scholarly journals Functional significance of the variations in the geometrical organization of tight junction networks.

1976 ◽  
Vol 68 (3) ◽  
pp. 688-704 ◽  
Author(s):  
B E Hull ◽  
L A Staehelin
Keyword(s):  
Tight Junction ◽  
Alimentary Tract ◽  
Freeze Fracture ◽  
Cell Types ◽  
Stress Conditions ◽  
Apical Region ◽  
Absorptive Cells ◽  
Stress Changes ◽  
Before And After ◽  
A Cell

Using freeze-fracture techniques, we have examined the morpholog of tight junction networks found along the length of the alimentary tract of Xenopus laevis before and after metamorphosis. We have developed the hypothesis, based on these observations, that the geometrical organization of the network determined by the stress-induced shape changes normally experienced by the cells linked by the network. Consistent with this theory, tight junctions can be classified into two distinct types of network organization which differ in their response normal and experimentally induced stress conditions: (a) loosely interconnected networks which can stretch or compress extensively under tension, thereby adapting to stress changes in the tissue; and (b) evenly cross-linked networks which retain their basic morphology under normal stress conditions. The absorptive cells of the large intestine as well as the mucous cells of the gastrointestine or stomach are sealed by the first, flexible type of tight junction. The second type of junctional organization, the evenly cross-connected network, is found between absorptive cells of the small intestine and ciliated cells of the esophagus, and reflects in its constant morphology the relative stability of the apical region of both of these cell types. Networks intermediate between these two types arise when a cell which would normally form a lossely interconnected network borders a cell which tends to form a more evenly cross-linked network, as is found in the esophagus where ciliated and goblet cells adjoin. Despite the change in the animal's diet during metamorphosis from herbivorous to carnivorous, the basic gemetrical organization of the networks associated with each tissue of the alimentary tract remains the same.

HOCl effects on the tight junctions of rabbit tracheal epithelium

1996 ◽  
Vol 270 (2) ◽  
pp. L224-L231 ◽  
Author(s):  
Y. Guo ◽  
M. Krumwiede ◽  
J. G. White ◽  
O. D. Wangensteen
Keyword(s):  
Tight Junction ◽  
Morphological Changes ◽  
Cell Damage ◽  
Freeze Fracture ◽  
Tracheal Epithelium ◽  
Epithelial Tissue ◽  
Laser Confocal Microscopy ◽  
Transmission Electron ◽  
Junction Protein ◽  
Before And After

We previously found that HOCl, produced from neutrophil products in infected airways, decreases electrical resistance (R) of rabbit tracheal epithelium. Interestingly, HOCl at 6 mM, a reasonable concentration in diseased airways, decreased R without apparent cell damage. This study sought to determine whether this noncytotoxic dose of HOCl causes morphological changes that correlate with the decrease in R. Excised rabbit tracheas were treated with 6 mM HOCl for 15 min, before and after which epithelial R was determined. Epithelial tissue was then fixed and prepared for transmission electron microscopy, immunofluorescent labeling of F-actin or the tight junction protein ZO-1, or freeze fracture to examine tight junction strands. HOCl treatment caused a 50% decrease in R. Electron micrographs showed no cell, cell membrane, or tight junction changes. By laser confocal microscopy, 6 mM HOCl did not affect the distribution of F-actin or ZO-1. However, morphometric analysis of freeze-fracture replicas showed that tight junction strand number was significantly decreased from 7.06 +/- 0.09 to 4.79 +/- 0.11 and junctional width was significantly decreased from 0.306 +/- 0.007 to 0.214 +/- 0.006 microns. These latter changes may have contributed to the observed decrease in epithelial R.

scholarly journals Role of claudin species–specific dynamics in reconstitution and remodeling of the zonula occludens

