Effect of Hyperthermia on the Plasma Membrane Structure of Chinese Hamster V79 Fibroblasts: A Quantitative Freeze-Fracture Study

1986 ◽  
Vol 106 (1) ◽  
pp. 47 ◽  
Author(s):  
G. Arancia ◽  
W. Malorni ◽  
G. Mariutti ◽  
P. Trovalusci
Keyword(s):  
Plasma Membrane ◽  
Membrane Structure ◽  
Freeze Fracture ◽  
Chinese Hamster ◽  
Fracture Study

scholarly journals Phagocytosis of bacteria by polymorphonuclear leukocytes: a freeze-fracture, scanning electron microscope, and thin-section investigation of membrane structure

1978 ◽  
Vol 76 (1) ◽  
pp. 158-174 ◽  
Author(s):  
PL Moore ◽  
HL Bank ◽  
NT Brissie ◽  
SS Spicer
Keyword(s):  
Plasma Membrane ◽  
Electron Microscope ◽  
Membrane Fusion ◽  
Thin Section ◽  
Membrane Structure ◽  
Freeze Fracture ◽  
Vacuole Membrane ◽  
Attachment Sites ◽  
Pmn Leukocytes ◽  
Scanning Electron

The changes in membrane structure of rabbit polymorphonuclear (PMN) leukocytes during bacterial phagocytosis was investigated with scanning electron microscope (SEM), thin-section, and freeze-fracture techniques. SEM observations of bacterial attachment sites showed the involvement of limited areas of PMN membrane surface (0.01-0.25μm(2)). Frequently, these areas of attachment were located on membrane extensions. The membrane extensions were present before, during, and after the engulfment of bacteria, but were diminished in size after bacterial engulfment. In general, the results obtained with SEM and thin-section techniques aided in the interpretation of the three-dimensional freeze-fracture replicas. Freeze-fracture results revealed the PMN leukocytes had two fracture faces as determined by the relative density of intramembranous particles (IMP). Membranous extensions of the plasma membrane, lysosomes, and phagocytic vacuoles contained IMP's with a distribution and density similar to those of the plasma membrane. During phagocytosis, IMPs within the plasma membrane did not undergo a massive aggregation. In fact, structural changes within the membranes were infrequent and localized to regions such as the attachment sites of bacteria, the fusion sites on the plasma membrane, and small scale changes in the phagocytic vacuole membrane during membrane fusion. During the formation of the phagocytic vacuole, the IMPs of the plasma membrane appeared to move in with the lipid bilayer while maintaining a distribution and density of IMPs similar to those of the plasma membranes. Occasionally, IMPs were aligned to linear arrays within phagocytic vacuole membranes. This alignment might be due to an interaction with linearly arranged motile structures on the side of the phagocytic vacuole membranes. IMP-free regions were observed after fusion of lysosomes with the phagocytic vacuoles or plasma membrane. These IMP-free areas probably represent sites where membrane fusion occurred between lysosomal membrane and phagocytic vacuole membrane or plasma membrane. Highly symmetrical patterns of IMPs were not observed during lysosomal membrane fusion.

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.

Sign in / Sign up

Export Citation Format

Share Document