Tuesday, April 2, 2019
Effects of Radiation in Biological Systems
Effects of Radiation in Biological SystemsAs verbalise in the oxford concise colour medical dictionary radiobiology is the leg of science dealing with the nubs of shaft of light therapy on biologic systems. It is foster stated that a sequence of events that deals with the absorption of aught from ionizing shaft sickness to the efforts of the existence in order to compensate for the military force of this talent absorption and the alter to the organism that whitethorn be produced.There argon a summate of topics of study in radiobiology. The effect of ionizing beam together with how it affects liveliness booths depart be win explained. Bushong (199829-32) states that the biologic cause of ionizing radiation represent the efforts of living things to deal with capability absorbed by them, after an fundamental interaction with such radiation. retained by the originator it is stated that when ionizing radiation interacts with a stallular telephone, ionisation and excitations argon produced in every vituperative biologic macromolecule c solelyed targets e.g. DND, or in the medium which boothular organelles be suspended eg. Water. Based on the site of these interactions, it canister be classified as all operate or in restrain.The personal effects of radiation on living electric cadres vary, depending on the vitrine, forte of exposure and the cadreular phone as discussed by Tubiana and Dutreix (199022). Radiation is an emission of ionising radiation. maintain by the in a nobleer place authors, at low levels, radiation wrongfulness can be repaired by living stalls with no effects, however, higher panes leas to sterility, mutation, which confuses cells resulting in the reproducing promptly cell ending. cellular phone damage can result in twain expressions namely take on radiation action, which harms molecules at present and indirect, by ionizing molecules play them into cyanogenic compounds causing damage.Some of the other aspects that argon going to be discussed and explained below ar cell structure, cycle and death pecker of cells direct and indirect effects of radiation interactions of da Gamma rays with matter foetal irradiation cell option curves properties of cell survival curves therapeutic implications oxygen effect situationors influencing oxygen effect the five Rs of radiobiology and lastly radiation protection. cellular phone STRUCTURE, CELL CYCLE CELL DEATHDiscussed by Ford (20015) Atoms form molecules which use up macromolecules, then build complex organic structures, and then cell which ar the main structural component of tissues as easily as reflects all features of life. They allow similar structures but specialize according to their location. jail cells contain inorganic compounds as well as organic compounds.Henry and Suntharalingam (200612) explain that on that point be two categories of cells namely prokaryotic and eukaryotic. Maintained by the higher up author . Prokaryotic cells sire no nucleus and are touch with a nuclear membrane. They do non contain any membrane-forming organelles e.g. Mitochondria. However. On the other hand, eukaryotic cells have membranous organelles as well as a real nucleus. They are to a greater extent exceedingly authoritative compared to prokaryotic cells.The cell cycle is defined as the interval surrounded by the midpoint of mitosis in a cell and the midpoint of the subsequent mitosis in both daughter cells according to Millar and Levine (1998102). Maintained by the supra authors it describes the dresss by which a cell passes through as it replicates. The length of duration a cell may take to complete the cell cycle is highly variable. The basic division of the cell cycle is mitosis and inter chassis. Cells may also be in a special state completen as the resting variety when not making any effort to divide and cells in this level are mostly terminally oppositeiated cells.According to Tubianna an d Dutreix (199086) the M phase is the period where the cell actively divides into two daughter cells. There are two re easyd events namely mitosis and cytokinesis. The synthesis and mitosis of the cell cycle are separate by two gaps, G1 and G2 when respectively, deoxyribonucleic acid has not been synthesised or desoxyribonucleic acid has been synthesised but other metabolic processes are taking place. Elizabeth (20031) explains that cells are mostly most radio- in the raw in the mitosis and G2 phases and most radio- broad in the easy S phase. Maintained by the to a higher place author Cytokinesis completes the M phase, however cells do not alship canal undergo cytokinesis, instead forming multinucleate giant cells. This can either be standard or can be imputable to errors in mitosis.Explained by Tubiana and Dutreix (1990 89) Cell death of static cells is defined as the dismissal of specific function. For stem cells and other cells capable of legion(predicate) divisions, cell death is defined as the loss of reproductive integrity (reproductive death).the above authors further explain that when cells are exposed to ionising radiation, the biological