[Azomethine from hydroxyanthrone derivatives and 4-nitrosodimethylaniline].
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Aniline Compounds↗
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Central nervous system tumours in children: epidemiology and risk factors.
In children, a variety of distinct tumour types arise in the central nervous system (CNS) but they are frequently considered by epidemiologists as a single entity. CNS tumours are the second most common childhood malignancy and occur more frequently in developed countries than developing nations. Approximately 50% of paediatric CNS tumours are gliomas, with astrocytomas of the piloctyic type predominating. Distributions of subtypes by age show that primitive neuroectodermal tumours (PNET) and ependymomas mainly occur in children less than 10 years. There is an ongoing debate with regard to the apparent increases in incidence over recent decades, which, it has been suggested, are accounted for by improved diagnostic technologies implemented in the mid 1980s. CNS tumours differ between children and adults with respect to the proportion of all cancers (20% in children, less than 2% in adults), their cellular origins, classification scheme, the proportions of pathological subtypes, and anatomic site. The causes of childhood CNS tumours are largely unknown; and although an estimated 5% or more may be explained by genetic predisposition, investigations of environmental aetiology have not been fruitful. Whilst high dose ionising radiation is an established risk factor for this group of tumours, reported associations with dietary N-nitroso compounds have not been consistent. Exposure to ELF EMF, at any level, has not been associated with childhood CNS tumours, but the current evidence base is inadequate for complete evaluation. The rarity of childhood CNS tumours necessitates careful attention being paid to the design of future aetiological studies.
Bias↗
Membrane mass spectrometer inlet for quantitation of nitric oxide.
Nitric oxide (NO) is an important physiological and biochemical messenger that may be involved in endogenous carcinogenesis and cell toxicity via formation of N-nitroso compounds or direct DNA damage by nitrosating agents arising from the reaction of NO with O2. To study the reaction of NO with O2 in model systems and the formation and disappearance of NO in more physiological systems such as cell cultures, we adapted and optimized a membrane mass spectrometer inlet specifically for such analyses. The inlet consisted of Silastic tubing inserted into a Swagelok 'tee', which was attached to the mass spectrometer via the tuning probe. Kinetics of NO disappearance can be followed under electron impact conditions until NO2 interferes via the formation of NO+ during fragmentation of NO2+. The aqueous NO concentration for minimum detection was determined to be 1.4 microM. The inlet response time to step changes in aqueous NO concentrations was 7.0 s, fast enough to permit real-time measurements of aqueous NO changes upon addition of O2. Finally, the depletion of aqueous NO was observed in the presence of O2. The relative steady state responses of inlets designed for gas or aqueous samples, and their relative response times, are explained by an analysis based on mass transfer theory.
Kinetics↗
Comparative genomic hybridization analysis of N-methyl-N'-nitrosoguanidine-induced rat gastrointestinal tumors discloses a cytogenetic fingerprint.
Exposure to N-nitroso compounds is thought to play a key role in the development of gastric cancer in humans. The alkylating agent N-methyl-N'-nitrosoguanidine (MNNG) is carcinogenic in a number of animal models and its preferential target tissue is the gastrointestinal (GI) tract. The genetic synteny among rats and humans makes the rat a useful model for induced tumorigenesis. However, because of the limited availability of genetic information, cytogenetic and molecular studies are rarely performed in the rat. We report an investigation of eight MNNG-induced rat gastric tumors by comparative genomic hybridization (CGH). The tumors were from forestomach (induced by a single dose of MNNG) and from pylorus (induced by chronic exposure). CGH identified a genetic fingerprint of chromosomal imbalances common to the two types of the tumors. Frequent gains were observed at 9q11-q12, 15q22-25, and Xq11-q12. Forestomach carcinomas were also characterized by gains in 7q11-q12, 20q13, and Yq12. Homology studies between the rat and human genomes indicate the presence of genes within these regions with potential relevance to tumorigenesis in the GI tract. Our findings provide new insights into the location of genes involved in MNNG-induced gastric cancer initiation and/or progression in the rat.
