Brunner's glands of the duckbilled platypus (Ornithorhynchus anatinus)

Brunner's glands in the platypus form a lobulated, glandular collar confined to the submucosa of the most distal portion of the stomach. The glands end immediately proximal to the gastrointestinal junction and excretory ducts empty in the region where the stratified squamous epithelium lining the stomach changes abruptly to the intestinal lining epithelium of the duodenum. An individual gland of Brunner is composed of several elongate lobules drained by intralobular ducts which often join to form a single excretory duct. Light and electron microscopic studies have shown the secretory tubules to be comprised of large, pyramidal cells limited basally by a delicate basal lamina. The ergastoplasm, cisternae of which are dilated and contain amorphous material, is associated with numerous ribosomes. In basal and perinuclear regions intercisternal granules and smooth surfaced vesicles are found. Numerous small vesicles found in supranuclear areas apparently form from the smooth membrane portions of ergastoplasm located adjacent to Golgi complexes. Membrane-bound amorphous granules of varying electron density occupy the apical cytoplasm and show a tendency to coalesce before emptying their contents into the adjacent lumen. The intralobular duct system is lined initially by a columnar epithelium which changes to a simple squamous form before the ducts combine to form a short excretory duct lined by stratified squamous epithelium. The epithelium lining the duct system contains relatively few organelles but appears to be engaged in a limited amount of synthesis and release of secretory material. Histochemical studies indicate that both the secretory tubules and the duct system elaborate a neutral mucopolysaccharide.     

Morphological and histochemical observations on the duodenal glands of eight wild ungulate species native to North America

The duodenal glands of the species examined (Alces alces, Ovis canadensis, Cervus canadensis, Oreamnos americanus, Bison bison, Antilocapra americana, Odocoileus virginianas, Odocoileus heminous) are confined primarily to the submucosa of the small intestine. In one species, the moose, a significant population of secretory tubules also is observed in the mucosa. The ducts of the duodenal glands pierce the overlying muscularis mucosae to empty most often independently into the intestinal lumen. Those of the bison, unlike the other species examined, drain into intestinal glands. The duodenal glands consist primarily of a simple columnar epithelium, the cells of which contain basally positioned round or oval nuclei. The lumina of scattered duodenal glands in the pronghorn and to some extent those of the moose, white-tailed deer, and mule deer may be extremely dilated, and the surrounding epithelium thin and attenuated. Component cells of the duodenal glands of all the species examined show remarkably similar ultrastructural features. They exhibit scattered profiles of rough endoplasmic reticulum, dilated cisternae of which contain an electrondense, amorphous material. Numberous well-developed Golgi complexes occupy the supranuclear region together with transport vesicles and forming secretory granules. Electron-dense, membrane-bound secretory granules generally are concentrated in the apical cytoplasm immediately subjacent to the cell membrane. The apical cell membrane exhibits short, scattered microvilli; and the basal cell membrane is smooth without apparent specialization. Histochemically, the duodenal glands of most species examined in this study consist of a heterogeneous population. The majority of the glands of the moose, elk, mountain goat, bison, pronghorn, and white-tailed deer elaborate a neutral mucin, whereas scattered individual glands, tubules or cells also produce acid mucins. Cells near the terminations of the ducts of the bighorn sheep are the only elements to produce acid mucins in the duodenal glands of this species. The duodenal glands of the bison are unusual in that only the peripheral portions of individual glands produce acid mucins. The remainder of the glands elaborate neutral mucins. Morphological differences between the two regions were not observed. The duodenal glands of the mule deer secrete both acid and neutral mucins. The structural and histochemical observations appear unrelated to the diet of individual species.     

