A functional approach to uncover the low-temperature adaptation strategies of the archaeon Methanosarcina barkeri.

Low-temperature anaerobic digestion (LTAD) technology is underpinned by a diverse microbial community. The methanogenic archaea represent a key functional group in these consortia, undertaking CO2 reduction as well as acetate and methylated C1 metabolism with subsequent biogas (40 to 60% CH4 and 30 to 50% CO2) formation. However, the cold adaptation strategies, which allow methanogens to function efficiently in LTAD, remain unclear.

Prevention of DMBA-induced rat mammary carcinomas comparing leuprolide, oophorectomy, and tamoxifen.

Leuprolide, a gonadotropin releasing hormone agonist, is currently being evaluated in a pilot study of premenopausal women for the prevention of breast cancer. However, little data is available regarding the efficacy of leuprolide in experimental animal models of carcinoma when administered prior to the carcinogen. In the present study the capacity of leuprolide to prevent tumor development was evaluated by comparing its pretreatment effects in the DMBA-induced rat mammary carcinoma model to pretreatment with tamoxifen and oophorectomy.

Mechanisms for metabolism of ethanol to 1-hydroxyethyl radicals in rat liver microsomes.

Experiments have been designed to reevaluate mechanisms for metabolism of ethanol to 1-hydroxyethyl radicals (HER) in rat liver microsomes. The variables tested include addition of azide, catalase, superoxide dismutase, and deferoxamine, or use of phosphate or Tris buffers. The results indicate that several mechanisms of HER formation are possible, depending on the experimental conditions used to study this process.

Free radical formation in livers of rats treated acutely and chronically with alcohol.

The spin trapping method was used to assess formation of free radical intermediates in vivo before and after acute alcohol administration to rats. Ascorbyl radicals and spin adducts of dietary alcohol or endogenous compounds, such as lipids, were detected with higher frequency in bile from alcohol-fed rats than in corresponding samples from rats fed control diets. When alcohol was given acutely to these animals, the 1-hydroxyethyl radical metabolite of ethanol was also formed at higher rates in livers of rats that had been fed ethanol chronically.

Spin trapping studies of alcohol-initiated radicals in rat liver: influence of dietary fat.

We conducted spin trapping experiments to test the effects of acute and chronic alcohol consumption in livers from rats that had been fed either high fat (35% of energy) or low fat (12% of energy) liquid diets. Rats were anesthetized with isoflurane, the spin trapping agent POBN [alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone] was administered by intravenous injection, and bile samples were collected for electron paramagnetic resonance (EPR) analyses. Two different types of EPR spectra were observed in bile from the animals in these studies.

The structure of free radical metabolites detected by EPR spin trapping and mass spectroscopy from halocarbons in rat liver microsomes.

Electron impact (EI) tandem mass spectrometry (MS/MS) combined with EPR spin trapping was used to detect and identify the free radical metabolites of various halocarbons in rat liver microsomal dispersions. EPR spectra of the spin adducts of radical metabolites derived from fluorine-containing halocarbons display fluorine hyperfine splitting, which can be used as proof for the identification of this kind of halocarbon-derived free radical spin adduct. For halocarbons without fluorine atoms, MS/MS was found to be a very useful and simple method for the detection and identification of the structures of halocarbon-derived spin adducts from radical metabolites.

Degradation of DMPO adducts from hydroxyl and 1-hydroxyethyl radicals by rat liver microsomes.

Hydroxyl and 1-hydroxyethyl radical adducts of 5,5-dimethylpyrroline N-oxide (DMPO) were prepared by photolysis, and mechanisms for loss of their EPR signals in rat liver microsomal suspensions were evaluated. Rates of NADPH-dependent EPR signal loss were more rapid in phosphate buffer than in Tris buffer. Addition of superoxide dismutase (SOD) partially protected the adducts when Tris was used as a buffer, but was relatively ineffective in the presence of phosphate.

In vivo spin trapping of nitric oxide generated in the small intestine, liver, and kidney during the development of endotoxemia: a time-course study.

Spin trapping of nitric oxide (NO.) in vivo in liver, small intestine, kidney, and plasma of intact rats was accomplished using diethyldithiocarbamate (DETC) administered intraperitoneally. DETC combines with Fe2+ to form (DETC)2-Fe and is an excellent trapping agent for nitric oxide.

Development of circulatory and metabolic shock following transient portal triad occlusion.

Liver ischemia is purposefully induced by portal triad occlusion (PTO) in several clinical situations including liver surgery for trauma, tumor, and transplantation. Despite significant morbidity from PTO, the hemodynamic and metabolic effects of PTO have not been evaluated relative to duration of ischemia. We investigated this using a total hepatic ischemia model.

Recurrent ischemia in the canine heart causes recurrent bursts of free radical production that have a cumulative effect on contractile function. A pathophysiological basis for chronic myocardial "stunning".

Open-chest dogs (total number used, 117) underwent 10 5-min coronary occlusions (O) interspersed with 10 min of reperfusion (R). When systolic thickening fraction was measured 9 min after each R, the first O-R cycle was found to cause the largest decrement, with only a slight additional loss during the next four cycles and no further loss during the last five cycles (group IV), suggesting that the first few episodes of ischemia preconditioned the myocardium against the stunning induced by the last five episodes. However, different results were obtained when the total deficit of wall thickening during the final 4-h R interval was measured.

A new model for inducing total hepatic ischemia while preventing circulatory collapse secondary to splanchnic vascular congestion.

