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PubMed1977

The development and ultrastructure of previously dissociated foetal human cerebral cortical cells in vitro.

Cells from foetal human cerebral cortex were mechanically dissociated and subsequently maintained in vitro for periods ranging between three and twenty-eight days. The ultrastructure of these cells at different stages of their development in culture was extensively examined. Nuclear and cytoplasmic features were extremely variable and a wide range of cell types was evidently represented. Of the three principal cell types found i.e. neurons, neuroglia and mesenchymal cells, only a minority of cells was classified with confidence, particularly during the first two weeks in culture. Extensive intercellular junctions of the adhaerens variety, common after 14 days in vitro were present at an earlier stage of development than synaptic profiles. First indications of synapse formation were observed after 21 days in vitro and after 24 days presynaptic sites filled with synaptic vesicles and with well defined presynaptic and postsynaptic thickenings were found. The significance of some of the features observed are both considered and discussed.

Cerebral Cortex↗
PubMed1983

Specific attachment of desmin filaments to desmosomal plaques in cardiac myocytes.

Intercellular junctions which are similar in ultrastructure and protein composition to typical desmosomes have so far only been found in epithelial cells and in heart tissue, specifically in the intercalated disks of cardiac myocytes and at cell boundaries between Purkinje fiber cells. In epithelial cells the cytoplasmic side of desmosomes, the 'desmosomal plaque', represents a specific attachment structure for the anchorage of intermediate filaments (IF) of the cytokeratin type. Cardiac myocytes do not contain cytokeratin filaments. In primary cultures of rat cardiac myocytes, we have examined by immunofluorescence and electron microscopy, using single and double label techniques, whether other types of IF are attached to the desmosomal plaques of the heart. Antibodies to desmoplakin, the major protein of the desmosomal plaque, have been used to label specifically the desmosomal plaques. It is shown that the desmoplakin-containing structures are often associated with IF stained by antibodies to desmin, i.e., the characteristic type of IF present in these cells. Like cytokeratin filaments in epithelial cells, desmin filaments attach laterally to the desmosomal plaque. They also remain attached to these plaques after endocytotic internalization of desmosomal domains by treatment of the cells with EGTA. These desmin filaments do not appear to attach to junctions of the fascia adherens type and to nexuses (gap junctions). These observations show that anchorage at desmosomal plaques is not restricted to IF of the cytokeratin type and that IF composed of either cytokeratin or desmin, specifically attach, in a lateral fashion, to desmoplakin-containing regions of the plasma membrane. We conclude that special domains exist in these two IF proteins that are involved in binding to the desmosomal plaque.

Animals↗
PubMed1992

Changes in Müller cell plasma membrane specializations during subretinal scar formation in the rabbit.

The aim of this study was to identify changes in Müller cell plasma membrane specializations during experimentally induced subretinal gliosis in rabbits. When rabbits are dosed with sodium iodate, large expanses of retinal pigment epithelium and photoreceptors are destroyed. They are replaced by a subretinal scar consisting mainly of the ascending processes of Müller cells. These processes transform from the slender, highly polarized structures seen in normal animals into irregular processes that form a glia limitans along the basement membrane of the pigment epithelium, left bare following its degeneration. As the scar processes extend through the subretinal space and contract this basement membrane, they undergo dramatic changes in shape that are especially apparent in three-dimensional computer reconstructions of serial thick sections examined by high-voltage electron microscopy. Other changes involve the intercellular junctions and apical microvilli normally associated with the external limiting membrane. These structures become scattered over the surfaces of the ascending processes and are eventually lost. Loss of microvilli is associated with disappearance of immunostaining for a specific glycoconjugate normally associated with the microvillar plasma membrane. The observations document profound changes in Müller cell structural and functional polarity during subretinal scar formation.

Animals↗
PubMed1997

[Peritoneum as a dialysis membrane. II. Pathology].

Peritoneal dialysis is an established method of treatment of chronic renal failure. In that paper morphological and functional changes of peritoneum due to the process of long-term dialysis are presented. Morphological changes are observed in mesothelial cells, intercellular junctions, interstitial tissue and blood vessels. Moreover morphological changes in typical complications of chronic peritoneal dialysis, e. g. peritonitis, eosinophilic peritonitis, and sclerosing encapsulating peritonitis are described. Mechanisms of functional disorders during chronic peritoneal dialysis, involving the decreased permeability of the peritoneum, the increased permeability of the peritoneum and the enhanced lymphatic drainage are discussed. The article is the second of two parts presenting physiology and pathology of peritoneum as dialysis membrane.

