scholarly journals ARTIFACTUAL LOCALIZATION OF FERRITIN IN THE CILIARY EPITHELIUM IN VITRO

1965 ◽  
Vol 25 (2) ◽  
pp. 1-7 ◽  
Author(s):  
John Mcd. Tormey
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Basement Membrane ◽  
Osmium Tetroxide ◽  
Colloidal Particles ◽  
Ciliary Epithelium ◽  
Albino Rabbit ◽  
Cytoplasmic Matrix ◽  
Tracer Particles

The accumulation of ferritin by the ciliary epithelium of the adult albino rabbit has been studied by electron microscopy. The experiments have been carried out under in vitro conditions, such that any uptake observed should be the result of passive diffusion of the tracerparticles rather than the product of active metabolic processes. The cells were fixed in osmium tetroxide and embedded in Araldite. Ferritin was found localized in three areas: in rows of apparent vesicles, free in the cytoplasmic matrix, and in the basement membrane. Some of the conclusions reached are as follows. The appearance of tracer in rows of vesicles is not in itself an adequate demonstration of pinocytosis. The permeability of the plasma membrane is drastically increased by osmium tetroxide fixation, so that tracer particles are free to diffuse across the membrane and wander through the cytoplasm. These results indicate the serious danger of being misled by artifacts when colloidal particles are used as tracers.

scholarly journals The fine structure produced in cells by primary fixatives 2. Potassium dichromate

1965 ◽  
Vol s3-106 (73) ◽  
pp. 15-21
Author(s):  
JOHN R. BAKER
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Nuclear Membrane ◽  
Osmium Tetroxide ◽  
Potassium Dichromate ◽  
Potassium Dichromate Solution ◽  
Zymogen Granules ◽  
Mouse Pancreas

The exocrine cells of the mouse pancreas were fixed in potassium dichromate solution, embedded in araldite or other suitable medium, and examined by electron microscopy. Almost every part of these cells is seriously distorted or destroyed by this fixative. The ergastoplasm is generally unrecognizable, the mitochondria and zymogen granules are seldom visible, and no sign of the plasma membrane, microvilli, or Golgi apparatus is seen. The contents of the nucleus are profoundly rearranged. It is seen to contain a large, dark, irregularly shaped, finely granular object; the evidence suggests that this consists of coagulated histone. The sole constituent of the cell that is well fixed is the inner nuclear membrane. The destructive properties of potassium dichromate are much mitigated when it is mixed in suitable proportions with osmium tetroxide or formaldehyde.

Endothelial Alterations During The Platelet Activating Factor (PAF) Respiratory Distress Syndrome

1981 ◽  
Author(s):  
J C Lewis ◽  
J T O’Flaherty ◽  
C M McCall ◽  
R L Wykle
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Platelet Activating Factor ◽  
Capillary Endothelium ◽  
Cytotoxic Action ◽  
High Concentration ◽  
Rabbit Lung ◽  
Capillary Endothelial Cells ◽  
Platelet Aggregates

PAF (l-0-alkyl-2-0-acetyl-sn-gylcero-3-phosphocholine) induces polymorphonucelar leukocyte and platelet stasis in rabbit lung capillaries in vitro and produces a model of acute respiratory disease. Since PAF mediates anaphylactic reactions, a study was done to determine the ultrastructural effects of PAF treatment. Mature rabbits were treated by intravenous administration of either PAF (0.15-10 μg/kg: 8 animals) or BSA (the PAF carrier: 3 animals) prior to sacrifice and intraventricular perfusion with 0.1 M phosphate buffered (pH 7.2) glutaraldehyde (2.5%). Animals (n=5) injected with a high concentration of PAF (3-10 μg/kg) and sacrificed within 15 minutes of PAF administration had grossly contracted lungs, the vasculature of which (as observed by scanning electron microscopy) contained numerous marginated leukocytes and platelet aggregates. Animals (n=3) given PAF in the concentration range 0.15-2.4 μg/kg had less consistent lung contraction and fewer platelet aggregates within capillaries. Luminal surfaces of capillary endothelial cells in all PAF treated animals (when observed by transmission electron microscopy [TEM]) were dramatically altered. In contrast to the uniformly smooth surfaces in control animals, vessels in the PAF treated animals had tortuous surfaces with plasma membrane discontinuities and protrusion of plasma membrane fragments into the capillary lumen. Morphometric analysis of TEM micrographs substantiated statistically significant (p<0.01) increases in the number and size of plasmalemmal vesicles.These observations clearly document a cytotoxic effect for capillary endothelium. This cytotoxic action may in part explain the clinical effect of PAF.

