adiation Biophysics

Our current radiation biophysics research mainly focuses on two areas, namely, (1) studying biological effects of alpha particles in vivo using zebrafish embryos, and (2) in vitro studies of radiation induced bystander effects.
Resources
Book chapter: Yu, K.N., Nikezic, D., "Alpha-Particle Radiobiological Experiments Involving Solid State Nuclear Track Detectors as Substrates", 2009, in Nuclear Track Detectors: Design, Methods and Applications, Eds. Maksim Sidorov and Oleg Ivanov, (Nova Science Publishers: New York) p. 133-154. (download pdf version) (purchase book)
Book chapter: Han, W., Yu, K.N., "Response of cells to ionizing radiation", 2009, in Advances in Biomedical Sciences and Engineering, Ed. S. C. Tjong, (Bentham Science Publishers: Illinois), Chapter 6, 204-262. (download pdf version) (purchase chapter/book)
Book chapter: Yu, K.N., Cheng, S.H., "In Vivo Studies of α-Particle Radiation Effects Using Zebrafish Embryos", 2009, in Advances in Biomedical Sciences and Engineering, Ed. S. C. Tjong, (Bentham Science Publishers: Illinois), Chapter 7, 263-283. (download pdf version) (purchase chapter/book)
Book chapter: Han, W., Yu, K.N., "Ionizing Radiation, DNA Double Strand Break and Mutation", 2010, in Advances in Genetics Research. Volume 4, Ed. Kevin V. Urbano, (Nova Science Publishers: New York), in press. (download pdf version) (purchase book)

 

Studying biological effects of alpha particles in vivo using zebrafish embryos

An adult zebrafish, Danio rerio.

In recent years, the zebrafish, Danio rerio, a small vertebrate from Southeast Asia, has become a preferred model for studying human disease, including carcinogenesis. The most important advantage is that the human and zebrafish genomes share considerable homology, including conservation of most DNA repair-related genes. Rapid embryonic development is another advantage so the effects can be assessed within 24 hours post fertilization (hpf). The studied biological effects of alpha particles in vivo include the hormetic effect and the bystander effect.

 
Hormetic effect
Dechorionated embryos at 1.5 hpf were  irradiated with a planar 241Am source (with an activity of 4.259 kBq). The average alpha-particle dose rate on an embryo was 1.4 mGy/min. Irradiation durations were chosen as 1, 2, 4 and 8 min, and 0 min (as controls), thereby providing alpha-particle doses of 1.4, 2.8, 5.6 and 11.2 mGy.

After alpha-particle irradiation at 1.5 hpf, the embryos were allowed to develop into 24 hpf and then analyzed for apoptosis. The mean number decreased significantly from 0-min irradiation (i.e., the controls) to 1-min irradiation, and then increased almost linearly to 2-min, 4-min and 8-min irradiation. The differences were statistically significant (p < 0.05) between 0- and 1-min irradiation, between 4-min and 1- or 2-min irradiation, and between 8-min irradiation and all other irradiations. This trend resembled that of a hormetic effect.

The relationship between the mean number of apoptotic cells (error bars showing one standard errors) obtained in zebrafish embryos irradiated for different durations.
 
Bystander effect
Dechorionated zebrafish embryos at 1.5 hpf were irradiated with a planar 241Am source (with an activity of 4.259 kBq). After irradiation, the embryos were transferred to an agarose plate, which was then incubated at 37oC with naïve embryos (unirradiated embryos having partnered with the irradiated embryos) in the same plate containing 3 ml medium. The irradiated and naïve embryos were accommodated in two shallow regions dredged in the agarose, separated by a small ridge. At 24 hpf, the embryos were collected and examined for apoptosis by vital dye staining using acridine orange.

One irradiated embryo was incubated with five naive embryos in the agarose plate. Three sets of experiments were performed. The combined results are shown on the right. These results supported a general positive correlation between the apoptotic signals in the naive embryos and the alpha-particle dose absorbed by the irradiated embryos. Nevertheless, a different trend in the low-dose region (i.e., < 1 mGy) could not be ruled out because of the relatively smaller number of data points in this region. 

