Developmental Changes in Colonic Myoelectric Activity in the Infant Primate

Abstract

When 15-day f e t a l mouse duodenum i s c u l t u r e d f o r 48 hours i n Trowel1 T8 medium, v i l l i do not form and c r y p t s o r c r y p t -l i k e s t r u c t u r e s a r e s c a n t y . I n vivo v i l l i d i f f e r e n t i a t e a t 16 days of --g e s t a t i o n and c r y p t s appear t h r e e days l a t e r . I f t h e same c u l t ur e medium i s supplemented w i t h an o r g a n i c e x t r a c t o f 19-day r a t a m n i o t i c f l u i d w e l l d i f f e r e n t i a t e d c r y p t s a r e p r e s e n t i n t h e exp l a n t s a f t e r 48 hours of c u l t u r e . This e f f e c t was a t t r i b u t e d t o t h e presence of a c r y p t d i f f e r e n t i a t i o n f a c t o r (CDF) i n t h e amn i o t i c f l u i d . When f e t a l duodenum i s c u l t u r e d w i t h immersed Eragments (25 mg) of 19-day f e t a l r a t v i s c e r a l yolk s a c (VYS) o r w i t h T8 medium c o n d i t i o n e d by a 24 hour i n c u b a t i o n w i t h VYS fragments, a high CDF a c t i v i t y i s observed. VYS incubated f o r 6 hours i n T8 medium is completely d e g r a n u l a t e d and t h e medium e x h i b i t s a s t r o n g CDF a c t i v i t y . S u b c e l l u l a r f r a c t i o n a t i o n of VYS by d i f f e r e n t l a l c e n t r i f u g a t i o n s u c r o s e r e v e a l t h a t t h e most a c t i v e f r a c t i o n 9. .showing CDF a c t l v l t y 1 s t h e r i c h e s t i n l a r g e g r a n u l e s . Human yolk s a c was taken from a 38-39 day embryo following a p r e v e n t i v e abort i o n ( t u b a 1 i m p l a n t a t i o n ) . When 15-day f e t a l inouse duodenum i s c u l t u r e d i n presence of h a l f of t h e human yolk s a c (HYS), v i l l i and c r y p t s d i f f e r e n t i a t e i n t h e duodenal segments. I t a p p e a r s t h a t HYS a l s o h a s a CDF a c t i v i t y . (Supported by g r a n t No. Previous studies have demonstrated a constant fetal cerebral 0 2 consumption over a range of arterial 0 2 content (Ca02) from 5 to 1 mM. T o determine t h e e f f e c t of such hypoxia on t h e "nonvital" tissues, w e measured hindlimb 0 2 consumption (Go2) in 5 fetal sheep (8-16 days post-op). Four t o six sample sets for hemoglobin concentration expressed a s oxygen capacity and 0 2 saturation were drawn from t h e external iliac a r t e r y (IA) and vein during a control period and a f t e r equilibration at progressively decreasing levels of arterial 0 2 saturation (Sa02, Oh). Hypoxia was produced by maternal common internal iliac a r t e r y occlusion yielding fetal CaO2 from 4.93 t o 0.95 mM. Blood flow (F, mlfmin) t o t h e pelvic limb was measured continuously with an ultrasonic blood flow transducer(Transonics Systems, Inc) placed around t h e IA. C a 0 2 (mM) and Go2 (umfmin) were calculated for e a c h set. Hindlimb F had a tendency to increase while Go2 remained constant t o a C a 0 2 -1.5 mM (Sa02-25°/~), below which both F and \jo2 fell sharply.We compared control with severe hypoxia ( C a 0 2 (1.5 mM) by paired We conclude t h a t 1) t h e f e t u s decieases...