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E G Janzen

Publications and source records attributed to E G Janzen.

At least 19 recordsLinked to original sources
PubMed1992

Spin trapping of free radical metabolites of carbon tetrachloride in vitro and in vivo: effect of acute ethanol administration.

A single dose of ethanol, when administered 18 hr prior to CCl4, potentiates the hepatotoxicity of the halocarbon. In these studies, spin trapping and electron spin resonance (ESR) spectroscopy methods were utilized to determine whether a single ethanol dose increased the metabolism of CCl4 to free radical intermediates. When hepatic microsomes from ethanol-treated or control rats were incubated with CCl4 and the spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN), the ESR signal of the trichloromethyl radical adduct of PBN was of similar intensity in both groups. The ethanol dose also failed to induce p-nitrophenol hydroxylase activity. When PBN and CCl4 were administered to rats, liver extracts contained ESR signals resulting primarily from the trichloromethyl radical adduct of PBN, and the signals were of similar intensity in both experimental groups. Higher concentrations of the carbon dioxide anion radical adduct of PBN were detected in plasma samples from ethanol-treated rats. However, when hepatocytes from ethanol-treated and control rats were incubated with PBN and CCl4, ESR signals of the carbon dioxide adduct were of similar intensity. These data suggest that the higher concentrations of the carbon dioxide adduct in the blood of ethanol-treated rats may be explained by early CCl4-induced damage to liver cell membranes, rather than increased rates of formation. The data in this report fail to support the hypothesis that a single dose of ethanol stimulates the hepatic metabolism of CCl4 to the trichloromethyl radical. Alternatively, ethanol may potentiate CCl4 toxicity by affecting some critical metabolic step subsequent to trichloromethyl radical formation.

Animals↗
PubMed1992

Use of 1H/23Na and 1H/31P double frequency tuned birdcage coils to study in vivo carbon tetrachloride-induced hepatotoxicity in rats.

In vivo 1H and 23Na magnetic resonance imaging (MRI) and 31P magnetic resonance spectroscopy (MRS) techniques were used to study CCl4-induced acute hepatotoxicity in rats in situ. One or two hours following exposure to CCl4, a localized edematous region was detected in the liver by 1H MRI. The CCl4-induced edema was localized in a region surrounding the hepatic portal vein. With the use of a 23Na/1H double frequency tuned bird-cage imaging coil an increase in Na+ ion flux was also observed in the same region as the edematous region detected by 1H-MRI. Pretreatment with alpha-phenyl-tert-butyl nitrone (PBN), a free radical spin trap, 30 min prior to CCl4 exposure, was found to reduce the CCl4-induced edematous response in the liver observed in either 1H or 23Na-NMR images. Inhibition of the CCl4-induced edematous response in rat liver by PBN demonstrates that free radical intermediates, arising from the metabolism of CCl4, are possibly the key causal agents in the initiation of the edematous response. In addition, with the use of a 31P/1H double frequency tuned bird-cage imaging/spectroscopy coil, localized 31P spectra (ISIS) were obtained from the regions of CCl4-induced "tissue damage" observed in the 1H-MRI images. The most notable changes observed from the 31P spectra were an increase in inorganic phosphate (Pi) and a decrease in hepatocytosolic pH in the CCl4-treated rat livers in comparison to saline-treated control livers.

Animals↗
PubMed1992

Stabilities of hydroxyl radical spin adducts of PBN-type spin traps.

The stability of the hydroxyl spin adduct of nine different PBN-type spin traps has been examined in phosphate buffer solutions of various pH. The hydroxyl adduct is produced by short illumination of hydrogen peroxide with UV light in the presence of spin trap and the decay of its EPR signal followed. The stability measured by the half life of the first-order decay is strongly dependent on the pH of the solution and the structure of the aromatic ring used in the trap. All hydroxyl adducts are more stable in acidic media. tert-Butyl hydroaminoxyl is detected as a degradation product of the hydroxyl adduct from all spin traps.

