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Oxidative Processes (oxidative + process)
Selected AbstractsOxidative processes of desulfurization of liquid fuelsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2010J.M. Campos-Martin Abstract Environmental concerns have introduced a need to remove sulfur-containing compounds from light oil. As oxidative desulfurization is conducted under very mild reaction conditions, much attention has recently been devoted to this process. In this contribution, the developments in selective removal of organosulfur compounds present in liquid fuels via oxidative desulfurization, including both chemical oxidation and biodesulfurization, are reviewed. At the end of each section, a brief account of the research directions needed in this field is also included. Copyright © 2010 Society of Chemical Industry [source] Bis(dithiolene) Molybdenum Complex that Promotes Combined Coupled Electron,Proton Transfer and Oxygen Atom Transfer Reactions: A Water-Active Model of the Arsenite Oxidase Molybdenum CenterEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2006Hideki Sugimoto Abstract Combined CEPT (coupled electron,proton transfer)/OAT (oxygen atom transfer) reactions were accomplished in (Bu4N)2[MoIVO(bdtCl2)2] (1) and (Bu4N)2[MoVIO2(bdtCl2)2] (2) complexes in aqueous media. The reaction mechanism of the CEPT reaction was analyzed electrochemically and the conversion of 1 to 2 was revealed to proceed by a two-proton two-electron oxidative process. The structural and reaction profiles provide a new model for the arsenite oxidase catalytic center. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A New Synthesis of Push-Pull Pyrroles, Their Oxidation to Stable 3H -Pyrroles and an Unexpected Anellation ReactionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2009Gunther Buehrdel Abstract A new synthesis of push-pull pyrroles of type 5 was developed starting from bis(imidoyl chlorides) 1 and various iminodiacetic acid derivatives 3. The use of appropriate N -trifluoroacetyl residues as protecting/activating group proved to be the method of choice for the straightforward preparation of the 3,4-diarylamino-1H -pyrroles 5. When benzothiazole substructures are present in 2,5-position of heterocycles 5, a two-electron oxidation leads to 3H -pyrroles of type 6 in excellent yields. However, in the case of cyano or ester groups, a further oxidative process immediately led to the new 3H -pyrrolo[3,4- b]quinoxalines 7 via intramolecular ring anellation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Evaluation of a sunscreen photoprotective effect by ascorbic acid assessment in human dermis using microdialysis and gas chromatography mass spectrometryEXPERIMENTAL DERMATOLOGY, Issue 3 2005Nathalie Lévêque Abstract:, Ultraviolet irradiation causes adverse effects like sunburn, photosensitivity reactions or immunologic suppression. The aim of this study was to evaluate the photo-protective outcome of a sunscreen cream (SPF8) by the determination of erythema indexes and the assessment of ascorbic acid and its metabolites in human dermis. These substances were used as markers of oxidative effect. Eight healthy female subjects were enrolled in this study. Two abdominal areas were exposed to solar simulated irradiation with three minimal erythema dose, one with SPF8 application and the other site without SPF8 application. Two other areas were used as control, one without SPF8 application and the other site after SPF8 application. Ascorbic acid and its metabolites (dehydroascorbic acid, threonic acid, oxalic acid and xylose) were collected from human dermis by microdialysis and assessed by gas chromatography mass spectrometry. Irradiated site without sunscreen application had significantly demonstrated lower dermis ascorbic acid concentrations and a higher erythema index than the three other sites (P < 0.05). Threonic acid, oxalic acid and xylose dermis concentrations were significantly higher in site III than in the control site I (P < 0.05). The protected-irradiated site did not show erythema formation and there was stability of ascorbic acid dermis concentrations with non-variation in its metabolites. The assessment of ascorbic acid and its metabolites in human dermis could be an efficient tool to demonstrate the oxidative process and consequently to control the efficiency of sunscreen creams against undesirable UV effects. [source] Reactivity of isobutane in fluorosulfonic based superacids,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 12 2002Alain Goeppert Abstract The behavior of isobutane in DSO3F containing various amounts of SbF5 has been studied in relation to the acid strength of the superacid system. In contrast to the DF,SbF5 system, H/D exchange occurs only in the