Alzheimer-type Dementia Brains Research Articles

Alzheimer brain-derived amyloid β-protein impairs synaptic remodeling and memory consolidation

Aggregation of the amyloid β-protein (Aβ) is believed to play a central role in initiating the molecular cascade that culminates in Alzheimer-type dementia (AD), a disease which in its early stage is characterized by synaptic loss and impairment of episodic memory. Here we show that intracerebroventricular injection of Aβ-containing water-soluble extracts of AD brain inhibits consolidation of the memory of avoidance learning in the rat and that this effect is highly dependent on the interval between learning and administration. When injected at 1 hour post training extracts from 2 different AD brains significantly impaired recall tested at 48 hours. Ultrastructural examination of hippocampi from animals perfused after 48 hours revealed that Aβ-mediated impairment of avoidance memory was associated with lower density of synapses and altered synaptic structure in the dentate gyrus and CA1 fields. These behavioral and ultrastructural data suggest that human brain-derived Aβ impairs formation of long-term memory by compromising the structural plasticity essential for consolidation and that Aβ targets processes initiated very early in the consolidation pathway.

Cdk5 and munc-18/p67 co-localization in early stage neurofibrillary tangles-bearing neurons in Alzheimer type dementia brains.

Hyperphosphorylation of tau protein occurs during the formation of paired helical filament (PHF) in the brain with Alzheimer's disease. As previously reported, cyclin-dependent kinase (cdk) 5 can phosphorylate tau at the site of abnormally phosphorylated in PHF. To characterize the relationship between cdk5 and PHF-tau, we investigated the localization of cdk5 and its regulator, p67 (munc 18), in the hippocampus and temporal lobes from 12 Alzheimer type dementia (ATD) patients and 5 controls using immunohistochemical procedures. The specificity of antibodies was confirmed with Western blot analysis. Anti-cdk5 antibody diffusely stained the perikarya of some tau2-positive or neurofibrillary tangle (NFT)-bearing neurons in ATD brains, while cdk5-positive staining was scarcely found in control brains. Anti-p67 antibody also showed stronger immunoreactivity of pyramidal neurons in ATD brains than in control brains. Double immunostaining with anti-cdk5 and anti-p67 antibodies revealed co-localization of both molecules in some pyramidal neurons. These findings suggest that cdk5 is activated by p67 at the early stage of NFT formation and accelerates NFT formation. In cdk5-positive and p67-negative neurons, cdk5 may be activated by other regulator molecules such as p35. In addition, cdk5-positive reactive astrocytes were found close to cdk5-positive NFT-bearing neurons m ATD brains but not in control brains, suggesting a correlation between NFT and reactive astrocytes.

Changes of monoamines in post-mortem brains from patients with diffuse Lewy body disease

1. 1. In the present study, we measured the concentrations of 5-hydroxytryptamine (5-HT), norepinephrine and dopamine in post-mortem brains from five patients with diffuse Lewy body disease (DLBD), in comparison with five brains from patients with Alzheimertype dementia (ATD), and five brains from normal controls. 2. 2. They were measured by means of high-performance liquid chromatography fluorometric detection. 3. 3. Compared with the ATD and normal control brains, the DLBD ones showed decreased concentrations of 5-HT, norepinephrine and dopamine in the putamen, and lower 5-HT and norepinephrine concentrations, and almost equal dopamine ones in the neocortex.

Fas antigen expression in brains of patients with Alzheimer-type dementia

Fas antigen (CD95) is a cell surface protein that mediates apoptosis. We have investigated the immunohistochemical localization of Fas antigen in postmortem brain tissue from control subjects, patients with Alzheimer-type dementia (ATD), and from a few patients with diffuse Lewy body disease, progressive supranuclear palsy and adrenoleukodystrophy. In all brains, including controls, vascular endothelial cells and residual blood plasma were weakly stained. In ATD brains, senile plaques and a small number of star-like cells were also stained for Fas. Fas-positive cells were identified as astrocytes on a morphological basis. Fas-positive astrocytes were also present in brains of patients with neurological diseases other than ATD. In double immunostaining for Fas and glial fibrillary acidic protein (GFAP). a small number of cells were positive for both antigens. The majority of Fas-positive astrocytes were, however, negative for GFAP. This implies the downregulation of GFAP production in these cells. Doubly labeled astrocytes were also fouond around senile plaques, suggesting that the Fas immunoreactivity in senile plaques was derived from astrocytic membranes. The results of this study indicate that Fas antigen is expressed by a subset of reactive astrocytes in degenerative neurological diseases. Such astrocytes may undergo the Fas-mediated apoptotic process.

