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Molecular and Cellular Radiation Biology Flashcards

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1
Q

Radiation Biology

Radiation biology is the branch of biology concerned with the effects of what on living systems?

Includes:

  • Sequence of events occuring after the ___ of energy from ___ radiation
  • Action of the living system to make up for the ___ of this energy ___
  • ___ to the living system that may be produced
A

Radiation Biology

Radiation biology is the branch of biology concerned with the effects of IONIZING RADIATION on living systems.

Includes:

  • Sequence of events occuring after the ABSORPTION of energy from IONIZING radiation
  • Action of the living system to make up for the CONSEQUENCES of this energy ASSIMILATION
  • INJURY to the living system that may be produced
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2
Q

Ionizing Radiation

Ionizing radiation damages living systems by ionizing the ___ comprising the ___ structure of these systems.

What is begun with the ionization produced by various types of radiation?

What are the types of radiation?

What will not bond properly in molecules?

A

Ionizing Radiation

Ionizing radiation damages living systems by ionizing the ATOMS comprising the MOLECULAR structure of these systems.

What is begun with the ionization produced by various types of radiation? BIOLOGICAL DAMAGE

What are the types of radiation? GAMMA RAYS (1), ALPHA PARTICLES (20), BETA PARTICLES (2), PROTONS (2), X-RAYS (1)

What will not bond properly in molecules? IONIZED ATOMS

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3
Q

Radiation Energy Transfer Determinants

Ionizing radiation causes ___ and the effects may vary in biologic tissue.

What three important concepts help us understand that?

A

Radiation Energy Transfer Determinants

Ionizing radiation causes INJURY and the effects may vary in biologic tissue.

What three important concepts help us understand that?

  1. RELATIVE BIOLOGIC EFFECTIVENES
  2. OXYGEN ENHANCEMENT RATIO
  3. LINEAR ENERGY TRANSFER
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4
Q

Linear Energy Transfer (LET)

LET is the average energy deposited per unit ___ of ___ by ___ radiation as it passes through and interacts with a ___ along its path.

What units is LET described in?

What is the rate of transfer from diagnostic to soft tissue?

A

Linear Energy Transfer (LET)

LET is the average energy deposited per unit LEGNTH of TRACK by IONIZING radiation as it passes through and interacts with a MEDIUM along its path.

What units is LET described in? keV/μm

What is the rate of transfer from diagnostic to soft tissue? 3 keV/μm

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5
Q

Linear Energy Transfer (LET)

LET is a very important factor in assessing potential ___ and ___ damage from exposure to ionizing radiation.

What are the 2 radiation categories according to LET?

When LET increases (more absorption), the chances of producing a significant biologic response in the ___ biologic response in the ___ ___ molecules grows (increases).

A

Linear Energy Transfer (LET)

LET is a very important factor in assessing potential TISSUE and ORGAN damage from exposure to ionizing radiation.

What are the 2 radiation categories according to LET?

  • LOW-LINEAR ENERGY TRANSFER RADIATION (kVp)
  • HIGH-LINEAR ENERGY TRANSFER RADIATION (MeV)

When LET increases (more absorption), the chances of producing asignificant biologic response in the RADIOSENSITIVE biologic response in the RADIOSENSITIVE DNA molecules grows (increases).

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6
Q

General Categories of Linear Energy Transfer Radiation

What are the low-LET types of radiation? (2)

What are the high-LET types of radiation? (4)

A

​General Categories of Linear Energy Transfer Radiation

What are the low-LET types of radiation? (2)

  1. Gamma Rays
  2. X-Rays

What are the high-LET types of radiation? (4)

  1. Charged particles released from interactions between neutrons and atoms
  2. Alpha Particles
  3. Low-energy neutrons
  4. Ions of heavy nuclei
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7
Q

Low – LET Energies

  • Has no ___ or no ___
  • Is ___ ionizing and interacts ___ along the length of its track
  • Causes ___ through ___ interactions (releases ___ ___)
  • Causes sublethal damage to the ___ or ___ ___
A

Low – LET Energies

  • Has no MASS or no CHARGE
  • Is SPARSELY ionizing and interacts RANDOMLY along the length of its track
  • Causes DAMAGES through INDIRECT interactions (releases FREE RADICALS)
  • Causes sublethal damage to the DNA or REPAIR ENZYMES
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8
Q

High-LET and Internal Contamination

High LET an internal contamination are radionuclides that are what?

___ damage due to ___ breaks in the ___ are possible.

A

High-LET and Internal Contamination

High LET an internal contamination are radionuclides that are what?

