Micronuclei In Cytokinesis-blocked Lymphocytes Research Articles

Effects of ochratoxin A on micronucleus frequency in human lymphocytes.

Ochratoxin A (OTA), a nephrotoxic and carcinogenic mycotoxin, was investigated to examine its potency to induce micronuclei (MN) in cultured human lymphocytes. Lymphocyte cultures were treated for the last 48 h with OTA at concentrations of 25 microM, 10 microM, 1 microM, 100 nM, 10 nM, 1 nM, and 100 microM and absolute ethanol. At the highest concentration, OTA was found to induce MN in cytokinesis-blocked lymphocytes (p < 0.05). The 25 microM OTA concentration also led to a clear decrease in the percentage of binucleated cells, probably due to cytotoxicity. OTA at the other concentrations tested did not induce MN frequency. These results indicate that a high concentration of OTA is genotoxic in cultured human lymphocytes.

Micronuclei in human lymphocytes: the Co-60 gamma-ray dose-response

Dose-response for micronuclei in cytokinesis-blocked lymphocytes after in vitro irradiation of whole blood from 3 donors with Co-60 gamma-rays in the range 0–5.0 Gy was established. The numerical relationship between radiation induced chromosomal aberrations, and micronuclei is also examined. An increased frequency of micronuclei following low doses of gamma-irradiation is reported from a study of 41 radiation workers.

Micronuclei in cytokinesis-blocked lymphocytes may predict patient response to radiotherapy.

We have applied the cytokinesis-block micronucleus assay to peripheral blood lymphocytes of patients undergoing radiotherapy in pelvic and pulmonary sites, in order to evaluate the individual cytogenetic response. Our cytogenetic data correlated with the equivalent whole-body dose are homogeneous and compare well with the data presented by other authors. We have used an exponential mathematical formula to calculate the attenuation of the cytogenetic effect with time. The k coefficient (cytogenetic recovery factor) in the formula expresses the degree of attenuation. In lymphocytes from patients after radiotherapy, the trend of the micronucleus frequency observed after 2 Gy of in vitro X-irradiation demonstrates that the cytogenetic effect obtained in vitro is added to that obtained in vivo. The k coefficient is inversely proportional to the micronucleus frequency observed after 2 Gy in vitro. The micronucleus assay and the cytogenetic recovery factor are proposed as suitable diagnostic tools for application in the field of radiotherapy.

Biological Dosimetry Using the Micronucleus Assay for Lymphocytes

The dose response of the number of micronuclei in cytokinesis-blocked lymphocytes after in-vitro irradiation of whole blood with x rays in the dose range 0-4 Gy was studied for a heterogeneous population of 10 donors. One thousand binucleated cells were systematically scored for micronuclei. A linear-quadratic dose dependency of the micronucleus yields was observed. The data were used to derive the accuracy of the dose assessment with the technique in case of a radiation accident. It was shown that for doses of 2 Gy and higher, the uncertainty of the dose was predominantly due to interindividual differences in the x-ray-induced micronucleus yields. At the 95% confidence level, doses lower than 0.3 Gy could not be unequivocally detected with the cytokinesis-blocked micronucleus assay due to the variability of the baseline micronucleus frequency within the donor population and the poor statistical accuracy when scoring 1,000 cells. The precision and sensitivity of the method in the low-dose range could be improved by the knowledge of individual pre-irradiation baseline values and an increase of the number of cells scored by automation of the technique.

Micronuclei in Cytokinesis-blocked Lymphocytes of Cancer Patients Following Fractionated Partial-body Radiotherapy

We applied the cytokinesis-block micronucleus assay to measure chromosome damage in lymphocytes of 11 cancer patients undergoing fractionated partial-body irradiation. Measurements performed before, during and after cessation of radiotherapy showed a dose-related increase in micronucleus frequency in each of the patients studied. When the results for micronucleus frequency (Y) were plotted against the estimated equivalent whole-body dose (X) the dose-response relationship obtained was Y = 75.8X + 49.5 (r = 0.783, P less than 0.0001). A general decline in MN frequency was observed during the post-treatment period down to 57 per cent (+/- 10) after 12 months but there was considerable variation between individuals. The advantages and disadvantages of the application of the cytokinesis-block micronucleus assay as a biological dosimeter for lymphocytes irradiated in vivo are discussed.