Effects of age, amyloid, sex, and APOE ε4 on the CSF proteome in normal cognition

Introduction

It is important to understand which biological processes change with aging, and how such changes are associated with increased Alzheimer's disease (AD) risk. We studied how cerebrospinal fluid (CSF) proteomics changed with age and tested if associations depended on amyloid status, sex, and apolipoprotein E Ɛ4 genotype.

Methods

We included 277 cognitively intact individuals aged 46 to 89 years from Alzheimer's Disease Neuroimaging Initiative, European Medical Information Framework for Alzheimer's Disease Multimodal Biomarker Discovery, and Metabolic Syndrome in Men. In total, 1149 proteins were measured with liquid chromatography mass spectrometry with multiple reaction monitoring/Rules-Based Medicine, tandem mass tag mass spectrometry, and SOMAscan. We tested associations between age and protein levels in linear models and tested enrichment for Reactome pathways.

Results

Levels of 252 proteins increased with age independently of amyloid status. These proteins were associated with immune and signaling processes. Levels of 21 proteins decreased with older age exclusively in amyloid abnormal participants and these were enriched for extracellular matrix organization.

Discussion

We found amyloid-independent and -dependent CSF proteome changes with older age, perhaps representing physiological aging and early AD pathology.

White Matter Hyperintensities Are No Major Confounder for Alzheimer's Disease Cerebrospinal Fluid Biomarkers

Background:

The cerebrospinal fluid (CSF) biomarkers amyloid-β 1–42 (Aβ₄₂), total and phosphorylated tau (t-tau, p-tau) are increasingly used to assist in the clinical diagnosis of Alzheimer’s disease (AD). However, CSF biomarker levels can be affected by confounding factors.

Objective:

To investigate the association of white matter hyperintensities (WMHs) present in the brain with AD CSF biomarker levels.

Methods:

We included CSF biomarker and magnetic resonance imaging (MRI) data of 172 subjects (52 controls, 72 mild cognitive impairment (MCI), and 48 AD patients) from 9 European Memory Clinics. A computer aided detection system for standardized automated segmentation of WMHs was used on MRI scans to determine WMH volumes. Association of WMH volume with AD CSF biomarkers was determined using linear regression analysis.

Results:

A small, negative association of CSF Aβ₄₂, but not p-tau and t-tau, levels with WMH volume was observed in the AD (r² = 0.084, p = 0.046), but not the MCI and control groups, which was slightly increased when including the distance of WMHs to the ventricles in the analysis (r² = 0.105, p = 0.025). Three global patterns of WMH distribution, either with 1) a low, 2) a peak close to the ventricles, or 3) a high, broadly-distributed WMH volume could be observed in brains of subjects in each diagnostic group.

Conclusion:

Despite an association of WMH volume with CSF Aβ₄₂ levels in AD patients, the occurrence of WMHs is not accompanied by excess release of cellular proteins in the CSF, suggesting that WMHs are no major confounder for AD CSF biomarker assessment.

Obesity and Brain Vulnerability in Normal and Abnormal Aging: A Multimodal MRI Study

Background:

How the relationship between obesity and MRI-defined neural properties varies across distinct stages of cognitive impairment due to Alzheimer’s disease is unclear.

Objective:

We used multimodal neuroimaging to clarify this relationship.

Methods:

Scans were acquired from 47 patients clinically diagnosed with mild Alzheimer’s disease dementia, 68 patients with mild cognitive impairment, and 57 cognitively healthy individuals. Voxel-wise associations were run between maps of gray matter volume, white matter integrity, and cerebral blood flow, and global/visceral obesity.

Results:

Negative associations were found in cognitively healthy individuals between obesity and white matter integrity and cerebral blood flow of temporo-parietal regions. In mild cognitive impairment, negative associations emerged in frontal, temporal, and brainstem regions. In mild dementia, a positive association was found between obesity and gray matter volume around the right temporoparietal junction.

Conclusion:

Obesity might contribute toward neural tissue vulnerability in cognitively healthy individuals and mild cognitive impairment, while a healthy weight in mild Alzheimer’s disease dementia could help preserve brain structure in the presence of age and disease-related weight loss.

