Ultrastructure of the kidney of the newt

In the newt [Triturus vulgaris (J.)] kidney a zone of single nephrons is distinguished, where there are ten nephrons, connected with the paramesonephral (Müller's) canal, and another zone of the renal mass; in the latter the main part of nephrons is situated, which are connected with the ureter by means of collecting tubules. In these zones of the kidney ultrastructure of epitheliocytes in the proximal and distal parts is different. The renal corpuscles of the epithelial cell in the cervical and in the intermediate parts are similar in both zones. In the zone of the single nephrons a specific peculiarity of epitheliocytes in the proximal and in the distal parts of the canaliculi is presence of numerous secretory granules in their cytoplasm. The canalicular epitheliocytes in the renal mass zone are different in the terminal and in the initial parts of the canaliculi: the former contains more mitochondria, and the area of the basolateral parts of plasmolemma is greater than those in the latter. These results are in accordance with the level of sodium ions transport in these parts of the canaliculus.     

Various structural aspects of the functional transformation of the kidneys during adaptation to fasting

Electron microscopic and morphometric investigations of the rat kidneys in 3-6 days after a complete fasting have revealed certain ultrastructural signs of an increased proteolysis in the proximal parts of the nephron canaliculi and structural manifestation in the glomerular blood stream changes, that represents an important condition for passing proteins the glomerular membrane. In this connection, it is supposed that at adaptation to fasting the kidney ensures proteolysis of endogenic-proteins--the first stage of their reconstruction. This function is ensured by structural-functional reconstruction of the juxtaglomerular complex, vessels of the filtrative apparatus and by the proteolytic system in the proximal part of the nephron canaliculus.     

A three-dimensional study of organelle interrelationships in regenerating rat liver. 3. Organelles related to bile.

A number of cell structures are described which show a morphological relationship to the bile canaliculi. Two types of peribiliary vesicles are identified: osmication positive ones occurring between the bile canaliculi and the osmicated immature Golgi cisternae and probably deriving from the latter, and osmication negative ones related to MVB, on which they appear as buds. Small coated vesicles are seen attached to this second type. Large lacunae may originate from MVB, as suggested by the MVB-like internal vesicles they may contain. Some stay in luminal continuity with the bile canaliculi. Canalicular coated vesicles are seen as parts of the canalicular plasma membrane and free in the cytoplasm.     

体外冲击波碎石术对兔肝酶活性的影响

采用超微组织化学方法,观察了体外冲击波碎石术(ESWL)对家免肝脏酶活性的影响。实施 ESWL 后,肝细胞的琥珀酸脱氢酶(SDH)和毛细胆管壁上的碱性磷酸酶(ALP)、焦磷酸硫胺素酶(TPPase)反应活性减弱或消失。TPPase 从损伤的肝细胞高尔基体分泌面扁囊、溶酶体样小泡和毛细胆管内溢出,并伴有肝细胞面的质膜上出现了 TPPase 反应产物和形成膜包内凹小泡。结果提示 ESWL 可对肝细胞及毛细胆管的功能和结构有损伤作用。     

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.     

Cytologic and ultrastructural organization of the kidney tubules of certain amphibia

As the investigation performed demonstrated, there is no principle differences in cytological organization in kidneys of five species of Amphibia whose mode of life to a certain extent is connected with water environment. Nevertheless, in different species epithelium of proximal parts of nephrons demonstrates various intensity of apocrinic secretion. Granules situating in the supranuclear zone of the epithelial cells of these parts are, in fact, autophagic lysosomes, their function is evidently connected with both lysis of the absorbed proteins and with autolysis of the apical cellular part in the process of secretion. The epithelial cytoplasm in the distal part of the nephron is characterized by a high succinate dehydrogenase activity; it is connected with its main function--osmoregulation. There are dark and light cells, resembling those in higher vertebrates, in the connecting part and in the collecting tubes. Ultrastructural organization of the brown frog nephron cells has much in common with that of epithelium of the secondary kidney urinary canaliculi.     

