The surface characteristics of the plasma membrane of the exocrine pancreas

Regional differentiation of the plasma membrane and related structures of the exocrine pancreas has been studied ultrastructurally and cytochemically. Fixation with an osmium tetroxide-silver acetate solution produced abundant fine precipitates on the luminal and basal surface of the centroacinar but not the acinar cells. Staining with dialyzed iron (DI) revealed the heaviest concentration of anionic sites on the luminal plasma membrane of the acinar cells, including the surface of both the intercellular canaliculi and the main lumen. The reactive sites on the apical acinar plasmalemma appeared to consist of discrete globules. DI-reactivity of the lateral basal membranes was most prominent in the centroacinar cells and essentially absent in the acinar cells but was weak relative to that of the acinar-cell apical plasmalemma. The lamina lucida of the basement membrane of the duct stained with DI, but that of basement membrane under acinar cells did not. Sialidase digestion prior to DI staining abolished the staining of plasma membranes. These results indicate that duct epithelial cells, including most prominently the centroacinar cells, are chiefly responsible for electrolyte and fluid transport.     

The fine structure of the exocrine pancreas of the mink (author's transl)]

The pancreas of female mink has been investigated by transmission electron microscopic means. The following results can be summarized: The pancreas of the mink is built up by the well known gland lobules as found in many other species; each lobule contains branched ducts with acini. The acinar cells are characteristically packed with granular endoplasmic reticulum, large Golgi apparatuses, and zymogen granules. Particularly interesting are large vacuoles, which seem to emerge directly from the endoplasmic reticular cysternae. The centroacinar cells form relatively extended protrusions or pseudopodia, which frequently penetrate into the intercellular spaces between neighbouring acinar cells. The peripheral isthmic parts of the ducts are covered by an isoprismatic epithelium. The adventitial tissue of the intralobular ducts contain mucous glands. Within the loose connective tissue between the exocrine cells, blood vessels as well as numerous nerves can be found. These results are compared to earlier reports on the same subject, and are also discussed together with available data from the literature.     

An autoradiographic study of the cell proliferation during involution of the rat pancreas

After ligation of the rat pancreas, DNA synthesis in centoacinar cells and cells of the intercalary ducts, proximal and distal to the ligature, was suppressed for about 18 hr. This preceded a large increase in thymidine labelling of the nuclei of these cells. The increase in the thymidine indices was much greater and more prolonged in the distal pancreas where duct-like structures were formed that replaced the acini. DNA synthesis in acinar cells proximal to the ligature was suppressed for 36 hr preceding an increase in the thymidine indices much smaller than that in the duct cells. DNA synthesis in acinar cells distal to the ligature ceased and the acinar cells progressively died. We propose that the pancreas is composed of proliferative units, each comprising acinar cells, centroacinar cells and intercalary ducts, which react as a whole when acinar cell loss occurs in pathological processes.     

An in vitro model of pancreatic carcinoma. Morphology and in vivo growth.

Pancreas rudiments from 13-day rat embryos were cultured in the presence of dimethylnitrosamine (DMN) for up to 10 weeks. Pancreas morphogenesis and differentiation occurred during the first week of culture. Acinar cell degeneration and necrosis began on the fifth day of culture and resulted in almost complete loss of acinar cells, islet cells, and fibroblasts by the end of the third week. This was associated with proliferation of cells without zymogen granules (centroacinar, ductal, or undifferentiated?). Theses cells formed glandular structures which extended to the surface of the explant. By the end of the fourth week, explants resembled ductal hyperplasia with foci of carcinoma in situ. The distribution pattern of neoplasia in 343 explants examined after 10 weeks of DMN treatment was as follows: 79% resembled ductal cell carcinoma; 9%, ductal hyperplasia; and 3%, acinar cell carcinoma. Nude mice injected with cell suspensions prepared from 10-week-old culture developed subcutaneous nodules. These nodules resembled duct cell carcinoma with desmoplastic reaction.     

