Electron paramagnetic resonance: A powerful tool of medical biochemistry in discovering mechanisms of disease and treatment prospects

EPR, free radicals, oxidative status, oxidative stress, antioxidants Kratak sadržaj: U patofiziološkim uslovima povezanim sa oksidativnim stresom, primenjivanje određenih antioksidativnih materija može biti od koristi za ljudsko zdravlje. Elektronska paramagnetna rezonantna (EPR) spektroskopija predstavlja tehniku koja pruža jedinstveni uvid u biohemijske redoks procese, zahvaljujući svom kapacitetu da: (i) razlikuje i kvantifikuje različite reaktivne vrste, kao što su hidroksil radikal, superoksid, ugljenični radikali, vodonični atom, azot monoksid, askorbil radikal, melanin i druge; (ii) odredi antioksidativne kapacitete različitih jedinjenje, ekstrakata i namirnica; (iii) pruži informacije o drugim važnim parametrima bioloških sistema. Kombinacija EPR spektroskopije i tradicionalnih biohemijskih metoda predstavlja efikasno oruđe u ispitivanju mehanizama oboljenja i moguće antioksidativne terapije, pružajući kompletniji uvid u redoks procese u ljudskom organizmu.In pathophysiological conditions related to oxidative stress, the application of selected antioxidants could have beneficial effects on human health. Electron paramagnetic resonance (EPR) spectroscopy is a technique that provides unique insight into the redox biochemistry, due to its ability to: (i) distinguish and quantify different reactive species, such as hydroxyl radical, superoxide, carbon centered radicals, hydrogen atom, nitric oxide, ascorbyl radical, melanin, and others; (ii) evaluate the antioxidative capacity of various compounds, extracts and foods; (iii) provide information on other important parameters of biological systems. A combination of EPR spectroscopy and traditional biochemical methods represents an efficient tool in the studies of disease mechanisms and antioxidative therapy prospects, providing a more complete view into the redox processes in the human organism

Multiple Sclerosis: Molecular Mechanisms and Therapeutic Opportunities

The pathophysiology of multiple sclerosis (MS) involves several components: redox, inflammatory/autoimmune, vascular, and neurodegenerative. All of them are supported by the intertwined lines of evidence, and none of them should be written off. However, the exact mechanisms of MS initiation, its development, and progression are still elusive, despite the impressive pace by which the data on MS are accumulating. In this review, we will try to integrate the current facts and concepts, focusing on the role of redox changes and various reactive species in MS. Knowing the schedule of initial changes in pathogenic factors and the key turning points, as well as understanding the redox processes involved in MS pathogenesis is the way to enable MS prevention, early treatment, and the development of therapies that target specific pathophysiological components of the heterogeneous mechanisms of MS, which could alleviate the symptoms and hopefully stop MS. Pertinent to this, we will outline (i) redox processes involved in MS initiation; (ii) the role of reactive species in inflammation; (iii) prooxidative changes responsible for neurodegeneration; and (iv) the potential of antioxidative therapy. Antioxid. Redox Signal. 19, 2286-2334

Comparative analysis of antioxidative systems in malignant and benign brain tumours

Objectives: Comparison of redox conditions in malignant and benign tumours is essential for understanding the role of reactive oxygen species in the pathophysiology of aggressive cancer profiles. Here we compare antioxidative systems in highly malignant brain tumour - glioblastoma multiforme (GBM), and in meningioma, a benign brain tumour. Methods: Tumour tissues and blood of 67 GBM patients (mean age: 52.9 +/- 11.5 years) and 67 meningioma patients (59.2 +/- 10.2 years), and blood of 30 control subjects (50.8 +/- 12.8 years) were analysed via biochemical assays. Results: Components of glutathione system, which is responsible for H2O2 removal, showed lower activity/level in GBM: glutathione peroxidase (GBM: 9.90 +/- 0.22; meningioma: 11.78 +/- 0.23 U/mg of proteins; P lt 0.001), glutathione reductase (GBM: 3.83 +/- 0.13; meningioma: 4.67 +/- 0.11 U/mg of proteins; P lt 0.001), and glutathione (GBM: 6.70 +/- 0.12; meningioma: 7.58 +/- 0.14 mu mol/g of tissue; P lt 0.001). In contrast, the rank order of glutathione reductase activity and glutathione level in erythrocytes was: GBM > meningioma > control. Superoxide dismutase and catalase activities were lower in the blood of cancer patients compared to controls. Discussion: Cells of malignant brain tumour show down-regulated antioxidative system which might result in increased levels of H2O2 compared to benign tumour tissue