Studies of Brunner's glands in the opossum. II. Postnatal development

The postnatal development of Brunner's glands in the opossum has been traced, using 170 specimens divided into 21 groups according to snout-rump length. The newborn opossum has a well developed small intestine, possessing villi and a differentiated intestinal epithelium with concentrations of PAS-positive material in the apical cytoplasm. The ducts of the glands begin to develop within 24 hours after birth and, as they proliferate, two cell types appear. A tall, columnar cell type lines the excretory duct whereas the intralobular duct system is lined by pyramidal cells. Intralobular ducts undergo differentiation by the 50 mm stage and, after this event, secretory units appear as outgrowths from the intralobular duct system. Development continues into early adulthood. Duodenal glands appear to evaginate simultaneously at localized foci, resulting in the formation of a duodenal sinus between glandular elements. The glands evaginate from the mucosa in the most proximal portion of the duodenum, involving both intestinal and gastric mucosal elements. That portion of mucosa lying between the forming glands is submerged and forms the floor of the duodenal sinus. Excretory duct epithelium often lines the sinus in part. The development of Brunner's glands in the opossum is completely independent both of pyloric and intestinal glands.     

Observations on the anatomy of the stomach and duodenum of the bowhead whale,Balaena mysticetus

Gastric and cranial duodenal structure of the bowhead whale (Balaena mysticetus) was examined grossly and microscopically. The stomach was arranged in a series of four compartments. The first chamber, or forestomach, was a large nonglandular sac. lined by a keratinized stratified squamous epithelium. It was followed by the fundic chamber, a large, somewhat globular and entirely glandular compartment. At the entrance of the fundic chamber, a narrow cardiac gland region could be defined. The remaining onucosa of the chamber contained the proper gastric glands. A narrow, tubular connecting channel, the third distinct gastric division, was lined by mucous glands and joined the fundic chamber with the final stomach compartment, or pyloric chamber. This fourth chamber was also tubular and lined by mucous glands but was of a diameter considerably larger than the connecting channel. The stomach terminated at the pyloric sphincter which consisted of a v/ell-developed band of circular smooth-muscle bundles effecting a division between the pyloric chamber and small intestine. The small intestine began with the duodenal ampulla, a dilated sac considerably smaller than the fundic chamber of the stomach. The rnucosa of this sac contained mucous glands throughout. The ampulla led without a separating sphincter into the duodenum proper which continued the intestine in a much more narrow tubular fashion. The mucosal lining of the duodenum was composed of villi and intestinal crypts. Although their occurrence varied among whales, enteroendocrine cells were identified within the mucous glands of the cardiac region, connecting channel, pyloric chamber, and cranial duodenum. The hepatopancreatic duct entered the wall of the duodenum shortly after the termination of the duodenal ampulla and continued intramurally along the intestine before finally joining the duodenal lumen.     

Subnuclear vacuolated mucous cells: a novel abnormality of simple mucin-secreting cells of non-specialized gastric mucosa and Brunner''s glands

We report a novel abnormality affecting simple mucin-secreting cells of the glands of pyloric gastric mucosa and of Brunner's glands. Subnuclear vacuolated mucous cells show a distinctive appearance on haematoxylin and eosin staining. They are columnar cells of similar size to simple mucin-secreting cells, but have a central nucleus beneath which the cytoplasm has a uniform glassy eosinophilic appearance or contains a clear area. Subnuclear vacuolated mucous cells are found focally lining the lower third of pyloric gastric glands or in Brunner's glands, and may be mistaken for a form of metaplasia. Histochemically, the apical portion of the cell stains for neutral mucin, but the basal portion stains only weakly and variably for protein. Electron microscopy reveals that the basal portion consists of a large, single, membrane-bound vacuole, variably indented by the nucleus, and probably derived from either endoplasmic reticulum or the Golgi apparatus. The vacuole contains granular material which varies in electron density from cell to cell. The apical portion of the cell contains organelles similar to simple mucin-secreting cells. These appearances are highly suggestive of an abnormal accumulation of non-glycoconjugated mucus core protein. Although the cause of this is unknown, it was associated with the histological changes of chronic gastritis in 10 of our 12 cases.     

Five types of pyloric cells in the antral mucosa of the stomach.