Cyclic N-Oxides↗
PubMed1992

Research note: an assessment of egg yolk structure using magnetic resonance imaging.

The purpose of the present experiment was to examine the inner structure of the egg using magnetic resonance imaging (MRI). Proton images of fertile and infertile eggs and eggs from hens fed a corn-based or a flax-based diet were generated using a Spectroscopy Imaging Systems unit. Phantom eggs, made from homogenized albumen and homogenized yolk in a plastic shell, were imaged as controls. Eggs were imaged individually on their side, in the sagittal plane. A single image was generated through the center of the yolk. Images clearly distinguished the eggshell, air space, albumen, and yolk. Within the yolk of both fertile and infertile eggs, the latebra, the neck of the latebra, and four to six pairs of concentric yolk rings were visible, although the rings were less clearly defined in eggs from hens fed the flax-based diet. The embryo was not visible after 24 h of incubation but yolk stratification could still be resolved. Rings were not evident in the phantom eggs. It was concluded that MRI can be used successfully in assessing the microanatomy of eggs.

Animal Feed↗
PubMed1991

Enhancement of carbon tetrachloride-induced liver injury by a single dose of ethanol: proton magnetic resonance imaging (MRI) studies in vivo.

Magnetic resonance imaging (MRI) and localized magnetic resonance spectroscopy (MRS) were used to study the effects of a single dose of ethanol, given 18 h prior to experiments, on CC14-induced acute hepatotoxicity in rats in situ. Localized edema in the centrilobular region of the liver, following exposure to ethanol and CCl4, was detected by 1H-MRI techniques. The edema was characterized by a volume selective spectroscopy (VOSY) method, which measured an increase in water concentration from ethanol and CCl4-treated rat livers, in comparison to control livers. Electron microscopy (EM) of the high intensity regions of the ethanol/CCl4 treated liver sections revealed dramatic subcellular changes such as fragmentation of the granular endoplasmic reticulum (ER), formation of large vacuoles and lipid droplets in the cytoplasmic matrix and extensive swelling of the mitochondria as well as disruption of the cristae. Pretreatment with alpha-phenyl tert-butyl nitrone (PBN), a free radical spin trap, prior to halocarbon exposure, was found to reduce the CC14-mediated high intensity region in the liver images. Electron microscopy of the PBN pretreated CCl4 exposed rat liver sections revealed only minor observable differences in subcellular organization, such as some swelling of the mitochondria, when compared to controls. In addition, these data suggest that ethanol may potentiate CCl4 hepatotoxicity by increased formation of free radical intermediates. Inhibition of the CCl4-induced edematous response in rat liver by PBN demonstrates that free radical intermediates, arising from the metabolism of CCl4, are possibly the causal factor in the initiation of the edema.

Animals↗
PubMed1991

Detection of spin adducts in blood after administration of carbon tetrachloride to rats.

Rats were treated with CCl4 and the spin trapping agent alpha-phenyl-N-t-butyl nitrone (PBN), followed by ESR investigations on samples of heparinized blood. The major signal detected was the ascorbate semidione radical, but smaller concentrations of the carbon dioxide radical anion spin adduct of PBN could also be detected. The ESR signals were more intense when experiments were conducted with plasma, rather than blood. The spin adducts detected were not associated with the red blood cells, and their apparent concentrations increased when the cells were removed by centrifugation. The addition of ascorbate oxidase to the samples markedly diminished the intensity of the ascorbate semidione radical. When plasma samples from CCl4-treated rats were extracted into toluene, the ESR spectrum of the trichloromethyl adduct of PBN was observed in the extract. Because the spectrum of this adduct was not observed in direct ESR studies of plasma, it is possible that immobilization occurred in the presence of plasma proteins. Evidence to support this hypothesis was developed by adding bovine serum albumin (BSA) to an aqueous solution of the trichloromethyl radical adduct of PBN. As the BSA concentration was increased, the intensity of the ESR spectrum was markedly diminished, and displayed features of an immobilized adduct.