2011 ◽  
Vol 22 (9) ◽  
pp. 1495-1504 ◽  
Author(s):  
Yuji Yamazaki ◽  
Reitaro Tokumasu ◽  
Hiroshi Kimura ◽  
Sachiko Tsukita
Keyword(s):  
Epithelial Cells ◽  
Critical Role ◽  
Freeze Fracture ◽  
Cell Types ◽  
Cell System ◽  
Loosely Coupled ◽  
Zonula Occludens ◽  
A Cell ◽  
Recovery Dynamics ◽  
Species Specific

Tight-junction strands, which are organized into the beltlike cell–cell adhesive structure called the zonula occludens (TJ), create the paracellular permselective barrier in epithelial cells. The TJ is constructed on the basis of the zonula adherens (AJ) by polymerized claudins in a process mediated by ZO-1/2, but whether the 24 individual claudin family members play different roles at the TJ is unclear. Here we established a cell system for examining the polymerization of individual claudins in the presence of ZO-1/2 using an epithelial-like cell line, SF7, which lacked endogenous TJs and expressed no claudin but claudin-12 in immunofluorescence and real-time PCR assays. In stable SF7-derived lines, exogenous claudin-7, -14, or -19, but no other claudins, individually reconstituted TJs, each with a distinct TJ-strand pattern, as revealed by freeze-fracture analyses. Fluorescence recovery after photobleaching (FRAP) analyses of the claudin dynamics in these and other epithelial cells suggested that slow FRAP-recovery dynamics of claudins play a critical role in regulating their polymerization around AJs, which are loosely coupled with ZO-1/2, to form TJs. Furthermore, the distinct claudin stabilities in different cell types may help to understand how TJs regulate paracellular permeability by altering the paracellular flux and the paracellular ion permeability.

scholarly journals Inhibitors of glycosphingolipid biosynthesis reduce transepithelial electrical resistance in MDCK I and FRT cells

2003 ◽  
Vol 284 (4) ◽  
pp. C1021-C1030 ◽  
Author(s):  
Lawrence W. Leung ◽  
Ruben G. Contreras ◽  
Catalina Flores-Maldonado ◽  
Marcelino Cereijido ◽  
Enrique Rodriguez-Boulan
Keyword(s):  
Tight Junction ◽  
Electrical Resistance ◽  
Freeze Fracture ◽  
Transepithelial Electrical Resistance ◽  
Fold Reduction ◽  
A Cell ◽  
Rat Thyroid ◽  
Sphingolipid Biosynthesis ◽  
Mdck I ◽  
Darby Canine Kidney

Madin-Darby canine kidney (MDCK) I and Fisher rat thyroid (FRT) cells exhibit transepithelial electrical resistance (TER) values in excess of 5,000 Ω · cm2. When these cells were incubated in the presence of various inhibitors of sphingolipid biosynthesis, a >5-fold reduction of TER was observed without changes in the gate function for uncharged solutes or the fence function for apically applied fluorescent lipids. The localization of ZO-1 and occludin was not altered between control and inhibitor-treated cells, indicating that the tight junction was still intact. Furthermore, the complexity of tight junction strands, analyzed by freeze-fracture microscopy, was not reduced. Once the inhibitor was removed and the cells were allowed to synthesize sphingolipids, a gradual recovery of the TER was observed. Interestingly, these inhibitors did not attenuate the TER of MDCK II cells, a cell line that typically exhibits values below 800 Ω · cm2. These results suggest that glycosphingolipids play a role in regulating the electrical properties of epithelial cells.

scholarly journals Troponin-I localizes selected apico-basal cell polarity signals

2018 ◽  
Author(s):  
Sergio Casas-Tintó ◽  
Alberto Ferrús
Keyword(s):  
Cell Polarity ◽  
Troponin I ◽  
Genome Instability ◽  
Cell Types ◽  
Wing Disc ◽  
Apical Region ◽  
Loss Of Function ◽  
Polar Localization ◽  
A Cell

