Fraction Of Activation Research Articles

Carbon dot crosslinking towards mechanochemically and photochemically induced fluorescence resonance energy transfer

Mechanochromism in polymers has attracted great interests in recent years. Herein, we develop a mechanochromic elastomer carrying spiropyran mechanophores in the chain and mechanoresponsiveness of elastomer is enhanced by embedding luminescent carbon dot ( CD ) nanoparticles as crosslinkers and energy donor in fluorescence resonance energy transfer (FRET). Compared with the control with physically blended CD , CD crosslinked elastomer exhibit excellent daylight and fluorescent colors change under stretching. The mechanochemically induced fluorescence change is a result of FRET between CD nanoparticles and the activated merocyanine. The control with physically blended CD nanoparticles shows low FRET in stretching due to lower fraction of spiropyran activation as a result of lower mechanical properties. Furthermore, the CD crosslinked elastomer has already been applied in rewritable mechanochemical and photochemical recording or printing. Our demonstration shows that interfacial chemical bonding plays a critical role in the reinforcement of mechanical properties for polymer composites and may exhibit great potential in the study of the acceleration of mechanoresponsiveness of polymer and multi-responsiveness of polymer nanocomposites. • Mechanochromic elastomers were prepared with SP being in chain and crosslinked by CD. • CD as nanofiller and energy donor improves mechanochromism of nanocomposites by FRET. • Elastomers enable use in rewritable mechano- and photochemical recording/printing.

Substantial Uncertainties in Arctic Aerosol Simulations by Microphysical Processes Within the Global Climate‐Aerosol Model CAM‐ATRAS

AbstractAerosols can modulate the Arctic climate through their interactions with radiation, clouds, and snow and ice surfaces. Atmospheric simulations of Arctic aerosols remain highly uncertain, for which the importance of aerosol microphysical properties and processes has not been properly evaluated. To identify the cause of this large uncertainty, we evaluate the variability ranges of aerosols in the Arctic resulting from uncertainties in various aerosol microphysical properties/processes, including particle size distributions at emission, particle mixing states, activation efficiency, and wet removal processes, by using a global climate‐aerosol model Community Atmosphere Model with the Aerosol Two‐dimensional bin module for foRmation and Aging Simulation. We find that the combined uncertainties associated with these multiple microphysical properties/processes yield a factor of 10–50 differences (maximum‐to‐minimum ratio) in the concentrations and radiative effects of aerosols in the Arctic. Black carbon shows the highest variability among aerosol species because its lower hygroscopicity and higher critical supersaturation cause the fraction of activation and wet removal during transport to be highly sensitive to the model treatment of aerosol and cloud microphysics. Aerosol‐radiation‐cloud interactions at the top of atmosphere vary from −0.40 to +0.30 W m−2 in the Arctic (from the preindustrial to present day) and can be positive or negative depending on the treatment of microphysical properties/processes. These results indicate that microphysical properties/processes are more important than previously thought in aerosol simulations in the Arctic and demonstrate that a better understanding and more sophisticated model representation of aerosol microphysical properties/processes are required to improve the accuracy of Arctic aerosol simulations and their impacts on climate.

Heterocyclic androstane and estrane d-ring modified steroids: Microwave-assisted synthesis, steroid-converting enzyme inhibition, apoptosis induction, and effects on genes encoding estrogen inactivating enzymes

d-ring–fused and d-homo lactone compounds in estratriene and androstane series were synthesized using microwave-assisted reaction conditions. Microwave-irradiated synthesis methods were convenient and effective, and provided high yields with short reaction times. Their inhibition of C17,20-lyase and 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) activities were studied in in vitro enzyme assays. d-ring–fused triazolyl estrone analog 24 showed potent inhibition of NADH-complexed 17β-HSD1, with a binding affinity similar to that of the substrate estrone; its inhibition against NADPH-complexed 17β-HSD1 was markedly weaker. Compound 24 also significantly and selectively reduced proliferation of cancer cell lines of gynecological origin. This estrane triazole changed the cell cycle and induced apoptosis of HeLa, SiHa, and MDA-MB-231 cancer cells, measured by both increased subG1 fraction of cells and activation of caspase-independent signaling pathways. A third mode of anti-estrogenic action of 24 saw increased mRNA expression of the SULT1E1 gene in HeLa cells; in contrast, its 3-benzyloxy analog 23 increased mRNA expression of the HSD17B2 gene, thus showing pronounced pro-drug anti-estrogenic activity. Estradiol-derived d-ring triazole compound 24 thus acts at the enzyme, gene expression and cellular levels to decrease the production of active estrogen hormones, demonstrating its pharmacological potential.

