scholarly journals FREEZE-FRACTURE OF MICROTUBULES AND BRIDGES IN MOTILE AXOSTYLES

1974 ◽  
Vol 62 (3) ◽  
pp. 660-671 ◽  
Author(s):  
Robert A. Bloodgood ◽  
Kenneth R. Miller
Keyword(s):  
Electron Microscopy ◽  
Binding Sites ◽  
Freeze Fracture ◽  
Sectioned Material ◽  
Fracture Study ◽  
Cross Bridges ◽  
Longitudinal Fractures

A freeze-fracture study of the motile axostyles of the flagellate protozoa Saccinobaculus and Pyrsonympha has been undertaken in order to obtain a view of the relationships of microtubules and their cross bridges not dependent on conventional preparative procedures. Reactivation studies using isolated axostyles prepared for freeze-fracture and then thawed demonstrate that we are observing the structure of a potentially functional axostyle. Cross fractures through the axostyle demonstrate more extensive interrow bridging than expected on the basis of observations of thin-sectioned material. Each microtubule has approximately sixfold bridge-binding sites with connections to as many as four interrow bridges. Measurements of microtubule diameter and spacing are significantly larger than those made from sectioned material and may indicate that conventional processing for electron microscopy results in the loss of structurally important water within the microtubule in addition to loss of intertubule material. Longitudinal fractures through the axostyle at various orientations demonstrate a minimum longitudinal periodicity of 160 Å for both the spacing of the globular subunits within the microtubule wall and the spacing of the intrarow bridges. While intrarow bridges are strictly periodic and always oriented in parallel, interrow bridges are not strictly periodic and can be oriented at varying angles to the microtubule axis.

Myocardial sarcolemma in ischemia: a quantitative freeze-fracture study

1988 ◽  
Vol 255 (3) ◽  
pp. H467-H475 ◽  
Author(s):  
J. S. Frank ◽  
S. Beydler ◽  
N. Wheeler ◽  
K. I. Shine
Keyword(s):  
Electron Microscopy ◽  
Analysis Of Variance ◽  
Freeze Fracture ◽  
Mixed Effects ◽  
Fracture Face ◽  
Intramembrane Particles ◽  
Fracture Study ◽  
K Concentration ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Freeze-fracture electron microscopy permits the visualization of the intramembrane particles (IMP). These IMPs are presumably proteins responsible for the main functions of the membrane. Quantitative techniques (Clark-Evan statistics) were applied to determine in a critical manner whether IMP pattern shifts (random, clustered, or ordered) occur under the ischemic conditions (5-45 min with and without reperfusion) and whether this change is related to the experimental condition. In each case three hearts, eight replicas/heart, one area of 0.25 micron 2 of membrane fracture face/replica was measured to give a total of 6 micron 2 of membrane counted for each condition (control vs. ischemic). A mixed effects nested model analysis of variance was performed in each variable. We found that IMP aggregation can be present in some control membranes, but the degree of aggregation was greater and more consistent in membranes made ischemic and followed by reperfusion. Most striking was the significant clustering of IMPs in membranes from hearts ischemic for only 5 min. Reperfusion after only 5 min of ischemia reversed IMP clustering. Functionally at this time there is an increase in K+ concentration in the interstitial space that reaches approximately 15 mM within 10 min and reverses on reperfusion. The structural alteration in IMPs appears to parallel the function in ischemic hearts.

Freeze–fracture studies on unmyelinated axolemma of rat cervical sympathetic trunk : correlation with saxitoxin binding

1988 ◽  
Vol 233 (1270) ◽  
pp. 45-54 ◽  
Keyword(s):  
Electron Microscopy ◽  
Binding Sites ◽  
Large Diameter ◽  
Freeze Fracture ◽  
Sympathetic Trunk ◽  
Particle Sizes ◽  
Cervical Sympathetic Trunk ◽  
Cervical Sympathetic ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

The density and diameter distributions of intramembranous particles (IMPS) within unmyelinated axolemma from rat cervical sympathetic trunk were examined with freeze–fracture electron microscopy. The axolemma displays a highly asymmetrical partitioning of IMPS with ca . 1200 IMPS μm –2 on P-faces and ca . 100 IMPS μm –2 on E-faces. Particle sizes (diameters) are unimodally distributed on both fracture faces, with a range from 2.4 nm to 15.6 nm. Approximately 16% of the particles on P-faces and 28% of particles on E-faces are of a large (greater than 9.6 nm) diameter. On both fracture faces, the IMPS appear to be randomly distributed; no aggregations of particles were observed. The results indicate that there are ca . 230 large IMPS μm –2 of unmyelinated axolemma from rat cervical sympathetic trunk. The density of these IMPS is similar to the density of saxitoxin binding sites on unmyelinated axolemma from rat cervical sympathetic trunk (Pellegrino et al . 1984 ( Brain Res . 305, 357–360)), which suggests that many of the large diameter particles may be the morphological correlate of voltage-sensitive Na + channels.

