Permanent increase of the GAD67/synaptophysin ratio in rat cerebral cortex nerve endings as a result of hypoxic ischemic encephalopathy sustained in early postnatal life: a confocal laser scanning microscopic study

The aim of this study was to investigate whether perinatal hypoxia-ischemia preferentially destroys GABAergic nerve endings in rat cerebral cortex tissue which, in its turn, could then account for the reported higher risk of developing epilepsy later in life. To that end rat pups, with an age of 12–13 days postnatally, were unilaterally to hypoxic-ischemic conditions. After a survival period of to 2 to 6 months, the animals were sacrificed by perfusion fixation and their brains were used for cutting transversal vibratome and frozen sections. These sections were double-stained with primary antibodies against one of the two GABA synthesizing enzymes, glutamic acid decarboxylase with a mol. wt. of 66,600 (GAD₆₇) and one of the intrinsic membrane proteins synaptic vesicles, synaptophysin, followed by fluorophore-conjugated second antibodies. By using the confocal laser scanning microscope, we determined the ratio between the amount of GAD₆₇/synaptophysin immunofluorescence in nerve endings per unit volume of tissue in the hypoxia-damaged neocortex. It turned out that this ratio, contrary to expectations, was significantly higher in the hypoxia-damaged cortical areas than in matched areas on the contralateral side. It appeared, moreover, that this effect was directly proportional to the severity of the incurred damage. The conclusion was drawn that these observations do not support the hypothesis that perinatal hypoxia-ischemia ultimately leads to a preferential loss of GABAergic nerve endings in the damaged neocortex and, as such, to a shortage of inhibition.     

Lesion-specific pattern of immunocytochemical distribution of growth-associated protein B-50 (GAP-43) in the cerebellum of weaver and PCD-mutant mice: Lack of B-50 involvement in neuroplasticity of Purkinje cell terminals?

The growth-associated protein B-50 (GAP-43) is thought to play a major role in the development and regeneration of neurons. The participation of B-50 in neuronal plasticity is well documented, especially for monoaminergic systems. However, such an important role for B-50 in GABAergic systems has not been substantiated to date. This study was performed to obtain detailed information about the identity of B-50 immunopositive axons and terminals in the cerebellum and to test the involvement of this protein during plastic changes as observed in the projections of GABAergic Purkinje cells to the lateral vestibular nucleus (LVN). For this purpose mutant mice with specific cerebellar cell loss were used. Weaver mutants (B6CBA wv/wv), PCD-mutants (B6C3Fe pcd/pcd), and their corresponding wild-type mice were investigated with immunocytochemical and immunoblot procedures at the age of 8--23 days and 5--6 months using polyclonal and monoclonal antibodies to B-50. Substantial differences in B-50 distribution wee detected between normals and mutants and between young and adult animals. These results demonstrate that the labeling of B-50 is mainly related to the outgrowth of parallel fibers and to a minor degree on the ingrowth of non-GABAergic cerebellar afferents. There was no immunocytochemical indication that B-50 is related to Purkinje cells or accompanies the plasticity of the GABAergic innervation of the LVN. © 1994 Wiley-Liss, Inc.     

Laminar distribution of the pathological changes in sporadic frontotemporal lobar degeneration with transactive response (TAR) DNA‐binding protein of 43 kDa (TDP‐43) proteinopathy: a quantitative study using polynomial curve fitting

R. A. Armstrong, R. L. Hamilton, I. R. A. Mackenzie, J. Hedreen and N. J. Cairns (2013) Neuropathology and Applied Neurobiology 39, 335–347 Laminar distribution of the pathological changes in sporadic frontotemporal lobar degeneration with transactive response (TAR) DNA‐binding protein of 43 kDa (TDP‐43) proteinopathy: a quantitative study using polynomial curve fitting Aims: Previous data suggest heterogeneity in laminar distribution of the pathology in the molecular disorder frontotemporal lobar degeneration (FTLD) with transactive response (TAR) DNA‐binding protein of 43 kDa (TDP‐43) proteinopathy (FTLD‐TDP). To study this heterogeneity, we quantified the changes in density across the cortical laminae of neuronal cytoplasmic inclusions, glial inclusions, neuronal intranuclear inclusions, dystrophic neurites, surviving neurones, abnormally enlarged neurones, and vacuoles in regions of the frontal and temporal lobe. Methods: Changes in density of histological features across cortical gyri were studied in 10 sporadic cases of FTLD‐TDP using quantitative methods and polynomial curve fitting. Results: Our data suggest that laminar neuropathology in sporadic FTLD‐TDP is highly variable. Most commonly, neuronal cytoplasmic inclusions, dystrophic neurites and vacuolation were abundant in the upper laminae and glial inclusions, neuronal intranuclear inclusions, abnormally enlarged neurones, and glial cell nuclei in the lower laminae. TDP‐43‐immunoreactive inclusions affected more of the cortical profile in longer duration cases; their distribution varied with disease subtype, but was unrelated to Braak tangle score. Different TDP‐43‐immunoreactive inclusions were not spatially correlated. Conclusions: Laminar distribution of pathological features in 10 sporadic cases of FTLD‐TDP is heterogeneous and may be accounted for, in part, by disease subtype and disease duration. In addition, the feedforward and feedback cortico‐cortical connections may be compromised in FTLD‐TDP.