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H Dertinger

Publications and source records attributed to H Dertinger.

At least 19 recordsLinked to original sources
PubMed1990

The DNA content of some mammalian cells measured by flow cytometry and its influence on radiation sensitivity.

The DNA content of nine mammalian cell lines was determined by flow cytometry. Using radiobiological data from this and other laboratories a correlation between DNA mass and 1/D0 for X-rays, alpha-particles, and heavy ions could be established when the quantities were plotted on a log-log scale. The slopes of the regression lines amounted to 0.65 (X-rays), 0.64 (alpha-particles) and 0.74 (heavy ions). A similar correlation was found between DNA content and mean inactivation dose. The rather uniform slopes close to 2/3 suggest that radiosensitivity may depend on the surface area of the sensitive target, (cell nucleus) indicating a possible non-uniform distribution of radiosensitive sites within the nucleus.

Alpha Particles↗
PubMed1990

Radioresistance of rat glioma cell lines cultured as multicellular spheroids. Correlation with electrical cell-to-cell-coupling.

Two chemically induced rat glioblastomas, RG2 and F98, were cultured as monolayers and as multicellular spheroids and subjected to Co-gamma-irradiation. In parallel, intercellular communication between cells was determined as electrical coupling between neighbouring cells using micro-electrode techniques. A third glioblastoma with known radiobiological response (9L) was assayed with respect to intercellular communication and included into this analysis. Electrical coupling was low for RG2, intermediate for F98, and high for 9L. Radioresistance of spheroids, as expressed in terms of the mean inactivation dose computed from the survival curves increased in the same direction (RG2: 2.4 Gy; F98: 5.1 Gy; 9L: 6.5 Gy). A comparison of these parameters demonstrates a correlation between solid tumor radioresistance and gap-junctional cell-to-cell communication, at least for the class of glioblastomas analysed in this study.

Animals↗
PubMed1984

Relationship between intercellular communication and radiosensitivity of human tumor xenografts.

Micro-electrode techniques permit the detection of electrical coupling between adjacent cells if they are connected by intercellular junctions (gap junctions). This technique was applied to four human tumors xenografted onto nude mice. In three of the tumors, which showed a 'contact resistance' after irradiation in vivo, electrical coupling could be established. No coupling was found in the other tumor, which did not exhibit contact resistance. These results are similar to those obtained recently with cultured spheroids of mammalian cell lines in which only the electrically coupled cell types developed contact resistance to ionizing radiation.

Adenocarcinoma↗
PubMed1984

Mean inactivation dose: a useful concept for intercomparison of human cell survival curves.

The mean inactivation dose (D) is calculated for published in vitro survival curves obtained from cell lines of both normal and neoplastic human tissues. Cells belonging to different histological categories (melanomas, carcinomas, etc.) are shown to be characterized by distinct values of D which are related to the clinical radiosensitivity of tumors from these categories. Compared to other ways of representing in vitro radiosensitivity, e.g., by the multitarget parameters D0 and n, the parameter D has several specific advantages: (i) D is representative for the whole cell population rather than for a fraction of it; (ii) it minimizes the fluctuations of the survival curves of a given cell line investigated by different authors; (iii) there is low variability of D within each histological category; (iv) significant differences in radiosensitivity between the categories emerge when using D. D appears to be a useful concept for specifying intrinsic radiosensitivity of human cell lines.

Ataxia Telangiectasia↗
PubMed1983

Is there a relationship between hypoxia, contact resistance, and intercellular communication?

This investigation addresses the shape of radiation survival curves of cells cultured as multicell spheroids. It is shown that spheroids of cells capable of intercellular communication by gap-junctions display survival curves lacking a radioresistant fraction of hypoxic cells. Compared to the corresponding monolayers, these spheroid survival curves exhibit a uniform increase in radioresistance due to the "contact effect". In contrast, biphasic survival curves indicative of hypoxic cells are obtained with non-communicating spheroids, however, without indication of a contact effect. Evidence is presented that this relationship between intercellular communication, hypoxia, and contact effect may possibly also hold for survival curves of solid tumors.

Animals↗
PubMed1983

Increased radioresistance of cells in cultured multicell spheroids. II. Kinetic and cytogenetic studies.

Using the Chinese hamster cell line B14 FAF28, several specific properties of the contact effect (CE) of radiation action in spheroids were investigated. CE was found to "protect" the spheroid cells against several types of radiation-induced cytogenetic misfunctions such as blockage in S and G2+M-phase, mutagenesis, and chromosome damage. However, repair of DNA strand-breaks was the same in monolayers and spheroids. Furthermore, CE is a property of the single cell and does not depend on the proliferative status (cycling or non-cycling) of the cells. We conclude that CE is the result of a physiological modification of the cells occurring during growth in the three-dimensional spheroid matrix and requiring metabolic cooperation and cyclic AMP for its induction.

Animals↗
PubMed1983

Radiosensitivity of four human tumor xenografts. Influence of hypoxia and cell-cell contact.

Contact effect (CE) and hypoxia have been studied in human tumor cell lines transplanted in athymic nude mice. Four cell lines--one melanoma (Bell) and three colorectal adenocarcinomas (HT29, HRT18, and HCT8)--were studied. Cell survival was determined with an in vivo to in vitro colony-forming assay. Survival curves were obtained under three different conditions: (1) tumor cells irradiated in air-breathing mice, (2) tumor cells irradiated in animals asphyxiated for 10 min, and (3) tumor cells plated and irradiated either immediately or 5 hr later. For all cell lines, radiosensitivity appeared to be lower when cells were irradiated in vivo than when they were irradiated in vitro. Only in the case of the HCT8 tumor did the relative in vivo radioresistance seem to be linked to hypoxia; in the other cell lines, hypoxia alone could not account for the lower in vivo radiosensitivity. Our results suggest that a CE plays an important role in the response of human tumor xenografts to irradiation.

