PubMed Health⌕ Search

Biomedical subjects

W R Redwood

Publications and source records attributed to W R Redwood.

At least 19 recordsLinked to original sources
PubMed1984

Solute-excluded volumes near the Novikoff cell surface.

A differential centrifugation technique, in which all extracellular water except that intimately associated with the cell (pericellular domain) is removed, has been applied to isolated Novikoff hepatoma cells. The pericellular volumes accessible to albumin, inulin, raffinose, and sucrose were inversely related to the molecular weights of the test solutes. This phenomenon was not detectable in erythrocytes or in fat cells. Selective removal of cell surface components by enzymatic treatment produced proportional changes in the relative volumes of distribution accessible to the solutes. This discrimination in the volume accessible to each of the solutes is analogous to that obtained in gel chromatographic separation and represents, in effect, excluded volumes which are inversely related to solute size. This exclusion is associated with components of the Novikoff cell surface, including the surface coat and the microvilli that cover the Novikoff cell. These structures provide an additional level of discrimination for the Novikoff cell not seen in certain other cell types.

Animals↗
PubMed1984

Specificity, efficacy, and toxicity of radioimmunotherapy in erythroleukemic mice.

Radioimmunotherapy with 131I-labeled monoclonal immunoglobulins was studied using the Rauscher murine erythroleukemia. Tumor-specific monoclonal antibody, nonrelevant monoclonal antibody, F(ab')2 fragments, polyclonal gamma-globulin, and serum albumin were used as carriers of 131I. Therapeutic effects as measured by the reduction in splenomegaly were seen with all the radiolabeled proteins tested, but not with 131I-tyrosine. Dose-response curves showed that about 90% reduction in spleen size occurred at 80 muCi injected per animal, irrespective of whether specific or nonrelevant monoclonal antibody was used. Therapeutic efficacy was affected by the size of the 131I-carrier and could be correlated with half-life of carrier protein in vivo. As expected, increase in the serum concentration of circulating antigen decreased the targeting of the tumor-specific monoclonal antibody and also contributed to a shorter half-life for the tumor-specific monoclonal antibody in leukemic animals compared to uninfected controls. This study showed that there was no therapeutic advantage to the use of tumor-specific monoclonal antibody over nonrelevant immunoglobulin as a carrier for 131I in the treatment of murine erythroleukemia and that, although it was extremely effective, radioimmunotherapy with 131I was not specific in this system.

Animals↗
PubMed1981

Permeability of Novikoff hepatoma cells to water and monohydric alcohols.

The permeability coefficients of Novikoff hepatoma ascites cell membranes for tritiated water (3HHO) and for a homologous series of monohydric alcohols (methanol through hexanol) were deduced from linear diffusion coefficients by means of a series-parallel pathway model (Redwood et al. (1974) J. Gen. Physiol. 64, 706-729). Membrane permeability coefficients for 3HHO at 20, 30 and 37 degrees C were (all x 10(-5)) 97, 125, and 163 cm . s-1, respectively, and were significantly smaller than the corresponding values for the alcohols tested. In the alcohols series, ethanol had the lowest permeability coefficient 198 x 10(-5) cm . s-1 at 20 degrees C. The apparent activation energy for water permeation was 6.7 +/- 1.9 S.E. kcal . mol-1. The apparent membrane diffusion coefficients for the alcohols were a complex function of molecular properties with less diffusional membrane resistance to the alcohols in the middle of the homologous series than would have been expected on the basis of oil-water partitioning or molar volume considerations. The conventional parallel aqueous lipophilic pathway model is not consistent with the present data which can be interpreted by consideration of parallel lipophilic pathways through the Novikoff hepatoma cell membrane.

Alcohols↗
PubMed1981

Osmotic permeability of Novikoff hepatoma cells.

The osmotic permeability coefficient (Pf) for water movement across Novikoff hepatoma cells was found to be 82 +/- 3 (S.E.) x 10(-5) cm . s-1 at 20 degrees C. The corresponding diffusional permeability coefficient for 3HHO (Pd) was 97 +/- 10 (S.E.) . 10(-5) cm . s-1, therefore the ratio Pf/Pd is close to unity. The apparent activation energy for water filtration was 10.4 +/- 0.4 (S.E.) kcal . mol-1. This value is significantly greater than the activation energy for the self diffusion of water. The product of the hydraulic permeability coefficient and the viscosity coefficient for water was temperature-dependent. However, the product of the hydraulic permeability coefficient and the viscosity coefficient for membrane lipid did not vary with temperature. These data are interpreted as evidence for water movement across a lipid membrane barrier rather than through aqueous channels.

Animals↗
PubMed1978

In vitro interaction of L1210 cells with phospholipid vesicles.

The in vitro uptake of phospholipid vesicles by mouse leukemia L1210 cells was examined. Liposomes were generated by prolonged ultrasonic dispersion of aqueous dispersions of mixed lipids in the presence of radiolabeled inulin. Multilamellar vesicles were separated from unilamellar vesicles by column chromatography. Vesicle populations were examined by electron microscopy. Neutral vesicles were generated from egg yolk phosphatidylcholine and cholesterol, and surface charge was introduced via either phosphatidylserine or octadecylamine. Uptake, measured as cell-associated radioactivity, was temperature dependent and was strongly decreased by metabolic inhibitors. These results suggested that liposomes are taken up to a major extent by an energy-dependent mechanism. The uptake of liposomes by cells of a young culture was about 2-fold higher than was the uptake of liposomes by cells of a stationary culture. The uptake of positively charged liposomes by cells was about 20-fold higher than that of either neutral or negatively charged vesicles. About one-half of the cell-associated radioactivity transferred by positively charged liposomes could be removed by cell surface treatment with trypsin or neuraminidase or by a short exposure to 0.6 N NaCl.