Animals↗
PubMed1991

In vivo proton magnetic resonance imaging and localized spectroscopic analysis of polycystic kidney disease in DBA/2FG-pyc mice.

Proton magnetic resonance imaging (MRI) and localized spectroscopy techniques were used to study polycystic kidney disease (PKD) in DBA/2FG-pcy (pcy) mice, which are an animal model for the adult form of human PKD. A volume selective spectroscopy (VOSY) method was used to obtain localized proton spectra as well as apparent T1 and T2 relaxation times of the kidneys of either pcy or DBA/2FG normal (DBA) mice. Localization of the proton spectra was based on spatial coordinates determined from the proton images. Increases in apparent kidney T1 and T2 relaxation times were observed for pcy mice in comparison to those measured in DBA mice. Localized kidney T1 values from pcy mice were found to range from 799 to 1395 msec whereas DBA mice kidney T1 values were 617 to 774 msec. Localized T2 values measured from pcy mice kidneys ranged from 90 to 172 msec in comparison to kidney T2 values of 50 to 72 msec for DBA mice. The onset of cyst formation in the kidneys of pcy mice as a function of age was also studied. As early as 4 to 5 weeks of age it was possible to detect in vivo changes in pcy mice kidney T1 and T2 values.

Age Factors↗
PubMed1991

Spin-trapping studies of hepatic free radicals formed following the acute administration of ethanol to rats: in vivo detection of 1-hydroxyethyl radicals with PBN.

The generation of free radicals in rat liver following the acute oral administration of ethanol was studied with the spin-trapping method, using a deuterated derivative of phenyl-N-tert-butylnitrone (PBN-d14) as the spin-trapping agent. After administration of ethanol and PBN-d14 to rats, organic extracts of the liver were prepared and subjected to ESR spectroscopy. In the case of ethanol-treated rats, the ESR spectra indicated that mixtures of radicals had been trapped, while spectra from control rats were essentially negative. The predominant spin adduct detected after ethanol treatment is proposed to be from a carbon-centered, primary alkyl radical, based on gamma-hydrogen hyperfine splitting patterns observed with PBN-d14. Oxygen-centered radicals also contributed to the ESR spectra. Liver extracts also contained low concentrations of the 1-hydroxyethyl radical spin adduct, which was indicated by weak spectral lines corresponding to those of the 1-13C-ethanol adduct. These data confirm previous suggestions that ethanol is metabolized to a free radical metabolite in rat liver. In addition, some information on types of lipid radicals generated during alcohol intoxication has been obtained.

Alcoholic Intoxication↗
PubMed1991

The role of mixed function oxidase (MFO) in the metabolism of the spin trapping agent alpha-phenyl-N-tert-butyl-nitrone (PBN) in rats.

It has been previously demonstrated that alpha-phenyl-N-tert-butyl-nitrone (PBN), one of the most widely used free radical trapping agents, is rapidly absorbed, evenly distributed among a wide range of tissues, and metabolized to form one metabolite. The objective of this study was to determine if the distribution and metabolism of PBN can be affected by inducers or inhibitors of the microsomal mixed function oxidase (MFO) system. Rats were pretreated with MFO inducers (phenobarbital and 3-methylcholanthrene) or MFO inhibitors (metyrapone and piperonyl butoxide) before 14C-PBN was injected (i.p.) The concentrations of 14C-PBN and its metabolite were measured in plasma, urine, liver, lung and kidney 2 hours after injection. The results indicated that when MFO was induced, the concentration of 14C-PBN metabolite was significantly reduced in all tissues measured. The maximum concentration of PBN parent compound in the tissues where MFO was induced was 50% of that found in saline controls. Manipulation of tissue MFO levels with inducers and inhibitors altered the ratio of 14C-PBN parent compound to the PBN-metabolite. When 14C-PBN was incubated with rat liver microsomes at 37 degrees C in the presence of NADPH, the rate of metabolism was 1,752 dpm of 14C-PBN-metabolite formed/nmole P-450/min. Inactivation of MFO by heat (80 degrees C for 1 min) or deletion of NADPH diminished the formation of PBN metabolite in vitro. It is concluded that the MFO system may be responsible for the metabolism of PBN. Tissue concentrations of PBN can be affected by drugs or toxins which are inducers or inhibitors of MFO.

