Fine structure of the liver in the larval lamprey, Petromyzon marinus L.; hepatocytes and sinusoids

The ultrastructure of hepatocytes, bile canaliculi, and hepatic sinusoids of the larval lamprey, Petromyzon marinus, was examined using thin-sectioned and freeze-fractured tissues. The liver is a "tubular gland" with hepatocytes arranged in a tubular fashion around large bile canaliculi. Hepatocytes are roughly conical in shape, with their tapered apices facing a bile canalicular lumen. They possess extensive rough and smooth endoplasmic reticulum, a well-developed Golgi complex, abundant mitochondria, and varying numbers of large secondary lysosomes. Both secondary lysosomes and the Golgi complex are concentrated in the apical or peribiliary cytoplasm, indicating a possible role in bile secretion. The apical surfaces of the hepatocytes bear numerous elongate microvilli and occasional cilia, which project into the bile canaliculi. The hepatocytes are joined, apically, by junctional complexes composed of zonulae occludentes and adhaerentes. In freeze-fracture, the zonulae occludentes are of variable apicobasal depth and consist of honeycomb-like meshworks of fibrils. Spaces of variable width frequently appear in the P-face grooves, indicating that the zonulae occludentes are "leaky." Numerous communicating (gap) junctions join the hepatocytes laterally. Varying numbers of lateral microvilli project into the intercellular spaces and, basally, the plasma membrane is deeply infolded, resulting in the formation of apparently interdigitating basal processes resting upon a thin basal lamina. Sinusoids are composed of both a heavily-fenestrated, continuous endothelium, and phagocytic reticulo-endothelial (Kupffer) cells. Depsite the difference in arrangement of their hepatocytes, the mammalian and lamprey livers show similar ultrastructural features.     

Gap junctions and zonulae occludentes of hepatocytes during biliary atresia in the lamprey

Gap junctions and zonulae occludentes of hepatocytes were examined in thin sections and freeze-fracture replicas from livers of larval and juvenile adult lampreys and during the phase of metamorphosis when bile ducts and bile canaliculi disappear (biliary atresia). Larvae possess zonulae occludentes at the canaliculi which are composed of one to five (mean = 2.81) junctional strands that provide a bile-blood barrier. Morphometry demonstrates that during biliary atresia the decreases in number of junctional strands and apico-basal depth of the zonulae occludentes are accompanied by an increase in the frequency of gaps or interruptions in the strands and in a breakdown of the bile-blood barrier. The zonulae occludentes completely disappear during metamorphosis and are not found in the adult liver. Gap junctions of the larval liver occupy 1% of the surface of the plasma membrane and have a mean area of 0.167 micron 2 but, following an initial decline in these parameters during early biliary atresia, they rise sharply in later stages of metamorphosis and in adults are 3.2% and 0.502 micron 2, respectively. The events of alteration in junctional morphology during lamprey biliary atresia is in many ways comparable to the changes in gap junctions and zonulae occludentes during experimental and pathological intra- and extrahepatic cholestasis in mammals.     

Loss and reappearance of gap junctions in regenerating liver

Changes in intercellular junctional morphology associated with rat liver regeneration were examined in a freeze-fracture study. After a two-thirds partial hepatectomy, both gap junctions and zonulae occludentes were drastically altered. Between 0 and 20 h after partial hepatectomy, the junctions appeared virtually unchanged. 28 h after partial hepatectomy, however, the large gap junctions usually located close to the bile canaliculi and the small gap junctions enmeshed within the strands of the zonulae occudentes completely disappeared. Although the zonulae occludentes bordering the bile canaliculi apparently remained intact, numerous strands could now be found oriented perpendicular to the canaliculi. In some instances, the membrane outside the canaliculi was extensively filled with isolated junctional strands, often forming very complex configurations. About 40 h after partial hepatectomy, very many small gap junctions reappeared in close association with the zonulae occludentes. Subsequently, gap junctions increased in size and decreased in number until about 48 h after partial hepatectomy when gap junctions were indistinguishable in size and number from those of control animals. The zonulae occludentes were again predominantly located around the canalicular margins. These studies provide further evidence for the growth of gap junctions by the accretion of particles and of small gap junctions to form large maculae.     

