وصفه و خلطة أعشاب

Threshold hypothesis is a theory that it has it's believers, believers in the threshold hypothesis believe that carcinogens, like other toxic compounds, have a no-effect level and a threshold dose. 1. Animal systems have a variety of defense mechanisms able to detoxify and dispose of xenobiotic chemicals. Many factors determine whether a particular chemical is activated to become a carcinogen or is rendered innocuous. 2. The high doses used in many experiments for carcinogenicity can change normal processes of cellular activation and deactivation and can overwhelm natural defense mechanisms. Tumors may be due to secondary effects of toxicity and tissue damage from excessive amounts of the fed compound. 3. Even in cases where the DNA is actually damaged, repair of the damage has been documented. Only under conditions in which the repair mechanisms are exhausted will the damage become irreversible. 4. Not all species show the same susceptibility. 5. D...