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Biomedical subjects

G P Raaphorst

Publications and source records attributed to G P Raaphorst.

At least 91 records · Page 5Linked to original sources
PubMed1988

Potentially lethal radiation damage repair and its inhibition by hyperthermia in normal hamster cells, mouse cells, and transformed mouse cells.

The capacity of plateau-phase Chinese hamster V79 and normal and transformed C3H-10T1/2 cells for repair of potentially lethal radiation damage (PLD) was evaluated for cells irradiated alone or given combined treatments of heat and radiation. The data show that all cell lines tested could repair PLD and that transformation to the tumorigenic state may reduce the capacity to repair PLD, especially if cells are evaluated at equal survival levels. Hyperthermia treatments before irradiation produced less sensitization than treatments after irradiation. In addition, hyperthermia treatment led to the inhibition of cellular capacity to repair PLD. This effect was the greatest for cells heated after irradiation, and repair of PLD could be completely eliminated. Several temperature isodose heat treatments were evaluated, and the lower temperature heat treatments were more effective in the inhibition of PLD than the higher temperature heat treatments; this is consistent with earlier results indicating temperature dependence in thermal radiosensitization (S. A. Sapareto et al., Int. J. Radiat. Oncol. Biol. Phys. 5, 343-347 (1979)).

Animals↗
PubMed1987

Effect of cholesterol alpha and beta epoxides on cell killing and transformation.

V-79 Chinese hamster lung fibroblasts and C3H-10T1/2 mouse embryo cells were used to study the toxicity and transformation effects of the 5 alpha,6 alpha, and 5 beta,6 beta-epoxy derivatives of cholesterol. Both epoxides were found to be carcinogenic, and the transformation frequency increased with epoxide concentration and exposure time. The 5 beta,6 beta-epoxide caused a higher level of transformation than the alpha-isomer, and this is consistent with its greater toxicity.

Animals↗
PubMed1987

Drug cytotoxicity at elevated temperature. In vitro study on the U-87MG glioma cell line.

The malignant glioma cell line U-87MG was used for 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), aziridinylbenzoquinone (AZQ), cis-diaminodichloroplatinum (II) (cis-DDP), and spirohydantoin mustard (SHM) treatments at 37 degrees and 42 degrees C. With the exception of SHM, all drugs killed a greater proportion of cells at the higher temperature, as assessed by the colony-formation assay. Drug-dose enhancement ratios were 1.6, 2.8, 2, and 1:1 for BCNU, AZQ, cis-DDP, and SHM, respectively. Because methods to heat discrete volumes of brain are now available, we conclude that hyperthermic increase of BCNU, AZQ, and cis-DDP cytotoxicity might have therapeutic application for malignant gliomas.

Antineoplastic Agents↗
PubMed1987

The use of flow cytometry to measure glucocorticoid-induced killing of lymphoid cell lines.

A flow cytometer method was developed to measure glucocorticoid-induced death in sensitive lymphoid cells. The murine lymphoma cell lines, R1.1, S49.1 and WEHI 7.1, and the human T-lymphocyte cell line, MOLT-4, were exposed to 10(-8) to 10(-6) mol/L dexamethasone or methylprednisolone. The cytogram for unstained, unfixed cells, produced by plotting the axial light loss versus the right-angle scatter using a He-Ne laser as the light source, showed two clearly separated peaks corresponding to live and dead cells. The ratio of live to dead cells seen in the cytogram correlated with that obtained by trypan blue staining. The flow cytometry method offers a number of advantages: 300 to 500 cells/s can be counted, yielding speed and good counting statistics; unstained, unfixed cells can be used; and the live and dead cells can be sorted for plating or biochemical analysis. S49.1 and R1.1 cells were sensitive to methylprednisolone and dexamethasone in the 10(-6) to 10(-8) mol/L concentration range, while MOLT-4 and WEHI 7.1 cells were less sensitive. After a 48-h exposure to 10(-8) mol/L dexamethasone, S49.1 and R1.1 cell cultures had 30% and 38% dead cells, respectively, while WEHI 7.1 and MOLT-4 cell cultures had less than 5% dead.

Animals↗
PubMed1986

A study of heat and radiation response of a malignant, melanin-producing cell line derived from C3H 10T1/2 cells transformed in culture by radiation.

The mouse C3H 10T1/2 cell line was transformed to the malignant state using ionizing radiation. One of the transformed lines (R25) that was isolated, displayed some properties similar to malignant melanoma cells. The cells became dark and pigmented after prolonged time in culture and this cell line produced tumors in C3H mice. The radiation survival curve of R25 had a large shoulder which was also observed for human melanoma cell lines. R25 was more resistant to heating at 45.0 degrees C than the normal cell line. Heating at 45.0 degrees C before irradiation resulted in a reduction of the survival curve shoulder. The heat and radiation sensitivity of R25 did not appear to be related to the melanin content of these cells.

Animals↗
PubMed1986

Fixation and repair by anisotonic treatment of radiation damage leading to oncogenic transformation.

