Intracranial volume and dementia: some evidence in support of the cerebral reserve hypothesis.

The brain reserve hypothesis has been posited as being one important mediating factor for developing dementia, especially Alzheimer's disease (AD). Evidence for this hypothesis is mixed though different methodologies have made these findings difficult to interpret. We examined imaging data from a large cohort (N=194) of mixed dementia patients and controls, 65years old and older from the Cache County, Utah Study of Memory and Aging for evidence of the brain reserve hypothesis using total intracranial volume (TICV) as a quantitative measure of pre-morbid brain size and a vicarious indicator of reserve. A broader spectrum of non-demented elderly control subjects from previous studies was also included for comparison (N=423). In addition, non-parametric Classification and Regression Tree (CART) analyses were performed to model group heterogeneity and identify any subgroups of patients where TICV might be an important predictor of dementia. Parametrically, no main effect was found for TICV when predicting a dementia diagnosis; however, the CART analysis did reveal important TICV subgroups, including a sex differential wherein ε4 APOE allele presence in males and low TICV predicted AD classification. TICV, APOE, and other potential mediator/moderator variables are discussed in the context of the brain reserve hypothesis.

Twin pairs discordant for neuropathologically confirmed Lewy body dementia.

AIM: Little is known about the concordance rate in twins for dementia with Lewy bodies (DLB). The rate of agreement between clinical and pathological diagnoses for DLB is typically low, necessitating confirmation of the diagnosis neuropathologically. METHODS: Participants were 17 twin pairs enrolled in the Duke Twins Study of Memory in Aging in which at least one member of the pair had an autopsy confirmed diagnosis of DLB, Alzheimer's disease (AD) with Lewy bodies or frontotemporal dementia with Lewy bodies. The characteristics of those with dementia were assessed and rates of concordance for pathological confirmed dementia were examined. RESULTS: Four monozygotic twin pairs had a proband with neuropathologically confirmed pure DLB; all remained discordant for dementia for periods up to 16 years or more. Five of 13 pairs in which the proband had AD plus DLB were concordant for dementia but only one pair was concordant for AD plus DLB, while the co-twins in the other four pairs had other types of dementia. CONCLUSIONS: The present study indicates that even among twins, a diagnosis of DLB in one twin does not predict the same diagnosis in the other twin. Neuropathological discordance in type of dementia among monozygotic pairs hints at environmental or epigenetic factors playing a role in Lewy body pathology.

Longitudinal follow-up of late-onset Alzheimer disease families.

Historically, data for genetic studies are collected at one time point. However, for diseases with late onset or with complex phenotypes, such as Alzheimer disease (AD), restricting diagnosis to a single ascertainment contact may not be sufficient. Affection status may change over time and some initial diagnoses may be inconclusive. Follow-up provides the opportunity to resolve these complications. However, to date, previous studies have not formally demonstrated that longitudinally re-contacting families is practical or productive. To update data initially collected for linkage analysis of late-onset Alzheimer disease (LOAD), we successfully re-contacted 63 of 81 (78%) multiplex families (two to 17 years after ascertainment). Clinical status changed for 73 of the 230 (32%) non-affected participants. Additionally, expanded family history identified 20 additional affected individuals to supplement the data set. Furthermore, fostering ongoing relationships with participating families helped recruit 101 affected participants into an autopsy and tissue donation program. Despite similar presentations, discordance between clinical diagnosis and neuropathologic diagnosis was observed in 28% of those with tissue diagnoses. Most of the families were successfully re-contacted, and significant refinement and supplementation of the data was achieved. We concluded that serial contact with longitudinal evaluation of families has significant implications for genetic analyses.

Microvascular injury and blood-brain barrier leakage in Alzheimer's disease.

