scholarly journals Open junctions in the endothelium of the postcapillary venules of the diaphragm.

1978 ◽  
Vol 79 (1) ◽  
pp. 27-44 ◽  
Author(s):  
N Simionescu ◽  
M Simionescu ◽  
G E Palade
Keyword(s):  
Horseradish Peroxidase ◽  
Carbon Black ◽  
Freeze Fracture ◽  
Intercellular Junctions ◽  
Intramembrane Particles ◽  
Size Limit ◽  
Mouse Diaphragm ◽  
Tracer Particles ◽  
Endothelial Junctions ◽  
Venular Endothelium

We have previously established that approximately 30% of the endothelial junctions in the pericytic venules of the mouse diaphragm are open to a gap of approximately 30--60 A, and are fully permeated by hemeundecapeptide (H11P) (mol diam approximately 20 A). To estimate the size limit for molecules that can permeate these junctions, we have administered graded tracers intravenously and studied their behavior at the level of pericytic venules in bipolar microvascular fields (BMFs) in the mouse diaphragm. Horseradish peroxidase (HRP) (mol diam approximately 50 A) permeated only approximately 50% of the open junctions of the venular endothelium. Outflow through venular junctions appeared to be modest since the tracer remained restricted to the perivenular spaces. Hemoglobin (Hb, mol diam 64 x 55 x 50 A) permeated only a few (less than 5%), and ferritin (mol diam 110 A), practically none, of the endothelial junctions of the pericytic venules. The findings suggest that under normal conditions the size limit for permeant molecules for open venular junctions is approximately 60 A. Replicas of freeze-fracture preparations from appropriate regions in BMF showed that the intercellular junctions of the venular endothelium have the same organization as previously described for the corresponding segments of the microvasculature in the omentum and mesentery: discontinuous creases or grooves either free of or marked by few intramembrane particles only. Administration of histamine (topically or systemically) and 5-hydroxytryptamine (5-HT) (topically) resulted in typical focal separations of the endothelial junctions and intramural deposits of large tracer particles (carbon black) in the postcapillary venules.

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).

Image Analysis of Intramembrane Particles in Freeze-Fractured Biomembranes Using Computer Simulation Techniques

1975 ◽  
Vol 33 ◽  
pp. 214-215
Author(s):  
D.J. Benefiel ◽  
R.S. Weinstein
Keyword(s):  
Membrane Proteins ◽  
Freeze Fracture ◽  
Integral Membrane Proteins ◽  
Systematic Evaluation ◽  
Intramembrane Particles ◽  
Modeling Methods ◽  
Simulation Techniques ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron ◽  
Computer Simulation Techniques

Intramembrane particles (IMP or MAP) are components of most biomembranes. They are visualized by freeze-fracture electron microscopy, and they probably represent replicas of integral membrane proteins. The presence of MAP in biomembranes has been extensively investigated but their detailed ultrastructure has been largely ignored. In this study, we have attempted to lay groundwork for a systematic evaluation of MAP ultrastructure. Using mathematical modeling methods, we have simulated the electron optical appearances of idealized globular proteins as they might be expected to appear in replicas under defined conditions. By comparing these images with the apearances of MAPs in replicas, we have attempted to evaluate dimensional and shape distortions that may be introduced by the freeze-fracture technique and further to deduce the actual shapes of integral membrane proteins from their freezefracture images.

Tight junctions in Gerbil von Ebner's Gland: Horseradish peroxidase and freeze-fracture studies

2015 ◽  
Vol 78 (3) ◽  
pp. 213-219 ◽  
Author(s):  
Anthony Y. Huang ◽  
Ming-Huei Chen ◽  
Sandy Y. Wu ◽  
Kuo-Shyan Lu
Keyword(s):  
Horseradish Peroxidase ◽  
Tight Junctions ◽  
Freeze Fracture

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.

