METHYL-ORANGE AS A PROBE OF PHOTOELECTROCHEMICAL REACTIONS SENSITIZED BY COLLOIDAL CDS

The kinetics of photoreduction of methyl orange by ethylenediaminetetraacetic acid (EDTA) sensitized by colloidal CdS are reported as a function of [methyl orange], [O2] and [EDTA]. The results are interpreted using a reaction scheme which was proposed in an earlier paper for the same reaction sensitized by a powdered dispersion of highly crystalline CdS. An analysis of the results for the CdS colloid based on this reaction scheme shows that the rate of dye reduction by photogenerated electrons is approximately 50 times greater than the rate of oxygen reduction and the rate of scavenging of the photogenerated holes is approximately 7000 times greater than the rate of recombination. These findings are discussed in the light of similar observations reported for powdered CdS.

Ultrastructural findings in solar retinopathy

This study documents the ultrastructural findings in a case of solar retinopathy, 6 days after sungazing. A malignant melanoma of the choroid was diagnosed in a 65-year-old man. On fundoscopy, the macula was normal. The patient agreed to stare at the sun prior to enucleation. A typical solar retinopathy developed, characterised by a small, reddish, sharply circumscribed depression in the foveal area. Structural examination of the fovea and parafovea revealed a spectrum of cone and rod outer segment changes including vesiculation and fragmentation of the photoreceptor lamellae and the presence of discrete 100-120 nm whorls within the disc membranes. Many photoreceptor cells, particularly the parafoveal rods, also demonstrated mitochondrial swelling and nuclear pyknosis. Scattered retinal pigment epithelial cells in the fovea and parafovea showed a degeneration characterised by loss of plasma membrane specialisations, swelling of the smooth endoplasmic reticulum and changes in the fine structure of the lipofuscin granules. The good visual prognosis in solar retinopathy was attributed to the resistance of the foveal cone cells to photochemical damage.

A Burkholderia cenocepacia MurJ (MviN) homolog is essential for cell wall peptidoglycan synthesis and bacterial viability

The cell wall peptidoglycan (PG) of Burkholderia cenocepacia, an opportunistic pathogen, has not yet been characterized. However, the B. cenocepacia genome contains homologs of genes encoding PG biosynthetic functions in other bacteria. PG biosynthesis involves the formation of the undecaprenyl-pyrophosphate-linked N-acetyl glucosamine-N-acetyl muramic acid-pentapeptide, known as lipid II, which is built on the cytosolic face of the cell membrane. Lipid II is then translocated across the membrane and its glycopeptide moiety becomes incorporated into the growing cell wall mesh; this translocation step is critical to PG synthesis. We have investigated candidate flippase homologs of the MurJ family in B. cenocepacia. Our results show that BCAL2764, herein referred to as murJBc, is indispensable for viability. Viable B. cenocepacia could only be obtained through a conditional mutagenesis strategy by placing murJBc under the control of a rhamnose-inducible promoter. Under rhamnose depletion, the conditional strain stopped growing and individual cells displayed morphological abnormalities consistent with a defect in PG synthesis. Bacterial cells unable to express MurJBc underwent cell lysis, while partial MurJBc depletion sensitized the mutant to the action of β-lactam antibiotics. Depletion of MurJBc caused accumulation of PG precursors consistent with the notion that this protein plays a role in lipid II flipping to the periplasmic compartment. Reciprocal complementation experiments of conditional murJ mutants in B. cenocepacia and Escherichia coli with plasmids expressing MurJ from each strain indicated that MurJBc and MurJEc are functional homologs. Together, our results are consistent with the notion that MurJBc is a PG lipid II flippase in B. cenocepacia.