scholarly journals The R-SNARE Endobrevin/VAMP-8 Mediates Homotypic Fusion of Early Endosomes and Late Endosomes

2000 ◽  
Vol 11 (10) ◽  
pp. 3289-3298 ◽  
Author(s):  
Wolfram Antonin ◽  
Claudia Holroyd ◽  
Ritva Tikkanen ◽  
Stefan Höning ◽  
Reinhard Jahn
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Subcellular Fractionation ◽  
Immunogold Electron Microscopy ◽  
Fusion Reactions ◽  
Coated Pits ◽  
Late Endosomes ◽  
Early Endosomes ◽  
Golgi Network

Endobrevin/VAMP-8 is an R-SNARE localized to endosomes, but it is unknown in which intracellular fusion step it operates. Using subcellular fractionation and quantitative immunogold electron microscopy, we found that endobrevin/VAMP-8 is present on all membranes known to communicate with early endosomes, including the plasma membrane, clathrin-coated pits, late endosomes, and membranes of thetrans-Golgi network. Affinity-purified antibodies that block the ability of endobrevin/VAMP-8 to form SNARE core complexes potently inhibit homotypic fusion of both early and late endosomes in vitro. Fab fragments were as active as intact immunoglobulin Gs. Recombinant endobrevin/VAMP-8 inhibited both fusion reactions with similar potency. We conclude that endobrevin/VAMP-8 operates as an R-SNARE in the homotypic fusion of early and late endosomes.

scholarly journals ELECTRON MICROSCOPY OF ORAL CELLS IN VITRO

1968 ◽  
Vol 36 (3) ◽  
pp. 443-452 ◽  
Author(s):  
M. Kumegawa ◽  
M. Cattoni ◽  
George G. Rose
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Cell Contact ◽  
Intercellular Contact ◽  
Kb Cells ◽  
Contact Areas ◽  
Subsurface Region ◽  
Oral Cells

Two special areas involving membranous components in strain KB cells were studied by electron microscopy. The first area described is that of the subsurface regions of two apposing cells in which flattened cisternae (one cisternae in each subsurface region) with membranes spaced 110–230 A apart were found in a confrontation alignment. The long dimension of the profiles of these cisternae ranges from 0.5 to 2 µ. At these intercellular contact areas, each cisterna is closely applied to the adjacent plasma membrane; the intervening space is 60–100 A. We have named the cisternae in these roughly symmetrical areas of cell contact the subsurface confronting cisternae. Communications between these cisternae and those of the rough-surfaced endoplasmic reticulum also were observed. The second area described is that of the intracytoplasmic confronting cisternae. These cisternae were observed as oval or round images about 0.3–1.4 µ in diameter, each image being composed of a pair of concentrically arranged confronting cisternae with membranes spaced 200–400 A apart. The apposing membranes of the two confronting cisternae are electron opaque, smooth, and free of ribosomes, whereas the unapposed membranes are less dense, scalloped, and associated with ribosomes. The spacing between the two intracytoplasmic confronting cisternae is 70–110 A.

scholarly journals ELECTRON PROBE ANALYSIS OF CATIONIC SPECIES IN PYROANTIMONATE PRECIPITATES IN EPON-EMBEDDED TISSUE

1969 ◽  
Vol 17 (2) ◽  
pp. 102-106 ◽  
Author(s):  
BERNARD P. LANE ◽  
EUGENE MARTIN
Keyword(s):  
Electron Microscopy ◽  
Electron Probe ◽  
Osmium Tetroxide ◽  
Vas Deferens ◽  
Apical Plasma Membrane ◽  
Mouse Vas Deferens ◽  
Electron Probe Analysis ◽  
Osmium Tetroxide Solution ◽  
Potassium Pyroantimonate

Electron microscopy of Epon-embedded mouse vas deferens eipthelium treated with buffered potassium pyroantimonate-osmium tetroxide solution revealed precipitates in the lamina propria and along the apical plasma membrane. Electron microprobe elemental analysis of adjacent sections demonstrated that the deposits contained sodium and antimony. Other cations noted to precipitate pyroantimonate in vitro were not present in large amounts compared to controls, and were randomly distributed.

