Radiation Biology: Early Effects

Question 1

non-Stochastic (deterministic effect)

Answer 1

Health effects for which the severity varies with the dose and for which a threshold normally exist.

1. Not normally seen in non-exposed population
2. Epilation- Hair loss
3. Erythema- reddening of skin, comes in waves, requires dose of 600 Rad
4. Acute Radiation Syndrome- Biologic changes and symptoms, including death, occur within weeks after a high- intensity total body irradation

Question 2

Stochastic Effect

Answer 2

Health effects that occur randomly and for which the probability of the effect occurring is assumed to be a linear function of dose without threshold.

All or none effect; once begun effect develops independent of dose.

Seen in non-exposed populations

Cancer- abnormal cells divide without control and aggressively migrate or are transported to other organs in the host.

Question 3

Somatic

Answer 3

Effects of radiation limited to the exposed individual.

These effects can be either stochastic or non-stochastic. classified by magnitude

Magnitude can either be high or low levels of exposure

length could vary between very short time duration (acute) exposures such as seconds to protracted or long duration (years)

Question 4

Hereditary (genetic) effects

Answer 4

Parent to offspring

altered genetic sex cells

Question 5

Teratogenic Effects

Answer 5

Radiation effects that may be observed in children who were exposed during the fetal and embryonic stages of development.

Question 6

Cell cycle as it pertains to radiation biology

Answer 6

Interphase: time between celll division, chromosomes not clearly visible. G1 (pre-DNA synthesis), S (DNA synthesis) and G2 (post DNA synthesis, premitosis)

Mitosis- Cellular division consisting of 5 stages involving chromosome movement

Question 7

When are cells most radiosensitive?

When are cells most resistant?

Answer 7

most radiosensitive at M and G2 phase

most resistant in late S phase, when nuclear envelope is protecting chromosomes

Question 8

Potential results of cellular DNA damage from radiation exposure

Answer 8

1. Cell dies
2. Cell divides and produces daughter that die
3. Cell divides and produces daughter that lives
4. Cell repair itself and lives

Question 9

Direct Damage to cell

Answer 9

radiation ionizing DNA through collision or charged particle interactions. Atoms of DNA then initiate the chain of events that leads to biological change

Neutrons and Alpha

Question 10

Indirect Damage

Answer 10

When radiation ionizes the water environment around DNA forming reactive chemicals. These reactive compounds may then chemically attack the DNA

Photons and beta particles

Question 11

Law of Bergonie and Trinondeau

Answer 11

cells tend to be radiosensitive if they

1. have a high division rate
2. long dividing future
3. are unspecialized cells

Organ Sensitivity

1. Blood Forming organs
2. Reproductive and Gastrointestinal
3. Skin
4. Muscle and Brain

Question 12

Modifiers of radiation sensitivity for whole body

effects of radiation can be enhanced or degraded by

Answer 12

1. chemical modifiers
   O2 concentration, Temperature (warmer more kinetic)
2. Physical Modifier- dose rate, fractionation
3. Biological Modifier- Age, gender, health

Question 13

Most radiosensitive cells in human body

Answer 13

Lymph cells

bone marrow cells

intestinal crypt cells

immature reproductive cells

erythrocytes

Question 14

Early effects of radiation on a biological system

Answer 14

ARS

1. Nausea and vomiting
2. Malaise and fatigue
3. Increased temperature
4. Blood Changes

Question 15

Threshold dose for onset of ARS

Answer 15

whole body dose of 100rem

Question 16

Four stages of ARS

Answer 16

1. Prodromal Stage- initial nausea, vomiting, diarrhea
2. Latent- symptoms subside for a time. hours to weeks depends on the dose
3. Manifest illness- symptoms of vomiting, nausea, diarrhea, malaise, fatigue, febrile, blood changes progress to an end point
4. Recovery or death

Question 17

class and range of ARS

Hematopoietic syndrome

Answer 17

1. Hematopoietic Syndrome- Occurs at lower doses, do to sensitivity of blood forming cells. Occurs at 100rem to 1,000.
   Sensitive individuals die 6-8 weeks dose 200 rad
2. first stage- nausea vomiting diarrhea
   Latent period- appears in hours can last up to 4 weeks. only sign of disease is low RBC and WBC and platelets

3.Symptoms- malaise. anemia, hemorrhage, and infection. Death may be from dehydration, imbalance of electrolytes, infections

Question 18

class and range of ARS

Gastrointestinal Syndrome

Answer 18

Occurs at 1,000 to 5,000 rad
most critical organ is the small intestine

prodromal symptoms, last one day

latent period 3-5 days

Manifest illness- nausea vomiting (prolonged) diarrhea. Lining of GI tract is being depopulated, results in dehydration

lethargy and anorexia ( medical intervention does not prevent progression)

death in 3-4 days

no human has survived 1,000 rad

Question 19

class and range of ARS

Cerebrovascular syndrome

Answer 19

occurs after 5,000 rad

death within hours, may take days

not sufficient time for hematopoietic and GI syndromes to manifest.

immediate nausea, vomiting person becomes confused and nervous. consciousness may be lost. latent period is short 6-12 hours. Ataxia ((loss of muscle coordination), convulsions, dyspnea, lethargy, coma. may happen before death.

cause death not known, possible intracranial pressure.

Question 20

The LD 50/60 for humans

Answer 20

value of the dose delivered to a group that 50% of them will survive for 60 days without medical treatment.

Estimated at 410 rad +/- 150 rad

Survival with medical treatment up to 1,000 rad. people have received 1,000 rad and survived 60 days but ultimately died.