Agnes Keszler

• PhD
• Researcher at Medical College of Wisconsin

Red light (670 nm) energy controls vasodilation via the formation of a transferable endothelium-derived nitric oxide (NO)-precursor-containing substance, its intracellular traffic, and exocytosis. Here we investigated the underlying mechanistic effect of oxidative stress on light-mediated vasodilation by using pressure myography on dissected murine...

We have previously established that 670 nm energy induces relaxation of blood vessels via an endothelium derived S -nitrosothiol (RSNO) suggested to be embedded in vesicles. Here, we confirm that red light facilitates the exocytosis of this vasodilator from cultured endothelial cells and increases ex vivo blood vessel diameter. Ex vivo pressurized...

Nitric oxide dependent vasodilation is an effective mechanism for restoring blood flow to ischemic tissues. Previously, we established an ex vivo murine model whereby red light (670 nm) facilitates vasodilation via an endothelium derived vasoactive species which contains a functional group that can be reduced to nitric oxide. In the present study w...

Preeclampsia is a serious pregnancy disorder which in extreme cases may lead to maternal and fetal injury or death. Preexisting conditions which increase oxidative stress, e.g., hypertension and diabetes, increase the mother’s risk to develop preeclampsia. Previously, we established that when the extracellular matrix is exposed to oxidative stress,...

Red light (670 nm) promotes ex vivo dilation of blood vessels in a nitric oxide (NO) dependent, but eNOS independent manner by secreting a quasi-stable and transferable vasoactive substance with the characteristics of S-nitrosothiols (RSNO) from the endothelium. In the present work we establish that 670 nm light mediated vasodilation occurs in vivo...

Preeclampsia is a leading cause of maternal morbidity and mortality worldwide, complicating 2–8% of pregnancies, and is recognized as an independent risk factor for CVD by the ACC/AHA. The etiology of preeclampsia is poorly understood. However, the role of placental extracellular matrix (pECM) and extravillous trophoblast in placental blood vessel...

In previous studies we demonstrated endothelial dependent vasodilation at 670nm red/near infrared light (670nm light) in healthy vessels and db/db mice related to S‐nitrosothiol release. Furthermore, the bath solution from intact 670nm light stimulated vessels could dilate 670nm light naïve vessels in a NO dependent manner. Therefore, we propose th...

Introduction In our previous work we demonstrated the importance of altered extracellular matrix (ECM) in disease processes and how treatment with 670 nm LLLT can restore cell behavior. Objective Of this study focuses on the signaling properties of altered ECM in preeclampsia, its contribution to preeclampsia, and the possibility of a novel therap...

There is significant therapeutic advantage of nitric oxide synthase (NOS) independent nitric oxide (NO) production in maladies where endothelium, and thereby NOS, is dysfunctional. Electromagnetic radiation in the red and near infrared region has been shown to stimulate NOS-independent but NO-dependent vasodilation, and thereby has significant ther...

Far red/near infrared (R/NIR) energy is a novel therapy, but its mechanism of action is poorly characterized. Cytochrome c oxidase (Cco) of the mitochondrial electron transport chain is considered the primary photoacceptor for R/NIR to photolyze a putative heme nitrosyl in Cco to liberate free nitric oxide (NO). We previously observed R/NIR light d...

Peripheral artery disease (PAD) is a morbid condition whereby ischemic peripheral muscle causes pain and tissue breakdown. Interestingly, PAD risk factors, e.g. diabetes mellitus, cause endothelial dysfunction secondary to decreased nitric oxide (NO) levels, which could explain treatment failures. Previously, we demonstrated 670nm light (R/NIR) inc...

Dinitrosyl iron complexes (DNIC) spontaneously form in aqueous solutions of Fe(II), nitric oxide (NO), and various anions. They exist as an equilibrium between diamagnetic, dimeric (bi-DNIC) and paramagnetic, monomeric (mono-DNIC) forms. Thiolate groups (e.g., on glutathione or protein cysteine residues) are the most biologically relevant anions to...

Introduction: Over 8 million Americans are treated for peripheral artery disease (PAD), i.e. intermittent claudication, impaired wound healing, and critical limb ischemia. Endothelial dysfunction of the microcirculation is a potential mechanism for the pathogenesis of PAD because risk factors for PAD- age, hypertension, atherosclerosis, diabetes me...

Far red/near infrared light (NIR) is beneficial against cardiac ischemia and reperfusion injury (I/R), although the exact underlying mechanism is unknown. Previously we established that NIR enhanced the cardioprotective effect of nitrite in the rabbit heart. Furthermore, we observed that the nitrosyl myoglobin (MbNO) level in ischemic tissue decrea...