Animals↗
Mutagenicity of urine from mice exposed orally to nitrite and various aminated antiparasitic drugs.
Mutagenic N-nitroso compound formation from the in vitro reaction of amebicides and anthelmintic drugs, which are pyrimidine derivatives or contain secondary aliphatic amines or heterocyclic nitrogens, has been previously described (Arriaga Alba et al.: Environmental and Molecular Mutagenesis 12:65-73, 1988). Under similar conditions, antiparasitic drugs containing halogenated derivatives of tertiary amines or quaternary ammonium salts do not form mutagenic nitrosated compounds. In the present study the mutagenic activity of mouse urine was determined after oral administration of sodium nitrite and the two above-mentioned groups of drugs (pyrantel pamoate, chloroquine, piperazine and dehydroemetine/iodochlorhydroxyquin and bephenium hydroxynaphthoate, respectively). Results show that the simultaneous administration of piperazine or chloroquine with sodium nitrite produced urinary mutagens that appeared conjugated as glucuronides, whereas pyrantel pamoate and dehydroemetine in the presence of nitrite caused only slightly mutagenic urine. No mutagenic activity was detected in the urine of mice to which halogenated derivatives of tertiary amines (iodochlorhydroxyquin) or quaternary ammonium salts (bephenium hydroxynaphthoate) were administered together with nitrite.
Amebicides↗
Nitrate and nitrite contents in Cuban cheese of the Gouda type.
The nitrate and nitrite contents in cheese of the Gouda type, produced by the Milk Complex of Havanna, were investigated and compared with those found in 5 types of imported cheese consumed in Cuba. No significant differences were found in the mean value (mean) of NaNO3, whereas in the mean value (mean) of NaNO2 differences were found when comparing all cheeses against each other. From these results it is inferred that the consumption of Gouda type cheese does not represent an important contribution to the daily intake of nitrates and nitrites, precursors in the synthesis of cancerogenic N-nitroso compounds.
Cheese↗
Estimation of the daily intake of nitrates and nitrites which children one to six years old, who attend State Nurseries in the City of Havanna, may consume.
The knowledge of the amounts of nitrates and nitrites consumed by the child population is of great importance due to three fundamental aspects: Reduction of nitrates to nitrites. Relation of these to methemoglobinemia. Carcinogenicity of the N-nitroso compounds, of which nitrites are the precursors. In the present article information is given as to the estimated amounts of nitrates and nitrites, which about 10 000 children between one and six years of age, who attend State Nurseries in the City of Havanna, may consume through the daily intake of food, milk and water offered by the Centralized Kitchen "Cuba-Finland Friendship". The method of analysis used to determine nitrates and nitrites is that reported by the Mixed Committee FAO/OMS in 1976, using a reducing column containing cadmium described by FOLLET et al. in 1963. The statistical method employed is the t-Test of the comparison of media. Estimated quantities of nitrates and nitrites, which these children may consume according to the offer of food, milk and water they receive, are: 25.6 mg of NaNO3 and 1.04 mg of NaNO2 for children one to three years of age, and 36.1 mg of NaNO3 and 1.48 mg of NaNO2 for children four to six. These values lie under those recommended as admissible daily intake reported by the Mixed Committee FAO/OMS. Therefore, there does not seem to exist a risk to health through consumption of nitrates and nitrites by the population under investigation.
Animals↗
Maternal medication use and the risk of brain tumors in the offspring: the SEARCH international case-control study.
