Authorship ignorance: views of researchers in French clinical settings.

OBJECTIVES: To assess the knowledge and behaviour of researchers regarding criteria for authorship, and the practices of ghost and gift authorship. DESIGN: Semidirective interviews of senior clinical researchers. SETTING: University hospital. PARTICIPANTS: Thirty-nine main investigators of clinical research programmes. MAIN MEASUREMENTS: Awareness and use of International Committee of Medical Journal Editors (ICMJE) criteria for authorship, and perceptions about ghost and gift authorship. RESULTS: A total of 48 protocols submitted by 42 principal investigators between 1994 and 1996 were identified. Thirty-nine investigators were contacted; 37 (one of whom delegated a co-author) were interviewed between May 2002 and March 2003. Two co-authors of two principal investigators were also interviewed. In all, 42 studies were represented. The interviews lasted for 40-90 minutes and were conducted with openness and respect for confidentiality. The choice of names of co-authors did not follow the ICMJE recommendations. Half of the respondents stated they were aware of criteria for authorship and knew of ICMJE, but most of them did not cite any of the ICMJE criteria among those they applied in deciding authorship. Most of them disagreed with the obligation to meet the three criteria justifying co-authorship because they found these too rigid and inapplicable. Gift authorship was a common practice; 59% of the respondents had been a recipient of gift authorship. Twenty-five (64%) were aware of ghost authorship and the majority considered it questionable and blameworthy. CONCLUSIONS: The ICMJE criteria were ignored by clinicians at a university hospital. Ghost and gift authorship were frequent among them. There is a need for French guidelines for authorship to be prepared and implemented.

Oxidative stress in gastric mucosa of asymptomatic humans infected with Helicobacter pylori: effect of bacterial eradication.

BACKGROUND: Inducible nitric oxide synthase (iNOS) and interleukin 8 (IL-8) are positive in approximately 50% of Helicobacter pylori-related diseases but it is not clear whether oxidative stress is also present in H. pylori asymptomatic humans. Our aim was to study the expression of iNOS, superoxide dismutase, catalase and IL-8 production in H. pylori-infected asymptomatic humans, and to investigate the effect of eradication of H. pylori. MATERIALS AND METHODS: Biopsies of corpus and antrum of asymptomatic H. pylori positive and negative humans served for determination of the gastritis score and H. pylori status; iNOS was measured by reverse transcriptase polymerase chain reaction and immunohistochemistry and superoxide dismutase and catalase by immunohistochemistry. IL-8 in biopsies was assessed by enzyme-linked immunosorbent assay. RESULTS: Immunostaining of iNOS, catalase and superoxide dismutase was significantly associated with H. pylori infection and was localized to inflammatory cells. IL-8 concentrations were greater in the H. pylori positive than H. pylori negative group and decreased after bacterial eradication. A decrease in staining for iNOS and catalase was observed after H. pylori eradication. CONCLUSIONS: INOS and antioxidant enzymes are present in gastric biopsies of asymptomatic H. pylori positive humans. Eradication caused a significant decrease in staining for iNOS and catalase. These results indicate that oxidative stress occurs in asymptomatic patients and can be modulated by H. pylori eradication.

Chlorination of guanosine and other nucleosides by hypochlorous acid and myeloperoxidase of activated human neutrophils. Catalysis by nicotine and trimethylamine.

Activated human neutrophils secrete myeloperoxidase, which generates HOCl from H2O2 and Cl(-). We have found that various (2'-deoxy)nucleosides react with HOCl to form chlorinated (2'-deoxy)nucleosides, including novel 8-chloro(2'-deoxy)guanosine, 5-chloro(2'-deoxy)cytidine, and 8-chloro(2'-deoxy)adenosine formed in yields of 1.6, 1.6, and 0.2%, respectively, when 0.5 mM nucleoside reacted with 0.5 mM HOCl at pH 7.4. The relative chlorination, oxidation, and nitration activities of HOCl, myeloperoxidase, and activated human neutrophils in the presence and absence of nitrite were studied by analyzing 8-chloro-, 8-oxo-7,8-dihydro-, and 8-nitro-guanosine, respectively, using guanosine as a probe. 8-Chloroguanosine was always more easily formed than 8-oxo-7,8-dihydro- or 8-nitro-guanosine. Using electrospray ionization tandem mass spectrometry, we show that several chlorinated nucleosides including 8-chloro(2'-deoxy)guanosine are formed following exposure of isolated DNA or RNA to HOCl. Micromolar concentrations of tertiary amines such as nicotine and trimethylamine dramatically enhanced chlorination of free (2'-deoxy)nucleosides and nucleosides in RNA by HOCl. As the G-463A polymorphism of the MPO gene, which strongly reduces myeloperoxidase mRNA expression, is associated with a reduced risk of lung cancer, chlorination damage of DNA /RNA and nucleosides by myeloperoxidase and its enhancement by nicotine may be important in the pathophysiology of human diseases associated with tobacco habits.