Immunocytochemical localization of a kallikrein-like serin protease (Esterase A) in rat salivary glands

Light and electron microscopic (EM) immunocytochemical methods have been used to localize arginine esterase A, a kinin-generating enzyme immunologically similar to tissue kallikrein, in rat salivary glands. Both polyclonal and monoclonal antibodies to arginine esterase A were used in these studies. By means of a polyclonal antiserum, esterase A was found in granular tubules of submandibular glands and in striated ducts of all three major salivary glands, in a distribution similar to that of tissue kallikrein. With recently developed specific monoclonal antibodies to esterease A, this enzyme was localized in the granules of some (but not all) granular convoluted tubule cells (GCT) and along the basal membranes (but not in apical granules) of striated ducts. By an EM immunoperoxidase method, esterase A was localized subcellularly in granules of some GCT cells and along the basal cell membranes of the tubule and duct system. Thus, this enzyme is found in some sites (GCT granules) shared with tissue kallikrein, but in some unique sites, i.e., basal membranes of striated ducts. The polyclonal antibody used in the present study cross-reacted with tissue kallikrein, but when absorbed with kallikrein, it gave the staining pattern characteristic of monoclonal antibody to esterase A.     

Immunocytochemical localization of a kallikrein-like serine protease (esterase A) in rat salivary glands

Light and electron microscopic (EM) immunocytochemical methods have been used to localize arginine esterase A, a kinin-generating enzyme immunologically similar to tissue kallikrein, in rat salivary glands. Both polyclonal and monoclonal antibodies to arginine esterase A were used in these studies. By means of a polyclonal antiserum, esterase A was found in granular tubules of submandibular glands and in striated ducts of all three major salivary glands, in a distribution similar to that of tissue kallikrein. With recently developed specific monoclonal antibodies to esterase A, this enzyme was localized in the granules of some (but not all) granular convoluted tubule cells (GCT) and along the basal membranes (but not in apical granules) of striated ducts. By an EM immunoperoxidase method, esterase A was localized subcellularly in granules of some GCT cells and along the basal cell membranes of the tubule and duct system. Thus, this enzyme is found in some sites (GCT granules) shared with tissue kallikrein, but in some unique sites, i.e., basal membranes of striated ducts. The polyclonal antibody used in the present study cross-reacted with tissue kallikrein, but when absorbed with kallikrein, it gave the staining pattern characteristic of monoclonal antibody to esterase A.     

Transient occurrence of 27 kDa heat‐shock protein in the terminal tubule cells during postnatal development of the rat submandibular gland

It has been suggested that the 27 kDa heat‐shock protein (Hsp27) plays a role at crucial cellular checkpoints for proliferation, apoptosis, and differentiation. We examined the immunolocalization of Hsp27 in the rat submandibular gland during postnatal development, wherein acinar cells proliferate and differentiate at earlier postnatal periods. At 2 weeks of age, weak Hsp27 immunoreactivity was distributed diffusely over all gland components. At 3 weeks, Hsp27 immunoreactivity disappeared in most parts of the acini and ducts, but was intensely accumulated in a small cell population located in the acinar center. This population was composed mostly of terminal tubule (TT) type I cells. At 4 weeks, the Hsp27‐immunopositive cell population in the acinar center was composed primarily of immature (type II) acinar cells, partly of immature (granulated) intercalated duct (ID) cells, and occasionally of apoptotic cells. After 5 weeks, all acinar components became mature and were no longer immunoreactive for Hsp27. When acinar cell differentiation was accelerated by administration of isoproterenol to 3‐week‐old rats for 7 days, the number of Hsp27‐positive cells was significantly lower than in the control gland at 4 weeks, confirming that Hsp27 expression is downregulated in mature acinar cells. These results suggest that at around 3–4 weeks in postnatal development, the centroacinar TT cells stop proliferating and begin to differentiate into acinar and ID cells, and occasionally undergo apoptosis. Hsp27 is transiently expressed in the centroacinar TT cells during this critical period, and thus may play a role in their differentiation into the immediate descendants. Anat Rec 264:358–366, 2001. © 2001 Wiley‐Liss, Inc.     

