Glucose Metabolism in Neisseria gonorrhoeae

The metabolism of glucose was examined in several clinical isolates of Neisseria gonorrhoeae. Radiorespirometric studies revealed that growing cells metabolized glucose by a combination on the Entner-Doudoroff and pentose phosphate pathways. A portion of the glyceraldehyde-3-phosphate formed via the Entner-Doudoroff pathway was recycled by conversion to glucose-6-phosphate. Subsequent catabolism of this glucose-6-phosphate by either the Entner-Doudoroff or pentose phosphate pathways yielded CO(2) from the original C6 of glucose. Enzyme analyses confirmed the presence of all enzymes of the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways. There was always a high specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) relative to that of 6-phosphogluconate dehydrogenase (EC 1.1.1.44). The glucose-6-phosphate dehydrogenase utilized either nicotinamide adenine dinucleotide phosphate or nicotinamide adenine dinucleotide as electron acceptor. Acetate was the only detectable nongaseous end product of glucose metabolism. Following the disappearance of glucose, acetate was metabolized by the tricarboxylic acid cycle as evidenced by the preferential oxidation of [1-(14)C]acetate over that of [2-(14)C]acetate. When an aerobically grown log-phase culture was subjected to anaerobic conditions, lactate and acetate were formed from glucose. Radiorespirometric studies showed that under these conditions, glucose was dissimilated entirely by the Entner-Doudoroff pathway. Further studies determined that this anaerobic dissimilation of glucose was not growth dependent.     

Ethanol-induced alterations of the antioxidant defense system in rat kidney

We report here the effects of chronic ethanol consumption on the antioxidant defense system in rat kidney. Thirty-two male Wistar rats were randomly divided in two identical groups and were treated as follows: control group (water for fluid) and the ethanol-fed group (2 g/kg body weight/24 h). The animals were sacrificed after 10 weeks, and respectively 30 weeks of ethanol consumption, and the renal tissue was isolated and analyzed. Results revealed that kidney alcohol dehydrogenase activities increased significantly after ethanol administration, but the electrophoretic pattern of alcohol dehydrogenase isoforms was unmodified. The SDS polyacrylamidegel electrophoretic study of kidney proteins has revealed the appearance of two new protein bands after long-term ethanol consumption. The kidney reduced glutathione/oxidized glutathione ratio decreased, indicating an oxidative stress response due to ethanol ingestion. The malondialdehyde contents and xanthine oxidase activities were unchanged. The antioxidant enzymatic defense system showed a different response during the two periods of ethanol administration. After 10 weeks, catalase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase were activated, while superoxide dismutase, glutathione transferase, and gamma-glutamyltranspeptidase levels were stationary. After 30 weeks, superoxide dismutase and glutathione peroxidase activities were unmodified, but catalase, glutathione transferase, gamma-glutamyltranspeptidase, glutathione reductase, and glucose-6-phosphate dehydrogenase activities were significantly increased. Remarkable changes have been registered after 30 weeks of ethanol administration for glutathione reductase and glucose-6-phosphate dehydrogenase activities, including an increase by 106 and 216' of control values, respectively. These results showed specific changes in rat kidney antioxidant system and glutathione status as a consequence of long-term ethanol administration.     

Regulation of alternate peripheral pathways of glucose catabolism during aerobic and anaerobic growth of Pseudomonas aeruginosa.

Glucose may be converted to 6-phosphogluconate by alternate pathways in Pseudomonas aeruginosa. Glucose is phosphorylated to glucose-6-phosphate, which is oxidized to 6-phosphogluconate during anaerobic growth when nitrate is used as respiratory electron acceptor. Mutant cells lacking glucose-6-phosphate dehydrogenase are unable to catabolize glucose under these conditions. The mutant cells utilize glucose as effectively as do wild-type cells in the presence of oxygen; under these conditions, glucose is utilized via direct oxidation to gluconate, which is converted to 6-phosphogluconate. The membrane-associated glucose dehydrogenase activity was not formed during anaerobic growth with glucose. Gluconate, the product of the enzyme, appeared to be the inducer of the gluconate transport system, gluconokinase, and membrane-associated gluconate dehydrogenase. 6-Phosphogluconate is probably the physiological inducer of glucokinase, glucose-6-phosphate dehydrogenase, and the dehydratase and aldolase of the Entner-Doudoroff pathway. Nitrate-linked respiration is required for the anaerobic uptake of glucose and gluconate by independently regulated transport systems in cells grown under denitrifying conditions.     