  • IMPLANTED
  • INGESTED
  • INJECTED
  • INHALED

IRREPARABLE damage due to STRAND breaks in the DNA are possible.

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9
Q

LET Energies Comparisons

The higher the LET of radiation, the greater the change for a ___ ___.

What is the LET for the following radiation types?

  • Cobalt – 60
  • 1 MeV Electrons
  • Diagnostic x-ray
  • 10 MeV
  • 2.5 mEv
  • 5 mEv
  • Heavy nuclei
A

LET Energies Comparisons

The higher the LET of radiation, the greater the change for a BIOLOGIC REACTION.

What is the LET for the following radiation types?

  • Cobalt – 60 … 0.25
  • 1 MeV Electrons … 0.3
  • Diagnostic x-ray … 3.0
  • 10 MeV … 4.0
  • 2.5 mEv … 20.0
  • 5 mEv … 100.0
  • Heavy nuclei … 1000.0
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10
Q

Relative Biologic Effectiveness (RBE)

  • Describes the relative capabilities of radiation with differing ___ to produce a particular biologic reaction
  • RBE of the type of radiation being used is the ratio of the dose of a ___ radiation (conventionally ___-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the ___ biologic reaction in a given experiment. The reaction is produced by a dose of the ___ radiation delivered under the ___ conditions.
A

Relative Biologic Effectiveness (RBE)

  • Describes the relative capabilities of radiation with differing LETs to produce a particular biologic reaction
  • RBE of the type of radiation being used is the ratio of the dose of a REFERENCE radiation (conventionally 250-kVp x-rays) to the dose of radiation of the type in question that is necessary to produce the SAME biologic reaction in a given experiment. The reaction is produced by a dose of the TEST radiation delivered under the SAME conditions.
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11
Q

Mathematical Expression of Relative Biologic Effectiveness

A

Mathematical Expression of Relative Biologic Effectiveness

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12
Q

RBE

Dose of ___ radiation necessary to produce a ___ effect

Dose of ___ radiation necessary to produce the ___ effect

• When mice are irradiated with 250 keV x-rays, death occurs at 650 rads. If similar mice are irradiated with fast neutrons, death occurs at only 210 rad. What is the RBE for the fast neutrons?
RBE = 650 rad = 3.1
210 rad

A

RBE

Dose of STANDARD radiation necessary to produce a GIVEN effect

Dose of TEST radiation necessary to produce the SAME effect

• When mice are irradiated with 250 keV x-rays, death occurs at 650 rads. If similar mice are irradiated with fast neutrons, death occurs at only 210 rad. What is the RBE for the fast neutrons?
RBE = 650 rad = 3.1
210 rad

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13
Q

Oxygen Enhancement Ratio (OER)

  • The ratio of the radiation dose required to cause a particular biologic response of ___ or ___ in any oxygen-deprived environment to the radiation dose required to cause an ___ response under ___ oxygenated conditions
  • In general, x-rays and gamma rays have an OER of about ___ when radiation dose is ___.
  • OER may be ___ (approximately ___) when radiation doses are below ___ Gyt.
A

Oxygen Enhancement Ratio (OER)

  • The ratio of the radiation dose required to cause a particular biologic response of CELLS or ORGANISMS in any oxygen-deprived environment to the radiation dose required to cause an IDENTICAL response under NORMAL oxygenated conditions
  • In general, x-rays and gamma rays have an OER of about 3.0 when radiation dose is HIGH.
  • OER may be LESS (approximately 2.0) when radiation doses are below 2 Gyt.
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14
Q

Oxygen Enhancement Ratio (OER)

The response of ___ to radiation is ___ when irradiated in the oxygenated or ___ state.

  • It is theorized that oxygen is needed in order for ___ ___ to form during ionization of ___.
  • With the free radicals, ___ ___ is not formed and thus ___ damage is ___.
A

Oxygen Enhancement Ratio (OER)

The response of TISSUE to radiation is GREATER when irradiated in the oxygenated or AEROBIC state.

  • It is theorized that oxygen is needed in order for FREE RADICALS to form during ionization of WATER.
  • With the free radicals, HYDROGEN PEROXIDE is not formed and thus CELL damage is REDUCED.
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15
Q

Molecular Effects of Irradiation

In living systems, biologic damage resulting from exposure to ionizing radiation may be observed on what three levels?