weakest superacid via deprotonation of the t -butyl ion intermediate formed by an oxidative process. Kinetic isotope effect determination shows that the slow step is hydride transfer. At higher acidity, the increasing stability of this intermediate impedes isotopic exchange. Copyright © 2002 John Wiley & Sons, Ltd. [source] Enantioselective Total Synthesis of Brevetoxin A: Convergent Coupling Strategy and CompletionCHEMISTRY - A EUROPEAN JOURNAL, Issue 36 2009Michael Abstract A highly convergent, enantioselective total synthesis of brevetoxin A is reported. The development of a [X+2+X] Horner,Wadsworth,Emmons/cyclodehydration/reductive etherification convergent coupling strategy allowed a unified approach to the synthesis of two advanced tetracyclic fragments from four cyclic ether subunits. The Horner,Wittig coupling of the two tetracyclic fragments provided substrates that were explored for reductive etherification, the success of which delivered a late-stage tetraol intermediate. The tetraol was converted to the natural product through an expeditious selective oxidative process followed by methylenation. [source] Oxidative stress parameters after combined fluoxetine and acetylsalicylic acid therapy in depressive patientsHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 4 2009Piotr Ga, ecki Abstract Objective There are numerous reports indicating disturbed equilibrium between oxidative processes and antioxidative defense in patients with depression. Moreover, depressive patients are characterized by the presence of elements of an inflammatory process, which is one of the sources of reactive oxygen species (ROS). In view of the above, it was decided to study both the effect of fluoxetine monotherapy and that of fluoxetine co-administered with acetylsalicylic acid on lipid peroxidation and antioxidative defense in patients with the first depressive episode in their life. Method Seventy seven patients with major depressive disorder (MDD), divided into two groups were included in the study. The first group, consisting of 52 patients, received fluoxetine 20 mg, and the second one, in addition to fluoxetine 20 mg, received 150 mg of acetylsalicylic acid. The activity of antioxidative enzymes, copper-zinc superoxide dismutase (CuZnSOD, SOD1), catalase (CAT), glutathione peroxidase (GPSH-x) and the concentration of malonyldialdehyde (MDA) was determined in erythrocytes, whereas the total antioxidant status (TAS) was determined in the plasma. All parameters were measured before and after three month therapy. Results The obtained results indicate a significant decrease in the activity of SOD1, CAT and GSHP-x, as well as in MDA concentration after the combined therapy. Also a significant TAS increase was observed after the combined therapy. The study demonstrated that combined therapy with fluoxetine and ASA is characterized by the same efficacy and clinical safety as fluoxetine monotherapy, resulting additionally in improvement of oxidative stress parameters in the patients treated for depression. Copyright © 2009 John Wiley & Sons, Ltd. [source] Theoretical studies on high-valent manganese porphyrins: Toward a deeper understanding of the energetics, electron distributions, and structural features of the reactive intermediates of enzymatic and synthetic manganese-catalyzed oxidative processesISRAEL JOURNAL OF CHEMISTRY, Issue 1 2000Abhik Ghosh We present here a relatively comprehensive theoretical study, based on nonlocal density functional theory calculations, of the energetics, electron distributions, and structural features of the low-lying electronic states of various high-valent intermediates of manganese porphyrins. Two classes of molecules have been examined: (a) compounds with the general formula [(P)MnX2]0 (P = porphyrin; X = F, Cl, PF6) and (b) high-valent manganese-oxo species. For [(P)Mn(PF6)2]0, the calculations reveal a number of nearly equienergetic quartet and sextet states as the lowest states, consistent with experimental results on a comparable species, [(TMP)Mn(ClO4)2]0 (TMP = tetramesitylporphyrin). In contrast, [(P)MnCl2]0 and [(P)MnF2]0 have a single well-defined S = 3/2 Mn(IV) ground state, again in agreement with experiment, with the three unpaired spins largely concentrated (>90%) on the manganese atom. Manganese(IV)-oxo porphyrins have an S = 3/2 ground state, with the three unpaired spins distributed approximately 2.3:0.7 between the manganese and oxygen atoms. The metal-to-oxygen spin delocalization, as measured by the oxygen spin population, for MnIV = O porphyrins is less than, but still qualitatively similar to, that in analogous iron(IV)-oxo intermediates, indicating that the MnIV = O bond is significantly weaker than the FeIV = O bond in an analogous molecule. Thus, the optimized