Only one type of pyloric cells in the exocrine antral glands is usually described in the literature. The review of 100 gastrectomy specimens revealed 5 types of pyloric cells: one composed of "ordinary" pyloric cells (i.e. cuboidal cells with ill-defined borders, pale, bubbly cytoplasm with an inconspicuous cytoplasmic network). The second type was characterized by pyloric cells with a small, regular vacuole, usually in a subnuclear position. The vacuole in such cells was negative for mucous stains. The third type of pyloric cells had a large intracytoplasmatic vacuole. Cells with this characteristic were found in cystically dilated pyloric glands. The vacuoles in such cells were usually negative for mucous stains although a rim of PAS or alcian blue positive substance was found in some vacuoles. The fourth type of pyloric cells had eosinophilic granules in the cytoplasm. These granules were proven to contain lysozyme. The fifth type had a non-vacuolated, homogeneous ("glassy") cytoplasm which was weakly positive for PAS but negative for acid mucins or mannosides. While the significance of the various types of pyloric cells herein described remains unclear, their easy identification in H & E stained preparations would permit more elaborated studies with histochemistry, immunohistochemistry and/or transmission electron microscopy in the future.     

Histochemical factors influencing the sulfation of the mucosubstances of the Brunner's glands of the human duodenum.

The mucopolysaccharides of the human Brunner's glands were sulfated by sulfuric acid diluted with acetic anhydride or nitrobenzene (1:50) in 5 min. They were recognized by toluidine blue at a pH of less than 1 by exhibiting a red-violet or violet-red metachromasia. The sulfated radicals were removed by methanol or butanol with HCl, H2SO4, Na or NaOH, aqueous Ba(OH)2 at 60 degrees C, or by acetic anhydride, acetyl chloride, benzoyl chloride, or bromine water at 25 degrees C. The carbohydrates were altered so that sulfation was prevented by prior treatment with aqueous Ba(OH)2, or by acetic anhydride with pyridine at 60 degrees C and by acetyl chloride and by bromine water at 25 degrees C. Periodic acid Schiff staining was prevented by sulfation with a nitrobenzene: H2SO4 mixture but not by an acetic anhydride: H2SO4 combination in 1 h suggesting an additional sulfate radical at hydroxyl sites 1 or 2. Brunner's glands contain a large amount of a neutral mucopolysaccharide and can be used as a model for testing a large number of chemical and blockage reactions. In nearly all instances, Brunner's glands reacted more like pyloric glands than duodenal goblet cells.     

Histochemical similarities of mucins produced by Brunner's glands and pyloric glands: A comparative study

Mucins of the gastroduodenal junction are secreted by the mucous surface and mucus-producing glandular cells in the stomach, and by goblet cells and Brunner's glands in the duodenum. Developmental studies have demonstrated that Brunner's glands can arise from undifferentiated gastric epithelium and/or intestinal epithelium in the proximal duodenum. The aim of this study was to investigate the carbohydrate composition of mucins from this region and compare it with that of mucins from Brunner's glands to evaluate the probable evolution of mucins from these glands. Toward that end, paraffin sections from 13 mammalian species were stained by classic carbohydrate histochemistry and treated with 13 lectins. In general, the mucous surface cells of the stomach, pyloric glands, duodenal goblet cells, and Brunner's glands secretory epithelium had different lectin-binding patterns. However, the lectin-binding profile of the secretory epithelium of Brunner's glands resembled that of pyloric glands more closely than that of duodenal goblet cells and mucous surface cells of the stomach. Mucins from Brunner's glands and pyloric glands showed a greater terminal carbohydrate residue diversity than those of gastric mucous surface cells or duodenal goblet cells. The lectin-binding profile argues for the evolution of similar mucins from the epithelia of Brunner's glands and pyloric glands. The greater diversity of carbohydrate residues in mucins secreted by Brunner's glands suggests that their mucus is more adaptable. This may explain why Brunner's glands metaplasia rather than goblet cell metaplasia is seen in the mucosa adjacent to chronic intestinal ulcers.     

