NeuN Immunoreactivity Research Articles

In Patas monkey, glutamic acid decarboxylase-67 and reelin mRNA coexpression varies in a manner dependent on layers and cortical areas.

In nonhuman and human primates, reelin immunoreactivity is expressed consistently in gamma-aminobutyric acid (GABA)-ergic interneurons of the three upper cortical layers (Impagnatiello et al. [1998] Proc. Natl. Acad. Sci. U S A 95:15718-15723; Rodriguez et al. [2000] Proc. Natl. Acad. Sci. U S A 97:3550-3555). To understand in detail the pattern of reelin synthesis in GABAergic interneurons of primate neocortex, a quantitative analysis of reelin and of glutamic acid decarboxylase-67 (GAD(67)) mRNA-positive neurons as well as a quantitative analysis of total neuronal density measured by neuron-specific nuclear protein (NeuN) immunoreactivity was carried out in Patas monkey neocortex (Brodmann's areas 2, 3, 4, 6, 9, 17, 18, and 24). Reelin mRNA is expressed in every cortical area and layer studied, but layer II of each cortical area consistently revealed the largest neuronal population expressing reelin mRNA compared with other layers. The percentages of GAD(67)-positive neurons in each layer of the eight cortical areas were 83-98% in layer I, 55-64% in layer II, 37-49% in layer III, 71-89% in layer IV, 54-68% in layer V, and 71-85% in layer VI. The percentages of GABAergic neurons expressing reelin were 86-100% in layer I, 76-84% in layer II, 52-96% in layer III, 23-33% in layer IV, 33-57% in layer V, and 34-54% in layer VI. These findings suggest that there may be two classes of GABAergic neurons that can be differentiated by their ability to express reelin mRNA and reelin protein. This differentiation may have a functional significance, considering that reelin is secreted into the extracellular matrix, where it plays a putative role in the maturation of newly formed dendritic spines and binds selectively to dendritic shafts and to spine postsynaptic densities and presumably to integrin receptors, including alpha(3) subunits (Rodriguez et al. [2000]).

Correlation between changes in apparent diffusion coefficient and induction of heat shock protein, cell-specific injury marker expression, and protein synthesis reduction on diffusion-weighted magnetic resonance images after temporary focal cerebral ischemia in rats.

The authors investigated the relationship between the time course of apparent diffusion coefficient (ADC) changes and stress protein induction, ischemic neuroglial damage, and cerebral protein synthesis (CPS) after temporary focal cerebral ischemia in rats. In Group I, ADC changes were measured on magnetic resonance (MR) images obtained during the second half of a 1-hour middle cerebral artery (MCA) occlusion, during a 1-hour reperfusion, and after 23 hours of reperfusion in rats. Immunohistochemical studies for heat shock protein (hsp) 70, glial fibrillary acidic protein (GFAP), and neuronal nuclear (NeuN) protein were performed. In Group II, CPS was assessed using autoradiographic studies obtained after occlusion. At 36 minutes of occlusion, MR imaging demonstrated significantly less ADC reduction in the frontoparietal cortex (82 +/- 9% of the contralateral hemisphere) than in the striatum (64 +/- 11%; p < 0.05). After 1 hour of reperfusion, the lesion resolved and the difference between cortex and striatum was no longer evident. After 23 hours of reperfusion, the ADC lesion recurred in striatum (76 +/- 12%) compared with frontoparietal cortex (100 +/- 11%; p < 0.05). Immunohistochemical studies showed hsp 70 expression and an increased GFAP reactivity localized in the frontoparietal cortex of the ischemic hemisphere, along with a significant drop in striatal NeuN immunoreactivity. A trend toward greater reduction in striatal CPS (53 +/- 15%) than in frontoparietal cortex CPS (78 +/- 23%) was also observed. Sequential ADC maps correlate with the expression of neuroglial stress and injury markers after temporary focal ischemia in rats, distinguishing the striatum (infarct core) from the cortex (ischemic penumbra). A greater reduction in striatal CPS further supports the conclusion that the striatum is more susceptible to temporary MCA occlusion than the cortex.

Expression of active caspase-3 in mitotic and postmitotic cells of the rat forebrain.

Active caspase-3 immunoreactivity was detected in the rat forebrain proliferative regions at birth and remained high in these areas for about 2 weeks, during which period labeled cells were present centroperipherally across the olfactory bulb. By the end of the third postnatal week, only a small number of immunolabeled cells remained in these forebrain structures. Active caspase-3 immunolabeling was localized mostly to cell nuclei and co-localized partially with TuJ1 and NeuN immunoreactivity, but not with glial fibrially acidic protein, OX-42, gamma-aminobutyric acid, or terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL)-positive labeling. Active caspase-3 and 5-bromo-2'-deoxyuridine (BrdU) double-labeled nuclei were seen in the proliferative regions after 2 hours and in the periglomerular region of the bulb after 7 days following BrdU injections. Examination of the cells with electron microscopy confirmed that the active caspase-3-containing nuclei in the proliferative regions often had infoldings and appeared to be undergoing division. Some of the cells with active caspase-3-labeled nuclei in the bulb had synapses on their somata or dendrites. Labeled dendritic spines and a few axon terminals were also observed in the olfactory bulb. Taken together, it appears that a wave of active caspase-3-positive cells are dividing in the proliferative zones and then migrating to the bulb as they differentiate into neurons. Therefore, active caspase-3 may play a role in cellular processes such as neuronal differentiation, migration, and plasticity, in addition to its role in cell death.