Appearance of clasmatosis in the normal and pathological liver

It was established that clasmatosis of cytoplasmic fragments toward sinusoids occurred under normal physiological conditions (embryogenesis of chick liver, the liver of starved grass carp and silver carp) and pathological conditions (disturbance of rat hepato-intestinal circulation). The clasmosomes of rat and chick liver cells contained free ribosomes and small vesicles while those in the liver of starved fish consisted of glycogen. It was also shown that mitochondria with the signs of complete clasmatosis appeared in the hepatocyte cytoplasm immediately after the beginning of intensive bile secretion to the bile canaliculus (in liver cells of rat and chick embryo and in those of frogs after complete metamorphosis). Such mitochondria were partially disintegrated and were located near the bile canaliculi. It is assumed that clasmatosis of the fragments of the liver cell cytoplasm or mitochondria takes places where it is necessary to rapidly supply the body or cell with some products of metabolism or to remove something from the cell as is the case with erythroblasts, i. e. clasmatosis is one of the mechanisms of the adaptation of the cell and its organelles to changes in the environment.     

白鲟肝脏和胰脏的组织学与形态学研究

白鲟肝脏较大,可分为左右两大叶及小的中叶,胆囊位于右叶的凹缺内。肝板多由双层细胞构成,肝小叶不明显。肝内毛细胆小管由4个肝实质细胞围成。胰脏有3支,被厚的浆膜。胰岛明显。胰管与胆管汇合后共同开口于小肠最前部背面。对肝、胰实质细胞的显微或亚显微结构进行了描述。     

中国大鲵肝脏的超微结构

应用透射电镜对中国大鲵的肝脏进行了超微结构研究.观察表明,大鲵肝不具肝小叶,与其他脊椎动物有所不同.肝细胞含有单个卵圆形的核;细胞质内含有粗面内质网、高尔基囊泡、线粒体、糖原颗粒和脂滴等细胞器和内含物.胆小管由两个相邻肝细胞质膜凹陷围成,而肝血窦则由内皮细胞的胞质构成.胆小管腔和窦周隙内浸润许多由肝细胞发出的微绒毛结构.还发现了枯否氏细胞和贮脂细胞.还讨论了中国大鲵肝脏的一般形态结构特点.     

Contacts between Wolffian and Müllerian cells at the tip of the outgrowing Müllerian duct in rat embryos

The developing Müllerian duct was studied at the light microscopic as well as the electron microscopic level in rat embryos, especially in the section of the terminal bud and its tip, where Wolffian and Müllerian duct are enclosed by a common basal membrane. In this zone desmosomes can be found among Wolffian cells and also among Müllerian cells. In addition, we found cell contacts between Müllerian and Wolffian cells, namely short electron-dense segments on adjacent surfaces or disc-shaped thickenings within opposite plasma membranes, as well as fusions of the plasmalemmata over short distances. Until now, these cell contacts have not been described in rat embryos.     

Ultrastructure of the kidney of a South American caecilian,Typhlonectes compressicaudus (Amphibia,Gymnophiona)

Summary The ultrastructure of the distal nephron, the collecting duct and the Wolffian duct was studied in a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) by transmission and scanning electron microscopy (TEM, SEM). The distal tubule (DT) is made up of one type of cell that has a well-developed membrane labyrinth established both by interdigitating processes and by interlocking ramifications. The processes contain large mitochondria, the ramifications do not. The tight junction is shallow and elongated by a meandering course. The connecting tubule (CNT) is composed of CNT cells proper and intercalated cells, both of which are cuboidal in shape. The CNT cells are characterized by many lateral interlocking folds. The intercalated cells have a dark cytoplasm densely filled with mitochondria. Their apical cell membrane is typically amplified by microplicae beneath which a layer of globular particles (studs) is found. The collecting duct (CD) is composed of principal cells and intercalated cells, again both cuboidal in shape. The CD epithelium is characterized by dilated intercellular spaces, which are often filled with lateral microfolds projecting from adjacent principal cells. The apical membrane is covered by a prominent glycocalyx. The intercalated cells in the CD are similar to those in the CNT. The Wolffian duct (WD) has a tall pseudostratified epithelium established by WD cells proper, intercalated cells and basal cells. The WD cells contain irregular-shaped dense granules located beneath the apical cell membrane. The intercalated cells of the WD have a dark cytoplasm with many mitochondria; their nuclei display a dense chromatin pattern.Research fellow of the Alexander von Humboldt Foundation     

The differentiation of oval cells into hepatocytes during induced hepatic carcinogenesis in mice. An electron microscopic study