Helicobacter pylori eradication attenuates oxidative stress in human gastric mucosa.

OBJECTIVE: Helicobacter pylori infection causes gastric diseases, but the responsible mechanisms are not completely understood. They can involve DNA and tissue damage induced by reactive oxygen and nitrogen species. Our aim is to investigate the effects of bacterial eradication on oxidative stress by measuring changes of relevant markers. METHODS: Antral biopsies were obtained from 34 patients with chronic atrophic gastritis and peptic ulcer disease before and after bacterial eradication. The expression of inducible nitric oxide synthase (iNOS) and levels of nitrotyrosine (NTYR) and 8-hydroxy-2'-deoxyguanosine were assessed immunohistochemically as markers of nitric oxide (NO) production and of damage to proteins and DNA, respectively. RESULTS: Before treatment, the percentages of patients with staining were: 56 for iNOS in inflammatory cells, 79 and 61 for NTYR and 8-hydroxy-2'-deoxyguanosine in foveolar cells, respectively, and 82 for 8-hydroxy-2'-deoxyguanosine in lymphoid follicles. NTYR staining was associated with the intensity of inflammation (p = 0.04) and gastritis activity (p = 0.07). The prevalence of 8-hydroxy-2'-deoxyguanosine tended to be associated with that of NTYR. After successful H. pylori eradication, the prevalence of iNOS and NTYR (in mild gastritis) staining decreased (p < 0.001 and p < 0.06, respectively). 8-Hydroxy-2'-deoxyguanosine staining disappeared in 24% of cases but appeared in 18% of previously negative cases despite eradication. CONCLUSION: Targets of oxidative stress associated with H. pylori infection are inflammatory and deep foveolar cells and lymphoid follicles. This is the first report of 8-hydroxy-2'-deoxyguanosine localization in gastric mucosa. Oxidative stress is reduced by bacterial eradication in the first stages of mild gastritis. Moderate-severe gastritis may be a step that is reversible for iNOS, but partly irreversible for NTYR and 8-hydroxy-2'-deoxyguanosine.

Increased oxidative and nitrative stress in human stomach associated with cagA+ Helicobacter pylori infection and inflammation.

In order to study the role of Helicobacter pylori infection in gastric carcinogenesis, we have measured oxidized (carbonyls) and nitrated (nitrotyrosine-containing) proteins as markers for oxidative and nitrative stress in 216 human gastric biopsies using dot and western immunoblots and correlated the results with H. pylori, cagA status, expression of interleukin-8 and inducible nitric oxide synthase (iNOS) mRNAs, and gastric pathology. Higher levels of both oxidized and nitrated proteins were found in patients with either chronic gastritis or duodenal ulcer than in those with normal mucosa. The levels of modified proteins were significantly higher in inflamed samples infected with H. pylori, especially cagA+ strains, and in those with expression of interleukin-8 and iNOS mRNAs than in those negative for these parameters. These results indicate that infection with cagA+ H. pylori induces significant oxidative and nitrative stress in stomach mucosa, contributing to the pathogenesis of H. pylori-associated gastroduodenal diseases.

Nitrated and oxidized plasma proteins in smokers and lung cancer patients.