Bidirectional flow of the funny current (If) during the pacemaking cycle in murine sinoatrial node myocytes

Sinoatrial node myocytes (SAMs) act as cardiac pacemaker cells by firing spontaneous action potentials (APs) that initiate each heartbeat. The funny current (If) is critical for the generation of these spontaneous APs; however, its precise role during the pacemaking cycle remains unresolved. Here, we used the AP-clamp technique to quantify If during the cardiac cycle in mouse SAMs. We found that If is persistently active throughout the sinoatrial AP, with surprisingly little voltage-dependent gating. As a consequence, it carries both inward and outward current around its reversal potential of -30 mV. Despite operating at only 2 to 5% of its maximal conductance, If carries a substantial fraction of both depolarizing and repolarizing net charge movement during the firing cycle. We also show that β-adrenergic receptor stimulation increases the percentage of net depolarizing charge moved by If, consistent with a contribution of If to the fight-or-flight increase in heart rate. These properties were confirmed by heterologously expressed HCN4 channels and by mathematical models of If Modeling further suggested that the slow rates of activation and deactivation of the HCN4 isoform underlie the persistent activity of If during the sinoatrial AP. These results establish a new conceptual framework for the role of If in pacemaking, in which it operates at a very small fraction of maximal activation but nevertheless drives membrane potential oscillations in SAMs by providing substantial driving force in both inward and outward directions.

Effect of wearing a face mask on fMRI BOLD contrast

International spread of the coronavirus SARS-CoV-2 has prompted many MRI scanning facilities to require scan subjects to wear a facial covering (“mask”) during scanning as a precaution against transmission of the virus. Because wearing a mask mixes expired air with the subject's inspired air stream, the concentration of inspired carbon dioxide [CO2] is elevated, resulting in mild hypercapnia. Changes in the inspired gas mixture have been demonstrated to alter R2*-weighted Blood Oxygen Dependent (BOLD) contrast. In this study, we investigate a potential for face masking to alter BOLD contrast during a sensory-motor task designed to activate visual, auditory, and sensorimotor cortices in 8 subjects. We utilize a nasal cannula to supply air to the subject wearing a surgical mask in on-off blocks of 90s to displace expired CO2, while the subject performs the sensory-motor task. While only a small fraction (2.5%) of the sensory-motor task activation is related to nasal air modulation, a 30.0% change in gray matter BOLD signal baseline is found due to air modulation. Repeating the scan with mask removed produces a small subject-specific bias in BOLD baseline signal from nasal air supply, which may be due to cognitive influence of airflow or cannula-induced hypoxia. Measurements with capnography demonstrate wearing a mask induces an average increase in ETCO2 of 7.4%. Altogether, these results demonstrate that wearing a face mask during gradient-echo fMRI can alter BOLD baseline signal but minimally affects task activation.

Myricitrin attenuates hypoxic-ischemia-induced brain injury in neonatal rats by mitigating oxidative stress and nuclear factor erythroid 2-related factor 2/hemeoxygenase-1/antioxidant response element signaling pathway

Background: Neonatal hypoxic ischemia (HI) is an overwhelming infantile neurological disability causing extreme morbidity and mortality with limited therapies available. Objectives: In this study, we aimed to explore the neuroprotective efficacy of myricitrin and elucidate the mechanism of action of myricitrin through the regulation of nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1)/antioxidant response element (ARE)-signaling pathways in neonatal rats. Materials and Methods: Seven-day-old neonatal rats were divided into four groups. Sham group served as the control group. After inducing HI through standard operation procedure, two groups of neonatal rats were intraperitoneally administered with 20 and 40 mg/kg bw of myricitrin twice a day for up to 1 week. At the end of the experiment, we assessed the brain infract area, edema, and motor coordination activity by using Rota Rod test. Furthermore, we measured the level of antioxidant enzymes and oxidative stress markers in the brain tissue samples. Real-time quantitative polymerase chain reaction was conducted to detect the inflammatory molecules expression including HO-1 being the activator of Nrf2 where further mediates the transcriptional activation of ARE. Subsequently, the hypothesis was further confirmed by the immunosorbent assay and Western blot analysis. Results: Myricitrin administration ameliorated HI-induced increase in infract volume and edema of the brain, as well as improved neurobehavioral impairments. Interestingly, myricitrin significantly reduced the level of nuclear factor kappa B (NF-κB) p65 and reduced the levels of nuclear fraction of Nrf2-ARE and cytosolic fraction of HO-1 enzyme activation. Conclusion: In summary, myricitrin improved the antioxidant defense mechanism and ameliorated the oxidative stress-associated neurological damage via modulating Nrf2/ARE-dependent HO-1 pathway in neonatal rats.