Morphological changes in the liver of the sea lamprey, Petromyzon marinus L., during metamorphosis. II. Canalicular degeneration and transformation of the hepatocytes

Degeneration of all bile canaliculi takes place in the liver of the sea lamprey, Petromyzon marinus, during metamorphosis. Disintegration of microvilli is observed during earlier stages, and membranous debris ultimately accumulates within the canalicular lumina. Complete occlusion of the lumina and disorganization of junctional complexes is followed by a complete loss of the exocrine biliary pole of hepatocytes and a reorganization of these cells into solid cords. An increase in the size and number of acid phosphatase-containing cytoplasmic bodies coincides with the events of canalicular degeneration. These secondary lysosomes apparently participate in some manner in the isolation and disposal of iron and other bile constituents which no longer can be excreted in bile canaliculi. The loss of the exocrine biliary pole of hepatocytes is concomitant with vascular disturbances in the form of disordered arrangements of sinusoidal endothelial cells and an increase in the population of activated Kupffer cells involved in erythrophagocytosis. The significance of the shift in functional organization of the liver in adult lampreys is discussed in relation to physiological changes in this organism and to human hepatic cholestasis, for which this organism is a potentially valuable experimental model.     

Age-related changes in the ultrastructural organization of the human gingival epithelium

By means of transmissive and scanning electron microscopy 103 gingival bioptates in practically healthy persons at the age of 18-80 years have been studied. At ageing essential changes take place in all structural elements of the epithelium. The basal membrane is intermittent and loose. In cytoplasm of the cells of the basal layer epithelium the amount of microfilaments increases essentially, and as a result it becomes electron opaque. Tonofibrillar fasciculi of the spinous layer cells are fragmented, their contours are indistinct. In cytoplasm of the granular layer cells amount of keratohyalin granules increases, their size becomes large and their typical form is lost. In cytoplasm of the basal, spinous and granular layer cells the amount of organells decreases. Mitochondria acquire the appearance of electron translucent cavities with discomplexic, and sometimes, destroyed cristae. Rather great changes occur in intercellular interrelations. In all the layers some intercellular spaces are widen, in the spaces formed isolated desmosomes and other debries of cellular structures are formed. Sharp changes of microrelief of the granular layer epitheliocytes are observed. The ultrastructural rearrangements of epitheliocytes, revealed in the human gingiva, demonstrate certain disturbances in keratinization processes, in mechanical firmness, as well as in barrier function of the epithelial layer.     

Epithelial structural changes in the urinary tubules of the kidney of the white rat in the early period of corrosive sublimate nephrosis

Examination of serial semithin (0.5 micron) methacrylate and paraffin (8 micron) sections of the rat kidney 6, 12, 24 and 48 hours after subcutaneous injection of sublimate in a dose of 0.6 mg/100 g bw has demonstrated that the damage to the different parts of the tubular component of nephron is heterogeneous in nature. Both complete and partial necrosis of nephrocyte cytoplasm can be seen in the proximal part of nephron. The distal parts of nephron and collective tubules are characterized by partial necrosis of the apical areas of the cytoplasm. During the period between 12 and 24 hours after sublimate injection, one can observe the onset of destructive processes together with intracellular recovery processes in partially damaged but still viable nephrocytes, which is confirmed by the enlargement of the nucleolar size. The regeneration of the tubular epithelium at the expense of cellular renewal was unmarked 24 hours after sublimate injection.     