metal,oxygen bond distances are 1.654 and 1.674 Å for (P)FeIV(O)(Py) and (P)MnIV(O)(Py), respectively (Py = pyridine). This is consistent with the experimental observation that MnIV = O stretching frequencies are over 10% lower than FeIV = O stretching frequencies for analogous compounds. For [(P)Mn(O)(PF6)]0, [(P)Mn(O)(Py)]+, and [(P)Mn(O)(F)]0, the ground states clearly correspond to a (dxy)2 Mn(V) configuration and the short Mn,O distances of 1.541, 1.546, and 1.561 Å for the three compounds, respectively, reflect the formal triple bond character of the Mn,O interaction. Interestingly, the corresponding Mn(IV)-oxo porphyrin cation radical states are calculated to be a few tenths of an electrovolt higher than the Mn(V) ground states, suggesting that the Mn(IV)-oxo porphyrin cation radicals are not likely to exist as ground-state species. [source] Histidine and not tyrosine is required for the Peroxide-induced formation of haem to protein cross-linked myoglobinIUBMB LIFE, Issue 8-9 2007Brandon J. Reeder Abstract Peroxide-induced oxidative modifications of haem proteins such as myoglobin and haemoglobin can lead to the formation of a covalent bond between the haem and globin. These haem to protein cross-linked forms of myoglobin and haemoglobin are cytotoxic and have been identified in pathological conditions in vivo. An understanding of the mechanism of haem to protein cross-link formation could provide important information on the mechanisms of the oxidative processes that lead to pathological complications associated with the formation of these altered myoglobins and haemoglobins. We have re-examined the mechanism of the formation of haem to protein cross-link to test the previously reported hypothesis that the haem forms a covalent bond to the protein via the tyrosine 103 residue (Catalano, C. E., Choe, Y. S., Ortiz de Montellano, P. R., J. Biol. Chem. 1989, 10534 - 10541). Comparison of native horse myoglobin, recombinant sperm whale myoglobin and Tyr103 , Phe sperm whale mutant shows that, contrary to the previously proposed mechanism of haem to protein cross-link formation, the absence of tyrosine 103 has no impact on the formation of haem to protein cross-links. In contrast, we have found that engineered myoglobins that lack the distal histidine residue either cannot generate haem to protein cross-links or show greatly suppressed levels of modified protein. Moreover, addition of a distal histidine to myoglobin from Aplysia limacina, that naturally lacks this histidine, restores the haem protein's capacity to generate haem to protein cross-links. The distal histidine is, therefore, vital for the formation of haem to protein cross-link and we explore this outcome. [source] Review Article: Fragrance technology for the dermatologist , a review and practical applicationJOURNAL OF COSMETIC DERMATOLOGY, Issue 3 2010Claudia S Cortez-Pereira MSc Summary Cosmetic product development has increased in recent years. The value of a product is emphasized in its safety and effectiveness. The stability study in the context of product quality evaluation during shelf life becomes primordial to guarantee the integrity of the physical, chemical, and olfactory properties. In this study, aromatic compositions had been submitted to the stability normal test, at low temperature (4.0 ± 2.0 °C), at room temperature (22.0 ± 2.0 °C), and in oven (45.0 ± 2.0 °C). The compositions were analyzed at 15, 30, 60, and 90 days versus a fresh aromatic composition 48 h after preparation, in which the organoleptic characteristics and pH value were evaluated besides undertaking sensory evaluation. The results demonstrated that at the high temperature (45.0 ± 2.0 °C), in which the oxidative processes of the fragrance components are accelerated, the cosmetic preparation "A" was chosen because it showed more acceptable physical,chemical properties and in terms of sensory evaluation of perfume character and intensity was approved for commercial use. [source] GRAPE SEED PROANTHOCYANIDIN EXTRACT CHELATES IRON AND ATTENUATES THE TOXIC EFFECTS OF 6-HYDROXYDOPAMINE: IMPLICATIONS FOR PARKINSON'S DISEASEJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2010TZU-HUA WU ABSTRACT Proanthocyanidins are potent antioxidants associated with protection against diseases. We tested the reducing capacity, iron chelating activity, and anti-auto-oxidation ability of grape seed proanthocyanidin extract (GSPE). The mechanisms underlying GSPE attenuation of oxidative processes induced by 6-hydroxydopamine (6-OHDA), a neurotoxin used to induce Parkinson's disease, were investigated in cell-based systems. At high concentrations, GSPE (50 µg/µL) was a mild pro-oxidant in a Fenton-type reaction. GSPE (300 µg/mL) was as potent as 30 µM deferoxamine in its iron-chelating