Abstract: A method for the selective determination of sialic acid-carrying glycolipid complexes in blood, in which the serum is diluted with water, then extracted with a water-immiscible organic solvent or solvent mixture to remove neutral lipids, a lipoprotein fraction containing sialic acid-carrying glycolipids is precipitated from the aqueous phase, the precipitated fraction is redissolved, and the sialic acid content of the solution or the amount and quality of the sialic acid-carrying glycolipid are determined by a method known per se. A water-soluble salt of a monovalent, bivalent or trivalent metal other than alkali metal is used as a precipitating agent in an amount corresponding to a final metal ion concentration of 0.005-0.1 mole/l in the mixture, and precipitation is performed at a pH of 1.5 to 8.0.

Abstract: The invention relates to a method for protecting plants against stress or for increasing their yield, in which the plant is treated in its intense development stage or directly after flowering or before, during or maximum 5 days after the occurrence of stress with 0.001-10 kg/hectare of a compound of Formula (I), ##STR1## wherein X.sup.- is an agriculturally acceptable inorganic or organic anion. The invention also relates to a composition for protecting plants against stress or for increasing their yield, which comprises as active ingredient 0.001-95% by weight of a compound of formula (I).