Ultrastructural study of liver cells from rooks living in ecologically unfavorable areas

The ultrastructure of liver cells was studied in rooks (Corvus frugilegus) living in radioactive and chemical contamination areas. The ultrastructure of liver cells from rook as well as jackdaw (Corvus monedula) and hooded crow (Corvus cornix) (Corvidae family) from a conventionally clean area was studied as control. Control hepatocytes proved to contain a great number of mitochondria, many of which were swollen and had clear matrix and disorganized cristae. The cristae nearly lacked glycogen and had abundant lipid droplets, which often tightly contacted mitochondria. The cytoplasm of hepatocytes in birds from both ecologically unfavorable areas had numerous mitochondria with the same ultrastructure. In contrast to control, the hepatocyte cytoplasm: (1) contained a lot of glycogen; (2) there were many lipid droplets, which directly contacted glycogen granules; and (3) had more abundant peroxisomes. In addition to normal erythrocytes, the sinusoids contained erythrocytes with mitochondria, vesicles, and lipid droplets in their cytoplasm. Analysis of many micrographs of lipid droplets contacting glycogen granules, mitochondria, peroxisomes, and cisterns of smooth endoplasmic reticulum allowed us to propose that glycogen is synthesized via gluconeogenesis from glycerol and products of fatty acid oxidation in the liver cell cytoplasm of rooks from ecologically unfavorable areas as distinct from control.     

Morphology of the bovine epididymis

The epididymis of the bull was divided into six regions, and morphological differences between regions were studied. The epithelium of all regions contained four cell types: principal and basal epithelial cells, and intraepithelial lymphocytes and macrophages. The epithelium of regions II-V also contained a few apical cells. Principal cells of all regions possessed an endocytotic apparatus including stereocilia underlain by canaliculi, coated vesicles, and subapical vacuoles (up to 1 micron in diameter); however, large vacuoles with a flocculent content and multivesicular bodies (up to 5 microns in diameter) were most numerous in regions II, III, and IV. The unique features of principal cells of region I were the presence of well-developed Golgi bodies, few lipid droplets, and whorls of smooth endoplasmic reticulum in the supranuclear cytoplasm. Numerous mitochondria, distended cisternae of rough endoplasmic reticulum, and dense granules characterized the infranuclear cytoplasm of the principal cells of regions II-VI; however, these features were more developed in region V. Apical cells were characterized by the apical location of the nucleus, many mitochondria in the apical cytoplasm, and few microvilli at the luminal border. Basal cells with few cytoplasmic lipid droplets were present throughout the length of the epididymis but appeared more numerous in region V. Intraepithelial lymphocytes were present at all levels of the epithelium but were never seen in the lumen. Intraepithelial macrophages containing heterogeneous granules, eccentric nuclei, and pseudopods were invariably seen near the basal area of the epithelium in all regions. These observations are discussed in an effort to define the role of each cell type in the epididymal epithelium.     

Fine structure of the Malpighian tubules in the housefly, Musca domestica

The epithelium of the Malpighian tubules in the housefly is comprised of four distinct cellular types. Type I cells are characterized by the presence of intimate associations between infoldings of basal plasma membrane and mitochondria. On the luminal surface, cytoplasm is extended into microvilli which contain mitochondria. Membrane-bound vacuoles in the cytoplasm seem to progressively accumulate granular material. Type II cells have dilated canaliculi. Microvilli lack mitochondria. The Type III cell has not been reported previously in Malpighian tubules. It has very well-developed granular endoplasmic reticulum which contains intracisternal bundles of tubules. Cytoplasm contains numerous electron dense bodies. Type IV cells occur in the common duct region of the Malpighian tubules. Mitochondria do not extend into the microvilli.     

Liver ultrastructure of juvenile Atlantic salmon (Salmo salar)

Light and transmission electron microscopy of the liver of juvenile Atlantic salmon (Salmo salar) reveals a tubular arrangement of parenchymal cells, with biliary passages typically located at the center of tubules. Hepatocytes generally contain a single nucleus surrounded by a cuff of rough endoplasmic reticulum (RER), with many round to elongate mitochondria associated with the perinuclear RER. Whereas glycogen deposits are common and usually lie at the cell periphery, parenchymal cells seldom contain lipid droplets. Golgi complexes and heterogeneous dense bodies also occur in many hepatocytes, often in close proximity to bile canaliculi. Numerous microvilli from hepatocytes extend into the subendothelial space of Disse, which is also the location of stellate fat-storing cells. Interhepatocytic macrophages, sometimes containing prominent phagolysosomes and residual bodies, are common in the liver. The intrahepatic biliary system consists of intercellular canaliculi, bile pre-ductules, ductules, and ducts. In contrast to some other teleosts, the liver of the Atlantic salmon contains no intracellular bile canaliculi or Kupffer cells. The hepatic endothelium, arterioles, and perivenous regions are also described.     

