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Biomedical subjects

C Streffer

Publications and source records attributed to C Streffer.

At least 109 records · Page 6Linked to original sources
PubMed1992

Adaptive response in mouse embryos?

Pre-implantation embryos of the mouse were studied for the occurrence of an adaptive response, i.e. induction of radio-resistance by a previous low dose. Various experimental designs were checked (initial doses between 3 and 10 cGy; second dose 2-6 Gy at 6-24 h after the first dose). Some of the experiments were carried out in exactly the same way that resulted in an adaptive response of human lymphocytes reported previously. However, when cell proliferation and differentiation of mouse embryos were examined, none of the conditions tested indicated the induction of an adaptive response.

Adaptation, Physiological↗
PubMed1992

Absence of adaptive response to low doses of X-rays in preimplantation embryos and spleen lymphocytes of an inbred mouse strain as compared to human peripheral lymphocytes: a cytogenetic study.

The adaptive response was studied in preimplantation embryos and spleen lymphocytes of a mouse inbred strain and in peripheral lymphocytes of three human donors, using chromosomal aberrations as the endpoint. Embryos were adapted to 0.05 Gy X-ray 50 h post-conception either in vitro or in vivo and challenged 6 h later. Chromosome aberrations of the 8----16 cell stage mitoses were scored. No adaptive response was seen in the embryos. Of 14 female mice studied, an adaptive response was seen in spleen lymphocytes of only one mouse. However, because variable chromosomal aberration levels were observed in lymphocytes of different donors, it is concluded that the adaptive response detected was merely a result of this heterogeneity. In human peripheral lymphocytes an adaptive response was seen in all three donors. It is speculated that the inbred mouse strain used is deficient in the adaptive response.

Adaptation, Physiological↗
PubMed1992

Flow cytometric analysis of colorectal mucosa from patients with Crohn's disease, ulcerative colitis and cancer.

Samples of colorectal mucosa from patients with Crohn's disease, ulcerative colitis and cancer were analyzed by means of flow cytometry. S- and G2-phase fractions were determined and mean values were calculated for different groups of patients. Almost identical results were obtained for inflamed and normal appearing mucosa from patients with Crohn's disease as well as inflamed mucosa from patients with ulcerative colitis. The mean S- and G2-phase fractions in normal appearing mucosa from cancer patients, however, were significantly higher. This seems to be due to the fact that patients with Crohn's disease are between 15 and 45 years old, while cancer patients are mostly over 45. A detailed analysis of the S- and G2-phase fractions in different age groups revealed a slight, but significant increase in colorectal proliferation between 25 and 75 years.

Adult↗
PubMed1992

Activity testing of alveolar macrophages and changes in surfactant phospholipids after irradiation in bronchoalveolar lavage: experimental and clinical data.

This study presents results of bronchoalveolar lavage (BAL) after irradiation to the lungs in mice as well as clinical data. The number of BAL cells, mainly macrophages, lymphocytes, and granulocytes, changed in a time-dependent manner. The phagocytic activity of the macrophages measured as the phagocytosis of microbeads and measured as the esterase activity also showed a strong time-dependent increase during the acute phase up to 21 days after irradiation. The contents of surfactant phospholipids (SF) and sphingomyelin (SPH; as a parameter for cell death) were quantified by HPLC. Both were significantly changed between day 2 and 21 after irradiation. Three BALs of a patient with idiopathic interstitial pneumonitis, who had received an allogenic bone marrow graft after total body irradiation with 10 Gy, showed similar effects in the cellular and surfactant parameters. These data indicate that there are positive interactions between the number of different BAL cells, macrophage activity, and SF and SPH content in the preclinical model of the mouse as well as in the clinical situation after lung irradiation.

Animals↗
PubMed1992

The cytoskeleton and proliferation of melanoma cells under hyperthermal conditions. A correlative double immunolabelling study.

Hyperthermia provides a potent therapeutical tool of cancer treatment, the cell biological effects of which are fairly understood. In the present study we applied hyperthermal shocks of 42 degrees C and 44 degrees C to human melanoma cells under tissue culture conditions. The integrity of the microtubular (mT) system and rate of DNA replication was assessed by indirect immunofluorescence using antibodies to tubulin as an mT marker and to BrdU as an indicator for DNA replication. Through this approach we obtained evidence that heat (44 degrees C for 60 min) exerts a profound damaging effect on the mT system accompanied by a change in the phenotypical appearance of melanoma cells. DNA replication, however, was still in progress in a significant number of heavily afflicted cells. From these data we conclude that a therapeutic regiment combining hyperthermia and mT inhibitors might prove useful in the treatment of human melanomas.

