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Biomedical subjects

G P Raaphorst

Publications and source records attributed to G P Raaphorst.

At least 73 records · Page 4Linked to original sources
PubMed1993

Repair of potentially lethal damage: its inhibition by hyperthermia in two human melanoma cell lines with different radio- and heat sensitivities.

The effect of hyperthermia on the inhibition of potentially lethal radiation damage repair (PLDR) was measured in two human melanoma cell lines of differing radiosensitivities. The HT144 cell line is radiation sensitive and has an exponential survival curve, while the SK-MEL-3 line is radiation resistant and has a shouldered survival curve. Both cell lines demonstrated a similar level of PLDR at isosurvival level radiation doses of 2.0 and 10 Gy for the HT144 and SK-MEL-3 lines, respectively. Hyperthermia (40-45 degrees C) could inhibit PLDR in both cell lines. This inhibition was greater in HT144 than in SK-MEL-3 at low temperatures (40 degrees C) and was reversed at higher temperatures (45 degrees C). There was also a sequence dependence of PLDR inhibition which showed a greater inhibition for heat before irradiation at 40 degrees C but the reverse for temperatures of 41 degrees, 43 degrees and 45 degrees C. These data show that hyperthermia can be an effective inhibitor of PLDR in both radiosensitive and resistant cell lines and that the degree of inhibition is not related to radiosensitivity.

Dose-Response Relationship, Radiation↗
PubMed1993

A comparison of the enhancement of radiation sensitivity and DNA polymerase inactivation by hyperthermia in human glioma cells.

Two human glioma cell lines (U87MG and U373MG) were evaluated for their thermal enhancement of radiation sensitivity and its correlation to the degree of inactivation of DNA polymerase alpha and beta. The data showed that hyperthermia increased radiation sensitivity in a time- and temperature-dependent manner. The differential heat sensitivity of the two cell lines was reflected in the degree of polymerase inactivation. Polymerase inactivation was also dependent on time and temperature and was greater for polymerase beta than alpha. The degree of polymerase inactivation correlated well with the thermal enhancement ratio (TER) calculated at the 1.0% survival level. This correlation was poor for the TER at the 50% survival level. The correlations were better for polymerase beta than alpha. The small differences in thermal sensitivity between the two cell lines primarily at 41 and 42 degrees C could not be explained by correlation between polymerase inactivation and TER. Incubation between hyperthermia and irradiation resulted in recovery of polymerase activity and loss of radiosensitization. Levels of polymerase beta after hyperthermia may be used to predict thermal enhancement of radiosensitivity for low survival levels, but possibly not in the shoulder region of the radiation survival curve. Small cell line-dependent differences in thermal sensitivity may not be resolved in these comparisons.

Brain Neoplasms↗
PubMed1992

Recovery of sublethal radiation damage and its inhibition by hyperthermia in normal and transformed mouse cells.

Radiation resistance may be related in part to the capacity of cells to repair radiation damage which can usually be characterized by the survival curve shoulder and split dose recovery. C3H-10T1/2 normal and transformed cells and V79 cells were evaluated for their ability to recover from sublethal radiation damage and for hyperthermia to affect this recovery. The transformed cell line of the 10T1/2 cell system displayed a much larger capacity to recover from radiation damage than did the parental strain. This was also correlated with an enlarged shoulder on the radiation survival curve. When hyperthermia was given, recovery of sublethal radiation damage could be inhibited in both cell lines. This inhibition was dependent on the sequence of hyperthermia treatment and correlated with the removal of the shoulder of the radiation survival curve. In Chinese hamster V79 cells, recovery was much smaller than in the mouse C3H-10T1/2 cell system. In the hamster cells, recovery could also be inhibited by a hyperthermia treatment. In all three cell lines the degree of inhibition was dependent on thermal dose and indicated that very small hyperthermia treatments would not inhibit recovery of sublethal damage but may in fact cause some increase possibly due to increasing the amount of damage available for repair. Thus if hyperthermia doses are sufficiently large, it may be used to overcome sublethal damage repair and may result in therapeutic gain in tumors which have a large capacity for such repair.

