3H]vesamicol binding in human brain cholinergic deficiency disorders

We measured the binding of the vesicular acetylcholine transport blocker [3H]vesamicol (2-[4-phenylpiperidino] cyclohexanol; AH-5183) to autopsied frontal cortex and amygdala of patients from 4 disorders having a marked brain cholinergic reduction, namely Alzheimer's disease, Parkinson's disease with dementia, dominantly inherited olivopontocerebellar atrophy and Down's syndrome. Although mean activity of the specific cholinergic marker enzyme choline acetyltransferase (ChAT) was markedly reduced by about 60% in frontal cortex in the 4 patient groups and by 80% or greater in amygdala of the Alzheimer's and Down's syndrome patients, [3H]vesamicol binding density was, on average, either normal or only slightly reduced as compared with the controls. This discrepancy suggests that in human brain [3H]vesamicol binding is either not preferentially localized to cholinergic nerve endings or, in these cholinergic deficiency syndromes, a substantial proportion of the vesamicol binding sites persist on cholinergic nerve terminals despite loss of ChAT activity.     

In vivo MRI identifies cholinergic circuitry deficits in a Down syndrome model

In vivo quantitative magnetic resonance imaging (MRI) was employed to detect brain pathology and map its distribution within control, disomic mice (2N) and in Ts65Dn and Ts1Cje trisomy mice with features of human Down syndrome (DS). In Ts65Dn, but not Ts1Cje mice, transverse proton spin–spin (T₂) relaxation time was selectively reduced in the medial septal nucleus (MSN) and in brain regions that receive cholinergic innervation from the MSN, including the hippocampus, cingulate cortex, and retrosplenial cortex. Basal forebrain cholinergic neurons (BFCNs) in the MSN, identified by choline acetyltransferase (ChAT) and nerve growth factor receptors p75^NTR and TrkA immunolabeling were reduced in Ts65Dn brains and in situ acetylcholinesterase (AChE) activity was depleted distally along projecting cholinergic fibers, and selectively on pre- and postsynaptic profiles in these target areas. T₂ effects were negligible in Ts1Cje mice that are diploid for App and lack BFCN neuropathology, consistent with the suspected relationship of this pathology to increased App dosage. These results establish the utility of quantitative MRI in vivo for identifying Alzheimer's disease-relevant cholinergic changes in animal models of DS and characterizing the selective vulnerability of cholinergic neuron subpopulations.     

The limbic system in Alzheimer's disease. A neuropathologic investigation.

The morphologic alterations of Alzheimer's disease, presenile and senile dementia, have conventionally been associated with the cerebral cortex; however, it is clear that other areas of the brain, notably the hippocampus and amygdala, are involved as well. These structures, together with others such as the fornix, cingulate gyrus, septal nuclei, and mamillary bodies, constitute the limbic system, which has been recognized as the anatomic substrate of memory, emotion, and learning. Disturbances in these modalities are central to the clinical expression of Alzheimer's disease; therefore, the limbic system was studied in its entirety in 9 patients with Alzheimer's disease and in 3 elderly individuals with Down's syndrome, in whom identical morphologic lesions were present. The findings disclose that the limbic system is regularly involved in Alzheimer's disease, to a severe degree and in a distinctively patterned distribution.     

Amino acid neurotransmitter deficits in adult Down's syndrome brain tissue

Neurotransmitter amino acids have been measured in several brain regions taken postmortem from 5 adults cases of Down's syndrome and 6 age-matched control subjects. A significant deficit of glutamate was found in the hippocampus in Down's syndrome, and gamma-aminobutyric acid was reduced in the hippocampus and temporal cortex in those patients with neocortical neurofibrillary tangles. These results are consistent with losses of cortical neurones containing these neurotransmitters, and resemble the deficits exhibited by the more severely affected cases of Alzheimer's disease.     