Cell Division↗
PubMed1992

Micronucleus assay prediction and application optimized by cytochalasin B-induced binucleated tumor cells.

Improvement in the predictive assertion of the micronucleus assay was achieved by treating human malignant melanoma cells (Mewo) with cytochalasin B (CB), generating binucleated cells (BNC) representing cells after a single karyokinesis. Optimal cell binucleation was determined by testing several cytochalasin B concentrations and different incubation times. On average, 56% binucleated cells were found after incubation with 2 to 3 micrograms/ml cytochalasin B for 48 h. Cells with at least one micronucleus (Mn) were defined as fraction of cells with micronuclei and describes the degree of damaged cells. We found in binucleated cells 2.2 fold the fraction of cells with micronuclei than in mononucleated cells (MNC), as expected assuming that an induced micronucleus is associated with only one single daughter cell after mitosis. The mean of micronuclei per binucleated cells, however, was enhanced about 2.9 fold in relation to that of micronuclei per mononucleated cells and is related to the nuclear damage per cell. The application of cytochalasin B did not enhance the fraction of damaged cells although the degree of the injury per cell is intensified. A micronuclei promoting or inhibiting effect of the experimental design due to changes in cell proliferation was excluded by cytofluorometric investigations of DNA content and synthesis after cytochalasin B application. A comparison of the modified with the conventional micronucleus assay shows the superiority of the former.

Cell Line↗
PubMed1992

In-vivo measurements of early and late effects in normal tissue after abdominal X-irradiation--development of a clinically orientated score for the determination of side-effects and the individual radiation response in a mouse model.

Heiligenberger mice received abdominal single X-ray doses of either 10 or 12 Gy. Early (up to one month) and late effects (two to eight months) were measured in vivo with ten parameters (nitrite, albumin, glucose, urobilinogen, bilirubin, haemoglobine, ketone, pH, weight development, general clinical conditions). These parameters permit the assessment of the condition of the essential organ systems. Thus, their use as screening parameters appears meaningful. By creating indices and integrating these in the animal index (range 1 to 3) it is possible to obtain an impression of the health condition of the individual animal. Early and late damage can be determined with certainty despite large individual variances. Radiation-induced chronic but not lethal changes can be measured. A large early damage is also predictive for a large late morbidity; not the individual parameters allow conclusions to be drawn but instead only the total number of the parameters used here are capable of this. The results have tended to show that the systematic listing of early responses also allows for very early indication of late morbidity or chronification events to be expected. The results have shown that the individual analysis of single parameters can give rise to important indications for a decisive diagnosis. This corresponds to the usual clinical procedure and can be applied to animal experiments without restriction.

Abdomen↗
PubMed1992

Vascular patterns of tumors: scanning and transmission electron microscopic studies on human xenografts.

The tumor vascular system plays a significant role both in tumor growth and metastasis as well as in therapy. However, there are comparatively few papers dealing with the morphology and architecture of tumor vascularity. This is inconceivable insofar as structural and architectural parameters determine tumor blood flow. Therefore, the vascular system of eight human tumor lines transplanted onto 121 thymus-aplastic nude mice was studied with light, scanning and transmission electron microscopy as well as microvascular corrosion casting. All tumors show a connective tissue-like capsule with a dense plexus of vessels forming a "vascular envelope". Particularly in early stages, these vessels follow a tortuous course with glomeruloidal arrangement and numerous indications of angiogenic activity. In the tumor centre regular arteries and veins are never to be seen. Instead, all vessels show a capillary wall construction with variations in height and electron densities of the endothelial cells. Changes in vessel diameter, lack of vascular hierarchy, blind ends as well as irregular sinusoidal systems originating from and draining to veins are common features. The vascular densities vary considerably within single tumors. Based on the vascular architecture and wall construction, necroses may occur even in areas with intervascular distances of only 15 microns. No significant differences in vascular architecture of the various cell lines could be observed.

Animals↗
PubMed1992

Preimplantation growth delay and micronucleus formation after in vivo exposure of mouse zygotes to fast neutrons.

Mouse zygotes were irradiated with fast neutrons (0.06 to 1.00 Gy) 1 h after conception and examined at various intervals (24 to 100 h after conception) for embryonic development and micronucleus formation. The frequency of micronuclei per cell increased linearly with dose in 2-cell embryos observed at 24 h after conception and in 4-cell and 8-cell embryos at 48 h after conception. Compared with X rays, the relative biological effectiveness of neutrons for the induction of micronuclei per embryo was 2.5 at 24 h after conception and 3.5 at 48 h after conception. Neutron-induced micronucleus formation was accompanied by morphological growth delay and a significant decrease in the number of cells in the embryos. An inverse relationship was found between the number of cells in embryos and the number of micronuclei when observed at 48 h after conception following irradiation with 0.12 to 1.00 Gy and at 78 h after conception following exposure to 0.50 Gy. The effect of neutron irradiation on embryonic development was likely to be mediated by cell death, as suggested by a significantly increased dead cell index in blastocysts following irradiation of zygotes.

