Ovarian Myxoma: Ultrastructural and Immunohistochemical Findings

The integrity of the colonic mucin layer has been reported to be altered during carcinogenesis in both humans and rodents. Prior to attempting scanning microscopic techniques on colonic mucosa of patients at high risk to develop colorectal cancer, these procedures were performed on colonic mucosa from rats with chemically induced colon cancers. Substantial technical difficulties in preparation and serious subjectivity in interpretation of the scanning micrographs were encountered. The major technical problem was the unpredictable retention of the mucin layer upon both normal and cancerous mucosae. Visual interpretation of the integrity or disruption of the mucin layer with the scanning electron microscope revealed variable fenestration and fraying of the mucin in both normal and cancerous colons. Our findings suggest that scanning electron microscopy of colonic mucin may not be a reliable screening procedure for (pre)cancerous changes in human colonic mucosae.     

The influence of diet and dimethylhydrazine on the large intestine of vervet monkeys: scanning and transmission electron microscope studies

The study was designed to identify diet and carcinogen-dependent ultrastructural changes in the epithelium of macroscopically normal colonic mucosa in primates. Seventy adult female vervet monkeys were divided into seven equal treatment groups. Four received a Western high-fat low fibre diet (WD), two a prudent low-fat higher fibre diet (PD) and one a control low-fat high fibre diet (CD). Three groups (2 WD, 1 PD) received dimethylhydrazine intramuscularly at 14 day intervals. After 18 months, monkeys of two groups on the WD were transferred to the PD (WD----PD) and 30 months later all were killed. Mucosae of caecum, colon transversum and rectum were examined by scanning and transmission electron microscopy and showed close similarity to that of humans. Rectal mucosae showed increased surface goblet cell secretory activity, mucin production and microvillar changes related to WD and WD----PD. The enhancing effect of a carcinogen on ultrastructural changes such as cellular pleomorphism, cytoplasmic interbridging, nuclear and nucleolar irregularities and appearance of argentaffin cells in the free surface epithelium were noted predominantly in high-fat treated animals. Such changes observed in the upper part of crypt, orifice and free surface epithelium can be characteristic for precancerous change and could be utilised practically in the detection of precursor lesions of the colon.     

The influence of diet and dimethylhydrazine on the large intestine of vervet monkeys: scanning and transmission electron microscope studies.

The study was designed to identify diet and carcinogen-dependent ultrastructural changes in the epithelium of macroscopically normal colonic mucosa in primates. Seventy adult female vervet monkeys were divided into seven equal treatment groups. Four received a Western high-fat low fibre diet (WD), two a prudent low-fat higher fibre diet (PD) and one a control low-fat high fibre diet (CD). Three groups (2 WD, 1 PD) received dimethylhydrazine intramuscularly at 14 day intervals. After 18 months, monkeys of two groups on the WD were transferred to the PD (WD----PD) and 30 months later all were killed. Mucosae of caecum, colon transversum and rectum were examined by scanning and transmission electron microscopy and showed close similarity to that of humans. Rectal mucosae showed increased surface goblet cell secretory activity, mucin production and microvillar changes related to WD and WD----PD. The enhancing effect of a carcinogen on ultrastructural changes such as cellular pleomorphism, cytoplasmic interbridging, nuclear and nucleolar irregularities and appearance of argentaffin cells in the free surface epithelium were noted predominantly in high-fat treated animals. Such changes observed in the upper part of crypt, orifice and free surface epithelium can be characteristic for precancerous change and could be utilised practically in the detection of precursor lesions of the colon.     

