Abstract: A light filter for filtering light for a human eye with the filter being formed of a plastic material in combination with the filtering material. The filtering material is added so as to provide the filter with spectral transmittance characteristics which include a cut-off location (.lambda.H) of 450 nm to 550 nm, a steepness (S) for the transmittance curve at the cut-off location of at least 1%.nm.sup.-1, a means transmittance (.tau..sub.2) in a spectral range from 380 to 450 nm of at most 20%, and a means transmittance (.tau..sub.3) in a spectral range from 450 to 550 nm of at least 40%. The filtering material preferably includes an organic dye dissolved in the plastic or an organic pigment finely distributed in the plastic material. In addition, the mean transmittance (.tau..sub.2) in the 380 to 450 nm spectral range is at most 10% and the means transmittance (.tau..sub.3) in the 450 to 550 nm spectral range is at least 60%. Further, the light filter has a means transmittance of (.tau..sub.

Abstract: Methine dyes which inhibit cell growth are identified by (1) determining the reduction potential of the dye, (2) determining the ability of the dye to sorb to the cells and (3) selecting those dyes which have a reduction potential more negative than about -0.8 volt and which are sorbed to the cells.

Abstract: The growth of sea urchin eggs is inhibited with a composition comprising a methine dye having a reduction potential equal to or more negative than -1.0 volt which is capable of being absorbed by the eggs, and an inert liquid carrier.