The relation between structure and function of bile ducts in man, some laboratory animals and the Adelie penguin.

The biliary trees of man, dog, cat, rabbit, rat, guinea pig and penguin were examined in histological sections and by latex casts. The trees of man, dog, and cat were similar with only minor differences. Tubulo-alveolar glands were present in all three species around large intrahepatic ducts and in large portal tracts there were zones of ductules (areas with many small bile ducts), surrounded by small vessels with no apparent relation to hepatocytes. Both these features were present in the guinea pig and tubulo-alveolar glands were present in the penguin liver. The biliary epithelium of the rat was comparatively simple but that of the rabbit appeared to be highly specialized. An estimation of the complexity of the biliary tree was obtained in the mammals by comparing the circumference of small portal venous branches with the circumference of the accompanying bile ducts, and obtaining a ratio. Man, dog, and cat had fewer and smaller bile ducts than the other species. The literature on the rate of formation and composition of bile in the species studied here was reviewed and it appears that the physiology of bile secretion can be related to the morphology of the biliary tree.     

Expression of neural cell adhesion molecule in human liver development and in congenital and acquired liver diseases

In the liver, neural cell adhesion molecule (NCAM) is a marker of immature cells committed to the biliary lineage and is expressed by reactive bile ductules in human liver diseases. We investigated the possible role of NCAM in the development of intrahepatic bile ducts and aimed at determining whether immature biliary cells can contribute to the repair of damaged bile ducts in chronic liver diseases. Therefore, we performed immunohistochemistry for NCAM and bile duct cell markers cytokeratin 7 and cytokeratin 19 on frozen sections of 85 liver specimens taken from 14 fetuses, 10 donor livers, 18 patients with congenital liver diseases characterized by ductal plate malformations (DPMs), and 43 cirrhotic explant livers. Duplicated ductal plates and incorporating bile ducts during development showed a patchy immunoreactivity for NCAM, while DPMs were continuously positive for NCAM. Bile ducts showing complete or patchy immunoreactivity for NCAM were found in cirrhotic livers, with higher frequency in biliary than in posthepatitic cirrhosis. Our results suggest that NCAM may have a function in the development of the intrahepatic bile ducts and that NCAM-positive immature biliary cells can contribute to the repair of damaged bile ducts in chronic liver diseases.     

Aquaporin-5 water channel in lipid rafts of rat parotid glands

Aquaporin-5 (AQP5), an apical plasma membrane (APM) water channel in salivary glands, lacrimal glands, and airway epithelium, has an important role in fluid secretion. The activation of M3 muscarinic acetylcholine receptors (mAChRs) or α1-adrenoceptors on the salivary glands induces salivary fluid secretion. AQP5 localizes in lipid rafts and activation of the M3 mAChRs or α1-adrenoceptors induced its translocation together with the lipid rafts to the APM in the interlobular ducts of rat parotid glands. This review focuses on the mechanisms of AQP5 translocation together with lipid rafts to the APM in the interlobular duct cells of parotid glands of normal rats and the impairment of AQP5 translocation in diabetes and senescence.     

Aquaporin-5 water channel in lipid rafts of rat parotid glands

Aquaporin-5 (AQP5), an apical plasma membrane (APM) water channel in salivary glands, lacrimal glands, and airway epithelium, has an important role in fluid secretion. The activation of M3 muscarinic acetylcholine receptors (mAChRs) or alpha1-adrenoceptors on the salivary glands induces salivary fluid secretion. AQP5 localizes in lipid rafts and activation of the M3 mAChRs or alpha1-adrenoceptors induced its translocation together with the lipid rafts to the APM in the interlobular ducts of rat parotid glands. This review focuses on the mechanisms of AQP5 translocation together with lipid rafts to the APM in the interlobular duct cells of parotid glands of normal rats and the impairment of AQP5 translocation in diabetes and senescence.     

The ultrastructure of the duct system in the rat extraorbital lacrimal gland

Summary The duct system of the rat exorbital lacrimal gland consists of intercalated ducts, interlobular ducts and excretory ducts. The morphological changes from one type of duct to the next are gradual. At the light microscopical level this consists of a change from a bilaminar epithelium in the intercalated ducts to an epithelium, consisting of approximately three layers — which may be pseudostratified — in the excretory ducts. The basal layer of the intercalated ducts consists of myoepithelial cells, whereas the inner epithelial cells may have both a secretory and an electrolyte transporting function. The interlobular duct epithelium contains many cells with deep infoldings of the basolateral plasma membranes and associated mitochondria, suggesting a similar function to the striated duct epithelium in salivary glands. Numerous basal cells in this epithelium have tentatively been interpreted as unusual myoepithelial cells. Nerve terminals have been observed in the ductal epithelium.This work was supported by the National Health and Medical Research Council of Australia. — We wish to thank Mrs. Eva Vasak for her expert technical assistance.     

