Ústav patologické fyziologie LF MU1
Experimentally induced acute radiation
syndrome in experimental animal
What is ionizing radiation?
particles or electromagnetic
radiation, where the particles /
photons carry enough energy to
ionize atoms and molecules (by
removing the electron from their
orbit).
It produces electrically charged
particles (= ions)
Ionization is biologically very
important in macromolecules that
are encompassed within the
human body.
Types of ionizing radiation?
 = –particles (atoms of helium)
 = electornes or positrones
 = electromagnetic radiation
(photons)
neutrons
Units?
the dose of ionizing radiation received by a person is expressed
as absorbed energy, the unit being gray (Gy)
1Gy = 1 J / kg (formerly rad)
same dose in Gy of different types of radiation causes different
biological effect (1Gy  -radiation has greater effect than 1Gy  radiation)
→ radiation effect is expressed as effective dose, unit
is sievert (Sv)
irrespective of the type of radiation, 1 Sv leads to the same
biological effect
example: 1Gy = 1Sv for  - or  radiation, 1Gy = 10Sv for
neutrons and 1Gy = 20Sv for -radiation
rate of radioactive decay of radioactive material expressed by
units of becquerel (Bq)
1 Bq = 1 atomic decay / s
What is radioactivity?
most atoms are stable: carbon-12 or oxygen-16
some have an excess of internal energy and decay spontaneously
to form new elements = "radioactive decay"
in decay, excess internal energy is released as -radiation or
particles
Sources of ionizing radiation?
Natural
cosmic
exposure increases with altitude
solar
especially -radiation
terrestrial resources
radioactive decay of natural radioisotopes
(soil and rock)
Radon
gas, formed by decay of Radio-226 (from
uranium)
has the largest share of the total. dose of
ionizing radiation
Artificial
medicine
diagnostics, therapy, sterilization
industry
nuclear energy production
agriculture
Biological effects and consequences
of ionizing radiation?
Direct ionization of macromolecules
Indirectly through "radiolysis" of
water
free oxygen radicals
Consequences:
cycle blockade → apoptosis
mitotic or post-mitotic death
(proliferating cells)
mutation (gene or chromosome)
reparation
unrepaired change
Types and consequences of DNA lesions?
point mutations
DNA repair: mismatch repair
Single Strand Breaks (SSB)
DNA repair: base excision repair
Double Strand Breaks (DSB)
lethal (apoptosis)
DNA repair: homologous recombination
(sometimes)
sometimes non-homologous repair
translocation
insertion
DNA repair
(in situ repair)
base excision repair
nucleotide excision repair
mismatch repair
Character of biological effect
Determinististic
severity depends („is determined by") on the
dose
specific manifestation
damage to typical tissues and organs
the effect occurs only when the threshold dose
is exceeded
damage is due to the death of a large number
of cells
onset of symptoms soon after exposure (short
latency)
Types:
acute radiation syndrome (ac. radiation
sickness)
whole-body irradiation with a dose> 1Gy
chronic post-radiation syndrome (general or
local)
sterility, cataract, radiation dermatitis, alopecia,
endarteritis obliterans, pneumonitis,…
fetal damage in utero
Stochastic
probability increases with dose (not
severity!)
non - specific manifestation
damage to various tissues and organs
a smooth risk increase without a “safe”
threshold dose
single cell damage is sufficient
delayed manifestation (long latency,
typically years)
Types:
somatic mutations - tumors
leukemia, št. gland, lungs, ml. gland,
skeleton
germinative mutations (oocyte, sperm) congenital
genetic defect
Deterministic  stochastic
Acute radiation syndrome
it affects the hematopoietic,
gastrointestinal and cerebrovascular
systems
time course, extent and severity depends
by dose – it is a typical deterministic effect
!!!
from several hours to several months after
exposure
Acute radiation syndrome
Hematopoietic syndrome (> 1Gy)
1) reticulocytopenia, lymphopenia + granulocytosis
2) granulocytopenia (immunodeficiency)
3) thrombocytopenia (bleeding)
4) anemia (hypoxia)
GIT syndrome (> 10Gy)
early (hours) - nausea, vomiting, diarrhea
late (days) - loss of intestinal integrity
malabsorption, dehydration, toxemia / sepsis, ileus, bleeding
Cerebrovascular syndrome (tens of Gy)
headache, cognitive impairment, disorientation, ataxia, convulsions, exhaustion
and hypotension
Cutaneous
erythema, burns, edema, impaired wound healing
epilation
Hematopoietic syndrome
irradiation of bone marrow (> 1Gy)
leads to exponential cell death hematological
crisis
hypoplasia to pulp aplasia + peripheral
pancytopenia (infection, bleeding)
subpopulation of stem cells. it is
selectively more radio-resistant
(probably due to the prevalence of bb in
the Go phase)
necessary for regeneration
anemia is a late consequence
(erythrocytes ~ 120 days)!
massive stress reactions
(glucocorticoids) contribute to
lymphopenia (cytolytic effect) and
paradoxically delay the onset of
granulocytopenia (release of stocks of
granulocytes from the pulp and spleen)
Exemplární příklad?