Changes in oxidative capacities and phospholipid remodeling accompany temperature acclimation in ectothermic animals. Both responses may alter redox status and membrane susceptibility to lipid peroxidation (LPO). We tested the hypothesis that phospholipid remodeling is sufficient to offset temperature-driven rates of LPO, and thus membrane suscepti...

Far red/near-infrared light (NIR) promotes a wide range of biological effects including tissue protection but whether and how NIR is capable of acutely protecting myocardium against ischemia and reperfusion injury in vivo is not fully elucidated. Our previous work indicates that NIR exposure immediately before and during early reperfusion protects...

Real‐time measurement of nitric oxide (NO) before, during and after study interventions has numerous advantages over multiple endpoint measurements at various times. However, no reliable method has been described in Langendorff‐prepared hearts. Rat isolated hearts were loaded for 30 min with 20 µM of the fluorescent dye 4,5‐diaminofluorescein (DAF‐...

Background: S-nitrosothiols have been recognized as biologically-relevant products of nitric oxide that are involved in many of the diverse activities of this free radical. Scope of review: This review serves to discuss current methods for the detection and analysis of protein S-nitrosothiols. The major methods of S-nitrosothiol detection includ...

S-nitrosothiols are products of nitric oxide (NO) metabolism that have been implicated in a plethora of signalling processes. However, mechanisms of S-nitrosothiol formation in biological systems are uncertain, and no efficient protein-mediated process has been identified. Recently, we observed that ferric cytochrome c can promote S-nitrosoglutathi...

Normally, cell free haemoglobin is bound by haptoglobin and efficiently cleared. However, the chronic haemolysis in sickle cell disease (SCD) overwhelms haptoglobin binding capacity and protein turnover, resulting in elevated cell free haemoglobin. Cell free haemoglobin acts as both a scavenger of vasoactive nitric oxide and a pro-oxidant. In addit...

A simple and easy preparative route to obtain permanganic acid and permanganate salts from Ba manganate and H2SO4 is described. H2SO4 reacts with Ba manganate to produce sparingly sol. Ba sulfate and very sol. permanganic acid or Ba permanganate. These in turn can be used to prep. other metal permanganates.

The reaction between NO, thiols, and oxygen has been studied in some detail in vitro due to its perceived importance in the mechanism of NO-dependent signal transduction. The formation of S-nitrosothiols and thiol disulfides from this chemistry has been suggested to be an important component of the biological chemistry of NO, and such subsequent th...

Although S-nitrosothiols are regarded as important elements of many NO-dependent signal transduction pathways, the physiological mechanism of their formation remains elusive. Here, we demonstrate a novel mechanism by which cytochrome c may represent an efficient catalyst of S-nitrosation in vivo. In this mechanism, initial binding of glutathione to...

Nitric oxide is an important messenger in numerous biological processes, such as angiogenesis, hypoxic vasodilation, and cardioprotection. Although nitric oxide synthases (NOS) produce the bulk of NO, there is increasing interest in NOS independent generation of NO in vivo, particularly during hypoxia or anoxia, where low oxygen tensions limit NOS...

Nitric oxide (NO*) participates in the regulation of a wide array of biological processes and its deficit contributes to the severity of many diseases. Recently, a role of NO deficiency that occurs as a result of intravascular hemolysis and increases in levels of cell-free hemoglobin in the pathway of chronic anemic pathologies has been suggested....

The nitrite anion (NO–2) has recently received much attention as an endogenous nitric oxide source that has the potential to be supplemented for therapeutic benefit. One major mechanism of nitrite reduction is the direct reaction between this anion and the ferrous heme group of deoxygenated hemoglobin. However, the reaction of nitrite with oxyhemog...

This review discusses proteomic methods to detect and identify S-nitrosated proteins. Protein S-nitrosation, the post-translational modification of thiol residues to form S-nitrosothiols, has been suggested to be a mechanism of cellular redox signaling by which nitric oxide can alter cellular function through modification of protein thiol residues....

The reaction of nitrite with hemoglobin has become of increasing interest due to the realization that plasma nitrite may act as an NO congener that is activated by interaction with red blood cells. Using a combination of spectrophotometry, immuno-spin trapping, and EPR, we have examined the formation of radicals during the oxidation of oxyhemoglobi...

Recent evidence suggests that the reaction between nitrite and deoxygenated hemoglobin provides a mechanism by which nitric oxide is synthesized in vivo. This reaction has been previously defined to follow second order kinetics, although variable product stoichiometry has been reported. In this study we have re-examined this reaction and found that...

S-Nitrosation of protein cysteinyl residues has been suggested to be an important nitric oxide-dependent posttranslational modification. The so-called biotin-switch method has been developed to identify S-nitrosated proteins. This method relies on the selective reduction of S-nitrosothiols by ascorbate. In this study we have assessed the ability of...