Animal models used to study liver ischemia are limited by the lethal effect of splanchnic venous engorgement from portal triad occlusion (PTO). We compared a passive porto-systemic shunt (PSS) to a pump-driven PSS. The passive and pumped PSS groups (n = 6) received 60 min of PTO followed by 2 h of reperfusion.

Metabolism of ethanol to 1-hydroxyethyl radicals in vivo: detection with intravenous administration of alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone.

Intravenous administration of the spin-trapping agent alpha-(4-pyridyl-1-oxide)-N-t-butylnitrone (POBN) to anesthetized but otherwise untreated rats was used to test for formation of 1-hydroxyethyl radicals in vivo. The only EPR signals observed in bile samples from rats that had received ethanol but no POBN could be attributed to low concentrations of ascorbyl radical. However, when POBN (700 mg/kg, intravenously) was also administered, a nitroxide with a six-line EPR spectrum was readily detected in bile.

Inhibitory effect of a hydrophilic alpha-tocopherol analogue, MDL 74,405, on generation of free radicals in stunned myocardium in dogs.

A previous study has demonstrated that the hydrophilic (alpha-tocopherol analogue, MDL 74,405, attenuates postischemic myocardial dysfunction ("stunning") in dogs. The present study was undertaken to determine directly whether the salutary effect of this drug on myocardial stunning results from inhibition of the generation of oxygen-derived free radicals. Open-chest dogs undergoing a 15-min coronary artery occlusion and 3 h of reperfusion received an intravenous infusion of either saline (controls, n = 7) or MDL 74,405 (n = 6) starting 30 min before coronary occlusion and ending 60 min after reflow at a dose of 0.

Inorganic phosphate promotes redox cycling of iron in liver microsomes: effects on free radical reactions.

The phosphate buffer concentration used in spin trapping experiments with liver microsomes markedly influenced rates of free radical formation from ethanol and dimethylsulfoxide, but not from carbon tetrachloride. Effects of phosphate concentration on ethanol radical formation were abolished by addition of deferoxamine or bathophenanthrolene, indicating that an iron-phosphate complex might be involved. High concentrations of phosphate stimulated rates of microsomal Fe+3 reduction and facilitated the mobilization of microsomal nonheme iron, but had little effect on a variety of microsomal monooxygenase enzyme activities.

Inhibition of doxorubicin-induced membrane damage by thiol compounds: toxicologic implications of a glutathione-dependent microsomal factor.

The hypothesis was tested that glutathione exerts its protective actions against doxorubicin-induced oxidative stress through an enzyme-dependent mechanism. Glutathione at biological concentrations decreased doxorubicin-dependent rat hepatic microsomal lipid peroxidation, whereas N-acetylcysteine had no effect. Glutathione was utilized during this inhibition at a rate dependent on the concentration of both doxorubicin and the sulfhydryl.

Catechol adrenergic agents enhance hydroxyl radical generation in xanthine oxidase systems containing ferritin: implications for ischemia/reperfusion.

Iron chelators have been reported to protect tissues against reperfusion injury. This implies that iron is being released into the plasma or is made accessible in tissues for oxidation-reduction reactions. It has been postulated that ferritin is a likely source for this iron.

Study of reproducibility of spin trapping results in the use of C-phenyl-N-tert-butyl nitrone (PBN) for trichloromethyl radical detection in CCl4 metabolism by rat liver microsomal dispersions. Biological spin trapping I.

The well-known metabolism of CCl4 to trichloromethyl radicals in rat liver microsomal dispersions has been reinvestigated with the goal to determine the repeatability and reproducibility of the EPR signal intensity of the EPR spectrum of the CCl3 adduct of PBN. It was found that at least eight repeat experiments were needed under identical conditions to obtain an average value with an error of +/- 10%. When the effect of changing the concentrations of CCl4, PBN or NADPH-generating system was investigated, the plots of EPR signal intensity vs.

Metabolism of ethanol to 1-hydroxyethyl radicals in rat liver microsomes: comparative studies with three spin trapping agents.

Metabolism of ethanol to 1-hydroxyethyl radicals by rat liver microsomes was studied with three nitrone spin trapping agents (POBN, PBN, and DMPO) under essentially comparable conditions. The data indicate that POBN was the superior spin trapping agent for 1-hydroxyethyl radicals, and that DMPO was least efficient. Addition of deferoxamine completely prevented detection of 1-hydroxyethyl radicals with PBN or DMPO, but caused only 50% decrease in EPR signals when POBN was the spin trap.

Characteristics of an oxidant formed during iron (II) autoxidation.

When ethanol (100 mM) and the spin trapping agent DMPO were added to a solution of FeSO4 (0.1 mM) in phosphate buffer (40 mM), pH 7.4, the spectrum of the 1-hydroxyethyl radical spin adduct of DMPO could be detected by ESR spectroscopy.

Intervention in hypercholesterolemic college students: a pilot study.

Purpose: Since atherosclerosis begins in childhood and cholesterol levels can track from adolescence to adulthood, early intervention to lower elevated levels may be important. Our objective was to test the effectiveness of a health education intervention in hypercholesterolemic college students.

Methods: Thirty-nine university students with plasma low-density lipoprotein cholesterol (LDL-C) levels > or = 75th percentile (2.

Oxygen radical formation in well-washed rat liver microsomes: spin trapping studies.

The generation of hydroxyl radicals by rat liver microsomes was monitored by spin trapping with 5,5-dimethylpyrroline N-oxide (DMPO). The results confirm and extend previous data which demonstrated that hydroxyl radicals are produced by microsomes in the presence of NADPH and O2, and without the exogenous addition of iron. No EPR signals could be detected unless catalase activity which was associated with the microsomes could be substantially diminished.