Effects of dimethylnitrosamine on organ-cultured adult human pancreas

Portions of adult human pancreas from 20 donors were organ-cultured in a chemically defined medium in the absence or presence of DMNA for up to 12 weeks. In the absence of DMNA, necrosis of some acini occurred during the first week, while some clusters of well-preserved acini were maintained for up to 3 weeks. Proliferation of the epithelial linings of main and smaller ducts and ductules was noted during the first 2 weeks of culture. Ductal epitheliums thereafter showed some degeneration but remained viable during the 12 weeks of culture. In contrast to controls, the DMNA-treated explants showed better preservation of both acinar and ductal cells. DMNA induced both ductal hyperplasia and atypia of the epithelial linings of main ducts, smaller ducts, and ductules within 6 weeks, and carcinoma by the tenth week of culture. At the end of the first week cells devoid of zymogen within the acinar complex proliferated and progressively replaced necrotic cells. During the ninth and tenth weeks, foci of atypical cells developed among these cells. Cells derived from 10-week-old DMNA-treated explants produced multiple nodules of carcinoma when injected subcutaneously into nude mice.     

CD56-positive cells with or without synaptophysin expression are recognized in the pancreatic duct epithelium: a study with adult and fetal tissues and specimens from chronic pancreatitis

We observed the distribution of CD56+ epithelial cells in the pancreatic duct system using 25 fetal, one infantile, 3 normal adult, 4 diabetic, and 8 chronically inflamed pancreatic tissue samples. In the early stage of gestation (12 to 17 weeks), CD56+ cells were commonly seen in the immature tubular structures. They were often continuous to pancreatic islets, and their distribution was similar to that of synaptophysin (Syn)+ cells, suggesting that they are precursors of islet neogenesis. Their number decreased in proportion to gestational age. Instead, from 24 weeks of gestation, luminal cell clusters that were common in interlobular ducts revealed CD56+. These cell clusters were unrelated to islet neogenesis and Syn expression. Similar CD56+ luminal cell clusters were also observed in cases of chronic pancreatitis, whereas they were scarce in normal adult and diabetic tissues. CD56+ cells were also occasionally seen in intralobular ducts, intercalated ducts, and centroacinar cells in cases of chronic pancreatitis. We conclude that there are two types of CD56+ epithelial cells in the pancreatic duct system: CD56+ endocrine cells are numerous during the early stage of gestation, when islet neogenesis appears, while CD56+ luminal cells may represent developmental and regenerative changes of pancreatic ducts.     

Mechanism of pseudoductular (tubular) formation during pancreatic carcinogenesis in the hamster model. An electron-microscopic and immunohistochemical study.

Electron-microscopic and immunohistochemical studies performed during pancreatic carcinogenesis in hamsters demonstrated that hypertrophy and hyperplasia of centroacinar cells were the earliest changes occurring in the pancreas. These altered centroacinar cells differentiated into either endocrine-type cells or elongated agranular cells with remarkably long cytoplasmic processes (CyPs). These CyPs seemed gradually to overlie and underlie the adjacent acinar cells and resulted in progressive degeneration and loss of acinar cells, which subsequently were replaced by altered centroacinar cells. The initially rather tiny and slender CyPs were characterized by the expression of blood group substances, which were also found in the surface of altered ductal cells. Because these antigens could not be demonstrated in normal pancreatic cells, they seemed to represent specific markers for altered ductal/ductular (centroacinar) cells. In no instance was there evidence of dedifferentiation of acinar cells into ductlike cells. The present data, along with our previous findings, demonstrate that centroacinar cells are the foundation for pseudoductular structures and are the progenitor cells of tumors arising from them.     

Histogenesis of solid pseudopapillary tumor of the pancreas: the case for the centroacinar cell of origin

Solid pseudopapillary tumor (SPT) is an unusual pancreatic neoplasm of low malignant potential that most frequently occurs in young women. The tumor is indolent, with long patient survival, even in the presence of extension into adjacent organs and metastases. Histologically, it is a solid and cystic tumor with a prominent vascular network and degenerative pseudopapillae formation. Despite its distinctive morphology and cytological features, its histogenesis is unclear. Herein, we report a case of solid pseudopapillary tumor in a 41-year-old female in which the tumor cells immunohistochemically and ultrastructurally suggest a centroacinar cell origin. The tumor cells and the normal centroacinar cells stained positive for alpha-antitrypsin (alpha-AT), CD10, cyclin D1 and NSE. Ultrastructural examination shows similarities in nuclear shape, nucleoli location and cytoplasmic contents between neoplastic cells and normal centroacinar cells of the pancreas. Based on both immunohistochemical and ultrastructural features, we propose that the centroacinar cell is the origin of SPT.     