Low Serum High-Density Lipoprotein Cholesterol Levels Associate with the C9orf72 Repeat Expansion in Frontotemporal Lobar Degeneration Patients

 Decreased levels of serum high-density lipoprotein (HDL) cholesterol have previously been linked to systemic inflammation and neurodegenerative diseases, such as Alzheimer’s disease. Here, we aimed to analyze the lipoprotein profile and inflammatory indicators, the high-sensitivity C-reactive peptide (hs-CRP) and glycoprotein acetyls (GlycA), in sporadic and C9orf72 repeat expansion-associated frontotemporal lobar degeneration (FTLD) patients. The C9orf72 hexanucleotide repeat expansion is the most frequent genetic etiology underlying FTLD. The concentrations of different lipid measures in the sera of 67 FTLD patients (15 C9orf72 repeat expansion carriers), including GlycA, were analyzed by nuclear magnetic resonance spectroscopy. To verify the state of systemic inflammation, hs-CRP was also quantified from patient sera. We found that the total serum HDL concentration was decreased in C9orf72 repeat expansion carriers when compared to non-carriers. Moreover, decreased concentrations of HDL particles of different sizes and subclass were consistently observed. No differences were detected in the very low- and low-density lipoprotein subclasses between the C9orf72 repeat expansion carriers and non-carriers. Furthermore, hs-CRP and GlycA levels did not differ between the C9orf72 repeat expansion carriers and non-carriers. In conclusion, the HDL-related changes were linked with C9orf72 repeat expansion associated FTLD but were not seen to associate with systemic inflammation. The underlying reason for the HDL changes remains unclear.

cCOG: A web-based cognitive test tool for detecting neurodegenerative disorders

INTRODUCTION

Web-based cognitive tests have potential for standardized screening in neurodegenerative disorders. We examined accuracy and consistency of cCOG, a computerized cognitive tool, in detecting mild cognitive impairment (MCI) and dementia.

METHODS

Clinical data of 306 cognitively normal, 120 mild cognitive impairment (MCI), and 69 dementia subjects from three European cohorts were analyzed. Global cognitive score was defined from standard neuropsychological tests and compared to the corresponding estimated score from the cCOG tool containing seven subtasks. The consistency of cCOG was assessed comparing measurements administered in clinical settings and in the home environment.

RESULTS

cCOG produced accuracies (receiver operating characteristic-area under the curve [ROC-AUC]) between 0.71 and 0.84 in detecting MCI and 0.86 and 0.94 in detecting dementia when administered at the clinic and at home. The accuracy was comparable to the results of standard neuropsychological tests (AUC 0.69-0.77 MCI/0.91-0.92 dementia).

DISCUSSION

cCOG provides a promising tool for detecting MCI and dementia with potential for a cost-effective approach including home-based cognitive assessments.

Metabolic Profiles Help Discriminate Mild Cognitive Impairment from Dementia Stage in Alzheimer's Disease

Accurate differentiation between neurodegenerative diseases is developing quickly and has reached an effective level in disease recognition. However, there has been less focus on effectively distinguishing the prodromal state from later dementia stages due to a lack of suitable biomarkers. We utilized the Disease State Index (DSI) machine learning classifier to see how well quantified metabolomics data compares to clinically used cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD). The metabolic profiles were quantified for 498 serum and CSF samples using proton nuclear magnetic resonance spectroscopy. The patient cohorts in this study were dementia (with a clinical AD diagnosis) (N = 359), mild cognitive impairment (MCI) (N = 96), and control patients with subjective memory complaints (N = 43). DSI classification was conducted for MCI (N = 51) and dementia (N = 214) patients with low CSF amyloid-β levels indicating AD pathology and controls without such amyloid pathology (N = 36). We saw that the conventional CSF markers of AD were better at classifying controls from both dementia and MCI patients. However, quantified metabolic subclasses were more effective in classifying MCI from dementia. Our results show the consistent effectiveness of traditional CSF biomarkers in AD diagnostics. However, these markers are relatively ineffective in differentiating between MCI and the dementia stage, where the quantified metabolomics data provided significant benefit.

Subtle Cognitive Impairment and Alzheimer's Disease-Type Pathological Changes in Cerebrospinal Fluid are Common Among Neurologically Healthy Subjects

BACKGROUND

The neuropathology of Alzheimer's disease (AD) has previously been shown to be rather common among the elderly.

OBJECTIVE

The aim of this study was to inspect the associations between cerebrospinal fluid (CSF) AD biomarker concentrations, age, the APOEɛ4 allele, cardiovascular diseases, diabetes, and cognitive performance in a cohort of a neurologically healthy population.

METHODS

This study included 93 subjects (42 men, mean age 67 years) without previous neurological symptoms or subjective cognitive complaints. Their cognition was assessed, and CSF biomarkers and APOEɛ4 status were analyzed.

RESULTS

Of the studied subjects, 8.6% (n = 8) had a pathological CSF AD biomarker profile. An increase in age correlated positively with CSF tau pathology and negatively with global cognitive performance.

CONCLUSION

AD-type pathological changes in CSF and subtle cognitive impairment are common within a population with no previous memory complaints. Age was the main risk factor for the changes.

