scholarly journals Topographical differences in the distribution of surface coat components and intramembrane particles. A cytochemical and freeze-fracture study in culture forms of Trypanosoma cruzi.

1976 ◽  
Vol 69 (2) ◽  
pp. 507-513 ◽  
Author(s):  
A Martínez-Palomo ◽  
W DeSouza ◽  
A Gonzalez-Robles
Keyword(s):  
Plasma Membrane ◽  
Binding Sites ◽  
Freeze Fracture ◽  
Ruthenium Red ◽  
Regional Differentiation ◽  
Surface Coat ◽  
Colloidal Iron ◽  
Regional Specialization ◽  
Poor Region ◽  
Fracture Study

A regional specialization of the cell surface of T. cruzi culture forms was found at the cytostome as a localized thick surface coat rich in carbohydrate-containing components. The prominent surface coat was located over a region of the plasma membrane where intramembranous particles were exceedingly low in number. In turn, the particle-poor region was related to specialized submembrane fibrils not present under other regions of the plasma membrane. The cystostome region provides a striking example of a stable regional differentiation of the plasma membrane, involving the outer surface, the membrane interior, and the underlying cytoplasm. In addition, independence of Con A receptors, colloidal iron binding sites, and ruthenium red-stainable surface components from membrane particles was demonstrated at the flagellar membrane.

The cell surface of Trypanosoma cruzi: cytochemistry and freeze-fracture

1978 ◽  
Vol 33 (1) ◽  
pp. 285-299
Author(s):  
W. De Souza ◽  
A. Martinez-Palomo ◽  
A. Gonzalez-Robles
Keyword(s):  
Plasma Membrane ◽  
Trypanosoma Cruzi ◽  
Freeze Fracture ◽  
Ruthenium Red ◽  
The Body ◽  
Surface Coat ◽  
Structural Variations ◽  
Poor Region ◽  
Flagellar Membrane ◽  
Two Stages

The ultrastructure of epimastigotes of Trypanosoma cruzi, obtained from acellular cultures, and bloodstream trypomastigotes, isolated from infected mice, were studied by thin-sectioning and freeze-fracturing techniques. Epimastigotes showed a thin (5 nm) surface coat when stained with ruthenium red, while the surface coat of trypomastigotes was more prominent (15 nm thick). Both P and E faces of the plasma membrane of T. cruzi had roughly the same number of intramembranous particles (IMP) as seen by freeze-fracture. The plasma membrane of bloodstream trypomastigotes had less IMP than epimastigotes. Several differentiations of the plasma membrane was observed. In epimastigotes a cytostome appears as a particle-poor region delimited by a pallisade-like row of adjacent IMP. Bloodstream trypomastigotes did not have a cytostome. Instead, abundant pinocytic vesicles were observed. At the base of the flagellum of epimastigotes a ciliary necklace was found. At this region, the surface coat was differentiated as long, hair-like projections after staining with ruthenium red. The flagellar membrane had less IMP than the body membrane. Clusters of IMP were present on both faces of the flagellar membrane at the flagellar-body adhesion zone of epimastigotes. Linear arrays of IMP were also seen. In bloostream trypomastigotes clusters of particles were observed both on the flagellar and cell body membranes. Our observations demonstrate the presence of considerable structural variations of the T. cruzi plasma membrane at the two stages of the life cycle studied.

scholarly journals Membrane structure and surface coat of Entamoeba histolytica. Topochemistry and dynamics of the cell surface: cap formation and microexudate.

1975 ◽  
Vol 64 (3) ◽  
pp. 538-550 ◽  
Author(s):  
P P Silva ◽  
A Martínez-Palomo ◽  
A Gonzalez-Robles
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Binding Sites ◽  
Membrane Structure ◽  
Ruthenium Red ◽  
Iron Binding ◽  
Con A ◽  
Colloidal Iron ◽  
Acidic Sites ◽  
Membrane Components

Treatment of living entamoeba histolytica cells with low concentrations of concanavalin A (con A) and peroxidase results in redistribution of the plasma membrane con A receptors to one pole of the cell where a morphologically distinct region--the uroid--is formed. Capping of con A receptors is not accompanied by parallel accumulation of ruthenium red-stainable components. In capped cells, the pattern of distribution of acidic sites ionized at pH 1.8 (labeled by colloidal iron) at the outer surface and of membrane particles (integral membrane components revealed by freeze-fracture) is not altered over the uroid region. Cytochemistry of substrate-attached microexudate located in regions adjacent to E. histolytica cells demonstrates the presence of con A binding sites and ruthenium red- and alcian blue-stainable components and the absent of colloidal iron binding sites. In a previous report we demonstrated that glycerol-induced aggregation of the plasma membrane particles is accompanied by a discontinuous distribution of colloidal iron binding sites, while con A receptors and acidic sites ionized at pH 4.0 remain uniformly distributed over the cell surface. Taken together, our experiments show that, in E. histolytica cells, peripheral membrane components may move independently of integral components and, also, that certain surface determinants may redistribute independently of others. These results point to the complexity of the membrane structure-cell surface relationship in E. histolytica plasma membranes relative to the membrane of the erythrocyte ghost where integral components (the membrane-intercalated particles) contain all antigens, receptors, and anionic sites labeled so far. We conclude that fluidity of integral membrane components (integral membrane fluidity) cannot be inferred from the demonstration of the mobility of surface components nor, conversely, can the fluidity of peripheral membrane components (peripheral membrane fluidity) be assumed from demonstration of the mobility of integral membrane components.