N-nitroso compounds (NOC) have been associated with carcinogenesis in a wide range of species, including humans. There is strong experimental data showing that nitrosamides (R(1)NNO.COR(2)), a type of NOC, are potent neuro-carcinogens when administered transplacentally. Some medications are a concentrated source of amides or amines, which in the presence of nitrites under normal acidic conditions of the stomach can form NOC. Therefore, these compounds, when ingested by women during pregnancy, may be important risk factors for tumors of the central nervous system in the offspring. The aim of the present study was to test the association between maternal use of medications that contain nitrosatable amines or amides and risk of primary childhood brain tumors (CBT). A case-control study was conducted, which included 1,218 cases and 2,223 population controls, recruited from 9 centers across North America, Europe and Australia. Analysis was conducted for all participants combined, by tumor type (astroglial, primitive neuroectodermal tumors and other glioma), and by age at diagnosis (< or =5 years; >5 years). There were no significant associations between maternal intake of medication containing nitrosatable amines or amides and CBT, for all participants combined and after stratification by age at diagnosis and histological subtype. This is the largest case-control study of CBT and maternal medications to date. Our data provide little support for an association between maternal use of medications that may form NOC and subsequent development of CBT in the offspring.
Adolescent↗
Cigarette smoking and risk of glioma: a prospective cohort study.
The etiology of glioma, the most commonly diagnosed malignant brain tumor among adults in the United States, is poorly understood. N-nitroso compounds are known carcinogens, which are found in cigarette smoke and can induce gliomas in rats. On this basis, it has been hypothesized that cigarette smoking may be associated with an increased risk of glioma. We investigated the association between cigarette smoking and glioma risk in the National Breast Screening Study, which included 89,835 Canadian women aged 40-59 years at recruitment between 1980 and 1985. Linkages to national cancer and mortality databases yielded data on cancer incidence and deaths from all causes, respectively, with follow-up ending between 1998 and 2000. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between cigarette smoking and risk of glioma. During a mean of 16.4 years of follow-up, we observed 120 incident glioma cases. Among ever smokers, women who reported having quit smoking had a 51% increase in risk of glioma compared with never smokers (HR = 1.51, 95% CI = 0.97-2.34), while current smokers did not appear to have an increase in risk. When the association with former smokers was further examined by years since quitting, women who had quit smoking >10 years before baseline were at a decreased risk of glioma compared with women who had quit within the 10 years prior to baseline (HR = 0.55, 95% CI = 0.29-1.07), indicating that the association between former smokers and glioma may be driven by women, who recently quit smoking. Compared with nonsmokers, duration of cigarette smoking, number of cigarettes smoked per day and pack-years of smoking were associated with increased glioma risk, although the increases in risk were relatively modest. The present study provides some support for a positive association between cigarette smoking and risk of glioma.
Adult↗
Transplacental induction of lymphomas in Swiss mice by carbendazim and sodium nitrite.
Swiss mice at different stages of pregnancy were treated intragastrically with the pesticide Carbendazim (MBC, BCM, methyl-2-benzimidazole carbamate) together with sodium nitrite. Lymphomas developed in 33.3% of young mice whose mothers were treated in the first week of pregnancy, in 53.3% of whose mothers were treated during the second week, and in 38.8% of those born of mothers treated during the third week. Treatment during the whole period of pregnancy yielded on an average 70.0% malignancy in offspring. However, administration of Carbendazim by itself did not produce lymphomas in the first generation. In lymphomas induced by in vivo-formed n-nitroso compounds, A- and C-type oncornavirus particles were observed with the electron microscope.
Animals↗
Survey of a population with a high incidence of oral and oesophageal cancer.
