Detection and partial purification of glial growth inhibitory factor(GGIF) in the conditioned medium of neuroblastoma cells

Morphological changes in the thalamus and neocortex of the cat brain after a restricted unilateral fetal neocortical lesion

In order to study the response of the brain to injury during early development, the neocortex of ten fetal kittens was lesioned at age E43-48, in either the frontal (n = 8) or parieto-occipital (n = 2) areas. The thalamus and neocortex of the lesioned animals were analyzed using quantitative morphometry and compared to intact control cats (n = 10). Ipsilaterally, the volumes of the remaining neocortex and of the thalamus were 26.5% and 25.7% smaller, respectively (P < 0.05). Contralaterally, the neocortex did not change in volume, whereas the thalamus tended to be smaller by a mean of 11.1%. Ipsilaterally, in all four thalamic nuclei studied, the neuronal and glial cell packing densities (NCPD and GCPD) and the cross sectional area of neuronal somata did not differ between lesioned and intact animals except for the principal ventromedial nucleus, where the GCPD was significantly lower (P < 0.05) in lesioned animals. Contralaterally, the NCPD and GCPD did not show any differences between groups, except for the principal ventromedial nucleus, in which the GCPD was lower in lesioned cats (P < 0.05). Furthermore, in the contralateral basal ventromedial nucleus, the cross sectional area of the neuronal somata was smaller in lesioned than in intact animals (P < 0.01). These results indicate loss of neurons and glia in the ipsilateral thalamus and probably in the neocortex. Since, at the time of the cortical resection, transient reciprocal thalamosubplate connections have been established in the cat, the lesion-induced deprivation of subplate target neurons and cortical inputs probably precluded the survival of a substantial number of developing thalamic neurons. In the cortex the hypothetical loss of neurons may, at least partly, be attributed to lesion-induced elimination of target neurons before establishment of corticocortical connections.

A novel glial growth inhibitory factor, gliostatin, derived from neurofibroma

Neurofibroma tissue was investigated for the presence of glial growth modulators that would suppress the proliferation of glial cells. A novel endogenous polypeptide inhibitor of proliferation and DNA synthesis in glial cells, gliostatin, was purified from the extracts of neurofibroma by a procedure comprising dye and anion-exchange column chromatography, and HPLC. A monoclonal antibody raised against partially purified gliostatin showed no cross-reactivity with known cytokines, but adsorbed the growth inhibitory activity of gliostatin and immunochemically visualized the putative gliostatin bands on western blot analyses. Although the product showed an apparent M(r) of 100,000 accompanied by an inhibitory activity on gel filtration column chromatography, it migrated at a lower apparent M(r) of 50,000 under the reducing conditions on western blotting, indicating that a homodimeric structure of native gliostatin consisted of 50-kDa subcomponents. Gliostatin was a potent growth inhibitor acting at nanomolar concentrations against all glial tumor cells and glia maturation factor-stimulated astroblasts, but not neuronal cells.

Induction of astroglial growth inhibition and differentiation by sialosyl cholesterol

Normal rat astroblasts in culture were exposed to 11 sialosyl or cholesterol derivatives at concentrations lower than 20 microM. Synthesized sialosyl cholesterols (alpha- and beta-D-N-acetyl neuraminyl cholesterols) and cholesterol sulfate showed a marked growth inhibitory action. Sialosyl cholesterol uniquely evoked an astroglia-like stellation resembling that induced by glia maturation factor (GMF) as well as a suppression of GMF-induced mitogenesis of astroblasts. The minimal incubation period of sialosyl cholesterol for the initiation of growth inhibition was as short as one hour. The inhibitory effect retained an irreversibility even after removal of the drug. Cytosolic protein with 58 kDa Mr in size was specifically phosphorylated by sialosyl cholesterol through a certain protein kinase dependent on neither Ca2+ nor cyclic AMP. The competition experiment of sialosyl cholesterol action revealed that sialosyl and cholesterol moieties were indispensable for the phenomena. These results most likely imply that sialosyl cholesterol alters the membrane microenvironment to affect the affinity of growth factor receptor, protein kinase activity, and/or cytoskeletal anchorages.