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Biomedical subjects

E Mayhew

Publications and source records attributed to E Mayhew.

At least 91 records · Page 5Linked to original sources
PubMed1981

Electrokinetic determinations of enzymatic susceptibilities of cell surface-associated RNA.

Earlier investigations suggested, using electrokinetic evidence, that RNA is present at the surfaces of some types of cultured and freshly isolated cells. In this report, further investigations of the nature of cell surface RNA of cultured Ehrlich ascites (EAT) cells are reported. These experiments were carried out by determining the changes in electrophoretic mobility of EAT cells after treatment with several highly purified nucleases, neuraminidase, and hyaluronidase. The results suggested that cell surface RNA is located at surface sites separate from those susceptible to neuraminidase and hyaluronidase, that alpha and omega termini of RNA are absent from the electrokinetic surface, and that the RNA present at the cell surface might exist predominantly in a double-stranded form. A model is proposed in which cell surface RNA strand termini are buried out of the electrokinetic surface, but where RNA extends from these buried termini into the electrokinetic surface in loops.

Animals↗
PubMed1981

Erythrosomes: large proteoliposomes derived from crosslinked human erythrocyte cytoskeletons and exogenous lipid.

Large (3-micrometers diameter) mechanically stable proteoliposomes (erythrosomes) were prepared in good yield by coating crosslinked erythrocyte cytoskeletons with phosphatidylcholine. The erythrosomes consist of the polypeptides designated band 1, 2, 3, 4.1 + 4.2, and 5 (less than 4% of the endogenous lipid) and enough added lipid to form a bilayer coating the surface. Electron microscopy shows only the large proteoliposomes in sealed preparations. The trapping of bovine serum albumin, mannitol, sucrose, glucose, cytosine arabinoside, and sodium in the erythrosomes was demonstrated, yielding an apparent volume of up to 100 liters/mol of phospholipid. This preparation possesses an effective diffusion barrier to glucose, sucrose, and sodium ion with half-equilibration times of 34, 29, and 170 hr, respectively. The results of the present study suggest that erythrosomes may be useful for membrane transport protein reconstitution and encapsulation systems.

Cross-Linking Reagents↗
PubMed1981

Cells from normal and malignant human colon mucosa differentially inhibit embryonic cell aggregation.

A model system for studying some aspects of the interaction of cancer cells in tumors and their surrounding nonmalignant tissue is the co-culture of cancer cells and embryonic chick neural retinal cells in gyratory shakers. Neural retina cell aggregation, under these conditions, has been shown to be differentially inhibited by small numbers of cultured mouse and human cancer cells. We extend here these observations to co-cultures of retinal cells with small numbers (60:1 ratio) of human cells isolated from normal colon mucosa or colonic adenocarcinoma tissue. The cells from the malignant tissue samples inhibited aggregation to a significantly greater extent than the cells from normal mucosa, even when both were from the same individual. Cells derived from nonmalignant tumors were more inhibitory than those from normal individuals, which is consistent with described differences in this 'transitional' region. Thus, the aggregation inhibition assay appears applicable to freshly isolated human tissues.

Adenocarcinoma↗
PubMed1980

Preparation of unilamellar liposomes of intermediate size (0.1-0.2 mumol) by a combination of reverse phase evaporation and extrusion through polycarbonate membranes.

Liposomes can be prepared by a combination of reverse phase evaporation and sequential extrusion through polycarbonate membranes. The vesicles have diameters in the range 0.05-0.5 micron and are mostly unilamellar as indicated by electon microscopy, capture volume, and availability of reactive groups to periodate oxidation. Sequential extrusion leads to a decrease in the encapsulation efficiency by 2-4-fold, depending upon the lipid composition. The inclusion of cholesterol at a 1 : 1 molar ratio of cholesterol-to-phospholipid increases both the mean size and the size heterogeneity of the liposomes as measured by negative-stain electron microscopy. The mean size of vesicles with an equal molar ratio of cholesterol-to-phospholipid after extrusion through a 0.1 micron membrane is 0.140 micron. Vesicles composed of phosphatidylglycerol/phosphatidylcholine (1 : 4) have a mean size of 0.08 micron after extrusion through a 0.1 micron membrane. The intermediate-size (0.1-0.2 micron) vesicles formed by this process have an aqueous space-to-lipid ratio of 3 : 5 and capture between 12 and 25% of the aqueous phase. The procedure is relatively simple, rapid, and yields almost quantitative recovery of vesicles that encapsulate a large percentage of the total aqueous space.

Carbonates↗
PubMed1980

Effect of actinomycin D-containing lipid vesicles on murine renal adenocarcinoma.