Nfkbie-deficiency leads to increased susceptibility to develop B-cell lymphoproliferative disorders in aged mice

Aberrant NF-κB activation is a hallmark of most B-cell malignancies. Recurrent inactivating somatic mutations in the NFKBIE gene, which encodes IκBε, an inhibitor of NF-κB-inducible activity, are reported in several B-cell malignancies with highest frequencies in chronic lymphocytic leukemia and primary mediastinal B-cell lymphoma, and account for a fraction of NF-κB pathway activation. The impact of NFKBIE deficiency on B-cell development and function remains, however, largely unknown. Here, we show that Nfkbie-deficient mice exhibit an amplification of marginal zone B cells and an expansion of B1 B-cell subsets. In germinal center (GC)-dependent immune response, Nfkbie deficiency triggers expansion of GC B-cells through increasing cell proliferation in a B-cell autonomous manner. We also show that Nfkbie deficiency results in hyperproliferation of a B1 B-cell subset and leads to increased NF-κB activation in these cells upon Toll-like receptor stimulation. Nfkbie deficiency cooperates with mutant MYD88 signaling and enhances B-cell proliferation in vitro. In aged mice, Nfkbie absence drives the development of an oligoclonal indolent B-cell lymphoproliferative disorders, resembling monoclonal B-cell lymphocytosis. Collectively, these findings shed light on an essential role of IκBε in finely tuning B-cell development and function.

Unique influence of rare earth (Pr, Nd, and Er) oxide surface acidic texture over CeO2/γ-Al2O3 catalysts for selective production of styrene using CO2 flow

Variety of rare earth oxide-doped CeO2/γ-Al2O3 catalysts were prepared by a wet impregnation method and evaluated for oxidative dehydrogenation of ethylbenzene (EB) using CO2 as soft oxidant in vapor-phase atmospheric-pressure conditions. Amongst the bare CeO2/γ-Al2O3 catalysts, 15 wt% CeO2/γ-Al2O3 exhibited excellent catalytic activity with noteworthy EB conversion and styrene selectivity. After incorporation of 3 wt% Er2O3, Pr2O3, or Nd2O3 oxide onto the 15 wt% CeO2/γ-Al2O3 (15CA) catalyst, unusual catalytic properties were observed in terms of formation of active solid-solution species. The greater fraction of CO2 molecule activation and dissociation phenomenon on the surface rare earth-doped CeO2/γ-Al2O3 catalysts compared with the bare CeO2/γ-Al2O3 catalyst were investigated. Among the rare earth-doped catalysts, 3ErCA showed superior mobile oxygen storage capacity and high CO2 utilization ability, along with optimal surface acidic properties compared with the rare earth solid-solution properties of (CexRE1−xO2−δ) Pr2O3 and Nd2O3 species. Moreover, the better catalytic activity of Er2O3 species can be explained on the basis of active metal–support synergistic interactions and noticeable surface acidic nature. All the catalysts were characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller (BET) surface area measurements, H2-temperature programmed reduction, ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy, temperature-programmed desorption (NH3-TPD), scanning electron microscopy (SEM), and CO2 and O2 pulse chemisorption techniques to elucidate the metal oxide composition and influence of rare earth clusters such as Pr2O3, Nd2O3, and Er2O3 oxides on the catalytic activity.