Animals↗
PubMed1992

A comparison of heat sensitivity, radiosensitivity and PLDR in four human melanoma cell lines.

Comparison of the heat sensitivity and radiosensitivity of four human melanoma cell lines in culture revealed a large variation in sensitivity amongst the four cell lines. Three of the four cell lines had large shoulders on the survival curves when exposed to hyperthermia (44 degrees C or 45 degrees C). These three cell lines also had demonstrable shoulders on the acute radiation dose response curves. The most radiosensitive cell line did not show a shoulder region in the heat or radiation survival curves (HT-144, Dq = 0.2 Gy). Despite this consistency in the presence or absence of shoulder, there was no correlation between heat and radiation sensitivity in the four melanoma cell lines. Furthermore, regardless of radiosensitivity, all four lines studied showed competent repair of potentially lethal damage. The recovery ratios at a surviving fraction of 0.001 ranged from 5.7 to 7.6. All four lines had a similar cell cycle distribution at the time of treatment, hence the variation observed in the response of these four lines to radiation and heat was not due to differences in cell cycle kinetics. Preliminary results of DNA polymerase-alpha and -beta activities do not demonstrate a clear correlation between cellular levels of these two enzymes and radiosensitivity.

Cell Cycle↗
PubMed1992

Response of transformed and normal mouse cell lines to anti-melanin compounds, hyperthermia, and radiation.

Five cell lines (one parental, two transformed melanin producing, and two transformed non-melanin producing) were evaluated for the responses to 2- and 4-hydroxyanisole (2HA, 4HA) alone or combined with hyperthermia or radiation. All cells exhibited a non-specific toxic response to the two compounds and the effect was exposure time and concentration dependent and was greater for 4HA compared to 2HA. In addition, the two melanin-producing cell lines were more sensitive, demonstrating specific toxicity to such cell lines. The treatment with either 2HA or 4HA combined with heat and radiation resulted mostly in additive or antagonistic effects, except for one combination of 2HA plus radiation in the melanin-producing R25 cells. Thus, while these compounds may be useful in therapy for pigmented melanomas, combined treatment with radiation is not recommended.

Animals↗
PubMed1992

The clinical use of thermocouple thermometry.

The development of a clinical thermometry system entails solving both clinical and technical problems. A thermometry system will, in general, be comprised of a temperature transducing element, a mechanism for interrogating the transducer temperature, and a means of interpreting, reporting and recording the measured temperature. Thermocouples are thermometers which report their own temperature, while the parameter of interest is the temperature of the medium. The two key questions which arise are then: (1) is the thermometer correctly reporting its own temperature, and (2) what is the relationship between the medium temperature and the thermometer temperature? In this work some of the important parameters influencing the temperature of the thermometer and the thermal relationship between the thermometer and the medium are investigated.

Body Temperature↗
PubMed1992

The effect of colcemid on the heat survival of mitotic V79 Chinese hamster cells.

V79 Chinese hamster cells were collected by colcemid addition to study the effect of heat on mitosis. When they were heated at 42 degrees C and 45 degrees C in the presence of 0.06 micrograms/mL colcemid, cell survival increased over the control samples, which were heated in ordinary medium. Scanning electron microscopy showed that cells heated to 45 degrees C in the presence or absence of colcemid had fewer microvilli on the surface, but they did not have increased bleb formation. Transmission electron microscopy showed that the chromatin was diffuse in the heated cells and the kinetochores were indistinct. The mitochondria in the heated cells were also swollen and contained visible particles.

Animals↗
PubMed1991

Hyperthermic potentiation of BCNU toxicity in BCNU-resistant human glioma cells.

