Rectal papillae in Musca domestica: the cuticle and lateral membranes

1979 ◽  
Vol 39 (1) ◽  
pp. 167-186
Author(s):  
N.E. Flower ◽  
G.D. Walker
Keyword(s):  
Cell Membranes ◽  
Plasma Membranes ◽  
Membrane Surface ◽  
Freeze Fracture ◽  
Cell Junctions ◽  
Septate Junctions ◽  
Main Site ◽  
Lanthanum Tracer ◽  
Pass Through ◽  
Permeability Studies

The role of specialized regions of insect rectal papillae in the regulation of water and ion uptake is well documented. Although the apparatus for active uptake of water or ions is located in various cell membranes, the absorbed molecules must first pass through the cuticle which lines the rectal epithelium. Most cuticle (e.g. abdominal) has been shown to be permeable only to molecules soluble in wax, and to be impermeable to water and ions. Obviously if such cuticle lined the rectum, absorption of water and ions would be severely restricted. The present freeze-fracture and lanthanum tracer study was undertaken to investigate in more detail both the morphological features of the rectal papillae cuticle which could be responsible for its anomalous permeability and the various cell membranes involved in this transport. It has been suggested from permeability studies that the anomalous permeability of rectal papillae cuticle could be due to the lack of a complete wax layer over the surface of the rectal cuticle. The present study strongly supports this suggestion. Thus, the freeze-fracture micrographs have shown that a surface layer of the cuticle reacts during fracturing like a lipid bilayer. However, in rectal papilla cuticle this surface bilayer is interrupted at each epicuticular depression by areas of different fracturing behaviour. These discontinuities in the surface bilayer probably allow the rectal contents to contact directly the true cuticular matrix. They could, therefore, explain the case with which water and ions penetrate the rectal cuticle and so gain access to the underlying epithelial cells. Although similar discontinuities are present on some of the rectal cuticle surface external to the rectal papillae, they appear to be filled in by plugs of lipid-like material. The lateral plasma membranes of the rectal papillae cells are generally considered to be the main site of active transport. The present lanthanum tracer and freeze-fracture study has shown that the lateral plasma membranes contain 3 distinct differentiations. Septate junctions are present at the apical and basal surfaces of the epithelial layer; a further membrane differentiation is found adjacent to the septate junctions; and thirdly, an array of short, variable length, non-anastomosing linear structures covers most of the lateral plasma membrane surface. These latter structures, unlike known types of cell junctions do not show equivalent arrays in apposing membranes even when the lateral plasma membranes of adjacent cells are closely apposed. The possible function of these structures is discussed.

scholarly journals Development of cell junctions in sea-urchin embryos

1983 ◽  
Vol 62 (1) ◽  
pp. 27-48
Author(s):  
E. Spiegel ◽  
L. Howard
Keyword(s):  
Epithelial Cells ◽  
Basement Membrane ◽  
Digestive Tract ◽  
Sea Urchin ◽  
Freeze Fracture ◽  
Cell Junctions ◽  
Septate Junctions ◽  
Thin Sections ◽  
Sea Urchin Embryos ◽  
Lanthanum Tracer

The development of cell junctions in sea-urchin embryos has been investigated using thin sections, lanthanum-tracer and freeze-fracture techniques. Three types of desmosomes are present: belt desmosomes and spot desmosomes, which attach cells to each other, and hemi-desmosomes, which attach cells to the basement membrane. Two types of septate junctions are present: the straight, unbranched, double-septum septate, which is present in epithelial cells throughout embryogenesis, and the pleated, anastomosing, single-septum septate. The latter is formed only on cells that have invaginated to the interior of the embryo to form the digestive tract. The pleated junctions are shown to replace the straight junctions that were originally present before the cells migrated to the interior. It is suggested that these pleated septates may be specialized for digestive processes, since they are developed just prior to feeding and are retained in the adult intestine. Tricellular junctions, which join the bicellular junctions of three adjoining cells, have been identified in the embryo and in the adult intestine. Evidence for the presence of gap junctions was not obtained, but there are indications of their presence.