The results of a survey of a population with a high incidence of oral and oesophageal cancer are presented. The population under study appears to have several epidemiologic characteristics, some of which may be associated with a high incidence of oral and oesophageal cancer. A remarkably high proportion (41%) of the men surveyed were nass users and this habit, like the use of other types of tobacco mixtures, has been related to oral cancer. Oral leukoplakia and chronic oesophagitis (conditions thought to be precursors of oral and oesophageal cancer) have been diagnosed in 11% and 60%, respectively, of the persons examined. Analysis of the relationship between nass use, cigarette smoking, oral leukoplakia and oesophagitis revealed that the prevalence of oral leukoplakia is highest among cigarette smokers who use nass. It appears that nass use does not affect the frequency of occurrence of chronic oesophagitis. However, a slight elevation of the prevalence odds ratio was observed for current smokers and drinkers. Biochemical analysis of the blood of a random sample of the surveyed population revealed low levels of riboflavin, vitamin A and carotenoids--vitamins that most probably have a protective effect against the development of cancer. The mutagenicity test has shown that nass contains a chemical or chemicals that exert a genotoxic effect. Chemical analysis revealed the presence in nass of tobacco-specific N-nitroso compounds.
Aged↗
Volatile nitrosamine levels and genotoxicity of food samples from high-risk areas for nasopharyngeal carcinoma before and after nitrosation.
Traditional life-style, especially food habits, infection by Epstein-Barr virus (EBV) and genetic factors, have been associated with an increased risk of nasopharyngeal carcinoma (NPC). N-Nitroso compounds and other carcinogens either present in food or formed endogenously, as well as food constituents that activate EBV, have been suspected as etiological factors in NPC pathogenesis. For their characterization preserved food items, frequently consumed in NPC endemic areas in Tunisia, South China and Greenland, were sampled and screened for the presence of mutagens and volatile nitrosamines before and after nitrosation. Aqueous extracts as well as 2 organic extracts of the samples were assayed for genotoxicity in 2 Salmonella typhimurium strains and the SOS chromotest. The same extracts had previously been analyzed for volatile nitrosamines and for EBV-activating substances in Raji cells. In our study, 13 out of 16 food samples showed a weak, directly-acting genotoxicity in the SOS chromotest in at least one of the extracts, but only one sample from Greenland was found to be weakly mutagenic in Salmonella TA 98. Chemical nitrosation for 9 out of 15 samples of aqueous food extracts increased the genotoxic effect in the SOS chromotest. Levels of volatile nitrosamines were also elevated for 12 out of 15 samples; highest levels of N-nitrosodimethylamine were found in hard salted and dried fish from China (1,200 micrograms/kg) and highest N-nitrosopyrrolidine levels in a Tunisian spice (3,840 micrograms/kg). In non-nitrosated aqueous food extracts, the level of volatile nitrosamines and genotoxic activities were not correlated with the EBV-inducing activity of the same samples. After chemical nitrosation, EBV-inducing activity was decreased or showed no change and was not correlated with increases in either the genotoxicity or the nitrosamine levels. Our results suggest that EBV-activating compounds belong to a different class of substances. However, there was an association between the changes in genotoxicity and nitrosamine levels due to nitrosation.
Carcinoma↗
A case-control study of gastric cancer and diet in Italy: II. Association with nutrients.
A case-control study involving interviews with 1,016 gastric cancer (GC) patients and 1,159 population-based controls in high- and low-risk areas was conducted to evaluate dietary factors and their contribution to the marked geographic variation in mortality from this cancer within Italy. Risks of GC were found to vary significantly with estimated nutrient intake. Risk rose with increasing consumption of nitrites and protein, and decreased in proportion to intake of ascorbic acid, beta-carotene, alpha-tocopherol, and vegetable fat. The associations with nitrite and beta-carotene tended to fade, however, in multivariate analyses adjusting for intake of other nutrients. Ascorbic acid showed the strongest geographic gradient, with highest consumption in low-risk areas. The findings suggest that the protective effects we previously reported for consumption of fresh fruit, fresh vegetables and olive oil may be linked to the vitamins C and E contained in these foods. The findings are consistent with the hypothesis that N-nitroso compounds are involved in GC risks, since elevated risks were apparent for agents (nitrites, protein) that promote nitrosation, while decreased risks were found for nutrients (ascorbic acid and alpha-tocopherol) which inhibit the process.
