Nanofiber‐Based Bulk‐Heterojunction Organic Solar Cells Using Coaxial Electrospinning

Nanofibers consisting of the bulk heterojunction organic photovoltaic (BHJ–OPV) electron donor–electron acceptor pair poly(3‐hexylthiophene):phenyl‐C₆₁‐butyric acid methyl ester (P3HT:PCBM) are produced through a coaxial electrospinning process. While P3HT:PCBM blends are not directly electrospinnable, P3HT:PCBM‐containing fibers are produced in a coaxial fashion by utilizing polycaprolactone (PCL) as an electrospinnable sheath material. Pure P3HT:PCBM fibers are easily obtained after electrospinning by selectively removing the PCL sheath with cyclopentanone (average diameter 120 ± 30 nm). These fibers are then incorporated into the active layer of a BHJ–OPV device, which results in improved short‐circuit current densities, fill factors, and power‐conversion efficiencies (PCE) as compared to thin‐film devices of identical chemical composition. The best‐performing fiber‐based devices exhibit a PCE of 4.0%, while the best thin‐film devices have a PCE of 3.2%. This increase in device performance is attributed to the increased in‐plane alignment of P3HT polymer chains on the nanoscale, caused by the electrospun fibers, which leads to increased optical absorption and subsequent exciton generation. This methodology for improving device performance of BHJ–OPVs could also be implemented for other electron donor–electron acceptor systems, as nanofiber formation is largely independent of the PV material.     

Nuclear Calcium Signaling Controls Expression of a Large Gene Pool: Identification of a Gene Program for Acquired Neuroprotection Induced by Synaptic Activity

Synaptic activity can boost neuroprotection through a mechanism that requires synapse-to-nucleus communication and calcium signals in the cell nucleus. Here we show that in hippocampal neurons nuclear calcium is one of the most potent signals in neuronal gene expression. The induction or repression of 185 neuronal activity-regulated genes is dependent upon nuclear calcium signaling. The nuclear calcium-regulated gene pool contains a genomic program that mediates synaptic activity-induced, acquired neuroprotection. The core set of neuroprotective genes consists of 9 principal components, termed Activity-regulated Inhibitor of Death (AID) genes, and includes Atf3, Btg2, GADD45β, GADD45γ, Inhibin β-A, Interferon activated gene 202B, Npas4, Nr4a1, and Serpinb2, which strongly promote survival of cultured hippocampal neurons. Several AID genes provide neuroprotection through a common process that renders mitochondria more resistant to cellular stress and toxic insults. Stereotaxic delivery of AID gene-expressing recombinant adeno-associated viruses to the hippocampus confers protection in vivo against seizure-induced brain damage. Thus, treatments that enhance nuclear calcium signaling or supplement AID genes represent novel therapies to combat neurodegenerative conditions and neuronal cell loss caused by synaptic dysfunction, which may be accompanied by a deregulation of calcium signal initiation and/or propagation to the cell nucleus.     

Optically Transparent Porous Medium for Nondestructive Studies of Microbial Biofilm Architecture and Transport Dynamics

We describe a novel and noninvasive, microscopy-based method for visualizing the structure and dynamics of microbial biofilms, individual fluorescent microbial cells, and inorganic colloids within a model porous medium. Biofilms growing in flow cells packed with granules of an amorphous fluoropolymer could be visualized as a consequence of refractive index matching between the solid fluoropolymer grains and the aqueous immersion medium. In conjunction with the capabilities of confocal microscopy for nondestructive optical sectioning, the use of amorphous fluoropolymers as a solid matrix permits observation of organisms and dynamic processes to a depth of 2 to 3 mm, whereas sediment biofilms growing in sand-filled flow cells can only be visualized in the region adjacent to the flow cell wall. This method differs fundamentally from other refractive index-matching applications in that optical transparency was achieved by matching a solid phase to water (and not vice versa), thereby permitting real-time microscopic studies of particulate-containing, low-refractive-index media such as biological and chromatographic systems.     