Animals↗
PubMed1991

Cell proliferation and vascularization in human breast carcinomas.

Cell proliferation and vascularization were studied in 10 human breast carcinomas by an immunoenzyme technique. The monoclonal antibody (MAb) Ki-67 was used as a marker for proliferating cells and a polyclonal antibody directed against human von-Willebrand factor to identify blood vessels. The proportion of Ki-67-labelled cells varied from 1% to 20%, the number of small blood vessels from 4.4/mm2 to 57.6/mm2. Within single histological sections of individual tumours the percentage of proliferating cells was not related to the number of small blood vessels. However, after evaluation of 5 sections of each tumour, the average values showed that tumours with a high grade of vascularization had a higher percentage of Ki-67-positive cells than poorly vascularized samples. The influence of vascular density on cell proliferation was investigated in a selected area of one of the tumours (in 2-dimensions) and with regard to the over- and underlying sections (in 3-dimensions). After 2-dimensional evaluation, distances from proliferating cells to the closest blood vessel between 10 and 390 microns were observed, and after 3-dimensional evaluation none of the proliferating cells measured was located more than 130 microns away from the closest vessel.

Antibodies↗
PubMed1991

Estimation of the dividing fraction and potential doubling time of tumors using cytochalasin B.

We devised a new in vitro method to estimate the proportion of dividing cells and the potential doubling time (Tpot) of tumors using the same technique as with the cytokinesis-block micronucleus assay. The usefulness of this methodology was confirmed by comparing the data with those obtained by flow cytometry after bromodeoxyuridine (BrdUrd) incorporation. Xenografted human and murine tumors were excised 0.5-8 h after BrdUrd injection and disaggregated to single cells. A portion of these cells was then plated in dishes to which 1 or 2 micrograms/ml cytochalasin B were added. These concentrations of cytochalasin B blocked cytokinesis but not karyokinesis with the result that cells became multinucleate after mitoses. At every 12 or 24 h of culture, the proportion of multinucleate cells and the total number of nuclei and cells were scored. The remaining cells were analyzed with a flow cytometer and the BrdUrd-labeling index and Tpot were determined. In all 8 tumor lines studied, the proportion of multinucleate cells reached a plateau within 3-7 days of culture, and we therefore defined the dividing fraction as the plateau value. The dividing fraction ranged between 33 and 98% and clearly tended to be high in rapidly growing tumors. A significant correlation was seen between the dividing fraction and BrdUrd-labeling index (r = 0.74, P less than 0.001). The increase in the average number of nuclei per cell also tended to be higher in rapidly growing tumors. The Tpot was estimated as the time for this nucleus/cell ratio to reach 2.0. In 7 of 8 tumor lines, Tpot values estimated by this method compared reasonably with those estimated by the BrdUrd method. Therefore, this simple technique, originally developed for radiosensitivity prediction, would also seem to be useful in estimating tumor proliferative activity.

Animals↗
PubMed1991

Direct evidence that radiation induced micronuclei of early embryos require a mitosis for expression.

The naturally synchronous development of early mouse embryos was exploited to address the question, whether micronuclei require a mitosis for expression or whether they can be expressed in the same cell cycle, in which exposure to X-rays or caffeine took place. Experiments with 2-cell and with 4-cell embryos showed that micronuclei are expressed only if a mitosis is completed. There was no indication, even after doses up to 20 Gy, that micronuclei can be expressed before the mitosis was reached, which followed exposure. Furthermore, no nuclear fragmentation pointing to apoptosis could be detected in the cycle, in which cells were exposed. The same results were obtained when caffeine (5 mM) was used as micronucleus inducing agent.

Animals↗
PubMed1991

Radiation-induced changes in lung tissue and development of fibrosis determined by quantitative morphometric methods.

This study presents results of morphometric investigations of mouse lungs after single irradiation. An automatic image analyser was used to monitor pathological changes in morphological structure, especially the size and distribution of collagen fibres, the thickness of the septa and the diameters of alveoli in the lung. Radiation-induced changes in the area of alveoli and septa as well as collagen content were seen 11 weeks after irradiation. A dose-dependent increase in tissue and decrease in alveolar surface as well as a quantifiable increase in radiation oedema were seen. The septa were thickened and the total collagen content increased in a dose-dependent manner. The morphometric methods used here are suitable for determining changes in lung structure, particularly those in collagen content in the early phase of a pathological response after thorax or total body irradiation for conditioning in bone marrow transplantation.