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.

scholarly journals Membrane specializations of dentritic spines and glia in the weaver mouse cerebellum: a freeze-fracture study.

1976 ◽  
Vol 68 (3) ◽  
pp. 403-410 ◽  
Author(s):  
R B Hanna ◽  
A Hirano ◽  
G D Pappas
Keyword(s):  
Electron Microscopy ◽  
Dendritic Spines ◽  
Synaptic Input ◽  
Freeze Fracture ◽  
Fracture Face ◽  
Entire Region ◽  
Parallel Fibers ◽  
Fracture Study ◽  
Weaver Mouse ◽  
Center Distance

Electron microscopy of thin-sectioned and freeze-fractured preparations of the cerebellum of the weaver mouse indicates that the dendritic spines are morphologically identical to those of their normal littermates. The weaver dendritic spines have been characterized as "unattached" since the synaptic input from the parallel fibers is absent (8-10). The entire region around the dendritic spines is taken up by astrocytic processes in the weaver. The outer fracture face of a normal dendritic spine contains aggregations of 10-nm wide particles in the immediate postsynaptic region. Similar particle aggregations occur in the unattached spines of the weaver. Freeze-fracture preparations reveal rectilinear arrays of particles, having a 7-nm center-to-center distance in the glial membranes. Rectilinear arrays are apparently distributed throughout the astrocyte membrane.

Freeze-Fracture Study of Microfilament Attachments to Membranes

1977 ◽  
Vol 35 ◽  
pp. 602-603
Author(s):  
N. Scott McNutt
Keyword(s):  
Cardiac Muscle ◽  
Thin Section ◽  
Actin Filaments ◽  
Particle Density ◽  
Freeze Fracture ◽  
Structural Type ◽  
Intercalated Disc ◽  
Fracture Study ◽  
Cross Bridges ◽  
Filamentous Material

Actin-containing microfilaments are part of contractile systems in many cells, and the functions of these systems require some type of attachment of microfilaments to membranes (1). This attachment is particularly necessary at the fascia adherens in the intercalated disc of cardiac muscle (2) and at the tips of intestinal microvilli (1). At these locations, the actin filaments are perpendicular to the membrane and a dense-filamentous material is present at the sites of attachment. Freeze-fracture studies of these membranes have revealed a decrease in P face particle density at the fascia adherens (2) and at the tips of intestinal microvilli (3). In contrast, when the microfilaments lie parallel to the plane of the membrane, another structural type of attachment is found which is mediated by fine cross-bridges instead of the dense filamentous material. These cross-bridges are visible in both thin-section and freeze-etch preparations (1,4). The freeze-fracture counterpart of this type of cross-bridge attachment has not been shown previously.

scholarly journals Membrane movements and fluidity during rotational motility of a termite flagellate. A freeze-fracture study.

1979 ◽  
Vol 80 (1) ◽  
pp. 141-149 ◽  
Author(s):  
S L Tamm
Keyword(s):  
Electron Microscopy ◽  
Shear Zone ◽  
Cell Shape ◽  
Freeze Fracture ◽  
Clockwise Rotation ◽  
Fracture Study ◽  
Freeze Fracture Electron Microscopy ◽  
Specific Membrane ◽  
Fracture Electron

Freeze-fracture electron microscopy was used to examine the structure of a region of plasma membrane that undergoes continual, unidirectional shear. Membrane shear arises from the continual clockwise rotation of one part (head) of a termite flagellate relative to the rest of the cell. Freeze-fracture replicas show that the lipid bilayer is continuous across the shear zone. Thus, the relative movements of adjacent membrane regions are visible evidence of membrane fluidity. The distribution and density of intramembrane particles within the membrane of the shear zone is not different from that in other regions of the cell membrane. Also, an additional membrane shear zone arises when body membrane becomes closely applied to the rotating axostyle as cells change shape in vitro. This suggests that the entire membrane is potentially as fluid as the membrane between head and body but that this fluidity is only expressed at certain locations for geometrical and/or mechanical reasons. Membrane movements may be explained solely by cell shape and proximity to rotating structures, although specific membrane-cytoskeletal connections cannot be ruled out. The membrane of this cell may thus be viewed as a fluid which adheres to the underlying cytoplasm/cytoskeleton and passively follows its movements.