Thinning and discontinuities within the vascular basement membrane (VBM) are associated with leakage of the plasma protein prothrombin across the blood-brain barrier (BBB) in Alzheimer's disease (AD). Prothrombin immunohistochemistry and ELISA assays were performed on prefrontal cortex. In severe AD, prothrombin was localized within the wall and neuropil surrounding microvessels. Factor VIII staining in severe AD patients indicated that prothrombin leakage was associated with shrinkage of endothelial cells. ELISA revealed elevated prothrombin levels in prefrontal cortex AD cases that increased with the Braak stage (Control=1.39, I-II=1.76, III-IV=2.28, and V-VI=3.11 ng prothrombin/mg total protein). Comparing these four groups, there was a significant difference between control and Braak V-VI (p=0.0095) and also between Braak stages I-II and V-VI (p=0.0048). There was no significant difference in mean prothrombin levels when cases with versus without cerebral amyloid angiopathy (CAA) were compared (p-value=0.3627). When comparing AD patients by APOE genotype (ApoE3,3=2.00, ApoE3,4=2.49, and ApoE4,4=2.96 ng prothrombin/mg total protein) an analysis of variance indicated a difference between genotypes at the 10% significance level (p=0.0705). Tukey's test indicated a difference between the 3,3 and 4,4 groups (p=0.0607). These studies provide evidence that in advanced AD (Braak stage V-VI), plasma proteins like prothrombin can be found within the microvessel wall and surrounding neuropil, and that leakage of the blood-brain barrier may be more common in patients with at least one APOE4 allele.

Effect of APOE genotype on microvascular basement membrane in Alzheimer's disease.

APOE4 homozygosity has been associated with an increased risk of sporadic Alzheimer's disease through a mechanism, which has yet to be defined. Recent evidence has suggested that microvascular basement membrane injury may be a critical factor in the pathogenesis of AD-related dementia. In previous studies, we have shown that the synaptic organizing protein agrin can be found in neurons, and is a major component of the brain microvascular basement membrane. Here, we compare the basement membrane surface area of cortical microvasculature in AD brains by staining with an anti-agrin antibody. Quantitative morphometric analysis was used to determine the mean basement area (micro(2)) of prefrontal cortical microvessels. An average of 10 capillaries was measured in each of 35 cases of AD genotyped for APOE status. APOE4,4 homozygotes had smaller capillary basement membrane areas (17.4 micro(2))+/-6.2) than APOE3,3 homozygotes (26.9 micro(2)+/-6.5), p<0.001. The capillary basement membrane areas (CBMA) of heterozygotes APOE3,4 did not differ significantly from APOE3,3 or APOE4,4. Braak stage did not contribute significantly to CBMA. However, a preliminary analysis suggests an interaction between APOE4,4 and Braak V-VI producing smaller CBMA, a finding which needs to be confirmed with a larger sample. These data support the hypothesis that APOE4,4 is associated with thinning of the microvascular basement membrane in Alzheimer's disease.

Human herpesvirus 6 limbic encephalitis after stem cell transplantation.

Central nervous system complications are common in stem cell transplant recipients, but selective involvement of the medial temporal area is unusual. The 5 patients reported here presented after stem cell transplantation with increased hippocampal T2 signal on magnetic resonance imaging and increased hippocampal glucose uptake on [F-18]fluorodeoxyglucose-positron emission tomography (FDG-PET) associated with short-term memory loss, insomnia, and temporal lobe electrographic seizure activity. The initial scalp electroencephalograms (EEGs) failed to detect seizure activity in these patients, although the memory dysfunction along with the magnetic resonance imaging and FDG-PET findings suggested subcortical seizure activity. However, extended EEG monitoring revealed repetitive temporal lobe electrographic seizure activity. Follow-up MRIs in 2 patients and postmortem findings on 1 patient suggested that hippocampal sclerosis had developed following the clinical syndrome. Cerebrospinal fluid studies revealed the presence of human herpesvirus 6, variant B, DNA in all of 3 patients who had lumbar punctures. Immunohistochemical staining for the P41 and P101 human herpesvirus 6 protein antigens showed numerous immunoreactive astrocytes and neurons in the hippocampus of 1 of the patients who died from other causes. Because of its subtle clinical presentation, this syndrome may be underrecognized, but can be diagnosed with appropriate magnetic resonance imaging techniques, EEG monitoring, and cerebrospinal fluid viral studies.

Endocytic disturbances distinguish among subtypes of Alzheimer's disease and related disorders.

