The effect of 3-acetylpyridine on the explanted chick embryo.

A structural analogue of nicotinic acid, 3-acetylpyridine, has been shown to produce morphological and physiological abnormalities in a variety of organisms. The effect of 3-acetylpyridine (AP) on chick embryos has been studied by several investigators using the technique of yolk-sac injection (Ackermann & Taylor, 1948; Zwilling & DeBell, 1950; Landauer, 1957; Herrmann, Clark & Landauer, 1963). Following AP treatment at 96 h of incubation, a reduction in body size, underdevelopment of leg musculature and edema were noted. Teratogenic effects of AP when administered after 24 h of incubation were much more diffuse and included instances of cerebral hernia and muscular hypoplasia (Landauer, 1957). Simultaneous injection of nicotinamide (Ackermann & Taylor, 1948; Landauer, 1957) decreased the incidence and severity of these conditions. Landauer (1957) noted the similarity of abnormalities found in AP-treated chick embryos to those of the crooked-neck dwarf mutant described by Asmundson (1945). Herrmann et al. (1963) found that different dose levels of AP reduced the wet weight of the leg musculature in such a way as to mimic the two phases of weight loss in the leg musculature of the crooked-neck dwarf mutant embryo. These observations suggested the need for a more detailed study of the AP-treated chick embryo. In particular, it appeared that studies of protein synthesis in these embryos would be of importance, since the most noticeable defect appeared to be a reduction in muscle growth. The use of a technique in which analogue administration and the stage of development of the embryos at the time of AP treatment could be closely controlled was desirable. Thus, the technique of explantation of chick embryos as described by Spratt (1947, 1948) was chosen.