An electron microscopic study of murine oval cells, induced by a single injection of genotoxic agent dipin and by a partial hepatectomy, has shown that their ultrastructure and direction of differentiation depend on localization in the liver lobule. Oval cells around portal tracts go through three stages of development: low differentiated cells 4.40 +/- 0.51 mu in diameter with ovoid nuclei 3.43 +/- 0.44 mu, intermediate cells, and young hepatocytes. They form common ducts surrounded by a basal lamina, and produce bile canaliculi-like structures and intermediate junctions between them. Another part of the oval cell population is organized similar to the bile duct epithelium. It consists of cells 9.37 +/- 1.1 mu in diameter with nuclei 7.28 +/- 1.16 mu in diameter and form a system of branching and anastomosing ducts widespread along the parenchyma from the portal to the central veins. Our data indicate that the oval cells can differentiate into hepatocytes, and support a hypothesis according to which the cells of terminal bile ductules are liver epithelial stem cells which can differentiate into a hepatocyte or a bile duct cell lineage in periportal microenvironment.     

Expression of ATP7B in normal human liver

ATP7B is a copper transporting P-type ATPase, also known as Wilson disease protein, which plays a key role in copper distribution inside cells. Recent experimental data in cell culture have shown that ATP7B putatively serves a dual function in hepatocytes: when localized to the Golgi apparatus, it has a biosynthetic role, delivering copper atoms to apoceruloplasmin; when the hepatocytes are under copper stress, ATP7B translocates to the biliary pole to transport excess copper out of the cell and into the bile canaliculus for subsequent excretion from the body via the bile. The above data on ATP7B localization have been mainly obtained in tumor cell systems in vitro. The aim of the present work was to assess the presence and localization of the Wilson disease protein in the human liver. We tested immunoreactivity for ATP7B in 10 human liver biopsies, in which no significant pathological lesion was found using a polyclonal antiserum specific for ATP7B. In the normal liver, immunoreactivity for ATP7B was observed in hepatocytes and in biliary cells. In the hepatocytes, immunoreactivity for ATP7B was observed close to the plasma membrane, both at the sinusoidal and at the biliary pole. In the biliary cells, ATP7B was localized close to the cell membrane, mainly concentrated at the basal pole of the cells. The data suggest that, in human liver, ATP7B is localized to the plasma membrane of both hepatocytes and biliary epithelial cells.     

Ultrastructure of the Protonephridium in Acteonemertes bathamae Pantin (Rhynchocoela: Enopla: Hoplonemertini)

The protonephridial system consists of terminal cell, protonephridial capillary, protonephridial tubule and efferent duct. The terminal cell is an elongated, thin-walled, fenestrated basket containing a ciliary flame circumscribed by a palisade of straight microvilli. The filtration area is confined to the terminal cell and consists of slits bridged by a filtration membrane. The cilia, as well as the microvilli, projects into the proximal bell-shaped part of the thin-walled protonephridial capillary. The terminal cells are often found in pairs connected to the same capillary, which has a very narrow lumen. The proximal part of the thick-walled, convoluted protonephridial tubule is ciliated and shows characteristic foldings of the luminal plasma membrane and numerous small vesicles in the cytoplasm. The cells of the following, non-ciliated part of the tubule have interdigitating lateral surfaces and the bases deeply invaginated to form compartments with numerous mitochondria; in the cytoplasm are many large vesicles, possibly containing lipid droplets, and small amounts of glycogen. The distal protonephridial tubule resembles various epithelia with an osmoregulatory function, including the vertebrate nephron.     

Some observations on the morphological evidence for mechanism of the bile secretion

The morphological evidence of the intracellular route of bile secretion was investigated in the liver of goldfish (Carassius auratus) as revealed by electron microscopy. Smooth surfaced tubules or cisterns within or adjacent to the Golgi apparatus showed linear saccular forms and contained sparse particulate or cloudy materials of low electron density. The isolated vacuoles were restrictedly found between the Golgi apparatus and the intracellular bile canaliculus or hepatocytic side at the zone of transition. These vacuoles showed no reaction for acid phosphatase activity, and contained only a few cloudy materials similar to those found in the saccular tubules and within the bile canaliculus. Some of these vacuoles fused with the luminal cytolemmas of the bile canaliculus. Bases on these findings, it was assumed that these vacuoles are structures participating in transport and secretion of bile constituents and derive from the linearly sacculated tubules or cisterns in the Golgi zone. Duct cells showed no morphological evidence to suggest bile secretion.     

Intraepithelial lymphocytes in the male reproductive tract of rats and rhesus monkeys.

