AIM:Тo examine the effects of nitroglycerine on portal vein haemodynamics and oxidative stress in patients with portal hypertension.METHODS:Thirty healthy controls and 39 patients with clinically verified portal hype...AIM:Тo examine the effects of nitroglycerine on portal vein haemodynamics and oxidative stress in patients with portal hypertension.METHODS:Thirty healthy controls and 39 patients with clinically verified portal hypertension and increasedvascular resistance participated in the study.Liver di-ameters,portal diameters and portal flow velocities were recorded using color flow imaging/pulsed Doppler detection.Cross-section area,portal flow and index of vascular resistance were calculated.In collected blood samples,superoxide anion radical (O 2-),hydrogen per-oxide (H 2 O 2),index of lipid peroxidation (measured as TBARS) and nitric oxide (NO) as a marker of endothelial response (measured as nitrite-NO 2-) were determined.Time-dependent analysis was performed at basal state and in 10th and 15th min after nitroglycerine (sublingual 0.5 mg) administration.RESULTS:Oxidative stress parameters changed sig-nificantly during the study.H 2 O 2 decreased at the end of study,probably via O 2-mediated disassembling in Haber Weiss and Fenton reaction;O 2-increased signifi-cantly probably due to increased diameter and tension and decreased shear rate level.Consequently O 2-and H 2 O 2 degradation products,like hydroxyl radical,initi-ated lipid peroxidation.Increased blood flow was to some extent lower in patients than in controls due to double paradoxes,flow velocity decreased,shear rate decreased significantly indicating non Newtonian char-acteristics of portal blood flow.CONCLUSION:This pilot study could be a starting point for further investigation and possible implemen-tation of some antioxidants in the treatment of portal hypertension.展开更多
Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mecha...Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.展开更多
S 3 1 is a simplified synthetic analogue of the active principle of Salvia miltiorrhioza. Electron spin resonance spectrometry using 5,5′ dimethyl 1 pyrroline N oxide as a scavenger of f...S 3 1 is a simplified synthetic analogue of the active principle of Salvia miltiorrhioza. Electron spin resonance spectrometry using 5,5′ dimethyl 1 pyrroline N oxide as a scavenger of free radicals indicated that 200 μg/ml of S 3 1 scavenged 1,1 diphenyl 2 picrylhydrazyl radicals completely. 25μg/ml of this compound quenched 100% of superoxide anion and a concentration of 250 μg/ml of S 3 1 quenched 63% of hydroxyl radicals. It was also shown that 3 56 mg/ml of S 3 1 could inhibit lipid peroxidation in microsome fraction from rat liver induced by FeSO 4 and cysteine. These results show that S 3 1 is an effective antioxidant by scavenging free radicals.展开更多
29Si-NMR and 1H-NMR were used to follow up the basic hydrolysis of tetraethyl orthosilicate （TOES） and the results showed that species of monomer, dimer, trimer, cyclic and polymer silicates were formed. The monomer...29Si-NMR and 1H-NMR were used to follow up the basic hydrolysis of tetraethyl orthosilicate （TOES） and the results showed that species of monomer, dimer, trimer, cyclic and polymer silicates were formed. The monomer and dimer were favorable for the high activity of zeolite. XRD, 13C CP/MAS and 29Si NMR were used to trace the crystallization process of hollow titanium silicalite zeolites （HTS）. The results showed that the induction period of HTS was 80 min, and subsequently it took next 10 min to form HTS and the remaining time of the crystallization period might function for cleaning up the pores and/or washing off the impurities from the HTS zeolite. The catalytic oxidation performance of HTS zeolite is different from that of the acid activity of zeolite in which the conventional definition of crystallinity does not reflect the catalytic oxidation activity proportionally. The synthesized HTS samples were character- ized by XRD, FT-IR, UV-Vis and Raman spectra. It was confirmed that Ti was incorporated into the zeolite framework. The synthesized HTS samples revealed good repeatability and high activity for oxidation of phenol into diphenol.展开更多
Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In...Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In this study, the authors used an ESR spin-trapping method to study the oxidation of triacylglycerols （TAG） containing different fatty acids （FAs） commonly found in food. The ESR adduct signals were analyzed to study the effect of double bonds and the chain length of the FAs of TAG on oxidation. Oxidation was conducted by applying UV irradiation to TAG by dissolving it in N-tert-buthyl〈t-phenylnitrone （PBN）, which trapped the radicals induced in the TAG as an ESR adduct signal. The detection was clearly successful. There were no differences in the spectra of tristearin （18：0） and tripalmitin （16：0）; thus, it can be concluded that the length of the carbon chain of the FAs of TAG does not affect the oxidation reactions. However, the ESR spectra of tristearin （18：0）, triolein （18：1） and trilinolein （18：3） were clearly different due to the presence/absence of a new peak corresponding to new induced radicals, leading to the conclusion that double bonds play a major role in the oxidation reactions of fats and oils.展开更多
基金Supported by The Grant from the Ministry of Science and Technical Development of the Republic of Serbia,No.175043
文摘AIM:Тo examine the effects of nitroglycerine on portal vein haemodynamics and oxidative stress in patients with portal hypertension.METHODS:Thirty healthy controls and 39 patients with clinically verified portal hypertension and increasedvascular resistance participated in the study.Liver di-ameters,portal diameters and portal flow velocities were recorded using color flow imaging/pulsed Doppler detection.Cross-section area,portal flow and index of vascular resistance were calculated.In collected blood samples,superoxide anion radical (O 2-),hydrogen per-oxide (H 2 O 2),index of lipid peroxidation (measured as TBARS) and nitric oxide (NO) as a marker of endothelial response (measured as nitrite-NO 2-) were determined.Time-dependent analysis was performed at basal state and in 10th and 15th min after nitroglycerine (sublingual 0.5 mg) administration.RESULTS:Oxidative stress parameters changed sig-nificantly during the study.H 2 O 2 decreased at the end of study,probably via O 2-mediated disassembling in Haber Weiss and Fenton reaction;O 2-increased signifi-cantly probably due to increased diameter and tension and decreased shear rate level.Consequently O 2-and H 2 O 2 degradation products,like hydroxyl radical,initi-ated lipid peroxidation.Increased blood flow was to some extent lower in patients than in controls due to double paradoxes,flow velocity decreased,shear rate decreased significantly indicating non Newtonian char-acteristics of portal blood flow.CONCLUSION:This pilot study could be a starting point for further investigation and possible implemen-tation of some antioxidants in the treatment of portal hypertension.
