Etiology of tumor: Physical and Biological carcinogenesis Bianchi Flashcards
(51 cards)
UV light exposure causes
skin cancers, and ionizing radiation exposure from medical or
occupational exposure, nuclear plant accidents, and atomic bomb detonations are associated
with a variety of cancers
contribution of ionizing radiation to the total human cancers is probably _____________, however,
they may arise decades later, a long periods of observation are necessary to ascertain its full effect
small
“Radio Therapy” exploits
ionizing radiation; generally, is provided as part of cancer treatment
to control or kill malignant cells, however, secondary malignancies are seen in some patients
- Alpha rays
- Beta rays
- Neutrons
- Protons
are potentially ______________
oncogenic
carcinogenic only if the wavelength is less than < 10-5 cm:
- Electric waves
- Radio waves
- Infrared
- Visible
- Ultraviolet rays
- X-rays
- γ-rays
ejection of electrons from the outer orbit with the formation of ions is called
IONIZATION
movement of electrons to a more external orbit with higher energy is called
EXCITATION
EXCITING RADIATIONS:
are electromagnetic radiations
with “low” energy and poor penetration potential (UV)
The main source of ultraviolet radiation is
the sun
the sunlight that
reaches the surface of the earth consists of:
-infrared (55%)
-visible photons (40%)
-UV-A rays (4.7%)
-UV-B rays (>290 nm) (0.3%)
The intensity of solar UV radiation varies according to:
- season (max summer)
- latitude (max equator)
- altitude (max high mountains)
- meteorological conditions (max cumulus clouds)
The mechanism of damaging by UV-A?
ultraviolet rays that
go deeper, reach the
dermis and can alter
and destroy elastic
fibers and collagen,
inducing oxidative
stress. They are
responsible for
premature skin aging
in people who are
chronically exposed
to the sun
UV-C and UV-B:
radiations (those with
wavelengths < 300 nm)
are absorbed by the
ozone and the
superficial layers of the
skin. UV-A and UV-B
between 295 and 305
nm reach the deepest
layers of the epidermis.
The latter are more
harmful because, being
endowed with
genotoxic power, they
can induce the
appearance of skin
neoplasms
The carcinogenic potential of UV-B radiation is related to the ability to
induce the formation of __________________
pyrimidine dimers
The carcinogenic potential of UV-B radiation is related to the ability to
induce the formation of?
pyrimidine dimers
Two consecutive pyrimidines can
absorb a UV photon and use its
energy to form a covalent bond
between them (formation of a
dimer)
Radium, discovered by Mr and Mrs Curie, was used to
make the fluorescent paint for watch dials.
Women who painted the quadrants developed?
osteosarcomas of the mastoid and carcinomas of the paranasal sinuses
PARTICULATE IONIZING RADIATIONS:
- α-rays
- β-rays
- Neutrons
- Protons
NON-PARTICULATED IONIZING RADIATION:
- γ-rays
- X-ray
Cosmic radiation:
(initially protons and helium nuclei, later γ and β rays)
Terrestrial radiation:
(especially K40 and C14, but also radium226 and radon86)
Gray (symbol Gy):
is the unit of measure for absorbed dose of radiation.
1 Gy = 1J/kg
Gray replaced the old unit, but rad is still sometimes used; the relation
1 Gy = 100 rad holds.
sievert (symbol Sv):
is the unit of measurement for the equivalent radiation dose. This
quantity has the same dimensions as the absorbed dose Gy, energy per unit mass
(1 Sv = 1 J/kg). Sv reflects the biological effects of radiation on the organism. The
absorbed dose is converted into equivalent dose by multiplying it by a dimensionless
factor depending on the type of radiation.
- X-rays, γ and β:
1 Gy = 1 Sv
- α-rays:
1 Gy = 20 Sv