capacity, and as efficient as 5 mM ascorbic acid in delaying 6-OHDA auto-oxidation. In PC-12 cell cultures, 100 and 300 µg/mL GSPE significantly protected (P < 0.05) cells from 6-OHDA-induced (400 µM) toxicity. GSPE-induced cytoprotection is enhanced by a nitric oxide synthase inhibitor (NOSI), implying that the cytoprotective effect of GSPE does not require NOS activation. In conclusion, the iron-chelating activity of GSPE minimizes its pro-oxidant activity and delays 6-OHDA auto-oxidation to provide cytoprotection. PRACTICAL APPLICATIONS Parkinson's disease is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons. The recognized pharmacological strategies to prevent or treat Parkinson's disease include the minimization of oxidative stress, iron release and excitotoxicity resulting from excess nitric oxide formation. One of the best ways to delay or prevent the onset of the disease is to improve the biological antioxidant status by providing additional radical scavengers that are not pro-oxidants. The pro-oxidant activity, such as that of the antioxidant ascorbic acid, enhances radical cycling under certain conditions, and therefore may be detrimental. Grape seed proanthocyanidin extracts (GSPEs) are used as a dietary supplement in food products in several countries. Our current report provides evidence that GSPE has limited pro-oxidant activity, presumably because of its iron-chelating abilities, and protects cells from neurotoxic insults. GSPE may be effective as a dietary supplement for prophylactic use against the progressive neurodegeneration seen in Parkinson's disease. [source] Disruption of Maternal Behavior by Alcohol Intoxication in the Lactating Rat: A Behavioral and Metabolic AnalysisALCOHOLISM, Issue 8 2002Marta Yanina Pepino Background Preweanling rats exhibit clear behavioral signs of distress after interacting with an alcohol-intoxicated dam. Interestingly, behavioral reactivity of infants to the experience of alcohol in the nursing context decreases as a function of repeated alcohol administrations to the mother. In this study, maternal activities were examined when dams were exposed to repeated administrations of a subnarcoleptic alcohol dose. Maternal changes in alcohol metabolism were also analyzed as a function of repeated exposures to the drug. Methods During postpartum days 3, 5, 7, 9, 11, and 13, nursing dams received an intragastric administration of either 2.5 g/kg of alcohol or water. Maternal behaviors were evaluated (experiment 1). Blood alcohol levels (BALs) of the dams were determined on postpartum day 16 after all mothers received either an intragastric (experiment 2) or an intraperitoneal (experiment 3) dose of alcohol. The doses used (2.5 g/kg intragastrically and 1.5 g/kg intraperitoneally) were chosen because they promote similar peak BALs in dams naive to alcohol. Results Maternal behaviors were strongly affected by the state of intoxication. Nevertheless, these disruptions clearly subsided with progression of alcohol-related experiences (experiment 1). Chromatographic analysis of alcohol metabolism indicated the development of tolerance in dams that had prior experience with alcohol (experiment 2). Changes in BALs as a function of prior experience with alcohol seemed related to first-pass alcohol metabolism rather than hepatic oxidative processes of the drug (experiments 2 and 3). Conclusions When the dam first experiences a moderate state of alcohol intoxication, maternal behaviors are uniformly disrupted. Subsequent exposures to alcohol lead to maternal metabolic tolerance. In conjunction with previous studies, these data indicate that infantile reactivity to alcohol is dependent on how the members of the dam/pup dyad express or perceive ethanol's postabsorptive effects. [source] Evidence for the involvement of lipoxygenase in the oxidative processes associated with the appearance of green staining alteration in the Gordal oliveJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 14 2003Lourdes Gallardo-Guerrero Abstract Lipoxygenase (LOX) activity and chloroplast pigment content were monitored during fruit growth in Gordal and Manzanilla olive varieties (Olea europaea regalis and Olea europaea pomiformis respectively). At all growth stages, LOX activity was greater in Gordal than in Manzanilla, and in both varieties, enzymatic activity peaks coincided with the maximum presence of oxidised chlorophyll pigments in the fruits. The higher lipid peroxidation potential measured directly in vitro and indirectly in vivo in the Gordal variety and its correspondence with higher contents of oxidised catabolites of chlorophyll suggested a greater tendency and sensitivity of this variety to oxidative processes. This could also explain the high organelle disorganisation