The change in membrane fluidity of neuroblastoma X glioma hybrid cells upon cell differentiation

Reduced lateral mobility of a fluorescent lipid analog in cell membranes of rat fibroblasts transformed by simian virus 40

In order to study the difference between normal and transformed cells, lateral motion of fluorescent molecules embedded into cell membranes of rat clonal fibroblasts and its SV40-transformed derivative cells was measured by the FPR technique. The lateral diffusion coefficient of a fluorescent fatty acid analog, F18, was smaller in transformed cells than normal cells. This indicates that the lipid phase of membranes from transformed cells is less fluid than that from normal cells. On the other hand, the lateral diffusion coefficient of S-F-concanavalin A was identical in both cells. These results suggest that the mobility of different molecules on the membranes is controlled by different mechanisms.

Lateral motion of fluorescent molecules embedded into cell membranes of clonal myogenic cells, L6, changes upon cell maturation

The lateral motion of fluorescent molecules embedded into cell membranes of myogenic cell line, L6, was measured. The motion of S-F-ConA became faster at cell fusion stage, and became slower after fusion. On the other hand, the motion of lipid analog, F18, was not changed at cell fusion stage. However, after fusion when myotubes were formed, the motion of F18 became slower. At cell fusion stage, there was a large variation in the motion of S-F-ConA. This means that at this stage the properties of myoblasts change drastically and rapidly.

Cell membrane expansion and blockade of action potentials produced by 2-decenoic acid in cultured dorsal root ganglion neurons

2-Decenoic acid, a fatty acid having 10 carbon atoms, blocks the action potentials of cultured dorsal root ganglion (DRG) neurons and this effect of 2-decenoic acid is reversible. From the analysis of the video pictures from Nomarski optics, relative values of the diameter and the thickness of the neurons increased to 1.06 and 1.14, respectively, when 2.1 mM 2-decenoic acid was applied to the neurons. The relative value of cell surface area, which was calculated from the equation for a spheroid, increased to about 1.20. On the other hand, relative fluorescence intensity of the fluorescent probe F18 (5-(octadecylthiocarbamoylamino)fluorescein) labeled neurons decreased to 0.81, when 2.1 mM 2-decenoic acid was applied to the neurons. This indicates that the relative cell surface area increased to 1.23, a value similar to that calculated from the results of the measurement of cell size. The time course of blocking action potentials after treatment of the fatty acid was similar to that of the cell membrane expansion. These results show that the fatty acid perturbs the cell membrane and expands the cell surface area and this expansion might reduce the opening ability of the Na+-channels in the membrane.

The maturation-dependent change in fibronectin receptor density of mouse dorsal root ganglion neurons

The maturation-dependent change in fibronectin receptor density of mouse dorsal root ganglion neurons were investigated by an immuno-cytofluorometric method. The receptor density showed a drastic decrease around birth and a smaller change after birth.

Lateral diffusion of membrane lipids changes with aging in C57BL mouse dorsal root ganglion neurons from a fetal stage to an aged stage

The membranes of dorsal root ganglion (DRG) neurons dissected from different age groups of C57BL mice, from 18-day fetal to 30-month-old mice, were labeled with the fluorescent analog of fatty acids, F18, after a day in culture. The fluorescent probe specifically labeled the cell surface. The lateral diffusion of F18 (5-(octadecylthiocarbamoylamino) fluorescein) was measured with fluorescence photobleaching recovery (FPR) method. During development, the lateral diffusion coefficients of F18 rapidly decreased from (0.34 +/- 0.07) X 10(-8) cm2/s (18-day-old fetus) to (0.22 +/- 0.07) X 10(-8) cm2/s (3-day-old newborn). Then the values slowly decreased and reached (0.13 +/- 0.05) X 10(-8) cm2/s in a 6-month-old stage. In stages older than 6-months the lateral diffusion coefficients scarcely changed with aging. As this decrease in the membrane fluidity with increasing age is parallelled to that in capacities of extending neurites, it is thought that the membrane fluidity might change with aging in concert with changes in important cell functions.

Effect of fatty acids on the membrane fluidity of cultured chick dorsal root ganglion measured by fluorescence photobleaching recovery

The effect of fatty acids on the membrane fluidity in tissue cultured chick embryo dorsal root ganglion was studied by fluorescence recovery method. Lateral motion of the lipid was measured by observing the fluorescent probe, 5-(octadecylthiocarbamoylamino) fluorescence, F18. The effective lateral diffusion coefficient of the membrane was around 0.30 X 10(-8) cm2/sec in control cells, 0.42 X 10(-8) cm2/sec in 2-decenoic acid treated cells, and 0.35 X 10(-8) cm2/sec in valeric acid treated cells. From these results it is concluded that effective mobilities of the membrane complex increased about 40% by the external application of 2-decenoic acid, while valeric acid increased it only 12%. From the physiological results that 2-decenoic acid inhibits the Na-channel, it is suggested that this increase in the membrane fluidity might affect the Na-channel.