Biocompatible Materials↗
PubMed1996

Design of the oxygen and substrate pathways. V. Structural basis of vascular substrate supply to muscle cells.

This paper quantifies the structural capacity of the transport steps for oxygen, glucose and fatty acids from the blood in capillaries to the cytosol of muscle cells and compares it with maximal rates of oxygen and substrate transport measured in the same animals and reported in the preceding papers of this series. Dogs have relatively more muscle per unit body mass than goats (37 versus 26%), but the maximal rate of oxidation per gram of muscle is still larger in the dog by a factor of 1.55. The maximal rates of substrate supply from the circulation are similar in both species. We predict that these differences in physiological parameters should be matched by proportional differences in structural capacity. We find that capillary volume and surface area are matched to maximal oxygen demand. The rate of vascular substrate supply is proportional neither to the capillary surface area nor to the length of intercellular junctions. The sarcolemmal surface area per gram of muscle is the same in both species. Using the physiological data presented in the companion papers of this series, we have calculated the maximal flux densities of circulatory glucose and fatty acids across the capillary wall and the sarcolemma. We find, for both substrates, that the flux densities across the sarcolemma reach a maximum at nearly the same level and at low exercise intensities in both species. In contrast, the flux densities across the capillary surface and the endothelial junctions are higher in goats than in dogs. We conclude that the capillaries are designed for O2 supply up to maximal rates of oxidation but not for the supply of the substrates (glucose and fatty acids) at the rates required at high exercise intensities. These are limited by the transport capacities of the sarcolemma.

Animals↗
PubMed1981

Electron microscopic study of the sarcolemma of Purkinje cells of the goat heart.

Three portions were characterized in the sarcolemma of Purkinje cells of the goat heart. These portions, i.e., intercalated disk, internal and surface sarcolemmal portion, show specific and distinctive characteristics. The surface density of both sarcoplasmic reticulum dyads and intercellular junctions were estimated in these three sarcolemmal portions. Dyads occupy 8, 1.6 and 0.3%, respectively, of the area of internal, intercalated disk, and surface sarcolemmal portions. Fasciae and maculae adherentes are 17 and 5% of the intercalated disk and the internal sarcolemma, respectively. The nexal area in the intercalated disk is twice that in the internal sarcolemma. These results are discussed in relation to the excitation-contraction coupling phenomenon and to conduction velocity.

Animals↗
PubMedDate not supplied

Autologous red blood cell and platelet engulfment in hairy cell leukemia.

Seven cases of hairy cell leukemia (leukemic reticulo-endotheliosis) are presented in which peripheral blood or splenic hairy cells or both were identified engulfing autologous red blood cells or platelets. In 3 patients, approximately 5-15% of their peripheral blood hairy cells were engulfing red cells and platelets. In 2 patients, intercellular junctions were present between processes of hairy cells and were similar to processes occasionally seen connecting Langerhans cells to each other. Also, parallel tubular arrays were identified in the cytoplasm of hairy cells from 2 other patients. We conclude that autologous red blood cell and platelet engulfment is a common finding in hairy cell leukemia.

Aged↗
PubMed2006

Antiparasitic effect of calcium and magnesium ion-free buffer treatments against a common monogenean Neobenedenia girellae.

This study investigated a new effective method for controlling the capsalid monogenean Neobenedenia girellae. We examined in vitro and in vivo the effect on the percentage survival of N. girellae in buffers containing different metallic ions. Decreased survival was observed in buffer solutions lacking two ions. In particular, the percentage survival of N. girellae was significantly decreased after 10 min exposure to buffer containing neither Ca(2+) nor Mg(2+). Transmission electron microscopic observations showed that treatment with this buffer disrupted intercellular junctions. This significant effect on percentage survival of N. girellae using Ca(2+)/Mg(2+)-free buffer was confirmed in an in vivo assay. Ca(2+)/Mg(2+)-free buffer had no effect on the condition of the host, spotted halibut Verasper variegates (Pleuronectidae). These results suggest that treatment with Ca(2+)/Mg(2+)-free buffer is a new effective control method, which could replace existing control methods.