levels reached during industrial processing of the fruit, allowing the formation of copper,chlorophyll complexes associated with the green staining alteration that affects Gordal olives. Copyright © 2003 Society of Chemical Industry [source] Oxidative effects in uninfected tissue in leaves of French bean (Phaseolus vulgaris) containing soft rots caused by Botrytis cinereaJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2003Ingo Muckenschnabel Abstract Several markers of oxidative processes have been measured in leaves of Phaseolus vulgaris infected with Botrytis cinerea, with the specific objective of investigating changes induced by this necrotrophic pathogen in tissue remote from the lesion. There was a progressive decrease with time in the contents of ascorbic acid (AA) in apparently healthy tissues from infected plants and non-inoculated plants grown under identical high-humidity conditions (abiotically stressed controls), and for periods >48 h this decrease was greater in the infected plants. This decline in AA content was accompanied by an elevation in the intensity of the electron paramagnetic resonance (EPR) signal from adducts of the spin trap ,-(4-pyridyl-1-oxide)- N - t -butylnitrone (POBN), a destabilisation of the (monodehydro) ascorbate radical (Asc·) signal in the presence of POBN, and an increase in the ratio of Asc· to AA in samples studied in the absence of the spin trap. These results are consistent with a shift in redox status to more oxidising conditions in apparently healthy tissue of infected plants and indicate the prevalence of chemical processes that are distinctly different from those in uninfected plants. However, no differences in lipid peroxidation products or the single-peak free radical and Fe(III) (g = 4.27) EPR signals were observed between these tissues distant from the lesions and those from abiotically stressed controls. In addition, the pathogen-derived sesquiterpene toxin botrydial and a second Mn(II) EPR signal, both of which are associated with Botrytis infection, were not detected in these ,apparently healthy' tissues. Copyright © 2003 Society of Chemical Industry [source] Modifications and oxidation of lipids and proteins in human serum detected by thermochemiluminescenceLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2003Sergei Shnizer Abstract Detection of electronically excited species (EES) in body fluids may constitute an important diagnostic tool in various pathologies. Examples of such products are triplet excited carbonyls (TEC), which can be a source for photon emission in the 400,550,nm range. The aim of the present study was to determine the actual contribution of lipid and protein components (protein carbonyls) to photon emission generated by thermochemiluminescence (TCL) during the heating of biological fluids. In this study, a new TCL Photometer device, designed by Lumitest Ltd, Israel, was used. Samples were heated to a constant temperature of 80,±,0.5°C for 280,s and photon emission was measured at several time points. In order to compare the results of TCL measurements to conventional methods of detecting lipid and protein oxidation, each examined sample was also heated in a waterbath at 80°C for 10,280,s. Lipid and protein oxidation were subsequently measured using conventional methods. The TCL of four polyunsaturated fatty acids (PUFA) with three to six double bonds was measured. The elevation of the PUFA TCL amplitude correlated with the increase in the number of double bonds of PUFA. A correlation between the increase in TCL intensity and protein carbonyl generation in bovine serum albumin (BSA) was also observed. In the venous blood serum, our study showed that an increase of TCL intensity during heating reflected the cleavage of TEC of lipid origin. Our study suggests that biological molecules such as proteins, lipids and other molecules, which may become unstable during heating, are capable of generating EES. We demonstrated that a TCL curve can be used as a kinetic model for measuring oxidative processes, which reflects modifications of different molecules involved in the oxidative stress phenomena. Copyright © 2003 John Wiley & Sons, Ltd. [source] Lactate efflux and the neuroenergetic basis of brain functionNMR IN BIOMEDICINE, Issue 7-8 2001Robert G. Shulman Abstract In the unstimulated brain energy is primarily supplied by the oxidation of glucose. However the oxygen-to-glucose index (OGI), which is the ratio of metabolic rates of oxygen to glucose, CMRO2/CMRglc, diverges from the theoretical value of 6 as activity is increased. In vivo measurements of brain lactate show its concentration to increase with stimulation. The decreasing OGI with stimulation had led to the suggestion that activation, unlike resting activity, is supported