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M Mallory

Publications and source records attributed to M Mallory.

86 records · Page 5Linked to original sources
PubMed1992

Amyloid precursor protein is localized in growing neurites of neonatal rat brain.

Previous studies have indicated that amyloid precursor protein (APP) might be a trophic agent in the nervous system, possibly through the regulation of cell adhesion and the protease/protease inhibitor activity. Additionally, APP is upregulated during the development of the nervous system. In order to further study the role of APP in neuritic outgrowth, we examined the patterns of distribution of APP in the immature neonatal rat brain (P1). Laser-scanning confocal imaging of double-immunolabeled sections showed that a subpopulation of the anti-GAP43-immunoreactive outgrowing neurites contained APP immunoreactivity in the neocortex and hippocampus. These fine, long neuritic processes were also positive with antibodies against phosphorylated neurofilaments and were glial fibrillary acidic protein (GFAP) negative. In addition, anti-APP strongly immunolabeled neurons in the inner cortical layers, while GAP43 strongly immunolabeled the neuropil surrounding them. These observations are consistent with a previous study where APP was localized to aberrant sprouting neurites and suggest a possible role for APP in neuritic outgrowth in plaques of patients with Alzheimer's disease (AD), which might explain the abnormal neuritic response found in AD.

Amyloid beta-Protein Precursor↗
PubMed1992

Localization of amyloid precursor protein in GAP43-immunoreactive aberrant sprouting neurites in Alzheimer's disease.

Previous in vitro studies have suggested that amyloid precursor protein (APP) could be involved in cell surface adhesion, neuritic growth and survival of hippocampal neurons. In the present study, involvement of APP in aberrant sprouting in Alzheimer's disease (AD) was studied by comparing immunolabeling patterns of anti-APP and anti-growth-associated protein 43 (anti-GAP43). Confocal laser imaging of frontal cortex sections double-immunolabeled for APP and GAP43 showed an increase, in AD, of presynaptic boutons immunostained with anti-GAP43 that contained anti-APP immunoreactivity. The neuritic plaques in AD cases presented intense anti-GAP43 immunoreactive abnormal neurites colocalized with anti-APP. Three-dimensional reconstruction of the plaques showed that anti-APP was colocalized with anti-GAP43 in 57.5% of the aberrant sprouting neurites. We conclude that co-expression of APP with GAP43 in the plaque might be involved in the aberrant sprouting response observed in AD.

Aged↗
PubMed1992

Three-dimensional analysis of the relationship between synaptic pathology and neuropil threads in Alzheimer disease.

Recent studies have shown that the Alzheimer disease (AD) neocortex is characterized by a loss of large neurons, the presence of dilated terminal axons, widespread loss of synapses, and a disruption of the dendritic cytoskeleton which is manifested as Tau immunoreactive threads. In the present study we have investigated the relationship between synaptic and dendritic abnormalities in the neocortex of Alzheimer patients and examined the extent to which these structural alterations correlate with the severity of cognitive impairment in AD. Quantitative neuroanatomical data were obtained from immunofluorescence-labeled specimens using a laser-scanning confocal microscope, computer-assisted image processing and serial section reconstruction techniques. We found that the AD cases showed a 34% loss in the number of presynaptic terminals per 100 square (sq) microns, many of which showed structural abnormalities. The AD neuropil had an average of 10 +/- 7 dendritic threads per 1,000 sq microns, with the average thread measuring 2 sq microns. Severe AD cases had thicker threads compared with mild to moderate AD cases. Three-dimensional analysis showed clustering of synapses around threads, as well as presynaptic boutons apposed to dendritic neuropil threads. Statistical analysis showed that the strongest correlation was between synapse density and Blessed score of cognitive impairment. Thread counts did not correlate with either but were correlated with tangle counts. Stepwise multiple regression analysis showed that tangle counts, but not threads, strengthened the correlation between Blessed score and synapses. We conclude that synaptic damage may precede dendritic thread and tangle formation, and that threads do not necessarily induce synaptic pathology. Instead, dendrite sprouting in the denervated regions could be associated with increased accumulation of cytoskeletal proteins observed in the dendritic threads.