Although lymphocytes are never present in 'normal ' seminiferous epithelium, they are found in the terminal portions of the seminiferous tubles near their junctions with the tubuli recti. Intraepithelia lymphocytes are also found in the tubuli recti testis, ductuli efferentes, epididymis and ductus deferens. The ultrastructural morphology of these cells closely resembles that of the intraepithelial lymphocytes in the intestinal mucosa and those obtained from the lymph nodes, spleen blood and thoracic duct. The mucleus is spherical and is characterized by clumps of chromatin near the nuclear membrane. A thin rim of cytoplasm is usually found, and is remarkably free of most cell organelles except for free ribosomes. Frequently, a blunt cytoplasmic process can be seen extending from one end of the cell. Membrane-bounded granules and other dense bodies are occasionally encountered in the cytoplasm. The possible functional significance of intraepithelial lymphocytes in the male reproductive tract is discussed.     

Immunocytochemical localization of actin in epithelial cells of rat small intestine by light and electron microscopy

We used post-embedding immunocytochemical techniques and affinity-purified anti-actin antibody to evaluate localization of actin in epithelial cells of small intestine by fluorescence and electron microscopy. Small intestine was fixed with 2% formaldehyde-0.1% glutaraldehyde and embedded in Lowicryl K4M. One-micron or thin sections were stained with antibody followed by rhodamine- or colloidal gold-labeled goat anti-rabbit IgG, respectively. Label was present overlying microvilli, the apical terminal web, and the cytoplasm directly adjacent to occluding and intermediate junctions. Label was associated with outer mitochondrial membranes of all cells and the supranuclear Golgi region of goblet cells. Lateral cytoplasmic interdigitations between mature cells and subplasmalemmal filaments next to intrusive cells were densely labeled. The cytoplasm adjacent to unplicated domains of lateral membrane was focally labeled. Label was prominent over organized filament bundles within the subplasmalemmal web at the base of mature cells, whereas there was focal labeling of the cytoplasm adjacent to the basal membrane of undifferentiated cells. Basolateral epithelial cell processes were labeled. Label was focally present overlying the cellular ground substance. Our results demonstrate that actin is distributed in a distinctive fashion within intestinal epithelial cells. This distribution suggests that in addition to its function as a structural protein, actin may participate in regulation of epithelial tight junction permeability, in motile processes including migration of cells from the crypt to the villus tip, in accommodation of intrusive intraepithelial cells and in adhesion of cells to one another and to their substratum.     

唐鱼肝脏显微和超微结构观察

应用光镜和透射电镜对繁殖期间唐鱼Tanichthys albonubes肝脏组织的显微和超微结构进行了观察。结果显示,唐鱼肝细胞具单核,中央核仁显著;细胞质内分布着粗面内质网、线粒体、糖原颗粒和脂滴等细胞器和内含物。胆小管由2～3个相邻肝细胞质膜凹陷围成,而肝血窦则由内皮细胞的胞质、成纤维细胞等参与构成。肝细胞与周边细胞通过3种不同方式进行联系:肝细胞之间的紧密连接;与血窦的间接连接;与胆小管的邻接。这些联系方式显示了肝脏具有内分泌腺和外分泌腺功能的特点。研究还发现雌性唐鱼肝脏具有"暗"细胞和"淡"细胞两种类型。本文还讨论了唐鱼肝脏与其他硬骨鱼类肝脏一般组织结构和超微结构的异同点。     

Uptake and transport of intact macromolecules in the intestinal epithelium of carp (Cyprinus carpio L.) and the possible immunological implications

Summary Two protein antigens, horseradish peroxidase (HRP) and ferritin, have been administered to the digestive tract of carp. Electron-microscopical observations reveal considerable absorption of both antigens in the second segment of the gut (from 70 to 95% of the total length) and also, although to a lesser extent, in the first segment (from 0 to 70% of the total length). Even when administered physiologically with food, a large amount of ferritin is absorbed by enterocytes in the second gut segment.HRP and ferritin are processed by enterocytes in different ways. HRP seems to adhere to the apical cell membrane, probably by binding to receptors, and is transported in vesicles to branched endings of lamellar infoldings of the lateral and basal cell membrane. Consequently, most of the HRP is released in the intercellular space where it contacts intra-epithelial lymphoid cells. Only small amounts of HRP become localized in secondary lysosomes of enterocytes. Ferritin does not bind to the apical cell membrane; after uptake by pinocytosis, it is present in small vesicles or vacuoles that appear to fuse with lysosome-like-bodies. In the second segment, intact ferritin ends up in the large supranuclear vacuoles (after 8 h), where it is digested slowly. Although no ferritin is found in the intercellular space, ferritin-containing macrophages are present between the epithelial cells, in the lamina propria and also to a small extent in the spleen. The transport of antigens from the intestinal lumen, through enterocytes, to intra-epithelial lymphoid cells or macrophages may have immunological implications, such as induction of a local immune response and prospectives for oral vaccination.     

