AdS_5/CFT_4 Four-point Functions of Chiral Primary Operators: Cubic Vertices

We study the exchange diagrams in the computation of four-point functions of all chiral primary operators in D=4, $\mathcal{N}=4$ Super-Yang-Mills using AdS/CFT correspondence. We identify all supergravity fields that can be exchanged and compute the cubic couplings. As a byproduct, we also rederive the normalization of the quadratic action of the exchanged fields. The cubic couplings computed in this paper and the propagators studied extensively in the literature can be used to compute almost all the exchange diagrams explicitly. Some issues in computing the complete four-point function in the massless sector is discussed.Comment: 15 pages, 1 figure; v2. typos correcte

S-Nitrosothiols in Blood: Does Photosensitivity Explain a 4-Order-of-Magnitude Concentration Range?

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Does the Inhibitory Action of Asymmetric Dimethylarginine (ADMA) on the Endothelial Nitric Oxide Synthase Activity Explain Its Importance in the Cardiovascular System? The ADMA Paradox

Asymmetric dimethylarginine (ADMA, NG, NG-dimethyl-L-arginine) is endogenously produced by asymmetric dimethylation of the guanidine group of L-arginine residues. ADMA is generally considered a powerful cardiovascular risk factor, an Übermarker, due to its inhibitory action on the activity of nitric oxide synthase (NOS) isoforms. In the endothelium, the constitutively expressed and Ca2+/calmodulin-dependent NOS (eNOS) catalyzes the conversion of L-arginine to nitric oxide (NO). NO is one of the most potent endogenous activators of soluble guanylyl cyclase which produces the second messenger cyclic guanosine monophosphate (cGMP). There is experimental evidence from in vitro and in vivo experiments that challenges the extraordinary importance of ADMA as the culprit of NO-related cardiovascular diseases in the human circulation. Most notably, we present data showing that ADMA is a weak competitive inhibitor of recombinant endothelial NOS (eNOS) activity (Ki 3.9 μM, IC50 12 μM). Thus, at its relatively low concentrations of 0.4 to 0.5 μM in the human blood, ADMA is unlikely to inhibit NO synthesis in the endothelium to an extent sufficient enough to cause endothelium dysfunction. Furthermore, ADMA does not “uncouple” eNOS and does not diminish the bioavailability of NO through its reaction with superoxide radical anions produced by “uncoupled” eNOS. Consequently, the particular importance assigned to ADMA in the human circulation is likely to be due to other not yet recognized biological actions beyond inhibition of eNOS activity. This “ADMA paradox” remains to be solved

The dilemma of oxidative stress personified by the diprosopus 8-iso-prostaglandin F2α and prostaglandin F2α

In general, the term “oxidative stress” describes an imbalance between oxidants and antioxidants in favor of the oxidants. While antioxidant defense is widely accepted to involve both enzymatic and non-enzymatic reactions, oxidants are generally assumed to be produced by non-enzymatic processes involving chemically produced free radicals. However, many oxidants are also formed by numerous enzymes and proteins. The F2-isoprostane 8-iso-prostaglandin F2α (8-iso-PGF2α) and malondialdehyde (MDA) are widely used as biomarkers of oxidative stress, although there is evidence that both 8-iso-PGF2α and MDA are also produced enzymatically from arachidonic acid by the action of cyclooxygenase (COX). On the contrary, there is also evidence that PGF2α is produced from arachidonic acid both by the action of COX and non-enzymatically. The duality of oxidative stress, personified by 8-iso-PGF2α and PGF2α, is a serious dilemma and demands new definitions and strategies from the scientists

Whole-body arginine dimethylation is associated with all-cause mortality in adult renal transplant recipients