scholarly journals A freeze-fracture study of membrane events during neurohypophysial secretion.

1978 ◽  
Vol 78 (2) ◽  
pp. 542-553 ◽  
Author(s):  
D T Theodosis ◽  
J J Dreifuss ◽  
L Orci
Keyword(s):  
Plasma Membrane ◽  
Unit Area ◽  
Freeze Fracture ◽  
Core Material ◽  
Number Of Clusters ◽  
Intramembrane Particles ◽  
En Face ◽  
Large Particles ◽  
Mean Diameter ◽  
Fracture Study

Freeze-fracture was used to study the membrane events taking place during neurosecretory granule discharge (exocytosis) and subsequent membrane internalization (endocytosis) in axons of neurohypophyses from control and water-deprived rats. En face views of the cytoplasmic leaflet (P face) of the split axolemma reveal circular depressions that represent the secretory granule membranes fused with the plasma membrane during exocytosis. These depressions often contain granule core material in the process of extrusion into the extracellular space. The membrane surrounding some of the exocytotic openings shows a decreased number of intramembrane particles (mean diameter, 8 nm) which are elsewhere more numerous and evenly distrubuted on the fracture face. Endocytotic sites appear as smaller plasma membrane invaginations, with associated intramembrane particles. Moreover, such invaginations often contain large particles (mean diameter, 12 nm) that appear as clusters on en face views of the membrane leaflet. Quantitative analysis indicates that the number of exocytotic images increases significantly in glands from water-deprived rats. Concomitantly, the number of endocytotic figures per unit area of membrane is raised as is the number of clusters of large particles. The observations demonstrate that, in the neurohypophysis, it is possible to distinguish exocytosis morphologically from endocytosis and that the two events can be assessed quantitatively.

Plasma membrane alterations of maturing goat (Capra indicus) spermatozoa: Lectin-binding and freeze-fracture study

1993 ◽  
Vol 271 (1) ◽  
pp. 159-168 ◽  
Author(s):  
H. K. Bains ◽  
S. R. Bawa ◽  
M. A. Pabst ◽  
S. Sehgal
Keyword(s):  
Plasma Membrane ◽  
Lectin Binding ◽  
Freeze Fracture ◽  
Fracture Study

A freeze-fracture study of the cuticle of adult Nippostrongylus brasiliensis (Nematoda)

Parasitology ◽  
1993 ◽  
Vol 107 (5) ◽  
pp. 545-552 ◽  
Author(s):  
D. L. Lee ◽  
K. A. Wright ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Freeze Fracture ◽  
Surface Coat ◽  
Nippostrongylus Brasiliensis ◽  
Freeze Fracturing ◽  
Transmission Electron ◽  
Fracture Study ◽  
20 Nm

SUMMARYThe surface of the cuticle of adult Nippostrongylus brasiliensis has been studied by means of the freeze-fracture technique and by transmission electron microscopy. Some of the surface coat appears to have been shed from the surface of the cuticle of adults fixed in situ in the intestine of its host and from the surface of individuals removed from the intestine and freeze-fractured. Freeze-fracturing the cuticle of individuals removed from the host has shown that this surface coat varies in thickness from 30 to 90 nm. The epicuticle is about 20 nm thick and cleaves readily to expose E- and P-faces. The P-face of the epicuticle possesses a small number of particles, similar to intra-membranous particles, whilst the E-face possesses a few, widely scattered depressions. Despite the presence of these particles the epicuticle is not considered to be a true membrane. Freeze-fracturing the remainder of the cuticle has confirmed its structure as described by conventional transmission electron microscopy. Clusters of particles on the P-face of the outer epidermal (hypodermal) membrane and corresponding depressions on the E-face of the membrane are thought to be associated with points of attachment of the cuticle to the epidermis (hypodermis). No differences in appearance of the cuticle and its surface layers were observed in individuals taken from 7-, 10-, 13- and 15-day infections.

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