Forty Balb C/CR mice inoculated with renal cell adenocarcinoma were divided into five groups. Group A (seven animals) received phosphate buffered saline intraperitoneally; group B (seven animals) received free actinomycin D 300 microgram/kg IP; group C (nine animals) received lipid vesicles containing actinomycin D 300 microgram/kg IP; group D (eight animals) received a mixture of free actinomycin D 300 microgram/kg and empty lipid vesicles IP. The median survival of group A was 32 days, of group B 30 days, of group C 45.2 days, of group D 54 days, and of group E 42 days. It is suggested that giving the mixture of the drug and the lipid vesicles produces a balance similar to that found in a vesicle solution containing the actinomycin D. It is also suggested that liposomes slow the absorption of actinomycin D from the peritoneum.

Adenocarcinoma↗
PubMed1976

Cell growth and quabain-sensitive 86Rg+ uptake and (Na++K+)-ATPase activity in 3T3 and SV40 transformed 3T3 fibroblasts.

The uptake of ouabain-sensitive 86Rb+ uptake measured at 5 min and the uptake measured at 60 min was 4.5- and 2.7-fold greater respectively for SV40 transformed 3T3 cells compared to 3T3 cells during the late log phase of growth. This uptake, however, varied markedly with cell growth. Ouabain-sensitive 86Rb+ uptake was found to be a sensitive indicator of protein synthesis as measured by total protein content. Cessation of cell growth as measured by total protein content was associated with a decline in ouabain-sensitive 86Rb+ uptake in both cell types. This increase ouabain-sensitive cation transport was reflected in increased levels of (Na++K)-ATPase activity for SV40 3T3 cells, which showed a 2.5-fold increase V but the same Km as 3T3 cells. These results are compared with the results of related work. Possible mechanisms for these effects are discussed and how changes in cation transport might be related to alterations in cell growth.

Adenosine Triphosphatases↗
PubMed1976

Differential inhibition of embryonic cell aggregation by cultured human cells with "malignant" of "normal" characteristics.

The effect that cultured human cells have on chick embryonic neural retina cell aggregation was examined. Different types of human cultured cells inhibited aggregation of chick neural retinal cells to differetn degrees when mixed at a human cell:retina cell ration of 1:60. It appeared from the eleven cell lines studied that cells with "malignant" characteristics inhibited retinal cell aggregation to a greater extent than those with more "normal" characteristics. The assay could be used as a further test for abnormality of cell types and also as a method for studying the interactions of malignant cells with cultured cells.

Cell Aggregation↗
PubMed1976

Inhibition of tumor cell growth in vitro and in vivo by 1-beta-D-arabinofuranosylcytosine entrapped within phospholipid vesicles.

Phospholipid vesicles have been used as a carrier vehicle to enhance the cytotoxic activity of 1-beta-D-arabinofuranosyl-cytosine (ara-C) and 1-beta-D-arabinofuranosylcytosine 5'-triphosphate against several tumor cell lines. The activity of both compounds in free solution or entrapped within phospholipid vesicles was compared against L1210 cells, Ehrlich ascites cells, and SV40-transformed 3T3 cells in vitro. In addition, the activity of vesicle-entrapped ara-C against L1210 cells was also studied in vivo. The results obtained in vitro with ara-C indicated no difference in the concentration needed to inhibit growth of cells by 50% between free ara-C and vesicle-entrapped ara-C. In contrast, 1-beta-D-arabinofuranosylcytosine 5'-triphosphate entrapped in phospholipid vesicles was a more potent inhibitor of L1210 in culture (ID50, 2 X 10(-8) M) compared to the relatively inactive free 1-beta-D-arabinofuranosylcytosine 5'-triphosphate (id50 greater than 10(-7) M). Experiments carried out with L1210 cells in mice showed that, after a single i.p. dose (10 mg/kg) of vesicle-entrapped ara-C, the average survival times of mice inoculated with 10(5) L1210 cells were increased by over 90%. In control experiments, free ara-C or vesicles plus free ara-C (10 mg/kg) did not prolong survival of mice.

Animals↗
PubMed1975

Increased ouabain-sensitive 86Rb+ uptake and sodium and potassium ion-activated adenosine triphosphatase activity in transformed cell lines.

During the log phase of growth both the active, ouabain-sensitive K+ uptake, measured as 86Rb+, and the sodium and potassium ion-activated ATPase ((Na+ + K+)-ATPase) activity of SV40-transformed 3T3 cells were 2.5-and 5,5-fold higher, respectively, than in untransformed 3T3 cells. A similar higher active K+ uptake was found for Rous sarcoma virus and SV40-transformed baby hamster kidney cells compared with untransformed BHK cells. The active K+ uptake in SV403T3 and normal 3T3 cells decreased when the growth rate of both cell types diminished. Reduction in ouabain-sensitive ATP hydrolysis only occurred later, however, when appreciable decreases in cell viability were seen. Arrhenius plots of the (Na+ + K+)-ATPase activity of SV403T3 cells indicated a discontinuity at 24 degrees, whereas no similar discontinuity was indicated for 3T3 cells. The consequences of elevated K+ transport and (Na+ + K+)-ATPase activity in transformed cells and the possibility that the increased activity might be related to differences inphospholipid fatty acyl chain fluidity are discussed.

Adenosine Triphosphatases↗