This is the 25'th update on my fly longevity experiments. Runs #19 and #20 investigated ways and means for blocking short-term glycerol induced "metabolic" toxicity. In place of the water normally used in these experiments, a 1:2 mixture of glycerin (glycerol) and water is used. This is quite dehydrating, so I expected the flies to die of dehydration after a short period, which is what happened. In run #19 good results were obtained by a grape proanthocyanidin mixture called leucoselect. The glycerol induced increase in mortality evident at the census on Day 5, 9, and 12 was completely reversed by leucoselect, so that survival rates were similar to a control bottle which used water in place of the glycerol mixture. Please note that all bottles included taurine, as a non-toxic larvicide, so as to avoid having to regularly change the fly food. Benzoate, and citric acid were also included to help eliminate pathogen growth on the 4-24 fly food, which itself already includes a not completely effective mold inhibitor.
RUN #19 Percent Survival on Day
5 9 12 17 20 25 32 37 43 55 60
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water cntl 97% 91% 77% 66% 54% 49% 37% 31% 14% 6% 3%
glycerol 1:2 cntl 62 29 10 0 - - - - - - -
+aloe vera 450 mg 81 52 43 5 0 - - - - - -
+lavendar 300 mg 73 40 20 0 - - - - - - -
+leucoselect 50 mg 91 87 83 30 4 0 - - - - -I was so impressed with the results with leucoselect that the glycerol experiment was immediately repeated. I also tested the effect of a higher dosage of leucoselect, as well as some related chemicals. For some reason the day 12 results were not quite as good, possibly because the flies used were a little older to start with in this run. However the higher 100 mg dosage of Leucoselect offered survival rates not significantly different from the water control on the day 4, and day 7 census.
RUN #20 Percent Survival on Day
4 7 12 19 26 30
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water cntl 100% 86% 79% 50% 21% 7%
glycerol 1:2 cntl 91 27 9 0 - -
+leucoselect 50 mg 87 67 40 0 - -
+leucoselect 100 mg 100 82 27 0 - -
+resveratrol 50 mg 95 70 40 0 - -
+pycnogenol 50 mg 93 60 33 0 - -
+green tea extract 75 mg 95 70 35 0 - -
It looks like a sufficiently high dosage of the grape extract
leucoselect can eliminate glycerol induced increases in mortality rates,
at least in the short term. I suspect quite a few other antioxidant
mixtures would have similar effects if a high enough dosage were to be
used.
The metabolic toxicity of glycerol investigated here may have little to
do with the toxic effects induced by the concentrated glycerol solutions
used in cryopreservation. These are administered at a lower temperature,
where metabolism is greatly reduced, so leucoselect might or might not
have any beneficial effect in this case.
In cryopreservation the major toxic effect of glycerol is known to be
osmotic, since glycerol only slowly passes through cellular membranes.
This feature renders glycerol of limited use for whole organ
cryopreservation, which requires cryoprotectants possessing much greater
permeability, so that organs can be protected from freezing injury in an
acceptible time frame.
Next I'll try to block the metabolic toxicity of alcohol.