CRITICAL REVIEW OF A TECHNICAL PAPER

Critical Review of a Technical Paper

Critical Review of a Technical Paper

Background

The article which I will be reviewing is titled as “Evidence for beneficial low level radiation effects and

Radiation hormesis” written by Le Feinendegen. This article mainly focus on the point that as doses in the mGy range cause a dual effect on cellular DNA. One is a relatively low probability

of DNA damage per energy deposition event and increases in proportion to the dose(Shadley, 1989). Whereas at background exposures this damage to DNA is orders of magnitude lower than that from endogenous sources, such as reactive oxygen species.

The other effect at comparable doses is adaptive protection against DNA damage from many, mainly endogenous, sources, depending on cell type, species and metabolism. Adaptive protection causes DNA damage prevention and repair and immune stimulation. The LNT hypothesis should be abandoned and be replaced by a hypothesis that is scientifically justified and causes less unreasonable fear and unnecessary expenditure.

The Main Theme of the Paper

The paper basically describes about these aspects

1. Effect of Ionizing radiation and endogenous toxins at low doses

The article tells that The reason for cellular responses to low values of absorbed doses of ionizing radiation are not readily predictable by extrapolation of responses observed at high doses energy distribution in low-dose exposed tissues. Whereas the other reason stems from various biological confounding factors, especially the abundant and constant metabolic generation of ROS and of other endogenous toxins, on top of which low-dose radiation acts(Wolff, 1988).

2. Ratio of DNA Damage and Cancer Probabilities

The article reveals that radiation induced DNA damage and genomic instability increases with absorbed dose. Such cellular effects come through direct energy deposition events from traversing particle tracks by which DNA damage rises proportional with dose(Wolff 1988).

Depending on the amount of energy deposited per cell, bystander effects in non-irradiated neighbouring cells may add to this damage in tissue at low doses. By measuring damage in multi cellular systems, values of damage per exposed cell or defined micro mass are calculated averages. This implies that any bystander phenomenon that may have occurred is coregistered and expressed in the observed values(Shadley, 1989).

3. Adaptive Responses, Protection

The article reveals that A sudden suprabasal yet non-lethal rise of toxin concentration in a biological target tends to elicit stress responses and to stimulate adaptation, usually in terms of protective mechanisms in the sense of hormesis (Feinendegen, 2005).

4. Damage Prevention

In the article it is evident that stimulation of detoxification of ROS appears to reach a maximum at about 4 h after irradiation and lasts for several hours or even weeks, depending on tissue and cell type (Feinendegen, 2005). The process involves a rise of free glutathione and increased levels of superoxide dismutase (SOD) with decreased lipid peroxidation lasting for weeks in some tissues.

5. Damage repair

One of the advantages,mentioned in this article about low level radiation is that as Protection against high-dose induced chromosomal aberrations and/or micronuclei formation in human lymphocytes and tissue culture cells increased to a maximum about 4 ...