by anaerobic glycolysis. To date a unifying concept that accommodates glucose oxidation at rest with lactate generation and OGI decrease during stimulation of brain is lacking. Furthermore, energetics that change with increasing activity are not consistent with a neuroenergetic model that has been proposed from 1- 13C-glucose MRS experiments. That model, based upon in vivo MRS measurements and cellular studies by Pellerin and Magistretti, showed that glutamate neurotransmitter cycling was coupled to glucose oxidation over a wide range of brain activities from rest down to deep anesthesia. Here we reconcile these paradoxical observations by suggesting that anaerobic glucose consumption (which can provide energy rapidly) increases with activation to meet the power requirements of millisecond neuronal firing. It is proposed, in accord with our neuroenergetic model, that the extra glucose mobilized rapidly for glial clearance of glutamate, is not needed for the oxidative processes that are responsible for neuronal firing and glutamate release, and consequently it is effluxed as lactate. A stoichiometric relation between OGI and lactate concentration is derived from the neuroenergetic model, showing that the enhanced glucose uptake during activation is consistent with neuronal activity being energetically supported by glucose oxidation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Vitamin B2 -sensitized Photo-oxidation of DopaminePHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2008Walter A. Massad Kinetics and mechanism of the photo-oxidation of the natural catecholamine-type neurotransmitter dopamine (DA) has been studied in aqueous solution, under aerobic conditions, in the presence of riboflavin (Rf, vitamin B2) as a photosensitizer. Results indicate the formation of a weak dark complex Rf,DA, with a mean apparent association constant Kass = 30 m,1, only detectable at DA concentrations much higher than those employed in photochemical experiments. An intricate mechanism of competitive reactions operates upon photoirradiation. DA quenches excited singlet and triplet states of Rf, with rate constants of 4.2 × 109 and 2.2 × 109 m,1 s,1, respectively. With the catecholamine in a concentration similar to that of dissolved molecular oxygen in air-saturated water, DA and oxygen competitively quench the triplet excited state of Rf, generating superoxide radical anion (O2,,) and singlet molecular oxygen (O2(1,g)) by processes initiated by electron and energy-transfer mechanisms, respectively. Rate constants values of 1.9 × 108 and 6.6 × 106 m,1 s,1 have been obtained for the overall and reactive (chemical) interaction of DA with O2(1,g). The presence of superoxide dismutase increases both the observed rates of aerobic DA photo-oxidation and oxygen uptake, due to its known catalytic scavenging of O2,,, a species that could revert the overall photo-oxidation effect, according to the proposed reaction mechanism. As in most of the catecholamine oxidative processes described in the literature, aminochrome is the DA oxidation product upon visible light irradiation in the presence of Rf. It is generated with a quantum yield of 0.05. [source] Ongoing activation of p53 pathway responses is a long-term consequence of radiation exposure in vivo and associates with altered macrophage activities,THE JOURNAL OF PATHOLOGY, Issue 5 2008PJ Coates Abstract The major adverse consequences of radiation exposure, including the initiation of leukaemia and other malignancies, are generally attributed to effects in the cell nucleus at the time of irradiation. However, genomic damage as a longer term consequence of radiation exposure has more recently been demonstrated due to untargeted radiation effects including delayed chromosomal instability and bystander effects. These processes, mainly studied in vitro, are characterized by un-irradiated cells demonstrating effects as though they themselves had been irradiated and have been associated with altered oxidative processes. To investigate the potential for these untargeted effects of radiation to produce delayed damaging events in vivo, we studied a well-characterized model of radiation-induced acute myeloid leukaemia in CBA/Ca mice. Haemopoietic tissues of irradiated CBA/Ca mice exhibit enhanced levels of p53 stabilization, increased levels of p21waf1, and increased amounts of apoptosis, as expected, in the first few hours post-irradiation, but also at much later times: weeks and months after the initial exposure. Because these responses are seen in cells that were not themselves directly irradiated but are the descendants of irradiated cells, the data are consistent with an initial radiation exposure leading to persistently increased levels of ongoing DNA damage, analogous to radiation-induced chromosomal instability. To investigate the potential source of ongoing oxidative processes, we show increased levels of 3-nitrotyrosine, a marker of damaging nitrogen/oxygen species in macrophages. Not all animals show increased oxidative activity or p53 responses as long-term consequences of irradiation, but increased levels of p53, p21, and apoptosis are directly correlated with increased 3-nitrotyrosine in individual mice post-irradiation. The data implicate persistent activation of inflammatory-type responses in irradiated tissues as a contributory bystander mechanism for causing delayed DNA damage. