A Very Fast and Momentum-conserving Tree Code.

The tree code for the approximate evaluation of gravitational forces is extended and substantially accelerated by including mutual cell-cell interactions. These are computed by a Taylor series in Cartesian coordinates and in a completely symmetric fashion, such that Newton's third law is satisfied by construction and that therefore momentum is exactly conserved. The computational effort is further reduced by exploiting the mutual symmetry of the interactions.

mRNA expression patterns in different stages of asbestos-induced carcinogenesis in rats.

Human malignant mesotheliomas are induced almost exclusively by fibrous dusts. The nature of interactions between fibers and target cells, and the molecular mechanisms leading to tumorigenesis, are not yet understood. Here, the mRNA expression patterns at different stages of asbestos-induced carcinogenesis in rats were monitored by suppression subtractive hybridization (SSH) and array assay.

DNA fingerprint analysis reveals differences in mutational patterns in experimentally induced rat peritoneal tumors, depending on the type of environmental mutagen.

We performed tumor DNA fingerprint analysis using the synthetic minisatellite probe S3315x2 based on the 33.15-repeat unit. The aim of the study was to investigate fingerprinting patterns of peritoneal tumors induced experimentally in Wistar rats by two carcinogens with unknown mechanism of action (crocidolite asbestos and nickel powder) and, as a positive control, benzo[a]pyrene.

Fiber-specific molecular features of tumors induced in rat peritoneum.

Molecular markers such as mutational spectra or mRNA expression patterns may give some indication of the mechanisms of carcinogenesis induced by fibers and other carcinogens. In our study, tumors were induced by application of crocidolite asbestos or benzo[a]pyrene (B[a]P) to rat peritoneum. DNA and RNA of these tumors were subjected to analysis of point mutations and to investigation of mRNA expression patterns.

P53 mutations in tumours induced by intraperitoneal injection of crocidolite asbestos and benzo[a]pyrene in rats.

Mutation analysis of the tumour suppressor gene p53 in tumours induced in the peritoneal cavity of rats revealed differences in the mutational pattern with regard to the carcinogenic substances applied. In tumours induced by benzo[a]pyrene a considerable amount of p53 mutations resulting in an altered protein structure could be detected. For the development of these tumours an escape from the p53 mediated cell cycle control can be assumed.

Sensitive gas chromatographic method for determination of mercapturic acids in human urine.

A method was developed for sensitive determination of the specific benzene metabolite S-phenylmercapturic acid and the corresponding toluene metabolite S-benzylmercapturic acid in human urine for non-occupational and occupational exposure. The sample preparation procedure consists of liquid extraction of urine samples followed by precolumn derivatization and a clean-up by normal-phase HPLC. Determination of analytes occurs by gas chromatography with electron-capture detection.

Sensitive determination of the benzene metabolite S-phenylmercapturic acid in urine by high-performance liquid chromatography with fluorescence detection.

A method was developed for the determination of the specific benzene metabolite S-phenylmercapturic acid in urine. The analyte is determined by HPLC with fluorescence detection after solid-phase extraction of urine with C18 material and hydrolysis followed by precolumn derivatization. The samples are separate by a column-switching method with a dual column system.

A study on urinary thioethers by detecting N-acetylcysteine and thiophenol after alkaline hydrolysis.

A method is described for the selective determination of thiol compounds liberated by alkaline hydrolysis of urine. It is based on the procedure described by Newton et al. Two thiol compounds were detected selectively: N-acetylcysteine and thiophenol.

[The correlation between the excretion of thioethers and their mutagenic activity in urine in workers of different occupational groups].

Electrophilic substances can be inactivated by binding to glutathione or other SH-bearing molecules leading to urinary excretion of mercapturic acids or other thioether products. The mutagenic activity in urine as detected by mutagenicity assay (Ames-Test) is caused by genotoxic agents or their electrophilic metabolites. Therefore, it has been suggested that an effective protection by the glutathione system may diminish the urinary excretion of mutagens after exposure to genotoxicants.

[Cellular and molecular biological aspects in environmental toxicology].

Health effects of substances in the environment are considered from the viewpoint of cellular and molecular biology. There are nephrotoxic effects of cadmium to be discussed as well as mechanisms of carcinogenesis and neurotoxicity. Finally, the influences of noxious substances on lung clearance and immune reactions are demonstrated.

Pulmonary changes in the rat following low phosgene exposure.

Minimal inhalation doses (or concentrations) of phosgene necessary for the production of changes within the blood-air barrier were determined in rats. At least 50 ppm.min (5 ppm X 10 min) was necessary for the production of alveolar oedema (the minimal effective phosgene concentration being 5 ppm).