Experimental evidence indicating potentiation of the cytotoxic effect of drugs at high temperatures suggests that the utilization of drug-heat combinations for gliomas of the brain might be therapeutically useful. Hyperthermia may increase the cytotoxicity of a particular drug in areas of low drug concentration/time and in cell populations resistant to the drug. We report in vitro experiments with a BCNU resistant, U-373MG, and a BCNU sensitive, U-87MG, human derived glioma cell lines under hyperthermic conditions. Temperatures equal or above 42 degrees C potentiate BCNU cell kill in both lines. The thermo-sensitizer lidocaine increases thermal cell kill but only minimally with concentrations corresponding to therapeutic plasma lidocaine levels. Within our experimental conditions, the best strategy to overcome BCNU resistance involved a combination of heat, BCNU and cis-DDP. BCNU resistant cells have no cross resistance to cis-DDP and the combination of BCNU and cis-DDP is synergistic. At modest hyperthermic conditions (42 degrees C) 99.4% BCNU resistant cells are killed by a combination of BCNU and cis-DDP at drug concentrations identical to plasma concentrations after standard IV doses. Clinical protocols using heat and drug may need to incorporate two or more drugs for optimal effects.

Carmustine↗
PubMed1991

The effect of lonidamine (LND) on radiation and thermal responses of human and rodent cell lines.

Rodent and human cells were tested for response to Lonidamine (LND) (1-(2,4 dichlorobenzyl) 1-indazol-3-carboxylic acid) combined with radiation or hyperthermia. Lonidamine exposure before, during, and after irradiation caused varying degrees of inhibition of potentially lethal damage (PLD) repair which was cell line dependent. In human glioma, melanoma, squamous cell carcinoma, and fibroblasts, LND exposure did not inhibit or only partially inhibited repair of potentially lethal damage. LND up to 100 micrograms/ml produced only a low level of toxicity in these cells and only slightly inhibited glucose consumption at the maximum concentration. In human glioma cells, LND treatment alone did not inhibit PLD repair, but when combined with hyperthermia treatment at moderate levels easily achievable in the clinic, there was complete inhibition of potentially lethal damage repair. These data suggest that LND effectiveness is cell type dependent. Combinations of LND, hyperthermia, and radiation may be effective in cancer therapy especially in tumors such as glioma in which repair of potentially lethal damage may be extensive.

Animals↗
PubMed1991

Thermal sensitivity and radiosensitization in Chinese hamster V79 cells exposed to 2-aminopurine or 6-thioguanine.

Chinese hamster V79 cells were exposed to 10(-6) mol liter-1 2-aminopurine (2-AP) or 6-thioguanine (6-TG) for 18 or 40 h, and then tested for sensitivity to X rays, heat, or a combined treatment of heat and radiation. Cells exposed to 6-TG were sensitive to X rays, while those treated with 2-AP showed little or no sensitivity. At 42 degrees and 45 degrees C moderate sensitization resulted from 2-AP treatment, with greater sensitization resulting from treatment with 6-TG. Combined heat and X-ray treatment of cells exposed to 2-AP yielded sensitization similar to heat treatment alone, while cells exposed to 6-TG before receiving the combined treatment showed a degree of sensitization greater than that due to either treatment by itself but less than that of the two treatments added together. Uptake of the purine analogues into cellular DNA was measured by high-pressure liquid chromatography. At the 1% detection level, after either an 18- or a 40-h exposure of cells to 10(-6) mol liter-1 2-AP or 6-TG, no base substitution was found. Analysis of cell cycle distributions by flow cytometry revealed only very small changes following exposure of cells to the purine analogues.

2-Aminopurine↗
PubMed1990

Inhibitors of repair of potentially lethal damage and DNA polymerases also influence the recovery of potentially neoplastic transforming damage in C3H10T-1/2 cells.