We determined whether isoflurane can confer delayed cardioprotection in the adult rat by triggering increased production of reactive oxygen (ROS) and nitrogen species (RNS). Our objectives were to determine 1) the concentration of isoflurane that confers delayed cardioprotection in the adult rat, 2) the role of ROS and RNS in the induction of delay...

Collection of EPR spectra in digital format permits post processing that can be more meaningful than multiple-scan averaging, especially for spectra that are overlapping and changing with time, as is characteristic of spectra acquired in spin-trapping studies. It is demonstrated that multiple linear regression analysis of multiple spectra acquired...

The mitochondria-targeted drugs mitoquinone (Mito-Q) and mitovitamin E (MitoVit-E) are a new class of antioxidants containing the triphenylphosphonium cation moiety that facilitates drug accumulation in mitochondria. In this study, Mito-Q (ubiquinone attached to a triphenylphosphonium cation) and MitoVit-E (vitamin E attached to a triphenylphosphon...

The reaction between low molecular weight S-nitrosothiols and hemoglobin is often used to synthesize S-nitrosohemoglobin, a form of hemoglobin suggested to be involved in the regulation of vascular oxygen delivery. However, this reaction has not been studied in detail, and several groups have reported a variable co-formation of oxidized methemoglob...

The kinetics of the reaction between superoxide and the spin trapping agents 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline N-oxide (DEPMPO), and 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) were re-examined in the superoxide-generating xanthine/xanthine oxidase system, by competition with spontane...

We investigated here the mechanism of cytoprotection of nitric oxide (*NO) in bovine aortic endothelial cells treated with H2O2. NONOates were used as *NO donors that released *NO slowly at a well defined rate in the extracellular and intracellular milieus. H2O2-mediated intracellular dichlorofluorescein fluorescence and apoptosis were enhanced by...

We have shown previously that peroxynitrite-induced nitration of a hydrophobic tyrosyl probe is greater than that of tyrosine in the aqueous phase (Zhang, H., Joseph, J., Feix, J., Hogg, N., and Kalyanaraman, B. (2001) Biochemistry 40, 7675-7686). In this study, we have tested the hypothesis that the extent of tyrosine nitration depends on the intr...

Dichlorodihydrofluorescein (DCFH) is one of the most frequently used probes for detecting intracellular oxidative stress. In this study, we report that H2O2-dependent intracellular oxidation of DCFH to a green fluorescent product, 2',7'-dichlorofluorescein (DCF), required the uptake of extracellular iron transported through a transferrin receptor (...

The oxidn. or consecutive ammoxidn. reaction of benzyl alc. with solid ammonium permanganate was studied. The first oxidn. step leads to the formation of benzaldehyde, ammonia, and MnO2. The MnO2 is present in the system in a colloidal form, which facilitates the reaction between aldehyde and ammonia, and this latter reaction then yields benzonitri...

We studied the possibility of direct GC-MS determination of amphetamine hydrochloride. In order to avoid the double peak we determined the optimal injector temperature (260°C) and heating rate (40°C min−1). In the direct analysis of amphetamine hydrochloride containing samples, calibration for fragmentm/z=59 (originating from amphetaminium ion frag...

Volatile compounds formed in the course of the thermal decomposition of hydroperoxides during storage of sunflower oil were analyzed by headspace solid-phase microextraction sampling followed by gas chromatographic separation and mass spectral detection. The determining role of alkoxyl radicals in the process has been proven by electron spin resona...

The crystal structures of ammonium permanganate and ammonium perchlorate at 293 K were determined and compared. X-ray and vibrational spectroscopic data confirmed the existence of weak hydrogen bonds in NH4MnO4. These hydrogen bonds proved to be slightly stronger than H-bonds in ammonium perchlorate. Difference between the results of diffuse reflec...

A preseparated fermentation broth of Trichoderma atroviride strain 11 is analyzed by gas chromatography followed by mass-spectral detection using a Finnigan MAT GCQ apparatus. After preseparation in a C18 and a silica gel column, nineteen pyrone and dioxolane derivatives and two aliphatic esters are obtained, respectively. Among these, the four dio...

Nitric acid activation of bentonite has been studied with the aim of harmonizing bleaching earth and ammonium nitrate fertilizer production, where the latter is obtained from waste acid via neutralization with ammonia. In this paper, a mathematical model is described for composition measurement of the waste acid formed during the activation of the...

ICP-OES (inductively coupled plasma optical emission spectrometry) was used to det. the element content of red wines. Development of the method involves various procedures of sample handling as well as repeatability and reproducibility measurements. Measurements were made for the following 16 elements: Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn,...

This article describes a simple detection method for 13CO2 by std. gas chromatog.-mass spectrometry techniques.