Hfe acts in hepatocytes to prevent hemochromatosis

Hereditary hemochromatosis (HH) is a prevalent, potentially fatal disorder of iron metabolism hallmarked by intestinal hyperabsorption of iron, hyperferremia, and hepatic iron overload. In both humans and mice, type I HH is associated with mutations in the broadly expressed HFE/Hfe gene. To identify where Hfe acts to prevent HH, we generated mice with tissue-specific Hfe ablations. This work demonstrates that local Hfe expression in hepatocytes serves to maintain physiological iron homeostasis, answering a long-standing question in medicine and explaining earlier clinical observations.     

Competition effect in DNA damage response

We have built an ion-microbeam for studies of the nuclear topography and kinetics of double-strand break repair at the single cell level. Here, we show that a first and a second, delayed single ion exposure at different nuclear sites led to comparable accumulations of phospho-ATM, γ-H2AX and Mdc1 at both earlier (e) and later (l) microirradiated sites. In contrast, accumulations of 53BP1 and the recombination protein Rad51 were strongly reduced at l-sites. This apparent competition effect is accompanied by a reduced amount of 53BP1 in undamaged areas of the irradiated nuclei. We suggest that a critically limited pool size combined with strong binding at irradiated sites leads to the exhaustion of unbound factors freely roaming the nuclear space. The undersupply of these factors at l-sites requires in addition a long-lasting binding at e-sites or a weaker binding at l-sites. The observed effects suggest that DNA damage response at individual nuclear sites depends on the time course of damage load. This may have implications for therapeutic radiation treatments. Christoph Greubel, Volker Hable and Guido A. Drexler contributed equally to this work.     

A prospective,randomized study of quadruple therapy and high-dose dual therapy for treatment of Helicobacter pylori resistant to both metronidazole and clarithromycin

Background and Aim. Failure of primary anti‐H. pylori therapy results in a high rate of antimicrobial resistance. Here, we investigated the efficacy of high‐dose dual therapy and quadruple therapy as salvage treatments for eradication of H. pylori resistant to both metronidazole and clarithromycin. Patients and Methods. Patients with at least one treatment failure and infected with H. pylori resistant to both metronidazole and clarithromycin, were randomized to receive either omeprazole 4 × 40 mg and amoxicillin 4 × 750 mg; or omeprazole 2 × 20 mg, bismuthcitrate 4 × 107 mg, metronidazole 4 × 500 mg and tetracycline 4 × 500 mg. Both regimens were given for 14 days. In cases of persistent infection, a cross‐over therapy was performed. Results. Eighty‐four patients were randomized. Cure of H. pylori infection was achieved in 31 patients after dual therapy and in 35 patients after quadruple therapy (per protocol: 83.8% (95% CI, 67.9–93.8) and 92.1% (95% CI, 78.6–98.3), respectively (p = 0.71); intention to treat: 75.6% (95% CI: 59.7–87.6) and 81.4% (95% CI: 66.6–91.6), respectively (p = 0.60)). Cross‐over therapy was performed in six of nine patients, four of whom were cured of the infection. Conclusion. Both high‐dose dual therapy and quadruple therapy are effective in curing H. pylori infection resistant to both metronidazole and clarithromycin in patients who experienced previous treatment failures.     

The presence of immunoglobulins in the gastric juice of patients infected with Helicobacter pylori is related to a reduced secretion of acid

Background. It has been reported that treatment with proton pump inhibitors (PPI) leads to partial elimination and suppression of Helicobacter pylori. In theory, since acid is known to denature immunoglobulins, this antibacterial activity of PPI may be due to a reduction in the acid output favouring humoral immunity. Materials and methods. We analysed prospectively fasting gastric juice in 54 consecutive patients attending upper endoscopy for pH and levels of IgG, IgA and IgM. In addition, two antral and two corpus biopsies were obtained and histologically examined for the presence of H. pylori. Results. 41/54 patients were infected with H. pylori. Immunoglobulines in the gastric juice of these patients were found in 25/41 (IgG), 27/41 (IgA), and 29/41 (IgM) patients. There was a highly significant difference in the gastric pH when H. pylori infected patients with measurable IgG, IgA, or IgM were compared with those in whom no immunoglobulines were found (median pH: 6 vs. 2 in each group; p < .001) Conclusions. There is a close correlation between a high gastric pH and the presence of IgG, IgA, and IgM antibodies. Hence, it may be speculated that the efficacy of humoral immunity following H. pylori infection depends on a high pH such as resulting from PPI treatment.