Anaerobic respiration of superoxide dismutase-deficientSaccharomyces cerevisiae under oxidative stress

The ethanol productivity of superoxide dismutase (SOD)-deficient mutants ofSaccharomyces cerevisiae was examined under the oxidative stress by Paraquat. It was observed that MnSOD-deficient mutant ofS. cerevisiae had higher ethanol productivity than wild type or CuZnSOD-deficient yeast both in aerobic and in anaerobic culture condition. Pyruvate dehydrogenase activity decreased by 35% and alcohol dehydrogenase activity increased by 32% were observed in MnSOD-deficient yeast grown aerobically. When generating oxygen radicals by Paraquat, the ethanol productivity was increased by 40% in CuZnSOD-deficient or wild strain, resulting from increased activity of alcohol dehydrogenase and decreased activity of pyruvate dehydrogenase. However, the addition of ascorbic acid with Paraquat returned the enzyme activities at the level of control. These results imply that SOD-deficiency in yeast strains may cause the metabolic flux to shift into anaerobic ethanol fermentation in order to avoid their oxidative damages by Paraquat.     

Oxidant-antioxidant imbalance in the erythrocytes of sporadic amyotrophic lateral sclerosis patients correlates with the progression of disease

Free radicals are implicated in numerous disease processes including motor neuron degeneration (MND). Antioxidant defense enzymes: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G-6-PDH) in the erythrocytes are capable of detoxifying reactive oxygen species produced endogenously or exogenously. In the present study, the extent of lipid peroxidation (LPO) and antioxidant defenses were evaluated in the erythrocytes of 20 sporadic amyotrophic lateral sclerosis (ALS) patients and 20 controls. We observed that lipid peroxidation in the erythrocytes of amyotrophic lateral sclerosis patients significantly increased with respect to controls (P<0.001). On the other hand, catalase activity was found to be significantly lower (P<0.001). The activities of glucose-6-phosphate dehydrogenase, glutathione reductase and glutathione levels were also found to be significantly reduced in ALS patients compared to healthy subjects (P<0.001, P<0.01 and P<0.01, respectively). It was further observed that lipid peroxidation started to increase and catalase, glutathione reductase, glucose-6-phosphate dehydrogenase enzyme activities and glutathione levels started to decrease as amyotrophic lateral sclerosis progressed from 6 to 24 months, suggesting a correlation between these parameters and duration of amyotrophic lateral sclerosis. This study confirms the involvement of oxidative stress during the progression of amyotrophic lateral sclerosis and the need to develop specific peripheral biomarkers.     

Development of a glucose-6-phosphate biosensor based on coimmobilized p-hydroxybenzoate hydroxylase and glucose-6-phosphate dehydrogenase

This work reports the development of an amperometric glucose-6-phosphate biosensor by coimmobilizing p-hydroxybenzoate hydroxylase (HBH) and glucose-6-phosphate dehydrogenase (G6PDH) on a screen-printed electrode. The principle of the determination scheme is as follows: G6PDH catalyzes the specific dehydrogenation of glucose-6-phosphate by consuming NADP(+). The product, NADPH, initiates the irreversible the hydroxylation of p-hydroxybenzoate by HBH in the presence of oxygen to produce 3,4-dihydroxybenzoate, which results in a detectable signal due to its oxidation at the working electrode. The sensor shows a broad linear detection range between 2 microM and 1000 microM with a low detection limit of 1.2 microM. Also, it has a fast measuring time which can achieve 95% of the maximum current response in 20s after the addition of a given concentration of glucose-6-phosphate with a short recovery time (2 min).     

Chloral hydrate anesthesia alters cerebral enzymes in the rat. A histochemical study

Cerebral forebrain arterioles and neuropil were analyzed histochemically to determine the effects of chloral hydrate anesthesia on key enzymes of aerobic and anaerobic metabolism, as well as the hexose monophosphate shunt in rats. Significant decreases were observed in cytochrome oxidase, and beta-hydroxybutyrate dehydrogenase in arterioles, while glucose-6-phosphate dehydrogenase and isocitric dehydrogenase showed a significant increase and lactate dehydrogenase showed no significant change. In the neuropil, cytochrome oxidase, isocitrate dehydrogenase and glucose-6-phosphate dehydrogenase showed significant increases following chloral hydrate administration, while beta-hydroxybutyrate dehydrogenase and lactate dehydrogenase showed no significant changes. These data suggest that surgical anesthetic levels of chloral hydrate can impair forebrain metabolism which may lead to altered electrophysiological responses.     