Junctional complexes of the tubular cells in the human kidney as revealed with freeze-fracture

Intercellular junctions between human kidney tubular cells were studied by the freeze-fracture technique. The number of strands of the zonulae occludentes increased gradually from the proximal segment to the collecting tubule. Only one strand was visible in the proximal segment (in contrast to 2-4 strands of the neighbouring Bowman's capsule). In the thin segment 2-4 strands were revealed. In the distal segment 1-5 strands were present in the pars recta, 4-6 in the pars convoluta. The most extensive and complex zonulae occludentes were found in the collecting tubule. Gap junctions were seen only between proximal tubular cells. The extent of the zonulae occludentes along the tubules in human kidneys is very similar to that observed in the kidney tubules of other mammals. The findings accord well with electrophysiological measurements and with the results of tracer studies on experimental animals.     

The ultrastructure of mammary explants from virgin ovariectomized goats during hormone-induced lactogenesis

The effect of insulin (I), cortisol (F) and prolactin (P) on the ultrastructural morphology of epithelial cells of cultured mammary explants from virgin ovariectomized (OV-X) goats were studied. The epithelial cells showed little structural organization and were devoid of fat droplets and secretory protein granules at zero time of culture. The cytoplasm contained few profiles of smooth and rough endoplasmic reticulum and the Golgi apparatus was rudimentary. After being cultured in Waymouth's medium without added hormones the epithelial cells were indistinguishable from epithelial cells of uncultured explants. The addition of I induced changes mainly in the appearance of nucleoli. The nucleoli were enlarged and fibrillogranular areas with light spaces were observed. The most obvious cytological changes of epithelial cells of explants cultured in the presence of I and F are translocation of the nucleus into the basal cytoplasm, increase of rough endoplasmic reticulum, an increase in the size of the Golgi apparatus, presence of one or two lipid droplets and in some cells vacuoles with protein granules were present. Mitochondria were more abundant. The epithelial cells of explants cultured in the presence of I, F and P were characterized by the polarization of organelles within the cytoplasm and by the formation and release of protein granules and small and large fat droplets. The cell nucleus was in the basal cytoplasm, the Golgi apparatus was supranuclear. The rough endoplasmic reticulum was extensively developed and formed large sacs. Golgi vacuoles contained protein granules.(ABSTRACT TRUNCATED AT 250 WORDS)     

Histology and ultrastructure of the hepatopancreas of the tigerfish,Hydrocynus forskahlii

Study of the histology and ultrastructure of the hepatopancreas of the tigerfish, Hydrocynus forskahlii shows that the liver parenchyma is divided into irregularly shaped lobules, separated by the exocrine pancreas and associated connective tissue. The hepatocytes are arranged in interconnecting cords or laminae, two to three cell layers in thickness. Sinusoids separate the laminae. The spherical to oval-shaped hepatocytes contain large, round, centrally situated nuclei with prominent nucleoli. The cytoplasm of the hepatocytes contains abundant rough and smooth endoplasmic reticulae, free polysomes, and mitochondria. Exocrine pancreatic tissue is scattered throughout the liver. This tissue is encapsulated by an endothelium resting on a thin layer of connective tissue and is separated from the liver parenchyma by a sinusoid. The nuclei of the exocrine pancreas cells are spherical, basally situated within the cells, and contain dark nucleoli. Vesicular rough endoplasmic reticulae and secretory granules lie in the apical regions of the exocrine pancreas cells. © 1996 Wiley-Liss, Inc.     

Structure of taste buds in foliate papillae of the rhesus monkey, Macaca mulatta

Taste buds in foliate papillae of the rhesus monkey were examined by electron microscopy. Three distinct cell types were identified. Type I cells were narrow elongated cells containing an oval nucleus, bundles of intermediate filaments, several Golgi bodies, and characteristic apical membrane-bounded dense granules. These cells exhibited morphological variations: some had a moderately dense cytoplasm, perinuclear free ribosomes, and flattened sacs of rough endoplasmic reticulum; others had a more lucent cytoplasm, dilated irregular rough endoplasmic reticulum, lysosome-like dense bodies, and lipid droplets. Type II cells typically contained a spherical, pale nucleus, a prominent nucleolus, supranuclear and infranuclear Golgi bodies, mitochondria with tubular cristae, and one or two centrioles. This cell type, too, showed some variation in the relative amounts of ribosomes and smooth endoplasmic reticulum, which varied inversely with each other. Type III cells were characterized by a clear apical cytoplasm essentially devoid of ribosomes and containing microtubules. In a few type III cells, the peri- and infranuclear regions contained many ribosomes and some rough endoplasmic reticulum. In most Type III cells, there were large numbers of dense and clear vesicles in the peri- and infranuclear regions; some of the vesicles were grouped in synapse-like arrangements with adjacent nerves. The morphological variations exhibited by all three cell types could be accounted for by age differences in each of the cells. This would be consistent with the notion that cell renewal occurs in each of the three cell populations.     