胚胎期及成年大白鼠肝脏的表皮角蛋白免疫细胞化学定位

应用自制的表皮角蛋白(EK)家兔抗体,对胚胎期及成年大白鼠的肝脏进行免疫细胞化学定位。结果表明,大白鼠肝脏内,肝细胞EK阴性,胆管上皮细胞EK明确阳性;大白鼠胚胎肝脏也显示出这种EK染色差别。随着肝内胆管上皮的形成,EK阳性物质在其胞浆内出现。作者认为,EK阳性物质的出现是肝内胆管上皮结构分化的结果。     

Administration of r-VEGF-A prevents hepatic artery ligation-induced bile duct damage in bile duct ligated rats

The hepatic artery, through the peribiliary plexus, nourishes the intrahepatic biliary tree. During obstructive cholestasis, the nutritional demands of intrahepatic bile ducts are increased as a consequence of enhanced proliferation; in fact, the peribiliary plexus (PBP) displays adaptive expansion. The effects of hepatic artery ligation (HAL) on cholangiocyte functions during cholestasis are unknown, although ischemic lesions of the biliary tree complicate the course of transplanted livers and are encountered in cholangiopathies. We evaluated the effects of HAL on cholangiocyte functions in experimental cholestasis induced by bile duct ligation (BDL). By using BDL and BDL + HAL rats or BDL + HAL rats treated with recombinant-vascular endothelial growth factor-A (r-VEGF-A) for 1 wk, we evaluated liver morphology, the degree of portal inflammation and periductular fibrosis, microcirculation, cholangiocyte apoptosis, proliferation, and secretion. Microcirculation was evaluated using a scanning electron microscopy vascular corrosion cast technique. HAL induced in BDL rats 1) the disappearance of the PBP, 2) increased apoptosis and impaired cholangiocyte proliferation and secretin-stimulated ductal secretion, and 3) decreased cholangiocyte VEGF secretion. The effects of HAL on the PBP and cholangiocyte functions were prevented by r-VEGF-A, which, by maintaining the integrity of the PBP and cholangiocyte proliferation, prevents damage of bile ducts following ischemic injury.     

Ultrastructure of human labial salivary glands. 3. Myoepithelium and ducts

Myoepithelial cells were present between the basal lamina and the acinar secretory cells of human labial salivary glands. In form and disposition, they resembled myoepithelial cells in the major salivary glands. Many of these cells possessed single cilia on their upper surfaces. Such cilia occasionally extended into invaginations of the overlying secretory cell. The intercalated ducts were variable in occurrence. Their epithelium ranged from columnar to squamous, and showed few signs of secretory activity. Few intralobular ducts possessed basal striations. While mitochondria were abundant in non-striated cells, they were randomly disposed in both basal and apical cytoplasm, and the basal plasmalemma showed only occasional infoldings. The paucity of true striated ducts in labial salivary glands may be responsible for the high concentration of sodium and chloride in unstimulated labial gland salivary secretions.     

Immunocytochemical identification of cell types in human mammary gland: variations in cellular markers are dependent on glandular topography and differentiation

Antiserum to epithelial membrane antigen and three monoclonal antibodies (MAb) to milk-fat globule membranes immunocytochemically stain only epithelial cells, whereas a fourth reacts also with myoepithelial cells in inter- and intralobular ducts of human breast. Staining with peanut lectin shows a gradual increase for epithelial cells, from little or no staining in ducts through variable staining in ductules to intense staining in secretory alveoli. Antisera and MAb to vimentin, smooth-muscle actin, MAb to the common acute lymphoblastic leukemia antigen and to a glycoprotein of 135 KD stain myoepithelial cells in main ducts, but this staining is reduced in inter- and intralobular ducts and ductules. MAb to epithelial-specific keratin 18 stain a minor population of ductal epithelial cells, the major population of epithelial cells in interlobular (ILD) and extralobular terminal ducts (ETD), and epithelial cells in a minority of ductules. In lactating glands most epithelial cells in ductules are stained, but the alveolar and myoepithelial cells are unstained. Keratin MAb PKK2 and LP34 strongly stain myoepithelial cells, but only a minor population of epithelial cells in main ducts. However, these MAb stain principally the epithelial cells in ILD, ETD, and a minority of ductules. In lactating glands most epithelial cells are stained in ductules, but the myoepithelial and not the alveolar cells are stained intensely in secretory lobules. It is suggested that the unusual staining pattern of cells found principally in the ILD, ETD, and some ductules may represent regions of growth and/or subpopulation(s) of cells intermediate between epithelial and myoepithelial cells.     

