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PubMed1982

Lanthanum as an electron microscopic stain.

Applications of lanthanum as an electron microscopic tracer have been reviewed. This electron-dense trivalent cation, which binds avidly to calcium binding sites, can be used as tracer for delineating extracellular spaces and intercellular junctions. It has served as a basis for classification of junctional structures. It can also be used as a calcium probe, a tracer in studying the permeability of barriers, as an intracellular marker and as an electron microscopic stain for such membrane components as surface glycoprotein. Each of these applications may require a different methodology. Thus methodological considerations in the use of this tracer have also been reviewed. The recent recognition that lanthanum is more than a passive tracer and that by reacting with different cell components may serve as a true stain, will extend the use of lanthanum in electron microscope histochemistry.

Animals↗
PubMedDate not supplied

Aberrant E-cadherin expression associated with loss of differentiation and advanced stage in human pancreatic cancer.

E-cadherin is a cell-cell adhesion molecule involved in tumour invasion and metastasis. We evaluated E-cadherin expression immunohistochemically in 43 formalin-fixed, paraffin-embedded specimens of pancreatic cancer and investigated its relationship to histopathological features. In non-cancerous pancreatic cells E-cadherin immunoreactivity was localized at the cell membrane, particularly at the intercellular junctions. Abnormal E-cadherin expression was found in 18 (42%) cases. A significantly higher proportion of poorly-differentiated tumours (71%) showed abnormal E-cadherin expression compared with moderately (50%) and well (19%) differentiated tumours (P = 0.037). There was a significant correlation between abnormal E-cadherin expression and lymph node involvement (P = 0.013), the presence of distant metastases (P = 0.034) and advanced tumour stage (P = 0.025). These findings suggest that loss of normal E-cadherin expression is involved in the progression of pancreatic cancer.

Cadherins↗
PubMed2001

beta-catenin: molecular plasticity and drug design.

The protein beta-catenin is an essential component of intercellular junctions and the Wnt growth factor signaling pathway. In many cancers, mutation of Wnt pathway components leads to activation of oncogenes by the beta-catenin-Tcf transcription factor complex. This complex is therefore an attractive target for anti-cancer drugs, but any such compound must selectively interfere with the beta-catenin-Tcf complex without disrupting other essential interactions of beta-catenin. Recent structural and biochemical studies have probed the molecular basis of ligand interaction by beta-catenin, and highlighted the possibilities and challenges of designing inhibitors of the beta-catenin-Tcf complex.

Animals↗
PubMed1993

Biliary atresia in lampreys.

The preceding pages have described an organism that is far removed from mammals on the taxonomic scale of vertebrates but one that has proven to have a unique and most useful system for studies of liver function and, in particular, bile product transport and excretion. It is also an organism in which iron loading can be studied in the liver and other organs and tissues. Many of the events that occur in this animal during its life cycle with regard to bile pigment metabolism as normal programmed phenomena are unparalleled among the vertebrates. In the larval (ammocoete) period of lampreys, there is an intrahepatic gallbladder and a biliary tree that is well equipped for the storage, transport, and elimination of bile products into the intestine for ultimate excretion with the feces. The importance of the patency of these bile ducts to bile excretion is illustrated in one species of lampreys in which the bile ducts of young ammocoetes become infested with larval nematodes to a degree that bile pigment regurgitation into the blood results in a green serum that is identified as biliverdin. Despite having serum levels of biliverdin that would be toxic to humans, these individuals live a complete larval life. The larvae of all lamprey species undergo a phase of metamorphosis in which they transform into adults. During this phase the larval gallbladder, the bile canaliculi of the hepatocytes, and all the intrahepatic bile ducts completely regress in a developmental process called lamprey biliary atresia. The epithelium of the extrahepatic common bile duct transforms and expands into a caudal portion of the endocrine pancreas of the adult. Many of the events of lamprey biliary atresia resemble events occurring during experimental and pathological conditions of mammalian cholestasis, including disruption to the bile-blood barrier (intercellular junctions), accumulation of bile components in the cytoplasmic inclusions, and alteration of the distribution of membrane enzymes in hepatocytes. Regression of the bile ducts and ductules is accompanied by a periductular fibrosis that seems to be a product of activity by lipocytes (Ito cells). The regurgitation of bile products into the interstitial tissue of the liver during early biliary atresia may be the stimulus for both inflammatory (granulomatous) and autoimmune responses. There are no bile ducts in adults lampreys, yet they seem to show no immediate consequences of the absence of an exocrine mechanism for the elimination of bile products.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1975

Ultrastructure of two cases of anaplastic giant cell tumor of the human thyroid gland.

