Lateral phase separations in binary lipid mixtures: Correlation between spin label and freeze-fracture electron microscopic studies

1974 ◽  
Vol 363 (2) ◽  
pp. 151-158 ◽  
Author(s):  
Chris W.M. Grant ◽  
Stephen Hong-Wei Wu ◽  
Harden M. McConnell
Keyword(s):  
Spin Label ◽  
Freeze Fracture ◽  
Electron Microscopic ◽  
Phase Separations ◽  
Lipid Mixtures ◽  
Microscopic Studies ◽  
Fracture Electron

A freeze-fracture electron microscopic study of Frankia in root nodules of Alnus incana grown at three oxygen tensions

1990 ◽  
Vol 36 (2) ◽  
pp. 97-108 ◽  
Author(s):  
R. M. Abeysekera ◽  
William Newcomb ◽  
W. B. Silvester ◽  
John G. Torrey
Keyword(s):  
Root Nodules ◽  
Freeze Fracture ◽  
Alnus Incana ◽  
Electron Microscopic ◽  
Protection Mechanism ◽  
Transmission Electron ◽  
Actinorhizal Nodules ◽  
The Mean ◽  
Cell Envelopes ◽  
Fracture Electron

Nodulated plants of Alnus incana ssp. rugosa and ssp. incana were grown with the roots exposed to 5, 21, and 40 kPa O2. The nodules were studied by freeze-fracture transmission electron microscopy to determine the effect of varying O2 tension on the numbers of lipid laminae in the Frankia envelope. Lipid laminae were present in the cell envelopes of hyphae, stalks, and symbiotic vesicles. The mean number of lipid laminae in hyphal envelopes varied from five to nine. Stalks of symbiotic vesicles contained mean numbers of 35–59 lipid laminae over the range of pO2's studied. Symbiotic vesicle envelopes showed mean numbers of lipid laminae varying from 48 to 94. The numbers of lipid laminae were observed to increase significantly in the distal regions of the symbiotic vesicles in response to raised pO2 while the numbers on the proximal portions remained unchanged. The increase in the numbers of lipid laminae in response to raised pO2 was not sufficient to account for the expected increase in resistance to O2 required at the symbiotic vesicle envelope if lipid laminae formed the exclusive diffusion barrier to O2. These results suggest that lipid laminae surrounding symbiotic vesicles may not constitute the only O2 protection mechanism in Alnus nodules. Key words: Alnus incana, Frankia, nitrogen fixation, actinorhizal nodules, Actinomycetes.

Determinants of biliary secretion in isolated perfused skate liver

1982 ◽  
Vol 242 (4) ◽  
pp. G319-G325 ◽  
Author(s):  
J. S. Reed ◽  
N. D. Smith ◽  
J. L. Boyer
Keyword(s):  
Tight Junctions ◽  
Bile Flow ◽  
Perfusion Pressure ◽  
Freeze Fracture ◽  
Biliary Tree ◽  
Solute Diffusion ◽  
Electron Microscopic ◽  
Bile Formation ◽  
Ionic Lanthanum ◽  
Microscopic Studies

In the isolated perfused liver of the little skate, Raja erinacea, bile flow averaged 5.07 +/- 0.58 (mean +/- SE) microliters.h-1.g liver-1 in 21 experiments at a perfusion pressure of 5.0 cm Ringer compared to 3.79 +/- 0.32 in 38 experiments at 2.5 cm (P less than 0.05). [14C]inulin readily entered skate bile. Bile-to-plasma [14C]inulin ratios corrected for delay in transit time, averaged 0.46 +/- 0.07 at 1 h and rose to 0.74 +/- 0.06 by 4 h, although bile flow remained constant. In experiments in which [14C]inulin reached equilibrium between bile and plasma, the bile-to-plasma ratio conformed to the theoretical relationship between bile flow, solvent drag, and inert solute diffusion predicted at extremely low bile flows, but demonstrated that the skate biliary tree is more permeable to inulin than that of the rat. Electron microscopic studies demonstrated that ionic lanthanum could traverse the tight junctions. However, freeze-fracture studies of junction structure did not differ qualitatively from similar studies in the rat. Partial dependence of bile flow on perfusion pressure, high bile-to-plasma inulin ratios, and permeability of the canalicular tight junctions to ionic lanthanum all suggest that the paracellular pathway may be an important component of bile formation in the skate.

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