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Biomedical subjects

B L Pool

Publications and source records attributed to B L Pool.

At least 37 records · Page 2Linked to original sources
PubMed1986

Determination of DNA single strand breaks and selective DNA amplification by N-nitrodimethylamine and analogs, and estimation of the indicator cells' metabolic capacities.

N-nitrodimethylamine is metabolized oxidatively to N-nitrohydroxymethylmethylamine, which decomposes to yield formaldehyde and N-nitromethylamine. All four compounds and N-nitromethylamine were tested for their ability to induce DNA single strand breaks in hepatocytes and in SV 40-transformed Chinese hamster embryo cell lines. Only the two monoalkylnitramines were positive. They induced single strand breaks in hepatocytes, but were not effective in the other cells. Formaldehyde and N-nitrohydroxymethylmethylamine were toxic to the cells. None of the compounds tested was able to induce selective DNA amplification in the two transformed cell lines. Enzymes involved in drug metabolism were assayed in the hamster cell lines. The activity of UDP-glucuronosyltransferase and cytosolic epoxide hydrolase were not detectable. N-nitrodimethylamine demethylation was low. The content of reduced glutathione and the activities of glutathione transferase and membrane bound epoxide hydrolase were comparable to values obtained in the rat liver.

Animals↗
PubMed1986

Biological activity of N-nitrosodiethanolamine and of potential metabolites which may arise after activation by alcohol dehydrogenase in Salmonella typhimurium, in mammalian cells, and in vivo.

The potent carcinogen N-nitrosodiethanolamine (NDELA) which is nonmutagenic in standard modifications of the S. typhimurium/mammalian microsome assay, can be activated effectively by alcohol dehydrogenase/NAD (ADH/NAD) to intermediates which are directly mutagenic in strains TA 98 and TA 100. The expected metabolites N-nitroso-2-hydroxymorpholine (NHMor), N-nitroso-(2-hydroxyethyl)-glycine (NHEG), N-nitrosoiminodiacetic acid (NIDA), and glycolaldehyde were assayed for their direct mutagenic activities in S. typhimurium TA 1535, TA 98, and TA 100. All compounds were clearly mutagenic in TA 100, but different specificities were observed for the other strains. NDELA and its putative mutagenic metabolites were also tested for induction of genotoxic activities by determination of DNA single strand breaks in primary rat hepatocytes. In these cells, NDELA and NHMor were clearly genotoxic, whereas NHEG and NIDA were inactive. In contrast, when assayed for the induction of selective DNA amplification NDELA and its metabolites were not found to induce SV40 DNA synthesis in SV40-transformed Chinese Hamster cells. The compounds were also assayed for induction of DNA single strand breaks in the liver after a single oral application to rats. NDELA and NHMor were about equally active in this in vivo test, whereas NHEG, NIDA and glycolaldehyde were inactive. Differences in biological activity in the cultivated cells, as compared to hepatocytes or to the in vivo situation may most probably be due to differences in metabolism and/or pharmacokinetics.

Acetaldehyde↗
PubMed1986

Identification and mutagenicity of metabolites of aristolochic acid formed by rat liver.

The rat liver 9000 g supernatant mediated metabolism of the carcinogenic aristolochic acid, which consists of aristolochic acid I (AAI) and aristolochic acid II (AAII), was investigated. Under anaerobic conditions the major metabolites were the corresponding aristolactams for both AAI and AAII. In contrast under aerobic conditions AAII was not detectably metabolized and the only metabolite found for AAI was the O-demethylated derivative aristolochic acid Ia (AAIa). The metabolites were identified by their u.v., mass and n.m.r. spectra and by comparison with reference standards. The mutagenic activities of the three metabolites were determined in Salmonella typhimurium strains TA1537 and TA 100. The aristolactams were mutagenic in both strains when a metabolizing system was present. These results indicate that AAI or AAII and their aristolactams exert their effect via a common reactive intermediate, probably the corresponding hydroxylamine. AAIa was only very weakly mutagenic and this metabolite may therefore not be regarded as a major mutagenic metabolite of AAI. These findings suggest that the acids are preferentially metabolized by two totally different pathways in vitro, namely an oxidative pathway for AAI and a reductive pathway for AAII.