Denaturation of protein by chlorine dioxide: oxidative modification of tryptophan and tyrosine residues

Oxychlorine compounds, such as hypochlorous acid (HOCl) and chlorine dioxide (ClO2), have potent antimicrobial activity. Although the biochemical mechanism of the antimicrobial activity of HOCl has been extensively investigated, little is known about that of ClO2. Using bovine serum albumin and glucose-6-phosphate dehydrogenase of Saccharomyces cerevisiae as model proteins, here I demonstrate that the antimicrobial activity of ClO2 is attributable primarily to its protein-denaturing activity. By solubility analysis, circular dichroism spectroscopy, differential scanning calorimetry, and measurement of enzymatic activity, I demonstrate that protein is rapidly denatured by ClO2 with a concomitant decrease in the concentration of ClO2 in the reaction mixture. Circular dichroism spectra of the ClO2-treated proteins show a change in ellipticity at 220 nm, indicating a decrease in alpha-helical content. Differential scanning calorimetry shows that transition temperature and endothermic transition enthalpy of heat-induced unfolding decrease in the ClO2-treated protein. The enzymatic activity of glucose-6-phosphate dehydrogenase decreases to 10% within 15 s of treatment with 10 microM ClO2. Elemental analyses show that oxygen, but not chlorine, atoms are incorporated in the ClO2-treated protein, providing direct evidence that protein is oxidized by ClO2. Furthermore, mass spectrometry and nuclear magnetic resonance spectroscopy show that tryptophan residues become N-formylkynurenine and tyrosine residues become 3,4-dihydroxyphenylalanine (DOPA) or 2,4,5-trihydroxyphenylalanine (TOPA) in the ClO2-treated proteins. Taking these results together, I conclude that microbes are inactivated by ClO2 owing to denaturation of constituent proteins critical to their integrity and/or function, and that this denaturation is caused primarily by covalent oxidative modification of their tryptophan and tyrosine residues.     

Influence of very low doses of ionizing radiation on Synechococcus lividus metabolism during the initial growth phase

Previous results from this laboratory have shown that very low chronic doses of gamma radiation can stimulate proliferation of the Cyanobacterium Synechococcus lividus. This modification of cell proliferation occurred during the first doubling. In this paper, we have compared the metabolism of cells cultivated in a normal environment or under chronic irradiation. Incubation of the cells in a new medium induced a high superoxide dismutase (EC 1.15.1.1, SOD) activity at the 18th hour and a degradation of phycocyanin, thus demonstrating that cells were submitted to a photooxidative stress. This increase in superoxide dismutase activity was followed by concomittant peaks of glutathione reductase (EC 1.6.4.2, GR) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49, G6P-DH) at the 24th hour. Irradiated cultures at a dose of 53.5 mGray/year show an earlier and higher peak of SOD, GR, and G6P-DH. In a second stage, cultures showed an earlier onset of photosynthesis under irradiation, as evidenced by an increase in pigment content and an enhancement of glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13, GAP-DH). These results show that the radiostimulation is related to the activation of enzymes protecting against peroxides that were induced under oxidative circumstances and to the activation of a glucose catabolism via the oxidative pentose phosphate pathway.Abbreviations mGy milli-Gray - SOD superoxide dismutase - G6P-DH glucose-6-phosphate dehydrogenase - GAP-DH glycer-aldehyde-3-phosphate dehydrogenase - GSSG oxidized glutathione     