Histogenesis of gastric foveolar metaplasia following duodenal ulcer: a definite reparative lineage of Brunner's gland

AIMS: We aimed to clarify the histogenesis of gastric metaplasia in the duodenal mucosa, particularly in association with a reparative lineage of Brunner's glands. METHODS AND RESULTS: Using immunohistochemical methods with recently developed antimucin monoclonal antibodies (mAbs) that distinguish foveolar and deep mucins of the gastric type, as well as mAb MIB-1, the histogenesis of gastric metaplasia was investigated in the duodenal wall of 20 surgically resected specimens. In duodenal ulcers extending into Brunner's glands with destruction of the muscularis mucosae, proliferating cells positive for MIB-1 were scattered in Brunner's glands. Interestingly, a group of proliferating cells was often seen next to the ulcerated surface. These cells were also positive for M1 (gastric-foveolar type mucin) but negative for M2 (deep gastric and Brunner glands' mucin). In regenerating ducts through granulation tissue, the proliferating cell zone was elongated, above which foveolar-type cells positive for M1 but negative for M2 were detected, indicating that the G-zone is newly established in Brunner's glands at the floor of an ulcer to produce gastric-foveolar cells. Subsequently, an organoid growth of the normal stomach mucosa is completed in the duodenum. CONCLUSIONS: This study indicates a possible histogenetic pathway of gastric metaplasia in close association with a reparative lineage of Brunner's glands, suggesting that the occurrence of the gastric-foveolar type epi-thelium is not a simple expansion of Brunner's duct but a true metaplasia.     

Immunolocalization of the water channel, aquaporin-5 (AQP5), in the rat digestive system

Aquaporin-5 (AQP5), an isoform of membrane water channel aquaporins, is expressed in the salivary and lacrimal glands. We surveyed the expression and immunohistochemical localization of AQP5 in the rat digestive system. RT-PCR analysis revealed that AQP5 is expressed in the submandibular gland, tongue, gastric corpus, pyloric region, duodenum, and liver. Immunofluorescence microscopy using AQP5-specific antibodies showed that AQP5 protein is present in the minor salivary glands of the tongue, the pyloric glands, and duodenal glands. To distinguish apical and basolateral domains of the plasma membrane of epithelial cells, double-immunofluorescence staining for AQP5 and tight junction protein occludin was performed. In the minor salivary gland, AQP5 was present in both the serous and mixed secretory end portions. AQP5 was found in the apical membrane of the secretory cells including intercellular secretory canaliculi demarcated with occludin. At higher magnifications, omega-shaped indentations of AQP5 labeling were seen along the apical membrane, suggesting a dynamic process for the apical membrane in exocytosis. Only weak labeling for AQP5 was detected in the basolateral domain. In the stomach, AQP5 was detected in the apical membrane of the pyloric gland secretory cells. In the duodenum, AQP5 was restricted to duodenal glands, where it was localized to the apical membrane. AQP5 was not detected in the intestinal glands or cells in the villi. These observations show that AQP5 is localized mainly in the apical membrane, including intercellular secretory canaliculi of secretory cells in the minor salivary glands, pyloric glands, and duodenal glands. AQP5 appears to play an important role in water transfer in these glands.     

Definition of gastroduodenal junction in healthy subjects.

To study the appearance and distribution of the normal mucosa at the gastroduodenal junction in man, 14 specimens of normal mucosa, eight obtained during pylorplasty, and "relatively" normal specimens from the distal stomach and whole duodenum were examined microscopically. Three histologically distinct types of normal duodenal mucosa were found at this junction. These were termed antral type duodenal mucosa, transitional type duodenal mucosa (which is also referred to as gastric surface epithelial metaplasia), and jejunal type duodenal mucosa. Antral type duodenal mucosa appeared as a series of finger-like processes 1-3 mm long, circumferentially located around the junction of the antrum and duodenum; transitional type duodenal mucosa extended 2-3 mm beyond this; and the rest of the mucosa was jejunal type duodenal mucosa. The mucosa of the pyloric antrum can therefore lie adjacent to antral type duodenal mucosa, or adjacent to either of the components of transitional type duodenal mucosa.     