Cigarette smoking is a cause of lung cancer and other respiratory diseases. Oxidants either present in cigarette smoke and/or formed in the lung of smokers may trigger oxidative and nitrative damage to DNA and cellular components, contributing to carcinogenesis. We have used immunodot and Western blot analyses to measure nitrated (nitrotyrosine-containing) and oxidized (carbonyl-containing) proteins in plasma samples collected from 52 lung cancer patients and 43 control subjects (heavy and light smokers, nonsmokers with or without exposure to environmental tobacco smoke). The levels of nitrated proteins were significantly higher in lung cancer patients than in controls (P = 0.003). On the other hand, the levels of oxidized proteins were significantly higher in smokers than in nonsmokers (P < 0.001). Western-blot analyses showed the presence of two to five nitrated proteins and one oxidized protein. Using immunoprecipitation and Western-blot analyses with eight different antibodies against human plasma proteins, we identified fibrinogen, transferrin, plasminogen, and ceruloplasmin as nitrated proteins and fibrinogen as the only oxidized protein present in human plasma of lung cancer patients and smokers. Our results indicate that cigarette smoking increases oxidative stress and that during lung cancer development, formation of reactive nitrogen species results in nitration and oxidation of plasma proteins.

Formation of N-nitrosamines and N-nitramines by the reaction of secondary amines with peroxynitrite and other reactive nitrogen species: comparison with nitrotyrosine formation.

Reactive nitrogen species, including nitrogen oxides (N(2)O(3) and N(2)O(4)), peroxynitrite (ONOO(-)), and nitryl chloride (NO(2)Cl), have been implicated as causes of inflammation and cancer. We studied reactions of secondary amines with peroxynitrite and found that both N-nitrosamines and N-nitramines were formed. Morpholine was more easily nitrosated by peroxynitrite at alkaline pH than at neutral pH, whereas its nitration by peroxynitrite was optimal at pH 8.5. The yield of nitrosomorpholine in this reaction was 3 times higher than that of nitromorpholine at alkaline pH, whereas 2 times more nitromorpholine than nitrosomorpholine was formed at pH <7.5. For the morpholine-peroxynitrite reaction, nitration was enhanced by low concentrations of bicarbonate, but was inhibited by excess bicarbonate. Nitrosation was inhibited by excess bicarbonate. On this basis, we propose a free radical mechanism, involving one-electron oxidation by peroxynitrite of secondary amines to form amino radicals (R(2)N(*)), which react with nitric oxide ((*)NO) or nitrogen dioxide ((*)NO(2)) to yield nitroso and nitro secondary amines, respectively. Reaction of morpholine with NO(*) and superoxide anion (O(2)(*)(-)), which were concomitantly produced from spermine NONOate and by the xanthine oxidase systems, respectively, also yielded nitromorpholine, but its yield was <1% of that of nitrosomorpholine. NO(*) alone increased the extent of nitrosomorpholine formation in a dose-dependent manner, and concomitant production of O(2)(*)(-) inhibited its formation. Reactions of morpholine with nitrite plus HOCl or nitrite plus H(2)O(2), with or without addition of myeloperoxidase or horseradish peroxidase, also yielded nitration and nitrosation products, in yields that depended on the reactants. Tyrosine was nitrated easily by synthetic peroxynitrite, by NaNO(2) plus H(2)O(2) with myeloperoxidase, and by NaNO(2) plus H(2)O(2) under acidic conditions. Nitrated secondary amines, e.g., N-nitroproline, could be identified as specific markers for endogenous nitration mediated by reactive nitrogen species.

The effect of intra-gastric acidity and flora on the concentration of N-nitroso compounds in the stomach.

BACKGROUND: Correa's hypothesis proposes that gastric carcinogenesis is due to atrophic gastritis and hypochlorhydria which permit gastric bacterial colonization, the reduction of dietary nitrates to nitrites and the formation of potentially carcinogenic N-nitroso compounds (NOCs). OBJECTIVE: To test the hypothesis that omeprazole-induced hypochlorhydria is associated with increased intra-gastric concentrations of nitrate-reducing bacteria (NRB), nitrites and NOCs. DESIGN: Single-blind study in healthy volunteers. PARTICIPANTS: Fourteen healthy subjects (seven female, mean age 24 years), free of Helicobacter pylori infection, received a one-week course of placebo followed by a two-week course of omeprazole, 20 mg daily. METHODS: Fasted gastric samples, aspirated using a sterile double-lumen nasogastric tube at the end of the 1 st week (placebo) and the 2nd and 3rd weeks (omeprazole), were cultured aerobically and anaerobically; gastric pH and intra-gastric concentrations of nitrates, nitrites and NOCs were also determined. RESULTS: After weeks 1, 2 and 3, the intra-gastric concentrations of nitrate-reducing bacteria exceeded 10(5) colony-forming units (c.f.u.)/ml in 3, 7 and 9 subjects, respectively (P > 0.05). A gastric pH greater than 4.0 was associated with increased NRB (P < 0.05); however, neither increased gastric pH nor increased NRB, alone or in combination, was associated with increased intra-gastric concentrations of nitrites or NOCs (P > 0.05). CONCLUSIONS: A two-week increase in gastric pH in healthy, H. pylori-negative subjects was associated with increased intra-gastric concentrations of nitrate-reducing bacteria but not of nitrites or N-nitroso compounds. These data suggest that reduced gastric acid secretion is not a necessary precursor to the formation of carcinogenic N-nitroso compounds and that other mechanisms should be invoked to explain gastric carcinogenesis.

