Radiation Therapy & Its Effect On the Cell Cycle

Radiation exposure can greatly alter cells. These effects may involve gross biological and physiological aberrations. Typically such changes are pathologic in nature. Nonetheless, radiation may be employed for therapeutic purposes. Changes in the cell cycle which contribute to cell death can potentially be used in the treatment of cancer.

The various forms of radiation include ionizing radiation, non-ionizing radiation, and electromagnetic fields. All of these different types have been shown both in vivo and in vitro to significantly alter cells (14:1135). Among the various treatment modalities for cancer, ionizing radiation (e.g., gamma-radiation or U.V. light), in particular, alters cells' ability to reproduce. This ultimately leads to cell death.

A typical eukaryotic response to ionizing radiation includes growth arrest, DNA repair, and lethality (1:637-642). In general, cell cycle perturbations corresponding to cellular changes appear early. Such damage may be inflicted before chromosome damage, mitosis, and mitotic death occur (15:59-74). Mammalian cells' sensitivity to ionizing radiation has been found to depend largely on their position in the cell cycle. While variation does exist among different cell lines, cells exposed in the G1 phase of the cell cycle can be the most vulnerable under certain conditions (4:23-38). In addition, early studies demonstrated that cells often experience

. . .
fixation of potentially cytotoxic chromosomal errors can be directly related to the amount of time between cells' irradiation and their onset of mitosis (4:23-38). The transition from G2 block to mitosis typically requires protein synthesis. Schneiderman and Hofer (1980) postulated that radiation-induced block results from some defect in cells' capacity to manufacture proteins. Likewise, G2 block might also be caused by some alteration in the synthesis of a specific protein or subset of proteins. Microbeam irradiation research--as well as studies involving the decay of DNA-incorporated 125I--has shown that the radiation-induced G2 delay is associated with either the nucleus or some perinuclear cytostructure. Therefore, the data suggest that nuclear protein or proteins may be involved (7:197). Researchers have measured overall protein synthesis following cell irradiation in exponentially growing cells. Certain of these analyses, for example, have involved [3H]leucine incorporation. These data indicate that total cellular protein synthesis does not undergo inhibition in response to irradiation (1:637-642). Investigators have also used electrophoretic techniques to identify proteins whose presence or synthesis
. . .

Some common words found in the essay are:
G1 S-phase, Likewise G2, EGR Furthermore, Gy/hour HeLa, G1 G2, Cycle Radiation, EL-4 Raji, Biology Physics, cell cycle, Conversely G2-deficient, July Concern, ionizing radiation, international journal, international journal radiation, journal radiation, radiation oncology biology, oncology biology, g2 arrest, radiation cell, radiation oncology, biology physics, journal radiation oncology, oncology biology physics, radiation exposure, radiation cell cycle,
Approximate Word count = 3175
Approximate Pages = 13 (250 words per page)

More Essays on Radiation Therapy & Its Effect On the Cell Cycle