Apical Membrane Expression of Distinct Sulfated Glycans Is a Characteristic Feature of Ductules and Their Reactive and Neoplastic Counterparts

Intrahepatic bile ducts transport bile between bile canaliculi and the extrahepatic bile duct. The luminal surface of this tract is lined by a layer of biliary epithelial cells, or cholangiocytes, which secrete mucins consisting of scaffold proteins and O-glycosidically linked carbohydrate side chains. Although mucin core proteins have been extensively investigated, the structure and function of carbohydrate side chains have not. Here, we demonstrate that distinct sulfated glycans positive for MECA-79, R-10G, and 297-11A, but not 5D4, monoclonal antibodies are expressed in the cytoplasm of cells of large-sized ducts and in the apical membrane of cells in ductules, and that R-10G immunolabeling is partially eliminated by endo-β-galactosidase digestion, supporting the presence of N-acetylglucosamine-6-O-sulfated N-acetyllactosamine structures. We observed comparable apical membrane-predominant staining in ductular reactions seen during regeneration that occurs in various liver diseases and in cholangiolocarcinoma, a subtype of small duct-type intrahepatic cholangiocarcinoma (iCCA). Apical membrane expression of distinct sulfated glycans in large duct-type iCCA was negligible. Intriguingly, under pathological conditions, endo-β-galactosidase digestion almost completely eliminated R-10G immunoreactivity. These findings suggest that apical membrane expression of distinct sulfated glycans is a characteristic feature of ductules and their reactive and neoplastic counterparts     

Scanning electron microscopy of normal rat liver: the surface structure of its cells and tissue components.

Scanning electron microscopy (SEM) allows the surface ultrastructure of intrahepatic cells and other tissue components of liver to be delineated. Excellent depth of focus of the SEM makes it possible to visualize surfaces of intact cells in their native configurations. This report details the surface characteristics and inter-relationships of hepatocytes and hepatic plates, sinusoidal endothelial cells and sinusoids, presumed Kupffer cells, vessels, bile ducts, connective tissue, and the capsule of rat liver. Hepatocytes present three structurally distinctive faces--the intercellular face containing flat surfaces and bile canaliculus, the sinusoidal face, and the connective tissue face which abuts portal tracts and hepatic veins. Sinusoidal endothelium is penetrated by large (1 to 3 mum) and small (0.1 mum) fenestrae, the latter occurring in clusters of up to 50. The width of bile canaliculi and distribution of large fenestrae vary proximodistally along hepatic plate or sinusoid. The cells of portal bile ductules contain microvilli located in linear rows and sparse cilia. Endothelium of hepatic artery and of portal vein is sparsely fenestrated.     

Intracellular trafficking of bile salt export pump (ABCB11) in polarized hepatic cells: constitutive cycling between the canalicular membrane and rab11-positive endosomes

The bile salt export pump (BSEP, ABCB11) couples ATP hydrolysis with transport of bile acids into the bile canaliculus of hepatocytes. Its localization in the apical canalicular membrane is physiologically regulated by the demand to secrete biliary components. To gain insight into how such localization is regulated, we studied the intracellular trafficking of BSEP tagged with yellow fluorescent protein (YFP) in polarized WIF-B9 cells. Confocal imaging revealed that BSEP-YFP was localized at the canalicular membrane and in tubulo-vesicular structures either adjacent to the microtubule-organizing center or widely distributed in the cytoplasm. In the latter two locations, BSEP-YFP colocalized with rab11, an endosomal marker. Selective photobleaching experiments revealed that single BSEP-YFP molecules resided in canalicular membranes only transiently before exchanging with intracellular BSEP-YFP pools. Such exchange was inhibited by microtubule and actin inhibitors and was unaffected by brefeldin A, dibutyryl cyclic AMP, taurocholate, or PI 3-kinase inhibitors. Intracellular carriers enriched in BSEP-YFP elongated and dissociated as tubular elements from a globular structure adjacent to the microtubule-organizing center. They displayed oscillatory movement toward either canalicular or basolateral membranes, but only fused with the canalicular membrane. The pathway between canalicular and intracellular membranes that BSEP constitutively cycles within could serve to regulate apical pools of BSEP as well as other apical membrane transporters.     

