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Hiroshima and Nagasaki: Part 5
The Effects of Radiation on Cellular Processes

Figure 1 - Fission

Figure 1 - Graphic credit: Bertell, R. (1985).

Figure 2 - Graphic credit: Atomicarchive.com

Figure 3 - Graphic credit: Radiation Effects Research Foundation

Of the four types of radiation emitted by the nuclear bombs deployed at Hiroshima and Nagasaki, gamma and neutron rays were the only types strong enough to reach ground and hurt people (see Part 2). The penetration of ionizing radiation into living human cells can result in cell alteration or death (Bertell, 1985). Figure 1 is a diagram depicting the process of ionization.

According to the U.S. Nuclear Regulatory Commission (2006), high doses of radiation tend to kill cells. If enough cells are killed, tissues and organs will suffer immediate damage. In Nagasaki and Hiroshima this phenomenon became known as Acute Radiation Syndrome (U.S. Nuclear Regulatory Commission) and resulted in thousands of fatalities.

The rapid invasion of energy into a human cell may also result in the loss of the cell's ability to reproduce itself or may cause the cell to produce an altered hormone or enzyme from what it would normally produce. These altered or mutated cells will replicate themselves, eventually resulting in the production of millions of such altered cells. This is known as biological magnification and causes many chronic diseases normally only associated with the elderly and aging (Bertell, 1985). An example of one such mutation is the destruction of the cell's ability to rest following cell division. A cell unable to rest will chaotically and rapidly produce an astronomical number of cells in one location, resulting in a tumor (either benign or malignant) (Bertell, 1985). Another cellular process affected by ionizing radiation is blood cell production. The rapid production of too many white blood cells (leukocytes) can cause leukemia, while a rapid proliferation of red blood cells (erythrocytes) often causes polycythemia vera. For more information on leukemia, access the National Cancer Institute's Leukemia Home Page at http://www.cancer.gov/cancertopics/types/leukemia. To learn about polycythemia vera, contact the Leukemia and Lymphoma Society at this link: http://www.leukemia- lymphoma.org/all_mat_toc.adp?item_id=9955.

Documented Effects of Nagasaki/Hiroshima Bombings on Cellular Processes

Survivors under shelter at the time of the blasts received less radiation exposure than those out in the open. A medical study conducted on Nagasaki/Hiroshima survivors who reported being in their homes at the time of the bombings indicated a direct correlation between dosage received and chromosomal abnormalities. Figure 2 shows this correlation (Radiation Effects Research Foundation, 2006).

According to Bertell, if radiation penetration affects germ cells (sperm or ovum), defective offspring may result. Chromosomal diseases resulting from germ cell radiation include Down's Syndrome, which is caused by failure of chromosomal separation (nondisjunction). In nondisjunction, one of the daughter cells resulting from cell division lacks a chromosome and the other daughter cell has an extra chromosome. In the case of Down's Syndrome, the extra chromosome is at location number 21 (trisomy 21). An individual with Down's Syndrome is generally moderately to severely retarded (Schull, 1995). For more information on Down's Syndrome, click on the following link: http://www.ndss.org/. For an animation of nondisjunction during meiosis resulting in Down's Syndrome, click here: http://www.tokyo-med.ac.jp/genet/mfi-e.htm.

According to Schull (1995), in children of survivors of Nagasaki and Hiroshima, the most commonly encountered sex chromosomal abnormalities were Klinefelter's Syndrome (a male abnormality resulting from an extra X chromosome) and Turner's Syndrome (a female abnormality resulting from an extra X chromosome). For more information on Klinefelter's Syndrome click on the following link: http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm. For more information about Turner's Syndrome click on this link: http://www.turner-syndrome-us.org/.



Note To Teacher

  1. Ionizing Radiation: High-energy radiation capable of producing ionization in substances through which it passes. It includes nonparticulate radiation, such as x-rays, and radiation produced by energetic charged particles, such as alpha and beta rays, and by neutrons, as from a nuclear reaction.
  2. Acute Radiation Syndrome: The immediate effects of a short term, whole body overexposure of a person to ionizing radiation.
  3. Biological Magnification: The rapid and abnormal replication of cells.
  4. Benign: Of no danger to health; not recurrent or progressive; not malignant: a benign tumor.
  5. Malignant: Tending to metastasize; cancerous.
  6. Leukemia: Any of various acute or chronic neoplastic diseases of the bone marrow in which unrestrained proliferation of white blood cells occurs.
  7. Polythycemia Vera: Abnormal and rapid red blood cell production.
  8. Sperm: A male gamete or reproductive cell.
  9. Ovum: A female gamete or reproductive cell.
  10. Nondisjunction: The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.
Definitions Credit: Answers.com (http://www.answers.com).

References

Answers.com (2006). Retrieved October 24, 2006 from http://www.answers.com

Bertell, R. (1985). No Immediate Danger, Prognosis for a Radioactive Earth. Summertown, TN: The Book Publishing Company.

National Down's Syndrome Society (2006). Retrieved October 25, 2006 from http:// www.ndss.org/

National Institute of Child Health and Development (2006). Retrieved October 24, 2006 from http://www.nichd.nih.gov/health/topics/klinefelter_syndrome.cfm

Numabe, H. (2006). Genetics Study Group. Tokyo Medical University. Retrieved Pctpber 26, 2006 from http://www.tokyo-med.ac.jp/genet/mfi-e.htm

Interactives

Worksheet: THE EFFECTS OF RADIATION ON CELLULAR PROCESSES


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