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Substrate oxidation and retention in pigs and poultryANIMAL SCIENCE JOURNAL, Issue 2 2002André CHWALIBOG ABSTRACT A model combining data from gas exchange measurements with nutrient balances, demonstrating energy transfer between the pools of protein, carbohydrate and fat and their partition in the body, is described. Data from energy metabolism experiments with growing pigs and laying hens is incorporated into the model in order to illustrate methods of calculations and interpretations of the model. The experiments with pigs were carried out with growing pigs (20,100 kg) measured alternately on high (ad libitum) and low (near maintenance) feed levels on diets with low or high fat concentration. When energy intake from digested carbohydrate covered the requirements for growth, heat from oxidation of carbohydrate contributed 85,90% to the total heat production, while there was no net oxidation of fat. When the intake of digested carbohydrate was not sufficient to cover requirements, fat was mobilized from the body and oxidized. Energy from oxidation of carbohydrate was in all measurements below the energy in the carbohydrate pool, indicating transfer of energy from carbohydrate to fat metabolism in the process of de novo lipogeneis. The experiments with hens were carried out with 62 hens during the laying period from 26 to 47 weeks of age. The hens originated from two strains (A and B); they were kept in battery cages either individually or 3 hens/cage and fed ad libitum with an identical commercial diet. The partition of the protein pool between oxidation and retention was not influenced by the housing system. However, the genetic origin of hens effected protein utilization with relatively lower oxidation and higher retention in Strain B. The main part of the carbohydrate pool was oxidized (45,60%), but the hens kept individually oxidized more carbohydrate than those kept 3 hens/cage. Further, there were significant differences between the strains. Generally, about half of the fat pool originated from de novo lipogenesis from carbohydrate, indicating the importance of this process for fat retention in eggs. Fat oxidation depended on the energy supply from carbohydrate, hence with higher use of carbohydrate for oxidation in Strain B less fat was oxidized and more was used for fat synthesis. The presented results indicate that by combining results from gas exchange measurements with nitrogen and energy balances it is possible to evaluate the contribution of nutrients to the oxidative processes and the energy transfer between substrate pools. [source] Peroxynitrite and nitrosoperoxycarbonate, a tightly connected oxidizing-nitrating couple in the reactive nitrogen-oxygen species family: new perspectives for protection from radical-promoted injury by flavonoidsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2007Radmila Pavlovic Peroxynitrite is the product of the reaction of nitric oxide with superoxide radical and is implicated in the pathogenesis of a wide variety of human diseases, being responsible for in-vivo oxidation/nitration events. Nitrosoperoxycarbonate anion, formed by the interaction of peroxynitrite with CO2/bicarbonate at physiological concentrations, provides a new interpretation of oxidative/nitrative processes formerly attributed to peroxynitrite. The aim of this review is to summarize the chemistry and biology of peroxynitrite and radical species related to nitrosoperoxycarbonate anion, as well as the information available regarding the molecular mechanisms that determine and regulate radical-promoted injury by the two tightly connected species at physiological concentrations. Interception of carbonate and nitro radicals produced by interaction of peroxynitrite with CO2/bicarbonate, as in-vivo prevention of pathological events, creates new perspectives for the evaluation of safe scavengers of oxidative/nitrative stress at the physiological level. In this respect, natural products such as flavonoids hold a preeminent position among the vast array of compounds endowed with such properties. [source] | ||||||||||||||||||||||||||||