chapter 3 Flashcards
What is mitotic delay?
delay in the entry of cells into mitosis
What is vivo?
living organism
what is vitro?
artificial environment (glassware)
what is mitotic overshoot?
Mitotic overshoot occurs after irradiation. The population of cells in mitosis is disturbed and the cells that were in mitosis at the time complete their division, but those about to enter division are delayed in G2. The mitotic indexes decreases for a period of time as some cells are stopped from proceeding through mitosis at their appointed time. If the dose is low enough, cells can recover from the delay and proceed through mitosis. The increase in the number of cells undergoing mitosis causes a mitotic overshoot.
what cell cycle is the most sensitive?
mitosis
what does tissue/organ response depends on 2 factors
- various cell populations in that
tissue or organ. - The turnover kinetics of each population in the tissue
how long is mitosis?
about an hour
what does bergonie and tribondeau study?
the role of cell division in radiation response
what is the law of radiosensitivity and the meaning
the radiosensitivity of cells is directly proportional to their reproductive activity and inversely proportional to their degree of differentiation.
the more they reproduce, the more sensitive. mitosis is the most sensitive.
observations based on the physician report are:
- x -rays appeared to destroy cells of tumor w/o permanently harming adjacent healthy tissue
- some tissues were damaged by doses of radiation that did not appear to harm other tisses
bergonie and tribondeau performed experiments on rodent testicles in which the tests contains
immature spermatogonia and spermatocytes and also mature cells(spermatozoa);these populations differ both in function and mitotic activity.
hypothesis
ionizing radiation is more effective against cells that are actively dividing, are undifferentiated and have a long dividing future.
bergonie and tribondeau defined cell sensitivity
terms of specific cellular characteristics, mitotic activity and differentiation, rather than on radiation
what is a differentiation cell?
a mature cell. it is specialized and more resistant to radiation effect.
what is a undifferentiated cell?
a cell that has a few specialized characteristics.
it is a immature cell (like a baby)
specialized functionally and/or morphol-
ogically (structurally)
various stages of differentiation example
testis
differentiated cell example
erythrocyte (RBC), no nucleus
undifferentiated example
erythroblast, stem cell for RBC, present in bone marrow, supplies cells which will differentiate to become erythrocytes.
3 categories of cell populations
stem cell-immature cell
transit cell-teenager cell
static population-senior citizen
stem cell population
divide to maintain own population(self-renewal) and produce cells for another population
undifferentiated cell
ex.cells in bone marrow, basal cell in epidermis of skin, cells in crypts, spermatogonia in testis.
transit population
move from 1 place to another
may or may not divide while in transit
ex. nucleated red cell(dividing cell) and reticulocyte in bone marrow (non dividing) cell that doesn’t divide
static population
loses cells throughout the life of the organism
fully differentiated cells
ex. adult nervous tissue and muscle
radioresistant
The process by which immature spermatogonia become mature spermatozoa is termed
differentiation
The spermatozoon is the that is morphologically and functionally specialized
mature, nondividing cell
5 classes of Mammalian cell population
- VIM
- DIM
- Multipotentional Connective Tissue Cells
- RPM
5.FPM
Does high let has a shoulder?
No, high let doesn’t have a shoulder.it goes straight down.
VIM
Vegetative Intermitotic cells
a. most radiosensitive and more differentiate.
b. rapidly dividing
c. most radiosensitive group cells
ex. basal cells of epidermis, erthyroblasts,
DIM
Differentiating Intermitotic Cells
-produced by division of VIM cells
-actively mitotic but more differentiated than VIM
- ex. type B spermatogonia
Multipotential Connective Tissue
a. Divide irregularly
b. More differentiated than DIM
c. Intermediate in radiation sensitivity
ex. endothelial cells, fibroblasts
RPM
Reverting Postmitotic Cells
a. Normally do not undergo mitosis
b. Retain capability to divide under special circumstances
c.long-lived cells
ex. liver cells, mature lymphocyte
FPM
Fixed Postmitotic Cells
a. Do not divide
b. Highly differentiated
c. Resistant to radiation
ex. muscle cells,RBCs, spermatozoa
Parenchymal compartment
cells characteristic of that individual tissue organ
stromal compartment
composed of connective tissue and vasculature which supports the organ structure.
parenchymal compartment
may be comprised of more than 1 category of cells
ex. testis
another example is hematopoietic bone marrow (stem cells) circulating blood cells; skin and intestinal tract
hypothesis
the difference in time it takes for damage to be expressed is simply due to differences in turnover kinetics of critical target cells in different tissues
how many normal tissues can be divided into 2 categories
acutely responding and late responding normal tissues
acute responding-
show injury within a few months after radiation is completed b/c they are self-renewal tissues containing rapidly dividing stem cell population
ex. breast cancer people getting radiation. you will see redness.
what are examples of acute responding
bone marrow, skin, intestine, and testis
late responding
injury not expressed for at least 3 months or longer b/c they contain slow dividing cell populations.
not critical
ex. lung, kidney
assays of radiation damage are divided into 3 categories
- clonogenic
- functional
3.lethality
d0 is 1.2
radiosensitive b/c number is low