Electron microscopy of two cases of anaplastic giant cell tumor of the thyroid revealed that these neoplasms consisted of pleomorphic cells with large, bizarre-shaped nuclei and relatively little cytoplasm rich in rough endoplasmic reticulum. The presence of various intercellular junctions, the resemblance of tumor cells to non-neoplastic epithelial cells of the thyroid follicles and the observation that follicular remnants were identified in the tumor, support the assumption that these tumors derive from the follicular epithelium and can be regarded as carcinomas. Aggregates of cytoplasmic spherical bodies, ultrastructurally similar to virus particles, were detected in some tumor cells. Further investigation is required to determine the nature of these structures and establish their pathogenetic role. In some tumor cells, tubuloreticular arrays were noted within the dilated cisternae of the endoplasmic reticulum; these may represent ultrastructural manifestations of nonspecific injury.

Aged↗
PubMed1984

Ultrastructure and immunohistochemical localization of estradiol in three thecomas.

Three ovarian thecomas were studied by ultrastructural and immunohistochemical techniques. In each tumor, a small number of tumor cells stained for estradiol. Vacuolated as well as plump non-vacuolated tumor cells were positive, but spindle-shaped cells were negative. Ultrastructural examination showed two principle cell types. Type I cells were immature mesenchymal cells that differed from typical steroid-secreting cells because only a minority had conspicuous smooth endoplasmic reticulum, although mitochondria often had tubular cristae. Type II cells were distinguished by abundant intermediate (10-nm) microfilaments and round mitochondria with incomplete cristae and empty centers. Focal smooth muscle differentiation was present in each tumor. Adherens-type intercellular junctions, including desmosomes in one case, and degenerate cells with markedly vesiculated cytoplasmic membrane systems were also present. Lipid was not abundant, but it was more conspicuous in degenerate cells and in type II cells. Thecoma cells thus closely resemble both ovarian stromal cells and theca interna cells, which are known to be capable of steroidogenesis. The localization of estradiol in a minority of tumor cells in each thecoma suggests that thecoma cells, too, are capable of steroid synthesis and supports the popular concept that hyperestrogenism in patients with thecomas may be the result of estradiol secretion by these tumors.

Adolescent↗
PubMed1979

[Changes in intercellular exchange intensity in an L cell culture].

Intercellular junctions permeable to fluorescein Na were studied with the aid of intracellular glass microelectrodes in the cultures of transformed mouse-embryo cells (L-strain). The degree of coupling was correlated with the cell culture density. In addition, the degree of coupling increased after short-time incubated of the cells with 1mM lanthanum. Such an incubation did not influence other features of cells: the value of the membrane potential, the character of growth or the inclusion of the vital dye neutral red. Some other factors stimulated cellular aggregation (concanavalin A, protamine, decreasing the pH) but did not influence the degree of coupling.

Animals↗
PubMed1984

Alcoholic liver injury in baboons: transformation of lipocytes to transitional cells.

Ultrastructure of the lipocytes (the main perisinusoidal cells) and their alterations in the progression of hepatic fibrosis were studied in liver biopsy specimens of baboons pair-fed with diets containing alcohol, or isocaloric carbohydrate, for up to 112 mo. In control baboons, 97% of the cells in the Disse space were lipocytes characterized by a volume density of lipid droplets occupying greater than 20% of the cell volume and by the presence of microfilament bundles with associated dense bodies and pinocytic vesicles. Intercellular junctions of the adherens type were present between lipocytes and hepatocytes. After alcohol consumption, the number of lipocytes (as assessed by light microscopy) was significantly decreased in fatty livers and at various stages of hepatic fibrosis; this was associated with a decreased hepatic vitamin A content. In baboons fed alcohol, only 48% of cells were lipocytes, whereas 52% were transitional cells defined by a volume of lipid droplets less than 20% of the cell. Like the lipocytes, transitional cells exhibited microfilament bundles, dense bodies, and pinocytic vesicles, and were attached to the hepatocytes by cell junctions. The rough endoplasmic reticulum in transitional cells was conspicuous and had an area significantly greater than that in lipocytes of controls and alcohol-fed animals (69% and 37%, respectively). There was a significant correlation between the percentage of transitional cells as well as the area of their rough endoplasmic reticulum and the degree of hepatic fibrosis. Thus, in baboons fed alcohol, the progression of hepatic fibrosis is associated with transformation of lipocytes to transitional cells characterized by a depletion of lipid droplets and a hypertrophy of the rough endoplasmic reticulum; these transitional cells may play a role in promoting hepatic fibrosis in alcoholic liver injury.

