A calcium requirement for fibroblast motility and prolifertion

Fibroblast motility and proliferation were found to be largely unaffected by wide variations in extracellular sodium or potassium concentrations or by tetrodotoxin or tetra-ethylammonium chloride. By contrast, EGTA, which reduced free calcium concentration to about 10⁻⁷ M, dramatically inhibited motility and proliferation, and these effects were reversible. These results and previous observations on procaine inhibition of fibroblast motility and proliferation are consistent with the hypothesis that fibroblast motive power derives from a calcium-controlled interaction between actin and myosin, as in skeletal muscle.     

Examining the role of olfaction in dietary choice

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Correlation of tumorigenicity with resistance to growth inhibition by cis-hydroxyproline

cis-Hydroxyproline, an inhibitor of collagen deposition, was examined for its effect on the growth of a variety of tumorigenic and non-tumorigenic cells. Virally, chemically, and spontaneously transformed murine cell lines were found to be less sensitive to cell spreading and growth inhibition by cis-hydroxyproline (CHP) than were their non-tumorigenic counterparts. The non-tumorigenic lines exhibited a higher rate of collagen accumulation in culture than the tumorigenic cell lines. The rate of collagen accumulation in culture without CHP and the growth inhibition by CHP were directly related. These results suggest that normal but not tumorigenic cells may require synthesis of an extracellular substrate containing collagen to support spreading and growth.     

Development and characterization of an Fv-1-sensitive retrovirus-packaging system: single-hit titration kinetics observed in restrictive cells.

We have constructed an RNA-packaging-deficient mutant of N-tropic murine leukemia virus WN1802N by removal of 330 nucleotides located between the upstream long terminal repeat and the start of the gag gene region. Transfection into mink CCL64 cells produced a cell line capable of packaging retrovirus vectors into ecotropic, Fv-1 N-tropic virions. Using retrovirus vectors that confer resistance to the antibiotic G418, we demonstrated that the magnitude of restriction in BALB/3T3 and SIM.R cells (both Fv-1b/b) and in RFM/3T3 cells (Fv-1nr/nr) is approximately 100-fold compared with that in AKR or NIH 3T3 cells (both Fv-1n/n). Furthermore, titration kinetics were single hit in restrictive cells. Colonies of antibiotic-resistant cells recovered after infection of genotypically restrictive cultures were phenotypically restrictive when reinfected, ruling out selection of stably nonrestrictive subpopulations. These results suggest that the ability to infect some fraction of cells in a genotypically restrictive culture does not require specific abrogation and that multihit kinetics may not be an essential feature of Fv-1 restriction.