Animals↗
PubMed1991

Catechol oxidation by peroxidase-positive astrocytes in primary culture: an electron spin resonance study.

In rodents, chronic estrogenization has been shown to induce degeneration of dendrites and myelin figures in the hypothalamic arcuate nucleus adjacent to peroxidase-positive astrocyte processes. Because in this brain region estradiol is metabolized to 2-hydroxyestradiol (catecholestrogen), we hypothesized that the latter may be oxidized by the astrocytic peroxidase activity to cytotoxic ortho-semiquinones as occurs in peripheral tissues. Cysteamine induces nonenzymatic peroxidase activity in cultured astroglia identical to that observed in vivo. Using electron spin resonance, we demonstrate robust peroxidase-catalyzed oxidation of 2-hydroxyestradiol and dopamine by cysteamine-pretreated astrocyte cultures relative to untreated controls. These results implicate the peroxidase-positive astrocytes in the pathogenesis of estradiol-related hypothalamic damage, parkinsonism, and other free-radical-related neurologic disorders.

3,3'-Diaminobenzidine↗
PubMed1990

Spin trapping and associated vocabulary.

Spin trapping as a technique for detecting free radicals in biological systems is developing rapidly. Two conferences have focused on this method and this paper introduces the contributions resulting from the second meeting held in the Ontario Veterinary College of the University of Guelph on July 2-7, 1989. On the preceding pages can be found a poem on free radicals in biology and medicine, and the names of the sponsors and financial supporters. I am very grateful to Dr. Jim Bolton for his helpful efforts with the manuscripts.

Cyclic N-Oxides↗
PubMed1990

Excretion, metabolism and tissue distribution of a spin trapping agent, alpha-phenyl-N-tert-butyl-nitrone (PBN) in rats.

The objective of this study is using radiolabelled PBN to determine the tissue distribution, excretion, and metabolism of PBN in rats in order to evaluate the effective time to trap free radical in appropriate tissue(s). Our results demonstrated that PBN is rapidly absorbed when it is injected intraperitoneally in the animal. PBN can be used as an effective spin trapping agent for a variety of tissues since it is evenly distributed among a wide range of tissues measured. Since there is no difference in the tissue concentrations and distribution pattern of PBN at 15, 30 and 60 min after injection of PBN, it is appropriate to choose any of these time intervals to terminate the experiment and extract the spin adduct. The excretion of PBN, however, is slow. The majority of the radioactivity (70%) was excreted by the first 3 days. Only 5.7% of radioactivity was collected from 3 to 14 days. The remaining 25% of the radioactivity may be in the form of expired 14CO2. Trace amounts of radioactivity were recovered in the feces. PBN has probably only one major form of metabolite excreted in the urine. A small amount of the parent compound, however, was also excreted in the urine. The chemical structure of the metabolite(s) is still unknown.

Animals↗
PubMed1990

The effect of phenyl tert-butyl nitrone (PBN) on CCl4-induced rat liver injury detected by proton magnetic resonance imaging (MRI) in vivo and electron microscopy (EM).