Adipose Tissue↗
PubMed1982

Organization of actin filaments in early chick embryo ectoderm: an ultrastructural and immunocytochemical study.

By combining transmission electron microscopy (TEM), scanning electron microscopy (SEM) and immunocytochemistry at both light and TEM levels the organization of actin in early chick ectoderm has been demonstrated. Every cell is encircled by a ring of actin filaments which are associated with apically situated intercellular junctions. In this way the actin ring of each individual cell is connected to that of surrounding cells and a continuous network is formed. As clearly shown by immunofluorescence and SEM studies on intact and Triton X-100 treated whole-mount preparations this network extends throughout the entire layer, interrupted only at the blastoderm margins and the primitive streak. A more diffuse arrangement was sometimes seen at cell bases. It is suggested that the network extending throughout the ectoderm gives it stability and cohesion and is important in gross morphogenetic movements involving the entire layer. The less-organized arrangement at cell bases is associated more with movements of individual cells.

Actins↗
PubMed1981

Polymorphonuclear leukocyte migration through human amnion membrane.

A new in vitro model has been developed for studying migration of human polymorphonuclear leukocytes (PMN) through living native cellular and matrix barriers. Human amnion membrane consists of a single layer of epithelium bound to a continuous basement membrane interfacing an avascular collagenous stroma. Living amnion was placed in plastic chambers with separate compartments on each side of the membrane. PMN were introduced on the epithelial side of the amnion, and a Millipore filter (Millipore Corp., Bedford, Mass.) was placed against the stromal side. In response to N-formylmethionyl-leucyl- phenylanlanine (FMLP) chemoattractant, PMN penetrated the full thickness of the amnion and were collected and counted on the filter. The rate of PMN traversal of the amnion was dependent on the concentration of FMLP (optimal at 10(-8)M) as well as the slope of the FMLP gradient across the amnion. The route of PMN migration was studied by transmission electron microscopy. PMN first attached to the epithelial surface, then infiltrated between intercellular junctions. PMN migrated around or through tight junction and hemidesmosome attachments. The PMN then penetrated the basement membrane and migrated through the dense collagenous stroma. The present amnion migration system has characteristics of the in vivo inflammatory state not described in any previous method for monitoring PMN migration in vitro. Prior methods have not used native epithelium, whole basement membrane, or collagenous stroma. PMN penetration of these barriers occurs in the normal inflammatory response and probably involves biochemical mechanisms not required for simple migration through the pores of an artificial filter. The amnion system can be useful for future biochemical and morphological studies of PMN penetration of these barriers and possible repair processes that may follow.

Amnion↗
PubMed1999

Intercalated duct cells in the chicken pancreatic islet with special reference to the alloxan administration.

The intercalated duct cells were observed in the A and B islets of the chicken pancreas. These cells adhered with each other by intercellular junctional complexes at the apical side. They had many microvilli projecting into the lumen. Abluminally, they displayed extended slender cytoplasmic processes between islet endocrine cells. Administration of alloxan resulted to denser cytoplasm and a more prominent thickening of cytoplasmic processes of the intercalated duct cells, although the blood glucose levels did not show appreciable changes by the treatment. The intercalated duct epithelial cells appeared clearly as stellate cells. The lysosomes increased in size and number with passage of time after alloxan administration. The present findings may suggest that intercalated ducts are not only anatomically important as a structure passing through the islet but also play physiologically by protecting the islet endocrine cells.

Alloxan↗
PubMed1992

The ventriculus terminalis and filum terminale of the human spinal cord.

Serial sections of the conus medullaris and the filum terminale of 23 randomly selected human spinal cords were studied by light and electron microscopy, and following immunoperoxidase staining for glial fibrillary acidic protein (GFAP), vimentin, neuron-specific enolase (NSE), amyloid beta protein, and S-100 protein. The intradural portion of the filum contains bundles of GFAP-positive glial fibers, scattered silver- and NSE-positive neurons, segments of peripheral nerve, blood vessels, fibrous connective tissue, and fat. Glial cell clusters varying from five to 100 cell layers thick at times constitute the bulk of the filum. The periependymal glial cells possess moderate amounts of eosinophilic cytoplasm and relatively uniform round to ovoid nuclei containing evenly distributed chromatin. They are distributed diffusely with no specific pattern of organization, although some of them showed a tendency to form acinar structures. A minority of the glial cells showed GFAP immunoreactivity, and some were immunoreactive for vimentin. Electron microscopy demonstrated the presence of periependymal cells showing cilia, microvilli, and the formation of intercellular junctional complexes, as well as cells containing bundles of glial filaments within the cytoplasm. Degenerated NSE-positive neurons and degenerated neurites resembling neuritic plaques were also demonstrated. However, immunoperoxidase staining for amyloid beta protein was negative in these structures. Thus, the filum terminale is endowed with an abundance of glial cells and neurons and is not simply a fibrovascular tag. Periependymal glial cells in the filum terminale should not be mistaken for neoplasm. The presence of neuropil with profuse astroglial and neuronal components within the filum terminale suggests a possible functional role for these structures.