Molecular characteristics and alterations during early development of the human vagina

Unresolved questions remain concerning the derivation of the vagina with respect to the relative contributions from the Müllerian ducts, the urogenital sinus, and the Wolffian ducts. Recent molecular and cellular studies in rodents have opened up a large gap between the level of understanding of vaginal development in mice and understanding of human vaginal development, which is based on histology. To compare the findings in mice with human vaginal development and to address this gap, we analysed molecular characteristics of the urogenital sinus, Wolffian ducts, and Müllerian ducts in 8-14-week-old human specimens using immunohistochemical methods. The monoclonal antibodies used were directed against cytokeratin (CK) 14, CK19, vimentin, laminin, p63, E-cadherin, caspase-3, Ki67, HOX A13, and BMP-4. The immunohistochemical analysis revealed that, during weeks 8-9, the epithelium of the Müllerian ducts became positive for p63 as p63-positive cells that originated from the sinus epithelium reached the caudal tip of the fused Müllerian ducts via the Wolffian ducts. The lumen of the fused Müllerian ducts was closed by an epithelial plug that contained both vimentin-positive and vimentin-negative cells. Subsequently, the resulting epithelial tube enlarged by proliferation of basal p63-positive cells. The first signs of squamous differentiation were detected during week 14, with the appearance of CK14-positive cells. According to our results, all three components, namely, the urogenital sinus, Wolffian ducts, and Müllerian ducts, interacted during the formation of the human vagina. The sinus epithelium provided p63-positive cells, the Wollfian ducts acted as a 'transporter', and the Müllerian ducts contributed the guiding structure for the vaginal anlagen. Epithelial differentiation began at the end of the period studied and extended in a caudo-cranial direction. The present study is one of the first to provide up-to-date molecular correlates for human vaginal development that can be compared with the results of cell biological studies in rodents.     

Differentiation and proliferation of endocrine cells in the regenerating rat pancreas after 90% pancreatectomy

The transplantation of pancreatic tissue has been anticipated to serve as a radical treatment for diabetes mellitus. However, the identification of the stem cells, and elucidation of their differential lineage and controlling mechanisms are prerequisites to ensure effective transplantation. We conducted an immunohistochemical study to determine the proliferation and differentiation dynamics of pancreatic endocrine cells in the rat pancreas 1 to 28 days after a 90% pancreatectomy. Regeneration of endocrine cells started immediately after pancreatectomy. The process of regeneration included the proliferation of preexisting islet cells and neogenesis of endocrine cells from epithelial cells of the most peripheral duct. Intercalated ductal cells and centroacinar cells were speculated to be the major sources of neogenesis, from which islet tissue was formed. Glucagon cells were the first endocrine cells differentiated, some of which transformed to insulin cells by a mechanism of non-replication. These results indicate that endocrine stem cells exist among the intercalated ductal and/or centroacinar cells, and these special regions should be utilized in transplantation for the successful treatment of diabetes.     

Transient occurrence of 27 kDa heat-shock protein in the terminal tubule cells during postnatal development of the rat submandibular gland.

