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|Title: ||Effects of alpha particles on zebrafish embryos in vivo|
|Other Titles: ||α-li zi dui huo ti ban ma yu pei tai de ying xiang|
|Authors: ||Yum, Hoi Wa (任凱華)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Master of Philosophy|
|Issue Date: ||2009|
|Publisher: ||City University of Hong Kong|
|Subjects: ||Alpha rays -- Physiological effect.|
Zebra danio -- Embryos -- Physiology.
|Notes: ||CityU Call Number: QP82.2.I53 Y85 2009|
v, 80 leaves : ill. (some col.) 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2009.
Includes bibliographical references (leaves 74-80)
|Abstract: ||It has been common to study DNA damage responses in vertebrates using cell
cultures. However, such experiments cannot be used to study dynamic in vivo
processes such as temporally and spatially regulated patterns of gene
expression. 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
in that major organ systems become evident within 48 hours postfertilization
Recently, a number of research works using the zebrafish embryo as an in vivo
model to study the DNA damage response to ionizing radiation have emerged.
Despite the success of using the zebrafish embryos to study the DNA damage
response to ionizing radiation, only energetic photons (X-rays and gamma
rays) were used. Studies using alpha particles will be of interest because alpha
particles are also an ionizing radiation, and with high linear energy transfer
(LET). Furthermore, alpha particles are emitted from radon and its progeny,
which are ubiquitous in our natural environment, and constitute the largest
natural radiation dose to human and can induce lung cancers.
The objective of this study was to investigate the effect of alpha particles on
zebrafish embryos. Hormetic effect and bystander effect were found in zebrafish embryos in vivo.
Chapter 1 gives the introduction and the literature review.
Chapter 2 describes the study of hormetic effect in zebrafish embryos in vivo.
Dechorionated zebrafish embryos were irradiated at 1.5 hpf to low-dose alpha
particles from an 241Am source, viz., 0.3, 0.6, 1.2, 2.4 mGy (determined using
Monte Carlo simulations). At 24 hpf, these embryos were then examined for
apoptotic cells through acridine orange staining. The mean number of
apoptotic cells was found to decrease significantly from controls to 0.3-mGy
irradiation, and then to increase almost linearly to 0.6, 1.2 and 2.4-mGy
irradiation. This trend was a typical characteristic of a hormetic effect.
Chapter 3 describes the study of bystander effect in zebrafish embryos in vivo.
Dechorionated zebrafish embryos at 1.25 hpf were irradiated with alpha
particles from an 241Am source. Thin polyallyldiglycol carbonate (PADC)
films with a thickness of 16 m were used as support substrates for holding
the embryos and recorded alpha-particle hit positions, and thus enabled
calculation of the dose absorbed by the embryos. The irradiated embryos were
subsequently incubated with naïve (unirradiated) embryos in such a way that
the irradiated and naïve embryos were spatially separated but the medium was
shared. Acridine orange was used to perform in vital staining to show cell
deaths in the naive embryos at 24 hpf. The results gave evidence in supporting
the existence of alpha-particle-induced bystander effects between zebrafish embryos in vivo, and a general positive correlation between the cell death
signals in the naive embryos and the alpha-particle dose absorbed by the
Chapter 4 gives the conclusions and discussion for further studies.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b3947664|
|Appears in Collections:||AP - Master of Philosophy |
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