X-Message-Number: 12045
Date: Thu, 1 Jul 1999 23:02:08 -0700 (PDT)
From: Doug Skrecky <>
Subject: mice benefit from gamma ray irradiation

  Caratero A.  Courtade M.  Bonnet L.  Planel H.  Caratero C.
  Laboratoire d'Histologie-Embryologie-Cytogenetique, Faculte de Medecine
  Toulouse-Rangueil, Toulouse, France. 
  Effect of a continuous
  gamma irradiation at a very low dose on the life span of
  Gerontology.  44(5):272-6, 1998.
  BACKGROUND: There is epidemiological evidence that suggests there are
  beneficial effects of ionizing radiation at low doses. Some
  experimental studies confirmed this hormetic effect with
  doses of about 1 cGy/day, but no data concerning very low dose rates are
  available. OBJECTIVE: The aim of this study was to determine the life span of
  mice exposed to very low doses of ionizing radiation. METHODS: Six hundred
  female C57BL/6 mice, 1 month old, were exposed to chronic
  gamma irradiation at very low dose rates of 7 or 14
  cGy/year. These doses are about 25 or 50 times higher than background, but
  much lower than the doses of about 1 cGy/day used in previous experiments.
  Three hundred mice living in the same room were used as controls. RESULTS:
  The life span, after the beginning of the experiment, determined by the
  survival time of 50% of each population, is increased in irradiated mice: 549
  days in controls, 673 days in both irradiated groups. The differences are
  significant between the control and the irradiation mice. Differences between
  mice irradiated with 7 or 14 cGy are not significant. CONCLUSIONS: These
  results confirm the possibility of a nonharmful effect
  (hormesis) of ionizing radiation. They demonstrate that the paradigm, which
  states that low-dose effects can be predicted high-dose
  effects, cannot be systematically applied in radiation
  biology in general and gerontology in particular.

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