The endocytic pathway is important in amyloid precursor protein (APP) processing and beta-amyloid formation. Our studies have shown that endocytic pathway activation is a prominent and early feature of neurons in vulnerable regions of the brain in sporadic Alzheimer's disease. We report that endocytic pathway abnormalities are present not only in neurons, but in cerebral endothelia in Alzheimer's disease caused by certain APP mutations. The presence or absence of endocytic abnormalities distinguish subtypes of familial Alzheimer's disease linked to APP mutations from presenilin mutations, supporting the notion that different cellular pathways are involved in the altered processing of APP leading to increased beta-amyloid generation in certain of these different Alzheimer's disease subtypes.

Recovery and expression of messenger RNA from postmortem human brain tissue.

The Bryan Alzheimer's Disease Research Center Rapid Autopsy Program at Duke University Medical Center obtains postmortem human brain tissue for experimental investigations. We evaluated 19 brains for RNA integrity and mRNA gene expression. Nine were from patients diagnosed with Alzheimer's disease, and ten were from nondemented controls. In all cases, the following variables were recorded: postmortem procurement delay (range, 1 hour and 10 minutes to 14 hours), pH of cerebrospinal fluid, premortem fever or sepsis, provision of supplemental oxygen in the agonal period, and temporal relation to time of death (either sudden death or protracted illness). Total RNA was extracted, quantified, and evaluated by agarose gel electrophoresis and quantitative gene expression analysis of 18S rRNA and edg-1 using TaqMan technology. All samples appeared to yield intact RNA without significant degradation, and expression of the edg-1 gene was detected by the real time reverse transcriptase polymerase chain reaction in all cases. We conclude that intact RNA can be obtained from postmortem human brain tissue, even in patients with severe premortem illnesses and delayed postmortem tissue procurement intervals. However, we caution that the successful expression of certain genes from postmortem brain tissue may require enhanced procurement efforts to maximize RNA integrity.

Inter-laboratory comparison of DNA preservation in archival paraffin-embedded human brain tissue from participating centres on four continents.

DNA extracted from formalin-fixed and paraffin-embedded brain tissue is known to contain as yet ill-characterized inhibitors of the PCR process. As part of a project that aims to clarify the role of mitochondrial DNA sequence variation in human neurodegenerative diseases using DNA from various ethnic backgrounds, we have investigated factors that influence the preservation of archival DNA and its suitability for PCR. In this study, neuropathological tissue samples were analysed that had been routinely processed in 18 international centres on four continents. Following DNA extraction, PCR amplification of mitochondrial and nuclear DNA sequences was performed with and without additional purification of the template DNA. In addition, the DNA used for PCR was analysed by HPLC. Phosphate-buffered formalin proved to be a superior fixative compared with unbuffered aldehyde: DNA extraction resulted in greater yields, the molecular weight of the isolated DNA was higher and PCR was more successful. PCR inhibitors were identified as (1) high concentrations of small (<300 bp) DNA fragments that competitively compete with template DNA and (2) contaminants of the DNA template solution including denatured protein that cannot be completely removed by phenolic extraction. HPLC analysis did not reveal significant qualitative differences between DNA isolated from fresh-frozen tissue samples and DNA recovered from formalin-fixed, paraffin-embedded brain tissue. The fact that DNA could be amplified from the majority of tissue specimens in this study suggests that rare diseases and diseases where ethnic background plays an important role can be sampled for genetic polymorphism analysis on a global scale using archival neuropathological collections.

Cortical alterations of angiotensin converting enzyme, angiotensin II and AT1 receptor in Alzheimer's dementia.

We investigated the immunohistochemical alterations of angiotensin converting enzyme (ACE), angiotensin II and AT1 receptor in the parietal cortex in Alzheimer's dementia (AD) to reveal the contributive role of the brain renin-angiotensin system in the disease process. In controls, ACE, angiotensin II and AT1 immunoreactivities were localized to pyramidal neurons of the cortex. The staining intensity was distinctly increased in AD for all three antigens, involving predominantly cortical layer V, which may reflect the enhanced brain renin-angiotensin system activity in the disease process. In addition, a prominent perivascular ACE and angiotensin II immunoreactivity surrounding some cortical vessels in aged controls and AD patients points to an underlying microvascular pathology in the process of neurodegeneration.

Ham56-immunoreactive macrophages in untreated infiltrating gliomas.