Animals↗
PubMed1985

Synthesis, toxicity, and therapeutic efficacy of 4-amino-N-(2'-aminophenyl)-benzamide: a new compound preferentially active in slowly growing tumors.

The present paper describes 4-amino-N-(2'-aminophenyl)benzamide (GOE1734) with regard to synthesis; toxicity in mice, rats, and dogs; and differential therapeutic efficacy in slowly and rapidly proliferating rat tumors. GOE1734, an analog of a group of compounds known for other than antitumor effects with relatively simple N-acyl-O-phenylenediamine structure, is characterized by a low bacterial mutagenic potential after in vitro metabolic activation and DNA-DNA crosslinking activity after in vivo treatment. Maximum tolerated doses in rats and dogs amount to 4 and 1 mg/kg, respectively. High growth-inhibiting efficacy was obtained in intratibially implanted osteosarcoma, in methylnitrosourea-induced primary mammary carcinoma, and in acetoxymethyl-methylnitrosamine-induced colorectal adenocarcinoma. GOE1734 proved to be ineffective in transplanted Yoshida sarcoma and Walker 256 carcinosarcoma when single or multiple doses were administered at dose levels that were moderately toxic or not toxic. Some antitumor effects were observed in L5222 leukemia after ip transplantation, but no effect could be observed after ic implantation or in vitro incubation and subsequent retransplantation of these cells. Since the latter three rat tumors are characterized by relatively short tumor volume doubling times (0.5-2 days), whereas the first three grow slower (tumor volume doubling time, 11-19 days), the remarkable differential antitumor activity of GOE1734 in fast and slowly growing malignancies is striking.

Animals↗
PubMed1984

Mutagenicity studies on N-nitrosated products of the Maillard browning reaction: N-nitroso-fructose-amino acids.

The N-nitroso derivatives of D-fructose-L-glycine, D-fructose-L-alanine, D-fructose-L-phenylalanine, D-fructose-L-serine, Dfructose-L-aspartic acid and D-fructose-L-tryptophan (a mixture of alpha-N-nitroso-D-fructose-L-tryptophan and 'indolyl-nitrosamine'-D-fructose-L-tryptophan) were tested for mutagenicity in five auxotrophic strains of Salmonella typhimurium with and without metabolic activation (S-9 mix). The alanine, phenylalanine and aspartic acid compounds were not mutagenic. The glycine and serine compounds showed a very low but reproducible increase in the numbers of his+ revertants in strain TA1535 without S-9 mix. The mixture containing both nitrosated D-fructose-L-tryptophan compounds was mutagenic in all five strains, with or without metabolic activation. The alpha-N-nitroso-D-fructose-L-tryptophan component of the mixture, which is nitrosated at the amino group, was isolated and tested without S-9 mix. It was mutagenic in three strains. Unnitrosated D-fructose-L-amino acids, D-fructose, and the individual L-amino acids were non-mutagenic when tested under those conditions for which a positive response had been obtained with the corresponding nitrosated compounds. These results indicate the potential value of developing analytical methods to identify alpha-N-nitroso-D-fructose-L-tryptophan in food or food extracts that are to be screened for mutagenic components.

Amino Acids↗
PubMed1984

Mutagenicity of the two main components of commercially available carcinogenic aristolochic acid in Salmonella typhimurium.

One of the 2 main components of the commercially available carcinogenic aristolochic acid (AA) was isolated, the other was enriched. Three different aristolochic acid samples (AAI 99% pure; AAI 65% + AAII 35%; AAI 32% + AAII 68%) were assayed for mutagenic activity in Salmonella typhimurium TA1537, TA100 and TA100 NR with and without the addition of a metabolizing mixture. The two main components (AAI and AAII) were direct mutagens in Salmonella strains TA1537 and TA100 with almost equal mutagenic potency. In TA100 NR the aristolochic acid samples showed no or only a very low level of biological activity, indicating the necessity of nitroreduction for the bioactivation of the samples. These findings suggest that both AAI as well as AAII can be used in further studies to elucidate the metabolism of aristolochic acid.

Aristolochic Acids↗
PubMed1984

Mutagenic properties of N-cyclopropyl and N-allyl-N-nitroso compounds. Studies on the nature of alkylating species.

