Biomedical subjects

R Thust

Publications and source records attributed to R Thust.

At least 55 records · Page 3Linked to original sources

PubMed1979

Activity of citrinin metabolized by rat and human microsome fractions in clastogenicity and SCE assays on Chinese hamster V79-E cells.

The mycotoxin citrinin is a potent inducer of chromosomal aberrations in the clastogenicity assay on V79-E cells when metabolized by rat and human liver microsomes. Rat and human liver microsomes, standardized on protein content, activate citrinin at equal levels. 5 X 10(-4) M citrinin induces complex translocations in a high frequency as well as defects of chromosomal coiling. Higher concentrations are cytotoxic, lower ones are almost inactive. After metabolization of mycotoxin by rat-kidney microsomes or an S9 mix fraction containing rat liver and kidney microsomes, toxic effects predominate and chromosomal aberrations are diminished. Clastogenic citrinin concentrations do not induce an increase of SCE frequency. Although the mode of action of this mycotoxin on chromosomal structure remains obscure, possible explanations are discussed.

Animals↗

PubMed1979

Cytogenetic properties of Chinese hamster V79-E cells: G-banding, C-banding, nucleolar organizer regions, and sister chromatid exchanges.

A line of the Chinese hamster V79 strain, denominated as V79-E, is cytogenetically characterized. It has a modal chromosome number of 22. Chromosome morphology, G- and C-banding reveal strong differences from the normal complement of the Chinese hamster presumably caused by rearrangements of chromosome segments during the past 20 years of in vitro culture. 4 chromosomes possess terminal nucleolar organizer regions. Spontaneous sister chromatid exchanges occur with a frequency of 0.38 sister chromatid exchanges per chromosome.

Animals↗

PubMed1978

Use of human-liver microsomes from kidney-transplant donors for the induction of chromatid aberrations and sister-chromatid exchanges by means of pre-carcinogens in Chinese hamster cells in vitro.

Samples of two human livers taken during operation of kidney donor patients were processed for microsome fractions and used for metabolization of cyclophosphamide (CP) and dimethylnitrosamine (DMN) in combination with the NADPH-generating system. Rat-liver microsomes were checked for comparison. Induction of chromatid aberrations and sister-chromatid exchanges in a newly isolated clone of Chinese hamster fibroblasts served as indicators of activity. Human S-9 fractions standardized on protein content showed strong variations of CP and DMN activation. Whereas liver microsomes of one patient (who also suffered from Gaucher's disease) were highly active for both pre-carcinogens and metabolized DMN at the same level as the uninduced rat-liver microsomes, the S-9 fraction from the second patient failed to activate CP, but was distinctly positive for DMN. It is suggested that samples of liver and other organs of renal transplant donors might be a practicable source of freshly prepared human microsome fractions usable in biochemical, genetic and carcinogenetic studies. Problems concerning the extrapolation of results are discussed.

Biotransformation↗

PubMed1978

Methylnitrosophenylurea--a highly carcinogenic compound.

In vitro, 1-methyl-1-nitroso-3-phenylurea (MNPU) was easily formed from 1-methyl-3-phenylurea (MPU) and sodium nitrite in an acid environment. In rats MNPU showed a strong carcinogenic effect, inducing tumors of the forestomach. MNPU was formed endogenously after combined administration of MPU and nitrite to rats, as indicated by the induction of forestomach tumors. MPU itself was not carcinogenic. In the metabolism of the herbicide 1,1-dimethyl-3-phenylurea (fenuron) MPU resulted as a demethylation product. The possible significance for preventive oncology and the role of MNPU as an environmental carcinogen are briefly discussed.

Animals↗

PubMed1978

No neoplastic alteration of metabolically competent rat liver cells in vitro by chemical carcinogens: 3-methylcholanthrene, dimethylnitrosamine and Natulan.