CONTEXT: Classic diagnostic neuropathologic teachings have cautioned against making the diagnosis of neoplasia in the presence of a macrophage population. The knowledge of macrophage distribution should prove useful when confronted with an infiltrating glioma containing macrophages. OBJECTIVE: To identify macrophages in untreated, infiltrating gliomas using the monoclonal antibody HAM56, and to confirm their presence in an untreated glioblastoma multiforme (GBM) with the serial analysis of gene expression (SAGE) method. METHODS: We evaluated the presence of macrophages in 16 cases of untreated, supratentorial infiltrating gliomas with the macrophage monoclonal antibody HAM56. We performed SAGE for one case of GBM and for normal brain tissue. RESULTS: In World Health Organization (WHO) grade II well-differentiated astrocytoma and oligodendroglioma, HAM56 reactivity was noted only in endothelial cells, and unequivocal macrophages were not identified. In WHO grade III anaplastic astrocytoma and anaplastic oligodendroglioma, rare HAM56-positive macrophages were noted in solid areas of tumor. In WHO grade IV GBM, HAM56-positive macrophages were identified in areas of solid tumor (mean labeling index, 8.6%). In all cases of GBM, nonquantitated HAM56-positive macrophages were identified in foci of pseudopalisading cells abutting necrosis and in foci of microvascular proliferations. In none of the cases were granulomas or microglial nodules found, and there was no prior history of surgical intervention, radiation therapy, chemotherapy, or head trauma in these cases. By SAGE, the macrophage-related proteins osteopontin and macrophage-capping protein were overexpressed 12-fold and eightfold, respectively, in one untreated GBM compared with normal brain tissue. In this case, numerous HAM56-positive macrophages (labeling index, 24.5%) were present in the solid portion of tumor, and abundant nonquantified macrophages were identified in foci of pseudopalisading cells abutting necrosis and in foci of microvascular proliferations. CONCLUSIONS: This study confirms the utility of the monoclonal antibody HAM56 in identifying macrophages within untreated infiltrating gliomas. The overexpression of macrophage-related proteins in one case of GBM as detected by SAGE signifies that macrophages may be present in untreated GBMs.

Dementia with Lewy bodies and Alzheimer's disease.

To investigate similarities and differences between Alzheimer's disease (AD) and dementia with Lewy bodies (DLB), we undertook a demographic analysis of 277 patients from the Kathleen Price Bryan Brain Bank with an antemortem diagnosis of probable AD. Patients with additional, possibly confounding clinical and pathologic diagnoses such as infarcts, hematomas, neoplasms, and other neurodegenerative disorders, were excluded from the analysis. Neuropathologically, AD alone was present in 192 subjects (69%), and DLB was found in 85 subjects (31%). All of the DLB cases had neuropathologic evidence of AD sufficient to meet CERAD criteria for a diagnosis of definite AD plus nigral Lewy bodies. Gender, apolipoprotein E (APOE) genotype, brain weight, age at death, duration of disease and Braak stage were compared between the two groups. Statistical analyses were performed using Fisher's exact test for comparisons of categorical data and Student's t-test for comparison of means for continuous outcomes. The proportion of males and females was balanced in the combined AD and DLB populations. There was a highly statistically significant increased frequency of APOE 3/4 in males with DLB (P = 0.007). We found higher brain weights in males with DLB versus males with AD (P = 0.012). AD was more frequent in females and DLB was more frequent in males (P = 0.019). Our findings with respect to age at death, duration of disease and Braak stage within diagnostic groups confirm previously reported findings. These data suggest that Lewy bodies are more common in males affected with dementia, especially those with the APOE 3/4 genotype.

Ectopic white matter neurons, a developmental abnormality that may be caused by the PSEN1 S169L mutation in a case of familial AD with myoclonus and seizures.

We report clinical, neuropathologic and molecular genetic data from an individual affected by a familial Alzheimer disease (AD) variant. The proband had an onset of dementia at age 29 followed by generalized seizures a year later. He died at age 40. Neuropathologically, he had severe brain atrophy and characteristic histopathologic lesions of AD. Three additional neuropathologic features need to be emphasized: 1) severe deposition of Abeta in the form of diffuse deposits in the cerebral and cerebellar cortices, 2) numerous Abeta deposits in the subcortical white matter and in the centrum semiovale, and 3) numerous ectopic neurons, often containing tau-immunopositive neurofibrillary tangles, in the white maner of the frontal and temporal lobes. A molecular genetic analysis of DNA extracted from brain tissue of the proband revealed a S169L mutation in the Presenilin 1 (PSEN1) gene. The importance of this case lies in the presence of ectopic neurons in the white matter, early-onset seizures, and a PSEN1 mutation. We hypothesize that the PSEN1 mutation may have a causal relationship with an abnormality in neuronal development.