The role of EPR spectroscopy in studies of the oxidative status of biological systems and the antioxidative properties of various compounds

In this era of intense study of free radicals and antioxidants, electron paramagnetic resonance (EPR) is arguably the best-suited technique for such research, particularly when considering biochemical and biological systems. No attempt was made to cover all the topics of EPR application but instead attention was restricted to two areas that are both novel and received less attention in previous reviews. In the first section, the application of EPR in assessing the oxidative status of various biological systems, using endogenous stabile paramagnetic species, such as the ascorbyl radical, semiquinone, melanin, and oxidized pigments, is addressed. The second section covers the use of EPR in the emerging field of antioxidant development, using EPR spin-trapping and spin-probing techniques. In both sections, in addition to giving an overview of the available literature, examples (mostly from the authors' recent work) are also presented in sufficient detail to illustrate how to explore the full potential of EPR. This review aims at encouraging biologists, chemists and pharmacologists interested in the redox metabolism of living systems, free radical chemistry or antioxidative properties of new drugs and natural products to take advantage of this technique for their investigations

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Prevalencija i stupanj infestacije gljivica kod upale vanjskog ušnog kanala u pasa

Otitis externa is a persistent and recurrent problem, and the resistance of the involved pathogens to conventional drugs has made this a serious issue in veterinary medicine. This is an inflammation of the external ear canal in dogs that can be caused by bacteria or yeast. Often, these two causative agents are isolated together in combination. This study aimed to determine the prevalence of yeast and the degree of infestation of the isolated pathogens in canine otitis externa at veterinary clinics for small pets at the Department of Veterinary Medicine, University of Novi Sad, Serbia. Samples were taken from 60 dogs with clinical symptoms of otitis externa using a sterile swab and sent to laboratory for further mycological and bacteriological examination. In order to isolate the bacteria and yeast, conventional methods were used under aerobic conditions. Of the total samples, 53 (88.33%) were positive for at least one of the causative agents of otitis externa. Yeasts were isolated from 36 (52.94%) samples. The study showed that in comparing mixed and independent types of infection, in most cases 15/23 (65.22%) the degree of infestation with yeast was highest when the infection was mixed with bacteria. In relation to dog breeds, their ear forms and type of infection, more yeast samples (either as solo or mixed infection) were isolated from dogs with pendulous ears. It has been confirmed that Malassezia pachydermatis is the most common yeast pathogen of otitis externa in dogs, compared to other species of this genus, and it occurs in a higher degree of infestation in mixed infections than in solo infections. Dog breeds with pendulous ear form are more predisposed to yeast otitis externa than erect eared dog breeds.Kao perzistentan i rekurentan problem, zbog prisustva rezistencije patogenih uzročnika na konvencionalne lijekove upala vanjskog ušnog kanala predstavlja ozbiljan problem u veterinarskoj medicini. Upala vanjskog ušnog kanala u pasa može biti prouzročena bakterijama i gljivicama. Ova se dva uzročnika često mogu izolirati zajedno, u kombinaciji. Predmet je ovog istraživanja bio utvrđivanje prevalencije gljivica i stupnja infestacije izoliranih patogena kod upale vanjskog ušnog kanala u pasa u Veterinarskoj klinici za male životinje Departmana za veterinarsku medicinu u Novom Sadu, Srbija. Uzorci su uzeti od 60 pasa s kliničkim simptomima upale vanjskog ušnog kanala pomoću sterilnog brisa, a poslani su u Laboratorij na daljnje mikološko i bakteriološko ispitivanje. Da bi se izolirale bakterije i gljivice, uporabljene su konvencionalne metode u aerobnim uvjetima. Od ukupnog broja uzoraka, 53 (88,33 %) su bila pozitivna na prisustvo najmanje jednog od uzročnika upale vanjskog ušnog kanala. Gljivice su izolirane iz ukupno 36 (52,94 %) uzoraka. Istraživanje je pokazalo da je u slučaju usporedbe između miješanih i samostalnih tipova infekcije u najvećem broju slučajeva 15/23 (65,22 %) stupanj infestacije gljivicama bio najviši kada je infekcija bila pomiješana s bakterijama. U odnosu na pasmine pasa, njihove tipove ušiju i vrstu infekcije, utvrđeno je da je više uzoraka s gljivicama bilo kao samostalna ili miješana infekcija izolirano u pasa s visećim ušima. Potvrđeno je da je Malassezia pachydermatis najčešći gljivični patogen upale vanjskog ušnog kanala pasa, u usporedbi s drugim vrstama ovoga roda. Kod mješovite infekcije javlja se u većem stupnju infestacije nego kod samostalne infekcije. Pasmine pasa s visećim ušima su sklonije nastanku upale vanjskog ušnog kanala prouzročene gljivicama nego pasmine pasa s uspravnim ušima