Acute intoxication by CCl4 induces morphological changes in rat liver which are readily detectable by 1H-NMR imaging techniques in situ. Two to four hours after the administration of CCl4, regions of high proton signal intensity are observed in the centrilobular region of the liver. The regions of high signal intensity are attributed to the formation of local edema as a result of CCl4-induced damage. Electron microscopy of the high intensity regions of CCl4 treated liver sections revealed characteristic subcellular changes which include the disapperance of ribosomes from the rough endoplasmic reticulum (RER), the fragmented appearance of the smooth endoplasmic reticulum (SER), formation of vacuoles in the cisternae and swelling of the mitochondria. Pretreatment of rats with alpha-phenyl-tert-butyl nitrone (PBN), a free radical spin trap, prior to halocarbon exposure, was found to reduce the halocarbon-induced edema in the liver. Electron microscopy of the PBN pretreated CCl4 exposed rat liver sections revealed no observable changes in subcellular organization when compared to controls.

Animals↗
PubMed1990

Structure identification of free radicals by ESR and GC/MS of PBN spin adducts from the in vitro and in vivo rat liver metabolism of halothane.

Free radicals were detected from the in vitro metabolism of halothane (rat liver microsomes) by the PBN spin trapping method. The detected radical species include the 1-chloro-2,2,2-trifluoro-1-ethyl radical (I), as determined by mass spectral analysis, and lipid-type radicals assigned by high resolution ESR spectroscopy with the use of d14-deuterated PBN. The lipid-derived radicals are a carbon-centred radical with the partially assigned structure CH2R and an oxygen-centred radical of the OR' type. From the mass spectral analysis of the spin adduct mixture there is also evidence for a halocarbon double adduct of PBN of the type I-PBN-I.

Animals↗
PubMed1990

Mass spectroscopy and chromatography of the trichloromethyl radical adduct of phenyl tert-butyl nitrone.

Positive structural identification of the PBN-trichloromethyl spin adduct in vitro was accomplished with the use of high pressure liquid chromatography and/or gas chromatography coupled with mass spectrometry. Both thin layer and liquid chromatography were used to separate a complex mixture of compounds from rat liver extracts treated with CCl4 in vitro and in vivo. Deuterated PBN's (PBN-d9; tert-butyl deuteration, or PBN-d14; both phenyl and tert-butyl deuteration) were also used to aid in the mass spectral analysis of spin adducts from liver extracts of CCl4 exposed rat livers, since the tert-butyl group fragment ion. C4D9+ (m/z = 66) is always present for PBN and PBN spin adducts. In addition, the masses of the ion peaks increase by the amount of deuteration, i.e. an increase of 9 for PBN-d9 or PBN-d14 in comparison to normally synthesized PBN.

Animals↗
PubMed1990

Investigations of the horse conceptus via magnetic resonance imaging (MRI) and nitroxide spin labels as contrast agents.

Results are presented which illustrate the usefulness of Magnetic Resonance Imaging as applied to the study of living embryos. Nitroxide spin labels were employed as contrast agents to study the structure and properties of the embryos. These spin labels offer the additional advantage that they may potentially be bound to biologically important molecules thereby imparting the ability to produce contrast in the MR images to these new molecules. The horse conceptus was chosen over other embryos due to its large size. Whereas the embryos of cattle and swine are sub-millimetre in size, the horse conceptus is on the order of 10 millimetres in diameter. The availability of microscopic imaging gradient coils will allow the techniques developed in this study to be applied to the smaller embryos of other species.

Animals↗
PubMed1990

Alpha-2,6-difluorophenyl-N-tert-butylnitrone: a spin trap for distinguishing different types of alkyl radicals based on long-range fluorine hyperfine splitting.

alpha-2,6-Difluorophenyl-N-tert-butylnitrone (F2PBN) was synthesized and evaluated. A number of alkyl adducts of F2PBN were studied by ESR/ENDOR. An additional hyperfine splitting (a triplet of doublets of doublets) is reported. The existence of two (one large, one small) F-hfsc's from the ortho-fluorine atoms in the phenyl ring of most alkyl adducts was confirmed by ENDOR spectroscopy.

Chemical Phenomena↗