Animals↗
PubMed1977

Membrane permeability of isolated lung cells to nonelectrolytes.

Mixtures of viable endothelial and epithelial cells were separated by enzymatic digestion from rabbit lung and recovered by centrifugation. The cells were mixed with an extracellular marker and packed by centrifugation into small-diameter polyethylene tubing and pulsed with tritiated water and 14C-labeled alcohols. Calculation of diffusion coefficients for the packed cell column (D), intracellular material (D2), and extracellular fluid (D1) was based on a local steady-state one-dimensional diffusional model. Permeability coefficients were: tritiated water, 288 X 10(-5) cm s-1; methanol, 385 X 10(-5) cm s-1; ethanol, 214 X 10(-5) cm s-1; propanol, 277 X 10(-5) cm s-1; and hexanol, 1255 X 10(-5) cm s-1. The permeability coefficients of these aliphatic alcohols show a minimum at ethanol with hexanol having the highest value of all substances tested. The results support the concept of parallel aqueous and lipid pathways for small solutes in the plasma membrane. Study of the permeability properties of isolated lung cells can provide information on the cellular pathway in the transcapillary transport of water and solutes in the lung.

Alcohols↗
PubMed1976

Lectin-receptor interactions in liposomes. II. Interaction of wheat germ agglutinin with phosphatidylcholine liposomes containing incorporated monosialoganglioside.

Bovine brain gangliosides incorporated into phospholipid liposomes provide receptors for wheat germ agglutinin. Purified monosialogangliosides were mixed with egg phosphatidylcholine, and unilamellar liposomes were generated. Addition of wheat germ agglutinin induced the liposomes to fuse, and gel filtration analysis revealed that the lectin was incorporated into the fused liposomes. The fusion process was studied by following the changes in the 90 degrees light scattering. Increasing the proportion of the monosialoganglioside in the liposomes was found to increase both the extent of the lectin-induced liposome fusion and the rate of the reaction; below a threshold of approx. 5 mol%, the process was extremely slow. The increase in light scattering could be prevented by the addition of the hapten inhibitor, N-acetyl-D-glucosamine (1 mM). Addition of the inhibitor, subsequent to the lectin, caused a partial decrease in light scattering due to the dissociation of unfused vesicle aggregates. Electron microscopic examination revealed that the ganglioside-containing liposomes were vesicles, 244 +/- 25 A (S.D.) in diameter. Upon addition of wheat germ agglutinin, the vesicles appeared to fuse to form larger vesicles, corresponding to dimers and trimers of the initial vesicles. Inhibition studies with a variety of monosaccharides indicated that the sialic acid moieties present in the ganglioside acted as the lectin-receptor sites. This was confirmed by the observation that wheat germ agglutinin did not interact with phosphatidylcholine vesicles containing desialyated ganglioside.

Binding Sites↗
PubMed1975

Lectin-receptor interactions in liposomes.

The major sialoglycoprotein of mammalian erythrocytes has been incorporated into phosphatidylcholine membranes to generate a model system, glycoprotein-liposomes. Electron microscopic examination revealed these structures to be vesicles, approximately 300 A in diameter. An aqueous compartment inside the glycoprotein-liposomes has been identified by trapped volume studies with [14C]sucrose. These glycoprotein-liposomes were found to interact with the lectins, wheat germ agglutinin, and phytohemagglutinin, to form aggregates of mainly unfused vesicles. The aggregation process has been studied by electron microscopy, 90 degrees light scattering, and differential ultracentrifugation analysis. Hapten inhibitors of the lectins were found to inhibit the lectin-induced aggregation of the glycoprotein-liposomes. Binding of 125I-labeled wheat germ agglutinin to glycoprotein-liposomes was studied by differential ultracentrifugation. Hapten inhibitors of wheat germ agglutinin were also found to inhbit the binding of 125I-labled wheat germ agglutinin to the glycoprotein-liposomes. The characteristics of the lectin interactions with glycoprotein-liposomes appeared to be phenomenologically similar to lectin-cell interactions.

Acetylglucosamine↗
PubMed1974

Red cell membrane permeability deduced from bulk diffusion coefficients.

The permeability coefficients of dog red cell membrane to tritiated water and to a series of[(14)C]amides have been deduced from bulk diffusion measurements through a "tissue" composed of packed red cells. Red cells were packed by centrifugation inside polyethylene tubing. The red cell column was pulsed at one end with radiolabeled solute and diffusion was allowed to proceed for several hours. The distribution of radioactivity along the red cell column was measured by sequential slicing and counting, and the diffusion coefficient was determined by a simple plotting technique, assuming a one-dimensional diffusional model. In order to derive the red cell membrane permeability coefficient from the bulk diffusion coefficient, the red cells were assumed to be packed in a regular manner approximating closely spaced parallelopipeds. The local steady-state diffusional flux was idealized as a one-dimensional intracellular pathway in parallel with a one-dimensional extracellular pathway with solute exchange occurring within the series pathway and between the pathways. The diffusion coefficients in the intracellular and extracellular pathways were estimated from bulk diffusion measurements through concentrated hemoglobin solutions and plasma, respectively; while the volume of the extracellular pathway was determined using radiolabeled sucrose. The membrane permeability coefficients were in satisfactory agreement with the data of Sha'afi, R. I., C. M. Gary-Bobo, and A. K. Solomon (1971. J. Gen. Physiol. 58:238) obtained by a rapid-reaction technique. The method is simple and particularly well suited for rapidly permeating solutes.

Amides↗