Aged↗
PubMed1992

Casein kinase II alteration precedes tau accumulation in tangle formation.

Previous studies have shown altered casein kinase II (CK-II) in Alzheimer's disease (AD). For the present study, the authors analyzed CK-II immunoreactivity at various stages of tangle formation using quantitative laser confocal microscopy and immunoelectron microscopy. AD hippocampal pyramidal cells without neurofibrillary tangles (NFTs) displayed 15% more anti-tau immunoreactivity (P less than 0.01) and 43% more anti-CKII immunolabeling than controls (P less than 0.001). In AD, tangle-bearing hippocampal neurons with strong anti-tau immunoreactivity (threefold increase from controls) showed a significant 22% increase in anti-CKII immunolabeling (P less than 0.01), compared with those without NFTs. Neurons with early neurofibrillary changes showed diffuse anti-CKII immunostaining in their cytoplasm and cell processes. In tangle-bearing neurons, in which a higher level of tau immunoreactivity was detected, anti-CKII immunolabeling was distributed along a fibrillar meshwork in cell bodies and processes. Linear regression analysis of anti-CKII and anti-tau immunoreactivity in AD showed a positive correlation (r = 0.53, P less than 0.001). At the ultrastructural level, anti-CKII was immunolocalized to the paired helical filaments (PHF) of the tangle-bearing neurons, as well as to PHF in neuropil threads and some dystrophic neurites in plaques. These results suggest a possible role for CK-II in tangle formation.

Aged↗
PubMed1991

Abnormal brain spectrin immunoreactivity in sprouting neurons in Alzheimer disease.

Brain spectrin is a major membrane skeleton protein that participates in cellular transport, cell morphogenesis, neurotransmitter release and growth cone adhesion. The present study showed that in Alzheimer disease (AD) neuropil, brain spectrin immunoreactivity is co-localized with synaptophysin in the presynaptic boutons. At the ultrastructural level, brain spectrin immunoreactivity was observed in the presynaptic terminals and in the axoplasm of some myelinated and unmyelinated fibers. In addition to this normal localization of brain spectrin in the AD brain, we also found brain spectrin immunoreactivity associated with abnormal patchy lesions in the AD neuropil. Confocal laser imaging and immunoelectron microscopy revealed that these lesions corresponded to thick cellular processes derived from neurons. The findings that these structures were anti-neurofilament positive but anti-glial fibrillary acidic protein (GFAP) and Ricinus communis agglutinin I (RCA-I) negative confirm their neuronal origin, and rule out the possibility of glial origin. These structures could represent either atypical axonal or dendritic processes derived from sprouting neurons or the accumulation of brain spectrin degradation products in degenerating neurons.

Aged↗
PubMed1991

Immunoelectron microscopic study of synaptic pathology in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by an extensive loss of neurons and synapses in the neocortex which correlates strongly with psychometric tests of dementia. To characterize the ultrastructural changes in presynaptic terminals in AD, we studied biopsy material from the frontal cortex. We also examined, at the ultrastructural level, abnormal neurites scattered in the AD neuropil and in the plaque region using sections from autopsy material immunolabeled with anti-synaptophysin. We found that, regardless of amyloid deposits, some presynaptic terminals were distended and contained swollen vesicles and dense bodies. These altered synaptic organelles were similar to those found in dystrophic neurites. The latter structures displayed synaptophysin immunoreactivity, mostly localized to outer membranes of synaptic vesicles and dense bodies. The present study supports the hypothesis of progressive synaptic pathology in AD neocortex and favors the notion that the dystrophic process originates from presynaptic terminals.

Aged↗
PubMed1991

Immunoreactivity of CD45, a protein phosphotyrosine phosphatase, in Alzheimer's disease.

