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.

Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

1977 ◽  
Vol 35 ◽  
pp. 596-597
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Candida Utilis ◽  
Synthetic Medium ◽  
Freeze Fracture ◽  
Translational Diffusion ◽  
Yeast Cells ◽  
Distilled Water ◽  
Intramembrane Particles ◽  
The Matrix ◽  
Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

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.

scholarly journals Membrane particle changes attending the acrosome reaction in guinea pig spermatozoa

1977 ◽  
Vol 74 (2) ◽  
pp. 561-577 ◽  
Author(s):  
DS Friend ◽  
L Orci ◽  
A Perrelet ◽  
R Yanagimachi
Keyword(s):  
Plasma Membrane ◽  
Guinea Pig ◽  
Acrosome Reaction ◽  
Plasma Membranes ◽  
Freeze Fracture ◽  
Phosphatidylcholine Liposomes ◽  
Acrosomal Membrane ◽  
Large Particles ◽  
Fracture Appearance ◽  
Preparatory Stage

To examine the freeze-fracture appearance of membrane alterations accompanying the preparation of sperm membranes for fusions-the first preparatory stage occurring before physiological release of the acrosomal content, the second afterward-we induced the acrosome reaction in capacitated guinea pig spermatozoa by adding calcium to the mixture. The most common features observed before fusion of the acrosomal and plasma membranes were the deletion of fibrillar intramembranous particles from the E-fracture faces of both membranes, and the clearance of globular particles from the P face of the plasma membrane-events taking place near the terminus of the equatorial segment. Large particles, >12nm, remained not far from the cleared E-face patches. The P face of the outer acrosomal membrane is virtually clear from the outset. In addition, when fusion was completed, occasional double lines of large particles transiently embossed the P face of the plasma membrane (postacrosomal) side of the fusion zone. Behind the line of fusion, another series of particle-cleared foci emerged. We interpreted these postfusion membrane clearances as a second adaptation for sperm-egg interaction. Induction of the acrosome reaction in media containing phosphatidylcholine liposomes resulted in their apparent attachment, incorporation, or exchange in both the originally and secondarily cleared regions. Our observations support the concepts that membranes become receptive to union at particle- deficient interfaces, and that the physiologically created barren areas in freeze-fracture replicas may herald incipient membrane fusion.

scholarly journals Freeze-fracture study on the erythrocyte membrane during malarial parasite invasion.

1981 ◽  
Vol 91 (1) ◽  
pp. 55-62 ◽  
Author(s):  
M Aikawa ◽  
L H Miller ◽  
J R Rabbege ◽  
N Epstein
Keyword(s):  
Erythrocyte Membrane ◽  
Cytochalasin B ◽  
Freeze Fracture ◽  
Malarial Parasite ◽  
Invasion Process ◽  
Parasite Invasion ◽  
Thin Sections ◽  
Intramembrane Particles ◽  
Fracture Study ◽  
Attachment Process

Invasion of erythrocytes by malarial merozoites requires the formation of a junction between the merozoite and the erythrocyte. Migration of the junction parallel to the long axis of the merozoite occurs during the entry of the merozoite into an invagination of the erythrocyte. Freeze-fracture shows a narrow circumferential band of rhomboidally arrayed particles on the P face of the erythrocyte membrane at the neck of the erythrocyte invagination and matching rhomboidally arrayed pits on the E face. The band corresponds to the junction between the erythrocyte and merozoite membranes observed in thin sections and may represent the anchorage sites of the contractile proteins within the erythrocyte. Intramembrane particles (IMP) on the P face of the erythrocyte membrane disappear beyond this junction. When the erythrocytes and cytochalasin B-treated merozoites are incubated together, the merozoite attaches to the erythrocyte membrane and a junction is formed between the two, but the invasion process does not advance further and no movement of the junction occurs. Although there is no entry of the parasite, the erythrocyte membrane still invaginates. Freeze-fracture shows that the P face of the invaginated erythrocyte membrane is almost devoid of the IMP that are found elsewhere on the membrane, suggesting that the attachment process in and of itself is sufficient to create a relatively IMP-free bilayer.

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