Immune exclusion of Haemonchus contortus larvae in the sheep: effects on gastric mucin of immunization, larval challenge and treatment with dexamethasone

The rapid expulsion of the gastric nematode Haemonchus contortus from primed sheep is a complex mechanism which probably involves immediate hypersensitivity reactions and mucus. Quantitative techniques were employed to determine the content and distribution of mucin in the gastric mucosae of sheep of varying immune status, following a single large challenge with H. contortus. Substantial depletion of both neutral and acidic mucin, following challenge, was noted in the gastric mucosae of naive sheep. When compared with normal controls, animals rendered immune by daily oral challenge had significant reductions in neutral mucin at the mucosal surface and increased quantities of acidic mucin deeper in the mucosa. Mucin distribution in immune sheep was not significantly altered 48 h after challenge. Treatment of immune animals with the corticosteroid dexamethasone, abrogated the protective response with gross depletion of mucus in challenged sheep, but had little measurable effect on the mucin profile of unchallenged animals, except for a slight increase in acidic mucin at the mucosal surface and the absence of any detectable mucin in the zone adjacent to the sub-mucosa. Immunity to H. contortus diminishes with time after immunization. Animals still immune 6 weeks after immunization were found to have mucin profiles which did not differ significantly from those of freshly immunized animals, whereas animals susceptible to re-infection 12 weeks after immunization had mucin profiles more closely resembling those seen in naive controls. Immunization by daily oral challenge was also accompanied by hyperplasia of the gastric mucosa which persisted for at least 12 weeks after immunization had ceased.     

Proliferation of D2-40-expressing intestinal lymphatic vessels in the lamina propria in inflammatory bowel disease

Lymphatic vessels in the colon are normally distributed beneath the muscularis mucosae with rare branches reaching through the muscularis mucosae to the most basal aspect of the colonic crypts. In chronic inflammatory bowel disease demonstrating acute inflammation and architectural disarray, lymph vessel proliferation is seen within the lamina propria and within the submucosa. We analyzed the number and distribution of lymphatic vessels within the lamina propria and submucosa in chronic active and treated ulcerative colitis with restoration of architecture by immunostaining with D2-40, a specific monoclonal antibody against lymphatic vessels. We found significantly increased numbers of lymph vessels in chronic active ulcerative colitis both within the lamina propria and the submucosa as compared to normal mucosa. Numbers of lymph vessels in lamina propria were highest in severe chronic active ulcerative colitis and less in moderate and minimal residual disease with minimal architectural disarray (p<0.05). Lymph vessels in the submucosa were increased significantly above normal values in both severe, moderate and minimal residual disease. We conclude that lymph vessel distribution in chronic active ulcerative colitis extends into the lamina propria. With restoration of architectural morphology, the integrity of the lamina propria in regards to the distribution of lymph vessels is restored.     

Distribution of monoclonal antibody-defined monosialoganglioside in normal and cancerous human tissues: an immunoperoxidase study

The immunoreactivity of a monosialoganglioside antigen defined by monoclonal antibody 116NS19-9 (19-9) was studied in neoplastic and normal glandular and mucosal epithelia using an indirect immunoperoxidase method. In neoplastic mucosae, the antigen was detected in the majority of colorectal and endometrial carcinomas, predominantly in a focal staining pattern. A substantial proportion of gastric and pancreatic tumors and an occasional breast carcinoma also reacted with the monoclonal antibody. Expression of the monosialoganglioside in normal colonic mucosa appeared to be restricted to areas adjacent to tumor tissue. In gastric mucosa, the antigen was confined to some areas showing intestinal metaplasia. The antigen was also detected in the epithelium of normal mucosa of the gall bladder and endocervix, as well as in some ductal epithelia of the pancreas and salivary glands. Most other mucosae were negative for antigen expression.     

Entamoeba histolytica-secreted products degrade colonic mucin oligosaccharides

Degradation of the mucus layer by Entamoeba histolytica is a prerequisite for invasion of the colonic mucosa. In this study, we demonstrate that amoeba-secreted products degrade (3)H-labeled and native colonic mucin oligosaccharides independently of proteolytic activity. We conclude that E. histolytica degrades mucin oligosaccharides, which may facilitate parasite invasion of the colon.     