Alzheimer patients and Down patients: abnormal presynaptic terminals are related to cerebral preamyloid deposits

In Alzheimer's disease, in Down syndrome and in normal aging, scattered deposits of amyloid fibril precursors occur in both cerebral cortex and subcortical grey structures. Within such preamyloid deposits, no degenerating neurites with paired helical filaments have ever been observed. This study, carried out on brains from Alzheimer patients and Down patients, reports on the relationship between preamyloid deposits and neuritic changes. These changes were represented by presynaptic terminal swellings immunolabeled by antisynaptophysin and antiubiquitin antibodies, not by Alz50. These findings support the view that the deposition of amyloid fibril precursors in the neuropil is closely related to presynaptic terminals, although whether the former precedes or follows the development of presynaptic terminal changes is still undetermined.     

A comparative study of choline acetyltransferase from normal and Alzheimer brain

A comparative study was made of the enzyme choline acetyltransferase (ChAT) from normal and Alzheimer (senile dementia of the Alzheimer type) brain. The number of molecular weight and charge forms of the enzyme were determined in the caudate region of both brains. Efficient purification of active ChAT was achieved using immuno-affinity purification. It was shown that the purified enzyme was identical in both cases, exhibiting a single charge (apparent pI approximately 8.2) and a single molecular weight (mol. wt. = 68,000). The idea of a selective loss of one particular isoform to explain the reduced levels of ChAT observed in Alzheimer's disease can be ruled out.     

Intraneuronal abeta-amyloid precedes development of amyloid plaques in Down syndrome

CONTEXT: Down syndrome patients who live to middle age invariably develop the neuropathologic features of Alzheimer disease, providing a unique situation in which to study the early and sequential development of these changes. OBJECTIVE: To study the development of amyloid deposits, senile plaques, astrocytic and microglial reactions, and neurofibrillary tangles in the brains of young individuals (<30 years of age) with Down syndrome. METHODS: Histologic and immunocytochemical study of a series of autopsy brains (n = 14, from subjects aged 11 months to 56 years, with 9 subjects <30 years) examined at the Office of the Chief Medical Examiner of the State of Maryland and The Johns Hopkins Hospital. RESULTS: The principal observations included the presence of intraneuronal Abeta immunostaining in the hippocampus and cerebral cortex of very young Down syndrome patients (preceding the extracellular deposition of Abeta) and the formation of senile plaques and neurofibrillary tangles. CONCLUSIONS: We propose the following sequence of events in the development of neuropathologic changes of Alzheimer disease in Down syndrome: (1) intracellular accumulation of Abeta in neurons and astrocytes, (2) deposition of extracellular Abeta and formation of diffuse plaques, and (3) development of neuritic plaques and neurofibrillary tangles with activation of microglial cells.     

Sodium-dependent glutamate binding in senile dementia

Sodium-dependent glutamate binding was studied as a possible index of the integrity of glutamate/aspartate (Glu/Asp) nerve endings in seven cortical areas from postmortem brains of 15 persons with senile dementia of the Alzheimer type (SD), 10 controls matched for age, sex and postmortem delay (PMD), and single cases of Down's syndrome and Parkinson-dementia. Binding affinities (Kd) were quite variable from brain to brain but showed no relation to sex, age, PMD or disease. Specific binding site densities did not vary with age or sex but showed overall a significant negative correlation with PMD, a significant decrease in SD, and a significant correlation in the SD--but not the control--samples with choline acetyltransferase (ChAT) activities. The binding data on individual brain regions, however, showed no significant difference between SD cases and controls despite highly significant differences in the ChAT activities. The overall results support but do not confirm a defect in cortical Glu/Asp systems in SD. Reported and obtained data on lesioned rats are summarized to suggest that sodium-dependent glutamate binding may be an ineffective index of Glu/Asp nerve endings.     

