Quintuple-Layered Membrane Junctions at Terminal Bars Between Endothelial Cells

Muir, A L; Peters, Alan

doi:10.1083/jcb.12.2.443

Cited by 108 publications

(39 citation statements)

References 15 publications

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“…Areas of membrane fusion have already been noted and described under various names in the capillary endothelium (22,21) especially in the central nervous system (22). Our observations extend these findings to other capillaries, and show that such zonules are of widespread occurrence in the endothelium of these vessels.…”

Section: Figure 20supporting

confidence: 77%

“…Within the luminal one-third of the junction, the intercellular gap is obliterated by a zone of fusion of the adjacent cell membranes which usually measures only -200 A in depth, but can be clearly recognized by its typical "quintuplelayered structure" (22). Wherever normally sectioned, the whole structure measures -150 A across with 30 A for each layer, including the central one (the line of fusion) which represents the fused outer leaflets of the two cell membranes involved in the junction (Figs.…”

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confidence: 99%

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Studies on Blood Capillaries

Bruns

Palade

1968

The Journal of Cell Biology

447

103

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The wall of the blood capillaries of skeletal muscles (diaphragm, tongue, hind legs) and myocardium of the rat, guinea pig, and hamster consists of three consecutive layers or tunics: the endothelium (inner layer), the basement membrane with its associated pericytes (middle layer), and the adventitia (outer layer). The flattened cells of the endothelium have a characteristic, large population of cytoplasmic vesicles which, within the attenuated periphery of the cells, may attain a maximum frequency of 1 20 /M 2 of cell front and occupy -18% of the cytoplasmic volume; these values decrease as the cells thicken toward the perikaryon. The vesicles are 650-750 A in over-all diameter and are bounded by typical unit membranes. They occur as single units or are fused to form short chains of two to three vesicles. Each configuration may lie entirely within the cytoplasm or open onto the cell surface. In the latter case, the unit membrane of the vesicle is continuous, layer by layer, with the plasmalemma. Chains of vesicles opening simultaneously on both the blood and tissue fronts of the endothelial tunic have not been observed either in sections or in a tridimensional reconstruction of a sector of endothelial cell cytoplasm. Adjacent endothelial cells are closely apposed to one another and appear to be joined over a large part of their margins, possibly over their entire perimeter, by narrow belts of membrane fusion (zonulae occludentes). Except for tongue capillaries, patent intercellular gaps are rare or absent. The middle layer is formed by a continuous basement membrane (500 A thick) and by pericytes which lie in between leaflets of this membrane. The tips of the pericyte pseudopodia penetrate through the inner leaflet of the basement membrane and join the endothelium in maculae occludentes. The adventitia is a discontinuous layer comprising cellular (macrophages, fibroblasts, mast cells) and extracellular (fibrils, amorphous matrix) elements. The same general type of construction appears to be used along the entire length of the capillary.

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Section: Figure 20supporting

confidence: 77%

mentioning

confidence: 99%

Studies on Blood Capillaries

Bruns

Palade

1968

The Journal of Cell Biology

447

103

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“…Evidence has been accumulating in recent years to show that where the free passage of ions is excluded across a layer of cells, the plasma membranes of adjacent cells come together to form zonulae occludentes [Muir and Peters, 1962;Farquhar and Palade, 1963]. These zonulse attach the cells together and form a complete band arouind every cell, so that the diffusion of ions between the cells of the layers appears unable to take place.…”

Section: Discussionmentioning

confidence: 99%

The Node of Ranvier in the Central Nervous System

Peters

1966

Exp Physiol

152

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The axolemma of myelinated nerve fibres of the central nervous system has been examined both at nodes and in the paranodal region. In the paranodal region, the outside of the axolemma is separated from the outer surface of the plasma membrane bounding the inner aspect of the paranodal cytoplasm by a distance of only 25-30 A, so that the two membranes form a complex. In longitudinal sections, a periodicity may be observed within this complex. It has been shown that this is mainly due to the form of the outer dense layer of the axolemma, which is modified into a series of bands or rings that circumscribe the axon. Each band is 120-150 A wide and the centre to centre spacing is 250-300 A. At the node, the axolemma does not show a periodicity and is not covered by a myelin sheath, but in the axoplasm beneath it there is a layer of osmiophilic granular material, about 250 A thick.NODES of Ranvier occur at intervals along the myelinated nerve fibres of both the peripheral and central nervous systems. They occur at the junctions between adjacent lengths of myelin, so that when sections of central nervous tissue are stained specifically to show the myelin and then examined with the light microscope [Hess and Young, 1952;Allison and Feindel, 1949], the nodes of Ranvier appear as short segments from which the myelin is absent.Any doubts that previously existed about the presence of nodes of Ranvier in the central nervous system were finally dispelled by electron microscope pictures of these structures [Metuzals, 1960; b; Uzman and Villegas, 1960]. These electron microscope studies clearly showed that as it approaches a node, the myelin sheath becomes thinner, the spiralled lamellae of the sheath [Maturana, 1960; a] terminating in such a way that each succeeding turn of the spiral overlaps, and projects beyond, the lamella lying inside it. In effect then, the lamellae terminate in a helical fashion. As they do so, the lamellae open up along the major dense line to enclose cytoplasm, the paranodal cytoplasm which, because of the mode of termination of the lamellao, has itself the form of a helix [Peters, 1960 b]. Consequently, in longitudinal sections through the paranodal region the appearance is given of a series of pockets of cytoplasm, lying on each side of the axon and separating it from the gradually thinning sheath ( fig. 1).Recently, it has become apparent that the unmyelinated portion of the axon at a node is surrounded by an extracellular space that in sections is somewhat larger than that occuring elsewhere within the central nervous system [Metuzals, 1965;Robertson, Bodenheimer and Stage, 1963], but little attention has been paid to the characteristics of the plasma membrane of the axon, the axolemma, at the node. This will be described in the present 229

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“…Transmission electron microscopy (TEM) demonstrated that the junctions between adjacent cerebral endothelial cells are characterized by fusion of the outer leaflets of adjacent plasma membranes at intervals along the interendothelial space, producing a pentalaminar appearance and forming tight or occluding junctions (Muir and Peters, 1962;Brightman and Reese, 1969;Nag et al, 1977) ( > Figure 3-1) that prevent paracellular diffusion of solutes via the intercellular route. These tight junctions form the most apical element of the junctional complex, which includes both tight and adherens junctions.…”

Section: Tight Junctionsmentioning

confidence: 99%

Structure and Pathology of the Blood–Brain Barrier

Nag¹

2007

Handbook of Neurochemistry and Molecular Neurobiology

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Quintuple-Layered Membrane Junctions at Terminal Bars Between Endothelial Cells

Cited by 108 publications

References 15 publications

Studies on Blood Capillaries

Studies on Blood Capillaries

The Node of Ranvier in the Central Nervous System

Structure and Pathology of the Blood–Brain Barrier

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