[Comparative study of the behavior of particulate emissions from diesel and gasoline engines in animal lungs: elimination rate and induction of benzo(a)pyrene hydroxylase and ethoxycoumarin de-ethylase].

The emitted particulates of five diesel-engined and two gasoline-engined passenger cars were investigated for the elimination rate from hamster lungs after intratracheal instillation. In addition extracts of these particulates were studied for their influence on the mixed function oxidase activity (MFO; Benzo(a)pyrene Hydroxylase, Ethoxycoumarine Deethylase). Differences in the elimination rates of diesel soot and particulates from gasoline engines were not found.

The influence of various factors on the methylation of DNA by the oesophageal carcinogen N-nitrosomethylbenzylamine. I. The importance of alcohol.

Alcohol appears to be a predisposing factor for the high incidence of oesophageal cancer in Western France. Therefore, we have investigated the influence of ethanol on the alkylation of DNA by a carcinogen which reacts selectively with oesophageal tissue. Female Wistar rats (approximately 80 g) received a single i.

[Studies on the induction by extracts from airborne particulates of benzo(a)pyrene hydroxylase and the binding of benzo(a)pyrene to DNA in the rat lung in vivo after pertracheal administration (author's transl)].

A method is described for the administration of suspended material into the rat lung. The rat is narcotized by CO2/air, the trachea is punctured and the suspension is sucked into the lung by the inhaled air (pertracheal administration, p. t.

[Studies on the mutagenic effect of extracts derived from airborne particulates within one year in differently burdened areas using the Ames test (author's transl)].

Suspended matter was collected at three sampling sites with different air pollution levels (DU = Duisburg, mining, iron and steel industry; D = Düsseldorf, residential city; K = Krahm, rural district) in 1978. The seasonal variations of the mutagenicity of extracts from samples collected monthly were assayed by the Ames-test. Th results are presented as the number of revertants related to air volume, weight of the suspended matter, weight of the dried extract and to the amount of benzo(a)pyrene in the extract.

[Studies on the activity of the aryl hydrocarbon hydroxylase and metabolism of benzo(a)pyrene in cell strains and cell lines used for testing cytotoxic and transforming ability of foreign compounds (author's transl)].

The activity of the AHH and the formation of polar metabolites from BaP was examined in several cell strains and lines, which are used for testing cytotoxic and transforming activity of environmental agents, the highest activity of the AHH and the highest capacity to metabolize BaP was found in hamster kidney cells. Much lower values were measured in kidney cells from Cercopithecus aethiops, BHK21/C13 cells, and SV-40 transformed hamster kidney cells (14-1b). The activity of AHH was inducible by BA in all these cells.

Effect of NO2 and SO2 inhalation on benzo(a)pyrene metabolism in rat lung.

Male Wistar rats were continuously exposed to NO2 (14.4 ppm), SO2 (46.5 ppm) and to a mixture of both gases and their effect on lung microsomal aryl hydrocarbon (benzo(a)pyrene) hydroxylase (AHH) activity was determined.

The mutagenicity of airborne particulate pollutants.

The mutagenic effect of extracts derived from airborne particulate matter was investigated with the Ames-test. The whole extract proved to be distinctly mutagenic. To find out whether the content of polycyclic aromatic hydrocarbons may be responsible for the mutagenic effect, the extract was split into several fractions.

Polycyclic aromatic hydrocarbons in human bronchial carcinoma.

A study was made to determine whether and to what extent polycyclic aromatic hydrocarbons (PAH) are present in human bronchial carcinoma. Twenty-four carcinomas, obtained from surgical operations and autopsies, were examined. The samples were tested for 12 PAH; these were determined by direct fluorescence analysis on thin-layer plates.

[Studies on the metabolism of benzo(a)pyrene in alveolar-macrophages. II. Kinetics of metabolism and characterization of the metabolites (author's transl)].

The purpose of this communication is to study the metabolism of benzo(a)pyrene by alveolar macrophages from guinea pigs. A column chromatographic technique using a gradient elution (fig. 1) followed by thin layer chromatography has been employed to separate the metabolites.

[Studies on the metabolism of benzo(a)pyren in alveolar-macrophages. I. Uptake of benzo(a)pyrene and induction of benzo(a)pyrene hydroxylase (author's transl)].

Alveolar macrophages play a significant role in the elimination of inhaled foreign compounds and particles from the lung. The question arises, if alveolar macrophages participate in the detoxification or activation of environmental carcinogenic compounds. In the first communication on this subject we describe experiments concerning the uptake of benzo(a)pyrene and the activity of the metobolizing enzymes.