Scientists

Bergonie and Tribondeau (1906) French Scientists :

Performed studies on:

• plant cells
• cancers of the human cervix (hela cells)
• sheep testicles (sperm cells)

They classified Cells into different groups:

Mitotic Index – percent of cells are going through Mitosis

Tc – population of cells

Tm – cells goin through Mitosis

MI = (lambda)Tm/Tc    (gives the percent of cells that are going through Mitosis)

Findings:

MI (cancer cells) : 40 – 50% are cycling at all times

MI (normal tissue) : 30% are cycling

Labeling Index - percent of cells in S Phase

LI – Labeling Index

Ts – cells going through S Phase

LI = (lambda) Ts/Tc

TL– number of cells lost

Tc Lost = TL/Tc

They wanted to figure out if something was going to shrink or if it was going to grow

• Growth Fraction – tells if a tumor is going to grow or shrink
• CCT - Cell cycle time : how fast the cell cycle is

If the Mitotic Index is High, the CCT is short the rate of cells lost is low : this indicates GROWTH

If the Mitotic Index is Low, the CCT is long and the rate of cell loss is high : this indicates SHRINKING

BASIC LAWS OF BERGONI AND TRIGBONDEAU

Basic Laws of Radiosensitivity

(note : there are exceptions)

A Cell is Considered Radiosensitive if:

Undifferentiated : An immature, embryonic or primitive cell. It has a non-specific appearance with multiple non-specific functions.

Differentiated : exhibiting biological specialization; To become distinct or specialized.   In our terms differentiation predicts how vunerable a cell will be to radiation.   The more differentiated a cells is the more radioresistant it will be.

Morphology –  The form and structure of an organism or part of an organism or cell; the study of form and structure.

Radiosensitivity of Different Types of Cells

Radiosensitive / Undifferentiated:

RadioResistant  / Differentiated:

Differentation in Gamete Production:

Males:

Spermatagonium (2n)- Undifferentiated

• Undergoes Mitosis

Primary Spermatocytes (2n)

• undergoes Mieosis 1

Secondary Spermatocytes (1n)

• undergoes Mieosis 2
• flaggela attach

Spermatozoa(G0 Phase / Fully matured)  - Differentiated

Females:

Oogonium (2n)

Primary Oocyte

• undergoes Mieosis 1

Seconday Oocyte

• undergoes Mieosis 2

Ovum

Cassarett Classification of Mammalian Cells

Cassarett :  classified mammalian cells into 4 categories

1. Vegatative InterMitotic Cells – primitive type cells
   • Spermatagonium
   • Bone marrow
2. Differentiated Intermitotic Cells
• Spermatocytes

3. Reverting Post Mitotic Cells
   • Cells in GQ
   • Bone , etc..
4. Fixed Post Mitotic Cells

• Cells in G0
• Neurons, lymphocytes

Division Delay

Division Delay : radiation causes a delay in cells if they are given a dose of 50cGy to 300cGy

Mitotic Overshoot - point where all of the cells that were synchronized are now all going through Mitosis at the same time  (is the basis for B.I.D. treatments)