scholarly journals Comparative analysis of the major polypeptides from liver gap junctions and lens fiber junctions.

1982 ◽  
Vol 92 (1) ◽  
pp. 53-59 ◽  
Author(s):  
E L Hertzberg ◽  
D J Anderson ◽  
M Friedlander ◽  
N B Gilula
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Peptide Mapping ◽  
Freeze Fracture ◽  
Apparent Molecular Weight ◽  
Lens Fiber ◽  
Physiological Properties ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

Gap junctions from rat liver and fiber junctions from bovine lens have similar septilaminar profiles when examined by thin-section electron microscopy and differ only slightly with respect to the packing of intramembrane particles in freeze-fracture images. These similarities have often led to lens fiber junctions being referred to as gap junctions. Junctions from both sources were isolated as enriched subcellular fractions and their major polypeptide components compared biochemically and immunochemically. The major liver gap junction polypeptide has an apparent molecular weight of 27,000, while a 25,000-dalton polypeptide is the major component of lens fiber junctions. The two polypeptides are not homologous when compared by partial peptide mapping in SDS. In addition, there is not detectable antigenic similarity between the two polypeptides by immunochemical criteria using antibodies to the 25,000-dalton lens fiber junction polypeptide. Thus, in spite of the ultrastructural similarities, the gap junction and the lens fiber junction are comprised of distinctly different polypeptides, suggesting that the lens fiber junction contains a unique gene product and potentially different physiological properties.

scholarly journals Immunolocalization of MP70 in lens fiber 16-17-nm intercellular junctions.

1987 ◽  
Vol 104 (3) ◽  
pp. 565-572 ◽  
Author(s):  
W T Gruijters ◽  
J Kistler ◽  
S Bullivant ◽  
D A Goodenough
Keyword(s):  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Membrane Structures ◽  
Outer Cortex ◽  
Double Membrane ◽  
Fiber Cells ◽  
Thin Section Electron Microscopy ◽  
Different Types ◽  
Section Electron ◽  
Section Electron Microscopy

Thin section electron microscopy reveals two different types of membrane interactions between the fiber cells of bovine lens. Monoclonal antibodies against lens membrane protein MP70 (Kistler et al., 1985, J. Cell Biol., 101:28-35) bound exclusively to the 16-17-nm intercellular junctions. MP70 localization was most dramatic in the lens outer cortex and strongly reduced deeper in the lens. In contrast, the 12-nm double membrane structures and single membranes were consistently unlabeled. In freeze-fracture replicas with adherent cortical fiber membranes, MP70 was immunolocalized in the junctional plaques which closely resemble the gap junctions in other tissues. MP70 is thus likely to be associated with intercellular communication in the lens.

scholarly journals STUDIES OF EXCITABLE MEMBRANES

1974 ◽  
Vol 63 (2) ◽  
pp. 567-586 ◽  
Author(s):  
John E. Rash ◽  
Mark H. Ellisman
Keyword(s):  
Electron Microscopy ◽  
Thin Section ◽  
Nerve Terminal ◽  
Freeze Fracture ◽  
Staining Procedure ◽  
Fiber Types ◽  
Mammalian Skeletal Muscle ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The neuromuscular junctions and nonjunctional sarcolemmas of mammalian skeletal muscle fibers were studied by conventional thin-section electron microscopy and freeze-fracture techniques. A modified acetylcholinesterase staining procedure that is compatible with light microscopy, conventional thin-section electron microscopy, and freeze-fracture techniques is described. Freeze-fracture replicas were utilized to visualize the internal macromolecular architecture of the nerve terminal membrane, the chemically excitable neuromuscular junction postsynaptic folds, and the electrically excitable nonjunctional sarcolemma. The nerve terminal membrane is characterized by two parallel rows of 100–110-Å particles which may be associated with synpatic vesicle fusion and release. On the postsynpatic folds, irregular rows of densely packed 110–140-Å particles were observed and evidence is assembled which indicates that these large transmembrane macromolecules may represent the morphological correlate for functional acetylcholine receptor activity in mammalian motor endplates. Differences in the size and distribution of particles in mammalian as compared with amphibian and fish postsynaptic junctional membranes are correlated with current biochemical and electron micrograph autoradiographic data. Orthogonal arrays of 60-Å particles were observed in the split postsynaptic sarcolemmas of many diaphragm myofibers. On the basis of differences in the number and distribution of these "square" arrays within the sarcolemmas, two classes of fibers were identified in the diaphragm. Subsequent confirmation of the fiber types as fast- and slow-twitch fibers (Ellisman et al. 1974. J. Cell Biol. 63[2, Pt. 2]:93 a. [Abstr.]) may indicate a possible role for the square arrays in the electrogenic mechanism. Experiments in progress involving specific labeling techniques are expected to permit positive identification of many of these intriguing transmembrane macromolecules.

scholarly journals On the structural organization of isolated bovine lens fiber junctions.

