Biomedical subjects

J Stap

Publications and source records attributed to J Stap.

25 records · Page 2Linked to original sources

PubMed1990

Comparison of radiation sensitivity for three cell lines as measured by the cloning assay and the micro-nucleus test.

The correlation between cell killing and the induction of micro-nuclei was studied for three cell lines after treatment with gamma radiation to investigate whether the frequency of micro-nucleated cells can be used to determine the radiation sensitivity of a cell type. R1 rat rhabdomyosarcoma cells showed a higher sensitivity for the induction of proliferative death than RUC rat ureter carcinoma cells and V79 Chinese hamster cells which had a similar radiation sensitivity. The frequencies of micro-nucleated cells were measured at 48 hours after the treatment. It was determined by time-lapse cinematography that almost all the cells in the treated cultures had divided at that time. Our results indicate that for these cell lines the correlation between the effectiveness for cell killing and the induction of micro-nuclei was the same, within the experimental errors.

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PubMed1987

Stabilization of chromosomes by DNA intercalators for flow karyotyping and identification by banding of isolated chromosomes.

A number of structurally unrelated DNA intercalators have been studied as stabilizers of mitotic chromosomes during isolation from rodent and human metaphase cells. Seven out of the nine intercalators tested were found to be useful as chromosome stabilizing agents. Chromosome suspensions prepared in this way could be preserved for long periods of time. After isolation the chromosomal DNA was longer than 150 kb. With intercalated chromosomes high resolution flow karyotypes could be obtained as illustrated for the non-fluorescent intercalators 9-methylene-(1,3-dimethyl-2,4-dionepyrimidine-5-yl)-phenanthrid in iumchloride and 4'-aminomethyl-4,5', 8-trimethylpsoralen combined with DAPI and 33258 Hoeschst for fluorescent staining and for the fluorescent intercalator propidium iodide used as a stabilizer and as a fluorochrome. Passage of the intercalated chromosomes through the laser beam had no measurable effect on the length of the chromosomal DNA subsequently isolated. After flow analysis and collection on slides human chromosomes could easily be banded by Giemsa staining methods with the same resolution as obtained in conventional metaphase spreads. This allowed a ready identification of about 80 percent of all chromosomes in the unfractionated suspension collected after passage through the laser beam.

Animals↗

PubMed1987

X-ray- and neutron-induced chromosome damage detected by flow cytometry compared to cell lethality and chromosome structural changes.

V79 Chinese hamster cells were irradiated in G0 phase with 200 kV X rays or 14 MeV neutrons, and dose-response curves were determined for three end points: chromosome damage detected by flow cytometric analysis of chromosomes isolated from metaphase cells in irradiated cultures; loss of clonogenic capacity; and induction of dicentric, tricentric, and ring chromosomes. The changes observed in the flow karyotypes from irradiated cultures were quantitatively evaluated by computer analysis. Estimates of the frequencies of chromosome lesions were derived from an analysis of the flow cytometric measurements by means of a comparison with model calculations simulating the effect of chromosome changes on flow karyotypes. The results indicate that lesions assayed by flow cytometry occur three times more frequently than lethal lesions, while the chromosomal structural changes detected by microscopic analysis were about 10 times less frequent than the lesions detected by flow cytometry. Dose-response curves for X rays and neutrons show that cell reproductive death and changes in flow karyotypes result from damage, induced with a similar relative biological effectiveness. Dose-effect relations derived from changes in flow karyotypes, which can be obtained within 24 h after irradiation, might be of value as a predictive test for the sensitivity of cells for loss of clonogenic capacity.

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PubMed1984

Preparation of chromosome suspensions from cells of a solid experimental tumour for measurement by flow cytometry.

A method is described by which metaphase chromosomes are isolated from cells of a transplantable rat sarcoma. The chromosomes are derived from cells in a suspension prepared by trypsinisation of tumours from rats that have been treated with vindesine 24 h before excision in order to accumulate cells in mitosis. Histograms obtained for the chromosomes of the solid tumour are compared with flow karyotypes of cells cultured for 20 h or for several generations in vitro.

Animals↗

PubMed1984

Proliferation kinetics of cultured cells after irradiation with X-rays and 14 MeV neutrons studied by time-lapse cinematography.

Exponentially growing cells of an established line derived from a mouse osteosarcoma (MOS) have been studied by time-lapse cinematography after irradiation with 3 Gy of 200 kV X-rays or 1.5 Gy of 14 MeV neutrons. Cell cycle times (Tc) of individual cells and their progeny in three subsequent generations as well as the occurrence of aberrant mitosis have been determined to evaluate the variation in expression of damage in relation to the stage in the intermitotic cycle and the radiation quality. The results show that the radiation doses applied cause an equal elongation of the mean Tc, which is largest in the irradiated cells but persists in the three subsequent generations. After 3 Gy of X-rays, mitotic delay is largest in cells irradiated in later stages of the cycle, but this difference is not observed after 1.5 Gy of 14 MeV neutrons. In subsequent generations the Tc values show larger variations among descendents of cells treated in the same stage of the cycle as compared to controls but this variation is equal for the doses of X-rays and neutrons applied. Division probability was significantly reduced in irradiated cells as well as in subsequent generations, whereby with neutrons as compared to X-rays the damage is expressed in earlier generations, with less variation as a function of the cell cycle.

Animals↗

PubMed1984

Analysis of X-ray-induced cell-cycle perturbations in mouse osteosarcoma cells: a two-signal cell-cycle model.

The effects of X-irradiation on mouse osteosarcoma cells have been studied by time-lapse cinematography and the resulting pedigrees have been analysed statistically. It is shown that the irradiation treatment causes three types of cell kinetic lesions: cell death (disintegration), cell sterilization (failure to divide) and proliferation delay. The first two lesions are the most important with regard to survival of the irradiated cell in a clonal assay. Of these two lesions, sterilization appears to be highly correlated for sister cells, while this is not true for cell disintegration. This indicates that cell survival in a clonal assay may be a function of the ratio of the incidences of these two types of lesions. The X-ray-induced proliferation delay was studied in terms of intermitotic time distributions, mother-daughter correlation and sibling correlation in relation to the current cell-cycle phase at the time of treatment. This analysis shows that the effects of irradiation on these cell-cycle characteristics is highly cell-cycle-dependent. A qualitative model to account for the observations is presented.

Animals↗

PubMed1979

Influence of the hypoxic cell sensitizer misonidazole on the proliferation of well-oxygenated cells in vitro during prolonged exposure.

Analysis of time-lapse cinematographic film permitted the construction of pedigrees from 88 well oxygenated cells of a mouse osteosarcoma (MOS). These cells have been chronically treated with various concentrations of the hypoxic cell sensitizer misonidazole (MIS) over periods of up to 96 h. At concentrations of 0.5 and 7 mM there is a 2--3 h increase in cell-cycle time. Concentrations of 2 mM show an intermitotic time delay of 7.6--10.3 h. At 4 mM cells divided only once. With increasing drug concentration there was an increase in the number of abnormal mitoses. These results were compared with cloning efficiency (PE) experiments. PE at 0.5 mM is 80%, at 1 mM 40 and at 2 mM is reduced to 4%. Cells treated with 2mM MIS over a period of 28.6 h resume their normal cycle when the drug is washed from the culture. This may indicate that DNA is not a major target for MIS. It is concluded that this hypoxic cell sensitizer is also toxic for MOS cells in well oxygenated conditions.

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