Worm Breeder's Gazette 8(1): 15

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Reversible Blocks of Aging and Development

P. Cuccaro, T. Johnson

Transient blocking of development produces a coordinate halt in the 
aging process.  We have blocked development of larvae at several 
distinct times in larval growth, still using starvation to block 
development.  We find that larvae survive starvation for periods up to 
two weeks.  Little mortality is seen before 5 days in typical 
experiments.  The survivors of the starvation period can resume 
immediate development when returned to growth conditions and still 
have normal adult life-spans.  This is all consistent with the idea 
that the 'aging clock' (if we can coin that phrase) doesn't really 
begin until development's clock has ended or that development and 
aging both respond to the same clock.
These observations fit in well with a body of information in the 
aging literature dealing with the phenomenon of 'caloric restriction'. 
This is-a regimen of systematic underfeeding, typically at 60% of 
what ad libitum fed controls would eat; this regimen has been shown to 
prolong life-span in a variety of different organisms and is currently 
being studied as a possible means of intervention into human aging.
We would like to try and test the model that there is a separate 
aging clock by asking if this clock may have properties different from 
the developmental clock.  One difference could be that the aging clock 
may not be stopped by starvation in adults, after the developmental 
clock has finished.
In trying to test this notion using N2, we discovered that L4's will 
complete development under the starvation regimen and turn into bags.  
All fecund adult stages respond similarly.  As a matter of fact, there 
appears to be a critical stage of larval development at about the time 
of the L3 to L4 molt at which time a developing worm becomes 
'committed' to the completion of development independently of the 
amount of food that the larva is given.  We're currently determining 
what this critical stage is.
We get around the bag problem by using temperature-sensitive 
embryonic lethals to block development of embryos within the bodies of 
starving mothers and ask if starvation has a similar effect at other 
times of life.  The results of these experiments are still unclear but 
it is apparent that there are significant differences in the response 
of life-span to starvation in adults as compared with the response of 
life-span to starvation in larvae.
We're still worried about possible selection that we may be 
artificially imposing on the population of animals that survive the 
starvation protocol and therefore are looking for less drastic ways to 
block development.  If anyone knows of some technique which can arrest 
development and is still reversible after a period of at least a few 
days we'd appreciate knowing about it.  We've tried using accumulator 
mutants (mutants that are arrested in larval development) from the 
Hirsh collection but an extensive although not exhaustive search of 
those stocks failed to yield any that were readily reversible after 
extended growth under the non-permissive conditions.