Factors Related to the Oxygen Tolerance of Anaerobic Bacteria

The effect of atmospheric oxygen on the viability of 13 strains of anaerobic bacteria, two strains of facultative bacteria, and one aerobic organism was examined. There were great variations in oxygen tolerance among the bacteria. All facultative bacteria survived more than 72 h of exposure to atmospheric oxygen. The survival time for anaerobes ranged from less than 45 min for Peptostreptococcus anaerobius to more than 72 h for two Clostridium perfringens strains. An effort was made to relate the degree of oxygen tolerance to the activities of superoxide dismutase, catalase, and peroxidases in cell-free extracts of the bacteria. All facultative bacteria and a number of anaerobic bacteria possessed superoxide dismutase. There was a correlation between superoxide dismutase activity and oxygen tolerance, but there were notable exceptions. Polyacrylamide gel electropherograms stained for superoxide dismutase indicated that many of the anaerobic bacteria contained at least two electrophoretically distinct enzymes with superoxide dismutase activity. All facultative bacteria contained peroxidase, whereas none of the anaerobic bacteria possessed measurable amounts of this enzyme. Catalase activity was variable among the bacteria and showed no relationship to oxygen tolerance. The ability of the bacteria to reduce oxygen was also examined and related to enzyme content and oxygen tolerance. In general, organisms that survived for relatively long periods of time in the presence of oxygen but demonstrated little superoxide dismutase activity reduced little oxygen. The effects of medium composition and conditions of growth were examined for their influence on the level of the three enzymes. Bacteria grown on the surface of an enriched blood agar medium generally had more enzyme activity than bacteria grown in a liquid medium. The data indicate that superoxide dismutase activity and oxygen reduction rates are important determinants related to the tolerance of anaerobic bacteria to oxygen.     

Enzymatic defenses against the toxicity of oxygen and of streptonigrin in Escherichia coli.

Anaerobically grown Escherichia coli K-12 contain only one superoxide dismutase and that is the iron-containing isozyme found in the periplasmic space. Exposure to oxygen caused the induction of a manganese-containing superoxide dismutase and of another, previously undescribed, superoxide dismutase, as well as of catalase and peroxidase. These inductions differed in their responsiveness towards oxygen. Thus the very low levels of oxygen present in deep, static, aerobic cultures were enough for nearly maximal induction of the manganese-superoxide dismutase. In contrast, induction of the new superoxide dismutase, catalase, and peroxidase required the much higher levels of oxygen achieved in vigorously agitated aerobic cultures. Anaerobically grown cells showed a much greater oxygen enhancement of the lethality of streptonigrin than did aerobically grown cells, in accord with the proposal that streptonigrin can serve as an intracellular source of superoxide. Anaerobically grown cells in which enzyme inductions were prevented by puromycin were damaged by exposure to air. This damage was evidenced both as a decline in viable cell count and as structural abnormalities evident under an electron microscope.     

Reactive oxygen intermediates metabolizing enzymes in Ancylostoma ceylanicum and Nippostrongylus brasiliensis

Adult worms of Ancylostoma ceylanicum and Nippostronglyus brasiliensis were found to possess an active system for the detoxification of reactive oxygen intermediates. Xanthine oxidase, which is known to produce superoxide anion, was detected in both the nematode parasites in significant activities. Superoxide anion, thus produced, may quickly be eliminated by superoxide dismutase. Both parasites also exhibited the presence of catalase, peroxidase, and glutathione peroxidase for efficient removal of hydrogen peroxide. Glutathione reductase and glucose-6-phosphate dehydrogenase were, however, detected in low levels of activities. Endowment of A. ceylanicum and N. brasiliensis with these antioxidant enzymes, therefore, enables them to evade the host's effector mechanism for their survival. Superoxide dismutase of both these nematodes showed marked inhibition by KCN and, hence, the enzyme appears to be of copper-zinc type.     

Halothane depletes cardiac microvasculature enzymes in the rat

Left ventricular arterioles from Sprague-Dawley rats were analyzed histochemically to determine the effects of halothane administration on key enzymes of aerobic and anaerobic metabolism, as well as on key enzymes of the hexose monophosphate shunt. Significant decreases occurred in cytochrome oxidase (-42%) and beta-hydroxybutyrate dehydrogenase (-57%). No significant changes were observed in isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, or lactate dehydrogenase. These data suggest that anesthetic levels of halothane can cause impaired metabolism in the coronary microvasculature.     