A series of directly acting N-nitroso compounds, N-nitroso-N-allyl urea 6, N-nitroso-N-cyclopropyl urea 7, N-nitroso-acetoxymethyl-allylamine 8, N-nitroso-acetoxymethyl- cyclopropylamine 9, N-nitroso(1- acetoxyethyl )allylamine 10 and N-nitroso(1- acetoxyethyl ) cyclopropylamine 11, which may hydrolize to liberate either cyclopropylating or allylating electrophiles, were synthesized and comparatively investigated for mutagenicity in Salmonella typhimurium TA 1535. Hydrolysis rates in aqueous buffered solution do not differ significantly in the allyl- and cyclopropyl series. Analysis of the hydrolysate of all compounds revealed only the presence of allylalcohol and not cyclopropanol . In contrast to the expected equal potencies, due to chemical rearrangement of the alkylating species from cyclopropylcation to allylcation , the results showed that the cyclopropylating analogs were much more effective mutagens than were the allylating compounds. We conclude that for the cyclopropylating compounds the diazonium ion intermediate - and not the free cation - is the alkylating species, during mutagenesis.

Alkylation↗
PubMed1984

Formaldehyde as a possible mutagenic metabolite of N-nitrodimethylamine and of other agents which are suggested to yield non-alkylating species in vitro.

N-Nitramines are biologically active compounds of environmental significance. In this study the suggested bioactivation of N- nitrodimethylamine via oxidation at the methyl-group was confirmed, as was indicated by formaldehyde liberation. N- Nitrodimethylamine and formaldehyde as well as the suggested metabolites, N- nitrohydroxymethylmethylamine and N- nitromethylamine were tested for mutagenicity in histidine auxotrophic Salmonella typhimurium strains in a variety of conditions. N- Nitrodimethylamine was mutagenic only in S. typhimurium TA 100 after pre-incubation with bacteria and a complete metabolizing mixture containing 9000 g liver supernatant and NADPH-regenerating cofactors. N- Nitrohydroxymethylmethylamine and formaldehyde were approximately equally mutagenic without the metabolizing mixture in TA 100 and TA 98, but not in TA 1535. The addition of the 9000 g supernatant of homogenized liver increased the yield of his+ revertants induced by the two compounds. N- Nitromethylamine was not mutagenic with or without the metabolic activation system. The results suggest that formaldehyde is possibly the mutagenically active intermediate formed during in vitro metabolism of N- nitrodimethylamine . Furthermore the participation of formaldehyde as the mutagenic intermediate of other non-alkylating N-nitro and N-nitroso compounds is demonstrated.

Animals↗
PubMed1984

Biochemical and biological properties of prospective N-nitrodialkylamine metabolites and their derivatives.

The metabolic conversion of N-nitrodimethylamine and of N-nitrosodimethylamine was compared in vitro. The biochemical properties of the two compounds were nearly identical; however, the biological activities (carcinogenicity, mutagenicity and toxicity) of the nitramine are many times less potent. N-Nitrodimethylamine was found to be mutagenic to Salmonella typhimurium TA100 when applied at above 200 mumol/plate with metabolic activation. Its suggested metabolite, N-nitromethylamine, was not mutagenic, N-Nitromethylhydroxymethylamine, N-nitromethylacetoxymethylamine and formaldehyde were mutagenic only to S. typhimurium TA100 at low concentrations and toxic above 2 mumol/ plate. The evidence suggests that formaldehyde is the intermediate responsible for the mutagenicity of the nitramine derivatives and of the parent compound, N-nitrodimethylamine.

Animals↗
PubMed1983

Criteria for the standardization of Salmonella mutagenicity tests: results of a collaborative study. IV. Relationship between the number of his- bacteria plated and number of his+ revertants scored in the Salmonella mutagenicity test.

Five laboratories participated in a joint ring study to investigate the role of bacterial cell number in the Salmonella mutagenicity test. A strictly standardized protocol, using sodium azide and TA 1535, was developed and employed to test the mutagenicity of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) with different dilutions of Salmonella typhimurium TA-100 and TA-1535 cultures. All laboratories detected the mutagenic activity of sodium azide with only a 2-fold variation of test results. For MNNG the interlaboratory variation was approximately 5-fold. Decreasing numbers of test bacteria employed resulted in lower numbers of MNNG-induced revertants in all laboratories. The number of preexisting revertants decreased in direct proportion to the reduced cell content, whereas the number of spontaneous revertants was not as greatly affected. A critical amount of test bacteria was required in order to obtain numbers of induced revertants which were equal to twice the number of spontaneous revertants. Two evaluation parameters which may be employed to describe the mutagenicity of a compound are compared.