Association Between Later Life Lifestyle Factors and Alzheimer's Disease Biomarkers in Non-Demented Individuals: A Longitudinal Descriptive Cohort Study

BACKGROUND

Lifestyle factors have been associated with the risk of dementia, but the association with Alzheimer's disease (AD) remains unclear.

OBJECTIVE

To examine the association between later life lifestyle factors and AD biomarkers (i.e., amyloid-β 1-42 (Aβ42) and tau in cerebrospinal fluid (CSF), and hippocampal volume) in individuals with subjective cognitive decline (SCD) and mild cognitive impairment (MCI). In addition, to examine the effect of later life lifestyle factors on developing AD-type dementia in individuals with MCI.

METHODS

We selected individuals with SCD (n = 111) and MCI (n = 353) from the DESCRIPA and Kuopio Longitudinal MCI studies. CSF Aβ42 and tau concentrations were assessed with ELISA assay and hippocampal volume with multi-atlas segmentation. Lifestyle was assessed by clinical interview at baseline for: social activity, physical activity, cognitive activity, smoking, alcohol consumption, and sleep. We performed logistic and Cox regression analyses adjusted for study site, age, gender, education, and diagnosis. Prediction for AD-type dementia was performed in individuals with MCI only.

RESULTS

Later life lifestyle factors were not associated with AD biomarkers or with conversion to AD-type dementia. AD biomarkers were strongly associated with conversion to AD-type dementia, but these relations were not modulated by lifestyle factors. Apolipoprotein E (APOE) genotype did not influence the results.

CONCLUSIONS

Later life lifestyle factors had no impact on key AD biomarkers in individuals with SCD and MCI or on conversion to AD-type dementia in MCI.

The influence of insulin resistance on cerebrospinal fluid and plasma biomarkers of Alzheimer's pathology

Background

Insulin resistance (IR) has previously been associated with an increased risk of developing Alzheimer’s disease (AD), although the relationship between IR and AD is not yet clear. Here, we examined the influence of IR on AD using plasma and cerebrospinal fluid (CSF) biomarkers related to IR and AD in cognitively healthy men. We also aimed to characterise the shared protein signatures between IR and AD.

Methods

Fifty-eight cognitively healthy men, 28 IR and 30 non-IR (age and APOE ε4 matched), were drawn from the Metabolic Syndrome in Men study in Kuopio, Finland. CSF AD biomarkers (amyloid β-peptide (Aβ), total tau and tau phosphorylated at the Thr181 epitope) were examined with respect to IR. Targeted proteomics using ELISA and Luminex xMAP assays were performed to assess the influence of IR on previously identified CSF and plasma protein biomarker candidates of AD pathology. Furthermore, CSF and plasma SOMAscan was performed to discover proteins that associate with IR and CSF AD biomarkers.

Results

CSF AD biomarkers did not differ between IR and non-IR groups, although plasma insulin correlated with CSF Aβ/tau across the whole cohort. In total, 200 CSF and 487 plasma proteins were differentially expressed between IR and non-IR subjects, and significantly enriched pathways, many of which have been previously implicated in AD, were identified. CSF and plasma proteins significantly associated with CSF AD biomarkers were also discovered, and those sensitive to both IR and AD were identified.

Conclusions

These data indicate that IR is not directly related to the level of CSF AD pathology in cognitively healthy men. Proteins that associated with both AD and IR are potential markers indicative of shared pathology.

Electronic supplementary material

The online version of this article (doi:10.1186/s13195-017-0258-6) contains supplementary material, which is available to authorized users.

Alzheimer's disease: a report from the 7th Kuopio Alzheimer symposium

The 7th Kuopio Alzheimer symposium was held on 11–13 June, 2015, in Kuopio, Finland and attracted ˜250 attendees from 14 different countries around the world. The theme for the symposium in its seventh year was ‘From mechanisms to prevention and intervention of Alzheimer's disease’. The 3-day international scientific symposium composed of seven oral sessions and a poster session. The program, spanning from molecular mechanisms to prevention, prediction, diagnosis and treatment of Alzheimer's disease, provided a forum for the attendees to share their research, network and to obtain a comprehensive overview of the current status and future directions of research into Alzheimer's disease.

Chasing the Effects of Pre-Analytical Confounders - A Multicenter Study on CSF-AD Biomarkers

Introduction

Core cerebrospinal fluid (CSF) biomarkers – Aβ42, Tau, and phosphorylated Tau (pTau) – have been recently incorporated in the revised criteria for Alzheimer’s disease (AD). However, their widespread clinical application lacks standardization. Pre-analytical sample handling and storage play an important role in the reliable measurement of these biomarkers across laboratories.

