ABSTRACT. The electrophoresis pattern of apoptotic cells detected by the comet assay has a characteristic small head and spread tail. Thi s image has been referred to as an apoptotic comet, but it has not been previously proven to be apoptotic cells by any direct method. In order to identify this image obtained by the comet assay as corresponding to an apoptotic cell, the frequency of appearance of apoptosis was examined using CHO-K1 and L5178Y cells which were exposed to gamma irradiation. As a method for detecting apoptosis, the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay was used. When the frequency of appearance of apoptotic cells following gamma irradiation was observed over a period of time, there was a significant increase in appearanc e of apoptosis when using the TUNEL assay. However, there was only a slight increase when using the comet assay. In order to verify th e low frequency of appearance of apoptosis when using the comet assay, we attempted to use the TUNEL assay to stain the apoptotic comets detected in the comet assay. The apoptotic comets were TUNEL positive and the normal comets were TUNEL negative. This indicate s that the apoptotic comets were formed from DNA fragments with 3'-hydroxy ends that are generated as cells undergo apoptosis. Th erefore, it was understood that the characteristic pattern of apoptotic comets detected by the comet assay corresponds to cells undergoing apoptosis.

ABSTRACT. Diseases of companion animals are shifting from infectious diseases to neoplasms (cancer), and since radiation therapy is one of the effective choices available for cancer treatment, the application of radiotherapy in veterinary medicine is likely to increase. However tumor tissues have different radiosensitivities, and therefore it is important to determine the intrinsic radiosensitivity of tumors in individual patients in advance of radiotherapy. We have studied the relationship between the surviving cell fraction measured by a clonogenic assay and DNA double strand breaks detected by a comet assay under neutral conditions in three canine tumor cell lines, after γ-ray and carbon ion irradiation. In all the cell lines, cell death assessed by the clonogenic assay was much higher following irradiation with carbon ions than with γ-rays. The initial and residual (4 hr) DNA damage due to γ-ray and carbon ion irradiation were higher in a radiosensitive cell line than in a radioresistant cell line. The surviving cell fraction at 2 Gy (SF2) showed a tendency for correlation with both the initial and residual DNA damage. In particular, the residual damage per Gy was significantly correlated with SF2, regardless of the type of radiation. This indicates that cellular radiosensitivity can be predicted by detection of radiation-induced residual DNA damage. KEY WORDS: canine tumor cell, comet assay, DNA damage, radiosensitivity, radiotherapy.J. Vet. Med. Sci. 67(11): 1089-1095, 2005 Due to recent improvements in the breeding environment and veterinary preventive medicine, companion animals live much longer than in the past. These improvements have made it possible to reduce severe infectious diseases, but conversely the incidence of tumors is increasing in animals. Radiation therapy is one of the effective choices available against such tumors and its use in veterinary medicine is likely to increase.In human medicine, advances have been made in new technologies, such as low linear energy transfer (LET) radiation using protons [16] and linear accelerator (LINAC) three dimensional X-rays. Because high LET radiation causes higher reproductive cell death than proton irradiation [5], clinical studies of radiation therapy using heavy-ion beams have started. However, a wide range of radiosensitivity is observed, even for tumors of the same histopathological origin [2]. Therefore, to improve local control of the tumor, and to set up an effective treatment plan with minimal side effects, it is necessary to predict the radiosensitivity of the tumor for an individual patient, both for high and low LET radiation. Therefore, development of a predictive assay for tumor radiosensitivity in medical practice and establishment of biological parameters are of importance.In general, the clonogenic survival assay is regarded as a good measure of radiosensitivity related to the effects of radiotherapy [4]. A good correlation has been found between the reproductive death of fibroblasts measured by the clonogenic assay and the severity of...

Dioxin is still long persistent in environment. The effect of Dioxin on thyroid function is inconsistent. Da Nang and Bien Hoa airbases have been hot spots for persistent contamination since 1961. Inhabitant living around these sites has been exposed to dioxin for a long time. Serum dioxin level of people was much higher than those in other sites. This study evaluates serum dioxin level using DR CALUX and thyroid function including T3, T4, FT3, FT4, TSH measurement. T3 level was found association with serum dioxin level. There were not any relation between T4, FT3, FT4 and TSH and dioxin level.

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