and the abolition of harm. The peripheral blood eosinophil count could be used towards reaching these aims.

Induction of zone-like liver function gradients in HepG2 cells by varying culture medium height.

In most laboratory-scale mammalian cell cultures, the primary mode of oxygen delivery to cultured cells is by passive diffusion through a thin layer of culture medium, and the height of culture medium chosen may therefore have a significant effect on the phenotype of oxygen-sensitive cell types. Many of the liver functions performed by hepatocytes are thought to be regulated into zones by the local oxygen concentration; of particular interest to in vitro toxicologists, the cytochrome P450 family of detoxification enzymes is known to be preferentially expressed by hepatocytes at low (perivenous) oxygen concentrations. Using an array of different medium heights in a 12-well plate format, we show that the height of culture medium has a significant effect on cytochrome P450 1A1 detoxification activity, glucose metabolism, and cell morphology of HepG2 hepatocellular carcinoma cultures. In particular, cytochrome P450 activity exhibits a maximum at medium heights corresponding to perivenous oxygen concentrations. This work demonstrates that optimizing cell culture performance is not always the same as maximizing oxygen delivery.

Size-dependent mobile surface charge model of cell electrophoresis.

A model that accurately predicts the effects of cellular size and electric field strength on electrophoretic mobility has been developed. Previous models have predicted that electrophoretic mobility (EPM) is dependent only on cell surface charge, bath viscosity and ionic strength of the electrolyte. However, careful analysis of experimental data from the literature shows that these models do not accurately depict the relationship between chemically determined surface charge and observed mobility. We propose a new model that accounts for electrically driven redistribution of mobile surface charge islands, such as the recently proposed lipid raft structures. This model predicts electrophoretic mobility as a function of a new dimensionless quantity, A, that incorporates the cell radius, the electric field strength, and the average diameter of charged membrane complexes.

Fabrication of a multiple-diameter branched network of microvascular channels with semi-circular cross-sections using xenon difluoride etching.

The majority of microfluidic devices employ networks of channels that have rectangular cross-sections. At the microvascular scale of 30 to 300 microm in diameter, however, the distribution of fluid mechanical stresses and the induced shape of cultured cells will be quite different in a rectangular channel from the near-circular cross-sections seen in vivo. While round-cross-section channels have been produced before by wet etching, fine control of feature size has not been demonstrated, and prior work has only produced channels of a single diameter on a given device. In this work, the xenon difluoride process for isotropic etching of silicon was optimized for production of channels with semicircular cross-sections. This process was then used to produce a network of microvessel-scale semicylindrical channels on a silicon chip, the diameter of which was decreased with each level of branching. Additionally, it was demonstrated that endothelial cells will adhere to both the bottom and sides of these channels, indicating that such chips may be useful in the future for culturing in vitro models of the microvasculature.