Pyloric gland-type tubular adenoma superimposed on intraductal papillary mucinous tumor of the pancreas

We report a rare case of pyloric gland-type tubular adenoma of the main pancreatic duct. It was a grossly visible polypoid nodule and was composed of closely packed pyloric-type glands. This adenoma was present within an intraductal papillary mucinous adenoma (IPMA). In this IPMA lesion, aggregations of pyloric-type glands were occasionally observed, and most of the cells including ductal lining cells expressed pyloric gland-type mucin. The IPMA of the present case showed more extensive pyloric gland metaplasia or differentiation than commonly noted in IPMAs. We consider this pyloric gland-type tubular adenoma to be derived from a selective growth of IPMA cells showing pyloric gland metaplasia.     

Adenoma with gastric differentiation (so-called pyloric gland adenoma) in a heterotopic gastric corpus mucosa in the rectum

In a 46-year-old man, a pedunculated rectal polyp measuring 3.0×3.0×2.0 cm was diagnosed histologically as a pyloric gland-type adenoma arising in heterotopic gastric corpus mucosa. The luminal site was covered by glands of the gastric foveolar type, displaying focal marked proliferation interpreted as low-grade intraepithelial neoplasia. A bidirectional gastric differentiation was found: most lower glandular structures showed positivity for the deep gastric mucin core protein Muc 6 and superficial positivity for gastric foveolar epithelium mucin core protein Muc 5AC. Pyloric gland adenoma has so far been described in one larger series only and a few case reports of the stomach, gallbladder, pancreatic duct and within heterotopic gastric corpus mucosa of the duodenal bulb. The present case report is the first case of a pyloric gland-type adenoma within a gastric corpus heterotopia of the rectal mucosa.     

Golgi apparatus of epithelial principal cells of the epididymal initial segment of the rat: structure, relationship with endoplasmic reticulum, and role in the formation of secretory vesicles.

The initial segment of the epididymis of rats, fixed with glutaraldehyde, was postfixed with reduced osmium, a technique that clearly delineates the membranes of cisternae of the endoplasmic reticulum (ER) and the various elements of the Golgi apparatus, or with tannic acid to enhance the coats of vesicles and ribosomes on ER cisternae. The material was also treated to demonstrate various phosphatase activities (NADPase, TPPase, CMPase, G-6-Pase) or impregnated with osmium tetroxide. In osmium-impregnated material, the Golgi apparatus of the epithelial principal cells of the initial segment appeared in the light microscope as a branching, anastomosing ribbon forming a large network in the supranuclear region. In the electron microscope, ER were of two types: the heavily granulated, flattened, rough ER seen in the infranuclear and juxtanuclear regions and the distended, tubular, sparsely granulated ER, showing only few ribosomes, seen interlaced with the Golgi ribbon in the supranuclear region and at the apical pole of the cell. Of particular interest in this cell was the fact that the sparsely granulated ER approximated the Golgi stack on both its cis- and trans-faces. On the cis-face of the Golgi stack, the sparsely granulated ER cisternae showed the usual finger- or bud-like protrusions directed toward the cis element of the Golgi stack and around which numerous small 80 nm vesicles or membranous tubules were clustered. The Golgi stack consisted of the following elements in a cis-trans axis: the cis osmiophilic element, a first saccule slightly dilated, saccules two to four (S2-S4), which were NADPase-positive, and saccules five to seven and the eight Golgi element, which were TPPase-positive. On the trans-aspect of the Golgi stacks, several (up to four) CMPase-positive trans-Golgi networks were observed often in close apposition to the sparsely granulated ER cisternae. One of the trans-Golgi networks showed a "peeling-off" configuration, i.e. part of it was closely apposed to the overlying Golgi element of the stack, whereas the remaining part was separated from the stack by a space occupied by a cisterna of sparsely granulated ER. The other trans-Golgi networks were completely separated from the stack and were often seen sandwiched between sparsely granulated ER cisternae. Thus, ER cisternae showed extensive areas of close apposition but no continuity with the trans-Golgi networks. Although the saccules of the Golgi stacks showed NADPase and/or TPPase activity, the trans-Golgi networks displayed CMPase activity, thus facilitating their identification from the closely associated unreactive sparsely granulated ER cisternae.(ABSTRACT TRUNCATED AT 400 WORDS)     

