Worm Breeder's Gazette 6(1): 37a

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.

Title unknown.

Authors unknown.

Encouraged by Stretton & Co.'s result that many minutes are required 
to wash the muscle-contracting effect of meta-aminolevamisole out of 
Ascaris muscle strips, we've synthesized tritiated meta-
aminolevamisole of high specific radioactivity.  By thin layer 
chromatography, the drug is greater than 97% radiochemically pure, has 
the same high biological potency on cut C.  elegans as the 
nonradioactive drug, and has a specific radioactivity of 15 to 30 
Ci/mmole.  We incubate the radioactive drug with total worm extract 
and collect any radioactivity bound to membrane fragments by passing 
the extract through a glass fiber fiIter.  A control assay is done in 
the presence of a thousand fold excess of nonradioactive drug.  
Specific binding is the difference between the total binding (first 
assay) and nonspecific binding (second assay).  We find that the wiId 
type nematode containing a high affinity, saturable binding activity.  
There is about 1 picomole of this activity per gram of worms, having a 
dissociation constant of roughly 1 x 10+E-8 M.  In agreement with 
Stretton's original finding, the drug dissociates very slowly from its 
bound state (half life ~10 min.).  The formation of the bound state 
also occurs relatively slowly.  The rate constant is ~1 x 10+E5 
liter/mole-sec at 0 C, several orders of magnitude slower than 
diffusion-limited binding, implying that a rate-limiting step such as 
a protein conformational change might be involved with the formation 
of the bound state observed in vitro.  We have screened extracts of 
several levamisole-resistant mutants having little or no response to 
the drug as living worms.  lev-1(x21) has normal binding activity 
while unc-74(x19) and unc-29(x29) have none.  Several other mutants, 
unc-38(x20), ), and unc-29(e1O72) apparently have 
activity altered in amount or affinity.  Anyway, all this is a 
definite first of some sort.  We'll try to figure out what and let you 
know more at the Worm Meeting.