Epithelial rat liver cell line RL-19 was checked for aryl hydrocarbon hydroxylase and dimethylnitrosamine demethylase activity. Aryl hydrocarbon hydroxylase activity was found at the rate of about 14.5 pmoles 3-hydroxy-benzopyrene per min per mg protein. This activity was not inducible by 3-methylcholanthrene or by phenobarbital and was independent of the subculture level. From the 45th up to the 59th subculture the mean demethylase activity was about 1.08 nmoles HCHO per min per mg protein, but was decreased to 0.64 nmoles HCHO per min per mg protein at the 131st subculture. RL-19 cells were treated with 3-methylcholanthrene (0.5-1.0 microgram/ml), dimethylnitrosamine (100-400 micrograms/ml), or Natulan (50 micrograms/ml), respectively, for 7 to 10 days. During a 6 months subsequent cultivation no neoplastic changes were observed as revealed by morphological investigation, soft agar assay, and transplantation. It is suggested that metabolic competence for carcinogen activation is only one prerequisite for neoplastic alteration in vitro, and that RL-19 cells are refractory to the action of carcinogens in spite of their metabolic capacity.

Animals↗

PubMed1977

Morphology of diethylnitrosamine-induced lung tumours in Dzungarian dwarf hamsters.

After transplacental application of 30 mg/kg b.w. diethylnitrosamine 16 out of 21 Dzungarian dwarf hamsters developed lung tumours. The histological picture of these tumours is described. The neoplasms are classified as papillary, tubular, or alveolar adenomas or adenocarcinomas, respectively. Different histological architectures occur in one and the same animal or even in different parts of the same tumour. The neoplasms derive from outgrowths of the epithelium of small bronchioles. The significance of the Dzungarian dwarf hamster as a suitable tool for transplacental and postnatal cancer research is discussed.

Adenocarcinoma↗

PubMed1977

[The biological behaviour of experimental tumours of the central nervous system (author's transl)].

In 31 experimental groups, 1955 rats were exposed to methyl-, dimethyl-, trimethyl-, and ethylnitrosourea or dimethylphenyltriazene. Altogether, 3102 tumours were registered. 1930 of them were located in the central nervous system. Derived from neurooncological classifications in man, these tumours were subdivided corresponding to a three-step grading scheme. In contrast to brain tumours in man, in rats the degree of dedifferentiation is of minor importance with regard to the clinical course of the cancer disease. In rats CNS tumours lead to death of the animals within a few hours or days after the onset of clinical symptomatology and should be regarded as biologically highly malignant. The grading allows a more exact valuation of the frequency of distinct tumour types in different experimental groups. Following transplacental application, isomorphous neoplasms occur significantly more frequent as compared with anisomorphous ones (grad II and III) which dominate when the carcinogen is given repeatedly to adult animals. Parallels are drawn to human neurooncology.

Animals↗

PubMed1977

[Transplacental carcinogenic action of diethylnitrosamine in the Dzungarian hamster (author's transl)].

After transplacental application (30 mg/kg i.p., 3 days until 6 hours a. p.), diethylnitrosamine induces a high rate (76.2 per cent) of bronchiolar tumours in the lung of the Dzungarian hamster. These tumours were classified as papillary or tubulous adenomas and carcinomas. Furthermore, eome tumours were observed in other organs. The problem of organotropism of diethylnitrosamine, especially among different hamster hamster species, is discussed.

Adenocarcinoma, Bronchiolo-Alveolar↗

PubMed1977

[On the transplacental induction of tumours by N-ethyl--N-nitrosourea in different species (author's transl)].

The transplacental activity of N-ethyl-N-nitrosourea (ENU) was tested in rats, rabbits, Syrian golden hamsters, Dzungarian dwarf hamsters, guinea pigs, dogs, and rhesus monkeys. In the offspring of rats, multiple tumours of the central and peripheral nervous system were found in 100 per cent, whereas in rabbits kidney tumours developed. In Syrian golden hamsters, the application led mostly to neoplasms of the thyroid gland. Dzungarian dwarf hamsters and monkeys prooved to be resistant. 9 out of 15 dogs died shortly after birth. In two dogs a carcinoma of the thyreoid gland and one of an ovary were found. Because of an infection, the experiments with guinea pigs were to be interrupted untimely. Therefore, a final answer is impossible. Own results were compared with the findings of other authors. The significance of the different susceptibility in distinct species is discussed.

Animals↗

PubMed1977

[Induction of malformations by N-methyl-N-nitrosourea (MNU) (author's transl))].

