Rad Safety Exam 3: Rad Bio Introduction

Germ cells vs somatic cells

Germ = responsible for reproduction

Somatic = responsible for maintaining the functions of the human body

Mutation

Alteration in the genetic material of a cell

Differentiate direct vs indirect paths of destruction

Direct = radiation interactions directly with the atom in the DNA and the molecular structure of the DNA double helix is broken when the atoms are ionized.

Indirect = Radiation interacts with a water molecule, forms free radicals, and then the free radicals interact with atoms in the DNA causing breaks in the strands

Free radical

A fragment of a molecule that has an unpaired electron. Highly reactive and can break the molecular structure of DNA

Single DNA breaks are more commonly associated with ...

Indirect action

Double DNA strand breaks are more commonly associated with ...

Direct action

A cell can repair itself before replication, but if it fails to do so, this can cause

a mutation

Some mutations can cause oncogenesis. What is this?

Oncogenesis is the biological process through which normal, healthy cells transform into cancer cells.

A little sunburn on the nose is a _______ strand break while a 2nd degree sunburn is like a ________ strand break.

Single, Double

Who discovered/characterized that certain cells are more radiosensitive?

1906, Bergonie and Tribondeau

What are the 3 laws of Bergonie and Tribondeau?

1. Relatively undifferentiated (primitive) like stem cells

2. Rapidly dividing at the time of exposure like fetus cells

3. Dividing for extended periods of time like cells of the GI tract

The LET of a charged particle or photon is ...

and what is it measured in?

the amount of energy it transfers to a medium per distance traveled in a medium.

measured in keV/um

Define RBE?

Relative Biological Effectiveness is the amount of radiation of a certain type required to reach a biological endpoint.

Higher LET radiation typically has a _________ RBE.

higher

What is a radiosensitizer?

A substance that increases biological damage from ionizing radiation

How do radiosensitizers increase radiation damage?

They bind with free radicals to create more toxic forms

How can radiosensitizers affect DNA?

They bind to damaged DNA, making it harder to repair.

What is the most common radiosensitizer?

Oxygen

What are other examples of radiosensitizers?

Nitroxoides, siRNAs, and oligonucleotides.

What is a radioprotector?

A substance that decreases a cell's sensitivity to radiation

How do radioprotectors decrease radiation damage?

Many of these "scavenge" free radicals by suppressing their formation or detoxifying them by reducing the oxygen content of the cells

What is an example of an FDA approved radioprotector?

Amifostine

Which portion of the cell cycle is the most sensitive time to be impacted by radiation?

Mitosis

Acute radiation exposure

Exposure over a short period of time

Chronic radiation exposure

Exposure over a longer period of time

Deterministic vs Stochastic Effects of radiation

Deterministic effects are quick onset symptoms that are generally observed soon after exposure and have a defined threshold.

Stochastic effects are probabilistic, meaning they may or may not occur in any given individual and a threshold might not be observed. Usually manifest after many years of the exposure.

*Deterministic can also be said that it is no doubt caused by radiation, while the same cannot be said for stochastic

Somatic vs Genetic

Somatic = physical effects of the person exposed themselves

Genetic = the children of those exposed

Teratogenic Effects

Effects observed when a fetus in utero is exposed to an acute high dose of radiation causing cancer or congenital malformation

What is external beam radiation

A common cancer treatment that uses high energy radiation beams to target and destroy cancer cells while minimizing damage to surrounding healthy tissue

What are theranostics

A newer treatment option for cancer involving radiopharmaceuticals that have a high LET and specific affinity to cancer cells to allow for direct targeted treatment to a tumor.