++++Lecture 8 Flashcards
Radiation life-shortening?
1-5% reduction in remaining life expectancy per Sv for acute exposure
Life shortening has been observed in
US radiologists * and the A-bomb survivors
life shortening also attributed to?
cancer and cancer with age specific diseases.
Life shortening for Mouse study displays?
increased relative risk with increased radiation dose.
Effects of IR on embryo?
pre- and neo-natal death *growth retardation *abnormalities *post-natal induction of cancer
In utero effects
- cells are more sensitive to IR than adults
- Larger life expectancy through adverse effects
The three stages of embryonic development?
The preimplantation
Organogenesis
fetal
Preimplantation stage
-Stage of conception until fetilised egg attaches to uterus wall 0-9 days
Pre-natal death is most common in this stage
-0.05Gy can kill
LD 50/30=1
The peak incidence of abnormalities is during what stage?
Organogenesis (10 days to 6 weeks)
CNS very sensitive
0.2Gy can increase some abnormalities
LD 50/30=1.5
Possible effects of organogenesis?
Malformation of organs
Small head size
Intrauterine growth retardation
Fetal stage?
LD 50/30 is 2-3Gy
(growth stage)
8-16 weeks
Nervous system may be affected and carcinogenesis
Threshold for mental retardation?
0.2 Fy
Observed shift in IQ is?
30 points per Gy during sensitive period
Natural incidence of fatal childhood cancer is?
1 in 2000 people
200-250 deaths for under 10 yrs/10mSv
1-2 Leukaemia
Total cancer induction period is?
20 yrs but leukaemia risk is doubled during in utero stage
A absorbed dose of 0.1 Gy to an embryo (organogenesis) can result in?
pre natal death or IQ loss
Risks of in-utero irradiation
0-2 wks Spontaneous abortion
2-10wks-Abnormality
2-15wks-Mental retardation
0-9mon-Cancer, growth retardation, genetic
Are there any genetic effects?
In humans no data
No human data because of?
- long life cycle (we live too long)
- studies require large populations > 1 million
- too few offspring
- large incidence of naturally occurring genetic damage
Is there evidence of heritable mutations in humans
Yes
Summary of Megamouse experiment?
Different gene loci have different rates of induction of mutation
- Mutation frequency is dose-rate dependent and sex dependent
- The time between irradiation and conception is important
- Magnitude of the effect depends upon the stage of sex cell irradiated
Are males or females more sensitive on average?
Male
At high dose rates 1Gy/min same
as it decreases males more sensitive
A delay in conception following irradiation means what?
reduces the effect of irradiation, due to repair (6 months)
Are later stages of male and female sex cells more sensitive?
Mature sex cells by a factor of 5
Doubling dose?
Doubles spontaneous rate
mutations per million 10mSv
(relative risk 1Gy)
(absolute risks 100 mutations/ 10mSv for future generations and 60 per million per 10mSv) mutations for working age population)
Sundry effects of IR?
Sterility
cataract formation
skin damage
epilation