It has been suggested that the 27 kDa heat-shock protein (Hsp27) plays a role at crucial cellular checkpoints for proliferation, apoptosis, and differentiation. We examined the immunolocalization of Hsp27 in the rat submandibular gland during postnatal development, wherein acinar cells proliferate and differentiate at earlier postnatal periods. At 2 weeks of age, weak Hsp27 immunoreactivity was distributed diffusely over all gland components. At 3 weeks, Hsp27 immunoreactivity disappeared in most parts of the acini and ducts, but was intensely accumulated in a small cell population located in the acinar center. This population was composed mostly of terminal tubule (TT) type I cells. At 4 weeks, the Hsp27-immunopositive cell population in the acinar center was composed primarily of immature (type II) acinar cells, partly of immature (granulated) intercalated duct (ID) cells, and occasionally of apoptotic cells. After 5 weeks, all acinar components became mature and were no longer immunoreactive for Hsp27. When acinar cell differentiation was accelerated by administration of isoproterenol to 3-week-old rats for 7 days, the number of Hsp27-positive cells was significantly lower than in the control gland at 4 weeks, confirming that Hsp27 expression is downregulated in mature acinar cells. These results suggest that at around 3-4 weeks in postnatal development, the centroacinar TT cells stop proliferating and begin to differentiate into acinar and ID cells, and occasionally undergo apoptosis. Hsp27 is transiently expressed in the centroacinar TT cells during this critical period, and thus may play a role in their differentiation into the immediate descendants.     

人胎胰腺GnRH免疫反应细胞

目的：探讨促性腺激素释的激素(GnRH)免疫反应细胞在人胎胰腺的存在部位和数量变化。方法：用免疫组织化学SABC法，对37例第10-32w人胎胰腺内的GnRH-IR细胞进行观察，并用体视方法分析其数量变化。结果：人胎胰腺GnRH-IR细胞出现于第13w，其数密度随胎龄增加而增大；分布于胰岛及外分泌部的腺泡上皮、导管上皮细胞间。位于胰岛的GnRH-IR细胞呈圆形、卵圆形或多边形。位于腺泡上皮细胞间的GnRH-IR细胞多为锥体形，外分泌部的GnRH-IR细胞均为开放型细胞。结论：胰腺GnRH-IR细胞于胚胎第13w出现，广泛存在于内、外分泌部，其数量随胎龄增加而增加。     

The immunhistochemical investigation of trypsin and trypsin-like-activity in the small intestine, pancreas and isolated Langerhans islets. A light-, fluorescent- and electron microscopic study (author's transl)]

By means of the indirect immunofluorescence and immunenzyme technique trypsin and trypsin-like activity in fixed cryostate sections of pancreas and gut and pellets of isolated pancreatic islets respectively were investigated using specific antiserum against trypsin. The enzyme was demonstrated in the cytoplasma of the acinus cells, the epithel cell of the intercalated ducts and the excretory (interlobular) ducts of the exocrine pancreas. By light and fluorescence microscopy we could also localize a high activity in pancreatic islets. Results taken from electron microscope show the enzyme in the region of the peripheral endoplasmatic reticulum, the surface of the mitochondria, the zymogen granules of the acinus cells and in the region of the membranes of the endoplasmatic reticulum and in the granules of the B-cells of the pancreatic islets. These results are discussed in correlation with biochemical data concerning the importance of trypsin/trypsin-like activity in the specific conversion of prohormones into hormones.     

Differentiation and proliferation of adrenocortical cells during the early stages of regeneration

Changes in the adrenal cortex of the rat were studied by stereologic and autoradiographic techniques during the early phases of regeneration. The adrenal cortex was enucleated on the left side, the right kidney and adrenal gland were removed, and rats were given 1% sodium chloride as drinking solution according to the procedure for inducing adrenal regeneration hypertension. The growth of adrenocortical cells during early stages of regeneration can be divided into two phases. During the first stage (0 to day 3), the cells remaining attached to the capsule recovered from trauma and began to differentiate from zona glomerulosa-like to those characteristic of the zona fasciculata. Mitochondria also divided, and there was increased surface area per cell of total mitochondrial membranes. The number of cells decreased in this initial phase, although the average cell volume increased, in preparation for mitotic division. This conclusion is supported by an increase in the percentage of cells labeled with 3H-thymidine at day 3. The second period (end of day 3 to day 7) was a proliferative phase reflected in a large number of labeled cells and a maximal number of grains per volume (reflecting activity of 3H-thymidine incorporation) followed by a blunting of the wave of proliferation at day 7. As cells divided, the total mitochondrial membranes and cristae per cell decreased. The first week after enucleation is characterized first by preparation for cell division, and in the second phase of the first week a wave of proliferation occurs. At the end of the first week, fewer labeled cells were seen, and there was a decrease in cristae membranes.     

