Ultrastructure of intestinal mucosa in diarrhea-predominant irritable bowel syndrome.

OBJECTIVES: Impaired intestinal barrier function has been demonstrated in the pathophysiology of diarrhea-predominant irritable bowel syndrome (IBS-D). This study aimed to describe the intestinal ultrastructural findings in the intestinal mucosal layer of IBS-D patients. METHODS: In total, 10 healthy controls and 10 IBS-D patients were analyzed in this study. The mucosa of each patient's rectosigmoid colon was first assessed by confocal laser endomicroscopy (CLE); next, biopsied specimens of these sites were obtained. Intestinal tissues of IBS-D patients and healthy volunteers were examined to observe cellular changes by transmission electron microscopy (TEM). RESULTS: CLE showed no visible epithelial damage or inflammatory changes in the colonic mucosa of IBS-D compared with healthy volunteers. On transmission electron microscopic examination, patients with IBS-D displayed a larger apical intercellular distance with a higher proportion of dilated (>20 nm) intercellular junctional complexes, which was indicative of impaired mucosal integrity. In addition, microvillus exfoliation, extracellular vesicle as well as increased presence of multivesicular bodies were visible in IBS-D patients. Single epithelial cells appeared necrotic, as characterized by cytoplasmic vacuolization, cytoplasmic swelling, and presence of autolysosome. A significant association between bowel habit, frequency of abdominal pain, and enlarged intercellular distance was found. CONCLUSION: This study showed ultrastructural alterations in the architecture of intestinal epithelial cells and intercellular junctional complexes in IBS-D patients, potentially representing a pathophysiological mechanism in IBS-D.

[Morphofunctional regeneration of epithelial cells in the colon and apudocytes in the pathogenesis and prognosis of the course of non-specific ulcerous colitis].

One hundred twenty patients with nonspecific ulcerative colitis (NUC) were examined. The patients were divided into three groups equal in number according to the severity of the disease. The controls were 24 practically healthy individuals, 64 patients with irritated bowel syndrome (IBS) without pathological changes in the colon mucosa, and 64 IBS patients with atrophic or inflammatory changes in the colon mucosa. The study showed that the development of NUC was associated with an abrupt decrease in the level of proliferation markers (cycline D, and proliferating cell nuclear antigen - PCNA) in the epithelial cells of the sigmoid colon. Their number progressively decreases in more severe cases, while cell apoptosis intensifies. Such changes in cell renewal are closely connected with the functional and structural rebuilding of the diffuse endocrine system, which manifests in an increase of the total number of apudocytes as well as serotonin- and melatonin-producing cells together with a decrease in the number of VIP-producing cells.

Carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1), apically expressed on human colonic M cells, are potential receptors for microbial adhesion.

In the human gut mucosa, specialized M cells deliver intact foreign macromolecules and commensal bacteria from the lumen to organized mucosal lymphoid tissues triggering immune responses. M cells are also major sites of adhesion and invasion for enteric pathogens. The molecular features of M cell apical surfaces that promote microbial normal attachment are still largely unknown. We have demonstrated previously that in the human colonic epithelium, carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1) are integral components of the apical glycocalyx which participate in epithelial-microbial interactions. In this study, based on the reactivity of specific monoclonal antibodies and on immunoelectron microscopy, we show that M cells of human colonic solitary lymphoid follicles express CEA and CEACAM1 on the apical surface. Recently these highly glycosylated molecules have been characterized as protein receptors for different bacteria. This leads us to propose a role for CEA and CEACAM1 in the adherence of enteric bacteria to the apical membrane of colonic M cells. We also hypothesize that, unlike colonic enterocytes, M cells lack the defense mechanism that eliminates CEA and CEACAM1 upon microbial binding and which is based on vesiculation of microvillus plasma membrane.

[Scanning electron microscopy of intestinal mucosa after enteric preparation in patients with carcinoma of large bowel].