Study on the antioxidant status of vitiligo patients of different age groups in Baroda

One of the major hypotheses in the pathogenesis of vitiligo is the oxidative stress hypothesis. Pollution plays a major role in the production of free radicals. Gujarat, a highly industrialized state in India has a high prevalence of vitiligo patients. No previous studies were done on the age-dependent antioxidant status of vitiligo patients in Baroda city, Gujarat. Blood samples were collected from vitiligo patients of different age groups (5-15, 16-25, 26-35, 36-45 yr) and from age matched healthy volunteers. Antioxidant enzymes in blood such as catalase, superoxide dismutase, glutathione peroxidase and non-enzymatic antioxidants such as reduced glutathione and plasma vitamin E were estimated. Lipid peroxidation levels in erythrocytes and the reducing equivalent system, i.e. glucose-6-phosphate dehydrogenase were also measured. Significant increase in superoxide dismutase activity and lipid peroxidation levels in erythrocytes was observed in all age groups of vitiligo patients as compared with age-matched healthy controls, wherein an increase of 55% (P < 0.02) was observed in superoxide dismutase activity and lipid peroxidation levels in 36-45 yr age group. Whole blood glutathione levels, erythrocyte glutathione peroxidase and glucose-6-phosphate dehydrogenase activity were decreased significantly, whereas erythrocyte catalase activity and plasma vitamin E levels were not different in vitiligo patients as compared with age-matched healthy controls. No specific age group showed a significant difference. This is the first report on the age-dependent antioxidant status of vitiligo patients in Baroda. The disease affects individuals of any age group as shown in this study and systemic oxidative stress might precipitate the pathogenesis of vitiligo in susceptible patients.     

Apparent oxygen-dependent inhibition by superoxide dismutase of the quinoprotein methanol dehydrogenase.

Methanol dehydrogenase activity, when assayed with phenazine ethosulfate (PES) as an electron acceptor, was inhibited by superoxide dismutase (SOD) and by Mn2+ only under aerobic conditions. Catalase, formate, and other divalent cations did not inhibit the enzyme. The enzyme also exhibited significantly higher levels of activity when assayed with PES under anaerobic conditions relative to aerobic conditions. The oxygen- and superoxide-dependent effects on methanol dehydrogenase were not observed when either Wurster's Blue or cytochrome c-55li was used as an electron acceptor. Another quinoprotein, methylamine dehydrogenase, which possesses tryptophan tryptophylquinone (TTQ) rather than pyrroloquinoline quinone (PQQ) as a prosthetic group, was not inhibited by SOD or Mn2+ when assayed with PES as an electron acceptor. Spectroscopic analysis of methanol dehydrogenase provided no evidence for any oxygen- or superoxide-dependent changes in the redox state of the enzyme-bound PQQ cofactor of methanol dehydrogenase. To explain these data, a model is presented in which this cofactor reacts reversibly with oxygen and superoxide, and in which oxygen is able to compete with PES as an electron acceptor for the reduced species.     

Hyperoxia results in transient oxidative stress and an adaptive response by antioxidant enzymes in goldfish tissues

The effects of hyperoxia on the status of antioxidant defenses and markers of oxidative damage were evaluated in goldfish tissues. The levels of lipid peroxides, thiobarbituric acid reactive substances, carbonyl proteins and the activities of some antioxidant enzymes were measured in brain, liver, kidney and skeletal muscle of goldfish, Carassius auratus L., over a time course of 3-12 h of hyperoxia exposure followed by 12 or 36 h of normoxic recovery. Exposure to high oxygen resulted in an accumulation of protein carbonyls in tissues throughout hyperoxia and recovery whereas lipid peroxides and thiobarbituric acid reactive substances accumulated transiently under short-term hyperoxia stress (3-6 h) but were then strongly reduced. This suggests that hyperoxia stimulated an enhancement of defenses against lipid peroxidation or mechanisms for enhancing the catabolism of peroxidation products. The activities of principal antioxidant enzymes, superoxide dismutase and catalase, were not altered under hyperoxia but catalase increased during normoxic recovery; activities may rise in anticipation of further hyperoxic excursions. In most tissues, the activities of glutathione-utilizing enzymes (glutathione peroxidase, glutathione-S-transferase, glutathione reductase) as well as glucose-6-phosphate dehydrogenase, were not affected under hyperoxia but increased sharply during normoxic recovery. Correlations between some enzyme activities and oxidative stress markers were found, for example, an inverse correlation was seen between levels of thiobarbituric acid reactive substances and glutathione-S-transferase activity in liver and catalase and glucose-6-phosphate dehydrogenase in kidney. The results suggest that liver glutathione-S-transferase plays an important role in detoxifying end products of lipid peroxidation accumulated under hyperoxia stress.     

