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Biomedical subjects

D S Lyles

Publications and source records attributed to D S Lyles.

65 records · Page 4Linked to original sources
PubMed1980

Minimal molecular requirements for reactivity of tumor cells with T cells.

We have investigated the minimal molecular requirements for T cell recognition of a previously described myeloma tumor (MOPC-315-EL), which reversibly alters its reactivity with T cells. Enucleation of MOPC-315 cells, either sensitive or resistant to reaction with T cells, did not alter the ability of the resulting cytoplasts to elicit or serve as targets for anti-H-2 or anti-Sendai viral cytotoxic T lymphocytes (CTL), despite the fact that there were no detectable differences in serologically defined H-2 or viral antigens on their surface. Likewise, when plasma membranes isolated from sensitive or resistant cells were tested for their ability to elicit anti-H-2 CTL, they retained the phenotype of the cells from which they were isolated. However, solubilized and partially purified H-2 antigens from both sensitive and resistant cells were able to elicit H-2-restricted anti-Sendai virus CTL when incorporated into liposomes with purified viral glycoproteins, and anti-H-2 CTL when incorporated alone into liposomes. These results suggest that a cellular surface component(s) exists that is probably not an H-2K or H-2D gene product and is responsible for the reversible variation in the reactivity of the tumor cells with T cells.

Animals↗
PubMed1979

Glycoproteins of Sendai virus are transmembrane proteins.

Radiolabeled Sendai viral envelope proteins were incorporated into human erythrocyte membranes by the process of fusion of the viral envelope with the erythrocyte membrane. Inside-out (IO) vesicles were prepared from the erythrocyte membranes containing viral proteins, and the presence of viral proteins was assessed by electrophoresis in sodium dodecyl sulfate/polyacrylamide gels. Proteolysis with trypsin, chymotrypsin, or Pronase, which digests only the external surface of the IO vesicles (the cytoplasmic surface of the erythrocyte membrane) revealed that the viral nucleocapsid and the nonglycosylated inner-envelope (M) proteins were present on the external surface. In addition, small segments of the viral envelope glycoproteins (HN and F1) were removed by these proteases, while the major portions of the glycoproteins were protected from digestion, indicating that in the erythrocyte membrane they are transmembrane proteins. Results of experiments carried out on right side-out membranes, unsealed membranes, and membranes containing attached virus that was unable to fuse indicated that the results obtained with IO membranes could not be accounted for by contamination with these membrane species. The identify of the proteolysis products was confirmed by peptide mapping. The selective exposure of the cytoplasmic surface, and hence the internal components of the virus, in IO vesicles makes this membrane system an attractive model for studying the interactions involved in virus maturation at host cell membranes.

Cell Fusion↗
PubMed1977

Odd-and even-numbered fatty acids. Their contrasting behavior in normal and fowlpox virus-infected epithelium.

Upon infection with fowlpox virus, the amount of odd-numbered fatty acids in chick scalp epithelium shows a significant decrease compared with control values. This effect begins quite early and progresses throughout the period of infection. Individual members of the odd-numbered family (C15--C27 inclusive) were quantitatively related to the group as a whole during most of the infection. Experiments involving the administration of labeled acetate in vivo demonstrated an increase in the synthesis of even-numbered fatty acids and a decrease in the synthesis of odd-numbered fatty acids in infected epithelium. The reduced synthesis of odd-numbered fatty acids in infected epithelium could also be demonstrated with labeled propionate. The influence of the alpha-oxidation pathway was assayed in chick scalp epithelium in vivo by the administration of [1-14C,9,10-3H] stearic acid. The C17 acids formed had a 3H/14C ratio similar to that of the C16 acids, indicating that most label incorporation into C17 was due to beta-oxidation to acetate followed by resynthesis into fatty acids. C17 fatty acids from control and infected epithelium had similar 3H/14C ratios, indicating that the alpha-oxidation pathway probably does not contribute to the differences in odd-numbered fatty acid content observed. In assays for fatty acid synthetase activty, both [14C] acetyl-CoA and [14C]-propionyl-CoA were used as initial acceptors. The specific activities of preparations from infected scalp were similar to those of control preparations with both substrates. These results suggest that there is no decline in the ability to utilize propionate for fatty acid synthesis in infected epithelium.

Acetates↗
PubMed1977

Sendai virus-induced hemolysis: reduction in heterogeneity of erythrocyte lipid bilayer fluidity.