effects of radiation results in the first place from damage to the DNA, however thither are also other sites at bottom the cell that, when damaged may poke out to cell death. The capability of a single cell to grow into a large colony appearances that the cell has retained its reproductive integrity.IRRADIATION OF CELLSElizabeth (200310) explains that when cells are exposed to ionizing radiation the model physical effects betwixt radiation and the atoms or molecules of the cell. The biological effects of radiation result mainly from damage to the DNA however, there are also other sites within the cell that, when damaged, may adept to cell deaths come about. Maintained by the above author a surviving cell that maintains its reproductive integrity and proliferates almost indefinitely into a large proced ure of progeny is said to be clonogenic. Sensitive component for radiation-induced cell cleansing rests in the cell nucleus and not in the cytoplasm. When ionizing radiation is directly absorbed in biological material, the damage to the cell may perish in either a direct or indirect mechanism. right away INDIRECT assemble OF RADIATIONAccording to Bomford and Kunkler (2006 265) in direct action, the radiation interacts directly with the critical target in the cell. The atoms of the target itself may be ionized or excited, leading to the chain of physical and chemical events that ultimately produce the biological damage. It is the dominant process in the interaction of high additive energy pitch particles such as neutrons or important particles with biological material. In direct action, ca apply by x-ray or da Gamma ray photons, the photon interaction with an atom in the cell produces a aerated particle (electron) which subsequently interacts with DNA directly as discussed b y Hendry and Suntharalingam (200624).antechamber and giaccia (200644) explain that in indirect action, the radiation interacts with other molecules and atoms (mainly water) within the cell to produce free radicals which can, through diffusion in the cell, damage the critical target within the cell. It can be modified by chemical sensitizers of radiation protectors. Further explained by the above authors, Basic radiochemical reactions that may occur in water molecules disrupt by the passing of an ionizing particle which are highly reactive species that are produced in water, through the radiochemical reactions. These reactive species come about the indirect radiation damage to biological systems by reacting and modify the molecules in the cell. The free radicals that break the chemical bonds and produce chemical changes that lead to biologclcal damage are highly reactive molecules because they have an unpaired valency electron. About two-thirds of the biological damage by low linea r energy transfer radiations e.g. X-rays , is due to indirect action and one-third due to direct action.INTERACTIONS OF GAMMA RAYS WITH MATTERDiscussed by Johnston and Fauber (201263)The steps involved in producing biological damage by the indirect action of x-rays are the primary photon interaction which includes he photoelectric effect, Compton scatter and pair production produces a high energy electron, high energy light charged particle in moving through tissue produces free radicals in water. Maintained by the above author the free radicals may produce chemical changes in DNA from the breakage of chemical bonds and the changes in the chemical bonds results in biological effects.FOETAL IRRADIATIONAccording to Isaac (200926) Foetal radiation is known as teratogen (causes birth defects). Between conception and birth, the fetus passes through different stages of development. When a mother is pregnant, the unborn child can be harmed by radiation which could result in the child havi ng cancer and genetic defects. Due to the fact that the foetus would be highly sensitive to radiation, they are rapidly dividing, undifferentiated and have a long mitotic future.Elizabeth, M (200316) a human conceptus exposed to a large amount of radiation before 2-3 weeks of maternity could result in a miscarriage. 4-11 weeks could result in severe ab principleities of organs and 11-15 weeks in mental retardation. However, after the 20th week, the human foetus is more radiosensitive and functional defects may occur.Effects of radiation on the foetus depends on two factors namely the dose to the foetus and secondly is the stage of development at the measure of exposure. An important factor to note is that an spontaneous abortion should be considered only when the foetal dose has exceeded 10 cGY. The principle effects of radiation on a foetus are foetal or neonatal death, malformations, growth retardation, congenital defects and cancer induction as retained by the above author. CELL SURVIVAL CURVESDiscussed by Hall and Giacca (2006 67) Cell survival curves which is the surviving constituent against the absorbed dose describes the relationship between the surviving fractions of cells that is the fraction of irradiated cells that maintain their integrity. Maintained by the above author, the cell survival against dose is graphically