  • Any ___ radiation-induced ___ of living systems at the ___ or ___ level always begin with damage at the ___ level.
  • Molecular damage results in the formation of ___ changed molecules that may impair ___ ___.
A

Molecular Effects of Irradiation

In living systems, biologic damage resulting from exposure to ionizing radiation may be observed on what three levels? MOLECULAR, ORGANIC, CELLULAR

  • Any VISIBLE radiation-induced INJURIES of living systems at the CELLULAR or ORGANIC level always begin with damage at the MOLECULAR level.
  • Molecular damage results in the formation of STRUCTURALLY changed molecules that may impair CELLULAR FUNCTIONING.
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16
Q

Effects of Irradiation on Somatic and Genetic Cells

  • exposure to ionizing radiation can alter a human cell’s ___ ___.
  • may disturb the cell’s ___ balance and ultimately the way it ___. The affected cell can then no longer ___ its ___ task.
  • If a sufficient quantity of ___ cells are affected, entire ___ processes may be ___.
  • If radiation damages the ___ cells, the damage may be passed on to future generations in the form of ___ ___.
A

Effects of Irradiation on Somatic and Genetic Cells

  • exposure to ionizing radiation can alter a human cell’s CONSTITUENT MOLECULES.
  • may disturb the cell’s CHEMICAL balance and ultimately the way it OPERATES. The affected cell can then no longer PERFORM its NORMAL task.
  • If a sufficient quantity of SOMATIC cells are affected, entire BODY processes may be DISRUPTED.
  • If radiation damages the GERM cells, the damage may be passed on to future generations in the form of GENETIC MUTATIONS.
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17
Q

Classification of Ionizing Radiation Interaction

What are two classifications of ionizing radiation interaction on a cell?

Essentially all effects of ___ in living cells result from ___ action, because the human body is composed of ___% ___ and less than ___% ___.

A

Classification of Ionizing Radiation Interaction

What are two classifications of ionizing radiation interaction on a cell?

  1. DIRECT ACTION (EX, IN DNA)
  2. INDIRECT ACTION (EX, IN WATER)

Essentially all effects of IRRADIATION in living cells result from INDIRECT action, because the human body is composed of 80% WATER and less than 1% DNA.

18
Q

Direct and Indirect Action

A

Direct and Indirect Action

19
Q

Radiolysis of Water (Indirect)

  • Ionization of….
  • Production of…
  • Production of undesirable…
  • Production of …. substances
  • Organic … formation
A

Radiolysis of Water (Indirect)

  • Ionization of WATER MOLECULES
  • Production of FREE RADICALS
  • Production of undesirable CHEMICAL REACTIONS AND BIOLOGIC DAMAGE
  • Production of CELL-DAMAGING substances
  • Organic FREE RADICAL formation
20
Q

Effects of Ionizing Radiation on DNA

Single-strand break

Ionizing radiation interacts with ___ ___, ___ ___, and ___ one of the molecule’s ___ ___ possibly ___ one of the sugar-phosphate chain ___ rails (called a ___ ___).

___ ___ are often capable of reversing this damage.

A

Effects of Ionizing Radiation on DNA

Single-strand break

Ionizing radiation interacts with DNA MACROMOLECULE, TRANSFERS ENERGY, and RUPTURES one of the molecule’s CHEMICAL BONDS possibly SEVERING one of the sugar-phosphate chain SIDE rails (called a POINT MUTATION).

REPAIR ENZYMES are often capable of reversing this damage.

21
Q

Effects of Ionizing Radiation on DNA

Double-strand break

  • Further exposure of the affected DNA macromolecule to ionizing radiation can lead to ___ ___ in the sugar-phosphate molecular chain(s).
  • Breaks may also be ___ but are not repaired as easily as ___ ___ breaks.
  • If repair does not take place, further ___ may occur in the DNA chains, threatening the ___ of the ___.
  • Occur more commonly with ___ ___ (___ ___) radiation.
A

Effects of Ionizing Radiation on DNA

Double-strand break

  • Further exposure of the affected DNA macromolecule to ionizing radiation can lead to ADDITIONAL BREAKS in the sugar-phosphate molecular chain(s).
  • Breaks may also be REPAIRED but are not repaired as easily as SINGLE STRAND breaks.
  • If repair does not take place, further SEPARATION may occur in the DNA chains, threatening the LIFE of the CELL.
  • Occur more commonly with DENSELY IONIZING (HIGH-LET) radiation.
22
Q

