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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ionic complex between lysozyme and either Escherichia coli DNA or pBR322 DNA was not crosslinked by two systems capable of producing nanomolar amounts of hydroxyl radicals, the oxidation of xanthine by xanthine oxidase and the iron catalyzed oxidation of ascorbic acid. Nor did effective crosslinking occur with micromolar quantities of hydroxyl radicals raised by the addition of adenosine nucleotides to ferrous iron and hydrogen peroxide. In this case, radical content was estimated by colorimetric analysis of formaldehyde following hydroxyl radical oxidation of dimethyl sulfoxide. Similar amounts of radicals generated by pulse radiolysis in a nitrous oxide atmosphere failed also to induce crosslinking. These findings do not support a role for hydroxy radicals in the N-acetoxy-2-acetylaminofluorene induced crosslinking of DNA to lysozyme proposed earlier.
Carcinogenesis 1985 Dec
PMID:Hydroxyl radicals do not crosslink a DNA-lysozyme complex. 299 38

Ethanol, potassium metabisulfite, formaldehyde and hydrogen peroxide were tested for tumor-promoting activity in a two-stage stomach carcinogenesis experiment. Male outbred Wistar rats were given N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the drinking water (100 mg/liter) and a diet supplemented with 10% sodium chloride for 8 weeks. Thereafter, they were maintained on drinking water containing either 10% ethanol, 1% potassium metabisulfite, 0.5% formalin (formaldehyde) or 1% hydrogen peroxide for 32 weeks and then sacrificed for necropsy and histological examination. In the pylorus of the glandular stomach, potassium metabisulfite and formaldehyde significantly increased the incidence of adenocarcinoma after initiation with MNNG and sodium chloride. Hydrogen peroxide did not enhance the tumor yield, and ethanol showed a tendency to decrease neoplastic development. In the forestomach the incidence of squamous cell papilloma was significantly increased in the groups given hydrogen peroxide or formaldehyde, irrespective of prior initiation. Duodenal adenocarcinoma was induced by the initiation alone (10%) and the incidence was not affected by the subsequent treatments. The results indicate that potassium metabisulfite and formaldehyde both exert tumor-promoting activity in the rat glandular stomach.
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PMID:Effects of ethanol, potassium metabisulfite, formaldehyde and hydrogen peroxide on gastric carcinogenesis in rats after initiation with N-methyl-N'-nitro-N-nitrosoguanidine. 308 23

Administration of formaldehyde at doses of 11 to 110 mg/kg body weight by gastric intubation to male F344 rats induced up to 100-fold increase in ornithine decarboxylase activity with a maximum after 16 hr and up to 49-fold increase in DNA synthesis with a maximum after 16 hr in the pyloric mucosa of the stomach. These results suggest that formaldehyde has tumor-promoting activity in carcinogenesis in the glandular stomach.
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PMID:Inductions of ornithine decarboxylase and DNA synthesis in rat stomach mucosa by formaldehyde. 314 27

Hydrazine is acutely neurotoxic, hepatotoxic and nephrotoxic; it is also carcinogenic to liver and lung in rodents. Administration of hydrazine results in formation of 7-methylguanine and O6-methylguanine in target organ DNA of rats, mice, hamsters and guinea-pigs. It has been suggested that hydrazine reacts with endogenous formaldehyde to form a condensation product which could be metabolized to a methylating agent. Solutions of 0.50 mM hydrazine and formaldehyde have, upon mixing, NMR spectra (300 MHz) consistent with the formation of formaldehyde hydrazone but not other possible condensation products such as tetraformyltriazine or formaldehyde azine. These same solutions evidencing hydrazone formation, when incubated in an in vitro system containing post-mitochondrial (S9), microsomal, cytosolic or mitochondrial cell fractions, resulted in the methylation of DNA guanine; S9 was the most active fraction. Neither the P-450 monooxygenase nor flavin monooxygenase systems appeared to be important in hydrazine/formaldehyde-induced methylation of DNA. However, sodium azide, cyanamide and carbon monoxide all inhibited S9-supported DNA methylation. Bovine liver catalase, a heme-containing cytochrome, readily transformed hydrazine/formaldehyde to a methylating agent. The data support formation of formaldehyde hydrazone as the condensation product of hydrazine and formaldehyde which is rapidly transformed in various liver cell fractions, perhaps by catalase and/or catalase-like enzymes, to a methylating agent.
Carcinogenesis 1988 Jan
PMID:Role of formaldehyde hydrazone and catalase in hydrazine-induced methylation of DNA guanine. 333 49