Effect of the degree of plastic deformation on the thermal electromotive force of Cu-X5crni1810 steel thermocouple

The thermal electromotive force (TEMF) and the thermal electromotive force coefficient (TEMFC) of the thermocouple consisting of a copper wire and an (X5CrNi1810) steel wire plastically deformed under tension or bending conditions were found to increase with increasing degree of plastic deformation. The increase in the degree of deformation disturbs the microstructure of steel due to increases in the density of chaotically distributed dislocations and internal microstress, resulting in a decrease in the electron density of states near the Fermi level. Through the effect of thermal energy, annealing at elevated temperatures up to 300°C leads to microstructural ordering along with simultaneous increases in the free electron density of states, TEMF and TEMFC. Based on the temporal change of the TEMF, the kinetics of microstructural ordering was determined. During the initial time interval, the process is a kinetically controlled first-order reaction. In the second time interval, the process is controlled by the diffusion of reactant species

An EPR spin-probe and spin-trap study of the free radicals produced by plant plasma membranes

Plant plasma membranes are known to produce superoxide radicals, while the production of hydroxyl radical is thought to occur only in the cell wall. In this work it was demonstrated using combined spin-trap and spin-probe EPR spectroscopic techniques, that plant plasma membranes do produce superoxide and hydroxyl radicals but by kinetically different mechanisms. The results show that superoxide and hydroxyl radicals can be detected by DMPO spin-trap and that the mechanisms and location of their production call be differentiated using the reduction of spin-probes Tempone and 7-DS. It was shown that the mechanism of production of oxygen reactive species is NADH dependent and diphenylene iodonium inhibited. The kinetics of the reduction of Temponc, combined with scavengers or the absence of NADH indicates that hydroxyl radicals are produced by a mechanism independent of that of superoxide production. It was shown that a combination of the spill-probe and spin-trap technique can be used in free radical studies of biological systems, with a number of advantages inherent to them

Development of Contingent/Contextual Theory: A State-of-the-Art Review

The contingent/contextual approach to the theory and practice of the organization arose in the 60s of the previous century, and its verification and empirical improvement are still ongoing, with increasing topicality and the presence of an increasingly strong trend of quantifying the influence of contingent/contextual factors and the increasing complexity of research with the same aim - it is expected that by mastering the effect of given factors, the overall efficiency of the company can be increased and that standardization in this field can bring great benefits. So far, the best researched and quantified is the impact of company size and technology on organizational structure factors. However, a large number of interdependencies are still not resolved among contingent factors, such as: a) the connection of decentralization with other contingent factors - company size, environment, etc., b) the influence of digitalization on the range of management, c) the direction of the influence of the degree of mass production on the number of hierarchical levels, d) the impact of innovation as a part of strategy on the organizational structure and many others. Various authors try to solve the above-mentioned questions, but the conclusions between them have not been confirmed so far; what's more, numerous results are released to the scientific public, which are mutually contradictory, as shown in the tabular presentation in the paper. In particular, the contribution of the latest version of the ISO 9001 standard from 2015, which for the first time recognizes the context in the given area, should be highlighted. Finally, it can be concluded that the empirical verification and theoretical enrichment of the contingent theory has been going on for decades, with the presence of an increasingly strong trend of quantifying the impact of contingent factors and the increasing complexity of research with the same goal - it is expected that mastering the effect of contingent factors can increase the overall efficiency of the company