Endothelin-1-like immunoreactivity in cerebral cortex of Alzheimer-type dementia

1. 1. Endothelin-1-like immunoreactivity (ET-1-LI) in cerebral cortex in postmortem brains obtained from patients with Alzheimer-type dementia (ATD) was measured by enzyme-immunoassay. 2. 2. The ET-1-LI in the ATD brains was significantly increased in frontal and occipital cortex than those in the control brains and a significant correlation was found between frontal and temporal lobe of ATD brains. 3. 3. These findings may explain the clinico-radiological results that the cerebral blood flow is decreased in ATD patients, the mechanism of which is still unknown.

Remarkable reduction in acetylcholine concentration in the cerebrospinal fluid from patients with Alzheimer type dementia

We determined the concentrations of acetylcholine (ACh) and choline (Ch) in the cerebrospinal fluid (CSF) of patients with Alzheimer type dementia (ATD) in comparison with controls. The ACh concentration was reduced significantly and remarkably (73%, P < 0.0002) in ATD patients and had a significant positive correlation with dementia scale scores ( r = 0.82, P < 0.05). The Ch concentration was unaltered in ATD patients. These results suggest that the progressive reduction in ACh in the ATD brain may be reflected in its concentrations in the CSF.

Amyloid-P-component-like immunoreactivity in beta/A4-immunoreactive deposits in Alzheimer-type dementia brains.

An immunohistochemical study using the mirror-image technique was performed in order to establish whether amyloid P component is involved in the mechanism of deposition of amyloid fibrils in senile plaques (SPs) in Alzheimer-type dementia (ATD). Ninety percent of beta/A4 protein-immunoreactive SPs were also stained by the anti-amyloid P component immunohistochemistry, and this applied to all of the diffuse, primitive and classical types of beta/A4 deposits. These findings may suggest an involvement of amyloid P component in the formation of amyloid fibrils in senile plaques in ATD brains.

Localization of calpain immunoreactivity in senile plaques and in neurones undergoing neurofibrillary degeneration in Alzheimer's disease

An antibody raised against the calcium activated neutral protease (calpain) was used to investigate the possible involvement of this enzyme in the formation of plaques and tangles in Alzheimer-type dementia (ATD) brain. Our results revealed the presence of a number of strongly stained calpain positive neurones in the normal human cerebral cortex and a loss calpain positive cells in ATD brain. Furthermore, double staining experiments revealed that calpain immunoreactivity was present in cells undergoing tangle formation, and was also present in senile plaques. These data suggest that activation of calpain may be an important factor in the abnormal proteolysis underlying the accumulation of plaques and tangles in ATD.

Demonstration of neurofibrillary tangles in parvalbumin-immunoreactive interneurones in the cerebral cortex of Alzheimer-type dementia brain

The pathological changes occurring in a population of parvalbumin-like immunoreactive cerebral cortical interneurones in postmortem Alzheimer-type dementia brain tissue were determined by double staining cerebral cortical sections for parvalbumin, tau and/or calpain-like immunoreactivities. By counting the number of double immunostained cells it was determined that 4% parvalbumin and 25% of calpain-like immunoreactive cells showed evidence of tau-like immunoreactivity, indicative of neurofibrillary tangles. These results suggest that cerebral cortical parvalbumin-like immunoreactive neurones are relatively resistant to the pathological changes underlying the formation of neurofibrillary tangles associated with Alzheimer-type dementia.

Parvalbumin-immunoreactive neurons in the cortex in Pick's disease

Parvalbumin (a calcium-binding protein)-immunoreactive (PV-Ir) neurons in the cerebral cortex were examined in 20 postmortem brains obtained from elderly controls and patients with Pick's disease (PD). The type of PV-Ir neurons and their distribution in control and PD brains were similar. The number of PV-Ir neurons in PD brains did not differ significantly from that in the control brains either. These findings suggested that PV-Ir neurons in the cortex are not affected in PD brains. A significant loss of PV-Ir neurons has already been reported in brains obtained from patients with Alzheimer-type dementia (ATD), and the present results suggest the possibility that the damage of PV-Ir neurons might be comparatively selective for ATD brains.

