Chromosome aberration is a biomarker to predict the level of cell damage caused by exposure to ionizing radiation on human body. Dicentric chromosome is a specific chromosome aberration caused by ionizing radiation and is used as a gold standard biodosimetry of individuals over exposed to ionizing radiation. In radiation accident the dicentric assays has been applied as biological dosimetry to estimate radiation absorbed dose and also to confirm the radiation dose received to radiation workers.The purpose of this study was to generate a dose response curve of chromosome aberration (dicentric) in human lymphocyte induced by gamma radiation. Peripheral blood samples from three non smoking healthy volunteers aged between 25-48 years old with informed consent were irradiated with dose between 0.1-4.0 Gy and a control using gamma teletherapy source. The culture procedure was conducted following the IAEA standard procedures with slight modifications. Analysis of dose-response curves used was LQ model Y = a + αD + βD 2. The result showed that α and β values of the curve obtained were 0.018 ± 0.006 and 0.013 ± 0.002, respectively. Dose response calibration curve for dicentric chromosome aberrations in human lymphocytes induced by gamma-radiation fitted to linear quadratic model. In order to apply the dose response curve of chromosome aberration disentric for biodosimetry, this standar curve still need to be validated.
ABSTRAK OPTIMALISASI TES KOMET UNTUK PENENTUAN TINGKAT KERUSAKAN DNA AKIBAT PAPARAN RADIASI PENGION.Tes komet dapat digunakan untuk mengukur tingkat kerusakan asam deoksiribonukleat (DNA) pada sel limfosit darah tepi akibat paparan radiasi pengion.Prinsip dasar dari tes komet adalah berdasarkan besarnya fragmen DNA terdenaturasi yang bermigrasi keluar dari inti sel selama proses elektroforesis. Terdapat beberapa aspek yang harus diperhatikan saat melakukan tes komet antara lain adalah konsentrasi agarose yang digunakan, waktu inkubasi pada alkali, kondisi elektroforesis (waktu, temperatur serta gradien voltase yang digunakan), serta parameter yang digunakan dalam analisis. Parameter yang sangat disarankan dalam menganalisis citra komet adalah persentase DNA ekor (% DNA ekor). Persentase DNA ekor dapat dikonversi menjadi frekuensi lesion per 10 6 pasangan basa (bp) DNA dengan menggunakan kurva yang menggambarkan hubungan antara dosis radiasi pengion dengan besarnya % DNA ekor. Untuk mendapatkan hasil analisis tes komet yang akurat perlu dilakukan pembuatan kurva kalibrasi yang menggambarkan hubungan antara dosis radiasi pengion dengan besarnya % DNA ekor. Analisis citra komet sebaiknya dilakukan dengan menggunakan perangkat lunak pengolahan citra sehingga dapat meningkatkan akurasi dan presisi serta mengurangi subjektivitas dalam menganalisis citra komet.Kata kunci: asam deoksiribonukleat (DNA), radiasi pengion, tes komet. ABSTRACT COMET ASSAY OPTIMIZATION FOR ASSESSMENT OF DNA DAMAGE DUE TO RADIATION EXPOSURE.Comet assay can be used to measure the deoxyribonucleic acid (DNA) damage level caused by ionizing radiation exposure in peripheral blood lymphocytes. The principle of the comet assay is based on the amount of denatured DNA fragments that migrated out of the cell nucleus during electrophoresis. There are several aspects that must be concerned when doing the comet assay. For example the agarose concentration, duration of alkaline incubation, electrophoresis conditions (time, temperature, and voltage gradient), and the measurement parameters that used in analyze the comet. Percentage of DNA in the comet tail (% tail DNA) is strongly recommended as a parameter when analyze the comet because it can be converted to lesions per 10 6 base pairs (bp) using calibration curve that show relationship between the dose of ionizing radiation and % tail DNA. To obtain an accurate result, the calibration curve must be made and comet should be analyzing using image processing analysis software since it can be increase the precision and reduce the subjectivity of the measurement process.
Medical workers representing the group is the most consistently are exposed to low doses of ionizing radiation, prolonged low-level ionizing radiation can induce chromosomal aberrations (CAs). This study would evaluate the cytogenetic effect using the CAs based on dicentric, and cytokinesis-blocked micronucleus (CBMN) assay on hospital workers. The exposed group dividedto Interventional and Diagnostic groups then compared to non exposed group. The accumulated absorbed doses calculated for the radiation workers were below 5mSv. Blood samples were obtained from 29 samples of medical workers , and 15 samples of control. The Study showed that the frequency of dicentric chromosomes both in exposed and control were not found. In case of micronuclei, the mean frequencies were observed in exposed group that was (19 ±6.22) and (16.25 ± 6.04) respectively and the control group was (10.4±7.79). Frequency MN/1000 cell in the lymphocytes both in the two exposed group was relatively higher compared to control group. However the MN frequencies in all sample group was still in normal range . In this study chronic low radiation dose exposure in the hospital had no significant effect on chromosome aberration nor micronuclei. The benefit of the study is to enrich the potential usefulness of cytogenetic assay providing safety index in medical surveillance programs. The results suggest that education and retraining of staff concerning radiation safety guidelines need to be done to maintain the safety aspects of radiation.
In the cytokinesis-block micronucleus (CBMN) assay, micronuclei (MNi), nucleoplasmic bridges (NPBs), and nuclear budding (NBUD) are the most commonly analysed morphological types of nuclear abnormalities. In contrast, tailed and dumbbell-shaped nucleus have historically received little attention in the CBMN assay. Interestingly, the incidence of tailed and dumbbell-shaped nuclei in lymphocytes is closely related with that of dicentric chromosomes or NPBs in the CBMN assay. To provide a better picture of the implications and significance of tailed and dumbbell-shaped nuclei as markers of radiation exposure, a literature review was performed in this study. Twenty articles were found in PubMed, PubMed Central, and manually searched. The articles were screened and those that met the inclusion criteria and did not meet the exclusion criteria were reviewed by all authors. At the end, nine articles were included. In conclusion, the assessment of in vivo tailed nuclei in blood smears and accounting for the occurrence of dumbbell-shaped nuclei in the CBMN assay can increase the sensitivity of the CBMN assay for biodosimetry involving a high dose exposure.
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