Coexpression of interleukin-8 and inducible nitric oxide synthase in gastric mucosa infected with cagA+ Helicobacter pylori.

The cagA-positive Helicobacter pylori strains are thought to be able to induce interleukin-8 expression and to be associated with gastroduodenal diseases. Inducible nitric oxide synthase (iNOS) may be involved in inflammatory pathogenesis. Our aim was to investigate the interrelationships between cagA and the expression of interleukin-8 and iNOS messenger RNAs, and with the type and degree of inflammation in gastric mucosa. In biopsies from 108 Chinese patients, the cagA, 16S rRNA, interleukin-8, and iNOS mRNAs were analyzed using reverse-transcription polymerase chain reaction. Specimens infected with cagA-positive strains had significantly more severe infiltration by mononuclear and polymorphonuclear leukocytes and more frequently expressed interleukin-8 and iNOS mRNAs than those infected with cagA-negative strains. iNOS and interleukin-8 mRNAs were significantly more frequently expressed together in the specimens with moderate or severe inflammation than in those with normal mucosa or mild inflammation. Our data suggest that interleukin-8 and excess nitric oxide play important roles in the pathogenesis of H. pylori-associated gastroduodenal diseases.

Endogenous N-nitroso compounds, and their precursors, present in bacon, do not initiate or promote aberrant crypt foci in the colon of rats.

Processed meat intake is associated with increased risk of colorectal cancer. This association may be explained by the endogenous formation of N-nitroso compounds (NOC). The hypothesis that meat intake can increase fecal NOC levels and colon carcinogenesis was tested in 175 Fischer 344 rats. Initiation was assessed by the number of aberrant crypt foci (ACF) in the colon of rats 45 days after the start of a high-fat bacon-based diet. Promotion was assessed by the multiplicity of ACF (crypts per ACF) in rats given experimental diets for 100 days starting 7 days after an azoxymethane injection. Three promotion studies were done, each in 5 groups of 10 rats, whose diets contained 7%, 14%, or 28% fat. Tested meats were bacon, pork, chicken, and beef. Fecal and dietary NOC were assayed by thermal energy analysis. Results show that feces from rats fed bacon-based diets contained 10-20 times more NOC than feces from control rats fed a casein-based diet (all p < 0.0001 in 4 studies). In bacon-fed rats, the amount of NOC input (diet) and output (feces) was similar. Rats fed a diet based on beef, pork, or chicken meat had less fecal NOC than controls (most p < 0.01). No ACF were detected in the colon of bacon-fed uninitiated rats. After azoxymethane injection, unprocessed but cooked meat-based diets did not change the number of ACF or the ACF multiplicity compared with control rats. In contrast, the bacon-based diet consistently reduced the number of large ACF per rat and the ACF multiplicity in the three promotion studies by 12%, 17%, and 20% (all p < 0.01). Results suggest that NOC from dietary bacon would not enhance colon carcinogenesis in rats.

Peroxynitrite: an endogenous oxidizing and nitrating agent.

Peroxynitrite, the reaction product between nitric oxide (.NO) and superoxide, has been presumed to be a mediator of cellular and tissue injury in various pathological situations. It is formed at the convergence of two independent radical-generating metabolic pathways. Its biological effects are due to its reactivity towards a large range of molecules including amino acids such as cysteine, methionine, tyrosine and tryptophan, nucleic bases and antioxidants (e.g. phenolics, selenium- and metal-containing compounds, ascorbate and urate). Peroxynitrite reactions involve oxidation and nitration. The chemical properties depend on the presence of CO2 and metallic compounds as well as the concentrations of reagents and kinetic laws. This complex chemistry can be explained by the formation of several structural forms and active intermediates released from peroxynitrite.