represented by plotting the surviving fraction on a logarithmic scale on the ordinate against dose on a linear scale. Typical survival curves for cells irradiate by densely ionizing radiation (low linear energy transfer).Tubiana and Dutreix (1990 26) the type of radiation catch the shape of the survival curve. For densely ionizing radiation (high linear energy transfer) the cell survival curve is almost an exponential function of dose which is shown by an almost uncoiled line on a log-linear plot. However, for sparsely ionizing radiation (low linear energy transfer) the survival curves show an initial slope followed by a should er region and then becoming n betimes straight at high doses as retained by the above authors. The soon used model for describing the cell survival curve is the linear-quadratic polynomial model with constants of import and Beta. The proportionality alpha/beta gives the dose at which the linear and quadratic components of cell killing are get even.PROPERTIES OF CELL SURVIVAL CURVESAdhikar (20032) explains that for late responding tissues the survival curves are more curved than those for early responding tissues. For early effects the ratio is large and dominates at low doses however for late effects it is underage and has an influence at doses lower than for early responding tissues. The above mentioned author goes on to explain that the effects of radiation on tissue as a function of dose are measured with assays and the measured results are presented in the form of cell survival curves and dose result curves.THERAPUTIC IMPLICATIONSBomford and Kunkler (200399) state that DN A cosmos the target of ionizing radiation leads to several important therapeutic implications. The radiation damage that occurs in clusters that match the size of a DNA shore may be more effective in causing damage. The above authors further explain that drugs target DNA have synergistic effects with radiation whilst people with genetic defects due to radiation damage response may break plusd levels of DNA mutation or cell death. Points in cell cycle where the DNA is more susceptible to damage are also more sensitive to radiation and the cycling of cells has an collision on the radio sensitivity of the cell type.OXYGEN EFFECTFranckowiak (20082) explains that when ionizing radiations cross(prenominal) through matter, they gradually loose energy through various interaction processes along their path. For certain absorbers the rate of energy loss depends on the type of radiation as well as the density of the material. Maintained by the above author the rate at which energy is depo sited as a charged particle travels through matter by a cross type of radiation is known as linear energy transfer which is a function of the mass and charge of the radiation.Carlton and Adler (2006344) explain that Electromagnetic radiation, having no mass or charge produces fast electrons with negligible mass and a negative charge. Due to this, the probability of an electron interacting with an atom is relatively fiddling resulting in the ionizations produced being distant and far from each other therefrom terming electromagnetic radiation as linear energy transfer radiation. In contrast to electromagnetic radiation, highly ionizing radiations e.g. Alpha-particles that have a predictable mass, have a greater chance of interacting with matter, producing utterly-change distance ionizations. Different linear energy transfer radiations produce different degrees of the very(prenominal) biologic response. However, equal doses of linear energy transfer do not produce the same biolo gic response. This was retained by the above authors.Travis (1989207) explains that the ability of radiation with different linear energy transfers produce a specific biologic response called the relative biologic effect. It is a comparison of a dose of render radiation that produces the same biological response. Maintained by the above author ,when comparing the two types of radiation that differ in nature or energy, the relative biological effectiveness when compared, represents the absorbed dose which results in a given biological effect. Therefore the concept must refer to a well-defined biological effect of a particular level.FACTORS INFLUENCING OXYGEN EFFECTFord (200110) discusses that some of the factors that influence the oxygen effect are chemical, biological and technical. In chemical, the oxygen concentration may be increased by internal or external methods. In biological, if the patient suffers from chronic air ways sickness or other problems with oxygen transport, the n the oxygen concentration will be lower and prevalence of hypoxic cells will be increased. However, in technical, these have minimal impact on the oxygen effect, maintained by the above author.THE FIVE RS OF RADIOBIOLOGYBomford and Kunkler (2003236) explain that there are five Rs in the actinotherapy process namely repair, redistribution, reoxygenation, repopulation and lastly radio sensitivity and these will be further explained below.REPAIRThis is one of the primary reasons to fractionate radiotherapy and there are