Pharyngeal movements during feeding sequences inNavanax inermis: a cinematographic analysis

Summary Pharyngeal movements during feeding inNavanax inermis were filmed and correlated with known neural activity controlling the pharynx. Seven distinct components of feeding were identified. Occurrence of a component was in some cases fixed, in that once initiated the act went to completion, and in other cases reflex, in that tonic stimulus control was needed for the act to be maintained. As few as 2 or as many as 7 different motor acts could occur in a feeding sequence. The specific acts which make up a sequence were dependent upon the nature of the prey stimuli that elicited feeding: qualitatively as well as quantitatively different feeding sequences were elicited by prey of differing sizes or by prey which was withdrawn fromNavanax at different stages in a movement. The data indicate that the sequence of pharyngeal movements is not preprogrammed, but rather the sequence is appropriate to a specific type of prey. Flexibility in fitting a feeding sequence to the prey that elicits the sequence is achieved by combining in different ways a limited number of specific, fairly stereotyped motor acts.     

Improved procedures to mine data obtained from spotted cDNA arrays

We studied six types of errors that affect the experimental results obtained with the spotted cDNA technology, proposing a new experimental strategy and a four-step algorithm to improve data accuracy. In an experiment analyzed with this method, mRNA extracted from neuroblastoma (N2A) cells and a clone transfected with the neuronal gap junction protein Cx36 were hybridized on 10 chips, each spotted with 2512 known mouse cDNAs. We found 53 upregulated and 23 downregulated genes with expression ratios exceeding 1.5-fold. By contrast, the newly introduced standard gene expression score, which considers the normal variability of gene expression in the reference cells, revealed that Cx36 transfection (p