Analysis of 3-nitrotyrosine in biological fluids and protein hydrolyzates by high-performance liquid chromatography using a postseparation, on-line reduction column and electrochemical detection: results with various nitrating agents.

Nitric oxide reacts rapidly with superoxide to form the strong nitrating agent peroxynitrite, which is responsible for much of the tissue damage associated with diverse pathophysiological conditions such as inflammation. The occurrence of free or protein-bound nitrotyrosine (NTYR) has been considered as evidence for in vivo formation of peroxynitrite. However, various agents can nitrate tyrosine, and their relative significance in vivo has not been determined due to lack of a sensitive method to analyze NTYR in tissue proteins and biological fluids. We have developed a new HPLC-electrochemical detection method to analyze NTYR in protein hydrolyzates or biological fluids. The sample is injected directly into a reversed-phase HPLC column and NTYR is subsequently reduced by a platinum column to 3-aminotyrosine, which is quantified with an electrochemical detector. The method is simple, selective, and sensitive (detection limit, 0.1 pmol per 20-microl injection). We have applied this method to compare in vitro the ability of various nitrating agents to form NTYR in bovine serum albumin and human plasma. Yields of NTYR formed in human plasma proteins incubated with 1 or 10 mM nitrating agent decreased in the following order: synthetic peroxynitrite > 3-morpholinosydonimine, a generator of both NO and superoxide > Angeli's salt, which forms nitroxyl anion (NO-) > spermine-NONOate, which releases NO > sodium nitrite plus hypochlorite, which forms the nitrating agent nitryl chloride (NO2Cl). A simple purification method using a C18 Sep-Pak cartridge is also described for analysis of free NTYR in human plasma.

Antimutagenic dietary phenolics as antigenotoxic substances in urothelium of smokers.

Human urine is known to contain substances that strongly inhibit bacterial mutagenicity of aromatic and heterocyclic amines in vitro. The biological relevance of these anti-mutagens was examined by comparing levels of tobacco-related DNA adducts in exfoliated urothelial cells from smokers with the anti-mutagenic activity in corresponding 24-h urine samples. An inverse relationship was found between the inhibition of PhIP-mutagenicity by urine extracts in vitro and two DNA adduct measurements: the level of the putatively identified ABP-dG adduct and the total level of all tobacco-smoke-related carcinogen adducts including those probably derived from PhIP. These substances appear to be dietary phenolics and/or their metabolites because (i) the anti-mutagenic activity of urine extracts (n=18) was linearly related to their content in phenolics; (ii) the concentration ranges of these substances in urine extracts were similar to those of various plant phenols (e.g., quercetin, isorhamnetin) for which an inhibitory effect on the liver S9-mediated mutagenicity of PhIP was obtained; (iii) treatment of urines with beta-glucuronidase and arylsulfatase enhanced both anti-mutagenicity and the levels of phenolics in urinary extracts; (iv) urinary extracts inhibited non-competitively the liver S9-mediated mutagenicity of PhIP as did quercetin, used as a model phenolics. Onion, lettuce, apples and red wine are important sources of dietary flavonoids which are probably responsible for the anti-mutagenicity associated with foods and beverages. After HPLC fractionation of urinary extracts, the distribution profile of anti-mutagenic activity corresponded roughly to that of onion and wine extract combined. Overall, our study strongly suggests that smokers ingesting dietary phenolics, probably flavonoids, are partially protected against the harmful effects by tobacco carcinogens within their bladder mucosal cells.

Inducible nitric oxide synthase, anti-oxidant enzymes and Helicobacter pylori infection in gastritis and gastric precancerous lesions in humans.