Aim

In this study, we aim to surpass the efforts from previous studies, by employing a multicenter approach to assess the impact of less studied CSF pre-analytical confounders in AD-biomarkers quantification.

Methods

Four different centers participated in this study and followed the same established protocol. CSF samples were analyzed for three biomarkers (Aβ42, Tau, and pTau) and tested for different spinning conditions [temperature: room temperature (RT) vs. 4°C; speed: 500 vs. 2000 vs. 3000 g], storage volume variations (25, 50, and 75% of tube total volume), as well as freezing-thaw cycles (up to five cycles). The influence of sample routine parameters, inter-center variability, and relative value of each biomarker (reported as normal/abnormal) was analyzed.

Results

Centrifugation conditions did not influence biomarkers levels, except for samples with a high CSF total protein content, where either non-centrifugation or centrifugation at RT, compared to 4°C, led to higher Aβ42 levels. Reducing CSF storage volume from 75 to 50% of total tube capacity decreased Aβ42 concentration (within analytical CV of the assay), whereas no change in Tau or pTau was observed. Moreover, the concentration of Tau and pTau appears to be stable up to five freeze–thaw cycles, whereas Aβ42 levels decrease if CSF is freeze-thawed more than three times.

Conclusion

This systematic study reinforces the need for CSF centrifugation at 4°C prior to storage and highlights the influence of storage conditions in Aβ42 levels. This study contributes to the establishment of harmonized standard operating procedures that will help reducing inter-lab variability of CSF-AD biomarkers evaluation.

GRN variant rs5848 reduces plasma and brain levels of granulin in Alzheimer's disease patients

Genetic variants in the granulin (GRN) gene have been shown to increase the risk of Alzheimer's disease (AD). Here, we report that the A allele of rs5848 in GRN reduces plasma granulin levels in a dose-dependent manner in a clinically-defined AD sample cohort. Similarly, the mRNA levels of granulin were decreased with respect to A allele of rs5848 in the inferior temporal cortex of neuropathologically confirmed AD patients. Our findings suggest that the A allele of rs5848 is functionally relevant by reducing the expression of granulin.

Distribution and pattern of pathology in subjects with familial or sporadic late-onset cerebellar ataxia as assessed by p62/sequestosome immunohistochemistry

We investigated whether ubiquitin-binding protein p62/sequestosome-1 could be utilized to evaluate the pathology seen in patients with a clinical diagnosis of progressive late-onset cerebellar ataxia (LOCA). p62-immunoreactive (IR) lesions were assessed by means of immunohistochemistry in the brains of six LOCA cases, one with the spinocerebellar ataxia type 1 mutation (SCA1), ages at death ranging from 46 to 56 years. All cases fulfilled the criteria of olivopontocerebellar atrophy (OPCA), i.e., displaying cell loss in the predilection brain areas. One case, genetics unknown, exhibited p62-IR neuronal intranuclear inclusions (NIs). Similar NIs were labeled with the 1C2 antibody that recognizes proteins containing large polyglutamine stretches. In this case, also fused in sarcoma-IR NIs were seen. In the remaining LOCA cases, including the case with the SCA1 mutation, different kinds of nuclear and cytoplasmic p62 and 1C2 labeling but no NIs were seen. The immunoreactivity and distribution of lesions while applying p62 and 1C2 immunohistochemistry varied in our six LOCA cases fulfilling the criteria of OPCA. In all cases except in the SCA1, diffuse nuclear p62 labeling was seen, not previously reported in SCA or other neurodegenerative disorders. Due to the variability noted here as well as the limited number of cases, no assessment of progression and distributional pattern of pathology could be conducted. Based on a literature search, it is apparent that there is a need for clinico-pathologic-genetical studies of LOCA, especially to obtain a deeper understanding of the regional distribution and progression of pathology.

An antibody with high reactivity for disease-associated α-synuclein reveals extensive brain pathology

α-Synuclein is the major protein associated with Lewy body dementia, Parkinson's disease and multiple system atrophy. Since α-synuclein is present in the brain in physiological conditions as a presynaptic protein, it is crucial to characterize disease-associated modifications to develop an in vivo biomarker. With the aim to develop antibodies showing high specificity and sensitivity for disease-associated α-synuclein, synthetic peptides containing different amino acid sequences were used for immunization of mice. After generation of α-synuclein aggregates, ELISA and immunoblotting were used to test the specificity of antibodies. Tissue microarray sections originating from different human α-synucleinopathies were used to compare immunostaining with other, commercially available antibodies. Immunization of mice with the peptide TKEGVVHGVATVAE (amino acid 44-57 of α-synuclein) resulted in the generation of a monoclonal antibody (5G4), which was able to bind aggregated α-synuclein preparation in sandwich ELISA or coated on magnetic beads. 5G4 proved to be superior to other antibodies in comparative immunohistochemical studies by revealing more widespread and distinct α-synuclein pathology. Immunoblotting of human brain tissue revealed an additional band seen in dementia with Lewy bodies, whereas the band representing monomeric α-synuclein was very weak or lacking. In summary, the 5G4 antibody is most promising for re-evaluation of archival material and may offer new perspective for the development of in vivo diagnostic assays for detecting disease-associated α-synuclein in body fluids.