Animals↗
PubMed2002

Chlamydia trachomatis disrupts N-cadherin-dependent cell-cell junctions and sequesters beta-catenin in human cervical epithelial cells.

The cadherin/catenin complex serves as an important structural component of adherens junctions in epithelial cells. Under certain conditions, beta-catenin can be released from this complex and interact with transcription factors in the nucleus to stimulate the expression of genes that regulate apoptosis and cell cycle control. While studying the effects of the bacterial pathogen Chlamydia trachomatis on human cervical epithelial cells in culture, we observed that C. trachomatis caused the epithelial cells to separate from each other without detaching from their growing surface. The objective of the present study was to determine if this effect might involve the disruption of the cadherin/catenin complex. Primary cultures of human cervical epithelial cells or HeLa cells were infected with C. trachomatis serovar E. Cadherin-like immunoreactive materials and beta-catenin were visualized by immunofluorescence. Preliminary studies showed that N-cadherin was the primary cadherin expressed in both the primary cultures and the HeLa cells. In noninfected cells, N-cadherin and beta-catenin were colocalized at the intercellular junctional complexes. By contrast, the infected cells showed a marked loss of both N-cadherin and beta-catenin labeling from the junctional complexes and the concomitant appearance of intense beta-catenin labeling associated with the chlamydial inclusion. The results of Western blot analyses of extracts of C. trachomatis showed no evidence of cross-reactivity with the beta-catenin antibody. These results indicate that C. trachomatis causes the breakdown of the N-cadherin/beta-catenin complex and that the organism can sequester beta-catenin within the chlamydial inclusion. This could represent an important mechanism by which C. trachomatis alters epithelial cell function.

Apoptosis↗
PubMed1991

Morphology of glial blood-brain barriers.

Glial cells, in certain situations in the CNS, may become modified to form the structural basis of the blood-brain barrier. This occurs in more primitive vertebrates, such as the elasmobranch fish, and in some higher invertebrates. In the latter, the outermost glial sheath, often called the perineurium in avascular ganglia, substitutes functionally for the vascular endothelium of higher organisms. The intercellular junctions between the lateral borders of these modified glial or perineurial cells may be of several types. In nearly all cases, adhesive and communicating (gap) junctions are found together with an occluding junctional structure. The latter is assumed to be the morphologic basis of the observed blood-brain barrier. It varies in nature and may be one in which the adjacent cell membranes fuse, partially or completely, to form a classical tight junction, or it may be one in which the cell membranes remain separated by a distinct intercellular cleft. If the latter, the cleft may be straddled by columns or septal ribbons, between which a charged matrix substance may be found. Restrictive linker junctions, recently found to be the basis of the interglial barrier in cephalopod CNS, as well as that of myriapods, are characterized by cross-striations or columns which, in combination with charged residues, inherent either in them or in the associated extracellular matrix, slow down the entry of exogenous molecules. Septate junctions, which occur between glial cells in certain other invertebrates, exhibit intercellular septal ribbons, which do not prohibit paracellular transport of all substances but may slow down the passage of some by virtue of charged moieties. There is an association of cytoskeletal components with these septate, linker, and tight junctions; the role of the cytoskeleton in tight junctions, which can be seen by freeze fracture to be based on simple ridges in insects or a more complex network of them in arachnids, may also be important in the regulation of paracellular permeability. The structural details of the junctions in different groups are summarized and their physiologic implications discussed.

Animals↗
PubMed1979

Carcinoma of the neck in young children: a light and electron microscopic study.

Two neck tumours in young children with similar clinical features were compared using light and electron microscopy. Both tumours consisted of uniform sheets of epithelial-like cells and there were scattered stromal elements in one. Tonofilaments in sheets or bundles reminiscent of squamous epithelium were striking in the epithelial cells. Intercellular junctions were frequent but true desmosomes were not seen. Most cells contained a few secretory droplets. Occasional secretory cells, foam cells and cilia were observed. Since these tumours were not sited superficially they are unlikely to have been derived from skin epithelium. An origin in branchial sinus remnants capable of differentiation towards squamous and ciliated epithelia is suggested.

Child, Preschool↗
PubMed1992

Immunolocalization of ubiquitin conjugates at Z-bands and intercalated discs of rat cardiomyocytes in vitro and in vivo.