Bile canalicular barrier function and expression of tight-junctional molecules in rat hepatocytes during common bile duct ligation

Tight junctions of hepatocytes form the intercellular barrier between the blood circulation and bile flow. We focused on early stages of common bile duct ligation to observe changes in tight junctions without the irreversible changes seen after lengthy ligation. Common bile ducts of 12-week-old male rats were ligated for 6 h because, at this time point, no histological changes were observed. Serum bilirubin and bile acid levels began to increase 3 h after ligation and were restored to the control level immediately after surgical removal of the ligation. To examine the barrier of hapatocytes, horseradish peroxidase was injected via the femoral vein, and bile was collected for the first 10 min. A four-fold elevation of the secretion and concentration was observed in the bile of ligated rats compared with that of control animals. We next examined lanthanum permeability by perfusion fixation of the liver. At 6 h after ligation, both dilation of the bile canaliculi and partial loss of microvilli were commonly observed. There were dense deposits of lanthanum in almost all bile canaliculi of ligated rats. In control animals, neither dilation of the bile canaliculi nor loss of microvilli was detected, and only 44% of bile canaliculi exhibited deposits. An apparent increase of occludin mRNA expression was detected in livers after 6 h ligation, whereas the expression of claudin-1, -2, and -3 was not influenced by ligation. These results indicate that regulation of occludin gene expression is different from that of claudin-1, -2, and -3. The early phase of bile stasis employed in this study is thought to be an indispensable approach for understanding the precise regulation of tight junctions.     

Curcumin Prevents Bile Canalicular Alterations in the Liver of Hamsters Infected with Opisthorchis viverrini

Opisthorchis viverrini infection causes inflammation and liver injury leading to periductal fibrosis. Little is known about the pathological alterations in bile canaliculi in opisthorchiasis. This study aimed to investigate bile canalicular alterations in O. viverrini-infected hamsters and to examine the chemopreventive effects of curcumin on such changes. Hamsters were infected with O. viverrini and one group of animals was fed with 1% dietary curcumin supplement. Animals were examined during the acute infection phase, days 21 and 30 post-infection (PI) and chronic infection phase (day 90 PI). Scanning electron microscopy revealed that in the infected group fed with a normal diet, bile canaliculi became slightly tortuous by 30 day PI and more tortuous at day 90 PI. Transmission electron microscopy showed a reduction in microvilli density of canaliculi starting at day 30 PI, with a marked loss of microvilli at day 90 PI. These ultrastructral changes were slightly seen at day 21 PI, which was similar to that found in infected animals fed with 1% curcumin-supplemented diet. Notably, curcumin treatment prevented the reduction of microvilli density, reduced the dilation of bile canaliculi, and decreased the tortuosity of the bile canaliculi relative to non-infected animals on a normal diet at days 30 and 90 PI. These results suggest that curcumin reduces alteration of bile canaliculi and may be a promising agent to prevent the onset of bile duct abnormalities induced by O. viverrini infection.     

Characteristics of destructive-regenerative processes in the kidneys of albino rats in conditions of necronephrosis caused by corrosive sublimate

Study of serial semi-thin (0.5 micron) metacrylate and paraffinic (8 microns) of rat kidney sections 6, 12, 24 and 48 h after subcutaneous injection of mercury bichloride at a dose of 0.6 mg/100 g bw has revealed that injury to different parts of the canalicular nephron is of heterogeneous character. The proximal part of the nephron demonstrates both complete and partial necrosis of nephrocyte cytoplasm. The distal parts of the nephron and collecting tubules are characterized by partial necrosis of the apical cytoplasm. Within the period between 12 and 24 h after the mercury bichloride injection, intracellular reparative processes are observed, in addition to destruction, in partially damaged but viable nephrocytes, which is confirmed by the enlargement of the nucleolic size. Regeneration of the tubular epithelium due to cellular restoration was unmarked 24 h after the mercury bichloride injection.     