Evidence for septate junctions in the syzygy of the protozoon Gregarina polymorpha (Protozoa, Apicomplexa)

1988 ◽  
Vol 89 (2) ◽  
pp. 217-224
Author(s):  
ROMANO DALLAI ◽  
MARIA VEGNI TALLURI
Keyword(s):  
Plasma Membrane ◽  
Intercellular Space ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Septate Junction ◽  
Fracture Face ◽  
Septate Junctions ◽  
Thin Sections ◽  
Intramembranous Particles ◽  
Lanthanum Tracer

A septate junction is described in reproductive pairs of the protozoon Gregarina polymorpha, using conventional thin sections, lanthanum tracer and freeze-fracture techniques. The septate junction is established between the plasma membranes at the tips of the joined epicytic folds. It is characterized by an intercellular space of 14–17 nm traversed by septa with a repeat of 15–25 nm. Lanthanum-treated material exhibits transparent curves forming a meshwork. Freeze-fracture replicas show membrane modifications in the shape of short rows of intramembranous particles on the E fracture face of the plasma membrane. The significance of the finding of such a septate junction between protozoan cells is discussed.

ZO-1 maintains its spatial distribution but dissociates from junctional fibrils during tight junction regulation

1993 ◽  
Vol 264 (5) ◽  
pp. C1096-C1101 ◽  
Author(s):  
J. L. Madara ◽  
S. Carlson ◽  
J. M. Anderson
Keyword(s):  
Spatial Distribution ◽  
Tight Junction ◽  
Tight Junctions ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Cell Junctions ◽  
Absorptive Cell ◽  
Physiological Regulation ◽  
Functional Relationships ◽  
Tight Junction Regulation

Tight junctions restrict diffusion of hydrophilic solutes through the paracellular pathways of columnar epithelia. It is now apparent that the barrier function of tight junctions is physiologically regulated. Current models of the tight junction envisage junctional subunits consisting of extracellular "kisses" between plasma membranes of adjacent cells, intramembrane components represented by freeze-fracture fibrils, and cytoplasmic elements of the cytoskeleton. Insights into functional relationships between these various components of tight junctions should be provided by mapping component interrelationships in states of altered junctional permeability. Here we define the spatial distribution of ZO-1 during a state of physiological regulation of intestinal absorptive cell tight junctions. Enhanced permeation of absorptive cell junctions in response to activation of apical membrane Na(+)-solute cotransporters does not lead to redistribution of the ZO-1 pool, as judged from quantitative ultrastructural immunolocalization studies employing two different ZO-1 antibodies. Surprisingly, ZO-1, which normally localizes under junctional kisses/fibrils, focally persists at sites where junctional kisses/fibrils are cleared. These findings suggest that 1) spatial redistribution of ZO-1 does not contribute to physiological regulation of junctions elicited by activation of Na(+)-solute cotransport and 2) ZO-1 and junctional fibrils may spatially dissociate during such regulated states.

Junctional structures in hydra

1977 ◽  
Vol 23 (1) ◽  
pp. 151-172
Author(s):  
B.K. Filshie ◽  
N.E. Flower
Keyword(s):  
Freeze Fracture ◽  
Septate Junctions ◽  
Detailed Understanding ◽  
Freeze Fracturing ◽  
Communicating Junctions ◽  
Lanthanum Tracer

The sealing and communicating junctions present in hydra have been examined using conventional staining, lanthanum tracer and freeze-fracturing techniques. The presence of distinct types of gap and septate junctions has been confirmed. Combined lanthanum tracer and freeze-fracture results have provided a more detailed understanding of these junctional structures. A model has been constructed which demonstrates the various aspects of the junction seen at different sectioning angles. The probable lengths of septa within septate junctions and the junctional ‘maze’ formed by them is discussed because of its bearing on the ‘sealing’ nature of the junction and also, to some extent, on its permeability to tracers such as lanthanum.