Mechanical Behavior and Microstructure Characteristics of Directionally Solidified TWIP Steel

The mechanical behavior and microstructure characteristics of three high Mn austenitic steels prepared by directional solidification at withdrawal rates of 60, 120, and 240 μm s−1 were investigated and compared with common TWIP steel with equiaxed grains. For each steel, the Hollomon analysis, differential C–J analysis, and modified C–J analysis as an alternative method to describe the work-hardening behavior were studied. The directionally solidified samples (DS samples) exhibited higher mechanical properties along the axis, five stages (A, B, C, D, and E) divided on the plot of stain hardening rate vs true strain, and a more stable and uniform deformation feature with larger strain-hardening coefficients when the true strain is over 0.25, in comparison with the common TWIP steel. The modified C–J analysis was found to be the best one for revealing the strain-hardening behavior characterized by several different stages with a definite work-hardening exponent n. In the case of DS samples, the dendrite spacings increase but the morphology becomes simple when decreasing the withdrawal rate. The larger volume fraction of twins and prevalent activation of twin systems, together with the fragmentations of the original grains in a sample solidified at a withdrawal rate of 120 μm s−1, lead to the best mechanical behavior in a medium-to-large strain range.

Stabilizing Switching Signals for Switched Systems

This article deals with stability of continuous-time switched systems under constrained switching. Given a family of systems, possibly containing unstable dynamics, we characterize a new class of switching signals under which the switched system generated by it and the family of systems is globally asymptotically stable. Our characterization of such stabilizing switching signals involves the asymptotic frequency of switching, the asymptotic fraction of activation of the constituent systems, and the asymptotic densities of admissible transitions among them. Our techniques employ multiple Lyapunov-like functions, and extend preceding results both in scope and applicability.

Activating PIK3CA mutations coexist with BRAF or NRAS mutations in a limited fraction of melanomas.

BackgroundActivated PI3K-AKT pathway may contribute to decrease sensitivity to inhibitors of key pathogenetic effectors (mutated BRAF, active NRAS or MEK) in melanoma. Functional alterations are deeply involved in PI3K-AKT activation, with a minimal role reported for mutations in PIK3CA, the catalytic subunit of the PI3K gene. We here assessed the prevalence of the coexistence of BRAF/NRAS and PIK3CA mutations in a series of melanoma samples.MethodsA total of 245 tumor specimens (212 primary melanomas and 33 melanoma cell lines) was screened for mutations in BRAF, NRAS, and PIK3CA genes by automated direct sequencing.ResultsOverall, 110 (44.9%) samples carried mutations in BRAF, 26 (10.6%) in NRAS, and 24 (9.8%) in PIK3CA. All identified PIK3CA mutations have been reported to induce PI3K activation; those detected in cultured melanomas were investigated for their interference with the antiproliferative activity of the BRAF-mutant inhibitor vemurafenib. A reduced suppression in cell growth was observed in treated cells carrying both BRAF and PIK3CA mutations as compared with those presenting a mutated BRAF only. Among the analysed melanomas, 12/245 (4.9%) samples presented the coexistence of PIK3CA and BRAF/NRAS mutations.ConclusionsOur study further suggests that PIK3CA mutations account for a small fraction of PI3K pathway activation and have a limited impact in interfering with the BRAF/NRAS-driven growth in melanoma.

A Series of NiM (M = Ru, Rh, and Pd) Bimetallic Catalysts for Effective Lignin Hydrogenolysis in Water

In this paper, NiRu, NiRh, and NiPd catalysts were synthesized and evaluated in the hydrogenolysis of lignin C–O bonds, which is proved to be superior over single-component catalysts. The optimized NiRu catalyst contains 85% Ni and 15% Ru, composed of Ni surface-enriched, Ru–Ni atomically mixed, ultrasmall nanoparticles. The Ni85Ru15 catalyst showed high activity under low temperature (100 °C), low H2 pressure (1 bar) in β-O-4 type C–O bond hydrogenolysis. It also exhibited significantly higher activity over Ni and Ru catalysts in the direct conversion of lignin into monomeric aromatic chemicals. Mechanistic investigation indicates that the synergistic effect of NiRu can be attributed to three factors: (1) increased fraction of surface atoms (compared with Ni), (2) enhanced H2 and substrate activation (compared with Ni), and (3) inhibited benzene ring hydrogenation (compared with Ru). Similarly, NiRh and NiPd catalysts were more active and selective than their single-component counterparts in the hydrogenolysis of lignin model compounds and real lignin.