Identification of AQP5 in lipid rafts and its translocation to apical membranes by activation of M3 mAChRs in interlobular ducts of rat parotid gland

Aquaporin-5 (AQP5), an apical plasma membrane (APM) water channel in salivary glands, lacrimal glands, and airway epithelium, has an important role in fluid secretion. M₃ muscarinic acetylcholine receptor (mAChR)-induced changes in AQP5 localization in rat parotid glands were investigated with immunofluorescence or immunoelectron microscopy, detergent solubility, and gradient density floatation assays. Confocal microscopy revealed AQP5 localization in intracellular vesicles of interlobular duct cells in rat parotid glands and AQP5 trafficking to the APM 10 min after injection of the mAChR agonist cevimeline. Conversely, 60 min after injection, there was a diffuse pattern of AQP5 staining in the cell cytoplasm. The calcium ionophore A-23187 mimicked the effects of cevimeline. Immunoelectron microscopic studies confirmed that cevimeline induced AQP5 trafficking from intracellular structures to APMs in the interlobular duct cells of rat parotid glands. Lipid raft markers flotillin-2 and GM1 colocalized with AQP5 and moved with AQP5 in response to cevimeline. Under control conditions, the majority of AQP5 localized in the Triton X-100-insoluble fraction and floated to the light-density fraction on discontinuous density gradients. After 10-min incubation of parotid tissue slices with cevimeline or A-23187, AQP5 levels decreased in the Triton X-100-insoluble fraction and increased in the Triton X-100-soluble fraction. Thus AQP5 localizes in the intracellular lipid rafts, and M₃ mAChR activation induces AQP5 trafficking to the APM with lipid rafts via intracellular Ca²⁺ signaling and induces AQP5 dissociation from lipid rafts to nonrafts on the APM in the interlobular duct cells of rat parotid glands. translocation; aquaporin-5     

Irisin immunohistochemistry in gastrointestinal system cancers

Cancer is the leading cause of morbidity and mortality worldwide. Some studies have shown that high heat kills cancer cells. Irisin is a protein involved in heat production by converting white into brown adipose tissue, but there is no information about how its expression changes in cancerous tissues. We used irisin antibody immunohistochemistry to investigate changes in irisin expression in gastrointestinal cancers compared to normal tissues. Irisin was found in human brain neuroglial cells, esophageal epithelial cells, esophageal epidermoid carcinoma, esophageal adenocarcinoma and neuroendocrine esophageal carcinoma, gastric glands, gastric adenosquamous carcinoma, gastric neuroendocrine carcinoma, gastric signet ring cell carcinoma, neutrophils in vascular tissues, intestinal glands of colon, colon adenocarcinoma, mucinous colon adenocarcinoma, hepatocytes, hepatocellular carcinoma, islets of Langerhans, exocrine pancreas, acinar cells and interlobular and interlobular ducts of normal pancreas, pancreatic ductal adenocarcinoma, and intra- and interlobular ducts of cancerous pancreatic tissue. Histoscores (area × intensity) indicated that irisin was increased significantly in gastrointestinal cancer tissues, except liver cancers. Our findings suggest that the relation of irisin to cancer warrants further investigation.     

Altered alkaline phosphatase activity in obese Zucker rats liver respect to lean Zucker and Wistar rats discussed in terms of all putative roles ascribed to the enzyme