Adolescent↗
PubMed1999

Evidence of blood-brain barrier dysfunction in human cerebral malaria.

Patients infected with the malaria parasite Plasmodium falciparum may develop a diffuse reversible encephalopathy, termed cerebral malaria. It is unclear how the intraerythrocytic parasite, which sequesters in the cerebral microvasculature but does not enter the brain parenchyma, induces this neurological syndrome. Adhesion of parasitized red blood cells in the brain microvasculature is mediated by specific receptors on the host endothelium, including intercellular adhesion molecule (ICAM)-1, CD36 and CD31. Leucocyte binding to cerebral endothelial cells in culture induces intracellular signalling via ICAM-1. The hypothesis that parasitized red blood cells binding to receptors on cerebral endothelial cells causes changes in the integrity of the blood-brain barrier was tested. Immunohistochemistry was used to examine the blood-brain barrier in human cerebral malaria, with antibodies to macrophage and endothelial activation markers, intercellular junction proteins, and plasma proteins. The distribution of the cell junction proteins occludin, vinculin and ZO-1 were altered in cerebral malaria cases compared to controls. While fibrinogen was the only plasma protein detected in the perivascular space, there was widespread perivascular macrophage activation, suggesting that these cells had been exposed to plasma proteins. It was concluded that functional changes to the blood-brain barrier occur in cerebral malaria, possibly as a result of the binding of parasitized red blood cells to cerebral endothelial cells. These changes require further examination in vitro.

Adolescent↗
PubMed1978

Studies on the ultrastructure and permeability of the hemotrichorial placenta. II. Fetal capillaries and tracer administration into the fetal blood circulation.

The distribution of horseradish peroxidase and lanthanum chloride within the full term chorioallantoic placenta of the rat was examined after administration of these tracers into the umbilical artery. Both tracers rapidly traverse the capillary endothelium. Transendothelial channels, fenestrations and micropinocytotic vesicles provide the main pathways. Intercellular clefts which are either patent or interrupted by leaky intercellular junctions, also contribute to a rapid passage of low and high molecular weight substances. Deep channel-like invaginations, effecting an increase of the exchange area of layer III, are freely accessible to the tracers from the interspace between the capillary endothelium and trophoblastic layer III. The invaginations, however, are not in continuity with the interspace between layers II and III, verifying the syncytial character of layer III. Neither an uptake of the tracers nor a passage across layer III is observed. The main permeability barrier to feto-maternal transfer within the chorioallantoic placenta is localized in the syncytiotrophoblastic layer III. This layer controls the passage of low molecular weight substances and restricts the penetration of high molecular weight substances.

Animals↗
PubMedDate not supplied

Cell incohesiveness and pattern of extension in a rare case of bronchioloalveolar carcinoma.

A unique case of adenocarcinoma of the lung that showed aerogenous extension is presented. Although the primary focus was the usual invasive bronchioloalveolar carcinoma, the tumor cells were dissociated, floating and filling the alveolar spaces, the bronchioli, and the small bronchi at the periphery of the primary tumor and in every involved area in other lobes of the lung. Massive tumor cells were expectorated in coincidence with the appearance of abnormal densities on chest X-ray films. Ultrastructurally the dissociated tumor cells had numerous microvilli on the cell surface and rarely showed intercellular junctions. The tumor cells also contained well-developed rough and smooth endoplasmic membranes, crista-vesicular-type mitochondria, electron-dense granules, and granules with myelinlike figures. No mucous granules and no Clara-cell-type secretory granules nor lamellar bodies of the type seen in normal granular pneumocytes were seen. From these findings, it was concluded that the tumor cells in this case were rather poorly differentiated but somewhat resembled the hyperplastic cuboidal alveolar cells seen in the damaged lung and that they proliferated freely in airways, presenting aerogenous metastases. The biologic behavior of this tumor might be partly explained by the incohesive nature of the tumor cells.

