From: Doug Skrecky (oberon@vcn.bc.ca)
Date: Sun Apr 20 2003 - 20:50:17 MDT
This is the 85'th update of my fly longevity experiments. Average
temperature was 20.3 C during this run. Since fly longevity is closely
tied to temperature, I've decided to use this to tie in the longevity
statistics in my own experiments, with those obtained by professionals
that publish in peer reviewed science magazines.
My own experiments labour under several advantages. First, I use a
random selection of flies from one breeding bottle to populate any given
run. The average lifespan measured in my experiments is always going to be
less than the real average lifespan of the flies I use, as some of them
are already middle aged, at the start of a run. Second, professional
experiments are usually conducted under "clean room" conditions, so that
pathogens such as viruses exert little or no impact on fly longevity. My
own experiments are compromised by pathogens, so again average longevity
will be reduced. Third professional experiments use only one sex, and the
use of mixed sexes will reduce average longevity in experiments such as
mine.
Maximal longevity should be less sensitive to experiment conditions,
but will tend to increase as more flies are used in an experiment. I use
the Oregon R substrain of drosophila melanogaster, which is known to be
genetically unstable, so longevity statistics will vary with different
stocks. Overall I believe that the maximal longevity found in professional
experiments using large numbers of flies, under carefully controlled
temperatures, would serve as a useful benchmark for my own experiments.
(Mechanisms of Ageing and Development 5: 347-370 1976) will serve as my
benchmark reference source. Here maximal lifespan of Oregon-R flies was 61
days at 27 C, and 128 days at 21 C. Using a linear extrapolation, maximal
longevity (MAX) can be expressed as a function of temperature (T in
centigrade) as follows:
MAX = 61 days + (128 - 61)*(27 - T)/(27-21) = 363 - 11.2*T days
For the present experiment with an average temperature of 20.3 C, this
equation yields a reference maximal longevity of 136 days, which is
comfortably in excess of the observed maximum of 84 days for this
experiment. Control longevity at 57 days was very poor. Detailed results
are listed below.
My previous results indicated that high dose nicotinamide can be very
toxic. Recently it has been discovered that one of the mechanisms of
nicotinamide toxicity is SIR2 depletion via nicotinamide competition with
NAD. Here I check to see if NAD can ameliorate low dose nicotinamide
toxicity, as well as check out NAD and niacin independantly.
The present results suggest that both NAD and niacin (a precursor of
NAD) may be beneficial for old flies. The addition of NAD to nicotinamide
did increase longevity, but any conclusions regarding the the SIR2 mode of
nicotinamide toxicity may be premature, since NAD by itself acted to
increase longevity, and in any case the low dosages of nicotinamide used
were themselves not toxic.
In other results, both raw coconut juice, and the yellow dye material
annatto appear to be helpful. Annatto toxicity is known to be mediated by
riboflavin depletion, the possibility exists that an annatto/riboflavin
combination might yield better results. This idea is being tested in run
#90.
Run #85 Percent Survival on Day
supplement 27 33 38 44 50 57 63 68 74 79 84 91
____________________________________________________________________
control 73 64 55 45 32 14 0 - - - - -
annatto 1/16 tsp 60 60 60 60 50 30 20 0 - - - -
annatto 1/4 tsp 69 63 63 63 56 44 31 25 25 19 6 0
coconut J, raw 64 60 56 48 44 40 36 24 12 8 8 0
NAD 0.6 mg 76 72 56 44 36 32 16 12 12 0 - -
NAD 2.5 mg 84 72 64 52 48 36 20 8 8 0 - -
niacin 25 mg 71 67 57 43 33 19 14 14 10 5 0 -
niacin 100 mg 89 83 78 67 56 33 22 22 11 11 6 0
nicotinamide 24 mg 58 58 58 50 38 17 4 4 0 - - -
nicotinamide 94 mg 72 72 72 61 61 28 11 6 0 - - -
nicotinamide 94 mg + NAD 2.5 mg 71 64 64 43 36 36 36 21 21 21 14 0
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