AbstractBeyond its well characterized role in muscle contraction,DrosophilaTroponin I (TnI) is expressed in other cell types where it plays a role in proliferation control. TnI traffics between the nucleus and the cytoplasm through a sumoylation-dependent mechanism. We address here the role of TnI in the cytoplasm. TnI accumulates in the apical region of epidermal cells and neuroblasts. TnI helps to localize and co-immunoprecipitates with Par-3/Bazooka and with disc large (Dlg), two components of the apico-basal polarity system. By contrast, Scribbled is not affected by TnI depletion. In neuroblasts, TnI is required for the polar localization of Miranda while non-polar Dlg is not affected. TnI loss-of-function triggers genome instability, cell apoptosis and extrusion from wing disc epithelia. However, rescue from apoptosis by p35 does not prevent genome instability demonstrating that both features, apoptosis and genome instability, are mechanistically independent. While PI3K is known to contribute to apico-basal polarity of epithelia in vertebrates,DrosophilaPI3K depletion alters neither the apical localization of TnI or Par3/Bazooka, nor the basal localization of Dlg. However, the overexpression of PI3K prevents the polarity defects caused by TnI depletion. Thus, TnI binds certain apico-basal polarity signals in a cell type dependent context, and it unveils a hitherto unsuspected diversity of mechanisms to allocate cell polarity factors.

Ultrastructure of melanocyte-keratinocyte interactions and pigment transfer in vitro

1978 ◽  
Vol 36 (2) ◽  
pp. 650-651
Author(s):  
Raul I. Garcia ◽  
Evelyn A. Flynn ◽  
George Szabo
Keyword(s):  
Direct Injection ◽  
Skin Pigmentation ◽  
Freeze Fracture ◽  
Pigment Granule ◽  
Time Lapse ◽  
Ultrastructural Level ◽  
Lanthanum Tracer ◽  
A Cell

Skin pigmentation in mammals involves the interaction of epidermal melanocytes and keratinocytes in the structural and functional unit known as the Epidermal Melanin Unit. Melanocytes(M) synthesize melanin within specialized membrane-bound organelles, the melanosome or pigment granule. These are subsequently transferred by way of M dendrites to keratinocytes(K) by a mechanism still to be clearly defined. Three different, though not necessarily mutually exclusive, mechanisms of melanosome transfer have been proposed: cytophagocytosis by K of M dendrite tips containing melanosomes, direct injection of melanosomes into the K cytoplasm through a cell-to-cell pore or communicating channel formed by localized fusion of M and K cell membranes, release of melanosomes into the extracellular space(ECS) by exocytosis followed by K uptake using conventional phagocytosis. Variability in methods of transfer has been noted both in vivo and in vitro and there is evidence in support of each transfer mechanism. We Have previously studied M-K interactions in vitro using time-lapse cinemicrography and in vivo at the ultrastructural level using lanthanum tracer and freeze-fracture.

Dendritic cells of the human epidermis: immuno-electron microscopic studies of la antigen reactivity

1978 ◽  
Vol 36 (2) ◽  
pp. 644-645
Author(s):  
G. Rowden ◽  
M. G. Lewis ◽  
T. M. Phillips
Keyword(s):  
Dendritic Cells ◽  
Langerhans Cells ◽  
Cell Types ◽  
Cell Type ◽  
Electron Microscopic ◽  
La Antigen ◽  
Microscopic Studies ◽  
A Cell ◽  
C3 Receptors ◽  
Antigen Reactivity

Langerhans cells of mammalian stratified squamous epithelial have proven to be an enigma since their discovery in 1868. These dendritic suprabasal cells have been considered as related to melanocytes either as effete cells, or as post divisional products. Although grafting experiments seemed to demonstrate the independence of the cell types, much confusion still exists. The presence in the epidermis of a cell type with morphological features seemingly shared by melanocytes and Langerhans cells has been especially troublesome. This so called "indeterminate", or " -dendritic cell" lacks both Langerhans cells granules and melanosomes, yet it is clearly not a keratinocyte. Suggestions have been made that it is related to either Langerhans cells or melanocyte. Recent studies have unequivocally demonstrated that Langerhans cells are independent cells with immune function. They display Fc and C3 receptors on their surface as well as la (immune region associated) antigens.