Oxidative stress in digestive gland and gill of the brown mussel (Perna perna) exposed to air and re-submersed

Mussels Perna perna were exposed to air for 24 h showing a clear increase in the levels of lipid peroxidation and oxidative DNA damage, measured as 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodGuo). The levels of lipid peroxidation increased both in the digestive gland and gills, while oxidative DNA damage increased only in the gills. After the 24 h of air exposure, mussels were re-submersed for a period of 3 h, leading values to return to a pre-aerial exposure levels. Control animals were kept immersed during the whole period. Several antioxidant and complementary enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), glutathione S-transferase (GST) and the levels of total glutathione (Total GSH) were assayed in a second set of experiments where one group of mussels were exposed to air for 18 h and other to 1 h re-submersion after 18 h aerial exposure. Only a 52% increase in the glutathione S-transferase activity was observed in the digestive gland, which remained elevated to about 40% after 1 h re-submersion, showing that defense systems can be modulated even during oxygen deprivation in P. perna. The DNA and lipid oxidative damage observed after aerial exposure indicates that mussels face an oxidative challenge, and are able to counteract such an “insult” as values of lipid peroxidation and DNA damage returned to control values after 3 h re-submersion.     

Electrophoretic analysis of protein systems of Ctenopharyngodon idella (Val.), Hypophthalmichthys nobilis (Rich.) and their F1 triploid hybrid

Electrophoretic analysis was performed on eight protein systems (lactate dehydrogenase, liver esterases, superoxide dismutase, haemoglobin, isocitrate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogIuconate dehydrogenase, transferrin) in Ctenopharyngodon idella, Hypophthalmichthys nobilis , and their F₁ triploid hybrid. The data demonstrated codominant Mendelian inheritance at individual loci for each protein system. Transferrin and superoxide dismutase were the only proteins found to be polymorphic in either parental species. Both parental alleles were present and functional at each enzyme locus examined in the F₁ triploid hybrid.     

Mechanisms contributing to hypochlorous acid resistance of a Salmonella isolate from a poultry-processing plant

AIMS: We have recently reported the isolation of Salmonella that have acquired tolerance to hypochlorous acid (HOCl) (Mokgatla et al. 1998). The aim of this work was to investigate possible protective mechanisms involved in the increased tolerance to HOCl of a selected resistant strain. METHODS AND RESULTS: One resistant (Salmonella 104) and one sensitive (Salmonella 81) isolate in exponential phase were exposed to HOCl at a final active concentration of 28 mg l(-1). Cultures were assayed for superoxide dismutase and catalase activity, as well as for four membrane-bound dehydrogenases (malate, lactate, glutamate and glucose-6-phosphate dehydrogenase). The degree of single-strand breaks in genomic DNA was analysed and lipopolysaccharide profiles determined. The resistant Salmonella isolate differed from the sensitive isolate in a number of ways. It responded within 10 min of exposure by producing catalase and decreasing the activity levels of four membrane-bound dehydrogenases. This combination would lead to lower levels of hydroxyl radicals and singlet oxygen, moieties thought to be integrally involved in the antibacterial action of HOCl. Furthermore, the resistant strain did not display the same degree of DNA damage as did the sensitive strain. CONCLUSIONS: Strain 104 is believed to grow in the presence of 28 mg l(-1) HOCl by protecting itself against HOCl by decreasing the levels of species that could react with HOCl to generate toxic reactive oxygen radicals and by improved DNA damage repair mechanisms. SIGNIFICANCE AND IMPACT OF THE STUDY: The occurrence of Salmonella able to grow in the presence of 28 mg l(-1) HOCl is of relevance to the food-processing and drinking water treatment industries as these strains would survive sanitation regimes.     

Evidence of an oxidative challenge in the Alzheimer's brain

Alzheimer's disease may arise from or produce oxidative damage in the brain. To assess the responses of the Alzheimer's brain to possible oxidative challenges, we assayed for glutathione, glucose-6-phosphate dehydrogenase, catalase and superoxide dismutase in twelve regions of Alzheimer's disease and aged control brains. In addition, we determined levels of malondialdehyde to evaluate lipid peroxidation in these brain regions. Most brain regions showed evidence of a response to an oxidative challenge, but the cellular response to this challenge differed among brain regions. These data suggest that the entire Alzheimer's brain may be subject to an oxidative challenge, but that some brain areas may be more vulnerable than others to the consequent neural damage that characterizes the disease.