Browsing by Subject "Radiation effects"

Now showing 1 - 4 of 4
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    A study comparing the effects of vincristine with those of ionizing radiation on the root meristem of Vicia faba
    (1972) Haddad, Dawne Merle
    Vincristine and vinblastine, two closely related alkaloids are extracted from the Madagaskar Periwinkle, Vinca rosea Linn. They have been shown to be effective oncolytic agents and cause arrest of mitosis at the metaphase stage, similar to that of colchicine andcolcimid. Clinically, vincristine has been found to produce a complete remission in patients with acute leukaemia. Tumour regression in patients with Hodgkin's disease, lymphosarcoma and certain childhood solid tumours have also been reported.
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    A study of the response of the root meristem of maize to fractionated and protracted doses of ionizing radiation
    (1971) Hering, Egbert Raymond
    Vicia faba and investigating the effects of ionizing radiation on its root system. In particular, species such as Tradescantia, Pisum, Allium and Mordeum vulgare have been extensively studied. Nevertheless an ever-increasing number of workers have used Vicia faba for explaining the basic problems of radio biology. One of the reasons is the small number of large chromosomes contained in the root meristem cells, which are particularly conducive to simple cytological analysis. The seedlings also have other attractive features.
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    The analysis of radiation-induced micronuclei in peripheral blood lymphocytes for purpose of biological dosimetry
    (1995) Le Roux, Jacques; Blekkenhorst, Gerhardus Hendrikus
    In the investigation of radiation accidents, it is of great importance to estimate the dose absorbed by exposed persons in order to plan their therapy. Although occasionally in these situations physical dose measurements are possible, most often biological methods are required for dose estimation. The aim of this investigation was to assess the suitability of the cytokinesis blocked (CB) micronucleus assay as a biodosimetric method using lymphocytes irradiated in vivo. The approach adopted to achieve this was to estimate whole body doses by relating micronuclei yields in patients undergoing radiotherapy treatment with an in vitro radiation dose-response curve. These biologically derived estimates were then compared with the corresponding doses obtained by physical measurement and calculation. As a first approach a study was performed of the in vitro dose-response of gamma-ray induced micronuclei following cytokinesis-block in the lymphocytes of peripheral blood samples obtained from 4 healthy donors. The results indicated that the distribution of the induced micronuclei were overdispersed. Furthermore, a linear dose-response relationship was established when a curve was fitted to the data by an iteratively reweighted least squares method. By means of an analysis of covariance it was demonstrated that this result is in agreement with the dose-response relationships found by various other workers (Fenech et al., 1985; Fenech et al., 1986; Fenech et al., 1989; Balasem et al., 1992, and Slabbert, 1993). To assess the suitability and accuracy of dose assessment using the CB micronucleus assay for in vivo exposure of lymphocytes, blood samples obtained from 8 patients undergoing radiotherapy before, during and after treatment were examined. The physical doses of these patients were determined according to conventional radiation treatment plans and cumulative dose-volume histograms. The dose-volume histograms permitted calculation of integral doses and subsequently the estimate of equivalent whole-body doses. The results of the CB micronucleus assay applied to peripheral blood lymphocytes of 6 patients undergoing fractionated partial-body irradiation showed a dose-related increase in micronucleus frequency in each of the patients studied. This demonstrated that micronuclei analysis may serve as a quantitative biological measure of such exposures. The pooled data of these patients compared to the pooled data of the healthy donors show that there was no statistically significant difference between in vitro and in vivo results, however a slightly lower induced micronuclei frequency was observed after in vivo exposure. When the biological dose estimates for equivalent whole-body doses obtained from the in vitro dose response curve were compared with calculated physical doses, it was found that: biologically estimated dose = 0.936 physical dose. However, there was inadequate statistical evidence to discard the hypothesis that the gradient of the equation was equal to one. Therefore, the analysis of micronuclei induced in lymphocytes in vivo yields highly quantitative information on the equivalent whole-body dose. The negative binomial method was used for analysing the micronucleus data from two patients who received single, relatively larger tumour doses of 10 Gy each, with the objective to obtain estimates of the exposed body fraction and the dose to this fraction. The dose estimates to the irradiated volume were found to be within 30% of the physical tumour dose. The irradiated volume estimates seemed to be higher than the physically calculated volumes but by discarding the correction for the loss of cells due to interphase death the agreement was good between the physically and biologically determined integral doses. This study has revealed that the CB micronucleus assay appears to offer a reliable, consistent and relatively rapid biological method of whole body dose estimation. It is recognised that further corroborative work using the techniques described in this thesis is required for estimating localized exposure.
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    Postradiation sarcomas
    (1995) Murray, Elizabeth Margaret; Werner, I D
    This report from Groote Schuur therefore sets out to review cases of postradiation sarcomas, including malignant mixed mullerian tumors (MMMT), presenting to the Radiation Oncology Departments of Groote Schuur Hospital and the affiliated hospitals (Frere Hospital, East London and Provincial Hospital, Port Elizabeth) or known to have occurred in patients initially treated in these hospitals. It aims [1] to establish the features of the initial malignancy as well as the latent period for the development of postradiation sarcoma, the type of postradiation tumor and the outcome of the disease; [2] to establish as accurately as possible dose levels at which the postradiation tumors have developed; and [3] to briefly describe possible risk factors such as a genetic predisposition to the development of malignancy, repeated courses of radiotherapy, surgery as part of the treatment of the initial tumor, and chemotherapy. Questions regarding the genesis of postradiation sarcomas cannot be answered by a review of 20 cases, even when combined with an analysis of literature. This review aims to add relevant information to the body of data from which the final answers may come. In view of the late diagnosis often made in cases of postradiation sarcoma (25, 94) the review also aims to heighten awareness of the condition so that it may be more often reported at a curable stage.