Abstract: There is provided a highly specific and highly sensitive assay method for platelet-activating factor (PAF). The invention may be employed to measure PAF levels in biological samples for elucidating the role of PAF in various pathological conditions. In addition, it is expected to facilitate diagnosis of various diseases associated with PAF fluctuation, and also contributing to evaluation of therapeutic effects on such diseases.

Abstract: A precursor of a C-terminal amidated peptide represented by the general formula P-X-Gly-Y.sub.n, wherein P is a peptide residue. X is an amino acid residue the C terminal of which (on the Gly side) can be converted in vivo to a --CONH.sub.2 group. Gly is a glycine residue, Y is a basic amino acid residue, n is an interger of 2 to 4 and a further amino acid residue other than Y or a peptide residue may be attached to Y.sub.n, is produced by a gene engineering technology. The precursor exhibits in vivo physiological activity like the C-terminal amidated peptide.

Abstract: Novel 1.alpha.-hydroxy-24-dehydrovitamin D.sub.3 and its hydroxyl-protected derivatives; novel 1.alpha.-hydroxy-24-dehydroprevitamin D.sub.3 and its hydroxyl-protected derivatives; and novel 1.alpha.,3.beta.-dihydroxycholesta-5,7,24-triene or its hydroxyl-protected derivatives which are key intermediates for preparing the aforesaid compounds. Novel processes for preparing these compounds are also provided. 1.alpha.-Hydroxy-24-dehydrovitamin D.sub.3 has a pharmacological action of controlling the calcium metabolism of warm-blooded animals, and is useful as a prophylactic or therapeutic pharmaceutical for vitamin D deficient disease and related diseases.