Adenocarcinoma↗
PubMed1982

Intercellular communication, three-dimensional cell contact and radiosensitivity.

When electrically coupled mammalian cells are cultured as spherical clones (spheroids) and exposed to ionizing radiation they are less radiosensitive than monolayers of the same cell line. Investigations into the possible role of coupling (gap junctions) and three-dimensional contact in the expression of this phenomenon revealed 1) a correlation between cell coupling and the activity of adenylate cyclase in monolayers, 2) a sharp drop of cyclase activity in spheroids of coupled cells compared to monolayers, and 3) a decrease of coupling with age ("maturation") of the spheroids. These results suggest profound physiological alterations in communicating cells induced under conditions of tight three-dimensional contact as a possible cause for the reduced radiosensitivity of spheroids.

Adenylyl Cyclases↗
PubMed1981

Increased radioresistance of cells in cultured multicell spheroids. I. Dependence on cellular interaction.

Monolayers of six different cell lines were investigated with respect to ionic coupling using micro-electrode techniques. In parallel, survival after Co-gamma-irradiation of monolayer- and spheroid cultures of these lines was compared. It was found that spheroids of coupled cell lines were more radioresistant than monolayers ("contact effect"). however, cell coupling did not enhance the survival of monolayers over single cells. This suggests that the contact effect is a "tissue phenomenon" requiring cellular interaction but is expressed only under conditions of three-dimensional growth.

Animals↗
PubMed1979

Biological effects of negative pions in monolayers and spheroids of Chinese hamster cells.

The therapeutic value of pion irradiation was critically challenged by examining, in a cell culture system, various parameters of biological significance such as relative biological efficiency (RBE), oxygen enhancement ratio (OER), DNA-break formation, changes in cell cycle kinetics and regrowth. In all parameters, pions were superior to conventional low-LET radiation.

Animals↗
PubMed1979

Kinetics of regrowth of V79 spheroids after gamma- and pi--irradiation.

Spheroids of V79 cells were irradiated with 180 MeV/c pi--mesons in the peak region and with gamma-rays. Doses of 900 and 1500 rad were applied, respectively, yielding 14% surviving cells. Regrowth of the spheroids was followed by measuring volume changes, cell multiplication as well as viability and proliferation of cycling and resting spheroid cells. While volume growth after irradiation was equal for both radiations, the time profiles of cell density, viability and mean DNA content per cell were found to be different. Consistently, a more prompt and pronounced response to pion irradiation could be inferred and was discussed in terms of LET dependent proliferation and elimination of inactivated cells and their subsequent substitution by viable progeny cells. Recruitment of resting cells was observed with both radiations.

Animals↗
PubMed1979

[Recovery and cycle progression in multicell spheroids after fractionated gamma-irradiation and combined hyperthermic treatment (author's transl)].

Spheroids of V79 cells were subjected to fractionated irradiation with two doses of gamma-radiation. In addition, a two hours hyperthermic treatment at 42 degrees C immediately following the first dose was applied. Cycling and resting cells of this in-vitro tumour model were then assayed for survival as function of the fractionation interval. In parallel, changes in cycle progression between the doses were measured by means of cytofluorometry. As main proliferative effects induced by this combined radiation and heat treatment transient S-phase blocking of cycling and recruitment of resting cells were observed. The split-dose survival curve displayed considerable synergistic action of heat and radiation and a six hours delay of Elkind-recovery in both cycling and resting cells.

Animals↗
PubMed1976

Negative pion irradiation of mammalian cells. 1. Survival characteristics of monolayers and spheroids of Chinese hamster lung cells.

Monolayers and spheroids of Chinese hamster cells (V79) were subjected to negative pion irradiation under aerobic conditions. R.b.e. values in the pion peak of 1-8 and 1-5 were obtained for monolayers and spheroids, respectively, whereas the r.b.e. for the plateau was found to be slightly higher than 1. In addition, it was observed that the higher resistance of the V79 spheroid cells than the monolayers to gamma-irradiation is not diminished in the pion peak, suggesting that the underlying phenomenon of intercellular communication influences cell survival even after high-LET irradiation.

Cell Line↗
PubMed1975

The action of ionizing radiation on DNA in the presence of quinacrine. I. UV absorption and fluorescence measurements.

It is shown by UV absorption and absolute fluorescence spectroscopy of solutions containing both DNA and quinacrine that the components experience mutual radio-protection due to scavenging of water radicals. From measurements at different ionic strengths it is inferred that quinacrine bound to DNA is more efficiently protected than the free compound. Furthermore, release of bound quinacrine from DNA is observed at higher doses.

Animals↗
PubMed1975

The action of ionizing radiation on DNA in the presence of quinacrine. II. DNA strand breakage.

Strand breakage of DNA irradiated in solution and in the dry state in the presence of quinacrine was investigated by sedimentation analysis. Determination of single strand breaks in solution combined with binding studies permits to conclude that bound quinacrine protects DNA more effectively than the free compound. In the dry state quinacrine is without detectable effect on both single and double strand break formation, neither under aerobic nor anaerobic conditions.

Aerobiosis↗