Mouse embryo (C3H 10T1/2) cells were exposed to anisotonic NaCl solutions or combined treatments of radiation and anisotonic solutions. Anisotonic treatment with 0.05 or 0.5 mol/l solutions did not cause transformation and only prolonged exposure at 1.5 mol/l caused significant increases in transformation. When cells were irradiated in the presence of 0.05 mol/l NaCl, increased transformation occurred than when cells were irradiated in medium. Thus, anisotonic treatment after irradiation resulted in fixation of potentially lethal and transformed radiation damage. Fixation of potentially transformed damage was greater for cells irradiated in the presence of 0.05 mol/l NaCl than for cells irradiated in medium. When the NaCl treatment after irradiation was delayed by incubation at 37 degrees C, recovery of potentially lethal and potentially transformed damage was observed.

Animals↗
PubMed1986

Oncogenic transformation of C3H10T1/2 mouse embryo cells by X-rays, hyperthermia, and combined treatments.

The C3H10T1/2 cell system was used to measure oncogenic transformation after heating and after combined treatments of heat and X-rays. Heat alone at 41.0, 42.0, and 45.0 degrees C caused no transformation. Prolonged heating at 42.0 degrees C, or incubation at 37 degrees C after heating at 45.0 degrees C, resulted in thermotolerance in terms of cell killing, but did not cause transformation. Combined treatments of heat and radiation resulted in small increases in the transformation frequency per viable cell when the two treatments were separated by incubation at 37 degrees C. For simultaneous treatments of heat and X-rays, or treatments immediately following each other, the transformation frequency was about the same as, or lower than, with X-rays alone. When transformation was calculated based on the cells at risk, hyperthermia treatment reduced the X-ray transformation frequency in all cases. Thus hyperthermia may not pose a carcinogenic risk in cancer therapy and could decrease the oncogenic potential of X-rays, depending on the treatment sequence.

Animals↗
PubMed1985

Fixation of radiation-induced potentially lethal damage by anisotonic treatment and its modification by DMSO or BrdUrd in V79 cells.

The effects of radiosensitization by bromodeoxyuridine (BrdUrd) substitution and radioprotection by dimethyl sulfoxide (DMSO) have been examined in relation to fixation and repair of radiation damage by anisotonic treatment. The fixation of radiation damage in cells exposed to 0.05 M or 1.5 M NaCl after irradiation was the same at equal survival levels irrespective of (BrdUrd) incorporation into the DNA. Also, during incubation between irradiation and a subsequent anisotonic treatment, cells containing BrdUrd repaired radiation damage to the same extents as cells without BrdUrd. DMSO treatment resulted in radioprotection. Fixation, by anisotonic salt treatment, of damage resulting from irradiation in the presence of DMSO was less extensive than from irradiation in the absence of DMSO, even though X-ray doses were adjusted to give equal survival levels. Recovery during incubation at 37 degrees C between irradiation and a subsequent salt treatment occurred for irradiation in the presence and absence of DMSO. These data show that the alteration of DNA radiosensitivity by BrdUrd had no effect on fixation or repair of radiation damage as assessed by salt treatment, while DMSO which is an OH scavenger caused the damage to be less susceptible to fixation and this damage was repaired during incubation at 37 degrees C.

Animals↗
PubMed1985

Hyperthermia enhances X ray cell killing in normal and homozygous and heterozygous ataxia telangiectasia human cells.

Two homozygous and heterozygous ataxia telangiectasia (AT) cell strains were compared to normal human cells for heat and radiation responses. The thermal sensitivities to one hour heating at 42.0 degrees C were comparable in the five cell strains. Thermal enhancement of radiosensitivity occurred in both homo- and hetero-zygous AT cell strains and was comparable to the thermal enhancement observed in the normal cell strain. Normal cells recovered during incubation at 37.0 degrees C between the two treatments of heat and X rays while homozygous AT cells showed no recovery. The heterozygous cell strains showed only a slight sequence dependence for heat and radiation sensitivity.

Ataxia Telangiectasia↗
PubMed1985

The use of flow cytometry to measure X-ray survival in cultured T lymphocytes.

Light-scattering signals produced in a flow cytometer containing unstained, irradiated T-lymphocytes (MOLT-4 cell line) were analysed by plotting the axial light loss versus right-angle scatter. The resulting three-dimensional scattergram separated into two regions, corresponding to live and dead cells, as confirmed by trypan blue staining. The method is simple, rapid, allows large numbers of cells to be measured, avoids staining artifacts and is suitable for measuring radiation-induced killing down to 0.5 to 0.1 Gy.

Cell Line↗
PubMed1985

In vitro transformation by bromodeoxyuridine and X irradiation in C3H 10T1/2 cells.