Plasma membranes, cell junctions and cuticle of the rectal chloride epithelia of the larval dragonfly Aeshna cyanea

1983 ◽  
Vol 59 (1) ◽  
pp. 159-182
Author(s):  
J. Kukulies ◽  
H. Komnick
Keyword(s):  
Gap Junctions ◽  
Structural Control ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Septate Junction ◽  
Cell Junctions ◽  
Junctional Complex ◽  
Apical Region ◽  
Thin Sections ◽  
Aeshna Cyanea

The cell membranes and cell junctions of the rectal chloride epithelia of the larval dragonfly Aeshna cyanea were examined in thin sections and by freeze-fracture. These epithelia function in active ion absorption and maintain a high concentration gradient between the haemolymph and the fresh-water environment. Freeze-fracturing reveals fine-structural differences in the intramembraneous particles of the luminal and contraluminal plasma membranes of these epithelia, reflecting the functional diversity of the two membranes, which are separated by the junctional complex. The particle frequency of the basolateral plasma membranes is reduced after transfer of the larvae into high concentrations of environmental salinity. The junctional complex is located in the apical region and composed of three types of cell junctions: the zonula adhaerens, seen in freeze-fracture as a nearly particle-free zone; the extended and highly convoluted pleated septate junction and randomly interspersed gap junctions of the inverted type. Gap junctions also occur between the basolateral plasma membranes. They provide short-cuts in the diffusion pathway for direct and rapid co-ordination of the interconnected cell processes. Colloidal and ionic lanthanum tracer solutions applied in vivo from the luminal side penetrate through the cuticle via epicuticular depressions, but invade only the apical portion of the junctional complex. This indicates that the pleated septate junction constitutes a structural control of the paracellular pathway across the chloride epithelia, which are devoid of tight junctions. The structure of the pleated septate junctions is interpreted as a device for the extension of the diffusion distance, which is inversely related to the net diffusion. A conservative estimate of the total length of the junction, and the number and extension of septa reveals that the paracellular route exceeds the transcellular route by a factor of 50.

Variations of separate junction structure in the invertebrates

1978 ◽  
Vol 36 (2) ◽  
pp. 338-339
Author(s):  
Colin R. Green
Keyword(s):  
Thin Section ◽  
Freeze Fracture ◽  
Epidermal Cells ◽  
Septate Junction ◽  
Septate Junctions ◽  
Wide Range ◽  
Lanthanum Tracer ◽  
Endodermal Cells ◽  
Junction Structure

Three main variations of the invertebrate septate junction are now generally accepted; the Hydra type, the pleated septate and the smooth septate junctions. A junctional study of many members of a wide range of invertebrate phyla using thin section, lanthanum tracer and freeze-fracture techniques has however revealed at least eight distinct septate junction types, including two anastomosing septate junctions in the higher invertebrate phyla.In the Coelenterata three forms of septate junction occur. The Hydra type found in Hydrozoa (Fig 1), a pegged junction seen in the epidermal cells of Anthozoa and a ladder-like junction seen in the endodermal cells of Anthozoa. The pegged Anthozoa junction consists of septa with distinct short pegs branching at right angles mainly from one side (fig 2). Where two septa run close together, the pegs may form crossbars linking them. The ladder junction has a pegged double septum with crossbars linking the two parts of each septum (fig 3).

Phylogenetic Relationships within Theinvertebrata in Relation to Thestructure of Septate Junctions and the development of ‘Occluding’ Junctional Types

1982 ◽  
Vol 53 (1) ◽  
pp. 279-305 ◽  
Author(s):  
COLIN R. GREEN ◽  
PATRICIA R. BERGQUIST
Keyword(s):  
Tight Junction ◽  
Phylogenetic Relationships ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Septate Junction ◽  
Simple Type ◽  
Septate Junctions ◽  
Exterior Surface ◽  
Lanthanum Tracer ◽  
To Come