Cardiovascular diseases and hippocampal infarcts

The prevalence of hippocampal lesions such as hippocampal infarcts have not been studied in detail even though hippocampal alterations are known to be associated with various clinical conditions such as age-related degenerative disorders and epilepsy.

METHODS

Here we defined the hippocampal infarcts and assessed the prevalence of this lesion in large unselected population of 1,245 subjects age ranging from 1 to 99 years (mean age 79 ± 1 S.E.M). Furthermore, we assessed the association of these lesions with various cardio- and cerebro-vascular disorders and other neurodegenerative lesions. The prevalence of hippocampal infarct in the study population of 1,245 subjects was 12%, increasing to 13% when only those with a clinically diagnosed cognitive impairment (n = 311) were analyzed. Large hemispheric brain infarcts were seen in 31% of the study subjects and these lesions were strongly associated with cardiovascular risk factors such as hypertension (43%), coronary disease (32%), myocardial infarct (22%), atrial fibrillation (20%), and heart failure (20%). In contrast, hippocampal infarcts displayed a significant association only with large hemispheric brain infarct, heart failure, and cardiovascular index as assessed postmortem. It is noteworthy that only widespread hippocampal infarcts were associated with clinical symptoms of cognitive impairment or epilepsy. The surprisingly low prevalence of 12% of hippocampal infarcts in aged population found here and the failure to detect an association between this lesion and various cerebro- cardio-vascular lesions is intriguing. Whether susceptibility to ischemia in line with susceptibility to neuronal degeneration in this region is influenced by still undetermined risk- factors need further investigation. Furthermore it should be noted that the size of the hippocampal tissue damage, i.e., small vs. large cystic infarcts is of significance regarding clinical alterations.

Unusual clinical presentation and neuropathology in two subjects with fused-in sarcoma (FUS) positive inclusions

We report two unusual autopsy cases with frontotemporal lobar degeneration (FTLD) that were hyperphosphorylated-tau- and TAR DNA binding protein 43 (TDP-43)- negative. The behavioral symptoms in both cases were compatible with frontotemporal dementia, but they exhibited more prominent speech and language related symptoms than previously reported. Moreover, they displayed a short duration of the disease; the male case had a disease onset age of 45 years, and duration of 5 years, and the female case suffered even shorter disease duration and a later onset of the symptoms, at the age of 67 years. Moreover, the motor functions had deteriorated in different ways in these cases. The male patient showed progressive motor symptoms, weakness of extremities and bulbar muscles suggesting motor neuron disease with a muscle biopsy supporting neurogenic deficits, whereas the female patient exhibited dyskinesias and tremor with progressive swallowing disorders. The father of the male case displayed dementia of similar type at the age of 68 years. In both cases, neuropathological examination showed fused-in sarcoma (FUS)-positive pathology. The male patient had intensely FUS-positive cytoplasmic and intranuclear inclusions that resembled the characteristics previously reported in FTLD FUS, whereas the female patient did not exhibit any cytoplasmic inclusions but had roundish, dense FUS-positive intranuclear inclusions. She also displayed a plethora of other pathologies including α-synuclein, hyperphosphorylated-tau, β-amyloid aggregation and some neuronal polyglutamine aggregation (1C2) but no well-demarcated inclusions were observed. We conclude that clinical phenotypes of FUS pathologies also include elderly patients and are more variable with motor and speech disorders than previously reported.

Immunohistochemical visualization of amyloid-beta protein precursor and amyloid-beta in extra- and intracellular compartments in the human brain

