New Evidence for Membrane Specialization in the Diatom Thalassiosira Antarctica Comber

1980 ◽  
Vol 38 ◽  
pp. 624-625
Author(s):  
Gregory J. Doucette
Keyword(s):  
Electron Microscopy ◽  
Thin Section ◽  
Freeze Fracture ◽  
Marine Diatom ◽  
Supplementary Data ◽  
Ultra Structure ◽  
Membrane Specialization ◽  
Freeze Fracture Electron Microscopy ◽  
New Evidence ◽  
Fracture Electron

The present investigation was undertaken to examine the nonsiliceous ultra-structure of diatoms (BacilIariophyta) by means of freeze fracture electron microscopy. Freeze fracture procedures are complicated by the difficulties encountered in fracturing silica-based components and the removal of these materials subsequent to replica casting. Supplementary data was obtained through conventional thin section methodologies. This report is a prelim¬inary account of observations made on selected nonsiliceous, cellular con¬stituents of Thalassiosira antarctica Comber, a planktonic, marine diatom.

scholarly journals Coalescence of microsomal vesicles from rat liver: a phenomenon occurring in parallel with enhancement of the glycosylation activity during incubation of stripped rough microsomes with GTP.

1980 ◽  
Vol 86 (1) ◽  
pp. 29-37 ◽  
Author(s):  
J Paiement ◽  
H Beaufay ◽  
D Godelaine
Keyword(s):  
Electron Microscopy ◽  
Thin Section ◽  
Rat Liver ◽  
Freeze Fracture ◽  
Endogenous Protein ◽  
Previously Treated ◽  
Nucleotide Sugars ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Rough microsomes from rat liver have been subjected to various treatments and incubated afterwards with UDP-N-acetyl-[14C]glucosamine and GDP-mannose in the presence of GTP (0.5 mM), or of other nucleotides. In agreement with earlier results from this laboratory, the preparations previously treated to strip off the ribosomes and incubated in the presence of GTP assembled dolichol-linked oligosaccharides and transferred these oligosaccharides to endogenous protein acceptors much more actively than untreated preparations, or stripped preparations incubated in the absence of GTP. Thin-section and freeze-fracture electron microscopy have revealed that pyrophosphate-treated preparations incubated with GTP are aggregated and contain numerous vesicles as large as 1-4 micrometer, or more. Such large vesicles were not present before incubation and thus were considered to have been formed through coalescence of regular-sized ones. Like glycosylation, the coalescence phenomenon depends upon the removal of ribosomes, because it occurred whether ribosomes had been stripped, at least partly, with pyrophosphate, KCl, or puromycin, but not when rough microsomes had been washed with 0.25 M sucrose or with KCl and MgCl2. Like glycosylation, it also depends on the addition of GTP and was not induced by ATP, UTP, CTP, and nonhydrolysable analogues of GTP. Rough microsomes coalesced, however, when pyrophosphate-treated preparations were incubated with GTP in the absence of nucleotide sugars, or in the presence f tunicamycin, indicating that the coalescence phenomenon does not result from the glycosylation of some membrane constituents.

scholarly journals Freeze-fracture Electron Microscopy on Microbubbles Used as Theranostics or Made of Lung Surfactant

2010 ◽  
Vol 16 (S2) ◽  
pp. 1172-1173
Author(s):  
B Papahadjopoulos-Sternberg ◽  
J Ackrell
Keyword(s):  
Electron Microscopy ◽  
Lung Surfactant ◽  
Freeze Fracture ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

Ultrastructural analysis of the apical ectodermal ridge during vertebrate limb morphogenesis

Development ◽  
1977 ◽  
Vol 41 (1) ◽  
pp. 223-232
Author(s):  
John F. Fallon ◽  
Robert O. Kelley
Keyword(s):  
Electron Microscopy ◽  
Gap Junctions ◽  
Freeze Fracture ◽  
Apical Ectodermal Ridge ◽  
Structural Requirements ◽  
Limb Morphogenesis ◽  
Vertebrate Limb ◽  
The Difference ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron

The fine structure of the apical ectodermal ridge of five phylogenetically divergent orders of mammals and two orders of birds was examined using transmission and freeze fracture electron microscopy. Numerous large gap junctions were found in all apical ectodermal ridges studied. This was in contrast to the dorsal and ventral limb ectoderms where gap junctions were always very small and sparsely distributed. Thus, gap junctions distinguish the inductively active apical epithelium from the adjacent dorsal and ventral ectoderms. The distribution of gap junctions in the ridge was different between birds and mammals but characteristic within the two classes. Birds, with a pseudostratified columnar apical ridge, had the heaviest concentration of gap junctions at the base of each ridge cell close to the point where contact was made with the basal lamina. Whereas mammals, with a stratified cuboidal to squamous apical ridge, had a more uniform distribution of gap junctions throughout the apical epithelium. The difference in distribution for each class may reflect structural requirements for coupling of cells in the entire ridge. We propose that all cells of the apical ridges of birds and mammals are electrotonically and/or metabolically coupled and that this may be a requirement for the integrated function of the ridge during limb morphogenesis.

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