Diagnostic challenge: Intraductal neoplasms of the pancreatobiliary system

To help pathologists avoid misdiagnosis of intraductal neoplasms arising from the pancreatobiliary system, we report two cases that illustrate diagnostic pitfalls. The first is of a 66-year-old man who complained of appetite loss. An early examination led to a diagnosis of intraductal papillary mucinous neoplasm. Macroscopically, a multilocular cyst without visible mucin was identified. Histologically, the compartments consisted of complex fusion of tubular glands surrounded by dilated pancreatic duct. The neoplasm resembled an acinar cell cystadenocarcinoma. However, the neoplastic cells were negative for trypsin. Thus, the final histopathologic diagnosis was an unusual cystic variant of intraductal tubulopapillary neoplasm (ITPN) of the pancreas. The second case is of a 71-year-old man who complained of right upper quadrant pain. Although bile duct stone was suspected, a polypoid nodule was extracted. Histologically, the nodule was composed of tubular glands, with some complex fusion and focal dysplasia, consistent with carcinoma. In addition, lack of MUC-5AC expression led to an initial impression of ITPN of the bile duct. However, the neoplasm showed dysplastic cells based on the columnar cells resembling pyloric glands, indicating the sequential progression. Thus, the final histopathological diagnosis was intraductal papillary neoplasm of the bile duct with high-grade intraepithelial neoplasia. Because phenotypic variants of intraductal neoplasms of the pancreatobiliary system exist, ITPN and ITPN-mimicking tumor must be carefully differentiated from other intraductal neoplasms.     

Scanning electron microscopic studies on the subepithelial tissue of the gastrointestinal mucosa of the rat

The three-dimensional architecture of the subepithelial tissue of the gastric, the small and the large intestinal mucosa of the rat was observed by scanning electron microscopy (SEM) after removal of cellular elements through prolonged osmication followed by ultrasonication (the method by Highison and Low, 1982), or by cell-maceration with a low temperature NaOH solution (the method by Ohtani, 1987). The basal lamina was exposed by the former method, and the collagenous fibrous sheet immediately under the basal lamina was disclosed by the latter. The surface of the subepithelial tissue is grossly smooth in the pyloric gland and crypts of the small and the large intestine. However, in the fundic glands of the stomach, the surface structure of the subepithelial tissue greatly differs according to glandular location. In the pit of the fundic glands, the surface of both the basal lamina and the sub-basal laminar fibrous sheet is smooth. In the neck region, however, shallow round depressions are seen. The most striking feature of the subepithelial tissue of the fundic glands is the presence of numerous hemispherical concavities in the middle and basal regions of the glands which harbor parietal cells. On the surface of the small intestinal villi, the basal lamina is elevated by the underlying capillary network and forms a meshwork of ridges that surround shallow basins in which numerous round fenestrations 1-5 microns in diameter are seen. The fibrous sheath of the marginal arteriole is observed as a cord-like protuberance on the apical margin of the villi; this suggests its role in the maintenance of the structural integrity of the villi. In the large intestine, well defined round fenestrations are clearly seen, mainly distributed on the upper third of the crypts, and continuing to the lamina propria.     

