RE: Life span and low dose rate gamma exposure

["North, David" <DNorth@LIFESPAN.ORG>]

This looks like a reasonable experiment, except for one thing. If chronic

low-level radiation dose lengthens life by stimulating the immune system,

keeping the mice in a "specific-pathogen-free" environment for their entire

lives might have obviated any influence of that effect. In other words,

their immune systems had little to protect them from anyway, so any

stimulated greater efficiency would go unmeasured. My two cents......



David L. North, Sc.M., DABR

Medical Physics

Main Bldg Rm 317

Rhode Island Hospital

593 Eddy St.

Providence, RI 02903

(401)444-5961

dnorth@lifespan.org





> ----------

> From: 	niton@mchsi.com

> Reply To: 	niton@mchsi.com

> Sent: 	Friday, September 12, 2003 14:39

> To: 	radsafe@list.vanderbilt.edu

> Subject: 	Life span and low dose rate gamma exposure

> 

> Interesting recent article with fairly decent sample size. 

> 

> Radiation Research: Vol. 160, No. 3, pp. 376-379.

> 

> No Lengthening of Life Span in Mice Continuously Exposed to Gamma Rays at

> Very 

> Low Dose Rates

> S. Tanaka,a, 1 I. B. Tanaka, III,a S. Sasagawa,a K. Ichinohe,a T.

> Takabatake,a 

> S. Matsushita,b T. Matsumoto,a H. Otsu,a and F. Satoa

> 

> aDepartment of Radiobiology, Institute for Environmental Sciences. 1-7, 

> Ienomae, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori 039-3212, Japan

> 

> bLaboratory of Animal Development and Research Group, National Institute

> of 

> Radiological Sciences. 4-9-1, Anagawa, Inage-ku, Chiba-shi, Chiba

> 263-8555, 

> Japan

>  

> 

> ABSTRACT

> 

> Tanaka, S., Tanaka, I. B. III., Sasagawa, S., Ichinohe, K., Takabatake,

> T., 

> Matsushita, S., Matsumoto, T., Otsu, H. and Sato, F. No Lengthening of

> Life 

> Span in Mice Continuously Exposed to Gamma Rays at Very Low Dose Rates.

> Radiat. 

> Res. 160, 376-379 (2003).

> 

> Late effects of continuous exposure to ionizing radiation are potential

> hazards 

> to workers in radiation facilities as well as to the general public.

> Recently, 

> low-dose-rate and low-dose effects have become a serious concern. Using a

> total 

> of 4000 mice, we studied the late biological effects of chronic exposure

> to low-

> dose-rate radiation as assayed by life span. Two thousand male and 2000

> female 

> 8-week-old specific-pathogen-free (SPF) B6C3F1 mice were randomly divided

> into 

> four groups (one nonirradiated control and three irradiated). Irradiation

> was 

> carried out for approximately 400 days using 137Cs  rays at dose rates of 

> 21 mGy day-1, 1.1 mGy day-1 and 0.05 mGy day-1 with total doses equivalent

> to 

> 8000 mGy, 400 mGy and 20 mGy, respectively. All mice were kept under SPF

> conditions 

> until they died spontaneously. Statistical analyses showed that the life

> spans 

> of mice of both sexes irradiated with 21 mGy day-1 (P < 0.0001) and of

> females 

> irradiated with 1.1 mGy day-1 (P < 0.05) were significantly shorter than

> those 

> of the control group. Our results show no evidence of lengthened life span

> in 

> mice continuously exposed to very low dose rates of  rays.

> 

> 

> 

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