Distribution of VIP-immunoreactive nerve cells and fibers in the human ileocecal region

VIP-containing nerve cells and fibers in the human ileocecal region (pre-junctional ileum, ileocecal and cecocolonic junctions, post-junctional cecum and colon) have been evaluated by immunocytochemistry. A high density of VIP-positive neurons and nerve fibers was found in all layers of the ileum. At all colonic levels examined and at both junctions, the percentage of VIP-containing cells was higher in the submucous plexus than in the myenteric plexus. At both junctions, the muscle wall was devoid of, and the myenteric plexus extremely poor in VIP-positive nerve fibers and cells. These data suggest that motility of these junctions is not--or only to a minor extent--regulated in man by VIP-containing nerves, at variance with other gut sphincteric areas.

[The differentiation of tumor cells of the human large intestine during the acquisition of multiple drug resistance]

By selection in the medium containing increasing actinomycin D concentrations two sublines with acquired multidrug resistance (MDR) caused by P-glycoprotein (P170) overproduction were isolated. The obtained cell lines as well as parent cells grow in vitro as morphologically organized aggregates, so-called organoids. Comparative electron microscopic study of sensitive and drug resistant organoids has shown that the development of MDR was accompanied by the enhancement of the tumour cell differentiation: the percentage of differentiated cells, the extent of their maturity, and the quantity of lumens were higher in MDR organoids than in parent cell line. The size of glandular structures in resistant organoids was also enlarged. Possible mechanisms of observed phenomenon are discussed.

Morphological evidence for a cecocolonic junction in man and functional implications

The region above, below and in front of the ileocecal valve opening has been studied in man using both light and electron microscopy. A cecocolonic junction, comprising the colonic basal portion of the ileocecal valve, could be demonstrated in man, due to the specific anatomy of the inner portion of the circular muscle. This muscle was arranged in anastomosing cords, richly innervated and enveloped by elastic fibers. Its smooth muscle cells were characterized by extremely wide sarcoplasmic cisternae and cell-to-cell junctions, numerous caveolae and large amounts of glycogen. Interstitial cells were rarely found. This junction might be considered responsible for (1) ileal flow accommodation, (2) colonic active movements and (3) ileocecal valve closing and opening.

Enzyme-histochemical study on the fine distribution of the intramural lymphatics at the ileocecal junction of the monkey intestine

The fine distribution of the intramural lymphatics at the ileocecal junction of the monkey intestine, especially in the lamina propria of the ileocecal valve, was examined by light and electron microscopy using enzyme-histochemical staining. The distinction between the lymphatics and the blood vessels was made by light microscopy on cold glycol methacrylate resin (JB-4) sections using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) double staining. The lymphatics were found to show strong 5'-Nase activity and to comprise irregularly shaped vessels or spaces. The central lymphatic vessels (central lacteals) in low villi were seen to lie deep within the ALPase-positive subepithelial capillary network. In the ileum side of the ileocecal junction, the 5'-Nase-positive lymphatics were seen both in the superficial layer and the deep layer of the lamina propria. On the contrary, in the cecum side the mucosal lymphatics were less numerous in the superficial layer and were distributed mainly in the deep layer near the lamina muscularis mucosae. These lymphatics ran through the lamina muscularis and merged into the lymphatic network in the submucosa. The submucosal lymphatics communicated with each other at the ileocecal junction and formed a well-developed network. Collecting lymphatics with valves were also seen near the tunica muscularis (sphincter muscle) in the deep submucosa. These lymphatics traversed the muscle layer and drained into the subserosal lymphatics.

Scanning electron and light microscopy of the mucosa of the equine ileocaecal junction

The ileocaecal junction mucosal surface morphology of 5 horses and 1 donkey was examined using scanning electron microscopy and light microscopy. Based on differences in surface morphology, the junction could be divided into 4 distinct regions. The distal extremity of the ileum was characterized by the presence of typical finger-like villi followed by a narrow zone displaying short, stubby villi which gradually merged into a 3rd region representing the true transitional zone between the small and large intestine. In this region the villi fused, forming low ridges arranged in circular, semi-circular or S-shaped patterns. Many of the fused villi were indented at the tips giving these structures a doughnut-like appearance. The caecal portion of the ileocaecal junction formed the 4th region and was characterized by the absence of villi and the occurrence of regularly spaced crypt openings each surrounded by a slightly raised circular mound.

Substance P: mechanism of action and receptor distribution at the feline ileocecal sphincter region

The purpose of this study was to determine the mechanism of action of substance P at the distal ileum, ileocecal sphincter (ICS), and proximal colon in the cat and to determine the localization of substance P receptors at these sites by autoradiography. Intraluminal pressures and myoelectric activity were recorded at the feline distal ileum, ICS, and colon. Substance P caused a tonic and phasic spike-dependent contractile response at all three sites. The antagonists propranolol, phentolamine, and naloxone did not affect the contractile response to substance P at the ileum, ICS, or colon. The ganglionic blocker trimethaphan camsylate potentiated the response to substance P at all three sites, P less than 0.05. Both atropine and tetrodotoxin reduced the response of substance P at the ileal site. At the ICS, atropine or tetrodotoxin reduced, but did not obliterate, the effect of substance P. Neither atropine nor tetrodotoxin reduced substance P-induced colonic contractions. By use of autoradiography, specific binding for substance P was determined to be present at all three sites with the greatest concentration of substance P receptors in the circular muscle layer. In conclusion, these studies suggest multiple sites of action of substance P. At the ileum, substance P causes contraction via a cholinergic pathway. At the ICS, substance P has an excitatory action through a cholinergic pathway and also at smooth muscle receptors. In the proximal colon, the excitatory action of substance P is via smooth muscle receptors. An inhibitory ganglionic pathway also exists at all three sites. Substance P receptors exist predominantly in the circular muscle region of the ileum, ICS, and the proximal colon.