Two cell-free filtrates were obtained by filtering the fresh crypt cell suspensions which were pretreated with freeze-thawing and ultrasonic disintegration res

pectively through the G

6

funnel. 0.4 ml of each filtrate or the fresh crypt cell suspension was administered separately into the lumen of a 3 cm jejunal segment in BALB/c mouse 1-3 hours following 15 Gy γ-ray total-body irradiation. Seventy-two hours later

no regenerating crypt could be found and the villi become remarkably shorter in the irradiated control

while in the jejunal segments receiving both filtrates or the fresh crypt cell suspensions

numerous newly-formed crypts were visible with the villi apparently normal

meanwhile

the columnar

goblet

argentaffin

Paneth cells as well as undifferentiated cells could

be identified in the crypt region under electron microscope. The new crypts were found to exist persistently in 14 days' experimental period after 9.4 Gy γ-ray abdominal irradiation and filtrates administration. The above findings suggest the presence of a crypt repair factor in cell-free filtrates prepared from the intestinal crypt cell suspension of normal mice.