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At least 19 recordsLinked to original sources
PubMed1975

Changes of tissue water proton relaxation rates during early phases of chemical carcinogenesis.

Water proton spin lattice relaxation rate (T1) was determined on tissues of rats experiencing early phases of chemical carcinogenesis. Rats were fed a fast acting carcinogen, 3'-methyldimethylaminoazobenzene, and a slower acting carcinogen, 2-acetylaminofluorene, for up to 4 weeks. T1 of blood serum and liver tissue was significantly higher than those of controls after 4 weeks of 3'-methyldimethylaminoazobenzene feeding. This was not the case for 2-acetylaminofluorene. The blood serum T1 increase reflected the onset of liver nodulation (assumed to be preneoplastic). Liver T1 values increased as the degree of nodulation increased. Blood serum T1 correlated inversely with protein content and directly with water content. Liver T1 values correlated with water content, but this was not true for spleen T1 values. Spleen T1 values were significantly lower than controls at the earliest sampling date for each carcinogen: one week for 3'-methyldimethylaminoazobenzene and 4 weeks for 2-acetylaminofluorene. The spleen T1 decrease paralleled an increase of iron detectable by electron spin resonance in this tissue. Spleen T1 decreases are probably not unique to chemical carcinogenesis.

Animals↗
PubMed1979

Differential perturbation of erythrocyte membrane-associated transport and enzyme activities by structurally related lipophilic compounds.

The alteration of two erythrocyte plasma membrane functions, acetylcholine hydrolysis and glucose exchange, by a series of structurally related small lipophilic compounds which exhibit antihemolytic behavior was studied. 2-Methyldimethylaminoazobenzene is a more potent inhibitor of acetylcholinesterase than the 3'-methyl analogue, while the unsubstituted compound fails to inhibit. Esterase inhibition by the 2-methyl compound is non-competitive and dependent on the anion composition of the assay buffer. The temperature dependence of acetylcholinesterase activity in the presence of the 2-methyl compound suggests that interaction with inhibitor is influenced by the state of lipids tightly bound to the enzyme. Glucose exchange is inhibited to the same extent by both methyl derivatives but not by the unsubstituted dye, and the temperature dependence in the presence of inhibitor is not grossly altered. The lack of correlation between inhibition of membrane function adn stabilization of erythrocytes against osmotic hemolysis is discussed.

Acetylcholine↗
PubMed1976

Analysis of lipophilic carcinogen-membrane interactions using a model human erythrocyte membrane system.

Human erythrocytes have been used as a model for evaluating the chemical carcinogen-plasma membrane interaction. The carcinogenic aromatic amines 2-acetylaminofluorene, dimethylaminoazobenzene, and 3'-methyldimethylaminoazobene stabilize erythrocytes against lysis in hypotonic solution. In general, the stabilization potential of these compounds reflects their oil:water partition coefficients and may be related to both their extracellular distribution and ultimate capacity for penetration of target cells. The polycyclic aromatic hydrocarbons, 3-methylcholanthrene and benz[a]anthracene, confer little protection against hemolysis and simultaneous incubation of nonprotective 3-methylcholanthrene and protective 3'-methyldimethylaminoazobenzene slightly alters the stabilization afforded by the latter. 7,12-dimethylbenz[a]anthracene exhibits greater protective capacity than does benz[a]anthracene. Polycyclic aromatic hydrocarbons manifested considerably higher degrees of absolute binding to erythrocytes in isotonic solution than did aromatic amines. The difference in erythrocyte binding and stabilization exhibited by the 2 classes of carcinogens suggest distinct mechanisms of membrane association that may relate to their metabolic disposition.

2-Acetylaminofluorene↗
PubMed1977

alpha-fetoprotein-containing cells in the early stages of liver carcinogenesis induced by 3'-methyl-4-dimethyl-aminoazobenzene and 2-acetylaminofluorene.

The morphology of rat liver cells containing alpha-feto-protein (AFP) during early stages of carcinogenesis induced by 3'methyl-4-dimethylaminoazobenzene and 2-acetylaminofluorene was investigated. Indirect immunofluorescence was used to detect AFP. AFP was not found in the cells of hyperplastic nodules but was present in the cells located in areas of transitional cell proliferation. A large proportion of the AFP-positive cells formed gland-like structures. The cells containing AFP were at various levels of differentiation according to morphological criteria. Poorly differentiated, small, basophilic cells were predominant amont the AFP-positive population. The most highly differentiated AFP-positive cells had the morphology of hepatocytes.

2-Acetylaminofluorene↗
PubMed1978

Histopathology of the rat liver following a single autoprotective dose of 3'-methyl-4-dimethylaminoazobenzene.

Male inbred Leeds strain rats were given single intragastric doses of 1200 mg/kg of 3'-methyl-4-dimethylaminoazobenzene, autoprotective against liver necrosis and then sacrificed at intervals up to 14 months. About 40 per cent of the animals died, apparently as a result of pancreatic necrosis, between 9 and 13 days after treatment while the remainder survived until they were killed. The liver changes induced included an early intense ductular cell reaction, presistent hepatocellular abnormalities and at later stages, cholangiofibrosis and increasing numbers of parenchymal clear cells. Although no tumours arose as a result of treatment, the observed histopathological changes are similar to those seen during liver carcinogenesis induced by a variety of carcinogens and may be due specifically to the carcinogenic action of the azo dye.

Animals↗
PubMed1975

Fine structural changes induced in rat hepatocytes by single doses of 3'-methyl-4-dimethylaminoazobenzene.

Male Leeds rats were given single oral doses of 150 or 300 mg/kg body weight of 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB). They were sacrificed 24 or 48 h after treatment and their hepatic tissues examined by electron microscopy. The development was observed of an unusual cytoplasmic change, which consisted of large perinuclear areas of decreased hyaloplasmic density, devoid of glycogen or organized structures, which displaced the organelles to the cell periphery. This arose by the formation of large glycogen lakes, which coalesced and then lost their glycogen content, and this was accompanied by nuclear irregularity and shrinkage. Other changes, affecting the endoplasmic reticulum and the cell surface, appeared to be similar to those induced by chronic azo dye feeding. It was concluded that the acute lesion observed may limit any specific responses of the hepatocytes to the presence of 3'-MeDAB.

Animals↗
PubMed1977

Protein composition of nuclear ribonucleoprotein particles isolated from liver of rats in the early stages of feeding of 3'-methyl-4-dimethylaminoazobenzene and from hepatoma induced by the same carcinogen.

The feeding of carcinogenic 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB) in the early stages results in a change in the protein composition of the nuclear ribonucleoprotein particles of the rat liver. These particles are associated with newly synthesized RNA and it is assumed that they are involved in the processing and in the transport of this RNA. After 6 weeks of feeding of this azocarcinogen, the amount of one of the main polypeptides (apparent molecular weight 42 000) is decreased and after 10 weeks of feeding the particles are devoid of this polypeptide completely. Feeding of the non-carcinogenic p-aminoazobenzene (AB) is without any effect. The loss of this polypeptide is not characteristic for the malignant transformation. In the nuclear ribonucleoprotein particles isolated from hepatoma which has been induced by 3'-MeDAB this polypeptide is present in even higher proportion to other polypeptides than it is in particles isolated from liver cells of control animals. The 3'-MeDAB binds to the proteins of the liver nuclear ribonucleoprotein particles and interferes with the RNA processing. It is proposed that the changes in the composition of the protein moiety of the particles reflect changes in the population of liver cells leading finally to the selection of hepatoma cells which are resistant to the toxic effect of 3'-MeDAB on RNA processing.

Animals↗