Use of lectin histochemistry method in the characterization of biopolymer glycosylation processes in duodenal gland cells

Potentialities of lectin histochemistry method for analysis of glycosylation processes within secretory epitheliocytes have been investigated using duodenal glands of cow and sheep as a model system. It has been ascertained, that con A- and LCA-binding sites (mannosglycans) localize exclusively in basal cytoplasm of duodenal gland epitheliocytes, which corresponds to rough endoplasmic reticulum. Manifestation of D-galactose, L-fucose, N-acetyl-D-galactosamine residues within oligosaccharide changes (PNA-, RCA-, WGA- and LAA-reactivity) was detected in the supranuclear region and apical cytoplasm of glandulocytes, that corresponds to Golgi complex, SBA-reactive glycoconjugates were determined only in poorly differentiated cells, forming initial parts of glandular ducts, but were absent in more differentiated cells of superficial and profound acini. The results obtained demonstrate fine prospects that are opened by the use of lectin-peroxidase kits in precise analysis of glycopolymers processing within functionally active and differentiating glandular cells.     

Organogenesis of the liver in sea bream

Development of the liver in sea bream, Sparus aurata , was studied using light and electron microscopy from hatching to the age of 23 days. Histochemical reactions were used to monitor changes in lipids and glycogen during this period. During the strictly endotrophic prelarval phase from hatching until mouth-opening, the primordial liver formed by budding on the gut wall and became organized in contact with the vitelline vesicle. The initially undifferentiated cells rapidly polarized and became pyramidal in outline with their apical extremities terminating in cavities corresponding to the future bile canaliculi. Sinusoids formed centripetally. Glycogen was stored in the cytoplasm of differentiating hepatocytes. At the beginning of the larval stage the hepatocytes multiplied, bile canaliculi were completed and the sinusoids acquired their final form. Glycogen reserves decreased strongly as bile secretion started. The end of the endo-extrophic period was marked by distinct recovery of glycogen storage, synthesis of numerous lipoproteins and discharge into the sinusoids.     

Plasma membranes of the rat liver. Isolation and enzymatic characterization of a fraction rich in bile canaliculi

A method is described for the rapid isolation of a plasma membrane fraction containing a high concentration of intact bile canaliculi from the rat liver. Isolated bile canaliculi retain most of the ultrastructural features exhibited in the intact liver cell. The final fraction contains 5''-nucleotidase activity at approximately the same concentration as that in previous preparations of plasma membranes. In the presence of 0.01 M Mg⁺⁺, 5''-nucleotidase exhibits a double pH optimum at pH values of 7.5 and 9.5. The activities of glucose-6-phosphatase and alkaline phosphatase are present in low amounts. Cytochrome P-450 is not detectable. Na⁺-K⁺-activation of ATPase is observed to the extent of 20–36% in about half of the assays. The availability of a method for preparation of intact bile canaliculi should prove useful for studying the biochemical events associated with the transport of bile constituents into canaliculi.     

Bile salt related secretion of acid phosphatase in rat bile

The biliary excretion of bile salts, lysosomal acid phosphatase, and total proteins were studied in rats under different experimental conditions: during bile salt loss through a bile fistula and after loading with exogenous sodium taurocholate. The experimental models were suitable to demonstrate that variations in the excretion of bile salts were associated with those of acid phosphatase output. During bile salt depletion, acid phosphatase output showed a decrease parallel to that of bile salts. Following a single i.v. injection of sodium taurocholate and during its i.v. infusion, a rapid increase of acid phosphatase excretion in bile was seen. The patterns of enzyme outputs observed after administration of sodium taurocholate suggested a bulk discharge in bile of lysosomal contents. The profiles of protein output were similar to those of acid phosphatase suggesting an association between the secretory mechanism of these bile constituents. In contrast to sodium taurocholate, 4-methylumbelliferone, which also increases canalicular bile flow, did not produce changes in the excretory patterns of the bile components studied. Therefore, the results suggested a bile salt related secretion of acid phosphatase in the rat, which may involve protein secretion in bile.     

