Ganglioside patterns and phenotypic characteristics in a normal variant and a transformed back variant of a simian virus 40-induced hamster tumor cell line

Cilia containing 9 + 2 structures grown from immortalized cells

Cilia depend on their highly differentiated structure, a 9 + 2 arrangement, to remove particles from the lung and to transport reproductive cells. Immortalized cells could potentially be of great use in cilia research. Immortalization of cells with cilia structure containing the 9 + 2 arrangement might be able to generate cell lines with such cilia structure. However, whether immortalized cells can retain such a highly differentiated structure remains unclear. Here we demonstrate that (1) using E1a gene transfection, tracheal cells are immortalized; (2) interestingly, in a gel culture the immortalized cells form spherical aggregations within which a lumen is developed; and (3) surprisingly, inside the aggregation, cilia containing a 9 + 2 arrangement grow from the cell's apical pole and protrude into the lumen. These results may influence future research in many areas such as understanding the mechanisms of cilia differentiation, cilia generation in other existing cell lines, cilia disorders, generation of other highly differentiated structures besides cilia using the gel culture, immortalization of other ciliated cells with the E1a gene, development of cilia motile function, and establishment of a research model to provide uniform ciliated cells.

Reverse transformation of multidrug-resistant cells

Spontaneously transformed Chinese hamster lung cells with high levels of resistance (approximately 100-fold to 70,000-fold) to actinomycin D, daunorubicin, or vincristine exhibit morphology and growth patterns characteristic of normal cells in vitro and reduced tumorigenicity in vivo. These reverse transformed, multidrug-resistant cells amplify and highly overexpress one or more genes encoding P-glycoprotein. Similarly, hydrocarbon-induced mouse sarcoma cells selected with actinomycin D, vincristine, or ethidium bromide developed high levels of resistance associated with reduced drug accumulation and suppression of malignancy. To determine whether human tumor cells would undergo similar changes and whether reverse transformation reflected an altered state of differentiation, nine multidrug-resistant sublines were selected with four agents from human neuroblastoma cells with well defined pathways of differentiation. Those five with resistance levels above about 125-fold showed a reduced tumor frequency as compared to control cells. All resistant sublines showed altered differentiation. The changes in transformation phenotype appear to be intrinsic and not the result of altered immunogenicity. Two additional consequences of high level multidrug resistance have been observed: change in ganglioside composition in the Chinese hamster cells, manifested as a block in higher ganglioside biosynthesis and/or a relative increase in GM3, and increase in epidermal growth factor receptor in all three cell systems. A tentative hypothesis links ganglioside and growth factor receptor changes to the change in transformation phenotype. The basis of the reverse transformation phenomenon is not known, but the major alterations in expression of P-glycoprotein, gangliosides, and the epidermal growth factor receptor implicate, in some way, the plasma membrane.

Physical studies of cell surface and cell membrane structure. Deuterium nuclear magnetic resonance studies of N-palmitoylglucosylceramide (cerebroside) head group structure

Deuterium Fourier-transform nuclear magnetic resonance spectra of N-palmitoyl[2,3,4,6,6-2H5]glucosylceramide, N-palmitoyl[1-2H]glucosylceramide, N-palmitoyl-[5,6,6-2H3]glucosylceramide, and N-palmitoyl[6,6-2H2]-glucosylceramide have been obtained at 55.3 MHz (corresponding to a magnetic field strength of 8.5 T) for lipids as multilamellar dispersions in excess water at 90 degrees C, above the gel to liquid-crystal phase transition temperature (Tc = 82 degrees C). Spectra were also obtained for these same lipids dispersed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, and cholesterol, all in excess water at 90 degrees C. The results are analyzed in terms of a model in which the lipid undergoes fast axial diffusion, together with a "wobbling" of the polar head group, by mathematical methods similar to those used previously for the choline and ethanolamine head groups in phosphatidylcholines and phosphatidylethanolamines [Skarjune, R., & Oldfield, E. (1979) Biochemistry 18, 5903--5909]. However, contrary to the results obtained in the previous study, which indicated many possible conformations for the choline and ethanolamine head groups, results with labeled cerebrosides yield at most a few orientations for the glucose head group in each of the systems studied. Furthermore, where multiple solutions do occur, they fall within a narrow orientational subspace so that all solutions exhibit the same general features. We also show that the order parameter describing the head group wobble is fully determined for each system, and it indicates a rather mobile structure for the cerebroside head group, in a variety of environments. In each system studied the polar head group projects essentially straight up from the bilayer surface into the aqueous region, thereby permitting maximum hydration of the four glucose hydroxyl groups by bulk water molecules.