scholarly journals ELECTRON MICROSCOPY OF ABSORPTION OF TRACER MATERIALS BY TOAD URINARY BLADDER EPITHELIUM

1965 ◽  
Vol 25 (2) ◽  
pp. 175-192 ◽  
Author(s):  
Jae Kwon Choi
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cells ◽  
Urinary Bladder ◽  
Colloidal Particles ◽  
Intermediate Stage ◽  
Toad Urinary Bladder ◽  
Intercellular Spaces ◽  
Bladder Epithelium ◽  
Physiological Factors ◽  
Tracer Particles

The absorption of Thorotrast and saccharated iron oxide by the epithelium of the toad urinary bladder was studied by electron microscopy. Whether the toads were hydrated, dehydrated, or given Pitressin, no significant differences in transport of colloidal particles by epithelial cells were observed. This implies that these physiological factors had little effect on the transport of the tracer particles. Tracer particles were encountered in three types of epithelial cells which line the bladder lumen, but most frequently in the mitochondria-rich cells. Tracer materials were incorporated into the cytoplasm of epithelial cells after being adsorbed to the coating layer covering the luminal surface of the cells. In the intermediate stage (1 to 3 hours after introducing tracer) particles were present in small vesicles, tubules, and multivesicular bodies. In the later stages (up to 65 hours), the particles were more commonly seen to be densely packed within large membrane-bounded bodies which were often found near the Golgi region. These large bodies probably were formed by the fusion of small vesicles. Irrespective of the stages of absorption, no particles were found in the intercellular spaces or in the submucosa. Particles apparently did not penetrate the intercellular spaces of the epithelium beyond the level of the tight junction.

scholarly journals FINE STRUCTURE OF THE CILIARY EPITHELIUM OF THE RABBIT, WITH PARTICULAR REFERENCE TO "INFOLDED MEMBRANES," "VESICLES," AND THE EFFECTS OF DIAMOX

1963 ◽  
Vol 17 (3) ◽  
pp. 641-659 ◽  
Author(s):  
John Mcd. Tormey
Keyword(s):  
Osmium Tetroxide ◽  
Plasma Membranes ◽  
Structural Changes ◽  
Secretory Activity ◽  
Structural Features ◽  
Ciliary Epithelium ◽  
Albino Rabbit ◽  
Serial Sections ◽  
Experimental Conditions ◽  
Tubular Endoplasmic Reticulum

The structure of the ciliary epithelium of the adult albino rabbit has been studied by electron microscopy. Material was fixed in osmium tetroxide and embedded in epoxy resins. Two hitherto unappreciated features of the non-pigmented epithelial layer are described. First, the "infolded plasma membranes" described by previous workers are shown by serial sections to be projections or interdigitations from adjacent cells. Second, the "rows of vesicles" described by previous workers are shown by serial sections to be part of an unusual form of smooth-surfaced tubular endoplasmic reticulum. The tubules are highly convoluted and extensively interconnected. They are arranged in sheets, so that a cross-section through a sheet gives the appearance of a row of vesicles. The other structural features of the ciliary epithelium are also described. Previous workers have reported that Diamox, which inhibits the secretory activity of the epithelium, causes profound structural changes. An effort has been made to confirm these reports under carefully controlled experimental conditions. It was found that secretion could be inhibited by a maximally effective dose of Diamox without the occurrence of any detectable structural changes. The physiological significance of these findings is discussed.

scholarly journals METABOLIC AND ULTRASTRUCTURAL CHANGES INDUCED IN ADIPOSE TISSUE BY INSULIN

1960 ◽  
Vol 8 (1) ◽  
pp. 83-101 ◽  
Author(s):  
Russell J. Barrnett ◽  
Eric G. Ball
Keyword(s):  
Adipose Tissue ◽  
Plasma Membrane ◽  
Plasma Membranes ◽  
Morphological Changes ◽  
Ultrastructural Changes ◽  
Cytoplasmic Matrix ◽  
Smooth Membrane ◽  
Metabolic Action ◽  
Rat Adipose Tissue