Both protein kinases and phosphoprotein phosphatases are important components of signal transduction systems in cells. Recent studies in Alzheimer's disease (AD) have shown abnormal protein phosphorylation in the cortex suggesting an alteration in these enzymes. In the present study, an antibody against CD45 was used to analyze the status of this protein phosphotyrosine phosphatase in AD. We studied and quantified the immunohistochemical and immunochemical distribution of this integral membrane protein in control and AD brain. We found that anti-CD45 immunostained the great majority of microglia, both resting and activated. These cells were Ricinus communis agglutinin I positive and glial fibrillary acidic protein and neurofilament negative. The AD frontal cortex showed a 35% (P less than 0.01) increase in the number of anti-CD45 immunoreactive microglia as compared with controls. These results were consistent with the immunoblot quantification of CD45 immunoreactivity following native gel electrophoresis. In AD, 30% of the CD45-immunostained microglia were clustered in the neuritic plaques (about six per plaque) while the remaining 70% were scattered in the neuropil. The AD hippocampus showed an increase in CD45-immunoreactive microglia in the molecular layer of the dentate gyrus. At the ultrastructural level, CD45 immunoreactivity was localized exclusively to the plasma membrane of the microglia. The presence of the anti-CD45 immunoreactivity in microglia suggests the possibility that they may require the presence of CD45 as a cell surface receptor which may regulate cell function through modulation of intracellular signaling.

Aged↗
PubMed1991

Reactive synaptogenesis assessed by synaptophysin immunoreactivity is associated with GAP-43 in the dentate gyrus of the adult rat.

Reactive synaptogenesis and terminal proliferation are known to occur in the dentate gyrus of the rat hippocampus following removal of specific afferents. In the present study we have examined the relation of synaptophysin immunoreactivity to the immunohistochemical staining pattern of GAP-43, a putative marker of neuritic growth. Within the molecular layer of the normal dentate gyrus, synaptophysin immunolabeling shows a trilaminar pattern, with the inner and outer layers having the greatest density of staining. Within the first week following denervation, there was a significant decrease in the staining density in the outer two-thirds of the molecular layer, followed by a moderate recovery at 14 days and 80% recovery by 30 days. This pattern is consistent with the time course of denervation and reinnervation in this system as determined previously by electron microscopy. By comparison, the staining pattern for GAP-43 in the intact dentate gyrus showed the middle and outer thirds of the molecular layer to be less densely stained than the inner third. Within a week following deafferentation, the outer two-thirds of the molecular layer displayed decreased levels of GAP-43 immunoreactivity, followed by recovery to normal levels by 30 days. By 84 days postlesion, patterns of both synaptophysin and GAP-43 immunostaining reflected an increased width of the inner molecular layer. Laser confocal imaging of double-immunolabeled sections at 14 days postlesion showed a 370% increase in the number of GAP-43-positive terminals in the molecular layer as compared to unoperated controls. Many of these GAP 43-positive terminals were synaptophysin negative. We conclude that GAP-43 may play a role in the synaptic remodeling that occurs in the denervated rat hippocampus and that quantitative morphometry of synaptophysin immunolabeling accurately reflects the fate of presynaptic terminals in this model of degeneration and reinnervation.

Animals↗
PubMed1991

Patterns of aberrant sprouting in Alzheimer's disease.

Alzheimer's disease (AD) is characterized by extensive synaptic and neuronal loss and by plaque formation in the cortex, but the mechanisms responsible for synaptic plasticity in the neocortex are still not completely understood. To analyze the sprouting response in AD cortex, we compared the patterns of GAP-43 with synaptophysin immunoreactivity. In AD, GAP-43 immunohistochemistry revealed extensive sprouting in the hippocampal molecular layer, stratum polymorphous, CA1 region, and prosubiculum. These regions presented abundant anti-GAP-43-immunoreactive coiled fibers and dystrophic neurites in association with plaques. Some of these sprouting structures were colocalized with anti-synapto-physin- and anti-neurofilament-positive neurites. The AD neocortex was characterized by an overall decrease in GAP-43 immunoreactivity accompanied by sprouting neurites in the areas of synaptic pathology. We conclude that GAP-43 might be involved in the mechanisms of synaptic plasticity in the AD cortex, as well as in the process of aberrant sprouting in the neuritic plaques.