CCAAT/enhancer binding protein α predicts poorer prognosis and prevents energy starvation-induced cell death in hepatocellular carcinoma

CCAAT enhancer binding protein α (C/EBPα) plays an essential role in cellular differentiation, growth, and energy metabolism. Here, we investigate the correlation between C/EBPα and hepatocellular carcinoma (HCC) patient outcomes and how C/EBPα protects cells against energy starvation. Expression of C/EBPα protein was increased in the majority of HCCs examined (191 pairs) compared with adjacent nontumor liver tissues in HCC tissue microarrays. Its upregulation was correlated significantly with poorer overall patient survival in both Kaplan-Meier survival (P = 0.017) and multivariate Cox regression (P = 0.028) analyses. Stable C/EBPα-silenced cells failed to establish xenograft tumors in nude mice due to extensive necrosis, consistent with increased necrosis in human C/EBPα-deficient HCC nodules. Expression of C/EBPα protected HCC cells in vitro from glucose and glutamine starvation-induced cell death through autophagy-involved lipid catabolism. Firstly, C/EBPα promoted lipid catabolism during starvation, while inhibition of fatty acid beta-oxidation significantly sensitized cell death. Secondly, autophagy was activated in C/EBPα-expressing cells, and the inhibition of autophagy by ATG7 knockdown or chloroquine treatment attenuated lipid catabolism and subsequently sensitized cell death. Finally, we identified TMEM166 as a key player in C/EBPα-mediated autophagy induction and protection against starvation.

CONCLUSION: The C/EBPα gene is important in that it links HCC carcinogenesis to autophagy-mediated lipid metabolism and resistance to energy starvation; its expression in HCC predicts poorer patient prognosis.

Inhibition of dUTPase induces synthetic lethality with thymidylate synthase-targeted therapies in non-small cell lung cancer

Chemotherapies that target thymidylate synthase (TS) continue to see considerable clinical expansion in non-small cell lung cancer (NSCLC). One drawback to TS-targeted therapies is drug resistance and subsequent treatment failure. Novel therapeutic and biomarker-driven strategies are urgently needed. The enzyme deoxyuridine triphosphate nucleotidohydrolase (dUTPase) is reported to protect tumor cells from aberrant misincorporation of uracil during TS inhibition. The goal of this study was to investigate the expression and significance of dUTPase in mediating response to TS-targeted agents in NSCLC. The expression of dUTPase in NSCLC cell lines and clinical specimens was measured by quantitative real-time reverse transcriptase PCR and immunohistochemistry. Using a validated RNA interference approach, dUTPase was effectively silenced in a panel of NSCLC cell lines and response to the fluoropyrimidine fluorodeoxyuridine (FUdR) and the antifolate pemetrexed was analyzed using growth inhibition and clonogenic assays. Apoptosis was analyzed by flow cytometry. Significant variation in the quantity and cellular expression of dUTPase was observed, including clear evidence of overexpression in NSCLC cell line models and tumor specimens at the mRNA and protein level. RNA interference-mediated silencing of dUTPase significantly sensitized NSCLC cells to growth inhibition induced by FUdR and pemetrexed. This sensitization was accompanied by a significant expansion of intracellular dUTP pools and significant decreases in NSCLC cell viability evaluated by clonogenicity and apoptotic analyses. Together, these results strongly suggest that uracil misincorporation is a potent determinant of cytotoxicity to TS inhibition in NSCLC and that inhibition of dUTPase is a mechanism-based therapeutic approach to significantly enhance the efficacy of TS-targeted chemotherapeutic agents.

Inhibition of O-GlcNAc transferase activity reprograms prostate cancer cell metabolism