Arginine residues in proteins can be singly or doubly methylated post-translationally. Proteolysis of arginine-methylated proteins provides monomethyl arginine, asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA). ADMA and SDMA are considered cardiovascular risk factors, with the underlying mechanisms being not yet fully understood. SDMA lacks appreciable metabolism and is almost completely eliminated by the kidney, whereas ADMA is extensively metabolized to dimethylamine (DMA), with a minor ADMA fraction of about 10% being excreted unchanged in the urine. Urinary DMA and ADMA are useful measures of whole-body asymmetric arginine-dimethylation, while urinary SDMA serves as a whole-body measure of symmetric arginine-dimethylation. In renal transplant recipients (RTR), we previously found that higher plasma ADMA concentrations and lower urinary ADMA and SDMA concentrations were associated with a higher risk of all-cause mortality. Yet, in this RTR collective, no data were available for urinary DMA. For the present study, we additionally measured the excretion rate of DMA in 24-h collected urine samples of the RTR and of healthy kidney donors in the cohort, with the aim to quantitate whole-body asymmetric (ADMA, DMA) and symmetric (SDMA) arginine-dimethylation. We found that lower DMA excretion rates were associated with higher all-cause mortality, yet not with cardiovascular mortality. In the healthy donors, kidney donation was associated with considerable decreases in ADMA (by - 39%, P < 0.0001) and SDMA (by - 21%, P < 0.0001) excretion rates, yet there was no significant change in DMA (by - 9%, P = 0.226) excretion rate. Our results suggest that protein-arginine dimethylation is altered in RTR compared to healthy kidney donors and that it is pronouncedly shifted from symmetric to asymmetric arginine-dimethylation, with whole-body protein-arginine dimethylation being almost unaffected

Kinetic Spectrophotometric Determination of N-Acetyl-L-cysteine Ethyl Ester (NACET) Generating Chromogenic Copper(I)Ln Complexes with Different Ligands

Three simple, sensitive and robust kinetic spectrophotometric methods for the determination of a novel lipophilic thiol compound, N-acetyl-L-cysteine ethyl ester (NACET), have been developed and validated. The methods are based on the reduction of Cu(II)-ligand complex to Cu(I)-ligand complex with the analyte. Studied ligands were neocuproine, bicinchoninic acid (BCA) and bathocuproine disulfonic acid (BCS). The development of chromogenic complexes was followed using kinetic setup with spectrophotometric detection at 458, 562 and 483 nm for the reactions of NACET with neocuproine, BCA and BCS, respectively. The calculated reaction orders with respect to NACET concentration were found to be 1.07, 1.01, 1.07, respectively, thus confirming a first order of reaction. The initial rate and fixed time methods were utilized for constructing calibration curves. Assays limits of detection were 1.4 × 10–7, 3.2 × 10−7 and 6.0 × 10−8 mol L–1, respectively. The analytical performance of the methods, in terms of accuracy and precision, was established. This work is licensed under a Creative Commons Attribution 4.0 International License

Essays on behavioral tax compliance and trust in government

Research on tax compliance has shown that nonpecuniary incentives are very important for explaining tax compliance, and may outweigh the importance of enforcing tax payments with deterring instruments. This thesis seeks to deepen the understanding of why and how taxpayers respond to nonpecuniary incentives to comply with the tax code. In particular, this thesis examines the importance of framing, reputational concerns, and the interplay of trust in authorities and deterrence exerted by the state. The second central research objective in this thesis is to explore the societal determinants and characteristics of trust in government. This dissertations shows that the objective trustworthiness of institutions does not necessarily coincide with the subjective trust people put in them. However, even with lacking accountability and reliability of institutions, this thesis suggests positive direct links between trust in government and countries' economic development

Developmental changes in the L-arginine/nitric oxide pathway from infancy to adulthood: plasma asymmetric dimethylarginine levels decrease with age

Background: The L-arginine/nitric oxide (NO) pathway has multiple physiological functions including vasodilation, inhibition of platelet aggregation and neurotransmission. Asymmetric dimethylarginine (ADMA), an endogenous inhibitor of all known NO synthase isoforms, has adverse effects on renal and cardiovascular function in adults. It is unknown whether ADMA might also exert similar effects in younger individuals including infants. Also, reference data for important members of the L-arginine/NO family, notably ADMA and the NO metabolites, nitrite and nitrate, in infancy are lacking. Methods: In the present study, we investigated the status of the L-arginine/NO pathway in 34 healthy volunteers aged 2days to 24years by measuring the concentration of ADMA, nitrite, nitrate and L-arginine in plasma and urine using gas chromatography-mass spectrometry and gas chromatography-tandem mass spectrometry methods. Results: We found that ADMA levels in plasma decreased with age (Pearson correlation coefficient r=-0.619, p<0.001). In contrast, urinary excretion of nitrate (r=0.471, p=0.036) and nitrite increased with age (r=0.484, p=0.037). Conclusions: Our study suggests that in infants ADMA biosynthesis accompanied by an inhibition of NO synthesis is higher than in adults and diminishes considerably with age. Clin Chem Lab Med 2007;45:1525-3