Radiation Biology: Early Effects Flashcards
non-Stochastic (deterministic effect)
Health effects for which the severity varies with the dose and for which a threshold normally exist.
- Not normally seen in non-exposed population
- Epilation- Hair loss
- Erythema- reddening of skin, comes in waves, requires dose of 600 Rad
- Acute Radiation Syndrome- Biologic changes and symptoms, including death, occur within weeks after a high- intensity total body irradation
Stochastic Effect
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.
Somatic
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)
Hereditary (genetic) effects
Parent to offspring
altered genetic sex cells
Teratogenic Effects
Radiation effects that may be observed in children who were exposed during the fetal and embryonic stages of development.
Cell cycle as it pertains to radiation biology
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
When are cells most radiosensitive?
When are cells most resistant?
most radiosensitive at M and G2 phase
most resistant in late S phase, when nuclear envelope is protecting chromosomes
Potential results of cellular DNA damage from radiation exposure
- Cell dies
- Cell divides and produces daughter that die
- Cell divides and produces daughter that lives
- Cell repair itself and lives
Direct Damage to cell
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
Indirect Damage
When radiation ionizes the water environment around DNA forming reactive chemicals. These reactive compounds may then chemically attack the DNA
Photons and beta particles
Law of Bergonie and Trinondeau
cells tend to be radiosensitive if they
- have a high division rate
- long dividing future
- are unspecialized cells
Organ Sensitivity
- Blood Forming organs
- Reproductive and Gastrointestinal
- Skin
- Muscle and Brain
Modifiers of radiation sensitivity for whole body
effects of radiation can be enhanced or degraded by
- chemical modifiers
O2 concentration, Temperature (warmer more kinetic) - Physical Modifier- dose rate, fractionation
- Biological Modifier- Age, gender, health
Most radiosensitive cells in human body
Lymph cells
bone marrow cells
intestinal crypt cells
immature reproductive cells
erythrocytes
Early effects of radiation on a biological system
ARS
- Nausea and vomiting
- Malaise and fatigue
- Increased temperature
- Blood Changes
Threshold dose for onset of ARS
whole body dose of 100rem
Four stages of ARS
- Prodromal Stage- initial nausea, vomiting, diarrhea
- Latent- symptoms subside for a time. hours to weeks depends on the dose
- Manifest illness- symptoms of vomiting, nausea, diarrhea, malaise, fatigue, febrile, blood changes progress to an end point
- Recovery or death
class and range of ARS
Hematopoietic syndrome
- 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 - 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
class and range of ARS
Gastrointestinal Syndrome
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
class and range of ARS
Cerebrovascular syndrome
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.
The LD 50/60 for humans
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.