Ultrastructural localization of argyrophilic substances in diffuse plaques of Alzheimer-type dementia demonstrated by methenamine silver staining

The ultrastructure of argyrophilic substances in diffuse plaques of an Alzheimer-type dementia brain was examined using methenamine silver (MS) electron microscopy with the pre-embedding method. Electron-dense substances, which were sparse aggregations of bundle-like structures with silver granules, were disseminated in the diffuse plaques. Comparison of serial MS and routine ultrathin sections revealed that diffuse plaques usually show scattered bundles of amyloid fibrils or amorphous materials, or both, between indistinct cell process membranes. Some of these processes were identified as astrocytic or dendritic in origin. A few degenerative neurites were frequently noted in large silver-positive areas but never in small areas. These findings suggest that the appearance of amyloid fibrils and amorphous materials between certain cell processes is a very early morphological change in the process of senile plaque formation.

ELECTRON MICROSCOPIC STUDIES OF DIFFUSE PLAQUES IN ALZHEIMER-TYPE DEMENTIA

In order to clarify the ultrastructural characterization of diffuse plaques (DP) in the frontal cortex and cerebellar molecular layer, four Alzheimer-type dementia brains were examined using 1) β/A4 immunoelectron microscopy, 2) pairs of routine electron microscopic sections and adjacent semithin sections, which were immunolabeled for β/A4 protein and 3) methenamine silver electron microscopy. In the frontal cortex, DP consisted of small bundles of amyloid fibrils, non-fibrillar β/A4 reactive substances and occasionally small degenerating neurites. The β/A4 reactive substances existed between cell processes and/or on part of cell membranes. The number of degenerating neurites was proportional to the amount of amyloid fibrils and the size of DP. Compared to frontal DP, cerebellar DP had fewer amyloid fibrils and more degenerating neurites. These results suggest that β/A4 protein initially appears between cell processes and/ or on parts of cell membranes as non-fibrillar forms and subsequently turns into fibrillar forms (amyloid fibrils).

Light and electron microscopic examination of amyloid-rich primitive plaques: comparison with diffuse plaques

In Alzheimer-type dementia brains, numerous "amyloid-rich primitive plaques (PPs)" were observed with beta-protein immunostaining and periodic-acid methenamine (PAM) staining. These amyloid-rich primitive plaques were accompanied by various degrees of small argyrophilic rod-like, granular or filamentous structures. Routine and modified-PAM electron microscopy revealed many bundles and flecks consisting of amyloid fibrils scattered widely throughout the plaques. Degenerate neurites, astrocytic processes and bundles of glial fibres also participated in the formation of the plaques. The similarities and differences between these amyloid-rich primitive plaques and diffuse plaques are described.

3H]N‐[1‐(2‐Thienyl)cyclohexyl]‐3,4‐Piperidine ([3H]TCP) Binding in Human Frontal Cortex: Decreases in Alzheimer‐Type Dementia

We studied [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine [( 3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer-type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40-50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X-100-treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. These results suggest that the primary change in NMDA receptor-ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal.

An immunohistochemical study of ?-protein in Alzheimer-type dementia brains

An immunohistochemical study with a polyclonal anti-beta-protein antiserum was performed in order to understand the mechanism of deposition of amyloid fibrils in senile plaques in Alzheimer-type dementia (ATD). Serial cortical sections cut from ATD brains were necessary to investigate the structural correlation between senile plaques and blood vessels. The senile plaques were stained well and a blood vessel or capillary-like structure was found in most of beta-protein-immunoreactive deposits. These findings may suggest an involvement of blood vessels in the formation of at least some of the amyloid deposits in ATD brains.

The formation of prostaglandins in the postmortem cerebral cortex of Alzheimer-type dementia patients.

The formation of arachidonic acid metabolites [prostaglandin (PG)D2, PGE2, PGF2 alpha, 6oxo-PGF1 alpha and thromboxane (TX)B2] has been examined in the frontal, temporal, and parieto-occipital regions of the cortex in the postmortem brains from five patients with a pathologically verified Alzheimer-type dementia (ATD) and in eight, age-matched controls. The study disclosed that the amount of PGD2 and TXB2 found in the ATD brains was greater than in controls, and that the formation of PGD2 was significantly increased in the frontal cortex of the ATD brains. Other PG metabolites, however, showed no significant changes in the ATD group. Since it is known that PGD2 is synthesized mainly in neurons, our results seem to suggest that the preserved cortical neurons in the ATD brain have an accelerated PGD2 production.

Changes in benzodiazepine receptors in Alzheimer-type dementia.