Predictors of functional mitral regurgitation improvement in a short-term observation after cardiac resynchronization therapy

Background: There is little knowledge on predictors of the functional mitral regurgitation (FMR) improvement (FMRI) after CRT implantation in a short-term observation. The role of preserved contractile reserve (CR) in prediction of FMRI is unclear. The study was undertaken to define predictors of FMRI and the impact of FMRI on the reversed remodelling (RR). Methods: This study is subanalysis of the multicenter Myocardial Viability in Cardiac Resynchronization Therapy (VIACRT) trial. Among 90 pts. with ischemic and nonischemic left ventricle dysfunction undergoing CRT therapy, in whom Doppler Echocardiography was performed one day before and 6 weeks after CRT implantation, 66 pts with at least moderate FMR [(grade 2+); mean age 64±10, mean ejection fraction LVEF 25,7%±6, ischemic etiology 48%] were included. The severity of FMR was estimated semiquantitavely from colour-flow Doppler images on a four –point scale. The FMRI was defined as the reduction of the severity for at least one grade. The pts were divided into: gr. A with FMRI (n = 30) and gr. B without FMRI (n=36). Baseline dyssynchrony was defined by TDI. Low-dose dobutamine stress echo (LDSE) was performed before CRT implantation. CR was defined as changes in LVEF > 20% and improvement of segmental contractility. The RR was defined as the reduction of the LV endsystolic volume LVESV >15%. Results: There were no differences concerning the age, gender, etiology (ischemic vs nonischemic), NYHA class and QRS width between both groups. No differences related to ejection fraction, dyssynchrony parameters and site of the latest activation were shown. Multivariate logistic regression analysis revealed the following predictive factors for FMRI: the presence of CR (improved contractility in >3 segments) with an OR = 5.7 (95% CI 1.81-17.97), p=0.005 with sensitivity 65.5% and specificity 72.2%; (AUC = 0.727) and baseline LV diastolic diameter LVDD ≤ 74 mm with an OR = 2.09 , (95% CI 0.75-5.78), p<0.05 , with sensitivity 80.0% and specificity 47.2% (AUC = 0.632). The FMRI was associated with significantly higher reduction of LVESV; gr. A: -38±27 mL vs -12±36 mL in gr. B, p=0.002 and higher increase in LVEF; in gr. A: +10.1±8.5% vs +2.3±5.5% in gr. B p<0.001 respectively. The higher rate of RR in gr. A comparing to gr. B (62.8% vs 37.2%, p<0.001) was noted. Conclusion: Preserved contractile reserve and lesser degree of LV dilation emerged as predictive factors of short-term FMRI after CRT implantation. FMRI is associated with higher rate of response to CRT in term of reverse remodelling.

Ultra-shallow junctions formed using microwave annealing

Microwave annealing is shown to be viable for achieving low thermal budget formation of ultra-shallow junctions. Regrowth of a 10 nm thick amorphous Si layer that is generated during a Ge amorphization process prior to BF2 or As dopant implantation proceeds at rates up to 0.53 nm/min for BF2 and up to 0.33 nm/min for As at 370 °C. The fraction of electrical activation for implanted dopants is as high as 13% for BF2 and 32% for As with negligible diffusion at 540 °C.

Cytometric assessment of DNA damage by exogenous and endogenous oxidants reports aging‐related processes

