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radiationlecture-170227063014.pptx
- 1. Biological Effects (Molecular andCellular) of Radiation Nasu sowmya sree Group – 10 Semesgter - 9 Guided by : Skorobogatova mam 1
- 2. Radiations • Radiation isenergy that comes from a source and travels through some material or through space. • The different types of radiation differ only in their respective wavelengths • Low wavelength UV has the highest energy and is potentially the most damaging • Sunscreens can protect us from UV damage 3
- 3. The Electromagnetic Spectrum Wecan see visible light. We can feel the heat from IR and microwave radiation. Our senses cannot detect most of the other wavelengths.
- 4. The Sun’s Radiation •More than half of the sun’s radiation is in the IR region of the spectrum • Nearly 40% is in the visible region of the spectrum • Only 8% is in the UV region, but this higher energy radiation can potential cause damage to living cells
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- 7. Types of Radiation •Radiation is classified into: 1. Ionizing radiation (nuclear radiation) Alpha particles Beta particles Gamma rays (or photons) X-Rays (or photons) 7
- 8. 2.Non-ionizing Radiation Sources Visiblelight Microwaves Radios Video Display Terminals Power lines Radiofrequency Diathermy (Physical Therapy) Lasers 8
- 9. Ionizing Vs Non-ionizing Radiation IonizingRadiation – Higher energy electromagnetic waves (gamma ) or heavy particles (beta and alpha). – High enough energy to pull electron from orbit. Non-ionizing Radiation – Lower energy electromagnetic waves. – Not enough energy to pull electron from orbit, but can excite the electron. 9
- 10. Factors affecting biologicalactivity of radiations • Penetrating power of radiations • Tissue sensitivity • Dose (energy) of radiations • Surface area exposed 10
- 11. Moderately radios ens itive •Skin •Vascular endothelium •Lung •Kidney •Liver •Lens(eye) Radiosensitivity of tissues Highly radios ens itive •Lymphoid tissue •Bone marrow •Gastrointestinal epithelium •Gonads •Embryonic tissues Bone marrow S kin CN S Least radios ens itive •Central nervous system (CNS) •Muscle •Bone and cartilage •Connective tissue
- 12. Ionizing (nuclear) radiation 12 Aradiation is said to be ionizing when it has enough energy to eject one or more electrons from the atoms or molecules in the irradiated medium. This is the case of alpha and beta radiations, as well as of electromagnetic radiations such as gamma radiations, X-rays and some ultra-violet rays. Visible or infrared light are not, nor are microwaves or radio waves.
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- 14. • Penetration inmaterials – Outside the body, an alpha emitter is not a hazard unless it is on the skin – Inside the body, an alpha emitter is a bigger hazard if it deposits its energy in sensitive tissue 14 Alpha rays • C o m m o n alpha-particle emitters – adon-222 ga s in the environment – Uranium-234 and -238) in the environment – Polonium-210 in tobacco • C o m m o n alpha-particle emitter uses – Smoke detectors – Cigarettes/cigars S ou rc e s
- 15. Beta rays • Penetrationin materials – At low energies, a beta particle is not very penetrating – stopped by the outer layer of skin or a piece of paper – At higher energies, a beta particle may penetrate to the live layer of skin . – Inside the body, a beta particle is not as hazardous as an alpha particle because it is not as big – Because it is not as big, it travels farther, interacting with more tissue (but each small piece of tissue gets less energy deposited17)
- 16. Gamma radiations 16 • Ionizingpower is poor • High penetrating power • Form free radicals • Injurious to health X rays Penetration power is sufficient to penetrate tissues and can be detected outside. Ionizing power is low
- 17. Properties of nuclearradiations 17 • High ionizing power- 1. alpha radiations Moderate ionizing power- beta rad. Low ionizing power- gamma & X rays High penetrating power- gamma & X rays Moderate penetrating power- Beta rays Low penetrating power- alpha rays
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- 19. • Radiation CausesIonizations of: ATOMS which may affect MOLECULES which may affect CELLS which may affect TISSUES which may affect ORGANS which may affect THE WHOLE BODY 19
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- 21. Types of UVRadiation
- 22. Biological Effects ofUV Radiation The consequences depend primarily on: 1. The energy associated with the radiation 2. The length of time of the exposure 3. The sensitivity of the organism to that radiation The most deadly form of skin cancer, melanoma, is linked with the intensity of UV radiation and the latitude at which you live.
