Ischaemia-induced change in clathrin preceding delayed neuronal death

Possibility for neurogenesis in substantia nigra of parkinsonian brain

Recent studies of enhanced hippocampal neurogenesis by antidepressants suggest enhancement of neurogenesis is a potentially effective therapy in neurodegenerative diseases. In this study, we evaluated nigral neurogenesis in animals and autopsy brains including patients with Parkinson's disease (PD). First, proliferating cells in substantia nigra were labeled with retroviral transduction of green fluorescent protein, which is an efficient method to label neuronal stem cells. Subsequent differentiation of labeled cells was followed; many transduced cells became microglia, but no differentiation into tyrosine hydroxylase-positive neurons was detected at 4 weeks after injection, in both intact rodents and those treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Second, polysialic acid (PSA)-like immunoreactivity, indicative of newly differentiated neurons, was detected in the substantia nigra of rodent, primate, and human midbrains. A large number of PSA-positive cells were detected in the substantia nigra pars reticulata of some patients with PD. In rats and a macaque monkey, the dopamine-depleted hemispheres showed more PSA staining than the intact side. A small number of tyrosine hydroxylase-positive cells were PSA-positive. Our results suggest enhanced neural reconstruction in PD, which may be important in the design of new therapies against the progression of PD.

IgG-immunostaining in the intact rabbit brain: variable but significant staining of hippocampal and cerebellar neurons with anti-IgG

A significant number of brain neurons in the rabbit brain were immunostained with anti-rabbit gamma-immunoglobulin (IgG). IgG-positive neurons were often found in the cerebellum, lower brainstem and motor nuclei. Similar IgG-positive neurons were occasionally found in the hippocampus, cerebral cortex and midbrain, but not in the striatum and thalamus. These neurons showed very clear Golgi-like staining of soma and dendrites but IgG staining was absent from the cell nuclei and axons. In particular, groups of Purkinje neurons in the rabbit cerebellum showed strong IgG-positive staining. To confirm whether the staining reflected the existence of IgG molecules in these neurons, staining specificity was carefully evaluated. Staining was specifically eliminated by pre-absorption of the antibodies with the purified rabbit IgG. An antibody to the neural cell adhesion molecule (NCAM or CD56), a member of the immunoglobulin superfamily, exhibited a completely different pattern of staining as that for IgG. To determine whether IgG-like immunoreactivity was a general feature of mammalian brain, brain sections of rabbits, rats, and mice were immunostained with antibodies to IgGs of each of the three species. Similar IgG-positive neurons were observed in all three species, although the distribution and frequency was characteristic for each species. In rabbit brain, anti-rabbit IgG stained-neurons were more abundant compared to rat and mouse brain. IgG-positive microglia-like cells were evident in mouse brain, but less frequent in rabbit and were hardly observed in rat brain. To evaluate whether stained neurons could synthesize IgG, in situ hybridization was carried out using an antisense oligonucleotide probe to rabbit IgG DNA. No significant label was observed in cerebellum. These results suggest that a significant number of neurons in the intact rabbit brain take up IgGs and concentrate them in their cytoplasm, although the molecular uptake mechanism is retained for future studies. Our results also suggest that the rabbit may be a suitable animal to study the function(s) of IgG in brain neurons.