Animals↗
PubMed1991

Evaluation of a new 2-nitroimidazole nucleoside analogue, RK-28 as a radiosensitizer for clinical use.

The experimental data previously reported on RK-28, a hypoxic cell sensitizer which is now being tested in a phase I clinical trial, are confusing. Some data indicate superiority of RK-28 over misonidazole (MISO), whereas others do not. This paper presents our experimental data on the efficacy, toxicity, and pharmacokinetics of RK-28, in comparison with those of MISO, and also summarizes the data of other investigators. In our experiments, RK-28 had a 1.5-2.5 times higher sensitizing activity in vitro on EMT6 and SCCVII cells than MISO, and the difference was larger when the pre-irradiation incubation time was longer. The latter was considered to be due to the time-dependent cellular uptake and reactivity of RK-28 with non-protein sulphydryls. In vivo, RK-28 was almost as efficient as or slightly inferior to MISO against SCCVII and EMT6 tumours when assayed with an in vivo/in vitro assay and a growth delay time assay. The LD50/7 by a single injection of RK-28 was half that of MISO, but when 60% of LD50/7 was injected into mice every day, the total dose that could be given was higher for RK-28 than for MISO. Pharmacokinetic studies using mice, rats, rabbits, and a dog showed that RK-28 was rapidly eliminated from the blood and various tissues. From our results it was concluded that the possible success of the clinical trial of RK-28 depends on its low cumulative toxicity.

Animals↗
PubMed1991

Micronuclei with kinetochores in human melanoma cells and rectal carcinomas.

Micronucleus frequencies were analysed in an X-irradiated human melanoma cell line and in untreated rectal carcinoma cells. As a special aspect of the micronucleus formation, micronuclei-containing kinetochores were analysed by the method of indirect immunofluorescence. The incidence of kinetochore-positive micronuclei was taken as a measure of chromosome loss. In order to show kinetochores, an anti-kinetochore serum of a CREST syndrome patient was used. In irradiated melanoma cells the mean number of micronuclei increased linearly with increasing dose whereas the proportion of kinetochore-positive micronuclei decreased. The analysis of the time-dependent formation of micronuclei revealed an increase of the micronucleus frequency from 24 to 48 h after irradiation (p.r.) and a slight decrease from 48 to 72 h p.r. The highest number of kinetochore-containing micronuclei was scored 72 h p.r. In rectal carcinoma cells a high rate of spontaneously formed micronuclei was observed. At least 30% of these micronuclei contained complete chromosomes, as indicated by the kinetochore-positive staining. We have attempted to summarize the data by means of a numerical expression which takes into account the relation between lost chromosomes, visible as kinetochore-positive micronuclei, and the total sum of micronuclei.

Centromere↗
PubMed1991

Biological indicators for radiation damage.

Methods for estimating radiation dose using biological indicators have made rapid progress during recent years. Chromosome analysis in lymphocytes still plays a central role, but it is no longer the only quantitative system in biological dosimetry. The best approach seems to be to combine several of the assays exploiting their specific advantages: the high sensitivity in the case of dicentrics in lymphocytes (starting at about 0.05 Gy low-LET radiation), the broad dose range covered by the electron spin resonance technique (0.5-100 Gy), the possibility of identifying the localization of partial-body exposure when determining hair diameter, and the individual prognostic information obtained from changes in the frequency of blood cells after exposures exceeding about 1 Gy. In specific situations other methods may replace or supplement these indicators for radiation damage.

Biomarkers↗
PubMed1991

Association of protein phosphorylation and cell cycle progression after X-irradiation of two-cell mouse embryos.

Studies of protein phosphorylation in the second cell cycle of mouse embryos were assessed by [32P]-incorporation and one- and two-dimensional electrophoresis. Unirradiated and X-irradiated embryos were compared. X-irradiation in the G2 phase led to a block in this cell cycle phase. The phosphorylation of proteins with molecular weights of 30 and 46 kDa specifically correlated with the G2 phase-mitosis transition in normally dividing and in irradiated embryos. The time lag in the phosphorylation of these proteins between the unirradiated and X-irradiated embryos was identical to the duration of the radiation-induced G2 block. X-irradiation immediately decreased the phosphorylation of a 29 kDa protein to below detectable levels. Re-phosphorylation of this protein preceded the following mitosis. It is suggested that the 29 kDa protein may be involved in the regulation of events that led to the radiation induced G2 block and the initiation of mitosis after release.

Animals↗