Effects of Ionizing Radiation on DNA

Double-strand break in same Rung of DNA

  • Result is a ___ or broken ___ with each new portion containing an ___ amount of ___ material
  • If damaged ___ divides, each new ___ cell will receive an ___ amount of ___ material culminating in the ___ or ___ functioning of the new ___ cell.
A

Effects of Ionizing Radiation on DNA

Double-strand break in same Rung of DNA

  • Result is a CLEAVED or broken CHROMOSOME with each new portion containing an UNEQUAL amount of GENETIC material
  • If damaged CHROMOSOMES divides, each new DAUGHTER cell will receive an INCORRECT amount of GENETIC material culminating in the DEATH or IMPAIRED functioning of the new DAUGHTER cell.
23
Q

Effects of Ionizing Radiation on DNA

Mutation

  • In general, interaction of high-energy radiation with a DNA molecule causes either a ___ of or ___ in a ___ ___ on the DNA chain.
  • Direct consequence of this damage is an ___ of the ___ ___, a ___.
  • May not be ___ and may cause ___ consequences for the cell
  • If cell remains ___, ___ ___ information will be ___ to one of the ___ ___ cells when the cell ___.
A

Effects of Ionizing Radiation on DNA

Mutation

  • In general, interaction of high-energy radiation with a DNA molecule causes either a LOSS of or CHANGE in a NITROGENOUS BASE on the DNA chain.
  • Direct consequence of this damage is an ALTERATION of the BASE SEQUENCE, a MUTATION.
  • May not be REVERSIBLE and may cause ACUTE consequences for the cell
  • If cell remains VIABLE, INCORRECT GENETIC information will be TRANSFERRED to one of the TWO DAUGHTER cells when the cell DIVIDES.
24
Q

Effects of Ionizing Radiation on DNA

Covalent cross-links

  • ___ unions created between atoms by the ___ sharing of ___ or ___ pairs of electrons
  • Initiated by ___ ___ radiation
  • Following irradiation, some molecules can ___ or change into ___, ___ molecules that become very ___ (“___”) when they themselves are exposed to ___, causing these molecules to ___ to other ___ or to other segments of the same ___ chain.
  • Can occur in many different ___
  • ___ cross-link
  • ___ cross-link
A

Effects of Ionizing Radiation on DNA

Covalent cross-links

  • CHEMICAL unions created between atoms by the SINGLE sharing of ONE or MORE pairs of electrons
  • Initiated by HIGH ENERGY radiation
  • Following irradiation, some molecules can FRAGMENT or change into SMALL, SPURLIKE molecules that become very INTERACTIVE (“STICKY”) when they themselves are exposed to RADIATION, causing these molecules to ATTACH to other MACROMOLECULES or to other segments of the same MACROMOLECULE chain.
  • Can occur in many different PATTERNS
  • INTRASTRAND cross-link
  • INTERSTRAND cross-link
25
Q

Effects of Ionizing Radiation on Chromosomes

  • Large-scale structural changes in a chromosome produced by ionizing radiation may be as grave for the cell as are ___-induced changes in ___.
  • Radiation-induced chromosome ___ in both ___ and ___ cells
  • Chromosomal ___
  • Chromosome ___ (Chromosome ___ and Chromatid ___)
  • Structural changes in biologic ___ caused by ionizing radiation
A

Effects of Ionizing Radiation on Chromosomes

  • Large-scale structural changes in a chromosome produced by ionizing radiation may be as grave for the cell as are RADIATION-induced changes in DNA.
  • Radiation-induced chromosome BREAKS in both SOMATIC and REPRODUCTIVE cells
  • Chromosomal FRAGMENTS
  • Chromosome ANOMALIES (Chromosome ABERRATIONS and Chromatid ABERRATIONS)
  • Structural changes in biologic TISSUE caused by ionizing radiation
26
Q

Consequences to the Cell from Structural Changes in Biologic Tissue

A

Consequences to the Cell from Structural Changes in Biologic Tissue

27
Q

Broken-end rearrangement producing grossly misshapen chromosomes

A

Broken-end rearrangement producing grossly misshapen chromosomes

28
Q

_Consequences to the Cell from Structural Changes in Biologic Tissu_e

Broken-end rearrangement without visible damage to the chromatids

A

Consequences to the Cell from Structural Changes in Biologic Tissue

Broken-end rearrangement without visible damage to the chromatids

29
Q

Target Theory: Master, or Key, Molecule

A master, or key molecule that maintains ___ cell function is believed to be ___ in every cell.

A

Target Theory: Master, or Key, Molecule

A master, or key molecule that maintains NORMAL cell function is believed to be PRESENT in every cell.