Kupffer cell structure in the juvenile Nile crocodile,Crocodylus niloticus

The morphology of Kupffer cells was examined in the liver of the juvenile Nile crocodile using light microscopy and transmission electron microscopy. Pleomorphic Kupffer cells were located in the sinusoids, in the space of Disse, in the hepatic parenchyma and often connected adjacent sinusoids. The cell surfaces were irregular due to the presence of filopodia and lamelliapodia with phagocytosis of white blood cells, red blood cells and thrombocytes being evident. The cells were in close contact with endothelial cells and pit cells in the sinusoidal lumen and with stellate cells in the space of Disse. The cytoplasm contained large phagosomes comprising a combination of ceroid pigment, melanosomes and siderosomes. The nuclei were often indented and eccentrically placed due to the presence of the phagosomes. Conspicuous clusters of membrane‐bound tubular organelles with a filamentous or crystalline interior were observed in the cytoplasm. The clusters were sometimes separated into smaller groups around phagosomes. A clear zone existed between the limiting membrane and the interior of these tubular organelles with the electron‐dense interior profiles being, respectively, circular, angular or divided. The tubular organelles have not previously been described in Kupffer cells and possibly represent lysosomes with specialized functions. Mitochondria, microtubules, Golgi profiles, granular and smooth endoplasmic reticulum, and a few cytoplasmic lipid droplets were also present. The presence of the tubular organelles and the occurrence of the Kupffer cells in different locations in the liver of the juvenile Nile crocodile are indicative of particularly active and mobile cells. J. Morphol. 275:1–8, 2014. © 2013 Wiley Periodicals, Inc.     

Ultrastructure of liver cells of shrews]

It was established that the hepatocytes of least shrew (Sorex minutissimus) contained 1-2 nucleus with wide nuclear pores and big nucleolus. There are abundant mitochondria with numerous crists in their matrix (many organelles were divided along the crists). Each mitochondrion was surrounded by the cistern of granular endoplasmic reticulum. The ultrastructure of Golgi complex (1-2 flat cisterns, small vesicles] indicated that the bile was secreted often, by small portions, that was the adaptation to repeated fractional feeding. There were many peroxisomes in the cytoplasm of hepatocytes. Lipid droplets were absent, glycogen granules were not at all hepatocytes. Sinusoidal cells had the usual structure. All sinusoids were open and consisted of the erythrocytes, fragments of hepatocyte cytoplasm and myelin figures in its lumen.     

Occurrence of unusual heterogeneous lipid-containing granule-storing cells in the main excretory duct epithelium of the male mouse submandibular gland

Summary The fine structure of the main excretory duct epithelium of the male mouse submandibular glands was investigated by scanning and transmission electron microscopy. Three principal cell-types were observed: type I and II, and basal cells. This epithelium was characterized by the presence of intercellular canaliculi. Type-I cells were the most numerous. They had an abundance of mitochondria, well-developed Golgi apparatus, a few electron-lucent lipid-containing granules and poorly developed basal infoldings. These cells were also characterized by many glycogen granules throughout the cytoplasm and abundant smooth endoplasmic reticulum in the apical cytoplasm. Type-II cells were the second most numerous. Their most characteristic feature was the presence of abundant heterogeneous lipid-containing granules having acid phosphatase activity at the periphery. They were concentrated in the infra- and supranuclear cytoplasm. The granules may be derived from mitochondrial transformation and seem to be a special kind of secondary autolysosome. Type-II cells also contained abundant mitochondria throughout the cytoplasm, much smooth endoplasmic reticulum in the apical cytoplasm, a well developed Golgi apparatus adjacent to the heterogeneous lipid-containing granules and no basal infoldings. Basal cells were situated adjacent to the basal lamina. They had a large nucleus and the cytoplasm was filled with glycogen granules.     