Hemolysis of human or chicken erythrocytes by Sendai virus causes a change in the structure of the erythrocyte membrane lipid bilayer that can be detected by spin label electron spin resonance. In the intact erythrocyte, the phosphatidylcholine derivative spin label exists in a more rigid environment than the corresponding phosphatidylethanolamine label. Virus-induced hemolysis tends to abolish this difference in fluidity, i.e., the region of the phosphatidylcholine spin label becomes more fluid and that of the phosphatidylethanolamine spin label becomes more rigid. Fatty acid derivative spin labels, which may detect some "average" environment, show no change in fluidity. The fluidity change is detected at several different positions in the fatty acyl chain of the phosphatidylcholine spin label. Sendai virions grown in Madin-Darby bovine kidney (MDBK) cells or grown in eggs and harvested early, which lack hemolytic activity, cause no significant change in bilayer structure. Hemolytic activity and the ability to alter erythrocyte bilayer fluidity can be activated in MDBK-grown Sendai virions by trypsin treatment in vitro and in early-harvest egg-grown Sendai virions by freezing and thawing. Erythrocyte ghosts prepared by osmotic hemolysis and resealed by treatment with Mg2+ or elevated ionic strength exhibit a difference in fluidity between phosphatidylcholine and phosphatidylethanolamine spin labels, although less than that observed in whole cells. Incubation of resealed ghosts with Sendai virus abolishes the difference in fluidity. Unsealed ghosts that have been extensively washed show no heterogeneity in membrane bilayer fluidity, and incubation with Sendai virus causes no further fluidity change. Virus-induced hemolysis as measured by hemoglobin release is more sensitive to inhibition by Ca2+ than is the associated fluidity change in the bilayer.

Animals↗
PubMed1976

V irus and lectin agglutination of erythrocytes: spin label study of membrane lipid-protein interactions.

Techniques of spin-label electron spin resonance have been used to prove changes in the structure of the lipid phase of erythrocyte membrane after agglutination by viruses and lectins. When chicken erythrocytes are agglutinated by Sendai and influenza viruses and by the lectins concanavalin A and wheat germ agglutinin, the membrane lipid phase becomes more fluid, as detected by three different lipophilic spin-laveled probes. Colchicine, vinblastine, and tetracaine inhibit the fluidization of chicken erythrocyte membrane by Sendai virus, whereas cytochalasin B has no effect. The effect of colchicine was time dependent, the initial inhibition decreasing with longer preincubation times. Extensive treatment of erythrocytes with proteases or neuraminidase, while not altering the bilayer structure, abolishes the effect of Sendai virus on the erythrocyte membrane, suggesting that a change in the interaction of the receptor protein with the lipid phase occurs upon virus attachment. Glutaraldehyde fixation increased the structural rigidity of the chicken erythrocyte membrane and inhibited the effect of viral agglutination. No change in bilayer structure was observed upon agglutination of human erythrocytes or the isolated plasma membranes of either human or chicken erythrocytes. This result is consistent with the drug sensitivity of the effects of agglutination upon chicken erythrocytes, since human erythrocytes and isolated membranes lack microtubule-like structures.

Animals↗
PubMed1975

The effect of essential fatty acid deficiency upon fatty acid uptake by the brain.

Young adult rats, either control or essential fatty acid deficient, were administered either [3-H] oleic acid or [3-H] arachidonic acid by stomach tube. In addition, a group of control rats was given [3-H] palmitic acid. The rats were killed at various times therafter, and the radioactivity of the lipids of brain and plasma was examined. In confirmation of previous work, the blood lipid label was found to rise rapidly and then fall, wheras the activity of brain lipids increased slowly and did not show a decline through the 24-h period studied. Analysis of the brain uptake data according to first-order kinetics confirmed the impressions gained from visual inspection of the data. The initial rate of uptake of arachidonic acid was about 4.5 times that of oleic acid in control animals and in deficient animals. Essential fatty acid deficiency, however, did not induce an altered rate of uptake for either oleic acid or arachidonic acid. The rate of uptake of palmitic acid by control rats was not significantly different from that of oleic acid. Even though the initial rates of incorporation of oleic and arachidonic acids were not changed during essential fatty acid deficiency, the final levels of radioactivity obtained in brain lipids were higher in deficient rats with both fatty acids. The plateau value obtained with oleic acid was 1.5 times higher in deficient animals, while the plateau value for arachidonic acid was 1.7 times higher. An experiment in which deficient animals were allowed access to a control diet for 12 or 24 h prior to the labeling experiment suggested that the higher levels of radioactivity found in brain lipids of deficient animals was not due to an isotope dilution effect. Such animals still displayed the labeling pattern of deficient animals with arachidonic acid, while the results with oleic acid varied somewhat. Our results suggest that essential fatty acid deficiency does not alter the ability of the brain to take up the fatty acids studied. However, the fatty acids, especially arachidonic, are retained in the brain to a greater extent in the deficient animals.

Animals↗