30
Q

Target Theory

  • Master, or key, molecule is ___ for the ___ of the cell.
  • Target theory may be used to explain cell ___ and ___ cell ___ caused by exposure to radiation.
A

Target Theory

  • Master, or key, molecule is NECESSARY for the SURVIVAL of the cell.
  • Target theory may be used to explain cell DEATH and NONFATAL cell ABNORMALITIES caused by exposure to radiation.
31
Q

Cell Radiosensitivity

Oxygen enhancement effects

  • Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing ___ ___.
  • During diagnostic imaging procedures, fully oxygenated human tissues are exposed to ___ radiation or ___ radiation.
  • In radiotherapy, when radiation is used to treat certain types of cancerous tumors, ___ ___ (___) oxygen has sometimes been used in conjunction with it to increase tumor ___.
A

Cell Radiosensitivity

Oxygen enhancement effects

  • Oxygen enhances the effects of ionizing radiation on biologic tissue by increasing TISSUE RADIOSENSITIVITY.
  • During diagnostic imaging procedures, fully oxygenated human tissues are exposed to X-radiation or GAMMA radiation.
  • In radiotherapy, when radiation is used to treat certain types of cancerous tumors, HIGH PRESSURE (HYPERBARIC) oxygen has sometimes been used in conjunction with it to increase tumor RADIOSENSITIVITY.
32
Q

Cell Radiosensivity

  • Bergonie and Tribondeau —– Radiosensitivity – 1906
  • Observed the effects of radiation by exposing ___ ___ to X-ray.
  • ___ were used as they contain both ___ and ___ cells.
  • ___ cells (___) execute the organ’s ___ function
  • ___ cells (___) evolve into ___, ___ cells

Law of Bergoine and Tribondeau
Law was originally applied only to ___ cells; it is actually true for all types of cells in the human body.

A

Cell Radiosensivity

  • Bergonie and Tribondeau —– Radiosensitivity – 1906
  • Observed the effects of radiation by exposing ​​RODENT TESTICLES to X-ray.
  • TESTES were used as they contain both MATURE and IMMATURE cells.
  • MATURE cells (SPERMATOZOA) execute the organ’s PRIMARY function
  • IMMATURE cells (SPERMATOCYTES) evolve into MATURE, FUNCTIONS cells

Law of Bergoine and Tribondeau
Law was originally applied only to GERM cells; it is actually true for all types of cells in the human body.

33
Q

Law of Bergonie and Tribondeau

Describes radiation ___ for all ___ cells

  1. ___ or ___ cells are more radiosensitive than ___ cells.
  2. Younger ___ or ___ are more radiosensitive than older ___ and ___.
  3. The higher the ___ cell activity, the more ___ it is.
  4. The greater the ___ and ___ rate for ___, the greater the radiosensitivity.

The law concludes that compared to a ___ or mature ___, the ___ is most radiosensitive.

Law was originally applied only to ___ cells; it is actually true for all types of cells in the human body.

A

Law of Bergonie and Tribondeau

Describes radiation SENSITIVITY for all BODY cells

  1. STEM or IMMATURE cells are more radiosensitive than MATURE cells.
  2. Younger TISSUE or ORGANS are more radiosensitive than older TISSUE and ORGANS.
  3. The higher the METABOLIC cell activity, the more RADIOSENSITIVE it is.
  4. The greater the PROLIFERATION and GROWTH rate for TISSUES, the greater the radiosensitivity.

The law concludes that compared to a CHILD or mature ADULT, the FETUS is most radiosensitive.

Law was originally applied only to GERM cells; it is actually true for all types of cells in the human body.

34
Q

Law of Bergonie and Tribondeau

The law concludes that compared to a child or mature adult, the fetus is most radiosensitive.

Other Factors: ___:

  • Age influences ___
  • Most radiosensitive in ___.
  • Radiosensitivity ___ until ___, the time when we are most ___.
  • With “___” age humans again tend to become more ___.

GENDER:
• Research have shown that females can tolerate approximately ____% more radiation than males.

A

Law of Bergonie and Tribondeau

The law concludes that compared to a child or mature adult, the fetus is most radiosensitive.

Other Factors: AGE:

  • Age influences RADIOSENSITIVITY
  • Most radiosensitive in UTERO.
  • Radiosensitivity DECLINES until MATURITY, the time when we are most RADIORESISTANT.
  • With “OLD” age humans again tend to become more RADIOSENSITIVE.

GENDER:
• Research have shown that females can tolerate approximately 5-10% more radiation than males.

