Experimental Characterization Of Electrical Current Leakage In Poly(Dimethylsiloxane) Microfluidic Devices

Poly(dimethylsiloxane) (PDMS) is usually considered as a dielectric material and the PDMS microchannel wall can be treated as an electrically insulated boundary in an applied electric field. However, in certain layouts of microfluidic networks, electrical leakage through the PDMS microfluidic channel walls may not be negligible, which must be carefully considered in the microfluidic circuit design. In this paper, we report on the experimental characterization of the electrical leakage current through PDMS microfluidic channel walls of different configurations. Our numerical and experimental studies indicate that for tens of microns thick PDMS channel walls, electrical leakage through the PDMS wall could significantly alter the electrical field in the main channel. We further show that we can use the electrical leakage through the PDMS microfluidic channel wall to control the electrolyte flow inside the microfluidic channel and manipulate the particle motion inside the microfluidic channel. More specifically, we can trap individual particles at different locations inside the microfluidic channel by balancing the electroosmotic flow and the electrophoretic migration of the particle

Constitutive TL1A (TNFSF15) Expression on Lymphoid or Myeloid Cells Leads to Mild Intestinal Inflammation and Fibrosis

TL1A is a member of the TNF superfamily and its expression is increased in the mucosa of inflammatory bowel disease patients. Moreover, a subset of Crohn's disease (CD) patients with the risk TL1A haplotype is associated with elevated TL1A expression and a more severe disease course. To investigate the in vivo role of elevated TL1A expression, we generated two transgenic (Tg) murine models with constitutive Tl1a expression in either lymphoid or myeloid cells. Compared to wildtype (WT) mice, constitutive expression of Tl1a in either lymphoid or myeloid cells showed mild patchy inflammation in the small intestine, which was more prominent in the ileum. In addition, mice with constitutive Tl1a expression exhibited enhanced intestinal and colonic fibrosis compared to WT littermates. The percentage of T cells expressing the gut homing chemokine receptors CCR9 and CCR10 was higher in the Tl1a Tg mice compared to WT littermates. Sustained expression of Tl1A in T cells also lead to increased Foxp3+ Treg cells. T cells or antigen presenting cells (APC) with constitutive expression of Tl1a were found to have a more activated phenotype and mucosal mononuclear cells exhibit enhanced Th1 cytokine activity. These results indicated an important role of TL1A in mucosal T cells and APC function and showed that up-regulation of TL1A expression can promote mucosal inflammation and gut fibrosis

The Formation and Evolution of the First Massive Black Holes

The first massive astrophysical black holes likely formed at high redshifts (z>10) at the centers of low mass (~10^6 Msun) dark matter concentrations. These black holes grow by mergers and gas accretion, evolve into the population of bright quasars observed at lower redshifts, and eventually leave the supermassive black hole remnants that are ubiquitous at the centers of galaxies in the nearby universe. The astrophysical processes responsible for the formation of the earliest seed black holes are poorly understood. The purpose of this review is threefold: (1) to describe theoretical expectations for the formation and growth of the earliest black holes within the general paradigm of hierarchical cold dark matter cosmologies, (2) to summarize several relevant recent observations that have implications for the formation of the earliest black holes, and (3) to look into the future and assess the power of forthcoming observations to probe the physics of the first active galactic nuclei.Comment: 39 pages, review for "Supermassive Black Holes in the Distant Universe", Ed. A. J. Barger, Kluwer Academic Publisher

Upregulated HSP27 in human breast cancer cells reduces Herceptin susceptibility by increasing Her2 protein stability

<p>Abstract</p> <p>Background</p> <p>Elucidating the molecular mechanisms by which tumors become resistant to Herceptin is critical for the treatment of Her2-overexpressed metastatic breast cancer.</p> <p>Methods</p> <p>To further understand Herceptin resistance mechanisms at the molecular level, we used comparative proteome approaches to analyze two human breast cancer cell lines; Her2-positive SK-BR-3 cells and its Herceptin-resistant SK-BR-3 (SK-BR-3 HR) cells.</p> <p>Results</p> <p>Heat-shock protein 27 (HSP27) expression was shown to be upregulated in SK-BR-3 HR cells. Suppression of HSP27 by specific siRNA transfection increased the susceptibility of SK-BR-3 HR cells to Herceptin. In the presence of Herceptin, Her2 was downregulated in both cell lines. However, Her2 expression was reduced by a greater amount in SK-BR-3 parent cells than in SK-BR-3 HR cells. Interestingly, co-immunoprecipitation analysis showed that HSP27 can bind to Her2. In the absence of Herceptin, HSP27 expression is suppressed and Her2 expression is reduced, indicating that downregulation of Her2 by Herceptin can be obstructed by the formation of a Her2-HSP27 complex.</p> <p>Conclusion</p> <p>Our present study demonstrates that upregulated HSP27 in human breast cancer cells can reduce Herceptin susceptibility by increasing Her2 protein stability.</p

The Formation of the First Massive Black Holes

Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z=6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, (e)LISA and other instruments.Comment: 47 pages with 306 references; this review is a chapter in "The First Galaxies - Theoretical Predictions and Observational Clues", Springer Astrophysics and Space Science Library, Eds. T. Wiklind, V. Bromm & B. Mobasher, in pres