Lysergic acid diethylamide-induced Fos expression in rat brain: role of serotonin-2A receptors

Lysergic acid diethylamide (LSD) produces altered mood and hallucinations in humans and binds with high affinity to serotonin-2A (5-HT(2A)) receptors. Although LSD interacts with other receptors, the activation of 5-HT(2A) receptors is thought to mediate the hallucinogenic properties of LSD. The goal of this study was to identify the brain sites activated by LSD and to determine the influence of 5-HT(2A) receptors in this activation. Rats were pretreated with the 5-HT(2A) receptor antagonist MDL 100907 (0.3 mg/kg, i.p.) or vehicle 30 min prior to LSD (500 microg/kg, i.p.) administration and killed 3 h later. Brain tissue was examined for Fos protein expression by immunohistochemistry. LSD administration produced a five- to eight-fold increase in Fos-like immunoreactivity in medial prefrontal cortex, anterior cingulate cortex, and central nucleus of amygdala. However, in dorsal striatum and nucleus accumbens no increase in Fos-like immunoreactivity was observed. Pretreatment with MDL 100907 completely blocked LSD-induced Fos-like immunoreactivity in medial prefrontal cortex and anterior cingulate cortex, but only partially blocked LSD-induced Fos-like immunoreactivity in amygdala. Double-labeled immunohistochemistry revealed that LSD did not induce Fos-like immunoreactivity in cortical cells expressing 5-HT(2A) receptors, suggesting an indirect activation of cortical neurons. These results indicate that the LSD activation of medial prefrontal cortex and anterior cingulate cortex is mediated by 5-HT(2A) receptors, whereas in amygdala 5-HT(2A) receptor activation is a component of the response. These findings support the hypothesis that the medial prefrontal cortex, anterior cingulate cortex, and perhaps the amygdala, are important regions involved in the production of hallucinations.     

Hypothesis: Alzheimer's disease is a phylogenetic disease

It is hypothesized that Alzheimer's disease is a human phylogenetic disease which has a common multifactorial pathogenesis in sporadic and familial cases and in Down syndrome, related to a genomic character function G(x). Increments in G(x) accompanied the increased gene expression that sustained brain growth and differentiation during hominid evolution, particularly of the regions liable to Alzheimer pathology, and further occur in Down syndrome [suggesting that genes on chromosome 21 are included in G(x)]. If genes which promoted human brain evolution contribute to the value of G(x), a better understanding of the genomic events which promoted this evolution, using molecular biological techniques, should elucidate the genetic basis of Alzheimer's disease, and vice versa.     

Abeta deposition is associated with enhanced cortical alpha-synuclein lesions in Lewy body diseases

In order to understand better the neuropathological substrate of dementia in Parkinson's disease (PD) and to examine its interactions with Alzheimer's disease (AD), we examined autopsy brains from 21 cases of PD and Lewy body disease (LBD) with dementia. We separated brains in two groups according to the presence of Abeta deposits. In brains without Abeta, we found few or no Lewy bodies (LB) in the cerebral cortex. By contrast, in brains with Abeta, we observed significant increases in LB in the cerebral cortex (p < 0.01) and alpha-synuclein immunoreactive lesions in the cingulate cortex (p < 0.01). Immunoblots of alpha-synuclein from cingulate cortex in brains with Abeta showed significantly higher levels of insoluble alpha-synuclein compared to brains without Abeta. Our observations indicate that in cases of PD with dementia, the neocortex is not necessarily involved by LB. Furthermore, the presence of Abeta deposits in the cerebral cortex was associated with extensive alpha-synuclein lesions and higher levels of insoluble alpha-synuclein. This suggests that Abeta enhances the development of cortical alpha-synuclein lesions in cases of PD.     

Neuropathological correlates of volumetric MRI in autopsy-confirmed Lewy body dementia