scholarly journals EMeth: An EM algorithm for cell type decomposition based on DNA methylation data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hanyu Zhang ◽  
Ruoyi Cai ◽  
James Dai ◽  
Wei Sun
Keyword(s):  
Dna Methylation ◽  
Tumor Cells ◽  
T Regulatory Cells ◽  
Simulated Data ◽  
Cell Types ◽  
Computational Method ◽  
Methylation Data ◽  
Cell Type ◽  
A Cell ◽  
Type Decomposition

AbstractWe introduce a new computational method named EMeth to estimate cell type proportions using DNA methylation data. EMeth is a reference-based method that requires cell type-specific DNA methylation data from relevant cell types. EMeth improves on the existing reference-based methods by detecting the CpGs whose DNA methylation are inconsistent with the deconvolution model and reducing their contributions to cell type decomposition. Another novel feature of EMeth is that it allows a cell type with known proportions but unknown reference and estimates its methylation. This is motivated by the case of studying methylation in tumor cells while bulk tumor samples include tumor cells as well as other cell types such as infiltrating immune cells, and tumor cell proportion can be estimated by copy number data. We demonstrate that EMeth delivers more accurate estimates of cell type proportions than several other methods using simulated data and in silico mixtures. Applications in cancer studies show that the proportions of T regulatory cells estimated by DNA methylation have expected associations with mutation load and survival time, while the estimates from gene expression miss such associations.

Thin-section, freeze-fracture, and energy dispersive x-ray analysis studies of the protein bodies of tomato seeds

1980 ◽  
Vol 58 (6) ◽  
pp. 699-711 ◽  
Author(s):  
Ernest Spitzer ◽  
John N. A. Lott
Keyword(s):  
Freeze Fracture ◽  
Protein Body ◽  
Cell Types ◽  
Energy Dispersive ◽  
Protein Bodies ◽  
Elemental Content ◽  
Tomato Seed ◽  
Endosperm Tissue ◽  
X Ray ◽  
Edx Analysis

Protein bodies of dry seeds of tomato (Lycopersicon esculentum) from radicle, hypocotyl, cotyledon, and endosperm tissue were extensively studied using thin-sectioning, freeze-fracturing and energy dispersive x-ray (EDX) analysis. Protein bodies varied in size, were oval to circular in section, and generally consisted of a proteinaceous matrix, globoid crystal, and protein crystalloid components. Size, shape, and arrangements of globoid crystals and protein crystalloids varied even within the same cell. Globoid crystals were generally oval to circular in section. They were always surrounded by a proteinaceous matrix. In a given protein body the number present ranged from a few to numerous. A protein body generally contained only one protein crystalloid. In section, protein crystalloids were irregular or angular in shape. They were composed of substructural particles which formed lattice planes. EDX analysis of tomato seed globoid crystals revealed the presence of P, K, and Mg in all cases, a fact that is consistent with globoid crystals being phytin-rich. Rarely, small amounts of calcium were found along with P, K, and Mg in globoid crystals of each of the tissue regions considered. The distribution pattern of cells with Ca containing globoid crystals was random. Small amounts of Fe and Mn were also found in the globoid crystals of protein bodies from certain cell types. These two elements, unlike calcium, were specific in terms of their distribution. Globoid crystals from the protodermal cells often contained Mn and Fe. The globoid crystals from provascular tissue of radicle, hypocotyl, and cotyledon regions often contained Fe while globoid crystals in the first layer of large cells surrounding these provascular areas always contained Fe. Results from EDX analysis of the proteinaceous material from the protein bodies are presented and discussed as are variations in elemental content due to different fixations.

scholarly journals Adhesive multiplicity in the interaction of embryonic fibroblasts and myoblasts with extracellular matrices.