We have investigated the effect of temperature on the postulated quasi-intramolecular acid-base reactions in aqueous solutions of Cu(NH3)4(MnO4)2 and Ag(NH3)2ClO4. Pure ammonium permanganate and perchlorate were obtained above 5 C and at room temperature, respectively, due to quasi-intramolecular acid-base reactions. ular acid-base reactions in aqu...

Based on environmental, safety, corrosion and technological considerations a new method has been developed for chlorination of PVC in aqueous hydrochloric acid solvent by controlled electrolytic in situ generation of chlorine using graphite and chlorine-selective Ti-RuO2 electrodes. The byproduct, HCl gas, is dissolved at the moment of its formatio...

The thermal decomposition of ammonium permanganate was studied by thermogravimetry-mass spectrometry (TG-MS). A Perkin Elmer TGS-2 thermobalance and a Hiden’s HAL 3F/PIC mass spectrometer equipped with a fast ion counter was used.Products of thermal decomposition of ammonium permanganate are oxygen, manganese oxides, water and ammonia. There is no...

A simple and easy preparative route to obtain permanganic acid and permanganate salts from barium manganate and sulphuric acid is described. Sulphuric acid reacts with barium manganate to produce sparingly soluble barium sulphate and well-soluble permanganic acid or barium permanganate, these in turn can be used to prepare other metal permanganates...

The main sorption conditions were optimized in the solid-phase microextraction (SPME) analysis of aldehydes that have different degrees of saturation. Aliphatic aldehydes were analyzed quantitatively in oil matrix and in aqueous solution by GC–MS using SPME sampling. The effectiveness of the immersion and the headspace techniques was compared in wa...

N,N’-dimethyl-N,N’-diphenylcarbamide (centralite) extracted from building materials was quantitated using ion trap GC-MS detection technique. Both linearity and standard deviation of the calibration curve were dependent on the conditions of the mass spectral detection. The most precise calibration has been achieved by quantification of a mass ion n...

Production and the mechanism of the interactions of free radicals generated by stimulated macrophages in the presence of luminol and a free radical inhibitor was investigated to determine the possibility of using luminol-dependent chemiluminescence for studying photodynamic effects in biology. Earlier measurements have been revisited and additional...

Decomposition of hydroperoxides in sunflower oil under strictly oxygen-free conditions was followed by measuring peroxide values against time, absorbance values at 232 and 268 nm, para-anisidine values, and by quantitative analyses of volatile products using various additives. The results were arranged in a matrix form and subjected to principal co...

Earlier results studying the effect of excited triplet photosensitizer on the zymosan-stimulated and luminol- dependent chemiluminescence of macrophages have been quantitatively re-evaluated and rate constant data indicate that the effect is due to triplet-doublet interactions between sensitizer and free radicals generated. Such interactions, named...

Chemiluminescence generated by zymosan-stimulated macrophage cells in the presence of luminol has been studied in order to obtain information concerning the possible interference with the free radical production in the course of the oxidation of luminol. Analytical solution of the corresponding differential equations and computer simulation reveale...

A fast and simple headspace SPME sampling method has been developed for quantification of volatile aliphatic aldehydes in sunflower oil. Analysis has been performed by gas chromatography, on a 30m×0.25 mm i.d. ×0.25 μm CP-Wax 52CB column, with mass spectrometric detection. Carryover from the SPME fiber could be eliminated by heating the fiber in th...

According to our hypothesis the interactions of triplet photosensitizer molecules with doublet free radicals generated in vivo (native free radicals) play an important role in the overall photodynamic effect (MTO mechanism). In order to support this mechanism, experiments have been performed recently in vivo, in vitro and in chemical model systems....

A mechanism is suggested for the oxidative decarboxylation of cyclohexane nonocarboxylic acid (exptl. results published earlier). In the thermal oxidn. the main chain carrier radicals are secondary and tertiary peroxy radicals. The main product, cyclohexanone, and the byproducts (hydroxy and keto acids) are formed in parallel reaction routes. Carbo...

A mechanism is suggested for the oxidative decarboxylation of cyclohexane monocarboxylic acid initiated by decomposition of H2O2. The process is a non-branching chain reaction. Cyclohexanone and cyclohexanol form in termination reactions.

Based on the experimental results obtained studying the oxidative decarboxylation of cyclohexane monocarboxylic acid and published earlier, a mechanism is suggested, according to which in the thermal oxidation two main chain carrier radicals exist: tertiary and secondary peroxy radicals yielding cyclohexanone as well as hydroxy and keto acids in pa...

Photoinitiated liquid phase oxidation of 1‐phenyl ethanol and benzyl alcohol have been investigated in the temperature range of 50–70°C using the intermittent illumination (rotating sector) technique. The rate of oxidation was followed by gas chromatography while the rate of initiation was determined by the inhibitor method. Results were explained...