Ubiquitin, a highly conserved 76-residue protein found in all eukaryotic cells, can be covalently bound to a wide variety of proteins in the nucleus, cytosol, cytoskeleton, and plasmalemma. This diversity of target proteins reflects a diversity of functions for ubiquitin conjugation. Previous studies have showed enhanced localization of ubiquitin conjugates to Z-bands of normal skeletal muscle and increased ubiquitination in atrophic muscles. These results have implicated a ubiquitin-mediated pathway in protein turnover and degradation in striated muscle. To investigate whether such a pathway might also exist in cardiac striated muscle, we used an affinity-purified polyclonal antibody (conjugate specific) and indirect immunofluorescence to localize ubiquitin conjugates in neonatal and adult rat cardiac myocytes both in vitro and in vivo. In both cultured myocytes and heart tissue, fluorescent ubiquitin conjugates were found in the nucleus as aggregates, in the cytoplasm in a striated pattern indicative of Z-bands, and in intercellular junctions at the intercalated discs between myocytes. Although the acceptor proteins and the physiological significance of ubiquitination at these locations are unknown, the targeting of ubiquitin to specific sites within the nucleus, myofibrils, and sarcolemma could provide a means for selective processing of individual components within these larger macromolecular assemblies, thus implying a regulatory role for ubiquitin conjugation in turnover or stability of proteins in the heart.

Animals↗
PubMed1999

The ultrastructural study of primary intracranial germ cell tumours.

We describe here ultrastructural and clinicopathological features of five primary intracranial germinomas. By electron microscopy, two major tumour components were defined as large, well differentiated tumour cells and non-neoplastic cells such as macrophages, astrocytes and lymphocytes. Nuclei of the tumour cells often presented irregularly contoured nuclear membranes with oval indentations and, occasionally, cytoplasmic invagination. Some of them constituted unusual conformational changes of nuclear membranes rarely described as intranuclear pockets. Desmosome-like intercellular junctions were observed in several neoplastic cells. Nucleoli were composed of a loose, fragmented nucleolonema whereas elongated, anastomosing and rope-like nucleolonemas, described previously as characteristic for germinomas were not seen. Typically, the cytoplasm contained glycogen particles. Most tumour cells had villous cytoplasmic projections sometimes intermingled with similar projections of macrophages. Scattered astrocytes typically containing abundant glial filaments were adjacent to primary tumour cells.

Adolescent↗
PubMed1986

Direct effects of E coli endotoxin on structure and permeability of pulmonary endothelial monolayers and the endothelial layer of intimal explants.

The direct structural, metabolic, and physiologic effects of Escherichia coli endotoxin on bovine pulmonary endothelial monolayers and on the intact endothelial layer of bovine pulmonary artery intimal explants were examined. Endothelial monolayers exposed to E coli endotoxin (0.001, 0.01, 0.1, 1.0, and 10 micrograms/ml) for 24 hours in the absence of bovine fetal calf serum (FCS) showed a dose-dependent response, as demonstrated by number of pyknotic cells and lactate dehydrogenase release that was enhanced by addition of FCS. Prostacyclin production was increased only in the presence of FCS. Endotoxin also caused an increase in permeability. Endothelial cells on nitrocellulose filters placed in chemotaxis chambers with radioactive tracers in the upper well showed a significant 25% increase in rate of equilibration (counts in lower well/counts in upper well) of 3H-water after 2 and 3 hours' incubation with endotoxin (3 hours' endotoxin = 0.89 +/- 0.03 m +/- SE; no endotoxin = 0.69 +/- 0.05) and a 40% increase in equilibration of 125I-albumin at three hours (3 hours' endotoxin = 0.40 +/- 0.03; no endotoxin = 0.27 +/- 0.02). An increase in hydraulic conductance was also seen at 1 hour. Electron microscopy of the endothelial layer of intimal explants showed dilatations in the intercellular junctions and cellular changes representing contraction--increased prominence of cytoplasmic filaments, nuclear crenation, and cytoplasmic protrusions--at 30 and 60 minutes. From 2 hours evidence of cell death was found. Thus, endotoxin causes structural and metabolic changes in pulmonary endothelial cells and an increase in permeability of the endothelial layer. The injury occurs in the absence of FCS but is enhanced by its addition.

Animals↗
PubMed1988

Binding and transcytosis of glycoalbumin by the microvascular endothelium of the murine myocardium: evidence that glycoalbumin behaves as a bifunctional ligand.