不同生殖期鳜肝脏超微结构变化的观察

应用透射电镜对生殖季节与非生殖季节鳜肝脏超微结构的变化进行了观察。鳜肝细胞含有单个卵圆形的核,核仁清楚;细胞质内含有粗面内质网、线粒体、糖原颗粒和脂滴等细胞器和内含物。胆小管由相邻的数个肝细胞质膜凹陷围成,而肝血窦则由内皮细胞的胞质构成。还发现了贮脂细胞、枯否氏细胞和成纤维细胞。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。鳜肝细胞的超微结构在产卵前后呈现明显变化：产卵前的肝细胞内富含线粒体、糖原颗粒和脂滴,粗面内质网发达;而产卵后的肝细胞内核仁发生迁移,部分细胞核囊泡化,糖原颗粒和脂滴排空,少数肝细胞具双核结构。非生殖期多数肝细胞核含有双核仁结构,胞质内溶酶体数量增多。     

Selenium treatment protects diabetes-induced biochemical and ultrastructural alterations in liver tissue

We have shown that a single dose of streptozotocin (STZ) (50 mg/kg body weight) injected into rats caused significant changes in some antioxidant enzyme activities, such as glutathione peroxidase, glutathione reductase, glutathione-S-transferase, glucose-6-phosphate dehydrogenase, and 6-phosphogluconate dehydrogenase activities, and acid-soluble sulfhydryl levels of the liver tissue with respect to the control rats. Furthermore, these alterations in the activities of the antioxidant enzymes were accompanied by significant changes in the ultrastructure of the liver tissue; mainly intercellular biliary canaliculi were distended and contained stagnant bile, swollen mitochondria in hepatocytes and disoriented and disintegrating cristae, dilatation of the rough endoplasmic reticulum (rER) with detachment of ribosomes, and dissociation of polysomes. Both diabetic and normal rats were treated with sodium selenite (5 micromol/kg/d, intra peritoneally) for 4 wk following 1 wk of diabetes induction. This treatment of diabetic rats improved significantly diabetes-induced alterations in liver antioxidant enzymes. Moreover, treating of diabetic rats with sodium selenite prevented primarily the variation in staining quality of hepatocytes nuclei, increased density and eosinophilia of the cytoplasm, focal sinusoidal dilatation and congestion, and increased numbers of mitochondria with different size and shape. In summary, treatment of diabetic rats with sodium selenite has beneficial effects on both antioxidant system and the ultrastructure of the liver tissue. These findings suggest that diabetes-induced oxidative stress can be responsible for the development of diabetic complications and antioxidant treatment can protect the target organs against diabetes.     

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.     

Fine structure of seminiferous tubules in antarctic seals

Summary The fine structure of seminiferous tubules from 5 crabeater, 2 leopard and 2 Ross seals showed that during the nonbreeding season the tubules were essentially similar in possessing spermatogenic and Sertoli cells. However, the tubules of leopard and Ross seals had more primary and secondary spermatocytes and spermatids than the crabeater seals. In general, the tubules were devoid of spermatozoa. The spermatids showed stages of maturation such as Golgi phase of acrosome formation, acrosomal cap formation and condensation of nuclei. Some spermatids degenerated in tubules. Both maturing and degenerating spermatids were closely associated with Sertoli cells. Junctional complexes with plaques of filaments were observed between Sertoli cells and the spermatogenic cells. Sertoli cells, irregular and polygonal, contained highly convoluted nuclei, strands of rough endoplasmic reticulum, smooth endoplasmic reticulum, Golgi complexes, small mitochondria, variable amounts of lipid droplets, lysosomes, lipofuscin granules and highly plicated plasma membranes. In brief, the spermatogenic activity had practically ceased in the testes and the animals probably secreted low levels of testosterone during the nonbreeding season.This research was supported in part by National Science Foundation Grants G.U. 30270 and G.U. 29829X from the Office of Polar Program and by NIH Grant 5 R01 AM11-376     

An observation of fine tubules within the endoplasmic reticulum in a dog liver

Summary During a survey of liver tissue from 100 dogs, fine tubules were observed within the cisternae of the endoplasmic reticulum of hepatocytes in one dog. The tubules were 300 Å in diameter with electron dense walls of 100 Å thickness. Many cells contained the tubules but their significance is unknown. The tubules varied from other reported microtubules in their location, size and characteristics of fixation and staining.     

Ultrastructure of the liver of the fingerling rainbow trout Salmo gairdneri Richardson

Portions of the livers of fingerling rainbow trout were studied by light and electron microscopy. The histology, cytology and ultrastructure of mesothelial cells, serosal fibroblasts, hepatocytes, sinusoidal endothelial cells, endothelial cells of central veins and blood cells were described. Mesothelial cells and fibroblasts constituted a very thin capsule. Hepatocytes contained extensive areas of rough surfaced endoplasmic reticulum, consisting mainly of parallel cisternae and pools of glycogen. One or two nuclei and numerous mitochondria occurred in the areas of endoplasmic reticulum, but never in the pools of glycogen. Hepatocyte surface possibilities included hepatocyte to hepatocyte, hepatocyte to bile canaliculus, hepatocyte to space of Disse and hepatocyte to serosa. The trout liver was compared compared to channel catfish liver and to rat liver. Functional implications of the structural features were discussed.