Metabolic networks are highly connected and complex, but a single enzyme, O-GlcNAc transferase (OGT) can sense the availability of metabolites and also modify target proteins. We show that inhibition of OGT activity inhibits the proliferation of prostate cancer cells, leads to sustained loss of c-MYC and suppresses the expression of CDK1, elevated expression of which predicts prostate cancer recurrence (p=0.00179). Metabolic profiling revealed decreased glucose consumption and lactate production after OGT inhibition. This decreased glycolytic activity specifically sensitized prostate cancer cells, but not cells representing normal prostate epithelium, to inhibitors of oxidative phosphorylation (rotenone and metformin). Intra-cellular alanine was depleted upon OGT inhibitor treatment. OGT inhibitor increased the expression and activity of alanine aminotransferase (GPT2), an enzyme that can be targeted with a clinically approved drug, cycloserine. Simultaneous inhibition of OGT and GPT2 inhibited cell viability and growth rate, and additionally activated a cell death response. These combinatorial effects were predominantly seen in prostate cancer cells, but not in a cell-line derived from normal prostate epithelium. Combinatorial treatments were confirmed with two inhibitors against both OGT and GPT2. Taken together, here we report the reprogramming of energy metabolism upon inhibition of OGT activity, and identify synergistically lethal combinations that are prostate cancer cell specific.

Enhanced bio-decolourisation of acid orange 7 by Shewanella oneidensis through co-metabolism in a microbial fuel cell

The decolourisation of acid orange 7 (AO7) (C.I.15510) through co-metabolism in a microbial fuel cell by Shewanella oneidensis strain 14063 was investigated with respect to the kinetics of decolourisation, extent of degradation and toxicity of biotransformation products. Rapid decolourisation of AO7 (>98% within 30 h) was achieved at all tested dye concentrations with concomitant power production. The aromatic amine degradation products were recalcitrant under tested conditions. The first-order kinetic constant of decolourisation (k) decreased from 0.709 ± 0.05 h−1 to 0.05 ± 0.01 h−1 (co-substrate – pyruvate) when the dye concentration was raised from 35 mg l−1 to 350 mg l−1. The use of unrefined co-substrates such as rapeseed cake, corn-steep liquor and molasses also indicated comparable or better AO7 decolourisation kinetic constant values. The fully decolourised solutions indicated increased toxicity as the initial AO7 concentration was increased. This work highlights the possibility of using microbial fuel cells to achieve high kinetic rates of AO7 decolourisation through co-metabolism with concomitant electricity production and could potentially be utilised as the initial step of a two stage anaerobic/aerobic process for azo dye biotreatment.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Films for Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Films for Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

Copper Doped Methylene Blue Sensitized Poly(vinyl alcohol)–Acrylamide Filmsfor Stable Diffraction Efficiency

Copper doped methylene blue sensitized poly(vinyl alcohol) (MBPVA)–acrylamide films were fabricated to improve the storage life of recorded gratings. The films were fabricated using gravity settling method and the copper chloride concentration was optimized as 3:18 10 3 mol/l for a dye concentration of 6:2 10 4 mol/l. The gratings recorded on the optimized film constitution could be stored for months with stable diffraction efficiency (24%) without any chemical or thermal fixing techniques. The resolution of the material is found to be unaffected with the addition of copper chloride.

CuInS2/In2S3 Cells using a Cost-effective Technique: Significance of Precursor Ratios on Cell Parameters

Thin film solar cells having structure CuInS2/In2S3 were fabricated using chemical spray pyrolysis (CSP) technique over ITO coated glass. Top electrode was silver film (area 0.05 cm2). Cu/In ratio and S/Cu in the precursor solution for CuInS2 were fixed as 1.2 and 5 respectively. In/S ratio in the precursor solution for In2S3 was fixed as 1.2/8. An efficiency of 0.6% (fill factor -37.6%) was obtained. Cu diffusion to the In2S3 layer, which deteriorates junction properties, is inevitable in CuInS2/In2S3 cell. So to decrease this effect and to ensure a Cu-free In2S3 layer at the top of the cell, Cu/In ratio was reduced to 1. Then a remarkable increase in short circuit current density was occurred from 3 mA/cm2 to 14.8 mA/cm2 and an efficiency of 2.13% was achieved. Also when In/S ratio was altered to 1.2/12, the short circuit current density increased to 17.8 mA/cm2 with an improved fill factor of 32% and efficiency remaining as 2%. Thus Cu/In and In/S ratios in the precursor solutions play a crucial role in determining the cell parameters