STING couples with PI3K to regulate actin reorganization during BCR activation

The adaptor protein, STING (stimulator of interferon genes), has been rarely studied in adaptive immunity. We used Sting KO mice and a patient's mutated STING cells to study the effect of STING deficiency on B cell development, differentiation, and BCR signaling. We found that STING deficiency promotes the differentiation of marginal zone B cells. STING is involved in BCR activation and negatively regulates the activation of CD1 9 and Btk but positively regulates the activation of SHIP. The activation of WASP and accumulation of F-actin were enhanced in Sting KO B cells upon BCR stimulation. Mechanistically, STING uses PI3K mediated by the CD19-Btk axis as a central hub for controlling the actin remodeling that, in turn, offers feedback to BCR signaling. Overall, our study provides a mechanism of how STING regulates BCR signaling via feedback from actin reorganization, which contributes to positive regulation of STING on the humoral immune response

Reverse Genetics in Ecological Research

By precisely manipulating the expression of individual genetic elements thought to be important for ecological performance, reverse genetics has the potential to revolutionize plant ecology. However, untested concerns about possible side-effects of the transformation technique, caused by Agrobacterium infection and tissue culture, on plant performance have stymied research by requiring onerous sample sizes. We compare 5 independently transformed Nicotiana attenuata lines harboring empty vector control (EVC) T-DNA lacking silencing information with isogenic wild types (WT), and measured a battery of ecologically relevant traits, known to be important in plant-herbivore interactions: phytohormones, secondary metabolites, growth and fitness parameters under stringent competitive conditions, and transcriptional regulation with microarrays. As a positive control, we included a line silenced in trypsin proteinase inhibitor gene (TPI) expression, a potent anti-herbivore defense known to exact fitness costs in its expression, in the analysis. The experiment was conducted twice, with 10 and 20 biological replicates per genotype. For all parameters, we detected no difference between any EVC and WT lines, but could readily detect a fitness benefit of silencing TPI production. A statistical power analyses revealed that the minimum sample sizes required for detecting significant fitness differences between EVC and WT was 2–3 orders of magnitude larger than the 10 replicates required to detect a fitness effect of TPI silencing. We conclude that possible side-effects of transformation are far too low to obfuscate the study of ecologically relevant phenotypes

Lymphomas driven by Epstein-Barr virus nuclear antigen-1 (EBNA1) are dependant upon Mdm2

Epstein-Barr virus (EBV)-associated Burkitt's lymphoma is characterised by the deregulation of c-Myc expression and a restricted viral gene expression pattern in which the EBV nuclear antigen-1 (EBNA1) is the only viral protein to be consistently expressed. EBNA1 is required for viral genome propagation and segregation during latency. However, it has been much debated whether the protein plays a role in viral-associated tumourigenesis. We show that the lymphomas which arise in EµEBNA1 transgenic mice are unequivocally linked to EBNA1 expression and that both C-Myc and Mdm2 deregulation are central to this process. Tumour cell survival is supported by IL-2 and there is a skew towards CD8-positive T cells in the tumour environment, while the immune check-point protein PD-L1 is upregulated in the tumours. Additionally, several isoforms of Mdm2 are upregulated in the EµEBNA1 tumours, with increased phosphorylation at ser166, an expression pattern not seen in Eµc-Myc transgenic tumours. Concomitantly, E2F1, Xiap, Mta1, C-Fos and Stat1 are upregulated in the tumours. Using four independent inhibitors of Mdm2 we demonstrate that the EµEBNA1 tumour cells are dependant upon Mdm2 for survival (as they are upon c-Myc) and that Mdm2 inhibition is not accompanied by upregulation of p53, instead cell death is linked to loss of E2F1 expression, providing new insight into the underlying tumourigenic mechanism. This opens a new path to combat EBV-associated disease

Characterization of Protective Human CD4+CD25+ FOXP3+ Regulatory T Cells Generated with IL-2, TGF-β and Retinoic Acid

BACKGROUND: Protective CD4+CD25+ regulatory T cells bearing the Forkhead Foxp3 transcription factor can now be divided into three subsets: Endogenous thymus-derived cells, those induced in the periphery, and another subset induced ex-vivo with pharmacological amounts of IL-2 and TGF-β. Unfortunately, endogenous CD4+CD25+ regulatory T cells are unstable and can be converted to effector cells by pro-inflammatory cytokines. Although protective Foxp3+CD4+CD25+ cells resistant to proinflammatory cytokines have been generated in mice, in humans this result has been elusive. Our objective, therefore, was to induce human naïve CD4+ cells to become stable, functional CD25+ Foxp3+ regulatory cells that were also resistant to the inhibitory effects of proinflammatory cytokines. METHODOLOGY/PRINCIPAL FINDINGS: The addition of the vitamin A metabolite, all-trans retinoic acid (atRA) to human naïve CD4+ cells suboptimally activated with IL-2 and TGF-β enhanced and stabilized FOXP3 expression, and accelerated their maturation to protective regulatory T cells. AtRA, by itself, accelerated conversion of naïve to mature cells but did not induce FOXP3 or suppressive activity. The combination of atRA and TGF-β enabled CD4+CD45RA+ cells to express a phenotype and trafficking receptors similar to natural Tregs. AtRA/TGF-β-induced CD4+ regs were anergic and low producers of IL-2. They had potent in vitro suppressive activity and protected immunodeficient mice from a human-anti-mouse GVHD as well as expanded endogenous Tregs. However, treatment of endogenous Tregs with IL-1β and IL-6 decreased FOXP3 expression and diminished their protective effects in vivo while atRA-induced iTregs were resistant to these inhibitory effects. CONCLUSIONS/SIGNIFICANCE: We have developed a methodology that induces human CD4(+) cells to rapidly become stable, fully functional suppressor cells that are also resistant to proinflammatory cytokines. This methodology offers a practical novel strategy to treat human autoimmune diseases and prevent allograft rejection without the use of agents that kill cells or interfere with signaling pathways