The ongoing DNA damage caused by reactive oxygen species generated during oxidative metabolism is considered a key factor contributing to cell aging as well as preconditioning cells to neoplastic transformation. We postulated before that a significant fraction of constitutive histone H2AX phosphorylation (CHP) and constitutive activation of ATM (CAA) seen in untreated normal and tumor cells occurs in response to such DNA damage. In the present study, we provide further evidence in support of this postulate. The level of ATM activation and H2AX phosphorylation, detected immunocytochemically, has been monitored in WI-38, A549, and TK6 cells treated with H2O2 as well as growing under conditions known or suspected to affect the level of endogenous oxidants. Thirty- to 60-min exposure of cells to 100 or 200 microM H2O2 led to an increase in the level of H2AX phosphorylation and ATM activation, particularly pronounced (nearly fivefold) in S-phase cells. Cell growth for 24-48 h under hypoxic conditions (3% O2) distinctly lowered the level of CHP and CAA while it had minor effect on cell cycle progression. Treatment (4 h) with 0.1 or 0.3 mM 3-bromopyruvate, an inhibitor of glycolysis and mitochondrial oxidative phosphorylation, reduced the level of CHP (up to fourfold) and also decreased the level of CAA. Growth of WI-38 cells in 2% serum concentration for 48 h led to a 25 and 30% reduction in CHP and CHA, respectively, compared with cells growing in 10% serum. The antioxidant vitamin C (2 mM) reduced CHP and CAA by 20-30% after 24 h of treatment, while the COX-2 inhibitor celecoxib (5 microM) had a minor effect on CHP and CAA, though it decreased the level of H2O2-induced H2AX phosphorylation and ATM activation. In contrast, dichloroacetate known to shift metabolism from anaerobic to oxidative glycolysis through its effect on pyruvate dehydrogenase kinase enhanced the level of CHP and CAA. Our present data and earlier observations strongly support the postulate that a large fraction of CHP and CAA occurs in response to DNA damage caused by metabolically generated oxidants. Cytometric analysis of CHP and CAA provides the means to measure the effectiveness of exogenous factors, which either through lowering aerobic metabolism or neutralizing radicals may protect DNA from such damage.

Influence of slightly soluble organics on aerosol activation

This paper examines the effects of slightly soluble organics on aerosol activation in a parcel of air rising adiabatically. Slightly soluble organics can affect aerosol activation by three mechanisms: lowering surface tension, altering the bulk hygroscopicity, and delaying the growth of particles because of their lower solubilities. The first and second mechanisms have already been addressed in a previous paper. Here we address the third mechanism by simulating the activation process of aerosol particles modeled using a single lognormal size distribution and consisting of an internal uniform chemical mixture of adipic acid (representing slightly soluble organics having extremely low solubility as a worst‐case scenario) and ammonium sulfate. The simulations were carried out using measured solubility of adipic acid spanning a wide range of physical and dynamical parameters. The same conditions were resimulated but assuming fully soluble aerosols. Results of the simulations show that although the low solubility of the adipic acid alters Köhler curves and increases critical supersaturation of the smaller particles (Köhler curves of the larger particles are not affected because these particles are completely dissolved at the initial supersaturation of zero), low solubility has minimal to no effect on the parcel supersaturation except for particles consisting of more than 95% adipic acid. Furthermore, since aerosols in realistic atmospheric conditions do not contain more than 90% organics, we should be only interested in smaller concentrations (less than 90% by mass). Accordingly, we conclude that the slightly soluble organics can be assumed to be fully soluble for the purpose of predicting the fraction of activation and the maximum supersaturation with negligible error and it is not necessary to retune the previously developed parameterization of aerosol activation.

MK-801 and 7-Ni attenuate the activation of brain NF-κB induced by LPS

The activation of nuclear factor-κB (NF-κB) leads to an increase in the expression of genes involved in important events in the central nervous system (CNS), such as development, plasticity and inflammation. It has been shown that inflammatory stimulus in the brain increases excitatory glutamatergic transmission, especially at N-methyl- d-aspartate (NMDA) receptor. These receptors have an important role in glutamate neurotoxicity and are in general coupled with the generation of nitric oxide (NO) through the activation of neuronal nitric oxide synthase (NOS). We have investigated the involvement of NMDA–NO pathway in LPS induction of NF-κB in CNS. Our results demonstrate that systemic LPS activates NF-κB in several regions of the CNS, which was partially reduced by the NMDA receptor antagonist dizolcipine (MK-801) and by the selective brain NOS inhibitor 7-Nitroindazol (7-Ni). 7-Ni effects were not synergic to MK-801 effects, suggesting that these compounds act through the same pathway. Dexamethasone caused a stronger reduction in LPS induction of NF-κB in CNS, demonstrating that MK-801 and 7-Ni act on a pathway that is responsible only by a fraction of the overall NF-κB activation. These results suggest that a considerable part of NF-κB activation by LPS is linked to the NMDA/NO pathway in CNS.

