Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

Abstract

The development of the small intestine in the insectivore Suncus murinus was noted during the period from 21 days' gestation to 20 days after birth. At 21 days of gestation, the proximal small intestine exhibited the beginning of villus formation, whereas the distal small intestine preserved the stratified epithelium. Stratified epithelium in the distal small intestine changed into a single layer by 24 days' gestation. At 26 days' gestation, each epithelial cell was immature; but by 28 days mature-looking epithelial cells were found. The shape of the villi changed from cuboid to columnar during the same period. The connective-tissue cores of the villi began to develop at 7 days after birth in the proximal small intestine and at 15 days after birth in the distal small intestine. Crypts appeared at 15 days after birth. Endocytosis of epithelial cells took place at 28 days of gestation. In the proximal small intestine, supranuclear vesicle clusters were observed first at birth; they began to decrease both in number and size at 10 days' gestation and then disappeared completely by 20 days after birth. In the distal small intestine, large supranuclear vacuoles were observed first at 28 days of gestation. Although these vacuoles invariably were found up to 15 days after birth, they also disappeared completely by 20 days. Epithelial cells showed a structure similar to those of the adult after weaning.

Developmental Changes in the Ferret Ileum During the Postnatal Period

“…There are many descriptions of the vacuolation of epithelial cells early in the development of several species (Clark, 1959;Clarke and Hardy, 1969, 1970, 1971Hardy et al, 1971;Rodenwald, 1973;Cathie and Beck, 1983;Kiso et al, 1988), and similar vacuolated cells occur transiently in the proximal colon of neonatal piglets (Wooding et al, 1978). These vacuolated cells have been implicated in the transfer of intact maternal antibodies from the colostrum for passive immunity, and in the transfer of macromolecules from the intestinal lumen for nutritional purposes during the neonatal period (Clark, 1959;Rodenwald, 1973).…”

Über die frühfetale Entwicklung der Dünndarm‐Mukosa des Rindes (Bos primigenius taurus).

“…Zotten-und Kryptenbildung Die Zotten-und Kryptenbildung beginnt bei Saugern rnit kurzer Graviditatsdauer im letzten Drittel der Trachtigkeit, wahrend sie bei Spezies mit langerer Intrauterinentwicklung schon friiher einsetzt und langsam voranschreitet (Kiso et al, 1988). obereinstimmend wird eine proximo-distale Richtung der Villogenese im Dunndarm beschreiben (u.a.…”

“…Im Zusammenhang mit der Zottenbildung kommt es im mehrschichtigen Epithelverband-neben den Verbindungskomplexen apikal zwischen den am weitesten zentral gelegenen Zellen-zur Ausbildung von weiteren Haftstrukturen/ Desmosomen (Ratte: Mathan et al, 1976; Mensch: Moxey und Trier, 1978; Streifenhornchen: Kiso et al, 1988). Sie befinden sich abluminal im Epithel und stellen die Pradestinationsstellen fiir die Bildung sekundarer, das heiBt interzellularer Lumina dar.…”

“…Kleine Vesikel in den umliegenden Zellen, die rnit den die Lumina begrenzenden Membranen fusionieren und diese damit verlangern, tragen zur Lumenerweiterung bei (Mathan et al, 1976;Toyota et al, 1989). In gleicher Weise wirken sich Mitosen der benachbarten Zellen aus (Mathan et al, 1976;Moxey und Trier, 1978;Kiso et al, 1988;Toyota et al, 1989;Yamamoto et al, 1992). Die Sekundarlumina stehen dabei zunachst nicht mit dem spaltformigen Zentrallumen in Verbindung (Mathan et al, 1976;Colony und Neutra, 1983).…”

“…Wahrenddessen dringen Mesenchymknospen gegen das Epithel vor und fiihren zur Bildung der Zotten (Mathan et al, 1976;Moxey und Trier, 1978;Kiso et al, 1988;Toyota et al, 1989;Yamamoto et al, 1992).…”