cron-web.org

[A1CR]

MR noted:

"I said, the most obvious thing for most people to do is
just think
twice before wearing extra clothes to make up for low body
temp: stay a
LITTLE too cool to be comfy."

However, what about this paper?:

Reynolds MA, Ingram DK, Talan M.
Relationship of body temperature stability to mortality in
aging mice.
Mech Ageing Dev. 1985 May 13;30(2):143-52.
PMID: 4021553

An age-related decline in the capacity for thermoregulation
among
homeothermic animals has been observed frequently under
conditions of
extreme ambient temperatures. We investigated the temporal
stability of the
internal body temperature of 69 C57BL/6J mice from 25 months
of age until
death in a controlled, neutral thermal environment.
Estimates of temporal
variability were calculated over consecutive 1-month
intervals using
(colonic) body temperature data collected weekly. The
results of this
longitudinal analysis indicated that the regulation of body
temperature, as
measured by its temporal stability, became increasingly less
precise with
advancing age. Body temperature exhibited a significant
decline as the
animal approached death. Individual differences in body
temperature and the
temporal regulation of body temperature were significantly
correlated with
lifespan, although the direction of the relations were
opposite. Body
temperature correlated positively with lifespan, whereas the
temporal
stability of body temperature correlated negatively with
lifespan. Thus,
animals exhibiting higher body temperatures and greater
temporal stability
also tended to live longer than their cohorts.

Another relevant paper finds:

"Some of the residual variation in this relationship
[between 'lifetime
expenditure of energy per gram of tissue'?] in mammals is
explained by
ambient temperature."

, may be:

Speakman JR.
Body size, energy metabolism and lifespan.
J Exp Biol. 2005 May;208(Pt 9):1717-30. Review.
PMID: 15855403

Bigger animals live longer. The scaling exponent for the
relationship
between lifespan and body mass is between 0.15 and 0.3.
Bigger animals also
expend more energy, and the scaling exponent for the
relationship of resting
metabolic rate (RMR) to body mass lies somewhere between
0.66 and 0.8.
Mass-specific RMR therefore scales with a corresponding
exponent
between -0.2 and -0.33. Because the exponents for
mass-specific RMR are
close to the exponents for lifespan, but have opposite
signs, their product
(the mass-specific expenditure of energy per lifespan) is
independent of
body mass (exponent between -0.08 and 0.08). This means that
across species
a gram of tissue on average expends about the same amount of
energy before
it dies regardless of whether that tissue is located in a
shrew, a cow, an
elephant or a whale. This fact led to the notion that ageing
and lifespan
are processes regulated by energy metabolism rates and that
elevating
metabolism will be associated with premature mortality--the
rate of living
theory. The free-radical theory of ageing provides a
potential mechanism
that links metabolism to ageing phenomena, since oxygen free
radicals are
formed as a by-product of oxidative phosphorylation. Despite
this potential
synergy in these theoretical approaches, the free-radical
theory has grown
in stature while the rate of living theory has fallen into
disrepute. This
is primarily because comparisons made across classes (for
example, between
birds and mammals) do not conform to the expectations, and
even within
classes there is substantial interspecific variability in
the mass-specific
expenditure of energy per lifespan. Using interspecific data
to test the
rate of living hypothesis is, however, confused by several
major problems.
For example, appeals that the resultant lifetime expenditure
of energy per
gram of tissue is 'too variable' depend on the biological
significance
rather than the statistical significance of the variation
observed.
Moreover, maximum lifespan is not a good marker of ageing
and RMR is not a
good measure of total energy metabolism. Analysis of
residual lifespan
against residual RMR reveals no significant relationship.
However, this is
still based on RMR. A novel comparison using daily energy
expenditure (DEE),
rather than BMR, suggests that lifetime expenditure of
energy per gram of
tissue is NOT independent of body mass, and that tissue in
smaller animals
expends more energy before expiring than tissue in larger
animals. Some of
the residual variation in this relationship in mammals is
explained by
ambient temperature. In addition there is a significant
negative
relationship between residual lifespan and residual daily
energy expenditure
in mammals. A potentially much better model to explore the
links of body
size, metabolism and ageing is to examine the intraspecific
links. These
studies have generated some data that support the original
rate of living
theory and other data that conflict. In particular several
studies have
shown that manipulating animals to expend more or less
energy generate the
expected effects on lifespan (particularly when the subjects
are
ectotherms). However, smaller individuals with higher rates
of metabolism
live longer than their slower, larger conspecifics. An
addition to these
confused observations has been the recent suggestion that
under some
circumstances we might expect mitochondria to produce fewer
free radicals
when metabolism is higher--particularly when they are
uncoupled. These new
ideas concerning the manner in which mitochondria generate
free radicals as
a function of metabolism shed some light on the complexity
of observations
linking body size, metabolism and lifespan.