Aged↗
PubMed1991

Protein kinase C alteration is an early biochemical marker in Alzheimer's disease.

Neuritic (senile) plaques are a hallmark of the pathology found in the brain of patients afflicted with Alzheimer's disease (AD). Neuritic plaques have been considered to be composed of an amyloid core surrounded by dilated neurites, although the use of anti-beta/A4-protein antibody revealed the presence of diffuse plaques without a nuclear-like central mass or surrounding paired helical filament (PHF)-containing neuritic components. The presence of diffuse plaques without PHF-containing neuritic components strongly suggests that the formation of amyloid precedes the degeneration of neurites that surround amyloid. Diffuse plaques are thus considered to be an early marker of AD pathology. In this article, we report that diffuse plaques, possible markers of early AD pathology, are immunostained with anti-protein kinase C(beta II) [anti-PKC(beta II)] antibodies. The PKC(beta II)-immunoreacting components of the diffuse plaques extend from neurons embedded in the plaques. Immunoelectron microscopy of diffuse and mature neuritic plaques shows that PKC(beta II)-like immunoreactivity in the plaques is closely associated with membranous structures of fine neuronal processes apposed to the amyloid fibers. These fine neuronal processes are distinct from classical neurites found typically in mature neuritic plaques. Furthermore, biochemical analysis demonstrates that PKC abnormalities, but not other AD markers (ubiquitin and A68), were found in the neocortex of clinically nondemented individuals with cortical plaques. Therefore, the PKC alteration in neurons might be involved in the early pathophysiology of AD.

Alzheimer Disease↗
PubMed1990

Diffuse plaques do not accentuate synapse loss in Alzheimer's disease.

Applying the relatively new technique of laser confocal imaging, vibratome sections which were double immunolabeled for amyloid beta protein and the presynaptic terminal marker synaptophysin were examined. It was found that while synaptic density was generally diminished in Alzheimer's disease (AD) cortical neuropil as compared to controls, the reduction was no greater within the diffuse plaques than outside them. Synapse loss was accentuated, however, within immature and mature plaques. These findings suggest that the pathogenetic process in AD might commence with synapse loss and neurodegeneration rather than with deposition of amyloid beta protein.

Aged↗
PubMedDate not supplied

PDGF is associated with neuronal and glial alterations of Alzheimer's disease.

In the present study we observed that while platelet-derived growth factor (PDGF)-BB is exclusively expressed by neurons in the human brain, PDGF-AA is expressed in neurons and blood vessels. In Alzheimer's disease (AD), antibodies against PDGF-BB (but not PDGF-AA) recognized the neurofibrillary alterations of this disease. The levels of PDGF-BB correlated with the patterns of synaptic loss and sprouting while PDGF-AA immunostaining of the vessels was correlated with glial proliferation. Immunostaining was completely abolished when the antibodies were preincubated with their respective purified recombinant PDGF. Western blot analysis showed that antibodies against PDGF recognized a 31 kDa protein that was mildly increased in AD. These data suggest that PDGF, as well as other neurotrophic factors, play an important role in the mechanisms of neurofibrillary pathology in AD.

Aged↗
PubMedDate not supplied

Neurofibrillary tangle-associated alteration of stathmin in Alzheimer's disease.

Stathmin (p19), a 19-kDa cytosolic phosphorotein, plays a key role in converting extracellular signals into intracellular biochemical changes. Antibodies and cDNA specific for stathmin were used to study its levels and localization in normal and Alzheimer's disease (AD) brain tissue. The stathmin protein concentration was reduced in AD neocortex as assessed by Western blotting, whereas the concentration of its mRNA detected by both in situ hybridization and slot blot were increased in AD. The alteration of the stathmin protein concentration was negatively correlated with neurofibrillary tangle numbers but not with plaque numbers. Immunoreactivity was evenly localized to the cytoplasm of neurons in control cortical sections, whereas in AD it was preferentially localized to some of the neurofibrillary tangle-bearing neurons. Numbers of stathmin-positive neurons were inversely correlated with tangle numbers but not with plaque numbers in the frontal cortex of AD patients.

Alzheimer Disease↗