The subsynaptosomal distribution and specific binding of 17beta-estradiol in vitro to mitochondria isolated from presynaptic nerve endings of female rat brain were examined. 17Beta-estradiol is (i) distributed unequally in synaptosomes and mitochondria posses the highest capacity to bind estradiol with respect to the available amount of the hormone. (ii) Estradiol binds specifically to isolated synaptosomal mitochondria. A Michaelis-Menten plot of specific binding was sigmoidal within a concentration range of 0.1-5 nM of added estradiol, with a saturation plateau at 3 nM. Binding of higher estradiol concentrations demonstrated an exponential Michaelis-Menten plot, indicating non-specific binding to mitochondria. Vmax and Km for the sigmoidal-shape range were estimated as 46 +/- 6 fmol of estradiol/mg of mitochondrial proteins and 0.46 +/- 0.07 nM free estradiol respectively. (iii) Estradiol binding is not affected by the removal of ovaries. The results show that inhibition of Na-dependent Ca2+ efflux from mitochondria by estradiol occurs according to an affinity change of the translocator for Na+, at the same estradiol concentrations that show specific binding to mitochondrial membranes. These data imply that physiological concentrations of estradiol, acting on mitochondrial membrane properties, extragenomically modulate the mitochondrial, and consequently the synaptosomal content of Ca2+, and in that way exert a significant change in nerve cell homeostasis.

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In the present study the developmental profile of ATP-hydrolyzing activity promoted by NTPDase 1, its kinetic properties and the enzyme protein abundance associated with synaptic plasma membrane from rat cerebral cortex were characterized. NTPDase 1 activity increased from birth to day 30; afterwards it decreased and remained unchanged from adulthood (90 days) to senescence (365 days). Kinetic analysis revealed that enzyme exhibited the highest specific activity at day 30 and highest apparent affinity for ATP at day 365; however, V(max)/K(m) values remained unchanged for each age studied. Immunoblot analysis demonstrated that relative abundance of NTPDase 1 is highest at day 15 during ontogeny. The discrepancy between maximum enzyme activity and maximum enzyme protein abundance indicates that NTPDase 1 may have an additional role during development.

The distribution of GM1 and GM3 gangliosides in human brain development between gestational week (g.w.) 6 and 15 was demonstrated by an immunocytochemical approach using polyclonal anti-GM1 and anti-GM3 antibodies. The first appearance of GM1- and GM3-positive cells was recorded as early as in g.w.6. Both antibodies labeled the cells in the ventricular zone of the telencephalic wall, with radially oriented fibers toward the pial surface, which represent radial glia cells with glia fibers. The intensive GM3 immunoreactivity was also exhibited in proliferating cells in the ventricular zone between g.w.6 and 12. During the period from g.w. 12 to 15, characterized by a rapid multiplication of neurons and glia cells, an increased number of GM1- and GM3-positive cells was observed. Prominent GM1 ganglioside staining was observed at the surface of the cell bodies in the ventricular zone. Besides surface labeling in migrating cells, GM1 immunoreactivity was identified inside the soma in the regions of cortical plate and subplate. GM1 immunoreactivity was more pronounced on the membrane of neuronal cells migrating along radial glia fibers, especially at the contact site between neuronal and glial cells. The GM3 ganglioside was localized mostly inside the soma, showing a granular immunoreactivity pattern. Our observations confirm the presence of GM1 and GM3 gangliosides in neuronal and glial cells in early human brain development. The involvement, especially of GM1 ganglioside in glia-neuronal contacts during migration of neuroblasts to their final destination, as well as the presence of GM3 ganglioside in proliferative cells in the ventricular zone of the telencephalic wall was also recorded.