Liver Ischemia and Ischemia–Reperfusion Induces and Trafficks the Multi-specific Metal Transporter Atp7b to Bile Duct Canaliculi: Possible Preferential Transport of Iron into Bile

Both Atp7b (Wilson disease gene) and Atp7a (Menkes disease gene) have been reported to be trafficked by copper. Atp7b is trafficked to the bile duct canaliculi and Atp7a to the plasma membrane. Whether or not liver ischemia or ischemia–reperfusion modulates Atp7b expression and trafficking has not been reported. In this study, we report for the first time that the multi-specific metal transporter Atp7b is significantly induced and trafficked by both liver ischemia alone and liver ischemia–reperfusion, as judged by immunohistochemistry and Western blot analyses. Although hepatocytes also stained for Atp7b, localized intense staining of Atp7b was found on bile duct canaliculi. Inductive coupled plasma-mass spectrometry analysis of bile copper, iron, zinc, and manganese found a corresponding significant increase in biliary iron. In our attempt to determine if the increased biliary iron transport observed may be a result of altered bile flow, lysosomal trafficking, or glutathione biliary transport, we measured bile flow, bile acid phosphatase activity, and glutathione content. No significant difference was found in bile flow, bile acid phosphatase activity, and glutathione, between control livers and livers subjected to ischemia–reperfusion. Thus, we conclude that liver ischemia and ischemia–reperfusion induction and trafficking Atp7b to the bile duct canaliculi may contribute to preferential iron transport into bile.     

Primary liver cell cultures grown on gas permeable membrane as source for the collection of primary bile

Summary Isolated rat hepatocytes maintained in primary culture on gas permeable membrane for 20 h form monolayers and establish at their cell borders a network of canaliculi (approximate diameter 3.5 μm). In the presence of the known choleretic bile acid dehydrocholate, dilation of canaliculi occurs. When nonfluorescent carboxyfluorescein diacetate ester is added to the culture medium, fluorescent carboxyfluorescein appears in the intracanalicular space. In the dilated state, fluid containing the fluorescent compound could be collected from the canaliculi by puncture with a micropipette. The intracanalicular space shows a negative electrical potential difference of 31 mV in reference to the bath solution and is 13.5 mV more positive with reference to recordings from the cytosol of cultured rat hepatocytes. Cultured rat hepatocytes grown on gas permeable membrane are energetically stable over 3 d. On Day 4, ATP levels increase markedly, whereas Na⁺−K⁺-ATPase activity declines. Ionic composition of hepatocytes, as measured by electronprobe element analysis on cryosection samples, does not change markedly during monolayer formation. With formation of bile canaliculi, the activity of alkaline phosphatase rapidly increases within 24 h and is stable for the next 3 d. Within that time the activity of γ-glutamyltranspeptidase, however, increases steadily, reaching a 1.6-fold higher activity than freshly isolated hepatocytes. Bile acids appear in the culture supernatant after 1 d. When unconjugated [¹⁴C]cholic acid is added to the cultures the supernatant contains also [¹⁴C]tauro- and [¹⁴C]glycocholic acid, indicating the preservation of conjugation capacity in these cultures. Total bile acid concentrations in the supernatant increase from 5 to 26 μM on Day 4. The cultures do not secrete α-fetoprotein. Monolayer cultures of hepatocytes in the presence of choleretic bile acids seem to be a suitable model system to collect and to analyze the composition of primary bile. In conjunction with the electrical parameters, it is possible to describe directly properties of bile secretion at the canalicular pole of the intact hepatocyte. This work was supported by the Deutsche Forschungsgemeinschaft, grant no. PE 250/5-1.     

Distribution of monoaminergic structures in the amphibian kidney

Distribution of monoaminergic structures in the kidney of two frog species has been studied by means of the fluorescent-histochemical method. Neural fibers containing catecholamines are revealed in the renal artery wall, in the portal veins walls, in the glomerular arteriole walls. No catecholamine-containing neural fibers have been revealed in the glomerular capillaries. The catecholamine-containing neural fibers tightly adjoining the walls of the proximal and distal parts of the nephron canaliculi have been revealed. The neural structures containing indolamines are not observed.     

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.