Physical studies of cell surface and cell membrane structure. Deuterium nuclear magnetic resonance investigation of deuterium-labelled N-hexadeconoylgalactosylceramides (cerebrosides)

1. Deuterium Fourier transform nuclear magnetic resonance spectra of a series of N-palmitoylgalactosylceramides (cerebrosides) specifically labelled with deuterium at one of positions 2', 6', 10' and 16' of the acyl chain, or in the C-6 hydroxymethyl group of the galactose residue, have been obtained using a spin-echo technique at 34.1 MHz with a homebuilt superconducting magnet spectrometer. 2. The effects of temperature and cholesterol on the deuterium spectra have been investigated. The results indicate, when compared at the same reduced temperature, that the hydrocarbon chain organization in the liquid crystalline phase of palmitoylgalactosylceramide is essentially identical to that seen in similar chain length glycerophospholipids. In particular, two sets of quadrupole splittings are seen for a 2'-labelled N-palmitoylgalactosylceramide, indicating non-equivalent deuterons as noted previously for phospholipids. 3. Two sets of quadrupole splittings are observed for the headgroup C-6-labelled N-palmitoylgalactosylceramide. It is proposed that these signals arise from the enantiomeric R and S lipids, and that motion of the hydroxymethyl group is slow (greater than 10(-5) S). These results suggest the presence of a hydrogen bond network in the polar headgroup region. 4. The effects of cholesterol on the deuterium spectra of N-palmitoylgalactosylceramide-labelled as C2H3 in the terminal methyl group, at 1:1 mol ratios and in excess water below the crystal to liquid-crystal phase transition temperature (Tc) of the pure lipid (82 degrees C), are different to the effects seen with the phosphatidylcholine-cholesterol system. The spectra below Tc are characterised by two overlapping powder patterns, one with a quadrupole splitting of approx. 6 kHz (fluid liquid-crystalline phase) and one with a quadrupole splitting of about 20--25 kHz (crystal or gel-state lipid). Exchange between these two environments is therefore slow, leading to the possibility of characterising the cerebroside-cholesterol phase diagram using deuterium nuclear magnetic resonance spectroscopy.

Biosynthesis and function of gangliosides

Gangliosides are unique acidic glycolipids that are selectively concentrated in the plasma membrane of cells. Surface labeling studies have demonstrated that at least a portion of the oligosaccharde chain of gangliosides extends beyond the hydrophe) is imbedded in the membrane bilayer. It is becoming increasingly apparent that gangliosides participate in the internalization of environmental signals elicited by cholera toxin and glycoprotein hormones such as thyrotropic hormone and chorionic gonadotropin as well as other substances such as interferon and possibly serotonin. The mechanism by which cholera toxin binds to a specific ganglioside receptor on the celraction of trophic agents with gangliosides. We would predict that analyogous phenomena involving gangliosides will be discovered in brain. The biosynthesis of gangliosides proceeds by the ordered sequential addition of sugars to the lipid moiety. These reactions are catalyzed by a cluster of membrane-bound glycosyltransferases. Any alteration in the activity or specificity of one of these enzymes will result in a dramatic change in the ganglioside pattern of an afflicted cell or organ. The drastic consequences that accompany abnormalities of ganglioside synthesis have been documented in a heritable metabolic disorder in vivo and in tumorigenic transformation of cells in vitro. In this article, we have attempted to unify these observations and to provide a reasonable interpretation of the role of gangliosides in mediating cell surface phenomena.

Some biochemical properties of Chinese hamster cells sensitive and resistant to actinomycin D

A graded series of drug-resistant Chinese hamster sublines has been examined for biochemical changes accompanying resistance to actinomycin D. The most highly resistant subline, DC-3F/AD X, is maintained at 10 microg/ml of the antibiotic. It was shown that over 250 times more actinomycin D is required to inhibit RNA synthesis in this subline than in the parental DC-3F line. The DC-3F/AD X subline was also shown to have a somewhat reduced capacity to transport uridine as compared to parental cells. Sensitive cells took up over 50 times more tritiated antibiotic than the most resistant cells, as determined in a 1-h assay. Uptake of actinomycin D was shown to be temperature-dependent in both resistant and sensitive cells and was not influenced by various metabolic inhibitors. Resistance could not be explained by a rapid uptake and release of the antibiotic, as demonstrated in efflux experiments, or by its metabolism. In addition, highly resistant cells which are cross-resistant to puromycin were shown to have a reduced capacity to take up labeled puromycin. These studies provide further evidence indicating that the mechanism of resistance to actinomycin D is reduced permeability to drug and suggesting that cell membrane alteration accounts for resistance to both actinomycin D and puromycin.