Modelling and simulation of a photovoltaic fuel cell hybrid system

A stand-alone power system is an autonomous system that supplies electricity to the user load without being connected to the electric grid. This kind of decentralized system is frequently located in remote and inaccessible areas. It is essential for about one third of the world population which are living in developed or isolated regions and have no access to an electricity utility grid. The most people live in remote and rural areas, with low population density, lacking even the basic infrastructure. The utility grid extension to these locations is not a cost effective option and sometimes technically not feasible. The purpose of this thesis is the modelling and simulation of a stand-alone hybrid power system, referred to as “hydrogen Photovoltaic-Fuel Cell (PVFC) hybrid system”. It couples a photovoltaic generator (PV), an alkaline water electrolyser, a storage gas tank, a proton exchange membrane fuel cell (PEMFC), and power conditioning units (PCU) to give different system topologies. The system is intended to be an environmentally friendly solution since it tries maximising the use of a renewable energy source. Electricity is produced by a PV generator to meet the requirements of a user load. Whenever there is enough solar radiation, the user load can be powered totally by the PV electricity. During periods of low solar radiation, auxiliary electricity is required. An alkaline high pressure water electrolyser is powered by the excess energy from the PV generator to produce hydrogen and oxygen at a pressure of maximum 30bar. Gases are stored without compression for short- (hourly or daily) and long- (seasonal) term. A proton exchange membrane (PEM) fuel cell is used to keep the system’s reliability at the same level as for the conventional system while decreasing the environmental impact of the whole system. The PEM fuel cell consumes gases which are produced by an electrolyser to meet the user load demand when the PV generator energy is deficient, so that it works as an auxiliary generator. Power conditioning units are appropriate for the conversion and dispatch the energy between the components of the system. No batteries are used in this system since they represent the weakest when used in PV systems due to their need for sophisticated control and their short lifetime. The model library, ISET Alternative Power Library (ISET-APL), is designed by the Institute of Solar Energy supply Technology (ISET) and used for the simulation of the hybrid system. The physical, analytical and/or empirical equations of each component are programmed and implemented separately in this library for the simulation software program Simplorer by C++ language. The model parameters are derived from manufacturer’s performance data sheets or measurements obtained from literature. The identification and validation of the major hydrogen PVFC hybrid system component models are evaluated according to the measured data of the components, from the manufacturer’s data sheet or from actual system operation. Then, the overall system is simulated, at intervals of one hour each, by using solar radiation as the primary energy input and hydrogen as energy storage for one year operation. A comparison between different topologies, such as DC or AC coupled systems, is carried out on the basis of energy point of view at two locations with different geographical latitudes, in Kassel/Germany (Europe) and in Cairo/Egypt (North Africa). The main conclusion in this work is that the simulation method of the system study under different conditions could successfully be used to give good visualization and comparison between those topologies for the overall performance of the system. The operational performance of the system is not only depending on component efficiency but also on system design and consumption behaviour. The worst case of this system is the low efficiency of the storage subsystem made of the electrolyser, the gas storage tank, and the fuel cell as it is around 25-34% at Cairo and 29-37% at Kassel. Therefore, the research for this system should be concentrated in the subsystem components development especially the fuel cell.

Cell coupling in mouse pancreatic beta-cells measured in intact islets of Langerhans

