Plasma and Cytoplasmic Membrane Fragments From Ehrlich Ascites Carcinoma

Wallach, Donald F. Hoelzl; Kamat, V.B.

doi:10.1073/pnas.52.3.721

Cited by 86 publications

(22 citation statements)

References 5 publications

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“…We have previously reported on this topic (4,14) and have shown that these particles have restricted permeabilities even to small, uncharged molecules. Studies on the turbidities of liver microsomes in media of differing osmotic activities but constant refractive index lead to a similar conclusion (42).…”

Section: Discussionmentioning

confidence: 99%

“…The gradients ~-ere centrifuged at 39,000 RPM for 16 hr at 4°C (Spinco L-2 preparative uhracentrifuge, SW 39 rotor). The tubes were then cut into ten fractions and the proteins and densities of each fraction determined as before (4). Unimodal density distributions were obtained.…”

Section: Preparation Of Membrane Componentsmentioning

confidence: 99%

“…The membrane components of Ehrlich ascites carcinoma (EAC) microsomes are fluid-filled vesicles arising primarily from the disrupted endoplasmic reticulum and the fragmented plasma membrane of these cells (1)(2)(3)(4)(5). They can be fractionated by ultracentrifugal methods into four distinct membrane classes (3,5,6): namely, (1) "rough" endoplasmic reticulum; (2) vesicles--here designated ER--arising primarily from the "smooth" endoplasmic reticulum; (3) vesicles--here designated PM--originating primarily from the plasma membrane of the intact cell; and (4) particles, of unknown origin, physiochemically related to--but immunologically distinct from --PM and separated from the latter by virtue of their lower density.…”

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confidence: 99%

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Physicochemical Differences Between Fragments of Plasma Membrane and Endoplasmic Reticulum

Wallach

Kamat

Gail

1966

The Journal of Cell Biology

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Specific turbidities, densities, and refractive indices of fragments of plasma membrane (PM) and endoplasmic reticulum (ER) from Ehrlich ascites carcinoma have been measured. A spherical shell model of specified dimensions and refractive index was established for PM fragments. The ionic composition of the dispersion medium was varied systematically. Increases in I'/2 caused increases in the turbidity of both PM and ER suspensions, the greatest effects being observed with Ca ~-and Mg 2+. In the case of PM this effect is attributable mainly to aggregation, whereas "structural" changes account for most of the turbidity increase with ER. The pH was also varied systematically to obtain pH-density and turbidity profiles and to establish the isoelectric pH of the two membrane types (PM--3.6; ER---4.35). Turbidity was maximum at "isoelectric" pH, which corresponds in each case to the region of minimum charge on the particle surfaces. Both PM and ER show large increases of density at the "isoelectric" pH, but only ER shows substantial structurally based turbidity increase under these conditions. Both PM and ER show operation of electrostatic attractions near "isoelectric" pH. PM has been shown to have ionically distinctive inner and outer surfaces while ER shows no such dissymmetry. The necessary theoretical background for interpretation of turbidity and density measurements is included, as well as a discussion of the limitations of our conclusions and the biological importance of our results.

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Section: Discussionmentioning

confidence: 99%

Section: Preparation Of Membrane Componentsmentioning

confidence: 99%

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confidence: 99%

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Physicochemical Differences Between Fragments of Plasma Membrane and Endoplasmic Reticulum

Wallach

Kamat

Gail

1966

The Journal of Cell Biology

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“…reference 11). If the microsomal membrane is not permeable to the solute used for building up the gradient, the osmotic response of the vesicles will affect the sedimentation behavior of the particles during centrifugation (12,13).…”

Section: Introductionmentioning

confidence: 99%

Permeability of Microsomal Membranes Isolated From Rat Liver

Nilsson

Peterson

Dallner

1973

The Journal of Cell Biology

117

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Water compartments, permeability, and the possible active translocation of various substances in rat liver microsomes were studied by using radioactive compounds and ultracentrifugation. The total water of the microsomal pellet, 3.4 #l/rag dry weight, is the sum of water in the extramicrosomal and intramicrosomal spaces, or 56 and 44%, respectively. Sucrose space accounts for 77% of the intramicrosomal water and the hydration water ~ 14 %, leaving almost no sucrose-impermeable space when using the ultracentrifugation approach. With increasing sucrose concentration, microsomes do not show an osmotic response. The intramicrosomal water decreases greatly-in the presence of Cs + and Mg ++ in rough but not in smooth microsomes. Uncharged substances of molecular weight of up to at least 600 freely penetrate microsomal membranes, which already become impermeable to charged substances at a molecular weight of 90. These substances also induce an osmotic response. The vesicles can be made permeable to charged substances after water treatment and cooling, which, however, does not increase glucose-6-phosphatase and inosine diphosphatase (IDPase) activities, and these enzymes can still be activated by deoxycholate. IDPase, reduced nicotinamide adenine dinucleotide-cytochrome c reductase, and reduced nicotinamide adenine dinucleotide phosphate-dependent hydroxylation reactions, performed in vitro, also disproved the hypothesis of an accumulation of charged substances inside of vesicles of being a major pathway. The products of the enzymic reactions as well as the glucuronidated form of a hydroxylated product can be recovered on the cytoplasmic side of membranes, and little accumulation occurs in the intravesicular compartment.

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“…5-7, for reviews). For endoplasmic reticulum membranes such determinations were made possible after it became apparent that microsomes, largely derived from these membranes, maintained proper sidedness [8,9], i.e. with the cytoplasmic surface of the endopl~mic reticulum forming the outside surface of the microsomal vesicles.…”

Section: Introductionmentioning

confidence: 99%