Mutations Affecting the Chemosensory Neurons of Caenorhabditis Elegans

We have identified and characterized 95 mutations that reduce or abolish dye filling of amphid and phasmid neurons and that have little effect on viability, fertility or movement. Twenty-seven mutations occurred spontaneously in strains with a high frequency of transposon insertion. Sixty-eight were isolated after treatment with EMS. All of the mutations result in defects in one or more chemosensory responses, such as chemotaxis to ammonium chloride or formation of dauer larvae under conditions of starvation and overcrowding. Seventy-five of the mutations are alleles of 12 previously defined genes, mutations which were previously shown to lead to defects in amphid ultrastructure. We have assigned 20 mutations to 13 new genes, called dyf-1 through dyf-13. We expect that the genes represented by dye-filling defective mutants are important for the differentiation of amphid and phasmid chemosensilla.     

Modeling flux of free and protein-bound radioisotopes into the pulmonary interstitium

Several groups of investigators are using external detection of radiolabeled protein to study the flux of protein from plasma into the pulmonary interstitium. A basic assumption for these studies has been that the unbound (free) tracer concentration is small and insignificant. The purpose of this study is to evaluate how free tracer influences the determination of normalized slope index. A five-compartment model for the lung was used with transport equations for both unbound and bound nuclide flux. Parameters of the unbound and bound transport equations were varied to evaluate the sensitivity of normalized slope index to each parameter. The model was also compared with published protein flux data to investigate the validity of the transport model. Application of the model to external scan data provides a sensitive method for evaluating the flux of bound and unbound tracers into the pulmonary interstitium. We conclude that because the distribution volume for unbound tracer is large with respect to protein distribution volume, even a small amount of unbound tracer (2-5%) can create large errors in the determination of normalized slope index.