Ontogeny and differentiation of regulatory peptide-and serotonin-immunoreactivity in the gastrointestinal tract of an elasmobranch

Abstract

A number of regulatory peptides and serotonin were studied by immunocytochemistry with respect to their appearance and distribution in the developing gastrointestinal tract of the selachian Scyliorhinus stellaris. In the earliest stage studied (fourth month developmental stage) glucagon-, somatostatin-, serotonin-, vasoactive intestinal peptide (VIP)-, cholecystokinin (CCK)-, and gastrin-immunoreactive cells were detected in the already differentiated intestinal epithelium, whereas only glucagon-, somatostatin-, and serotonin-immunoreactive cells were seen in the not yet differentiated stomach epithelium. Glucagon-immunoreactive cells were present in the gastric portion only; in the pyloric portion, they appeared in the next stage, together with CCK-, peptide histidine isoleucine (PHI)-, and bombesin-immunoreactive cells, and disappeared before birth. PHI-immunoreactive cells were restricted to the pyloric portion, whereas VIP-and gastrin-immunoreactive cells were detected in the spiral gut only. At the beginning, immunoreactive cells were few, but they grew in number until birth, when some of them presented a more elevated frequency than that seen in adults. Immunoreactive endocrine cells were of open type and showed a distribution similar to that seen in adults. PHI-immunoreactive nerve fibers appeared early, first in the lamina propria, then in the muscular layer; the opposite was seen for VIPimmunoreactive fibers that were shown successively, first in the muscular layer, then in the lamina propria. Intestinal bombesin and P-endorphin were shown after birth only. The early appearance of the peptides tested is consistent with the hypothesis that they play a role on cell growth and differentiation.

Dietary Lipid Modulation of Intestinal Serotonin in Ballan Wrasse (Labrus bergylta)—In Vitro Analyses

“…At the same time, a similar organization of the development of 5-HT cells within the spinal cord and brain (23,24) and a similar organization of the enteric nervous system (25,26) have been reported in teleost and cartilaginous fish. Besides, the organization of the brain serotonergic system in many fish species is considered similar to that in other vertebrates at different levels; for instance, the mRNA expression of enzymes and transporters involved in the serotonergic system is similarly regulated within vertebrates, as well as the strong implication of 5-HT in controlling GI motility (16).…”

Ontogenetic and Phylogenetic Development of the Endocrine Pancreas (Islet Organ) in Fishes

“…The intestine contained abundant glucagon and a few insulin, somatostatin, and PP/PYY-immunoreactive cells; the stomach possessed only a few somatostatin-immunoreactive cells. At 4 months of development of S. stellaris, the differentiated intestine and the undifferentiated stomach possess glucagon and somatostatin; glucagon appears first in the gastric glands before the pyloric crypts (Tagliafierro et al, 1989b). According to the latter authors, the early appearance of these peptides, and others (for example, vasoactive intestinal peptide, Tagliafierro et al, 1988), is support for the view that regulatory peptides play a role in cell growth and differentiation.…”