one-third types of damage that ionizing radiation can cause to cells. These are lethal, sub lethal and potentially lethal damages. Maintained by the above authors, by splitting radiation dose into smaller parts cells are allowed to repair sub lethal damage depending on the ability to tell apart damage, repair pathways and cell cycle arrest. However, normal cells with intact repair pathways are able to repair the sub lethal damage by the time the next fraction is deli vered. However, if the dose rate is sufficiently low, repair may be able to take place during radiotherapy treatment which reduces the cell death and is one reason low dose treatment show reduces effectiveness to high dose rate treatment as stated by Isaac (200920).REDISTRIBUTIONSunthalingam and Hendry (200612) state that redistribution occurs during low dose rate which may increase cell killing, although it is minimal compare to the increased repair. When radiotherapy is given to a population of cells, they may be in different parts of the cell cycle. A small dose of radiation delivered over a short time period will kill a lot of sensitive cells and less of the resistant cells.REOXYGENATIONOxygenation status may change during treatment due to tumours being acutely or chronically hypoxic. Acute hypoxia is due to the resolving power of capillaries or arterioles supplying parts of the tumour. While closed, tumour cells become hypoxic and resistant to the indirect action of radiation . These vessels are usually closed for a short time but may occur during a fractionated dose of radiation. ripping dose into fractions raises possibility of closed vessels being opened the next time, indeed allowing the tumour cells to be killed as explained by Sunthalingam and Hendry (200613).Maintained by the above authors, chronic hypoxia is due to the poor vasculature of tumours and oxygen has to travel far to relieve oneself cells that are far. These cells are resistant to radiation, fractionated radiation therapy kills cells that lie close to capillary tubing more effectively thus being able to move contiguous to their nutrition source becoming relatively toxic and these cells can be killed.REPOPULATIONBomford and Kunler (2003237) explain that repopulation is the increase in cell division that is seen in normal and malignant cells at some point after radiation is delivered. Repopulation of normal tissues occurs at different speeds depending on the tissue. Maintained by the above authors, early responding tissues begin repopulation and by increasing treatment over a certain time period reduces early toxicity in that tissue. However late responding tissue only begin repopulation after the radiation cause has being completed and therefore repopulation has minimal effects.Adhikar (20034) explains that repopulation of malignant tissues are when some tumours exhibit accelerated repopulation which is a vulnerable phenomenon that must be counted if treatment time extends. Methods to do this include accelerated treatment with hyper fractionation to minimise late effects.RADIOSENSITIVITYRadio sensitivity cells include haematological cell. Radio resistant cells include myocytes, neurons and tumour cells such as melanoma and sarcoma as explained by Adhikar (20034).RADIATION PROTECTIONAs discussed by Carlton and Adler (2006 153-155) there are three principles of personnel exposure reduction namely time distance and shielding. A decrease in time working with or i n the neighborhood of radiation will increase exposure and decrease the dose. Maintained by the above author increasing the distance between the source of radiation and the individual will decrease exposure. Bushong (199854) also mentions that shielding decreases the exposure that is used when time and distance cannot be implemented. Examples of shielding are gonad shields, lead aprons, lead line doors etc.CONCLUSIONAs we all know now know, radiobiology deals with the effects of radiation in biological systems. Radiation is energy in the form of waves and particles that are emitted from a source that comes in many forms however it may not always be a dangerous thing. The forms of radiation that are especially dangerous to living things are those with energy sufficient to penetrate tissues and then ionize the atoms they pass along the way which damage tissues by disrupting normal cellular chemistry and are mutagenic and carcinogenic.Cell damage can result in two ways namely direct r adiation action, which harms molecules directly and indirect, by ionizing molecules turning them into toxic compounds causing damage. Discussed above and throughout the assignment we see how a cell together with their structure until death occurs due to irradiation of cells by either direct or indirect effects of radiation. We also looked at interactions of gamma rays with matter as well as effects of foetal irradiation. Cell survival curves together with their properties as well as theraputic implications and oxygen effect were explained. The five Rs in radiobiology play an important aspect together with ways of protecting yourself and others from the harmful effects of radiation.