Case-Control Studies↗
Occurrence of non-gastric cancer in the digestive tract after remote partial gastrectomy: analysis of an Amsterdam cohort.
If peptic ulcer surgery favors the formation of carcinogenic N-nitroso compounds in the gastric remnant, an increased risk of cancer at sites in the gastrointestinal tract distant from the stomach might be predicted. To estimate the risk of carcinomas in the digestive tract, other than the stomach, occurring after partial gastrectomy, we analyzed an Amsterdam cohort of 2,633 post-gastrectomy patients operated on for benign disease between 1931 and 1960. Mortality in the study population was compared with the general Dutch population through person-year analysis. An excess mortality of biliary tract cancer (O/E:2.64; CL:1.32-4.72; p less than 0.01) and pancreatic cancer (O/E:1.65; CL:1.06-2.44; p less than 0.05) was found in males more than 5 years after surgery; females showed only an increased risk of pancreatic cancer in the first 5 years postoperatively (O/E:15.33; CL:1.85-55.43; p less than 0.01), probably due to misdiagnosis. All other non-gastric sites of the digestive tract carried no increased risk for cancer. In males, mortality due to colorectal cancer more than 5 years post-operatively was significantly decreased (O/E:0.58; CL 0.34-0.92; p less than 0.01). The excess mortality of biliary-tract and pancreatic cancer in males, which increases with the duration of post-operative interval, is consistent with a dose-response phenomenon. This study therefore supports the hypothesis that carcinogens are not only locally activated in the gastric remnant, but are hepatically excreted and initiate cancer in the biliary tree and pancreatic duct. Further exploration of this mechanism of carcinogenesis is warranted, since it may also explain the pathogenesis of pancreatic and biliary cancers in patients without gastrectomy.
Biliary Tract Neoplasms↗
Cytotoxic and cytostatic effects of arecoline and sodium nitrite on human cells in vitro.
Arecoline, an active alkaloid of Areca catechu L., and sodium nitrite, a food additive, are highly cytotoxic and cytostatic on the Hep 2 cell line when administered in an acidic environment (pH 4.2) in the presence of S-9 mixture. Hep 2 cells (10(6)) were treated with either 0.145, 0.725 or 1.449 mM sodium nitrite or 0.042, 0.085 or 0.339 mM arecoline or sodium nitrite (0.145 mM) plus varied concentrations of arecoline (0.042, 0.085 or 0.339 mM). Their effects were additive in nature. Hep 2 cells exposed to this combination showed reduced cell survival, and lower rates of DNA and protein syntheses. Involvement of N-nitroso derivatives of arecoline is suggested to explain the results. On the basis of these studies, we speculate that N-nitroso compounds derived from arecoline can (weakly) interact with DNA.
Arecoline↗
Dietary carcinogens and the risk for glioma and meningioma in Germany.
A population-based case-control study was performed in South-West Germany in 1987/88 with 115 histological confirmed glioma and 81 meningioma cases and 418 randomly selected controls. On the basis of information from a food-frequency questionnaire and questions on food preparation and food supply, the role of dietary carcinogens, in particular N-nitroso compounds or their precursors, on risk for glioma and meningioma were analyzed by multiple logistic regression. Eleven food groups were investigated. The intake of processed meat was significantly associated with an increased risk of glioma. The intake of any food group was not significantly related to meningioma risk. Among single meat products, a significantly higher risk of glioma was found for cooked ham, processed pork meat and fried bacon. For the consumption of 3 N-nitrosamines, assessed from the intake of processed meat and cheese, significant positive relations to glioma risk were found. These N-nitrosamines were also related to meningioma risk, although to a less pronounced extent. The risk for occurrence of glioma was significantly increased for those using vegetable fat frequently for deep frying, as compared with non-users. For the dietary intake of nitrate, nitrite, vitamin C, specific alcoholic beverages, total alcohol, and water from a non-central supply, no elevated risk was found in this study.
