CHANGES IN M-CSF-LIKE ACTIVITY DURING CHICKEN EMBRYONIC-DEVELOPMENT

We have established a method for separation of chicken bone-marrow cel ls using Percoll density gradient centrifugation, and have developed a new method for determining chicken M-CSF-like activity employing a li quid culture. Using this method, we determined M-CSF-like activities i n egg yolk, chorioallantoic fluid (CAF) and amniotic fluid (AmF), and studied the effects of M-CSF on development of chicken embryos. M-CSF- like activity in egg yolk was at a high level before the incubation of the egg; it began to decrease on the third day of incubation and rapi dly decreased on the fourth day, and no significant activity was detec ted after the tenth day of incubation. M-CSF-like activity in CAF was very low, and it exhibited almost no change during development. No M-C SF-like activity was detected in AmF throughout the experimental perio d.