A scanning electron microscopic study of the liver of the monkey Macaca speciosa

Summary The bile canalicular network of the monkey was studied by fracturing fixed liver tissue and examination by scanning electron microscopy. Bile canaliculi do not differ remarkably from those described in other species. Their course and luminal diameter vary, depending on their position in the liver lobule. In one specimen the continuity of a canaliculus with a terminal bile ductule (canal of Hering) is presented. Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the gallbladder. A common feature is the presence of microplicae on their lateral cell surfaces.

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Zusammenfassung Das Netzwerk der Gallekanälchen beim Affen wird durch Brechen von fixiertem Lebergewebe sichtbar. Strukturen der Portalfelder und der extrahepatischen Gänge werden durch Schneiden von Gewebe dargestellt. DieGallekanälchenunterscheidensichnichtwesentlich von den bei anderen Spezies beschriebenen. Ihr unterschiedlicher Verlauf und Lumendurchmesser hängen von ihrer intralobulären Lage ab. Die Kontinuität eines Gallekanälchens mit einem Ductulus (Heringscher Kanal) wird in einem Fall dargestellt. Im ductulären Lumen kommen mehrere Konstriktionen vor. Die Wand der interlobulären Gallengänge weist zwei Arten von Nischen auf. Eine Einzelzilie kommt aus den primären Nischen. Sekundäre Nischen bestehen aus mehreren primären Nischen. Einschichtiges hochprismatisches Epithel kleidet den Ductus choledochus, den Ductus pancreaticus und die Gallenblase aus. Ein gemeinsames Merkmal ihrer lateralen Zelloberflächen sind Mikroplicae.

     

Fine structure and its functional properties of the ependymal cell in the frog median eminence

Summary Intercellular canaliculi surrounded by several ependymal cells, having numerous microvilli and a few cilia on the apical surface, are present throughout the frog median eminence. The intercellular canaliculi penetrate deeply near the portal vessel from the third ventricle. They are separated from the pericapillary space only by the thin cytoplasm of the ependymal cell.The cytoplasmic protrusions containing a large number of clear vesicles are often found at the apical surface of ependymal cells facing the third ventricle or the lumen of intercellular canaliculus. The ependymal cell shows well developed Golgi apparatus and well developed rough endoplasmic reticulum in its cytoplasm. Dense granules of about 1200–1500 A diameter suggesting secretory materials are found in small number near the Golgi apparatus and abundantly in the ependymal process lying around the portal vessel.Synaptic contacts between the ependymal cell and two different types of the nerve endings, monoaminergic and peptidergic, are frequently observed. A few small flasklike caveolae suggesting micropinocytosis are found in the post-synaptic membrane as well as in the lateral and basal plasma membranes of the ependymal cell. The author consideres that the ependymal cell in this region has secretory and transport (absorption) activities.     

Fine reconstruction of the pancreatic ductular system at the onset of pancreatitis

The three-dimensional structure of the pancreatic ductular system (from the intercalated duct to the intercellular secretory canaliculus) is controversial and unclear. The aim of this study is to reveal the three-dimensional structure of the pancreatic ductular sysytem at the onset of pancreatitis. One day following rat pancreatic duct ligation, dilated lumina from the pancreatic ductular system were reconstructed by light microscopic and scanning electron microscopic examination of pancreatic tissue serial sections. The existence of the intra-acinar duct, which is formed only by centroacinar cells and interconnects the adjacent central lumina in an acinus, was demonstrated. The intercellular secretory canaliculi, which are the terminal parts of the pancreatic ductular system, anastomose and end blindly in the intercellular space located between adjacent lateral surfaces of the acinar cells. The intercalated ducts, the intra-acinar ducts, the central lumina, and the intercellular secretory canaliculi are arranged together in a complex connecting and branching system. However, there were no anastomoses found among the central lumina or acini.     

THE FINE STRUCTURE OF VON EBNER'S GLAND OF THE RAT

The fine structure of von Ebner's gland was studied in untreated rats and rats stimulated to secrete by fasting-refeeding or injection of pilocarpine. Cytological features were similar to those reported for pancreas and parotid gland. Abundant granular endoplasmic reticulum filled the basal portion of the cell, a well-developed Golgi complex was located in the vicinity of the nucleus, and the apical portion of the cell was filled with dense secretory granules. Dense heterogeneous bodies resembling lysosomes were closely associated with the Golgi complex. Coated vesicles were seen in the Golgi region and also in continuity with the cell membrane. Granule discharge occurred by fusion of the granule membrane with the cell membrane at the secretory surface. Successive fusion of adjacent granules to the previously fused granule formed a connected string of granules in the apical cytoplasm. Myoepithelial cells were present within the basement membrane, and nerve processes were seen adjacent to acinar and myoepithelial cells. Duct cells resembled the intercalated duct cells of the major salivary glands.