Venkatachalam Perumal

Assessment of dose and DNA damages in individuals exposed to low dose and low dose rate ionizing radiations during computed tomography imaging.

PURPOSE Computed tomography (CT) is a frequently used imaging modality that contributes to a tenfold increase in radiation exposure to the public when compared to other medical imaging modalities. The use of radiation for therapeutic need is always rationalized on the basis of risk versus benefit thereby increasing concerns on the dose received by patients undergoing CT imaging. Therefore, it was of interest to us to investigate the effects of low dose and low dose-rate X-irradiation in patients who underwent CT imaging by recording the doses received by the eye, forehead and thyroid, and to study the levels of damages in the lymphocytes in vivo. MATERIALS AND METHODS Lithium manganese borate doped with terbium (LMB:Tb) thermo luminescence dosimeters (TLD) were used to record the doses in the patients (n = 27) eye, forehead, and thyroid and compared with the dose length product (DLP) values. The in vivo DNA damages measured were compared before and after CT imaging using chromosomal aberration (CA) and micronucleus (MN) assays. RESULTS The overall measured organ dose ranged between 2 ± 0.29 and 520 ± 41.63 mGy for the eye, 0.84 ± 0.29 and 210 ± 20.50 mGy for the forehead, and 1.79 ± 0.43 and 185 ± 0.70 mGy for the thyroid. The in vivo damages measured from the blood lymphocytes of the subjects showed an extremely significant (p < 0.0001) increase in CA frequency and significant (p < 0.001) increase in MN frequency after exposure, compared to before exposure. CONCLUSION The results suggest that CT imaging delivers a considerable amount of radiation dose to the eye, forehead, and thyroid, and the observed increase in the CA and MN frequencies show low dose radiation effects calling for protective regulatory measures to increase patients safety. This study is the first attempt to indicate the trend of doses received by the patients eye, forehead and thyroid and measured directly in contrast to earlier values obtained by extrapolation from phantoms, and to assess the in vivo low dose effects in an Indian patient population undergoing CT procedures.

Modification of 2-deoxy-D-glucose on radiation-and chemotherapeutic drug-induced chromosomal aberrations.

BACKGROUND Chemotherapy is the treatment of cancer with drugs, often used as either adjuvant or neoadjuvant or in conjunction with radiation and surgery. Unfortunately, majority of the drugs are toxic to normal tissues, the toxicity being resulting from multidrug protocol used to induce remissions and achieve tumor care. While it has been demonstrated for compounds like the 2-deoxy-glucose (2-DG) used as a modulator for radiation-induced damages, such studies were rarely reported for chemotherapeutic drugs. OBJECTIVE To study the effect of 2-DG on radiation-and chemotherapeutic drug-induced chromosomal aberrations in normal and tumor cells exposed in vitro. MATERIALS AND METHODS The peripheral blood lymphocytes (PBLs) and BMG-1 cells were exposed to radiation and chemotherapeutic drugs (bleomycin and mitomycin-C) in the presence and absence of 2-DG. The treated cells were cultured for various durations, arrested at either metaphase or cytokinesis stage of the cell cycle. The stable and unstable aberrations were recorded using Giemsa staining and FISH technique. The cell cycle kinetics was studied using fluorescence plus Giemsa (FPG) staining. RESULTS The presence of 2-DG reduced stable and unstable chromosome aberrations (CA) significantly (P < 0.001), in PBLs induced by radiation, bleomycin and mitomycin-C, when compared to cells treated with radiation or the drugs and increased significantly in BMG cells (P < 0.001). Furthermore, the presence of 2-DG altered the cell cycle kinetics in the PBLs and BMG-1 cells. Thus the overall results showed protection effect on the normal cell damages induced by radiation and chemotherapeutic drugs, while sensitizes the tumor cell. CONCLUSION The obtained results suggest that 2-DG in combination with radiotherapy/chemotherapy could lead to an improvement in tumor therapy by sensitizing the tumor cells while protecting the normal cells.

Radiation signature on exposed cells: Relevance in dose estimation

The radiation is considered as a double edged sword, as its beneficial and detrimental effects have been demonstrated. The potential benefits are being exploited to its maximum by adopting safe handling of radionuclide stipulated by the regulatory agencies. While the occupational workers are monitored by personnel monitoring devices, for general publics, it is not a regular practice. However, it can be achieved by using biomarkers with a potential for the radiation triage and medical management. An ideal biomarker to adopt in those situations should be rapid, specific, sensitive, reproducible, and able to categorize the nature of exposure and could provide a reliable dose estimation irrespective of the time of the exposures. Since cytogenetic markers shown to have many advantages relatively than other markers, the origins of various chromosomal abnormalities induced by ionizing radiations along with dose-response curves generated in the laboratory are presented. Current status of the gold standard dicentric chromosome assay, micronucleus assay, translocation measurement by fluorescence in-situ hybridization and an emerging protein marker the γ-H2AX assay are discussed with our laboratory data. With the wide choice of methods, an appropriate assay can be employed based on the net.