The perforated whole-cell configuration of the patch-clamp technique was applied to functionally identified beta-cells in intact mouse pancreatic islets to study the extent of cell coupling between adjacent beta-cells. Using a combination of current- and voltage-clamp recordings, the total gap junctional conductance between beta-cells in an islet was estimated to be 1.22 nS. The analysis of the current waveforms in a voltage-clamped cell ( due to the. ring of an action potential in a neighbouring cell) suggested that the gap junctional conductance between a pair of beta-cells was 0.17 nS. Subthreshold voltage-clamp depolarization (to -55 mV) gave rise to a slow capacitive current indicative of coupling between beta-cells, but not in non-beta-cells, with a time constant of 13.5 ms and a total charge movement of 0.2 pC. Our data suggest that a superficial beta-cell in an islet is in electrical contact with six to seven other beta-cells. No evidence for dye coupling was obtained when cells were dialysed with Lucifer yellow even when electrical coupling was apparent. The correction of the measured resting conductance for the contribution of the gap junctional conductance indicated that the whole-cell K(ATP) channel conductance (G(K,ATP)) falls from approximately 2.5 nS in the absence of glucose to 0.1 nS at 15 mM glucose with an estimated IC(50) of approximately 4 mM. Theoretical considerations indicate that the coupling between beta-cells within the islet is sufficient to allow propagation of [Ca(2+)](i) waves to spread with a speed of approximately 80 mu m s(-1), similar to that observed experimentally in confocal [Ca(2+)](i) imaging.

Differential effects of formaldehyde exposure on the cell influx and vascular permeability in a rat model of allergic lung inflammation

Exposure to air pollutants such as formaldehyde (FA) leads to inflammation, oxidative stress and immune-modulation in the airways and is associated with airway inflammatory disorders such as asthma. The purpose of our study was to investigate the effects of exposure to FA on the allergic lung inflammation. The hypothesized link between reactive oxygen species and the effects of FA was also studied. To do so, male Wistar rats were exposed to FA inhalation (1%, 90 min daily) for 3 days. and subsequently sensitized with ovalbumin (OVA)-alum by subcutaneous route One week later the rats received another OVA-alum injection by the same route (booster). Two weeks later the rats were challenged with aerosolized OVA. The OVA challenge of rats upon FA exposure induced an elevated release of LTB(4). TXB(2), IL-1 beta, IL-6 and VEGF in lung cells, increased phagocytosis and lung vascular permeability, whereas the cell recruitment into lung was reduced. FA inhalation induced the oxidative burst and the nitration of proteins in the lung Vitamins C, E and apocynin reduced the levels of LTB(4) in BAL-cultured cells of the FA and FA/OVA groups, but Increased the cell influx into the lung of the FA/OVA rats. In OVA-challenged rats, the exposure to FA was associated to a reduced lung endothelial cells expression of intercellular cell adhesion molecule 1 (ICAM-1) In conclusion, our findings suggest that FA down regulate the cellular migration into the lungs after an allergic challenge and increase the ability of resident lung cells likely macrophages to generate inflammatory mediators, explaining the increased lung vascular permeability Our data are indicative that the actions of FA involve mechanisms related to endothelium-leukocyte interactions and oxidative stress, as far as the deleterious effects of this air pollutant on airways are concerned. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

The allergic inflammatory reaction in neonatal streptozotocininduced diabetic rats: evidence of insulin resistance and microvascular dysfunction

To investigate the allergic reaction in neonatal streptozotocin (nSTZ)-induced diabetes mellitus. Male newborn Wistar rats were made diabetic by the injection of streptozotocin (160 mg/kg, i. p.) and used 8 weeks thereafter. Animals were sensitized against ovalbumin (OA, 50 mu g and Al(OH)3, 5 mg, s. c.) and challenged 14 or 21 days thereafter. OA-induced airway inflammation and OA-induced pleurisy models were used to investigate leukocyte migration (total and differential leukocyte counts) and lung vascular permeability (Evans blue dye extravasation). nSTZ-diabetic rats presented glucose intolerance and insulin resistance. Relative to controls, nSTZ rats exhibited a 30% to 50% reduction in lung vascular permeability. Leukocyte infiltration in both models of allergen-induced inflammation, and number of pleural mast cells did not differ between groups. Data suggest that the reduction of allergic inflammatory reactions in nSTZ rats is restricted to microvascular dysfunctions and associated, probably, with insulin resistance in lung microvascular endothelium.