Brain expression of presenilins in sporadic and early-onset, familial Alzheimer's disease.

BACKGROUND: Mutations in the presenilin proteins cause early-onset, familial Alzheimer's disease (FAD). MATERIALS AND METHODS: We characterized the cellular localization and endoproteolysis of presenilin 2 (PS2) and presenilin 1 (PS1) in brains from 25 individuals with presenilin-mutations causing FAD, as well as neurologically normal individuals and individuals with sporadic Alzheimer's disease (AD). RESULTS: Amino-terminal antibodies to both presenilins predominantly decorated large neurons. Regional differences between the broad distributions of the two presenilins were greatest in the cerebellum, where most Purkinje cells showed high levels of only PS2 immunoreactivity. PS2 endoproteolysis in brain yielded multiple amino-terminal fragments similar in size to the PS1 amino-terminal fragments detected in brain. In addition, two different PS2 amino-terminal antibodies also detected a prominent 42 kDa band that may represent a novel PS2 form in human brain. Similar to PS1 findings, neither amino-terminal nor antiloop PS2 antibodies revealed substantial full-length PS2 in brain. Immunocytochemical examination of brains from individuals with the N141I PS2 mutation or eight different PS1 mutations, spanning the molecule from the second transmembrane domain to the large cytoplasmic loop domain, revealed immunodecoration of no senile plaques and only neurofibrillary tangles in the M139I PS1 mutation stained with PS1 antibodies. CONCLUSIONS: Overall presenilin expression and the relative abundance of full-length and amino-terminal fragments in presenilin FAD cases were similar to control cases and sporadic AD cases. Thus, accumulation of full-length protein or other gross mismetabolism of neither PS2 nor PS1 is a consequence of the FAD mutations examined.

FDG PET imaging in patients with pathologically verified dementia.

UNLABELLED: The purpose of this study was to confirm with pathologic verification 2 beliefs related to Alzheimer's disease (AD): (a) the long-standing impression that bilateral temporo-parietal hypometabolism, as noted on FDG PET imaging, is the metabolic abnormality associated with Alzheimer's disease (AD) and (b) that the sensitivity, specificity, and diagnostic accuracy of the metabolic pattern of bilateral temporo-parietal hypometabolism allows differentiation between other degenerative causes of dementia. METHODS: Twenty two individuals (8 women, 14 men) with difficult-to-characterize memory loss or dementia (using standard clinical criteria), and who eventually received pathologic confirmation of diagnosis, were evaluated. FDG PET brain scans were obtained and visually graded by an experienced nuclear medicine physician as to the presence of classic bilateral temporo-parietal hypometabolism as seen in Alzheimer's type dementia. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the metabolic pattern of bilateral temporo-parietal hypometabolism were determined using pathologic diagnosis as the gold standard. RESULTS: The clinical diagnosis of possible or probable AD was determined as the primary cause of dementia in 12 patients. The sensitivity and specificity of the clinical diagnosis for probable AD were 63% and 100%, respectively. The sensitivity and specificity of the clinical diagnosis for possible and probable AD were 75% and 100%, respectively. The sensitivity, specificity, and diagnostic accuracy of bilateral temporo-parietal hypometabolism being associated with AD were 93%, 63%, and 82%, respectively. CONCLUSION: This study confirms that bilateral temporo-parietal hypometabolism is indeed the classic metabolic abnormality associated with AD. Furthermore, in individuals with dementia whose FDG PET scans indicated a metabolic pattern other than bilateral temporo-parietal hypometabolism, a cause of dementia other than AD should be suspected. These observations may be of clinical importance in differentiating dementia syndromes. The sensitivity, specificity, and diagnostic accuracy of FDG PET are acceptable as tests to be used in the evaluation of dementia and particularly to confirm the clinical suspicion of AD.

Alterations in trk A, trk B and trk C receptor immunoreactivities in parietal cortex and cerebellum in Alzheimer's disease.