Entrance surface dose and induced DNA damage in blood lymphocytes of patients exposed to low-dose and low-dose-rate X-irradiation during diagnostic and therapeutic interventional radiology procedures

The ionizing radiation received by patients and health workers due to radiological imaging may increase the risks of radiation effects, such as cancer and cataracts. We have investigated the dose received by specific areas around the head and related this to DNA damage in the blood lymphocytes of subjects exposed to interventional imaging. The entrance surface doses (ESD) to the forehead, neck, and shoulder were measured with a thermoluminescence dosimeter (CaSO4 disc or polycrystalline powder of lithium tetraborate doped with Mn) and compared with that of dose area product (DAP). DNA damage was measured by γ-H2AX, p53ser15, chromosomal aberration (CA), and micronucleus (MN) assays in lymphocytes of patients (n=75), before and 2 and 24h after exposure. The measured ESD values were 230.5±4.9, 189.5±3.55 and 90.7±3.4mGy for the forehead, neck, and shoulder, respectively. The DAP varied from 1.8 to 2047 Gy*cm2, showing a correlation with fluoroscopy time (r=0.417). Received doses did not increase early markers of DNA damage (γ-H2AX and p53ser15 assays), but residual damage (CA and MN frequencies) showed a significant (p<0.001) increase at 2 and 24h post-exposure compared to pre-imaging, despite poor correlation with DAP (r=0.1). Our results show that interventional imaging procedures deliver significant radiation doses and induce measurable DNA damage in lymphocytes of subjects, highlighting the need for rigorous patient safety protocols.

Protective effect of a polyherbal aqueous extract comprised of nigella sativa (Seeds), hemidesmus indicus (Roots), and smilax glabra (Rhizome) on bleomycin induced cytogenetic damage in human lymphocytes

This study was carried out to determine the chemoprotective potential of a polyherbal aqueous decoction comprised of Nigella sativa (seeds), Hemidesmus indicus (roots), and Smilax glabra (rhizome) against bleomycin induced cytogenetic damage in human lymphocytes. Isolated peripheral blood lymphocytes (PBLs) were exposed to bleomycin at a dose of 40 µg/mL for 2 hrs in the presence or absence of different doses of the decoction (100, 300, and 600 µg/mL). Modulatory effect of the decoction on bleomycin induced cytogenetic damage was evaluated by (a) degree of chromosomal aberrations (CA), (b) formation of micronuclei (MN), and (c) induction of γH2AX foci in lymphocytes exposed to bleomycin. Lymphocytes pretreated with the decoction showed that a significant reduction (p < 0.05) in bleomycin induced (a) stable and unstable chromosome aberrations (CA), (b) MN formation, and (c) formation of γH2AX foci, when compared to lymphocytes treated only with bleomycin. The decoction by itself did not induce any significant cytogenetic damage in PBLs. Overall results of the present study confirm that the decoction can attenuate the cytogenetic damage mediated by bleomycin in human PBLs.

Reciprocal Microduplication of the Williams-Beuren Syndrome Chromosome Region in a 9-Year-Old Omani Boy

BACKGROUND Microdeletions of the 7q11.23 Williams-Beuren syndrome chromosome region (WBSCR) are reported with a frequency of 1 in 10,000, whereas microduplications of the region, although expected to occur at the same frequency, are not widely reported. METHOD We evaluated a 9-year old Omani boy for idiopathic intellectual disability using genetic methods, including multiplex ligation-dependent probe amplification (MLPA), for detection of microdeletions (P064-B3). RESULTS MLPA analysis revealed that the boy has a rare microduplication of the WBSCR. Prominent clinical features include global developmental delay with pronounced speech delay, dysmorphic facies, and autistic features. CONCLUSION Microduplications, in general, are reported at a lesser frequency, perhaps owing to their milder phenotype. Complete genetic assessment in children with idiopathic intellectual disability would help in identifying rare conditions such as duplication of the WBSCR.