The structures of 13 variants of invertebrate septate junction are reviewed on the basis offreeze-fracture, lanthanum tracer and thin-section studies. In addition, a simple type ofoccluding junction in the phylum Porifera, a variation of tight junction in the phylum Tunicateand the vertebrate tight junction are covered. All the junctions considered form a belt around the apical circumference of cells lining a lumen or an exterior surface. The large number of these junctions now recognized permits discussion relating to invertebrate classification and suggested phylogenetic relationships, and to the development of intercellular junctions. The relationships revealed are discussed under three headings: Coelenterates and lower invertebrates, Proterostomia (the annelid, molluscan and arthropod lineage) and the Deuterostomia(the echinoderm and chordate lineage). It is proposed that the pleated septate junction of the lower invertebrates resembles that of the hydrozoan rather than anthozoan Coelenterates. This lower invertebrate pleated septate junction occurs in several lower invertebrate phyla including the Annelida (of the proterostome lineage), but also occurs in the Sipunculoidea, a group supposedly on the deuterostome lineage.The proterostome line includes the molluscs and the arthropods, which have the molluscarthropodpleated septate junction. Several variations of the smooth septate junction are alsoseen in Arthropoda. Among the deuterostomes the Chaetognatha have both a paired septatejunction and a pleated junction and are therefore considered to be not very far removed fromthe Sipunculoidea. The echinoderms and hemichordates also have double-septum septatejunctions. In addition however, these two phyla have anastomosing septate junctions thatare very similar, varying only in their final configuration. Of the two, the echinoderm anastomosingseptate junction most closely resembles the tight junction seen in the tunicates, and the Hemichordata are therefore considered to be a lateral development from the main lineof chordate evolution. The tunicates have a tight junction similar to that seen in vertebrates;it is however more ‘leaky’ and has distinctive freeze-fracture characteristics.In the phylum Porifera a form of simple parallel membrane junction appears to serve anoccluding function. This junction has regular intercellular spacing in the absence of any septaand it is suggested that the spacing in septate junctions is probably not dictated by the septa.This interpretation is reasonable particularly when the diversity of septal types in conjunctionwith stable intercellular spacing is considered. Finally, a theory is put forward suggesting thatin evolution a change from the septate to the tight junction could simply involve a modificationof a ‘membrane spacing factor’, which allows the membranes of adjacent cells to come together at intervals, in the normal tight junction pattern.

scholarly journals Tetrameric assembly of CHIP28 water channels in liposomes and cell membranes: a freeze-fracture study.

1993 ◽  
Vol 123 (3) ◽  
pp. 605-618 ◽  
Author(s):  
J M Verbavatz ◽  
D Brown ◽  
I Sabolić ◽  
G Valenti ◽  
D A Ausiello ◽  
...  
Keyword(s):  
Water Permeability ◽  
Cho Cells ◽  
Cell Membranes ◽  
Plasma Membranes ◽  
Single Channel ◽  
Water Channel ◽  
Freeze Fracture ◽  
Water Channels ◽  
Straight Tubules ◽  
Tetrameric Assembly

Channel forming integral protein of 28 kD (CHIP28) functions as a water channel in erythrocytes, kidney proximal tubule and thin descending limb of Henle. CHIP28 morphology was examined by freeze-fracture EM in proteoliposomes reconstituted with purified CHIP28, CHO cells stably transfected with CHIP28k cDNA, and rat kidney tubules. Liposomes reconstituted with HPLC-purified CHIP28 from human erythrocytes had a high osmotic water permeability (Pf0.04 cm/s) that was inhibited by HgCl2. Freeze-fracture replicas showed a fairly uniform set of intramembrane particles (IMPs); no IMPs were observed in liposomes without incorporated protein. By rotary shadowing, the IMPs had a diameter of 8.5 +/- 1.3 nm (mean +/- SD); many IMPs consisted of a distinct arrangement of four smaller subunits surrounding a central depression. IMPs of similar size and appearance were seen on the P-face of plasma membranes from CHIP28k-transfected (but not mock-transfected) CHO cells, rat thin descending limb (TDL) of Henle, and S3 segment of proximal straight tubules. A distinctive network of complementary IMP imprints was observed on the E-face of CHIP28-containing plasma membranes. The densities of IMPs in the size range of CHIP28 IMPs, determined by non-linear regression, were (in IMPs/microns 2): 2,494 in CHO cells, 5,785 in TDL, and 1,928 in proximal straight tubules; predicted Pf, based on the CHIP28 single channel water permeability of 3.6 x 10(-14) cm3/S (10 degrees C), was in good agreement with measured Pf of 0.027 cm/S, 0.075 cm/S, and 0.031 cm/S, respectively, in these cell types. Assuming that each CHIP28 monomer is a right cylindrical pore of length 5 nm and density 1.3 g/cm3, the monomer diameter would be 3.2 nm; a symmetrical arrangement of four cylinders would have a greatest diameter of 7.2 nm, which after correction for the thickness of platinum deposit, is similar to the measured IMP diameter of approximately 8.5 nm. These results provide a morphological signature for CHIP28 water channels and evidence for a tetrameric assembly of CHIP28 monomers in reconstituted proteoliposomes and cell membranes.

