Worm Breeder's Gazette 9(3): 109

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.

More on the Developmental Interaction Between AVM and the BDU Neurons

B. Walthall, C. Masuoka and M. Chalfie

We previously reported that ablation of the BDU cells at hatching 
disrupts the ability of the postembryonic touch cell AVM to mediate a 
head touch response (CSH meeting, 1985). This dependence of AVM on the 
BDU cells is restricted to early postembryonic development, as removal 
o at 24 hours or more after hatching no longer affects the touch 
sensitivity mediated by AVM.
We have examined in the electron microscope AVM neurons that have 
grown in the absence of the BDU cells and found a range of changes in 
the morphology of the synaptic branch. Five animals were examined: one 
had a normal synaptic branch directed toward the nerve ring; a second 
had a small, anteriorly displaced branch that appeared to enter one of 
the circumferential commissures In the other three no sign of a 
synaptic branch was seen We interpret these results to mean that the 
process giving rise to the synaptic branch of the postembryonic AVM is 
dependent upon the presence of the BDU 
BDU may affect AVM development in two ways. First, the BDU cell may 
induce the formation of the synaptic branch. Alternatively, BDU may 
provide a path into the nerve ring and the synapses formed between 
these cells serve both to stabilize the branch and to guide it through 
an essentially mature nerve ring In the absence of the stabilizing 
influence the branch must find an alternative to survive Because 
branches were present in two of the five animals we examined and 
because based on adult reconstructions White, et al , 1986) the AVM 
process appears to branch before contacting the BDU cell, we favor the