Biomedical subjects
Publications and source records attributed to J Kummermehr.
The authors applied the method of regrowth delay in order to investigate the effect of a therapy combination consisting of cis-platinum and irradiation on the fibrosarcoma SSK2 in C3H mice. An independent addition of the effects of both therapy modalities was found. It could be shown especially that no elective radiosensitization of hypoxic tumor cells is caused by cis-platinum.
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Various preclinical tests have been performed to determine the properties of fast neutrons of a mean energy of 2 MeV produced by an U-235 converter plate in the research reactor of the Technical University of Munich. Experiments have been carried out using two specific beams denoted as RENT I and RENT II (RENT stands for Reaktor Neutron Therapy). RENT II is the unmodified beam with a dose rate of 65 rd/min and a gamma-contamination of nearly 50% in 2 cm depth of a perspex phantom. In RENT I the gamma-component is reduced to 25% after filtration of the beam with 2.5 cm lead, whereas the total dose rate is reduced to 22 rd/min.
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The fibrosarcoma SSK31 was irradiated under ambient or hypoxic conditions either acutely or at various intervals after a priming dose of 13 Gy. The absence of local recurrences was determined. The hypoxic fraction and the time course of reoxygenation were calculated on the basis of a comparison of the cure curves.
The effects of 13-cis-retinoic acid, which is clinically very effective in the treatment of severe acne, on sebaceous glands in humans was studied by means of histology, planimetry, and autoradiography. Histologically and planimetrically, one finds a marked decrease of size of sebaceous glands of up to 90% of the pretreatment values after 12 weeks of treatment. Additionally, the ratio of the so-called "differentiating cell pool (DCP)" vs. the so-called "undifferentiating cell pool (UCP)" changed from 2:1 to 1:7, probably indicating a disturbance of differentiation (lipid-production) of sebocytes. The labeling index of sebocytes also regressed significantly under therapy with 13-cis-retinoic acid.
The growth of 148 untreated metastases to the lung was determined in 47 patients. Pulmonary metastases of squamous-cell carcinomas, sarcomas and malignant melanomas exhibited exponential growth, the doubling times were distributed log-normally, the geometric mean amounted to six weeks. The growth rate of adenocarcinomas decreased with increasing tumor size approximately in accordance with a Gompertzian function.
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Radiation sensitivity of the hamster melanoma AMel 3 was studied in vivo and in vitro. In vitro, a dose-effect curve with the dose Do=155 rd and the extrapolation number 10 was obtained. In consideration of an oxygen enhancement factor of 2.5, the results of in-vivo examination with the quantitative transplantation method did not differ from in-vitro results. In living animals, about 40% of the tumor cells generally are hypoxic. These data do not verify the hypothesis of a particular radiation resistance of melanoma cells.
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