Lateral patterns of the neural cell adhesion molecule on the surface of hippocampal cells developing in vitro.

In monolayer cultures of hippocampal neurons from newborn rats, an immunocytochemical quantitative study was carried out to investigate age-dependent arrangement of the neural cell adhesion molecules in different parts of cell membranes. On the fifth and 12th day in vitro, neural cell adhesion molecules were labelled with specific antibodies and protein A conjugated to colloidal gold particles. Samples of randomly selected electron micrographs that displayed labelled membrane fragments of cell bodies, growth cones, and axons were numerically analysed for the five- and 12-day in vitro neurons. Neural cell adhesion molecules surface topography was quantitatively described and compared, using a statistical stereological approach. The mean surface density of labelled neural cell adhesion molecules was found to be approximately 2.5 times higher in growth cone membranes relative to somatic and axonal membranes in five-day in vitro neurons. By the 12th day in vitro, this density decreases in somatic membranes (approximately 18%) and increases in axonal membranes (approximately 60%). Representative spectra of lateral intervals between labels as well as images that show typical topography of label on membrane surfaces were simulated. The results revealed regular patterns of neural cell adhesion molecules on the somatic surface and allowed consideration of neural cell adhesion molecules arrangement in a view of membrane adhesion properties. Participation of cytoskeleton in neural cell adhesion molecules rearrangement is discussed.

Changes in the neural cell adhesion molecule patterns on the rat glial cell surfaces with development and contact formation in vitro.

In monolayer cultures of newborn rat hippocampal cells, immunogold-labelling at the electron microscope level was used to study quantitatively the neural cell adhesion molecule (N-CAM) arrangement on the surface of glial soma and processes on 5 and 12 days in vitro (DIV). Four corresponding samples of micrographs were formed. To quantify the labelling, a stochastic geometry approach was used. Spectra of lateral distances between labels as well as simulated images of the surface label arrangement (invisible in micrographs) were derived and compared. The data show that, on both 5 and 12 DIV, N-CAM density on the surface of processes is approximately 2 times higher than that in somata; 12-DIV cells showing a lower (approximately 25%) N-CAM surface density as compared with the 5-DIV cells. This suggests that N-CAM expression in glia surfaces decreases while the cells form contacts, and N-CAM sorting between soma and processes remains stable. The simulated topographies of the lateral N-CAM arrangement might highlight fundamental mechanisms that underlie formation of the neural network.

[Inhibition of the high-threshold calcium current in hippocampal neurons of rats subjected to intraperitoneal injection of phenylalanine]. / Podavlenie vysokoporogovogo kal'tsievogo toka v neironakh gippokampa krys, podvergnutykh intraperitonal'noi in"ektsii fenilalanina.

Effect of intraperitoneal injection of phenylalanine on the calcium current of hippocampal neurons of rats has been studied by the voltage clamp method of the whole-cell recordings. Calcium currents in hippocampal neurons of control animals after 5-7 days in culture can be separated into two components: low and high voltage-activated ones. The value of high voltage-activated calcium current was 69 +/- 13% at Vt = -10 mV from total calcium inward current in these neurons. High voltage-activated Ica in neurons of phenylalaninemic rats was significantly depressed and its value was 32 +/- 14%, the Vt value being the same. Low voltage-activated calcium current was resistant to intraperitoneal injection of L-phenylalanine.

[Restoration of the potential-dependent L-phenylalanine-inhibited calcium current by L-tyrosine in cultured hippocampal neurons]. / Vosstanovlenie L-tirozinom potentsialozavisimogo kal'tsievogo toka, podavlennogo L-fenilalaninom, v kul'tiviruemykh neironakh gippokampa.

Calcium currents were recorded in cultured (5-7 days) hippocampal neurons isolated from one-day rats. The animals were intraperitoneally injected L-phenylalanine which induced in their brain biochemical changes typical of phenylketonuria. It has been found that in neurons from injected animals the amplitude of the high-threshold calcium current was substantially inhibited and amounted to 40 +/- 30% at Vt = +20 mV (amplitude of calcium currents at Vt = -10 mV taken as 100%). Addition of L-tyrosine to the cultivation medium (50 mumol/l) restored the high-voltage calcium current, its relative amplitude reaching 280 +/- 57%.