scholarly journals A freeze-fracture and lanthanum tracer study of the complex junction between Sertoli cells of the canine testis.

1978 ◽  
Vol 76 (1) ◽  
pp. 57-75 ◽  
Author(s):  
C J Connell
Keyword(s):  
Tight Junctions ◽  
Sertoli Cells ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Septate Junction ◽  
Septate Junctions ◽  
Thin Sections ◽  
En Face ◽  
Lanthanum Tracer ◽  
Complex Junction

What appear to be true septate junctions by all techniques currently available for the cytological identification of intercellular junctions are part of a complex junction that interconnects the Sertoli cells of the canine testis. In the seminiferous epithelium, septate junctions are located basal to belts of tight junctions. In thin sections, septate junctions appear as double, parallel, transverse connections or septa spanning an approximately 90-A intercellular space between adjacent Sertoli cells. In en face sections of lanthanum-aldehyde-perfused specimens, the septa themselves exclude lanthanum and appear as electron-lucent lines arranged in a series of double, parallel rows on a background of electron-dense lanthanum. In freeze-fracture replicas this vertebrate septate junction appears as double, parallel rows of individual or fused particles which conform to the distribution of the intercellular septa. Septate junctions can be clearly distinguished from tight junctions as tight junctions prevent the movement of lanthanum tracer toward the lumen, appear as single rows of individual or fused particles in interlacing patterns within freeze-fracture replicas, and are seen as areas of close membrane apposition in thin sections. Both the septate junction and the tight junction are associated with specializations of the Sertoli cell cytoplasm. This is the first demonstration in a vertebrate tissue of a true septate junction.

Cholesterol distribution in cells of the stria vascularis of the mammalian cochlea and some effects of ototoxic diuretics

1985 ◽  
Vol 79 (1) ◽  
pp. 181-197
Author(s):  
A. Forge
Keyword(s):  
Cell Membranes ◽  
Plasma Membranes ◽  
Early Stage ◽  
Stria Vascularis ◽  
Freeze Fracture ◽  
Ultrastructural Level ◽  
Body Region ◽  
Intermediate Cell ◽  
Marginal Cells ◽  
In Cells

The distribution of cholesterol in cells of the stria vascularis of guinea pigs and gerbils has been investigated at the ultrastructural level by incubation of tissue in filipin, followed by freeze-fracture. Verification of results has been sought by using tomatin. It is shown that in the cell body region of the marginal cells, the apical and lateral membranes reacted intensely with both agents, but the membranes of the basal processes of the marginal cells did not respond significantly to either filipin or tomatin. On basal cell membranes, filipin-cholesterol complexes were present at a high density, even within the strands of the tight-junctional network of these cells and occasionally within the gap-junctional areas also. Complexes were present on intermediate cell membranes at a lower density than on other plasma membranes that showed a positive response. Tissue from animals that had received an ototoxic diuretic, either ethacrynic acid or furosemide, was characterized by the appearance of membrane regions with closely clustered filipin complexes, suggesting some change in cell membrane structure. At an early stage following diuretic administration, such clusters were particularly noticeable on the membranes of intermediate cells. As intercellular spaces enlarged in response to the effects of diuretics, vesicles released into the extracellular spaces appeared to be cholesterol-enriched. The results are discussed in relation to known features of the structure and function of cells in the normal stria vascularis and of the changes that follow from acute diuretic ototoxicity.

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