文摘Hexagonal boron nitride(h-BN)is a highly selective catalyst for oxidative dehydrogenation of light alkanes to produce the corresponding alkenes.Despite intense recent research effort,many aspects of the reaction mechanism,such as the observed supra-linear reaction order of alkanes,remain unresolved.In this work,we show that the introduction of a low concentration of propane in the feed of ethane oxidative dehydrogenation is able to enhance the C_(2)H_(6) conversion by 47%,indicating a shared reaction intermediate in the activation of ethane and propane.The higher activity of propane makes it the dominant radical generator in the oxidative co-dehydrogenation of ethane and propane(ODEP).This unique feature of the ODEP renders propane an effective probe molecule to deconvolute the two roles of alkanes in the dehydrogenation chemistry,i.e.,radical generator and substrate.Kinetic studies indicate that both the radical generation and the dehydrogenation pathways exhibit a first order kinetics toward the alkane partial pressure,leading to the observed second order kinetics of the overall oxidative dehydrogenation rate.With the steady-state approximation,a radical chain reaction mechanism capable of rationalizing observed reaction behaviors is proposed based on these insights.This work demonstrates the potential of ODEP as a strategy of both activating light alkanes in oxidative dehydrogenation on BN and mechanistic investigations.
文摘S 3 1 is a simplified synthetic analogue of the active principle of Salvia miltiorrhioza. Electron spin resonance spectrometry using 5,5′ dimethyl 1 pyrroline N oxide as a scavenger of free radicals indicated that 200 μg/ml of S 3 1 scavenged 1,1 diphenyl 2 picrylhydrazyl radicals completely. 25μg/ml of this compound quenched 100% of superoxide anion and a concentration of 250 μg/ml of S 3 1 quenched 63% of hydroxyl radicals. It was also shown that 3 56 mg/ml of S 3 1 could inhibit lipid peroxidation in microsome fraction from rat liver induced by FeSO 4 and cysteine. These results show that S 3 1 is an effective antioxidant by scavenging free radicals.
基金Project supported by the National Science Foundation of China(2006CB202508)
文摘29Si-NMR and 1H-NMR were used to follow up the basic hydrolysis of tetraethyl orthosilicate （TOES） and the results showed that species of monomer, dimer, trimer, cyclic and polymer silicates were formed. The monomer and dimer were favorable for the high activity of zeolite. XRD, 13C CP/MAS and 29Si NMR were used to trace the crystallization process of hollow titanium silicalite zeolites （HTS）. The results showed that the induction period of HTS was 80 min, and subsequently it took next 10 min to form HTS and the remaining time of the crystallization period might function for cleaning up the pores and/or washing off the impurities from the HTS zeolite. The catalytic oxidation performance of HTS zeolite is different from that of the acid activity of zeolite in which the conventional definition of crystallinity does not reflect the catalytic oxidation activity proportionally. The synthesized HTS samples were character- ized by XRD, FT-IR, UV-Vis and Raman spectra. It was confirmed that Ti was incorporated into the zeolite framework. The synthesized HTS samples revealed good repeatability and high activity for oxidation of phenol into diphenol.
文摘Oxidation of fats and oils during storage causes their degradation and loss of nutritional value and appearance. Electron spin resonance （ESR） is the only method that can be used to directly observe the radicals. In this study, the authors used an ESR spin-trapping method to study the oxidation of triacylglycerols （TAG） containing different fatty acids （FAs） commonly found in food. The ESR adduct signals were analyzed to study the effect of double bonds and the chain length of the FAs of TAG on oxidation. Oxidation was conducted by applying UV irradiation to TAG by dissolving it in N-tert-buthyl〈t-phenylnitrone （PBN）, which trapped the radicals induced in the TAG as an ESR adduct signal. The detection was clearly successful. There were no differences in the spectra of tristearin （18：0） and tripalmitin （16：0）; thus, it can be concluded that the length of the carbon chain of the FAs of TAG does not affect the oxidation reactions. However, the ESR spectra of tristearin （18：0）, triolein （18：1） and trilinolein （18：3） were clearly different due to the presence/absence of a new peak corresponding to new induced radicals, leading to the conclusion that double bonds play a major role in the oxidation reactions of fats and oils.