The effects of aphidicolin and beta Ara A on radiation sensitivity were evaluated in terms of cell killing, recovery, and neoplastic transformation in the C3H10T-1/2 cell system. When cells were held in plateau phase, recovery of potentially lethal damage (PLD) and potentially transforming damage (PTD) occurred. The addition of beta Ara A resulted in reduced PLD recovery for both the survival and neoplastic transformation end points. The addition of aphidicolin did not affect recovery of PLD or PTD. These data show that the inhibition of polymerase alpha by aphidicolin does not affect recovery of damage leading to cell death or neoplastic transformation. However, the inhibition of both polymerase alpha and beta by beta Ara A resulted in inhibition of recovery of damage leading to both cell death and neoplastic transformation. These data indicated that polymerase beta may be involved in both PLD and PTD recovery.

Animals↗
PubMed1989

A comparison of heat and radiation sensitivity of three human glioma cell lines.

Three human glioma cell lines were tested for radiation and hyperthermia sensitivity and compared to the responses of a normal human fibroblast cell line. The radiation response of the glioma cell lines exhibited a large shoulder on the radiation survival curve indicating radioresistance when compared to the more radiosensitive fibroblast cell line. The hyperthermia response for the glioma cell lines was qualitatively similar to responses reported for other cell lines. When compared to normal human fibroblasts the glioma cells were found to be more sensitive to hyperthermia than the normal fibroblasts indicating hyperthermia may be a promising method or adjunct to radiotherapy in the treatment of resistant glioma cells or tumors. The results also show that both the radiation and thermal response is influenced by cell culture conditions and growth status. Two of the cell lines grown to confluency and treated in confluency showed an increased radiation resistance at low doses and the cell lines showed decreased resistance at high doses compared to cells plated to confluency (see Methods and Materials). An increased thermal resistance, especially at the lower heating temperatures, was also observed for cells grown to confluency. Measurements of residual glucose in the culture medium at the time of irradiation was about the same for the two culture methods (55%-65%). Cell cycle analysis showed that the differences were not related to changes in cell cycle distribution.

Adaptation, Physiological↗
PubMed1989

Morphological effects of lonidamine on two human-tumor cell culture lines.

Lonidamine, 1-(2-4-dichlorobenzyl)-1-H-indazol-3-carboxylic acid, is an anticancer drug that has its primary action on cellular metabolism rather than cell division. Since lonidamine is not effective in all tumor cells, we have tested it in two human-tumor cell culture lines: MOLT-4, a T-leukemia and U-87 MG, a glioma. Lonidamine exposure of MOLT-4 cells at 50 micrograms/mL and pH 6.7 disrupted the mitochondria within 1 h of treatment. The mitochondria were swollen and the cristae were disrupted. When the treated cells were re-incubated in fresh medium at pH 7.4 the mitochondria rapidly returned to their normal morphology. The U-87 MG glioma cells did not show ultrastructural disruption after 1-h treatment with lonidamine at concentrations up to 200 micrograms/mL at pH 6.7. In the concentration range of 25 micrograms/mL to 200 micrograms/mL, lonidamine did not produce any cell killing in MOLT-4 after a 1-h exposure at pH 7.4, although the drug had some limited effectiveness at pH 6.7. Compared to sham-treated controls, long exposures to 100 micrograms/mL of lonidamine at pH 6.7 reduced survival in MOLT-4 to 92% and 53% after 6-h and 24-h exposures, respectively. Survival of U-87 MG glioma cells was also strongly pH dependent, a 2-h exposure to 50 micrograms/mL lonidamine at pH 7.4 did not cause cell death; however, survival dropped to 84% of the control at pH 6.65.

Antineoplastic Agents↗
PubMed1988

Reduced pH increases recovery from radiation damage potentially leading to cell death and to in vitro transformation.

C3H-10T1/2 cells were grown to plateau phase and assessed for recovery from radiation damage under acidic and normal pH conditions. Repair of potentially lethal damage (PLD) was observed after X-ray doses of 5.0, 6.0 and 12.0 Gy and repair increased with dose. The repair at an acidic pH of 6.8 was greater than at the normal pH of 7.4. Repair of potentially transforming damage (PTD) was also observed when cells were held in plateau phase after irradiation. Repair of PTD was greater at the acidic pH than at the normal pH. When PTD recovery was plotted vs PLD recovery the results showed a good linear correlation with approximately twice as much PTDR. The experimental conditions allowing PLDR and PTDR indicate that the repair process may be error-free, since transformation was reduced in all experiments which showed recovery from PLD.

