topic1-intro to radbio.1

7/29/2019 Topic1-Intro to Radbio.1

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Introduction to

RADIOBIOLOGY

(HUMAN BIOLOGY)


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Effect of x-rays on human isthe result of interactions at the

atomic level

The deposited energy canresult in a molecular change

The abnormal molecule mayin time function improperly or

cease to function or cell death


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This process is reversible,

ionized atoms can become

neutral by attracting a freeelectron

Molecules can be mended by

repair enzymes

Cell and tissues can

regenerate and recover from

the radiation injury


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Sequence of Events after Radiation Exposure


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EARLY Responses to Radiation

1. Acute radiation syndrome

1.1. Hematological Syndrome

1.2. Gastrointestinal Syndrome

1.3. Central Nervous SystemSyndrome


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2. Local tissue damage- 2.1. Skin

- 2.2. Gonads

- 2.3. Extremities

3. Hematological depression

4. Cytogenetic damage


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LATE Responses to Radiation

1. Leukemia

2. Other malignant diseases2.1. Bone Cancer

2.2. Lung Cancer

2.3. Thyroid Cancer2.4. Breast Cancer


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3. Local tissue damage

3.1. Skin3.2. Gonads

3.3. Eyes

4. Shortened life span 5. Genetic damage

5.1. Cytogenetic damage

5.2. Doubling dose5.3. Genetically significant dose


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Effects of Fetal Irradiation

1. Prenatal death

2. Neonatal death

3. Congenital malformations

4. Childhood malignancy

5. Diminished growth anddevelopment


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Composition of the Human Body

At the most basic level, the humanbody is made up of atoms.

The atomic composition of the bodydetermines the character and degreeof the radiation interaction.

The molecular and tissue compositiondefines the nature of the radiationresponse.


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60 %..................Hydrogen25.7 %..................Oxygen10.7 %..................Carbon2.4 %..................Nitrogen0.2 %..................Calcium0.1 %..................Phosphorus0.1 %..................Sulfur0.8 %..................Trace Elements

ATOMIC COMPOSITION OF THE

BODY


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Molecular Composition

There are five principal types ofmolecules in the body:

Four are macromolecules:

Proteins

Lipids (fats)

Carbohydrates (sugars and starches)

Nucleic Acids


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80% Water

15% Protein

2% Lipids1% Carbohydrates

1% Nucleic Acid

1% Other


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WATER

the most

abundant molecular

constituent of the

body


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Water also plays

an important role

in transporting

chemicals within

the body

most metabolic reactions occur in water


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Blood is mostly water which

carries vital substances

Oxygen, sugars, salts,

vitamins

It also carries waste materialsCO2, urea

HOMEOSTASIS


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ANABOLISM

the production of large

molecules from small

CATABOLISM

the breaking down into

smaller units ofmacromolecules


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Protein

makes up 15 % of cell content

the basic building block of cell


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Protein

Proteins are long chains ofmacromolecules consisting of amino

acids connected by peptide bonds.

There are 22 amino acids used in

protein synthesis or the metabolic

production of protein.


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Uses of Protein

Proteins provide structure and

support.

Proteins function as:

Enzymes

Hormones Antibodies


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LIPIDS or FATS

not soluble in water but aresoluble in certain solvents such

as alcohol, ether or chloroform

FUNCTION:

storage of energy protection against cold

assistance in digestive

processes


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CARBOHYDRATES composed of: carbon hydrogen oxygen

- provides most of the cells energy

- stored throughout the body butprimarily in the liver and muscles- classified as:

Monosaccharides

Disaccharides

Polysaccharides


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NUCLEIC ACIDS

constitute genes, the instructions

that control cells activities and playimportant role in protein synthesis

- very large and complex

- contain atoms of carbon, hydrogen,

nitrogen and phosphorous which

form the nucleotides (building

blocks of DNA)


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DNA

has a unique ability to make copies of

or replicate themselves.

it replicates prior to cell division andeach newly formed cell receives an

exact copy of the original cellsDNAs

molecules double helix

the radio-sensitive target molecule


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RNA

helps synthesize protein

single helix


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Sodium (Na+)

Chloride (Cl-)Potassium (K+)

Calcium (Ca+2)

ions that play important role inmetabolic processes

-maintains proper water

concentration in body fluids, pH,

blood clotting, muscle and nerve

functions


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THE HUMAN CELL


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Nucleus

DNA, RNA, protein and water

Cytoplasm

makes up the bulk of the cell andmolecular

components/organelles

2 MAJOR PARTS:


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Endoplasmic Reticulum

Mitochondria

Ribosomes

Lysosomes


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the nucleus is more

radioresistant than cytoplasm.


