Question

25. Briefly summarize how the "Law of Bergonie and Tribondeau' and "Oxygen Effect" might apply to the effect of radiation on one type of human stem cell of your choice and how radiation effects on this stem cell could adversely impact the quality of human life. 26. What is the principal difference between the indirect"effect of radiation and a "direct" effect on a chemical or biological system? Give and example of each type of effect showing the general mechanism as to how each effect occurs.

Answer 1

25) -Law of Bergonie and Tribondeau emphasized the link between proliferation and radiosensitivity.

-Oxygen Effect in radiobiology refers to enhancement of therapeutic or detrimental effect of ionizing radiation due to presence of oxygen.

- Ionizing radiation weakens and breaks up DNA ,either damaging cells enough to kill them or causing them to mature in ways that may eventually lead to cancer.

-Radiation effects on human proceed from the lowest to the highest levels; from cells to tissue and from tissue to organs and ultimately may affect the whole body.

-In Ionizing radiation of Human Embryonic stem cell,it is found that these pluripotent cells undergo apoptosis when exposure to low doses and at higher dose robust apoptosis response observed.

Adverse effects of Radiation on stem cells:-

Radio-destruction of healthy tissue stem cells may leads to loss of vision,Cancer ,memory disorder and cardiovascular complications.

26) Indirect effect of radiation -

If a cell is exposed to radiation.the probability of radiation interacting with DNA molecule is very small since these critical components make up such a small part of the cell.However each cell just as in case for human body is mostly water .Therefore there is much higher probability of radiation interaction with water that makes up most of the cells volume.When radiation interact with water it may break the bonds that hold water molecules together producing fragments such as hydrogen (H)and hydroxyte (OH).These fragments may recombind or many interact with other fragments or ions to form compound such as water which not harm cell.However they may combine to form Hydrogen peroxide which may cause destruction of the cells.

Direct effect of radiation:-

If radiation interacts with the atoms of DNA molecules or some other cellular components critical to the survival of cell,it is referred to as a direct effect of radiation.Such an interaction may affect ability of cell to reproduce.If enough atoms are affected such that chromosome don't replicate properly and if significant interaction in the information carried by the DNA molecules then cell may be destroyed by direct interaction.