STUDIES ON THE ORGANIZATION OF THE BRUSH BORDER IN INTESTINAL EPITHELIAL CELLS

Two of the fractions obtained by density gradient centrifugation of Tris-disrupted brush borders from hamster intestinal mucosa have been identified as the microvillus cores and their surrounding membranous coats, respectively. This identification has the following morphological basis. In shadowed preparations one fraction (cores) appears as rounded, compact rods, and the other fraction (coats) appears as flattened sheets. Both rods and sheets have dimensions appropriate to the identities assigned to them. In addition, negative staining shows that the rods are composed of aligned particles of roughly 60 A, consistent with the appearance of the core in tissue section, where 60-A fibrils are characteristic. The sheets are covered by non-aligned particles of approximately the same size. Sectioned preparations show that the core fraction contains predominantly fibrous material with some membranous contamination and that the coat fraction is apparently composed exclusively of elongated sacs with a unit membrane structure. Some details of the structure of the core are evident in cases where the compact rod appears to be loosened, revealing a doubled strand. The strand is approximately 350 A wide; the compact rod is roughly twice this width. With negative staining the strand shows a dense central region. The morphological identification presented here is consistent with the distribution of enzymic activity among the density gradient fractions described in the preceding paper.

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Uranyl Acetate and Rotary Shadowing to Increase the Contrast of Small Aggregated Virus Particles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100064037 ◽

1969 ◽

Vol 27 ◽

pp. 424-425

Author(s):

Lee F. Ellis ◽

Richard M. Van Frank ◽

Walter J. Kleinschmidt

Keyword(s):

Electron Microscopy ◽

Tissue Culture ◽

Density Gradient ◽

Density Gradient Centrifugation ◽

Gradient Centrifugation ◽

Uranyl Acetate ◽

Interferon Inducer ◽

Virus Particles ◽

Staining Methods ◽

Rotary Shadowing

The extract from Penicillum stoliniferum, known as statolon, has been purified by density gradient centrifugation. These centrifuge fractions contained virus particles that are an interferon inducer in mice or in tissue culture. Highly purified preparations of these particles are difficult to enumerate by electron microscopy because of aggregation. Therefore a study of staining methods was undertaken.

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The Combining Ability of Glycoproteins IIb, IIIa and Ca2+ in EDTA-Treated Nonaggregable Platelets

Thrombosis and Haemostasis ◽

10.1055/s-0038-1665326 ◽

1983 ◽

Vol 50 (04) ◽

pp. 848-851 ◽

Cited By ~ 11

Author(s):

Marjorie B Zucker ◽

David Varon ◽

Nicholas C Masiello ◽

Simon Karpatkin

Keyword(s):

Density Gradient ◽

Combining Ability ◽

Density Gradient Centrifugation ◽

Gradient Centrifugation ◽

Electrophoretic Pattern ◽

Sucrose Density Gradient ◽

Irreversible Loss ◽

Sucrose Density Gradient Centrifugation ◽

Crossed Immunoelectrophoresis ◽

Triton X

SummaryPlatelets deprived of calcium and incubated at 37° C for 10 min lose their ability to bind fibrinogen or aggregate with ADP when adequate concentrations of calcium are restored. Since the calcium complex of glycoproteins (GP) IIb and IIIa is the presumed receptor for fibrinogen, it seemed appropriate to examine the behavior of these glycoproteins in incubated non-aggregable platelets. No differences were noted in the electrophoretic pattern of nonaggregable EDTA-treated and aggregable control CaEDTA-treated platelets when SDS gels of Triton X- 114 fractions were stained with silver. GP IIb and IIIa were extracted from either nonaggregable EDTA-treated platelets or aggregable control platelets with calcium-Tris-Triton buffer and subjected to sucrose density gradient centrifugation or crossed immunoelectrophoresis. With both types of platelets, these glycoproteins formed a complex in the presence of calcium. If the glycoproteins were extracted with EDTA-Tris-Triton buffer, or if Triton-solubilized platelet membranes were incubated with EGTA at 37° C for 30 min, GP IIb and IIIa were unable to form a complex in the presence of calcium. We conclude that inability of extracted GP IIb and IIIa to combine in the presence of calcium is not responsible for the irreversible loss of aggregability that occurs when whole platelets are incubated with EDTA at 37° C.

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