Pattern of chromosomal aberrations and expression profile of p53ser15 and BAX protein in peripheral blood lymphocytes of healthy subjects and cancer patients

Introduction: Chemotherapy is an important treatment option which is used for all cancer types. The basic mechanism of action of chemotherapy is that the drugs cause damage to the cancer cells by breaking down DNA, interfere with replication, or enhance the cell killing. Emerging studies have shown that despite tremendous improvements on the therapeutic options, benefit derived from the therapy is not desirable. It is because, interindividual variations among the patient′s response to therapy as well as complex signaling molecules and mechanism involved, determining the final outcome of the therapy. Therapeutic efficacy can be improved by predicting a patient response to that agent, adopting a suitable marker. Materials and Methods: This study involves analysis of the frequencies of chromosomal aberrations and micronucleus, expression profile of p53 ser15 and BAX in healthy subjects and cancer patients, to identify a novel marker to predict their response to chemotherapy agents. For this, peripheral blood sample (4 ml) from cancer patients (solid tumors) was obtained before and after chemotherapy (n = 20). The change in those marker in cancer patients were compared with age- and sex-matched healthy subjects (n = 20). Results: The present study results indicated substantial increase in all four biomarkers for postchemotherapy compared to that obtained before therapy; however, the increase was not significant (P > 0.05), whereas a significant increase (P < 0.05) was observed in all markers from cancer patients compared to that of healthy volunteers relate the genetic instability to the disease status. Furthermore, on comparison, the levels of all those changes are increased in samples obtained posttherapy, despite the magnitude of BAX expression is considerably higher when compared to other markers. Conclusion: Therefore, the study results implied that BAX can be used as a better marker to predict the patient response to chemotherapy.

Mutation Analysis of TBX1 in Children with Conotruncal Heart Anomalies

To the Editor: Conotruncal heart anomalies (CTA) are structural malformations involving the outflow tract. While the exact incidence of CTA in India is not known, it remains the most common type of structural birth defect with a major impact on pediatric morbidity and mortality. While most CTA are sporadic, a few are associated with genetic syndromes; the 22q11 deletion syndrome (22q11.2DS) being the predominate one. The CTA related to the 22q11.2DS are usually associated with a common 3 Mb or 1.5 Mb proximally deleted region, both of which include the TBX1 gene. However, mutations of the TBX1 gene have also been reported in patients who do not have the 22q11.2 deletion but present with CTA. The TBX1 gene encodes a transcription factor of the T-box family and mouse models have demonstrated that TBX1 haploinsufficiency cause cardiac outflow tract lesions. In a casecontrol study involving 96 cases of CTA and 100 control subjects, ranging in age from newborns to 18 y, fluorescence in situ hybridization (FISH) was performed on the cases to rule out the 22q11.2 μ-deletion. Further, screening for mutations or sequence variants in four exons of the Tbox region, which showed 98 % homology to mouse TBX1, was performed using Sanger sequencing. One out of the 96 cases with CTA (1 %) was found to have the 22q11.2 μ-deletion. However, no pathogenic mutations or sequence variants of TBX1 were detected in the patients and healthy controls. While this is in agreement with the report by Conti et al. [1], it is also in contrast with a few studies that have documented either mutations or polymorphisms in TBX1 associated with isolated CTA [2–5]. Our results, though negative, provide corroborative evidence that TBX1 mutations may not be associated with CTA in the selected pediatric population.

Does proliferation capacity of lymphocytes depend on human blood types?: VISWANATHAN et al.

In vitro human lymphocyte culture methodology is well established yet certain confounding factors such as age, medical history as well as individual’s blood type may potentially modulate in vitro proliferation response. These factors have to be carefully evaluated to release reliable test report in routine cytogenetic evaluation for various genetic conditions, radiation biodosimetry, etc. With this objective, the current study was focused on analyzing the proliferation response of lymphocytes drawn from 90 individuals (21‐29 years) with different blood types. The proliferation response was assessed in the cultured lymphocytes by cell cycle, mitotic index (MI), and nuclear division index (NDI) after stimulation with phytohaemagglutinin (PHA). To investigate the toxic effect on proliferation, MI was calculated in representative samples of each blood type were X‐irradiated. The results showed that there was no significant difference among the cell cycle phases of lymphocytes in different blood types (P > 0.05). Similarly, both MI and NDI of lymphocytes derived from different blood types also did not show significant difference ( P > 0.05). The extensive interindividual variation within and among the blood types is likely responsible for the lack of significant difference in lymphocyte proliferation. Although spontaneous proliferation efficiency of lymphocytes of different blood types after PHA stimulation was grossly similar, the MI observed after radiation exposure showed a significant difference ( P < 0.05) indicating a differential proliferation response among the blood types. Our results suggest that the blood types did not have any impact on PHA‐induced proliferation; however, a specific differential lymphocyte proliferation observed after radiation exposure needs to be considered.

A comparison of estimates of doses to radiotherapy patients obtained with the dicentric chromosome analysis and the γ-H2AX assay: Relevance to radiation triage

The γ-H2AX assay was investigated as an alternative to the time-consuming dicentric chromosome assay (DCA). Radiation doses to 25 radiotherapy patients were estimated in parallel by DCA and the γ-H2AX assay. The γ-H2AX assay yielded doses in line with the calculated equivalent whole body doses in 92% of the patients, whereas the success rate of DCA was only 76%. The result shows that the γ-H2AX assay can be effectively used as a rapid and more precise alternative to DCA.