Alcohol Drinking↗
Perinatal and early postnatal risk factors for malignant brain tumours in New South Wales children.
A population-based case-control study of incident primary malignant brain tumours diagnosed during 1985-1989 in children aged 0 to 14 years was carried out in the coastal conurbation of New South Wales comprising Sydney, Wollongong and Newcastle in the period 1988 to 1990. Personal interviews were conducted using a structured questionnaire with mothers of 82 cases and 164 control children individually matched to the cases by sex and age. Among the hypotheses examined were those related to: N-nitroso compounds (sources included diet, dummies, medications, tobacco smoke); factors associated with the birth of the child; trauma to the head; and irradiation (X-rays and electromagnetic radiation through electric blankets or water beds). Reported ever-use of a dummy increased the risk of childhood brain tumours (OR = 2.9, 95% CI 1.6 to 5.4), although there did not appear to be any consistent indication of rising risk with reported increased levels of use. Compared with children who had never used a dummy, categories of use during the first year of life of a maximum of "no more than 1 hour per day or night", "several hours per day or night", and "most of the day or night" had statistically significant odds ratios of 2.6, 3.4, and 2.7 respectively. Consumption of fruit by the child before the age of one appeared to be protective. No association was found between childhood brain tumours and birth weight, being the first-born child, or factors linked with the child's birth; head injuries; exposure to X-rays; contact with horses, or living on a farm; pesticide treatment of the house during the child's lifetime; or exposure to burning incense.
Adolescent↗
Endothelium-derived relaxing and contracting factors.
Key discoveries in the past decade revealed that the endothelium can modulate the tone of underlying vascular smooth muscle by the synthesis/release of potent vasorelaxant (endothelium-derived relaxing factors; EDRF) and vasoconstrictor substances (endothelium-derived contracting factors; EDCF). It has become evident that the synthesis and release of these substances contribute to the multitude of physiological functions the vascular endothelium performs. Accumulating evidence suggests that at least one of the EDRFs is identical with nitric oxide (NO) or a labile nitroso compound, which is produced from L-arginine by an NADPH- and Ca(2+)-dependent enzyme, arginine oxidase. The existence of more than one chemically distinct EDRF has been proposed, including an endothelium-derived hyperpolarizing factor (EDHF). The target of EDRF (NO) is soluble guanylate cyclase (increase in cyclic GMP) while EDHF appears to activate a K(+)-channel in vascular smooth muscle. Recent data suggest that muscarinic receptor subtypes selectively mediate the release of EDRF(NO) (M2) and EDHF (M1). EDRF(NO) affects not only the underlying vascular smooth muscle, but also platelets, inhibiting their aggregation and adhesion to the endothelium. The antiaggregatory effect of EDRF is synergistic with prostacyclin, so their combined release may represent a physiological mechanism aimed at preventing thrombus formation. An additional proposed biological function of EDRF(NO) is cytoprotection by virtue of scavenging superoxide radicals. The endothelium can also mediate vasoconstriction by the release of a variety of endothelium-derived contracting factors (EDCF). Other than the unique peptide endothelin, the nature of EDCFs has not yet been firmly established. Autoregulation of cerebral and renal blood flow and hypoxic pulmonary vasoconstriction may represent the physiological role of endothelium-dependent vasoconstriction. Growing evidence indicates that the endothelium can serve as a unique mechanoreceptor, sensing and transducing physical stimuli (e.g., shear forces, pressure) into changes in vascular tone by the release of EDRFs or EDCFs. In physiological states, a delicate balance exists between endothelium-derived vasodilators and vasoconstrictors. Alterations in this balance can result in local (vasospasm) and generalized (hypertension) increase in vascular tone and also in facilitated thrombus formation. Endothelial dysfunction may also contribute to the pathophysiology of angiopathies associated with hypercholesterolemia and atherosclerosis.
Animals↗