Growth enhancement of plants by femtomole doses of colloidally dispersed triacontanol.

Colloidal dispersions of crystalline 1-triacontanol in water, upon foliar application to corn (Zea mays L.) seedlings, resulted in growth increases at femtomole dosages (spray concentrations as low as 1 nanogram per cubic decimeter). The maximum growth increase occurred at 100 nanograms per cubic decimeter; at both higher and lower concentrations lessened growth increase was observed. The dispersions were prepared by sonication, with control of temperature and composition. Selected surfactants, which facilitate the dispersion process, are effective at 1 percent of the 1-triacontanol composition and are nontoxic.

An improved assay for measuring the antimotility activity of chemical agents towards spermatozoa.

An assay which allows relatively precise determination of the minimum concentration of test compound required to completely immobilize sperm is described. The use of rectangular cross-section capillaries to contain diluted semen allows facile direct comparison of many individual systems under well-controlled conditions. As a result, simultaneous determination of activity in both saline and serum media is feasible. Using this assay, abrupt loss of motility is observed between adjacent cepillaries differing in test compound concentration by as small a factor as 2 1/3 (1.260).

Sizing of phosphatidylcholine vesicles by transmission electron microscopy.

Coating of support films for transmission electron microscopy with silica by evaporation of "silicon monoxide" provides a surface which is easily wetted by aqueous systems. Dispersed colloidal particles spread on this surface without the use of added soluble wetting agents. Such coated supports are found to be particularly useful for the quantitative characterization of the size distribution of vesicles prepared from saturated phosphatidylcholine. The weight average vesicle sizes determined for several samples from measurements of negatively stained electron micrographs are in good agreement with values measured by light scattering and ultracentrifugation.