Nitrosodimethylamine (NDMA), like several other nitrosamines, is activated by the enzymes--mixed-function oxidases--present in the tissue microsomal fractions, producing mutagenic and carcinogenic effects. Previous studies in BALB/c mice have shown an age, sex and androgenic regulation of NDMA-induced mutagenicity. The present study was designed to test the correlation between renal NDMA-demethylase activity and previously published reports on NDMA-induced mutagenicity. Renal and hepatic NDMA-demethylases were determined from the microsomal fractions by quantitating formaldehyde. Renal NDMA-demethylase showed the presence of two isozymes, I and II, with Km values of 0.6 +/- 0.2 and 20.2 +/- 6.8 mM respectively. Isozyme I was detected in adult males and first appeared at the onset of puberty; it was absent in adult females and in immature mice. Renal isozyme II was detected in both males and females and was independent of age. Testosterone treatment of adult females resulted in the appearance of renal isozyme I. Castration of adult males caused a dramatic decrease in activity, whereas testosterone administration to such castrates increased activity, of renal isozyme I. Hepatic NDMA-demethylase activities were independent of age, sex or testosterone treatment. In conclusion, these results show an age, sex and tissue specific regulation of renal NDMA activity. Renal and hepatic NDMA-demethylase activities correlated positively with earlier studies on NDMA-induced mutagenesis and carcinogenesis.
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PMID:Tissue specific regulation of renal N-nitrosodimethylamine-demethylase activity by testosterone in BALB/c mice. 339 Feb 28

The effects of benzo[a]pyrene (BAP) and formaldehyde (HCHO), alone and combined, on cell growth and DNA damage were determined in primary cultures of rat tracheal epithelial cells dissociated from rat tracheas. Cell cultures treated with 25 microM BAP for 24 h or 200 microM HCHO for 90 min did not have a marked reduction in cell growth. However, their combined treatment reduced cell growth by 60% of control when cultures were exposed to BAP followed by HCHO as well as the reverse order. None of these treatments significantly decreased cell viability as judged by dye exclusion, nor did they enhance cell terminal differentiation as measured by cornified envelope formation. Alkaline elution analysis of DNA damage detected both DNA-protein crosslinks (DPC) and DNA single-strand breaks (SSB) as a result of HCHO treatment, whereas BAP treatment caused only SSB. While HCHO-induced SSB were repaired within 2 h, BAP-induced SSB were detected 3 days after treatment. Combined treatment of cell cultures with BAP followed by HCHO resulted in more SSB than was obtained from either agent alone, but less DPC than was detected from HCHO alone. The increased number of SSB obtained from this combined treatment may be related to the marked enhancement of carcinogenesis observed in earlier in vivo-in vitro studies.
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PMID:Growth inhibition and DNA damage induced by benzo[a]pyrene and formaldehyde in primary cultures of rat tracheal epithelial cells. 341 44

The interdisciplinary evaluation of risks from carcinogens utilizes, inter alia, data on the activities of the compounds in short-term assays. A systematic approach is being used to determine mutagenesis in bacteria (the study of direct activities and specific modes of metabolic activation), DNA damage within primary mammalian cells (DNA single-strand breaks and persistence of damage, by a method extendable to the in vivo situation) and amplified DNA sequences in cultured cells (as an endpoint probably relevant to carcinogenesis). This test combination was expected to reduce some of the shortcomings of other batteries of tests, which suffer from a lack of appropriate metabolic conversion of compounds, irrelevancy of genetic endpoints and pharmacokinetic limitations. Furthermore, as each assay in the test strategy differs from the others only by one of the parameters described above, a reasonable understanding of divergent test results from assay to assay was anticipated. Several substances were investigated to elucidate why their activities in short-term assays and in carcinogenesis experiments do not correlate. The substances were N-nitrodimethylamine, for which formaldehyde is the reactive intermediate in bacterial mutagenesis but not in mammalian cells or in vivo, N-nitrosodiethanolamine, a carcinogen that must be activated by external alcohol dehydrogenase to be mutagenic in bacteria, N-nitrosodialkylamines, with unique organotropism in vivo for which organ-specific activation was studied in vitro, N-nitroso compounds that are inactivated in vivo but not in vitro, and components of the aristolochic acid mixture which may be metabolized oxidatively or reductively, as well as numerous miscellaneous compounds that were expected to be genotoxins on account of their chemical structure. In addition to the assessment of genotoxicity, the results obtained in individual tests of this strategy yield important data on mechanisms of activity, such as organ-specific activation and deactivation, species variations, in vitro/in vivo correlation and persistence or repair of damage.
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PMID:Detection of mutations in bacteria and of DNA damage and amplified DNA sequences in mammalian cells as a systematic test strategy for elucidating biological activities of chemical carcinogens. 353 93