Biliary complications often lead to acute and chronic liver injury after orthotopic liver transplantation (OLT). Bile composition and secretion depend on the integrated action of all the components of the biliary tree, starting from hepatocytes. Fatty livers are often discarded as grafts for OLT, since they are extremely vulnerable to conventional cold storage (CS). However, the insufficiency of donors has stimulated research to improve the usage of such marginal organs as well as grafts. Our group has recently developed a machine perfusion system at subnormothermic temperature (20°C; MP20) that allows a marked improvement in preservation of fatty and even of normal rat livers as compared with CS. We sought to evaluate the response of the biliary tree of fatty liver to MP20, and a suitable marker was essential to this purpose. Alkaline phosphatase (AlkP, EC 3.1.3.1), frequently used as marker of membrane transport in hepatocytes and bile ducts, was our first choice. Since no histochemical data were available on AlkP distribution and activity in fatty liver, we have first settled to investigate AlkP activity in the steatotic liver of fatty Zucker rats (fa/fa), using as controls lean Zucker (fa/+) and normal Wistar rats. The AlkP reaction in Wistar rats was in accordance with the existing data and, in particular, was present in bile canaliculi of hepatocytes in the periportal region and midzone, in the canals of Hering and in small bile ducts but not in large bile ducts. In lean ZR liver the AlkP reaction in Hering canals and small bile ducts was similar to Wistar rat liver but hepatocytes had lower canalicular activity and besides presented moderate basolateral reaction. The difference between lean Zucker and Wistar rats, both phenotypically normal animals, could be related to the fact that lean Zucker rats are genotypically heterozygous for a recessive mutated allele. In fatty liver, the activity in ductules and small bile ducts was unchanged, but most hepatocytes were devoid of AlkP activity with the exception of clusters of macrosteatotic hepatocytes in the mid-zone, where the reaction was intense in basolateral domains and in distorted canaliculi, a typical pattern of cholestasis. The interpretation of these data was hindered by the fact that the physiological role of AlkP is still under debate. In the present study, the various functions proposed for the role of the enzyme in bile canaliculi and in cholangiocytes are reviewed. Independently of the AlkP role, our data suggest that AlkP does not seem to be a reliable marker to study the initial step of bile production during OLT of fatty livers, but may still be used to investigate the behaviour of bile ductules and small bile ducts.     

Biliary papillary neoplasm of the liver

Biliary papillary neoplasia of the liver characterized by intraductal papillary growth of neoplastic biliary epithelia with a fine fibrovascular stalk has been sporadically reported, and includes intraductal growing cholangiocarcinoma and biliary papillomatosis. In addition, biliary papillary dysplasia and in situ and microinvasive carcinoma with papillary configuration reported in hepatolithiasis and in other chronic biliary diseases, could be included in this category. Usually, they arise in the intrahepatic large bile ducts, and the neoplastic and non-neoplastic parts of the intrahepatic biliary tree show saccular and segmental dilatation with mucin hypersecretion. This neoplasia frequently shows intraductal spreading and peribiliary glandular involvement. Acute repeated episodes of cholangitis or obstructive jaundice are a frequent clinical manifestation. Gastroenteric metaplasia with aberrant expression of cytokeratin 20, MUC2, MUC5AC, and/or MUC6, is frequent in the neoplastic parts, and biliary epithelial dysplasia with such metaplasia may give rise to in situ and then invasive carcinoma in hepatolithiasis. Interestingly, this type tends to contain foci of mucinous carcinoma elements, and this element may be predominant (mucinous carcinoma). Some may progress to "mucinous biliary cystadenocarcinoma" without ovarian mesenchymal stroma and with intraluminal continuous growth into the neighboring bile duct lumens. Interestingly, the biliary papillary neoplasm resembles histologically, phenotypically and clinically intraductal papillary mucinous neoplasm of the pancreas which is now being established as an infrequent, slow-growing pancreatic neoplasm. Recognition of such biliary papillary neoplasm with respect to the pancreatic equivalent may lead to a better understanding and further studies of the intrahepatic biliary neoplasm.     

Histological study of the teleost liver. III. The system of biliary pathways]

In the liver of Haplochromis burtoni four divisions of the intrahepatic biliary pathways can be distinguished: canaliculus, canaliculus ductulus transition, ductulus biliferus, ductus biliferus. There are no transitional stages between the hepatocytes and biliary epithelial cells. The results of the investigation suggest that the ductules open into the ducts in two ways, directly and by graded transition of structure. The first part of the ductulus has a very narrow lumen and therefore is similar to the "Schaltstück" of salivary glands. Terminal ductulus cells can protrude into the canaliculus (= lumen of the liver tubulus), giving the appearance of centrotubular cells in cross-section. In the liver of most of the teleosts investigated here the canaliculi are intercellular. Tangentially cut diverticuli of the canaliculi appear to be unicellular ("intracellular") canaliculi, but are, however, merely unicellular ("intracellular") protrusions of the intercellular canaliculi. On the other hand the three cyprinid species (Barbus tetrazona, Idus idus, Carassius auratus) possess true unicellular ("intracellular") canaliculi. These can definitely be distinguished from the diverticuli of intercellular canaliculi by several criteria. Phylogenetically the unicellular ("intracellular") canaliculus must be regarded as derivative, and the intercellular canaliculus as the original form. The morphology of the wall of the gall-bladder of Haplochromis burtoni indicates that transfer of substances is increased together with transportation and drainage of fluids and variations in volume. The ultrastructure of the epithelial cells reveals a zonal arrangement.     