35
Q

Effect of age on radiosensitivity

A

Effect of age on radiosensitivity

36
Q

Chemical Agents:

Some chemical may ___ the radiation response of ___, ___, and ___.

For these chemicals to be effective, they must be ___ at the time of ___.

These chemicals are called ___ (___ agents).

Examples are: ___, ___ ___, and vitamin ___.

• (NOTE: Experiments on mice to develop a radioprotector compounds have not been proven effective for humans. The dose amount would be have to be a high toxic rate.)

A

Chemical Agents:

Some chemical may MODIFY the radiation response of CELLS, TISSUES, and ORGANS.

For these chemicals to be effective, they must be PRESENT at the time of IRRADIATION

These chemicals are called RADIOSENSITIZER (SENSITIZING agents).

Examples are: METHOTREXATE, ACITOMYCIN D, and vitamin K.

• (NOTE: Experiments on mice to develop a radioprotector compounds have not been proven effective for humans. The dose amount would be have to be a high toxic rate.)

37
Q

Cell Radiosensitivity

  • Cell ___ and ___
  • The human body is composed of different types of ___ and ___, which vary in their degree of ___.

What are the radioinsensitive cells?

What are the radiosensitive cells?

A

Cell Radiosensitivity

  • Cell MATURITY and SPECIALIZATION
  • The human body is composed of different types of CELLS and TISSUES, which vary in their degree of RADIOSENSITIVITY.

What are the radioinsensitive cells? BRAIN, MUSCLE, AND NERVE (MOST RADIORESISTANT) CELLS

What are the radiosensitive cells? BASAL CELLS OF THE SKIN, BLOOD CELLS (LYMPHOCYTES AND ERYTHROCYTES), INTESTINAL CRYPT CELLS, REPRODUCTIVE (GERM) CELLS

38
Q

Damage to cell’s nucleus will reveal itself in one of the following:

  • ___ death – will occur in ___ numbers of cells when a volume of ___ Gyt given in a few seconds.
  • ___ Death – results from exposure of cells to doses of ___ to ___ Gyt.
A

Damage to cell’s nucleus will reveal itself in one of the following:

  • INSTANT death – will occur in LARGE numbers of cells when a volume of 1000 Gyt given in a few seconds.
  • REPRODUCTIVE Death – results from exposure of cells to doses of 1 to 10 Gyt.
39
Q

Cell Radiosensitivity

Effects of ionizing radiation on human Blood cells

  • ___ depression – ___ Gyt (Depletion of ___ blood cells – ___ ___ dose)
  • ___ after a period of ___ – if bone marrow is:
  • < ___ Gyt bone marrow can regrow within ___ week)
  • > ___ Gyt bone marrow requires a ___ period of time and a ___ of ___ cells
  • Effects on stem cells of the ___ system – ___ are one of the most ___ of human tissue.
  • ___ ___ to whole body usually leads to death of person.
  • Whole-body doses in excess of ___ gyt - this is the ___ dose!
  • LD ___/___ means: ___% of the ___ will ___ in ___ days

Effects of ionizing radiation on lymphocytes

  • Lymphocytes only live for ___ hours
  • Most ___ blood cell
  • ___ Gyt will ___ the number in the circulating blood
  • ___ to ___ Gyt the cell count will ___ to ___ within a ___ days
A

Cell Radiosensitivity

Effects of ionizing radiation on human Blood cells

  • HEMATOLOGIC depression – 0.25 Gyt (Depletion of IMMATURE blood cells – BONE MARROW dose)
  • REPOPULATION after a period of RECOVERY – if bone marrow is:
  • < 1 Gyt bone marrow can regrow within 1 week)
  • > 10 Gyt bone marrow requires a LONG period of time and a DECREASE of STEM cells
  • Effects on stem cells of the HEMATOPOIETIC system – ERYTHROCYTES are one of the most SENSITIVES of human tissue.
  • HIGH DOSE to whole body usually leads to death of person.
  • Whole-body doses in excess of 5 gyt - this is the LETHAL dose!
  • LD 50/30 means: 50% of the POPULATION will DIE in 30 days
  • Effects of ionizing radiation on lymphocytes
  • Lymphocytes only live for 24 hours
  • Most RADIOSENSITIVE blood cell
  • 0.25 Gyt will REDUCE the number in the circulating blood
  • 0.5 to 1 Gyt the cell count will DROP to 0 within a FEW days
40
Q
A

Radiation Protection and Biology (10 decks)

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