The binding and transport of glycoalbumin (gA) by the endothelium of murine myocardial microvessels were studied by perfusing in situ 125I-gA or gA-gold complexes (gA-Au) and examining the specimens by radioassays and EM, respectively. After a 3-min perfusion, the uptake of radioiodinated gA is 2.2-fold higher than that of native albumin; it is partially (approximately 55%) competed by either albumin or D-glucose, and almost completely abolished by the concomitant administration of both competitors or by gA. D-mannose and D-galactose are not effective competitors. Unlike albumin-gold complexes that bind restrictively to plasmalemmal vesicles, gA-Au labels the plasma-lemma proper, plasmalemmal vesicles open on the lumen, and most coated pits. Competing albumin prevents gA-Au binding to the membrane of plasmalemmal vesicles, while glucose significantly reduces the ligand binding to plasmalemma proper. Competition with albumin and glucose gives additive effects. Transcytosis of gA-Au, already detected at 3 min, becomes substantial by 30 min. No tracer exit via intercellular junctions was detected. gA-Au progressively accumulates in multivesicular bodies. The results of the binding and competition experiments indicate that the gA behaves as a bifunctional ligand which is recognized by two distinct binding sites: one, located on the plasma membrane, binds as a lectin the glucose residues of gA; whereas the other, confined to plasmalemmal vesicles, recognizes presumably specific domains of the albumin molecule.

Animals↗
PubMed2001

[Primary culture of epithelial secretory cells from venom gland of the common adder Vipera berus].

A primary culture of epithelial secretory cells from the venom gland of Vipera berus was obtained. The cells adhered to collagen 1 and to a mixture of adhesion proteins (Matrigel), proliferated and retained the features of differentiation. Electron microscopy demonstrated the presence of all ultrastructures typical of these cells in vivo, a full complex of intercellular junctions, and cellular membrane polarity. The immunohistochemistry confirmed the capacity of secretory cells to synthesize venom in culture. We have studied the role of carbochole, an agonist of M-cholinoreceptor, in the initiation of the secretory cycle in cells in vitro. We propose that M-cholinoreceptors may play an important role in the initiation of the secretory cycle in vivo.

Animals↗
PubMed1989

[Ultrastructure of capillary permeability in malignant lymphoma].

The ultrastructure of the blood vessels of primary central nervous system malignant lymphoma was studied and compared with those in glial, non-glial and metastatic brain tumors. Five surgical specimens were studied by conventional ultrathin section and freeze-fracture replica techniques. Tumor vessels of various sizes were found. The luminal surfaces of the tumor vessels were irregular and the basal lamina had multiple-layer structure. The perivascular spaces were enlarged and infiltrated with tumor cells. The endothelium had marked infoldings, increased pinocytotic vesicles and fenestrations. The intercellular junctions were short but no obvious opening was seen. On the replica specimen pinocytotic vesicles were calculated on an average of 28 per microns2. The essential features of the blood vessels in primary central nervous system malignant lymphoma were the fenestrated vessels. They resembled the blood vessels found in non-glial and metastatic brain tumors, but were distinctly different from those seen in glial tumors with non-fenestrated vessels.

Adult↗
PubMed1978

Electron microscopy of retinal tapetum (Caiman crocodilus).

The distribution and ultrastructure of the retinal tapetum lucidum in Caiman crocodilus is described. In the light adapted eye the tapetum is recognized in the superior half of the fundus. It consists of guanine containing crystalline platelets which are spread almost over the entire retinal pigment epithelial cells which can be divided into different layers: 1. The basal surface facing the choriocapillary vessels is differentiated into numerous densely packed true microfolds which are commonly described as "basal infoldings". 2. A remarkable high content of mitochondria as well as a great number of lipid droplet-like spherical bodies is observed. 3. In the nuclear zone a Golgi apparatus and all stages of phagocytosis are found. 4. Within the level of intercellular junctions, crystalline platelets are arranged mainly perpendicularly to the long axis of the neighbouring receptor cells, whereas 5. platelets in large pigment epithelial cell processes extending from the apical cell surface between the photoreceptors are oriented parallel to the receptor axis. 6. Heavy pigmentation of the apical tips of pigment cell processes by melanosomes is observed, but only within the lower half of the fundus. The functional significance of the tapetum of Caiman crocodilus is discussed.

Alligators and Crocodiles↗