05. Radiation Toxicity

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 Radiation Toxicity Medical effects of radiation exposure can be divided into two categories known as Acute Radiation Syndrome (ARS) and Delayed Effects of Acute Radiation Exposure (DEARE)Acute radiation exposure consists of health effects that immediately exposure of the body to a relatively high dose (>2-5Gy) delivered with high dose rate. ARS is visible as three syndromes based on the radiosensitivity of organs. Those are Hematopoietic syndrome (occurring after exposure 0.7-10Gy), Gastrointestinal syndrome (usually greater than 10 Gy), and Cardiovascular/Central nervous system syndrome ( dose greater than >50 Gy).DEARE is visible months or years after the radiation exposure symptoms such as prolonged gastrointestinal dysfunction, skin injury, renal failure, and lung injury. Radiation-induced damage occurs from long-lived free radicals, reactive oxygen species, and pro-inflammatory cytokines/chemokines which damage the recovery and repopulation of stem cells. The limita...
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03.Cellular Response for Ionizing Radiation

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 Cellular Response for Ionizing Radiation

Radiation sources are all around the environment and every time we are exposed to different kinds of radiation from low-frequency to high-frequency electromagnetic range. Studies of radiation mainly use for radiotherapy and space exploration. Biologically cells respond to radiation depending on their energy. When we consider radiotherapy it exposed cells intentionally and damages cell structures which cell harmful to the body with various mutations called tumors. Progress of this treatment depends on the radioresistance of tumor cells and induced damage to normal cells located near to tumor. Increasing radiodensities of tumor cells and specific radioprotection of normal tissues are strategies used to decrease the amount of damage to normal cells in radiotherapy, in a Space environment definitely produce highly protective fabrics and covers to reduce endanger of astronauts from cosmic radiation. 

As mentioned in my previous blog qualities of ionizing radiation depend on mean energy deposition per track length called Linear energy transfer (LET). (Radiation Sources in Cosmic Environment). Ionizing radiation is caused mainly for DNA damage or changes in sequence. DNA and ionizing radiation interact in two ways: direct action and indirect action.in Direct action initiate with high LETs hit the DNA and caused double-strand breaks and producing lethal damage.in indirect action, ionizing radiation is induced for the ionization of water molecules and produces OH- radicals (H2O→ H+ + OH-) and damage DNA by its electrostatic changes.

When DNA damage from ionizing radiation double strand breaks is mostly lethal.in beginning, the DNA damage response (DDR) initiates the arrest cell cycle and facilitates DNA repair and maintenance of the genome. tumor suppressor protein p53 is then activated by various phosphorylating kinases responding to release within DNA damage and arrest cell cycle from G2 to M phase. Repairing DNA will initiate nonhomogeneous end joining (NHEJ) or homogenous recombination (HR). NHEJ can repair DSBs throughout the cell cycle but during the G1 phase. But it will become inaccurate and complete DNA with error because its repair process depends only on correcting complementary overhangs and just phosphorylate 5’ and 3’ ends. In contrast, HR is less free cause it requires an error-free sister chromatid for recombination but the issue is HR is only available in the late S or G2 phases. If the repairing process is completed successfully, the cell will continue its cell cycle and undergo repopulation but DNA improper repair initiate cell death by apoptosis, mitotic death,or senescence.

Stay Tuned!

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