The effects of exposure to benzo[a]pyrene (BAP) and formaldehyde (HCHO), alone and combined, on the induction of carcinogenesis in rat tracheal implants was determined as the number of growth-altered cell populations (tumor-initiation sites, TIS) per trachea. While exposure twice-weekly for 4.5 months to 0.2% HCHO solution gave only a weak response (0.25 TIS/trachea), 2.37 TIS per trachea were detected after exposure to 20 micrograms BAP in the same regimen. The combination of BAP followed by HCHO had a greater response than either agent alone (7.83 TIS/trachea), while the reverse exposure gave 1.49 TIS per trachea, which was less than BAP alone. Thus, the induction of TIS by combined exposure to BAP and HCHO was dependent on the order of exposure, and could not be predicted from their individual exposures.
Carcinogenesis 1987 Dec
PMID:The induction of growth-altered cell populations (tumor-initiation sites) in rat tracheal implants exposed to benzo[a]pyrene and formaldehyde. 367 20

The metabolism of N-nitrosomorpholine by rat liver microsomes gave acetaldehyde, formaldehyde, glyoxal and N-nitroso-2-hydroxymorpholine. Oxidation of N-nitrosomorpholine by Fenton's reagent gave acetaldehyde, glycolaldehyde, glyoxal, (2-hydroxyethoxy)acetaldehyde and N-nitroso-2-hydroxymorpholine. N-Nitroso-3-hydroxymorpholine was synthesised. In water the new compound gave mainly acetaldehyde, with glycolaldehyde, (2-hydroxyethoxy)acetaldehyde and glyoxal. These observations indicated the probability of 3-hydroxylation in the biological and chemical oxidations. N-Nitroso-3-morpholone behaved similarly in water to the 3-hydroxy compound, and gave mainly acetaldehyde, with glycollic acid, (2-hydroxyethoxy)acetic acid and glyoxal. N-Nitroso-3-morpholone and N-nitroso-3-hydroxymorpholine reacted with 3,4-dichlorobenzenethiol. The action of light or alkali on N-nitrosomorpholine gave glyoxal and labile glyoxal-yielding compounds.
Carcinogenesis 1986 Apr
PMID:The metabolism of N-nitrosomorpholine by rat liver microsomes and its oxidation by the Fenton system. 369 87

Acetaldehyde and formaldehyde have been found to induce nasal cancer in two species of rodents. To understand the mechanism of carcinogenesis by acetaldehyde, studies were carried out to determine whether acetaldehyde can react with DNA in target tissues of the rat nasal cavity. When fresh homogenates of the nasal respiratory mucosa were incubated with acetaldehyde (distilled under N2) at concentrations of 10, 100, or 500 mM, followed by solubilization and extraction with a strongly denaturing aqueous-immiscible organic solvent mixture, a decrease was observed in the amount of DNA partitioned into the aqueous phase at the two higher acetaldehyde concentrations. The absent DNA was recovered from the interfacial layer by proteolytic digestion. Similarly, incubation of calf thymus nucleohistones with acetaldehyde (100, 300, Similarly, incubation of calf thymus nucleohistones with acetaldehyde (100, 300, or 1000 mM) or with formaldehyde (10, 30, or 100 mM) followed by precipitation of the DNA with H2SO4 and analysis of the supernatants by sodium dodecyl sulfate-polyacrylamide gel electrophoresis resulted in concentration-dependent decreases in the quantities of histone proteins released from the DNA. These results indicate that acetaldehyde as well as formaldehyde can form DNA-protein crosslinks in vitro. A single 6-hr exposure of male Fischer-344 rats to acetaldehyde (100, 300, 1000, or 3000 ppm) resulted in a significant increase relative to air-exposed controls in the percent interfacial DNA from the nasal respiratory mucosa at concentrations equal to or greater than 1000 ppm. No increase in the interfacial DNA from the olfactory mucosa was detected after a single 6-hr exposure (1000 or 3000 ppm), but a significant increase was found in rats hr/day for 5 days) to acetaldehyde (1000 ppm). Thus, evidence has been obtained hr/day for 5 days) to acetaldehyde (1000 ppm). Thus, evidence has been obtained for the formation of DNA-protein crosslinks by acetaldehyde in target tissues of the rat nasal cavity at concentrations similar to those that induced nasal cancer.
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PMID:Decreased extractability of DNA from proteins in the rat nasal mucosa after acetaldehyde exposure. 369 37


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