The neurotrophins nerve growth factor, brain-derived neurotrophic factor and neurotrophin-3 bind to the tyrosine kinase (trk) receptors trk A, trk B and trk C, respectively, with high affinity. We investigated the expression of the trk receptors in the parietal cortex (PC) and cerebellum of patients with Alzheimer's disease (AD) and age-matched controls. Cortical layers II-VI displayed a distinct cellular immunoreactivity for trk A and C with an emphasis in the pyramidal neurons of layers III and V. Trk B immunoreactivity was primarily located in the deeper cortical layers with a predominance in layer V. There was a decrease in trk A and C immunoreactivity in the PC of AD cases, while trk B density appeared to be unchanged. In addition, cerebellar Purkinje cells revealed a distinct immunoreactivity for trk C both in control and AD cases, suggesting trk C may be important in the maintenance of these cells in the aged brain.

Temozolomide delivered by intracerebral microinfusion is safe and efficacious against malignant gliomas in rats.

Intracerebral microinfusion (ICM) is an innovative technique of delivering therapeutic agents throughout large portions of the brain that circumvents the blood-brain barrier, minimizes systemic toxicity, and provides a homogeneous distribution of the infused agent. Temozolomide is a novel methylating agent with proven efficacy against malignant gliomas (MGs) after systemic administration but with dose-limiting myelotoxicity. Because MGs rarely metastasize, systemic drug delivery is unnecessary. Therefore, we evaluated the efficacy and toxicity of ICM with temozolomide in an athymic rat model of human MGs. Treatment of rats by ICM with temozolomide 3 days after intracerebral challenge with D54 human MG xenograft increased median survival by 128% compared with rats treated by ICM with saline, by 113% compared with rats treated with i.p. saline, and by 100% compared with rats treated with i.p. temozolomide (P < 0.001). Delay of treatment until 9 days after tumor challenge still resulted in a 23% increase in median survival in rats treated by ICM of temozolomide compared with rats treated with i.p. temozolomide. In addition, overall, 21.7% of rats treated by ICM with temozolomide survived for > 100 days without clinical or histological evidence of tumor. The dose of temozolomide delivered by ICM in this study was limited only by drug solubility, and no neurological or systemic toxicity could be attributed to ICM with temozolomide. Therefore, ICM of temozolomide may offer significant advantages in the treatment of MGs.

Lewy body and Alzheimer pathology in a family with the amyloid-beta precursor protein APP717 gene mutation.

Mutations in the amyloid precursor protein (APP) gene cause one form of early onset familial Alzheimer's disease (AD). One such family has been studied genetically and neuropathologically and represents the basis of the present report. Four siblings with the APP717 Val to Ile mutation, aged 59, 65, 61 and 64 years, apolipoprotein E (APOE) genotyped 2,4 (first three) and 2,3 respectively, had severe AD, Braak stage VI with frequent neurofibrillary tangles in the primary visual cortex, Brodmann area 17. The first one also met McKeith criteria for the limbic stage of dementia with Lewy bodies but did not have substantia nigra Lewy bodies. The second two met McKeith criteria for the neocortical stage of dementia with Lewy bodies and both had substantia nigra Lewy bodies. The fourth had AD but no Lewy bodies. A cousin without the APP717 mutation who was APOE 3, 4, developed dementia at age 60 and died at age 75. She had severe cerebrovascular atherosclerosis, less severe AD, Braak stage V, with sparing of area 17. She also had Lewy bodies in the substantia nigra and in the cortex and met McKeith criteria for neocortical stage of dementia with Lewy bodies. Extrapyramidal features were present in all five. Lewy bodies have been described in 53% of reported autopsies on individuals with the APP717 Val to Ile mutation coincident with dementia and AD neuropathologic changes. These observations suggest an association between the chromosome 21 APP mutation and Lewy body formation, possibly mediated by other environmental or genetic factors.

Alterations in neurotrophins and neurotrophin receptors in Alzheimer's disease.

We demonstrated that nerve growth factor (NGF) levels were increased in hippocampus and cortical areas, as well as in cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD). Such increases may, at least in part, be due to a decreased expression of the NGF high affinity receptor trkA. Measurement of CSF levels of NGF may add to the repertoire of potential biochemical diagnostic markers in living AD patients.