The objective of this study was to determine the neuropathological correlates of regional medial temporal lobe volume measures on magnetic resonance imaging (MRI) in subjects with Lewy body dementia (LBD). Twenty-three autopsy-confirmed LBD cases with an MRI scan close to death (mean 1.5 years) were studied. MRI-based volumetric measures were calculated for total intracranial volume, hippocampus, entorhinal cortex, and amygdala. Quantitative neuropathological analysis of plaques, tangles, and Lewy bodies were carried out in the same regions. Spearman's rho was used to examine correlations between MRI volumes and neuropathology measures and linear regression to assess the relationship between neuropathology and MRI volumes. A significant inverse correlation was observed between normalized amygdala volume and percent area of Lewy bodies in the amygdala (r = -0.461, p = 0.035). There were no other significant correlations between regional MRI volume and measures of neuropathology. Lewy body, but not Alzheimer's disease (AD) pathology was associated with reduced amygdala volume in pathologically-verified LBD cases but neither Lewy body nor Alzheimer's disease pathology was associated with volume loss in the hippocampus or entorhinal cortex, suggesting other neuropathological factors account for atrophy in these structures in LBD.     

Mostly separate distributions of CLAC- versus Abeta40- or thioflavin S-reactivities in senile plaques reveal two distinct subpopulations of beta-amyloid deposits

Collagenous Alzheimer amyloid plaque component (CLAC) is a unique non-Abeta amyloid component of senile plaques (SP) derived from a transmembrane collagen termed CLAC-precursor. Here we characterize the chronological and spatial relationship of CLAC with other features of SP amyloid in the brains of patients with Alzheimer's disease (AD), Down syndrome (DS), and of PSAPP transgenic mice. In AD and DS cerebral cortex, CLAC invariably colocalized with Abeta42 but often lacked Abeta40- or thioflavin S (thioS)-reactivities. Immunoelectron microscopy of CLAC-positive SP showed labeling of fibrils that are more loosely dispersed compared to typical amyloid fibrils in CLAC-negative SP. In DS cerebral cortex, diffuse plaques in young patients were negative for CLAC, whereas a subset of SP became CLAC-positive in patients aged 35 to 50 years, before the appearance of Abeta40. In DS cases over 50 years of age, Abeta40-positive SP dramatically increased, whereas CLAC burden remained at a constant level. In PSAPP transgenic mice, CLAC was positive in the diffuse Abeta deposits surrounding huge-cored plaques. Thus, CLAC and Abeta40 or thioS exhibit mostly separate distribution patterns in SP, suggesting that CLAC is a relatively early component of SP in human brains that may have inhibitory effects against the maturation of SP into beta-sheet-rich amyloid deposits.     

Antibodies raised against different portions of A4 protein identify a subset of plaques in Down's syndrome

Antisera were raised to peptides corresponding to residues 1-10 and 12-28 of the published sequence of A4 protein, a 42/43 amino acid long peptide isolated from the brains of patients with Down's syndrome and Alzheimer's disease. Immunohistochemical studies performed on sections of temporal lobe from 12 cases of Down's syndrome showed that the number of senile plaques in the molecular layer of the dentate gyrus which were identified by antibody to A4(1-10) was only 23% (range 11-53%) of that recognised by antibody to A4(12-28). This observation has important consequences for both the diagnosis and the pathogenesis of Down's syndrome and Alzheimer's disease.     

Choline acetyltransferase immunoreactivity in neuritic plaques of Alzheimer brain

We have observed dystrophic choline acetyltransferase (ChAT)-positive processes surrounding the amyloid core of neuritic plaques in human neocortex, amygdala and hippocampus, using a polyclonal anti-human ChAT antiserum. These data, and those from studies of the aged monkey by other investigators, provide a morphologic counterpart for the biochemical abnormality of the cholinergic system in Alzheimer's disease and senile dementia of the Alzheimer type.     

Preservation of 5-hydroxytryptamine1A receptor-G protein interactions in the cerebral cortex of patients with Alzheimer's disease.