Results on the relationship between the apoptotic signal in the naive embryos with the alpha-particle dose absorbed by the irradiated embryos. The linear best-fit line is shown with the parameters (A as intercept and B as slope) and the corresponding 95% confidence intervals.
 
Adaptive response
We have designed the experimental setup and the associated procedures for alpha-particle-induced adaptive response in zebrafish embryos in vivo. Thin PADC films with a thickness of 16 μm were fabricated and employed as support substrates for holding dechorionated zebrafish embryos for alpha-particle irradiation from the bottom through the films. Embryos were collected within 15 min when the light photoperiod began, which were then incubated and dechorionated at 4 hours post fertilization (hpf). They were then irradiated at 5 hpf by alpha particles using a planar 241Am source with an activity of 0.1151 mCi for 24 s (priming dose), and subsequently at 10 hpf using the same source for 240 s (challenging dose). The levels of apoptosis in irradiated zebrafish embryos at 24 hpf were quantified through staining with the vital dye acridine orange, followed by counting the stained cells under a florescent microscope. The results revealed the presence of the adaptive response in zebrafish embryos in vivo, and demonstrated the feasibility of the adopted experimental setup and procedures.

Apoptotic signals of 25 hpf zebrafish embryos revealed by acridine orange staining: (Upper) the zebrafish embryo has received a priming dose at 5 hpf and a challenging dose at 10 hpf; (Lower) the zebrafish embryo has received the challenging dose at 10 hpf only.
  Publications
  • Yum, E.H.W., Ng, C.K.M., Lin, A.C.C., Cheng, S.H., Yu, K.N., 2007. Experimental setup for studying the effects of alpha particles on zebrafish embryos. Nuclear Instruments and Methods in Physics Research B, 264, 171–176.
  • Yum, E.H.W., Cheng, S.H., Yu, K.N., 2009. Zebrafish embryos for studying radiation response in vivo. Journal of Radiation Research, 50, Supplement A, A93.
  • Yum, E.H.W., Choi, V.W.Y., Nikezic, D., Li, V.W.T., Cheng, S.H., Yu, K.N., 2009. Alpha-particle-induced bystander effects between zebrafish embryos in vivo. Radiation Measurements, 44, 1077-1080.
  • Choi, V.W.Y., Lam, R.K.K., Chong, E.Y.W., Cheng, S.H., Yu, K.N., 2010. Designing experimental setup and procedures for studying alpha-particle-induced adaptive response in zebrafish embryos in vivo. Nuclear Instruments and Methods in Physics Research B, 268 651–656.
  • Yum, E.H.W., Li, V.W.T., Choi, V.W.Y., Cheng, S.H., Yu, K.N., 2010. Effects of alpha particles on zebrafish embryos. Applied Radiation and Isotopes, 68, 714-717.
  • Choi, V.W.Y., Konishi, T., Oikawa, M., Iso, H., Cheng, S.H., Yu, K.N., 2010. Adaptive response in zebrafish embryos induced using microbeam protons as priming dose and x-ray photons as challenging dose. Journal of Radiation Research 51, 657–664.
  • Choi, V.W.Y., Cheng, S.H., Yu, K.N., 2010. Radioadaptive Response Induced by Alpha-Particle-Induced Stress Communicated in Vivo between Zebrafish Embryos. Environmental Science & Technology, 44, 8829-8834.
  • Choi, V.W.Y., Wong, M.Y.P., Cheng, S.H., Yu, K.N., 2011. Dosimetric study of radioadaptive response of zebrafish embryos using PADC-film substrates. Radiation Measurements 46, 1795-1798.
  • Choi, V.W.Y., Ng, C.Y.P., Cheng, S.H., Yu, K.N., 2012. α-Particle irradiated zebrafish embryos rescued by bystander unirradiated zebrafish embryos. Environmental Science & Technology, 46, 226–231.
 

In vitro studies of radiation induced bystander effects (RIBE)

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Nuclear Radiation Unit
Department of Physics and Materials Science
City University of Hong Kong
Tat Chee Ave, Kowloon Tong, Hong Kong
Email: apnru@cityu.edu.hk

 

Page last modified on 3-Feb-2012

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