Chronic inflammation induced by Helicobacter pylori infection has been associated with an increased risk of stomach cancer. We have analysed 167 stomach biopsies from 99 patients for H. pylori infection and immunohistochemically for the expression of inducible nitric oxide synthase (iNOS), catalase and superoxide dismutases (SODs) as markers of oxidative stress. Biopsies were graded as follows on the basis of histology: normal, superficial gastritis, variable severity of atrophic gastritis with or without intestinal metaplasia, and dysplasia. iNOS was detected in inflammatory cells in all types of gastritis with or without H. pylori infection and independently of its severity. In foveolar cells, iNOS was observed in approximately 25% of all biopsies showing any type of gastritis, but in a markedly higher proportion of dysplastic samples. Catalase and Mn-type SOD in inflammatory cells and catalase in foveolar cells were more frequently observed in marked atrophic gastritis biopsies than in less severe gastritis. Individual differences were found in the expression of these enzymes within groups with the same severity of gastritis. Prolonged oxidative stress in severe gastritis and dysplasia may play an important role in gastric carcinogenesis, through increased damage of DNA and tissue by reactive oxygen and nitrogen species.

Dietary phenolics as anti-mutagens and inhibitors of tobacco-related DNA adduction in the urothelium of smokers.

Human urine is known to contain substances that strongly inhibit bacterial mutagenicity of aromatic and heterocyclic amines in vitro. The biological relevance of these anti-mutagens was examined by comparing levels of tobacco-related DNA adducts in exfoliated urothelial cells from smokers with the anti-mutagenic activity in corresponding 24-h urine samples. An inverse relationship was found between the inhibition of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-mutagenicity by urine extracts in vitro and two DNA adduct measurements: the level of the putatively identified N-(deoxyguanosine-8-yl)-4-aminobiphenyl adduct and the total level of all tobacco-smoke-related carcinogen adducts including those probably derived from PhIP. Urinary anti-mutagenicity in vitro appears thus to be a good indicator of the anti-genotoxicity exerted by substances excreted in urine, that protect the bladder mucosal cells (and possibly other cells) against DNA damage. These substances appear to be dietary phenolics and/or their metabolites because (i) the anti-mutagenic activity of urine extracts (n = 18) was linearly related to their content in phenolics; (ii) the concentration ranges of these substances in urine extracts were similar to those of various plant phenols (quercetin, isorhamnetin and naringenin) for which an inhibitory effect on the liver S9-mediated mutagenicity of PhIP was obtained; (iii) treatment of urines with beta-glucuronidase and arylsulfatase enhanced both anti-mutagenicity and the levels of phenolics in urinary extracts; (iv) urinary extracts inhibited noncompetitively the liver S9-mediated mutagenicity of PhIP as did quercetin, used as a model phenolics. Several structural features of the flavonoids were identified as necessary for the inhibition of PhIP and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxiline mutagenicity. Fractionation by reverse-phase HPLC and subsequent analysis of two urinary extracts, showed the presence of several anti-mutagenic substances and phenolics; more lipophilic phenolics displayed the highest specific inhibitory activity. This suggests that enzymatic conversion of dietary flavonoids into their more lipophilic and anti-mutagenic O-methylcatechol derivatives, as noted for quercetin, may occur in vivo in man. Onion, lettuce, apples and red wine are important sources of dietary flavonoids which are probably responsible for the anti-mutagenicity associated with foods and beverages. After HPLC fractionation of urinary extracts, the distribution profile of anti-mutagenic activity corresponded roughly to that of onion and wine extract combined. Our study strongly suggests that smokers ingesting dietary phenolics, probably flavonoids, are partially protected against the harmful effects by tobacco carcinogens within their bladder mucosal cells. This protective effect of dietary phenolics against the cancer of the bladder (and possibly other sites) should be verified and explored as a part of a chemoprevention strategy.

Bacterial overgrowth during treatment with omeprazole compared with cimetidine: a prospective randomised double blind study.