UNLABELLED: After observing multiple malformations in a stillborn infant whose mother was in contact with MNU during pregnancy, the inhalation of evaporated MNU solution or diazomethane was regarded as a possible cause. An attempt was made to reproduce the same conditions in experiments with rats. MATERIAL AND METHODS: The experiments were carried out with 46 pregnant rats yielding 370 fetuses. With the aid of an atomizer a solution of 50 mg MNU was atomized in a container of 12 liters. In each test up to 3 rats were exposed for 30 min (group A1). In other groups (B1--3) rats placed into the same container breathed diazomethane which was produced by dropping NaOH on MNU. During this experiment, rats were apathetic and their respiration was accelerated. In group C1--9, MNU was injected intraveneously or intraperitoneally. Animals which had no contact neither with complete MNU nor with its decomposition products served as control (group D1). Rats were killed at the 21st day of pregnancy. After laparotomy, fetuses were weighed and fixed in Bouin's solution or in ethanol. Fetuses were examined macroscopically. Afterwards the head and the trunk were dissected. In a number of cases the skeleton was stained with alizarin red S. RESULTS: Malformations that affected the skeleton and the central nervous system could be found only in those experiments in which rats were exposed to the complete teratogenic agent. By means of external inspection microcephalia, micrognathia, cleft palate, micromelia, syn- and polydactylia, lordosis and skoliosis of the spinal column as well as deviations of the extremities were observed. Above this, by bone preparation by alizarin red S malformations of the skull (micrognathia, aplasia of the zygomatic bone) hypoplasia and deformations of the clavicula, scapula, ribs as well as of bones of the extremities were found. MNU led to complex malformations in the central nervous system comprising microencephalia, hydrocephalus as well as defects of the septum pellucidum and the corpus callosum. Frequency and spectrum of malformations depended on the dosage and the age of pregnancy. As the embryotoxic activity was relatively low at day 13 and as malformations were observed in all cases, this day proved to be most effective one. In contrast to the application of MNU, after inhalation of diazomethane malformations did not occur. However, as a toxic effect a significant increase in dead fetuses and a reduction of the body weight was registered. After inhalation of atomized MNU solution, neither malformations nor toxic injuries could be observed. The experiments do not support the hypothesis, that anomalies found in the stillborn infant are caused by mother's contact with MNU. As demonstrated, in most cases it is very difficult to prove any interrelationship between a chemical agent and the occurrence of malformations in man. Therefore, similar observations should be published even if the connection cannot be ascertained exactly, for only by an accumulation of related cases a positive correlation can be verified.

Animals↗

PubMed1976

[Long-term cultures of experimental CNS tumours as models in neurooncological research (author's transl)].

Experiences with the behaviour of long-term cultures of experimental CNS tumours of rats induced by methylnitosourea of ethylnitrosourea, resp., are reported. Differences in cell kinetic parameters result in a selection of the best adapted cell type among those ones existing in the primary tumour. In some long-term cultures of gliomas and neurinomas an increasing polymorphism is observed by which these lines gain the morphological appearance of a glioblastoma multiforme. The loss of cell-specific morphological differentiations is a further type of anaplastic changes. In neuroectodermal tumour strains these alterations are temporarily reversible by means of addition of dibutyryl cyclic AMP to the culture fluid. There is no relationship between the type of tumour and the degree of anaplastic changes in vitro. Some cell strains remain constant for years and retain their specific properties. Their application as tester strains in neurooncological studies is recommended.

Animals↗

PubMed1976

Screening of potential chemical carcinogens by means of mammalian cells in vitro.

A survey is presented about the current state of the efforts to the development of rapid screening systems for carcinogenic substances by means of mammalian cells in vitro. At present two fundamental ways for the realization of this task seem possible: a) So-called host-mediated assays which are a combination of carcinogen application into intact animals (possibly pregnant animals) and succeeding explantation of organs from these animals or establishment of cell cultures from fetuses following transplacental action of the compound tested. In this type of experiment the metabolization of the compound is accomplished within the organism and the critical problem of metabolic competence of cultured cells is bypassed. b) Direct application of the carcinogen into cell cultures. Beside the hitherto most used fresh embryonic cells there is an increasing tendency to use established cell lines with a rigid post-confluence inhibition of proliferation and an extremely low background of spontaneous alteration in vitro. Possibilities for the metabolic activation in this system are pointed out. The value of "indicators" of carcinogen-induced alterations in relation to neoplastic properties is discussed. Most of the higherto existing test systems are problematic in their relevancy, but the findings published in literature indicate that cell cultures offer a very promissing possibility for the early detection of carcinogenic agents in human environment.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1975

Differential morphological reaction of experimental CNS tumour clones in vitro to dibutyryl cyclic AMP or serum-free medium, resp.

