The ultrastructure and renewal of the intestinal epithelium of the juvenile grasscarp, Ctenopharyngodon idella (Val.)

Abstract

The intestinal absorptive epithelium of starved and fed fish has been studied electron microscopically. After feeding, cells of the proximal segment of the intestine show morphological characteristics of lipid absorption. Absorptive cells in the middle segment contain many pinocytotic vesicles in both fasted and fed specimens. Absorption of protein macromolecules is supposed to be one of the main functions of this part of the gut. In the most caudal part of the intestine, absorptive cells carry relatively few and short microvilli. The proximal and distal segments show structural indications of a function in osmoregulation. The renewal of the epithelium has been studied with light microscopic autoradiography, using tritiated thymidine. The intestinal mucosal fold epithelium represents a cell renewal system. The cells proliferate at the base of the fold and migrate towards the apex in 10--15 days at 20 degrees C. The functional absorptive cells proved to be generally present in the intestinal epithelium, including the proliferative area. Undifferentiated cells have not been identified. The results will be compared with data on absorption of lipid and protein macromolecules in teleostean and mammalian intestines and with descriptions of the cell renewal system in the mammalian intestine.

Comparative study on the intestine of Schilbe mystus and Labeo niloticus in correlation with their feeding habits

“…These observations suggest that the enterocytes of the anterior portion of the intestine are involved in lipid absorption. This suggestion is in accordance with that of Stroband and Debets (1978), in Ctenopharyngodon idella, Anderson (1986), in Girella tricuspidata, Deplano et al (1989), in Dicentrarchus labrax, Olsen et al (1999), in Salvelinus alpinus, Gallagher et al (2001), in Lagodon rhomboids, Caballero et al (2003), in Sparus aurata, Kozarić et al (2004), in Merluccius merluccius, and Carrassón et al (2006), in Dentex dentex. Moreover, Fontagné et al (1998), in Cyprinus carpio, stated that the intestinal fat droplets can be interpreted as a temporary storage form of the re-esterified fatty acids.…”

“…NoaillacDepeyre and Gas (1974 and1976), in Cyprinus carpio and Tinca tinca, respectively, and Olsen et al (1999), in Salvelinus alpinus, suggested that the endocytosis of lipid is not a major route of lipid absorption in the anterior intestine enterocytes. Moreover, Stroband and Debets (1978) stated that the anterior and middle segments of the intestine of the herbivorous Ctenopharyngodon idella possess endocytotic vesicles to uptake protein macromolecules.…”

Gnotobiotic zebrafish reveal evolutionarily conserved responses to the gut microbiota

“…Segment 2 of the intestine (Fig. 1 A) is involved in absorption of other macromolecules, whereas a short distal domain (segment 3) is postulated to participate in water and ion transport (26,38,39).…”

“…In larval and adult stomachless teleosts, macromolecules taken up from the segment 2 lumen are transported through a network of superficial invaginations and vesicles in enterocytes to large supranuclear vacuoles, where they are stored and͞or degraded (26,38,39). A similar tubulovesicular network exists in neonatal mammalian enterocytes (40)(41)(42) but disappears at the time of initiation of protein digestion.…”

“…As in mice and humans, the intestinal epithelium undergoes renewal throughout life. A proliferative compartment, analogous to the mammalian crypt of Lieberkühn, is located at the bases of intestinal villi (26,27). Epithelial progenitors give rise to cell types encountered in other vertebrates, including absorptive enterocytes, mucus-producing goblet cells, and an enteroendocrine lineage (22,28).…”