BACKGROUND: Gastric and duodenal bacterial overgrowth frequently occurs in conditions where diminished acid secretion is present. Omeprazole inhibits acid secretion more effectively than cimetidine and might therefore more frequently cause bacterial overgrowth. AIM: This controlled prospective study compared the incidence of gastric and duodenal bacterial overgrowth in patients treated with omeprazole or cimetidine. METHODS: 47 outpatients with peptic disease were randomly assigned to a four week treatment regimen with omeprazole 20 mg or cimetidine 800 mg daily. Gastric and duodenal juice were obtained during upper gastrointestinal endoscopy and plated for anaerobic and aerobic organisms. RESULTS: Bacterial overgrowth (> or = 10(5) cfu/ml) was present in 53% of the patients receiving omeprazole and in 17% receiving cimetidine (p < 0.05). The mean (SEM) number of gastric and duodenal bacterial counts was 6.0 (0.2) and 5.0 (0.2) respectively in the omeprazole group and 4.0 (0.2) and 4.0 (0.1) in the cimetidine group (p < 0.001 and < 0.01; respectively). Faecal type bacteria were found in 30% of the patients with bacterial overgrowth. Basal gastric pH was higher in patients treated with omeprazole compared with cimetidine (4.2 (0.5) versus 2.0 (0.2); p < 0.001) and in patients with bacterial overgrowth compared with those without bacterial overgrowth (5.1 (0.6) versus 2.0 (0.1); p < 0.0001). The nitrate, nitrite, and nitrosamine values in gastric juice did not increase after treatment with either cimetidine or omeprazole. Serum concentrations of vitamin B12, beta carotene, and albumin were similar before and after treatment with both drugs. CONCLUSIONS: These results show that the incidence of gastric and duodenal bacterial overgrowth is considerably higher in patients treated with omeprazole compared with cimetidine. This can be explained by more pronounced inhibition of gastric acid secretion. No patient developed signs of malabsorption or an increase of N-nitroso compounds. The clinical significance of these findings needs to be assessed in studies with long-term treatment with omeprazole, in particular in patients belonging to high risk groups such as HIV infected and intensive care units patients.

Does increased endogenous formation of N-nitroso compounds in the human colon explain the association between red meat and colon cancer?

High red meat diets have been linked with risk of sporadic colorectal cancer; but their effects on mutations which occur in this cancer are unknown. G-->A transitions in K-ras occur in colorectal cancer and are characteristic of the effects of alkylating agents such as N-nitroso compounds (NOC). We studied th effect of red meat consumption on faecal NOC levels in eight male volunteers who consumed diets low or high in meat (60 or 600 g/day), as beef, lamb or pork, whilst living in a metabolic suite. Increased intake of red meat induced a significant (P<0.024) 3-fold increase from 40 + or - 7 to ab average of 113 + or - 25 microgram/day NOC, a range of exposure in faeces similar to that from tobacco-specific NOC in cigarette smoke. THe diets were isoenergetic and contained equal amounts of fat, but concentrations of heterocyclic amines were low. Faecal excretion of the promotor ammonia was significantly increased to 6.5 + or - 1.08 mmol/day. When the high red meat diets were supplemented with 20 g phytate-free wheat bran in six volunteers there was no reduction in NOC levels (mean 138 + or - 41 microgram/day NOC), but faecal weight increased. Higher starch and non-starch polysaccharide intakes reduced intraluminal cross-linking in microcapsules (r=-0.77) and reduced faecal pH (r=-0.64). In two volunteers there was no effect of 600 g white meat and fish o faecal NOC (mean low white meat diet 68 + or - 10 microgram/day, high white meat 56 + or -6 microgram/day nor on faecal nitrate, nitrite and iron. Faecal nitrite levels increased on changing from a white to red meat diet (mean high white meat diet 46 + or - 7 mg/day, high red meat diet mean 80 + or - 7 mg/day.) Increased endogenous production of NOC and precursors from increased red meat, but not white meat and fish, consumption may be relevant to the aetiology of colorectal cancer.

Formation of 8-nitroguanine by the reaction of guanine with peroxynitrite in vitro.

Nitric oxide and superoxide anion, both formed in inflamed tissues, react rapidly to form the peroxynitrite anion (ONOO-), a strong oxidant which can initiate reactions characteristic of hydroxyl radical (HO.), nitronium ion (NO2+) and nitrogen dioxide radical (NO2.). Peroxynitrite, therefore, may cause DNA or tissue damage, contributing to the multistage carcinogenesis process. We have studied reactions of various bases, nucleosides or deoxynucleosides with peroxynitrite in vitro. Guanine reacted rapidly with peroxynitrite under physiological conditions and formed several substances, two of which were yellow, a characteristic of nitro and nitroso compounds. On the basis of chromatographic and spectral evidence we identified the major compound (which accounts for approximately 80% of all compounds formed) as 8-nitroguanine. Its formation was maximal at approximately pH 8 and increased dose-dependently with peroxynitrite concentration, but was not dependent on guanine concentration. The presence of ferric ions, which has been shown to catalyse nitration of tyrosine, did not affect nitration of guanine. 8-Nitroguanine could act as a specific marker for DNA damage induced by peroxynitrite in inflamed tissues.