The permeability of arterial endothelium to horseradish peroxidase

1970 ◽  
Vol 174 (1037) ◽  
pp. 435-443 ◽  
Keyword(s):  
Horseradish Peroxidase ◽  
Intercellular Junctions ◽  
Elastic Tissue ◽  
Endothelial Layer ◽  
The Media ◽  
Rats And Mice ◽  
Arterial Endothelium

The protein horseradish peroxidase when injected intravenously into rats and mice rapidly begins to pass from the blood into the walls of arteries. It is found in the intercellular junctions of the endothelium and appears to be crossing the endothelial layer by this route. It is present also in the system of caveolae and vesicles, but it is not clear whether or to what extent these form a means of transport across this layer. It enters multi-vesicular bodies and other relatively large vesicles of the endothelium. Within a few minutes of injection it penetrates through elastic tissue and muscle layers and becomes widely dispersed in the tissue spaces of the media.

scholarly journals Freeze-fracture studies of frog neuromuscular junctions during intense release of neurotransmitter. I. Effects of black widow spider venom and Ca2+-free solutions on the structure of the active zone.

1979 ◽  
Vol 81 (1) ◽  
pp. 163-177 ◽  
Author(s):  
B Ceccarelli ◽  
F Grohovaz ◽  
W P Hurlbut
Keyword(s):  
Neuromuscular Junctions ◽  
Freeze Fracture ◽  
Spider Venom ◽  
Presynaptic Membrane ◽  
Black Widow ◽  
Black Widow Spider ◽  
Intramembrane Particles ◽  
Black Widow Spider Venom ◽  
Active Zones ◽  
Widow Spider

Black widow spider venom (BWSV) was applied to frog nerve-muscle preparations bathed in Ca2+-containing, or Ca2+-free, solutions and the neuromuscular junctions were studied by the freeze-fracture technique. When BWSV was applied for short periods (10-15 min) in the presence of Ca2+, numerous dimples (P face) or protuberances (E face) appeared on the presynaptive membrane and approximately 86% were located immediately adjacent to the double rows of large intramembrane particles that line the active zones. When BWSV was applied for 1 h in the presence of Ca2+, the nerve terminals were depleted of vesicles, few dimples or protuberances were seen, and the active zones were almost completely disorganized. The P face of the presynaptic membrane still contained large intramembrane particles. When muscles were soaked for 2-3 h in Ca2+-free solutions, the active zones became disorganized, and isolated remnants of the double rows of particles were found scattered over the P face of the presynaptic membrane. When BWSV was applied to these preparations, dimples or protuberances occurred almost exclusively alongside disorganized active zones or alongside dispersed fragments of the active zones. The loss of synaptic vesicles from terminals treated with BWSV probably occurs because BWSV interferes with the endocytosis of vesicle membrane. Therefore, we assume that the dimples or protuberances seen on these terminals identify the sites of exocytosis, and we conclude that exocytosis can occur mostly in the immediate vicinity of the large intramembrane particles. Extracellular Ca2+ seems to be required to maintain the grouping of the large particles into double rows at the active zones, but is not required for these particles to specify the sites of exocytosis.

Morphological Changes of Intercellular Junctions in the Rat Submandibular Gland Treated by Long-term Repeated Administration of Isoproterenol

1987 ◽  
Vol 66 (8) ◽  
pp. 1303-1309 ◽  
Author(s):  
T. Inoue ◽  
H. Yamane ◽  
T. Yamamura ◽  
M. Shimono
Keyword(s):  
Gap Junctions ◽  
Tight Junctions ◽  
Morphological Changes ◽  
Freeze Fracture ◽  
Acinar Cells ◽  
Intercellular Junctions ◽  
Repeated Administration ◽  
Experimental Conditions ◽  
Significant Difference

Long-term repeated administration of isoproterenol (lPR) 2 mg/100 g bw, once daily for ten days, resulted in morphological changes in the intercellular junctions of rat submandibular glands, which were investigated by means of the freeze fracture technique. A significantly increased number of tight-junctional strands was present. These junctional strands extended much deeper toward the basal membrane than those in normal acinar cells. The basal frontier strands that branched from the networks of tight junctions were elongated and had either free-endings or terminal loops, which were more frequently observed in the IPR-treated acinar cells than in untreated acinar cells. Some of the strands of tight junctions were connected to small gap junctions. The diameters of gap junctions were not significantly different from those of control acinar cells. However, smooth areas devoid of particles were found intermingling with the usual packed particles in irregularly shaped small gap junctions. There was no significant difference between the desmosomes of IPR-treated and untreated acinar cells, in terms of either morphology or distribution. These changes in junctional morphology in the IPR-treated acinar cells resemble those seen in salivary glands during development, and in some experimental conditions including tumorous changes.

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