Serum non-esterified very long-chain PUFA are associated with markers of endothelial dysfunction

The objective of this study was to investigate the pattern of serum non-esterified fatty acid (NEFA) fraction in association with atherosclerosis development. We have studied possible relationships between eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (AA) in the NEFA fraction and biochemical markers of endothelial activation or dysfunction. The study population consisted of 152 elderly men with high risk for coronary heart disease. The composition of fasting serum NEFA was analysed by gas–liquid chromatography. Endothelial activation was evaluated using biochemical analyses of some markers of endothelial function. A significant inverse linear association was found between serum non-esterified EPA and DHA, and soluble vascular cell adhesion molecule-1 (sVCAM-1) ( P=0.02 and 0.001, respectively). An inverse linear association was found between serum non-esterified AA and sVCAM-1 ( P=0.001) and von Willebrand Factor ( P=0.005). The significant inverse associations for DHA and AA were independent from the serum content of other NEFAs. Taken together, negative associations were found between sVCAM-1 and the serum levels of non-esterified DHA, EPA and AA. The inverse relation between the levels of sVCAM-1 and very long-chain n-3 fatty acids might indicate an anti-inflammatory effect of the latter.

Glucose catabolism in cancer cells: identification and characterization of a marked activation response of the type II hexokinase gene to hypoxic conditions.

One of the most common signatures of highly malignant tumors is their capacity to metabolize more glucose to lactic acid than their tissues of origin. Hepatomas exhibiting this phenotype are dependent on the high expression of type II hexokinase, which supplies such tumors with abundant amounts of glucose 6-phosphate, a significant carbon and energy source especially under hypoxic conditions. Here we report that the distal region of the hepatoma type II hexokinase promoter displays consensus motifs for hypoxia-inducible factor (HIF-1) that overlap E-box sequences known to be related in other gene promoters to glucose response. Moreover, we show that subjecting transfected hepatoma cells to hypoxic conditions activates the type II hexokinase promoter almost 3-fold, a value that approaches 7-fold in the presence of glucose. Consistent with these findings is the induction under hypoxic conditions of the HIF-1 protein. Reporter gene analyses with a series of nested deletion mutants of the hepatoma type II hexokinase promoter show that a significant fraction of the total activation observed under hypoxic conditions localizes to the distal region where the overlapping HIF-1/E-box sequences are located. Finally, DNase I footprint analysis with a segment of the promoter containing these elements reveals the binding of several nuclear proteins. In summary, these novel studies identify and characterize a marked glucose-modulated activation response of the type II hexokinase gene to hypoxic conditions within highly glycolytic hepatoma cells, a property that may help assure that such cells exhibit a growth and survival advantage over their parental cells of origin.

Role of Protein Phosphorylation in Activation of Phospholipase A2 by the Polychlorinated Biphenyl Mixture Aroclor 1242

Polychlorinated biphenyls (PCBs) activate neutrophils to induce degranulation and undergo superoxide production through a mechanism that involves stimulation of phospholipase A2 (PLA2). Since the biochemical processes leading to the PCB-induced activation of this enzyme are unknown, the objective of this study was to determine whether protein phosphorylation has a role in this mechanism. Isolated rat neutrophils were labeled with [3H]-arachidonic acid ([3H]-AA), and activation of PLA2 was determined from release of radioactivity into the medium. Exposure to the PCB mixture Aroclor 1242 induced release of [3H]-AA, and pretreatment with bromoenol lactone (BEL), an inhibitor of calcium-independent PLA2, diminished release by 80%. Genistein, an inhibitor of tyrosine kinases, caused a small but significant decrease in Aroclor 1242-stimulated release of [3H]-AA. Daidzein, a genistein analog with no activity to inhibit tyrosine kinases, had no effect on [3H]-AA release. An inhibitor of p38 mitogen-activated protein kinase (MAPK), SB203580, did not affect Aroclor 1242-induced PLA2 activity at concentrations selective for p38 MAPK; however, PD 98059, which inhibits MAPK kinase (MEK), decreased [3H]-AA release to about the same extent as genistein. Treatment of neutrophils with Aroclor 1242 induced phosphorylation of p44 MAPK, and this phosphorylation was unaffected by BEL but was inhibited by PD 98059. Staurosporine, a nonselective inhibitor of protein kinase C (PKC), inhibited PCB-induced release of [3H]-AA. Ro 32-0432, a selective inhibitor of PKCα and PKCβ1, produced the greatest degree of inhibition (40%) among the tested protein kinase inhibitors. These results suggest that tyrosine kinases, PKC, and the MEK/MAPK pathway are involved in a fraction of Aroclor 1242-induced activation of PLA2.