The addition in vitro of insulin to rat adipose tissue (epididymal) produces marked metabolic changes which may be followed by measurement of the net gas exchange of the tissue. Using this method to monitor the metabolic action of insulin, concomitant observations with the electron microscope on the tissue have been made. These reveal that pronounced morphological changes are induced by insulin. The plasma membranes of the adipose cells become invaginated at many sites to form minute finger-like indentations. Numerous tiny, membrane-bounded vesicles are also present and arranged in relationship to the plasma membrane in such a way as to suggest that their formation occurred when a recessed fold was pinched off. Deeper in the cytoplasm, especially in specimens that had been incubated a longer time, numerous large, smooth, membrane-limited vesicles are seen. Finally, in these incubated specimens the cytoplasmic matrix has lost much of its granular nature, small lipid droplets are frequently found in the cytoplasm and suggestive changes have occurred in mitochondria. In control specimens, incubated without insulin for identical periods of time, indentations and vesicles in the plasma membrane are sparse at best and no vesicles or membrane-bound spaces appear deeper in the cytoplasm. The metabolic and morphologic changes induced by insulin seem to be interdependent events. Both changes appear to be initiated rapidly and concomitantly in the tissue. Both processes are initiated by insulin at concentrations considered to be physiological, 0.004 µg. (100 µunits) per ml. Insulin treated with alkali fails to initiate either process. It is concluded that insulin initiates pinocytosis in rat adipose tissue and the possible significance of this process in the mode of action of insulin is discussed.

Nuclear change during differentiation of Entamoeba invadens

1992 ◽  
Vol 50 (1) ◽  
pp. 916-917
Author(s):  
M. Morales-Vallarta ◽  
B. Mata-Cárdenas ◽  
E. Ramírez-Bon
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Experimental Model ◽  
Phosphate Buffer ◽  
Osmium Tetroxide ◽  
Nuclear Division ◽  
Differentiation Process ◽  
Nuclear Change ◽  
Entamoeba Invadens

The cyst of Entamoeba histolytica is the infective phase of this parasite, but much of its differentiation process remains unknown since it is not possible its in vitro encystation. However, differentiation of E. invadens, an ameba that parasites reptiles is used as an experimental model for amebiasis research, specially in differentiation aspects, since E. invadens can be induced to in vitro encystation.The nuclear division during encystation of E. invadens has been described by some authors, but this work, has described this process through light microscopy. In the present work we report the morphologic nuclear change and the chromatin organization observed by electron microscopy.Trophozoites of E. invadens IP-1 were grown in TP-S-1 medium, and encysted in Rengpien and Bailey medium (AEM). During encystation several samples were analysed for different times. The cysts of trophozoites were washed with phosphate buffer saline, postfixed in 1% osmium tetroxide in 0.2 M phosphate buffer pH 7.2 dehydrated in ethyl alcohol and embedded in epoxi resin.

scholarly journals Organization of actin in the leading edge of cultured cells: influence of osmium tetroxide and dehydration on the ultrastructure of actin meshworks.

1981 ◽  
Vol 91 (3) ◽  
pp. 695-705 ◽  
Author(s):  
J V Small
Keyword(s):  
Electron Microscopy ◽  
Actin Filament ◽  
Actin Filaments ◽  
Osmium Tetroxide ◽  
Cultured Cells ◽  
Leading Edge ◽  
Cultured Fibroblasts ◽  
Cell Biol ◽  
Filament Bundles

The ordered structure of the leading edge (lamellipodium) of cultured fibroblasts is readily revealed in cells extracted briefly in Triton X-100-glutaraldehyde mixtures, fixed further in glutaraldehyde, and then negatively stained for electron microscopy. By this procedure, the leading edge regions show a highly organised, three-dimensional network of actin filaments together with variable numbers of radiating actin filament bundles or microspikes. The use of Phalloidin after glutaraldehyde fixation resulted in a marginal improvement in filament order. Processing of the cytoskeletons though the additional steps generally employed for conventional electron microscopy resulted in a marked deterioration or complete disruption of the order of the actin filament networks. In contrast, the actin filaments of the stress fiber bundles were essentially unaffected. Thus, postfixation in osmium tetroxide (1% for 7 min at room temperature) transformed the networks to a reticulum of kinked fibers, resembling those produced by the exposure of muscle F-actin to OsO4 in vitro (P. Maupin-Szamier and T. D. Pollard. 1978. J. Cell Biol. 77:837--852). While limited exposure to OsO4 (0.2+ for 20 min at 0 degrees C) obviated this destruction, dehydration in acetone or ethanol, with or without post-osmication, caused a further and unavoidable disordering and aggregation of the meshwork filaments. The meshwork regions of the leading edge then showed a striking resemblance to the networks hitherto described in critical point-dried preparations of cultured cells. I conclude that much of the "microtrabecular lattice" described by Wolosewick and Porter (1979. J. Cell Biol. 82:114--139) in the latter preparations constitutes actin meshworks and actin filament arrays, with their associated components, that have been distorted and aggregated by the preparative procedures employed.

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