Amyloid-beta (Abeta) peptide, a cleavage product of the amyloid-beta protein precursor (AbetaPP), has been reported to be detected in the intracellular compartment. Most studies reporting the presence of intracellular Abeta are based on the use of immunohistochemistry. In this study, the presence of AbetaPP and Abeta was assessed by applying immunohistochemistry in postmortem human brain tissue samples obtained from 10 neurologically intact subjects, the youngest being 2 years of age, one aged with mild cognitive impairment, 14 neurologically diseased, and in one brain biopsy sample obtained from a subject with normal pressure hydrocephalus. Intracellular immunoreactivity was detected in all ages independent of the disease state or existence of extracellular Abeta aggregates with all antibodies directed to AbetaPP, with three Abeta antibodies (4G8, 6E10, and 82E1), clones that are unable to distinguish Abeta from AbetaPP. These results suggest that it is AbetaPP rather than Abeta that is detected intracellularly when using the antibodies listed above. Furthermore, the staining results varied when different pretreatment strategies were applied. Interestingly intracellular Abeta was detected with antibodies directed to the C-terminus of Abeta (neoepitope) in subjects with Alzheimer's disease. The lack of intracellular immunoreactivity in unimpaired subjects, when using antibodies against neoepitopes, may be due to a lack or a low level of the protein that is thus undetectable at light microscopic level by immunohistochemistry method. The staining results and conclusions depended strongly on the chosen antibody and the pretreatment strategy and thus multiple antibodies must be used when assessing the intracellular accumulation of Abeta.

Expression of collagen XVII and ubiquitin-binding protein p62 in motor neuron disease

Collagen involvement in motor neuron disease has been suggested by several earlier studies. Recently, we found collagen XVII to be expressed in locations in the human brain that include those damaged in motor neuron disease. In this study, we examined the extent of motor neuron disease-related changes in the brain of 9 subjects using ubiquitin-binding protein p62/sequestosome 1 (p62) immunohistochemistry. We then assessed whether or not the expression of collagen XVII was altered in relation to the p62 immunoreactive lesions. We found that neuronal collagen XVII expression in motor neuron disease remains similar to that seen in the normal human brain and thus a change in collagen XVII expression is not an immunohistochemically detectable feature of motor neuron disease. We also found that the regional distribution of p62 varied according to clinical presentation: p62 immunoreactive inclusions were found in the frontal cortex, hippocampus and cerebellum only in subjects with a history of psychiatric morbidity. Our study supports the re-definition of motor neuron disease as a multisystem disorder with a wide clinicopathological spectrum, and we advocate addressing psychiatric symptomology in future studies of motor neuron disease.

Interlaboratory comparison of assessments of Alzheimer disease-related lesions: a study of the BrainNet Europe Consortium

This interlaboratory study evaluated the reproducibility of the assessments of neuritic plaques and neurofibrillary tangles (NFTs)--the hallmark lesions of Alzheimer disease--and compared the staining between the BrainNet Europe centers. To reduce the topography-related inconsistencies in assessments, we used a 2-mm tissue microarray (TMA) technique. The TMA block included 42 core samples taken from 21 paraffin blocks. The assessments were done on Bielschowsky and Gallyas silver stains using an immunohistochemical (IHC) method with antibodies directed to beta-amyloid (IHC/Abeta) and hyperphosphorylated tau (IHC/HPtau). The staining quality and the assessments differed between the participants, being most diverse with Bielschowsky (good/acceptable stain in 53% of centers) followed by Gallyas (good/acceptable stain in 57%) and IHC/Abeta (good/acceptable stain in 71%). The most uniform staining quality and assessment was obtained with the IHC/HPtau method (good/acceptable stain in 94% of centers). The neuropathologic diagnostic protocol (Consortium to Establish a Registry for Alzheimer Disease, Braak and Braak, and the National Institute of Aging and Reagan [NIA-Reagan] Institute) that was used significantly influenced the agreement, being highest with NIA-Reagan (54%) recommendations. This agreement was improved by visualization of NFTs using the IHC/HPtau method. Therefore, the IHC/HPtau methodology to visualize NFTs and neuropil threads should be considered as a method of choice in a future diagnostic protocol for Alzheimer disease.

Projections from the amygdaloid complex to the claustrum and the endopiriform nucleus: a Phaseolus vulgaris leucoagglutinin study in the rat

The claustrum and the endopiriform nucleus contribute to the spread of epileptiform activity from the amygdala to other brain areas. Data of the distribution of pathways underlying the information flow between these regions are, however, incomplete and controversial. To investigate the projections from the amygdala to the claustrum and the endopiriform nucleus, we injected the anterograde tracer Phaseolus vulgaris leucoagglutinin into various divisions of the amygdaloid complex, including the lateral, basal, accessory basal, central, anterior cortical and posterior cortical nuclei, the periamygdaloid cortex, and the amygdalohippocampal area in the rat. Analysis of immunohistochemically processed sections reveal that the heaviest projections to the claustrum originate in the magnocellular division of the basal nucleus. The projection is moderate in density and mainly terminates in the dorsal aspect of the anterior part of the claustrum. Light projections from the parvicellular and intermediate divisions of the basal nucleus terminate in the same region, whereas light projections from the accessory basal nucleus and the lateral division of the amygdalohippocampal area innervate the caudal part of the claustrum. The most substantial projections from the amygdala to the endopiriform nucleus originate in the lateral division of the amygdalohippocampal area. These projections terminate in the central and caudal parts of the endopiriform nucleus. Lighter projections originate in the anterior and posterior cortical nuclei, the periamygdaloid cortex, the medial division of the amygdalohippocampal area, and the accessory basal nucleus. These data provide an anatomic basis for recent functional studies demonstrating that the claustrum and the endopiriform nucleus are strategically located to synchronize and spread epileptiform activity from the amygdala to the other brain regions. These topographically organized pathways also provide a route by means of which the claustrum and the endopiriform nucleus have access to inputs from the amygdaloid networks that process emotionally significant information.

