PURPOSE: The aim of this study was to evaluate a natural history of @entity8593 (IA) in the @entity1573 embryo and to assess the type and nature of changes in the intestine at various developmental stages. METHODS: @entity1573 embryos underwent operative induction of IA on the 12th day of incubation. The procedure consisted of electrocoagulation of the mesenteric vessels supplying a 7- to 8-mm intestinal segment. The embryos were subjected to macroscopic examination, histologic and ultrastructural studies of the preatretic and postatretic bowel using the light microscope, scanning, and transmission electron microscopes. All investigations were performed in an experimental group (operated embryos), in a control group, and in a sham-operated group on the 15th, 17th, 19th, and 21st day of incubation. RESULTS: The original technique of an iatrogenic "vascular event" proved to be effective because IA developed in 96% of embryos surviving the procedure. The affected portion of the bowel underwent progressive @entity39 , and signs of @entity1744 could be observed 48 hours after operation. Cord @entity1146 (type II) developed in 81% of embryos. Histologic investigations showed progressive thinning of mucosa, flattening of mucosal folds, and epithelial detachment within the intestine proximal to @entity1146 . There was only mild @entity1184 of the muscular layers. All these pathomorphologic changes were of rapidly progressive nature until the 17th day of incubation. Later, the rate of distension of preatretic bowel and histologic changes were less. Ultrastructural investigation of the proximal bowel showed progressive flattening of the enterocytes associated with their apical bulging, widening of the intercellular spaces, and microvilli @entity194 . Surprisingly, at days 19 and 21 of incubation, signs of induction of adaptive mechanisms with partial restoration of near-normal microvilli pattern were observed. CONCLUSIONS: Study of natural history of experimental IA indicates that histologic and ultrastructural lesions of the bowel are of dynamic nature and are not only the effect of pathologic intraluminal pressure.

Natural history of experimental intestinal XXXX : morphologic and ultrastructural study.

@entity39 :: ('MESH:D009336', 'Disease') :: ['necrosis'] @entity1184 :: ('MESH:D006984', 'Disease') :: ['hypertrophy'] @entity1573 :: ('9031', 'Species') :: ['Chick', 'chick'] @entity194 :: ('MESH:D001284', 'Disease') :: ['atrophy'] @entity1146 :: ('MESH:D018633', 'Disease') :: ['atresia'] @entity1744 :: ('MESH:D043183', 'Disease') :: ['bowel obstruction'] @entity8593 :: ('MESH:D007409', 'Disease') :: ['congenital intestinal atresia']
@entity1146 :: (MESH:D018633,Disease) :: ['atresia']