Animals↗
PubMed1988

The use of immunostaining to quantify x-ray and heat-induced multiple microtubule organizing centers in normal and transformed cells.

Microtubule organizing centers (MTOC) in control, irradiated and heated C3H 10T1/2 mouse embryo cells and two radiation-transformed sublines, R1 and R25, were made visible by indirect immunofluorescence using antibody against tubulin. The MTOC were reformed by 5-min incubation in fresh medium after the microtubules were depolymerized with nocodazole. The R1 line had a different distribution of MTOC/cell than the parent 10T1/2 line or R25, which had similar distributions. After irradiation, multiple MTOC appeared in the normal and radiation-transformed cells irradiated to 10 Gy and incubated for 24 or 48 h. The multiple foci of microtubule reformation in the irradiated cells indicate that radiation damage is expressed in structural elements in the cytoplasm. After heat treatment of the three cell lines (43 degrees C for 93 min and 45 degrees C for 25 min), the MTOC were disrupted and many cells did not have visible organizing centers at 24 or 48 h, while others had a large number of small centers of microtubule reformation. The distribution of MTOC/cell seen in R25 cells after the treatment had similar patterns to those of the 10T1/2 line rather than to those of the other radiation-transformed line, R1. Thus, the radiation or heat response seen in the MTOC is not dependent upon cell transformation.

Animals↗
PubMed1988

Poly(ADP-ribose) synthetase inhibitors increase radiation and thermal sensitivity but do not affect thermotolerance.

The effects of 3-aminobenzamide and benzamide (inhibitors of poly(ADP-ribose] synthetase on heat and radiation responses of Chinese hamster V79 cells have been examined. Consistent with earlier reports the inhibitors of poly(ADP-ribose) formation caused radiosensitization and inhibition of repair of radiation-induced potentially lethal damage. Both benzamide and 3-aminobenzamide caused thermosensitization for heating temperatures ranging from 42-45 degrees C. Benzamide had a greater effect than 3-aminobenzamide at equimolar concentrations. Thermosensitization increased with concentration of the inhibitors and was greater for prolonged heating times. While both inhibitors caused thermosensitization, they did not affect the time scale for the development of thermotolerance at 42 degrees C or after acute heating at 45 degrees C. The inhibitors of poly(ADP-ribosylation) radiosensitizers and thermosensitizers may be of use in the treatment of cancer using a combined modality of radiation and hyperthermia.

Adaptation, Physiological↗
PubMed1988

Thermal enhancement of cellular radiation damage: a review of complementary and synergistic effects.

Hyperthermia treatment can kill mammalian cells in a time and temperature dependent manner. Thermal sensitivity varies extensively among various cell lines in culture and cellular molecular and ultrastructural studies have not resolved which cellular mechanisms underlie thermal cell killing and radiosensitization. The response of cells to heat and radiation are complementary under certain conditions found in human tumors, such as hypoxia, low pH, low nutrient and the S-phase of the cell cycle. Thus, hyperthermia can be used as a complementary treatment modality in the radiotherapy of human cancer. Further studies show that heat treatment causes radiosensitization which is in part associated with the inhibition of repair of radiation damage and is strongly dependent on temperature and on the sequencing. In addition, the conditions such as pH and oxygenation during treatment sequencing can influence the degree of recovery of cells. These factors may be exploited in optimizing therapeutic gain in clinical cancer therapy. Data are shown that transformation from the normal to the tumorigenic state causes random small changes in radiosensitivity and heat sensitivity. Also, treatments combining heat and radiation can lead to increased or decreased transformation in cells depending on the treatment sequence.

Anaerobiosis↗