To study the function of the first immunoglobulin (Ig)-like domain of the neural cell adhesion molecule (NCAM), it was produced as a recombinant fusion protein in a bacterial expression system and as a recombinant protein in a eukaryotic expression system of the yeast Pichia pastoris. For comparison, other NCAM domains were also produced as fusion proteins. By means of surface plasmon resonance analysis, it was shown that the first Ig-like NCAM domain binds the second Ig-like NCAM domain with a dissociation constant 5.5 +/- 1.6 x 10(-5) M. Furthermore, it was found that the first Ig-like domain binds heparin. It was also demonstrated that the second Ig-like NCAM domain binds heparin and that both domains bind collagen type I via heparin but not collagen type I directly.

The effect of the antiepileptic drug topiramate on Ca2+ uptake through (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionate (AMPA) and kainate (KA) receptors was investigated in different cell culture systems consisting of neurons from the cerebral cortex, hippocampus, and cerebellum. Ca2+ influx was assayed using a fluorescent Ca2+ chelator to monitor changes in the intracellular Ca2+ concentration or cobalt staining to assess the effect of topiramate on Ca2+-permeable AMPA/KA receptors. In all types of neuronal cultures studied, AMPA and KA were found to elicit an influx of Ca2+ in a subset of the neuronal population. Topiramate, at concentrations of 30 and 100 microM, inhibited Ca2+ influx by up to 60%. Modulation of AMPA and KA-evoked Ca2+ influx may contribute to both the antiepileptic and neuroprotective properties of topiramate.

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Microwell cultures of dissociated tissue from prenatal rat hippocampus and cerebral cortex as well as from early postnatal cerebellum were used for quantification of neuronal aggregation, process extension, and fasciculation. It was shown that the cells in culture from these different brain regions developed differently with regard to both architecture and rate of differentiation. The effect of a polyclonal antibody against the neural cell adhesion molecule (NCAM), the excitatory amino acid receptor agonist N‐methyl‐D‐aspartate (NMDA), and the neurotoxin acrylamide on aggregation and fiber formation was investigated. Exposure to the NCAM antibody led to formation of fewer but larger aggregates and stimulated the morphological development of the cultures. Acrylamide affected aggregate formation, leading to smaller but more numerous aggregates, and it inhibited process extension and fasciculation. Treatment with NMDA affected process formation and led to formation of more numerous but smaller aggregates. Some of these effects were strongly tissue‐dependent. Thus, large differences were seen regarding the effect of the NCAM antibody on aggregation and process extension in cultures from the different brain areas. The culture systems appear to represent convenient and reliable screening tools to study the influence of putative morphoregulatory substances on cell‐cell interactions during early neuronal development. J. Neurosci. Res. 47:163–172, 1997. © 1997 Wiley‐Liss, Inc.

The role of taurine in the process of neuronal migration was studied in a microwell cell culture system. Immunocytochemical analysis of the cellular composition of this culture system revealed the presence of the astrocytic marker GFAP in some structures such as the aggregates of neuronal bodies and in those cables used for migration, resembling what is described in vivo. The neuronal marker gamma-enolase stained practically all structures, including the aggregates and all cables. The intracellular taurine concentration was reduced by 60% in mouse cerebellar granule cells treated with a blocker of taurine transport, guanidinoethane sulfonate (GES). Under these conditions cell migration was markedly reduced to approximately 50% of that in untreated cultures. Both, taurine depletion and impairment of cell migration induced by GES were prevented by adding taurine to the culture medium. Taurine deficiency similarly affected different morphological parameters such as the number of cables suitable for neuronal migration as well as the number of migrating neurons. The number of aggregates of neuronal bodies was significantly increased, by about 30%, as a consequence of the reduced migration. Taurine alone did not exert any effect on the parameters evaluated. GES treatment of granule cells did not affect mitochondrial metabolism or K(+)-stimulated Ca(2+)-dependent [3H]-D-aspartate release. This suggests that the described effects of taurine deficiency were not due to an alteration of neuronal viability and that the action of GES was not simply due to unspecific and deleterious effects. These results are in agreement with those obtained in in vivo studies. This approach represents a useful model to investigate the role played by taurine in the process of neuronal migration.