Animals↗
PubMed1983

Genotoxicity of brown-colored polymerization products formed in smoke flavors.

Smoke aroma essences, which are prepared from smokehouse smoke by condensation and purification, are used for flavoring raw food products. The essences spontaneous decompose and produce brown-colored polymerization products, which may react with protein and be liberated within the acidic environment of the human stomach. The potential of these products to cause DNA damage was studied in two microbial and two in vivo assay systems. The polymerization products induced his+ reversion in Salmonella typhimurium TA 100 after metabolic activation by liver enzymes. There was no significant activity in a differential killing assay with repair-deficient strains of Escherichia coli WP2. In vivo tests demonstrated significant increases in the rate of sister chromatid exchanges in bone marrow cells of Chinese hamsters, but no increase in micronuclei was detectable. Thus, genotoxic components may be present in the brown-colored fractions of smoke aroma essences, but further study is needed.

Animals↗
PubMed1983

Biological activity of benzylating N-nitroso compounds. Models of activated N-nitrosomethylbenzylamine.

Unsymmetrically substituted N-nitrosomethylbenzylamine is an oesophageal carcinogen with potential methylating and benzylating properties. Whereas the methylating activity of the compound has been investigated, little is known of its potential benzylating properties. In order to elucidate the biological consequences of benzylation, related model compounds which are presumed benzylating agents were synthesized and tested for mutagenicity. N-nitrosobenzylurea and its structural analogue N-nitroso-p-methylbenzylurea were direct acting mutagens in Salmonella typhimurium TA 98. Activity was also present in TA 1535, but it was less pronounced. N-nitroso-alpha-acetoxybenzyl-benzylamine was equally mutagenic in S. typhimurium TA and TA 1535. N-nitroso-acetoxymethyl-benzylamine and N-nitrosoacetoxy-methyl-p-methylbenzylamine are two model compounds which may decompose by hydrolysis or through esterases to yield intermediates also though to arise after alpha-C hydroxylation of the methyl group of the parent nitrosamines. These compounds needed additional activation by enzymes present in the post-mitochondrial supernatant of rat liver. They were distinctly mutagenic in TA 98. Furthermore, all compounds also caused the induction of phage lambda in a qualitative assay with Escherichia coli Br 513. Thus, benzylation of DNA clearly results in a biological consequence. These findings are supportive of the theory that if enzymic attack occurs on the methyl group of N-nitrosomethylbenzylamine, benzylation may also contribute to the overall biological activity of the compound.

Animals↗
PubMed1982

Mutagenicity testing in the Salmonella typhimurium assay of phenolic compounds and phenolic fractions obtained from smokehouse smoke condensates.

Smokehouse smoke, which is used for flavouring meat products, was investigated for its mutagenic activity in the Salmonella typhimurium assay. We were chiefly concerned with the fractions free of polycyclic aromatic hydrocarbons but containing phenol compounds, which are responsible for the preservative and aromatizing properties of the smoke. The most abundantly occurring phenol compounds (phenol, cresols, 2,4-dimethylphenol, brenzcatechine, syringol, eugenol, vanilline and guaiacol) gave negative results when they were tested for mutagenicity at five concentrations up to 5000 micrograms/plate, with and without S-9 mix, using five strains of S. typhimurium. Even when phenol was further investigated in a variety of test conditions, no induction of his+ revertants was observed. When smokehouse smoke was condensed and fractionated the majority of the various phenolic fractions also gave negative results when tested at five concentrations using five strains of S. typhimurium. However there was a slight increase in the number of revertants in a few cases. The presence in the phenolic fractions of very small amounts of mutagenic impurities, the nature of which needs further investigation, cannot be excluded. These results support the further development of non-hazardous smoke-aroma preparations, based on the phenolic components of smokehouse smoke.

Animals↗
PubMed1982

Genotoxicity of 5-methoxypsoralen and near ultraviolet light in repair-deficient strains of Escherichia coli WP2.