Adenocarcinoma↗
PubMedDate not supplied

Endothelial cell-cell adhesion and mechanosignal transduction.

Recent reports indicate that in addition to proteins that form various types of intercellular junctions, a considerable number of proteins are localized to the area of endothelial cell-cell association. Many of these are signaling proteins, suggesting that this is an area of active signaling. In this article, we have attempted to compile a list of proteins that have been localized to the area of interendothelial association and to briefly discuss what is known about each. Since various investigators including ourselves have proposed that the region of interendothelial cell association is an important site for mechanosignaling, we will focus our discussion on the possible role of these proteins in mechanosignal transduction. We will also review the available evidence for PECAM-1 as a mechanotransducing molecule in endothelial cells.

Animals↗
PubMed2003

Constitutive activation of Rho proteins by CNF-1 influences tight junction structure and epithelial barrier function.

The apical-most epithelial intercellular junction, referred to as the tight junction (TJ), regulates paracellular solute flux in diverse physiological and pathological states. TJ affiliations with the apical filamentous actin (F-actin) cytoskeleton are crucial in regulating TJ function. F-actin organization is influenced by the Rho GTPase family, which also controls TJ function. To explore the role of Rho GTPases in regulating TJ structure and function, we utilized Escherichia coli cytotoxic necrotizing factor-1 (CNF-1) as a tool to activate constitutively Rho, Rac and Cdc42 signaling in T84 polarized intestinal epithelial monolayers. The biological effects of the toxin were polarized to the basolateral membrane, and included profound reductions in TJ gate function, accompanied by displacement of the TJ proteins occludin and zonula occludens-1 (ZO-1), and reorganization of junction adhesion molecule-1 (JAM-1) away from the TJ membrane. Immunogold electron microscopy revealed occludin and caveolin-1 internalization in endosomal/caveolar-like structures in CNF-treated cells. Immunofluorescence/confocal microscopy suggested that a pool of internalized occludin went to caveolae, early endosomes and recycling endosomes, but not to late endosomes. This provides a novel mechanism potentially allowing occludin to evade a degradative pathway, perhaps allowing efficient recycling back to the TJ membrane. In contrast to the TJ, the characteristic ring structure of proteins in adherens junctions (AJs) was largely preserved despite CNF-1 treatment. CNF-1 also induced displacement of a TJ-associated pool of phosphorylated myosin light chain (p-MLC), which is normally also linked to the F-actin contractile machinery in epithelial cells. The apical perjunctional F-actin ring itself was maintained even after toxin exposure, but there was a striking effacement of microvillous F-actin and its binding protein, villin, from the same plane. However, basal F-actin stress fibers became prominent and cabled following basolateral CNF-1 treatment, and the focal adhesion protein paxillin was tyrosine phosphorylated. This indicates differences in Rho GTPase-mediated control of distinct F-actin pools in polarized cells. Functionally, CNF-1 profoundly impaired TJ/AJ assembly in calcium switch assays. Re-localization of occludin but not E-cadherin along the lateral membrane during junctional reassembly was severely impaired by the toxin. A balance between activity and quiescence of Rho GTPases appears crucial for both the generation and maintenance of optimal epithelial barrier function. Overactivation of Rho, Rac and Cdc42 with CNF-1 seems to mirror key barrier-function disruptions previously reported for inactivation of RhoA.

Actins↗
PubMed1985

The interphotoreceptor matrix and the interphotoreceptor space of the vertebrate retina.

The interphotoreceptor space (IPS) of the vertebrate retina is the adult corollary of the lumen within the embryonic optic vesicle. The inner limit of the IPS is formed by the intercellular junctions of Muller cells and photoreceptors forming the external limiting membrane (ELM). The apical surface of the retinal pigment epithelium (RPE) is the outer limit of the IPS. Most of the volume of the IPS is occupied by the inner and outer segments of the photoreceptors, with the microvillous processes of the RPE, and the small microvilli of the Muller cells filling lesser portions. SEM of samples fixed in glutaraldehyde containing 0.5% ruthenium red show the interstitial spaces are filled with interphotoreceptor matrix (IPM). Biochemical studies and our enzyme digestion studies suggest this extracellular material is enriched in glycoproteins and glycosaminoglycans. The carbohydrates are two-thirds sulfated, 25% sialic acid enriched, and about 10% hyaluronic acid. Most of the IPM proteins can be identified as products of adjacent cells.

Animals↗