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Cellular Irradiation

When the critical macromolecular

cellular components are irradiated, a

dose of about 1 Mrad or 10 kGyt is

required to produce a measurable

change in physical characteristics of

the cell.


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When such a molecule is incorporated

into the apparatus of a living cell, only

a few rad are necessary to produce a

measurable response.

Some single cell organisms require

massive exposure to produce a lethal

dose.


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Human cells can be killed with a doseless than 100 rad (1Gy).

The nucleus is much more sensitivethan the cytoplasm to radiation

exposure.

Interference with any phase of protein

synthesis could result in cell damage

particularly DNA.


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The act of a single cell or

group of cells to reproduce and

multiply in number

2 General Types of Cell:

SOMATIC

GENETIC


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SOMATIC CELLS undergo

MITOSISduring cell division

GENETIC undergoes

MEIOSIS


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Phases of Mitosis

Interphase

-has the DNA forming

chromosomes.

Prophase

-the nucleus swells and the DNA

takes a more structural form.

Metaphase

the chromosomes appear and line up

along the equator of the nucleus. During

metaphase, mitosis can be stopped and

damage can be analyzed.


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-the chromosomes slowly migrate

toward the spindle.

Anaphase

each chromosomes splits to

form a centromere and twochromatids connected by a fiber

to the poles of the nucleus.

These poles are called spindles

and the fiber called spindle

fibers.

the number of chromosomes

have been reduced by half.


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Telophase

is characterized by thedisappearance of the

chromosomes into a mass of

DNA and closing off of thenucleus like a pair of dumbbells

into two nuclei.

the cytoplasm divides equallyinto two cells and interphase

begins.


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Cell Cycle

Cell biologist identify four phases of

the cell cycle

1. M

2. G1 first growth

3. S synthesis

4. G2 second growth

DNA synthesis is in the S phase


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Phases of Meiosis

Genetic cell division is called

meiosis.

Genetic cells begin with 46

chromosomes like somatic cells.

During the first division, the

daughter, replicated the DNA with 46

chromosomes.


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During the second meiosis, there is no

S phase so the DNA does not replicate.Granddaughter cells have 23

chromosomes.

There is some exchange of

chromosomal or crossover resulting

in the genetic constitution andchanges in inheritable traits.


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Human Development

During the development andmaturation of a human from the two

united genetic cells, a number of cell

types evolve.

Collections of cells of similar

structure and function form tissue.

Tissue forms organs and organs form

organ systems.


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two parents give rise to an offspring


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two parents give rise to an offspring

with a unique gene combination from

either of them

each parent gives 1/2 of his/her genes

to the offspring.

a gene is a discrete unit of information

on the DNA that codes for one protein,

perhaps one of the many enzymes needed

by our bodies.


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Immature cells are called:

undifferentiated cells

precursorstem cells

Mature cells less

radiosensitive that stem cells


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NERVOUS

REPRODUCTIVE

DIGESTIVERESPIRATORY

ENDOCRINE

ORGAN SYSTEMS:

*Cells of organ systems are identifiedby their rate of proliferation and stage

of development.


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EPITHELIUM- covers the skin, bloodvessels, abdominal and chest cavitiesand GI tract

CONNECTIVE high in protein,consists of fibers (bone ligaments,cartilage)

MUSCLE a special type of tissue thatcan contract , also high in protein canbe found throughout the body


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NERVOUS consists of

specialized cells calledneurons, transmits electrical

impulses for control and

response.

topic1-intro to radbio.1

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