Discovered on gastrointestinal stromal tumor 1 (DOG1) is expressed in pancreatic centroacinar cells and in solid-pseudopapillary neoplasms--novel evidence for a histogenetic relationship

Solid-pseudopapillary neoplasms of the pancreas are tumors of low malignant potential whose histogenesis has been discussed controversially. In the series of 15 solid-pseudopapillary neoplasms presented here, we demonstrate that discovered on gastrointestinal stromal tumor 1 is expressed significantly by these tumors (diffuse expression in 8 cases, focal expression in 4 cases, and scarce expression in 3 cases). Similar to the high expression of CD117, this finding parallels the immunohistochemical findings in gastrointestinal stromal tumors. Using double immunohistochemistry and immunofluorescence, we furthermore show that centroacinar cells express discovered on gastrointestinal stromal tumors 1. Thus, our findings suggest that, similarly to CD10 or vimentin, the expression of discovered on gastrointestinal stromal tumors 1 may serve as a novel marker for centroacinar cells and for solid-pseudopapillary neoplasms, which is suggestive of a centroacinar origin of these neoplasms.     

Expression of HLA-DR antigens on interlobular bile ducts in primary biliary cirrhosis and other hepatobiliary diseases: an immunohistochemical study

Using a monoclonal antibody to alpha chains of HLA-DR antigens, we found that damaged biliary epithelial cells in primary biliary cirrhosis (PBC) and, to a lesser degree and frequency, in other hepatobiliary diseases expressed HLA-DR antigens, while normal bile ducts did not. There was no correlation between biliary epithelial expression of HLA-DR antigens and intraepithelial migration of HLA-DR-positive cells. In PBC, HLA-DR antigens were strongly expressed on the damaged bile ducts surrounded by no or mild inflammatory cell infiltration (nonflorid duct lesion) and on those surrounded by intense lymphoid cells (florid duct lesion). Immunoelectron microscopy confirmed the presence of HLA-DR antigens on the cellular membranes of damaged biliary epithelial cells. Although expression of HLA-DR antigens on bile ducts may itself be a nonspecific epiphenomenon of damaged bile ducts, it seems possible in PBC that biliary epithelial cells are at first damaged in some way and express HLA-DR antigens (and probably self-antigens), and then fall victim to an autoimmune reaction characterized by marked lymphoid cell infiltration (florid duct lesions). The agent causing nonflorid duct lesions is unknown. The reasons why such expression does not lead to immunologic reactions in other hepatobiliary diseases are only speculative.     

Functional units in rainbow trout (Salmo gairdneri,Richardson) liver: II. The biliary system

The intrahepatic biliary system was studied in the rainbow trout (Salmo gairdneri), a teleost known to form liver neoplasms after exposure to various carcinogens. Normal adults (N = 25) were examined using light microscopic, enzyme histochemical, and transmission and scanning electron microscopic methods. In light micrographs, longitudinal arrays of hepatocytes appeared as double rows incompletely divided by elongated darkly stained cells. Electron micrographs showed tubules of five to nine pyramidally shaped hepatocytes with their apices directed toward a central biliary passageway and their bases directed toward sinusoids. Sequentially, beginning with hepatocytes, biliary passageways included canaliculi, preductules, ductules, and ducts. Canaliculi were short and joined transitional passageways (preductules) formed by junctional complexes between plasma membranes of hepatocytes and small, electron-dense cells with a high nuclear to cytoplasmic ratio. Ductules, completely lined by biliary epithelial cells, occupied central regions of hepatic tubules. Relatively elongated, ductular cells were intimately associated with surrounding hepatocytes, separated from them by only a thin extracellular space devoid of a basal lamina. Epithelium of bile ducts included cuboidal through mucus-laden columnar cells, surrounded by basal lamina and, in larger ducts, by fibroblasts, smooth muscle cells, and a capillary plexus. Bile ducts and hepatic arterioles, but not venules, were distributed together. The ultrastructure of biliary epithelium, periductular, and periductal cells is presented.