Influence of blood storage after in vitro exposure to ionizing radiations on the yield of chromosome aberrations observed in human lymphocytes

Extension of lymphocyte viability for radiation biodosimetry: Potential implications for radiological/nuclear mass casualty incidents

Dicentric chromosome assay (DCA) is routinely used for estimating the absorbed radiation dose in exposed humans. Optimal lymphocyte viability is crucial for reliable dose estimation and most cytogenetic laboratories prefer the receipt of blood samples within 24 to 36 hours after collection. Delays in the shipment/receipt of samples can occur sometimes under certain unforeseen circumstances: (1) Adverse weather conditions, (2) distant location of blood collection sites, and (3) shipping and handling of a large number of samples after radiological/nuclear mass casualty incident(s). To circumvent some of these limitations, we evaluated the suitability of ex vivo irradiated blood samples stored in the presence of phytohemagglutinin (PHA) for 7 days at ambient temperature (22-24°C) for radiation biodosimetry. Blood samples stored in the presence of PHA for up to 7 days showed a higher mitotic index than blood samples stored without PHA. To verify the use of stored blood samples for DCA, frequencies of X-rays induced dicentric chromosomes were analyzed in the blood samples that were cultured either 24 hours after exposure or 7 days later after storage. Our results indicate that storage of ex vivo irradiated blood samples in the presence of PHA at ambient temperature was found optimal for DCA and that the radiation doses estimated by dicentric chromosome frequencies were grossly similar between the fresh and stored blood samples. Our study suggests that reliable and accurate biodosimetry results can be obtained for triage using blood samples stored for up to a week at ambient temperature in the presence of PHA.

Influence of anticoagulants and storage temperatures on blood counts and mitotic index of blood samples collected for cytogenetic biodosimetry

PURPOSE

In order to establish suitable protocols of blood culture to obtain sufficient numbers of metaphases for dicentric chromosome assay (DCA), we have examined the effect of storage temperature, storage time, and anticoagulant type.

MATERIALS AND METHODS

Peripheral blood was collected from five healthy donors with lithium heparin and ethylenediaminetetraacetic acid dipotassium salt (EDTA-2K). These samples were irradiated with X-rays at 3 Gy or sham; the samples were further divided into groups that were either stored at room temperature (RT) or 5.2 ± 1.0 °C. After 6, 24, 48, 72, and 168 h of storage, both blood counts and the mitotic index (MI) were analyzed.

RESULTS

Heparinized blood samples stored under cold conditions exhibited low white blood cell, lymphocyte, and platelet counts. EDTA-treated blood samples did not show such obvious changes in cell counts. After 6 h of storage, heparinized blood samples stored at RT had MI of 21.5-29.3%. Similar MI was obtained in the EDTA-washed group stored for 6, 24, 48, and 72 h.

CONCLUSIONS

Our study confirms that heparinized blood samples should be stored at RT to get sufficient metaphases for DCA, and that EDTA blood samples also can be used for blood culture after washing and storage under 5.2 ± 1.0 °C.

Effect of blood storage on radiation-induced micronuclei in human lymphocytes

To evaluate the effect of blood storage on the yield of micronuclei (MN) in both irradiated (in vivo and ex vivo) and unirradiated peripheral blood lymphocytes (PBL), we applied the MN assay in cytokinesis-blocked (CB) PBL obtained from healthy subjects (n=11), and from cancer patients (n=10) who were undergoing fractionated partial-body radiotherapy (xRT). The heparinized blood samples were exposed to 137Cs-irradiation (0 Gy or 2 Gy) immediately after blood collection and were stored upright in test tubes either at room temperature (22 degrees C) or in the refrigerator (5 degrees C). Duplicate whole blood cultures from each sample were set up at 0 h, 96 h, and 120 h after ex vivo irradiation. Giemsa (10%) stained slides were prepared from each culture. MN yield was determined per 1000 binucleated cells. As compared to that obtained from the corresponding fresh blood samples, we found that (1) the 22 degrees C blood storage temperature did not affect MN yields in PBL of either healthy subjects or cancer patients up to 96 h, either with or without ex vivo irradiation; and (2) while blood samples were stored at 5 degrees C, the MN yield increased significantly in PBL of healthy subjects (with or without ex vivo irradiation) at 120 h, and in cancer patients (with ex vivo irradiation) at 96 h and 120 h. Since handling of the blood sample is important for CBMN assay during shipment or in the laboratory, our findings showed that blood storage at 22 degrees C or at 5 degrees C up to 96 h appeared to provide insignificant variations of the MN results as compared to fresh blood samples. However, the 96 h of blood storage at 5 degrees C elevated the MN frequency in ex vivo irradiated PBL of cancer patients who were undergoing xRT.

Chromosome analysis of lymphocytes from workers at an ethylene oxide plant

Samples of peripheral blood were collected from 33 men who had been employed in the manufacture of ethylene oxide for between 1 and 14 years, and from 32 men from other parts of the same plant who were used as controls. Their lymphocytes were analysed for chromosome damage. There were low frequencies of polyploidy, chromatid aberrations and chromosome breaks in the cells of the 65 men. A slightly higher frequency of chromatid aberrations was observed in the cells of the ethylene oxide workers than in those of the controls, but the difference between the two groups was not statistically significant. There was a positive correlation between length of employment in the ethylene oxide group and the numbers of aberrations in the cultures of each individual. This trend was not solely attributable to the age of the men. The levels of chromatid and chromosome damage observed in this study are consistent with those in humans who have not recently been exposed to known chromosome-breaking agents.