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.

Sites of Insulin Action Using Ferritin Labeling

1971 ◽  
Vol 29 ◽  
pp. 540-541
Author(s):  
Burton B. Silver ◽  
Ronald S. Nelson
Keyword(s):  
Electron Microscopy ◽  
Binding Sites ◽  
Anterior Pituitary ◽  
Insulin Action ◽  
Diabetic Rats ◽  
Insulin Antibody ◽  
Fat Pad ◽  
Target Organs ◽  
Uranium Salts ◽  
Sugar Levels

Some investigators feel that insulin does not enter cells but exerts its influence in some manner on the cell surface. Ferritin labeling of insulin and insulin antibody was used to determine if binding sites of insulin to specific target organs could be seen with electron microscopy.Alloxanized rats were considered diabetic if blood sugar levels were in excess of 300 mg %. Test reagents included ferritin, ferritin labeled insulin, and ferritin labeled insulin antibody. Target organs examined were were diaphragm, kidney, gastrocnemius, fat pad, liver and anterior pituitary. Reagents were administered through the left common carotid. Survival time was at least one hour in test animals. Tissue incubation studies were also done in normal as well as diabetic rats. Specimens were fixed in gluteraldehyde and osmium followed by staining with lead and uranium salts. Some tissues were not stained.

Freeze-Fracture Replication of Frozen Outer Segments of Rat Retinal Rods

1969 ◽  
Vol 27 ◽  
pp. 392-393
Author(s):  
Thomas S. Leeson ◽  
C. Roland Leeson
Keyword(s):  
Electron Microscopy ◽  
Cross Section ◽  
Outer Segment ◽  
Freeze Fracture ◽  
X Ray Diffraction ◽  
X Ray ◽  
Outer Segments ◽  
Retinal Rods ◽  
Temperature Electron ◽  
Freeze Etching

Numerous previous studies of outer segments of retinal receptors have demonstrated a complex internal structure of a series of transversely orientated membranous lamellae, discs, or saccules. In cones, these lamellae probably are invaginations of the covering plasma membrane. In rods, however, they appear to be isolated and separate discs although some authors report interconnections and some continuities with the surface near the base of the outer segment, i.e. toward the inner segment. In some species, variations have been reported, such as longitudinally orientated lamellae and lamellar whorls. In cross section, the discs or saccules show one or more incisures. The saccules probably contain photolabile pigment, with resulting potentials after dipole formation during bleaching of pigment. Continuity between the lamina of rod saccules and extracellular space may be necessary for the detection of dipoles, although such continuity usually is not found by electron microscopy. Particles on the membranes have been found by low angle X-ray diffraction, by low temperature electron microscopy and by freeze-etching techniques.

Cryomicroscopy of multiphase latices

1991 ◽  
Vol 49 ◽  
pp. 1060-1061
Author(s):  
O. L. Shaffer ◽  
M.S. El-Aasser ◽  
C. L. Zhao ◽  
M. A. Winnik ◽  
R. R. Shivers
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Freeze Fracture ◽  
Particle Morphology ◽  
Second Stage ◽  
Transmission Electron ◽  
Important Approach ◽  
Carbon Coated ◽  
Preparation Techniques

Transmission electron microscopy is an important approach to the characterization of the morphology of multiphase latices. Various sample preparation techniques have been applied to multiphase latices such as OsO4, RuO4 and CsOH stains to distinguish the polymer phases or domains. Radiation damage by an electron beam of latices imbedded in ice has also been used as a technique to study particle morphology. Further studies have been developed in the use of freeze-fracture and the effect of differential radiation damage at liquid nitrogen temperatures of the latex particles embedded in ice and not embedded.Two different series of two-stage latices were prepared with (1) a poly(methyl methacrylate) (PMMA) seed and poly(styrene) (PS) second stage; (2) a PS seed and PMMA second stage. Both series have varying amounts of second-stage monomer which was added to the seed latex semicontinuously. A drop of diluted latex was placed on a 200-mesh Formvar-carbon coated copper grid.

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