Spontaneous hyperplastic and metaplastic duct epithelium in the sublingual salivary glands of Wistar rats

Focal epithelial hyperplasia and metaplasia were observed in the intralobular ducts of the sublingual salivary glands of 302 out of 1142 Wistar rats. These rats (aged 16-145 weeks) served as controls in toxicological experiments. The ductal changes varied from small groups of irregular cylindrical cells with basophilic cytoplasm and vesicular nuclei, with often prominent nucleoli, to large areas of non-keratinized stratified squamous epithelium with marked mitotic activity and necrotic superficial cells being released in the lumen. Mononuclear inflammatory cells were often present in fibrous tissue surrounding altered ducts. Within certain limits the degree and incidence of the changes increased with increasing age; their aetiology is unknown.     

Immunolocalization of PTHrP in the sublingual glands of three mammals

The present study deals with immunohistochemical localization of PTHrP in sublingual glands of white mouse, bank vole, and common vole. PTHrP immunoreactivity was observed in epithelial cells of striated, interlobular and main excretory ducts of the salivary glands in all the three animal species tested. However, we found no positive reaction for PTHrP in epithelial cells of the intercalated ducts. In striated duct cells, the reaction intensity was species-dependent. In bank vole and common vole, the reaction was very strong, while in white mouse very weak. In the remaining segments of excretory ducts (interlobular and main excretory duct) we found no species-related differences in the reaction intensity or character. Myoepithelial cells surrounding ducts and mucous tubules with serous demilunes in sublingual glands were also PTHrP-negative in all the three animal species tested.     

Comparative distribution of carbonic anhydrase isozymes III and II in rodent tissues

Carbonic anhydrase (CA) III was demonstrated immunocytochemically in epithelium in some regions of salivary gland ducts, colon, bronchi, and male genital tract and in adipocytes, in addition to skeletal muscle and liver where the isozyme was previously localized. Basal cells beneath the submandibular gland's excretory ducts in guinea pig stained for CA III. Carbonic anhydrase III occurred alone in some and with CA II in other sites but was often absent from CA-II-containing types of cells. This was exemplified by CA III's abundance in CA-II-positive proximal colon and its sparsity in the CA-II-rich distal colon of the mouse. Striated ducts in guinea pig, but not mouse salivary glands, stained darker for CA and appeared accordingly to function more actively in ion transport compared with excretory ducts. Carbonic anhydrase content varied among genera in liver and pancreas and between mouse species and strains in salivary glands and kidney. Newly observed murine sites of CA II activity included Auerbach's plexus and a population of leukocytes infiltrating the lamina propria in small intestine, and several types of cells in the male genital tract. In immunoblot tests, antisera to CA III showed no cross reactivity with antisera to CA II, but those to CA II disclosed weak cross reactivity with CA III.     

Guanylin and uroguanylin in the parotid and submandibular glands: potential intrinsic regulators of electrolyte secretion in salivary glands

The intestinal peptides guanylin and uroguanylin regulate the electrolyte/water transport in the gastrointestinal epithelium via activation of cystic fibrosis transmembrane conductance regulator (CFTR), the cystic fibrosis gene product. Because a major but incompletely understood function of the salivary glands is the CFTR-mediated secretion of an electrolyte-rich fluid, we investigated the rat and guinea pig parotid and submandibular glands for expression, cellular distribution, and subcellular localization of guanylin and uroguanylin. RT-PCR analyses with guanylin and uroguanylin-specific primers revealed that both peptides are highly expressed in the parotid and submandibular glands. At the translational level, western blotting analyses with peptide-specific guanylin and uroguanylin antibodies identified the expected 12.5-kDa immunoreactive peptides in these organs. At the cellular level, guanylin and uroguanylin were exclusively confined to epithelial cells of the intralobular and interlobular ducts. At the subcellular level, the immunoreactivities were localized by preembedding immunoelectron microscopy to small vesicles which were concentrated at the apical part of the secretory epithelial cells. The expression and cell-specific localization of guanylin and uroguanylin in the salivary glands indicate that these peptides may be specifically involved in the regulation of CFTR-mediated electrolyte/water secretion in the salivary gland ductal system.