From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Thu Jul 09 1998 - 03:47:10 MDT
Authors
Koizumi A. Wada Y. Tuskada M. Kayo T. Naruse M. Horiuchi K. Mogi T.
Yoshioka M. Sasaki M. Miyamaura Y. Abe T. Ohtomo K. Walford RL.
Institution
Department of Hygiene, Akita University School of Medicine, Japan.
koizumi:med.akita-u.ac.jp
Title
A tumor preventive effect
of dietary restriction is antagonized by a high housing temperature through
deprivation of torpor.
Source
Mechanisms of Ageing & Development. 92(1):67-82, 1996 Nov 29.
Abstract
Energy restriction (ER) has proven to be the only effective
means of retarding aging in mice. The mechanisms of multiplicity of
effects of ER on aging remain, however, fragmentary. ER
induces daily torpor, the induction of which is reduced by increasing the
ambient temperature to 30 degrees C. The effects of
preventing hypothermia in ER animals were studied in terms of the expected
consequences of ER on survival, disease pattern and a number of physiological
parameters in autoimmune prone MRL/lpr mice and lymphoma prone C57BL, 6 mice.
The results demonstrate that torpor plays a crucial role in the prevention of
lymphoma development but does not have an affect on other aspects of ER, such
as prevention of autoimmune diseases.
Additional data added here by the poster:
Mortality data for the autoimmune MRL strain and the lymphoma prone
C57BL strain of mice are as follows: (data derived from table 1)
Survival (days) Percentage alive
75% 50% 25% at 1300 days
________________________________________________________
MRL Control 167 205 255 0%
Cntl/30C 170 213 230 0
CR 217 269 519 8
CR/30C 201 284 340 0
C57BL Control 559 778 880 0
CR 941 1143 1264 19
CR/30C 739 810 1049 0
Storage temperature had no effect on early autoimmune related MRL
mortality, which was mostly cerebral hemorrhage, subarachnoid hemorrhage
and rupture of aortic aneurysms. However later mortality was reduced in
calorie restricted MRL mice stored at room temperature as opposed to
those stored at 30C. Presumably this is due to the anticancer effect of
CR induced hyperthermia, which is antagonized by elevated storage
temperatures.
Storage at 30C largely reversed the early antilymphoma effect of CR in
C57BL mice, reducing the 47% increase in the 50% survival found in CR
mice to just 4% for the CR/30C group.
The survival for control C57BL mice varies dramatically from experiment
to experiment. In one control group from (Experimental Gerontology 15:
237-258 1980) the 50% survival was about 960 days, which is roughly
midway between the CR and CR/30C groups in the present experiment.
Variations in temperature regulation of the laboratory may account for
some of these differences.
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