A NATURALLY OCCURRING DEVELOPMENTAL SYNERGISM BETWEEN THE CELLULAR SLIME MOLD,DICTYOSTELIUM MUCOROIDES AND THE FUNGUS,MUCOR HIEMALIS

We here report the second record of a developmentally aberrant strain of a cellular slime mold from natural populations and demonstrate that this Dictyostelium mucoroides variant is capable of undergoing normal morphogenesis in the presence of the phycomycete fungus, Mucor hiemalis. The synergism is induced by an extracellular product(s) which is diffusable through thin agar membranes and is released by the fungus. The presence of the fungus not only induces stalk formation in this stalkless variant, but also increases the rate of sorocarp formation in 3 of 5 additional species of cellular slime molds assayed.     

Analysis of ligand-receptor binding by the difference method

A new method has been proposed for analysis of experimental data on ligand-receptor binding at equilibrium. This method makes it possible to detect heterogeneity of a receptor system in cases where the contribution of the high-affinity site to total binding is rather small and the problem of graphic discrimination of a model cannot be solved unambiguously by other methods. The difference method permits us to exclude experiments on measuring nonspecific binding. A computer program for analysis of ligand-receptor binding has been worked out in which the difference method and traditional methods of binding isotherm analysis are realized. Numerical modeling has shown that the best strategy in experimental data processing is the treatment of total binding isotherms by both the difference method and regression analysis, including the nonspecific binding constant as one of the regression parameters.     

The effect of sedimentation and microbial nitrogen regeneration in a plankton community: a simulation investigation

A computer simulation model was developed to investigate nitrogenfluxes associated with microbial interactions in plankton communities.A short time scale was used, appropriate to the build-up anddecline of phytoplankton blooms in temperate shelf waters aftera mixing or upwelling event. The model depicts a continuum ofevents, many of which have been observed in coastal, upwellingand oceanic systems, including two phytoplankton peaks correspondingto ‘new production’ and ‘regenerated production’.It predicts that nitrogen loss through sedimentation of phytoplanktonand faeces may result in a smaller bloom with a delayed onsetand prolonged duration. Microbial regeneration of nitrogen wasfound to be important in sustaining the middle stages of a phytoplanktonbloom, whereas micro- and meso-zooplankton regeneration occurredtowards the end of the bloom.     

Kinetics of dark repair inhibition in ultraviolet damaged DNA by substituted quinolines

The effects of chloroquine on the kinetics of the dark repair process were investigated by employing a cellular system. Lineweaver-Burke plots and Dixon plots of chloroquine inhibition, respectively, showed that there was an increase in slope with increasing concentration of inhibitor which followed an enzyme-like pattern. These results are consistent with a model for excision-repair in which chloroquine may block the excision repair pathway.     

Volatiles from the epicuticular wax of watercress (Rorippa nasturtium-aquaticum)

Volatiles from the epicuticular wax of watercress were collected by ether washing and examined using gas chromatographic and mass spectrometric analysi