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Biomedical subjects

J de Ronde

Publications and source records attributed to J de Ronde.

11 recordsLinked to original sources
PubMed1988

Interaction between X-ray and alpha-particle damage in V79 cells.

V79 cells have been exposed to X-rays or 238Pu alpha-particles or to X-rays following priming alpha-particle doses of 0.5, 2 or 2.5 Gy. The survival curve for exposure to alpha-particles was exponential with a D0 of 0.89 Gy. Following exposure to priming alpha-particle doses the resulting X-ray survival curves had the same slope as the single dose X-ray curve, but a reduced shoulder. For alpha-particle priming doses of 0.5 and 2 Gy this reduction was the same as for the same X-ray doses. 2.5 Gy alpha-particles reduced the subsequent X-ray curve Dq to almost zero. alpha-particles do cause damage capable of interacting with X-ray damage.

Alpha Particles↗
PubMed1984

The effect of prolonged high dose misonidazole on tumor response to radiation.

WHFIB and SA F tumors were exposed to misonidazole (MISO) concentrations of 2.5 mM or more for up to 4 hours (SA F) or 6 hours (WHFIB). There was no increase in the MISO enhancement ratio (SER) in the SA F for a 4 hour exposure to MISO relative to that following a single injection. In the WHFIB tumor, the ER increased from 2.2 for a single MISO injection to 2.5 for a 4 hour contact with MISO for tumor growth delay, and from 2.1 to 2.3 for a cloning assay. (These differences may not be statistically significant) Prolonged contact with MISO was toxic and reduced the body temperature by 4 to 5 degrees C. For WHFIB cells in vitro, when the contact time (in hypoxia) with 2.5 mM MISO was increased from 0.5 to 2.5 hours, the ER increased from 2.1 to 2.9 at 37 degrees C and from 1.9 to 2.5 at 33 degrees C.

Animals↗
PubMed1984

The effect of sequential irradiation with X-rays and fast neutrons on the survival of V79 Chinese hamster cells.

V79 Chinese hamster cells have been exposed to X-rays or fast neutrons or to the two radiations given sequentially. Cells exposed to a priming dose of X-rays and then exposed immediately to a series of neutron doses regard the X-ray dose as equivalent to a neutron dose giving the same surviving fraction (iso-effective). If the cells are exposed to a neutron dose followed by X-rays the resulting survival is higher than would be obtained if the primary dose had been an iso-effective X-ray dose. However, it is lower than would be expected if the two radiations acted independently. The results imply that there is interaction between the damage caused by X-rays and fast neutrons. If the two radiations are given 3 hours apart they act independently.

Animals↗
PubMed1983

Enhancement of the action of alkylating agents by single high, or chronic low doses of misonidazole.

Misonidazole (MISO) given as a large single dose enhanced the action of cyclophosphamide (Cy) and melphalan (L-PAM) in two mouse tumours. Below a dose of about 500 mg kg-1 it had no chemosensitizing effect. When MISO was given as a series of small doses by repeat injection over an 8 h period, in order to stimulate human pharmacokinetics, it significantly enhanced the action of Cy in the SA F tumour. It also enhanced the action of Cy and L-PAM in the WHFIB tumour as assayed by tumour cell survival in vitro following treatment in vivo but not when the assay was tumour growth delay. There was no enhancement by MISO of the leukopenia due to Cy or L-PAM. The results suggest that, in some tumours there may be benefit from the combination of clinically relevant MISO doses with alkylating agents. The leucopenia induced by these agents should not be enhanced by the MISO.

Animals↗
PubMed1980

Radiobiological studies of tumours in situ compared with cell survival.

The dose of radiation needed to eradicate a tumor depends on the radiosensitivity of the individual cells. Direct measurements of tumour cell survival require removal of the cells from their normal environment and may not reflect the course of events in the undisturbed tumour. In situ assays preserve this environment, but only give indirect estimates of tumour cell survival. A major cause of discrepancies between different methods of assaying tumour response is recovery from potentially lethal damage (PLD). For instance, it can affect estimates of the hypoxic fraction and hence of the pattern of reoxygenation. Not all tumours show recovery from PLD. In such tumours, where comparisons have been made between different assays, they have shown differences in the effects of radiation quality and modifying agents and in the capacity for recovery from sublethal damage between tumour cell survival in vivo and in vitro after treatment in vivo. No single assay method can give an adequate description of the response of a tumour to radiation. It is only by comparing different methods of assay that the basic biological properties of tumors that govern their response to therapy will be understood.

Animals↗
PubMed1979

Recovery from sublethal damage by acutely hypoxic tumour cells in vivo and in vitro.

The ability of acutely hypoxic tumour cells to recover from sublethal damage following irradiation in vivo and in vitro has been measured using a single tumour system. The methods of assay were tumour growth delay, local tumour control and tumour cell survival in vitro following treatment in vivo or in vitro. Tumours in vivo or cells in vitro rendered acutely hypoxic during irradiation were irradiated with either single doses or two doses 24 hours apart. Cells left in situ had a greater capacity for recovery than those treated either in vivo or in vitro and then assayed in vitro. It is suggested that tumours may not show a systematically reduced capacity for recovery relative to normal tissues, unless chronically hypoxic tumour cells have a reduced capacity for recovery and determine the response. However, the results imply that deductions as to the ability of tumour cells to recover from sublethal damage (whether chronically hypoxic or not), which rely on in vitro assays, may underestimate the extent of recovery.

Animals↗
PubMed1978

Interaction between electron-affinic sensitizers.

Measurements of effect of pairs of the sensitizers PNAP, misonidazole and oxygen have shown that if one sensitizer is giving an enhancement ratio (ER) of about 1.6 or less and the other is giving a larger ER, the combination behaves as if only the latter is present. There is only an additive effect of the two if they both give ERs less than 1.6 or greater than 1.6. These results show that at low concentrations sensitizers only act on damage associated with the "fast component" of the oxygen effect. This could result from interaction with two distinct species, or there could be only one critical species formed initially but more than one step by which it could be converted to a lethal form.

Acetophenones↗
PubMed1976

The effect of repeated small doses of radiation on recovery from sub-lethal damage by Chinese hamster cells irradiated in the plateau phase of growth.

Unfed plateau-phase cells have been irradiated with either single doses or up to ten fractions of X-rays 6 hours apart. The single-dose survival curve had an extrapolation number of 11-4, and the oxygen-enhancement ratio (o.e.r.) was 3-1. Cells were exposed to multiple fractions of 200 rad or 150 rad in air and 600 rad or 450 rad in hypoxia. The resulting survival curves did not fit a multi-target, single-hit model of cell survival, being much steeper than that would predict. The curves were exponential up to five fractions of X-rays, but tended to bend downwards with increasing number of fractions. Cells that had survived five fractions of 200 rad (or 600 rad in hypoxia) 6 hours apart, were less able to absorb damage as sub-lethal than those which had not previously been exposed to radiation. The ratio of the initial slopes of the fractionated survival curves for irradiation in air and hypoxia was 2-1, implying that the o.e.r. "on the shoulder" may be less than that in the exponential region of survival.

Cell Line↗