The fine structure and histochemistry of human bile duct in obstruction and choledocholithiasis

Biopsies from the common bile ducts from seven patients undergoing surgery for biliary obstruction due to stones or malignancy were studied histochemically and electron microscopically. The surface of the bile duct is lined by a tall epithelium which extends into diverticula. Apically, they contain some neutral and sialated mucosubstances. Fucosyl residues were found in the Golgi apparatus and along the apical cell membrane. The latter is lined by microvilli. There was a well-developed rough endoplasmic reticulum and Golgi apparatus and a small number of apical secretory droplets. Large numbers of lipid droplets were present basally in some cells. Lipid-containing macrophages were also seen intra-epithelially and in the lamina propria. This suggests a possible pathway for lipid transport. The glands were lined by cuboidal cells, some containing much mucus--sulphated, sialated, and neutral with a basal nucleus. A well-developed endoplasmic reticulum and Golgi apparatus were found with abundant secretory droplets. The glandular epithelium contained lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. These may play a protective role. The lamina propria contained scattered smooth muscle cells amongst the fibroblasts and inflammatory cells.     

Metaplastic lesions of the extrahepatic bile ducts: a morphologic and immunohistochemical study.

Although metaplastic changes can occur in the extrahepatic bile ducts, a detailed morphologic study of these lesions has not been done. We examined the bile duct mucosa in 42 pancreaticoduodenectomy specimens, 32 with neoplastic lesions and ten with inflammatory lesions of the extrahepatic bile ducts, to assess the prevalence and type of metaplastic lesions. For comparison, the common bile ducts from 10 autopsy cases were reviewed. Twenty of the 42 total cases (48%), 13 of the 32 neoplastic cases (40%), and 7 of the 10 inflammatory cases (70%) had metaplastic changes. Pyloric gland metaplasia was the most common type (16/20 cases; 80%), whereas intestinal metaplasia was seen in 1/20 cases (5%). A combination of pyloric gland and intestinal metaplasia occurred in 2/20 cases (10%), and squamous metaplasia plus the above-mentioned two types of metaplasia was seen in 1/20 cases (5%). None of the normal common bile ducts obtained from ten autopsies had metaplastic changes. Endocrine cells were identified in nine (56%) of 17 metaplastic lesions. In contrast, endocrine cells within the intramural glands were seen in only 2 of the 10 normal common bile ducts. Although a significant proportion of carcinomas (6/13 cases) was in close proximity to areas of metaplasia, we were unable to find dysplastic foci within the metaplastic glands or the metaplastic surface epithelium. Reactive atypical cells involved the surface biliary epithelium and intramural glands and were associated with inflammation and metaplastic changes. The presence of goblet, mucinous, squamous, and reactive atypical cells in association with hyperplasia of intramural glands in frozen sections or small biopsy specimens may be mistaken for malignancy; hence, recognition of these lesions is of diagnostic importance.     

Microangioarchitecture of the guinea pig common bile duct and duodenal papilla: A scanning electron and light microscopic study

Background: The microvascular pattern of the duodenal papilla is unknown. Since the duodenal papilla is located in the transition zone between the stomach and duodenum, and because it regulates bile transfer into the duodenum, a particular microangioarchitecture can be expected. Therefore, we examined the microvasculature of the papilla using guinea pigs as a model. Methods: The microvascularization of the duodenal papilla and common bile duct was studied in 26 adult guinea pigs (Cavia porcellus), using scanning electron microscopy of microvascular corrosion casts and critical point dried specimens, and light microscopy of tissue sections. Results: The duodenal papilla is located in the cranial portion of the duodenum, approximately 5 mm beyond the pyloric valve. At the most luminal aspect of the cast papilla, ring-shaped capillaries, resembling those of the cast gastric mucosa, are present. Deeper parts of the papilla are provided with villi. Subepithelial capillaries of the papilla are 15 μm thick in average. These capillaries have a dual blood supply either via the straight long arterioles arising from the submucosa or by the pericryptal capillaries. The common bile duct comprises numerous mucoid glands with their pits surrounded by ring-shaped capillaries in corresponding casts. Conclusions: The special arrangement of different capillary patterns, together with their luminal size and the dual blood supply, favor their protective role from the gastric chyme. © 1994 Wiley-Liss, Inc.