- 23. Protection from UVRadiation
- 24. Effect of radiationon body (1) Hair The losing of hair quickly and in clumps occurs with radiation exposure at 200 rems or higher. (2) Brain Since brain cells do not reproduce, they won't be damaged directly unless the exposure is 5,000 rems or greater. can cause seizures and immediate death. (3) Thyroid The thyroid gland is susceptible to radioactive iodine. In sufficient amounts, radioactive iodine can destroy all or part of the thyroid. (4) Reproductive Tract Because reproductive tract cells divide rapidly, these areas of the body can be damaged at rem levels as low as 200. Long- term, some radiation sickness victims will become sterile.28
- 25. (5) Blood System Whena person is exposed to around 100 rems, the blood's lymphocyte cell count will be reduced, victim more susceptible to infection. This refered to as mild radiation sickness. Early symptoms of radiation sickness mimic those of flu. According to data from Hiroshima and Nagaski, show that symptoms may persist for up to 10 years and may also have an increased long-term risk for leukemia and lymphoma. (6) Heart Intense exposure to radioactive material at 1,000 to 5,000 rems would do immediate damage to small blood vessels and probably cause heart failure and death directly. (7) Gastrointestinal Tract Radiation damage to the intestinal tract lining will cause nausea, bloody vomiting and diarrhea. This is occurs when the victim's exposure is 200 rems or more. 25
- 26. The Effects ofRadiation on the Cell at the Molecular Level 26 •When radiation interacts with target atoms, energy is deposited, resulting in ionization or excitation. •The absorption of energy from ionizing radiation produces damage to molecules by direct and indirect actions. •For direct action, da ma ge occurs a s a result of ionization of atoms on key molecules in the biologic system. This causes inactivation or functional alteration of the molecule. •Indirect action involves the production of reactive free radiacals whose toxic dama ge on the key molecule results in a biologic effect.
- 27. Damage by ionising radiation •Indirect effect: – Ionising event can break molecular bonds but effect may manifest elsewhere – e.g. ionisation of water molecules can produce free radicals (molecule with unpaired electron in outer shell). •Highly reactive •Capable of diffusing a few micrometres to reach and damage molecular bonds in DNA 31
- 28. Indirect Action 28 • Theseare effects mediated by free radicals. • A free radical is an electrically neutral atom with an unshared electron in the orbital position. The radical is electrophilic and highly reactive. Since the predominant molecule in biological systems is water, it is usually the intermediary of the radical formation and propagation.
- 29. Indirect Action- Radiolysisof Water Free radicals readily recombine to electronic and orbital neutrality. However, when many exist, as in high radiation fluence, orbital neutrality can be achieved by: 1.Hydrogen radical dimerization (H2) 2.The formation of toxic hydrogen peroxide (H2O2). 3. The radical can also be transferred to an organic molecule in the cell. H-O-H ® H + + OH- H-O-H ® H0 +OH0 29 (ionization) (free radicals)
- 30. Indirect Action 30 • H0+ OH0 ®HOH (recombination) • H0 + H0 ® H2 (dimer) • OH0 + OH0 ® H2O2 (peroxide dimer) • OH0 + RH ® R0 + HOH (Radical transfer) • The presence of dissolved oxygen can modify the reaction by enabling the creation of other free radical species with greater stability and lifetimes • H0 +O2 ® HO2 (hydroperoxy free radical) 0 • R0 +O2 ®RO2 (organic peroxy free radical) 0
- 31. Indirect Action -The Lifetimes of Free Radicals • The lifetimes of simple free radicals (H0 or OH0) are very short, on the order of 10-10 sec. While generally highly reactive they do not exist long enough to migrate from the site of formation to the cell nucleus. However, the oxygen derived species such as hydroperoxy free radical does not readily recombine into neutral forms. These more stable forms have a lifetime long enough to migrate to the nucleus where serious damage can occur. 31
- 32. Indirect Action- Free Radicals 32 •The transfer of the free radical to a biologic molecule can be sufficiently damaging to cause bond breakage or inactivation of key functions • The organic transfer the peroxy radical free form radical can molecule to molecule causing damage at each encounter. Thus a cumulative effect can occur, greater than a single ionization or broken bond.