1982 ◽  
Vol 93 (1) ◽  
pp. 175-189 ◽  
Author(s):  
G Zampighi ◽  
S A Simon ◽  
J D Robertson ◽  
T J McIntosh ◽  
M J Costello
Keyword(s):  
Gap Junctions ◽  
Lipid Bilayers ◽  
Freeze Fracture ◽  
Apparent Molecular Weight ◽  
Surface Topology ◽  
Square Lattice ◽  
Lens Fiber ◽  
Fiber Cells ◽  
Junction Protein ◽  
Freeze Fracture Electron Microscopy

Junctions between fiber cells of bovine lenses have been isolated in milligram quantities, without using detergents or proteases. The structure of the isolated junctions has been studied by thin-section, negative-stain, and freeze-fracture electron microscopy and by x-ray diffraction. The junctions are large and most often have an undulating surface topology as determined by thin sectioning and freeze-fracture. These undulations resemble the tongue-and-groove interdigitations between lens fiber cells previously seen by others (D. H. Dickson and G. W. Crock, 1972, Invest. Ophthalmol. 11:809-815). In sections, the isolated junctions display a pentalamellar structure approximately 13-14 nm in overall thickness, which is significantly thinner than liver gap junctions. Each junctional membrane contains in the plane of the lipid bilayers distinct units arranged in a square lattice with a center-to-center spacing of 6.6 nm. Freeze-fracture replicas of the junctions fractured transversely show that the repeating units extend across the entire thickness of each membrane. Each unit is probably constructed from four identical subunits, with each subunit containing a protein of an apparent molecular weight of 27,000. We conclude that the lens junctions are structurally and chemically, different from gap junctions and could represent a new kind of intercellular contact, not simply another crystalline state of the gap junction protein.

Effects of tamoxifen citrate and cycloheximide on estradiol induction of rat myometrial gap junctions

1986 ◽  
Vol 64 (6) ◽  
pp. 703-706 ◽  
Author(s):  
L. W. MacKenzie ◽  
R. E. Garfield
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Hormone Treatment ◽  
Control Groups ◽  
Estradiol Treatment ◽  
Myometrial Cells ◽  
Tamoxifen Citrate ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Junction Proteins

Longitudinal muscle of myometrial tissues from immature rats were examined by quantitative thin section electron microscopy for the presence of gap junctions after treatment with estradiol with and without tamoxifen, and cycloheximide for 1–6 days. Gap junctions were present between myometrial cells on days 4, 5, and 6 after treatment with estradiol (500 μg/day). Tamoxifen administered concomitantly with estradiol over the 6-day period completely prevented induction of the junctions. Gap junctions were not detected in the myometrium after treatment with tamoxifen alone. Administration of cycloheximide together with estradiol on day 0 of the 6-day period had no effect on gap junction frequency but resulted in a reduction in gap junction size in the myometrium after continued treatment with the hormone. Treatment with cycloheximide on day 1, however, significantly suppressed the effect of further estradiol treatment on the induction of gap junctions in the myometrium. Junctions were not visible in the tissues from animals treated with cycloheximide alone or in the control groups treated with sesame oil. These results indicate that estradiol influences the presence of gap junctions in the myometrium by regulating the synthesis of gap junction proteins through the steroid receptor mechanism.

Freeze-Fracture Appearance of Rabbit Cardiac Sarcoplasmic Reticulum

1980 ◽  
Vol 38 ◽  
pp. 630-631
Author(s):  
Paul C. Dolber ◽  
Joachim R. Sommer
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Freeze Fracture ◽  
Rabbit Heart ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Cytoplasmic Surface ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Fracture Appearance ◽  
Section Electron Microscopy ◽  
Dense Vesicles

A number of investigators have demonstrated by thin-section electron microscopy the presence of "coated dense vesicles" associated with the sarcoplasmic reticulum (SR) of mammalian cardiac muscle. The similarity of such vesicles to junctional SR (JSR) has been reported: They are at¬tached to SR tubules, they have "feet" at their cytoplasmic surface, and they contain electron-dense material (Fig. 1). Accordingly, and In con¬sideration of their shape, they have been named corbular SR (CSR). We here report the freeze-fracture appearance of the SR, especially the CSR, in the rabbit heart.

The Infection of Cells by Bullet-Shaped Viruses

1969 ◽  
Vol 27 ◽  
pp. 372-373
Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield
Keyword(s):  
Electron Microscopy ◽  
Physical Properties ◽  
Host Cell ◽  
Thin Section ◽  
Cultured Cells ◽  
Cell Infection ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

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