Six clones from methylnitrosourea (MNU) or ethylnitrosourea (ENU) induced tumours obtained in the nervous system of the rat were cultured in serum-free medium or treated with dibutyryl cyclic AMP (db cAMP) in vitro. All clones originated from longterm cultures. Three clones forming sarcomas after syngeneic transplantation showed only very slight changes following treatment, whereas the three glioma clones showed striking alterations. They formed long processes or showed rounding of their perikarya. In serum-free medium the cellular shape is intermediate between that seen in normal conditions and the seen in db cAMP treated cultures. The altered cultures resemble the primary cultures of the respective tumours. The relationship of these alterations to tumour types are discussed.

Animals↗

PubMed1975

[DNA-synthesis in the final stages of the S-phase and G-banding in neoplastic cells of the rat (author's transl)].

QUESTION: In literature reports on quantitative studies concerning DNA-synthesis during the final stages of the S-phase in normal cells of men and of rats are available whereas observations on tumor cells are scarce. Therefore, in this study 2 clones isolated from chemically induced tumors in the nervous system of the rat have been investigated to enable comparisons with normal cells. Furthermore, the G-banding pattern was studied in the same material. MATERIAL AND METHODS: The experiments were performed on clones from experimentally induced tumors of the rat central nervous system (Rattus norvegicus) which were isolated in the own laboratory. PIE 2-3: Clone from an intermedullary tumor induced by intravenous application of methylnitroso urea (MNU) (dosis: 25 mg/kg at 4 weeks intervals) in a male Hauben rat (experiment no. 1190). After twofold intracerebral transplantation the tumor was cultured and the clone isolated by means of a modified feederlayer-technique (THUST 1975). Following reimplantation PIE-2-3 developed spindle cell sarcomas (THUST and WARZOK 1972). PIE 27-1: This clone was isolated from an MNU-induced adventitial sarcoma in the base of the brain (dosis: 20 mg/kg at 4 weeks intervals) in a male Hauben rat (experiment no. 744). Before cloning this tumor was 47 times intracerebrally transplanted. PIE 27-1 develops in vivo undifferentiated densely packed sarcomas. The clones were in vitro cultured in Eagle's MEM supplemented by of 20% bovine serum and 0.25% lactalbumin hydrolysate, then passaged by means of trypsin solution at a ratio 1:10 at weekly intervals. Autoradiography: 3H-thymidine (specific activity: 14 Ci/mM;N.V. Phillips-Duphar, Holland) was administered to the cultures in a concentration of 0.5 muCi/ml. 30 min before chromosome preparations colcemide (0.01 mug/ml) was added to the corresponding culture flasks. 2.5 hours after 3/-thymidine administration chromosome preparations were processed at 30 min intervals. The preparations were stained with carbol fuchsin and covered with a Formvar membrane (STUBBLEFIELD 1965). For preparation of autoradiographs Kodak AR 10 film was used. After 10 days exposition the preparations were developed for 5 min at 18 degrees C in Kodak D19b. The autoradiographs were photographed at 400-fold initial magnification, afterwards the stripping film was removed and, for better identification of the particular chromosomes, the same mitoses were photographed again. Silver grain countering and mode of evaluation have been described in detail in an earlier study on normal cells (THUST and DIETZ 1972; see also PASSARGE et al. 1969). When the autoradiographs were examined the G-bandings were yet not available. Therefore some chromosome pairs of the rat karyotype could not be differentiated (teleocentric chromosomes X, 4-10 and XX, 4-10, respectively, as well as the metacentric chromosomes no. 11-12, 15-18 and 20). For this reason the evaluation was based on the average length of these chromosomes...

Animals↗

PubMed1974