The effect of 10(-5) M bromodeoxyuridine (BrdUrd) substitution in C3H 10T1/2 cells was evaluated. Cellular toxicity increased rapidly for BrdUrd exposure times that were longer than the population doubling time. Radiosensitization by BrdUrd exposure was almost complete after one cell doubling time and was characterized by a decrease in D0 and the survival curve shoulder. Exposure to BrdUrd for one cell doubling time produced only very low transformation levels, but for prolonged BrdUrd exposure times, the transformation frequency per viable cell increased significantly. BrdUrd incorporation also enhanced radiation induction of transformation above the transformation levels resulting from the independent action of X rays or BrdUrd treatment. These results show that BrdUrd is a transforming agent in C3H 10T1/2 cells and thus may be a carcinogen and that BrdUrd can enhance radiation-induced transformation.

Animals↗
PubMed1985

Ataxia-telangiectasia homo- and heterozygous cells show a normal repair and fixation response to anisotonic NaCl treatment after irradiation.

The effect of anisotonic NaCl treatment on fixation and repair of radiation-induced potentially lethal damage (PLD) was tested in normal human cells and in three homozygous ataxia-telangiectasia (A-T) and two heterozygous A-T cell strains. Fixation of radiation-induced PLD occurred in all cell strains exposed to 0.05, 0.5, or 1.5 mole/liter NaCl solutions immediately after irradiation. This effect was observed in both plateau-phase and exponentially growing normal and A-T cells. When an incubation period at 37 degrees C was introduced between irradiation and the subsequent anisotonic treatment, recovery was observed in both normal and A-T cells strains. These data show that A-T cells are as proficient as normal cells in repairing PLD that is sensitive to anisotonic NaCl treatment. It is proposed that two PLD repair systems may exist, one that is expressed after irradiation in proliferatively arrested cells and another that occurs in plateau-phase as well as exponentially growing cells, and is expressed by the postirradiation treatments described here and by Raaphorst and Azzam (Radiat. Res. 86, 52-66 (1981].

Ataxia Telangiectasia↗
PubMed1985

Ataxia telangiectasia cells exhibit the same radiosensitization response by incorporation of BrdUrd or IdUrd as do normal human cells.

Normal and ataxia telangiectasia (AT) human cells were exposed to 10(-5) mole/liter bromodeoxyuridine (BrdUrd) or iododeoxyuridine (IdUrd). High-pressure liquid chromatography (HPLC) measurements showed that up to 26 and 23% of the thymidine in DNA was substituted by BrdUrd in normal and AT cells, respectively. The incorporation of BrdUrd or IdUrd into DNA resulted in radiosensitization in normal and AT cells. When exposed to equal concentrations of BrdUrd and IdUrd, the BrdUrd caused greater radiosensitization than IdUrd in both normal and AT cells.

Ataxia Telangiectasia↗
PubMed1985

Comparison of heat and/or radiation sensitivity and membrane composition of seven X-ray-transformed C3H 10T1/2 cell lines and normal C3H 10T1/2 cells.

C3H 10T1/2 mouse embryo cells were transformed by X-irradiation, and seven transformed clones were isolated and propagated as cell lines. Some of these cell lines produced tumors in syngeneic mice and grew in agarose while the normal C3H 10T1/2 cell line did not possess these characteristics. Exponentially growing cell cultures with comparable cell-cycle distributions as measured by flow cytometry were tested for heat and X-ray sensitivity. The heat and X-ray sensitivity varied randomly compared to the normal cell line. One cell line was more heat resistant and one more heat sensitive than the normal cell line, and the others had sensitivities comparable to the normal cell line. Measurements on some of the biochemical parameters of the particulate fraction of cells after sonication and 24,000 X g centrifugation showed that altered thermal sensitivity was not correlated with protein, cholesterol, or phospholipid content of this fraction.

Animals↗
PubMed1985

Modification of cell survival and transformation by exposure to anisotonic solutions during irradiation.

C3H 10T 1/2 cells were exposed to a wide range of anisotonic NaCl solutions and were irradiated during the last few minutes of the salt treatment. Radiosensitization in terms of cell killing and transformation was observed for hypotonic NaCl treatment. Hypertonic treatment with 0.5 mol/liter NaCl also caused radiosensitization for cell killing and transformation, while extreme hypertonic treatment (1.5 mol/liter) resulted in radioprotection for both end points. Radiosensitization for both end points declined as the hypotonic treatment (0.05 mol/liter) was prolonged. To a lesser extent, a decline in radioprotection by 1.5 mol/liter treatment occurred as exposure time increased.

Animals↗
PubMed1985

Growth of a radiation-transformed clone of C3H 1OT1/2 cells into melanin-producing colonies.

When R25, a radiation-transformed clone of C3H 1OT1/2 cells, was plated in soft agarose, a fraction of the colonies became pigmented. The morphologies of the white and dark colonies and their cells were compared by optical, transmission and scanning electron microscopy. The transformed R25 cells had apparently differentiated into melanin-producing cells in the soft agarose, with the white colonies containing actively growing cells having only a few melanosomes, and the dark colonies being made up of stationary-phase cells filled with electronopaque melanosomes. Exposure of the R25 cells to 4.0 Gy of X-rays decreased the percentage of dark colonies, while exposure to 1% DMSO had no effect.

Animals↗