Microbial Colonization of the Intestinal Epithelium in Suckling Mice

Colonization by indigenous microorganisms of the mucosal epithelia of the large bowels of suckling mice was followed by microbial culture techniques and by light, fluorescence, and electron microscopy. Certain microbes colonize in distinctive patterns the cecal and colonic epithelia in these mice. Coliforms and enterococci colonize the large bowel 7 to 9 days after birth and reach high population levels during the second week. During that period, these facultative anaerobes can be detected by immunofluorescence techniques in microcolonies in the mucin on the epithelium. During the third week, however, after their populations decline to the low levels characteristic of adult mice, coliforms and enteroccoci can be observed only infrequently in the mucous layer. Anaerobic fusiform-shaped bacteria appear in the mucous layers along with the microcolonies of enterococci and coliforms during the second week after birth. These anaerobes increase in numbers in the mucin until they form thick layers on the mucosal epithelium by the end of the third week. They remain in the mucous layer throughout the life of the normal mouse. Anaerobic spiral-shaped microbes also colonize the mucous layer on the cecal and colonic epithelium. But these organisms can be detected by immunofluorescence in 1-week-old mice, well in advance of the time the fusiform-shaped bacteria can be found. In the second week, the latter microbes co-inhabit the mucous layer with the spiral-shaped organisms. The fusiform- and spiral-shaped microbes remain associated in the mucin on the cecal and colonic mucosal epithelia into the adult life of mice.     

Abnormal patterns of colorectal mucin secretion after urinary diversion of different types: histochemical and lectin binding studies

Clinical and experimental evidence indicates that ureterosigmoidostomy is associated with a high risk for the development of colonic cancer, while there is no reported evidence of increased risk in patients who undergo urinary diversion of other types. In the present study the histochemical and lectin binding characteristics of goblet cell mucin were investigated in biopsy specimens from patients who had undergone ureterosigmoidostomy and from patients who had undergone rectal bladder surgery. Specimens from transitional mucosa surrounding colonic cancers and from normal rectal mucosa were also studied. For histochemical studies the high iron diamine-Alcian blue method was used. FITC-conjugated Dolichus biflorus agglutinin (FITC-DBA) and Arachis hypogaea agglutinin (FITC-PNA) were used for the study of lectin binding characteristics. In contrast to the striking increase in numbers of sialomucin-containing goblet cells found in the patients who had undergone ureterosigmoidostomy, the mucin proved to be histochemically normal in the rectal bladder surgery group. Abnormal lectin binding patterns were observed in colorectal mucosa after urinary diversion of both types, with the abnormalities consisting of dramatic decreases in FITC-DBA labeling (compared with controls) and the appearance of substantial numbers of FITC-PNA-labeled goblet cells. These findings indicate that the pattern of mucin secretion is definitely abnormal in patients who have undergone urinary diversion. Whether this abnormality is an indicator of premalignant changes remains to be established. These data, however, confirm that endoscopic and histologic follow-up studies may be of value in assessing the risk for the development of cancer in these patients.     

Adhesion of enteroaggregative Escherichia coli to pediatric intestinal mucosa in vitro.

Organ cultures of small- and large-intestinal mucosa from children were used to examine the interactions of enteroaggregative Escherichia coli (EAEC) with human intestine. Mucosae from patients aged between 3 and 190 months were cultured with five EAEC strains isolated from infants with diarrhea in the United Kingdom and with two well-described prototype EAEC strains, 17-2 and 221. The prototype strains adhered to jejunal, ileal, and colonic mucosae. The wild-type strains also adhered to this tissue but showed a variable pattern of adhesion: two adhered to all intestinal levels, one adhered to jejunum and ileum, one adhered to ileum only, and one adhered to ileum and colon. Adherence was in an aggregative or stacked-brick pattern, resembling that seen on HEp-2 cells. Electron microscopy of infected small intestinal mucosa revealed bacteria in association with a thick mucus layer above an intact enterocyte brush border, which contained extruded cell fragments. This mucus layer was not present on controls. EAEC adherence to colonic mucosa was associated with cytotoxic effects including microvillous vesiculation (but without evidence of an attaching/effacing lesion), enlarged crypt openings, the presence of intercrypt crevices, and increased epithelial cell extrusion. These results demonstrate that in vitro organ culture of intestinal mucosa from children can be used to investigate EAEC pathogenesis in childhood directly. EAEC strains appear able to colonize many regions of the gastrointestinal tract, without overt changes to small intestinal mucosa but with cytotoxic effects on colonic mucosa.