- 33. BIOCHEMICAL REACTIONS WITH IONIZINGRADIATION • DNA is the most important material making up the chromosomes and serves as the master blueprint for the cell. It determines what types of RNA are produced which, in turn, determine the types of protein that are produced. I I 33 S-AT-S I I P P I I S-CG-S I I P P I I S-GC-S I I P P I I S-TA-S I I
- 34. • There isconsiderable evidence suggesting that DNA is the primary target for cell damage from ionizing radiation. effects at low to moderate (cell killing, mutagenesis, • Toxic doses and malignant transformation) appear to result from damage to DNA. Thus, ionizing cellular radiation is agent. a classical genotoxic 38
- 35. • The lethal 35 andmutagenic effects of moderate doses of radiation result primarily from damage to cellular DNA. • Although radiation can induce a variety of DNA lesions including specific base damage, it has long been assumed that unrejoined DNA double strand breaks are of primary importance in its cytotoxic effects in mammalian cells.
- 36. • Active enzymaticrepair processes exist for the repair of both DNA base damage and strand breaks. In many cases breaks in the double-strand DNA can be repaired by the enzymes, DNA polymerase, and DNA ligase. • The repair of double strand breaks is a 36 complex recombinational process involving events, depending upon the nature of the initial break.
- 37. • Residual unrejoineddouble strand breaks are lethal to the cell, whereas incorrectly recoined breaks may produce important mutagenic lesions. In many cases, this DNA misrepair apparently leads to DNA deletions and rearrangements. Such large-scale changes in DNA structure are characteristic of most radiation induced mutations. 37
- 38. Radiation Induced Chromosome Da m a g e 38 •Chromosomes are composed of deoxyribonucleic acid (DNA), a macromolecule containing genetic information. This large, tightly coiled, double stranded molecule is sensitive to radiation damage. Radiation effects range from complete breaks of the nucleotide chains of DNA, to point mutations which are essentially radiation- induced chemical changes in the nucleotides which may not affect the integrity of the basic structure.
- 39. Radiation Induced Chromosome Da m a g e 39 • After irradiation, chromosomes may appear to be "sticky" with formation of temporary or permanent preventing normal interchromosomal bridges chromosome separation during mitosis and transcription addition, radiation of genetic can cause information. In structural aberrations with pieces of the chromosomes break and form aberrant shapes. Unequal division of nuclear chromatin material between daughter cells may result in production of nonviable, abnormal nuclei.
- 40. Radiation Induced Membrane 40 Dam ag e • Biological membranes serve as highly specific mediators between the cell (or its organelles) and the environment. Alterations in the proteins that form part of a membrane ’ s changes in its structure can cause permeability molecules, i.e., electrolytes. In to various the case of nerve cells, this would affect their ability to conduct electrical impulses. In the case of lysosomes, the unregulated release of its catabolic enzymes into the cell could be disastrous. Ionizing radiation has been suggested as playing a role in plasma membrane damage, which may be an important factor in cell death (interphase death)
- 41. Cell Cycle 41 • Irradiationof the cell causes cell death at mitosis as a result of the inability to divide.(Mitotic death) • RNA and protein synthesis do not halt in the sterilized cell. The result is the production of the giant cell, whose unbalanced growth eventually proves lethal to the cell.
- 42. applications 42 • Contrast mediaand diagnosis • Therapeutic applications teletherapy: removal of lesions not possible by surgery (gamma) surface source: dermatologic and ophthalmic use (beta) extracorporeal (on blood vessels): change in immune response (x ray) infusions: to treat peritoneal and pleural diffusion in malignant tumours (gamma and beta ray)
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