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Biomedical subjects

C Streffer

Publications and source records attributed to C Streffer.

At least 271 records · Page 15Linked to original sources
PubMedDate not supplied

Correlation of (S+G2)-phase fractions determined by flow cytometry and Ki-67 labelling indices in colorectal carcinomas.

Samples from 14 human colorectal carcinomas were analysed by means of classical (one-parameter) flow cytometry. (S+G2)-phase fractions were calculated from DNA histograms with the help of two different algorithms. At the same time, the percentage of cells positive for the Ki-67 antibody, which recognizes proliferating cells, was determined in cytocentrifuge preparations. Significant correlations between the two indices were found only if the histogram analysis included background subtraction and aggregate correction. This finding may throw some light on the reliability of prognosis based on flow cytometry.

Aged↗
PubMedDate not supplied

Effects of local hyperthermia on the tissue levels and toxicity of three radiosensitizers in mice.

The toxicity of the radiosensitizers misonidazole (MISO), demethylmisonidazole (DEMISO) and pimonidazole (PIM) in mice can be affected differently when combined with local hyperthermia at 43 degrees C for 30 min. At a dose of 1 mg/g, only MISO plus heat resulted in 50% lethality in animals over a period of 7 days post-treatment, whereas 100% survival was observed in the case of DEMISO and PIM. The enhanced lethality may be associated with the production of toxic intermediates of MISO. Heat did not affect the levels of DEMISO in the tissues studied (plasma, brain and tumour), whereas those of PIM were markedly lowered in tumour but not affected in brain for up to 4 h after combined treatment. MISO was found to be decreased in the tumour at all times but affected differently in brain after 1 and 2 h, initially decreasing and then increasing significantly. In all cases the treatment sequence, i.e. sensitizer plus heat or vice-versa, did not affect the rate of survival. At a dose of 2 mg/g, DEMISO plus heat was found to be more toxic when DEMISO was given first (25% survival) compared to 58% on reversal. However, the levels of DEMISO in the tissues were not affected by heat. Thus, it would appear that there is no correlation between parent drug levels measured in plasma, tumour or brain and hyperthermia-induced drug lethality.

Adenocarcinoma↗
PubMedDate not supplied

Bioluminescence imaging of metabolites in a human tumour xenograft after treatment with hyperthermia and/or the radiosensitizer pimonidazole.

The levels and distribution of ATP, glucose and lactate in human tumour xenografts following either single or combined treatment with hyperthermia (43 degrees C for 30 min) and/or pimonidazole (1 mg/g b.w) were determined by bioluminescence and compared with the mean 'global' levels obtained from the same tumours using conventional biochemical analysis. In general, the levels of ATP, glucose and lactate measured with both methods were in good agreement although the latter was consistently lower after bioluminescence determination. Compared with controls, neither the levels of ATP nor glucose were greatly affected in this tumour following treatment with the various modalities, whereas those of lactate were considerably increased as determined by both methods. The spatial distribution of ATP and glucose from controls and treated tumours was largely confined to the periphery and generally remained unchanged irrespective of treatment without any apparent alterations in the shape of the distribution curve. However, the increased lactate levels tended to accumulate towards the central region of the tumour after hyperthermia and/or sensitizer, showing an almost Gaussian-like distribution compared with controls. These results are in agreement with previous studies of global tumour metabolism showing an enhanced glycolytic activity with increased lactate levels after single or combined modality treatment.

Adenosine Triphosphate↗
PubMedDate not supplied

Oxygenation status and tumor response during fractionated irradiation in two murine tumor cell lines of same origin but different intrinsic radiosensitivities.

Two murine tumor cell lines derived from the same origin and having different intrinsic radiosensitivities, one radiosensitive, SHA3K4-Ic (Ic), and the other relatively radioresistant, SHA3K4-III19 (III19), were compared in vivo regarding oxygenation, proliferation, and tumor response during fractionated irradiation. Tumors transplanted into nude mice were irradiated five times a week with a fraction size of 3 Gy up to a total dose of 30 Gy. Oxygenation status was analyzed using a non-invasive system with near infrared reflection spectroscopy. Proliferation status was quantified as the percentage of bromodeoxyuridine-labelled tumor cells and the percentage of necrotic area. All parameters were compared between untreated and irradiated tumors of the two lines. The oxygenation status in the untreated tumors did not correlate with tumor response. However, for the radioresponsive line, Ic, O2 saturation was significantly higher in irradiated than in untreated tumors, suggesting the existence of reoxygenation following fractionated irradiation. On the other hand, oxygenation status remained almost unchanged for the non-radioresponsive line, III19. Proliferation status did not correlate with tumor response. The results indicate that comprehensive investigations, including oxygen measurements, are necessary to understand the various intrinsic and extrinsic factors determining in vivo tumor radioresponse.

Animals↗
PubMedDate not supplied

DNA measurements and micronuclei in human rectal carcinoma.

It has been recognized that the variability among individual human tumors is tremendous. We investigated DNA content and cell proliferation in 81 patients with rectal carcinoma by cytophotometric methods. Among them, 32 patients showed only diploid cells and 41 patients hyperploid cells, and the former had better prognoses than the latter. The percentage of S cells calculated from the DNA histograms and the number of cells with micronuclei were higher in proliferative tumors. Clinically, probably due to repopulation in the tumor 10 to 15 days after preoperative radiotherapy, the number of S cells increased and local recurrence was found several months after surgical resection in more than a few cases. These data suggest that the biological variability of human tumors is extraordinary and individualization of tumor therapy is greatly indicated. Furthermore, the above parameters may help to obtain indicators for the prognosis and thereby improve therapy.

Astrocytoma↗