5-Methoxypsoralen (5-MOP) is used in cosmetic suntan preparations to stimulate the production of skin pigments. Although its isomer 8-methoxypsoralen (8-MOP) has been shown to be genotoxic in numerous biological systems, 5-MOP has not been so extremely investigated, but it has recently been reported to be mutagenic and carcinogenic. We have studied the lethal effects of 5-MOP and near ultraviolet light (NUV) on repair-deficient Escherichia coli strains. After treatment with 5-MOP at concentrations above 2 microgram/ml in combination with UV light survival of the repair-deficient strains was considerably reduced and strain WP100 UVRA- recA- was more sensitive than strain WP2 UVRA-. The effect was dependent on the time of irradiation and on the presence or absence of S-9 mix which inhibited the lethal activity of 5-MOP/NUV particularly when the NADP-generating system was included. These results support other indications that the use of 5-MOP in cosmetic preparations should be controlled.

5-Methoxypsoralen↗
PubMed1982

In vitro formation of methyldiethyldithiocarbamate after the reaction of nitrosoacetoxymethylmethylamine or methylnitrosourea with disulfiram.

Analysis by scintillation measurement, mass spectrometry and h.p.l.c. showed that diethyldithiocarbamic acid (DDTC), the main metabolite of disulfiram (DSF), forms methyldithiocarbamate (MeDDTC) when incubated with [14C]nitrosoacetoxymethylmethylamine ([14C]NAMM) or [14C]methylnitrosourea ([14C]MNU) in different media (bacteria, esterases, rat liver 9000 x g supernatant fraction and microsomes). When DSF instead of DDTC was used, MeDDTC was formed only when soluble enzymes were present which are required to split DSF into two DDTC moieties. No physiological methylation of DDTC takes place as was shown by experiments with [3H]MNU. [14C]Methanol, formed by the decay of [14C]NAMM and [14C]MNU was shown to have no alkylating properties.

Animals↗
PubMed1982

Fluoro-substituted N-nitrosamines. 2. Metabolism of N-nitrosodiethylamine and of fluorinated analogs in liver microsomal fractions.

In vitro metabolism of N-nitrosodiethylamine (NDEA) and of its two fluorinated analogs N-nitroso-2,2,2-trifluoroethyl-ethylamine (NDEA-F3) and N-nitroso-bis(2,2,2-trifluoro-ethyl)amine (NDEA-F6) was comparatively investigated using rat liver microsomes and S-9 fraction. Aldehydes, nitrite and unchanged nitrosamines were determined. Additionally the mutagenicity was measured in a Salmonella/mammalian microsome assay. NDEA and NDEA-F3 were deethylated and, to a smaller extent, denitrosated. Dealkylation of NDEA-F3 at the fluorinated ethyl group, however, was strongly inhibited. NDEA-F6 was practically not metabolized under the in vitro conditions used. In contrast to NDEA, the mutagenicity of NDEA-F3 was at best marginal; NDEA-F6 was not mutagenic. The results show that substitution of fluorine in beta-position of NDEA strongly influences alpha-C-hydroxylation and denitrosation.

Aldehydes↗
PubMed1982

Mutagenicity and synthesis of alpha-substituted N-nitrosamines: derivatives with dithiocarbamic acid.

Disulfiram (DSF) can considerably alter the organotropy of chemical carcinogens. For N-nitrosodimethylamine and for N-nitrosodiethylamine the organotropy is shifted from the liver to the nasal cavity or the oesophagus, respectively. Whereas the influence of DSF or its metabolites on enzyme systems has been studied, little is known about its interaction with the carcinogens at a molecular level. Therefore, postulated reaction products of a series of alpha-hydroxylated N-nitroso-dialkylamines and dithiocarbamate were synthesized and tested for mutagenicity in Salmonella typhimurium TA 1535. The results show that the compounds conjugated at a primary alpha-C-atom are not mutagenic, whereas those conjugated at a secondary alpha-C-atom are active. The primary N-nitroso-dithiocarbamates represent unique examples of inactivated dialkyl-nitrosamine derivatives. In addition, their formation in vitro was indirectly demonstrated. The possible role these inactivated compounds may play during the DSF-modulation of carcinogenesis will be discussed.

Chemical Phenomena↗