Dopamine-modulated behaviors, including information processing and reward, are subject to behavioral plasticity. Disruption of these behaviors is thought to support drug addictions and psychoses. The plasticity of dopaminemediated behaviors, for example, habituation and sensitization, are not well understood at the molecular level. We show that in the nematode Caenorhabditis elegans, a D1-like dopamine receptor gene (dop-1) modulates the plasticity of mechanosensory behaviors in which dopamine had not been implicated previously. A mutant of dop-1 displayed faster habituation to nonlocalized mechanical stimulation. This phenotype was rescued by the introduction of a wild-type copy of the gene. The dop-1 gene is expressed in mechanosensory neurons, particularly the ALM and PLM neurons. Selective expression of the dop-1 gene in mechanosensory neurons using the mec-7 promoter rescues the mechanosensory deficit in dop-1 mutant animals. The tyrosine hydroxylase-deficient C. elegans mutant (cat-2) also displays these specific behavioral deficits. These observations provide genetic evidence that dopamine signaling modulates behavioral plasticity in C. elegans.

The effects of monospecific antibodies to the viral glycoprotein with hemagglutinating and neuraminidase activity (HN) and the viral glycoprotein with membrane-fusing activity (F) of the paramyxovirus simian virus 5 (SV5) on the spread of infection in two cell types have been investigated. In CV-1 cells, infection can spread by either released progeny virus adsorbing to and infecting other cells, or by fusion of an infected cell with an adjacent cell as a result of the cell-fusing activity of the F glycoprotein. In these cells, antibodies specific for the HN glycoprotein prevented the dissemination of infection by released infectious virus, but spread by cell fusion was not inhibited. Antibodies to the F glycoprotein completely prevented the spread of infection in these cells. In Madin-Darby bovine kidney cells, which are relatively resistant to SV5-induced fusion, antibodies to either the HN or F glycoproteins were capable of preventing the dissemination of infection. These results indicate that effective immunological prevention of the spread of paramyxovirus infection requires the presence of antibodies that inactivate the F glycoprotein. This requirement for anti-F antibodies has obvious implications for the design of effective paramyxovirus vaccines and provides an explanation for previous failures of formalin-inactivated paramyxovirus vaccines as well as additional insight into the possible immunopathological mechanisms involved in the atypical and severe infections that have occurred in individuals who received inactivated paramyxovirus vaccines and were subsequently infected by the virus.

The unc-52 gene of Claenorhabditis elegans encodes a homologue of the basement membrane heparan sulfate proteoglycan perlecan. Viable alleles reduce the abundance of UNC-52 in late larval stages and increase the frequency of distal tip cell (DTC) migration defects caused by mutations disrupting the UNC-6/netrin guidance system. These unc-52 alleles do not cause circumferential DTC migration defects in an otherwise wild-type genetic background. The effects of unc-52 mutations on DTC migrations are distinct from effects on myofilament organization and can be partially suppressed by mutations in several genes encoding growth factor-like molecules, including EGL-17/FGF, UNC-129/TGF-beta, DBL-1/TGF-beta, and EGL-20/WNT. We propose that UNC-52 serves dual roles in C. elegans larval development in the maintenance of muscle structure and the regulation of growth factor-like signaling pathways.