We studied benzodiazepine receptors in brains obtained at autopsy from 7 normal controls and 7 patients with Alzheimer-type dementia, using 3H-flunitrazepam as a ligand. Compared with controls, 3H-flunitrazepam binding sites were significantly reduced in number in frontal and temporal cortex and hippocampus in the Alzheimer-type dementia brains. These results suggest that there are significant changes in the number of benzodiazepine receptors in selected brain regions of patients with Alzheimer-type dementia.

Diffuse type of senile plaques in the brains of Alzheimer-type dementia

We studied the nature of diffuse type of senile plaques (SP) in the brains of six autopsied subjects with Alzheimer-type dementia (ATD). The densities of SP in the entorhinal cortex were evaluated using serial sections stained by four different methods. Compared with beta protein immunostaining (100% as a reference), the modified Bielschowsky stain (103%) and the periodic acid-methenamine silver (PAM) stain (109%) labeled similar numbers of SP, whereas the Bodian stain labeled only a minor proportion (42%) of these. The vast majority of Bodian-negative plaques were diffuse plaques, which were seen as ill-defined areas of fine fibrillar material after beta protein immunostain with formic acid pretreatment, modified Bielschowsky stain, and PAM stain. They were not stained by Congo red or periodic acid-Schiff stains. Double staining using Bodian and beta protein methods demonstrated that diffuse plaques were free of swollen neurites. Argyrophilia of the diffuse plaques shown by the modified Bielschowsky and PAM stains, became undetectable when sections were pretreated with formic acid. Such treatment made the diffuse plaques immunoreactive to beta protein antiserum, suggesting that diffuse plaques consisted mainly of amyloid, but not neuritic components. The diffuse plaques were distributed in various cortical areas and in the amygdala, and comprised a considerable population of the SP in the ATD brains.

A variety of cerebral amyloid deposits in the brains of the Alzheimer-type dementia demonstrated by beta protein immunostaining.

We studied cerebral amyloid deposits in the hippocampal area immunohistochemically, using antiserum to synthetic beta peptide (1-28) in 66 patients with or without dementia and aged 17 to 91 years old. Senile plaques (SP) and amyloid angiopathy (AA) were detected in 36 (55%) and 19 (29%) patients, respectively. Also, cerebral amyloid deposits from the brains of seven patients with dementia and five patients without were studied in serial sections stained with Bodian, modified Bielschowsky, Congo red, and beta protein immunostain. In the patients with Alzheimer-type dementia (ATD) diffuse plaques, typical of this group, were stained with beta protein antiserum but not with Bodian stain, because the plaques were devoid of abnormally swollen neuritic processes. The diffuse plaques often contained one or more neuronal cell bodies. As well as primitive and classic plaques and AA, the beta protein immunostain demonstrated small deposits among the SP, small stellate deposits of layer 1, subpial fibrillar deposits, and focal cribriform deposits of parasubiculum, which may be new types of amyloid deposits. Amyloid plaques within the subcortical white matter were only found in ATD brains. In the non-demented patients various kinds of SP, including diffuse and compact ones, were immunostained. They tended to be small and few. beta protein immunostain with formic acid pretreatment is a useful method for the identification of a variety of senile cerebral amyloid deposits.

Biochemical Characterization of α‐Adrenergic Receptors in Human Brain and Changes in Alzheimer‐Type Dementia

Using ligand binding techniques, we studied alpha-adrenergic receptors in brains obtained at autopsy from seven histologically normal controls and seven patients with histopathologically verified Alzheimer-type dementia (ATD). Binding of the alpha-adrenergic antagonists [3H]prazosin and [3H]yohimbine to membranes of human brains exhibited characteristics compatible with alpha 1- and alpha 2-adrenergic receptors, respectively. Binding of both ligands was saturable and reversible, with dissociation constants of 0.15 nM for [3H]prazosin and 5.5 nM for [3H]yohimbine. [3H]Prazosin binding was highest in the hippocampus and frontal cortex and lowest in the caudate and putamen in the control brains. [3H]Yohimbine binding was highest in the nucleus basalis of Meynert (NbM) and frontal cortex and lowest in the caudate and cerebellar hemisphere in the control brains. Compared with values for the controls, [3H]prazosin binding sites were significantly reduced in number in the hippocampus and cerebellar hemisphere, and [3H]yohimbine binding sites were significantly reduced in number in the NbM in the ATD brains. These results suggest that alpha 1- and alpha 2-adrenergic receptors are present in the human brain and that there are significant changes in numbers of both receptors in selected regions in patients with ATD.