Projections from the amygdaloid complex to the magnocellular cholinergic basal forebrain in rat

The amygdaloid complex has a key role in the modulation of behavioral responses in life-threatening situations, including the direction of attentional responses to sensory stimuli. The pathways from the amygdala to the basal forebrain cholinergic system, which projects to the cortex, are proposed to contribute to the modulation. To further explore the topography and postsynaptic targets of these pathways, we investigated the projections from the different divisions of the lateral, basal, accessory basal, and central nuclei of the amygdala to the cholinergic basal forebrain in rat using a sensitive anterograde tracer, Phaseolus vulgaris leucoagglutinin. The most substantial projections from the amygdala to the basal forebrain are directed to the ventrolateral and dorsomedial aspects of the substantia innominata and the fundus of the striatum. The heaviest projections originate in the capsular, lateral, and intermediate divisions of the central nucleus as well as in the magnocellular and parvicellular divisions of the basal nucleus. Light microscopic analysis of double-stained preparations revealed that the distribution of amygdaloid efferents and cholinergic neurons overlaps most prominently in the ventrolateral substantia innominata. Despite the fact that the central nucleus efferents and cholinergic elements overlap in the ventrolateral substantia innominata, electron microscopic analysis revealed, first, that the postsynaptic targets of the central nucleus efferents are non-cholinergic, probably GABAergic, neurons. Second, 80% of the synaptic contacts were symmetric. The present data extend previous observations showing that the different amygdaloid nuclei provide projections to the selective basal forebrain areas. Further, the central nucleus efferents modulate cholinergic neurons in the basal forebrain indirectly via the GABAergic interneurons.

Projections from the lateral, basal and accessory basal nuclei of the amygdala to the perirhinal and postrhinal cortices in rat

The projections from the amygdaloid complex to the hippocampus and surrounding cortex have a critical role in the formation of memories for emotionally arousing stimuli and in the spread of epileptic seizures. The present study investigated the organization of amygdaloid projections to the perirhinal and postrhinal cortices by injecting the anterograde tracer Phaseolus vulgaris leucoagglutinin into the different subdivisions of the lateral, basal or accessory basal nuclei of the amygdala in rat (n = 53). Analysis of immunohistochemically stained sections indicated that the medial and dorsolateral divisions of the lateral nucleus project heavily to layers I-V of caudal area 35 and to layers I-III of the rostroventral postrhinal cortex. The dorsolateral division also moderately innervates layer I of caudoventral area 36. The magnocellular division of the basal nucleus projects moderately to layers V and VI of rostral areas 35 and 36. The parvicellular division of the accessory basal nucleus projects moderately to layer V of caudal area 35, whereas the magnocellular division projects moderately to layers I and II of rostral area 35. Via these substantial, topographically organized projections, the amygdaloid complex might modulate information processing at different levels of the medial temporal lobe memory system.

Interconnectivity between the amygdaloid complex and the amygdalostriatal transition area: a PHA-L study in rat

The amygdala orchestrates the formation of behavioral responses to emotionally arousing stimuli. Many of these responses are initiated by the central nucleus, which converges information from other amygdaloid nuclei. Recently, we observed substantial projections from the amygdala to the amygdalostriatal transition area, which is located dorsal to the central nucleus. These projections led us to question whether the amygdalostriatal transition area has a role in the initiation of behavioral responses in emotionally arousing circumstances. To explore this anatomically, we traced the interconnections between the amygdalostriatal transition area and the amygdaloid complex using the anterograde tracer Phaseolus vulgaris-leucoagglutinin. The lateral (the medial division and the caudal portion of the dorsolateral division) and the accessory basal nuclei (the parvicellular division) provide moderate-to-heavy projections to the amygdalostriatal transition area. Projections back to the amygdala are light and are composed of thin, faintly stained varicose fibers that resemble the labeling of cholinergic terminals. The extra-amygdaloid outputs of the amygdalostriatal transition area are sparse and include moderate projections to the caudoventral globus pallidus, the ansa lenticularis, and the substantia nigra pars lateralis. These data suggest that the amygdalostriatal transition area is one of the major targets for projections originating in the lateral and accessory basal nuclei of the amygdala. Via these pathways, emotionally significant stimuli can evoke behavioral responses that are different from those initiated via projections from the amygdala to the central nucleus. One such candidate response is the orienting response (i.e., saccadic eye movements and head direction) in a pathway that includes a projection from the lateral/accessory basal nucleus of the amygdala to the amygdalostriatal transition area, and from there to the substantia nigra, pars lateralis.