In this study, 6 patients were randomly divided into three groups, receiving different intestinal preparations. Colonic mucosa were biopsied for S-520 scanning electron microscopy. Of them, only a tiny minority of bacteria were found in the specimen of the first group. Bacteria weren't discovered in the other two groups. Therefore, three conventional enteric preparations are equally effective and efficient in eliminating intestinal flora. The causes of postoperative incisional infection are many and varied.

Colonic involvement in Fabry's disease.

The case of a 54 year old man with Fabry's disease and extensive jejunal and colonic diverticulosis causing colonic stricture is presented. Histological examination of the resected colon revealed evidence of ceramide trihexose deposition in the myenteric nerve plexus. Colonic involvement in Fabry's disease has not been reported before.

Intraoperative colonic lavage: failure to decrease mucosal microflora.

Few data exist concerning the ability of intraoperative colonic lavage to decrease colonic bacterial counts, and nothing is known about its effect on the recently described mucosa-associated bacteria. The goal of our study was to determine the impact of intraoperative colonic lavage on both the intraluminal and mucosal microflora. After intraoperative colonic washout in 10 adult male Sprague-Dawley rats, quantitative and qualitative aerobic and anaerobic cultures of the intraluminal and mucosal bacteria were obtained. Tissue was also removed for scanning electron microscopic examination of the colon wall. Whereas 1000-fold to 10,000-fold reductions of aerobic and anaerobic intraluminal flora were achieved with mechanical lavage, reductions of aerobic or anaerobic mucosal bacteria were not significant. Failure to diminish bacterial colonization in this ecologic niche may be partly responsible for the persistently high infection rate after emergency colorectal surgery.

Brown bowel syndrome.

The brown bowel syndrome (BBS) is a rare disease characterized by malabsorption and accumulation of lipofuscin in the smooth muscle cells of the muscularis externa of the small intestine. Recently, we incidentally observed a case of BBS in a colon operated on because of a neoplasm. Our ultrastructural investigation, which demonstrated changes in the mitochondria, further supports the significance of mitochondrial damage in BBS.

Glucagon-, glicentin-, and pancreatic polypeptide-like immunoreativities in rectal carcinoids and related colorectal cells.

Three nonargentaffin rectal carcinoids have been investigated immunohistochemically. In one case most tumor cells reacted with antiglucagon sera as well as with antiglicentin, antibovine pancreatic polypeptide (BPP), and antihuman pancreatic polypeptide (HPP) sera; they were identified ultrastructurally as L cells. Another case showed glucagon-, glicentin-, and BPP-immunoreactive cells but lacked HPP immunoreactivity. In the third case glucagon- and glicentin-immunoreactive cells were well represented, while PP immunoreactivities were scarce. Parallel investigations of human rectal and sigmoid mucosa showed numerous cells reacting with glucagon, glicentin, and BPP antisera, most of which lacked HPP immunoreactivity. Cells reacting with glucagon and glicentin antisera, while lacking PP immunoreactivities, were also found. Thus, both tumor and nontumor cells produce glucagonlike immunoreactive (GLI) peptides--one of which may be glicentin or a related molecule--as well as PP-related sequences, although differing histochemically and ultrastructurally from glucagon or PP cells of the human pancreas. It is concluded that nonargentaffin rectal carcinoids are histogenetically linked to nonargentaffin endocrine cells of the human rectum.

Histologic appearance of the intestinal urinary conduit.

The histology of intestinal urinary conduits (8 ileal and 2 sigmoid) in place for 10 months to 10 years was studied in 10 patients between 20 and 65 years old. It is concluded that the ileum and the large intestine do not undergo adaptive metaplastic transformation. The only changes observed are related to a condition of chronic irritation to which the response is a chronic inflammatory reaction. Structures proving to be the most resistant were the cells of Paneth. The latter were not damaged in appearance and number as compared to normal, even when the conduit was in place for 10 years.