1984 ◽  
Vol 99 (4) ◽  
pp. 1398-1404 ◽  
Author(s):  
C Decker ◽  
R Greggs ◽  
K Duggan ◽  
J Stubbs ◽  
A Horwitz
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Cardiac Fibroblasts ◽  
Cell Types ◽  
Extracellular Matrices ◽  
Common Denominator ◽  
Cell Matrix ◽  
Skeletal Myoblasts ◽  
A Cell ◽  
Cell Matrix Adhesion

Neff et al. (1982, J. Cell Biol., 95:654-666) have described a monoclonal antibody, CSAT, directed against a cell surface antigen that participates in the adhesion of skeletal muscle to extracellular matrices. We used the same antibody to compare and parse the determinants of adhesion and morphology on myogenic and fibrogenic cells. We report here that the antigen is present on skeletal and cardiac muscle and on tendon, skeletal, dermal, and cardiac fibroblasts; however, its contribution to their morphology and adhesion is different. The antibody produces large alterations in the morphology and adhesion of skeletal myoblasts and tendon fibroblasts; in contrast, its effects on the cardiac fibroblasts are not readily detected. The effects of CSAT on the other cell types, i.e., dermal and skeletal fibroblasts, cardiac muscle, 5-bromodeoxyuridine-treated skeletal muscle, lie between these extremes. The effects of CSAT on the skeletal myoblasts depends on the calcium concentration in the growth medium and on the culture age. We interpret these differential responses to CSAT as revealing differences in the adhesion of the various cells to extracellular matrices. This interpretation is supported by parallel studies using quantitative assays of cell-matrix adhesion. The likely origin of these adhesive differences is the progressive display of different kinds of adhesion-related molecules and their organizational complexes on increasingly adhesive cells. The antigen to which CSAT is directed is present on all of the above cells and thus appears to be a lowest common denominator of their adhesion to extracellular matrices.

scholarly journals Participation of plasma membrane proteins in the formation of tight junction by cultured epithelial cells

1983 ◽  
Vol 96 (3) ◽  
pp. 693-702 ◽  
Author(s):  
EB Griepp ◽  
WJ Dolan ◽  
ES Robbins ◽  
DD Sabatini
Keyword(s):  
Protein Synthesis ◽  
Steady State ◽  
Tight Junction ◽  
Messenger Rna ◽  
Freeze Fracture ◽  
Epithelial Cell Line ◽  
Experimental Conditions ◽  
Tight Junction Formation ◽  
Junction Formation ◽  
Spinner Culture

Measurements of the transepithelial electrical resistance correlated with freeze-fracture observations have been used to study the process of tight junction formation under various experimental conditions in monolayers of the canine kidney epithelial cell line MDCK. Cells derived from previously confluent cultures and plated immediately after trypsin- EDTA dissociation develop a resistance that reaches its maximum value of several hundred ohms-cm(2) after approximately 24 h and falls to a steady-state value of 80-150 ohms- cm(2) by 48 h. The rise in resistance and the development of tight junctions can be completely and reversibly prevented by the addition of 10 μg/ml cycloheximide at the time of plating, but not when this inhibitor is added more than 10 h after planting. Thus tight junction formation consists of separable synthetic and assembly phases. These two phases can also be dissociated and the requirement for protein synthesis after plating eliminated if, following trypsinization, the cells are maintained in spinner culture for 24 h before plating. The requirement for protein synthesis is restored, however, if cells maintained in spinner culture are treated with trypsin before plating. Actinomycin D prevents development of resistance only in monolayers formed from cells derived from sparse rather than confluent cultures, but new mRNA synthesis is not required if cells obtained from sparse cultures are maintained for 24 h in spinner culture before plating. Once a steady-state resistance has been reached, its maintenance does not require either mRNA or protein synthesis; in fact, inhibition of protein synthesis causes a rise in the resistance over a 30-h period. Following treatments that disrupt the junctions in steady- state monolayers recovery of resistance also does not require protein synthesis. These observations suggest that proteins are involved in tight junction formation. Such proteins, which do not turn over rapidly under steady-state conditions, are destroyed by trypsinization and can be resynthesized in the absence of stable cell-cell or cell-substratum contact. Messenger RNA coding for proteins involved in tight junction formation is stable except when cells are sparsely plated, and can also be synthesized without intercellular contacts or cell-substratum attachment.

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