Super quick explanation of the what the Chernobyl nuclear disaster and reactor number 4 including it’s timeline of events in the seconds and
minutes and days following April 26th, 1986 and what radioactivity is
Origin Relationship w/ territory Place w/in Food Web
Originates w/in
zone
Originates outside
of zone
Lives on/in ground
Lives above ground
Higher in web
Lower in web
Gulakov, Andrey Vladimirovich 2014. Rask, Martti 2012.
Bioacumulation
EXPERIMENTALLY INDUCED
ACUTE RADIATION SYNDROME IN
EXPERIMENTAL ANIMAL
Practical:
Aim of the practical
to document the deterministic nature of radiation effects on the
practical examples
to monitor the dynamics of peripheral blood count changes as a
result of the bone marrow
acute radiation syndrome is a model situation on which the principle
of hematopoiesis regulation can be demonstrated
Practical experiment I - design
Practical experiment I – surgery technique
Practical experiment I - evaluation
Effects of ionizing radiation on
haematopoietic tissue
Practical experiment II – evaluation of
peripheral blood smears
Control questions
What is ionizing radiation?
What is radioactivity?
How are the biological effects of ionizing radiation mediated?
Types of biological effects of radiation + examples?
Hematopoeisis
Hematopoiesis = bone marrow
bone marrow
(1) haematopoietic cells.
(2) hematopoietic stroma - essential for normal
production of blood cells.
fibroblasts, adipocytes, macrophages, T-lymphocytes,
connective tissue, fat
own hematopoietic bb. - tribal bb.
pluripotent hematopoietic stem cell
differentiation into all series + self-renewal !!!
unclear phenotype - antigen classification CD34 +
in the pulp <0.01%
progenitor (determined) stem bb.
do not have long-term self-renewal ability
unclear phenotype - classification according to the
ability to form colonies (CFU-E, CFU-M, CFU-G,
CFU-Meg,…)
blood precursors bb.
clear phenotype (morphology, histochemistry)
in medulla ~ 90%
proerythroblast - basosile erythroblast polychromatophilic
erythroblast - orthochromic
erythroblast - reticulocyte - erythrocyte
myeloblast - promyelocyte - myelocyte metamyelocyte
- granulophyte (rod)
promonocyte - monocyte
megakaryoblast - megakaryocyte
mature elements
basic properties of KB are
self-renewal
division without differentiation
(asymmetric)
production of specialized bb. (tissue
regeneration)
KB types
mature KB (pluripotent)
adult, somatic
individual KBs give rise to a limited
repertoire of bb.
eg haematopoietic KB,
mesenchymal KB,…
early KB (toti- / omnipotent)
embryonic (blastocyst)
they give rise to all types of body
cells
they are the only ones that do not
need growth factors to stimulate
division, in all others the cell cycle is
initiated by mitogens
Stem cells
Stem cells
Somatic stem cells
located in most body tissues as a source
of cells for constant self-renewal and
replacement
they are pluripotent
give rise to all bb. of a specific type of
tissue, but not another (this is only the
ability of embryonic KB)
however, it appears that some universality
is possible
Regulatory factors
interplay of autocrine,
paracrine and endocrine
factors
endocrine
erythropoietin (kidney)
thrombopoietin (liver)
cytokines
para- / autocrine
hematopoietic growth
factors (cytokines)
produced by stromal cells,
eg CSFs (colony-stimulating
factors)
Erythropoetin (EPO)
90% oxygen in the body is used for ox.
phosphorylation - ATP production
oxygen is relatively insoluble in water - Hb allows
100- more oxygen to be transported by blood
than would be possible only in physically
dissolved form
EPO is hl. regulator conc. Hb and hence oxygen
availability
1893 - alpine environment leads to increase in Hb
in humans – adaptation to hypoxia!
1950 - A humoral factor produced by the kidneys
stimulating erythropoiesis
bilateral nephrectomy in rats led to anemia
1977 purification of EPO from the urine of a
patient with aplastic anemia
1983 cloning of EPO gene - recombinant EPO
production (epoetin)
long-term treatment of renal failure and some
anemia
EPO production - peritubular fibroblasts of kidney
(deep in cortex and outer cortex)
why kidney?
phylogenesis - in lower organisms, the kidney is a
haemopoietic organ
more sensitive sensing of the actual Hb content
and hence oxygen (after separation of plasma
and circulating elements) at glom. filtration
Blood count – reference values
Muži Ženy
Ery [RBC] (1012/l) 4.2 – 5.8 3.8 – 5.2
Leu [WBC] (109/l) 5 – 10
Tromb (109/l) 150 - 400
hematocrit (%) 0.38 - 0.49 0.35 – 0.46
hemoglobin (g/l) 135 – 175 120 - 168
Mean volume Ery [MCV] (fl) 80 - 95 80 - 95
Average Hb content in ERY [MCH] (pg)
MCH = Hb  10/RBC
27 - 32 27 - 32
Average concentration of Hb [MCHC]
MCHC = Hb  100/hematocrit
0.32 – 0.37 0.32 – 0.37
Red Cell Distribution Width [RDW] (%) 11 - 15
Peripheral blood cells
Differential white blood count
Practical experiment II