The coupling of 5-hydroxytryptamine1A (5-HT1A) receptors to guanine nucleotide binding (G) proteins was investigated in membranes prepared from frontal and parietal cortices of control and Alzheimer's disease brains by characterising the effect of guanosine 5'-[beta gamma-imido]diphosphate (Gpp[NH]p) on [3H]8-hydroxy-2-(di-n-propylamino)-tetralin ([3H]8-OH-DPAT) binding parameters. In the absence of guanine nucleotides, [3H]8-OH-DPAT bound to a single high affinity binding site in all membrane types. The number of [3H]8-OH-DPAT binding sites was significantly decreased in the parietal cortex of Alzheimer's disease samples compared with controls, whereas in the frontal cortex the number of binding sites remained unchanged. Gpp[NH]p reduced the [3H]8-OH-DPAT binding affinity and the number of binding sites to the same degree in both regions in control and Alzheimer's disease cases. [3H]8-OH-DPAT binding was inhibited in a concentration dependent manner with an IC50 value of approximately 1 microM in all cases. These results suggest that the 5-HT1A receptor-G protein complex is functionally intact in these regions in Alzheimer's disease brain.     

Alzheimer's-type neuropathology in the precuneus is not increased relative to other areas of neocortex across a range of cognitive impairment

We studied Alzheimer's disease (AD) pathology in the precuneus and surrounding brain areas. Anatomically, the precuneus corresponds to the medial portion of human cerebral cortical Brodmann Area 7. This study utilized patients from the University of Kentucky Alzheimer's Disease Center autopsy cohort. Data from 47 brains were used comprising patients of differing antemortem cognitive impairment severities, each with longitudinal clinical data and extensive neuropathological data. We assessed whether the precuneus and surrounding areas are differentially vulnerable to AD-type pathological lesions (diffuse amyloid plaques, neuritic amyloid plaques, and neurofibrillary tangles). Eleven areas of brain were evaluated for each case: amygdala, hippocampal CA1, subiculum, entorhinal cortex, frontal cortex, superior and middle temporal gyri, inferior parietal lobule, occipital cortex, posterior cingulate gyrus, Brodmann Area 31, and the precuneus proper. Like other areas of neocortex, the precuneus demonstrated increased diffuse and neuritic amyloid plaques early in the evolution in AD, and increased neurofibrillary tangles late in AD. Correcting for the antemortem cognitive status of the patients, there was no evidence of an increase in the density of AD-type pathology in the precuneus or neighboring areas relative to other areas of cerebral neocortex. Our results are not consistent with the idea that the precuneus is involved in a special way with plaques or tangles relative to other areas of neocortex.     

Reduced amounts of immunoreactive somatostatin in the temporal cortex in senile dementia of Alzheimer type

Post-mortem brain tissue from 15 patients dying with a diagnosis of senile dementia of Alzheimer type (SDAT) was compared with tissue obtained from 16 control patients at routine post-mortem. A significant fall in choline acetyltransferase (ChAT) activity was observed in the cortex, hippocampus and amygdala of the SDAT cases and was maximal in the temporal cortex. The fall in ChAT activity observed in the temporal cortex was accompanied by a significant reduction (47%) in immunoreactive somatostatin.     

Biomarkers and evolution in Alzheimer disease

Brain regions and their highly neuroplastic long axonal connections that expanded rapidly during hominid evolution are preferentially affected by Alzheimer disease. There is no natural animal model with full disease pathology (neurofibrillary tangles and neuritic amyloid plaques of a severity seen in Alzheimer's disease brains). Biomarkers such as reduced glucose metabolism in association neocortex, defects in long white matter tracts, RNA neurochemical changes, and high CSF levels of total and phosphorylated tau protein, which are helpful to identify MCI and preclinical Alzheimer disease patients, may also provide insights into what brain changes led to this disease being introduced during hominid evolution.     

Correlation of choline acetyltransferase activity between the nucleus basalis of Meynert and the cerebral cortex

Choline acetyltransferase (ChAT) activities were measured in the cerebral cortex and the nucleus basalis of Meynert (nbM) of post-mortem human brains from 8 cases with Alzheimer type dementia (ATD) and 5 age-matched control subjects. The lowest ChAT activity was detected in the temporal cortex (Brodmann's area 22) and the nbM in ATD. A significant correlation was found between ChAT activities in the nbM and those in Brodmann's areas 4, 7, 10, 17 and 22. Present results provide evidence of a cholinergic projection from the nbM to the cerebral cortex observed by retrograde or anterograde degeneration studies in animals.