Reciprocal connections between the amygdala and the hippocampal formation, perirhinal cortex, and postrhinal cortex in rat. A review

Recent anterograde and retrograde studies in the rat have provided detailed information on the origin and termination of the interconnections between the amygdaloid complex and the hippocampal formation and parahippocampal areas (including areas 35 and 36 of the perirhinal cortex and the postrhinal cortex). The most substantial inputs to the amygdala originate in the rostral half of the entorhinal cortex, the temporal end of the CA1 subfield and subiculum, and areas 35 and 36 of the perirhinal cortex. The amygdaloid nuclei receiving the heaviest inputs are the lateral, basal, accessory basal, and central nuclei as well as the amygdalohippocampal area. The heaviest projections from the amygdala to the hippocampal formation and the parahippocampal areas originate in the lateral, basal, accessory basal, and posterior cortical nuclei. These pathways terminate in the rostral half of the entorhinal cortex, the temporal end of the CA3 and CA1 subfields or the subiculum, the parasubiculum, areas 35 and 36 of the perirhinal cortex, and the postrhinal cortex. The connectional data are summarized and the underlying principles of organization of these projections are discussed.

Projections from the lateral, basal, and accessory basal nuclei of the amygdala to the hippocampal formation in rat

The amygdaloid complex and hippocampal formation mediate functions involving emotion and memory. To investigate the connections that regulate the interactions between these regions, we injected the anterograde tracer Phaseolus vulgaris-leucoagglutinin into various divisions of the lateral, basal, and accessory basal nuclei of the rat amygdala. The heaviest projection to the entorhinal cortex originates in the medial division of the lateral nucleus which innervates layer III of the ventral intermediate and dorsal intermediate subfields. In the basal nucleus, the heaviest projection arises in the parvicellular division and terminates in layer III of the amygdalo-entorhinal transitional subfield. In the accessory basal nucleus, the parvicellular division heavily innervates layer V of the ventral intermediate subfield. The most substantial projection to the hippocampus originates in the basal nucleus. The caudomedial portion of the parvicellular division projects heavily to the stratum oriens and stratum radiatum of CA3 and CA1. The accessory basal nucleus projects to the stratum lacunosum-moleculare of CA1. The subiculum receives a substantial input from the caudomedial parvicellular division. The parasubiculum receives dense projections from the caudal portion of the medial division of the lateral nucleus, the caudomedial parvicellular division of the basal nucleus, and the parvicellular division of the accessory basal nucleus. Our data show that select nuclear divisions of the amygdala project to the entorhinal cortex, hippocampus, subiculum, and parasubiculum in segregated rather than overlapping terminal fields. These data suggest that the amygdaloid complex is in a position to modulate different stages of information processing within the hippocampal formation.

A time-resolved immunofluorometric assay of sialyl Lewis x-degrading alpha 2,3-sialidase activity

We have developed an assay for alpha 2,3-sialidase (EC 3.2.1.18) which employs a biotinylated carbohydrate-polyacrylamide conjugate as substrate for the enzyme. The solution-phase sialidase reactions are followed by a selective capture of biotinylated neoglycoconjugates onto a microtitration plate coated with streptavidin. The amount of the reaction product formed is then rapidly and easily quantified using a product-specific primary antibody and europium chelate-labeled secondary antibody. This method combines the advantages of solution-phase enzymatic reaction and suitability for high-throughput screening typical of solid-phase assays. The assay gives a detectable signal with 0.4% of substrate sites desialylated. We have demonstrated the utility of the assay by measuring alpha 2,3-sialidase activity from crude lysates of cultured rat endothelial cells by using biotinylated sialyl Lewis x glycoconjugate as substrate. Endothelial sialidase(s) showed up to 250-fold higher activity toward soluble compared to immobilized substrate. Product formation detected with an anti-Lewis x antibody was linear in the range of 0.1-4 micrograms/ml of protein in endothelial cell lysate. High sensitivity of the assay was achieved by using solution-phase enzyme reaction and time-resolved fluorometric detection. The same assay format used here is easily adapted to detect activities of several different glycosidases or glycosyl-transferases by using appropriate substrates and antibodies.